Indian Patents. 268235:NOVEL BENZOTHIAZOLE OR BENZOXAZOLE LINKED PYRROLO [2,1-C][1,4] BENZODIAZEPINE HYBRID AS POTENTIAL ANTITUMUOR AGENT AND PROCESS FOR THE PREPARATION THEREOF

Title of Invention	NOVEL BENZOTHIAZOLE OR BENZOXAZOLE LINKED PYRROLO [2,1-C][1,4] BENZODIAZEPINE HYBRID AS POTENTIAL ANTITUMUOR AGENT AND PROCESS FOR THE PREPARATION THEREOF
Abstract	The present invention provides a compound of general formula 9, useful as potential antitumour agents against human cancer cell lines. The present invention further provides a process for the preparation of pyrrolo [2,1-c][1,4]benzodiazepine hybrids of general formula 9

Full Text	" FIELD OF THE INVENTION The present invention relates to novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine hybrid as potential antitumour agent. The present invention also relates to a process for the preparation of novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine hybrid. More particularly, the present invention relates to benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine hybrid of general formula 9 (Figure Removed) The present invention further relates to a process for the preparation of 7- methoxy-8-{n-[4-(1,3-benzothiazol-2-yl)-2-substitutedphenoxy]alkyl}oxy-(11 aS)- 1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one / 7-methoxy-8-{n-[4- (1,3-benzoxazol-2-yl)-2-substituted phenoxy]alkyl}oxy-(11aS)-1, 2,3,11a-tetrahydro-5Hpyrrolo[ 2,1-c][1,4]benzodiazepin-5-one / 7-methoxy-8-{n-[N1-(4-(7-substituted-1,3-benzo thiazol-2-yl)phenyl)]alkanecarboxamide}oxy-(11aS)-1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1- c][1,4]benzodiazepin-5-one with aliphatic chain length variations. BACKGROUND OF THE INVENTION Pyrrolo [2,1-c][1,4]benzodiazepines (PBDs), a group of potent naturally occurring antitumour antibiotics from various Streptomyces species, are of considerable interest because of their ability to recognize and subsequently form covalent bonds to specific base sequence of double strand DMA (Dervan, P. B. Science 1989, 232, 464.; Hurley, L. H. J. Med. Chem. 1989, 32, 2027.; Thurston, D. E.; Thompson, A. S. Chem. Br. 1990, 26, 767). Well-known members of this group include anthramycin, DC-81, sibiromycin, tomamycin, chicamycin and neothramycin.of A and B (Hurley, L. H. J. Antibiot. 1977, 30, 349.; Schimizu, K.; Kawamoto, I.; Tomita, F.; Morimoto, M.; Fujimoto, K. J. Antibiot. 1982, 35, 992.; Lown, J. W.; Joshua, A. V. Biochem. Pharmacol. 1979, 28, 2017.; Thurston, D. E.; Bose, D. S. Chem. Rev. 1994, 94, 433.; Molina, P.; Diaz, I.; Tarraga, A. Tetrahedron 1995, 51, 5617.; Kamal, A.; Rao, N. V. Chem. Commun. 1996, 385.; Kamal, A.; Reddy, B. S. P.; Reddy, B. S. N. Tetrahedron Lett. 1996, 37, 6803). The cytotoxicity and antitumour activity of these agents are attributed to their property of sequence selective covalent binding to the N2 of guanine in the minor groove of duplex DNA via an acid-labile aminal bond to the electrophilic imine at the N10-C11 position (Kunimoto, S.; Masuda, T.; Kanbayashi, N.; Hamada, M.; Naganawa, H.; Miyamoto, M.; Takeuchi, T.; Unezawa, H. J. Antibiot., 1980, 33, 665.; Kohn, K. W. and Speous, C. L. J. Mol. Biol., 1970, 51, 551.; Hurley, L. H.; Gairpla, C. and Zmijewski, M. Biochem. Biophys. Acta., 1977, 475, 521.; Kaplan, D. J. and Hurley, L. H. Biochemistry, 1981, 20, 7572). The molecules have a right-handed twist, which allows them to follow the curvature of the minor groove of B-form double-stranded DNA spanning three base pairs. A recent development has been the linking of two PBD units through their C-8 positions to give bisfunctional-alkylating agents capable of cross-linking DNA (Thurston, D. E.; Bose, D. S.; Thomson, A. S.; Howard, P. W.; Leoni, A.; Croker, S. J.; Jenkins, T. C.; Neidle, S. and Hurley, L H. J. Org. Chem. 1996, 61, 8141). Recently, PBD dimers have been developed that comprise of two C2-exomethylene substituted DC-81 subunits tethered through their C-8 position via an inert propanedioxy linker (Gregson, S. J.; Howard, P. W.; Hartely, J. A.; Brooks, N. A.; Adams, L. J.; Jenkins, T. C.; Kelland, L. R. and Thurston, D. E. J. Med. Chem. 2001, 44, 737). A non-cross-linking mixed imine-amide PBD dimers have been synthesized that have significant DNA binding ability and potent antitumour activity (Kamal, A.; Ramesh, G. Laxman, N.; Ramulu, P.; Srinivas, O.; Neelima, K.; Kondapi, A. K.; Srinu, V. B.; Nagarajaram, H. M. J. Med. Chem. 2002, 45, 4679). However, the clinical efficacy for these antibiotics is hindered by several limitations, such as poor water solubility, cardiotoxicity, development of drug resistance and metabolic inactivation. Due to the excellent activity of these molecules, there is need to develop novel derivatives which are devoid of above limitations. Benzothiazoles are small synthetic molecules that contain a benzene ring fused to a thiazole ring. These simple molecules have shown remarkable antitumour properties and some of them are undergoing evaluation in clinical trials (Shi, D.-F.; Bradshaw, T. D.; Wrigley, S.; McCall, C. J.; Lelieveld, P.; Fichtner, I.; Stevens, M. F. G. J. Med. Chem. 1996, 39, 3375; Kashiyama, E.; Hutchinson, I.; Chua, M.-S.; Stinson, S. F.; Phillips, L. R.; Kaur, G.; Sausville, E, A.; Bradshaw, T. D.; Westwell, A. D.; Stevens, M. F. G. J. Med. Chem. 1999, 42, 4172; Hutchinson, I.; Chua, M.-S.; Browne, H. L.; Trapani, V.; Bradshaw, T. D.; Westwell, A. D.; Stevens, M. F. G. J. Med. Chem. 2001, 44, 1446). Recently Westwell and coworkers have prepared a series of benzothiazole derivatives and evaluated for anticancer activity, One of these analogues has shown excellent anticancer activity (Mortimer, C. G.; Wells, G.; Crochard, J.-P.; Stone, E. L.; Bradshaw, T. D.; Stevens, M. F. G.; Westwell, A. D. J. Med. Chem. 2006, 49, 179). The structurally related benzoxazoles have also been reported to possess anticancer activity (Kumar, D.; Jacob, M. R.; Reynold, M. B.; Kerwin, S. M. Bioorg. Med. Chem. 2002, 10, 3994; Gong, B.; Hong, F.; Kohm, C.; Bonham, L.; Klein, P. Bioorg. Med. Chem. Lett. 2004, 14, 1455). Based on the potent anticancer activity of pyrrolo[2,1- c][1,4]benzodiazepines, benzothiazoles and benzoxazoles, new PBD hybrids have been designed and synthesized by linking benzothiazole and benzoxazole moieties at C8- position of pyrrolo[2,1-c][1,4]benzodiazepine with varying alkane and alkylamide spacers. OBJECTIVES OF THE INVENTION The main objective of the present invention is to provide novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid useful as antitumour agent. Yet another object of the present invention is to provide a process for the preparation of novel benzothiazole or benzoxazole linked pyrrolo[2,1-c] [1,4]benzodiazepine hybrids. SUMMARY OF THE INVENTION Accordingly the present invention provides novel benzothiozole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines of formula 9, Wherein: n = 3-4, X = S or O; Y = NH or 0; Z = CO or CH2; R, RI = H or F; R2 = OCH3 or H. In an embodiment of the present invention the representative compounds of formula 9 are as follows: 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11aS)-1,2,3,11atetrahydro- 5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a); 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl}oxy-(11aS)- 1,2,3,11 a-tetrahydro-5H-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one (9b); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro- 5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS)- 1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin -5-one(9d); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11 aS)-1,2,3,11 atetra- hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS) 1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9f); 7-Methoxy-8-{5-[A/r-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarboxamide}oxy- (11aS)-1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9g); and 7-Methoxy-8-{5-[A/r-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane carboxamide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4] benzodiazepin-5-one (9h). In yet another embodiment the structural formula of the representative compounds 9a-h are: (Figure Removed) In yet another embodiment the compounds of formula 9 exhibits binding affinity with calf thymus (CT) DMA at a molar ratio of 1:5 in aqueous sodium phosphate buffer at pH 7. In yet another embodiment the compounds of formula 9 exhibit in-vitro cytotoxicity against human tumor cells derived from nine cancer types of leukemia, nonsmall- cell lung, colon, CMS, melanoma, ovarian, prostate, and breast cancer. In yet another embodiment the compound 9a exhibits in-vitro cytotoxicity in mean graph midpoint value of -6.30(mol/lit), -5.63(mol/lit), and -4.75(mol/lit) for log™ GI50, logio TGI and logic LC50, respectively, against nine human tumor cell lines. In yet another embodiment the compound 9b exhibits in-vitro cytotoxicity in mean graph midpoint value of Iog10 TGI, logic LC50,logio GI50. In-vitro cytotoxicity data in mean graph midpoint value of -6.07, -5.47, and -4.67 for log™ GI50, log™ TGI and log™ LC50, respectively, against nine human tumor cell lines. In yet another embodiment the compound 9c exhibits in-vitro cytotoxicity in mean graph midpoint value of -6.15, -5.30, and -4.35 for log™ GI50, log™ TGI and log™ LC50 , respectively, against nine human tumor cell lines. In yet another embodiment the compound 9d exhibits in-vitro cytotoxicity in mean graph midpoint value of -7.09, -5.78, and -4.37 for log™ GI50, log™ TGI and log™ LC50 , respectively, against nine human tumor cell lines. In yet another embodiment the compound 9a exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of -6.08 to -6.73. In yet another embodiment the compound 9b exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of -5.85 to -6.45. In yet another embodiment the compound 9c exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of -5.87 to -6.65. In yet another embodiment the compound 9d exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of -6.79 to -7.51. The present invention further provides a process for the preparation of novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines of formula 9, wherein: 'n1 is 3-4, X = S or O; Y = NH or O; Z = CO or CH2; R, RI = H or F; R2 = OCHa or H and the said process comprising the steps of: a) reacting a compound of formula 1 or formula 2 (Figure Removed) with benzothiazole or benzoxazole derivative selected from the compounds of formula 3 and 6, in the presence of K2CO3, in organic solvent, under refluxing temperature to obtain the resultant nitro compound of formula 4 or 7; b) reducing the above said nitro compound of formula 4 or 7obtained in step (a) with SnCb.2H2O in an organic solvent, under reflux temperature and isolating the corresponding amino compound of formula 5 or 8, respectively, and (Figure Removed) c) reacting the above said amino compound of formula 5 or 8 obtained in step (b) with a deprotecting agent by known method to obtain the desired compound of formula 9. In yet another embodiment the organic solvent used in step (a) is acetone and in step (b) is ethanol or methanol In yet another embodiment in step (a) the compound of formula 2 is reacted with benzothiazole or benzoxazole derivative of formula 3 to obtain the resultant nitro compound of formula 4. In yet another embodiment in step (a) the compound of formula 1 is reacted with benzothiazole or benzoxazole derivative of formula 6 to obtain the resultant nitro compound of formula 7. In yet another embodiment the compound of formula 1 used in step (a) is (2S)-N- [4-hydroxy-5-methoxy-2-nitrobenzoyl]pyrrolidine-2-carbox aldehyde diethylthioacetal. In yet another embodiment the compound of formula 2 used in step (a) is selected from (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2-nitrobenzoyl) pyrrolidine-2- carboxarbaldehyde diethylthioacetal (2a) and (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy- 2-nitrobenzoyl]pyrrolidine-2-carboxaldehyde diethylthioacetal (2b). In yet another embodiment in step (a) the compound of formula 3 used is selected from the group consisting of 4-(benzothiazol-2-yl)phenol (3a), 4-(1,3- benzothiazol-2-yl)-2-methoxyphenol (3b), 4-(benzoxazol-2-yl)phenol (3c), and 4-(1,3- benzoxazol-2-yl)-2-methoxyphenol (3d). In yet another embodiment in step (a) the compound of formula 4 obtained is selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2- yl)phenoxy]butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (4a), (2S)-A/-{4-(n-[4-(1,3-benzothi azol-2-yl)-2-methoxyphenoxy] butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (4b), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl) phenoxy] pentyl)oxy-5-methoxy-2- nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthio acetal (4c), (2S)-A/-{4-(n-[4-(1,3- benzothiazol-2-yl)-2-methoxyphenoxy]pentyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine- 2-carboxaldehydediethylthioacetal (4d), (2S)-/V-{4-(n-[4-(1,3-benzoxozol-2- yl)phenoxy]pentyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (4e) and (2S)-/V-{4-(n-[4-(1,3-benzoxozole-2-yl)-2- methoxyphenoxy]pentyl)oxy-5-methoxy-2-nitro benzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (4f). In yet another embodiment in step (b) the compound of formula 5 obtained is selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzo thiazol-2- yl)phenoxy]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (5a), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxyJ butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine -2-carbox aldehyde diethylthioacetal (5b), (2S)-/N/-{4-(n-[4-(1,3-benzothiazol-2-yl)phenoxy] pentyl)oxy-5-methoxy-2- aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethyl thioacetal (5c), (2S)-A/-{4-(n-[4- (1,3-benzothi azol-2-yl)-2-methoxy phenoxy] pentyl)oxy-5-methoxy-2-aminobenzoyl}- pyrrolidine-2-carboxaldehyde diethyl thioacetal (5d), (2S)-A/-{4-(n-[4-(1,3-benzoxozol-2- yl)phenoxy]pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (5e) and (2S)-A/-{4-(n-[4-(1,3-benzxozole-2-yl)-2- methoxyphenoxy]pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal(Sf). In yet another embodiment the compound of formula 6 used in step (a) is selected from A/1-[4-(1,3-benzothiazol-2-yl)phenyl]-5-bromopentanamide (6a) or /V1-[4- (6-fluoro-1,3-benzothiazol-2-yl)phenyl]-5-bromopentanamide (6b). In yet another embodiment the compound of formula 7 obtained in step (a) is selected from (2S)-A/-{4-(5-[N1-(4-(1,3-benzothiazol-2-yl)phenyl)]- pentanecarboxamide)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (7a) or (2S)-A/-{4-(5-[N1-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)- pentanecarboxamide]oxy)-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (7b). In yet another embodiment the compound of formula 8 obtained in step (b) is selected from the group consisting of (2S)-/V-{4-(n-[4-(1,3-benzothiazol-2-yl)phenoxy ]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox aldehyde diethyl thioacetal (8a) and (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl) oxy-5- methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox aldehyde diethylthioace (8b). In yet another embodiment the representative compounds of formula 9 obtained in step (c) are as follows: 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11aS)-1,2,3,11atetrahydro- 5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a); 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl}oxy-(11 aS)- 1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9b); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro- 5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy- (11aS)-1 ,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one (9d); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11aS) 1,2,3,11atetra- hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS) 1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9f); 7-Methoxy-8-{5-[A/^-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox amide}oxy-(11 aS)-1,2,3,11 a-tetra-hydro-5H-pyrrolo[2,1 -c][1,4]benzodi azepin- 5-one (9g) and 7-Methoxy-8-{5-[A/J-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane carboxamide}oxy-(11 aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4] benzodiazepin-5-one (9h). DETAILED DESCRIPTION OF THE INVENTION The precursors 4-(1,3-benzothiazol-2-yl)phenol/4-(1,3-benzothiazol-2-yl)-2- methoxyphenol of formula 3a-b (Ben-Allum, A.; Bakkas, S.; Soufiaoui, M. Tetrahedron Lett. 1997, 38, 6395; Wells, G.; Lowe, P. R.; Stevens, M. F. G. ARKIVOC 2000, 1, 779) and (2S)-N-[4-(hydroxy-5-methoxy-2-nitrobenzoyl] pyrrolidine-2-carboxaldehyde diethylthioacetal of formula 2 (Thurston, D. E.; Murthy, V. S.; Langley, D. R.; Jones, G. B. Synthesis. 1990, 81) have been prepared by literature methods. The benzoxazole precursors 3c-d have been prepared by condensation of 2-aminophenols with benzylated protected benzaldehydes, oxidation followed by debenzylation with palladium on charcoal (Centore, R.; Panunzi, B.; Roviello, A.; Sirigu, A.; Villano, P. J. Polym. Sci. Part A: Polym. Chem. 1996, 34, 3203). Amide derivatives of benzothiazoles of formula 6a-b have been prepared by coupling bromoacid chlorides with corresponding 2-(4-aminophenyl)benzothiazoles. Some representative compounds of formula 9 for the present inventions are given below a) 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11aS)-1,2,3,11 atetrahydro- 5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one b) 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl} oxy-(11aS)- 1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one c) 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro- 5/-/-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one d) 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl} oxy-(11aS)- 1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one e) 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11 aS) 1,2,3,11 atetra- hydro-5H-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one f) 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl} oxy-(11aS) 1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one g) 7-Methoxy-8-{5-[/V*-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox amidejoxy- (11aS)-1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodi azepin-5-one h) 7-Methoxy-8-{5-[A/y-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane carboxamide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4] benzodiazepin-5-one These new analogues of pyrrolo[2,1-c][1,4]benzodiazepine hybrids linked at C-8 position have shown promising DNA binding activity and efficient anticancer activity in various cell lines. The molecules synthesized are of immense biological significance with potential sequence selective DNA-binding property. This present invention is illustrated in Scheme 1 and scheme 2 as herein given below: 1) The ether linkage at C-8 position of DC-81 intermediates with benzothiazole and benzoxazole moieties. 2) Refluxing the reaction mixtures for 48 h. 3) Synthesis of C-8 linked PBD antitumour antibiotic hybrid imines. 4) Purification by column chromatography using different solvents like ethyl acetate, hexane, chloroform and methanol. Representative compounds 9a-h of general structural formula 9 Compound (Figure Removed) The following examples are given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of present invention in any way. EXAMPLE 1 To a solution of (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2-nitrobenz oyl) pyrrolidine-2-carboxarbaldehyde diethylthioacetal 2a (535 mg, 1 mmol) in acetone (10 mL) was added anhydrous K2CO3 (552 mg, 4 mmol) and the 4-(benzothiazol-2- yl)phenol 3a (227 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetate-hexane (1:1) as eluant to afford pure compound of 4a (511 mg, 75%). 1H NMR (CDCI3): 8 8.0 (d, 2H, J = 8.8 Hz), 7.9 (d, 1H, J = 8 Hz), 7.7 (s, 1H), 7.3-7.5 (m, 3H), 7.0 (d, 2H, J= 8.8 Hz), 6.8 (s, 1H), 4.9 (d, 1H, J = 3.7 Hz), 4.7 (m, 1H), 4.2 (m, 4H), 3.90 (s, 3H), 3.2 (m, 2H), 2.7-2.9 (m, 4H), 1.7-2.3 (m, 8H), 1.2-1.4 (m, 6H). ESIMS:m/z683(lvr+1). To compound 4a (682 mg, 1 mmol) in methanol (20 mL) was added SnCI2.2H2O (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 mL and 2x30 mL). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethylthioacetal 5a (522 mg, 80%), which was used directly in the next step. A solution of 5a (652 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 mL) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20 mL), brine (20 mL) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCI3 (4%) to give compound 9a (316 mg, 60%). This material was repeatedly evaporated from CHCI3 in vacuum to generate the imine form. 1H NMR (CDCI3): 6 8.0 (d, 2H, J = 8.8 Hz), 7.9 (d, 1H, J = 8 Hz), 7.65 (d, 1H, J = 4.0 Hz), 7.5 (s, 1H), 7.3-7.45 (m, 3H), 7.0 (d, 2H, J = 8.8 Hz), 6.8 (s, 1H), 4.1 (m, 4H), 3.90 (s, 3H), 3.5-3.85 (m, 3H), 1.9-2.3 (m, 8H). FABMS:528(M++1). EXAMPLE 2 To a solution of (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2-nitrobenzoyl) pyrrolidine-2-carboxarbaldehyde diethylthioacetal 2a (535 mg, 1 mmol) in acetone (10 ml_) was added anhydrous K2CO3(552 mg, 4 mmol) and the 4-(1,3-benzothiazol-2-yl)-2- methoxyphenol 3b (257 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetatehexane (3:2) as eluant to afford pure compound of 4b 1H NMR (CDCI3): 8 8.0 (d, 1 H, J = 8.8 Hz), 7.85 (d, 1 H, J = 8.8 Hz), 7.7 (m, 2H), 7.5 (dd, 1H, J = 1.6, 8 Hz), 7.45 (t, 1H, J = 8 Hz), 7.3 (t, 1H, J = 8 Hz), 6.90 (d, 1H, J = 8.8 Hz), 6.7 (s, 1H), 4.8 (d, 1H, J = 3.9 Hz), 4.65 (m, 1H), 4.2 (m, 4H), 4.0 (s, 3H), 3.9 (s, 3H), 3.2 (m, 2H), 2.6-2.8 (m, 4H), 1.8-2.4 (m, 8H), 1.2-1.4 (m, 6H). FABMS:m/z712(M+). To compound 4b (712 mg, 1 mmol) in methanol (20 ml_) was added SnCl2.2H2O (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 mL and 2x30 mL). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethylthioacetal 5b (511 mg, 75%), which was used directly in the next step. A solution of 5b (682 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 mL) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20 ml), brine (20 ml) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCI3 (5%) to give compound 9b (312 mg, 56%). This material was repeatedly evaporated from CHCI3 in vacuum to generate the imine form. 1H NMR (CDCI3): 5 8.05 (d, 1H, J = 7.8 Hz), 7.9 (d, 1H, J = 7.8 Hz), 7.64-7.72 (m, 2H), 7.3-7.6 (m, 4H), 6.9 (d, 1H, J = 7.8 Hz), 6.82 (s, 1H), 4.1-4.4 (m, 4H), 4.0 (s, 3H), 3.9 (s, 3H), 3.5-3.85 (m, 3H), 2.0-2.3 (m, 8H). FABMS:m/z558(M++l). EXAMPLE 3 To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitro benzoyl] pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml) was added anhydrous K2COs (552 mg, 4 mmol) and the 4-(benzothiazol-2-yl)phenol 3a (227 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetate-hexane (1:1) as eluant to afford pure compound of 4c (522 mg, 75%). 1H NMR (CDCI3): 6 8.1 (d, 2H, J = 8.8 Hz), 7.7-7.9 (m, 2H) 7.3-7.5 (m, 3H), 7.0 (d, 2H, J = 8.8 Hz), 6.75 (s, 1H), 4.85 (d, 1H, J= 3.8 Hz), 4.75 (m, 1H), 4.15 (m, 4H), 4.0 (s, 3H), 3.2 (m, 2H), 2.6-2.8 (m, 4H), 2.3 (m, 2H), 2.0 (m, 5H ), 1.6-1.8 (m. 3H), 1.35 (q, 6H, J = 7.5 Hz). FABMS: m/z 696 (IvT). To compound 4c (696 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 mL and 2x30 mL). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethyl thioacetal 5c (533 mg, 80%), which was used directly in the next step. A solution of 5c (666 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCOs (20 ml), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCb (4%) to give compound 9c (323 mg, 60%). This material was repeatedly evaporated from CHCb in vacuum to generate the imine form. 1H NMR (CDCI3): 8 8.0 (d, 1H, J = 8.6 Hz), 7.85 (d, 1H, J = 8.6 Hz), 7.65 (d, 1H, J = 3.9 Hz), 7.3-7.55 (m, 5H), 7.0 (d, 2H, J = 8.6 Hz), 6.82 (s, 1H), 4.0-4.2 (m, 4H), 3.9 (s, 3H), 3.6-3.8 (m, 3H), 2.2-2.4 (m, 2H), 1.8-2.0 (m, 5H), 1.6-1.8 (m. 3H). FABMS:m/z542(M++1). EXAMPLE 4 To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl] pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml_) was added anhydrous K2CO3 (552 mg, 4 mmol) and the 4-(1,3-benzothiazol-2-yl)-2- methoxyphenol 3b (257 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetatehexane (3:2) as eluantto afford pure compound of 4d (508 mg, 70%). 1H NMR (CDCb): 8 8.0 (d, 1H, J = 8.7 Hz), 7.85 (d, 1H, J = 8.7 Hz), 7.7 (d, 1H, J= 1.6 Hz), 7.65 (s, 1H), 7.53 (dd, 1H, J= 1.6, 8 Hz), 7.45 (dt, 1H, J= 1.6, 8 Hz), 7.33 (dt, 1H, J = 1.6, 8 Hz), 6.90 (d, 1H, J = 8.7 Hz), 6.78 (s, 1H), 4.85 (d, 1H, J = 3.9 Hz), 4.7 (m, 1H), 4.1 (m, 4H), 4.0 (s, 3H), 3.9 (s, 3H), 3.2 (m, 2H), 2.6-2.8 (m, 4H), 1.7-2.3 (m, 10H), 1.2-1.4(m,6H). FABMS: m/z 726 (M+). To compound 4d (726 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 ml and 2x30 ml). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethyl thioacetal 5d (557 mg, 80%), which was used directly in the next step. A solution of 5d (696 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaC03 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 ml) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCOs (20 ml_), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCIs (5%) to give compound 9d (314 mg, 55%). This material was repeatedly evaporated from CHCb in vacuum to generate the imine form. 1H NMR (CDCb): 6 8.0 (d, 1H, J = 8.2 Hz), 7.9 (d, 1H, J = 8.2 Hz), 7.64-7.72 (m, 2H), 7.3-7.6 (m, 4H), 6.95 (d, 1H, J = 8.2 Hz), 6.80 (s, 1H), 4.1 (m, 4H), 4.0 (s, 3H), 3.95 (s, 3H), 3.5-3.8 (m, 3H), 1.7-2.3 (m, 10H). FABMS:m/z572(lvr+1). EXAMPLE 5 To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl] pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml) was added anhydrous KaCOa (552 mg, 4 mmol) and the 4-(benzoxazol-2-yl)phenol 3d (212 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetate-hexane (2:3) as eluant to afford pure compound of 4e (533 mg, 80%). 1H NMR (CDCI3): 6 8.05 (d, 2H, J = 8.9 Hz), 7.6 (m, 1H), 7.5 (s, 1H), 7.4 (m, 1H), 7.2 (m, 2H), 6.9 (d, 2H, J= 8.9 Hz), 6.64 (s, 1H), 4.7 (d, 1H, J= 3.8 Hz), 4.55 (m, 1H), 4.0 (m, 4H), 3.80 (s, 3H), 3.1 (m, 2H), 2.52-2.8 (m, 4H), 1.5-2.1 (m, 10H), 1.2 (q, 6H, J= 7.4 Hz). LCMS:/77/z680(M++1). To compound 4e (665 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 ml_ and 2x30 ml). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethylthioacetal 5e which was used directly in the next step. A solution of 5e (649 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaC03 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20 mL), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCI3 (4%) to give compound 9e (263 mg, 50%). This material was repeatedly evaporated from CHCIs in vacuum to generate the imine form. 1H NMR (CDCI3): 6 8.2 (d, 2H, J = 8.6 Hz), 7.72 (m, 1H), 7.65 (d, 1H, J = 3.9 Hz), 7.5 (m, 2H), 7.3-7.4 (m, 2H), 7.0 (d, 2H, J = 8.6 Hz), 6.8 (s, 1H), 4.1 (m, 4H), 3.90 (s, 3H), 3.5-3.8 (m, 3H), 2.3 (m, 2H), 1.5-2.1 (m, 8H). LCMS:m/z526(M++1). EXAMPLE 6 To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl] pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml) was added anhydrous K2CO3 (552 mg, 4 mmol) and the 4-(1,3-benzoxazol-2-yl)-2- methoxyphenol 3d (241 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetatehexane (1:1) as eluant to afford pure compound of 4f (522 mg, 75%). 1H NMR (CDCI3): 6 7.62-7.8 (m, 3H), 7.63 (s, 1H), 7.52 (m, 1H), 7.3 (m, 2H), 6.95 (d, 1H, J = 8.5 Hz), 6.75 (s, 1H), 4.82 (d, 1H, J = 3.8 Hz), 4.65 (m, 1H), 4.1 (m, 4H), 4.0 (s, 3H), 3.94 (s, 3H), 3.2 (m, 2H), 2.6-2.8 (m, 4H), 1.6-2.3 (m, 10H), 1.35 (q, 6H, J = 7.6 Hz). To compound 4f (695 mg, 1 mmol) in methanol (20 ml) was added SnCI2.2H20 (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 ml_ and 2x30 ml). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethylthioacetal 5f which was used directly in the next step. A solution of 5f (679 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaC03 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20 ml), brine (20 ml) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCIs (5%) to give compound 9f (278 mg, 50%). This material was repeatedly evaporated from CHCb in vacuum to generate the imine form. 1H NMR (CDCI3): 5 7.7-7.84 (m, 3H), 7.62 (d, 1H, J = 4.0 Hz), 7.43-7.58 (m, 2H), 7.3-7.4 (m, 2H), 6.9 (d, 1H, J = 8.6 Hz), 6.8 (s, 1H), 3.9-4.2 (m, 10H), 3.5-3.7 (m, 3H), 1.6-2.3 (m, 10H). LCMS:m/z556(M++1). EXAMPLE 7 To a solution of 1 (400 mg, 1 mmol) in acetone (10 ml_) was added anhydrous K2C03 (552 mg, 4 mmol) and the 6a (389 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetate-hexane (3:2) as eluant to afford pure compound of 7a (496 mg, 70%). 1H NMR (CDCI3): 5 8.5 (s, 1H), 8.0 (m, 3H), 7.82 (d, 1H, J = 7.6 Hz), 7.62 (m, 3H), 7.45 (t, 1H, J = 7.6 Hz), 7.3 (t, 1H, J = 7.6 Hz), 6.8 (s, 1H), 4.82 (d, 1H, J = 3.8 Hz), 4.65 (m, 1H), 4.15 (m, 2H), 3.9 (s, 3H), 3.1-3.3 (m, 2H), 2.6-2.8 (m, 4H), 2.45 (m, 2H), 1.7-2.3 (m, 8H), 1.3(q, 6H, J=6.8Hz). To compound 7a (709 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 ml_ and 2x30 ml_). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethylthioacetal 8a which was used directly in the next step. A solution of 8a (679 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20 ml), brine (20 ml) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCI3 (5%) to give compound 9g (277 mg, 50%). This material was repeatedly evaporated from CHCI3 in vacuum to generate the imine form. 1H NMR (CDCI3): 8 8.8 (s, 1H), 8.05 (m, 3H), 7.9 (d, 1H, J = 7.9 Hz), 7.7-7.8 (m, 3H), 7.6 (s, 1H), 7.3-7.5 (m, 2H), 6.9 (s, 1H), 4.2 (m, 2H), 3.9 (s, 3H), 3.5-3.8 (m, 3H), 2.6 (m, 2H), 1.6-2.3 (m,8H). LCMS:m/z555(M++l). EXAMPLE 8 To a solution of 1 (400 mg, 1 mmol) in acetone (10 ml) was added anhydrous K2C03 (552 mg, 4 mmol) and the 6b (407 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion of the reaction as indicated by TLC, potassium carbonate was removed by suction filtration and the solvent was removed under vacuum. The crude product thus obtained was purified by column chromatography using ethylacetate-hexane (3:2) as eluant to afford pure compound of 7b (545 mg, 75%). 1H NMR (CDCIs): S 8.7 (bs, 1H), 7.9 (m, 3H), 7.7 (m, 3H), 7.5 (dd, 1H, J = 2.3, 7.8 Hz), 7.1-7.2 (m, 1H), 6.8 (s, 1H), 4.8 (d, 1H, J- 3.9 Hz), 4.7 (m, 1H), 4.1 (m, 2H), 3.9 (s, 3H), 3.2-3.3 (m, 2H), 2.7-2.8 (m, 4H), 2.45 (m, 2H), 1.8-2.3 (m, 8H), 1.2-1.4 (m, 6H). LCMS: m/z 727 (M+). To compound 7b (727 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O (1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was completed. The methanol was evaporated under vacuum, the aqueous layer was then carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl acetate and chloroform (2x30 ml_ and 2x30 ml). The combined organic phase was dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethylthioacetal 8b, which was used directly in the next step. A solution of 8b (697 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246 mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for overnight. The reaction mixture was diluted with ethyl acetate (30 ml) filtered through a celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20 ml), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic layer was evaporated under vacuum and purified by column chromatography using MeOH-CHCI3 (5%) to give compound 9h (286 mg, 50%). This material was repeatedly evaporated from CHCI3 in vacuum to generate the imine form. 1H NMR (CDCI3): 8 8.8 (bs, 1H), 7.95 (m, 3H), 7.6 (m, 3H), 7.7-7.8 (m, 2H), 7.1 (m, 1H), 6.7 (s, 1H), 4.1 (m, 2H), 3.8 (s, 3H), 3.4-3.75 (m, 3H), 2.5 (m, 2H), 1.6-2.3 (m, 8H). LCMS: m/z 573 (M++1). Biological Activity: DMA binding affinity of novel benzothiazole, benzoxazole linked PBD hybrids (9ah): Compounds have been subjected to thermal denaturation studies with duplexform calf thymus DMA (CT-DNA) using an modification of a reported procedure (Newman, M. S. Carcinog-compr. Surv. 1976, 1, 203; (b) Hecht, S. S.; Loy, M.; Hoffman, Carcinog-compr. Surv. 1976, 1, 325). . Working solutions in aqueous buffer (10 mM NaH2PO4/Na2HPO4, 1 mM Na2EDTA, pH 7.00 + 0.01) containing CT-DNA (100 urn in phosphate) and the PBD (20 urn) have been prepared by addition of concentrated PBD solutions in DMSO to obtain a fixed [PBD]/[DNA] molar ratio of 1:5. The DNA-PBD solutions have been incubated at 37 °C for 0 and 18 h prior to analysis. Samples have been monitored at 260 nm using a Beckman DU-800 spectrophotometer fitted with high performance temperature controller, and heated at 1 °C min"1 in the 40-110 °C range. DNA helix->coil transition temperatures (7m) have been obtained from the maxima in the d(/\26o)/dT derivative plots. Drug-induced alterations in DNA melting behavior are given by: A7m = 7m(DNA + PBD) - 7m(DNA alone), where the 7m value for the PBD-free CT-DNA is 69.1 ± 0.01. The fixed [PBD]/[DNA] ratio used has not resulted in binding saturation of the host DNA duplex for any compound examined. The DNA binding activity for these novel C8-linked benzothiazole, benzoxazole- PBD hybrids has been examined by thermal denaturation studies using calf thymus (CT) DNA. Melting studies show that these compounds stabilize the thermal helix -> coil or melting stabilization (A7m) for the CT-DNA duplex at pH 7.0, incubated at 37 °C, where PBD/DNA molar ratio is 1:5. The data for the compounds 9a-h is included in Table 1 for comparison. Table 1. Thermal denaturation data for benzothiazole and benzoxazle linked PBD (Table Removed) For CT-DNA alone at pH 7.00 ± 0.01, Tm = 69.1 °C ± 0.01 (mean value from 10 separate determinations), all A7"m values are ± 0.1 - 0.2 °C. b For a 1:5 molar ratio of [PBD]/[DNA], where CT-DNA concentration = 100 uM and ligand concentration = 20 uM in aqueous sodium phosphate buffer [10 mM sodium phosphate + 1 mM EDTA, pH 7.00 ±0.01]. Anticancer activity: In vitro biological activity studies were carried out at the National Cancer Institute (USA). The compounds were evaluated for in vitro anticancer activity against sixty human tumour cells derived from nine cancer types (leukemia, non-small-cell lung, colon, CMS, melanoma, ovarian, prostate, and breast cancer) as shown in Table 3. For each compound, dose response curves for each cell line were measured at a minimum of five concentrations at 10 fold dilutions. A protocol of 48 h continuous drug exposure was used and a sulforhodamine B (SRB) protein assay was used to estimate cell viability or growth. The concentration causing 50% cell growth inhibition (GI50), total cell growth inhibition (TGI 0%growth) and 50% cell death (LC50, -50% growth) compared with the control was calculated. The mean graph midpoint values of logic TGI and log™ LC50 as well as logio GI50 for 9a, 9b, 9c and 9d are listed in Table 2. As demonstrated by mean graph pattern, compound 9d exhibits an interesting profile of activity and selectivity for various cell lines. The mean graph mid point of Iog10 TGI and log-io LC50 showed similar pattern to the Iog10 GI50 mean graph mid points. Table 2. LogioGI50 logioTGI and logioLC50 mean graphs midpoints (MG_MID) of in (Table Removed) Each cancer type represents the average of six to nine different cancer cell lines. We claim 1. Novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines of formula 9, wherein: n = 3-4, X = S or O; Y = NH or O; Z = CO or CH2; R, RI = H or F; R2 = OCH3 or H. 2. The compound as claimed in claim 1, wherein the representative compounds of formula 9 are as follows: 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11 aS)-1,2,3,11 atetrahydro- 5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a); 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl} oxy-(11 aS)- 1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9b); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro- 5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS)- 1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one (9d); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11aS) 1,2,3,11atetra- hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl} oxy-(11 aS) 1,2,3,11 a-tetra-hydro-5/-/-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one (9f); 7-Methoxy-8-{5-[A/t-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox amidejoxy- (11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodi azepin-5-one (9g); and 7-Methoxy-8-{5-[N1-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane carboxamide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4] benzodiazepin-5-one (9h). 3. The compound as claimed in claims 1-2, wherein the structural formula of the representative compounds 9a-h are: (Figure Removed) 4. The compound as claimed in claim 1 exhibits binding affinity with calf thymus (CT) DNA at a molar ratio of 1:5 in aqueous sodium phosphate buffer at pH 7. 5. The compound as claimed in claim 1 exhibit in-vitro anticancer activity against human tumor cells derived from nine cancer types of leukemia, non-small-cell lung, colon, CNS, melanoma, ovarian, prostate, and breast cancer. 6. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepine as claimed in claim 1, wherein the compound 9a exhibits in-vitro cytotoxicity in mean graph midpoint value of -6.30(mol/lit), -5.63(mol/lit), and -4.75(mol/lit) for logio GI50, logic TGI and logio LC50, respectively, against nine human tumor cell lines. 7. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine as claimed in claim 1, wherein the compound 9b exhibits in-vitro cytotoxicity in mean graph midpoint value of log™ TGI, Iog10 LC50,logi0 GI50. In-vitro cytotoxicity data in mean graph midpoint value of -6.07, -5.47, and -4.67 for logio GI50, logic TGI and logic LC50, respectively, against nine human tumor cell lines. 8. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine as claimed in claim 1, wherein the compound 9c exhibits in-vitro cytotoxicity in mean graph midpoint value of -6.15, -5.30, and -4.35 for log™ GI50, log™ TGI and logic LC50 , respectively, against nine human tumor cell lines. 9. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine as claimed in claim 1, wherein the compound 9d exhibits in-vitro cytotoxicity in mean graph midpoint value of -7.09, -5.78, and -4.37 for log™ GI50, log™ TGI and log™ LC50 , respectively, against nine human tumor cell lines. 10. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine as claimed in claim 1, wherein the compound 9a exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of -6.08 to -6.73. 11. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine as claimed in claim 1, wherein the compound 9b exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of - 5.85 to-6.45. 12. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine as claimed in claim 1, wherein the compound 9c exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of-5.87 to-6.65. 13. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine as claimed in claim 1, wherein the compound 9d exhibits log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of-6.79 to-7.51. 14. A process for the preparation of novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines of formula 9, (Figure Removed) wherein: 'n' is 3-4, X = S or O; Y = NH or O; Z = CO or CH2; R, RI = H or F; R2 = OCH3 or H and the said process comprising the steps of: a) reacting a compound of formula 1 or formula 2 (Figure Removed) with benzothiazole or benzoxazole derivative selected from the compounds of formula 3 and 6, (Figure Removed) in the presence of K2C03, in an organic solvent, under refluxing temperature to obtain the resultant nitro compound of formula 4 or 7; (Figure Removed) b) reducing the above said nitro compound of formula 4 or 7obtained in step (a) with SnCI2.2H2O in an organic solvent, under reflux temperature and isolating the corresponding amino compound of formula 5 or 8, respectively, and NH2 pH(SEt)2 8a-b c) reacting the above said amino compound of formula 5 or 8 obtained in step (b) with a deprotecting agent by known method to obtain the desired compound of formula 9. 15. A process as claimed in claim 14 wherein the organic solvent used in step (a) is acetone and in step (b) is ethanol or methanol. 16. A process as claimed in claim 14, wherein in step (a) the compound of formula 2 is reacted with benzothiazole or benzoxazole derivative of formula 3 to obtain the resultant nitro compound of formula 4. 17. A process as claimed in claim 14, wherein in step (a) the compound of formula 1 is reacted with benzothiazole or benzoxazole derivative of formula 6 to obtain the resultant nitro compound of formula 7. 18. A process as claimed in claim 14, wherein the compound of formula 1 used in step (a) is (2S)-N-[4-hydroxy-5-methoxy-2-nitrobenzoyl]pyrrolidine-2-carbox aldehyde diethylthioacetal. 19. A process as claimed in claim 14, wherein the compound of formula 2 used in step (a) is selected from (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2- nitrobenzoyl) pyrrolidine-2-carboxarbaldehyde diethylthioacetal (2a) and (2S)- N-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl]pyrrolidine-2- carboxaldehyde diethylthioacetal (2b). 20. A process as claimed in claim 14, wherein the compound of formula 3 obtained in step (a) is selected from the group consisting of 4-(benzothiazol-2-yl)phenol (3a), 4-(1,3-benzothiazol-2-yl)-2-methoxyphenol (3b), 4-(benzoxazol-2- yl)phenol (3c), and 4-(1,3-benzoxazol-2-yl)-2-methoxyphenol (3d). 21. A process as claimed in claim 14, wherein the compound of formula 4 obtained in step (a) is selected from the group consisting of (2S)-/V-{4-(n-[4-(1,3- benzothiazol-2-yl)phenoxy]butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2- carboxaldehyde diethylthioacetal (4a), (2S)-A/-{4-(n-[4-(1,3-benzothi azol-2-yl)- 2-methoxyphenoxy] butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carbox aldehyde diethylthioacetal(4b), (2S)-N-{4-(n-[4-(1,3-benzothiazol-2-yl) phenoxy] pentyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthio acetal (4c), (2S)-/V-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-methoxy phenoxy]pentyl) oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine -2-carboxaldehyde diethylthioacetal (4d), (2S)-/V-{4-(n-[4-(1,3-benzoxozol-2-yl)phenoxy]pentyl)oxy-5-methoxy-2- nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (4e) and (2S)-/V- {4-(n-[4-(1,3-benzoxozole-2-yl)-2-methoxyphenoxy]pentyl)oxy-5-methoxy-2- nitro benzoylj-pyrrolidine -2-carboxaldehyde diethylthioacetal (4f). 22. A process as claimed in claim 14, wherein the compound of formula 5 obtained in step (a) is selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzo thiazol-2-yl)phenoxy]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbo xaldehyde diethylthioacetal (5a), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2- methoxyphenoxy] butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox aldehyde diethylthioacetal (5b), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)phenoxy] pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethyl thioacetal (5c), (2S)-A/-{4-(n-[4-(1,3-benzothi azol-2-yl)-2-methoxy phenoxy] pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethyl thioacetal (5d), (2S)-A/-{4-(n-[4-(1,3-benzoxozol-2-yl)phenoxy]pentyl)oxy-5- methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (5e) and (2S)-A/-{4-(n-[4-(1,3-benzxozole-2-yl)-2-methoxyphenoxy]pentyl)oxy-5- methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal(5f). 23. A process as claimed in claim 14, wherein the compound of formula 6 used in step (a) is selected from N1-[4-(1,3-benzothiazol-2-yl)phenyl]-5- bromopentanamide (6a) or N1-[4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl]-5- bromopentanamide (6b) 24. A process as claimed in claim 14, wherein the compound of formula 7 obtained in step (a) is selected from (2S)-/V-{4-(5-[N1-(4-(1,3-benzothiazol-2-yl)phenyl)]- pentanecarboxamide)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2- carboxaldehyde diethylthioacetal (7a) or (2S)-A/-{4-(5-[N1-(4-(6-fluoro-1,3- benzothiazol-2-yl)phenyl)-pentanecarboxamide]oxy)-5-methoxy-2- nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (7b). 25. A process as claimed in claim 14, wherein the compound of formula 8 obtained is selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2- yl)phenoxy ]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox aldehyde diethyl thioacetal (8a) and (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2- methoxyphenoxylpentyl) oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox aldehyde diethylthioace (8b). 26. A process as claimed in claim 14, wherein the representative compound of formula 9 obtained are as follows: 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11 aS)-1,2,3,11atetrahydro- 5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a); 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl}oxy-(11 aS)- 1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9b); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro- 5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c); 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy- (11aS)-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one (9d); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11aS) 1,2,3,11atetra- hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e); 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS) 1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9f); 7-Methoxy-8-{5-[A/r-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox amide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodi azepin- 5-one (9g) and 7-Methoxy-8-{5-[N1-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane carboxamide}oxy-(11 aS)-1,2,3,11 a-tetra-hydro-5H-pyrrolo[2,1 -c][1,4] benzodiazepin-5-one (9h). 27 Novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines useful as antitumour agents and a process for the preparation thereof, substantially as herein described with reference to the examples.

Full Text

" FIELD OF THE INVENTION
The present invention relates to novel benzothiazole or benzoxazole linked
pyrrolo[2,1-c][1,4] benzodiazepine hybrid as potential antitumour agent. The present
invention also relates to a process for the preparation of novel benzothiazole or
benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine hybrid.
More particularly, the present invention relates to benzothiazole or benzoxazole
linked pyrrolo[2,1-c][1,4] benzodiazepine hybrid of general formula 9
(Figure Removed)
The present invention further relates to a process for the preparation of 7-
methoxy-8-{n-[4-(1,3-benzothiazol-2-yl)-2-substitutedphenoxy]alkyl}oxy-(11 aS)-
1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one / 7-methoxy-8-{n-[4-
(1,3-benzoxazol-2-yl)-2-substituted phenoxy]alkyl}oxy-(11aS)-1, 2,3,11a-tetrahydro-5Hpyrrolo[
2,1-c][1,4]benzodiazepin-5-one / 7-methoxy-8-{n-[N1-(4-(7-substituted-1,3-benzo
thiazol-2-yl)phenyl)]alkanecarboxamide}oxy-(11aS)-1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-
c][1,4]benzodiazepin-5-one with aliphatic chain length variations.
BACKGROUND OF THE INVENTION
Pyrrolo [2,1-c][1,4]benzodiazepines (PBDs), a group of potent naturally occurring
antitumour antibiotics from various Streptomyces species, are of considerable interest
because of their ability to recognize and subsequently form covalent bonds to specific
base sequence of double strand DMA (Dervan, P. B. Science 1989, 232, 464.; Hurley,
L. H. J. Med. Chem. 1989, 32, 2027.; Thurston, D. E.; Thompson, A. S. Chem. Br. 1990,
26, 767). Well-known members of this group include anthramycin, DC-81, sibiromycin,
tomamycin, chicamycin and neothramycin.of A and B (Hurley, L. H. J. Antibiot. 1977,
30, 349.; Schimizu, K.; Kawamoto, I.; Tomita, F.; Morimoto, M.; Fujimoto, K. J. Antibiot.
1982, 35, 992.; Lown, J. W.; Joshua, A. V. Biochem. Pharmacol. 1979, 28, 2017.;
Thurston, D. E.; Bose, D. S. Chem. Rev. 1994, 94, 433.; Molina, P.; Diaz, I.; Tarraga, A.
Tetrahedron 1995, 51, 5617.; Kamal, A.; Rao, N. V. Chem. Commun. 1996, 385.;
Kamal, A.; Reddy, B. S. P.; Reddy, B. S. N. Tetrahedron Lett. 1996, 37, 6803). The
cytotoxicity and antitumour activity of these agents are attributed to their property of
sequence selective covalent binding to the N2 of guanine in the minor groove of duplex
DNA via an acid-labile aminal bond to the electrophilic imine at the N10-C11 position
(Kunimoto, S.; Masuda, T.; Kanbayashi, N.; Hamada, M.; Naganawa, H.; Miyamoto, M.;
Takeuchi, T.; Unezawa, H. J. Antibiot., 1980, 33, 665.; Kohn, K. W. and Speous, C. L. J.
Mol. Biol., 1970, 51, 551.; Hurley, L. H.; Gairpla, C. and Zmijewski, M. Biochem.
Biophys. Acta., 1977, 475, 521.; Kaplan, D. J. and Hurley, L. H. Biochemistry, 1981, 20,
7572). The molecules have a right-handed twist, which allows them to follow the
curvature of the minor groove of B-form double-stranded DNA spanning three base
pairs. A recent development has been the linking of two PBD units through their C-8
positions to give bisfunctional-alkylating agents capable of cross-linking DNA (Thurston,
D. E.; Bose, D. S.; Thomson, A. S.; Howard, P. W.; Leoni, A.; Croker, S. J.; Jenkins, T.
C.; Neidle, S. and Hurley, L H. J. Org. Chem. 1996, 61, 8141).
Recently, PBD dimers have been developed that comprise of two C2-exomethylene
substituted DC-81 subunits tethered through their C-8 position via an inert
propanedioxy linker (Gregson, S. J.; Howard, P. W.; Hartely, J. A.; Brooks, N. A.;
Adams, L. J.; Jenkins, T. C.; Kelland, L. R. and Thurston, D. E. J. Med. Chem. 2001, 44,
737). A non-cross-linking mixed imine-amide PBD dimers have been synthesized that
have significant DNA binding ability and potent antitumour activity (Kamal, A.; Ramesh,
G. Laxman, N.; Ramulu, P.; Srinivas, O.; Neelima, K.; Kondapi, A. K.; Srinu, V. B.;
Nagarajaram, H. M. J. Med. Chem. 2002, 45, 4679). However, the clinical efficacy for
these antibiotics is hindered by several limitations, such as poor water solubility,
cardiotoxicity, development of drug resistance and metabolic inactivation. Due to the
excellent activity of these molecules, there is need to develop novel derivatives which
are devoid of above limitations.
Benzothiazoles are small synthetic molecules that contain a benzene ring fused
to a thiazole ring. These simple molecules have shown remarkable antitumour
properties and some of them are undergoing evaluation in clinical trials (Shi, D.-F.;
Bradshaw, T. D.; Wrigley, S.; McCall, C. J.; Lelieveld, P.; Fichtner, I.; Stevens, M. F. G.
J. Med. Chem. 1996, 39, 3375; Kashiyama, E.; Hutchinson, I.; Chua, M.-S.; Stinson, S.
F.; Phillips, L. R.; Kaur, G.; Sausville, E, A.; Bradshaw, T. D.; Westwell, A. D.; Stevens,
M. F. G. J. Med. Chem. 1999, 42, 4172; Hutchinson, I.; Chua, M.-S.; Browne, H. L.;
Trapani, V.; Bradshaw, T. D.; Westwell, A. D.; Stevens, M. F. G. J. Med. Chem. 2001,
44, 1446). Recently Westwell and coworkers have prepared a series of benzothiazole
derivatives and evaluated for anticancer activity, One of these analogues has shown
excellent anticancer activity (Mortimer, C. G.; Wells, G.; Crochard, J.-P.; Stone, E. L.;
Bradshaw, T. D.; Stevens, M. F. G.; Westwell, A. D. J. Med. Chem. 2006, 49, 179). The
structurally related benzoxazoles have also been reported to possess anticancer activity
(Kumar, D.; Jacob, M. R.; Reynold, M. B.; Kerwin, S. M. Bioorg. Med. Chem. 2002, 10,
3994; Gong, B.; Hong, F.; Kohm, C.; Bonham, L.; Klein, P. Bioorg. Med. Chem. Lett.
2004, 14, 1455). Based on the potent anticancer activity of pyrrolo[2,1-
c][1,4]benzodiazepines, benzothiazoles and benzoxazoles, new PBD hybrids have been
designed and synthesized by linking benzothiazole and benzoxazole moieties at C8-
position of pyrrolo[2,1-c][1,4]benzodiazepine with varying alkane and alkylamide
spacers.
OBJECTIVES OF THE INVENTION
The main objective of the present invention is to provide novel benzothiazole or
benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid useful as antitumour agent.
Yet another object of the present invention is to provide a process for the
preparation of novel benzothiazole or benzoxazole linked pyrrolo[2,1-c]
[1,4]benzodiazepine hybrids.
SUMMARY OF THE INVENTION
Accordingly the present invention provides novel benzothiozole or benzoxazole
linked pyrrolo[2,1-c][1,4]benzodiazepines of formula 9,
Wherein: n = 3-4, X = S or O; Y = NH or 0; Z = CO or CH2; R, RI = H or F; R2 =
OCH3 or H.
In an embodiment of the present invention the representative compounds of
formula 9 are as follows:
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11aS)-1,2,3,11atetrahydro-
5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a);
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl}oxy-(11aS)-
1,2,3,11 a-tetrahydro-5H-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one (9b);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro-
5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS)-
1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin -5-one(9d);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11 aS)-1,2,3,11 atetra-
hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS)
1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9f);
7-Methoxy-8-{5-[A/r-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarboxamide}oxy-
(11aS)-1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9g);
and
7-Methoxy-8-{5-[A/r-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane
carboxamide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]
benzodiazepin-5-one (9h).
In yet another embodiment the structural formula of the representative
compounds 9a-h are:
(Figure Removed)

In yet another embodiment the compounds of formula 9 exhibits binding affinity
with calf thymus (CT) DMA at a molar ratio of 1:5 in aqueous sodium phosphate
buffer at pH 7.
In yet another embodiment the compounds of formula 9 exhibit in-vitro
cytotoxicity against human tumor cells derived from nine cancer types of leukemia, nonsmall-
cell lung, colon, CMS, melanoma, ovarian, prostate, and breast cancer.
In yet another embodiment the compound 9a exhibits in-vitro cytotoxicity in mean
graph midpoint value of -6.30(mol/lit), -5.63(mol/lit), and -4.75(mol/lit) for log™ GI50,
logio TGI and logic LC50, respectively, against nine human tumor cell lines.
In yet another embodiment the compound 9b exhibits in-vitro cytotoxicity in mean
graph midpoint value of Iog10 TGI, logic LC50,logio GI50. In-vitro cytotoxicity data in
mean graph midpoint value of -6.07, -5.47, and -4.67 for log™ GI50, log™ TGI and log™
LC50, respectively, against nine human tumor cell lines.
In yet another embodiment the compound 9c exhibits in-vitro cytotoxicity in mean
graph midpoint value of -6.15, -5.30, and -4.35 for log™ GI50, log™ TGI and log™ LC50 ,
respectively, against nine human tumor cell lines.
In yet another embodiment the compound 9d exhibits in-vitro cytotoxicity in mean
graph midpoint value of -7.09, -5.78, and -4.37 for log™ GI50, log™ TGI and log™ LC50 ,
respectively, against nine human tumor cell lines.
In yet another embodiment the compound 9a exhibits log™ GI50 (mole/lit)
anticancer activity against nine cancer cell type in the range of -6.08 to -6.73.
In yet another embodiment the compound 9b exhibits log™ GI50 (mole/lit)
anticancer activity against nine cancer cell type in the range of -5.85 to -6.45.
In yet another embodiment the compound 9c exhibits log™ GI50 (mole/lit)
anticancer activity against nine cancer cell type in the range of -5.87 to -6.65.
In yet another embodiment the compound 9d exhibits log™ GI50 (mole/lit)
anticancer activity against nine cancer cell type in the range of -6.79 to -7.51.
The present invention further provides a process for the preparation of novel
benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines of formula 9,
wherein: 'n1 is 3-4, X = S or O; Y = NH or O; Z = CO or CH2; R, RI = H or F;
R2 = OCHa or H and the said process comprising the steps of:
a) reacting a compound of formula 1 or formula 2
(Figure Removed)

with benzothiazole or benzoxazole derivative selected from the compounds
of formula 3 and 6,
in the presence of K2CO3, in organic solvent, under refluxing temperature to
obtain the resultant nitro compound of formula 4 or 7;
b) reducing the above said nitro compound of formula 4 or 7obtained in step (a)
with SnCb.2H2O in an organic solvent, under reflux temperature and isolating
the corresponding amino compound of formula 5 or 8, respectively, and
(Figure Removed)

c) reacting the above said amino compound of formula 5 or 8 obtained in step
(b) with a deprotecting agent by known method to obtain the desired
compound of formula 9.
In yet another embodiment the organic solvent used in step (a) is acetone and in
step (b) is ethanol or methanol
In yet another embodiment in step (a) the compound of formula 2 is reacted with
benzothiazole or benzoxazole derivative of formula 3 to obtain the resultant nitro
compound of formula 4.
In yet another embodiment in step (a) the compound of formula 1 is reacted with
benzothiazole or benzoxazole derivative of formula 6 to obtain the resultant nitro
compound of formula 7.
In yet another embodiment the compound of formula 1 used in step (a) is (2S)-N-
[4-hydroxy-5-methoxy-2-nitrobenzoyl]pyrrolidine-2-carbox aldehyde diethylthioacetal.
In yet another embodiment the compound of formula 2 used in step (a) is
selected from (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2-nitrobenzoyl) pyrrolidine-2-
carboxarbaldehyde diethylthioacetal (2a) and (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-
2-nitrobenzoyl]pyrrolidine-2-carboxaldehyde diethylthioacetal (2b).
In yet another embodiment in step (a) the compound of formula 3 used is
selected from the group consisting of 4-(benzothiazol-2-yl)phenol (3a), 4-(1,3-
benzothiazol-2-yl)-2-methoxyphenol (3b), 4-(benzoxazol-2-yl)phenol (3c), and 4-(1,3-
benzoxazol-2-yl)-2-methoxyphenol (3d).
In yet another embodiment in step (a) the compound of formula 4 obtained is
selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-
yl)phenoxy]butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal (4a), (2S)-A/-{4-(n-[4-(1,3-benzothi azol-2-yl)-2-methoxyphenoxy]
butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal
(4b), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl) phenoxy] pentyl)oxy-5-methoxy-2-
nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthio acetal (4c), (2S)-A/-{4-(n-[4-(1,3-
benzothiazol-2-yl)-2-methoxyphenoxy]pentyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-
2-carboxaldehydediethylthioacetal (4d), (2S)-/V-{4-(n-[4-(1,3-benzoxozol-2-
yl)phenoxy]pentyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal (4e) and (2S)-/V-{4-(n-[4-(1,3-benzoxozole-2-yl)-2-
methoxyphenoxy]pentyl)oxy-5-methoxy-2-nitro benzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal (4f).
In yet another embodiment in step (b) the compound of formula 5 obtained is
selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzo thiazol-2-
yl)phenoxy]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal (5a), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxyJ
butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine -2-carbox aldehyde diethylthioacetal
(5b), (2S)-/N/-{4-(n-[4-(1,3-benzothiazol-2-yl)phenoxy] pentyl)oxy-5-methoxy-2-
aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethyl thioacetal (5c), (2S)-A/-{4-(n-[4-
(1,3-benzothi azol-2-yl)-2-methoxy phenoxy] pentyl)oxy-5-methoxy-2-aminobenzoyl}-
pyrrolidine-2-carboxaldehyde diethyl thioacetal (5d), (2S)-A/-{4-(n-[4-(1,3-benzoxozol-2-
yl)phenoxy]pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal (5e) and (2S)-A/-{4-(n-[4-(1,3-benzxozole-2-yl)-2-
methoxyphenoxy]pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal(Sf).
In yet another embodiment the compound of formula 6 used in step (a) is
selected from A/1-[4-(1,3-benzothiazol-2-yl)phenyl]-5-bromopentanamide (6a) or /V1-[4-
(6-fluoro-1,3-benzothiazol-2-yl)phenyl]-5-bromopentanamide (6b).
In yet another embodiment the compound of formula 7 obtained in step (a) is
selected from (2S)-A/-{4-(5-[N1-(4-(1,3-benzothiazol-2-yl)phenyl)]-
pentanecarboxamide)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal (7a) or (2S)-A/-{4-(5-[N1-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)-
pentanecarboxamide]oxy)-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde
diethylthioacetal (7b).
In yet another embodiment the compound of formula 8 obtained in step (b) is
selected from the group consisting of (2S)-/V-{4-(n-[4-(1,3-benzothiazol-2-yl)phenoxy
]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox aldehyde diethyl thioacetal
(8a) and (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl) oxy-5-
methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox aldehyde diethylthioace (8b).
In yet another embodiment the representative compounds of formula 9 obtained
in step (c) are as follows:
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11aS)-1,2,3,11atetrahydro-
5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a);
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl}oxy-(11 aS)-
1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9b);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro-
5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-
(11aS)-1 ,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one (9d);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11aS) 1,2,3,11atetra-
hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS)
1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9f);
7-Methoxy-8-{5-[A/^-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox
amide}oxy-(11 aS)-1,2,3,11 a-tetra-hydro-5H-pyrrolo[2,1 -c][1,4]benzodi azepin-
5-one (9g) and
7-Methoxy-8-{5-[A/J-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane
carboxamide}oxy-(11 aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]
benzodiazepin-5-one (9h).
DETAILED DESCRIPTION OF THE INVENTION
The precursors 4-(1,3-benzothiazol-2-yl)phenol/4-(1,3-benzothiazol-2-yl)-2-
methoxyphenol of formula 3a-b (Ben-Allum, A.; Bakkas, S.; Soufiaoui, M. Tetrahedron
Lett. 1997, 38, 6395; Wells, G.; Lowe, P. R.; Stevens, M. F. G. ARKIVOC 2000, 1, 779)
and (2S)-N-[4-(hydroxy-5-methoxy-2-nitrobenzoyl] pyrrolidine-2-carboxaldehyde
diethylthioacetal of formula 2 (Thurston, D. E.; Murthy, V. S.; Langley, D. R.; Jones, G.
B. Synthesis. 1990, 81) have been prepared by literature methods. The benzoxazole
precursors 3c-d have been prepared by condensation of 2-aminophenols with
benzylated protected benzaldehydes, oxidation followed by debenzylation with
palladium on charcoal (Centore, R.; Panunzi, B.; Roviello, A.; Sirigu, A.; Villano, P. J.
Polym. Sci. Part A: Polym. Chem. 1996, 34, 3203). Amide derivatives of benzothiazoles
of formula 6a-b have been prepared by coupling bromoacid chlorides with
corresponding 2-(4-aminophenyl)benzothiazoles.
Some representative compounds of formula 9 for the present inventions are given
below
a) 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11aS)-1,2,3,11 atetrahydro-
5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one
b) 7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl} oxy-(11aS)-
1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one
c) 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro-
5/-/-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one
d) 7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl} oxy-(11aS)-
1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one
e) 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11 aS) 1,2,3,11 atetra-
hydro-5H-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one
f) 7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl} oxy-(11aS)
1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one
g) 7-Methoxy-8-{5-[/V*-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox amidejoxy-
(11aS)-1,2,3,11a-tetra-hydro-5/-/-pyrrolo[2,1-c][1,4]benzodi azepin-5-one
h) 7-Methoxy-8-{5-[A/y-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane
carboxamide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]
benzodiazepin-5-one
These new analogues of pyrrolo[2,1-c][1,4]benzodiazepine hybrids linked at C-8
position have shown promising DNA binding activity and efficient anticancer activity in
various cell lines. The molecules synthesized are of immense biological significance
with potential sequence selective DNA-binding property. This present invention is
illustrated in Scheme 1 and scheme 2 as herein given below:
1) The ether linkage at C-8 position of DC-81 intermediates with benzothiazole and
benzoxazole moieties.
2) Refluxing the reaction mixtures for 48 h.
3) Synthesis of C-8 linked PBD antitumour antibiotic hybrid imines.
4) Purification by column chromatography using different solvents like ethyl acetate,
hexane, chloroform and methanol.
Representative compounds 9a-h of general structural formula 9
Compound
(Figure Removed)

The following examples are given by way of illustration of the working of the
invention in actual practice and therefore should not be construed to limit the scope of
present invention in any way.
EXAMPLE 1
To a solution of (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2-nitrobenz oyl)
pyrrolidine-2-carboxarbaldehyde diethylthioacetal 2a (535 mg, 1 mmol) in acetone (10
mL) was added anhydrous K2CO3 (552 mg, 4 mmol) and the 4-(benzothiazol-2-
yl)phenol 3a (227 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After
completion of the reaction as indicated by TLC, potassium carbonate was removed by
suction filtration and the solvent was removed under vacuum. The crude product thus
obtained was purified by column chromatography using ethylacetate-hexane (1:1) as
eluant to afford pure compound of 4a (511 mg, 75%).
1H NMR (CDCI3): 8 8.0 (d, 2H, J = 8.8 Hz), 7.9 (d, 1H, J = 8 Hz), 7.7 (s, 1H), 7.3-7.5 (m,
3H), 7.0 (d, 2H, J= 8.8 Hz), 6.8 (s, 1H), 4.9 (d, 1H, J = 3.7 Hz), 4.7 (m, 1H), 4.2 (m, 4H),
3.90 (s, 3H), 3.2 (m, 2H), 2.7-2.9 (m, 4H), 1.7-2.3 (m, 8H), 1.2-1.4 (m, 6H).
ESIMS:m/z683(lvr+1).
To compound 4a (682 mg, 1 mmol) in methanol (20 mL) was added SnCI2.2H2O
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 mL and 2x30 mL). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino
diethylthioacetal 5a (522 mg, 80%), which was used directly in the next step.
A solution of 5a (652 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 mL) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20
mL), brine (20 mL) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCI3 (4%) to give compound 9a (316 mg, 60%). This material was repeatedly
evaporated from CHCI3 in vacuum to generate the imine form.
1H NMR (CDCI3): 6 8.0 (d, 2H, J = 8.8 Hz), 7.9 (d, 1H, J = 8 Hz), 7.65 (d, 1H, J = 4.0
Hz), 7.5 (s, 1H), 7.3-7.45 (m, 3H), 7.0 (d, 2H, J = 8.8 Hz), 6.8 (s, 1H), 4.1 (m, 4H), 3.90
(s, 3H), 3.5-3.85 (m, 3H), 1.9-2.3 (m, 8H).
FABMS:528(M++1).
EXAMPLE 2
To a solution of (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2-nitrobenzoyl)
pyrrolidine-2-carboxarbaldehyde diethylthioacetal 2a (535 mg, 1 mmol) in acetone (10
ml_) was added anhydrous K2CO3(552 mg, 4 mmol) and the 4-(1,3-benzothiazol-2-yl)-2-
methoxyphenol 3b (257 mg, 1 mmol). The reaction mixture was heated to reflux for 48
h. After completion of the reaction as indicated by TLC, potassium carbonate was
removed by suction filtration and the solvent was removed under vacuum. The crude
product thus obtained was purified by column chromatography using ethylacetatehexane
(3:2) as eluant to afford pure compound of 4b
1H NMR (CDCI3): 8 8.0 (d, 1 H, J = 8.8 Hz), 7.85 (d, 1 H, J = 8.8 Hz), 7.7 (m, 2H), 7.5 (dd,
1H, J = 1.6, 8 Hz), 7.45 (t, 1H, J = 8 Hz), 7.3 (t, 1H, J = 8 Hz), 6.90 (d, 1H, J = 8.8 Hz),
6.7 (s, 1H), 4.8 (d, 1H, J = 3.9 Hz), 4.65 (m, 1H), 4.2 (m, 4H), 4.0 (s, 3H), 3.9 (s, 3H),
3.2 (m, 2H), 2.6-2.8 (m, 4H), 1.8-2.4 (m, 8H), 1.2-1.4 (m, 6H).
FABMS:m/z712(M+).
To compound 4b (712 mg, 1 mmol) in methanol (20 ml_) was added SnCl2.2H2O
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 mL and 2x30 mL). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino
diethylthioacetal 5b (511 mg, 75%), which was used directly in the next step.
A solution of 5b (682 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 mL) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20
ml), brine (20 ml) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCI3 (5%) to give compound 9b (312 mg, 56%). This material was repeatedly
evaporated from CHCI3 in vacuum to generate the imine form.
1H NMR (CDCI3): 5 8.05 (d, 1H, J = 7.8 Hz), 7.9 (d, 1H, J = 7.8 Hz), 7.64-7.72 (m, 2H),
7.3-7.6 (m, 4H), 6.9 (d, 1H, J = 7.8 Hz), 6.82 (s, 1H), 4.1-4.4 (m, 4H), 4.0 (s, 3H), 3.9 (s,
3H), 3.5-3.85 (m, 3H), 2.0-2.3 (m, 8H).
FABMS:m/z558(M++l).
EXAMPLE 3
To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitro benzoyl]
pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml)
was added anhydrous K2COs (552 mg, 4 mmol) and the 4-(benzothiazol-2-yl)phenol 3a
(227 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion
of the reaction as indicated by TLC, potassium carbonate was removed by suction
filtration and the solvent was removed under vacuum. The crude product thus obtained
was purified by column chromatography using ethylacetate-hexane (1:1) as eluant to
afford pure compound of 4c (522 mg, 75%).
1H NMR (CDCI3): 6 8.1 (d, 2H, J = 8.8 Hz), 7.7-7.9 (m, 2H) 7.3-7.5 (m, 3H), 7.0 (d, 2H, J
= 8.8 Hz), 6.75 (s, 1H), 4.85 (d, 1H, J= 3.8 Hz), 4.75 (m, 1H), 4.15 (m, 4H), 4.0 (s, 3H),
3.2 (m, 2H), 2.6-2.8 (m, 4H), 2.3 (m, 2H), 2.0 (m, 5H ), 1.6-1.8 (m. 3H), 1.35 (q, 6H, J =
7.5 Hz).
FABMS: m/z 696 (IvT).
To compound 4c (696 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 mL and 2x30 mL). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethyl
thioacetal 5c (533 mg, 80%), which was used directly in the next step.
A solution of 5c (666 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCOs (20
ml), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCb (4%) to give compound 9c (323 mg, 60%). This material was repeatedly
evaporated from CHCb in vacuum to generate the imine form.
1H NMR (CDCI3): 8 8.0 (d, 1H, J = 8.6 Hz), 7.85 (d, 1H, J = 8.6 Hz), 7.65 (d, 1H, J = 3.9
Hz), 7.3-7.55 (m, 5H), 7.0 (d, 2H, J = 8.6 Hz), 6.82 (s, 1H), 4.0-4.2 (m, 4H), 3.9 (s, 3H),
3.6-3.8 (m, 3H), 2.2-2.4 (m, 2H), 1.8-2.0 (m, 5H), 1.6-1.8 (m. 3H).
FABMS:m/z542(M++1).
EXAMPLE 4
To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl]
pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml_)
was added anhydrous K2CO3 (552 mg, 4 mmol) and the 4-(1,3-benzothiazol-2-yl)-2-
methoxyphenol 3b (257 mg, 1 mmol). The reaction mixture was heated to reflux for 48
h. After completion of the reaction as indicated by TLC, potassium carbonate was
removed by suction filtration and the solvent was removed under vacuum. The crude
product thus obtained was purified by column chromatography using ethylacetatehexane
(3:2) as eluantto afford pure compound of 4d (508 mg, 70%).
1H NMR (CDCb): 8 8.0 (d, 1H, J = 8.7 Hz), 7.85 (d, 1H, J = 8.7 Hz), 7.7 (d, 1H, J= 1.6
Hz), 7.65 (s, 1H), 7.53 (dd, 1H, J= 1.6, 8 Hz), 7.45 (dt, 1H, J= 1.6, 8 Hz), 7.33 (dt, 1H,
J = 1.6, 8 Hz), 6.90 (d, 1H, J = 8.7 Hz), 6.78 (s, 1H), 4.85 (d, 1H, J = 3.9 Hz), 4.7 (m,
1H), 4.1 (m, 4H), 4.0 (s, 3H), 3.9 (s, 3H), 3.2 (m, 2H), 2.6-2.8 (m, 4H), 1.7-2.3 (m, 10H),
1.2-1.4(m,6H).
FABMS: m/z 726 (M+).
To compound 4d (726 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 ml and 2x30 ml). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino diethyl
thioacetal 5d (557 mg, 80%), which was used directly in the next step.
A solution of 5d (696 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaC03 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 ml) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCOs (20
ml_), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCIs (5%) to give compound 9d (314 mg, 55%). This material was repeatedly
evaporated from CHCb in vacuum to generate the imine form.
1H NMR (CDCb): 6 8.0 (d, 1H, J = 8.2 Hz), 7.9 (d, 1H, J = 8.2 Hz), 7.64-7.72 (m, 2H),
7.3-7.6 (m, 4H), 6.95 (d, 1H, J = 8.2 Hz), 6.80 (s, 1H), 4.1 (m, 4H), 4.0 (s, 3H), 3.95 (s,
3H), 3.5-3.8 (m, 3H), 1.7-2.3 (m, 10H).
FABMS:m/z572(lvr+1).
EXAMPLE 5
To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl]
pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml)
was added anhydrous KaCOa (552 mg, 4 mmol) and the 4-(benzoxazol-2-yl)phenol 3d
(212 mg, 1 mmol). The reaction mixture was heated to reflux for 48 h. After completion
of the reaction as indicated by TLC, potassium carbonate was removed by suction
filtration and the solvent was removed under vacuum. The crude product thus obtained
was purified by column chromatography using ethylacetate-hexane (2:3) as eluant to
afford pure compound of 4e (533 mg, 80%).
1H NMR (CDCI3): 6 8.05 (d, 2H, J = 8.9 Hz), 7.6 (m, 1H), 7.5 (s, 1H), 7.4 (m, 1H), 7.2
(m, 2H), 6.9 (d, 2H, J= 8.9 Hz), 6.64 (s, 1H), 4.7 (d, 1H, J= 3.8 Hz), 4.55 (m, 1H), 4.0
(m, 4H), 3.80 (s, 3H), 3.1 (m, 2H), 2.52-2.8 (m, 4H), 1.5-2.1 (m, 10H), 1.2 (q, 6H, J= 7.4
Hz).
LCMS:/77/z680(M++1).
To compound 4e (665 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 ml_ and 2x30 ml). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino
diethylthioacetal 5e which was used directly in the next step.
A solution of 5e (649 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaC03 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20
mL), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCI3 (4%) to give compound 9e (263 mg, 50%). This material was repeatedly
evaporated from CHCIs in vacuum to generate the imine form.
1H NMR (CDCI3): 6 8.2 (d, 2H, J = 8.6 Hz), 7.72 (m, 1H), 7.65 (d, 1H, J = 3.9 Hz), 7.5
(m, 2H), 7.3-7.4 (m, 2H), 7.0 (d, 2H, J = 8.6 Hz), 6.8 (s, 1H), 4.1 (m, 4H), 3.90 (s, 3H),
3.5-3.8 (m, 3H), 2.3 (m, 2H), 1.5-2.1 (m, 8H).
LCMS:m/z526(M++1).
EXAMPLE 6
To a solution of (2S)-A/-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl]
pyrrolidine-2-carboxaldehyde diethylthioacetal 2b (549 mg, 1 mmol) in acetone (10 ml)
was added anhydrous K2CO3 (552 mg, 4 mmol) and the 4-(1,3-benzoxazol-2-yl)-2-
methoxyphenol 3d (241 mg, 1 mmol). The reaction mixture was heated to reflux for 48
h. After completion of the reaction as indicated by TLC, potassium carbonate was
removed by suction filtration and the solvent was removed under vacuum. The crude
product thus obtained was purified by column chromatography using ethylacetatehexane
(1:1) as eluant to afford pure compound of 4f (522 mg, 75%).
1H NMR (CDCI3): 6 7.62-7.8 (m, 3H), 7.63 (s, 1H), 7.52 (m, 1H), 7.3 (m, 2H), 6.95 (d,
1H, J = 8.5 Hz), 6.75 (s, 1H), 4.82 (d, 1H, J = 3.8 Hz), 4.65 (m, 1H), 4.1 (m, 4H), 4.0 (s,
3H), 3.94 (s, 3H), 3.2 (m, 2H), 2.6-2.8 (m, 4H), 1.6-2.3 (m, 10H), 1.35 (q, 6H, J = 7.6
Hz).
To compound 4f (695 mg, 1 mmol) in methanol (20 ml) was added SnCI2.2H20
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 ml_ and 2x30 ml). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino
diethylthioacetal 5f which was used directly in the next step.
A solution of 5f (679 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaC03 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20
ml), brine (20 ml) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCIs (5%) to give compound 9f (278 mg, 50%). This material was repeatedly
evaporated from CHCb in vacuum to generate the imine form.
1H NMR (CDCI3): 5 7.7-7.84 (m, 3H), 7.62 (d, 1H, J = 4.0 Hz), 7.43-7.58 (m, 2H), 7.3-7.4
(m, 2H), 6.9 (d, 1H, J = 8.6 Hz), 6.8 (s, 1H), 3.9-4.2 (m, 10H), 3.5-3.7 (m, 3H), 1.6-2.3
(m, 10H).
LCMS:m/z556(M++1).
EXAMPLE 7
To a solution of 1 (400 mg, 1 mmol) in acetone (10 ml_) was added anhydrous
K2C03 (552 mg, 4 mmol) and the 6a (389 mg, 1 mmol). The reaction mixture was
heated to reflux for 48 h. After completion of the reaction as indicated by TLC,
potassium carbonate was removed by suction filtration and the solvent was removed
under vacuum. The crude product thus obtained was purified by column
chromatography using ethylacetate-hexane (3:2) as eluant to afford pure compound of
7a (496 mg, 70%).
1H NMR (CDCI3): 5 8.5 (s, 1H), 8.0 (m, 3H), 7.82 (d, 1H, J = 7.6 Hz), 7.62 (m, 3H), 7.45
(t, 1H, J = 7.6 Hz), 7.3 (t, 1H, J = 7.6 Hz), 6.8 (s, 1H), 4.82 (d, 1H, J = 3.8 Hz), 4.65 (m,
1H), 4.15 (m, 2H), 3.9 (s, 3H), 3.1-3.3 (m, 2H), 2.6-2.8 (m, 4H), 2.45 (m, 2H), 1.7-2.3
(m, 8H), 1.3(q, 6H, J=6.8Hz).
To compound 7a (709 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 ml_ and 2x30 ml_). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino
diethylthioacetal 8a which was used directly in the next step.
A solution of 8a (679 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 ml_) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20
ml), brine (20 ml) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCI3 (5%) to give compound 9g (277 mg, 50%). This material was repeatedly
evaporated from CHCI3 in vacuum to generate the imine form.
1H NMR (CDCI3): 8 8.8 (s, 1H), 8.05 (m, 3H), 7.9 (d, 1H, J = 7.9 Hz), 7.7-7.8 (m, 3H),
7.6 (s, 1H), 7.3-7.5 (m, 2H), 6.9 (s, 1H), 4.2 (m, 2H), 3.9 (s, 3H), 3.5-3.8 (m, 3H), 2.6 (m,
2H), 1.6-2.3 (m,8H).
LCMS:m/z555(M++l).
EXAMPLE 8
To a solution of 1 (400 mg, 1 mmol) in acetone (10 ml) was added anhydrous
K2C03 (552 mg, 4 mmol) and the 6b (407 mg, 1 mmol). The reaction mixture was
heated to reflux for 48 h. After completion of the reaction as indicated by TLC,
potassium carbonate was removed by suction filtration and the solvent was removed
under vacuum. The crude product thus obtained was purified by column
chromatography using ethylacetate-hexane (3:2) as eluant to afford pure compound of
7b (545 mg, 75%).
1H NMR (CDCIs): S 8.7 (bs, 1H), 7.9 (m, 3H), 7.7 (m, 3H), 7.5 (dd, 1H, J = 2.3, 7.8 Hz),
7.1-7.2 (m, 1H), 6.8 (s, 1H), 4.8 (d, 1H, J- 3.9 Hz), 4.7 (m, 1H), 4.1 (m, 2H), 3.9 (s, 3H),
3.2-3.3 (m, 2H), 2.7-2.8 (m, 4H), 2.45 (m, 2H), 1.8-2.3 (m, 8H), 1.2-1.4 (m, 6H).
LCMS: m/z 727 (M+).
To compound 7b (727 mg, 1 mmol) in methanol (20 ml_) was added SnCI2.2H2O
(1.125 g, 5 mmol) and refluxed for 5 h or until the TLC indicated that reaction was
completed. The methanol was evaporated under vacuum, the aqueous layer was then
carefully adjusted to pH 8 with 10% NaHCO3 solution and then extracted with ethyl
acetate and chloroform (2x30 ml_ and 2x30 ml). The combined organic phase was
dried over Na2SO4 and evaporated under vacuum to afford the crude amino
diethylthioacetal 8b, which was used directly in the next step.
A solution of 8b (697 mg, 1 mmol), HgCI2 (613 mg, 2.26 mmol) and CaCO3 (246
mg, 2.46 mmol) in acetonitrile-water (4:1) was stirred slowly at room temperature for
overnight. The reaction mixture was diluted with ethyl acetate (30 ml) filtered through a
celite pad. The clear organic supernatant was extracted with saturated 5% NaHCO3 (20
ml), brine (20 ml_) and the combined organic phase was dried (Na2SO4). The organic
layer was evaporated under vacuum and purified by column chromatography using
MeOH-CHCI3 (5%) to give compound 9h (286 mg, 50%). This material was repeatedly
evaporated from CHCI3 in vacuum to generate the imine form.
1H NMR (CDCI3): 8 8.8 (bs, 1H), 7.95 (m, 3H), 7.6 (m, 3H), 7.7-7.8 (m, 2H), 7.1 (m, 1H),
6.7 (s, 1H), 4.1 (m, 2H), 3.8 (s, 3H), 3.4-3.75 (m, 3H), 2.5 (m, 2H), 1.6-2.3 (m, 8H).
LCMS: m/z 573 (M++1).
Biological Activity:
DMA binding affinity of novel benzothiazole, benzoxazole linked PBD hybrids (9ah):
Compounds have been subjected to thermal denaturation studies with duplexform
calf thymus DMA (CT-DNA) using an modification of a reported procedure
(Newman, M. S. Carcinog-compr. Surv. 1976, 1, 203; (b) Hecht, S. S.; Loy, M.;
Hoffman, Carcinog-compr. Surv. 1976, 1, 325). . Working solutions in aqueous buffer
(10 mM NaH2PO4/Na2HPO4, 1 mM Na2EDTA, pH 7.00 + 0.01) containing CT-DNA (100
urn in phosphate) and the PBD (20 urn) have been prepared by addition of concentrated
PBD solutions in DMSO to obtain a fixed [PBD]/[DNA] molar ratio of 1:5. The DNA-PBD
solutions have been incubated at 37 °C for 0 and 18 h prior to analysis. Samples have
been monitored at 260 nm using a Beckman DU-800 spectrophotometer fitted with high
performance temperature controller, and heated at 1 °C min"1 in the 40-110 °C range.
DNA helix->coil transition temperatures (7m) have been obtained from the maxima in
the d(/\26o)/dT derivative plots. Drug-induced alterations in DNA melting behavior are
given by: A7m = 7m(DNA + PBD) - 7m(DNA alone), where the 7m value for the PBD-free
CT-DNA is 69.1 ± 0.01. The fixed [PBD]/[DNA] ratio used has not resulted in binding
saturation of the host DNA duplex for any compound examined.
The DNA binding activity for these novel C8-linked benzothiazole, benzoxazole-
PBD hybrids has been examined by thermal denaturation studies using calf thymus
(CT) DNA. Melting studies show that these compounds stabilize the thermal helix -> coil
or melting stabilization (A7m) for the CT-DNA duplex at pH 7.0, incubated at 37 °C,
where PBD/DNA molar ratio is 1:5. The data for the compounds 9a-h is included in
Table 1 for comparison.
Table 1. Thermal denaturation data for benzothiazole and benzoxazle linked
PBD
(Table Removed)

For CT-DNA alone at pH 7.00 ± 0.01, Tm = 69.1 °C ± 0.01 (mean value from 10
separate determinations), all A7"m values are ± 0.1 - 0.2 °C. b For a 1:5 molar ratio of
[PBD]/[DNA], where CT-DNA concentration = 100 uM and ligand concentration = 20 uM
in aqueous sodium phosphate buffer [10 mM sodium phosphate + 1 mM EDTA, pH 7.00
±0.01].
Anticancer activity: In vitro biological activity studies were carried out at the National
Cancer Institute (USA).
The compounds were evaluated for in vitro anticancer activity against sixty
human tumour cells derived from nine cancer types (leukemia, non-small-cell lung,
colon, CMS, melanoma, ovarian, prostate, and breast cancer) as shown in Table 3. For
each compound, dose response curves for each cell line were measured at a minimum
of five concentrations at 10 fold dilutions. A protocol of 48 h continuous drug exposure
was used and a sulforhodamine B (SRB) protein assay was used to estimate cell
viability or growth. The concentration causing 50% cell growth inhibition (GI50), total cell
growth inhibition (TGI 0%growth) and 50% cell death (LC50, -50% growth) compared
with the control was calculated. The mean graph midpoint values of logic TGI and log™
LC50 as well as logio GI50 for 9a, 9b, 9c and 9d are listed in Table 2. As demonstrated
by mean graph pattern, compound 9d exhibits an interesting profile of activity and
selectivity for various cell lines. The mean graph mid point of Iog10 TGI and log-io LC50
showed similar pattern to the Iog10 GI50 mean graph mid points.
Table 2. LogioGI50 logioTGI and logioLC50 mean graphs midpoints (MG_MID) of in
(Table Removed)

Each cancer type represents the average of six to nine different cancer cell lines.

We claim
1. Novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines
of formula 9,
wherein: n = 3-4, X = S or O; Y = NH or O; Z = CO or CH2; R, RI = H or F; R2 =
OCH3 or H.
2. The compound as claimed in claim 1, wherein the representative compounds of
formula 9 are as follows:
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11 aS)-1,2,3,11 atetrahydro-
5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a);
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl} oxy-(11 aS)-
1,2,3,11a-tetrahydro-5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9b);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro-
5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS)-
1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one (9d);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11aS) 1,2,3,11atetra-
hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl} oxy-(11 aS)
1,2,3,11 a-tetra-hydro-5/-/-pyrrolo[2,1 -c][1,4]benzodiazepin-5-one (9f);
7-Methoxy-8-{5-[A/t-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox amidejoxy-
(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodi azepin-5-one (9g);
and
7-Methoxy-8-{5-[N1-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane
carboxamide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]
benzodiazepin-5-one (9h).
3. The compound as claimed in claims 1-2, wherein the structural formula of the
representative compounds 9a-h are:
(Figure Removed)
4. The compound as claimed in claim 1 exhibits binding affinity with calf thymus (CT)
DNA at a molar ratio of 1:5 in aqueous sodium phosphate buffer at pH 7.
5. The compound as claimed in claim 1 exhibit in-vitro anticancer activity against
human tumor cells derived from nine cancer types of leukemia, non-small-cell
lung, colon, CNS, melanoma, ovarian, prostate, and breast cancer.
6. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepine
as claimed in claim 1, wherein the compound 9a exhibits in-vitro cytotoxicity in
mean graph midpoint value of -6.30(mol/lit), -5.63(mol/lit), and -4.75(mol/lit) for
logio GI50, logic TGI and logio LC50, respectively, against nine human tumor cell
lines.
7. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine
as claimed in claim 1, wherein the compound 9b exhibits in-vitro cytotoxicity in
mean graph midpoint value of log™ TGI, Iog10 LC50,logi0 GI50. In-vitro
cytotoxicity data in mean graph midpoint value of -6.07, -5.47, and -4.67 for logio
GI50, logic TGI and logic LC50, respectively, against nine human tumor cell
lines.
8. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine
as claimed in claim 1, wherein the compound 9c exhibits in-vitro cytotoxicity in
mean graph midpoint value of -6.15, -5.30, and -4.35 for log™ GI50, log™ TGI
and logic LC50 , respectively, against nine human tumor cell lines.
9. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4] benzodiazepine
as claimed in claim 1, wherein the compound 9d exhibits in-vitro cytotoxicity in
mean graph midpoint value of -7.09, -5.78, and -4.37 for log™ GI50, log™ TGI
and log™ LC50 , respectively, against nine human tumor cell lines.
10. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]
benzodiazepine as claimed in claim 1, wherein the compound 9a exhibits
log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the
range of -6.08 to -6.73.
11. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]
benzodiazepine as claimed in claim 1, wherein the compound 9b exhibits log™
GI50 (mole/lit) anticancer activity against nine cancer cell type in the range of -
5.85 to-6.45.
12. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]
benzodiazepine as claimed in claim 1, wherein the compound 9c exhibits
log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the
range of-5.87 to-6.65.
13. The novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]
benzodiazepine as claimed in claim 1, wherein the compound 9d exhibits
log™ GI50 (mole/lit) anticancer activity against nine cancer cell type in the
range of-6.79 to-7.51.
14. A process for the preparation of novel benzothiazole or benzoxazole linked
pyrrolo[2,1-c][1,4]benzodiazepines of formula 9,
(Figure Removed)

wherein: 'n' is 3-4, X = S or O; Y = NH or O; Z = CO or CH2; R, RI = H or F;
R2 = OCH3 or H and the said process comprising the steps of:
a) reacting a compound of formula 1 or formula 2
(Figure Removed)

with benzothiazole or benzoxazole derivative selected from the compounds
of formula 3 and 6,
(Figure Removed)

in the presence of K2C03, in an organic solvent, under refluxing temperature
to obtain the resultant nitro compound of formula 4 or 7;
(Figure Removed)
b) reducing the above said nitro compound of formula 4 or 7obtained in step
(a) with SnCI2.2H2O in an organic solvent, under reflux temperature and
isolating the corresponding amino compound of formula 5 or 8,
respectively, and
NH2 pH(SEt)2
8a-b
c) reacting the above said amino compound of formula 5 or 8 obtained in
step (b) with a deprotecting agent by known method to obtain the desired
compound of formula 9.
15. A process as claimed in claim 14 wherein the organic solvent used in step (a)
is acetone and in step (b) is ethanol or methanol.
16. A process as claimed in claim 14, wherein in step (a) the compound of formula 2
is reacted with benzothiazole or benzoxazole derivative of formula 3 to obtain
the resultant nitro compound of formula 4.
17. A process as claimed in claim 14, wherein in step (a) the compound of formula 1
is reacted with benzothiazole or benzoxazole derivative of formula 6 to obtain
the resultant nitro compound of formula 7.
18. A process as claimed in claim 14, wherein the compound of formula 1 used in
step (a) is (2S)-N-[4-hydroxy-5-methoxy-2-nitrobenzoyl]pyrrolidine-2-carbox
aldehyde diethylthioacetal.
19. A process as claimed in claim 14, wherein the compound of formula 2 used in
step (a) is selected from (2S)-N-[4-(3-bromobutyl)oxy-5-methoxy-2-
nitrobenzoyl) pyrrolidine-2-carboxarbaldehyde diethylthioacetal (2a) and (2S)-
N-[4-(5-bromopentyloxy)-5-methoxy-2-nitrobenzoyl]pyrrolidine-2-
carboxaldehyde diethylthioacetal (2b).
20. A process as claimed in claim 14, wherein the compound of formula 3 obtained
in step (a) is selected from the group consisting of 4-(benzothiazol-2-yl)phenol
(3a), 4-(1,3-benzothiazol-2-yl)-2-methoxyphenol (3b), 4-(benzoxazol-2-
yl)phenol (3c), and 4-(1,3-benzoxazol-2-yl)-2-methoxyphenol (3d).
21. A process as claimed in claim 14, wherein the compound of formula 4 obtained
in step (a) is selected from the group consisting of (2S)-/V-{4-(n-[4-(1,3-
benzothiazol-2-yl)phenoxy]butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-
carboxaldehyde diethylthioacetal (4a), (2S)-A/-{4-(n-[4-(1,3-benzothi azol-2-yl)-
2-methoxyphenoxy] butyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carbox
aldehyde diethylthioacetal(4b), (2S)-N-{4-(n-[4-(1,3-benzothiazol-2-yl) phenoxy]
pentyl)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthio
acetal (4c), (2S)-/V-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-methoxy phenoxy]pentyl)
oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine -2-carboxaldehyde diethylthioacetal
(4d), (2S)-/V-{4-(n-[4-(1,3-benzoxozol-2-yl)phenoxy]pentyl)oxy-5-methoxy-2-
nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (4e) and (2S)-/V-
{4-(n-[4-(1,3-benzoxozole-2-yl)-2-methoxyphenoxy]pentyl)oxy-5-methoxy-2-
nitro benzoylj-pyrrolidine -2-carboxaldehyde diethylthioacetal (4f).
22. A process as claimed in claim 14, wherein the compound of formula 5 obtained
in step (a) is selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzo
thiazol-2-yl)phenoxy]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbo
xaldehyde diethylthioacetal (5a), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-
methoxyphenoxy] butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox
aldehyde diethylthioacetal (5b), (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)phenoxy]
pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethyl
thioacetal (5c), (2S)-A/-{4-(n-[4-(1,3-benzothi azol-2-yl)-2-methoxy phenoxy]
pentyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethyl
thioacetal (5d), (2S)-A/-{4-(n-[4-(1,3-benzoxozol-2-yl)phenoxy]pentyl)oxy-5-
methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (5e)
and (2S)-A/-{4-(n-[4-(1,3-benzxozole-2-yl)-2-methoxyphenoxy]pentyl)oxy-5-
methoxy-2-aminobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal(5f).
23. A process as claimed in claim 14, wherein the compound of formula 6 used in
step (a) is selected from N1-[4-(1,3-benzothiazol-2-yl)phenyl]-5-
bromopentanamide (6a) or N1-[4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl]-5-
bromopentanamide (6b)
24. A process as claimed in claim 14, wherein the compound of formula 7 obtained
in step (a) is selected from (2S)-/V-{4-(5-[N1-(4-(1,3-benzothiazol-2-yl)phenyl)]-
pentanecarboxamide)oxy-5-methoxy-2-nitrobenzoyl}-pyrrolidine-2-
carboxaldehyde diethylthioacetal (7a) or (2S)-A/-{4-(5-[N1-(4-(6-fluoro-1,3-
benzothiazol-2-yl)phenyl)-pentanecarboxamide]oxy)-5-methoxy-2-
nitrobenzoyl}-pyrrolidine-2-carboxaldehyde diethylthioacetal (7b).
25. A process as claimed in claim 14, wherein the compound of formula 8 obtained
is selected from the group consisting of (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-
yl)phenoxy ]butyl)oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox
aldehyde diethyl thioacetal (8a) and (2S)-A/-{4-(n-[4-(1,3-benzothiazol-2-yl)-2-
methoxyphenoxylpentyl) oxy-5-methoxy-2-aminobenzoyl}-pyrrolidine-2-carbox
aldehyde diethylthioace (8b).
26. A process as claimed in claim 14, wherein the representative compound of
formula 9 obtained are as follows:
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)phenoxy]butyl}oxy-(11 aS)-1,2,3,11atetrahydro-
5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9a);
7-Methoxy-8-{4-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]butyl}oxy-(11 aS)-
1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9b);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)phenoxy]pentyl}oxy-(11aS)-1,2,3,11atetrahydro-
5/-/-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9c);
7-Methoxy-8-{5-[4-(1,3-benzothiazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-
(11aS)-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin -5-one (9d);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)phenoxy]pentyl}oxy-(11aS) 1,2,3,11atetra-
hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9e);
7-Methoxy-8-{5-[4-(1,3-benzoxazol-2-yl)-2-methoxyphenoxy]pentyl}oxy-(11 aS)
1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one (9f);
7-Methoxy-8-{5-[A/r-(4-(1,3-benzothiazol-2-yl)phenyl)]pentanecarbox
amide}oxy-(11aS)-1,2,3,11a-tetra-hydro-5H-pyrrolo[2,1-c][1,4]benzodi azepin-
5-one (9g) and
7-Methoxy-8-{5-[N1-(4-(6-fluoro-1,3-benzothiazol-2-yl)phenyl)]pentane
carboxamide}oxy-(11 aS)-1,2,3,11 a-tetra-hydro-5H-pyrrolo[2,1 -c][1,4]
benzodiazepin-5-one (9h).
27 Novel benzothiazole or benzoxazole linked pyrrolo[2,1-c][1,4]benzodiazepines
useful as antitumour agents and a process for the preparation thereof,
substantially as herein described with reference to the examples.

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http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=6g9q/XqaBNV0xj57nthhMQ==&loc=+mN2fYxnTC4l0fUd8W4CAA==

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Patent Number

268235

Indian Patent Application Number

277/DEL/2007

PG Journal Number

35/2015

Publication Date

28-Aug-2015

Grant Date

22-Aug-2015

Date of Filing

13-Feb-2007

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	AHMED KAMAL	BIOTRANSFORMATION LAB ORGANIC DIVISION-1, DISCOVERY IICT, TARNAKA HYDERABAD-7
2	K. SRINIVASA REDDY	BIOTRANSFORMATION LAB ORGANIC DIVISION-1, DISCOVERY IICT, TARNAKA HYDERABAD-7
3	M. NASEER AHMED KHAN	BIOTRANSFORMATION LAB ORGANIC DIVISION-1, DISCOVERY IICT, TARNAKA HYDERABAD-7
4	RAJESH V.C.R.N.C. SHETTI	BIOTRANSFORMATION LAB ORGANIC DIVISION-1, DISCOVERY IICT, TARNAKA HYDERABAD-7

PCT International Classification Number

C07D237/26

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA