Title of Invention

NOVEL TRIALKYLAMMONIUM 2,4-DINITROPHENYL BARBITURATES AS ANTICONVULSANT AGENTS

Abstract

NOVEL TRIALKYLAMMONIUM 2,4-DINITROPHENYL BARBITURATES AS ANTICONVULSANT AGENTS Abstract: New barbiturates have been synthesised from the ethanolic solution of 1-chioro-2,4-dinitrobenzene, barbituric acid and amines (triethylamine and tri-n-butylamine). The structure of the isolated molecules have been confirmed from UV-VIS IR. PMR, C NMR, COSY MASS spectral and single crystal X-ray studies. Elemental analysis and other qualitative tests have also been carried out to throw light on the proposed structures. The anticonvulsant activity of the synthesized barbiturates have been tested by Maximal Electro Shock. Albino rats of either sex weighing 150g - 200g have been subjected for the study. The drugs have been given one hour before the induction of Maximal Electro Shock. The different stages of convulsions such as Tonic flexor, Tonic extensor, Clones convulsion. Stupor and Recovery / Death have been examined. Reduction in extensor phase of convulsion have been noted for the synthesized barbiturates. Keywords: barbiturates, car anionic sigma complex, anticonvulsant, 1-chloro-2,4-dinitrobenzene

Full Text

Background of invention The invention includes the synthesis of novel barbiturates (la and lb) from 1-chloro-2,4-dinitrobenzene, barbituric acid and amines (triethylamine and tri n-butylamine). These barbiturates have admirable anticonvulsant activity. Introduction Barbiturates are drugs that act as sedative - hypnotic agents. The short acting barbiturates such as thiopental are used as intravenous an aesthetics. The long acting barbiturates such as phenobarbital are anticonvulsant agents, They are used for the suppression of anxiety, the induction of sleep and the control of seizures [(Thomas Nogrady, 1988); (Ashutoshkar. 1993); (Hardman and Limbird, 2001); (Yadav, 2004); (Nadkarni et al., 2005); (Jain et al., 2006). Epilepsy affects approximately 1% of the world's population and many of the marketed anticonvulsant drugs have profound side effects [(Huseyin et al., 1998); (Srivastava et al.. 2000); (Dipiro et al., 2002); (Gitto et al., 2006); (Rana et a!., 2007)]. Hence it is necessary to search for safer and more effective new antiepileptic drugs. A number of stable crystalline adducts have been reported from the electron-deficient nitro aromatics and p-diketones [(Terrier, 1982); (Gnanadoss and Kalaivani, 1985); (Gnanadoss and Kalaivani, 1985)]. As barbituric acid contains an active methylene group like p-diketones, an attempt has now been made to prepare crystalline carbanionic sigma adducts from it. Detailed description of the invention Analar grade 1-chloro-2,4-dinitrobenzene (DNCB) and barbituric acid (BBA) were used as such, Triethylamine and tri-n-butylamine were refluxed over small quantities of phenyl isocyanate and distilled (Saur, 1963). DNCB (0.01 mol) in absolute ethanol was mixed with 0.01 mol of barbituric acid in absolute ethanol. Amine (0.02mol) was then added and the mixture was shaken well for 5 to 6 hours. The solution was filtered and kept as such for 48 hours. On standing, coloured crystals come out from the solution. The crystals were powdered well and washed with absolute ethanol and copious amount of dry ether and recrystallised from absolute alcohol. The visible data were obtained on a Perkin - Elmer Lambda15 UVA/IS spectrometer. The IR spectra were recorded using Perkin - Elmer spectrum RXI infrared spectrophotometer as KBr pellets. The NMR spectra were obtained from Bruker DRX-300 spectrometer with (DMSO) de as solvent and TMS as an internal reference. The FAB mass spectra were recorded on a JEOL SX 102/DA-6000 Mass spectrometer. The important characteristics and spectral data of the synthesised barbiturates (la and lb) are presented in tables 1-4. Though a number of trinitro aromatics gave pasty mass with barbituric acid, the ethanolic solution of 1-chloro-2,4-dinitrobenzene and barbituric acid in the presence of excess amines yielded crystalline products. The isolated barbiturates are coloured because of the delocalization of the charge. Qualitative tests (Vogel, 1978) on the synthesised barbituratess reveal the presence of nitrogen atom, nitro groups and the absence of chlorine. In DNCB, a strong sharp absorption band characteristic of C - CI stretching mode has been observed at 732cm'\ which is absent in the isolated barbiturates, clearly shows that during the formation of barbiturates, chlorine is removed from DNCB. Since upon the formation of the barbiturates, the aromatic nitro group is converted to one bearing partial negative charge, the asymmetric and symmetric absorption frequencies are expected to decrease [(Terrier, 1982); (Gnandoss and Kalaivani, 1985); (Kalaivani et al., 2005)]. This has been obsen/ed in the present study also. The broad band observed between ~2700-3400 cm'^ in barbiturates is characteristic of trialkyi ammonium cation (Silverstein and Webster, 2004). In the synthesised barbiturates C = C stretching band appears at ~ 1600cm'^ as strong sharp band instead of at ~1640cm"\ This may be probably due to stretching of C = C bond during delocalization. In barbituric acid N - H proton signal appears at 5 11.09. During the formation of barbiturates, the negative charge is delocallzed over a large area upto the keto functions nearer the N - H groups. Hence the N - H protons are shielded to some extent and show shift towards upfield. The adjacent ring protons of the nitromoiety appear as double doublet in DNCB, whereas in barbiturates it has become a multiplet supporting the delocalization of the negative charge. Proton - Proton COSY of barbiturates revealed that ^H - 'H coupling has occurred between the protons in the cation moiety. ^^C spectrum of barbituric acid exhibits two signals at 8151.7 and 5 167.8 due to the keto group carbon atoms. Six signals have been observed in the ^^C spectrum of DNCB. Carbon atom bearing CI appears at 5133.6. The synthesized barbiturates la exhibits 11 signals in the ^^C spectrum. The absorption peaks at 58.6 and 545.8 are due to the carbon environments of CH3 and CH2 groups respectively of triethylammoniuim ion. The absorption peak at 586.6 is not noticed in DNCB and barbituric acid but only in the barbiturates may be due to the newly formed carbon environment (C = C) (Kemp, 1991). In FABMS, base peak corresponds to triethylammonium cation (m/z = 102) is found. ^^C spectrum of lb exhibits 13 signals. The absorption peak at 586.69 corresponds to the newly developed C = C environment. In FABMS, base peak corresponds to tri-n-butylammonium cation (m/z = 186) is found. Based on the spectral observation, the barbiturates may probably have structures 1a and lb (Scheme 1). The structure of triethylammoniam 2,4-dinitrophenyl barbiturates (1a) has also been proved through single crystal X-ray analysis (Altornare, 1993); (Farrugia, 1997); (Sheldrick,1997); (Farrugia,1999); (Bruker,1999); (Brune,2002); (Bruker,2004). Single crystal X-ray analysis of barbiturate la Crystal data Formula C16H21N5O7 Formula weight 395.38 Crystal system space group Monoclinic C2/c Unit cell dimensions a = 29.7900 (8) A b = 10.4533(3) A 0 = 11.9606(3) A a = 90° p = 97.90° Y = 90° HYDROGEN BONDING PATTERN OF BARBITURATE la Anti convulsant activity of barbiturates 1a & 1b The synthesised barbiturates are screened for anticonvulsant activity (Kulkarini, 1999). The barbiturates have been given one hour before the Induction of Maximal Electro Shock (150nnA/0.2 sec). The current has been applied on the animals using the corneal electrodes. The barbiturates show activity even at low concentration (50mg/kg) (Table?). The synthesised barbiturates may probably be potent anticonvulsant agent in future due to the following reasons. • high stability • high solubility in water • presence of polar and non-polar ends within the same molecule • low toxicity • easy method of preparation • high yield References: 1. Altornare, A., Gascarano, G., Giacovazzo, C, Guagliardi, A., 1993, SIR92. J.Appl.Cryst.26, 343-350. 2. Ashutoshkar, Medicinal Chemistry, Wiley Eastern Ltd., 1993, 75-109. 3. Bruker 1999, SADABS, Bruker AXS Inc., Madison, Wisconsin, USA. 4. Bruker 2004, APEX-II and SAINT-Plus (Version 7.06a). Bruker AXS Inc., Madison, Wisconsin, USA. 5. Bruno, I.J., Cole, J.C., Edington, PR., Kessler, M., Macrae, C.F., McCabe, P., Pearson, J., Taylor, R. 2002, Acta Cryst. B58-389-397. 6. Craven, B.M., 1964, Acta Cryst. 17,282. 7. Dipiro, J.T., Talbert, R.L., Yee, G.C., Matzke, G.R., Wells, B.G., and Posey, L.M. Pharmacotherapy - a pathophysiologic approach, 5'" Ed., Mc Graw Hill Company, 2002,1031-1059. 8. Farrugia, L.J. 1997, 0RTEP3 for windows. J.Appl.Cryst. 30,565. 9. Farrugia, L.J. 1999, WinGX. J. Appl. Cryst. 32, 837-838 10. Gitto, R.S., Caruso, R., pagano, B., De Luca, L, Citraro., R., Russo, E., De Sarro, G., and Chimirri, A.J. Med. Chem., 2006,49, 5618-5622. 11. Gnanadoss L.M., Kalaivani D. J. Org. Chem. 1985, 50, 1174. 12. Gnanadoss L.M., Kalaivani D. J. Org. Chem. 1985, 50, 1178. 13. Hardman, J.G., and Limbird, L.E. The pharmacological basis of therapeutics, 10"" Ed., McGraw-Hill, 2001,1143-1170. 14. Huseyin, U., Vanderpoorten, K., Cacciaguerra, S., Spampinato, S., Stables, J.P., Depovere, P., Isa, M., Maserecl, B., Delarge, J., and poupaert, J.H. J.Med.Chem., 1998, 41, 1138. 15. Jain, K.S., Chitra, T.S., Miniyar P.B., Kathiravan, M.K., Bendre, V.S., Veer, V.S., Shahane, S.R., and Shishoo, C.J. Current Science, 2006, 90,793-803. 16. Kalaivani, D., Usha V., Subbalakshmi, R., Malarvizhi, R., and Saratha, A. IJSAC, 2005, 2, 1 - 7. 17. Kemp, W., Organic Spectroscopy, Palgrave, 1991, 192. 18. Kulkarini, S.K. Handbook of Experimental pharmacology, VallabhPrakashan, 1999,131. 19. Nadkarni, S., Lajoie, J., and Devinsky, O. Neurology, 2005, 64, S2-S11. 20. Rana, A., Siddiqui, N., and Khan, S.A. Indian Journal of pharmaceutical sciences, 2007, 69(1), 10-17. 21. Saur, J. C. Organic Synthesis Collect. Vol. IV, John Wiley and Sons Inc. New York, 1963. 22. Sheldrick, G.M. 1997, SHELXL 97. University of G/"ottingen, Germany. 23. Silverstein, R.M., Webster.F.X., Spectrometric identification of Organic compounds, John Wiley and Sons Inc., New York, 2004,103. 24. Srivastava, S.K., Srivastava, S.L., and Srivastava, S.D. J. Indian Chem. Soc, 2000,77,104-105. 25. Terrier F. Chem. Rev. 1982, 82, 77. 26. Thomas Nogrady. Medicinal Chemistry, Oxford University Press, New York, 1988. 27. Vogel, A. I. Textbook of Practical Organic Chemistry, Longman, London, 1978, 776. 28. Yadav, A.V. A textbook of pharmacology and toxicology, 11'" Ed., Nirali Prakas, 2004, 57-67. I CLAIM 1. For the new trialkylammonium 2 4-dinitrophenyl barbiturates 1a and 1b which have admirable anticonvulsant activity and low toxicity. 2. For the process of preparing the new barbiturates 1a and 1b.

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