Title of Invention	PROCESS FOR THE PREPARATION OF ENANTIOMERICALLY ENRICHED AMINO ACIDS
Abstract	The present invention relates to a process for the resolution of derivatives of alpha-amino acids. In particular the process is concerned with the resolution of a mixture of enantiomers of N-protected amino acids by crystallization with enantiomerically pure N-unprotected beta-amino acid derivatives.

Full Text

WO 2005/058776 PCT/EP2004/013194 1 Process for the Preparation of Enantiomerically Enriched Amino Acids The present invention is concerned with a process for the resolution of a mixture of enantiomers of N-protected amino acids, in particular a-amino acids. Especially, this process claims a crystallisation of a diastereomeric salt pair consisting of one enantiomer of an N-protected amino acid and an enantiomerically pure N-unprotected B-amino acid derivative. Enantiomerically enriched amino acids, especially a-amino acids, are versatile tools for synthesising enantiomerically pure bio-actives, intermediates for Pharmaceuticals or for infusion liquors for parenteral nutrition. A large amount of these amino acids, especially L-lysine, is produced for feed additive compositions. The resolution of mixtures of enantiomers of amino acids, e.g. racemates, via classical crystallisation techniques is a rather old and common method for the generation of enantiomerically enriched amino acids. Although there have been great efforts to create new methodologies which allow to synthesise the amino acids in pure form via e.g. biotechnological means, the classical pathway is still an option for special amino acids which are not or only poorly generated by these methods (Izumi et al. Angew. chem. 1978, 90, 187; B. Hoppe et al. Chemie in unserer Zeit, 1984, 18, 73) . The object of the present invention was, therefore, to create a technical process for the resolution of enantiomeric mixtures of such amino acids. In particular the process should allow to gain especially pure forms of one enantiomer of these amino acids in a robust and easy to handle mode. From the perspective of an economical and ecological viewpoint the present process shall be advantageous over those described in the prior art, in WO 2005/058776 PCT/EP2004/013194 2 particular for the generation of those amino acids which are disadvantageously produced via known methods. Mentioned objective is addressed properly by applying a process according to features of present claim 1 or 7. Independent claims 2 to 6 or 8 to lldepict preferred embodiments of the process according to the invention. By performing a process for the preparation of enantiomerically enriched N-protected amino acids, wherein a mixture of both enantiomers of an N-protected amino acid is resolved through crystallisation of the salt of one enantiomer of the N-protected amino acid and an enantiomerically pure N-unprotected p-amino acid derivative, the solution to the mentioned object is attained, in particular in a manner that is surprising, by no means foreseeable and, according to the invention, particularly advantageous. The instant process is very feasibly performed even on large scale and allows to produce enantiomerically enriched amino acids in an extremely easy and robust fashion. Nonetheless, the results achieved in view of enantiomeric purity and yield are outstandingly superb in the light of the easiness of the process of the invention. In view of the N-protected amino acids used for instant process, these can be chosen by the skilled man. Amino acids preferably resolved are, however, a- and b-amino acids. Taking these N-protected a-amino acids are most preferred. The process of the present invention is advantageously performed in an organic solvent which can contain water to an extent that it does not adversely affect the crystallisation, e. g. through phase separation. In particular the solvent used is a polar one, preferably selected from the group consisting of esters, ethers, ketones, alkohols, aromatic hydrocarbons or mixtures WO 2005/058776 PCT/EP2004/013194 3 thereof. Especially preferred is a process in which the solvent is selected from the group consisting of ethyl acetate, ethanol, methyl-tert.-butyl ether, toluene. The choice of an enantiomerically pure N-unprotected b-amino acid derivative as resolving agent is up to the skilled man's discretion. The b-amino acid derivative used may be chosen by performing routine testing in present process and comparing the results. Enaniomerically pure b-amino acids are commercially available or can advantageously be made according to processes known in the art (DE10220740 or DE10320211 and cited literature). Also the generation of the respective derivatives, like esters or amides, is known to the skilled worker (Chemistry of Amino Acids, Wiley&Sons 1961, J.P. Greenstein, M Winitz). Preferably an enantiomerically pure N-unprotected P-amino acid derivative according to formula (I) or (II) is used, wherein R1, R2 independently of one another denote H or R, R, R' independently of one another denote (C1-C6) -alkyl, (C2-C8)-alkoxyalkyl, (C6-C18) -aryl, (C7-C19) -aralkyl, (C3-C18) -heteroaryl, (C4-C19) -hcteroaralkyl, (C1-C8) -alkyl- (C6-C16)-aryl. (C1-C8) -alkyl- (C3-C18) -heteroaryl, (C3-C8)- cycloalkyl, (C3-C8)-alkyl-(C3-C8)-cycloalkyl, (C3-C8)- cycloalkyl- (C1-C8) -alkyl, or R and R' or R and R'/R1 or R' and R'/R1 represent a (C3-C5)-alkylene bridge mono- or polysubstituted with (C3-C6) -alkyl, HO- (C1 -C8) -alkyl, (C1-C8)-alkoxy, (C2-C8)-alkoxyalkyl, (C6-C18)-aryl, (C7-C19) -aralkyl, WO 2005/058776 PCT/EP2004/013194 4 (C1-C8) -alkyl- (C6-C18) -aryl. (C3-c8) -cycloalkyl, (C1-C8) -alkyl- (C3-C8) -cycloalkyl, (C3-C8)-cycloalkyl-(C1-C8)-alkyl, R" being HO-, (C1-C8)-alkyl, (C2-C8)-alkoxyalkyl, (C6-C18)-aryl, (C7-C19) -aralkyl, (C3-C18)-heteroaryl, (C4-C19)-heteroaralkyl, (C1-C8) -alkyl- (C6-C18) -aryl, (C1-C8)-alkyl-(C3-C18)-heteroaryl, (C3-C8)-cycloalkyl, (C1-C8)-alkyl- (C3-C8) -cycloalkyl, (C3-C8) -cycloalkyl- (C1-C8) -alkyl. Especially, suitable for present process are esters of b-amino acids. Preferably aromatic ester like 3-amino-3-phenylpropionic acid ethyl ester or the respective amide is used. The temperature applied during the crystallisation process shall be as high or as low to allow a maximum crystallisation yield with an optimum of enantiomeric excess in view of the N-protected amino acids. The temperature is, therefore, preferably held within a range of -30° to 100°C. More preferably the temperature is set to -25 to 50°C, and most preferred the temperature varies between -20°C and 30°C. After crystallisation the mixture is worked-up according to the knowledge of a skilled worker. Most convenient seems to be to separate the solid material from the mixture via filtration. Subsequently the already highly enriched diastereomeric salt pair can be recrystallised to maximise diastereomeric purity. Afterwards the enantiomerically enriched N-protected amino acid can be liberated from this salt by measures known to the man in the art, e.g. ion-exchange or classical acidification and extraction techniques. It is possible in view of the instant invention to exchange substrates and crystallising agent for each other to make the process one, which allows to obtain enantiomerically enriched N-unprotected b-amino aicds. Hence, the present WO 2005/058776 PCT/EP2004/013194 5 invention also concerns a process} for the preparation of enantiomerically enriched N-unprotected P-amino acid derivates, wherein a mixture of both enantimers of an N-unprotected b-amino acid derivative is resolved through crystallisation of the salt of one enantiomer of the N-unprotected b-amino acid derivative and an enantiomerically pure N-protected a-amino acid. Preferred embodiments of this process are in line with those mentioned for performing the process for the preparation of N-protected amino acids. Thus the present invention can easily be performed e.g. by dissolving the racemic N-protected amino acid in an appropriate solvent. Upon total dissolution the enantiomerically pure N-unprotected b-anuno acid derivative, especially the ester, is added in an amount sufficient to obtain optimal crystallisation results in view of yield and diastereomeric purity. The molar ratio of added enantiomerically pure N-unprotected P-amino acid derivative to the antipode of N-protected amino acid to be crystallised can vary from 1:0,1 to 1:2, preferably from 1:0,5 to 1:1,8 or most preferably from 1:0,7 to 1:1,5. Preferably after cooling and completion of crystallisation the solid material is - as already stated - separated via filtration from the mixture and optionally recrystallised. Liberation of the desired N-protected amino acid takes place preferably through acidification and extraction. In view of the production of P-amino acid derivates above mentioned procedure can be applied like with the exception that N-protected amino acids have to be substituted for N-unprotected b-amino acid derivates and vice versa. N-Protected amino acid mean any carboxylic acid having both a carboxyl-function and an protected amino-function within one molecule. Preferably an a-amino acid being protected by a common protective group at the a-nitrogen atom of the amino acid is used. Suitable protective groups are known to WO 2005/058776 PCT/EP20O4/013194 6 the skilled worker (Green et al. Protective Groups in Organic Chemistry, Wiley&Sons, 1981). Preferably residues selected from the groups consisting of Z-, Boc-, Moc-, Eoc-, Fmoc-, formyl-, acetyl-, phthaloyl-radicals are chosen. a-Amino acid denotes a naturally or unnaturally occurring amino acid like depicted in Bayer-Walter, Lehrbuch der organischen Chemie, S. Hirzel Verlag, Stuttgart, 22. Auflage, S. 822 et seq. Unnatural amino acids are those mentioned for example in DE19903268.8. Most preferred in this regard is the resolution of N-protected tert.-leucine. Methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl or octyl, together with all their bond isomers, can be considered as (C1-C8)-alkyl radicals. The (C1-C8)-alkoxy radical corresponds to the (C1-C8) -alkyl radical, with the proviso that this is bonded to the molecule via an oxygen atom. As (C2-C8) -alkoxyalkyl, radicals in which the alkyl chain 1 is interrupted by at least one oxygen function are meant, wherein two oxygen atoms cannot be joined to one another. The number of carbon atoms gives the total number of carbon atoms contained in the radical. A (C3-C5)-alkylene bridge is a carbon chain with three to five C atoms, this chain being bonded to the molecule in question via two different C atoms. The bridge optionally can be unsaturated and or can contain one or more heteroatoms like N, O, S within the chain. The radicals just described can be mono- or polysubstituted with (C1-C8) -alkoxy, (C1-C8) -alkyl, halogens and/or radicals containing N, 0, P, S or Si atoms. These are particularly alkyl radicals of the type mentioned above having one or more of these hetercatoms in their chain or being bonded to the molecule via one of these heteroatoms. (C3-C8)-Cycloalkyl means cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl radicals etc. These WO 2005/058776 PCT/EP2004/013194 7 can be substituted with one or more halogens and/or radicals containing N, 0, P, S or Si atoms and/or can have N, 0, P or S atoms in the ring, such as e.g. 1-, 2-, 3-, 4-piperidyl, 1-, 2-, 3-pyrrolidinyl, 2-, 3-tetrahydrofuryl, 2-, 3-, 4-morpholinyl. A (C3-C8)-Cycloalkyl- (C1-C8)-alkyl radical refers to a cycloalkyl radical as set out above, which is bonded to the molecule via an alkyl radical as stated above. (C1-C8) -Acyloxy within the framework of the invention means an alkyl radical as defined above with a maximum of 8 C atoms, which is bonded to the molecule via a COO- function. (C1-C8)-Acyl within the framework of the invention means an alkyl radical as defined above with a maximum of 8 C atoms, which is bonded to the molecule via a CO- function. A (C6-C18) -aryl radical is understood to mean an aromatic radical with 6 to 18 C atoms. These include in particular compounds such as phenyl, naphthyl, anthryl, phenanthryl or biphenyl radicals, or systems of the type described above annelated to the molecule in question, such as e.g. indenyl systems, which can optionally be substituted with (C1-C8)-alkyl, (C1-C8)-alkoxy, (C1-C8)-acyl or (C1-C8)-acyloxy. A (C7-Ci9)-aralkyl radical is a (C6-C18)-aryl radical bonded to the molecule via a (Ci-C8)-alkyl radical. A (C3-C18) -heteroaryl radical within the framework of the invention refers to a five-, six- or seven-membered aromatic ring system of 3 to 18 C atoms, which contains heteroatoms such as e.g. nitrogen, oxygen or sulfur in the ring. In particular, radicals such as 1-, 2-, 3-furyl, such as 1-, 2-, 3-pyrrolyl, 1-, 2-, 3-thienyl, 2-, 3-, 4-pyridyl, 2-, 3-, 4-, 5-, 6-, 7-indolyl, 3-, 4-, 5-pyrazolyl, 2-, 4-, 5-imidazolyl, acridinyl, quinolinyl, phenanthridinyl and 2-, 4-, 5 , 6-pyrimidinyl are considered as such heteroaromatics . WO 2005/058776 PCT/EP2004/013194 8 A (C4-C19)-heteroaralkyl means a heteroaromatic system corresponding to the (C7-C19)-aralkyl radical. Fluorine, chlorine, bromine and iodine are suitable as halogens (Hal). The term enantiomerically enriched within the framework of the invention means the proportion of an enantiomer in a mixture with its optical antipode in a range of >50 % and follows: ((Enantiomerl ] - [Enantiomer2]) / ( [Enantiomerl] ? (Enantiomer2)) «ec value The term diastereomerically enriched or diastereomeric purity is meant as to define the proportion of one diastereomer in a mixture with its other diastereomers in a range of >50 % and The naming of the molecules used according to the invention contains, within the framework of the invention,,all possible diastereomers, the two optical antipodes of any diastereomer also being included therein. The literature references cited in this document are deemed to be contained in the disclosure. WO 2005/058776 PCT/EP2004/01J194 9 Examples: Example 1: A solution of 59,9 g Benzyloxycarbonylphenylalanine in ethyl acetate was treated with 60 g (R)-3-Amino-3-phenylpropionic acid ethyl ester in ethyl acetate at 35°C, cooled to 0°C and stirred for 40 h. After filtration and drying 30,5 g of a 1:1 salt of R-Benzyloxycarbonylphenylalanine x (R)-3-Amino-3-phenylpropionic acid ethyl ester (86:14 optical purity) was obtained. Example 2: A solution of 50,2 g Benzyloxycarbonylvaline in methyl-tert.-butyl ether was treated with 60 g (S)-3-Amino-3-phenylpropionic acid ethyl ester in methyl-tert.pbutyl ether at 30°C, cooled to 0°C and stirred for 30 h. After i filtration and drying 27,1 g of a 1:1 salt of (S)-Benzyloxycarbonylvaline x (S) -3-Amino-3-phenylpropionic acid ethyl ester (97:3 optical purity) was obtained. Example 3: A solution of 47,6 g Benzyloxycarbonylamino-butyric acid in methyl-tert.-butyl ether was treated with 21,3 g (S)-3-Amino-3-phenylpropionic acid ethyl ester in methyl-tert. -butyl ether at 30°C, cooled to 10°C and stirred for 10 h. After filtration and drying 45,1 g of a 1:1 salt of (S)-Benzyloxycarbonylamino-butyric acid x (S)-3-Amino-3-phenylpropionic acid ethyl ester (92:8 optical purity) was obtained. Example 4: A solution of 106,1 g Benzyloxycarbonylami.no-tert. leucine in methyl-tert.-butyl ether was treated with 42,56 g (R)-3-Amino-3-phenylpropionic acid ethyl ester in methyl-tert.-butyl ether at 35°C, cooled to 0°C and stirred for 15 h. After filtration and drying 71,8 g of a 1:1 salt of (R)-Benzyloxycarbonylamino-butyric acid x (R)-3-Amino-3-phenylpropionic acid ethyl ester (97:3 optical purity) was obtained. Example 5: A solution of 59,9 g Benzyloxycarbonylamino-tert.-leucine in ethyl acetate was treated with 60 g (R)-3-Amino-3-phenylpropionic acid ethyl ester in ethyl acetate at 42°C, cooled to -10°C and stirred for 10 h. After filtration and drying 38,5 g of a 1:1 salt of (R)-Benzyloxycarbonylamino-tert.-leucine x (R)-3-Amino-3-phenylpropionic acid ethyl ester (98,8:1,2 optical purity) was obtained. After recristallisation all salt pairs were obtained in an optical purity of >99:1. WO 2005/058776 PCT/EP2004/013194 11 Claims: 1. Process for the preparation of enantiomerically enriched N-protected amino acids, wherein a mixture of both enantiomers of an N-protected amino acid is resolved through crystallisation of the salt of one enantiomer of the N-protected amino acid and an enantiomerically pure N-unprotected P-amino acid derivative. 2. Process according to claim 1, wherein the N-protected amino acid is an N-protected a-amino acid. 3. Process according to claim 1 and/or 2, wherein the crystallisation is performed in a polar solvent. 4. Process according to one or more of the preceding claims, wherein the enantiomerically pure N- unprotected b-amino acid derivative is an ester or an amide. 5. Process according to one or more of the prebeding claims, wherein the temperature during crystallisation is between -20°C and 30°C. 6. Process according to one or more of the preceding claims, wherein the crystallised salt is separated from the mixture via filtration. 7. Process for the preparation of enantiomerically enriched N-unprotected b-amino acid derivates, wherein a mixture of both enantiomers of an N-unprotected b- amino acid derivate is resolved through crystallisation of the salt of one enantiomer of the N-unprotected b-amino acid derivative and an enantiomerically pure N-protected a-amino acid. 8. Process according to claim 7, wherein the crystallisation is performed in a polar solvent. WO 2005/058776 PCT/EP2004/013194 12 9. Process according to claims 7 to 8, wherein the enantiomerically pure N-unprotected P-amino acid derivative is an ester or an amide. 10. Process according to claims 7 to 9, wherein the temperature during crystallisation is between -20°C and 30°C. 11. Process according to claims 7 to 10, wherein the crystallised salt is separated from the mixture via filtration. Dated the 24th day of May.2006.

Documents:

01387-kolnp-2006 abstract.pdf

01387-kolnp-2006 assignment.pdf

01387-kolnp-2006 claims.pdf

01387-kolnp-2006 correspondence others.pdf

01387-kolnp-2006 description (complete).pdf

01387-kolnp-2006 form-1.pdf

01387-kolnp-2006 form-2.pdf

01387-kolnp-2006 form-3.pdf

01387-kolnp-2006 form-5.pdf

01387-kolnp-2006 international publication.pdf

01387-kolnp-2006 international search report.pdf

01387-kolnp-2006 pct form.pdf

01387-kolnp-2006 priority document.pdf

01387-kolnp-2006-correspondence others-1.1.pdf

01387-kolnp-2006-correspondence-1.2.pdf

01387-kolnp-2006-form-18.pdf

01387-kolnp-2006-international search authority report-1.1.pdf

1387-KOLNP-2006 RECONSTITUET.pdf

1387-KOLNP-2006-(12-06-2013)-CORRESPONDENCE.pdf

1387-KOLNP-2006-(12-08-2013)-CORRESPONDENCE.pdf

1387-KOLNP-2006-ABSTRACT.pdf

1387-KOLNP-2006-ASSIGNMENT 1.1.pdf

1387-KOLNP-2006-CLAIMS.pdf

1387-KOLNP-2006-CORRESPONDENCE 1.2.pdf

1387-KOLNP-2006-CORRESPONDENCE-1.1.pdf

1387-KOLNP-2006-DESCRIPTION COMPLATE.tif

1387-KOLNP-2006-FORM 1.pdf

1387-KOLNP-2006-FORM 13.1.1.pdf

1387-KOLNP-2006-FORM 13.1.2.pdf

1387-KOLNP-2006-FORM 13.pdf

1387-KOLNP-2006-FORM 2.pdf

1387-KOLNP-2006-OTHERS.pdf

1387-KOLNP-2006-PA.pdf

1387-KOLNP-2006-PETITION UNDER RULE 137.pdf

1387-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf