Microbial/enzymatic synthesis of chiral drug intermediates

Biocatalytic processes were used to prepare chiral intermediates for pharmaceuticals. These include the following processes. Enzymatic synthesis of [4S-(4a,7a,10ab)]1-octahydro-5-oxo-4-[[(phenylmethoxy) carbonyl]amino]-7H-pyrido-[2,1-b] [1,3]thiazepine-7-carboxylic acid methyl ester (BMS-199541-01), a key chiral intermediate for synthesis of a new vasopeptidase inhibitor. Enzymatic oxidation of the epsilon-amino group of lysine in dipeptide dimer N2-[N[[(phenylmethoxy)carbonyl] L-homocysteinyl] L-lysine)1,1-disulfide (BMS-201391-01) to produce BMS-199541-01 using a novel L-lysine epsilon-aminotransferase from S. paucimobilis SC16113 was demonstrated. This enzyme was overexpressed in E. coli, and a process was developed using recombinant enzyme. The aminotransferase reaction required alpha-ketoglutarate as the amine acceptor. Glutamate formed during this reaction was recycled back to alpha-ketoglutarate by glutamate oxidase from S. noursei SC6007. Synthesis and enzymatic conversion of 2-keto-6-hydroxyhexanoic acid 5 to L-6-hydroxy norleucine 4 was demonstrated by reductive amination using beef liver glutamate dehydrogenase. To avoid the lengthy chemical synthesis of ketoacid 5, a second route was developed to prepare the ketoacid by treatment of racemic 6-hydroxy norleucine (readily available from hydrolysis of 5-(4-hydroxybutyl) hydantoin, 6) with D-amino acid oxidase from porcine kidney or T. variabilis followed by reductive amination to convert the mixture to L-6-hydroxynorleucine in 98% yield and 99% enantiomeric excess. Enzymatic synthesis of (S)-2-amino-5-(1,3-dioxolan-2-yl)-pentanoic acid (allysine ethylene acetal, 7), one of three building blocks used for synthesis of a vasopeptidase inhibitor, was demonstrated using phenylalanine dehydrogenase from T. intermedius. The reaction requires ammonia and NADH. NAD produced during the reaction was recycled to NADH by oxidation of formate to CO2 using formate dehydrogenase. Efficient synthesis of chiral intermediates required for total chemical synthesis of a beta 3 receptor agonist was demonstrated. These include: (a) microbial reduction of 4-benzyloxy-3-methanesulfonylamino-2'-bromoacetophenone 9 to corresponding (R)-alcohol 10 by S. paucimobilis SC16113, (b) enzymatic resolution of racemic alpha-methyl phenylalanine amide 11 and alpha-methyl-4-hydroxyphenylalanine amide 13 by amidase from M. neoaurum ATCC 25795 to prepare corresponding (S)-amino acids 12 and 14, and (c) asymmetric hydrolysis of methyl-(4-methoxyphenyl)-propanedioic acid ethyl diester 15 to corresponding (S)-monoester 16 by pig liver esterase. (S)[1-(acetoxyl)-4-(3-phenyl)butyl]phosphonic acid diethyl ester 21, a key chiral intermediate required for total chemical synthesis of BMS-188494 (an anticholesterol drug) was prepared by stereoselective acetylation of racemic [1-(hydroxy)-4-(3-phenyl)butyl]phosphonic acid diethyl ester 22 using G. candidum lipase. Lipase-catalyzed stereoselective acetylation of racemic 7-[N,N'-bis-(benzyloxy-carbonyl)N-(guanidinoheptanoyl)]-alpha-hydroxy-glycine 24 to corresponding S-(-)-acetate 25 was demonstrated. S-(-)-acetate 25 is a key intermediate for total chemical synthesis of (-)-15-deoxyspergualin 23, an immunosuppressive agent and antitumor antibiotic. Stereoselective microbial reduction of (1S)[3-chloro-2-oxo-1-(phenyl-methyl)propyl] carbamic acid, 1,1-dimethyl-ethyl ester 26 to corresponding chiral alcohol 27a (a key chiral intermediate for HIV protease inhibitors) was also demonstrated. Stereospecific enzymatic hydrolysis of racemic epoxide RS-1-[2',3'-dihydro benzo[b]furan-4'-yl]-1,2-oxirane 29 the corresponding R-diol 30 and unreacted chiral S-epoxide 28 was demonstrated using R. glutinis and A. niger. Dynamic resolution of racemic diol RS-1-[2',3'-dihydrobenzo[b]furan-4'-yl]-ethane-1,2-diol 32 to corresponding S-diol S-1-[2',3'-dihydrobenzo[b]furan-4'-yl]-ethane-1,2-diol 31 was demonstrated using C. boidinii and P. methanolica. Chiral (S)-epoxide 28 and (S)-diol 31 are key intermediates for a new prospective circadian modulator drug. Enzymatic resolution of racemic 2-pentanol and 2-heptanol by lipase B from Candida antarctica was demonstrated. S-(+)-2-pentanol is a key chiral intermediate required for synthesis of anti-Alzheimer's drugs.