A new synthesis of enantiopure (1'S,3'R,2R)- and ( 1'R, YS,2R)-3'-aminocyclopentylglycines (-)-12a and (-)-12b was performed by taking advantage of (+/-)-2-amino-3-oxo-norbornane-2-carboxylic acid derivative exo-2 as the starting material. The use of an acylase from Aspergillus melleus in phosphate buffer allowed the 'one-pot' transformation of the beta-ketoester (+/-)-exo-2 into 3'-carboxy-cyclopentylglycine (+/-)-3a and (+/-)-3b, via a retro-Dieckman reaction, which, by direct kinetic resolution, were isolated as compounds (-)-3a and (-)-3b.Starting from a mixture of (-)-3a and (-)-3b, enantiopure 3'-aminocyclopentylglycines (-)-12a and (-)-12b as well as differently substituted 3-amino derivatives were prepared efficiently using a very simple synthetic protocol that requires a single chromatographic purification. (C) 2008 Elsevier Ltd. All rights reserved.
Chemoenzymatic resolution of epimeric cis 3-carboxycyclopentylglycine derivatives
reactions. The synthesis incorporates a concise and inexpensive chemoenzymatic resolution of racemic compounds 4,5a, the N,O-protected derivatives of aminoacids 10,11. Systematic screening with different enzymes and microorganisms was performed to select a very efficient catalyst for the separation of the racemic mixtures. The reaction conditions allowing deprotection of both ester and amino functions