Lipase-catalyzed Kinetic Resolution of (±)-trans- andcis-2-Azidocycloalkanols

The lipase-catalyzed kinetic resolution of trans- and cis-2-azidocycloalkanols and the preparation of enantiomerically pure trans- and cis-2-aminocycloalkanols are described. Four kinds of lipases were screened for the acetylation of trans- and cis-2-azidocycloalkanols. Among them, Pseudomonas sp. lipases (lipase PS and lipase AK, Amamo Pharmaceutical Co.) showed the highest enantioselectivity. These products were converted to the corresponding 2-aminocycloalkanols to determine their enantiomeric excess (ee) and absolute configurations by HPLC and CD analyses, using (S)-TBMB carboxylic acid [(S)-2-tert-butyl-2-methyl-1,3-benzodioxole-4-carboxylic acid] as the chiral conversion reagent. The results of the CD analysis proved N,O-bis-(S)-TBMB carboxylated cis-2-aminocycloalkanols to adopt a predominantly N-equatorial conformation. The partially resolved trans- and cis-2-aminocycloalkanols, except for trans-2-aminocyclopentanol, were recrystallized from ethyl acetate to give enantiomerically pure forms.