Synthesis of enantiopure 1,4-ethyl- and 1,4-ethylene-bridged cispentacin by lipase-catalyzed enantioselective ring opening of β-lactams
摘要:
1, 4-Ethyl- and 1,4-ethylene-bridged cispentacin enantiomers 1a, 1c and 2a, 2c were prepared through the lipase-catalyzed enantioselective ring opening of racemic exo-3-azatricyclo[4.2.1.0(2.5)]nonan-4-one, (+/-)-1, and exo-3-azatricyclo[4.2.1.0(2.5)]non-7-en-4-one, (+/-)-2. High enantioselectivity (E >200) was observed when the Lipolase-catalyzed reactions were performed with 1 equiv of H2O in diisopropyl ether at 70degreesC. The resolved beta-amino acids 1a and 2a (yield,46%) and beta-lactams 1b and 2b (yield greater than or equal to40%) could be easily separated. The ring opening of lactam enantiomers with 18% HCl afforded the corresponding beta-amino acid hydrochloride enantiomers (ee greater than or equal to98%). (C) 2004 Elsevier Ltd. All rights reserved.