LIPASE-CATALYZED TRANSESTERIFICATION IN ORGANIC-SOLVENTS - PREPARATION AND ENANTIODIFFERENTIATION OF OPTICALLY ENRICHED 4(5)-ALKYLATED 1,4(1,5)-OLIDES

Porcine pancreatic lipase (PPL) catalyzed intramolecular transesterification of n-propyl esters of 4(5)-hydroxyalkanoic acids (C5-C12) in diethyl ether (20-degrees-C) yielded (S)-4-alkylated 1,4-olides of high optical purity (ee > 80%) and optically pure (R)-4-hydroxyalkanoic-n-propylesters, but exhibited low enantioselectivity for (S)-5-alkylated 1,5-olides (ee = 10-20%). The chiral analysis of 4(5)-hydroxyalkanoic esters was performed by HRGC and HPLC after their derivatization with (R)-(+)-1-phenylethylisocyanate, (S)-O-acetyllactic acid chloride, and (R)-(+)-alpha-methoxy-alpha-trifluoromethylphenylacetic acid chloride. The enantiodifferentiation of 1,4(1,5)-olides was achieved by HPLC on a chiral phase (ChiraSpher) using an on-line optical rotation detector (ChiraMonitor).