Lipase promoted asymmetric trans-esterification of 4-alkyl-, 3-alkyl- and 3,4-dialkyloxetan-2-ones with ring-opening

Kinetic resolution of (+/-)-4-substituted [(+/-)-1], 3-substituted [(+/-)-4 ] and 3,4-disubstituted oxetan-2-ones [(+/-)-7] was effected by the action of lipases in organic solvents. The substrates (+/-)-1, (+/-)-4 and (+/-)-7 were prepared by [2 + 2] cycloaddition of aldehydes with ketene, intramole cular substitution of 3-bromoalkanoic acids and the Adams cyclization of an ti- and syn-3-hydroxyalkanoic acids, respectively. Lipase PS exhibited good activity towards all the oxetanones and was employed for the resolution ex periments except with (+/-)-4-methyloxetan-2-one (+/-)-1a for which PPL was used. The stereoselectivity was satisfactory for obtaining oxetan-2-ones o f high ee's except for a few cases. The configuration of new compounds was established by chemical correlation and CD spectroscopy.