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, intramolecular substitution of 3-bromoalkanoic acids and the Adams cyclization of anti- and syn-3-hydroxyalkanoic acids, respectively. Lipase PS exhibited good activity towards all the oxetanones and was employed for the resolution experiments except with (±)-4-methyloxetan-2-one (±)-1a for which PPL was used. The stereoselectivity was satisfactory for obtaining oxetan-2-ones of high ee’s except for a few cases. The configuration of new compounds was established by chemical correlation and CD spectroscopy.