Kinetic resolution of oxime esters with lipases — synthesis of enantiomerically enriched building blocks with quaternary carbon centers and formal total synthesis of perhydro histrionicotoxin

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Abstract
Enantiomerically enriched oximes bearing stereogenic quaternary carbon centers can be obtained by lipase-catalyzed kinetic resolution of oxime esters. Substrate specificity, solvent effects, and the use of different lipases are discussed. Kinetic resolution of butyrylated oximes by lipase PS in the presence of n-butanol gave the best ee-values of both the saponified oxime and the residual oxime ester. Subsequent stereospecific Beckmann rearrangement of an enantiomerically enriched oxime provided lactams, which could be employed for the synthesis of optically active perhydro histrionicotoxin.Key words: oxime, lipase, kinetic resolution, Beckmann rearrangement, perhydro histrionicotoxin.