Asymmetric Michael addition of the enamine derived from 2,2-dimethylcyclopentanecarbox-aldehyde and (S)-prolinol methyl ether to nitroethylene afforded the adduct of 75-76% ee, which finally yielded enantiomerically pure (+)-polyzonimine, a nitrogen-containing spirocyclic compound isolated from the defensive glands of a milliped, Polyzonium rosalbum. By converting (+)-polyzonimine into (4S,5R,6S)-(+)-nitropolyzonamine, the hitherto uncertain absolute configuration of the former was established as S.
alkaloids; asymmetric synthesis; insects; spirocyclic compounds
