Studies on the Synthesis of Phlegmarine-Type Lycopodium Alkaloids: Enantioselective Synthesis of (−)-Cermizine B, (+)-Serratezomine E, and (+)-Luciduline

The synthesis of the Lycopodium alkaloids, (−)-cermizine B, (+)-serratezomine E, and (+)-luciduline using phenylglycinol-derived tricyclic lactams as chiral scaffolds, is reported. The requisite lactams are prepared by a cyclocondensation reaction between (R)- or (S)-phenylglycinol and the substituted δ-keto ester 11, easily accessible from (R)-pulegone. The factors governing the stereoselectivity of these cyclocondensation reactions are discussed. Key steps of the synthesis from the stereochemical standpoint are the stereoselective elaboration of the allyl substituent to the (S)-2-(piperidyl)­methyl moiety and the stereoselective removal of the chiral inductor to give a cis-decahydroquinoline.