Convergent asymmetric synthesis of indolizidines from (S)-5-(tosylmethyl)-2-pyrrolidinone: synthesis of (-)-delta-coniceine

The enantiomerically pure (S)-5-(tosylmethyl)-2-pyrrolidinone 2, prepared f rom commercially available (S)-pyroglutaminol, is dialkylated at the nitrog en atom and the cc-sulfonyl position using several dielectrophiles using so dium hydride as the base to diastereoselectively afford indolizidine deriva tives 5 and the less common hexahydropyrrolo[1,2-a]azepin-3-one 6 in modera te to good yield. This domino process has been applied to the synthesis of (-)-delta -coniceine. (C) 2001 Elsevier Science Ltd. All rights reserved.