Total synthesis of (+/-)-stemonamide and (+/-)-isostemonamide

Two different approaches to the alkaloids stemonamide and isostemonamide using N-acyliminium chemistry are described. The approach using an aldol spirocyclization to construct the second contiguous spirocenter was successful. The total synthesis of these products was completed by 1,4-addition of an appropriate side chain, alpha -methylenation by Mannich reaction, double bond isomerization and closure of the azepine ring. (C) 2002 Elsevier Science Ltd. All rights reserved.