Construction of 4a,8a-cis-octahydroquinolin-7-one core using an intramolecular aldol type of cyclization: An application to enantioselective total synthesis of lepadin B

An intramolecular aldol type of cyclization of the piperidine derivative 1 proceeded in highly stereoselective manner to afford the desired 4a,8a-cis- octahydroquinolin-7-one. This key step involves a feature of the use of A(( 1,3)) strain as a control element, in biasing 1 towards the conformer desir ed for the above cyclization. An application of this aldol reaction to enan tioselective total synthesis of the marine alkaloid lepadin B is also descr ibed. (C) 1999 Elsevier Science Ltd. All rights reserved.