摘要:
                                A highly diastereoselective 1,4-addition involving Davies' lithium amide is employed as the key reaction to prepare, in five steps from ethyl acetoacetate, an enantiomerically pure keto protected beta,beta'-ketoaminoester. This latter was reacted with aldehydes in an intramolecular Mannich process and furnished a direct and stereoselective access to substituted homopipecolates. The validity of this approach was achieved through a new formal asymmetric synthesis of alkaloid (+)-Calvine. (C) 2004 Elsevier Ltd. All rights reserved.