Asymmetric synthesis of the core structure of the melodinus alkaloids

The strategy developed for an asymmetric synthesis of (+)-meloscine (1) fea tures an early incorporation of the aromatic ring in 1 as the 5-benzyl subs tituent in 2. The highly diastereoselective Birch reduction-alkylation 2 -- > 3, the unraveling of 3 to the butyrolactone carboxylic acid 7, and the Ma nnich cyclization 9c --> 10c are the key steps in the synthesis of the core tricyclic unit in 1. (C) 1999 Elsevier Science Ltd. All rights reserved.