Asymmetric Synthesis of the Core Structure of the Melodinus Alkaloids.

Abstract The strategy developed for an asymmetric synthesis of (+)-meloscine ( 1 ) features an early incorporation of the aromatic ring in 1 as the 5-benzyl substituent in 2 . The highly diastereoselective Birch reduction-alkylation 2 → 3 , the unraveling of 3 to the butyrolactone carboxylic acid 7 , and the Mannich cyclization 9c → 10c are the key steps in the synthesis of the core tricyclic unit in 1 .