Synthesis of optically pure a-tert-butyl 0-methyl (2S, 3R)-3-ethylhexahydroquinolinate (18) in 54-59% yield from L-aspartic acid was the foundation for a practical synthesis of (+)- vincamine. Conversion of L-aspartic acid to 18 was accomplished via two routes. In the first route, esterification was followed by mono-N-alkylation to attach the three-carbon residue. Nitrogen protection and intramolecular C-alkylation gave the piperidine, which was ...
[Baldwin, Jack E.; Moloney, Mark G.; North, Michael Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1989 , p. 833 - 834]