ASYMMETRIC-SYNTHESIS OF INDOLE ALKALOIDS FROM (L)-TRYPTOPHAN - FORMAL SYNTHESES OF (-)-KOUMINE, (-)-TABERPSYCHINE AND (-)-KOUMIDINE

The reaction of (L)-tryptophan methyl ester with methyl 4-oxobutanoate under conditions of kinetic control gave a high yield of the cis-1,3-disubstituted tetrahydro-beta-carboline (6); a simple five step procedure allowed this to be transformed into the optically pure (e.e. > 95%) bridged ketone (-)-(17), whose (+) isomer has previously been used in the syntheses of (+)-koumine (1), (+)-taberpsychine (2) & (+)-koumidine (3).