TOTAL SYNTHESIS OF (-(8S,13R)-CYCLOCELABENZINE())

An asymmetric synthesis of the spermidine alkaloid (+)-cyclocelabenzin e (la) and its (-)-(13S)-epimer Ib is described using optically active (+)-(3S)-3-amino-3-phenylpropionic acid as the chiral building block. The isoquinolin-1-one fragment 15 was synthesized by a modified Bisch ler-Napieralski reaction. The relative configuration of the (-)-isomer was determined by an X-ray crystal-structure analysis, which enabled us to determine the absolute configuration of natural (+)-1a as (8S,13 R).