An asymmetric synthesis of the spermidine alkaloid (+)-cyclocelabenzine (1a) and its (−)-(13S)-epimer 1b is described using opticallyactive (+)-(3S)-3-amino-3-phenylpropionic acid as the chiral building block. The isoquinolin-1-one fragment 15 was synthesized by a modified Bischler-Napieralski reaction. The relativeconfiguration of the (−)-isomer was determined by an X-ray crystal-structure analysis