Antineoplastic agents. 450. Synthesis of (+)-pancratistatin from (+)-narciclasine as relay(1a)

(+)-Narciclasine (2) available in quantity from certain Amaryllidaceae species or by total synthesis was employed as a precursor for a 10-step synthetic conversion (3.6% overall yield) to natural (+)-pancratistatin (1a). The key procedures involved epoxidation of natural (+)-narciclasine (2) to epoxide 6, reduction to diol 8, and formation of cyclic sulfate 12 and its ring opening with cesium benzoate followed by saponification of the benzoate to afford (+)-pancratistatin (1a).