Total synthesis of polycavernoside A

Abstract

The first total synthesis of polycavernoside A (1), which was isolated from the red alga Polycayernosa tsudai as a causative toxin of fatal human intoxication in Guam in 1991, is described. The synthetic key steps involve the connection of the acyl anion equivalent (9) derived from 3 with aldehyde (8), the stereoselective formation of 6-membered cyclic methyl acetal (7) by lactonizationfrom the requisite secoic acid (22), the stereoselective hydrolytic reconstruction of the acetal moiety of 7 leading to 5-membered cyclic hemiacetal (6), the glycosylation of 6 with 4 derived from L-fucose and D-xylose, and the final triene formation using cross-coupling reaction.