Total synthesis and stereochemical reassignment of tasiamide B.

The first total synthesis of tasiamide B, an octapeptide bearing 4-amino-3-hydroxy-5-phenylpentanoic acid unit isolated from the marine cyanobacteria Symploca sp. is described. A simple and efficient way was found to avoid the pyroglutamylation of N(alpha)-Me-Gln and led to a reassignment of the N(alpha)-Me-L-Phe of tasiamide B to be N(alpha)-Me-D-Phe, which was also supported by 1D and 2D NMR.