TOTAL SYNTHESIS AND ASSIGNMENT OF CONFIGURATION OF LISSOCLINAMIDE-7

The first total synthesis of lissoclinamide 7, a 21-membered cyclopept ide isolated from Lissoclinum bistratum, was accomplished in 23 steps and 4.4% overall yield. The extraordinary configurational lability of the thiazoline segments was overcome by a novel strategy combining the use of the Burgess reagent for multiple simultaneous oxazoline and th iazoline formations and an efficient oxazoline --> thiazoline heterocy cle interconversion. In addition to the total synthesis, this work hig hlights the scope of alternative strategies toward Lissoclinum peptide s and presents the preparation of analogues for SAR studies of the cyt otoxic effects of this family of marine natural products.