Dehydromicrosclerodermin B and Microsclerodermin J: Total Synthesis and Structural Revision

Abstract

The total synthesis of dehydromicrosclerodermin B and microsclerodermin J is described. Efficient approaches to the unusual amino acids in the target molecules were developed on the basis of a Negishi coupling (for Trp-2-CO2 H) and Blaise reaction (for Pyrr). An incorrect assignment of the pyrrolidinone stereochemistry of both compounds was confirmed by synthesizing epimers of the proposed structures. The spectroscopic data of these epimers were in complete agreement with those for the naturally derived material.

Keywords: cross-coupling; cyclic peptides; pyrrolidinones; structure elucidation; total synthesis.