SYNTHETIC STUDIES ON MPC1001: A DIPOLAR CYCLOADDITION APPROACH TO THE PYRROLIDINE RING SYSTEM

Synthesis of Violaceic Acid and Related Compounds through Aryl Triazene

MPC1001 is a potent anticancer natural product that contains a violaceic acid moiety. Herein we report the total synthesis of the natural product violaceic acid and its derivative. In this approach, a triazene-directed Ullman coupling proved to be highly effective. We converted the triazene to a hydroxy group by means of a palladium-catalyzed reaction. Treatment of the triazene with trifluoroacetic acid generated an arenediazonium ion that produced an aryl radical, leading to the protodediazoniation and a tricyclic product.

Emestrins: Anti-Cryptococcus Epipolythiodioxopiperazines from Podospora australis

Eleven emestrin-type epipolythiodioxopiperazines, including four new compounds, emestrins H-K (1-4), were isolated from the crude extracts of two strains of the coprophilous fungus Podospora australis. The structures of 1-4 were established primarily by analysis of NMR data, and the absolute configuration of C-6 in 1 was independently assigned using the modified Mosher method. Four of the known emestrins obtained (emestrins C-E and MPC1001C) were found to selectively inhibit the growth of Cryptococcus neoformans. These results also represent the first report of chemistry from any strain of P. australis.