Sirodesmins A, B, C, and G, antiviral epipolythiopiperazine-2,5-diones of fungal origin: X-ray analysis of sirodesmin A diacetate

Abstract

The isolation, structures, and absolute configurations of sirodesmins A, B, C, and G, epipolythiopiperazine-2,5-dione antibiotics produced by Sirodesmium diversum, are reported. The structure of sirodesmin A (1), an epidithiopiperazinedione, was determined by X-ray analysis of the derived diacetate (6). The structures of sirodesmins B (3), C (2), and G (7), epi-tetra-,-tri-, and -di-thiopiperazinediones, respectively, were determined by comparison of their chemical and spectroscopic properties with those of sirodesmin A. Sirodesmins B and C differ from sirodesmin A only in the size of the polysulphide bridge; sirodesmins A and G are epimers.