Sporidesmins. Part IX. Isolation and structure of sporidesmin E

Abstract

Pithomyces chartarum produces metabolites similar to sporidesmin (I) having a sulphur–chlorine ratio greater than two. A fraction having a sulphur–chlorine ratio of three has been isolated and the crystalline meterial obtained, named sporidesmin E, was converted into sporidesmin when treated with triphenylphosphine. When sporidesmin was sulphurated with phosphorus pentasulphide and sulphur, it was possible to isolate sporidesmin E from the products. The n.m.r. spectrum of sporidesmin E at 25° was complex but at 95° was similar in many respects to the spectrum of sporidesmin. The facts are interpreted in terms of an epitrithiadioxopiperazine formula (III) though dimeric structures are not rigorously excluded.