Structure of virescenoside C, a new metabolite of Oospora virescens (Link) Wallr

Abstract

Chemical investigation of the glycosidic constituents of Oospora virescens (Link) Wallr. resulted in the isolation of several glycosides. We have shown recently [1] that two of them, named virescenoside A (I) and B (II) are β‐d‐altropyranosides of virescenol A and B; these diterpenic aglycones have been found to have the structure of isopimaradien‐2α,3β‐19‐triol (IV) and isopimaradien‐3β,19‐diol (V), respectively [2].In this paper we describe the isolation and structure of virescenoside C, a new metabolite of Oospora virescens. The results obtained show that virescenoside C (IIIa), C26K40O7, m. p. 160—162°, [α]d− 71,4°, is a β‐d‐altropyranoside of virescenol C, which is found to have the structure of 3‐keto 19‐hydroxy isopimaradiene (VIa).These results are based on physical evidence (infra‐red, nuclear magnetic resonance and mass spectra) and particularly on the chemical correlation with virescenol B and virescenoside B.Virescenoside C seems to be the third example of an altroside found in nature.