Fungal products. Part II. Structure and stereochemistry of the acid C18H16O5, a degradation product of wortmannin

Abstract

Degradation of the fungal metabolite, wortmannin, by dilute mineral acid yields, inter alia, an acid C₁₈H₁₆O₅ to which structure (Ia) is assigned from the spectroscopic properties of its derivatives. The assigned structure (Ia) is supported by dehydrogenation of the methyl ether methyl ester (Id) to methyl 2,3-dihydro-10-methoxy-6-methyl-3-oxo-1H-cyclopenta[7,8]naphtho[2,3-b]furan-7-carboxylate (VII), a previously described degradation product of the fungal metabolite, viridin (VI; X = O).