Metabolites produced by the Scleroderris canker fungus, Gremmeniellaabietina. Part 4. Biosynthetic studies

The biosynthetic origin of the carbon atoms of the most highly oxidized, polyketide derived, ring (carbons 1–3) of the Gremmeniellaabietina metabolites sclerodione (3), scleroderolide (4), sclerodin (5), and Scleroderris green (6) has been studied. It is shown that both C-1 and C-3 of 3 and 4 are derived from C-1 of acetate, and that C-2 of scleroderolide (4) is derived from C-2 of acetate while C-3 is derived from C-1 of acetate. As expected, C-1 and C-3 of Scleroderris green (6) originate from the carboxyl carbon of acetate, while C-2 originates from the methyl carbon of acetate. Complete 13 C and 1 H nuclear magnetic resonance spectra of these metabolites are reported. It has also been shown that ent-atrovenetin (ent-7a) is a metabolite of G. abietina.