Botcinins E and F and botcinolide from Botrytis cinerea and structural revision of botcinolides

Botcinins E and F were isolated together with the known botcinolide. The structures of botcinins E and F were determined to be 3-O-deacetylbotcinin A ( 5) and 3-O-deacetyl-2-epi-botcinin A ( 6), respectively, by spectroscopic methods and chemical conversion. The structure of botcinolide was revised on the basis of spectroscopic data and chemical conversion. Botcinolide was originally reported as a nine-membered lactone ( 7), but the revised structure is the seco acid of botcinin E ( 13). Thus botcinolide is renamed botcinic acid, and homobotcinolide is renamed botcineric acid. Reinvestigation of the spectroscopic data reported for all botcinolide analogues indicates that 4-O-methylbotcinolide and 3-O-acetyl-2-epibotcinolide are the same as a methyl ester of botcinic acid (13a) and botcinin A ( 1), respectively, and that 2-epibotcinolide may be the same as botcinin E ( 5). Compounds 5, 6, and 13 showed weak antifungal activity against Magnaporthe grisea, a pathogen of rice blast disease.