METABOLITES OF THE HIGHER FUNGI .18. 3-BUTYL-4-METHYLFURAN-2(5H)-ONE AND 3-BUTYL-4-METHYLENEFURAN-2(5H)-ONE - NEW GAMMA-BUTYROLACTONES FROM THE FUNGUS HYPOXYLON-SERPENS (PERSOON EX FRIES) KICKX

Culture solutions of the fungus Hypoxylon serpens contain a mixture of two isomeric γ-butyrolactones. These have been identified as 3-butyl-4-methylfuran-2(5H)-one (1a) and 3-butyl-4-methylenefuran-2(5H)-one (2). The synthesis of (1a) and the isomeric 4-butyl-3-methylfuran-2(5H)-one (1b) is described. At room temperature lactone (2) isomerises slowly to yield lactone (1a). This is the first report of the occurrence of a 4-exo-methylene γ-lactone as a natural product.