Diplofuranones A and B, two further new 4-monosubstituted 2(3H)-dihydrofuranones produced by Diplodia corticola, a fungus pathogen of cork oak

Two new 4-monosubstituted 2(3H)-dihydrofuranones, named diplofuranones A (I) and B (II), were isolated from liq. cultures of Diplodia corticola, a plant pathogenic fungus causing a canker disease of cork oak (Quercus suber L.). The same fungus also produces several metabolites, such as the diplopyrone, the (3S,4R)-trans- and the (3R,4R)-cis-4-hydroxymellein, the sapinofuranone B and its (S,S)-enantiomer, the well known sphaeropsidins A-C, and the diplobifuranylones A and B. The diplofuranones A and B were characterized, using spectroscopic (essentially NMR and MS techniques) methods, as the 4-[(1E,3E)-5-hydroxyhexadienyl]butan-4-olide and its corresponding 3,4-dihydro side chain deriv. The stereochem. of the stereogenic secondary hydroxylated carbon of the side chain of diplofuranone A was detd. by application of Mosher's method and proved to be R. Diplofuranone A tested at 0.2 mg mL-1 on non-host plant did not show phytotoxic activity.