Four new tetrahydropyran derivatives called ophiocerins A-D (1-4) and a new africane sesquiterpenoid (ophioceric acid; 5) have been isolated from cultures of the aquatic fungus Ophioceras venezuelense, together with the known compound regiolone. The structures and relative stereochemistry of these compounds were determined by analysis of 1D and 2D NMR data, while absolute stereochemical assignments for 1-4 were proposed by application of the exciton chirality CD method.

Two new benzofuran-derived metabolites of polyketide origin called phaeofurans A and B (1-2), along with three sorbicillin analogs (3-5) have been obtained from a fungicolous isolate of the genus Phaeoacremonium (NRRL 32148). The structures were determined by analysis of MS and 2D NMR data. The antifungal effects of the extract were ascribed to the sorbicillin analogs.Previous chemical studies of mycoparasites and fungicolous fungi that attack the nutrient-rich stromata of wood-decay fungi have yielded novel metabolites with antifungal effects and other biological activities. 1-6 As part of our ongoing studies of these types of fungi, chemical investigations of a culture identified as Phaeoacremonium sp. (Incertae sedis; NRRL 32148) isolated from field-collected stromata of Hypoxylon truncatum (Xylariaceae) produced two new polyketides named phaeofurans A and B (1-2) and three sorbicillin analogs (3-5), two of which have not been previously reported. Details of the isolation and structure determination of these compounds are presented here. Results and discussionSolid-substrate fermentation cultures of a Phaeoacremonium species grown on rice were extracted with ethyl acetate. The resulting extract showed antifungal activity against Aspergillus flavus and Fusarium verticillioides, and was partitioned between acetonitrile and hexane to yield an acetonitrile-soluble mixture that was subsequently fractionated over Sephadex LH-20. Active fractions were subjected to silica gel flash chromatography and/or reversed phase HPLC to yield compounds 1-5.Phaeofuran A (1) was isolated as a white film that formed fine needles upon evaporation of an acetone solution. The formula of 1 was tentatively assigned as CgHgCX based on analysis of EIMS (apparent M + at m/z 168) and NMR data ( Table 1). The intensities of the EIMS M + ion and the ESIMS M+H ion proved to be insufficient for obtaining high resolution MS data, but the NMR data suggested the presence of two exchangeable protons in the molecule, so a diacetate derivative of 1 was prepared. With five unsaturations, four olefinic or aromatic sp 2 carbon atoms (two of them protonated), four oxygenated sp 3 methines, and no carbonyl carbons, phaeofuran A (1) must contain three rings, two double bonds, and two OH groups. In addition, observation of four pairs of signals with very similar 13 C NMR chemical shifts (Table 1) suggested a pseudo-symmetrical structure. The NMR shifts for two of the oxymethine units (δ C 55.9 and 55.5/δ H 3.40 and 3.38) were diagnostic for the presence of a 1,2-disubstituted epoxide. Each of the epoxide protons was coupled to one of the other two oxymethines with a small J-value, enabling construction of a substructure corresponding to the C4-C7 unit in 1. The same unit was evident in the 1 H NMR spectrum of the diacetate, except that the signals for the oxymethine protons at C-4 and C-7 were downfield shifted from δ 5.05/5.06 to δ 6.12/6.18. The remaining two 1 H NMR signals in the spectrum of 1 corresponded to olefinic/aromatic protons that show...