Absolute Stereochemistry of Novel Isochromanone Derivatives fromLeptosphaeriasp. KTC 727

Abstract

A novel isochromanone, (S)-8-hydroxy-6-methoxy-4,5-dimethyl-3-methylene-isochromen-1-one (1), known 2 and previously reported metabolites from Leptosphaeria sp. KTC 727 (JCM 13076 = MAFF 239586) were isolated from the same source by culturing for a relatively long period. The results of the present study disclose their structures involving the absolute stereochemistry. The planar structures of these molecules were established by ESIMS and NMR spectral analyses. The absolute configuration of 1 was established by comparing its electronic circular dichroism (ECD) spectrum with that of structurally-related known compound 3. The relative stereochemistry of 2 was revealed by a combination of nuclear Overhauser effect (NOE) experiments and thermodynamic discussions. Successful transformation of 1 to 2 led us to assign the configuration of 2 after comparing their ECD spectra. These compounds exhibited weak antifungal activities against Cochliobolus miyabeanus.

Soudanones A–G: Antifungal Isochromanones from the Ascomycetous Fungus Cadophora sp. Isolated from an Iron Mine

“…fungus (IC 50 = 2.6−4.7 μg/mL against multidrug-resistant Plasmodium falciparum K1). 9 A subset of the 3-alkyl isochromanones identified in this study (2,3,6,9) were therefore tested against drug-sensitive P. falciparum NF 54 , but none were active at 10 μg/mL. These data suggest the importance of the saturated 7-C alkyl chain and/or a shorter 3-C alkyl chain (n = 5) for antimalarial activity.…”

Isochromenones, isobenzofuranone, and tetrahydronaphthalenes produced by Paraphoma radicina, a fungus isolated from a freshwater habitat

“…1 and Table S1). Compound 2 was first isolated in 2002 from the EtOAc extract of a broth of the marine fungus Halorosellinia oceanica ( Chinworrungsee et al, 2002), and compounds 1, 2 and 4 were isolated in 2011 from the culture broth of Leptosphaeria sp., which was collected from woody debris ( Tayone et al, 2011a andTayone et al, 2011b). Compound 4 was re-isolated in 2012 from a complex microbial mat that occupied an iron-rich freshwater spring and was ascribed the trivial name clearanol C ( Gerea et al, 2012).…”

“…Herein, details of the isolation, structural elucidation, and determination of the absolute configuration of these compounds are presented. Structurally related compounds have been reported to have various degrees of antifungal activity ( Gerea et al, 2012, Tayone et al, 2011aand Tayone et al, 2011b and mild antimycobacterial activity ( Chinworrungsee et al, 2002). As such, compounds 1-9 were evaluated against a panel of microorganisms; the most promising (4) was also tested in a Staphylococcus aureus biofilm assay.…”

Secondary metabolites from the endolichenic fungusOphiosphaerella korrae

“…The 1D and 2D NMR spectra (Table 3 and Fig. 2) of 5 closely resembled those of (S)-8-hydroxy-6-methoxy-4,5-dimethyl-3-methylene-isochromen-1-one, 18,19 except that a hydroxyl is in the place of from H-2 to C-4 and C-6 and from H-5 to C-3 together with the proton spin system CH 2 (4)-CH(5)-CH 3 (14) indicated by the 1 H-1 H COSY correlations (Fig. 2).…”

“…Medium Pressure Liquid Chromatography (MPLC) was carried out on a Lisure EZ Purier apparatus equipped with a dual-wavelength UV-Vis detector (Lisure Science (Suzhou) Co., ltd.) and an ODS column (column size: 30 Â 130 mm). Semipreparative HPLC was accomplished on an Agilent 1100 series instrument with Eclipse XDB-C 18…”