Absolute stereochemistry of altersolanol A and alterporriols.

The absolute stereochemistry of altersolanol A (1) was established by observing a positive exciton couplet in the circular dichroism (CD) spectrum of the C3,C4-O-bis(2-naphthoyl) derivative 10 and by chemical correlations with known compound 8. Before the discussion, the relative stereochemistry of 1 was confirmed by X-ray crystallographic analysis. The shielding effect at C7'-OMe group by C1-O-benzoylation established the relative stereochemical relationship between the C8-C8' axial bonding and the C1-C4/C1'-C4' polyol moieties of alterporriols E (3), an atropisomer of the C8-C8' dimer of 1.

Absolute stereochemistry of novel isochromanone derivatives from Leptosphaeria sp. KTC 727.

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.

Stereochemical investigations of isochromenones and isobenzofuranones isolated from Leptosphaeria sp. KTC 727.

Two new metabolites, (R)-3,4-dihydro-4,6,8-trihydroxy-4,5-dimethyl-3-methyleneisochromen-1-one (1) and (R)-7-hydroxy-3-((S)-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran-1(3H)-one (2), were isolated along with two structurally known related compounds (3 and 4) from the culture broth of Leptosphaeria sp. KTC 727 (JCM 13076 = MAFF 239586). These structures were disclosed mainly with (1)H and (13)C NMR spectroscopic analyses.