Hedkrangines A–F, drimane sesquiterpene–amino acid conjugates from a Thai cultivar of Schizophyllum commune

Six previously undescribed drimane sesquiterpene conjugates of phenylalanine, tryptophan, and valine, designated hedkrangines A–F ( 1–6 ), together with six known compounds, schizine A ( 7 ), epischizine A ( 8 ), schizine B ( 9 ), schizomycin I ( 10 ), 5α,6α-epoxy-( 22E ,24 R )-ergosta-8,22-diene-3β,7α-diol ( 11 ), and 1-linoleoyl- rac -glycerol ( 12 ), were isolated from the fruiting bodies of a Thai cultivar of Schizophyllum commune . The structures of the new compounds were elucidated by comprehensive spectroscopic analyses, including HR-ESI-TOFMS and one- and two-dimensional NMR spectroscopy, and their absolute configurations were established by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Hedkrangines A–F represent a rare series of naturally occurring drimane sesquiterpene–amino acid conjugates incorporating phenylalanine, tryptophan, and valine, with hedkrangines E and F being the first valine-conjugated members of this class reported from S. commune .