(±)-Usphenethylones A–C, three pairs of heterodimeric polyketide enantiomers from Aspergillus ustus 3.3904

Abstract

Three pairs of new heterodimeric polyketide enantiomers, (±)-usphenethylones A–C (1–3), were isolated from the culture extract of Aspergillus ustus 3.3904. Compounds 1–3 present two heterodimerization patterns by a phenylethyl unit connected to an α-pyrone moiety, of which usphenethylones A–B (1–2) feature a 2,6,18-trioxa-tetracyclo-[8.8.0.0^3,8.0^11,16]octadecane core and usphenethylone C (3) possesses a 2-phenyl-3,4-dihydro-pyrano[4,3-b]pyran-5-one scaffold. The structures of (±)-1–3 were elucidated based on spectroscopic data analyses, and their absolute configurations were determined by single-crystal X-ray diffraction analysis and ECD calculation. Plausible biosynthetic pathways for 1–3 were proposed. Compounds (+)-3 and (−)-3 exhibited moderate inhibitory effects against ConA-induced T cell and LPS-induced B cell proliferation.