Structure and absolute configuration of acetosellin, a new polyketide from a phytotoxic strain of Cercosporella acetosella.

A new yellow pigment, designated acetosellin 1, was isolated from the mycelium of Cercosporella acetosella as a reduced azaphilone metabolite. The structure of 1 was determined by spectroscopic investigations and chemical evidence. Compound 1 possesses a novel carbon skeleton that of a naphtopyrane derivative, linked to an extensively conjugated chain. The absolute configuration was determined by NOE experiments and CD correlations.