Homopetasinic acid isolated from Diaporthe sp. strain 1308-05

Abstract Homopetasinic acid ( 1 ) was isolated from fungi of the Diaporthe sp. strain 1308-05. NMR spectroscopic structural analysis revealed a petasol ( 3 ) substructure and a (4 E ,6 E )-7-carboxy-3-hydroxy-2-methylhepta-4,6-dienoate side chain. The absolute configuration of the petasol moiety was established by the specific rotation value after basic hydrolysis. The (2′S,3′S)-configuration of the side chain was determined by NMR empirical methods as well as comparison of the spectral data with related model compounds. The absolute structure of the side chain moiety was established on the basis of ECD spectral analyses involving theoretical calculations. The biological activities of 1 are also discussed.