Megasporizine, a new dioxopiperazine derivative, has been isolated from Penicillium megasporum NHL 2977, together with physcion (parietin), 7-hydroxy-4,6 dimethylphthalide, asperphenamate, and phyllostine. Megasporizine was also isolated from the strains NRRL 2232 and ATCC 48997 along with physcion, asperphenamate, and penicillic acid. The structure of megasporizine has been investigated by spectroscopic means. Megasporizine is a dioxopiperazine which has a methoxy group at the a-carbon of an amino acid residue. Three cyanogenic glycosides, passicoriacin, epicoriacin and epitetraphyllin B, have had their structures reassigned as epivalkenin, taraktophyllin and volkenin respectively, based on a reinterpretation of their spectral data.