New convulsive compounds, brasiliamides A (1) and B (2), were isolated by activity-guided fractionation from okara fermented with a soil isolate of Penicillium brasilianum Batista JV-379. Their structures were elucidated on the basis of spectral and chemical evidence and by X-ray crystallography of the hydrogenated product of 2. In the 1 H-and 13 C-NMR spectra of 2, the signals were complicated, all being doubled or broadened in several deuterated solvents at room temperature. The conformational change of 2 was clariˆed as the rotational isomerization of amide bonds in solution by NMR measurements at various temperatures. Four rotamers of 2 at two amide bonds were presented at -609 C in CDCl 3 , whereas only two isomers were apparent at room temperature, owing to rapid rotation of one of the amide bonds. Brasiliamides A and B respectively showed convulsive activity against silkworms with ED 50 values of 300 and 50 mg W g of diet.