Novel antiinsectan oxalicine alkaloids from two undescribed fungicolous Penicillium spp.

15-Deoxyoxalicine B (1) and decaturins A (2) and B (3) have been isolated from Penicillium decaturense and Penicillium thiersii, two previously undescribed species obtained as colonists of wood-decay fungi. The structures were determined by 2D NMR experiments and/or single-crystal X-ray diffraction analysis. These compounds are members of a rare structural class, and decaturins A and B feature a new polycyclic ring system. Decaturin B (3) exhibited potent antiinsectan activity against the fall armyworm (Spodoptera frugiperda).