Verrucine F, a quinazoline from Penicillium verrucosum

Verrucine F (3), a quinazoline similar to verrucines A (1) and B (2), contains one anthranilic acid residue, one L-glutamine residue, and one alpha,beta-unsaturated phenylalanine residue, as determined by NMR, MS, and chemical methods. Compounds 1 and 3, but not 2, were produced by Penicillium verrucosum J255 and eight additional P. verrucosum strains. Verrucines were typically more concentrated in the inner (older) parts of the colony, and 3 peaked 4-8 days after 1, but at 10-fold lower concentrations (approximately 200 microg/g). Verrucine F (3) formed spontaneously from 1 in buffered water solutions, probably by oxidation at C-1 followed by water elimination.