Progress toward a biosynthetic rationale of the aflatoxin pathway

Specifical ly—labeled samples of averufin have been synthesized and incorporated intact into aflatoxin B1, versicolorin A and versiconal acetate as determined by NMR spectroscopy. [1—'3C]--Hexanoic acid has been shown to be uti I ized as the primer of the pathway whi le a group of alternative starters was found to be degraded to acetate prior to incorporation. The correct structure of nidurufin has been established and it and its 2'—epimer, pseudonidurufin, in labeled form have failed to be utilized in aflatoxi n biosynthesis under two experimental protocols. [1 '..l8, 5' —'3C]—Averufi n, however, was observed to label versiconal acetate in such a way that the acetyl carbonyl bore 80% of the original 180—label. A biogenetic scheme is proposed to account for these findings that is supported in the cat ionic regime by preliminary model studies.