The first biosynthetic studies of the azinomycins: acetate incorporation into azinomycin B.

13C-labelled acetate efficiently labels the antitumour natural product azinomycin B, revealing a polyketide origin for the naphthoate fragment, that threonine is the probable precursor of the enol fragment, and that alpha-ketoglutarate is a probable precursor of the aziridine fragment.