The biosynthesis of rubrofusarin, a polyketide naphthopyrone from Fusarium culmorum: 13C n.m.r. assignments and incorporation of 13C- and 2H-labelled acetates

Abstract

The polyketide chain in rubrofusarin biosynthesis has been shown to adopt the folding pattern B by the incorporation of ¹³CH₃¹³CO₂ Na and of CD₃¹³CO₂ Na, with observation of the β-isotopic shifts in the ¹³C n.m.r. spectrum, in the rubrofusarin derivative (5). The extent of retention of deuterium at the various sites is interpreted in terms of an unusual sequence of biosynthetic steps. The assignment of the ¹³C n.m.r. spectrum of rubrofusarin dimethyl ether (2) was made with the aid of specific deuteriation and ¹H–¹³C n.O.e.'s as well as more standard techniques.