Studies in terpenoid biosynthesis. Part 26. Applications of 2H and 13C n.m.r. spectroscopy to the biosynthesis of the illudin sesquiterpenoids

Abstract

The ¹³C n.m.r. resonances of the illudins have been assigned. The labelling pattern of illudin M and illudin S derived from [1,2-¹³C₂]acetate and the induced coupling between C-6 and C-7 in samples biosynthesized from [1-¹³C]acetate are in accord with the previous dissection of the carbon skeleton into isoprene units. The enrichment from [2-²H₃]acetate and [2-²H₂]mevalonate indicates that one mevalonoid label is lost from C-12 during the biosynthesis. The retention of a ²H–¹³C coupling at H-6 in illudin M which was biosynthesized from [5-²H₂,5-¹³C]mevalonate shows that this hydrogen atom is not involved in a hydride rearrangement in contrast to previous conclusions.