Ring D expansion and aromatisation in the biosynthesis of Nic-1, an antifeedant steroid from Nicandra physaloides

Abstract

Isotope administration experiments with Nicandra physaloides plants using [3′-C²H₃]- and [3′-¹⁴C₃]-mevalonic acid, analysed by ²H NMR and by degradation, respectively, show that the aromatic ring-D of Nic-1 2is formed by ring-o expansion in a steroid precursor with oxidative inclusion of the C/Dangular methyl.