Biosynthesis of the insect antifeedant steroid Nic-1: origins of the aromatic ring-D

Abstract

Isotope administration experiments with Nicandra physaloides plants using [3′-C²H₃]- and [3′-¹⁴CH₃]-mevalonic acid, analysed by ²H n.m.r. and by degradation, respectively, show that the aromatic ring-D of Nic-1 (1) is formed by ring-D expansion in a steroid precursor with oxidative inclusion of the C/D angular methyl.