The stereochemistry of hydrogen elimination from C-7 during biosynthesis of ecdysones in insects and plants

Abstract

1. [7α-3H1]- and [7β-3H1]-Cholesterol were synthesized by a modified method. 2. The stereochemistry of Δ7-bond formation during ecdysone and ecdysterone biosynthesis in the insect, Calliphora erythrocephala and the plants, Taxus baccata and Polypodium vulgare was investigated by using [4-14C,7α-3H1]cholesterol and [4-14C,7β-3H1]cholesterol. 3. In each case, the 7β hydrogen was stereospecifically eliminated. 4. The possible significance of the results is discussed in relation to double-bond formation in other systems and the stage at which the Δ7 bond is introduced during ecdysone biosynthesis.