Stereospecificity in the side-chain formation of 24β-ethylsterols in tissue cultures of Trichosanthes kirilowii

Abstract

In the biosynthesis of 22-dihydrochondrillasterol (4) from [2-¹³C,2-²H₃] acetate and [1,2-¹³C₂] acetate in cell cultures of Trichosanthes kirilowii, the hydrogen atom coming from C-4 of mevalonic acid was revealed by ¹³C n.m.r. spectroscopy to be located at C-24, and that the protonation at C-25 of the 24β-ethyl-Δ²⁵ precursor, to form the saturated side chain of (4), was most likely to occur from the Re-face.