Stereochemistry of the hydrogen addition to C-25 of desmosterol by sterol-Δ24-reductase of the silkworm, Bombyx mori

Abstract

The C-25 stereochemistry of the reaction catalysed by sterol-Δ²⁴-reductase from the insect, B. mori, has been investigated by the use of ¹³C NMR spectroscopy; incubation of isopropylidene (E)-methyl-¹³C labelled desmosterol afforded cholesterol with the label at pro-R-methyl of the isopropyl group, and the results indicated the C-25 hydrogen was introduced stereospecifically from the si-face of the double bond.