Stereochemical fate of the isopropylidene methyl groups of lanosterol during the biosynthesis of isofucosterol in Pinus pinea

[26-3H]Lanosterol (16) was administered to Pinus pinea and the [26-3H]isofucosteryl acetate (6) obtained was chemically transformed into [26-3H]cholesterol (13). Compound (13) was incubated with rat-liver mitochondria to yield [3-3H] propionic acid. The data obtained are consistent with a biosynthetic pathway in which the pro-E isopropylidene methyl group of the Δ24-precursor becomes the pro-R isopropyl methyl group in isofucosterol.