Stereochemistry of the reduction of 24-ethyldesmosterol to sitosterol in tissue cultures of Oryza sativa

Feeding of [26-13C]- and [27-13C]-24-ethyldesmosterols to cultured cells of Oryza sativa followed by 13C-NMR analysis of the biosynthesized sitosterol revealed that the reduction of 24(25)-double bond proceeds with an anti-addition of hydrogen atoms, thus the E-methyl group of the olefinic precursor becomes the pro-S-methyl on C-25 of sitosterol.