ChemInform Abstract: Synthesis of (24R,28R)- and (24S,28S)-24,28-Methylene-5-stigmasten-3β-ol and Biosynthetic Implications of Cyclopropyl Cleavage to 24-Substituted Cholesterols.

ChemInform Abstract

Treatment of methylenestigmastenol (I) with trifluoroacetic acid results in opening of the cyclopropane ring, producing the olefins (II) -(IV). The stereoisomers (V) - (VII) yield the same mixture of (II) -(IV) in the presence of TFA. The natural (24E)-24-propylidenecholesterol (VIII) is not formed in these isomerization experiments. The synthesis of the starting materials is also described in the original paper. (¹³C and deuterium labeling studies, intermediates, mechanism).