Biosynthetic studies of marine lipids. 22 : Calysterol: Some aspects of sterol cyclopropene biosynthesis in the sponge calyx nicaeensis

Abstract

Calysterol ( 1) was shown not to be biosynthesized by direct dehydrogenation of its cyclopropane analog, dihydrocalysterol ( 5). Loss of H-28 from 5 during the biosynthesis of 1 was demonstrated, which implies that either 24- H-isocalysterol ( 2) or (23 S)-23 H-isocalysterol ( 4) is the direct dehydrogenation product of 5. A novel synthesis of 5 is described which allowed facile introduction of tritium at C-28.