Biosynthetic studies of marine lipids. 37. Enzymatic desaturation of 24(S)-methylcholesterol to 23,24-methylenecholesterol, norficisterol, and norhebesterol. Further evidence for a unified biosynthesis of marine sterols with unique side chains
作者:Christopher J. Silva、Jose Luis Giner、Carl Djerassi
DOI:10.1021/ja00027a037
日期:1992.1
The enzymatic desaturation of 24(S)-methylcholesterol to 23,24-methylenecholesterol, 29-norhebesterol, and norficisterol was demonstrated in the sponge, Petrosia ficiformis, by feeding the [3-H-3]-labeled analogue. [3-H-3]-24(R)-Methylcholesterol and [3-H-3]-24(R)-ethylcholesterol were not metabolized, though comparable amounts of each of the three precursors were isolated from the sponge. [3-H-3]Cholesterol was converted to 24-methylenecholesterol and clionasterol, presumably by its desaturation to desmosterol and subsequent biomethylation. The structure and stereochemistry of 29-norhebesterol was proven by partial synthesis. The possible role of a similar enzymatic process in the biosynthesis of cyclopropene-containing sterols is also considered.