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Abstract

Cholesterol is essential for the survival of the nematode Caenorhabditis elegans. Recent studies have demonstrated that cholesterol derivatives regulate two processes in the life cycle of worms: controlling molting and inducing a specialized non-feeding larval stage. However, the chemical structure of the cholesterol-derived signalling molecules for these or any other functions has not yet been identified. Herein, we describe the regio- and stereospecific synthesis of a number of cholesterol derivatives. The lithium-ammonia reduction of 4-cholesten-3-one was utilized to develop a general method for the introduction of diverse functional groups at C-4 of 5-cholestan-3-ol. Stereoselective functionalization at C-7 was achieved starting from 7-ketocholesterol derivatives. 6-Keto-5-cholestan-3-ol was utilized for specific functionalizations at C-6 and C-7. The structure-activity relationships of the different cholesterol derivatives have been investigated by feeding worms of different genetic background with these compounds. Our study is the first step in assigning the relationships of hormonal activity in C. elegans on the substitution at different positions of cholesterol.