Some stereochemical functions of the cholesteryl group

Abstract

Two stereochemical functions of the cholesteryl group were investigated and are described in Sections "A" and "B".In Section "A" cholesterol has been investigated as a potential resolving group. PART I of this Section deals with the preparation of (+/-)-hydratropic acid, (+/-)-hydratropoyl chloride and the synthesis and partial resolution of cholesteryl (+/-) hydratropate. A review of the various methods of making (+/-)-hydratropic acid is given. PART II deals with the resolution of (+/-)-hydratropic acid, the preparation of optically pure (+)- and (-)-hydratropyl alcohol, optically pure cholesteryl (+) hydratropate, cholesteryl (-) hydratropate and cholesteryl (+/-) hydratropate. The synthesis of optically pure (-)-hydratropyl alcohol from cholesteryl (+) hydratropate is described.In Section "B" is described the use of cholesterol as an activating alcohol for asymmetric synthesis and its comparison with (-)-menthol. It deals with the preparation of (-)-menthyl benzoylformate and cholesteryl benzoylformate and their reduction by(a) Lithium aluminium hydride,(b) Aluminium amalgam, Sodium borohydride and Aluminium isopropoxide followed by Lithium aluminium hydride. Cholesterol was found to exert an opposite activating influence to that of (-)-menthol on the course of asymmetric synthesis.