Substitution reactions of 5[alpha]-Cholestan-6[alpha]-ols

The primary objective of the present study was to reexamine the original reaction of 5a-cholestan-6a-ol with phosphorus pentachloride using modern techniques to determine whether 6a-chloro-5a-cholestane is the sole product, or whether the epimeric 63-chloro-5a-cholestane is also formed and, if so, to what extent. A secondary objective was the synthesis of 3a-halogen substitued 5a-cholestan-6a-ols, the 3a-substituent of which might be capable by steric interaction with the 6a-halophosphonate moiety thus influencing the steric course of the reaction. The 3a,6a-distance is ca. 5A, and for suitably sized 3a-substituents is capable of being spanned by the large phosphorus atom of a 6a-halophosphonate.