Stereospecificity and Regiospecificity of the Phosphorus Oxychloride Dehydration of Sterol Side Chain Alcohols

Article abstract of DOI:10.1021/jo00263a020

Stigmasta-5,23(E)-dien-3β-ol (2) and stigmasta-5,23(Z)-dien-3β-ol (3), sterols of potential biosynthetic interest, were synthesized by phosphorus oxychloride dehydration.High stereospecificity and regiospecificity in this reaction is evident in the dehydrations of several steroidal side chain alcohols.A two-step hydroboration-phosphorus oxychloride dehydration procedure is described for reversing the geometry of trisubstituted double bonds.Surprisingly facile borane migration with retention of the configuration at C24 was observed in the hydroboration of steroidalside chain olefins.Phosphorus oxychloride dehydration was used to introduce deuterium into the vinylic position of isofucosterol (15) via its i-methyl ether.