Ozonization of Cholesterol in Nonparticipating Solvents

Article abstract of DOI:10.1021/jo00238a014

Reaction of ozone with cholesterol (or cholesterol 3β-acetate) in dilute CCl4 or hexane solutions gave the heretofore undescribed isomeric 1,2,4-trioxolane ozonides 5,7α-epidioxy-5α-B-homo-6-oxacholestan-3β-ol and 5,7β-epidioxy-5β-B-homo-6-oxacholestan-3β-ol (or their 3β-acetates).Structures are supported by proton and carbon spectra and by Zn/acetic acid reduction to 3β-hydroxy(or 3β-acetoxy)-5-oxo-5,6-secocholestan-6-al.At higher cholesterol concentrations oxidized dimeric and oligomeric products are formed at the expense of 1,2,4-trioxolane ozonides.The major dimer 6ξ-(cholest-5'-en-3'β-yloxy)-5,6ξ-epidioxy-5ξ-5,6-secocholestane-3β,5-diol formed monoesters and was reduced by Zn/acetic acid to equivalent amounts of 3β-hydroxy-5-oxo-5,6-secocholestan-6-al and cholesterol.Also formed from cholesterol were dimeric ozonides 6ξ-(5',7'α-epidioxy-5'α-B'-homo-6'-oxacholestan-3'β-yloxy)-5,6ξ-epidioxy-5ξ-5,6-secocholestane-3β,5-diol and 6ξ-(5',7'β-epidioxy-5'β-B'-homo-6'-oxacholestan-3'β-yloxy)-5,6ξ-epidioxy-5ξ-5,6-secocholestane-3β,5-diol and dimeric epoxides 5,6ξ-epidioxy-6ξ-(5',6'α-epoxy-5'α-cholestan-3'β-yloxy)-5ξ-5,6-secocholestane-3β,5-diol and 5,6ξ-epidioxy-6ξ-(5',6'β-epoxy-5'β-cholestan-3'β-yloxy)-5ξ-5,6-secocholestane-3β,5-diol.Oligomeric 1,2,4-trioxolane ozonide isomers were also formed.Ozone thus reacts with cholesterol in two ways, by epoxidation and putatively by carbonyl oxide formation, with subsequent carbonyl oxide cyclization to 1,2,4-trioxolane ozonides or interception of cholesterol, cholesterol epoxides, and cholesterol ozonides (as alcohols) to yield dimeric and oligomeric species.