Stereochemical Analysis of Chiral Alcohol, Epoxide and Sulphoxide Metabolites by Chiral Stationary Phase High-Performance Liquid Chromatography

Summary

Several commercially available chiral stationary phase high-performance liquid chromatography (CSP-HPLC) columns have been used in the analysis of enantiomers resulting from enzyme-catalysed oxidations at carbon and sulphur atoms in cyclic systems.

Monohydroxylation reactions have been studied at both benzylic and allylic methylene groups. The metabolism of arenes, dihydroarenes and tetrahydroarenes in fungi, bacteria and animal liver systems have been investigated by the CSP-HPLC method. This procedure was particularly useful in the stereochemical analysis of arene hydrates, a new type of unstable metabolite, formed from dihydroarenes by allylic or benzylic hydroxylation.

A Chiralcel OB (Daicel Industries) column has been found to be successful in the resolution of non-K-region arene oxides and thus in the estimation of enzymatic stereopreference for one prochiral face during the metabolism of polycyclic aromatic hydrocarbons (PAHs) by hepatic monooxygenase enzymes.

The determination of optical purity of cis-dihydrodiols produced by bacterial metabolism of PAHs proved difficult by direct CSP-HPLC analysis. An indirect method involving hydrogenation, cyclic carbonate formation followed by CSP-HPLC analysis was more successful.

The ability of chiral sulphoxidising agents (chemical and enzymatic) to stereo-differentiate between prochiral lone pairs on a sulphur atom and prochiral sulphur atoms on a carbon atom has been investigated using a single CSP-HPLC system to separate both cis- and trans-sulphoxide isomers and individual sulphoxide enantiomers.