Detailed study of oxidative esterification and elimination reactions undergone by a steroidal 17α-benzoyloxy-20-oxo-21-aldehyde

Article abstract of DOI:10.1002/jps.2600790502

The reaction of 17α-benzoyloxy-11β-hydroxy-3,20-dioxo-1,4-pregnadien-21-al as the hemiacetal (1) with methanol:acetic acid:potassium cyanide:manganese dioxide followed by acetylation and preparative HPLC of the reaction mixture afforded 11 crystalline products. These products can be conveniently divided into three categories representing side-chain cleavage and oxidative esterification with or without elimination of the benzoyloxy group. Of special interest was the stereospecific formation of the C-17 cyanohydrin acetate 4a and the cis Δ¹⁷(20) enol acetate methyl ester 5. On the other hand, nonstereospecific addition of HCN to the side chain gave the C-20 epimeric cyanohydrin acetates 7a and 7b. The use of activated versus nonactivated MnO₂ plays a major role in determining the quantitative distribution of the products. It was also discovered that even in the absence of MnO₂, the reaction goes to completion. A proposed mechanism which explains the formation of all products is presented.