Regiospecific Deoxygenation of the Dihydroxyacetone Moiety at C-17 of Corticoid Steroids with Iodotrimethylsilane

Abstract

Reaction of the corticoids 1-6 with iodotrimethylsilane in MeCN produced the regiospecifically deoxygenated products, 21-hydroxy-20-ketones 7-11, in moderate to high yields. On the other hand, employment of CHCl₃ as a solvent resulted in lower yields of the 21-ketols 7 and 8, accompanied by increased production of the 20-ketones 12 and 13. The 21-ketol 7 was efficiently converted into the 20-ketone 12, while the 17α-hydroxy isomer 14 was recovered unchanged. Rapid and quantitative conversion of the 21-iodo-20-ketone 17 into the 20-ketone 12 by this iodosilane treatment suggests that the conversion of the ketol 7 into the ketone 12 probably occurs via the iodide 17.