Regioselective epoxidation by air of sterol esters bearing several double bonds using a ruthenium porphyrin catalyst
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A series of sterol esters bearing varying patterns of unsaturation on the nucleus, side chain, and acyl substituent were epoxidized using trans-dioxoruthenium(VI) tetramesitylporphyrin as catalyst and air as source of oxygen. Attack at the steroid nucleus is generally favored, and a high degree of β-stereoselectivity is obtained except for conjugated 5,7 diene systems which yield a ca. 1∶1 mixture of 5,6α and 5,6β epoxides.
KeywordsOxygen Ester Physical Chemistry Steroid Catalysis
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