Cephalostatin studies. 34. Oxidation 9. Ruthenium-catalyzed mild C-H oxyfunctionalization of cyclic steroidal Ethers

Ruthenium-catalyzed site-specific C-H oxyfunctionalization of steroidal ethers with periodate or bromate as terminal oxidants in phosphate buffer provided the acid-sensitive C-16 hydroxy compounds in high yields. Phosphate buffer (pH 7.5) significantly inhibits formation of unwanted side products generated under more acidic reaction conditions. A key example is demonstrated at the 100 g scale.