17α-hydroxy-20-phenoxypregna-4,9(11),20-trien-3-one (4.04 grams, 10 mmoles) is slurried in pH 8 potassium phosphate buffer (50 ml, 0.02M PO4 57 ), 40 ml methylene chloride, 0.222 grams (1 mmole), of Ansul ether 181 (C10H22O5) and 20 ml acetone and the two phase mixture heated to 25° C. and adjusted to pH 8.5 with 30% potassium hydroxide. 18.4 grams, 30 mmoles of OXONE® (2KHSO5.KHSO4.K2SO4) is dissolved in 90 ml of water and 10 ml of a 5% by weight solution of Na4EDTA and the resulting solution added dropwise at 25° C. with vigorous agitation while maintaining the pH at 8.0-8.5 with 30% potassium hydroxide. When the reaction is complete the phases are separated hot and the aqueous phase extracted twice with 50 ml of methylene chloride. The combined organics are washed twice with 100 ml of aqueous 5% sodium hydroxide and clarified thru a solka flok filter and concentrated on a rotary evaporator to yield 17α-hydroxy-20,21-epoxy-20-phenoxypregna-4,9(11)-diene-3-one.
