The oxidation of 11beta,17,21-trihydroxypregnan-1,4-diene-3,20-dione (I) with sodium metaperiodate in THF/methanol gives 11beta,17alpha-dihydroxy-3-oxoandrosta-1,4-diene-17beta-carboxylic acid (II), which is treated with ethyl chloroformate and triethylamine in dichloromethane yielding 17alpha-(ethoxycarbonyloxy)-11beta-hydroxy-3-oxoandrosta-1,4-diene-17beta-carboxylic acid (III). Finally, this compound is esterified with chloromethyl iodide and NaOH in methanol/water.