A solution of diazomethane in diethyl ether was prepared by adding N-nitroso-N-methylurea to a mixture of 50% aqueous potassium hydroxide solution and diethyl ether in accordance with the method described in Organic Syntheses Collective Volume 2, p. 165 (1943) and this solution was added to a solution of 85 mg of 1α,3β-bis(methoxycarbonyloxy)pregna-5,7-diene-20-carboxylic acid (prepared in Example 6 above) in 5 ml of diethyl ether until the yellow color of diazomethane would be persistent. After the excess diazomethane was decomposed by addition of acetic acid, the reaction mixture was washed with aqueous sodium hydrogen carbonate solution and aqueous sodium chloride solution, dried over sodium sulfate, and concentrated. The residue was purified by silica gel column chromatography to give 79 mg of methyl 1α,3β-bis(methoxycarbonyloxy)pregna-5,7-diene-20-carboxylate.
