A solution of 17β-carbomethoxy-6-t-butylcarboxy-6-azaandrost-4-en-3-one (2.00 g, 4.63 mmol), prepared in Example 3, part E, in dioxane (50 mL) is treated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ, 1.37 g, 6.02 mmol) and p-nitrophenol (10 mg). The reaction is heated to reflux for 2 hrs, poured into ice water (150 mL), extracted with ethyl acetate (3×100 mL), extracts washed with saturated aqueous NaHSO3, 2N NaOH, saturated aqueous NaCl, dried over MgSO4, concentrated and chromatographed on silica gel (40% ethyl acetate/hexanes) to give crude 17β-carbomethoxy-6-t-butylcarboxy-6-azaandrost-1,4-dien-3-one as a tan solid of sufficient purity to carry on to the following steps; yield: 1.53 g (76%).
