“…The mixture was stirred at 0°C for 30 min, and the solvent was evaporated to give a pale yellow oil. This was chromatographed on a silica gel column, eluting with benzene:ethyl acetate (3:5) to yield 236 mg (73.2%) of 2 as colorless crystals, mp 211-214 "C; 'H NMR: 0.98 (s, 3H, 10-CH,), 1.48 (s, 3H, 13 Anal.-C2,H,,0,: C, H. Methyl 17a,21 -diacetoxy -1 1 P-hydroxy-3,20-dioxo-pregna-l,4 -diene-l6a-carhoxylate IPIGCMl7,ZlAc; 3 t T o a mixture of glacial acetic acid (1.5 mL, dried over a 4 A molecular sieve) and trifluoroacetic anhydride (0.6 mL) was added a solution of 2 (100 mg, 0.2 mmol) and pyridinium p-toluenesulfonate catalyst (50 mg). The mixture was stirred for 3.5 h a t room temperature and then poured into distilled water (100 mL).…”