To a solution of 2b (67.0 mg, 0.14 mmol) in THF (3 mL) and 1,2-propanediol (3 mL) was added aqueous potassium hydroxide (0.40 mL of a 8 M solution in water, 3.20 mmol). The mixture was stirred at 110° C. for 18 h and then cooled to room temperature. The reaction mixture was diluted with water, acidified with 1 N hydrochloric acid and extracted three times with EtOAc. The combined organic extracts were washed with water, dried (MgSO4) and concentrated. Flash chromatography of the residue (silica gel; dichloromethane/methanol/concentrated aqueous ammonium hydroxide (85:15:1) gave a solid (48.0 mg) that was triturated with ether/hexane to provide 2c as a solid (38 mg), m.p. 205-210° C. (dec.).
