To a solution of Example 12E (0.390 g, 1.097 mmol) in N,N-dimethylformamide (3.66 mL) were added pyridine (4.44 mL, 54.9 mmol) and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (0.421 g, 2.195 mmol) and the mixture was stirred at room temperature for 1 hour. The solution was concentrated, water was added to the residue, and the product was extracted twice with ethyl acetate. The combined organic washes were dried over sodium sulfate, concentrated and dried under vacuum at room temperature overnight. It was then passed through a 5 gram silica gel cartridge eluting first with dichloromethane, then with 2% methanol/dichloromethane and finally with 5% methanol/dichloromethane to obtain the title compound. An aliquot of material was further purified for analytical purposes by preparative HPLC to afford the title compound as the trifluoroacetic acid salt. 1H NMR (500 MHz, DMSO-d6) δ ppm 10.21 (s, 1H), 9.52 (s, 1H), 7.54-7.48 (m, 5H), 6.90 (d, J=8.6, 1H), 6.70-6.60 (m, 2H), 4.45 (s, 2H), 3.74 (s, 3H), 3.67-3.07 (m, 7H), 3.22-3.04 (m, 2H), 2.61 (dd, J=7.0, 13.5, 1H), 2.00 (d, J=13.5, 1H); MS (ESI) m/z 338.1 (M+H)+.
