In a 5-mL round bottom flask, a solution of Example 176 (25 mg, 0.049 mmol), 1,1′-thiocarbonyldiimidazole (13.75 mg, 0.073 mmol), and 1,8-diazabicyclo[5.4.0]undec-7-ene (30.1 μL, 0.195 mmol) in anhydrous acetonitrile (490 μL) was stirred under nitrogen at 25° C. for 2 hours. The reaction was diluted with ethyl acetate (50 mL) and H2O (10 mL), and the pH was adjusted to ˜3 with 1 N aqueous HCl. The layers were separated, and the organic phase was washed with brine (10 mL), dried over anhydrous MgSO4, filtered, and concentrated by rotary evaporation. The crude material was purified by SiO2 flash chromatography (Alltech Extract-Clean™ column, 10 g bed) eluting with a step gradient of 5% to 7.5% methanol/CH2Cl2 to afford the title compound as a yellow solid (22 mg, 0.039 mmol, 80%). 1H NMR (400 MHz, DMSO-d6) δ ppm 0.50-0.62 (m, 1H), 0.81-0.91 (m, 1H), 0.94-1.04 (m, 2H), 1.73-1.89 (m, 2H), 2.34-2.42 (m, 1H), 2.56-2.66 (m, 2H), 3.17 (s, 3H), 3.66-3.85 (m, 2H), 7.10 (s, 1H), 7.35 (t, J=8.89 Hz, 2H), 7.40 (s, 2H), 7.90 (s, 1H), 7.95 (dd, J=8.08, 5.80 Hz, 2H); MS (ESI+) m/z 554 (M+H)+, 1107 (2M+H)+; MS (ESI−) m/z 552 (M−H)−, 1105 (2M−H)−.
