A solution of 4 (170 mg, 0.62 mmol) in dry ethanol (15 mL) was treated with 5 (0.355 g, 1.24 mmol) and stirred for overnight (17 h) at room temperature. The reaction mixture was diluted with saturated NaHCO3 solution (100 mL) and extracted with CH2Cl2 (2×50 mL). The combined organic fractions were washed with brine (50 mL), dried (Na2SO4) and concentrated. The crude product was purified by dry column chromatography (MeOH:CH2Cl2, 2:98 followed by 2 N NH3 in MeOH:CH2Cl2 3:97) to give compound 45 (177 mg, 74%) as a yellow solid. 1H-NMR (DMSO-d6) δ: 1.38-1.69 (m, 8H), 1.83-1.89 (m, 2H), 2.02-2.12 (m, 2H), 2.19 (s, 3H), 2.65-2.68 (m, 2H), 2.80-3.12 (m, 5H), 6.32 (brs, 2H), 6.62-6.64 (m, 2H), 6.85-6.88 (d, 1H, J=8.9 Hz), 7.06-7.09 (t, 1H, J=3.8 Hz), 7.56-7.58 (d, 1H, J=5.0 Hz), 7.69-7.71 (d, 1H, J=3.6 Hz); ESI-MS (m/z, %): 383 (MH+, 33), 192 (100), 142 (51). ESI-HRMS calculated for C22H30N4S (MH+), calculated: 383.2253; observed: 383.2263; HPLC-purity: 93.49% by area.
