N-(2-(1,1-dioxido-4-thiomorpholinyl)ethyl)-2-nitrobenzenesulfonamide (0.500 g, 1.38 mmol) was combined with 4-(2-hydroxyethyl)thiomorpholine 1,1-dioxide (0.296 g, 1.65 mmol) in THF (10 mL). To this mixture was added triphenylphosphine (0.541 g, 2.06 mmol) and diethyl azodicarboxylate (0.359 g, 2.06 mmol). The resulting mixture was stirred at rt for 72 h. The mixture was concentrated in vacuo, then redissolved in acetonitrile. Purification by reverse phase preparative HPLC gave the title compound as a pale yellow solid (0.863 g, 83% yield) bis-TFA salt. LCMS: m/z 525 (M+H+), retention time 1.25 min (method 11). 1H NMR (500 MHz, MeOD) δ ppm 2.85 (t, J=6.71 Hz, 4H) 3.14 (d, J=5.49 Hz, 8H) 3.18 (d, J=5.80 Hz, 8H) 3.51 (t, J=6.71 Hz, 4H) 7.71-7.75 (m, 1H) 7.75-7.84 (m, 2H) 8.05 (d, J=7.63 Hz, 1H).
