Reaction Steps
Sodium perborate tetrahydrate (97 mg, 0.63 mmol) was added as a solid to a stirred solution of (2R)-3-(4′-Indol-1-ylbiphen-4-ylmethylsulfanyl)-2-[2-(3-nitrophenyl)-acetylamino]-propionic acid (330 mg, 0.58 mmol) in acetic acid (10 mL) at 40° C. This solution was stirred at 40° C. for 2 hours (HPLC control) and then diluted with ethyl acetate (50 mL), washed with water, brine (2×), dried over anhydrous MgSO4, filtered and concentrated in vacuo. Purification by trituration of the product with diethyl ether afforded the title compound as a light brown solid (206 mg, 61%): mp. 197-198° C. Rf 0.15 (15% methanol in dichloromethane): 1H NMR (DMSO-d6, 300 MHz) δ 8.46 (1H, d, J=8 Hz, NH), 8.18 (1H, t, J=2 Hz, Ar—H), 8.08 (1H, ddd, J=8, 2, 1 Hz, Ar—H), 7.87 (2H, d, J=8 Hz, Ar—H), 7.72 (2H, d, J=8 Hz, Ar—H), 7.54-7.69 (7H, m, Ar—H), 7.35 (2H, d, J=8 Hz, Ar—H), 7.21 (1H, td, J=7, 2 Hz, Ar—H), 7.14 (1H, td, J=7, 2 Hz, Ar—H), 6.71 (1H, d, J=3 Hz, Ar—H), 4.36 (1H, m, CHN), 4.20 (1H, d, J=13 Hz, PhCHHS), 3.84 (1H, d, J=13 Hz, PhCHHS), 3.66 (2H, m, PhCH2CO), 3.11 (1H, dd, J=13, 5 Hz, CHHCHN), 2.99 (1H, dd, J=13, 8 Hz, CHHCHN); ESI-LCMS e/z calcd for C32H27N3O6S 581.646, found 582 (M+H)+, 604 (M+Na)+.
