Reaction Steps
D-Leucinamide (1.0 g, 6.0 mmol), 1-(t-butyloxycarbonyl)-5-formylindole (Example 1, 1.23 g, 5.0 mmol) and DCE (15 mL) were mixed at room temperature. Sodium triacetoxyborohydride (1.48 g, 7.0 mmol) was added in one portion with vigorous stirring. After 2 h, another portion (0.15 g, 0.7 mmol) was added and stirring was continued for an additional 6 h. The reaction mixture was diluted with a saturated NaHCO3 solution (10 mL). Three extractions with EtOAc, washing the combined organic layers with brine, drying over Na2SO4 and filtration provided a solution. Removal of solvent in vacuo afforded an oil. Column chromatography (DCM:MeOH:95:5) provided three fractions, after removal of solvent in vacuo: (1) 1-(t-Butyloxycarbonyl)-5-hydroxymethylindole (162 mg, 11% yield, Rf=0.5): 1H NMR (CDCl3, 300 MHz): 8.11 (d, 1H, J=8), 7.61 (d, 1H, J=2), 7.54 (s, 1H), 7.31 (dd, 1H, J=8,2), 6.55 (d, 1H, J=3), 4.75 (s, 2H), 1.69 (s, 9H); (2) 2R-bis-(1-t-butyloxycarbonylindol-5-ylmethyl)amino-4-methylpentanamide BMS594447 (382 mg, 12% yield, Rf=0.4): 1H NMR (CDCl3, 300 MHz): 8.1 (d, 2H, J=8), 7.61 (d, 2H, J=2), 7.52 (s, 2H), 7.31 (dd, 2H, J=8,2), 6.62 (m, 1H), 6.56 (d, 2H, J=4), 6.05 (br s, 1H), 3.85 (d, 2H, J=16), 3.66 (d, 2H, J=16), 3.35 (m, 1H), 1.69 (s, 18H), 0.96 (d, 3H, J=7), 0.87 (d, 3H, J=7); MS (ES+): 589.4 (C35H45N3O5) and (3) the title product (986 mg, 55% yield, Rf=0.3): 1H NMR (CDCl3, 300 MHz): 8.10 (d, 1H, J=8), 7.61 (d, 1H, J=2), 7.49 (d, 1H, J=1), 7.28–7.20 (m, 3H), 6.55 (d, 1H, J=4), 3.93 (d, 1H, J=16), 3.77 (d, 1H, J=16), 3.28–3.20 (m, 1H), 1.69 (s, 9H), 0.94 (d, 3H, J=7), 0.85 (d, 3H, J=7); MS (ES+): 360 (C20H30N3O3, M++H).
