Reaction Steps
To a stirred solution of (2S*,3S*,5R*)-3-amino-1-benzyloxycarbonyl-5-methoxycarbonyl-2-phenylpiperidine (0.84 g, 2.28 mmol) and 2-methoxy-5-trifluoromethoxybenzaldehyde (0.63 g, 2.85 mmol) in CH2Cl2 (18.0 ml) was added NaB(OAc)3H (0.73 g, 3.42 mmol) potionwise at room temperature. After the turbid reactin mixture was stirred vigorously at room temperature for 4 hours, sat. Na2CO3 aq. solution (15.0 ml) was added to make the mixture to be basic (pH10-11). The CH2Cl2 layer was separated from the mixture, and the aqueous layer was extracted with CH2Cl2 (×4). The combined CH2Cl layer and extracts were dried (Na2SO4), and concentrated in vacuo to give a viscous pale yellow oil (1.49 g). This was chromatographed over SiO2 (Merck Kieselgel 60, 30.0 g). Elution with CH2Cl2 --MeOH (300:1/250:1) gave title compound (1.26 g, 96.2%) as a viscous colorless oil. IR νmax (film): 3450(w), 3330(w), 1740(shoulder, s), 1735(s), 1703(s), 1700(s), 1687(s), 1610(w), 1497(s), 1160(br., s), 1030(s), 815(m), 765(s), 740(s), 700(s) cm-1 ; 1H-NMR δ: 7.65-7.50(m, 1H), 7.52-7.38(m, 1H), 7.40-7.11(m, 8H), 7.2-6.96(m, 2H), 6.74(br.d, J=8.8 Hz, 1H), 5.45-5.34(m, 0.5H), 5.20-5.00(m, 2H), 5.17-5.05(m, 0.5H), 4.49-4.33(m, 0.5H), 4.35-4.17(m, 0.5H), 3.90-3.53(m, 2H), 3.69(br.s, 6H), 3.20(br.dd, J=13.2, 13.2 Hz, 1H), 3.20-3.00(m, 1H), 2.83-2.60(m, 1H), 2.26-1.99(m,2H), 1.52(br.s, 1H) ppm.
