反应详情

A suspension of L-norvaline 1 (1.0 g, 8.53 mmol) benzyl alcohol (5 cm3) and p-toluenesulphonic acid (1.70 g, 8.96 mmol) was heated under reflux in benzene (25 cm3) with the removal of water (Dean-Stark trap) for 17 h (a solution resulted after 5 min). The solution was then cooled to room temperature and dry ether was added. Upon cooling to 0° C. a white solid precipitated and was collected by filtration, washed with dry ether and dried to give p-toluenesulphonate 2 (3.07 g, 95%) as a white solid: mp 142-144° C.; [α]D −1.45 (c 1 in dichloromethane); δH (200 MHz; CDCl3; Me4Si) 0.7 (3H, t, J 7.1, 5-H3), 1.09-1.37, (2H, m, 4-H2), 1.74, (2H, app. quartet, J 7.9, 3-H2), 2.30 (3H, s, Ar—CH3), 3.99 (1H, t, J 6.2, 2-H2), 4.98 (1H, d, J 12.3, OCHAHBPh), 5.11 (1H, d, J 12.3, OCHAHBPh), 7.07 (2H, d, J 8.0, 3′-H); 7.22-7.30 (5H, m, Ph-H) and 7.74 (2H, d, J 8.0, 2′-H); δC (50 MHz; CDCl3) 13.4 (CH3, 5-C), 17.9 (CH2, 4-C), 21.2 (CH3, Ar—CH3) 32.3 (CH2, 3-C), 53.1 (CH, 2-C), 67.6 (CH2, OCH2Ph), 126.0 (CH, Ph), 128.2 (CH, Ph), 128.3 (CH, Ph), 128.4 (CH, Ph), 128.7 (CH, Ph), 134.8 (quat., Ph), 140.2 (quat., Ph), 141.4 (quat., Ph) and 169.4, (quat., 1-C); m/z (FAB) 587.2777[M2.pTsOH.H+: (C12H17NO2)2.C7H8O3S.H requires 587.2791].

1. temperaturewas heated
2. customresulted after 5 min)
3. temperatureUpon cooling to 0° C. a white solid
4. customprecipitated
5. filtrationwas collected by filtration
6. washwashed with dry ether
7. customdried