反应详情

温度

0 °C

To a stirred solution of benzyl N-benzyloxycarbonyl-glycyl-L-proline 3 (0.4 g, 1.3 mmol) under nitrogen in dry dichloromethane (20 cm3) was added diisopropylethylamine (0.31 cm3, 1.76 mmol). The suspension was stirred for 5 min (a solution was obtained), cooled to 0° C. and ethyl chloroformate (0.166 cm3, 1.73 mol) was added. After 45 min a solution of diisopropylethylamine (0.31 cm3, 1.76 mmol) and p-toluenesulphonate 2 (0.644 g, 1.70 mmol) in dry dichloromethane (20 cm3) was added dropwise over 5 min. The cooling bath was removed and the resultant solution was stirred overnight. The solvent was removed in vacuo and the residue was chromatographed (silica gel, 50-100% ethyl acetate-hexane) to give fully protected tripeptide 4 (0.502 g, 78%) as a colourless oil. Tripeptide 4 was shown to be a 84:16 trans.-cis mixture of conformers by 13C NMR analysis (the ratio was estimated from the integration of the ψEβ-C carbons at δ 34.0 and 33.6 and the Eγ-C carbons at δ 18.5 and 18.8 of the major and minor conformers respectively): [α]D −70.3 (c 0.8 in dichloromethane); δH (300 MHz; CDCl3; Me4Si) 0.87 (3H, d, J 6.0, Eγ-CH3), 1.26-1.33 (2H, m, Eγ-H2), 1.58-1.68 (1H, m, Eβ-HAHB), 1.70-2.26 (5H, m, Eβ-HAHB, Proβ-H2, and Proγ-H2), 3.38 (0.84H, d, J 7.6, Proδ-HAHB), 3.51-3.56 (0.84H, m, Proδ-HAHB), 3.60-3.65* (0.32H, m, Proδ-H2), 3.76* (0.16H, d, J 16.5, Glyα-HAHB), 3.91 (1.84H, m, Glyα-H2), 4.37* (0.16H, br s, Proα-H), 4.49-4.62 (2H, m, Proα-H, Eα-H), 5.09-5.21 (4H, m, 2×OCH2Ph), 5.85 (1H, br s, Gly-NH), 7.2 (1H, d, J 5.5, Eα-NH) and 7.34 (10H, s, 2×Ph); δC (75 MHz; CDCl3) 13.4 (CH3, Eγ-CH3), 13.5* (CH3, Eγ-CH3), 18.5 (CH2, Eγ-C), 18.8* (CH2, Eγ-C), 22.2* (CH2, Proγ-C), 24.7 (CH2, Proγ-C), 27.7, (CH2, Proβ-C) 31.9* (CH2, Proβ-C) 33.6* (CH2, Eβ-C), 34.0 (CH2, Eβ-C), 43.3 (CH2, Glyα-C), 46.2 (CH, Proδ-C), 47.0* (CH, Proδ-C), 52.1* (CH, Eα-C), 52.3 (CH, Eα-C), 59.9 (CH, Proα-C), 66.8 (CH2, OCH2Ph), 67.1* (CH2, OCH2Ph), 127.9 (CH, Ph), 127.99 (CH, Ph), 128.0 (CH, Ph), 128.1* (CH, Ph), 128.2 (CH, Ph), 128.4 (CH, Ph), 128.5 (CH, Ph), 135.4 (quat., Ph), 136.3 (quat., Ph), 156.2 (quat., NCO2), 156.4* (quat., NCO2), 167.9 (quat., Gly-CO), 168.2* (quat., Gly-CO), 170.7 (quat., Pro-CON), 171.1* (quat., Pro-CON) and 172.1 (quat., Eα-CO); m/z (FAB+) 495.2381 (MH+.C27H33N3O6 requires 495.2370). ψE refers to the proline analog portion in question* Denotes resonances assigned to minor conformer.

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2. customThe cooling bath was removed
3. stirringthe resultant solution was stirred overnight
4. customThe solvent was removed in vacuo
5. customthe residue was chromatographed (silica gel, 50-100% ethyl acetate-hexane)