反应详情

The experimental procedure employed for the synthesis of compound 5b was followed using the (5S)-5-[(N-benzoyl)amino]-4-oxo-6-phenyl-hexanoyl-L-phenylalanine methyl ester (200 mg, 0.4094 mmol, 1.0 eq.), 0.5N LiOH (5.0 mL) and a mixture THF-MeOH (ratio 3:2) (10 mL) was added 0.5N LiOH (5.0 mL). Work-up and column chromatography on silica gel elution with 20% MeOH-EtOAc afforded the free acid (5S)-5-[(N-benzoyl)amino]-4-oxo-6-phenyl-hexanoyl-L-phenylalanine 5c as a yellow oil (0.187 g, 97%); IR (liquid film) ν 1720 (CO), 3100 (broad, COOH) cm−1; 1H NMR (300 MHz, CDCl3) δH 2.46 (2H, m, —CH2CO), 2.80 (2H, m, —CH2CO), 3.00-3.31 (4H, m, 2×—CH2Ph), 4.81 (1H, q, J=6.0 Hz), 4.98 (1H, ddd, J=2.5, 7.0 and 9.0 Hz, —CH—), 6.30 (1H, m, —NH), 6.94 (1H, t, J=9.3 Hz, Ar—H) and 7.10-7.74 (16H, m, Ar—H and —NH); 13C NMR (75 MHz, CDCl3) δC 29.1, 29.7, 35.3, 36.8, 37.3, 53.3, 59.5, 59.6, 67.7, 127.1 (2C), 127.2 (2C), 128.5, 128.6, 128.7, 129.2, 129.3, 129.4, 131.9, 133.5, 135.8, 136.1, 167.5, 172.0, 174.9 and 207.7; HRMS m/z calcd for C28H28N2O5 (M+) 472.19982, found 472.19982. [± The carboxylic acid and amide protons were not observed, presumably, due to rapid exchange with water in the deuteriated NMR solvent.]

1. washcolumn chromatography on silica gel elution with 20% MeOH-EtOAc