HCID 57956922, compound → Compound 20

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Reaction Steps

To a stirred solution of the (5S)-5-[(N-benzoyl)amino]-4-oxo-6-phenyl-hexanoyl-L-proline benzyl ester (100 mg, 0.1951 mmol) in dry EtOAc-MeOH (3:1 ratio) (10 mL) was added 10% Pd/C (100 mg) and the resulting mixture stirred at room temperature under 1 atmosphere of hydrogen for 24 h. Filtration of the black Pd residue and evaporation of the filtrate gave a pale yellow crude residue. Column chromatography on silica gel elution with 37% MeOH-EtOAc afforded the (5S)-5-[(N-benzoyl)amino]-4-oxo-6-phenyl-hexanoyl-L-proline 5a as a white solid powder (68 mg, 82%): mp 148-149° C. (lit.12 mp 151-153° C.); Rf 0.28 (37% MeOH-EtOAc); IR (KBr) ν 1765 (CO), 3300 (broad, COOH) cm−1; 1H NMR (300 MHz, CD3OD) δH 2.01 (2H, m, —CH2), 2.51 (4H, m, —CH2CO and —CH2CH2N), 2.78 (2H, m, —CH2CO), 3.02-3.38 (4H, m —CH2Ph and —CH2N—), 4.84 (1H, m, —CH—), 4.98 (1H, m, —CH—) and 7.08-7.68 (10H, m, Ar—H); 13C NMR (75 MHz, CD3OD) δC 22.6, 24.5, 28.6, 34.3, 36.2, 46.4, 59.9, 61.8, 126.6 (2C), 126.8 (2C), 128.4, 128.9 (2C), 129.0, 131.6, 133.5, 136.6, 136.9, 167.9, 171.0, 179.3 and 208.9; HRMS m/z calcd for C24H26N2O5 (M+) 422.18417, found 422.18417. [± The carboxylic acid and amide protons were not observed, presumably, due to rapid exchange with water in the deuteriated NMR solvent.]

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