Reaction Steps
The ester (56a) (210 mg, 0.356 mmol) in dichloromethane (0.5 ml) was cooled to 0° C. and treated with trifluoroacetic acid (0.5 ml), stirred and warmed to 20° C. over 30 minutes. The solution was evaporated to dryness under reduced pressure, redissolved in dichloromethane and concentrated (x3). The residue was triturated with ethyl acetate and diluted with ether to afford the title compound 162 mg (85%) as a colorless solid: m.p. 165-8° C. (decomposition); [α]D23 −38.8° (c 0.1, CH3OH); IR (KBr) 3332, 3275, 1723, 1658, 1649, 1597, 1581, 1562, 1526, 1432, 1385, 1258, 1218, 1206; 1H NMR (d6-DMSO) δ 8.96 (1H, d, J=7.3), 8.34 (1H, s), 7.85 (1H, dd, J=7.3), 7.58 (3H, m), 7.35 (5H, m), 6.29 (1H, t, J=7.3), 5.26 (2H, m), 5.15 (2H, s), 4.69 (3H, m), 2.75 (2H, m). Anal. Calcd. C27H23N3O9Cl2: C, 53.66; H, 3.84; N, 6.95. Found: C, 53.36; H, 3.90; N, 6.81. M.S. (+FAB); 604 (M++1), 285, 241, 195, 173, 149, 91. N-2-(6-Benzyl-1,2-dihydro-2-oxo-3-(3-phenylpropionyl) amino-1-pyridyl)acetyl-3-amino-5-(2,6-dichloro-benzoyloxy)-4-oxo-pentanoic acid (57b; P), was prepared by the method described for 57a which afforded the title compound (78%) as colorless crystals: m.p. 116-120° C. (decomposition); [α]D26 −41.1° (c 0.1, CH3OH); IR (KBr) 3299, 1739, 1715, 1689, 1666, 1645, 1598, 1563, 1518, 1432, 1209, 1151; 1H NMR (d6-DMSO) δ 9.24 (1H, s), 8.88 (1H, d, J=7.6), 8.18 (1H, d, J=7.7), 7.60 (3H, m), 7.26 (10H, m), 6.06 (1H, d, J=7.7), 5.23 (2H, ABq), 4.69 (3H, m), 3.93 (2H, s), 2.78 (6H, m). Anal. Calcd. for C35H31N3O8Cl2. H2O: C, 59.16; H, 4.68; N, 5.91. Found: C, 59.38; H, 4.53; N, 5.84. M.S. (+FAB); 694, (Cl=35, 37), (M++1); 692 (Cl=35, 35), (M++1).
