To a solution of (1S,9S) t-butyl 9-amino-6,10-dioxo-octahydro-6H-pyyridazino [1,2-a][1,2]diazepine-1-carboxylate (690 mg; 2.32 mmol; GB 2128984) in dioxane (16 ml) and water (4 ml) at 0° C. was added solid sodium bicarbonate (292 mg; 3.48 mmol) followed by dropwise addition of 3-phenylpropionyl chloride (470 mg; 2.78 mmol). The mixture was stirred at room temperature for 2 h then more sodium bicarbonate (200 mg; 2.38 mmol) and 3-phenylpropionyl chloride (100 mg; 0.6 mmol) was added. The mixture was stirred for a further 2 h at room temperature, diluted with ethyl acetate (50 ml), washed with saturated sodium bicarbonate (2×25 ml) then dried (MgSO4) and concentrated. The residue was purified by flash chromatography (0-50% ethyl acetate/chloroform) and finally crystallized by trituration with ether to afford 860 mg (86%) of a white solid: mp. 137-138° C.; [α]D23 −95.1° (c 0.549, CH2Cl2); IR (KBr) 3327, 1736, 1677, 1664, 1536, 1422, 1156; 1H NMR (CDCl3) δ 7.24 (5H, m), 6.50 (1H, d, J=7.5), 5.24 (1H, m), 4.90 (1H, m), 4.60 (1H, m), 3.44 (1H, m), 2.93 (2H, m), 2.84 (1H, m), 2.64 (1H, m), 2.54 (2H, m), 2.26 (2H, m), 1.70 (4H, m), 1.70 (9H, s). MS(FAB, m/z): 430 (M++1), 374, 242, 105, 91. (1S,9S)t-Butyl octahydro-10-oxo-9-(3-phenylpropionylamino)-6H-pyridazino-[1,2-a][1,2]diazepine-1-carboxylate (44b), was prepared from (1S,9S)-t-butyl 9-amino-octahydro-10-oxo-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxylate (Attwood et al., J. Chem. Soc. Perkin 1, pp. 1011-19 (1986)) as for 44a, to afford 810 mg (81%) of a colorless oil: [α]D23 −33.5° (c 0.545, CH2Cl2); IR (film) 3334, 2935, 1737, 1728, 1659, 1642; 1H NMR (CDCl3) δ 7.24 (5H, m), 6.75 (1H, d, J=6.7), 5.27 (1H, m), 4.92 (1H, m), 3.39 (1H, m), 3.03 (4H, m), 2.55 (3H, m), 2.33 (1H, m), 2.17 (1H, m), 1.80 (5H, m), 1.47 (9H, s), 1.39 (1H, m). MS(FAB, m/z): 416 (M++1), 360, 211, 143, 97. (1S,9S) 6,10-Dioxo-octahydro-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxylic acid (45a). To a solution of (1S,9S) t-butyl 6,10-dioxo-octahydro-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxylate (44a) (800 mg; 1.863 mmol) in dry dichloromethane (5 ml) at 0° C. was added trifluoroacetic acid (5 ml). The solution was stirred at room temperature for 3 h then concentrated. Dry ether (10 ml) was added to the residue then removed under vacuum. This process was repeated three times to afford a crystalline solid. The solid was triturated with ether and filtered to afford 590 mg (85%) of a white crystalline solid: mp. 196-197.5° C.; [α]D23 −129.5° (c 0.2, CH3OH); IR (KBr) 3237, 1729, 1688, 1660, 1633, 1574, 1432, 1285, 1205; 1H NMR (CD3OD) δ 8.28 (1H, d, J=7.4), 7.22 (5H, m), 5.32 (1H, dd, J=5.9, 2.9), 4.75 (1H, m), 4.51 (1H, m), 3.50 (1H, m), 3.01 (1H, m), 2.91 (2H, m), 2.55 (2H, m), 2.29 (3H, m), 1.95 (2H, m), 1.71 (2H, m). Anal. Calcd for C19H23N3O5: C, 61.12; H, 6.21; N, 11.25. Found: C, 60.80; H, 6.28; N, 10.97. MS(FAB, m/z) 374 (M++1), 242, 105, 91. (1S,9S) Octahydro-10-oxo-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a]-[1,2]diazepine-1-carboxylic acid (45b), was prepared from (1S,9S) t-butyl octahydro-10-oxo-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxylate (44b) by the method described for compound 45a to afford 657 mg (96%) of 45b as a crystalline solid: mp. 198-202° C.; [α]D23 86.2° (c 0.5, CH3OH); IR (KBr) 3294, 2939, 1729, 1645, 1620, 1574, 1453, 1214; 1H NMR (CD3OD) δ 7.92 (1H, d, J=7.9), 7.20 (5H, m), 5.29 (1H, m), 4.90 (1H, m), 3.47 (1H, m), 3.08 (2H, m), 2.90 (2H, m), 2.55 (3H, m), 2.36 (1H, m), 1.81 (5H, m), 1.43 (2H, m). MS(FAB, m/z) 360 (M++1), 211,143,91. [3S,2R,S,(1S,9S)] N-(2-Benzyloxy-5-oxotetrahydrofuran-3-yl)-6,10-dioxo-octahydro-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxamide (46a). To a solution of (1S,9S) 6,10-dioxo-octahydro-9-(3-phenyl-propionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxylic acid (45a) (662 mg; 1.773 mmol) in dry dichloromethane (9 ml) and dry dimethyl formamide (3 ml) at room temperature was added bis(triphenylphosphine)palladium chloride (30 mg) and (3S,2R,S)-3-allyloxycarbonylamino-2-benzyloxy-5-oxotetrahydrofuran (Chapman, Biorg. Med. Chem. Lett., 2, pp. 613-18 (1992)) (568 mg; 1.95 mmol) followed by dropwise addition of tri-n-butyltin hydride (1.19 g; 4.09 mmol). 1-Hydroxy-benzotriazole (479 mg; 3.546 mmol) was added to the mixture and the mixture was cooled to 0° C. before addition of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (408 mg; 2.128 mmol). The mixture was stirred at room temperature for 3.25 h then diluted with ethyl acetate (50 ml), washed twice with dilute hydrochloric acid (20 ml), twice with saturated sodium bicarbonate (20 ml), once with brine then dried (MgSO4) and concentrated. The resulting oil was purified by flash chromatography (0-100% ethyl acetate/chloroform) to afford 810 mg (81%) of 46a as a mixture of anomers: mp. 92-94° C.; IR (KBr) 3311, 1791, 1659, 1651, 1536; 1H NMR(CDCl3) δ 7.49, 6.56 (1H, 2d, J=6.7, 7.8), 7.29 (10H, m), 6.37, 6.18 (1H, 2d, J=7.7,7.6), 5.56, 5.34 (1H, d, s, J=5.2), 5.08-4.47 (6H), 3.18-2.80 (5H), 2.62-2.28 (5H), 2.04-1.53 (5H). MS(FAB, m/z), 563 (M+1), 328, 149, 91. [3S,2R,S, (1S,9S)] N-(2-Benzyloxy-5-oxotetrahydrofuran-3-yl)-octahydro-10-oxo-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxamide (46b), was prepared from 45b by the method described for 46a to yield 790 mg (96%) of a glass: m.p. 58-60° C.; IR (KBr) 3316, 2940, 1793, 1678, 1641, 1523, 1453, 1120; 1H NMR (CDCl3) δ 7.28 (10H, m), 6.52, 6.42 (1H, 2d, J=7.2, 7.1), 5.53, 5.44 (1H, d, s, J=5.2), 5.35 (1H, m), 4.6-4.9, 4.34 (4H, m), 3.1-2.8 (6H, m), 2.6-2.1 (7H), 1.95-1.05 (5H). MS(FAB, m/z), 549 (M++1), 400, 310, 279, 91. [3S, (1S,9S)] 3-(6,10-Dioxo-octahydro-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxamido)-4-oxobutanoic acid (47a). A mixture of [3S,2R,S, (1S,9S)] N-(2-benzyloxy-5-oxotetrahydrofuran-3-yl)-6,10-dioxo-octahydro-9-(3-phenylpropionylamino)-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxamide (46a) (205 mg; 0.364 mmol), 10% palladium on carbon (200 mg) and methanol (20 ml) was stirred under hydrogen at atmospheric pressure for 5 h. The mixture was filtered then concentrated to yield 154 mg (90%) of a glass: mp. 116-118° C.; [α]D23 −140° (c 0.1, CH3OH); IR (KBr) 3323 (br), 1783, 1731, 1658, 1539, 1455, 1425; 1H NMR (CD3OD) δ 7.21 (5H, m), 5.17 (1H, m), 4.73 (1H, m), 4.50 (2H, m), 4.23 (1H, m), 3.38 (1H, m), 3.06 (1H, m), 2.91 (2H, m), 2.73-2.18 (6H, m) and 2.01-1.59 (5H, m). Anal. Calcd for C23H27N4O7 +H2O: C, 56.32; H, 6.16; N, 11.42. Found: C, 56.29; H, 6.11; N, 11.25. MS(FAB, m/z) 473 (M++1), 176, 149, 105, 91. [3S,(1S,9S)]3-(Octahydro-10-oxo-9-(3-phenylpropionylamino)-6H-pyridazino-[1,2-a][1,2]diazepine-1-carboxamido)-4-oxobutanoic acid (47b), was prepared from 46b by the method described for 47a. The residue was purified by flash chromatography (0-10%methanol/chloroform) to afford 65 mg (52%) of a glass; m.p. 87-90° C.; [α]D23 −167.0° (c 0.1, methanol); IR (KBr) 3329, 2936, 1786, 1727, 1637; 1H NMR (CD3OD) δ 7.23 (5H, m), 5.29 (1H, m), 4.83 (1H, m), 4.59 (1H, d, J=3.6), 4.29 (1H, m), 3.3-3.0 (3H, m), 2.91 (2H, m), 2.70-2.34 (5H, m), 2.19 (2H, m), 1.75 (4H, m), 1.36 (2H, m). Anal. Calcd for C23H30N4O6+0.5H2O: C, 59.09; H, 6.68; N, 11.98. Found: C, 58.97; 6.68; N, 11.73. MS(FAB, m/z) 459 (M++1), 310, 149, 105, 91.
