[NH2:1][CH2:2][C:3]1[C:4]([CH2:21][CH2:22][CH2:23][CH2:24][C:25]([O:27][CH2:28][CH3:29])=[O:26])=[C:5]([C:14]2[CH:15]=[N:16][CH:17]=[C:18]([CH3:20])[CH:19]=2)[C:6]2[N:7]([C:9]([CH2:12][CH3:13])=[CH:10][CH:11]=2)[N:8]=1.[C:30](O)(=[O:37])[C:31]1[CH:36]=[CH:35][CH:34]=[CH:33][CH:32]=1.Cl.C(N=C=NCCCN(C)C)C>CN(C)C=O>[C:30]([NH:1][CH2:2][C:3]1[C:4]([CH2:21][CH2:22][CH2:23][CH2:24][C:25]([O:27][CH2:28][CH3:29])=[O:26])=[C:5]([C:14]2[CH:15]=[N:16][CH:17]=[C:18]([CH3:20])[CH:19]=2)[C:6]2[N:7]([C:9]([CH2:12][CH3:13])=[CH:10][CH:11]=2)[N:8]=1)(=[O:37])[C:31]1[CH:36]=[CH:35][CH:34]=[CH:33][CH:32]=1A mixture of ethyl 5-[2-(aminomethyl)-7-ethyl-4-(5-methyl-3-pyridinyl)pyrrolo[1,2-b]pyridazin-3-yl]pentanoate (75 mg), benzoic acid (27.9 mg), 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (54.7 mg) and 1-hydroxybenotriazole (38.5 mg) in dimethylformamide (2 mL) was stirred at ambient temperature for 2 hours. The mixture was partitioned between ethyl acetate and water. The organic layer was separated, washed with saturated sodium bicarbonate solution, water and brine, dried over magnesium sulfate, and evaporated in vacuo. The residue was purified by preparative silica gel column chromatography eluting with a mixture of chloroform and methanol (20:1) to give ethyl 5-[2-[(benzoylamino)methyl]-7-ethyl-4-(5-methyl-3-pyridinyl)pyrrolo[1,2-b]pyridazin-3-yl]pentanoate as yellow oil (60 mg).
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