N1C=CC(CNC(C2C3OCCOC=3C=CC=2)=O)=CC=1.[C:21]([O:25][C:26]([N:28]1[CH2:33][CH2:32][N:31](S(CCCI)(=O)=O)[CH2:30][CH2:29]1)=[O:27])([CH3:24])([CH3:23])[CH3:22].[I-].[Na+]>C(#N)C.CO.O.[Pt](=O)=O>[C:21]([O:25][C:26]([N:28]1[CH2:33][CH2:32][NH:31][CH2:30][CH2:29]1)=[O:27])([CH3:24])([CH3:22])[CH3:23]A stirred solution of the 2,3-dihydrobenzo[1,4]dioxine-5-carboxylic acid (pyridin-4-ylmethyl)amide (1.30 g, 4.8 mmol) and 4-(3-iodopropane-1-sulfonyl)piperazine-1-carboxylic acid tert-butyl ester (prepared from the corresponding chloro compound by treatment with sodium iodide in actone) (2.12 g, 5.1 mmol) in acetonitrile (25 mL) was heated under reflux for 8 hours. The mixture was concentrated in vacuo and the residue was triturated with ethyl acetate. Filtration gave the crude pyridinium iodide which was dissolved in methanol (25 mL) and water (5 mL), and hydrogenated over platinum(IV) oxide (450 mg) at atmospheric pressure for 16 hours. The mixture was filtered through Celite® and the filtrate was partitioned between dichloromethane and aqueous ammonium hydroxide. The dichloromethane was dried (Na2SO4) and evaporated in vacuo. Purification of the residue by silica gel chromatography gave 4-[3-(4-{[2,3-dihydrobenzo[1,4]dioxin-5-carbonyl)amino]methyl}pyridin-1-yl)propane-1-sulfonyl]piperazine-1-carboxylic acid tert-butyl ester (1.05 g, 39%).
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