N1-(Benzo[d]isothiazol-3-yl)-N3-((4′-methoxybiphenyl-4-yl)methyl)propane-1,3-diamine (100 mg, 0.25 mmol), 2-carboxymethyl-pyrrolidine-1-carboxylic acid tert-butyl ester (68 mg, 0.34 mmol), and 1-(3-dimethylaminopropyl)-3-ethylcarboduimide hydrochloride (58 mg, 0.30 mmol) were dissolved in anhydrous methylene chloride (10 mL). Diisopropylethylamine (52 μL, mmol) added to the mixture. The reaction was allowed to stir overnight at room temperature. The solution was washed with water, then dried over anhydrous sodium sulfate and concentrated under reduced pressure. Purification by column chromatography, on silica gel, eluting with a mixture of 3:1 hexanes:ethyl acetate yielded tert-butyl 2-(2-((3-(benzo[d]isothiazol-3-ylamino)propyl)((4′-methoxybiphenyl-4-yl)methyl)amino)-2-oxoethyl)pyrrolidine-1-carboxylate as a solid (30 mg). 1H NMR (300 MHz, CDCl3): 7.90-7.95 (m, 1H), 7.75-7.85 (m, 1H), 7.35-7.55 (m, 6H), 7.19-7.25 (m, 2H), 6.95-7.00 m, 2H), 4.90-5.00 (m, 1H), 4.55-4.65 (m, 2H), 4.19-4.25 (m, 1H), 3.85 (s, 3H), 3.55-3.65 (m, 2H), 3.30-3.35 (m, 2H), 3.10-3.19 (m, 1H), 2.35-2.45 (m, 1H), 2.05-2.15 (m, 1H), 1.80-1.90 (m, 4H), 1.50 ppm (s, 9H). MW=615 confirmed by LC-MS, tr=5.12 min (Method B) MH+=614-616.
