Potassium Carbonate → 6-[4-(2-Tert-butoxycarbonylamino-2-carboxy-ethyl)-phenoxy]-nicotinic acid methyl ester

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Potassium carbonate (1.23 g, 8.9 mmol) and methyl 6-chloronicotinate (1.8 g, 10.66 mmol) were added to a solution of Boc-tyrosine (1.0 g, 3.55 mmol) in anhydrous DMF (15 mL). The resulting suspension was refluxed at 70 deg C. under an atmosphere of argon. After 72 hrs, the reaction mixture was cooled to room temperature, diluted with water (100 mL) and extracted with EtOAc (2×100 mL). The aqueous layer was collected, acidified with 5.0 M HCl to pH ˜2.5 and extracted with EtOAc (2×100 mL). The resulting EtOAc layer was extracted with water (1×150 mL) and brine (1×150 mL), dried over anhydrous magnesium sulfate, filtered and concentrated and flash chromatographed (30-40% ethyl acetate in hexane with 1% acetic acid) to yield desired ester, 17 as a solid (1.4 g). 1H NMR (400 MHz, DMSO-d6): 12.45 (s, 1H), 8.68 (br, 1H), 8.29 (dd, J=8.4 and 2.4 Hz, 1H), 7.31 (d, J=8.4 Hz, 2H), 7.14 (d, J=8.8 Hz, 1H), 7.08 (m, 3H), 4.12 (m, 1H), 3.85 (s, 3H), 3.05 (dd, J=14.0 and 4.0 Hz, 1H), 2.84 (dd, J=14.0 and 10.8 Hz, 1H) 1.33 (s, 9H)

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