6-Methoxy-quinoline-3-carboxylic acid (27 mg, 0.13 mmol, 1.0 eq) is added at room temperature to a stirred solution of 3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carboxylic acid (trans-4-hydroxymethyl-cyclohexyl)-amide (47 mg, 0.13 mmol, 1.0 eq) in N,N-dimethylformamide (2 mL), followed by N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (28 mg, 0.15 mmol, 1.10 eq) and 4-(dimethylamino)pyridine (24 mg, 0.20 mmol, 1.50 eq). After 15 hours stirring at room temperature, solvent is evaporated and the residue is extracted with dichloromethane (3×10 mL) and water (10 mL). The combined organic layers are dried over sodium sulfate, filtered and concentrated to give a residue that is purified by preparative HPLC to afford 6-methoxy-quinoline-3-carboxylic acid trans-4-[(3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carbonyl)-amino]-cyclohexylmethyl ester as a white solid (7 mg, 10% yield).
