TEA (0.657 ml, 4.71 mmol) was added to a stirred mixture of HOBT (313 mg, 2.04 mmol), WSCDI (361 mg, 1.89 mmol), 6-(4-oxospiro[chroman-2,4′-piperidin]-6-yl)nicotinamide dihydrochloride (2.61 g, 6.97 mmol) and 2,6-diethoxy-4′-(methoxycarbonyl)biphenyl-4-carboxylic acid (2.00 g, 5.81 mmol) in DMF (30 ml) and the mixture was stirred at room temperature for 3 days. The reaction mixture was poured into water (600 ml) and stirred for 30 min. The resulted precipitate was filtered, washed with water and the solid was dried in vacuo at 70° C. The crude product was purified by silicagel column chromatography (CHCl3/Acetone) to give intended compound (3.85 g, quantitative) as a colorless solid.
