Et3N (209 uL), HOBT (91.2 mg) and WSC (115 mg) were added to a suspension of 1-cyclopropyl-4-(methyloxy)-1H-indole-6-carboxylic acid (145 mg) and N-carbamoylmethyl-4-oxo-spiro[chroman-2,4′-piperidine]-6-carboxamide hydrochloride (354 mg) in DMF (3 mL), and the mixture was stirred overnight at 50° C. After cooled to room temperature, the mixture was diluted with water, and the formed solid was collected by filtration. The solid was dried and purified on silica gel preparative TLC (development: CHCl3/MeOH) to obtain the intended compound as colorless foam. 1H-NMR (400 MHz, DMSO-d6) δ: 8.84-8.72 (1H, m), 8.80-8.62 (1H, m), 8.33-8.29 (1H, m), 8.08 (1H, dd, J=8.7, 2.3 Hz), 7.35 (1H, s), 7.28 (1H, d, J=3.2 Hz), 7.23-7.16 (2H, m), 6.99 (1H, s), 6.58 (1H, d, J=1.0 Hz), 6.39 (1H, dd, J=3.2, 0.7 Hz), 4.40-4.02 (2H, br m), 3.87 (3H, s), 3.80-3.76 (2H, br m), 3.48-3.25 (4H, m), 2.98 (2H, s), 2.06-1.56 (2H, m), 1.09-1.01 (2H, m), 0.95-0.89 (2H, m); MS [M+H]+=531.
