A stirred suspension of 4-(pyridin-4-yl)naphth-1-ylacetic acid (D7, 0.18 g, 0.7 mmole) in dichloromethane (15 ml) was treated with oxalyl chloride (0.18 ml, 2.1 mmole), then stirred at room temperature for 3 hours, before evaporating to dryness. The solid residue was suspended in dichloromethane (15 ml), cooled to 0° C. and treated with a solution of 5-amino-3-(1-methylpiperidin-4-yl)-1H-indole (D2, 0.13 g, 0.56 mmole) in dichloromethane (15 ml). The mixture was stirred at 0° for 1 hour and then a solution of triethylamine (0.25 ml) in dichloromethane (5 ml) was added dropwise. The mixture was allowed to warm to room temperature and stir overnight, then evaporated to dryness and the residue subjected to flash chromatography on silica gel eluting with CH2Cl2/MeOH/NH4OH (100:5:0.5 to 100:10:1 gradient elution) to afford the title compound as a pale cream powder (0.04 g).
