Triethylamine (0.2 mL, 1.219 mmol) and DPPA (0.3 mL, 1.219 mmol) were added to a solution of nicotinic acid (150 mg, 1.219 mmol) in toluene (12 mL) under nitrogen atmosphere and stirred at room temperature for 1.5 hours. The reaction mixture was allowed to reflux at 70° C. for 1.5 hours. The reaction was monitored by TLC (5% MeOH in DCM). This was followed by the addition of 1-(benzothiazol-6-ylamino)-butan-2-one (I-168a: 241 mg, 1.097 mmol) at room temperature. The resulting reaction mass was heated at 100° C. overnight. The reaction mixture was cooled to room temperature, concentrated under reduced pressure and the crude residue was partitioned between water and DCM. The organic layer was washed with water, brine solution, dried over Na2S4 and concentrated to afford the crude product. Purification by column chromatography on silica gel (1.5% methanol in chloroform) followed by preparative HPLC afforded 5 mg of the product (1.5% yield).
