1-tert-Butoxycarbonyl-piperidine-4-carboxylic acid (0.5 g; 2.18 mmol) is dissolved in DMF (10 mL) at ambient temperature. 1-Hydroxybenzotriazole (0.37, 2.74 mmol), triethylamine (0.46 mL, 3.3 mmol), 1,7-di-(3-pyridyl)-heptan-4-ol (0.59 g; 2.4 mmol) as prepared according to WO 98/20893 A1 assigned to Vertex Pharmaceuticals, and N-(3-dimethylamino-propyl)-N′-ethylcarbodiimide hydrochloride (0.46 g; 2.4 mmol) are added sequentially. The mixture is stirred at ambient temperature for 18 hours. The mixture is then poured onto ethyl acetate (150 mL) and washed successively with water (50 mL), saturated aqueous sodium bicarbonate (10 mL), and brine (30 mL). The organic layer is dried over MgSO4, filtered, and concentrated in vacuo. The residue is purified via silica gel chromatography with gradient elution (0%→25% methanol in methylene chloride) affording the desired product (0.3754 g) as a yellow solid. ESMS: MH+ 482.4.
