A stirred solution of 4-[5-(4-cyanophenoxy)pentyloxy]-2-hydroxy-N,N-bis(1-methylethyl)benzamide (0.5 g, 1.18 mmol) in 10.0 mL of N,N-dimethylformamide is treated with 60% sodium hydride (47 mg, 1.18 mmol) and ethyl bromoacetate (144 μL, 1.3 mmol), and heated at 70° C. for 2.5 hours. The reaction is partitioned between ethyl acetate and water, dried over sodium sulfate and concentrated in vacuo to afford yellow foam. The resulting ethyl 5-[5-(4-cyanophenoxy)pentyloxy]-2-[N,N-bis(1-methylethyl)aminocarbonyl]phenoxyacetate in 50 mL of anhydrous ethanol at 0° C. is treated with anhydrous hydrogen chloride gas over 30 minutes. This solution is stirred at room temperature for 20 hours and concentrated in vacuo. This material is purified by chromatography on silica gel with 60% ethyl acetate/hexane as the eluent to afford ethyl 4-[5-[3-ethoxycarbonylmethoxy-4-[N,N-bis(1- methylethyl)aminocarbonyl]phenoxy]pentyloxy]benzenecarboximidoate monohydrochloride as colorless foam.
