2,4-Bis-benzyloxy-5-isopropylbenzoic acid (1.25 g, 3.32 mmol) was dissolved in dichloromethane (50 mL) and cooled in an ice bath. Oxalyl chloride (0.32 mL, 3.65 mmol) was added followed by the dropwise addition of DMF (0.1 mL). The reaction was stirred at room temperature for 1 hr then evaporated to dryness under reduced pressure to produce a brown solid. This solid was dissolved in THF (50 mL) and cooled in an ice bath. A solution of 4-Methoxy-N3-methyl-N3-propyl-benzene-1,3-diamine (0.71 g, 3.65 mmol) in THF (20 mL) was added dropwisely followed by the triethylamine (1.6 mL) and the reaction was stirred at room temperature for 16 hrs. Ethyl acetate (50 mL) and water (100 mL) were added. The ethyl acetate layer was washed with water (3×50 mL), dried over magnesium sulfate, filtered and evaporated to dryness to produce the crude product as a brown solid. Purification by silicagel chromatography (elution with 25% ethyl acetate/hexane) provided the desired compound as a white solid (1.8 g, 93%).
