2,4-Bis-benzyloxy-5-isopropyl-N-[4-methoxy-3-(methylpropylamino)phenyl]benzamide (700 mg, 1.27 mmol) and Lawesson's reagent (0.31 g, 0.76 mmol) were dissolved in toluene (20 mL) and heated to 110° C. for 3 hrs then evaporated to dryness under reduced pressure to produce a yellow oil. This crude product was dissolved in dioxane (10 mL), anhydrous hydrazine (0.6 mL) was added and the reaction was heated to 80° C. for 30 min. After cooling, ethyl acetate (50 mL) and water (50 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. This solid was dissolved in ethyl acetate (50 mL), CDI (0.66 g, 4.08 mmol) was added then the reaction was heated to reflux for 3 hrs. Removal of the solvent under reduced pressure followed by purification by silicagel chromatography (elution with 50% ethyl acetate/hexane) provided the desired compound as a white solid (250 mg, 33% over 3 steps).
