A solution of diphenylphosphorylazide (0.93 g, 3.4 mmol), 4-hexyloxybenzoic acid (0.68 g, 3.1 mmol) and triethylamine (0.34 g, 3.4 mmol) in toluene (10 ml) was stirred at room temperature for 3.5 hrs and heated at about 90° C. for 2 hrs with stirring. After allowing the mixture to cool (under 0° C.), a solution of 4-(2-aminophenethyl)-2,6-di-tert-butylphenol (1.0 g, 3.1 mmol) in toluene (4 ml) was added dropwise. The solution was warmed up to room temperature and stirred overnight. After distilling off the solvent and purification of the residue by a silica gel column chromatography, recrystallization from ethyl acetate/hexane afforded N-[2-(3,5-di-tert-butyl-4-hydroxyphenethyl)phenyl]-N'-(4-hexyloxyphenyl)urea (1.2 g, 71% yield). m.p. 174°-176° C.
