To a solution of 2,2-diphenylethylamine (0.45 g, 2.3 mmol) and triethylamine (0.35 mL, 2.5 mmol) in methylene chloride (10 mL) is added 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI) (0.48 g, 2.5 mmol), followed by (±)-[2-[[2,6-bis(1-methylethyl)phenyl]amino]-2-oxoethyl]phosphonic acid, ethyl ester (Example 5) (0.74 g, 2.3 mmol). 4-Dimethylaminopyridine (DMAP) (0.1 g) is added and the solution is stirred for 48 hours at room temperature. Additional portions of triethylamine (0.1 mL) and EDCI (0.1 g) are added and stirring is continued for another 24 hours. The reaction mixture is diluted with methylene chloride, washed with water, brine, dried over magnesium sulfate, and concentrated. Flash chromatography (ethyl acetate) affords 0.22 g of the product as a white solid. Recrystallization from ethyl acetate/hexane affords 0.18 g of the title compound as a white solid; mp 172°-176° C.
