A solution of 1 g (3.31 mmol) of [2-phenyl-1-[[(phenylmethoxy)carbonyl]amino]ethyl]phosphinic acid, 0.66 g (3.75 mmol) of methyl α-methylenebenzenepropanoate and 3.1 ml of N,O-bis(trimethylsilyl)acetamide is maintained at 60° C. for 24 hours. After cooling, 60 ml of a 1/1 ethyl acetate/water mixture are added. The aqueous phase is extracted with ethyl acetate. The combined organic phases are washed with water, dried over sodium sulphate, filtered and evaporated under vacuum. The residue is purified by recrystallization from a mixture of ethyl acetate and hexane. 1.04 g of product are recovered (yield=67%).
