A solution of sodium diethyldihydroaluminate (4.44 ml, 8.9 mmole) in a concentration of 2 moles per liter in toluene, is added to a solution of cyclohexylamine (1.76 g, 2.03 ml, 18 mmole) in anhydrous toluene (60 ml). The reaction mixture is heated to 110° C. for 1 hour, then a solution of methyl-5-[benzyl{2-(2-methoxyphenoxy)ethyl}amino]pentanoate (6 g, 16 mmole) in toluene (25 ml) is added dropwise. The mixture is heated under reflux for 3 hours and left for 18 hours at 20° C., then neutralised with a 10% solution of acetic acid. The organic phase is extracted then washed successively with a saturated solution of sodium hydrogen carbonate then with water. After drying over magnesium sulfate and evaporation of the solvents under reduced pressure, the product is purified by flash chromatography over silica gel in a mixture of ethyl acetate/heptane (2/1). 3.3 g (47%) of the desired product are obtained in the form of an oil.
