To a solution of 1.85 g (5.1 mmol) of N,N'-di-BOC-N-[2-(2-pyridyl)-ethyl]-1,3-propanediamine in 20 ml of dioxane there are added, with stirring, 0.4 g (10 mmol) of sodium hydride dispersion (approximately 60% in oil; Fluka, Buchs, Switzerland) and, after 20 minutes, a solution of 1.23 ; (6 mmol) of N-BOC-N-ethyl-3-bromo-propylamine in 2 ml of dioxane. The reaction mixture is stirred at 50° C. for 18 hours, a further 0.4 g (10 mmol) of sodium hydride dispersion (approximately 60%) and 1.23 g (6 mmol) of N-BOC-N-ethyl-3-bromo-propylamine are added at 25° C., the mixture is stirred at 50° C. for a further 18 hours and is then coded to room temperature, 50 ml of water are added, and the reaction mixture is extracted with methylene chloride. The methylene chloride extract is dried over sodium sulfate and concentrated by evaporation. and the residue is purified by flash chromatography on silica gel having a particle size of 0.04-0.063 mm using tert-butyl methyl ether. After concentration of the product-containing fractions by evaporation, the title compound is obtained in the form of an oil, Rf value=0.37 (silica gel/tert-butyl methyl ether).
