KOCN (3.33 g, 41.0 mmol, 5.85 eq.) and Bu4NBr (1.77 g, 5.49 mmol, 0.8 eq.) were added to a solution of the 10-bromodecylmethacrylate from the 1st step (8.36 g, 27.4 mmol, 3.9 eq.) in anhydrous acetonitrile (55 ml) and the reaction mixture was stirred for 64 h. The reaction mixture was subsequently concentrated in vacuo and hexane (100 ml) was added. After filtration of the obtained solution and concentrating in vacuo 4.75 g of a yellow oil was obtained. To this oil a solution of 2-hydroxymethyl-1,3-propylene-bisphosphonic acid tetraethylester (2.41 g, 7.0 mmol) in anhydrous dichloromethane (2.0 ml) and a 1% solution of Metatin 712 in dichloromethane (2.0 ml) were added and the reaction mixture was stirred for 15 h at room temperature. After concentrating in vacuo the obtained crude product was purified by column chromatography (eluent: ethyl acetate/methanol 95:5). 3.85 g (90% yield) of the product was obtained as a colorless oil.
