Tetraethyl methylenediphosphonate (Lancaster) in benzene was added to a benzene solution of sodium hydride (NaH). The product from Example 54, also dissolved in benzene, was then added dropwise to the reaction mixture. After stirring the resulting mixture for 2 h under an Ar atmosphere, the reaction was diluted with CHCl3 /H2O (2/1). The CHCl3 layer was separated and the aqueous layer extracted with CHCl3. Chromatography of the residue after removal of all solvent from the combined extracts gave the title product.
