be limiting the scope of the invention in the examples the following analysis and measurements were conducted using apparatus specified below nmr model am 400 400 mh 2 manufactured by bruker inc internal reference 1 h nmr tetramethylsilane external reference 31 p nmr 85 phosphoric acid optical purity high speed liquid chromatography waters liquid chromatography model 510 manufactured by nippon millipore ltd 34 detector uv detector lambda max model 481 manufactured by nippon millipore ltd 111 g 0 6 mole of 3 bromo 1 5 dimethylbenzene was reacted with 14 6 g 0 6 mole of magnesium metal in 350 ml of dehydrated thf tetrahydrofuran thereby preparing a grignard reagent 57 g 0 3 mole of diethylamidophosphonic dichloride was added dropwise thereto under reflux over a period of 2 hours the resulting mixture was heated under reflux for an additional 2 hours to allow it to react thereafter 400 ml of ice water and 150 ml of a saturated aqueous solution of ammonium chloride were added to the reaction mixture to decompose the salt the thf layer was separated from the aqueous layer 500 ml of concentrated hydrochloric acid was added to the thf layer with ice cooling and the mixture was reacted at 80 u00b0 c for 5 hours the resulting precipitate was filtered off washed with water and then dried thereby obtaining 81 2 g of a crude product this crude product was added to 1 liter of an aqueous solution of 17 8 g of sodium hydroxide to give a uniform solution the insoluble matter was removed by filtration and 20 sulfuric acid was.