To a solution of 1.529 g (6.759 mM) of S-(diethoxyphosphorylmethyl) thioacetate in 30 ml of methanol was added 1.30 g (6.76 mM) of 28% sodium methoxide-methanol under ice-cooling and the mixture was stirred at the prevailing temperature for 20 minutes. To this reaction mixture was added crude tert-butyl 4-(mesyloxymethyl)piperidine-1-carboxylate [which was prepared by adding 0.73 ml (9.46 mM) of methanesulfonyl chloride to a solution of 1.75 g (8.11 mM) of tert-butyl 4-(hydroxymethylthiomethyl)piperidine-1-carboxylate and 1.51 ml (10.8 mM) of triethylamine in 30 ml of tetrahydrofuran with ice-cooling, stirring the mixture at the prevailing temperature for 0.5 hour, pouring the mixture in water, extracting it with 2 portions of ethyl acetate, drying the pooled organic layer over MgSO4, and concentrating it], and the mixture was refluxed for 3 hours. The solvent was distilled off under reduced pressure and the residue was diluted with water and extracted with 2 portions of ethyl acetate. The organic layers were pooled and dried over MgSO4 and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (hexane-ethyl acetate: 3/1 to ethyl acetate) to provide the title compound.
