[CH3:1][P:2](=[O:7])([O:5][CH3:6])[O:3][CH3:4].C([Li])CCC.[CH3:13][CH:14]([CH2:20][CH2:21][CH2:22][CH3:23])[CH2:15][C:16](OC)=[O:17].C(O)(=O)C>C1COCC1.O>[CH3:13][C@@H:14]([CH2:20][CH2:21][CH2:22][CH3:23])[CH2:15][C:16](=[O:17])[CH2:1][P:2](=[O:7])([O:5][CH3:6])[O:3][CH3:4]
To a solution of dimethyl methylphosphonate (32.5 g, 0.262 mol) in anhydrous THF (480 ml) was dropwise added 1.63N n-butyl lithium (160 ml, 0.261 mol) at -78° C. After stirring for 30 minutes, a solution of methyl l-3-methylheptanoate (16.5 g, 0.104 mol) in anhydrous THF (25 ml) was added dropwise, and the mixture was stirred at -78° C. for one hour and at room temperature for 2 hours. Acetic acid (19 ml) and water (100 ml) were added to the reaction mixture. After distilling off THF, the residue was extracted with ether (500 ml×3). The combined organic layers were washed with brine (250 ml×2), dried over anhydrous sodium sulfate, and concentrated. The residue was distilled under reduced pressure to give dimethyl (4S)-4-methyl-2-oxo-octylphosphonate (23.6 g, 0.094 mol, 90%, b.p.=124°-125° C./0.5 mmHg). The structure was confirmed by the following data.
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