C(N[CH:5]([CH3:7])[CH3:6])(C)C.[Li].CN(C)P(N(C)C)(N(C)C)=O.[CH3:20][C:21]1([CH2:26][CH2:27][C:28]([O:30][CH2:31][CH3:32])=[O:29])[O:25][CH2:24][CH2:23][O:22]1.C(I)CC>C1COCC1>[CH3:20][C:21]1([CH2:26][CH:27]([CH2:7][CH2:5][CH3:6])[C:28]([O:30][CH2:31][CH3:32])=[O:29])[O:22][CH2:23][CH2:24][O:25]1To a cooled (−78° C.) solution of lithium diisopropylamine (30 mL; 60 mmol; 2N in THF) in THF (8 mL) was added hexamethylphosphoramide (12 mL) and the solution was stirred for 30 min. A solution of ethyl 3-(2-methyl-1,3-dioxolan-2-yl)propanoate (9.4 g; 50 mmol), in THF (9 mL), was added over 30 min and stirring was continued for 1 h. Propyl iodide (6.84 mL; 70 mmol) was slowly added and the solution was allowed to warm to room temperature for 4 h. the reaction was quenched by adding a saturated aqueous solution of ammonium chloride. The two phases were separated and the aqueous layer was extracted with ethyl acetate (50 mL) and the combined organic layers were dried with sodium sulphatesulphate, filtered and concentrated under reduced pressure. The crude residue was purified by flash-chromatography on silica gel using a gradient of ethyl acetate (0-40%) in heptane to furnish 9.8 g (85%) of ethyl 2-((2-methyl-1,3-dioxolan-2-yl)methyl)pentanoate as an oil.
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