[H-].[Na+].[C:3]([O:11][CH2:12][CH3:13])(=[O:10])[CH2:4][C:5]([O:7][CH2:8][CH3:9])=[O:6].[H][H].CS(O[C@@H:21]([CH3:26])[CH2:22][CH2:23][CH2:24][CH3:25])(=O)=O.[Cl-].[NH4+]>COCCOC.CN(C)C=O.CCOCC>[CH3:26][C@@H:21]([CH:4]([C:5]([O:7][CH2:8][CH3:9])=[O:6])[C:3]([O:11][CH2:12][CH3:13])=[O:10])[CH2:22][CH2:23][CH2:24][CH3:25]At room temperature, a three-neck flask with internal thermometer, dropping funnel and stirrer was initially charged under protective nitrogen gas with 14.7 g of sodium hydride (95% pure, 0.583 mol) in 290 ml of dry 1,2-dimethoxyethane and 50 ml of dry dimethylformamide. Subsequently, 97.5 g of diethyl malonate (0.609 mol) were added dropwise at from 25 to 30° C. with evolution of hydrogen. The clear mixture was stirred at 25° C. for 30 min and 93 g of (S)-1-methylpentyl methanesulfonate (0.516 mol) were added undiluted. The mixture was heated to 80° C. and stirred for 5 h. After cooling to 25° C., the suspension was admixed with 600 ml of ether and 500 ml of saturated ammonium chloride solution. After phase separation, the organic phase was washed with 250 ml of water and then dried over sodium sulfate. After distillative removal of solvent, diethyl [(R)-1-methylpentyl]malonate was obtained in a yield of 119 g (94% of theory) and a chemical purity of 95% (GC).
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