[O-]CC.[Na+].[C:5]([O:13][CH2:14][CH3:15])(=[O:12])[CH2:6][C:7]([O:9][CH2:10][CH3:11])=[O:8].CS(O[C@@H:21]([CH3:25])[CH2:22][CH2:23][CH3:24])(=O)=O.[Cl-].[NH4+]>COCCOC.C(O)C.C(Cl)Cl>[CH3:25][C@@H:21]([CH:6]([C:7]([O:9][CH2:10][CH3:11])=[O:8])[C:5]([O:13][CH2:14][CH3:15])=[O:12])[CH2:22][CH2:23][CH3:24]At room temperature, a three-neck flask with internal thermometer, dropping funnel and stirrer was initially charged under protective nitrogen gas with 41.8 g of sodium ethoxide (95% pure, 0.583 mol) in 250 ml of dry 1,2-dimethoxyethane and 30 ml of dry ethanol. Subsequently, 97.5 g of diethyl malonate (0.609 mol) were added dropwise at from 20 to 40° C., in the course of which a clear solution formed. The clear mixture was stirred at 40° C. for 30 min, and 85.7 g of (S)-1-methylbutyl methanesulfonate (0.516 mol) were added undiluted. The mixture was heated to 80° C. and stirred for 6 h. After cooling to 25° C., the suspension was admixed with 800 ml of methylene chloride and 500 ml of 5% by weight ammonium chloride solution. After phase separation, the organic phase was washed with 200 ml of water and then dried over sodium sulfate. After distillative removal of solvent, diethyl [(R)-1-methylbutyl]malonate was obtained in a yield of 113 g (95% of theory) and a chemical purity of 96% (GC).
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