C[O-].[Na+].[C:4]([O:12][CH2:13][CH3:14])(=[O:11])[CH2:5][C:6]([O:8][CH2:9][CH3:10])=[O:7].CS(O[C@@H:20]([CH3:24])[CH2:21][CH2:22][CH3:23])(=O)=O.[Cl-].[NH4+]>C(OCC)(=O)C.C(Cl)Cl>[CH3:24][C@@H:20]([CH:5]([C:6]([O:8][CH2:9][CH3:10])=[O:7])[C:4]([O:12][CH2:13][CH3:14])=[O:11])[CH2:21][CH2:22][CH3:23]
At room temperature, a three-neck flask with internal thermometer, dropping funnel and stirrer was initially charged under protective nitrogen gas with 33.1 g of sodium methoxide (95% pure, 0.583 mol) in 250 ml of dry ethyl acetate. Subsequently, 97.5 g of diethyl malonate (0.609 mol) were added dropwise at from 20 to 30° C. The clear mixture was stirred at 25° C. for 30 min, and 85.7 g of (S)-1-methylbutyl methanesulfonate (0.516 mol) were added undiluted. The mixture was heated to 79° C. and stirred for 7 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 150 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 105 g. The product contains dimethyl ester and ethyl methyl ester, formed by transesterification (GC purity: sum of Me/Me, Me/Et, Et/Et: 96%). The corrected yield is 96% of theory.
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