[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+]>CN(C)C=O.C(Cl)Cl>[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%, 0.583 mol) in 300 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 85° C. and stirred for 5 h. After cooling to 25° C., the suspension was admixed with 1000 ml of methylene chloride and 600 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-methylpentyl]malonate was distilled (85° C., 0.6 mbar) and obtained in a yield of 48 g (38% of theory).
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