Sodium borohydride was slowly added to pre-cooled tetrahydrofuran at -5-0°C and stirred for 5 min. BF3-etherate (25.6 g) was slowly added to the reaction mixture at -5-0°C and stirred for 15 min at the same temperature. (R)-2-(2-(tert-butoxy)-2-oxoethyl)pentanoic acid (23 g) was added to the reaction mixture and stirred for 3 h. The reaction mixture was slowly quenched with water and raised the temperature of the reaction mixture to 25-30°C. Separated both the aqueous and organic layers and the aqueous layer was extracted with ethyl acetate. Combined the organic layers and washed with aqueous sodium chloride solution. Distilled off solvent completely from the organic layer to get tert-butyl (R)-3-(hydroxymethyl)hexanoate.Yield: 16.2 g.
