(S)-( + )-Ethyl 3-Hydroxybutanoate (CAS no ), which is also known as Ethyl (S)-3-hydroxybutanoate, could be produced through the following synthetic route.

A 4-L, three-necked, round-bottomed flask equipped with mechanical stirrer, bubble counter, and a stopper is charged with 1.6 L of tap water, 300 g of sucrose, and 200 g of baker's yeast, which are added with stirring in this order. The mixture is stirred for 1 hr at about 30°C, 20.0 g (0.154 mol) of ethyl acetoacetate is added, and the fermenting suspension is stirred for another 24 hr at room temperature. A warm (ca. 40°C) solution of 200 g of sucrose in 1 L of tap water is then added, followed 1 hr later by an additional 20.0 g (0.154 mol) of ethyl acetoacetate. Stirring is continued for 50–60 hr at room temperature. When the reaction is complete by gas chromatographic analysis, the mixture is worked up by first adding 80 g of Celite and filtering through a sintered-glass funnel (porosity 4, 17-cm diam). After the filtrate is washed with 200 mL of water, it is saturated with sodium chloride and extracted with five 500-mL portions of ethyl ether. The combined ether extracts are dried over magnesium sulfate, filtered, and concentrated with a rotary evaporator at 35°C bath temperature to a volume of 50–80 mL. This residue is fractionally distilled at a pressure of 12 mm through a 10-cm Vigreux column, and the fraction boiling at 71–73°C (12 mm) is collected to give 24–31 g (59–76%) of (S)-( + )-ethyl 3-hydroxybutanoate; the specific rotation [α]_D²⁵ + 37.2° (chloroform, c 1.3) corresponds to an enantiomeric excess of 85%.

The enantiomeric excess may be enhanced by several crystallizations of the 3,5-dinitrobenzoate derivative (Note 10) or else by using "starved" yeast.