Synthesis of chiral ethyl 3-hydroxybutanoate


To performe a stereoselective reduction of a carbonyl compound with a biological reagent to obtain chiral ethyl 3-hydroxybutanoate.

stereoselective reduction. Synthesis of chiral ethyl 3-hydroxybutanoate
Synthesis of chiral ethyl 3-hydroxybutanoate


The reduction of ethyl acetoacetate using common baker’s yeast is an example of enzymatic reduction of carbonyl compounds to alcohols in the presence of ester groups. The procedure performed in water shows the stereoselective power of biochemical systems. In this case, the reduction of ethyl 3-acetoacetate with baker’s yeast gives the corresponding (S)-hydroxy ester with a yield from 30 to 70 % and a 58-97 % e.e.

Experimental procedure

A) Yeast reduction of a ketone

To a 500 ml Erlenmeyer flask equipped with a stir bar, add 150 ml of water, and warm to 35 ºC using a hot plate set on low (monitor temperature with a thermometer). When the temperature is stabilized at 35 ºC, add sucrose (7 g) and baker’s yeast (7 g). Let this solution sit for 15 min at 35 ºC. In a test tube, dissolve ethyl acetoacetate (3 g) in hexane (8 ml). Add this solution to the yeast mixture, and stir for 3 h while maintaining the temperature at 35 ºC. At the end of the period, store the reaction mixture at r.t. until the next day.

B) Isolation of the alcohol product

To the yeast solution, add Celite® (5 g) and stir for 1 min. Let the solid settle as much as possible (wait about 5 min). While the solution is settling, set up a vacuum filtration apparatus with a trap using the large Büchner funnel with the corresponding filter paper. First, decant and filter as much of the clear supernatant liquid as possible before adding the Celite® slurry. Wash the Celite® residue with 20 ml of water, and filter the solution once more using the plastic stericup filtration apparatus. To the filtered solution, add 20 g of NaCl and swirl the solution until it dissolves. Extract the aqueous solution with diethyl ether (2 × 50 ml) using a 250 ml separatory funnel. An emulsion occasionally forms. If this happens drain off the lower aqueous layer up to the emulsion. By gently stirring the emulsion with a stirring rod, help break it up. If necessary, transfer the emulsified portions to glass centrifuge tubes, and centrifuge the mixture in order to separate it. Dry the combined ether extracts in an Erlenmeyer flask over anhydrous magnesium sulfate MgSO(approximately 1 g) for 5 min. Eliminate the desiccant by gravity filtration to a tared beaker, and evaporate under vacuum (rotary evaporator) until the volume of liquid remains constant (approximately 1-2 ml). This is the final product, ethyl 3-hydroxybutanoate (an alcohol). Determine and record the weight of the product and calculate the yield.

Physico-chemical properties

This table collects data for the molecular weight (Mw), melting point (M.p.) boiling point (B.p.) and density of the reactives and compounds used in this laboratory experiment.

Name Mw (g/mol) M.p. (ºC) B.p. (ºC) Density (g/ml)
Celite® S - - - -
Diethyl ether74.12-11634.60.71
Ethyl acetoacetate130.14-431811.029
MgSO4120.371124 -1.070

GHS pictograms

Hazard pictograms form part of the international Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and are collected in the followinf Table for the chemical compounds used in this experiment.

Name GHS
Celite® S ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
Diethyl ether ghs02  Danger Warning Flammable pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
Ethyl acetoacetate ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
Hexane ghs02  Danger Warning Flammable pictogram ghs08  Danger Warning Systemic health hazards pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram ghs09  Warning (for cat. 1) (for cat. 2 no signal word) Environmental hazard pictogram
MgSO4 Non-hazardous
NaCl Non-hazardous

International Chemical Identifier

The IUPAC InChI key identifiers for the main compounds used in this experiment are provided to facilitate the nomenclature and formulation of chemical compounds and the search for information on the Internet for these compounds.

Celite® S