Asymmetric Reduction of Ketones Using Bakers Yeast

10 Asymmetric Reduction of Ketones Using Bakers Yeast 

Among the strategies developed for the preparation of optically active ester derivatives, the bakers yeast reduction of the corresponding 0-ketoesters is one of the most useful methods. Because of its low cost, ready availability and its utility, bakers yeast can be considered as a relatively simple reagent which is very easy to handle11-31. 

A 2 L three-necked round-bottomed flask equipped with a bubbler and a thermometer was charged with tap water (400 mL), sucrose (75 g) and dried yeast (10 g), added in this order. The mixture was stirred very gently (150 r.p.m.). 

After 1 hour, carbon dioxide should be evolved at approximately 12 bubbles/second. Alternatively the whole reaction may be carried out in a 2 L conical-flask placed in an orbital shaker at 30 °C and 220 r.p.m. 

Ethyl acetoacetate (5 g) was then added dropwise to the fermenting solution and the mixture stirred at ambient temperature for 24 hours. 

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