OXIDATIVE RESOLUTION WITH BAKERS-YEAST FOR LARGE-SCALE PRODUCTION OF CHIRAL 1,2-ALKANEDIOLS

We studied oxidative resolution with bakers' yeast for the large-scale preparation of chiral 1,2-alkanediol. First, we estimated the outline of the enantioselective oxidation, especially in relation to oxygen t ransfer, from the transformation of (R)-1,2-propanediol to acetol. In this yeast-mediated oxidation, we found that 1.7 mol of acetol was pro duced with consumption of 1 mol of oxygen (85% efficiency). The oxidat ion rate per gram of baker' yeast was correlated to the product of k(L )a, controlled by changing the concentration of bakers' yeast and/or t he agitation rate, and p(o2). It increased with increasing k(L)a . P-o 2, then became constant at a value above 100 atm/h. Treatment of racem ic 1,2-propanediol, -butanediol, or -pentanediol in a 19-l bubble-colu mn reactor afforded mixtures of the corresponding (S)-1,2-alkanediols with about 79% enantiomeric excess and the corresponding 1-hydroxy-2-a lkanones. The latter were easily separated as an aqueous solution, tha t was directly used in the bakers' yeast-mediated bioreduction to prep are (R)-1,2-alkanediols.