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 transfer, from the transformation of (R)-1,2-propanediol to acetol. In this yeast-mediated oxidation, we found that 1.7 mol of acetol was produced with consumption of 1 mol of oxygen (85% efficiency). The oxidation 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 the agitation rate, and p(o2). It increased with increasing k(L)a . P-o2, then became constant at a value above 100 atm/h. Treatment of racemic 1,2-propanediol, -butanediol, or -pentanediol in a 19-l bubble-column reactor afforded mixtures of the corresponding (S)-1,2-alkanediols with about 79% enantiomeric excess and the corresponding 1-hydroxy-2-alkanones. The latter were easily separated as an aqueous solution, that was directly used in the bakers' yeast-mediated bioreduction to prepare (R)-1,2-alkanediols.