Although yeast reduction of α-diketones 1 affords a mixture of two α-hydroxy ketones and a vic-diol, the use of methyl vinyl ketone as an enzyme inhibitor prevents the production of the diol. Regioselectivity in the reduction to afford α-hydroxy ketones is improved by thermal pre-treatment of baker's yeast. Thus, 1-phenyl-2-hydroxy-1-propanone 3a is obtained in 80 % yield with >98% e.e.