Seven fungi, which are found to reduce ethyl 3-oxobutanoate in high yields,
were tested for their reducing ability for ethyl 2-methyl 3-oxobutanoate.
We obtained some interesting findings. In particular, Penicillium purpuroge
num reduced ethyl 2-methyl 3-oxobutanoate to the corresponding alcohols wit
h the diastereomer (anti/syn) ratio of 93/7 with the enantiomeric excess of
anti-(2S,3S)- and syn-(2S,3R)-hydroxy esters of 90 and >99 ee%, respective
ly.