Microbial reduction of alpha-substituted-alpha-acetyl-gamma-butyrolactones

The microbial reduction of alpha-methyl, allyl and benzyl derivatives of alpha-acetyl-gamma-butyrolactones was carried out. It has been shown that different microorganisms, Kluyveromyces marxianus, Hansenula sp., Geotrichum candidum and Aspergillus niger, are capable to carry out the enantiospecific/selective reduction of these compounds. In the examples studied K. marxianus afforded the best results in terms of diastereo and enantioselectivity. It was found that depending on the particular microorganism used, a particular enantiomer can be obtained. Since these microorganisms are wild type, that is, are not engineered, they are robust and can be used to scale up these processes, which is going to be the next step of our study. It has been definitively proved that this microbial reduction occurs via the keto form, so clarifying the mechanism of these reactions firstly carried out with unsubstituted compounds.