Engineering a Keto-Reductase for the Mass-Efficient Synthesis of a Key Building Block, Trans -Ethyl (3-Hydroxycyclobutyl)Acetate

The chiral building block ethyl (3-hydroxycyclobutyl)acetate is vital for synthesizing several drug classes. Traditional chemical synthesis often suffers from multi-step routes with low overall yield and significant challenges in achieving efficient stereocontrol for this chiral cyclobutane derivative. This study develops a new route to its trans isomer via AI-driven enzyme engineering. A tailored keto-reductase ( Bu KRED-M3) was created using semi-rational design and machine learning method, achieving >98.0% de for this non-native substrate. The resulting biocatalytic process cuts production costs by 33.8% versus prior routes, featuring a shorter, higher-yielding synthesis with reduced PMI, thereby offering a promising approach to more efficient manufacturing of this chiral intermediate.