Cascade Biotransformations via Enantioselective Reduction, Oxidation, and Hydrolysis: Preparation of (R)-δ-Lactones from 2-Alkylidenecyclopentanones

The first cascade biotransfomation involving enantioselective reduction of a C=C double bond, Baeyer-Villiger oxidation, and lactone hydrolysis was developed as a green and sustainable tool for synthesizing enantiopiire delta-lactones. One-pot cascade biotransformations were achieved with Acinetobacter sp. RS1 containing a novel enantioselective reductase and an enantioselective lactone hydrolase and Escherichia coli coexpressing cyclohexanone monooxygenase and glucose dehydrogenase, converting easily available 2-alkylidenecyclopentanones 1-2 into the corresponding valuable flavors and fragrances (R)-delta-lactones 5-6 in high ee. The one-pot synthesis is better than the reported two-step preparation. This concept is useful in developing other redox cascades with the substrates containing C=C double bond.