Microwave-Assisted Enantioselective Synthesis of (2R,5S)-Theaspirane: A Green Chemistry Approach

The banana weevil (<i>Cosmopolites sordidus</i>) is a significant pest that reduces banana yields and can result in plant mortality. (2<i>R</i>,5<i>S</i>)-theaspirane, a kairomone from senesced banana leaves, is one of the natural banana volatiles, aiding weevil attraction. A rapid and cost-effective synthesis of (2<i>R</i>,5<i>S</i>)-theaspirane was developed utilizing microwave-assisted conditions and the principles of green chemistry. The process comprised five steps, beginning with the reduction of dihydro-β-ionone, followed by lipase-mediated kinetic resolution to attain high enantiomeric excess. Microwave-assisted heating significantly reduced reaction times. Optimized cyclization with the minimum quantities of selenium dioxide oxidation was employed. The final diastereomers were separated by chromatography, yielding compounds which exceeded 99% enantiomeric purity.