Asymmetric Synthesis of Functionalized 2-Isoxazolines

The asymmetric synthesis of the isoxazoline skeleton was achieved by the oxidation of hydroxylaminoalkyl furan prepared from simple starting materials: 2-methylfuran and (<i>S</i>)-epichlorohydrin. The synthesis features an NBS-mediated oxidation of hydroxylaminoalkyl furan to give an α,β-unsaturated ketone intermediate which cyclized to the isoxazoline. The α,β-unsaturated double bond was successfully cleaved with RuCl₃·<i>x</i>H₂O catalysis en route to the isoxazoline skeleton bearing alcohol, aldehyde, and carboxylic acid functionalities.