Synthesis of Bispidine–Isoxazolidine-Fused Multicyclic Scaffolds via Nitrone [3+2] Cycloaddition: Toward “Hetero-Lupine Alkaloids”

We present a highly efficient strategy for the assembly of bispidine–isoxazolidine-fused multicyclic structures via [3+2] cycloaddition of alkenes to a nitrone-functionalized bispidine framework. The reaction smoothly delivers diverse hybrid heterocycles featuring complex stereochemistry at the isoxazolidine–bispidine junction point in high yields and good selectivity. This approach opens a straightforward pathway to new synthetic analogues of natural compounds (primarily lupine alkaloids) and may prove to be useful for the discovery of new bioactive molecules and ligands for catalysis.