One-Pot Stereoselective Synthesis of Different Fused Multicyclic Iminosugars Based on the Iminium-Ion Intermediate

Different novel fused multicyclic iminosugars were synthesized from D-ribose tosylate, aniline and vinyl ethyl ether by one-pot three-component stereoselective [4+2] reaction at different temperatures. The iminium-ion is the key intermediate for the reaction. As a result, several complex fused iminosugars 3a were obtained by aza-Diels-Alder mechanism at 60 C-degrees, while a series of aza-C-glycosides 5a were prepared by Mannich reaction at room temperature accompanied by another tetrahydroquinoline-fused iminosugars 4a (tricyclic derivatives) through aza-Diels-Alder cycloaddition. This strategy will help to construct structurally diverse and bioactive iminosugar analogues.