New concise total synthesis of (+)-lentiginosine and some structural analogues.

An efficient and concise total synthesis of (+)-lentiginosine (1) starting from an L-tartaric acid-derived nitrone using organometallic addition, indium-catalyzed reduction, and ring-closing metathesis reaction as the key steps is reported. Structural analogues of (+)-1 have been also synthesized, and their inhibitory activity toward 22 commercially available glycosidases has been evaluated.