A concise synthetic approach for isoiminosugars

Isoiminosugars are highly biological active substances. Herein, we report a concise synthetic approach for this class of compounds. The key step relies on a stereospecific 1,2-hydride shift in O-2 tosylated glycopyranosides leading to C-2 branched glycofuranosides. This approach enables a 4-step synthesis of powerful β-galactosidase inhibitor 4-epi-isofagomine starting from a simple d-glucopyranoside.