An S2-Type Strategy toward 1,2--Furanosides.

The stereoselective construction of 1,2- furanosidic linkage is synthetically challenging. A strategy that applies to all furanose types remains elusive. In this work, a solution is developed based on gold catalysis and the deployment of the directing-group-on-leaving-group strategy, where a basic oxazole group in the gold-activated leaving group facilitates the stereoinvertive attack by glycosyl acceptors. In addition to exhibiting good to excellent 1,2- selectivities, these furanosylation reactions are high-yielding and mostly complete in 30 min to 2 h. A broad range of 1,2--furanosides is prepared. Although some are uncommon, the ease of access enabled by this approach presents new opportunities to study their applications in medicine and materials research.