Convenient Synthesis of 3-Glycosylated Isocoumarins

A new route for the synthesis of 3-substituted and 8-hydroxy-3-substituted isocoumarins was developed by modified Julia olefination for initial C–C bond formation between aldehydes and benzylic sulfones. Palladium-catalyzed Meinwald rearrangement was used as a key step for the obtainment of ketone intermediates, which – upon base-promoted intramolecular cyclization – afforded the desired isocoumarins. The developed method paves the way to hitherto unknown 3-glycosylisocoumarins, in general, and 3-glucosylisocoumarins, in particular, wherein the glucosyl moiety is attached to the pyrone ring of the isocoumarin framework.