Synthesis of C-arylglycosides via ruthenium-catalyzed cyclotrimerization

Abstract

In the presence of catalytic amounts of an organoruthenium complex, Cp*RuCl(cod), the partially intramolecular cyclotrimerizations of various C-alkynylglycosides proceeded at ambient temperature to afford C-arylglycosides. The [2 + 2 + 2] cycloaddition of α,ω-diynes with C-alkynylglycosides successfully afforded C-arylglycosides in good yields. This method was further extended to the cycloaddition of C-diynylglycosides to obtain C-aryldisaccharides. Spirocyclic C-arylglycosides were also synthesized in good yields via the [2 + 2 + 2] cycloaddition of sugar diynes derived from appropriately protected 5-gluconolactones. This strategy was also extended to the synthesis of spirocyclic C-arylribosides from the known γ- ribonolactone derivative. Moreover, silver-catalyzed iodination of the sugar diynes followed by ruthenium-catalyzed [2 + 2 + 2] cycloaddition with acetylene delivered spirocyclic C-iodophenylglycosides and ribosides, which were then subjected to palladium-catalyzed C-C bond formations such as Sonogashira, Mizoroki-Heck, and Suzuki-Miyaura couplings, or copper-catalyzed Ullmann coupling with nitrogen heterocycles, resulting in the production of various interesting spirocyclic C-arylglycosides.