Stereoselective synthesis of β-C-d-glucopyranosides using the reaction of TMSCN and Grignard reagents with cyclic five-membered sulfonium salt intermediates

In the presence of a Lewis acid, ArSCl adducts of tri-O-benzyl-d-glucal react with vinyl ethers to form cyclic five-membered sulfonium salt intermediates. The latter are capable of reacting with TMSCN and Grignard reagents furnishing exclusively 2-S-(aryl)-2-thio-β-C-d-glucopyranosides. The one-pot reaction also proceeds with high stereoselectivity of C–C bond formation in the lateral chain providing exclusively or predominantly C-glycosides with (S)-configuration of the chiral center in the lateral chain.