Chelation-controlled regioselective endo cleavage and stereoselective C-1 alkylation of pentofuranosides
Combinations of Lewis acids and nucleophilic reagents trigger endo-opening of the furanoside ring of methyl furanosides 1, 10 and 13, resulting in the attachment of the nucleophilic group at C-1 of the carbohydrate. The stereoselectivity in the C-C bond-forming step is low for the 2-deoxyfuranosides but very high (dr 1:99) for the furanosides carrying a methoxy group in the 2-position when a combi