1′-cyclopropane 5, its methyl α-D-glycoside 7 and its benzyl β-D-glycoside 13 from D-glucose is described, and their conformation in solution is discussed. A Königs-Knorr glycosidation of 10 reveals the ionic intermediate of a 1, 1-(dibromocyclopropyl)carboxonium ion type to be stable against opening of the cyclopropane ring. Very weak inhibition of saccharase was observed for the α-D-configurated