Synthesis of methyl 4,6- O-methylene- D-glycopyranosides

Abstract

Methyl 4,6- O-methylene- D-glycopyranosides having the α- D- altro, α- and β- D- gluco, α- D- manno, and α- D- galacto configurations were prepared in 3.4 to 27.4% yields by condensing formaldehyde from 1,3,5-trioxane with the methyl glucosides in anhydrous 1,4-dioxane at 95° with boron trifluoride as the catalyst. A crystalline methyl 2,3:4,6-di- O-methylene-α- D-mannopyranoside was also isolated. Crystalline methyl 4,6- O-methylene 2,3-di- O-p-tolylsulfonyl-α- D-galacto- and α- D-glucopyranosides were prepared in 78 and 54.4% yields. N.m.r. coupling constants of the 2,3-di- O-acetyl derivatives of the 4,6- O-methylene glycosides were used to establish the Cl( D) conformation for each derivative.