A pyranose ring contraction of 2,3-di- O -silylated O -galactopyranosides with retention of aglycone promoted by anhydrous trifluoroacetic acid (TFA) in CH2 Cl2 was demonstrated for the first time. In addition, TFA-promoted pyranose ring contraction of 2,3-bis- O -(triisopropylsilyl)- d -galactopyranose with formation of the corresponding anomeric triols in furanose form was successfully performed. A representative series of β- d -galactopyranosides with Me, Bn, allyl, or 3-(trifluoroacetamido)propyl aglycones has been investigated. TBDPS protective groups were found to be more stable than TIPS groups under conditions of TFA-promoted pyranose ring contraction. An easy access to 2,3-di- O -TBDPS-substituted allyl and benzyl galactofuranosides and 2,3-bis- O -(triisopropylsilyl)-β- d -galactofuranose may present an advantage in synthesis of selectively protected monosacharide building blocks, useful for the synthesis of biologically important oligosaccharides. [ABSTRACT FROM AUTHOR]