Pentafluoropropionyl and trifluoroacetyl groups for temporary hydroxyl group protection in oligomannoside synthesis

Pentafluoropropionyl (PFP) and trifluoroacetyl (TFA) esters were demonstrated to be useful in facile oligosaccharide synthesis. These were well compatible with glycosylation conditions and removable by treatment with pyridine-EtOH, with complete preservation of acetyl groups. Analytically pure products were obtained quantitatively, simply by evaporating the reaction mixtures. Using O-PFP and O-TFA carrying glycosyl halides, trisaccharide (Manalpha1-->2Manalpha1-->2Man) and tetrasaccharide (Glcalpha1-->3Manalpha1-->2Manalpha1-->2Man) portions of monoglucosylated high-mannose type dodecasaccharide (Glc(1)Man(9)GlcNAc(2)), a putative ligand for the ER chaperon, calnexin and calreticulin, were synthesized.