Synthesis of 4-methylumbelliferyl glycosides for the detection of α- and β-D-galactopyranosaminidases

Reaction at room temperature of either 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α- or -β-D-galactopyranosyl chloride with a twofold excess of 4-methylumbelliferone and silver trifluoromethanesulfonate in dichloromethane containing an equimolar amount of.sym-collidine yielded 4-methylumbelliferyl tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranoside in 33% yield. The β anomer was formed in 20 and 10% yields, respectively. Reduction of the azido group, acetylation followed by de-O-acetylation, provided the desired 4-methylumbelliferyl 2-acetamido-2-deoxy-α- and -β-D-galactopyranosides (N-acetyl-α- and -β-D-galactopyranosaminides). The α-glycoside proved to be an effective substrate for the highly sensitive fluorimetric detection of N-acetyl-α-D-galactopyranosaminidase activity in human tissues and was used to examine the deficiency of this activity, which is the enzymatic defect in Schindler disease. Keywords: synthesis of 4-methylumbelliferyl N-acetyl-α- and -β-D-galactopyranosaminides, N-acetyl-α-D-galactosaminidase deficiency (Schindler disease).