Condensation of 4-methylumbelliferone (7-hydroxy-4-methylcoumarin) with 1,2,3,4,6-penta- O-acetyl-β- d-glucopyranose ( 1) and 1,2,3,4,6-penta- O-acetyl-β- d-galactopyranose ( 9) in the presence of zinc chloride gave, respectively, a mixture of α-( 2) and β- d-glucopyranosides ( 3) in the ratio of 2:3, and a mixture of α- d-galactopyranoside ( 10), β- d-galactofuranoside, and β- d-galactopyranoside ( 11) in the ratio of 10:17:23. The proportion of 1,2- cis-glycosides could be slightly increased by treating 1 and 9 with the O-trimethylsilyl derivative of 4-methylumbelliferone in the presence of stannic chloride. Condensations of the sodium salt of 4-methylumbelliferone with 2,3,4,6-tetra- O-acetyl-β- d-glucopyranosyl chloride, 2,3,4,6-tetra- O-acetyl-β- d-galactopyranosyl chloride, and 2,3,4,6-tetra- O-acetyl-α- d-mannopyranosyl bromide in hexamethylphosphoric triamide gave, respectively, pure 2, pure 10, and a mixture of α- and β- d-mannopyranosides in the ratio of 1:3, with much better yields. O-Deacetylation of 2, 3, 10, and 11, followed by platinum-catalyzed oxidation, afforded the corresponding 4-methylumbelliferyl d-glycopyranosiduronic acids.