Employing the Michaelis-Arbuzov reaction of 1-O-acetyl-2,3,4,6-tetra-O-benzyl-D-galactopyranose with triethyl phosphite and trimethylsilyl trifluoromethanesulfonate, α- and β-D-galactopyranosylphosphonic acids were prepared in 33 and 28% yields, respectively. (α-D-Galactopyranosylmethyl)phosphonic acid was synthesized by a five-step route from 2,3,4,6-tetra-O-benzyl-D-galactopyranose in 52% overall yield. When tested against bovine α-1,3- and β-1,4-galactosyltransferases, all three compounds showed, at best, very poor inhibitions. Both enzymes were inhibited more effectively by β-D-galactopyranosylphosphonic acid (IC50 = 17 mmol l-1 at 13.5 μmol l-1 of UDP-Gal for β4GalT).