βGal(1→S-4)βGlcNAc-OR: A Galactosidase-Stable Substrate for α(1→3)Fucosyltransferase.

1'-4 Thio-N-acetyllactosamine was chemically synthesized as a galactosidase-stable substrate for alpha(1-->3)fucosyltransferase. The product of enzymatic fucose addition was confirmed to be the thio-Le X analog.