The resulting CMP-sialic acid analogue (which in FIG. 3 is illustrated as the CMP derivative of Neu5Ac, i.e., CMP-Neu5Ac) is then combined with the derivatized βGal(1→3)βGlcNAc-OR compound in the presence of the βGal(1→3/4)βGlcNAc α(2→3)sialyltransferase or the βGal(1→3)GalNAc α(2→3)sialyltransferase under conditions wherein sialic acid is transferred to the 3 position of the galactose to form a αNeu5Ac(2→3)βGal linkage. Suitable conditions, known in the art, include the addition of the sialyltransferase to a mixture of the derivatized βGal(1→3)βGlcNAc-OR compound and of the CMP-sialic acid in a appropriate buffer such as 0.1M sodium cacodylate in appropriate conditions of pH and temperature such as at a pH of 6.5 to 7.5 and a temperature between 25° and 45° C., preferably 35°-40° C., while incubating for 12 hours to 4 days. The resulting sialylated product can be isolated and purified using conventional methodology comprising HPLC, ion exchange-, gel-, reverse-phase- or adsorption chromatography.
