Examples of useful X' functional groups include amines, activated esters, maleimides, isocyanates, isothiocyanates alkyl halide (e.g., iodoacetate), alpha-halo-ketones, alpha-halo-acids, hydrazides, thiols, imidates, aldehydes, photolytic conjugating groups, and the like.
Activated esters may be employed to conjugate the galactose cluster to amines (primary or secondary), hydroxyls, sulfhydryls, and the like.