Protection of amines as their tetrachlorophthalimide derivatives, by reaction with the anhydride in the presence of triethylamine, has been found to be useful in oligosaccharide chemistry. The group is stable to a wide range of reagents but can be selectively cleaved with ethylenediamine at lower temperatures than for the parent phthalimide derivatives; in particular, carboxylic esters are not cleaved under these conditions.