The 5-amino-N,N'-bis(2,3-dihydroxypropyl)isophthalamide is preferably prepared by reduction of 5-nitro-N, N'-bis(2,3-dihydroxypropyl)isophthalamide, for example, by hydrogenation in the presence of a hydrogenation catalyst such as platinum, palladium or PdO/charcoal.