The reaction of 5-acetamido-N-(2-hydroxyethyl)isophthalamic acid (I) with 3-chloropropane-1,2-diol (II) and NaOH gives 5-[N-(2,3-dihydroxypropyl)acetamido]-N-(2-hydroxyethyl)-2,4,6-triiodoisophthalamic acid (III), which is acetylated with hot acetic anhydride to the corresponding triacetate (IV). The reaction of (IV) with hot SOCl2 affords the corresponding acyl chloride (V), which is condensed with 2,3-dihydroxypropylamine (VI) by means of triethylamine in dimethylacetamide to give the diamide (VII). Finally, this compound is deacetylated with NaOH in methanol/water.

The reaction of 5-acetamido-N-(2-hydroxyethyl)isophthalamic acid (I) with 3-chloropropane-1,2-diol (II) and NaOH gives 5-[N-(2,3-dihydroxypropyl)acetamido]-N-(2-hydroxyethyl)-2,4,6-triiodoisophthalamic acid (III), which is acetylated with hot acetic anhydride to the corresponding triacetate (IV). The reaction of (IV) with hot SOCl2 affords the corresponding acyl chloride (V), which is condensed with 2,3-dihydroxypropylamine (VI) by means of triethylamine in dimethylacetamide to give the diamide (VII). Finally, this compound is deacetylated with NaOH in methanol/water.