It can be prepared in three related ways: 1) The reaction of 5-amino-2,4,6-triiodoisophthalic acid (I) with refluxing SOCl2 gives 5-amino-2,4,6-triiodoisophthaloyl chloride (II), which is condensed with 2-acetoxypropionyl chloride (III) in dimethylacetamide to afford 5-(2-acetoxypropionylamido)-2,4,6-triiodoisophthaloyl chloride (IV). The condensation of (IV) with 1,3-dihydroxyisopropylamine (V) by means of tributylamine in dimethylacetamide yields 5-(2-acetoxypropionylamido)-2,4,6-triiodoisophthalic acid di-(1,3-dihydroxyisopropylamide) (VI), which is finally hydrolyzed with NaOH in water.
2) The reaction of 5-amino-2,4,6-triiodoisophthalic acid (I) with refluxing SOCl2 gives 5-amino-2,4,6-triiodoisophthaloyl chloride (II), which is condensed with 1,3-dihydroxyisopropylamine (V) by means of tributylamine in dimethylacetamide to give 5-amino-2,4,6-triiodoisophthalic acid di-(1,3-dihydroxyisopropylamide) (VII), which is then condensed with 2-acetoxypropionyl chloride (III) to give 5-(2-acetoxypropionylamido)-2,4,6-triiodoisophthalic acid di-(1,3-dihydroxyisopropylamide) (VI), which is finally hydrolyzed with NaOH in water.
3) Dimehtyl 5-nitroisophthalate (VIII) is treated with dihydroisopropylamine (V) at 140-50 C to yield 5-nitroisophthalic acid di-(1,3-dihydroxyisopropylamide) (IX), which is hydrogenated with H2 over Pd/C in ethanol giving 5-aminoisophthalic acid di-(1,3-dihydroxyisopropylamide) (X). The reaction of (X) with KICl2 in acidic water at 50-60 C affords 5-amino-2,4,6-triiodoisophthalic acid di-(1,3-dihydroxyisopropylamide) (VII), which is finally acylated with 2-acetoxypropionyl chloride (III) to afford 5-(2-acetoxypropionylamido)-2,4,6-triiodoisophthalic acid di-(1,3-dihydroxyisopropylamide) (VI), which is finally hydrolyzed with NaOH in water