合成路线1

Chlorination of 5-amino-2,4,6-triiodoisophthalic acid (I) with SOCl2 in EtOAc or toluene affords acid chloride (II). Yields have been improved with the addition of benzyltriethylammonium chloride as a catalyst. Acid chloride (II) is then condensed with 3-amino-1,2-propanediol (III) to produce diamide (IV). Compound (IV) is converted to the tetraacetate ester (V) employing acetic anhydride in pyridine. Subsequent acylation of the amino group of (V) with acetoxyacetyl chloride (VI) gives amide (VII). After saponification of the ester groups of (VII), the resultant hydroxy acetamide (VIII) is alkylated by 2-chloroethanol (IX) to furnish the title compound. Alternatively, amide (VIII) is alkylated by bromoethyl acetate (X), producing (XI). Hexa-ester (XI) is finally hydrolyzed with aqueous sulfuric acid. An improved procedure for this final hydrolysis step uses 1,1,2-trichloroethane as co-solvent.