Synthesis of Iopromide

lopromide was synthesized from 3-amino-5-(2,3-diacetoxypropylcarbamoyl)-2,4,6- triiodobenzoic acid(6) by reaction with methoxyacetyl chloride,hydrolysis with NaHCO_3 and chlorination to give 3- (2-methoxyacetylamino)-5-(2,3-dihydroxypropylcarbamoyl)-2,4,6-triiodobenzoyl chloride(4),followed by reaction with N-methyl-2,3-dihydroxypropylamine with an overall yield of about 80%(based on 6).