Synthesis of an Alleged Byproduct Precursor in Iodixanol Preparation.

N 1,N 3-Bis(2,3-dihydroxypropyl)-2,4,6-triiodo-5-(N-(oxiran-2-ylmethyl)acetamido)isophthalamide (1), the alleged precursor of several minor byproducts formed when the X-ray contrast agent iodixanol is synthesized from 5-acetamido-N 1,N 3-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide (2), has been successfully prepared with an overall yield of 25%. Epoxide 1 enabled the confirmation of its presence in the reaction mixture during the preparation of iodixanol when amide 2 was used as the starting material.