A process for the preparation of iosimenol comprising reacting 5,5′-[(1,3-dioxo-1,3-propanediyl)diimino]bis[N-(2,3-dihydroxypropyl)-2,4,6-triiodo-1,3-benzenedicarboxamide] (C-VI) with a 3-halo-1,2-propanediol in an aqueous solvent. A process for the preparation of C-VI comprising reacting 3,3′-[(1,3-dioxo-1,3-propanediyl)diimino]bis[5-(aminocarbonyl)-2,4,6-triiodobenzoyl chloride] (C-V) with 3-amino-1,2-propanediol in the presence of an inorganic base and a suitable non-aqueous polar solvent. A process for the preparation of C-V comprising reacting 3-amino-5-(aminocarbonyl)-2,4,6-triiodobenzoyl chloride (C-IV) with malonyl dichloride in a solvent comprising a suitable ester solvent, a suitable nitrile solvent or mixtures thereof.