Idoxuridine can be obtained by several related ways: 1) The reaction of 5-iodouracil (I) with refluxing POCl3 and dimethylaniline gives 2,4-dichloro-5-iodopyrimidine (II), which by reaction with NaOCH3 in refluxing methanol, is converted into 2,4-dimethoxy-5-iodopyrimidine (III). The reaction of (III) with 2-deoxy-3,6-di-O-p-toluoyl-D-ribofuranosyl chloride (IV) in acetonitrile yields the ribofuranosyl pyridone (V), which is demethylated with acetic anhydride - dry HCl to afford 2'-deoxy-5-iodo-3',6'-di-O-p-toluoyluridine (VI). Finally, this compound is hydrolyzed with NaOCH3 in methanol. 2) The acetylation of 5-iodouracil (I) with refluxing acetic anhydride gives 1-acetyl-5-iodouracil (VII), which by reaction with mercuric acetate in refluxing methanol is converted into the corresponding mercurium salt (VIII). The condensation of (VIII) with the ribofuranosyl chloride (IV) in chloroform affords the protected 2'-deoxy-5-iodouridine (VI), already obtained. 3) The iodination of 2'-deoxyuridine (IX) with iodine, iodic acid, acetic anhydride, CCl4 and water gives 2'-deoxy-5,6-diiodo-5,6-dihydrouridine (X), which is then treated with NaOH to eliminate HI. 4) By direct iodination of 2'-deoxyuridine (IX) with iodine and nitric acid in refluxing chloroform.