5-Chloromercuri-2'-deoxyuridine (II) is prepared from 2'-deoxyuridine (I) by reaction with mercuriacetate and natrium chloride (1). Condensation of (II) with ethylacrylate (A) and lithium palladium chloride gives (E)-5-(2-carbethoxyvinyl)-2'-deoxyuridine (III), which is readily hydrozyled to (E)-5-(2-carboxyvinyl)-2'-deoxyuridine (IV) under basic conditions (0.5M NaOH). The final step involves the reaction of (IV) with N-bromosuccinimide to produce (E)-5-(2-bromovinyl)-2'-deoxyuridine.
The condensation of 2-deoxy-3,5-di-O-(phenylacetyl)-beta-D-erythro-pentofuranosyl chloride (I) with 2,4-bis-O-(trimethylsilyl)-5(E)-(2-bromovinyl)uracil (II) in acetonitrile (Lewis acid catalyst), or in CHCl3-pyridine (Bronsted acid catalyst), gives 3',5'-di-O-(phenylacetyl)-5(E)-(2-bromovinyl)-2'-deoxyuridine (III) and its anomer that is eliminated by TLC (silicagel). Finally, (III) is treated with sodium methoxide in methanol.