Treatment of 5-hydroxymethyl-1-beta-D-arabinofuranosyluracil (I) with hydrogen chloride in dioxane affords the 5-chloromethyl derivative (II), which is converted to the triphenylphosphonium salt (III). The Wittig reaction of (III) by means of paraformaldehyde and n-butyllithium in DMF yields the 5-vinyl derivative (IV), and bromination of (IV) with bromine in DMF under a heated condition affords BVAU.
A new synthesis of BVAU has been described: The condensation of 1-(beta-D-arabinofuranosyl)-5-formyluracil (I) with malonic acid (II) by means of piperidine in hot anhydrous pyridine gives the carboxyvinyl derivative (III), which is then treated with N-bromosuccinimide in basic medium.