Process to prepare pyrimidine nucleosides

Pyrimidine nucleosides are important antiviral agents, increased attention has recently been focused on these compounds with the FDA approval of 3′-azido-2′,3′-dideoxythymidine (AZT) stavudine (D T) as an effective treatment for Acquired Immunodeficiency Syndrome (AIDS). Since the synthesis of such agents utilizes the pyrimidine nucleoside -thymidine as a starting material, new methods for the low-cost production of this and other synthetic intermediates are also becoming important. The present invention involves an expeditious route to the O ,2′-anhyro-l-( -arabinofuranosyl) 5-hydroxy 5,6 dihydro pyrimidine nucleosides, a class of compounds easily converted to the -pyrimidine derivatives. Analogous syntheses of these anhydronucleosides is described in the following publications. A process for the production of a compound of the formula: wherein Ris hydrogen, alkyl, C-Csubstituted alkyl, aryl, substituted aryl, aralkyl, substituted aralkyls, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, cyano, carboxy, carboxy esters, carboxamido, N-mono substituted and N,N-disubstituted carboxamido with alkyl, aralkyl and aryl groups; Ris hydrogen, alkyl C-Csubstituted alkyl, aryl, substituted aryl, aralkyl, substituted aralkyls, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl; Ris alkyl C-C, branched alkyl, aryl C-C, substituted aryl and Ris halogen or H.A condensation reaction is effected between compounds of the formulae: to form a novel compound of the formula: Compound () is acylated with a compound of the formula:RCOClto form a novel compound of the formula: Compound () is mixed with pyridine and is reacted with thionyl chloride to form compound () and compound () is dehalogenated to form compound ().