The reaction of diethyl malonate (I) with (R)-(-)-epichlorohydrin (II) by means of sodium ethoxide in refluxing ethanol gives the 3-oxa-2-oxobicyclic compound (III), which by reduction with NaBH4 in ethanol yields (1S,2R)-1,2-bis(hydroxymethyl)cyclopropanecarboxylic acid ethyl ester (IV). The reaction of (IV) with diphenyldiazomethane by means of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in dichloroethane affords (1R,7R)-4,4-diphenyl-3,5-dioxabicyclo[5.1.0]octane-1-carboxylic acid ethyl ester (V), which is reduced with LiBH4 in THF giving the carbinol (VI). The reaction of (VI) with CBr4 and triphenylphosphine in dichloromethane yields the bromomethyl derivative (VII), which is condensed with 5-(2-(E)-bromovinyluracil (VIII) by means of K2CO3 and 18-crown-6 in hot DMF affording the expected addition compound (IX). Finally, this compound is deprotected with HCl in methanol.