Unsaturated acyclic pyrimidine analogues, 1-{1-[1-(hydroxymethyl) prop-2-enyloxy] prop-2- enyl} uracil, 1-{1-[1-(hydroxymethyl) prop-2-enyloxy] prop-2-enyl} thymine and 1-{1-[1- (hydroxymethyl) prop-2-enyloxy] prop-2-enyl} cytosine having two asymmetric carbon atoms have been prepared in good yield starting from uridine and 5-methyluridine. The bis-vinyl thymine derivative underwent ring closure metathesis to give d4T, thus providing a novel ...