The synthesis of 3'-O-2-(azaheterocycle)-thymidines is presented from 1-thi
a-3-aza-1,3-butadiene precursors (N-thioacylamidines). A variety of heteroc
ycles is accessible using the dienic, the electrophilic or the nucleophilic
reactivity of these thia-azabutadiene systems. 3'-O-2-(azaheterocycle)-thy
midine analogues are regarded as potential substrates to interfere with the
DNA-polymerization process.