Nucleosides 6a, 6b and 16-18 having additional carbocycle or oxygen he
terocycle fused to the ribose moiety have been synthesized by two rout
es. While 6a and 6b could be obtained from thymidine using 1, 3-dipola
r cycloaddition approach, Vorbruggen reaction on appropriate preformed
carbocyclic derivatives furnished 16-18. (C) 1997 Published by Elsevi
er Science Ltd.