Synthesis of (Carbo) nucleoside Analogues by [3+2] Annulation of Aminocyclopropanes

(Carbo) nucleoside derivatives constitute an important class of pharmaceuticals, yet there are only few convergent methods to access new analogues. Here, we report the first synthesis of thymine-, uracil-, and 5-fluorouracil-substituted diester donor-acceptor cyclopropanes and their use in the indium-and tin-catalyzed [3+2] annulations with aldehydes, ketones, and enol ethers. The obtained diester products could be easily decarboxylated and reduced to the corresponding alcohols. The method gives access to a broad range of new (carbo) nucleoside analogues in only four or five steps and will be highly useful for the synthesis of libraries of bioactive compounds.