Nucleoside Analogues: Synthesis from Strained Rings
Nucleoside analogues are widely employed as bioactive compounds against cancer and viral infections. Consequently, it is important to develop efficient synthetic methods to access them with high efficiency and structural diversity. Herein, we present a full account of our work on the synthesis of nucleoside analogues via annulations of donor acceptor aminocyclopropanes and aminocyclobutanes. Thymine- and uracil-derived diester cyclopropanes were accessed from the corresponding nucleobases via vinylation and rhodium-catalyzed cyclopropanation, and were then used in (3+2) annulations with aldehydes, ketones and enol ethers. The obtained analogues could be transformed into important hydroxymethyl derivatives. Thymine and fluoro-uracil-derived diester cyclobutanes obtained from the nucleobases via vinylation and (2+2) cycloaddition could also be used in a (4+2) annulation with aldehydes. Finally, purine-derived diester cyclopropanes could be accessed using the condensation of nucleobases with chloromethyl ethylidene malonates, but annulation reactions with this class of substrates were not successful.