Click fleximers: a modular approach to purine base-expanded ribonucleoside analoguesElectronic supplementary information (ESI) available: Complete experimental details and characterization of compounds 2c, 2d, 3c, 3d, 4a-g, 5a-g and the fluorescence data for 4f, 4g, 5d, 5f, and 5g and details of the computational studies. See DOI: 10.1039/c2ob25678a

The synthesis of nucleoside analogues incorporating 4-(5-pyrimidinyl)-1,2,3-triazole aglycons as expanded purine nucleobase mimics were accessed using the copper-catalyzed azide-alkyne Huisgen cycloaddition between a ribosyl azide and 5-alkynylpyrimidines. Depending on the nature of the alkyne employed, other nucleoside analogues that possess fluorescence or potential metal-binding properties were prepared. Computational studies were undertaken on the purine analogues and indicate that the heterocycles of the unfused nucleobase prefer a coplanar arrangement and the anti -glycosidic conformer is favoured in most instances. Nucleoside analogues incorporating 4-(5-pyrimidinyl)-1,2,3-triazole aglycons as expanded purine nucleobase mimics have been synthesized by use of the copper-catalyzed azide-alkyne Huisgen cycloaddition between a ribosyl azide and 5-alkynylpyrimidines. Computational studies are presented that predict the favoured conformation of these new analogues.