Triazolyl Donor/Acceptor Chromophore Decorated Unnatural Nucleosides and Oligonucleotides with Duplex Stability Comparable to That of a Natural Adenine/Thymine Pair

We report the design and synthesis of triazolyl donor/acceptor
unnatural nucleosides via click chemistry and studies on the duplex
stabilization of DNA containing two such new nucleosides. The observed
duplex stabilization among the self-pair/heteropair has been found
to be comparable to that of a natural A/T pair. Our observations on
the comparable duplex stabilization has been explained on the basis
of possible π–π stacking and/or charge transfer
interactions between the pairing partners. The evidence of ground-state
charge transfer complexation came from the UV–vis spectra and
the static quenching of fluorescence in a heteropair. We have also
exploited one of our unnatural DNAs in stabilizing abasic DNA.