Substituent effects on the in situ activation of the double activated cross-linking reaction

We have previously reported that the oligonucleotides (ODN) containing 2-amino-6-(1-ethylsulfinyl)vinyl purine derivatives (2) exhibit selective and efficient cross-linking to a cytidine at the target site under neutral conditions. In addition, bis-alkylsulfinyl derivative (3b) as the stable precursor of 2 showed the moderate reactivity. In this study, we have searched other bis-alkylsulfinyl precursors to achieve higher cross-linking ability, and found that acetamidoethyl and hydroxyethyl derivatives showed highly efficient and selective reactivity.