Novel cross-linking reaction of oligonucleotides incorporating new base analogs with selective reactivity toward cytidine.

2-Amino-6-vinylpurine analog (1) has been proven to react with cytidine and guanosine in a model reaction of cross-linking. However, its incorporation into the ODNs was unsuccessful because of the high reactivity of its vinyl group. A new precursor for 1, 2-amino-6-[2-(phenylthio)ethyl]purine (2), was designed so as to generate the reactive vinyl group after introduction into the oligomers. In this paper, synthesis of ODN containing 2, easy generation of the vinyl group within the oligomer, and interstrand cross-linking between the ODN incorporating 1 and the target DNA, are described.