Cross-linked DNA: Propargylated ribonucleosides as "click" ligation sites for bifunctional azides

2′-O or 3′-O-propargylated adenosines and ribothymidines were used as click targets for cross-linking of oligonucleotides with aliphatic and aromatic azides. The cross-link generates a sugar modification at the 2′-O-ligation site. Inexpensive ribonucleosides were used as starting materials. Cross-linking of oligonucleotides was performed at internal or terminal positions. Hybridization of homodimers with two complementary single strands resulted in stable ligated DNA duplexes.