Synthesis and application of a 5′-aldehyde phosphoramidite for covalent attachment of DNA to biomolecules

We recently reported the use of covalently attached DNA as a structural constraint for rational control of macromolecular conformation. Reductive amination was employed to attach each strand of the duplex DNA constraint to RNA, utilizing an aldehyde tethered to the 5′-terminus of the DNA. Here we describe the synthesis of a thymidine phosphoramidite that has the 5′-tethered aldehyde masked as a 1,2-diol. We also describe optimized reductive amination conditions for linking 5′-aldehyde-DNA with 2′-amino-2′-deoxy-RNA. These procedures should be generally applicable for attaching DNA to biomolecules.