Synthesis of Oligodeoxynucleotide Containing Pseudo-Deoxycytidine and Its Triphosphate Derivative

This article describes a detailed synthetic protocol for the preparation of oligodeoxynucleotide (ODN) containing pseudo-deoxycytidine (ψdC) and its triphosphate derivative (ψdCTP). These molecules were synthesized as novel compounds that recognize iso-2'-deoxyguanosine (iso-dG) in DNA. Iso-dG is one of the tautomers of 2-hydroxy-2'-deoxyadenosine (2-OH-dA), which is known as an oxidatively damaged nucleobase, and its selective recognition in DNA is expected to play a very important role in the diagnosis and pathogenesis of diseases. The hydroxyl groups of the known glycal compound were protected with silyl groups, and then coupled with 5-iodouracil under Mizorogi-Heck reaction conditions, yielding ψdU after desilylation and diastereoselective reduction. The endocyclic amino group of ψdU was protected by the benzyl group. Subsequently, the carbonyl group at the 6-position of the nucleobase was activated and converted to an amino group through treatment with aqueous ammonia. The benzyl group was removed, and the exocyclic amino group was protected with a benzoyl group. On one hand, the silyl groups at the 3' and 5' positions were deprotected, converted into a phosphoramidite unit, and incorporated into an ODN. On the other hand, the hydroxyl group at the 5' position was selectively deprotected and then directly converted into the triphosphate using Van Boom's reagent under acidic conditions. © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Synthesis of ODNs having ψdC and ψdCTP Basic Protocol 2: Melting temperature of duplex formation between ODNs containing ψdC unit and 2-OH-dA Basic Protocol 3: A single nucleotide primer extension reaction of ψdCTP for a template strand containing 2-OH-dA.