This unit describes the detailed synthetic protocol for the preparation of the phosphoramidite units of the 2'-deoxy-4-aminopyridinylpseudocytidine derivatives. These C-nucleoside derivatives are useful units for the incorporation into triplex forming oligonucleotides (TFOs) to form the stable triplex DNA containing the CG interrupting sites. Commercially available 1-methyl-2'-deoxypseudouridine is prepared from thymidine and 5-iodo-uracil by a simple method, that is, coupling of glycal and 5-iodo-1-methyluracil by the Heck reaction, followed by desilylation and diastereoselective reduction. The carbonyl group at the 4 position of the pseudouridine derivative is activated by 3-nitorotriazole and treated with the corresponding aromatic amine compounds to produce the 2'-deoxy-4-aminopyridinylpseudocytidine derivatives. These derivatives are then successfully converted to the phosphoramidite units and incorporated into the oligodeoxynucleotides. © 2019 by John Wiley & Sons, Inc.