Chemical Synthesis of Oligonucleotides Containing N 6 ‐Methyladenine Residues in the GATC Site

To investigate by NMR the effects of adenine methylation, a set of oligodeoxynucleotides has been synthesized by phosphotriester or phosphoramidite procedures on silica‐gel support. The preparation of fully protected 2′‐deoxy‐ N 6 ‐methyladenosine 3′‐phosphate 4 and (2′‐deoxy‐ N 6 ‐methyladenosin‐3′‐ O ‐yl)(methoxy)morpholinophosphine 5 is described. The large‐scale chemical synthesis, purification by HPLC, and characterization by MS of these molecules containing N 6 ‐methyladenine is reported.