Preparation of Oligodeoxynucleotides Containing 6-Methylthiopurine Residues by Chemical Synthesis or Specific Methylation

Two methods (chemical synthesis and specific methylation) are described for the preparation of oligodeoxynucleotides containing 6-methylthiopurine residues. 6-Methylthiopurine phosphoramidite (6) is prepared and incorporated into oligomers. Methylation with methyl iodide of 6-thiopurine (or 6-thioguanine) in oligonucleotides also leads to exclusive production of 6-methylthiopurine (or 6-methylthioguanine) oligomers.