A rapid and effective method of an automatic oligoribonucleotide synthesis alternative to the phosphoramidite one was developed. This method is based on the phosphotriester approach to internucleotide bond formation under intramolecular O-nucleophilic catalysis and the use of an azidomethyl group for protection of a nucleotide 2′-hydroxyl function. © 2009 Pleiades Publishing, Ltd.