Further improvement in protecting method for the oligonucleotide synthesis in terms of a cellulose acetate derivative as a polymer support.

For further improvement in the investigation to utilize a cellulose acetate derivative as a novel type of polymer-support for the synthesis of oligonucleotides, the investigations on utilizing another spacer; on protecting groups for O6-position of guanosine unit, ribothymidine, and pseudouridine; and on a novel protecting group for the introduction of phosphate function at 5'-terminal position, targeting the syntheses of 13-mer, ApApGpGpApApApApUpUpApUpG, 11-mer, pCpUpCpGpUpCpCpApCpCpA, and 12-mer, UpCpCpGpGprTp- psipCpGpApUpU, found in the partial structures of a yeast tRNA(Ala), will be described in detail.