AbstractThis article described the preparation and the protection of 3′‐DMP and dihydrouridine (Dr) as well as the synthesis of four oligoribonucleotides composed of them.DMP and Dr were obtained by hydrogenation of 3′‐UMP and Ur under acidic conditions in the presence of platinum dioxide. They were monomethoxytritylated and benzoylated to (MeOTr)‐Dbzpand (MeOTr) Dbzs, respectively. The latter was converted to Dbzs, by demonomethoxytritylation.The oligoribonucleotides containing DMP or Dr—ApGpD, DpApG, ApGpDpC and ApGpDpCpGpG were synthesized via phosphodiester approach and DCC was used as condensing reagent. DpApG was also synthesized via phosphotriester approach and TPST, MSTe, MSNI and MSNT were used as condensing reagents for a preliminary comparison of the coupling yields.These synthetic oligoribonucleotides were checked for purity and nucleotide sequences as usual. ApGpDpCpGpG and DpApG had been used for enzymatic synthesis of ApGpDpCpGpGpDpApG, which had been in turn successfully used for the total syntheses of the 5′‐half molecule and the whole molecule of yea