A novel method for the synthesis of RNA oligomers with 2-cyanoethoxymethyl (CEM) as the 2'-hydroxyl protecting group has been developed. The new method allows the synthesis of oligoribonucleotides with an efficiency and final purity comparable to that obtained in DNA synthesis. [structure: see text]

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Pentafluorophenyl phenyl telluride and 3,5-dichloro-2,4,6-trifluorophenyl phenyl telluride reacted with pentafluorophenyllithium or 3,5-dichloro-2,4,6-trifluorophenyllithium at low temperature to form the corresponding tellurium ate complexes as sole intermediates of the ligand exchange on the hypervalent tellurium centers. In these tellurium ate complexes electron-withdrawing aryl ligands were arranged at apical positions and the ligand exchanges took place between the apical-directing groups.

Pentafluorophenyl phenyl telluride (1) and 3,5-dichloro-2,4,6-trifluorophenyl phenyl telluride (2) react with pentafluorophenyllithium or 3,5-dichloro-2,4,6-trifluorophenyllithium