Chemical Synthesis of a Pentaribonucleoside Tetraphosphate Constituting the 3'-Acceptor Stem Sequence of E. coli tRNAIle Using 2'-O-(3-Methoxy-1,5-dicarbomethoxypentan-3-yl)-ribonucleoside Building Blocks. Application of a New Achiral and Acid-labile 2'-Hydroxyl Protecting Group in tRNA Synthesis.

Abstract

A synthesis of a pentaribonucleotide fragment constituting the residues 59-63 of 3'-terminus of E. coli tRNAIle, 5'-ApGpUpCpC-3', has been carried out using a new, easily accessible and achiral 2'-ketal protecting group. The new 2'-ketal group has an additional advantage in that it is easily functionalized to the diamide with aqueous ammonia in the penultimate step of deblocking of fully protected oligoribonucleotides. Such a functionalization of the 2'-ketal group at the penultimate step of deblocking of the fully protected tRNA molecule enhances its relative rate of removal under an acidic condition with a minimum of damage of the target tRNA molecule.