The synthesis of oligoribonucleotides V. The stepwise synthesis of the 3′-terminal heptanucleotide sequence of tRNAfMet from E. coli

The stepwise synthesis of a heptaribonucleotide GpCpApApCpCpA corresponding to the 3′-terminus of tRNA fMet from E. coli is described. The procedure takes advantage of the ease of obtaining ribonucleoside units bearing a tert-butyldimethylsilyl group on the 2′-position. These units, bearing a 5′-methoxytrityl group are phosphorylated at the 3′-position and coupled to the free 5′-position of the growing nucleotide chain using the chlorophosphite coupling procedure. Yields varied from 87 to 50% over the entire sequence.