Oligoribonucleotide synthesis. X. An improved synthesis of the anticodon loop region of methionine transfer ribonucleic acid from E. coli

Nonaribonucleotide, GpCmpUpCpApUpApApC, was synthesized using a block phosphotriester method. Its sequence corresponds to that of the anticodon loop of transfer RNA f Met (E. coli). Protected tetramer, GCmUC and pentamer nucleotides, AUAAC, assembled stepwise from nucleoside derivatives, were joined together to give protected nonamer which on deblocking, gave the free nonaribonucleotide in milligram amounts. The superior internucleotide coupling efficiency of mesitylenesulfonyl triazolide (MST) over triisopropylbenzenesulfonyl chloride (TPS) is demonstrated.