Studies on transfer ribonucleic acids and related compounds. XXXIX. Chemical synthesis of heptadeca- and hexadecaribonucleotides corresponding to the 3'-terminus of the tRNAfMet of E. coli.

A heptadecanucleotide corresponding to the 3'-end (bases 61-77) of the tRNAMetf of E.coli was synthesized by the phosphotriester method involving condensation of protected oligonucleotides with chain lengths of 3 to 6. 2'-O-(o-Nitrobenzyl) derivatives of N-acyl-5'-O-monomethoxytrityl nucleosides were used as the starting materials. To protect the 3'-end of the heptadecanucleotide with phosphorodianilidate during the synthesis, protected AACCAp having 3'-phosphorodianilidate was used as the starting nucleotide block. Condensation of protected CCCCGCp or successive condensations of protected CCCp and CGCp gave the protected undecamer in satisfactory yields. The final condensation of the undecamer to protected UCCGGCp yielded the protected heptadecamer, and the product was deprotected to give the 3'-phosphorylated heptadecanucleotide UCCGGCCCCCGAACCAp. A hexadecanucleotide corresponding to the 3'-end of the same tRNAMetf was also synthesized by the phosphotriester method by condensation of the undecamer with protected CCGGCp. The hexadecamer was deblocked and purified by chromatography on ion-exchange and reverse phase supports. This deprotected hexadecanucleotide CCGGCCCCCGCAACCAp (corresponding to bases 62-77) can be joined to the previously synthesized heptamer corresponding to the eukaryotic loop VI sequences to construct a hybrid tRNA.