Total synthesis of the structural gene for the precursor of a tyrosine suppressor transfer RNA from Escherichia coli. 5. Synthesis of the deoxyribopolynucleotide segments representing the nucleotide sequence 71-103.

Chemical syntheses of the pentadecanucleotide, d(G-G-T-G-G-G-G-T-T-C-C-C-G-A-G), the undecanucleotides, d(G-G-T-G-G-G-G-T-T-C-C) and d(C-C-C-C-A-C-C-A-C-G-G), the decanucleotide, d(G-T-A-A-T-G-C-T-T-T), and the nonanucleotides, d(A-T-T-A-C-C-C-G-T) and d(A-G-T-A-A-A-A-G-C) are described. The deoxyribopolynucleotides together represent the DNA duplex corresponding to the nucleotide sequence 71-103 (from the 3'-end) of the gene for the tyrosine suppressor tRNA. Synthesis of the guanine-rich undecanucleotide d(G-G-T-G-G-G-G-T-T-C-C) was performed by the use of a new protecting group for the guanine ring, the methylbutyryl group. The heptanucleotide d[(MeOTr)mbG-mbG-T-mbG-mbG-mbG-mbG], prepared by the new method, was condensed with the tetranucleotide d[panC-anC-T-T(Ac)]. All of the condensations described followed previously developed chemical principles and started with the N- and 5'-protected deoxyribonucleosides. Successive condensations at the 3'-end with protected mononucleotides, preformed di-, tri-, or tetranucleotides gave products which were separated by anion exchange chromatography and characterized by chemical and enzymatic methods.