Synthesis of oligonucleotides with sequences identical with or analogous to the 3'-end of 16s ribosomal rna of escherichia coli: preparation op U-C-C-U-U-A and A-C-C-U-C-C-U-U-A via the modified phosphotriester method

The synthesis of oligoribonucleotides U-C-C-U-U-A and A-C-C-U-C-C-U-U-A, which are located at the 3'-terminus of 16S rRNA of E. coli, is described. The key-intermediates in the synthesis of these compounds are the fully-protected mononucleotides 5a-c, which can be rapidly (2-4 min) functionalized by either of the two following specific deblocking procedures: (i) at the 3'-tenninus with zinc in pyridine-2,4,6-triisopropylbenzenesul-phonic acid and (ii) at the 5'-terminus with 0.5M hydrazine in pyridine-acetic acid. The fully-protected hexamer 17a and nonamer 19, prepared by utilizing these deblocking conditions, were completely deprotected by the action of fluoride ion, followed by treatment with base and acid to give the required oligonucleotides in high yield.