The chemical synthesis of the anticodon loop of an eukaryotic initiator tRNA containing the hypermodified nucleoside N6-/N-threonylcarbonyl/-adenosine/t6A/1

In this work, the first example of chemical synthesis of oligoribonucleotide containing the hypermodified nucleoside N6-/N-threonylcarbonyl/-adenosine/t6A/ is presented. Synthesis of the heptamer C-C-C-A-U-t6A-A <unl>IX</unl>, the sequence of which is related to the anticodon loop of the initiator tRNA from yellow lupine, was achieved by: /i/ phosphotriester block synthesis of suitably protected heptamer <unl>VI</unl> containing an adenosine unit with a free exo-NH<inf>2</inf> group, /ii/ highly effective “one-flask” procedure for the transformation of the free exo-NH<inf>2</inf> group of adenosine unit of heptamer <unl>VI</unl> into a N,N′-disubstituted urea system of t<inf>6</inf>A of heptamer <unl>VII</unl> /hypermodification/, and /iii/ final deprotection of <unl>VIII</unl> /32% total yield/ with the use of a new approach for simultaneous hydrogenolysis /Pd0-hydrogen-pyridine/ of the p-nitrobenzyl group and 2,2,2-trichloroethyl groups from carboxyl function of t6A and internucleotide phosphates respectively.