A new and efficient method for synthesis of 5′-conjugates of oligonucleotides through amide-bond formation on solid phase
An efficient method for synthesis of oligonucleotide 5′-conjugates through amide-bond formation on solid phase is described. Protected oligonucleotides containing a 5′-carboxylic acid function were obtained by use of a novel non-nucleosidic phosphoramidite building block, where the carboxylic acid moiety was protected by a 2-chlorotrityl group. The protecting group is stable to the phosphoramidite coupling conditions used in solid-phase oligonucleotide assembly, but is easily deprotected by mild acidic treatment. The protecting group may be removed also by ammonolysis. 5′-Carboxylate-modified oligonucleotides were efficiently conjugated on solid support under normal peptide-coupling conditions to various amines or to the N-termini of small peptides to yield products of high purity. The method is well-suited in principle for the synthesis of peptide-oligonucleotide conjugates containing an amide linkage between the 5′-end of an oligonucleotide and the N-terminus of a peptide.
Kachalova, Anna V.,Stetsenko, Dmitry A.,Romanova, Elena A.,Tashlitsky, Vadim N.,Gait, Michael J.,Oretskaya, Tatiana S.