Oligonucleotides with 2′-O-carboxymethyl group: synthesis and 2′-conjugation via amide bond formation on solid phase†
Abstract
An efficient method for synthesis of oligonucleotide 2′-conjugates via amide bond formation on solid phase is described. Protected oligonucleotides containing a 2′-O-carboxymethyl group were obtained by use of a novel uridine 3′-phosphoramidite, where the carboxylic acid moiety was introduced as its allyl ester. This protecting group is stable to the conditions used in solid-phase oligonucleotide assembly, but easily removed by Pd(0) and morpholine treatment. 2′-O-Carboxymethylated oligonucleotides were then efficiently conjugated on a solid support under normal peptide coupling conditions to various amines or to the N-termini of small peptides to give products of high purity in good yield. The method is well suited in principle for the preparation of peptide–oligonucleotide conjugates containing an amide linkage between the 2′-position of an oligonucleotide and the N-terminus of a peptide.
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