A convenient solid phase approach to obtain lipophilic 5′-phosphoramidate derivatives of DNA and RNA oligonucleotides

Abstract

This paper explores the potential of a modified phosphotriester approach to the synthesis of 5'-phosphoramidate derivatives of DNA and RNA oligonucleotides. The modification of 5'-deprotected support-bound oligonucleotides is done in two steps: i) conversion of the 5'-OH group of an oligonucleotide into an activated phosphodiester, and ii) treatment of the activated phosphodiester with an aminocompound. The approach is efficient and compatible with conventional solid phase oligonucleotide synthesis. It can be used for the conjugation of therapeutically relevant oligonucleotides with functional moieties or carrier constructions, which are to be removed after endocytosis.

Convenient Solid-Phase Attachment of Small-Molecule Ligands to Oligonucleotides via a Biodegradable Acid-Labile P-N-Bond

“…We also showed that the formation of mono conjugates requires the removal of activating agents (Ph 3 P/(PyS) 2 /DMAP) and the three-fold washing of the support with the attached oligonucleotide before coupling with the amino-containing ligand. The treatment by an aqueous solution of methylamine or its mixture with ammonia to remove the protective groups and cleave the oligonucleotide from the polymer carrier did not destroy the P-N-bond [ 19 , 20 , 24 ]. In our work, we used an aqueous solution of methylamine.…”

“…For example, the authors of [ 22 , 23 ] obtained a phosphoramide bond through the Staudinger reaction between azidoalkyl-modified lipophilic molecules and an internucleoside 2-cyanoethylphosphite of the polymer-bound protected oligonucleotide, which is formed at the condensation stage in a standard automated synthesis. Dovydenko et al [ 24 ] proposed a variant of the solid-phase phosphotriester approach: the active 5′-arylphosphodiester derivative reacted with the polymer-bound protected oligonucleotide, with the subsequent replacement of the azole moiety by an alkyl amine.…”