Synthesis of Oligoribonucleic Acid Conjugates Using a Cyclooctyne Phosphoramidite

Abstract

The conjugation of a ribonucleic acid 16-mer with the cationic amphiphilic peptide penetratin and an anionic hyaluronan tetrasaccharide by means of Cu-free "click" chemistry is reported. The alkyne-functionalized 16-mer was prepared by automated solid-phase synthesis, using a newly developed strained cyclooctyne phosphoramidite in the final coupling. Cycloaddition of the alkyne functionalized RNA to the azide containing biomolecules led to a clean conversion into the corresponding nucleic acid conjugates.

Efficient Synthesis of DNA Conjugates by Strain‐Promoted Azide–Cyclooctyne Cycloaddition in the Solid Phase

“…SPAAC is not a perfect reaction and the formation of regioisomeric triazoles is deemed as an acceptable trade off for the avoidance of a copper catalyst in azide-alkyne bioconjugations. Consistent with triazole formation with little regard for regioselectivity, [32,35] two product peaks were observed for both 16a and 16b; a minimal bias was seen for the regioisomer with slightly longer retention time.…”

“…dibenzocyclooctyne. [32,33] It is known that lipid conjugation facilitates both cellular uptake and intracellular delivery of oligonucleotides and so provides hope for a nontoxic alternative to the cationic lipophilic or polymeric siRNA delivery systems, [41,42] and we wished to extend the scope of the SPAAC reaction to include steroidal examples. However, despite the advances in methodologies for the postsynthetic modification of oligonucleotides, the synthesis of steroidal conjugates remains nontrivial.…”

“…[26] Applications of strain-promoted conjugation are numerous and span diverse areas including bioimaging, [17,27,28] quantum dot formation, [29] peptide conjugation, [30] drug discovery, [18] drug delivery, [31] synthetic chemistry [23] and surface and materials science. [22,24] We have previously reported the postsynthetic modification of oligonucleotides by strain-promoted nitrile oxide cycloaddition chemistry (SPNOC), [8] and Filippov [32] and Manoharan [33] independently demonstrated conjugate formation by cycloaddition of azides to oligonucleotide cyclic alkynes. In their elegant studies, Filippov and Manoharan have concentrated on solution rather than solid phase conjugation.…”

Oligonucleotide Tagging for Copper-Free Click Conjugation

“…However, the use of copper for oligonucleotide conjugation may be compromised due to potential metal-catalyzed strand degradation and/or difficulties in final purification [13][14][15]. Although new ligands reduce the chance of undesired chain cleavage during copper-catalyzed click reaction [16][17][18], strain-promoted azide-alkyne cycloaddition (SPAAC) offers the possibility of oligonucleotide conjugation in the absence of copper [19][20][21][22][23] as demonstrated for oligonucleotides labeled with plain cyclooctyne (OCT) [15] or the more reactive dibenzofused cyclooctyne DIBO [24]. Most recently, Brown et al [25,26] further extended the latter approach by ON incorporation of aminoalkyl thymidine derivatives, followed by selective N-acylation with azide or cyclooctyne after cleavage from support.…”

Insight Into the Inhibition of Ribonucleotide Reductases by 2'-chloro-2'-deoxynucleotides and 2'-azido-2'-deoxynucleotides: Biomimetic Studies with Model Substrates

“…The use of azido oligonucleotides gained interest with the introduction of strain-promoted azide−alkyne cycloaddition (SPAAC). 101 The azido compounds can be coupled with both terminal alkynes in a Cu (I)-catalyzed reaction (CuAAC) and strained cycloalkynes. It has been reported that the Staudinger reaction does not take place between the azide group in the support-bound growing nucleotide chain and the phosphoramidite reagents.…”