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

Abstract

Conjugation of ligands to DNA oligonucleotides has been achieved in the solid phase by strain-promoted azide-alkyne cycloaddition (SPAAC). The oligonucleotide, modified with a simple nonfluroinated, monocyclic octyne, efficiently forms conjugates with a range of azide dipoles with varying steric

Fast RNA conjugations on solid phase by strain-promoted cycloadditions

“…39,40 The fluorescein azide 21 was selected to demonstrate the potential of SPAAC for introduction of fluorescent tags. Having previously demonstrated that 21 required post-synthetic conjugation to DNA, 32 the same strategy was adopted for RNA-cyclooctyne 12. Thus, 12 (0.025 μmol, 1 eq., 200 μM), obtained from 7 following cleavage from the resin and deprotection, was exposed to a solution of 21 (40 eq.)…”

“…Thus, 7 was treated with biotinyl- (19), 32 cholesteryl-(20) 32 or fluoresceinyl- (21) 32 azides in both aqueous and non-aqueous media at room temperature. Conjugation to the biotinyl azide (19), furnished 23c after 4 h in 90% (v/v) aqueous DMSO, whilst DCM was the solvent of choice for cholesteryl conjugation.…”

“…30,31 We have previously reported post-synthetic modification of DNA by strain-promoted cycloaddition of both azide and nitrile oxide dipoles to solid-supported DNA-cyclooctyne substrates. 32,33 Filippov et al, 34 and Manoharan et al, 35 have demonstrated azide-mediated oligonucleotide-dibenzocyclooctyne conjugation in solution phase, using the same methodology as that described for DNA-templated "click"-ligation demonstrated by Brown and El-Sagheer. 36 As part of an ongoing programme to prepare siRNA conjugates with improved potential for cellular delivery, we became interested in the possibility of RNA functionalization using strain-promoted cycloaddition chemistry.…”

Copper‐Free Postsynthetic Labeling of Nucleic Acids by Means of Bioorthogonal Reactions

“…There is an increasing number of examples of building blocks for DNA and RNA functionalized with ring‐strained conjugation partners. Heaney et al reported the use of the resin‐supported conjugation method for postsynthetic modification of DNA at the 5′‐end of oligonucleotides (Scheme ) 46. They efficiently conjugated a simple nonfluorinated, monocyclic octyne (building block 17 ) that reacts with a range of azide dipoles with varying steric and electronic characteristics.…”

C‐3β‐Tethered Functional Cholesterol Conjugates by Nitrile Oxide Alkyne Cycloaddition (NOAC)

“…[2k-2m] In addition, catalyst-free routes to triazole-linked cholesterol-oligonucleotide conjugates have been reported. [3] However, aside from exploitation of the masked functionality of the isoxazole nucleus to access polyhydroxylated steroids, cholesterol conjugates with this heterocyclic linker are relatively unknown. Thermally promoted cycloadditions to C-17-anchored steroidal alkynes have yielded important reaction intermediates.…”