jo500392j_si_001.pdf (3.76 MB)
Oligonucleotides with “Clickable” Sugar Residues: Synthesis, Duplex Stability, and Terminal versus Central Interstrand Cross-Linking of 2′-O-Propargylated 2‑Aminoadenosine with a Bifunctional Azide
journal contribution
posted on 2014-05-16, 00:00 authored by Suresh
S. Pujari, Peter Leonard, Frank SeelaDuplex
DNA with terminal and internal sugar cross-links were synthesized
by the CuAAC reaction from oligonucleotides containing 2′-O-propargyl-2-aminoadenosine as a clickable site and a bifunctional
azide (4). Stepwise click chemistry was employed to introduce
cross-links at internal and terminal positions. Copper turnings were
used as catalyst, reducing the copper load of the reaction mixture
and avoiding complexing agents. For oligonucleotide building block
synthesis, a protecting group strategy was developed for 2′-O-propargyl-2-aminoadenosine owing to the rather different
reactivities of the two amino groups. Phosphoramidites were synthesized
bearing clickable 2′-O-propargyl residues
(14 and 18) as well as a 2′-deoxyribofuranosyl
residue (10). Hybridization experiments of non-cross-linked
oligonucleotides with 2,6-diaminopurine as nucleobase showed no significant
thermal stability changes over those containing adenine. Surprisingly,
an isobutyryl group protecting the 2-amino function has no negative
impact on the stability of DNA–DNA and DNA–RNA duplexes.
Oligonucleotide duplexes with cross-linked 2′-O-propargylated
2-aminoadenosine (1) and 2′-O-propargylated adenosine
(3) at terminal positions are significantly stabilized
(ΔTm = +29 °C). The stability
results from a molecularity change from duplex to hairpin melting
and is influenced by the ligation position. Terminal ligation led
to higher melting duplexes than corresponding hairpins, while duplexes
with central ligation sites were less stable.