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The 10–23 DNAzyme is an artificially developed Mg2+‐dependent catalytic oligonucleotide that can cleave an RNA substrate in a sequence‐specific fashion. In this study, new split 10–23 DNAzymes made of two nonfunctional fragments, one of which carries a boronic acid group at its 5′ end, while the other has a ribonucleotide at its 3′ end, were designed. Herein it is demonstrated that the addition of Mg2+ ions leads to assembly of the fragments, which in turn induces the formation of a new boronate internucleoside linkage that restores the DNAzyme activity. A systematic evaluation identified the best‐performing system. The results highlight key features for efficient control of DNAzyme activity through the formation of boronate linkages. [ABSTRACT FROM AUTHOR]

The use of the Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction for the preparation of oligonucleotide conjugates is by now familiar. However, the selective introduction of boronic acids into DNA and RNA sequences by CuAAC reactions has long been considered impossible due to the incompatibility of the boronic acid moiety with copper salts. Here we describe two new methods for the selective on-column functionalization of oligonucleotides with boronic acids via two different CuAAC reactions. The first one allows the introduction of a phenylboronic acid at the 5′-extremity of oligonucleotides, while the selective intrastrand positioning of the modification can be achieved with the second one. Both methods were applied to the DNA and RNA series (up to a 20-mer) with good isolated yields and excellent purities. These results illustrate the potential of the reported methods for selective incorporation of boronic acids into oligonucleotides. [ABSTRACT FROM AUTHOR]

Boronate esters formed by reaction of an oligonucleotide carrying a 5'-boronic acid moiety with the 3'-terminal cis-diol of another have been shown previously to assist assembly of fragmented DNAzymes. Here we demonstrate that boronate esters replacing the natural phosphodiester linkage at selected sites of two functional RNAs, the hairpin ribozyme and the Mango aptamer, allow assembly of functional structures. The hairpin ribozyme, a small naturally occurring RNA that supports the reversible cleavage of appropriate RNA substrates, is very sensitive to fragmentation. Splitting the ribozyme at four different sites led to a significant decrease or even loss of cleavage and ligation activity. Ribozymes assembled from fragments capable of boronate ester formation showed restoration of cleavage activity in some but not all cases, dependent on the split site. Ligation proved to be more challenging, no supportive effect of the boronate ester was observed. Split variants of the Mango aptamer also showed a dramatic loss of functionality, which however, was restored when 5'-boronic acid modified fragments were used for assembly. These studies show for the first time that boronate esters as internucleoside linkages can act as surrogates of natural phosphodiesters in functional RNA molecules., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The first bio-inspired N-Heterocyclic Carbene (NHC)-catalyzed Stetter reaction in aqueous medium is reported with benzaldehyde and chalcone as model substrates. A screening of azolium salts as precatalysts revealed the remarkable efficiency of synthetic thiazolium salt 8 (up to 90% conversion in pure water at 75 °C). The reaction was successfully extended to various simple aldehyde substrates. The effect of temperature was also investigated in order to extend the reaction to lower temperature allowing a potential application to sensitive biomolecules. This study highlighted the influence of both solvent and temperature on the 1,4-diketone 3/benzoin 4 ratio. New precatalysts 26 and 27 were designed and synthesized to explore a possible compartmentalization of the reaction in aqueous conditions. Owing to the use of inexpensive metal-free N-Heterocyclic Carbene (NHC) as a bioinspired catalyst, we anticipate that this green strategy in aqueous conditions will be attractive for bioconjugation of many biomolecule-type aldehydes and enone derivatives., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)