New solid support for the synthesis of 3'-oligonucleotide conjugates through glyoxylic oxime bond formation

Synthesis and Exon-Skipping Properties of a 3'-Ursodeoxycholic Acid-Conjugated Oligonucleotide Targeting DMD Pre-mRNA: Pre-Synthetic versus Post-Synthetic Approach

Steric blocking antisense oligonucleotides (ASO) are promising tools for splice modulation such as exon-skipping, although their therapeutic effect may be compromised by insufficient delivery. To address this issue, we investigated the synthesis of a 20-mer 2'-OMe PS oligonucleotide conjugated at 3'-end with ursodeoxycholic acid (UDCA) involved in the targeting of human DMD exon 51, by exploiting both a pre-synthetic and a solution phase approach. The two approaches have been compared. Both strategies successfully provided the desired ASO 51 3'-UDC in good yield and purity. It should be pointed out that the pre-synthetic approach insured better yields and proved to be more cost-effective. The exon skipping efficiency of the conjugated oligonucleotide was evaluated in myogenic cell lines and compared to that of unconjugated one: a better performance was determined for ASO 51 3'-UDC with an average 9.5-fold increase with respect to ASO 51.

Chemistry of Peptide-Oligonucleotide Conjugates: A Review

Peptide-oligonucleotide conjugates (POCs) represent one of the increasingly successful albeit costly approaches to increasing the cellular uptake, tissue delivery, bioavailability, and, thus, overall efficiency of therapeutic nucleic acids, such as, antisense oligonucleotides and small interfering RNAs. This review puts the subject of chemical synthesis of POCs into the wider context of therapeutic oligonucleotides and the problem of nucleic acid drug delivery, cell-penetrating peptide structural types, the mechanisms of their intracellular transport, and the ways of application, which include the formation of non-covalent complexes with oligonucleotides (peptide additives) or covalent conjugation. The main strategies for the synthesis of POCs are viewed in detail, which are conceptually divided into (a) the stepwise solid-phase synthesis approach and (b) post-synthetic conjugation either in solution or on the solid phase, especially by means of various click chemistries. The relative advantages and disadvantages of both strategies are discussed and compared.

Efficient Buchwald-Hartwig-Migita Cross-Coupling for DNA Thioglycoconjugation

An efficient method for the thioglycoconjugation of iodinated oligonucleotides by Buchwald-Hartwig-Migita cross-coupling under mild conditions is reported. The method enables divergent synthesis of many different functionalized thioglycosylated ODNs in good yields, without affecting the integrity of the other A, C, and G nucleobases.

Aminooxylated Carbohydrates: Synthesis and Applications

Among other classes of biomolecules, carbohydrates and glycoconjugates are widely involved in numerous biological functions. In addition to addressing the related synthetic challenges, glycochemists have invested intense efforts in providing access to structures that can be used to study, activate, or inhibit these biological processes. Over the past few decades, aminooxylated carbohydrates have been found to be key building blocks for achieving these goals. This review provides the first in-depth overview covering several aspects related to the syntheses and applications of aminooxylated carbohydrates. After a brief introduction to oxime bonds and their relative stabilities compared to related C═N functions, synthetic aspects of oxime ligation and methodologies for introducing the aminooxy functionality onto both glycofuranosyls and glycopyranosyls are described. The subsequent section focuses on biological applications involving aminooxylated carbohydrates as components for the construcion of diverse architectures. Mimetics of natural structures represent useful tools for better understanding the features that drive carbohydrate-receptor interaction, their biological output and they also represent interesting structures with improved stability and tunable properties. In the next section, multivalent structures such as glycoclusters and glycodendrimers obtained through oxime ligation are described in terms of synthetic design and their biological applications such as immunomodulators. The second-to-last section discusses miscellaneous applications of oxime-based glycoconjugates, such as enantioselective catalysis and glycosylated oligonucleotides, and conclusions and perspectives are provided in the last section.

Concise Synthesis of Triazole-Linked 5'-Peptide-Oligonucleotide Conjugates by Click Chemistry

A concise synthesis of oligonucleotide 5'-peptide-conjugates via copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition in aqueous solution is described. Synthesis of reagents was accomplished by on-column derivatization of corresponding peptides and oligonucleotides. This method is well suited for the preparation of peptide-oligonucleotide conjugates containing 1,2,3-triazole linkage between the 5'-position of an oligonucleotide and the N-terminus of a peptide.

Solid-phase supports for oligonucleotide synthesis

This unit attempts to provide a reasonably complete inventory of over 280 solid supports available to oligonucleotide chemists for preparation of natural and 3'-modified oligonucleotides. Emphasis is placed on non-nucleosidic solid supports. The relationship between the structural features of linkers and their behavior in oligonucleotide synthesis and deprotection is discussed wherever the relevant observations are available.

α-Oxo aldehyde or glyoxylyl group chemistry in peptide bioconjugation

Since the 1990s, α-oxo aldehyde or glyoxylic acid chemistry has inspired a vast array of synthetic tools for tailoring peptide or protein structures, for developing peptides endowed with novel physicochemical properties or biological functions, for assembling a large diversity of bioconjugates or hybrid materials, or for designing peptide-based micro or nanosystems. This past decade, important developments have enriched the α-oxo aldehyde synthetic tool box in peptide bioconjugation chemistry and explored novel applications. The aim of this review is to give a large overview of this creative field.

Integrin targeted delivery of gene therapeutics

Integrins have become key targets for molecular imaging and for selective delivery of anti-cancer agents. Here we review recent work concerning the targeted delivery of antisense and siRNA oligonucleotides via integrins. A variety of approaches have been used to link oligonucleotides to ligands capable of binding integrins with high specificity and affinity. This includes direct chemical conjugation, incorporating oligonucleotides into lipoplexes, and use of various polymeric nanocarriers including dendrimers. The ligand-oligonucleotide conjugate or complex associates selectively with the integrin, followed by internalization into endosomes and trafficking through subcellular compartments. Escape of antisense or siRNA from the endosome to the cytosol and nucleus may come about through endogenous trafficking mechanisms, or because of membrane disrupting capabilities built into the conjugate or complex. Thus a variety of useful strategies are available for using integrins to enhance the pharmacological efficacy of therapeutic oligonucleotides.

Dendri-RAFTs: a second generation of cyclopeptide-based glycoclusters

Synthetic glycoclusters and their related biological applications have stimulated increasing interest over the last decade. As a prerequisite to discovering active and selective therapeuticals, the development of multivalent glycoconjugates with diverse topologies is faced with inherent synthetic and structural characterisation difficulties. Here we describe a new series of molecularly-defined glycoclusters that were synthesized in a controlled manner using a robust and versatile divergent protocol. Starting from a Regioselectively Addressable Functionalized Template (RAFT) carrier, either a polylysine dendritic framework or a second RAFT, then 16 copies of βGal, αMan, βLac or cancer-related Thomsen-Freidenreich (αTF) antigen were successively conjugated within the same molecule using oxime chemistry. We thus obtained a new generation of dendri-RAFTs glycoclusters with high glycosidic density and variable spatial organizations. These compounds displaying 16 endgroups were unambiguously characterized by NMR spectroscopy and mass spectrometry. Further biological assays between a model lectin from Canavalia ensiformis (ConA) and mannosylated glycoclusters revealed a higher inhibition potency than the tetravalent counterpart, in particular for the hexadecavalent polylysine skeleton. Together with the efficiency of the synthetic and characterisation processes, this preliminary biological study provided clear evidence of promising properties that make the second generation of cyclopeptide-based glycoclusters attractive for biomedical applications.

Oligonucleotide sequential bis-conjugation via click-oxime and click-Huisgen procedures

A novel procedure has been developed for the bis-conjugation of oligonucleotides using CuAAC (click-H) and oxime (click-O) tethering strategies. Oligonucleotides bearing a 5'-alkyne function and a 3'-aldehyde precursor were synthesized and were bis-conjugated with various reporters including azido carbohydrate or fluorescent dye and aminooxy peptide or carbohydrate. Versatility of the method was demonstrated by performing click-O prior to click-H and vice versa. Interestingly, when click-O is achieved prior to click-H, no purification is required in between, allowing a sequential one-pot protocol.

Chemical strategies for the synthesis of peptide-oligonucleotide conjugates

The use of synthetic oligonucleotides and their mimics to inhibit gene expression by hybridizing with their target sequences has been hindered by their poor cellular uptake and inability to reach the nucleus. Covalent postsynthesis or solid-phase conjugation of peptides to oligonucleotides offers a possible solution to these problems. As feasible chemistry is a prerequisite for biological studies, development of efficient and reproducible approaches for convenient preparation of peptide-oligonucleotide conjugates has become a subject of considerable importance. The present review gives an account of the main synthetic methods available to prepare covalent conjugation of peptides to oligonucleotides.