Gilles Doisneau

Leishmaniasis and trypanosomiasis are severe parasitic infections with significant impacts on veterinary and public health, particularly affecting the poorest populations. The therapeutic arsenal against these neglected tropical diseases is limited, and the emergence of resistance to available medicines complicates treatment. These kinetoplastid parasites share a unique DNA modification, that is β‐ d ‐glucosyl‐5‐hydroxymethyluracil (base J), which appears to play an essential role in parasite development and survival through an original epigenetic mechanism, allowing adaptation to environmental changes. To date, the regulatory pathway of this unique nucleobase has not been explored as a potential therapeutic target. In this work, we report the synthesis of several families of base J analogues and assess their potential against different kinetoplastid species. Some compounds have shown antiparasitic activity and no toxicity toward human primary fibroblasts, revealing promising new strategies for antiparasitic therapy.

The asymmetric reduction of β‐ketoesters using the Noyori catalyst is a highly effective synthetic methodology, offering excellent stereocontrol for the preparation of enantiopure β‐hydroxyesters from prochiral substrates in high yields. This reaction has been used in the total synthesis of mycolic acids, which are α‐alkyl, β‐hydroxy fatty acids forming the main part of the mycobacterial cell outer membrane. Recently, the metabolism of mycobacteria has been explored using the chemical reporter strategy with bioorthogonal analogs or precursors of mycolic acids. Introducing a bioorthogonal alkyne into these compounds is a challenging task and particularly valuable for subsequent probe attachment via click chemistry. This work presents approaches for the synthesis of several alkyne‐containing mycolic acids featuring the native structure of natural mycolic acids. The chemoselectivity of the enantioselective reduction of several β‐ketoesters using the Noyori catalyst in the presence of a protected terminal alkyne group is investigated. Conditions have been optimized to ensure that the alkyne remains intact during the reduction process. This study provides valuable tools for further mycomembrane studies using the CuAAC reaction and the optimized conditions extends the possibilities in the synthesis of β‐ketoesters with an alkyne function.

The asymmetric reduction of β-ketoester using the Noyori catalyst is a highly effective synthetic methodology, offering excellent stereocontrol for the preparation of enantiopure -hydroxyesters from prochiral substrates in high yields. This reaction has been used in a total synthesis of mycolic acids, which are α-alkyl, β-hydroxy fatty acids forming the main part of the mycobacterial cell outer membrane. Recently, the metabolism of mycobacteria has been explored using the chemical reporter strategy with bioorthogonal analogues or precursors of mycolic acids. Introducing a bioorthogonal alkyne into these compounds is a challenging task and particularly valuable for subsequent probe attachment via click chemistry. This work presents approaches for the synthesis of several alkyne-containing mycolic acids featuring the native structure of natural mycolic acids. The chemoselectivity of the enantioselective reduction of several β-ketoesters using the Noyori catalyst in the presence of a terminal alkyne group was investigated. Conditions have been optimized to ensure that the alkyne remains intact during the reduction process. This study provides valuable tools for further mycomembrane studies using the CuAAC reaction and the optimized conditions extends the possibilities in the synthesis of β-ketoesters with an alkyne function.

A variety of proteins interact with DNA and RNA, including polymerases, histones, ribosomes, transcription factors, and repair enzymes. However, the transient non‐covalent nature of these interactions poses challenges for analysis. Introducing a covalent bond between proteins and DNA via photochemical activation of a photosensitive functional group introduced onto nucleic acids offers a means to stabilize these often weak interactions without significantly altering the binding interface. Consequently, photoactivatable oligonucleotides are powerful tools for investigating nucleic acid‐protein interactions involved in numerous biological and pathological processes. In this review, we provide a comprehensive overview of the chemical tools developed so far and the different strategies used for incorporating the most commonly used photoreactive reagents into oligonucleotide probes or nucleic acids. Furthermore, we illustrate their application with several examples including protein binding site mapping, identification of protein binding partners, and in cell studies.

Both sugars and lipids are important biomolecular building blocks with exceptional conformational flexibility and adaptability to their environment. Glycolipids bring together these two molecular components in the same assembly and combine the complexity of their conformational landscapes. In the present study, we have used selective double resonance vibrational spectroscopy, in combination with a computational approach, to explore the conformational preferences of two glycolipid models (3-0-acyl catechol and guaiacol α-D-glucopyranosides), either fully isolated in the gas phase or controlled interaction with a single water molecule. We could identify the preferred conformation and structures of the isolated and micro-hydrated species and evidence of the presence of a strong water pocket, which may influence the conformational flexibility of such systems, even in less controlled environments.

Protein mycoloylation is a newly characterized post-translational modification (PTM) specifically found in Corynebacteriales , an order of bacteria that includes numerous human pathogens. Their envelope is composed of a unique outer membrane, the so-called mycomembrane made of very-long chain fatty acids, named mycolic acids. Recently, some mycomembrane proteins including PorA have been unambiguously shown to be covalently modified with mycolic acids in the model organism Corynebacterium glutamicum by a mechanism that relies on the mycoloyltransferase MytC. This PTM represents the first example of protein O -acylation in prokaryotes and the first example of protein modification by mycolic acid. Through the design and synthesis of trehalose monomycolate (TMM) analogs, we prove that i ) MytC is the mycoloyltransferase directly involved in this PTM, ii ) TMM, but not TDM, is a suitable mycolate donor for PorA mycoloylation, iii ) MytC is able to discriminate between an acyl and a mycoloyl chain in vitro unlike other trehalose mycoloyltransferases. We also solved the structure of MytC acyl-enzyme obtained with a soluble short TMM analogs which constitutes the first mycoloyltransferase structure with a covalently linked to an authentic mycolic acid moiety. These data highlight the great conformational flexibility of the active site of MytC during the reaction cycle and pave the way for a better understanding of the catalytic mechanism of all members of the mycoloyltransferase family including the essential Antigen85 enzymes in Mycobacteria .

5‐Hydroxymethyl‐pyrimidine‐based nucleobases have attracted attention in the last years due to their important role in gene regulation. It prompted the development of efficient routes to the corresponding nucleoside building blocks for further incorporation into oligonucleotides. Several pathways have been employed in recent years to access properly protected 5‐hydroxymethyl‐pyrimidine based nucleosides, including hydroxymethylation of 2’‐deoxyuridine, radical bromination of thymidine followed by bromine substitution, or carbonylative coupling through Stille conditions starting from 5‐iodo‐2’‐deoxyuridine. In this study, we review the different approaches currently used to introduce the 5‐hydroxymethyl moiety, we reinvestigate some of them, and finally, we propose an alternative route based on the oxidation of the methyl of thymidine followed by its reduction that allows access to protected 5‐hydroxymethyl‐2’‐deoxyuridine in a simple way with good yields. Finally, we present some examples of application including the synthesis of base J and 5‐azidomethyl‐2’‐deoxyuridine.

5-Hydroxymethyl derivatives of pyrimidine nucleosides are an important class of biologically relevant compounds. In addition, such derivatives and related compounds can be functionalized for various applications. To enable fast, economical, and efficient access to 5-hydroxymethylated derivatives of 2′-deoxyuridine, we report a method for the O-5 chemoselective transformation of unprotected 5-(hydroxymethyl)-2′-deoxyuridine through selective etherification in the presence of an alcohol promoted by acidic Amberlyst 15 resin at room temperature. These mild conditions constitute a significant improvement compared with the harsh conditions previously described. Applied to various primary or secondary alcohols, the reaction showed a broad substrate scope, and 24 C(5)-modified derivatives of 5hmdU were synthesized with good isolated yields. Notably, this efficient procedure represents a straightforward method for preparing (i) several useful building blocks for subsequent chemical ligation by using CuAAC reactions; (ii) natural hypermodified thymidines and analogues, including glycosylated derivatives; and (iii) cyanoethyl-protected 5hmdU, useful for solid-phase oligonucleotide syntheses.

Arylborinic acids represent new, efficient, and underexplored hydrogen peroxide‐responsive triggers. In contrast to boronic acids, two concomitant oxidative rearrangements are involved in the complete oxidation of these species, which might represent a major limitation for an efficient effector (drug or fluorophore) release. Herein, a comprehensive study of H₂O₂‐mediated unsymmetrical arylborinic acid oxidation to investigate the factors that could selectively guide their oxidative rearrangement is described. The o‐CF₃ substituent was found to be an excellent directing group allowing a complete regioselectivity on borinic acid models. This result was successfully applied to synthesizing new borinic acid‐based fluorogenic probes, which exclusively release the fluorescent moiety upon H₂O₂ treatment. These compounds maintained their superior kinetic properties compared to boronic acids, thus further enhancing the potential of arylborinic acids as valuable new H₂O₂‐sensitive triggers.