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Université de Fribourg

Photochemical methods in metathesis reactions

Harvey, Freya M. ; Bochet, Christian G.

In: Organic & Biomolecular Chemistry, 2020, vol. 18, no. 40, p. 8034–8057

Metathesis reactions are one of the most reliable and prevalent ways of creating a C– C bond in synthesis. Photochemical variants exist, and they have proven extremely useful for the construction of complex molecules, from natural products to Möbius rings. A variety of starting materials can undergo photometathesis reactions, including alkenes, alkynes, carbonyls, thiocarbonyls, and...

Université de Fribourg

A simple reaction for dna sensing and chemical delivery

Janett, Elia ; Diep, Kim-Long ; Fromm, Katharina M. ; Bochet, Christian G.

In: ACS Sensors, 2020, vol. 5, no. 8, p. 2338–2343

Reactions templated by nucleic acids are currently at the heart of applications in biosensing and drug release. The number of chemical reactions selectively occurring only in the presence of the template, in aqueous solutions, and at room temperature and able to release a chemical moiety is still very limited. Here, we report the use of the p-nitrophenyl carbonate (NPC) as a new reactive...

Université de Fribourg

On the sustainability of photochemical reactions

Bochet, Christian G.

In: CHIMIA International Journal for Chemistry, 2019, vol. 73, no. 9, p. 720–723

Photochemical reactions are often presented as intrinsically environmentally friendly ('green'). This may be indeed the case, but only in particular circumstances. This short essay comments on various aspects of the greenness of photochemical reactions, both in a historical (when only mercury-based hard UV light sources were available) and a current (with the recent introduction of LED...

Université de Fribourg

Photochemical amplifier based on self-immolative dendritic spacers

Kastrati, Agonist ; Bochet, Christian G.

In: The Journal of Organic Chemistry, 2019, vol. 84, no. 12, p. 7776–7785

A self-immolative dendritic structure was synthesized. It is based on phenol derivatives with three hydroxymethyl arms at both ortho and para positions of the core unit, potentially releasing up to 27 leaving groups in a third-generation dendrimer. The triggering event is the photolysis of a photosentive ortho-nitrobenzyl group. In doing so, we expected to transform a weak chemical or...

Université de Fribourg

Secondary metabolites from Triclisia gilletii (De Wild) Staner (Menispermaceae) with antimycobacterial activity against Mycobacterium tuberculosis

Tiam, Eric Robert ; Ngono Bikobo, Dominique Serge ; Zintchem, Auguste Abouem A. ; Mbabi Nyemeck II, Norbert ; Moni Ndedi, Esther Del Florence ; Betote Diboué, Patrick Hervé ; Nyegue, Maximilienne Ascension ; Atchadé, Alex de Théodore ; Pegnyemb, Dieudonné Emmanuel ; Bochet, Christian G. ; Koert, Ulrich

In: Natural Product Research, 2019, vol. 33, no. 5, p. 642–650

Triclisinone (2), a new ochnaflavone derivative, was isolated from the aerial parts of Triclisia gilletii, along with known drypemolundein B (1) and eight other known compounds. The chemical shifts of drypemolundein B (1) have been partially revised based on reinterpretation of NMR spectroscopic data. The eight other secondary metabolites are composed of: (+)-nonacosan-10-ol (3); stigmasterol...

Université de Fribourg

Synthesis of different glutathione–sulfur mustard adducts of verified and potential biomarkers

Bielmann, Andreas ; Sambiagio, Nicolas ; Wehr, Nathalie ; Gerber-Lemaire, Sandrine ; Bochet, Christian G. ; Curty, Christophe

In: RSC Advances, 2018, vol. 8, no. 42, p. 23881–23890

Sulfur Mustard (SM) is a blistering agent used as a chemical weapon. Glutathione (GSH) is involved in the β-lyase degradation pathway of SM and recently, bioadducts between SM and GSH were observed in vitro. While these bioadducts have never been isolated from in vivo tests or real poisoning with SM, they could be of interest as potential future biomarkers for the retrospective validation of...

Université de Fribourg

Application of photoclick chemistry for the synthesis of pyrazoles via 1,3‐dipolar cycloaddition between alkynes and nitrilimines generated in situ

Remy, Richard ; Bochet, Christian G.

In: European Journal of Organic Chemistry, 2018, vol. 2018, no. 3, p. 316–328

The photochemical extrusion of gaseous nitrogen from 2,5-disubstituted tetrazoles to generate reactive nitrilimines in situ represents an efficient and attractive way to form dipoles that can be used to provide useful chemicals via 1,3-dipolar cycloadditions. The concept of “photoclick chemistry” already inspired numerous researchers, who exploited photochemical processes involving...

Université de Fribourg

In vitro antitubercular activity of extract and constituents from the stem bark of Disthemonanthus benthamianus

Evina, Jean Noel ; Ngono Bikobo, Dominique Serge ; Zintchem, Auguste Abouem A. ; Mbabi Nyemeck II, Norbert ; Moni Ndedi, Esther Del Florence ; Betote Diboué, Patrick Hervé ; Nyegue, Maximilienne Ascension ; Atchadé, Alex de Théodore ; Pegnyemb, Dieudonné Emmanuel ; Koert, Ulrich ; Bochet, Christian G.

In: Revista Brasileira de Farmacognosia, 2017, vol. 27, no. 6, p. 739-743

A new C-glycosylflavone, apigenin 7-methyl ether 6-C-[β-xylopyranosyl-(1→3)-β- glucopyranoside] named distemonanthoside was isolated from the stem bark of Distemonanthus benthamianus Baill., Fabaceae, along with six known compounds, sitosterol 3-O-β-d-glucopyranoside, 4-methoxygallic acid, syringic acid, quercetin, 6″- O-acetylvitexin, quercetin 3-O-β-d-glucopyranoside. The structures...

Université de Fribourg

A new procyanidin B from Campylospermum zenkeri (Ochnaceae) and antiplasmodial activity of two derivatives of (±)-serotobenine

Mbabi Nyemeck II, Norbert ; Ngono Bikobo, Dominique Serge ; Zintchem, Auguste Abouem A. ; Schäfer, Eva-Maria ; Bochet, Christian G. ; Pegnyemb, Dieudonné Emmanuel ; Koert, Ulrich

In: Natural Product Research, 2017, vol. 31, no. 24, p. 2875-2884

Phytochemical investigation of the stem bark of Campylospermum zenkeri led to the isolation of five known compounds: (Z,Z)-9,12-octadecadienoic acid (1), serotobenine (2), agathisflavone (3), lophirone A (4) and lophirone F (5), together with a new derivative of procyanidin B, a catechin dimer named zenkerinol (6). Serotobenine (2) is structurally related to decursivine which shows moderate...

Université de Fribourg

Probing Mechanisms of Photochemical Reactions: How to Teach a Young Dog Old Tricks

Bochet, Christian G.

In: CHIMIA International Journal for Chemistry, 2016, vol. 70, no. 3, p. 182-185

The mechanism of photochemical reactions can be difficult to study because of the very short-lived intermediates involved. State-of-the art ultrafast spectroscopic tools can be used to probe these processes, but we will show in this account that old- fashioned techniques, such as the determination of quantum yields, the measurement of isotope effects or the use of triplet quenchers and...