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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

Stereospecific hydrogenolysis of benzylic alcohols over Pd/C

Harvey, Freya M. ; Bochet, Christian G.

In: The Journal of Organic Chemistry, 2020, vol. 85, no. 11, p. 7611–7619

Hydrogenolysis of tertiary benzylic alcohols on palladium on carbon (Pd/C) generally proceeds with inversion of configuration. However, little is known about the hydrogenolysis mechanism of primary and secondary benzylic alcohols. Literature precedents suggest that these substrates may interact differently with the catalyst. To study the mechanism, we synthesized a pair of deuterated...

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

Contortamide, a new anti-colon cancer cerebroside and other constituents from Tabernaemontana contorta Stapf (Apocynaceae)

Ebede, Guy R. ; Ndongo, Joseph T. ; Mbing, Joséphine N. ; Kenfack, Hector C. M. ; Pegnyemb, Dieudonné E. ; Bochet, Christian G.

In: Natural Product Research, 2019, p. 1–9

A new cerebroside, Contortamide (1) together with nine known compounds spegatrine (2), affinisine (3), Nb-methylaffinisine (4), ursolic acid (5), α-amyrin (6), bauerenol acetate (7), lupeol (8), betulinic acid (9) and β-sitosterolglycoside (10) were isolated from the trunk bark of Tabernaemontana contorta Stapf. The new compound 1 showed significant activity against Caco-2 colon cancer...

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

Rauvolfianine, a new antimycobacterial glyceroglycolipid and other constituents from Rauvolfia caffra. Sond (Apocynaceae)

Messanga, Robert Ebeh ; 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, 2018, vol. 32, no. 16, p. 1971–1976

The chemical investigation of the extract of the dried leaves of Rauvolfia caffra (Sond) (synonym Rauvolfia macrophylla) (Apocynaceae) led to isolation of a new glycoside derivative, rauvolfianine (1) as well as six known compounds: oleanolic acid (2), sitosterol-3-O-β-D-glucopyranoside (3), betulinic acid (4), vellosimine (5), sarpagine (6) and...

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

Antitubercular evaluation of root extract and isolated phytochemicals from Lophira lanceolata against two resistant strains of Mycobacterium tuberculosis

Nkot, Jeanne Louise ; Bikobo, Dominique Serge Ngono ; Zintchem, Auguste Abouem A ; Nyemeck II, Norbert Mbabi ; Moni Ndedi, Esther Del Florence ; Diboué, Patrick Hervé Betote ; Pegnyemb, Dieudonné Emmanuel ; Bochet, Christian G. ; Koert, Ulrich

In: Pharmaceutical Biology, 2018, vol. 56, no. 1, p. 318–324

Context: The roots of Lophira lanceolata Van Tiegh. Ex Keay (Ochnaceae) have numerous medicinal values in the Central African region. Even though the MeOH extract of the roots has shown antimycobacterial activities, the constituents responsible for this inhibitory activity remain unknown.Objective: Phytochemical investigation of the MeOH root extract of L. lanceolata and determination of the ...