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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

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 ...

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

Solid‐phase synthesis of the aged‐nonapeptide‐nerve‐agent adduct of butyrylcholinesterase as reference materials for analytical verification

Bielmann, Andreas ; Curty, Christophe ; Bochet, Christian G.

In: Helvetica Chimica Acta, 2017, vol. 100, no. 11, p. -

Two pathways were developed and investigated for the synthesis of the ‘aged’- nonapeptide nerve-agent bioadduct of human butyrylcholinesterase (BuChE). Considering the fast ageing of nerve-agent adducts of BuChE in patients and biomedical samples this target molecule is of paramount relevance for quantitative analysis with respect to the Chemical Weapons Convention. Two approaches using a ...

Université de Fribourg

Photochemical C–H activation: generation of indole and carbazole libraries, and first total synthesis of clausenawalline D

Alimi, Isak ; Remy, Richard ; Bochet, Christian G.

In: European Journal of Organic Chemistry, 2017, vol. 2017, no. 22, p. 3197–3210

The photolysis of N-aryltriazoles and N-arylbenzotriazoles leads to indoles and carbazoles, respectively. Because libraries of triazoles can be accessed rapidly, for example by the copper-catalyzed [3+2] cycloaddition reaction between alkynes and azides, this reaction allows the preparation of indoles in a single operation, by the simultaneous photolysis of the precursor library. As an example of...