Piétrick Hudhomme

Cell wall integrity and high osmolarity glycerol pathways are required for adaptation of Alternaria brassicicola to cell wall stress caused by brassicaceous indolic phytoalexins

Camalexin, the characteristic phytoalexin of Arabidopsis thaliana, inhibits growth of the fungal necrotroph Alternaria brassicicola. This plant metabolite probably exerts its antifungal toxicity by causing cell membrane damage. Here we observed that activation of a cellular response to this damage requires cell wall integrity (CWI) and the high osmolarity glycerol (HOG) pathways. Camalexin was found to activate both AbHog1 and AbSlt2 MAP kinases, and activation of the latter was abrogated in a AbHog1 deficient strain. Mutant strains lacking functional MAP kinases showed hypersensitivity to camalexin and brassinin, a structurally related phytoalexin produced by several cultivated Brassica species. Enhanced susceptibility to the membrane permeabilization activity of camalexin was observed for MAP kinase deficient mutants. These results suggest that the two signalling pathways have a pivotal role in regulating a cellular compensatory response to preserve cell integrity during exposure to camalexin. AbHog1 and AbSlt2 deficient mutants had reduced virulence on host plants that may, at least for the latter mutants, partially result from their inability to cope with defence metabolites such as indolic phytoalexins. This constitutes the first evidence that a phytoalexin activates fungal MAP kinases and that outputs of activated cascades contribute to protecting the fungus against antimicrobial plant metabolites.

[4+2] Cycloaddition of C60 to 2-(thi)oxo-4,5-bis(methylene)-1,3-dithioles: en route to the bis-linking of tetrathiafulvalene to C60

Abstract The title reaction carried out from S-propargyl xanthate 3 or 2-(thi)oxo-4,5-bis(bromomethyl)-1,3-dithioles 4a and 4b with C60 is presented and some conversions of the synthesized cycloadducts 2a and 2b in several 1,3-dithiole derivatives are described.

A new strategy to reach highly extended and quinonoid tetrathiafulvalene (TTF) derivatives

Abstract 2,3-Bis(bromomethyl)TTFs 4 are used as precursors of 2,3-dimethylene-[2H]-TTFs 5 to reach cycloadducts of high synthetic interest via a [4+2] cycloaddition with quinonic derivatives. Subsequent Horner-Wadsworth-Emmons olefinations with a 1,3-dithiole phosphonate anion afforded highly extended and sulfur-rich analogs of tetrathiafulvalene 1.

A novel array in extended tetrathiafulvalenes (TTF): the ‘H’ shape

The highly extended, cross-conjugated and sulfur rich π-electron donor 2a was synthesized and characterized introducing the ‘H’ shape as a new approach in the tetrathiafulvalene (TTF) array.

Synthesis and properties of new 2-mono and 2,3-bis(hydroxymethyl)-6,7-ethylenedithio TTF vinylogs

Abstract The synthesis of title compounds prone to generate hydrogen bonds thanks to their alcohol functionalities is depicted. Cyclic voltammetry proves these derivatives to be strong π-donors, able to act as convenient precursors of related organic metals.

Resolution of multifunctional carbon compounds derivated from N-protected 2-cyano glycinates

Abstract Synthesis and resolution of covalent diastereoisomers from some N-protected 2-cyanoglycinates using (S)-(−)-ethyl lactate as a resolving reagent, give rise after transesterification with titanium tetraisoproposide, to chiral multifunctional carbon compounds 1 , valuable chiral auxiliaries as key precursors in organic synthesis.

Control of the enantiomeric purity and correlation with the absolute configuration of N-protected 2-cyanoglycinates

Abstract The enantiomeric purity of substituted N-phthaloyl-2-cyanoglycine methyl esters obtained by resolution of covalent diastereoisomers was easily established by measuring the shift separation of signals using Eu(hfc)3. A correlation with the absolute configuration of enantiomers was observed.

Resolution of 2-methyoxy-2-(2'-thiazinyl)glycinates

Abstract The synthesis and the resolution of α-methoxy α-(2-thiazinyl)glycinate diasteroisomers, using (S)-(-)-ethy lactate as a resolving reagent, is described. The X-ray crystal structure of a pure diastereoisomer is reported. These chirally substituted thiazines are key intermediates for multistep syntheses of 7-methoxy cephems.

Novel highly extended and sulfur rich tetrathiafulvalene (TTF) derivatives through an unprecedented TTF core building process

A new and unexpected tetrathiafulvalene (TTF) core building process is observed via reaction of a 1,3-dithiole phosphonate anion with a 2-oxo-1,3-dithiole functionality.

α-Methoxy-α-(6H-1,3-thiazin-2-yl)glycinates precursors of 7-methoxycephems by [3+3] cyclocondensation reaction

Abstract We report here a new widely useful and applicable preparation of functionalised 6H-1,3-thiazinic cycloadducts, versatile key intermediates in the total multistep syntheses of 7-methoxycephems (as analogues of 7-methoxycephalosporins).