Nadine Pirio

Metabolism of stilbene phytoalexins by Botrytis cinerea: 1. Characterization of a resveratrol dehydrodimer

Abstract Resveratrol, a grapevine phytoalexin, is metabolized by a laccase-like stilbene-oxidase of Botrytis cinerea, the causal organism for grey mould. Characterization of one major metabolite formed during this degradation process as a resveratrol dehydrodimer allowed us to precize the reaction mechanism of this enzyme on stilbenes.

Characterization of a Pterostilbene Dehydrodimer Produced by Laccase of Botrytis cinerea.

ABSTRACT In the interaction between grapevines and Botrytis cinerea, one of the main aspects of pathogenicity is fungal ability to degrade phytoalexins synthesized by the plant in response to infection. Laccase-like stilbene oxidase activity in liquid cultures of B. cinerea has been shown to be related to the decrease of phytoalexin concentrations. Recent research and results presented in this paper determined the chemical structure of a pterostilbene metabolite produced by B. cinerea. Study of degradation of pterostilbene that has just one free hydroxy phenyl group function allowed us to determine the oxidative dimerization process undergone by grapevine phytoalexins after B. cinerea infection. The phytopathological significance of this degradation process in the B. cinerea interaction has also been discussed.

Syntheses and properties of some exo,exo-bis(isodicyclopentadienyl)titanium low-valent complexes

Abstract The paramagnetic compounds exo,exo-bis(η5-isodicyclopentadienyl)chlorotitanium(III) (3) and its analogue with trimethylsilyl-substituted isodicyclopentadienide (isodiCp) ligand (4), and the similar pair of diamagnetic exo,exo-bis(isodicyclopentadienyl)[η2-bis(trimethylsilyl)ethyne]titanium(II) complexes 5 and 6 were obtained by common reduction procedures from exo,exo-bis(isodicyclopentadienyl)titanium(IV) dichloride (1) and exo,exo-bis[η5-2-(trimethylsilyl)isodicyclopentadienyl]titanium(IV) dichloride (2), respectively. As indicated by ESR spectroscopy compound 3 is a dimer in the solid state and in frozen toluene glass but monomeric in toluene solution. Compound 4 is monomeric in solution as well as in the solid state. As judged from the red shift of the ν(CC) vibration, compound 6 binds bis(trimethylsilyl)ethyne more strongly than compound 5. A comparison of their wavenumbers with those of the [Ti(C5H5−nMen)2(η2-Me3SiCCSiMe3)] (n=2–5) complexes shows that Lewis acidity of the central titanium atom decreases in the order of ligands 1,3-dimethylcyclopentadienyl>isodiCp∼1,2,3-trimethylcyclopentadienyl>(trimethylsilyl)isodiCp∼tetramethylcyclopentadienyl. The crystal structure of the most bulky complex 6 shows a bis-lateral (anti) conformation of the isodiCp ligands with the π-coordinated five-membered rings nearly eclipsed.

Zirconocene [Cp2Zr] synthon and benzynezirconocene complexes as tools in main group element chemistry

Abstract Interactions between zirconocene or benzyne zirconocene and unsaturated species incorporating main group elements lead to a variety of new metallaheterocycles. Efficient new methodologies of regiospecific syntheses of mono-, bi-, or tricyclic systems incorporating phosphorus, nitrogen, selenium, antimony, germanium or tin are reported.

Activation of terminal alkynes with cis-[RuCl2(Ph2PCH2PPH2)2]: new vinylidene– and acetylide–ruthenium complexes and crystal structures of [(Ph2PCH2PPH2)2(Cl)RuCCH2]PF6 and [(Ph2PCH2PPH2)2(Cl)RuCCH] complexes

The activation of alkynes HCCR with cis-[RuCl2(Ph2PCH2PPh2)2]1 leads to vinylidenes trans-[(Ph2PCH2PPh2)2(Cl)Ru+CCHR], even directly from acetylene itself (R = H) or prop-2-ynyl alcohol, from which the Ru+CCH(CH2OH) moiety is resistant to dehydration, and deprotonation with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) directly affords trans-[(Ph2PCH2PPh2)2(Cl)Ru–CC–R] derivatives.

Isolation, dynamic NMR study and X-ray characterisation of a bis sulfonium zirconocene-ate dimer

The novel dimer [Cp(2)Zr[upper bond start]([minus sign in circle])S([plus sign in circle])CH(Ph)CH[double bond]C[upper bond end]PPh(2)](2), the first example of a structurally characterised sulfur-bridged binuclear zirconathiolane complex, was prepared, characterised by NMR spectroscopy and X-ray crystallography, and some aspects of its solution behaviour were studied.

Liquid-crystalline gold(I)-carbene complexes

Gold(I)–(alkoxy)(amino)carbenes, the first liquid-crystalline transition metal–carbene complexes, are prepared and shown to form enantiotropic smectic A phases.

ansa-[(tert-Butylamino)(isodicyclo­pentadienyl)dimethylsilane]Zr(NMe2)2 prepared by an amine-elimination reaction

An amine-elimination reaction was used to obtain the title compound, i.e. (N-tert-butyl-N-[[(1,2,3,3a,7a-eta)-4,5,6,7-tetrahydro-4,7-methano-1H-inden-2-yl]dimethylsilyl]amido-kappaN)bis(N-methylmethanaminato-kappaN)zirconium(IV) or [isodiCpSiMe(2)N-tert-butyl]Zr(NMe(2))(2) (Cp is cyclopentadienyl), [Zr(C(16)H(25)NSi)(C(2)H(6)N)(2)], in very good yield. Treatment of isodiCpHSiMe(2)NH-tert-butyl with Zr(NMe(2))(4) leads to the formation of a yellow solid that can be purified by sublimation. The single-crystal structure of the product shows the exo complexation of the isodicyclopentadienyl ligand to the Zr atom. The Cp portion of this ligand is bonded to the Zr atom in a eta(5) manner, with a Zr-Cg (Cg is the ring centroid) distance of 2.2352 (10) A. The isodiCpSiMe(2)N-tert-butyl ligand has a constrained geometry, which is exhibited by the small angle of 95.55 (10) degrees for N-Si-C(Cp).

CCDC 1485961: Experimental Crystal Structure Determination

Related Article: Nejib Dwadnia, Julien Roger, Nadine Pirio, Helene Cattey, Ridha Ben Salem, Jean-Cyrille Hierso|2017|Chem.Asian J.|12|459|doi:10.1002/asia.201601583

A doubly bridged isodicyclopentadienyl zirconium complex: bis{N-(3,5-dimethylphenyl)-N-[(η5-isodicyclopentadien-2-yl)dimethylsilyl]amido-κN}zirconium(II) diethyl ether solvate

Transmetallation of the dilithium salt of (3,5-dimethyphenylamino)(isodicyclopentadienyl)dimethylsilane by treatment with zirconium tetrachloride in a 2:1 ratio leads to the substitution of all four chloride ligands. With the applied stoichiometry, the title complex, [Zr(C(20)H(25)NSi)(2)].C(4)H(10)O, was obtained and crystallized from diethyl ether. X-ray diffraction characterization showed that both isodicyclopentadienyl ligands (alternatively called 4,5,6,7-tetrahydro-4,7-methano-1H-indene) are complexed to the metal on their exo face in a completely stereoselective manner and that they are eta(5)-bonded to the Zr atom.