Resveratrol (3,5,4′‐trihydroxystilbene) is one of the stress metabolites produced by grapevines in response to fungal infection or injury. The distribution of this compound in limited lesions caused by Botrytiscinerea on ripe grape clusters in the vineyard has been examined. Resveratrol was present predominantly in the non‐infected fruits close to the necrotic area. This localized response can help to arrest the spread of established B. cinerea lesions as long as climatic conditions are unfavourable to the pathogen. When conditions become favorable, i.e. after a mild and humid period rapidly spreading lesions are observed on fruits despite the continued increasing production of resveratrol in the grapes which can reach three‐ to five‐fold the value found before rot intensification. Significant amounts of resveratrol can be found prior to any detectable lesions in fruits collected from apparently healthy clusters thus suggesting that phytoalexin response in initiated soon after the recognition of the pathogen by the plant. The involvement of one or more endogenous signals coming from either the fungus or the plant in the induction of host defence responses has also been discussed.

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A reversed-phase HPLC method useful for the analysis of the grapevine phytoalexins resveratrol, its β-d-glucoside, ε-viniferin, and pterostilbene in leaf extracts was developed by coupling diode array detection and fluorometry. Phytoalexins were extracted from UV-irradiated grapevine leaves with methanol/water (80:20) and prepurified on C18 solid phase extraction cartridges. Separation by HPLC was achieved using a C18 column and a gradient elution with acetonitrile and water (from 10 to 85% acetonitrile). Analyses of grapevine leaf extracts were performed by injecting the equivalent of 1 mg of leaf fresh weight. Recovery was nearly 100% for the three stilbenes resveratrol, pterostilbene, and ε-viniferin (ranging from 100.2 to 104.8%), and replicate analyses gave coefficients of variation of 0.6−2.5%. Identification of each phytoalexin was accomplished by line spectral comparisons with known standards, and ε-viniferin was further characterized by MS and GC/MS. Simultaneously, stilbenes were detected by fluorometry, allowing specific identification of these compounds. This procedure provided excellent separation and enabled quantitation of all grapevine phytoalexins present in the extracts. The method can easily be extended to the analysis of wine or biological fluids.

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Herein, we report on (31)P(31)P solution-phase "through-space" nuclear spin-spin coupling constants (J(PP)) from a novel family of organometallic tetraphosphine nickel and palladium complexes. These J(PP) constants were accurately determined through NMR iterative simulation based on the second-order spectra obtained for the compounds. The corresponding solid-state X-ray structures of the complexes were determined, and the "through-space" P.P distances are reported. Due to the blocked conformation of the species in solution, a qualitative and semiquantitative experimental correlation is obtained, which links the geometric parameters and the intensity of the corresponding P.P coupling constant. The lone-pair overlap theory developed for (19)F(19)F and (15)N(19)F "through-space" couplings in organic compounds [J. Am. Chem. Soc. 1973, 95, 7747-7752; 2000, 122, 4108-4116] appears to be a reliable foundation on which to account for our results. Based on the reported observations, the lone-pair overlap model is extended to "through-space" (31)P(31)P coupling, and the model is broadened to encompass metal orbital contributions for coordination complexes. Some of the predictions and consequences of the proposed theory are discussed.

The system combining the new ferrocenyl tetraphosphine 1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di-tert-butylferrocene (called Fc(P) 4 t Bu, 1) and [PdCl(η 3 -C 3 H 5 )] 2 has been found to be an active catalyst for the cross-coupling of aryl halides with aryl boronic acids (i.e., Suzuki reaction) and for the vinylation of aryl halides with alkenes (Heck reaction). A variety of chlorides reacts in good yield with aryl boronic acids in the presence of 1-0.01% catalyst. The more reactive aryl bromides were reacted with aryl boronic acids or alkenes in the presence of 0.01-0.0001% catalyst. This system compares well with other catalytic systems that have been described for Suzuki or Heck reactions. 1 H, 13 C, and 31 P NMR studies in solution were conducted with the view to obtain a better understanding of the interaction involving the palladium dimeric precursor and the tetraphosphine. The initial formation of kinetic and then different thermodynamic species was evidenced. A dynamic evolution from labile Pd(π-allyl)/tetraphosphine species toward the well-defined, stable, and nonfluxional complexes [PdCl 2 {Fc(P) 4 t Bu}] (3) and [Pd 2 Cl 4 {Fc(P) 4 t Bu}] (4) is observed. This behavior is different from the other known active tetraphosphine Tedicyp [cis,cis,2,3,cyclopentane]. The palladium mononuclear 3 and dinuclear 4 complexes were isolated and fully characterized in the solid state by X-ray diffraction analysis and in solution by multinuclear NMR. The blocked conformation in solution of compounds 1, 3, and 4 respectively leads to original AA′BB′, ABMX, and A 2 B 2 31 P NMR spin-systems for the four phosphorus atoms.

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