B. Caro

Solution- and crystal-phase covalent modification of lysozyme by a purpose-designed organoruthenium complex. A MALDI-TOF MS study of its metal binding sites.

Study of the reaction between the transition organometallic complex 4‐ruthenocenyl 2,6‐dimethylpyrylium tetrafluoroborate and the enzyme hen egg white lysozyme (HEWL) in solution and by diffusion in crystals was performed by use of a combination of spectroscopic and chromatographic methods. Conjugation involving the lysine residues of lysozyme appeared to occur readily, yielding very stable ruthenocenyl pyridinium adducts with average degrees of incorporation ranging from 0.2 to 1.8 metal complexes per protein molecule, depending on reaction conditions. Matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) revealed that the protein conjugates were in fact mixtures of unmodified, mono‐, di‐ and sometimes tripyridinium adducts. In combination with reversed‐phased HPLC, we were able to show that six different monoruthenocenyl pyridinium adducts were formed in solution. This result was confirmed by trypsin digestion of a ruthenocenyl pyridinium conjugate and MALDI‐TOF MS analysis of the peptide mixture, which showed that lysines 1, 13, 33, 96, 97 and 116 were involved in the reaction with the pyrylium complex, lysines 13, 33 and 116 being the major binding sites. In the tetragonal crystal state, no binding of the ruthenium complex was shown to occur at lysine 116, owing to steric hindrance at this particular position.

Reactivity of carbanions of Fischer-type carbene complexes with pyrylium salts. Synthesis of new γ-methylenepyran carbene complexes via an addition-oxidation-deprotonation process

Abstract The condensation reaction between γ-unsubstituted pyrylium salts and carbanions of Fischer-type carbene complexes allowed the synthesis of new γ-methylenepyran carbene complexes. 13C NMR data and single cristal X-ray analysis suggest a delocalisation of the oxygene lone pair of the heterocycle.

Comportement des allylbenzènes chrometricarbonyle en milieu basique

Abstract Allylbenzene, estragole and safrole complexed by a Cr(CO)3 unit react in THF and in the presence of tBuOK, with carbonyl compounds to produce exclusively the γ adducts. The para methoxy allylbenzene complexe opposed with OCHO and furfural in excess affords ketones via in situ OPPENAUER-WOODWARD oxydation.

Mono et dinitrosation en position benzylique des complexes du benz'ene chrometricarbonyle. Synth'ese directe d'oximes et d'hydroximates

Abstract In basic media, aromatic hydrocarbons and benzylmethylethers complexed by Cr(CO)3 units are readily nitrosated at the benzylic position bytBuONO, giving rise to Z and E oximes and hydroximates in moderate to excellent yields. With the meta-xylene and isochromane complexes it is possible to obtain a dinitrosation.

Synthèse directe de phénylpyruvates chromé tricarbonyle. Influences de la substitution sur la nature cétonique ou énolique des produits isolés, et du groupement Cr(CO)3 sur l'équilibre tautomère

Abstract Phenylpyruvate derivatives can be readily obtained as stable enols and ketones via a new functionalization of arene Cr(CO)3 complexes. An X-Ray structure and theoretical calculations indicate that conjugation stabilizes the enol forms. The complexation of phenylpyruvic acid lowers the conjugation and shifts the heto-enolic equilibrium to the ketonic form.

Addition de carbanions α benchrotréniques sur divers aldéhydes non énolisables; évolution des produits primaires d'addition par oxydation d'Oppenauer-Woodward, influence de la substitution

Abstract Aromatic hydrocarbons complexed with a Cr(CO) 3 unit react with benzaldehydes and furfural in THF and in the presence of t-BuOK at the benzylic position to give condensation products in good yields. Formation of ketones by “in situ Oppenauer-Woodward” oxidation is observed. Influence of ring substituents on this formation is discussed.

Formation et reactivite des carbanions benchrotreniques dans le thf. addition d'oxalate d'ethyle et de benzaldehyde. evolution des produits d'addition par oxydation d'oppenauer-woodward

Abstract Aromatic hydrocarbons complexed by a Cr(CO) 3 unit react in THF and in the presence of t-BuOK, at the benzylic position with (COOEt 2 and PhCHO to give good yields of condensation products. With PhCHO formation of ketone via “in situ” Oppenauer—Woodward oxidation, is observed.

Problemes de stereoselectivite en serie du benchrotene: cyclisation des acides α- et β-alcoyl β-phenyl propioniques. Influence de l'encombrement sterique sur la stereochimie de la reaction

Abstract The cyclisation in polyphosphoric acid of α-alkyl-β-phenylpropionic acids gave rise to exo and endo diastereoisomers of indanone-Cr(CO) 3 . In both cases selectivity appears to be under steric control in spite of fundamental differences. The use of optically active substrates to ascertain the endo and exo configurations is described. A method based on optical isomery has allowed the determination of the kinetic product in a thermodynamically controlled reaction

Reaction of carbanion of Fischer-type carbene complexes with pyrylium salts. One pot substituted benzophenones formation by subsequent cyclization and double hydrogen β-elimination

Abstract Carbanions of Fischer-type carbene complex react with pyrylium salts. The unstable dienone formed gives substituted benzophenones after ring-closure and aromatization by double hydrogen β -elimination.

Problemes de stereoselectivite en serie du benchrotrene: Reduction d' indanones chrome tricarbonyle á et β Substituees endo et exo par les borohydrures de sodium et de potassium. Stereospecificite de la reaction et applications synthetiques

Abstract Borohydride reduction of endo- and exo-α- and β-alkylindanonetricarbonyl-chromium in protic solvents was stereospecific leading solely to the endo-alcohol whose configuration has been ascertained by IR and NMR. This remarkable stereospecificity together with an easy and quantitative decomplexation of the organometallic alcohols has allowed the liberation of cis-and trans-indanols and initiated a study on the stereochemistry of the reduction by KBH4 of free α- and β-alkylindanones.