Synthesis and luminescence properties of new red-shifted absorption lanthanide(III) chelates suitable for peptide and protein labelling.

The synthesis and photo-physical properties of an original bis-pyridinylpyrazine chromophore efficiently sensitising europium(III) and samarium(III) are described. The corresponding lanthanide(III) complexes display in aqueous solutions a maximum excitation wavelength which is significantly red-shifted compared to the usual terpyridine-based chelates, and a valuable luminescence brightness above 2,000 dm(3) mol(-1) cm(-1) at 345 nm was obtained with a europium(III) derivative. Further functionalisation with three different bioconjugatable handles was also investigated and their ability to efficiently label a model hexapeptide was evaluated and compared. Finally, the best bioconjugatable europium(III) chelate was used in representative labelling experiments involving monoclonal antibodies and the luminescence features of the corresponding bioconjugates remained satisfactory.

V-shaped 4,6-bis(arylvinyl)pyrimidine oligomers: synthesis and optical properties.

A series of V-shaped 4,6-bis(arylvinyl)pyrimidines have been efficiently prepared by aldol condensation between 4,6-dimethylpyrimidine and the appropriate aromatic aldehyde. The methodology also proved successful when dendritic first generation poly(phenylenevinylene) aldehydes were used. Moreover, asymmetrically functionalized molecules were also obtained by the stepwise incorporation of arms in a controlled manner. The optical absorption and emission properties of these systems were studied in different solvents and media. The materials display strong emission solvatochromism that is reflected by a large red shift in their fluorescence emission maxima on increasing the solvent polarity. This change is accompanied by a successive decrease in fluorescence intensity. This behavior suggests a highly polar emitting state, which is characteristic of compounds that undergo an internal charge transfer upon excitation. The abilities of these molecules to function as colorimetric and luminescence pH sensors were demonstrated with dramatic color changes and luminescence switching upon the introduction of acid.

ortho-Metalation of enantiopure aromatic sulfoxides and stereocontrolled addition to imines.

Enantiopure aromatic (phenyl, naphthyl) and heteroaromatic (pyridyl, quinolyl, diazinyl) sulfoxides have been synthesized by reaction of (S)-tert-butyl tert-butanethiosulfinate with aryl- or heteroaryllithium derivatives. The ortho-directed metalation of the sulfoxides was performed with lithium bases. Subsequent addition of the lithiated intermediates to N-tosylimines afforded tosylaminoalkyl tert-butylsulfinyl arenes. In most cases a complete asymmetric induction was highlighted in favor of (S,S) isomers. Heating the aminosulfoxides provided an original cyclization to form novel cyclic sulfenamides. A novel enantiopure synthesis of a benzylamine was described. An application of an enantiopure aminosulfoxide as N,S ligand for the asymmetric catalysis of allylic nucleophilic substitution has been successfully tested.

Diastereoselective addition of enantiopure lithium tert-butylsulfinylferrocene to imines.

(S)-tert-Butylsulfinylferrocene was submitted to ortho-metalation, and the corresponding lithium derivative was trapped by alkyl or aryl imines bearing various electron-withdrawing groups on the nitrogen atom (Ts, Dpp, Boc). New aminosulfoxides were obtained with complete diastereocontrol when Dpp or Boc groups were used. The absolute configuration (SS,SFc,S) has been determined by single-crystal X-ray analysis and chemical correlation. An unusual pseudocyclic boatlike transition state has been proposed to explain the stereochemical course of this reaction.

Synthesis of pyrazine alcaloids from Botryllus leachi. Diazines 43.

[reaction: see text] Regioselective metalation of pyrazines and cross-coupling reactions provides an easy access to botryllazines A and B and to an isomer of botryllazine A with good yields from chloropyrazine.

Solid-phase syntheses of 6-arylpyridazin-3(2H)-ones.

The 3-chloropyridazine moiety was immobilized on a Wang resin, using two different methodologies. The first of these involved direct nucleophilic substitution of 3,6-dichloropyridazine with the alcoholate of Wang resin. The experimental conditions were optimized. The second method involved a Mitsunobu reaction between the Wang resin and 6-chloropyridazin-3-ol during which a problem of regioselectivity was observed. The so-obtained chloropyridazine-containing resins were subsequently reacted with various arylboronic acids under Suzuki conditions. Acid cleavage yielded 6-arylpyridazin-3(2H)-ones with high chemical purity.