Acylation des β-énaminoesters: Regio et stéréoformation des β-énaminoesters N- ou C-acylés

The reaction of acyl chlorides with cyclic five-membered β-enaminoesters gave exclusively N-acylated products while reaction of acyl chlorides with cyclic seven-membered β-enaminoesters gave only C-acylated products. In the case of cyclic six-membered β-enaminoesters, the reaction of acyl chlorides gave a mixture of N-acylated and C-acylated products.     

Synthesis, Conformational Studies, X-ray Structures, and Complexation Properties of Semirigid Macrocyclic Phosphonamides

The semirigid phosphonamide ligands 1-5 have been synthesized from the macrocyclic precursors 6-9 by reaction with 1,3-propanediol ditosylate or 1,2-dichloroethane. For the thiophosphoryl compounds 1 and 2, and the phosphoryl derivative 5, the reactions were carried out in biphasic aqueous NaOH solutions. The phosphoryl derivatives 3 and 4 were better obtained from NaH in anhydrous tetrahydrofuran. The conformations of the hosts in solution were deduced from low-temperature NMR and NOE difference experiments. Conformational equilibria between exo and endo forms are observed for the 18-membered macrocycles 1 and 3. The exo conformer predominates in solution for the 21-membered macrocycle 2, whereas 4 exists as rapidly exchanging conformers. The X-ray crystal structures of macrocycles 1, 2, and 5 have been determined as well as the complexes 1.Hg(SCN)(2) and 5.LiNO(3). In the Hg(2+) complex the metal ion is located out of the macrocyclic cavity and is coordinated to the thiophosphoryl unit. In 5.LiNO(3)()()the Li(+) cation is located inside the macrocyclic cavity and is coordinated to a tetrahedral array of oxygen donors. Free energies of complexation (DeltaG degrees ) of the phosphorylated ligands 3-5 with alkali metal and ammonium cations were determined in CHCl(3) saturated with H(2)O by picrate extraction experiments. The -DeltaG degrees values are greatest for 4 complexing K(+) and NH(4)(+) (7.3 and 8.0 kcal/mol, respectively). The relationships between structure and binding are discussed.     

Synthesis and Photoreaction of 5-Aikenyloxypsoralen Derivatives

Abstract— In order to investigate the intramolecular "quenching" of the photoexcitation of some 5-alkenyloxypsoralen derivatives, we have prepared model compounds in which a psoralen moiety was linked at position 5 to a terminal double bond via a polymethylenic chain of various length (n = 2-9). The isolation and characterization of photocycloadducts obtained for each compound after irradiation at 365 nm in a polar solvent was performed. The results on the photoreactivity of this series of compounds show that the 3,4-pyrone double bond of 5-alkoxypsoralens is the most reactive. Four kinds of intramolecular photocycloadducts between the 3,4-pyrone double bond and the chain unsaturation were obtained according to the length of the linking chain: cis-syn, trans-syn, cis-anti and trans-anti. Their structures were established by a combination of ¹H and ¹³C NMR and fully assigned by ^lH NOE (nuclear Overhauser effect) and ¹H-¹³C HMQC (heteronuclear multiquantum correlation) spectroscopies. No traces of 4',5' adducts were detected.     

Photophysical and Redox Properties of a Series of Phthalocyanines: Relation with Their Photodynamic Activities on TF-1 and Daudi Leukemic Cells

Abstract— The photodynamic therapy (PDT) efficiency of five phthalocyanines, chloroaluminum phthalocyanine (AlPc), dichlorosilicon phthalocyanine (SiPc), bis (tri- n -hexylsi-loxy)silicon phthalocyanine (PcHEX), bis (triphenyl-siloxy)silicon phthalocyanine (PcPHE) and nickel phthalocyanine (NiPc), was assessed on two leukemic cell lines TF-1 and erythroieukemic and B lymphoblastic cell lines, Daudi, respectively. AlPc showed the best photocytotox-icity leading to 0.008 surviving fraction at 2 × 10⁻⁹ M for TF-1 and 4 × 10⁻⁹ M for Daudi. At 5 × 10⁻⁷ M , SiPc and PcHEX induced a significant photokilling, whereas NiPc and PcPHE were inactive. Laser flash photolysis and photoredox properties of the phthalocyanines were investigated to try to relate these parameters with the biological effects. AlPc showed the longest triplet lifetime: 484 fis in dimethyl sulfoxide/H₂O. This value was increased up to 820 u.s when AlPc was complexed with human serum albumin used as a membrane model. Such an enhancement was not observed with the silicon phthalocyanines. Upon irradiation, all the phthalocyanines generated singlet oxygen with 0.29–0.37 quantum yield values. The reduction potentials of the excited states obtained from measurement in the ground state and energy of the excited triplets show that AlPc is the best electron acceptor. The in vitro photocytotoxicity observed and the measured parameters are in agreement with a key role of electron transfer in PDT assays involving these phthalocyanines.     

Incorporation of a minimal nucleotide into DNA

Abasic sites are amongst the most frequent DNA lesions and result from spontaneous hydrolysis of the glycosidic bond or from the removal of damaged nucleobases. These depurination events can also occur on free deoxyribonucleoside triphosphates present in cells and lead to the formation of an abasic site triphosphate of which very little is known. Herein, we report the synthesis and biochemical characterization of the minimal triphosphate dФTP. Unexpectedly, dФTP is tolerated by various DNA polymerases and the incorporation efficiency obeys the A-rule. Single incorporation of dФMP units were also observed opposite abasic sites and the addition of prosthetic molecules mimicking base-pairs do not seem to favor the process.     

Synthese et reactivite d''organometalliques perfluores. VII [1] reactivite comparee de derives perfluoroalkyles satures et insatures de l''etain et du mercure vis-a-vis d''electrophiles.

The reactivity of some derivatives of perfluorooctenyl-tin, perfluorooctenyl-mercury and perfluorooctyl-mercury towards protic acids, especially hydrogen chloride, is studied.

The easy cleavage of the tin - sp² carbon bond is painted out, and used to study possibilities of transferring the perfluorooctenyl radical on mercury, upon reaction with mercuric salts.

The mercury-perfluoroalkyl radical bond is shown to be, on the contrary, very resistant to an electrophilic attack.

These results are compared to those concerning the hydrocarbon analogs, and an interpretation, relied to the electronic density on the carbon atom bound to the metallic atom, is given.     

Perturbative solution of the RPA equation. An application to the calculation of rotational strengths

The RPA equation is solved by perturbation in Møller-Plesset (MP) and Epstein-Nesbet (EN) partitions, which are first compared on a specific example. To still accelerate the faster one (EN), a third scheme is proposed, which involves preliminary diagonalization within a limited subset , followed by usual EN perturbation between and the rest of the whole configuration space. Criteria for the choice of are given.     

Regioselectivite de la reaction des dialkyl cuprates de magnesium sur des aldehydes α,β-ethyleniques

Various magnesium organocuprates give conjugative addition products with α,β-ethylenic aldehydes, and even with acrolein. The enolates may be trapped with bromine or trimethylsilyl chloride.     

Photocyclisation d'hydroxyalkyl glycosides en orthoesters glycosidiques

A free-radical cyclization process makes glycosidic orthoester structures readily available in a one-pot procedure.