Synthesis of a tetrahydropyran NK1 receptor antagonist via asymmetric conjugate addition

Two asymmetric syntheses of the NK(1) receptor antagonist 1-[2-(R)-{1-(R)-[3,5-bis(trifluoromethyl)phenyl]ethoxy}-3-(R)-(3,4-difluorophenyl)-4-(R)-tetrahydro-2H-pyran-4-ylmethyl]-3-(R)-methylpiperidine-3-carboxylic acid (1) were developed. In both routes, the core tetrahydropyran stereochemistry was established by asymmetric conjugate addition to an alpha,beta-unsaturated ester (6), using an amide of the chiral auxiliary pseudoephedrine. Selective ester reduction then allowed formation of lactone 2 with the thermodynamically preferred trans geometry. The chiral ether side chain (3) was attached by stereoselective acetal substitution. In the first route, the chiral piperidine ester fragment was installed at the end by N-alkylation. In the shorter second synthesis, this piece was appended to the Michael acceptor at the beginning.     

Direct measurement of the hyperfine and g-tensors of a Mn(III)-Mn(IV) complex in polycrystalline and frozen solution samples by high-field EPR

The g-tensors and hyperfine tensors of the S = (1)/(2) ground state of the mixed valence [LMn(IIImu-O)(2)Mn(IV)L](3+) complex (L = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine) was deter-mined in the solid-state and frozen acetonitrile solution by high-field EPR. Both samples exhibited complex anisotropic temperature behaviors that precluded the use of routine spectrum simulation procedures to extract the spin parameters. To circumvent this problem, the parameters were measured directly by using multifrequency techniques. In the case of the frozen solution, this approach yielded seven of the nine spin parameters with varying uncertainty, the two extreme principal g-values, the four hyperfine couplings associated with each of these two g-values, and the middle g-value. This latter parameter was obtained from a first moment analysis. Unlike simulations, the statistical errors associated with each value could be assigned in a straightforward and rigorous manner. The directly measured g-values were different in frozen solution and polycrystalline powder. The temperature dependence of the high-field EPR spectra of the polycrystalline powder revealed a spin-spin interaction between the neighboring binuclear complexes.     

From metal to ligand electroactivity in nickel(II) oxamato complexes

The locus of oxidation in square-planar nickel(ii) oxamato complexes can be continuously shifted from the metal to the ligand by an appropriate choice of electron-donating substituents on the aromatic moiety of the ligand.     

Trans influence and charge transfer transitions X → Co in cobalt (III) complexes of the type trans [CO(en)2XY]z

The energies of the CT transitiopns X → Co have been measured for a series of compounds of the type trans [CO(en)₂XY]^+z, with X = Cl, Br and Y = Cl, Br, NH₃, OH, NCS, No₂, SO₃, CN. They depend upon the nature of the Yl igand. Values of the optical electronegativity of the CO d_z2 orbitals have been calculated, showing that the covalent character of the CoX bond increases in the following order of the Y ligands: NCS ≈ NH₃ ≈CN < OH < NO₂ < Cl ≈ Br < SO₃. This result is discussed along with the variations of the Co bonding forces.     

Synthesis and X-ray structure of the MnIICl2 and MnIIIF2 complexes of N,N'-dimethyl-2,11-diaza[3,3](2,6)pyridinophane. High-field electron paramagnetic resonance and density functional theory studies of the MnIII complex. Evidence for a low-lying spin triplet state

Two manganese complexes, (py2(NMe)2)MnIICl2 (1) and [(py2(NMe)2)MnIIIF2]+ (2), are here described with the macrocyclic ligand py2(NMe)2 (py2(NMe)2 = N,N'-dimethyl-2,11-diaza[3,3](2,6)pyridinophane). For both, the crystal structure is reported. The UV-visible spectrum of 2 exhibits a very broad near-infrared (NIR) band corresponding to the transition between the two e(g)-type orbitals split by the Jahn-Teller effect. A negative D value of ca. -4 cm(-1) was estimated by high-field and high-frequency electron paramagnetic resonance (HF-EPR) spectroscopy, which was consistent with symmetry considerations. Density functional theory (DFT) calculations on 2 support the 5B1 electronic ground state predicted from the X-ray structure. Moreover, to explain the large value of the D parameter, a spin triplet first excited spin state was postulated to occur at low energy. This was confirmed by the DFT calculations.     

Porphyrin-aminoquinoline conjugates as telomerase inhibitors

A series of metalloporphyrins was prepared in order to target the G-quadruplex structure of telomeric DNA for the design of antitelomerase compounds. The initial cationic tetramethylpyridiniumyl porphyrin was modified by the replacement of one or two methylpyridiniumyl groups by one or two 4-aminoquinoline moieties, at the meso position, in order to increase the cell penetration and the quadruplex affinity. The porphyrins were either metallated by manganese or by nickel. The degradation of quadruplex DNA was assayed in vitro with the manganese redox-active derivatives. All porphyrins complexes were capable of inhibiting the telomerase enzyme with IC50 values in the micromolar range (TRAP assay).     

Synthesis, structure, and characterisation of a new phenolato-bridged manganese complex [Mn2(mL)2]2+: chemical and electrochemical access to a new mono-mu-oxo dimanganese core unit

The dinuclear phenolato-bridged complex [(mL)Mn(II)Mn(II)(mL)](ClO(4))(2) (1(ClO(4))(2)) has been obtained with the new [N(4)O] pentadentate ligand mL(-) (mLH=N,N'-bis-(2-pyridylmethyl)-N-(2-hydroxybenzyl)-N'-methyl-ethane-1,2-diamine) and has been characterised by X-ray crystallography. X- and Q-band EPR spectra were recorded and their variation with temperature was examined. All spectra exhibit features extending over 0-800 mT at the X band and over 100-1450 mT at the Q band, features that are usually observed for dinuclear Mn(II) complexes. Cyclic voltammetry of 1 exhibits two irreversible oxidation waves at E(1)(p)=0.89 V and E(2)(p)=1.02 V, accompanied on the reverse scan by an ill-defined cathodic wave at E(1')(p)=0.56 V (all measured versus the saturated calomel electrode (SCE)). Upon chemical oxidation with tBuOOH (10 equiv) at 20 degrees C, 1 is transformed into the mono-mu-oxo species [(mL)Mn(III)-(mu-O)-Mn(III)(mL)](2+) (2), which eventually partially evolves into the di-mu-oxo species [(mL)Mn(III)-(mu-O)(2)-Mn(IV)(mL)](n+) (3) in which one of the aromatic rings of the ligand is decoordinated. The UV/Vis spectrum of 2 displays a large absorption band at 507 nm, which is attributed to a phenolate-->Mn(III) charge-transfer transition. The cyclovoltammogram of 2 exhibits two reversible oxidation waves, at 0.65 and 1.16 V versus the SCE, corresponding to the Mn(III)Mn(III)/Mn(III)Mn(IV) and Mn(III)Mn(IV)/Mn(IV)Mn(IV) oxidation processes, respectively. The one-electron electrochemical oxidation of 2 leads to the mono-mu-oxo mixed-valent species [(mL)Mn(III)-(mu-O)-Mn(IV)(mL)](3+) (2 ox). The UV/Vis spectrum of 2 ox exhibits one large band at 643 nm, which is attributed to the phenolate-->Mn(IV) charge-transfer transition. 2 ox can also be obtained by the direct electrochemical oxidation of 1 in the presence of an external base. The 2 ox and 3 species exhibit a 16-line EPR signal with first peak to last trough widths of 125 and 111 mT, respectively. Both spectra have been simulated by using colinear rhombic Mn-hyperfine tensors. Mechanisms for the chemical formation of 2 and the electrochemical oxidation of 1 into 2 ox are proposed.     

Selective Lewis acid catalyzed transformation (gamma-butyrolactone versus cyclopropane) of 2-methoxy-4-benzyltetrahydrofuran derivatives. Efficient synthesis of lignan lactones

[reaction: see text]. A short synthesis of lactone lignans exploiting a three-component coupling strategy is presented using a new Lewis acid catalyzed ring-opening/cyclization reaction of 2-methoxytetrahydrofuran derivatives 4 leading to gamma-butyrolactones as a key step. By simply changing the reaction conditions, it was possible, from the same substrates 4, to obtain selectively cyclopropane derivatives.     

Detection of secondary biomarker of met-eGH as a strategy to screen for somatotropin misuse in horseracing

Since the Australian commercialisation of the recombinant equine growth hormone (reGH) in 1998 (EquiGen-5), Bresagen), this reGH, which differs only from eGH by an additional methionine at the N-terminal end (met-eGH), is worldwide suspected to be administered to racehorses as a doping agent. Indeed, the use of this biological drug is considered as a threat to horseracing since it acts both on growth, development or reproductive functions, and on the improvement of performances. In this work, we describe two reliable techniques based on surface plasmon resonance biosensor immunoassay (SPR-BIA) and solid-phase enzyme-linked immunosorbent assay (ELISA) as new, rapid and efficient long-term screening methods applicable to horseracing antidoping analysis. The ELISA and SPR-BIA tests were applied to octanoic acid purified IgGs from serum/plasma samples collected on two thoroughbreds treated with recombinant equine growth hormone for a period of two weeks. The first kinetic study of serum/plasma antibodies raised as a consequence of recombinant equine growth hormone administrations, which allows the detection from eight days up to 200 days after the beginning of the treatment, was performed. In order to trace the occurrence of anti-reGH antibodies in routine analysis and to monitor the animal level exposure to this forbidden molecule, a random population study was conducted on 233 post-race horses.     

Physico-chemical investigation of asymmetrical peptidolipidyl-cyclodextrins

A new class of amphiphilic peptidolipidyl-cyclodextrins is reported. The derivatives are chiral due to the presence of an L-leucine in the spacer arm that links a saccharide moiety and a grafted, saturated hydrocarbon chain. Self-assembly properties of the peptidolipidyl-cyclodextrins are characterized by quasi-elastic light scattering, turbidity and UV-visible absorption measurements. NMR experiments give insight into the intermolecular dipolar interactions as a function of temperature and concentration. N-dodecyl-N alpha-(6 I-amidosuccinyl-6 1-deoxy-cyclomaltoheptaose)-L-leucine (1) is poorly soluble in aqueous media. N-dodecyl-N(alpha)-(6 I-amidosuccinyl-6 I-deoxy-2 I,3 I-di-O-methyl-hexakis-(2 II-VII,3 II-VII,6 II-VII-tri-O-methyl)-cyclomaltoheptaose)-L-leucine (2) is found to be more soluble and self-assembles into stable supramolecular colloidal aggregates with nanometric dimensions above a critical aggregation concentration (CAC). It has a propensity for solubilization of hydrophobic species revealing a micellar-like behavior, which is compared to that of the non-ionic detergent octyl glucoside. On the contrary, compound 1 precipitates in a crystalline phase beyond its water solubility limit, and it does not display any solubilizing capacity. The observed behavior corroborates at the molecular level with the NMR results.