Nitrostyrene Derivatives of Adenosine 5′-Glutarates Modified with an Alkyl Spacer and their inhibitory activity on epidermal growth factor receptor protein tyrosine kinase

β-Nitrostyrene derivatives of adenosine 5′-glutarates are potent and selective bisubstrate-type inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF-R PTK). In an attempt to improve the inhibitory activity, this type of compounds was modified with alkyl spacers of varying length between the nitrostyrene and the glutaryl units. The spacers consisted of 1, 3, 4, and 5 atoms to give compounds of the benzyl, oxyethyl, oxypropyl, and oxybutyl series, respectively (Schemes 1 and 2). Adenosine 5′-esters were prepared in the benzyl and oxypropyl series only. Compared to the compounds in the parent series without spacer (IC₅₀ = 0.7–12 μM ), most of the modified compounds inhibited the EGF-R PTK only marginally or were inactive (IC₅₀ ≥ 100 μM ). The only exceptions were the free acids 19 and 20 with IC₅₀ values of ca. 5 μM . It is noteworthy that esterification of these two hydrogen glutarates with either MeOH or adenosine yielded inactive compounds, which is in contrast to the corresponding substances without spacers.     

Off-shell behaviour of theN-N interaction in a six-quark resonating group model of the deuteron

Two different 6-quark resonating group models of the deuteron are investigated to study the off-shell property of theN-N interaction. In the first model the quarks interact by a central one-gluon-exchange potential plus confinement potential. The meson-exchange contribution to then-p potential is simulated by a central GaussianN-N potential. In the second model the quarks interact by one-gluon-and one-pion-exchange potentials (central and noncentral) plus confinement potential. A small additional -exchange potential between neutron and proton binds the deuteron at the correct energy.Several off-shell variants of the two resonating group models are compared with each other by analyzing their elastic electron scattering cross sections. It is found that the standard renormalized version of the resonating group model yields potentials and wave functions that may be considered physical within the limitations of the model. Unitary off-shell transformations, which modify potentials and wave functions in any sizeable way, lead to a disagreement between the charge distribution predicted by the model via analysis of electron scattering and the charge distribution following from the microscopic quark distribution.Both of the 6-quark models support a soft repulsive core of the tripletn-p potential with a core height of around 900 MeV.     

Fluorescence from the second excited singlet state of [18] annulenes

The emission spectra of the second excited singlet state of [18] annulene and of monofluoro [18] annulene (in a 3-methylpentane glass at 4 K) are reported. The large energy gap between the first and second excited singlet states inhibits fast internal conversion and favours the appearance of S₂ → S₀ emission. In addition, fluorescence from the S₁ state can be observed in monofluoro [13] annulene by exciting into the S₂ or directly into the S₁ absorption.     

Catalyseurs Zieger-Natta supportés sur MgCl2 pour la polymérisation stéréorégulée du propène. II. Système catalytique simple: Solide binaire MgCl2-TiCl4 et solution cocatalytique triéthylaluminium,benzoate d'ethyle

The kinetics of propene polymerization in heptane slurry at 1–4 bars was studied with a catalytic system that consisted of a solid catalyst prepared by adsorption of TiCI₄ on pure porous MgCl₂ (by dehydrating MgCl₂, 6 H₂O with thionyl chloride) and a cocatalytic, heptanic solution of ethylbenzoate (BE) and triethylaluminium (TEA). At a temperature approaching 60°C/polymerization began immediately after the introduction of the monomer. The polymerization rate decreased continuously during the reaction. The loss in activity, however, was not due to a diffusional effect (e.g., blocking of the catalyst by the growing polymer). Studies of the ageing of the catalytic system showed a deactivation of the catalytic system itself as a function of the time of contact between the catalyst and the cocatalyst. The product of the thermal decomposition of the complex 1:2 formed by the reaction of BE with TEA was not associated with the deactivation process or stereospecific control, which depend on the BE/AI ratio and the presence of the complex.     

Tetrakis (methylidene)cyclobutane (‘[4]Radialene’): Electronic states of the molecular ion

The photoelectron spectrum of tetrakis (methylidene)cyclobutane ( 1 , ‘[4]radialene’) is reported. The electronic states of 1 ⁺ are assigned on the basis of model calculations and with reference to related systems. Jahn-Teller activity in the degenerate states is discussed. A failure of the simple LCBO-model for the π(e_g)-orbital of 1 is noted and traced to the fact that this orbital, though having a symmetry-equivalent π*-counterpart, does not interact with it. This feature is confined to [4n]radialenes; their total π-energies are therefore higher than those of the other members. It is shown that radialenes, in principle, do not constitute a class analogous to that of the linear polyenes as inferred earlier.     

Präparative chromatographische Enantiomerentrennung von synthetisch nützlichen cyclischen Acetalen

Preparative Chromatographic Resolution of Synthetically Useful Cyclic Acetals Racemic cyclic acetals derived from aldehydes and glycine, glycolic acid, thioglycolic acid, formylacetic acid, and acetoacetic acid (oxazolidinones 4 – 13 , dioxolanones 14 , 15 , oxathiolanone 16 , dioxinones 17 – 23 ) are resolved by preparative high-pressure liquid chromatography on silica gel coated with the polymer from N-acryloylphenylalanine ethyl ester (Chiraspher®). The separation factors α range from1,1 to 2,4. Use of a Prepbar®-chromatography system allows injection of several grams at a time. The enantiomeric acetals thus obtained are fully characterized. First application to amino-acid synthesis are mentioned.     

Die Deprotonierung von Metallaquoionen II: Aquochrom(III)-ion. Zur Struktur aktiver Chromhydroxide

On alkalinization of solutions of the chromiun(III)-aquo ion simple deprotonation takes place first. The degree of hydroxylation n _OH however can be brought up to only about 1 (the exact value depending on the total concentration [Cr]_t), before the uncharged complex Cr(OH)₃(OH₂)₃ is precipitated. The structure of the very sparingly soluble complex (solubility ～10^?7M ) is held together by hydrogen bonds of type I between the molecules, so that its formula may be written as Cr(OH)₂H_6/2-lattice. The formation of the well ordered structure is extremely fast. On aging, the metallic centers become connected by μ-hydroxo-bridges (type II) and the substances become amorphous and very insoluble. The dinuclear (H₂O)₄Cr(OH)₂Cr(OH₂)₄⁴⁺ behaves similar on deprotonation. Concerning the various equilibria constants see Table 1.