Methyl 7,8-diacet­oxy-11-oxo-5-(2-oxo­pyrrolidin-1-yl)-7,9-epoxy­cyclo­penta­[4,5]pyrido[1,2-a]quinoline-10-carboxyl­ate sesquihydrate

The title compound, C26H28N2O9·1.5H2O, the product of an acid-catalysed Wagner–Meerwein skeletal rearrangement, crystallizes as a sesquihydrate with the O atom of one of the two independent water mol­ecules occupying a special position on a twofold axis. The organic mol­ecule comprises a fused penta­cyclic system containing two five-membered rings (cyclo­pentane and tetra­hydro­furan) and three six-membered rings (piperidinone, tetra­hydro­pyridine and benzene). The five-membered rings have the usual envelope conformations, and the central six-membered piperidinone and tetra­hydro­pyridine rings adopt boat and sofa conformations, respectively. In the crystal, there are three independent O—H⋯O hydrogen bonds, which link the organic mol­ecules and water mol­ecules into complex two-tier layers parallel to (001). The layers are further linked into a three-dimensional framework by attractive inter­molecular carbon­yl–carbonyl inter­actions

(6aS*,6bS*,11R*,11aR*)-6-(2-Furyl­methyl)-5,12-dioxo-5,6,6a,6b,7,11,11a,12-octa­hydro­furo[3′,2′:5,6]isoindolo[2,1-a]quinazoline-11-carb­oxy­lic acid

The title compound, C23H18N2O6, is the product of an intra­molecular thermal cyclo­addition within 1-malein-2-[(E)-2-(2-fur­yl)vin­yl]-4-oxo-3,4-dihydro­quinazoline. The mol­ecule comprises a previously unknown fused penta­cyclic system containing two five-membered rings (2-pyrrolidinone and furan) and three six-membered rings (benzene, 2,3-dihydro-4-pyrimidinone and dihydro­cyclo­hexa­ne). The central five-membered pyrrolidinone ring has the usual envelope conformation. The six-membered dihydro­pyrimidinone and dihydro­cyclo­hexane rings adopt a half-boat and a half-chair conformation, respectively. The dihedral angle between the planes of the terminal benzene and furan rings is 45.99 (7)°. In the crystal, O—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers. Weak C—H⋯O hydrogen bonds consolidate further the crystal packing, which exhibits π–π inter­actions, with a short distance of 3.556 (3) Å between the centroids of benzene rings of neighbouring mol­ecules

One-Dimensional Confinement and Enhanced Jahn-Teller Instability in LaVO3_3

Ordering and quantum fluctuations of orbital degrees of freedom are studied theoretically for LaVO$_3$ in spin-C-type antiferromagnetic state. The effective Hamiltonian for the orbital pseudospin shows strong one-dimensional anisotropy due to the negative interference among various exchange processes. This significantly enhances the instability toward lattice distortions for the realistic estimate of the Jahn-Teller coupling by first-principle LDA+$U$ calculations, instead of favoring the orbital singlet formation. This explains well the experimental results on the anisotropic optical spectra as well as the proximity of the two transition temperatures for spin and orbital orderings.Comment: 4 pages including 4 figure

Precision determination of band offsets in strained InGaAs/GaAs quantum wells by C-V-profiling and Schroedinger-Poisson self-consistent simulation

The results of measurements and numerical simulation of charge carrier distribution and energy states in strained quantum wells In_xGa_{1-x}As/GaAs (0.06 < x < 0.29) by C-V-profiling are presented. Precise values of conduction band offsets for these pseudomorphic QWs have been obtained by means of self-consistent solution of Schroedinger and Poisson equations and following fitting to experimental data. For the conduction band offsets in strained In_xGa_{1-x}As/GaAs - QWs the expression DE_C(x) = 0.814x - 0.21x^2 has been obtained.Comment: 9 pages, 12 figures, RevTeX

Lattice Distortion and Magnetism of 3d-t2gt_{2g} Perovskite Oxides

Several puzzling aspects of interplay of the experimental lattice distortion and the the magnetic properties of four narrow $t_{2g}$-band perovskite oxides (YTiO$_3$, LaTiO$_3$, YVO$_3$, and LaVO$_3$) are clarified using results of first-principles electronic structure calculations. First, we derive parameters of the effective Hubbard-type Hamiltonian for the isolated $t_{2g}$ bands using newly developed downfolding method for the kinetic-energy part and a hybrid approach, based on the combination of the random-phase approximation and the constraint local-density approximation, for the screened Coulomb interaction part. Then, we solve the obtained Hamiltonian using a number of techniques, including the mean-field Hartree-Fock (HF) approximation, the second-order perturbation theory for the correlation energy, and a variational superexchange theory. Even though the crystal-field splitting is not particularly large to quench the orbital degrees of freedom, the crystal distortion imposes a severe constraint on the form of the possible orbital states, which favor the formation of the experimentally observed magnetic structures in YTiO$_3$, YVO_, and LaVO$_3$ even at the HF level. Beyond the HF approximation, the correlations effects systematically improve the agreement with the experimental data. Using the same type of approximations we could not reproduce the correct magnetic ground state of LaTiO$_3$. However, we expect that the situation may change by systematically improving the level of approximations for dealing with the correlation effects.Comment: 30 pages, 17 figures, 8 tables, high-quality figures are available via e-mai

Синтез та антимікробна активність 3-(2-метил-4-оксо-1,4-дигідрохінолін-3-іл)пропанових кислот

In order to reveal the possible regularities of the structure–activity relationship the derivatives of 3-(2-methyl-4- oxo-1,4-dihydroquinoline-3-yl)propanoic acid having various substituents in α-position of the acidic moiety of propanoic acid such as alkyl, carboxyl, acyl and acetamide substituents have been synthesized. The synthesis of the target compounds has been carried out using 3-dimethylaminomethyl-2-methyl-1,4-dihydroquinoline-4-one as a versatile alkylating reagent. Its interaction with methylene active substances allowed to obtain monoalkyldicarbonyl compounds, which further hydrolysis gave the derivatives of 3-(2-methyl-4-oxo-1,4-dihydroquinoline-3yl)propanoic acid. The structures of the compounds obtained have been confirmed by the data of 1H NMR and elemental analysis. The results of the screening performed by the agar diffusion method have shown different levels of the antimicrobial activity. For two compounds – 1,3-diethoxy-2-[(2-methyl-4-oxo-1,4-dihydroquinolin-3-yl)methyl]-1,3-dioxopropan-2-yl-carbamic acid and 3-(2-methyl-4-oxo-1,4-dihydroquinolin-3-yl)propanoic acid a moderate broad-spectrum activity has been found in the screening method. The results of the research have shown the perspectiveness of further search for novel antibacterial agents based on 4-quinolon-3-yl-propanoic acids, therefore, it is necessary to expand the range of the compounds with this scaffold.C целью выявления возможных закономерностей связи структура – действие были синтезированы производные 3-(2-метил-4-оксо-1,4-дигидрохинолин-3-ил)пропановой кислоты с различными заместителями в α-положении остатка пропановой кислоты – алкильными, карбоксильными, ацильными и ацетамидными. Синтез целевых соединений был осуществлен с использованием 3-диметиламинометил-2-метил-1,4-дигидрохинолин-4-она в качестве удобного алкилирующего реагента. Его взаимодействие с метиленактивными веществами позволило получить моноалкилдикарбонильные соединения, последующий гидролиз которых давал производные 3-(2-метил-4-оксо-1,4-дигидрохинолин-3-ил)пропановой кислоты. Структуры полученных соединений были подтверждены на основе данных 1Н ЯМР и элементного анализа. По результатам скрининга, выполненного методом диффузии в агар, выявлены различные уровни антимикробной активности для исследуемых веществ. Однако два соединения: 1,3-диэтокси-2-[(2-метил-4-оксо-1,4-дигидрохинолин-3-ил)метил]-1,3-диоксопропан-2-ил карбаминовая кислота и 3-(2-метил-4-оксо-1,4-дигидрохинолин-3-ил)пропановая кислота показали умеренную активность широкого спектра действия. Проведенные исследования показали перспективность дальнейшего поиска потенциальных антибактериальных агентов на основе 4-хинолон-3-ил-пропановой кислоты, для чего необходимо расширить диапазон соединений, содержащих данный скаффолд.З метою виявлення можливих закономірностей зв’язку структура – дія були синтезовані похідні 3-(2-метил- 4-оксо-1,4-дигідрохінолін-3-іл)пропанової кислоти з різними замісниками в α-положенні залишку пропанової кислоти – алкільними, карбоксильними, ацильними та ацетамідними. Синтез цільових сполук проводили з використанням 3-диметиламінометил-2-метил-1,4-дигідрохінолін-4-ону в якості зручного алкілуючого реагента. Його взаємодією з метиленактивними речовинами були одержані моноалкілдикарбонільні сполуки, подальший гідроліз яких приводив до похідних 3-(2-метил-4-оксо-1,4-дигідрохінолін-3-іл)пропанової кислоти. Структури отриманих сполук були підтверджені на основі даних 1Н ЯМР та елементного аналізу. За результатами скринінгу, виконаного методом дифузії в агар, виявлені різні рівні антимікробної активності для досліджуваних речовин. Проте дві сполуки: 1,3-діетокси-2-[(2-метил-4-оксо-1,4-дигідрохінолін-3-іл)метил]-1,3-діоксопропан-2-іл карбамінова кислота та 3-(2-метил-4-оксо-1,4-дигідрохінолін-3-іл)пропанова кислота показали помірну активність широкого спектра дії. Проведені дослідження показали перспективність подальшого пошуку потенційних антибактеріальних агентів на основі 4-хінолон-3-іл-пропанової кислоти, для чого необхідно розширити діапазон сполук, що містять даний скаффолд