Chirality organization of ferrocenes bearing dipeptide chains of heterochiral sequence

[structures: see text] The symmetrical introduction of two dipeptide chains of heterochiral sequence (-L-Ala-D-Pro-NHPy) into the ferrocene scaffold as a central reverse-turn unit was demonstrated to induce both antiparallel beta-sheet-like and type II beta-turn-like structures simultaneously, affording the chirality-organized structure. The ferrocene bearing only one dipeptide chain (-L-Ala-D-Pro-NHPy) exhibited a left-handed helically ordered molecular assembly through a network of intermolecular hydrogen bonds instead of intramolecular hydrogen bonds.     

Generalized doubly symbolic formulation for integral-driven direct configuration interaction method

Summary A direct configuration interaction (CI) scheme using the generalized double symbolism both for the external space and for the internal space is proposed in an integral-driven context. The reason why the double symbolism is used in the present formulation is that the main target is in investigating large molecular systems. The integrals, configuration state functions, and energy expressions are systematically classified in terms of the orbital labels and their mutual relations. Various types of CI wavefunctions can be set up flexibly. The resulting structure of integral processings in the sigma vector construction is complicated. The number of unique loop types for two-electron integrals is 1325. Because the parallel architecture is gaining importance in the recent computational platforms, the parallelism is also addressed.     

Constituents of the underground parts of Glehnia littoralis

From the underground parts of Glehnia littoralis FR. Schmidt ex Miquel (Umbelliferae), 26 compounds, including two new lignan glycosides [giehlinosides A (1) and B (2)], a new neolignan glycoside [glehlinoside C (3)], and a new phenylpropanoid glycoside 14-[beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranosyloxyl-3-methoxypropiophenone (4)1, were obtained and their structures were determined by analysis of their spectral data. The 1,1-diphenyl-2-picrylhydrazyl radical-scavenging assay disclosed quercetin (8), isoquercetin (9), rutin (10), chlorogenic acid (11), and caffeic acid (24) as the major antioxidative constituents in this crude drug.     

Self-assembly control of a pyridine-containing diblock copolymer by perfluorinated counter anions during salt-induced micellization

The micelle formation of poly[(4-pyridinemethoxymethyl)styrene]-block-polystyrene (PPySt-b-PSt) was studied in the nonselective solvent using perfluoroalkyl carboxylic acids. PPySt-b-PSt showed no self-assembly into micelles in THF, because this solvent was nonselective for the copolymer. Dynamic light scattering demonstrated that the diblock copolymer formed the micelles in the solvent in the presence of perfluoroalkyl carboxylic acids in which the number of carbons in the perfluoroalkyl chains was over eight. ¹H NMR revealed that the micellization proceeded through the salt formation of the pyridinium perfluoroalkyl carboxylate and through the aggregation of the perfluoroalkyl chains in the counter anions. The hydrodynamic radius and the aggregation number of the micelles increased with an increase in the length of the perfluoroalkyl chain. The copolymer needed less carboxylic acid with longer perfluoroalkyl chain to form the micelles. The copolymer produced the micelles with lower aggregation number and higher critical micelle concentration at higher temperature, although the micellar size was almost independent of the temperature. The micelles were unstable with respect to the variation in the temperature, and were dissociated into the unimers with the increase in the temperature. The micelles, however, were reconstructed by decreasing the temperature. This dissociation–reconstruction of the micelles was controlled reversibly not only by the temperature but also by the concentration of the perfluoroalkyl carboxylic acid. An increase in the acid concentration suppressed the dissociation into the unimers, while promoting the reconstruction of the micelles.     

Concise synthesis of cyclic ethers via the palladium-catalyzed coupling of ketene acetal triflates and organozinc reagents. Application to the iterative synthesis of polycyclic ethers

The reaction of the ketene acetal triflates 9a-e and a zinc homoenolate 10 in the presence of a catalytic amount of Pd(PPh(3))(4) gave the enol ethers 11a-e in good yields. The products were converted to the corresponding cyclic ethers 14a and 14b by hydroboration and lactonization. The present methodology allowed us to synthesize the DE and GH ring segment of gambierol in a concise manner. Iterative syntheses of the polycyclic ethers 26 and 32 are also described.     

Selective single ring-opening polymerization of spiroorthoesters with aluminium (III) acetylacetonate

A spiroorthoester, 2-methyl-1,4,6-trioxaspiro[4.6]undecane ( 1 ), was polymerized with aluminium (III) acetylacetonate as a catalyst. The resulting polymer structure was analyzed in detail by FT-IR and 270 MHz ¹H NMR, and consisted of poly(orthoester) which was obtained by selective ring-opening of the seven-membered ring. In contrast, 2-methyl-1,4,6-trioxaspiro[4.5]decane ( 2 ) and 2-methyl-1,4,6-trioxaspiro[4.4]nonane ( 3 ) did not afford any polymers. The reactivity difference of these monomers was discussed in terms of their strain energies on the basis of MM2 calculations.     

Role of Organic Additives in the Sol-Gel Synthesis of Porous CaF2 Anti-Reflective Coatings

Porous CaF₂ anti-reflective coating films were prepared by the sol-gel method. Effects of organic additives on deposition and optical properties of the films were investigated. Amino alcohols (2-aminoethanol, 2-dimethylaminoethanol, and triethanolamine) and alcohols with larger molecular weights (ethyleneglycol, 2-methoxyethanol, cyclohexanol, and 2-(2-n-butoxyethoxy)ethanol) were chosen as the organic additives. Among these additives, cyclohexanol was the most effective to control the surface morphology and the optical properties of the films. By changing the amount of cyclohexanol in the coating solution, it was possible to control the optical thickness of the CaF₂ films. Accordingly, the wavelength giving the maximum transmittance could be changed in the UV region.     

Novel norcassane-type diterpene from the seed kernels of Caesalpinia crista

Three novel norcassane-type diterpenes were isolated from a CH₂Cl₂ extract of the seed kernels of Caesalpinia crista together with four known cassane-type diterpenes. All the new compounds represent unprecedented carbon framework. Norcaesalpinin A (1) and B (2) had 17-norcassane skeleton, while norcaesalpinin C (3) had 16-norcassane skeleton. Their structures were elucidated on the basis of spectral analysis.     

Structural effects on valence tautomerism : VII. An NMR and molecular mechanics study of the steric effects of t-butyl substituents on the cycloheptatriene-norcaradiene equilibrium of 7-cyano-7-m

7-Cyano-7-methylcycloheptatrienes containing one t-butyl group on the 1-position ($\text{2}$) or two t-butyl groups on the 1- and 3-, 1- and 4-, or 1- and 5-positions ($\text{3}$, $\text{4}$, or $\text{5}$, respectively) were synthesized and their cyclo- heptatriene (CHT)-norcaradiene (NCD) equilibria measured by variable-temperature ¹H NMR for CS₂-CD₂Cl₂ solutions. The ¹H NMR chemical shifts of the 7-methyl group indicate that these compounds are composed of essentially one CHT and one NCD tautomer with an endo geometry of the methyl group. The introduction of a t-butyl group at the 1-position of 7-cyano-7-methylcycloheptatriene ($\text{1}$) markedly shifts the equilibrium to the NCD side and the addition of the second t-butyl group further favors the NCD form, with the NCD populations for $\text{2}$, $\text{3}$, $\text{4}$, and $\text{5}$ at 25 °C 70.9, 96.5, 92.3, and 99.3%, respectively. An application of molecular mechanics (MMPI) calculations to various t-butylated CHT-NCD systems suggests that the t-butyl groups sterically destabilize the CHT form more than the NCD form, bringing about increased NCD populations.     

Sequence-specific gene silencing in mammalian cells by alkylating pyrrole-imidazole polyamides

Gene silencing was examined by sequence-specific alkylation of DNA by N-methylpyrrole (Py)-N-methylimidazole (Im) hairpin polyamides. Polyamides ImImPyPygammaImImPyLDu86 (A) and ImImPyPygammaImPyPyLDu86 (B) selectively alkylated the coding regions of the renilla and firefly luciferases, respectively, according to the base pair recognition rule of Py-Im polyamides. Two different plasmids, encoding renilla luciferase and firefly luciferase, were used as vectors to examine the effect of alkylation on gene silencing. Transfection of the alkylated luciferase vectors-by polyamide A or B-into HeLa, 293, and NIH3T3 cells demonstrated that these sequence-specific DNA alkylations lead to selective silencing of gene expression. Next, the vectors were cotransfected into HeLa cells and the cells were treated with polyamide A or B. Selective reduction of luciferase activities was caused by both polyamides. On the basis of this sequence-specific alkylation and gene silencing activity, these alkylating Py-Im polyamides thus have potential as antitumor drugs to target specific gene expression in human cells.