New antitumor principles, casearins A-F, for Casearia sylvestris Sw. (Flacourtiaceae)

New antitumor clerodane diterpenes, named casearins A-F, have been isolated from the leaves of Casearia sylvestris Sw. (Flacourtiaceae). These structures have been completely elucidated by two dimensional nuclear magnetic resonance, circular dichroism spectroscopy, X-ray analysis, and chemical evidences.     

Preparation of Super-Water-Repellent Fluorinated Inorganic-Organic Coating Films on Nylon 66 by the Sol-Gel Method Using Microphase Separation

We have prepared super-water-repellent fluorinated inorganic-organic coating films on nylon 66 substrate from poly(methyl methacrylate) (PMMA), tetraethoxysilane (TEOS), and 2-perfluorooctylethyltriethoxysilane (17F) by the sol-gel method. The contact angle for water of the film was 149°. The fluorinated inorganic-organic film including PMMA particles exhibits the super-water-repellence on nylon 66 and the high ultrasonics-resistance in spite of the low 17F content of the molar ratio of 0.001 per mol of TEOS. The surfaces of the films were characterized by using XPS and SEM in combination with the surface roughness data. It was considered that the fluorinated component was segregated to form separated microphase regions, appropriate surface roughness being resulted to develop high water-repellence.     

Capillary electrophoresis for simultaneous determination of emodin,chrysophanol, and their 8-beta-D-glucosides

The simultaneous separation and determination of the major anthraquinones, emodin, chrysophanol, and their glucosides, of Rumex japonicus HOUTT., and emodin and emodin glucoside, of Cassia tora L., Rhamnus purshiana DC., Polygonum multiflorum THUNB., and P. cuspidatum SIEB. et ZUCC., were achieved by cyclodextrin modified capillary zone electrophoresis. The running electrolyte used in this method was 0.005 M alpha-cyclodextrin in 0.03 M borate buffer (pH 10.5) containing 10% acetonitrile, with an applied voltage of 20 kV.     

New antimitotic bicyclic peptides, celogentins D-H, and J, from the seeds of Celosia argentea

Six new bicyclic peptides, celogentins D-H (1-5) and J (6) have been isolated from the seeds of Celosia argentea, and the structures including its absolute stereochemistry were determined by using extensive NMR methods and chemical means. Celogentins E-H (2-5) and J (6) showed potent inhibition of tubulin polymerization, while the inhibitory activity of celogentin D (1) was modest. Structure-activity relationship study indicates that ring size of the bicyclic ring system including unusual β^s-Leu, Trp, and His residues would be important for their biological activity.     

Electrochemical quartz crystal microbalance analysis of the cathodic process in a lithium-ion battery

The surface processes at carbon and platinum electrodes have been studied using the electrochemical quartz crystal microbalance technique in organic electrolyte solutions for lithium ion batteries. The changes in resonance frequency were analyzed as a function of the electrode potential, indicating that the process depended not only on the electrode material but also on the cathode potential. In the solution containing LiBF₄ as the electrolyte, the main product at the platinum surface was Li₂CO₃ and LiF, whereas formation of lithium alkylcarbonates was the primary process at the platinum and carbon electrodes in LiPF₆ solution.     

Antiviral agents of plant origin. II. Antiviral activity of scopadulcic acid B derivatives

Scopadulcic acid B derivatives were synthesized and their antiviral activities against herpes simplex virus type 1 (HSV-1) were examined. All the derivatives synthesized showed lower inhibitory activities against HSV-1 than scopadulcic acid B (2). Five compounds, 7, 8, 15, 16, and 18, however, had in vitro therapeutic indexes larger than 7 and were considered to merit further investigation.     

Control in spin-delocalization into the 2-substituted π-systems in 3-oxophenalenoxyl neutral radicals: evaluation by their dimeric structures and DFT calculations

3-Oxophenalenoxyl derivatives, neutral π-radicals having two oxygen atoms at 1,3-position on a phenalenyl skeleton, possess most of their spin densities at the two oxygen atoms and the 2-position, featuring in easy dimerization at the 2-position. For the decrease in spin density at the 2-position by invoking spin-delocalization into the 2-substituted π-systems, we have designed 2-thienyl-3-hydroxyphenalenone derivatives as synthetic precursors of neutral π-radicals, and conducted their oxidation reactions by using a variety of oxidants. The chemical structures of the dimer obtained were unambiguously determined by FABMS, IR, and NMR spectra with help of density functional theory calculations, showing the formation of the bonds on the thienyl moieties. These observations and DFT calculations illustrate the occurrence of a considerable amount of spin-delocalization into the 2-substituted-thienyl moieties from the 3-oxophenalenoxyl skeletons.     

CNDO/2 calculations and configuration analyses for some hydrogen-bonded systems

The potential energy curves of hydrogen-bonded systems were calculated for the water, methanol, and formic acid dimers and for the hydrogen maleate ion by a modified CNDO/2 method, the core resonance integrals between-electrons being distinguished from those between-electrons, the different bonding parameters being used for -O- and =O, and the core potential integralsV _AB ^c for O-H, C=O, and O...O being determined semi-empirically. Consequently, the following results were obtained: 1) a potential energy curve with a single minimum atr(O-H)=0.95 Å and with a concavity near 1.70 Å for the linear chain dimers of water and methanol; 2) a symmetrical potential energy curve with two minima atr(O-H)=0.95 and 1.78 Å for the cyclic dimer of formic acid; 3) a flat-bottomed symmetrical potential energy curve for the hydrogen maleate ion. The configuration analysis method was applied to the hydrogen-bonded systems; the contributions of the covalent ((O-H-O)^–1) and ionic (O^–H⁺O^–) structures being 54% and 39%, respectively, for the symmetrical hydrogen bonding of the hydrogen maleate ion.

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Zusammenfassung Die Kurven potentieller Energie von Systemen mit H-Brücken wurden im Fall von H₂O-, CH₃OH- und HCOOH-Dimeren und für das Hydrogen-Maleatanion mittels eines modifizierten CNDO-Verfahrens berechnet, wo für Rumpf-- und --Elektronen jeweils verschiedene Resonanzintegrale und verschiedene Bindungsparameter für =O und -O- verwendet und wo die Rumpfpotential-Integrale für O-H, C=O und O...O semiempirisch bestimmt werden.Die Resultate sind 1) eine Potentialkurve mit einem einfachen Minimum für lineare Ketten von H₂O und CH₃OH, 2) eine symmetrische Potentialkurve mit zwei Minima für das cyclische Diniere von HCOOH und 3) eine Potentialkurve mit einem flachen Minimum für das Maleatanion. Konfigurationsanalyse ergab einen Beitrag von 39% für die ionischen Strukturen.

     

Molecular rectification of a helical peptide with a redox group in the metal-molecule-metal junction

A helical hexadecapeptide immobilized on gold via a thiophenyl group at the N-terminal was analyzed by scanning tunneling microscopy under ultrahigh vacuum to obtain the I-V response at a molecular level. The attenuation factor of the electron transfer through the hexadecapeptide was determined by applying the Simons model to the I-V response to show better molecular conductance of the hexadecapeptide than dodecanethiol. Chemical modification at the C-terminal of the hexadecapeptide with a ferrocene unit, on the other hand, brought about significant changes in the I-V response, where the helical peptide became more conductive at the negative bias voltage. The molecular rectification behavior is due to the ferrocene unit regulating the direction of the electron transfer at the metal-molecule junction.     

Synthesis and redox behavior of azulene-substituted benzene derivatives and (eta(5)-cyclopentadienyl)[tetra- and di(6-azulenyl)cyclobutadiene]cobalt complexes

1,2-Di(6-azulenyl)tetraphenylbenzenes and (6-azulenyl)pentaphenylbenzenes were synthesized by Diels-Alder reactions of di(6-azulenyl)acetylenes and 6-(phenylethynyl)azulenes with tetraphenylcyclopentadienone. Cobalt-mediated cyclooligomerization of mono- and di(6-azulenyl)acetylenes afforded 1,3,5- and 1,2,4-tri(6-azulenyl)benzene derivatives together with (eta(5)-cyclopentadienyl)[tetra- and di(6-azulenyl)cyclobutadiene]cobalt complexes. The redox behavior of these novel (6-azulenyl)benzene derivatives and [tetra- and di(6-azulenyl)cyclobutadiene]cobalt complexes was examined by cyclic voltammetry (CV). Mono(6-azulenyl)benzenes exhibited a reduction wave upon CV. In contrast, 1,2-di(6-azulenyl)benzenes showed a two-step reduction wave at the similar potential region upon CV, which revealed the formation of a dianion stabilized by 6-azulenyl substituents under electrochemical reduction conditions. Three 6-azulenyl substituents on benzene in a 1,2,4 relationship also increased electron-accepting properties because of the formation of a closed-shell dianionic structure, whereas 1,3,5-tri(6-azulenyl)benzenes were reduced stepwise.