Determination of acidic saponins in crude drugs by high- performance liquid chromatography on octadecylsilyl porous glass

High-performance liquid chromatographic (HPLC) analysis on octadecylsilyl porous glass was investigated for acidic saponins in ginseng, bupleurum root and senega. The acidic saponins, malonyl-ginsenosides, malonyl-saikosaponins and senegins, as well as neutral saponins in the crude drugs were separated rapidly by HPLC on this column with aqueous acetonitrile containing KH₂ PO₄ as the mobile phase at room temperature.     

Formation of η′(958) Meson Bound States and Chiral Symmetry In-Medium

We theoretically discuss the feasibility to observe the η′(958)-mesic nuclei by using the missing mass spectroscopy. We evaluate the η′-nucleus optical potential including the contribution of lowest order in density together with the second order terms account for η′ absorption by two nucleons, based on a recent model of the η′N interaction. We show the calculated formation cross section of the η′ bound states from (π, N) reaction with pion beam momentum p _π = 1.8 GeV/c and (p, d) reaction with proton kinetic energy T _p = 2.5 GeV.     

Solid-state photochemistry of the mixed crystals between benzoquinones and polymethylbenzenes

Nine mixed crystals combined 1,4-benzoquinone (1), 2,5-xyloquinone (2) and duroquinone (3) with durene (a), pentamethylbenzene (b) and hexamethylbezene (c) were prepared by a melting-resolidifying process and characterized by powder X-ray diffractometry, DSC and IR. Only the mixed crystal of 3 and a formed a 2:1 novel molecular crystal (4); other eight mixed crystals were simple polycrystalline mixtures of the two components. Irradiation of the molecular crystal 4 (3/a) and the mixed crystals 1/a, 1/b and 3/b caused intermolecular hydrogen abstraction to give hydroquinones and in some cases adducts. Product selectivities in the solid state were different from those in solution. Correlation between the crystal structure and the reactivity of 4 is discussed.     

Reaction of 2,5-diisopropyl- and 2,5-di-sec-butylpyrazine 1-oxide. Derivatives with phosphoryl chloride and acetic anhydride

In order to examine the α-substitution of side chains, various derivatives of 2,5-diisopropyl- and 2,5-disec-butylpyrazine 1-oxides were subjected to the reaction with phosphoryl chloride and acetic anhydride. Chlorination and acetoxylation were recognized to take place on the pyrazine ring in almost all cases.     

Enantiomorphism in the super helices of poly-γ-benzyl-glutamate

Summary Aggregates of poly--benzyl-d (orl-glutamate were precipitated by mixing of its solution in dimethylformamide or dioxane with propionic acid. Electron micrographs showed that the aggregates were composed of well-developed helical fibrils. The sence of helix was right-handed for thed-isomer and left-handed for thel-isomer; an enantiomorphic relation was shown for the helical aggregate of optical active macromolecule. Two recent publications have given conflicting results for the helical sense of the aggregate. This seems to be ascribed to carelessness in determining the helical sense from the electron micrographs.

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Zusammenfassung Es wurden Aggregate von Poly--benzyl-d (oderl)-glutamat durch Mischung von deren Lösung in Dimethylformamid oder Dioxan mit Propionsäure ausgefällt. Die elektronenmikroskopischen Bilder zeigen, daß die Aggregate aus gut ausgebildeten Helixfibrillen bestehen. Der Drehsinn der Helix war rechtsläufig für dasd-Isomer und linksläufig für dasl-Isomer. Eine enantiomorphe Beziehung läßt sich für die Helix-Aggregate zu den optisch aktiven Strukturen der Makromoleküle zeigen. Zwei kürzliche Veröffentlichungen ergaben zu dem hier Festgestellten widersprüchliche Ergebnisse über den Schraubensinn der Helices der aggregate. Dies scheint der Sorglosigkeit bei der Bestimmung des Schraubensinns von elektronenmikroskopischen Bildern zuzuschreiben zu sein.

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With 1 figure in 3 details     

Absolute asymmetric photocyclization of isopropylbenzophenone derivatives using a cocrystal approach involving single-crystal-to-single-crystal transformation

Absolute asymmetric photocyclization of isopropylbenzophenone derivatives was achieved by means of a cocrystal approach. Three chiral salt crystals formed by carboxylic acid derivatives with achiral amines could be prepared by spontaneous crystallization. In the M-crystal of 4-(2,5-diisopropylbenzoyl)benzoic acid with 2,4-dichlorobenzylamine, a twofold helical arrangement occurs in a counterclockwise direction to generate the crystal chirality. Conversely, the clockwise helix exists alone in the P-crystal. Irradiation of the M-crystal at >290 nm caused highly enantioselective Norrish type II cyclization to give the (R,R)-cyclopentenol, (R)-cyclobutenol, and (R)-hydrol in a 6:3:1 molar ratio, resulting in successful absolute asymmetric synthesis, while irradiation at around 350 nm afforded the (R,R)-cyclopentenol as the sole product. The reaction proceeded via single-crystal-to-single-crystal transformation, and therefore the reaction path producing the (R,R)-cyclopentenol could be traced by X-ray crystallographic analysis before and after irradiation.     

The first isolation of allenylselenonium salts: their synthesis and properties as electrophiles

The first synthesis of allenylselenonium salts and their reactivities are described. The corresponding allenyl methyl selenides were alkylated with methyl trifluoromethanesulfonate to afford the desired compounds. Their reactions with active methylene carbanions produced furan, dihydrofuran or methylene cyclopropane derivatives via the Michael addition of nucleophiles to the selenonium salts.     

Aqueous chromatographic system for separation of biomolecules using thermoresponsive polymer modified stationary phase

We have investigated a new method for HPLC using packing materials modified with a functional polymer, such as thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm). PNIPAAm-modified silica exhibits temperature-controlled hydrophilic-hydrophobic surface property changes in aqueous systems. Temperature-responsive chromatography is performed with an aqueous mobile phase without using an organic solvent. We designed ternary copolymers of NIPAAm introduced 2-(dimethyl-amino) ethyl methacrylate (DMAEMA) as a cationic monomer and butyl methacrylate (BMA) as a hydrophobic monomer. A cationic thermoresponsive hydrogel grafted surface would produce an alterable stationary phase with both thermally regulated hydrophobicity and charge density for separation of bioactive compounds. In this study, we achieved successful separation of lysozyme without the loss of bioactivity by temperature-responsive chromatography. The electrostatic and hydrophobic interactions could be modulated simultaneously with the temperature in an aqueous mobile phase, thus the separation system would have potential applications in the separation of biomolecules.