New approach to C-aryl glycosides starting from phenol and glycosyl fluoride. Lewis acid-catalyzed rearrangement of O-glycoside to C-glycoside

C-Glycosidation of phenols is achieved by treatment of glycosyl fluoride with phenolic compound under Lewis acidic conditions, which leads to initial O-glycoside formation followed by rearrangement to C-congener. Cp₂HfCl₂-AgClO₄ is particularly effective for this conversion.     

Inclusion effect and structural basis of cyclodextrins for increased extraction of medicinal alkaloids from natural medicines

The enhancing effects of alpha-, beta-, and gamma-cyclodextrins (CyDs) on the aqueous extraction of ephedrine and berberine from the natural medicines were investigated in HPLC analysis, and the greatest effect was observed for beta- and gamma-CyDs. To clarify the structural basis of such an increased extraction effect with beta-CyD, possible interaction modes of (1R,2S)-ephedrine with alpha-, beta-, and gamma-CyDs were investigated using molecular dynamic simulations in an aqueous solution system. It was shown that the wrapping model of ephedrine by beta-CyD is the most compact and thus increases the solubility most effectively, compared with those by other CyDs. The same mode could be possible for the greatest effect of gamma-CyD on the extraction of berberine from natural medicines. This clearly shows that CyDs are useful additives for the effective extraction of bioactive alkaloids from natural medicines.     

Existence of clathrate-like structures in supercooled water: X-ray diffraction evidence

X-ray diffraction study of supercooled water has been performed using an imaging-plate X-ray detector down to −15 °C. The peak at 10.8 Å, which grows with decreasing temperature, in the radial distribution function {D(r) − 4πr²ρ₀} indicates the existence of clathrate-like structures in supercooled water. It is suggested that anomalous properties of water, which become more pronounced at low temperatures, are closely linked to the development of clathrate-like structures in water at low temperatures.     

Mixing effect of filler and polymer by an elastic melt extruder

Summary In order to examine the mixing effect of fillers and polymers by the elastic melt extruder, an apparatus was constructed and extrusions of glass beads/polyethylene and calcium carbonate/polyethylene were carried out. To ensure the stable operation a submechanism was connected in series to the main shearing zone of the apparatus. The content of filler in the extrudate was determined at stated time interval. The variation of filler content with time was represented by simple equations derived from the assumption that the material newly fed was mixed instantaneously with the material in the shearing zone. It was also found that the distribution of filler in the extrudate was satisfactory.

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Zusammenfassung Zur Untersuchung der Mischwirkung des Maxwell-Extruders (elastic melt extruder) bei Polymeren mit Füllstoff wurde ein solches Gerät konstruiert und damit die Extrusion von Polyäthylen mit Glaskugeln bzw. Kalziumkarbonat untersucht. Zur Gewährleistung einer stabilen Arbeitsweise wurde der Hauptscherzone des Geräts eine Hilfseinrichtung nachgeschaltet. Der Füllstoffgehalt im Extrudat wurde in regelmäßigen Zeitabständen bestimmt. Die Variation des Füllstoffgehalts mit der Zeit ließ sich durch einfache Gleichungen beschreiben, die aufgrund der Annahme abgeleitet worden waren, daß das eingegebene Material mit dem Material in der Scherzone momentan zur Durchmischung kommt. Es wurde eine zufriedenstellende Gleichmäßigkeit der Füllstoffverteilung im Extrudat gefunden.

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With 3 figures and 1 table     

Gelation Rate Modulation of an α‐Cyclodextrin and Poly(ethylene glycol)‐Grafted Hyaluronic Acid Solution System by Inclusion Complexation of a Microphase‐Separated Structure

Summary: The gelation rate of a poly(ethylene glycol)‐grafted hyaluronic acid (PEG‐graft‐HA) solution with adding α‐CD was investigated in term of the microphase separation between the grafted PEG and HA. The gelation rate of PEG‐graft‐HA exhibiting the microphase‐separated structure was two times higher than that of PEG‐graft‐HA showing a homogeneous miscible state.

The formation of microphases by PEG‐graft‐HA contributes to its rapid gelation upon the addition of α‐CDs.     

Electronic structure of highly ruffled low-spin iron(III) porphyrinates with electron withdrawing heptafluoropropyl groups at the meso positions

Bis(pyridine)[meso-tetrakis(heptafluoropropyl)porphyrinato]iron(III), [Fe(THFPrP)Py(2)](+), was reported to be the low-spin complex that adopts the purest (d(xz), d(yz))(4)(d(xy))(1) ground state where the energy gap between the iron d(xy) and d(π)(d(xz), d(yz)) orbitals is larger than the corresponding energy gaps of any other complexes reported previously (Moore, K. T.; Fletcher, J. T.; Therien, M. J. J. Am. Chem. Soc. 1999, 121, 5196-5209). Although the highly ruffled porphyrin core expected for this complex contributes to the stabilization of the (d(xz), d(yz))(4)(d(xy))(1) ground state, the strongly electron withdrawing C(3)F(7) groups at the meso positions should stabilize the (d(xy))(2)(d(xz), d(yz))(3) ground state. Thus, we have reexamined the electronic structure of [Fe(THFPrP)Py(2)](+) by means of (1)H NMR, (19)F NMR, and electron paramagnetic resonance (EPR) spectroscopy. The CD(2)Cl(2) solution of [Fe(THFPrP)Py(2)](+) shows the pyrrole-H signal at -10.25 ppm (298 K) in (1)H NMR, the CF(2)(α) signal at -74.6 ppm (298 K) in (19)F NMR, and the large g(max) type signal at g = 3.16 (4.2 K) in the EPR. Thus, contrary to the previous report, the complex is unambiguously shown to adopt the (d(xy))(2)(d(xz), d(yz))(3) ground state. Comparison of the spectroscopic data of a series of [Fe(THFPrP)L(2)](+) with those of the corresponding meso-tetrapropylporphyrin complexes [Fe(TPrP)L(2)](+) with various axial ligands (L) has shown that the meso-C(3)F(7) groups stabilize the (d(xy))(2)(d(xz), d(yz))(3) ground state. Therefore, it is clear that the less common (d(xz), d(yz))(4)(d(xy))(1) ground state can be stabilized by the three major factors: (i) axial ligand with low-lying π* orbitals, (ii) ruffled porphyrin ring, and (iii) electron donating substituent at the meso position.     

Molecular diffusivity of sample solutes in a number of eluents and the implications with regard to the design of capillary chromatographic systems

The properties of sample solutes and eluents injected into capillary tubes were studied in order to develop improved chromatographic instrumentation technology. Use of a new apparatus to determine molecular diffusion coefficients (D) of solutes in both aqueous and organic eluents under laminar flow conditions provided results more rapidly than older methods. The experimental results obtained were in agreement with theoretical predictions and will be useful in the design of chromatographic systems.     

The Solid-State and Solution Conformations of (+)-Chelidonine

The solid-state and solution conformations of (+)-chelidonine ( 1 ), a biologically active alkaloid, were determined by X-ray diffraction and ¹H-NMR spectroscopy, X-Ray diffraction analysis revealed a conformer with B/C ‘anti-type’ cis conjunction, a half-chair of ring B , and a twist half-chair of ring C. One H₂O molecule per one alkaloid molecule was cocrystallized and stabilized by H-bonding with OH? C(11). Analysis of the thermal behavior of the crystal showed more thermal stability in the monohydrate than the anhydrate. The NMR measurement of concentration and temperature dependences in CDCl₃ and in (CD₃)₂SO suggested that the OH group of 1 was intramolecularly H -bonded to N(5) in (CD₃)₂SO and intermolecularly H-bonded to the solvent in CDCl₃. Conformational-energy calculations by the MNDO method showed that the intramolecular H -bond was little affected by the conformational stabilization of 1 .     

Phase-resolved correlation and its application to analysis of low-coherence interferograms

A new signal-processing technique is proposed that involves a phase-resolved correlation method that one can use to determine the phase distribution of low-coherence interferograms. This method improves the sensitivity and resolution of low-coherence interferometers. The depth structure of an aluminum oxide-coated aluminum mirror was determined by use of a low-coherence interferometer with this method. Three signal peaks were successfully extracted from a noisy interferogram.     

Biosynthesis of Benzo[c]phenanthridine Alkaloids Sanguinarine,Chelirubine and Macarpine

The biosynthesis of the benzo[c]phenanthridine alkaloids was investigated in a cell suspension culture of Macleaya cordata (papaveraceae). Feeding experiments define the biosynthetic pathway (–)-7,8,13,13a-tetrahydrocoptisine →(–)-cis-N-methyl-7,8,13,13a-tetrahydrocoptisinium salt 15 → protopine (5) → sanguinarine (1) → chelirubine (3) → macarpine (4) .