Withanolide derivatives from the roots of Withania somnifera and their neurite outgrowth activities

Five new withanolide derivatives (1, 9-12) were isolated from the roots of Withania somnifera together with fourteen known compounds (2-8, 13-19). On the basis of spectroscopic and physiochemical evidence, compounds 1 and 9-12 were determined to be (20S,22R)-3 alpha,6 alpha-epoxy-4 beta,5 beta,27-trihydroxy-1-oxowitha-24-enolide (1), 27-O-beta-D-glucopyranosylpubesenolide 3-O-beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranoside (withanoside VIII, 9), 27-O-beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranosylpubesenolide 3-O-beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranoside (withanoside IX, 10), 27-O-beta-D-glucopyranosylpubesenolide 3-O-beta-D-glucopyranoside (withanoside X, 11), and (20R,22R)-1 alpha,3 beta,20,27-tetrahydroxywitha-5,24-dienolide 3-O-beta-D-glucopyranoside (withanoside XI, 12). Of the isolated compounds, 1, withanolide A (2), (20S,22R)-4 beta,5 beta,6 alpha,27-tetrahydroxy-1-oxowitha-2,24-dienolide (6), withanoside IV (14), withanoside VI (15) and coagulin Q (16) showed significant neurite outgrowth activity at a concentration of 1 microM on a human neuroblastoma SH-SY5Y cell line.     

Synthesis of poly(phenylacetylene)s containing trifluoromethyl groups for gas permeable membrane

Poly(phenylacetylene)s containing trifluoromethyl groups on their benzene rings were synthesized, and gas permeation behaviors of their films were examined. Permeability coefficients for O₂ and N₂, diffusion selectivity (D_o2/D_N2) and solubility selectivity (SO₂/SN₂) were estimated. The gas permeability of polymer films were found to be enhanced remarkably with introduction of trifluoromethyl groups into the polymers: poly[2,4,5-tris(trifluoromethyl)phenylacetylene], Po₂ = 7.8 × 10^?8 [cm³ (STP) cm cm^?2 s^?1 cm Hg^?1], Po₂/PN₂ = 2.1. The relationship between the polymer structures and their gas permeability was discussed.     

Mechanical properties of oriented polyvinylchloride composites filled with ultrafine particles

The tensile stress-strain behaviour of undrawn and drawn polyvinylchloride (PVC) composites filled with ultrafine SiO₂ and micron sized glass particles were discussed as functions of filler content and size. For the undrawn PVC composites filled with ultrafine SiO₂ particles, Young's moduli, yield and breaking stresses increased with filler content and decreasing filler size. Whereas for the composites filled with micron sized glass particles, their Young's moduli slightly increased with filler content but both the yield and breaking stresses decreased. Oriented PVC composites were made by uniaxially drawing to × 2.5 at 100 °C. Anisotropic mechanical properties of oriented specimens were discussed in terms of compliance tensor and yield stress measured in the direction of 0°, 45° and 90° to the original stretching direction at room temperature. In the case of 70A SiO₂, all the compliance decreased with filler content, whereas those of 65μ glass, this relation was reversed. The yield stress of the oriented PVC composites showed filler size dependence similar to Young's moduli. The anisotropic yield stress of oriented PVC composites were reasonably analysed by Hill's yield criterion.     

Synthesis in the diazasteroid group. V. Synthesis of the 9,14-diazasteroid system

By the condensation reaction of 2-chloroquinoline (X) and ethyl 2-pyrrolidineacetate (II), 2-[1′-(2′-carboethoxymethyl)pyrrolidyl]quinoline (XI) was prepared. Compound XI was converted to the quarternary base (XIII) having a 9,14-diazasteroid skeleton by the reduction of the ester to the corresponding alcohol followed by the quaternarization via tosylation. Compound XIII was reduced with sodium borohydride to 9,14-diazagona-1,3,5(10)-triene (III), which is suggested to have the trans-anti-trans conformation.     

Cytotoxic and apoptosis-inducing ent-kaurane-type diterpenoids from the Japanese liverwort Jungermannia truncata NEES

Five new ent-kaurane-type diterpenoids and a new gymnomitrane (=barbatane)-type sesquiterpenoid have been isolated from the Japanese liverwort Jungermannia truncata NEES, together with twelve previously known ent-kaurane-type diterpenoids. The structures of the new compounds were elucidated by two-dimensional (2D) NMR experiments and chemical reaction. Some of the isolated compounds showed cytotoxicity against human leukemia cell lines and induced apoptosis.     

Kinetic isotope effects on the rate-limiting step of heme oxygenase catalysis indicate concerted proton transfer/heme hydroxylation

Heme oxygenase (HO) catalyzes the O2 and NADPH/cytochrome P450 reductase-dependent conversion of heme to biliverdin, free iron ion, and CO through a process in which the heme participates as both dioxygen-activating prosthetic group and substrate. We earlier confirmed that the first step of HO catalysis is a monooxygenation in which the addition of one electron and two protons to the HO oxy-ferroheme produces ferric-alpha-meso-hydroxyheme (h). Cryoreduction/EPR and ENDOR measurements further showed that hydroperoxo-ferri-HO converts directly to h in a single kinetic step without formation of a Compound I. We here report details of that rate-limiting step. One-electron 77 K cryoreduction of human oxy-HO and annealing at 200 K generates a structurally relaxed hydroperoxo-ferri-HO species, denoted R. We here report the cryoreduction/annealing experiments that directly measure solvent and secondary kinetic isotope effects (KIEs) of the rate-limiting R --> h conversion, using enzyme prepared with meso-deuterated heme and in H2O/D2O buffers to measure the solvent KIE (solv-KIE), and the secondary KIE (sec-KIE) associated with the conversion. This approach is unique in that KIEs measured by monitoring the rate-limiting step are not susceptible to masking by KIEs of other processes, and these results represent the first direct measurement of the KIEs of product formation by a kinetically competent reaction intermediate in any dioxygen-activating heme enzyme.The observation of both solv-KIE(298) = 1.8 and sec-KIE(298) = 0.8 (inverse) indicates that the rate-limiting step for formation of h by HO is a concerted process: proton transfer to the hydroperoxo-ferri-heme through the distal-pocket H-bond network, likely from a carboxyl group acting as a general acid catalyst, occurring in synchrony with bond formation between the terminal hydroperoxo-oxygen atom and the alpha-meso carbon to form a tetrahedral hydroxylated-heme intermediate. Subsequent rearrangement and loss of H2O then generates h.     

Novel quaternary ammonium borates as latent catalysts for epoxy–phenolic resins

Novel tetrabutylammonium tetrakis(substituted benzoyloxy)borate salts ( 1a – 1d ) were synthesized by the reaction of tetrabutylammonium tetraphenylborate and corresponding substituted benzoic acids. Polyaddition reactions of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐bisphenol F (44BPF) or bisphenol F (BPF‐D) with the ammonium borates were investigated as model reactions of epoxy/phenol–novolac resin systems with respect to the thermal latency and storage stability of the catalyst. The polyaddition of DGEBA/44BPF with the ammonium borates in diglyme at 150 °C for 6 h proceeded up to 84–94% conversions and gave polymers with number‐average molecular weights of 3750–5750, whereas the polyaddition at 80 °C for 6 h gave less than 9% conversions. The catalytic activity of ammonium borates 1a – 1d depended on the substituent of the phenyl group of the borates, and the order of activity was 1b (p‐OMe) > 1a (? H) > 1c (p‐NO₂) > 1d [3,5‐(NO₂)₂]. The ammonium borate catalyst with the substituent that yielded lower acidity of the corresponding substituted benzoic acid tended to reveal higher activity. In comparison with tetrabutylammonium bromide (TBAB) as a conventional ammonium salt, 1a – 1d revealed better thermal latency. The storage stability of DGEBA/BPF‐D with the ammonium borate catalysts in bulk at 40 °C was better than that with TBAB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2689–2701, 2002     

Phthalocyanines and related macrocycles for multi-electron transfer in catalysis,photochemistry and photoelectrochemistry

At different phthalocyanines and related macrocycles it is shown that one-step, multi-electron transfer and one-step, multi-change of oxidation states occur. At first, the catalytic oxidations of thiols and sulfide in the presence of different Co(II)phthalocyanines are discussed. Thiolates are oxidized to disulfides via a two-electron transfer whereas the reduction of O₂ occurs via a two- or four-electron transfer to H₂O₂ or H₂O. Zn(II) and Al(III)phthalocyanines are efficient sensitizers for the conversion of triplet to singlet dioxygen under illumination with visible light. In the presence of thiolates or sulfides an efficient photo-oxidation to sulfonic acids or sulfate is observed. The oxidation state of sulfur changes from ?2 to +4 or +6, respectively. This process of singlet oxygen reactions finds application in the photodynamic therapy of cancer. The unsubstituted zinc(II)-phthalocyanine as p-type molecular semiconductor can efficienfly reduce O₂ in photoelectrochemical experiments whereas zinc(II)phthalocyanines with electronwithdrawing groups as n-type conductors are active in the photoelectrochemical oxidation of thiols. All processes include multi-electron transfer. The electrocatalytic reduction of CO₂ is investigated at electrodes modified with Co(II)phthalocyanine. In particular, the phthalocyanine in a polyvinylpyridine membrane is active, so the CO₂ is reduced to CO by multi-electron transfer. In addition, two photon excitations of a Mg(II)phthalocyanine are presented and some examples are reviewed.     

The effect of basis set superposition error on the convergence of intermolecular interaction energies for deprotonated complexes

The intermolecular interaction energies of the deprotonated hydrogen-bonded complexes F(-)(HF), F(-)(H(2)O), F(-)(NH(3)), Cl(-)(HF), SH(-)(HF), H(2)P(-)(HF), OH(-)(H(2)O), OH(-)(H(2)O)(2), OH(-)(NH(3)), Cl(-)(H(2)O), SH(-)(H(2)O), H(2)P(-)(H(2)O), Cl(-)(NH(3)), SH(-)(NH(3)), H(2)P(-)(NH(3)), Cl(-)(HCl), Cl(-)(H(2)S), Cl(-)(PH(3)), SH(-)(H(2)S), SH(-)(PH(3)), and H(2)P(-)(PH(3)) were calculated with correlation consistent basis sets at the MP2, MP4, QCISD(T), and CCSD(T) levels. When the basis set is smaller, the counterpoise-uncorrected intermolecular interaction energies are closer to the complete basis set limit than the counterpoise-corrected intermolecular interaction energies. The counterpoise-uncorrected intermolecular interaction energies obtained at the MP2/aug-cc-pVDZ level of theory are close to the interaction energies obtained at the extrapolated complete basis set limit in most of the complexes. Also, we investigate the accuracy of the other levels.     

Resolution of racemic 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid with enantiopure (S)-phenylalanine N-benzylamide via diastereomeric salt formation

The resolution of racemic 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid 1, a potent chiral synthon with high pharmacological activity, was investigated with a variety of basic chiral resolving agents via diastereomeric salt formation. The findings in the optimization of resolution conditions aiming at an industrial-scale production revealed that (S)-phenylalanine benzylamide (S)-10 and 2-propanol containing ca. 4 mol % of water to (RS)-1 were the best conditions for obtaining enantiopure less-soluble diastereomeric salt, (S)-1/(S)-10/0.5H₂O (81%, 98% de, E 79%). X-ray crystallographic analysis of the salt clearly revealed that water molecules play a key role in crystallizing the enantiopure salt crystals, while stabilizing the crystal structure via three types of hydrogen-bond network associated with water molecules in addition to usual acid–base hydrogen bond.