Transition-metal (Ti,V,Cr,Mn,Fe,Co,Cu) containing ordered nanoporous materials: novel heterogeneous catalysts for selective oxidation reactions

Transition-metal (Ti,V,Cr,Mn,Fe,Co,Cu) containing periodic nanoporous catalysts, were synthesized hydrothermally and characterized using various analytical and spectroscopic techniques. The catalytic performance of the different catalysts was systematically evaluated with a detailed study on TiMCM-41. All the catalysts showed promise for the selective oxidation of cycloalkanes, viz., cyclohexane, cyclooctane, and cyclododecane, under mild reaction conditions. Furthermore, these mesoporous molecular sieves were also active for all the chosen reactions even after several recycling and/or washing treatments. Among the various materials under investigation, the catalysts TiMCM-41 and VMCM-41 showed much higher substrate conversion and excellent product selectivity in conjunction with a minimal leaching of the active species. More importantly, the influence of pore size on the catalytic activity of the bulkier substrates such as cyclooctane and cyclododecane is demonstrated.

(–)Schisandrin B is more potent than its enantiomer in enhancing cellular glutathione and heat shock protein production as well as protecting against oxidant injury in H9c2 cardiomyocytes

Effects of schisandrin B enantiomers ((+)Sch B and (-)Sch B) treatment on cellular reduced glutathione (GSH) level and heat shock protein (Hsp)25/70 production were investigated in H9c2 cardiomyocytes. (+)Sch B and (-)Sch B at 6.25 muM produced a time-dependent and biphasic change in cellular GSH level and Hsp25/70 production, with the stimulatory effect of (-)Sch B being more potent. The GSH- and Hsp-enhancing effects were accompanied by a parallel cytoprotection against xanthine oxidase/xanthine-induced toxicity, with the biphasic time course of (+)Sch B- or (-)Sch B-induced protection being superimposed with that of the increase in GSH level but not Hsp25/70 production. The results indicate that (-)Sch B produces more potent enhancing effects on cellular GSH and Hsp production as well as protection against oxidative injury than (+)Sch B in cardiomyocytes.

Cyclooctadiene Ru(II) complexes of thiophene-2-carboxaldehyde-derived thiosemicarbazones: synthesis, characterization and antiamoebic activity

Thiosemicarbazones (TSC) 1-10 were synthesized by condensing substituted thiosemicarbazide with thiophene-2-carboxaldehyde. These thiosemicarbazones were further reacted with [Ru(eta4-C8H12)(CH3CN)2Cl2] to form complexes of the type [Ru(eta4-C8H12)(TSC)Cl2] 1a-10a. Thiosemicarbazones exhibited antiamoebic activity in the range IC50=1.09-5.42 microM. In vitro assessment of antiamoebic activity indicated that the thiosemicarbazones 3, IC50=1.67 microM, 4, IC50=1.11 microM and 6, IC50=1.09 microM showed substantially less IC50 value than metronidazole (IC50=1.87 microM), a commonly used drug against amoebiasis. Cyclooctadiene Ru(II) complexes of thiosemicarbazones showed significant improvement in antiamoebic activity (IC50=0.30-1.39 microM). All the complexes possess noteworthy potencies and showed less IC50 values than metronidazole against HK-9 strain of Entamoeba histolytica. Among all the complexes, the most promising antiamoebic activities was shown by the complexes 4a and 6a (IC50=0.31 microM of 4a and IC50=0.30 microM of 6a versus metronidazole).

Schisandrin B: a dual inhibitor of P-glycoprotein and multidrug resistance-associated protein 1

We recently reported that schisandrin B (Sch B) was a novel P-glycoprotein (P-gp) inhibitor. In this study, we revealed that Sch B was also an effective inhibitor of multidrug resistance-associated protein 1 (MRP1). The activities of Sch B to reverse MRP1-mediated drug resistance was tested using HL60/ADR and HL60/MRP, the human promyelocytic leukemia cell lines with the overexpression of MRP1 but not P-gp. Sch B resumed daunorubicin and carboxyfluorescein diacetate (CFDA, a specific substrate for MRP1) accumulation and retention in HL60/ADR cells in a time and concentration dependent manner. At the equimolar concentration, Sch B demonstrated significantly stronger potency than probenecid, a MRP1 inhibitor. This study, together with the previous findings, demonstrated that Sch B was a dual inhibitor of P-gp and MRP1, a type suggested to be preferable to the use of combination of two specific modulators to prevent drug-drug interaction and cumulative toxicities.

Schisandrene, a dibenzocyclooctadiene lignan from Schisandra chinensis: structure-antioxidant activity relationships of dibenzocyclooctadiene lignans

Phytochemical investigation of the fruits of Schisandra chinensis led to the isolation of 13 lignans including schisandrene (13), a new lignan based on a dibenzocyclooctadiene backbone with an exocyclic double bond. Its structure and absolute configuration were established using NMR, MS, and CD data. Antioxidant activity of the lignans was evaluated using a DCFH-DA cellular-based assay. The structure-activity relationships of the dibenzocyclooctadiene lignans showed that the exocyclic methylene functionality was essential for antioxidant activity, with the benzoyloxy group probably enhancing such effects.

From Common Carbohydrates to Enantiopure Cyclooctane Polyols and Glycomimetics via Deoxygenative Zirconocene Ring Contraction

D-Arabinose and D-glucose are transformed into the identical vinyl furanoside, whose role is to serve as the precursor to enantiopure cyclooctadienone 6. The key steps of this relay involve a zirconocene-promoted ring contraction and [3,3] sigmatropic rearrangement of an enynol. Subsequently defined are convenient synthetic routes to several cyclooctane-1,2,3-triols, 1,2,3,4,5-pentaols, and structurally related glycomimetics.

A New Triterpene and Dibenzocyclooctadiene Lignans from Schisandra propinqua (WALL.) BAILL

A new triterpene and two new natural dibenzocyclooctadiene lignans were isolated from the stems of Schisandra propinqua. In addition, three known lignans, octadecanoic acid, 2,3-dihydroxypropyl ester and beta-sitosterol were isolated. The structures of the new triterpene and new natural products were elucidated base on spectral analysis, including 1D and 2D NMR experiments. The isolates were tested for their cytotoxic effects against several tumor cell lines by MTT assay.

General Strategy for Stereoselective Synthesis of 1-Substituted Exo,Endo-2,6-Diaryl-3,7-dioxabicyclo[3.3.0]octanes: Total Synthesis of (±)-Gmelinol

[reaction: see text] A general strategy for stereoselective synthesis of 1-substituted exo,endo-2,6-diaryl-3,7-dioxabicyclo[3.3.0]octanes including (+/-)-gmelinol from (2,3-trans)-(4,5-cis)-alpha-aroylparaconic esters, which are readily obtained from the reaction of vicinal dianions derived from alpha-aroylsuccinic esters with aromatic aldehydes, is described. The synthetic sequence involves alpha-methylation or alpha-hydroxylation, reduction, bislactonization, and reduction followed by furofuran formation.

Asymmetric Total Synthesis of Dibenzocyclooctadiene Lignan Natural Products

[structure: see text] Full details of the asymmetric total syntheses of the dibenzocyclooctadiene lignans interiotherin A, angeloylgomisin R, gomisin O, and gomisin E (epigomisin O) are presented. The syntheses were based on a unified synthetic strategy involving a novel crotylation using the Leighton auxiliary that occurred with excellent asymmetric induction (>98:2 enantiomeric ratio), a diastereoselective hydroboration/Suzuki-Miyaura coupling reaction sequence, and an atropdiastereoselective biarylcuprate coupling, both of which occurred with total (>20:1) stereocontrol. The syntheses were achieved in six to eight steps from simple aromatic precursors.

Studies towards the total synthesis of di- and sesterterpenes with dicyclopenta[a,d]cyclooctane skeletons. Three-component approach to the A/B rings building block

Sesqui- and sesterterpenes of ophiobolin and fusicoccin families are important synthetic targets because of complexity of structure and potentially useful physiological activities, including anti-tumor activity. A synthesis of versatile building blocks for these terpenoids is described. Cyclopenta[8]annulene rings system with properly dislocated substituents was constructed using as key steps ring closing metathesis reaction and Wagner - Meerwein rearrangement. Ring closing metathesis reaction leading to cyclopenta[8]annulene was studied in detail.

Schisandrin B—A novel inhibitor of P-glycoprotein

P-glycoprotein-mediated drug efflux is one of the major causes of the cancer multidrug resistance (MDR). Inhibition of P-glycoprotein could reverse cancer MDR. Here, we show that schisandrin B, a naturally occurring compound from Schisandra chinensis (Turcz.) Baill, bears strong potency to inhibit P-glycoprotein. Schisandrin B reversed the drug resistance of four MDR cell lines characterized with overexpression of P-glycoprotein and fully restored the intracellular drug accumulation by interacting with P-glycoprotein. Schisandrin B has a core structure of dibenzocyclooctadiene, representing a novel P-glycoprotein inhibitor. To our best knowledge, the role of schisandrin B to inhibit P-glycoprotein has not been reported.

Structural determinants of schisandrin B which enhance mitochondrial functional ability and glutathione status as well as heat shock protein expression in rat hearts and H9c2 cells

Using an ex vivo model of isolated-perfused rat hearts and cultured H9c2 cells, the structure-activity relationships of schisandrin B (Sch B), and analogs lacking either the methylendioxy group or cyclooctadiene ring, schisandrin A (Sch A) and dimethyl diphenyl bicarboxylate (DDB), respectively, were investigated. Pretreatment with Sch B, but not with Sch A or DDB, protected against myocardial ischemia-reperfusion (I-R) injury in rats. Although Sch B pretreatment largely prevented H9c2 cells from menadione-induced cytotoxicity, Sch A pretreatment produced only a marginal protection. However, DDB pretreatment did not cause any detectable effect. The myocardial and cellular protection afforded by Sch B pretreatment correlated with increases in mitochondrial ATP generation capacity and/or reduced glutathione level as well as heat shock protein (Hsp)25/70 expression, under both control and oxidative stress conditions. The results indicate that the methylenedioxy group and the cyclooctadiene ring are important structural determinants of Sch B in enhancing mitochondrial functional ability and glutathione status, as well as tissue Hsp 25/70 expression, thereby protecting the myocardium against I-R injury.

Antihepatitis activity (anti-HBsAg and anti-HBeAg) of C19 homolignans and six novel C18 dibenzocyclooctadiene lignans from Kadsura japonica

Bioassay-directed fractionation of the EtOAc extract of Kadsura japonica has led to the isolation of six new C18 dibenzocyclooctadiene lignans, schizanrins I, J, K, L, M, N, along with four known C19 homolignans, taiwanschirins A, B, C, and heteroclitin F. The elucidations of the new structures were based on spectral analysis. Bioassay evaluation against human type B hepatitis revealed that taiwanschirins A and B showed strong activity for anti-HBsAg and a medium effect for anti-HBeAg at 25 microg/mL (12.9 and 11.9 microM for taiwanschirins A and B, respectively).

Photoinduced Plasticity in Cross-Linked Polymers

Chemically cross-linked polymers are inherently limited by stresses that are introduced by post-gelation volume changes during polymerization. It is also difficult to change a cross-linked polymer's shape without a corresponding loss of material properties or substantial stress development. We demonstrate a cross-linked polymer that, upon exposure to light, exhibits stress and/or strain relaxation without any concomitant change in material properties. This result is achieved by introducing radicals via photocleavage of residual photoinitiator in the polymer matrix, which then diffuse via addition-fragmentation chain transfer of midchain functional groups. These processes lead to photoinduced plasticity, actuation, and equilibrium shape changes without residual stress. Such polymeric materials are critical to the development of microdevices, biomaterials, and polymeric coatings.

Dibenzo[a,c]cyclooctadiene lignans of the genus Schisandra: importance, isolation and determination

The drug Wuweizi (dried fruits of Schisandra chinensis or S. sphenantherd) is one of important medicinal means used in the Oriental medicine. The lignans of dibenzo[a,c]cyklooctadiene type are major constituents, a volatile oil with mono- and ses-quiterpens, an oil, organic acids and small amounts of additional compounds are also present. The content of major lignans (schizandrin, deoxyschizandrin, gomisin A, gomisin N, gamma-schizandrin, wuweizisu C) in commercially available drugs ranges usually between 3 and 5%. The present paper biefly comments the isolation and biological activity of the lignans and is especially concerned with analytical methods (TLC and HPLC) for the determination of the drug fingerprint and methods for the determination of constituents in drugs, mixtures and biological materials. HPLC methods using RP-silica bonded phases and diluted methanol, acetonitrile (or a mixture of both), are most important for these purposes. Electromigration methods are less suitable and the importance of hyphenation procedures is practically negligible.

Exploratory studies aimed at a synthesis of vinigrol. 2. Attempts to exploit ring-closing metathesis for construction of the central cyclooctane belt

A program directed to the possible adaptation of ring closing metathesis to a total synthesis of vinigrol is described. With a convenient route to intermediates of general type 3 available from a prior investigation, several candidate substrates were prepared. These included the epoxy dienes 10 and 22, the diacetoxy triene 42, and the heavily functionalized cyclohexane 48. The central issue of this approach was to convey a maximum degree of conformational flexibility to these functionalized intermediates, such that the olefinic termini of the side chains could enter into intramolecular carbon-carbon bond formation. In no example was ring closure observed to operate. Instead, the strategically placed pi-bonds were seen to migrate internally to the chain in select examples. Although the pivotal transformations failed, the deployment of a number of useful stereo-controlled reactions has ultimately resulted in the preparation of heavily substituted cis-decalins.

GABA receptor antagonists and insecticides: common structural features of 4-alkyl-1-phenylpyrazoles and 4-alkyl-1-phenyltrioxabicyclooctanes

Fipronil [5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulfinylpyrazole] is one of the most important insecticides. Structure-activity studies described here reveal that fipronil retains its very high binding potency at the human beta3 and house fly gamma-aminobutyric acid (GABA) receptors and toxicity to house flies on replacing the pyrazole trifluoromethylsulfinyl moiety with tert-butyl or isopropyl and the phenyl trifluoromethyl substituent with ethynyl, trifluoromethoxy, bromo or chloro. Among the compounds studied, those with other alkyl groups at the 4-position of the pyrazole, as well as phenyl substitution without one or both of the 2,6-dichloro groups, are less effective. 5-Amino-4-tert-butyl-3-cyano-1-(2,6-dichloro-4-ethynylphenyl)pyrazole is highly effective and almost isosteric with 4-tert-butyl-3-cyano-1-(4-ethynylphenyl)-2,6,7-trioxabicyclo[2.2.2]octane (the most potent 4-alkyl-1-phenyltrioxabicyclooctane) as a noncompetitive GABA antagonist and insecticide. These findings are interpreted as three binding subsites in the GABA receptor: a hydrophobic site undergoing steric interaction with the tert-butyl or equivalent group; a hydrogen bonding site to pyrazole N-2; a pi bonding site to the face of the phenyl moiety; with supplemental enhancement by the 3-cyano and 4-ethynyl substituents.

A strain-promoted [3 + 2] azide-alkyne cycloaddition for covalent modification of biomolecules in living systems

Selective chemical reactions that are orthogonal to the diverse functionality of biological systems have become important tools in the field of chemical biology. Two notable examples are the Staudinger ligation of azides and phosphines and the Cu(I)-catalyzed [3 + 2] cycloaddition of azides and alkynes ("click chemistry"). The Staudinger ligation has sufficient biocompatibility for performance in living animals but suffers from phosphine oxidation and synthetic challenges. Click chemistry obviates the requirement of phosphines, but the Cu(I) catalyst is toxic to cells, thereby precluding in vivo applications. Here we present a strain-promoted [3 + 2] cycloaddition between cyclooctynes and azides that proceeds under physiological conditions without the need for a catalyst. The utility of the reaction was demonstrated by selective modification of biomolecules in vitro and on living cells, with no apparent toxicity.

Intramolecular [2 + 2] Photocycloaddition/Thermal Fragmentation: Formally “Allowed” and “Forbidden” Pathways toward 5−8−5 Ring Systems

The thermal fragmentation of highly functionalized, linear polycyclobutanes with a cis,syn,cis-relative stereochemistry is shown to offer a rapid entry into the dicyclopenta[a,d]cyclooctenyl (5-8-5) ring system. The thermolysis of polyfused cyclobutanes with a cis,syn,cis- or a cis,anti,cis-relationship proceeds in a formally "symmetry-allowed" manner through the intermediacy of a cis,trans-cyclooctadiene. When a bridging tether used to establish the cis,syn,cis-stereochemistry in the intramolecular [2 + 2] photocyclization is present in the thermolysis step, however, the result of a formally "symmetry-forbidden" fragmentation is observed yielding cis,cis-cyclooctadiene-containing 5-8-5 products. In general, the stereochemical observations noted in these fragmentations offer new opportunities for accessing a variety of stereochemical relationships in these 5-8-5 ring systems.

Down-modulation of heat shock protein 70 and up-modulation of Caspase-3 during schisandrin B-induced apoptosis in human hepatoma SMMC-7721 cells

AIM: To investigate the effect of schisandrin B (Sch B) on proliferation and apoptosis of human hepatoma SMMC-7721 cells in vitro and regulation of Hsp70 and Caspases-3, 7, 9 expression by Sch B.

METHODS: Human hepatoma cell line SMMC-7721 was cultured and treated with Sch B at various concentrations. Growth suppression was detected with MTT colorimetric assay. Cell apoptosis was confirmed by DNA ladder detection and flow cytometric analysis. The expression of Hsp70, Caspases-3, 7, 9 were analyzed by Western blot analysis.

RESULTS: Sch B inhibited the growth of hepatoma SMMC-7721 cells in a dose-dependent manner, leading to a 50% decrease in cell number (LC50) value of 23.50 mg/L. Treatment with Sch B resulted in degradation of chromosomal DNA into small internucleosomal fragments, evidenced by the formation of a 180-200 bp DNA ladder on agarose gels. FCM analysis showed the peak areas of subdiploid at the increased concentration of Sch B. The results of Western bolt analysis showed that Hsp70 was down-regulated and Caspase-3 was up-regulated, while the activity of Caspases-7, -9 had no significant change.

CONCLUSION: Sch B is able to inhibit the proliferation of human hepatoma SMMC-7721 cells and induce apoptosis, which goes through Caspase-3-dependent and Caspase-9-independent pathway accompanied with the down-regulation of Hsp70 protein expression at an early event.

Ring synthesis by stereoselective, methylene-free enyne cross metathesis

Tandem enyne metathesis between 1-alkynes and 1,5-cyclooctadiene or all-cis-1,4-polybutadiene resulted in a direct, one-step ring synthesis of cyclohexadienes by methylene-free metathesis. The use of methylene-free metathesis conditions provided apparent Z-selectivity in the intermolecular enyne metathesis step.

[Study on the simultaneous spectrophotometric determination of three components including deoxyschizandrin by ridge regression method]

Ridge Regression (RR) spectrophotometry was used in the present paper to analyse three components: deoxyschizandin, schisandrin, and gamma-schisandrin. The basic principle and the analytical steps of the approach are described in detail. The computer program of RR is based on VB language. The experimental results show that the RR method has no systematical error as compared to classical method, and the average recovery of each component is all in the range of 92.35% to 108.69%. High accuracy of RR method was obtained. Each component was determined with satisfactory results without any pre-separation. As compared with conventional methods, this method is simple, rapid and suitable for the computer-aided analysis. It was developed in statistical literature to treat these ill-conditioned systems and is an useful analytical method.

Bismercaptoethanediazacyclooctane as a N2S2 Chelating Agent and Cys−X−Cys Mimic for Fe(NO) and Fe(NO)2

The N-protonated bismercaptoethanediazacyclooctane serves as a bidentate dithiolate ligand to oxidized Fe(NO)(2) of Enemark-Feltam notation, E-F [Fe(NO)(2)],(9) mimicking Cys-X-Cys binding of Fe(NO)(2) to proteins or thio-biomolecules. The neutral compound is characterized by the well-known g = 2.03 EPR signal which is a hallmark of dinitrosyl iron complexes, DNIC's. The Fe(NO)(2) unit can be removed from the chelate by excess PhS(-), producing (PhS)(2)Fe(NO)(2)(-). Transfer of NO from Fe(H(+)bme-daco)(NO)(2) (nu(NO) = 1740, 1696 cm(-)(1)) to Fe(II) of [(bme-daco)Fe](2) yields the five-coordinate, square-pyramidal N(2)S(2)Fe(NO) (nu(NO) = 1649 cm(-)(1)), where NO is in the apical position. Its isotropic EPR signal at g = 2.05 is consistent with E-F [Fe(NO)](7) formulation. In excess NO, Roussin's red ester-type molecules are formed as dinuclear or tetranuclear species, [(micro-SRS)[Fe(2)(NO)(4)]](n)() (n =1, 2). These well-characterized molecules furnish reference points for positions and patterns in nu(NO) vibrational spectroscopy expected to be useful for in vivo studies of NO degradation of iron-sulfur clusters in ferredoxins.