Showing papers in "Arkivoc in 2004"
TL;DR: In this paper, two small sets of aromatic Schiff bases and 2,3-diaryl-1,3thiazolidin-4-one derivatives have been prepared and tested for antiinflammatory and antinociceptive activities.
Abstract: Two small sets of aromatic Schiff bases and 2,3-diaryl-1,3-thiazolidin-4-one derivatives have been prepared and tested for antiinflammatory and antinociceptive activities. The thiazolidinone derivatives have been obtained from the azomethines through the addition of α-mercaptoacetic acid. Both types of compounds displayed good level of activity against carrageenan induced edema in rat hind paw, while only moderate activity was observed in the writhing test in mice.
80 citations
TL;DR: A short review of the indole ring implicated multicomponent reactions, and simple functional group transformation-based approaches, developed over the last thirty years for the synthesis of various biologically interesting indole heterocyclic ring systems is given in this article.
Abstract: This short review offers a non-exhaustive panorama of the indole ring implicated multicomponent reactions, and simple functional group transformation-based approaches, developed over the last thirty years for the synthesis of various biologically interesting indole heterocyclic ring systems.
56 citations
TL;DR: In this paper, per-O-acetylated and -benzoylated β-D-glucopyranosyl cyanides were transformed into the corresponding 5-(D-Glucopyrusyl)tetrazoles.
Abstract: Per-O-acetylated and -benzoylated β-D-glucopyranosyl cyanides were transformed into the corresponding 5-( β-D-Glucopyranosyl)tetrazoles, 2-( β-D-glucopyranosyl)benzothiazoles, and, via the benzoylated C-( β-D-glucopyranosyl) ethyl thioformimidate, 2-( β-D-glucopyranosyl)- benzimidazoles. Acylation of the tetrazoles, either by acetic or trifluoroacetic anhydride, gave 5-( β-D-glucopyranosyl)-2-methyl- and -2-trifluoromethyl-1,3,4-oxadiazoles, respectively. Removal of the protecting groups furnished new inhibitors of glycogen phosphorylase exhibiting inhibitor constants in the micromolar range.
49 citations
TL;DR: Preliminary molecular modeling investigations yielded free energy of binding values in harmony with the corresponding experimental findings, which revealed that an optimized balance of opposing electrostatic contributions must be realized to gain tight enzyme-inhibitor binding.
Abstract: N 1 -[1-Aryl-2-(1H-imidazol-1-yl and 1H-1,2,4-triazol-1-yl)-ethylidene]-pyridine-2-carbo xamidrazone derivatives were synthesized and tested for their in vitro antifungal and antimycobacterial activity. Some compounds showed a very good activity against the tested clinical isolates of Candida albicans 685 and Candida glabrata 523. The same compounds exhibited an interesting, even if moderate, activity against the tested strain of Mycobacterium tuberculosis H 37Rv. Preliminary molecular modeling investigations yielded free energy of binding values in harmony with the corresponding experimental findings. They further revealed that an optimized balance of opposing electrostatic contributions must be realized to gain tight enzyme-inhibitor binding.
45 citations
TL;DR: In this article, the microwave assisted synthesis of 1H,3H-thiazolo(3,4-a)benzimidazoles, 2-aryl-1-benzylbenzymidazole and 2,3-diaryl-1,3thiazolidin-4-ones, which achieved reductions in reaction times, higher yields, cleaner reactions than for the previously- described synthetic processes.
Abstract: In this paper we describe the microwave-assisted synthesis of 1H,3H-thiazolo(3,4- a)benzimidazoles, 2-aryl-1-benzylbenzimidazoles and 2,3-diaryl-1,3-thiazolidin-4-ones, which achieved reductions in reaction times, higher yields, cleaner reactions than for the previously- described synthetic processes. In some cases eco-friendly solventless methodology has been used.
43 citations
TL;DR: Trimethylsilylation of alcohols, phenols and naphthols using HMDS catalyzed by commercially available H-β zeolite under solvent free conditions has been presented as discussed by the authors.
Abstract: Trimethylsilylation of alcohols, phenols and naphthols using HMDS catalyzed by commercially available H-β zeolite under solvent free conditions has been presented The heterogeneous reaction conditions provided environmentally friendly protocol
41 citations
TL;DR: The main components in the three essential oils were the same but in different relative amounts as mentioned in this paper, and the type and quantitative variations of the chemical components of the analyzed oils in relation to the extraction methods were greater for O. micranthum.
Abstract: Essential oils (EO) from leaves of Ocimum gratissimum L., Ocimum micranthum Willd. and Ocimum selloi Benth. obtained by steam distillation (SD), microwave oven distillation (MO) and supercritical extraction with CO2 (SC) showed different composition by GC/MS analysis. The main components in the three essential oils were the same but in different relative amounts. The oil from O. gratissimum obtained by SD presented eugenol (54.0%) and 1,8-cineole (21.6%) as main components, by MO eugenol (34.6%) and 1,8-cineole (22.6%), and by SC eugenol (73.1%) and 1,8-cineole (5.6%). The essential oil from O. micranthum obtained by SD showed mainly eugenol (64.8 %), (E)-β-caryophyllene (14.3%) and bicyclogermacrene (8.1%); by MO eugenol (30.6 %), trans-β-caryophyllene (19.8 %) and elemicin (19.0), and the oil obtained by SC presented eugenol (56.7%), elemicin (16.0%) and trans-β-caryophyllene (4.0%). Essential oil of O. selloi obtained by SD presented anethole (64.6%) and linalool (20.6%); by MO anethole (67.4%) and linalool (20.9%) and by SC anethole (31.9%) and linalool (23.2%) as main constituents. The type and quantitative variations of the chemical components of the analyzed oils in relation to the extraction methods were greater for O. micranthum.
41 citations
40 citations
TL;DR: In this article, tri-O-galloyl, 2,4-chebuloyl-β-D-glucopyranoside (chebulinic acid, 1) and its novel thrice- hydrolyzed derivative, galloyl free chebulinica acid, 2), together with ellagic (3) and gallic acids (4), ethyl gallate (5), and luteolin (6), were isolated from the dried fruit of Terminalia chebula by bioactivity-guided fractionation of the extract.
Abstract: Tri-O-galloyl-2,4-chebuloyl-β-D-glucopyranoside (chebulinic acid, 1) and its novel thrice- hydrolyzed derivative, 2,4-chebuloyl-β-D-glucopyranoside (galloyl-free chebulinic acid, 2), together with ellagic (3) and gallic acids (4), ethyl gallate (5), and luteolin (6), were isolated from the dried fruit of Terminalia chebula by bioactivity-guided fractionation of the extract. The compounds were variously identified on the basis of UV, MS, and NMR data. The latter proved that the glucose unit in 1 adopts a well defined 1 C4 chair conformation with all substituents in axial positions. However, the absolute configurations of the three stereocenters in the chebuloyl group have been reassigned. For 2, a solvent-dependent mixture of both open-chain and cyclic pyranose forms was observed, the latter with a β configuration for the anomeric C-1 sugar carbon being heavily preferred in aqueous solution. In contrast to 1, a dynamic equilibrium consisting of several possible skew conformers ( 5 S1, 1 S5, 1 S3, and 2 SO) was designated for the sugar ring of 2. Antioxidant activities of the isolated compounds were assessed by measuring their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and to inhibit the autoxidation of methyl linoleate in vitro. Of the isolated compounds, 1 showed the highest radical scavenging activity in the DPPH assay. For the methyl linoleate assay, 2 and 4−6 all exhibited strong antioxidant activities whereas the activities of 1 and 3 were only moderate. The fruit extract itself was highly effective in both tests.
40 citations
TL;DR: Reactions of sulfonamides with readily available N-acylbenzotriazoles (RCOBt, where R is an aryl, heteroaryl, or N-Cbz-protected-α-amino(alkyl) group), in the presence of NaH, produced N- acylsulfonamide in 76−100% yields.
Abstract: Reactions of sulfonamides with readily available N-acylbenzotriazoles (RCOBt, where R is an aryl, heteroaryl, or N-Cbz-protected-α-amino(alkyl) group), in the presence of NaH, produced N- acylsulfonamides in 76−100% yields. The ability to utilize N-acylbenzotriazoles for which the corresponding acid chlorides are not easily prepared, may be especially advantageous.
37 citations
TL;DR: Polymer-supported Nacylation utilizing carbodiimides with additives, direct coupling reagents (phosphonium salts and uronium salt), N-acylazoles, and other reagents have been discussed as discussed by the authors.
Abstract: Polymer-supported N-acylation utilizing carbodiimides with additives, direct coupling reagents (phosphonium salts and uronium salts), N-acylazoles, and other reagents have been discussed.
TL;DR: In this article, a new method of metal-coordinating controlled oxidative degradation of chitosan leading to low molecular weight chitosa with uniform molecular weight distribution is reported.
Abstract: A new method of metal-coordinating controlled oxidative degradation of chitosan leading to low molecular weight chitosan with uniform molecular weight distribution is reported in this paper. Chitosan is converted into chitosan-metal complex in which chitosan chain can be easily broken at weak points caused by coordinating bond. IR, UV, XRD, DSC and elemental analysis proved coordination between chitosan and the metal ion and the presence of weak points existing on the chitosan chain of complexes. Coordinating conditions (such as metal amount, speed of stirring, speed of metal salt addition) are controlled to obtain the complex with uniform metal distribution and uniform weak points distribution. H2O2 is added to break chitosan chain at those weak points to get low molecular weight chitosan. Degradative speed with different metal ion is different as follow: Cu 2+ > Co 2+ > Mn 2+ > Ni 2+ . With the increase of oxidant amount, temperature, and pH, and decrease of O2 content, degradative velocity increase. HPLC/GPC spectra show that degradative velocity of complexes is faster than that of chitosan, and the molecular weight distribution is much more narrow than that of chitosan. Low molecular weight chitosan and its complexes with Cu(II) or Co(II) possess good O2 .- scavenging activity.
TL;DR: In this article, the essential oil from the aerial parts of Baccharis trinervis (Lam.) Pers, obtained by hydrodistillation, was analyzed by GC-MS, as well as by 1 H and 13 C NMR.
Abstract: The essential oil from the aerial parts of Baccharis trinervis (Lam.) Pers., obtained by hydrodistillation, was analyzed by GC-MS, as well as by 1 H and 13 C NMR. α-Thujene, α-pinene, sabinene, β-pinene, β-phellandrene, (E)-lachnophyllum acid methylester and (Z)-lachnophyllum acid methyl ester were found to be the major components among the identified constituents. Evaluation of the in vitro antimicrobial activity of the essential oil against four bacteria and one fungus is also reported.
TL;DR: A review of the recent progress in α-aminoalkyl radical generation can be found in this paper, where the intramolecular additions of C-centered neutral α-AMAL radicals onto suitably positioned C-C double bonds provide a ready access into functionalized carbocycles and heterocycles.
Abstract: The intramolecular additions of C-centered neutral α-aminoalkyl radicals onto suitably positioned C-C double bonds provide a ready access into functionalized carbocycles and heterocycles. This strategy offers considerable versatility in the selection of starting materials since a number of methods using different functional groups and reagents are available for αaminoalkyl radical generation. This review covers the recent progress in this field.
TL;DR: In this paper, a short review describes the most recent work on the synthesis, biological evaluation and transformation of 2- and 3-styrylchromones, as well as their 3-isoanalogues.
Abstract: Styrylchromones, although scarce in nature, constitute a group of oxygen heterocyclic compounds which have shown significant biological activities. Their transformation and the transformation of their 3-isoanalogues into other biologically active compounds have been exploited. This short review describes the most recent work on the synthesis, biological evaluation and transformation of 2- and 3-styrylchromones.
TL;DR: Applications of FMS for the preparation of 2 enantiomers of pyridovericin, 16 diastereomers of murisolin, and a 560-member mappicine library are highlighted in this article.
Abstract: Fluorous mixture synthesis (FMS) is a newly developed highly-efficient solution-phase technology. A set of substrates attached to homologous fluorous tags is mixed and taken through a sequence of organic reactions. The final mixtures are demixed by fluorous HPLC and detagged to give individually pure final products. Applications of FMS for the preparation of 2 enantiomers of pyridovericin, 16 diastereomers of murisolin, and a 560-member mappicine library are highlighted in this article.
TL;DR: Two new steroidal saponins are isolated from the organic extract of the sponge Erylus lendenfeldi collected in the Red Sea with an unusual 8α,9α- epoxy-4α-methyl-8,9-secocholesta-7,9(11),14-triene skeleton which appears to be unprecedented in nature.
Abstract: Our search for biologically active marine natural products has led to the isolation of two new steroidal saponins, eryloside K (2) and eryloside L (3) together with the known antitumor and antifungal glycoside eryloside A (1) from the organic extract of the sponge Erylus lendenfeldi (Geodiidae) collected in the Red Sea. The structures of the new compounds were elucidated on the basis of comprehensive spectral analyses ( 1H, 13C, COSY, HMQC, HMBC and TOCSY NMR) as well as GC/MS analysis to infer the absolute stereochemistry of the sugar moieties. Eryloside K (2) is the 24,25-didehydro congener of 1, while eryloside L (3) features an unusual 8α,9α- epoxy-4α-methyl-8,9-secocholesta-7,9(11),14-triene skeleton which appears to be unprecedented in nature. Eryloside A (1) displayed antibacterial activity against Bacillus subtilis and Escherichia coli together with antifungal activity against Candida albicans.
TL;DR: Dibromo-(4H)-3,1-benzoxazinone 1a was synthesized and allowed to react with some nitrogen nucleophiles namely, hydroxylamine hydrochloride, 4-aminoacetophenone, o- phenylenediamine, sulfanilamide, sulfamethoxazole, semicarbazide hydrochlorides and ethanolamine to afford 3-substituted-4(3H)-quinazolinones 2-8, 10-12 and triazolo(2,3-c)
Abstract: Dibromo-(4H)-3,1-benzoxazinone 1a was synthesized and allowed to react with some nitrogen nucleophiles namely, hydroxylamine hydrochloride, 4-aminoacetophenone, o- phenylenediamine, sulfanilamide, sulfamethoxazole, semicarbazide hydrochloride and ethanolamine to afford 3-substituted-4(3H)-quinazolinones 2-8, 10-12 and triazolo(2,3- c)quinazoline 9. 6-Bromo(4H)-3,1-benzoxazin-4-one 1b was also synthesized and converted into 3-amino-4(3H) quinazolinone 13 by reaction with hydrazine hydrate. The latter product was utilized to construct new heterocyclic systems namely, triazino(2,3-c) quinazoline 14 and the thiazole derivative 16. An interesting heterocyclic transformation occurred on treatment of benzoxazinone 1a with malononitrile in presence of sodium ethoxide to give quinoline derivative 18 which reacted with phenyl isocyanate to yield oxazinoquinoline 19. The reaction of benzoxazinone 1a with Grignard' reagents afforded unexpected products 20 and 21 whereas Friedel-Crafts reaction of the same oxazinone with some aromatic hydrocarbons namely, benzene, ethylbenzene, m- and p-xylenes afforded either two benzophenone derivatives 20 and 22 or 23 and 24 in case of less bulky hydrocarbons i.e., benzene and ethylbenzene or only one product 25 and 26 in case of more bulky m- and p-xylenes. Oxazinone ring cleavage occurred when barbituric and/or thiobarbituric acid reacted with benzoxazinone 1a in refluxing pyridine to give the corresponding 5-arylidene derivatives 27a,b.
TL;DR: The macrocycles 1 coordinate palladium(0), platinum (0), and silver(I), and the palladium complexes are useful and reutilizable catalysts or precatalysts in Suzuki cross-couplings, butadiene telomerization, hydroarylation of alkynes, and in the Heck reaction as mentioned in this paper.
Abstract: E,E,E)-1,6,11-Tris(arenesulfonyl)-1,6,11-triazacyclopentadeca-3,8,11-trienes, 1, are prepared from arenesulfonamides and trans-1,4-dibromo-2-butene. Macrocycles 1 coordinate palladium(0), platinum(0), and silver(I), and the palladium complexes are useful and reutilizable catalysts or precatalysts in Suzuki cross-couplings, butadiene telomerizations, hydroarylation of alkynes, and in the Heck reaction. Structurally related macrocycles are also available by similar synthetic procedures.
TL;DR: In this article, the microwave irradiation assisted and thermal solvent-free Knoevenagel condensations of aromatic ketones with malononitrile catalyzed by NH4OAc or silica gel were investigated.
Abstract: The microwave irradiation-assisted and thermal solvent-free Knoevenagel condensations of aromatic ketones with malononitrile catalyzed by NH4OAc or silica gel, and the uncatalyzed Knoevenagel condensations in refluxing water have been investigated.
TL;DR: The rationalisation of the new multidrug and multitarget concept of therapy in classical medicine will have great implication on the future basic research in phytomedicine and an evidence based phytotherapy and requires a concerted cooperation between phytochemists, molecular biologists, pharmacologists and clinicians.
Abstract: The rationalisation of the new multidrug and multitarget concept of therapy in classical medicine will have also great implication on the future basic research in phytomedicine and an evidence based phytotherapy. It requires a concerted cooperation between phytochemists, molecular biologists, pharmacologists and clinicians with the aim to use modern high-tech methods for the standardisation of phytopreparation, to integrate new molecular biological assays into the screening of plant extracts and plant constituents and to increase the efforts into the efficacy proof of phytopreparations by controlled clinical trials which should be paralleled or followed pharmacocinetic and bioavailability studies. One major concern will be to investigate the multivalent and multitarget actions of plant constituents and standardized extracts with the aim of rationalizing the therapeutic superiority of many plant extracts over single isolated constituents. The new strategies are demonstrated on several examples of the own research projects and those of other laboratories.
TL;DR: Arylnaphthalene type lignan named rufescidride, the first containing an unusual anhydride moiety, has been isolated from the stem and branches of Cordia Rufescens as mentioned in this paper.
Abstract: A new arylnaphthalene type lignan named rufescidride, the first containing an unusual anhydride moiety, has been isolated from the stem and branches of Cordia rufescens. Its structure was elucidated on the basis of spectral data (IR, MS and NMR), mainly 1D and 2D NMR.
TL;DR: In this article, Diabl diselenides and related benzisoselenazol-3(2H)-ones are presented as the catalyst for hydogen peroxide and t-butylhydroperoxide oxidation of various types of organic substrates.
Abstract: Diaryl diselenides and related benzisoselenazol-3(2H)-ones are presented as the catalyst for hydogen peroxide and t-butylhydroperoxide oxidation of various types of organic substrates. Most of the reactions studied in our laboratory have a practical value. The aromatic aldehydes and ketones are oxidized to arenecarboxylic acids or converted to the phenols while cycloalkanones gave cycloalkanecarboxylic acids with ring contraction. From the azomethine compounds, depending on their structure, nitriles, parent carbonyl compounds, carboxylic acids or their esters are produced. Primary benzylamines gave nitriles, while the secondary are oxidized to nitrones. Alkylarenes are oxidized to the alkylaryl ketones and alkenes to epoxides. By oxidation of 1,4-dimethoxysubstituted and some polycondensed arenes the quinones are produced. The postulated mechanisms are discussed and the methods for synthesis of the title compounds are described.
TL;DR: Extension of this methodology to other fused ring systems has provided 1-alkyl- and 1-arylpyrido(1,2-a)quinolin- 3-ones 20a,b (40%) and 5-phenylthiazolo(3,2,a)pyrimidin-7-one (22) (54%) in moderate yields.
Abstract: As novel 1,3-bis-electrophilic synthons, 1-benzotriazolyl-2-propynones provide access to the fused ring systems of pyrido(1,2-a)pyrimidin-2-ones and 2H-quinolizin-2-ones, known for their diverse biological activities. Reactions of N-(phenylpropioyl)benzotriazole (13a) with substituted 2-aminopyridines 14 afforded pyrido(1,2-a)pyrimidin-2-ones 16a-c in good yields (71-73%). Likewise, 2H-quinolizin-2-ones 18a-f were obtained in moderate to good yields (39-81%) from reactions of benzotriazolyl-2-propynones 13a,b with substituted 2-picolines 14. Extension of this methodology to other fused ring systems has provided 1-alkyl- and 1-arylpyrido(1,2-a)quinolin- 3-ones 20a,b (40%) and 5-phenylthiazolo(3,2-a)pyrimidin-7-one (22) (54%) in moderate yields.
TL;DR: By coupling 5-bromo-(chloro)-7-formyl-8-hydroxyquinoline with 2-methylene-1,3,3-trimethyl- indoline, the 6'-halogeno-spiro(indoline-2,2'-(3,2-h)-pyrido(2H-1)benzopyrans) 3 have been prepared and their photochromic behaviors studied.
Abstract: By coupling 5-bromo-(chloro)-7-formyl-8-hydroxyquinoline with 2-methylene-1,3,3-trimethyl- indoline, the 6'-halogeno-spiro(indoline-2,2'-(3,2-h)-pyrido(2H-1)benzopyrans) 3 have been prepared and their photochromic behaviors studied. The photoinduced merocyanine forms 4 of the spiropyrans form fluorescent complexes with divalent metal ions (Mg 2+ , Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ ).
TL;DR: A catalytic method for the asymmetric 1,4 conjugate addition of achiral CH-acids to 1 promoted by TADDOLs with enantioselective catalytic protonation of the intermediate enolate in the stereodetermining stage of the reaction.
Abstract: We describe herein the elaboration of a new type of a substrate based on the Ni(II) complex of a Schiff base of dehydroalanine, 1, and Michael addition of nucleophiles to it, leading to the synthesis of racemic α-amino acids. We have also developed a catalytic method for the asymmetric 1,4 conjugate addition of achiral CH-acids to 1 promoted by TADDOLs with enantioselective catalytic protonation of the intermediate enolate in the stereodetermining stage of the reaction. A sizable 80% ee of the product was observed.
TL;DR: Amines in the form of amine hydrochlorides are efficiently acylated with anhydrides in an aqueous medium on addition of NaHCO3.
Abstract: Amines in the form of amine hydrochlorides are efficiently acylated with anhydrides in an aqueous medium on addition of NaHCO3. Both cyclic and acyclic anhydrides react with equal ease with an amine and amines of various stereo-electronic factors react with the same rates with an anhydride. No chromatographic separation is needed for isolation of the acylated product. Reactions in aqueous medium, innocuous by-products and chemoselective acylation of amines in the presence of phenols and thiols have been achieved with high selectivity.
TL;DR: A rapid, sensitive and reliable reverse-phase HPLC method was used for quantitative determination of the antitumoral and antioxidant quinonemethide triterpenes, 22β-hydroxymaytenin and maytenin in callus of Maytenus ilicifolia.
Abstract: Cell culture of Maytenus ilicifolia were established in order to produce and to quantify the antitumoral and antioxidant quinonemethide triterpenes. In vitro calli were induced from leaf explants of native plants and cultured in semi-solid medium under controlled conditions of humidity, temperature and photoperiod. The quinonemethide triterpenes showed maximum accumulation in the logarithmic phase growth of the cell culture. A rapid, sensitive and reliable reverse-phase HPLC method was used for quantitative determination of the antitumoral and antioxidant quinonemethide triterpenes, 22β-hydroxymaytenin and maytenin in callus of Maytenus ilicifolia. Well resolved peaks with good detection response and linearity in the range 1.0 - 100 µg/mL were obtained. This quantitative work was performed by an external standard method.
TL;DR: Cyclopalladated ferrocenylimines were found to be efficient phosphine-free catalysts for the Suzuki-Miyaura reaction of aryl iodides, bromides or chlorides with arylsboronic acids.
Abstract: Cyclopalladated ferrocenylimines were found to be efficient phosphine-free catalysts for the Suzuki-Miyaura reaction of aryl iodides, bromides or chlorides with arylboronic acids. Moderate to excellent yields and high turnover numbers were obtained under certain reaction conditions. The stability, efficiency and activity of the catalyst 1 ({PdCl(C5H5FeC5H3C(CH3)=N-(C6H4-CH3))}2) were studied.