Showing papers in "Molecules in 2004"
TL;DR: The applications of luminescent cyanine and squarylium dyes are reviewed and the main advantage of noncovalent labeling is that it affects the functional activity of the biomolecule to a lesser extent.
Abstract: Biopolymers such as proteins and nucleic acids can be labeled with a fluorescent marker to allow for their detection. Covalent labeling is achieved by the reaction of an appropriately functionalized dye marker with a reactive group on a biomolecule. The recent trend, however, is the use of noncovalent labeling that results from strong hydrophobic and/or ionic interactions between the marker and biomolecule of interest. The main advantage of noncovalent labeling is that it affects the functional activity of the biomolecule to a lesser extent. The applications of luminescent cyanine and squarylium dyes are reviewed.
156 citations
TL;DR: Ten new azo Schiff bases 5a-h and 7a-b were prepared in excellent yields via the condensation of different aromatic amines and azoaldehyde, 2-hydroxy-3- methoxy-5-(4-methoxyphenylazo)benzaldehyde (4) by two different methods and none of them were active against the fungi species tested.
Abstract: Ten new azo Schiff bases 5a-h and 7a-b were prepared in excellent yields via the condensation of different aromatic amines and a new azoaldehyde, 2-hydroxy-3- methoxy-5-(4-methoxyphenylazo)benzaldehyde (4) by two different methods. All new compounds were tested against five microorganisms: Staphylococcus aureus (Gram positive and methicillin resistant), Bacillus subtilis (Gram positive), Kelebsiella pneumonia, Pseudomonas aeruginosa and Escherichia coli (all Gram negative). Compounds 4, 5a, 5c, 5d and 5g were moderately active against Staphylococcus aureus and Bacillus subtilis. Compound 7b was highly active against Bacillus subtilis and moderately active against Staphylococcus aureus. Other compounds were inactive against these strains of bacteria. The antifungal activities of these compounds were also tested against eight different fungal species. None of them were active against the fungi species tested.
134 citations
TL;DR: A quantitative structure-antioxidant activity relationship (QSAR) study of 36 flavonoids was performed using the partial least squares projection of latent structures (PLS) method, which gave a proper description and a suitable prediction of the antioxidant activities of a diverse set of flavonoid having clustering tendency.
Abstract: A quantitative structure – antioxidant activity relationship (QSAR) study of 36 flavonoids was performed using the partial least squares projection of latent structures (PLS) method. The chemical structures of the flavonoids have been characterized by constitutional descriptors, two-dimensional topological and connectivity indices. Our PLS model gave a proper description and a suitable prediction of the antioxidant activities of a diverse set of flavonoids having clustering tendency. Keywords: Antioxidants, free radicals, flavonoids, QSAR, chemometrics, partial least squares, PLS Introduction Flavonoids (see Figure 1), a group of polyphenolic compounds, can widely be found in fruits and vegetables. Numerous positive health effects of flavonoids have been described. They have been reported to exhibit anti-cancer [1-3], anti-viral [4] and anti-inflammatory [3,5-6] effects, and to reduce the risk of cardiovascular diseases [3,7-9]. These activities are generally associated with antioxidant or free radical-scavenging properties of flavonoids. The number of flavonoid derivatives is more than 4000 and their antioxidant properties are very different. It is a complex task to select the most effective antioxidants from
125 citations
TL;DR: The furan-2-carboxylic acid hydrazide compounds were converted into 1,4-substituted thiosemicarbazides and the azomethines prepared from the corresponding arylaldehydes and the 4-amino-5-(furan- 2-yl or benzyl)-4H-1,2, 4-triazole-3-thiols 7 and 10.
Abstract: In this study appropriate hydrazide compounds, furan-2-carboxylic acid hydrazide (1) and phenylacetic acid hydrazide (2) were converted into 1,4-substituted thiosemicarbazides 4a-e and 5a-e and 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The 1,4-substituted thiosemicarbazides were then converted into 5-(furan-2-yl or benzyl)-4-(aryl)-4H-1,2,4-triazole-3-thiols 8a-e and 9a-e. In addition, the azomethines 11a-d and 12a-d were prepared from the corresponding arylaldehydes and the 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The structures of all the synthesized compounds were confirmed by elemental analyses, IR, (1)H-NMR and(13) C-NMR spectra.
76 citations
TL;DR: Liquid or low melting association products of carbon dioxide and a secondary amine, both neutral molecules that may be gaseous, are recognised as "distillable" ionic media.
Abstract: Liquid or low melting association products of carbon dioxide and a secondary amine, both neutral molecules that may be gaseous, are recognised as "distillable" ionic media.
72 citations
TL;DR: The atom, atom-type and total linear indices of the molecular pseudograph's atom adjacency matrix appear to be a very promising structural invariant, useful for QSPR/QSAR studies and computer-aided "rational" drug design.
Abstract: In this paper we describe the application in QSPR/QSAR studies of a new group of molecular descriptors: atom, atom-type and total linear indices of the molecular pseudograph’s atom adjacency matrix. These novel molecular descriptors were used for the prediction of boiling point and partition coefficient (log P ), specific rate constant (log k ), and antibacterial activity of 28 alkyl-alcohols and 34 derivatives of 2-furylethylenes, respectively. For this purpose two quantitative models were obtained to describe the alkyl-alcohols’ boiling points. The first one includes only two total linear indices and showed a good behavior from a statistical point of view (R 2 = 0.984, s = 3.78, F = 748.57, q 2 = 0.981, and s cv = 3.91). The second one includes four variables [3 global and 1 local (heteroatom) linear indices] and it showed an improvement in the description of physical property (R² = 0.9934, s = 2.48, F = 871.96, q 2 = 0.990, and s cv = 2.79). Later, linear multiple regression analysis was also used to describe log
67 citations
TL;DR: 2,4-Dihydropyrazole glucosides 3a-3c were prepared and tested for their antitumor activity and shows an in vitro IC(50) value of 16.4 muM against proliferation of the human promyelotic leukemia (HL60) cell line.
Abstract: 2,4-Dihydropyrazole glucosides 3a-3c were prepared and tested for theirantitumor activity. The structures of these compounds were established by 1H and 13C-NMR spectroscopy. Glucoside 3b shows an in vitro IC50 value of 16.4 μM againstproliferation of the human promyelotic leukemia (HL60) cell line.
67 citations
TL;DR: A flavanone and a Flavanone glycoside, together with vomifoliol, have been isolated for the first time from the aerial parts of the plant Echiochilon fruticosum and identified.
Abstract: A flavanone and a flavanone glycoside, together with vomifoliol, have been isolated for the first time from the aerial parts of the plant Echiochilon fruticosum and identified. Their structures were established on the basis of spectroscopic measurements, mainly 2D NMR using COSY, HMQC and HMBC experiments.
60 citations
TL;DR: The developed QSAR model allowed 80% correct categorical classification of antibacterial potencies of the CAMEL-s both in the training and the validation sets, demonstrating that a narrow set of 3D sensitive 'inductive' descriptors can adequately describe the aspects of intra- and intermolecular interactions that are relevant for antibacterial activity of the cationic polypeptides.
Abstract: On the basis of the inductive QSAR descriptors we have created a neural network-based solution enabling quantification of antibacterial activity in the series of 101 synthetic cationic polypeptides (CAMEL-s). The developed QSAR model allowed 80% correct categorical classification of antibacterial potencies of the CAMEL-s both in the training and the validation sets. The accuracy of the activity predictions demonstrates that a narrow set of 3D sensitive 'inductive' descriptors can adequately describe the aspects of intra- and intermolecular interactions that are relevant for antibacterial activity of the cationic polypeptides. The developed approach can be further expanded for the larger sets of biologically active peptides and can serve as a useful quantitative tool for rational antibiotic design and discovery.
49 citations
TL;DR: In this article, a set of macromolecular descriptors of relevance to protein QSAR/QSPR studies, protein's quadratic indices, were calculated from the pseudograph's alpha-carbon atom adjacency matrix.
Abstract: This report describes a new set of macromolecular descriptors of relevance to protein QSAR/QSPR studies, protein's quadratic indices. These descriptors are calculated from the macromolecular pseudograph's alpha-carbon atom adjacency matrix. A study of the protein stability effects for a complete set of alanine substitutions in Arc repressor illustrates this approach. Quantitative Structure-Stability Relationship (QSSR) models allow discriminating between near wild-type stability and reduced-stability A-mutants. A linear discriminant function gives rise to excellent discrimination between 85.4% (35/41)and 91.67% (11/12) of near wild-type stability/reduced stability mutants in training and test series, respectively. The model's overall predictability oscillates from 80.49 until 82.93, when n varies from 2 to 10 in leave-n-out cross validation procedures. This value stabilizes around 80.49% when n was > 6. Additionally, canonical regression analysis corroborates the statistical quality of the classification model (Rcanc = 0.72, p-level <0.0001). This analysis was also used to compute biological stability canonical scores for each Arc A-mutant. On the other hand, nonlinear piecewise regression model compares favorably with respect to linear regression one on predicting the melting temperature (tm)of the Arc A-mutants. The linear model explains almost 72% of the variance of the experimental tm (R = 0.85 and s = 5.64) and LOO press statistics evidenced its predictive ability (q2 = 0.55 and scv = 6.24). However, this linear regression model falls to resolve t(m) predictions of Arc A-mutants in external prediction series. Therefore, the use of nonlinear piecewise models was required. The tm values of A-mutants in training (R = 0.94) and test(R = 0.91) sets are calculated by piecewise model with a high degree of precision. A break-point value of 51.32 degrees C characterizes two mutants' clusters and coincides perfectly with the experimental scale. For this reason, we can use the linear discriminant analysis and piecewise models in combination to classify and predict the stability of the mutants' Arc homodimers. These models also permit the interpretation of the driving forces of such a folding process. The models include protein's quadratic indices accounting for hydrophobic (z1), bulk-steric (z2), and electronic (z3) features of the studied molecules. Preponderance of z1 and z3 over z2 indicates the higher importance of the hydrophobic and electronic side chain terms in the folding of the Arc dimer. In this sense, developed equations involve short-reaching (k < or = 3), middle- reaching (3 < k < or = 7) and far-reaching (k= 8 or greater) z1, 2, 3-protein's quadratic indices. This situation points to topologic/topographic protein's backbone interactions control of the stability profile of wild-type Arc and its A-mutants. Consequently, the present approach represents a novel and very promising way to mathematical research in biology sciences.
48 citations
TL;DR: The syntheses of some new sugar-based monocyclic β-lactams possessing several other functionalities in addition to the carbohydrate moiety are described, found to be active against Staphilococcus citrus, Klebsiella pneumoniae, Escherichia coli and Bacillus subtilis.
Abstract: The syntheses of some new sugar-based monocyclic β-lactams possessing several other functionalities in addition to the carbohydrate moiety are described. The key step was the Staudinger [2+2] cycloaddition of chiral carbohydrate Schiff base 5 with phthalimidoacetyl chloride to yield the sugar-based monocyclic β-lactam 6 as a single isomer. Treatment of protected β-lactams 6 and 8 with methylhydrazine afforded the free amino β-lactams 9 and 10. Acylation of these free amino β-lactams with benzoyl, phenoxyacetyl, cinnamoyl and phenylacetyl chloride in the presence of pyridine afforded β-lactams 11a-d and 12a-d. Some of these novel β-lactams were found to be active against Staphilococcus citrus, Klebsiella pneumoniae, Escherichia coli and Bacillus subtilis.
TL;DR: An overview of the synthesis of the fungal metabolites, plus methodology leading potentially toward extended quinones such as (3S,3'S)-xylindein, and the enantiopure ventiloquinones L, E and G are presented.
Abstract: : An overview of the synthesis of the fungal metabolites (+)-dermolactone, (–)-semixanthomegnin, (+)- and (–)-mellein, (–)-ochratoxin α, (–)-(1 R ,3 S )-thysanone, the enantiopure ventiloquinones L, E and G, and 8-desmethyleleutherin from a common chiral intermediate, is presented. Further methodology leading potentially toward extended quinones such as (3 S ,3' S )-xylindein is also outlined. Keywords: Stereospecific synthesis; fungal metabolites; quinones; isochromanones. Introduction Biologically active aromatic systems with appended pyran or pyranone (δ-lactone) rings are widespread in nature, being found in a wide variety of organisms, including fungi. Our interest in these molecules was ignited by our need to synthesise just one member of the group in order to establish the absolute stereochemical configuration of that natural product, but has subsequently broadened in scope to become the first versatile total synthesis of a number of natural products in enantiomerically pure form.
TL;DR: This paper reports the synthesis of ten quinazolinediones from the seed husks of Mexican Zanthoxylum species with wide array of pharmacological properties.
Abstract: Quinazolinone and quinazolinedione derivatives are of considerable interest due to their wide array of pharmacological properties. In this paper we report the synthesis of ten quinazolinediones. The previous isolation of two of these compounds, namely 1-methyl-3-(2'-phenylethyl)-1H,3H-quinazoline-2,4-dione and 1-methyl-3-[2'-(4'- methoxyphenyl)ethyl]-lH,3H-quinazoline-2,4-dione, from the seed husks of Mexican Zanthoxylum species has been reported
SIDI1
TL;DR: A new glycoside flavone, chrysin-7-O-beta-D-[(6"-acetyl)glycopyranoside] (2) was isolated from the flowers and leaves of Calycotome Villosa Subsp.
Abstract: The known flavonoid chrysin-7-O-(beta-D-glycopyranoside) (chrysin glucoside,1) as a major fraction and a new glycoside flavone, chrysin-7-O-beta-D-[(6"-acetyl)glycopyranoside] (2) were isolated from the flowers and leaves of Calycotome Villosa Subsp. Intermedia, They were identified by UV-Vis, 1R, (1)H-, (13)C-NMR and ESI-MS.
TL;DR: The ability of models induced by an artificial intelligence methodology to accommodate complex interactions in detailed systems, and the demonstrated reliability of the approach evaluated, indicate that the methodology may have application in broadening the scope of biodegradability models.
Abstract: This study presents a review of biodegradability modeling efforts including a detailed assessment of two models developed using an artificial intelligence based methodology. Validation results for these models using an independent, quality reviewed database, demonstrate that the models perform well when compared to another commonly used biodegradability model, against the same data. The ability of models induced by an artificial intelligence methodology to accommodate complex interactions in detailed systems, and the demonstrated reliability of the approach evaluated by this study, indicate that the methodology may have application in broadening the scope of biodegradability models. Given adequate data for biodegradability of chemicals under environmental conditions, this may allow for the development of future models that include such things as surface interface impacts on biodegradability for example.
TL;DR: TPSA and nC=O (number of -C(O)- fragments) parameters give the best statistically significant mono- and bidescriptor models confirming the importance of H-bonding capability of the alkaloids for binding at the receptor site.
Abstract: A QSAR toxicity analysis has been performed for a series of 19 alkaloids with the lycoctonine skeleton. GA-MLRA (Genetic Algorithm combined with Multiple Linear Regression Analysis) technique was applied for the generation of two types of QSARs: first, models containing exclusively 3D-descriptors and second, models consisting of physicochemical descriptors. As expected, 3D-descriptor QSARs have better statistical fits. Physicochemical-descriptor containing models, that are in a good agreement with the mode of toxic action exerted by the alkaloids studied, have also been identified and discussed. In particular, TPSA (Topological Polar Surface Area) and nC=O (number of -C(O)- fragments) parameters give the best statistically significant mono- and bidescriptor models (when combined with lipophilicity, MlogP) confirming the importance of H-bonding capability of the alkaloids for binding at the receptor site.
TL;DR: Many furocoumarins and their analogs possess a prominent photobiological activity and some of them are successfully used as drugs in phototherapy of skin diseases.
Abstract: Many furocoumarins and their analogs possess a prominent photobiological activity. Some of them are successfully used as drugs in phototherapy of skin diseases. Fries rearrangement of acyloxyheteroarenes, condensation of acylhydroxyheteroarenes with α-carbonyl compounds under base catalysis and transformations of dihydrofurocoumarinones are new trends in synthesis of furocoumarins and their analogs.
TL;DR: The dithiadiazolyl radical p-NCC6F 4C6F4CNSSN* retains its monomeric nature in the solid state with molecules linked together into chains via supramolecular CN-S interactions and behaves as a near-ideal Curie paramagnet.
Abstract: : The dithiadiazolyl radical p -NCC 6 F 4 C 6 F 4 CNSSN • ( 4 ) retains its monomeric nature in the solid state with molecules linked together into chains via supramolecular CN···S interactions. Variable temperature magnetic studies on 4 show that it behaves as a near-ideal Curie paramagnet (|θ| less than 0.1 K), indicating negligible intermolecular exchange. The effective magnetic moment (1.78 µ B ) is temperature independent and in excellent agreement with the value expected for an S = ½ paramagnet with g = 2.01 (1.74µ B ). The lack of exchange coupling between radicals is attributed to the absence of significant orbital overlap between radical centres. Keywords: Magnetic properties, dithiadiazolyl, molecular magnetism, organic magnet. Introduction The development of organic molecular magnetic materials is a field which is still very much in its infancy. The design of organic molecular magnets is conceptually simple; an organic molecular ferromagnet can be considered as a regular array of organic free radicals in which ferromagnetic interactions propagate throughout the lattice. For the majority of organic radicals the magnetic anisotropy is rather low and, to a good approximation, they can be considered as Heisenberg spin
TL;DR: The results indicate that the simple counts work at least as well as E-state descriptors in building models for solubility and BBB, while surprisingly, simple counts have outperformed E-states by 18% and 30%, respectively, when building the models for HIA and clogP.
Abstract: Performance of the E-state descriptors was tested against simple counts of the 35 atom types that the Kier-Hall E-states are based upon, by building PLS models for clogP, aqueous solubility, human intestinal absorption (HIA) and blood brain barrier (BBB). The results indicate that the simple counts work at least as well as E-state descriptors in building models for solubility and BBB, while surprisingly, simple counts have outperformed E-states by 18% and 30%, respectively, when building the models for HIA and clogP.
TL;DR: A new method has been designed to prepare the known benzoxaz inone derivative 2-(N-phthaloylmethyl)-4H-3,1-benzoxazin-4-one by reacting with cyanuric chloride, used as a cyclization agent, to produce the benzxazinone derivative.
Abstract: A new method has been designed to prepare the known benzoxazinone derivative 2-(N-phthaloylmethyl)-4H-3,1-benzoxazin-4-one (4). The acyl chloride derivative N-phthaloylglycine reacts with anthranilic acid in chloroform, in the presence of triethylamine, to give an intermediate that is then reacted with cyanuric chloride, used as a cyclization agent, to produce the benzoxazinone derivative.
TL;DR: The variable Zagreb (v)M(2) index is introduced and applied to the structure-boiling point modeling of benzenoid hydrocarbons and Surprisingly, the model based on the variable vertex-connectivity index (S(fit)=6.8 degrees C) is comparable to the modelbased on (v]M2 index.
Abstract: The variable Zagreb vM2 index is introduced and applied to the structure-boiling point modeling of benzenoid hydrocarbons. The linear model obtained (thestandard error of estimate for the fit model Sfit=6.8 oC) is much better than thecorresponding model based on the original Zagreb M2 index (Sfit=16.4 oC). Surprisingly,the model based on the variable vertex-connectivity index (Sfit=6.8 oC) is comparable tothe model based on vM2 index. A comparative study with models based on the vertex-connectivity index, edge-connectivity index and several distance indices favours modelsbased on the variable Zagreb vM2 index and variable vertex-connectivity index.However, the multivariate regression with two-, three- and four-descriptors givesimproved models, the best being the model with four-descriptors (but vM2 index is notamong them) with Sfit=5 oC, though the four-descriptor model contaning vM2 index isonly slightly inferior (Sfit=5.3 oC).
TL;DR: Examples of the synthesis of chiral building blocks from achiral materials utilizing asymmetric hydrogenation and asymmetric epoxidation are presented.
Abstract: In the past decade there has been a significant growth in the sales of pharmaceutical drugs worldwide, but more importantly there has been a dramatic growth in the sales of single enantiomer drugs. The pharmaceutical industry has a rising demand for chiral intermediates and research reagents because of the continuing imperative to improve drug efficacy. This in turn impacts on researchers involved in preclinical discovery work. Besides traditional chiral pool and resolution of racemates as sources of chiral building blocks, many new synthetic methods including a great variety of catalytic reactions have been developed which facilitate the production of complex chiral drug candidates for clinical trials. The most ambitious technique is to synthesise homochiral compounds from non-chiral starting materials using chiral metal catalysts and related chemistry. Examples of the synthesis of chiral building blocks from achiral materials utilizing asymmetric hydrogenation and asymmetric epoxidation are presented.
TL;DR: The structural interpretation of the developed QSPR model shows that most probably the most important mechanisms are the addition to multiple bonds and the hydrogen atom abstraction at allylic sites.
Abstract: Volatile organic compounds (VOCs) play an important role in different photochemical processes in the troposphere. In order to predict their impact on ozone formation processes a detailed knowledge about their abundance in the atmosphere as well as their reaction rate constants is required. The QSPR models were developed for the prediction of reaction rate constants of volatile unsaturated hydrocarbons. The chemical structure was encoded by constitutional and topological indices. Multiple linear regression models using CODESSA software was developed with the RMS(CV) error of 0.119 log units. The chemical structure was encoded by six topological indices. Additionally, a regression model using a variable connectivity index was developed. It provided worse cross-validation results with an RMS(CV) error of 0.16 log units, but enabled a structural interpretation of the obtained model. We differentiated between three classes of carbon atoms: sp2-hybridized, non-allylic sp3-hybridized and allylic sp3-hybridized. The structural interpretation of the developed model shows that most probably the most important mechanisms are the addition to multiple bonds and the hydrogen atom abstraction at allylic sites.
TL;DR: The syntheses of representative examples of five classes of new heterocyclic ligands are described, which include N,N'-chelating bis-heterocycles, binucleating ligands, cyclometallated compounds, chiral ligands and a family of polyheteroaryl-linked arenes.
Abstract: The syntheses of representative examples of five classes of new heterocyclic ligands are described. These include N,N'-chelating bis-heterocycles, binucleating ligands, cyclometallated compounds, chiral ligands and a family of polyheteroaryl-linked arenes.
TL;DR: The Hurd-Mori and Lalezari methods were used, respectively, for the preparation of these 1,2,3-thiadiazole and 1,1,1-selenadiazoles derivatives, which are important for photocrosslinking processes and due to their potential biological activity.
Abstract: New 1,2,3-thiadiazole and 1,2,3-selenadiazole derivatives, 14-23, were prepared from the ketones 1-5 via the corresponding semicarbazones or hydrazones 6-12. The Hurd-Mori and Lalezari methods were used, respectively, for the preparation of these 1,2,3-thiadiazole and 1,2,3-selenadiazole derivatives. The intermediate 13 was also trapped, separated and fully characterized. These derivatives are important for photocrosslinking processes and due to their potential biological activity.
TL;DR: A series of substituted 2-phenacyl-3-phenyl-1H-pyrrole-4-carboxylates were prepared from substituted acetophenones in 6 steps as discussed by the authors.
Abstract: A series of substituted 2-phenacyl-3-phenyl-1H-pyrrole-4-carboxylates were prepared from substituted acetophenones in 6 steps. The final condensations between a chloroenal and an aminoketone were carried out under neutral conditions in parallel to yield the series listed below. Selected pyrrole derivatives proved to be potent hypolipidemic agents lowering serum triglyceride concentrations in CF-1 male mice after 14 days of I.P. administration. One agent orally lowered serum cholesterol in Sprague-Dawley male rats at 2mg/kg/day after 14 days. The agents demonstrated a lowering of mouse serum LDL- cholesterol levels and selected compounds showed an elevation of serum HDL-cholesterol levels. The cholesterol concentrations in the liver were raised while the cholesterol and triglyceride contents of the aorta were significantly lowered by the selected trisubstituted pyrrole.
TL;DR: The compounds prepared were tested against Escherichia coli, Staphilococcus citrus, Klebsiella pneumanie and Bacillus subtillis and some of these compounds showed potential antimicrobial activities.
Abstract: Reaction of the amino acid D-phenylalanine ethyl ester (4) with cinnamaldehyde gave chiral Schiff base 5, which underwent an asymmetric Staudinger [2+2] cycloaddition reaction with phthalimidoacetyl chloride to give the monocyclic β-lactam 6 as a single stereoisomer. Ozonolysis of 6 followed by reduction with lithium aluminum tri(tert-butoxy) hydride afforded the hydroxymethyl β-lactam 8. Treatment of 8 with methansulfonyl chloride gave the mesylated monocyclic β-lactam 9, which was converted to the bicyclic β-lactam 10 upon treatment with 1,8-diazabicyclo[5,4.0] undec- 7-ene (DBU). Deprotection of the phthalimido group in β-lactams 6 and 10 by methylhydrazine and subsequent acylation of the free amino β-lactams with different acyl chlorides in the presence of pyridine afforded mono and bicyclic β-lactams 14a-d and 15a-d respectively. The compounds prepared were tested against Escherichia coli, Staphilococcus citrus, Klebsiella pneumanie and Bacillus subtillis. Some of these compounds showed potential antimicrobial activities.
TL;DR: A series of polymer-supported chiral ammonium salts which have been employed as phase-transfer catalysts in the asymmetric benzylation of an N-(diphenylmethylene)glycine ester can be easily recovered by simple filtration after the reaction and reused.
Abstract: Alkaloids such as cinchonidine, quinine and N-methylephedrine have been N-alkylated using polymeric benzyl halides or co-polymerized and then N-alkylated, thus affording a series of polymer-supported chiral ammonium salts which have been employed as phase-transfer catalysts in the asymmetric benzylation of an N-(diphenylmethylene)glycine ester. These new polymeric catalysts can be easily recovered by simple filtration after the reaction and reused. The best ee's were achieved when Merrifield resin-anchored cinchonidinium ammonium salts were employed.
TL;DR: The reactivity of thiohydantoin derivatives 2a-c towards N,N-dimethylformamide diethylacetal (DMF-DEA) was explored using solvent-free technique under microwave irradiation (mu omega).
Abstract: A new route to 5-(imidazolidin-2-ylidene)-2-methylsulfanyl-3,5-dihydro-imidazol-4-ones 4a-c using ketene dithioacetal intermediates 3a-c is described. Thereactivity of thiohydantoin derivatives 2a-c towards N,N-dimethylformamide diethylacetal(DMF-DEA) was also explored using solvent-free technique under microwave irradiation(μω). The 1H- and 13C-NMR spectra of some representative products are discussed.
TL;DR: The results of a calculation of the normal boiling points of a representative set of 200 organic molecules through the application of QSPR theory are reported, using a particular set of flexible molecular descriptors, the so called Correlation Weighting of Atomic Orbitals with Extended Connectivity of Zero- and First-Order Graphs of atomic Orbitals.
Abstract: We report the results of a calculation of the normal boiling points of a representative set of 200 organic molecules through the application of QSPR theory. For this purpose we have used a particular set of flexible molecular descriptors, the so called Correlation Weighting of Atomic Orbitals with Extended Connectivity of Zero- and First-Order Graphs of Atomic Orbitals. Although in general the results show suitable behavior to predict this physical chemistry property, the existence of some deviant behaviors points to a need to complement this index with some other sort of molecular descriptors. Some possible extensions of this study are discussed.