bluuebunny/crossref_metadata_2025 huggingface dataset:
Free energy profiles of amino acid side chain analogs near water‐vapor interface obtained via MD simulations
Authors: Shaytan Alexey K. , Ivanov Victor A. , Shaitan Konstantin V. , Khokhlov Alexei R.
Published: May 2009

Solvation of 13 neutral amino acid side chain analogs at water–vapor interface was studied by computing high precision free energy profiles of the molecules across the interface using molecular dynamics (MD) simulations. The SPC water model (Berendsen, H. J. C., Postma, J. P. M., van Gunsteren, W. F., Hermans, P. A. K. J., Dixon, R., Cornell, W., Fox, T., Chipot, C., Pohorille, A. In: Wilkinson, A., Weiner, P. and van Gunsteren, W. F. editors. Intermolecular Forces, 1981, 3, 331) and OPLS‐AA (Jorgensen et al., J Am Chem Soc, 1996, 118, 11225) potential parameter sets were used. A rigorous approach for the computation of high precision free energy profiles at water–vapor interface using constraint force technique is implemented. Methodology of obtaining high precision potential of mean force (PMF) profiles free of simulation artifacts in MD simulations is outlined and discussed. The accuracy of the calculations is examined by comparing the hydration free energies of studied solutes obtained from PMF calculations and separately using Bennett acceptance ratio technique by decoupling solvent‐solute interactions in the bulk. All molecules exhibit a free energy minimum at interface. No significant desolvation barrier is observed for any of the studied species. Adsorption energies for studied molecules at water–vapor interface are estimated and compared with experimental observations. We find that for modeled neutral compounds pronounced surface influence on solute solvation vanishes already at 6–7 Å behind the water surface as the solvation free energy approaches the bulk value. The possibility of force field refinement using adsorption free energies is outlined. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010
Quantum control implemented as combinatorial optimization
Authors: Strohecker Traci , Rabitz Herschel
Published: May 2009

Optimal control theory provides a general means for designing controls to manipulate quantum phenomena. Traditional implementation requires solving coupled nonlinear equations to obtain the optimal control solution, whereas this work introduces a combinatorial quantum control (CQC) algorithm to avoid this complexity. The CQC technique uses a predetermined toolkit of small time step propagators in conjunction with combinatorial optimization to identify a proper sequence for the toolkit members. Results indicate that the CQC technique exhibits invariance of search effort to the number of system states and very favorable scaling upon comparison to a standard gradient algorithm, taking into consideration that CQC is easily parallelizable. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010
Properties of halogen atoms for representing intermolecular electrostatic interactions related to halogen bonding and their substituent effects
Authors: Torii Hajime , Yoshida Masaki
Published: May 2009

The electrostatic properties of halogen atoms are studied theoretically in relation to their ability of halogen bonding, which is an attractive intermolecular interaction of a covalently bonded halogen atom with a negatively charged atom of a neighboring molecule. The electric quadrupole (of electronic origin) with a positive zz component Θzz of a covalently bonded halogen atom, where the z axis is taken along the covalent bond involving the halogen atom, is mainly responsible for the attractive electrostatic interaction with a negatively charged atom. This positive Θzz is an intrinsic property of halogen atoms with the px2py2pz configuration of the valence electronic shell, as shown by ab initio molecular orbital calculations for isolated halogen atoms with this electronic configuration, and increases in the order of F < Cl < Br < I, in parallel with the known general sequence of the strength of halogen bonding. For halogen‐containing aromatic compounds, the substituent effects on the electrostatic properties are also studied. It is shown that the magnitude of Θzz and the electric field originating from it are rather insensitive to the substituent effect, whereas the electric field originating from atomic partial charges has a large substituent effect. The latter electric field tends to partially cancel the former. The extent of this partial cancellation is reduced in the order of Cl < Br < I and is also reducible by proper substitution on or within the six‐membered ring of halobenzene. Perspectives on the development of potential function parameters applicable to halogen‐bonding systems are also briefly discussed. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010
Reconstructing the equilibrium Boltzmann distribution from well‐tempered metadynamics
Authors: Bonomi M. , Barducci A. , Parrinello M.
Published: May 2009

Metadynamics is a widely used and successful method for reconstructing the free‐energy surface of complex systems as a function of a small number of suitably chosen collective variables. This is achieved by biasing the dynamics of the system. The bias acting on the collective variables distorts the probability distribution of the other variables. Here we present a simple reweighting algorithm for recovering the unbiased probability distribution of any variable from a well‐tempered metadynamics simulation. We show the efficiency of the reweighting procedure by reconstructing the distribution of the four backbone dihedral angles of alanine dipeptide from two and even one dimensional metadynamics simulation. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009
Application of the topological analysis of the electronic localization function to archetypical [Pb(II)Ln]pcomplexes: The bonding of Pb2+revisited
Authors: van Severen Marie‐Céline , Gourlaouen Christophe , Parisel Olivier
Published: May 2009

The coordination of neutral ligands (L =OC, HCN,NH3,PH3,SH2, HNCOand H2O) to Pb2+is investigated and analyzed by means of the topological analysis of the Electronic Localization Function (ELF). It is shown that the mean charge density of theV(Pb) basin (〈ρ〉V(Pb)) can reach a ligand‐independent limiting value fromn= 6, a coordination number from which the [PbLn]2+complexes adopt holodirected structures. The investigations performed on anionic series (L = HS−,OH−,CN−, F−, Cl−, and Br−) lead to optimized stable structures in which the coordination number does not exceedn= 4, even in the presence of a model aqueous solvent. This different behavior with respect to the neutral ligand series is interpreted by means of natural populations and electrostatic repulsions. The main result of this contribution is that stable Pb(II) complexes could be those exhibiting reasonable values of 〈ρ〉V(Pb), namely those not exceeding the saturation plateau evidenced in the present piece of work. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010
Excess electron is trapped in a large single molecular cage C60F60
Authors: Wang Yin‐Feng , Li Zhi‐Ru , Wu Di , Sun Chia‐Chung , Gu Feng‐Long
Published: May 2009

A new kind of solvated electron systems, sphere‐shaped e−@C60F60 (Ih) and capsule‐shaped e−@C60F60 (D6h), in contrast to the endohedral complex M@C60, is represented at the B3LYP/6‐31G(d) + dBF (diffusive basis functions) density functional theory. It is proven, by examining the singly occupied molecular orbital (SOMO) and the spin density map of e−@C60F60, that the excess electron is indeed encapsulated inside the C60F60 cage. The shape of the electron cloud in SOMO matches with the shape of C60F60 cage. These cage‐like single molecular solvated electrons have considerably large vertical electron detachment energies VDE of 4.95 (Ih) and 4.67 eV (D6h) at B3LYP/6‐31+G(3df) + dBF level compared to the VDE of 3.2 eV for an electron in bulk water (Coe et al., Int Rev Phys Chem 2001, 20, 33) and that of 3.66 eV for e−@C20F20 (Irikura, J Phys Chem A 2008, 112, 983), which shows their higher stability. The VDE of the sphere‐shaped e−@C60F60 (Ih) is greater than that of the capsule‐shaped e−@C60F60 (D6h), indicating that the excess electron prefers to reside in the cage with the higher symmetry to form the more stable solvated electron. It is also noticed that the cage size [7.994 (Ih), 5.714 and 9.978 Å (D6h) in diameter] is much larger than that (2.826 Å) of (H2O)20− dodecahedral cluster (Khan, Chem Phys Lett 2005, 401, 85). © 2009 Wiley Periodicals, Inc. J Comput Chem 2010
Sterilization system for air purifier by combining ultraviolet light emitting diodes with TiO2
Authors: Huang Xiaohui , Wang Huaibing , Yin Song , Chen Xiaorong , Chen Wei , Yang Hui
Published: May 2009

BACKGROUND: Ultraviolet light emitting diodes (UV LEDs) were used as a light source in TiO2 photocatalysis because of their many advantages, such as, long life, safety, low pollution, etc. In this experiment, a light source panel was successfully fabricated with UV LEDs, the light intensities of which were relatively uniform.

RESULTS: The sterilization process comprised two steps. First, an aerosol was blocked by high efficient particulate air (HEPA) filter paper coated with TiO2 photocatalyst. Second, Staphylococcus aureus in the aerosol decreased gradually in the photocatalysis process of UV LED/TiO2. After 52 h irradiation all the S. aureus were killed.

CONCLUSION: The UV LED light source panel had a larger surface for irradiation than a mercury lamp. Thus, its sterilization efficiency was much better than that of traditional methods. The feasibility of UV LED/TiO2 for photocatalysis was proved. Copyright © 2009 Society of Chemical Industry
Lysosomal and alkaline phosphatase activity indicate macromolecule transport across the uterine epithelium in two viviparous skinks with complex placenta
Authors: Biazik Joanna M. , Thompson Michael B. , Murphy Christopher R.
Published: May 2009

In addition to water and small inorganic ions, macromolecules traverse the uterine epithelium in viviparous skinks to be absorbed by the developing fetus. In some species of lizards with complex placenta, the paracellular pathway across the uterine epithelium becomes tighter and more highly regulated as gestation progresses, suggesting that the transcellular pathway may be an alternative route for molecules to travel across the epithelium. In this study, we identified an extensive formation of a lysosomal system in the apical region of uterine epithelial cells in the highly secretory omphaloplacental region of the skink placenta in two species from the Pseudemoia genus. We suggest that this lysosomal system assists apocrine secretion by digesting large macromolecules into smaller particles, allowing more effective transport across the plasma membrane of uterine epithelial cells. We also demonstrate alkaline phosphatase (AP) activity along the apical plasma membrane of uterine epithelial cells in the omphaloplacental region of skink uterus, an enzyme usually associated with active transport in secretory cells. Apocrine secretion, an extensive lysosomal system and AP activity, offer strong evidence that macromolecules are transported across uterine epithelium of the omphaloplacenta. Our study is the first to provide histochemical evidence of macromolecular transport across this region of the placenta in two species of skinks from the genus with the most complex placenta described in Australia. J. Exp. Zool. (Mol. Dev. Evol.) 312B:817–826, 2009. © 2009 Wiley‐Liss, Inc.
Cinnoline chemistry. XI. The ultraviolet spectra of halogen substituted 4‐hydroxy‐ and 4‐mercaptocinnolines
Authors: Shoup Regitze R. , Castle Raymond N.
Published: May 2009

The ultraviolet spectra of a series of 4‐hydroxy‐ and 4‐mercaptocinnolines substituted with fluorine, chlorine or bromine in the 5‐, 6‐, 7‐ and 8‐position have been obtained in absolute methanol solution between 200 and 500 mμ. The spectra were used, to make structural assignments for the products of cyclization from mesoxalyl chloride, m‐fluoro‐and m‐bromophenylhydrazones.
Structure of products from reactions of phosphorus pentachloride with phenyl salicylate and 2‐hydroxybenzophenone; related compounds. p31 N.M.R. and chemical studies
Authors: Pinkus A. G. , Waldrep P. G. , Ma S. Y.
Published: May 2009

The compounds obtained from the reactions of phenyl salicylate and 2‐hydroxybenzo‐phenone with phosphorus pentachloride have been shown to have structures I A and II A, respectively, rather than alternative heterocyclic structures on the basis of the comparison of the P31 chemical shifts with appropriate reference compounds and additional chemical evidence. Compound I reacts with two equivalents of phenol in the presence of two equivalents of triethylamine to form mainly compound VIII (substitution on phosphorus). Structure VIII is confirmed via P31 n.m.r. and IR spectra and the fact that partial hydrolysis forms the same compound (VII) that is obtained from the reaction of compound III with phenol (only phosphorus substitution possible). A mechanism with initial reaction of phosphorus pentachloride (as tetrachlorophosphonium ion) on the phenolic hydroxyl is postulated on the basis of the available evidence. The P31 chemical shifts for compounds XIV A and XV A confirm these structures as heterocyclic in accord with previous chemical evidence. Structure XIV A is of historical importance as one of the first three cyclic structures ever published in the classical paper in which Couper announced his structural theory of organic chemistry.
Reduction products of 2‐pyridylmethylene‐1‐indanones. Indanols and indenoindolizines
Authors: Sam Joseph , Alwani Dru W. , Aparajithan K.
Published: May 2009

Several 2‐pyridylmethylene‐1‐indanones (I) were prepared and reduced to 2‐pyridyl‐methyl‐1‐indanones (II). The reductive cyclization of 5, 6‐dimethoxy‐ and 6‐hydroxy‐5‐methoxy‐2‐pyridylmethylene‐1‐indanone gave the corresponding 5a, 6, 6a, 7, 8, 9, 10, 11a‐octahydroindeno[2, 1‐b]indolizines (X).
A novel 7,6,5‐ring system: Triazolobenzoxazepinone
Authors: Wood Clair G. , Geertsema Abel , Freeburg Linnea , Reardon Edward J. , Jurgens Harold R. , Clapp Leallyn B.
Published: May 2009

A new ring system, a triazolobenzoxazepinone, has been synthesized in which the conformation of the 7‐membered ring is rather rigidly imposed by the system. The conformation of the intermediates, nitro‐ and aminobenzoxazepinones, appear to be more sterically hindered than any precursors of the 7, 6‐ring system. The formation of the 7,6‐ and 7,6,5‐ring systems and the preceding transition states must therefore be sterically accelerated through regulation of rotational conformation.
New reactions of pyrroles. II. Preparation and reactions of pyrroleglyoxyloyl derivatives
Authors: Archibald John L. , Freed Meier E.
Published: May 2009

Pyrroles treated with oxalyl chloride produced pyrroleglyoxyloyl chlorides. Unsubstituted and C‐alkyl pyrroles gave products stable only at low temperatures. N‐Substitution or presence on the ring of an electron withdrawing group (e.g. carbonyl) increased the stability of the glyoxyloyl chlorides considerably. Substitution occurred at the 2‐position unless both 2 and 5 positions of the pyrrole nucleus were blocked. When this was the case substitution occurred slowly at position 3.
Some reactions of 3,6‐disubstituted‐s‐tetrazines; A new synthesis of the 1,2,4‐triazine ring system
Authors: Roffey Patrick , Verge John P.
Published: May 2009

The synthesis of variously substituted pyridazines by 1,4‐cycloaddition of cyclic enol ethers, esters, and some electron‐rich acetylenes is described. Extension of the scheme to include some imino‐ethers as dienophiles resulted in the synthesis of 1,2,4‐triazine derivatives.
Pyrazoles VI: The electron‐releasing capacity of the pyrazole ring
Authors: Wijnberger C. , Habraken Clarisse L.
Published: May 2009

UV and PMR spectral data and CO frequencies of some methylpyrazoles containing in the 3‐, 4‐ or 5‐position, a formyl‐, acetyl‐ or ethoxycarbonyl group are reported. These data confirm earlier conclusions that, in particular, the 4‐pyrazolyl group acts as an electron releasing group. The syntheses of a number of formyl‐, acetyl‐ and ethoxycarbonyl pyrazoles are described. In addition, some 4‐dicyanovinyl‐ and 4‐tricyanovinylpyrazoles were investigated.
Studies on the syntheses of heterocyclic compounds. Part CCCXXX Synthesis of a homocularine type compound
Authors: Kametani T. , Terui T.
Published: May 2009

An intramolecular Ullmann reaction of bromophenethylisoquinoline (X) was investigated in order to obtain the homocularine type compound (V), which could be one of the potential alkaloids belonging to 1‐phenethylisoquinoline series. Methylation of the phenolic 8‐hydroxyisoquinoline (XVIII), one of the position isomers which was separated by silica gel chromatography from a mixture of 6‐hydroxy‐ (XVII) and 8‐hydroxyisoquinoline (XVIII) prepared as usual, gave the starting material (X), which was cyclized by the Ullmann reaction in the presence of cupric oxide. The structure of our objective homocularine (V) was assigned from spectral data.
Synthesis of some 5H‐imidazo[4,5‐e]‐as‐triazin‐6‐(7H)ones (6‐azapurin‐8‐ones)
Authors: Yoneda Fumio , Higuchi Masatsugu , Nitta Yoshihiro
Published: May 2009

Treatment of 1,3‐dialkyl‐7‐azalumazine derivatives with alcoholic sodium hydroxide caused a benzylic acid type rearrangement followed by decarboxylation and oxidation by air to give the corresponding 5,7‐dialkyl‐5H‐imidazo[4,5‐e]‐as‐triazin‐6‐(7H)ones (7,9‐dialkyl‐6‐azapurin‐8‐ones).
Pyrazoles by dealkylation of pyrazolium salts
Authors: Cross Barrington , Arotin Robert L. , Ruopp Charles F.
Published: May 2009

A rapid, convenient conversion of 1,2‐dimethylpyrazolium salts (1) to 1‐methylpyrazoles (2) is accomplished in piperidine or 3‐methylpiperidine at temperatures ≥ 106°. This demethylation represents a particularly useful procedure for the synthesis of 3‐ and 5‐substituted aminopyrazoles, which are not readily obtainable by other methods. The 50:50 mixture of piperidinopyrazole isomers 2b can be obtained directly by treating 3‐chloro‐1,2‐dimethyl‐5‐phenylpyrazolium iodide (3b) with piperidine in ethanol at 106°.
Studies on cycloimmonium ylids. Synthesis of some new 2,4,6‐triaryl‐substituted pyridinesviapyridinium, picolinium and isoquinolinium ylids
Authors: Tewari R. S. , Misra N. K. , Dubey A. K.
Published: May 2009

Reaction of pyridinium phenacylids and their picolinium and isoquinolinium counterparts with substituted benzylideneacetophenones gave a wide variety of 2,4,6‐triaryl‐substituted pyridines which are expected to have some potential biological activities. Ammonium acetate in glacial acetic acid was used as the cyclization agent. The structures of resulting pyridines are supported by nmr and ir spectral data.
Studies on tertiary amine oxides. LXVIII. . Reactions of aromatic N‐oxides with 2‐substituted 2‐oxazolin‐5‐ones in the presence of acetic anhydride
Authors: Yousif Mohammed M. , Saeki S. , Hamana M.
Published: May 2009

Quinoline l‐oxides 1a‐f readily react with 2‐phenyl‐ and 2‐methyl‐2‐oxazolin‐5‐ones, 2a and 2b, in the presence of acetic anhydride to afford 2‐substituted 4‐(2‐quinolyl)‐2‐oxazolin‐5‐ones 3a‐h in good yields. Hydrolysis of 3a‐f with 10% hydrochloric acid under refluxing conditions gives the corresponding 2‐amino‐methylquinoline dihydrochlorides 5a‐e or monohydrochloride 5f also in good yields. Similar results are obtained from reactions of isoquinoline 2‐oxide 9 with 2a,b under the same conditions.
Synthesis of 2,2a,4,5‐tetraazabenz[cd] azulene derivatives
Authors: Imafuku Kimiaki , Sumio Miyuki , Matsumura Hisashi
Published: May 2009

3‐Methyl‐1,8‐dihydrocycloheptapyrazol‐8‐one hydrazone (5) reacted with triethyl ortho‐formate, orthoacetate and orthopropionate to afford 2,2a,4,5‐tetraazabenz[cd]azulene derivatives (7a‐c). 3‐Methyl‐ (7b) and 3‐phenyl‐substituted compounds (7d) were also obtained by the reactions of 5 with acetyl and benzoyl chlorides, respectively.
The synthesis of deuterium labeled macrocyclic polyethers (crown ethers)
Authors: Whitney Richard R. , Jaeger David A.
Published: May 2009

Five tetradeuterated analogues (1a, 1b, 1c, 1d, and 1e) of 3,6,9,12,15‐pentaoxa‐21‐aza‐bicyclo[15.3.1]heneicosa‐1(21),17,19‐triene (pyridyl‐18‐crown‐6, 1) have been prepared corresponding to the five unique protonated carbon atoms of the polyether cycle. Deuterium labeling was ≥ 99% for four of the compounds and ≥ 97% for the other (1a).
Synthesis of 1‐(5‐phenyl‐2H‐tetrazol‐2‐ylacetyl)‐4‐substituted thiosemicarbazides as possible antiinflammatory agents
Authors: Raman Krishna , Parmar Surendra S. , Singh Shiva P.
Published: May 2009

A series of 1‐(5‐phenyl‐2H‐tetrazol‐2‐ylacetyl)‐4‐substituted thiosemicarbazids were prepared as possible antiinflammatory agents. Their antiproteolytic activity was reported.
Synthesis of pyrano[3,4‐c]pyrazole and pyrazolo[3,4‐d][1,2]diazepine derivatives
Authors: Migliara Onofrio , Sprio Vincenzo
Published: May 2009

By the action of thionyl chloride on 3(5)‐R‐4‐phenacylpyrazole‐5(3)‐carboxylic acid (3c,d), 3‐R‐5‐phenylpyrano[3,4‐c]pyrazole‐7‐(1H)ones (4c,d) were obtained. When 4c,d were treated with hydrazine hydrate followed by refluxing in ethanol containing acetic acid, 4,7‐dihydro‐3‐R‐5‐phenylpyrazolo[3,4‐d][1,2]‐diazepin‐8‐(1H)ones (6c,d) were formed. Compounds 6c,d, in turn, were refluxed in ethanol saturated with hydrochloric acid to yield 6‐amino‐1,6‐dihydro‐3‐R‐5‐phenyl‐7H‐pyrazolo[3,4‐c]pyridin‐7‐ones (7c,d). Compounds 7c,d could be obtained directly from 5c,d. The starting materials 3c,d were prepared by hydrolysis of the oxime of 3(5)‐R‐4‐phenacyl‐5(3)carboalcoxypyrazoles (1a,b). Structural assignments rested on correct elemental analysis, molecular weights determined by mass spectrometry, and spectroscopic evidence.
Alkylation des pyrimidines en catalyse par transfert de phase
Authors: Hedayatullah Mir
Published: May 2009

Nous rapportons ici, la première étude concernant l'alkylation simple et efficace, en catalyse par transfert de phase, de dianions pyrimidiques ambidents dérivés de l'uracile, de la thymine, du nitro‐5 uracile, du fluoro‐5 uracile, du chloro‐6 uracile, de la tétrahydro‐1,2,3,4 dioxo‐2,4 quinazoline, conduisant sélectivement et avec de hauts rendements, aux dérivés N1,N3‐dialkylés correspondants.
Studies in the heterocyclic series. XIX. Synthesis of 1,4‐diazaphenothiazine and its benzo derivatives
Authors: Okafor Charles O.
Published: May 2009

1,4‐Diazaphenothiazine, the parent compound of this heterocyclic ring has now been prepared from 2,3‐dichloropyrazine and 2‐aminothiophenol. Replacement of 2,3‐dichloropyrazine with 2,3‐dichloroquinoxaline and 2,3,6‐trichloroquinoxaline led to the corresponding 1,4‐diazabenzo[b]phenothiazine in good yields. Structural assignments were made by spectroscopic studies and by certain chemical transformations.
Pyridinethiones. VI. The synthesis of 2H‐Thiopyrano[2,3‐b]pyridin‐2‐ones
Authors: Christensen Mads ChR. , Becker Jan
Published: May 2009

A general and versatile method for the preparation of 2H‐thiopyrano[2,3‐b]pyridin‐2‐ones is described. The starting materials, the β, β‐disubstituted vinyl‐1‐t‐butyl‐2‐(1H)pyridinethiones were prepared from the synthon 3‐formyl‐1‐t‐butyl‐2‐(1H)pyridinethione by condensation. 13H nmr spectra showed the vinyl double bond of the condensation products to have the trans configuration with the smallest group close to the sulfur atom. Some reactions of these new azaanalogues of thiocoumarins are reported.
Synthèse de dérivés indoliques substitués in 7
Authors: Ta Kim Phieo , Guilard Roger , Samreth Soth , Sornay Roland
Published: May 2009

La synthèse et quelques aspects de la réactivité chimique d'acétyl‐7, de benzoyl‐7 et de bromo‐7 indoles sont décrits.
Derivatives of 5,6‐Dimethoxybenzo[b]thiophen‐2‐(3H)one. Synthesis of 5,6‐Dimethoxybenzo[b]thieno[2,3‐b]quinoline
Authors: Camoutsis Charalabos , Catsoulacos Panayotis , Salem G. , Terzis A. , Filippakis S. E.
Published: May 2009

Substituted‐3‐benzylidenebenzo[b]thiophen‐2‐ones have been synthesized. 5,6‐Dimethoxybenzo[b]‐thiophen‐2‐(3H)one with aniline and triethyl orthoformate gives the 3‐anilinomethylene compound, which can be hydrolysed to give the corresponding 3‐hydroxymethylene derivative. Dimethoxybenzo[b]thieno[2,3‐b]‐quinoline has been synthesized.
Synthesis and antifolate activity of 8,10‐dideazaminopterin
Authors: Degraw Joseph I. , Kelly Lawrence F. , Kisliuk Roy L. , Gaumont Yvette , Sirotnak Francis M.
Published: May 2009

A synthesis of 8,10‐dideazaminopterin, using 2,4‐diamino‐6‐bromomethyl‐8‐deazapteridine (2) as a key intermediate, is described. Condensation of the triphenylphosphinylide derived from 2 with p‐formylbenzoyl‐L‐glutamate afforded a 9,10‐dehydro‐8,10‐dideazaminopterin ester intermediate 5. Hydrogenation of the olefinic linkage and subsequent hydrolysis of the glutamate ester gave the title compound. 8,10‐Dideazaminopterin was a potent growth inhibitor of folate dependent bacteria. It was 16 times more potent then methotrexate as an inhibitor of dihydrofolate reductase derived from L1210 leukemia cells, and showed strong activity against L1210 in mice.
Synthesis and characterization of ethidium analogs: Emphasis on amino and azido substituents
Authors: Firth William J. , Watkins Charles L. , Graves David E. , Yielding Lerena W.
Published: May 2009

A series of eight ethidium derivatives has been synthesized in which the substituents at R3 and R8 have been varied with hydrogen, azido and amino functions. Three of these compounds are new and their synthesis and characterization by uv‐visible, ir and 1H nmr spectroscopy are presented. The synthesis and characterization of the other compounds are also given for comparison, because the compounds served as precursors, or the synthetic route undertaken for these compounds differed from that reported previously.
The synthesis of all of the dimethyldibenzothiophenes and monoethyldibenzothiophenes
Authors: Tedjamulia Marvin L. , Tominaga Yoshinori , Castle Raymond N. , Lee Milton L.
Published: May 2009

The synthesis of all four isomers of the monoethyldibenzothiophenes and all of the sixteen isomers of the dimethyldibenzothiophenes has been accomplished.
Polycyclic nitrogen compounds. Part iii. Synthesis of 3,3a‐dihydrothiazolo[3,4‐α]quinoxalin‐4‐ones
Authors: Adegoke E. A. , Alo Babajide
Published: May 2009

New tricyclic quinoxalinone skeletons with bridge‐head nitrogen atoms and containing sulphur in a fully‐reduced five‐membered ring C were obtained. 3,3a‐Dihydrothiazolo[3,4‐α]quinoxalin‐4‐ones I‐III were prepared by metal‐acid reductive cyclisation of N‐(nitrophenyl)‐ and N‐(dinitrophenyl)thiazolidine‐4‐carboxylic acids IVa,b,c. Attempts to obtain the skeleton by selective hydrogen transfer reductive cyclisation of the corresponding esters Va,b,c were unsuccessful.
Research on heterocyclic compounds. XIII. Synthesis of 4,5‐dihydro‐5‐oxo‐3‐isoxazoleacetic acid and related compounds
Authors: Abignente Enrico , De Caprariis Paolo , Liguori Michele
Published: May 2009

Some new 4,5‐dihydro‐5‐oxoisoxazole derivatives were synthesized as part of a study to prepare potential antiinflammatory agents. The reaction of the diethyl ester of 3‐oxopentanedioic acid with hydroxylamine afforded the 3‐hydroxyimino derivative, which was then cyclized to the title compound. This reacted with diazomethane to give a couple of isomeric methyl derivatives, namely methyl 2,5‐dihydro‐2‐methyl‐5‐oxo‐3‐isoxazoleacetate and methyl 5‐methoxy‐3‐isoxazoleacetate. Reaction of these compounds with ammonia gave the corresponding acetamides. All compounds were characterized by elemental analysis, uv, ir, and 1H‐nmr spectra.
An unexpected preparation of 4‐oxo‐2H‐1,3‐benzothiazines
Authors: Golec Frederick A. , Lee Paul , Lloyd John R.
Published: May 2009

Treatment of compound N,N‐(dithiobis(3‐chloro‐2,1‐phenylene)dicarbonylbis (N‐cyclopentylglycine)diethyl ester (3) with methanolic sodium hydroxide does not produce the expected hydrolysis product N,N‐(dithiobis‐(3‐chloro‐2,1‐phenylene)dicarbonylbis (N‐cylcopentylglycine) (4) but yields a mixture of compounds 8‐chloro‐3‐cyclopentyl‐3,4‐dihydro‐4‐oxo‐2H‐1,3‐benzothiazine‐2‐carboxylic acid (6) and N‐(3‐chloro‐2‐mercaptobenzoyl)‐N‐cyclopentylglycine (7). This unexpected observation has the potential of a new heterocyclic synthesis method for the 4‐oxo‐2H‐1,3‐benzothiazine class of compounds.
Novel synthesis of pyrido[2,1‐f]‐as‐triazinium system and its zwitterionic derivatives. Different reactivities of 1‐ and 3‐olates with electrophiles
Authors: Bátori S. , Juhász‐Riedl Z. S. , Sándor P. , Messmer A.
Published: May 2009

A novel convenient synthesis of the title system has been developed using α‐carbonyl derivatives of N‐aminopyridine and formamide (and its substituted derivatives) in the presence of phosphorus oxychloride or boron trifluoride. Quaternization of zwitterionic 1‐ and 3‐olates (4a, 4b; 11) with soft and hard methylating agents has been studied. Mechanistic suggestion are given to explain the formation of the different (solely N‐Me; N‐Me and O‐Me; solely OMe) products.
Reaction of sulfenes with heterocyclic N,N‐disubstituted α‐aminomethyleneketones. XII. Synthesis of [1]benzothiepino[4,5‐e][1,2]oxathiin derivatives
Authors: Menozzi Giulia , Bargagna Alberto , Mosti Luisa , Schenone Pietro
Published: May 2009

The 1,4‐cycloaddition of sulfene to N,N‐disubstituted (E)‐4‐aminomethylene‐3,4‐dihydro[1]benzothiepin‐5(2H)‐ones I occurred only in the case of aliphatic N,N‐disubstitution to give in good yield 4‐dialkylamino‐3,4,5,6‐tetrahydro[1]benzothiepino[4,5‐e][1,2]oxathiin 2,2‐dioxides, which are derivatives of the new heterocyclic system [1]benzothiepino[4,5‐e][1,2]oxathiin. Also the reaction of I with chlorosulfene occurred only in the case of aliphatic N,N‐disubstitution to afford chiefly trans‐4‐dialkylamino‐3‐chloro‐3,4,5,6‐tetrahydro‐[1]benzothiepino[4,5‐e][1,2]oxathiin 2,2‐dioxides III in satisfactory yield. Adducts III were dehydrochlorinated with DBN to 4‐dialkylamino‐5,6‐dihydro[1]benzothiepino[4,5‐e][1,2]oxathiin 2,2‐dioxides in good yield.
Pyrrolidine‐2,3‐dione, 1‐allylpyrrolidine‐2,3‐dione and 1‐ethoxypyrrolidine‐2,3‐dione
Authors: Sundberg Richard J. , Pearce Bradley C. , Laurino Joseph P.
Published: May 2009

Authentic pyrrolidine‐2,3‐dione has been prepared by two different routes. It is shown that the material previously reported is actually a hydrolysis product, 4‐amino‐2‐oxobutyric acid. 1‐Allyl‐ and 1‐ethoxypyrroli‐dine‐2,3‐dione have been prepared as N‐protected pyrrolidine‐2,3‐diones potentially useful in synthesis.
Reinvestigation of the reported preparation of 3‐(4‐nitrophenyl)thiazolo[2,3‐c][1,2,4]triazepines
Authors: Peet Norton P. , Sunder Shyam
Published: May 2009

2‐(1H‐Pyrazol‐1‐yl)‐4‐(4‐nitrophenyl)thiazoles 2a and 2b, resulting from the condensation of 2‐hydrazino‐4‐(4‐nitrophenyl)thiazole (1) and acetylacetone and dibenzoylmethane, respectively, were previously [4] misas‐signed as 3‐(4‐nitrophenyl)thiazolo[2,3‐c][1,2,4]triazepines 3a and 3b. The assignments were corrected by authentic syntheses of 2a and 2b from 2‐chloro‐5‐(4‐nitrophenyl)thiazole (6) and 3,5‐dimethyl‐1H‐pyrazole and 3,5‐diphenyl‐1H‐pyrazole, respectively. In addition, the mass spectrum of 2a is reported. An apparent ionmolecule reaction produces an ion of significant intensity at m/e 394.
Modification of pyridine‐3‐carboxamide (nicotinamide) by radical substitution
Authors: Tada Masaru , Yokoi Yurie
Published: May 2009

Pyridine‐3‐carboxamide (1) was reacted with alkyl radicals to give mono‐, di‐, and tri‐alkylated products. The t‐butyl radical gives only 6‐t‐butylpyridine‐3‐carboxamide (4a). The reactivity decreases in the order of t‐butyl, isopropyl, and ethyl radicals. The product 4a reacts further with the 2‐phthalimidoethyl radical to give 2‐ and 4‐substituted products 9 and 10, which were transformed into tetrahydronaphthyridinone derivatives 11 and 12.
Synthesis of novel dihydro‐2H‐1,2,4‐oxadiazin‐5(6H)‐ones
Authors: Ürögdi László , Kisfaludy Lajos , Patthy Ágnes , Moravcsik Ernö , Tüdös Helga , Tegyei Zsuzsanna , Ötvös László
Published: May 2009

The title compounds 4 were synthesized via the acid‐catalyzed reaction of α‐(acylaminooxy)carboxylic acid amides 6 with carbonyl compounds, and controlled catalytic hydrogenation of the resulting 2‐benzyloxy‐carbonyldihydro‐2H‐1,2,4‐oxadiazin‐5(6H)‐ones 7 (R6 = PhCH2O).
Novel resolution of chiral lactams
Authors: Ürögdi László , Kisfaludy Lajos , Patthy Ágnes , Vezér Csilla
Published: May 2009

A practical method of resolving chiral lactams, e.g. 1, has been evolved, based on the hydroxymethylation of the lactam, followed by esterification of the product 2 with an optically active N‐protected amino acid derivative, e.g. N‐benzyloxycarbonylphenylalanine pentafluorophenyl ester 3. Chromatographic separation of the unreacted hydroxymethylated lactam 2 and the ester 4 and subsequent dehydroxymethylation of the former and aminolysis of the latter afforded pure enantiomer, (R)‐1 and (S)‐1.
Differentiation of isomeric 1‐, 3‐ and 7‐deazaadenosines by electron ionization mass spectrometry
Authors: Reddy A. Mahender , Reimer Mark L. J. , Schram Karl H. , Grifantini Mario , Cristalli Gloria
Published: May 2009

The low and high resolution electron ionization mass spectra of 1‐deazaadenosine, 3‐deazaadenosine and 7‐deazaadenosine are reported. Fragmentation pathways and ion structures are proposed with the aid of linked‐scan, daughter‐ion spectra. Results indicate that the N‐3 position of the purine ring serves as an important acceptor site in fragmentation processes involving hydrogen transfer from the sugar to the base. A mixture analysis of the trimethylsilyl derivatives of adenosine, 1‐, 3‐ and 7‐deazaadenosine by combined gas chromatography/mass spectrometry is also described.
S,N‐heterocycles 2. A convenient, one‐pot synthesis of 2‐alkylamino‐4H‐1,3,4‐benzothiadiazines
Authors: Sanemitsu Yuzuru , Manabe Akio , Kawamura Shinichi , Satoh Junichi , Tanabe Yoo
Published: May 2009

2‐Alkylamino‐4H‐1,3,4‐benzothiadiazines 3 are prepared in a one‐pot synthesis from 1‐phenyl‐3‐thiosemi‐carbazides 1 and bromine through an oxidative cyclization.
The synthesis of aryl 4‐nitro‐5‐imidazolyl sulfone radiation sensitizers sterically protected against glutathione reaction
Authors: Egolf Roger A. , Heindel Ned D.
Published: May 2009

2,6‐Disubstituted aryl 1‐methyl‐4‐nitro‐5‐imidazolyl sulfones 4 and aryl 1‐neopentyl‐2‐tert‐butyl‐4‐nitro‐5‐imidazolyl sulfones 10 have been synthesized and tested as radiation sensitizers of hypoxic carcinoma cells. These sterically crowded imidazoles show decreased displacement reactivity with glutathione at C‐5, a major metabolic reaction known to deplete effective plasma drug levels in traditional aryl imidazolyl sulfone radiation sensitizers.
Selective N‐1 alkylation of unsymmetrically substituted pyrazoles
Authors: Malhotra Nageshwar , Fält‐Hansen Birgitte , Becher Jan
Published: May 2009

A series of C‐substituted pyrazoles have been N‐alkylated. The alkylation occurs preferentially at the N‐1 position when a tert‐butyl group is present at the pyrazole C‐3 position.
A simple aza wittig‐mediated pyrimidine annulation reaction
Authors: Taylor Edward C. , Patel Mona
Published: May 2009

Treatment of heterocyclico‐aminonitriles ando‐aminoesters1a‐5awith dibromotriphenylphosphorane gives iminophosphoranes1b‐5bwhich undergo a facile aza‐Wittig reaction at room temperature with phenyl isocyanate to provide the carbodiimides1c‐5c. Treatment of the latter intermediates with ammonia leads to intramolecular ring closure of the initially formed guanidines to provide the fused 4‐aminopyrimidines and 4(3H)‐pyrimidinones1d‐Sd.
Action of (2‐benzothiazolyl)methyllithium with organic polar functions
Authors: Costa Maria Virginia , Brembilla Alain , Roizard Denis , Lochon Pierre
Published: May 2009

(2‐Benzothiazolyl)methyllithium reacts quickly at low temperature (‐78°) with a variety of organic electrophiles like aldehydes, ketones, carboxylic esters, nitriles and acyl chlorides. Such reactions lead to an easy introduction of alcohol, keto‐enol or amine‐enamine functional groups in extracyclic position with a stereoselective preference. These polyfunctional compounds whose synthesis is difficult by other pathways, are interesting, in particular, because of their ability to form intramolecular hydrogen bonds.
On the synthesis of geminally functionalized heterocyclic aminocarboxylic acid esters
Authors: Coutouli‐Argyropoulou E. , Thessalonikeos E.
Published: May 2009

The title compounds 5 can be easily obtained by two alternative procedures: 1,3‐dipolar cycloaddition to benzamidocinnamates 3 prepared by methanolysis of the corresponding oxazolones 1 or methanolysis of the spirooxazolones 4 synthesized by 1,3‐dipolar cycloaddition to oxazolones 1. Both reaction sequences show the same stereo and regioselectivity.
An entry into the novel tetracyclic system 6H‐pyrido[1′,2′:4,5]pyrazino[1,2‐a]benzimidazole. Synthesis and conformational study of the 1,2,3,4,13,13a‐hexahydro‐3,3‐ethylenedioxy and 3‐ketone derivatives
Authors: Compernolle Frans , Saleh M.‐Ashty , Toppet Suzanne , De Buysser Wim , Hoornaert Georges
Published: May 2009

The synthesis of the tetracyclic title compounds, acetal 5 and ketone 6, is presented. The key step, formation of the imidazole ring to give compound 5, involved the acid catalysed dehydration of the 2‐(o‐aminophenyl)lactam 7b. This was generated from lactam 4 via N‐substitution with o‐nitrofluorobenzene and reduction of the nitro group. Deprotection of acetal 5 afforded ketone 6 which through a temperature dependence study of vicinal coupling constants was shown to occur as an equilibrium of trans‐ and cis‐fused forms A and B.
2‐Aryl‐substituted 4H‐3,1‐benzoxazin‐4‐ones as novel active substances for the cardiovascular system
Authors: Rose Ulrich
Published: May 2009

4H‐3,1‐Benzoxazin‐4‐ones of the structural types 3 and 4 are accessible by cyclization reactions. The introduction of the phosphonate group was achieved by way of Wohl‐Ziegler bromination and subsequent Michaelis‐Arbuzow reaction with a trialkyl phosphite. Pharmacological investigations on isolated left atria, ileum specimens, and Langendorff hearts as well as in vivo circulatory studies on anesthetized rats revealed that the phosphonates 4 exert calcium antagonistic effects. Whereas 2‐(arylvinyl)benzoxazinones gave rise to pronounced negative inotropic effects, compound 3e exhibited relaxing effects on smooth musculature in particular and markedly increased the coronary flow through Langendorff hearts.
Improved syntheses of thieno[2,3‐b]‐ and [3,2‐b]‐fused naphthyridines
Authors: Björk Patrick , Aakermann Torunn , Hörnfeldt Anna‐Britta , Gronowitz Salo
Published: May 2009

The preparation of eight isomeric thieno[2,3‐b]‐ and [3,2‐b]‐fused naphthyridines [1] was improved through the Pd(0) catalyzed cross‐coupling of 3‐formyl‐4‐iodopyridine, 2‐formyl‐3‐iodopyridine, 3‐bromo‐4‐formylpyridine and 2‐bromo‐3‐formylpyridine with t‐butyl N‐(2‐trimethylstannyl‐3‐thienyl)car‐bamate and t‐butyl N‐(3‐trimethylstanny‐2‐thienyl)carbamate.
Synthesis of 2H‐pyrano[2,3‐b]quinolines. Part II. Preparation and 1H‐nmr investigations of 4‐hydroxy‐2‐methyl‐3,4‐dihydro‐2H‐pyrano[2,3‐b]quinolines
Authors: Cziáky Zoltán , Szabó Zoltán
Published: May 2009

Diastereoisomers of 4‐hydroxy‐2‐methyl‐3,4‐dihydro‐2H‐pyrano[2,3‐b]quinolines 8 and 9 were synthesized starting from the appropriate 2‐chloroquinoline‐3‐carboxaldehydes 1. The relative configuration of the 1,3‐diol intermediates 4 and 5 was determined on the basis of the 13C‐nmr spectra of their acetonides. The relative stereochemistry of title compounds was confirmed by using homonuclear NOE and selective decoupling experiments, as well as by analysis of the coupling patterns observed in their 1H‐nmr spectra.
A versatile synthesis of functionalised 2‐aminoquinolines by mercury controlled cyclisation of 2‐vinylphenylthioureas
Authors: Wiggall Kenneth J. , Richardson Stewart K.
Published: May 2009

4‐(4‐Hydroxyphenyl)‐2‐phenylamino‐1,8‐naphthyridine was prepared via cyclisation of N‐phenyl‐N′‐3‐(4‐hydroxyphenethen‐1‐yl)pyridin‐2‐ylthiourea in the presence of mercuric oxide. Derivatives of 4‐methyl‐2‐aminoquinolines were prepared in a similar manner from 2‐vinylphenylthioureas.
Syntheses of new 2‐hydroxythiazol‐5‐yl and 3‐hydroxy‐1,2,4‐triazol‐5‐ylphosphonic acids as potential cyclic spatial mimics of glyphosate
Authors: Anderson D. Keith , Deuwer David L. , Sikorski James A.
Published: May 2009

A low temperature lithiation/phosphorylation procedure has been successfully applied to 2‐methoxythia‐zole and 1‐substituted 3‐alkoxy or 3‐silyloxy‐1H‐1,2,4‐triazoles to provide a series of novel hydroxy‐substituted heterocyclic phosphonates and phosphonic acids as potental cyclic spatial mimies of glyphosate.
The potential utility of homoacylation through the pummerer rearrangement‐intermediates. A direct approach to the 1‐benzene‐sulfonyl‐4‐keto‐8‐methoxy‐1,2,2a,3,4,5‐hexahydrobenz‐[cd]indole via intra‐homoacylation
Authors: Stamos Ioannis K. , Kotzamani Heleni K.
Published: May 2009

A convenient synthesis of tricyclic ketone 7 is described based on an intra‐homoacylation via a Pummerer intermediate. The indole 3, was both annelated and functionalized for the next step through its protected indoline 4 using the single reagent dimsyllithium. The produced sulfoxide 5 generated the thionium ion intermediate upon treatment with trifluoroacetic anhydride, which subsequently underwent intramolecular cyclization to ketone 6 in the presence of a Lewis acid.
Synthesis of some new imidazo[1,2‐a]pyrimidin‐5(1H)‐ones as potential antineoplastic agents
Authors: Badawey El‐Sayed , Kappe Thomas
Published: May 2009

Some substituted imidazo[1,2‐a]pyrimidin‐5(1H)‐ones have been synthesized via the reaction of 2‐aminoimidazole sulfate with some β‐keto esters, diethyl ethoxymethylenemalonate and ethyl ethoxymethylenecyanoacetate. Several compounds were screened for their in vitro antineoplastic and anti‐HIV activity but were inactive.
Regioselective conversion of 3‐cyano‐6‐hydroxy‐2‐pyridones into 3‐cyano‐6‐amino‐2‐pyridones
Authors: Katritzky Alan R. , Rachwal Stanislaw , Smith Terrance P.
Published: May 2009

The reaction of a tautomeric mixture of 1‐butyl‐1,2‐dihydro‐6‐hydroxy‐4‐methyl‐2‐oxopyridine‐3‐carbonitrile and its 2‐hydroxy‐6‐oxo analog with phosphorus oxychloride gave 1‐butyl‐6‐chloro‐1,2‐dihydro‐4‐methyl‐2‐oxopyridine‐3‐carbonitrile (68%) and 1‐butyl‐2‐chloro‐1,6‐dihydro‐4‐methyl‐6‐pyridine‐3‐car‐bonitrile (3%). Both chloropyridones were converted to their corresponding aminopyridones by reaction with liquid ammonia. Strong support for the molecular structure of 6‐amino‐1‐butyl‐1,2‐dihydro‐4‐methyl‐2‐oxopyridine‐3‐carbonitrile was obtained on the basis of nmr techniques.
Antineoplastic anthraquinones. II. Design and synthesis of 1,2‐Heteroannelated anthraquinones
Authors: Chang Pong , Chen Chia‐Fu
Published: May 2009

Based on the “2‐phenyinaphthalene‐type” structural pattern hypothesis, a number of heterocycle‐fused anthraquinones were designed by taking morindaparvin‐A (2a) as the lead structure. The compounds we synthesized and tested for antineoplastic activity include 1,2‐alkylenedioxyanthraquinone, naphtho [2,3‐f]‐quinoxaline‐7,12‐dione, anthra[1,2‐d]imidazole‐6,11‐dione and naphtho[2,3‐f]quinoxaline‐7,12‐dione derivatives. Most of the synthesized anthraquinones possessed various degrees of anticancer activity. One of these compounds, 2‐chloromethyl‐1H‐anthra[1,2‐d]imidazole‐6,11‐dione (4b), exhibited cytotoxic activity against all tested human carcinoma cell lines.
Streptonigrin and related compounds. 6. Synthesis and activity of some quinoxaline analogues
Authors: Rao Koppaka V. , Rock Charles P.
Published: May 2009

Streptonigrin is an antitumor antibiotic with significant in vitro and in vivo antitumor activity spectrum. Besides the total syntheses, numerous syntheses of the partial structures have been carried out in order to assess the structural requirements for the activity. The present publication deals with the synthesis of selected quinoxalinequinones to study the effect of changes in the B‐ring of streptonigrin.

A convenient 3‐step synthesis of the required quinoxaline starting material that provides the necessary control of the desired substituent pattern is described. A series of 7‐amino‐6‐methoxy‐quinoxalinequinones were prepared in which substitution at 3‐ was varied (from H to Cl, OCH3, CN, COOCH3 and OH). A few selected 6‐aminoquinones (with 6‐NH2 and 6‐piperidinyl) were also prepared for comparison. The quinones (18) were tested in three different in vitro test systems: cytotoxicity to mouse leukemia (L‐1210) cells, antibacterial activity against Bacillus subtilis and inhibition of root growth. Several of the aminoquinones showed significant activity in comparison to that shown by streptonigrin.
Synthesis of 3‐methyl‐substituted pyrazolotriazolopyrimidin‐4‐one and pyrazolothiazolopyrimidin‐4‐one derivatives
Authors: Guccione Salvatore , Scolaro Luigi Monsù , Russo Filippo
Published: May 2009

As a part of a research on anti‐inflammatory analgesic compounds 3‐methyl substituted pyrazolotria‐zolopyrimidin‐4‐one and pyrazolothiazolopyrimidin‐4‐one derivatives were prepared by previously reported procedures. None of the compounds showed improved activity when compared with the previously reported unsubstituted analogs.
Synthesis and fluorescence properties of novel benzo[a]phenoxazin‐5‐one derivatives
Authors: Long Jiang , Wang Yong‐Mei , Matsuura Teruo , Meng Ji‐Ben
Published: May 2009

Thirteen, benzo[a]phenoxazin‐5‐one derivatives 3a‐m were synthesized from 4‐nitrosoaniline hydrochlorides 1a‐m and ethyl 1,3‐dihydroxynaphthoate 2 and their fluorescence properties were discussed in terms of the electronic effect of substituents. A coupling reaction was carried out with 6‐carbethoxy‐9‐N‐(2‐hydroxyethyl)‐N‐methylamino‐5H‐benzo[a]phenoxazin‐5‐one (3k) and acetyl‐DL‐alanine to afford N‐[(6‐carbethoxy‐5‐oxo‐5H‐benzo[a]phenoxazin)‐9‐yl]‐N‐methylaminoethylene acetyl‐DL‐alanine ester (4).
Synthesis and complete1Hand13C assignments of thiazolo[3,2‐a]quinolinium derivatives
Authors: Cox Osvaldo , Prieto José A. , Ramírez Lorna , Rodríguez Margarita , Martínez José R.
Published: May 2009

Several hitherto unknown thiazolo[3,2‐a]quinolinium salts derivatives were prepared and characterized. Two‐dimensional high field nmr methods were employed to make complete assignments of the proton and carbon nmr spectra for these compounds.
Electrochemical and electron spin resonance studies of selected benzazolo[3,2‐a]quinolinium salts
Authors: Cox Osvaldo , Dumas José A. , Rivera Luis A. , García Carmelo , Alegria Antonio E.
Published: May 2009

The electrochemical reduction of the chloride or perchlorate salts of benzazolo[3,2‐a]quinolinium ion and several of its analogues is reported. The compounds studied are the perchlorate salt of 3‐nitrobenzothiazolo‐and 3‐nitro‐9‐methoxybenzothiazolo[3,2‐a]quinolinium, and the chloride salts of 7‐ethyl‐, 3‐nitro‐7‐methyl‐, 3‐nitro‐7‐ethyl‐, 3‐nitro‐7‐isopropyl‐, 3‐nitro‐7‐butyl‐ and 3‐nitro‐7‐benzylbenzimidazolo[3,2‐a]‐quinolinium, respectively. Cyclic voltammetry of the corresponding 3‐nitrobenzothiazolo[3,2‐a]quinolinium derivatives inN,N‐dimethylformamide shows an irreversible peak potential at ‐0.6 and a quasi‐reversible peak at ‐(1.2–1.3) volts, respectively, relative to the standard calomel electrode. In contrast, the corresponding 3‐nitrobenzimidazolo[3,2‐a]quinolinium derivatives show, in general, reversible peaks at near ‐0.8 and ‐(1.2–1.4) volts, respectively. Upon electrolytic reduction, only the nitro‐substituted derivatives produced observable electron paramagnetic resonance electron spin resonance spectra. This observation is explained in terms of the stabilization of the radicals produced by the nitro group. Theoretical MM+/AM1/UHF calculations support the idea that the larger nitrogen splitting is caused by N‐12 and the minor splittings by N‐7 in the benzimidazolo[3,2‐a]quinolinium ion series.
A new synthesis of symmetrical 2,5‐disubstituted 1,3,4‐oxadiazoles
Authors: Bentiss Fouad , Lagrenée Michel
Published: May 2009

Several new 2,5‐disubstituted 1,3,4‐oxadiazoles have been synthesized in good yields by reaction of aromatic acids with hydrazine dihydrochloride in a mixture of orthophosphoric acid, phosphorus pentoxide and, in general, with addition of phosphorus oxychloride to the reaction mixture. The structures of new oxadiazoles derivatives were confirmed by analytical and spectral data.