bluuebunny/crossref_metadata_2025 huggingface dataset:
Hétérocyclisations a partir des dérivés des thioamides trifluoropyruviques
Authors: Maliverney C. , Merényi R. , Viehe H. G.
Published: September 2010

2‐Aminothioamides as derivatives of trifluoroalanine, and also 2‐tertiary hydroxythioamides as derivatives of trifluorolactic acid have recently been prepared. They have made now the synthesis of new five‐membered heterocycles possible by reaction with phosgeniminium chloride, with phosgene or with methanesulfonyl chloride: thus trifluoromethyl thiazole, ‐thiazolone, ‐benzothiazole and ‐sultones have been obtained.
What Rules the Melting Point of Semi‐Crystalline Polymers?
Authors: Huyskens P. , Groeninckx G. , Vandevyvere P.
Published: September 2010

The melting point Tm of semi‐crystalline polyethylene terephthalate is correlated with the thickness lc/nm of the crystalline lamellae by the unique relation 1/Tm = 1/594.5 + 0.001759/lc. This correlation is independent of the temperature of crystallization, the molecular weight or the annealing. This demonstrates that the melting point is ruled only by the characteristics of the crystalline parts. The molar heat of fusion is 18.4 kJmol−1 per crystallized segment and the corresponding entropy change 30.5 JKmol−1. Both are independent of lc. In the amorphous parts the two segments adjacent to the crystalline lamella have their entropy reduced by 15 J/Kmol as a consequence of the limitations in their possibilities of orientation. However this is a constant effect, independent of the thickness of the amorphous zones, possible entanglements or other characteristics of the amorphous parts.
In‐Situ Composites Based on Thermoplastic and Thermotropic Liquid Crystalline Polymers
Authors: Crevecoeur G. , Groeninckx G.
Published: September 2010

Thermotropic liquid crystalline polymers (TLCPs) can be used to reinforce thermoplastic polymers in so‐called in‐situ composites. A brief introduction on contemporary TLCPs is given, followed by the basic ideas and principles behind in‐situ composites. The state‐of‐the‐art of in‐situ composites is presented in terms of morphology and mechanical properties. Composite models that describe the mechanical properties of in‐situ composites are discussed. Finally, some rheological parameters determining the processing and morphologies of in‐situ composites are emphasized. At the end of the paper an outlook on possible topics of future interest is given.
Synthesis and Stability of Functionalized Epoxides Topologically Related to β‐Lactam Antibiotics
Authors: Marchand‐Brynaert Jacqueline , Ferroud Didier , Serckx‐Poncin Béatrice , Ghosez Léon
Published: September 2010

Epoxides 3‐4 topologically related to penicillins and oxamazins have been designed as potential alkylating inhibitors of bacterial D, D‐peptidases. A series of N‐acylated olefins 17‐19 and 22 have been prepared. It was found that the corresponding epoxides bearing a free carboxyl group were unstable. Neither the olefinic precursors nor the lactones 23 resulting from ring opening of the epoxides 4 exhibited any antibacterial activity.
Dimérisation De Dienes Conjugués A L'Aide De Complexes Du Nickel En Présence De Ligands De Type Aminophosphinite Étude D'Optimisation
Authors: Masotti Henrietta , Peiffer Gilbert , Siv Chhan , Courbis Pierre , Sergent Michelle , Phan Tan Luu Roger
Published: September 2010

New chiral aminophosphinite ligands are readily prepared and their behaviour as homogeneous catalysts was investigated in the linear dimerization of butadiene and isoprene. This latter reaction has been optimised using experimental research methodology, leading to a conversion rate above 50%.
First Derivative of the Ratio Spectra Method for Resolving 3‐Hydroxybenzaldehyde and 4‐Hydroxybenzaldehyde in Binary Mixtures
Authors: Berzas Nevado J. J. , Guiberteau Cabanillas C. , Salinas López F.
Published: September 2010

A method for the simultaneous determination of the isomers 3‐hydroxybenzaldehyde and 4‐hydroxybenzaldehyde in binary mixtures is proposed. The method is based on the use of the first derivative of the ratio spectra obtained by dividing the amplitudes, at appropriate wavelengths, of the absorption spectra of the mixtures by a standard of 4‐hydroxybenzaldehyde for determining 3‐hydroxybenzaldehyde and by a standard of 3‐hydroxybenzaldehyde for determining 4‐hydroxybenzaldehyde. The method compares favourably with other spectrophotometric methods.
The Preparation of α‐Hydro‐ω‐Hydroxypoly(Oxyethane‐1,2‐Diyl) Ditosylate (Peg(OTs)2) Revisited
Authors: van Den Berge L. , van Damme S. , Anteunis M. J. O. , Tavernier D.
Published: September 2010

An improved protocol for the preparation of the title compound [PEG(OTs)2] from polyethylene glycol, tosyl chloride, 4‐dimethylaminopyridine (DMAP) and triethylamine is described. PEG(OTs)2 reacts slowly with DMAP to yield, by a nucleophilic displacement of ‐OTs, PEG(DMAP)2+ (OTs−)2 (DMAP+ = 4‐dimethylamino‐pyridinium‐1‐yl). PEG(OTs)2, heated in N,N‐dimethylformamide, is extensively transformed into ‐PEG‐OC(=O2)H.
Une Nouvelle Récyclisation De Cations 1,3‐Hétérocycliques En Cations Benzimidazolium Et Perimidinium
Authors: Védernikova I. V. , Konstantinchenko A. A. , Ryabukhin Yu. I.
Published: September 2010

In this work we have examined the new recyclisation of 1,3‐heterocyclic cations activated towards 1,4‐binucleophyles: o‐phenylenediamines and 1,8‐naphthalenediamines. This reaction leads to the formation of benzimidazolium and perimidinium cations.
One‐Pot Synthesis of 2,2,4‐Trichlorobutanal from Tetrahydrofuran
Authors: De Buyck Laurent , Menke Niclas , Louagie Jan
Published: September 2010

Tetrahydrofuran was converted to 2,2,4‐trichlorobutanal (1) in 60‐73% overall yield by isomerisation of intermediate 2,3,3‐trichlorotetrahydrofuran (2) in the presence of 4‐6% (w:w) of aluminum trichloride at 100‐140°C for 40‐60 rain. Zinc chloride and titanium tetrachloride were less effective as catalysts, while hydrogen chloride and paratoluenesulfonic acid were ineffective.
Spectroscopic Electronegativities of Halogens are Transferable and Additive Parameters. Examples of Correlations with Thermochemical and Nuclear Magnetic Resonance Spectroscopic Data
Authors: Screttas Constantinos G. , Micha‐Screttas Maria
Published: September 2010

Sets of enthalpies of formation of a) halogens and interhalogens b) tetrahalomethanes c) haloethenes and d) hexahaloethanes are correlated with the corresponding sums of the spectroscopic electronegativity parameters. Similarly, carbon‐13 NMR shifts of tetrahalomethanes are linearly related to the respective sums of the above electronegativities. The latter correlation allowed the prediction of the C‐13 chemical shifts of 28 tetrahalomethanes, several of which are well outside the range of a low power NMR instrument.
New Cs2CO3 Catalyst for the Wittig‐Horner Synthesis of Acrylates in Interfacial Solid Liquid Conditions
Authors: Sinisterra J. V. , Barrios J. , Mouloungui Z. , Delmas M. , Gaset A.
Published: September 2010

Cesium carbonate is described as an efficient catalyst for the Wittig‐Horner reaction in interfacial solid‐liquid conditions. This solid is more effective catalyst than potassium carbonate or activated barium hydroxide catalyst (C‐200), under the same experimental conditions. Phenolic aldehydes or aldehydes with N‐H group can only carry to acrylate in the presence of cesium carbonate. These aldehydes are not reactive when potassium carbonate or C‐200 are used as catalysts. The synthetic method is described and the influence of the cesium carbonate structure on the yield is discussed. The mechanism of the reaction is qualitatively described in terms of the nature of adsorbed species and the influence of the solid cell lattice on the yield. The difference in the catalytic activity observed in the solid bases tested is discussed on the bases of an interfacial solid‐liquid mechanism.
Photochromisme des Spiropyranes. Étude de la Colorabilité et de la Photodégradation de Dérivés Non‐Azahétérocycliques
Authors: Gaude Didier , Gautron René , Guglielmetti R.
Published: September 2010

Study of the photodegradation and the “colorability” of non‐azaheterocyclic spiropyrans by repeated flashes showed the influence of different effects involving the heteroatom, the substituent and the concentration. Substituents in 3′, 6′ and 8′ positions of the benzopyran part are very important for stabilization of the colored open form (thermal bleaching kinetic constant), for “colorability” and photodegradation. The primary photochemical process is essentially localized in the benzopyran part but in the photomerocyanine isomer there is interaction between the two moieties. The “colorability” and the photodegradation vary inversely with concentration. All compounds present generally a bad “colorability” but also a sufficient light‐stability at high concentrations. A general scheme for the photocoloration and photodegradation of spiropyrans is also proposed.
Étude par Photolyse à Éclairs Répétés de la Photodégradation et de la Colorabilité de Quelques Spiro[Indoline‐Oxazines]
Authors: Gautron René , Eloy Dominique , Escaffre Pascale , Guglielmetti Robert , Pottier Eliane , Tardieu Pascale
Published: September 2010

The “colorability” and the photodegradation by repeated flashes have been studied for 3 series of photochromic spiro[indoline‐oxazines], A comparison has been established, in the same conditions, with indoline derivatives in benzopyran and naphthopyran reference series. The oxazine compounds present generally a better behaviour to the light but the low photodegradation depends also on the UV region of irradiation, the pane glass (λ > 335 nm) being an interesting filter. The spiro [indoline‐oxazines] have a good balance between photocoloration and photodegradation.
Identification D'isomères du Dodécane Mesures des Indices de Rétention a Plusieurs Températures
Authors: De Laet M. , Tilquin B.
Published: September 2010

Pure 3‐methylpentane was irradiated in its solid vitreous state at 77 K. The qualitative analysis of the dimeric products was made by mean of capillary chromatography coupled with mass spectrometry. The identification of the dimers, highly branched dodecanes, required the synthesis of compounds whose structure was defined by NMR 13C DEPT; they were characterised by their retention index measured at several temperatures on the capillary SE30 column.
Reductive Cleavage of Cyclic Ketals with ZrCl4‐LiAlH4
Authors: Shaozu Wu , Tianhui Ren , Yulan Zhang
Published: September 2010

Both aliphatic and aromatic cyclic ketals were selectively reduced to the corresponding glycol monoethers in high yield with ZrCl4‐LiAlH4 at 30°C in Et2O for 12 hr.
Synthesis and Crystal Structure Determination of 3,4‐Dimethoxybenzyl 2,3,4‐Trimethoxyphenyl Ketone
Authors: Arriortua M. I. , Via J. , Urtiaga M. K. , Domínguez E. , Igartua A. , Sotomayor N.
Published: September 2010

X‐Ray crystallographic investigation of the product obtained by acylation of 1,2,3‐trimethoxybenzene with 3,4‐dimethoxyphenylacetyl chloride is reported. The IR and NMR spectral studies in solution are in agreement with the crystal structure. The structure confirms the distorted tetrahedral arrangements around the methylene group as observed for other deoxybenzoins.
Novel 4,5‐Dihydropyrazolo[3,4‐d]Pyrimidin‐4‐Ones and 3,4‐Dihydropyrazolo[3,4‐d]‐1,2,3‐Triazin‐4‐Ones
Authors: Maquestiau A. , Banneux F. , Vanden Eynde J.‐J.
Published: September 2010

β‐benzylidene 3− and 5‐amino‐1‐methyl‐1H‐pyrazole‐4‐carboxhydrazides 3 and 4 readily react with orthoesters to yield the 4,5‐dihydropyrazolo [3,4‐d] pyrimidin‐4‐ones 5‐8.

Syntheses of 3,4‐dihydropyrazolo [3,4‐d]‐1,2,3‐triazin‐4‐ones 9, 10, 13 and 14 were achieved by nitrosation of various 3− and 5‐amino‐1‐methyl‐1H‐pyrazole‐4‐carboxhydrazides.
Reaction of Carbon Monoxide with Iron(II) Thiolates. Preparation and Structure of fac‐[Na(15‐Crown‐5)][Fe(CO)3(SPh)3] and fac‐[K(18‐Crown‐6)][Fe(CO)3(SPh)3]
Authors: Nagy‐Magos Zsuzsa , Markó László , Szakács‐Schmidt Anikó , Gervasio Giuliana , Belluso Elena , Kettle Sidney F.
Published: September 2010

Solutions of Fe(II) and thiolates (RS‐: Fe2+ > 2; R = alkyl, phenyl) absorb carbon monoxide and ‐ depending on the reaction conditions ‐ several different anionic iron carbonyl derivatives are formed. Two of these complexes, fac‐[Na(15‐crown‐5)][Fe(CO)3(SPh)3] (1) and fac‐[K(18‐crown‐6)][Fe(CO)3(SPh)3] (2) were isolated and their crystal structures determined. (1) Crystallizes in the triclinic space group P1 with a = 11.915(3)Å, b = 12.391(3)Å, c = 14.337(3)Å, α = 65.77(5), β = 116.28(5)°, γ = 105.87(5)°, V = 1720(1)Å3, Z = 2, dcalcd = 1.30 gcm−3; (2) crystallizes in the cubic space group Pa3, with a = 19.609(4)Å, V = 7540(3)Å3, Z = 8, dcalcd = 1.4 gcm−3. Final agreement factors were R = 0.092, Rw = 0.102 (3919 reflections with F>7σ(F)) for (1); and R = 0.069, Rw = 0.050 (1125 reflections with F>4σ(F)) for (2). Both [Fe(CO)3(SPh)3]− anions of 1 and 2 have the same octahedral ligand arrangement with the carbonyl ligands cis to each other and trans with respect to the thiolato ligands. In complex 2 the K+ lies on the crystallographic threefold axis and is therefore exactly equidistant (3.475(2)Å) from the three sulphur atoms; on the contrary in complex 1 in the Na+ is nearer to two of the three sulphur atoms (3.083(6)Å and 3.334(6)Å for the two different Na…S distances). The infrared spectra of the compounds were recorded in a variety of solvents and in the solid state. The Raman of crystalline 2 was also recorded. The failure of the vibrational spectra of crystalline 2 to follow either molecular point group or factor group predictions is explained in terms of an effective vibrational unit ‐ and so, effective factor group ‐ similar to that implicit in a factor group analysis of 1.
Synthesis and Flash‐pyrolysis of Organotin ‐Substituted Carbamates and Oxalates
Authors: Ratier Max , Khatmi Djamel , Duboudin Jean‐Georges
Published: September 2010

Organotin ‐substituted alcohols react readily with aryl(alkyl) isocyanates and oxalyl chloride to give the corresponding organotin ‐ substituted carbamates and oxalates. Under flash pyrolytic conditions, these esters decompose into vinyltin derivatives.
C‐Versus N‐Substitution at 1,5‐Diarylformazans with Cyclopropenylium Electrophiles
Authors: Weiss Robert , Lowack Rainer H.
Published: September 2010

Synthesis and properties of the first formazan substituted with a cyclopropenylio group in the 5− or 3‐position are described. The latter isomer can adopt syn,s‐cis or anti,s‐trans configurations and can be oxidized to the corresponding cyclopropenyliotetrazolium salt.
Influence of the Hydroxyl Groups on the Basicity of Alkanolamines in Water and in Ethanol‐Water Mixtures
Authors: Stevens G. , Chen S. , Huyskens P. , De Jaegere S.
Published: September 2010

The presence of the OH groups in alkanolamines weakens the basicity of the lone pair of electrons as expressed by the pKaof the compounds in water or in water‐ethanol mixtures. This can be ascribed to a residual electronic delocalization from the N atom to the O atom crossing the CH2groups. The effect that is of the order of −1 pKaunit for two intermediary CH2groups, gradually decreases when this number increases and becomes completely negligible beyond four groups. When two or three OH groups are present in the amino compound the effects are additive as long as the groups are located at different sides of the nitrogen atom (di‐ or trialkanolamines). When two OH groups are situated at the same side of the N atom as in 1‐amino‐2, 3‐diols, the contribution of the end group in the delocalization becomes negligible. The effects remain quantitatively the same in the less polar ethanol‐water mixture.
Synthesis of Methyl 3‐(N‐Bromoacetylamino)‐2‐Naphthoate
Authors: Párkányi Cyril , Sappok‐Stang Annette
Published: September 2010

Methyl 3‐(N‐bromoacetylamino)‐2‐naphthoate (3) was obtained from 3‐amino‐2‐naphthoic acid (1) as the starting material, with methyl 3‐amino‐2‐naphthoate (2) as the intermediate.
Synthesis and Evaluation of the Hydrolytical Stability of Ethyl 2‐(α‐Amino acid)Glycolates and Ethyl 2‐(α‐Amino Acid)Lactates
Authors: Crommen Jan H. L. , Schacht Etienne H.
Published: September 2010

Four depsipeptides, ethyl 2‐(O‐glycyl)glycolate (1), ethyl 2‐(O‐glycyl)lactate (2), ethyl 2‐(O‐alanyl)glycolate (3) and ethyl 2‐(O‐alanyl)lactate (4) have been synthesized under mild reaction conditions and in relatively high yield. The hydrolytic stability of these esters in methanol, in presence of water and an organic base has been studied by means of proton NMR‐spectroscopy. It was found that, under these conditions, these compounds hydrolyse slowly under and that no intermolecular condensation reactions occur. It was further demonstrated that the glycolate or lactate ester bond in these compounds hydrolyses much faster when compared to the ethyl ester. The potential use of these derivatives in synthesis and application of biodegradable polymers is discussed.
Accuracy in Single‐Crystal X‐Ray Diffractometry: Influence of Atmospheric Pressure, Scan Mode and Crystal Settlement on Intensity Profiles
Authors: Lenstra A. T. H. , Verbruggen M. , Bracke B. , van Dijk B. , Vanhulle C. , Vanhouteghem F.
Published: September 2010

Simple statistical analysis of time series of intensity control reflections leads to: (i) quantitative description of the influence of atmospheric pressure on X‐ray intensity measurements, which supplies arguments not to optimize an experimental instability factor p in the least‐squares analysis, as is sometimes practised. (ii) the detection of scan mode ω vs ω/2θ) as a factor in the reproducibility of reflection profiles. The distribution of profile gravity centers revealed a random alignment error due to tolerance in diffractometer gear‐wheels and a systematic one due to friction in the same parts during movements, (iii) a sensitive test to detect small movements (settlements) of the crystal during the data collection. It allows to omit dedicated orientation control measurements, using instead the profiles of intensity control reflections to trigger a re‐orientation procedure, (iv) the recognition of severe limitations to fit observed profiles onto “learned” ones and of limitations in the precision of cell dimension determinations.
NO3−‐ CO32‐Anion Exchange During Washing of Ni‐Al Hydroxycompounds
Authors: Evana Eugenia , Marchidan Rodica , Mănăila Rodica
Published: September 2010

An anion exchange of NO3−with CO32−anions was evidenced by X‐ray diffraction, chemical analysis and IR spectroscopy, during washing of Ni‐Al hydroxycompounds (HCPs) precipitated at pH values less than 7. The anionic composition of the resulting HCP is determined by the pH value of the washing water. In the ‘increasing pH’ method of HCP preparation, the precipitation process is shown to be accompanied by a process of anion exchange. The degree of disorder of the interlayer and in the brucite‐like layer stacking is discussed in terms of the IR spectroscopy data and XRD line broadening.
Modulation De La Regiochimie De La Reaction Du Fluoroborate De 2‐Benzoyl‐1,2‐Dihydroisoquinaldonitrile Sur L'Indene
Authors: Monnier Karin , Schmitt Gérard , Mercier Marie‐France , Rodier Noël , Theobald François
Published: September 2010

The reaction of the 2‐benzoyl‐1,2‐dihydroisoquinaldonitrile fluoroborate salt with indene leads to a single indeno[1,2‐c]pyrrole derivative. But nmr data did not prove the regiochemistry of the reaction and a chemical demonstration has been carried out. It allows to obtain the regioisomeric indeno[1,2‐c]pyrrole derivative. Moreover the last structure was also established by a radiocristallographic study.
Non‐Invasive in Vivo Determination of the Absolute ATP Concentration in the Rat Liver by 31P NMR Spectroscopy
Authors: Miot Françoise , van Cauteren Marc , Rooze A. Katelijne , Geerts Albert , Osteaux Michel , Willem Rudolph
Published: September 2010

The concentration of ATP in the rat liver was determined in vivo by means of surface coil 31P NMR spectroscopy. The double standard method was used in order to achieve absolute quantification of ATP through its 31P β‐resonance. Contamination of the 31P NMR liver spectra by contributions from abdominal muscle tissue was minimized by applying the FROGS presaturation sequence. Difficulties inherent to the B1 inhomogeneity of surface coils were overcome by the use of adiabatic half passage sech/tanh RF pulses. While in the normal rat liver the mean ATP concentration was 3.39 ± 0.31 mM, fibrotic rat livers exhibited a significantly lower average ATP concentration of 2.29 ± 0.31 mM.
Syntheses De Carbonates Et Carbamates Benzyliques Et Allyliques
Authors: Kryczka Boguslaw
Published: September 2010

Different methods for the preparation of carbonates and carbamates derived from 1‐phenylethyl, 2‐cyclohexenyl and 1‐methyl‐2‐propenyl are described. These compounds have been synthesized by the reactions of alcohols, phenols or amines with chloroformiates, imidazolocarbonates or corresponding mixed p‐nitrophenylcarbonates.

It is shown that these reactions can also be used for the introduction of 1‐phenylethyloxycarbonyl ‐ (I), 2‐cyclohexenyloxycarbonyl ‐ (II) and 1‐methyl‐2‐propenyloxycarbonyl ‐ (III) groups into alcohols, phenols and amines for the protection of hydroxyls and amino‐groups.
Preparation of D‐[1‐14C,1‐2H]Glucose and D‐[U‐14C,1‐2H]Glucose
Authors: Malaisse‐Lagae F. , Zähner D. , Sener A. , Malaisse W. J.
Published: September 2010

An enzymic method is presented for the preparation of 14C‐labelled and C1‐deuterated D‐glucose, to be used as a radioactive tracer in metabolic studies dealing with the fate of D‐[1‐2H]glucose. The procedure takes advantage of the deuteration of 14C‐labelled D‐fructose 6‐phosphate during exposure to phosphomannoisomerase in D2O. It further includes the conversion of the deuterated hexose monophosphates to D‐fructose 1,6‐bisphosphate, its isolation and hydrolysis to D‐fructose 6‐phosphate and the partial conversion of the latter ester to D‐glucose 6‐phosphate, which is then isolated by ion exchange chromatography and hydrolyzed to unesterified D‐glucose. The extent of deuteration on the C1 of D‐glucose was judged, after conversion to D‐glucose 6‐phosphate, from the isotopic discrimination in reaction velocity exerted towards the C1‐deuterated ester by glucose‐6‐phosphate dehydrogenase. The degree of isotopic discrimination was virtually identical to that found with D‐glucose 6‐phosphate prepared from pure D‐[1‐2H]glucose.
Phase Transitions in Oxides Studied by Thermal Expansion Measurements
Authors: Brabers V. A. M.
Published: September 2010

In this paper, thermal expansion measurements on AgNbO3, YBa2Cu3O7‐δ, Bi2Sr2Ca2Cu3O10+δ, MnxFe3‐xO4, MgFe2O4 and Co3O4 are reported, from which the advantages of thermal mechanical analysis (TMA) in the study of phase transitions is demonstrated. Especially, the quantitative analysis of the cation disordering in MgFe2O4 and the LS‐HS spin transition in Co3O4 shows the possibilities of TMA. For the disordering reactions in MgFe2O4, activation energies of 125 and 145 kJ/mol are found, for the LS‐HS transition in Co3O4 a reaction energy of 30 kJ/mol.
Nucleophilic Displacement Reactions on Sterically Hindered Chloro‐Pyridines: Some Optimisation Studies
Authors: Pascual A.
Published: September 2010

A Factorial Design has been used to optimise the reaction conditions for the nucleophilic displacement of chlorine in 2‐chloro‐4,6‐diisopropyl‐5‐nitropyridine (1B) by 4‐chlorophenol. The results obtained have been successfully applied to a large variety of phenols and thiophenol.
Syntheses of New 4‐Trifluoromethylated 1,3‐Oxazin‐6‐Ones from the Enamine of Ethyl Trifluoroacetoacetate
Authors: Decock‐Plancquaert Marie‐Aimée , Evariste François , Guillot Nadine , Janousek Zdenek , Maliverney Christian , Merényi Robert , Viehe Heinz G.
Published: September 2010

New 4‐trifluoromethyl‐1,3‐oxazin‐6‐ones have been prepared in excellent yields from ethyl 3‐amino‐4,4,4‐trifluorocrotonate (ATFC) by two original procedures: reaction of ATFC with phosgeniminium chlorides to give 2‐dialkylamino‐4‐trifluoromethyl‐1,3‐oxazin‐6‐ones, or action of chlorinating agents on N‐acyl ATFC. The reactivity of ATFC in these reactions is compared with non‐fluorinated analogs.
ω‐Substituted α,α‐Dichloroaldehydes and Derivatives Via Formolysis or Acetolysis of 2,3,3‐Trichlorotetrahydrofuran and 2,3,3‐Trichlorotetrahydropyran
Authors: De Buyck Laurent , Vanhulle Peter
Published: September 2010

Preferable routes to the 2‐hydroxyderivatives 7 resp. 8 of 2,3,3‐trichloro THP (1) or 2,3,3‐trichloro THP (2) involve the uncatalyzed methanolysis of the corresponding 2‐formates or 2‐acetates. These activated esters were rapidly formed from 1 or 2 in a hot slurry of sodium carboxylate and carboxylic acid. They suffered partial isomerization to ω‐acyloxy‐α,α‐dichloroaldehydes in the presence of strong acid. A useful ring opening to ω,1,1‐triacetates 13 resp. 14 occurred with H2SO4in a mixture of acetic acid and acetic anhydride (2–4 d at 135 °C). To prepare the pure aldehydes 10 and 12 acetic anhydride was split off from the triacetates (NaOAc, 150‐190°C in vacuo). The ester function of 10 and 12 is sensitive to uncatalyzed methanolysis, apparently because of intramolecular assistance in the hemiacetal forms. The behavior of 7 and 8 as hidden α, α‐dichloro‐ω‐hydroxyaldehydes is further demonstrated by their reduction (NaBH4, EtOH) to the 2,2‐dichloro‐1,ω‐diols 19 resp. 24.
Lanthanide Complexes of Di(4‐Hydroxycoumarinyl‐3)‐Acetic Acid and Their Anticoagulant Action
Authors: Deng Ru Wen , Wu Ji Gui , Long La Sheng
Published: September 2010

The lanthanide complexes of di(4‐hydroxycoumarinyl‐3)—acetic acid (M2L3 · 10H2O) have been synthesized and characterized by IR, HNMR, electronic spectra, thermoanalysis and molar conductance. The metallic ions substituted two hydrogen atoms of carboxyl and hydroxy groups and are also bonded to the oxygen atom of the carbonyl group of the benzopyranyl ring. Electronic spectra showed that the lanthanide—ligand bond had some covalent character and the involvement of 4f orbital was very small. The light lanthanide complexes revealed the nice anticoagulant action especially the lanthanum coordination compound.
Solvent Parameters and the Thermodynamics of Mobile Disorder in Liquids
Authors: Huyskens Pierre L. , Vael‐Pauwels Christine , Seghers Katarine
Published: September 2010

According to the basis ideas of Gutmann, specific cohesion forces are in many cases more important for solvent effects than non‐specific interactions. In this work the fundamental differences between H‐bonds or n‐σ EDA bonds and non‐specific dipole‐dipole interactions are outlined: stechiometry, directionality, and especially the essential difference between the two active sites. As a consequence the capacity of a solvent to form specific bonds with the solute cannot be described by a single parameter. As pointed out by Gutmann, two different capacities of the solvent have to be considered. The solvents can be classed according to the presence in their molecule of active sites of one or another kind. The theoretical ground for the use of solvent parameters is studied in the frame of the thermodynamics of the Mobile Disorder in liquids developed by Huyskens and Siegel. A new solvent parameter based on the ratio of the molar volumes of solute and solvent PVB/VS is introduced which is equal to (0.5 — rS)(vB/vS) + 0.5 ln(VB/VS) ‐ 0.5. rS takes the value of one for amphiphilic solvents with one proton donor site, of two for the solvents with two hydroxylic protons and of zero for the others. For amphiphilic solutes (with one OH group) rS has to be added to the former expression. This purely entropic parameter is independent of all the others. A positive value of PVB/VS corresponds to a decrease of μB/RT and a stabilization of the solute in the solution. At high dilution the solute‐solvent specific forces decrease μB/RT by an amount ln(1 + K/VS) where K is the stability constant of the bond. The latter depends on both the solvent and the solute. The values ln(1 + Kref/VS) of various solvents can be compared for some reference solute. This constitutes the thermodynamical basis for the use of solvent parameters. The acceptor and the donor parameters AN and DN of Gutmann are discussed from this point of view.
An Explorative Investigation into the Reaction of Ammonia with Ketones. Mediated by Low‐Valent Titanium
Authors: Volckaerts E. , Geise H. J. , Daelemans F.
Published: September 2010

Mediated by low‐valent titanium, generated from TiCl3/LiAl4. ammonia is incorporated into benzophenone to give N‐(diphenylmethylene)‐N‐(diphenylmethyl) amine in a synthetically useful reaction. A good yield (65 %) requires that the temperatures of the reaction stages are well controled and that ammonia and ketone are simultaneously introduced keeping their molar ration 1:1. The possible sequence of reactions is discussed.
‘Stilbene to Phenanthrene’ Type Photocyclization of a Bis‐(4‐Anthryl) Ethylene. A New Access to the Dibenzopicene Skeleton
Authors: Segura C. , Parella T. , Sanchez‐Ferrando F. , Bouas‐Laurent H. , Desvergne J.‐P.
Published: September 2010

1,8‐Didecyloxyanthracene is a starting material for a new synthesis through a photochemical step of a derivative of dibenzo [b,l] picene, soluble in organic solvents.
Heterocyclic π‐Donors, Macrocycles and Cage Molecules
Authors: Becher Jan , Hansen Thomas K. , Jørgensen Tine , Stein Paul
Published: September 2010

Reaction of dmit‐salts 2 and bis‐alkylating agents leads to macrocycles annelated to a 1,3‐dithiole‐2‐thione ring. Intermolecular coupling of monomers MC[n,1] leads to TTF‐crowns of type A whereas intramolecular coupling of dimers MC[n,2] gives TTF‐cages of type B. The complex formation of type A and B host molecules with alkali metal ions is discussed.
New Fused as‐Triazines with Bridgehead Nitrogen Synthesis and Reactivity
Authors: Hajós György , Messmer András , Bátori Sándor , Riedl Zsuzsanna
Published: September 2010

Two synthetic pathways have been elaborated for the synthesis of pyrido[1,2‐b]‐as‐triazinium salts and were also extended to the linearly fused as‐triazino[2,3‐b]isoquinolinium and the angularly fused as‐triazino[3,2‐a]isoquinolinium systems. The ring closures were found to proceed in regioselective manner which was rationalized by assumption of the different charge distribution in acidic and basic conditions.

Preparative route has also been worked out for the synthesis of pyrido[2,1‐f]‐as‐triazinium salts and its differently (linearly and angularly) fused benzologues. The new heteroaromatic ring systems easily formed covalent hydrate salts under acidic conditions and pseudo bases with nucleophiles under basic conditions.
Synthesis and Reactions of Oxazolones from L‐Tryptophan and α‐Haloacetic Anhydrides
Authors: Bergman Jan , Lidgren Göran , Gogoll Adolf
Published: September 2010

Optically active 5(4H)‐oxazolones have been synthesized from L‐tryptophan and an excess of trifluoro‐, trichloro‐, and dichloroacetic anhydrides. Some of the 5(4H)‐oxazolones have been further transformed to the isomeric 5(2H)‐oxazolones as well as oxazolones with exocyclic double bonds. Treatment of the various oxazolones under hydrolytic, acidic and Friedel‐Crafts acylation conditions gave indole‐3‐pyruvic acid, α,β‐dehydrotryptophans, β‐carbolines as well as the functionalized cyclopentanoindole 32. Treatment of the 4‐(3‐indolylmethyl)‐2‐trifluoromethyl‐5(2H)‐oxazolone (17) with trifluoroacetic acid gave the 3,4‐bridged azepinoindole 35.
Rotating Ring‐Disk Study of the Influence of PH on The Cu(II)/Cu(I)/Cu(0) Electrode Reactions at Gold in Aqueous 0.5 M Sulphate Solution
Authors: Vandenbruwaene J. , Temmerman E.
Published: September 2010

Depending on pH and copper(II) concentration up to three reduction and four oxidation waves may be observed by cyclic voltammetry at a rotating polycrystalline gold ring‐disk electrode in sulphate solution. These are related to the reduction of copper(II) (oxidation of deposited copper metal), to underpotential deposition (dissolution), the deposition (dissolution) of a copper layer adjacent to the underpotential layer and of bulk copper. Analysis of the dependence of the ring currents on electrode rotation rate and copper(II) concentration shows the importance of the dismutation of copper(I). The observed pH effects can be explained by the presence of different hydrated copper(II) species, hydrolysis of copper(I) and the formation of Cu2O on the disk electrode surface.
Synthesis of Dipeptide Esters of Metronidazole and Evaluation of Their Hydrolytic Stability
Authors: Permentier Dirk , Vansteenkiste Stefan , Schacht Etienne , Vermeersch Hans , Remon Jean Paul
Published: September 2010

Amino acid and dipeptide esters of metronidazole were synthesized and evaluated on their hydrolytic stability in various buffers and culture media. The hydrolytic susceptibility of the different esters was minimal in the pH range 3 ‐ 5. In the alkaline region, pH 6.5 ‐ 8, the half‐lifes were of the order of 1 ‐ 6.6 hrs. At alkaline pH the dipeptide esters were more susceptible towards hydrolysis. At pH 8.8 the observed half‐life for the gly‐gly and the gly‐phe esters was 0.2 h, whereas for the gly and the phe ester it was 1.1 h, respectively 2.7 h. It was demonstrated that the increased rate of hydrolysis for the dipeptide esters was due to an intramolecular aminolysis with the formation of a diketopiperazine accompanied by the release of free metronidazole.
Kinetic Study of the Electrophilic Reaction Between iPRI and ICI
Authors: Verbiest P. , Verdonck L. , Van Kelen G. P. Der
Published: September 2010

The kinetics of the electrophilic reaction between iPrI and ICI are presented. A rate equation first order in iPrI and second order in ICI is found. A mechanism is proposed involving Charge‐Transfer as the driving force for reaction.
Photooxidations of Organic Substrates in Presence of Copper Complexes: The Validity of The Geminate‐Pair Scavenging Mechanism
Authors: Sýkora J. , Molčan M.
Published: September 2010

The validity of the Noyes geminate‐pair scavenging mechanism for the photoredox reactivity of chlorocopper (II) complexes in acetonitrile in presence of methanol, isopropanol, acetone and benzene as scavengers for chloride radicals has been tested. Experimentally obtained linear dependence of Cu(l) quantum yield formation on the square root of scavenger concentration within the range where scavenging reaction competes with the secondary recombination justifies that the Noyes mechanism is operative. The estimated values for scavenging rate constants are in good agreement with those previously reported using another experimental method. It has been found that the photoredox reactivity of the lowest spin‐allowed doublet LMCT excited state of the tetrachlorocuprate (II) complex at 460 nm is higher than that of LMCT lying at 313 nm.
Extraction Spectrophotometric Determination of Vanadium in Steels with Thiosalicylic Acid (TSA)
Authors: Salinas F. , Martínez‐Vidal J. L. , Martínez‐Galera M.
Published: September 2010

In this paper thiosalicylic acid (TSA) is proposed for a simple, rapid and selective method for the spectrophotometric determination of vanadium based upon the formation of the TSA‐vanadium complex and its extraction into Adogen 464‐toluene solution.

Under optimum operating conditions, a green colour is formed when the complex is extracted, from weak acidic 40% ethanolic solution, In the organic solvent (apparent molar absorptivity 1,700 L.mol−1·cm−1 at wavelength of 600 nm). The relative error is 2.3%, in the determination of 16 μg.mL−1 of vanadium, and its limit of detection is 3 μg·mL−1. The method has been applied to the determination of vanadium in steels.
Etude De La Conformation D'oximes Thiopheniques
Authors: Oussaid Boualem , Fayet Jean‐Pierre , Pelletier Gilles , Garrigues Bernard
Published: September 2010

The condensation of 2,5‐diformylthiophene with hydroxylamine hydrochloride leads to the formation of three isomers. Two isomers 1′ and 1” present a second order axis of symmetry; compound 1′ is present with the configuration ZZ and exists in the conformation a and compound 1” is present with the configuration EE and exists in the conformation b. The last isomer 1”′ presents the e (Z,E) conformation.
Bioelectrocatalytical Method for Glucose Determination in Foodstuffs
Authors: Stoytcheva Margarita
Published: September 2010

A bioelectrocatalytical method for the glucose contents in foodstuffs is proposed. Conserving the advantages of the photometrical enzymic methods, it is rapid, simple and economizing, too. It is also much better than certain bioelectrocatalytical methods with which the glucose is determined indirectly ‐ by O2 or H2O2 concentration change during the reaction: Glucose + O2 → Gluconolactone + H2O2.
Étude de La Réactivite de La 7‐Phényl‐1,4‐Diazepine‐5‐One
Authors: Chammache M. , Essassi E. M. , Salem M. , Zniber R.
Published: September 2010

The reactivity of 7‐phenyl‐1,4‐diazepin ‐5‐ one have been described. The new compounds obtained have been characterized by 1H NMR, IR, MS and microanalysis.
An Electrochemical Study of Thiamine Disulphide on Mercury
Authors: López Fonseca J. M. , Lois B. , García Monteagudo J. C. , Sastre De Vicente M. E.
Published: September 2010

The electroreduction of thiamine disulphide was studied by using dc, dp, np and rp polarography in aqueous buffered media. Depending on thiamine disulphide concentration, pH, temperature and drop time, up to four waves (peaks), I‐IV, were obtained. Waves II and III are characterized as adsorption post‐waves and wave I corresponds to the “main wave”, the latter being the only wave previously described in the literature. Involvement of the product of the charge transfer reaction (thiolic form of thiamine) in an irreversible chemical reaction was detected. Taking into account additional recent kinetic studies on the structural transformations of thiamine, a mechanism for the electroreduction of thiamine disulphide that explains the observed dependence of E1/2 of I on pH is proposed.
Transformations of N‐Methyl‐4,5‐Dihydroisoxazolium Methylsulphates
Authors: Kwiatkowski Stefan , Ostrowski Stanisław
Published: September 2010

Reactions of N‐methyl‐4,5‐dihydroisoxazolium methylsulphates with: H2O, H2O2 or KMnO4, NaNO2, NEt3, NaCN, NaN3 yielded respectively: β‐methylaminoxyketones, β‐hydroxyketones, β‐(N‐nitroso)methylaminoxyketones, a mixture of N‐methyl‐2,5‐dihydroisoxazole and N‐methyl‐3‐methylenetetrahydroisoxazole, 3‐cyano‐N‐methyltetrahydroisoxazoles and 3‐azido‐N‐methyltetrahydroisoxazoles.
Selective Cleavage of Asymmetric Acetals to Hemiacetal Acetates. Ring Opening of Chlorinated 2‐Alkoxytetrahydrofuran and ‐Tetrahydropyran Derivatives
Authors: De Buyck Laurent , Verhue Ann
Published: September 2010

Asymmetric acetals of α‐chloro and α,α‐dichloroaldehydes in acetic anhydride containing sulfuric acid afforded hemiacetal acetates at convenient rates at room temperature resp. at 127°C. The main product involved cleavage to the better stabilized α‐alkoxycarbenium ion intermediate, with a typical ratio 87:13 for ethyl:methyl and 94:6 for propyl:2‐chloroethyl. For 2‐alkoxytetrahydrofuran and ‐tetrahydropyran substrates (alkyl = methyl, ethyl, 2‐chloroethyl) ring cleavage was predominant (89‐98%).

The kinetics were affected by several factors: the concentration of strong acid and of acetic anhydride (ionizing power of the medium), the ring size, nature and conformation of the 2‐alkoxygroup and by a minor side‐reaction that consumes acid by alkylation of its anion (OMe > OEt; eq. OMe > ax. OMe).
Caractéristiques Électrochimiques Et Énergétiques D'Électrodes Composites a La Chloranile Contenant de La Tourbe
Authors: Kone A. , Dieng M. M. , Fall M. , Aaron J. J.
Published: September 2010

The effect of peat on several electrochemical and energetic properties of new solid composite electrodes, constituted of chloranil, peat and acetylene black has been evaluated. Optimal electrodes have been found to include 60% of chloranil, 19% of acetylene black 19% of peak and 2% of teflon. The influence of the proportion of chloranil and of the acidity of the electrolytic medium (sulfuric acid) on the capacity of the redox system has been also studied.
Molecular Interaction in Aqueous Sugar Solutions ‐ a Nuclear Magnetic Relaxation Study
Authors: Sattiacoumar S. , Arulmozhi V.
Published: September 2010

Proton Magnetic Resonance (PMR) spin‐lattice relaxation times (T1) were measured in aqueous solutions of maltose and galactose in the concentration range 0‐2 molar and at a temperature of 37° C. The spin‐lattice relaxation time (T1) is found to decrease with the increase of sugar concentration. On the otherhand, the relaxation time is found to be lower for maltose solutions as compared to galactose solutions. These results were discussed on the basis of molecular association between sugar and water molecules through hydrogen bonding and the two‐state fast exchange model of water molecules.
Coordination Compounds of S‐Benzyl‐(Ferrocenyl)Ethylidene‐Dithiocarbazate with Rare Earth Metals
Authors: Gang Zhao , Zhi‐Quan Jiang
Published: September 2010

A new ligand. S‐benzyl‐(ferrocenyl)ethylidenedithiocarbazate FcC(CH3) = NNHCSSCH2C6H5 (Ftsbh) (Fc = η5‐C5H5FeC5H4) and its complexes with lanthanide, Ln(Ftsb)3 (Ln = lanthanide) have been prepared and characterized. The data of elemental analyses, IR, UV, NMR, molar conductance. TG and DTA show that the ligand coordinates with Ln(III) in thiol form with a molar ratio of 3:1. The complexes are non‐electrolytes in DMF and the C‐N bonds in complexes became very strong and much more thermostable than that in the ligand due to forming the chelate rings.
Effet du Spin Électronique Sur La Conduction De Semiconducteurs Impliques Dans des Jonctions de Type Semiconducteur‐Métal
Authors: Gire A. , Lomaglio Mme G. , Théobald J. G.
Published: September 2010

The spin of the electrons has an incidence on the electrical transport properties, especially on the recombination of charge carriers. The minority carriers are usually considered to have a negligible effect on the behaviour of semiconductor‐metal junctions. We describe an experience which shows, that their role is evident. The experience consists in studying the efficiency of a junction while producing E.S.R., which modifies the recombination rate of minority carriers.
Étude de La Synthèse de Tétrachalcogenofulvalenes Dissymétriquement Substitués Par Réaction de Type Wittig‐Horner
Authors: Fabre J. M. , Serhani D. , Saoud K. , Gouasmia A. K.
Published: September 2010

The synthesis of functionalized unsymmetrically substituted tetrathiafulvalenes 1, 2 and 3, 4 (see scheme in the introduction) was described. Two routes were used. A cross‐coupling preparation from appropriate 1,3‐dithiolium salts which offered poor yields and a WITTIG‐HORNER type reaction which was studied in details. A solvent modification in the later reaction, allowed us to improve the yield of 1 and 2 obtained selectively.
Vinylogous transamination of enamines with ene‐1,1‐diamines to diene‐1,1‐diamines
Authors: Leurs Stefan , Vandenbulcke‐Coyette Brigitte , Viehe Heinz G.
Published: September 2010

We report the chain extension of enamines by two carbon atoms through acid catalyzed nucleophilic substitution of the amine function by ene‐1,1‐diamines 2. By this vinylogous transamination we have prepared a series of diene‐1,1‐diamines 10a‐h, 12a‐e and diene‐1,1,4‐triamines 14a‐e.
Simple and efficient preparation of dihydropyrans and spiroketals using the intramolecular silyl modified Sakurai (ISMS) reaction
Authors: Markó István E , Bayston Daniel J. , Mekhalfia Abdelaziz , Adams Harry
Published: September 2010

Substituted tetrahydropyrans, spiroethers and spiroketals can be prepared in a single step using the ISMS reaction between the bis‐silylated reagent 7b and aldehydes (acetals), ketones (ketals) and ortholactones respectively. This simple methodology was applied to the rapid synthesis of a pheromone containing a [4,5]‐spiroketal unit.
Synthesis and characterization study on some metal complexes of a schiff base derived from ninhydrin with s‐methylhydrazine‐carbodithioate
Authors: Hassaan Aly M. A.
Published: September 2010

Synthesis and characterization of a Schiff base ligand of ninhydrin with S‐methylhydrazinecarbodithioate and its chromium (III), manganese (II), iron (III), cobalt (II), nickel (II), copper (II), zinc (II), and cadmium (II) complexes are reported. Elemental analysis molar conductivity, magnetic moment, spectral 1H NMR, UV/Visible and IR data have been used to characterize these complexes. It has been found that ligand behaves as a mononegative ONS tridentate towards divalent metal ions forming 1:2 (metal:ligand) stoichiometry and as a mononegative NS bidentate towards trivalent metal ions forming 1:3 (metal:ligand) stoichiometry. For all complexes, a non‐electrolytic nature is observed. Some available spectral parameters are calculated. Octahedral and distorted octahedral geometries have been proposed for the complexes on the basis of magnetic and spectral measurements.
Complexation of Cd2+ by cysteine at ionic strength of 0.7 m studied by differential pulse polarography
Authors: Vilariño T. , Brandariz I. , Fiol S. , López Fonseca J. , Sastre De Vicente M.
Published: September 2010

Differential pulse polarography (DPP) was used to study the complexation of cadmium by cysteine (CySH) at pH = 7.8 and l = 0.7 M (KNO3), as well as to determine the stability constants of the equilibria Cd2+ + CyS− ⇄ Cd(CyS)+ and Cd(CyS)+ + CyS− ⇄ Cd(CyS)2.
Réactions De P‐Phényl C‐Amino Alkylidenephosphines Avec Les Diazocomposes
Authors: Rahmouni M. , Abbari M. , Carrié R. , Soufiaoui M.
Published: September 2010

P‐Phenyl C‐aminophosphaalkenes 1 react with some disubstituted diazocompounds at −20°C leading to tricoordinated phosphorus compounds 2, 9, 11 and 12 via a Staudinger type reaction. These compounds decompose already at room temperature and quickly by heating. Azines are isolated after extrusion of phenyl phosphinidene.
Synthesis of dipeptides containing propargylglycine and 2‐aminopimelic acid
Authors: Auger Geneviève , van Heijenoort Jean , Blanot Didier
Published: September 2010

Two dipeptides containing antibacterial amino acids, 2‐aminopimelic acid (Apm) and propargylglycine (Pra), were synthesized: L‐Pra‐ambo‐Apm (1) and ambo‐Apm‐L‐Pra (2). 1 was easily obtained from the protected derivative resulting from the coupling (carbodiimide method) of Boc‐L‐Pra‐OH with H‐ambo‐Apm(OBu1)‐OBu1. For 2, we followed a synthesis scheme in which the e‐carboxyl group of Apm was unprotected: after the coupling of Boc‐rac‐Apm‐N3 with H‐L‐Pra‐OBu1, mild acidolytic treatment afforded the desired dipeptide. 2 displayed weak antibacterial activity against some species.
Studies in the azole series. CIII. adamantyl and halogeno pyrazolin‐5‐ones
Authors: Cabildo Pilar , Claramunt Rosa M , Elguero José , Foces‐Foces Concepción , Llamas‐Saiz Antonio L. , Cano Fé Lix H.
Published: September 2010

Nine new pyrazolinones are described together with the crystal structure of one of them, namely 3‐(4‐chloropyrazol‐1‐yl)‐4,4‐dichloro‐2‐pyrazolin‐5‐one, 8, which has been solved, by X‐ray crystallography. The molecule is planar since it lies on a mirror plane and packs first in chains through hydrogen bonds, then in sheets through strong Cl…O interactions. An NMR study in the solid state and in solution proves that the major tautomer is the 3‐pyrazolin‐5‐one c..
Synthèse de 1,2,3‐Triazolines par Cycloaddition Dipolaire‐1,3 de Diazoalcanes à des Esters D'Oximes
Authors: Perrocheau J. , Carrié R.
Published: September 2010

Oximino‐cyanacetic or malonesters 1, 2, 3 and 4 lead with diazoalcanes RCHN2 (R = H, CH3 Ph) to 1,2,3‐triazolines. These triazolines present a low stability, however they are obtained crystallized with good yields They are fully characterized and orientation of the cycloaddition is established.
AMINOACIDES, PEPTIDES ET CHIMIE HETEROCYCLIQUE
Authors: Guibourdenche C. , Lazaro R. , Ma S. , Roumestant M. L. , Tabcheh M. F. , Viallefont P. H.
Published: September 2010

In this report the importance of heterocycles in amino acid and peptide chemistry is pointed out. Neuroexcitatory amino acids, kainic acid, quisqualic acid, of which new syntheses are given, are representative examples of the role of the heterocycle in the recognition of receptor sites. It is also shown that a heterocyclic structure can replace advantageously a peptide turn. The synthesis of a functionnalized diazepinone, a γ‐turn mimetic, is described