bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hexakis(imidazole)nickel(II) formate, an example of a coordination compound containing uncoordinated formate ions
Authors: Jansen J.C. , Reedijk J. 
Published: September 2010

AbstractThe preparation and characterisation of hexakis(imidazole)nickel(II) formate is described. The compound is unique in the sense that it contains formate anions, that are not coordinated to the metal ion. The crystal lattice of this compound ‐ and the isomorphous CoIIand CdIIcompounds ‐ seems to be stabilized by very strong hydrogen bond interactions between the N‐H group of imidazole and the formate anion.A warning is made against the use of the common dehydrating agent triethyl orthoformate, in the presence of ligands that contain protic groups.
13C NMR study of the complex formation of sorbitol (glucitol) with multivalent cations in aqueous solution using lanthanide(III) nitrates as shift reagents
Authors: Kieboom A. P. G. , Sinnema A. , van der Toorn J. M. , van Bekkum H. 
Published: September 2010

AbstractComplexation of sorbitol (glucitol) in aqueous solutions with the lanthanide ions LaIII, PrIII, EuIII and YbIII, as model systems for the complexation with the isosteric CaII, was studied by 13C NMR spectroscopy. Ytterbium(III) nitrate proved to be the reagent of choice, in effectiveness and in linearity vs concentration of the induced upfield shift. Tridentate complexation of YbIII with O‐2, O‐3 and O‐4 was established and the conformation of the sorbitol‐YbIII complex in water was found to be the same as that of the sorbitol‐PrIII complex, as inferred from 1H NMR spectra.Off‐resonance decoupling and the isotope effects observed in sorbitol‐1‐d and sorbitol‐5‐d, allowed the complete, reliable assignment of the 13C NMR spectrum of sorbitol. Assignments in the literature proved to be incorrect.
The “overirradiation products” of previtamin D and tachysterol: Toxisterols
Authors: Boomsma F. , Jacobs H. J. C. , Havinga E. , van der Gen A. 
Published: September 2010

AbstractThe structures of the “toxisterols”, products formed upon prolonged irradiation of previtamin D and its photoisomers, have been investigated. Irradiations (λ > 300 nm) were carried out both in diethyl ether and in alcoholic solvents under conditions where the thermal isomerization to vitamin D is suppressed. From the irradiation mixtures a total of thirteen toxisterols have been isolated. On the basis of structural similarities they have been classified into six categories. In ethereal solution two bicyclo[3.1.0]hexeno compounds (toxisterols C) constitute the major fraction of the irradiation mixture; in addition, a partly deconjugated 9,10‐seco‐triene (toxisterol D1), two C‐8 spiro compounds (toxisterols A) and a cyclobuteno compound (toxisterol E1) are found. In alcoholic solutions about half of the irradiation mixture consists of three alcohol addition products (toxisterols B) ‐ which, upon chromatography, in part give rise to two conjugated 9,10‐seco‐trienes (toxisterols D2 and D3) ‐ and a reduction product (toxisterol R1); furthermore, three toxisterols A, two toxisterols C and toxisterol D1 are found. Toxisterols A, B and R represent novel types of products in hexatriene photochemistry.
On the closure of the 4,5‐oxygen bridge in morphinans 1H and 13C NMR spectroscopy of brominated intermediates. (Chemistry of opium alkaloids, Part IX)
Authors: Olieman C. , Maat L. , Beyerman H. C. 
Published: September 2010

Abstract1H and 13C Nuclear magnetic resonance spectra of brominated dihydrothebainones, needed for the closure of the oxygen bridge of morphinans to form morphine derivatives, were studied. Bromination of (‐)‐dihydrothebainone (1) yielded successively 1‐bromo‐, 1,7α‐dibromo‐, and 1,5β,7α‐tribromo‐dihydrothebainone (2,3,4). 1‐Bromo‐O4‐methyldihydrothebainone (12) gave, after bromination, a stable crystalline l,5β,7α‐tribromo derivative (15). A 5β,7α‐dibromo derivative (9) was formed also starting with l‐methyldihydrothebainone (7).Closure of the oxygen bridge in 1,5β,7α‐tribromodihydrothebainone (4) in boiling ethanol, yields an equilibrium mixture of 1,7β‐ and 1,7β‐dibromodihydrothebainone (5:6, ∼ 35 : 65). 5β,7α‐Dibromo‐l‐methyldihydrothebainone (9) gave the same result.13C NMR spectra of the model compounds cyclohexanone, 2‐bromo‐, 2,2‐dibromo‐, cis‐ and trans‐2,6‐dibromo‐cyclohexanone were studied.
A convenient and general synthesis of 1,2‐dimethylenecycloalkanes
Authors: van Straten J. W. , van Norden J. J. , van Schaik T. A. M. , Franke G. Th. , de Wolf W. H. , Bickelhaupt F. 
Published: September 2010

AbstractCycloalkanones can be converted to the corresponding 1,2‐dimethylenecycloalkanes (1), in 10‐50% overall yield by a four‐step sequence involving Mannich condensation, Wittig reaction and Hofmann degradation. The conformation of 1 is briefly discussed.
Poly(iminomethylenes). 7. Synthesis of diphenylphosphine‐substituted poly[(l‐phenylethyl)iminomethylene]
Authors: Naaktgeboren A. J. , Nolte R. J. M. , Drenth W. 
Published: September 2010

AbstractPolymer‐anchored phosphine functions were obtained in two ways: by diphenylphosphination of poly[[l‐(4‐bromophenyl)ethyl]iminomethylene] and by polymerization of l‐[4(diphenylphosphino)phenyl]‐l‐isocyanoethane. The synthesis of the monomers and polymers is described.
Poly(iminomethylenes). 10. Esterolytic catalysis by poly(carbylhistidine) and poly(carbylhistamine)
Authors: van der Eijk J.M. , Gusdorf Ch. F. , Nolte R.J.M. , Drenth W. 
Published: September 2010

AbstractThe catalytic activities in the hydrolysis of 4‐nitro‐ and 2,4‐dinitrophenyl acetate were determined for a polymer of 3‐(4‐imidazolyl)‐2‐isocyanopropanoic acid (1a) and of 2‐(4‐imidazolyl)‐1‐isocyanoethane (1b). A detailed kinetic analysis has been performed. The reaction starts with acylation of the imidazole groups followed by deacylation. With excess of substrate the second step is rate‐determining and the system shows burst kinetics behaviour. The rate of acylation of 1a can be analyzed by a two term equation; the major term involves the COOH groups. A transition state is proposed in which COOH stabilizes the negative charge developing on carbonyl oxygen. This system is approximately 400 times more active than e.g. histidine. The data for 1b reveal that the polymer imidazole groups are approximately six times more active than e.g. the imidazole group of histamine. This phenomenon is ascribed to a cooperative effect of the polymer imidazoles.The deacylation is general base catalysed. Its rate constants are almost equal to those of acetylimidazole.For comparison, the hydrolysis of the charged substrates 4‐acetoxy‐3‐nitrobenzoic acid anion and 3‐acetoxy‐N,N,N‐trimethylanilinium iodide by 1a and 1b has been included.
Synthesis of 1‐isocyano‐1‐tosyl‐1‐alkenes and their use in the preparation of imidazoles
Authors: van Leusen Albert M. , Schaart Fokko J. , van Leusen Daan 
Published: September 2010

Abstract1‐Isocyano‐1‐tosyl‐1‐alkenes (1) are useful new synthons. They are obtained by dehydration of the corresponding N‐(1‐tosyl‐1‐alkenyl)formamides (4), which are reaction products of tosylmethyl isocyanide (2) and aldehydes or ketones. 1‐Isocyano‐1‐tosyl‐1‐alkenes 1 react smoothly with primary aliphatic amines (or ammonia) to give 1,5‐disubstituted (or 5‐monosubstituted) imidazoles (7) in high yields.
Photocatalysis IV. Preparation and characterization of a stable copper(I) triflate·trans‐cycloheptene complex
Authors: Evers J. Th. M. , Mackor A. 
Published: September 2010

AbstractWhen copper(I) triflate·cis‐cycloheptene is irradiated at 254 nm in n‐hexane solution, cis → trans‐isomerization occurs and the stable complex copper (I) triflate·trans‐cycloheptene precipitates. This complex has been isolated, purified and characterized by elemental analysis and by its 1H and 13C NMR, Raman and UV spectra.
Stereoselective synthesis of (+)‐pilocarpine, an imidazole alkaloid used in ophthalmology (Imidazole Chemistry, Part VII)
Authors: Noordam A. , Maat L. , Beyerman H. C. 
Published: September 2010

AbstractThe synthesis of a mixture of (+)‐pilocarpine and (+)‐isopilocarpine from L‐histidine is described. Their separation is known.
Synthesis of fragments of human β‐lipotropin, βh‐LPH. Part II. The synthesis of βh‐LPH‐(61‐91), βh‐endorphin
Authors: van Nispen J. W. , Bijl W. A. A. J. , Greven H. M. 
Published: September 2010

AbstractThe classical fragment condensation approach was used to synthesize the hentriacontapeptide human β‐endorphin [βh‐LPH‐(61‐91)].
Helical configuration of poly(tert‐butyliminomethylene). Complete resolution and maximum optical rotation
Authors: van Beijnen A. J. M. , Nolte R. J. M. , Drenth W. 
Published: September 2010

AbstractBy repeated chromatography over optically active poly(sec‐butyliminomethylene) on glass beads complete resolution of poly(tert‐butyliminomethylene) was obtained. The specific rotation increases with molecular weight up to [α]20578 = 56 ± 2° at approximately 20 repeating units.
Gold‐phosphine cluster compounds: The reactions of [Au9L8]3+ (L = PPh3) with L, SCN− and Cl− to [Au8L8]2+ (Au11L8(SCN)2]+ and [Au11L8Cl2]+
Authors: Vollenbroek F. A. , Bour J. J. , van der Veden J. W. A. 
Published: September 2010

Abstract[Au9L8]3+ reacts with L to give [Au8L8]2+ via the intermediate [Au8L7]2+. The reaction of [Au9L8]3+ with SCN− and Cl− results in the formation of [Au11L8(SCN2]+ and [Au11L8Cl2]+, respectively. [Au8L8]2+ acts as an intermediate in this conversion of Au9 into Au11. The 2+ charge on the [Au8L8]2+ cluster and its diamagnetic nature can be rationalized by a simple Hückel MO calculation.
Coordination compounds of platinum(II) with 2‐methylimidazole and 1,2‐dimethylimidazole
Authors: Marcelis A. T. M. , van Kralingen C. G. , Opschoor J. , Reedijk J. 
Published: September 2010

AbstractThe synthesis and characterization of new Pt(II) coordination compounds with the nitrogen‐donor ligands 2‐methylimidazole (2MIz) and 1,2‐dimethylimidazole (DMIz) are described. The compounds concerncis‐Pt(2MIz), X2,cis‐Pt(DMIz)2X2, [Pt(2MIz)4]X2(H2O)n, [Pt(DMIz)4]X2,trans‐Pt(DMIz)2X2where X = Cl, Br or I and n = 0 or 2, andtrans‐Pt(2MIz)2I2. Despite several attempts no other puretrans‐platinum compounds of 2MIz could be obtained.The new compounds were characterized by chemical analyses, X‐ray powder diffraction photographs, vibrational spectroscopy (IR and far‐IR) and proton nuclear magnetic resonance.In all cases the metal(II) ions are square‐planar coordinated.
The oxidation of hexahelicenes. Synthesis of hexahelicene‐5,6‐quinone
Authors: Diesveld J. W. , Borkent J. H. , Laarhoven W. H. 
Published: September 2010

AbstractThe remarkable ease with which 1,3,14,16‐tetramethylhexahelicene can be oxidised has to be ascribed to the electronic effect of multiple methyl substitution and not to disturbance of the helical conformation, as might be concluded from the polarographic oxidation potentials of hexahelicene and some of its methyl derivatives. Oxidation of hexahelicene with chromic acid in acetic acid gives hexahelicene‐5,6‐quinone in 70% yield. Its structure was proven by spectroscopic methods.
The synthesis of aldehydes by means of a modified Rosenmund reduction of acid chlorides
Authors: Peters J. A. , van Bekkum H. 
Published: September 2010

AbstractAliphatic as well as aromatic acid chlorides are reduced smoothly into aldehydes at room temperature and atmospheric pressure by hydrogenation, using palladium on carbon as the catalyst, acetone or ethyl acetate as solvent and ethyldiisopropylamine as hydrogen chloride acceptor. The reaction has a high selectivity and under the conditions used, no over‐reduction nor reduction of aromatic rings, of nitro and chloro substituents in benzoyl chlorides, or double bonds in cinnamoyl chlorides, was observed. The selectivity is probably the result of a combination of factors, such as selective adsorption of the acid chloride on the catalyst (with respect to the aldehyde) and partial poisoning of the catalyst surface by co‐adsorption of ethyldiisopropylamine and its hydrochloride.
Reaction of spiro[1,3‐benzodioxole‐benzothiazines] with hydroxylamine and active methylene compounds
Authors: Latif N. , Zeid I. F. , Mishriky N. , Assad F. M. 
Published: September 2010

AbstractThe reactivity of the title spiranes (1) towards cleavage by different nucleophiles in ethanolic solutions has been investigated. The spiranes are cleaved by ethyl p‐aminobenzoate to give 2‐aryl‐3‐(4‐methoxycarbonylphenyl)‐3H‐quinazoline‐4‐thiones (2b–d) together with tetrachlorocatechol, in a manner similar to the reaction with anilines and hydrazines. However, cleavage with hydroxylamine in ethanol affords ethyl 2‐(thioaroylamino)benzoates (4) in addition to the expected 2‐aryl‐3‐hydroxy‐3H‐quinazoline‐4‐thiones (2e‐f).In contrast to the situation found with amines and hydrazines, the spiranes give 4‐(dicyanomethylene)‐and 4‐[cyano(ethoxycarbonyl)methylene]‐2‐aryl‐3,1‐benzothiazines (5) along with the 2‐(thioaroylamino)benzoates (4) when reacted with malononitrile and with ethyl cyanoacetate. In all cases, tetrachlorocatechol is produced. Reaction pathways are discussed.
Conformational studies on helicenes VII. Synthesis and conformation of 5,6‐dihydrohexahelicene
Authors: Borkent J. H. , Diesveld J. W. , Laarhoven W. H. 
Published: September 2010

AbstractIrradiation of 2,7‐distyrylnaphthalene or 2‐styrylbenzo[c]phenanthrene under completely oxygen‐free conditions gives rise to the formation of 5,6‐dihydrohexahelicene (2) as a consequence of H‐shifts in the primary formed cyclization product. The conformation of2was analysed by NMR spectroscopy. From the chemical shifts of the aromatic protons, the coupling constants of the saturated moiety and the temperature independence of the spectrum it could be concluded that2occurs in one conformation, in which the axial proton at C(5) is directed towards the opposite ring. The resemblance of the spectra of2and l‐phenylbenzo[c]phenanthrene affirms that this conformation is the less hindered one.
Synthesis of peptide‐morphinans based on Diels‐Alder adducts of thebaine with enkephalin moieties (chemistry of opium alkaloids, Part XVI)
Authors: Beyerman H. C. , Lie T. S. , Maat L. , Noordam‐Weissdorf M. 
Published: September 2010

AbstractThe preparation of Diels‐Alder adducts of (‐)‐thebaine and ethyl acrylate is described. Hydrolysis of the major adduct gave the 7α‐carboxylic acid which was coupled with the ethyl esters of L‐leucine, L‐phenylalanyl‐L‐leucine and glycyl‐L‐phenylalanyl‐L‐leucine, respectively, three peptide segments derived from the endogenous opiate, leucine‐enkephalin. These compounds, as well as the 7β‐ethoxycarbonyl isomer, were O‐demethylated to give the corresponding 3,6‐dihydro‐xymorphinan derivatives. N‐(6,14‐endo‐Etheno‐6,7,8,14‐tetrahydrothebaine‐7α‐carbonyl)‐L‐phenylalanyl‐L‐leucine ethyl ester and its 7,8‐dihydromorphine analogue were reduced to the corresponding leucinols.Pharmacological screeningDr. A. E. Jacobson, National Institutes of Health, Bethesda, Maryland, U.S.A.
showed that several of these compounds are morphine‐like analgesics, notably compound 11, N‐(6,14‐endo‐etheno‐7,8‐dihydromorphine‐7α‐carbonyl)‐L‐leucine ethyl ester.
1‐Methylpyridinio and 2,4‐dinitrophenyl groups as electron acceptors in poly(iminomethylenes)
Authors: Oostveen E. A. , Drenth W. 
Published: September 2010

AbstractThe synthesis and charge‐transfer (CT) spectra are described for a series of homopolymers and copolymers of poly(iminomethylenes), magnified image, which contain pyridinium groups as acceptor and iodide ions as donor. The group R includes 3‐[1‐CH3‐N⊕C5H4]CH2‐(1c), 3‐[1‐CH3‐N⊕C5H4]CH(CH3)‐ (2c), 4‐[1‐CH3‐N⊕C5H4]CH(CH3)‐ (3c) and 4‐[1‐CH3‐N⊕C5H4]CH2CH2‐ (4c), I− being the counter ion. The copolymers consist of either the monomeric units of 1c and 4c [ratio 1: 1 (5c) and 1:2 (5d] or of [3−[1−[2,4−(NO2)2C6H4CH2]−N⊕C5H4]]CH(CH3)N=magnified image and C6H5CH(CH3)N=magnified image (7c), Comparison is made between the iodide to pyridinium CT spectra of 1,3‐dimethylpyridinium iodide (8) and the polymer of 4‐vinyl‐1‐methylpyridinium iodide (9). With respect to the former compound, these CT bands of the polymers 1c‐4c show a large bathochromic shift, which is largely attributed to their low microenvironment polarity. An even larger bathochromic shift was observed in the CT spectra of the copolymers 5a and 5d. This additional effect is attributed to iodide ions being intercalated between pyridinium cations. On complexing copolymer 7c with N,N,N′,N′‐tetramethyl‐1,4‐benzenediamine, complete charge transfer occurred. This phenomenon is attributed to intercalation of the diamine between two dinitrophenyl groups.
Chemistry of crown ethers XIX. Functionalized crown ethers for the solubilization of barium sulfate
Authors: de Jong F. , van Zon A. , Reinhoudt D. N. , Torny G. J. , Tomassen H. P. M. 
Published: September 2010

AbstractThe use of seawater as injection fluid in oil‐producing formations often leads to blocking of the wells as a result of barium sulfate‐scale formation. Macrocyclic complexants specifically designed to solubilize barium sulfate efficiently into water have been synthesized and their BaSO4‐solubilizing capacities have been determined. The stability of barium complexes of macrocyclic polyethers can be greatly increased by the introduction of flexible side‐chains containing anionic groups. Most of the newly synthesized complexants, based mainly on diaza‐18‐crown‐6, give very stable complexes. However, many of them are extremely insoluble in water. Only bis(carboxymethyl)diaza‐18‐crown‐6, bis(phosphonomethyl)diaza‐18‐crown‐6 and, to a lesser extent, bis‐(dicarboxymethyl)diaza‐18‐crown‐6 and bis[(hydroxyphosphinyl)methyl]diaza‐18‐crown‐6 are efficient solubilizers of BaSO4 in water.
The Chichibabin amination of 4‐phenyl‐ and 4‐tert‐butyl‐pyrimidine
Authors: Breuker J. , van der Plas H. C. 
Published: September 2010

AbstractDuring a study on the amination of 4‐phenylpyrimidine in potassium amide/ liquid ammonia it was found that the extent to which the SN(ANRORC) mechanism operates in the amination largely depends upon whether an ammonium salt is used in quenching the reaction. The composition of the σ‐adduct mixture, the structure of the open‐chain intermediates, the inhibition of the SN(ANRORC) mechanism and the course of the amination in apolar solvents have been investigated. In addition, it has been found that, in the amination of 4‐tert‐butylpyrimidine, the SN(ANRORC) mechanism occurs to only a very limited extent.
Synthesis of fragments of human β‐lipotropin, βh‐LPH. Part VI. The synthesis of des‐1‐tyrosine‐α‐endorphin and shortened peptides
Authors: Bijl W. A. A. J. , van Nispen J. W. , Greven H. M. 
Published: September 2010

AbstractThe synthesis of des‐1‐tyrosine‐α‐endorphin and fourteen fragments of this psychostimulant type of neuropeptide is described. In these syntheses use has been made of the classical fragment condensation approach.
Selective allylation of sugar derivatives containing the 1,1,3,3‐tetraisopropyldisiloxane‐1,3‐diyl protective group
Authors: Oltvoort J. J. , Kloosterman M. , van Boom J. H. 
Published: September 2010

AbstractUsing the method of Guibe et al. we were able to selectively introduce an allyl group at the 2‐position in methyl‐4,6‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)‐α‐D‐glucopyranoside and benzyl‐4,6‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)‐β‐D‐glucopyranoside. The dynamic properties of the tetraisopropyldisiloxane‐1,3‐diyl protective group gave us access to a glucose derivative which carried a 1‐propenyl group at the 2‐position, an allyl group at the 6‐position and a tetraisopropyldisiloxane‐1,3‐diyl at the 3,4‐position together with a glucose derivative protected with an allyl, an acetyl and a 3‐hydroxytetraisopropyldisiloxanyl at the 2‐, 3‐ and 4‐positions, respectively.
Cycloaddition of (dimethylamino)allene to some electrophilic alkenes and its application to the synthesis of 3‐alkylidenecyclobutenes
Authors: Klop W. , Klusener P. A. A. , Brandsma L. 
Published: September 2010

Abstract(Dimethylamino)allene and electrophilic alkenes react under mild conditions to give [2 + 2]‐ and [2 + 4]‐cycloadducts in excellent yields. Conversion of the amino group in the [2 + 2]‐adducts into quaternary salts, followed by elimination of tertiary amine and hydrogen halide, under the influence of l,8‐diazabicyclo[5. 4. 0]undec‐7‐ene (DBU) in hexamethylphosphoric triamide (HMPT), affords 3‐alkylidenecyclobutenes in high yields.
Characterization of a glassy‐carbon‐electrode surface pretreated with rf‐plasma
Authors: Schreurs J. , van den Berg J. , Wonders A. , Barendrecht E. 
Published: September 2010

AbstractThe composition of oxidic groups at a glassy‐carbon surface has been studied using phase‐sensitive ac‐voltammetry. Two types of quinones have been identified, i.e. the 1, 2‐naphtoquinone‐ and the 9, 10‐phenanthrenequinone‐like structures. The 1, 4‐naphtoquinone‐ and 9, 10‐anthraquinone‐like structures are, most probably, also present at the glassy‐carbon surface, although in lower surface concentrations. The o‐quinones can be converted into the corresponding benzophenazines (by reaction with o‐phenylenediamine), which are also electroactive. The differences in redox potentials between the quinones and phenazines make detection of intermediate reaction stages possible. The effect of oxygen and argon rf‐plasma treatment upon the composition of the quinone‐surface groups has also been studied. Pretreatment of the glassy‐carbon surface by an oxygen rf‐plasma is a very powerful and clean oxidation technique. Argon rf‐plasma increases the 9, 10‐phenanthrenequinone‐like structures, while oxygen rf‐plasma, with successive cooling in an argon atmosphere, diminishes the surface concentration of quinone structures and increases that of the acidic surface groups, as can be concluded from modification experiments. From phase‐sensitive ac‐voltammetry measurements, a lower limit of 103 s−1 was determined for both the quinone and the phenazine surface reaction rate constants (ks).
The structure of cis‐platinum trinucleoside diphosphate species; the influence of ligand substitutions upon the conformation of the adducts
Authors: den Hartog Jeroen H. J. , Altona Cornelis , van Boom Jacques H. , Reedijk Jan 
Published: September 2010

AbstractThe conformations of the trinucleoside diphosphates in cis‐Pt(LL)[d(GpCpG)‐N7(1), N7(3)] complexes have been studied with LL = (NH3)2 1, cyclohexane‐1, 1‐bis(methanamine) (chbma) 2, 1, 2‐ethanediamine (en) 3, or N, N, N′ N′ ‐tetramethyl‐1, 2‐ethanediamine (tmen) 4. The 1H NMR chemical shifts, together with the conformational equilibria in the sugar rings and the nuclear Overhauser enhancements, have been studied as a probe for structural changes. It appears that the structure of the oligonucleotide part of the molecule is to a large extent the same in 1, 2 and 3. In contrast, the tmen ligand induces relatively large chemical‐shift changes in 4 with respect to 1, 2 and 3. It is suggested that this behaviour is caused by a retarded rotation about the Pt – N7 bonds, giving rise to a more rigid, preferred conformer in the case of 4. The conformational freedom observed in compounds 1, 2 and 3 is indicative of fast rotation on the NMR time scale along the Pt‐N7 bonds and thus of a “head‐to‐tail” arrangement around the platinum atom.
An investigation of the electronic structure of α, β‐unsaturated acetylamino acid ethyl esters using He(I) and He(II) photoelectron spectroscopy
Authors: Ajò D. , Casarin M. , Granozzi G. , Ottenheijm H. C. J. , Plate R. 
Published: September 2010

AbstractThe He(I)‐ and He(II)‐excited photoelectron spectra of the ethyl esters of α, β‐unsaturated acetylamino acids (1a–4a) are presented and discussed. The spectra are assigned by comparison with those of related molecules and by analysis of the relative band intensities under different radiation sources. The effects of β‐substitution on the electronic structure and conformation are also discussed.