bluuebunny/crossref_metadata_2025 huggingface dataset:
1H‐NMR study and conformational aspects of some bicyclo[3.2.0]heptane derivatives
Authors: De Bruyn André , Termont Daniel , De Keukeleire Denis , Anteunis Marc J. O.
Published: September 2010

The 1H‐NMR parameters of endo 2‐hydroxy‐bicyclo[3.2.0]heptan‐6‐one (1), 6,6‐dimethoxy‐bicyclo[3.2.0]heptan‐2‐one (2) and bicyclo[3.2.0]heptane‐2, 6‐dione (3) are discussed, allowing configurational and conformational descriptions. The usual 1H‐nmr criterion based on the observation of one single coupling to state the configuration of the ring annelation in bicyclo[3.2.0]heptane derivatives being not safe, a complete analysis of the ring system seems to be the only alternative as is illustrated for 1. It is found that the five‐membered rings occur in a twist(T)conformation, somewhat more flattened in 2 and 3.
Studies on organophosphorus compounds XX. syntheses of thioketones
Authors: Pedersen B. S. , Scheibye S. , Nilsson N. H. , Lawesson S.‐O.
Published: September 2010

Substituted benzophenones, 2‐benzoylthiophene, 3‐benzoylpyridine, dicyclopropyl ketone, and camphor are converted into the corresponding thioketones after reaction with the dimer of p‐methoxyphenylthionophosphine sulfide, 1. Except for the pyridine derivatives (2‐ and 4‐benzoylpyridines, respectively, gave no thioketones) very high yields are found. Under the same conditions dibenzylketone gave 1,3‐diphenylpropene‐2‐thiol and 1,9‐benzanthr‐10‐one yielded the dimer of 1,9‐benzanthr‐10‐thione. Aromatic thioketones are also obtained by reacting gem‐dichlorides with 2‐methyl‐2‐propane‐thiol in the presence of catalytic amounts of CF3COOH (or AlCl3). A mechanism is suggested based on kinetic measurements. 13C NMR data of the thiocarbonyls of all thioketones are recorded and a function describing the relation between the chemical shifts of CS and CO is found: δCS1.57 δCO=71.45
Studies on organophosphorus compounds XXII The dimer of p‐methoxyphenylthionophosphine sulfide as thiation reagent. a new route to O‐substituted thioesters and dithioesters
Authors: Pedersen B. S. , Scheibye S. , Clausen K. , Lawesson S.‐O.
Published: September 2010

Simple alifatic and aromatic esters, such as ethyl, iso‐propyl, and benzyl benzoates, benzyl butanoate, ethyl heptanoate, and ethyl 1‐ and 2‐naphthoate, respectively, react with the dimer of p‐methoxyphenylthiono‐phosphine sulfide 1 in anhydrous xylene at 140°C to give the corresponding 0‐substituted thioesters in nearly quantitative yields. Also simple alifatic and aromatic S‐substituted thioesters, such as S‐phenyl, S‐benzyl and S‐tert‐butyl thiobenzoates, S‐phenyl and S‐benzyl thioacetates, and S‐ethyl thiobutanoate, produced the corresponding dithioesters in nearly quantitative yields upon treatment with 1 in anhydrous toluene at 110°C. 13C NMR data for the carbonyl‐ and corresponding thiocarbonyl carbons, have been recorded and a linear relation between the chemical shifts of CS and CO is found: δ(CS) = 1.75·δ (CO) ‐ 79.6 for 0‐substituted thioesters and δ(CS) = 1.31.δ (CO) ‐ 22.1 for dithioesters. An anomalous reaction has been observed: Thiobenzoic acid, S,S'‐methylene ester 2 reacted with 1 to give 4,5‐diphenyl‐1‐1,3‐dithiol‐2‐thion 3.
Studies on organophosphorus compounds XXIII synthesis of salicylthioamides and 4H‐1,3,2‐benzoxaphoshorine derivatives from the dimer of p‐methoxyphenylthionophosphine sulfide and salicylamides
Authors: Scheibye S. , Pedersen B. S. , Lawesson S.‐O.
Published: September 2010

By heating secondary O‐hydroxybenzamides at 110‐120 °C with the dimer of p‐methoxyphenylthionophosphine sulfide, 1, in HMPA, the main product is the corresponding thioamide (15‐51 %) but in addition two phosphorheterocyclic systems are isolated, namely 2,3‐dihydro‐2‐(4‐methoxyphenyl)‐4H‐1,3,2‐benzooxazaphosphorine‐4‐thione 2‐sulfide, 4 (5‐23 %) and the corresponding 2‐oxide, 5 (13‐21 %). Cyclohexylsalicylamide at somewhat elevated temperature (∼ 120°C), only gives one phosphorus containing product besides the thioamide. This product is not a benzoxazaphosphorine derivative but a ring opened phosphonthioamidate, 6. A mechanism is suggested. The structures are determined by 1 H, 13 C, and 31 P NMR spectroscopy, as well as UV, IR, and MS spectrometry, and elemental analyses.
Correlation Corrections to the Molecular Dipole Moment of Closed Shell Molecules via Møller‐Plesset Perturbation Theory
Authors: Figeys H. P. , Geerlings P. , van Alsenoy C.
Published: September 2010

Using Møller‐Plesset perturbation theory a general expression is derived for the second order correlation corrections to the molecular dipole moment obtained via a Spin Unrestricted Hartree Fock procedure. It is shown that this expression can be considerably simplified in the case of a closed‐shell molecule. The final result is computationally attractive.
Regio‐and Stereochemical Effects in the Chemical Ionization Mass Spectra of Isomeric Bicyclo|3, 2, O| Heptan‐2‐One Trimethylsiloxy Derivatives1
Authors: Claeys M. , Matveeva H. , Devreese A. , Termont D. , Vandewalle M.
Published: September 2010

Isomers of bicyclo |3, 2, O| heptan‐2‐one trimethylsiloxy derivatives, produced by (π2+π2) photocycloaddition reactions between cyclopent‐2‐enones and trimethylsiloxy alkenes, have been investigated by methane and isobutane chemical ionization mass spectrometry. Head‐to‐head and head‐to‐tail regioisomers and the syn‐and anti‐epimers in each regioisomeric set can be identified by means of these ionization methods. Prominent fragmentation patterns are discussed.
Heterocyclisations with New Fluorinated Reagents from Phosgeniminium Salts(1)
Authors: Gorissen J. , Viehe H. G.
Published: September 2010

N,N‐Dimethyl‐Dichloromethyleniminium chloride, in other words: Phosgeniminium chloride (PI) forms 2‐fluoro‐1, 3‐dichlorotrimethine cyanines 1 and 2‐fluorovinylurea dichlorides 6 with tertiary and secondary acetamides, respectively. Further, PI reacts with fluoroacetyl chloride to the 1‐chloro‐2‐fluoro‐2‐chlorocarbonyl enamines 14. These reactive compounds are cyclized to fluorine‐bearing pyrazoles, oxazoles, pyrimidines and a benzodiazepine.
Urey‐Bradley Force Constants of Some Pentafluoride Compounds of Group via Elements
Authors: So S. P. , Li K. K. , Hung L. K.
Published: September 2010

The Urey‐Bradley force constants of SF5O−, SF5Br, SF5Cl, SeF5Cl and TeF5Cl have been determined by least‐squares‐fit method using published fundamental frequencies. Results appear to suggest that some of the reported assignments are questionable.
Benzo‐and Indoloquinolizine Derivatives XVa. Conformational Analysis of 6,7,12,13‐Tetrahydro‐11bH‐Dibenzo[a,f]Quinolizine Derivatives by 1H AND 13C NMR
Authors: Tourwé D. , Van Brandt W. Den , van Binst G.
Published: September 2010

The influence of the nitrogen lone pair delocalisation with the adjacent aromatic ring in the trans‐quinolizidine conformation of the title compound on the proton and carbon‐13 n.m.r. spectral parameters distinguishes the assignment criteria for these compounds from the previously studied benzo‐substituted quinolizidines.
Tricyclo‐Oxy‐and Tricyclo‐Peroxycolupulones
Authors: De Potter Marc , De Keukeleire Denis , De Bruyn André , Verzele Maurice
Published: September 2010

Four new tricyclic oxidation products, formed in high yield from colupulone (1) in brewing circumstances, are isolated by preparative‐scale high pressure liquid chromatography. Spectral identification leads to the following structures: the C3‐epimers of 7 ‐(3‐methylbut‐2‐enyl)‐3‐(1‐hydroxy‐1‐methylethyl)‐4, 4‐dimethyl‐9‐(2‐methylpropanoyl)‐tricyclo[5.3.1.o1,5]undeca‐8,10,11‐trione (2 and 3, respectively) and the C3,‐epimers of 7‐(3‐methylbut‐2‐enyl)‐3‐(1‐hydroperoxy‐1‐methylethyl)‐4,4‐dimethyl‐9‐(2‐ methylpropanoyl)‐tricyclo [5.3.1.o1,5] undeca‐8,10,11‐trione (5 and 6, respectively). The reaction mechanism is discussed.
Chemical studies of marine invertebrates. XXXIV(1). Herbadysidolide and herbasolide, two unusual sesquiterpenoids from the sponge dysidea herbacea(2)
Authors: Charles C. , Braekman J. C. , Daloze D. , Tursch B. , Declercq J. P. , Germain G. , van Meerssche M.
Published: September 2010

The isolation and structure determination of the sesquiterpene herbadysidolide (1) and the norsesquiterpene herbasolide (2) from the sponge Dysidea herbacea are described.
Mesure Quantitative de L'Activité de la Desoxyribonuclease Plasmatique et de Son Inhibition Par le Complexe Daunorubicine‐ADN
Authors: Hulhoven R. , Desager J. P. , Zenebergh A.
Published: September 2010

A sensitive, fast and quantitative method was described to estimate plasma deoxyribonuclease (DNase) activity. This method was using125I DNA as substrate and the activity of the enzyme was measured by the increase of radioactivity in the TCA‐soluble fraction. The method was enough sensitive to detect the activity of about long of pure DNase I. The coefficient of variation was always lower than 10% at the weakest activity and lower than 2% at higher activities. Experimental results did confirm the weak activity of human plasma DNase, which was about 5‐fold lower than the rabbit's one. In presence of a daunorubicin‐DNA complex with a molar ratio of 20, this activity was inhibited by half.
Negative‐ion mass spectra of organophosphorus compounds containing PO AND PS groups
Authors: Meyer H. J. , Larsson F. C. V. , Lawesson S. ‐O. , Bowie J. H.
Published: September 2010

Compounds containing the (XO or S) unit yield negative‐ion spectra, which are dominated by peaks arising by α or ß cleavage to PX.

Molecular ions are generally absent in these spectra, except in cases where the molecule contains an additional electron‐capture group (e.g. p‐nitrophenyl). Simple cleavage is accompanied by a characteristic rearrangement reaction for certain compounds containing the ‐C(X)‐Y‐P(S) unit (XO or S, YO, S, or NH); the rearrangement is most pronounced when YNH. Compounds containing the PS moiety are prone to thermal decomposition; such decompositions may be detected by the presence of peaks corresponding to Sn (n=1‐10) in the negative‐ion spectra.
Chemical studies of marine invertebrates. XXXVI(1). Strongylosterol, a novel C‐30 sterol from the sponge strongylophora durissima Dendy (2).
Authors: Bortolotto M. , Braekman J. C. , Daloze D. , Tursch B.
Published: September 2010

A novel sterol, strongylosterol, has been isolated from the sponge Strongylophora durissima. It has been demonstrated to be 3β‐hydroxy‐24°‐ethyl‐27‐methylcholesta‐5, 25(26)‐diene (1).
Some applications of the empirical force field method to stereochemistry
Authors: Mislow Kurt , Dougherty Dennis A. , Douglas Hounshell W.
Published: September 2010

The empirical force field (or molecular mechanics) method has become increasingly popular as a computational tool in chemistry. Examples are adduced from work in our laboratories to illustrate some of the power and scope of this method as applied to problems in static and dynamic stereochemistry.
The 1H NMR spectra of the strychnos alkaloids retuline isoretuline, and their N‐deacetyl compounds.
Authors: Tavernier D. , Anteunis M. J. O. , Tits M. J. G. , Angenot L. J. G.
Published: September 2010

The 300 MHz 1H NMR spectra of the title compounds are discussed. The vicinal coupling constants 3J H2, H16 and H16, H15 are about 10 Hz and 4 Hz in the iso series, and about 7 Hz and 1 Hz for 1 and 2. In isoretuline, the piperidine ring (ring D) has a chair conformation, but in retuline a boat conformation, with C21 in the tip position, prevails. This conclusion is based on the pattern of allylic and homoallylic couplings around the double bond, and rests also on comparison with the spectrum of strychnine. Evidence is presented for a hydrogen bond between the C17 hydroxymethyl and the Nl‐COCH3, group in isoretuline.
Mass Analyzed Ion Kinetic Energy Spectrometry with a Modified AEI MS 902 Spectrometer
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Abrassart M. , Finet D.
Published: September 2010

A conventional double focusing mass spectrometer has been modified in order to obtain mass‐analyzed ion kinetic energy spectra.
Stereochemical aspects of proton chemical shifts. VII‐4‐fluoro‐prolines. A FURTHER CASE OF VIOLATION OF THE “SYN‐UPFIELD” RULE IN1H‐NMR.
Authors: Anteunis M. J. O. , Cuypers P. , Liberek Bogdan , Kolodziejczyk A.
Published: September 2010

It is reported that, as previously also found for ‐N°Me3groupings, the “syn‐upfield” effect caused by F fails for 4‐F‐prolines and their derivatives.
Chemical studies of marine invertebrates. XXXVII(1). Three novel meroditerpenoids from the sponge strongylophora durissima(2).
Authors: Braekman J. C. , Daloze D. , Hulot G. , Tursch B. , Declercq J. P. , Germain G. , van Meerssche M.
Published: September 2010

Three novel meroditerpenoids, strongylophorine‐1 (1), ‐2 (2) and ‐3 (3) have been isolated from the sponge Strongylophora durissima, Strongylophorine‐1 and ‐3 possess structure 1 and 3 respectively, as established by their spectral properties, hemisynthesis and chemical intercorrelation. The structure of strongylophorine‐2 has been shown to be 2 by X‐ray diffraction analysis on its monoacetylderivative (13).
On The Mechanism of the Conversion of α‐Cyanoenamines into Amides
Authors: Kimpe Norbert De , Verhé Roland , Buyck Laurent De , Schamp Niceas
Published: September 2010

The conversion of α‐cyanoenamines into N‐monosubstituted carboxylic acid amides by means of hydrogen chloride in various alcohols under strictly anhydrous conditions was shown to occur with incorporation of the alcohol‐oxygen atom into the final amides. α‐Cyanoenamine hydrochlorides were obtained as stable salts by reaction of α‐cyanoenamines with hydrogen chloride in benzene.
6,6‐Dimethoxy Bicyclo[3.2.0]Heptan‐2‐One: An Intermediate for Prostanoid Synthons
Authors: Keukeleire Denis De , de Wilde Hugo , Verzele Frank , Wyffels Wilfried , Vandewalle Maurits
Published: September 2010

The known 6,6‐dimethoxy bicyclo [3.2.0]heptan‐2‐one, obtained by (π 2 + π 2) photocycloaddition of 2‐cyclopentenone and 1, 1‐dimethoxyethene, is an adequate precursor for prostanoid synthons. Its conversion into intermediates for the 11‐desoxyprostaglandin (PG) series and for PGC2 is described.
New Members of the hop anti iso‐α‐Acids Series
Authors: Taeye Leo De , Keukeleire Denis De , Verzele Maurice
Published: September 2010

Two new compounds, 4‐hydroxy‐5‐(3‐methylbutanoyl)‐2‐(3‐methyl‐2‐butenyl) furan(2H)‐3‐one(5) and 2‐(3‐methyl‐2‐butenyl)‐4‐ethanoyl‐3,4‐dihydroxy‐5‐(2‐methylpropylidene)‐2‐cyclopentene‐1‐one (12) have been isolated from isomerisation reaction mixtures of humulone (1). As both formation mechanisms show, the compounds are rearranged derivatives of the hop anti iso‐α‐acids.
A novel structure for substituted dithiooxamide Pd(II) and Pt(II) complexes
Authors: Dommisse R. A. , Aarts A. J. , Desseyn H. O. , Alderweireldt F. C.
Published: September 2010

As a part of our study on the spectral properties of N, N′‐dialkyldithiooxamide Pd(II) and Pt(II) complexes, their 1H‐ and 13C‐NMR spectra were studied. The structure formerly proposed in the literature cannot be maintained (1, 2). It is shown that these complexes exist with coordination to both sulfur atoms.
Structure de la Dibenzyl‐4,4′Diphényl‐2,2′ [Biimidazoline‐4:4′] Dione‐5,5′
Authors: Tinant B. , Germain G. , Declercq J. P. , van Meerssche H.
Published: September 2010

The crystal and molecular structure of the title compound, C32H26N4O2, has been determined by direct methods from diffractometer intensities. The structure is that of a racemic formed by dl dimers.

Crystal data are as follow: monoclinic, P21/c, a = 9.991 (2), b = 13.709 (6), c = 18.961 (8) Å, β = 96.89° (3), Z = 4, Dx = 1.28 Mg m−3
A Re‐Investigation of the Conformational Behaviour of CIS‐D‐Allo‐Hydroxyproline in Solution
Authors: Anteunis Marc J. O. , Cuypers Paul , Buďêsínský Milos
Published: September 2010

The 1H NMR spectral changes observed at 300 MHz during titration in D2O of cis‐D‐allohydroxyproline (aHyp) allow to define the approximate ring conformation in solution and the rotational behaviour of the carboxyl around Cα‐C′. The cationic species is characterized by ring conformers close to the envelopes with Cγ‐endo and Cδ‐exo as the flap. The carboxyl plane is in the direction of Cδ/Cγ (Ψ = 60‐90°), allowing for an interaction with the quasi‐axial γ‐OD. During titration of the carboxylic group this plane rotates nearer to γ‐OD. The latter picture is consistent with observations reported in the literature for the behaviour in Pro and trans‐Hyp2, 4. When the amine function is titrated (pD > 10) the carboxylate group becomes coplanar with D‐N‐Cα (Ψ ∼ 0°). In conjunction the ring escapes into a form best defined by a twist having Cδ exo and N endo. The possibility for intramolecular hydrogen bonding (e.g. between the carboxylic group and the hydroxyl function in the cation and zwitterion or between the same group on the amine function in the anion) contributes little to the inherent pyrrolidine ring conformation, although a restriction of conformational freedom to δ+ in D2O for the zwitterionic state could be revealed by comparison to DMSO‐d6, where concomitantly the γ− form also is present.
Chemical Studies of Marine Invertebrates. XL. Δ9 (12)‐Capnellene‐2β, 5α, 8β, 10α‐Tetrol, a New Sesquiterpene Alcohol from the Soft Coral Capnella Imbricata
Authors: Kaisin M. , Tursch B. , Declercq J. P. , Germain G. , van Meerssche M.
Published: September 2010

Δ9(12)‐Capnellene‐2β,5α,8β,10α‐tetrol [1], a new sesquiterpene of the capnellene sesquiterpene class has been isolated from the alcyonarian Capnella imbricata. Its structure and relative configuration were determined by X‐ray diffraction analysis.
The Crystal Structure of 1‐{2,4‐Dichloro‐β‐ [(2,4‐Dichloro‐Benzyl)Oxy] Phenethyl} Imidazole Hemihydrate: Miconazole. 1/2 H2O
Authors: Peeters O. M. , Blaton N. M. , De Ranter C. J.
Published: September 2010

The structure of the title compound has been investigated as part of a general study on the chelating properties of therapeutically active imidazole derivatives. The compound crystallizes in the monoclinic system, space group P21/n, with lattice parameters a = 14.614(5), b = 33.206(12), c = 8.062(3) Å, β = 91.24(3)°, Z = 8 and Dm = 1.42, Dc = 1.44 Mg m−3. The structure was solved by direct methods and refined to a final R‐value of 0.086. The asymmetric unit contains two miconazole molecules linked by the water molecule.
Spectres R.M.N.‐13C D'Hydroxy‐5 Isoflavones et de Diméthyl‐2,2 Phénylacetyl‐6 Chromènes
Authors: Vilain C. , Jadot J.
Published: September 2010

13C NMR assignments previously given for A‐nuclei (C‐5, 6, 7, 8, 9, 10) of 5‐hydroxy‐isoflavones (Ie, IIe, IIIb) have been reconsidered on the basis of the proton‐coupled spectrum of 5‐hydroxy‐7, 4′‐dimethoxyisoflavone (Ie) (cf:Bull. Soc. Chim. Belg., 76 n°6/473, 1977).

Furthermore, in order to generalize the method employed to predict resonances of the aromatic carbons of the 2,2‐dimethylchromene ring, we have recorded and fully analysed the spectra of the model compound (IV) and of the 2,2‐dimethylphenylacetyl‐6‐chromenes (V) and (VI).
Hydrogenolysis of Alkanes on Alumina Supported Platinum Kinetic Study and Effect of the Hydrocarbon Structure
Authors: Leclercq G. , Leclercq L. , Maurel R.
Published: September 2010

The kinetics of the hydrogenolysis of some light saturated hydrocarbons has been studied and the results have been rationalized by using a rate expression derived from the kinetic scheme originally proposed by CIMINO, BOUDART and TAYLOR for ethane hydrogenolysis.

magnified image

This kinetic study leads to the conclusion that the influence of the structure of the hydrocarbon on its reactivity is mainly due to change in its adsorption equilibrium constant rather than to changes in the reactivity of the adsorbed species. Those results are in a good agreement with Anderson's conclusions on the involvement of 1, 2 and 1, 3 diadsorbed species in the hydrogenolysis of saturated hydrocarbons on platinum.

The effect of the hydrocarbon structure on its reactivity and on the selectivity of its reactions with hydrogen have been investigated. This study confirms our previous conclusions since they emphasize the influence of the neighbor carbon atoms of the C‐C bond to be broken on its reactivity. Our results cannot all be rationalized by a single reaction mechanism but support the view that 1, 2‐, 1, 3‐, 1, 4‐ and 1, 5‐ diadsorbed species can all play a role in reactions between hydrogen and hydrocarbons on platinum.
Études dans la Série des Pyrano [2,3‐c] Pyrazole‐3(2H)‐Ones
Authors: Maquestiau A. , van Haverbeke Y. , Vanden Eynde J. ‐J.
Published: September 2010

A number of pyrano [2,3‐c] pyrazole‐3(2H)‐ones are obtained by reaction of 3‐hydroxypyrazolin‐5‐one with β‐dicarbonyl compounds.

The position of the substituents on the 6‐membered ring of these bicyclic derivatives is determined by 1H NMR.

The orientation of the cyclocondensation is discussed.
Un Nouvel Exemple de Migration D'Hydrogène Intramoleculaire Dans Un Radical Vinylique: Addition Radicalaire de l'Acétone À l'Octyne‐1
Authors: Gardrat C. , Montaudon E. , Lalande R.
Published: September 2010

Addition of acetonyl radicals to 1‐octyne leads to the formation of 1/1 adducts. Besides the normal product, appear two kinds of cyclic derivatives. Formation of the latter is explained by hydrogen shifts in the transient vinyl radical. 1,5‐hydrogen shift is predominant, but 1,6‐hydrogen shift is evidenced for the first time in such a radical.
Rearrangement of 1‐aryl‐2,2‐Dichloro‐1‐Alkanones and 1‐Aryl‐2,2‐Dichloro‐1‐Alkanols with Methylmagnesium Iodide
Authors: de Kimpe Norbert , Verhé Roland , de Buyck Laurent , Schamp N.
Published: September 2010

1‐Aryl‐2,2‐dichloro‐1‐alkanones were shown to rearrange with methyl magnesium iodide in ether under reflux into highly sterically hindered alkohols. The mechanism proceeds by a pseudo pinacol type rearrangement of the initially formed carbonyl adduct. The mechanism of the rearrangement was proven by the synthesis of authentic reaction intermediates. The rearrangement was also extended to 1‐aryl‐2,2‐dichloro‐1‐alkanols which behaved analogously towards methylmagnesium iodide.
Force field studies of some XY3 planar molecules and ions
Authors: Jothi A. , Shanmugam G.
Published: September 2010

Redington and Aljibury's parametric method has been applied to study the force fields of some XY3 planar molecules and ions. Interatomic force constants and interaction force constants were calculated. Other molecular constants like coriolis coupling constants, mean amplitudes of vibration and centrifugal distortion constants were calculated and found to agree with the available literature values.
Enzymatic “in vitro” Reduction of ketones. I. Kinetics of coupled‐substrate coenzyme recycling systems
Authors: Lemière G. L. , van Osselaer T. A. , Lepoivre J. A. , Alderweireldt F. C.
Published: September 2010

The kinetics of the coupled‐substrate coenzyme recycling system, which is a very useful enzymatic method for preparative purposes, are studied. A full steady‐state rate equation and a much more useful initial rate equation are elaborated. These equations are built up with kinetic constants from the two composing single reactions. This enables synthetists to predict rate and equilibrium of recycling systems from the kinetic constants of the single reactions.
Enzymatic “In Vitro” Reduction Of Ketones. V. (1) Reduction of 1‐alkyl‐4‐piperidones in an ethanol ‐ NAD+ ‐ HLAD ‐ system
Authors: van Luppen J. J. , Lepoivre J. A. , van Osselaer T. A. , Lemière G. L. , Alderweireldt F. C.
Published: September 2010

In a previous paper (2) the coupled‐substrate coenzyme recycling system ketone‐ethanol‐NAD+‐HLAD has been described as an excellent tool for the reduction of alicyclic ketones. Now we report similar reductions for a series of 1‐alkyl‐4‐piperidones.

Although it is generally known that nitrogen heterocycles (3) are very effective inhibitors of HLAD, these products are readily reduced. However the rates of reduction of these products are much smaller than those of the corresponding cyclohexanone derivatives (4, 5) (e.g. the reduction rate of 1‐n‐butyl‐4‐piperidone is 40x lower than that of cyclohexanone). This is mainly reflected in an increase of the enthalpy of activation. Detailed results will be published soon.
The synthesis of 10‐fluorobenzo[a]pyrene
Authors: Newman Melvin S. , Khanna Vinod K.
Published: September 2010

The synthesis of 10‐fluorobenzo[a]pyrene in four steps from 11‐fluoro‐12‐methylbenz[a]anthracene is described.

A current hypothesis concerning the metabolism which is responsible for the carcinogenic activity of benzo[a]pyrene, BP, maintains that BP is converted into isomers of 7,8‐dihydroxy‐9,10‐epoxy‐7,8,9, 10‐tetrahydrobenzo[a]pyrene which are the true carcinogens.1 If any of 7‐,8‐,9‐, and 10‐fluorobenzo[a]pyrenes proved carcinogenic an alternate mechanism for carcinogenesis would be required. If all four fluorinated compounds were non‐carcinogenic strong support of the current hypothesis would be provided.2 Accordingly we planned to synthesize the fluoro BP compounds so that adequate testing could be carried out.
Pyrazines III Condensation Des Dihydropyrazines Avec Les Composés Carbonyles: Synthèse De Pyrazines Substituées Et De Dihydro‐6, 7‐5E‐Cyclopenta [b] pyrazines
Authors: Flament Ivon , Sonnay Philippe , Ohloff Günther
Published: September 2010

Dihydropyrazines have been found to condense easily and in good yields with carbonyl compounds. 2,3‐Dihydropyrazines were treated with aliphatic, terpenic, aromatic and furan aldehydes and with aliphatic and alicyclic ketones leading to trisubstituted pyrazines. When α, β‐unsaturated carbonyl compounds are used the formation of 6,7‐dihydro‐5E‐cyclopenta [b] pyrazines is observed. When autocondensation of α‐aminoacetone is conducted in the presence of aldehydes these compounds react immediately with the intermediate 3,6‐dihydropyrazine to give trisubstituted pyrazines.
A new hypothesis explaining synergy between two phases in heterogeneous catalysis the case of hydrodesulfurization catalysts
Authors: Delmon Bernard
Published: September 2010

We propose a new mechanistic model, explaining the properties of catalysts composed of sulfides of Group VI and sulfides of Group VIII metals. Spill‐over hydrogen, emitted by the latter, modulates, or controls, the catalytic centers at the surface of the former sulfide. Slightly reduced centers formed by spill‐over hydrogen would be active in hydrogenation, and deeply reduced centers, in hydrodesulfurization. The theory resting on this concept of a remote control agrees qualitatively with all the known catalytic and physico‐chemical properties of the catalysts.
The reaction of β‐ and γ‐lactones with chlorotrimethylsilane + metal halides
Authors: Scheibye S. , Thomsen I. , Lawesson S.‐O.
Published: September 2010

Great efforts have been made to develop non‐saponificative hydrolysis of carboxylates and other esters. Useful methods are so‐called SN2‐type dealkylation of esters1 and the use of halotrimethylsilanes. Thus iodotrimethylsilane2‐4 (ITMS) was originally used and later chlorotrimethylsilane (CTMS) + sodium iodide5 was found to convert alkyl esters into the corresponding trimethylsilyl esters. Also alkyl phosphonates have been cleaved in the same way.6‐10 Bromotrimethylsilane (BTMS) does not react with esters.2 However, in a recent note11 it is stated that BTMS cleaves lactones, which prompt us to publish some of our results at this stage of the investigation.

It has been found that CTMS is unreactive towards esters and lactones under different conditions studied. However, when β‐propiolactone was refluxed with CTMS in acetonitrile with anhydrous sodium chloride, sodium bromide, or potassium iodide present the corresponding trimethylsilyl‐3‐halopropanoates, IIa‐c, were isolated in reasonable yields. Both NaI, H2O, and anhydrous magnesium bromide do cleave β‐propiolactone at room temperature to give, after acidification, 3‐iodo‐ and 3‐bromopropanoic acids, respectively. Butyrolactone did only react with CTMS in the presence of potassium iodide to give trimethylsilyl‐4‐iodobutanoate. In the presence of sodium bromide and sodium chloride no reaction took place. In our hands certain lactones such as γ‐valerolactone, 2‐bromobutyrolactone, thiobutyrolactone, and angelica lactone were totally unreactive.

All silyl esters were characterized by MS, NMR, IR, and elementary analyses. Hydrolysis also gave known acids.
Structure Cristalline de la L‐(1‐Tosylamino‐2‐Phényl)‐Éthyl Chlorométhyl Cétone (TPCK), Un Inhibiteur Spécifique de l'α‐Chymotripsine
Authors: Michel A. , Durant F. , King G. S. D.
Published: September 2010

The title compound is a specific inhibitor of a‐chymotrypsin, a proteolytic enzyme which hydrolyses aromatic peptide linkages. Its crystal structure has been investigated by X‐ray diffraction in order to ascertain the molecular conformation and to see how this molecule could fit with specific substrates of this enzyme such as ATEE or BTEE which is closely structurally related.

The structure has been solved using direct methods and refined by full matrix least‐squares techniques to R = 0.057.
Conformational Study Of 3‐OXO‐ and 4‐OXO‐thiane‐L‐oxide and their dimethyl acetals. Exemplification of short‐range electrostatic stabilization contributions
Authors: Nachtergaele W. A. , Tavernier D. , Anteunis M. J. O.
Published: September 2010

Both 3‐oxo‐ (3) and 4‐oxo‐thiane‐l‐oxide (1) exist in the chair form with axial sulfoxide bonds. The axial preference is retained in the dimethyl acetal of (1) but not in the dimethyl acetal of (3). Beside steric strain, local electrostatic stabilization identified as a gauche 1,4‐ or a 1,5 (g±, g±)‐interaction between opposite residual charges rationalize the conformational preferences.
Approche Théorique du Problème de la Tautomérie des Triades HX‐YZXY‐ZN. II. Cas des Imines, Hydrazones et Oximes (Y = N, Z = CH2)
Authors: Lhamyani‐Chraibi M. , Gélizé‐Duvigneau M. , Arriau J. , Elguero J.
Published: September 2010

The tautomerism of three classes of related compounds (imines, hydrazones and oximes) has been examined by means of the CNDO/2 and PCILO methods with complete geometry optimization. The calculated geometries agree with the experimental ones but the N‐O distance in the oxime. The total energies favoured the azo and nitroso tautomers at variance with the experiment. The electrostatic potentials of the common anions to both tautomers allow a prediction of the protonation site. This dynamic approach of the prototropic tautomerism gives a better description of the reality than the static approach based on calculated energies.
Enzymatic in vitro reduction of ketones VI. (1) reduction rates and stereochemistry of the HLAD‐catalyzed reduction of 3‐alkyl‐ and 4‐alkylcyclohexanones
Authors: van Osselaer T. A. , Lemière G. L. , Lepoivre J. A. , Alderweireldt F. C.
Published: September 2010

Reaction rate constants for the catalytic step HLAD‐NADH + ketone → HLAD‐NAD+ + alcohol in the HLAD‐catalyzed reduction of 3‐alkyl‐ and 4‐alkylcyclohexanones are determined from initial rate measurements in the coenzyme recycling system ketone‐ethanol‐NAD+‐HLAD. By rate measurements at several temperatures, activation parameters were determined and isokinetic relationships tracked down. Two different isokinetic relationships show that the 3‐alkylcyclohexanones pass through an other type of transition state than cyclohexanone and the 4‐alkylcyclohexanones, which means that they have a different arrangement on the HLAD‐NADH complex. The results are rationalized in view of the most recent principles on nucleophilic additions to carbonyl functions. The resulting model for the HLAD‐catalyzed reduction adequately explains the observed rate accelerating and decelerating effects and the stereochemistry of the reduction as well.
Light‐Intensity Dependence In The Kinetics Of N‐Gap Photoelectrode Stabilization
Authors: van Overmeire F. , Vanden Kerchove F. , Gomes W. P. , Cardon F.
Published: September 2010

The influence of the light intensity (L) and the concentration (y) of the Fe(CN)64 ion on the stabilization of n‐GaP photoelectrodes was studied in alkaline medium by means of the rotating ring‐disk technique. The steady‐state stabilization ratio increased with increasing y or decreasing L. A kinetic model, involving surface intermediates, is proposed in order to explain the experimental results.
Étude Par Spectrométrie De Diffusion Ionique De La Structure De La Bi‐Couche D'Oxyde De Molybdene Et De Cobalt A La Surface Du Support Des Catalyseurs D'Hydrodésulfuration
Authors: Delannay F. , Haeussler E. N. , Delmon B.
Published: September 2010

Ion scattering spectrometry (ISS), a method which allows to measure the atomic composition of the uppermost surface monolayer, has been used to study the atomic arrangement of cobalt and molybdenum deposited on the surface of CoMo/y‐AL2O3, hydrodesulfurization catalysts in their oxidic precursory form. The results prove that the oxidic molybdenum layer is on top of the oxidic cobalt layer. The depth profiling measurements are in excellent agreement with calculations from a straightforward model of the process.
Schwefelhaltige Derivate des Dibenzoylmethans
Authors: Senning Alexander
Published: September 2010

A number of sulfur‐containing derivatives of dibenzoylmethane were obtained by conversions involving the active methylene group.
Dielectric studies of hydrogen bonded complexes in n‐butanol‐carbonyls systems
Authors: Shanmugasundaram V. , Mohan R.
Published: September 2010

Dielectric polarization studies of a few alcohol‐carbonyls systems have been carried out. The formation constants and the dipole moments of the complexes are reported and the observed enhancement of the dipole moment of the complexes is discussed.
Lanthanide perchlorate complexes of o,o' diisopropyl, n(‐4‐antipyryl) phosphoramidate
Authors: Premlatha C. , Soundararajan S.
Published: September 2010

Five new complexes of lanthanide perchlorates with a new ligand O,O' diisopropyl N(‐4‐antipyryl) phosphoramidate (DIAP) of the general formula Ln(DIAP)4(ClO4)3 where Ln = La, Pr, Nd, Sm and Gd, have been synthesised and characterized by chemical analysis, IR(200–4000cm−1) and electronic spectra and electrical conductance data.

Infrared spectral data indicate the coordination of the ligand to the metal ions in a bidentate fashion, through the C=O oxygen of the antipyrine group and the P=O group. IR and conductance values show that the three perchlorate groups are ionic. Electronic spectrum of the Nd3+ complex in the visible region, indicates reasonable covalency in the metal‐ligand bond. The available data point to an eight coordinate geometry around the metal ions, with each ligand behaving in a bidentate ‘00’ fashion.
The crystal structure of tetragonal nickel(ii)‐hydrogen‐(1)‐malate tetra hydrate
Authors: van Havere W. , Lenstra A. T. H.
Published: September 2010

The title compound Ni2+ (C4H5O5)2−. 4H2O crystallizes in the tetragonal space group P41212 with Z = 4.

At ∼ 300°K, the œll constants are: a = 7.49(1)Å, c = 27.40(1)Å. The central skeleton has an “anti” conformation.
The polarographic behaviour of cinnamylidenebenzoichydrazide in solutions of varying ph at the dropping mercury electrode and the effect of surface active substances
Authors: Temerk T. M. , Abu Zhrui A. Z.
Published: September 2010

The polarographic behaviour of cinnamylidenebenzoichydrazide (CHB) in solutions of varying pH has been studied both in the absence and presence of cationic, anionic and nonionic surfactants. The mechanism for the reduction in alkaline and acid media is discussed. The adsorption effects of electrochemically inactive surfactants on the polarographic waves of CBH has been investigated. The values of the kinetic parameters for the electrode reaction at different pH values have been computed.
Influence of the dielectric constant of the medium on the dipole moment of 1/1 complexes between trialkylamines and carboxylic acids
Authors: Huyskens P. L. , Cl. Haulait‐Pirson M. , Kapuku F.
Published: September 2010

When carboxylic acids are dissolved in trialkylamines, the dipole moments μab of the 1/1 complexes increase when the molefraction of the acid becomes greater. This is due to the enhancement of the dielectric constant of the medium which affects the transfer constant Kt of the proton in the hydrogen bonds, causing an increase of the proportion of the ion‐pairs with respect to the number of complexes where no proton transfer occurs. An equation is proposed which takes quantitatively this effect into account. The transfer constant Kt in a given medium at roomtemperature is nearly the same in the complexes of propanoic, butanoic and pentanoic acid by is significantly higher in the complexes of tributylamine than in those of triethylamine. This can be explained by the higher pKa of the former base. In these ab complexes the transfer constant remains always smaller than one.
Déplacement spectral de la bande π‐π*(1Lb) du benzaldéhyde par effet de solvant
Authors: Morales Raúl G. E.
Published: September 2010

This work determines the spectral solvent shift of the first π‐π* band of benzaldehyde corresponding to the 1A−1 Lb electronic transition. The spectral shift in solution relative to the vapor phase is obtained by determining the maximum of absorption in the vapor phase (36705 cm−l) corresponding to the maximum of absorption in solution.

The maximum vibronic transition in the vapor phase is located to 1230 cm−l from the 0'–0” transition. This determination has been done through an analysis of the band intensities as a function of temperature (77°K to 398°K), and the curve fitting procedure of the pseudovibronic bands, which simulate the solution spectra. The spectral shifts vary from 500 to 1000 cm−l.
The sulfoxide bond as stereochemical probe in methyl‐1,4‐thiazane‐1‐oxide. Conformational preference in 1,4‐thiazane‐l‐oxide
Authors: Nachtergaele Willy A. , Anteunis Marc J. O.
Published: September 2010

Oxidation of 3‐methyl‐l,4‐thiazane provides two sulfoxide isomers. The isomer with the axial sulfoxide bond is formed in threefold excess. Comparison of 1H NMR spectral characteristics of cis‐ and trans‐3‐methyl‐l,4‐thiazane‐l‐oxide with these of 1,4‐thiazane‐1‐oxide points out that in the conformational equilibrium of the latter the sulfoxide bond in axial, position is somewhat favoured. From the “slow exchange” 13C NMR spectrum we estimate the axial sulfoxide isomer to be present for 57% (ΔG° = 0.46 kJ/mol ± 0.35 kJ/mol) at 203 K. Estimation from proton shifts and interproton couplings result in an axial population ranging from 53 to 69%. The presence of the N‐lone pair orbital influences substantially the conformational behaviour, as follows from the increased axial sulfoxide character in the protonated and N‐acetyl‐derivatives.
Conductometric titrations in the presence of indifferent electrolyte
Authors: Tan S. H. , Kies H. L.
Published: September 2010

Favourable conductograms are obtained in various titrations of solutions in the presence of a large excess of indifferent electrolyte. Titration cells with high cell constants, up to 2000 cm−1, are used in conjunction with a differential measuring bridge. Conductivity cells with lower cell constants (ca. 25 cm−1), equipped with three electrodes also provide effective elimination of polarization effects, and are used for the titration of solutions with moderate electrolyte concentration, such as complexometric titrations in buffered media, using a conventional measuring bridge. To avoid adsorption effects, platinization of the electrodes has been avoided.
Enamine chemistry XX. synthesis of furan derivatives by reductive cyclisation of enamines
Authors: Carlsson S. , El‐Rarbary A. A. , Lawesson S. ‐O.
Published: September 2010

Enamines, I, prepared from cyclohexanones or cyclopentanones and pyrrolidine are alkylated with 2‐bromoesters (ethyl 2‐bromoethanoate, ethyl 2‐bromopropanoate, methyl 2‐bromopropanoate) to give the new enamines, II, which after treatment with LiAlH4 undergo reductive cyclisation reactions giving the furan derivatives, III (7a‐pyrrolidino‐octahydrobenzofurans, 6a‐pyrrolidino‐hexahydrocyclopentafurans) in almost quantitative yields. The compounds III are hydrolyzed with hydrochloric acid to octahydrobenzofuran‐7a‐ols or hexahydrocyclopentafuran‐6a‐ols, IV. Elimination of pyrrolidine from III with oxalic acid in anhydrous dioxane yields condensed dihydrofurans, V.
Formation de dioxolannes a partir de l'épichlorhydrine du glycerol. Hydrolyse aisée de dioxolannes par le tosylate de pyridinium
Authors: Thuy Vu Moc , Petit Huguette , Maitte Pierre
Published: September 2010

We described a versatile synthesis of dioxolanne from 1‐chlor 2, 3‐epoxypropane epichlorhydrine and different carbonyl compounds in presence of activated montmorillonite which is easily eliminated after the reaction. The hydrolysis was performed in mild conditions with pyridinium p‐toluene sulfonate.
Thienoisothiazoles, thienoisoselenazoles et selenoloisoselenazoles
Authors: Onyaraboko N. V. , Weber R. , Dereu N. , Renson M. , Paulmier C.
Published: September 2010

Synthesis of five new fundamental biheterocyclic systems was realized through condensation of the isothiazole or isoselenazole ring on the thiophene or selenophene ring.

These new heterocycles were characterized by elemental analysis, U. V., N. M. R. 1H, 13C, 77Se spectroscopy and by mass spectrometry.
Reactions of trimethyltinsodium with alkyl halides. effects of structure and solvent on course of reaction and reactivity
Authors: Kuivila Henry G. , Reeves William G.
Published: September 2010

The reactions of eleven alkyl chlorides and bromides with trimethyltinsodium have been examined. It has been found that primary and secondary halides react smoothly and rapidly to provide good yields of substitution products in THF and TG at 0°. The reaction is less satisfactory for allyl bromide and unsatisfactory for cinnamyl chloride and tertiary halides. Trimethyltinsodium and 2‐chlorobutane react with second order kinetics. Relative reactivities of the halides have been determined in the two solvents and are discussed. Lithium, sodium and potassium as counterions yielded the same results in the reaction of the trimethyltin‐alkalis with primary, secondary and tertiary butyl bromides in THF.
Synthesis and x‐ray crystal structure of two triorganostannylcobalt complexes
Authors: Gielen M. , Vanden Eynde I. , Polet F. , Meunier‐Piret J. , van Meerssche M.
Published: September 2010

The synthesis and X‐ray crystal structure analysis of two triorganostannylcobalt complexes (I) and (II) containing an asymmetric tin and an asymmetric carbon atom,

magnified image

with R;CH2‐C*H(CH3)(C6H5) and R;C6H5 for (I) and R;C(C6H5)3 and R′N(CH3)[(S)‐C*H(CH3)(C6H5)] for (II) are described.
Endothermic or exothermic character of the dissociation of ion pairs
Authors: Huyskens P. L.
Published: September 2010

In the gaseous phase the dissociation enthalpy ΔHd, of ion pairs is always positive. In the liquid phase the polarization of the molecules of the medium around the separate ions decreases the dissociation enthalpy and in some cases renders it negative. Other factors which influence the enthalpy of dissociation are the formation of hydrogen bonds or charge transfer bonds between the ions or between the ions and the solvent molecules. An equation based on the theories of Denison and Ramsey and of Gilkerson which takes these effects into account is: ΔHd, = (e2N/aD) (1 + d In D/d ln T) ‐ ΔH*h ‐ ΔH*s. This equation is confronted with the data of the literature.
Metalloimmunoassay. IV. Manganese‐labelled metallohaptens via cymantrene derivatives
Authors: Cais Michael , Tirosh Nilly
Published: September 2010

The principle of metalloimmunossay (MIA) is briefly described. Results are presented for the synthesis of phenobarbitone metallohaptens incorporating manganese atom labels via functionalized cymantrene derivatives. An atomic absorption calibration curve for the measurement of Mn concentrations with these metallohaptens indicates the feasibility of quantitative detection in the 10−9g. ml−1 range.
Instrumental Neutron Activation Analysis of Geological Materials With Low Energy Photon Detectors: Monte Carlo Evaluation of Photon Absorption in the Samples
Authors: Hertogen J.
Published: September 2010

Small, extra‐high resolution semiconductor detectors are extremely useful for the measurement of low energy gamma‐and X‐rays (< 100 keV) emitted during the decay of neutron activated geological materials. However, photon absorption in the samples is a potential source of substantial systematic errors.

Photon absorption effects in cylindrical samples have been evaluated with the aid of Monte Carlo computer simulations. For accurate absorption corrections, it is essential to calculate the apparent absorption for a given sample‐detector geometry. For cylindrical samples this correction strongly depends upon the diameter/height ratios. However, the choice of an appropriate standard rock can eliminate the need for cumbersome absorption corrections in routine analyses.
Réactivité de L'Acide Fulminique=Transfert Intramoléculaire Du Proton Et Protonation Des Produits D'Addition
Authors: Nguyen Minh‐Tho , Sana Michel , Leroy Georges
Published: September 2010

In this work we study the further transformations of the addition products of the fulminic acid HCNO. The proton 1,3‐and 1,4‐intramolecular transfer and the anions protonation are investigated. All the calculations have been carried out by using the LCAO‐SCF‐MO method of Roothaan and the STO‐3G and 4‐31G basis sets of Pople.

We show the transformation can follow different ways. The electrostatic potential is unable to predict the site of the anion protonation.

Finally the proton 1,3‐and 1,4‐intramolecular transfer have activation barriers respectively of about 60 kcal mol−1 and 10 kcal mol−1 in gaseous phase (4‐31G basis set).
Empirical Force Field Calculations XIII. The Ring Interconversion Modes of cis‐1, 2, 3, 4, 4a, 5, 8, 8a‐Octahydronaphthalene and its 1α, 4α‐Dimethyl Derivative
Authors: Vanhee P. , Tavernier D. , Baas J. M. A. , van De Graaf B.
Published: September 2010

The inversion of the (half‐chair) chair conformers of cis‐1, 2, 3, 4, 4a, 5, 8, 8a‐octahydronaphthalene (1) and of its 1α, 4α‐dimethyl derivative (2) are studied with molecular mechanics using the white and Bovill empirical force field. It is a multi‐stage process: first the chair form of the saturated ring transforms into a twist conformation, then the (half‐chair) twist form can follow several pseudorotational paths on which the one half‐chair form of the unsaturated ring passes into the other via a boat form, and finally the twisted saturated ring converts into the inverted chair conformation. In 1 the first part of this process is of higher energy (ΔH≠ = 34.4 kJ mol−1) than the lowest pseudorotational path (30.8 kJ mol−1), in 2 it is the pseudorotational part of the inversion that is of somewhat higher energy (34.0 kJ mol−1) than the chair‐to‐twist stage (32.9 kJ mol−1). The methyl substituents cut off low energy pseudorotational paths available to 1 and direct the pseudorotation in 2 to regions of higher energy. The experimental determination of the inversion barrier of 1 yields ΔG≠ = 41.4 kJ mol−1.
The Synthesis of 1,8‐Diazaspiro|4,5|‐Decanes
Authors: van Parys Marc , Vandewalle Maurits
Published: September 2010

The synthesis of some substituted 1,8‐diazaspiro|4,5|decanes starting from l‐benzyl‐4‐oxo‐piperidine is described. This skeleton is isosteric to the 1,3,8‐triazaspiro|4,5|‐decane structure present in important neuroleptic agents.
Étude Conformationnelle D'Analgésiques Narcotiques: Structure Cristalline de r 1000: Chlorhydrate de Phényl‐4(Phényl‐3 Propényl‐2)‐1 Piperidine‐4 Carboxylate D'Éthyle
Authors: Lamotte C. , Eloy B. , Evrard G. , Durant F.
Published: September 2010

The title compound is a narcotic analgesic belonging to the 4 phenyl piperidine family. Its crystal structure has been investigated by X‐ray diffraction in order to ascertain the molecular conformation and compare it to those of other derivatives of this family such as phenoperidine, meperidine and β‐prodine.