bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nature et stabilité des complexes métalliques de cryptands dinucléants en solution II. Polythiamacrotricycles et monocycles apparentés
Authors: Arnaud‐Neu Françoise , Almasio Marie‐Christine , Spiess Bernard , Schwing‐Weill Marie‐José , Sullivan Sally A. , Lehn Jean‐Marie 
Published: December 2004

Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution II. Polythiamacrotricycles and Related Monocyclic SubunitsThe stability constants of the Cu2+ and Ag+ complexes of the cylindrical macrotricycle 1a (1,7,13,19‐tetraaza 4,16‐dioxa 10,22,27,32‐tetrathiatricyclo[17.5.5.5]tetratriacontane) have been determined by pH‐metry, as well as those of the Cu2+, Co2+, Zn2+, Cd2+, Pb2+, and Ag+ complexes of the monocyclic subunit 2a (1,7‐dimethyl‐1,7‐diaza 4,10‐dithiacyclododecane), in aqueous solutions (NaClO4) at 25°. In the Cu(II) systems, equilibria were reached slowly, and the results established by pH‐metry were confirmed by UV/VIS spectrophotometric studies. The tricycle 1a forms dinuclear cryptates with copper and silver, with overall stability constants log β210 (Cu2‐1a)4+ = 18.5, log β21‐2 (Cu2‐1a(OH)2)2+ = 4.8, log β210(Ag2‐1a)2+ = 23.0. Ag+ also forms a mononuclear (Ag‐1a)+ complex, with log β110 = 13.1, but no mononuclear species were detected in the Cu‐1a system. The absorption spectra of the bis‐Cu(II) complexes of 1a and 2a in aqueous medium, MeOH and propylene carbonate (PC) are given, as well as those, in MeOH and PC, of the bis‐copper complexes of the related monocycles 3 and 4 (1,7‐diaza‐4,10,13‐trithiacyclopentadecane and 1.10‐diaza 4,7,13,16‐tetrathiacyclooctadecane, respectively), and tricycle 5 with two benzyl groups in the lateral chains.The complexing properties of the polyoxa‐ and polythia macrotricycles (Parts I and II of this series) are compared to those of other bis‐chelating ligands, the bicyclic bis‐tren and the monocyclic bis‐dien.
Aromatic Nucleophilic Substitution. Part 1. Regiospecific Substitution of the Nitro Groups in 3,5‐Dinitrophthalic‐Acid Derivatives
Authors: Fischer Walter , Kvita Vratislav 
Published: December 2004

AbstractThe regioselectivity of nucleophilic substitution of the nitro groups in 3,5‐dinitrophthalic anhydrides and 3,5‐dinitrophthalimides (Scheme) with a variety of nucleophiles (Nu−) was studied. In all cases, the 3‐nitro group was selectively substituted. With excess of the same nucleophilic reagent or with other nucleophiles, the 5‐nitro group could subsequently be replaced.
Inductive Charge Dispersal in Quinuclidinium Ions. Polar Effects, Part 13
Authors: Grob Cyril A. 
Published: December 2004

AbstractInductive charge dispersal to the α‐ β‐ and γ‐positions of the solvated quinuclidinium ion has been examined by comparing the pKa and the derived inductivities ρI of several 2‐ 3‐ and 4‐substituted quinuclidinium perchlorates 4, 5, and 6, respectively. The same inductivity is observed at the practically equidistant β‐ and γ‐positions. It, therefore, appears that polar substituent effects are transmitted directly through the molecule. As expected, inductivity is considerably higher at the α‐positions where through‐bond and direct induction coincide. The fact that the pKa of all three series of salts correlate linearly with each other points to the common nature of these inductive electron displacements.
Isolation and Structure of a New Antibiotic Related to Rubiflavin A
Authors: Nadig Heinz , Séquin Urs , Bunge Richard H. , Hurley Timothy R. , Murphey David B. , French James C. 
Published: December 2004

AbstractA novel antibiotic, PD 121,222, was isolated from a complex of pluramycin‐like compounds containing mostly kidamycin and neopluramycin. Spectral analyses showed that this compound is the 14,16‐dihydroxy analog of rubiflavin A.
Preparative Asymmetric Reduction of 3‐Ketobutyrate and ‐valerate by Suspended Cells of Thermophilic Bacteria (Thermoanaerobium brockii) in Ordinary Laboratory Equipment
Authors: Seebach Dieter , Giovannini Fabio , Lamatsch Bernd 
Published: December 2004

AbstractThe thermophilic and anaerobic bacteria specified in the title are isolated on a 0.8 kg scale by tangential flow filtration and centrifugation from a 300‐1 bioreactor. The microorganisms are stored in a freezer (−20°) and used, analogously to baker's yeast, for asymmetric reductions. Thus, ethyl 3‐ketovalerate (4.3) g/1 (H2O) is converted in 40% yield to (S)‐3‐hydroxyvalerate (6), with an enantiomeric excess of 93% (24 h at 72°).
σ‐Skeletal‐Rearrangement of Heptalenes: Thermal Transformation of Heptalene‐1,2‐dicarboxylates into Heptalene‐1,3‐dicarboxylates
Authors: Bernhard Werner , Brügger Paul , Daly John J. , Englert Gerhard , Schönholzer Peter , Hansen Hans‐Jürgen 
Published: December 2004

AbstractIt is shown that dimethyl heptalene‐1,2‐dicarboxylates undergo rearrangements at temperatures > 200° to yield the corresponding 1,3‐dicarboxylates, which are isolated as the more stable 3,5‐dicarboxylates. 2H‐ and 13C‐labelling experiments with dimethyl 7‐isopropyl‐5,10‐dimethylheptalene‐1,2‐dicarboxylate (1) which is rearranged into dimethyl 9‐isopropyl‐1,6‐dimethylheptalene‐3,5‐dicarboxylates. (2) indicate that the reaction occurs by interchange of C(2) and C(3) in the heptalene skeleton of 1. Thus, the transformation of 1 into 2 represents the first thermal σ‐skeletal rearrangement of heptalenes. The structures of 1 and 2 are discussed in terms of an X‐ray analysis and the spectral data.
Thermal Reactions of Epoxyenones and Epoxydienes in the Ionone Series
Authors: O'Sullivan Anthony , Bischofberger Norbert , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractOn flash vaccum thermolysis at temperatures between 390 and 585°, the epoxyenones 1–9 and the epoxydienes 10–12 undergo various types of reactions involving CC and/or CO bond cleavage in the oxirane ring. Thus, the compounds 1, 4–9, 11, and 12 were transformed to the divinyl ethers 13, 20, 21, 24, 25, 29, and 38 by a reversible [1,5] homosigmatropic H‐shift. On thermolysis of the epoxides 1–12, several products formed via carbonyl‐ylide intermediates were also isolated. The extent of the formation of ylide products is clearly related to the conjugating ability of the functional groups neighboring the oxirane. Thus, the epoxides 3, 5, and 7–10, bearing a C(3)C(4) bond, a 5‐oxo function, a 3,4‐epoxy or a 3,4‐methano group, preferentially underwent reactions via a carbonyl‐ylide intermediate. As a further reaction pathway, the epoxides 1–12 undergo cleavage of the C–O bonds of the oxirane, which, however, is presumably an acid‐catalyzed rather than a thermal reaction.
N,O‐Acetals from Pivalaldehyde and Amino Acids for the α‐Alkylation with Self‐Reproduction of the Center of Chirality. Enolates of 3‐Benzoyl‐2‐(tert‐butyl)‐1,3‐oxazolidin‐5‐ones
Authors: Seebach Dieter , Fadel Antoine 
Published: December 2004

AbstractThe sodium salts of (S)‐alanine, (S)‐phenylalanine, (S)‐valine, and (S)‐methionine are condensed with pivalaldehyde to imines 5. Cyclization by treatment with benzoyl chloride in cold CH2Cl2 gives mainly (4:1 to > 99:1) the (2S,4S)‐4‐alkyl‐3‐benzoyl‐2‐(tert‐butyl)‐1,3‐oxazolidin‐5‐ones (6; cis‐configuration) in high yields (85–95%). The oxazolidinones 6 and 7 are deprotonated with lithium diethylamide (LDEA) in tetrahydrofuran (THF) and alkylated (Mel, benzyl bromide) or hydroxyalkylated (benzaldehyde) to 4,4‐disubstituted oxazolidinones 9 and 10, respectively, with high diastereoselectivity (9:1 to 50:1; relative topicity ul). Hydrolysis of three of the oxazolidinones to amino acids of known configuration and optical purity indicates that little if any racemization occurs in the process.
The Phloroglucinols of Dryopteris aitoniana PICHI SERM. (Dryopteridaceae, Pteridophyta)
Authors: v. Euw Josef , Reichstein Tadeus , Widén Carl‐Johan 
Published: December 2004

AbstractThe phenolic compounds of the fern Dryopteris aitoniana were analyzed by improved methods avoiding alcaline reagents and contact with unbuffered SiO2, which can cause deterioration. We confirmed the presence of five of the formerly (1971) reported six compounds, while the sixth, formerly incorrectly assumed to be aspidin (based on a spot in TLC), has now been isolated as cristals (TR‐1579). It has the empirical formula C27H52O2, but its structure is still unknown. Five other compounds were isolated in pure form, tetra‐albaspidin BBBB (25‐BBBB) a known but rare phloroglucinol, and four new compounds: penta‐albaspidin BBBBB (37‐BBBBB), hexa‐albaspidin BBBBBB (38‐BBBBBB), tetraflavaspidic acid BBBB (26‐BBBB) and hexaflavaspidic acid BBBBBB (39‐BBBBBB). The structures were established by degradation NMR and partly by field‐desorption and fast‐atom‐bombardment (FAB) mass spectra. The oligoflavaspidic acids are very unstable compounds, deteriorating during isolation procedures using the older ‘standard method’.
Die Sattelkonformation der hydroporphinoiden Nickel(II)‐Komplexe: Struktur, Ursprung und stereochemische Konsequenzen
Authors: Kratky Christoph , Waditschatka Rudolf , Angst Christof , Johansen Jon E. , Plaquevent Jean C. , Schreiber Jakob , Eschenmoser Albert 
Published: December 2004

The Saddle Conformation of Hydroporphinoid Nickel(II) Complexes: Structure, Origin, and Stereochemical ConsequencesThirteen crystal structures document the general phenomenon of coordination‐hole contraction in hexahydro‐ and tetrahydroporphinoid ligands of complexes with small metal ions such as low‐spin Ni(II). The contraction is characterized by a deformation of the ligand system towards a saddle‐shaped, ruffled conformation of approximate S4 symmetry. The central metal ion is coplanar with the four coordinating N‐centers whereas the four C(meso)‐atoms are situated alternately above and below this coordination plane. Increasing steepness of the saddle (parameter dm) is associated with decreasing metal‐N distances. For metal pyrrocorphinates, dm increases in the order Cu(II) < (pyridine) Co(II) < Ni(II), for Ni(II) complexes it does so in the order porphyrin < chlorin < bacteriochlorin < isobacteriochlorin < pyrrocorphin. In the saddle conformation of hydroporphinoid Ni(II) complexes, the hydropyrrole rings assume half‐chair conformations whereby the individual half‐chairs are conformationally constrained in such a way that the inclination of their peripheral single bond parallels the inclination of the ligand saddle (W‐conformation of the ensemble of 5‐membered ring half‐chairs). There are only two such conformations available for a given complex; they interrelate by saddle inversion with concomitant inversion of the ensemble of half‐chairs. The coordination‐hole contraction of hydroporphinoid ligands is expected and observed experimentally to exert control on the stereochemistry and reactivity of the ligand periphery as well as on the axial electrophilicity of the central metal ion. Tetracoordinate nickel(II) pyrrocorphinates are found to favor the tctct configuration of substituents at the ligand periphery, nickel(II) isobacteriochlorinates the tct configuration, whereas nickel(II) bacteriochlorinates are expected to favor the ttt configuration. Relative rates and regioselectivities of autoxidation of nickel(II) pyrrocorphinates to corresponding bacterio‐and isobacteriochlorinates depend on the configuration and conformation of the ligand periphery. The residual axial electrophilicity of the metal ion in tetracoordinate Ni(II) complexes of the octaethyl series appears to increase in the order chlorin < isobacteriochlorin ≲ bacteriochlorin < pyrrocorphin. All hydroporphinoid metal complexes used in the X‐ray structure studies were prepared as part of exploring the porphyrinogen → pyrrocorphin tautomerization, a novel structural transformation of porphyrinogens.
Synthese neuer Nonafulvene
Authors: Sabbioni Gabriele , Otter Albin , Millar Ross W. , Neuenschwander Markus 
Published: December 2004

Synthesis of New NonafulvenesNonafulvenes 1c and 1m–s are prepared by the following methods: (a) Elimination of AcOH from acetoxyalkyl‐cyclononatetraenes (Scheme 2; 1m); (b) alkylation of nonafulvenolates (Scheme 3; 1c, 1n); (c) elimination of alcohol from di‐ and trialkoxymethyl‐cyclononatetraenes (Scheme 5; 1o, 1p, 1q); (d) deprotonation of intermediary formed formamidiniumcyclononatetraenes (Scheme 6; 1r, 1s). Scope and limitations of these preparative sequences are discussed and compared with the corresponding pentafulvene syntheses.
Reaktionskinetik einer Monomolekularen Oberflächenbelegung von Germanium mit 4‐(Trichlorsilylmethyl)benzonitril mit Hilfe von FTIR‐Experimenten
Authors: Calzaferri Gion , Gori Marcel 
Published: December 2004

Kinetics of Monomolecular Surface Modification of 4‐(Trichlorosilylmethyl)benzonitrile on Germanium by Means of FTIR ExperimentsA Fourier transform‐attenuated total internal reflection‐infrared spectroscopy (FT‐ATR‐IR) technique is described, which allows to observe the kinetics of monomolecular surface modification on materials which are feasible to total internal reflection experiments in an appropriate wavelength region. First results are reported for the reaction of 4‐(trichlorosilymethyl)benzonitrile on germanium. The reaction is slower than expected and is only completed after approximately 4 h.
Plantes de Nouvelle‐Calédonie. 94e Communication. Alcaloïdes monoterpéniques de Scaevola racemigera DÄNIKER
Authors: Skaltsounis Alexios‐Léandros , Michel Sylvie , Tillequin François , Koch Michel , Pusset Jacques , Chauvière Gérard 
Published: December 2004

Monoterpene Alkaloids of Scaevola racemigera DÄNIKERNine alkaloids have been isolated from the aerial parts of Scaevola racemigera. Two of them are the known compounds cantleyine (1) and tetrahydrocantleyine (2). The seven others are novel alkaloids, strychnovoline (3), 6‐O‐nicotinoylstrychnovoline (4), 6‐O‐nicotinoyltetrahydrocantleyine (5), 6‐O‐(5‐vinylnicotinoyl)tetrahydrocantleyine (6), racemigerine (7), 6,7‐epoxyracemigerine (8), and scaevoline (9). The structures of the new compounds have been elucidated by their spectral data and confirmed by chemical correlations. Moreover, the absolute configuration of 2, which had not been previously determined, has been elucidated.
Das Carotinoidspektrum der Antheren und Petalen von Lilium tigrinum cv. ‘Red Night’
Authors: Märki‐Fischer Edith , Eugster Conrad Hans 
Published: December 2004

Carotenoids from Anthers and Petals of Lilium tigrinum cv. ‘Red Night’Amongst the 29 carotenoids separated and characterized by modern methods the following are worth mentioning: (9′Z)‐, (9Z)‐, (13′Z)‐ und (13Z)‐capsanthins (20–23), the novel 6‐epikarpoxanthin (= (3S,5R,6S,3′R)‐5,6‐dihydro‐β,β‐carotene‐3,5,6,3′‐tetrol; 25), karpoxanthin (= (3S,5R,6R,3′R)‐5,6‐dihydro‐β,β‐carotene‐3,5,6,3′‐tetrol; 28), and lilixanthin (= (3S,4S,3′S,5′R)‐3,4,3′‐trihydroxy‐β,κ‐carotene‐6′‐one; 26). The main carotenoids from the petals, in comparison with those of the anthers, represent a more advanced metabolic state.
Acid‐Catalyzed Cleavage of 1,4‐Dimethyl‐1,4‐dihydronaphthalene 1,4‐Endoperoxide. Reactivity of the Resulting Hydroperoxy Carbocation with Nucleophiles
Authors: Jefford Charles W. , Rossier Jean‐Claude , Kohmoto Shigeo , Boukouvalas John 
Published: December 2004

AbstractIn the presence of acids, 1,4‐dimethyl‐1,4‐dihydronaphthalene 1,4‐endoperoxide readily reacts with nucleophiles to produce methyl‐ and ring‐substituted naphthalenes in high yields. The regioselectivity observed depends on the nucleophile. The key intermediate is shown to be the corresponding hydroperoxy carbocation which could be intercepted in certain cases prior to aromatization. The hydroperoxide also undergoes Hock‐type cleavage and dimerization giving 2,3‐dihydro‐1‐benzoxepins, 4‐methyl‐1‐naphthol, and a 1,2,5,6‐tetraoxocane as by‐products.
Zur Anionenselektivität von Distannylderivaten in Membranen
Authors: Wuthier Urs , Pham Hūng Viêt , Pretsch Ernö , Ammann Daniel , Beck Albert K. , Seebach Dieter , Simon Wilhelm 
Published: December 2004

Anion‐Selectivity of Distannyl Derivatives in MembranesA series of distannyl derivatives (2,2‐bis(trimethylstannyl)‐1,3‐dithiane, 2,2‐bis(tributylstannyl)‐1,3‐dithiane, hexamethyldistannane, hexabutyldistannane, hexaphenyldistannane, bis(triphenylstannyl)sulfide, o‐bis(trimethylstannyl)benzene) has been studied in view of their applicability as anion‐selective ionophores in solvent polymeric membranes. None of these compounds induces significant changes in the anion‐selectivity pattern as compared with the membranes containing no organotin compound. Representatives with tributylstannyl groups, however, undergo chemical reactions leading to highly active anion ionophores of the type Bu3SnX, several of which (e.g. Bu3SnCl and Bu3SnOH) may be present in equilibrium in the membrane phase depending on the measuring conditions.
Synthèse des (R)‐ et (S)‐O‐isopropylidène‐1,2‐glycérols. Détermination de la pureté optique
Authors: Hirth Georges , Walther Willy 
Published: December 2004

Synthesis of the (R)‐ and (S)‐Glycerol Acetonides. Determination of the Optical PurityThe optical purity of (R)‐glycerol acetonide (1) and (S)‐glycerol acetonide (1′) has been determined with great accuracy by gas chromatography after derivatization. The optical purity of (S)‐glycerol actonide prepared from D‐mannitol was > 99.4% while for (R)‐glycerol acetonide obtained from L‐serine it was 95%.
Aniono‐pentaaminecobalt(III) complexes with polyamine ligands. Part 23. A chloropentaamine by‐product from the preparation of the trans‐CoCl2(en) cation
Authors: House Donald A. 
Published: December 2004

AbstractThe isolation and characterisation of [CoCl(en)(L)]ZnCl4, L = NH2CH2CHNCH2CH2NH2 (1,4,7‐triazahept‐3‐ene), as a by‐product (∼ 8% yield) from the H2O2 synthesis of trans‐CoCl2(en), is described.
Photo‐Emde Degradation of 1,2,3,4‐Tetrahydroquinolinium Salts
Authors: Partali Vassilia , Jolidon Synèse , Hansen Hans‐Jürgen 
Published: December 2004

AbstractIt is shown that 1,1‐dimethyl‐1,2,3,4‐tetrahydroquinolinium ions undergo, under direct irradiation through quartz in CH3OH and independent of the nature of the counterion (I−, BF), a reductive cleavage of the N(1)–C(8a) bond (photo‐Emde degradation). The corresponding N,N‐dimethyl‐3‐phenylpropylamines are formed in high yields and without contamination by Hofmann degradation products of the tetrahydroquinolinium salts. Me groups at C(2) as well as substituents at C(6) (CH3, Cl, CH3O) favour the photo‐Emde degradation. The aromatic Cl‐substituent is reductively split off in the course of the photoreaction.
Cycloaddition of 2H‐Pyran‐2‐thiones with Nitroso Derivatives. An Unexpected Cycloaddition‐Rearrangement Reaction
Authors: Defoin Albert , Augelmann Gérard , Fritz Hans , Geffroy Guillaume , Schmidlin Christian , Streith Jacques 
Published: December 2004

AbstractReaction of pyran‐2‐thiones 4 with nitroso derivatives led surprisingly to type‐8 (19) adducts which proved to be isomeric with the initially expected primary Diels‐Alder cycloadducts 5. Methyl 2‐thioxo‐2H‐pyran‐5‐carboxylate (4f), when reacted with nitrosobenzene at ‐10°, led quantitatively to the thieto‐oxazine intermediate 13, which turned out to be the cornerstone of the complex cycloaddition‐rearrangement 5 → 8 reaction pathway (Scheme 3). Differential scanning calorimetry, as performed for the 18a → 19a conversion, permitted to demonstrate that this multistep rearrangement is overall a higly exothermal process, the final product 19 representing an energy‐sink along this reaction pathway.
Significance of the Geminal Dimethyl Group in the Odor Principle of Ambrox®
Authors: Ohloff Günther , Giersch Wolfgang , Pickenhagen Wilhelm , Furrer Anton , Frei Beatrice 
Published: December 2004

AbstractThe diastereoisomeric 18‐nor‐ and 19‐norambrox ((6α)‐ and (6β)‐dodecahydro‐3a,6,9a‐trimethylnaphtho[2,1‐b]furans resp.) as well as the corresponding 18,19‐dinor‐derivatives (dodecahydro‐3a,9a‐dimethylnaphtho[2,1‐b]furans) have been synthesized and subjected to sensory evaluation. Threshold data and odor determination give an enlarged insight into the structure‐activity relationship (SAR) in ambrox‐type ambergris fragrances. As a general conclusion, the accumulation of axial CH3 groups in the tricyclic ethers 1–12 leads to the strongest receptor affinity.
Synthese von 12‐Cyano‐15‐hexadecanolid durch Ringerweiterung von 1‐(3′‐Hydroxybutyl)‐2‐oxocyclododecan‐1‐carbonitril
Authors: Milenkov Branimir , Süsse Manfred , Hesse Manfred 
Published: December 2004

Synthesis of 12‐Cyano‐15‐hexadecanolide by Ring Enlargement of 1‐(3′‐Hydroxybutyl)‐2‐oxocyclododecane‐1‐carbonitrileIn the presence of Bu4NF, 2‐oxocyclododecane‐1‐carbonitrile (1) reacted with acrylaldehyde to form the corresponding aldehyde 2 which was methylated, e.g. with CH3 Ti[OCH(CH3)2]3. The resulting 1‐(3′‐hydroxybutyl)‐2‐oxocyclododecane‐1‐carbonitrile (5) was converted to 12‐cyano‐15‐hexadecanolide (6) in nearly quantitative yield under the influence of Bu4NF.
Phosphoramidites of Chiral (Rp)‐and (Sp)‐Configurated d(T[P‐18O]‐A): Synthesis, Configurational Assignment, and Use as Dimer Blocks in Oligonucleotide Synthesis
Authors: Herdering Wilhelm , Kehne Andreas , Seela Frank 
Published: December 2004

AbstractThe N,N‐diisopropylphosphoramidites 10a and 10b of appropriately protected chiral diastereoisomers of d(T[P‐18O]‐A) (8a and 8b, resp.), chiral by virtue of the isotope 18O at the P‐atom, have been synthesized. The 18O‐isotope was incorporated by oxidation of the phosphite triester 3 with H2[18O]/I2. Separation of the diastereoisomers was accomplished by flash chromatography of the O‐3′‐deprotected phosphate triesters 5a/b. The absolute configuration at the chiral P‐atom was deduced from the methylation products of the fully deprotected diastereoisomers 8a and 8b. Phosphinylation of 5a and 5b yielded the configurationally pure phosphoramidites 10a and 10b, respectively, which were then employed in solid‐phase synthesis to yield the self‐complementary oligomers d(G‐A‐G‐T‐(Rp)‐[P‐18O]‐A‐C‐T‐C) (13) and d(G‐A‐G‐T‐(SP)‐[P‐18O]‐A‐C‐T‐C) (14), respectively.
Polar Effects. Part 14. Inductive Charge Dispersal in Bicyclo[2.2.2]oct‐1‐yl Cations
Authors: Bielmann Rolf , Grob Cyril A. , Küry Dieter , Yao Guo Wei 
Published: December 2004

AbstractThe rate constants (log k) for solvolysis of 2‐, 3‐, and 4‐substituted bicyclo[2.2.2]octyl p‐nitrobenzenesulfonates 10, 11 and 12, respectively, correlate linearly with the corresponding inductive substituent constants s̀. The formation of the ion pairs 9 is, therefore, controlled by the I effect of neighboring substituents. It follows from the corresponding reaction constants ρ1 of −1.54, −1.12, and −1.22 that inductivity is highest at the positions α to C(1). It is lower and practically equal at the β‐ and γ‐positions. Therefore, charge dispersal is similar to that previously observed in the quinuclidinium ion 7.
Cyclisation of 7‐Deazaxanthine‐9‐propionic Acid to an Active‐Site‐Directed, Irreversibly Acting Inhibitor of Xanthine Oxidase
Authors: Rosemeyer Helmut , Kretschmer Uwe , Seela Frank 
Published: December 2004

AbstractPhase‐transfer alkylation of 2,4‐dimethoxy‐7H‐pyrrolo[2,3‐d]pyrimidine (2) with ethyl 3‐bromopropionate leads regioselectively to ethyl 2,3‐dimethoxy‐7H‐pyrrolo[2,3‐d]pyrimidine‐7‐propionate (3a). After saponification and ether cleavage, the functionalised 7‐deazaxanthine 4b was obtained. Reaction of 4b with H2O‐soluble carbodiimide resulted in an intramolecular acylation at N(3) with formation of the tricyclic compound 5. Compound 5 ‐ bearing a reactive lactam ring ‐ is an active‐site‐directed, irreversibly acting inhibitor of xanthine oxidase from cow's milk.
The Structure Elucidation of Pseudothiocolchicine
Authors: Danieli Bruno , Lesma Giordano , Palmisano Giovanni , Riva Renata 
Published: December 2004

AbstractA colchicine derivative, previously isolated from the reaction of isocolchicine with sodium thiomethoxide in aqueous MeOH, was now identified as 11‐(methylthio)isocolchicine on the basis of 1H‐, 13C‐NMR spectra and chemical correlation. This reaction represents the first example of abnormal nucleophilic displacement (telesubstitution) in the colchicine chemistry.