bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transformations in the Isoxazole Series: Synthesis of Substituted 2‐Aminothiazoles
Authors: Pascual Alfons 
Published: December 2004

AbstractSubstitued N‐(isoxazol‐4‐yl)thioureas 1 undergo a transformation in the presence of hexacarbonylmolybdenum and acid to yield functionalized thiazoles 3 in a one‐pot reaction. In a few cases, 1,4,5‐trisubstituted dihydroimidazolethiones 4 are also isolated as side products. Mechanistic considerations are outlined and scope and limitations of this new methodology discussed.
4H‐Chromenone Glycosides from Eranthis hyemalis (L.) SALISBURY
Authors: Kopp Brigitte , Kubelka Erika , Reich Christian , Robien Wolfgang , Kubelka Wolfgang 
Published: December 2004

AbstractInvestigation of the tubers of Eranthis hyemalis (Ranunculaceae) afforded six chromenone glycosides. Their structures have been elucidated mainly by spectroscopic (FAB‐MS, 2D‐NMR techniques) and chemical methods (acidic and enzymatic hydrolysis) as 9‐{[(β‐D‐glucopyranosyl)oxy]methyl}‐8,11‐dihydro‐5‐hydroxy‐2‐methyl‐4H‐pyrano[2,3‐g][1]benzoxepin‐4‐one (1), 9‐{[(β‐D‐gentiobiosyl)oxy]methyl}‐8,11‐dihydro‐5‐hydroxy‐2‐methyl‐4H‐pyrano[2,3‐g][1]benzoxepin‐4‐one(2), 9‐{[(β‐D‐glucopyranosvl)oxy]melhyl}‐8,11‐dihydro‐5‐hydroxy‐2‐(hydroxy‐methyl)‐4H‐pyrano[2,3‐g][1]benzoxepin‐4‐one(3), 8‐{(2E)‐4‐[(β‐D‐glucopyranosyl)oxy]‐3‐methylbut‐2‐enyl}‐5,7‐dihydroxy‐2‐methyl‐4H‐1‐benzopyran‐4‐one (4), 8‐{(2E)‐4‐[(β‐D‐glucopyranosyi)oxy]‐3‐methylbut‐2‐enyl}‐5,7‐dihydroxy‐2‐(hydroxymethyl)‐4H‐1‐benzopyran‐4‐one (5), and 7‐{[(β‐D‐glucopyranosy1)oxy]methyl}‐2,3‐dihydro‐2‐(l‐hydroxy‐1‐methylethyl)‐4‐methoxy‐5H‐furo[3,2‐g][1]benzopyran‐5‐one (6). Compound 2 exhibited negative inotropic activity.
Lithium‐Salt Effects in Peptide Synthesis. Part I. Conditions for the Use of Lithium‐Salts in Coupling Reactions
Authors: Thaler Adrian , Seebach Dieter , Cardinaux Francis 
Published: December 2004

AbstractThe influence of Li‐salts on the course of peptide‐coupling reactions was investigated. As a model for segment couplings, Ac‐Phe‐OH was coupled to HCl·H‐Ala‐OMe using the mixed anhydride, DCC1, DCCl/HOBt, BOP‐Castro and TBTU‐Knorr methods. As a model for stepwise synthesis Z‐Phe‐OH was coupled with HCl·Ala‐O(t‐Bu), using symmetrical anhydrides and active esters. The effects of salt additives such as LiCl, LiBr, LiC104, and ZnCl2 on yields, side‐product formation, racemisation, and reaction rates are reported.
On the Methyl‐Transfer Reaction in Crystalline Methyl 2‐(Methylthio)benzenesulfonate: a Thermally Induced Non‐Topochemical Solid‐State Reaction
Authors: Venugopalan P. , Venkatesan K. , Klausen Jörg , Novotny‐Bregger Elisabeth , Leumann Christian , Eschenmoser Albert , Dunitz Jack D. 
Published: December 2004

AbstractThe rearrangement of methyl 2‐(methylthio)benzenesulfonate (1) to the zwitterionic 2‐(dimethyl‐sulfonium)benzenesulfonate (2) is known to proceed in solution by intermolecular Me transfers. The same rearrangement has been observed to occur in crystalline 1, but the crystal structure shows that the molecular packing is not conducive to intermolecular Me transfer. The reaction has been carried out with mixed crystals composed of 1 and deuteriomethylated (D6)‐l. By fast‐atom‐bombardment mass spectroscopy, it has been shown that the product consists of a 1:2:1 mixture of the non‐, tri‐, and hexadeuterated species, the mixture expected, if the solid‐state reaction proceeds by intermolecular Me transfers. From this result, together with the slower rates of conversion in the single crystal compared with the melt, it can be concluded that the reaction must occur not topochemically but rather at defects such as microcavities, surfaces, and other irregularities in the ordered crystal arrangement.
Synthesis of the Bretonins, Polyolefinic Esterified Glyceryl Ethers of an Unidentified Sponge from the North‐Brittany Sea: Absolute Configuration and Novel Structure Assignment
Authors: Mancini Ines , Guella Graziano , Pietra Francesco 
Published: December 2004

AbstractThe absolute configurations of acetylated bretonin A (= (+}‐(R)‐1‐[(acetoxy)methyl]‐2‐{[(4E,6E,8E)‐dodeca‐4,6,8‐trienyl]oxy}ethyl 4‐acetoxybenzoate; (−)‐1b) and isobretonin A (= (+)‐(S)‐3‐{[(4E,6E,8E)‐do‐deca‐4,6,8‐trienyl]oxy}‐2‐hydroxypropyl 4‐hydroxybenzoate; (+)‐2), previously isolated from an undetermined sponge of the North Brittany sea, were established by comparison with synthetic (+)‐lb and (+)‐2, obtained from the condensation of commerical (−)‐(R)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl p‐toluenesuifonate ((−)‐(R)‐15) with a mixture of (4E,6E,8E)‐ (14e) and (4E,6Z,8E)‐dodeca‐4,6,8‐trien‐1‐ol (14z). This also allowed confirming the structure and configuration of bretonin B (= (S)‐2‐{[(4E,6Z,8E)‐dodeca‐4,6,8‐trienyl]oxy}‐1‐(hydroxy‐methyl)ethyl 4‐hydroxybenzoate; 3) which was also isolated from the same sponge, albeit in a too small amount for a complete study. As concerns the glyceryl ethers precursors of the bretonins, co‐occurrence of the usual (S)‐con‐figuration (from 1a) with the unusual (R)‐configuration (from (+)‐2)) poses intriguing biogenetic problems.
Stereo and Face Selectivity in Cycloadditions of 1,2,3‐Trichloro‐3‐fluorocyclopropenes to Acyclic Dienes and Furans
Authors: Müller Paul , Bernardinelli Gérald , Pfyffer Jean , Schaller Jean‐Pierre 
Published: December 2004

AbstractThe stereo and face selectivities of the cycloaddition of 1,2,3‐trichloro‐3‐fluorocyclopropene (1a) with acyclic dienes and furans has been re‐investigated by X‐ray determination and correlation of 19F‐NMR data. The isolated adducts of dienes exclusively have exo‐configuration, and exo‐Configuration predominates with furans. The Cl substituents of the resulting cyclopropane ring are cis‐oriented. The face selectivity of the reaction with both types of substrates is attributed to electrostatic interactions between the F and the bridgehead Cl substituents, which destabilize the F‐cis‐transition state (13 (F‐cis)) over 13 (F‐trans).
Conformational Analysis of the cis‐ and trans‐Isomers of FK506 by NMR and Molecular Dynamics
Authors: Mierke Dale F. , Schmieder Peter , Karuso Peter , Kessler Horst 
Published: December 2004

AbstractThe potent immunosuppressant drug FK506 (2) has been examined by 1H‐ and 13C‐NMR spectroscopy and NOE‐restrained molecular dynamics to elucidate the conformation in solution. A combination of two‐ and three‐dimensional NMR techniques was used to completely assign the 1H‐ and 13C‐NMR chemical shifts of the two configurational isomers resulting from the cis‐trans isomerization about the single amide bond. Hetero‐ and homonuclear coupling constants were measured to assign the diastereotopic methylene protons at C(16), C(18), and C(23). Intramolecular HH distances were defined from NOESY spectra recorded at −30° in CDCl3 and used as constraints in molecular‐dynamics simulations. The conformational preferences of 2 in solution are discussed in light of the constitutional features recently proposed to be necessary for binding and activity.
α‐Methylidene‐ and α‐Alkylidene‐β‐lactams from Nonproteinogenic Amino Acids
Authors: Buchholz Rainer , Hoffmann H. Martin R. 
Published: December 2004

AbstractTreatment of methyl 2‐(1‐hydroxyalkyl)prop‐2‐enoates 1 with conc. HBr solution afforded methyl (Z)‐2‐(bromomethyl)alk‐2‐enoates 2, which were transformed regioselectively into N‐substituted methyl (E)‐2‐ (aminomethyl)alk‐2‐enoates 3 (SN2 reaction) and into N‐substituted methyl 2‐(1‐aminoalkyl)prop‐2‐enoates 4(SN2′ reaction). Regiocontrol of nucleophilic attack by amine was accomplished simply by choice of solvent, the SN2 reaction occurring in MeCN and the SN2′ reaction in petroleum ether. Hydrolysis and lactamization afforded β‐lactams 7 and 8, containing an exocyciic alkylidene and methylidene group at C(3), respectively.
Synthese von ‘Push‐Pull’‐Oligoacetylenen
Authors: Bartlome Andreas , Stämpfli Urs , Neuenschwander Markus 
Published: December 2004

Synthesis of ‘Push‐Pull’‐OligoAcetylenes‘Push‐pull’ triacetylenes 11a, b, c, as well as ‘push‐pull’ tetraacetylene 13b have been prepared by reaction of the corresponding trichloroene(oligoinyl)amines 9 and 10 with 2 mol‐equiv. of BuLi followed by acylation. The sequences (Schemes 3 and 4) are very simple and straightforward, they could in principle be applied to the synthesis of ‘push‐pull’ pentaAcetylenes 15 and hexaacetylenes 17 (Scheme 5). Main limitations are the moderate yields as well as the low thermal stability of push‐pull oligoacetylenes.
High‐Resolution Solid‐State MAS13C‐ and 1H‐NMR Spectra of Benzenoid Aromatics Adsorbed on Alumina and Silica: Successful Applications of 1D and 2D Pulse Experiments from Liquid‐State NMR
Authors: Ebener Michael , Fircks Gero Von , Günther Harald 
Published: December 2004

AbstractStrong line‐narrowing effects in solid‐state, magic‐angle‐spinning (MAS) 13C‐ as well as 1H‐NMR spectra of benzenoid aromatics adsorbed at alumina or silica surfAccs indicate high mobility of the organic adsorbates. Even under modest spinning rales (1 kHz), dipolar couplings are sufficiently reduced to allow scalar 13C,1H couplings to be measured. Hetero‐ and homonuclear pulse sequences known from high‐resolution NMR in liquids, like SEFT, J‐RESOLVED, DEPT, COSY, and 13C,1H shift‐correlation experiments are successfully applicable. 13C spin‐lattice relaxation limes are as short as 0.5 s (CH) and 1.1 s (Cq), and T1(1H) values are in the order of 0.3 s.
Gas‐Phase Chemistry of Ti+ to Zn+ with Butyl Isothiocyanate
Authors: Eller Karsten , Akkök Semiha , Schwarz Helmut 
Published: December 2004

AbstractUsing a complete set of 2H‐labeled isotopomers, the gas‐phase reactions of Ti+ to Zn+ with butyl isothio‐cyanate are studied. The main product for most of the metal ions is MHNCS+ formed by an ion/dipole mechanism. Exceptions are Cr+, which yields significant amounts of H2 and H2S loss, Mn+, which is the only ion that does not form MHNCS+ at all but produces mainly C2H4 and C3H6, and Zn+, which predominantly reacts by charge transfer.
Preparative Resolution of Heterocyclic Acetals Derived from Glycine, Mercapto‐acetic Acid, β‐Alanine, and Formyl‐ or Acetylacetic Acid by Recycling Chromatography onChiraspherand Temperature Dependence of Separation Factors
Authors: Kinkel Joachim N. , Gysel Urs , Blaser Denis , Seebach Dieter 
Published: December 2004

AbstractChiraspher, a polymer of ethylN‐acryloylphenylalanine on spherical silica gel, is used for the preparative separation by recycling chromatography of the enantiomers of oxazolidinonesrac‐5, thioxolanonerac‐6, per‐hydropyrimidinonerac‐7, and dioxinonesrac‐9and10derived from the acids listed in the title (Figs.1–5). The oxazolidinonesrac‐1a,‐2, and‐4show a peculiar peak of the separation efficiences upon lowering theChiraspher‐column temperature to 15° (Fig.6). In some cases, multigram amounts of enantiomerically pure heterocycles could thus be prepared. The absolute configurations of most enantiomers are assigned. First applications of thetert‐butyl 5‐oxo‐2‐phenyloxazolidine‐3‐carboxylate (5) as a nucleophilic chiral glycine building block are described (products13–16,Scheme 2). A list of enantiomerically pure 1,3‐dioxinones is presented (Table 1), showing a correlation between their absolute configuration, sense of optical rotation, and elution behavior onChiraspher.
Studies for a Diastereoselective Synthesis of the Tetracyclic Diterpenic Diol Stemarin: A Model Study for a New Preparation of the Key Intermediate and the Synthesis of (+)‐18‐Deoxystemarin
Authors: Berettoni Marco , Bettolo Rinaldo Marini , Montanari Vittorio , Prencipe Teresa , Romeo Sergio 
Published: December 2004

AbstractMethods for a stereoselective preparation of compounds of type 2b, a key intermediate of a previous synthesis of the tetracyclic diterpene stemarin (la), have been tested on model compounds 5a, 5c, and 8a. Thus, (±)‐(1RS,6SR,8SR,11SR)‐hydroxytricyclo[6.2.2.0l,6]dodecan‐9‐one (5a) was transformed by the Mitsunobu reaction into (±)‐(1RS,6SR,8SR,11RS)‐11‐(benzoyloxy)tricyclot[6.2.2.01,6]dodecan‐9‐one (6b; Scheme 2). The latter was also obtained from (±)‐(1RS,6SR,8SR,11RS)‐11‐[(4)‐toluenesulfonyloxy]tricyclo[6.2.2.01,6]dodecan‐9‐one (5c) by the action of Et4N (PhCOO) in acetone. Compound 6b was then converted into (±)‐(1RS,6RS,8RS,9RS)‐tricyclo[6.2.2.01,6]dodecan‐9‐ol (8b), a model for 2b. Compound 8b was also prepared from its epimer 8a by the Mitsunobu reaction via ester 7b. The inversion of configuration of bicyclo[2.2.2]octan‐2‐ols or derivates was not previously described. The model studies paved the way to the diastereoselective synthesis of (+)‐18‐deoxystemarin (1b) via 12β‐hydroxy‐13‐methyl‐9β,13β‐ethano‐9β‐podocarpan‐15‐one (10a) and 13‐methyl‐9β,13β‐ethano‐9β‐podpcarpan‐12α‐ol (11b).
Coenzyme F430 from Methanogenic Bacteria: Detection of a Paramagnetic Methylnickel(II) Derivative of the Pentamethyl Ester by 2H‐NMR Spectroscopy
Authors: Lin Shu‐Kun , Jaun Bernhard 
Published: December 2004

AbstractA methylnickel(II) derivative of coenzyme F430 (1) was proposed as an intermediate in the enzymic process catalyzed by methyl‐CoM reductasc. Indirect evidence points to formation of CH3–F430MII in the reaction of F30M1 (obtained from F430MII (2)) with eleclrophilic methyl donors. The results presented here show, that such a compound does exist. A paramagnetic CD3–NiII derivative 5b of the pentamethyl ester 2 (F430M) of coenzyme F430 was prepared by in situ methylation with (CD3)2Mg and characterized by its isotropically shifted 2H‐NMR spectrum. At −40°, the very broad D‐signal of the axially coordinated CD3 group is found at −490 ppm. Comparison with the 2H‐ and 1H‐NMR spectra of mcthyl(tetramethylcyclam)nickel(II) derivatives 4 ([NiII(CH3))(tmc)]CF3SO3 (4a) is the only isolated CH3–Ni derivative of a N4macrocyclic NiII complex' shows that the large isotropic shift to high field is characteristic for a Me group axially bound to the Ni center. The temperature dependence of the isotropic shift of the CD3–Ni group in both 4b and 5b follows Curie's law and yields 2H hyperfine coupling constants of −0.65 (4b) and −0.85 MHz (5b), respectively. The 1H‐NMR spectrum indicates that, in contrast to the five‐coordinate monochloro complex [NiIICl(tmc)]+, intermolecular exchange of the axial ligand in [NiII(CH3)(tmc)]+ 4a is either slow at the NMR time scale or does not occur at all.
Isomerès optiques du naftidrofuryl ( = 2‐[(naphth‐1‐yl)méthyl]‐3‐(tétrahydrofur‐2‐yl)propanoate de 2‐(diéthylamino) éthyle)
Authors: Descours Denis , Festal Didier , Leger Jean‐Michel , Carpy Alain 
Published: December 2004

AbstractOptical Isomers of Naftidrofuryl( = 2‐(Diethylamino)ethyl 2‐[(Naphth‐1‐yl)methyl]‐3‐(tetrahydrofur‐2‐yl)propanoate)The four optical isomers of naftidrofuryl (1) were prepared in two ways, by separation and resolution of the two diastereoisomeric racemates and by synthesis from the enantiomers of tetrahydrofuran‐2‐methanol (6); see Scheme}. The absolute configuration of one of the isomer as a tartrate monohydrate was established by X‐ray crystallography thus allowing the deduction of the absolute configurations of the other three optical isomers.
Addition of Carbon Nucleophiles to Tricarbonylchromium Complexes of 1,2‐Dihydrocyclobutabenzene, Indane, 1,2,3,4‐Tetrahydronaphtbalene and ortho‐Xylene
Authors: Kündig E. Peter , Grivet Chantal , Wenger Eric , Bérnardinelli Gerald , Williams Alan F. 
Published: December 2004

Abstract3‐Substituted 1,2‐dihydrocyclobutabenzenes (bicyclo[4. 2. 0]octa‐1,3,5‐triene) are readily accessible from [Cr(CO)3(1,2‐dihydrocyclobutabenzene)] (1) via a two‐step sequence which involves addition of a nucleophile and oxidation of the intermediate anionic cyclohexadienyl complex. Nucleophiles used include LiCMe2CN (A), LiCH2CN (B), LiC(Me)(OR)CN (C), (D), (E), LiCMe2CO2Me (F), and LiCH2CO2(t‐Bu) (G). [Cr(CO)3(Indane)] (2) also reacts highly regioselectively to give α‐substitution, whereas [Cr(CO)3(tetrahydronaphthalene)] (3) and [Cr(CO)3(o‐xylene)] (4) give mixtures of products. In several cases, the mixtures of the intermediate anionic cyclohexadienyl complexes can be equilibrated to give, after oxidation, β‐substituted derivatives of 1,2,3,4‐tetrahydronaphthalene and ortho‐xylene selectively. EHMO calculations were carried out, and they rationalize the observed α‐regioselectivity of nucleophilic addition under kinetic control, The X‐ray structures of 1 and 4 are reported and in both compounds the Cr(CO)3 group adopts in the solid state a staggered syn‐conformation with respect to the substituted aromatic C‐atonis.
Glycosylidene Carbenes. Part 5. Synthesis of Glycono‐1,5‐lactone Tosylhydrazones as Precursors of Glycosylidene Carbenes
Authors: Mangholz Sissi E. , Vaseha Andrea 
Published: December 2004

AbstractThe benzyl‐ and the acyl‐protected glyconolactone tosylhydrazones 6, 9, 12, 16, and 19 (Scheme 1) were prepared in good yields by treating the hemiacetals 4, 7, 10, 14, and 17 with N‐tosylhydrazine, to give the N‐glycosylhydrazines 5, 8,11,15, and 18, and by oxidizing these hydraz tries with N‐bromosuccinimide (NBS) in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), with CrO3–dipyridine complex or with pyridinium dichromate. Photolysis of the sodium sail 20 of 6 (Scheme 2) in the presence of N‐phenylmaleimide, dimethyl fumarate, or acrylonitrile gave the corresponding cyctopropanes 21–28 in satisfactory yields. Phololytic or thermolytic glycosidation of phenol and 4‐melhoxyphenol by 20 yielded the anomeric glycosides 29/30 and 31/32, yields being marginally higher for the Ihermolytic process. Phololytic glycosidation of propan‐2‐ol gave the glycosides 33 and 34 in low yields only. Yields and ratios of products were compared to those obtained with the diazirine 1 as a source of glycosylidene carbenes. While the yields from 20 are lower, the ratios of products obtained in the photolytic reactions are in agreement with the formation of a common intermediate from both carbene precursors.
Asymmetric Diels‐Alder Cycloadditions with Chiral Carbamoyl Dienophiles
Authors: Defoin Albert , Brouillard‐Poichet Agnès , Streith Jacques 
Published: December 2004

AbstractChiral acylnitroso dienophiles 14, which were obtained from L‐proline and from D‐mandelic acid, reacted with cyclohexa‐1,3‐diene to give the expected diastereoisomers 15 and 16 (Scheme 2 and Table 1). The d.e. values for these Diels‐Alder reactions were moderate; they are related to the molecular stiffness of the dienophiles. The absolute configuration of the major cycloadducts was interpreted in terms of HOMO/LUMO interactions, the approach being ‘endo’ and the acylintroso dienophiles reacting from their s‐cis‐conformation.
Catalytic asymmetric synthesis of Secondary (E)‐allyl alcohols from acetylenes and aldehydes via (1‐alkenyl)zinc intermediates. Preliminary Communication
Authors: Oppolzer Wolfgang , Radinov Rumen N. 
Published: December 2004

AbstractHydroboration of aliphatic 1‐alkynes with freshly prepared dicyclohexylborane (1 mol‐equiv., hexane), treatment of the resulting [(E)‐1‐alkenyl]boranes 5 with Et2Zn or Me2Zn (1.05 mol‐equiv.) followed by addition of (−)‐3‐exo‐(dimethylamino)isoborneol (DAIB, 8; 0.01 mol‐equiv.), subsequent addition of a solution of an aromatic or aliphatic aldehyde (1 mol‐equiv., hexane), and quenching with aq. NH4Cl provided (E)‐allyl alcohols 6 usually in 70–95% yield with 79–98% enantiomeric excess (Scheme 3 and Table).
Investigations of the Molecular Surface of a Few Sandalwood‐Odor Molecules and Related Structures: Conformational calculations on sandalwood odorants. VI
Authors: Buchbauer Gerhard , Leonhardsberger Karin , Winiwarter Susanne , Wolschann Peter 
Published: December 2004

AbstractThe calculated molecular surfaces for some Sandalwood‐odor molecules and structurally similar inactive compounds were compared with the calculated mean surface obtained from five Sandalwood odorants included in the set, and their individual agreement and deviations were estimated. Especially the investigation of selected parts of the surfaces seems very promising in finding structure subunits which might be important for an association to a possible receptor site.
Syntheses and X‐Ray Structures for Model Compounds of a Pyrimidinediyl‐Based Rigid‐Rod Aromatic Polyamide
Authors: Oertli Alfred G. , Meyer Werner R. , Suter Ulrich W. , Joho Felix B. , Gramlich Volker , Petter Walter 
Published: December 2004

AbstractA variety of model compounds for the pyrimidinediyl‐based rigid‐rod polyamide poly[imino‐(pyrimidine‐2,5‐diyl)‐imino‐tetraphthaloyl] (PPYMT) was prepared, in order to compare their conformations to several model compounds of the related, fully aromatic polymer poly(p‐phenyleneterephthalamide) (PPTA). In particular, the structures of N‐(2‐pyrimidyl)benzamide (PYMB) and its complexed form bis[(N‐pyrimidin‐2‐yl)benzamide]nickel(II) dichloride (NiPYMB) were determined by X‐ray diffraction. The molecular packing in these crystals provides us with a model for the possible ‘cross‐linking’ of PPYMT fibers. The structures of the trimer model compounds N,N′ ‐bis(2‐pyrimidyl)terephthalamide (PYTA) and N,N′ ‐bis(benzoyl)‐2,5‐diaminopyrimidine (BDAP) yield information about the conformation of PPYMT chains and are compared to analogous model compounds of PPTA.
Multinuclear NMR Studies of Ligand‐Exchange Reactions on Analogous Technetium(V) and Rhenium(V) Complexes. Relevance to nuclear medicine
Authors: Helm Lothar , Deutsch Karen , Deutsch Edward A. , Merbach André E. 
Published: December 2004

AbstractThe kinetics of pyridine exchange on trans‐[MO2(py)4]+ have been followed by 1H‐NMR in CD3NO2 for M = Re, Tc: k298S−1 = (5.5 ± 0.1) × 10−6, 0.04 ± 0.02; ΔH≠/kJmol−1 = 111 ± 3, 101 ± 9; ΔS≠/JK−1mol−1 = +28 ± 10, +68 ± 35. For the Rev complex, pyridine and oxygen exchanges have been measured simultaneously by 1H‐ and 17O‐NMR in deuterated water: k298/s−1 = (8.6 ± 0.2) × 10−6 (py), (14.5 ± 0.3) × 10−6 (oxygen); ΔH≠/kJmol−1 = 111 ± 1, 91 ± 1; ΔS /JK−1mol−1 = +32 ± 3, −32 ± 4. For both complexes, the rate law for pyridine exchange is first‐order in complex and zero‐order in pyridine; together with the activation parameter values, and the fact that the rate does not depend significantly on the nature of the solvent, this strongly implies the operation of a dissociative mechanism. The ratio of pyridine exchange rates for the Tc and Re complexes at room temperature is ca. 8000. The consequences of these observations for radiopharmaceutical synthesis are discussed.
Cyclohexanecarboxylic‐Acid Derivatives from Psiadia trinervia
Authors: Wang Ying , Hamburger Matthias , Gueho Joseph , Hostettmann Kurt 
Published: December 2004

AbstractFrom a MeOH extra of Psiadia trinervia, seven phenolic compounds were isolated by gel filtration and reversed‐phase chromatography. Six of them are known compounds, namely 3,4‐di‐O‐caffeoylquinic acid (2), 3,5‐di‐O‐caffeoylquinic acid (3), caffeic acid, and three 3‐methoxyflavonoids. Compound 1 is a 3,4‐di‐O‐caffeoyl derviative of (1S,3R,4R,5R)‐1,3,4, 5‐tetrahydroxycyclohexanecarboxylic acid, a novel steroisomer of (−)‐quinic acid. Following hydrolytic treatment of the MeOH extract, ethyl 3‐O‐caffeoylquinate (4), ethyl 3,4‐di‐O‐caffeoylquinate (5), and ethyl 3,5‐O‐caffeoylquinate (6) were isolated. The latter three compounds are artifacts. The configuration of 1‐3 was established by NMR and CD (exciton chirality method).
Electrochemical Oxidation of Ergolines
Authors: Seifert Karlheinz , Phuong Nguyen Minh , Vincent Beverly R. 
Published: December 2004

AbstractAn electrochemical procedure for the preparation of D‐3‐alkoxy‐halogen‐2,3‐dihydro‐6‐methyl‐2‐oxoergolines‐I is described.
Crystal Structure of Bis(η6‐mesitylene)iron(II) Hexafluorophosphate
Authors: Cameron T. Stanley , Linden Anthony , Sturge K. Craig , Zaworotko Michael J. 
Published: December 2004

AbstractThe crystal Structure of [Fe(η6‐mesitylene)2](PF6)2 (1) is reported. The Structure is intricately disordered with the Fe‐atom occupying an m3m cubic site, but nonetheless the conformation and bonding is confirmed. The structure is discussed in the general context of FeII sandwich complexes.