bluuebunny/crossref_metadata_2025 huggingface dataset:
Membrane structure and biologic activity of adrenocorticotropin (ACTH) and melanotropin (MSH) peptides. Estimation of structural parameters including the influence of the helix dipole moment
Authors: Schwyzer Robert
Published: December 2004

Estimation of preferred conformation, orientation, and accumulation of adrenocorticotropin (1–24)‐peptide at an aqueous‐hydrophobic interface produced a model that agreed with that developed from experimental observations with lipid membranes. Thus, the N‐terminal message segment (residues 1–11) was incorporated into the hydrophobic phase as an α‐helical, perpendicularly oriented domain with an apparent dissociation constant of ca. 5 · 10−5 M. The C‐terminal address segment (residues 12‐24) remained in the aqueous phase as a random‐coil domain. Three parameters proved sufficient to define the model: the Gibbs free energy of hydrophobic association, the molecular amphiphilic moment, and the molecular electric dipole moment. For estimating interactions with biologic membranes (that carry a net negative charge), the Boltzmann distribution of charged peptides was also considered. The estimations were extended to adrenocorticotropin (1‐10)‐peptide and α‐melanotropin. In the first case, the prediction agreed with the earlier observations, in the second, it awaits its experimental proof. The estimated membrane structures were compared with available biologic data. As for opioid peptides, it appears that the amphiphilic moment is an important new parameter for determining quantitative structure‐activity relationships (QSAR) in receptor selection and biologic potency.
Synthese und Struktur zweier Gold‐Komplexe des Triphenylphosphonium‐[bis(diphenylphosphino)methylids]
Authors: Schmidbaur Hubert , Graf Wilhelm , Müller Gerhard
Published: December 2004

Synthesis and Structure of Two Gold Complexes of Triphenylphosnium [Bis(diphenylphosphino)methylide]

Triphenylphosphonium [bis(diphenylphosphino)methylide] (1) reacts with 1 or 2 equiv. of (CO)AuCl in a solvent to give mono‐ or binuclear Au(I) complexes 2 or 3, respectively. The Au‐atoms are bound exclusively to P‐atoms, and the ylidic C‐atom remins an uncoordinated link between the three P‐atoms. Contrary to findings with the free ligand 1, 31P‐NMR spectra of 3 are in agreement with free PC bond rotation in solution. 197Au‐Mössbauer data for both complexes indicate the presence of Au(I) centers in a very similar environment. X‐Ray structure analysis shows that the basic geometry of the free ligand is essentially retained in the complexes. Apart from the different degree of complexation, the structures of 2 and 3 differ only slightly in the conformation of the phenyl rings.
Nucleotides. Part XXV. Chemical synthesis of the hexaribonucleotide C‐A‐A‐C‐C‐A
Authors: Lchiba Misuzu , Charubala Ramamurthy , Varma Rajendra S. , Pfleiderer Wolfgang
Published: December 2004

The chemical synthesis of the ribo‐hexamer C‐A‐A‐C‐C‐A has been achieved by two different routes applying the phosphotriester approach and using the (p‐nitrophenyl)ethyl group for phosphate protection. The 2′‐hydroxy groups as well as the terminal 2′,3′‐diol function have been blocked by the (tert‐butyl) dimethylsilyl group as permanent protection throughout all the synthetic steps with great success. Final deblocking of all protective groups could be performed with 80% yield to give the hexamer 23. The various protected intermediates have been characterized by elemental analysis and UV spectra.
Membrane Structure of Substance P. III. Secondary Structure of Substance P in 2,2,2‐Trifluoroethanol, Methanol, and on Flat Lipid Membranes Studied by Infrared Spectroscopy
Authors: Erne Daniel , Rolka Krzysztof , Schwyzer Robert
Published: December 2004

IR data of the neuropeptide substance P (1) and its synthetic segments des‐(Arg1‐Gln6)‐substance P (6), des‐(Arg1‐Pro4)‐substance P (4), des‐(Arg1‐Lys3)‐substance P (3), and des‐Arg1‐substance P (2) indicate predominant β‐structures in the solid state and α‐helical structures in CF3CH2OH (amide I band shape analysis). In MeOH, the spectra of 1 suggest a partly helical structure. On membranes prepared from 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine, a C‐terminal α‐helix consisting of 8 or 9 peptide bonds appears to be induced (IR attenuated total reflection studies). Its perpendicular orientation on the membrane is suggested by the dichroic ratios of the amide‐I and ‐II bands. This study is consistent with our CD experiments and lends support to the membrane structure of 1 predicted from the estimated amphiphilic moment, hydrophobic‐association constant, and helix length.
Metal complexes of macrocyclic ligands. Part XXIV. Binuclear complexes with tetraazamacrocycle‐N,N′,N″,N‴‐tetraacetic acids
Authors: Riesen Andreas , Zehnder Margareta , Kaden Thomas A.
Published: December 2004

The three ligands H4dota, H4teta, and H4heta give binuclear complexes with Cu2+ and Ni2+, the spectral properties of which have been studied. The structures of Cu2(dota)·5H2O and Cu2(teta)·6H2O have been established by X‐ray diffraction analysis.
Ionization Energies of 1‐R‐2,2‐dimesitylethenols, 1,2‐Dimesityl‐2‐phenylethenol, and Some of their Keto Tautomers
Authors: Lecoultre Jacques , Heilbronner Edgar , Biali Silvio E. , Rappoport Zvi
Published: December 2004

The He(Iα) PE spectra of the two pairs of 1(Ph)‐3 and 2–4 have been recorded and assigned by comparison with spectra of related molecules, or by using simple MO arguments. This analysis shows that the PE spectra are in agreement with the assumption that the twist angles observed in the crystalline state are more or less conserved in the gas phase. The observed first adiabatic ionization energies I allow the calculation of the molar reaction enthalpy ΔrH which accompanies the enolization of the radical cations of the title compounds. It is found that ΔrH ≈︁ –−70 kJ mol−1 is roughly the same for both keto/enol pairs, in qualitative and quantitative agreement with expectation. These results complement and correct ionization energies determined previously by mass spectrometric methods and conclusions based on them.
Charge Dispersal in the Quinuclidine Radical Cation and in the Quinuclidinium Ion, as Revealed by PE and ICR Spectroscopy
Authors: Heilbronner Edgar , Honegger Evi , Lecoultre Jacques , Grob Cyril A. , Houriet Raymond , Rolli Eric
Published: December 2004

The n ionization energies I and the gas‐phase basicities GB of CH3‐, Cl‐, or CN‐substituted quinuclidines have been measured by PE and ICR spectroscopy. The dependence of the shifts ΔI and ΔGB (relative to the values of the parent molecule) allow conclusions about the charge dispersal accompanying the n ionization or the protonation of quinuclidine in the gas phase. The agreement with the results of a minimal basis set ab initio calculation is excellent. Comparison of the solution pKa values with either I or GB reveals that 2‐substituted quinuclidines exhibit sizeable solvent‐induced proximity effects, i.e. that the corresponding quinuclidinium ions are more acidic in solution than expected on the basis of the gas‐phase basicities. This agrees with earlier results concerning 2‐substituted pyridines.
3‐Hydroxyglutarate and β,γ‐Epoxy Esters as Substrates for Pig Liver Esterase (PLE) and α‐Chymotrypsin
Authors: Mohr Peter , Rösslein Lukas , Tamm Christoph
Published: December 2004

The pH dependence of the α‐chymotrypsin‐catalyzed hydrolysis of dimethyl 3‐hydroxyglutarate (3) has been studied. The e.e. was determined by HPLC analysis of diastereoisomeric camphanoic‐acid derivatives. Kinetic resolution of the β,α‐epoxy esters 10 and 24 by pig liver esterase has been shown to provide an alternative access to chiral β‐hydroxy esters and acids of high optical purity. By this latter method, the unnatural enantiomer of γ‐amino‐β‐hydroxybutyric acid (GABOB) has been synthesized. Finally, dimethyl meso‐3,4‐epoxyadipate (19) was hydrolyzed by pig liver esterase with almost 100% selectivity.
Herstellung und Charakterisierung in Membranen von Ionophoren mit Selektivität fü Natrium‐Ionen
Authors: Bongardt Frank , Vögtle Fritz , Wegmann Dorothée , Ammann Daniel , Maruizumi Takuya , Simon Wilhelm
Published: December 2004

Preparation of Neutral Sodium‐Selective Ionophores and their Characterization in Membrane Electrodes

Different ionopbores based on N,N′‐dibenzyl‐N,N′‐diphenyl‐1,2‐phenylenedioxydiacetamide (1) have been prepared by substitution of the aromatic ring carrying the ether O‐atoms. Substituents of widely different electronegativity (CH3, CH3O, CHO, CN NO2, Br) do not relevantly influence the ion selectivity.
Aza‐2‐dienes‐1,3. Partie 5. Préparation de N‐aminoimidazoles, 3H‐pyrroles, triazolo[1,2,4][1,5‐a]pyrazines et imidazo[1,2‐a]pyrazines
Authors: Legroux Didier , Schoeni Jean‐Paul , Pont Christiane , Fleury Jean‐Pierre
Published: December 2004

2‐Aza‐1,3‐dienes. Access to N‐Aminoimidazoles, 3H‐Pyrroles, [1,2,4]Triazolo[1,5‐a]pyrazines, or Imidazo[1,2‐a]pyrazines

Nucleophilic attack of 5‐(dialkylamino)‐2‐aza‐1,3‐diene‐1,1‐dicarbonitriles (or their 1‐methoxycarbonyl analogous) by hydrazines or hydrazdes gives substituted N‐aminoimidazoles, [1,2,4]triazolo‐[1,5‐a]pyrazines, or α‐dihydrazino derivatives. With α‐amino esters (or analogous), imidazo[1,2‐a]pyrazines are produced. Addtion of cyanide anions occurs also with formation of substituted 3H‐pyrroles. Structures and rationalisation of this nucleophilic attack are discussed.
Electrochemical Investigation of Potassium Heptacyanorhenate(III) in Aqueous Solution
Authors: Marty Werner , Renaud Philippe , Gampp Harald
Published: December 2004

The electrochemistry of potassium heptacyanorhenate(III) in aqueous solution was studied by cyclic and by rotating disk voltammetry at planar microelectrodes. The results are consistent with a single, reversible electron transfer: Re(CN)3−7 + e⇄Re(CN)4−7 with E′0 = 643 mV vs. NHE. A single protonation equilibrium is observed: Re(CN)4−7 + H+⇄ Re(CN)7H3− with pK = 1.31 determined from combined voltammetric and pH data. The Re–CN bond appears to be kinetically inert, and none of the cyano complexes in other oxidation states of Re claimed in the literature was found in the potential range − 2 V to + 1 V.
Asymmetric Diels‐Alder Reactions of Cyclopentadiene with N‐Crotonoyl‐ and N‐Acryloyl‐4,4‐Dimethyl‐1,3‐Oxazolidin‐2‐one, Mediated by Chiral Lewis Acids
Authors: Chapuis Christian , Jurczak Janusz
Published: December 2004

One‐pot Diels‐Alder reactions of cyclopentadiene with 3‐crotonoyl‐ (2) and 3‐acryloyl‐4,4‐dimethyl‐1,3‐oxazolidin‐2‐one (3), Mediated by chiral Lewis acids, are described. AlCl3, EtAlCl2, Et2AlCl, TiCl4, ZrCl4, SnCl4, SiCl4, and BBr3, modified with derivatives of D‐mannitol, L‐tartaric acid, and (R)‐binaphthol, were applied as chiral promotors. The reaction with dienophile 2, carried out in CH2Cl2 at −78° with high yield, was characterized by excellent π‐face selectivity. In case of the reaction with dienophile 3, the efficiency of the chirality transfer was much lower.
Synthesis of the (+)‐Enantiomer of Taonianone, a Furanoid Diterpene from Brown Algae
Authors: Huckestein Martina , Kreiser Wolfgang , Rüschenbaum Volker
Published: December 2004

The constitution and absolute configuration of the furanoditerpene taonianone (1) has been established by synthesis starting from (–)‐carveol (2).
Molluscicidal Saponins from Swartzia madagascariensis DESVAUX
Authors: Borel Christian , Hostettmann Kurt
Published: December 2004

The phytochemical investigation of the dried fruits of Swartzia madagascariensis (Leguminosae) afforded the five triterpenoid saponins 1–5. They were shown to be glucuronides of oleanolic acid and of gypsogenin by chemical and spectral means (FAB‐MS, 13C‐NMR, GC/MS). One of the isolated compounds, identified as 3‐O‐[O‐α‐L‐rhamnopyranosyl‐(1→3)‐(β‐D‐glucopyranosyluronic acid)]oleanolic acid, was responsible for the high molluscicidal activity of Swartzia madagascariensis fruits against the schistosomiasis‐transmitting snails Biomphalaria glabrata and Bulinus globosus.
Catalysis of Friedel‐Crafts Alkylation by a Montmorillonite Doped with Transition‐Metal Cations
Authors: Laszlo Pierre , Mathy Arthur
Published: December 2004

Catalysts are obtained by exchange of the interstitial cations in the K10 montmorillonite. They are applied to Friedel‐Crafts alkylations with halides, alcohols, and olefins. They are quite effective even with unactivated hydrocarbons. Isomer distribution depends little on the catalyst used. Thermodynamic equilibration does not take place, the reactions appear to be kinetically controlled. Efficiency of the catalysts bears no apparent relation to that of the corresponding Lewis acids under homogeneous conditions, and it depends on the nature of the alkylating agent. Zr(IV) and Ti(IV), in general, give the best results.
Fe(II)‐Induced Fragmentation Reaction of γ‐Hydroperoxy‐α,β‐enones. Part 1. Synthesis of 13(14→8)‐abeo‐Steroids
Authors: Canonica† Luigi , Danieli Bruno , Lesma Giordano , Palmisano Giovanni , Mugnoli Angelo
Published: December 2004

Some steroidal analogues embodying the hitherto unknown 13(14→8)‐abeo skeleton have been synthesized by Fe(II)‐induced rearrangement (tandem β‐fission/reductive alkylation) of 14α‐hydroperoxy‐7‐en‐6‐ones. The configurational assignment was made by thorough analysis of NMR spectra; the structure of one of the products was unambiguously assessed by X‐ray single‐crystal analysis.
Chirale Alkoxytitan(IV)‐Komplexe für enantioselektive nucleophile Additionen an Aldehyde und als Lewis‐Säuren in Diels‐Alder‐Reaktionen
Authors: Seebach Dieter , Beck Albert K. , Imwinkelzied René , Roggo Silvio , Wonnacott Anne
Published: December 2004

Chiral Alkoxytitanium(iv) Complexes for Enantioselective Nucleophilic Additions to Aldehydes and as Lewis Acids in Diels‐Alder Reactions

A Number of chiral 1,2‐1,3 and 1,4‐diols were prepared and used as alkoxy ligands on Ti for enantioselective nucleophilic transfer of methyl, butyl, cyclopropyl, allyl, alkinyl, and phenyl groups to aromatic aldehydes, as well as for the enantioselective[4+2]cycloaddition of acrylate to cyclopentadiene. The 1,2‐diols were pinane diol 7 and 1,2:5.6‐diacetonide‐protected mannitol 9 (Scheme 3) and tartrates. The 1,3‐diols were obtained from the yeast‐reduction products of 2‐oxocyclopentane‐ and 2‐oxocyclohexanecarboxylates and excess MeLi, BuLi, or PhLi (or the corresponding Grignard reagents; see4–6.) As 1,4‐diols, we used the products 2 and 3 from tartrate acetals and methyl or Pheny1 Grignard reagents, the bis(benzaldehyde) acetal 8 of d‐mannitol and o,o'‐binaphthol (22). These diols were attached to the Ti‐atom by azeotropic removal of i‐PrOH from a mixture with [TiCi(i‐PrO)3]. Addition of various organometallic reagents R‐metal (metal = Li, BR3, MgX, MnC1, CuLiR) was followed by combination with aldehydes at – 75., a warm up period, quenching with aqueous KF solution, and workup (for results see Tables 1–6 and Formulae 17–20). The enantiomeric excess of the secondary alcohols obtained varies greatly, certain combinations of chiral ligands, nucleophilic groups, and aldehyde substrates give rise to values as high as 90% ee; see e.g. Table 4. The Ti‐complexes of the general formula [Ti(R*O)2Ci2] or [Ti(R*O)2(i‐PrO)CI] induced the Diels‐Alder addition of methyl acrylate to cyclopentadience to take place at –30.. The best enantioselectivity (50% ee) was observed with the binaphthol derivative (Table 7). The structures of the complexes involved in these reactions are unknown. The substitution on C(2) of the dioxolanes 2 and 3 (derived from tartaric acid) has a pronounced effect on the selectivities of both reactions studied here (Tables 2, 3, and 7). This remote effect (1,6‐distance between the stereogenic acetal‐C‐atom and the Ti‐centers) must be caused by conformational changes in the vicinity of the reactive site, i.e. the TiC bond in the nucleophilic addition reactions and the Ti‐acrylate‐oxygen complexation in the Diels‐Alder reaction.
Bildung tricyclischer Thietan‐Derivate durch intramolekulare(2+2)‐Cycloaddition
Authors: Wipf Peter , Heimgartner Heinz
Published: December 2004

Formation of Thietane Derivatives via Intramolecular (2+2) Cycloaddition

On irradiation, the two 4‐vinyl‐1,3‐thiazole‐5(4H)‐thiones 1a, b, synthesized from thiobenzoic acid and the corresponding 3‐amino‐2H‐azirines 2a,b, undergo an intramolecular (2+2)‐cycloaddition reaction of the CS and CC bonds to give the tricyclic thietane derivatives 3a,b.
Photochemical Synthesis of 2‐Alkylidene‐1,3‐cyclocalkanediones. Preliminary Communication
Authors: Hobel Klaus , Margaretha Paul
Published: December 2004

Photolysis (λ = 254 nm) of 4‐(tert‐butyl)‐4,6,7,8‐tetrahydro‐7,7‐dimethy‐2H‐1‐benzopyran‐2,5(3H)‐dione (3a) in t‐BuOH affords 2‐(2,2‐dimethylpropylidene)‐5,5‐dimethyl‐1,3‐cyclohexanedione (1a) in 80% yield via homolysis of the lactone OCO bond and subsequent ketene elimination.
Oxidationsreaktionen methyl‐substituierter 2,1,3‐Benzothiadiazole und 2,1,3‐Benzoselenadiazole mit Selen‐dioxid
Authors: Neidlein Richard , Knecht Dagmar
Published: December 2004

Oxidation Reactions of Methyl Substituted 2,1,3‐Benzothiadiazoles and 2,1,3‐Benzoselenadiazoles with Selenium Dioxide

The synthesis 5–8 by oxidation of 4‐methyl‐(1),5‐methyl(2), 5,6‐dimethyl‐2,1,3‐benzoselenadiazole (3), and 5,6‐dimethyl‐2,1,3‐benzothiadiazole (4), respectively, with selenium dioxide as well as their spectroscopic properties are described.
Some Cyclic Oligopeptide with S2n Symmetry
Authors: Tomasic Lera , Lorenzi Gian Paolo
Published: December 2004

Some cyclic oligopeptides formed by an equal number of alternating D‐ and L‐amino‐acid residues have been synthesized by using the hydrochloride of the open‐chain peptide acid as precursor and the mixed‐anhydride condensation method. The cyclic oligopeptides (tetra‐, hexa‐, and octavaline, hexaleucine, and hexaphenylalanine) form very stable H‐bonded structures (IR‐amide band at 3270–3290 cm−1) which are insoluble in common organic solvents. In CF3COOH/CDCI3 (25°), they yield 1H‐NMR spectra snowing the expected equivalency of the various amino‐acid residues.
Control of Diels‐Alder Addition, Stereo‐ and Regioselectivity by Remote Substituents and Tricarbonyl(diene)iron Moieties
Authors: Zwick Jean‐Christophe , Voge Pierre , Mange Vladimir , Chapuis Gervals
Published: December 2004

A stereoselective synthesis of tricarbonyl‐[((1RS,2RS,4RS,5RS,6RS)‐C‐5,6,C‐η‐(5,6,7,8,‐tetramethylidenbicyclo[2.2.2]octan‐2‐ol)]iron (11),and of its tosylate 12 and benzoate 13 is reported. The bulk of the ‘endo’‐Fe(CO))3 moiety and of the ester groups in 13 renders its Diels‐Alder additions to methyl propynoate (15)), butynone (16), and 1‐cyanovinyl acetate highly ‘para’ regioselective. The cycloadditions of diene‐alcohol 11 are either ‘meta’‐ or ‘para’‐regioselective depending on the nature of the dienophile. In the presence of BF3. Et2O, the addition of 11 to methyl vinyl ketone is highly stereo‐ (Alder mode) and ‘para’‐regioselective, giving adduct 52 (tricarbonyl [((1 RS,4RS,8RS,9RS,10RS,12RS)‐C,9,10,C‐η‐(12‐hydroxy‐9,10‐dimethylidenetricyclo[6.2.2.02,7]dodec‐2(7)‐en‐4 yl methyl ketone)]iron) whose structure has been established by single‐crystal X‐ray crystallography.
Synthèse d'homologues de la (–)‐‐(1R,2S)‐norephedrine
Authors: Lamant Maurice , Guignard Alain
Published: December 2004

Synthesis of (–)‐(1R,2S)‐Norephedrine Homologues

The amino function of esters of some simple natural amino acids I is blocked in the form of a cyanoenamine by means of 2‐oxocyclopentanecarbonitrile, so that the corresponding cyanoenamino esters II are obtained. The reaction of a disubstituted lithium amide with II leeds to the cyanoenamino‐amides VI. The amide function present in VI is then transformed into an aromatic ketone by means of phenyllithium, to give the (benzoylalkyl)aminocyclopentenecarbonitriles VII. Reduction of Compounds VII with NaBH4 in EtOH −80° affects only the keto function and leads to the [(α‐hydroxybenzyl)alkyl]amino‐cyclopentenecarbonitriles VIII. The amino function is then deprotected by acid hydrolysis to give the amino‐alcohols IX with yields close to 50%; in every amino‐alcohol IX, the erythro isomer, homologous to natural (–)‐(1R,2S)‐norephedrine is the more abundant or the single product. All the polyfunctional compounds prepared conserve optical activity; it has been demonstrated that the amino‐alcohols IX are pure enantiomers and that no racemisation lakes place at any step of their synthesis.
Structures and Mutagenic Properties of Products Obtained by C‐Nitrosation of Opipramol
Authors: Faigle Johann W. , Blattner Hans , Glatt Hansruedi , Kriemler Hans‐Peter , Mory Hans , Storni Angelo , Winkler Tammo , Oesch Franz
Published: December 2004

Reaction of the tricyclic psychotropic drug opipramol (1) with an excess of HNO2 affords a product mixture mutagenic for Salmonella typhimurium. The main product is a tetracyclic furoxan 2 (yield ca. 80%), resulting from nitrosation at C(10) and C(11) of 1. Compound 2 is not mutagenic. The essential mutagen is a nitroarene 3 formed via contraction of the central ring of 1, and nitrosation at C(2). Its yield is extremely low (<0.1%). Nitroarenes have previously not been encountered as mutagenic products of the interaction of drugs with nitrite.
Short Syntheses of (±)‐Grandisol and (±) Lineatin via, a common Intermediate
Authors: Aljancic‐Solaja Ivana , Rey Max , Dreiding André S.
Published: December 2004

A 6‐step synthesis of (±)‐grandisol (1) is presented, which involves dichloroketene addition to 3‐methyl‐3‐butenyl acetate (4), reductive dechlorination of the adduct 6 to the ketone 7 and saponification to 8, aldolization of 7 or 8 with acetone and cyclization to the bicyclic ketone 9, Wolff‐kishner, reduction to 14, and finally ring opening to 1. Since 9 is a known intermediate of the synthesis of (±)‐lineatin (2), the latter can now be obtained in 6 steps.
Herstellung enantiomerenreiner Derivate von 3‐Amino‐ und 3‐Mercaptobuttersäure durch SN2‐Ringöffnung des β‐Lactons und eines 1,3‐Dixoanons aus der 3‐Hydroxybuttersä ure
Authors: Griesbeck Axel , Seebach Dieter
Published: December 2004

Preparation of Enantiomerically Pure Derivatives of 3‐Amino‐ and 3‐Mercaptobutanoic Acid by SN2 Ring Opening of the β‐Lactone and a 1,3‐Dioxanone Derived from 3‐Hydroxybutanoic Acid

From (S)‐4‐methyloxetan‐2‐one (1), the β‐butyrolactone readily available from the biopolymer (R)‐polyhydroxybutyrate (PHB) and various C, N, O and S nucleophiles, the following compounds are prepared:(s)‐2‐hydroxy‐4‐octanone (3), (R)‐3‐aminobutanoic acid (7) and its N‐benzyl derivative 5, (R)‐3‐azidobutanoic acid (6) (R)‐3‐mercaptobutanoic acid (10), (R)‐3‐(phenylthio)butanoic acid (8) and its sulfoxide 9. The (6R)‐2,6‐dimethyl‐2‐ethoxy‐1,3‐dioxan‐4‐one (4) from (R)‐3‐hydroxybutanoic acid undergoes SN2 ring opening with benzylamine to give the N‐benzyl derivative (ent‐5) of (S)‐3‐aminobutanoic acid in 30‒40% yield.
Asymmetric Dihydroxylations of β‐Substituted N‐(α,β‐Enoyl)bornane‐10,2‐sultams
Authors: Oppolzer Wolfgang , Barras Jean‐Pierre
Published: December 2004

Pure (E)‐ or (Z)‐enoylsultams 2 were Oxidized with OsO4/N‐Methylmorpholine N‐oxide in a stereospecific and highly π‐face‐selective manner. Acetalization of the resulting 1,2‐diols furnished, after purification, the stable, crystalline acetals 6 in >99% d.e. and in 63–74% overall yield from 2. Reductive or hydrolytic cleavage of 6 gave enantiomerically pure alcohols 8 or carboxylic acids 9 with recovery of the sultan auxiliary 1.
Synthese von N‐Methyl‐ und N,N‐Dimethylmerucathin sowie von N‐Methyl‐ und N,N‐Dimethylpseudomerucathin aus L‐Alanin
Authors: Stoll Hanspeter , Wolf Jean‐Pierre , Pfander Hanspeter
Published: December 2004

Synthesis of N‐Methyl‐ and N,N‐Dimethylmerucathine and of N‐Methyl‐ and N,N‐‐Dimethylpseudomerucathine Starting from L‐Alanine

Starting form L‐alanine, N‐methylmerucathine (= (3R,4S)‐4‐(methylamino)1‐phenyl‐1‐penten‐3‐ol; (3R,4S,)‐6), N,N‐dimethylmerucathine (= (3R,4S)‐4‐(dimethylamino)‐1‐phenyl‐1‐penten‐3‐ol; (3R,4S)‐9), N‐methylpseudomerucathine (= (3S,4S)‐4‐(methylamino)‐1‐phenyl‐1‐penten‐3‐01; (3S,4S)‐6), and N,N‐dimethylpseudomerucathine (= (3S,4S)‐4‐(dimethylamino)‐1‐phenyl‐1‐penten‐3‐ol; (3S,4S)‐9) were synthesized. The four compounds were analyzed by HPLC and compared with a natural khat extract.
Synthesis of 1‐Fluoro‐2‐amino‐1,3‐cyclohexadienes and 1‐Fluorobicyclo[2.2.2]octan‐2‐ones
Authors: Pick‐Schliebs Heike , Margaretha Paul
Published: December 2004

Conjugated β‐fluoro‐enamines 4 undergo cycloaddtion to methyl acrylate regio‐ and stereospecifically, affording the 1‐fluorobicyclo[2.2.2]octan‐2‐one 6a after hydrolysis.
β‐Cleavage of Bis(homoallylic) Potassium Alkoxides. Two‐Step Preparation of Propenyl Ketones from Carboxylic Esters. Synthesis of ar‐Turmerone, α‐Damascone, β‐Damascone, and β‐Damascenone
Authors: Snowden Roger L. , Linder Simon M. , Muller Bernard L. , Schulte‐Elte Karl H.
Published: December 2004

The transformation of 36 bis(homoallylic) alcohols VII to alkenones IX and X via β‐cleavage of their potassium alkoxides VIIa in HMPA has been investigated (cf. Scheme 2). These studies have established an order of β‐cleavage for 2‐propenyl, 1‐methyl‐2propenyl, 2‐methyl‐2‐propenyl, 1,1‐dimethyl‐2propenyl, and benzyl groups in alkoxides 49a–56a and have allowed a comparison between the β‐cleavege reaction and the oxy‐Cope rearrangement in alkoxides 74a–83a. As illustrative syntheti applications, a two‐step preparatio of propenyl ketones 15–42 from carboxylic esters is described, together with syntheses of ar‐turmerone (48), α‐damascone ((E)‐71), β‐damascone ((E)‐109), and β‐damascenone ((E)‐111).
Formation and Structure of the Phosphoranyl Radical Derived from 1,2‐Phenylene Phosphorochloridate: a Solid‐State ESR Study
Authors: Cattani‐Lorente Maria , Bernardinelli Gérald , Geoffroy Michel
Published: December 2004

The crystal structure of 1,2‐ phenylene phosphorochloridate has been determined. X‐Ray irradiation of these crystals, at low temperature, leads to the formation of a radical exhibiting hyperfine structure with P and Cl nuclei. The corresponding ESR tensors are obtained, and they show that this radical is a phosphoranyl radical adopting a slightly distorded σ* structure. The same species could be produced in frozen solution, its hyperfine tensors are, then, more in accordance with a trigonal‐bipyramid structure. The effects of the host matrix on the stabilization of the structure of phosphoranyl are investigated.
Isolierung und Strukturaufklärung von 36 Diterpenoiden aus Trichomen von Plectranthus edulis (VATKE) T.T. AYE
Authors: Künzle Josef Max , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Isolation and Structure Elucidation of 36 Diterpenoids from Leaf‐Glands of Plectranthus edulis (VATKE) T.T. AYE

Analysis of the polar diterpenoids from the yellow glands of the title plant from Kenya and Abyssinia led to the identification of several novel abietanoids. Main compound is the known edulon A (40), a 5(4→3) abeo‐abietane. Minor compounds include 6 different royleanones, 15 spirocoleons, 3 vinylogous quinones, 8 acylhydroquinones (as their 6,7‐dioxo compounds or the tautomeric disophenols), 2 naphthaquinones (as the 1,10‐seco‐abietanoids), and deacetyledulon A. The known coleon‐A‐lactone (37) now has also been found in Plectranthus edulis. The intermediacy of the γ‐enollactol 44, combined with a leaving group on C(3) is postulted to explain the biogenesis of the unusual 4H‐5‐oxaaceanthrylen skeleton of edulon A.
Synthesis of trans‐10,11‐Dihydro‐10,11‐dihydroxy‐5H‐dibenz[b,f]azepine‐5‐carboxamide, a Major Metabolite of Carbamazepine
Authors: Heckendorn Roland
Published: December 2004

The stereoselectivity of the reduction of 5‐carbamoyl‐10,11‐dihydro‐11‐oxo‐5H‐dibenz[b,f]azepine‐10‐yl acetate (6), prepared in two steps from 10,11‐dihydro‐10‐oxo‐5H‐dibenz[b,f]azepine‐5‐carboxamide (4), has been studied. Among the reagents used, diisobutylaluminum hydride (DIBAH) was found to give the highest trans/cis diol ratio. This allowed the preparation of the important trans‐diol metabolite 3 of carbamazepine (1).
The Aluminum‐Bromide‐Catalyzed Adamantane Rearrangement of syn‐ and anti‐Tricyclo[4.2.1.12,5]decane
Authors: Brossi Marco , Ganter Camille
Published: December 2004

In the presence of AlBr3 in CS2 at temperatures below 0°, syn‐tricyclo[4.2.1.12,5]decane (1) isomerizes exclusively to anti‐tricyclo[4.2.1.12,5]decane (2) at a higher rate than the latter rearranges to 2‐exo,3‐exo‐trimethylene‐8,9,10‐trinorbornane (4). However, at temperature above 0°, the anti‐isomer 2 isomerizes to 4 faster than 1 to 2 and 4. As a consequence, hydride abstraction occurs at C(3) (→carbocation a, which rearranges to carbocation b (anti‐skeleton)) in the syn‐isomer 1, and more readily at C(9) (→carbocation c) than at C(3) (→carbocation b) in the anti‐isomer 2.
10′‐Apolycopin‐10′‐ol und 10′‐Apolycopin‐10′‐säure aus Blüten der Rosenhybride ‘Maréchal Niel’. 6. Mitteilung über Farbstoffe aus Rosen
Authors: Märki‐Fischer Edith , Uebelhart Peter , Eugster Conrad Hans
Published: December 2004

10′‐Apolycopen‐10′‐ol and 10′‐Apolycopen‐10′‐oic Acid from the Petals of the Rose Hybrid ‘Maréchal Niel’

The novel 10′‐apolycopen‐10′‐ol (1) and 10′‐apolycopen‐10′‐oic acid (4) were isolated from the yellow petals of the once world‐renowned rose hybrid ‘Maréchal Niel’. The relative amount of either 1 or 4 produced by the plant depends upon the climatic conditions. Both 1 and 4 together with related compounds were synthetisized and characterized by spectral data.
Functionalisation of saturated hydrocarbons. Part XI. Oxidation of cedrol, β‐ and γ‐eudesmol, sclareol, manoyl oxide, 1,9‐dideoxyforskolin, methyl trans‐dihydroiasmonate, and tetrahydrolinalool by the ‘Gif system’
Authors: Barton Derek H. R. , Beloeil Jean‐Clauude , Billion Annick , Boivin Jean , Lallemand Jean‐Yves , Lelandais Patrick , Mergui Simone
Published: December 2004

The oxidation of cedrol (1), β‐ and γ‐eudesmol (6 and 7, resp.), sclareol (14) manoyl oxide (15), 1,9‐dideoxyforskolin (22) (±)‐methyl trans‐dihydrojasmonate (28), and tetrahydrolinalool (32) nearly all of natural terpenoid origin, by the ‘Gif system’ has afforded a number of novel products (3, 11, and 12, 16/17, 18/19, 26, 29–31, and ketones corresponding to 34–35, res.). The structures of these compounds were established by spectroscopic techniques including 2D‐NMR and, where appropriate, by comparison with authentic samples.
Halochrome Molekeln. 7. Mitteilung. Synthese und acidobasisches Verhalten substituierter Heteroarenochinazoline
Authors: Gunzenhauser Sigmund , Balli Heinz
Published: December 2004

Halochromic Molecules. Synthesis and Acidobasic Properties of Substituted Heteroarenoquinazolines

We have synthetized a series of substituted heteroarenoquinazolines. The 90‐MHz FT 1H‐NMR spectra of starting and final products supported the postulated structures. Fragmentation in the mass spectra also were consistant with the assumed structures. With acid, the compounds partly from ring‐opened, intensely coloured triphenylcarbenium salts of the Rhoduline‐R type (C. I. 42565). UV/VIS spectra of the salts are discussed on the basis of VEPPP‐CI calculations. The ϵpH* curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds undergo very complex protonation equilibria.
Metal Complexes with Macrocyclic Ligands. Part XXVI. Synthesis and spectral properties of Cu2+ complexes with mono‐N‐functionalized 1,4,8‐trimethyl‐1,4,8,11‐tetraazacyclotetradecanes
Authors: Tschudin Daniel , Basak Arup , Kaden Thomas A.
Published: December 2004

A series of mono‐N‐functionalized 1,4,8‐trimethyl‐1,4,8,11‐tetraazacyclotetradecanes 3–14 were synthesized by alkylating the secondary N‐atom of the macrocycle 1. The spectral properties of the Cu2+ complexes, studied under different pH conditions, are discussed in relation to the possibility of coordination of the donor group of the side chain to the axial position of the metal ion and to the effect of the length of the side chain.
Silicon‐Directed Nazarov Cyclizations. Part V. Substituent and heteroatom effects on the reaction
Authors: Denmark Scott E. , Habermas Karl L. , Hite Gary A.
Published: December 2004

The ability to incorporate alkyl, alkenyl, aryl, and heteroatomic groups into substrates for the silicon‐directed Nazarov cyclization and their subsequent reactions has been investigated. In general, most of the groups are compatible with the conditions for the cyclization and do not interfere even when directly attached to the divinyl ketone. The influence of substituents on the rate of the cyclization has been addressed and is consistent with a simple mechanistic picture. O‐ and N‐Containing functions are tolerated except when attached to the α‐vinyl C‐atom of the divinyl ketone. The diastereoface‐directing effect of a fused cyclobutane is discussed.
Konformationsanalysen von Modell‐Tripeptiden: Der Einfluss von α,α‐disubstituierten α‐Aminosäuren auf die Sekundärstruktur. Teil I. NMR‐ und CD‐Untersuchungen
Authors: Wipf Peter , Heimgartner Heinz
Published: December 2004

Conformational Analysis of Tripeptide Models: The Influence of α,α‐disubstituted α‐Amino Acids on the Secondary Structure. NMR and CD Investigations

The conformational properties of α,α‐disubstituted α‐amino acids are discussed on the basis of NMR, CD, X‐ray, and molecular‐mechanics studies on tripeptide models 1. It is shown that different disubstituted amino acids do not exert the same influence on secondary‐structure formation. Thus, the choice of substituents allows the construction and stabilisation of different conformations of oligopeptide chains.
Synthese von (−)‐(R)‐Nephthenol und (−)‐(R)‐Cembren A
Authors: Schwabe Rudolf , Farkas Imre , Pfander Hanspeter
Published: December 2004

Synthesis of (−)‐(R)‐Nephthenol and (−)‐(R)‐Cembren A

Starting for L‐serine,(−)‐(R)‐nephthenol((−)‐2) and (−)‐(R)‐cembren A((−)‐3) were synthesized.
[4 + 2]‐Cycloadditionen von α,β‐ungesättigten Hydrazonen. Teil 1. Pyridin‐2,3‐dicarboximide aus 1‐(Dimethylamino)‐1,4‐dihydropyridin‐Derivaten
Authors: Waldner Adrian
Published: December 2004

[4 + 2] Cycloadditions of α,β‐Unsaturated Hydrazones to Pyridine‐2,3‐dicarboximides via 1‐(Dimethylamino)‐1,4‐dihydropyridine Derivatives

The [4 + 2] Cycloaddition of α,β‐unsaturated hydrazones of type 1 (1‐aza‐1,3‐butadienes) with 2‐halogenomaleimides 4 affords 1,4‐dihydropyridines 6 which, after treatment with an acid, yield highly substituted pyridine‐2,3‐dicarboximide derivatives 7 (Scheme 1).
Sambucinic Acid, a New Metabolite of Fusarium sambacinum. 45th communication on verrucarins and roridins
Authors: Rösslein Lukas , Tamm Christoph , Zücher Werner , Riesen Andreas , Zehnder Margareta
Published: December 2004

Sambucinic acid (5), a C15‐trichothecene with a modified strure, has been isolated from cultures of Fusarium sambucinum. The structure is established by spectroscopic data and X‐ray diffraction analysis. A hypothetical biogenetic pathway is proposed.
Alkylation of Adenine, Adenosine, and NAD+with 1,3‐Propanesultone. Synthesis ofN6‐(3‐sulfonatopropyl)‐NAD+, a new NAD+derivative with substantial coenzyme activity
Authors: Carrea Gianconno , Ottolina Gianluca , Riva Sergio , Danieli Bruno , Lesma Giordano , Palmisano Giovanni
Published: December 2004

The reactivity of 1,3‐propanesultone with adenine, adenosine, and NAD+was studied in order to prepareN6‐(3‐sulfonatopropyl)‐NAD+(3b), a new NAD+derivative substituted at the purine moiety with sunstantial coanzyme activity for several dehydrogenases. The regiochemistry of the alkylation at the purione nucleus was investigated by UV,1H‐NMR, and FAB‐MS proved to be a powerful tool for determining the molecular weight of these polar and poorly volatile compounds. In addition, regular framgmentation of3band other NAD+derivatives was observed.
Identifizierung von 2‐Acetamido‐2‐desoxy‐α‐D‐glucopyranosyl‐1‐phosphat in Kuhmilch als Wachstumsfaktor für Treponema vincentii
Authors: Bernet Bruno , Wyss Christoph
Published: December 2004

Identification of 2‐Acetamido‐2‐deoxy‐α‐D‐glucopyranosyl 1‐Phosphate in Cow‐Milk as Growth Factor for Treponema vincentii

A 7:3 mixture of 2‐acetamido‐2‐deoxy‐α‐D‐glucopyranosyl and ‐α‐D‐galactopyranosyl 1‐phosphate (1 and 2, resp.) was isolated from cow‐milk and identified by 1H‐ and 13C‐NMR spectroscopy. The 2‐acetamido‐2‐deoxy‐α‐D‐glucopyranosyl 1‐phosphate is a growth factor for Treponema vincentii.
Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part 1. Bromotri‐μ‐carbonyloctacarbonyltetrairidate(1–)
Authors: Strawczynski Andrés , Ros Renzo , Roulet Raymond
Published: December 2004

A 2D and variable‐temperature 13C‐NMR study indicates that a CO‐site exchange occurs in the title complex via several consecutive processes, the first being a ‘merry‐go‐round’ of the basal CO's, the second a switch of basal face not involving unbridged intermediates.
Metabolism of carotenoids in salmonids. Part 2. Distribution and absolute configuration of idoxanthin in various organs and tissues of one atlantic salmon (Salmo salar, L.) fed with astaxanthin
Authors: Schiedt Katharina , Mayer Hans , Vecchi Max , Glinz Ernst , Storebakken Trond
Published: December 2004

The content of total carotenoids and the ratio astaxanthin/idoxanthin ( = 3,3′‐dihydroxy‐β,β‐carotene‐4,4′‐dione/3,3′,4′‐trihydroxy‐β,β‐caroten‐4‐one) in varoius organs and tissues of one Atlantic salmon (Salmo salar, L.) reared indoors in a tank were analyzed after feeding ‘racemic’ ((3R,3′R)/(3R,3′S; meso)/(3S,3′S) 1:2:) astaxanthin (90 mg/kg feed) during one yera. Configurational analysis of astaxanthin was carried out via the (−)‐dicamphanate derivative and that of idoxanthin after reaction with (+)‐(S)‐l‐(l‐naphthyl)ethyl isocyanate. Separation of all eight optical isomers of idoxanthin‐tricarbamate derivatives by HPLC is described. In salmon, enzymatic reduction of astaxanthin was found to be sterospecific leading to th (4′R)‐hydroxy group irrespective of the configuration at C(3′), thus resulting in four different stereoisomers of idoxanthin formed from (3R,3′R), (3R,3′S; meso)‐, and (3S3′S)‐astaxanthin present in the diet.
Radical Ions in the Pentalene Series. Part III. Three paramagnetic redox stages of a dicyclopenta[a,e]pentalene
Authors: Gerson Fabian , Gescheidt Georg , Hafner Klaus , Nimmerfroh Norbert , Stowasser Berndt
Published: December 2004

Five redox stages have been observed for the recently synthesized 1,3,5,7‐tetra(tert‐butyl) derivative 1 of the dicyclopenta[a,e]pentalene, a novel non‐alternant hydrocarbon: the radical cation \documentclass{article}\pagestyle{empty}\begin{document}$1^{+ \atop \dot{}}$\end{document}, the neutral compound 1, the radical anion \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}, the dianion 12−, and the radical trianion \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}. Information about the the electronic structure of the three paramagnetic stages, \documentclass{article}\pagestyle{empty}\begin{document}$1^{+ \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} is provided by the use of ESR, ENDOR, and TRIPLE resonance spectroscopy. The unpaired electron in the trianion resides mainly on the ‘inner’ butadiene‐π‐system. Whereas in the cation and the anion, it is largely localized on the two ‘outer’ five‐membered rings.
Norbornanes. Part 21. Bridging strain in norbornyl and oxanorbornyl cations
Authors: Flury Peter , Grob Cyril A. , Wang Guang Yi , Lennartz Hans‐Werner , Roth Wolfgang R.
Published: December 2004

Further evidence is presented that the 2‐norbornyl cation is stabilized primarily by C(2)–C(6) bridging, and that C(2)–C(7) bridging leads to prohibitive strain. Thus, a comparison of the heats of hydrogenation of nortricyclene 17 and bicyclo[3. 2. 0. 0.2,7]heptane 18 indicates that the strain energy of the latter is ca. 21.5 kcal/mol higher that that of 17. Furthermore, 6‐exo‐2‐oxabicyclo[2. 2. 1]heptyl sulfonates 8 ionize with strong O(2) participation to the bridged oxonium ion 12. In contrast, 2‐endo‐7‐oxabicyclo[2.2.1]heptyl sulfonates 11 ionize without O(7) participation to form the unbridged carbenium ion 15.
Leiopathic Acid, a Novel Optically Active Hydroxydocosapentaenoic Acid, and related compounds, from the black coral Leiopathes sp. of Saint Paul Island (S. Indian Ocean)
Authors: Guerriero Antonio , D'Ambrosio Michele , Peitra Francesco
Published: December 2004

The antipatharian Leiopathes sp., collected around Saint Paul Island, is shown here to contain, in relatively high amounts, the novel fatty acid leiopathic acid ( = (+)‐(10R,7Z,11E,13Z,16Z,19Z)‐10‐hydroxy‐7,11,13,16,19‐docosapentaenoic acid; (+)‐1), besides (+)‐(8R,5Z,9E,11Z,14Z,17Z)‐8‐hydroxy‐5,9,11,14,17‐icosapentaenoic acid ((+)‐11) and (+)‐(8R,5Z,9E,11Z,14Z,)‐8‐hydroxy‐05,9,11,14‐icosatetraenoic acid ((+)‐16) and their ethyl ester (+)‐2, (+)‐12, and (+)‐17.
Synthesis and 1H‐, 13C‐, and 57Fe‐NMR spectra of mono‐ and bis[tricarbonyl(η4‐diene)iron], and (η3‐allyl)tetracarbonyliron trifluoroborate complexes
Authors: Adams Christoph M. , Cerioni Giovanni , Hafner Andreas , Kalchhauser Hermann , von Philipsborn Wolfgang , Prewo Roland , Schwenk Andreas
Published: December 2004

A variety of mono‐ and bis[Fe(CO)3(η4‐diene)] complex with alky, CH2OH, CHO, COCH3, COOR, and CN substituents on the 1,3‐diene system have been synthesized. Dienes with a (Z)‐configuration terminal Me group show steric inhibition of metal complexation resulting in lower yields and formation of tetracarbonyl(η2‐diene) and tricarbonyl(η4‐heterodiene) complexes as additional products. Regioselective attack by C‐nucleophiles at the carbonyl C‐atoms of the functional group with or without concomitant 1,3 mogration of the Fe(CO)3 group was used to synthesize polyenes and isoprenoid building blocks as mono‐ or dinucliar Fe(CO)3 complexes. Wittig‐Horner‐type reactions of Fe(co)3‐complexed synthons result in sterospecific formation of (E)‐configurated olefins. The 1H‐, 13C‐ and 57Fe‐NMR spectra of olefinic and allylic organoiron complexes are reported, H,H,C,H, and C,C coupling constants have been evaluated and are analyzed in terms of the geometry of the coordinated diene. The results are corroborated by the crystal structure of tricarbonyl[3–6‐η‐((E)‐6‐methyl‐3,5‐heptadiene‐2‐one)]iron(34) which shows an unusual distortion of the (CH3)2C = group, The 57Fe‐NMR chemical shifts extend over the ranges of 0–600 ppm for [Fe(CO)3(η4‐diene)] complexes, 780–1710 ppm for [Fe(CO)4(η3‐allyl)] [BF4] and [FeX(CO)3(η4‐allyl)] complexes, and 1270–1690 ppm for [Fe(CO)3(η4‐enone)] complexes, relative to Fe(CO)5.
[1,1‐bis (trimethylsilyl)]‐1H‐cyclopropa [b] napththalene[tricarbonyl‐chromium]: The first arene‐chromium complex of a cycloproparene
Authors: Müller Paul , Bernardinelli Gérald , Jacquier Yvan
Published: December 2004

[1,1‐Bis (trimethylsilyl)]‐1H‐cyclopropa [b] naphthalene rricarbonylchromium (2) was synthesized by reaction of 1,1‐bis (trimethylsilyl) cyclopropa [b] naphthalene (1b) with tricarbonyltris(acetonitrile) chromium.
The solution structure and reactivity of decavanadate
Authors: Comba Peter , Helm Lothar
Published: December 2004

The oxygen‐exchange reaction of V10O with bulk water has been followed by time‐dependent 17O‐NMR spectroscopy (buffered solutions, pH ∼ 5.5, [V10]total ∼ 0.17m, T = 298 K). It is shown that all seven structurally different sites of O‐atoms are kinetically similar but, in contrast to earlier studies, not identical (6 h ⩽ ‘t1/2’ ⩽ 11 h). The kinetic similarity of the various structural sites implies the some (but not full) O scrambling is involved. Two possible mechanisms with a ‘half‐bonded’ and an ‘open’ intermediate are discussed in detail to interpret the experimental results. A computer simulation of the exchange reaction based on these models is presented. It is shown that the ‘half‐bonded‐intermediate’ mechanism is consistent with the experimental data and the following parameters are calculated: formation of the intermediate: k1 = 5.8 · 10−3 s−1, k−1 = 6.7 · 10−2 s−1, [intermediate]∞ ≈ 8%; all activated O‐atoms exchange within the lifetime of the intermediate (τ ∼ 15 s), and the calculated exchange rate of the intermediate (k2 ⩾ 0.60 s−1) is consistent with earlier assumptions (k2 ≈ 0.5 s−1). It is shown that a simulation based on the ‘open‐intermediate’ mechanism results in kinetic parameters which are not consistent with the kinetics of the formation of cyclic metavanadates ((VO)n, n = 4,5) from decavanadate, since the required formation rate is by a factor ∼ 102 too fast, and the equilibrium concentration of metavanadates is by a factor of ∼ 2 too large (under the conditions of the O‐exchange experiments of decavanadate (T = 298 K, [V10]total ≈ 0.17m, pH ∼ 5.55) the total amount of metavanadates present is ∼ 8%, with [(VO)4]/[(VO)5] ∼ 4:1; a qualitative analysis of the kinetics of the formation of metavanadates (vo kinetics; the exact mechanism of the back‐reaction (at least second‐order) is not known with certainty) leads to k1 ⩾ 4·10−5 s−1). O exchange of decavanadates via equilibrated metavanadates would lead to full scrambling of the O sites and is not consistent with the observed differences in the exchange rates. From the qualitative kinetic parameters of the metavanadate formation kinetics, it can be concluded that any contribution of an ‘open’ or an ‘metavanadate’ mechanism is of the order of 1–2% at most.
Lavandulifolioside: A New Phenylpropanoid Glycoside from Stachys lavandulifolia
Authors: Başaran Arif Ahmet , Çaliş İhsan , Anklin Clemens , Nishibe Sansei , Sticher Otto
Published: December 2004

A new phenlypropanoid glycoside has been isolated from the methanolic extract of the aerial parts of Stachys lavandulifolia (Lamiaceae), lavandulifolioside (1). On the basis of chemical and spectral data the structure of the new compound 1 has been elucidated as β‐(3,4‐dihydroxyphenyl)ethyl O‐α‐L‐arabinopyranosyl‐(1→2)‐α‐L‐rhamnopyranosyl‐(1→3)‐4‐O‐caffeoyl‐β‐D‐glucopyranoside.
Rosafluin, ein neues Diapocarotindiol aus Rosenblüten. 8. Mitteilung über Rosenfarbstoffe
Authors: Märki‐Fischer Edith , Eugster Conrad Hans
Published: December 2004

Rosafluine, a Novel Diapocarotenediol from Rose Petals

A strongly fluorescent trace compound from rose petals was identified as the as yet unknown 10,10′‐diapocarotene‐10,10′‐diol ( = 4,9‐dimethyldodeca‐2,4,6,8,10‐pentaene‐1,12‐diol; 2).
Polar Effects. Part 15. Twin γ‐substituent effects in the formation of adamantyl‐1‐cations
Authors: Grob Cyril A. , Gründel Martin , Sawlewicz Pawel
Published: December 2004

Solvolysis rates of several adamant‐1‐yl ( = tricyclo[3.3.1.13,7]dec‐1‐yl) p‐toluenesulfonates and bromides 2 identically substituted at C(3) and C(5) (twin substitution) have been determined and compared with the rates of the corresponding 3‐monosubstituted compounds 1. As expected, the rate factors for twin substitution are much larger, but less than the square of the rate factors for single substitution. Also the rates factors per substitutent in 2 are considerably smaller than those for one substituent in 1. This attenuation is attributed to electron repulsion which limits the convergence of electron density to the cationic center. On the other hand, the inductivity for twin substitution (ρ1 = −2.55) is ca. twice as high as for mono‐substitution (ρ1 = −1.26).
The mild bromination of adamantane and (trimethylsilyl) adamantanes
Authors: Grob Cyril A. , Sawlewicz Pawel
Published: December 2004

Small amounts of H2O or MeOH catalyze the reaction of Br2 with adamantane and its 1‐(trimethylsilyl) and 1,3‐bis(trimethylsilyl) derivatives.