bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propellanes. Part LXXI. Confirmation of predicted regiospecificity in Diels‐Alder reactions of certain propellanes with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione
Authors: Ashkenazi Pnina , Kaftory Menachem , Sayraç Tuǧmaç , Maier Günther , Ginsburg David 
Published: December 2004

AbstractTwo isomeric propellane epoxides 1a and 1b containing a cyclohexadiene ring are attacked by the title dienophile as predicted, syn to the five‐membered ether ring whose α‐hydrogens exert less repulsion than the α‐epoxy hydrogens or the epoxide oxygen, respectively, of the cyclobutane ring.
Hydroboration and Oxymercuration of Some 1‐Substituted Norborn‐2‐enes
Authors: Luef Wolfgang , Vögeli Ulrich‐Christian , Keese Reinhart 
Published: December 2004

AbstractThe 1‐substituted norborn‐2‐enes 11–13 and 18 react with electrophiles under kinetic control preferentially in 2‐position. The regioselectivity in oxymercuration is higher than in hydroboration and reaction with aqueous palladium chloride.
(5R,6S,5′R,6′S)‐5,6,5′,6′‐Diepoxy‐β,β‐cartin: Sythese, Spectroskopische, chiroptische und chromatographische Eigenschaften
Authors: Acemoglu Murat , Eugster Conrad Hans 
Published: December 2004

(5R,6S,5′R,6′S)‐5,6,5′,6′‐Diepoxy‐β,β‐Carotene: Synthesis, Spectroscopical and Chiroptical Properties, and HPLC‐BehaviourUsing the scheme C13 + C2→C15 + C10→C40, whereby C13 = (5R,6S)‐5,6‐epoxy‐β‐ionone [8], the title compound 11a, (R = H), has been prepared and characterized. It exhibits nearly identical CD spectra as violaxanthin (11b, R = OH).
On the Stereochemistry of Natural Irones, Dihydroirones, and their Precursors
Authors: Krick Wolfgang , Marner Franz‐Josef , Janicke Lothar 
Published: December 2004

AbstractNatural irones from the essential oil of Iris rhizomes develop by oxidative degradation of C31‐triterpenoids produced by the plant. Two enantiomeric forms of irones are found in Iris, oils of different origin. The optical properties and CD spectra of irones, dihydroirones and their C31‐precursors are reported and their absolute stereochemistry is determined.
On the Stereochemistry of Irones
Authors: Rautenstrauch Valentin , Willhalm Bruno , Thommen Walter , Ohloff Güther 
Published: December 2004

AbstractIn view of the demonstration by Janeicke et al. that different Iris varieties produce enantiomeric irones [6], we complement our 1971 paper on the stereochemistry of the irones [3]. (1) We give what information we have on the origin of the Iris oil used in [3]; (2) we sow that we and Ruzicka et al. on whose degradation work our determination of the C(2)‐configurations was based hd the same irones in hand; (3) we summarize independent assignments of the C(2)‐configurations and the relative configurations of the α‐irones. (4) We also describe the indentification of a trace of the missing trans‐γ‐irone in our oil, and (5) revise the preferred conformation of the cis‐α‐irones in solution.
The photooxygenation of Δ9(11)‐dehydroestrone and its 3‐methyl ether potochemical reactions XX. Preliminary communication
Authors: Lupón Pilar , Grau Farran , Bonet Juan‐Julio 
Published: December 2004

AbstractThe photosensitized oxygenation of Δ9(11)‐dehydroestrone yields a complex mixture mainly of unstable compounds, while its 3‐methyl ether gives 3‐methoxy‐9, 17 ‐dioxo‐ 9,11‐seco‐1,3,5(10)‐estratrien‐11‐al, in good yield.
Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Struktur des proteinfreien Faktors
Authors: Livingston Douglas A. , Pfaltz Andreas , Schreiber Jakob , Eschnmoser Albert , Ankel‐Fuchs Dorothe , Moll Johanna , Jaenchen Rolf , Thauer Rudolf K. 
Published: December 2004

Factor F430 from Methanogenic Bacteria: Structure of the Protein‐free FactorFactor F430, the porphinoid nickel‐containing coenzyme of the methylcoenzyme‐M reductase of metanogenic bacteria is shown to be the 33,83,122,133,182‐pentaacid derivative of the pentamethylester F430M, the structure of which had been determined previously (see structural formulae 1 and 2). The structure assignment rests on chromatographic, UV/VIS‐, CD‐, IR‐, and 13C‐NMR‐spectroscopic as well as FAB‐mass spectral comparision of F430 with F430M and the pentaacid prepared by acid‐catalyzed hydrolysis of F430M.In the cells of Methanobacterium thermoautotrophicum, factor F430 is present in a ‘bound’ and also, depending on the growth conditions, in ‘free’ form, the latter being defined as the part of total F430 that can be extracted from the cells under extremely mild conditions (80% EtOH at 0–4°). From the (protein)‐‘bound’ form, F430 is extracted by subsequently treating the cells at 0–4° with 80% EtOH containing (e.g.), 2m LiCi.From both sources, the extracted factor is the same pentaacid, and there is no indication for the existence of a protein‐free F430 species that would contain additional (covalently bound) structural elements.
Parallelism Between Nucleophilically Solvent‐Assisted and Phenyl‐Assisted Reactions. Possible Existence of Nucleophilically β‐Phenyl‐Solvated Ion Pairs
Authors: Laureillard Jeane , Casadevall André , Casadevall Eliette 
Published: December 2004

AbstractSolvolysis rate constants in MeOH and t‐BuOh are compared for β‐methyl and β‐phenyl derivatives of two cycloakyl systems. It appears that the β‐phenyl derivatives solvolyse at te same rate as the β‐methyl ones. The lack of deceleration is attributed to phenyl assistance. It is established by configurational analysis of the reaction products, that those products which necessarily originate from a cationic species are the most abundant ones. It is suggested that these reactions could proceed through ion‐pair intermediates, which are nucleophilically solvated by phelyl or by the solvent. A parallel between phenyl assistance and ‘SN2 (intermediate)’ mechanism, suggested by Bentely & Schleyer, is drawn.
Boron‐nitrilotriacetate, N(CH2COO)3B: Synthesis and Crystal‐Structure Determinations at 293K and 110K
Authors: Müller Edgard , Bürgi Hans‐Beat 
Published: December 2004

AbstractThe title compound is insoluble in aprotic solvents and decomposes in protic ones. Its crystal structure consists of discrete molecules with non‐crystallographic C30‐symmetry and a transannular dative BN bond (1.620(3) (Å). The molecules pack tightly (density 1.804 g cm−2) interacting via O…C contacts between carbonyl groups (2.92–3.05 Å)). The atoms show small vibrational motion which may be interpreted in terms of a rigid body model. Distances and angles obtained at 293 and 110 were corrected for effects of rigid body motion and do not show significant differences.
First Direct Synthesis of Optically Active 3‐Methylcyclopentene
Authors: Silwka Hans‐Richard , Hansen Hans‐Jürgen 
Published: December 2004

Abstract(−)‐(S)‐ and (+)‐(R)‐3‐methylcyclopentene (1) has been prepared in a stereochemically unambiguous synthesis. The (S)‐configuration for (−)‐1 was confirmed by correlation with (−)‐(S)‐1‐methylindane.
Die diasteromeren Aurochrome: Synthese, Analytik und Chiroptische Eigenschaften
Authors: Acemoglu Murat , Eugster Conrad Hans 
Published: December 2004

The Diastereomeric Aurochromes: Their Synthesis, Analysis and Chiroptical Properties(all‐E)‐Aurochrome (5,8:5′,8′‐diepoxy‐5,8,5′,8′‐tetrahydro‐β,β‐carotene; 1) has two pairs of constitutionally identical chiral centres and, therefore, is expected to exist in four pairs of enantiomers and two meso‐forms. Using starting materials with well‐defined configuration, we performed the syntheses of the following pure aurochromes: (5R,8R,5′R,8′R)‐aurochrome (2) and its racemate, Meso‐(5R,8R,5′S,8′S)‐aurochrome (3), (5 R,8 S,5′ R,8′ S)‐aurochrome (4) and its racemate, meso‐(5R,8S,5′S,8′R)‐aurochrome (5), (5R,8R,5′R,8′S)‐aurochrome (6) and its racemate. The (5RS,8RS,5′SR,8′RS)‐aurochrome (7) was detected chromatographically, using a HPLC system that allows clean separation of the four racemic‐ (or optically active) and the two meso‐aurochromes. The optically active autochromes 2 and 4 exhibit non‐conservative CD spectra with strong Cotton effects of opposite but not mirror‐like tracings. Solutions of aurochromes in CHCl3, in the presence of HCl, undergo epimerization at C(8). Those epimers with CH3 trans to C(9) slightly predominate under equilibrium conditions. Deprotonation of the phosphonate (±)‐14 with strong base causes isomerization at the terminal oxirane into a dihydrofuran. This reaction allowed convenient syntheses of the diastereoisomeric aurochromes (±)‐2, 3, (±)‐4, 5, (±)‐6, and (±)‐7 and of (5RS, 8RS)‐ and (5RS, 8SR)‐12′‐apo‐aurochrome‐12′‐als (21 and 22, respectively).
Synthese eines cyclischen Depsipeptides mittels Amidcyclisierung
Authors: Obrecht Daniel , Heimgartner Heinz 
Published: December 2004

Synthesis of a Cyclic Depsipeptide via an Amide CyclizationThe synthesis of (S)‐Pms‐(R)‐Pro‐(S)‐Ala‐Aib‐N(CH3)2 (12) has been achieved according to Scheme 3. For the formation of fragment 11, the reaction of Z‐alanine (Z = benzyloxycarbonyl) and 3‐dimethylamino‐2,2‐dimethyl‐2‐azirine (1) has been used, whereby 1 serves as an aminoisobutyric‐acid dimethylamide (aib‐N(CH3)2) equivalent. Treatment of a suspension of 12 in toluene with HCl gas at 100° led to the cyclic depsipeptide 13 in 72% yield (Scheme 4). In presence of water, the acid 14 was isolated as the sole product. A mechanism for the formation of 13 and 14 via an oxazolinone intermediate, is postulated in Scheme 4.
Isolierung und Struktur von Pteridinen (Lumazinen) aus Russula sp. (Täublinge; Basidiomycetes)
Authors: Iten Peter Xaver , Märki‐Danzig Hana , Koch Herbert , Eugster Conrad Hans 
Published: December 2004

Isolation and Structure Elucidation of Pteridines (Lumazines) from Russula sp. (Basidiomycetes)Extensive chromatogaphic separations and spectroscopic investigations have led to the isolation and identification of several water‐soluble pteridines from Russula sp., the so‐called russupteridines, namely: 1‐(5‐amino‐2‐6‐dioxo‐1,2,3,6‐tetrahydeopyrimidin‐4‐yl)amino‐1‐deoxy‐D‐ribitol (1; a pro‐lumazine; first identification in a basidiomycete(; l‐deoxy‐l‐(6‐methyl‐2‐4,7‐trioxo‐1,2,3,4,7,8‐hexahydro‐pteridin‐8‐yl)‐D‐ribitol (3) and l‐deoxy‐1‐(2,4,7‐trioxo‐1,2,3,4,7,8‐hexahydeopteridin‐8‐yl)‐D‐ribitol (4); both compounds found for the first time in higher fungi; they belong to the components with the strongest violet‐blue fluorescence in Russula sp.; riboflavine (6; now recognized as an important yellow colorant in a great many of Russula sp.); russupteridine‐yellow I (= l‐(6‐amino‐7‐(N‐fromylimino)‐2,4‐dioxo‐1,2,3,4,7,8‐hexahydropteridin‐8‐yl)‐1‐deoxy‐D‐ribitol; 5; a component with very strong fluorescence; the first derivative of the novel 6,7‐diamino‐lamazine); russupteridine‐yellow IV (= l‐deoxy‐1‐)(2,6,8‐trioxo‐2,4,5,6,7,8‐hexahydro‐1H‐imidazolo[4,5‐g]pteridin‐4‐yl)‐D‐ribitol (7)). Two further yellow russupteridines (yellow II and Yellow V) with very strong fluorescence have been isolated and characterized.
Synthesen von Aminolumazinen
Authors: Märki‐Danzig Hana , Eugster Conrad Hans 
Published: December 2004

Syntheses of Aminolumazines6‐aminolumazien 2 (1‐(6‐amino‐2,4,7‐trioxo‐1,2,3,4,7,8‐hexahydropteridin‐8‐yl)‐1‐deoxy‐D‐ribitol), a degradation product of russupteridine‐yellow I (1) has been prepared from l‐deoxy‐l‐(2,4,7‐trioxo‐1,2,3,4,7,8‐hexahydeopteridin‐8‐yl)‐D‐ribitol (5) via the azo compound 6 and its reduction with Sn/HCOOH. Condensation of 5‐amono‐6‐(D‐ribitylamino)uracil (8) with parabanic acid (9) has led to ta synthesis of russupteridine‐yellow IV (4); l‐deoxy‐l‐(2,6,8‐trioxo‐2,4,5,6,7,8‐hexahydro‐lH‐imidazolo[4,5‐g]pteridin‐4‐yl‐D‐ribitol), albeit in low yield.
Synthesen, chemische und elektrische Eigenschaften von Tetrathiafulvalen mit 1,6‐Methano[10]annulen‐Partialstruktur und von Chalcogendiimid‐derivaten
Authors: Neidlein Richard , Droste‐Tran‐Viet Dao , Gieren Alfred , Kokkinidis Michail , Wilckens Rudolf , Geserich Hans‐Peter , Ruppel Wofgang 
Published: December 2004

Syntheses, Chemical and Electrical Properties of Tetrathiafulvalene with a 1,6‐Methano[10]annulene Moiety and of Chalcogendiimide‐DerivativesThe synthesis of the tetrathiafulvalene 6 has been described: the reaction of 1 with the benzenedithoil 2 yielded the bis‐dithioacetal 3 of 1,6‐methano[10]annulene‐dicarbaldehyde 1. The oxidation of 3 in the presence of HBF4 in Et2O yielded the salt 4, elimination of a hydride anion with triphenylmethylium tetrafluoroborate the salt 5, and elimination of a proton in 5 with Et3N the tetrathiafulvalene 6 with a 1,6‐methano[10]annulene moiety. The spectroscopic and electrochemical properties of 6 are described, and also the syntheses and properties of charge‐trasnfer complexes 7 and 8, including the properties of electric conductivity of 7 and 8. the syntheses of 9‐13 are reported and also their spectroscopic properties.
Structural Studies of Crystalline Pentacalent Organobismuth Compounds
Authors: Barton Derek H. R. , Charpiot Brigitte , Dau Elise Tran Huu , Motherwell William B. , Pascard Claudine , Pichon Clotilde 
Published: December 2004

AbstractThe syntheses and X‐Ray analyses of three pentavalent organobismuth compounds are described; one of these compounds has a novel diphenylbis(trifluoroacetato)‐bismuthate anion with trigonal bipyramidal geometry and a stereochemically active lone pair. Analysis of these structures together with other data from the literature allows a mapping of the reaction coordinate for bismuth polyhedra.
Stereoselective Introduction of Steroid Side Chains. Synthesis of Chenodeoxycholic Acid
Authors: Wovkulich Peter M. , Batcho Andrew D. , Uskoković Milan R. 
Published: December 2004

AbstractA new short route to chenodeoxycholic acid has been developed. The synthesis is based on the stereoselective introduction of the steroidal side chain via an ene reaction of methyl acrylate and a (17Z)‐ethylidene steroid prepared from androstenedione.
Estimation of Dimerisation Constants from Complexatin‐Induced Displacements of 1H‐NMR Chemical Shifts: Dimerisation of Caffeine
Authors: Horman Ian , Dreux Bernard 
Published: December 2004

AbstractThe determination of the dimerisation constant (KD) for the weak self‐association of a compound C in dilute solution according to the equilibrium, 2C⇌C2 is described. The method uses chemical shifts measured on a series of solutions of C at different concentrations: the optimum KD is defined by a linear regression best‐fit procedure, which simultaneously determines optimum values for δo and also for δ∞, the intrinsic chemical shifts for nuclei in the monomer and dimer species. The dimerisation of caffeine in D2O is used as a model to demonstrate the working of the method and the quality of results obtained. The most probable value of KD for caffeine at 30.5° is found in the range 5.5–6.0 kg solution · mol−1, and the enthalpy and entropy of dimerisation are found to be ΔH⊖ = −15.1 kJ · mol−1 and ΔS⊖ = −35.3 J · °C−1 · mol−1, respectively. The influence of small errors in δo on the confidence limits of KD is discussed.
Voltammetrische Untersuchungen der Oxydation der symmetrischen Triazacarbocyanine in Acetonitril
Authors: Hellrung Bruno 
Published: December 2004

Voltammetric Investigations on the Oxidation Step of Symmetrical Triazacarbocyanine Dyes in Acetonitrile SolutionThe oxidation behaviour of twelve symmetrical triazacarbocyanine dyes with different heterocycles in MeCN (containing tetrabutylammonium perchlorate) has been investigated by means of dc‐, ac‐ and cyclic triangular wave voltammetry. The oxidation mechanism has been found to be of the type ec, with the electrochemical step being reversible to irreversible. Oxidation potentials and transfer coefficients have been measured (E1/2 1.60 to 2.12 V vs. Ag/AgCl) and compared with known properties of carbocyanines. The effect of substituents X has been studied on the compounds 1,3‐diethyl‐2‐[3‐(1,3‐diethyl‐5‐X‐benzimidazolin‐2‐ylidene)‐1‐triazeno]‐5‐X‐benzimidazolium tetrafluoroborate ((1a(X)) and 3‐ethyl‐2‐[3‐ethyl‐5‐X‐Δ4‐1,3‐thiazolin‐2‐ylidene)‐1‐triazeno]‐5‐X‐1,3‐thiazolium tetrafluoroborate (1g(X)), and ρ‐values of 0.425 and 0.565 V, respectively, have been found.
Photochemical reactions, 135th communication Photochemistry of Homoconjugated Cyclobutanones. II. Decisive Effect of gem‐ Dimethyl Substitution on the Course of the Oxa‐di‐π‐methane Rearrangement
Authors: Lyle Terry A. , Mereyala Hari Babu , Pascual Alfons , Frei Bruno 
Published: December 2004

AbstractThe synthesis and photolysis of the spirocyclobutanones 4–7 incorporating a cyclohexa‐, cyclohepta‐ and cyclooctadiene moiety, respectively, is described. On triplet excitation, these compounds undergo isomerization via a 1,2‐acyl shift involving one or both double bonds of the diene system. The presence of a gem‐dimethyl group as in 1, 4 and 7 dramatically changes the photoproduct distribution, since only these substrates leads to the products 3, 29 and 34 resulting from vinylogous ring closure (Scheme 5). Those substrates without methyl substitution (5 and 6) give only products of a rearrangement involving one double bond.
High performance liquid chromatography (HPLC) of natural products part VI. Sulfoxides of penicillin N and cephalosporin c and their role in biosynthesis of β‐lactam antibiotics
Authors: Kukolja S. , Miller R. D. , Duckworth D. C. , Dorman D. E. , Huckstep L. L. , Neuss Norbert , Quenner S. W. 
Published: December 2004

AbstractPure pencillin N α‐sulfoxide (1) and penicillin N β‐sulfoxide (2) were obtained by HPLC and tested as substrates for deacetoxycephalosporin C synthetase (DXCS). Neither one of the sulfoxides was utilized under conditions of conversion of penicillin N (8) to deacetoxycephalosporin C (9). The cephalosporin C α and β‐sulfoxides (3 and 4, resp.) were also prepared. Relative stabilities of the sulfoxides 3 and 4 are discussed by interpretation of the 13C‐NMR spectra.
Die Busseine C, D, E, F, G, H, J, K, L und M, zehn neue Tetranortriterpene aus Entandrophragma bussei Harms.
Authors: Guex Matthias , Tamm Christoph 
Published: December 2004

The Business C,D,E,F,G,H,J,K,L und M, Ten New Tetranortriterpenes from Entandrophragma Bussei HarmsTen new tetranortriterpenes, busseins C, D, E, F, G., H, J, K, L and M have been isolated from the petroleum ether extract of the timber of Entandrophragma bussei Harms. utilizing separation by high‐pressure liquid chromatography (HPLC). The structural assignments are based mainly on spectral evidence. For the 1H‐NMR spectroscopy extensive use of nuclear Overhauser effects (NOE) was made.
The Synthesis and Application of Novel Nitrating and Nitrosating Agents
Authors: Hakimalahi Gholam H. , Sharghi Hashem , Zarrinmayeh Hamide , Khalafi‐Nezhad Ali 
Published: December 2004

AbstractAlcohols and phenols are efficiently nitrated with thionyl chloride nitrate or thionyl nitrate, even in the presence of an aromatic moiety. While thionyl chloride nitrate is suitable for nitration of primary OH‐groups in carbohydrates, thionyl nitrate is reactive enough to react with secondary OH‐groups as well. These reagents permit the highly selective nitration of the 5′‐,2′5′‐ and 3′, 5′‐OH‐groups of ribonucleosides to produce either mono‐or diprotected nitro derivatives in high yields. Carbon acids and the enol form of some ketones are efficiently nitrated with trifluoromethanesulfonyl nitrate/potassium tert‐butoxide. Lutidine N‐oxide (2,6‐(CH3)2C5H3N O) was found to have a marked effect on nitration reactions. Similarly, thionyl chloride nitrite and thionyl nitrite exhibit an excellent capacity for nitrosation of the aforementioned substrates.
1,2‐Epoxycarotinoide. 3. Mitteilung. Isolierun von 1,2‐Epoxy‐1,2‐dihydrolycopin aus Tomaten
Authors: Berset Daniel , Pafander Hansperter 
Published: December 2004

1,2‐Epoxycarotenoids: Isolation of 1,2‐Epoxy‐1,2‐dihydrolycopene from TomatoesThe optically active, 1,2‐epoxy‐1,2‐dihydrolycopene was isolated from tomatoes. Its constitution was established by comparison with the racemic synthetic compound.
Plectranthone A, B, C und D. Diterpenoide Phenanthren‐1,4‐dione aus Blattdrüsen einer Plectranthuus sp. (Labiatae)
Authors: Alder Alfredo Carlos , Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

Plectranthons A, B, C, and D. Diterpenoid Phenanthrene‐1,4‐diones from Leaf‐glands a Plectranthus sp. (Labiatae)The following structures of four new 1,4‐phenanthraquionones, isolated in minute amounts from the coloured leaf‐glands of a Plectranthus sp. obtained from the borders of Lake Kiwu2, Rwanda, are proposed: plectranthon A (1; 3‐hydroxy‐5, 7,8‐trimethyl‐2‐(2‐propenyl)phenanthrene‐1, 4‐dione), plectranthon B (2; 2‐(2ξ‐acetoxypropyl)‐3‐hydroxy‐5,7,8‐trimethylphenanthrene‐1,4‐dione), plextranthon C (3; 3‐hydroxy‐ 7,8‐diemethyl‐2‐(2‐propenyl)phenanthrene‐1,4‐dione), and plectranthon D (4; 3‐hydroxy‐7,8,10‐trimethyl‐2‐(2‐propenyl)phenanthrene‐1,4‐dione). 2‐(2ξ‐Hydroxypropyl)‐3,6‐dihydroxy‐5,7,8‐trimethylphenanthrene‐1,4‐dione (11), a compound very similar to 1–4, was prepared by a Wagner‐Meerwein, rearrangement of coleon E (5). Biogenetically, the plectranthons are derived from abietanoic precursors. The compounds 1, 2 and 4 are the first natural C20‐phenanthrenes of diterpenoid origin.
Stabilities and Redox Properties of Cu(I) and Cu(II) Complexes with Macrocyclic Ligands Containing the N2S2 donor Set
Authors: Balakrishnan Karappulli P. , Kaden Thomas A. , Siegfried Liselotte , Zuberbühler Andreas D. 
Published: December 2004

AbstractThe complexation of Cu(I) and Cu(II) by a series of 12‐, 14‐ and 16‐membered macrocyclic ligands 1–6 containing the N2S2 donor set has been studied potentiometrically, spectrophotometrically and voltammetrically.In the case of Cu(II), mononuclear complexes CuL2+ with stability constants of 1010–1015 are formed. In addition, partially hydrolyzed species Cu(L)OH+ are observed at pH > 10 for the 12‐membered ligands. For Cu(I), beside the specis CuL+ with stabilities of 1012–1014, the unexpected formation of protonated species CuLH2+ was detected. In contrast to the well‐known general trends in coordination chemistry, the stability of these protonated species increases relative to that of the complexes with the neutral ligand when the ring size and concomitantly the distance between neighbouring donor atoms is decreased. From the stability constants of the Cu(I)‐ and Cu(II)‐complexes the redox potentials have been calculated and are compared to the values of E1/2 obtained by cyclic voltammetry. Despite the identical donor set the Cu(II)/Cu(I) redox potentials of the complexes are spanning a range of 340 mV or six orders of magnitude in relative stability, reflecting the importance of subtle differences in steric requirements.
Syntheses of (±)‐ and Enantiomerically Pure (+)‐Longifolene and of (±)‐ and Enantiomerically Pure (+)‐Sativene by an Intramolecular de Mayo Reaction
Authors: Oppolzer Wolfgang , Godel Thierry 
Published: December 2004

AbstractStarting from 2‐cyclopentenoyl chloride ((RS)‐ or (S)‐8), the racemic as well as the enantiomerically pure (+)‐sesquiterpenes longifolene ((±)‐ and (+)‐1, resp.) and sativene ((±)‐ and (+)‐2, resp.) were synthesized efficiently by a sequence of nine and ten steps, respectively. The key sequence 10 → 16 → 3 is the first strategic application of an intramolecular photoaddition/retro‐aldolization sequence (intramolecular de Mayo reaction) in organic synthesis.
Cyclodopa glucoside ( = (2S)‐5‐(β‐D‐glocopyranosyloxy)‐6‐hydroxyindoline‐2‐carboxylic acid) and its occurrence in red beet (beta vulgaris var. rubra L.)
Authors: Wyler Hugo , Meuer Ursula , Bauer Jacques , Stravs‐Mombelli Luisa 
Published: December 2004

AbstractCyclodopa glucoside ( = (2S)‐5‐(β‐D‐glucopyranosyloxy)‐6‐hydroxyindoline‐2‐carboxylicacid; 1a) is prepared from betainin (2a) via a base exchange reaction. Its purification and physical properties are described. The compound is N‐formylated in dilute HCOOH solution. Cyclodopa glucoside is contained in considerable amount in redbeet juice varying from 0.07 to 1.9 mmol/kg or from 12 to 46% relative to teh content of betanin. Teh occurrence of free cyclodopa glucoside supports its role as intermediate in betanin biosynthesis.