bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereoselective Control in the Base‐Catalyzed H/D Exchange of 5,6‐Dimethylidene‐2‐bicyclo[2.2.n]alkanone Tricarbonyliron Complexes. Revision of the Structures of Tricarbonyliron Complexes of 5,6‐Dimethylidenebicyclo[2.2.2]oct‐2‐ene and 5,6‐Dimethylidenebicyclo[2.2.1]hept‐2‐ene
Authors: Barras Charls A. , Roulet Rymond , Carrupt Pierre‐Alain , Berchier Fabienne , Vogel Pierre
Published: December 2004

Oxidative hydroboration of exo‐ (1) and end‐Fe(CO)3 (2) complexes of 5,6‐dimethylidenebicyclo[2.2.2]oct‐2‐ene are highly stereoselective and give endo ‐alcohol 3 and exo ‐alcohol 4 as major products, respectively, Collins oxidations of 3 and 4 furnish the corresponding exo ‐Fe(CO)3 ‐complexed 5,6‐dimethylidene‐2‐bicyclo‐[2.2.2]octanone 7 and 8. NaBH4 reduction of exo‐complexes 7 gives a mixture of 3 and isomeric exo‐alcohol 18, whereas reduction of endo‐complexes 8 gives the endo‐alcohol, endo‐complexes 19, as the sole product. The base‐catalyzed H/D exchange of 7 and 8 afford the dideuterated exo‐complex 35 and the monodeuterated endo‐complex 32, respectively. Oxidative hydroborations of the exo‐(9) and endo‐Fe(CO)3 (10) complexes of 5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐ene give the corresponding exo‐alcohols 39 and 40. Oxidation of 39 and 40 gives the exo‐ and endo‐complexes 41 and 42, respectively, of 5,6‐dimethylidene‐2‐bicyclo[2.2.]heptanone. Only Hexo C(3) can be exchanged in 42, wheres both H‐atoms at C(3) in 41 are exchangeable. The endo‐Fe(CO)3 group in 8 and 42 blocks the base‐catalyzed H/D exchange of Hendo C(3), thus providing a test for the configuration of Fe(CO)3 group in these systems. These studies have led to a revision of the iron configurations proposed by Hansen et al, [2] for 1, 2, 9 and 10.
Monohaptenic Nα‐Benzoyl‐L‐lysine Derivatives as Anaphylactogens: the Importance of the Unsubstituted Carboxyl Group
Authors: Guenin Raymond , Schneider Conrad H.
Published: December 2004

Nα‐L‐Iysine with a 2‐carboxy‐4, 6‐dinitrophenyl (Dncp) haptenic group on the ε‐amino function is a potent anaphylactogen in the guinea pig. We prepared Nε ‐Dncp‐ Nα‐benzoly‐L‐Iysinamide and Nε‐Dncp‐Nα‐benzoyl‐L‐lysyl‐1‐aminopropane where the carboxyl group of Iysine is blocked. Both compounds were non‐elections of anaphylaxis.
Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by 17O‐ and 1H‐NMR in Nematic Phases
Authors: Tricot Yves , Niederberger Werner
Published: December 2004

Linear relationships between the inverse of the quadrupolar coupling constant, 1/χ and the asymmetry parameter η are obtained for the 7O‐nucleus of acetone oriented in four different nematic phases, using the information contained in 1H‐ and 17O‐NMR spectra. The absence of a unique intersecting point of thee relations shows that the quadrupolar constants differ slightly between polar and apolar nematic phases, while the orientation remains similar. By combination of the experimentally derived relations with predictions from the theory of Townes and Dailey, values for χ = 11.15 MHz and η = 0.47 in polar media and χ = 11.35 Mhz and η = 0.15 in an apolar medium are obtained, which are similar to those found in the gas and solid phases.
Acetyl‐cobalamin from Photoinduced Carbonylation of Methyl‐cobalamin
Authors: Kräutler Bernhard
Published: December 2004

Irradiation with visible light of a deoxygenated aqueous solution of methyl‐cobalamin (1) under an atmosphere of CO and at ambient temperature converts 1 into acetyl‐cobalamin (2). This carbonylation has potential relevance with respect to bacterial acetate biosynthesis from CO2.
The Reaction of Singlet Oxygen with 1,3‐Dimethylindole in the Presence of Aldehydes. Formation of 1,2,4‐Trioxanes
Authors: Jefford Charles W. , Jaggi Danielle , Boukouvalas John , Kohmoto Shigeo , Bernardinelli Gérald
Published: December 2004

The dye‐sensitized photo‐oxygenation of 1,3‐dimethylindole in the presence of aldehydes initially generates a zwitterionic peroxide which condenses with the carbonyl function to give the corresponding cis‐fused 1,2,4‐trioxanes. Acetaldehyde gives a pair of diastereomers, one of whose structures was determined by X‐ray analysis (cis,cisisomer), whereas pivaladehyde gives only the cis,cis diastereomer.
Spectroscopic Characterization of Open‐Shell Cations: Emission and Laser Excitation spectra of Rotationally Cooled CH3(CC)2X+, X = Cl, Br
Authors: Klapstein Dieter , Kuhn Robert , Maier John P. , Misev Liubomir , Ochsner Martin
Published: December 2004

Gas phase emission and laser excitation spectra of the Ã2E↔X̃2E (Σ = +½, −½) transition of rotationally/vibrationally cooled 1‐chloro‐ and 1‐bromo‐1,3‐pentadiyne cations have been obtained. The emission was excited by electron impact on a seeded helium supersonic free jet and the fluorescence by laser excitation of cations produced by Penning ionization and collisional relaxation. From these two sets of data the origin bands of the spin‐orbit systems are located and for the bromo species this leads to better values of the spin‐orbit splitttings in the two electronic states and of the first adiabatic ionization energy. The vibrational frequencies of many of the fundamentals of these cations in the X̃2E and Ã2E states have been obtained to within ±2 cm−1.
Synthèse facile de dérivés du diphényl‐2,4‐aza‐3‐bicyclo[3.3.1]nonane et du diphényl‐7,8‐aza‐8‐bicyclo[4.3.1]décane
Authors: Campo Carmen Del , Martinez Ernesto , Trigo Gregorio G.
Published: December 2004

Facile synthesis of derivatives of 2,4‐diphenyl‐3‐azabicyclo[3.3.1]nonane and 7,9‐diphenyl‐8‐azabicyclo[4.3.1]decane

The facile synthesis of hydantoins, cyanhydrins and aminonitriles derived from 2,4‐diphenyl‐3‐azabicyclo[3.3.1]nonanone and 7,9‐diphenyl‐8‐azabicyclo[4.3.1]decanone is described. Configurations at C(9) or C(10) of the new compounds wth pharmaceutical and synthetical utility is deduced from their spectral properties.
Preparation of Ru(CO)(diene)2 Complexes by Electron‐Beam Evaporation of Ruthenium. Preliminary Communication
Authors: Cox David N. , Roulet Raymond
Published: December 2004

Ru‐atoms (0.5–1.5 g) have been generated by electron bombardment and, in separate experiments, were co‐condensed at 7 K with excess of 2,3‐dimethylbutadiene or 1,3‐ or 1,4‐cyclohexadiene. The complexes Ru(CO)(η4‐C6H10)2 (1) and Ru(CO)(η4‐C6H8)2 (2), respectively, have been isolated in 25–30% yields on warming the condensate under CO.
Electron‐Transfer‐Induced Conformational Changes. The Example of 1,8‐Dimethyl[14]annulene
Authors: Huber Walter
Published: December 2004

This communication reports ESR‐spectroscopic investigations of the radical anion of 1,8‐dimethyl[14]annulene (1) which possesses a flexible molecular framework allowing configurational and conformational mobility. The ESR and ENDOR spectra indicate that at higher temperatures (T > 160 K), \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{- \atop \dot{}} $\end{document} exists as a mixture of several distinct isomers. One of them, the sole product at T < 160 K, is found to be energetically preferred. The configuration and the conformation of this species can be determined by interpretation of the hyperfine data in terms of a singly occupied MO of the 14‐membered π‐perimeter.
Camphor‐Derived N‐Acryloyl and N‐Crotonoyl Sultams: Practical Activated Dienophiles in Asymmetric Diels‐alder Reactions. Preliminary Communication
Authors: Oppolzer Wolfgang , Chapuis Christian , Bernardinelli Gérald
Published: December 2004

Starting from (+)‐camphor‐10‐sulfonyl chloride (5), the crystalline sultam 8 was easily prepared. Lewis‐acid‐promoted Diels‐Alder additions of the crystalline N‐acry‐loyl and N‐crotonoyl derivatives 9 and 10, respectively, to cyclopentadiene and 1,3‐butadiene at −130 to −78° furnished adducts 11, 12 and 17 with high chiral efficiency. Crystallization of the adducts and nondestructive removal of 8 gave either alcohols 13, 14 and 18 ir acid 19 in 99% enantiomeric purity. The sense of induction was reversed on using the enantiomer of 8 as the auxiliary. The structure of 10 was established by X‐ray diffraction analysis.
Fast‐atom‐bombardment mass spectrometry and 1H‐NMR spectrometry in studies of the transformations of thiamine in strongly basic solutions
Authors: Horman Ian
Published: December 2004

Fast‐atom‐bombardment (FAB) mass spectra have been used to establish or confirm the nature of the yellow‐product and open‐chain forms of thiamine produced in the presence of excess (5 mol‐equivb.) of strong base. Time‐dependent changes in 1H‐NMR spectra show that the rates of disappearance of the yellow form and of formation of the open‐chain form are the same at pH 12.5, having a pseudo‐first‐order rate constant of k = 2.2 × 10−3 sec−1. The implications of these results are discussed in the light of current ideas on the acid‐base dependence of thiamine structures.
Photochemistry of 8,8,9,9‐tetramethyl‐1,3,4,6,7,8‐hexahydro‐1,4‐ethanonaphthalene‐2,5‐dione, a δ‐oxo‐β,γ‐unsaturated ketone
Authors: Kilger Ralf , Körner Wolfgang , Margaretha Paul
Published: December 2004

The oxa‐di‐π‐methane rearrangement product 4,4,9,9‐tetramethyltetracyclo [6.4.0.01,5.02,8]dodecane‐7,12‐dione (2) is formed selectively in a variety of solvents on either direct (λLD = 254, 300, 350 nm) or sensitized (xanthone, acetone, benzene) irradiation of the title compound 1. The efficiency for this rearrangement is higher on So–S1 excitation (Φ−1 = 0.67) than on either So–S2 or So–S3 excitation (Φ−1 = 0.58).
Transition metal complexes with bidentate ligands spanning trans‐positions part XV X‐ray structural and 31P‐NMR solution studies of some three‐coordinate silver complexes of 2,11‐bis[di(tert‐butyl)phosphinomethyl]benzo[c]phenathrene and related ligands
Authors: Camalli Merceds , Caruso Francesco , Chaloupka Stanislav , Kapoor Pramesh N. , Pregosin Paul S. , Venanzi Luigi M.
Published: December 2004

A series of three‐coordinate bis(dialkylphosphinomethyl)benzo[c]phenanthrene Ag(I) complexes, alkyl= t‐Bu, (1b), and cyclohexyl, (1c), anion = BF4, CIO4, CIO4, NO3, Cl, Br, I, have been prepared and thier 31P‐NMR characteristics recorded. The solid state structures of [Ag(1b)Br], [Ag(1b)Cl] and [Ag(1b)CIO4] have been determined by X‐ray diffraction. The Ag atom in these complexes shows distorted trigonal geometry. Selected bond lengths and angles are as follows: Ag‐P = 2.463(4) Å and 2.433(5) Å, P‐Ag‐P=141.6(2)° in the bromo complex, Ag‐P = 2.457(2) Å and 2.427(2) Å, P‐Ag‐P = 142.6(1)° ion the chloro complex, and Ag‐P = 2.394(2) and 2.393 (2) Å, P‐AG‐P = 161.5(1)° in the perchlorato complex.
Optical resolution of 7‐oxabicyclo[2.2.1]hept‐21‐ene derivatives. Diastereoselectivity in the formation of cyanohydrine‐brucine complexes
Authors: Black Kersey A. , Vogel Pierre
Published: December 2004

A new, practical method for the optical resolution of bicyclic ketones if illusttrated by the preparation of (+)‐(1R,4R)‐7‐oxabicyclo[2.2.1]bept‐5‐en‐2‐one ((+)‐1) and (+)‐(1R, 2S,4R)‐2‐cyano‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐yul acetate ((+)‐4). It involves the diastereoselective formation of a brucine complex with the corresponding cyanhydrine mixture.
Hydroxyalkylierungen von Cystein über das Enolat von (2R,5R)‐2(tert‐Butyl)‐1‐aza‐3‐oxa‐7‐thiabicyclo[3.3.0]octan‐4‐on und unter Selbstreproduktion des Ciralitätszentrums
Authors: Seebach Dieter , Weber Theodor
Published: December 2004

Hydroxyalkylations of Cysteine through the Enolate of (2R,5R)‐2(tert‐Butyl)‐1‐aza‐3‐oxa‐7‐thiabicyclo[3.3.0]octan‐4‐one with Self‐Reproduction of the Center of Chirality

The heterobicyclic compound 1 specified in the title is readily prepared as a single stereoisomer from (R)‐cysteine, formaldehyde, and pivalaldhyde. While it is not possible to generate the enolate 10 from 1 qunatitatively – due to β‐elimination of thiolate (→6) – an in‐situ addition to aromatic aldehydes such as benzaldehydes (→13–16), pyrrol‐, furan‐, and thiophen‐2‐carbaldehydes (→17–19), pyridine‐3‐carbaldehyde (→21), as well as to other non‐enolizable aldehydes like cinnamaldehyde (→22), can be achieved in yields of ca. 50%. The adducts (8 and 9) of lithium diisopropylamide or t‐butoxide to these aldehydes are acting, probably as bases for deprotonation and as in‐situ sources of the electrophilic aldehyde species (cf. 11, 12). ‐ Of the four possible diastereoisomeric products, one is usually formed with >90% selectivity (Table). It is assumed that the preferred stereochemical course of the reaction corresponds to that observed previously with the analogous proline‐derived enolate (See 23,24). A chemical correlation with l‐α‐methyl‐β‐phenylserine (25) proves the relative configuration of the benzaldehyde adduct 13. All hydroxyalkylated products (13–19, 21, 22) are obtained as crystalline, diastereoisomerically pure compounds and are fully characterized. – The benzaldehyde derivative 13 was used to exemplify the various possible transformations of these products to monocyclic or acyclic amino‐acid derivatives such as the oxazolidionenes 26 and 29 (cleavage of the ring containing the S‐atom), the thiazolidines 28, 31, and 32 (cleavage of the cyclic N,O‐acetal) and the α‐branched cysteine 27 and the phenylserines 25 and 30 (cleavage of both rings to give open‐chain aminoacids).
Electrostatic Defromation Properties in the Crystal Structure of Tricyclo[4.4.1.01,6]undeca‐2,4,7,9‐tetraene‐11,11‐dicarbonitrile
Authors: Bianchi Riccardo , Pilati Tullio , Simonetta Massimo
Published: December 2004

The deformation density and potential have been determined in molecular crystals of tricyclo[4.4.1.01,6]ndeca‐2,4,7,9‐tetraene‐11,11‐dicarbonitrile at 150 K from X‐ray diffraction measurements. A significant degformation density peak is found near the mid‐poind of the the transannular bond. The four short bonds in the annuelene ring acquire slightly more residual density compared to the other bonds, confirming the bisnorcaradienic character of the molecule. Similar trends are noted in the deformation electrostatic potential maps.
Photochemical reactions. 140th Communication. Acid‐catalyzed rearrangement and electron transfer photooxygenation of cyclopropanols and their silyl ethers
Authors: Scheller Markus E. , Mathies Peter , Petter Walter , Frei Bruno
Published: December 2004

On acid‐catalyzed hydrolysis, the tricyclic compounds 2 and 10, incorporating cyclopropyl‐silyl‐ether moieties undergo rearrangement to the cis‐decalones 3 and 7, respectively. Hydrolysis of 2 and 10 in the presence of oxygen leads additionally to the formation of the 1,2‐dioxolan‐3‐ols 9 and 13, respectively, which involves an electron‐transfer oxygenation process as could be demonstrated by photooxygenation of the silyl ether 10 and the cyclopropanol 14 in the presence of 9,10‐dicyanoanthracene. The configurations of 3 and 9 were assigned by X‐ray analysis of the latter compound as well as of the p‐nitrobenzoate 8 of 3.
Synthese des Dysidins
Authors: Köhler Hermann , Gerlach Hans
Published: December 2004

Synthesis of Dysidin

The synthesis of dysidin ((−)‐1), the enantiomer of a metabolite of the marine sponge Dysidea herbacea, is described. To effect the synthesis, (±)‐5‐isopropyl‐4‐methoxy‐3‐pyrrolin‐2‐one (7) is converted to its lithium salt and reacted with (−)‐(5R,2E)‐3‐methoxy‐5‐trichloromethyl‐2‐hexenoyl chloride ((‐)‐11) to give (−)‐1 and its diastereoisomer (+)‐5‐epidysidin ((+)‐12) epimeric at C(5) of the pyrrolinone ring. The (−)‐acyl chloride (−)‐11 has been synthesized from (+)‐(R)‐3‐(trichloromethyl)butanoic acid ((+)‐8) via the intermediates (+)‐9 and (−)‐10, the pyrrolinone 7 from N‐benzyl‐oxycarbonyl‐L‐valine via the intermediate 5. The enantiomers of acid 8 have been resolved by fractional crystallization of their diastereoisomeric N‐(1‐phenylethyl)amides. The (R)‐chirality of (+)‐8 was determined by comparing the 1H‐NMR spectra of the diastereoisomeric N‐(1‐phenylethyl)amides 16 and 17, made from (+)‐8 by substituting deuterium for chlorine, with the spectra of the N‐(1‐phenylethyl)amides 14 and 15 of known absolute configuration. This correlation shows that literature value (R) for (−)‐8 is in error. Therefore, the structural formulae of (−)‐dysidenin and (+)‐isodysidenin, two other metabolites of D.herbacea, have to be changed to their mirror images as shown in formulae (−)‐3 and (+)‐4, respectively.
Light‐induced Dehydrodimerization of 3‐Hydroxypyrroles
Authors: Ghaffari‐Tabrizi Ramin , Margaretha Paul , Schmalle Helmut W.
Published: December 2004

Irradiation (λ > 280 nm) of 3‐hydroxy‐1H‐pyrrole‐2‐carboxylates 1 in CH3CN gives the [2.2′‐bi(3‐oxo‐2,3‐dihydro‐1H‐pyrrole)]‐2‐,2′‐dicarboxylates 2 in reasonable to good yields. The corresponding N‐methylpyrroles 3 only undergo slow photodecomposition under similar conditions. Several 2‐methyl‐3‐oxo‐2,3‐dihydro‐1H‐pyrrole‐2‐carboxylates 4 and 5 were synthesized to compare their spectral data with those of the dehydrodimers 2. A X‐ray structure analysis was performed for diethyl [2,2′‐bi(4,5‐dimethyl‐3‐oxo‐2,3‐dihydro‐1 H‐pyrrole)]‐2,2′‐dicarboxylate (2b). The originally proposed [3,3′‐bi(3H‐pyroole)] structure for compounds 2a‐e proves incorrect.
Conversion of 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (mptp) and its 5‐methyl analog into pyridinium salts
Authors: Gessner Wieslaw , Brossi Arnold , Shen Rong‐Sen , Fritz Richard R. , Abell Creed W.
Published: December 2004

Monoamine oxidase B metabolizes 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP; 1) first to 1‐methyl‐4‐phenyl‐2,3‐dihydropyridinium salt (MPDP+; 5), and then to 1‐methyl‐4‐phenylphridinium salt (MPP+; 7). Chemical synthesis of MPDP+ and its 5‐methyl analog 6 was accomplished from the N‐oxides 3 and 4 of MPTP and its 5‐methyl analog, respectively, by a Polonovski reaction. Oxidation of MPDP+ to MPPM+ was accomplished with air, and greatly accelerated by Pt catalyst. Reduction of MPDP+ and MPP+ with NaBH4 afforded MPTP.
The Synthesis and Structure of Pentacarbonyl (5H‐dipyrrolo[1,2‐c: 2′,1′‐e]imidazol‐5‐yl)manganese
Authors: Burger Ulrich , Perret Celia , Bernardinelli Gérald , Kündig E. Peter
Published: December 2004

The dipyrroloimidazolyl ligand is found to bind the pentacarbonylmanganese group to its central ring via a carbon‐metal σ‐bond. This bonding mode differs greatly from that of known imidazole complexes and from the pentahapto mode encountered with the isoelectronic fluorenyl ligand. The X‐ray structure of the title compound is reported.
Cuprous complexes and dioxygen. Part X. Influence of ring size on the autoxidation of Cu(I) complexes with cis‐and trans‐N2S2 macrocyclic ligands
Authors: Balakrishnan Karappulli P. , Zuberbühler Andreas D.
Published: December 2004

The autoxidation of the Cu+ complexes with a series of six 12‐, 14‐ and 16‐membered macrocycles containing the N2S2 set of donor atoms has been studied with an oxygen electrode and with the stopped‐flow technique. Inspite of the identical set of coordinating groups, the reactivity of the Cu= complexes towards O2 varies by more than 5 orders of magnitude, with rate constants between <0.1 and 2·104 M−1S−1. Simple bimolecular rate laws are obtained from initial rates of autoxidation, but successive one‐electron transfers with intermediate formation of superoxide are implied from the analysis of complete reaction curves for complexes with the 12‐membered macrocycles. The kinetic parameters are compared with the redox potentials for the corresponding CuL2+/CuL+ couples. Only a rather rough correlation is found and steric factors must in addition be responsible for the observed reactivity pattern which shows a decrease of autoxidation rate with increasing size of the macrocyclic ring. No systematic effect was observed for the influence of cis‐ vs. trans‐configuration of the donor atoms.
Substitution électrophile aromatique dans l'anhydride sulfureux liquide. Influence de la concentration en bromure et rôle du solvant sur la réactivité des anisoles au cours de la réaction de bromation
Authors: Castellonése Paul , Villa Pierre
Published: December 2004

Electrophilic Aromatic Substitution in Liquid Sulfur Dioxide. Kinetic Dependance of Rate on the Bromide Concentration and Influence of the Solvent during the Course of the Reaction

On the reported data for bromination of anisole and eleven of its derivatives in liquid SO2, it was shown that, with a large excess of bromide, the rate of reaction, obeys a first‐order law. Rate constants thus obtained do not discriminate between the two different forms of bromide, e.g. Br2 and Br−3 present as the A+Br−3 form, and corrections were made by use of the apparent equilibrium constant K′ for tribromide formation. The variations of rate constants with initial concentration of bromide has been studied and the effect results in a retardation of the bromination rate. Moreover, the ratio [Br2] [A+Br−]T, which is constant during an experiment, varies with initial bromide concentrations, this variation affecting the total rate. To account for the bromide effect on the reactivity, variations of ko,pg {1 + K′[A+Br−]T}VS[A+Br−]T were studied over a 0.01 to 1M range of bromide concentration. The mechanism proposed shows that liquid SO2 helps the reactive intermediate to be deprotonated and because of solvation of reactive species this step would probably be rate determining. Bromination by molecular bromine is more sensitive to substituent effects in liquid SO2 than in water. This result is ascribed to the +M effect of the methoxy group which increase the conjugation of ortho‐substituted derivatives (p+p = −7.83; p+o= −10.47).
Eine Neuuntersuchung der Carotinoide aus Rosa foetida: Struktur von 12 neuen Carotinoiden; stereoisomere Luteoxanthine, Auroxanthine, Latoxanthine und Latochrome
Authors: Märki‐Fischer Edith , Buchecker Richard , Eugster Conrad Hans
Published: December 2004

Reinvestigation of the Carotenoids from Rosa foetida, structures of 12 Novel Carotenoids; Stereoisomeric Luteoxanthins, Auroxanthins, Latoxanthins and Latochromes

From petals of the yellow Rosa foetida HERRM., more than 35 individual carotenoids were isolated and identified. Thereof, 87% belong to the expoxycarotenes. Structures were assigned for the first time to 4 auroxanthins ((8R,8′S), 6; (8S,8′S), 7; (8R,8′R), 8; (9Z,8R,8′R), 12), to 4 luteoxanthins ((8′R), 4; (8′S), 5; (9Z,8′R), 9; (9Z,8′S) 10(e)) and to novel latoxanthins and latochromes, very polar carotenoids having (3S,5R,6R)‐trihydroxy β‐end groups (latoxanthins 13 and 16, latochromes 14 and 15).
Hyperbolic Reaction Curves with Concentration‐Independent Relaxation Times
Authors: Balakrishnan Karappulli P. , Gampp Harald , Zuberbühler Andreas D.
Published: December 2004

Hyperbolic reaction curves with concentration‐independent relaxation times are obtained from the simple reaction scheme A⇌I + P; A + I → P. While a mathematically perfect hyperbola is only obtained, if two of the three rate constants are accidentally degenerate, the same function can still be used as a very close approximation in the general case, and the differences may go unnoticed even for well‐defined stopped‐flow experiments. In view of the simplicity of the reaction, it is suggested that reaction curves with second‐order (hyperbolic) shapes, but concentration‐independent relaxation times may be a common feature in chemical kinetics.
Luteochrome; spektroskopische, chiroptische und chromatographische Eigenschaften
Authors: Acemoglu Murat , Eugster Conrad Hans
Published: December 2004

Two Optically Active Luteochromes: Preparation, Spectra and Chiroptical and Chromatographic Properties

Selective rearrangement of (5R,6S,5′ R,6′S)‐5,6:5′, 6′ ‐diepoxy‐5,6,5′, 6′ ‐tetrahydro‐ β,β ‐carotene with the aid ofan ethereal solution of malonic acid leads to the mixture of the C(8′)‐epimeric luteochromes. HPLC separation gave the pure isomers. This is the first report on th preparation of optically active luteochromes.
Gerüstumlagerung eines α,β ‐ungesättigten γ,δ‐Epoxiketons bei der Birch‐Reduktion: Strukturaufklärung mittels 13C‐INADEQUATE‐NMR‐Spektroskopie
Authors: Kreiser Wolfgang , Rüschenbaum Voker , Bauer Hans , Buddrus Joachim
Published: December 2004

Skeleton Rearrangement of an α‐β‐Unsaturated γ,δ‐Epoxyketone during Birch Reduction: Structure Elucidation by Means of 13C‐INADEQUATE‐NMR Spectroscopy

When the γ‐epoxide 2 of β‐ionone is treated under standard Birch‐reduction conditions, unexpectedly a 70% combined yield of regioisomeric octalones 4 and 5 is isolated. These products unquestionably result form cleavage of the central epoxide CC bond. The structure of compounds 4 and 5 could be determined by means of 13C‐INADEQUATE‐NMR spectroscopy.
Aromatization of 1,4‐Dihydropyridines by Clay‐Supported Metal Nitrates
Authors: Balogh Maria , Hermecz Iatván , Ménszáros Zoltán , Laszlo Pierre
Published: December 2004

1,4‐Dihydropyridines can be aromatized under very mild conditions by K 10 Claysupported ferric and cupric nitrates.
Melanotropin Receptors I. Synthesis and Biological Activity of Nα‐(5‐Bromovaleryl)‐Nα‐deacetyl‐α‐melanotropin
Authors: Wunderlin Rudolf , Minakakis Panagiota , Tun‐Kyi Aung , Sharma Shub Dev , Schwyzer Robert
Published: December 2004

Chemical synthesis and biological activities of a new α‐melanotropin derivative are described. Nα‐(5‐Bromovaleryl)‐Nα‐deacetyl‐α‐melanotropin contains the 5‐bromopentanoyl group as a chemical ‘handle’ in place of the acetyl group of the natural hormone. The synthesis involved a new protected intermediate which allowed the selective deprotection of either the Nα or Nα amino group. The title compound reacted with sodium thiosulfate to give Nα‐deacetyl‐Nα‐(5‐(sulfothio)valeryl)‐α‐melanotropin, a key intermediate for the preparation of tobaccomosaic virus/α‐melanotropin disulfide conjugates. As a basis for the study of the conjugates, biological activities of the title compound on Cloudman S‐91 mouse melanoma cell cultures (tyrosinase stimulation, binding, and cyclic AMP accumulation) were determined. They proved to be quite similar to the corresponding α‐melanotropin activities. Differences in bindings may be explained by stronger hydrophobic interaction of the new derivative with the lipid phase of the target cell membranes.
Melanotropin Receptors II. Synthesis and Biological Activity of α‐Melanotropin/Tobacco Mosaic Virus Disulfide Conjugates
Authors: Wunderlin Rudolf , Sharma Shub Dev , Minakakis Panagiota , Schwyzer Robert
Published: December 2004

Asymmetric disulfide conjugates of mercaptosuccinyl tobacco mosaic virus (TMV ∼ SH) with Nα‐desacetyl‐Nα‐5‐(mercaptovaleryl)‐α‐melanotropin were prepared via the S‐sulfoderivative of the peptide. The conjugates, TMV ∼ SS ∼ α‐MSH(n), contained up to n = 330 disulfide‐linked peptide molecules/virion. Similarly, fluorescent conjugates, Rh(m) ∼ TMV ∼ SS ∼ α‐MSH(n) were prepared, containing m ≈︁ 200 rhodamine molecules linked to the virions by thiourea bridges. Such conjugates were designed to study α‐MSH receptor localization and dynamics (mainly internalization), because the carrier virions which served to enhance specific receptor binding and as fluorescent or radioactive markers may be detached from the neuropeptides at will by reduction. Reduction occurred in solution and on the cell surface, but not in the cytoplasm, thus allowing detection of internalized agonist‐receptor complexes. The conjugates were superpotent agonists for tyrosinase stimulation in Cloudman S‐91 melanoma cell cultures, but were inactive for cyclic AMP accumulation. Their rather rapid internalization and the influence of reducing agents and other agonists on their biologic activity suggest a close connection between receptor location and biologic response as well as the presence of essential receptor HS‐groups.
Sesquiterpenoids of the Sponge Dysidea fragilis of the North‐Brittany Sea
Authors: Guella Graziano , Guerriero Antonio , Pietra Francesco
Published: December 2004

The title sponge is shown to contain eight new sesquiterpenoids for which a common, unusual biogenetic origin is postulated. The compounds are shown to be: (–)‐(1R*,4R*)‐3‐(3′‐furyl)methyl‐2‐p‐menthen‐7‐yl acetate ((–)‐8b); two diols separated as the monoacetates (–)‐(1S*,4R*)‐3‐(3′‐furyl)methyl‐l‐hydroxy‐2‐p‐menthen‐7‐yl acetate ((–)‐13a) and the (–)‐(1R*,4R*)‐epimer (–)‐13b, the two C(4)‐epimeric 4‐ethoxy‐3‐(1′(7′),2′‐p‐menthadien‐3′‐yl)methyl‐2‐buten‐4‐olides ((+)‐14a and (–)‐14b), (–)‐3‐(3′‐furyl)methyl‐7‐nor‐2‐p‐menthen‐l‐one ((–)‐11), (–)‐(3Z)‐1‐(3′‐furyl)‐4,8‐dimethylnona‐3, 7‐dien‐2‐yl acetate ((–)‐17), and (+)‐3‐(5′,7′‐seco‐2′(10′)‐pinen‐7′‐yl)methylfuran ((+)‐15).
Stoffwechselprodukte von Mikroorganismen. 231. Mitteilung. Bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranosid): Strukturaufklärung durch chemische Verknüpfung mit Bafilomycin A1 und Leucanicidin
Authors: Meyer Michael , Keller‐Schierlein Walter , Drautz Hannelore , Blank Wolfgang , Zähner Hans
Published: December 2004

Isolation of Bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranoside). Structural Determination by Chemical Correlation with Bafilomycin A1 and Leucanicidin

From cultures of an actinomycete strain, the known antifungal and insecticidal antibiotic leucanicidin (1) and a hitherto unknown antifungal antibiotic, bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranoside) (2), were isolated. The latter is spectroscopically closely related to 1 and bafilomycin A1 (3) and gave degradation products identical with compounds obtained by analogous degradation of 1 and 3.
α‐Alkylation of Amino Acids without Racemization. Preparation of Either (S)‐ or (R)‐α‐Methyldopa from (S)‐Alanine
Authors: Seebach Dieter , Aebi Johannes D. , Naef Reto , Weber Theodor
Published: December 2004

Enantiomerically pure cis‐ and trans‐5‐alkyl‐1‐benzoyl‐2‐(tert‐butyl)‐3‐methylimidazolidin‐4‐ones (1, 2, 11, 15, 16) and trans‐2‐(tert‐butyl)‐3‐methyl‐5‐phenylimidazolidin‐4‐one (20), readily available from (S)‐alanine, (S)‐valine, (S)‐methionine, and (R)‐phenylglycine are deprotonated to chiral enolates (cf. 3, 4, 12, 21). Diastereoselective alkylation of these enolates to 5,5‐dialkyl‐ or 5‐alkyl‐5‐arylimidazolidinones (5, 6, 9, 10, 13a‐d, 17, 18, 22) and hydrolysis give α‐alkyl‐α‐amino acids such as (R)‐ and (S)‐α‐methyldopa (7 and 8a, resp.), (S)‐α‐methylvaline (14), and (R)‐α‐methyl‐methionine (19). The configuration of the products is proved by chemical correlation and by NOE 1H‐NMR measurements (see 23, 24). In the overall process, a simple, enantiomerically pure α‐amino acid can be α‐alkylated with retention or with inversion of configuration through pivaladehyde acetal derivatives. Since no chiral auxiliary is required, the process is coined ‘self‐reproduction of a center of chirality’. The method is compared with other α‐alkylations of amino acids occurring without racemization. The importance of enantiomerically pure, α‐branched α‐amino acids as synthetic intermediates and for the preparation of biologically active compounds is discussed.
Nucleophilic 1,2‐Shifts of Alkoxycarbonyl and Carboxylate Groups in the Benzilic‐Acid Type Rearrangement of α,β‐Dioxobutyric Esters
Authors: Gowal Heike , Dao Lê H. , Dahn Hans
Published: December 2004

tert‐Butyl α,β‐dioxobutyrate (hydrate; 1d) undergoes, at medium or high pH, the benzilic‐acid rearrangement with exclusive 1,2‐shift of the COO(t‐Bu) group; the same is true for the corresponding isopropyl ester 1c and ethyl ester 1b at high pH, whereas at lower pH, the overall picture of these reactions is complicated by concurrent hydrolysis of the ester, followed by a 1,2‐shift of the COO− group. Consequently, the shift of these electron‐attracting groups cannot be considered to be systematically disfavoured (compared, e.g., with alkyl‐group shifts). Kinetic measurements of the rearrangement show for both esters (as well as for the analogous ethyl ester 1b, and also for ethyl 3‐cyclopropyl‐α,β‐dioxopropionate (4)) a characteristic rate profile: at relatively low pH, k is proportional to [HO−], approaching saturation with increasing [HO−] (interpreted as complete transformation of the substrate into the hydrate monoanion), which is followed at higher pH by another rate increase with k proportional to [HO−] (probably due to the reaction of the hydrate dianion). The similarity of k values for 1b‐d shows that in the shift of COOR steric hindrance caused by R is negligible.
Photochemical reactions. 142nd communication. Photochemistry of a 6,7‐epoxy‐1,3‐diene of the ionone series
Authors: Mathies Peter , Frei Bruno , Jeger Oskar
Published: December 2004

On singlet excitation (λ = 254 nm), the epoxydiene (E)‐3 underwent (E)/(Z)‐isomerization, electrocyclic ring closure of the diene side chain leading to the cyclobutenes 4A + B, and rearrangement to the cyclohexanones 5A + B. Compounds 5A + B were presumably formed in a series of processes including a 1,3‐acyl shift of the homoconjugated ketone 8, arising from (Z)‐3 by a 1,5‐H‐shift accompanied by cleavage of the C,O‐bond of the oxirane.
Synthese und Reaktionen von Bicyclo[6.4.0]dodecan‐3‐carbonsäure‐Derivaten
Authors: Buchbauer Gerhard , Gabmeier Johanna , Haslinger Ernst , Robien Wolfgang , Steindl Harald
Published: December 2004

Synthesis and Reactions of the Bicyclo[6.4.0]dodecane‐3‐carboxylic Acid Derivatives

The synthesis and some consecutive reactions of the compounds 5‐8, derivatives of bicyclo[6.4.0]dodecane‐3‐carboxylic acid (1), are described. The esters 7 and 8 can be obtained by Baeyer‐Villiger oxidation of 2‐hydroxy‐8‐methyltricyclo[7.3.1.02,7]tridecan‐13‐one (4) and subsequent hydrolysis of the lactone 5. The structure and configuration of these compounds has been evaluated by spectroscopic techniques (mainly 2D‐NMR methods). The formation of 7 via 1,2‐H shift and subsequent isomerization to 8 has been studied. The esters 11 and 13 are formed stereospecifically from 7 and 8.
Synthesen von stellungsisomeren Alkoxyformylderivaten des 1,6‐Methano[10]annulens
Authors: Neidlein Richard , Hartz Georg
Published: December 2004

Syntheses of Positionisomeric Alkoxyformylderivatives of 1,6‐Methano[10]annulenes

Different aldehydes of 1,6‐methano[10]annulene – namely 3–6, 11, 12, 15, and 19 – were synthesized. They can be used as starting materials for synthetic reactions of other new bridged systems; the results of 1H‐NMR‐ and 13C‐NMR measurements are included.
The Radical Anions of syn‐1,6:8,13‐Bridged [14] Annulenes. A Compilation of Hyperfine Data
Authors: Gerson Fabian , Knöbel Jürgen , Lopez Javier , Vogel Emmanuel
Published: December 2004

Hyperfine coupling constants and g‐factors determined by ESR and ENDOR spectroscopy are given for the radical anions of 21 syn‐1,6:8,13‐bridged [14]annulenes. The great majority of these values is reported for the first time. The hyperfine data are consistent with the single occupancy of an orbital which resembles a π‐perimeter‐LUMO of the same nodal properties. The sum of the coupling constants of the protons attached to the π‐perimeter can be used as a planarity criterion for this perimeter.
Synthese von 3,3‐Dimethylperhydro‐1,4‐diazepin‐2,5,7‐trionen aus 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirin und Malonsäuremonoamiden
Authors: Obrecht Daniel , Scholl Bernhard , Heimgartner Heinz
Published: December 2004

Synthesis of 3,3‐Dimethylperhydro‐1,4‐diazepin‐2,5,7‐triones from 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine and Malonic Acid Monoamides

Reaction of the aminoazirine 1 and malonic acid monoamides 5 in CH3CN yielded triamides of type 6 (Scheme 2), which were transformed to the corresponding phenylthioates 9 by treatment of a solution of 6 and thiophenol in CH3CN with HCl (Scheme 4). Cyclization of 9 to give the 1,4‐diazepin‐2,5,7‐trione of type 10 was achieved with NaH in toluene at about 90°. It has been shown that 2‐oxazolin‐5‐ones are intermediates in the selective cleavage of the therminal amide function of 6 (Scheme 3).
The Crystal Structure of trans‐2,2′‐Azoquinoxaline
Authors: Krieger Claus , Koçak Ahmet , Bekâroǧlu Özer
Published: December 2004

The structure of the title compound obtained from 2(1H)‐quinoxalinone oxime by the template effect of Co(II) and Ni(II) ion has been determined by three dimensional X‐ray analysis.
Liquid Crystals with Large Negative Dielectric Anisotropy. Part V
Authors: Osman Maged A.
Published: December 2004

Liquid crystals with negative Δϵ can be obtained by incorporating a cyano group in the terminal alkyl substituent or in an ethylene bridge between the cyclic units of the rigid core. The clearing points of such compounds are higher than those of the corresponding derivatives where the cyano group is laterally attached to a phenyl moiety. In compounds where both cyclic units of the rigid core are cyclohexyl, this type of substitution leads to an optimal contribution to ϵ⟂ in contrast to the cyanophenyl derivatives.
Synthese und Hydrolyse von 4‐substituierten p‐Nitrobenzolsulfonsäure (2‐adamantyl)estern
Authors: Grob Cyril A. , Wittwer Gerhard , Rama Rao K.
Published: December 2004

Synthesis and Hydrolysis of 4‐Substituted 2‐Adamantyl p‐Nitrobenzenesulfonates

Several 4e ‐substituted 2e‐ and 2a‐adamantyl p‐nitrobenzensulfonates have been prepared by new routes. Their hydrolysis products are described.
Synthesis and Antagonistic Activity of Two Covalently Linked Dimers of Adrenocorticotropin‐(11‐24)‐tetradecapeptide
Authors: Fauchère Jean‐Luc
Published: December 2004

The chemical synthesis of two dimers of the sequence 11 to 24 of adrenocorticotropin is described. The two monomers were covalently linked through their N‐or C‐termini, respectively, using N‐acetylglutamic acid or lysine amide as spacers. Compared to the monomer, the first dimer showed moderately, the second strongly increased inhibitory potency upon steroidogenesis in isolated adrenal cells.
Isomérisation cis‐trans en Série Alkyl‐4‐vinyl‐3‐pipéridine par Sigmatropie [3.3]. Synthèse des Epivinyl Isomères des Alcaloïdes du Quinquina
Authors: Engler Gérard , Strub Henri , Fleury Jean‐Pierre , Fritz Hans
Published: December 2004

cis, trans Isomerization of 4‐Alkyl‐3‐vinylpiperidines by [3.3] Sigmatropic Rearrangement. Synthesis of Epivinyl Isomers of Cinchona Alkaloids

Isomerization of 4‐alkyl‐3‐vinylpiperidines induced by formaldehyde has been studied for ethyl meroquinate and quinotoxine. The equilibration of cis‐ and trans‐isomers occurs by involvement of a [3.3] sigmatropic rearrangement. This process permits an easy access to the trans‐isomers from natural products of cis‐configuration and has been used to obtain the epivinyl isomers of cinchona alkaloids.
The Synthesis and Some Physical Properties of New Laterally Substituted Phenyl Ethers Containing a trans‐1,4‐Disubstituted Cyclohexane Ring
Authors: Kelly Stephen M. , Schad Hanspeter
Published: December 2004

The synthesis, liquid‐crystal transition temperatures, and some physical properties of a variety of substituted phenyl ethers, most of which incorporate a lateral substituent, are reported. Many of the liquid crystals described exhibit nematic phases with negative dielectric anisotropy at elevated temperatures. The relationship between the nature of the lateral substituents and the observed liquid crystal phases and transition temperatures is discussed.
Reaction of Anthranilamide with Phosphorus Pentasulfide: Formation of 2‐Mercapto‐(1H)‐1,3,2λ5‐benzodiazaphosphorine‐2,4‐dithione
Authors: Nagarajan Kuppuswamy , Shenoy Sharada J. , Fritz Hans , Hosang Othmar , Richter Wilhelm J.
Published: December 2004

The reaction of anthranilamide with phosphorus pentasulfide in boiling pyridine leads to the benzodiazaphosphorine‐pyridine salt 2. The structure is established by elemental analysis, 1H‐ 13C‐ 15N‐ 31P‐NMR, and mass spectral data.
Makrocyclische Ionophore beruhend auf oligomeren Terephthaldiamiden mit von Gastmolekülen abhängiger Selektivität
Authors: Behm Felix , Simon Wilhelm , Müller Walter M. , Vögtle Fritz
Published: December 2004

Macrocyclic Oligolactams Based on Terephthalic Acid as Ionophores with Selectivity Depending on Included Guest Molecules

Macrocyclic 20‐ to 60‐membered oligolactam hosts exhibit ion selectivities in poly(vinyl chloride) membranes which depend on the ring size and on the substituents of the amide N‐atoms. The selectivity may be changed by loading the macrocyclic host with CHCl3 as guest molecule.
Enzyme‐Catalyzed Peptide‐Bond Formation: Elastase‐ and δ‐Chymotrypsin‐Assisted Synthesis of Oligopeptides
Authors: Bizzozero Spartaco A. , Dutler Hans , Franzstack Ruth , Rovagnati Bruno A.
Published: December 2004

A series of penta‐ and hexapeptides of the structure Ac‐Lxn‐ …‐Lx1‐Ly1‐…‐Lym‐NH2 with phenylalanine or tyrosine in Lx1 and glycine or alanine in the other positions were synthesized using elastase and δ‐chymotrypsin to catalyse the formation of the peptide bonds adjacent to the aromatic residue. Such oligopeptides are useful substrates for studying the secondary specificity of chymotrypsin‐like proteases.
Synthesis and Conformation of (5R,8R,10R)‐8‐(Methylthiomethyl)ergoline‐6‐carboxamidine
Authors: Nordmann René , Loosli Hans‐Rudolf
Published: December 2004

The title compound 7 and two related novel ergolines have been synthesised from (5R,8R,10R)‐8‐(methyl‐thiomethyl)ergoline‐6‐carbonitrile (4). The guanidine function of 7 induces a boat conformation of ergoline‐ring D, as demonstrated by a careful NMR spectroscopic analysis of 7 and its N‐hydroxy congener 6. Diphenylphosphinodithioic acid has been used to convert the cyanamide function of 4 into the thiourea function at (5R,8R,10R)‐8‐(methylthiomethyl)ergoline‐6‐thiocarboxamide (5).
Structures of Ring‐Enlargement Products
Authors: Aono Tetsuya , Bieri Jost H. , Hesse Manfred , Kostova Kalina , Lorenzi‐Riatsch Annalaura , Nakashita Yoshihiko , Prewo Roland
Published: December 2004

Crystal structures have been determined of methyl trans‐1‐hydroxy‐6‐nitro‐3‐oxobicyclo[4.4.0]decane‐2‐carboxylate (19), cis‐3‐methyl‐6‐nitro‐2‐oxabicyclo[4.4.0]decan‐1‐ol (2), cis‐7‐hydroxy‐1‐nitrobicyclo[5.4.0]undecan‐9‐one (13), and the medium‐ring compounds 2‐acetyl‐4‐nitrocyclooctanone (9), methyl 5‐nitro‐2‐oxocyclooctane‐carboxylate (4), 2‐acetyl‐4‐nitrocyclononanone (11), 2‐acetyl‐4‐nitrocyclodecanone (15), benzyl 5‐nitro‐2,11‐dioxocycloundecanecarboxylate (24), methyl 5‐nitro‐2,12‐dioxocyclododecanecarboxylate (21), and 8‐nitro‐11‐oxo‐13‐tridecanolide (7), which are intermediates, side products, or end products of the ‘Zip’ ring‐enlargement reaction. The conformations of most of the medium‐ring compounds are very similar to equal‐sized ring compounds previously determine by other authors.
Thermal Rearrangement of 5,6‐Epimino‐5,6‐dihydro‐β‐ionone and Derivatives
Authors: Müller Ernst Peter
Published: December 2004

Thermolysis of 5,6‐epimino‐5,6‐dihydro‐β‐ionone (1) and its N‐methyl derivative (2) leads to their monocyclic isomers 6 and 10, respectively, presumably due to a direct [1,5]‐H shift; on prolonged heating, these isomers are converted easily into pyrrole derivatives. In contrast, the thermoisomer 12 resulting from 5,6‐(N‐methoxycarbonyl)epimino‐5,6‐dihydro‐β‐ionone (3) by the same mechanism, does not undergo further ring transformation, but equilibrates with its more stable tautomer 13.
The Quest for Bridgehead Bridgehead Dications with Bicyclo[2.2.2]octyl Skeletons
Authors: de Meijere Armin , Schallner Otto , Mateescu G. D. , Gölitz Peter , Bischof Peter
Published: December 2004

It is predicted by MINDO/3 calculations that the 1,5‐trishomobarrelenediyl dication 4 would be as much stabilized over the bicyclo[2.2.2]octanediyl dication 3 as the monocation 7‐H is energetically favored over the hypothetical 1‐bicyclo[2.2.2]octyl 10‐H. In spite of this, the bridgehead cations generated from the 1,5‐dihalo‐trishomobarrelenes 6‐F, 6‐Cl, 6‐Br, and 6‐I and from the 1,5‐diol 6‐OH under long‐lived ion conditions were only the 5‐substituted monocations 7‐F, 7‐Cl, 7‐Br, 7‐I, and 7‐OH, respectively, unequivocally identified by their 1H‐ and 13C‐NMR spectra as well as quenching products. Although there is efficient charge delocalization in 7‐X, as revealed by the 13C‐chemical shifts, the lack of formation of the bridgehead bridgehead dication 4 is not due to an unforeseen destabilization by the three α‐annellated cyclopropyl groups. Even the 1,5‐dichlorotetracyclo[3.3.2.02,4.06,8]decanes 17‐Cl2 and 19‐Cl2 and 1,5‐dichlorotricyclo[3.2.2.02,4]nonane 12‐Cl2 with only two and one α‐cyclopropyl groups, respectively, gave the bridgehead monocations 18‐Cl, 20‐Cl, and 13‐Cl, respectively.
Synthesis of Substituted 2‐Amino‐6H‐1,3‐oxazin‐6‐ones
Authors: Kristinsson Haukur , Winkler Tammo , Rihs Grety , Fritz Hans
Published: December 2004

Derivatives of the unknown 2‐amino‐6H‐1,3‐oxazin‐6‐one 2 have been synthesized for the first time in two steps and in excellent yields, starting from N‐cyanocarbonimidates 3a–c and cyanoacetates. The structures of 2a–c are assigned by NMR‐spectroscopic methods and corroborated by an X‐ray structure analysis of 2c.
Propellanes. Part LXXXI. Why are tetrakis[organoboranediylbis(oxy)]cyclobutanes formed without a trace of the isomeric tetrakis‐dioxabora[3.3.2]propellanes?
Authors: Stanger Amnon , Apeloig Yitzhak , Ginsburg David
Published: December 2004

MNDO and STO‐3G calculations rationalize the relative instability of the title propellanes vis‐à‐vis the title products that are formed exclusively.
Motional Anisotropy of 1‐Phenyladamantane
Authors: Kołodziejski Wacław , Laszlo Pierre
Published: December 2004

13C‐NMR longitudinal relaxation rates are analysed with the Woessner equations: in CDCl3 solution at room temperature, 1‐phenyladamantane has rotational diffusion coefficients R‖ = 8.1 × 1010 rad · s−1 and R⊥ = 1.1 × 1010 rad · s−1 corresponding to high motional anisotropy (σ = 7.4).
Stereoselective Synthesis of Masked Amino‐polyols via Osmylation of 4,5‐Dihydro‐5‐vinylisoxazoles
Authors: Annunziata Rita , Cinquini Mauro , Cozzi Franco , Raimondi Laura , Restelli Angelo
Published: December 2004

Variously substituted 4,5‐dihydro‐5‐vinylisoxazoles, obtained by regio‐ and stereospecific cycloaddition of nitrile oxides to dienes, undergo smooth OsO4‐catalyzed cis‐hydroxylation to give amino‐polyol precursors. The reaction is ‘anti’‐selective, the diastereoisomeric ratios ranging from 73:27 up to ≥ 99:1. Thus, the cycloaddition/osmylation sequence allows the control of the relative configuration of up to four contiguous asymmetric centers. A sulfoxide‐mediated approach to enantiomerically pure compounds is also described.
Stereospecific Molecular Design. Synthesis of a New Heterotricyclic System
Authors: Tschamber Théophile , Fritz Hans , Streith Jacques
Published: December 2004

UV irradiation of the bicyclic enimine 1 led stereospecifically to the anti‐tricyclic isomer 2 which reverted back to 1, either by thermal activation or by acid catalysis at room temperature. Catalytic hydrogenation of 2 gave compound 4 whose configuration was fully ascertained by high‐field 1H‐NMR measurements.
Lösungsmittel‐, Viskositäts‐, Säure‐ und Substituenteneinflüsse auf die Photoisomerisierung und Relaxation symmetrischer Triazacarbocyanine bei 283 bis 323 K
Authors: Balli Heinz , Hellrung Bruno
Published: December 2004

Influence of Solvents, Viscosity, Acid, and Substituents on the Photoisomerization and the Relaxation of Symmetrical Triazacarbocyanine Dyes at 283 to 323 K

Photobleaching and the reverse dark reaction of seven symmetrical triazacarbocyanine dyes with different heterocycles were studied dependent on solvent effects (protic and aprotic solvents), on effects of viscosity (glycerol/EtOH mixtures), and on effects of added acid. No effects of dissolved O2 or added I2 has been observed. Kinetic data (ΔH≠, ΔS≠, and ΔG) of the reverse reaction are given. The effect of the substituents has been studied on two series of substituted triazacarbocyanine dyes. The mechanism of the reverse reaction is discussed.