bluuebunny/crossref_metadata_2025_split huggingface dataset:
Complexes of Rhodium(III) with Two Chelating C⁁N Ligands and One Diimine Ligand
Authors: Maeder Urs , Von Zelewsky Alex , Stoeckli‐Evans Helen 
Published: December 2004

AbstractThe synthesis of two series of cyclometalated RhIIIcompounds is described, namely of 5 dinuclear chlorobridged species [{Rh(C⁁N)2} (μ‐Cl)2]Aand of 15 mononuclear complexes [Rh(C⁁N)2(N⁁N)]+B; C⁁N stands for five different cyclometalating ligands,i.e.deprotonated phenylpyridine, deprotonated 2‐(thienyl)pyridine, and three deprotonated 1‐aryl‐1H‐pyrazoles, and N⁁N for six diimine ligands such as 2,2‐bihyridine, 2,2′‐bi‐1H‐imidazole, and 2,2′‐bipyrimidine. For (2,2′‐bipyridine)bis[2‐(thien‐2‐yl)pyridinato‐N,C3′]rhodium(III) chloride, an X‐ray structure determination was carried out. In the other cases,1H‐NMR spectra established the configuration of the complexes. All mononuclear and dinuclear complexes show a C,Ccis‐configuration. The UV/VIS‐absorption bands at longest wavelength are most likely due to metal‐to‐ligand charge‐transfer (MLCT) transitions, depending on the nature of the cyclometalating ligand C⁁N and on the diimine ligand N⁁N. The receptor orbital is in some cases on the cyclometalating ligand, in others on the diimine. All monomer complexes exhibit at least one reversible reduction wave in the cyclovoltammogram in dimethylformamide solutions, attributable to a ligand‐centered reduction. It is, therefore, concluded that the LUMO in [Rh(C⁁N)2(N⁁N)]+is of L(π*) character, as opposed to [Rh(bpy)3]3+, where it is a metal d‐orbital. The crystal system of (2,2′‐bipyridine)bis[2‐(thien‐2‐yl)pyridinato‐N,C3′]rhodium(III) chloride—water (1/2.125) is tetragonal (space groupP4;R= 0.036,Rw= 0.040). The Rh‐atom has slightly distorted octahedral environment; the average distances are (RhN/thienylpyridine) = 2.060 (3), RhC = 1.9885 (3), and RhN(bipyridine) = 2.1415 (3) Å. Of the three ligands the 2,2′‐bipyridine is the most planar.
Fixation of 1,3,5‐Trithiane to a Trinuclear Ruthenium Framework: Synthesis, structure, and fluxionality of [Ru3(CO)6(μ2‐CO)3{μ3‐(η3‐C3S3H6)}]
Authors: Hoferkamp Lisa , Rheinwald Gerd , Stoeckli‐Evans Helen , Süss‐Fink Georg 
Published: December 2004

AbstractThe reaction of dodecacarbonyltriruthenium with 1,3,5‐trithiacyclohexane (1,3,5‐trithiane) in refluxing THF yields [Ru3(CO)6(μ2‐CO)3{μ3‐(η3‐C3S3H6)}] (1) in which the three S‐atoms of the cyclic ligand coordinate to the three Ru‐atoms of the metal core. X‐Ray diffraction reveals a nearly perfect C3v symmetry for the molecule. The variable‐temperature 13C‐NMR spectra show the carbonyl ligands to be fluxional in solution.
Photoisomerization of 2H,6H‐Thiin‐3‐ones to 2‐(Alk‐1‐enyl)thietan‐3‐ones
Authors: Er Erhan , Margaretha Paul 
Published: December 2004

AbstractReaction of 3‐bromo‐3‐methylbutan‐2‐one (1) with mercapto‐esters 2 affords 5‐oxo‐3‐thiahexanoates 3 which cyclize to thiane‐3,5‐diones 4. Conversion of these dicarbonyl compounds to their ethyl enol ethers 5–7 followed by reduction with LiAlH4 gives 2H,6H‐thiin‐3‐ones 8–10. On irradiation (350 nm) in either MeCN, benzene, or i‐PrOH, these newly synthesized heterocycles isomerize efficiently to 2‐(alk‐l‐enyl)thietan‐3‐ones 11–13. The rearrangement seems to proceed from an excited singlet state, as it is not quenched by naphthalene, and also occurs with the same efficiency in the presence of added alkene. A (9‐S‐3) sulfuranyl‐alkyl biradical formed by bonding of C(α) of the enone CC bond on sulfur is discussed as possible intermediate.
Reactions of 2‐Monosubstituted 3‐Amino‐2H‐azirines with NH‐Acidic Heterocycles
Authors: Villalgordo José M. , Linden Anthony , Heimgartner Heinz 
Published: December 2004

Abstract2‐Monosubstituted 3‐amino‐2H‐azirines 2 react with several heterocycles containing acidic NH groups via ring expansions, leading to benzo[g][1,2,5]thiadiazocin 1,1‐dioxide derivatives 6 and imidazoles 9, 10, and 13, respectively.
New Hydroxylated Spermidine Alkaloids from Pleurostylia opposita(WALL.) MERILL‐METCALF
Authors: Séguineau Corinne , Richomme Pascal , Bruneton Jean , Pusset Jacques 
Published: December 2004

AbstractThe leaves of a New Caledonian celastraceae, Pleurostylia opposita (WALL.) MERRILL‐METCALF, have yielded three new spermidine alkaloids, 7‐hydroxypleurostyline (1), 7‐hydroxycelacinnine (2), and 7′‐hydroxy‐7′,8′‐dihydropleurostyline (3), as minor basic constituents, together with three related alkaloids pleurostyline (4), celacinnine (5), and celallocinine (6).
Base‐Modified Nucleosides Related to 2‐Chloro‐2′‐deoxyadenosine
Authors: Kazimierczuk Zygmunt , Vilpo Juhani A. , Seela Frank 
Published: December 2004

AbstractDerivatives of 2‐chloro‐2′‐deoxyadenosine (1a) containing secondary 6‐NH2 groups (5a‐c) or a 8‐Br substituent (9) were synthesized. They were tested together with ring‐modified congeners containing a pyrrolo[2,3‐b]pyridine, pyrrolo[3,2‐c]pyridine, or pyrazolo[3,4‐d]pyrimidine ring system as inhibitors of various leukemic cell lines. Only the 8‐Br derivatives 9 showed inhibitory activity, whereas the base‐modified congeners were not active. Compound 1a was protonated at a pKa = 1.4 (2′‐deoxyadenosine at pKa = 3.8). Protonation occurred at N(7) and not at N(1) as observed for dA.
Untersuchungen zur Stabilität und Reaktivität von (3‐Cyclopropylidenprop‐1‐enyl)‐ethyl‐ether
Authors: Stadlwieser Josef , Kienzle Frank , Arnold Wolf , Gubernator Klaus , Schönholzer Peter 
Published: December 2004

Stability and Reactivity of 3‐Cyclopropylideneprop‐1‐enyl Ethyl Ether3‐Cyclopropylideneprop‐1‐enyl ethyl ether (1) dimerizes to a cyclobutane derivative 2 which, upon prolonged heating, is converted to a cyclooctadiene (3). The reactivity of 1 is discussed. The structures of 2 and 3 as well as of their derivatives have been determined using 1H‐NMR spectroscopy and X‐ray crystal‐structure analysis.
Studies On Rare‐Earth Complexes with Crown Ethers. Part XXV. Synthesis, characterization, and structure of the complexes of lanthanide nitrates with 13‐crown‐4
Authors: Lu Tongbu , Wang Xin , Tan Minyu , Liu Yu , Inoue Yoshihisa , Hakushi Tadao 
Published: December 2004

AbstractThe lanthanide nitrate complexes with 13‐crown‐4(13‐C‐4) have been prepared in AcOEt. These new complexes with the general formula Ln(NO3)3.(13‐c‐4) (Ln = La–Nd, Sm–Lu) have been characterized by means of elemental analysis, IR and 1H‐NMR spectra, conductivity measurements, and TG‐DTA techniques. The crystal and molecular structure of Nd(No3)3. (13‐c‐4) has been determined by single crystal X‐ray diffraction. It crystallizes in the monoclinic space group P21/a with Z = 8. Lattice parameters are a = 15.393(1), b = 12.578(1), c = 19.279(2) Å, β = 113.05(1)°, V = 3435 Å3, Dc = 2.01 g cm−3, μ = 31.0 cm−1 (Mok2), F(000) = 2056. The structure was solved by Patterson and Fourier techniques and refined by least‐squares to a final conventional R value of 0.032 for 5218 independent reflections with I ⩽ 3σ(I). There are two independent Nd(No3)3 · (13‐C‐4) monomers in one asymmetrical unit. The coordination numbers are ten in these two independent monomers.
Nucleosides. Part LI The 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) and 2‐(2,4‐dinitrophenyl)ethoxycarbonyl (dnpeoc) groups for protection of hydroxy functions in ribonucleosides and 2′ ‐deoxyribonucleosides
Authors: Schirmesiter Helga , Himmelsbach Frank , Pfleiderer Wolfgang 
Published: December 2004

AbstractThe Common 2′ ‐deoxypyrimidine and ‐purine nucleosides, thymidine (4), O4‐[2‐(4‐nitrophenyl)ethyl]‐thymidine (17), 2′‐deoxy‐N4‐[2‐(4‐nitrophenyl)ethoxycarbonyl]cytidine (26), 2′‐deoxy‐N6‐[2‐(4‐nitrophenyl)‐ethoxycarbonyl]adenosine‐39, and 2′‐deoxy‐N2‐[2‐(4‐nitrophenyl)(ethoxycarbonyl]‐O6‐[2–4‐nitrophenyl)ethyl]‐guanosine (52) were further protected by the 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) and the 2‐(2,4‐dinitrophenyl)ethoxycarbonyl (dnpeoc) group at the OH functions of the sugar moiety to form new partially and fully blocked intermediates for nucleoside and nucleotide syntheses. The corresponding 5′‐O‐monomethoxytrityl derivatives 5, 18, 30, 40, and 56 were also used as starting material to synthesize some other intermediates which were not obtained by direct acylations. In the ribonucleoside series, the 5′ ‐O‐monomethoxytrityl derivatives 14, 36, 49, and 63 reacted with 2‐(4‐nitrophenyl) ethyl chloroformate (1) to the corresponding 2′,3′‐bis‐carbonates 15, 37, 50, and 64 which were either detriylated to 16, 38, 51, and 65, respectively, or converted by 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) treatment to the 2′,3′‐cyclic carbonates 66–69. The newly synthesized compounds were characterized by elemental analyses and UV and 1H‐NMR spectra.
Anatoliosides: Five Novel Acyclic Monoterpene Glylcosides from Viburnum orientale
Authors: Çaliş Ihsan , Yürüker Ayşen , Rüegger Heinz , Wright Anthony D. , Sticher Otto 
Published: December 2004

AbstractFive new acyclic monoterpene glycosides 1–5 were isolated from the leaves of Viburnum orientale (Caprifoliaceae). Anatolioside (1) is a monoterpene diglycoside and its structure was elucidated as linalo‐6‐yl 2′‐O‐(α‐L‐rhamnopyranosyl)β‐D‐glucopyranoside (arbitrary numbering of linalool moiety). Compounds 2–5 are all derivatives of 1, containing additional monoterpene and sugar units, connected by ester and glycoside bonds. Their structures were established as linalo‐6‐yl O‐[(2E,6R)‐6‐hydroxy‐2, 6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl‐(1″‴ → 2″″)‐β‐D‐glucopyranoside ( = anatolioside A; 2), linalo‐6‐yl O‐β‐D‐glucopyranosyl‐(1‴ → 6‴)‐O‐[(2E,6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl‐(1″ → 2′)–β‐D‐glucopyranoside ( = anatolioside B; 3), linalo‐6‐yl O‐β‐Dribo‐hexopyranos‐3‐ulosyl‐(1′‴ → 6‴)‐O‐[(2E,6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl‐(1″ → 2′)‐β‐D‐glucopyranoside ( = anatolioside C; 4) and linalo‐6‐yl O‐[(2E, 6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1″‴ → 2″″)‐O‐β‐D‐glucopyranosly‐(1″″ → 6‴)‐O‐[(2E,6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl(1″ → 2′)‐β‐D‐glucopyranoside ( = anatolioside D; 5). The structure determinations were based on spectroscopic and chemical methods (acid and alkaline hydrolysis, acetylation and methylation).
The Synthesis of Natural Acetylenic Compounds from Eutypa lata (Pers; F.) TUL
Authors: Defranq Eric , Zesiger Thierry , Tabacchi Rattaele 
Published: December 2004

AbstractThe synthesis of a series of novel acetylenic compounds 1–7, isolated recently from the fungus Eutypa lata, is described. The crucial step is the coupling reaction between a protected aryl halogenide and the acetylenic chain as a cuprous acetylide (Scheme 1). A more efficient method using bis(triphenylphosphine)palladium dichloride ([Pd(PPh3)2Cl2]) as catalyst was also carried out with success.
Enantiomeric Purities of (R)‐ and (S)‐Camphors from the Chiral Pool and High Enantiomeric Purities in General
Authors: Rautenstrauch Valentin , Lindström Mikael , Bourdin Bernadette , Curie Jane , Oliveros Esther 
Published: December 2004

AbstractThe commercially available camphor enantiomers are extensively used in several important areas of chemical research, and it seems that they are often considered to be enantiomerically pure (the meaning of the term is discussed); there are certainly no enantiomeric purities (e.p.) on record. By standard GLC on a modified cyclodextrin column, we have now found five commercial (R)‐camphors to have the same high but imperfect e.p., (99.62 ± 0.02)% (R), a sixth a slightly higher e.p., (99.76 ± 0.06) % (R), and three (S)‐camphors to have different and lower e.p. Nailing down these e.p. is useful by itself and puts into focus the sensitivity of present day GLC, and how little is know about high e.p. in general.
The Dynamic Behaviour and NMR Solution structures of complexes of the type (Bisphosphine)(cycloocta‐1,5‐diene)iridium(I) and the X‐ray crystal structure of (cycloocta‐1,5‐diene)((−)‐norphos)iridium(I) hexafluorophosphate
Authors: Hälg Werner J. , Öhrström Lars R. , Rüegger Heinz , Venanzi Luigi M. , Gerfin Tobias , Gramlich Volker 
Published: December 2004

AbstractA square‐planar coordination geometry was found for the complex [Ir(cod){(−)‐norphos}][PF6] (1b[PF6]; cod = cylcoocta‐1,5‐diene and (−)‐norphos = [(2R,3R)‐8‐9‐10‐trinorborn‐5‐ene‐2,3‐diyl]bis(diphenylphosphine)) in the solid state by X‐ray diffraction. Crystal data: monoclinic, space group P21, a = 10.751 (6), b = 18.669(14), c = 12.037(8) Å, β = 114.82(5)°, Z = 2. A total structural assignment including the configurational and conformational aspects of this and the related compounds [Ir(bishosphine)(cod)]X (bisphosphine = (−)‐chiraphos = (2S,3S)‐2,3‐bis(diphenylphosphino)butane and (−)‐norphos, X = Cl, CF3SO3, or PF6) was carried out in solution by one‐ and two‐dimensional NMR spectroscopy. The complexes containing the CF3SO3− and PF6− anions are four‐coordinate cations with square‐planar geometry, whereas the chlorides are five‐coordinate neutral compounds showing solvent‐dependent dynamic behaviour. In toluene, two diastereoisomers of [IrCl(cod){(−)‐norphos}] (2b) exist and interconvert slowly at room temperature. This interchange is fast in CDCl3 solution, and it is likely to involve Cl dissociation and the formation of the cation [Ir(cod){(−)‐norphos}]+ as an intermediate.
Zum Mechanismus der sequentiellen Radikal‐Cyclisierung von (Bromomethyl)silyl‐ethern terpenoider Alkohole
Authors: Lakomy Ivo , Scheffold Rolf 
Published: December 2004

On the Mechanism of Sequential Radical Cyclization of (Bromomethyl)silyl Ethers of Terpernoid AlcoholsThe cyclic products of the Bu3SnH‐promoted radical reaction of (E)‐1‐[(bromomethyl)dimethylsilyloxy]‐2‐methylhept‐2‐ene (6) consists to 98% of a 1:2 mixture of (±)‐(4RS,5RS)‐ and (±)‐(4‐RS,5SR)‐4‐butyl‐2,2,5‐trimethyl‐1‐oxa‐2‐silacyclohexane (8a and 8b, respectively). It is, therefore, concluded that the 6‐‘endo’→5‐‘exo’ tandem cyclization of the 5‐mehtyl‐3‐oxa‐2‐siladeca‐5,9‐dien‐l‐yl radical (reaction 1 → 2) is not necessarily a concerted process, but may be explained as a sequence of individual steps via free‐radical intermediates.
Luminescence of Europium(III) Chelates with 4‐(Arylethynyl)pyridines as Ligands
Authors: Takalo Harri , Hänninen Elina , Kankare Jouko 
Published: December 2004

AbstractSome Spectral properties and luminescence intensities of EuIII chelates with 4‐(arylethynyl)pyridine‐2,6‐dicarboxylic acids 1–15 and 2,2′,2″,2′″‐{[4‐(arylethynyl)pyrridine‐2,6‐diyl]bis(methylenenitrilo)} tetrakis(acetic acids) 16–26 were measured both in H2O and EtOH solutions for the purpose of developing suitable labels to be used in time‐resolved luminescence‐based bioaffinity assays (Tables 1 and 2). The substitution at the Ar group has a significant effect upon the observed luminescence intensities, excitation wavelengths, and decay constants of the complexes, Moreover, the changes in the environment cause great variation in those properties of certain EuIII chelates.
Molecular Geometries by the Extended‐Hückel Molecular Orbital method II: Hydrocarbons and organic molecules containing O, N, and S
Authors: Brändle Martin , Calzaferri Gion 
Published: December 2004

AbstractBond lengths and bond angles of hydrocarbons and of organic molecules containing oxygen, nitrogen, and sulfur have been investigated by the extended‐Hückel method in its improved ASED (atom superposition and electron delocalization) form. We have examined in detail bond lengths and bond angles of hydrocarbon ‐aliphatic, conjugated, rings, and aromatic – and we have also studied reaction enthalpies. Both properties can be calculated resonably well, if a small adjustment of the parameter k in the distance dependent Wolfsberg‐Helmholz formula is accepted. We have also found that moderate contraction of the usually applied 2s‐oxygen, the 2s‐nitrogen, and the 3s‐sulfur Slater exponents is sufficient to obtain astonishingly good geometries for important classes of organic molecules containing these elements. The three‐membered rings (CH2)2X(X  CH2, NH, O, and S) which have attracted much interest and stimulated theoretical studies have been investigated, and we have found that their geometries can be reproduced nicely. It is important that geometry calculation of the investigated molecules can be carried out without losing transparency and well established prediction capabilities of the original EHMO procedure. The extended‐Hückel method in its improved ASED form is, therefore, a useful tool for combining the information of EHMO results with good geometry calculation.
Triplet‐State Energy of the Photostabilizer Tinuvin P
Authors: Allan Michael , Asmis Knut , Bulliard Christophe , Haselbach Edwin , Suppan Paul 
Published: December 2004

AbstractElectron‐energy‐loss spectroscopy shows that the lowest triplet level of the photostabilizer molecule Tinuvin P (= 2‐(2′‐hydroxy‐5′‐methylphenyl)benzotriazole) is at ca. 3.0 eV. Tinuvin P acts as a photostable inner filter rather than as a quencher of excited impurity sites.
Synthese eines 1,2‐trans‐konfigurierten, äquatorialen Glycosyl‐phosphonat‐Analogen von D‐myo‐Inositol‐1,4,5‐trisphosphat
Authors: Czollner LáSzló , Baudin Gisèle , Bernet Bruno , Vasella Andrea 
Published: December 2004

Synthesis of a 1,2‐trans‐Configurated, Equatorial Glycosylphosphonate Analogue of D‐myo‐Inositol 1,4,5‐TrisphosphateThe diphosphonate analogue 3 of D‐myo‐inositol 1,4,5‐trisphosphate (1), a 1,2‐trans‐configurated, equatorial glycosylphosphonate, was synthesized and characterized as its hexasodium salt 3a. In a first approach, the silylated galactal 4 (Scheme 1) was transformed into the oxirane 5 and hence, by treatment with Me3SiP(OMe)2, into a mixture of the glycosylphosphonate 6 and its silyl ether 7. This mixture was desilylated and then treated with acetone and FeCl3 to yield 8 and 9 (64 and 22%, resp., from 4). In a second approach, the acetates 11/12(Scheme 2) were treated with P(OMe)3/Me3SiOTf in MeCN to afford the anomeric glycosylphosphonates 16/17 (1:1, 60%), while the trichloroacetimidate 10 gave mostly the αD‐anomer 16. The αD‐anomer 20 was obtained from 12 and P(OPh)3. The highest yield of a β‐Dphosphonate was realized by treating 12 with the cyclic phosphite 15 (→ 18/19, 40% each). The β‐D‐phosphonate 17 was debenzylated (→21) and protected to give 8. Transformation of 8 into the bromide 22 (43%) proved difficult due to the facile demethylation of thephosphonate, and was best followed by treatment of the crude product with CH2N2 and 2,2‐dimethoxyporpane. Phosphorylation of 22 yielded 41% of the (dimethoxyphosphoryl)phosphate 23. The conditions of the Arbuzov reaction slowly converted the bromide 23 into the bis(phosphoryl)phosphate 24 (69%), which was then deprotected. The resulting 3 was purified via the ammonium salt and transformed into 3a (72%).
Development of Luminescent Europium(III) and Terbium(III) chelates of 2,2′:6′,2″‐ terpyridine derivatives for protein labelling
Authors: Mukkala Veli‐Matti , Helenius Matti , Hemmilä Ilka , Kankare Jouko , Takalo Harri 
Published: December 2004

AbstractThe synthesis and luminescence properties are reported for 20 different chelates composed of 2,2′:6′,2″‐terpyridine as the energy‐absorbing and donating group, EuIIIand TbIII as the emitting ions, methylenenitrilo(acetic acids) as the stabel chelate‐forming moieties, and isothiocyanato or(4,6‐dichloro‐1,3,5‐triazin‐2‐yl)amino groups as the activated moieties for coupling to biomolecules.
Stabilizing Effect by Geminal Dioxy Substitution and Anomeric Effect in 3,6‐Dihydro‐6‐methoxy‐1,2‐oxathiin 2‐Oxides
Authors: Deguin Brigitte , Vogel Pierre 
Published: December 2004

AbstractThe hetero‐Diels‐Alder addition of SO2 to (E)‐hexa‐1,3‐diene (4) gives first 6‐ethyl‐3,6‐dihydro‐1,2‐oxathiin 2‐oxide (= 6‐ethylsultine) with the Et group occupying a pseudoaxial position, and then the more stable stereoisomer 6 with the Et substituent in a pseudoequatorial position. The SO2 additions to 1‐methoxybuta‐1,3‐diene (7) and to 1‐methoxy‐3‐[(trimethylsilyl)oxy]buta‐1,3‐diene (8) give the 6‐methoxysultines 9 and 10, respectively, with the MeO groups in pseudoaxial positions and which do not equilibrate with sultines having pseudoequatorial MeO substituents (anomeric effect). A lower limit of ΔΔG = 3.9 kcal/mol was evaluated at −60° for the stabilizing effect arising from the geminal vicinity of a MeO and sulfinate moiety in 3,6‐dihydro‐6‐methoxy‐4‐[(trimethylsilyl)oxy]‐1,2‐oxathiin 2‐oxide.
Structural Investigations of 13‐O‐Demethyl‐FK506 and Its Isomers Generated by in vitro Metabolism of FK506 Using Human‐Liver Microsomes
Authors: Schüler Wolfgang , Schmieder P. , Kessler Horst , Christians Uwe , Holze Ines , Sewing Karl‐Friedrich , Schiebel Hans‐Martin 
Published: December 2004

AbstractFK506 is currently under investigation as immunosuppressant after organ transplantation and in immune diseases. The structure of a demethylated metabolite 1 of FK506 isolated after in vitro metabolism by human‐liver microsomes was established using two‐dimensional homo‐ and heteronuclear NMR experiments. The demethylation position was found to be at OC(13) using HMBC spectra. In contrast to FK506, 7 different isomers could be differentiated in COSY, HMBC, and HMQC spectra. The intensity of their signals was 50:18:11:9:6:6 (one isomer could not be quantified). This isomerization may be explained by epimerization at C(10) or alternative formations of the hemiketal ring between C(10) and C(13) or C(9) and C(13), in addition to cis/trans‐isomerism about the amide bond (see Scheme). The structural variation is possible by participation of the OH group at C(13) formed after demethylation and could be derived from HMBC spectra. Chemical exchange evidenced by ROESY spectra proved the rotational isomerism. NMR investigation of the structure of 13‐O‐demethyl‐FK 506 (1) revealed at least seven isomers.
Lacton‐Bildung durch Ringerweiterung unter Alkalimetall‐halogenid‐Katalyse
Authors: Stojanova Diana S. , Milenkov Branimir , Hesse Manfred 
Published: December 2004

Lactone Formation by Ring Enlargement Catalyzed by Alkali‐Metal HalogenidesIn the presence of alkali‐metal or tetraalkylammonium halogenides, 1‐(3′‐hydroxypropyl)‐2‐oxocyclododecane‐1‐carbonitrile (1) underwent ring enlargement to give 12‐cyanopentadecan‐15‐olide (2). In DMF solution, the halogenides catalyzed this reaction, the influence of more basic anions being more pronounced. The rearrangement was strongly influenced by H2O: in the presence of, e.g., 10 equiv. of H2O, it was nearly blocked. On boiling in pure solvent, 1 was rearranged thermally to 2.
Ring‐Transformationen bei der Umsetzung von 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin mit 1‐substituierten Imidazolidin‐2,4,5‐trionen
Authors: Schläpfer‐Dähler Marlise , Heimgartner Heinz 
Published: December 2004

Ring‐Transformations in the Reaction of 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirines with 1‐Substituted Imidazolidine‐2,4,5‐trionesReaction of 1‐substituted imidazolidine‐2,4,5‐triones ( = N‐substituted parabanic acids; 2) and 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) in i‐PrOH or MeCN at room temperature yields 5,6,7,7a‐tetrahydro‐3H‐imidazo[3,4‐a]imidazole‐5,7‐diones 3 (Scheme 1). By 15N‐NMR studies, using (3‐15N)‐2a, it has been shown that only N(1) in (15N)‐3a is labelled and, hence, N(4) stems from 1, e.g. the azirine reacts via cleavage of the N(1)=C(3) bond. In MeCN at room temperature, the azacyclols 3 rearrange slowly to give monocyclic 2H, 5H‐imidazol‐2‐ones 4 (Scheme 3); the 15N‐label in (15N)‐4a is in position 1. Both reactions proceed via deep‐seated skeletal rearrangements, most probably via ring‐expansion/ring‐contraction processes.