Determination of the Stereochemistry of Substituted 4-(Sulfo- and Sulfonamidoalkyl) piperidine-2-carboxylic Acids with H NMR,COSY, and Homonuclear NOE Experiments

Basically the aim of this work is to define the accurate configuration of 4-substituted (sulfo- and sulfonamidoalkyl)piperidine-2-carboxylic acids which have been conceived as potential NMDA antagonists. H NMR and 2D NMR (COSY) followed by qualitative Homonuclear NOE have led to the assignement of the (±) cis and (±) trans configuration of the whole family's compounds.     

Chromatographic Separation and Mass Spectrometric Analysis of Bacterial Cell Wall Synthesizing Enzyme Complexes

ABSTRACT

Penicillin-binding proteins (PBPs) were shown to associate non-covalently with many other morphogene proteins (MGPs). Specific associations were assigned. The PBPs were labeled with spectroscopic/fluorescence (F/S) groups in the form of dansylated β-lactam probes. Competitive β-lactam binding of non-denatured PBP/MGP complexes led to characteristic patterns of F/S labeling by the probes. The salt-bridge specific reagent, ethanedinitrile, covalently linked various MGPs to the F/S labeled PBPs. Proteolysis of chromatographically purified F/S labeled fractions gave sets of peptides analyzed by MALDI-TOF to give MH data. Peptide mass-fingerprinting analysis revealed that covalent linkage occurred with other MGPs and not with non-MGP proteins of ～3400 proteins in the SWISS-PROT r33 data base for E. coli K-12.     

Stereochemie von Metallocenen, 44. Mitt.: Darstellung und Konfiguration von Tricarbonylchrom-Komplexen der Diphensäure und ihrer Derivate 3. Mitt. über Biphenyl-tricarbonylchrom-Komplexe

Mono and bis tricarbonylchromium complexes of diphenic acid and its monomethylester (3, 4, 15, 16) were prepared by treating the corresponding methyl and trimethylsilylesters (e.g.12) with Cr(CO)₆ and subsequent hydrolysis of the complexes1, 2, 13, and14. Diborane reduction of the carboxylic acids gave hydroxymethyl derivatives, amongst which the diol8 a is a key substance for configurational analyses by¹H-nmr and ir spectroscopy. In this context monosubstituted biphenyl complexes (9–11) were prepared as reference substances. Complexation of the lactone23 of 2-hydroxymethyl biphenyl-2-carboxylic acid afforded (besides two isomeric monocomplexes) mainly thetrans-biscomplex26 b, a key intermediate for ring opening and cyclization reactions.The stereochemical possibilities of the biscomplexes are discussed. The racemate configuration is preliminarily assigned to diphenic acid bistricarbonylchromium and its derivatives.

2. Mitt.; 1. Mitt.:K. Schlögl undR. Schölm, Mh. Chem.109, 1227 (1978).     

氰根桥连配合物的结构与磁性研究

由于氰根配体能够桥连相同或不同的金属离子形成多种多样的桥连结构而引起了人们的广泛关注。尤其在分子磁体领域，此类配合物的优异磁性质吸引了许多化学家开展了这方面的研究。本文综述了近年来国内外相关研究进展，介绍了一些具有代表性的实例，并进一步展望了今后的研究和发展方向。     

Ethylene polymerization by novel phenylenedimethylene bridged homobinuclear titanocene/MAO systems

Reaction of (o, m, p) disodium(phenylenedimethylene)dicyclopentadienide C₆H₄(CH₂C₅H₄Na)₂ with 2 equiv of (MeCp)TiCl₃ yields the phenylenedimethylene bridged binuclear titanocenes complexes [(MeC₅H₄)TiCl₂](C₅H₄CH₂C₆H₄CH₂C₅H₄)[(MeC₅H₄)TiCl₂] (3, 4, 5) in high yield, which were characterized by ¹H NMR and elemental analysis. They were used successfully as efficient catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO). The catalytic activities of 4 and 5 are somewhat higher than that of 3 and the molecular weight distributions (MWD = 4.8-6.2) of the polymers generated from the bimetallic catalytic systems are obviously higher than that obtained by conventional Cp₂TiCl₂.     

Recent Advances in the Synthesis of N‐Heteroatom Substituted Imido Complexes Containing a Nitrido Bridge [M=N—E] (M = Group 4, 5 and 6 Metal,E = B,Si, Ge,P, S)

The focus of the current report lies on recent developments of synthetic methods applied to the synthesis of some high‐valent complexes containing the nitrido functionality [N]^3— as a link between a group 4, 5 or 6 transition metal and a main group element E (E = B, Si, Ge, P, S). Emphasis is put on results, that have been obtained within the “Schwerpunktprogramm “Nitridobrücken” funded by the Deutsche Forschungsgemeinschaft. The synthetic methods include condensation reactions of reactive chloro and oxo complexes (M = V, Nb, Ta, Cr, Mo, W) with silylamines, sulfonylamides, with N‐silyl and N‐lithio iminophosphoranes, furthermore methatesis reactions of oxo complexes with N‐sulfonyl sulfinyl amides (M = V, Cr, Mo, W), the oxidative addition of element azides to d² metal centers (M = V, W), and finally transamination reactions of N‐H iminophosphoranes with amido complexes (M = Ti, Sm).     

Polynuclear nitrosyl carbonyl ReI complexes with thiolate and sulfide bridges

The reaction of the complex Re₂(CO)₄(NO)₂Cl₄ (1) with NaSCMe₃ (2) (in THF or MeCN, 65–80°C, 24 h) was studied at different ratios of the reagents (from 1∶2 to 1∶6). At the reagent ratio of 1∶2, the binuclear complex Re₂(CO)₄(NO)₂Cl₂(μ-SCMe₃)₂ (3) was obtained as a mixture ofsyn andanti isomers (3a and3b, respectively) containing Re₂S₂ fragments with different structures (the butterfly-like structure in3a and the planar fragment in3b). When the initials were taken in ratios from 1∶4 to 1∶6, two compounds were isolated: the binuclear complex Re₂(CO)₄(NO)₂(μ-SCMe₃)₂(μ-S)4 (cocrystallized as a mixture ofsyn andanti isomers,4a and4b, respectively) and the triangular cluster Re₃(CO)₃(NO)₃(μ-SCMe₃((μ₃-S)(μ₃-Cl) (5). Apparently, complex4 is formed in the course of isolation as a result of elimination of SR₂ from the unstable tetrathiolate dimer Re₂(CO)₄(NO)₂(SCMe₃)₂(μ-SCMe₃)₂ (6). Cluster5 is the product of the reaction between compounds3 and4. Products of interaction of compound6 with silica gel upon column chromatography of the reaction mixture were studied. Four complexes containing hydroxy and oxo bridging groups, (CO)₂(NO)Re(μ-SCMe₃)₂(μ-OH)Re(SCMe₃)(CO)(NO) (7), (CO)₃(NO)₃RE₃(μ-SCMe₃)₃(μ₃-SCME₃)(μ₃-O) (8), [(CO)₂(NO)₂Re₂(SCMe₃)₂(μ-SCMe₃)₂(μ-OH)][Na(THF)(Et₂O)] (9), and [(CO)₂(NO)₂Re₂(SCMe₃)₂(μ-SCMe₃)₂(μ-OH)]₂−[Na(H₂O)₆][H₅O₂] (10), were isolated. The structures of complexes3, 4, 5, 7, 8, 9, and10 were established by X-ray diffraction study. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1030–1044, May, 1998.     

Theoretical Studies of Inorganic Compounds. 27 Quantum Chemical Investigations of Transition Metal Nitrido Complexes with a TM‐N‐E Linkage (E = Main Group Element)

It is reported about quantum chemical DFT calculations of various transition metal (TM) nitrido complexes which contain a TM‐N‐E linkage. The goal is to elucidate the nature of the TM‐N‐E bonding situation with modern quantum chemical tools. Five comparative investigations have been carried out. (a) Comparison of the N‐donor ability in the nitrido complexes Cl₃W‐N‐ECl_n where ECl_n = NaCl, MgCl₂, AlCl₃. (b) Comparative analysis of the bonding situation in Cl₄W‐N‐X where X = Na, MgCl, AlCl₂, SiCl₃, PCl₂, SCl, Cl. (c) Comparison of the structure and bonding in Cl₅W‐NPH₃, Cl₅W‐OPH₃⁺, Cl₄W‐(NPH₃)(OPH₃)⁺. (d) Comparative analysis of the bonding situation in Cl₅Ta‐OPH₃, Cl₅W‐NPH₃, Cl₅Re‐CPH₃. (e) Energy decomposition analysis of the bonding of the isolobal ligands NPH₃ and Cp with WCl₅.     

From [M≡N] and [M—N—E] Complexes to Models for Metal Oxidoreductases

The article reviews results of research that was initially aiming at complexes containing new and unusual [M—N—E] element combinations (M = transition metal, E = main group element), but soon turned into studies on model complexes for metal enzymes such as nitrogenases, hydrogenases or CO dehydrogenases, because several of the resulting [M—N—E] complexes exhibited reactions relevant to these enzymes. It could be shown that alkylation of transition metal thiolate nitride complexes gives alkylimido complexes when bulky and mild alkylation reagents, e.g. Ph₃C⁺, are used. Hydride addition to [Ru(NO)(py^buS₄)]⁺ yielded [Ru(HNO)(py^buS₄)], which contains a bifurcated [M—N(X, Y)] bridge. The diazene complex [μ‐N₂H₂{Ru(PCy₃)(S₄)}₂] undergoes H⁺/D⁺ and H⁺/D₂ exchange reactions that enabled to rationalize the until then inexplicable ‘N₂ dependent HD formation’ catalyzed by nitrogenases. Out of a larger number of [Ni(NE)(S₃)] complexes, the compound [Ni(NHPPr₃)(S₃)] proved capable to model structure and reactivity features of [NiFe] hydrogenases. The [Ni(L)(S₃)] complexes with L = N₃^— and N(SiMe₃)₂^— exhibit extremely high reactivity towards CO, CO₂ and SO₂. The reactions lead to NCO^—, CN^— and NSO^— complexes and bear potential relevance for carbon monoxide dehydrogenase reactions.     

Supramolecular porphyrin assemblies through amidinium-carboxylate salt bridges and fast intra-ensemble excited energy transfer

Well‐defined supramolecular assemblies of Zn and free‐base porphyrins are constructed through the formation of amidinium–carboxylate salt bridges. A one‐to‐one donor–acceptor pair and a four‐to‐one antenna‐type assembly are investigated. The steady‐state and time‐resolved fluorescence measurements unequivocally showed that efficient singlet–singlet excited energy transfer from the Zn–porphyrin complex to the free‐base porphyrin takes place in these assemblies. Indeed, the observed energy‐transfer rates in both types of assemblies are much faster than those the Förster mechanism would suggest, implying the involvement of an intermolecular through‐bond mechanism.