bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymeric Antitumor Agents on a Molecular and on a Cellular Level?
Authors: Gros Leo , Ringsdorf Helmut , Schupp Hans 
Published: December 2003

Abstract“Chemistry has become a mature science, with all the advantages and handicaps of maturity: harvest is abundant, but many people think future and adventure are to be found elsewhere”[1a]. This holds true—in 1981, the year ofHermann Staudinger's100th birthday—for macromolecular chemistry, too. Where can the polymer chemists seek adventures? Unsolved problems in neighboring fields like medicine and molecular biology attract his zeal. Cancer chemotherapy is such a field. Can the polymer chemist help to solve its problems?Polymers may be pharmacologically active as such. If used as carriers, they may, due to their intrinsic properties, influence body distribution, excretion or cell uptake of the pharmaca they carry. Hence, there is a chance for new ways in therapy, including affinity chemotherapy using synthetic macromolecules.Our own body has a perfect biological system for affinity therapy: immune response to infection selectively attacks foreign cells, It is fascinating to observe what the immune system does to a tumor cell which could not escape immune surveillance (cf. Fig. 14). Can these specific cell‐cell interactions be mimicked? What do we have to learn for an experimental approach to this adventure? Stable membrane and cell models can be synthesized, a first step towards this goal.Macromolecular chemistry is far from being able to offer satisfying solutions for a specific tumor therapy; striving for it, polymer chemists can learn lots of things. In order to do so, they will have to enter neighboring fields and they will have to be willing and able to cooperate.
Cells with Manipulated Functions: New Perspectives for Cell Biology, Medicine, and Technology
Authors: Zimmermann Ulrich , Scheurich Peter , Pilwat Günter , Benz Roland 
Published: December 2003

AbstractExposure to electrical fields can reversibly increase the electrical conductivity and permeability of a cell membrane, which regulates and directs the exchange of materials and information between the cell and its environment. If cell membranes (or artificial lipid membranes) are exposed to a field pulse of high intensity and short duration (ns to μs), local electrical breakdown occurs in them. This electrical breakdown is associated with a large permeability change in the membrane, which is such that substances or particles (up to the size of genes) which cannot normally permeate through the membrane, are able to traverse the membrane into the cell. The original properties of the membrane are restored within μs to min, depending on the experimental conditions and the membrane properties.Electrical breakdown in the zone of contact between the membranes of cells (or lipid vesicles), which have been made to adhere to each other by the action of weak inhomogeneous alternating electrical fields, leads to fusion of these cells with formation of a single cell having new functional characteristics. The electrical fusion method is very mild, and the yield of fused cells is high.The electrically induced fusion and entrapment of membrane‐impermeable substances and genes in cells provide a new tool for the productions of a wide range of cells with manipulated functions, which could be used (or are being used) for the solution of a number of problems in cell biology, medicine and technology.The application of electrical membrane breakdown to clinical diagnostics, the development of cellular carrier systems for the selective transport of drugs to a site of action within the organism and the potential applications of electrically induced fusion for breeding salt‐tolerant crop plants for converting solar energy into ethanol, for synthesizing natural materials and manipulating genes, are described.
N‐Methyl Inversion Barriers in Six‐membered Rings
Authors: Katritzky Alan R. , Patel Ranjan C. , Riddell Frank G. 
Published: December 2003

AbstractConformational conversions of N‐methylazacyclohexanes are of particular interest: they can proceed either via ring‐ or nitrogen‐inversion processes. In both procedures an equatorial N‐methyl group is converted into an axial one, and the converse. It is appropriate to dissociate the energy barriers for N‐methyl inversion into two “half‐barriers” for the steps, axial form → transition state and equatorial form → transition state, and to report both values separately.—In this article the N‐methyl inversion barriers of numerous methylated oligoazacyclohexanes, including species with oxygen or nitrogen atoms in the ring, are discussed.
Structure and Decay of Gaseous Organic Radical Cations Studied by Their Radiative Decay, Exemplified by the 1,3‐Pentadiyne Cation
Authors: Maier John P. 
Published: December 2003

AbstractThe radiative decay of over a hundred open‐shell organic radical cations has now been established. As a result, the spectral structure of such cations in their ground and excited electronic states can be probed with resolutions of the order of ⩽ 1 cm−1. This is achieved by means of emission and laser‐induced fluorescence techniques. The analysis of the emission and excitation spectra provides the vibrational frequencies of many of the totally symmetric fundamentals of the cations in the two electronic states. In order to study the relaxation behavior of these cations under “isolated conditions”, the lifetimes and fluorescence quantum fields can be obtained by means of photoelectron‐photon coincidence measurements. These data yield the radiative and non‐radiative rate constants as a function of the internal energy of the cations. The structural and decay information obtained from each of these techniques is illustrated using the 1,3‐pentadiyne radical cation as example.
Anodic and Cathodic CC‐Bond Formation
Authors: Schäfer Hans J. 
Published: December 2003

AbstractElectrolysis allows the reactivity of a substrate to be changed, or its polarity to be reversed (“redox umpolung”). The carbon skeleton and the functional groups of a synthetic building block can thus be utilized more economically, and at the same time the number of reaction steps in multistage syntheses can be reduced. The tools necessary for an electrolytic process are a cell, a power source, electrodes, and an electrolyte, the latter being chosen in accordance with the reduction or oxidation potential of the substrate. A series of electroanalytical methods provides information on the electrode reaction mechanisms. At the anode, arenes, phenolic ethers, and electron‐rich olefins dimerize via intermediate radical cations. In the Kolbe electrolysis, carboxylic acid anions decarboxylate to form radicals which can couple to forme.g.long chain alkene derivatives having pheromone activity, or add to ole‐fins. At the cathode, activated olefins hydrodimerize via radical anions or, in the presence of appropriate reagents, can be acylated, alkylated, and carboxylated. Pinacols, crossed hydrodimers, and cyclic and arylated compounds are accessible via the cathodically produced radicals, while the formation of strained small rings or the reductive addition of halides to carbonyl compounds takes place through intermediate carbanions.
Optimal Parameters in High Speed Liquid Chromatography (HPLC)
Authors: Halász István , Görlitz Gerhard 
Published: December 2003

AbstractAfter a decade, the first storm of development in high performance liquid chromatography seems to be abating. Providing the stationary phase and eluent are optimized, most routine analytical and semi‐preparative separation problems require columns having between 1000 and 10000 theoretical plates. Commercial apparatus and columns completely satisfy these requirements. For many separation problems the efficiency of the columns on offer is greater than required. Since optimal (not maximal) separation is required with shorter analysis times, the column inlet pressure is increased in order to increase the eluent velocity, while at the same time reducing the column efficiency. The same result can be obtained by using shorter columns and lower pressures. Since inlet pressures of more than 100 bar are seldom required in routine analysis, the term “high pressureliquid chromatography” is a misnomer.—It is probable that difficult separation problems, where several 100 000 theoretical plates are required, will be studied in the next phase of development. It can be shown using nomograms that such problems can be solved within acceptable time limits using inlet pressures of less than 500 bar. Further possible directions of development are indicated.
Stereocontrolled Synthesis of (+)‐Sarracenin via Photochemical Cycloaddition
Authors: Tietze Lutz‐F. , Glüsenkamp Karl‐Heinz , Nakane Masami , Hutchinson C. Richard 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 126. DOI:10.1002/anie.198201260
Methylene Bridging of two Gold Atoms through Double Oxidative Addition of Methylene Dihalides to a Cyclic Ylide Complex
Authors: Jandik Petr , Schubert Ulrich , Schmidbaur Hubert 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1. DOI:10.1002/anie.198200010
The Effect of an Annelated Cyclobutene or Cyclobutadiene Ring on the Norcaradiene—Cycloheptatriene Equilibrium
Authors: Klärner Frank‐Gerrit , Schmidt Eckhart K. G. , Rahman Mahmoud Abdel 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 331. DOI:10.1002/anie.198203310
The Question of the Antiaromaticity of 1,3‐Cyclobutadiene: Thermal Valence Isomerization of the Tricyclo[5.2.0.03,5]nona‐1,6,8‐triene System
Authors: Klärner Frank‐Gerrit , Schmidt Eckhart K. G. , Rahman Mahmoud A. Abdel , Kollmar Herbert 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 338. DOI:10.1002/anie.198203380
C‐Carboxylation of Nitroalkanes with 1‐Ethoxycarbonylbenzotriazole
Authors: Proštenik Mladen V. , Butula Ivan 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 225. DOI:10.1002/anie.198202250
“Bichromocenylene”: A Sandwich with Partly Decoupled Electrons
Authors: Köhler Frank Herwig , Doll Karl Heinz , Prössdorf Wolfram , Müller Jörn 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 283. DOI:10.1002/anie.198202830
Antimony Homologues of Dinitrogen and Azobenzene as Complex Ligands: Preparation and Structure of [SbSb{W(CO)5}3] and [PhSbSbPh{W(CO)5}3]
Authors: Huttner Gottfried , Weber Ute , Sigwarth Beate , Scheidsteger Olaf 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 411. DOI:10.1002/anie.198204110
Geminal Vinyl Diazides: Potential Precursors of Functionalized Alkylidenecarbenes; Synthesis and Reactions of 3,3‐Diazido‐2‐cyanoacrylic Acid Methyl Ester
Authors: Carrié Robert , Danion Daniel , Ackermann Erich , Saalfrank Rolf W. 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 660. DOI:10.1002/anie.198206600
Substituent‐Dependent Competition between 1,5‐ and 3,5‐Cyclization in Vinly Azides; 4H‐Triazoles from 3,3‐Diazido‐2‐cyanoacrylic Acid Methyl Ester and Primary Amines
Authors: Carrié Robert , Danion Daniel , Ackermann Erich , Saalfrank Rolf W. 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 668. DOI:10.1002/anie.198206680
A Bishomocyclooctatetraene Dianion
Authors: Huber Walter , Müllen Klaus , Busch Ralf , Grimme Wolfram , Heinze Jürgen 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 566. DOI:10.1002/anie.198205660
N‐(Pentafluoro‐λ6‐sulfanyl)iminosulfur tetrafluoride by reaction of thiazyl trifluoride with fluorine
Authors: Waterfeld Alfred , Mews Rüdiger 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 827. DOI:10.1002/anie.198208270
Triphosphaalkanes R2P—CH2—PR—CH2—PR2 (R = Cl, CH3)
Authors: Hietkamp Sibbele , Sommer Herbert , Stelzer Othmar 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 817. DOI:10.1002/anie.198208170
Reaction of 4‐Methyl‐1,2,4‐triazoline‐3,5‐dione with Fulvenes: A 1,3‐Sigmatropic Shift involving a Dipolar Intermediate
Authors: Olsen Henrik 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 893. DOI:10.1002/anie.198208930
A Mononuclear Hydroxoiron(III) Complex of a Porphinoid Ligand System with Bifacial Steric Hindrance
Authors: Buchler Johann W. , Lay K. Lam , Lee Young J. , Scheidt W. Robert 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 996. DOI:10.1002/anie.198209960
Monomolecular Membranes from Synthetic Macrotetrolides
Authors: Fuhrhop Jügen‐Hinrich , Ellermann Karin , David Hans Herrmann , Mathieu Joachim 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 980. DOI:10.1002/anie.198209800
Bis(dinitrogen)‐ and Diethylene‐molybdenum(0) Complexes
Authors: Carmona Ernesto , Marín José M. , Poveda Manuel L. , Atwood Jerry L. , Rogers Robin D. , Wilkinson Geoffrey 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1116. DOI:10.1002/anie.198211160
CαCα‐Coupling of Two {(CO)5CrCNEt2} Fragments by Reductive Dimerization of a Cationic Carbyne Complex
Authors: Fischer Ernst Otto , Wittmann Dieter , Himmelreich Dieter , Neugebauer Dietmar 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1036. DOI:10.1002/anie.198210360
4‐Oxo‐2‐cyclopentenyl Acetate—A Synthetic Intermediate
Authors: Harre Michael , Raddatz Peter , Walenta Rainer , Winterfeldt Ekkehard 
Published: December 2003

AbstractThe present day importance of cyclopentenone derivatives in preparative organic chemistry and especially in natural product chemistry is demonstrated by the stereoselective synthesis of substituted and annelated cyclopentanone derivatives. It has been found that 4‐oxo‐2‐cyclopentenyl acetate (“4‐acetoxy‐2‐cyclopenten‐1‐one”) can be used in many reactions as a substitute for cyclopentadienone, which is itself too unstable to be isolated. A large variety of polyfunctionalized cyclopentanone derivatives, as well as carbocyclic and heterocyclic annelation products, can thus be obtained in a simple way. Various stereoselective transformations of the adducts so formed are presented, using the total synthesis of brefeldin A—a typical natural product of this series—as example. Several methods for the synthesis of 4‐oxo‐2‐cyclopentenyl acetate are outlined and, in addition, the more important methods for the enantioselective synthesis of other 4‐substituted 2‐cyclopenten‐1‐ones are discussed.
Chain and Ring Phosphorus Compounds—Analogies between Phosphorus and Carbon Chemistry
Authors: Baudler Marianne 
Published: December 2003

AbstractUp to about 15 years ago compounds with a skeleton of phosphorus chains or rings were regarded as “exotic” in the field of nonmetal chemistry. Aside from a number of examples of molecules with two P atoms directly bonded to each other and a few sporadically discovered monocyclic ring compounds, only solids of undefined composition and structure were known. Since then the state of our knowledge in this sector has made considerable progress: between PH3 and its derivatives on the one hand, and the high‐molecular modifications of elementary phosphorus on the other, an unexpected variety of well defined compounds have been discovered, showing many similarities to the analogous compounds of carbon. However, surprises can still occur even with “small” phosphorus‐containing molecules, as shown by the likewise recently discovered field of phosphorus three‐membered ring compounds.
[Mo4(NO)4(S2)6O]2−, A Novel Highly Symmetric Polynuclear Complex with Two “Handle‐Shaped” and Four “Roof‐Shaped” Coordinated S Bridging Ligands at a Tetragonal Mo4 Disphenoid
Authors: Müller Achim , Eltzner Werner , Bögge Hartmut , Sarkar Sabyachi 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1167. DOI:10.1002/anie.198211670
S6N5O4, A Compound with Separately Stacked Cyclic Radical Cations S3N and Cyclic Anions S3N3O
Authors: Roesky Herbert W. , Witt Michael , Schimkowiak Jürgen , Schmidt Martin , Noltemeyer Mathias , Sheldrick George M. 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1273. DOI:10.1002/anie.198212730
Basic Principles of the CIP‐System and Proposals for a Revision
Authors: Prelog Vladlmir , Helmchen Günter 
Published: December 2003

Abstract“From Configurational Notation of Stereoisomers to the Conceptual Basis of Stereochemistry” is the title of a lecture [V. Prelog, ACS Symp. Ser. No. 12 (1975) 179] in which the chronologically and alphabetically third member of the CIP‐triumvirate discusses the history of the CIP‐system. The experience accumulated in the meantime, particularly the efforts to teach computers to use the system as described in 1966 by Cahn, Ingold and Prelog, has shown that certain of its aspects must be more strictly formulated and others modified. Questions dealing with stereoisomers (and stereotopicity), which previously have been treated predominantly in a pragmatic manner, are now discussed in a systematic way.
Induction of Asymmetry by Amino Acids
Authors: Drauz Karlheinz , Kleeman Axel , Martens Jürgen 
Published: December 2003

AbstractSince the stereoisomers of molecules with one or more asymmetric centers often exhibit different biological activities (e.g. thalidomide, pheromones), stereoselective synthesis as a method of preparative chemistry is rapidly attaining importance. Of the numerous drugs prepared by total synthesis that contain at least one asymmetric center, only about 20% have so far been used in sterically pure form. Amino acids constitute the greatest “chiral pool” of compounds whose enantiomers can be obtained commercially in large amounts; they are gradually being used more and more frequently as auxiliary agents or educts in asymmetric syntheses.
Synthesis and Valence Isomerization of 2,7‐Dihydro‐2,2,7,7‐tetramethylpyrene
Authors: Ackermann Jean , Angliker Herbert , Hasler Erich , Wirz Jakob 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1429. DOI:10.1002/anie.198214290
Determination of the Conformation of Acyclic α,β‐Unsaturated Aldehydes and Ketones from Their Infrared and Raman Spectra—Results and Limitations of Model Calculations
Authors: Oelichmann Hans‐Joachim , Bougeard Daniel , Schrader Bernhard 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1404. DOI:10.1002/anie.198214040
Synthetic Membranes—Preparation, Structure, and Application
Authors: Pusch Wolfgang , Walch Axel 
Published: December 2003

AbstractAfter a long period of dormancy, membrane separation processes have begun to emerge as technically significant and commercially relevant unit operations. Prior to the mid‐sixties, synthetic membranes were employed for those few specialized laboratory applications which could tolerate low permeability and poor selectivity or in electrochemical applications excluding, e. g., batteries, fuel cells, chloride‐alkali electrolysis, where marginal chemical stability remained a severe limitation. Within the framework of a broad R & D program started in the US in the mid‐fifties and devoted to the production of fresh water from brackish and seawater, developments of more suitable membranes arose out of the application of the principles of physical chemistry, modern polymer chemistry (especially surface or interfacial polymerization and polycondensation technology), and electron microscopy. In particular, it was learned that asymmetric membrane structures comprise a very thin consolidated barrier layer (5000 Å or less for membranes with economically practical filtration rates) supported by an integral but less dense substrate which does not participate in the transport process. Later and after much effort, composite membranes were developed in which the salt‐rejecting skin (still only 5000 Å thick) was placed atop a supporting matrix formed from a more chemically and mechanically stable polymer.—The main desalination research effort led to several spin‐off developments in related membrane fields, e.g. the successful preparation and commercialization of ultrafiltration technology in the automobile, food, and chemical industries. Also, ion‐exchange membranes prepared from perfluorinated polymers offered the electrochemical industry much better chemical stability than the earlier phenolic‐resin‐based ion‐exchange membranes.—Current efforts are aimed at the improved selectivity and stability required for very specific separation processes (e.g. separation of heavy metal salts from waste water or selective enrichment of gases). In the future, the mechanisms of biological processes will have to be exploited for successful development of synthetic membranes suitable for more sophisticated separations.
Vacuum Dynamic Gas Phase/Solid‐Phase Reactions: N‐Chlorination of Primary Amines and α‐Elimination of the Resulting Chloramines; Synthesis of Reactive (E)‐ and (Z)‐Aldimines
Authors: Guillemin Jean‐Claude , Denis Jean‐Marc 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1515. DOI:10.1002/anie.198215150
A Ring Building‐Up Synthesis of N‐Glycosides: Dehydrogenation of Glycosyltriazeno‐1H‐pyrazoles
Authors: Ege Günter , Gilbert Karlheinz , Heck Reinhard 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1508. DOI:10.1002/anie.198215080
Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)
Authors: Hoffmann Roald 
Published: December 2003

AbstractRobert B. Woodward, a supreme patterner of chaos, was one of my teachers. I dedicate this lecture to him, for it is our collaboration on orbital symmetry conservation, the electronic factors which govern the course of chemical reactions, which is recognized by half of the 1981 Nobel Prize in Chemistry. From Woodward I learned much: the significance of the experimental stimulus to theory, the craft of constructing explanations, and the importance of asethetics in science. I will try to show you how these characteristics of chemical theory may be applied to the construction of conceptual bridges between inorganic and organic chemistry.