bluuebunny/crossref_metadata_2025 huggingface dataset:
Rationally Designed Inorganic Catalysts for Environmentally Compatible Technologies
Authors: Thomas John Meurig , Zamaraev Kirill Ilyich
Published: December 2003

“Catalysis research is not black magic!”maintain proponents of rational design in catalysis research, in response to the assertion made by R. Schlögl (Angew. Chem. Int. Ed. Chem.1993,32, 381–383) that the development of practical catalysts is still dependent on empirical facts. A number of industrial processes that depend on finely tuned catalysts are cited in support of their premise. In his reply Schlögl restates his thesis and encourages the productive cooperation of “scientific” and “intuitive” approaches to catalyst design.
Complex‐Stabilized Alkynyl and Cycloalkenyl Isocyanides
Authors: Kunz Rainer , Fehlhammer Wolf P.
Published: December 2003

The electrophilic N‐alkynylation of cyano ligands by alkynyliodonium salts provides a convenient route to metal‐coordinated forms (1a–c) of the “interstellar” ethynyl isocyanide 2a (which can only be isolated in trace amounts in the laboratory) and other new members (2b, 2c) of this class of compounds. Alkynyliodonium compounds with Ralkyl react differently: instead of undergoing a 1,2‐alkyl migration, the isocyanovinylidene intermediate is stabilized by insertion into the (alkyl)CH bond.
equation image
FAST NOESY Experiments—An Approach for Fast Structure Determination
Authors: Köck Matthias , Griesinger Christian
Published: December 2003

NOESY spectra can be acquired five to ten times faster with the procedure described here. The reliability of the internuclear distances obtained from these spectra does not suffer. In addition to recording the FAST NOESY spectra, only the relaxation times T1 of the protons must be determined.
Enzymatic Hydrolysis of Hydrophilic Diethyleneglycol and Polyethyleneglycol Esters of Peptides and Glycopeptides by Lipases
Authors: Kunz Horst , Kowalczyk Danuta , Braun Peter , Braum Günther
Published: December 2003

New potentials not only in peptide synthesis are opened up by esters of diethyleneglycol monomethyl ether (MEE esters). Surprisingly, these esters can be hydrolyzed by lipases in neutral media. It was previously assumed that lipases cleave only esters that have both hydrophobic and polar regions, like the natural lipase substrates. During the ester hydrolysis, peptide linkages and common protective groups in peptide and carbohydrate chemistry remain intact. Remarkably, lipases in neutral medium can be used not only for MEE esters but also for polyethyleneglycol esters.
Organic and Organometallic Molecular Magnetic Materials—Designer Magnets
Authors: Miller Joel S. , Epstein Arthur J.
Published: December 2003

Magnets composed of molecular species or polymers and prepared by relatively low‐temperature organic synthetic methodologies are a focus of contemporary materials science research. The anticipated properties of such molecular‐species‐based magnetic materials, particularly in combination with other properties associated with molecules and polymers, may enable their use in future generations of electronic, magnetic, and/or photonic/photronic devices ranging from information storage and magnetic imaging to static and low‐frequency magnetic shielding. A tutorial of typical magnetic behavior of molecular materials is presented. The three distinct models (intramolecular spin coupling through orthogonal orbitals in the same spatial region within a molecule/ion, intermolecular spin coupling through pairwise “configuration interaction” between spin‐containing moieties, and dipole—dipole, through‐space interactions) which enable the design of new molecular‐based magnetic materials are discussed. To achieve the required spin couplings for bulk ferro‐ or ferrimagnetic behavior it is crucial to prepare materials with the necessary primary, secondary, and tertiary structures akin to proteins. Selected results from the worldwide effort aimed at preparing molecular‐based magnetic materials by these mechanisms are described. Some organometallic solids comprised of linear chains of alternating metallocenium donors (D) and cyanocarbon acceptors (A) that is, …︁D•+ A•− D•+ A•−…︁, exhibit cooperative magnetic phenomena. Bulk ferromagnetic behavior was first observed below the critical (Curie) temperature Tc of 4.8 K for [FeIII(C5Me5)2]•+ [TCNE]•− (Me = methyl; TCNE = tetracyanoethylene). Replacement of FeIII with MnIII leads to a ferromagnet with a Tc of 8.8 K in agreement with mean‐field models developed for this class of materials. Replacement with CrIII, however, leads to a ferromagnet with a Tc lowered to 3.65 K which is at variance with this model. Extension to the reaction of a vanadium(o) complex with TCNE leads to the isolation of a magnet with a Tc ≈ 400 K, which exceeds the thermal decomposition temperature of the material. This demonstrates that a magnetic material with a Tc substantially above room temperature is achievable in a molecule/organic/polymeric material. Finally, a new class of one‐dimensional ferrimagnetic materials based on metalloporphins is discussed.
Generation of the Parent Allyl Cation in a Superacid Cryogenic Matrix
Authors: Buzek Peter , von R. Schleyer Paul , Vančik Hrvoj , Mihalic Zlatko , Gauss Jürgen
Published: December 2003

By using cyclopropyl bromide as precursor, the allyl cation C3H can be generated at low temperature in an SbF5 matrix and observed by IR spectroscopy; the experimental IR spectrum agrees well with that computed by ab initio methods. Characterization by 13C NMR spectroscopy failed, but the 13C NMR chemical shifts of this and other allyl cations could be predicted accurately for the first time by the GIAO/MP‐2 method.
Nitrile Imines: From Matrix Characterization to Stable Compounds
Authors: Bertrand Guy , Wentrup Curt
Published: December 2003

The concept of 1,3‐dipolar cycloaddition was developed, starting in the late 1950s, largely by Rolf Huisgen and his students in Munich, and it has led to one of the most versatile methods for the construction of five‐membered ring heterocycles. Although first known only as transient intermediates, nitrile imines have been at the heart of mechanistic studies of this type of cycloaddition reactions. Hundreds of mechanistic papers appeared in 1960s and 1970s; reliable spectroscopic observations were achieved in the early 1980s both at low temperatures and in the gas phase; finally, the first crystalline nitrile imine was reported in 1988. The unusual structures found by X‐ray analyses as well as the facile rearrangements observed experimentally have fostered a new interplay between experiment and theory. The story of nitrile imines, from matrix characterization to stable compounds, nicely illustrates the role that main group elements can play in organic chemistry.
Chiral Aziridines—Their Synthesis and Use in Stereoselective Transformations
Authors: Tanner David
Published: December 2003

The preparation of enantiomerically pure compounds is one of the major areas of organic chemistry. Much emphasis is placed on the elaboration of naturally occurring starting materials and on the development of techniques for enantio‐selective transformations of achiral substrates. In this field, chiral aziridines form an attractive class of compounds, since they are available in enantiomerically pure (or highly enriched) form by a variety of procedures and can be used for asymmetric synthesis in a number of different ways. The chemistry of aziridines is dominated by ring‐opening reactions, the driving force for which is relief of ring strain. By suitable choice of sub‐stituents on the carbon and nitrogen atoms, excellent stereo‐ and regiocontrol can be attained in ring‐opening reactions with a wide variety of nucleophiles, including organometallic reagents; this makes chiral aziridines useful as substrates for the synthesis of important biologically active species including alkaloids, amino acids, and /Mactam antibiotics. Substrate‐controlled diastereo‐selective synthesis is also possible by use of aziridines as removable chiral auxiliaries, while metalation at a ring carbon atom allows aziridines to be used as chiral reagents for asymmetric synthesis. Chiral bisaziridines can act as ligands for transition metals, and applications in the challenging field of enantioselective catalysis can be envisioned. Today, the exclusion of three‐membered carbo‐ and heterocycles from the arsenal of the organic chemist is inconceivable.

H. Heimgartner, Angew. Chem. 1991, 103, 271; Angew. Chem. Int. Ed. Engl. 1991, 30, 238.
Theoretical Definition of a Functional Group and the Molecular Orbital Paradigm
Authors: Bader Richard Frederick William , Popelier Paul Lode Albert , Keith Todd Alan
Published: December 2003

It is the purpose of this review to demonstrate that the empirical classification of the observations of chemistry in terms of the properties assigned to functional groups is a consequence of and is predicted by physics. This is accomplished by showing that the atoms and functional groups of chemistry can be identified with bounded space‐filling objects whose properties are defined by quantum mechanics. The quantum mechanical definition of a group is combined with a new pictorial representation of its form to obtain a unified picture which should make it eminently recognizable to chemists. This picture, when combined with the demonstrated ability of these groups to recover the measured properties of atoms in molecules, is offered as one which meets the expectations a chemist associates with the concept of a functional group. The manner in which this physical definition of a group differs fundamentally from models of functional groups based upon molecular orbital theory is discussed.
Liquid Sulfur Dioxide as a Lewis‐Acidic Solvent for the Alkylation and Alkoxyalkylation of Allylsilanes
Authors: Mayr Herbert , Gorath Gorden , Bauer Bernhard
Published: December 2003

The ionizing power of liquid SO2 is sufficient to induce reactions between acetals or SN1‐active alkyl chlorides with allylsilanes without additional Lewis acids [Eq. (a), X  OCH3, R  PhCH(OCH3), n‐C6H13CH(OCH3), etc.; X  Cl, R  Ph3C, PhMe2C, etc.]. Reactions in liquid SO2 are economical and ecologically advantageous. An additional benefit: they are extremely simple to perform!
equation image
Determination of Reaction Paths for Pentacoordinate Metal Complexes with the Structure Correlation Method
Authors: der Heyde Thomas Auf
Published: December 2003

Crystal structures potentially deliver far more information than is present in the average structural communication—if sufficient structural data on closely related molecules or molecular fragments are available, it may be possible to infer details of geometric changes occurring along certain reaction pathways for the species of interest. This geometric information is extrapolated from an analysis of the similarities between the structures of the fragment in the various crystalline environments, by a method that is now known as structure correlation analysis. Since it was first proposed twenty years ago, the method has been applied to a large variety of chemical systems, but none have received as much attention as the class of five‐coordinate compounds. Comparative analyses of the structures of pentacoordinate complexes have yielded information about the intimate mechanisms of substitution and addition/elimination reactions at tetrahedral and square‐planar complexes, and about intramolecular isomerizations of five‐coordinate compounds. Since its inception, the structure correlation method has gradually adapted techniques from other branches of science, in particular group‐theoretical and multivariate statistical techniques, which have been shown to be enormously powerful tools for probing geometrically complex systems. This review traces the development of the method of structure correlation and the evolution of these co‐opted techniques, with a specific emphasis on studies of five‐coordinate metal complexes.
The Absolute Configuration of (+)‐α‐1,2,3,4,5,6‐Hexachlorocyclohexane, and Its Permeation through the Seal Blood‐Brain Barrier
Authors: Möller Kattrin , Bretzke Cornelia , Hühnerfuss Heinrich , Kallenborn Roland , Kinkel Jochen N. , Kopf Jürgen , Rimkus Gerhard
Published: December 2003

Not the result of enzymatic degradation processes, but of the “preferential permeability” of the blood–brain barrier for (+)‐α‐hexachlorocyclohexane (HCH)—this is the interpretation of the selective accumulation of this enantiomer in seal brain. This conclusion could be drawn only after the α‐HCH isomers were successfully separated on a chiral phase by HPLC. The structure of the (+) enantiomer was determined by X‐ray crystallography, but the structural elements responsible for the selective transfer are still unknown.
Ligands as “Compass Needles”: How Orientations of Alkene, Alkyne, and Alkylidene Ligands Reveal π‐Bonding Features in Tetrahedral Transition Metal Complexes
Authors: Gibson Vernon C.
Published: December 2003

This article outlines the strikingly simple structural pattern to which transition metal complexes containing π‐bonding ligands conform, and suggests simple rules (and ligand classifications) by which the pattern can be understood, and by which individual structures can be rationalized or predicted. Alkenes, alkynes, and alkylidene ligands adopt distinct orientations with respect to other ligands attached to a transition metal because of competition between the various ligand types for metal‐ligand π bonds, whatever the coordination geometry. However, a particularly interesting feature of the tetrahedral geometry is that “single‐faced” π ligands can function as “sensors” of relative ligand π‐donor capacities for all other groups attached to the metal. Here, using simple “triad representations” of tetrahedral complexes, a simple qualitative analysis is presented that builds on calculations by Hoffmann et al. and which allows preferred ligand orientations and relative ligand π‐bond strengths to be deduced for a wide variety of these transition metal complexes.
Sterically Stabilized Vesicles
Authors: Lasic Danilo D.
Published: December 2003

After significant developments in liquid crystal and polymer research, scientists became interested in lyotropic systems containing polymers. These studies investigated, for instance, phase behavior and stability characteristics of suspensions of colloidal particles containing water‐soluble or surface‐adsorbed polymers or block copolymers. The most frequently studied were micelles, latex prticles, and lipid vesicles (liposomes). Liposomes aggregate and fuse in the presence of hydrophilic polymers but their properties were difficult to explain when block copolymers were adsorbed or surfactants with larger polymeric polar heads were inserted into the liposome membrane, because such systems are inherently ill defined. Liposomes containing diacyl surfactants with covalently linked, longer polymer chains display many new properties with very important consequences for both basic and applied research. They stimulate fundamental studies on phase behavior and polymer conformation, scaling laws, colloidal and surface properties, and cell function: applications deal predominantly with liposomes as drug delivery systems. While in basic research theory is currently more advanced than experiment, in medical applications theoretical understanding lags behind experimental achievements. It was discovered only relatively late that liposomes with an appropriate polymer coating are significantly more stable in a biological milieu, a necessary condition for their utility as drug carriers. In particular in medical applications, this practice has rejuvenated the field of anticancer therapy and targeted drug deliviery. All these advances were made possible by an effective and synergistic overlap of many different disciplines.
The Structures of Two Lithium Hydrazides: Is There Electron‐Deficient Bonding?
Authors: Metzler Nils , Nöth Heinrich , Sachdev Hermann
Published: December 2003

For corrigendum see DOI:10.1002/anie.199419881
Ligand Effects on the Chemoselectivity of Transition Metal Catalyzed Reactions of α‐Diazo Carbonyl Compounds
Authors: Padwa Albert , Austin David J.
Published: December 2003

The transition metal catalyzed reaction of α‐diazo carbonyl compounds has found numerous applications in organic synthesis, and its use in either heterocyclic or carbocyclic ring formation is well precedented. Early work in this area made use of insoluble copper catalysts. Although these catalysts are still employed today, their use has decreased significantly with the advent of homogeneous copper catalysts and catalysts based on other metals. The discovery that RhII carboxylates facilitate nitrogen loss from diazo compounds rekindled significant interest in the field of diazo/carbenoid chemistry. Since the realization that RhII carboxylates are superior catalysts for the generation of transient electrophilic metal carbenoids from α‐diazo carbonyl compounds, intramolecular carbenoid addition and insertion reactions have assumed strategic importance in CC bond‐forming reactions in organic synthesis. In contrast to other catalysts that are suitable for carbenoid reactions of diazo compounds, those constructed with the dirhodium(II) framework are most amenable to ligand modifications that, in turn, can influence reaction selectivity. This article will emphasize the chemical behavior of transition metal carbenoid complexes that are greatly affected by the nature of the ligand groups attached to the metal center. Much of the discussion will center on the ability of the dirhodium(II) ligands to determine reaction preference toward different functional groups on the same molecule.
On the Mechanism of Fullerene Formation
Authors: Belz Thilo , Werner Harald , Zemlin Friedrich , Klengler Ursula , Wesemann Michael , Tesche Bernd , Zeitler Elmar , Reller Armin , Schlögl Robert
Published: December 2003

A tangle of threadlike carbon polymers, which do not form two‐dimensional layers, was observed in the transmission electron micrograph of the fullerene black produced in an electric arc. Curved polycyclic layer structures were also formed. Both of the suggested mechanisms for fullerene formation—via small rings, which then condense, or via macrocycles, which then isomerize—thus seem possible. Which of the two dominates depends on the reaction conditions.
Toxicity of Chlorinated Organic Compounds: Effects of the Introduction of Chlorine in Organic Molecules
Authors: Henschler Dietrich
Published: December 2003

Industrial “chlorine chemistry” is accused of polluting the environment with its products and having adverse effects on health. The accusation has been followed by the demand that this ill‐defined branch of chemistry be simply abolished, a demand which has been repeated vigorously now for years. It grew out of misgivings such as those summarized here: 1. A number of polychlorinated cyclic compounds are very stable and highly lipophilic so that they accumulate in the environment and affect mankind through the food chain. Prominent examples are chlorinated pesticides, biphenyls, dibenzodioxins, and dibenzofurans. 2. Many chlorinated compounds are toxic for man and animals. Their genotoxicity (mutagenicity and carcinogenicity) plays a role in risk assessment; more and more chlorinated organic compounds are being shown to be carcinogenic and classified accordingly.

To date there are no comprehensive reviews of the toxicology of chlorinated organic compounds. The present treatise is the result of an attempt to analyze the situation systematically. It makes generalizations as to the kind and degree of toxicity of the most important classes of chlorinated organic compounds and elaborates recommendations for reduction and avoidance of risk during production, occupational handling, and general use.
Unequivocal Partitioning of Crystal Structures, Exemplified by Intermetallic Phases Containing Aluminum
Authors: Häussermann Ulrich , Wengert Steffen , Nesper Reinhard
Published: December 2003

For corrigendum see DOI:10.1002/anie.199502401
Otto Roelen, Pioneer in Industrial Homogeneous Catalysis
Authors: Cornils Boy , Herrmann Wolfgang A. , Rasch Manfred
Published: December 2003

Otto Roelen discovered the oxo synthesis (hydroformylation) in 1938, and despite all the problems created by the war years he was able to explore successfully the fundamental aspects related to its application up to the point of building the first plant. At the same time he laid the groundwork for industrial utilization of homogeneous organometallic catalysts. Almost simultaneously, his contemporary, Walter Hieber, was investigating the basic chemistry of the same catalysts, but with no knowledge whatsoever of their potential application. Hydroformylation today constitutes one of the most important industrial examples of a homogeneous catalytic process.

For corrigendum see DOI:10.1002/anie.199423481
From an Insecticide to Plato's Universe—The Pagodane Route to Dodecahedranes: New Pathways and New Perspectives
Authors: Prinzbach Horst , Weber Klaus
Published: December 2003

The original concept for the synthesis of pentagonal dodecahedranes by the conversion of structurally similar, high‐energy [1.1.1.1]pagodanes relied on catalytic dehydrocyclizations. As a consequence, preparative limitations were preprogrammed. With multiple functionalization of these pagodanes, alternative cyclization methods became viable. These efficient processes allowed access to a multitude of pentagonal and nonpentagonal, carba‐ and heterocyclic dodecahedral skeletons with widely variable substitution patterns. Such a roundabout route provided the (CH)20 basic framework with high efficiency, and long‐lacking thermochemical data could be ascertained calorimetrically. In spite of the unusually pronounced pyramidalization of their olefinic centers, singly and doubly unsaturated dodecahedranes with isolated CC bonds proved to be kinetically quite stable, but underwent dimerization on thermal activation. Dodecahedranes with a higher degree of unsaturation (trienes–decaenes, C20 fullerene?) have been found so far only in the gas phase. Higher fullerenes, including C60, have been identified by mass spectrometry after exposure of halogenated dodecahedranes and pagodanes to a 248‐nm excimer laser. Transannular electron delocalization has been verified for the “slender” pagodane/isopagodane and even for the “spherical” dodecahedrane cages.
Structure of a Mixed Phosphate/Phosphonate Layered Zirconium Compound from Synchrotron X‐Ray Powder Diffraction Data
Authors: Poojary Damodara M. , Zhang Baolong , Clearfield Abraham
Published: December 2003

A big step forward through synchrotron irradiation: The novel phosphatozirconium compound 1 is the structure with the largest organic complexant that has been successfully analyzed by powder diffraction methods. Even the light atoms could be localized and refined. The layers of ZrO6 octahedra and tetrahedra of PO4 and PO3C are linked together by hydrogen bonds, and could therefore be suitable for ion‐exchange and intercalation reactions.
equation image
One Hundred Years Lock‐and‐Key Principle
Authors: Eschenmoser Albert
Published: December 2003

Emil Fischer and supramolecular chemistry: The link between the discoverer of the lock‐and‐key concept and major aspects of this new branch of chemistry is tracked down by A. Eschenmoser in his introductory comments at a symposium in Mainz, Germany, in August 1994. He also comments on the two fundamental selection types—postsynthesis selection and presynthesis selection, or in other words, discovery and design.
100 Years “Schlüssel‐Schloss‐Prinzip”: What Made Emil Fischer Use this Analogy?
Authors: Lichtenthaler Frieder W.
Published: December 2003

Emil Fischer's famous lock‐and‐key analogy (Schlüssel‐Schloss‐Prinzip) for the specifity of enzyme action has provided successive generations of scientists with a mental picture of molecular recognition processes, and thus has shaped to a marked degree the development not only of organic chemistry, but, through its extension to basic live processes, that of biology and medicine as well. The hundredth anniversary of the first use of this most fertile metaphor provides a welcome opportunity not only for highlighting its paramount importance, but for gaining an understanding and appreciation of the creative processes involved, of the constructive reasoning and the thought patterns underlying the fundamental insight. Accordingly, this account attempts to trace how Fischer was led to the lock‐and‐key analogy, based on the state of knowledge and the views prevailing at the time. It reveals that Fischer, who had a pronounced tendency against any sort of theoretical speculation, refrained from taking this metaphor any further, that is to the obvious extensions of what turns the key, and what kind of doors are then opened. Except for a small refinement–the differentiation of main key and special keys to account for the fact that some yeasts can ferment a larger number of hexoses than others—he rather expounded on the scope of the lock‐and‐key picture: “I am far from placing this hypothesis side by side to the established theories of our science, and readily admit, that it can only be thoroughly tested, when we are able to isolate the enzymes in a pure state and thus investigate their configuration.” Others, most notably P. Ehrlich und F. Lillie, by introduction of the concept of stereocomplementarity into medicine and biology, induced the lock‐and‐key analogy to become something of a dogma for explaining principal life processes.
Fine Feathers Make Fine Birds: The Heck Reaction in Modern Garb
Authors: de Meijere Armin , Meyer Frank E.
Published: December 2003

The palladium‐catalyzed coupling of haloarenes and haloalkenes with alkenes, which was discovered by Richard F. Heck in the late sixties, has been a topic of fluctuating interest; however, in the last six years activity in this area has flourished. Careful choice of substrates and skillful tailoring of reaction conditions lead to impressive sequences consisting of even different reaction types that occur not only in a consecutive mode, but also in a single operation. The wellestablished Heck reaction, together with other mechanistically related palladiumcatalyzed transformations with arene, alkene, and alkyne derivatives, opens the door to a tremendous variety of elegant and highly convergent routes to structurally complex molecules. The reaction is not disturbed by heteroatoms such as oxygen and nitrogen (nor by sulfur and phosphorus with some limitations). The spectrum of recent achievements starts with a range of chemoselective and regioselective monocouplings of highly functionalized substrates with unsymmetrical and multisubstituted reaction partners. Other advances include cascade reactions in which three, four, five, and even eight new CC bonds are formed to yield oligofunctional and oligocyclic products with impressive molecular complexity. Even the enantioselective construction of complex natural products with quaternary stereocenters has been achieved with Heck reactions in key steps, as exemplified by the synthesis of crinan, picrotoxinin, and morphine. Today, the Heck reaction is indispensible in the arsenal of synthetic methods available to organic chemists. Certainly it is only a matter of time before the Heck reaction is applied in industrial syntheses.
Dendrimers: From Generations and Functional Groups to Functions
Authors: Issberner Jörg , Moors Rolf , Vögtle Fritz
Published: December 2003

Not just the size but also the multiplication of functions possible through branching is at the forefront of dendrimer chemistry. Owing to the numerous recent key publications by Newkome, Fréchet, Moore, Majoral, Meijer, and others, this Highlight has the dimensions of a minireview.
Enzymes in Organic Synthesis: Application to the Problems of Carbohydrate Recognition (Part 1)
Authors: Wong Chi‐Huey , Halcomb Randall L. , Ichikawa Yoshitaka , Kajimoto Tetsuya
Published: December 2003

Carbohydrates on cell surfaces are information molecules. Although only seven or eight monosaccharides are commonly used as building blocks in mammalian systems, the multifunctionality of these monomers can lead to the assembly of an immense variety of complex structures. Millions of different tetrasaccharide structures, for example, can be constructed from this small number of building blocks, if branching, the stereochemistry of glycosidic linkages, and the modification of hydroxyl and amino groups are taken into consideration. Oligosaccharides therefore represent an effective class of biomolecules that code for a vast amount of information required in various biological recognition processes, such as intercellular communication, signal transduction, cell adhesion, infection, cell differentiation, development and metastasis. The pace of development of pharmaceuticals based on carbohydrates has, however, been slower than that based on other classes of biomolecules. Part of the reason is the lack of technologies for the study of complex carbohydrates. There is no method to amplify oligosaccharides for sequence analysis. There is no machine available for automated synthesis of oligosaccharides. In addition, the possibly poor bioavailability and difficulties in the large‐scale synthesis of carbohydrates have undoubtedly contributed to this slow pace. The enzymatic and chemoenzymatic methods, especially those based on aldolases and glycosyltransferases, described here appear to be useful for the synthesis of mono‐ and oligosaccaharides and related molecules. Further advances in glycobiology will probably lead to the development of new technologies for the study of carbohydrate recognition and for the synthesis of bioactive carbohydrates and mimetics to control the recognition processes.
Sulfoxide‐Stabilized Giant Palladium Clusters in Catalyzed Oxidations
Authors: van Benthem Rolf A. T. M. , Hiemstra Henk , van Leeuwen Piet W. N. M. , Geus John W. , Speckamp W. Nico
Published: December 2003

Transmission electron microscopy has been used to characterize the large solvent‐stabilized palladium clusters with uniform size distribution that are formed in homogeneous PdII‐catalyzed oxidations in dimethyl sulfoxide.
Enzymes in Organic Synthesis: Application to the Problems of Carbohydrate Recognition (Part 2)
Authors: Wong Chi‐Huey , Halcomb Randall L. , Ichikawa Yoshitaka , Kajimoto Tetsuya
Published: December 2003

Recognition of carbohydrates by proteins and nucleic acids is highly specific, but the dissociation constants are relatively high (generally in the mM to high μM range) because of the lack of hydrophobic groups in the carbohydrates. The high specificity of this weak binding often comes from many hydrogen bonds and the coordination of metal ions as bridge between sugars and receptors. Though weak hydrophobic interactions between sugars and proteins have also been identified, the unique shape of a complex carbohydrate under the influence of anomeric and exo anomeric effects (the glycosidic torsion angles are therefore often not flexible but are typically somewhat restricted) and the topographic orientation of the hydroxyl and charged groups contribute most significantly to the recognition process. Studies on the structure–function relationship of a complex carbohydrate therefore require deliberate manipulation of its shape and functional groups, and synthesis of oligosaccharide analogs from modified monosaccharides is often useful to address the problem. The availability of various monosaccharides and their analogs for the synthesis of complex carbohydrates together with the information resulting from structural studies (such a NMR or X‐ray studies on sugar–protein complexes) will certainly provide a basic understanding of complex carbohydrate recognition. An ultimate goal is to develop simple and easy‐to‐make non‐carbohydrate molecules that resemble the active structure involved in carbohydrate–receptor interaction or the transition‐state of an enzyme‐catalyzed transformation (for example, glycosidase or glycosyltransferase reactions) and have the approprite bioavailability to be used to control the carbohydrate function in a specific manner. In part one of this review we described various enzymatic approaches to the synthesis of monosaccharides, analogs, and related structures. We describe in this part enzymatic and chemoenzymatic approaches to the synthesis of oligosaccarides and analogs, including those involved in E‐selectin recognition, and strategies to inhibit glycosidases and glycosyltransferases.
Biosynthesis of Vitamin B1 (Thiamin): An Instance of Biochemical Diversity
Authors: Spenser Ian D. , White Robert L.
Published: December 2003

The elucidation of the biosynthetic pathway to thiamin (Vitamin B1) and its pyrophosphate ester, the important coenzyme “cocarboxylase”, has challenged researchers for many years and continues to do so. The problem of the origin of thiamin can be separated into three parts: the independent pathways to the pyrimidine moiety 4‐amino‐5‐hy‐droxymethyl‐2‐methylpyrimidine and to the thiazole moiety 5‐(2‐hydroxyethyl)‐4‐methylthiazole, and the route from these subunits to the vitamin. The steps in the latter process were fully established some twenty years ago, and it was shown that the route in aerobic bacteria and yeast differs to some extent from that in enteric bacteria. The pathways to the subunits, on the other hand, are still not clarified. Significant differences exist in the routes whereby each of the two subunits, the pyrimidine moiety and the thiazole moiety, originate in bacteria and yeast. One difficulty that delayed progress was that the incorporation patterns of labeled precursors, which were observed by different research groups in different microorganisms, could not be reconciled on the basis of a single pathway to each of the two subunits. It is now accepted that in each case different pathways exist in enteric bacteria and yeast, and that the biosynthesis of Vitamin B1 represents an instance of biochemical diversity. A second factor that added to the difficulties is the minute amount of thiamin synthesized in microbiological cultures (about 15 μg per L culture). This limited the investigations until very recently either to the use of radioactive tracers or to the use of stable isotopes in conjunction with mass spectrometric analysis. It is widely recognized that both methods are associated with pitfalls in the interpretation of results. High‐field 13C NMR, the most powerful modern method available for the determination of incorporation patterns, has only very recently been successfully employed in investigations of thiamin biosynthesis. As a result of the conceptual and experimental problems, even the primary precursors of each of the two relatively simple heterocyclic subunits of thiamin are still not completely established. A search for committed intermediates, the study of the enzymes, and identification of the genes that are involved are the matter of current research.
The Covalent Chemistry of Higher Fullerenes: C70 and Beyond
Authors: Thilgen Carlo , Herrmann Andreas , Diederich François
Published: December 2003

Although higher fullerenes are not yet available in larger amounts, their accessibility, like that of C60, has gradually improved since the early days of fullerence chemistry. Today, many of the soluble larger carben can be purchased either in pure form or as isomeric mixtures. In particular, pure C70 is available in preparative amounts from fullerene soot without the need for tedious separation by high‐performance liquid chromatography; this has had a major impact on the progress of the chemistry of this higher fullerene. Over the last years C70 has been functionalized in many ways, and pure derivatives of even the larger, more complex carbon spheres C76, C84, and recently also C78, have been isolated and characterized. From the collected body of data, first general principles of reactivity and selectivity begin to emerge for these fullerenes, which are all less symmetric than C60. Important information is provided by multiple additions to higher fullerenes, in which certain isomers are formed with a remarkable selectivity that exceedes that observed for C60. A particularly attractive aspect is the chirality of certain allotropes and many derivatives. Although the chirality of fullerene derivatives is not restricted to the larger carbon cages, it was sofar mostly explored through their chemistry and can be related to different structural characteristics. A recently proposed system allows simple specification by a single descriptor of the configuration of chiral fullerenes and fullerene derivatives with a chiral functionalization pattern, including highly branched carbon frameworks with a multitude of possible stereogenic centers.
Catalytic Conversion of Methane into Aromatic Hydrocarbons over Iron Oxide Loaded ZSM‐5 Zeolites
Authors: Weckhuysen Bert M. , Wang Dingjun , Rosynek Michael P. , Lunsford Jack H.
Published: December 2003

Without an oxidant like O2, Fe/H‐ZSM‐5 catalysts are able to convert methane selectively into benzene, toluene, and naphthalene. Methane is activated on iron oxide clusters, and the primary product ethylene undergoes subsequent oligomerization and cyclization reactions on Brønsted acidic sites to form the aromatic products.
Understanding Reactivity Patterns of Radical Cations
Authors: Schmittel Michael , Burghart Armin
Published: December 2003

Over the last 15 years electron transfer activation has emerged as a valuable concept for accomplishing novel reactions and has found widespread application in the selective transformation of increasingly complex molecules. This review presents in a conceptualized manner the vast number of radical cation reactions obtained after chemical, electrochemical, and photoinduced one‐electron oxidation. To familiarize the reader with the concepts of electron transfer a simple and straightforward classification of radical cation reactions has been devised to allow the presentation of a manifold of reactions in a readily understandable manner. Whenever possible, thermochemical and kinetic data are provided.
Altered course of the right testicular artery
Authors: Özdemir M. Bülent , Çelik H. Hamdi , Aldur M. Mustafa
Published: December 2003

An unusual course of the right testicular artery was observed during routine dissection of the posterior abdominal wall of a 60‐year‐old male cadaver. It arose from the abdominal aorta, inferior and posterior to the origin of the right renal artery, and passed posterior to the inferior vena cava and right renal vein; it then arched anterior to the inferior pole of the right kidney and descended anterior to the psoas major muscle, crossing anterior to the genitofemoral nerve, ureter and the proximal part of the external iliac artery. Finally, it passed to the deep inguinal ring and through the inguinal canal to enter the spermatic cord with the other constituents. The left testicular artery arose from the abdominal aorta about 1 cm higher than the right testicular artery and followed a normal course. The embryologic basis and clinical importance of this case are discussed. Clin. Anat. 17:67–69, 2004. © 2003 Wiley‐Liss, Inc.
Micro‐venous valves in the superficial veins of the human lower limb
Authors: Phillips M.N. , Jones G.T. , van Rij A.M. , Zhang M.
Published: December 2003

It is commonly believed that venous valves are not present in veins smaller than 2 mm in diameter. Venous valves, however, have been identified recently in small veins in several regions of the body. This study was undertaken to determine the size distribution of venous valves in the human lower limb micro‐venous circulation. Vascular casts were made from six adult lower limbs and the sampled areas were viewed by scanning electron microscopy. In total, 2,376 valves were identified from 410 cm3 of subcutaneous tissue. The vast majority (94%) of the valves were in veins less than 300 μm in luminal diameter, with 65% of the valves present in venous channels less than 100 μm in luminal diameter. The smallest valves identified were present in venous channels 18 μm in diameter. All valves were bicuspid and often associated with a tributary. Endothelial cells on the vein wall not associated with a valve were fusiform and arranged parallel to the long axis of the vessel, however, the endothelial cells on the luminal and valve sinus surfaces of the cusp were more polyhedral in shape and showed no obvious pattern of alignment. This study provides direct evidence to show that small superficial veins of the human lower limb do contain abundant venous valves and, for the first time, shows that the majority of these valves are present within venous channels less than 100 μm in luminal diameter. Clin. Anat. 17:55–60, 2004. © 2003 Wiley‐Liss, Inc.
Main trunk of the left coronary artery: Anatomic study of the parameters of clinical interest
Authors: Reig J. , Petit M.
Published: December 2003

The objective of this study was to analyze in one single series all the characteristics of the main trunk of the left coronary artery (MT) that may be of use in the diagnosis and treatment of its pathologies. One‐hundred human hearts from autopsies were used. The average age of the sample studied was 63.15 years ± 18.76 (range = 17–94 years). The heart was removed after resection of the costosternum and placed in 10% formaldehyde. With gradual separation and retraction of the myocardial fasciculi the MT was exposed. The length of the MT, the luminal diameter of the MT at its midpoint, and the luminal diameter of the left coronary orifice were measured with a caliper. The angle of division between the anterior interventricular and circumflex branches was also measured, and the number of terminal branches originating from the MT was recorded. In four cases, there was no MT and the anterior interventricular and circumflex branches originated directly from the left aortic sinus. The average length of the MT was 10.8 ± 5.52 mm (range = 2–23 mm); the average diameter at its midpoint was 4.86 ± 0.80 mm; and there was no significant difference noted between the midpoint diameter of the MT and the diameter of the left coronary orifice. The most frequent type of division of the MT was bifurcation (62%); in 38% of cases the MT divided into three or more branches. An average value of 86.7 ± 28.8° was obtained for the angle of division of the terminal branches of the MT (range = 40–165°). There was a positive correlation between the length of the MT and the angle of division of its terminal branches, with the longest MTs having the largest angle of division. Clin. Anat. 17:6–13, 2004. © 2003 Wiley‐Liss, Inc.
Neonatal behaviors associated with ultrasonic vocalizations in mice (mus musculus): A slow‐motion analysis
Authors: Branchi Igor , Santucci Daniela , Puopolo Maria , Alleva Enrico
Published: December 2003

Infant rodents emit ultrasonic vocalizations (USVs) when isolated from the mother and littermates. While USVs reportedly promote maternal behavior, their communicatory role is still controversial. We performed a detailed behavioral characterization in 7‐day‐old CD‐1 Swiss mice to describe (a) behavioral patterns accompanying or immediately preceding or following the USV and (b) how selected USV features are modulated according to the behavioral pattern being performed. The present results represent an ethogram of mouse pup behavior in close temporal proximity to USV, providing further information to evaluate the functional role of USVs in the framework of the mother–offspring relationship. A significant increase of head rising behavior immediately prior to the USV and a behavioral activation displayed by pups in conjunction with it suggest that pups behave in a way that may favor interaction with their mothers. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 44: 37–44, 2004.
Comparative psychology, a new perspective for the 21st century: Up the spiral staircase
Authors: Greenberg Gary , Partridge Ty , Weiss Emily , Pisula Wojciech
Published: December 2003

This article responds to the continuing obituaries for Comparative Psychology. We understand the field to be ageneralpsychology, a way of understanding the origins of all behavior of all species. We outline a methodological and conceptual foundation for comparative psychology to enter the new millennium—with an anagenetic and dynamic systems perspective. We see an important role to be played by comparative psychologists in managing resources, increasing our activity in social and political issues, and transcending our traditional role as the study of animal behavior to one that makes significant contributions to psychology and humanity by studying relationships between animals and changing environments, and by providing a historical perspective on human evolution. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 44: 1–15, 2004.
Diet quality differentially affects breeding effort of Mastomys coucha and M. natalensis: Implications for rodent pests
Authors: Jackson Timothy P. , Van Aarde Rudi J.
Published: December 2003

In this study we compare the reproductive ability of Mastomys natalensis, an agricultural rodent pest and that of the closely related species M. coucha, which has not been ascribed as a pest. We suggest that the ability of M. natalensis to plague, as well as dominate, resource‐limited habitats, may in part be related to its differential breeding response to variation in diet quality. Thus, we examined the reproductive response of M. coucha and M. natalensis mothers to variation in dietary protein intake. Our results demonstrated that typical levels of reproduction extended over a narrower range of dietary protein content for M. coucha than M. natalensis females. Only M. natalensis females bred on 6% protein diets, while on 20% protein diets the reproductive output of M. coucha was lower than on diets containing 10– and 15% protein. M. natalensis responded to low protein diets by reducing litter size and litter mass but not individual pup mass. Thus, providing diet quality improves before parturition, conception under sub‐optimal conditions may not compromise individual pup growth. Furthermore, the ability of M. natalensis to breed under conditions of low diet quality may advance their breeding season compared to species that cannot breed until diet quality improves, allowing M. natalensis to produce additional litters through the season, while more daughters could reproduce during the season of their birth, both factors that are known to contribute to the plaguing tendency of M. natalensis. J. Exp. Zool. 301A:97–108, 2004. © 2004 Wiley‐Liss, Inc.
The labour market effects of globalization in Kenya
Authors: Manda Damiano Kulundu , Sen Kunal
Published: December 2003

Since the 1980s, Kenya has been gradually integrating with the global economy. Using both industry‐level and firm‐level data, the paper examines the effects of globalization on employment and earnings in the Kenyan manufacturing sector. The industry‐level analysis suggests that the overall effect of international trade on manufacturing employment has been negative in the 1990s. The firm‐level analysis indicates that less skilled workers experienced losses in earnings, and that the inequality in earnings between skilled and unskilled workers increased during this period. This suggests that globalization has been associated with adverse labour market outcomes in Kenya. Copyright © 2004 John Wiley & Sons, Ltd.