摘要:

AbstractThe covalently bound carbohydrate moiety in glycoproteins can stabilize the protein molecule intramolecularly, or it may have an intermolecular function as receptor in biological recognition. The discovery of these biological phenomena has led to a renaissance of the chemistry and biochemistry of carbohydrates. BothN‐glycoproteins as well asO‐glycoproteins contain special, invariant oligosaccharide chains in the protein‐binding region, which occur again in all glycoproteins, and are described as the “core regions.” This review describes the various methods of oligosaccharide synthesis that may be used to arrive at the basic core structures by chemical means. Methods of oligosaccharide synthesis have improved so much that it is possible to synthesize complex lactosamine‐type structures, and “bisected”‐type structures up to nona‐ and undecasaccharides respectively. Oligosaccharide chains are considerably less flexible than peptide chains. Using modern methods of NMR spectroscopy, their preferred solution conformation can readily be determined. In the case of one branched octasaccharide, a comparison of the conformations in solution and in the crystal is possible. Oligosaccharides may be linked to the amide group of an asparagine, or to the hydroxyl groups of serine or threonine. By using suitable protecting groups, the glycosyl amino acids obtained can be extended with further amino acids at theN‐ orC‐terminus, thus arriving at the desired glycopeptide sequences. In the linkage region, glycopeptides prefer certain conformations. Future research into glycoprotein functions may involve the synthesis and biochemical study of modifie

ISSN:0570-0833    

DOI:10.1002/anie.199008233

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA variety of transition‐metal cluster structures are found within the extended arrays of solidstate materials. Although molecular analogues of some of these clusters have been synthesized—either by the self‐assembly of smaller components in solution or by the excision of intact cluster units directly from the solid‐state phase—molecular chemists are often unaware of the rich structural variety expressed in solid‐state clusters. This article presents these diverse structural types as potential targets for synthetic molecular chemistry by describing fundamental solid‐state cluster topologies in transition‐metal chalcogenide/halide phases and detailing cases where molecular counterparts have been prepared. Particular emphasis is placed on cluster excision as a method of molecular cl

ISSN:0570-0833    

DOI:10.1002/anie.199008401

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe design, synthesis, characterization, and understanding of new molecular and macro‐molecular substances with “metal‐like” electrical properties represents an active research area at the interface of chemistry, physics, and materials science. An important, long‐range goal in this field of “materials by design” is to construct supermolecular assemblies which exhibit preordained collective phenomena by virtue of “engineered” interactions between molecular building blocks. In this review, such a class of designed materials is discussed which, in addition, bridges the gap between molecular and polymeric conductors: assemblies of electrically conductive metallomacrocycles. It is seen that efforts to rationally construct stacked metal‐like molecular arrays lead logically to structure‐enforced macromolecular assemblies of covalently linked molecular subunits. Typical building blocks are robust, chemically versatile metallophthalocyanines. The electrical optical, and magnetic properties of these metallomacrocyclic assemblies and the fragments thereof, provide fundamental information on the connections between local atomic‐scale architecture, electronic structure, and the macroscopic collective prope

ISSN:0570-0833    

DOI:10.1002/anie.199008571

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199008801

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199008821

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199008841

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199008861

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199008881

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199008901

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199008911

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY