摘要:

AbstractRadialenes are alicyclic compounds in which every ring atom is sp2‐hybridized and carries an exocyclic CC double bond. Because of their unusual topology and electronic structures these hydrocarbons have aroused the interest of both preparative chemists and theoreticians. Although considerable progress has been achieved recently, directed and efficient syntheses of these molecules remain a challenge. The study of their chemical behavior offers vast opportunities. Very recently materials scientists have become interested in these unusual compounds in their search for organic conductors and ferromagn

ISSN:0570-0833    

DOI:10.1002/anie.199209313

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the past decade new syntheses and numerous structural determinations have enlivened studies in the still relatively young field of nitrido‐transition‐metal complexes. Aside from the terminal function of the nitrido ligand MN:, this group also occurs as linear μ2‐bridging ligand in symmetric and asymmetric coordination; examples are known with almost right‐angled bridge function; and, finally, it also functions as μ3‐bridging ligand. Accordingly, the fresh impulses given to synthetic chemistry by nitrido complexes are also many‐sided: such complexes are used, inter alia, for the preparation of phosphaniminato and thionitrosyl complexes as well as for the synthesis of metallaheterocycles of the type MN3S2and MN3P2with delocalized π‐systems. In technetium chemistry complexes with terminal nitrido group are employed as radiopharmaceuticals, and, owing to the strongtransinfluence of the MN: group, nitrido complexes of molybdenum are suitable as catalysts in olefin metathesis. Finally, nitrido complexes are also of wide interest in

ISSN:0570-0833    

DOI:10.1002/anie.199209551

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractIn vitro selection is a method that allows the simultaneous screening of very large numbers of nucleic acid molecules for a wide range of properties from binding characteristics to catalytic properties; moreover, the isolation of the very rare functional molecules becomes possible. Binding sites between proteins and nucleic acids, for example, have been evaluated by this methodology in order to gain information about protein/nucleic acid interactions. Structure and function of catalytic RNA (“ribozymes”) has been studied by in vitro selection and has led to new ribozymes with improved catalytic function. Substrate specificity of catalytic RNA has been changed and has led to a ribozyme that cleaves DNA. Other applications include the isolation of nucleic acids that bind specifically to small organic molecules and of RNA molecules that form triple helices with double‐stranded DNA. In this article we discuss the background, design, and results of in vitro genetic experiments, which bridge biochemical/molecular biological and organic chemical approaches to molecular recogn

ISSN:0570-0833    

DOI:10.1002/anie.199209791

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractSince Pasteur's epochal discoveries a century and a half ago, the concept of chirality has continued to play a central role in chemistry and biochemistry. Can chirality be measured? It has long been known that molecular chirality can be given a quantitative meaning through functions specifically parametrized to match the magnitude of pseudoscalar observables. However, chirality is a property that is independent of its physical and chemical manifestations : for a system to be chiral, all that is required is the absence of improper rotations in the symmetry group of the system. This being the case, how can chirality be measured if the “system” is an abstract geometric figure, for example, a scalene triangle in the plane or an asymmetric tetrahedron in three‐dimensional space? How does chirality vary as a function of pure shape? In this review we describe recent efforts designed to answer these and related ques

ISSN:0570-0833    

DOI:10.1002/anie.199209891

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199210081

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199210101

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199210131

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199210171

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199210191

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.199210211

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY