摘要:

AbstractNumerous orders of arthropods have organs which produce and store defensive substances. The purpose of our studies was to learn more about the chemical composition of these defensive secretions. In this work, we had to forego a priori many of the possibilities of classical organic‐chemical analysis, since some of the insects were difficult to obtain and operation with substantial amounts of material was precluded. However, the defensive substances of various families of Arthropoda were characterized by using modern chemical and physical analytical procedures and our own methods of separation, purification, and enrichment which we developed specifically for this purpos

ISSN:0570-0833    

DOI:10.1002/anie.196400731

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractThe Diels‐Alder adducts of cyclooctatetraene and its derivatives are derived from the bicyclo[4,2,0]octane structure. A kinetic investigation shows that the Diels‐Alder addition of dienophiles to cyclooctatetraene and phenylcyclooctatetraene is preceded by a valence tautomerism equilibrium with bicyclo[4,2,0]octa‐2,4,7‐triene or its 7‐phenyl d

ISSN:0570-0833    

DOI:10.1002/anie.196400831

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractThe isosterism of BN and CC grouping invites comparisons. Recent investigations on substituted aminoboranes R1R2NBR3R4have been attempted in order to evaluate this concept of isosterism. Some of the latest results include evidence for geometric isomerism due to hindered rotation about the BN bond, isolation of isomeric compounds which can be considered as formal analogues of cyclohexanes, and the incorporation of BN groups into aromatic syst

ISSN:0570-0833    

DOI:10.1002/anie.196400861

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractKinetic investigations of the polyreaction of isoprene with organolithium compounds as initiators in n‐heptane as solvent indicate the following sequence of reactions: 1. formation of an adduct between a monomeric form of the organolithium compound and the isoprene and 2. reaction of this adduct with an associated form of the organolithium compound with insertion of the isoprene. The adduct formation is considered to be due to chemisorption, and proof of such chemisorption of a monomer (ethylene) is also demonstrated for a homogeneous Ziegler‐type catalyst. All the reactions can be formulated in the form of cyclic structures with electron‐deficient character. Postulation of such ring structures explains the surprising values obtained for the frequency factors and equilibrium cons

ISSN:0570-0833    

DOI:10.1002/anie.196400931

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractAn optical assay, according to Warburg, for measuring the activity of the enzyme threonine deaminase (threonine → α‐ketobutyrate + NH +4) is described. Some of the properties of the enzyme from yeast have been studied using this assay. Pyridoxal phosphate and pyridoxamine phosphate stabilize the enzyme in the crude extract. Valine, leucine, and isoleucine, and to a lesser extent threonine, NH +4, and K+ protect the enzyme from inactivation when diluted with buffer. The enzyme is inhibited by isoleucine. The extend of the inhibition is dependent on the pH. Thus, in yeast, just as described for Escherichia coli by Umbarger, isoleucine exerts a control on its biosynthesis from threonine by means of a feed‐back mechanism, the extend of the control being related to the consumption of isoleucine in protein synthesis. NH +4represses the biosynthesis of threonine deaminase. This mechanism regulates the threonine deaminase‐catalysed formation of NH +4from threonine in accordance with the NH +4‐requirements

ISSN:0570-0833    

DOI:10.1002/anie.196401011

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractFrom theoretical considerations of the Lewis‐acid character of the organoaluminum compounds AlR3and AlEt2X and of possible combinations of these acids with Lewis bases‐chiefly anions combined with alkali metal ions – by reactions analogous to neutralizations, as well as on the basis of experimental findings, the compounds AlEt2X and the alkali salts MY can be arranged in the order of their tendency to form complexes, in dependence on the nature of X and Y, respectively. – Numerous displacement reactions, in which a stronger complexing group replaces a weaker one, confirm these series. These reactions have led to the formation of new complex compounds of alkylaluminum with the hitherto unknown alkyls of calcium, strontium, and barium, and also to the preparation of [NEt4][AlEt4] and [SbEt4][AlEt4]. Displacement of ethylsodium from NaAIEt4with the aid of NaOR – which is readily complexed – in the presence of benzene provides a simple mode of conversion of alkylaluminum into phenylaluminu

ISSN:0570-0833    

DOI:10.1002/anie.196401071

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractThe abundant experimental material available on the chenistry of the pteridines, as well as the reports given at the Third International Symposium on Pteridines have been reviewed and the most important results of the past ten years incorporated into the present article. Syntheses, reactions, and structural problems are reviewed and natural pteridines and their possible biochemical significance are discussed.

ISSN:0570-0833    

DOI:10.1002/anie.196401141

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196401322

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196401332

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196401342

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY