摘要:

AbstractDer bei der Bildung einer Metallmonoschicht fliessende Polarisationsstrom setzt sich aus einem durch die Depolarisatoradsorption bedingten, der zeitlichen Änderung der Oberflächenkonzentration des Mez+‐Ions proportionalen Nettostrom und einem depolarisatorunabhängigen Grundstrom zusammen. Es werden Beziehungen zwischen Nettostrom, Elektrodenpotential und Versuchszeit diskutiert, die sich unter der Annahme quasistatischer, diffusionskontrollierter und diffusions‐durchtritts‐kontrollierter Mez+‐Adsorpti

ISSN:0018-019X    

DOI:10.1002/hlca.19700530102

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractUsing only amino acids occurring in proteins it should, in principle, be possible to synthetize peptide molecules capable of complexing metal cations. The approach described in this contribution is to build cages of oxygen atoms that could contain A‐cations of specific diameter (in a manner similar to nigericin, nonactin, valinomycin, and other antibiotics) by binding together face‐to‐face and in the correct distance from one another two homodetic cyclic peptide rings. Using a link that may be formed and broken in a reversible manner (for example oxidativeformationon the outside of the cell membrane and reductive cleavage on the inside), one should even be in a position to construct a model for active, energy‐coupled transport of cations across the cell membrane.An example of this type of synthetic products is the bicyclic peptide S, S′‐bis‐cyclo‐glycyl‐L‐hemicystyl‐glycyl‐glycyl‐L‐prolyl. This compound, the first to contain two homodetic peptide rings bound together, was prepared by stepwise synthesis from the C‐terminal of the S‐protected pentapeptide active ester, glycyl‐(S‐diphenylmethyl)‐L‐cysteyl‐glycyl‐glycyl‐L‐proline‐p‐nitro‐phenyl ester, using active esters of protected amino acids, followed by cyclization of this inter‐mediate, cleavage of the diphenylmethyl protecting group, and final oxidation of the thiol group to the disulfide function. EMF.‐Measurements on membranes bySimonandPiodaaccording to the method ofStefanac&Simon[4] revealed cation specificity in the order: K+>Na+>Li+>Ca++. Optical rotatory dispersion shows that there is a conformational transition during complexation. Circular dichroism points to a 75–90° dihedral angle and right‐handed helicity of the disulfide bond. On this basis the models shown in Fig. 6 were constructed as hypothetical representations of the

ISSN:0018-019X    

DOI:10.1002/hlca.19700530103

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractThe roots ofMargaretta rosea Oliv., subsp.rosea Bullockcontain cardenolides mixed withKeddenegative ester glycosides. 6 Cardenolides were identified by paper chromatography (PC) and thin layer chromatography (TLC). Three of them were free aglycones (uzarigenin (1), corotoxigenin (3) and coroglaucigenin (5), the other three their corresponding 6‐deoxy‐β‐D‐allo‐pyranosides (ascleposide (2), gofruside (4) and frugoside (6). Only two cardenolides (1and5) were isolated in crystalline form. The behaviour of the more polar portion of the glycoside mixture shows thatD‐gluco derivatives of at least 5 of the 6 cardenolides mentioned were also present.TheKedde.negative glycosides were a complicated mixture containing mainly 2,6‐dideoxysugars linked to esterified polyhydroxy‐pregnanes. After mild acid hydrolysis cymarose, oleandrose and digitoxose could be identified by PC and TLC. From the crude aglycone portion only one cristalline genin (M) could be isolated. This was still a mixture, but its main component according to the mass spectrum was a monobenzoyl derivative C28H38O7. ‐ A small amount of cristalline O‐acetyl‐β‐amyrin was isolated from t

ISSN:0018-019X    

DOI:10.1002/hlca.19700530104

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractThe reduction of benzonitrile with sodium borohydride in aqueous methanol in the presence ofRaneynickel as a catalyst provides high yields of benzylamine as compared with the known low yields in the absence ofRaneynickel. An explanation is proposed. Butyronitrile gives similar good yields ofn‐butylamin

ISSN:0018-019X    

DOI:10.1002/hlca.19700530105

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractElectric discharge reactions in the systems PH3+ H2O, PH3+ H2O + NH3and PH3+ H2O + NH3+ CH4have been studied.In the system PH3+ H2O, they produce polyphosphines (insoluble in water) and hypophosphorous, phosphorous and orthophosphoric acids.In the system PH3+ H2O + NH3, besides the above products, hypophosphate, pyrophosphate, polyphosphates and possibly polyhyphosphates are also present.In the system PH3+ H2O + NH3+ CH4, besides all the above inorganic P compounds, organic phosphorus derivatives such as aminoalkyl phosphates and aminoalkanephosphonates are also formed, as well as other non‐phosphorus containing organic products (amino acids, ethanolamine, etc.). The presence of phosphine (or its transformation products), seems to promote condensation reactions in this system since the ratio of amino acids found after hydrolysis (in 6N HCl) to amino acids found before hydrolysis is greater in this system. than in the system (CH4+ H2O+ NH3)iiot containing phosphin

ISSN:0018-019X    

DOI:10.1002/hlca.19700530106

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractThe syntheses of seven tripeptide isomers containingL‐histidine,L‐proline andL‐glutamic acid residues, the same as found in the natural thyrotropin‐releasing hormone (TRH), are reported. In additionL‐pyroglutamyl‐L‐histidyl‐L‐proline and its amide as well as Nα‐acetyl‐L‐glutamyl‐L‐histidyl‐L‐proline are described. Whereas eight peptides are inactive andL‐pyroglutamyl‐L‐histidyl‐L‐proline shows a slight TRH activity,L‐pyroglutamyl‐L‐histidyl‐L‐proline‐amide has the full biological activity of the isolated thyrotropin‐releasing hormone and, at the p

ISSN:0018-019X    

DOI:10.1002/hlca.19700530107

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

Abstract1. The kinetics and the mechanism of the diazo coupling reaction of 2‐diazophenol‐4‐sulphonic acid with 1‐naphthol‐2‐sulphonic acid have been investigated at 0° and ionic strengthI=0.45.2. The pKa‐value of the hydroxyl group in 2‐diazophenol‐4‐sulphonic acid has been determined: pKa=‐ 0.04 ± 0.10. It is the diazonium‐phenolate anion which actually enters into the diazo coupling reaction.3. The reaction is subject to general base catalysis. It is shown that no intermediate is enriched during the reaction at pH 11.3–11.6 which proceeds by a two‐step mechanism wit

ISSN:0018-019X    

DOI:10.1002/hlca.19700530108

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

Abstract1. In 0.1N HCl/H2O,o‐ andp‐nitrobenzenediazonium ions rapidly form a complex with 2‐naphthol‐6, 8‐disulphonic acid anions. Visible and NMR, spectra show that it has the structure of a charge‐transfer complex (π‐complex). The latter is probably an intermediate in the electrophilic aromatic substitution (diazo coupling reaction).2. Diazonium ions form charge‐transfer complexes with naphthalene, 1‐methylnaphthalene, naphthalene‐1‐sulphonic acid, 1‐naphthyl‐methanesulphonic acid and also 2‐naphthol‐1‐sulphonic acid. The equilibrium constants of all these complexes have been determined.3. The stabilisation of diazonium salts by arylsulphonic acids with regard to decomposition is due to charge‐transfer complex formation and not to formation of diazosulphonates as assumed by former investigators. The sulphonic group is not essential for the stabilisation.4. Charge‐transfer complex formation decreases the electrophilicity of the diazonium ion (rate of di

ISSN:0018-019X    

DOI:10.1002/hlca.19700530109

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractCyclisation of 2‐methyl‐3‐phenyl‐but‐3‐en‐anilide (III) with polyphosphoric acid gavecis‐3, 4‐dimethyl‐4‐phenyl‐3, 4‐dihydro‐carbostyril (VII) in 61% yield together with a small amount of 2, 3‐dimethylindenone (VIII), whereas with AlCl3a phenyl group was split off to give 3, 4‐dimethylcarbostyril (VI). The anilide III isomerises tocis‐ andtrans‐2, 3‐dimethyl‐cinnam‐anilide (IV resp. V) under basic conditions.The anilides IV and V gave only small yields of the dihydrocarbostyril VII with polyphosphoric acid. Chlorination of VII in position 3 using PCl5yielded IX which, on splitting out HCl, gave 3‐methylene‐4‐methyl‐4‐phenyl‐3, 4‐dihydro‐carbostyril (X). X was converted totrans‐3, 4‐dimethyl‐4

ISSN:0018-019X    

DOI:10.1002/hlca.19700530110

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractThe ESR.‐spectrum of the radical anion of 1,6‐imino‐[10]annulene (II) has been recorded. Its hyperfine structure reflects the reduced symmetry (Cs) of the molecule, as compared with that (C2v) of 1,6‐methano‐ and 1,6‐oxido‐[10]annulenes (I and III, resp.). The coupling constants of the ring protons in II⊖are intermediate between the corresponding values of I⊖and III⊖. The ESR.‐spectrum of the radical anion of 1,6‐methylimino‐[10]annulene (IV) has also been obtained, but not analysed in detail. The relative stabilities of the radical anions of the four bridged [10]annulenes are: I⊖≫II⊖>III⊖>IV⊖. The main secondary product identified by ESR.‐spectroscopy after the decay of II⊖, III⊖and IV⊖is the naphthalene radical anion. A remarkable exception is IV, when reduced with sodium in 1,2‐dimethoxyethane: in this case the ESR.‐sp

ISSN:0018-019X    

DOI:10.1002/hlca.19700530111

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY