ISSN:0018-019X    

DOI:10.1002/hlca.19710540502

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe chiroptical properties (CD. and ORD.) of four stereoisomeric yohimbanes (1–4) and the corresponding 17‐keto derivatives5–8have been studied. The aromatic and the ketonicCottoneffects have been considered in terms of the appropriate Sector and Octant Rules, respectively. Positively charged nitrogen makes an ‘anti‐octant’ contribution to the ketonicCottoneffect.The chiroptical properties, the NMR. spectra and dehydrogenation reactions with mercuric acetate together indicate the presence of a C/D‐trans‐quinolizidine system in all the compounds studied, except those of thepseudoseries (3and7), in which a C/D‐cis‐quinolizidine system is present. An explanation of the unexpectedly slow dehydrogenation of the 3‐epi‐allocompounds4and8is suggested.Conformational analysis of the results of equilibration experiments on pairs of 3‐epimeric compounds (in both glacial acetic acid at 145° and in K‐t‐butylate at 211°) leads independently to conclusions which agree with those drawn from the physical methods. The great differences between the equilibrium positions of the free bases and the protonated forms are due to the presence in the latter cases of or

ISSN:0018-019X    

DOI:10.1002/hlca.19710540503

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe non‐planar conformations of benzylideneanilines and the almost planar conformations of stilbene and azobenzene are consistently reproduced by a simple model, which takes into account the dependence of π‐electron energy and non‐bonded interactions on molecular conformation. Other aspects of the molecular geometry of benzylideneanilines.(bond angles influence ofp‐substituents) are also d

ISSN:0018-019X    

DOI:10.1002/hlca.19710540504

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractWith a view to rendering ACTH peptides absorbable by the oral route, a series of such peptides with increased lipophilic character was built up. This paper describes the synthesis of eleven derivatives of the ACTH peptide [D‐Ser1, Lys17,18]‐β‐corticotrophin‐(1–19)‐nonadeca‐peptide, containing lipophilic alkyl substituents of different kinds and sizes, bound to the carboxyl of terminal proline either by ester or amide linkage.The unsubstituted peptide [D‐Ser1, Lys17,18]‐β‐corticotrophin‐(1–19)‐nonadecapeptide, and its C‐termina

ISSN:0018-019X    

DOI:10.1002/hlca.19710540505

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

Abstract3, 4‐Diphenyl‐sydnone (1a) and 3‐p‐tolyl‐4‐phenyl‐sydnone (1b) on irradiation with a mercury high‐pressure lamp in pyrex vessels yield 2,4,5‐triphenyl‐ (3a) and 2‐p‐tolyl‐4,5‐diphenyl‐1,2,3‐triazole (3b), respectively. Irradiation of1aand1bin the presence of dimethyl acetylene‐dicarboxylate or indene leads to the formation of the pyrazoles4aand4band the Δ2‐pyrazolines5aand5b, respectively. Reactive intermediates of the photoreaction of1aand1bseem to be the diazirines2aand2b, which open to gi

ISSN:0018-019X    

DOI:10.1002/hlca.19710540506

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractFor the synthesis of analogues ofErythrophleumalkaloids the tricyclic ketones3(trans‐anti‐trans) and5(trans‐anti‐cis) were prepared. Reaction of3and5with triethyl phosphonoacetate led to a mixture ofcis/transcompounds, which could be separated in a preparative scale into the uniform racemic isomers8and9, 22and23, respectively. Transesterification of these compounds gave the corresponding 2‐dimethylamino‐e

ISSN:0018-019X    

DOI:10.1002/hlca.19710540507

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe structures of four synthetic isomeric analogues of cassaine were confirmed by detailed interpretation of their NMR. spectra.

ISSN:0018-019X    

DOI:10.1002/hlca.19710540508

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractA computer program is described, which generates a simplified pictorial representation of computed molecular orbitals. As examples, the highest occupied MO's of the twoC8‐rotamers of the cyclopropylcarbinylcation (C4H7+), of pyridine and of barrelene (bicyclo[2.2.2]octatriene) are give

ISSN:0018-019X    

DOI:10.1002/hlca.19710540509

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractTetrakis‐triphenylphosphine‐platinum(0) catalyses selectively the addition of silane to terminal olefinic double bonds. Neither hydrosilylation of internal double bonds nor isomerisations occur with this catal

ISSN:0018-019X    

DOI:10.1002/hlca.19710540510

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe first and second harmonic CH and CD valence vibrations of alkanes andt‐butyl halides have been measured. A model is proposed for the methyl and methylene groups, which allows the calculation of the anharmonicity constants of every vibrational mode and of the couplings between the modes. The already known large values (−100 to −150 cm−1) for the anharmonicity constants that couple the symmetrical with the asymmetrical modes are confirmed. As compared with lower harmonics combination bands become predominant for the higher ones; they allow the application of a diatomic model to estimate higher harmonics and the energy of d

ISSN:0018-019X    

DOI:10.1002/hlca.19710540511

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY