摘要:

Es wird gezeigt, dass bei der Racemisierung der aus natürlichem Colchicin leicht zugänglichenSchiff‐Base1, mit Kaliumhydroxyd in Methanol, neben Benzaldehyd, Benzylamin und (−)‐N‐Desacetylcolchicinsäure (4), auch die beiden tricyclischen Verbindungen2order5erhalten werden. Die Überführung des Ketimins2in das Diketon5gelingt leicht durch saure Hydrolyse. Letzteres kann mit Benzylamin unter den gewählten Racemisierungsbedingungen direkt in (−)‐N‐Desacetyl‐colchicinsäure (4) übergeführt werden. Ein Vergleich der NMR.‐Spektren von5und seiner beiden Methyläther6und7, mit Substanzen der Colchicin‐Reihe, gestattet die Identifizierung von6als 7‐Oxo‐desacetamidoisocolchicin und von7als 7‐Oxo‐desacetamidocolchicin, erlaubt jedoch keine eindeutige Zuordnung der beiden Sauerstoffunktionen im Ring C des Diketons5. Eine solche konnte jedoch durch eine Röntgenanalyse weiter präzisiert werden. Diese ergibt nämlich, dass das Diketon5ein durch Wasserstoffbrücken stabilisiertes Dimeres der Tautomeren5a(Ring C wie Isocolchicei

ISSN:0018-019X    

DOI:10.1002/hlca.19780610402

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractA seven‐step stereoselective synthesis of (±)‐sweroside agluconeO‐methyl ether (16a) was achieved in 27% overall yield from 1, 4‐cyclohexadiene (4) and methyl diformylacetate (5). Secologanin agluconeO‐methyl ether (18a) was then formed from16ain 90% overall yield by a straightforward process. The key step in the synthesis was a [2+2]‐enone‐photoannelation of4and5to form the key intermediate6which possessed the desiredcis‐fused ring configuration, and all the caron atoms needed to complete the synth

ISSN:0018-019X    

DOI:10.1002/hlca.19780610403

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Synthesis of Two Naturally Occurring 10‐Membered Ring Lactones: (±)‐Phoracantholide J and ITwo 10‐membered ring lactones7and11from the metasternal secretion of the eucalypt longicornPhoracantha synonymahave been synthesized by the following method. Reaction of the dilithium derivative of 4‐pentynoic acid (3) with 4‐tetrahydropyranyloxy‐1‐pentylbromide (2), followed by removal of the protecting group and by esterification with diazomethane, gave methyl 9‐hydroxy‐4‐decynoate (4; s.Scheme 1). Partial hydrogenation of the triple bond in4withLindlarpalladium catalyst, followed by saponification lead tocis‐9‐hydroxy‐4‐decenoic acid (6). The 9‐hydroxydecanoic acid (9) was synthesized by addition of methyl magnesium iodide to methyl 8‐formyloctanoate (8) followed by saponification (s.Scheme 2). The hydroxy acids6and9were converted into theS‐(2‐pyridyl) thioesters and cyclized in dilute benzene solution under the influence of silver ions to yield (±)‐phoracantholide J (7) and I

ISSN:0018-019X    

DOI:10.1002/hlca.19780610404

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe use of tobacco mosaic virus (TMV) covalently loaded with hormones or other small molecules for various purposes including receptor detection and isolation is proposed. The basic principle is that ofcooperative affinity interactionsinvolving (large) numbers of artificially introduced sites (e.g.hormones) of the modified virus on the one hand and membrane‐bound sites (e.g.receptors) of a cell or of a cellmembrane particle on the other. In order to test the feasibility of such TMV/hormone conjugates, TMV carrying about 500 molecules of a biologically active α‐melanotropin analogue was synthesized, and characterized by its aspect under the electron microscope, by its infectivity, its melanophore‐stimulating activity, and its reaction with antisera against α‐melanotropin. The observed hormonal activity is in accordance with the idea of cooperative affinity int

ISSN:0018-019X    

DOI:10.1002/hlca.19780610405

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractA (3‐mercapto‐1‐succinyl)‐TMV ϵ‐maleimidohexanoyl‐[1‐asparagine, 5‐valine]‐angiotensin II conjugate was prepared and used for cooperative affinity labeling of bovine adrenal cortex cell membrane vesicles containing angiotensin‐binding sites. The labeling was demonstrated by electron microscopy and by CsCl and sucrose density gradient centrifugation Preliminary evidence for specific binding and for the postulated cooperative affinity int

ISSN:0018-019X    

DOI:10.1002/hlca.19780610406

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe stereochemistry oftrans‐ andcis‐2, 4‐dimethyl‐tetrahydroquinolines,6and7were derived from1H‐NMR. studies. These were converted respectively intotrans‐ andcis‐5, 6‐dihydro‐4, 6‐dimethyl‐4H, 8H‐pyrido [3, 2, 1‐de]phenanthridin‐8‐ones18and20by aPschorrreaction on the anthranilamides10and15. Bromophenanthridones19and21were similarly prepared from bromoanthranilamides12and17. Detailed1H‐NMR. studies on18and20indicated axial disposition of the methyl groups at C(2) in both compounds in contrast to the situation in6and7. This is presumably to avoid adverse CH3CO group interaction of the A (1, 3) type. The severity of this is gauged by the preference of20for a normally forbidding 1, 3‐diaxial orientation of two methyl groups. X‐ray crystallographic studies on19and20con

ISSN:0018-019X    

DOI:10.1002/hlca.19780610407

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

5, 7‐Dihydroxy‐8‐methoxy‐chroman‐4‐one from the Bulb Wax of Eucomis comosaFrom the bulb wax ofEucomis comosa(HOUTT.) WEHRH. (Liliaceae) 5, 7‐dihydroxy‐8‐methoxy‐chroman‐4‐one (1) was isolated. The structure was confirmed by direct comparison with a synthetic specimen.1is the first natural chroman‐4‐one which is unsubstitut

ISSN:0018-019X    

DOI:10.1002/hlca.19780610408

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe title compounds14–16were obtainedviaan intramolecularMannichcondensation by treating11–13with CH2O at RT. The unsaturated ketones14and15were reduced to the allylic alcohols18and19respectively. Ring cleavage of compound18on treatment with 2N HCl gave the substituted aminopropanol20. The allylic alcohols18and19were hydrogenated to22and23respectively. With CH2O, the amino‐alcohol23gave the methano‐naphthoxazocine24, whereas22and23, on heating in polyphosphoric acid (PPA), afforded the naphthazepines25and26respectively. With organolithium compounds, the unsaturated ketones14and16gave the teriary allylic alcohols27–29, which were hydrogenated and dehydrated to the olefins36–40; these were cyclizedviaan intramolecular alkylation to the methanodibenzo‐octahydrocyclooctapyridines41–43. On heating in PPA, the allylic alcohol29was converted into the naphthazepine44. With CH2O, the naphthol49gave the naphthoxazocine50, in equilibrium with the spiro‐naphthalene‐pyrrolidinone51in solution. Finally, in the presence of CH2O, the naphthazepine57afforded the methano‐naphthazepinone58, which, by a 4‐stage degradation, was transformed to

ISSN:0018-019X    

DOI:10.1002/hlca.19780610409

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Anab initiotheoretical study of all fifteen fully staggered conformations of aminodihydroxymethane, CH(OH)2NH2has been performed. Optimization of the CO and CN bond lengths, population analyses and orbital localisation reveal the presence of marked conformation dependent stereoelectronic effects which influence bond lengths and overlap populations. These effects may be parametrized as a function of number and nature of antiperiplanar (app) oriented electronic lone pairs (1p) and polar bonds. In a YCX fragment anapporientation between a lone pair on Y and the CX bond increases the length and weakens the CX bond, shortens and strengthens the CY bond. Thus a CX (X  O, N) bond of CH(OH)2NH2is longest and weakest when: (i) it isappto two vicinal lp's; (ii) the X 1p's are not app to a vicinal polar bond; (iii) the conformation of the molecule has as many axially oriented lp's as possible. Results (i) and (ii) agree with a simple hyperconjugation picture involving interaction between an electronic 1p and anapporiented antibonding bond orbital σ* (CX). Bond properties, relative energies and effects on reactivity of the tetrahedral species are discussed, as well as their relations to experimental results on the cleavage of tetrahedral intermediates and

ISSN:0018-019X    

DOI:10.1002/hlca.19780610410

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractSeveral long chain primary alcohols (saturated, monoolefinic and methyl branched) have been convertedviatheir mesylates into various long chain alkylated aromatic compounds with basic character, and their mass spectra compared. The spectra of 2‐alkylaminopyridines and to some extent those of 3‐alkylaminopyridines exhibit most clearly the structure of the aliphatic chain, allowing the localization of branchings and double bo

ISSN:0018-019X    

DOI:10.1002/hlca.19780610411

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY