摘要:

AbstractThis paper presents a cell system in which a photoinduced redox reaction occurs in the cathodic compartment which is coupled to a RuO2‐anode. The light induced oxidation of the ruthenium complex Ru (bipy) 32+by peroxodisulfate is used to illustrate that even under diffuse room light irradiation the photopotentials developed at the Pt‐cathode are sufficient to afford water oxidation in the anode compartment. The oxygen produced at the RuO2‐electrode stands in a stochiometric relation to the current passed through the circuit. Implications for a cell system in which H2and O2are produced in separate compartments under illumination are di

ISSN:0018-019X    

DOI:10.1002/hlca.19800630502

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Abstractα‐Aminoadipoyl‐alanyl‐valine, α‐aminoadipoyl‐serinyl‐valine and α‐aminoadipoyl‐serinyl‐isodehydrovaline have been isolated from the fermentation broth ofP. chrysogenum.The configuration of α‐aminoadipoyl‐serinyl‐valin

ISSN:0018-019X    

DOI:10.1002/hlca.19800630503

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Syntheses of 3‐Hydroxy‐4‐methyl‐3‐cyclobutene‐1,2‐dione (Methylmoniliformin)New routes to 3‐hydroxy‐4‐methyl‐3‐cyclobutene‐1,2‐dione(9), the lowest homologue of the mycotoxine moniliformin are described. A common feature of all pathways is the synthesis of methylcyclobutanes having the oxidation level 6. Precursors, which are easily transformed to9by acid catalyzed hydrolysis, include [2+2]‐cycloadducts ofin situgenerated methyl ketene to tetraethoxyethylene and [2+2]‐photocycloadducts of dichlorovinylenecarbonate with 1,1‐dichloro‐1‐propene. The acid hydrolysis of [2+2]‐cycloadducts of chlorotrifluoroethylene toN, N‐diethyl‐1‐propynylamine yields the diethylamide of9 (=22)in 50% overall yield. In addition, a convenient one‐pot‐two‐steps synthesis of a new electronrich ethylene, 1,1,2‐tri

ISSN:0018-019X    

DOI:10.1002/hlca.19800630504

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Eurekanic Acid, a Degradation Product of Flambamycin and Avilamycin: Determination of the Configuration by X‐Ray Structural Analysis and DegradationThe relative configuration of methylO‐acetyleurekanate(6), obtained by mild methanolysis of avilamycin A(2)and subsequent acetylation, was determined by an X‐ray structural investigation. Methyl dihydroeurekanate(7), similarly obtained from avilamycin C(3)and from reduced avilamycin A methyl ether, was degraded to L‐threonolactone(14)which allowed to determine the chirality of eurekanic

ISSN:0018-019X    

DOI:10.1002/hlca.19800630505

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractPalladium‐catalyzed double carbomethoxylation of theDiels‐Alderadduct of furan and maleic anhydride yielded the methyl all‐exo‐7‐oxanorbornane‐2,3,5,6‐tetracarboxylate(7)which was transformed in three steps into 2,3,5,6‐tetramethylidene‐7‐oxanorbornane(1), a useful synthon. Six isomeric methyl 7‐oxanor‐bornane‐2,3,5,6‐tetracarboxylates(7–12)have been isolated and their1H

ISSN:0018-019X    

DOI:10.1002/hlca.19800630506

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Structure of a O,N‐Keteneacetal: (1RS, 8SR, 10SR, 4(15)Z)‐4‐Ethylidene‐5‐oxa‐3‐azatricyclo [8.4.0.03,8]tetradecaneDie C‐Atome der äthylidenseitenkette der Titelverbindung1sind als C(15) und C(16) (s.Fig. 1) statt systematisch als C(1′) und C(2′) gekennzeichnet. Verbindung1kann auch als kondensiertes heterocyclisches Ringsystem benannt werden: 1‐äthyliden‐perhydro[1,3]oxazixino‐[3,4‐b]isochinolin.Methods for the preparation of a series of model compounds which were required for stereochemical studies are described: the tricyclicO, N‐keteneacetal1, the two diastereomeric bicyclic amino acids7and10(seeScheme 2), and the two diastereomeric conformationally fixed tetrahydro‐1,3‐oxazines (=1,3‐oxazixanes)9and11.An x‐ray analysis of racemic1reveals a quasi‐tetrahedral nitrogen pyramid of theO, N‐ketene acetal grouping, and an almost perfect conformational analogy between theN‐ andC

ISSN:0018-019X    

DOI:10.1002/hlca.19800630507

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Abstract2,3‐Dimethylidenebicyclo [2.1.1]hexane(4)was isolated from direct irradiation (253.7 nm) of 5,6‐dimethylidene‐2‐norbornanone(3). Quenching experiments at 253.7 nm, as well as direct and sensitized irradiations at>300 nm suggested that a high vibrationally excitedS1‐ or aS2‐state is required for the photodecarbonylation of3in contrast with other β, γ‐unsaturated ketones for which α‐cleavage occurs with lower excitation‐energy. The new diene4reacted toward tetracyano‐ethylene (k 39.5°II(1mol−1s−1))=(3.1±0.34) · 10−3) in toluene and (6.2±0.11) · 10−3in benzene only 60 times more slowly than 2,3‐dimethylidenenorbornane(5)andca.850 times as fast as 2,3‐dimethylidene‐syn

ISSN:0018-019X    

DOI:10.1002/hlca.19800630508

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Synthesis of Terminal Acetylenic Sugars Derivatives and Ynuronic Acids Derivatives by Use of aWittigReactionThe method described for the preparation of terminal acetylenic sugars presents two advantages over earlier procedures: no new asymmetric center is created and the chain can be extended by one or more C‐atoms. The method also allows preparation of ynuronic acids. The aldehydosugars derivatives1–7gave in good to excellent yields the correspondinggem‐dibromoenoses8–14from which either the terminal acetylenic sugars derivatives15–21or the ynuronic acids22–24were easily prepared. A few examples of 1,3‐dipolar cycloadditions (leading to28–30) with these acetylenic sugar derivatives are

ISSN:0018-019X    

DOI:10.1002/hlca.19800630509

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe pyrrolate ion(5)is shown to produceN, N′‐dipyrrolyl methane(4)when reacted with dichloromethane under conditions of weak counter‐ion association. 1‐Azoniafulvene ion(13)is suggested to be the key intermediate in this reaction.N, N′‐Dipyrrolyl methane(4)undergoes intramolecular oxidative coupling when treated with butyllithium and Cu(II)chloride, yielding the novel ring system of dipyrrolo [1,2c: 2′, 1′e]‐2H‐imidazole(3). The latter upon reaction with methyl lithium forms theHückel‐aromatic anion2.Solutions of the lithium salt are stable for several days. Reaction of the dianion of 2,2′‐bipyrrole(11)with dichloro‐methane does not produce3, but a pyrrolophane‐type dimer(12)having its two anticoplanarN, N′‐bipyrrolediyl subunits arranged in a double layer and joined

ISSN:0018-019X    

DOI:10.1002/hlca.19800630510

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Abstractdl‐β‐Bulnesene(1)anddl‐1‐epi‐α‐bulnesene(15)have been synthesized starting from the bromide4(Schemes 2and3). In the key step9→10the bonds of the final product were formed by an intramolecular photoaddition. The synthesis was completed by the fragmentation12→14and theWitt

ISSN:0018-019X    

DOI:10.1002/hlca.19800630511

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY