摘要:

AbstractSix iridoid glucosides have been isolated fromGlobularia cordifoliaby the combination of open column ‐ and high performance liquid chromatography. The structure of the new compound, named globularifolin, and the identity of the others have been established by chemical transformations and spectral evidence of the compounds and their derivative

ISSN:0018-019X    

DOI:10.1002/hlca.19800630112

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractSeveral attempts to prepare 3‐acetyl‐5‐benzyl‐3‐pyrrolin‐2‐one (7) from phenylalanine are described. This goal was only reached formally, because compound7exists in the tautomeric form of (Z)‐5‐benzyl‐3‐(1′‐hydroxyethylidene)‐4‐pyrrolin‐2‐one (17) according to the spectral data. The problem of tautomerism in

ISSN:0018-019X    

DOI:10.1002/hlca.19800630113

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe interaction of selected tetramethylpiperidine derivatives with radicals arising from theNorrish‐type I cleavage of dibenzyl ketone under oxygen was studied. Product analyses and kinetic studies showed that the investigated sterically hindered piperidine derivatives have a pronounced effect on both the nature and distribution of the products of photolysis of dibenzyl ketone in the presence of oxygen. Observations indicated that the phenylperacetoxyl radical is formed as an intermediate during irradiation and that it interacts with the additives used. Possible mechanisms of the reactions studied are discussed.The observation that oxidation of an isolated double bond by the radicals formed in dibenzyl ketone photolysis under oxygen is strongly inhibited in the presence of the studied sterically hindered amines is discussed in the light of the results presented. The findings are considered in relation to the problem of polymer stabilizatio

ISSN:0018-019X    

DOI:10.1002/hlca.19800630114

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractPolarized neutron diffraction has been used to investigate the spin delocalization from the high‐spin Fe(III) sites to the low‐spin Fe(II) in deuteriated Prussian Blue, Fe4[Fe(CN)6]3· xD2O. Measurements of the 111, 200, and 400 reflections were made on a powdered sample at 3 K and 4.8 T using a neutron wavelength of 1.074 Å. The expectation value of S at the Fe(II) site is ‐ 0.008 ± 0.028 corresponding to an upper limit of about 5% of an electron for the spin deloca

ISSN:0018-019X    

DOI:10.1002/hlca.19800630115

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

The Photochemistry of Tetraalkyl Substituted γ‐Keto‐olefinesThe photochemistry of 7,8‐dihydro‐β‐ionone (1) in solution is shown to depend on temperature, polarity and viscosity of the solvent. UV. irradiation (λ ≥ 245 nm) in pentane at +25° converts1to the isomeric ethers3(16%),5A(48%) and5B(22%), whereas at −65° 7,8‐dihydro‐γ‐ionone (26) is obtained in 12% yield together with 13% of3, 12% of5Aand 9% of5B. The1n,π*‐excitation of1in acetonitrile gives similar results. In the more viscous 1,2,3‐triacetoxypropane the photoisomerization1 → 26takes place even at + 60° (10% yield,cf. 40% at −15°). In alcoholic solvents, however, no formation of26is detected, but the hitherto unknown [2+2]‐photocycloaddition1 → 11can be observed (4% at −7°, 15% at −65S° in 2‐propanol). An intermediateemay be involved(Scheme 14). In addition to the photoreactions1 → 3, 5A, 5Band11the isomerization of1to the novel spirocyclic ketone28takes place in alcoholic solvents only.Photoisomerization1 → 3is presumably a photo‐ene process involving a stereoselective intramolecular H‐transfer. This type of photoisomerization is restricted to cyclic γ‐keto‐olefines. The tetraalkylated acyclic γ‐keto‐olefines14and15photoisomerize exclusively by [2+2]‐cycloaddition, independent of the solvent.On1n,π*‐excitation the δ,ϵ‐unsaturated bicyclic ketone44undergoesNorrish‐Type‐II photofragmentation to the diene45or isomerizes to the γ, ϵ‐unsaturated ketone17. Competition between these two reactions is strongly temperature dependent: photolysis in pentane at −72° yields quantitatively45, whereas at + 35° only 30% of45and 68% of17are obtained.UV. irradiation of the novel spirocyclic ketone28gives as primary photoproduct the isomeric aldehyde29, and in a secondary photoreaction the isomeric oxetanes30Aand30B. Experiments wi

ISSN:0018-019X    

DOI:10.1002/hlca.19800630116

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Ionophores of the Type of 3‐Oxapentane DiamidesA series of lipophilic 3‐oxapentane diamides were prepared and their selectivity in membranes was studied.N, N, N′, N′‐Tetracyclohexyl‐3‐oxapentane diamide forms 1:2‐ and 1:3‐metal/ligand‐complexes with Mg2+and Ca2+respectively and induces a selectivity in membranes for Ca2+over Mg2+by a

ISSN:0018-019X    

DOI:10.1002/hlca.19800630117

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Preparation forerythro‐2‐Hydroxy‐succinic Acid Derivatives from Malic EstersAs a contribution to the much discussed diastereoselective synthesis of enantiomers of open chain compounds,>90%erythro‐selective branching of malic esters by alkylation of the doubly deprotonated derivative2(alkoxide‐enolate) with methyl, allyl, and benzyl halides in THF at −78° (→3aa, 3ba, 3bb, 3bc,Table 1) is described. A second alkylation (→4) and addition of2to acetone (→5) are also possible. Cyclization of2to the enantiomerically puretrans‐epoxides6is achieved by treatment with iodine. Cuprate opening of6bfurnishes the same product3baobtained from the methylation of2b, establishing the config

ISSN:0018-019X    

DOI:10.1002/hlca.19800630118

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Abstract2‐Oxocephalexin4, a very labile representative of the novel group of 2‐oxocephem‐4‐carboxylic acids, has been synthesized from het

ISSN:0018-019X    

DOI:10.1002/hlca.19800630119

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractA synthesis of the novel C10H16hydrocarbon 1,7‐trimethylenenorbornane (13), one of the 19 members of the adamantane family, is describe

ISSN:0018-019X    

DOI:10.1002/hlca.19800630120

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

N,N,N′,N′‐Tetrabutyl‐3,6‐dioxaoctane‐dithioamide, an Ionophore with Selectivity for Cd2+The dioxa‐dithioamide3behaves as a highly selective ionophore for Cd2+in solvent polymeric membranes. It induces cation‐permselectivity in these membranes with a transference number of 1 for Cd(NO3)2‐ and of 2 for CdCl2‐solutions. In the presence of a proton carrier,3may be used to selectively pump Cd2+through membranes by coupling

ISSN:0018-019X    

DOI:10.1002/hlca.19800630121

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY