ISSN:0018-019X    

DOI:10.1002/hlca.19810640102

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThe four new iridoid glucosides globularicisin(2), globularidin(5), globularimin(9), and globularinin(13), the lignan diglucoside liriodendrin(18), and syringin(20)have been isolated fromGlobularia alypumL. along with the previously reported glucosides globularin(1)and catalpol(4). Compound 2 is the first report of any cinnamoyl iridoid with acis‐configuration at the acyl double bond. Compound5is another novel iridoid which lacks the characteristic C(3), C(4) double bond in the aglucone part. Compounds9and13are diastereomeric and contain highly oxygenated aglucone structures. The isolation of liriodendrin, fromGlobularia alypumis the first demonstration of the occurrence of a lignan in the familyGlobulariaceae.The structures have been elucidated by1H‐ and13C‐NMR. spectroscopy as well as by chemical transformations. Taxonomical significance of the cooccurrence of iridoid and lignan glycosides as well as the antileukemic potentiality of the latter are also appr

ISSN:0018-019X    

DOI:10.1002/hlca.19810640103

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractA new iridoid glucoside, named ladroside, together with mussaenoside(1)[2], has been isolated fromVeronica officinalisL. The structure of ladroside(4)and the identity of mussaenoside have been established by spectral analysis. Additionally, the absolute configuration at C(8) carrying the tertiary hydroxyl group has been established by chemical evidence.

ISSN:0018-019X    

DOI:10.1002/hlca.19810640104

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractStereoselective syntheses of (±)‐epi‐β‐santalene(1)and (±)‐epi‐β‐santalol(2), minor constituents of East Indian sandalwood oil, are described. The starting material for both syntheses is the tricyclic hemiacetal4, readily accessible in two steps

ISSN:0018-019X    

DOI:10.1002/hlca.19810640105

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThe complexation kinetics of 2,6,9, 13‐tetraazatetradecane(1), 1,4,8, 11‐tetraazacyclotetradecane(2)andN,N′,N″,N'‐tetramethyl‐1,4,8, 11‐tetraazacyclotetradecane(3)with Ni2+were studied by the stopped‐flow technique in DMSO and DMF. The biomecular rate constants kLNi(Table 2) follow in both solvents the order1≳2>3.The similar complexation rates of1and2in their unprotonated form indicate that for both the open chain and the cyclic ligand the same mechanism holds. By comparison with the solvent exchange the rate determining step of the complexation is the dissociation of the first solvent molecule in the outer‐sphere complex. The lower reactivity of3is probably due to steric effects.In the case of2a second step in the complexation process was observed and explained by a rearrangement of the ligand already coordinat

ISSN:0018-019X    

DOI:10.1002/hlca.19810640106

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

Azimines IV. Kinetics and Mechanism of the Thermal Stereoisomerization of 2,3‐Diaryl‐1‐phthalimido‐azimines1)Mixtures of (1E, 2Z)‐ and (1Z, 2E)‐2‐phenyl‐1‐phthalimido‐3‐p‐tolyl‐azimine (3aand3b, resp.) and (1E, 2Z)‐ and (1Z, 2E)‐3‐phenyl‐1‐phthalimido‐2‐p‐tolylazimine (4aand4b, resp.) were obtained by the addition of oxidatively generated phthalimido‐nitrene(6)to (E)‐ and (Z)‐4‐methyl‐azobenzene (7aand7b, resp.). Whereas complete separation of the 4 isomers3a, 3b, 4aand4bwas not possible, partial separation by chromatography and crystallization led to 5 differently composed mixtures of azimine isomers. The spectroscopic properties of these mixtures (UV.,1H‐NMR.) were used to determine the ratios of isomers in the mixtures, and served as a tool for the assignment of constitution and configuration to those isomers which were dominant in each of these mixtures, respectively.Investigation of the isomerization of the azimines3a, 3b, 4aand4bwithin the 5 mixtures at various concentrations by1H‐NMR.‐spectroscopy at room temperature revealed that only stereoisomers are interconverted (3a ⇄ 3b; 4a ⇄ 4b)and that the (1E, 2Z) ⇄ (1Z, 2E) stereoisomerization is a unimolecular reaction. These observations exclude an isomerization mechanismviaan intermediate 1‐phthalimido‐triaziridine(2)orviadimerization of 1‐phthalimido‐azimines(1), respectively. The 3‐p‐tolyl substituted stereoisomers3aand3bisomerized slightly slower than the 3‐phenyl substituted ones4aand4b, an effect which is consistent with the assumption that the rate determining step of the interconversion of (1E, 2Z)‐ and (1Z, 2E)‐1‐phthalimido‐azimines(1a ⇄ 1b)is the stereoisomerization of the stereogenic center at N(2), N(3), either by inversion of N(3) or by rotation around the N(2), N(3) bond. The total isomerization process is assumed to occurviathe thermodynamically less stable (1Z, 2Z)‐ and (1E, 2E)‐isomers1cand1d, respectively, as intermediates in undetectably low concentrations which stay in rapidly established equilibria with the observed, thermodynamically more stable (1E, 2Z)‐ and (1Z, 2E)‐isomers1aand1b, respectively.At higher temperatures, the azimines

ISSN:0018-019X    

DOI:10.1002/hlca.19810640107

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

Reaction of 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine with Barbituric AcidThe reaction of 3‐dimethylamino‐2,2‐dimethyl‐2H‐azirine(1)with barbituric acid(4)in dimethyl formamide at room temperature yields a mixture of several compounds. The two main products5and6have been isolated in 40 and 10% yield, respectively, and their structures established by X‐ray analysis. InSchemes 4–6reaction mechanisms for the formation of5and6are postulated, the first step beeing either aC‐ or anN‐alkylation of barbituric acid.Reduction of5and6with NaBH4in ethanol at room temperature yields 6,6‐dimethyl‐1,5,6,7‐tetrahydro‐pyrrolo[2,3‐d]pyrimidin‐2,4(3H)‐dione(7)and 3,3‐dimethyl‐2,3‐dihydro‐imidazo[1,2‐c]pyrimidin‐5,7(1H, 6H)‐dione(8)in 38 and 48% yield, respectively. Treatment of6with 3Naqueous NaOH at room temperature gives 3,3‐dimethyl‐imidazo[1,2‐c]

ISSN:0018-019X    

DOI:10.1002/hlca.19810640108

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

Halogenated Cyclobutanones as Highly Versatile Precursors of Pyrethroids: Synthesesvia[2+2]‐Cycloadditions of Haloketenes to 1,1‐Disubstituted Ethylenes[2+2]‐Cycloaddition reactions of the new chloro‐(2,2,2‐trichloroethyl)ketene(9)with various 1,1‐disubstituted ethylenes as well as [2+2]‐cycloadditions of highly halogenated ketenes of type32are described. The halogenated cyclobutanones thus obtained represent valuable intermediates in a new synthesis of insecticidal pyrethroids (Scheme 1). Ketene9, prepared insitufrom readily available precursors, parallels, if not exceeds, dichloroketene in its reactivity. With isobutene, the cyclobutanone10(a precursor forcis‐3‐(2,2‐dichlorovinyl)‐2,2‐dimethylcyclopropane carboxylic acid) is obtained in 70% yield. The reaction of9with propene is stereospecific and leads tocis‐17, exclusively. This result may be explained in terms of the energetically most favourable approach of the reacting molecule

ISSN:0018-019X    

DOI:10.1002/hlca.19810640109

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractFive iridoid glucosides have been isolated from the whole plant ofEuphrasia salisburgensis. The structure of the new compound, named euphroside, and the identity of the others have been established by chemical transformations and spectral data.

ISSN:0018-019X    

DOI:10.1002/hlca.19810640110

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractSingle crystals of dihydrodibenzo[b,i]‐1, 4, 8, 11‐tetraazacyclotetradecinenickel iodide show metallic conductivity between room temperature and approx. 110 K. The crystals are orthorhombic, space groupIbamwith four formula units per cell of the following dimensions:a= 20.245,b= 13.416,c= 6.418 Å. The analogous palladium complex is isomorphous, the cell constants beinga= 20.452,b= 13.430 andc= 6.499 Å. A number of other partially oxidized metal tetraaza [14]annulenes also show electrical conduct

ISSN:0018-019X    

DOI:10.1002/hlca.19810640111

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY