摘要:

AbstractNovel tricyclic heterocycles were prepared and evaluated for their affinity to the central benzodiazepine receptor. The most potent compounds withIC50's in the nanomolar range were; found among thienoquinolizines and benzo[a]quinolizines (cf. Tables 2–5). The central ring of the tricyclic ring system may be partially unsaturated (cf. Tables 2and4) or fully unsaturated (cf. Tables 3and5) without loss of the high affinity to the receptor. The position of the ester group in the pyridinone ring is crucial for good binding (cf. Tables 1and2). It may be replaced by a broad variety of functional groups,e.g.amides, alkyl carbamates, alkyl groups, and hydroxyalkyl groups (cf. Tables 2–5). In the benzo[a]quinolizines, shifting the halogen atom from C(10) to C(9) leads to complete loss of affinity to the benzodiazepine receptor (cf. Table

ISSN:0018-019X    

DOI:10.1002/hlca.19900730402

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Separation and Quantitation of All Eight Stereoisomers of α‐Tocopherol by ChromatographyThe results of the analysis of several derivatives of (all‐rac)‐α‐tocopherol by HPLC on a chiral stationary phase and by capillary GC on a achiral stationary phase are reported. Consecutive application of both methods to the ethyl‐ether derivative allows the separation and quantification of all eight possible stereoisomers of (all‐rac)

ISSN:0018-019X    

DOI:10.1002/hlca.19900730403

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

A New Synthetic Route to UbiquinonesUbiquinones11have been prepared employing a new strategy: as key step, theDiels‐Alderreaction of 1,1,2‐trichloroethene3with 2,5‐bis[(trimethylsilyl)oxy]‐3‐methylfuran (2) has been used for the construction of the quinone part. After methanolysis of the [4 + 2] adducts4a/4b, further reaction with cyclopentadiene and substitution of the Cl‐atoms by MeO groups, the intermediate7is obtained. Diketone7can easily be alkylated with the desired polyprenyl side chain9(X = Br) using a strong base to yield, after aretro‐Diels‐Alderreaction, the corresponding ubiquinones1

ISSN:0018-019X    

DOI:10.1002/hlca.19900730404

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Synthesis of 2,4‐Diamino‐thieno[2,3‐d]pyrimidinesCondensation of 2‐aminothiophene‐3‐carbonitrile (4) with guanidine or sequential addition of CS2and NH3to4provides 2,4‐diaminothieno[2,3‐d]pyrimidine (7). This compound yields, after sequential addition ofsec‐BuLi and either [3‐(trifluoromethyl)benzene]sulfenyl chloride (8) or the corresponding disulfide9, followed by acidic work up, 2,4‐diamino‐6‐{[3‐(trifluoromethyl)phenyl]thio}thieno[2,3‐d]pyrimidine (10). In another approach, 2‐amino‐5‐{[3‐(trifluoromethyl)phenyl]thio}thiophene‐3‐carbonitrile (11) obtained from4and8is transformed to10by condensation with guanidine. Corresponding to the second route, 2,4‐diamino‐6‐[(naphth‐2‐yl)thio]thieno‐[2,3‐d]pyrimidine (16) is synthesized. Oxidation of10withm‐chloroperbenzoic acid gives 2,4‐diamino‐6‐{[3

ISSN:0018-019X    

DOI:10.1002/hlca.19900730405

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Mediterranean alcyonaceanAlcyonium ( = Parerythropodium) coralloides(Pallas, 1766) is shown here to contain coralloidolide F ( = (+)‐(3a‐R*, 7R*, 8R*, 9R*, 12R*, 12aS*)‐8,9‐epoxy‐1,3a,6,7,8,9,10,11,12,12a‐decahydro‐3a‐hydroxy‐12‐isopropenyl‐2,5‐dimethyl‐1‐oxocyclopfintacycloundecene‐9,7‐carbolactone; (+)‐2), the first example of a 2,6‐cyclized cembranolide. Structural assignments are mainly

ISSN:0018-019X    

DOI:10.1002/hlca.19900730406

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Pteridines: Synthesis and Characteristics of 5,6‐Dihydro‐6‐(1,2,3‐trihydroxypropyl)pteridines: Covalent Intramolecular AdductsVarious 5,6‐diaminopyrimidines (1, 15, 24, 33) were condensed with the phenylhydrazones ofL‐(2) andD‐arabinose (3) in acidic medium under N2to give formal 5,6‐dihydro‐6‐(1,2,3‐trihydroxypropyl)pteridines (see,e.g.,4and5), the latter turned out to exist preferentially as intramolecular adducts, the hexahydropyrano‐[3,2‐g]pteridines6, 7, 16, 17, 25, 26, and34, formed subsequently by addition of the terminal OH group of the side‐chain to the C(7)N(8) bond of the pteridine moiety. Spectroscopically, the isomeric hexahydrofuro‐[3,2‐g]pteridines10,11,18,19, and35were also detected as minor components in the equilibrium mixtures. In the 4‐amino‐2‐(methylthio)pteridine series, crystallization of6and7led to the stereochemically pure (3S,4R,4aR, 10aS)‐6‐amino‐3,4,4a,5,10,10a‐hexahydro‐8‐(methylthio)‐2H‐pyrano[3,2‐g]pteridine‐3,4‐diol (8) and its corresponding enantiomer9, respectively Structure8was proven by X‐ray analysis. Acylation of the hexahydropyrano[3,2‐g]pteridines yielded the more stable tri‐, tetra‐, and pentaacetyl derivatives12–14, 20–23, 27–32, and37–39which were characterized and of which the absolute and relative configurations were determined

ISSN:0018-019X    

DOI:10.1002/hlca.19900730407

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThree new synthetic procedures for and thermal 1,6‐electrocyclizations of acceptor‐substituted 2,3‐divinyl‐1H‐indoles leading to functionalizing carbazoles are described. The scope and limitations as well as some mechanistic aspects of the methodologies are discussed. The key strategies employed include Pd(II)‐catalyzed coupling andWitti

ISSN:0018-019X    

DOI:10.1002/hlca.19900730408

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Constitutional Isomerism in Polycondensates. Synthesis and Properties of Perfectly Regular and Random Bipolyamides fromcis‐2,6‐Dimethylpiperazine and 1,2,5‐Thiadiazole‐3,4‐dicarbonyl DichlorideThe synthesis of constitutionally perfectly regular and random alternating copolyamides from the ‘symmetric’ monomer 1,2,5‐thiadiazol‐3,4‐dicarbonyl dichloride (4) and the ‘non‐symmetric’ monomercis‐2,6‐dimethylpiper‐azine (7) by solution and interfacial polycondensation methods is described. Their constitutional regularities (svalues) were determined by high‐resolution13C‐NMR spectroscopy in CDCl3solutions. Ordered and random copolyamides were amorphous withTgvalues ofca.200°. However, the regular head/tail and the random copolyamides with low molecular weights could be partially crystallized by annealing and showed large differences in their melting points (54°). Beside other physical properties, the membrane properties of the copolyamides were carefully investigated. In H2O desalination by reverse osmosis, no differences in salt rejections and permeabilities between constitutionally regular and random copolyamides were found (within experimental errors). In contrast, the regular head/head/tail/tail‐ and head/tail‐type copolyamides showed considerably larger separation factors in the gas separatio

ISSN:0018-019X    

DOI:10.1002/hlca.19900730409

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractCyclohex‐2‐enones1a–1cundergo photocycloaddition to tetramethoxyethylene in benzene to afford 1‐oxa‐spiro[3.5]non‐5‐enes3in very good yields. In MeCN as solvent, higher relative amounts of bicyclo[4.2.0]octan‐2‐ones4are formed. Results from similar experiments with the same enones and 2,3‐dimethylbut‐2‐ene or 1,1‐dimethoxyethene indicate that the driving force for oxetane formation is a sufficiently large difference in redox potentials betweenEredof the enone andEoxof the alkene. A mechanism is proposed for cycloalk‐2‐enone + alkene photocycloadditions wherein the cyclobutane adducts arise from an exciplex intermediate and the oxetanes from a subsequ

ISSN:0018-019X    

DOI:10.1002/hlca.19900730410

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractStarting from the readily available, optically active (4R)‐4‐hydroxy‐2,2,6‐trimethylcyclohexanone (1), a new technical synthesis of (3R,3′R)‐zeaxanthin is described. According to a 2(C9+ C6) + C10= C40construction scheme, the ketone1was first transformed with (E)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol (5) into a C15‐intermediate which, by a three‐step sequence, could be converted into the known olefinic C15‐Wittigsalt4. Optimized conditions for the finalWittigreaction of4with the C10‐dialdehyde3are discussed. Based on1, the overall yield of th

ISSN:0018-019X    

DOI:10.1002/hlca.19900730411

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY