ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Asymmetric synthesis  (18)
  • Wiley-Blackwell  (18)
  • Annual Reviews
  • National Academy of Sciences
  • Nature Publishing Group
  • Oxford University Press
  • Periodicals Archive Online (PAO)
  • 2000-2004  (18)
Sammlung
Verlag/Herausgeber
  • Wiley-Blackwell  (18)
  • Annual Reviews
  • National Academy of Sciences
  • Nature Publishing Group
  • Oxford University Press
  • +
Erscheinungszeitraum
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1623-1626 
    ISSN: 1434-193X
    Schlagwort(e): Iridoid glucoside ; (8S)-Kingiside ; (8S)-Loganin ; (8S)-7-Ketologanin ; Asymmetric synthesis ; Natural products ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The tetraacetyl derivative 8 of the naturally occurring kingiside (8a) was prepared from aucubin (1). Intermediates in the synthesis were (8S)-tetraacetyl loganin (6) and (8S)-tetraacetyl-7-ketologanin (7), whose free (8R)-epimers occur in many different plants (Caprifoliaceae, Loganiaceae). The 13C NMR spectrum allows the structure to be unequivocally identified.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1677-1683 
    ISSN: 1434-193X
    Schlagwort(e): Radicals ; Cyclizations ; Pyridinethione ; Tetrahydrofurans ; Asymmetric synthesis ; Thiazolethione ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The trisubstituted functionalized tetrahydrofurans 10, 11, 16, 18, and 19 were photochemically prepared from 2,3-syn- and 2,3-anti-configuredN-(3-benzoyloxy-5-hexen-2-oxy)thiazole-2(3H)-thione anti-6, pyridinethiones 7, anti-8, and BrCCl3. The formation of tetrahydrofurans was achieved by an efficient and highly regioselective alkoxyl radical cyclization (5-exo-trig). The 2,3-anti substituted intermediates 9 and 12 cyclize stereoselectively whereas a 2,3-syn-configured O-radical affords both possible diastereomeric addition products in equal amounts. The cyclized tetrahydrofuryl methyl radicals were trapped with the bromine atom donor BrCCl3 to afford the bromomethyl-substituted cyclic ethers 10, 11, 18, and 19 in excellent yields. The utility of this reaction was stressed by conversion of one of the newly prepared tetrahydrofurans in a two-step synthesis into (+)-allo-muscarine (+)-20.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99590_s.pdf or from the author.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Zinc ; Transition structures ; QM/MM computations ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Trimethylsilyl substitutions of the fenchyl alcohols [(1R,2R,4S)-exo-(2-Ar)-1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol, Ar = 2-methoxyphenyl (1) and Ar = 2-(dimethylaminomethyl)phenyl (2)] yield the chiral ligands 3 [Ar = 2-methoxy-3-(trimethylsilyl)phenyl] and 4 [Ar = 2-(dimethylaminomethyl)3-(trimethylsilyl)phenyl]. Increased reactivities and enantioselectivities in diethylzinc additions to benzaldehyde are obtained from 3 (63% ee R) and 4 (93% ee S), relative to 1 (26% ee S) and 2 (73% ee S). X-ray crystal structures of 3 and of its methylzinc complex 3-Zn reveal out-of-plane bending of the methoxy groups as major geometrical consequences of the trimethylsilyl substitutions. Analyses of QM/MM ONIOM μ-O transition-structure models for 1, 2, 3, and 4 show that trimethylsilyl-induced distortions of methoxy and of dimethylaminomethyl groups explain the observed increased enantioselectivities.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1815-1820 
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Palladium-catalysed couplings ; Palladacycles ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Chiral C2-symmetric N-benzylazetidines have been conveniently prepared from optically pure anti-1,3-diols without loss of enantiomeric purity. N-Debenzylation led to the corresponding N-unsubstituted azetidines, which were then subjected to palladium-catalysed coupling reactions with aryl bromides to afford chiral N-arylazetidines. (R,R)-N-Benzyl-2,4-dimethylazetidine has been employed in the synthesis of a new cyclopalladated complex, which can be used, for instance, as a chiral recognition agent for phosphorus ligands.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 807-811 
    ISSN: 1434-193X
    Schlagwort(e): Proline analogues ; Asymmetric synthesis ; Schöllkopf's method ; Silicon ; Amino acids ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The asymmetric synthesis of a new proline surrogate, incorporating the dimethylsilyl group at position 4 of proline using Schöllkopf's bis-lactim ether method, is described.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Addition reactions ; Sulfones ; Alkylations ; Amines ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The aza-Michael addition of enantiopure 1-aminopyrrolidines to (E)-alkenyl sulfones in the presence of a catalytic amount of ytterbium trifluoromethanesulfonate [Yb(OTf)3] yields β-hydrazino sulfones in moderate to good yields and with diastereoselectivities of up to ≥ 98%. The latter undergo reductive N-N bond cleavage with BH3 · THF and, after N-protection with Boc2O or benzyl bromide, afford N-protected β-amino sulfones with moderate to high enantiomeric excesses (ee = 42 to ≥96%) without racemization. Subsequent α-alkylation of the N,N-dibenzyl protected β-amino sulfones with various electrophiles yields α-alkyl-β-amino sulfones in excellent yields (88-97%) with high diastereomeric (de ≥96 to ≥98%) and enantiomeric purity (ee = 94 to ≥96%). The absolute configuration of the new stereogenic centre was determined by X-ray structural analysis and confirmed by NMR spectroscopy (NOE experiments). Possible reaction mechanisms for the conjugate addition and α-alkylation are presented.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 611-616 
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Grignard reactions ; Dynamic kinetic resolution ; Asymmetric synthesis ; Unsymmetrical 1,2-diamines ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A diastereoselective synthesis of tert-butyl-1,2-diamines has been developed from the addition of tert-butylmagnesium chloride to the 1,2-bisimines derived from glyoxal and chiral amines such as 1-(S)-ethylphenylamine, 1-(S)-phenylpropylamine or 1-(S)-(p-chlorophenyl)ethylamine. The influence of solvent, temperature and chiral auxiliaries on the chemical reactivity and stereoselectivity has been fully studied. Evidence of a dynamic kinetic resolution during the bis-addition process of the organometallic, leading to the 1,2-di-tert-butylethanediamine,[1] as a single diastereomer, has been demonstrated. This resolution has been applied with high diastereoselectivities to the synthesis of unsymmetrical disubstituted 1,2-diamines, by addition of one equivalent of tert-butylmagnesium chloride, followed by one equivalent of a second Grignard reagent. Several chiral 1-tert-butyl-1,2-diamines have also been synthesized by monoaddition of tert-butylmagnesium chloride to the bisimines, followed by hydride reduction of the chiral intermediate imines.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1387-1389 
    ISSN: 1434-193X
    Schlagwort(e): Natural products ; Epoxidations ; Asymmetric synthesis ; Fluorine ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The synthesis of enantiomerically and diastereomerically pure (-)-(1R,2R,5R)- and (-)-(1R,2S,5R)-2-fluoro frontalin (7) starting from (+)-(1S)-menthyl-(R)-toluene-4-sulfinate, methylmagnesium bromide, methyl fluoroacetate, 4-pentenyl bromide and diazomethane is described. The absolute stereochemistry was unambiguously determined by X-ray analysis of (+)-(1S,2R,5S,RS)-5, an intermediate in the synthesis of the enantiomeric (+)-(1S,2R,5S)-2-fluoro frontalin (7).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    ISSN: 1434-193X
    Schlagwort(e): Alkaloids ; Alkylations ; Asymmetric synthesis ; Grignard reactions ; Nitrogen heterocycles ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Treatment of salts 1a-b with Grignard reagents gives, after reduction of the resulting unstable dihydropyridines 7, the tetrahydropyridines 8a-c, with modest selectivities but in very few steps and under practical conditions. Higher stereo- and regioselectivities are obtained with salt 1c which gives the tetrahydropyridines 15a-e. In addition, the dihydropyridine intermediates 11b cyclize to give the new oxazolidine derivatives 12a-e, which turn out to be good precursors of the 2,6-trans-disubstituted tetrahydropyridines 21a-e. Selective syntheses of (-)-lupetidin, (+)-solenopsin, and indolizidines (-)-5 and (-)-6 are presented as representative examples of applications.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1443-1449 
    ISSN: 1434-193X
    Schlagwort(e): Amino acids ; Alkylations ; Phase-transfer catalysis ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---N-(2-Nitrophenylsulfonyl)- (o-NBS-AA-OMe, 4) and N-(4-Nitrophenylsulfonyl)-α-amino acid methyl esters (p-NBS-AA-OMe, 5) were N-alkylated with a variety of alkyl halides 6 under solid-liquid phase-transfer catalysis (SL-PTC) conditions, affording the alkylated products o-NBS-N-R2-AA-OMe 7 and p-NBS-N-R2-AA-OMe 8 in excellent yields without any detectable racemization.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 11
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Sulfoxides ; Asymmetric hydroxylations ; Lactones ; Sulfoxides ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A general synthetic strategy towards the two bis(lactones) (-)-colletol (1) and (+)-colletodiol (2) is described. A common intermediate in this synthesis is the 6-membered hydroxy lactone (+)-(3R,5R)-3-hydroxy-5-hexanolide (6), readily prepared by stereoselective reduction of (+)-(SR)-methyl 3,5-dioxo-6-(p-toluenesulfinyl)hexanoate (7). Stereoselective hydroxylation of this hydroxy lactone has allowed efficient access to (+)-colletodiol (2).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 12
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Nucleophilic formylation ; Addition reactions ; Lactones ; Formyl anion equivalent ; Domino reactions ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---An efficient asymmetric synthesis of α-substituted β-formyl δ-lactones 5 (de ≥ 98%, ee = 80-95%) and 4-substituted furofuran lactones 6 (de ≥ 98%, ee = 80-〉98%) in acceptable overall yields is reported. Key steps of the new procedure are an asymmetric Michael addition of formaldehyde SAMP-hydrazone (1) to 5,6-dihydro-2H-pyran-2-one (2) under neutral conditions, followed by trans-selective α-alkylation and subsequent cleavage of the auxiliary by ozonolysis or a hydrolytic domino reaction protocol, respectively. The absolute configurations given for the title compounds are based on three X-ray structure analyses and NOE measurements.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 13
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Phosphazene base ; Pyridyl epoxide ; Furyl epoxide ; Pyridyl alcohol ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---trans-1-(2-Pyridyl)-, trans-1-(3-pyridyl)-, trans-1(2-furyl)-, and trans-1(3-furyl)-2-phenyl epoxides with enantiomeric purities ranging from 96.8 to 99.8% [in favor of the (+, EtOH)-isomer] are obtained in two steps from pure (R,R,R)-oxathiane which is recovered (85-90%) and reused. The chiral bidentate ligand 2-phenyl-(S)-1-(2-pyridyl)ethanol with 99.6% ee was obtained in three steps and 67% overall isolated yield.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 14
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1319-1325 
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Tetrahydroisoquinolines ; Cyclizations ; Diastereoselective alkylation of Amides ; Phenylglycinol ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: -Bischler-Napieralski cyclisation of optically active β-substituted phenylethylamines 4a-c followed by diastereoselective reduction led to 1,4-disubstituted tetrahydroisoquinolines 6a-c and 8a-c. The same methodology afforded the 4-benzyl pyrroloisoquinolines 10.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 15
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 789-799 
    ISSN: 1434-1948
    Schlagwort(e): Asymmetric synthesis ; Chirality ; Computer chemistry ; Lithium ; Dilithiomethane ; Sulfoximines ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis and X-ray analysis of chiral dilithiomethane analogues derived from sulfoximines are presented. The structures of the sulfoximine-stabilised mono- and dilithio salts have been compared and allow a rationalization of the second lithiation. Organophosphorus-based dilithiomethane derivatives are also structurally described. The gas-phase structures of N,S,S-trimethylsulfoximine 19 and of its mono- and dilithiated isomers 20-21 were calculated by ab initio methods employing different levels of theory. For an application in asymmetric synthesis, the dilithiation of (N-methyl)-S-ethyl-S-phenylsulfoximine (11) afforded a chiral dinucleophile that undergoes highly regio- and stereoselective alkylation reactions with electrophiles. The transmetallation of a chiral dilithiomethane reagent such as 14 with ClTi(OiPr)3 followed by addition of an aldehyde, constitutes a simple one-pot process for the formation of (E)-alkenylsulfoximines with excellent diastereoselectivity.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 16
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1297-1305 
    ISSN: 1434-193X
    Schlagwort(e): Amino acids ; Asymmetric synthesis ; Carboxylation ; N-(α-Lithioalkyl)oxazolidin-2-ones ; Isotopic labeling ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: -N-(α-Stannylalkyl)oxazolidinones can be obtained as a mixture of diastereomers in three steps from aldehydes with yields dependent on the R group of R-CHO. They can be transformed by a tin-lithium exchange to N-(α-lithioalkyl)oxazolidinones which equilibrate rapidly to one diastereomer. These compounds give rise, after carboxylation, to the diastereopure N-(α-carboxyalkyl)oxazolidinones. Transformation of the oxazolidinone moiety to a free amino group is accomplished by a Birch-type reduction. Using this method, L-methionine, L-alanine, L-leucine and L-homocysteine were obtained in good yields and ee = 92% to ≥ 95%. The short time required for the whole sequence makes this method ideal for synthesising 1-[11C]amino acids.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 17
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Amino alcohol ; Bispidine ; Enantioselective catalysis ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Two generally applicable routes for the synthesis of chiral amino alcohols embodying the bispidine framework have been developed. In linear route A the bispidine framework is built up successively from chiral primary amines via intermediate formation of a piperidinone and a bispidinone. In convergent route B an achiral bispidine is formed first and then the N-substituents are introduced by reaction of the nitrogen bases with chiral electrophiles. In order to determine if the bispidine core and its N-substituents can influence the steric course of enantioselective transformations, bispidine amino alcohols built up by these two routes were investigated as chiral ligands in the enantioselectively catalyzed addition of diethylzinc to aldehydes and chalcone. In general, tridentate ligands containing one chiral amino alcohol fragment and a second amino substituent without a stereogenic center were more efficient than tetradentate ligands with two amino alcohol structural units. With the best ligands the enantioselective addition of diethylzinc to aromatic and aliphatic aldehydes proceeded with 83-98% ee and the nickel-catalyzed addition of diethylzinc to chalcone was achieved with up to 85% ee.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 18
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; Nitrogen heterocycles ; Heterocycles ; Pyrrolidines ; Piperidines ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Chiral, nonracemic 2-substituted pyrrolidines and piperidines were prepared in high ee and moderate to good chemical yields in three steps from (R)-phenylglycinol and γ- or δ-chloroketones. The key step of the synthesis was the stereoselective reductive ring-opening of chiral bicyclic 1,3-oxazolidines prepared by condensation of (R)-phenylglycinol and the corresponding ketones.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...