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  • Organic Chemistry  (9)
  • 1995-1999  (9)
  • 1965-1969
  • 1997  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Ein erstes Beispiel eines porphyrinoiden Fulvalens: Synthese, Struktur, ESR- und elektrochemische UntersuchungenProf. Dr. Fabian Gerson in Anerkennung seiner Beiträge zum Verständnis von π-Systemen gewidmet (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 2456-2476 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A First Example of a Porphyrinoid Fulvalene: Synthesis, Structure, ESR and Electrochemical InvestigationsThe macrocyclic tetraepoxy-1H-[21]annulen-1-one 4 can by synthesized by the cyclizing Wittig reaction of 5,5′-carbonylbis[furan-2-carboxaldehyde] (11) and the bisphosphonium salt 12, obtained from 2,2′-bifuran-5,5′-dicarboxaldehyde (13). According to an X-ray structure analysis, the annulenone 4 is not planar in the crystal; the 1H-NMR spectra of 4 reveal an averaged planarity with respect to the NMR timescale. The McMurry reaction of 4 yields fulvalene 3 in 43% yield as the most expanded fulvalene hithertoo known. The X-ray structure analyses of 3 surprising establishes a ‘syn’-orientation of the two rings with respect to the central C=C bond, thus forming a basket-like molecule. The 1H-NMR spectrum confirms the averaged planarity of both macrocycles in 3. CV and spectroelectrochemical measurements of 3 suggest a reversible two-electron reduction producing dianion 15 with two aromatic, anionic 5a,15a-didehydro-10H-21,22,23,24-tetraoxa-5a,15a-dihomocorrole (= tetraoxa[22]porphyrin(2.1.2.0)) ring systems containing 22π electrons each. The formation of 15 can also be achieved chemically by reaction of 3 with metallic potassium. The dication 16 of 3 may be antiaromatic, but the exact electronic structure is dubious. ESR and ENDOR investigations on the radical cation and the radical anion of 3 indicate that the free electron is delocalized in the entire molecule.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800814
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  • 2
    Electronic Resource
    Electronic Resource
    Glycosyl Imidates, 78Part 77: Ref.[1].. An Efficient Synthesis of Galactinol and Isogalacatinol (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 859-863 
    Details
    ISSN: 0947-3440
    Keywords: myo-Inositol, racemate resolution ; Glycosylation, trichloroacetimidate method ; Tin(II) trifluoromethanesulfonate catalyst ; Oligosaccharide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2:3,4:5-Di-O-cyclohexylidene-D-/L-myo-inositol (2) could be readily converted into 6-O- and 1-O-unprotected L- and D-myo-inositol derivatives L- and D-4 and L- and D-6, respectively. Their reaction with trichloroacetimidate 7 as galactosyl donor in the presence of tin(II) trifluoromethanesulfonate as catalyst afforded the desired α(1-6)- and α(1-1)-connected galactopyranosides 8, 11 and 12. Compound 11 could be readily deprotected to afford target molecule (galactinol) 1 in high overall yield; from 12, the diastereoisomer 13 was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970511
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of a Central Intermediate in the Biosynthesis of Di- and TrideoxysugarsDedicated to Professor Gottfried Huttner on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1907-1914 
    Details
    ISSN: 0947-3440
    Keywords: Nucleoside diphosphate sugars, synthesis ; Biosynthesis ; Deoxysugars ; Glycosyl phosphites ; Glycosyl phosphates ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of disodium (6-deoxy-α-D-ribo-hexopyran-3-ulosyl) (2′-deoxythymidin-5′-yl) diphosphate (1) is described. To this end, D-glucose is transformed into known furanose derivative 2 possessing a 3-C-methylene group as latent functionality for 3-ulose generation. From 2, 3,6-dideoxy derivative 6 was synthesized; ensuing acid catalyzed cleavage of the 1,2-O-isopropylidene group and then O-acetylation furnished the required pyranose 8α,β, which could be selectively deacetylated at the anomeric oxygen to afford 9α,β. Treatment with phosphitylating agent 13e and then oxidation led to dibenzylphosphate derivative 15e which could be chemoselectively debenzylated by hydrogenolysis without affecting the olefinic double bond (→ 17); de-O-acetylation and then ozonolysis afforded the unprotected phosphate intermediates 18 and 19, respectively. Both compounds could be successfully used for the synthesis of 1 by employing the nucleoside phosphate morpholidate procedure for the generation of nucleoside diphosphate sugars. Ozone cleavage of the olefinic double bond in 20 could be successfully performed even in the presence of the thymine moiety.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970916
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  • 4
    Electronic Resource
    Electronic Resource
    Oxokohlenstoffe und verwandte Verbindungen. 27. Synthese von Dihydrocyclobuta[a]naphthalen-1,2-dionen und Cyclobuta[a]naphthalen-1,2-dionen durch Anellierung von Alkoxy-(1-alkenyl)benzolen mit 3-Chlor-3-cyclobuten-1,2-dion. Anwendungsbereich und Grenzen (1997)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 564-574 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxocarbons and Related Compounds. 27. Synthesis of Dihydrocyclobuta[a]naphthalene-1,2-diones and Cyclobuta[a]naphthalene-1,2-diones via Annulation of Alkoxy-(1-alkenyl)benzenes with 3-Chloro-3-cyclobutene-1,2-dione. Scope and LimitationsThe reaction of alkoxy-(1-alkenyl)benzenes with semisquaric chloride (3) has been investigated systematically. 1,2-Dialkoxy- and 1-alkoxy'-2-alkoxy″-4-(1-alkenyl)benzenes (6a-j) and (11a-i) react with 3 to give the 3,4-dihydrocyclobuta[a]naphthalene-1,2-diones (8a-j) and (12a-i). Treatment of the dihydrocyclobuta[a]naphthalene-1,2-diones with 1.2 equiv. bromine effects dehydrogenation and affords cyclobuta[a]naphthalene-1,2-diones (9a-e) and (13b-f). Any efforts to extend this annulation reaction to dimethoxy-(1-alkenyl)benzenes with the methoxy groups in other than the 1,2-positions, e. g. 14a, b, 16a, b have been unsuccessful. The reaction of 1,2,3-trimethoxy-4-(1-propenyl) [and 4-(1-butenyl)]-benzenes (18a) and (18b) with semisquaric chloride (3) leads to the elimination of HCl and CH3OH and gives 5,6-dimethoxy-3-methyl [and 3-ethyl]-cyclobuta[a]naphthalene-1,2-diones (20a) and (20b). The reaction pathway of this novel annulation reaction is discussed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199733901100
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  • 5
    Electronic Resource
    Electronic Resource
    Massenspektroskopische Charakterisierung von ω-ChloralkylphenylphosphanenHerrn Prof. Dr. Siegfried Engels (Halle/S.) anläßlich seines 65. Geburtstages gewidmet (1997)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 482-484 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Mass Spectrometric Characterization of ω-Chloralkylphenylphosphines
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19973390187
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  • 6
    Electronic Resource
    Electronic Resource
    Methyltrioxorhenium - from oxidation and cyclopropanation to metathesis (1997)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 493-496 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19973390190
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  • 7
    Electronic Resource
    Electronic Resource
    A General Method for the Synthesis of C-Glycosides of Nojirimycin (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1315-1321 
    Details
    ISSN: 0947-3440
    Keywords: C-Glycosides ; Azasugars ; Piperidinosyl fluoride ; O-Piperidinosyl trichloroacetimidate ; Nojirimycin ; Deoxynojirimycin ; Glycosylations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl 2,3,4,6-tetra-O-acetyl-N-(benzyloxycarbonyl)nojirimycin (3) can be readily transformed into the corresponding azaglycal 6 or fluoride 7, which are versatile glycosyl/piperidinosyl donors. Reaction of 7 with allyltrimethylsilane, propinyltrimethylsilane, trimethylsilyl cyanide, and trimethylsilyl enol ether as carbon nucleophiles, afforded, in the presence of BF3 · OEt2 as catalyst, the corresponding C-glycosides 8-10 and 12-14 in good yields. The anomeric configurations of the C-glycosides are ascertained with the help of ROESY-NMR data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970706
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of Thio-Linked Analogues of Lewis X and Sialyl Lewis XDedicated to Professor Hans Paulsen on the occasion of his 75th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1303-1313 
    Details
    ISSN: 0947-3440
    Keywords: S-Glycosylation, base-promoted, acid-catalyzed ; S-Glycosides ; Anomeric S-alkylation ; Glycosyltrichloroacetimidates ; Lewis X analogues ; Oligosaccharides, thio- ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of thio-linked Lewis X and sialyl Lewis X-derived epitopes 3-5 has been achieved using a small number of building blocks. The key building-block was 1-O-silyl-protected 4-S-acetyl-2,6-di-O-benzoyl-3-S-(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-3,4-dithio-β-D-glucopyranose (15), which was obtained from the fucosyl donor 6 together with 3-thiogalactose 7 as the acceptor. Their acid-catalyzed S-glycosylation afforded the thio-linked disaccharide 8 which was subsequently converted to the 4a-O-unprotected derivative 12. Conversion to the 4a-triflate followed by treatment with KSAc in tetrahydrofuran led, under inversion of configuration, to 15 in good overall yield. Selective removal of the S-acetyl group followed by base-promoted S-glycosylation with acetobromogalactose gave the acyl-protected Lewis X analogue 25. Acetobromogalactose gave the acyl-protected Lewis X analogue 25. Transformation into trichloroacetimidate 27, followed by acid-catalyzed S-glycosylation of heptylthiol and complete deacylation afforded target molecule 3. Similarly, acid-catalyzed reaction of donor 27 and the 3b,4b-O-unprotected lactose derivative 31 as acceptor led to pentasaccharide 32, complete deacylation of which afforded target molecule 4. Transformation of 15 into the donor trichloroacetimidate 34, followed by acid-catalyzed S-glycosylation of heptylthiol afforded thioglycoside 35. Selective removal of the S-acetyl group and subsequent base-promoted S-glycosylation with the known donor 37 furnished the thio-linked tetrasaccharide 38. Cleavage of all the O-acyl groups and hydrolysis of the methyl ester moiety afforded the sialyl Lewis X analogue 5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970705
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis of the Thio-Linked Ganglioside GM3 epitope (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 865-872 
    Details
    ISSN: 0947-3440
    Keywords: Glycosylations, sulfur ; Glycosyl trichloroacetimidates ; Protecting groups, acyl, selective removal of ; Oligosaccharides ; S-Glycosides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of sulfur-linked GM3 epitope 2 is based on acid-catalyzed and base-promoted S-glycosylation processes. As a precursor, 2-O-benzoyl-3-thiogalactoside 10 was required, and was obtained from 4,6-O-benzylidene-galactoside 3 in six high-yielding steps. Base-promoted S-glycosylation of 10 with neuraminic acid functionalized β-halogenose 11 in the presence of NaH as base and Kryptofix 21 as coactivator afforded α(2-3)-thio-linked disaccharide 13, which was readily converted to α-halogenose 20. Heptyl 1-thioglycoside 22 was obtained from O-galactosyl trichloroacetimidate 21 and heptylthiol via acid-catalyzed S-glycosylation. 22 was transformed into 2,3,6-tri-O-acylgalactoside 26 which, via the 4-O-triflate and treatment with potassium thioacetate, followed by selective removal of the S-acetyl group, furnished the 2,3,6-tri-O-acyl-4-thioglucoside 28. Base-promoted S-glycosylation of 28 with halogenose 20 led to fully acylated target molecule 29, which was quantitatively converted into 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970512
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