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  • Organic Chemistry  (3)
  • 1990-1994  (3)
  • 1985-1989
  • 1991  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Tieffarbige Systeme mit Oxalsäurestruktur  -  eine Strukturkorrektur (1991)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 333 (1991), S. 555-559 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deep Coloured Systems with Oxalic Acid Substructure-a Structural CorrectionBasing on a recent spectroscopic investigation the structure of earlier described deeply coloured systems derived from oxalic acid imidochlorides and thioacetamide has to be revised. Due to the poor solubility of these systems their spectroscopic characterization led to the misinterpretation as tetramethin-bridged thiazolines 1. By means of 1H-NOE-Difference-Spectroscopy of newly synthesized derivatives with lipophilic substituents a imidazolin-thion substructure 4 has been found. Such an arrangement of the heteroatoms clearly reflects a 1,3-rearrangement with participation of the oxalic acid system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19913330406
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  • 2
    Electronic Resource
    Electronic Resource
    Zur stereoselektiven Synthese von 1-O-Alkyl-3-O-benzyl-sn-glycerolen und 1-O-Alkyl-2-O-methyl-3-O-β-D-glycosyl-sn-glycerolen (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 765-768 
    Details
    ISSN: 0170-2041
    Keywords: Lysoglycolipids, glyceryl ethers ; Stereoselective synthesis ; Koenigs-Knorr reaction ; Glyceryl ethers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Synthesis of 1-O-Alkyl-3-O-benzyl-sn-glycerols and 1-O-Alkyl-2-O-methyl-3-O-β-D-glycosyl-sn-glycerolsStarting with D-mannitol, the yield of the synthesis of 3-O-benzyl-sn-glycerol (1) could be improved. The regioselective alkylation of 1 at the primary hydroxy group to the 1-O-alkyl-3-O-benzyl-sn-glycerols 3 was achieved by using the dibutylstannylene protecting group. The 1-O-alkyl-2-O-methyl-sn-glycerols 4, readily obtainable from 3, were successfully glycosylated under the conditions of the Koenigs-Knorr reaction to give 1-O-alkyl-2-O-methyl-3-O-β-D-glycosyl-sn-glycerols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1991199101131
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of Shikonin and Alkannin (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 1157-1164 
    Details
    ISSN: 0170-2041
    Keywords: Naphthoquinone ; Aldol addition ; (R)-Shikonin ; (S)-Alkannin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomeric naturally occurring naphthoquinones shikonin [(R)-1] and alkannin [(S)-1] have been synthesized in a thirteen-step procedure in 44 to 65% e.e. The stereogenic centers of (R)-1 and (S) are created by the reaction of naphthaldehyde 3 with (R)- and (S)-2-hydroxy-1,2,2-triphenylethyl acetate (2), respectively. In order to find out a rationalization for the unexpectedly low diastereoselectivity in this aldol addition, a series of substituted aromatic aldehydes 12a-h has been treated with (R)-2.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1991199101199
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