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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1571-1575 
    ISSN: 0947-3440
    Keywords: Natural products ; Carbohydrates ; Praecoxin B ; Pterocarinin C ; Diastereoselective esterification ; Acylations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure diphenic ester 3 was obtained by esterification of acyl chloride 2 with the glucose derivative 1 by kinetic resolution. Hydrolysis of the ester 3, acylation of the free OH groups at C-4 and C-6 of the diol 4 with acid 5 followed by irradiation led to the anomerically deprotected α- and β-anomers (7) (4:1). The natural product praecoxin B (8) was obtained by hydrogenative debenzylation. A second member of the ellagitannin group pterocarinin C (11) was obtained from the common intermediate 7 by acylation in the anomeric position to 10 followed by debenzylation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1981-1985 
    ISSN: 0947-3440
    Keywords: Angucyclines ; Diels-Alder reactions ; Photooxygenation ; Methoxylation ; Osmylation ; X-ray ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Osmylation of the Diels-Alder adduct 3 afforded the cis-diol 4, which was dehydrated by acid treatment to the phenol 6. Reaction with tetrafluoroboric acid converted the diol 4 by intramolecular acyl shift into the acetate 7. The relative stereochemistry of 7 was determined by single-crystal X-ray analysis. Photooxygenation of 4 afforded the C-1 carbonyl compound 8 and treatment with sulfuric acid the silanol 9. Functionalization of C-6 was achieved by treatment of 4 with methanolic KOH to yield the cis-methyl ether 11.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 1109-1112 
    ISSN: 0170-2041
    Keywords: Tetrangomycin ; Angucyclines ; Diels-Alder reaction ; Silicon-oxygen exchange ; Photochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of racemic tetrangomycin (11) is reported. In the key step the hexahydrobenz[α]anthraquinone 8 is generated in a regioselective Diels-Alder reaction of diene 5 with bromonaphthoquinone 7. The conversion of 8 into 11 involves only three operations: treatment with diethyl ether-boron trifluoride, hydrogen peroxide and photooxygenation.
    Type of Medium: Electronic Resource
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