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  • 1
    Electronic Resource
    Electronic Resource
    Total synthesis of angucyclinones, 6Part 5: K. Krohn, W. Dröge, Annul. Quim 1995, submitted.. Synthesis of naturally (MM 47755; X-14881 E) and non-naturally occurring aromatic angucyclinones (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1529-1537 
    Details
    ISSN: 0947-3440
    Keywords: Angucyclinones ; MM 47755 ; X-14881 E ; Diels-Alder reactions ; Silicon-oxygen exchange ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Diels-Alder reactions of the naphthoquinones 1-4 with the dienes 5a-7 were investigated. The regioisomeric outcome of the adducts 10a-10g, 16, and 23 is in agreement with theoretical predictions from frontier orbital calculations. The adduct 10a was further converted to the non-natural (e.g. 15) and the adduct 16 to the natural angucyclinones MM 47755 (19a) and X-14881 E (22) by silicon-oxygen exchange and photooxygenation. The addition of naphtoquinones 2 and 4 to dienes 6 and 7 afford the Diels-Alder adducts 16 and 23, respectively, which are valuable intermediates for further transformation into non-aromatic angucyclinones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199508209
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  • 2
    Electronic Resource
    Electronic Resource
    The First Total Synthesis of Praecoxin B and Pterocarinin C, Two Natural Products of the Tannin Class (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1571-1575 
    Details
    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
    URL: http://dx.doi.org/10.1002/jlac.199719970738
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  • 3
    Electronic Resource
    Electronic Resource
    Total synthesis of angucyclines, 7Part 6: Ref.. Hydroaromatic angucyclines of the SF-2315 type (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1981-1985 
    Details
    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
    URL: http://dx.doi.org/10.1002/jlac.1995199511277
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  • 4
    Electronic Resource
    Electronic Resource
    Total Synthesis of Angucyclines, 4. Synthesis of rac-Tetrangomycin (1994)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 1109-1112 
    Details
    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
    URL: http://dx.doi.org/10.1002/jlac.199419941109
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  • 5
    Electronic Resource
    Electronic Resource
    Transition Metal-catalyzed Oxidations, 6. - Total Synthesis of Hallachrome and Related 1,2-anthraquinones (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 905-909 
    Details
    ISSN: 0170-2041
    Keywords: Hallachrome ; 1,2-Anthraquinones ; 9,10-Anthraquinones ; Oxygenation ; 1-Anthracenols ; Mimoun complex ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 9,10-Anthraquinones 3b-3k are prepared by Diels-Alder reaction of juglone (5a) and 7-methyljuglone (5b) with the dienes 4a and 4b, then reduced to the corresponding 1-anthracenols 2b-2d, 2f and 2i that are immediately oxygenated to the ortho-anthraquinones 1b-1d, 1f and 1i with [MoO(O2)2]·py·HMPT. The 1,2-anthraquinones dimerize in solution or upon BBr3 treatment. The naturally occurring 1,2-anthraquinone hallachrome (1a) is prepared by selective protection of the bisphenol 3h as monosilyl ether 3i, oxygenation to the silylated ortho-anthraquinone 1i and fluoride-mediated deprotection to 1a.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301142
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