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  • 1
    Electronic Resource
    Electronic Resource
    Oxidation of o-Methoxyphenols with a Hypervalent Iodine Reagent: Improved Synthesis of Asatone and Demethoxyasatone (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2579-2581 
    Details
    ISSN: 1434-193X
    Keywords: Hypervalent iodine ; Phenols ; Oxidation ; Cyclohexa-2,4-dienones ; Dimerization ; Asatone ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidation of the 2-methoxyphenols 1c-f with phenyliodonium(III) diacetate (PIDA) in methanol resulted in the formation of the cyclohexa-2,4-dienones 4c-f, which dimerized spontaneously to a single product (5c-f) in each case. Using this method the synthesis of asatone (5a) and its demethoxy analogue (5b) was also accomplished starting from the readily available phenol derivatives 1a and 1b, respectively.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Cyclodehydrogenation of 2′-hydroxychalcones with hypervalent iodine reagent: A new synthesis of flavonesDedicated to Prof. Dr. Sándor Makleit on the occasion of his 65th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1711-1715 
    Details
    ISSN: 0947-3440
    Keywords: Cyclodehydrogenation ; 2′-Hydroxychalcones ; Flavones ; Iodosobenzene diacetate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthesis of chrysin (1) and luteolin (4) was accomplished by the cyclodehydrogenation of the appropriately substituted 2′-hydroxychalcones 21 and 22 in the presence of iodosobenzene diacetate/potassium hydroxide in methanol. The scope and limitation of this transformation is discussed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199509240
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  • 3
    Electronic Resource
    Electronic Resource
    Prenylated Flavanones from Monotes engleri: On-line Structure Elucidation by LC/UV/NMR (1998)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 81 (1998), S. 754-763 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CH2Cl2 extract of Monotes engleri Gilg. (Dipterocarpaceae) showed antifungal activity against the yeast Candida albicans in our bioautographic TLC assays. After a first fractionation of the crude extract, the bioactivity was located in one of the fractions. To perform an efficient targeted isolation of the active compounds, LC/UV/MS and LC/UV/NMR analyses of the crude extract and the active fraction were performed. LC/UV/, LC/MS, and LC/NMR data (1D and 2D) allowed the identification of 1 as (2S)-2,3-dihydro-5,7-dihydroxy-{3-hydroxy-4-[(3-methylbut-2-enyl) oxy]phenyl}-4H-1-benzopyran-4-one, a new prenylated flavanone, named monoteson A. Subsequent isolation of 1 has permitted the determination of its absolute configuration on the basis of CD measurements. Theree other prenylated flavanoes 2-4 were isolated from the same extract. Compound 3 was identified as 2- (3, 5-dihydroxyphenyl) -2,3-dihydro-5, 7-dihydroxy-6, 8-bis (3-methylbut-2-enyl)-4 H-1-benzopyran-4-one, another new natural product, named monotesone B. The structures of 2 and 4 were established as selinone and lonchocarpol A, respectively. The antifungal activity against Candida albicans was determined for all compounds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19980810325
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  • 4
    Electronic Resource
    Electronic Resource
    Oxidation von 1,3-Diphenyl-1,3-propandionen mit Thallium-(III)-nitrat in Methanol (1980)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 1271-1282 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Oxidation of 1,3-Diphenyl-1,3-propanediones with Thallium(III) Nitrate in MethanolOn oxidation with thallium(III) nitrate in methanol, 1,3-diphenyl-1,3-propanediones 1 rearrange to give 3-oxo-2,3-diphenylpropanoic esters 2 and products derived therefrom. However, 1-(2-hydroxyphenyl)-3-phenyl-1,3-propanediones 1h-k undergo oxidative cyclization to 2-aroyl-3(2H)-benzofuranones 5. The alkali and acid catalysed cleavage of 5 is discussed.
    Notes: Bei der Oxidation mit Thallium(III)-nitrat in Methanol werden die 1,3-Diphenyl-1,3-propandione 1 zu den 3-Oxo-2,3-diphenylpropansäureestern 2 und deren Folgeprodukte umgelagert. Die 1-(2-Hydroxyphenyl)-3-phenyl-1,3-propandione 1h-k werden dagegen oxidativ zu den 2-Aroyl-3(2H)-benzofuranonen 5 cyclisiert.  -  Der durch Alkalilauge und Säure katalysierte Abbau von 5 wird diskutiert.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198019800811
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  • 5
    Electronic Resource
    Electronic Resource
    Versuche zur Synthese des Polystachins (1984)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1984 (1984), S. 1068-1077 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: An Attempted Synthesis of Polystachin[1′RS(3RS)]-1-(2,3-Dihydro-4-hydroxy-6-methoxy-1-benzofuran-3-yl)-2-methyl-1,2-propandiol (21), a partial structure of the title substance 1 was synthetized in 11 steps from phloroglucinol. The key steps were the oxidative rearrangement of the benzylidenacetone derivative 5 by Tl(NO3)3 in methanol to yield the 2-aryl-1,1-dimethoxythane 8 followed by ring closure involving the hydroxy group of 9 liberated by debenzylation. Conversion of 21 into compounds of structure 1 was just as unsuccessful as the synthesis of rac-polystachin (rac-1) from tachrosin (23 via the flavone derivative 29.
    Notes: [1′RS(3RS)]-1-(2,3-Dihydro-4-hydroxy-6-methoxy-1-benzofuran-3-yl)-2-methyl-1,2-propandiol (21), eine Teilstruktur der Titelsubstanz 1, wurde aus Phloroglucin in 11 Schritten synthetisiert. Als Schlüsselreaktion diente die oxidative Umlagerung des Benzalacetonderivates 5 mit Tl(NO3)3 in Methanol zu dem 2-Aryl-1,1-dimethoxyethan 8 gefolgt vom Ringschluß an der durch Entbenzylierung freigesetzten Hydroxygruppe von 9. Die Überführung von 21 in Verbindungen der Struktur 1 blieb ebenso erfolglos wie die Synthese von rac-Polystachin (rac-1) aus Tachrosin (23) über das Flavonderivat 29.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198419840603
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  • 6
    Electronic Resource
    Electronic Resource
    Oxidative Umlagerung von α-Benzylidenketonen mit Thallium(III)-nitrat in Methanol (1980)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 1283-1295 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Oxidative Rearrangement of α-Benzylideneketones with Thallium(III) Nitrate in MethanolSterically unhindered arylidene- and diarylideneacetones 1 or 2 having electron releasing aryl groups yielded with thallium(III) nitrate in methanol β-ketoacetals 3, 4 and 5, respectively. Electronegatively substituted 1f and sterically hindered 1g and 1h gave the 4-arylcrotonic esters 7 and by-products, while 1,3-dibenzylidenacetone (2a) yielded besides the expected products also the branched acetal esters 13a and 13b. Formation of the anomalous products 7 and 13 can be rationalized assuming a common cyclopropanone type intermediate.
    Notes: Sterisch unbehinderte Aryliden- und Diarylidenacetone 1 bzw. 2 mit elektronenspendenden Aryl-gruppen liefern mit Thallium(III)-nitrat in Methanol die β-Ketoacetale 3, 4 bzw. 5. Das elektronegativ substituierte 1f sowie die sterisch gehinderten Acetonderivate 1g und 1h ergeben die 4-Arylcrotonsäureester 7 und Nebenprodukte, während aus 1,3-Dibenzylidenaceton (2a) neben den erwarteten Produkten auch die verzweigten Acetalester 13a und 13b entstehen. Für die Bildung der anomalen Produkte 7 und 13 wird als gemeinsames Zwischenprodukt ein Cyclopropanonderivat vorgeschlagen.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198019800812
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  • 7
    Electronic Resource
    Electronic Resource
    Synthese von rac-4′-O-Methylglabridin, einem antimikrobiellen prenylierten Isoflavan aus Glycyrrhiza glabra L. (1983)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 2034-2037 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of rac-4′-O-Methylglabridin, an Antimicrobial Prenylated Isoflavan from Glycyrrhiza glabra L.A synthesis of racemic -4′-O-methylglabridin (1) is described. The key steps are the transformation of the isoflavan-4-one 4 into a dithioacetal 5 followed by desulfuration with Raney nickel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198319831119
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  • 8
    Electronic Resource
    Electronic Resource
    Circulardichroismus, LXXXI. Synthese und Circulardichroismus von Steroiden mit Isochromanon-Chromophor (1983)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 2247-2261 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Circular Dichroism, LXXXI. - Synthesis and Circular Dichroism of Steroids with an Isochromanone ChromophoreStarting from cholesterol the three possible stereoisomeric isochromanes 10-12 have been synthesized; their oxidation gave the corresponding lactones 13-15. The → π* band of the isochromanone („benzoic acid ester“) chromophore could unequivocally be identified in the CD spectra between 245 and 265 nm. For its Cotton effect the same helicity rule is valid as for homochirally analogous 1-tetralones: its sign, and also that of the Cotton effect within the α band of the otherwise not substituted benzene chromophore, is opposite to that of the torsional angle (O=)C—C(=Ctransoid); the sign of the Cotton effect within the „conjugation band“ is the same as that of this torsional angle. The correlation between absolute configuration and CD of natural isochromanone derivatives is discussed: only for the Cotton effect within the n → π* band the mentioned helicity rule is independent of the substitution of the benzene ring. The invalidity of the helicity rule of chiral tetralins for homochirally analogous isochromanes can be explained with the help of Petruska's „q values“.
    Notes: Ausgehend von Cholesterin wurden die drei möglichen stereoisomeren Isochromane 10-12 synthetisiert, die durch Oxidation die entsprechenden Lactone 13-15 ergaben. Die n → π*-Bande des Isochromanon-(„Benzoesäureester“-)Chromophors konnte in den CD-Spektren zwischen 245 und 265 nm eindeutig identifiziert werden. Für ihren Cotton-Effekt gilt die gleiche Helizitätsregel wie für homochiral analoge 1-Tetralone: sein Vorzeichen sowie das des Cotton-Effekts innerhalb der α-Bande des sonst unsubstituierten Benzolchromophors ist entgegengesetzt zum Vorzeichen des Torsionswinkels (O=)C—C(=Ctransoid); das Vorzeichen des Cotton-Effekts innerhalb der “Konjugationsbande“ ist gleich dem dieses Torsionswinkels. Der Zusammenhang zwischen absoluter Konfiguration und CD natürlicher Isochromanonderivate wird diskutiert: nur für den Cotton-Effekt innerhalb der n → π*-Bande ist die genannte Helizitätsregel von der Benzolring-substitution unabhängig. Die Ungültigkeit der Helizitätsregel chiraler Tetraline für homochiral analoge Isochromane kann mit Hilfe der „q-Werte“ von Petruska erklärt werden.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198319831218
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