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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 55 (1990), S. 3064-3067 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 2
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Nutrition 23 (2003), S. 229-261 
    ISSN: 0199-9885
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Intestinal epithelial cell turnover (proliferation, migration, differentiation, and apoptosis) and gut barrier functions are dynamic processes that are markedly affected by nutritional status, the route of feeding, and the adequacy of specific nutrients in the diet. Emerging studies are defining potential therapeutic roles for specific nutrients and diet-derived compounds (including arginine, glutamate, glutamine, glutathione, glycine, vitamin A, zinc, and specific lipids) in gut mucosal turnover, repair, adaptation after massive bowel resection, and barrier function. The role and regulation of endogenous bowel flora in generating short-chain fatty acids from diet-derived fiber and other diet-derived compounds and the effects of these agents on gut function are increasingly being elucidated. Results of these investigations should define new nutritional methods for trophic and cytoprotective effects on the intestine in conditions such as inflammatory bowel disease, malnutrition, and short bowel syndrome.
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  • 4
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enol Ethers, XVII. Acylation of Trimethylsilyl Enol Ethers with Malonyl Dichloride  -  Synthesis of 4-Hydroxy-2H-pyran-2-onesTrimethylsilyl enol ethers of aldehydes 1, acyclic and cyclic ketones 4 and 10, respectively, are acylated by malonyl dichloride (2) at room temperature or even at -60°C. After aqueous workup, the 6-unsubstituted 4-hydroxy-2H-pyran-2-ones 3 are obtained from 1-(trimethyl-siloxy)alkenes 1, whereas the 5,6-alkylene-bridged 4-hydroxy-2H-pyran-2-ones 11 are formed from 1-(trimethylsiloxy)cycloalkenes 10. Acylation of 2-(trimethylsiloxy)-1-propene (4a) and 3-(trimethylsiloxy)-2-pentene (4b) results in mixtures of 4-(trimethylsiloxy)-2H-pyran-2-ones 5 (main products) and phloroglucinol tris(trimethylsilyl) ethers 6 (by-products).
    Notes: (Trimethylsilyl)enolether von Aldehyden 1 und nichtcyclischen bzw. cyclischen Ketonen 4 bzw. 10 lassen sich mit Malonyldichlorid bei Raumtemperatur bzw. bereits bei -60°C acylieren. Hierbei entstehen nach wäßriger Aufarbeitung aus den 1-(Trimethylsiloxy)alkenen 1 die bislang nur schwer zugänglichen 6-unsubstituierten 4-Hydroxy-2H-pyran-2-one 3 und aus den 1-(Trimethylsiloxy)cycloalkenen 10 die 5,6-Alkylen-überbrückten 4-Hydroxy-2H-pyran-2-one 11. Die Acylierung von 2-(Trimethylsiloxy)-1-propen (4a) und 3-(Trimethyl-siloxy)-2-penten (4b) führt zu Gemischen aus 4-(Trimethylsiloxy)-2H-pyran-2-onen 5 (Hauptprodukte) und Phloroglucin-tris(trimethylsilylethern) 6 (Nebenprodukte).
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1339-1346 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diels-Alder Reactions with 2H-Pyran-2-ones: Reactivity and Selectivity2H-Pyran-2-ones 1 react with maleic anhydride (2) in a double Diels-Alder reaction to give bicyclo[2.2.2]oct-2-ene-5,6:7,8-tetracarboxylic dianhydrides 5; the syn/syn structure was established. As expected, the reactivity of 1 was increased by electron donor substituents (OR, alkyl) and diminished by electron withdrawing substituents (CO2R). The steric influence of substituents at C-6 also decrease the reactivity of 1. - Methyl propiolate (6) and phenylacetylene (9) react with 1 to form the Diels-Alder products 7 which suffer CO2 elimination to yield methyl benzoates 8 with low and biphenyls 10 with high regioselectivity, respectively.
    Notes: 2H-Pyran-2-one 1 gehen mit Maleinsäureanhydrid (2) eine zweifache Diels-Alder-Reaktion zu Bicyclo[2.2.2]oct-2-en-5,6:7,8-tetracarbonsäure-dianhydriden 5 ein, deren syn/syn-Struktur nachgewiesen wurde. Die Reaktivität von 1 wird erwartungsgemäß durch Donor-Substituenten (OR, Alkyl) erhöht und durch Acceptor-Substituenten (CO2R) verringert; Substituenten in 6-Stellung der α-Pyrone 1 führen infolge ihres sterischen Einflusses zu einer deutlichen Reaktivitätsverminderung. - Aus 1 und Propiolsäuremethylester (6) bzw. Phenylaceylen (9) entstehen über die primären Diels-Alder-Cycloadditionsprodukte 7 unter CO2-Abspaltung isomere Benzoesäure-methylester 8 mit geringer bzw. Biphenyle 10 mit hoher Regioselektivität.
    Additional Material: 11 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1347-1355 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses of Highly Substitued Benzenes via Diels-Alder Reactions with 2H-Pyran-2-onesThe 2H-pyran-2-ones (α-pyrones) 1 react as dienes in Diels-Alder reactions with acetylene derivatives. The primarely formed cycloadducts immediately aromatize to benzenes by CO2 elimination. Thus, methyl acetylenedicarboxylate (2a) gives dimethylphthalates 3, and methyl acetylenediphosphonate (2b) gives dimethyl 1,2-phenylenediphosphonates 8. The reactions of 1-(dimethylamino)-1-methoxyethene (9) with 1 regioselectively produce N,N-dimethylanilines 10 and isomeric homophthalate derivatives 12. Naphthoquinones 14 could be generated from 1,4-benzoquinone (13) and 1 in the presence of acetic anhydride and Pd/C. Hydroxy-2H-pyran-2-ones 4 react via their trimethylsilyl ether 6 analogously with 2a to give dimethyl (trimethylsiloxy)-phthalates 7 which are easily converted to phenols 5 by acidcatalyzed hydrolysis.
    Notes: Acetylenderivate reagieren mit 2H-Pyran-2-onen (α-Pyronen) 1 als Dien-Komponenten primär zu Diels-Alder-Cycloadditionsprodukten, die sofort unter CO2-Abspaltung zu Benzolderivaten aromatisieren. So werden mit Acetylendicarbonsäure-dimethylester (2a) Phthalsäure-dimethylester 3 und mit Acetylenbis(phosphonsäure-dimethylester) (2b) 1,2-Phenylenbis(phosphonsäure-dimethylester) 8 erhalten. 1-(Dimethylamino)-1-methoxyethen (9) sowie 2,3-Pentadiendisäure-dimethylester (11) bilden mit 1 regioselektiv N,N-Dimethylaniline 10 sowie isomere Homophthalsäure-Derivate 12. Aus 1,4-Benzochinon (13) und 1 entstehen in Gegenwart von Acetanhydrid und Pd/C Naphthochinone 14. Hydroxy-2H-pyran-2-one 4 lassen sich über ihre Trimethylsilylether 6 mit 2a zu den (Trimethylsiloxy)phthalsäure-dimethylestern 7 umsetzen, deren säurekatalysierte Hydrolyse glatt zu den Phenolen 5 führt.
    Additional Material: 13 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 741-752 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enol Ethers, XVI. Synthesis of 4-Hydroxy-2H-pyran-2-onesEnol ethers 1 are acylated by malonyl dichlorides 2 to yield pentanoic acid derivatives 3; cyclisation of 3 with conc. sulfuric acid/10% SO3 results in the formation of 6-unsubstituted 4-hydroxy-2H-pyran-2-ones 4. The formation of pyrylium salts is decisive for the avoidance of side reactions. Spectroscopic investigations establish the structure of the compounds 4 as α-pyran-ones B.
    Notes: Enolether 1 werden mit Malonyldichloriden 2 zu Pentansäurederivaten 3 acyliert, deren Cyclisierung mit konz. Schwefelsäure/10% SO3 zu in 6-Stellung unsubstituierten 4-Hydroxy-2H-pyran-2-onen 4 führt. Die Bildung von Pyryliumsalzen ist entscheidend für die Vermeidung von Nebenreaktionen. Spektroskopische Untersuchungen beweisen das Vorliegen der Verbindungen 4 in der angegebenen α-Pyranon-Struktur B.
    Additional Material: 8 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 125-130 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Intramolecular Friedel-Crafts Acylation of N-Phthaloyl-Substituted Arylalanyl and Homophenylalanyl ChloridesN-Phthaloyl-protected arylalanyl and homophenylalanyl chlorides 5 are acylated intramolecularly to 2-phtahlimido-1-indanones 6 and -1-tetralone (6d) with AlCl3 (two-fold molar amounts) or catalytic amounts of FeCl3. The cycloacylation to the tetralone 6d with AlCl3 or FeCl3 proceeds without racemisation in very good yields, whereas the cycloacylation to the indanone 6a with FeCl3 gives rise to racemisation. Mixed anhydrides 11 of N-phthaloyl-α-amino acids and trifluoromethanesulfonate were prepared from the N-phthaloylamino acid chlorides and silver triflate. Acylation of arenes 12 with 11a as well as cycloaddition of (S)-O-methyl-N-phthaloyltyrosine triflate [(S)-11e] can be achieved without racemisation and without a catalyst.
    Notes: Die intramolekulare Acylierung von N-Phthaloyl-geschützten Aryl- und Homophenylalanychloriden 5 mit zweifach molaren Mengen AlCl3 oder katalytischen Mengen FeCl3 führt zu 2-Phthal-imido-l-indanonen 6 bzw. -1-tetralon (6d). Während die Cyclo-acylierung zum Tetralon 6d mit AlCl3 und mit FeCl3 racemisierungsfrei mit sehr guten Ausbeuten abläuft, erfolgt die Bildung des Indanons 6a mit FeCl3 unter Racemisierung. N-Phthaloyl-geschützte α-Aminosäurechloride bilden mit Silber-trifluormethansulfonat gemischte Anhydride (z.B. 11a), die ohne Verwendung eines Katalysators racemisierungsfrei cyclisieren (s. z.B. 6e).
    Additional Material: 4 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2766-2782 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enol Ethers, XIII. Acylation of Enol Ethers with Reactive Carbonyl ChloridesEnol ethers 2 are acylated under mild conditions with activated acyl chlorides, e.g. chloroacetyl chlorides 1a, b, cyanoacetyl chloride (6c), and malonic acid chlorides 6a,b in good yields. The products formed and the yield depend on the acylation potential of the acyl chlorides. The potential β-keto aldehydes 4, 5, and 1,3,5-tricarbonyl compounds 8 obtained are valuable intermediates for heterocyclic synthesis.
    Notes: Enolether 2 lassen sich mit aktivierten Säurechloriden wie den Chloressigsäurechloriden 1a und 1b, Cyanacetylchlorid (6c) oder Malonylchloriden 6a, b unter milden Bedingungen in guten Ausbeuten acylieren. Die Abhängigkeit der Produktbildung und der Ausbeuten vom Acylierungspotential der eingesetzten Säurechloride wird aufgezeigt. Die erhaltenen potentiellen β-Ketoaldehyde 4, 5 bzw. 1,3,5-Tricarbonylverbindungen 8 sind wertvolle Zwischenprodukte für die Synthese von Heterocyclen.
    Additional Material: 6 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1651-1659 
    ISSN: 0009-2940
    Keywords: (R)-2-Hydroxy aldehydes, O-protected ; Hydrocyanation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of O-Protected (R)-2-Hydroxy Aldehydes and Their HydrocyanationThe synthesis of O-silyl- and O-benzyl-protected (R)-2-hydroxy aldehydes (R)-6 from (R)-2-hydroxy carboxylic acids (R)-1 is described. While attempts for their diastereoselective hydrocyanation with hydrocyanic acid and (R)-oxynitrilase as catalyst have not been successful, the cyano silylation with trimethylsilyl cyanide occurred diastereoselectively with a ratio of 81 : 19 preferring the threo form without racemization at C-2 of the 2-hydroxy aldehyde.
    Additional Material: 6 Tab.
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