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  • Organic Chemistry  (14)
  • Inorganic Chemistry  (8)
  • Koenigs-Knorr reaction  (2)
  • Anhydrofuranoses  (1)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 534-540 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two pyruvated galactosyl donors, 2,3-di-O-benzoyl-4,6-O-[1-(R)-methoxycarbonyl(ethylidene)]-α-D-galactopyranosyl chloride (6) and trichloroacetimidate 13, were coupled to position 3 of suitably protected mono and disaccharide benzyl glucoside acceptors. For both donors, an unusual high content of the α-(1 → 3)-linked products was obtained. The corresponding β-(1 → 3)-linked di- and trisaccharides are related to exopolysaccharides of Rhizobium leguminosarum.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 373-378 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: In boiling 1,2-dichloroethane 3-ethoxyacryloyl chloride (1) reacts with phenols 2 to yield 3-ethoxyacrylates 3, which by treatment with conc. sulfuric acid/10% SO3 cyclize to give coumarins 9 in good yields. The methoxy-substituted compounds 3d and 3k do not react to coumarins 9 with H2SO4/SO3 but with POCl3/H2O at room temperature.
    Notes: Aus 3-Ethoxyacryloylchlorid (1) und Phenolen 2 entstehen in siedendem 1,2-Dichlorethan 3-Ethoxyacrylsäure-arylester 3, die sich mit konz. H2SO4/10% SO3 bei 0°C in guten Ausbeuten zu Cumarinen 9 cyclisieren lassen. Die 3-Ethoxyacrylsäure-methoxy-phenylester 3d und 3k cyclisieren unter diesen Bedingungen nicht, lassen sich jedoch mit POCl3/H2O bei Raumtemperatur ebenfalls in guten Ausbeuten in die entsprechenden Cumarine 9d und 9k überführen.
    Additional Material: 5 Tab.
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  • 3
    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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  • 4
    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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  • 5
    ISSN: 0170-2041
    Keywords: Carbohydrates ; Furanoses, 3,6-anhydro ; Glycosides, pyruvylated ; Anhydrofuranoses ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of methyl 2,3-di-O-acyl-D-glycopyranosides 1 of glucose and mannose with catalytic amounts of trifluoromethanesulfonic acid afforded the corresponding bis(5-O-acyl-3,6-anhydro-D-glycofuranose) 1,2′:2,1′-dianhydrides 6 in 12-58% yield the structure of which was confirmed for the α-D-glucose derivative 6a by an X-ray analysis. In addition, in the presence of methyl pyruvate (2a) or methyl 2-acetoxy-acrylate (2b) various amounts of diastereomeric 3,6-anhydro-5-O-benzoyl-1,2-O-(1-methoxycarbonyl)ethylidene-α-D-glucofuranoses 5 and acylated methyl α-D-glucopyranosides 3 and 4, respectively, were formed.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 659-664 
    ISSN: 0170-2041
    Keywords: Glycosylations ; Protecting groups ; Benzoyl, 2-chloroacetoxymethyl- ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of the 2-(chloroacetoxymethyl)benzoyl (CAMB) group to the O-protection of position 2 in glycosyl donors is described. Saponification of the phthalide and subsequent chloroacetylation of 2-(hydroxymethyl)benzoic acid (1) gave 2-(chloroacetoxymethyl)benzoic acid (2). Treatment of 2 with thionyl chloride afforded the acyl chloride 3. Acylation of O-2 of 1,3,4,6-tetra-O-acetyl-α-D-glucopyranose (4a), galactopyranose (4b) and of the amino group of 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-β-D-glucopyranose (4c) afforded the fully protected pyranose derivatives 5a-c in high yields. Compounds 5a and 5b were converted with HBr in acetic acid into the corresponding 2-O-CAMB-protected bromides 6a, b in excellent yields. Silver trifluoromethanesulfonate promoted glycosylation of the latter with 2-hydroxyethyl benzoate yielded the β-glycosides 8a (74%) and 8b (69%). Direct activation of the glucosamine derivative 5c with ferric chloride gave the glucoside 8c (54%). Furthermore, the galactosyl bromide 6b was coupled with methyl 2,3,4-tri-O-benzoyl-β-D-glucopyranoside (11) affording the 2′-O-CAMB-protected methyl glycoside disaccharide 12 (63%). Similarly, condensation of the glucosyl bromide 6a with 4a gave the β-(1→2)-linked disaccharide 13 (45%). Treatment of compounds 8a and 13 with thiourea resulted in the deblocked glycosides 9a and 14. Similar deprotection of 8b gave 2-benzoyloxyethyl 3,4,6-tri-O-acetyl-β-D-galactopyranoside (9b) and the 2-O-[2-(hydroxymethyl)benzoyl] derivative 10. Reaction of 8c with thiourea afforded solely the dechloroacetylated glucoside 9c.
    Additional Material: 2 Tab.
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  • 7
    ISSN: 0170-2041
    Keywords: Galactosides, 3,4-pyruvylated ; Oligosaccharides ; Carbohydrates ; Escherichia coli ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of phenyl 1-thio- and allyl 2,6-di-O-benzoyl-D-galactopyranosides 3 with methyl pyruvate and BF3 · Et2O in various solvents gave 1,6-anhydro-3,4-di-O-benzoyl-2-deoxy-2-phenylthio-β-D-idopyranose (4) and the corresponding diastereomers of 3,4-O-pyruvate acetal-containing galactosides 5. The phenyl 1-thio-β-galactoside R-5a and the allyl a-galactoside R-5b were both converted into methyl 3,4-O-[1-(R)-(methoxycarbonyl)ethylidene]-β-D-galactopyranoside (9), the structure of which as well as that of 4 was confirmed by X-ray crystallography. Compound R-5a was converted into 5-[(benzyloxycarbonyl)amino]pentyl 6-O-benzoyl-3,4-O-[1-(R)-(methoxycarbonyl)ethylidene]-β-D-galactopyranoside (18) by using the (2-chloroacetoxymethyl)benzoyl (CAMB) group for the temporary protection of position 2. Glucosamination of 18 and subsequent deblocking of the intermediate disaccharide gave β-D-GlcpNAc-(1→2)-3,4-(S)-pyruvate-β-D-Galp-O(CH2)5NH2 (21) which represents a fragment of the Escherichia coli K 47 polysaccharide.
    Additional Material: 1 Ill.
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  • 8
    ISSN: 0170-2041
    Keywords: Anomerization ; Glycosides ; Glycosyl donors, pyruvylated ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of 4,6-O-(1-methoxycarbonylethylidene)-D-glycopyranosides 5 starting from 2,3-di-O-benzoyl-D-glycopyranosides 1 and their 4,6-bis-O-trimethylsilyl ethers 2 using methyl 2,2-bis(phenylthio)propionate (4) and methyl pyruvate (3), respectively, under Lewis acid catalysis conditions is described. In the D-gluco series anomerisation of alkyl β-D-glucopyranosides is observed as a side reaction, giving complex mixtures and low yields of the title compounds whereas alkyl-α-D-glucopyranosides and alkyl or phenyl 1-thio-β-D-glucopyranosides react without anomerisation. The reactions are accompanied by isomerisation of the initially formed diastereomer (R)-5 having an equatorial methoxycarbonyl group to the thermodynamically favoured diastereomer (S)-5 having the methoxycarbonyl group in an axial position. In the D-galacto series similar side reactions are observed accompanied by rearrangement to furanosides 9 of alkyl and phenyl β-D-galactopyranosides. The results are used for efficient syntheses of two protected disaccharides 8 and 11 representing structural fragments of the polysaccharide repeating units of Mycobacteria and Rhizobia via pyruvate acetal-containing glucosyl and galactosyl donors 7 and 10.
    Additional Material: 5 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 1125-1131 
    ISSN: 0170-2041
    Keywords: Glycosyl halides ; Haloacetates ; Koenigs-Knorr reaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chloroacetylation of alkyl glycopyranosides of β-D-galactose, β-D-glucose and α-D-mannose as well as of free D-glucose, D-galactose, D-mannose and D-xylose, using chloroacetic anhydride as acylating reagent, gave the corresponding fully chloroacetylated pyranose derivatives in excellent yields. From D-glucose, 1,2,3,6-tetra-O-chloroacetyl-α-D-glucopyranose (9) was also obtained. Subsequent treatment of the fully chloroacetylated α-D-glycopyranoses 3, 8, 13 and 15 of galactose, glucose, mannose, and xylose, respectively, with HBr resulted in 2,3,4,6-tetra-O-chloroacetyl-α-D-galactopyranosyl bromide (4, 98%), -glucopyranosyl bromide (10, 92%), -mannopyranosyl bromide (14, 72%) and 2,3,4-tri-O-chloroacetyl-α-D-xylopyranosyl bromide (16, 68%). 10 reacted with D-pantholactone (17) and silver trifluoromethanesulfonate under acidic conditions to give the corresponding α-linked (18, 45%) and β-linked (20, 38%) glucopyranosides. Under basic conditions the corresponding ortho ester product 21 was formed (92%) which upon treatment with BF3 gave the glucosides 18 and 20. Silver silicate as the catalyst gave only traces of 18. Thus, 20 was isolated in 80% yield. Reaction of 10 with silver crotonate and silver laurate gave 1-O-crotonoyl- (22) and 1-O-lauroyl-2,3,4,6-tetra-O-chloroacetyl-β-D-glucopyranose (24), respectively. 18 and 22 were dechloroacetylated with thiourea, affording the corresponding deblocked glucose derivatives 19 and 23, respectively.
    Additional Material: 1 Tab.
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  • 10
    ISSN: 0170-2041
    Keywords: Cyanohydrins and cyanohydrin esters, optically active ; Resolutions, kinetic enzyme-catalyzed ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enzyme-Catalyzed Reactions, 71). - Enantioselective Esterification of Racemic Cyanohydrins and Enantioselective Hydrolysis or Transesterification of Cyanohydrin Esters by LipasesPure cyanohydrin enantiomers (S)-1/(R)-1 and their O-acyl derivatives (R)-3/(S)-3 are obtained from three different lipasecatalyzed reactions: i) enantioselective hydrolysis of aliphatic and aromatic racemic cyanohydrin esters 3, ii) enantioselective acylation of racemic cyanohydrins 1, iii) enantioselective transesterification of 3 with primary alcohols. Both the cyanohydrin esters and the free cyanohydrins (which are prone to racemization) are isolated as enantiomers with high optical purity on a preparative scale. Hydrolysis of the racemic butyrates 3b, e with Candida cylindracea lipase and pseudomonas sp. lipase, respectively, for example, affords the free (S)-cyanohydrins (S)-2-hydroxypentanenitril [(S)-1a] and (S)-mandelonitrile [(S)-1b)] in high yield with 97 and 96% ee, respectively. (S)-1a is obtained with the same optical purity by candida sp. lipase-catalyzed transesterification of 3b with 1-octanol.
    Additional Material: 4 Tab.
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