ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Organic Chemistry  (14)
  • (R)-2-Hydroxy aldehydes, O-protected  (1)
  • 1
    ISSN: 0947-3440
    Keywords: Carbohydrates ; Disaccharides ; Glycosylation, intramolecular ; β-L-Rhamnoside ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Disaccharides containing a β-L-rhamnosyl residue were prepared by a novel intramolecular glycosylation strategy. Thus, suitably benzyl-protected L-rhamnosyl donors (ethyl and phenyl 1-thiorhamnoside 7, 18) were prearranged in positions 2 and 3 with benzyl 2-O-benzoyl-4,6-O-benzylidene-α-D-glucopyranoside 8 in position 3 by a malonyl, succinyl and phthaloyl bridge, respectively, to give the corresponding connected saccharides 9, 12, 16 and 20. After regioselective opening of the benzylidene ring of the glucoside residue to give compounds 10, 13, 17 and 21, the latter afforded the 3,2′- and 3,3′-bridged disaccharides 22-25 upon intramolecular glycosylation with a thiophilic reagent. The anomeric selectivity of this intramolecular glycosylation is strongly influenced by the nature of the alkanoyl and aroyl bridge, its position at the rhamnosyl residue and the solvent used for the coupling. Best results were obtained in acetonitrile with the succinyl „spacer“ attached to position 2 of the phenyl 1-thiorhamnoside and position 3 of the glucoside that afforded the corresponding β-(1→4)-linked disaccharide 22β in 76% yield.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyruvated di- and trisaccharide fragments representing the immunodominant side chains of Klebsiella K26 capsular polysaccharides are prepared. Phenyl 4′,6′-O-benzylidene-1-thio-β-D-lactoside (1) is converted in 4 steps into the corresponding pyruvated 1-thio-lactoside (2) and transformed into the imidate (4). Coupling of the latter with Z-protected 5-aminopentanol gives the pyruvated disaccharide fragment (6) upon deblocking. Similarly, imidate (4) is coupled to allyl 2,3-di-O-benzoyl-3-O-(1-fluoro-1,1,3,3-tetraisopropyl-1,3-disiloxane-3-yl)-α-D-glucopyranoside (8) to give the corresponding trisaccharide fragment upon deblocking.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0947-3440
    Keywords: Carbohydrates ; Tetrasaccharide, bacterial ; Glycosylation, intramolecular ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The blockwise synthesis of the pyruvated tetrasaccharide 4,6-(S)-pyruvic-acetal-β-d-GlcNAcp-(1→3)-α-d-Galp-(1→4)-β-l-Rhap-(1→4)-β-d-Glcp-O(CH2)5NH2 (32), related to the repeating unit of the capsular polysaccharide of Streptoccus pneumoniae type 27, by coupling of the suitably protected disaccharide blocks 4,6(S)-pyruvic-acetal-β-d-GlcNAcp-(1→3)-α-d-Galp-trichloroacetimidate (13) and β-l-Rhap-(1→4)-β-d-Glcp-O(CH2)5NHZ (29β) is described. The latter disaccharide acceptor was prepared via prearranged glycosides by intramolecular glycosylation of a protected 5-aminopentyl β-d-glucopyranoside linked by a succinyl bridge at C-3 to C-2 of ethyl 1-thio-α-l-rhamnopyranoside. The dependence of the anomeric selectivity of the coupling on the nature of the protecting group at C-4 of the rhamnosyl moiety is studied.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 1-O-trimethylsilyl-glycoses, 1-O-acylglycoses and glycosyl fluorides, respectively, with silylated alcohols (glycodesilylations) are summarized. Synthetic strategies toward oligosaccharides using glycodesilylations are discussed as well and some typical experimental procedures are given.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0170-2041
    Keywords: 2-Amino alcohols ; Cyanohydrins ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enzyme-Catalyzed Reactions, 8. - Stereoselective Synthesis of 2-Amino Alcohols from (R)- and (S)-Cyanohydrinserythro-2-Amino alcohols (1R,2S)- and (1S,2R)-4 may be synthesized stereoselectively by addition of Grignard compounds to cyanohydrins (R)-, (S)-1 and their O-trimethylsilyl derivatives 3, respectively, followed by hydrogenation. The threo-2-amino alcohols (1S,2S)- and (1R,2R)-4 are easily accessible by inversion at C-1 of the (1R,2S) and (1S,2R) compounds.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0170-2041
    Keywords: Glycosylation ; Koenigs-Knorr reaction ; Acyl-group migration ; Transesterification ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-O-[2,2,2-D3]Acetyl-3,4,6-tri-O-acetyl-α-D-galactopyranosyl bromide (3) was prepared and used as the glycosyl donor in studying the silver trifluoromethanesulfonate-promoted reaction with methyl 2,3,4-tri-O-benzoyl-β-D-galactopyranoside (4) and methyl 2,4,6-tri-O-benzoyl-β-D-galactopyranoside (7). In addition to the expected β-linked disaccharides, methyl 6-O-[2,2,2-D3]acetyl-2,3,4-tri-O-benzoyl-β-D-galactopyranoside (6) and methyl 3-O-[2,2,2-D3]acetyl-2,4,6-tri-O-benzoyl-β-D-galactopyranoside (9), respectively, were formed. The latter compounds were isolated from the reaction mixture and their structures were confirmed based on spectral data. Thus, it has been proven that, with fully acetylated glycosyl halides as glycosyl donors, in silver trifluoromethanesulfonate-promoted couplings, O-acetylation of the nucleophile occurs as a side reaction, the acetyl group involved originating from position 2 of the glycosyl halide.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...