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  • Koenigs-Knorr reaction  (2)
  • Oligosaccharides  (2)
  • Cyanohydrins  (1)
  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 269-273 
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 181-186 
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Oligosaccharides ; Glycosylations ; Organic synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The tetrasaccharide 5-aminopentyl glycoside β-D-Manp-(1→4)-β-D-Glcp-(1→4)-α-L-Rhap-(1→3)-β-D-Glcp-1-O-(CH2)5NH2(22) related to the exopolysaccharide of Arthrobacter sp. CE-17 was synthesized by coupling of the properly protected disaccharide blocks β-D-Manp-(1→4)-β-D-Glcp-1-S-Ph (11) and α-L-Rhap-(1→3)-β-D-Glcp-1-O-(CH2)5NHZ (20). Building block 11 was obtained by intramolecular β-mannosylation of a malonyl-tethered disaccharide glycoside which was prepared from phenyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside (1) and ethyl 2,3,4-tri-O-benzyl-1-thio-α-D-mannopyranoside (5) in 5 steps. Building block 20 was obtained by coupling N-Z-protected 5-aminopentyl 2-O-benzyl-4,6-O-benzylidene-β-D-glucopyranoside (14) obtained from the non-benzylated counterpart 12 with ethyl 2,3-di-O-benzoyl-4-O-chloroacetyl-1-thio-α-L-rhamnopyranoside (18) obtained in 3 steps from ethyl 2,3-O-isopropylidene-1-thio-α-L-rhamnopyranoside (15).
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 613-615 
    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.
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