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  • Articles: DFG German National Licenses  (10)
  • Trichloroacetimidates  (10)
  • 1
    Electronic Resource
    Electronic Resource
    The Dimethylmaleoyl Group as Amino Protective Group - Application to the Synthesis of Glucosamine-Containing Oligosaccharides (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2305-2316 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Protecting groups ; Amino sugars ; Glycosylations ; Trichloroacetimidates ; Glycosides, glucosamine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Glucosamine was readily transformed into N-dimethylmaleoyl (DMM) protected derivative 1 which furnished trichloroacetimidate 4 as glycosyl donor. Reaction with various acceptors (5a-g) in the presence of TMSOTf as the catalyst afforded the corresponding β-glycosides 6a-g generally in high yields. Cleavage of the DMM group was readily accomplished by treatment with aqueous NaOH and then with HCl (pH 5). Starting from 1 also DMM group containing glycosyl acceptors 9 and 14a-c were synthesized. They furnished with trichloroacetimidates 12 and 4 as glycosyl donors β(1-4)- and β(1-3)-linked disaccharides 13 and 15a-c, respectively. From 18 as galactosyl donor and 14a as acceptor β(1-3)-linked disaccharide 19 was obtained in high yield, which is a versatile building block for the important Galβ(1-3)GlcNAc unit. 19 was transformed into trichloroacetimidate 21; glycosylation with 5e as acceptor gave trisaccharide 22 which furnished on partial deprotection Galβ(1-3)GlcNAcβ(1-4)Glc derivative 24. Thus, the wide applicability of DMM as amino protective group in oligosaccharide synthesis is exhibited.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of Lacto-N-neohexaose and Lacto-N-neooctaose Using the Dimethylmaleoyl Moiety as an Amino Protective Group (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 319-326 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Amino sugars ; Protecting groups ; Glycosylations ; Trichloroacetimidates ; Oligosaccharides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The N-DMM-Protected lactosamine derivative 2 was readily transformed into the corresponding glycosyl donor 4 and into acceptor 5. A TMSOTf-catalyzed glycosidation afforded the derived tetrasaccharide 6 which led to glycosyl donor 9. Reaction of 9 with lactose derivative 10 as acceptor gave the desired hexasaccharide 11. Cleavage of all protective groups and N-acetylation afforded the target molecule 1b (lacto-N-neohexaose). Glycosylation of acceptor 10 with donor 4 furnished tetrasaccharide 16 which, employing standard procedures, gave acceptor 18. Glycosylation of 18 with donor 9 furnished, under standard conditions, octasaccharide 19. Cleavage of all protective groups and N-acetylation afforded the target molecule 1c (lacto-N-neooctaose). Both 1b and 1c were obtained in good overall yields.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Glycosyl imidates, 70. Synthesis of a coumarin C-glucoside (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 467-469 
    Details
    ISSN: 0947-3440
    Keywords: Glycosides ; Carbohydrates ; Trichloroacetimidates ; Coumarin derivatives ; Fries rearrangement ; Perkin reaction ; Wittig reaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,5-Dimethoxyphenol (2) was glycosylated with O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl) trichloroacetimidate (1) and trimethylsilyl triflate (TMSOTf) as the promoter to yield the aryl C-glycoside 3 via an O-glycoside intermediate and subsequent Fries rearrangement. After formylation, the coumarin C-glycoside 7 was synthesized either by Perkin reaction with acetic anhydride or by Wittig reaction followed by cyclization at 150°C. Deprotonation yielded the coumarin 8-C-glycoside 8, a dimethyl ether of an isomer of naturally occurring coumarin 6-C-glycosides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950363
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  • 4
    Electronic Resource
    Electronic Resource
    Glycosyl imidates, 69. Synthesis of flavone C-glycosides vitexin, isovitexin, and isoembigenin (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 461-466 
    Details
    ISSN: 0947-3440
    Keywords: Glycosides ; Flavones ; Vitexin ; Isovitexin ; Isoembigenin ; Carbohydrates ; Trichloroacetimidates ; Fries rearrangement ; Baker-Venkataraman rearrangement ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Hydroxy-4,6-dimethoxyacetophenone (4) was glycosylated with O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl) trichloroacetimidate (5) and trimethylsilyl triflate as promoter to yield directly the C-glycoside 6. Construction of the flavone system by application of a Baker-Venkataraman-type rearrangement followed by deprotection yielded isoembigenin (2). Glycosylation of 4,6-bis(tert-butyldimethylsilyloxy)-2-hydroxyacetophenone (17) with the trichloroacetimidate 5 afforded the O-glycoside intermediate 18 which was converted via Fries rearrangement into the C-glycoside 21. Applying again the Baker-Venkataraman rearrangement and cyclization gave isovitexin and vitexin derivatives 25 and 26, which were completely deprotected to yield isovitexin (1b) and vitexin (1a), respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950362
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  • 5
    Electronic Resource
    Electronic Resource
    Glycosyl imidates, 47. Stereospecific synthesis of α- and β-L-fucopyranosyl phosphates and of gdp-fucose via trichloroacetimidate (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 121-124 
    Details
    ISSN: 0170-2041
    Keywords: Fucopyranosyl phosphate ; Fucose 1-phosphate ; Glycosyl phosphate ; GDP-fucose ; Guanosine diphosphofucose ; Trichloroacetimidates ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the benzyl- and acetyl-protected α-trichloroacetimidates 1 and 6α with dialkyl and diaryl phosphates in the presence of traces of acid affords stereoelectively the thermodynamically more stable α-L-fucopyranosyl phosphates 2, 7 and 8, respectively, in high yields. The use of very pure, recrystallized dibenzyl phosphate results in the stereoeletive formation of the β-L-fucopyranosyl phosphates 3 and 9. In each case separation of the anomers is not required because of the very high stereoselectivity of the reactions. After deprotection the fucose 1-phosphate 12 is coupled with GMP morpholidate 10 to yield GDP-fucose 13. After the development of a new purification procedure for GDP-fucose 13 we have obtained a very pure compound suitable for biochemical investigations. Analytical and preparative HPLC has been performed on reversed-phase columns using a volatile buffer system (triethylammonium hydrogen carbonate) as the eluant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199119910122
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  • 6
    Electronic Resource
    Electronic Resource
    Glycosyl Imidates, 62. - Synthesis of the Heptasaccharide Moiety of Ganglioside BGM1 (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 859-864 
    Details
    ISSN: 0170-2041
    Keywords: Glycosphingolipids ; Ganglio series ; Blood group B determinant ; Glycosides ; Trichloroacetimidates ; Saccharides ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the O-acetyl protected heptasaccharide moiety (2) of BGM1 was performed according to the following reaction sequence: Reaction of 2,3-di-O-acetyl-4,6-O-benzylidenegalactosyl trichloroacetimidate 4 (as donor) with 3-O-unprotected 2-azidogalactose 5 (as acceptor) gave β(1→3)-connected disaccharide 6. Subsequent O-deacetylation followed by reaction with galactosyl donor 8 afforded regioselectively trisaccharide 9 which was converted into tetrasaccharide 12 by treatment with fucosyl donor 11. Transformation of 12 via acid-catalyzed O-deisopropylidenation, O-acetylation, anomeric O-desilylation, and then base-catalyzed treatment with trichloroacetonitrile afforded trichloroacetimidate 16 as tetraosyl donor. Reaction of 16 with the known 4b-O-unprotected sialyllactose derivative 17 gave in acetonitrile at -40°C in the presence of TMSOTf as the catalyst the desired heptasaccharide 18. Azido group reduction with propanedithiol, N-acetylation, hydrogenolytic O-debenzylation, and O-debenzylidenation under acidic conditions followed by O-acetylation afforded the target molecule 2. The structural assignments were based on the 1H-NMR data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301136
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  • 7
    Electronic Resource
    Electronic Resource
    Glycosyl Imidates, 66. Synthesis of the Tetrasaccharide Moiety of Plant Growth Regulator Calonyctin A (1994)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 645-651 
    Details
    ISSN: 0170-2041
    Keywords: Calonyctin A ; Saccharides ; Resin glycosides ; Glycosides ; Trichloroacetimidates ; Carbohydrates ; D-Quinovose ; L-Rhamnose ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-O-Benzyl-protected quinovose 6 was transformed into 1,2-O-unprotected derivative 9 which on treatment with TBS-Cl in the presence of a base gave selectively 2-O-unprotected glycosyl acceptor 10. Similarly, 3-O-allyl-protected quinovose 11 was transformed into 1,2-O-unprotected derivative 14. 1,2-O-Acetylation of 14, selective removal of the 1-O-acetyl group with hydrazinium acetate, and subsequent treatment with trichloroacetonitrile in the presence of DBU furnished the versatile 2-O-acetyl-3-O-allyl-protected quinovosyl donor 17. Reaction of donor 17 with acceptor 10 in the presence of TMSOTf as the catalyst gave disaccharide 19. Treatment of 19 with NaOMe/MeOH provided 2b-O-unprotected derivative 20 which gave with rhamnosyl donor 18 in the presence of TMSOTf as the catalyst trisaccharide 21. 3b-O-Deallylation of 21 and subsequent reaction with donor 17, again in the presence of TMSOTf as the catalyst, gave target tetrasaccharide 2. Removal of all O-protective groups furnished D-Quiß(1→3)[L-Rhaα(1→2)]D-Quiß(1→2)D-Qui (3), the tetrasaccharide moiety of calonyctin A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199419940702
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of 4-Epoxy-4-c-methyleneglycosylceramides, Potential Glycosyltransferase Inhibitors (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 699-708 
    Details
    ISSN: 0170-2041
    Keywords: Carbohydrates ; Trichloroacetimidates ; Azidosphingosines ; Glycosphingolipids ; Enzyme inhibitors ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: D-Glucose was transformed into the 4-deoxy-4-C-methylene derivative 1. Dihydroxylation of 1 and then selective O-tosylation afforded 4-C-(tosyloxymethyl)glucoside 3. Subsequent hydrogenolytic O-debenzylation, selective O-acetylation, treatment with a base, selective removal of the anomeric O-acetyl group, and then treatment with trichloroacetonitrile in the presence of a base furnished 4-epoxy-4-C-methyleneglucosyl donor 7 (α,β mixture). Reaction of 7 with 3-O-acyl-protected azidosphingosines 8a-c in the presence of Et2O.BF3 gave β-glycosides 9a-c. Compounds 9a-c were transformed into the corresponding glucosylceramide derivatives 10a-c by treatment with triphenylphosphane/water and acyl anhydrides. Satisfactory removal of the O-benzoyl protective group was difficult; however, O-acetyl and O-isobutyryl protective groups could be removed by methanolysis, thus affording from 10b, c the target molecules 11 and 12 with varying alkyl-chain length. The epoxide 16 with galacto configuration, readily obtained from 1, on treatment with p-toluenesulfonic acid furnished 4-C-(tosyloxymethyl)galactoside 18; this was transformed, as outlined for 3, into the target molecules 25b, c having galacto configuration in the sugar moiety.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1992199201118
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  • 9
    Electronic Resource
    Electronic Resource
    Glycosyl Imidates, 61. - Synthesis of the Hexasaccharide Moiety of the Saponin Holotoxin A (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 853-858 
    Details
    ISSN: 0170-2041
    Keywords: Glycosides ; Trichloroacetimidates ; Xylose ; Quinovose ; Saponins ; Holotoxin A ; Sea cucumbers ; Stichopus japonicus SELENCA ; Carbohydrates ; Saccharides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of O-(3-O-methylglucosyl) trichloroacetimidate 2a as glycosyl donor and 1,2:5,6-di-O-isopropylidene-D-glucofuranose (3) as glycosyl acceptor furnished in the presence of TMSOTf as catalyst the β-(1→3)-connected disaccharide 5a. Similarly, from O-quinovosyl trichloroacetimidate 2b and 3 the disaccharide 5b was obtained. Compound 5a was transformed via acid-catalyzed O-deisopropylidenation, O-acetylation, and selective 1-O-deacetylation into 7. Treatment of 7 with trichloroacetonitrile in the presence of DBU furnished trichloroacetimidate 8 as glycosyl donor. Reaction of 8 with 2,4-O-unprotected xylopyranoside 9 as glycosyl acceptor afforded selectively trisaccharide 10. Similarly, reaction of 8 with 2,4-O-unprotected quinovoside 12 furnished selectively trisaccharide 13 which gave upon O-acetylation, 1-O-desilylation, and then treatment with trichloroacetonitrile in the presence of DBU trichloroacetimidate 15 as triosyl donor. Reaction of 10 with 15 in the presence of TMSOTf as catalyst led to hexasaccharide 16; ensuing hydrogenolytic O-debenzylation and then O-acetylation afforded the desired hexasaccharide 17.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301135
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  • 10
    Electronic Resource
    Electronic Resource
    Glycosyl Imidates, 56. Synthesis of the Hexasaccharide Moiety of Pectinioside E (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 975-982 
    Details
    ISSN: 0170-2041
    Keywords: Steroids ; Glycosides ; Saponins ; Pectinioside E ; Saccharides ; Trichloroacetimidates ; Carbohydrates ; Starfishes ; Asterina pectinifera ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the hexasaccharide moiety 2 of pectinioside E (1), isolated from the whole bodies of the starfish Asterina pectinifera Müller et Troschel, is described. Building block 4 was prepared by a six-step procedure from D-glucose. A reasonable yield was obtained via selective glycosylation of 4 at 2-OH with donor 5 to give the desired disaccharide 6 which served as an acceptor in the following fucosylation with 9 to afford the crucial trisaccharide 10. This was easily transformed into trichloroacetimidate 12. Disaccharide 17, obtained in high yield by glycosylation of donor 13 with acceptor 14 followed by deacetylation, turned out to be more reactive at 4b-OH than at 2b-OH. Thus, the reaction of donor 12 with acceptor 17 gave the desired pentasaccharide 18 β in an acceptable yield; 18 β was readily transformed into the hexasaccharide 20 by glycosylation with donor 15. Debenzylation of 20 followed by deacylation furnished the target hexasaccharide 2 which was characterized by its per-O-acetylated product 21.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1992199201160
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