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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of Hetaryl Glycosides and Their Glycosyl Donor Properties (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1353-1360 
    Details
    ISSN: 1434-193X
    Keywords: Heterocycles ; Substitution ; Carbohydrates ; Anomeric O-hetarylation ; Glycosylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Anomeric O-hetarylation of tetra-O-benzyl- and tetra-O-acetylglucose (1a, b) can be directly performed with electron-deficient heteroaromatic/heterocyclic systems 2-14, which contain imide halide moieties. The reactions were carried out in the presence of a base and led, through an exchange of the halide by the glucopyranosyloxy moiety, to the products 2a-14a, 7b-14b. Predominantly or exclusively β-products were obtained. Systems bearing more than one imide halide moiety, such as cyanuric fluoride (15) or 5-chloro-2,4,6-trifluoropyrimidine (16), can be employed for successive anomeric O-hetarylations. Investigation of the glycosyl donor properties of O-glucosyl heteroaromatic imidates with 6-O- and 4-O-unprotected glucose derivatives 18 and 19 as acceptors and comparison of the results obtained with data for the corresponding β-trichloroacetimidates 17aβ and 17bβ, reveals that 2,3,5,6-tetrafluoropyridin-4-yl glucopyranosides 14aβ and 14bβ exhibit similar properties. For specific tasks, for instance α-glucopyranoside formation, 14aβ may even be advantageous.
    Type of Medium: Electronic Resource
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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Glycosyl Phosphatidylinositol (GPI) Anchor Synthesis Based on Versatile Building Blocks - Total Synthesis of a GPI Anchor of Yeast (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1153-1165 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Phospholipids ; Glycolipids ; Sphingosines ; Ceramides ; Ceramides-1-phosphates ; Glycosylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -For the design of a synthesis of target molecule 1 the retrosynthetic analysis yielded building blocks 2-5, of which ceramide 2-phosphite derivative 2 and aminoethyl phosphite derivative 5 are known. The generation of α-glucosaminyl (1→6)inositol building block 3 was based on pseudodisaccharide 6 which was selectively benzoylated at 6b-O and then selectively benzylated at 3b-O to give 3. The synthesis of tetramannosyl building block 4 started from known ortho ester derivative 8 which was transformed into versatile mannosyl donors 13 and 18 and into acceptor 22. Reaction of 13 with 22 gave α-disaccharide 23, deacetylation and then mannosylation with 18 gave trisaccharide 25; ensuing deacetylation and mannosylation with 13 gave tetrasaccharide 27; deallylation, acetylation, regioselective removal of the anomeric O-acetyl group and treatment with CCl3CN/DBU afforded 4. Glycosylation of 3 with donor 4 led to pseudohexasaccharide 31 in high yield. Replacement of the O-acyl groups by O-benzyl groups and then exchange of the menthyloxycarbonyl group by an O-acetyl group gave 36 which enabled regioselective attachment of 2 and 5. To this end, the 6e-O-silyl group was removed and then the aminoethyl phosphate residue was attached with reagent 5 to give 38 in high yield. 1a-O-Deacetylation and then reaction with 2 afforded 40 as fully protected 1 which was liberated in two steps; treatment with acid removed all acid labile protective groups and finally catalytic hydrogenation afforded the desired GPI anchor 1 which could be fully structurally assigned.
    Type of Medium: Electronic Resource
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Glycosyl Imidates, 55. Synthesis of the Pentasaccharide Moiety of an Asterosaponin (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 817-823 
    Details
    ISSN: 0170-2041
    Keywords: Glycosyl trichloroacetimidates ; Glycosylation ; D-Xylose ; D-Quinovose ; Steroids ; Saponins ; Starfish ; Asterias amurensis ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 2-O-acetyl-protected O-galactosyl trichloroacetimidate 3 as glycosyl donor and 2,4-di-O-unprotected xylopyranoside 2 as glycosyl acceptor furnished in the presence of Et2O · BF3 as catalyst regioselectively β-(1→4)-connected disaccharide 4 which gave upon subsequent reaction with O-quinovosyl trichloroacetimidate 5 as donor β-(1→2)-connection, thus affording trisaccharide 6. Removal of the 2-O-acetyl group from the galactosyl moiety yielded acceptor 7; its glycosylation with donor 5 furnished β-connected tetrasaccharide 8. This compound was transformed via 1-O-desilylation and then treatment with trichloroacetonitrile in the presence of a base into O-tetraosyl trichloroacetimidate 10 as glycosyl donor. Reaction of 10 with 3-O-unprotected 2,4-di-O-acetyl- and 2,4-di-O-benzyl-protected quinovosides 13 and 16 furnished the desired fully O-protected pentasaccharides 17 and 18, respectively. Hydrogenolytic O-debenzylation of 18 furnished the O-unprotected target molecule 19 which was characterized as its O-acetyl product 20.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1992199201135
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  • 9
    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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  • 10
    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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