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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 755-764 
    ISSN: 0947-3440
    Keywords: Phytosphingosine ; Sphinganine ; Galactal ; 2-Deoxy-D-galactose ; D-Arabitol ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,4,6-Tri-O-benzyl-D-galactal (3) was directly converted into 3,4,6-tri-O-benzyl-2-deoxy-D-galactose (5). Wittig reaction of 5 with alkyltriphenylphosphonium salts in the presence of n-butyllithium as the base afforded olefins 6a, b which could be readily transformed into phytosphingosines 1a, b via different routes: (i) at first azido group introduction and then double bond and protective group removal, and azido group generation via hydrogenation; (ii) 2-O-mesylation, then double bond and benzyl group removal via hydrogenation, and finally nitrogen introduction; (iii) selective double bond hydrogenation, then nitrogen introduction, and finally benzyl group removal and amino group generation via hydrogenation. Wittig reaction of 5 with alkyltriphenylphosphonium salt in the presence of potassium tert-butoxide as the base afforded diene 7a which proved to be a convenient precursor for sphinganine syntheses; thus, 2-O-mesylation, then double bond and benzyl group removal via hydrogenation and 1,3-O-acetylation, and finally nitrogen introduction and de-O-acetylation afforded 23a. Based on the convenient transformation of D-arabitol into the 1,3-O-benzylidene derivative 25 a further phytosphingosine synthesis is outlined.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1303-1313 
    ISSN: 0947-3440
    Keywords: S-Glycosylation, base-promoted, acid-catalyzed ; S-Glycosides ; Anomeric S-alkylation ; Glycosyltrichloroacetimidates ; Lewis X analogues ; Oligosaccharides, thio- ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of thio-linked Lewis X and sialyl Lewis X-derived epitopes 3-5 has been achieved using a small number of building blocks. The key building-block was 1-O-silyl-protected 4-S-acetyl-2,6-di-O-benzoyl-3-S-(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-3,4-dithio-β-D-glucopyranose (15), which was obtained from the fucosyl donor 6 together with 3-thiogalactose 7 as the acceptor. Their acid-catalyzed S-glycosylation afforded the thio-linked disaccharide 8 which was subsequently converted to the 4a-O-unprotected derivative 12. Conversion to the 4a-triflate followed by treatment with KSAc in tetrahydrofuran led, under inversion of configuration, to 15 in good overall yield. Selective removal of the S-acetyl group followed by base-promoted S-glycosylation with acetobromogalactose gave the acyl-protected Lewis X analogue 25. Acetobromogalactose gave the acyl-protected Lewis X analogue 25. Transformation into trichloroacetimidate 27, followed by acid-catalyzed S-glycosylation of heptylthiol and complete deacylation afforded target molecule 3. Similarly, acid-catalyzed reaction of donor 27 and the 3b,4b-O-unprotected lactose derivative 31 as acceptor led to pentasaccharide 32, complete deacylation of which afforded target molecule 4. Transformation of 15 into the donor trichloroacetimidate 34, followed by acid-catalyzed S-glycosylation of heptylthiol afforded thioglycoside 35. Selective removal of the S-acetyl group and subsequent base-promoted S-glycosylation with the known donor 37 furnished the thio-linked tetrasaccharide 38. Cleavage of all the O-acyl groups and hydrolysis of the methyl ester moiety afforded the sialyl Lewis X analogue 5.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 1099-1106 
    ISSN: 0170-2041
    Keywords: Lactose ; Azidolactose ; Glycosyl acceptors ; Glycosyl donors ; Regioselective protection ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Glycosylimidate, 42. - Selektiv geschützte Lactose und 2-Azidolactose als Bausteine für die Synthese von GlycolipidenDurch regioselektive Alkylierung der 3′-OH-Gruppe von Benzyl-β-lactosid mit der Stannylierungsmethode wurden die 3′-OH- und 4′-OH-ungeschützten Lactosederivate 5 und 10 sowie das 4′-OH-ungeschützte Lactosederivat 9 hergestellt, das aufgrund seiner unterschiedlichen Schutzgruppe für 3′-OH für weitere Umwandlungen geeignet ist. Diese Bausteine sind wertvolle Glycosylakzeptoren für die Synthese von Glycolipiden. Zur Synthese von Glycosyldonoren mit Gal(β1 → 4)GlcNAc-Struktur wurde das 2-Azidolactosederivat 19 verwendet. Durch regioselektive Alkylierung der 3′-OH-Gruppe mit der Stannylierungsmethode sowie durch Anwendung anderer regioselektiver Schutzgruppen-Verfahren wurden die Trichloroacetimidate 17, 24 und 30 hergestellt, die aufgrund ihrer speziellen Schutzgruppen für 3′-OH, 4′-OH und 6′-OH für weitere Umwandlungen geeignet sind.
    Notes: Performing regioselective alkylation at 3′-OH of benzyl β-lactoside 1 by the stannylation method we prepared the 3′-OH- and 4′-OH-unprotected lactose derivatives 5 and 10 and the 4′-OH-unprotected lactose derivative 9 containing a different protecting group at 3′-OH, suitable for further transformations. These building blocks are valuable glycosyl acceptors in glycolipid synthesis. For the synthesis of glycosyl donors with Gal(β1 → 4)GlcNAc-structure we used the 2-azido lactose derivative 19. By regioselective alkylation of 3′-OH by the stannylation method and application of other common regioselective protecting procedures we prepared the trichloroacetimidates 17, 24, and 30 containing special protecting groups at 3′-OH, 4′-OH, and 6′-OH which are suitable for further transformations in these positions.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 371-375 
    ISSN: 0170-2041
    Keywords: Trifluoromethanesulfonates, secondary alkyl, as alkylating agents ; Disaccharides, synthesis of (1→3)- and (1→4)-connected ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Base-promoted reaction of tetra-O-benzyl-glucose 1a with secondary alkyl trifluoromethanesulfonates 2 and 3 in toluene provides in the presence of 15-crown-5 preferentially β-glycosides 2aβ and 3aβ, respectively, in high yields. For reactions carried out at lower temperatures and with trifluoromethanesulfonates derived from secondary hydroxy groups of sugars aprotic dipolar solvents (HMPT/DMF, HMPT/THF) are required. Thus, treatment of 1-O-unprotected hexoses 1a-e with trifluoromethanesulfonates 4, 6, and 7 affords the corresponding (1→4)-connected disaccharides 4a-e and the (1→3)-connected disaccharides 6b and 7b, respectively, in high yields. Under these conditions the α:β ratio of the products resembled the anomeric ratio of the starting material.
    Additional Material: 1 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 377-382 
    ISSN: 0170-2041
    Keywords: Glycosides ; Disaccharides ; Undecaose ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From 4-O-unsubstituted glucose derivatives 1a, b the 4-hydroxymethyl-substituted glucose derivatives 9a, b were obtained via oxidation to the ketone, Wittig reaction with methylenetriphenylphosphorane, borane addition, and subsequent oxidation to yield the diastereomeric galactose-derived compounds 5a, b; the required inversion of configuration at C-4 was accomplished through oxidation to the formyl derivatives, base-catalyzed isomerisation, and then reduction. Transformation of hydroxymethyl derivatives 9a, b into the iodo derivatives 11a, b and reaction with n-butyllithium generated the C-lithiated species 11aA, bA which furnished with O-benzyl-protected gluconolactone 12 the ketose derivatives 13a, b. Treatment with Et2O-BF3 afforded under concomitant 6-O-debenzylation the spiroketals 15a, b. Hydrogenolytic O-debenzylation and subsequent O-acetylation led to compounds 16a and 16b, respectively. The anomeric ketoside configuration was derived from NOE experiments.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 877-881 
    ISSN: 0170-2041
    Keywords: O-Glycosyl trichloroacetimidates ; Glycosyl bromides ; Glycopyranosyl donors ; Glycosyl acceptors, polyvalent ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of different glycosyl donors with 5-hydroxy-N-methyl-2,3-diphenylindole (1C) led only to O-glycosylation (compounds 6a-c and 8c-α,β). Depending on the O-protection of the glycosyl donors (2a-c, 3b, 4c), the β-products were obtained mainly or exclusively. The corresponding N-unsubstituted indole 1B and donors 2b and 5a, respectively, also yielded only O-glycosylated products (compounds 11b and 13a). Depending on the glycosyl donor (2a or 2c), the N-unsubstituted 5-methoxy-2,3-diphenylindole (1A) led to N- and/or C-glycosides (compounds 16a, 14a-α,β, and 14c-α,β). The structures were assigned with the help of 1H-NMR data of these products or their derivatives.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 297-303 
    ISSN: 0170-2041
    Keywords: Carbohydrates ; Glycals ; C-Glycosides ; Hept-2-enoses, lyxo- ; D-Galactal-1-ylmethylphosphonates ; L-Fucal-1-ylmethylphosphonates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct lithiation of 2-phenylsulfinyl- and 2-phenylsulfonylsubstituted galactal derivatives 3a-c and subsequent reaction with DMF gave 1-C-formyl derivatives 4a-c. Reduction afforded hydroxymethyl derivatives 5a-c which were transformed into mesylates 7 and 9, respectively. Treatment with trimethyl phosphite furnished phosphonates 8 and 10; by treatment with sodium in liquid ammonia and subsequent reaction with acetic anhydride in pyridine both compounds were converted into monomethyl galactal-1-ylmethylphosphonate (11) which could not be completely demethylated without structural change. O-Acetyl-protected mesylate 18, obtained from galactosyl cyanide in a few steps, was transformed into bromide 19 which on treatment with P(OSiMe3)3 gave bis(trimethylsilyl) phosphonate 20. Reaction with NaOMe/MeOH afforded the unprotected disodium salt of D-galactal-1-ylmethylphosphonate 1. Similarly, from L-fucopyranosyl cyanide 22 the corresponding target molecule 2 was obtained.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 645-651 
    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.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 483-489 
    ISSN: 0170-2041
    Keywords: D-Galactal, 1-C-lithiation ; Octose synthesis ; C-β-D-Galactopyranosides ; Nucleoside antibiotics ; Octosylic acids ; Ezomycins ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct 1-C-lithiation of the readily available 2-phenylsulfinyl-D-galactals 3h, 1 leads to reactive intermediates, which on reaction with glyoxal monodiethyl acetal as electrophile yield compounds 7. Subsequent O-benzylation of the unprotected hydroxy group, removal of the phenylsulfinyl group with Raney nickel, and diastereospecific 3-hydrogen and 4-hydroxy transfer provide a convenient entry into functionalized C-β-D-galactopyranosides or 3,7-anhydrooctoses 11, respectively. Acid-catalyzed deacetalization and furanose formation with acetic anhydride/pyridine affords 3,7-anhydrooctofuranoses-(1,4) 14. The O-acetylated D-erythro-L-talo isomer (R)-17 reacts with the cytidine derivative 18, leading to the ezomycin A basic structure 4.
    Additional Material: 1 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 817-823 
    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.
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