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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.
    Type of Medium: Electronic Resource
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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 1997 (1997), S. 1315-1321 
    ISSN: 0947-3440
    Keywords: C-Glycosides ; Azasugars ; Piperidinosyl fluoride ; O-Piperidinosyl trichloroacetimidate ; Nojirimycin ; Deoxynojirimycin ; Glycosylations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl 2,3,4,6-tetra-O-acetyl-N-(benzyloxycarbonyl)nojirimycin (3) can be readily transformed into the corresponding azaglycal 6 or fluoride 7, which are versatile glycosyl/piperidinosyl donors. Reaction of 7 with allyltrimethylsilane, propinyltrimethylsilane, trimethylsilyl cyanide, and trimethylsilyl enol ether as carbon nucleophiles, afforded, in the presence of BF3 · OEt2 as catalyst, the corresponding C-glycosides 8-10 and 12-14 in good yields. The anomeric configurations of the C-glycosides are ascertained with the help of ROESY-NMR data.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 2113-2121 
    ISSN: 0947-3440
    Keywords: C-Saccharides ; C-Glycosides ; C-Lactosamine ; 1-Lithiogalactal ; Vinyllithium ; Branched sugars ; Glucosamine, C-formyl ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-C-Formyl-2-azidoglucopyranoside 12a, required for N-acetyl-C-lactosamine synthesis as electrophile, was obtained from thexyldimethylsilyl 2-azido-2-deoxy-glucopyranoside 3 via readily available 4-O-unprotected 6a and then 4-C-methylene derivative 8a in overall seven steps. Alternatively, regioselective silylation of 3 with tert-butyldimethylsilyl chloride gave 4-O-unprotected 6b which was transformed by a similar reaction sequence into 12a. In order to circumvent a Wittig reaction, 6a was transformed into triflate 13 the reaction of which with 4-C-cyano derivative 14 followed by reduction with DIBAH and base-catalyzed isomerization also afforded 12a. Reaction of 12a with 1-C-lithiated 2-phenylsul-finyl-D-galactal 15 as nucleophile furnished C-disaccharide intermediates 16a and 16b as diastereoisomers. Ensuing removal of the phenylsulfinyl group with Raney nickel and diastereospecific 2b-hydrogen and 3b-hydroxy transfer afforded β(1→4)-connected N-acetyl-C-lactosamines 19a and 19b; their structures were deduced from derivatives 20a, b and 21a, b on the basis of 1H-NMR data. Hydrogenolytic O-debenzylation of 19b afforded hydroxymethylene-bridged N-acetyl-C-lactosamine 2b′.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 859-863 
    ISSN: 0947-3440
    Keywords: myo-Inositol, racemate resolution ; Glycosylation, trichloroacetimidate method ; Tin(II) trifluoromethanesulfonate catalyst ; Oligosaccharide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2:3,4:5-Di-O-cyclohexylidene-D-/L-myo-inositol (2) could be readily converted into 6-O- and 1-O-unprotected L- and D-myo-inositol derivatives L- and D-4 and L- and D-6, respectively. Their reaction with trichloroacetimidate 7 as galactosyl donor in the presence of tin(II) trifluoromethanesulfonate as catalyst afforded the desired α(1-6)- and α(1-1)-connected galactopyranosides 8, 11 and 12. Compound 11 could be readily deprotected to afford target molecule (galactinol) 1 in high overall yield; from 12, the diastereoisomer 13 was obtained.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 865-872 
    ISSN: 0947-3440
    Keywords: Glycosylations, sulfur ; Glycosyl trichloroacetimidates ; Protecting groups, acyl, selective removal of ; Oligosaccharides ; S-Glycosides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of sulfur-linked GM3 epitope 2 is based on acid-catalyzed and base-promoted S-glycosylation processes. As a precursor, 2-O-benzoyl-3-thiogalactoside 10 was required, and was obtained from 4,6-O-benzylidene-galactoside 3 in six high-yielding steps. Base-promoted S-glycosylation of 10 with neuraminic acid functionalized β-halogenose 11 in the presence of NaH as base and Kryptofix 21 as coactivator afforded α(2-3)-thio-linked disaccharide 13, which was readily converted to α-halogenose 20. Heptyl 1-thioglycoside 22 was obtained from O-galactosyl trichloroacetimidate 21 and heptylthiol via acid-catalyzed S-glycosylation. 22 was transformed into 2,3,6-tri-O-acylgalactoside 26 which, via the 4-O-triflate and treatment with potassium thioacetate, followed by selective removal of the S-acetyl group, furnished the 2,3,6-tri-O-acyl-4-thioglucoside 28. Base-promoted S-glycosylation of 28 with halogenose 20 led to fully acylated target molecule 29, which was quantitatively converted into 2.
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  • 7
    ISSN: 0947-6539
    Keywords: computer simulations ; conformations ; Lewis glycolipids ; molecular dynamics ; thioglycosides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several monomeric and dimeric Lewis glycolipids have been investigated by NMR spectroscopy, and structural aspects were modelled by computer. From the pseudo-C2-symmetric tetrasaccharide unit that forms the recognition domain of the Lewis Y and Lewis b antigens, a totally C2-symmetric tetrasaccharide was designed that contains the structural element common to all Lewis antigens. Finally, a model for the presentation of dimeric Lewis antigens at membrane surfaces was derived. The overall shapes of the dimeric Lewis oligosaccharides are defined by the connectivity of the sugar residues within rigid tri- and tetrasaccharide building blocks.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 502-510 
    ISSN: 0947-6539
    Keywords: alkynes ; C-glycosides ; cobalt complexes ; cyclizations ; enzyme inhibitors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of gluconolactone 2 with allylmagnesium bromide at low temperatures afforded ketopyranose 3, which could easily be converted into open-chain ketoses (R)-6 and (S)-6. Their reaction with lithioacetylide 9 afforded propargylic alcohol derivatives (R)-10 and (S)-10, which could not be cyclized directly to the desired C-ketosides. They were converted by standard procedures into (R)-14 and (S)-14 and then into dicobalthexacarbonyl complexes (R)-16 and (S)-16. A facile acid-catalyzed ring closure gave the desired C-ketosides (R)-18 α/β and (S)-18α/β, respectively, in different ratios. In order to demonstrate that removal of the protective groups and hydrogenation of the CC triple bond proceed smoothly, (R)-18 α was transformed into the deprotected target molecule (R)-1 α. For the assignment of the new chiral centers at C-2/2′ and at C-8, (S)-18α was transformed into azido derivative (S)-22α, which underwent intramolecular cycloaddition to afford the spiro derivative (S)-25α. Because of the conformational constraints in this molecule, unequivocal configurational assignment was possible with the help of NMR data.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 101 (1968), S. 590-594 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Es werden neue und einfache Verfahren zur Synthese von Adenosin-5′-carbonsäure (2), 5′-O-Tosyl-adenosin (3), 5′-O-Tosyl-adenosin-5′.5′-d2 (11) und 5′-Amino-5′-desoxy-adenosin (4) ausgehend von 2′.3′-O-Isopropyliden-adenosin beschrieben.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 102 (1969), S. 269-274 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogensulfid reagiert mit 3-Aza-pyryliumsalzen (1) in 6-Stellung und führt zu β-Acylamino vinyl-thiocarbonylverbindungen (3). Die dehydratisierende Cyclisierung von 3 liefert das neue heterocyclische System der 3-Aza-thiopyryliumsalze (5). Die Reaktionen von 5 mit nucleophilen Sauerstoff-, Kohlenstoff- und Schwefelverbindungen zeigen, daß 5 analog wie 1 zur Übertragung vielseitig substituierter, ungesättigter C3-Reste auf nucleophile Reaktionspartner geeignet ist. Der Verlauf der Cyclisierung der Verbindungen 3,4 und 6 wird diskutiert.
    Additional Material: 3 Tab.
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