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Details van artikel 224 van 252 gevonden artikelen
| Titel: |
Synthetic Studies on Sialoglycoconjugates 23: Total Synthesis of Sialyl-α(2↠6)-Lactotetraosylceramide and Sialyl-α(2↠6)-Neolactotetraosylceramide |
| Auteur: |
Hasegawa, Akira Hotta, Kenji Kameyama, Akihiko Ishida, Hideharu Kiso, Makoto |
| Verschenen in: |
Journal of carbohydrate chemistry |
| Paginering: | Jaargang 10 (1991) nr. 3 pagina's 439-459 |
| Jaar: |
1991 |
| Inhoud: |
The first total syntheses of sialyl-α(2→6)-lactotetraosylceramide (29, IV6NeuAcLc4Cer) and sialyl-α(2→6)-neolatotetraosylceramide (33, IV6NeuAcnLc4Cer) are described. Methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→6)-2,4-di-O-benzoyl-3-O-benzyl-1-thio-ss-D-galactopyranoside (11), the key glycosyl donor was prepared, via glycosylation of 2-(trimethylsilyl)ethyl 3-O-benzyl-ss-D-galactopyranoside (2) with the methyl α-thioglycoside 3 of N-acetylneuraminic acid, benzoylation, replacement of the 2-(trimethylsilyl)ethyl group by acetyl, and introduction of the methylthio group with (methylthio)trimethylsilane. Each coupling of 2-(trimethylsilyl)ethyl O-(2-acetamido-4,6-O-benzylidene-2-deoxy-ss-D-glucopyranosyl)-(1→3')-per-O-benzyl-ss-lactoside (12) or 2-(trimethylsilyl)ethyl O-(2-acetamido-3-O-acetyl-6-O-benzyl-2-deozy-ss-D-glucopyranosyl)-(1→3')-per-O-benzyl-ss-D-lactoside (14) prepared from 12 by O-acetylation and reductive opening of the benzylidene acetal, with 11 gave the pentasaccharides 16 and 20 in good yields. Compounds 16 and 20 were converted into the corresponding α-trichloroacetimidates 19 and 24 which, on coupling with (2S, 3R, 4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (25), gave the ss-glycosides 26 and 30, respectively. Finally, 26 and 30 were transformed, via selective reduction of the azide group, condensation with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester group, into 29 and 33, respectively. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 224 van 252 gevonden artikelen
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