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Synthesis of methyl 3-O-(α- and β-d-galactopyranosyl)4-O-(β-d-glucopyranosyluronic acid)-α-l-rhamnopyranoside using photolabile methyl 2,3-O-(2-nitrobenzylidene)-α-l-rhamnopyranoside

✍ Scribed by Frederick C. Baines; Peter M. Collins; Farnoosh Farnia

Publisher
Elsevier Science
Year
1985
Tongue
English
Weight
683 KB
Volume
136
Category
Article
ISSN
0008-6215

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✦ Synopsis

The title branched-trisaccharide derivatives (9 and 13) have been synthesised from methyl 2,3-O-(2-nitrobenzylidene)-a-L-rhamnopyranoside (2) using the 2nitrobenzylidene residue as a temporary blocking-group. Condensation of 2 with methyl (2,3,4-tri-O-acetyl-a-D-glucopyranosyl bromide)uronate afforded the blocked disaccharide 3 which, on sequential photolysis and oxidation, gave methyl 4-0-(methyl 2,3,4-tri-O-acetyl-~-D-glucopyranosyluronate)-2-O-(Znitrobenzoyl)-(4) and -3-0-(2-nitrobenzoyl)-cY-L-rhamnopyranoside (5) as a 4: 1 mixture. Galactosylation of HO-3 of 4 gave two fully protected trisaccharides having paa and /3@ configuration which, on deacylation, saponification, and treatment with ionexchange resins, gave the free acids 9 and 13. *The Photochemistry of Carbohydrate Derivatives. Part 8. For Part 7. see ref. 1.

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