Preparation of disaccharides having a β-d-mannopyranosyl group from N-phthaloyllactosamine derivatives by double or triple SN2 substitution
✍ Scribed by Jocelyne Alais; Serge David
- Book ID
- 102994764
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 643 KB
- Volume
- 201
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
Condensation of 1,2,3,4,6-penta-O-acetyl-P-o_galactopyranose with methyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido+D-glucopyranoside, followed by alkaline methanolysis, gave a derivative of lactosamine that has an unsubstituted /?-D-galactopyranosyl group. Tributyltin oxide-mediated allylation gave a good yield of the 3'-O-allyl(9) and a poor yield of the 3',6'-di-O-ally1 ether (8). Protection of 9 at O-6' was achieved by reductive opening of the 4',6'-0-anisylidene derivative, to give the 6'-0-(4-methoxybenzyl) ether 15. Conversion of 8 and 15 to their 2',4'-bis(trifluoromethanesulfonates), followed by S,2 reaction with benzoate, gave the corresponding P-D-mannopyranosyl disaccharides. However, the model methyl 3-0allyl-P-D-galactopyranoside and 9 were converted into p-D-mannopyranosyl derivatives in better yield (52-55%) by a one-pot, triple S,2 substitution of the tris(trifluoromethanesulfonates).