Prearranged Glycosides, Part 12, Intramolecular Mannosylations of Glucose Derivatives via Prearranged Glycosides

✍ Scribed by Gregor Lemanski; Thomas Ziegler

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: German
• Weight: 284 KB
• Volume: 83
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/1522-2675(20001004)83:10<2655::aid-hlca2655>3.0.co;2-u

✦ Synopsis

A series of prearranged glycosides 5, 17, 23, 28, 37, and 41, having a benzyl-protected 1-thiomannosyl donor linked through its positions 2, 3, 4, and 6 via succinate and malonate tethers, respectively, to positions 2, 3, and 6 of a benzyl glucopyranoside acceptor, were prepared by condensation of the respective mannosyl succinates and malonates with suitably protected benzyl glucopyranosides. The prearranged glycosides were intramolecularly coupled under various conditions to give the corresponding tethered (1 3 4)-linked disaccharides. The yields and anomer ratios of the products of these couplings were interpreted in terms of the thermodynamic stability of the resulting disaccharides. In the case of prearranged glycoside 17, having positions 3 of both the donor and the acceptor linked by a succinate tether, a strong dependence of the diastereoselectivity of the intramolecular glycosylation on the activation procedure was observed. All other cases did not show a significant dependence of the outcome of the anomeric configuration in intramolecular glycosylation on the activation procedure or the solvent.