ChemInform Abstract: Prearranged Glycosides. Part 12. Intramolecular Mannosylations of Glucose Derivatives via Prearranged Glycosides.
Abstract
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ChemInform Abstract
The intramolecular glycosylation reaction of various prearranged glycosides, consisting of a thiomannosyl donor linked to the glucopyranoside acceptor via succinate or malonate tethers at different positions of donor and acceptor, provides the corresponding cyclized (1→4)-linked disaccharides in good yields. The diastereoselectivity of glycosylation is influenced by the position of the tether, providing pure α-linked disaccharides (II), (VII) and (VIII), and, in the case of disaccharide (IV), by the cyclization conditions. Interestingly, glycoside (IX) does not cyclize under various reaction conditions, while its succinate analogue (V) readily affords the α-linked disaccharide (VI) in good yield with 5% of its β-anomer. The stereochemical outcome of all glycosylation reactions is verified by calculation of the thermodynamic stability of the disaccharides.
