| Abstract
| - The effect of conformation on glycoside reactivity was investigated by studying the hydrolysis ofa selection of 3,6-anhydroglucosides as models for glucose in the highly reactive 1C4 conformation. Methyl3,6-anhydro-β-d-glucopyranoside was found to hydrolyze 200−400 times faster than methyl glucosides inthe 4C1 conformation, while methyl 3,6-anhydro-β-d-galactopyranoside, which is in the B1,4 conformation,was less reactive than methyl β-d-galactopyranoside. Methyl (3,6-anhydro-β-d-glucopyranosyl)-(1 → 6)-α-d-glucopyranoside, methyl (3,6-anhydro-α-d-glucopyranosyl)-(1 → 6)-α-d-glucopyranosyl-(1 → 6)-α-d-glucopyranoside, and methyl (3,6-anhydro-β-d-glucopyranosyl)-(1 → 6)-α-d-glucopyranosyl-(1 → 6)-α-d-glucopyranoside were prepared and found to react selectively at the anhydro residue. The finding that 1C4conformers of glucosides are highly reactive species is in accordance with and supports previous resultsshowing that axial OH groups are less electron withdrawing than equatorial OH groups.
|
