Synthesis of β- l-fucopyranosyl phosphate and l-fucofuranosyl phosphates by the MacDonald procedure

Fusion or β- l-fucopyranose tetraacetate with phosphoric acid for 1 min at 50° gives a 9:1 anomeric mixture of the α-and β-pyranosyl phosphates. Longer fusion times give the α-anomer exclusively. The l-fucofuranose tetraacetates were synthesized for the first time by acetolysis or methyl-2,3,5-tri- O-acetyl-β- l-fucofuranoside. Fusion or the furanose tetraacetates with phosphoric acid gave a mixture or the fucofuranosyl phosphates in which the β-anomer predominated (β/α = 2.4). Anomeric pairs in the fucofuranose series appear to be distinguishable by the chemical shift of the C-6 methyl protons, as already shown by Sinclair and Sleeter in the pyranose series.