Synthesis of 1,4-anhydro-2,3,6-tri-O-benzyl-α-D-glucopyranose by cis-ring-closure of a glycosyl chloride

Article abstract of DOI:10.1016/0008-6215(90)84090-H

A synthetic approach to 1,4-anhydro-2,3,6-tri-O-benzyl-α-D-glucopyranose by cis-ring closure of a glycosyl chloride has been studied to furnish a starting sugar for the synthesis of a linear (1->4)-linked polysaccharide.Cyclomaltoheptaose was benzylated and the product hydrolyzed to afford 2,3,6-tri-O-benzyl-α-D-glucopyranose, which was converted by HCl-Et2O into the corresponding glycosyl chloride.Treatment of the latter with NaH in Me2SO gave mainly 2-benzyloxy-3,6-di-O-benzyl-D-glucal, with 1,4-anhydro-2,3,6-tri-O-benzyl-α-D-glucopyranose as a byproduct.However, the 1,4-anhydro sugar could be prepared in good yield by cis ring-closure of 2,3,6-tri-O-benzyl-α-D-glucopyranosyl chloride in a mixture of tetrahydrofuran and sodium hydride.