APPLICATION OF A RADICAL REACTION TO THE SYNTHESIS OF L-IDURONIC ACID DERIVATIVES FROM D-GLUCURONIC ACID ANALOGUES

Article abstract of DOI:10.1016/S0008-6215(00)90357-4

Commercially available D-glucofuranuro-6,3-lactone was transformed into the known, crystalline methyl (5R)-1,2,3,4-tetra-O-acetyl-5-C-bromo-β-D-glucopyranuronate (3) in three steps.Reduction with tributyltin hydride gave crystalline methyl 1,2,3,4-tetra-O-acetyl-α-L-idopyranuronate (4) in ca. 30percent yield, together with the crystalline methyl 1,2,3,4-tetra-O-acetyl-β-D-glucopyranuronate (1, 63.5percent) which may be separated and converted back by Ferrier's photobromination into 3.This procedure provides the first practical and expenditious conversion of D-glucuronic into L-iduronic acid by epimerization.Acetate 4 was converted in quantitative yield into methyl (2,3,4-tri-O-acetyl-α-L-idopyranosyl bromide)-uronate (22), and then into methyl 3,4-di-O-acetyl-β-L-idopyranuronate 1,2-(methyl orthoester) (23), which are useful compouns for glycosylation reactions.Various β-D-glucuronic acid derivatives have been epimerized to α-L-iduronic acid analogues by this novel procedure.