Rapid Synthesis of l-Idosyl Glycosyl Donors from α-Thioglucosides for the Preparation of Heparin Disaccharides

Article abstract of DOI:10.1002/ejoc.201800425

A new methodology for the synthesis of the most challenging heparin building block has been developed. Orthogonally protected l-idosyl glycosyl donors were prepared by C5 epimerization of the corresponding thioglucosides using the hydroboration/oxidation method followed by a 4,6-acetal formation. The α-anomeric configuration was crucial, and the bulky C4 substituent was advantageous for the high l-ido diastereoselectivity. The 4,6-arylmethylene group proved to be a directing element in glycosylation, whereby stereoselective α-idosylation could be achieved by using idosyl donors without a C-2 participating group.