De novo synthesis of differentially protected l-iduronic acid glycosylating agents

A divergent de novo synthesis of six differentially protected l-iduronic acid thioglycosides from a common advanced precursor is described. The key step of this synthetic sequence is the stereoselective elongation of dithioacetal protected C5-dialdehyde 11 via a highly diastereoselective MgBr2·OEt2-mediated cyanation. Orthogonally protected l-iduronic acid building blocks obtained by this synthesis are expected to facilitate access to differentially sulfated heparins for microarray-based structure–activity relationship studies.