Highly Stereoselective Synthesis of Oligosaccharides Motifs From <i>Stichopus herrmanni</i> Fucan Sulfate With Anticoagulant Activities

Fucan sulfate represents an interesting target for the development of anticoagulant therapeutics. However, the heterogeneous issue of isolated fucan sulfate and structural complexity hinders structure–activity relationships studies. Herein, we report the highly stereoselective synthesis of desulfated oligosaccharide motifs 3‐mer, 5‐mer, and 10‐mer and sulfated oligosaccharide 3‐mer from Stichopus herrmanni fucan sulfate with anticoagulant activities. The synthetic approach features the following: (1) ten contiguous (1→3)‐α‐L‐Fuc linkages were efficiently assembled through the recently developed synergistic 1,2‐ cis ‐fucosylation method; (2) iterative 1,2‐ cis ‐fucosylation and selective removal of Lev group strategy was adopted to elongate the carbohydrate chain; (3) highly stereoselective installation of the strong and nucleophilic aminopentyl linker into the reducing end for further biological studies.