Reagent Controlled Stereoselective Assembly of α‐(1,3)‐Glucans

Pre‐activation based glycosylations have become a very powerful tool in the assembly of oligosaccharides and the use of nucleophilic additives allows for the in situ generation of reactive intermediates with tailored reactivity. We here use a glycosylation strategy that is based on the use of per‐benzylated imidate building blocks for the fully stereoselective construction of a spacer equipped Aspergillus fumigatus α‐1,3‐octaglucan. We have used the trimethylsilyl iodide (TMSI)‐triphenylphosphine oxide (Ph(3)P=O) for the stereoselective installation of an azidopropanol spacer and triflic acid (TfOH)‐dimethyl formamide (DMF) enabled glycosylations for the coupling reactions with the secondary glucosyl C‐3‐alcohols. An operationally simple in situ activation coupling procedure is introduced and used for the final glycosylation events towards the octasaccharide.