Synthesis of thiomaltooligosaccharides by a thio-click approach.

Phenyl 2,3,6,2',3',6'-hexa-O-acetyl-4'-S-acetyl-1,4,4'-trithio-β-d-maltoside and its tri-, tetra- and pentasaccharide homologues were prepared by completely regio- and stereoselective photoinitiated thiol-ene coupling reactions of 2-acetoxy-glucal and 4-thioglucose type reaction partners. Complex protecting group strategies could be avoided since all thiols and glucals were prepared from a single starting material, phenyl 2,3,6-tri-O-acetyl-4-S-acetyl-1,4-dithio-β-d-glucopyranoside. The method represents a simple alternative to the known syntheses of similar products.