The synthesis of β-S-Gal(1→3)GlcNAc thiodisaccharide, which can be considered mimetic of the repeating unit of keratan was achieved by SN2 displacement of a triflate group allocated at the 3-position of a convenient 2-azido-4,6-O-benzylidene-2-deoxy-β-d-allopyranose precursor by the corresponding nucleophilic suitable protected thioaldose derived from galactose (Gal). The study of the reaction led to the finding that the vinyl azide formed by competitive E2 reaction of the mentioned triflate was an interesting precursor of a new kind of 2,3-dideoxy-2-azido-(1→2) thiodisaccharides through an addition reaction. Determination of the stereochemistry of the new stereocenter at C-2 was achieved by NOESY experiments. Final protecting group manipulation of the (1→3) thiodisaccharide led to a family of derivatives that could be used as building blocks for the synthesis of complex glycomimetics.

Synthesis of β-S-Gal(1-3)GlcNAc Thiodisaccharide: Serendipitous Formation of 2,3-dideoxy-(1-2)-thiodisaccharides through a Vinyl Azide Intermediate

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