Glycosyl dithiocarbamates: β-selective couplings without auxiliary groups.

Area of Science:

• Carbohydrate Chemistry
• Organic Synthesis
• Glycosylation Methods

Background:

• Oligosaccharide synthesis is crucial for understanding biological processes.
• Developing efficient and stereoselective glycosylation methods remains a challenge.
• Glycosyl dithiocarbamates (DTCs) have emerged as versatile intermediates.

Purpose of the Study:

• To evaluate glycosyl dithiocarbamates (DTCs) with unprotected C2 hydroxyls as donors in β-linked oligosaccharide synthesis.
• To develop a mild, one-pot method for generating and utilizing these DTC donors.

Main Methods:

• Conversion of glycals into β-glycosyl DTCs via DMDO oxidation and ring opening with DTC salts.
• Activation of glycosyl DTCs using copper(I) or copper(II) triflate at low temperatures.
• Application in reiterative synthesis strategies for oligosaccharide construction.

Main Results:

• A mild, one-pot procedure for synthesizing β-glycosyl DTCs from glycals.
• High β-selectivity in glycosyl DTC couplings, even with unprotected C2 hydroxyls.
• Efficient synthesis of a tri-β-1,6-linked tetrasaccharide using reiterative coupling.

Conclusions:

• Glycosyl DTCs with unprotected C2 hydroxyls are effective donors for β-oligosaccharide synthesis.
• The C2 hydroxyl group itself mediates stereodirecting effects, likely through a cis-fused bicyclic intermediate.
• This method provides a valuable tool for constructing complex β-linked oligosaccharides.