Abstract
The glycosylation reaction is one of the important aspects of carbohydrate chemistry,
where two different units are frequently linked through C–O bonds. In the pursuit
of advancing this field, the design and development of sustainable catalytic methods
for O-glycosylation, which can provide an alternate and effective tool to traditional
protocols involving stoichiometric promoters and classical donors, are considered
as highly challenging, yet important facets of glycochemistry. Herein, we report a
simple and efficient Fe(III)-catalyzed method for O-glycosylation through the activation
of bifunctional phenylpropiolate glycoside (PPG) donors. This mild and effective method
involves the use of the inexpensive and less toxic FeCl3 as catalyst and easily synthesizable, benchtop-stable glycosyl ester-based PPG donors,
which react with various sugar as well as non-sugar-based acceptors to deliver the
corresponding O-glycosides in good yields with moderate anomeric selectivity, along with regeneration
of easily separable phenylpropiolic acid. Importantly, d-mannose and l-rhamnose-based PPG donors afforded the corresponding O-glycosides in high α-anomeric selectivity. The reaction conditions were further explored
for the synthesis of trisaccharides.
Key words
glycosylation - bifunctional donors - phenylpropiolate glycosides - iron catalysis
- stereoselectivity
