SFox imidates as versatile glycosyl donors for chemical glycosylation.

Described herein is a continuation of our studies dedicated to the development of novel classes of leaving groups based on O - and S -imidates. The main focus of the study presented herein is the synthesis of novel 3,3-difluoro-3 H -indol-2-ylthio (SFox) imidates and their application as glycosyl donors in chemical glycosylation. Being thioimidates, these compounds are more stable than O -imidates albeit much more reactive than conventional alkyl/arylthio glycosides. This study demonstrates that SFox imidates can be activated either with soft thiophilic reagents ( N -iodosuccinimide or transition metal salts), typical for the activation of thioglycosides or thioimidates, or hard electrophilic reagents (protic or Lewis acids) common for the activation of O -imidates. Expectedly, complete β-selectivity was obtained from SFox donors equipped with 2- O -benzoyl group. Surprisingly, complete α-selectivity was obtained from 2- O -benzylated SFox imidates in all investigated cases.