Hydrogen-Bond-Mediated Glycosylation Reactions with Glycosyl Picolinates

Herein, we report a generally applicable hydrogen-bond-mediated glycosylation protocol of glycosyl picolinate donors with a charged (thio)urea hydrogen-bond-donor catalyst. A variety of nucleophiles, including complex natural products, glycosides, amino acids, and less nucleophilic phenolic acceptors were also glycosylated successfully. Hydrogen-bond-mediated glycosylation systems combined with different strategies were also explored to achieve stereoselective glycosylation. A mechanistic study revealed that catalysts form the donor-catalyst noncovalent complex through hydrogen bonds and then produce the oxocarbenium species.