Stereoselective α-Sialylation with Sialyl Pentenoates as Donors and PhSeOTf as the Activator †

-bromophenyl phthalates, and sialyl phthalates were not satisfactory. Fortunately, how-ever, we were able to achieve the stereoselective α-sialylation employing the glycosyl pentenoates/PhSeOTf method, which also we introduced previously for the stereoselective β-manno-sylation and other glycosylations.