Modulation of the stereoselectivity and reactivity of glycosylation via ( p -Tol) 2 SO/Tf 2 O preactivation strategy: From O -, C -sialylation to general O -, N -glycosylation

The synthesis of O-, C-, and N-glycoconjugates has continuously been an attractive research subject due to the growing biological importance of various glycoconjugates. In recent years, by careful changing the glycosylation reaction conditions, especially the amount of activators and the preactivation temperature, (p-Tol)2SO/Tf2O preactivition strategy was developed as a general method for the synthesis of various O-, C-, and N-glycoconjugates, including related biological active glycoconjugates, such as nucleosides and antigen Lewisa etc. High yields and excellent stereoselectivities were obtained even without the anchimeric assistance at the adjacent position of anomeric carbon. In this review, we predominantly make a review on the progress of the (p-Tol)2SO/Tf2O preactivition strategy from O-, C-sialylation to general O-, N-glycosylation.