Nucleoside phosphorylases catalyze the reversible phosphorolysis of nucleosides to the corresponding nucleobases and pentose-1-phosphates (Scheme 1). This reactivity can be employed in reverse to transfer the glycosyl moiety from one nucleoside (or a pentose-1-phosphate) to another nucleobase, a reaction typically referred to as a (trans-)glycosylation. While such (trans-)glycosylation processes are well established as synthetic tools, they inherently suffer from thermodynamic limitations, as the final yield of these reactions is dictated solely by the substratedependent thermodynamics of the respective (reverse) phosphorolytic steps as well as the employed reaction con-Scheme 1. Nucleoside phosphorolysis and strategies for apparent equilibrium shifts. NB = nucleobase. ditions. Although some progress has been made to mitigate or exploit the tight thermodynamic control in these systems (e.g., via (by)product precipitation, enzymatic product removal or application of recoverable excess reagent ) and irreversible phosphorolysis of 6-oxopurines is well established, there currently exists no general method for the direct manipulation of glycosylation equilibria.