Lanthanide Catalyzed Cyclization of Uridine 3′-p-Nitrophenyl Phosphate

Steady state kinetics and 15N isotope effects have been used to study the cyclization reaction of uridine 3′-p-nitrophenyl phosphate. The cyclization reaction is catalyzed by transition metal ions and lanthanides, as are substitution reactions of many phosphate esters. Kinetic analysis reveals that the erbium-catalyzed cyclization reaction involves the concerted deprotonation of the 2′-OH group and departure of the leaving group. The transition state is very late, with a very large degree of bond cleavage to the leaving group, which could be due to a large degree of polarization of the PO bonds by erbium.