Lanthanide catalyzed cyclization of uridine 3 '-p-nitrophenyl phosphate

Steady state kinetics and N-15 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 sub stitution reactions of many phosphate esters. Kinetic analysis reveals that the erbium-catalyzed cyclization reaction involves the concerted deprotona tion 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 leavin g group, which could be due to a large degree of polarization of the P-O bo nds by erbium. (C) 2000 Academic Press.