2,6-Bis(1,4,7,10-tetraazacyclododecan-1-ylmethyl)pyridine and Its Benzene Analog as Nonmetallic Cleaving Agents of RNA Phosphodiester Linkages

2,6-Bis(1,4,7,10-tetraazacyclododecan-1-ylmethyl)pyridine (11a) and 1,3-bis(1,4,7,10-tetraazacyclododecan-1-ylmethyl)benzene (11b) have been shown to accelerate at 50 mmol·L-1 concentration both the cleavage and mutual isomerization of uridylyl-3',5'-uridine and uridylyl-2',5'-uridine by up to two orders of magnitude. The catalytically active ionic forms are the tri- (in the case of 11b) tetra- and pentacations. The pyridine nitrogen is not critical for efficient catalysis, since the activity of 11b is even slightly higher than that of 11a. On the other hand, protonation of the pyridine nitrogen still makes 11a approximately four times more efficient as a catalyst, but only for the cleavage reaction. Interestingly, the respective reactions of adenylyl-3',5'-adenosine were not accelerated, suggesting that the catalysis is base moiety selective.