Density functional theory study of water-assisted deprotonation of the C8 intermediate in the reaction of the 2-fluorenylnitrenium ion with guanosine to form a C8 adduct

A density functional theory study of the deprotonation reaction of the “C8 intermediate (8-(2-fluorenylamino)-guanosine cation)”, which is the intermediate of reaction of 2-fluorenylnitrenium ion with guanosine, to produce the C8 adduct final product is described. The barrier to reaction is high in the gas phase and becomes substantially lower when explicit hydrogen bonding of water molecules is considered. This is consistent with the experimentally observed decay of the “C8 intermediate” on the millisecond time scale. Bulk solvent effects caused only moderate changes in the barrier to reaction in the deprotonation reaction systems that include water molecules. Thus, the hydrogen bonding of the water molecules appears to account for most of the differences between the gas phase and aqueous solution barriers for the deprotonation reaction of the C8 intermediate to form the C8 adduct product. These results suggest that a water-assisted deprotonation mechanism transforms the “C8 intermediate” into the C8 adduct final product in the reactions of arylnitrenium ions with guanine derivatives in aqueous environments.