Nitrosative Guanine Deamination. Ab Initio Study of Deglycation of N-Protonated 5-Cyanoimino-4-Oxomethylene-4,5-Dihydroimidazoles

Sundeep Rayat, Zhengyu Wu and Rainer Glaser*

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Online Visualization: Substrates, Products, Pre- and Post-Coordination Complexes, and Reaction Transition State Structures

Figure 1. Cyano-N protonated cations 6a (R = Me) and 8b-Sg (R = MOM) and imino-N protonated cations 7a (R = Me) and 9a-Sg (R = MOM).

Figure 2. N-[4-(oxomethylene)-imidazol-5-yl]carbodimide 10b and isomeric N-[4-(oxomethylene)-imidazol-5-yl]cyanamides 11a and 11b.

Figure 3. Methyl and methoxymethyl cations 12 and 13 and their water aggregates 14 and 15. Two Cs conformations for the methoxymethyl cation were optimized, cis-ip 13, and trans-ip 13'. The vibrational analysis revealed that the former is a minimum while the later is a transition state.

Figure 4. Pre-coordination complex 16, transition state 24 (transition vector animation), and post-coordination complex 20 for the demethylation of 6a (R = Me).

Figure 5. Pre-coordination complex 17, transition state 25 (transition vector animation), and post-coordination complex 21 for the demethylation of 7a (R = Me).

Figure 6. Pre-coordination complex 18 and post-coordination complex 22 for the dealkylation of 8b-Sg (R = MOM). The transition state structure 26 (transition vector animation) is in the transition state region of the S_N process and features complete C-N bond heterolysis.

Figure 7. Pre-coordination complex 19 and post-coordination complex 23 for the dealkylation of 9a-Sg (R = MOM). The transition state structure 27 (transition vector animation) is in the transition state region of the S_N process and features complete C-N bond heterolysis.