9-Methyladenine, formation

It has been demonstrated that the tran5 -[(NH3)2PtCl] adduct of 1-methylcytosine, bound via N-3, can form crosslinks with either 9-ethylguanine or 9-methyladenine as a result of Cl substitution by purine N-7 atoms. Additional H-bonds between exocyclic groups of cross-linked nucleic acid bases provide additional stabihzation of the individual complexes (Figure 13d). Binding of the related complex [(NH3)2Pt(N-3-cytosine)Cl]+ with d(GG) leads to the formation of a major product in which the platinum is bound only to N-7 of the 5 -nucleotide. ... 

An attempt to prepare 5-methyladenine (176) from the imidazole (175) and formamidine resulted in the formation of the imidazotriazine (177) (Scheme 84). ... 

Etter et al. reported the solid-state co-crystaUisation of 9-methyladenine and 1-methylthymine, driven by the formation of hydrogen-bonded Eloogsteen... 

The data assembled in Table 9 allow at least one more interesting conclusion In all instances the formation degree of the macrochelates increases in the order M(AMP)ci < M(IMP)ci < M(GMP)ci. This increase for M(IMP)d < M(GMP)d is in accord with the increased basicity of N7 in GMP compared with that of N7 in IMP [74], However, with AMP the situation is more complicated 9-methylguaninehas ap aOf3.11 i 0.06 [143,144] for its (N7)H site and this value is rather close to the micro acidity constant for the same site in 9-methyladenine, P 1ni = 2.96 0.10 [143]. Hence, the N7 basicity cannot be responsible for the decreased complex stabihty. Similar to the simation with pyrimidine derivatives as discussed in Section 4.2, the reduced stabihty by about 0.5 log unit of Cd(AMP), compared to that of Cd(GMP), is to be attributed to the steric inhibition which (C6)NH2 exercises on a metal ion coordinated at N7 [71]. The (C6)0 group does not have such an effect. In contrast, it rather promotes the stability by forming outersphere bonds to a water molecule of the N7-bound metal ion [74]. 

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