Pyrimidines metal complexes

Table 1. Stability constants of some purine and pyrimidine metal complexes (1, 2, 69)...

Stability constants of metal complexes of 9-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-one [Ni(II), Co(II), Zn(II), and Cd(II)] were determined by potentiometric and polarographic investigations (93JCC283). The distribution coefficient of risperidone (11) in H20- -octanol at pH 7.4 (log D — 2.04) was determined by an RP-HPLC method (01JMC2490). 

Transition Metal Complexes of l-(2-Methylphenyl)-4, 4, 6-Trimethyl Pyrimidine-2-thione Synthesis and Biological Studies... 

Photoreactions of Metal Complexes with DNA closer to the purine strand than to the pyrimidine strand in the major groove. 

The bleomycins (50) are hardly simple amines, but they do have two NH2 groups and a CONH2 group at the N-terminal domain, as well as potential donor nitrogens in pyrimidine and imidazole, which can complex metal ions." " The complexing of iron to bleomycin" " " has a significant effect on bleomycin-DNA interactions—metal complexes can mediate strand scission—and on alkene oxidation. Both may involve hydroperoxide intermediates." " " " ... 

The following Table (Table 1) shows the values of the stability constants of some purines and pyrimidines with a number of transition metal ions (7, 2, 36, 69). Procedures for the synthesis of Cu, Co and Ni complexes with pyrimidines have been reported (65, 92, 93). The preparation of purine-metal compounds are described elsewhere (94, 95). There seem to be great difficulties in the quantitative study of metal complex formation, especially with the free purines, since the resulting metal chelates are almost insoluble in aqueous solution. Therefore, dioxane-water mixtures have been employed in a number of experiments. 

In general the pyrimidines show a much lower reactivity towards the metal ions. Apparently no reaction was observed with uracil while the stability constants of Cu-cytosine are even lower than the lgJCi and gK% values of Cu(NH3)62+ (79). The high stability of the purine metal complexes can be attributed to the binding site at the imidazole residue. There the imino proton competes with the metal ion. Fig. 1 presents a model of the 2 1 complex of Cu-(adenine)%. 

Metal complexes of pyrimidine nucleotides have been studied much less intensively than those involving purines, undoubtedly reflecting the weaker coordination ability of the pyrimidine N-3 atom, relative to atoms N-7 and N-1 of purines. Nonetheless, the principal structures of such complexes have been determined. " Some of these are described below. 

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