COMPLETE DISPLACEMENT OF N,O BOUND AMINO-ACIDS (AMACH) IN CIS-[(NH3)2PT(AMAC)]NO3 CHELATES BY 9-METHYLGUANINE (9-MEGH) AND 9-METHYLADENINE (9-MEA) - THE CRYSTAL-STRUCTURE OF CIS-[(NH3)2PT(9-MEA-N7)2](NO3)2.1.5H2O

The reactions of the complexes cis-[(NH3)2Pt(amac)]NO3, where amac are glycine (gly), L-alanine (L- ala) and 2-aminobutyric acid (2-aba), chelated to Pt(II), with 9-methylguanine (9-MeGH) and 9- methyladenine (9-MeA) were studied in neutral and acidic aqueous solutions. Complete displacement of the amino acids resulted in the formation of the compounds cis-[(NH3)2Pt(9-MeGH)2](NO3)2 in neutral and cis-[(NH3)2Pt(9-MeA)2](NO3)2 in strongly acidic media. The latter compound contained two 9-MeA molecules, both coordinated through N(7). Its crystal structure was solved with X-ray diffraction techniques. Crystal data: space group C2/c, a = 18.506(2), b = 15.770(2), c = 16.422(2) Å, β = 108.38(2)°, V = 4548(2) Å3, Z = 8, R = 0.022 for 4447 independent reflections. The results are compared with other analogous cis-[(NH3)2Pt(purine derivative)2]2+ structures and discussed in terms of a possible cross-link between two N(7) sites of adjacent adenines in DNA. © 1990.