Enantiomeric complexes of formula [PtCl(2)L(2)] [L(2) is (R)-(+)-
BINAP and (
S)-(-)-BINAP, where
BINAP is 2,2'-bis(diphenylphosphane)-1,1'-binaphthyl, and (R)-(+)-DABN and (S)-(-)-DABN, where DABN is 1,1'-binaphthyl-2,2'-
diamine], were tested for their cytotoxic activity against three
cancer cell lines and for their ability to bind to the human telomeric sequence folded in the G-quadruplex structure. Similar experiments were carried out on prototypal complexes
cisplatin and cis-[PtCl(2)(PPh(3))(2)] for comparison.
Platinum complexes containing phosphanes proved less cytotoxic to
cancer cell lines and less likely to interact with the nucleobases of the G-quadruplex than those containing
amines; in both cases the S-(-) isomer was more active than the R-(+) counterpart. More specifically, whereas all the
platinum complexes were able to platinate the G-quadruplex structure from the human telomeric repeat, the extent and sites of platination depended on the nature of the
ligands. Complexes containing (bulky) phosphanes interacted only with the adenines of the loops, whereas those containing the less sterically demanding
amines interacted with adenines and some guanines of the G-quartet.