Salt-induced conversions of phosphorus(V) into phosphorus(IV) in solvents of different polarity. A tentative model for the initiation of conformational changes in DNA via the P(IV) residues

Evidence is presented for the involvement of pentaco-ordinated phosphorus intermediates in the rate-determining step of the de-alkylation reactions of some phosphates and phosphonates with LiCl and LiBr. Such involvement is suggested to lead to the zwitterionic pentaco-ordinated phosphorus complexes 5a and 5b, respectively when compounds 2a and 2b are treated with LiCl and LiBr. The existence of these complexes shows unambiguously the possibility of inducing (slight) conformational changes of phosphorus in the presence of cations and anions (or nucleophilic solvents). This approach may also be useful for the description of conformational changes in phosphate residues in DNA, thus leading to different conformations of DNA.