Trapping phosphodiester-quinone methide adducts through in situ lactonization.

The goal of in situ modification of DNA via phosphodiester alkylation has led to our design of quinone methide derivatives capable of alkylating dialkyl phosphates. A series of catechol derivatives were investigated to trap the phosphodiester-quinone methide alkylation adduct through in situ lactonization. The catechol derivatives were uniquely capable of characterizable p-quinone methide formation for mechanistic clarity. These investigations revealed that with a highly reactive lactonization group (phenyl ester), lactonization competed with quinone methide formation. Lactone-forming groups of lower reactivity (methyl ester, n-propyl ester, and dimethyl amide) allowed quinone methide formation followed by phosphodiester alkylation; however, they were ineffective at in situ lactonization to drain the phosphodiester alkylation equilibrium to the desired phosphotriester product. The derivatives tethered with lactone-forming functionality of intermediate reactivity (chloro-, trichloro-, and trifluoroethyl esters), allowed quinone methide formation, phosphodiester alkylation, and in situ lactonization to efficiently afford the trapped phosphotriester adduct.