title: Quinone methide phosphodiester alkylations under aqueous conditions.
abstract: A detailed analysis of the alkylation of phosphodiesters with a p-quinone methide under aqueous conditions has been accomplished. The relative rates of phosphodiester alkylation and hydrolysis have been examined by (1)H NMR analysis of the reaction of 2,6-dimethyl-p-quinone methide in a buffered diethyl phosphate/acetonitrile solution (1:9 v/v, pH 4.0). The rate of hydrolysis of the quinone methide was confirmed by UV analysis in 28.5% solutions of aqueous inorganic phosphate in acetonitrile at pH 4.0 and 7.0. Similarly, the rate of phosphodiester alkylations by the quinone methide was also confirmed by UV analysis in 28.5% solutions of aqueous dibenzyl, dibutyl, or diethyl phosphate in acetonitrile at pH 4.0 and 7.0. These kinetic studies further establish that the phosphodiester alkylation reactions are acid-catalyzed, second-order processes. The rate constant for phosphodiester alkylation was found to range from approximately 370-3700 times the rate constant of quinone methide hydrolysis with diethyl and dibenzyl phosphate, respectively (pH 4.0, 28.5% aqueous acetonitrile).
authors.affiliation: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Zhou
authors.forename: K D
authors.initials: KD
authors.lastname: Turnbull
mesh_terms: D000097:Acetonitriles / Q000494:pharmacology; D002021:Buffers; D015195:Drug Design; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis / Q000187:drug effects; D045563:Indolequinones; D007211:Indoles / Q000737:chemistry*; D007700:Kinetics; D010755:Organophosphates / Q000737:chemistry*; D011809:Quinones / Q000737:chemistry*
chemical_list: D000097:Acetonitriles; D002021:Buffers; D045563:Indolequinones; D007211:Indoles; D010755:Organophosphates; D011809:Quinones; C068040:quinone methide; C032159:acetonitrile