Action of trimethylphosphate on thymidine 5′-phosphate, deoxycytidine 5′-phosphate, deoxyadenosine 5′-phosphate, and deoxyguanosine 5′-phosphate at 37–60 °C, and pH 7–10 gave their methyl esters and base-methylated derivatives. Esterification took place in all deoxyribonucleotides to the almost same extent and its rate was enhanced by the reaction temperature, while being independent of pH in the