Disclosed are compounds including phosphate and N-oxide prodrugs of the NK1 antagonist netupitant, useful in the prevention and/or treatment of diseases including emesis induced by chemotherapy. Also disclosed are methods of making a di-tert-butyl (chloromethyl) phosphate useful in the manufacture of such prodrugs by reacting a dialkylphosphate salt with an acid to obtain the corresponding ester of phosphoric acid, reacting the ester with a quaternary ammonium hydroxide base to form a monobasic salt, and reacting the monobasic salt with chloroiodomethane to form the corresponding chloromethyl dialkyl phosphate.