How is Dimethyl hydrogen phosphate (CAS: 813-78-5) typically synthesized?

Dimethyl hydrogen phosphate is typically synthesized by the reaction of phosphoric acid with dimethyl sulfate. The process involves the addition of dimethyl sulfate to water or an alcohol solution of phosphoric acid, followed by workup to obtain the phosphate ester. The reaction is often catalyzed by sulfuric acid and has a yield of about 90%. High selectivity is achieved under controlled conditions.