Mass spectral characterization of acyloxymethyl phosphates

A series of organophosphates having one or two acyloxymethyl groups have been characterized by methane chemical ionization mass spectrometry: twelve are model compounds with phenyl and benzyl groups while four are derived from pyrimidine-3'-deoxyriboside-5'-monophosphates. Some are protonated cyclohexyl-ammonium salts. In addition the phenyl and benzyl phosphate spectra exhibit an abundance of fragmentation and rearrangement ions, the majority of which were products of three processes--expulsion of formaldehyde, loss of the acyloxymethyl group with transfer of hydrogen to the phosphate, and fission of the methylene-acyloxy bond. The pyrimidine-3'-deoxyriboside-5'-monophosphate esters give less fragmentation under similar circumstances; prominent ions in their spectra are the protonated molecular ions and losses of one and two molecules of formaldehyde from them and the protonated bases.