Abstract: The invention provides an improved process for the synthesis of compounds carrying at least one phosphate group, especially polyalkylene glycol phosphate compounds, said process comprising the steps of: (a) reacting a compound containing at least one primary alcohol moiety with a diaryl- or diaralkyl-halophosphate whereby to form the corresponding diaryl- or diaralkyl-phosphate ester; (b) reductively cleaving the resulting product; and (c) if desired, repeating steps (a) and (b) with the product of step (b) whereby to produce a compound carrying two or more phosphate groups. Advantages of the process in accordance with the invention are that this avoids the production of by-products and results in products which are low in impurities. Also provided are novel diaryl- and diaralkyl-phosphate ester compounds, in particular polyethylene glycol diphenylphosphate ester and derivatives thereof.