By action of formaldehyde and hydrochloric acid on 5,5-diphenylhydantoin was
prepared 3-hydroxymethyl-5,5-diphenyl-imidazolidine-2,4-dione which was
converted by action PCl3 to 3-chloromethyl-5,5-diphenyl-imidazolidine-2,4-
dione by action PCl3. Then the chlorine atom was substituted on P(O)(OBz)Ogroup by action of argentum salt of phosphoric acid dibenzyl ester. Removal of
the protecting groups by hydrogenolysis gives the 2,4-imidazolidinedione, 5,5-
diphenyl-3-((phosphonooxy)methyl)- (fosphenytoin).
In practice it is usually used as sodium salt.
