Heating of 1-substituted biguanide with benzil in ethanol was found to give 2-substituted guanidilidene-5, 5-diphenylhydantoin, which was easily converted into 1, 1-diphenyl-1-substituted biguanidoacetic acid by hydrolysis with hydrochloric acid. The structureand the formation mechanism of 2-substituted guanidilidene-5, 5-diphenylhydantoin was also discussed.
