Sarcosine → N-methyl-N-carboxymethyl-N'-phenylurea

To a stirred solution of 70 g. of N-methylaminoacetic acid and 70 g. of sodium hydroxide in 500 ml. of water were added portion-wise over twenty minutes 100 g. of phenyl isocyanate. Following complete addition, the aqueous reaction mixture was stirred at 24° C. for two hours. The mixture was then filtered and the filtrate was acidified to pH 2 by the addition of corc. hydrochloric acid. The precipitate which formed was collected by filtration to provide N-methyl-N-carboxymethyl-N'-phenylurea.