Hi,
First you have to chlorinated to chloroacetic acid, then generates the sodium salt which is then reacted with sodium cyanide to the cyano acetic acid salt in a nucleophilic substitution. The nitrile group can be hydrolysed with sodium hydroxide to sodium malonate and acidification affords malonic acid.
Once you have the malonic acid you can obtain barbituric acid in a condensation reaction with urea.