The intramolecular cyclization 2-Iodo-3-ureidopropionic acid.

2-Iodo-3-ureidopropionic acid resulting from the hydrolysis of 5-iodo-5,6-dihydrouracil catalyzed by either dihydrouracil amidohydrolase or hydroxide ion cyclizizes to yield 2-amino-2-oxazoline-3-carboxylic acid. This cyclization involves intramolecular attack of the ureido oxygen atom on carbon two of the ureidoacid to yield iodide ion and the oxazoline as products. The kinetics of this cyclization indicate that from pH 2 to 9 the reaction rate is pH independent. Below pH 2 the rate is diminished due to protonation of the ureido group. Above pH 12 the rate increases dramatically probably due to proton abstraction which would dramatically increase the nucleophilic character of the ureido function. In the pH independent region the reaction is not subject to catalysis by external buffers.