Allantoin is prepared by oxidation of the aqueous solution of glyoxal into glyoxylic acid which is then used to synthesize allantoin.

• 尿囊素的合成是用硝酸氧化乙二醛溶液制得乙醛酸后，再加入氢氧化钙和氯化钙，使乙醛酸以钙盐形式析出，然后在盐酸介质中与尿素缩合而成。