dl-O-ureidohomoserine (α-amino-γ-ureido-oxybutyric acid), ureido-oxyacetic acid and their derivatives were synthesized by reaction of the corresponding amino-oxy acids with potassium cyanate. The reactions of amino-oxyacetic acid with arylisocyanates and phosgene were studied. The copper complex and cyclohexylammonium salt of amino- oxyacetic acid were isolated.