Valproic acid, an antiepileptic drug, is extensively metabolized in humans. Two putative metabolites, 2-n-propyl-3-aminopentanoic acid (3-aminovalproic acid, 3-amino-VPA; 2a) and 2-n-propyl-4-aminopentanoic acid (4-amino-valproic acid, 4-amino-VPA; 4a), which may result from the transamination of the respective keto acids 1a and 3a may explain the unusual extended seizure protection elicited by valproic acid. The title compounds were synthesized as their diasteriomeric ethyl esters 2b and 4b and submitted for anticonvulsant evaluation by the Antiepileptic Drug Development Program of the National Institute of Neurological and Communicative Disorders and Stroke. The results verified our hypothesis, as 4b was active in the subcutaneous pentylenetetrazol (scMet) evaluation at 30 mg/kg. Both compounds were highly toxic at 300 mg/kg.