<jats:title>Abstract</jats:title> <jats:p>Cyclopropylalanine, an antifungal amino acid, has been isolated from the mushroom Amanita virgineoides Bas. Its structure has been elucidated as (2S)-2-amino-3-cyclopropylpropionic acid, on the basis of the spectroscopic analysis and its synthesis from L-allylglycine.