Incorporation of DL-2-aminohexanedioic acid, DL-2-amino-5-methoxycarbonyl-pentanoic acid and DL-methionine into 3-methoxycarbonylpropylglucosinolate have been demonstrated using an Erysimum species. The data support the following sequence of biosynthetic reactions: 2-aminohexanedioic acid is methylated by methionine; the resulting 2-amino-5-methoxycarbonyl-pentanoic acid is then converted into the glucosinolate. 2-Amino-5-methoxycarbonyl-pentanoic acid has been tentatively identified as a natural product in the plant.