Nocobactin NA, a lipid-soluble iron-chelating product with an unusual and characteristic u.v.-absorption spectrum, was isolated from Nocardia asteroides grown under conditions of iron deficiency. Its structure was determined by physical methods and by synthesis of one of its degradation products. Nocobactin NA was obtained as a homologous mixture of compounds with side chains of differing length, and resembles mycobactin M in structure except that it has an oxazole ring in place of an oxazoline ring, and the side chains in the cobactin fragment are considerably shorter.
