(Fig. 2) the oxygens linked to iron are derived from 2,3-dihydroxybenzoyl-L-serine and D chelates result. These correspond, respectively, to left- and right-hand coordination propellers. Geometrical isomers, cis and trans, are also possible, except in the two archetypal siderophores just cited steric restraints confine the isomers to the cis form.
The three catechol rings wrap around the Fe(III) to afford a right-handed (D) coordination propeller with the highest known binding constant for ferric ion (9). Enterobactin is produced generally by enteric bacteria.