Ethylenediamine-N,N'-disuccinic acid (EDDS) is an aminopolycarboxylic acid. It is a colourless solid that is used as chelating agent that may offer a biodegradable alternative to EDTA, which is currently used on a large scale in numerous applications. EDDS has two chiral centers, and as such three stereoisomers. These are the enantiomeric (R,R) and (S,S) isomers and the achiral meso (R,S) isomer. As a biodegradable replacement for EDTA, only the (S,S) stereoisomer is of interest. The (R,S) and (R,R) stereoisomers are less biodegradable, whereas the (S,S) stereoisomer has been shown to be very effectively biodegraded even in highly polluted soils. EDDS was first synthesized from maleic acid and ethylenediamine. (S,S)-EDDS is produced stereospecifically by the alkylation of an ethylenedibromide with L-aspartic acid. Racemic EDDS is produced by the reaction of ethylenediamine with fumaric acid or maleic acid.
