D-Aspartic acid (Aldrich)
Ca(OH)₂
NaOH (50% aqueous w/v)
1,2-dibromoethane

D-aspartic acid (6.083 g, 0.045 mol), Ca(OH)₂ (1.653 g, 0.023 mol), NaOH (50% aqueous w/v, 3.60 g), and deionized water (8.5 ml) were placed in a 3-necked round bottom flask, and fitted with a water condenser. 1,2-dibromoethane (1.6 ml, 3.47 g, 0.018 mol) was added through one of the side arms. The reaction mixture was heated to reflux. Over approximately 6 h NaOH (50% aqueous w/v, 2.98 g) was added dropwise using a syringe pump, whilst under reflux. Water (20 ml) was added, and the system refluxed for a further hour. The system was cooled to room temperature, then acidified to pH 3 using HCl (35%). A white precipitate was collected and was placed in water (23 ml). NaOH (50% aqueous w/v) was added until pH 11, then HCl (35%) was added carefully until pH 3.5. The white precipitate was collected, and dried under vacuum at 65 °C. Yield: 1.417 g, 26%

The aspartic acid is used in excess to the dibromoethane, there should be a 2:1 stoichiometry.During the addition of NaOH over 6 h the pH of the reaction mixture is best between pH 9-13. The crude product will include many side products and the unreacted aspartic acid. Since aspartic acid is more soluble in water, it should remain in solution during the recrystallisation.

H-NMR (300MHz, D₂O/NaOH) 2.24 (dd, 2H, ³J_HH=8.0Hz, ²J_HH=15.1Hz, CH₂COO), 2.41 (dd, 2H, ³J_HH=5.7Hz, ²J_HH=15.1Hz, CH₂COO), 2.53 (m, 2H, CH₂CH₂), 3.29 (dd, 2H, ³J_HH=5.7Hz, ³J_HH=8.0Hz), 4.79 (solvent peak D₂O/NaOH);C-NMR (D₂O/NaOH): 41.3 (CH2-CH2 or CH2COO), 46.6 (CH2-CH2 or CH2COO), 61.3 (CH), 179.8 (COO quaternary), 181.5 (COO quaternary); ESI Positive m/z 293.09 ([EDDS + H]⁺)

J. A. Neal and N. J. Rose, Inorg. Chem., 1968, 7, 2405-2412 doi:10.1021/ic50069a043

A.Damiamoglou et al. A New Reference Material for UV-visible Circular Dichroism Spectroscopy, Chirality, 2008. doi:10.1002/chir.20566
Personal communications from Jim Barker, Innospec

The S,S-isomer of this compound (known as EDDS) is manufactured by Innospec under the trade name  octaquest as a biodegradable alternative to EDTA in e.g. microelement fertilisers and detergents, photographic processing or as molluscicide. The R,R-isomer is not readily biodegradable.

C13NMR spectrum of R,R-Ethylenediaminedisuccinic acid

HNMR Spectrum of R,R-Ethylenediaminedisuccinic acid