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Alkylation of D-Aspartic acid; R,R-Ethylenediaminedisuccinic acid

SyntheticPage 297
DOI: 10.1039/SP297
Submitted Aug 28, 2008, published Aug 28, 2008
Neetisha Mistry (n.s.mistry@warwick.ac.uk)
A contribution from Scott group, Warwick University


			Reaction Scheme: Alkylation of <span id="csm1268911286311" class="csm-chemical-name" title="D-Aspartic acid"><em>D</em>-Aspartic acid</span>

Chemicals Used

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

Procedure

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%

Author's Comments

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.

Data

H-NMR (300MHz, D2O/NaOH) 2.24 (dd, 2H, 3JHH=8.0Hz, 2JHH=15.1Hz, CH2COO), 2.41 (dd, 2H, 3JHH=5.7Hz, 2JHH=15.1Hz, CH2COO), 2.53 (m, 2H, CH2CH2), 3.29 (dd, 2H, 3JHH=5.7Hz, 3JHH=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]+)

Lead Reference

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

Other References

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

Supplementary Information

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




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Get structure file (.cdx, .sk2, .mol)

Keywords: amino acids, aspartic acid, dibromoethane, nucleophilic, substitution

Post new comment
  • Registered user marto leshAug 31 2008 12:08AM

    I was wondering why do you need Calcium hydroxide? ...Is it for masking carboxyl group?

  • Registered user Neetisha MistrySep 6 2008 9:05AM

    The calcium hydroxide is another method to raise the pH of the reaction mixture to a more preferable range of 9-13, aswell as the sodium hydroxide.

  • Registered user Peter ScottSep 6 2008 5:56PM

    I suspect that the Ca2+ ion preorganises the reagents. The product EDDS ligand is a known chelator for Ca2+, and this enantiomer is biodegradable unlike EDTA.

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