DL-Aspartic acid

Abstract

CommentInterest in D,L-aspartic acid has spanned several decades, from the first structural determination by Rao (1973), due to its acting as important ligand in the preparation of transition metal complexes (Ciunik, 1987;Casellato et al., 1991;Barfod et al., 1999). In exploring the possibility of introducing D,L-aspartic acid into a phosphite system, we unexpectedly obtained the title compound. To the best of our knowledge, there are only four reports on the structure of D,L-aspartic acid (Rao et al., 1968;Rao, 1973;Sequeira et al., 1989;Flaig et al., 1998). The present structure of D,L-aspartic acid differs slightly from these previously reported ones, since it presents the same space group and a similar molecular disposition, but with an a parameter some 7-8% shorter.The molecules (Fig. 1) are interconnected with each other by hydrogen bonds to form a 3-D supramolecular network (Table 1 and Fig. 2). ExperimentalThe title compound was obtained by hydrothermal methods. A mixture of Zn(CH 3 COO) 2 ·2H 2 O (0.16 g), H 3 PO 3 (0.19 g), D,L-aspartic acid (0.25 g) and H 2 O (8 ml), was sealed in a 25 ml Teflon-lined steel autoclave and heated under autogenous pressure at 363 K for 3 days. Then, the filtrate was kept at room temperature and colorless prism-like crystals were obtained after three weeks. RefinementAll the H atoms were located from difference-density maps in a difference Fourier map and their positions and isotropic displacement parameters were refined.

Chiral Asymmetric Structures in Aspartic Acid and Valine Crystals Assessed by Atomic Force Microscopy

“…As shown in Figure , the crystal periodicity is given by the unit cell dimensions and is indicated by two orthogonal arrows. The FFT spectrum is shown in the top right inset, and the indicated periodicity is 0.74 and 0.91 nm, which are in agreement with the values for bulk periodicity …”

“…The FFT spectrum is shown in the top right inset, and the indicated periodicity is 0.74 and 0.91 nm, which are in agreement with the values for bulk periodicity. 18 Apparently the frequency of the precipitation pattern of amino acids is not equal for all configurations;…”

“…The standard calibration procedures that have been described in the previous work were followed by a finer calibration procedure using a dl -asp sample. The scanners were recalibrated by comparing the reported lattice parameters a = 1.758 nm, b = 0.7439 nm and c = 0.9181 nm with the measured periodicity. As shown in Figure , the crystal periodicity is given by the unit cell dimensions and is indicated by two orthogonal arrows.…”

Amino Acid Structures

“…In this paper, the authors stated that the new form "crystallizes in the same space group as the previously reported form but with a slightly different a axis." However, when inspecting the structure, it was found that the simple unit cell transformation (transformation matrix 1 0 2/0 1 0/0 0 À1) from the original cell as published by Rao (1973) yields the cell found by Wang et al (2007). Consequently it is evident that this crystal does not represent a novel phase.…”

“…Recently, a study proposed another "form of DL-aspartic acid" (Wang et al 2007). In this paper, the authors stated that the new form "crystallizes in the same space group as the previously reported form but with a slightly different a axis."…”