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organic compounds
3-{[(Benzyloxy)carbonyl]amino}butanoic acid
aDepartment of Biological Science and Technology, Tokai University, 317 Nishino, Numazu, Shizuoka 410-0321, Japan, and bSchool of Science, Tokai University, 4-1-1 Kitakaname, Hiratuka, Kanagawa 259-1292, Japan
*Correspondence e-mail: fujii@wing.ncc.u-tokai.ac.jp
In the title compound, C12H15NO4, the butyric acid group has a stretched trans conformation. The dihedral angle between the phenyl ring and the oxycarboxyamino N—(C=O)—O—C plane is 56.6 (2)°. In the crystal, an inversion dimer is formed by a pair of O—H⋯O hydrogen bonds. The dimers are further linked by N—H⋯O hydrogen bonds between amide groups, forming a tape along the b axis.
Related literature
For general background to 3-aminobutanoic acid, see: Cohen et al. (2011). For bond-length data, see: Allen et al. (1987
). For structures of related metallo-organic compounds, see: Bryan et al. (1961
); Böhm & Seebach (2000
); Gross & Vahrenkamo (2005
).
Experimental
Crystal data
|
Refinement
|
|
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995
); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008
); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008
); molecular graphics: ORTEP-3 (Farrugia, 1997
); software used to prepare material for publication: PLATON (Spek, 2009
) and WinGX (Farrugia, 1999
).
Supporting information
https://doi.org/10.1107/S1600536811035276/is2769sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811035276/is2769Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536811035276/is2769Isup3.cml
The title compound was purchased from Aldrich-Sigma Co. Ltd. Rod-like colourless crystals suitable for X-ray diffraction were obtained by vapour-phase diffusion of an ethanol and chloroform mixture solution at 297 K.
All H atoms were located in a difference-Fourier map. H atoms bonded to N and O atoms were then refined isotropically. Other H atoms were positioned geometrically and refined using a riding model, with C—H = 0.95–0.99 Å and with Uiso(H) = 1.2 (1.5 for methyl groups) times Ueq(C).
Solid-phase synthesis is now the accepted method for peptide synthesis, in which the protected natural or non-natural amino acids are widely used. 3-Aminobutanoic acid (BABA) is one of the non-protein amino acids, and it attracts attentions to building block. At the same time, BABA potentially possesses various bioactivities. Downy mildew of lettuce (Bremia lactucae) is a serious disease, but BABA is considered with one of the disease resistance inducers (Cohen et al., 2011). Despite the agrichemical or pharmaceutical desires, crystal structures of BABA derivatives have not been cleared except for the structures of some metallo-organic compounds (Bryan et al., 1961; Gross & Vahrenkamo, 2005; Böhm & Seebach, 2000) because of its difficulty in crystallization.
Fortunately, the title compound, 3-benzyloxycarbonylaminobutanoic acid (Cbz-BABA), (I), was crystallized, and we herein report on the β-position the benzyloxycarboxyamino group is attached perpendicular to the butyric acid group. The phenyl group is twisted against the least-squares plane of the oxycarboxyamino group (N1/C5/O3/O4/C6/C7) with the dihedral angle of 56.6 (2)°.
The molecular structure of (I) is shown in Fig. 1. The bond lengths (Allen et al., 1987) and angles are within normal ranges except for the O-H bond length at the carboxy dimer. The part of BABA is essentially similar with that reported by Gross & Vahrenkamo (2005). The butyric acid group owns a stretched trans-conformation (O1-C1-C2-C3-C4). At theIn the
an makes a planar structure with the intermolecular hydrogen bond (N1—HN1···O3) along the b axis. The planar structure is stacked to the layer along the c axis. The carboxy dimer is made from the enantiomeric isomers with the intermolecular hydrogen bond (O1—H1···O2). The H atom is shared by carboxy dimer then the bond distance O1—H1 is longer than that of general carboxy group. The hydrophobic and hydrophilic layers are well separated along the a axis. The structure shows a herring bone stacking mode (Fig. 2).For general background to 3-aminobutanoic acid, see: Cohen et al. (2011). For bond-length data, see: Allen et al. (1987). For structures of related metallo-organic compounds, see: Bryan et al. (1961); Böhm & Seebach (2000); Gross & Vahrenkamo (2005).
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell
CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: PLATON (Spek, 2009) and WinGX (Farrugia, 1999).C12H15NO4 | F(000) = 504 |
Mr = 237.25 | Dx = 1.271 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.54184 Å |
Hall symbol: -P 2ybc | Cell parameters from 25 reflections |
a = 23.1413 (7) Å | θ = 30.0–35.0° |
b = 4.9589 (4) Å | µ = 0.8 mm−1 |
c = 11.0879 (6) Å | T = 297 K |
β = 103.075 (6)° | Rod, colourless |
V = 1239.41 (13) Å3 | 0.4 × 0.2 × 0.2 mm |
Z = 4 |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.023 |
Radiation source: sealed X-ray tube | θmax = 74.9°, θmin = 2.0° |
ω/2θ scans | h = −28→28 |
Absorption correction: ψ scan (North et al., 1968) | k = −6→0 |
Tmin = 0.74, Tmax = 0.856 | l = −13→0 |
2696 measured reflections | 3 standard reflections every 300 reflections |
2547 independent reflections | intensity decay: none |
1669 reflections with > 2σ(i) |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.046 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.131 | w = 1/[σ2(Fo2) + (0.0542P)2 + 0.3091P] where P = (Fo2 + 2Fc2)/3 |
S = 1.02 | (Δ/σ)max < 0.001 |
2547 reflections | Δρmax = 0.14 e Å−3 |
164 parameters | Δρmin = −0.14 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), FC*=KFC[1+0.001XFC2Λ3/SIN(2Θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0020 (4) |
C12H15NO4 | V = 1239.41 (13) Å3 |
Mr = 237.25 | Z = 4 |
Monoclinic, P21/c | Cu Kα radiation |
a = 23.1413 (7) Å | µ = 0.8 mm−1 |
b = 4.9589 (4) Å | T = 297 K |
c = 11.0879 (6) Å | 0.4 × 0.2 × 0.2 mm |
β = 103.075 (6)° |
Enraf–Nonius CAD-4 diffractometer | 1669 reflections with > 2σ(i) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.023 |
Tmin = 0.74, Tmax = 0.856 | 3 standard reflections every 300 reflections |
2696 measured reflections | intensity decay: none |
2547 independent reflections |
R[F2 > 2σ(F2)] = 0.046 | 0 restraints |
wR(F2) = 0.131 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.02 | Δρmax = 0.14 e Å−3 |
2547 reflections | Δρmin = −0.14 e Å−3 |
164 parameters |
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles |
Refinement. Refinement on F2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The observed criterion of F2 > σ(F2) is used only for calculating -R-factor-obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.00381 (6) | 0.2239 (3) | 0.60261 (14) | 0.0693 (5) | |
O2 | 0.05705 (6) | 0.5990 (3) | 0.61469 (14) | 0.0671 (5) | |
O3 | 0.20820 (7) | 0.8467 (3) | 0.78378 (18) | 0.0841 (7) | |
O4 | 0.25967 (6) | 0.5196 (3) | 0.71327 (15) | 0.0686 (5) | |
N1 | 0.18104 (7) | 0.4105 (3) | 0.78288 (15) | 0.0513 (5) | |
C1 | 0.04634 (8) | 0.3818 (4) | 0.65874 (18) | 0.0501 (6) | |
C2 | 0.07918 (8) | 0.2819 (4) | 0.78120 (17) | 0.0536 (6) | |
C3 | 0.13228 (8) | 0.4484 (4) | 0.84471 (16) | 0.0511 (6) | |
C4 | 0.15096 (11) | 0.3763 (6) | 0.9808 (2) | 0.0862 (9) | |
C5 | 0.21503 (8) | 0.6116 (4) | 0.76220 (18) | 0.0536 (6) | |
C6 | 0.29917 (11) | 0.7210 (6) | 0.6843 (3) | 0.1074 (13) | |
C7 | 0.34503 (10) | 0.5785 (5) | 0.6328 (3) | 0.0770 (9) | |
C8 | 0.40323 (12) | 0.6072 (8) | 0.6870 (3) | 0.1103 (13) | |
C9 | 0.44560 (14) | 0.4824 (10) | 0.6379 (4) | 0.142 (2) | |
C10 | 0.4307 (2) | 0.3267 (10) | 0.5382 (5) | 0.150 (2) | |
C11 | 0.3731 (2) | 0.2940 (10) | 0.4833 (4) | 0.1460 (19) | |
C12 | 0.32992 (13) | 0.4217 (8) | 0.5303 (3) | 0.1111 (13) | |
H1 | −0.0229 (13) | 0.297 (7) | 0.505 (3) | 0.135 (11)* | |
HN1 | 0.1926 (9) | 0.252 (5) | 0.7727 (19) | 0.066 (6)* | |
H2A | 0.09260 | 0.09990 | 0.77080 | 0.0640* | |
H2B | 0.05180 | 0.27210 | 0.83560 | 0.0640* | |
H3 | 0.12080 | 0.63910 | 0.83810 | 0.0610* | |
H4A | 0.16100 | 0.18830 | 0.98910 | 0.1290* | |
H4B | 0.11890 | 0.41270 | 1.02020 | 0.1290* | |
H4C | 0.18490 | 0.48230 | 1.01930 | 0.1290* | |
H6A | 0.31780 | 0.82000 | 0.75840 | 0.1290* | |
H6B | 0.27740 | 0.84750 | 0.62410 | 0.1290* | |
H8 | 0.41460 | 0.71210 | 0.75800 | 0.1320* | |
H9 | 0.48550 | 0.50720 | 0.67510 | 0.1710* | |
H10 | 0.45980 | 0.24110 | 0.50670 | 0.1790* | |
H11 | 0.36230 | 0.18520 | 0.41350 | 0.1750* | |
H12 | 0.29020 | 0.39990 | 0.49140 | 0.1330* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0694 (9) | 0.0549 (8) | 0.0760 (10) | −0.0139 (7) | 0.0005 (7) | 0.0066 (7) |
O2 | 0.0658 (9) | 0.0513 (8) | 0.0775 (10) | −0.0062 (7) | 0.0023 (7) | 0.0186 (7) |
O3 | 0.0803 (11) | 0.0347 (7) | 0.1441 (16) | 0.0014 (7) | 0.0394 (10) | −0.0024 (8) |
O4 | 0.0618 (8) | 0.0487 (8) | 0.1039 (11) | −0.0028 (6) | 0.0369 (8) | 0.0035 (8) |
N1 | 0.0533 (9) | 0.0339 (8) | 0.0699 (10) | 0.0031 (7) | 0.0207 (7) | −0.0012 (7) |
C1 | 0.0456 (9) | 0.0415 (9) | 0.0642 (11) | 0.0040 (8) | 0.0145 (8) | 0.0028 (9) |
C2 | 0.0532 (10) | 0.0466 (10) | 0.0626 (12) | 0.0030 (8) | 0.0162 (9) | 0.0091 (9) |
C3 | 0.0533 (10) | 0.0466 (10) | 0.0551 (11) | 0.0056 (8) | 0.0161 (8) | −0.0010 (8) |
C4 | 0.0801 (15) | 0.119 (2) | 0.0582 (13) | 0.0027 (16) | 0.0129 (11) | 0.0025 (14) |
C5 | 0.0518 (10) | 0.0385 (10) | 0.0696 (12) | 0.0031 (8) | 0.0119 (9) | 0.0036 (9) |
C6 | 0.0802 (16) | 0.0665 (16) | 0.194 (3) | −0.0051 (13) | 0.0697 (19) | 0.0239 (19) |
C7 | 0.0555 (12) | 0.0749 (16) | 0.1052 (19) | −0.0028 (11) | 0.0281 (12) | 0.0230 (15) |
C8 | 0.0677 (16) | 0.140 (3) | 0.124 (2) | −0.0100 (18) | 0.0234 (16) | −0.005 (2) |
C9 | 0.0618 (17) | 0.180 (4) | 0.190 (4) | 0.009 (2) | 0.038 (2) | 0.004 (3) |
C10 | 0.123 (3) | 0.147 (4) | 0.212 (5) | 0.000 (3) | 0.108 (3) | −0.013 (3) |
C11 | 0.148 (3) | 0.170 (4) | 0.142 (3) | −0.040 (3) | 0.079 (3) | −0.037 (3) |
C12 | 0.0780 (18) | 0.142 (3) | 0.113 (2) | −0.017 (2) | 0.0209 (17) | 0.007 (2) |
O1—C1 | 1.301 (2) | C9—C10 | 1.328 (7) |
O2—C1 | 1.231 (2) | C10—C11 | 1.344 (7) |
O3—C5 | 1.208 (2) | C11—C12 | 1.381 (6) |
O4—C5 | 1.350 (2) | C2—H2A | 0.9700 |
O4—C6 | 1.438 (3) | C2—H2B | 0.9700 |
O1—H1 | 1.18 (3) | C3—H3 | 0.9800 |
N1—C3 | 1.459 (2) | C4—H4A | 0.9600 |
N1—C5 | 1.322 (3) | C4—H4B | 0.9600 |
N1—HN1 | 0.85 (2) | C4—H4C | 0.9600 |
C1—C2 | 1.483 (3) | C6—H6A | 0.9700 |
C2—C3 | 1.515 (3) | C6—H6B | 0.9700 |
C3—C4 | 1.515 (3) | C8—H8 | 0.9300 |
C6—C7 | 1.492 (4) | C9—H9 | 0.9300 |
C7—C12 | 1.356 (5) | C10—H10 | 0.9300 |
C7—C8 | 1.353 (4) | C11—H11 | 0.9300 |
C8—C9 | 1.372 (5) | C12—H12 | 0.9300 |
O1···C2i | 3.357 (2) | H1···O1iii | 2.74 (3) |
O1···O1ii | 3.156 (2) | H1···O2iii | 1.48 (3) |
O1···O2iii | 2.650 (2) | H1···C1iii | 2.38 (3) |
O2···O1iii | 2.650 (2) | H1···H1iii | 2.29 (5) |
O2···N1 | 3.188 (2) | HN1···O3vii | 2.04 (2) |
O2···C1iii | 3.412 (2) | HN1···H2A | 2.4300 |
O3···N1iv | 2.865 (2) | H2A···HN1 | 2.4300 |
O1···H2Bi | 2.7500 | H2A···H3vii | 2.4500 |
O1···H1iii | 2.74 (3) | H2B···H4B | 2.3800 |
O2···H2Bv | 2.8300 | H2B···O1v | 2.7500 |
O2···H3 | 2.5900 | H2B···O2i | 2.8300 |
O2···H1iii | 1.48 (3) | H2B···C1i | 3.0000 |
O3···HN1iv | 2.04 (2) | H3···O2 | 2.5900 |
O3···H3 | 2.4600 | H3···O3 | 2.4600 |
O3···H6A | 2.6200 | H3···H2Aiv | 2.4500 |
O3···H6B | 2.6400 | H4B···H2B | 2.3800 |
O3···H12vi | 2.9200 | H4B···C1ix | 2.9100 |
O4···H12 | 2.7700 | H4C···H6Bvi | 2.3500 |
N1···O2 | 3.188 (2) | H6A···O3 | 2.6200 |
N1···O3vii | 2.865 (2) | H6A···H8 | 2.3000 |
C1···O2iii | 3.412 (2) | H6B···O3 | 2.6400 |
C2···O1v | 3.357 (2) | H6B···H4Cx | 2.3500 |
C1···H2Bv | 3.0000 | H8···H6A | 2.3000 |
C1···H1iii | 2.38 (3) | H12···O4 | 2.7700 |
C1···H4Bviii | 2.9100 | H12···O3x | 2.9200 |
C5—O4—C6 | 115.96 (18) | C3—C2—H2B | 108.00 |
C1—O1—H1 | 116.0 (16) | H2A—C2—H2B | 107.00 |
C3—N1—C5 | 122.56 (16) | N1—C3—H3 | 108.00 |
C5—N1—HN1 | 117.3 (15) | C2—C3—H3 | 108.00 |
C3—N1—HN1 | 118.9 (15) | C4—C3—H3 | 108.00 |
O1—C1—O2 | 122.37 (18) | C3—C4—H4A | 109.00 |
O1—C1—C2 | 114.36 (17) | C3—C4—H4B | 109.00 |
O2—C1—C2 | 123.24 (18) | C3—C4—H4C | 109.00 |
C1—C2—C3 | 115.92 (16) | H4A—C4—H4B | 110.00 |
C2—C3—C4 | 110.66 (17) | H4A—C4—H4C | 109.00 |
N1—C3—C2 | 110.09 (15) | H4B—C4—H4C | 109.00 |
N1—C3—C4 | 111.15 (17) | O4—C6—H6A | 110.00 |
O3—C5—N1 | 125.75 (19) | O4—C6—H6B | 110.00 |
O3—C5—O4 | 123.51 (18) | C7—C6—H6A | 110.00 |
O4—C5—N1 | 110.74 (17) | C7—C6—H6B | 110.00 |
O4—C6—C7 | 107.4 (2) | H6A—C6—H6B | 109.00 |
C6—C7—C8 | 120.2 (3) | C7—C8—H8 | 120.00 |
C6—C7—C12 | 121.4 (3) | C9—C8—H8 | 120.00 |
C8—C7—C12 | 118.4 (3) | C8—C9—H9 | 119.00 |
C7—C8—C9 | 120.4 (3) | C10—C9—H9 | 119.00 |
C8—C9—C10 | 121.2 (4) | C9—C10—H10 | 120.00 |
C9—C10—C11 | 119.4 (4) | C11—C10—H10 | 120.00 |
C10—C11—C12 | 120.1 (4) | C10—C11—H11 | 120.00 |
C7—C12—C11 | 120.5 (3) | C12—C11—H11 | 120.00 |
C1—C2—H2A | 108.00 | C7—C12—H12 | 120.00 |
C1—C2—H2B | 108.00 | C11—C12—H12 | 120.00 |
C3—C2—H2A | 108.00 | ||
C6—O4—C5—O3 | −1.5 (3) | O4—C6—C7—C8 | −122.5 (3) |
C6—O4—C5—N1 | 178.82 (19) | O4—C6—C7—C12 | 58.6 (4) |
C5—O4—C6—C7 | 179.6 (2) | C6—C7—C8—C9 | −178.2 (3) |
C5—N1—C3—C2 | 139.00 (18) | C12—C7—C8—C9 | 0.7 (5) |
C5—N1—C3—C4 | −98.0 (2) | C6—C7—C12—C11 | 179.3 (3) |
C3—N1—C5—O3 | −4.8 (3) | C8—C7—C12—C11 | 0.3 (5) |
C3—N1—C5—O4 | 174.88 (16) | C7—C8—C9—C10 | −1.4 (7) |
O1—C1—C2—C3 | 175.10 (16) | C8—C9—C10—C11 | 1.0 (8) |
O2—C1—C2—C3 | −6.8 (3) | C9—C10—C11—C12 | 0.1 (7) |
C1—C2—C3—N1 | −73.0 (2) | C10—C11—C12—C7 | −0.8 (7) |
C1—C2—C3—C4 | 163.72 (18) |
Symmetry codes: (i) −x, y−1/2, −z+3/2; (ii) −x, −y, −z+1; (iii) −x, −y+1, −z+1; (iv) x, y+1, z; (v) −x, y+1/2, −z+3/2; (vi) x, −y+3/2, z+1/2; (vii) x, y−1, z; (viii) x, −y+1/2, z−1/2; (ix) x, −y+1/2, z+1/2; (x) x, −y+3/2, z−1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2iii | 1.18 (3) | 1.48 (3) | 2.650 (2) | 177 (2) |
N1—HN1···O3vii | 0.85 (2) | 2.04 (2) | 2.865 (2) | 165 (2) |
C3—H3···O3 | 0.98 | 2.46 | 2.825 (3) | 101 |
Symmetry codes: (iii) −x, −y+1, −z+1; (vii) x, y−1, z. |
Experimental details
Crystal data | |
Chemical formula | C12H15NO4 |
Mr | 237.25 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 297 |
a, b, c (Å) | 23.1413 (7), 4.9589 (4), 11.0879 (6) |
β (°) | 103.075 (6) |
V (Å3) | 1239.41 (13) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.8 |
Crystal size (mm) | 0.4 × 0.2 × 0.2 |
Data collection | |
Diffractometer | Enraf–Nonius CAD-4 |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.74, 0.856 |
No. of measured, independent and observed [ > 2σ(i)] reflections | 2696, 2547, 1669 |
Rint | 0.023 |
(sin θ/λ)max (Å−1) | 0.626 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.046, 0.131, 1.02 |
No. of reflections | 2547 |
No. of parameters | 164 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.14, −0.14 |
Computer programs: CAD-4 Software (Enraf–Nonius, 1989), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), PLATON (Spek, 2009) and WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 1.18 (3) | 1.48 (3) | 2.650 (2) | 177 (2) |
N1—HN1···O3ii | 0.85 (2) | 2.04 (2) | 2.865 (2) | 165 (2) |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) x, y−1, z. |
Acknowledgements
The authors would like to thank T. Watadani of Daito Chem and Dr Y. Takahasi for their experimental support.
References
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Solid-phase synthesis is now the accepted method for peptide synthesis, in which the protected natural or non-natural amino acids are widely used. 3-Aminobutanoic acid (BABA) is one of the non-protein amino acids, and it attracts attentions to building block. At the same time, BABA potentially possesses various bioactivities. Downy mildew of lettuce (Bremia lactucae) is a serious disease, but BABA is considered with one of the disease resistance inducers (Cohen et al., 2011). Despite the agrichemical or pharmaceutical desires, crystal structures of BABA derivatives have not been cleared except for the structures of some metallo-organic compounds (Bryan et al., 1961; Gross & Vahrenkamo, 2005; Böhm & Seebach, 2000) because of its difficulty in crystallization.
Fortunately, the title compound, 3-benzyloxycarbonylaminobutanoic acid (Cbz-BABA), (I), was crystallized, and we herein report on the crystal structure. The molecular structure of (I) is shown in Fig. 1. The bond lengths (Allen et al., 1987) and angles are within normal ranges except for the O-H bond length at the carboxy dimer. The part of BABA is essentially similar with that reported by Gross & Vahrenkamo (2005). The butyric acid group owns a stretched trans-conformation (O1-C1-C2-C3-C4). At the β-position the benzyloxycarboxyamino group is attached perpendicular to the butyric acid group. The phenyl group is twisted against the least-squares plane of the oxycarboxyamino group (N1/C5/O3/O4/C6/C7) with the dihedral angle of 56.6 (2)°.
In the crystal structure, an enantiomer makes a planar structure with the intermolecular hydrogen bond (N1—HN1···O3) along the b axis. The planar structure is stacked to the enantiopure layer along the c axis. The carboxy dimer is made from the enantiomeric isomers with the intermolecular hydrogen bond (O1—H1···O2). The H atom is shared by carboxy dimer then the bond distance O1—H1 is longer than that of general carboxy group. The hydrophobic and hydrophilic layers are well separated along the a axis. The structure shows a herring bone stacking mode (Fig. 2).