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The title compound, C6H11NO3, a chiral source for ligands utilized in asymmetric catalysis, was synthesized from commercial (S)-(+)-valine. The stereochemistry is unchanged by the reaction and the structure consists of a single enantiomer. The structure displays O—H...O and N—H...O hydrogen bonding that links the mol­ecules into a complex three-dimensional hydrogen-bonded network. The isopropyl group is disordered over two positions, with site-occupancy factors 0.819 (6) and 0.181 (6).

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807041311/gk2094sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536807041311/gk2094Isup2.hkl
Contains datablock I

CCDC reference: 660369

Key indicators

  • Single-crystal X-ray study
  • T = 291 K
  • Mean [sigma](C-C) = 0.004 Å
  • Disorder in main residue
  • R factor = 0.045
  • wR factor = 0.132
  • Data-to-parameter ratio = 11.5

checkCIF/PLATON results

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Alert level C PLAT220_ALERT_2_C Large Non-Solvent C Ueq(max)/Ueq(min) ... 2.74 Ratio PLAT242_ALERT_2_C Check Low Ueq as Compared to Neighbors for C1 PLAT301_ALERT_3_C Main Residue Disorder ......................... 9.00 Perc. PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........ 6
Alert level G REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is correct. If it is not, please give the correct count in the _publ_section_exptl_refinement section of the submitted CIF. From the CIF: _diffrn_reflns_theta_max 28.69 From the CIF: _reflns_number_total 1234 Count of symmetry unique reflns 1239 Completeness (_total/calc) 99.60% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 0 Fraction of Friedel pairs measured 0.000 Are heavy atom types Z>Si present no PLAT791_ALERT_1_G Confirm the Absolute Configuration of C2 = . S PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints ....... 17
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 4 ALERT level C = Check and explain 3 ALERT level G = General alerts; check 1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 2 ALERT type 2 Indicator that the structure model may be wrong or deficient 2 ALERT type 3 Indicator that the structure quality may be low 2 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check
checkCIF publication errors
Alert level A PUBL024_ALERT_1_A The number of authors is greater than 5. Please specify the role of each of the co-authors for your paper.
Author Response: The role of each author is listed below: Grant A. Boyle- supervised student in laboratory and contributed to writing of the paper. Thavendran Govender- Co-supervisor of project. Hendrik G. Kruger- Supervisor of project. Glenn E.M. Maguire- Co-supervisor of project. Tyrone K. Negus- Student involved in synthesis of crystal. Melanie Rademeyer- Collected X-ray diffraction data and contributed to writing of the paper.


1 ALERT level A = Data missing that is essential or data in wrong format 0 ALERT level G = General alerts. Data that may be required is missing

Comment top

The title compound (I) was used as a source of chirality for various pentacycloundecane ligands (Boyle et al., 2004a) and macrocycles (Boyle et al., 2004b) that were synthesized for applications in asymmetric catalysis. Here we report the crystal stucture of the title compound, (I). The compound was derived from commercially available (S)-(+)-valine and exists as a single enantiomer since the stereochemistry of the amino acid is unchanged during the reaction. The geometry and labelling scheme employed for the molecule is illustrated in Fig. 1.

In the molecule the iso-propyl moiety is disordered over two positions, with site occupancy factors of 0.82 and 0.18 for atoms C4A and C4B respectively. Atoms C1, C2, C3 and C5 are co-planar.

The molecules are involved in intermolecular O—H···O and N—H···O hydrogen bonding. The hydrogen bonding geometry is listed in Table 1. The molecular packing and hydrogen bonding interactions are illustrated in Fig. 2. The O2—H2A···O3i ((i) -x + 3/2, -y + 1, z - 1/2) interaction links molecules in a head to tail fashion to form a corrugated, one-dimensional hydrogen bonded chain that extends along the a-direction. Neighbouring chains are connected via the N1—H1O···O1ii ((ii)-x + 2, y - 1/2, -z + 1/2) interaction. It is interesting to note that each chain interacts with four other chains, two above it and two below it, when viewed down the a axis. In the interaction with the chains above, one of the neighbouring chains act as N—H···O hydrogen bond donor to the chain considered, while the second chain above acts as hydrogen bond acceptor to the chain under discussion. The same is true for the interactions to the hydrogen bonded chains below the chain. A three-dimensional hydrogen bonding network results, with the smallest hydrogen bonded ring described by the graph set notation R66(34).

Related literature top

For related literature, see: Boyle et al. (2004a,b, 2007); Muramatsu (1965).

Experimental top

Acetic anhydride (30 mol equivalents) was added dropwise to a stirred solution of (S)-(+)-valine (1 mol equivalent) in formic acid (approximately 30 ml per 1.0 g of amino acid) at 0°C. After addition of the acetic anhydride, the external ice bath was removed and the solution stirred at room temperature during 24 h. The solution was treated with water (60 ml) and stirred for 1 hr. The solvent was removed under reduced pressure to yield a white residue. This residue was recrystallized from water to yield the pure product (Muramatsu, 1965). Yield 72%. Colourless crystals suitable for X-ray diffraction were obtained by evaporation of water at room temperature in a fume hood over a period of 2 days.

Refinement top

Friedel pairs were merged before the final refinement. Hydrogen atoms H1 and H6 were placed as observed in the Fourier map and refined. All other hydrogen atoms were placed in calculated positions, with methyl C—H distances of 0.96 Å and methine C—H distances of 0.98 Å, and were refined using a riding model, with Uiso(H)=1.2Ueq of the parent atom. The iso-propyl group is disordered over two positions, with site occupancy factors of 0.784 (5) and 0.216 (5) for atoms C4A and C4B respectively.

Structure description top

The title compound (I) was used as a source of chirality for various pentacycloundecane ligands (Boyle et al., 2004a) and macrocycles (Boyle et al., 2004b) that were synthesized for applications in asymmetric catalysis. Here we report the crystal stucture of the title compound, (I). The compound was derived from commercially available (S)-(+)-valine and exists as a single enantiomer since the stereochemistry of the amino acid is unchanged during the reaction. The geometry and labelling scheme employed for the molecule is illustrated in Fig. 1.

In the molecule the iso-propyl moiety is disordered over two positions, with site occupancy factors of 0.82 and 0.18 for atoms C4A and C4B respectively. Atoms C1, C2, C3 and C5 are co-planar.

The molecules are involved in intermolecular O—H···O and N—H···O hydrogen bonding. The hydrogen bonding geometry is listed in Table 1. The molecular packing and hydrogen bonding interactions are illustrated in Fig. 2. The O2—H2A···O3i ((i) -x + 3/2, -y + 1, z - 1/2) interaction links molecules in a head to tail fashion to form a corrugated, one-dimensional hydrogen bonded chain that extends along the a-direction. Neighbouring chains are connected via the N1—H1O···O1ii ((ii)-x + 2, y - 1/2, -z + 1/2) interaction. It is interesting to note that each chain interacts with four other chains, two above it and two below it, when viewed down the a axis. In the interaction with the chains above, one of the neighbouring chains act as N—H···O hydrogen bond donor to the chain considered, while the second chain above acts as hydrogen bond acceptor to the chain under discussion. The same is true for the interactions to the hydrogen bonded chains below the chain. A three-dimensional hydrogen bonding network results, with the smallest hydrogen bonded ring described by the graph set notation R66(34).

For related literature, see: Boyle et al. (2004a,b, 2007); Muramatsu (1965).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Mercury (Bruno et al., 2002); software used to prepare material for publication: PLATON (Spek, 2003) and WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound showing atomic numbering scheme and displacement ellipsoids drawn at the 50% probability level.
[Figure 2] Fig. 2. The molecular packing, viewed down the a axis, showing intermolecular hydrogen bonding (dashed lines).
(S)-(+)-2-Formylamino-3-methylbutanoic acid top
Crystal data top
C6H11NO3F(000) = 312
Mr = 145.16Dx = 1.174 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 2582 reflections
a = 7.0760 (6) Åθ = 4.0–32.0°
b = 9.5221 (8) ŵ = 0.09 mm1
c = 12.1934 (12) ÅT = 291 K
V = 821.57 (13) Å3Plate, colourless
Z = 40.20 × 0.20 × 0.05 mm
Data collection top
Oxford Diffraction Xcalibur2
diffractometer
1234 independent reflections
Radiation source: fine-focus sealed tube780 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.023
ω scansθmax = 28.7°, θmin = 4.0°
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2006)
h = 99
Tmin = 0.962, Tmax = 0.995k = 129
7394 measured reflectionsl = 1616
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.045Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.132H atoms treated by a mixture of independent and constrained refinement
S = 0.98 w = 1/[σ2(Fo2) + (0.1363P)2]
where P = (Fo2 + 2Fc2)/3
1234 reflections(Δ/σ)max < 0.001
107 parametersΔρmax = 0.16 e Å3
17 restraintsΔρmin = 0.19 e Å3
Crystal data top
C6H11NO3V = 821.57 (13) Å3
Mr = 145.16Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 7.0760 (6) ŵ = 0.09 mm1
b = 9.5221 (8) ÅT = 291 K
c = 12.1934 (12) Å0.20 × 0.20 × 0.05 mm
Data collection top
Oxford Diffraction Xcalibur2
diffractometer
1234 independent reflections
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2006)
780 reflections with I > 2σ(I)
Tmin = 0.962, Tmax = 0.995Rint = 0.023
7394 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.04517 restraints
wR(F2) = 0.132H atoms treated by a mixture of independent and constrained refinement
S = 0.98Δρmax = 0.16 e Å3
1234 reflectionsΔρmin = 0.19 e Å3
107 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
O30.8283 (3)0.57349 (19)0.48653 (15)0.0656 (6)
O20.8665 (3)0.42040 (17)0.16325 (16)0.0678 (6)
H2A0.81010.42680.10470.081*
O10.9249 (3)0.64337 (18)0.13073 (16)0.0779 (7)
C60.8854 (4)0.4570 (3)0.45614 (19)0.0528 (6)
C21.0487 (3)0.5464 (2)0.29479 (19)0.0494 (6)
H21.02020.63630.33030.059*
C31.2604 (4)0.5434 (4)0.2727 (3)0.0826 (9)
H3B1.28640.62330.22420.099*0.819 (6)
H3A1.28720.44750.25410.099*0.181 (6)
C51.3680 (6)0.5682 (6)0.3806 (4)0.1294 (16)
H5A1.32250.50440.43550.155*
H5B1.34820.66310.40460.155*
H5C1.50060.55260.36890.155*
C4A1.3294 (6)0.4166 (5)0.2145 (4)0.1077 (18)0.819 (6)
H4A31.46340.42370.20360.129*0.819 (6)
H4A11.26760.40920.14460.129*0.819 (6)
H4A21.30180.33460.25750.129*0.819 (6)
C4B1.334 (3)0.6303 (19)0.1810 (11)0.087 (6)0.181 (6)
H4B11.46830.61820.17550.104*0.181 (6)
H4B21.30580.72730.19470.104*0.181 (6)
H4B31.27540.60150.11370.104*0.181 (6)
H60.855 (6)0.366 (4)0.492 (3)0.104*
H11.013 (6)0.354 (4)0.357 (3)0.104*
N10.9895 (3)0.4357 (2)0.36939 (16)0.0505 (5)
C10.9393 (3)0.5421 (2)0.18868 (18)0.0473 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O30.0753 (12)0.0554 (10)0.0662 (11)0.0019 (9)0.0235 (10)0.0055 (8)
O20.0863 (13)0.0493 (10)0.0677 (11)0.0118 (10)0.0304 (10)0.0097 (8)
O10.1141 (17)0.0465 (10)0.0730 (12)0.0149 (11)0.0281 (13)0.0134 (10)
C60.0603 (14)0.0536 (15)0.0443 (11)0.0022 (13)0.0000 (11)0.0018 (11)
C20.0581 (14)0.0455 (12)0.0445 (11)0.0007 (11)0.0020 (11)0.0003 (11)
C30.0542 (16)0.116 (3)0.0779 (18)0.011 (2)0.0072 (15)0.015 (2)
C50.090 (3)0.171 (4)0.128 (3)0.027 (3)0.050 (3)0.015 (3)
C4A0.061 (2)0.157 (4)0.106 (3)0.024 (3)0.019 (2)0.001 (3)
C4B0.078 (11)0.098 (13)0.083 (12)0.037 (10)0.017 (10)0.003 (11)
N10.0673 (12)0.0412 (10)0.0431 (9)0.0048 (10)0.0042 (10)0.0006 (9)
C10.0544 (13)0.0406 (11)0.0468 (12)0.0028 (10)0.0004 (11)0.0017 (11)
Geometric parameters (Å, º) top
O3—C61.238 (3)C3—H3B0.98
O2—C11.305 (3)C3—H3A0.96
O2—H2A0.8200C5—H5A0.96
O1—C11.200 (3)C5—H5B0.96
C6—N11.305 (3)C5—H5C0.96
C6—H60.99 (4)C4A—H4A30.96
C2—N11.454 (3)C4A—H4A10.96
C2—C11.508 (3)C4A—H4A20.96
C2—C31.522 (4)C4B—H4B10.96
C2—H20.98C4B—H4B20.96
C3—C4A1.484 (4)C4B—H4B30.96
C3—C4B1.484 (5)N1—H10.81 (4)
C3—C51.539 (5)
C1—O2—H2A109.5H5A—C5—H5B109.5
O3—C6—N1124.5 (2)C3—C5—H5C109.5
O3—C6—H6126 (2)H5A—C5—H5C109.5
N1—C6—H6110 (2)H5B—C5—H5C109.5
N1—C2—C1111.65 (18)C3—C4A—H4A3109.5
N1—C2—C3112.4 (2)C3—C4A—H4A1109.5
C1—C2—C3110.6 (2)H4A3—C4A—H4A1109.5
N1—C2—H2107.3C3—C4A—H4A2109.5
C1—C2—H2107.3H4A3—C4A—H4A2109.5
C3—C2—H2107.3H4A1—C4A—H4A2109.5
C4A—C3—C2115.1 (3)C3—C4B—H4B1109.5
C4B—C3—C2117.9 (9)C3—C4B—H4B2109.5
C4A—C3—C5111.8 (4)H4B1—C4B—H4B2109.5
C4B—C3—C5112.6 (8)C3—C4B—H4B3109.5
C2—C3—C5109.4 (3)H4B1—C4B—H4B3109.5
C4A—C3—H3B106.4H4B2—C4B—H4B3109.5
C2—C3—H3B106.1C6—N1—C2123.9 (2)
C5—C3—H3B107.7C6—N1—H1115 (3)
C4B—C3—H3A106.5C2—N1—H1121 (3)
C2—C3—H3A104.7O1—C1—O2122.7 (2)
C5—C3—H3A104.5O1—C1—C2121.8 (2)
C3—C5—H5A109.5O2—C1—C2115.51 (18)
C3—C5—H5B109.5
N1—C2—C3—C4A64.7 (4)C1—C2—N1—C6105.3 (3)
C1—C2—C3—C4A60.8 (4)C3—C2—N1—C6129.6 (3)
N1—C2—C3—C4B167.5 (9)N1—C2—C1—O1157.9 (2)
C1—C2—C3—C4B41.9 (9)C3—C2—C1—O176.1 (3)
N1—C2—C3—C562.1 (3)N1—C2—C1—O223.8 (3)
C1—C2—C3—C5172.3 (3)C3—C2—C1—O2102.2 (3)
O3—C6—N1—C21.6 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2A···O3i0.821.742.559 (2)173
N1—H1···O1ii0.81 (4)2.06 (4)2.849 (3)165 (4)
Symmetry codes: (i) x+3/2, y+1, z1/2; (ii) x+2, y1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC6H11NO3
Mr145.16
Crystal system, space groupOrthorhombic, P212121
Temperature (K)291
a, b, c (Å)7.0760 (6), 9.5221 (8), 12.1934 (12)
V3)821.57 (13)
Z4
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.20 × 0.20 × 0.05
Data collection
DiffractometerOxford Diffraction Xcalibur2
Absorption correctionMulti-scan
(CrysAlis RED; Oxford Diffraction, 2006)
Tmin, Tmax0.962, 0.995
No. of measured, independent and
observed [I > 2σ(I)] reflections
7394, 1234, 780
Rint0.023
(sin θ/λ)max1)0.675
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.045, 0.132, 0.98
No. of reflections1234
No. of parameters107
No. of restraints17
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.16, 0.19

Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), Mercury (Bruno et al., 2002), PLATON (Spek, 2003) and WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2A···O3i0.821.742.559 (2)173.4
N1—H1···O1ii0.81 (4)2.06 (4)2.849 (3)165 (4)
Symmetry codes: (i) x+3/2, y+1, z1/2; (ii) x+2, y1/2, z+1/2.
 

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