Redetermined crystal structure of N-(β-carb-oxy-eth-yl)-α-isoleucine.

Redetermination of the crystal structure of N-(β-carb-oxy-eth-yl)-α-isoleucine, C9H18N2O3, reported earlier by Nehls et al. [Acta Cryst. (2013), E69, o172-o173], was undertaken in which the ionization state assigned to the mol-ecule as unionized has been modified as zwitterionic in the present work. Single-crystal X-ray intensity data obtained from freshly grown crystals and freely refining the amino H atoms provide enhanced refinement and structural parameters, particularly the hydrogen-bonding scheme. N-H⋯O hydrogen bonds dominate the inter-molecular inter-actions along with a C-H⋯O hydrogen bond. The inter-molecular inter-action pattern is a three-dimensional network. The structure was refined as a two-component perfect inversion twin.

Related literature

For earlier work on the crystal structure of N-(β-carb­oxy­eth­yl)-α-isoleucine, see: Nehls et al. (2013 ▸). For the crystal structure of l-isoleucine and its indolylacetyl derivative, respectively, see Görbitz & Dalhus (1996 ▸); Kojić-Prodić et al. (1991 ▸). For the importance of freely refining the positions of amino-group H atoms, see: Görbitz (2014 ▸). For absolute configuration and structure parameters, see Flack (1983 ▸); Flack & Bernardinelli (2000 ▸); Hooft et al. (2008 ▸); Spek (2009 ▸); Parsons et al. (2013 ▸). For chiral and achiral crystal structures, see Flack (2003 ▸).

Experimental

Crystal data

C9H18N2O3

M = 202.25

Orthorhombic,

a = 5.2996 (5) Å

b = 9.0053 (7) Å

c = 23.211 (2) Å

V = 1107.75 (17) Å3

Z = 4

Mo Kα radiation

μ = 0.09 mm−1

T = 293 K

0.26 × 0.18 × 0.10 mm

Data collection

Bruker APEXII CCD diffractometer

Absorption correction: multi-scan (SADABS; Bruker, 2009 ▸) T min = 0.97, T max = 0.99

22904 measured reflections

3127 independent reflections

2538 reflections with I > 2σ(I)

R int = 0.036

Refinement

R[F 2 > 2σ(F 2)] = 0.042

wR(F 2) = 0.102

S = 1.08

3127 reflections

146 parameters

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.30 e Å−3

Δρmin = −0.19 e Å−3

Absolute structure: refined as a perfect inversion twin.

Absolute structure parameter: fixed at 0.5 and not refined

Data collection: APEX2 (Bruker, 2009 ▸); cell refinement: SAINT (Bruker, 2009 ▸); data reduction: SAINT; program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008 ▸); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015 ▸); molecular graphics: PLATON (Spek, 2009 ▸); software used to prepare material for publication: SHELXL2014.

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S2056989015014498/bg2563sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015014498/bg2563Isup2.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S2056989015014498/bg2563Isup3.cml

Click here for additional data file.

. DOI: 10.1107/S2056989015014498/bg2563fig1.tif

Thermal ellipsoid plot of the title compound, showing the atom numbering scheme.

Click here for additional data file.

N . DOI: 10.1107/S2056989015014498/bg2563fig2.tif

The characteristic head-to-tail N—H⋯O hydrogen bonds involving the carboxyl­ate and the amino groups. Non pariticipating N-carb­oxy­ethl group atoms have been omitted for clarity.

Click here for additional data file.

a . DOI: 10.1107/S2056989015014498/bg2563fig3.tif

Carbamoyl group N2 and O3 forming N—H⋯O hydrogen-bonds within themselves leading to C32(8) chains linking screw related mol­ecules along the a axis.

CCDC reference: 1416394

Additional supporting information: crystallographic information; 3D view; checkCIF report

C9H18N2O3	F(000) = 440
Mr = 202.25	Dx = 1.213 Mg m−3Dm = 1.21 Mg m−3Dm measured by floatation method
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
a = 5.2996 (5) Å	µ = 0.09 mm−1
b = 9.0053 (7) Å	T = 293 K
c = 23.211 (2) Å	Needle, colourless
V = 1107.75 (17) Å3	0.26 × 0.18 × 0.10 mm
Z = 4

Bruker APEXII CCD diffractometer	2538 reflections with I > 2σ(I)
ω and φ scans	Rint = 0.036
Absorption correction: multi-scan (SADABS; Bruker, 2009)	θmax = 29.9°, θmin = 2.4°
Tmin = 0.97, Tmax = 0.99	h = −7→7
22904 measured reflections	k = −12→11
3127 independent reflections	l = −31→32

Refinement on F2	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.042	w = 1/[σ2(Fo2) + (0.0479P)2 + 0.1014P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.102	(Δ/σ)max < 0.001
S = 1.08	Δρmax = 0.30 e Å−3
3127 reflections	Δρmin = −0.19 e Å−3
146 parameters	Absolute structure: Refined as a perfect inversion twin.
0 restraints	Absolute structure parameter: 0.5

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. Refined as a 2-component perfect inversion twin.

	x	y	z	Uiso*/Ueq
O1	0.2868 (2)	0.54162 (13)	0.74549 (7)	0.0379 (4)
O2	0.2473 (3)	0.77532 (13)	0.71778 (7)	0.0383 (4)
O3	0.6665 (3)	0.6614 (2)	0.94137 (7)	0.0550 (5)
N1	0.7861 (3)	0.57896 (16)	0.76272 (6)	0.0213 (3)
N2	1.0857 (4)	0.6555 (3)	0.95384 (9)	0.0475 (5)
C5	0.7705 (8)	0.7167 (5)	0.55526 (12)	0.0942 (12)
H5A	0.9472	0.7357	0.5606	0.141*
H5B	0.7017	0.7884	0.5290	0.141*
H5C	0.7479	0.6188	0.5398	0.141*
C4	0.6370 (5)	0.7281 (3)	0.61215 (10)	0.0506 (6)
H4A	0.4584	0.7101	0.6062	0.061*
H4B	0.6555	0.8285	0.6267	0.061*
C3	0.7352 (4)	0.6194 (2)	0.65736 (8)	0.0329 (4)
H3	0.9199	0.6235	0.6558	0.040*
C6	0.6603 (6)	0.4612 (3)	0.64363 (10)	0.0571 (7)
H6A	0.7232	0.3961	0.6731	0.086*
H6B	0.7304	0.4330	0.6071	0.086*
H6C	0.4797	0.4540	0.6420	0.086*
C2	0.6583 (3)	0.66957 (19)	0.71782 (7)	0.0224 (4)
H2	0.7123	0.7729	0.7227	0.027*
C1	0.3732 (3)	0.66295 (19)	0.72788 (8)	0.0244 (4)
C7	0.7684 (4)	0.6481 (2)	0.82050 (8)	0.0297 (4)
H7A	0.5926	0.6536	0.8319	0.036*
H7B	0.8340	0.7485	0.8187	0.036*
C8	0.9134 (4)	0.5614 (2)	0.86493 (8)	0.0354 (5)
H8A	1.0912	0.5611	0.8551	0.042*
H8B	0.8547	0.4594	0.8655	0.042*
C9	0.8776 (4)	0.6301 (2)	0.92372 (8)	0.0348 (4)
H1N1	0.723 (4)	0.488 (2)	0.7648 (9)	0.029 (5)*
H2N1	0.947 (4)	0.568 (2)	0.7544 (9)	0.027 (5)*
H2N2	1.228 (6)	0.631 (3)	0.9411 (11)	0.051 (7)*
H1N2	1.082 (6)	0.697 (3)	0.9890 (13)	0.064 (9)*

	U11	U22	U33	U12	U13	U23
O1	0.0150 (6)	0.0337 (7)	0.0651 (10)	−0.0005 (5)	0.0039 (6)	0.0146 (6)
O2	0.0213 (7)	0.0261 (6)	0.0675 (10)	0.0044 (6)	−0.0089 (7)	−0.0012 (6)
O3	0.0324 (8)	0.0925 (14)	0.0400 (9)	0.0071 (9)	0.0034 (7)	−0.0200 (8)
N1	0.0129 (6)	0.0224 (7)	0.0287 (8)	−0.0001 (5)	0.0007 (5)	−0.0012 (6)
N2	0.0339 (11)	0.0737 (15)	0.0348 (10)	−0.0011 (10)	−0.0030 (8)	−0.0149 (10)
C5	0.101 (3)	0.142 (3)	0.0405 (15)	−0.019 (3)	0.0009 (16)	0.0249 (17)
C4	0.0549 (15)	0.0597 (14)	0.0371 (11)	−0.0110 (12)	−0.0076 (11)	0.0114 (11)
C3	0.0225 (9)	0.0464 (11)	0.0299 (9)	−0.0034 (9)	0.0010 (8)	−0.0003 (8)
C6	0.080 (2)	0.0488 (14)	0.0423 (13)	0.0016 (14)	0.0050 (13)	−0.0135 (11)
C2	0.0141 (7)	0.0235 (8)	0.0296 (8)	−0.0012 (6)	−0.0007 (6)	0.0019 (7)
C1	0.0142 (7)	0.0270 (8)	0.0319 (9)	−0.0006 (7)	−0.0014 (7)	−0.0027 (7)
C7	0.0266 (9)	0.0320 (9)	0.0305 (9)	0.0073 (8)	−0.0013 (7)	−0.0079 (7)
C8	0.0320 (11)	0.0428 (11)	0.0313 (10)	0.0088 (9)	−0.0057 (8)	−0.0070 (9)
C9	0.0319 (10)	0.0430 (11)	0.0295 (9)	0.0018 (9)	−0.0019 (9)	−0.0027 (8)

O1—C1	1.253 (2)	C4—H4B	0.9700
O2—C1	1.234 (2)	C3—C6	1.513 (3)
O3—C9	1.224 (3)	C3—C2	1.530 (2)
N1—C7	1.481 (2)	C3—H3	0.9800
N1—C2	1.487 (2)	C6—H6A	0.9600
N1—H1N1	0.89 (2)	C6—H6B	0.9600
N1—H2N1	0.88 (2)	C6—H6C	0.9600
N2—C9	1.326 (3)	C2—C1	1.530 (2)
N2—H2N2	0.84 (3)	C2—H2	0.9800
N2—H1N2	0.90 (3)	C7—C8	1.504 (3)
C5—C4	1.502 (4)	C7—H7A	0.9700
C5—H5A	0.9600	C7—H7B	0.9700
C5—H5B	0.9600	C8—C9	1.510 (3)
C5—H5C	0.9600	C8—H8A	0.9700
C4—C3	1.527 (3)	C8—H8B	0.9700
C4—H4A	0.9700
C7—N1—C2	112.03 (13)	H6A—C6—H6B	109.5
C7—N1—H1N1	108.3 (13)	C3—C6—H6C	109.5
C2—N1—H1N1	111.9 (14)	H6A—C6—H6C	109.5
C7—N1—H2N1	107.9 (14)	H6B—C6—H6C	109.5
C2—N1—H2N1	110.4 (14)	N1—C2—C3	111.07 (14)
H1N1—N1—H2N1	106.1 (19)	N1—C2—C1	108.74 (14)
C9—N2—H2N2	121.0 (18)	C3—C2—C1	113.06 (15)
C9—N2—H1N2	122 (2)	N1—C2—H2	107.9
H2N2—N2—H1N2	117 (3)	C3—C2—H2	107.9
C4—C5—H5A	109.5	C1—C2—H2	107.9
C4—C5—H5B	109.5	O2—C1—O1	125.42 (16)
H5A—C5—H5B	109.5	O2—C1—C2	118.20 (15)
C4—C5—H5C	109.5	O1—C1—C2	116.38 (15)
H5A—C5—H5C	109.5	N1—C7—C8	111.73 (14)
H5B—C5—H5C	109.5	N1—C7—H7A	109.3
C5—C4—C3	113.6 (2)	C8—C7—H7A	109.3
C5—C4—H4A	108.9	N1—C7—H7B	109.3
C3—C4—H4A	108.9	C8—C7—H7B	109.3
C5—C4—H4B	108.9	H7A—C7—H7B	107.9
C3—C4—H4B	108.9	C7—C8—C9	110.04 (16)
H4A—C4—H4B	107.7	C7—C8—H8A	109.7
C6—C3—C4	111.70 (19)	C9—C8—H8A	109.7
C6—C3—C2	113.68 (17)	C7—C8—H8B	109.7
C4—C3—C2	110.48 (17)	C9—C8—H8B	109.7
C6—C3—H3	106.9	H8A—C8—H8B	108.2
C4—C3—H3	106.9	O3—C9—N2	122.98 (19)
C2—C3—H3	106.9	O3—C9—C8	120.75 (18)
C3—C6—H6A	109.5	N2—C9—C8	116.27 (19)
C3—C6—H6B	109.5
C5—C4—C3—C6	−71.2 (3)	N1—C2—C1—O2	144.24 (16)
C5—C4—C3—C2	161.2 (2)	C3—C2—C1—O2	−91.9 (2)
C7—N1—C2—C3	165.30 (14)	N1—C2—C1—O1	−36.3 (2)
C7—N1—C2—C1	−69.67 (18)	C3—C2—C1—O1	87.5 (2)
C6—C3—C2—N1	62.6 (2)	C2—N1—C7—C8	−176.01 (15)
C4—C3—C2—N1	−170.95 (17)	N1—C7—C8—C9	−176.58 (17)
C6—C3—C2—C1	−60.0 (2)	C7—C8—C9—O3	48.8 (3)
C4—C3—C2—C1	66.5 (2)	C7—C8—C9—N2	−130.4 (2)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N1···O2i	0.89 (2)	1.96 (2)	2.7772 (19)	152 (2)
N1—H2N1···O1ii	0.88 (2)	1.83 (2)	2.7047 (19)	174 (2)
N2—H1N2···O3iii	0.90 (3)	2.11 (3)	2.970 (3)	161 (3)
N2—H2N2···O3ii	0.84 (3)	2.34 (3)	3.092 (3)	149 (2)
C2—H2···O1iv	0.98	2.53	3.469 (2)	160

Table 1

Hydrogen-bond geometry (, )

DHA	DH	HA	D A	DHA
N1H1N1O2i	0.89(2)	1.96(2)	2.7772(19)	152(2)
N1H2N1O1ii	0.88(2)	1.83(2)	2.7047(19)	174(2)
N2H1N2O3iii	0.90(3)	2.11(3)	2.970(3)	161(3)
N2H2N2O3ii	0.84(3)	2.34(3)	3.092(3)	149(2)
C2H2O1iv	0.98	2.53	3.469(2)	160

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .