2-Aza­niumyl-4-(ethyl­carbamo­yl)butano­ate: the zwitterionic form of the amino acid theanine

Kang, S.-K.; Chen, Y.-H.; Qian, S.-S.; Hu, H.

doi:10.1107/S1600536810050701

organic compounds

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Volume 67| Part 1| January 2011| Page o82

https://doi.org/10.1107/S1600536810050701

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2-Azaniumyl-4-(ethylcarbamoyl)butanoate: the zwitterionic form of the amino acid theanine

Shou-Kai Kang,^a Yue-Hu Chen,^a Shao-Song Qian ^a and Hao Hu ^a ^*

^aSchool of Life Science, ShanDong University of Technology, ZiBo 255049, People's Republic of China
^*Correspondence e-mail: huhao@sdut.edu.cn

(Received 2 November 2010; accepted 3 December 2010; online 11 December 2010)

In the title zwitterion, C₇H₁₄N₂O₃, the ethylamino and the 5-oxo groups are positionally disordered with occupancy ratios of 0.50:0.50 and 0.70:0.30, respectively. The terminal ethyl –CH₃ group undergoes considerable thermal motion. In the crystal, molecules are linked via N—H⋯O hydrogen bonds, forming a two-dimensional arrangement propagating in the bc plane.

Related literature

For details of the physiological activity of the amino acid theanine, commonly found in certain teas, see: Li et al. (2006 ).

Experimental

Crystal data

C₇H₁₄N₂O₃
M_r = 174.20
Monoclinic, P 2₁ /c
a = 19.606 (6) Å
b = 4.7904 (15) Å
c = 9.812 (3) Å
β = 90.501 (6)°
V = 921.5 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 273 K
0.15 × 0.12 × 0.06 mm

Data collection

Bruker SMART CCD area-detector diffractometer
5580 measured reflections
2218 independent reflections
1276 reflections with I > 2σ(I)
R_int = 0.039

Refinement

R[F² > 2σ(F²)] = 0.051
wR(F²) = 0.147
S = 1.01
2218 reflections
148 parameters
26 restraints
H-atom parameters constrained
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.20 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O2ⁱ	0.89	1.89	2.776 (2)	174
N1—H1B⋯O1ⁱⁱ	0.89	1.96	2.8332 (19)	165
N1—H1C⋯O1ⁱⁱⁱ	0.89	1.97	2.850 (2)	171
N2—H2⋯O3^iv	0.86	2.16	2.93 (2)	149
N2′—H2′⋯O3′^iv	0.86	2.01	2.85 (3)	166
Symmetry codes: (i) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iii) $[x, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]$ ; (iv) x, y-1, z.

Data collection: SMART (Bruker, 2007 ); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009 ); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810050701/su2225sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810050701/su2225Isup2.hkl

checkCIF report

Comment top

In recent years, increasing attention has been drawn towards the physiological and pharmacological applications of theanine, which besides its favorable taste has been reported to be biologically active promoting relaxation, inhibiting negative effects of caffeine and enhancing anti-tumor activity. Moreover, it has been found to have physiological activities including Neuroprotection and anti-obesity (Li et al., 2006).

The title molecule was found to crystallize in the Zwitter ion form (Fig. 1). The ethylamino group (atoms N2,C6,C7/N2',C6',C7': occupancies 0.5/0.5) and the 5-oxo (O2/O2': occupancies 0.7/0.3) atom are positionally disordered. The terminal ethyl CH₃ group (C7 and C7') undergoes considerable thermal motion.

In the crystal the molecules are linked via N-H···O hydrogen bonds to form a two-dimensional arrangement propagating in the bc-plane (Table 1, Fig. 2).

Related literature top

For details of the physiological activity of the amino acid theanine, commonly found in certain teas, see: Li et al. (2006).

Experimental top

The title compound was synthesized according to a Chinese Patent (Li, et al., 2006). 20 g of L-pyrrolidone carboxylic acid were reacted with 20 g of anhydrous ethylamine in helium gas under a pressure of 7 MPa for 4hr. 23.3 g of the theanine were obtained. The single crystals, of the title compound, suitable for X-ray diffraction analysis, were obtained by the hanging-drop method with water as solvent.

Structure description top

In the crystal the molecules are linked via N-H···O hydrogen bonds to form a two-dimensional arrangement propagating in the bc-plane (Table 1, Fig. 2).

For details of the physiological activity of the amino acid theanine, commonly found in certain teas, see: Li et al. (2006).

Computing details top

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. The ethylamino group (atoms N2,C6,C7/N2',C6',C7': occupancies 0.5/0.5) and the 5-oxo (O2/O2': occupancies 0.7/0.3) atom are positionally disordered.
	Fig. 2. A view along the b-axis of the crystal packing of the title compound. The N-H···O hydrogen bonds are shown as dashed lines - see Table 1 for details (H-atoms not involved in hydrogen bonding have been omitted for clarity).

2-Azaniumyl-4-(ethylcarbamoyl)butanoate top

Crystal data top

C₇H₁₄N₂O₃	F(000) = 376
M_r = 174.20	D_x = 1.256 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 838 reflections
a = 19.606 (6) Å	θ = 4.2–23.0°
b = 4.7904 (15) Å	µ = 0.10 mm⁻¹
c = 9.812 (3) Å	T = 273 K
β = 90.501 (6)°	Prism, colourless
V = 921.5 (5) Å³	0.15 × 0.12 × 0.06 mm
Z = 4

Data collection top

Bruker SMART CCD area-detector diffractometer	1276 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.039
Graphite monochromator	θ_max = 28.3°, θ_min = 2.1°
phi and ω scans	h = −21→25
5580 measured reflections	k = −6→6
2218 independent reflections	l = −13→9

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.147	H-atom parameters constrained
S = 1.01	w = 1/[σ²(F_o²) + (0.0696P)²] where P = (F_o² + 2F_c²)/3
2218 reflections	(Δ/σ)_max < 0.001
148 parameters	Δρ_max = 0.23 e Å⁻³
26 restraints	Δρ_min = −0.20 e Å⁻³

Crystal data top

C₇H₁₄N₂O₃	V = 921.5 (5) Å³
M_r = 174.20	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 19.606 (6) Å	µ = 0.10 mm⁻¹
b = 4.7904 (15) Å	T = 273 K
c = 9.812 (3) Å	0.15 × 0.12 × 0.06 mm
β = 90.501 (6)°

Data collection top

Bruker SMART CCD area-detector diffractometer	1276 reflections with I > 2σ(I)
5580 measured reflections	R_int = 0.039
2218 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.051	26 restraints
wR(F²) = 0.147	H-atom parameters constrained
S = 1.01	Δρ_max = 0.23 e Å⁻³
2218 reflections	Δρ_min = −0.20 e Å⁻³
148 parameters

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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

	x	y	z	U_iso*/U_eq	Occ. (<1)
O1	0.10121 (7)	0.5612 (3)	0.46220 (12)	0.0493 (4)
O2	0.05541 (6)	0.8285 (3)	0.30018 (12)	0.0396 (4)
O3	0.3108 (4)	0.734 (2)	0.0555 (10)	0.099 (3)	0.70
O3'	0.2918 (9)	0.741 (4)	0.013 (2)	0.062 (3)	0.30
N1	0.07561 (7)	0.4367 (3)	0.10890 (14)	0.0357 (4)
H1A	0.0325	0.4110	0.1338	0.054*
H1B	0.0881	0.2996	0.0532	0.054*
H1C	0.0793	0.5997	0.0660	0.054*
C1	0.08906 (9)	0.6232 (3)	0.34041 (17)	0.0319 (4)
C2	0.12060 (9)	0.4366 (3)	0.23210 (16)	0.0313 (4)
H2A	0.1243	0.2458	0.2675	0.038*
C3	0.19192 (9)	0.5443 (4)	0.19622 (19)	0.0405 (5)
H3A	0.1879	0.7328	0.1609	0.049*
H3B	0.2194	0.5525	0.2788	0.049*
C4	0.22817 (11)	0.3658 (5)	0.0926 (3)	0.0708 (8)
H4A	0.2382	0.1859	0.1334	0.085*
H4B	0.1976	0.3338	0.0159	0.085*
C5	0.29288 (12)	0.4882 (5)	0.0407 (3)	0.0633 (7)
N2	0.3323 (10)	0.312 (4)	−0.0317 (13)	0.066 (4)	0.50
H2	0.3217	0.1382	−0.0386	0.079*	0.50
C6	0.3928 (6)	0.420 (2)	−0.0976 (13)	0.099 (4)	0.50
H6A	0.4174	0.5415	−0.0355	0.119*	0.50
H6B	0.3798	0.5269	−0.1775	0.119*	0.50
C7	0.4368 (6)	0.183 (3)	−0.1378 (15)	0.137 (5)	0.50
H7A	0.4453	0.0661	−0.0602	0.205*	0.50
H7B	0.4793	0.2540	−0.1713	0.205*	0.50
H7C	0.4145	0.0771	−0.2081	0.205*	0.50
N2'	0.3403 (10)	0.302 (4)	0.0159 (13)	0.069 (4)	0.50
H2'	0.3293	0.1295	0.0275	0.083*	0.50
C6'	0.4104 (5)	0.357 (2)	−0.0298 (10)	0.087 (3)	0.50
H6'1	0.4414	0.2225	0.0113	0.105*	0.50
H6'2	0.4243	0.5420	−0.0011	0.105*	0.50
C7'	0.4137 (8)	0.336 (4)	−0.1820 (13)	0.159 (5)	0.50
H7'1	0.3892	0.1728	−0.2119	0.238*	0.50
H7'2	0.4604	0.3213	−0.2094	0.238*	0.50
H7'3	0.3935	0.4989	−0.2223	0.238*	0.50

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0812 (11)	0.0390 (8)	0.0277 (7)	0.0014 (7)	−0.0001 (6)	0.0010 (6)
O2	0.0481 (8)	0.0319 (7)	0.0389 (7)	0.0056 (6)	0.0051 (6)	0.0004 (6)
O3	0.072 (5)	0.045 (3)	0.181 (8)	−0.013 (3)	0.046 (4)	−0.019 (4)
O3'	0.050 (7)	0.032 (4)	0.104 (7)	−0.001 (5)	0.025 (5)	0.009 (5)
N1	0.0426 (9)	0.0328 (8)	0.0317 (8)	−0.0019 (7)	0.0044 (7)	−0.0035 (6)
C1	0.0394 (10)	0.0263 (9)	0.0301 (9)	−0.0065 (8)	0.0040 (7)	−0.0002 (7)
C2	0.0419 (10)	0.0236 (8)	0.0284 (9)	0.0010 (7)	0.0002 (7)	0.0009 (7)
C3	0.0410 (11)	0.0343 (10)	0.0463 (11)	−0.0018 (8)	0.0019 (8)	−0.0039 (8)
C4	0.0524 (14)	0.0498 (14)	0.111 (2)	−0.0112 (11)	0.0364 (14)	−0.0275 (14)
C5	0.0549 (14)	0.0419 (13)	0.0936 (19)	−0.0060 (11)	0.0271 (13)	−0.0113 (13)
N2	0.068 (7)	0.042 (3)	0.089 (8)	−0.003 (4)	0.045 (6)	−0.013 (5)
C6	0.088 (8)	0.078 (6)	0.134 (9)	0.005 (4)	0.079 (7)	0.008 (6)
C7	0.092 (7)	0.120 (8)	0.199 (13)	0.018 (5)	0.084 (9)	0.003 (7)
N2'	0.048 (4)	0.053 (4)	0.107 (10)	−0.012 (3)	0.032 (7)	−0.010 (7)
C6'	0.059 (5)	0.067 (5)	0.137 (9)	−0.006 (4)	0.038 (5)	−0.001 (5)
C7'	0.125 (12)	0.216 (17)	0.136 (9)	−0.046 (11)	0.055 (8)	0.002 (11)

Geometric parameters (Å, º) top

O1—C1	1.252 (2)	C5—N2	1.351 (18)
O2—C1	1.246 (2)	N2—C6	1.45 (2)
O3—C5	1.237 (10)	N2—H2	0.8600
O3'—C5	1.24 (2)	C6—C7	1.479 (12)
N1—C2	1.490 (2)	C6—H6A	0.9700
N1—H1A	0.8900	C6—H6B	0.9700
N1—H1B	0.8900	C7—H7A	0.9600
N1—H1C	0.8900	C7—H7B	0.9600
C1—C2	1.524 (2)	C7—H7C	0.9600
C2—C3	1.534 (2)	N2'—C6'	1.47 (2)
C2—H2A	0.9800	N2'—H2'	0.8600
C3—C4	1.511 (3)	C6'—C7'	1.499 (13)
C3—H3A	0.9700	C6'—H6'1	0.9700
C3—H3B	0.9700	C6'—H6'2	0.9700
C4—C5	1.491 (3)	C7'—H7'1	0.9600
C4—H4A	0.9700	C7'—H7'2	0.9600
C4—H4B	0.9700	C7'—H7'3	0.9600
C5—N2'	1.31 (2)

C2—N1—H1A	109.5	O3'—C5—N2	120.2 (13)
C2—N1—H1B	109.5	O3—C5—C4	125.2 (5)
H1A—N1—H1B	109.5	O3'—C5—C4	116.5 (9)
C2—N1—H1C	109.5	N2'—C5—C4	113.6 (9)
H1A—N1—H1C	109.5	N2—C5—C4	115.2 (9)
H1B—N1—H1C	109.5	C5—N2—C6	119.1 (15)
O2—C1—O1	125.80 (16)	C5—N2—H2	120.5
O2—C1—C2	117.32 (15)	C6—N2—H2	120.5
O1—C1—C2	116.84 (16)	N2—C6—C7	109.2 (11)
N1—C2—C1	108.93 (14)	N2—C6—H6A	109.8
N1—C2—C3	110.36 (14)	C7—C6—H6A	109.8
C1—C2—C3	109.80 (14)	N2—C6—H6B	109.8
N1—C2—H2A	109.2	C7—C6—H6B	109.8
C1—C2—H2A	109.2	H6A—C6—H6B	108.3
C3—C2—H2A	109.2	C5—N2'—C6'	126.7 (16)
C4—C3—C2	113.51 (15)	C5—N2'—H2'	116.6
C4—C3—H3A	108.9	C6'—N2'—H2'	116.6
C2—C3—H3A	108.9	N2'—C6'—C7'	109.9 (10)
C4—C3—H3B	108.9	N2'—C6'—H6'1	109.7
C2—C3—H3B	108.9	C7'—C6'—H6'1	109.7
H3A—C3—H3B	107.7	N2'—C6'—H6'2	109.7
C5—C4—C3	114.44 (18)	C7'—C6'—H6'2	109.7
C5—C4—H4A	108.7	H6'1—C6'—H6'2	108.2
C3—C4—H4A	108.7	C6'—C7'—H7'1	109.5
C5—C4—H4B	108.7	C6'—C7'—H7'2	109.5
C3—C4—H4B	108.7	H7'1—C7'—H7'2	109.5
H4A—C4—H4B	107.6	C6'—C7'—H7'3	109.5
O3—C5—N2'	117.9 (10)	H7'1—C7'—H7'3	109.5
O3'—C5—N2'	129.3 (13)	H7'2—C7'—H7'3	109.5
O3—C5—N2	119.6 (10)

O2—C1—C2—N1	−31.8 (2)	O3—C5—N2—C6	−3.8 (16)
O1—C1—C2—N1	150.42 (15)	O3'—C5—N2—C6	26.3 (18)
O2—C1—C2—C3	89.14 (19)	N2'—C5—N2—C6	−95 (5)
O1—C1—C2—C3	−88.62 (18)	C4—C5—N2—C6	173.9 (10)
N1—C2—C3—C4	−61.8 (2)	C5—N2—C6—C7	164.9 (13)
C1—C2—C3—C4	178.08 (18)	O3—C5—N2'—C6'	−16.3 (16)
C2—C3—C4—C5	171.3 (2)	O3'—C5—N2'—C6'	12 (2)
C3—C4—C5—O3	−14.3 (6)	N2—C5—N2'—C6'	84 (5)
C3—C4—C5—O3'	−43.0 (10)	C4—C5—N2'—C6'	−177.0 (10)
C3—C4—C5—N2'	144.8 (7)	C5—N2'—C6'—C7'	−94.9 (15)
C3—C4—C5—N2	168.1 (7)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O2ⁱ	0.89	1.89	2.776 (2)	174
N1—H1B···O1ⁱⁱ	0.89	1.96	2.8332 (19)	165
N1—H1C···O1ⁱⁱⁱ	0.89	1.97	2.850 (2)	171
N2—H2···O3^iv	0.86	2.16	2.93 (2)	149
N2′—H2′···O3′^iv	0.86	2.01	2.85 (3)	166

Symmetry codes: (i) −x, y−1/2, −z+1/2; (ii) x, −y+1/2, z−1/2; (iii) x, −y+3/2, z−1/2; (iv) x, y−1, z.

Experimental details

Crystal data
Chemical formula	C₇H₁₄N₂O₃
M_r	174.20
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	273
a, b, c (Å)	19.606 (6), 4.7904 (15), 9.812 (3)
β (°)	90.501 (6)
V (Å³)	921.5 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.15 × 0.12 × 0.06

Data collection
Diffractometer	Bruker SMART CCD area-detector
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	5580, 2218, 1276
R_int	0.039
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.051, 0.147, 1.01
No. of reflections	2218
No. of parameters	148
No. of restraints	26
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.23, −0.20

Computer programs: SMART (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O2ⁱ	0.89	1.89	2.776 (2)	174
N1—H1B···O1ⁱⁱ	0.89	1.96	2.8332 (19)	165
N1—H1C···O1ⁱⁱⁱ	0.89	1.97	2.850 (2)	171
N2—H2···O3^iv	0.86	2.16	2.93 (2)	149
N2'—H2'···O3'^iv	0.86	2.01	2.85 (3)	166

Symmetry codes: (i) −x, y−1/2, −z+1/2; (ii) x, −y+1/2, z−1/2; (iii) x, −y+3/2, z−1/2; (iv) x, y−1, z.

Acknowledgements

This project was sponsored by the Doctoral Research Foundation of ShanDong University of Technology, People's Republic of China.

References

Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Li, J., Li, P. & Liu, F. (2006). LWT Food Sci. Technol. 41, 883–889. Web of Science CrossRef Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar

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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

2-Aza­niumyl-4-(ethyl­carbamo­yl)butano­ate: the zwitterionic form of the amino acid theanine

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Experimental

Crystal data

Data collection

Refinement

Supporting information

Acknowledgements

References

organic compounds

2-Azaniumyl-4-(ethylcarbamoyl)butanoate: the zwitterionic form of the amino acid theanine