L-Alanyl-L-threonine

The crystal structure of the title compound, C₇H₁₄N₂O₄, contains an intramolecular hydrogen bond between the side-chain hydroxyl group and the main-chain carboxyl­ate group. This is the first observation of such an interaction for a C-terminal L-Ser or L-Thr residue.

Key indicators

• Single-crystal X-ray study
• T = 105 K
• Mean [sigma](C-C) = 0.001 Å
• R factor = 0.027
• wR factor = 0.075
• Data-to-parameter ratio = 15.3

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?

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           34.99
           From the CIF: _reflns_number_total               2171
           Count of symmetry unique reflns         2187
           Completeness (_total/calc)             99.27%
           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

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

L-Alanyl-L-threonine

Crystal data

C7H14N2O4	Dx = 1.459 Mg m^−3
Mr = 190.20	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121	Cell parameters from 8870 reflections
a = 6.0399 (1) Å	θ = 2.5–35.0°
b = 9.7642 (2) Å	µ = 0.12 mm^−1
c = 14.6820 (4) Å	T = 105 K
V = 865.87 (3) Å^3	Block, colourless
Z = 4	0.45 × 0.18 × 0.14 mm
F(000) = 408

Data collection

Siemens SMART CCD diffractometer	2171 independent reflections
Radiation source: fine-focus sealed tube	2087 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
Detector resolution: 8.3 pixels mm^-1	θmax = 35.0°, θmin = 2.5°
Sets of exposures each taken over 0.3° ω rotation scans	h = −9→9
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −15→15
Tmin = 0.929, Tmax = 0.986	l = −21→23
11596 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.075	H atoms treated by a mixture of independent and constrained refinement
S = 1.14	w = 1/[σ^2(Fo^2) + (0.0486P)^2 + 0.0543P] where P = (Fo^2 + 2Fc^2)/3
2171 reflections	(Δ/σ)max = 0.003
142 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.19 e Å^−3

Special details

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. Data were collected by measuring five sets of exposures with the detector set at 2θ = 29°, crystal-to-detector distance 5.00 cm. Refinement of F² against ALL reflections.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.31462 (11)	0.49629 (10)	0.54567 (5)	0.02228 (15)
O2	−0.08708 (10)	0.49939 (7)	0.76669 (4)	0.01676 (12)
H5	−0.072 (3)	0.5633 (15)	0.8033 (12)	0.025*
O3	0.52447 (11)	0.66402 (7)	0.84564 (4)	0.01663 (12)
O4	0.15799 (12)	0.69214 (6)	0.86230 (4)	0.01559 (12)
N1	0.69505 (12)	0.35868 (8)	0.49325 (5)	0.01407 (12)
H1	0.712 (3)	0.2794 (15)	0.5309 (10)	0.021*
H2	0.807 (3)	0.3587 (17)	0.4490 (11)	0.021*
H3	0.565 (3)	0.3539 (17)	0.4639 (11)	0.021*
N2	0.48439 (12)	0.54476 (7)	0.68085 (5)	0.01240 (12)
H4	0.607 (3)	0.5429 (14)	0.7105 (10)	0.015*
C1	0.71079 (13)	0.48608 (9)	0.54955 (5)	0.01445 (14)
H11	0.821 (3)	0.4768 (15)	0.5950 (10)	0.017*
C2	0.77358 (17)	0.60742 (10)	0.48943 (6)	0.01910 (16)
H21	0.9193	0.5942	0.4660	0.029*
H22	0.7694	0.6896	0.5246	0.029*
H23	0.6713	0.6144	0.4401	0.029*
C3	0.48312 (13)	0.50811 (9)	0.59271 (5)	0.01406 (13)
C4	0.28098 (13)	0.58214 (8)	0.72729 (5)	0.01114 (12)
H41	0.2001	0.6457	0.6890	0.013*
C5	0.13295 (12)	0.45530 (8)	0.74426 (5)	0.01227 (13)
H51	0.1256	0.4057	0.6903	0.015*
C6	0.22662 (15)	0.36179 (8)	0.81750 (6)	0.01552 (14)
H61	0.1400	0.2796	0.8206	0.023*
H62	0.2221	0.4077	0.8752	0.023*
H63	0.3769	0.3390	0.8029	0.023*
C7	0.32871 (13)	0.65284 (8)	0.81904 (5)	0.01180 (12)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0123 (2)	0.0435 (4)	0.0110 (2)	0.0042 (3)	−0.0026 (2)	−0.0045 (3)
O2	0.0096 (2)	0.0250 (3)	0.0157 (2)	0.0011 (2)	−0.0001 (2)	−0.0037 (2)
O3	0.0162 (3)	0.0216 (3)	0.0120 (2)	−0.0018 (2)	−0.0036 (2)	−0.0011 (2)
O4	0.0182 (3)	0.0162 (2)	0.0123 (2)	0.0015 (2)	0.0036 (2)	−0.0029 (2)
N1	0.0137 (3)	0.0183 (3)	0.0103 (2)	0.0023 (2)	0.0019 (2)	0.0015 (2)
N2	0.0105 (2)	0.0184 (3)	0.0083 (2)	0.0009 (2)	0.0001 (2)	−0.0015 (2)
C1	0.0113 (3)	0.0223 (3)	0.0097 (3)	0.0016 (3)	0.0006 (2)	−0.0015 (2)
C2	0.0194 (4)	0.0208 (3)	0.0172 (3)	−0.0035 (3)	0.0032 (3)	−0.0021 (3)
C3	0.0114 (3)	0.0220 (3)	0.0088 (3)	0.0027 (3)	0.0005 (2)	−0.0007 (2)
C4	0.0108 (3)	0.0145 (3)	0.0081 (3)	0.0013 (2)	0.0003 (2)	−0.0008 (2)
C5	0.0102 (3)	0.0159 (3)	0.0108 (3)	0.0000 (2)	0.0000 (2)	−0.0029 (2)
C6	0.0167 (3)	0.0138 (3)	0.0161 (3)	−0.0001 (3)	−0.0003 (3)	0.0006 (3)
C7	0.0152 (3)	0.0115 (2)	0.0086 (3)	−0.0002 (2)	−0.0001 (2)	0.0001 (2)

Geometric parameters (Å, º)

O1—C3	1.2353 (10)	C1—C3	1.5292 (11)
O2—C5	1.4352 (10)	C1—H11	0.949 (16)
O2—H5	0.828 (16)	C2—H21	0.9540
O3—C7	1.2500 (10)	C2—H22	0.9540
O4—C7	1.2704 (10)	C2—H23	0.9540
N1—C1	1.4966 (11)	C4—C7	1.5409 (10)
N1—H1	0.957 (16)	C4—C5	1.5477 (11)
N1—H2	0.937 (17)	C4—H41	0.9699
N1—H3	0.895 (18)	C5—C6	1.5199 (11)
N2—C3	1.3427 (10)	C5—H51	0.9301
N2—C4	1.4517 (10)	C6—H61	0.9586
N2—H4	0.860 (16)	C6—H62	0.9586
C1—C2	1.5254 (13)	C6—H63	0.9586
C5—O2—H5	105.8 (14)	O1—C3—C1	119.74 (7)
C1—N1—H1	110.3 (9)	N2—C3—C1	115.58 (7)
C1—N1—H2	109.7 (10)	N2—C4—C7	111.40 (6)
H1—N1—H2	108.9 (14)	N2—C4—C5	111.30 (6)
C1—N1—H3	111.4 (11)	C7—C4—C5	109.02 (6)
H1—N1—H3	109.3 (14)	N2—C4—H41	108.3
H2—N1—H3	107.3 (13)	C7—C4—H41	108.3
C3—N2—C4	120.99 (7)	C5—C4—H41	108.3
C3—N2—H4	119.1 (10)	O2—C5—C6	111.25 (7)
C4—N2—H4	119.8 (10)	O2—C5—C4	109.38 (6)
N1—C1—C2	109.99 (7)	C6—C5—C4	112.31 (6)
N1—C1—C3	106.78 (7)	O2—C5—H51	107.9
C2—C1—C3	110.73 (7)	C6—C5—H51	107.9
N1—C1—H11	110.8 (9)	C4—C5—H51	107.9
C2—C1—H11	107.8 (9)	C5—C6—H61	109.5
C3—C1—H11	110.8 (9)	C5—C6—H62	109.5
C1—C2—H21	109.5	H61—C6—H62	109.5
C1—C2—H22	109.5	C5—C6—H63	109.5
H21—C2—H22	109.5	H61—C6—H63	109.5
C1—C2—H23	109.5	H62—C6—H63	109.5
H21—C2—H23	109.5	O3—C7—O4	125.82 (7)
H22—C2—H23	109.5	O3—C7—C4	119.29 (7)
O1—C3—N2	124.64 (8)	O4—C7—C4	114.87 (7)
N1—C1—C3—N2	136.81 (7)	C4—N2—C3—O1	−3.75 (14)
C1—C3—N2—C4	173.74 (7)	N1—C1—C3—O1	−45.57 (11)
C3—N2—C4—C7	−166.22 (7)	C2—C1—C3—O1	74.16 (10)
N2—C4—C7—O3	−3.67 (10)	C2—C1—C3—N2	−103.47 (9)
N2—C4—C5—C6	71.62 (8)	C3—N2—C4—C5	71.88 (9)
N2—C4—C5—O2	−164.34 (6)	C5—C4—C7—O3	119.55 (8)
C4—C5—O2—H5	−44.0 (11)	N2—C4—C7—O4	178.01 (7)
C7—C4—C5—C6	−51.65 (8)	C5—C4—C7—O4	−58.77 (8)
C7—C4—C5—O2	72.38 (8)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O4^i	0.957 (16)	1.950 (16)	2.8160 (10)	149.5 (14)
N1—H2···O3^ii	0.937 (18)	1.842 (17)	2.7597 (9)	166.0 (15)
N1—H3···O4^iii	0.895 (18)	2.061 (17)	2.9137 (10)	158.9 (15)
N2—H4···O2^iv	0.860 (16)	2.067 (16)	2.9127 (9)	167.6 (13)
O2—H5···O4	0.828 (16)	2.065 (18)	2.7756 (10)	143.6 (18)

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