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X-ray diffraction data up to d = 0.50 Å resolution have been collected at 100 K for a DL-alanyl-methionine single crystal using a CCD area detector. Multipolar crystallographic refinement was carried out and the electron density of the molecule has been analyzed. The deformation electron density around the S atom reveals two lone pairs with an sp3 hybridization and agrees with the results of density functional theory calculations. The topological properties of the covalent bonds and of the hydrogen bonds have been investigated. Two weak polar intramolecular interactions of the type C5 (pentagonal cyclic structure) have unfavorable geometrical parameters for hydrogen bonds and are devoid of critical points. The two electron lone pairs of the carbonyl oxygen appear asymmetric in the experimental deformation density. This could be attributed to the different strength of the hydrogen bond and intramolecular polar interaction involving the carbonyl oxygen. In the ab-initio-derived deformation maps, the asymmetry of the electron doublets is reproduced only very partially.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768101007212/bm0043sup1.cif
Contains datablock BM0043

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768101007212/bm0043Isup2.hkl
Contains datablock I

CCDC reference: 170353

Computing details top

Data collection: COLLECT software (Nonius ,1998); cell refinement: DENZO, SCALEPACK Otwinowski & Minor,(1997); data reduction: SORTAV Blessing; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
[Figure 5]
[Figure 6]
[Figure 7]
[Figure 8]
Δ,L-Alanyl-L,D-methionine top
Crystal data top
C8H16N2O3SF(000) = 472
Mr = 220.29Dx = 1.390 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71070 Å
a = 13.089 (2) ÅCell parameters from 159 reflections
b = 5.329 (1) Åθ = 3.0–19.0°
c = 15.921 (6) ŵ = 0.29 mm1
β = 108.57 (2)°T = 100 K
V = 1052.7 (3) Å3Irregular, colourless
Z = 40.52 × 0.49 × 0.29 mm
Data collection top
Nonius Kappa-CCD
diffractometer
8736 independent reflections
Radiation source: fine-focus sealed tube6979 reflections with > σ(I)
Graphite monochromatorRint = 0.049
oscillation scansθmax = 45.2°, θmin = 3.6°
Absorption correction: empirical (using intensity measurements)
SORTAV Blessing (1997)
h = 2626
Tmin = 0.854, Tmax = 0.871k = 1010
100180 measured reflectionsl = 3131
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)] = 0.030Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.025H atoms treated by a mixture of independent and constrained refinement
S = 1.52 w = 1/[σ2(Fo2) + (0.0605P)2]
where P = (Fo2 + 2Fc2)/3
7619 reflections(Δ/σ)max = 0.001
191 parametersΔρmax = 0.63 e Å3
0 restraintsΔρmin = 0.49 e Å3
Crystal data top
C8H16N2O3SV = 1052.7 (3) Å3
Mr = 220.29Z = 4
Monoclinic, P21/cMo Kα radiation
a = 13.089 (2) ŵ = 0.29 mm1
b = 5.329 (1) ÅT = 100 K
c = 15.921 (6) Å0.52 × 0.49 × 0.29 mm
β = 108.57 (2)°
Data collection top
Nonius Kappa-CCD
diffractometer
8736 independent reflections
Absorption correction: empirical (using intensity measurements)
SORTAV Blessing (1997)
6979 reflections with > σ(I)
Tmin = 0.854, Tmax = 0.871Rint = 0.049
100180 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0300 restraints
wR(F2) = 0.025H atoms treated by a mixture of independent and constrained refinement
S = 1.52Δρmax = 0.63 e Å3
7619 reflectionsΔρmin = 0.49 e Å3
191 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*/Ueq
N10.427362 (10)0.05001 (2)0.613740 (8)0.01083 (8)
H110.41280.23610.59640.016*
H120.41600.04870.55570.016*
H130.50650.02370.65260.016*
C1A0.354002 (10)0.04696 (2)0.660310 (8)0.01073 (9)
H1A0.37490.24440.67650.050*
C1B0.237652 (10)0.02747 (2)0.599510 (8)0.01692 (11)
H1B10.22620.14570.54390.050*
H1B20.22150.16110.57890.050*
H1B30.18400.08480.63340.050*
C10.367822 (10)0.10629 (2)0.744040 (8)0.01047 (9)
O10.390342 (10)0.33249 (2)0.747420 (8)0.01411 (8)
N20.347542 (10)0.02002 (2)0.809530 (8)0.01167 (8)
H20.33530.17810.80300.014*
C2A0.345292 (10)0.09803 (2)0.891330 (8)0.01044 (9)
H2A0.40680.24590.90980.050*
C2B0.235272 (10)0.21813 (2)0.880880 (8)0.01286 (9)
H2B10.21430.34350.82380.050*
H2B20.24240.33350.93910.050*
C2G0.145782 (10)0.02659 (2)0.869940 (8)0.01637 (11)
H2G10.13380.09010.81130.050*
H2G20.16720.09790.92730.050*
S2D0.020882 (10)0.18454 (2)0.861990 (8)0.02164 (5)
C2E0.059588 (10)0.08541 (2)0.866730 (8)0.02542 (15)
H2E10.14210.02420.85650.050*
H2E20.03020.17130.93220.050*
H2E30.05580.21700.81550.050*
C20.375272 (10)0.09560 (2)0.966500 (8)0.01006 (8)
O20.382592 (10)0.01904 (2)1.042860 (8)0.01454 (9)
O220.388922 (10)0.31918 (2)0.947440 (8)0.01328 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.01297 (18)0.01095 (18)0.01017 (17)0.00029 (14)0.00594 (14)0.00051 (13)
C1A0.0135 (2)0.0111 (2)0.00888 (18)0.00085 (16)0.00538 (16)0.00062 (14)
C1B0.0130 (2)0.0251 (3)0.0128 (2)0.0022 (2)0.00434 (18)0.0040 (2)
C10.0130 (2)0.01081 (19)0.00827 (18)0.00053 (16)0.00431 (15)0.00006 (14)
O10.0213 (2)0.01106 (17)0.01112 (16)0.00305 (15)0.00673 (15)0.00079 (12)
N20.0174 (2)0.01053 (18)0.00872 (16)0.00101 (15)0.00649 (15)0.00028 (13)
C2A0.0134 (2)0.01043 (19)0.00846 (18)0.00061 (16)0.00490 (15)0.00019 (14)
C2B0.0144 (2)0.0123 (2)0.0126 (2)0.00086 (17)0.00529 (17)0.00029 (16)
C2G0.0135 (2)0.0150 (2)0.0207 (3)0.00043 (18)0.0055 (2)0.00102 (19)
S2D0.01546 (8)0.01934 (9)0.03244 (11)0.00232 (5)0.01090 (7)0.00346 (6)
C2E0.0180 (3)0.0268 (4)0.0327 (4)0.0038 (3)0.0099 (3)0.0023 (3)
C20.0121 (2)0.00999 (19)0.00883 (17)0.00114 (15)0.00429 (15)0.00003 (14)
O20.0235 (2)0.01206 (17)0.00885 (16)0.00114 (15)0.00631 (15)0.00081 (12)
O220.0195 (2)0.00950 (16)0.01211 (17)0.00044 (14)0.00678 (15)0.00015 (12)
Geometric parameters (Å, º) top
N1—C1A1.4807 (5)C2A—C2B1.5363 (5)
C1A—C11.5260 (5)C2B—C2G1.5211 (5)
C1A—C1B1.5260 (5)C2G—S2D1.8086 (6)
C1—O11.2402 (5)S2D—C2E1.8017 (6)
C1—N21.3381 (5)C2—O21.2567 (5)
N2—C2A1.4556 (5)C2—O221.2580 (5)
C2A—C21.5348 (5)
N1—C1A—C1109.57 (4)N2—C2A—C2B111.7 (4)
N1—C1A—C1B109.53 (4)C2—C2A—C2B111.35 (4)
C1—C1A—C1B109.54 (4)C2G—C2B—C2A113.11 (4)
O1—C1—N2124.12 (4)C2B—C2G—S2D109.93 (4)
O1—C1—C1A121.37 (4)C2E—S2D—C2G98.75 (4)
N2—C1—C1A114.39 (4)O2—C2—O22124.63 (4)
C1—N2—C2A123.02 (4)O2—C2—C2A117.16 (4)
N2—C2A—C2109.39 (4)O22—C2—C2A118.20 (4)

Experimental details

Crystal data
Chemical formulaC8H16N2O3S
Mr220.29
Crystal system, space groupMonoclinic, P21/c
Temperature (K)100
a, b, c (Å)13.089 (2), 5.329 (1), 15.921 (6)
β (°) 108.57 (2)
V3)1052.7 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.29
Crystal size (mm)0.52 × 0.49 × 0.29
Data collection
DiffractometerNonius Kappa-CCD
diffractometer
Absorption correctionEmpirical (using intensity measurements)
SORTAV Blessing (1997)
Tmin, Tmax0.854, 0.871
No. of measured, independent and
observed [ > σ(I)] reflections
100180, 8736, 6979
Rint0.049
(sin θ/λ)max1)0.999
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.025, 1.52
No. of reflections7619
No. of parameters191
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.63, 0.49

Computer programs: COLLECT software (Nonius ,1998), DENZO, SCALEPACK Otwinowski & Minor,(1997), SORTAV Blessing, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997).

Selected bond lengths (Å) top
N1—C1A1.4807 (5)C2A—C2B1.5363 (5)
C1A—C11.5260 (5)C2B—C2G1.5211 (5)
C1A—C1B1.5260 (5)C2G—S2D1.8086 (6)
C1—O11.2402 (5)S2D—C2E1.8017 (6)
C1—N21.3381 (5)C2—O21.2567 (5)
N2—C2A1.4556 (5)C2—O221.2580 (5)
C2A—C21.5348 (5)
 

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