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Despite the extra functional group in the serine side chain, the crystal packing arrangement of the title compound {systematic name: (S)-3-hy­droxy-2-[(S)-pyrrolidine-2-carboxamido]­pro­pan­oic acid monohydrate}, C8H14N2O4·H2O, is essentially the same as observed for a series of L-Pro-L-Nop peptide hydrates, where Nop is a strictly nonpolar residue. This is rendered possible by a monoclinic P21 packing arrangement with Z′ = 2 that deviates from ortho­rhom­bic P212121 symmetry only for the seryl hy­droxy groups, which form infinite O—H...O—H hydrogen-bonded chains along the 5.3 Å a axis. At the same time, cocrystallized water mol­ecules form parallel water wires.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270113010299/fa3314sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270113010299/fa3314Isup2.hkl
Contains datablock I

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S0108270113010299/fa3314sup3.pdf
Supplementary material

cml

Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270113010299/fa3314Isup4.cml
Supplementary material

CCDC reference: 950380

Comment top

Dipeptides are known to form nanoporous structures belonging to three different classes (Görbitz, 2007). A large number of compounds belong to the Val–Ala class, with hydrophobic pores, while seven structures belong to the Phe–Phe class, with hydrophilic pores (all amino acids discussed here are of the L-configuration, stereochemical indicators are thus not included). The third class has but a single member, Leu–Ser (Görbitz et al., 2005; Cambridge Structural Database refcode JAZBOC; Allen 2002). In a search for additional Leu–Ser class structures with hydrophobic pores, Pro–Ser.H2O, (I), was synthesized and investigated by single-crystal X-ray diffraction methods.

The asymmetric unit of (I) (Fig. 1) contains two peptide molecules (A and B), as well as two water molecules. As reflected by the torsion angles listed in Table 1, the peptide backbones occur in very similar semiextended conformations with ϕ2 (C5—N2—C6—C8) close to -80°. The Pro pyrrolidinium rings exhibit envelope conformations with C4—N1—C1—C2 torsion angles close to 0° and endo puckering for C3 (see Supplementary materials). Molecules A and B are interconnected by hydrogen bonds between the L-Ser side chains, but the strong amino–carboxylate interactions in Table 2 connect only identical molecules within two independent hydrogen-bonded sheets in a structure that is clearly layered and nonporous (Fig. 2a). A recent review of the crystal structures of dipeptides (Görbitz, 2010a) showed that most structures in fact incorporate two-dimensional sheets with two coexisting C(8) head-to-tail hydrogen-bonded chains. Neighbouring molecules along such chains were found to be related either by just translation (T) or by a screw (S) operation, while a third hydrogen-bonded chain, involving the amide >N—H donor, is of type C(4) or C(5). This leads to four basic patterns called T4, T5, S4 and S5. The structure of (I) belongs to the T5 group, as can be seen from the hydrogen-bonded sheet depicted in Fig. 3, which is derived solely from A molecules. A total of 17 other structures with similar sheets are listed in Table 3. The geometric parameters given in the table display small variations among the structures, but x reaches the smallest value for (I) (crystallographic a axis) while y has the largest value (c axis).

Table 3 furthermore shows that crystals with T5 sheets occur mainly for dipeptides with the sequences Pro–Nop, Gly–Nop and Pol–Nop, where Nop is a nonpolar residue and Pol is a polar (but uncharged) residue. The title compound belongs to none of these groups and is only the second T5 structure after Glu–Glu (CSD refcode BELCUQ; Eggleston & Hodgson, 1982) with a polar C-terminal residue. Compared to e.g. Pro–Val (BIBVOX; Narasimhan et al., 1982), (I) introduces an extra side-chain hydrogen-bond donor that needs to find a suitable acceptor atom. Fig. 2(a) reveals how this has been achieved: the symmetry of the orthorhombic P212121 space group of Pro–Val in Fig. 2(b) has been retained for peptide main chains, Pro side chains and water molecules, but is broken locally as consecutive peptide molecules along the a-axis shift between two different Ser side chain conformations (gauche– for molecule A, gauche+ for molecule B, Table 1) to form a hydrogen-bonded co-operative chain of hydroxy groups (Fig. 4). Consequently, the r.m.s. deviation for the best overlay between molecules A and B is 0.554 Å when all heavy atoms are included, but only 0.066 Å when the O—H group is excluded from the calculation (illustrations available as Supplementary materials). The resulting pseudo-orthorhombic [β = 90.829 (3)°] structure of (I) is the only entry in Table 3 with Z' = 2. Fig. 4 also highlights the water wires running parallel to the hydroxy chains. Investigations of small molecule crystal structures with water wires (Prohens et al., 2013; Le Duc et al., 2011; Görbitz, 2010b; Raghavender et al., 2010) has attracted considerable attention recently as models for single lane water channels in proteins such as aquaporin, a biologically important transmembrane protein that carries water molecules in a single line into a cell from its extracellular environment (Yu et al., 2011; Agre, 2004; Kozono et al., 2002), and also for their suspected roles in a series of disorders and diseases, including amyloid formation (Thirumalai et al. 2012).

Finally, the reason why Pol-Nop peptides in Table 3 can pack in the same manner as Pro–Nop peptides as well as (I) is evident from a comparison of Pro–Val (BIBVOX; Narasimhan et al., 1982) in Fig. 2(b) and Ser–Val (EYIVAJ; Moen et al., 2004) in Fig. 2(c): the extra amino N—H donor of Ser compared to Pro needs an additional hydrogen-bond acceptor, which is provided by the side chain of the polar, N-terminal residue. At the same time, the side chain fuctional group, in this case –OH, saturates the hydrogen-bond accepting capacity of the C-terminal carboxylate group, a role taken by the solvent water molecules in the structures with N-terminal Pro such as (I).

Related literature top

For related literature, see: Agre (2004); Allen (2002); Eggleston & Hodgson (1982); Görbitz (2007, 2010a, 2010b); Görbitz et al. (2005); Kozono et al. (2002); Le Duc, Michau, Gilles, Gence, Legrand, van der Lee, Tingry & Barboiu (2011); Moen et al. (2004); Narasimhan et al. (1982); Prohens et al. (2013); Raghavender et al. (2010); Thirumalai et al. (2012); Yu et al. (2011).

Experimental top

The title compound was prepared by solution-phase reaction processes described in the Supplementary materials. About 1 mg of (I) was dissolved in 40 µl of water in a 30 × 6 mm test tube. To this solution, 10 µl of tetramethoxysilane was added, and after 1 min of vigorous stirring the mixture was sealed with parafilm and left for 1 h to polymerize. A small hole was then pricked in the parafilm and the tube was placed inside a larger sealed test tube containing 1 ml of acetonitrile. The system was ultimately capped and left for one week at 293 K. Small crystals were formed as the organic solvent diffused into the gel.

Refinement top

Positional parameters of water and hydroxy H atoms, which had been located in a difference map, were refined with their respective O—H distances restrained to 0.85 (2) Å. N—H and C—H distances were fixed to 0.92 (NH2+), 0.88 (>N—H), 0.99 (CH2) or 1.00 (CH) Å, respectively. Uiso(H) values were set at 1.5Ueq of the carrier atom for H(—O) and at 1.2Ueq for H(—C/N). In the absence of significant anomalous scattering effects, 1950 Friedel pairs were merged.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The asymmetric unit of (I). Displacement ellipsoids are shown at the 50% probability level.
[Figure 2] Fig. 2. The crystal packing of (a) (I), (b) Pro–Val (CSD refcode BIBVOX; Narasimhan et al., 1982) and (c) Ser–Val (EYIVAJ; Moen et al., 2004). Symbols for symmetry elements are included with pseudo-elements as open symbols in (a). Peptide molecules A and B in (a) have C atoms in light and dark grey, respectively, O1W is yellow, while O2W is violet. A pair of water molecules are shown in a space-filling representation. Two different hydrogen-bonded sheets, seen here edge-on, are highlighted in grey, while a pair of Ser side chains that break the regular twofold screw symmetry are inside a dashed ellipse. The dashed circle in (c) focuses on hydrogen bonding, see Comment for details.
[Figure 3] Fig. 3. The hydrogen-bonded sheet formed by amino–carboxylate interactions between peptide A molecules (B is equivalent, see Supplementary materials). Side-chain atoms have been omitted. The two head-to-tail C(8) chains have been highlighted in blue, while a C(5) chain involving the amide >N—H is shown in red. The combination of a translation-only (T) relationship between individual molecules (that is no screw operations are involved) and a C(5) chain generates a T5 pattern (Görbitz, 2010a). Additional Cα—H···OC< interactions are shown in orange. The parameters x and y define the dimensions of the pattern, which for (I) corresponds to the lengths of the a axis and the c axis, respectively; the angle ϕ is 95.04 (4)° in the triclinic P1 structure of Pro–Tyr (SOJPAI; Klein et al., 1991), but 90.00° in all other T5 structures.
[Figure 4] Fig. 4. Hydrogen-bonded chains from hydroxy groups (red) and water molecules (blue) in the structure of (I). Colour coding as in Fig. 2.
(S)-3-Hydroxy-2-[(S)-pyrrolidine-2-carboxamido]propanoic acid top
Crystal data top
C8H14N2O4·H2OF(000) = 472
Mr = 220.23Dx = 1.419 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ybCell parameters from 1767 reflections
a = 5.3101 (12) Åθ = 2.8–22.4°
b = 29.081 (7) ŵ = 0.12 mm1
c = 6.6757 (15) ÅT = 105 K
β = 90.829 (3)°Needle, colourless
V = 1030.8 (4) Å30.31 × 0.09 × 0.06 mm
Z = 4
Data collection top
Bruker APEXII CCD
diffractometer
2165 independent reflections
Radiation source: fine-focus sealed tube1768 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.047
Detector resolution: 8.3 pixels mm-1θmax = 26.5°, θmin = 2.8°
Sets of exposures each taken over 0.5° ω rotation scansh = 66
Absorption correction: multi-scan
(SADABS; Bruker, 2007)
k = 3635
Tmin = 0.838, Tmax = 0.993l = 88
8313 measured reflections
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)] = 0.044Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.110H atoms treated by a mixture of independent and constrained refinement
S = 1.05 w = 1/[σ2(Fo2) + (0.0625P)2 + 0.1448P]
where P = (Fo2 + 2Fc2)/3
2165 reflections(Δ/σ)max < 0.001
291 parametersΔρmax = 0.26 e Å3
7 restraintsΔρmin = 0.25 e Å3
Crystal data top
C8H14N2O4·H2OV = 1030.8 (4) Å3
Mr = 220.23Z = 4
Monoclinic, P21Mo Kα radiation
a = 5.3101 (12) ŵ = 0.12 mm1
b = 29.081 (7) ÅT = 105 K
c = 6.6757 (15) Å0.31 × 0.09 × 0.06 mm
β = 90.829 (3)°
Data collection top
Bruker APEXII CCD
diffractometer
2165 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2007)
1768 reflections with I > 2σ(I)
Tmin = 0.838, Tmax = 0.993Rint = 0.047
8313 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0447 restraints
wR(F2) = 0.110H atoms treated by a mixture of independent and constrained refinement
S = 1.05Δρmax = 0.26 e Å3
2165 reflectionsΔρmin = 0.25 e Å3
291 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
O1A0.9100 (5)0.64715 (11)0.1962 (4)0.0288 (7)
O2A0.9929 (6)0.76776 (10)0.2147 (5)0.0331 (7)
H4A1.142 (5)0.766 (2)0.172 (7)0.047 (16)*
O3A0.8843 (5)0.61158 (9)0.3430 (4)0.0230 (6)
O4A0.5391 (5)0.65596 (9)0.3468 (4)0.0237 (6)
N1A1.2941 (6)0.60745 (11)0.3792 (4)0.0196 (7)
H1A1.39850.62220.46950.024*
H2A1.12990.61350.41270.024*
N2A1.1228 (6)0.67033 (11)0.0773 (5)0.0195 (7)
H3A1.27220.67500.12890.023*
C1A1.3436 (7)0.62424 (14)0.1712 (6)0.0193 (8)
H11A1.48980.64590.17180.023*
C2A1.4047 (8)0.58105 (14)0.0493 (6)0.0256 (9)
H21A1.32760.58270.08640.031*
H22A1.58900.57700.03700.031*
C3A1.2900 (9)0.54221 (15)0.1709 (6)0.0283 (9)
H31A1.10680.53950.14370.034*
H32A1.37200.51250.14110.034*
C4A1.3420 (8)0.55686 (14)0.3847 (6)0.0262 (9)
H41A1.22710.54120.47830.031*
H42A1.51840.55020.42500.031*
C5A1.1038 (7)0.64878 (13)0.0974 (6)0.0203 (8)
C6A0.8974 (7)0.68629 (13)0.1845 (6)0.0183 (8)
H61A0.77680.69780.08230.022*
C7A0.9600 (8)0.72644 (14)0.3213 (6)0.0236 (9)
H71A1.11620.71940.39430.028*
H72A0.82240.73040.42140.028*
C8A0.7663 (7)0.64746 (13)0.3006 (5)0.0189 (8)
O1B0.5901 (5)0.85064 (11)0.6766 (4)0.0297 (7)
O2B0.4713 (6)0.77900 (10)0.0200 (5)0.0321 (7)
H4B0.616 (5)0.7856 (17)0.072 (7)0.040 (14)*
O3B0.6174 (5)0.88334 (9)0.1501 (4)0.0238 (6)
O4B0.9599 (5)0.83898 (10)0.1422 (4)0.0243 (6)
N1B0.2005 (6)0.88486 (11)0.8591 (5)0.0201 (7)
H1B0.09400.86940.94320.024*
H2B0.36380.87850.89780.024*
N2B0.3786 (6)0.82456 (12)0.4015 (5)0.0215 (7)
H3B0.23130.81900.34430.026*
C1B0.1553 (7)0.86953 (14)0.6450 (5)0.0197 (8)
H11B0.01030.84770.63610.024*
C2B0.0944 (8)0.91468 (14)0.5320 (6)0.0248 (9)
H21B0.17140.91470.39780.030*
H22B0.08990.91880.51610.030*
C3B0.2073 (8)0.95224 (13)0.6627 (6)0.0249 (9)
H31B0.39080.95510.64180.030*
H32B0.12620.98230.63500.030*
C4B0.1526 (8)0.93601 (14)0.8721 (6)0.0261 (9)
H41B0.02410.94250.90820.031*
H42B0.26680.95070.97160.031*
C5B0.3937 (7)0.84702 (14)0.5745 (6)0.0208 (8)
C6B0.6101 (7)0.80928 (13)0.3083 (6)0.0197 (8)
H61B0.72900.80000.41860.024*
C7B0.5713 (8)0.76720 (14)0.1728 (6)0.0254 (9)
H71B0.73470.75140.15620.031*
H72B0.45500.74550.23850.031*
C8B0.7374 (7)0.84796 (13)0.1909 (5)0.0182 (8)
O1W0.8723 (5)0.51850 (10)0.2377 (5)0.0286 (7)
H11W0.862 (10)0.5474 (8)0.263 (8)0.043*
H12W0.717 (5)0.5105 (19)0.251 (8)0.043*
O2W0.6245 (6)0.97668 (10)0.2452 (5)0.0292 (7)
H21W0.637 (9)0.9494 (9)0.200 (7)0.044*
H22W0.776 (5)0.9870 (17)0.235 (8)0.044*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O1A0.0192 (14)0.0429 (18)0.0245 (15)0.0014 (13)0.0017 (11)0.0077 (14)
O2A0.0347 (18)0.0225 (15)0.0419 (19)0.0031 (14)0.0049 (14)0.0008 (13)
O3A0.0251 (14)0.0185 (15)0.0254 (15)0.0001 (11)0.0036 (11)0.0013 (11)
O4A0.0192 (14)0.0280 (16)0.0240 (15)0.0004 (11)0.0013 (11)0.0043 (12)
N1A0.0207 (16)0.0221 (17)0.0160 (16)0.0019 (13)0.0011 (12)0.0001 (13)
N2A0.0159 (15)0.0220 (17)0.0206 (17)0.0004 (13)0.0000 (12)0.0029 (14)
C1A0.0171 (18)0.022 (2)0.019 (2)0.0009 (15)0.0009 (14)0.0017 (16)
C2A0.031 (2)0.025 (2)0.020 (2)0.0083 (18)0.0007 (16)0.0031 (17)
C3A0.040 (2)0.023 (2)0.022 (2)0.0003 (18)0.0015 (17)0.0019 (17)
C4A0.038 (2)0.020 (2)0.020 (2)0.0016 (18)0.0049 (17)0.0004 (17)
C5A0.0219 (19)0.0180 (19)0.021 (2)0.0005 (15)0.0038 (15)0.0039 (16)
C6A0.0184 (18)0.020 (2)0.016 (2)0.0004 (14)0.0037 (14)0.0017 (15)
C7A0.029 (2)0.021 (2)0.021 (2)0.0007 (16)0.0026 (16)0.0005 (16)
C8A0.024 (2)0.021 (2)0.0117 (18)0.0009 (16)0.0028 (14)0.0021 (15)
O1B0.0190 (14)0.0434 (19)0.0267 (16)0.0036 (13)0.0022 (11)0.0078 (13)
O2B0.0306 (16)0.0343 (18)0.0313 (17)0.0035 (14)0.0022 (13)0.0050 (14)
O3B0.0296 (15)0.0201 (15)0.0217 (15)0.0005 (12)0.0032 (11)0.0015 (12)
O4B0.0199 (14)0.0314 (16)0.0218 (15)0.0006 (11)0.0013 (11)0.0025 (12)
N1B0.0199 (16)0.0200 (18)0.0203 (18)0.0007 (13)0.0014 (12)0.0022 (13)
N2B0.0207 (16)0.0265 (18)0.0173 (16)0.0017 (13)0.0005 (12)0.0003 (14)
C1B0.0184 (19)0.023 (2)0.017 (2)0.0013 (15)0.0005 (14)0.0013 (16)
C2B0.030 (2)0.022 (2)0.022 (2)0.0034 (17)0.0008 (16)0.0012 (17)
C3B0.033 (2)0.016 (2)0.026 (2)0.0016 (17)0.0004 (17)0.0032 (16)
C4B0.033 (2)0.023 (2)0.023 (2)0.0042 (17)0.0013 (16)0.0035 (17)
C5B0.0196 (19)0.019 (2)0.023 (2)0.0001 (15)0.0033 (15)0.0036 (16)
C6B0.0200 (18)0.019 (2)0.020 (2)0.0015 (15)0.0011 (15)0.0022 (15)
C7B0.031 (2)0.020 (2)0.026 (2)0.0038 (17)0.0045 (16)0.0030 (17)
C8B0.0195 (19)0.023 (2)0.0122 (18)0.0000 (16)0.0027 (13)0.0045 (15)
O1W0.0277 (15)0.0217 (15)0.0362 (18)0.0014 (13)0.0027 (13)0.0047 (13)
O2W0.0284 (16)0.0214 (15)0.0379 (19)0.0021 (13)0.0003 (13)0.0049 (14)
Geometric parameters (Å, º) top
O1A—C5A1.231 (5)O2B—H4B0.87 (2)
O2A—C7A1.406 (5)O3B—C8B1.239 (5)
O2A—H4A0.84 (2)O4B—C8B1.257 (4)
O3A—C8A1.252 (5)N1B—C4B1.512 (5)
O4A—C8A1.265 (5)N1B—C1B1.513 (5)
N1A—C4A1.494 (5)N1B—H1B0.9200
N1A—C1A1.498 (5)N1B—H2B0.9200
N1A—H1A0.9200N2B—C5B1.329 (5)
N1A—H2A0.9200N2B—C6B1.455 (5)
N2A—C5A1.330 (5)N2B—H3B0.8800
N2A—C6A1.461 (5)C1B—C5B1.506 (5)
N2A—H3A0.8800C1B—C2B1.546 (5)
C1A—C2A1.534 (5)C1B—H11B1.0000
C1A—C5A1.534 (5)C2B—C3B1.517 (6)
C1A—H11A1.0000C2B—H21B0.9900
C2A—C3A1.523 (6)C2B—H22B0.9900
C2A—H21A0.9900C3B—C4B1.508 (6)
C2A—H22A0.9900C3B—H31B0.9900
C3A—C4A1.511 (6)C3B—H32B0.9900
C3A—H31A0.9900C4B—H41B0.9900
C3A—H32A0.9900C4B—H42B0.9900
C4A—H41A0.9900C6B—C8B1.534 (5)
C4A—H42A0.9900C6B—C7B1.534 (5)
C6A—C7A1.522 (5)C6B—H61B1.0000
C6A—C8A1.531 (5)C7B—H71B0.9900
C6A—H61A1.0000C7B—H72B0.9900
C7A—H71A0.9900O1W—H11W0.86 (2)
C7A—H72A0.9900O1W—H12W0.86 (2)
O1B—C5B1.242 (5)O2W—H21W0.85 (2)
O2B—C7B1.426 (5)O2W—H22W0.86 (2)
C7A—O2A—H4A103 (4)C4B—N1B—C1B108.6 (3)
C4A—N1A—C1A108.2 (3)C4B—N1B—H1B110.0
C4A—N1A—H1A110.1C1B—N1B—H1B110.0
C1A—N1A—H1A110.1C4B—N1B—H2B110.0
C4A—N1A—H2A110.1C1B—N1B—H2B110.0
C1A—N1A—H2A110.1H1B—N1B—H2B108.3
H1A—N1A—H2A108.4C5B—N2B—C6B118.7 (3)
C5A—N2A—C6A120.5 (3)C5B—N2B—H3B120.6
C5A—N2A—H3A119.7C6B—N2B—H3B120.6
C6A—N2A—H3A119.7C5B—C1B—N1B107.5 (3)
N1A—C1A—C2A105.4 (3)C5B—C1B—C2B112.8 (3)
N1A—C1A—C5A107.0 (3)N1B—C1B—C2B103.9 (3)
C2A—C1A—C5A113.1 (3)C5B—C1B—H11B110.8
N1A—C1A—H11A110.4N1B—C1B—H11B110.8
C2A—C1A—H11A110.4C2B—C1B—H11B110.8
C5A—C1A—H11A110.4C3B—C2B—C1B104.6 (3)
C3A—C2A—C1A103.6 (3)C3B—C2B—H21B110.8
C3A—C2A—H21A111.0C1B—C2B—H21B110.8
C1A—C2A—H21A111.0C3B—C2B—H22B110.8
C3A—C2A—H22A111.0C1B—C2B—H22B110.8
C1A—C2A—H22A111.0H21B—C2B—H22B108.9
H21A—C2A—H22A109.0C4B—C3B—C2B103.2 (3)
C4A—C3A—C2A103.0 (3)C4B—C3B—H31B111.1
C4A—C3A—H31A111.2C2B—C3B—H31B111.1
C2A—C3A—H31A111.2C4B—C3B—H32B111.1
C4A—C3A—H32A111.2C2B—C3B—H32B111.1
C2A—C3A—H32A111.2H31B—C3B—H32B109.1
H31A—C3A—H32A109.1C3B—C4B—N1B102.7 (3)
N1A—C4A—C3A103.0 (3)C3B—C4B—H41B111.2
N1A—C4A—H41A111.2N1B—C4B—H41B111.2
C3A—C4A—H41A111.2C3B—C4B—H42B111.2
N1A—C4A—H42A111.2N1B—C4B—H42B111.2
C3A—C4A—H42A111.2H41B—C4B—H42B109.1
H41A—C4A—H42A109.1O1B—C5B—N2B124.0 (4)
O1A—C5A—N2A124.2 (3)O1B—C5B—C1B119.6 (3)
O1A—C5A—C1A120.4 (3)N2B—C5B—C1B116.4 (3)
N2A—C5A—C1A115.3 (3)N2B—C6B—C8B112.1 (3)
N2A—C6A—C7A110.7 (3)N2B—C6B—C7B112.9 (3)
N2A—C6A—C8A112.1 (3)C8B—C6B—C7B109.9 (3)
C7A—C6A—C8A111.3 (3)N2B—C6B—H61B107.2
N2A—C6A—H61A107.5C8B—C6B—H61B107.2
C7A—C6A—H61A107.5C7B—C6B—H61B107.2
C8A—C6A—H61A107.5O2B—C7B—C6B112.7 (3)
O2A—C7A—C6A112.2 (3)O2B—C7B—H71B109.1
O2A—C7A—H71A109.2C6B—C7B—H71B109.1
C6A—C7A—H71A109.2O2B—C7B—H72B109.1
O2A—C7A—H72A109.2C6B—C7B—H72B109.1
C6A—C7A—H72A109.2H71B—C7B—H72B107.8
H71A—C7A—H72A107.9O3B—C8B—O4B126.7 (4)
O3A—C8A—O4A125.9 (4)O3B—C8B—C6B119.5 (3)
O3A—C8A—C6A120.2 (3)O4B—C8B—C6B113.7 (3)
O4A—C8A—C6A113.8 (3)H11W—O1W—H12W101 (5)
C7B—O2B—H4B95 (3)H21W—O2W—H22W103 (5)
N1A—C1A—C5A—N2A173.0 (3)N1B—C1B—C5B—N2B169.3 (3)
C1A—C5A—N2A—C6A166.6 (3)C1B—C5B—N2B—C6B169.1 (3)
C5A—N2A—C6A—C8A80.3 (4)C5B—N2B—C6B—C8B81.6 (4)
N2A—C6A—C8A—O3A19.8 (5)N2B—C6B—C8B—O3B14.7 (5)
N1A—C1A—C2A—C3A21.0 (4)N1B—C1B—C2B—C3B21.7 (4)
C1A—C2A—C3A—C4A37.9 (4)C1B—C2B—C3B—C4B38.8 (4)
C2A—C3A—C4A—N1A40.2 (4)C2B—C3B—C4B—N1B40.1 (4)
C3A—C4A—N1A—C1A27.5 (4)C3B—C4B—N1B—C1B27.0 (4)
C4A—N1A—C1A—C2A3.9 (4)C4B—N1B—C1B—C2B3.2 (4)
N2A—C6A—C7A—O2A76.3 (4)N2B—C6B—C7B—O2B80.3 (4)
C4A—N1A—C1A—C5A124.6 (3)C4B—N1B—C1B—C5B123.0 (3)
C5A—C1A—C2A—C3A95.6 (4)C5B—C1B—C2B—C3B94.4 (4)
C6A—N2A—C5A—O1A12.2 (6)C6B—N2B—C5B—O1B10.0 (6)
N1A—C1A—C5A—O1A8.1 (5)N1B—C1B—C5B—O1B11.5 (5)
C2A—C1A—C5A—O1A107.6 (4)C2B—C1B—C5B—O1B102.4 (4)
C2A—C1A—C5A—N2A71.3 (4)C2B—C1B—C5B—N2B76.8 (4)
C5A—N2A—C6A—C7A154.7 (3)C5B—N2B—C6B—C7B153.7 (3)
C8A—C6A—C7A—O2A158.2 (3)C8B—C6B—C7B—O2B45.6 (4)
C7A—C6A—C8A—O3A104.8 (4)C7B—C6B—C8B—O3B111.6 (4)
N2A—C6A—C8A—O4A160.9 (3)N2B—C6B—C8B—O4B166.7 (3)
C7A—C6A—C8A—O4A74.5 (4)C7B—C6B—C8B—O4B67.0 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2A—H4A···O2Bi0.84 (2)2.05 (3)2.856 (4)162 (5)
N1A—H1A···O4Aii0.921.732.638 (4)168
N1A—H2A···O3Aiii0.922.102.882 (4)142
N2A—H3A···O4Ai0.882.122.900 (4)148
C1A—H11A···O1Ai1.002.243.083 (5)142
O2B—H4B···O2A0.87 (2)2.29 (3)3.094 (4)154 (5)
N1B—H1B···O4Biv0.921.762.656 (4)165
N1B—H2B···O3Biii0.922.152.924 (4)142
N2B—H3B···O4Bv0.882.042.829 (4)148
C1B—H11B···O1Bv1.002.253.062 (5)137
C1B—H11B···O2Aiv1.002.533.226 (5)126
O1W—H11W···O3A0.86 (2)1.95 (2)2.797 (4)171 (5)
O1W—H12W···O2Wvi0.86 (2)2.07 (2)2.905 (4)166 (5)
O2W—H21W···O3B0.85 (2)1.95 (2)2.788 (4)167 (5)
O2W—H22W···O1Wvii0.86 (2)2.08 (2)2.937 (4)173 (5)
Symmetry codes: (i) x+1, y, z; (ii) x+1, y, z+1; (iii) x, y, z+1; (iv) x1, y, z+1; (v) x1, y, z; (vi) x+1, y1/2, z; (vii) x+2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC8H14N2O4·H2O
Mr220.23
Crystal system, space groupMonoclinic, P21
Temperature (K)105
a, b, c (Å)5.3101 (12), 29.081 (7), 6.6757 (15)
β (°) 90.829 (3)
V3)1030.8 (4)
Z4
Radiation typeMo Kα
µ (mm1)0.12
Crystal size (mm)0.31 × 0.09 × 0.06
Data collection
DiffractometerBruker APEXII CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2007)
Tmin, Tmax0.838, 0.993
No. of measured, independent and
observed [I > 2σ(I)] reflections
8313, 2165, 1768
Rint0.047
(sin θ/λ)max1)0.627
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.110, 1.05
No. of reflections2165
No. of parameters291
No. of restraints7
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.26, 0.25

Computer programs: APEX2 (Bruker, 2007), SAINT-Plus (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected torsion angles (º) top
N1A—C1A—C5A—N2A173.0 (3)N1B—C1B—C5B—N2B169.3 (3)
C1A—C5A—N2A—C6A166.6 (3)C1B—C5B—N2B—C6B169.1 (3)
C5A—N2A—C6A—C8A80.3 (4)C5B—N2B—C6B—C8B81.6 (4)
N2A—C6A—C8A—O3A19.8 (5)N2B—C6B—C8B—O3B14.7 (5)
N1A—C1A—C2A—C3A21.0 (4)N1B—C1B—C2B—C3B21.7 (4)
C1A—C2A—C3A—C4A37.9 (4)C1B—C2B—C3B—C4B38.8 (4)
C2A—C3A—C4A—N1A40.2 (4)C2B—C3B—C4B—N1B40.1 (4)
C3A—C4A—N1A—C1A27.5 (4)C3B—C4B—N1B—C1B27.0 (4)
C4A—N1A—C1A—C2A3.9 (4)C4B—N1B—C1B—C2B3.2 (4)
N2A—C6A—C7A—O2A76.3 (4)N2B—C6B—C7B—O2B80.3 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2A—H4A···O2Bi0.84 (2)2.05 (3)2.856 (4)162 (5)
N1A—H1A···O4Aii0.921.732.638 (4)168.2
N1A—H2A···O3Aiii0.922.102.882 (4)141.6
N2A—H3A···O4Ai0.882.122.900 (4)147.5
C1A—H11A···O1Ai1.002.243.083 (5)141.7
O2B—H4B···O2A0.87 (2)2.29 (3)3.094 (4)154 (5)
N1B—H1B···O4Biv0.921.762.656 (4)165.4
N1B—H2B···O3Biii0.922.152.924 (4)141.7
N2B—H3B···O4Bv0.882.042.829 (4)148.0
C1B—H11B···O1Bv1.002.253.062 (5)137.0
C1B—H11B···O2Aiv1.002.533.226 (5)126.4
O1W—H11W···O3A0.86 (2)1.95 (2)2.797 (4)171 (5)
O1W—H12W···O2Wvi0.86 (2)2.07 (2)2.905 (4)166 (5)
O2W—H21W···O3B0.85 (2)1.95 (2)2.788 (4)167 (5)
O2W—H22W···O1Wvii0.86 (2)2.08 (2)2.937 (4)173 (5)
Symmetry codes: (i) x+1, y, z; (ii) x+1, y, z+1; (iii) x, y, z+1; (iv) x1, y, z+1; (v) x1, y, z; (vi) x+1, y1/2, z; (vii) x+2, y+1/2, z.
Dipeptides with T5 hydrogen-bonding patterns top
Group/refcodeSequenceHydrationSpace groupx (Å)*y (Å)*
Pro–Npo
BAPBEZ10Pro–MethydrateP215.472 (4)6.411 (5)
BIBVOXPro–ValhydrateP2121215.436 (2)6.549 (2)
BUHGIUPro–GlyhydrateP215.417 (2)6.553 (2)
LPRLALPro–AlahydrateP215.52 (2)6.58 (2)
SEYWEYPro–IlehydrateP215.413 (3)6.601 (3)
SOJPAIPro–TyrhydrateP15.524 (3)6.621 (2)
Pol–Npo
EYIVAJSer–ValP215.383 (4)6.315 (4)
GUKVUDSer–LeuP215.3288 (3)6.3696 (6)
JUKMORHis–LeuP215.451 (1)6.559 (1)
PAJFIQSer–PheP2121215.3382 (13)6.3827 (16)
RAVZAQHis–MetP215.4676 (11)6.5893 (13)
TIPTUHGlu–ValP215.505 (2)6.487 (2)
Gly–Npo
GLYLEU10Gly–LeuP215.565 (5)6.369 (5)
QQQEVJ01Gly–PheP215.4926 (17)6.433 (2)
WEVWOKGly–ValP2121215.5238 (7)6.299 (1)
Other
DEZQOOAla–LeuhemihydrateC25.5592 (8)6.3349 (7)
BELCUQGlu–GluP215.524 (3)6.621 (2)
(I)Pro–SerhydrateP215.3101 (12)6.6757 (15)
Note: (*) see Fig. 2.
 

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