organic compounds
N-Butoxycarbonyl-5-oxo-L-proline ethyl ester
aDepartment of Physics, Thiagarajar College, Madurai 625 009, India, and bX-ray Crystallography Unit, school of Physics, Universiti Sains Malaysia, 11800-USM, Penang, Malaysia
*Correspondence e-mail: vasan692000@yahoo.co.in
The molecular structure of the title compound, C12H19NO5, may be visualized as made up of two nearly perpendicular planes [dihedral angle = 87.39 (12)°] and its is a good example of C—H⋯O interactions assuming significance in optimizing supramolecular aggregation in crystals in a molecule which is severely imbalanced in terms of donors to acceptor atoms. The pyrrolidine ring adopts a (3T2) twist conformation with puckering parameters Q = 0.2630 (4) Å and φ = 59 (9)°. The features R24(10) and R34(26) ring motifs formed by four weak C—H⋯O interactions, leading to supramolecular sheets lying parallel to the bc plane.
Related literature
For general background, see: Holladay et al. (1991); Kayushina & Vainshtein (1966); Wu (2009). For the biological activity of proline derivatives, see: Hayashi et al. (2003); Nishikawa & Murakami (2005). For hydrogen bonding, see: Bernstein et al. (1995). For puckering parameters, see: Cremer & Pople (1975). For a description of the Cambridge Structural Database, see: Allen (2002).
Experimental
Crystal data
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Refinement
|
Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).
Supporting information
10.1107/S1600536813007265/bx2436sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536813007265/bx2436Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536813007265/bx2436Isup3.cml
To a solution of oxo proline ethylester (0.5 g,3.26 mmol) in dichloromethane (10 ml), was added triethylamine (0.5 ml, 3.26 mmol), di-tert-butyl-dicarbonate (1.4 g, 6.52 mmol) and 4-(dimethylamino)-pyridine (0.4 g, 3.26 mmol) under N2. The resulting yellow solution was stirred at room temperature for 2 h. The reaction mixture was concentrated. The residue was purified by
to afford boc-oxo-L-proline ethylester (0.8 g, 95%). Crystals of the title compound were grown from its solution in ethanol by slow evaporation at room temperature.All the hydrogen atoms were placed at geometrically calculated positions. They were allowed to ride on respective parent atoms with Uiso values constrained to 1.2 times Ueq (1.5 times for ethyl H atoms) and the target C—H distance fixed at 0.96 Å for ethyl hydrogen atoms and 0.93 Å for all others.
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).C12H19NO5 | F(000) = 552 |
Mr = 257.28 | Dx = 1.276 Mg m−3 |
Orthorhombic, P212121 | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 2145 reflections |
a = 26.6884 (13) Å | θ = 5.2–67.7° |
b = 5.7650 (3) Å | µ = 0.83 mm−1 |
c = 8.7054 (4) Å | T = 100 K |
V = 1339.40 (11) Å3 | Block, colourless |
Z = 4 | 0.44 × 0.21 × 0.11 mm |
Bruker SMART APEXII CCD area-detector diffractometer | 2184 independent reflections |
Radiation source: fine-focus sealed tube | 2144 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.049 |
ϕ and ω scans | θmax = 65.0°, θmin = 7.1° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −31→31 |
Tmin = 0.711, Tmax = 0.914 | k = −5→6 |
9641 measured reflections | l = −10→10 |
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)] = 0.060 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.166 | H-atom parameters constrained |
S = 1.09 | w = 1/[σ2(Fo2) + (0.0688P)2 + 1.9721P] where P = (Fo2 + 2Fc2)/3 |
2184 reflections | (Δ/σ)max < 0.001 |
167 parameters | Δρmax = 0.37 e Å−3 |
0 restraints | Δρmin = −0.22 e Å−3 |
C12H19NO5 | V = 1339.40 (11) Å3 |
Mr = 257.28 | Z = 4 |
Orthorhombic, P212121 | Cu Kα radiation |
a = 26.6884 (13) Å | µ = 0.83 mm−1 |
b = 5.7650 (3) Å | T = 100 K |
c = 8.7054 (4) Å | 0.44 × 0.21 × 0.11 mm |
Bruker SMART APEXII CCD area-detector diffractometer | 2184 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 2144 reflections with I > 2σ(I) |
Tmin = 0.711, Tmax = 0.914 | Rint = 0.049 |
9641 measured reflections |
R[F2 > 2σ(F2)] = 0.060 | 0 restraints |
wR(F2) = 0.166 | H-atom parameters constrained |
S = 1.09 | Δρmax = 0.37 e Å−3 |
2184 reflections | Δρmin = −0.22 e Å−3 |
167 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.90408 (10) | 0.9206 (5) | 0.6629 (3) | 0.0370 (7) | |
O4 | 0.87203 (9) | 0.6029 (5) | 0.3651 (3) | 0.0363 (6) | |
O3 | 0.95830 (10) | 1.1864 (5) | 0.2879 (3) | 0.0385 (6) | |
O2 | 0.91287 (10) | 0.5496 (5) | 0.7415 (3) | 0.0418 (7) | |
O5 | 0.88646 (10) | 0.8660 (5) | 0.1762 (3) | 0.0390 (7) | |
N1 | 0.93969 (11) | 0.8201 (6) | 0.3819 (3) | 0.0322 (7) | |
C5 | 0.96730 (14) | 1.0270 (7) | 0.3731 (4) | 0.0336 (8) | |
C4 | 1.00831 (15) | 1.0151 (7) | 0.4918 (4) | 0.0386 (9) | |
H4A | 1.0015 | 1.1235 | 0.5774 | 0.046* | |
H4B | 1.0411 | 1.0549 | 0.4456 | 0.046* | |
C3 | 1.00806 (15) | 0.7635 (7) | 0.5485 (4) | 0.0378 (9) | |
H3A | 1.0148 | 0.7561 | 0.6603 | 0.045* | |
H3B | 1.0335 | 0.6700 | 0.4938 | 0.045* | |
C2 | 0.95504 (14) | 0.6769 (7) | 0.5120 (4) | 0.0346 (8) | |
H2A | 0.9563 | 0.5103 | 0.4803 | 0.042* | |
C1 | 0.92075 (14) | 0.7041 (7) | 0.6499 (4) | 0.0362 (9) | |
C6 | 0.87505 (15) | 0.9735 (8) | 0.8004 (4) | 0.0412 (9) | |
H6A | 0.8760 | 1.1427 | 0.8195 | 0.049* | |
H6B | 0.8904 | 0.8948 | 0.8898 | 0.049* | |
C7 | 0.82162 (16) | 0.8971 (8) | 0.7847 (5) | 0.0473 (10) | |
H7A | 0.8025 | 0.9492 | 0.8744 | 0.071* | |
H7B | 0.8203 | 0.7276 | 0.7781 | 0.071* | |
H7C | 0.8072 | 0.9647 | 0.6915 | 0.071* | |
C8 | 0.89734 (14) | 0.7707 (7) | 0.2939 (4) | 0.0351 (9) | |
C9 | 0.82710 (14) | 0.4960 (7) | 0.2939 (5) | 0.0414 (9) | |
C10 | 0.81499 (16) | 0.3074 (8) | 0.4085 (6) | 0.0484 (11) | |
H10A | 0.8427 | 0.1963 | 0.4126 | 0.073* | |
H10B | 0.7843 | 0.2271 | 0.3769 | 0.073* | |
H10C | 0.8101 | 0.3764 | 0.5102 | 0.073* | |
C11 | 0.78525 (15) | 0.6769 (8) | 0.2898 (6) | 0.0510 (11) | |
H11A | 0.7814 | 0.7463 | 0.3920 | 0.077* | |
H11B | 0.7538 | 0.6023 | 0.2597 | 0.077* | |
H11C | 0.7937 | 0.7981 | 0.2153 | 0.077* | |
C12 | 0.83972 (17) | 0.3976 (8) | 0.1365 (5) | 0.0483 (11) | |
H12A | 0.8695 | 0.2986 | 0.1444 | 0.072* | |
H12B | 0.8464 | 0.5251 | 0.0650 | 0.072* | |
H12C | 0.8114 | 0.3056 | 0.0987 | 0.072* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0497 (15) | 0.0307 (15) | 0.0307 (14) | −0.0008 (11) | 0.0045 (11) | 0.0004 (11) |
O4 | 0.0413 (14) | 0.0347 (15) | 0.0327 (14) | −0.0024 (11) | −0.0049 (11) | 0.0012 (11) |
O3 | 0.0514 (15) | 0.0343 (15) | 0.0299 (13) | −0.0023 (12) | 0.0013 (11) | 0.0055 (13) |
O2 | 0.0514 (16) | 0.0403 (17) | 0.0337 (14) | −0.0004 (12) | −0.0029 (12) | 0.0086 (13) |
O5 | 0.0558 (16) | 0.0319 (15) | 0.0292 (14) | 0.0016 (12) | −0.0065 (11) | 0.0035 (11) |
N1 | 0.0416 (16) | 0.0317 (17) | 0.0233 (14) | 0.0021 (13) | −0.0015 (13) | −0.0043 (14) |
C5 | 0.043 (2) | 0.033 (2) | 0.0250 (17) | 0.0001 (16) | 0.0050 (15) | −0.0017 (17) |
C4 | 0.044 (2) | 0.042 (2) | 0.0294 (19) | −0.0046 (18) | 0.0010 (16) | −0.0040 (18) |
C3 | 0.042 (2) | 0.043 (2) | 0.0288 (19) | 0.0037 (17) | −0.0004 (15) | 0.0043 (17) |
C2 | 0.044 (2) | 0.029 (2) | 0.0311 (18) | 0.0025 (16) | −0.0027 (15) | 0.0054 (16) |
C1 | 0.0379 (19) | 0.041 (2) | 0.0293 (19) | −0.0021 (16) | −0.0072 (15) | −0.0011 (18) |
C6 | 0.051 (2) | 0.045 (2) | 0.0272 (18) | 0.0005 (18) | 0.0077 (17) | −0.0008 (18) |
C7 | 0.052 (2) | 0.046 (3) | 0.044 (2) | 0.0044 (19) | 0.0069 (19) | −0.002 (2) |
C8 | 0.041 (2) | 0.030 (2) | 0.034 (2) | 0.0048 (15) | 0.0007 (16) | 0.0002 (16) |
C9 | 0.041 (2) | 0.034 (2) | 0.048 (2) | −0.0004 (17) | −0.0083 (17) | −0.005 (2) |
C10 | 0.048 (2) | 0.037 (3) | 0.061 (3) | −0.0058 (18) | −0.001 (2) | 0.004 (2) |
C11 | 0.044 (2) | 0.040 (3) | 0.069 (3) | 0.0004 (18) | −0.011 (2) | −0.003 (3) |
C12 | 0.064 (3) | 0.037 (2) | 0.044 (2) | −0.002 (2) | −0.015 (2) | −0.003 (2) |
O1—C1 | 1.330 (5) | C6—C7 | 1.499 (6) |
O1—C6 | 1.458 (4) | C6—H6A | 0.9900 |
O4—C8 | 1.332 (5) | C6—H6B | 0.9900 |
O4—C9 | 1.484 (5) | C7—H7A | 0.9800 |
O3—C5 | 1.205 (5) | C7—H7B | 0.9800 |
O2—C1 | 1.214 (5) | C7—H7C | 0.9800 |
O5—C8 | 1.198 (5) | C9—C10 | 1.510 (6) |
N1—C8 | 1.395 (5) | C9—C12 | 1.521 (6) |
N1—C5 | 1.404 (5) | C9—C11 | 1.529 (6) |
N1—C2 | 1.461 (5) | C10—H10A | 0.9800 |
C5—C4 | 1.506 (5) | C10—H10B | 0.9800 |
C4—C3 | 1.533 (6) | C10—H10C | 0.9800 |
C4—H4A | 0.9900 | C11—H11A | 0.9800 |
C4—H4B | 0.9900 | C11—H11B | 0.9800 |
C3—C2 | 1.534 (5) | C11—H11C | 0.9800 |
C3—H3A | 0.9900 | C12—H12A | 0.9800 |
C3—H3B | 0.9900 | C12—H12B | 0.9800 |
C2—C1 | 1.517 (5) | C12—H12C | 0.9800 |
C2—H2A | 1.0000 | ||
C1—O1—C6 | 116.4 (3) | H6A—C6—H6B | 107.9 |
C8—O4—C9 | 121.1 (3) | C6—C7—H7A | 109.5 |
C8—N1—C5 | 124.7 (3) | C6—C7—H7B | 109.5 |
C8—N1—C2 | 122.5 (3) | H7A—C7—H7B | 109.5 |
C5—N1—C2 | 112.0 (3) | C6—C7—H7C | 109.5 |
O3—C5—N1 | 125.2 (3) | H7A—C7—H7C | 109.5 |
O3—C5—C4 | 127.0 (4) | H7B—C7—H7C | 109.5 |
N1—C5—C4 | 107.8 (3) | O5—C8—O4 | 127.4 (4) |
C5—C4—C3 | 105.1 (3) | O5—C8—N1 | 124.9 (4) |
C5—C4—H4A | 110.7 | O4—C8—N1 | 107.7 (3) |
C3—C4—H4A | 110.7 | O4—C9—C10 | 101.3 (3) |
C5—C4—H4B | 110.7 | O4—C9—C12 | 110.6 (3) |
C3—C4—H4B | 110.7 | C10—C9—C12 | 111.9 (4) |
H4A—C4—H4B | 108.8 | O4—C9—C11 | 108.5 (3) |
C4—C3—C2 | 104.2 (3) | C10—C9—C11 | 110.5 (4) |
C4—C3—H3A | 110.9 | C12—C9—C11 | 113.3 (4) |
C2—C3—H3A | 110.9 | C9—C10—H10A | 109.5 |
C4—C3—H3B | 110.9 | C9—C10—H10B | 109.5 |
C2—C3—H3B | 110.9 | H10A—C10—H10B | 109.5 |
H3A—C3—H3B | 108.9 | C9—C10—H10C | 109.5 |
N1—C2—C1 | 112.7 (3) | H10A—C10—H10C | 109.5 |
N1—C2—C3 | 103.6 (3) | H10B—C10—H10C | 109.5 |
C1—C2—C3 | 111.0 (3) | C9—C11—H11A | 109.5 |
N1—C2—H2A | 109.8 | C9—C11—H11B | 109.5 |
C1—C2—H2A | 109.8 | H11A—C11—H11B | 109.5 |
C3—C2—H2A | 109.8 | C9—C11—H11C | 109.5 |
O2—C1—O1 | 125.1 (4) | H11A—C11—H11C | 109.5 |
O2—C1—C2 | 123.3 (4) | H11B—C11—H11C | 109.5 |
O1—C1—C2 | 111.5 (3) | C9—C12—H12A | 109.5 |
O1—C6—C7 | 111.7 (3) | C9—C12—H12B | 109.5 |
O1—C6—H6A | 109.3 | H12A—C12—H12B | 109.5 |
C7—C6—H6A | 109.3 | C9—C12—H12C | 109.5 |
O1—C6—H6B | 109.3 | H12A—C12—H12C | 109.5 |
C7—C6—H6B | 109.3 | H12B—C12—H12C | 109.5 |
C8—N1—C5—O3 | −0.8 (6) | N1—C2—C1—O2 | 149.4 (4) |
C2—N1—C5—O3 | −171.0 (4) | C3—C2—C1—O2 | −94.8 (4) |
C8—N1—C5—C4 | 177.3 (3) | N1—C2—C1—O1 | −35.4 (4) |
C2—N1—C5—C4 | 7.1 (4) | C3—C2—C1—O1 | 80.3 (4) |
O3—C5—C4—C3 | −171.4 (4) | C1—O1—C6—C7 | −81.1 (4) |
N1—C5—C4—C3 | 10.6 (4) | C9—O4—C8—O5 | 5.8 (6) |
C5—C4—C3—C2 | −23.0 (4) | C9—O4—C8—N1 | −174.7 (3) |
C8—N1—C2—C1 | −72.0 (4) | C5—N1—C8—O5 | 19.8 (6) |
C5—N1—C2—C1 | 98.5 (4) | C2—N1—C8—O5 | −170.9 (4) |
C8—N1—C2—C3 | 167.9 (3) | C5—N1—C8—O4 | −159.7 (3) |
C5—N1—C2—C3 | −21.6 (4) | C2—N1—C8—O4 | 9.5 (5) |
C4—C3—C2—N1 | 26.7 (4) | C8—O4—C9—C10 | 175.3 (3) |
C4—C3—C2—C1 | −94.6 (4) | C8—O4—C9—C12 | 56.5 (5) |
C6—O1—C1—O2 | 1.3 (5) | C8—O4—C9—C11 | −68.4 (4) |
C6—O1—C1—C2 | −173.7 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2A···O3i | 1.00 | 2.51 | 3.436 (5) | 154 |
C3—H3B···O3ii | 0.99 | 2.46 | 3.095 (5) | 121 |
C6—H6B···O5iii | 0.99 | 2.50 | 3.344 (5) | 143 |
C12—H12A···O5i | 0.98 | 2.55 | 3.327 (5) | 136 |
Symmetry codes: (i) x, y−1, z; (ii) −x+2, y−1/2, −z+1/2; (iii) x, y, z+1. |
Experimental details
Crystal data | |
Chemical formula | C12H19NO5 |
Mr | 257.28 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 100 |
a, b, c (Å) | 26.6884 (13), 5.7650 (3), 8.7054 (4) |
V (Å3) | 1339.40 (11) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.83 |
Crystal size (mm) | 0.44 × 0.21 × 0.11 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.711, 0.914 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9641, 2184, 2144 |
Rint | 0.049 |
(sin θ/λ)max (Å−1) | 0.588 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.060, 0.166, 1.09 |
No. of reflections | 2184 |
No. of parameters | 167 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.37, −0.22 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2A···O3i | 1.00 | 2.51 | 3.436 (5) | 154 |
C3—H3B···O3ii | 0.99 | 2.46 | 3.095 (5) | 121 |
C6—H6B···O5iii | 0.99 | 2.50 | 3.344 (5) | 143 |
C12—H12A···O5i | 0.98 | 2.55 | 3.327 (5) | 136 |
Symmetry codes: (i) x, y−1, z; (ii) −x+2, y−1/2, −z+1/2; (iii) x, y, z+1. |
Acknowledgements
The authors thank Dr MutharasuDevarajan, Associate Professor, and the staff of the X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, for their help with the data collection.
References
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Proline (Kayushina & Vainshtein, 1966) is a functional amino acid that participates in the regulation of key metabolic pathways essential for maintenance, growth, reproduction and immunity (Wu, 2009). Many substituted proline derivatives are known for their active role in biological functions. For instance, 5-oxo-proline or pyroglutamic acid, found in many proteins including bacteriorhodopsin, acts as a proton pump, captures light energy and uses it to move protons across the membrane out of the cell (Hayashi, et al., 2003; Nishikawa, et al., 2005). Also, N-boc-4-oxo-L-proline ethyl ester is a part of the starting material on stereoselective synthesis of peptide hormone cholecystokinin (Holladay, et al., 1991). The present paper describes the accurate description of the crystal structures of N-boc-5-oxo-L-proline ethyl ester (Fig.1).
The molecular mainframe of the title compound may be visualized as made up of two nearly perpendicular planes (N1/C8/O4/O5) and (O1/C1/O2/C2) with 87.39 (12) °. The orientation of the carbonyl O3 (substituted to the pyrrolidine ring), O4 (ethyl ester carbonyl) and O5 (tert-butyloxycarbonyl) may be described by the torsion angles about the C2—N1 bond which are -171.05 (4) °, -54.37 (6) ° and -170.82 (4) °, respectively. The pyrrolidine adopts the twisted conformation (3T2) with C2 and C3 atoms deviating from the plane defined by the rest of the atoms by about -0.3872 (6) Å and 0.4068 (6) Å, respectively with the associated puckering parameters (Cremer & Pople, 1975) of Q=0.2630 (4) Å, ϕ= 59 (9) °.
The crystal structure of the title compound is a simple example which demonstrates the importance of weak C–H···O interactions assuming significance in optimizing supramolecular aggregation in crystals. The molecule may be thought of as highly imbalanced in terms of donors to acceptor atoms which has at least three carbonyl O atoms O3, O4 and O5, out of the total five O atoms (O1→O5), available for participation in intermolecular interactions. O1 and O2 of the respective ethyl ester and the tert-butyloxy groups do not participate in the hydrogen-bonding environment owing to unfavourable steric reasons. The intermolecular interaction patterns may be vizualized as molecular chains interconnected to each other to form a sheet. The ethyl C2 and ethyl C3 atoms act as donors to the carbonyl O3 which is a bifurcated acceptor at (x, y - 1, z) and (-x + 2, y - 1/2, -z + 1/2), respectively. The associated graph-set motif (Bernstein et al., 1995) is a R42(10) ring through C2—H2A···O3 and C3—H3A···O3 hydrogen bond leading to chains parallel to the b-axis (Fig.2). The ethyl C6 and ethyl C12 atoms act as donors to the bifurcated acceptor (carbonyl) O5 at (x, y, z + 1) and (x, y - 1, z), respectively, forming a R43 (26) ring motif through a C6—H6B···O5 and C12—H12A···O5 hydrogen bonds forming sheets parallel to the bc-plane (Fig.3).