organic compounds
Ethyl 6-ethoxycarbonylmethyl-4-(2-hydroxyphenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
aFaculty of Pharmacy, Comenius University, Odbojarov 10, SK-83232 Bratislava, Slovakia
*Correspondence e-mail: kettmann@fpharm.uniba.sk
The title compound, C17H20N2O6, belongs to the monastrol-type of anticancer agents and was selected for determination in order to confirm its molecular structure and explore some aspects of its structure–activity relationships. The central tetrahydropyrimidine ring has a flat-envelope conformation. The 4-hydroxyphenyl group occupies a pseudo-axial position and is inclined at an angle of 87.7 (2)° to the mean plane of the heterocyclic ring. Of the two ethyl ester groups, one (in the 5-position) is in a coplanar and the other (in the 6-position) is in a perpendicular orientation with respect to the heterocyclic plane. There is a three-dimensional hydrogen-bonding network in which all hydrogen-bond donors and acceptors are involved.
Related literature
For related literature, see: Allen (2002); Azizian et al. (2007); Qing-Fang et al. (2007); Endow & Baker (2003); Kettmann & Svetlík (1997); Světlík et al. (1991); Wood & Bergnes (2004).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: XSCANS (Siemens, 1991); cell XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.
Supporting information
10.1107/S1600536808012683/wk2083sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808012683/wk2083Isup2.hkl
Synthesis of the title compound, (2), has been described (Azizian et al., 2007). In short, heating of salicylaldehyde (0.52 ml, 5 mmol) with diethyl acetone-1,3-dicarboxylate (0.91 ml, 5 mmol) and urea (0.36 g, 6 mmol) under p-toluenesulfonic acid (0.04 g, 0.2 mmol) catalysis without solvent at 353–363 K for 3 h gave the desired product (50% yield; m.p. 488–490 K). Crystalssuitable for the X-ray analysis were obtained by a slow crystallization from ethanol.
H atoms were visible in difference maps and were subsequently treated as riding atoms with distances C—H = 0.93 Å (CHarom), 0.97 (CH2) or 0.98 Å (CH), 0.96 Å (CH3) and N—H = 0.86 Å and O—H = 0.82 Å; Uiso of the H atoms were set to 1.2 (1.5 for the methyl and hydroxy H atoms) times Ueq of the parent atom.
Data collection: XSCANS (Siemens, 1991); cell
XSCANS (Siemens, 1991); data reduction: XSCANS (Siemens, 1991); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).C17H20N2O6 | Z = 2 |
Mr = 348.35 | F(000) = 368 |
Triclinic, P1 | Dx = 1.351 Mg m−3 |
Hall symbol: -P 1 | Melting point: 489 K |
a = 8.783 (2) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 9.336 (3) Å | Cell parameters from 20 reflections |
c = 11.415 (4) Å | θ = 7–18° |
α = 71.47 (4)° | µ = 0.10 mm−1 |
β = 82.78 (5)° | T = 296 K |
γ = 75.05 (4)° | Prism, colourless |
V = 856.5 (5) Å3 | 0.30 × 0.25 × 0.20 mm |
Siemens P4 diffractometer | Rint = 0.040 |
Radiation source: fine-focus sealed tube | θmax = 30.0°, θmin = 1.9° |
Graphite monochromator | h = −1→12 |
ω/2θ scans | k = −12→12 |
5849 measured reflections | l = −16→16 |
4950 independent reflections | 3 standard reflections every 97 reflections |
3935 reflections with I > 2σ(I) | intensity decay: none |
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)] = 0.057 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.174 | H-atom parameters constrained |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0972P)2 + 0.1877P] where P = (Fo2 + 2Fc2)/3 |
4950 reflections | (Δ/σ)max = 0.001 |
229 parameters | Δρmax = 0.31 e Å−3 |
0 restraints | Δρmin = −0.32 e Å−3 |
C17H20N2O6 | γ = 75.05 (4)° |
Mr = 348.35 | V = 856.5 (5) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.783 (2) Å | Mo Kα radiation |
b = 9.336 (3) Å | µ = 0.10 mm−1 |
c = 11.415 (4) Å | T = 296 K |
α = 71.47 (4)° | 0.30 × 0.25 × 0.20 mm |
β = 82.78 (5)° |
Siemens P4 diffractometer | Rint = 0.040 |
5849 measured reflections | 3 standard reflections every 97 reflections |
4950 independent reflections | intensity decay: none |
3935 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.057 | 0 restraints |
wR(F2) = 0.174 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.31 e Å−3 |
4950 reflections | Δρmin = −0.32 e Å−3 |
229 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 | ||
N1 | 0.10214 (15) | 0.47412 (12) | 0.13671 (11) | 0.0350 (3) | |
H1 | 0.0749 | 0.5465 | 0.0692 | 0.042* | |
C2 | 0.11515 (15) | 0.32189 (14) | 0.13967 (13) | 0.0315 (3) | |
O1 | 0.06497 (13) | 0.29448 (11) | 0.05495 (10) | 0.0408 (3) | |
N3 | 0.17844 (14) | 0.21317 (12) | 0.24052 (11) | 0.0344 (3) | |
H3 | 0.1615 | 0.1218 | 0.2584 | 0.041* | |
C4 | 0.27587 (15) | 0.24302 (13) | 0.32230 (12) | 0.0304 (3) | |
H4 | 0.2669 | 0.1704 | 0.4051 | 0.037* | |
C5 | 0.21064 (15) | 0.40660 (14) | 0.33107 (12) | 0.0307 (3) | |
C6 | 0.13046 (15) | 0.51589 (13) | 0.23577 (12) | 0.0302 (3) | |
C7 | 0.44794 (15) | 0.21163 (14) | 0.27695 (12) | 0.0315 (3) | |
C8 | 0.51674 (18) | 0.32744 (17) | 0.19754 (16) | 0.0431 (3) | |
H8 | 0.4584 | 0.4297 | 0.1753 | 0.052* | |
C9 | 0.6717 (2) | 0.2929 (2) | 0.15072 (18) | 0.0521 (4) | |
H9 | 0.7161 | 0.3715 | 0.0975 | 0.063* | |
C10 | 0.75860 (19) | 0.1417 (2) | 0.18372 (18) | 0.0519 (4) | |
H10 | 0.8617 | 0.1182 | 0.1519 | 0.062* | |
C11 | 0.69370 (19) | 0.02481 (19) | 0.26383 (17) | 0.0469 (4) | |
H11 | 0.7536 | −0.0768 | 0.2867 | 0.056* | |
C12 | 0.53881 (16) | 0.05890 (15) | 0.31031 (14) | 0.0353 (3) | |
O2 | 0.46665 (14) | −0.05252 (12) | 0.38635 (12) | 0.0489 (3) | |
H2 | 0.5328 | −0.1341 | 0.4106 | 0.073* | |
C13 | 0.24784 (17) | 0.43413 (15) | 0.44190 (13) | 0.0367 (3) | |
O3 | 0.31840 (19) | 0.33335 (14) | 0.52678 (12) | 0.0602 (4) | |
O4 | 0.19773 (16) | 0.58055 (12) | 0.44378 (11) | 0.0485 (3) | |
C14 | 0.2312 (3) | 0.6194 (2) | 0.55027 (18) | 0.0582 (5) | |
H14A | 0.3441 | 0.6037 | 0.5551 | 0.070* | |
H14B | 0.1912 | 0.5542 | 0.6260 | 0.070* | |
C15 | 0.1516 (3) | 0.7858 (2) | 0.5332 (2) | 0.0668 (6) | |
H15A | 0.1992 | 0.8497 | 0.4624 | 0.100* | |
H15B | 0.1627 | 0.8131 | 0.6055 | 0.100* | |
H15C | 0.0417 | 0.8016 | 0.5208 | 0.100* | |
C16 | 0.06044 (17) | 0.68574 (14) | 0.22359 (14) | 0.0363 (3) | |
H16A | −0.0109 | 0.7274 | 0.1562 | 0.044* | |
H16B | −0.0022 | 0.6925 | 0.2988 | 0.044* | |
C17 | 0.17511 (19) | 0.78803 (15) | 0.20076 (15) | 0.0403 (3) | |
O5 | 0.13786 (18) | 0.91436 (13) | 0.21651 (16) | 0.0651 (4) | |
O6 | 0.31602 (15) | 0.72710 (13) | 0.15956 (13) | 0.0521 (3) | |
C18 | 0.4286 (3) | 0.8264 (3) | 0.1244 (3) | 0.0778 (7) | |
H18A | 0.4017 | 0.9049 | 0.0460 | 0.093* | |
H18B | 0.4240 | 0.8786 | 0.1864 | 0.093* | |
C19 | 0.5842 (3) | 0.7343 (3) | 0.1139 (4) | 0.0954 (9) | |
H19A | 0.6129 | 0.6613 | 0.1931 | 0.143* | |
H19B | 0.6572 | 0.8004 | 0.0864 | 0.143* | |
H19C | 0.5870 | 0.6792 | 0.0553 | 0.143* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0449 (6) | 0.0191 (5) | 0.0410 (6) | −0.0060 (4) | −0.0108 (5) | −0.0068 (4) |
C2 | 0.0302 (6) | 0.0220 (5) | 0.0430 (7) | −0.0070 (4) | −0.0017 (5) | −0.0100 (5) |
O1 | 0.0490 (6) | 0.0278 (5) | 0.0503 (6) | −0.0086 (4) | −0.0120 (5) | −0.0145 (4) |
N3 | 0.0371 (6) | 0.0183 (4) | 0.0485 (6) | −0.0078 (4) | −0.0076 (5) | −0.0076 (4) |
C4 | 0.0316 (6) | 0.0192 (5) | 0.0374 (6) | −0.0034 (4) | −0.0032 (5) | −0.0057 (4) |
C5 | 0.0309 (6) | 0.0208 (5) | 0.0386 (6) | −0.0023 (4) | −0.0031 (5) | −0.0086 (4) |
C6 | 0.0301 (6) | 0.0200 (5) | 0.0400 (6) | −0.0040 (4) | −0.0043 (5) | −0.0086 (4) |
C7 | 0.0306 (6) | 0.0246 (5) | 0.0377 (6) | −0.0014 (4) | −0.0050 (5) | −0.0098 (5) |
C8 | 0.0376 (7) | 0.0299 (6) | 0.0546 (9) | −0.0049 (5) | 0.0012 (6) | −0.0062 (6) |
C9 | 0.0421 (8) | 0.0477 (9) | 0.0610 (10) | −0.0127 (7) | 0.0082 (7) | −0.0108 (7) |
C10 | 0.0331 (7) | 0.0566 (10) | 0.0660 (11) | −0.0028 (7) | 0.0024 (7) | −0.0262 (8) |
C11 | 0.0364 (7) | 0.0375 (7) | 0.0644 (10) | 0.0053 (6) | −0.0075 (7) | −0.0210 (7) |
C12 | 0.0345 (6) | 0.0257 (6) | 0.0450 (7) | −0.0006 (5) | −0.0095 (5) | −0.0118 (5) |
O2 | 0.0458 (6) | 0.0227 (5) | 0.0677 (8) | −0.0004 (4) | −0.0063 (5) | −0.0039 (5) |
C13 | 0.0402 (7) | 0.0268 (6) | 0.0403 (7) | −0.0018 (5) | −0.0062 (5) | −0.0094 (5) |
O3 | 0.0838 (10) | 0.0372 (6) | 0.0517 (7) | 0.0105 (6) | −0.0301 (7) | −0.0116 (5) |
O4 | 0.0702 (8) | 0.0307 (5) | 0.0453 (6) | 0.0010 (5) | −0.0188 (5) | −0.0164 (4) |
C14 | 0.0785 (13) | 0.0520 (10) | 0.0517 (10) | −0.0078 (9) | −0.0171 (9) | −0.0264 (8) |
C15 | 0.0932 (16) | 0.0557 (11) | 0.0642 (12) | −0.0218 (11) | 0.0058 (11) | −0.0351 (10) |
C16 | 0.0368 (6) | 0.0207 (5) | 0.0507 (8) | 0.0016 (5) | −0.0126 (6) | −0.0121 (5) |
C17 | 0.0508 (8) | 0.0217 (5) | 0.0483 (8) | −0.0047 (5) | −0.0154 (6) | −0.0082 (5) |
O5 | 0.0715 (9) | 0.0265 (5) | 0.1037 (11) | −0.0072 (5) | −0.0159 (8) | −0.0272 (6) |
O6 | 0.0534 (7) | 0.0329 (5) | 0.0741 (8) | −0.0180 (5) | 0.0064 (6) | −0.0185 (5) |
C18 | 0.0722 (14) | 0.0501 (11) | 0.116 (2) | −0.0352 (10) | 0.0059 (13) | −0.0184 (12) |
C19 | 0.0650 (14) | 0.0790 (17) | 0.154 (3) | −0.0359 (13) | 0.0172 (16) | −0.0439 (18) |
N1—C6 | 1.3761 (18) | C12—O2 | 1.366 (2) |
N1—C2 | 1.3859 (16) | O2—H2 | 0.8200 |
N1—H1 | 0.8600 | C13—O3 | 1.2161 (19) |
C2—O1 | 1.2319 (17) | C13—O4 | 1.3299 (17) |
C2—N3 | 1.3385 (19) | O4—C14 | 1.456 (2) |
N3—C4 | 1.4733 (18) | C14—C15 | 1.490 (3) |
N3—H3 | 0.8600 | C14—H14A | 0.9700 |
C4—C5 | 1.5172 (17) | C14—H14B | 0.9700 |
C4—C7 | 1.5196 (19) | C15—H15A | 0.9600 |
C4—H4 | 0.9800 | C15—H15B | 0.9600 |
C5—C6 | 1.3553 (19) | C15—H15C | 0.9600 |
C5—C13 | 1.458 (2) | C16—C17 | 1.505 (2) |
C6—C16 | 1.5134 (17) | C16—H16A | 0.9700 |
C7—C8 | 1.390 (2) | C16—H16B | 0.9700 |
C7—C12 | 1.3997 (18) | C17—O5 | 1.2047 (18) |
C8—C9 | 1.393 (2) | C17—O6 | 1.318 (2) |
C8—H8 | 0.9300 | O6—C18 | 1.461 (2) |
C9—C10 | 1.376 (3) | C18—C19 | 1.428 (4) |
C9—H9 | 0.9300 | C18—H18A | 0.9700 |
C10—C11 | 1.381 (3) | C18—H18B | 0.9700 |
C10—H10 | 0.9300 | C19—H19A | 0.9600 |
C11—C12 | 1.391 (2) | C19—H19B | 0.9600 |
C11—H11 | 0.9300 | C19—H19C | 0.9600 |
C6—N1—C2 | 123.64 (12) | C12—O2—H2 | 109.5 |
C6—N1—H1 | 118.2 | O3—C13—O4 | 121.72 (14) |
C2—N1—H1 | 118.2 | O3—C13—C5 | 123.83 (13) |
O1—C2—N3 | 124.46 (12) | O4—C13—C5 | 114.46 (12) |
O1—C2—N1 | 119.97 (13) | C13—O4—C14 | 118.33 (13) |
N3—C2—N1 | 115.52 (12) | O4—C14—C15 | 107.06 (16) |
C2—N3—C4 | 122.97 (11) | O4—C14—H14A | 110.3 |
C2—N3—H3 | 118.5 | C15—C14—H14A | 110.3 |
C4—N3—H3 | 118.5 | O4—C14—H14B | 110.3 |
N3—C4—C5 | 109.07 (11) | C15—C14—H14B | 110.3 |
N3—C4—C7 | 109.88 (11) | H14A—C14—H14B | 108.6 |
C5—C4—C7 | 113.81 (11) | C14—C15—H15A | 109.5 |
N3—C4—H4 | 108.0 | C14—C15—H15B | 109.5 |
C5—C4—H4 | 108.0 | H15A—C15—H15B | 109.5 |
C7—C4—H4 | 108.0 | C14—C15—H15C | 109.5 |
C6—C5—C13 | 125.23 (12) | H15A—C15—H15C | 109.5 |
C6—C5—C4 | 119.05 (12) | H15B—C15—H15C | 109.5 |
C13—C5—C4 | 115.65 (11) | C17—C16—C6 | 116.62 (12) |
C5—C6—N1 | 119.39 (11) | C17—C16—H16A | 108.1 |
C5—C6—C16 | 127.74 (12) | C6—C16—H16A | 108.1 |
N1—C6—C16 | 112.86 (11) | C17—C16—H16B | 108.1 |
C8—C7—C12 | 118.38 (13) | C6—C16—H16B | 108.1 |
C8—C7—C4 | 122.55 (12) | H16A—C16—H16B | 107.3 |
C12—C7—C4 | 118.97 (12) | O5—C17—O6 | 124.41 (16) |
C7—C8—C9 | 121.11 (15) | O5—C17—C16 | 122.19 (16) |
C7—C8—H8 | 119.4 | O6—C17—C16 | 113.38 (12) |
C9—C8—H8 | 119.4 | C17—O6—C18 | 116.16 (15) |
C10—C9—C8 | 119.64 (16) | C19—C18—O6 | 109.59 (19) |
C10—C9—H9 | 120.2 | C19—C18—H18A | 109.8 |
C8—C9—H9 | 120.2 | O6—C18—H18A | 109.8 |
C9—C10—C11 | 120.39 (15) | C19—C18—H18B | 109.8 |
C9—C10—H10 | 119.8 | O6—C18—H18B | 109.8 |
C11—C10—H10 | 119.8 | H18A—C18—H18B | 108.2 |
C10—C11—C12 | 120.09 (15) | C18—C19—H19A | 109.5 |
C10—C11—H11 | 120.0 | C18—C19—H19B | 109.5 |
C12—C11—H11 | 120.0 | H19A—C19—H19B | 109.5 |
O2—C12—C11 | 122.69 (13) | C18—C19—H19C | 109.5 |
O2—C12—C7 | 116.89 (13) | H19A—C19—H19C | 109.5 |
C11—C12—C7 | 120.39 (15) | H19B—C19—H19C | 109.5 |
C6—N1—C2—O1 | 168.78 (13) | C8—C9—C10—C11 | −0.7 (3) |
C6—N1—C2—N3 | −8.8 (2) | C9—C10—C11—C12 | 1.0 (3) |
O1—C2—N3—C4 | 162.57 (13) | C10—C11—C12—O2 | 177.68 (15) |
N1—C2—N3—C4 | −19.99 (19) | C10—C11—C12—C7 | −0.3 (2) |
C2—N3—C4—C5 | 36.47 (17) | C8—C7—C12—O2 | −178.66 (14) |
C2—N3—C4—C7 | −88.92 (15) | C4—C7—C12—O2 | −2.32 (19) |
N3—C4—C5—C6 | −27.05 (17) | C8—C7—C12—C11 | −0.5 (2) |
C7—C4—C5—C6 | 96.02 (15) | C4—C7—C12—C11 | 175.82 (13) |
N3—C4—C5—C13 | 155.91 (12) | C6—C5—C13—O3 | 179.07 (16) |
C7—C4—C5—C13 | −81.02 (15) | C4—C5—C13—O3 | −4.1 (2) |
C13—C5—C6—N1 | −179.52 (13) | C6—C5—C13—O4 | −0.8 (2) |
C4—C5—C6—N1 | 3.74 (19) | C4—C5—C13—O4 | 176.03 (12) |
C13—C5—C6—C16 | −1.2 (2) | O3—C13—O4—C14 | 0.9 (3) |
C4—C5—C6—C16 | −177.95 (12) | C5—C13—O4—C14 | −179.27 (15) |
C2—N1—C6—C5 | 16.6 (2) | C13—O4—C14—C15 | −175.54 (17) |
C2—N1—C6—C16 | −161.95 (13) | C5—C6—C16—C17 | 71.9 (2) |
N3—C4—C7—C8 | 93.30 (16) | N1—C6—C16—C17 | −109.73 (15) |
C5—C4—C7—C8 | −29.33 (19) | C6—C16—C17—O5 | −163.22 (15) |
N3—C4—C7—C12 | −82.87 (15) | C6—C16—C17—O6 | 18.42 (19) |
C5—C4—C7—C12 | 154.50 (12) | O5—C17—O6—C18 | −3.9 (3) |
C12—C7—C8—C9 | 0.8 (2) | C16—C17—O6—C18 | 174.44 (17) |
C4—C7—C8—C9 | −175.40 (15) | C17—O6—C18—C19 | 164.6 (2) |
C7—C8—C9—C10 | −0.2 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1i | 0.86 | 1.97 | 2.788 (2) | 159 |
O2—H2···O3ii | 0.82 | 1.95 | 2.772 (2) | 177 |
N3—H3···O5iii | 0.86 | 2.20 | 3.0014 (18) | 155 |
Symmetry codes: (i) −x, −y+1, −z; (ii) −x+1, −y, −z+1; (iii) x, y−1, z. |
Experimental details
Crystal data | |
Chemical formula | C17H20N2O6 |
Mr | 348.35 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 296 |
a, b, c (Å) | 8.783 (2), 9.336 (3), 11.415 (4) |
α, β, γ (°) | 71.47 (4), 82.78 (5), 75.05 (4) |
V (Å3) | 856.5 (5) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.30 × 0.25 × 0.20 |
Data collection | |
Diffractometer | Siemens P4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5849, 4950, 3935 |
Rint | 0.040 |
(sin θ/λ)max (Å−1) | 0.703 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.057, 0.174, 1.04 |
No. of reflections | 4950 |
No. of parameters | 229 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.31, −0.32 |
Computer programs: XSCANS (Siemens, 1991), XSCANS (Siemens, 1991), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2003).
N1—C6 | 1.3761 (18) | N3—C4 | 1.4733 (18) |
N1—C2 | 1.3859 (16) | C4—C5 | 1.5172 (17) |
C2—O1 | 1.2319 (17) | C5—C6 | 1.3553 (19) |
C2—N3 | 1.3385 (19) | ||
C5—C4—C7—C8 | −29.33 (19) | C5—C6—C16—C17 | 71.9 (2) |
C6—C5—C13—O3 | 179.07 (16) | C6—C16—C17—O6 | 18.42 (19) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1i | 0.86 | 1.97 | 2.788 (2) | 158.6 |
O2—H2···O3ii | 0.82 | 1.95 | 2.772 (2) | 177.1 |
N3—H3···O5iii | 0.86 | 2.20 | 3.0014 (18) | 154.9 |
Symmetry codes: (i) −x, −y+1, −z; (ii) −x+1, −y, −z+1; (iii) x, y−1, z. |
Acknowledgements
This work was supported by the Grant Agency of the Slovak Republic, project Nos. 1/4298/07 and 1/4299/07.
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Recently, while we have been continuing in our programme aimed at synthesis of monastrol (1) analogues as valuable antitumour drugs (Wood & Bergnes, 2004), a related tetrahydropyrimidine compound (2) has been described by another group (Azizian et al., 2007). As we had reported earlier (Světlík et al., 1991; Kettmann & Svetlík, 1997) that classical Biginelli condensation with salicylaldehyde gives oxygen-bridged pyrimidine (3) rather than the 'open' molecule (4), the formation of (2) was accordingly unexpected. Thus, to verify the correctness of the title structure (2), an X-ray analysis was undertaken. As the cytotoxic activity of these derivatives is related to inhibition of the kinesin Eg5 protein (Endow & Baker, 2003), another purpose of this work was to determine detailed molecular conformation which is indispensable for an analysis of structure-activity relationships.
The structure determination has confirmed (Fig. 1) that the compound studied here has indeed the structure (2) (Fig. 2). As retrieved from the Cambridge Structural Database (Version of 2007; Allen, 2002), the bond lengths and angles (Table 1) within the tetrahydropyrimidine ring are equal within experimental error to those previously reported for a number of structures incorporating this molecular fragment (see, e.g., Qing-Fang et al., 2007). Bonding characteristics in other parts of the molecule also agree with those generally expected.
As noted above, from the biological standpoint, the conformational properties of the molecule are of prime interest here. First, the conformation of the central heterocycle can best be described as a flat envelope with atom C4 (at the flap) deviating by 0.433 (2) Å from the mean plane of the remaining atoms. As to the ring substituents, the 4-hydroxyphenyl group occupies the pseudoaxial position and is in a perpendicular orientation with respect to the tetrahydropyrimidine ring [dihedral angle 87.7 (2)°]; the conformation of the substituent on the exocyclic C4—C7 bond is synperiplanar, i.e. the hydroxy group is on the same side as the H atom on C4 (Fig.1). The ester group on C5 lies approximately in the plane of the C5=C6 double bond, with the carbonyl function oriented cis relative to this double bond. By contrast, the ethoxycarbonyl moiety of the 6-substituent is oriented, due to rather free rotation about the two C16 methylenic bonds, perpendicularly with respect to the mean plane of the heterocycle.
The crystal packing is dominated by hydrogen bonding. As shown in Table 2 and Fig. 3, each molecule forms two pairs of hydrogen bonds (N1-H···O1 and O2-H···O3) across centres of symmetry, which results in formation of chains of hydrogen-bonded molecules. The chains are interconnected by another independent hydrogen bond, N3-H···O5.