Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801006493/ci6021sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536801006493/ci6021Isup2.hkl |
CCDC reference: 165662
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (C-C) = 0.003 Å
- R factor = 0.028
- wR factor = 0.076
- Data-to-parameter ratio = 8.2
checkCIF results
No syntax errors found ADDSYM reports no extra symmetry General Notes
REFLT_03 From the CIF: _diffrn_reflns_theta_max 71.90 From the CIF: _reflns_number_total 2499 Count of symmetry unique reflns 1945 Completeness (_total/calc) 128.48% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 554 Fraction of Friedel pairs measured 0.285 Are heavy atom types Z>Si present no WARNING: CuKa measured Friedel data can be used to determine absolute structure in a light-atom study only if the Friedel fraction is large.
The synthesize of (III) has been reported elsewhere (Bourry et al., 2001). Crystals were obtained by slow evaporation of a methanol solution at room temperature.
Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1992); cell refinement: CAD-4 EXPRESS; data reduction: PLATON (Spek, 2001); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2001); software used to prepare material for publication: SHELXL97.
Fig. 1. ORTEPII (Johnson, 1976) representation of compound (III) with ellipsoids at the 50% probability level. |
C18H20N2O6 | Dx = 1.393 Mg m−3 |
Mr = 360.36 | Cu Kα radiation, λ = 1.54178 Å |
Orthorhombic, P212121 | Cell parameters from 25 reflections |
a = 9.077 (1) Å | θ = 38–42° |
b = 11.065 (1) Å | µ = 0.89 mm−1 |
c = 17.106 (1) Å | T = 293 K |
V = 1718.1 (3) Å3 | Prism, colorless |
Z = 4 | 0.40 × 0.30 × 0.20 mm |
F(000) = 760 |
Enraf Nonius CAD-4 diffractometer | 2443 reflections with I > 2σ(I) |
Radiation source: long fine-focus sealed tube | Rint = 0.017 |
Graphite monochromator | θmax = 71.9°, θmin = 4.8° |
θ/2θ scans | h = −11→11 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→13 |
Tmin = 0.718, Tmax = 0.843 | l = 0→21 |
2767 measured reflections | 3 standard reflections every 200 reflections |
2499 independent reflections | intensity decay: 2% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.028 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.076 | w = 1/[σ2(Fo2) + (0.048P)2 + 0.307P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max = 0.002 |
2499 reflections | Δρmax = 0.15 e Å−3 |
304 parameters | Δρmin = −0.15 e Å−3 |
0 restraints | Absolute structure: Flack (1983) |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.02 (19) |
C18H20N2O6 | V = 1718.1 (3) Å3 |
Mr = 360.36 | Z = 4 |
Orthorhombic, P212121 | Cu Kα radiation |
a = 9.077 (1) Å | µ = 0.89 mm−1 |
b = 11.065 (1) Å | T = 293 K |
c = 17.106 (1) Å | 0.40 × 0.30 × 0.20 mm |
Enraf Nonius CAD-4 diffractometer | 2443 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.017 |
Tmin = 0.718, Tmax = 0.843 | 3 standard reflections every 200 reflections |
2767 measured reflections | intensity decay: 2% |
2499 independent reflections |
R[F2 > 2σ(F2)] = 0.028 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.076 | Δρmax = 0.15 e Å−3 |
S = 1.03 | Δρmin = −0.15 e Å−3 |
2499 reflections | Absolute structure: Flack (1983) |
304 parameters | Absolute structure parameter: 0.02 (19) |
0 restraints |
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 | ||
O4 | 0.65292 (15) | −0.07332 (10) | 0.31666 (7) | 0.0417 (3) | |
O1 | 1.02055 (14) | 0.02901 (12) | 0.23901 (7) | 0.0456 (3) | |
O6 | 0.73025 (15) | 0.41152 (11) | 0.23706 (8) | 0.0442 (3) | |
O5 | 0.83230 (17) | 0.27203 (13) | 0.31446 (9) | 0.0571 (4) | |
O3 | 0.83223 (16) | 0.18354 (12) | −0.04648 (7) | 0.0452 (3) | |
O2 | 1.00349 (16) | 0.06747 (13) | 0.00935 (7) | 0.0525 (4) | |
N15 | 0.65467 (15) | 0.09593 (11) | 0.24057 (7) | 0.0308 (3) | |
N9 | 0.86115 (15) | 0.11939 (12) | 0.15461 (7) | 0.0300 (3) | |
C5 | 0.63993 (18) | 0.00644 (14) | 0.10766 (9) | 0.0310 (3) | |
C10 | 0.99349 (18) | 0.10759 (15) | 0.19085 (9) | 0.0340 (3) | |
C14 | 0.90850 (19) | 0.14268 (15) | 0.01317 (9) | 0.0333 (3) | |
C20 | 0.7383 (2) | 0.30329 (16) | 0.26952 (10) | 0.0362 (4) | |
C19 | 0.61078 (18) | 0.22276 (15) | 0.24416 (10) | 0.0337 (4) | |
C13 | 0.86715 (19) | 0.20578 (15) | 0.08980 (9) | 0.0312 (3) | |
C12 | 0.9975 (2) | 0.28767 (16) | 0.11357 (10) | 0.0378 (4) | |
C2 | 0.4604 (2) | −0.08132 (17) | −0.01366 (11) | 0.0430 (4) | |
C16 | 0.61977 (18) | 0.03318 (15) | 0.30564 (9) | 0.0336 (4) | |
C6 | 0.4916 (2) | 0.03643 (16) | 0.10346 (11) | 0.0396 (4) | |
C8 | 0.73798 (17) | 0.04173 (15) | 0.17618 (9) | 0.0295 (3) | |
C17 | 0.5348 (2) | 0.11439 (18) | 0.35939 (11) | 0.0427 (4) | |
C11 | 1.0951 (2) | 0.20481 (19) | 0.16222 (11) | 0.0427 (4) | |
C7 | 0.4044 (2) | −0.00690 (19) | 0.04351 (13) | 0.0461 (4) | |
C4 | 0.6967 (2) | −0.06930 (17) | 0.05058 (11) | 0.0400 (4) | |
C3 | 0.6090 (2) | −0.11197 (19) | −0.00953 (11) | 0.0463 (5) | |
C18 | 0.4913 (2) | 0.22025 (17) | 0.30842 (11) | 0.0429 (4) | |
C1 | 0.3655 (3) | −0.1274 (2) | −0.07933 (12) | 0.0612 (6) | |
H1A | 0.2791 | −0.1652 | −0.0581 | 0.092* | |
H1B | 0.4200 | −0.1852 | −0.1096 | 0.092* | |
H1C | 0.3368 | −0.0611 | −0.1122 | 0.092* | |
H501 | 0.7800 (19) | −0.0312 (16) | 0.1973 (10) | 0.027 (4)* | |
H502 | 0.449 (2) | 0.0796 (19) | 0.1425 (12) | 0.042 (5)* | |
H503 | 0.394 (3) | 0.207 (2) | 0.2831 (12) | 0.051 (6)* | |
H504 | 0.957 (2) | 0.355 (2) | 0.1456 (12) | 0.047 (5)* | |
H505 | 0.306 (3) | 0.012 (2) | 0.0440 (14) | 0.057 (6)* | |
H506 | 0.800 (2) | −0.0943 (18) | 0.0533 (11) | 0.044 (5)* | |
H507 | 0.576 (2) | 0.2520 (15) | 0.1947 (11) | 0.030 (4)* | |
H508 | 1.047 (2) | 0.3168 (19) | 0.0683 (12) | 0.048 (6)* | |
H509 | 0.776 (2) | 0.2496 (15) | 0.0843 (11) | 0.029 (4)* | |
H510 | 0.854 (3) | 0.146 (2) | −0.0888 (13) | 0.052 (6)* | |
H511 | 1.140 (2) | 0.2421 (18) | 0.2059 (13) | 0.047 (6)* | |
H512 | 0.647 (3) | −0.1681 (19) | −0.0488 (12) | 0.052 (6)* | |
H513 | 1.172 (3) | 0.164 (2) | 0.1314 (14) | 0.065 (7)* | |
H514 | 0.491 (3) | 0.294 (2) | 0.3353 (13) | 0.058 (6)* | |
H515 | 0.815 (3) | 0.455 (2) | 0.2473 (14) | 0.067 (7)* | |
H516 | 0.463 (3) | 0.077 (2) | 0.3791 (13) | 0.058 (7)* | |
H517 | 0.595 (3) | 0.137 (2) | 0.4025 (14) | 0.061 (7)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O4 | 0.0551 (7) | 0.0347 (6) | 0.0352 (6) | 0.0043 (6) | 0.0087 (6) | 0.0066 (5) |
O1 | 0.0415 (7) | 0.0525 (7) | 0.0429 (6) | 0.0090 (6) | −0.0066 (6) | 0.0120 (6) |
O6 | 0.0425 (7) | 0.0330 (6) | 0.0571 (8) | −0.0037 (6) | −0.0077 (6) | 0.0023 (6) |
O5 | 0.0598 (9) | 0.0501 (8) | 0.0615 (8) | −0.0040 (7) | −0.0244 (8) | 0.0071 (7) |
O3 | 0.0597 (8) | 0.0449 (7) | 0.0309 (6) | 0.0079 (7) | −0.0107 (6) | −0.0007 (6) |
O2 | 0.0512 (7) | 0.0657 (8) | 0.0407 (7) | 0.0206 (7) | −0.0054 (6) | −0.0103 (6) |
N15 | 0.0339 (6) | 0.0288 (6) | 0.0296 (6) | 0.0012 (6) | 0.0031 (6) | 0.0009 (5) |
N9 | 0.0293 (6) | 0.0331 (7) | 0.0275 (6) | 0.0010 (6) | −0.0004 (5) | 0.0030 (5) |
C5 | 0.0335 (8) | 0.0279 (7) | 0.0315 (7) | −0.0046 (7) | 0.0017 (7) | 0.0040 (6) |
C10 | 0.0322 (8) | 0.0407 (8) | 0.0292 (7) | 0.0048 (8) | −0.0009 (7) | −0.0032 (7) |
C14 | 0.0329 (8) | 0.0355 (8) | 0.0315 (8) | −0.0024 (7) | −0.0026 (7) | 0.0039 (7) |
C20 | 0.0401 (9) | 0.0342 (8) | 0.0343 (8) | 0.0039 (7) | 0.0019 (8) | −0.0025 (7) |
C19 | 0.0365 (9) | 0.0309 (8) | 0.0338 (8) | 0.0042 (7) | 0.0004 (7) | −0.0006 (7) |
C13 | 0.0301 (8) | 0.0319 (8) | 0.0316 (8) | 0.0022 (7) | 0.0011 (7) | 0.0042 (7) |
C12 | 0.0390 (9) | 0.0351 (8) | 0.0392 (9) | −0.0050 (8) | 0.0043 (8) | −0.0005 (8) |
C2 | 0.0478 (10) | 0.0436 (9) | 0.0376 (9) | −0.0129 (8) | −0.0036 (8) | 0.0032 (8) |
C16 | 0.0336 (8) | 0.0366 (8) | 0.0305 (8) | −0.0007 (7) | 0.0008 (7) | 0.0002 (7) |
C6 | 0.0384 (9) | 0.0390 (9) | 0.0415 (9) | 0.0031 (8) | 0.0016 (8) | −0.0050 (8) |
C8 | 0.0315 (8) | 0.0270 (7) | 0.0299 (8) | 0.0025 (6) | 0.0017 (6) | 0.0027 (6) |
C17 | 0.0430 (10) | 0.0477 (11) | 0.0376 (9) | 0.0021 (9) | 0.0099 (8) | −0.0012 (8) |
C11 | 0.0348 (9) | 0.0512 (11) | 0.0421 (9) | −0.0067 (8) | −0.0042 (8) | −0.0008 (9) |
C7 | 0.0362 (9) | 0.0505 (11) | 0.0514 (10) | 0.0012 (8) | −0.0063 (9) | 0.0022 (9) |
C4 | 0.0345 (9) | 0.0400 (9) | 0.0454 (9) | −0.0044 (8) | 0.0050 (8) | −0.0070 (8) |
C3 | 0.0481 (11) | 0.0487 (11) | 0.0421 (10) | −0.0127 (9) | 0.0067 (9) | −0.0140 (9) |
C18 | 0.0396 (10) | 0.0409 (9) | 0.0483 (10) | 0.0056 (8) | 0.0088 (9) | −0.0033 (9) |
C1 | 0.0625 (14) | 0.0718 (14) | 0.0493 (11) | −0.0168 (12) | −0.0105 (11) | −0.0028 (11) |
O4—C16 | 1.231 (2) | C12—C11 | 1.522 (3) |
O1—C10 | 1.223 (2) | C12—H504 | 1.00 (2) |
O6—C20 | 1.322 (2) | C12—H508 | 0.95 (2) |
O6—H515 | 0.92 (3) | C2—C7 | 1.376 (3) |
O5—C20 | 1.199 (2) | C2—C3 | 1.393 (3) |
O3—C14 | 1.313 (2) | C2—C1 | 1.505 (3) |
O3—H510 | 0.86 (2) | C16—C17 | 1.499 (2) |
O2—C14 | 1.200 (2) | C6—C7 | 1.382 (3) |
N15—C16 | 1.350 (2) | C6—H502 | 0.91 (2) |
N15—C19 | 1.460 (2) | C8—H501 | 0.963 (18) |
N15—C8 | 1.465 (2) | C17—C18 | 1.513 (3) |
N9—C10 | 1.358 (2) | C17—H516 | 0.84 (3) |
N9—C8 | 1.458 (2) | C17—H517 | 0.95 (3) |
N9—C13 | 1.465 (2) | C11—H511 | 0.95 (2) |
C5—C4 | 1.386 (2) | C11—H513 | 0.99 (3) |
C5—C6 | 1.388 (2) | C7—H505 | 0.91 (2) |
C5—C8 | 1.523 (2) | C4—C3 | 1.383 (3) |
C10—C11 | 1.499 (3) | C4—H506 | 0.98 (2) |
C14—C13 | 1.532 (2) | C3—H512 | 0.98 (2) |
C20—C19 | 1.524 (2) | C18—H503 | 1.00 (2) |
C19—C18 | 1.544 (2) | C18—H514 | 0.94 (2) |
C19—H507 | 0.959 (19) | C1—H1A | 0.9600 |
C13—C12 | 1.545 (2) | C1—H1B | 0.9600 |
C13—H509 | 0.963 (19) | C1—H1C | 0.9600 |
C20—O6—H515 | 110.4 (15) | N15—C16—C17 | 108.55 (14) |
C14—O3—H510 | 111.4 (15) | C7—C6—C5 | 120.75 (18) |
C16—N15—C19 | 113.31 (13) | C7—C6—H502 | 119.2 (12) |
C16—N15—C8 | 122.06 (13) | C5—C6—H502 | 119.8 (12) |
C19—N15—C8 | 124.48 (13) | N9—C8—N15 | 110.18 (13) |
C10—N9—C8 | 120.42 (13) | N9—C8—C5 | 113.87 (12) |
C10—N9—C13 | 112.05 (13) | N15—C8—C5 | 112.47 (13) |
C8—N9—C13 | 127.21 (13) | N9—C8—H501 | 106.6 (10) |
C4—C5—C6 | 117.95 (16) | N15—C8—H501 | 105.3 (10) |
C4—C5—C8 | 118.68 (15) | C5—C8—H501 | 107.8 (10) |
C6—C5—C8 | 123.05 (15) | C16—C17—C18 | 104.17 (15) |
O1—C10—N9 | 123.62 (15) | C16—C17—H516 | 110.8 (17) |
O1—C10—C11 | 127.36 (15) | C18—C17—H516 | 113.9 (16) |
N9—C10—C11 | 109.02 (14) | C16—C17—H517 | 109.4 (15) |
O2—C14—O3 | 125.11 (16) | C18—C17—H517 | 113.4 (16) |
O2—C14—C13 | 122.59 (15) | H516—C17—H517 | 105 (2) |
O3—C14—C13 | 112.26 (14) | C10—C11—C12 | 104.65 (14) |
O5—C20—O6 | 124.75 (17) | C10—C11—H511 | 108.7 (12) |
O5—C20—C19 | 123.65 (16) | C12—C11—H511 | 114.9 (13) |
O6—C20—C19 | 111.59 (15) | C10—C11—H513 | 106.1 (14) |
N15—C19—C20 | 111.51 (14) | C12—C11—H513 | 113.5 (14) |
N15—C19—C18 | 101.78 (13) | H511—C11—H513 | 108.6 (19) |
C20—C19—C18 | 109.96 (14) | C2—C7—C6 | 121.54 (19) |
N15—C19—H507 | 112.2 (10) | C2—C7—H505 | 120.1 (15) |
C20—C19—H507 | 107.7 (10) | C6—C7—H505 | 118.3 (16) |
C18—C19—H507 | 113.7 (11) | C3—C4—C5 | 121.07 (18) |
N9—C13—C14 | 111.06 (13) | C3—C4—H506 | 119.4 (12) |
N9—C13—C12 | 102.24 (13) | C5—C4—H506 | 119.6 (12) |
C14—C13—C12 | 107.75 (14) | C4—C3—C2 | 120.78 (18) |
N9—C13—H509 | 111.7 (11) | C4—C3—H512 | 121.5 (14) |
C14—C13—H509 | 110.9 (11) | C2—C3—H512 | 117.6 (14) |
C12—C13—H509 | 112.8 (10) | C17—C18—C19 | 103.95 (14) |
C11—C12—C13 | 103.66 (14) | C17—C18—H503 | 111.5 (13) |
C11—C12—H504 | 111.5 (12) | C19—C18—H503 | 108.6 (12) |
C13—C12—H504 | 107.4 (12) | C17—C18—H514 | 113.1 (13) |
C11—C12—H508 | 111.8 (13) | C19—C18—H514 | 109.6 (15) |
C13—C12—H508 | 110.4 (12) | H503—C18—H514 | 110 (2) |
H504—C12—H508 | 111.7 (17) | C2—C1—H1A | 109.5 |
C7—C2—C3 | 117.90 (17) | C2—C1—H1B | 109.5 |
C7—C2—C1 | 121.43 (19) | H1A—C1—H1B | 109.5 |
C3—C2—C1 | 120.7 (2) | C2—C1—H1C | 109.5 |
O4—C16—N15 | 124.16 (15) | H1A—C1—H1C | 109.5 |
O4—C16—C17 | 127.28 (16) | H1B—C1—H1C | 109.5 |
C8—N9—C10—O1 | 4.5 (2) | C10—N9—C8—N15 | 88.46 (17) |
C13—N9—C10—O1 | −169.40 (15) | C13—N9—C8—N15 | −98.66 (17) |
C8—N9—C10—C11 | −175.30 (14) | C10—N9—C8—C5 | −144.11 (15) |
C13—N9—C10—C11 | 10.81 (19) | C13—N9—C8—C5 | 28.8 (2) |
C16—N15—C19—C20 | 96.67 (16) | C16—N15—C8—N9 | −129.78 (15) |
C8—N15—C19—C20 | −79.00 (18) | C19—N15—C8—N9 | 45.53 (19) |
C16—N15—C19—C18 | −20.52 (18) | C16—N15—C8—C5 | 102.01 (17) |
C8—N15—C19—C18 | 163.80 (15) | C19—N15—C8—C5 | −82.68 (18) |
O5—C20—C19—N15 | −33.3 (2) | C4—C5—C8—N9 | 67.95 (19) |
O6—C20—C19—N15 | 147.95 (15) | C6—C5—C8—N9 | −118.78 (16) |
O5—C20—C19—C18 | 78.9 (2) | C4—C5—C8—N15 | −165.81 (14) |
O6—C20—C19—C18 | −99.93 (16) | C6—C5—C8—N15 | 7.5 (2) |
C10—N9—C13—C14 | 89.68 (16) | O4—C16—C17—C18 | −165.01 (18) |
C8—N9—C13—C14 | −83.70 (19) | N15—C16—C17—C18 | 14.4 (2) |
C10—N9—C13—C12 | −25.02 (17) | O1—C10—C11—C12 | −171.22 (17) |
C8—N9—C13—C12 | 161.60 (14) | N9—C10—C11—C12 | 8.6 (2) |
O2—C14—C13—N9 | −42.7 (2) | C13—C12—C11—C10 | −22.94 (18) |
O3—C14—C13—N9 | 139.52 (14) | C3—C2—C7—C6 | −0.1 (3) |
O2—C14—C13—C12 | 68.5 (2) | C1—C2—C7—C6 | −179.37 (19) |
O3—C14—C13—C12 | −109.27 (16) | C5—C6—C7—C2 | 0.3 (3) |
N9—C13—C12—C11 | 28.42 (17) | C6—C5—C4—C3 | 1.1 (3) |
C14—C13—C12—C11 | −88.68 (16) | C8—C5—C4—C3 | 174.77 (16) |
C19—N15—C16—O4 | −176.29 (16) | C5—C4—C3—C2 | −1.0 (3) |
C8—N15—C16—O4 | −0.5 (3) | C7—C2—C3—C4 | 0.4 (3) |
C19—N15—C16—C17 | 4.3 (2) | C1—C2—C3—C4 | 179.70 (19) |
C8—N15—C16—C17 | −179.89 (15) | C16—C17—C18—C19 | −26.0 (2) |
C4—C5—C6—C7 | −0.8 (3) | N15—C19—C18—C17 | 27.80 (18) |
C8—C5—C6—C7 | −174.15 (16) | C20—C19—C18—C17 | −90.51 (18) |
Experimental details
Crystal data | |
Chemical formula | C18H20N2O6 |
Mr | 360.36 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 293 |
a, b, c (Å) | 9.077 (1), 11.065 (1), 17.106 (1) |
V (Å3) | 1718.1 (3) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.89 |
Crystal size (mm) | 0.40 × 0.30 × 0.20 |
Data collection | |
Diffractometer | Enraf Nonius CAD-4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.718, 0.843 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2767, 2499, 2443 |
Rint | 0.017 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.076, 1.03 |
No. of reflections | 2499 |
No. of parameters | 304 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.15, −0.15 |
Absolute structure | Flack (1983) |
Absolute structure parameter | 0.02 (19) |
Computer programs: CAD-4 EXPRESS (Enraf-Nonius, 1992), CAD-4 EXPRESS, PLATON (Spek, 2001), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 1997), SHELXL97.
Azatoxin, an anticancer drug, is an inhibitor of both topoisomerase II and tubulin polymerization (Leteurtre et al., 1995). Recently, the crystal structure of methyl N-[(4-methoxyphenyl)(3,4,5-trimethoxyphenyl)methyl]pyroglutamate, (I), an aryl derivative of a precursor of two azatoxin analogues, has been studied (Camus et al., 2000). This aryl compound presents mild anticancer properties (Bourry et al., 2001). During various attempts to obtain (I) stereoselectively, the reactivity of other reactants were tested and methyl 1-{[2-(methoxycarbonyl)-5-oxopyrrolidin-1-yl](3,4,5-trimethoxyphenyl)methyl}- pyroglutamate, (II), was obtained. The spatial structure of the diester (II) was confirmed by an X-ray analysis of a rather similar compound, NN-{[2-carboxy-5-oxopyrrolidin-1-yl](p-tolyl)methyl}pyroglutamic acid, (III).
In this compound, the sp2 hybridization of N9 and N15 is confirmed [sum of bond angles around N9 and N15 is 359.7 (1) and 359.8 (1)° respectively]. Moreover, the torsion angle C19—N15—C8—N9 of 45.5 (2)° brings the C20-carrying carboxylic acid function just above the second pyrrolidine cycle. Furhermore, a π–π interaction orients the C14-carried carboxylic acid group just above the aromatic ring, imposing a torsion angle C13—N9—C8—C5 of 28.8 (2)°.