Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101003250/gg1046sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101003250/gg10461sup2.hkl |
CCDC reference: 164665
For related literature, see: Allen & Kennard (1993); Cottam et al. (1996); Ferrand et al. (1996); Hueso-Ureña, Jiménez-Pulido, Moreno-Carretero, Quirós-Olazábal & Salas-Peregrín (1998a, 1998b, 1999); Lang et al. (1995); Molina et al. (1999); Norrestam et al. (1972); Ochoa et al. (1996).
A sample of (1) was prepared according to the published method of Molina et al. (1999). Crystals of (1).DMSO suitable for single-crystal X-ray diffraction were grown from a solution of (1) in DMSO.
The title compound crystallized in the triclinic system, and space group P1 was assumed and confirmed by the analysis. H atoms were treated as riding atoms, with C—H distances of 0.98 (CH3) or 0.99 Å (CH2), except for H7, whose position was located on a difference map and thereafter kept fixed.
Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2001); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).
C11H12N4O5·C2H6OS | Z = 2 |
Mr = 358.37 | F(000) = 376 |
Triclinic, P1 | Dx = 1.457 Mg m−3 |
a = 8.8926 (2) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 10.2539 (2) Å | Cell parameters from 3282 reflections |
c = 10.8500 (4) Å | θ = 2.9–27.1° |
α = 62.2233 (10)° | µ = 0.24 mm−1 |
β = 82.4797 (10)° | T = 150 K |
γ = 69.1050 (14)° | Lath, colourless |
V = 817.03 (4) Å3 | 0.25 × 0.10 × 0.10 mm |
KappaCCD diffractometer | 3528 independent reflections |
Radiation source: fine-focus sealed X-ray tube | 2790 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.037 |
ϕ scans, and ω scans with κ offsets | θmax = 27.0°, θmin = 3.2° |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | h = −11→11 |
Tmin = 0.943, Tmax = 0.977 | k = −13→13 |
7717 measured reflections | l = −13→13 |
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)] = 0.045 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.121 | H-atom parameters constrained |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0602P)2 + 0.1126P] where P = (Fo2 + 2Fc2)/3 |
3528 reflections | (Δ/σ)max = 0.001 |
222 parameters | Δρmax = 0.26 e Å−3 |
0 restraints | Δρmin = −0.47 e Å−3 |
C11H12N4O5·C2H6OS | γ = 69.1050 (14)° |
Mr = 358.37 | V = 817.03 (4) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.8926 (2) Å | Mo Kα radiation |
b = 10.2539 (2) Å | µ = 0.24 mm−1 |
c = 10.8500 (4) Å | T = 150 K |
α = 62.2233 (10)° | 0.25 × 0.10 × 0.10 mm |
β = 82.4797 (10)° |
KappaCCD diffractometer | 3528 independent reflections |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | 2790 reflections with I > 2σ(I) |
Tmin = 0.943, Tmax = 0.977 | Rint = 0.037 |
7717 measured reflections |
R[F2 > 2σ(F2)] = 0.045 | 0 restraints |
wR(F2) = 0.121 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.26 e Å−3 |
3528 reflections | Δρmin = −0.47 e Å−3 |
222 parameters |
Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm [Fox, G·C. & Holmes, K·C. (1966). Acta Cryst. 20, 886–891]which effectively corrects for absorption effects. High redundancy data were used in the scaling program hence the 'multi-scan' code word was used. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size' command in the SHELXL97 input file. |
Geometry. Mean-plane data from the final SHELXL97 refinement run:- |
x | y | z | Uiso*/Ueq | ||
N1 | 0.20984 (17) | 0.78664 (15) | 0.49222 (15) | 0.0223 (3) | |
C11 | 0.2364 (2) | 0.62775 (19) | 0.6044 (2) | 0.0315 (4) | |
C2 | 0.19117 (19) | 0.81001 (19) | 0.35871 (19) | 0.0225 (4) | |
O2 | 0.19373 (15) | 0.70316 (14) | 0.33631 (14) | 0.0311 (3) | |
N3 | 0.16521 (17) | 0.96046 (16) | 0.25231 (15) | 0.0228 (3) | |
C31 | 0.1448 (2) | 0.9872 (2) | 0.1094 (2) | 0.0312 (4) | |
C4 | 0.1674 (2) | 1.08632 (19) | 0.26898 (19) | 0.0230 (4) | |
C4a | 0.18943 (19) | 1.05304 (18) | 0.41223 (18) | 0.0197 (4) | |
O4 | 0.14977 (17) | 1.21352 (14) | 0.16784 (13) | 0.0344 (3) | |
N5 | 0.18648 (16) | 1.17123 (15) | 0.43783 (15) | 0.0216 (3) | |
C6 | 0.20671 (19) | 1.13969 (18) | 0.56744 (18) | 0.0203 (4) | |
C61 | 0.1968 (2) | 1.26821 (19) | 0.60216 (19) | 0.0241 (4) | |
O61 | 0.47876 (16) | 1.17528 (19) | 0.65920 (17) | 0.0440 (4) | |
C62 | 0.3422 (2) | 1.23076 (19) | 0.68481 (19) | 0.0249 (4) | |
O62 | 0.30103 (14) | 1.27098 (14) | 0.78809 (13) | 0.0270 (3) | |
C63 | 0.4326 (3) | 1.2460 (2) | 0.8712 (2) | 0.0394 (5) | |
C7 | 0.2319 (2) | 0.98491 (19) | 0.67638 (18) | 0.0215 (4) | |
O7 | 0.25198 (16) | 0.95999 (14) | 0.80495 (13) | 0.0288 (3) | |
N8 | 0.23388 (17) | 0.86859 (16) | 0.65320 (15) | 0.0220 (3) | |
C8a | 0.21190 (19) | 0.90451 (18) | 0.51996 (18) | 0.0190 (4) | |
S1 | 0.25987 (6) | 0.54432 (5) | 1.05050 (5) | 0.02738 (16) | |
C71 | 0.0732 (2) | 0.5694 (2) | 1.1328 (2) | 0.0313 (4) | |
C72 | 0.3856 (2) | 0.4063 (2) | 1.2018 (2) | 0.0391 (5) | |
O1 | 0.29834 (17) | 0.69205 (14) | 1.00686 (13) | 0.0348 (3) | |
H111 | 0.1554 | 0.5883 | 0.5948 | 0.047* | |
H112 | 0.2274 | 0.6293 | 0.6947 | 0.047* | |
H113 | 0.3442 | 0.5593 | 0.5987 | 0.047* | |
H311 | 0.1745 | 0.8864 | 0.1078 | 0.047* | |
H312 | 0.2142 | 1.0451 | 0.0482 | 0.047* | |
H313 | 0.0321 | 1.0482 | 0.0767 | 0.047* | |
H611 | 0.1847 | 1.3658 | 0.5145 | 0.029* | |
H612 | 0.0997 | 1.2871 | 0.6561 | 0.029* | |
H631 | 0.4952 | 1.1340 | 0.9178 | 0.059* | |
H632 | 0.3894 | 1.2830 | 0.9413 | 0.059* | |
H633 | 0.5023 | 1.3039 | 0.8107 | 0.059* | |
H7 | 0.2670 | 0.8445 | 0.8803 | 0.035* | |
H711 | −0.0141 | 0.6436 | 1.0621 | 0.047* | |
H712 | 0.0746 | 0.6102 | 1.1981 | 0.047* | |
H713 | 0.0558 | 0.4684 | 1.1836 | 0.047* | |
H721 | 0.4984 | 0.3812 | 1.1759 | 0.059* | |
H722 | 0.3572 | 0.3108 | 1.2460 | 0.059* | |
H723 | 0.3709 | 0.4505 | 1.2672 | 0.059* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0283 (8) | 0.0203 (7) | 0.0226 (8) | −0.0112 (6) | 0.0017 (6) | −0.0111 (6) |
C11 | 0.0483 (12) | 0.0204 (9) | 0.0274 (11) | −0.0163 (8) | 0.0001 (9) | −0.0082 (8) |
C2 | 0.0200 (9) | 0.0252 (8) | 0.0273 (10) | −0.0091 (7) | 0.0015 (7) | −0.0150 (8) |
O2 | 0.0406 (8) | 0.0296 (7) | 0.0345 (8) | −0.0168 (6) | 0.0033 (6) | −0.0204 (6) |
N3 | 0.0257 (8) | 0.0239 (7) | 0.0220 (8) | −0.0077 (6) | −0.0024 (6) | −0.0127 (6) |
C31 | 0.0385 (11) | 0.0335 (10) | 0.0263 (10) | −0.0093 (9) | −0.0037 (8) | −0.0180 (9) |
C4 | 0.0244 (9) | 0.0217 (8) | 0.0243 (10) | −0.0075 (7) | −0.0014 (7) | −0.0110 (8) |
C4a | 0.0203 (8) | 0.0197 (8) | 0.0211 (9) | −0.0075 (7) | 0.0000 (7) | −0.0099 (7) |
O4 | 0.0549 (9) | 0.0244 (7) | 0.0222 (7) | −0.0137 (6) | −0.0056 (6) | −0.0073 (6) |
N5 | 0.0225 (7) | 0.0207 (7) | 0.0234 (8) | −0.0085 (6) | 0.0012 (6) | −0.0106 (6) |
C6 | 0.0191 (8) | 0.0201 (8) | 0.0230 (9) | −0.0064 (7) | 0.0005 (7) | −0.0107 (7) |
C61 | 0.0281 (9) | 0.0212 (8) | 0.0258 (10) | −0.0082 (7) | 0.0005 (7) | −0.0128 (7) |
O61 | 0.0260 (8) | 0.0636 (10) | 0.0617 (11) | −0.0150 (7) | 0.0093 (7) | −0.0457 (9) |
C62 | 0.0288 (10) | 0.0219 (8) | 0.0297 (10) | −0.0123 (7) | 0.0050 (8) | −0.0145 (8) |
O62 | 0.0300 (7) | 0.0289 (6) | 0.0283 (7) | −0.0099 (5) | −0.0016 (5) | −0.0172 (6) |
C63 | 0.0417 (12) | 0.0438 (12) | 0.0398 (13) | −0.0138 (10) | −0.0104 (9) | −0.0218 (10) |
C7 | 0.0224 (8) | 0.0237 (8) | 0.0219 (9) | −0.0097 (7) | 0.0037 (7) | −0.0124 (7) |
O7 | 0.0462 (8) | 0.0245 (6) | 0.0192 (7) | −0.0150 (6) | 0.0012 (6) | −0.0103 (5) |
N8 | 0.0259 (8) | 0.0221 (7) | 0.0212 (8) | −0.0107 (6) | 0.0020 (6) | −0.0106 (6) |
C8a | 0.0174 (8) | 0.0212 (8) | 0.0228 (9) | −0.0087 (7) | 0.0025 (6) | −0.0122 (7) |
S1 | 0.0375 (3) | 0.0246 (2) | 0.0236 (3) | −0.0140 (2) | 0.00578 (19) | −0.0123 (2) |
C71 | 0.0286 (10) | 0.0290 (9) | 0.0352 (11) | −0.0074 (8) | 0.0011 (8) | −0.0153 (9) |
C72 | 0.0287 (10) | 0.0299 (10) | 0.0411 (13) | −0.0105 (8) | 0.0020 (9) | −0.0019 (9) |
O1 | 0.0563 (9) | 0.0267 (7) | 0.0234 (7) | −0.0239 (6) | 0.0003 (6) | −0.0054 (6) |
N1—C2 | 1.376 (2) | C31—H311 | 0.9800 |
C2—N3 | 1.386 (2) | C31—H312 | 0.9800 |
N3—C4 | 1.391 (2) | C31—H313 | 0.9800 |
C4—C4a | 1.452 (2) | C6—C61 | 1.502 (2) |
N5—C4a | 1.355 (2) | C61—C62 | 1.501 (2) |
N5—C6 | 1.310 (2) | C61—H611 | 0.9900 |
C6—C7 | 1.426 (2) | C61—H612 | 0.9900 |
C7—N8 | 1.323 (2) | O62—C63 | 1.447 (2) |
N1—C8a | 1.381 (2) | C63—H631 | 0.9800 |
N8—C8a | 1.338 (2) | C63—H632 | 0.9800 |
C4a—C8a | 1.382 (2) | C63—H633 | 0.9800 |
C2—O2 | 1.220 (2) | O7—H7 | 1.050 |
C4—O4 | 1.223 (2) | S1—O1 | 1.5148 (13) |
C62—O61 | 1.200 (2) | S1—C72 | 1.770 (2) |
C62—O62 | 1.332 (2) | S1—C71 | 1.7723 (19) |
C7—O7 | 1.320 (2) | C71—H711 | 0.9800 |
N1—C11 | 1.464 (2) | C71—H712 | 0.9800 |
C11—H111 | 0.9800 | C71—H713 | 0.9800 |
C11—H112 | 0.9800 | C72—H721 | 0.9800 |
C11—H113 | 0.9800 | C72—H722 | 0.9800 |
N3—C31 | 1.467 (2) | C72—H723 | 0.9800 |
C2—N1—C8a | 122.15 (14) | C6—C61—H612 | 109.0 |
C2—N1—C11 | 116.88 (14) | H611—C61—H612 | 107.8 |
C8a—N1—C11 | 120.89 (15) | O61—C62—O62 | 124.12 (17) |
N1—C11—H111 | 109.5 | O61—C62—C61 | 124.41 (17) |
N1—C11—H112 | 109.5 | O62—C62—C61 | 111.45 (14) |
H111—C11—H112 | 109.5 | C62—O62—C63 | 116.13 (15) |
N1—C11—H113 | 109.5 | O62—C63—H631 | 109.5 |
H111—C11—H113 | 109.5 | O62—C63—H632 | 109.5 |
H112—C11—H113 | 109.5 | H631—C63—H632 | 109.5 |
O2—C2—N1 | 121.04 (16) | O62—C63—H633 | 109.5 |
O2—C2—N3 | 121.89 (17) | H631—C63—H633 | 109.5 |
N1—C2—N3 | 117.05 (14) | H632—C63—H633 | 109.5 |
C2—N3—C4 | 125.12 (15) | O7—C7—N8 | 119.82 (15) |
C2—N3—C31 | 117.68 (14) | O7—C7—C6 | 117.48 (15) |
C4—N3—C31 | 117.06 (14) | N8—C7—C6 | 122.70 (16) |
N3—C31—H311 | 109.5 | C7—O7—H7 | 113.6 |
N3—C31—H312 | 109.5 | C7—N8—C8a | 115.78 (15) |
H311—C31—H312 | 109.5 | N8—C8a—N1 | 117.35 (14) |
N3—C31—H313 | 109.5 | N8—C8a—C4a | 122.67 (15) |
H311—C31—H313 | 109.5 | N1—C8a—C4a | 119.97 (15) |
H312—C31—H313 | 109.5 | O1—S1—C72 | 103.63 (9) |
O4—C4—N3 | 120.46 (16) | O1—S1—C71 | 106.23 (9) |
O4—C4—C4a | 124.74 (16) | C72—S1—C71 | 97.93 (9) |
N3—C4—C4a | 114.79 (14) | S1—C71—H711 | 109.5 |
N5—C4a—C8a | 120.82 (16) | S1—C71—H712 | 109.5 |
N5—C4a—C4 | 118.42 (14) | H711—C71—H712 | 109.5 |
C8a—C4a—C4 | 120.76 (15) | S1—C71—H713 | 109.5 |
C6—N5—C4a | 117.84 (14) | H711—C71—H713 | 109.5 |
N5—C6—C7 | 120.17 (15) | H712—C71—H713 | 109.5 |
N5—C6—C61 | 119.93 (15) | S1—C72—H721 | 109.5 |
C7—C6—C61 | 119.85 (15) | S1—C72—H722 | 109.5 |
C62—C61—C6 | 112.81 (14) | H721—C72—H722 | 109.5 |
C62—C61—H611 | 109.0 | S1—C72—H723 | 109.5 |
C6—C61—H611 | 109.0 | H721—C72—H723 | 109.5 |
C62—C61—H612 | 109.0 | H722—C72—H723 | 109.5 |
C8a—N1—C2—O2 | 178.16 (15) | C6—C61—C62—O62 | −137.11 (15) |
C11—N1—C2—O2 | 1.4 (2) | C7—C6—C61—C62 | 55.9 (2) |
C8a—N1—C2—N3 | −3.5 (2) | N5—C6—C61—C62 | −126.59 (17) |
C11—N1—C2—N3 | 179.70 (14) | O61—C62—O62—C63 | 0.7 (3) |
O2—C2—N3—C4 | −177.14 (16) | C61—C62—O62—C63 | −177.54 (15) |
N1—C2—N3—C4 | 4.5 (2) | N5—C6—C7—O7 | 179.82 (14) |
O2—C2—N3—C31 | −1.6 (2) | C61—C6—C7—O7 | −2.6 (2) |
N1—C2—N3—C31 | −179.91 (15) | N5—C6—C7—N8 | −0.9 (3) |
C2—N3—C4—O4 | 176.93 (15) | C61—C6—C7—N8 | 176.61 (15) |
C31—N3—C4—O4 | 1.4 (2) | O7—C7—N8—C8a | 179.73 (14) |
C2—N3—C4—C4a | −3.9 (2) | C6—C7—N8—C8a | 0.5 (2) |
C31—N3—C4—C4a | −179.42 (14) | C7—N8—C8a—N1 | −178.66 (14) |
O4—C4—C4a—N5 | 1.8 (3) | C7—N8—C8a—C4a | 0.4 (2) |
N3—C4—C4a—N5 | −177.41 (14) | C2—N1—C8a—N8 | −178.73 (14) |
O4—C4—C4a—C8a | −178.62 (16) | C11—N1—C8a—N8 | −2.1 (2) |
N3—C4—C4a—C8a | 2.2 (2) | C2—N1—C8a—C4a | 2.2 (2) |
C8a—C4a—N5—C6 | 0.5 (2) | C11—N1—C8a—C4a | 178.83 (15) |
C4—C4a—N5—C6 | −179.91 (14) | N5—C4a—C8a—N8 | −0.9 (3) |
C4a—N5—C6—C7 | 0.4 (2) | C4—C4a—C8a—N8 | 179.47 (15) |
C4a—N5—C6—C61 | −177.14 (14) | N5—C4a—C8a—N1 | 178.11 (14) |
C6—C61—C62—O61 | 44.7 (2) | C4—C4a—C8a—N1 | −1.5 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7···O1 | 1.05 | 1.48 | 2.517 (2) | 168 |
C31—H311···O1i | 0.98 | 2.56 | 3.472 (3) | 156 |
C61—H612···O2ii | 0.98 | 2.57 | 3.382 (2) | 140 |
C71—H711···O4ii | 0.98 | 2.44 | 3.362 (2) | 157 |
C71—H712···O2iii | 0.98 | 2.60 | 3.521 (2) | 157 |
Symmetry codes: (i) x, y, z−1; (ii) −x, −y+2, −z+1; (iii) x, y, z+1. |
Experimental details
Crystal data | |
Chemical formula | C11H12N4O5·C2H6OS |
Mr | 358.37 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 150 |
a, b, c (Å) | 8.8926 (2), 10.2539 (2), 10.8500 (4) |
α, β, γ (°) | 62.2233 (10), 82.4797 (10), 69.1050 (14) |
V (Å3) | 817.03 (4) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.24 |
Crystal size (mm) | 0.25 × 0.10 × 0.10 |
Data collection | |
Diffractometer | KappaCCD diffractometer |
Absorption correction | Multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.943, 0.977 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7717, 3528, 2790 |
Rint | 0.037 |
(sin θ/λ)max (Å−1) | 0.639 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.121, 1.05 |
No. of reflections | 3528 |
No. of parameters | 222 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.26, −0.47 |
Computer programs: KappaCCD Server Software (Nonius, 1997), DENZO-SMN (Otwinowski & Minor, 1997), DENZO-SMN, SHELXS97 (Sheldrick, 1997), PLATON (Spek, 2001), SHELXL97 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).
N1—C2 | 1.376 (2) | N1—C8a | 1.381 (2) |
C2—N3 | 1.386 (2) | N8—C8a | 1.338 (2) |
N3—C4 | 1.391 (2) | C4a—C8a | 1.382 (2) |
C4—C4a | 1.452 (2) | C2—O2 | 1.220 (2) |
N5—C4a | 1.355 (2) | C4—O4 | 1.223 (2) |
N5—C6 | 1.310 (2) | C62—O61 | 1.200 (2) |
C6—C7 | 1.426 (2) | C62—O62 | 1.332 (2) |
C7—N8 | 1.323 (2) | C7—O7 | 1.320 (2) |
C6—C61—C62—O61 | 44.7 (2) | C7—C6—C61—C62 | 55.9 (2) |
C6—C61—C62—O62 | −137.11 (15) | N5—C6—C61—C62 | −126.59 (17) |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7···O1 | 1.05 | 1.48 | 2.517 (2) | 168 |
C31—H311···O1i | 0.98 | 2.56 | 3.472 (3) | 156 |
C61—H612···O2ii | 0.98 | 2.57 | 3.382 (2) | 140 |
C71—H711···O4ii | 0.98 | 2.44 | 3.362 (2) | 157 |
C71—H712···O2iii | 0.98 | 2.60 | 3.521 (2) | 157 |
Symmetry codes: (i) x, y, z−1; (ii) −x, −y+2, −z+1; (iii) x, y, z+1. |
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Synthetic analogues of naturally occurring polyaza-heteroaromatic compounds, such as pteridines, are of considerable interest because of their extensive pharmaceutical potential, for example, as inhibitors of folic acid biosynthesis (Lang et al., 1995) and their action as antiallergic (Ferrand et al., 1996), antihelminthic (Ochoa et al., 1996), anti-inflammatory (Cottam et al., 1996) and antiviral agents (Molina et al., 1999). We report here the structure of one such synthetic pteridine, methyl 7-hydroxy-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydropteridine-6-carboxylate, C11H12N4O5, (1), which is a useful intermediate for the synthesis of folic acid analogues (Molina et al., 1999) and which crystallizes from dimethyl sulfoxide (DMSO) solution as the monosolvate, i.e. (1).DMSO.
The bond lengths within the heteroaromatic portion of the molecule show clearly that form (1) carrying a hydroxyl group at position 7 is the correct representation, as opposed to the possible alternative tautomer (1a). In particular, the C7—O7 distance is very similar to the C62—O62 distance in the ester portion and much greater than the C2—O2 and C4—O4 distances; secondly, the bond lengths in the pyrazine portion of the heterocycle indicate considerable aromatic delocalization, with C—N distances consistently shorter than those in the pyrimidinedione portion. Moreover, the hydroxyl group O7—H7 forms a rather short and strong O—H···O hydrogen bond with O1 in the DMSO component as hydrogen-bond acceptor (Table 2), which could favour tautomer (1) over (1a). The non-H atoms in (1) are virtually coplanar, apart from those in the methoxycarbonyl fragment (Table 1). Overall, the bond lengths in the heterocyclic ring are similar to those in the unsubstituted pteridine-2,4-dione (2) (Norrestam et al., 1972) and in methylated pteridinediones in a variety of metal complexes retrieved from the Cambridge Structural Database (CSD; Allen & Kennard, 1993), exemplified by PUSJUI (Hueso-Ureña et al., 1998a), GAZTOQ, GAZZOW and GEBKUT (Hueso-Ureña et al., 1998b), and LIVJIJ (Hueso-Ureña et al., 1999).
The molecules of (1) and DMSO are linked by a series of hydrogen bonds (Table 2) into chains of fused centrosymmetric rings. In addition to the O—H···O hydrogen bond within the asymmetric unit (Fig. 1), there are C—H···O hydrogen bonds which link pairs of such units into centrosymmetric four-component aggregates: atoms C61 and C71 in the asymmetric unit at (x, y, z) act as donors, via H612 and H711, respectively, to O2 and O4, both at (-x, 2 - y, 1 - z), so generating a centrosymmetric dimer in which the two individual hydrogen bonds generate R22(18) and R44(24) rings, respectively (Fig. 2). The effect of these mutually reinforcing C—H···O hydrogen bonds is further enhanced by aromatic π–π-stacking interactions between the two heteroaromatic rings within this cyclic aggregate; the perpendicular distance between the two ring planes is ca 3.41 Å, and the centroid offset between the pyrazine ring in one pteridine and the pyrimidine ring in the other is only ca 0.46 Å giving almost perfect overlap.
The four-component cyclic aggregates are linked into chains by a further pair of C—H···O hydrogen bonds: C31 at (x, y, z) acts as donor, via H311, to O1 at (x, y, -1 + z), while C71 at (x, y, -1 + z) acts as donor, via H712, to O2 at (x, y, z), so generating an R22(9) motif (Fig. 3). These interactions serve to link the cyclic aggregates (Fig. 2) into chains running parallel to the [001] direction, in which the cyclic aggregates are centred at (0, 1, 0.5+n) (n = zero or integer) and the rings between them are centred at (0, 1, n) (n = zero or integer).