Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101003316/da1159sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101003316/da1159Isup2.hkl |
CCDC reference: 164683
For related literature, see: Allen & Kennard (1993); Argay et al. (1997); Arigoni et al. (1995); Coterrell et al. (1970); Daly (1997); Griffin et al. (1984); Guang-Yi, Gray, Patalinghug, Skelton, Waterman & White (1989); Jain et al. (1995); Mohamad et al. (1999); Soriano-García, Toscano, Ortíz, Navarrete, Sanchez-Obregon, Barrios & Yuste (1987); Tessier et al. (1982); Watson et al. (1987).
The resin from Protium crenatum Sandwith was obtained by making incisions in the bark of trees found at the Forest Reserve of Ticoporo, Barinas State, Venezuela, at an altitude of about 200 m. The resin was dissolved in diethyl ether and filtered to remove solid impurities. It was then fractionated over silica gel, eluting with hexane and hexane–diethyl ether mixtures. Fractions eluted with 8% Et2O were subjected to preparative thin layer chromatography, yielding 310 mg of pure 3α-hydroxytirucalla-7,24-diene-21-oic acid (m.p. 473–475 K), suitable for X-ray analysis. Spectroscopic data: IR (KBr, νmax, cm-1): 3470, 1688; EIMS: M+, 456 (C30H48O3, 11°). Assignment of 1H NMR and 13C NMR signals was made by use of standard two-dimensional NMR techniques. 1H NMR (400 MHz, CDCl3, δ, p.p.m.): 5.24 (1H, br s, H7), 5.09 (1H, t, J = 7.2 Hz, H24), 3.50 (1H, br s, H3), 2.32 (1H, m, H9), 2.30 (1H, dt, J = 9.8, 4.1 Hz, H20), 2.05 (1H, d, J = 8.3 Hz, H6α), 1.99 (1H, m, H17), 1.96 (1H, m, H22a), 1.94 (1H, m, H23a), 1.90 (1H, m, H2α), 1.85 (1H, m, H22b), 1.77 (1H, m, H6β), 1.72 (1H, dd, J = 11.8, 5.6 Hz, H5), 1.70 (1H, m, H15α), 1.67 (3H, s, H27), 1.62 (1H, m, H23b), 1.60 (1H, dd, J = 3.2, 7.9 Hz), 1.57 (3H, s, H26), 1.52 (1H, m, H1α), 1.51 (1H, m, H15β), 1.45 (1H, m, H16α), 1.42 (1H, m, H12α), 1.40 (1H, m, H12β), 1.32 (1H, d, J = 3.2 Hz, H1β), 1.26 (1H, m, H11α), 0.95 (3H, s, H30), 0.94 (3H, s, H29), 0.92 (3H, s, H18), 0.84 (1H, m, H11β), 0.80 (3H, s, H28), 0.72 (3H, s, H19); 13C NMR (400 MHz, CDCl3, δ, p.p.m.): 181.8 (C21), 145.3 (C8), 132.1 (C25), 123.7 (C24), 118.2 (C7), 76.5 (C3), 51.0 (C14), 49.7 (C17), 48.2 (C9), 47.8 (C20), 44.5 (C5), 43.3 (C13), 37.3 (C4), 34.8 (C10), 33.4 (C12), 32.4 (C22), 31.2 (C1), 30.2 (C15), 27.7 (C28), 27.3 (C30), 27.0 (C11), 25.7 (C27), 25.3 (C2), 23.9 (C6), 21.8 (C18), 21.7 (C29), 17.6 (C26), 17.5 (C16), 12.9 (C19).
All H atoms were placed in geometrically calculated positions and their isotropic displacement parameters were set to 1.2 times (1.5 times for CH3 groups) the equivalent displacement parameter of their parent atoms.
Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: PLATON (Spek, 2000) and SHELXL97.
C30H48O3 | Dx = 1.106 Mg m−3 |
Mr = 456.68 | Mo Kα radiation, λ = 0.71073 Å |
Trigonal, P3121 | Cell parameters from 3464 reflections |
Hall symbol: P 31 2" | θ = 3.0–50.7° |
a = 11.3717 (6) Å | µ = 0.07 mm−1 |
c = 36.739 (3) Å | T = 293 K |
V = 4114.4 (4) Å3 | Plate, colourless |
Z = 6 | 0.4 × 0.3 × 0.3 mm |
F(000) = 1512 |
Siemens SMART CCD area-detector diffractometer | 1621 reflections with I > 2σ(I) |
Radiation source: normal-focus sealed tube | Rint = 0.088 |
Graphite monochromator | θmax = 25.4°, θmin = 1.7° |
ω scans | h = −11→13 |
22258 measured reflections | k = −13→13 |
2915 independent reflections | l = −44→44 |
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)] = 0.049 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.140 | H-atom parameters constrained |
S = 0.90 | Calculated w = 1/[σ2(Fo2) + (0.0844P)2] where P = (Fo2 + 2Fc2)/3 |
2915 reflections | (Δ/σ)max < 0.001 |
295 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.16 e Å−3 |
C30H48O3 | Z = 6 |
Mr = 456.68 | Mo Kα radiation |
Trigonal, P3121 | µ = 0.07 mm−1 |
a = 11.3717 (6) Å | T = 293 K |
c = 36.739 (3) Å | 0.4 × 0.3 × 0.3 mm |
V = 4114.4 (4) Å3 |
Siemens SMART CCD area-detector diffractometer | 1621 reflections with I > 2σ(I) |
22258 measured reflections | Rint = 0.088 |
2915 independent reflections |
R[F2 > 2σ(F2)] = 0.049 | 0 restraints |
wR(F2) = 0.140 | H-atom parameters constrained |
S = 0.90 | Δρmax = 0.20 e Å−3 |
2915 reflections | Δρmin = −0.16 e Å−3 |
295 parameters |
Experimental. X-ray data were collected on a Siemens SMART CCD diffractometer equipped with a normal focus 2.4 kW sealed tube X-ray source (Mo Kα radiation, λ = 0.71073 Å) operating at 40 kV and 30 mA. The data collection covered about 1.3 hemispheres of reciprocal space by a combination of three sets of exposures; each set had a different ϕ angle (0, 90, 180°) for the crystal and each exposure of 14 s covered 0.3° in ω to give a total of 1321 frames. The crystal-to-detector distance was 5.029 cm and the detector swing angle was 30°. Coverage of the unique set was over 99% complete. Crystal decay was monitored by repeating fifty frames from the initial set at the end of the data collection. |
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 | 0.6514 (3) | 0.8987 (4) | 0.1073 (1) | 0.117 (1) | |
O2 | 0.1191 (3) | 0.0090 (3) | 0.12822 (6) | 0.0665 (7) | |
O3 | −0.1017 (3) | −0.0722 (3) | 0.13326 (6) | 0.0682 (8) | |
C1 | 0.4061 (4) | 0.7267 (5) | 0.1486 (1) | 0.075 (1) | |
C2 | 0.5009 (5) | 0.8781 (5) | 0.1556 (1) | 0.089 (2) | |
C3 | 0.5726 (5) | 0.9507 (5) | 0.1210 (1) | 0.079 (1) | |
C4 | 0.4740 (4) | 0.9379 (4) | 0.0909 (1) | 0.067 (1) | |
C5 | 0.3720 (4) | 0.7848 (4) | 0.08495 (9) | 0.057 (1) | |
C6 | 0.2703 (4) | 0.7586 (4) | 0.0545 (1) | 0.080 (1) | |
C7 | 0.1735 (4) | 0.6115 (5) | 0.0489 (1) | 0.075 (1) | |
C8 | 0.1573 (4) | 0.5128 (4) | 0.07231 (9) | 0.056 (1) | |
C9 | 0.2395 (4) | 0.5477 (4) | 0.10661 (9) | 0.059 (1) | |
C10 | 0.2998 (4) | 0.6963 (4) | 0.11885 (9) | 0.058 (1) | |
C11 | 0.1717 (5) | 0.4400 (4) | 0.13608 (9) | 0.068 (1) | |
C12 | 0.1100 (5) | 0.2928 (4) | 0.12471 (9) | 0.066 (1) | |
C13 | 0.0957 (3) | 0.2698 (4) | 0.08331 (8) | 0.0511 (9) | |
C14 | 0.0501 (4) | 0.3658 (4) | 0.06645 (9) | 0.055 (1) | |
C15 | 0.0194 (5) | 0.3142 (4) | 0.0272 (1) | 0.077 (1) | |
C16 | −0.0398 (4) | 0.1597 (4) | 0.02985 (9) | 0.071 (1) | |
C17 | −0.0186 (4) | 0.1288 (4) | 0.07000 (8) | 0.055 (1) | |
C18 | 0.2314 (4) | 0.2961 (5) | 0.0673 (1) | 0.073 (1) | |
C19 | 0.1862 (5) | 0.7187 (5) | 0.1339 (2) | 0.096 (2) | |
C20 | 0.0000 (4) | 0.0049 (4) | 0.07446 (9) | 0.0558 (9) | |
C21 | 0.0013 (4) | −0.0240 (4) | 0.1147 (1) | 0.0540 (9) | |
C22 | −0.1113 (4) | −0.1222 (4) | 0.0556 (9) | 0.060 (1) | |
C23 | −0.0908 (5) | −0.2444 (5) | 0.0581 (1) | 0.081 (1) | |
C24 | −0.1921 (5) | −0.3640 (5) | 0.0363 (1) | 0.084 (1) | |
C25 | −0.3025 (5) | −0.4710 (5) | 0.0477 (1) | 0.087 (1) | |
C26 | −0.3459 (7) | −0.4949 (8) | 0.0861 (2) | 0.158 (3) | |
C27 | −0.3944 (4) | −0.5847 (4) | 0.0220 (1) | 0.138 (2) | |
C28 | 0.4098 (4) | 1.0248 (4) | 0.1010 (1) | 0.108 (2) | |
C29 | 0.5555 (5) | 0.9971 (5) | 0.0555 (1) | 0.098 (2) | |
C30 | −0.0832 (4) | 0.3475 (5) | 0.0833 (1) | 0.085 (1) | |
H1 | 0.7163 | 0.9197 | 0.1208 | 0.175* | |
H2 | 0.1110 | −0.0100 | 0.1499 | 0.100* | |
H1A | 0.3595 | 0.6841 | 0.1711 | 0.090* | |
H1B | 0.4603 | 0.6861 | 0.1417 | 0.090* | |
H2A | 0.4488 | 0.9178 | 0.1650 | 0.106* | |
H2B | 0.5677 | 0.8898 | 0.1738 | 0.106* | |
H3 | 0.6321 | 1.0472 | 0.1265 | 0.095* | |
H5 | 0.4278 | 0.7479 | 0.0756 | 0.069* | |
H6A | 0.2196 | 0.8039 | 0.0603 | 0.096* | |
H6B | 0.3193 | 0.7973 | 0.0320 | 0.096* | |
H7 | 0.1207 | 0.5857 | 0.0279 | 0.090* | |
H9 | 0.3191 | 0.5410 | 0.0997 | 0.071* | |
H11A | 0.2387 | 0.4579 | 0.1548 | 0.082* | |
H11B | 0.1006 | 0.4516 | 0.1471 | 0.082* | |
H12A | 0.0209 | 0.2411 | 0.1357 | 0.079* | |
H12B | 0.1660 | 0.2576 | 0.1342 | 0.079* | |
H15A | 0.1016 | 0.3555 | 0.0127 | 0.092* | |
H15B | −0.0457 | 0.3350 | 0.0163 | 0.092* | |
H16A | 0.0067 | 0.1305 | 0.0132 | 0.085* | |
H16B | −0.1357 | 0.1123 | 0.0238 | 0.085* | |
H17 | −0.1010 | 0.1089 | 0.0834 | 0.066* | |
H18A | 0.2566 | 0.2352 | 0.0782 | 0.109* | |
H18B | 0.3003 | 0.3881 | 0.0722 | 0.109* | |
H18C | 0.2222 | 0.2815 | 0.0415 | 0.109* | |
H19A | 0.1196 | 0.6987 | 0.1152 | 0.144* | |
H19B | 0.2240 | 0.8115 | 0.1414 | 0.144* | |
H19C | 0.1440 | 0.6599 | 0.1543 | 0.144* | |
H20 | 0.0879 | 0.0266 | 0.0640 | 0.067* | |
H22A | −0.1982 | −0.1457 | 0.0664 | 0.072* | |
H22B | −0.1146 | −0.1016 | 0.0301 | 0.072* | |
H23A | −0.0001 | −0.2181 | 0.0497 | 0.097* | |
H23B | −0.0973 | −0.2712 | 0.0834 | 0.097* | |
H24 | −0.1740 | −0.3616 | 0.0115 | 0.101* | |
H26A | −0.4299 | −0.5793 | 0.0881 | 0.236* | |
H26B | −0.3585 | −0.4221 | 0.0946 | 0.236* | |
H26C | −0.2777 | −0.4989 | 0.1005 | 0.236* | |
H27A | −0.4701 | −0.6537 | 0.0353 | 0.207* | |
H27B | −0.3443 | −0.6230 | 0.0111 | 0.207* | |
H27C | −0.4269 | −0.5492 | 0.0033 | 0.207* | |
H28A | 0.3479 | 1.0175 | 0.0822 | 0.162* | |
H28B | 0.4798 | 1.1179 | 0.1035 | 0.162* | |
H28C | 0.3615 | 0.9931 | 0.1236 | 0.162* | |
H29A | 0.4952 | 0.9906 | 0.0363 | 0.146* | |
H29B | 0.5995 | 0.9469 | 0.0488 | 0.146* | |
H29C | 0.6227 | 1.0906 | 0.0593 | 0.146* | |
H30A | −0.1546 | 0.2553 | 0.0800 | 0.128* | |
H30B | −0.1075 | 0.4075 | 0.0714 | 0.128* | |
H30C | −0.0699 | 0.3684 | 0.1088 | 0.128* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.065 (2) | 0.174 (4) | 0.110 (3) | 0.058 (2) | −0.017 (2) | −0.020 (2) |
O2 | 0.060 (2) | 0.095 (2) | 0.054 (1) | 0.046 (2) | −0.004 (1) | 0.001 (1) |
O3 | 0.052 (2) | 0.095 (2) | 0.047 (1) | 0.029 (2) | −0.001 (1) | 0.006 (1) |
C1 | 0.075 (3) | 0.081 (3) | 0.055 (2) | 0.028 (3) | −0.007 (2) | −0.008 (2) |
C2 | 0.087 (3) | 0.088 (4) | 0.064 (3) | 0.024 (3) | −0.010 (3) | −0.011 (3) |
C3 | 0.055 (3) | 0.085 (3) | 0.075 (3) | 0.020 (3) | 0.001 (2) | −0.013 (3) |
C4 | 0.048 (2) | 0.067 (3) | 0.072 (3) | 0.019 (2) | 0.001 (2) | 0.000 (2) |
C5 | 0.044 (2) | 0.062 (2) | 0.061 (2) | 0.023 (2) | −0.007 (2) | 0.001 (2) |
C6 | 0.061 (3) | 0.070 (3) | 0.090 (3) | 0.017 (2) | −0.022 (2) | 0.014 (2) |
C7 | 0.059 (3) | 0.074 (3) | 0.066 (3) | 0.014 (2) | −0.025 (2) | 0.006 (2) |
C8 | 0.042 (2) | 0.063 (3) | 0.053 (2) | 0.018 (2) | −0.0055 (17) | 0.013 (2) |
C9 | 0.064 (2) | 0.063 (3) | 0.047 (2) | 0.029 (2) | −0.009 (2) | 0.007 (2) |
C10 | 0.046 (2) | 0.065 (3) | 0.058 (2) | 0.026 (2) | −0.002 (2) | −0.004 (2) |
C11 | 0.081 (3) | 0.070 (3) | 0.038 (2) | 0.026 (2) | −0.002 (2) | 0.000 (2) |
C12 | 0.081 (3) | 0.066 (3) | 0.043 (2) | 0.030 (2) | −0.009 (2) | 0.001 (2) |
C13 | 0.046 (2) | 0.066 (2) | 0.036 (2) | 0.024 (2) | 0.001 (2) | 0.003 (2) |
C14 | 0.043 (2) | 0.063 (3) | 0.045 (2) | 0.017 (2) | −0.007 (2) | 0.004 (2) |
C15 | 0.083 (3) | 0.074 (3) | 0.052 (2) | 0.023 (3) | −0.020 (2) | 0.008 (2) |
C16 | 0.072 (3) | 0.077 (3) | 0.048 (2) | 0.025 (2) | −0.014 (2) | −0.002 (2) |
C17 | 0.050 (2) | 0.062 (3) | 0.044 (2) | 0.022 (2) | −0.000 (2) | 0.004 (2) |
C18 | 0.048 (3) | 0.077 (3) | 0.082 (3) | 0.023 (2) | 0.002 (2) | −0.005 (2) |
C19 | 0.071 (3) | 0.076 (3) | 0.136 (4) | 0.034 (3) | 0.029 (3) | 0.014 (3) |
C20 | 0.052 (2) | 0.072 (3) | 0.042 (2) | 0.031 (2) | 0.003 (2) | −0.000 (2) |
C21 | 0.053 (3) | 0.063 (3) | 0.052 (2) | 0.034 (2) | −0.001 (2) | −0.001 (2) |
C22 | 0.067 (3) | 0.069 (3) | 0.042 (2) | 0.032 (2) | −0.004 (2) | −0.004 (2) |
C23 | 0.079 (3) | 0.075 (3) | 0.088 (3) | 0.038 (3) | 0.000 (3) | −0.004 (3) |
C24 | 0.099 (4) | 0.075 (3) | 0.071 (3) | 0.038 (3) | 0.003 (3) | −0.013 (3) |
C25 | 0.088 (4) | 0.082 (3) | 0.087 (3) | 0.038 (3) | 0.003 (3) | 0.000 (3) |
C26 | 0.127 (5) | 0.173 (7) | 0.107 (5) | 0.026 (5) | 0.044 (4) | 0.024 (4) |
C27 | 0.125 (5) | 0.087 (4) | 0.178 (6) | 0.035 (4) | −0.026 (4) | −0.042 (4) |
C28 | 0.085 (4) | 0.059 (3) | 0.167 (5) | 0.026 (3) | 0.009 (3) | 0.006 (3) |
C29 | 0.066 (3) | 0.087 (3) | 0.087 (3) | −0.001 (3) | −0.004 (3) | 0.012 (3) |
C30 | 0.052 (3) | 0.074 (3) | 0.123 (4) | 0.026 (2) | −0.005 (3) | 0.006 (3) |
O1—C3 | 1.392 (6) | C10—C19 | 1.539 (6) |
O2—C21 | 1.296 (4) | C11—C12 | 1.515 (5) |
O3—C21 | 1.223 (4) | C12—C13 | 1.538 (5) |
C1—C2 | 1.528 (6) | C13—C18 | 1.535 (5) |
C1—C10 | 1.536 (5) | C13—C14 | 1.552 (5) |
C2—C3 | 1.514 (6) | C13—C17 | 1.554 (5) |
C3—C4 | 1.529 (6) | C14—C15 | 1.530 (5) |
C4—C28 | 1.539 (6) | C14—C30 | 1.551 (6) |
C4—C29 | 1.542 (6) | C15—C16 | 1.539 (6) |
C4—C5 | 1.551 (5) | C16—C17 | 1.563 (4) |
C5—C6 | 1.529 (5) | C17—C20 | 1.535 (5) |
C5—C10 | 1.553 (5) | C20—C21 | 1.516 (5) |
C6—C7 | 1.486 (6) | C20—C22 | 1.53 (2) |
C7—C8 | 1.353 (5) | C22—C23 | 1.522 (6) |
C8—C9 | 1.499 (5) | C23—C24 | 1.502 (6) |
C8—C14 | 1.513 (5) | C24—C25 | 1.305 (6) |
C9—C11 | 1.523 (5) | C25—C26 | 1.474 (6) |
C9—C10 | 1.539 (5) | C25—C27 | 1.518 (6) |
C2—C1—C10 | 113.9 (4) | C18—C13—C12 | 109.6 (3) |
C3—C2—C1 | 111.0 (3) | C18—C13—C14 | 111.5 (3) |
O1—C3—C2 | 111.0 (4) | C12—C13—C14 | 108.6 (3) |
O1—C3—C4 | 107.2 (3) | C18—C13—C17 | 108.7 (3) |
C2—C3—C4 | 112.7 (4) | C12—C13—C17 | 116.7 (3) |
C3—C4—C28 | 109.0 (3) | C14—C13—C17 | 101.5 (3) |
C3—C4—C29 | 108.4 (3) | C8—C14—C15 | 117.5 (3) |
C28—C4—C29 | 107.4 (4) | C8—C14—C30 | 106.5 (3) |
C3—C4—C5 | 108.0 (3) | C15—C14—C30 | 107.6 (3) |
C28—C4—C5 | 115.2 (3) | C8—C14—C13 | 110.7 (3) |
C29—C4—C5 | 108.7 (3) | C15—C14—C13 | 101.5 (3) |
C6—C5—C4 | 112.9 (3) | C30—C14—C13 | 113.2 (3) |
C6—C5—C10 | 111.0 (3) | C14—C15—C16 | 105.3 (3) |
C4—C5—C10 | 118.1 (3) | C15—C16—C17 | 106.7 (3) |
C7—C6—C5 | 112.5 (3) | C20—C17—C13 | 119.1 (3) |
C8—C7—C6 | 124.2 (3) | C20—C17—C16 | 114.5 (3) |
C7—C8—C9 | 120.5 (3) | C13—C17—C16 | 102.1 (3) |
C7—C8—C14 | 121.8 (3) | C21—C20—C22 | 109 (3) |
C9—C8—C14 | 117.6 (3) | C21—C20—C17 | 108.9 (3) |
C8—C9—C11 | 112.8 (3) | C22—C20—C17 | 112.9 (3) |
C8—C9—C10 | 114.4 (3) | O3—C21—O2 | 122.4 (3) |
C11—C9—C10 | 116.3 (3) | O3—C21—C20 | 122.0 (3) |
C1—C10—C19 | 109.8 (3) | O2—C21—C20 | 115.6 (3) |
C1—C10—C9 | 108.9 (3) | C23—C22—C20 | 114 (1) |
C19—C10—C9 | 109.6 (3) | C24—C23—C22 | 113.4 (9) |
C1—C10—C5 | 108.9 (3) | C25—C24—C23 | 128.1 (4) |
C19—C10—C5 | 113.3 (4) | C24—C25—C26 | 123.8 (5) |
C9—C10—C5 | 106.2 (3) | C24—C25—C27 | 121.7 (4) |
C12—C11—C9 | 117.4 (3) | C26—C25—C27 | 114.4 (5) |
C11—C12—C13 | 114.3 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O3i | 0.82 | 2.08 | 2.825 (4) | 151 |
O2—H2···O3ii | 0.82 | 1.91 | 2.666 (3) | 153 |
Symmetry codes: (i) x+1, y+1, z; (ii) −x, −x+y, −z+1/3. |
Experimental details
Crystal data | |
Chemical formula | C30H48O3 |
Mr | 456.68 |
Crystal system, space group | Trigonal, P3121 |
Temperature (K) | 293 |
a, c (Å) | 11.3717 (6), 36.739 (3) |
V (Å3) | 4114.4 (4) |
Z | 6 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.4 × 0.3 × 0.3 |
Data collection | |
Diffractometer | Siemens SMART CCD area-detector diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 22258, 2915, 1621 |
Rint | 0.088 |
(sin θ/λ)max (Å−1) | 0.602 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.140, 0.90 |
No. of reflections | 2915 |
No. of parameters | 295 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.20, −0.16 |
Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 1998), PLATON (Spek, 2000) and SHELXL97.
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O3i | 0.82 | 2.08 | 2.825 (4) | 151.4 |
O2—H2···O3ii | 0.82 | 1.91 | 2.666 (3) | 152.7 |
Symmetry codes: (i) x+1, y+1, z; (ii) −x, −x+y, −z+1/3. |
Subscribe to Acta Crystallographica Section C: Structural Chemistry
The full text of this article is available to subscribers to the journal.
- Information on subscribing
- Sample issue
- Purchase subscription
- Reduced-price subscriptions
- If you have already subscribed, you may need to register
The title compound, (I), was isolated from the resin of Protium crenatum Sandwith (Burseraceae), a tree about 35 m tall that grows in lowland, lower mountain and riparian forests in northern Brazil, Colombia, Guyana and Venezuela (Daly, 1997). The resin is used by the indigenous peoples as an antiinflamatory agent. Similar tirucallane compounds have been isolated previously from elemi resin (Arigoni et al., 1995; Coterrell et al., 1970; Argay et al., 1997), which is produced by a Burseraceae tree from the Philippine Islands. It has also been reported as a constituent of the oleoresin of Aucoumea klaideana, a large tree from equatorial Africa (Tessier et al., 1982; Guang-Yi et al., 1989). New tirucallane triterpenes have recently been reported as constituents of the bark of Dysoxylum macranthum, a Meliaceae tree from New Caledonia (Mohamad et al., 1999). \sch
The structure of (I) was initially inferred from 13C and 1H NMR data and HMBC (please define), and solved from single-crystal X-ray diffraction, which confirmed its true composition and stereochemistry. However, the absolute structure was not established in this study. The configuration adopted was that occurring in all tirucallene structures found in the Cambridge Structural Database (Allen & Kennard, 1993), which implied refining the structure in the enantiomorphous space group P3121.
The molecular structure of (I) (Fig. 1) shows that the A, B, C and D rings adopt chair [ΔC2(2–3)min = 1.8 (6), ΔC2(3–4)max = 9.4 (6), ΔCs(2)min = 4.2 (4), ΔCs(1)max = 8.9 (5)], half-chair [ΔC2(7–8) = 6.5 (6)], half-chair [ΔC2(9–11) = 6.5 (6)], and half-chair [ΔC2(13–14) = 8.4 (5)] conformations, respectively (Griffin et al., 1984).
The hydroxyl group at position 3, the methyl group at position 13 and the aliphatic chain at position 17 are substituents of the α-face of the triterpene ring system, while the methyl groups at positions 10 and 14 project out of the β-face. A similar arrangement is found in other tirucallene compounds such as Schinol, a triterpene found in the pink peppercorn (Schinus terebinthifolius; Jain et al., 1995), and in Cuachalalic acid, a triterpene from Amphyterygium adstringens (Watson et al., 1987; Soriano-García et al., 1987). This conformation seems to persist in solution, as shown by the 1H NMR signal from the β hydrogen on C3 at δ 3.50 p.p.m. (singlet). The C7═C8 bond length of 1.353 (5) Å is slightly higher than the average distance of 1.32 (1) Å observed in 15 tirucallene fragments found in the Cambridge Structural Database (Allen & Kennard, 1993).
The side-chain conformation plays an important role in the inhibitory activity of cell membranes (see, for example, Jain et al., 1995). In compound (I), the aliphatic acidic side chain adopts a fully extended configuration in the `left-hand' orientation [C22 anti to C13: C13—C17—C20—C22 - 172.2 (3)°], extending by 7.248 (5) Å out of the tetracyclic nucleus. This orientation is in contrast with that found in the closely related triterpene 3-oxo-5α,13α,14β,17α-lanosta-7,24-dien-20-oic acid methyl ester from elemi resin (Argay et al., 1997), in which the side chain extends towards the`right-hand' side.
The geometrical data for the principal intermolecular contacts of (I) are reported in Table 1 and these interactions are shown in Fig. 2. Chains of molecules related by a unit-cell translation along the a and b axes are linked by O—H···O═C hydrogen bonds and additional weak van der Waals C22—H22a···O1iii contacts of 3.404 (6) Å [symmetry code: (iii) x - 1, y - 1, z]. A second hydrogen bond, of the type C—O—H···O═C involving the carboxylic groups of molecules related by the 31 screw axes, results in an extended ribbon of molecules running in the [110] direction. The borders of each ribbon consist of hydrophobic methyl groups which do not form any inter-ribbon contacts.