Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010400839X/fr1475sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S010827010400839X/fr1475Isup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S010827010400839X/fr1475IIsup3.hkl |
CCDC references: 243603; 243604
(-)-Santonic acid, derived from (-)-α-santonin of known absolute stereochemistry, was subjected to the acidic pyrolysis procedure described by Woodward & Kovach (1950). Crystals of (II) suitable for X-ray analysis (m.p. 376 K) were obtained from diisopropyl ether. Basic hydrolysis of (II), as described by the same source, then gave (I); crystals were obtained from methanol (m.p. 448 K).
All H atoms for both (I) and (II) were found in electron density difference maps but were placed in calculated positions for the C-bound H atoms (0.97 Å for the methylene H atoms, 0.98 Å for the methine H atoms and 0.96 Å for the methyl H atoms) and allowed to refine as riding on their respective C atoms; their displacement parameters were fixed at 120% of those of their respective C atoms. The rotational parameter of all methyl groups for (II) was allowed to vary. The hydroxy H atom was allowed to vary positionally and its displacement parameter was fixed at 0.080 Å2. The absolute configuration was not determinable for either (I) or (II) but is based on the reported absolute configuration of the synthetic starting material (see Experimental). Friedel pairs for both (I) and (II) were merged.
For both compounds, data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXP97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.
C15H20O4 | Dx = 1.267 Mg m−3 |
Mr = 264.31 | Melting point: 448 K |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 30 reflections |
a = 6.770 (2) Å | θ = 2.6–10.0° |
b = 13.160 (3) Å | µ = 0.09 mm−1 |
c = 15.553 (4) Å | T = 296 K |
V = 1385.7 (6) Å3 | Block, colourless |
Z = 4 | 0.46 × 0.25 × 0.11 mm |
F(000) = 568 |
Siemens P4 diffractometer | 1065 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.048 |
Graphite monochromator | θmax = 25.1°, θmin = 2.0° |
2θ/θ scans | h = −8→8 |
Absorption correction: numerical (SHELXTL; Sheldrick, 1997) | k = −15→15 |
Tmin = 0.976, Tmax = 0.990 | l = −18→18 |
2846 measured reflections | 3 standard reflections every 97 reflections |
1424 independent reflections | intensity decay: variation < 3.5% |
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)] = 0.050 | H-atom parameters constrained |
wR(F2) = 0.128 | w = 1/[σ2(Fo2) + (0.049P)2 + 0.3537P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max < 0.001 |
1424 reflections | Δρmax = 0.15 e Å−3 |
173 parameters | Δρmin = −0.17 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.022 (4) |
C15H20O4 | V = 1385.7 (6) Å3 |
Mr = 264.31 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 6.770 (2) Å | µ = 0.09 mm−1 |
b = 13.160 (3) Å | T = 296 K |
c = 15.553 (4) Å | 0.46 × 0.25 × 0.11 mm |
Siemens P4 diffractometer | 1065 reflections with I > 2σ(I) |
Absorption correction: numerical (SHELXTL; Sheldrick, 1997) | Rint = 0.048 |
Tmin = 0.976, Tmax = 0.990 | 3 standard reflections every 97 reflections |
2846 measured reflections | intensity decay: variation < 3.5% |
1424 independent reflections |
R[F2 > 2σ(F2)] = 0.050 | 0 restraints |
wR(F2) = 0.128 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.15 e Å−3 |
1424 reflections | Δρmin = −0.17 e Å−3 |
173 parameters |
Experimental. 'crystal mounted on glass fiber using cyanoacrylate cement' |
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 | 0.1938 (5) | 0.7000 (2) | 0.79366 (18) | 0.0604 (9) | |
O2 | 0.6548 (5) | 0.7015 (3) | 0.5960 (2) | 0.0736 (10) | |
O3 | 0.2061 (4) | 0.7479 (3) | 0.9997 (2) | 0.0679 (9) | |
O4 | 0.0056 (4) | 0.8401 (3) | 0.91676 (17) | 0.0578 (9) | |
H4 | −0.0793 | 0.8108 | 0.9450 | 0.087* | |
C1 | 0.3164 (6) | 0.8703 (3) | 0.7938 (2) | 0.0384 (9) | |
C2 | 0.1860 (7) | 0.9630 (3) | 0.7684 (2) | 0.0527 (11) | |
H2A | 0.0476 | 0.9440 | 0.7672 | 0.063* | |
H2B | 0.2031 | 1.0180 | 0.8092 | 0.063* | |
C3 | 0.2563 (8) | 0.9957 (4) | 0.6780 (3) | 0.0634 (14) | |
H3A | 0.1536 | 0.9834 | 0.6358 | 0.076* | |
H3B | 0.2889 | 1.0674 | 0.6775 | 0.076* | |
C3A | 0.4382 (7) | 0.9322 (3) | 0.6577 (2) | 0.0492 (11) | |
C4 | 0.3959 (6) | 0.8292 (3) | 0.6144 (2) | 0.0455 (10) | |
H4A | 0.3822 | 0.8362 | 0.5519 | 0.055* | |
C5 | 0.5758 (6) | 0.7670 (4) | 0.6381 (3) | 0.0501 (11) | |
C6A | 0.5149 (6) | 0.8954 (3) | 0.7466 (3) | 0.0452 (10) | |
H61A | 0.5895 | 0.9485 | 0.7765 | 0.054* | |
C6 | 0.6437 (6) | 0.8029 (4) | 0.7267 (3) | 0.0547 (12) | |
H6A | 0.7823 | 0.8215 | 0.7257 | 0.066* | |
H6B | 0.6243 | 0.7501 | 0.7693 | 0.066* | |
C7 | 0.2140 (6) | 0.7763 (3) | 0.6547 (2) | 0.0399 (9) | |
H7A | 0.0986 | 0.8185 | 0.6414 | 0.048* | |
C8 | 0.2360 (5) | 0.7750 (3) | 0.7521 (2) | 0.0365 (9) | |
C9 | 0.3531 (6) | 0.8523 (3) | 0.8905 (2) | 0.0425 (10) | |
H9A | 0.4601 | 0.8023 | 0.8939 | 0.051* | |
C10 | 0.1817 (6) | 0.8069 (3) | 0.9395 (2) | 0.0465 (10) | |
C11 | 0.4232 (9) | 0.9444 (4) | 0.9418 (3) | 0.0698 (15) | |
H11A | 0.4428 | 0.9253 | 1.0007 | 0.105* | |
H11B | 0.3255 | 0.9972 | 0.9386 | 0.105* | |
H11C | 0.5454 | 0.9688 | 0.9182 | 0.105* | |
C12 | 0.1744 (7) | 0.6709 (4) | 0.6175 (3) | 0.0594 (12) | |
H12A | 0.0608 | 0.6419 | 0.6451 | 0.089* | |
H12B | 0.2872 | 0.6282 | 0.6272 | 0.089* | |
H12C | 0.1504 | 0.6764 | 0.5569 | 0.089* | |
C13 | 0.5966 (10) | 0.9900 (4) | 0.6053 (3) | 0.0782 (17) | |
H13A | 0.5417 | 1.0109 | 0.5512 | 0.117* | |
H13B | 0.7077 | 0.9463 | 0.5953 | 0.117* | |
H13C | 0.6389 | 1.0488 | 0.6369 | 0.117* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.080 (2) | 0.0541 (17) | 0.0468 (16) | −0.0119 (18) | −0.0023 (17) | 0.0086 (15) |
O2 | 0.066 (2) | 0.080 (2) | 0.075 (2) | 0.015 (2) | 0.0129 (18) | −0.0223 (19) |
O3 | 0.0442 (16) | 0.107 (2) | 0.0529 (16) | −0.0010 (19) | 0.0022 (14) | 0.0368 (17) |
O4 | 0.0410 (16) | 0.084 (2) | 0.0484 (16) | 0.0077 (17) | 0.0055 (13) | 0.0183 (16) |
C1 | 0.037 (2) | 0.045 (2) | 0.0334 (19) | 0.0014 (19) | 0.0000 (18) | 0.0025 (16) |
C2 | 0.059 (3) | 0.059 (2) | 0.041 (2) | 0.013 (3) | 0.001 (2) | 0.004 (2) |
C3 | 0.093 (4) | 0.049 (2) | 0.048 (3) | 0.013 (3) | 0.000 (3) | 0.009 (2) |
C3A | 0.058 (3) | 0.055 (3) | 0.034 (2) | −0.006 (2) | 0.006 (2) | 0.0055 (19) |
C4 | 0.047 (2) | 0.060 (3) | 0.0297 (19) | −0.003 (2) | 0.0051 (17) | −0.0012 (18) |
C5 | 0.041 (2) | 0.063 (3) | 0.047 (2) | −0.003 (2) | 0.013 (2) | −0.001 (2) |
C6A | 0.045 (2) | 0.054 (2) | 0.0367 (18) | −0.015 (2) | 0.0016 (18) | 0.0045 (19) |
C6 | 0.0322 (19) | 0.086 (3) | 0.046 (2) | 0.003 (2) | 0.0049 (18) | −0.002 (2) |
C7 | 0.035 (2) | 0.048 (2) | 0.037 (2) | 0.002 (2) | −0.0023 (17) | 0.0017 (16) |
C8 | 0.0300 (18) | 0.044 (2) | 0.0351 (18) | 0.0022 (18) | 0.0024 (16) | 0.0044 (18) |
C9 | 0.044 (2) | 0.052 (2) | 0.0321 (19) | −0.003 (2) | 0.0022 (17) | 0.0017 (17) |
C10 | 0.045 (2) | 0.061 (2) | 0.033 (2) | −0.001 (2) | −0.0007 (18) | 0.006 (2) |
C11 | 0.088 (4) | 0.078 (3) | 0.043 (2) | −0.027 (3) | 0.004 (3) | −0.008 (2) |
C12 | 0.062 (3) | 0.063 (3) | 0.054 (3) | −0.018 (3) | −0.002 (2) | −0.013 (2) |
C13 | 0.116 (4) | 0.068 (3) | 0.051 (3) | −0.038 (3) | 0.013 (3) | 0.006 (2) |
O1—C8 | 1.214 (4) | C5—C6 | 1.528 (6) |
O2—C5 | 1.208 (5) | C6A—C6 | 1.529 (6) |
O3—C10 | 1.227 (5) | C6A—H61A | 0.9800 |
O4—C10 | 1.319 (5) | C6—H6A | 0.9700 |
O4—H4 | 0.8200 | C6—H6B | 0.9700 |
C1—C8 | 1.514 (5) | C7—C8 | 1.522 (5) |
C1—C9 | 1.542 (5) | C7—C12 | 1.527 (6) |
C1—C2 | 1.556 (6) | C7—H7A | 0.9800 |
C1—C6A | 1.566 (6) | C9—C10 | 1.511 (6) |
C2—C3 | 1.546 (6) | C9—C11 | 1.528 (6) |
C2—H2A | 0.9700 | C9—H9A | 0.9800 |
C2—H2B | 0.9700 | C11—H11A | 0.9600 |
C3—C3A | 1.521 (6) | C11—H11B | 0.9600 |
C3—H3A | 0.9700 | C11—H11C | 0.9600 |
C3—H3B | 0.9700 | C12—H12A | 0.9600 |
C3A—C4 | 1.540 (6) | C12—H12B | 0.9600 |
C3A—C13 | 1.547 (7) | C12—H12C | 0.9600 |
C3A—C6A | 1.555 (5) | C13—H13A | 0.9600 |
C4—C5 | 1.514 (6) | C13—H13B | 0.9600 |
C4—C7 | 1.547 (5) | C13—H13C | 0.9600 |
C4—H4A | 0.9800 | ||
C10—O4—H4 | 109.5 | C5—C6—H6A | 110.8 |
C8—C1—C9 | 110.4 (3) | C6A—C6—H6A | 110.8 |
C8—C1—C2 | 109.6 (3) | C5—C6—H6B | 110.8 |
C9—C1—C2 | 117.4 (3) | C6A—C6—H6B | 110.8 |
C8—C1—C6A | 106.4 (3) | H6A—C6—H6B | 108.8 |
C9—C1—C6A | 110.6 (3) | C8—C7—C12 | 112.6 (3) |
C2—C1—C6A | 101.7 (3) | C8—C7—C4 | 109.3 (3) |
C3—C2—C1 | 105.9 (3) | C12—C7—C4 | 113.3 (3) |
C3—C2—H2A | 110.5 | C8—C7—H7A | 107.1 |
C1—C2—H2A | 110.5 | C12—C7—H7A | 107.1 |
C3—C2—H2B | 110.5 | C4—C7—H7A | 107.1 |
C1—C2—H2B | 110.5 | O1—C8—C1 | 122.0 (3) |
H2A—C2—H2B | 108.7 | O1—C8—C7 | 121.1 (4) |
C3A—C3—C2 | 106.6 (3) | C1—C8—C7 | 116.9 (3) |
C3A—C3—H3A | 110.4 | C10—C9—C11 | 106.8 (3) |
C2—C3—H3A | 110.4 | C10—C9—C1 | 115.4 (3) |
C3A—C3—H3B | 110.4 | C11—C9—C1 | 115.9 (4) |
C2—C3—H3B | 110.4 | C10—C9—H9A | 106.0 |
H3A—C3—H3B | 108.6 | C11—C9—H9A | 106.0 |
C3—C3A—C4 | 115.0 (4) | C1—C9—H9A | 106.0 |
C3—C3A—C13 | 113.6 (4) | O3—C10—O4 | 122.4 (4) |
C4—C3A—C13 | 109.4 (3) | O3—C10—C9 | 122.1 (4) |
C3—C3A—C6A | 104.9 (3) | O4—C10—C9 | 115.3 (3) |
C4—C3A—C6A | 100.2 (3) | C9—C11—H11A | 109.5 |
C13—C3A—C6A | 113.0 (4) | C9—C11—H11B | 109.5 |
C5—C4—C3A | 102.7 (3) | H11A—C11—H11B | 109.5 |
C5—C4—C7 | 107.3 (3) | C9—C11—H11C | 109.5 |
C3A—C4—C7 | 111.5 (3) | H11A—C11—H11C | 109.5 |
C5—C4—H4A | 111.6 | H11B—C11—H11C | 109.5 |
C3A—C4—H4A | 111.6 | C7—C12—H12A | 109.5 |
C7—C4—H4A | 111.6 | C7—C12—H12B | 109.5 |
O2—C5—C4 | 127.6 (4) | H12A—C12—H12B | 109.5 |
O2—C5—C6 | 125.3 (4) | C7—C12—H12C | 109.5 |
C4—C5—C6 | 107.1 (3) | H12A—C12—H12C | 109.5 |
C6—C6A—C3A | 105.0 (3) | H12B—C12—H12C | 109.5 |
C6—C6A—C1 | 114.7 (3) | C3A—C13—H13A | 109.5 |
C3A—C6A—C1 | 101.3 (3) | C3A—C13—H13B | 109.5 |
C6—C6A—H61A | 111.7 | H13A—C13—H13B | 109.5 |
C3A—C6A—H61A | 111.7 | C3A—C13—H13C | 109.5 |
C1—C6A—H61A | 111.7 | H13A—C13—H13C | 109.5 |
C5—C6—C6A | 104.9 (4) | H13B—C13—H13C | 109.5 |
C8—C1—C2—C3 | −81.1 (4) | O2—C5—C6—C6A | 172.3 (4) |
C9—C1—C2—C3 | 152.0 (4) | C4—C5—C6—C6A | −7.1 (4) |
C6A—C1—C2—C3 | 31.3 (4) | C3A—C6A—C6—C5 | −20.8 (4) |
C1—C2—C3—C3A | −6.9 (5) | C1—C6A—C6—C5 | 89.5 (4) |
C2—C3—C3A—C4 | 88.3 (4) | C5—C4—C7—C8 | 61.8 (4) |
C2—C3—C3A—C13 | −144.5 (4) | C3A—C4—C7—C8 | −50.0 (4) |
C2—C3—C3A—C6A | −20.7 (5) | C5—C4—C7—C12 | −64.6 (4) |
C3—C3A—C4—C5 | −155.6 (3) | C3A—C4—C7—C12 | −176.4 (3) |
C13—C3A—C4—C5 | 75.1 (4) | C9—C1—C8—O1 | 5.6 (5) |
C6A—C3A—C4—C5 | −43.8 (4) | C2—C1—C8—O1 | −125.2 (4) |
C3—C3A—C4—C7 | −40.9 (4) | C6A—C1—C8—O1 | 125.5 (4) |
C13—C3A—C4—C7 | −170.2 (4) | C9—C1—C8—C7 | −173.2 (3) |
C6A—C3A—C4—C7 | 70.9 (4) | C2—C1—C8—C7 | 56.0 (4) |
C3A—C4—C5—O2 | −147.1 (5) | C6A—C1—C8—C7 | −53.2 (4) |
C7—C4—C5—O2 | 95.3 (5) | C12—C7—C8—O1 | −10.9 (6) |
C3A—C4—C5—C6 | 32.4 (4) | C4—C7—C8—O1 | −137.7 (4) |
C7—C4—C5—C6 | −85.3 (4) | C12—C7—C8—C1 | 167.8 (3) |
C3—C3A—C6A—C6 | 159.5 (3) | C4—C7—C8—C1 | 41.0 (4) |
C4—C3A—C6A—C6 | 40.0 (4) | C8—C1—C9—C10 | −50.7 (5) |
C13—C3A—C6A—C6 | −76.2 (4) | C2—C1—C9—C10 | 75.9 (5) |
C3—C3A—C6A—C1 | 39.9 (4) | C6A—C1—C9—C10 | −168.1 (3) |
C4—C3A—C6A—C1 | −79.6 (3) | C8—C1—C9—C11 | −176.6 (4) |
C13—C3A—C6A—C1 | 164.2 (3) | C2—C1—C9—C11 | −50.0 (5) |
C8—C1—C6A—C6 | −40.9 (4) | C6A—C1—C9—C11 | 66.0 (5) |
C9—C1—C6A—C6 | 78.9 (4) | C11—C9—C10—O3 | −83.5 (5) |
C2—C1—C6A—C6 | −155.7 (4) | C1—C9—C10—O3 | 146.1 (4) |
C8—C1—C6A—C3A | 71.5 (4) | C11—C9—C10—O4 | 92.3 (4) |
C9—C1—C6A—C3A | −168.6 (3) | C1—C9—C10—O4 | −38.1 (5) |
C2—C1—C6A—C3A | −43.2 (4) |
C15H18O3 | Dx = 1.235 Mg m−3 |
Mr = 246.29 | Melting point: 376 K |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 33 reflections |
a = 8.562 (2) Å | θ = 2.3–10.8° |
b = 11.656 (3) Å | µ = 0.09 mm−1 |
c = 13.275 (4) Å | T = 296 K |
V = 1324.8 (6) Å3 | Block, colourless |
Z = 4 | 0.24 × 0.17 × 0.06 mm |
F(000) = 528 |
Siemens P4 diffractometer | 875 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.061 |
Graphite monochromator | θmax = 25.6°, θmin = 2.3° |
2θ/θ scans | h = −10→10 |
Absorption correction: numerical (SHELXTL; Sheldrick, 1997) | k = −14→14 |
Tmin = 0.972, Tmax = 0.990 | l = −16→16 |
2891 measured reflections | 3 standard reflections every 97 reflections |
1446 independent reflections | intensity decay: variation < 1.5% |
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)] = 0.052 | H-atom parameters constrained |
wR(F2) = 0.093 | w = 1/[σ2(Fo2) + (0.0211P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.00 | (Δ/σ)max < 0.001 |
1446 reflections | Δρmax = 0.18 e Å−3 |
167 parameters | Δρmin = −0.13 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0148 (11) |
C15H18O3 | V = 1324.8 (6) Å3 |
Mr = 246.29 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 8.562 (2) Å | µ = 0.09 mm−1 |
b = 11.656 (3) Å | T = 296 K |
c = 13.275 (4) Å | 0.24 × 0.17 × 0.06 mm |
Siemens P4 diffractometer | 875 reflections with I > 2σ(I) |
Absorption correction: numerical (SHELXTL; Sheldrick, 1997) | Rint = 0.061 |
Tmin = 0.972, Tmax = 0.990 | 3 standard reflections every 97 reflections |
2891 measured reflections | intensity decay: variation < 1.5% |
1446 independent reflections |
R[F2 > 2σ(F2)] = 0.052 | 0 restraints |
wR(F2) = 0.093 | H-atom parameters constrained |
S = 1.00 | Δρmax = 0.18 e Å−3 |
1446 reflections | Δρmin = −0.13 e Å−3 |
167 parameters |
Experimental. 'crystal mounted on glass fiber using cyanoacrylate cement' |
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 | 0.8794 (3) | 0.4348 (2) | 0.2972 (2) | 0.0540 (8) | |
O2 | 0.5827 (4) | 0.2070 (3) | 0.5513 (2) | 0.0686 (9) | |
O3 | 1.1011 (4) | 0.4217 (3) | 0.2096 (3) | 0.0923 (12) | |
C1 | 0.7504 (4) | 0.2659 (3) | 0.2405 (3) | 0.0357 (9) | |
C2 | 0.6469 (4) | 0.2992 (4) | 0.1505 (3) | 0.0464 (11) | |
H2A | 0.6586 | 0.2450 | 0.0955 | 0.056* | |
H2B | 0.6720 | 0.3756 | 0.1264 | 0.056* | |
C3 | 0.4802 (4) | 0.2949 (4) | 0.1947 (3) | 0.0491 (11) | |
H3A | 0.4429 | 0.3716 | 0.2097 | 0.059* | |
H3B | 0.4087 | 0.2591 | 0.1475 | 0.059* | |
C3A | 0.4932 (4) | 0.2231 (3) | 0.2920 (3) | 0.0403 (9) | |
C4 | 0.5140 (4) | 0.2950 (3) | 0.3884 (3) | 0.0409 (10) | |
H4A | 0.4147 | 0.3242 | 0.4147 | 0.049* | |
C5 | 0.5931 (5) | 0.2108 (4) | 0.4603 (3) | 0.0465 (10) | |
C5A | 0.6590 (4) | 0.1673 (3) | 0.2862 (3) | 0.0382 (10) | |
H51A | 0.6591 | 0.1002 | 0.2417 | 0.046* | |
C6 | 0.6976 (5) | 0.1334 (3) | 0.3952 (3) | 0.0460 (11) | |
H6A | 0.8071 | 0.1468 | 0.4099 | 0.055* | |
H6B | 0.6741 | 0.0531 | 0.4070 | 0.055* | |
C7 | 0.6378 (5) | 0.3876 (3) | 0.3799 (3) | 0.0395 (10) | |
C8 | 0.7486 (4) | 0.3656 (3) | 0.3130 (3) | 0.0382 (10) | |
C9 | 0.9263 (4) | 0.2561 (4) | 0.2193 (3) | 0.0514 (12) | |
H9A | 0.9711 | 0.2070 | 0.2718 | 0.062* | |
C10 | 0.9834 (5) | 0.3763 (4) | 0.2383 (4) | 0.0589 (13) | |
C11 | 0.9774 (5) | 0.2072 (4) | 0.1179 (3) | 0.0746 (15) | |
H11A | 1.0894 | 0.2062 | 0.1145 | 0.112* | |
H11B | 0.9368 | 0.2541 | 0.0646 | 0.112* | |
H11C | 0.9383 | 0.1304 | 0.1110 | 0.112* | |
C12 | 0.6355 (6) | 0.4862 (3) | 0.4533 (3) | 0.0598 (13) | |
H12A | 0.7314 | 0.5284 | 0.4481 | 0.090* | |
H12B | 0.6244 | 0.4571 | 0.5206 | 0.090* | |
H12C | 0.5493 | 0.5358 | 0.4380 | 0.090* | |
C13 | 0.3592 (5) | 0.1379 (4) | 0.3058 (3) | 0.0616 (12) | |
H13A | 0.2625 | 0.1790 | 0.3122 | 0.092* | |
H13B | 0.3768 | 0.0932 | 0.3655 | 0.092* | |
H13C | 0.3540 | 0.0880 | 0.2484 | 0.092* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0413 (16) | 0.0524 (17) | 0.0682 (19) | −0.0119 (16) | −0.0001 (17) | 0.0085 (17) |
O2 | 0.089 (2) | 0.085 (2) | 0.0313 (18) | −0.010 (2) | 0.0112 (17) | −0.0008 (19) |
O3 | 0.056 (2) | 0.108 (3) | 0.113 (3) | −0.025 (2) | 0.025 (2) | 0.023 (3) |
C1 | 0.0309 (18) | 0.041 (2) | 0.035 (2) | 0.004 (2) | 0.0023 (18) | 0.0029 (19) |
C2 | 0.051 (3) | 0.053 (3) | 0.035 (2) | 0.006 (3) | 0.001 (2) | −0.002 (2) |
C3 | 0.043 (2) | 0.062 (3) | 0.042 (2) | 0.001 (2) | −0.011 (2) | −0.009 (2) |
C3A | 0.038 (2) | 0.042 (2) | 0.041 (2) | −0.013 (2) | 0.004 (2) | −0.005 (2) |
C4 | 0.038 (2) | 0.045 (2) | 0.040 (2) | 0.004 (2) | 0.0075 (19) | −0.008 (2) |
C5 | 0.050 (3) | 0.048 (3) | 0.042 (2) | −0.017 (2) | 0.002 (2) | −0.003 (2) |
C5A | 0.047 (2) | 0.034 (2) | 0.033 (2) | 0.003 (2) | 0.000 (2) | −0.005 (2) |
C6 | 0.059 (3) | 0.042 (2) | 0.037 (2) | 0.001 (2) | 0.004 (2) | 0.006 (2) |
C7 | 0.042 (2) | 0.036 (2) | 0.039 (2) | 0.000 (2) | −0.004 (2) | 0.000 (2) |
C8 | 0.033 (2) | 0.036 (2) | 0.045 (3) | −0.004 (2) | −0.008 (2) | 0.006 (2) |
C9 | 0.042 (2) | 0.066 (3) | 0.046 (3) | 0.011 (2) | 0.006 (2) | 0.014 (3) |
C10 | 0.038 (2) | 0.073 (3) | 0.065 (3) | −0.002 (3) | 0.008 (2) | 0.023 (3) |
C11 | 0.065 (3) | 0.100 (4) | 0.059 (3) | 0.024 (3) | 0.020 (3) | 0.006 (3) |
C12 | 0.077 (3) | 0.054 (3) | 0.048 (3) | −0.002 (3) | 0.000 (3) | −0.009 (2) |
C13 | 0.052 (3) | 0.068 (3) | 0.065 (3) | −0.018 (3) | −0.001 (3) | −0.010 (3) |
O1—C10 | 1.367 (5) | C5—C6 | 1.536 (5) |
O1—C8 | 1.396 (4) | C5A—C6 | 1.536 (5) |
O2—C5 | 1.212 (5) | C5A—H51A | 0.9800 |
O3—C10 | 1.200 (5) | C6—H6A | 0.9700 |
C1—C8 | 1.509 (5) | C6—H6B | 0.9700 |
C1—C5A | 1.518 (5) | C7—C8 | 1.324 (5) |
C1—C9 | 1.536 (5) | C7—C12 | 1.507 (5) |
C1—C2 | 1.538 (5) | C9—C10 | 1.506 (6) |
C2—C3 | 1.544 (5) | C9—C11 | 1.525 (5) |
C2—H2A | 0.9700 | C9—H9A | 0.9800 |
C2—H2B | 0.9700 | C11—H11A | 0.9600 |
C3—C3A | 1.544 (5) | C11—H11B | 0.9600 |
C3—H3A | 0.9700 | C11—H11C | 0.9600 |
C3—H3B | 0.9700 | C12—H12A | 0.9600 |
C3A—C13 | 1.528 (5) | C12—H12B | 0.9600 |
C3A—C4 | 1.540 (5) | C12—H12C | 0.9600 |
C3A—C5A | 1.563 (5) | C13—H13A | 0.9600 |
C4—C7 | 1.517 (5) | C13—H13B | 0.9600 |
C4—C5 | 1.527 (5) | C13—H13C | 0.9600 |
C4—H4A | 0.9800 | ||
C10—O1—C8 | 108.7 (3) | C5A—C6—C5 | 104.7 (3) |
C8—C1—C5A | 108.8 (3) | C5A—C6—H6A | 110.8 |
C8—C1—C9 | 100.7 (3) | C5—C6—H6A | 110.8 |
C5A—C1—C9 | 121.5 (3) | C5A—C6—H6B | 110.8 |
C8—C1—C2 | 107.2 (3) | C5—C6—H6B | 110.8 |
C5A—C1—C2 | 101.8 (3) | H6A—C6—H6B | 108.9 |
C9—C1—C2 | 116.2 (3) | C8—C7—C12 | 126.2 (4) |
C1—C2—C3 | 103.2 (3) | C8—C7—C4 | 114.4 (3) |
C1—C2—H2A | 111.1 | C12—C7—C4 | 119.0 (4) |
C3—C2—H2A | 111.1 | C7—C8—O1 | 124.3 (4) |
C1—C2—H2B | 111.1 | C7—C8—C1 | 125.8 (4) |
C3—C2—H2B | 111.1 | O1—C8—C1 | 109.9 (3) |
H2A—C2—H2B | 109.1 | C10—C9—C11 | 113.8 (4) |
C3A—C3—C2 | 105.6 (3) | C10—C9—C1 | 102.6 (3) |
C3A—C3—H3A | 110.6 | C11—C9—C1 | 118.1 (4) |
C2—C3—H3A | 110.6 | C10—C9—H9A | 107.3 |
C3A—C3—H3B | 110.6 | C11—C9—H9A | 107.3 |
C2—C3—H3B | 110.6 | C1—C9—H9A | 107.3 |
H3A—C3—H3B | 108.7 | O3—C10—O1 | 120.5 (4) |
C13—C3A—C4 | 110.0 (3) | O3—C10—C9 | 129.1 (5) |
C13—C3A—C3 | 113.5 (3) | O1—C10—C9 | 110.4 (3) |
C4—C3A—C3 | 114.1 (3) | C9—C11—H11A | 109.5 |
C13—C3A—C5A | 114.7 (3) | C9—C11—H11B | 109.5 |
C4—C3A—C5A | 99.3 (3) | H11A—C11—H11B | 109.5 |
C3—C3A—C5A | 104.5 (3) | C9—C11—H11C | 109.5 |
C7—C4—C5 | 101.2 (3) | H11A—C11—H11C | 109.5 |
C7—C4—C3A | 114.0 (3) | H11B—C11—H11C | 109.5 |
C5—C4—C3A | 102.8 (3) | C7—C12—H12A | 109.5 |
C7—C4—H4A | 112.7 | C7—C12—H12B | 109.5 |
C5—C4—H4A | 112.7 | H12A—C12—H12B | 109.5 |
C3A—C4—H4A | 112.7 | C7—C12—H12C | 109.5 |
O2—C5—C4 | 127.8 (4) | H12A—C12—H12C | 109.5 |
O2—C5—C6 | 125.6 (4) | H12B—C12—H12C | 109.5 |
C4—C5—C6 | 106.5 (3) | C3A—C13—H13A | 109.5 |
C1—C5A—C6 | 117.4 (3) | C3A—C13—H13B | 109.5 |
C1—C5A—C3A | 100.0 (3) | H13A—C13—H13B | 109.5 |
C6—C5A—C3A | 104.8 (3) | C3A—C13—H13C | 109.5 |
C1—C5A—H51A | 111.3 | H13A—C13—H13C | 109.5 |
C6—C5A—H51A | 111.3 | H13B—C13—H13C | 109.5 |
C3A—C5A—H51A | 111.3 | ||
C8—C1—C2—C3 | −71.5 (4) | O2—C5—C6—C5A | 176.2 (4) |
C5A—C1—C2—C3 | 42.7 (4) | C4—C5—C6—C5A | −6.6 (4) |
C9—C1—C2—C3 | 176.9 (4) | C5—C4—C7—C8 | 83.4 (4) |
C1—C2—C3—C3A | −18.2 (4) | C3A—C4—C7—C8 | −26.1 (4) |
C2—C3—C3A—C13 | −137.7 (3) | C5—C4—C7—C12 | −89.8 (4) |
C2—C3—C3A—C4 | 95.3 (4) | C3A—C4—C7—C12 | 160.6 (3) |
C2—C3—C3A—C5A | −12.1 (4) | C12—C7—C8—O1 | −3.0 (6) |
C13—C3A—C4—C7 | −176.3 (3) | C4—C7—C8—O1 | −175.6 (3) |
C3—C3A—C4—C7 | −47.5 (4) | C12—C7—C8—C1 | 179.4 (3) |
C5A—C3A—C4—C7 | 63.1 (4) | C4—C7—C8—C1 | 6.7 (5) |
C13—C3A—C4—C5 | 75.2 (4) | C10—O1—C8—C7 | 168.2 (4) |
C3—C3A—C4—C5 | −156.0 (3) | C10—O1—C8—C1 | −13.8 (4) |
C5A—C3A—C4—C5 | −45.5 (3) | C5A—C1—C8—C7 | −27.8 (5) |
C7—C4—C5—O2 | 92.4 (5) | C9—C1—C8—C7 | −156.5 (4) |
C3A—C4—C5—O2 | −149.6 (4) | C2—C1—C8—C7 | 81.6 (4) |
C7—C4—C5—C6 | −84.7 (3) | C5A—C1—C8—O1 | 154.3 (3) |
C3A—C4—C5—C6 | 33.2 (4) | C9—C1—C8—O1 | 25.5 (4) |
C8—C1—C5A—C6 | −49.2 (4) | C2—C1—C8—O1 | −96.3 (3) |
C9—C1—C5A—C6 | 66.8 (5) | C8—C1—C9—C10 | −26.2 (4) |
C2—C1—C5A—C6 | −162.1 (3) | C5A—C1—C9—C10 | −146.2 (4) |
C8—C1—C5A—C3A | 63.4 (3) | C2—C1—C9—C10 | 89.1 (4) |
C9—C1—C5A—C3A | 179.4 (3) | C8—C1—C9—C11 | −152.2 (4) |
C2—C1—C5A—C3A | −49.5 (3) | C5A—C1—C9—C11 | 87.8 (5) |
C13—C3A—C5A—C1 | 162.8 (3) | C2—C1—C9—C11 | −36.9 (6) |
C4—C3A—C5A—C1 | −80.0 (3) | C8—O1—C10—O3 | 175.5 (4) |
C3—C3A—C5A—C1 | 38.0 (3) | C8—O1—C10—C9 | −4.8 (4) |
C13—C3A—C5A—C6 | −75.2 (4) | C11—C9—C10—O3 | −31.0 (7) |
C4—C3A—C5A—C6 | 42.0 (3) | C1—C9—C10—O3 | −159.7 (5) |
C3—C3A—C5A—C6 | 160.0 (3) | C11—C9—C10—O1 | 149.3 (3) |
C1—C5A—C6—C5 | 87.6 (4) | C1—C9—C10—O1 | 20.5 (4) |
C3A—C5A—C6—C5 | −22.2 (4) |
Experimental details
(I) | (II) | |
Crystal data | ||
Chemical formula | C15H20O4 | C15H18O3 |
Mr | 264.31 | 246.29 |
Crystal system, space group | Orthorhombic, P212121 | Orthorhombic, P212121 |
Temperature (K) | 296 | 296 |
a, b, c (Å) | 6.770 (2), 13.160 (3), 15.553 (4) | 8.562 (2), 11.656 (3), 13.275 (4) |
V (Å3) | 1385.7 (6) | 1324.8 (6) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.09 | 0.09 |
Crystal size (mm) | 0.46 × 0.25 × 0.11 | 0.24 × 0.17 × 0.06 |
Data collection | ||
Diffractometer | Siemens P4 diffractometer | Siemens P4 diffractometer |
Absorption correction | Numerical (SHELXTL; Sheldrick, 1997) | Numerical (SHELXTL; Sheldrick, 1997) |
Tmin, Tmax | 0.976, 0.990 | 0.972, 0.990 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2846, 1424, 1065 | 2891, 1446, 875 |
Rint | 0.048 | 0.061 |
(sin θ/λ)max (Å−1) | 0.596 | 0.607 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.050, 0.128, 1.06 | 0.052, 0.093, 1.00 |
No. of reflections | 1424 | 1446 |
No. of parameters | 173 | 167 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.15, −0.17 | 0.18, −0.13 |
Computer programs: XSCANS (Siemens, 1996), XSCANS, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXP97 (Sheldrick, 1997), SHELXL97.
O3—C10 | 1.227 (5) | O4—C10 | 1.319 (5) |
O3—C10—C9 | 122.1 (4) | O4—C10—C9 | 115.3 (3) |
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Our continuing interest in the crystal structures of solid ketocarboxylic acids lies in defining the molecular characteristics that control their various hydrogen-bonding modes. For simple keto acids, five of these are known, including two in which the ketone does not participate, viz. the common acid dimer and the rare acid-to-acid catemer motifs. Among factors that appear to discourage dimerization are (i) restrictions in the conformations available and (ii) the presence of a single enantiomer. A factor that ought to favor carboxy-to-ketone hydrogen-bonding patterns is (iii) the presence of multiple ketone receptors for the hydrogen bond.
The title compounds are derived from a sesquiterpenoid isolate of Artemisia, (-)-α-santonin, whose transformations have provided rich subject material for numerous structural, analytical and synthetic studies over the years (Cannizzaro, 1885; Woodward et al., 1948; Mislow & Djerassi, 1960; Hirakura et al., 1962). We have previously reported the structures of several keto acid santonin derivatives (Brunskill et al., 1999, 2001, 2002; Thompson & Lalancette, 2003). We now report that the title compound, (I), embodying all of the features enumerated above, adopts the rare acid-to-acid catemeric hydrogen-bonding mode in the solid state. Like its isomer, santonic acid (Brunskill et al., 1999), (I) is a tricyclic γ,ε-diketo acid. It differs from santonic acid in the relative sizes of two of the rings in its tricyclic system and in the absolute configuration at the site adjacent to the carboxy group, whose chirality is independent of the rest of the molecule. This center is S in santonic acid but R in (I) and its enol lactone, parasantonide, (II), whose structure we also report.
Fig. 1 shows the asymmetric unit of (I), with its numbering. The rigidity of the tricyclic framework leaves conformationally significant rotations possible only about C1—C9 and C9—C10. Of these, the arrangement about the former is staggered, with the C9 methyl group and the γ-ketone anti to one another [torsion angle C8—C1—C9—C11 = −176.6 (4)°]. The carboxy group is rotated to a C1—C9—C10—O3 torsion angle of 146.0 (4)°, so that the carboxy group and the γ-ketone carbonyl groups point in similar directions. The stereochemistry of the methyl group at atom C7 is thought to arise during the generation of (I), by hydrolysis of (+)-parasantonide, and evidently represents the thermodynamically favored configuration at this site (Woodward & Kovach, 1950).
Averaging of C—O bond lengths and C—C—O angles by disorder, although common in carboxy dimers, is not observed in any other keto acid aggregation mode, since other geometries cannot support the averaging processes involved. In (I), which is not dimeric, these C—O bond lengths are 1.227 (5) and 1.319 (5) Å, with angles of 122.1 (4) and 115.3 (3)°. Our own survey of 56 keto acid structures that are not acid dimers gives average values of 1.20 (1) and 1.32 (2) Å, and 124.5 (14) and 112.7 (17)°, for these lengths and angles, in accordance with typical values of 1.21 and 1.31 Å, and 123 and 112°, cited for highly ordered dimeric carboxyls (Borthwick, 1980).
Fig. 2 illustrates the packing, which involves acid-to-acid catemers whose hydrogen-bonding follows the 21 screw axis along a, from each carboxy H to the C=O group of a neighboring carboxy group [O···O = 2.672 (4) Å; O—H···O = 172.9 °]. Two parallel counterdirectional single-strand chains pass through the cell in the a direction. This hydrogen-bonding mode is quite rare, with only three or four occurrences in the keto acid X-ray literature. Among the 90-odd keto acids whose structures we have determined, this is only the second acid-to-acid catemer we have observed, the other also being a chiral non-racemate (Lalancette et al., 1998), in common with all other instances we are aware of.
We characterize the geometry of hydrogen bonding to carbonyls using a combination of the H···O=C angle and the H···O=C—C torsion angle. These describe the approach of the acid H atom to the receptor O atom in terms of its deviation from, respectively, C=O axiality (ideal = 120°) and planarity with the carbonyl (ideal = 0°). In (I) the values for these two angles are 136.2 and −0.8°.
Two intermolecular C=O···H—C close contacts exist for (I), involving atoms O1 (2.53 Å to H13C) and O3 (2.44 Å to H9A). These distances all lie within the 2.7 Å range we normally employ for non-bonded H···O packing interactions (Steiner, 1997). Using compiled data for a large number of C—H···O contacts, Steiner & Desiraju (1998) find significant statistical directionality, even as far out as 3.0 Å, and conclude that these are legitimately viewed as `weak hydrogen bonds', with a greater contribution to packing forces than simple van der Waals attractions.
Fig. 3 shows the structure of (+)-parasantonide, (II), which is the synthetic precursor to (I) and is itself formed from (-)-santonic acid by acidic reflux and pyrolysis at temperatures up to 573 K. All the major structural features of (I) may be seen either in obvious or incipient form in (II), including the R configuration at the C9 chiral center and the enol-lactone, which gives rise on hydrolysis to the carboxy group, the γ-ketone and the stereochemistry at atom C7 in (I). The packing of (II) (Z = 4) lacks hydrogen bonding and involves no C—H···O contacts closer than 2.7 Å.
The solid-state (KBr) IR spectrum of (I) has absorption bands at 1743 (strained ε-ketone) and 1709 cm−1 (carboxy C=O and γ-ketone). In CHCl3 solution, the relative intensities and widths of these bands are altered but the frequencies are unchanged.