Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100013135/fr1300sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270100013135/fr1300Isup2.hkl |
CCDC reference: 156184
Commercial gibberellic acid, obtained from Acros Organics/Fisher Scientific, Springfield, NJ, USA, and sold as "90%+ pure," was treated with refluxing 1.75 M HCl as described by Cross (1954). Compound (I), mp 538 K, was slowly deposited from the decanted aqueous layer in extremely low yield, and was recrystallized from ethyl acetate, yielding the crystal used for this study.
All non-carboxyl H atoms were found in electron-density difference maps but placed in calculated positions and allowed to refine as riding models with temperature factors set at 120% of their respective carbon atoms. The hydroxyl H atom also was found in electron-density difference maps and its positional parameters were allowed to refine; its isotropic temperature factor was set at 150% of its oxygen atom. The carboxyl H atom was found in difference maps and was allowed to ride on its oxygen atom at 0.82 Å. The absolute configuration was chosen to the known configuration of other gibberellins (Mander, 1992).
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: SHELXL97; software used to prepare material for publication: SHELXL97.
C19H24O6·H2O | Dx = 1.311 Mg m−3 |
Mr = 366.40 | Melting point: 538 K |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
a = 9.730 (1) Å | Cell parameters from 39 reflections |
b = 10.661 (2) Å | θ = 4.2–14.0° |
c = 17.898 (3) Å | µ = 0.10 mm−1 |
V = 1856.6 (5) Å3 | T = 293 K |
Z = 4 | Rhombohedron, colorless |
F(000) = 784 | 0.40 × 0.30 × 0.20 mm |
Siemens P4 diffractometer | Rint = 0.063 |
Radiation source: normal-focus sealed tube | θmax = 25.0°, θmin = 2.3° |
Graphite monochromator | h = −11→11 |
2θ/θ scans | k = −12→12 |
3758 measured reflections | l = −21→21 |
1879 independent reflections | 3 standard reflections every 97 reflections |
1054 reflections with I > 2σ(I) | intensity decay: Variation < 1% |
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)] = 0.053 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.108 | w = 1/[σ2(Fo2) + (0.0359P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.02 | (Δ/σ)max < 0.001 |
1879 reflections | Δρmax = 0.31 e Å−3 |
247 parameters | Δρmin = −0.17 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0034 (10) |
C19H24O6·H2O | V = 1856.6 (5) Å3 |
Mr = 366.40 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 9.730 (1) Å | µ = 0.10 mm−1 |
b = 10.661 (2) Å | T = 293 K |
c = 17.898 (3) Å | 0.40 × 0.30 × 0.20 mm |
Siemens P4 diffractometer | Rint = 0.063 |
3758 measured reflections | 3 standard reflections every 97 reflections |
1879 independent reflections | intensity decay: Variation < 1% |
1054 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.053 | 0 restraints |
wR(F2) = 0.108 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.02 | Δρmax = 0.31 e Å−3 |
1879 reflections | Δρmin = −0.17 e Å−3 |
247 parameters |
Experimental. 'Crystal mounted on glass fiber using epoxy resin' |
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 after merging Friedel equivalents. 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 | 0.1933 (4) | 0.5707 (4) | 0.7472 (2) | 0.0553 (11) | |
O2 | 0.6888 (5) | 0.2159 (3) | 0.6040 (2) | 0.0634 (13) | |
O3 | 0.7335 (4) | 0.3052 (4) | 0.71322 (19) | 0.0582 (12) | |
O4 | 0.6641 (5) | 0.7805 (3) | 0.5551 (2) | 0.0623 (12) | |
O5 | 0.5026 (4) | 0.6364 (3) | 0.5350 (2) | 0.0441 (10) | |
O6 | 0.7986 (4) | 0.4545 (4) | 0.4036 (2) | 0.0613 (13) | |
O7 | 0.5625 (5) | 0.9829 (4) | 0.6327 (2) | 0.0606 (13) | |
C1 | 0.7299 (5) | 0.5688 (5) | 0.5151 (3) | 0.0393 (13) | |
C2 | 0.7379 (6) | 0.5687 (5) | 0.4278 (3) | 0.0462 (14) | |
C3 | 0.5957 (6) | 0.5808 (7) | 0.3913 (3) | 0.0599 (17) | |
C4 | 0.4837 (6) | 0.5000 (6) | 0.4268 (3) | 0.0524 (16) | |
C4A | 0.4987 (6) | 0.5019 (5) | 0.5115 (3) | 0.0390 (13) | |
C4B | 0.3995 (5) | 0.4296 (5) | 0.5594 (3) | 0.0369 (13) | |
C5 | 0.2464 (6) | 0.4592 (5) | 0.5609 (3) | 0.0499 (16) | |
C6 | 0.1761 (6) | 0.3734 (5) | 0.6181 (3) | 0.0506 (16) | |
C7 | 0.2514 (6) | 0.3673 (5) | 0.6942 (3) | 0.0412 (14) | |
C8 | 0.2754 (6) | 0.5030 (6) | 0.7146 (3) | 0.0419 (15) | |
C9 | 0.4152 (5) | 0.5422 (4) | 0.6864 (3) | 0.0389 (14) | |
C9A | 0.4648 (5) | 0.4289 (5) | 0.6385 (3) | 0.0335 (12) | |
C10 | 0.6223 (5) | 0.4298 (5) | 0.6226 (3) | 0.0337 (12) | |
C10A | 0.6405 (5) | 0.4583 (4) | 0.5384 (3) | 0.0345 (14) | |
C11 | 0.3996 (6) | 0.3217 (4) | 0.6827 (3) | 0.0407 (15) | |
C12 | 0.6864 (6) | 0.3052 (5) | 0.6440 (3) | 0.0382 (13) | |
C13 | 0.8710 (5) | 0.5777 (5) | 0.5499 (3) | 0.0546 (16) | |
C14 | 0.6342 (7) | 0.6739 (5) | 0.5371 (3) | 0.0444 (15) | |
C15 | 0.1690 (7) | 0.2933 (5) | 0.7509 (3) | 0.0640 (19) | |
H3 | 0.7673 | 0.2365 | 0.7227 | 0.087* | |
H6 | 0.891 (7) | 0.469 (6) | 0.398 (3) | 0.092* | |
H7A | 0.577 (7) | 0.905 (6) | 0.605 (3) | 0.091* | |
H7B | 0.627 (6) | 1.044 (6) | 0.622 (4) | 0.091* | |
H2 | 0.7956 | 0.6389 | 0.4115 | 0.055* | |
H3A | 0.5673 | 0.6680 | 0.3937 | 0.072* | |
H3B | 0.6036 | 0.5583 | 0.3390 | 0.072* | |
H4A | 0.3939 | 0.5320 | 0.4129 | 0.063* | |
H4B | 0.4911 | 0.4145 | 0.4087 | 0.063* | |
H4C | 0.4058 | 0.3427 | 0.5419 | 0.044* | |
H5A | 0.2070 | 0.4457 | 0.5118 | 0.060* | |
H5B | 0.2324 | 0.5463 | 0.5745 | 0.060* | |
H6A | 0.1703 | 0.2894 | 0.5975 | 0.061* | |
H6B | 0.0831 | 0.4030 | 0.6263 | 0.061* | |
H9A | 0.4776 | 0.5577 | 0.7276 | 0.047* | |
H9B | 0.4086 | 0.6175 | 0.6562 | 0.047* | |
H10 | 0.6654 | 0.4969 | 0.6519 | 0.040* | |
H10A | 0.6685 | 0.3824 | 0.5115 | 0.041* | |
H11A | 0.4458 | 0.3094 | 0.7302 | 0.049* | |
H11B | 0.4019 | 0.2439 | 0.6546 | 0.049* | |
H13A | 0.9253 | 0.5071 | 0.5345 | 0.066* | |
H13B | 0.8626 | 0.5780 | 0.6033 | 0.066* | |
H13C | 0.9147 | 0.6538 | 0.5338 | 0.066* | |
H15A | 0.1659 | 0.2067 | 0.7363 | 0.077* | |
H15B | 0.0772 | 0.3260 | 0.7533 | 0.077* | |
H15C | 0.2116 | 0.3003 | 0.7991 | 0.077* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.052 (3) | 0.051 (2) | 0.062 (2) | −0.001 (2) | 0.009 (2) | −0.028 (2) |
O2 | 0.102 (4) | 0.034 (2) | 0.055 (2) | 0.020 (3) | −0.007 (3) | −0.004 (2) |
O3 | 0.071 (3) | 0.050 (2) | 0.054 (2) | 0.010 (2) | −0.018 (2) | 0.010 (2) |
O4 | 0.073 (3) | 0.033 (2) | 0.081 (3) | −0.001 (2) | 0.010 (3) | −0.006 (2) |
O5 | 0.050 (3) | 0.0337 (19) | 0.049 (2) | 0.007 (2) | 0.006 (2) | 0.0078 (18) |
O6 | 0.059 (3) | 0.051 (2) | 0.074 (3) | 0.003 (2) | 0.021 (2) | −0.009 (2) |
O7 | 0.064 (3) | 0.053 (2) | 0.065 (3) | −0.002 (2) | −0.002 (3) | −0.014 (2) |
C1 | 0.039 (3) | 0.029 (2) | 0.051 (3) | 0.002 (3) | 0.006 (3) | 0.000 (3) |
C2 | 0.048 (4) | 0.037 (3) | 0.053 (3) | 0.003 (4) | 0.018 (3) | 0.001 (3) |
C3 | 0.063 (4) | 0.074 (4) | 0.043 (3) | −0.002 (4) | 0.002 (3) | 0.005 (4) |
C4 | 0.052 (4) | 0.061 (4) | 0.044 (3) | 0.007 (4) | 0.004 (3) | −0.001 (3) |
C4A | 0.045 (3) | 0.034 (3) | 0.038 (3) | 0.002 (3) | −0.002 (3) | 0.001 (3) |
C4B | 0.037 (3) | 0.035 (3) | 0.039 (3) | 0.004 (3) | −0.003 (3) | −0.002 (3) |
C5 | 0.053 (4) | 0.060 (4) | 0.037 (3) | −0.007 (3) | −0.008 (3) | −0.001 (3) |
C6 | 0.047 (4) | 0.051 (3) | 0.054 (4) | −0.003 (3) | 0.000 (3) | −0.012 (3) |
C7 | 0.046 (4) | 0.034 (3) | 0.043 (3) | −0.009 (3) | 0.009 (3) | 0.004 (3) |
C8 | 0.051 (4) | 0.045 (3) | 0.031 (3) | 0.001 (3) | −0.007 (3) | −0.010 (3) |
C9 | 0.042 (4) | 0.037 (3) | 0.038 (3) | −0.003 (3) | −0.002 (3) | −0.001 (3) |
C9A | 0.036 (3) | 0.029 (2) | 0.036 (3) | 0.002 (3) | −0.004 (2) | 0.003 (3) |
C10 | 0.040 (3) | 0.024 (2) | 0.037 (3) | 0.002 (3) | −0.008 (2) | 0.001 (3) |
C10A | 0.041 (3) | 0.027 (3) | 0.035 (3) | 0.003 (2) | 0.003 (3) | −0.005 (2) |
C11 | 0.056 (4) | 0.024 (3) | 0.042 (3) | −0.002 (3) | −0.004 (3) | −0.002 (3) |
C12 | 0.039 (4) | 0.037 (3) | 0.038 (3) | 0.001 (3) | −0.003 (3) | 0.006 (3) |
C13 | 0.054 (4) | 0.044 (3) | 0.065 (4) | −0.012 (3) | 0.000 (3) | 0.011 (3) |
C14 | 0.056 (5) | 0.034 (3) | 0.043 (3) | −0.003 (3) | 0.009 (3) | 0.006 (3) |
C15 | 0.073 (5) | 0.054 (4) | 0.065 (4) | −0.004 (4) | 0.013 (4) | −0.011 (4) |
O1—C8 | 1.224 (6) | C10—C10A | 1.549 (7) |
O2—C12 | 1.191 (5) | O3—H3 | 0.8200 |
O3—C12 | 1.320 (6) | O6—H6 | 0.92 (7) |
O4—C14 | 1.216 (6) | O7—H7A | 0.98 (7) |
O5—C14 | 1.342 (7) | O7—H7B | 0.92 (7) |
O5—C4A | 1.496 (6) | C2—H2 | 0.9800 |
O6—C2 | 1.420 (6) | C3—H3A | 0.9700 |
C1—C14 | 1.509 (7) | C3—H3B | 0.9700 |
C1—C13 | 1.510 (7) | C4—H4A | 0.9700 |
C1—C10A | 1.522 (7) | C4—H4B | 0.9700 |
C1—C2 | 1.565 (7) | C4B—H4C | 0.9800 |
C2—C3 | 1.535 (8) | C5—H5A | 0.9700 |
C3—C4 | 1.528 (8) | C5—H5B | 0.9700 |
C4—C4A | 1.522 (6) | C6—H6A | 0.9700 |
C4A—C4B | 1.503 (7) | C6—H6B | 0.9700 |
C4A—C10A | 1.533 (7) | C9—H9A | 0.9700 |
C4B—C5 | 1.523 (7) | C9—H9B | 0.9700 |
C4B—C9A | 1.553 (6) | C10—H10 | 0.9800 |
C5—C6 | 1.534 (7) | C10A—H10A | 0.9800 |
C6—C7 | 1.547 (7) | C11—H11A | 0.9700 |
C7—C8 | 1.510 (7) | C11—H11B | 0.9700 |
C7—C15 | 1.516 (7) | C13—H13A | 0.9600 |
C7—C11 | 1.535 (8) | C13—H13B | 0.9600 |
C8—C9 | 1.511 (7) | C13—H13C | 0.9600 |
C9—C9A | 1.557 (6) | C15—H15A | 0.9600 |
C9A—C11 | 1.528 (6) | C15—H15B | 0.9600 |
C9A—C10 | 1.558 (7) | C15—H15C | 0.9600 |
C10—C12 | 1.517 (7) | ||
C14—O5—C4A | 108.5 (4) | O6—C2—H2 | 109.0 |
C14—C1—C13 | 114.0 (5) | C3—C2—H2 | 109.0 |
C14—C1—C10A | 98.7 (4) | C1—C2—H2 | 109.0 |
C13—C1—C10A | 117.1 (4) | C4—C3—H3A | 108.6 |
C14—C1—C2 | 106.9 (4) | C2—C3—H3A | 108.6 |
C13—C1—C2 | 111.5 (5) | C4—C3—H3B | 108.6 |
C10A—C1—C2 | 107.5 (4) | C2—C3—H3B | 108.6 |
O6—C2—C3 | 108.5 (5) | H3A—C3—H3B | 107.6 |
O6—C2—C1 | 109.0 (5) | C4A—C4—H4A | 109.7 |
C3—C2—C1 | 112.3 (4) | C3—C4—H4A | 109.7 |
C4—C3—C2 | 114.8 (5) | C4A—C4—H4B | 109.7 |
C4A—C4—C3 | 109.8 (5) | C3—C4—H4B | 109.7 |
O5—C4A—C4 | 107.1 (4) | H4A—C4—H4B | 108.2 |
C4B—C4A—C4 | 119.9 (5) | C4A—C4B—H4C | 105.2 |
O5—C4A—C10A | 100.3 (4) | C5—C4B—H4C | 105.2 |
O5—C4A—C4B | 110.3 (4) | C9A—C4B—H4C | 105.2 |
C4B—C4A—C10A | 104.1 (4) | C4B—C5—H5A | 109.9 |
C4—C4A—C10A | 113.3 (5) | C6—C5—H5A | 109.9 |
C4A—C4B—C5 | 122.2 (5) | C4B—C5—H5B | 109.9 |
C4A—C4B—C9A | 105.1 (4) | C6—C5—H5B | 109.9 |
C5—C4B—C9A | 112.6 (4) | H5A—C5—H5B | 108.3 |
C4B—C5—C6 | 109.0 (5) | C5—C6—H6A | 108.8 |
C5—C6—C7 | 113.6 (5) | C7—C6—H6A | 108.8 |
C8—C7—C15 | 114.7 (5) | C5—C6—H6B | 108.8 |
C8—C7—C11 | 101.0 (5) | C7—C6—H6B | 108.8 |
C15—C7—C11 | 114.9 (5) | H6A—C6—H6B | 107.7 |
C8—C7—C6 | 104.3 (4) | C8—C9—H9A | 110.9 |
C15—C7—C6 | 111.1 (5) | C9A—C9—H9A | 110.9 |
C11—C7—C6 | 109.9 (4) | C8—C9—H9B | 110.9 |
O1—C8—C7 | 125.5 (6) | C9A—C9—H9B | 110.9 |
O1—C8—C9 | 125.7 (5) | H9A—C9—H9B | 108.9 |
C7—C8—C9 | 108.8 (5) | C12—C10—H10 | 109.1 |
C8—C9—C9A | 104.4 (4) | C10A—C10—H10 | 109.1 |
C11—C9A—C4B | 107.8 (4) | C9A—C10—H10 | 109.1 |
C11—C9A—C9 | 99.6 (3) | C1—C10A—H10A | 110.3 |
C4B—C9A—C9 | 111.8 (4) | C4A—C10A—H10A | 110.3 |
C11—C9A—C10 | 120.5 (4) | C10—C10A—H10A | 110.3 |
C4B—C9A—C10 | 103.6 (4) | C9A—C11—H11A | 111.2 |
C9—C9A—C10 | 113.6 (4) | C7—C11—H11A | 111.2 |
C12—C10—C10A | 111.7 (4) | C9A—C11—H11B | 111.2 |
C12—C10—C9A | 110.7 (4) | C7—C11—H11B | 111.2 |
C10A—C10—C9A | 107.0 (4) | H11A—C11—H11B | 109.1 |
C1—C10A—C4A | 101.2 (4) | C1—C13—H13A | 109.5 |
C1—C10A—C10 | 118.9 (4) | C1—C13—H13B | 109.5 |
C4A—C10A—C10 | 105.2 (4) | H13A—C13—H13B | 109.5 |
C9A—C11—C7 | 102.8 (4) | C1—C13—H13C | 109.5 |
O2—C12—O3 | 123.9 (5) | H13A—C13—H13C | 109.5 |
O2—C12—C10 | 123.7 (5) | H13B—C13—H13C | 109.5 |
O3—C12—C10 | 112.3 (4) | C7—C15—H15A | 109.5 |
O4—C14—O5 | 120.9 (6) | C7—C15—H15B | 109.5 |
O4—C14—C1 | 128.0 (6) | H15A—C15—H15B | 109.5 |
O5—C14—C1 | 111.1 (5) | C7—C15—H15C | 109.5 |
C12—O3—H3 | 109.5 | H15A—C15—H15C | 109.5 |
C2—O6—H6 | 107 (4) | H15B—C15—H15C | 109.5 |
H7A—O7—H7B | 114 (6) | ||
C14—C1—C2—O6 | −165.9 (4) | C8—C9—C9A—C4B | 80.2 (5) |
C13—C1—C2—O6 | 68.8 (6) | C8—C9—C9A—C10 | −163.0 (4) |
C10A—C1—C2—O6 | −60.8 (5) | C11—C9A—C10—C12 | 9.9 (6) |
C14—C1—C2—C3 | −45.7 (7) | C4B—C9A—C10—C12 | −110.6 (5) |
C13—C1—C2—C3 | −170.9 (5) | C9—C9A—C10—C12 | 127.9 (4) |
C10A—C1—C2—C3 | 59.5 (6) | C11—C9A—C10—C10A | 131.9 (4) |
O6—C2—C3—C4 | 77.0 (6) | C4B—C9A—C10—C10A | 11.3 (5) |
C1—C2—C3—C4 | −43.5 (7) | C9—C9A—C10—C10A | −110.1 (5) |
C2—C3—C4—C4A | 40.5 (7) | C14—C1—C10A—C4A | 41.3 (4) |
C14—O5—C4A—C4B | 136.0 (5) | C13—C1—C10A—C4A | 164.1 (5) |
C14—O5—C4A—C4 | −91.9 (5) | C2—C1—C10A—C4A | −69.6 (5) |
C14—O5—C4A—C10A | 26.6 (5) | C14—C1—C10A—C10 | −73.1 (5) |
C3—C4—C4A—O5 | 53.0 (6) | C13—C1—C10A—C10 | 49.6 (7) |
C3—C4—C4A—C4B | 179.6 (5) | C2—C1—C10A—C10 | 176.0 (4) |
C3—C4—C4A—C10A | −56.7 (7) | O5—C4A—C10A—C1 | −42.2 (5) |
O5—C4A—C4B—C5 | 62.7 (6) | C4B—C4A—C10A—C1 | −156.4 (4) |
C4—C4A—C4B—C5 | −62.4 (7) | C4—C4A—C10A—C1 | 71.7 (6) |
C10A—C4A—C4B—C5 | 169.6 (5) | O5—C4A—C10A—C10 | 82.2 (4) |
O5—C4A—C4B—C9A | −67.1 (5) | C4B—C4A—C10A—C10 | −32.1 (5) |
C4—C4A—C4B—C9A | 167.8 (5) | C4—C4A—C10A—C10 | −164.0 (5) |
C10A—C4A—C4B—C9A | 39.8 (5) | C12—C10—C10A—C1 | −114.2 (5) |
C4A—C4B—C5—C6 | −177.1 (4) | C9A—C10—C10A—C1 | 124.6 (5) |
C9A—C4B—C5—C6 | −50.5 (6) | C12—C10—C10A—C4A | 133.5 (4) |
C4B—C5—C6—C7 | 47.4 (6) | C9A—C10—C10A—C4A | 12.3 (5) |
C5—C6—C7—C8 | 49.5 (6) | C4B—C9A—C11—C7 | −69.1 (5) |
C5—C6—C7—C15 | 173.6 (5) | C9—C9A—C11—C7 | 47.7 (4) |
C5—C6—C7—C11 | −58.1 (6) | C10—C9A—C11—C7 | 172.5 (4) |
C15—C7—C8—O1 | −35.9 (8) | C8—C7—C11—C9A | −43.2 (5) |
C11—C7—C8—O1 | −160.1 (5) | C15—C7—C11—C9A | −167.2 (4) |
C6—C7—C8—O1 | 85.8 (6) | C6—C7—C11—C9A | 66.5 (5) |
C15—C7—C8—C9 | 145.7 (5) | C10A—C10—C12—O2 | −34.4 (8) |
C11—C7—C8—C9 | 21.5 (6) | C9A—C10—C12—O2 | 84.7 (7) |
C6—C7—C8—C9 | −92.6 (5) | C10A—C10—C12—O3 | 148.5 (5) |
O1—C8—C9—C9A | −170.8 (5) | C9A—C10—C12—O3 | −92.4 (5) |
C7—C8—C9—C9A | 7.6 (6) | C4A—O5—C14—O4 | −179.6 (5) |
C4A—C4B—C9A—C11 | −160.3 (4) | C4A—O5—C14—C1 | 0.2 (6) |
C5—C4B—C9A—C11 | 64.5 (6) | C13—C1—C14—O4 | 27.9 (8) |
C4A—C4B—C9A—C9 | 91.2 (5) | C10A—C1—C14—O4 | 152.9 (6) |
C5—C4B—C9A—C9 | −44.0 (6) | C2—C1—C14—O4 | −95.7 (7) |
C4A—C4B—C9A—C10 | −31.5 (5) | C13—C1—C14—O5 | −151.8 (5) |
C5—C4B—C9A—C10 | −166.8 (4) | C10A—C1—C14—O5 | −26.9 (5) |
C8—C9—C9A—C11 | −33.5 (5) | C2—C1—C14—O5 | 84.5 (6) |
Experimental details
Crystal data | |
Chemical formula | C19H24O6·H2O |
Mr | 366.40 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 293 |
a, b, c (Å) | 9.730 (1), 10.661 (2), 17.898 (3) |
V (Å3) | 1856.6 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.40 × 0.30 × 0.20 |
Data collection | |
Diffractometer | Siemens P4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3758, 1879, 1054 |
Rint | 0.063 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.053, 0.108, 1.02 |
No. of reflections | 1879 |
No. of parameters | 247 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.31, −0.17 |
Computer programs: XSCANS (Siemens, 1996), XSCANS, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXL97.
In our pursuit of X-ray crystal structures of keto carboxylic acids (Lalancette et al., 1999), acidic degradation was carried out on commercial gibberellic acid (gibberellin A3). In addition to the desired gibberic acid, this gave a minute yield of a by-product we have identified as gibberellin C, whose monohydrate, (I), yielded the X-ray structure and solid-state hydrogen-bonding pattern we now report. \sch
The gibberellins are an important family of diterpenoid plant growth factors first isolated from cultures of the fungus Gibberella fujikuroi in the late 1930 s. However (I) is almost certainly not a `primary' gibberellin, isolatable directly from such sources without synthetic transformation, despite one suggestion of such a source (Connolly & Hill, 1991). Gibberellin C is known to arise from gibberellin A1 by acid-catalyzed rearrangement of the bridged C/D ring juncture (Mander, 1992; Stork et al., 1965). Since the gibberellin A3 of commerce is offered in a purity of only ca 90%, isolation of (I) in our case undoubtedly resulted from transformation of gibberellin A1 present as an impurity. Both the structure (Cross et al., 1961) and stereochemistry (Hartsuck & Lipscomb, 1963; McCapra et al., 1966) of gibberellin C have long been firmly established, but the stereochemistry at C4B shown in the reference cited above (Connolly & Hill, 1991) is incorrect. The early structure-elucidation literature on gibberellins is both voluminous and replete with provisional structural (Takahashi et al., 1959) and stereochemical (Cross et al., 1961) assignments subsequently superseded. An excellent and exhaustive more recent review of the chemistry of the gibberellins is available (Mander, 1992).
Fig. 1 shows the asymmetric unit for (I) with its Chemical Abstracts `gibbane' numbering, which differs from the alternative `gibberellin' numbering often encountered (Mander, 1992; Budavari,1989). The H atoms at C4B and C10A, as well as the methyl at C1, the hydroxyl at C2, the methano (C11) bridge and the carboxyl all lie on the `upper' β face of the molecule. Only the lactone and ketone bridges have α stereochemistry. The molecule has very little conformational flexibility and the only available skeletal rotation of significance involves the carboxyl, which is turned so that its C═O is toward the β face. The H of the axial hydroxyl is aimed away from the ring system toward a water of hydration, which in turn donates hydrogen bonds to two different C═O groups in separate molecules (see below). Fig. 1 shows this water, arbitrarily, in its hydrogen-bonding relationship to the lactone carbonyl (O4).
Because the carboxyl is not dimerized but hydrogen bonded to other species, it shows no disorder. Averaging of C—O bond lengths and C—C—O angles by disorder is common in carboxyl dimers (Leiserowitz, 1976) but is not seen in catemers and other hydrogen-bonding arrangements whose geometry cannot support the mechanisms responsible for such averaging. In (I), these C—O bond lengths are 1.191 (5) and 1.320 (6) Å, with angles of 123.7 (5) and 112.3 (5)°. Our own survey of 56 keto acid structures which 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 accord with typical values of 1.21 and 1.31 Å and 123 and 112°, cited for highly ordered dimeric carboxyls (Borthwick, 1980). No discernable disorder was observed for either methyl group.
Fig. 2 illustrates the packing arrangement with its complex hydrogen bonding. Compound (I) was not intended as part of our study of keto-acid hydrogen bonding, which avoids hydroxyl groups as complicating factors. Nevertheless, (I) adheres to a standard keto-acid hydrogen-bonding motif in forming acid-to-ketone catemers [O···O distance = 2.694 (5) Å; O—H···O angle = 168°], whose components are screw-related in b (Brunskill et al., 1999). Two counterdirectional, screw-related sets of helices exist, and the carboxyl and lactone carbonyl groups in translationally related molecules within a given helix both act as acceptors for hydrogen bonds from a single water of hydration [O···O distances 2.819 (6) & 2.749 (5) Å, respectively; O—H···O angles 155 (6) & 160 (6)°, respectively], whose oxygen, in turn accepts a hydrogen bond from the hydroxyl group of a third, screw-related molecule in an adjacent counterdirectionally oriented helix [O···O distance = 2.732 (6) Å; O—H···O angle = 167 (6)°]. Thus, molecules of water act both to brace each helix and to bridge it, alternatingly, to two different screw-related neighboring chains in a complex three-dimensional array. While each water participates in hydrogen bonds to three separate gibberellin molecules, each gibberellin receives a hydrogen bond to each of its three carbonyls and donates hydrogen bonds from both its OH and COOH groups. Only the `ether O' of the lactone is not involved in the hydrogen bonding.
We have characterized 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 H atom to the O in terms of its deviation from, respectively, C═O axiality (ideal = 120°) and planarity with the carbonyl (ideal = 0°). In (I), these criteria are applicable to three of the four hydrogen bonds present. Approach angles for the acid-to-ketone hydrogen bond are: H···O═C, 123.8° and H···O═C—C, −6.2°. The analogous angles for the water-to-acid hydrogen bond are 129.8 and 50.2°, and for the water-to-lactone hydrogen bond, 134.8 and 18.9°.
In addition to the hydrogen bonds, a variety of O···H—C close contacts lie within the 2.7 Å limit we have often used for such non-bonded packing interactions (Steiner, 1997). Steiner & Desiraju (1998) have compiled data for a large number of C—H···O contacts and found significant statistical directionality even at cutoff distances as great as 3.0 Å, leading to the conclusion that these may be legitimately viewed as `weak hydrogen bonds', presumably contributing significantly more to packing forces than simple van der Waals attractions. In (I), these include contacts to neighbors screw-related in c for O2 (2.70 Å to H5A), for O5 (2.69 Å to H13C), and for O6 (2.56 Å to H11B), plus one for the water (O7) (2.65 Å) involving H9A of a molecule screw-related in a.