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The title compound, 2-[1,2,3,4,4a,4b,5,6,7,8,8a,9-dodecahydro-7-hydroxy-4b,8,8-trimethylphenanthren-2-yl]propenoic acid, C
20H
30O
3, is a naturally occurring diterpenoid which was isolated from
Rabdosia macrocalyx. The hydroxy and carboxy groups, which are located at the two ends of the molecule, both serve as simultaneous hydrogen-bond donors and acceptors. Two intermolecular O-H
O hydrogen bonds are present and link each molecule to four neighbours, thus forming an extensive hydrogen-bond network within the crystal.
Supporting information
CCDC reference: 180175
Dried powder (7.5 kg) of the whole herb of Rabdosia macrocalyx were soaked three
times with 95% EtOH at room temperature. The solvent was removed by
evaporation at reduced pressure, the residue was successively fractioned with
petroleum ether, EtOAc and n-BuOH. The residue of the EtOAc fraction was
subjected to column chromatography over silica gel. The column was eluted with
a petroleum ether–EtOAc mixture. The crude compound was purified by column
chromatography on silica gel with an acetone–chloroform mixture, producing
210 mg of macrocalyxin A and 60 mg of the pure title compound, (1) [m.p.:
490.5–492.5 K (CHCl3/CH3COCH3)]. 13C NMR (125 MHz, pyridine): δ
(p.p.m.) 169.8 (C16), 147.5 (C15), 137.2 (C8), 121.7 (C17), 121.2 (C7), 75.1
(C3), 52.4 (C9), 44.3 (C5), 41.7 (C6), 39.7 (C13), 37.5 (C4), 35.3 (C10), 32.3
(C14), 32.2 (C12), 29.3 (C19), 26.4 (C11), 25.7 (C1), 23.3 (C2), 23.1 (C18),
15.3 (C20). Crystals suitable for X-ray structure analysis were obtained by
slow evaporation from an aqueous solution solution in chloroform and methanol
(1:1) at room temperature.
H atoms were placed in the geometrically calculated positions and included in
the final refinement as riding, with Uiso values equal to
1.2Ueq of the carrier atom. An attempt to establish the absolute
configuration failed. The Flack (1983) parameter obtained was -0.9 (16). The
Friedel pairs were merged before the final refinement and only the relative
stereochemistry is shown in the Scheme and Figures.
Data collection: XSCANS (Siemens, 1994); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL/PC (Siemens, 1991); software used to prepare material for publication: SHELXTL/PC.
2-[1,2,3,4,4a,4 b,5,6,7,8,8a,9-dodecahydro-7-hydroxy-4 b,8,8-trimethylphenanthren- 2-yl]propenoic acid
top
Crystal data top
C20H30O3 | Dx = 1.176 Mg m−3 |
Mr = 318.44 | Melting point: 490.5-492.5K K |
Monoclinic, C2 | Mo Kα radiation, λ = 0.71073 Å |
a = 24.066 (2) Å | Cell parameters from 25 reflections |
b = 10.017 (1) Å | θ = 3.3–12.3° |
c = 7.608 (1) Å | µ = 0.08 mm−1 |
β = 101.35 (1)° | T = 295 K |
V = 1798.2 (3) Å3 | Prism, colorless |
Z = 4 | 0.50 × 0.50 × 0.40 mm |
F(000) = 696 | |
Data collection top
Siemens P4 diffractometer | Rint = 0.016 |
Radiation source: normal-focus sealed tube | θmax = 27.5°, θmin = 1.7° |
Graphite monochromator | h = 0→31 |
ω scans | k = 0→13 |
2311 measured reflections | l = −9→9 |
2178 independent reflections | 3 standard reflections every 97 reflections |
1605 reflections with I > 2σ(I) | intensity decay: 1.3% |
Refinement top
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.040 | w = 1/[σ2(Fo2) + (0.0509P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.097 | (Δ/σ)max < 0.001 |
S = 0.98 | Δρmax = 0.15 e Å−3 |
2178 reflections | Δρmin = −0.12 e Å−3 |
214 parameters | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
1 restraint | Extinction coefficient: 0.035 (2) |
Primary atom site location: structure-invariant direct methods | Absolute structure: see text |
Secondary atom site location: difference Fourier map | |
Crystal data top
C20H30O3 | V = 1798.2 (3) Å3 |
Mr = 318.44 | Z = 4 |
Monoclinic, C2 | Mo Kα radiation |
a = 24.066 (2) Å | µ = 0.08 mm−1 |
b = 10.017 (1) Å | T = 295 K |
c = 7.608 (1) Å | 0.50 × 0.50 × 0.40 mm |
β = 101.35 (1)° | |
Data collection top
Siemens P4 diffractometer | Rint = 0.016 |
2311 measured reflections | 3 standard reflections every 97 reflections |
2178 independent reflections | intensity decay: 1.3% |
1605 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.040 | 1 restraint |
wR(F2) = 0.097 | H-atom parameters constrained |
S = 0.98 | Δρmax = 0.15 e Å−3 |
2178 reflections | Δρmin = −0.12 e Å−3 |
214 parameters | Absolute structure: see text |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.90473 (7) | 0.3283 (2) | 0.8642 (2) | 0.0532 (5) | |
H1O | 0.9180 | 0.3124 | 0.9699 | 0.064* | |
O2 | 0.53159 (7) | 0.75895 (18) | 0.8040 (3) | 0.0541 (5) | |
O3 | 0.45819 (7) | 0.62074 (19) | 0.7549 (3) | 0.0648 (6) | |
H3O | 0.4414 | 0.6885 | 0.7756 | 0.078* | |
C1 | 0.83633 (10) | 0.5363 (3) | 0.9824 (3) | 0.0532 (7) | |
H1A | 0.8278 | 0.5933 | 1.0767 | 0.064* | |
H1B | 0.8295 | 0.4447 | 1.0134 | 0.064* | |
C2 | 0.89867 (11) | 0.5522 (3) | 0.9736 (4) | 0.0579 (8) | |
H2A | 0.9063 | 0.6450 | 0.9508 | 0.070* | |
H2B | 0.9219 | 0.5275 | 1.0882 | 0.070* | |
C3 | 0.91440 (10) | 0.4655 (3) | 0.8268 (3) | 0.0488 (7) | |
H3 | 0.9547 | 0.4779 | 0.8259 | 0.059* | |
C4 | 0.87985 (10) | 0.4993 (3) | 0.6406 (3) | 0.0470 (6) | |
C5 | 0.81543 (9) | 0.4995 (2) | 0.6465 (3) | 0.0396 (5) | |
H5 | 0.8062 | 0.4054 | 0.6611 | 0.048* | |
C6 | 0.77756 (10) | 0.5410 (3) | 0.4699 (3) | 0.0531 (7) | |
H6A | 0.7857 | 0.6329 | 0.4434 | 0.064* | |
H6B | 0.7858 | 0.4854 | 0.3738 | 0.064* | |
C7 | 0.71645 (11) | 0.5280 (3) | 0.4782 (3) | 0.0534 (7) | |
H7 | 0.6900 | 0.5310 | 0.3712 | 0.064* | |
C8 | 0.69758 (10) | 0.5125 (3) | 0.6285 (3) | 0.0426 (6) | |
C9 | 0.73609 (9) | 0.5174 (3) | 0.8114 (3) | 0.0400 (5) | |
H9 | 0.7413 | 0.4247 | 0.8524 | 0.048* | |
C10 | 0.79625 (10) | 0.5718 (3) | 0.8048 (3) | 0.0407 (6) | |
C11 | 0.70718 (9) | 0.5897 (4) | 0.9470 (3) | 0.0616 (8) | |
H11A | 0.7297 | 0.5768 | 1.0664 | 0.074* | |
H11B | 0.7063 | 0.6847 | 0.9215 | 0.074* | |
C12 | 0.64725 (10) | 0.5421 (3) | 0.9445 (3) | 0.0592 (8) | |
H12A | 0.6311 | 0.5924 | 1.0313 | 0.071* | |
H12B | 0.6479 | 0.4486 | 0.9781 | 0.071* | |
C13 | 0.61058 (9) | 0.5600 (3) | 0.7583 (3) | 0.0432 (6) | |
H13 | 0.6131 | 0.6541 | 0.7256 | 0.052* | |
C14 | 0.63637 (10) | 0.4785 (3) | 0.6268 (3) | 0.0544 (7) | |
H14A | 0.6337 | 0.3846 | 0.6549 | 0.065* | |
H14B | 0.6145 | 0.4929 | 0.5069 | 0.065* | |
C15 | 0.54878 (10) | 0.5299 (3) | 0.7544 (3) | 0.0486 (6) | |
C16 | 0.51282 (10) | 0.6467 (3) | 0.7736 (3) | 0.0429 (6) | |
C17 | 0.52643 (13) | 0.4102 (3) | 0.7418 (5) | 0.0889 (13) | |
H17A | 0.4883 | 0.3992 | 0.7450 | 0.107* | |
H17B | 0.5487 | 0.3362 | 0.7297 | 0.107* | |
C18 | 0.90256 (13) | 0.6308 (3) | 0.5786 (5) | 0.0764 (10) | |
H18A | 0.9416 | 0.6198 | 0.5705 | 0.092* | |
H18B | 0.8994 | 0.7000 | 0.6633 | 0.092* | |
H18C | 0.8809 | 0.6547 | 0.4631 | 0.092* | |
C19 | 0.89093 (12) | 0.3919 (3) | 0.5080 (4) | 0.0627 (8) | |
H19A | 0.8738 | 0.3094 | 0.5336 | 0.075* | |
H19B | 0.9310 | 0.3795 | 0.5194 | 0.075* | |
H19C | 0.8749 | 0.4196 | 0.3880 | 0.075* | |
C20 | 0.79329 (13) | 0.7233 (3) | 0.7790 (4) | 0.0625 (8) | |
H20A | 0.8286 | 0.7551 | 0.7545 | 0.075* | |
H20B | 0.7862 | 0.7650 | 0.8860 | 0.075* | |
H20C | 0.7632 | 0.7450 | 0.6802 | 0.075* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0468 (10) | 0.0565 (11) | 0.0572 (11) | 0.0140 (8) | 0.0123 (9) | 0.0107 (9) |
O2 | 0.0397 (10) | 0.0500 (11) | 0.0724 (12) | 0.0019 (8) | 0.0103 (8) | −0.0115 (10) |
O3 | 0.0347 (9) | 0.0578 (13) | 0.1020 (16) | 0.0043 (9) | 0.0137 (10) | −0.0135 (11) |
C1 | 0.0421 (14) | 0.073 (2) | 0.0420 (14) | 0.0109 (13) | 0.0028 (11) | −0.0117 (14) |
C2 | 0.0450 (14) | 0.070 (2) | 0.0551 (16) | 0.0043 (13) | 0.0001 (12) | −0.0117 (15) |
C3 | 0.0335 (12) | 0.0515 (16) | 0.0622 (17) | 0.0016 (11) | 0.0111 (11) | −0.0009 (13) |
C4 | 0.0421 (13) | 0.0496 (15) | 0.0531 (15) | 0.0028 (11) | 0.0184 (11) | 0.0066 (12) |
C5 | 0.0396 (12) | 0.0390 (14) | 0.0410 (12) | 0.0057 (10) | 0.0098 (10) | 0.0000 (11) |
C6 | 0.0556 (15) | 0.0665 (19) | 0.0389 (13) | 0.0123 (14) | 0.0132 (11) | 0.0056 (13) |
C7 | 0.0461 (14) | 0.0743 (19) | 0.0363 (13) | 0.0144 (14) | −0.0001 (11) | −0.0022 (14) |
C8 | 0.0388 (12) | 0.0466 (14) | 0.0409 (12) | 0.0114 (11) | 0.0043 (10) | −0.0059 (11) |
C9 | 0.0373 (12) | 0.0460 (13) | 0.0366 (12) | 0.0133 (11) | 0.0073 (9) | 0.0012 (11) |
C10 | 0.0381 (12) | 0.0413 (13) | 0.0417 (13) | 0.0060 (10) | 0.0051 (10) | −0.0022 (11) |
C11 | 0.0397 (13) | 0.103 (2) | 0.0408 (14) | 0.0161 (15) | 0.0036 (11) | −0.0162 (16) |
C12 | 0.0452 (14) | 0.088 (2) | 0.0461 (15) | 0.0207 (15) | 0.0122 (11) | 0.0002 (15) |
C13 | 0.0362 (12) | 0.0439 (14) | 0.0491 (14) | 0.0104 (11) | 0.0077 (10) | 0.0032 (12) |
C14 | 0.0437 (14) | 0.0656 (19) | 0.0527 (15) | 0.0064 (13) | 0.0063 (11) | −0.0126 (13) |
C15 | 0.0413 (13) | 0.0454 (15) | 0.0595 (15) | 0.0048 (12) | 0.0111 (11) | 0.0001 (13) |
C16 | 0.0337 (12) | 0.0513 (16) | 0.0423 (14) | 0.0052 (11) | 0.0043 (10) | −0.0005 (12) |
C17 | 0.060 (2) | 0.0477 (19) | 0.166 (4) | 0.0026 (16) | 0.038 (2) | −0.001 (2) |
C18 | 0.0600 (18) | 0.073 (2) | 0.103 (3) | 0.0001 (17) | 0.0308 (17) | 0.024 (2) |
C19 | 0.0587 (17) | 0.076 (2) | 0.0580 (17) | 0.0187 (16) | 0.0238 (13) | 0.0033 (16) |
C20 | 0.0612 (18) | 0.0430 (16) | 0.084 (2) | 0.0073 (13) | 0.0164 (15) | −0.0148 (15) |
Geometric parameters (Å, º) top
O1—C3 | 1.432 (3) | C9—C10 | 1.557 (3) |
O1—H1O | 0.8200 | C9—H9 | 0.9800 |
O2—C16 | 1.217 (3) | C10—C20 | 1.530 (4) |
O3—C16 | 1.320 (3) | C11—C12 | 1.516 (4) |
O3—H3O | 0.8200 | C11—H11A | 0.9700 |
C1—C2 | 1.523 (3) | C11—H11B | 0.9700 |
C1—C10 | 1.539 (3) | C12—C13 | 1.525 (3) |
C1—H1A | 0.9700 | C12—H12A | 0.9700 |
C1—H1B | 0.9700 | C12—H12B | 0.9700 |
C2—C3 | 1.520 (4) | C13—C15 | 1.512 (3) |
C2—H2A | 0.9700 | C13—C14 | 1.516 (3) |
C2—H2B | 0.9700 | C13—H13 | 0.9800 |
C3—C4 | 1.533 (4) | C14—H14A | 0.9700 |
C3—H3 | 0.9800 | C14—H14B | 0.9700 |
C4—C19 | 1.534 (4) | C15—C17 | 1.310 (4) |
C4—C18 | 1.535 (4) | C15—C16 | 1.479 (3) |
C4—C5 | 1.560 (3) | C17—H17A | 0.9300 |
C5—C6 | 1.526 (3) | C17—H17B | 0.9300 |
C5—C10 | 1.552 (3) | C18—H18A | 0.9600 |
C5—H5 | 0.9800 | C18—H18B | 0.9600 |
C6—C7 | 1.490 (3) | C18—H18C | 0.9600 |
C6—H6A | 0.9700 | C19—H19A | 0.9600 |
C6—H6B | 0.9700 | C19—H19B | 0.9600 |
C7—C8 | 1.320 (3) | C19—H19C | 0.9600 |
C7—H7 | 0.9300 | C20—H20A | 0.9600 |
C8—C14 | 1.510 (3) | C20—H20B | 0.9600 |
C8—C9 | 1.513 (3) | C20—H20C | 0.9600 |
C9—C11 | 1.535 (3) | | |
| | | |
C3—O1—H1O | 109.5 | C1—C10—C9 | 108.47 (19) |
C16—O3—H3O | 109.5 | C5—C10—C9 | 106.37 (18) |
C2—C1—C10 | 113.0 (2) | C12—C11—C9 | 113.5 (2) |
C2—C1—H1A | 109.0 | C12—C11—H11A | 108.9 |
C10—C1—H1A | 109.0 | C9—C11—H11A | 108.9 |
C2—C1—H1B | 109.0 | C12—C11—H11B | 108.9 |
C10—C1—H1B | 109.0 | C9—C11—H11B | 108.9 |
H1A—C1—H1B | 107.8 | H11A—C11—H11B | 107.7 |
C3—C2—C1 | 111.2 (2) | C11—C12—C13 | 110.5 (2) |
C3—C2—H2A | 109.4 | C11—C12—H12A | 109.6 |
C1—C2—H2A | 109.4 | C13—C12—H12A | 109.6 |
C3—C2—H2B | 109.4 | C11—C12—H12B | 109.6 |
C1—C2—H2B | 109.4 | C13—C12—H12B | 109.6 |
H2A—C2—H2B | 108.0 | H12A—C12—H12B | 108.1 |
O1—C3—C2 | 109.2 (2) | C15—C13—C14 | 114.1 (2) |
O1—C3—C4 | 108.4 (2) | C15—C13—C12 | 112.5 (2) |
C2—C3—C4 | 112.6 (2) | C14—C13—C12 | 108.22 (19) |
O1—C3—H3 | 108.9 | C15—C13—H13 | 107.2 |
C2—C3—H3 | 108.9 | C14—C13—H13 | 107.2 |
C4—C3—H3 | 108.9 | C12—C13—H13 | 107.2 |
C3—C4—C19 | 108.7 (2) | C8—C14—C13 | 113.5 (2) |
C3—C4—C18 | 108.2 (2) | C8—C14—H14A | 108.9 |
C19—C4—C18 | 106.3 (2) | C13—C14—H14A | 108.9 |
C3—C4—C5 | 109.60 (18) | C8—C14—H14B | 108.9 |
C19—C4—C5 | 108.8 (2) | C13—C14—H14B | 108.9 |
C18—C4—C5 | 115.1 (2) | H14A—C14—H14B | 107.7 |
C6—C5—C10 | 109.80 (19) | C17—C15—C16 | 119.4 (2) |
C6—C5—C4 | 113.58 (19) | C17—C15—C13 | 124.9 (2) |
C10—C5—C4 | 118.2 (2) | C16—C15—C13 | 115.6 (2) |
C6—C5—H5 | 104.6 | O2—C16—O3 | 121.8 (2) |
C10—C5—H5 | 104.6 | O2—C16—C15 | 123.2 (2) |
C4—C5—H5 | 104.6 | O3—C16—C15 | 115.0 (2) |
C7—C6—C5 | 111.2 (2) | C15—C17—H17A | 120.0 |
C7—C6—H6A | 109.4 | C15—C17—H17B | 120.0 |
C5—C6—H6A | 109.4 | H17A—C17—H17B | 120.0 |
C7—C6—H6B | 109.4 | C4—C18—H18A | 109.5 |
C5—C6—H6B | 109.4 | C4—C18—H18B | 109.5 |
H6A—C6—H6B | 108.0 | H18A—C18—H18B | 109.5 |
C8—C7—C6 | 123.9 (2) | C4—C18—H18C | 109.5 |
C8—C7—H7 | 118.0 | H18A—C18—H18C | 109.5 |
C6—C7—H7 | 118.0 | H18B—C18—H18C | 109.5 |
C7—C8—C14 | 121.4 (2) | C4—C19—H19A | 109.5 |
C7—C8—C9 | 122.7 (2) | C4—C19—H19B | 109.5 |
C14—C8—C9 | 115.8 (2) | H19A—C19—H19B | 109.5 |
C8—C9—C11 | 110.90 (18) | C4—C19—H19C | 109.5 |
C8—C9—C10 | 112.76 (19) | H19A—C19—H19C | 109.5 |
C11—C9—C10 | 113.8 (2) | H19B—C19—H19C | 109.5 |
C8—C9—H9 | 106.3 | C10—C20—H20A | 109.5 |
C11—C9—H9 | 106.3 | C10—C20—H20B | 109.5 |
C10—C9—H9 | 106.3 | H20A—C20—H20B | 109.5 |
C20—C10—C1 | 110.3 (2) | C10—C20—H20C | 109.5 |
C20—C10—C5 | 112.2 (2) | H20A—C20—H20C | 109.5 |
C1—C10—C5 | 110.02 (19) | H20B—C20—H20C | 109.5 |
C20—C10—C9 | 109.4 (2) | | |
| | | |
C10—C1—C2—C3 | −58.3 (3) | C4—C5—C10—C20 | 78.8 (3) |
C1—C2—C3—O1 | −60.9 (3) | C6—C5—C10—C1 | −176.9 (2) |
C1—C2—C3—C4 | 59.6 (3) | C4—C5—C10—C1 | −44.4 (3) |
O1—C3—C4—C19 | −49.2 (3) | C6—C5—C10—C9 | 65.8 (2) |
C2—C3—C4—C19 | −170.1 (2) | C4—C5—C10—C9 | −161.74 (19) |
O1—C3—C4—C18 | −164.2 (2) | C8—C9—C10—C20 | 75.4 (3) |
C2—C3—C4—C18 | 74.9 (3) | C11—C9—C10—C20 | −52.0 (3) |
O1—C3—C4—C5 | 69.6 (2) | C8—C9—C10—C1 | −164.2 (2) |
C2—C3—C4—C5 | −51.4 (3) | C11—C9—C10—C1 | 68.4 (3) |
C3—C4—C5—C6 | 176.3 (2) | C8—C9—C10—C5 | −45.9 (3) |
C19—C4—C5—C6 | −65.1 (3) | C11—C9—C10—C5 | −173.3 (2) |
C18—C4—C5—C6 | 54.0 (3) | C8—C9—C11—C12 | 48.0 (3) |
C3—C4—C5—C10 | 45.5 (3) | C10—C9—C11—C12 | 176.4 (2) |
C19—C4—C5—C10 | 164.2 (2) | C9—C11—C12—C13 | −58.2 (3) |
C18—C4—C5—C10 | −76.7 (3) | C11—C12—C13—C15 | −172.9 (2) |
C10—C5—C6—C7 | −50.2 (3) | C11—C12—C13—C14 | 60.1 (3) |
C4—C5—C6—C7 | 175.1 (2) | C7—C8—C14—C13 | −135.3 (3) |
C5—C6—C7—C8 | 14.4 (4) | C9—C8—C14—C13 | 49.0 (3) |
C6—C7—C8—C14 | −170.3 (3) | C15—C13—C14—C8 | 178.3 (2) |
C6—C7—C8—C9 | 5.1 (4) | C12—C13—C14—C8 | −55.7 (3) |
C7—C8—C9—C11 | 141.2 (3) | C14—C13—C15—C17 | 41.7 (4) |
C14—C8—C9—C11 | −43.2 (3) | C12—C13—C15—C17 | −82.1 (4) |
C7—C8—C9—C10 | 12.3 (3) | C14—C13—C15—C16 | −140.8 (2) |
C14—C8—C9—C10 | −172.1 (2) | C12—C13—C15—C16 | 95.4 (3) |
C2—C1—C10—C20 | −75.0 (3) | C17—C15—C16—O2 | 172.4 (3) |
C2—C1—C10—C5 | 49.2 (3) | C13—C15—C16—O2 | −5.3 (4) |
C2—C1—C10—C9 | 165.2 (2) | C17—C15—C16—O3 | −7.8 (4) |
C6—C5—C10—C20 | −53.7 (3) | C13—C15—C16—O3 | 174.6 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3O···O1i | 0.82 | 1.85 | 2.662 (3) | 169 |
O1—H1O···O2ii | 0.82 | 1.97 | 2.771 (3) | 164 |
Symmetry codes: (i) x−1/2, y+1/2, z; (ii) −x+3/2, y−1/2, −z+2. |
Experimental details
Crystal data |
Chemical formula | C20H30O3 |
Mr | 318.44 |
Crystal system, space group | Monoclinic, C2 |
Temperature (K) | 295 |
a, b, c (Å) | 24.066 (2), 10.017 (1), 7.608 (1) |
β (°) | 101.35 (1) |
V (Å3) | 1798.2 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.50 × 0.50 × 0.40 |
|
Data collection |
Diffractometer | Siemens P4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2311, 2178, 1605 |
Rint | 0.016 |
(sin θ/λ)max (Å−1) | 0.650 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.040, 0.097, 0.98 |
No. of reflections | 2178 |
No. of parameters | 214 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.15, −0.12 |
Absolute structure | See text |
Selected geometric parameters (Å, º) topO1—C3 | 1.432 (3) | C13—C15 | 1.512 (3) |
O2—C16 | 1.217 (3) | C15—C17 | 1.310 (4) |
O3—C16 | 1.320 (3) | C15—C16 | 1.479 (3) |
C7—C8 | 1.320 (3) | | |
| | | |
O1—C3—C2 | 109.2 (2) | O2—C16—O3 | 121.8 (2) |
O1—C3—C4 | 108.4 (2) | O2—C16—C15 | 123.2 (2) |
C17—C15—C16 | 119.4 (2) | O3—C16—C15 | 115.0 (2) |
C17—C15—C13 | 124.9 (2) | | |
| | | |
C17—C15—C16—O2 | 172.4 (3) | C17—C15—C16—O3 | −7.8 (4) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3O···O1i | 0.82 | 1.85 | 2.662 (3) | 169.4 |
O1—H1O···O2ii | 0.82 | 1.97 | 2.771 (3) | 163.9 |
Symmetry codes: (i) x−1/2, y+1/2, z; (ii) −x+3/2, y−1/2, −z+2. |
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Rabdosia macrocalyx is widely distributed in Anhui, Jiangsu,Zhejiang, Jiangxi, Fujian, Hunan, Guangdong, Guangxi and Taiwan provinces, China. It has been used as a folk medicine in China. Its decoctions are used as antibiotics and for antitumor treatment. Macrocalyxins A, B (Cheng et al., 1984), C (Wang et al., 1984), D (Wang et al., 1985), E (Wang et al., 1986), F, G and H (Wang et al., 1995) have been isolated previously from this plant. In order to isolate more bioactive constituents from this plant, we investigated the whole herb of Rabdosia macrocalyx, which led to the isolation of the title compound, the natural diterpenoid Macrocalyxin I, (1), which was isolated from Rabdosia macrocalyx Hara for the first time. Its structure was established from spectral evidence and was confirmed by this X-ray diffraction study.
The molecule of (1) (Fig. 1) is composed of three six-membered rings. Rings A (C1–C5/C10) and C (C8/C9/C12–C14) adopt a chair conformation, with mean torsion angles of 51.4 and 52.4°, respectively. Ring B (C5–C9/C10) adopts a half-chair conformation owing to the double bond between C7 and C8. The stereochemistry of the A/B ring junction is trans, and the dihedral angle between rings A and B is 17.6°; the dihedral angle between rings B and C is 14.9°. The configurations at the other chiral centers are as follows: C3—OH, C10—Me, C9—H and C13—H are axial and the 1-carboxylethenyl group is equatorial at C13.
The C17—C15—C16—O2 torsion angle has a vlaue of 172.4 (3)° because of the conjugated double bound. The best least-squares plane formed by atoms C17/C15/C16/O2/O3 has a maximum deviation of 0.0592 Å, and the dihedral angle between this plane and ring C is 114.2°. The hydroxyl group located at C3 and the carboxyl group located at C15 participate in hydrogen bonding. Both groups serve as simultaneous hydrogen-bond donors and acceptors. Two intermolecular O—H···O hydrogen bonds (Table 2) are present and link each molecule to four adjacent neighbours (Fig. 2). The overall result is an extended hydrogen-bonding network throughout the structure (Fig. 3).