Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107015533/sk3116sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270107015533/sk3116Isup2.hkl |
CCDC reference: 652508
For related literature, see: Allen et al. (1987); Altona et al. (1968); Cepa et al. (2005); Cremer & Pople (1975); Duax & Norton (1975); Griffin et al. (1980); Johnson (1976); Marsh et al. (1985); Schmidt et al. (1993).
To an ice-cooled solution of formestane (0.3 g, 0.99 mmol) in pyridine (5.0 ml), acetyl chloride (0.11 ml, 1.48 mmol) was added, and the reaction was stirred for 3 h until completion. Dichloromethane (100 ml) was then added, and the organic layer was washed with aqueous 0.25 N HCl (2 × 100 ml), 10% NaHCO3 (2 × 100 ml) and water (2 × 100 ml), dried over anhydrous MgSO4 and evaporated to dryness giving the desired title compound as a yellow crystalline solid (yield 0.335 g, 98%). Crystals of (I) of good quality suitable for X-ray crystallographic analysis were grown from ethyl acetate [m.p. 457–458 K; literature value 457–457.5 K (Marsh et al., 1985)]. IR (Medium?, ν, cm-1): 1758, 1735, 1681, 1625; 1H NMR (CDCl3, δ, p.p.m.): 0.91 (s, 3H, 18-H3), 1.27 (s, 3H, 19-H3), 2.24 [s, 3H, CH3C(O)O], 2.73 (ddd, 1H, J6α-6β = 15.0 Hz, J6α-7α = 4.0 Hz, J6α-7β = 2.5 Hz, 6α-H).
All H atoms were refined as riding on their parent atoms, with C—H = 0.96–0.98 Å and with Uiso(H) = 1.2Ueq(C), or 1.5Ueq(C) for methyl H. [Please check added text] The absolute configuration was not determined from the X-ray data but was known from the synthesis route. Friedel pairs were merged before refinement.
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: PLATON (Spek, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.
Fig. 1. A plot of the title compound. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. |
C21H28O4 | Dx = 1.213 Mg m−3 |
Mr = 344.43 | Melting point: 457.5(5) K |
Orthorhombic, P212121 | Cu Kα radiation, λ = 1.54180 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 25 reflections |
a = 11.5681 (3) Å | θ = 16.4–26.9° |
b = 12.0702 (3) Å | µ = 0.66 mm−1 |
c = 13.512 (2) Å | T = 294 K |
V = 1886.6 (3) Å3 | Prism, colourless |
Z = 4 | 0.36 × 0.17 × 0.17 mm |
F(000) = 744 |
Enraf–Nonius MACH-3 diffractometer | 1795 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.022 |
Graphite monochromator | θmax = 73.8°, θmin = 4.9° |
profile data from ω–2θ scans | h = −14→14 |
Absorption correction: ψ scan (North et al., 1968) | k = −6→15 |
Tmin = 0.851, Tmax = 0.890 | l = −16→16 |
3577 measured reflections | 3 standard reflections every 300 min |
2135 independent reflections | intensity decay: 2.2% |
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)] = 0.029 | H-atom parameters constrained |
wR(F2) = 0.088 | w = 1/[σ2(Fo2) + (0.0374P)2 + 0.3523P] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max = 0.025 |
2128 reflections | Δρmax = 0.16 e Å−3 |
230 parameters | Δρmin = −0.15 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: 0.0095 (6) |
C21H28O4 | V = 1886.6 (3) Å3 |
Mr = 344.43 | Z = 4 |
Orthorhombic, P212121 | Cu Kα radiation |
a = 11.5681 (3) Å | µ = 0.66 mm−1 |
b = 12.0702 (3) Å | T = 294 K |
c = 13.512 (2) Å | 0.36 × 0.17 × 0.17 mm |
Enraf–Nonius MACH-3 diffractometer | 1795 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.022 |
Tmin = 0.851, Tmax = 0.890 | 3 standard reflections every 300 min |
3577 measured reflections | intensity decay: 2.2% |
2135 independent reflections |
R[F2 > 2σ(F2)] = 0.029 | 0 restraints |
wR(F2) = 0.088 | H-atom parameters constrained |
S = 1.09 | Δρmax = 0.16 e Å−3 |
2128 reflections | Δρmin = −0.15 e Å−3 |
230 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
O3 | 0.16071 (19) | 0.83111 (14) | 0.70155 (15) | 0.0703 (6) | |
O4 | 0.01306 (13) | 0.69137 (13) | 0.60928 (11) | 0.0478 (4) | |
O17 | 0.43619 (16) | 0.00475 (15) | 0.59791 (15) | 0.0676 (5) | |
O41 | 0.14471 (17) | 0.7197 (2) | 0.49048 (14) | 0.0755 (6) | |
C1 | 0.30303 (18) | 0.57501 (18) | 0.7628 (2) | 0.0483 (6) | |
H1A | 0.3546 | 0.5482 | 0.8141 | 0.058* | |
H1B | 0.3476 | 0.5818 | 0.7022 | 0.058* | |
C2 | 0.2583 (2) | 0.6892 (2) | 0.7922 (2) | 0.0572 (6) | |
H2A | 0.2211 | 0.6846 | 0.8564 | 0.069* | |
H2B | 0.3228 | 0.7402 | 0.7978 | 0.069* | |
C3 | 0.1739 (2) | 0.73266 (18) | 0.71761 (18) | 0.0487 (5) | |
C4 | 0.10241 (18) | 0.64852 (18) | 0.66895 (16) | 0.0417 (5) | |
C5 | 0.10965 (18) | 0.53964 (17) | 0.68459 (16) | 0.0398 (5) | |
C6 | 0.02065 (19) | 0.46203 (19) | 0.6436 (2) | 0.0506 (6) | |
H6A | −0.0273 | 0.5018 | 0.5967 | 0.061* | |
H6B | −0.0287 | 0.4368 | 0.6970 | 0.061* | |
C7 | 0.0733 (2) | 0.3617 (2) | 0.5922 (2) | 0.0548 (6) | |
H7A | 0.1094 | 0.3852 | 0.5309 | 0.066* | |
H7B | 0.0124 | 0.3096 | 0.5759 | 0.066* | |
C8 | 0.16294 (18) | 0.30427 (17) | 0.65691 (17) | 0.0419 (5) | |
H8 | 0.1251 | 0.2762 | 0.7167 | 0.050* | |
C9 | 0.25714 (17) | 0.38909 (16) | 0.68698 (15) | 0.0379 (4) | |
H9 | 0.2870 | 0.4201 | 0.6250 | 0.046* | |
C10 | 0.20659 (17) | 0.48954 (17) | 0.74670 (16) | 0.0383 (4) | |
C11 | 0.36155 (19) | 0.33567 (18) | 0.73938 (18) | 0.0457 (5) | |
H11A | 0.4223 | 0.3906 | 0.7457 | 0.055* | |
H11B | 0.3385 | 0.3137 | 0.8056 | 0.055* | |
C12 | 0.41010 (18) | 0.23401 (19) | 0.68508 (19) | 0.0473 (5) | |
H12A | 0.4450 | 0.2571 | 0.6231 | 0.057* | |
H12B | 0.4695 | 0.1995 | 0.7252 | 0.057* | |
C13 | 0.31464 (18) | 0.15127 (18) | 0.66461 (16) | 0.0421 (5) | |
C14 | 0.22060 (18) | 0.20822 (18) | 0.60298 (17) | 0.0440 (5) | |
H14 | 0.2603 | 0.2409 | 0.5459 | 0.053* | |
C15 | 0.1488 (2) | 0.1118 (2) | 0.5620 (2) | 0.0603 (7) | |
H15A | 0.1044 | 0.1344 | 0.5046 | 0.072* | |
H15B | 0.0967 | 0.0826 | 0.6118 | 0.072* | |
C16 | 0.2418 (2) | 0.0265 (2) | 0.5341 (2) | 0.0628 (7) | |
H16A | 0.2147 | −0.0482 | 0.5467 | 0.075* | |
H16B | 0.2619 | 0.0328 | 0.4646 | 0.075* | |
C17 | 0.3454 (2) | 0.05331 (19) | 0.59882 (19) | 0.0503 (5) | |
C18 | 0.2694 (3) | 0.0988 (2) | 0.76160 (19) | 0.0583 (7) | |
H18A | 0.3318 | 0.0623 | 0.7951 | 0.087* | |
H18B | 0.2100 | 0.0459 | 0.7464 | 0.087* | |
H18C | 0.2382 | 0.1557 | 0.8034 | 0.087* | |
C19 | 0.1564 (2) | 0.4529 (2) | 0.84711 (17) | 0.0529 (6) | |
H19A | 0.1259 | 0.5163 | 0.8812 | 0.079* | |
H19B | 0.2162 | 0.4197 | 0.8863 | 0.079* | |
H19C | 0.0956 | 0.4001 | 0.8364 | 0.079* | |
C41 | 0.0471 (2) | 0.7260 (2) | 0.51771 (18) | 0.0501 (6) | |
C42 | −0.0518 (3) | 0.7691 (3) | 0.4599 (2) | 0.0684 (8) | |
H42A | −0.0444 | 0.8479 | 0.4525 | 0.103* | |
H42B | −0.1226 | 0.7524 | 0.4938 | 0.103* | |
H42C | −0.0526 | 0.7349 | 0.3957 | 0.103* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O3 | 0.0844 (13) | 0.0391 (8) | 0.0872 (14) | 0.0084 (9) | 0.0022 (12) | −0.0050 (9) |
O4 | 0.0459 (8) | 0.0518 (8) | 0.0457 (8) | 0.0133 (7) | 0.0034 (7) | 0.0097 (7) |
O17 | 0.0640 (11) | 0.0637 (11) | 0.0753 (12) | 0.0153 (9) | 0.0043 (10) | −0.0155 (10) |
O41 | 0.0620 (11) | 0.1170 (18) | 0.0476 (10) | 0.0101 (13) | 0.0109 (9) | 0.0080 (11) |
C1 | 0.0406 (11) | 0.0453 (12) | 0.0590 (14) | −0.0004 (9) | −0.0086 (11) | −0.0013 (11) |
C2 | 0.0543 (13) | 0.0484 (12) | 0.0688 (16) | −0.0013 (11) | −0.0109 (13) | −0.0129 (12) |
C3 | 0.0485 (12) | 0.0410 (11) | 0.0567 (14) | 0.0050 (10) | 0.0101 (11) | −0.0031 (10) |
C4 | 0.0382 (10) | 0.0451 (11) | 0.0418 (11) | 0.0067 (9) | 0.0021 (9) | 0.0047 (10) |
C5 | 0.0350 (9) | 0.0446 (11) | 0.0398 (11) | 0.0012 (9) | 0.0031 (9) | 0.0041 (9) |
C6 | 0.0376 (11) | 0.0483 (12) | 0.0660 (15) | 0.0013 (10) | −0.0098 (11) | 0.0055 (11) |
C7 | 0.0446 (12) | 0.0533 (13) | 0.0666 (15) | −0.0013 (10) | −0.0186 (12) | −0.0031 (12) |
C8 | 0.0360 (9) | 0.0411 (10) | 0.0485 (12) | −0.0033 (9) | −0.0032 (9) | 0.0026 (9) |
C9 | 0.0350 (9) | 0.0393 (10) | 0.0395 (11) | −0.0013 (8) | −0.0009 (9) | 0.0057 (9) |
C10 | 0.0369 (10) | 0.0405 (10) | 0.0377 (10) | 0.0000 (8) | −0.0025 (9) | 0.0036 (9) |
C11 | 0.0401 (11) | 0.0450 (11) | 0.0522 (13) | 0.0026 (9) | −0.0094 (10) | −0.0034 (10) |
C12 | 0.0378 (10) | 0.0495 (12) | 0.0545 (13) | 0.0034 (9) | −0.0045 (10) | 0.0001 (11) |
C13 | 0.0441 (11) | 0.0413 (10) | 0.0409 (11) | 0.0016 (9) | 0.0020 (9) | 0.0027 (9) |
C14 | 0.0426 (11) | 0.0444 (11) | 0.0449 (11) | −0.0035 (9) | −0.0028 (10) | 0.0011 (10) |
C15 | 0.0528 (14) | 0.0559 (14) | 0.0723 (17) | −0.0050 (12) | −0.0117 (13) | −0.0118 (13) |
C16 | 0.0670 (15) | 0.0524 (14) | 0.0689 (17) | −0.0026 (14) | −0.0067 (15) | −0.0165 (13) |
C17 | 0.0553 (13) | 0.0454 (12) | 0.0504 (13) | 0.0008 (11) | 0.0042 (12) | 0.0011 (11) |
C18 | 0.0737 (17) | 0.0504 (13) | 0.0508 (14) | 0.0011 (13) | 0.0101 (13) | 0.0089 (11) |
C19 | 0.0562 (13) | 0.0580 (14) | 0.0444 (12) | 0.0072 (12) | 0.0062 (11) | 0.0088 (11) |
C41 | 0.0591 (14) | 0.0514 (13) | 0.0396 (12) | 0.0082 (12) | 0.0021 (11) | −0.0007 (10) |
C42 | 0.0817 (19) | 0.0746 (18) | 0.0490 (14) | 0.0250 (16) | −0.0076 (14) | 0.0031 (13) |
O3—C3 | 1.218 (3) | C10—C19 | 1.541 (3) |
O4—C41 | 1.364 (3) | C11—C12 | 1.536 (3) |
O4—C4 | 1.409 (3) | C11—H11A | 0.9700 |
O41—C41 | 1.190 (3) | C11—H11B | 0.9700 |
O17—C17 | 1.203 (3) | C12—C13 | 1.514 (3) |
C1—C2 | 1.525 (3) | C12—H12A | 0.9700 |
C1—C10 | 1.535 (3) | C12—H12B | 0.9700 |
C1—H1A | 0.9700 | C13—C17 | 1.521 (3) |
C1—H1B | 0.9700 | C13—C14 | 1.533 (3) |
C2—C3 | 1.498 (3) | C13—C18 | 1.547 (3) |
C2—H2A | 0.9700 | C14—C15 | 1.533 (3) |
C2—H2B | 0.9700 | C14—H14 | 0.9800 |
C3—C4 | 1.465 (3) | C15—C16 | 1.536 (4) |
C4—C5 | 1.334 (3) | C15—H15A | 0.9700 |
C5—C6 | 1.498 (3) | C15—H15B | 0.9700 |
C5—C10 | 1.526 (3) | C16—C17 | 1.518 (4) |
C6—C7 | 1.522 (3) | C16—H16A | 0.9700 |
C6—H6A | 0.9700 | C16—H16B | 0.9700 |
C6—H6B | 0.9700 | C18—H18A | 0.9600 |
C7—C8 | 1.523 (3) | C18—H18B | 0.9600 |
C7—H7A | 0.9700 | C18—H18C | 0.9600 |
C7—H7B | 0.9700 | C19—H19A | 0.9600 |
C8—C14 | 1.523 (3) | C19—H19B | 0.9600 |
C8—C9 | 1.549 (3) | C19—H19C | 0.9600 |
C8—H8 | 0.9800 | C41—C42 | 1.480 (3) |
C9—C11 | 1.541 (3) | C42—H42A | 0.9600 |
C9—C10 | 1.569 (3) | C42—H42B | 0.9600 |
C9—H9 | 0.9800 | C42—H42C | 0.9600 |
C41—O4—C4 | 114.84 (17) | C9—C11—H11B | 108.8 |
C2—C1—C10 | 113.44 (18) | H11A—C11—H11B | 107.7 |
C2—C1—H1A | 108.9 | C13—C12—C11 | 110.33 (17) |
C10—C1—H1A | 108.9 | C13—C12—H12A | 109.6 |
C2—C1—H1B | 108.9 | C11—C12—H12A | 109.6 |
C10—C1—H1B | 108.9 | C13—C12—H12B | 109.6 |
H1A—C1—H1B | 107.7 | C11—C12—H12B | 109.6 |
C3—C2—C1 | 111.2 (2) | H12A—C12—H12B | 108.1 |
C3—C2—H2A | 109.4 | C12—C13—C17 | 116.68 (19) |
C1—C2—H2A | 109.4 | C12—C13—C14 | 108.73 (17) |
C3—C2—H2B | 109.4 | C17—C13—C14 | 101.35 (17) |
C1—C2—H2B | 109.4 | C12—C13—C18 | 111.2 (2) |
H2A—C2—H2B | 108.0 | C17—C13—C18 | 104.83 (18) |
O3—C3—C4 | 121.7 (2) | C14—C13—C18 | 113.80 (19) |
O3—C3—C2 | 122.9 (2) | C8—C14—C13 | 113.10 (18) |
C4—C3—C2 | 115.29 (19) | C8—C14—C15 | 120.89 (18) |
C5—C4—O4 | 119.9 (2) | C13—C14—C15 | 103.89 (18) |
C5—C4—C3 | 125.2 (2) | C8—C14—H14 | 106.0 |
O4—C4—C3 | 114.60 (18) | C13—C14—H14 | 106.0 |
C4—C5—C6 | 121.0 (2) | C15—C14—H14 | 106.0 |
C4—C5—C10 | 121.6 (2) | C14—C15—C16 | 102.60 (18) |
C6—C5—C10 | 117.43 (18) | C14—C15—H15A | 111.2 |
C5—C6—C7 | 113.01 (18) | C16—C15—H15A | 111.2 |
C5—C6—H6A | 109.0 | C14—C15—H15B | 111.2 |
C7—C6—H6A | 109.0 | C16—C15—H15B | 111.2 |
C5—C6—H6B | 109.0 | H15A—C15—H15B | 109.2 |
C7—C6—H6B | 109.0 | C17—C16—C15 | 105.55 (19) |
H6A—C6—H6B | 107.8 | C17—C16—H16A | 110.6 |
C6—C7—C8 | 111.9 (2) | C15—C16—H16A | 110.6 |
C6—C7—H7A | 109.2 | C17—C16—H16B | 110.6 |
C8—C7—H7A | 109.2 | C15—C16—H16B | 110.6 |
C6—C7—H7B | 109.2 | H16A—C16—H16B | 108.8 |
C8—C7—H7B | 109.2 | O17—C17—C16 | 125.4 (2) |
H7A—C7—H7B | 107.9 | O17—C17—C13 | 126.0 (2) |
C7—C8—C14 | 111.73 (19) | C16—C17—C13 | 108.6 (2) |
C7—C8—C9 | 109.17 (17) | C13—C18—H18A | 109.5 |
C14—C8—C9 | 108.69 (16) | C13—C18—H18B | 109.5 |
C7—C8—H8 | 109.1 | H18A—C18—H18B | 109.5 |
C14—C8—H8 | 109.1 | C13—C18—H18C | 109.5 |
C9—C8—H8 | 109.1 | H18A—C18—H18C | 109.5 |
C11—C9—C8 | 113.28 (16) | H18B—C18—H18C | 109.5 |
C11—C9—C10 | 112.26 (17) | C10—C19—H19A | 109.5 |
C8—C9—C10 | 112.53 (16) | C10—C19—H19B | 109.5 |
C11—C9—H9 | 106.0 | H19A—C19—H19B | 109.5 |
C8—C9—H9 | 106.0 | C10—C19—H19C | 109.5 |
C10—C9—H9 | 106.0 | H19A—C19—H19C | 109.5 |
C5—C10—C1 | 110.22 (17) | H19B—C19—H19C | 109.5 |
C5—C10—C19 | 108.71 (17) | O41—C41—O4 | 122.3 (2) |
C1—C10—C19 | 110.0 (2) | O41—C41—C42 | 126.4 (2) |
C5—C10—C9 | 107.30 (16) | O4—C41—C42 | 111.3 (2) |
C1—C10—C9 | 108.73 (16) | C41—C42—H42A | 109.5 |
C19—C10—C9 | 111.83 (17) | C41—C42—H42B | 109.5 |
C12—C11—C9 | 113.65 (18) | H42A—C42—H42B | 109.5 |
C12—C11—H11A | 108.8 | C41—C42—H42C | 109.5 |
C9—C11—H11A | 108.8 | H42A—C42—H42C | 109.5 |
C12—C11—H11B | 108.8 | H42B—C42—H42C | 109.5 |
C10—C1—C2—C3 | −56.0 (3) | C8—C9—C10—C1 | −173.61 (18) |
C1—C2—C3—O3 | −150.6 (2) | C11—C9—C10—C19 | −64.5 (2) |
C1—C2—C3—C4 | 33.0 (3) | C8—C9—C10—C19 | 64.7 (2) |
C41—O4—C4—C5 | −106.1 (2) | C8—C9—C11—C12 | 48.8 (2) |
C41—O4—C4—C3 | 80.0 (2) | C10—C9—C11—C12 | 177.61 (18) |
O3—C3—C4—C5 | −178.2 (2) | C9—C11—C12—C13 | −52.8 (3) |
C2—C3—C4—C5 | −1.7 (3) | C11—C12—C13—C17 | 171.83 (19) |
O3—C3—C4—O4 | −4.7 (3) | C11—C12—C13—C14 | 58.1 (2) |
C2—C3—C4—O4 | 171.77 (19) | C11—C12—C13—C18 | −68.0 (2) |
O4—C4—C5—C6 | −3.0 (3) | C7—C8—C14—C13 | 177.81 (19) |
C3—C4—C5—C6 | 170.2 (2) | C9—C8—C14—C13 | 57.3 (2) |
O4—C4—C5—C10 | 178.55 (17) | C7—C8—C14—C15 | −58.2 (3) |
C3—C4—C5—C10 | −8.3 (3) | C9—C8—C14—C15 | −178.7 (2) |
C4—C5—C6—C7 | 132.7 (2) | C12—C13—C14—C8 | −63.0 (2) |
C10—C5—C6—C7 | −48.7 (3) | C17—C13—C14—C8 | 173.56 (17) |
C5—C6—C7—C8 | 50.7 (3) | C18—C13—C14—C8 | 61.6 (2) |
C6—C7—C8—C14 | −176.56 (18) | C12—C13—C14—C15 | 164.16 (19) |
C6—C7—C8—C9 | −56.3 (2) | C17—C13—C14—C15 | 40.7 (2) |
C7—C8—C9—C11 | −171.32 (19) | C18—C13—C14—C15 | −71.3 (2) |
C14—C8—C9—C11 | −49.2 (2) | C8—C14—C15—C16 | −169.1 (2) |
C7—C8—C9—C10 | 60.0 (2) | C13—C14—C15—C16 | −40.9 (3) |
C14—C8—C9—C10 | −177.90 (17) | C14—C15—C16—C17 | 24.5 (3) |
C4—C5—C10—C1 | −14.1 (3) | C15—C16—C17—O17 | −179.5 (3) |
C6—C5—C10—C1 | 167.4 (2) | C15—C16—C17—C13 | 0.6 (3) |
C4—C5—C10—C19 | 106.6 (2) | C12—C13—C17—O17 | 36.9 (3) |
C6—C5—C10—C19 | −72.0 (2) | C14—C13—C17—O17 | 154.7 (2) |
C4—C5—C10—C9 | −132.3 (2) | C18—C13—C17—O17 | −86.6 (3) |
C6—C5—C10—C9 | 49.2 (2) | C12—C13—C17—C16 | −143.2 (2) |
C2—C1—C10—C5 | 45.7 (3) | C14—C13—C17—C16 | −25.3 (2) |
C2—C1—C10—C19 | −74.2 (3) | C18—C13—C17—C16 | 93.3 (2) |
C2—C1—C10—C9 | 163.0 (2) | C4—O4—C41—O41 | 0.4 (4) |
C11—C9—C10—C5 | 176.38 (17) | C4—O4—C41—C42 | 179.7 (2) |
C8—C9—C10—C5 | −54.4 (2) | C19—C10—C13—C18 | −0.06 (19) |
C11—C9—C10—C1 | 57.2 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
C6—H6A···O4 | 0.97 | 2.34 | 2.808 (3) | 109 |
C6—H6B···O3i | 0.97 | 2.42 | 3.358 (3) | 164 |
C11—H11B···O41ii | 0.97 | 2.54 | 3.459 (3) | 159 |
Symmetry codes: (i) −x, y−1/2, −z+3/2; (ii) −x+1/2, −y+1, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C21H28O4 |
Mr | 344.43 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 294 |
a, b, c (Å) | 11.5681 (3), 12.0702 (3), 13.512 (2) |
V (Å3) | 1886.6 (3) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.66 |
Crystal size (mm) | 0.36 × 0.17 × 0.17 |
Data collection | |
Diffractometer | Enraf–Nonius MACH-3 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.851, 0.890 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3577, 2135, 1795 |
Rint | 0.022 |
(sin θ/λ)max (Å−1) | 0.623 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.088, 1.09 |
No. of reflections | 2128 |
No. of parameters | 230 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.16, −0.15 |
Computer programs: CAD-4 Software (Enraf–Nonius, 1989), CAD-4 Software, PLATON (Spek, 2003), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), SHELXL97.
O4—C4 | 1.409 (3) | C4—C5 | 1.334 (3) |
C2—C3 | 1.498 (3) | C9—C10 | 1.569 (3) |
C3—C4 | 1.465 (3) | C12—C13 | 1.514 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
C6—H6A···O4 | 0.97 | 2.34 | 2.808 (3) | 109 |
C6—H6B···O3i | 0.97 | 2.42 | 3.358 (3) | 164 |
C11—H11B···O41ii | 0.97 | 2.54 | 3.459 (3) | 159 |
Symmetry codes: (i) −x, y−1/2, −z+3/2; (ii) −x+1/2, −y+1, z+1/2. |
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Following our interest in preparing steroidal enzymatic inhibitors aimed at breast cancer treatment, and in studying their structure–activity relationships (Cepa et al., 2005), the title compound, (I), which is the acetate derivative of formestane, was prepared as previously described in the literature (Marsh et al., 1985). We report here the molecular structure of (I) determined by single-crystal X-ray analysis, and compare it with that of the free molecule as given by quantum-mechanical ab initio calculations.
An ORTEPII (Johnson, 1976) plot of (I) is shown in Fig. 1. The 4-acetoxy substituent is positioned on the α face of the steroid nucleus. Average values for the atomic distances are in good agreement with reported ones (Allen et al., 1987), although for the Csp3—Csp3 bonds extreme values of 1.514 (3) (C12—C13) and 1.569 (3) Å (C9—C10) were found, deviating significantly from the average value of 1.535 (14) Å. The abnormally large value is probably due to the severe distortion of ring A (C1–C5/C10). A similar C9—C10 bond length was observed for one of the non-equivalent molecules in the asymmetric unit of formestane [1.571 (3) Å; Griffin et al., 1980].
As a consequence of the C4═C5 double bond present in ring A, this ring assumes a conformation intermediate between 1α,2β-half chair and 1α-sofa [asymmetry parameters (Duax & Norton, 1975) ΔC2(1,2) = 12.5 (3)°, ΔCs(1) = 13.7 (2)° and ΔCs(3) = 45.1 (2)°]. Rings B (C5–C10) and C (C8/C9/C11–C14) have sightly distorted chair conformations with average torsion angles of 54.0 (18) and 55 (2)°, respectively. The five-membered ring D (C13–C17) has a 14α-conformation, most common for these 17-one steroids [puckering parameters (Cremer & Pople, 1975) q2 = 0.417 (3) Å and ϕ2 = 215.6 (4)°; pseudo-rotation (Altona et al., 1968) and asymmetry parameters (Duax & Norton, 1975): Δ = -34.4 (4)°, ϕm = 42.7 (1)°, ΔCs(14) = 0.7 (2)°, ΔC2(13,14) = 20.0 (2)°]. The distance between terminal atoms O3 and O17 is 10.564 (2) Å. The C19—C10···C13—C18 pseudo-torsion angle of -0.06 (19)° indicates that the molecule is not twisted. The dihedral angle between the least-squares plane of the four non-H atoms of the acetate group and that of ring A is 79.78 (10)°.
In order to check whether the observed large deviations from the mean of the C9—C10 and C12—C13 bond lengths were intrinsic to the free steroid molecule or rather due to an influence of crystal packing, we have performed a quantum chemical calculation of the equilibrium geometry of the free molecule. These calculations were performed with the computer program GAMESS (Schmidt et al., 1993). A molecular orbital Roothan Hartree–Fock method was used with an extended 6–31 G(d,p) basis set. Tight conditions for convergence of both the self-consistent field cycles and the maximum density and energy gradients were imposed (10-5 atomic units). The programs were run on a Pentium IV PC (3.0 GHz) running Linux. Interestingly, the calculations reproduce the long C9—C10 bond [calculated value 1.570 Å]. For the shorter Csp3—Csp3 bond, the calculations give a slightly higher value than the observed one [calculated value 1.526 Å]. Overall, there is a very good agreement between the remaining calculated and observed bond lengths. However, the equilibrium geometry of the isolated molecule has a significantly more twisted steroid nucleus [calculated pseudo-torsion angle C19—C10···C13—C18 = 4.9°]. There is considerable freedom of rotation of the acetoxy group around the C4—O4 and O4—C41 bonds, as evidenced by the torsion angles C3—C4—O4—C41 [experimental 80.0 (2)°; calculated 77.0°] and C4—O4—C41—O41 [experimental 0.4 (4)°; calculated 15.4°].
Owing to the absence of a strong hydrogen-bond donor, cohesion of the structure of (I) is mainly achieved by van der Waals and weak C—H···O interactions. One intramolecular C—H···O short contact between the single-bonded O atom of the 4-acetoxy group and a neighbouring H atom of ring B is present, C6—H6A···O4 = 2.808 (5) Å. There are, in addition, two intermolecular C—H···O short distances of 3.357 (6) and 3.459 (6) Å between H atoms of rings B and C and O atoms.