organic compounds
(1S*,3S*,8S*,10S*)-10-Fluoro-15-oxatetracyclo[6.6.1.01,10.03,8]pentadeca-5,12-dien-3-ol
aDepartment of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, Karnataka, India
*Correspondence e-mail: gmsc@uohyd.ernet.in
The title compound, C14H17FO2, was obtained from anti-4a,9a:8a,10a-diepoxy-1,4,4a,5,8,8a,9,9a,10,10a-decahydroanthracene via tandem hydrogen-fluoride-mediated epoxide ring-opening and transannular oxacyclization. With the two cyclohexene rings folded towards the oxygen bridge, the title tetracyclic fluoroalcohol molecule displays a conformation reminiscent of a pagoda. The crystal packing is effected via intermolecular O—H⋯O hydrogen bonds, which link the molecules into a zigzag chain along the b axis.
Related literature
For applications of organofluorine compounds as pharmaceuticals, see: Kirsch (2004); Bégué & Bonnet-Delpon (2006); Müller et al. (2007). For the use of diethylaminosulfur trifluoride, 1-chloromethyl-4-fluorodiazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) and pyridinium poly(hydrogen fluoride) as reagents for selective introduction of C—F bonds, see: Middleton (1975); Olah et al. (1979); Banks et al. (1992). For the preparation of the title compound, see: Mehta et al. (2007); Mehta & Sen (2010).
Experimental
Crystal data
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Refinement
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Data collection: SMART (Bruker, 1998); cell SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and CAMERON (Watkin et al., 1993); software used to prepare material for publication: PLATON (Spek, 2009).
Supporting information
10.1107/S1600536811026857/is2740sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811026857/is2740Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536811026857/is2740Isup3.cml
A solution of the anti-diepoxide 3 (35 mg, 0.162 mmol) in 1 ml of dry THF was treated with pyridine- poly(hydrogen fluoride) (0.5 ml, 27.5 mmol) at 273 K. The reaction was allowed to proceed for 7 h at ambient temperature. The mixture was then quenched with saturated sodium bicarbonate solution. The product was extracted with ethyl acetate; the combined extracts were washed with brine and then dried over anhydrous sodium sulfate. Removal of solvent,
over silica gel and subsequent recrystallization using 20% EtOAc-petroleum ether afforded 4 (25 mg, 65%) as a colorless crystalline solid.The methine (CH) and methylene (CH2) H atoms were placed in geometrically idealized positions with C—H distances 0.93 and 0.97 Å respectively, and allowed to ride on their parent atoms with Uiso(H) = 1.2Ueq(C). The hydroxyl hydrogen atom was constrained to an ideal geometry with the O—H distance fixed at 0.82 Å and Uiso(H) = 1.5Ueq(O). During
the hydroxyl group was however allowed to rotate freely about its C—O bond.Data collection: SMART (Bruker, 1998); cell
SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and CAMERON (Watkin et al., 1993); software used to prepare material for publication: PLATON (Spek, 2009).C14H17FO2 | F(000) = 504 |
Mr = 236.28 | Dx = 1.308 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 4978 reflections |
a = 8.1603 (6) Å | θ = 2.4–26.4° |
b = 10.9148 (8) Å | µ = 0.10 mm−1 |
c = 13.5558 (10) Å | T = 291 K |
β = 96.285 (3)° | Block, colorless |
V = 1200.13 (15) Å3 | 0.26 × 0.22 × 0.12 mm |
Z = 4 |
Bruker SMART APEX CCD area-detector diffractometer | 2454 independent reflections |
Radiation source: fine-focus sealed tube | 2038 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.020 |
ϕ and ω scans | θmax = 26.4°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | h = −10→10 |
Tmin = 0.976, Tmax = 0.989 | k = −13→12 |
10752 measured reflections | l = −16→16 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.041 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.113 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0537P)2 + 0.3336P] where P = (Fo2 + 2Fc2)/3 |
2454 reflections | (Δ/σ)max < 0.001 |
155 parameters | Δρmax = 0.19 e Å−3 |
0 restraints | Δρmin = −0.21 e Å−3 |
C14H17FO2 | V = 1200.13 (15) Å3 |
Mr = 236.28 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 8.1603 (6) Å | µ = 0.10 mm−1 |
b = 10.9148 (8) Å | T = 291 K |
c = 13.5558 (10) Å | 0.26 × 0.22 × 0.12 mm |
β = 96.285 (3)° |
Bruker SMART APEX CCD area-detector diffractometer | 2454 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 2038 reflections with I > 2σ(I) |
Tmin = 0.976, Tmax = 0.989 | Rint = 0.020 |
10752 measured reflections |
R[F2 > 2σ(F2)] = 0.041 | 0 restraints |
wR(F2) = 0.113 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.19 e Å−3 |
2454 reflections | Δρmin = −0.21 e Å−3 |
155 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. |
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 | ||
F1 | 0.50293 (10) | −0.03822 (8) | 0.17755 (7) | 0.0539 (3) | |
O1 | 0.92031 (13) | −0.15772 (9) | 0.33199 (8) | 0.0491 (3) | |
O2 | 0.86964 (11) | 0.13521 (8) | 0.21690 (6) | 0.0368 (2) | |
C1 | 0.61016 (16) | 0.05894 (12) | 0.20951 (11) | 0.0395 (3) | |
C10 | 1.2213 (2) | 0.0155 (2) | 0.34728 (15) | 0.0648 (5) | |
C11 | 1.1499 (2) | 0.08929 (18) | 0.40684 (13) | 0.0614 (5) | |
C12 | 0.96990 (19) | 0.11773 (14) | 0.39499 (11) | 0.0466 (4) | |
C13 | 0.87362 (16) | 0.05869 (11) | 0.30592 (9) | 0.0340 (3) | |
C14 | 0.68963 (16) | 0.03854 (13) | 0.31557 (10) | 0.0392 (3) | |
C2 | 0.5123 (2) | 0.17729 (15) | 0.19553 (13) | 0.0553 (4) | |
C3 | 0.4910 (3) | 0.21989 (19) | 0.09124 (16) | 0.0818 (7) | |
C4 | 0.5907 (3) | 0.18950 (17) | 0.02523 (15) | 0.0786 (7) | |
C5 | 0.7339 (2) | 0.10512 (18) | 0.04581 (11) | 0.0610 (5) | |
C6 | 0.76146 (17) | 0.05679 (12) | 0.15111 (10) | 0.0392 (3) | |
C7 | 0.84679 (18) | −0.06886 (13) | 0.16311 (11) | 0.0442 (3) | |
C8 | 0.94747 (17) | −0.05946 (12) | 0.26624 (11) | 0.0388 (3) | |
C9 | 1.13154 (18) | −0.04261 (15) | 0.25771 (13) | 0.0531 (4) | |
H1 | 0.9770 | −0.2167 | 0.3197 | 0.074* | |
H2A | 0.4045 | 0.1650 | 0.2178 | 0.066* | |
H2B | 0.5683 | 0.2405 | 0.2367 | 0.066* | |
H3 | 0.4022 | 0.2709 | 0.0713 | 0.098* | |
H4 | 0.5705 | 0.2227 | −0.0381 | 0.094* | |
H5A | 0.8327 | 0.1478 | 0.0313 | 0.073* | |
H5B | 0.7184 | 0.0360 | 0.0008 | 0.073* | |
H7A | 0.9182 | −0.0825 | 0.1115 | 0.053* | |
H7B | 0.7666 | −0.1346 | 0.1614 | 0.053* | |
H9A | 1.1803 | −0.1220 | 0.2473 | 0.064* | |
H9B | 1.1448 | 0.0078 | 0.2002 | 0.064* | |
H10 | 1.3331 | −0.0010 | 0.3620 | 0.078* | |
H11 | 1.2156 | 0.1257 | 0.4592 | 0.074* | |
H12A | 0.9561 | 0.2058 | 0.3898 | 0.056* | |
H12B | 0.9234 | 0.0913 | 0.4543 | 0.056* | |
H14A | 0.6692 | −0.0438 | 0.3382 | 0.047* | |
H14B | 0.6492 | 0.0971 | 0.3610 | 0.047* |
U11 | U22 | U33 | U12 | U13 | U23 | |
F1 | 0.0442 (5) | 0.0448 (5) | 0.0715 (6) | −0.0124 (4) | 0.0006 (4) | −0.0057 (4) |
O1 | 0.0522 (6) | 0.0300 (5) | 0.0669 (7) | 0.0054 (4) | 0.0147 (5) | 0.0108 (5) |
O2 | 0.0422 (5) | 0.0291 (5) | 0.0387 (5) | −0.0068 (4) | 0.0022 (4) | 0.0038 (4) |
C1 | 0.0360 (7) | 0.0309 (7) | 0.0508 (8) | −0.0029 (5) | 0.0007 (6) | −0.0021 (6) |
C2 | 0.0473 (8) | 0.0422 (9) | 0.0736 (11) | 0.0093 (7) | −0.0056 (7) | −0.0028 (8) |
C3 | 0.1079 (17) | 0.0514 (11) | 0.0764 (13) | 0.0268 (11) | −0.0331 (12) | −0.0016 (10) |
C4 | 0.1288 (19) | 0.0463 (10) | 0.0522 (10) | −0.0003 (11) | −0.0282 (11) | 0.0103 (8) |
C5 | 0.0777 (12) | 0.0640 (11) | 0.0400 (8) | −0.0165 (9) | 0.0000 (8) | 0.0061 (8) |
C6 | 0.0445 (7) | 0.0343 (7) | 0.0382 (7) | −0.0062 (6) | 0.0023 (6) | −0.0016 (5) |
C7 | 0.0470 (8) | 0.0374 (7) | 0.0498 (8) | −0.0010 (6) | 0.0127 (6) | −0.0089 (6) |
C8 | 0.0374 (7) | 0.0297 (7) | 0.0503 (8) | 0.0017 (5) | 0.0096 (6) | 0.0032 (6) |
C9 | 0.0374 (8) | 0.0498 (9) | 0.0742 (11) | 0.0044 (7) | 0.0153 (7) | 0.0081 (8) |
C10 | 0.0351 (8) | 0.0794 (13) | 0.0784 (12) | −0.0069 (8) | −0.0007 (8) | 0.0220 (11) |
C11 | 0.0535 (9) | 0.0697 (12) | 0.0568 (10) | −0.0230 (9) | −0.0128 (8) | 0.0114 (9) |
C12 | 0.0585 (9) | 0.0369 (7) | 0.0423 (8) | −0.0066 (7) | −0.0036 (6) | 0.0018 (6) |
C13 | 0.0378 (7) | 0.0270 (6) | 0.0371 (7) | −0.0016 (5) | 0.0040 (5) | 0.0036 (5) |
C14 | 0.0395 (7) | 0.0354 (7) | 0.0442 (7) | 0.0028 (6) | 0.0112 (6) | −0.0001 (6) |
F1—C1 | 1.4126 (15) | C7—H7A | 0.9700 |
O1—C8 | 1.4272 (16) | C7—H7B | 0.9700 |
O1—H1 | 0.8200 | C8—C7 | 1.545 (2) |
O2—C13 | 1.4650 (15) | C8—C9 | 1.530 (2) |
O2—C6 | 1.4611 (16) | C9—C10 | 1.490 (3) |
C1—C14 | 1.527 (2) | C9—H9A | 0.9700 |
C1—C2 | 1.520 (2) | C9—H9B | 0.9700 |
C2—C3 | 1.480 (3) | C10—H10 | 0.9300 |
C2—H2A | 0.9700 | C11—C10 | 1.320 (3) |
C2—H2B | 0.9700 | C11—H11 | 0.9300 |
C3—H3 | 0.9300 | C12—C11 | 1.493 (2) |
C4—C3 | 1.316 (3) | C12—H12A | 0.9700 |
C4—H4 | 0.9300 | C12—H12B | 0.9700 |
C5—C4 | 1.490 (3) | C13—C12 | 1.5109 (19) |
C5—H5A | 0.9700 | C13—C14 | 1.5371 (18) |
C5—H5B | 0.9700 | C13—C8 | 1.5448 (18) |
C6—C1 | 1.538 (2) | C14—H14A | 0.9700 |
C6—C5 | 1.515 (2) | C14—H14B | 0.9700 |
C6—C7 | 1.5387 (19) | ||
F1—C1—C14 | 111.36 (11) | C6—C7—H7A | 111.2 |
F1—C1—C2 | 107.49 (11) | C6—C7—H7B | 111.2 |
F1—C1—C6 | 109.63 (11) | C6—O2—C13 | 97.25 (9) |
O1—C8—C13 | 108.46 (11) | C8—C7—H7A | 111.2 |
O1—C8—C7 | 114.30 (11) | C8—C7—H7B | 111.2 |
O1—C8—C9 | 111.00 (12) | C8—C9—H9A | 109.0 |
O2—C13—C12 | 112.20 (10) | C8—C9—H9B | 109.0 |
O2—C13—C14 | 102.58 (10) | C8—O1—H1 | 109.5 |
O2—C13—C8 | 99.41 (10) | C9—C10—H10 | 118.4 |
O2—C6—C1 | 98.18 (10) | C9—C8—C13 | 110.46 (12) |
O2—C6—C5 | 112.86 (12) | C9—C8—C7 | 111.63 (12) |
O2—C6—C7 | 102.79 (11) | C10—C11—C12 | 123.78 (15) |
C1—C14—C13 | 102.54 (10) | C10—C11—H11 | 118.1 |
C1—C14—H14A | 111.3 | C10—C9—C8 | 112.88 (14) |
C1—C14—H14B | 111.3 | C10—C9—H9A | 109.0 |
C1—C2—H2A | 109.0 | C10—C9—H9B | 109.0 |
C1—C2—H2B | 109.0 | C11—C10—C9 | 123.21 (15) |
C1—C6—C7 | 109.80 (11) | C11—C10—H10 | 118.4 |
C2—C1—C14 | 113.86 (12) | C11—C12—C13 | 114.63 (14) |
C2—C1—C6 | 112.91 (12) | C11—C12—H12A | 108.6 |
C2—C3—H3 | 118.2 | C11—C12—H12B | 108.6 |
C3—C2—C1 | 113.04 (15) | C12—C11—H11 | 118.1 |
C3—C2—H2A | 109.0 | C12—C13—C14 | 114.86 (12) |
C3—C2—H2B | 109.0 | C12—C13—C8 | 116.47 (12) |
C3—C4—C5 | 124.00 (17) | C13—C12—H12A | 108.6 |
C3—C4—H4 | 118.0 | C13—C12—H12B | 108.6 |
C4—C3—C2 | 123.59 (18) | C13—C14—H14A | 111.3 |
C4—C3—H3 | 118.2 | C13—C14—H14B | 111.3 |
C4—C5—C6 | 115.07 (16) | C13—C8—C7 | 100.45 (10) |
C4—C5—H5A | 108.5 | C14—C1—C6 | 101.55 (10) |
C4—C5—H5B | 108.5 | C14—C13—C8 | 109.40 (10) |
C5—C4—H4 | 118.0 | H12A—C12—H12B | 107.6 |
C5—C6—C1 | 115.79 (13) | H14A—C14—H14B | 109.2 |
C5—C6—C7 | 115.37 (13) | H2A—C2—H2B | 107.8 |
C6—C5—H5A | 108.5 | H5A—C5—H5B | 107.5 |
C6—C5—H5B | 108.5 | H7A—C7—H7B | 109.1 |
C6—C7—C8 | 103.06 (11) | H9A—C9—H9B | 107.8 |
F1—C1—C14—C13 | 129.67 (11) | C6—O2—C13—C14 | −52.46 (11) |
F1—C1—C2—C3 | −78.24 (18) | C6—O2—C13—C8 | 59.99 (11) |
O1—C8—C7—C6 | 127.74 (11) | C7—C6—C1—C14 | 61.64 (13) |
O1—C8—C9—C10 | −74.33 (17) | C7—C6—C1—C2 | −176.04 (12) |
O2—C13—C12—C11 | −88.81 (15) | C7—C6—C1—F1 | −56.23 (14) |
O2—C13—C14—C1 | 23.37 (12) | C7—C6—C5—C4 | 152.45 (15) |
O2—C13—C8—C7 | −43.94 (11) | C7—C8—C9—C10 | 156.88 (14) |
O2—C13—C8—C9 | 74.02 (13) | C8—C13—C12—C11 | 24.79 (18) |
O2—C13—C8—O1 | −164.13 (10) | C8—C13—C14—C1 | −81.47 (12) |
O2—C6—C1—C14 | −45.18 (11) | C8—C9—C10—C11 | −26.7 (2) |
O2—C6—C1—C2 | 77.13 (13) | C9—C8—C7—C6 | −105.25 (13) |
O2—C6—C1—F1 | −163.06 (10) | C12—C11—C10—C9 | 3.5 (3) |
O2—C6—C5—C4 | −89.78 (17) | C12—C13—C14—C1 | 145.38 (11) |
O2—C6—C7—C8 | 24.13 (13) | C12—C13—C8—C7 | −164.63 (11) |
C1—C2—C3—C4 | −23.8 (3) | C12—C13—C8—C9 | −46.66 (16) |
C1—C6—C5—C4 | 22.3 (2) | C12—C13—C8—O1 | 75.19 (14) |
C1—C6—C7—C8 | −79.56 (13) | C13—C12—C11—C10 | −2.2 (2) |
C2—C1—C14—C13 | −108.60 (13) | C13—C8—C7—C6 | 11.85 (13) |
C5—C4—C3—C2 | 2.2 (4) | C13—C8—C9—C10 | 46.01 (18) |
C5—C6—C1—C14 | −165.54 (13) | C13—O2—C6—C1 | 60.29 (11) |
C5—C6—C1—C2 | −43.22 (17) | C13—O2—C6—C5 | −177.19 (12) |
C5—C6—C1—F1 | 76.59 (15) | C13—O2—C6—C7 | −52.26 (11) |
C5—C6—C7—C8 | 147.40 (13) | C14—C1—C2—C3 | 157.92 (15) |
C6—C1—C14—C13 | 13.05 (12) | C14—C13—C12—C11 | 154.56 (13) |
C6—C1—C2—C3 | 42.79 (19) | C14—C13—C8—C7 | 63.06 (13) |
C6—C5—C4—C3 | −1.3 (3) | C14—C13—C8—C9 | −178.98 (12) |
C6—O2—C13—C12 | −176.26 (11) | C14—C13—C8—O1 | −57.12 (14) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 0.82 | 2.14 | 2.9554 (14) | 177 |
Symmetry code: (i) −x+2, y−1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C14H17FO2 |
Mr | 236.28 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 291 |
a, b, c (Å) | 8.1603 (6), 10.9148 (8), 13.5558 (10) |
β (°) | 96.285 (3) |
V (Å3) | 1200.13 (15) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.26 × 0.22 × 0.12 |
Data collection | |
Diffractometer | Bruker SMART APEX CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.976, 0.989 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10752, 2454, 2038 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.626 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.041, 0.113, 1.03 |
No. of reflections | 2454 |
No. of parameters | 155 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.19, −0.21 |
Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1998), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and CAMERON (Watkin et al., 1993), PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 0.82 | 2.14 | 2.9554 (14) | 177 |
Symmetry code: (i) −x+2, y−1/2, −z+1/2. |
Acknowledgements
We thank the Department of Science and Technology (DST), India, for the CCD facility at the Indian Institute of Science (IISc), Bangalore. GM thanks the Council for Scientific and Industrial Research (CSIR), India, for research support and the award of a Bhatnagar Fellowship.
References
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Organofluorine compounds, while rarely occurring naturally, constitute around 20% of all known pharmaceuticals (Bégué & Bonnet-Delpon, 2006; Müller et al., 2007). The wide- spread applications of fluorinated organic compounds in the therapeutic arena has been attributed to the fact that incorporating fluorine in a drug can significantly enhance its lipophilicity and in vitro stability towards cytochrome P450 enzymatic oxidation (Kirsch, 2004; Müller et al., 2007).
Not surprisingly, various reagents, such as diethylaminosulfur trifluoride (DAST) (Middleton, 1975) and 1-chloromethyl-4-fluorodiazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) (Banks et al., 1992) have been developed over the years for achieving controlled and selective introduction of C—F bonds. The Olah's reagent [pyridinium poly(hydrogen fluoride)] was, in this context, among the first such fluorinating agents to be reported (Olah et al., 1979; Müller et al., 2007).
In a recent endeavor, we employed this reagent as means of accessing the difluorodiol 1 via one-pot HF-mediated ring-opening in the syn-diepoxide 2 (Fig. 1; Mehta & Sen, 2010). The complete regio- and stereoselectivity, observed in this bis-fluorination step, was intriguing and goaded us to investigate the outcome of reacting pyridine poly(hydrogen fluoride) with the anti-diepoxide 3 (Fig. 2; Mehta et al., 2007).
The title compound 4, bearing a 7-oxanorbornane core inscribed in a 1,4,4a,5,8,8a,9,9a,10,10a-decahydroanthracene framework, was obtained as the major product. Formation of the tetracyclic fluoroalcohol 4 can be explained by an initial HF-mediated epoxide ring opening in 3 to yield the fluorohydrin 5, followed by a novel variant of a hydroxy-mediated bishomo-Payne rearrangement in 5 to afford 4 (Fig. 3).
The crystal structure of 4 was solved and refined in the centrosymmetric monoclinic space group P21/c (Z = 4). The two flanking cyclohexene rings, folded towards the oxa bridge of the bicyclic core, and the pendant syn-4-fluoro-butan-1-ol moiety afforded the molecule an interesting pagoda-like architecture (Fig. 4). Crystal packing in 4 was effected via the agency of intermolecular O—H···O hydrogen bonds which linked the tetraacetate molecules into zigzag chains along the b axis (Fig. 5).