Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807039232/bt2471sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807039232/bt2471Isup2.hkl |
CCDC reference: 660293
A magnetically stirred solution of a 5:3 mixture of the benzylidene acetals (I) and (II) (88 mg, 0.23 mmol) in anhydrous dichloromethane/pentane (1.4 ml of a 1:1 v/v mixture) was cooled to 195 K then treated, dropwise, with DIBAL-H (1.15 ml of a 1.0 M solution in dichloromethane). The resulting mixture was warmed to 233 K and after 6 h at this temperature was treated with sodium potassium tartrate (5 ml of a 1 M aqueous solution). The ensuing mixture was allowed to stir at 291 K for 2 h then the separated aqueous fraction was extracted with dichloromethane (3 × 40 ml). The combined organic phases were washed with brine (1 × 50 ml) then dried (MgSO4), filtered and concentrated under reduced pressure to give a clear, colourless oil. Subjection of this material to flash chromatography (silica, 1:4 v/v ethyl acetate/hexane elution) afforded two fractions, A and B.
Concentration of fraction A (Rf = 1/5) under reduced pressure afforded the benzyl ether (III) [41 mg, 74% based on available (I)] as a clear, colourless oil, [α]D -59.9 (c 0.05, CHCl3) (Found: M+., 384.0570. C17H2179BrO5 requires M+., 384.0572). 1H NMR (300 MHz, CDCl3) δ 7.33 (2H, d, J = 8.7 Hz), 6.90 (2H, d, J = 8.7 Hz), 6.24 (1H, d, J = 3.6 Hz), 4.84 (1H, d, J = 10.8 Hz), 4.68–4.61 (2H, complex m), 4.36 (2H, m), 4.15–4.10 (2H, complex m), 3.81 (3H, s), 1.43 (3H, s), 1.36 (3H, s); 13C NMR (75 MHz, CDCl3) δ 159.8, 130.1, 129.9, 128.6, 124.2, 114.1, 110.1, 77.9, 75.4, 74.0, 73.4, 70.5, 55.5, 28.1, 26.2 (one signal obscured or overlapping); νmax (NaCl)/cm-1 3460, 2924, 1612, 1516, 1464, 1254, 1089, 1046; MS (EI, 70 eV) 386 and 384 (M+., both 3%), 256 (7), 137 (20), 121 (100), 101 (20), 81 (37), 69 (81), 55 (42), 43 (53).
Concentration of fraction B (Rf = 0.30) under reduced pressure afforded a solid that upon recrystallization (diethyl ether) gave the acetal (II) (30 mg, 90% recovery) as white plates, m.p. = 649–651 K, [α]D = +49.4 (c 0.21, CHCl3) [Found: (M – H.)+, 381.0334. C17H1979BrO5 requires (M – H.)+, 381.0338]. 1H NMR (300 MHz, CDCl3) δ 7.40 (2H, d, J = 8.4 Hz), 6.79 (2H, d, J = 8.4 Hz), 6.25 (1H, d, J = 3.6 Hz), 5.86 (1H, s), 4.91 (1H, d, J = 6.0 Hz), 4.64–4.60 (3H, complex m), 3.73 (3H, s), 1.40 (3H, s), 1.38 (3H, s); νmax (NaCl)/cm-1 2979, 2896, 1647, 1615, 1589, 1517, 1382, 1337, 1249, 1220, 1175, 1090, 1060, 1025, 948, 832; MS (EI, 70 eV) 384 and 382 (M+., both 15%), 383 and 381 [(M – H.)+, both 29], 336 and 334 (both 2), 200 (16), 161 (31), 137 (38), 136 (60), 135 (100), 108 (53), 77 (29), 43 (52).
Hydrogen atoms were included at calculated positions and ride on the atoms to which they are bonded. The biggest features in a final difference electron density map are close to the Br atoms.
As part of a program directed towards exploiting microbially derived and enantiomerically pure cis-1,2-dihydrocatechols in the synthesis of certain biologically active natural products (Banwell et al., 2003), we generated an epimeric mixture of compounds (I) and (II) then subjected this to reaction with DIBAL-H. At 195–233 K one of these two benzylidene acetals participated more readily in the anticipated reductive cleavage reaction leading to the desired p-methoxybenzyl ether (III). The unreacted epimer was recovered and subjected to single-crystal X-ray analysis and thus establishing that it was compound (II) incorporating an exo-orientated or R-configured 4-methoxyphenyl group at C2. This outcome is consistent with the notion that the reactive epimer (I) can, by virtue of reduced steric effects, complex DIBAL-H at the O1-acetal oxygen more readily than (II) and thus engage, selectively, in the ring-cleavage process leading to target (III). The present structure represents only the second reported for a 4-methoxyphenylacetal derivative of a cis-cyclohexane-1,2-diol (Hulme et al., 2005).
The crystallographic asymmetric unit within the solid-state structure of compound (II) consists of two independent molecules. The compound is enantiomerically pure and its absolute configuration has been determined by refinement of the Flack parameter. The outcome of this determination is in agreement with that predicted on the basis of the absolute configuration of the precursor, viz. (1S,2S)-3-bromo-3,5-cyclohexadiene-1,2-diol (Boyd et al., 1991). The three non-aromatic rings within the title compound are each close to planar and with the two 1,3-dioxolane rings clearly attached to the opposite faces of the central cyclohexene residue. The allylic and homo-allylic C–O bonds associated with the two heterocyclic rings are all of similar length (1.430–1.438 Å) but the C2–O3 bond is notably shorter than the three remaining acetal carbon to oxygen bonds (1.418 vs 1.438–1.444 Å) within the molecule. The origins of this variation are unclear at the present time.
For related literature, see: Banwell et al. (2003); Boyd et al. (1991); Hulme et al. (2005).
Data collection: COLLECT (Nonius, 1997); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: ORTEPII (Johnson, 1976) in TEXSAN (Molecular Structure Corporation, 1997); software used to prepare material for publication: CRYSTALS.
C17H19BrO5 | F(000) = 784 |
Mr = 383.24 | Dx = 1.537 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
a = 5.2285 (1) Å | Cell parameters from 55931 reflections |
b = 33.4467 (9) Å | θ = 2.6–25° |
c = 9.4726 (3) Å | µ = 2.51 mm−1 |
β = 91.7226 (12)° | T = 200 K |
V = 1655.78 (7) Å3 | Plate, colourless |
Z = 4 | 0.45 × 0.14 × 0.05 mm |
Nonius KappaCCD diffractometer | 4970 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.038 |
φ and ω scans with CCD | θmax = 25.0°, θmin = 2.8° |
Absorption correction: integration via Gaussian method (Coppens, 1970) implemented in maXus (Mackay et al., 1999) | h = −6→6 |
Tmin = 0.546, Tmax = 0.892 | k = −39→39 |
20604 measured reflections | l = −11→11 |
5796 independent reflections |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters not refined |
R[F2 > 2σ(F2)] = 0.034 | Method = Modified Sheldrick
w = 1/[σ2(F2) + (0.03P)2 + 0.44P], where P = [max(Fo2,0) + 2Fc2]/3 |
wR(F2) = 0.078 | (Δ/σ)max = 0.001 |
S = 0.97 | Δρmax = 0.58 e Å−3 |
5796 reflections | Δρmin = −0.82 e Å−3 |
416 parameters | Absolute structure: Flack (1983), 2828 Friedel pairs |
1 restraint | Absolute structure parameter: −0.012 (6) |
Primary atom site location: structure-invariant direct methods |
C17H19BrO5 | V = 1655.78 (7) Å3 |
Mr = 383.24 | Z = 4 |
Monoclinic, P21 | Mo Kα radiation |
a = 5.2285 (1) Å | µ = 2.51 mm−1 |
b = 33.4467 (9) Å | T = 200 K |
c = 9.4726 (3) Å | 0.45 × 0.14 × 0.05 mm |
β = 91.7226 (12)° |
Nonius KappaCCD diffractometer | 5796 independent reflections |
Absorption correction: integration via Gaussian method (Coppens, 1970) implemented in maXus (Mackay et al., 1999) | 4970 reflections with I > 2σ(I) |
Tmin = 0.546, Tmax = 0.892 | Rint = 0.038 |
20604 measured reflections |
R[F2 > 2σ(F2)] = 0.034 | H-atom parameters not refined |
wR(F2) = 0.078 | Δρmax = 0.58 e Å−3 |
S = 0.97 | Δρmin = −0.82 e Å−3 |
5796 reflections | Absolute structure: Flack (1983), 2828 Friedel pairs |
416 parameters | Absolute structure parameter: −0.012 (6) |
1 restraint |
x | y | z | Uiso*/Ueq | ||
O1 | 0.3464 (5) | 0.40867 (9) | 0.5958 (3) | 0.0442 | |
C2 | 0.2738 (7) | 0.40850 (12) | 0.7402 (4) | 0.0359 | |
O3 | 0.0221 (5) | 0.39302 (8) | 0.7424 (3) | 0.0393 | |
C4 | −0.0224 (7) | 0.37075 (11) | 0.6148 (4) | 0.0358 | |
C5 | 0.0579 (8) | 0.32792 (11) | 0.6278 (4) | 0.0382 | |
C6 | 0.2260 (8) | 0.30950 (12) | 0.5503 (4) | 0.0384 | |
C7 | 0.3623 (7) | 0.32944 (11) | 0.4320 (4) | 0.0345 | |
O8 | 0.3249 (5) | 0.30663 (8) | 0.3051 (2) | 0.0349 | |
C9 | 0.1349 (7) | 0.32616 (11) | 0.2148 (4) | 0.0348 | |
O10 | 0.0409 (5) | 0.35852 (8) | 0.2978 (2) | 0.0374 | |
C11 | 0.2475 (7) | 0.37002 (11) | 0.3917 (4) | 0.0364 | |
C12 | 0.1353 (7) | 0.39397 (12) | 0.5098 (4) | 0.0360 | |
C13 | 0.2790 (7) | 0.44947 (11) | 0.8044 (4) | 0.0333 | |
C14 | 0.1061 (8) | 0.47884 (12) | 0.7616 (4) | 0.0402 | |
C15 | 0.1102 (8) | 0.51620 (12) | 0.8225 (4) | 0.0408 | |
C16 | 0.2883 (7) | 0.52469 (11) | 0.9305 (4) | 0.0347 | |
C17 | 0.4642 (8) | 0.49634 (12) | 0.9723 (4) | 0.0422 | |
C18 | 0.4595 (8) | 0.45874 (12) | 0.9093 (4) | 0.0408 | |
Br19 | −0.11756 (10) | 0.29887 (3) | 0.76809 (4) | 0.0609 | |
C20 | −0.0808 (7) | 0.29762 (13) | 0.1827 (4) | 0.0448 | |
C21 | 0.2636 (8) | 0.34112 (13) | 0.0852 (4) | 0.0465 | |
O22 | 0.2709 (5) | 0.56229 (8) | 0.9893 (3) | 0.0439 | |
C23 | 0.4571 (9) | 0.57223 (12) | 1.0977 (4) | 0.0480 | |
O101 | 0.8242 (5) | 0.60404 (8) | 0.6747 (3) | 0.0444 | |
C102 | 0.7448 (7) | 0.60523 (11) | 0.5282 (4) | 0.0356 | |
O103 | 0.4861 (5) | 0.61825 (8) | 0.5250 (3) | 0.0392 | |
C104 | 0.4501 (7) | 0.64154 (11) | 0.6503 (4) | 0.0353 | |
C105 | 0.5211 (7) | 0.68426 (11) | 0.6330 (4) | 0.0337 | |
C106 | 0.6957 (7) | 0.70409 (11) | 0.7083 (4) | 0.0352 | |
C107 | 0.8556 (7) | 0.68488 (11) | 0.8242 (4) | 0.0325 | |
O108 | 0.8519 (4) | 0.70848 (9) | 0.9508 (2) | 0.0342 | |
C109 | 0.6632 (7) | 0.69170 (12) | 1.0426 (4) | 0.0358 | |
O110 | 0.5563 (5) | 0.65805 (8) | 0.9668 (2) | 0.0378 | |
C111 | 0.7488 (8) | 0.64532 (11) | 0.8725 (4) | 0.0363 | |
C112 | 0.6229 (8) | 0.61987 (12) | 0.7581 (4) | 0.0362 | |
C113 | 0.7651 (7) | 0.56493 (11) | 0.4605 (4) | 0.0323 | |
C114 | 0.6019 (8) | 0.53372 (12) | 0.4985 (4) | 0.0399 | |
C115 | 0.6187 (8) | 0.49680 (11) | 0.4347 (4) | 0.0388 | |
C116 | 0.7973 (7) | 0.49055 (11) | 0.3318 (4) | 0.0355 | |
C117 | 0.9609 (8) | 0.52082 (12) | 0.2951 (4) | 0.0414 | |
C118 | 0.9423 (7) | 0.55802 (12) | 0.3611 (4) | 0.0392 | |
Br119 | 0.32031 (9) | 0.71174 (3) | 0.49172 (4) | 0.0513 | |
C120 | 0.4578 (8) | 0.72146 (13) | 1.0659 (5) | 0.0527 | |
C121 | 0.7960 (9) | 0.67800 (14) | 1.1778 (4) | 0.0505 | |
O122 | 0.7948 (6) | 0.45324 (8) | 0.2698 (3) | 0.0429 | |
C123 | 0.9839 (9) | 0.44560 (13) | 0.1674 (4) | 0.0483 | |
H21 | 0.3917 | 0.39055 | 0.7960 | 0.0430* | |
H41 | −0.2078 | 0.37220 | 0.5861 | 0.0429* | |
H61 | 0.2651 | 0.28080 | 0.5711 | 0.0459* | |
H71 | 0.5489 | 0.33217 | 0.4563 | 0.0414* | |
H111 | 0.3748 | 0.38645 | 0.3405 | 0.0436* | |
H121 | 0.0332 | 0.41686 | 0.4701 | 0.0432* | |
H141 | −0.0240 | 0.47275 | 0.6851 | 0.0480* | |
H151 | −0.0141 | 0.53715 | 0.7893 | 0.0487* | |
H171 | 0.5957 | 0.50268 | 1.0478 | 0.0504* | |
H181 | 0.5880 | 0.43815 | 0.9403 | 0.0487* | |
H201 | −0.0197 | 0.27581 | 0.1198 | 0.0536* | |
H202 | −0.2251 | 0.31227 | 0.1341 | 0.0536* | |
H203 | −0.1412 | 0.28577 | 0.2727 | 0.0536* | |
H211 | 0.1346 | 0.35471 | 0.0216 | 0.0560* | |
H212 | 0.4012 | 0.36053 | 0.1135 | 0.0560* | |
H213 | 0.3405 | 0.31807 | 0.0343 | 0.0560* | |
H231 | 0.4256 | 0.60002 | 1.1320 | 0.0576* | |
H232 | 0.6324 | 0.57057 | 1.0587 | 0.0576* | |
H233 | 0.4434 | 0.55302 | 1.1780 | 0.0576* | |
H1021 | 0.8522 | 0.62490 | 0.4770 | 0.0427* | |
H1041 | 0.2679 | 0.63956 | 0.6788 | 0.0424* | |
H1061 | 0.7226 | 0.73307 | 0.6875 | 0.0424* | |
H1071 | 1.0354 | 0.68137 | 0.7934 | 0.0391* | |
H1111 | 0.8841 | 0.62966 | 0.9249 | 0.0436* | |
H1121 | 0.5266 | 0.59745 | 0.8019 | 0.0436* | |
H1141 | 0.4723 | 0.53827 | 0.5723 | 0.0480* | |
H1151 | 0.5024 | 0.47460 | 0.4625 | 0.0465* | |
H1171 | 1.0916 | 0.51623 | 0.2219 | 0.0499* | |
H1181 | 1.0616 | 0.57999 | 0.3348 | 0.0472* | |
H1201 | 0.5305 | 0.74480 | 1.1196 | 0.0633* | |
H1202 | 0.3854 | 0.73078 | 0.9727 | 0.0633* | |
H1203 | 0.3194 | 0.70884 | 1.1213 | 0.0633* | |
H1211 | 0.6672 | 0.66636 | 1.2420 | 0.0606* | |
H1212 | 0.8821 | 0.70132 | 1.2252 | 0.0606* | |
H1213 | 0.9267 | 0.65726 | 1.1558 | 0.0606* | |
H1231 | 0.9627 | 0.41776 | 0.1303 | 0.0580* | |
H1232 | 0.9630 | 0.46507 | 0.0878 | 0.0580* | |
H1233 | 1.1584 | 0.44861 | 0.2123 | 0.0580* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0511 (17) | 0.0465 (17) | 0.0355 (14) | −0.0169 (13) | 0.0087 (13) | −0.0127 (13) |
C2 | 0.035 (2) | 0.039 (2) | 0.034 (2) | −0.0014 (17) | −0.0008 (16) | −0.0041 (17) |
O3 | 0.0432 (16) | 0.0415 (15) | 0.0333 (14) | −0.0120 (13) | 0.0064 (11) | −0.0104 (12) |
C4 | 0.037 (2) | 0.039 (2) | 0.0318 (19) | −0.0038 (17) | −0.0044 (16) | −0.0093 (16) |
C5 | 0.050 (3) | 0.032 (2) | 0.031 (2) | −0.0090 (18) | −0.0070 (18) | −0.0013 (17) |
C6 | 0.051 (2) | 0.032 (2) | 0.032 (2) | 0.0052 (17) | −0.0079 (17) | 0.0006 (16) |
C7 | 0.037 (2) | 0.033 (2) | 0.033 (2) | 0.0052 (17) | −0.0006 (17) | −0.0070 (17) |
O8 | 0.0360 (14) | 0.0368 (16) | 0.0312 (13) | 0.0076 (11) | −0.0078 (11) | −0.0084 (11) |
C9 | 0.037 (2) | 0.036 (2) | 0.032 (2) | 0.0106 (16) | −0.0030 (16) | −0.0073 (16) |
O10 | 0.0478 (15) | 0.0364 (14) | 0.0277 (13) | 0.0114 (12) | −0.0035 (11) | −0.0080 (11) |
C11 | 0.045 (2) | 0.034 (2) | 0.0309 (19) | −0.0037 (17) | 0.0001 (16) | −0.0034 (16) |
C12 | 0.050 (2) | 0.030 (2) | 0.0274 (19) | 0.0009 (17) | −0.0008 (17) | −0.0041 (15) |
C13 | 0.039 (2) | 0.034 (2) | 0.0274 (19) | −0.0039 (17) | 0.0035 (16) | −0.0057 (16) |
C14 | 0.044 (2) | 0.042 (2) | 0.034 (2) | 0.0015 (19) | −0.0099 (18) | −0.0020 (18) |
C15 | 0.050 (2) | 0.034 (2) | 0.038 (2) | 0.0044 (18) | −0.0057 (18) | 0.0018 (17) |
C16 | 0.045 (2) | 0.028 (2) | 0.0310 (19) | −0.0050 (17) | 0.0054 (16) | −0.0016 (15) |
C17 | 0.044 (2) | 0.040 (2) | 0.042 (2) | 0.0012 (19) | −0.0105 (18) | −0.0111 (18) |
C18 | 0.044 (2) | 0.037 (2) | 0.041 (2) | 0.0050 (18) | −0.0100 (18) | −0.0079 (17) |
Br19 | 0.0886 (4) | 0.0553 (3) | 0.0393 (2) | −0.0281 (3) | 0.0087 (2) | 0.0010 (2) |
C20 | 0.034 (2) | 0.045 (2) | 0.055 (2) | 0.003 (2) | −0.0052 (17) | −0.015 (2) |
C21 | 0.053 (3) | 0.052 (3) | 0.035 (2) | 0.006 (2) | 0.0036 (19) | −0.0011 (19) |
O22 | 0.0618 (18) | 0.0291 (15) | 0.0407 (16) | −0.0040 (14) | −0.0010 (13) | −0.0046 (12) |
C23 | 0.070 (3) | 0.035 (2) | 0.039 (2) | −0.018 (2) | −0.001 (2) | −0.0034 (18) |
O101 | 0.0498 (17) | 0.0489 (18) | 0.0337 (14) | 0.0165 (14) | −0.0081 (12) | −0.0132 (12) |
C102 | 0.034 (2) | 0.038 (2) | 0.034 (2) | 0.0044 (17) | −0.0005 (16) | −0.0067 (17) |
O103 | 0.0385 (15) | 0.0420 (15) | 0.0367 (14) | 0.0062 (12) | −0.0059 (11) | −0.0133 (12) |
C104 | 0.038 (2) | 0.035 (2) | 0.033 (2) | 0.0003 (17) | 0.0032 (16) | −0.0087 (16) |
C105 | 0.039 (2) | 0.034 (2) | 0.0290 (19) | 0.0018 (17) | 0.0033 (16) | −0.0022 (16) |
C106 | 0.043 (2) | 0.031 (2) | 0.0314 (18) | −0.0011 (17) | 0.0072 (16) | 0.0014 (15) |
C107 | 0.033 (2) | 0.034 (2) | 0.0303 (19) | 0.0008 (16) | 0.0020 (15) | −0.0057 (16) |
O108 | 0.0395 (13) | 0.0340 (14) | 0.0293 (13) | −0.0040 (12) | 0.0048 (10) | −0.0065 (13) |
C109 | 0.037 (2) | 0.039 (2) | 0.0310 (19) | −0.0071 (17) | 0.0038 (16) | −0.0057 (16) |
O110 | 0.0482 (16) | 0.0351 (15) | 0.0305 (13) | −0.0101 (12) | 0.0081 (12) | −0.0061 (11) |
C111 | 0.047 (2) | 0.031 (2) | 0.031 (2) | 0.0025 (17) | 0.0043 (17) | −0.0026 (16) |
C112 | 0.051 (2) | 0.031 (2) | 0.0268 (19) | −0.0019 (18) | 0.0058 (17) | −0.0039 (15) |
C113 | 0.036 (2) | 0.032 (2) | 0.0291 (18) | −0.0013 (17) | −0.0023 (16) | −0.0030 (16) |
C114 | 0.047 (2) | 0.040 (2) | 0.033 (2) | −0.0009 (19) | 0.0068 (18) | −0.0068 (17) |
C115 | 0.046 (2) | 0.036 (2) | 0.035 (2) | −0.0040 (18) | 0.0020 (18) | −0.0010 (17) |
C116 | 0.044 (2) | 0.029 (2) | 0.033 (2) | 0.0036 (17) | −0.0062 (17) | −0.0038 (16) |
C117 | 0.044 (2) | 0.043 (2) | 0.038 (2) | −0.0008 (19) | 0.0136 (18) | −0.0103 (18) |
C118 | 0.040 (2) | 0.035 (2) | 0.043 (2) | −0.0019 (18) | 0.0066 (18) | −0.0076 (18) |
Br119 | 0.0586 (3) | 0.0541 (3) | 0.0406 (2) | 0.0124 (2) | −0.00977 (18) | 0.0001 (2) |
C120 | 0.038 (2) | 0.052 (3) | 0.068 (3) | 0.001 (2) | 0.006 (2) | −0.016 (2) |
C121 | 0.061 (3) | 0.060 (3) | 0.031 (2) | −0.009 (2) | −0.003 (2) | 0.002 (2) |
O122 | 0.0602 (19) | 0.0300 (15) | 0.0386 (16) | 0.0026 (13) | 0.0018 (13) | −0.0065 (12) |
C123 | 0.067 (3) | 0.041 (2) | 0.037 (2) | 0.018 (2) | 0.001 (2) | −0.0042 (19) |
O1—C2 | 1.431 (4) | O101—C102 | 1.436 (4) |
O1—C12 | 1.439 (4) | O101—C112 | 1.436 (4) |
C2—O3 | 1.415 (4) | C102—O103 | 1.421 (4) |
C2—C13 | 1.499 (5) | C102—C113 | 1.498 (5) |
C2—H21 | 1.000 | C102—H1021 | 1.000 |
O3—C4 | 1.433 (4) | O103—C104 | 1.437 (4) |
C4—C5 | 1.497 (5) | C104—C105 | 1.486 (5) |
C4—C12 | 1.524 (5) | C104—C112 | 1.527 (5) |
C4—H41 | 1.000 | C104—H1041 | 1.000 |
C5—C6 | 1.315 (5) | C105—C106 | 1.320 (5) |
C5—Br19 | 1.904 (4) | C105—Br119 | 1.911 (4) |
C6—C7 | 1.502 (6) | C106—C107 | 1.503 (5) |
C6—H61 | 1.000 | C106—H1061 | 1.000 |
C7—O8 | 1.432 (4) | C107—O108 | 1.436 (4) |
C7—C11 | 1.528 (5) | C107—C111 | 1.513 (5) |
C7—H71 | 1.000 | C107—H1071 | 1.000 |
O8—C9 | 1.448 (4) | O108—C109 | 1.448 (4) |
C9—O10 | 1.433 (4) | C109—O110 | 1.439 (4) |
C9—C20 | 1.502 (5) | C109—C120 | 1.486 (6) |
C9—C21 | 1.503 (5) | C109—C121 | 1.510 (5) |
O10—C11 | 1.431 (4) | O110—C111 | 1.430 (4) |
C11—C12 | 1.509 (5) | C111—C112 | 1.513 (5) |
C11—H111 | 1.000 | C111—H1111 | 1.000 |
C12—H121 | 1.000 | C112—H1121 | 1.000 |
C13—C14 | 1.387 (5) | C113—C114 | 1.402 (5) |
C13—C18 | 1.385 (5) | C113—C118 | 1.360 (5) |
C14—C15 | 1.376 (6) | C114—C115 | 1.379 (5) |
C14—H141 | 1.000 | C114—H1141 | 1.000 |
C15—C16 | 1.391 (5) | C115—C116 | 1.386 (5) |
C15—H151 | 1.000 | C115—H1151 | 1.000 |
C16—C17 | 1.371 (5) | C116—C117 | 1.377 (5) |
C16—O22 | 1.379 (4) | C116—O122 | 1.379 (4) |
C17—C18 | 1.392 (5) | C117—C118 | 1.397 (5) |
C17—H171 | 1.000 | C117—H1171 | 1.000 |
C18—H181 | 1.000 | C118—H1181 | 1.000 |
C20—H201 | 1.000 | C120—H1201 | 1.000 |
C20—H202 | 1.000 | C120—H1202 | 1.000 |
C20—H203 | 1.000 | C120—H1203 | 1.000 |
C21—H211 | 1.000 | C121—H1211 | 1.000 |
C21—H212 | 1.000 | C121—H1212 | 1.000 |
C21—H213 | 1.000 | C121—H1213 | 1.000 |
O22—C23 | 1.433 (4) | O122—C123 | 1.429 (5) |
C23—H231 | 1.000 | C123—H1231 | 1.000 |
C23—H232 | 1.000 | C123—H1232 | 1.000 |
C23—H233 | 1.000 | C123—H1233 | 1.000 |
C2—O1—C12 | 108.6 (3) | C102—O101—C112 | 109.0 (3) |
O1—C2—O3 | 106.8 (3) | O101—C102—O103 | 106.1 (3) |
O1—C2—C13 | 112.5 (3) | O101—C102—C113 | 111.5 (3) |
O3—C2—C13 | 109.5 (3) | O103—C102—C113 | 110.3 (3) |
O1—C2—H21 | 109.3 | O101—C102—H1021 | 109.6 |
O3—C2—H21 | 109.3 | O103—C102—H1021 | 109.6 |
C13—C2—H21 | 109.3 | C113—C102—H1021 | 109.6 |
C2—O3—C4 | 107.8 (3) | C102—O103—C104 | 107.3 (3) |
O3—C4—C5 | 113.0 (3) | O103—C104—C105 | 113.0 (3) |
O3—C4—C12 | 102.1 (3) | O103—C104—C112 | 101.9 (3) |
C5—C4—C12 | 112.7 (3) | C105—C104—C112 | 112.7 (3) |
O3—C4—H41 | 109.6 | O103—C104—H1041 | 109.7 |
C5—C4—H41 | 109.6 | C105—C104—H1041 | 109.7 |
C12—C4—H41 | 109.6 | C112—C104—H1041 | 109.7 |
C4—C5—C6 | 126.4 (4) | C104—C105—C106 | 126.5 (3) |
C4—C5—Br19 | 113.9 (3) | C104—C105—Br119 | 113.9 (3) |
C6—C5—Br19 | 119.7 (3) | C106—C105—Br119 | 119.5 (3) |
C5—C6—C7 | 123.3 (3) | C105—C106—C107 | 122.7 (3) |
C5—C6—H61 | 118.4 | C105—C106—H1061 | 118.7 |
C7—C6—H61 | 118.4 | C107—C106—H1061 | 118.7 |
C6—C7—O8 | 109.5 (3) | C106—C107—O108 | 110.7 (3) |
C6—C7—C11 | 112.9 (3) | C106—C107—C111 | 113.1 (3) |
O8—C7—C11 | 102.8 (3) | O108—C107—C111 | 102.3 (3) |
C6—C7—H71 | 110.5 | C106—C107—H1071 | 110.1 |
O8—C7—H71 | 110.5 | O108—C107—H1071 | 110.1 |
C11—C7—H71 | 110.5 | C111—C107—H1071 | 110.2 |
C7—O8—C9 | 109.2 (3) | C107—O108—C109 | 108.4 (3) |
O8—C9—O10 | 104.9 (2) | O108—C109—O110 | 105.4 (3) |
O8—C9—C20 | 109.3 (3) | O108—C109—C120 | 109.8 (3) |
O10—C9—C20 | 108.9 (3) | O110—C109—C120 | 109.1 (3) |
O8—C9—C21 | 108.5 (3) | O108—C109—C121 | 108.8 (3) |
O10—C9—C21 | 111.4 (3) | O110—C109—C121 | 110.4 (3) |
C20—C9—C21 | 113.4 (3) | C120—C109—C121 | 113.1 (4) |
C9—O10—C11 | 106.2 (3) | C109—O110—C111 | 105.9 (3) |
C7—C11—O10 | 101.5 (3) | C107—C111—O110 | 101.6 (3) |
C7—C11—C12 | 116.5 (3) | C107—C111—C112 | 115.6 (3) |
O10—C11—C12 | 107.5 (3) | O110—C111—C112 | 108.4 (3) |
C7—C11—H111 | 110.3 | C107—C111—H1111 | 110.3 |
O10—C11—H111 | 110.3 | O110—C111—H1111 | 110.3 |
C12—C11—H111 | 110.3 | C112—C111—H1111 | 110.3 |
C4—C12—C11 | 116.3 (3) | C104—C112—C111 | 116.6 (3) |
C4—C12—O1 | 103.0 (3) | C104—C112—O101 | 103.6 (3) |
C11—C12—O1 | 107.0 (3) | C111—C112—O101 | 106.9 (3) |
C4—C12—H121 | 110.1 | C104—C112—H1121 | 109.8 |
C11—C12—H121 | 110.1 | C111—C112—H1121 | 109.8 |
O1—C12—H121 | 110.1 | O101—C112—H1121 | 109.8 |
C2—C13—C14 | 121.7 (3) | C102—C113—C114 | 120.6 (3) |
C2—C13—C18 | 119.9 (3) | C102—C113—C118 | 120.5 (3) |
C14—C13—C18 | 118.4 (4) | C114—C113—C118 | 118.9 (3) |
C13—C14—C15 | 121.3 (4) | C113—C114—C115 | 120.5 (4) |
C13—C14—H141 | 119.4 | C113—C114—H1141 | 119.8 |
C15—C14—H141 | 119.4 | C115—C114—H1141 | 119.8 |
C14—C15—C16 | 119.7 (4) | C114—C115—C116 | 119.8 (4) |
C14—C15—H151 | 120.2 | C114—C115—H1151 | 120.1 |
C16—C15—H151 | 120.2 | C116—C115—H1151 | 120.1 |
C15—C16—C17 | 119.9 (4) | C115—C116—C117 | 120.2 (4) |
C15—C16—O22 | 115.6 (3) | C115—C116—O122 | 116.0 (3) |
C17—C16—O22 | 124.5 (3) | C117—C116—O122 | 123.8 (3) |
C16—C17—C18 | 119.9 (4) | C116—C117—C118 | 119.3 (4) |
C16—C17—H171 | 120.1 | C116—C117—H1171 | 120.3 |
C18—C17—H171 | 120.0 | C118—C117—H1171 | 120.3 |
C17—C18—C13 | 120.8 (4) | C117—C118—C113 | 121.3 (4) |
C17—C18—H181 | 119.6 | C117—C118—H1181 | 119.4 |
C13—C18—H181 | 119.6 | C113—C118—H1181 | 119.4 |
C9—C20—H201 | 109.5 | C109—C120—H1201 | 109.5 |
C9—C20—H202 | 109.5 | C109—C120—H1202 | 109.5 |
H201—C20—H202 | 109.5 | H1201—C120—H1202 | 109.5 |
C9—C20—H203 | 109.5 | C109—C120—H1203 | 109.5 |
H201—C20—H203 | 109.5 | H1201—C120—H1203 | 109.5 |
H202—C20—H203 | 109.5 | H1202—C120—H1203 | 109.5 |
C9—C21—H211 | 109.5 | C109—C121—H1211 | 109.5 |
C9—C21—H212 | 109.5 | C109—C121—H1212 | 109.5 |
H211—C21—H212 | 109.5 | H1211—C121—H1212 | 109.5 |
C9—C21—H213 | 109.5 | C109—C121—H1213 | 109.5 |
H211—C21—H213 | 109.5 | H1211—C121—H1213 | 109.5 |
H212—C21—H213 | 109.5 | H1212—C121—H1213 | 109.5 |
C16—O22—C23 | 116.7 (3) | C116—O122—C123 | 116.9 (3) |
O22—C23—H231 | 109.5 | O122—C123—H1231 | 109.5 |
O22—C23—H232 | 109.5 | O122—C123—H1232 | 109.5 |
H231—C23—H232 | 109.5 | H1231—C123—H1232 | 109.5 |
O22—C23—H233 | 109.5 | O122—C123—H1233 | 109.5 |
H231—C23—H233 | 109.5 | H1231—C123—H1233 | 109.5 |
H232—C23—H233 | 109.5 | H1232—C123—H1233 | 109.5 |
Experimental details
Crystal data | |
Chemical formula | C17H19BrO5 |
Mr | 383.24 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 200 |
a, b, c (Å) | 5.2285 (1), 33.4467 (9), 9.4726 (3) |
β (°) | 91.7226 (12) |
V (Å3) | 1655.78 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 2.51 |
Crystal size (mm) | 0.45 × 0.14 × 0.05 |
Data collection | |
Diffractometer | Nonius KappaCCD |
Absorption correction | Integration via Gaussian method (Coppens, 1970) implemented in maXus (Mackay et al., 1999) |
Tmin, Tmax | 0.546, 0.892 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 20604, 5796, 4970 |
Rint | 0.038 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.078, 0.97 |
No. of reflections | 5796 |
No. of parameters | 416 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters not refined |
Δρmax, Δρmin (e Å−3) | 0.58, −0.82 |
Absolute structure | Flack (1983), 2828 Friedel pairs |
Absolute structure parameter | −0.012 (6) |
Computer programs: COLLECT (Nonius, 1997), DENZO/SCALEPACK (Otwinowski & Minor, 1997), DENZO/SCALEPACK, SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), ORTEPII (Johnson, 1976) in TEXSAN (Molecular Structure Corporation, 1997), CRYSTALS.
As part of a program directed towards exploiting microbially derived and enantiomerically pure cis-1,2-dihydrocatechols in the synthesis of certain biologically active natural products (Banwell et al., 2003), we generated an epimeric mixture of compounds (I) and (II) then subjected this to reaction with DIBAL-H. At 195–233 K one of these two benzylidene acetals participated more readily in the anticipated reductive cleavage reaction leading to the desired p-methoxybenzyl ether (III). The unreacted epimer was recovered and subjected to single-crystal X-ray analysis and thus establishing that it was compound (II) incorporating an exo-orientated or R-configured 4-methoxyphenyl group at C2. This outcome is consistent with the notion that the reactive epimer (I) can, by virtue of reduced steric effects, complex DIBAL-H at the O1-acetal oxygen more readily than (II) and thus engage, selectively, in the ring-cleavage process leading to target (III). The present structure represents only the second reported for a 4-methoxyphenylacetal derivative of a cis-cyclohexane-1,2-diol (Hulme et al., 2005).
The crystallographic asymmetric unit within the solid-state structure of compound (II) consists of two independent molecules. The compound is enantiomerically pure and its absolute configuration has been determined by refinement of the Flack parameter. The outcome of this determination is in agreement with that predicted on the basis of the absolute configuration of the precursor, viz. (1S,2S)-3-bromo-3,5-cyclohexadiene-1,2-diol (Boyd et al., 1991). The three non-aromatic rings within the title compound are each close to planar and with the two 1,3-dioxolane rings clearly attached to the opposite faces of the central cyclohexene residue. The allylic and homo-allylic C–O bonds associated with the two heterocyclic rings are all of similar length (1.430–1.438 Å) but the C2–O3 bond is notably shorter than the three remaining acetal carbon to oxygen bonds (1.418 vs 1.438–1.444 Å) within the molecule. The origins of this variation are unclear at the present time.