organic compounds
Bruceolline J: 2-hydroxy-3,3-dimethyl-2,3-dihydrocyclopenta[b]indol-1(4H)-one
aDepartment of Chemistry, Dartmouth College, Hanover, NH 03755-3564, USA, and bDepartment of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA
*Correspondence e-mail: jjasinski@keene.edu
The 12-membered cyclopenta[b]indole ring system in the title compound, C13H13NO2, deviates only slightly from planarity (r.m.s. deviation = 0.051 Å). In the crystal, N—H⋯O and O—H⋯O hydrogen bonds link the molecules into sheets parallel to (100). The five-membered cyclopentanone ring is in slightly distorted with the C atom bearing the hydroxy substituent as the flap.
Related literature
For a review of compounds isolated from Brucea sp. plants, see: Liu et al. (2009). For the first isolation of bruceolline J, see: Chen et al. (2011). For the DDQ-mediated selective oxidation of indole side chains, see: Oikawa & Yonemitsu (1977). For examples of the reduction of α-keto with sodium borohydride, see Dalla et al. (1999). For the enantioselective reduction of related sterically hindered with β-chlorodiisopinocampheylborane, see: Brown et al. (1986). For the isolation of related bruceollines, see: Ouyang et al. (1994a,b, 1995). For the of bruceolline D, see: Lopchuk et al. (2013). For the total synthesis and of bruceolline E, see: Jordan et al. (2011, 2012). For bond-length data, see: Allen et al. (1987).
Experimental
Crystal data
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Data collection: CrysAlis PRO (Agilent, 2012); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: SHELXL2012 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: XP in SHELXTL.
Supporting information
10.1107/S1600536813020527/bt6922sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536813020527/bt6922Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536813020527/bt6922Isup3.cml
To an ice-cold solution of bruceolline E (50 mg, 0.234 mmol, 1.0 equiv.) in dry THF (10 mL) was added sodium borohydride (5 mg, 0.117 mmol, 0.5 equiv.) in one portion (Fig. 3). After stirring at 0°C for 5 minutes, the reaction was quenched with water (5 mL) and concentrated to half the original volume. The mixture was extracted with ethyl acetate (3 x 40 mL). The organic extracts were combined, dried over Na2SO4, and concentrated in vacuo to an off-white solid. The residue was purified by flash
(50% ethyl acetate in pentane) to afford the desired product (I) as a white solid (50 mg, 98% yield). Single crystals suitable for diffraction were grown from ethyl acetate (slow evaporation) at ambient temperature [m.p. 466-467 K (dec); no literature value available].All H atoms were found in a difference map. Nevertheless, they were placed in their calculated positions and then refined using the riding model with Atom—H lengths of 0.95Å, 1.000Å (CH), 0.98Å (CH3), 0.88Å (NH) or 0.84Å (OH). Isotropic displacement parameters for these atoms were set to 1.2 (CH, NH) or 1.5 (CH3, OH) times Ueq of the parent atom. The methyl groups and the hydroxyl group were refined as rotating groups allowed to rotate but not to tip.
Data collection: CrysAlis PRO (Agilent, 2012); cell
CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: SHELXL2012 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: XP in SHELXTL (Sheldrick, 2008).C13H13NO2 | F(000) = 456 |
Mr = 215.24 | Dx = 1.315 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.7107 Å |
a = 8.2951 (3) Å | Cell parameters from 3528 reflections |
b = 12.3070 (4) Å | θ = 3.3–32.9° |
c = 10.7340 (4) Å | µ = 0.09 mm−1 |
β = 97.207 (3)° | T = 173 K |
V = 1087.15 (7) Å3 | Irregular, colourless |
Z = 4 | 0.44 × 0.38 × 0.34 mm |
Agilent Xcalibur (Eos, Gemini) diffractometer | 3753 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 2888 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.035 |
Detector resolution: 16.0416 pixels mm-1 | θmax = 33.0°, θmin = 3.4° |
ω scans | h = −12→12 |
Absorption correction: multi-scan (CrysAlis PRO and CrysAlis RED; Agilent, 2012) | k = −17→18 |
Tmin = 0.782, Tmax = 1.000 | l = −16→15 |
13545 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.048 | H-atom parameters constrained |
wR(F2) = 0.134 | w = 1/[σ2(Fo2) + (0.0662P)2 + 0.2062P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max < 0.001 |
3753 reflections | Δρmax = 0.40 e Å−3 |
148 parameters | Δρmin = −0.25 e Å−3 |
0 restraints |
C13H13NO2 | V = 1087.15 (7) Å3 |
Mr = 215.24 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 8.2951 (3) Å | µ = 0.09 mm−1 |
b = 12.3070 (4) Å | T = 173 K |
c = 10.7340 (4) Å | 0.44 × 0.38 × 0.34 mm |
β = 97.207 (3)° |
Agilent Xcalibur (Eos, Gemini) diffractometer | 3753 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO and CrysAlis RED; Agilent, 2012) | 2888 reflections with I > 2σ(I) |
Tmin = 0.782, Tmax = 1.000 | Rint = 0.035 |
13545 measured reflections |
R[F2 > 2σ(F2)] = 0.048 | 0 restraints |
wR(F2) = 0.134 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.40 e Å−3 |
3753 reflections | Δρmin = −0.25 e Å−3 |
148 parameters |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.83909 (11) | 0.55666 (6) | 0.93513 (8) | 0.03008 (19) | |
O2 | 1.13253 (11) | 0.51818 (7) | 0.82424 (8) | 0.0297 (2) | |
H2 | 1.1552 | 0.4933 | 0.8972 | 0.045* | |
N1 | 0.76891 (11) | 0.21451 (7) | 0.76238 (9) | 0.0246 (2) | |
H1 | 0.7945 | 0.1602 | 0.7152 | 0.030* | |
C1 | 0.83979 (13) | 0.31258 (8) | 0.77083 (10) | 0.0221 (2) | |
C2 | 0.98429 (13) | 0.35821 (9) | 0.71904 (10) | 0.0233 (2) | |
C3 | 0.98044 (14) | 0.47719 (8) | 0.77069 (10) | 0.0242 (2) | |
H3 | 0.9398 | 0.5254 | 0.6986 | 0.029* | |
C4 | 0.85291 (13) | 0.47926 (8) | 0.86414 (9) | 0.0230 (2) | |
C5 | 0.76844 (13) | 0.37877 (9) | 0.85201 (10) | 0.0233 (2) | |
C6 | 0.64335 (13) | 0.31588 (9) | 0.90039 (10) | 0.0239 (2) | |
C7 | 0.53565 (14) | 0.33227 (11) | 0.98851 (11) | 0.0301 (2) | |
H7 | 0.5298 | 0.4006 | 1.0290 | 0.036* | |
C8 | 0.43771 (15) | 0.24690 (12) | 1.01561 (13) | 0.0365 (3) | |
H8 | 0.3650 | 0.2567 | 1.0764 | 0.044* | |
C9 | 0.44313 (15) | 0.14681 (12) | 0.95594 (14) | 0.0383 (3) | |
H9 | 0.3739 | 0.0899 | 0.9768 | 0.046* | |
C10 | 0.54722 (15) | 0.12837 (10) | 0.86689 (13) | 0.0333 (3) | |
H10 | 0.5498 | 0.0604 | 0.8252 | 0.040* | |
C11 | 0.64742 (13) | 0.21344 (9) | 0.84131 (10) | 0.0249 (2) | |
C12 | 1.13707 (14) | 0.29740 (10) | 0.77445 (12) | 0.0309 (2) | |
H12A | 1.2332 | 0.3343 | 0.7503 | 0.046* | |
H12B | 1.1332 | 0.2228 | 0.7424 | 0.046* | |
H12C | 1.1429 | 0.2961 | 0.8662 | 0.046* | |
C13 | 0.96704 (18) | 0.35481 (12) | 0.57537 (11) | 0.0364 (3) | |
H13A | 0.8664 | 0.3917 | 0.5411 | 0.055* | |
H13B | 0.9636 | 0.2790 | 0.5471 | 0.055* | |
H13C | 1.0601 | 0.3916 | 0.5460 | 0.055* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0424 (5) | 0.0199 (4) | 0.0285 (4) | 0.0036 (3) | 0.0066 (3) | −0.0047 (3) |
O2 | 0.0386 (5) | 0.0241 (4) | 0.0273 (4) | −0.0099 (3) | 0.0075 (3) | 0.0006 (3) |
N1 | 0.0267 (4) | 0.0190 (4) | 0.0284 (4) | 0.0002 (3) | 0.0046 (3) | −0.0042 (3) |
C1 | 0.0248 (5) | 0.0199 (4) | 0.0216 (4) | 0.0009 (4) | 0.0033 (3) | −0.0015 (4) |
C2 | 0.0279 (5) | 0.0229 (5) | 0.0197 (4) | −0.0015 (4) | 0.0056 (4) | −0.0019 (4) |
C3 | 0.0332 (6) | 0.0189 (4) | 0.0210 (5) | −0.0019 (4) | 0.0051 (4) | 0.0009 (4) |
C4 | 0.0303 (5) | 0.0184 (4) | 0.0201 (4) | 0.0036 (4) | 0.0023 (4) | 0.0001 (3) |
C5 | 0.0266 (5) | 0.0210 (5) | 0.0228 (5) | 0.0021 (4) | 0.0056 (4) | −0.0008 (4) |
C6 | 0.0233 (5) | 0.0238 (5) | 0.0245 (5) | 0.0022 (4) | 0.0027 (4) | 0.0020 (4) |
C7 | 0.0265 (5) | 0.0358 (6) | 0.0289 (5) | 0.0046 (4) | 0.0064 (4) | 0.0019 (5) |
C8 | 0.0271 (6) | 0.0474 (7) | 0.0364 (6) | 0.0022 (5) | 0.0090 (5) | 0.0099 (6) |
C9 | 0.0282 (6) | 0.0386 (7) | 0.0485 (8) | −0.0043 (5) | 0.0068 (5) | 0.0136 (6) |
C10 | 0.0293 (6) | 0.0262 (6) | 0.0436 (7) | −0.0029 (4) | 0.0022 (5) | 0.0052 (5) |
C11 | 0.0232 (5) | 0.0227 (5) | 0.0283 (5) | 0.0013 (4) | 0.0017 (4) | 0.0023 (4) |
C12 | 0.0276 (6) | 0.0250 (5) | 0.0405 (6) | 0.0014 (4) | 0.0062 (4) | −0.0033 (5) |
C13 | 0.0477 (7) | 0.0408 (7) | 0.0217 (5) | −0.0070 (6) | 0.0080 (5) | −0.0050 (5) |
O1—C4 | 1.2341 (13) | C6—C11 | 1.4136 (15) |
O2—H2 | 0.8400 | C7—H7 | 0.9500 |
O2—C3 | 1.4122 (14) | C7—C8 | 1.3812 (19) |
N1—H1 | 0.8800 | C8—H8 | 0.9500 |
N1—C1 | 1.3406 (13) | C8—C9 | 1.392 (2) |
N1—C11 | 1.3956 (14) | C9—H9 | 0.9500 |
C1—C2 | 1.4928 (15) | C9—C10 | 1.3849 (19) |
C1—C5 | 1.3793 (14) | C10—H10 | 0.9500 |
C2—C3 | 1.5675 (15) | C10—C11 | 1.3854 (16) |
C2—C12 | 1.5267 (16) | C12—H12A | 0.9800 |
C2—C13 | 1.5313 (15) | C12—H12B | 0.9800 |
C3—H3 | 1.0000 | C12—H12C | 0.9800 |
C3—C4 | 1.5467 (15) | C13—H13A | 0.9800 |
C4—C5 | 1.4194 (15) | C13—H13B | 0.9800 |
C5—C6 | 1.4425 (15) | C13—H13C | 0.9800 |
C6—C7 | 1.3948 (15) | ||
C3—O2—H2 | 109.5 | C6—C7—H7 | 120.8 |
C1—N1—H1 | 125.9 | C8—C7—C6 | 118.46 (12) |
C1—N1—C11 | 108.15 (9) | C8—C7—H7 | 120.8 |
C11—N1—H1 | 125.9 | C7—C8—H8 | 119.2 |
N1—C1—C2 | 132.79 (9) | C7—C8—C9 | 121.50 (12) |
N1—C1—C5 | 110.80 (10) | C9—C8—H8 | 119.2 |
C5—C1—C2 | 116.19 (9) | C8—C9—H9 | 119.3 |
C1—C2—C3 | 99.60 (8) | C10—C9—C8 | 121.45 (11) |
C1—C2—C12 | 109.66 (9) | C10—C9—H9 | 119.3 |
C1—C2—C13 | 112.76 (9) | C9—C10—H10 | 121.5 |
C12—C2—C3 | 111.89 (9) | C9—C10—C11 | 117.03 (12) |
C12—C2—C13 | 110.31 (10) | C11—C10—H10 | 121.5 |
C13—C2—C3 | 112.23 (9) | N1—C11—C6 | 108.88 (9) |
O2—C3—C2 | 114.89 (9) | C10—C11—N1 | 128.63 (11) |
O2—C3—H3 | 107.5 | C10—C11—C6 | 122.44 (11) |
O2—C3—C4 | 112.27 (8) | C2—C12—H12A | 109.5 |
C2—C3—H3 | 107.5 | C2—C12—H12B | 109.5 |
C4—C3—C2 | 106.90 (8) | C2—C12—H12C | 109.5 |
C4—C3—H3 | 107.5 | H12A—C12—H12B | 109.5 |
O1—C4—C3 | 122.49 (10) | H12A—C12—H12C | 109.5 |
O1—C4—C5 | 130.25 (10) | H12B—C12—H12C | 109.5 |
C5—C4—C3 | 107.22 (8) | C2—C13—H13A | 109.5 |
C1—C5—C4 | 109.06 (9) | C2—C13—H13B | 109.5 |
C1—C5—C6 | 107.19 (10) | C2—C13—H13C | 109.5 |
C4—C5—C6 | 143.48 (10) | H13A—C13—H13B | 109.5 |
C7—C6—C5 | 135.84 (11) | H13A—C13—H13C | 109.5 |
C7—C6—C11 | 119.12 (10) | H13B—C13—H13C | 109.5 |
C11—C6—C5 | 104.97 (9) | ||
O1—C4—C5—C1 | −172.60 (11) | C4—C5—C6—C11 | −173.69 (15) |
O1—C4—C5—C6 | 0.2 (2) | C5—C1—C2—C3 | −7.02 (12) |
O2—C3—C4—O1 | 41.66 (14) | C5—C1—C2—C12 | 110.49 (11) |
O2—C3—C4—C5 | −136.56 (9) | C5—C1—C2—C13 | −126.17 (11) |
N1—C1—C2—C3 | 178.95 (11) | C5—C6—C7—C8 | −175.79 (12) |
N1—C1—C2—C12 | −63.53 (15) | C5—C6—C11—N1 | 0.33 (12) |
N1—C1—C2—C13 | 59.81 (16) | C5—C6—C11—C10 | 177.91 (11) |
N1—C1—C5—C4 | 176.56 (9) | C6—C7—C8—C9 | −0.91 (19) |
N1—C1—C5—C6 | 1.03 (13) | C7—C6—C11—N1 | −177.07 (10) |
C1—N1—C11—C6 | 0.28 (12) | C7—C6—C11—C10 | 0.51 (17) |
C1—N1—C11—C10 | −177.10 (12) | C7—C8—C9—C10 | 0.1 (2) |
C1—C2—C3—O2 | 134.83 (9) | C8—C9—C10—C11 | 0.97 (19) |
C1—C2—C3—C4 | 9.56 (10) | C9—C10—C11—N1 | 175.78 (11) |
C1—C5—C6—C7 | 175.93 (13) | C9—C10—C11—C6 | −1.28 (18) |
C1—C5—C6—C11 | −0.81 (12) | C11—N1—C1—C2 | 173.45 (11) |
C2—C1—C5—C4 | 1.24 (13) | C11—N1—C1—C5 | −0.82 (12) |
C2—C1—C5—C6 | −174.29 (9) | C11—C6—C7—C8 | 0.61 (17) |
C2—C3—C4—O1 | 168.51 (10) | C12—C2—C3—O2 | 19.00 (12) |
C2—C3—C4—C5 | −9.72 (11) | C12—C2—C3—C4 | −106.28 (10) |
C3—C4—C5—C1 | 5.44 (12) | C13—C2—C3—O2 | −105.63 (11) |
C3—C4—C5—C6 | 178.25 (14) | C13—C2—C3—C4 | 129.09 (10) |
C4—C5—C6—C7 | 3.0 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O1i | 0.84 | 1.90 | 2.7245 (12) | 168 |
N1—H1···O2ii | 0.88 | 1.91 | 2.7500 (12) | 158 |
Symmetry codes: (i) −x+2, −y+1, −z+2; (ii) −x+2, y−1/2, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O1i | 0.84 | 1.90 | 2.7245 (12) | 168.2 |
N1—H1···O2ii | 0.88 | 1.91 | 2.7500 (12) | 157.8 |
Symmetry codes: (i) −x+2, −y+1, −z+2; (ii) −x+2, y−1/2, −z+3/2. |
Acknowledgements
JML acknowledges support from a Graduate Assistance in Areas of National Need (GAANN) fellowship. GWG acknowledges support by the Donors of the Petroleum Research Fund (PRF), administered by the American Chemical Society, and by Wyeth. JPJ acknowledges the NSF MRI program (grant No. CHE-1039027) for funds to purchase the X-ray diffractometer.
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Bruceolline J is a cyclopenta[b]indole alkaloid which has been recently isolated from the stems of Brucea mollis Wall (Chen et al., 2011). Our total synthesis of racemic bruceolline J was achieved by the oxidation of bruceolline D to bruceolline E with DDQ followed by the selective reduction of bruceolline E with sodium borohydride in 98% yield. Enantioselective reductions with β-chlorodiisopinocampheylborane gave both the natural and unnatural enantiomers in excellent yields and enantioselectivites. Further isolation studies of the Brucea mollis shrubs have resulted in the discovery of a myriad of other bruceollines and cathan-6-one alkaloids (Ouyang et al., 1994a; Ouyang et al., 1994b; Ouyang et al., 1995). Although there has been limited attention from the synthetic community given to these compounds, a previous synthesis of bruceolline E has been reported (Jordan et al., 2011). The crystal structures of bruceolline D (Lopchuk et al., 2013) and bruceolline E (Jordon et al., 2012) have been disclosed. In view of the importance of cyclopenta[b]indole alkaloids, we report here the crystal structure of the title compound, C13H13NO2, (I).
The title compound, crystallizes with one molecule in the asymmetric unit. The 12-membered cyclopenta[b]indole ring system deviates only slightly from planarity (r.m.s. deviation 0.051Å) (Fig. 1). The 5-membered cyclopentanone ring is in slightly distorted envelope configuration (Q= 0.1012 (12)Å, ϕ = 66.4 (7)°) with C3 as the flap Bond lengths are in normal ranges (Allen et al., 1987). In the crystal N—H···O and O—H···O hydrogen bonds (Table 1) link the molecules into sheets parallel to (1 0 0) and contribute to crystal packing stability (Fig. 2).