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Acta Crystallogr Sect E Struct Rep Online. 2009 December 1; 65(Pt 12): o3237–o3238.
Published online 2009 November 28. doi:  10.1107/S1600536809050326
PMCID: PMC2971845

7-Chloro-3,3-dimethyl-9-phenyl-1,2,3,4-tetra­hydro­acridin-1-one

Abstract

In the title salt, C21H18ClNO, the quinoline ring system is approximately planar [maximum deviation = 0.035 (2) Å], and forms a dihedral angle of 71.42 (6)° with the attached phenyl ring. The cyclo­hexa­none ring exists in a half-boat conformation. In the crystal packing, C—H(...)O contacts link the mol­ecules into extended supra­molecular chains along the c axis.

Related literature

For background to and biological activity of quinolines, see: Morimoto et al. (1991 [triangle]); Michael (1997 [triangle]); Markees et al. (1970 [triangle]); Campbell et al. (1988 [triangle]); Maguire et al. (1994 [triangle]); Kalluraya & Sreenivasa (1998 [triangle]); Roma et al. (2000 [triangle]); Chen et al. (2001 [triangle]). For the synthesis of quinoline derivatives, see: Fun, Loh et al. (2009 [triangle]); Fun, Yeap et al. (2009 [triangle]). For a related structure: see: Loh et al. (2009 [triangle]). For ring conformations, see: Cremer & Pople (1975 [triangle]). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-o3237-scheme1.jpg

Experimental

Crystal data

  • C21H18ClNO
  • M r = 335.81
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-o3237-efi1.jpg
  • a = 9.8375 (1) Å
  • b = 10.0525 (1) Å
  • c = 10.1076 (1) Å
  • α = 79.162 (1)°
  • β = 63.389 (1)°
  • γ = 70.928 (1)°
  • V = 843.59 (2) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.23 mm−1
  • T = 100 K
  • 0.30 × 0.20 × 0.15 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2005 [triangle]) T min = 0.933, T max = 0.965
  • 18373 measured reflections
  • 4882 independent reflections
  • 3915 reflections with I > 2σ(I)
  • R int = 0.030

Refinement

  • R[F 2 > 2σ(F 2)] = 0.045
  • wR(F 2) = 0.111
  • S = 1.04
  • 4882 reflections
  • 289 parameters
  • All H-atom parameters refined
  • Δρmax = 0.47 e Å−3
  • Δρmin = −0.29 e Å−3

Data collection: APEX2 (Bruker, 2005 [triangle]); cell refinement: SAINT (Bruker, 2005 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809050326/tk2581sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809050326/tk2581Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

HKF and WSL thank USM for a Research University Golden Goose Grant (1001/PFIZIK/811012). WSL thanks the Malaysian Government and USM for the award of the post of Assistant Research Officer under the Research University Golden Goose Grant (1001/PFIZIK/811012). VV is grateful to the DST-India for funding through the Young Scientist Scheme (Fast Track Proposal).

supplementary crystallographic information

Comment

Quinolines and their derivatives are very important compounds because of their wide occurrence in natural products (Morimoto et al., 1991; Michael, 1997) and biologically active compounds (Markees et al., 1970; Campbell et al., 1988). A large variety of quinolines have interesting physiological activities and have found attractive applications as pharmaceuticals, agrochemicals and as synthetic building blocks (Maguire et al., 1994; Kalluraya & Sreenivasa, 1998; Roma et al., 2000; Chen et al., 2001). Because of their great importance, the synthesis of new derivatives of quinoline remains an active research area. Recently, we have reported the synthesis of some novel quinoline derivatives (Fun, Loh et al., 2009; Fun, Yeap et al., 2009).

In the title compound (Fig. 1), the quinoline ring system (C1–C8/C13/N1) is approximately planar with a maximum deviation of 0.035 (2) Å at atom C13. The mean plane through the quinoline ring forms a dihedral angle of 71.42 (6)° with the phenyl ring (C14–C19). The cyclohexanone (C8–C13) ring exists in a half-boat conformation. The puckering parameters (Cremer & Pople, 1975) are Q = 0.5017 (17) Å; Θ = 126.65 (18)° and [var phi] = 352.8 (2)°. Bond lengths and angles are comparable to that in a closely related structure (Loh et al., 2009).

In the crystal packing (Fig. 2), C3—H3···O1 (Table 1) hydrogen bonds link neighbouring molecules, forming extended one-dimensional chains along c axis.

Experimental

A 1:1 mixture of 2-amino-5-chlorobenzophenone (0.2 g, 0.001 M), 5,5-dimethyl-1,3-cyclohexanedione (0.14 g, 0.001 M), and 1.0 ml concentrated HCl in distilled ethanol was irradiated for about 12 min under microwave irradiation at 240 W in a domestic microwave oven. The resulting mixture was poured on to ice and neutralized. The solid that formed was filtered, dried and purified by column chromatography using a 1:1 mixture of chloroform and petroleum ether. M. pt.: 459–461 K, yield: 45%.

Refinement

All hydrogen atoms were located from the difference Fourier map and were refined freely [range of C–H = 0.936 (19) to 1.020 (2) Å].

Figures

Fig. 1.
The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme.
Fig. 2.
The crystal packing of the title compound, viewed approximately along the a axis, showing extended one-dimensional chains. The intermolecular interactions are shown as dashed lines.

Crystal data

C21H18ClNOZ = 2
Mr = 335.81F(000) = 352
Triclinic, P1Dx = 1.322 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 9.8375 (1) ÅCell parameters from 6537 reflections
b = 10.0525 (1) Åθ = 2.3–32.2°
c = 10.1076 (1) ŵ = 0.23 mm1
α = 79.162 (1)°T = 100 K
β = 63.389 (1)°Block, colourless
γ = 70.928 (1)°0.30 × 0.20 × 0.15 mm
V = 843.59 (2) Å3

Data collection

Bruker SMART APEXII CCD area-detector diffractometer4882 independent reflections
Radiation source: fine-focus sealed tube3915 reflections with I > 2σ(I)
graphiteRint = 0.030
[var phi] and ω scansθmax = 30.0°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Bruker, 2005)h = −13→13
Tmin = 0.933, Tmax = 0.965k = −14→14
18373 measured reflectionsl = −14→13

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.045Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.111All H-atom parameters refined
S = 1.04w = 1/[σ2(Fo2) + (0.0441P)2 + 0.4367P] where P = (Fo2 + 2Fc2)/3
4882 reflections(Δ/σ)max = 0.001
289 parametersΔρmax = 0.47 e Å3
0 restraintsΔρmin = −0.29 e Å3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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)

xyzUiso*/Ueq
Cl11.00497 (5)0.24082 (4)0.06504 (4)0.03117 (11)
O10.66039 (14)0.51264 (12)0.86939 (12)0.0328 (3)
N10.55017 (13)0.70933 (12)0.44602 (12)0.0164 (2)
C10.65323 (15)0.59559 (14)0.36408 (14)0.0165 (3)
C20.67188 (17)0.59806 (16)0.21588 (15)0.0205 (3)
C30.77851 (18)0.49116 (16)0.12519 (16)0.0230 (3)
C40.87017 (17)0.37689 (15)0.18098 (15)0.0214 (3)
C50.85517 (16)0.36841 (15)0.32311 (15)0.0194 (3)
C60.74409 (15)0.47799 (14)0.41947 (14)0.0159 (3)
C70.72349 (15)0.47749 (14)0.56874 (14)0.0152 (2)
C80.61798 (15)0.59343 (14)0.65057 (14)0.0157 (2)
C90.58812 (16)0.60312 (15)0.80857 (15)0.0190 (3)
C100.46337 (18)0.73000 (15)0.89036 (15)0.0214 (3)
C110.45479 (17)0.86542 (14)0.79119 (15)0.0192 (3)
C120.41995 (16)0.83686 (14)0.66761 (15)0.0177 (3)
C130.53443 (15)0.70831 (14)0.58292 (14)0.0150 (2)
C140.81958 (15)0.35147 (14)0.62420 (14)0.0163 (3)
C150.78844 (16)0.22131 (15)0.64521 (16)0.0203 (3)
C160.88422 (18)0.10146 (16)0.68699 (18)0.0250 (3)
C171.01186 (18)0.11037 (16)0.70617 (18)0.0260 (3)
C181.04371 (17)0.23964 (16)0.68430 (17)0.0239 (3)
C190.94831 (16)0.35960 (15)0.64384 (15)0.0198 (3)
C200.6109 (2)0.90496 (18)0.72693 (19)0.0273 (3)
C210.3203 (2)0.98557 (16)0.88205 (18)0.0274 (3)
H12B0.4182 (19)0.9185 (18)0.5958 (19)0.020 (4)*
H12A0.313 (2)0.8231 (17)0.7114 (18)0.020 (4)*
H50.920 (2)0.2884 (19)0.3566 (19)0.027 (5)*
H190.967 (2)0.4527 (18)0.6301 (19)0.022 (4)*
H30.791 (2)0.4926 (19)0.025 (2)0.032 (5)*
H150.702 (2)0.2166 (18)0.6296 (19)0.026 (4)*
H20C0.700 (2)0.8310 (18)0.664 (2)0.025 (4)*
H171.077 (2)0.0280 (19)0.733 (2)0.030 (5)*
H181.130 (2)0.2447 (19)0.698 (2)0.029 (5)*
H21C0.312 (2)1.073 (2)0.819 (2)0.031 (5)*
H10B0.484 (2)0.7408 (19)0.974 (2)0.034 (5)*
H20.608 (2)0.681 (2)0.183 (2)0.033 (5)*
H10A0.361 (2)0.7063 (18)0.933 (2)0.026 (4)*
H160.863 (2)0.011 (2)0.703 (2)0.030 (5)*
H21B0.215 (2)0.962 (2)0.928 (2)0.035 (5)*
H21A0.342 (2)1.006 (2)0.963 (2)0.037 (5)*
H20B0.635 (2)0.918 (2)0.807 (2)0.040 (5)*
H20A0.602 (2)0.994 (2)0.671 (2)0.039 (5)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Cl10.0372 (2)0.0252 (2)0.02082 (18)−0.00849 (15)−0.00046 (15)−0.00871 (14)
O10.0348 (6)0.0349 (6)0.0200 (5)0.0068 (5)−0.0154 (5)−0.0010 (5)
N10.0181 (5)0.0169 (5)0.0169 (5)−0.0055 (4)−0.0098 (4)0.0005 (4)
C10.0182 (6)0.0181 (6)0.0170 (6)−0.0083 (5)−0.0090 (5)0.0006 (5)
C20.0250 (7)0.0232 (7)0.0181 (6)−0.0102 (6)−0.0115 (5)0.0016 (5)
C30.0302 (7)0.0268 (8)0.0157 (6)−0.0138 (6)−0.0086 (6)−0.0010 (5)
C40.0235 (7)0.0195 (7)0.0184 (6)−0.0093 (5)−0.0024 (5)−0.0054 (5)
C50.0196 (6)0.0173 (7)0.0200 (6)−0.0061 (5)−0.0065 (5)−0.0006 (5)
C60.0167 (6)0.0167 (6)0.0171 (6)−0.0076 (5)−0.0077 (5)−0.0002 (5)
C70.0144 (6)0.0158 (6)0.0172 (6)−0.0066 (5)−0.0075 (5)0.0019 (5)
C80.0169 (6)0.0168 (6)0.0154 (6)−0.0058 (5)−0.0084 (5)0.0012 (5)
C90.0214 (6)0.0206 (7)0.0162 (6)−0.0064 (5)−0.0092 (5)0.0013 (5)
C100.0282 (7)0.0194 (7)0.0157 (6)−0.0044 (6)−0.0097 (6)−0.0014 (5)
C110.0256 (7)0.0164 (6)0.0179 (6)−0.0060 (5)−0.0105 (5)−0.0015 (5)
C120.0202 (6)0.0155 (6)0.0191 (6)−0.0033 (5)−0.0109 (5)−0.0003 (5)
C130.0160 (6)0.0151 (6)0.0165 (6)−0.0058 (5)−0.0082 (5)0.0002 (5)
C140.0160 (6)0.0165 (6)0.0154 (6)−0.0036 (5)−0.0065 (5)0.0002 (5)
C150.0186 (6)0.0187 (7)0.0249 (7)−0.0053 (5)−0.0107 (5)0.0004 (5)
C160.0246 (7)0.0164 (7)0.0336 (8)−0.0057 (6)−0.0133 (6)0.0026 (6)
C170.0211 (7)0.0211 (7)0.0324 (8)−0.0024 (6)−0.0131 (6)0.0054 (6)
C180.0175 (6)0.0270 (8)0.0284 (7)−0.0067 (6)−0.0119 (6)0.0035 (6)
C190.0195 (6)0.0192 (7)0.0211 (6)−0.0071 (5)−0.0089 (5)0.0024 (5)
C200.0338 (8)0.0263 (8)0.0308 (8)−0.0141 (7)−0.0179 (7)0.0006 (6)
C210.0376 (9)0.0194 (7)0.0233 (7)−0.0019 (6)−0.0134 (7)−0.0056 (6)

Geometric parameters (Å, °)

Cl1—C41.7402 (14)C11—C121.5306 (19)
O1—C91.2122 (17)C11—C201.532 (2)
N1—C131.3200 (16)C12—C131.5075 (18)
N1—C11.3665 (17)C12—H12B0.989 (17)
C1—C61.4209 (18)C12—H12A0.987 (17)
C1—C21.4216 (18)C14—C191.3960 (19)
C2—C31.367 (2)C14—C151.3965 (19)
C2—H20.965 (19)C15—C161.3931 (19)
C3—C41.409 (2)C15—H150.944 (18)
C3—H30.966 (19)C16—C171.386 (2)
C4—C51.366 (2)C16—H160.969 (19)
C5—C61.4210 (19)C17—C181.390 (2)
C5—H50.962 (18)C17—H170.944 (18)
C6—C71.4288 (18)C18—C191.3859 (19)
C7—C81.3866 (18)C18—H180.936 (19)
C7—C141.4959 (17)C19—H190.986 (17)
C8—C131.4363 (17)C20—H20C0.989 (18)
C8—C91.5052 (18)C20—H20B0.98 (2)
C9—C101.510 (2)C20—H20A0.97 (2)
C10—C111.5339 (19)C21—H21C0.987 (19)
C10—H10B0.99 (2)C21—H21B1.02 (2)
C10—H10A0.996 (18)C21—H21A1.00 (2)
C11—C211.529 (2)
C13—N1—C1118.00 (11)C13—C12—C11114.16 (11)
N1—C1—C6122.92 (12)C13—C12—H12B108.2 (10)
N1—C1—C2117.86 (12)C11—C12—H12B111.5 (10)
C6—C1—C2119.21 (12)C13—C12—H12A107.6 (10)
C3—C2—C1121.05 (13)C11—C12—H12A108.9 (10)
C3—C2—H2123.0 (11)H12B—C12—H12A106.2 (13)
C1—C2—H2115.9 (11)N1—C13—C8123.51 (12)
C2—C3—C4118.94 (13)N1—C13—C12115.64 (11)
C2—C3—H3121.0 (11)C8—C13—C12120.85 (11)
C4—C3—H3120.0 (11)C19—C14—C15119.32 (12)
C5—C4—C3122.32 (13)C19—C14—C7120.81 (12)
C5—C4—Cl1119.04 (11)C15—C14—C7119.67 (12)
C3—C4—Cl1118.64 (11)C16—C15—C14120.08 (13)
C4—C5—C6119.59 (13)C16—C15—H15121.3 (11)
C4—C5—H5119.5 (11)C14—C15—H15118.6 (11)
C6—C5—H5120.9 (11)C17—C16—C15120.26 (14)
C1—C6—C5118.86 (12)C17—C16—H16119.0 (11)
C1—C6—C7118.33 (12)C15—C16—H16120.7 (11)
C5—C6—C7122.77 (12)C16—C17—C18119.75 (13)
C8—C7—C6118.01 (11)C16—C17—H17119.3 (11)
C8—C7—C14124.97 (11)C18—C17—H17121.0 (11)
C6—C7—C14117.02 (11)C19—C18—C17120.37 (14)
C7—C8—C13119.21 (11)C19—C18—H18120.5 (11)
C7—C8—C9122.07 (11)C17—C18—H18119.1 (11)
C13—C8—C9118.72 (12)C18—C19—C14120.22 (13)
O1—C9—C8121.74 (13)C18—C19—H19121.7 (10)
O1—C9—C10120.60 (12)C14—C19—H19118.0 (10)
C8—C9—C10117.65 (11)C11—C20—H20C111.5 (10)
C9—C10—C11113.43 (12)C11—C20—H20B110.4 (12)
C9—C10—H10B107.8 (11)H20C—C20—H20B108.1 (15)
C11—C10—H10B111.5 (11)C11—C20—H20A110.4 (12)
C9—C10—H10A106.2 (10)H20C—C20—H20A110.1 (16)
C11—C10—H10A109.8 (10)H20B—C20—H20A106.1 (17)
H10B—C10—H10A107.7 (15)C11—C21—H21C110.1 (11)
C21—C11—C12109.62 (12)C11—C21—H21B111.3 (11)
C21—C11—C20109.35 (12)H21C—C21—H21B108.7 (15)
C12—C11—C20110.87 (12)C11—C21—H21A110.5 (11)
C21—C11—C10109.44 (12)H21C—C21—H21A107.0 (15)
C12—C11—C10106.87 (11)H21B—C21—H21A109.1 (16)
C20—C11—C10110.65 (12)
C13—N1—C1—C6−0.51 (19)C8—C9—C10—C11−34.80 (18)
C13—N1—C1—C2−178.97 (12)C9—C10—C11—C21177.24 (12)
N1—C1—C2—C3176.78 (13)C9—C10—C11—C1258.62 (16)
C6—C1—C2—C3−1.7 (2)C9—C10—C11—C20−62.19 (16)
C1—C2—C3—C40.3 (2)C21—C11—C12—C13−172.63 (12)
C2—C3—C4—C50.7 (2)C20—C11—C12—C1366.54 (15)
C2—C3—C4—Cl1179.70 (11)C10—C11—C12—C13−54.13 (15)
C3—C4—C5—C6−0.2 (2)C1—N1—C13—C8−0.93 (19)
Cl1—C4—C5—C6−179.21 (10)C1—N1—C13—C12179.64 (11)
N1—C1—C6—C5−176.26 (12)C7—C8—C13—N11.2 (2)
C2—C1—C6—C52.18 (19)C9—C8—C13—N1−178.91 (12)
N1—C1—C6—C71.61 (19)C7—C8—C13—C12−179.39 (12)
C2—C1—C6—C7−179.94 (12)C9—C8—C13—C120.50 (18)
C4—C5—C6—C1−1.2 (2)C11—C12—C13—N1−154.25 (12)
C4—C5—C6—C7−179.02 (13)C11—C12—C13—C826.30 (18)
C1—C6—C7—C8−1.27 (18)C8—C7—C14—C19−72.90 (18)
C5—C6—C7—C8176.52 (12)C6—C7—C14—C19106.43 (15)
C1—C6—C7—C14179.35 (11)C8—C7—C14—C15112.34 (15)
C5—C6—C7—C14−2.86 (19)C6—C7—C14—C15−68.33 (16)
C6—C7—C8—C13−0.03 (18)C19—C14—C15—C160.7 (2)
C14—C7—C8—C13179.29 (12)C7—C14—C15—C16175.57 (13)
C6—C7—C8—C9−179.91 (12)C14—C15—C16—C17−0.8 (2)
C14—C7—C8—C9−0.6 (2)C15—C16—C17—C180.3 (2)
C7—C8—C9—O13.4 (2)C16—C17—C18—C190.2 (2)
C13—C8—C9—O1−176.50 (14)C17—C18—C19—C14−0.2 (2)
C7—C8—C9—C10−176.29 (13)C15—C14—C19—C18−0.2 (2)
C13—C8—C9—C103.83 (18)C7—C14—C19—C18−175.01 (13)
O1—C9—C10—C11145.52 (14)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C3—H3···O1i0.962 (19)2.39 (2)3.225 (2)145.6 (17)

Symmetry codes: (i) x, y, z−1.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: TK2581).

References

  • Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
  • Campbell, S. F., Hardstone, J. D. & Palmer, M. J. (1988). J. Med. Chem. 31, 1031–1035. [PubMed]
  • Chen, Y.-L., Fang, K.-C., Sheu, J.-Y., Hsu, S.-L. & Tzeng, C.-C. (2001). J. Med. Chem. 44, 2374–2377. [PubMed]
  • Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107.
  • Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358.
  • Fun, H.-K., Loh, W.-S., Sarveswari, S., Vijayakumar, V. & Reddy, B. P. (2009). Acta Cryst. E65, o2688–o2689. [PMC free article] [PubMed]
  • Fun, H.-K., Yeap, C. S., Sarveswari, S., Vijayakumar, V. & Prasath, R. (2009). Acta Cryst. E65, o2665–o2666. [PMC free article] [PubMed]
  • Kalluraya, B. & Sreenivasa, S. (1998). Farmaco, 53, 399–404. [PubMed]
  • Loh, W.-S., Fun, H.-K., Sarveswari, S., Vijayakumar, V. & Reddy, B. P. (2009). Acta Cryst. E65, o3144–o3145. [PMC free article] [PubMed]
  • Maguire, M. P., Sheets, K. R., McVety, K., Spada, A. P. & Zilberstein, A. (1994). J. Med. Chem. 37, 2129–2137. [PubMed]
  • Markees, D. G., Dewey, V. C. & Kidder, G. W. (1970). J. Med. Chem. 13, 324–326. [PubMed]
  • Michael, J. P. (1997). Nat. Prod. Rep. 14, 605–608.
  • Morimoto, Y., Matsuda, F. & Shirahama, H. (1991). Synlett, 3, 202–203.
  • Roma, G., Braccio, M. D., Grossi, G., Mattioli, F. & Ghia, M. (2000). Eur. J. Med. Chem. 35, 1021–1026. [PubMed]
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Spek, A. L. (2009). Acta Cryst. D65, 148–155. [PMC free article] [PubMed]

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