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Acta Crystallogr Sect E Struct Rep Online. 2010 September 1; 66(Pt 9): o2248.
Published online 2010 August 11. doi:  10.1107/S1600536810030679
PMCID: PMC3008104

1-sec-Butyl-3-[hy­droxy(1-methyl-1H-indol-3-yl)methyl­idene]pyrrolidine-2,4-dione

Abstract

In the title compound, C18H20N2O3, the dihedral angle between the indole ring system (r.m.s. deviation = 0.018 Å) and the hy­droxy­methyl­enepyrrolidine-2,4-dione plane (r.m.s. deviation = 0.036 Å) is 9.87 (7)°. The keto and enol groups are involved in an intra­molecular O—H(...)O hydrogen bond. An intra­molecular C—H(...)O inter­action also occurs. The sec-butyl group is disordered over two orientations corresponding to an approximate 180° rotation about the N—C bond, with occupancies of 0.670 (6) and 0.330 (6). In the crystal, mol­ecules are linked into chains along the c axis by C—H(...)O hydrogen bonds.

Related literature

For the anti­biotic activity of 3-acyl­pyrrolidine-2,4-dione compounds, see: Baan et al. (1978 [triangle]); Holzapfel et al. (1970 [triangle]); Mackellar et al. (1971 [triangle]); Matsuo et al. (1980 [triangle]); Rinehart et al. (1963 [triangle]); Sticking (1959 [triangle]); Wu et al. (2002 [triangle]). For a related structure, see: Ellis & Spek (2001 [triangle]). For bond-length data, see: Allen et al. (1987 [triangle]).

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Object name is e-66-o2248-scheme1.jpg

Experimental

Crystal data

  • C18H20N2O3
  • M r = 312.36
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-o2248-efi1.jpg
  • a = 11.781 (2) Å
  • b = 10.529 (2) Å
  • c = 12.644 (3) Å
  • β = 97.18 (3)°
  • V = 1556.1 (5) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.09 mm−1
  • T = 113 K
  • 0.18 × 0.16 × 0.10 mm

Data collection

  • Rigaku Saturn diffractometer
  • Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 [triangle]) T min = 0.984, T max = 0.991
  • 12618 measured reflections
  • 3698 independent reflections
  • 2687 reflections with I > 2σ(I)
  • R int = 0.034

Refinement

  • R[F 2 > 2σ(F 2)] = 0.055
  • wR(F 2) = 0.168
  • S = 1.13
  • 3698 reflections
  • 218 parameters
  • 10 restraints
  • H-atom parameters constrained
  • Δρmax = 0.66 e Å−3
  • Δρmin = −0.57 e Å−3

Data collection: CrystalClear (Rigaku, 2005 [triangle]); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810030679/ci5139sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810030679/ci5139Isup2.hkl

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

Acknowledgments

The authors gratefully acknowledge financial support from the National Natural Science Foundation of China (grant No. 20772066).

supplementary crystallographic information

Comment

Many compounds containing the 3-acylpyrrolidine-2,4-dione moiety are novel heterocyclic compounds with antibiotic activity. Some of them are tenuazonic (Sticking, 1959), streptolydigin (Rinehart et al., 1963), tirandamycin (Mackellar et al., 1971), malonomycin (Baan et al., 1978), alpha-cyclopiazonic acid (Sticking, 1959) and bata-cyclopiazonic acid (Holzapfel et al., 1970). All these compounds possess a 3-acyltetramic acid moiety as a tricarbonylmethane structure and their hydrogen chemical shift of the enol hydroxy is about 11 p.p.m. (Wu et al., 2002). On the other hand, most of the excellent inhibitors of p-hydroxyphenylpyruvate dioxygenase also possess similar characteristics, which are crucial for their bioactivity. Up to now, we have synthesized a series of 3-(un)substituted aroyl-1-benzylpyrrolidine-2,4- dione compounds and some of them have high herbicidal activity. The structure of the title compound, (I), helps us to investigate the relationship between structure and herbicidal activity.

The molecular structure of (I) is shown in Fig. 1. Atom H1, involved in intramolecular hydrogen bonding between O1 and O3, was assigned to O1 rather than to O3, based on bond lengths. The C14—O3 distance is 1.254 (2) Å, which is longer than the C12—O2 distance of 1.231 (2) Å. In contrast, the C10—O1 distance [1.322 (2) Å] is intermediate between the normal carbonyl bond and the C—O single bond length (Allen et al. 1987). A similar situation has been found in 3-(1-hydroxyethylidene)-1- phenylpyrrolidine-2,4-dione, which contains the same pyrrolidine skeleton (Ellis & Spek, 2001). The dihedral angle formed by the indole ring system (r.m.s. deviation 0.018 Å) and the hydroxymethylene-pyrrolidine-2,4-dione plane (r.m.s. deviation 0.036 Å) is 9.87 (7)°.

Experimental

The title compound was obtained according to the reported procedure of Matsuo et al. (1980). Colourless single crystals were obtained by recrystallization of the title compound from petroleum ether and ethyl acetate.

Refinement

The sec-butyl group is disordered over two orientations corresponding to an approximately 180° rotation about the N2—C15 bond, with refined occupancies of 0.670 (6) and 0.330 (6). All C—C distances in this group were restrained to 1.540 (5) Å. H atoms were placed in calculated positions, with C–H = 0.95–0.98 Å and O–H = 0.84 A°, and included in the final cycles of refinement using a riding model, with Uiso(H) = 1.2Ueq(C) and 1.5Ueq(O).

Figures

Fig. 1.
The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme. Both disorder components are shown.

Crystal data

C18H20N2O3F(000) = 664
Mr = 312.36Dx = 1.333 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4289 reflections
a = 11.781 (2) Åθ = 2.5–27.9°
b = 10.529 (2) ŵ = 0.09 mm1
c = 12.644 (3) ÅT = 113 K
β = 97.18 (3)°Prism, yellow
V = 1556.1 (5) Å30.18 × 0.16 × 0.10 mm
Z = 4

Data collection

Rigaku Saturn diffractometer3698 independent reflections
Radiation source: fine-focus sealed tube2687 reflections with I > 2σ(I)
graphiteRint = 0.034
ω scansθmax = 27.9°, θmin = 2.6°
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)h = −9→15
Tmin = 0.984, Tmax = 0.991k = −13→13
12618 measured reflectionsl = −16→16

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)] = 0.055Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.168H-atom parameters constrained
S = 1.13w = 1/[σ2(Fo2) + (0.0947P)2 + 0.1812P] where P = (Fo2 + 2Fc2)/3
3698 reflections(Δ/σ)max = 0.001
218 parametersΔρmax = 0.66 e Å3
10 restraintsΔρmin = −0.57 e Å3

Special details

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*/UeqOcc. (<1)
O10.66886 (10)1.07272 (11)0.42060 (10)0.0232 (3)
H10.62681.06430.46910.035*
O20.93397 (11)0.78344 (12)0.54741 (11)0.0297 (3)
O30.59380 (11)1.00771 (11)0.58894 (10)0.0258 (3)
N10.98265 (12)0.96858 (14)0.26733 (12)0.0224 (3)
N20.69798 (14)0.85187 (15)0.68474 (13)0.0282 (4)
C10.83455 (14)1.00283 (15)0.35989 (13)0.0194 (4)
C20.81236 (14)1.06960 (15)0.25917 (13)0.0202 (4)
C30.72166 (16)1.14252 (16)0.20819 (15)0.0253 (4)
H30.65601.15950.24250.030*
C40.72960 (18)1.18928 (18)0.10697 (15)0.0306 (4)
H40.66771.23680.07140.037*
C50.82620 (19)1.16822 (18)0.05608 (16)0.0319 (5)
H50.82991.2041−0.01230.038*
C60.91688 (17)1.09601 (17)0.10329 (15)0.0278 (4)
H60.98271.08100.06870.033*
C70.90694 (15)1.04631 (16)0.20424 (14)0.0216 (4)
C80.93954 (14)0.94263 (16)0.35943 (14)0.0211 (4)
H80.97570.89100.41540.025*
C91.08481 (15)0.91093 (18)0.23351 (16)0.0285 (4)
H9A1.12850.86810.29430.043*
H9B1.13220.97700.20650.043*
H9C1.06230.84890.17700.043*
C100.75981 (14)0.99897 (15)0.44100 (13)0.0186 (4)
C110.76929 (14)0.92599 (15)0.53493 (14)0.0201 (4)
C120.84678 (15)0.82736 (17)0.57785 (14)0.0236 (4)
C130.80043 (16)0.77699 (18)0.67725 (16)0.0298 (4)
H13A0.78160.68550.66960.036*
H13B0.85690.78900.74130.036*
C140.67860 (15)0.93502 (16)0.60328 (14)0.0220 (4)
C150.61807 (18)0.8307 (2)0.76310 (17)0.0412 (6)
H150.55200.88980.74550.049*
C160.6765 (2)0.8655 (4)0.87609 (19)0.0717 (10)
H16A0.70460.95110.87620.108*0.670 (6)
H16B0.62180.85820.92600.108*0.670 (6)
H16C0.73910.80850.89620.108*0.670 (6)
H16D0.70430.95110.87560.086*0.330 (6)
H16E0.74110.81060.89450.086*0.330 (6)
C170.5719 (2)0.6974 (2)0.7563 (2)0.0582 (8)
H17A0.51870.68740.80730.070*0.670 (6)
H17B0.63360.63880.77490.070*0.670 (6)
H17C0.53730.68200.68460.087*0.330 (6)
H17D0.63280.63780.77450.087*0.330 (6)
H17E0.51550.68750.80430.087*0.330 (6)
C180.5146 (3)0.6638 (3)0.6507 (3)0.0524 (13)0.670 (6)
H18A0.44530.71530.63460.079*0.670 (6)
H18B0.49390.57360.64950.079*0.670 (6)
H18C0.56620.68000.59710.079*0.670 (6)
C18'0.5954 (8)0.8519 (12)0.9604 (7)0.087 (4)0.330 (6)
H18D0.52550.90070.93870.130*0.330 (6)
H18E0.63260.88401.02870.130*0.330 (6)
H18F0.57580.76210.96780.130*0.330 (6)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0214 (6)0.0279 (7)0.0218 (7)0.0049 (5)0.0084 (5)0.0028 (5)
O20.0252 (7)0.0340 (7)0.0313 (8)0.0094 (6)0.0096 (6)0.0056 (6)
O30.0230 (6)0.0314 (7)0.0240 (7)0.0073 (5)0.0073 (5)0.0040 (5)
N10.0202 (7)0.0254 (7)0.0229 (8)−0.0016 (6)0.0077 (6)−0.0021 (6)
N20.0258 (8)0.0336 (8)0.0275 (8)0.0063 (7)0.0119 (7)0.0098 (6)
C10.0201 (8)0.0194 (8)0.0193 (8)−0.0042 (6)0.0051 (7)−0.0015 (6)
C20.0228 (8)0.0190 (8)0.0198 (8)−0.0036 (6)0.0063 (7)−0.0012 (6)
C30.0251 (9)0.0254 (9)0.0268 (10)−0.0003 (7)0.0085 (8)0.0016 (7)
C40.0356 (10)0.0301 (9)0.0265 (10)0.0024 (8)0.0062 (8)0.0053 (8)
C50.0441 (12)0.0315 (10)0.0222 (9)0.0004 (9)0.0123 (9)0.0059 (8)
C60.0333 (10)0.0275 (9)0.0248 (9)−0.0033 (8)0.0124 (8)−0.0010 (7)
C70.0235 (8)0.0198 (8)0.0227 (9)−0.0035 (7)0.0072 (7)−0.0025 (6)
C80.0203 (8)0.0242 (8)0.0194 (9)−0.0030 (7)0.0049 (7)−0.0021 (6)
C90.0219 (9)0.0339 (10)0.0318 (10)0.0016 (8)0.0120 (8)−0.0040 (8)
C100.0181 (8)0.0182 (8)0.0200 (9)−0.0017 (6)0.0039 (6)−0.0027 (6)
C110.0196 (8)0.0207 (8)0.0205 (9)−0.0002 (6)0.0051 (7)0.0003 (6)
C120.0233 (9)0.0260 (9)0.0222 (9)−0.0014 (7)0.0058 (7)0.0010 (7)
C130.0282 (9)0.0324 (10)0.0304 (10)0.0071 (8)0.0103 (8)0.0106 (8)
C140.0219 (8)0.0247 (8)0.0198 (9)−0.0015 (7)0.0046 (7)0.0006 (7)
C150.0355 (11)0.0539 (13)0.0387 (12)0.0133 (10)0.0218 (10)0.0209 (10)
C160.0500 (16)0.129 (3)0.0391 (15)0.0170 (17)0.0182 (13)0.0283 (16)
C170.0434 (13)0.0516 (14)0.086 (2)0.0139 (11)0.0349 (15)0.0354 (14)
C180.042 (2)0.0387 (19)0.080 (3)−0.0026 (16)0.020 (2)0.0083 (18)
C18'0.079 (6)0.126 (8)0.058 (6)0.012 (6)0.021 (5)0.010 (5)

Geometric parameters (Å, °)

O1—C101.322 (2)C10—C111.407 (2)
O1—H10.84C11—C121.443 (2)
O2—C121.231 (2)C11—C141.459 (2)
O3—C141.254 (2)C12—C131.527 (2)
N1—C81.355 (2)C13—H13A0.99
N1—C71.387 (2)C13—H13B0.99
N1—C91.459 (2)C15—C171.504 (3)
N2—C141.349 (2)C15—C161.550 (3)
N2—C131.455 (2)C15—H151.00
N2—C151.467 (2)C16—C18'1.525 (5)
C1—C81.390 (2)C16—H16A0.96
C1—C101.433 (2)C16—H16B0.96
C1—C21.450 (2)C16—H16C0.96
C2—C31.405 (2)C16—H16D0.96
C2—C71.406 (2)C16—H16E0.96
C3—C41.385 (3)C17—C181.462 (4)
C3—H30.95C17—H17A0.96
C4—C51.393 (3)C17—H17B0.96
C4—H40.95C17—H17C0.96
C5—C61.384 (3)C17—H17D0.96
C5—H50.95C17—H17E0.96
C6—C71.398 (3)C18—H18A0.98
C6—H60.95C18—H18B0.98
C8—H80.95C18—H18C0.98
C9—H9A0.98C18'—H18D0.98
C9—H9B0.98C18'—H18E0.98
C9—H9C0.98C18'—H18F0.98
C10—O1—H1109.5N2—C15—H15107.6
C8—N1—C7109.27 (14)C17—C15—H15107.6
C8—N1—C9125.41 (16)C16—C15—H15107.6
C7—N1—C9124.87 (15)C18'—C16—C15112.1 (5)
C14—N2—C13111.38 (14)C18'—C16—H16A109.5
C14—N2—C15123.56 (16)C15—C16—H16A109.6
C13—N2—C15124.71 (15)C15—C16—H16B109.2
C8—C1—C10128.05 (16)H16A—C16—H16B109.5
C8—C1—C2106.28 (14)C18'—C16—H16C106.5
C10—C1—C2125.66 (15)C15—C16—H16C109.6
C3—C2—C7118.22 (15)H16A—C16—H16C109.5
C3—C2—C1135.34 (15)H16B—C16—H16C109.5
C7—C2—C1106.40 (15)C18'—C16—H16D109.7
C4—C3—C2118.86 (17)C15—C16—H16D109.2
C4—C3—H3120.6H16B—C16—H16D109.7
C2—C3—H3120.6H16C—C16—H16D109.7
C3—C4—C5121.56 (19)C18'—C16—H16E108.7
C3—C4—H4119.2C15—C16—H16E109.2
C5—C4—H4119.2H16A—C16—H16E107.6
C6—C5—C4121.27 (17)H16B—C16—H16E111.7
C6—C5—H5119.4H16D—C16—H16E107.8
C4—C5—H5119.4C18—C17—C15113.6 (2)
C5—C6—C7116.82 (17)C18—C17—H17A108.8
C5—C6—H6121.6C15—C17—H17A109.0
C7—C6—H6121.6C18—C17—H17B108.5
N1—C7—C6128.67 (16)C15—C17—H17B109.1
N1—C7—C2108.13 (14)H17A—C17—H17B107.6
C6—C7—C2123.20 (17)C15—C17—H17C108.7
N1—C8—C1109.93 (16)H17A—C17—H17C112.4
N1—C8—H8125.0H17B—C17—H17C110.0
C1—C8—H8125.0C18—C17—H17D107.9
N1—C9—H9A109.5C15—C17—H17D110.0
N1—C9—H9B109.5H17A—C17—H17D107.3
H9A—C9—H9B109.5H17C—C17—H17D109.5
N1—C9—H9C109.5C18—C17—H17E105.9
H9A—C9—H9C109.5C15—C17—H17E109.8
H9B—C9—H9C109.5H17B—C17—H17E109.7
O1—C10—C11117.53 (14)H17C—C17—H17E109.5
O1—C10—C1113.52 (15)H17D—C17—H17E109.5
C11—C10—C1128.93 (15)C17—C18—H18A109.5
C10—C11—C12133.64 (15)H17C—C18—H18A107.5
C10—C11—C14118.53 (15)C17—C18—H18B109.5
C12—C11—C14107.45 (14)H17C—C18—H18B118.4
O2—C12—C11131.76 (16)H18A—C18—H18B109.5
O2—C12—C13121.67 (16)C17—C18—H18C109.5
C11—C12—C13106.56 (14)H17C—C18—H18C102.1
N2—C13—C12104.50 (14)H18A—C18—H18C109.5
N2—C13—H13A110.9H18B—C18—H18C109.5
C12—C13—H13A110.9C16—C18'—H18D109.5
N2—C13—H13B110.9H16B—C18'—H18D104.2
C12—C13—H13B110.9C16—C18'—H18E109.5
H13A—C13—H13B108.9H16B—C18'—H18E113.9
O3—C14—N2124.21 (16)H18D—C18'—H18E109.5
O3—C14—C11125.70 (16)C16—C18'—H18F109.5
N2—C14—C11110.08 (15)H16B—C18'—H18F110.2
N2—C15—C17111.19 (18)H18D—C18'—H18F109.5
N2—C15—C16109.75 (18)H18E—C18'—H18F109.5
C17—C15—C16112.9 (2)
C8—C1—C2—C3176.72 (18)C1—C10—C11—C12−5.6 (3)
C10—C1—C2—C3−1.9 (3)O1—C10—C11—C140.5 (2)
C8—C1—C2—C7−0.62 (18)C1—C10—C11—C14−177.42 (16)
C10—C1—C2—C7−179.19 (15)C10—C11—C12—O25.9 (3)
C7—C2—C3—C4−0.7 (3)C14—C11—C12—O2178.41 (19)
C1—C2—C3—C4−177.76 (18)C10—C11—C12—C13−173.30 (18)
C2—C3—C4—C5−1.6 (3)C14—C11—C12—C13−0.80 (19)
C3—C4—C5—C62.1 (3)C14—N2—C13—C121.2 (2)
C4—C5—C6—C7−0.4 (3)C15—N2—C13—C12174.59 (18)
C8—N1—C7—C6180.00 (18)O2—C12—C13—N2−179.49 (17)
C9—N1—C7—C6−7.3 (3)C11—C12—C13—N2−0.2 (2)
C8—N1—C7—C2−0.17 (19)C13—N2—C14—O3177.45 (17)
C9—N1—C7—C2172.49 (15)C15—N2—C14—O34.0 (3)
C5—C6—C7—N1177.90 (17)C13—N2—C14—C11−1.8 (2)
C5—C6—C7—C2−1.9 (3)C15—N2—C14—C11−175.24 (17)
C3—C2—C7—N1−177.39 (15)C10—C11—C14—O3−3.8 (3)
C1—C2—C7—N10.49 (18)C12—C11—C14—O3−177.61 (17)
C3—C2—C7—C62.5 (3)C10—C11—C14—N2175.43 (15)
C1—C2—C7—C6−179.67 (16)C12—C11—C14—N21.6 (2)
C7—N1—C8—C1−0.24 (19)C14—N2—C15—C17115.6 (2)
C9—N1—C8—C1−172.85 (15)C13—N2—C15—C17−57.0 (3)
C10—C1—C8—N1179.06 (16)C14—N2—C15—C16−118.7 (2)
C2—C1—C8—N10.53 (18)C13—N2—C15—C1668.7 (3)
C8—C1—C10—O1176.19 (15)N2—C15—C16—C18'177.0 (5)
C2—C1—C10—O1−5.5 (2)C17—C15—C16—C18'−58.3 (6)
C8—C1—C10—C11−5.8 (3)N2—C15—C17—C18−57.2 (3)
C2—C1—C10—C11172.44 (16)C16—C15—C17—C18178.9 (2)
O1—C10—C11—C12172.36 (17)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O1—H1···O30.841.722.5003 (19)154
C8—H8···O20.952.122.916 (2)140
C9—H9C···O2i0.982.513.441 (3)159

Symmetry codes: (i) x, −y+3/2, z−1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: CI5139).

References

  • Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.
  • Baan, J. L. van der, Barnick, J. W. F. K. & Bickelhaupt, F. (1978). Tetrahedron, 34, 223–231.
  • Ellis, D. D. & Spek, A. L. (2001). Acta Cryst. C57, 433–434. [PubMed]
  • Holzapfel, C. W., Hutchison, R. D. & Wilkins, D. C. (1970). Tetrahedron, 26, 5239–5246. [PubMed]
  • Mackellar, F. A., Grostic, M. F., Olson, E. C., Wnuk, R. J., Branfman, A. R. & Rinehart, K. L. Jr (1971). J. Am. Chem. Soc.93, 4943–4945. [PubMed]
  • Matsuo, K., Kitaguchi, I., Takata, Y. & Tanaka, K. (1980). Chem. Pharm. Bull.28, 2494–2502. [PubMed]
  • Rigaku (2005). CrystalClear Rigaku Corporation, Tokyo, Japan.
  • Rinehart, K. L., Beck, J. R., Borders, D. B., Kinstle, T. H. & Krauss, D. (1963). J. Am. Chem. Soc.85, 4038–4039.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Sticking, C. E. (1959). Biochem. J.72, 332–334.
  • Wu, C.-S., Huang, J.-L., Sun, Y.-S. & Yang, D.-Y. (2002). J. Med. Chem.45, 2222–2228. [PubMed]

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