PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of actaeInternational Union of Crystallographysearchopen accessarticle submissionjournal home pagethis article
 
Acta Crystallogr Sect E Struct Rep Online. 2008 February 1; 64(Pt 2): o440.
Published online 2008 January 16. doi:  10.1107/S1600536807067530
PMCID: PMC2960275

Ethyl 3′-cyano-1′-methyl-2-oxo-4′-phenylspiro­[acenaphthene-1,2′-pyrrolidine]-3′-carboxyl­ate

Abstract

In the title compound, C26H22N2O3, the acenaphthen-1-one ring system is nearly planar and the pyrrolidine ring adopts a distorted envelope conformation. An inter­molecular C—H(...)O hydrogen bond stabilizes the crystal structure.

Related literature

For related literature, see: Ma & Hecht (2004 [triangle]); Usui et al. (1998 [triangle]); Raghunathan & Suresh Babu (2004 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-64-0o440-scheme1.jpg

Experimental

Crystal data

  • C26H22N2O3
  • M r = 410.46
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-64-0o440-efi1.jpg
  • a = 7.564 (3) Å
  • b = 14.549 (6) Å
  • c = 19.397 (8) Å
  • V = 2134.7 (15) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.08 mm−1
  • T = 294 (2) K
  • 0.22 × 0.18 × 0.14 mm

Data collection

  • Bruker SMART 1000 CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996 [triangle]) T min = 0.982, T max = 0.988
  • 12376 measured reflections
  • 2513 independent reflections
  • 1924 reflections with I > 2σ(I)
  • R int = 0.049

Refinement

  • R[F 2 > 2σ(F 2)] = 0.041
  • wR(F 2) = 0.101
  • S = 1.13
  • 2513 reflections
  • 282 parameters
  • H-atom parameters constrained
  • Δρmax = 0.15 e Å−3
  • Δρmin = −0.16 e Å−3

Data collection: SMART (Bruker, 1998 [triangle]); cell refinement: SAINT (Bruker, 1999 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997 [triangle]); molecular graphics: SHELXTL (Bruker, 1999 [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/S1600536807067530/rz2186sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807067530/rz2186Isup2.hkl

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

Acknowledgments

This project was supported by the National Science Found­ation of China (No. 20572057) and the Natural Science Foundation of Shandong Province (Y2006B11) and the Doctoral Foundation of Qingdao University of Science and Technology.

supplementary crystallographic information

Comment

Spiro compounds represent an important class of naturally occurring substances characterized by highly pronounced biological properties. The spirooxindole system is the core structure of many pharmacological agents and natural alkaloids (Ma & Hecht, 2004). Spirotryprostatin A, a natural alkaloid isolated from the fermentation broth of Aspergillus fumigatus, has been identified as a novel inhibitor of microtubule assembly (Usui et al., 1998). Because of their synthetic and biological potential, considerable interest has been focused on the synthesis of spirooxindole derivatives via 1,3-dipolar cycloaddition reactions (Raghunathan & Suresh Babu, 2006). In order to develop new biological activities, we synthesized the title compound, the structure of which is reported here.

In the molecule of the title compound (Fig. 1) there is one spiro junction at atom C12. The 2H-acenaphthylen-1-one ring system (C1—C12) is nearly planar, with a maximum displacement of 0.081 (3) Å for atom C1. The pyrrolidine ring adopts a distorted envelope conformation, with atom C12 forming the flap of the envelope displaced by 0.288 (2) A%. The mean plane through the pyrrolidine ring is almost perpendicular to the 2H-acenaphthylen-1-one ring (dihedral angle 86.62 (7)°). The crystal structure (Fig. 2) is stabilized by an intermolecular C—H···O hydrogen bond (Table 1).

Experimental

A mixture of acenaphthylene-1,2-dione (1 mmol, 0.182 g), sarcosine (1 mmol, 0.089 g), benzaldehyde (1 mmol, 0.106 g), cyanoacetic acid ethyl ester (1 mmol, 0.113 g), and acetonitrile (15 ml) in a 25 ml flask was stirred for 3 h under reflux and monitored by TLC). After cooling to room temperature, the solid product was filtered off. Single crystals of the title compound were obtained by slow evaporation of an ethanol solution (m.p. 458 K).

Refinement

All H atoms were placed in calculated positions, with C—H = 0.93–0.98 Å, and included in the final cycles of refinement using a riding model, with Uiso(H) = 1.2 Ueq(C) or 1.5 Ueq(C) for methyl H atoms. In the absence of significant anomalous scattering effects, Friedel pairs were merged in the final refinement.

Figures

Fig. 1.
The molecular structure of the title compound with 35% probability ellipsoids.
Fig. 2.
Packing diagram of the title compound viewed along the b axis. Intermolecular H bonds are shown as dashed lines.

Crystal data

C26H22N2O3Dx = 1.277 Mg m3
Mr = 410.46Melting point: 458 K
Orthorhombic, P212121Mo Kα radiation λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 3377 reflections
a = 7.564 (3) Åθ = 2.5–22.3º
b = 14.549 (6) ŵ = 0.08 mm1
c = 19.397 (8) ÅT = 294 (2) K
V = 2134.7 (15) Å3Prism, brown
Z = 40.22 × 0.18 × 0.14 mm
F000 = 864

Data collection

Bruker SMART 100 CCD area-detector diffractometer2513 independent reflections
Radiation source: fine-focus sealed tube1924 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.049
T = 294(2) Kθmax = 26.4º
[var phi] and ω scansθmin = 1.8º
Absorption correction: multi-scan(SADABS; Sheldrick, 1996)h = −9→7
Tmin = 0.982, Tmax = 0.988k = −17→18
12376 measured reflectionsl = −23→24

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.041H-atom parameters constrained
wR(F2) = 0.101  w = 1/[σ2(Fo2) + (0.0449P)2 + 0.2087P] where P = (Fo2 + 2Fc2)/3
S = 1.13(Δ/σ)max < 0.001
2513 reflectionsΔρmax = 0.15 e Å3
282 parametersΔρmin = −0.16 e Å3
Primary atom site location: structure-invariant direct methodsExtinction correction: none

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*/Ueq
O11.0623 (3)0.94458 (13)0.30244 (11)0.0575 (6)
O20.5975 (3)0.73612 (15)0.19934 (13)0.0628 (6)
O30.6641 (2)0.88028 (13)0.22923 (11)0.0481 (5)
N11.1489 (3)0.74780 (15)0.28010 (11)0.0376 (5)
N21.0479 (4)0.90974 (17)0.13933 (13)0.0585 (8)
C10.9708 (4)0.88274 (18)0.32249 (14)0.0374 (6)
C20.8422 (4)0.88321 (19)0.37975 (13)0.0376 (6)
C30.7857 (4)0.9520 (2)0.42294 (16)0.0505 (8)
H30.82821.01170.41830.061*
C40.6623 (5)0.9298 (3)0.47409 (16)0.0612 (9)
H40.62040.97600.50290.073*
C50.6013 (4)0.8416 (3)0.48296 (15)0.0557 (9)
H50.51860.82950.51730.067*
C60.6615 (4)0.7694 (2)0.44122 (14)0.0423 (7)
C70.6195 (4)0.6742 (2)0.44642 (15)0.0524 (8)
H70.54060.65390.47990.063*
C80.6951 (4)0.6131 (2)0.40222 (15)0.0525 (8)
H80.66900.55100.40750.063*
C90.8115 (4)0.63939 (19)0.34877 (14)0.0433 (7)
H90.86000.59550.31950.052*
C100.8515 (3)0.73065 (18)0.34083 (13)0.0341 (6)
C110.7806 (3)0.79340 (18)0.38829 (12)0.0338 (6)
C120.9724 (3)0.78274 (17)0.29125 (12)0.0320 (6)
C131.1399 (4)0.6722 (2)0.23060 (15)0.0463 (7)
H13A1.13950.61360.25430.056*
H13B1.24060.67400.19960.056*
C140.9672 (4)0.68563 (16)0.19040 (13)0.0357 (6)
H140.88300.64070.20880.043*
C150.9028 (3)0.78135 (17)0.21481 (12)0.0314 (6)
C161.2531 (4)0.7268 (3)0.34135 (17)0.0578 (9)
H16A1.25160.77860.37200.087*
H16B1.37270.71360.32810.087*
H16C1.20350.67430.36430.087*
C170.9744 (5)0.67010 (18)0.11349 (14)0.0460 (8)
C181.1162 (6)0.6991 (2)0.07389 (17)0.0716 (12)
H181.20910.73110.09410.086*
C191.1185 (9)0.6799 (3)0.0032 (2)0.1023 (19)
H191.21340.6990−0.02380.123*
C200.9814 (10)0.6332 (3)−0.0262 (2)0.107 (2)
H200.98470.6201−0.07310.128*
C210.8409 (8)0.6057 (3)0.0116 (2)0.0861 (14)
H210.74730.5750−0.00940.103*
C220.8374 (5)0.6235 (2)0.08185 (16)0.0591 (9)
H220.74160.60370.10800.071*
C230.9873 (4)0.85531 (18)0.17424 (14)0.0365 (6)
C240.7021 (4)0.79504 (19)0.21206 (14)0.0370 (6)
C250.4781 (4)0.9068 (2)0.2361 (2)0.0607 (9)
H25A0.42090.90620.19140.073*
H25B0.41680.86390.26600.073*
C260.4721 (5)0.9978 (3)0.2651 (3)0.0941 (14)
H26A0.52260.99690.31050.141*
H26B0.35161.01810.26770.141*
H26C0.53831.03910.23640.141*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0665 (15)0.0462 (12)0.0598 (13)−0.0230 (12)0.0173 (12)−0.0112 (10)
O20.0395 (12)0.0543 (13)0.0945 (18)−0.0096 (11)−0.0045 (12)−0.0145 (13)
O30.0324 (10)0.0414 (11)0.0706 (14)0.0034 (9)0.0027 (10)−0.0039 (10)
N10.0311 (11)0.0483 (13)0.0335 (12)0.0031 (10)−0.0026 (10)−0.0012 (10)
N20.0741 (19)0.0453 (15)0.0561 (16)−0.0064 (14)0.0201 (15)0.0074 (13)
C10.0370 (15)0.0385 (14)0.0365 (14)−0.0067 (13)−0.0005 (12)−0.0024 (12)
C20.0384 (15)0.0433 (15)0.0312 (13)0.0010 (13)0.0001 (12)−0.0016 (12)
C30.0575 (19)0.0464 (17)0.0477 (17)0.0045 (15)0.0032 (16)−0.0073 (14)
C40.065 (2)0.073 (2)0.0458 (18)0.016 (2)0.0149 (17)−0.0116 (17)
C50.0451 (19)0.083 (3)0.0386 (17)0.0052 (17)0.0114 (14)0.0015 (16)
C60.0340 (15)0.0610 (18)0.0320 (14)−0.0032 (15)−0.0006 (13)0.0070 (13)
C70.0482 (19)0.071 (2)0.0380 (17)−0.0146 (16)−0.0013 (14)0.0183 (16)
C80.060 (2)0.0519 (18)0.0456 (17)−0.0141 (17)−0.0057 (16)0.0170 (15)
C90.0525 (18)0.0398 (16)0.0377 (15)−0.0043 (14)−0.0028 (14)0.0046 (12)
C100.0338 (14)0.0377 (14)0.0307 (14)−0.0025 (12)−0.0028 (11)0.0041 (11)
C110.0319 (14)0.0426 (15)0.0269 (13)−0.0009 (12)−0.0054 (11)0.0015 (11)
C120.0301 (13)0.0373 (14)0.0287 (13)−0.0023 (11)0.0002 (11)−0.0005 (10)
C130.0448 (16)0.0455 (16)0.0486 (17)0.0104 (14)0.0008 (14)−0.0063 (14)
C140.0438 (15)0.0297 (13)0.0336 (14)−0.0011 (12)0.0025 (12)−0.0001 (11)
C150.0328 (13)0.0319 (13)0.0293 (13)−0.0014 (11)0.0007 (11)0.0003 (11)
C160.0418 (18)0.081 (2)0.0503 (19)0.0054 (17)−0.0088 (14)0.0014 (17)
C170.074 (2)0.0295 (14)0.0348 (15)0.0050 (15)0.0030 (16)−0.0001 (11)
C180.120 (3)0.0406 (17)0.055 (2)−0.018 (2)0.033 (2)−0.0067 (15)
C190.200 (6)0.048 (2)0.059 (2)−0.013 (3)0.060 (3)0.0018 (19)
C200.228 (7)0.055 (2)0.038 (2)0.008 (4)0.001 (3)−0.0052 (18)
C210.141 (4)0.065 (2)0.052 (2)0.016 (3)−0.029 (3)−0.012 (2)
C220.081 (2)0.0478 (17)0.0484 (18)0.0094 (19)−0.0120 (18)−0.0104 (15)
C230.0376 (16)0.0357 (14)0.0363 (14)0.0031 (12)0.0035 (13)0.0001 (12)
C240.0373 (15)0.0394 (16)0.0343 (14)−0.0020 (13)0.0005 (12)0.0038 (12)
C250.0289 (16)0.065 (2)0.089 (2)0.0090 (15)0.0051 (17)−0.0028 (18)
C260.045 (2)0.068 (2)0.169 (4)0.0164 (19)−0.002 (3)−0.025 (3)

Geometric parameters (Å, °)

O1—C11.200 (3)C13—C141.534 (4)
O2—C241.193 (3)C13—H13A0.9700
O3—C241.316 (3)C13—H13B0.9700
O3—C251.465 (4)C14—C171.510 (4)
N1—C121.445 (3)C14—C151.550 (3)
N1—C161.458 (4)C14—H140.9800
N1—C131.461 (3)C15—C231.479 (4)
N2—C231.138 (3)C15—C241.532 (4)
C1—C21.476 (4)C16—H16A0.9600
C1—C121.576 (4)C16—H16B0.9600
C2—C31.374 (4)C16—H16C0.9600
C2—C111.397 (4)C17—C221.382 (4)
C3—C41.401 (4)C17—C181.385 (5)
C3—H30.9300C18—C191.400 (5)
C4—C51.374 (5)C18—H180.9300
C4—H40.9300C19—C201.365 (8)
C5—C61.401 (4)C19—H190.9300
C5—H50.9300C20—C211.352 (7)
C6—C111.410 (4)C20—H200.9300
C6—C71.425 (4)C21—C221.388 (5)
C7—C81.362 (5)C21—H210.9300
C7—H70.9300C22—H220.9300
C8—C91.413 (4)C25—C261.440 (5)
C8—H80.9300C25—H25A0.9700
C9—C101.371 (4)C25—H25B0.9700
C9—H90.9300C26—H26A0.9600
C10—C111.403 (4)C26—H26B0.9600
C10—C121.528 (3)C26—H26C0.9600
C12—C151.574 (3)
C24—O3—C25118.7 (2)C13—C14—C15103.1 (2)
C12—N1—C16116.8 (2)C17—C14—H14106.5
C12—N1—C13108.7 (2)C13—C14—H14106.5
C16—N1—C13113.8 (2)C15—C14—H14106.5
O1—C1—C2128.3 (2)C23—C15—C24108.4 (2)
O1—C1—C12124.3 (2)C23—C15—C14110.8 (2)
C2—C1—C12107.4 (2)C24—C15—C14114.7 (2)
C3—C2—C11120.4 (3)C23—C15—C12110.3 (2)
C3—C2—C1131.8 (3)C24—C15—C12111.3 (2)
C11—C2—C1107.7 (2)C14—C15—C12101.19 (19)
C2—C3—C4118.1 (3)N1—C16—H16A109.5
C2—C3—H3121.0N1—C16—H16B109.5
C4—C3—H3121.0H16A—C16—H16B109.5
C5—C4—C3121.9 (3)N1—C16—H16C109.5
C5—C4—H4119.0H16A—C16—H16C109.5
C3—C4—H4119.0H16B—C16—H16C109.5
C4—C5—C6121.2 (3)C22—C17—C18118.9 (3)
C4—C5—H5119.4C22—C17—C14119.0 (3)
C6—C5—H5119.4C18—C17—C14122.0 (3)
C5—C6—C11116.3 (3)C17—C18—C19119.5 (4)
C5—C6—C7127.9 (3)C17—C18—H18120.3
C11—C6—C7115.8 (3)C19—C18—H18120.3
C8—C7—C6119.8 (3)C20—C19—C18120.0 (5)
C8—C7—H7120.1C20—C19—H19120.0
C6—C7—H7120.1C18—C19—H19120.0
C7—C8—C9123.2 (3)C21—C20—C19121.2 (4)
C7—C8—H8118.4C21—C20—H20119.4
C9—C8—H8118.4C19—C20—H20119.4
C10—C9—C8118.8 (3)C20—C21—C22119.5 (5)
C10—C9—H9120.6C20—C21—H21120.2
C8—C9—H9120.6C22—C21—H21120.2
C9—C10—C11118.2 (2)C17—C22—C21120.9 (4)
C9—C10—C12133.1 (3)C17—C22—H22119.6
C11—C10—C12108.6 (2)C21—C22—H22119.6
C2—C11—C10113.8 (2)N2—C23—C15175.6 (3)
C2—C11—C6122.1 (3)O2—C24—O3125.8 (3)
C10—C11—C6124.1 (3)O2—C24—C15124.8 (3)
N1—C12—C10118.2 (2)O3—C24—C15109.3 (2)
N1—C12—C1599.43 (19)C26—C25—O3107.9 (3)
C10—C12—C15112.7 (2)C26—C25—H25A110.1
N1—C12—C1112.9 (2)O3—C25—H25A110.1
C10—C12—C1102.2 (2)C26—C25—H25B110.1
C15—C12—C1111.8 (2)O3—C25—H25B110.1
N1—C13—C14106.1 (2)H25A—C25—H25B108.4
N1—C13—H13A110.5C25—C26—H26A109.5
C14—C13—H13A110.5C25—C26—H26B109.5
N1—C13—H13B110.5H26A—C26—H26B109.5
C14—C13—H13B110.5C25—C26—H26C109.5
H13A—C13—H13B108.7H26A—C26—H26C109.5
C17—C14—C13116.9 (3)H26B—C26—H26C109.5
C17—C14—C15116.6 (2)
O1—C1—C2—C33.3 (5)C2—C1—C12—C10−5.6 (3)
C12—C1—C2—C3−178.0 (3)O1—C1—C12—C15−66.0 (3)
O1—C1—C2—C11−174.2 (3)C2—C1—C12—C15115.2 (2)
C12—C1—C2—C114.6 (3)C12—N1—C13—C1421.8 (3)
C11—C2—C3—C4−1.6 (4)C16—N1—C13—C14153.8 (2)
C1—C2—C3—C4−178.8 (3)N1—C13—C14—C17137.8 (2)
C2—C3—C4—C51.7 (5)N1—C13—C14—C158.5 (3)
C3—C4—C5—C60.5 (5)C17—C14—C15—C23−44.9 (3)
C4—C5—C6—C11−2.8 (4)C13—C14—C15—C2384.6 (2)
C4—C5—C6—C7176.0 (3)C17—C14—C15—C2478.2 (3)
C5—C6—C7—C8−178.0 (3)C13—C14—C15—C24−152.3 (2)
C11—C6—C7—C80.8 (4)C17—C14—C15—C12−161.9 (2)
C6—C7—C8—C9−2.1 (5)C13—C14—C15—C12−32.4 (2)
C7—C8—C9—C100.3 (4)N1—C12—C15—C23−72.4 (2)
C8—C9—C10—C112.7 (4)C10—C12—C15—C23161.5 (2)
C8—C9—C10—C12178.2 (3)C1—C12—C15—C2347.1 (3)
C3—C2—C11—C10−179.3 (3)N1—C12—C15—C24167.3 (2)
C1—C2—C11—C10−1.5 (3)C10—C12—C15—C2441.2 (3)
C3—C2—C11—C6−0.8 (4)C1—C12—C15—C24−73.2 (3)
C1—C2—C11—C6177.0 (2)N1—C12—C15—C1445.0 (2)
C9—C10—C11—C2174.3 (3)C10—C12—C15—C14−81.1 (2)
C12—C10—C11—C2−2.3 (3)C1—C12—C15—C14164.5 (2)
C9—C10—C11—C6−4.2 (4)C13—C14—C17—C22138.3 (3)
C12—C10—C11—C6179.2 (2)C15—C14—C17—C22−99.1 (3)
C5—C6—C11—C23.0 (4)C13—C14—C17—C18−40.0 (4)
C7—C6—C11—C2−176.0 (3)C15—C14—C17—C1882.5 (4)
C5—C6—C11—C10−178.7 (3)C22—C17—C18—C19−0.6 (5)
C7—C6—C11—C102.4 (4)C14—C17—C18—C19177.7 (3)
C16—N1—C12—C10−49.9 (3)C17—C18—C19—C200.2 (6)
C13—N1—C12—C1080.4 (3)C18—C19—C20—C210.8 (7)
C16—N1—C12—C15−172.1 (2)C19—C20—C21—C22−1.4 (7)
C13—N1—C12—C15−41.8 (2)C18—C17—C22—C210.0 (5)
C16—N1—C12—C169.2 (3)C14—C17—C22—C21−178.4 (3)
C13—N1—C12—C1−160.4 (2)C20—C21—C22—C171.0 (6)
C9—C10—C12—N1−46.5 (4)C25—O3—C24—O22.2 (5)
C11—C10—C12—N1129.4 (2)C25—O3—C24—C15−174.6 (3)
C9—C10—C12—C1568.7 (4)C23—C15—C24—O2131.9 (3)
C11—C10—C12—C15−115.4 (2)C14—C15—C24—O27.5 (4)
C9—C10—C12—C1−171.1 (3)C12—C15—C24—O2−106.6 (3)
C11—C10—C12—C14.7 (3)C23—C15—C24—O3−51.2 (3)
O1—C1—C12—N145.1 (4)C14—C15—C24—O3−175.7 (2)
C2—C1—C12—N1−133.6 (2)C12—C15—C24—O370.2 (3)
O1—C1—C12—C10173.2 (3)C24—O3—C25—C26171.4 (3)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C26—H26B···O1i0.962.533.276 (5)135

Symmetry codes: (i) x−1, y, z.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RZ2186).

References

  • Bruker (1998). SMART Bruker AXS Inc., Madison, Wisconsin, USA.
  • Bruker (1999). SAINT and SHELXTL Bruker AXS Inc., Madison, Wisconsin, USA.
  • Ma, J. & Hecht, S. M. (2004). Chem. Commun.10, 1190–1191. [PubMed]
  • Raghunathan, R. & Suresh Babu, A. R. (2006). Tetrahedron Lett.47, 9221–9225.
  • Sheldrick, G. M. (1996). SADABS University of Göttingen, Germany.
  • Sheldrick, G. M. (1997). SHELXS97 and SHELXL97 University of Göttingen, Germany.
  • Usui, T., Kondoh, M., Cui, C.-B., Mayumi, T. & Osada, H. (1998). Biochem. J.333, 543–548. [PubMed]

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography