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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 67| Part 4| April 2011| Page o936
doi:10.1107/S1600536811009950

(S)-2-Amino-2-(2-chloro­phen­yl)cyclo­hexa­none

Manfred Biermann,a Kenneth I. Hardcastle,b Nikolai V. Moskaleva and Peter A. Crooksc*

aResodyn Corporation, 130 North Main Street, Suite 600, Butte, MT 59701, USA, bDepartment of Chemistry, Emory University, Atlanta, GA 30322, USA, and cDepartment of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536, USA
*Correspondence e-mail: pcrooks@email.uky.edu

(Received 11 January 2011; accepted 16 March 2011; online 19 March 2011)

The crystal structure of the title compound, C12H14ClNO, was determined in order to confirm that the chiral center of the mol­ecule has an S configuration. The cyclo­hexa­none ring adopts a chair conformation. The 2-chloro­phenyl ring is slightly twisted from the axial C—N bond, with a N—C—C—C torsion angle of −5.7 (2)°. In the crystal, an inter­molecular N—H⋯O hydrogen bond links adjacent mol­ecules into an infinite chain, which propagates in the b-axis direction.

Related literature

For background literature on the preparation and use of some anesthetics, see: Holtman et al. (2006[Holtman, J., Johnson, J., Crooks, P. & Wala, E. (2006). J. Pain, 7, S43.]); Heshmati et al. (2003[Heshmati, F., Zeinali, M., Noroozinia, H., Abbacivash, R. & Mahoori, A. (2003). Iran. J. Allergy Asthma Immunol. 2, 175-180.]); Kohrs & Durieux (1998[Kohrs, R. & Durieux, M. E. (1998). Anesth. Analg. 87, 1186-1193.]). For information on the synthetic transformations used, see: Kolb et al. (1994[Kolb, H. C., VanNieuwenhze, M. S. & Sharpless, B. K. (1994). Chem. Rev. 94, 2483-2547.]); Parcell & Sanchez (1981[Parcell, R. F. & Sanchez, P. J. (1981). J. Org. Chem. 46, 5055-5060.]); Senanayake et al. (1996[Senanayake, C. H., Larsen, R. D., DiMichele, L. M., Liu, J., Toma, P. H., Ball, R. G., Verhoeven, T. R. & Reider, P. J. (1996). Tetrahedron Asymmetry, 7, 1501-1506.]); Yang & Davisson (1985[Yang, J. & Davisson, J. N. (1985). J. Med. Chem. 28, 1361-1365.]).

[Scheme 1]

Experimental

Crystal data

  • C12H14ClNO

  • Mr = 223.69

  • Orthorhombic, P 21 21 21

  • a = 7.2437 (5) Å

  • b = 7.4244 (5) Å

  • c = 20.4794 (15) Å

  • V = 1101.38 (13) Å3

  • Z = 4

  • Cu Kα radiation

  • μ = 2.84 mm−1

  • T = 173 K

  • 0.43 × 0.15 × 0.03 mm
Data collection

  • Bruker SMART APEX II diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.375, Tmax = 0.920

  • 3449 measured reflections

  • 1538 independent reflections

  • 1521 reflections with I > 2σ(I)

  • Rint = 0.022
Refinement

  • R[F2 > 2σ(F2)] = 0.023

  • wR(F2) = 0.059

  • S = 1.01

  • 1538 reflections

  • 136 parameters

  • H-atom parameters constrained

  • Δρmax = 0.14 e Å−3

  • Δρmin = −0.15 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 545 Friedel pairs

  • Flack parameter: 0.060 (13)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
N1—H1A⋯O1i 0.91 2.20 3.066 (2) 160
Symmetry code: (i) [-x+1, y-{\script{1\over 2}}, -z+{\script{3\over 2}}].

Data collection: SMART (Bruker, 2007[Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2007[Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811009950/nk2080sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811009950/nk2080Isup2.hkl

checkCIF report


Comment top

KetalarTM, the racemic mixture of R- and S-Ketamines is becoming the sedative and anesthetic of choice for emergency sedation in children and victims with unknown medical history, e.g. from traffic accidents to battlefield conditions, because it causes minimal respiratory depression in comparison to other anesthetics (Heshmati et al., 2003). S-Ketamine was found 3–4 times more potent as an anesthetic than its R-enantiomer, and twice as potent as KetalarTM with fewer side effects such as psychedelic, disorientation and anxiety (Kohrs & Durieux, 1998). S-Norketamine, the major metabolite of S-Ketamine in humans and animals, is emerging as a novel drug for treatment of neuropathic pain and for analgesia (Holtman et al., 2006). To confirm the absolute configuration of (+)-norketamine, herein we report on the X-ray crystallographic characterization of crystalline S-norketamine.

The chirality of the molecule is confirmed (Figure 1). In the structure, the cyclohexanone ring adopts a chair conformation. The 2-chlorophenyl ring is slightly twisted from the axial C—N bond, with a torsion angle of -5.7 (2)°. In the crystal, an N–H···O hydrogen bond links adjacent molecules into an infinite chain which propagates in the b-axis direction (Figure 2).

Related literature top

For background literature on the preparation and use of some anesthetics, see: Holtman et al. (2006; Heshmati et al. (2003); Kohrs & Durieux (1998). For information on the synthetic transformations used, see: Kolb et al. (1994); Parcell & Sanchez (1981); Senanayake et al. (1996); For related literature, see: Yang & Davisson (1985).

Experimental top

With 2-chlorophenyl-1-cyclohexene as pro-chiral starting material, the enantioselective synthesis of S-norketamine was first time accomplished via a 3-step synthesis route. In the first step the chiral quarternary C-1 atom of the ketamine parent structure was generated in utilizing an adapted Sharpless-Asymmetric Dihydroxylation method (Kolb et al., 1994). Asymmetric dihydroxylation was conducted with osmiumtetroxide modified with hydroquinine 1,4-phthalazinediyl diether ((DHQ)2PHAL) as chiral ligand in tert-butanol yielding (-)-(1S, 2S)-1-(2-chlorophenyl)cyclohexane-1,2-diol in 92% yield and with 82–85% ee after crystallization from n-heptane. In the second step (-)-(1S, 2S)-1-(2-chlorophenyl) cyclohexane-1,2-diol was subjected to the condition of the Ritter Reaction (Senanayake et al., 1996) which produced (-)-(1S, 2S)-1-amino-1(2-chlorophenyl) cyclohexane-2-ol, which was obtained with 95% ee after crystallization from n-hexane. In the third step modified Jones Oxidation (Yang et al., 1985) of (-)-(1S, 2S)-1-amino-1(2-chlorophenyl) cyclohexane-2-ol produced (S)-2-amino-2-(2-chlorophenyl)cyclohexanone ((+)-S- norketamine) which was initially obtained as a solid white crystalline material after crystallization from n-heptane (Mp. 68–69°C) which was previously described as an oil (Parcell & Sanchez, 1981). The chiral purity was ee 99% determined by chiral HPLC (Chiralpak AD—H column). The specific rotation of the free S-norketamine base was established to be [a]D +3.2° (c = 2, EtOH). Intermediates and end product were characterized by infrared, NMR and MS-spectroscopy.

Refinement top

All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were positioned geometrically and refined as riding atoms. The Flack parameter was determined from 545 Friedel pairs (Flack, 1983).

Computing details top

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The asymmetric unit, with displacement ellipsoids drawn at the 30% probability level.
[Figure 2] Fig. 2. N–H···O hydrogen bonding interactions (blue dotted lines) in the crystal packing form an infinite chain.
(S)-2-Amino-2-(2-chlorophenyl)cyclohexanone top
Crystal data top
C12H14ClNOF(000) = 472
Mr = 223.69Dx = 1.349 Mg m−3
Orthorhombic, P212121Cu Kα radiation, λ = 1.54178 Å
Hall symbol: P 2ac 2abCell parameters from 3161 reflections
a = 7.2437 (5) Åθ = 4.3–64.6°
b = 7.4244 (5) ŵ = 2.84 mm−1
c = 20.4794 (15) ÅT = 173 K
V = 1101.38 (13) Å3Block, colourless
Z = 40.43 × 0.15 × 0.03 mm
Data collection top
Bruker SMART APEX II
diffractometer		1538 independent reflections
Radiation source: fine-focus sealed tube1521 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.022
ω scansθmax = 64.7°, θmin = 4.3°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		h = −7→7
Tmin = 0.375, Tmax = 0.920k = −8→8
3449 measured reflectionsl = −24→19
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.023H-atom parameters constrained
wR(F2) = 0.059 w = 1/[σ2(Fo2) + (0.0302P)2 + 0.1P]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
1538 reflectionsΔρmax = 0.14 e Å−3
136 parametersΔρmin = −0.15 e Å−3
0 restraintsAbsolute structure: Flack (1983), 545 Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.060 (13)
Crystal data top
C12H14ClNOV = 1101.38 (13) Å3
Mr = 223.69Z = 4
Orthorhombic, P212121Cu Kα radiation
a = 7.2437 (5) ŵ = 2.84 mm−1
b = 7.4244 (5) ÅT = 173 K
c = 20.4794 (15) Å0.43 × 0.15 × 0.03 mm
Data collection top
Bruker SMART APEX II
diffractometer		1538 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		1521 reflections with I > 2σ(I)
Tmin = 0.375, Tmax = 0.920Rint = 0.022
3449 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.023H-atom parameters constrained
wR(F2) = 0.059Δρmax = 0.14 e Å−3
S = 1.01Δρmin = −0.15 e Å−3
1538 reflectionsAbsolute structure: Flack (1983), 545 Friedel pairs
136 parametersAbsolute structure parameter: 0.060 (13)
0 restraints
Special details top

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.

There were problems during data colleciton that were only realised after refinement of the results. The data were quite weak at high angle and although data were collected out to 0.85 Angstrons, the processed data were only 89% complete; however the overall statistics and quality of the results appeared quite good.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.2928 (2)0.4934 (2)0.84577 (8)0.0241 (3)
C20.4469 (2)0.3899 (2)0.88115 (7)0.0248 (4)
C30.5543 (3)0.4618 (2)0.93085 (7)0.0288 (4)
C40.6938 (3)0.3647 (2)0.96124 (9)0.0389 (4)
H40.76370.41780.99540.047*
C50.7303 (3)0.1905 (3)0.94148 (10)0.0463 (5)
H50.82640.12360.96170.056*
C60.6268 (3)0.1144 (2)0.89243 (10)0.0434 (5)
H60.6508−0.00550.87870.052*
C70.4874 (3)0.2131 (2)0.86316 (8)0.0336 (4)
H70.41660.15830.82950.040*
C80.1313 (2)0.5361 (2)0.89240 (8)0.0301 (4)
H8A0.06530.42280.90260.036*
H8B0.18220.58380.93380.036*
C9−0.0066 (2)0.6718 (2)0.86506 (9)0.0379 (4)
H9A−0.07120.61840.82710.045*
H9B−0.10010.70030.89880.045*
C100.0903 (3)0.8435 (2)0.84417 (9)0.0380 (4)
H10A0.15240.89860.88230.046*
H10B−0.00180.93060.82740.046*
C110.2330 (3)0.8039 (2)0.79098 (8)0.0340 (4)
H11A0.16910.75980.75140.041*
H11B0.29860.91650.77950.041*
C120.3715 (2)0.6647 (2)0.81317 (7)0.0258 (4)
Cl10.52113 (6)0.68279 (5)0.958904 (19)0.03641 (13)
N10.2147 (2)0.39391 (19)0.79034 (7)0.0358 (3)
H1A0.30790.35500.76410.054*
H1B0.15020.29740.80550.054*
O10.53524 (16)0.67977 (16)0.80222 (6)0.0351 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0209 (9)0.0303 (7)0.0211 (8)−0.0004 (7)−0.0008 (7)−0.0029 (6)
C20.0218 (9)0.0330 (8)0.0197 (8)−0.0022 (6)0.0041 (7)0.0037 (6)
C30.0267 (10)0.0373 (8)0.0223 (8)−0.0045 (7)0.0038 (7)0.0031 (6)
C40.0300 (10)0.0599 (11)0.0267 (9)−0.0057 (8)−0.0052 (8)0.0135 (8)
C50.0389 (11)0.0555 (11)0.0444 (11)0.0114 (10)0.0014 (9)0.0248 (9)
C60.0478 (13)0.0346 (9)0.0477 (12)0.0070 (8)0.0074 (10)0.0117 (8)
C70.0382 (11)0.0326 (7)0.0300 (9)−0.0014 (8)0.0040 (8)0.0029 (6)
C80.0232 (9)0.0409 (9)0.0262 (9)−0.0019 (7)0.0036 (7)−0.0012 (7)
C90.0234 (9)0.0546 (10)0.0357 (9)0.0059 (10)0.0011 (7)−0.0063 (7)
C100.0345 (10)0.0427 (9)0.0367 (10)0.0112 (8)−0.0040 (8)−0.0027 (8)
C110.0351 (10)0.0375 (8)0.0293 (8)0.0039 (8)−0.0035 (8)0.0031 (7)
C120.0279 (10)0.0344 (8)0.0150 (7)0.0001 (7)−0.0020 (6)−0.0016 (6)
Cl10.0387 (2)0.0428 (2)0.0278 (2)−0.00777 (19)−0.00231 (17)−0.00948 (14)
N10.0314 (9)0.0453 (7)0.0307 (8)−0.0022 (7)−0.0032 (7)−0.0123 (6)
O10.0266 (7)0.0477 (6)0.0310 (6)−0.0013 (6)0.0023 (5)0.0107 (5)
Geometric parameters (Å, º) top
C1—N11.468 (2)C8—C91.525 (2)
C1—C21.537 (2)C8—H8A0.9900
C1—C81.543 (2)C8—H8B0.9900
C1—C121.545 (2)C9—C101.517 (3)
C2—C31.388 (2)C9—H9A0.9900
C2—C71.394 (2)C9—H9B0.9900
C3—C41.389 (3)C10—C111.530 (3)
C3—Cl11.7548 (16)C10—H10A0.9900
C4—C51.380 (3)C10—H10B0.9900
C4—H40.9500C11—C121.511 (2)
C5—C61.375 (3)C11—H11A0.9900
C5—H50.9500C11—H11B0.9900
C6—C71.384 (3)C12—O11.212 (2)
C6—H60.9500N1—H1A0.9100
C7—H70.9500N1—H1B0.9100
N1—C1—C2113.13 (13)C9—C8—H8B108.8
N1—C1—C8106.87 (14)C1—C8—H8B108.8
C2—C1—C8111.20 (13)H8A—C8—H8B107.7
N1—C1—C12102.84 (13)C10—C9—C8110.82 (15)
C2—C1—C12110.31 (13)C10—C9—H9A109.5
C8—C1—C12112.21 (13)C8—C9—H9A109.5
C3—C2—C7115.98 (16)C10—C9—H9B109.5
C3—C2—C1124.08 (15)C8—C9—H9B109.5
C7—C2—C1119.93 (15)H9A—C9—H9B108.1
C2—C3—C4122.46 (16)C9—C10—C11110.58 (15)
C2—C3—Cl1121.54 (13)C9—C10—H10A109.5
C4—C3—Cl1116.01 (14)C11—C10—H10A109.5
C5—C4—C3119.62 (18)C9—C10—H10B109.5
C5—C4—H4120.2C11—C10—H10B109.5
C3—C4—H4120.2H10A—C10—H10B108.1
C6—C5—C4119.67 (18)C12—C11—C10111.48 (14)
C6—C5—H5120.2C12—C11—H11A109.3
C4—C5—H5120.2C10—C11—H11A109.3
C5—C6—C7119.77 (18)C12—C11—H11B109.3
C5—C6—H6120.1C10—C11—H11B109.3
C7—C6—H6120.1H11A—C11—H11B108.0
C6—C7—C2122.49 (18)O1—C12—C11122.06 (16)
C6—C7—H7118.8O1—C12—C1121.14 (16)
C2—C7—H7118.8C11—C12—C1116.62 (15)
C9—C8—C1113.91 (15)C1—N1—H1A109.3
C9—C8—H8A108.8C1—N1—H1B109.2
C1—C8—H8A108.8H1A—N1—H1B109.5
N1—C1—C2—C3173.46 (15)C1—C2—C7—C6178.79 (17)
C8—C1—C2—C3−66.3 (2)N1—C1—C8—C9−68.43 (18)
C12—C1—C2—C358.89 (19)C2—C1—C8—C9167.66 (14)
N1—C1—C2—C7−5.7 (2)C12—C1—C8—C943.57 (19)
C8—C1—C2—C7114.58 (16)C1—C8—C9—C10−54.5 (2)
C12—C1—C2—C7−120.26 (15)C8—C9—C10—C1160.3 (2)
C7—C2—C3—C4−0.1 (2)C9—C10—C11—C12−56.4 (2)
C1—C2—C3—C4−179.30 (15)C10—C11—C12—O1−137.39 (18)
C7—C2—C3—Cl1179.79 (12)C10—C11—C12—C147.45 (19)
C1—C2—C3—Cl10.6 (2)N1—C1—C12—O1−101.44 (18)
C2—C3—C4—C50.7 (3)C2—C1—C12—O119.5 (2)
Cl1—C3—C4—C5−179.21 (14)C8—C1—C12—O1144.07 (16)
C3—C4—C5—C6−0.7 (3)N1—C1—C12—C1173.77 (17)
C4—C5—C6—C70.2 (3)C2—C1—C12—C11−165.31 (14)
C5—C6—C7—C20.4 (3)C8—C1—C12—C11−40.72 (19)
C3—C2—C7—C6−0.4 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O1i0.912.203.066 (2)160
Symmetry code: (i) −x+1, y−1/2, −z+3/2.

Experimental details

Crystal data
Chemical formulaC12H14ClNO
Mr223.69
Crystal system, space groupOrthorhombic, P212121
Temperature (K)173
a, b, c (Å)7.2437 (5), 7.4244 (5), 20.4794 (15)
V (Å3)1101.38 (13)
Z4
Radiation typeCu Kα
µ (mm−1)2.84
Crystal size (mm)0.43 × 0.15 × 0.03
Data collection
DiffractometerBruker SMART APEX II
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.375, 0.920
No. of measured, independent and
observed [I > 2σ(I)] reflections		3449, 1538, 1521
Rint0.022
(sin θ/λ)max (Å−1)0.586
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.023, 0.059, 1.01
No. of reflections1538
No. of parameters136
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.14, −0.15
Absolute structureFlack (1983), 545 Friedel pairs
Absolute structure parameter0.060 (13)

Computer programs: SMART (Bruker, 2007), SAINT (Bruker, 2007), SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

Selected bond and torsion angles (º) top
C3—C2—C1124.08 (15)C2—C3—Cl1121.54 (13)
C7—C2—C1119.93 (15)C4—C3—Cl1116.01 (14)
N1—C1—C2—C3173.46 (15)N1—C1—C2—C7−5.7 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O1i0.912.203.066 (2)160
Symmetry code: (i) −x+1, y−1/2, −z+3/2.
 

Acknowledgements

The research was funded by the US Army Medical Research Material Command, Combat Casualty Care Research, Fort Detrick, MD contract W81XWH-06–1–0275 (NVM, MB, and KIH), and by Yaupon Therapeutics, Inc. (PAC).

References

First citationBruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
 First citationFlack, H. D. (1983). Acta Cryst. A39, 876–881.  CrossRef CAS Web of Science IUCr Journals Google Scholar
 First citationHeshmati, F., Zeinali, M., Noroozinia, H., Abbacivash, R. & Mahoori, A. (2003). Iran. J. Allergy Asthma Immunol. 2, 175–180.  PubMed CAS Google Scholar
 First citationHoltman, J., Johnson, J., Crooks, P. & Wala, E. (2006). J. Pain, 7, S43.  CrossRef Google Scholar
 First citationKohrs, R. & Durieux, M. E. (1998). Anesth. Analg. 87, 1186–1193.  Web of Science CAS PubMed Google Scholar
 First citationKolb, H. C., VanNieuwenhze, M. S. & Sharpless, B. K. (1994). Chem. Rev. 94, 2483–2547.  CrossRef CAS Google Scholar
 First citationParcell, R. F. & Sanchez, P. J. (1981). J. Org. Chem. 46, 5055–5060.  CrossRef CAS Web of Science Google Scholar
 First citationSenanayake, C. H., Larsen, R. D., DiMichele, L. M., Liu, J., Toma, P. H., Ball, R. G., Verhoeven, T. R. & Reider, P. J. (1996). Tetrahedron Asymmetry, 7, 1501–1506.  CrossRef CAS Google Scholar
 First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
 First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationYang, J. & Davisson, J. N. (1985). J. Med. Chem. 28, 1361–1365.  CrossRef CAS PubMed Web of Science Google Scholar

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ISSN: 2056-9890
Volume 67| Part 4| April 2011| Page o936
doi:10.1107/S1600536811009950
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