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ISSN: 2056-9890

(2S)-Ethyl 2-[(Ss)-benzyl­sulfinyl­amino]-3,3-di­methylbutanoate

aDepartment of Chemistry of Natural Drugs, School of Pharmacy, Fudan University, Shanghai 200032, People's Republic of China, bShanghai Institute of Organic Chemistry, Shanghai 200032, People's Republic of China, and cDepartment of Chemistry, Fudan University, Shanghai 200032, People's Republic of China
*Correspondence e-mail: sunxunf@shmu.edu.cn

(Received 30 July 2008; accepted 8 September 2008; online 13 September 2008)

The title compound, C15H23NO3S, is an unexpected 1,3-migration product in the addition of benzyl­zinc bromide to N-tert-butane­sulfinyl imino­acetate. In the crystal structure, mol­ecules are linked by N—H⋯O hydrogen bonds and weak C—H⋯O hydrogen bonds.

Related literature

For general background, see: Ellman et al. (2002[Ellman, J. A., Owens, T. D. & Tang, T. P. (2002). Acc. Chem. Res. 35, 984-995.]); Lin et al. (2008[Lin, G.-Q., Xu, M.-H., Zhong, Y.-W. & Sun, X.-W. (2008). Acc. Chem. Res. 41, 831-840.]); Daniel & Stockman (2006[Daniel, M. & Stockman, R. A. (2006). Tetrahedron, 62, 8869-89085.]). For the synthesis of the titled compound, see: Sun et al. (2008[Sun, X., Zheng, W. & Wei, B.-G. (2008). Tetrahedron Lett. 49, 6195-6197.]).

[Scheme 1]

Experimental

Crystal data
  • C15H23NO3S

  • Mr = 297.40

  • Monoclinic, P 21

  • a = 11.166 (2) Å

  • b = 7.1917 (14) Å

  • c = 11.460 (2) Å

  • β = 115.473 (3)°

  • V = 830.8 (3) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.20 mm−1

  • T = 293 (2) K

  • 0.49 × 0.41 × 0.17 mm

Data collection
  • Bruker SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2001[Bruker (2001). SAINT, SMART and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.908, Tmax = 0.967

  • 4782 measured reflections

  • 3221 independent reflections

  • 2661 reflections with I > 2σ(I)

  • Rint = 0.120

Refinement
  • R[F2 > 2σ(F2)] = 0.054

  • wR(F2) = 0.134

  • S = 0.97

  • 3221 reflections

  • 189 parameters

  • 2 restraints

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.43 e Å−3

  • Δρmin = −0.23 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 1295 Friedel pairs

  • Flack parameter: −0.09 (11)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C7—H7B⋯O1 0.96 2.61 3.234 (5) 123
C9—H9B⋯O3i 0.97 2.48 3.296 (5) 142
N1—H1A⋯O3i 0.859 (17) 2.13 (2) 2.932 (3) 156 (3)
Symmetry code: (i) [-x, y-{\script{1\over 2}}, -z+1].

Data collection: SMART (Bruker, 2001[Bruker (2001). SAINT, SMART and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2001[Bruker (2001). SAINT, SMART and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

N-tert-Butanesulfinylamide has received considerable attention in the auxiliary-aided asymmetric synthesis of a broad range of chiral amines (Ellman et al., 2002; Stockman et al., 2006; Lin et al., 2008). In our research on the asymmetric addition of organozinc reagents to chiral N-tert-butanesulfinyl iminoacetates, an unexpected rearrangement product was obtained instead of the desired nucleophilic addition product. The structure of the compound obtained by 1,3-migration of the tert-butyl group was determined to be (2S)-ethyl 3,3-dimethyl-2-((Ss)-benzylsulfinylamino)butanoate. The reaction sequence (Sun et al., 2008) is briefly shown in Fig. 4. The absolute configuration at the sulfur atom (as determined by the Flack parameter) is S as in the starting material. The new chiral center at C1 also exhibits an S-configuration. We believe this unusual rearrangement reaction could be developed to be a novel and convenient approach to prepare tert-leucine.

The crystal packing in the title compound is stabilized by an intramolecular hydrogen interaction (C7—H7B···O1) and by two intermolecular hydrogen bonds (N1—H1A···O3i and C9—H9B···O3i, symmetry operator: (i) -x, y-1/2, -z+1) which lead to the formation of an one-dimensional hydrogen bonded chain along the b axis as shown in Fig. 3.

Related literature top

For related literature, see: Ellman et al. (2002); Lin et al. (2008); Sun et al. (2008); Daniel & Stockman (2006).

Experimental top

To a solution of ethyl N-(tert-butanesulfinyl)iminoacetate (1 mmol) and Ni(acac)2 (10 mol%) in anhydrous THF (10 ml) was added freshly prepared benzylzinc bromide (2.5 ml, 1 M in THF) at 195 K under an argon atmosphere. Then the mixture was allowed to warm to room temperature. After stirring for another 6 h, the reaction was quenched with saturated aqueous NH4Cl (4 ml). The mixture was extracted with EtOAc (10 ml) twice. The combined organic phases were washed with brine and dried with anhydrous Na2SO4. After concentrating under reduced pressure, the residue was purified by silica gel chromatography to give the title compound (yield: 47%). Suitable crystals were obtained by recrystallization from acetone (m.p. 421–423 K). [α]D25 132.2 (c = 0.60, CHCl3). 1H NMR (δ, CDCl3) 7.31-7.42 (m, 5H), 4.33 (d, J = 9.0, 1H), 4.12-4.20 (m, 2H), 4.03 (s, 2H), 3.48 (d, J = 9.0, 1H), 1.24 (t, J = 7.0, 3H), 0.83 (s, 9H). HRMS for (C15H23NO3S) found 289.1469, Calcd 289.1477.

Refinement top

Hydrogen atoms bonded to carbon were generated geometrically (C—H = 0.93, 0.98, 0.97 or 0.96 Å for phenyl, tertiary, methylene or methyl H atoms respectively) and refined in the riding model approximation. The hydrogen atom bound to the N atom was located from a difference density Fourier map, was refined isotropically and the N—H distance was restrained to 0.86 (2) Å. The displacement parameters of methyl H atoms were set to 1.5 times Ueq of the equivalent isotropic displacement parameters of their parent atoms, while those of other H atoms bound to C were set to 1.2 times Ueq.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SMART (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Plot of C15H23NO3S with 50% probability levels. H atoms are drawn as spheres of arbitrary radius.
[Figure 2] Fig. 2. Hydrogen bonding in the title compound. Symmetry code: (i) -x, y-1/2, -z+1.
[Figure 3] Fig. 3. Molecular packing plot showing the one-dimensional polymeric chains of the title compound. Hydrogen bond interactions are shown as dashed lines.
[Figure 4] Fig. 4. Reaction sequence.
(2S)-Ethyl 2-[(Ss)-benzylsulfinylamino]-3,3-dimethylbutanoate top
Crystal data top
C15H23NO3SF(000) = 320
Mr = 297.40Dx = 1.189 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ybCell parameters from 1845 reflections
a = 11.166 (2) Åθ = 3.4–23.9°
b = 7.1917 (14) ŵ = 0.20 mm1
c = 11.460 (2) ÅT = 293 K
β = 115.473 (3)°Prismatic, colorless
V = 830.8 (3) Å30.49 × 0.41 × 0.17 mm
Z = 2
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
3221 independent reflections
Radiation source: fine-focus sealed tube2661 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.120
ϕ and ω scansθmax = 27.0°, θmin = 2.0°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
h = 1114
Tmin = 0.908, Tmax = 0.967k = 89
4782 measured reflectionsl = 1413
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)] = 0.055H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.134 w = 1/[σ2(Fo2) + (0.0662P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.97(Δ/σ)max = 0.001
3221 reflectionsΔρmax = 0.43 e Å3
189 parametersΔρmin = 0.23 e Å3
2 restraintsAbsolute structure: Flack (1983), 1295 Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.09 (11)
Crystal data top
C15H23NO3SV = 830.8 (3) Å3
Mr = 297.40Z = 2
Monoclinic, P21Mo Kα radiation
a = 11.166 (2) ŵ = 0.20 mm1
b = 7.1917 (14) ÅT = 293 K
c = 11.460 (2) Å0.49 × 0.41 × 0.17 mm
β = 115.473 (3)°
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
3221 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
2661 reflections with I > 2σ(I)
Tmin = 0.908, Tmax = 0.967Rint = 0.120
4782 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.055H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.134Δρmax = 0.43 e Å3
S = 0.97Δρmin = 0.23 e Å3
3221 reflectionsAbsolute structure: Flack (1983), 1295 Friedel pairs
189 parametersAbsolute structure parameter: 0.09 (11)
2 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
S10.04167 (7)0.26178 (12)0.67424 (6)0.0442 (2)
O10.3061 (3)0.0339 (4)0.5596 (3)0.0741 (8)
O20.4124 (3)0.2630 (5)0.6946 (2)0.0696 (7)
O30.0313 (3)0.3869 (4)0.5670 (2)0.0665 (7)
N10.1252 (2)0.0717 (4)0.6804 (2)0.0420 (6)
C10.2690 (3)0.0814 (4)0.7500 (3)0.0397 (6)
H10.29010.18730.80940.048*
C20.3305 (3)0.1206 (5)0.6568 (3)0.0501 (8)
C30.4801 (5)0.3093 (8)0.6131 (5)0.0923 (17)
H3A0.53480.20580.61080.111*
H3B0.41550.33530.52550.111*
C40.5613 (6)0.4705 (9)0.6677 (5)0.108 (2)
H4A0.50560.57750.65470.162*
H4B0.61890.49000.62630.162*
H4C0.61360.45160.75860.162*
C50.3281 (3)0.0954 (5)0.8332 (3)0.0478 (7)
C60.4791 (4)0.0865 (6)0.8887 (4)0.0681 (10)
H6A0.51670.19120.94450.102*
H6B0.50990.02640.93710.102*
H6C0.50570.08920.81940.102*
C70.2792 (4)0.2720 (5)0.7539 (4)0.0649 (10)
H7A0.31850.37810.80760.097*
H7B0.30390.27020.68330.097*
H7C0.18440.27910.72060.097*
C80.2833 (4)0.0948 (6)0.9414 (3)0.0653 (10)
H8A0.18820.09090.90480.098*
H8B0.31910.01240.99520.098*
H8C0.31450.20550.99240.098*
C90.1205 (3)0.1504 (5)0.6172 (3)0.0513 (8)
H9A0.18800.24550.59750.062*
H9B0.13840.08340.53800.062*
C100.1293 (3)0.0198 (5)0.7130 (3)0.0494 (8)
C110.1140 (4)0.1679 (6)0.7036 (4)0.0664 (10)
H110.10140.21450.63400.080*
C120.1169 (5)0.2890 (6)0.7960 (5)0.0895 (15)
H120.10620.41610.78850.107*
C130.1357 (5)0.2210 (10)0.8991 (5)0.0940 (15)
H130.13740.30230.96150.113*
C140.1515 (5)0.0390 (8)0.9098 (5)0.0903 (16)
H140.16510.00560.97940.108*
C150.1479 (4)0.0835 (6)0.8193 (4)0.0702 (11)
H150.15790.21010.82890.084*
H1A0.102 (3)0.001 (3)0.614 (2)0.049 (7)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0470 (4)0.0432 (4)0.0420 (3)0.0052 (4)0.0189 (3)0.0057 (4)
O10.0850 (19)0.095 (2)0.0564 (14)0.0256 (17)0.0441 (13)0.0240 (15)
O20.0750 (16)0.0817 (16)0.0677 (13)0.0294 (18)0.0455 (12)0.0137 (18)
O30.0640 (16)0.0639 (16)0.0641 (15)0.0019 (13)0.0206 (12)0.0255 (13)
N10.0404 (14)0.0454 (15)0.0379 (12)0.0008 (11)0.0146 (11)0.0041 (11)
C10.0383 (15)0.0425 (17)0.0387 (14)0.0046 (13)0.0168 (12)0.0055 (13)
C20.0424 (17)0.060 (2)0.0489 (18)0.0037 (16)0.0205 (14)0.0013 (16)
C30.098 (4)0.119 (5)0.086 (3)0.040 (3)0.065 (3)0.019 (3)
C40.105 (4)0.132 (5)0.112 (4)0.035 (4)0.070 (3)0.001 (3)
C50.0499 (18)0.0452 (17)0.0415 (16)0.0018 (15)0.0132 (13)0.0001 (14)
C60.048 (2)0.073 (2)0.064 (2)0.0088 (19)0.0065 (17)0.002 (2)
C70.067 (2)0.048 (3)0.067 (2)0.0015 (18)0.0159 (17)0.0079 (17)
C80.080 (3)0.067 (2)0.0490 (19)0.004 (2)0.0276 (18)0.0121 (18)
C90.0421 (17)0.065 (2)0.0451 (16)0.0087 (16)0.0174 (14)0.0066 (15)
C100.0369 (17)0.059 (2)0.0522 (18)0.0030 (14)0.0190 (14)0.0005 (15)
C110.062 (2)0.070 (3)0.064 (2)0.0145 (19)0.0243 (18)0.0035 (18)
C120.092 (4)0.058 (3)0.113 (4)0.018 (2)0.038 (3)0.011 (2)
C130.086 (3)0.108 (4)0.094 (3)0.021 (4)0.044 (2)0.033 (4)
C140.095 (4)0.121 (5)0.077 (3)0.006 (3)0.057 (3)0.012 (3)
C150.074 (3)0.075 (3)0.074 (2)0.001 (2)0.043 (2)0.002 (2)
Geometric parameters (Å, º) top
S1—O31.487 (2)C6—H6C0.9600
S1—N11.639 (3)C7—H7A0.9600
S1—C91.824 (4)C7—H7B0.9600
O1—C21.201 (4)C7—H7C0.9600
O2—C21.316 (4)C8—H8A0.9600
O2—C31.471 (4)C8—H8B0.9600
N1—C11.455 (4)C8—H8C0.9600
N1—H1A0.859 (17)C9—C101.480 (5)
C1—C21.523 (4)C9—H9A0.9700
C1—C51.555 (4)C9—H9B0.9700
C1—H10.9800C10—C111.371 (5)
C3—C41.439 (7)C10—C151.398 (5)
C3—H3A0.9700C11—C121.382 (6)
C3—H3B0.9700C11—H110.9300
C4—H4A0.9600C12—C131.375 (7)
C4—H4B0.9600C12—H120.9300
C4—H4C0.9600C13—C141.334 (8)
C5—C71.520 (5)C13—H130.9300
C5—C81.524 (5)C14—C151.374 (6)
C5—C61.526 (5)C14—H140.9300
C6—H6A0.9600C15—H150.9300
C6—H6B0.9600
O3—S1—N1112.37 (15)H6A—C6—H6C109.5
O3—S1—C9104.90 (15)H6B—C6—H6C109.5
N1—S1—C996.19 (15)C5—C7—H7A109.5
C2—O2—C3116.2 (3)C5—C7—H7B109.5
C1—N1—S1117.2 (2)H7A—C7—H7B109.5
C1—N1—H1A111.1 (19)C5—C7—H7C109.5
S1—N1—H1A120.2 (19)H7A—C7—H7C109.5
N1—C1—C2110.4 (2)H7B—C7—H7C109.5
N1—C1—C5111.9 (2)C5—C8—H8A109.5
C2—C1—C5112.4 (3)C5—C8—H8B109.5
N1—C1—H1107.3H8A—C8—H8B109.5
C2—C1—H1107.3C5—C8—H8C109.5
C5—C1—H1107.3H8A—C8—H8C109.5
O1—C2—O2123.9 (3)H8B—C8—H8C109.5
O1—C2—C1124.3 (3)C10—C9—S1112.7 (2)
O2—C2—C1111.8 (3)C10—C9—H9A109.1
C4—C3—O2107.8 (4)S1—C9—H9A109.1
C4—C3—H3A110.1C10—C9—H9B109.1
O2—C3—H3A110.1S1—C9—H9B109.1
C4—C3—H3B110.1H9A—C9—H9B107.8
O2—C3—H3B110.1C11—C10—C15117.5 (4)
H3A—C3—H3B108.5C11—C10—C9121.1 (3)
C3—C4—H4A109.5C15—C10—C9121.4 (3)
C3—C4—H4B109.5C10—C11—C12121.0 (4)
H4A—C4—H4B109.5C10—C11—H11119.5
C3—C4—H4C109.5C12—C11—H11119.5
H4A—C4—H4C109.5C13—C12—C11119.8 (4)
H4B—C4—H4C109.5C13—C12—H12120.1
C7—C5—C8109.2 (3)C11—C12—H12120.1
C7—C5—C6109.4 (3)C14—C13—C12120.2 (4)
C8—C5—C6110.6 (3)C14—C13—H13119.9
C7—C5—C1111.6 (2)C12—C13—H13119.9
C8—C5—C1107.2 (3)C13—C14—C15120.8 (5)
C6—C5—C1108.8 (3)C13—C14—H14119.6
C5—C6—H6A109.5C15—C14—H14119.6
C5—C6—H6B109.5C14—C15—C10120.8 (4)
H6A—C6—H6B109.5C14—C15—H15119.6
C5—C6—H6C109.5C10—C15—H15119.6
O3—S1—N1—C184.8 (2)N1—C1—C5—C6172.6 (3)
C9—S1—N1—C1166.3 (2)C2—C1—C5—C647.8 (3)
S1—N1—C1—C295.2 (3)O3—S1—C9—C10179.6 (3)
S1—N1—C1—C5138.8 (2)N1—S1—C9—C1065.2 (3)
C3—O2—C2—O12.6 (6)S1—C9—C10—C1199.0 (4)
C3—O2—C2—C1178.3 (4)S1—C9—C10—C1578.2 (4)
N1—C1—C2—O151.2 (4)C15—C10—C11—C120.1 (6)
C5—C1—C2—O174.6 (4)C9—C10—C11—C12177.4 (4)
N1—C1—C2—O2128.0 (3)C10—C11—C12—C130.1 (7)
C5—C1—C2—O2106.3 (3)C11—C12—C13—C140.2 (8)
C2—O2—C3—C4178.3 (4)C12—C13—C14—C150.7 (9)
N1—C1—C5—C751.8 (3)C13—C14—C15—C100.9 (7)
C2—C1—C5—C773.1 (4)C11—C10—C15—C140.5 (6)
N1—C1—C5—C867.8 (3)C9—C10—C15—C14177.8 (4)
C2—C1—C5—C8167.4 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C7—H7B···O10.962.613.234 (5)123
C9—H9B···O3i0.972.483.296 (5)142
N1—H1A···O3i0.86 (2)2.13 (2)2.932 (3)156 (3)
Symmetry code: (i) x, y1/2, z+1.

Experimental details

Crystal data
Chemical formulaC15H23NO3S
Mr297.40
Crystal system, space groupMonoclinic, P21
Temperature (K)293
a, b, c (Å)11.166 (2), 7.1917 (14), 11.460 (2)
β (°) 115.473 (3)
V3)830.8 (3)
Z2
Radiation typeMo Kα
µ (mm1)0.20
Crystal size (mm)0.49 × 0.41 × 0.17
Data collection
DiffractometerBruker SMART APEX CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2001)
Tmin, Tmax0.908, 0.967
No. of measured, independent and
observed [I > 2σ(I)] reflections
4782, 3221, 2661
Rint0.120
(sin θ/λ)max1)0.639
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.055, 0.134, 0.97
No. of reflections3221
No. of parameters189
No. of restraints2
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.43, 0.23
Absolute structureFlack (1983), 1295 Friedel pairs
Absolute structure parameter0.09 (11)

Computer programs: SMART (Bruker, 2001), SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C7—H7B···O10.962.613.234 (5)122.8
C9—H9B···O3i0.972.483.296 (5)142.2
N1—H1A···O3i0.859 (17)2.13 (2)2.932 (3)156 (3)
Symmetry code: (i) x, y1/2, z+1.
 

Acknowledgements

The work was financially supported by the National Science Foundation of China (grant No. 20772017) and the Shanghai Municipal Committee of Science and Technology (grant No. 07DZ19713).

References

First citationBruker (2001). SAINT, SMART and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationDaniel, M. & Stockman, R. A. (2006). Tetrahedron, 62, 8869–89085.  Google Scholar
First citationEllman, J. A., Owens, T. D. & Tang, T. P. (2002). Acc. Chem. Res. 35, 984–995.  Web of Science CrossRef PubMed CAS Google Scholar
First citationFlack, H. D. (1983). Acta Cryst. A39, 876–881.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationLin, G.-Q., Xu, M.-H., Zhong, Y.-W. & Sun, X.-W. (2008). Acc. Chem. Res. 41, 831–840.  Web of Science CrossRef PubMed CAS Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSun, X., Zheng, W. & Wei, B.-G. (2008). Tetrahedron Lett. 49, 6195–6197.  Web of Science CrossRef CAS Google Scholar

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