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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 68| Part 12| December 2012| Pages o3260-o3261

(25R)-16β-Acet­­oxy-3β-bromo-23′,26-ep­­oxy-23′,25-di­methyl-5α-cholest-23,23′-en-6-one di­chloro­methane monosolvate

aDivisión de Posgrado, Instituto Tecnológico de Mérida, Avenida Tecnológico, Km 4.5 S/N C.P. 97118, Mérida Yucatán, Mexico, bDepartamento de Química, CINVESTAV–IPN, Apdo. Postal 14-740, 07000 México, D.F., Mexico, cInstituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, C.P. 58000, Mexico, and dFacultad de Química, Departamento de Química Orgánica, Universidad Nacional Autónoma de México, México D.F., 04510, Mexico
*Correspondence e-mail: susana74a@yahoo.com

(Received 14 October 2012; accepted 21 October 2012; online 3 November 2012)

The crystal structure of the title compound, C31H45BrO5·CH2Cl2, prepared in six steps from diosgenin, confirmed that the configurations of the stereogenic centers, positions 20S and 25R, remain unchanged during the reaction. The six-membered A, B and C rings have chair conformations. The five-membered ring D has an envelope conformation (with the methyl-substituted C atom fused to ring C as the flap) and the six-membered dihydro­pyran ring E adopts a twist-boat conformation. In the crystal, mol­ecules are linked via C—H⋯O and C—H⋯Cl hydrogen bonds, the latter involving the dichloro­methane solvent mol­ecule, forming a three-dimensional supra­molecular network.

Related literature

For a review on saponins, see: Hostettmann & Marston (1995[Hostettmann, K. & Marston, A. (1995). Saponins. Cambridge University Presss.]). For the use of spiro­stane sapogenins in the synthesis of biologically active compounds, see: Lee et al. (1976[Lee, E., Liu, Y. T., Solomon, P. H. & Nakanishi, K. (1976). J. Am. Chem. Soc. 98, 1634-1635.], 2009[Lee, S., LaCour, T. G. & Fuchs, P. L. (2009). Chem. Rev. 109, 2275-2314.]); Phillips & Shair (2007[Phillips, S. T. & Shair, M. D. (2007). J. Am. Chem. Soc. 129, 6589-6598.]); Pettit et al. (1988[Pettit, G. R., Inoue, M., Kamano, Y., Herald, D. L., Arm, C., Dufresne, C., Christie, N. D., Schmidt, J. M., Doubek, D. L. & Krupa, T. S. (1988). J. Am. Chem. Soc. 110, 2006-2007.]). For compounds used in the sythesis and for various details of the synthetic procedure, see: Corey & Suggs (1975[Corey, E. J. & Suggs, J. W. (1975). Tetrahedron Lett. 16, 2647-2650.]); Steele & Mosettig (1963[Steele, J. A. & Mosettig, E. (1963). J. Org. Chem. 28, 571-572.]); Iglesias-Arteaga et al. (1998[Iglesias-Arteaga, M. A., Pérez Gil, R., Leliebre Lara, V., Coll Manchado, F. & Pérez Martínez, C. S. (1998). Synth. Commun. 28, 75-81.]); Monroe & Serota (1956[Monroe, E. W. & Serota, S. (1956). J. Am. Chem. Soc. 78, 1747-1750.]); Rincón et al. (2006[Rincón, S., del Río, R. E., Sandoval-Ramírez, J., Meza-Reyes, S., Montiel-Smith, S., Fernández, M. A., Farfán, N. & Santillan, R. (2006). Tetrahedron, 62, 2594-2602.]). For the crystal structure of a related steroidal compound containing bromine in the same position, see: Castro-Méndez et al. (2002[Castro-Méndez, A., Sandoval-Ramírez, J. & Bernès, S. (2002). Acta Cryst. E58, o606-o608.]). For standard bond lengths, see: Allen et al. (1987[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.]). For conformational analysis, see: Cremer & Pople (1975[Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354-1358.]).

[Scheme 1]

Experimental

Crystal data
  • C31H45BrO5·CH2Cl2

  • Mr = 662.51

  • Orthorhombic, P 21 21 21

  • a = 7.4423 (1) Å

  • b = 15.6578 (2) Å

  • c = 26.8496 (3) Å

  • V = 3128.79 (7) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 1.52 mm−1

  • T = 293 K

  • 0.15 × 0.10 × 0.08 mm

Data collection
  • Nonius KappaCCD diffractometer

  • 37310 measured reflections

  • 7934 independent reflections

  • 5668 reflections with I > 2σ(I)

  • Rint = 0.088

Refinement
  • R[F2 > 2σ(F2)] = 0.068

  • wR(F2) = 0.181

  • S = 1.03

  • 7934 reflections

  • 362 parameters

  • H-atom parameters constrained

  • Δρmax = 0.75 e Å−3

  • Δρmin = −0.68 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 3453 Friedel pairs

  • Flack parameter: 0.031 (13)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C5—H5⋯O22i 0.98 2.54 3.491 (6) 165
C18—H18C⋯O30ii 0.96 2.59 3.545 (7) 173
C27—H27B⋯Cl2iii 0.96 2.32 2.957 (18) 124
C32—H32A⋯O6iv 0.97 2.23 3.00 (2) 135
C32—H32B⋯Cl1v 0.97 2.16 2.89 (3) 130
Symmetry codes: (i) [-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (ii) x+1, y, z; (iii) [-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]; (iv) [-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]; (v) [x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z].

Data collection: COLLECT (Nonius, 1999[Nonius (1999). KappaCCD Server Software. Nonius BV, Delft, The Netherlands.]); cell refinement: SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]) and SCALEPACK; 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: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: WinGX (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]).

Supporting information


Comment top

Steroidal saponins are plant metabolites with a broad range of biological activities (Hostettmann & Marston, 1995). They are composed by a glycoside and a triterpene or steroidal fragment. Hydrolysis of saponins provides a glycoside free portion termed sapogenin which can be of the cholestane, furostane or spirostane type. The spirostane sapogenins also display economic importance due to their application in the synthesis of biologically active compounds such as insect hormones (Lee et al., 1976) cephalostatins and ritterazines (Lee et al., 2009, Phillips & Shair, 2007 and Pettit et al., 1988). In previous studies we reported the preparation of epoxycholestane derivatives as useful intermediates in the synthesis of norbrassinosteroid analogues (Rincón et al., 2006), in continuation with our studies we report herein on the synthesis and crystal structure of the title compound, (I), obtained by treatment of the previously reported (25R)-23-acetyl-3β-bromo-16β-acetoxy-22,26-epoxy-5α-cholest-22-en-6-one(Castro-Méndez et al., 2002) with p-toluenesulfonic acid. In turn, the 22,26-epoxy-5α-cholestanic derivative was obtained in five steps using a modified procedure of the reported methodology (Castro-Méndez et al., 2002).

The title compound is interesting because it is a useful intermediate to introduce functionality at the 2 and 3 positions of brassinosteroid analogues. The X-ray crystal structure analysis showed that the configuration at the stereogenic centers C20S and C25R are retained (Fig. 1). The steroid nucleus shows that the A/B, B/C and C/D rings junctions are trans. The presence of the bromine bonded to C3 does not disturb the chair conformation of the A ring [puckering parameters for ring (C1—C5/C10) are Q = 0.576 (5) Å, θ = 2.2 (5)°, ϕ = 323 (20)°; Cremer & Pople, 1975 ]. Ring B assumes an almost perfect chair conformation which contains a carbonyl group at C5 [puckering parameters: Q = 0.565 (5) Å, θ = 14.0 (5)°,ϕ = 278 (2)°, if the calculation starts from C5 to C10 and proceeds in counterclockwise direction]. The same chair conformation was observed for the C ring [puckering parameters (C8/C9/C11—C14) Q = 0.570 (5) Å, θ = 4.8 (5)°, ϕ = 251 (6)°]. The five-membered D ring has an envelope conformation with atom C13 as the flap [puckering parameters (C13/C14/C15/C16/C17) q2 = 0.480 (5) Å and ϕ2 = 188.7 (6)°]. The six-membered dihydropyran E ring adopts a twisted-boat conformation [puckering parameters (O26/C23A/C23—C26) Q = 0.472 (10) Å, θ = 122.8 (10)°, ϕ = 79.5 (11)°].

The bond distances for C6—O6 and C23—C23A are 1.205 (6) Å and 1.344 (9) Å, respectively, confirming the existence of a double bond. The C3—Br1 bond distance is 1.977 (5) Å being slightly longer than the average values reported for Br—C*= 1.966 (29) (Allen et al., 1987) and C3—Br1 = 1.966 (5) Å in a related steroidal compound containing bromine in the same position (Castro-Méndez et al., 2002). The bromine at position three is equatorial and antiperiplanar to the C4—C5 bond with a torsion angle -178.1 (3). The bond distances for C23A—O26 and C26—O26 are 1.365 (8) Å and 1.460 (13) Å, respectively (Table 1); these values are in the range reported for bond distances in a similar compound, that is the cholestane derivative from diosgenin [C22—O26, 1.365 (5) Å and C26—O26 1.441 (5) Å; Castro-Méndez et al., 2002] and are in the average range reported for Csp2—O(2) in enol ethers C C—O—C*= 1.354 (16) Å and Csp3—O(2) in tetrahydropyran 1.441 (15) Å (Allen et al., 1987).

In the crystal, molecules are linked by C—H···O and C—H···Cl hydrogen bonds (Table 1), the latter involve the dichloromethane solvent molecule, forming a three-dimensional supramolecular architecture.

Related literature top

For a review on saponins, see: Hostettmann & Marston (1995). For the use of spirostane sapogenins in the synthesis of biologically active compounds, see: Lee et al. (1976, 2009); Phillips & Shair (2007); Pettit et al. (1988). For compounds used in the sythesis and for various details of the synthetic procedure, see: Corey & Suggs (1975); Steele & Mosettig (1963); Iglesias-Arteaga et al. (1998); Monroe & Serota (1956); Rincón et al. (2006). For the crystal structure of a related steroidal compound containing bromine in the same position, see: Castro-Méndez et al. (2002). For standard bond lengths, see: Allen et al. (1987). For conformational analysis, see: Cremer & Pople (1975).

Experimental top

Tosylation of diosgenin with TsCl in pyridine (Monroe et al., 1956), followed by preparation of the i-steroid derivative using a methodology previously described (Steele et al., 1963), oxidation with PDC (Corey & Suggs, 1975) and subsequent treatment with HBr/AcOEt (Iglesias-Arteaga et al., 1998) gave 25R-3β-bromo-5α-spirostan-6-one which was transformed into (25R)-23-acetyl-3β-bromo-16β-acetoxy-22,26-epoxy-5α-cholest-22-en-6-one using ZnCl2 instead of the previously described methodology (Castro-Méndez et al., 2002). Finally, the title compound was obtained by treatment of (25R)-23-acetyl-3β-bromo-16β-acetoxy-22,26-epoxy-5α-cholest-22-en-6-one (0.260 g, 0.493 mmol) with p-toluenesulfonic acid (0.260 g,1.36 mmol)in 0.7 ml toluene at 393 K for 30 minutes under vigorous stirring in a pressure tube. The solvent was evaporated under vacuum and the organic phase extracted with CH2Cl2-water, neutralized with NaHCO3 and dried over Na2SO4 to give a 0.160 g (61% yield) as white crystals which were purified by chromatography using a mixture of 70:30 hexane:ethyl acetate. (m.p. 468 – 470 K). Analysis calc.: C31H45O5Br: C 64.46, H 7.85, Br 13.85, O 13.85 %. Found: C 64.0, H 8.10 %. Block-like colourless crystals of the title compound, suitable for X-ray analysis, were grown by slow evaporation in a mixture of hexane:ethyl acetate (70:30) and a minimum quantity of CH2Cl2. Spectroscipic data for the title compound are given in the archived CIF.

Refinement top

All H atoms were placed in calculated positions and treated as riding atoms: C-H = 0.98, 0.97 and 0.96 Å for CH, CH2 and CH3 H atoms, respectively, with Uiso(H) = k × Ueq(C), where k = 1.5 for CH3 H atoms and = 1.2 for other H atoms.

Computing details top

Data collection: COLLECT (Nonius, 1999); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 2012).

Figures top
[Figure 1] Fig. 1. A view of the molecular structure of the title compound, with the atom numbering. Displacement ellipsoids are drawn at 30% probability level.
(25R)-16β-Acetoxy-3β-bromo-23',26-epoxy-23',25-dimethyl-5α-cholest-23,23'-en-6-one dichloromethane monosolvate top
Crystal data top
C31H45BrO5·CH2Cl2Dx = 1.406 Mg m3
Mr = 662.51Melting point: 468(2) K
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 600 reflections
a = 7.4423 (1) Åθ = 3.5–28.7°
b = 15.6578 (2) ŵ = 1.52 mm1
c = 26.8496 (3) ÅT = 293 K
V = 3128.79 (7) Å3Block, colourless
Z = 40.15 × 0.10 × 0.08 mm
F(000) = 1392
Data collection top
Nonius KappaCCD
diffractometer
5668 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.088
Graphite monochromatorθmax = 28.7°, θmin = 3.5°
Detector resolution: 9 pixels mm-1h = 99
ϕ and ω scansk = 2021
37310 measured reflectionsl = 3636
7934 independent reflections
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.068 w = 1/[σ2(Fo2) + (0.087P)2 + 3.6522P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.181(Δ/σ)max < 0.001
S = 1.03Δρmax = 0.75 e Å3
7934 reflectionsΔρmin = 0.68 e Å3
362 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0038 (10)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), 3453 Friedel pairs
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.031 (13)
Crystal data top
C31H45BrO5·CH2Cl2V = 3128.79 (7) Å3
Mr = 662.51Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 7.4423 (1) ŵ = 1.52 mm1
b = 15.6578 (2) ÅT = 293 K
c = 26.8496 (3) Å0.15 × 0.10 × 0.08 mm
Data collection top
Nonius KappaCCD
diffractometer
5668 reflections with I > 2σ(I)
37310 measured reflectionsRint = 0.088
7934 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.068H-atom parameters constrained
wR(F2) = 0.181Δρmax = 0.75 e Å3
S = 1.03Δρmin = 0.68 e Å3
7934 reflectionsAbsolute structure: Flack (1983), 3453 Friedel pairs
362 parametersAbsolute structure parameter: 0.031 (13)
0 restraints
Special details top

Experimental. Spectroscopic data for the title compound: UV λmax 269 nm (ε 624); IR νmax cm-1(KBr): 2959 (CH), 1737 (OAc), 1711 (CO), 1665 (CO), 1452 (CH3), 1334 (CH), 1247 (C—O), 988 (C C), 710 (CH2), MS, m/z: (%): 578 ([M+], 1.4), 206 (18), 205 (32), 191 (10), 166 (10), 140 (15), 139 (100), 43 (59); 1H NMR (300 MHz, CDCl3) δ: 5.02 (1H, m, H-16), 4.09 (1H, d, J = 11.0 Hz, H-26), 3.94 (1H, m, H-3), 3.40 (1H, t, J = 10.0 Hz, H-26), 3.20 (1H, dq, J17–20 = 10.6 Hz, J20–21 = 6.94 Hz, H-20), 2.06 (3H, s, 3-OCOCH3), 2.14 (3H, s, 23''-CH3), 1.90 (3H, s, 16-OCOCH3),1.10 (3H, d, J = 6.9 Hz, CH3-27), 1.02 (3H, d, J = 6.1 Hz, CH3-21), 0.88 (3H, s, CH3-19), 0.81 (3H, s, CH3-18). 13C NMR (100 MHz, CDCl3) δ: 203.9 (22-CO), 169.8 (16-OCOCH3), 164.9 (C-23'), 59.1 (C-5), 209.3(C-6), 107.6 (C-23), 75.4 (C-16), 50.6 (C-3), 71.9 (C-26), 56.1 (C-17), 54.2 (C-14), 53.8 (C-9), 42.9 (C-13), 39.2 (C-12), 38.7 (C-20), 31.8 (C-4), 33.5 (C-1), 40.8 (C-10), 34.4 (C-15), 46.4 (C-7), 37.3 (C-8), 30.9 (C-24), 32.5 (C-2), 26.9 (C-25), 21.3 (16-OCOCH3), 21.5 (C-11), 21.0 (C-23''), 19.6 (C-19), 17.3 (C-21), 17.1 (C-27), 13.3 (C-18).

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
Br10.80129 (8)0.99071 (3)0.28226 (2)0.0514 (2)
O60.3019 (5)0.7718 (2)0.35688 (17)0.0616 (13)
O160.3802 (5)0.2944 (2)0.41187 (13)0.0429 (11)
O220.4244 (5)0.1706 (2)0.31163 (14)0.0531 (11)
O260.4238 (10)0.0251 (3)0.4188 (2)0.108 (3)
O300.0825 (6)0.2752 (3)0.41123 (19)0.0793 (18)
C10.8950 (6)0.7228 (3)0.29478 (19)0.0393 (14)
C20.9275 (7)0.8200 (3)0.2955 (2)0.0430 (14)
C30.7592 (6)0.8661 (3)0.27962 (19)0.0411 (13)
C40.5983 (7)0.8440 (3)0.3109 (2)0.0440 (16)
C50.5683 (6)0.7469 (3)0.31053 (17)0.0360 (12)
C60.4036 (7)0.7210 (3)0.3384 (2)0.0433 (14)
C70.3660 (6)0.6261 (3)0.3402 (2)0.0437 (14)
C80.5314 (6)0.5704 (3)0.35181 (18)0.0347 (12)
C90.6928 (6)0.5994 (3)0.31974 (16)0.0337 (11)
C100.7360 (6)0.6949 (3)0.32813 (16)0.0337 (12)
C110.8546 (6)0.5399 (3)0.3259 (2)0.0410 (14)
C120.8068 (7)0.4453 (3)0.31787 (19)0.0400 (14)
C130.6532 (5)0.4169 (3)0.35206 (16)0.0330 (12)
C140.4942 (6)0.4770 (3)0.34192 (18)0.0360 (12)
C150.3379 (6)0.4350 (3)0.3697 (2)0.0420 (14)
C160.3743 (6)0.3378 (3)0.36390 (17)0.0357 (12)
C170.5626 (6)0.3305 (3)0.33936 (17)0.0343 (12)
C180.7143 (7)0.4186 (3)0.40677 (18)0.0427 (14)
C190.7786 (8)0.7143 (3)0.38279 (18)0.0447 (16)
C200.6614 (6)0.2460 (3)0.35157 (18)0.0387 (14)
C210.8164 (7)0.2293 (3)0.3151 (2)0.0477 (16)
C220.5302 (7)0.1703 (3)0.34636 (18)0.0397 (14)
C230.5464 (8)0.1008 (3)0.3826 (2)0.0500 (18)
C23A0.4238 (10)0.0378 (4)0.3836 (2)0.065 (2)
C23B0.2656 (11)0.0256 (5)0.3511 (3)0.086 (3)
C240.7091 (12)0.0994 (3)0.4160 (2)0.071 (2)
C250.7367 (14)0.0126 (5)0.4400 (3)0.096 (3)
C260.5590 (18)0.0187 (6)0.4580 (3)0.118 (5)
C270.8847 (18)0.0162 (7)0.4812 (4)0.136 (5)
C300.2270 (7)0.2641 (3)0.4302 (2)0.0470 (17)
C310.2554 (9)0.2139 (4)0.4772 (2)0.0613 (19)
Cl10.6265 (19)0.2328 (4)0.0142 (2)0.431 (7)
Cl20.818 (2)0.3949 (7)0.0006 (3)0.398 (8)
C320.803 (4)0.3144 (11)0.0383 (7)0.268 (15)
H1A1.003210.694030.305910.0472*
H1B0.871570.704980.260800.0472*
H2A0.961140.837860.328830.0512*
H2B1.025240.834270.273100.0512*
H30.733080.850390.245040.0493*
H4A0.492720.872530.297740.0527*
H4B0.616980.863430.344750.0527*
H50.547700.730930.275710.0434*
H7A0.317080.608550.308260.0525*
H7B0.274970.615400.365250.0525*
H80.562410.577450.387050.0419*
H90.654520.594140.284950.0403*
H11A0.903830.546980.359040.0490*
H11B0.946780.556190.302140.0490*
H12A0.771920.436590.283440.0479*
H12B0.911930.410450.324380.0479*
H140.466910.472140.306320.0434*
H15A0.223630.450600.354900.0502*
H15B0.337470.451500.404540.0502*
H160.283010.311660.342460.0427*
H170.542640.330590.303290.0409*
H18A0.617010.400560.427780.0639*
H18B0.749360.475620.415640.0639*
H18C0.814480.380730.411060.0639*
H19A0.679650.696630.403290.0669*
H19B0.797850.774540.386810.0669*
H19C0.884950.683910.392540.0669*
H200.708000.248190.385680.0459*
H21A0.901620.275180.317090.0720*
H21B0.770020.225650.281820.0720*
H21C0.874550.176530.323640.0720*
H23A0.304280.020340.317110.1293*
H23B0.186800.073820.354210.1293*
H23C0.203030.025350.360830.1293*
H24A0.694990.142160.441810.0850*
H24B0.814720.114040.396610.0850*
H250.778210.026800.414020.1156*
H26A0.574850.074430.473090.1415*
H26B0.515360.019840.483560.1415*
H27A0.994940.036710.466970.2046*
H27B0.903120.039900.494630.2046*
H27C0.846980.054130.507260.2046*
H31A0.381160.212550.485100.0921*
H31B0.212440.156580.472590.0921*
H31C0.190640.240320.504030.0921*
H32A0.768770.334330.071120.3239*
H32B0.919480.286760.041000.3239*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0619 (3)0.0273 (2)0.0649 (3)0.0021 (2)0.0020 (3)0.0035 (2)
O60.046 (2)0.0369 (18)0.102 (3)0.0036 (19)0.017 (2)0.0094 (18)
O160.0381 (17)0.0397 (18)0.051 (2)0.0033 (14)0.0011 (15)0.0094 (15)
O220.066 (2)0.0364 (18)0.057 (2)0.0089 (18)0.018 (2)0.0031 (16)
O260.160 (6)0.051 (3)0.114 (4)0.036 (3)0.010 (4)0.034 (3)
O300.041 (2)0.101 (4)0.096 (3)0.006 (2)0.002 (2)0.044 (3)
C10.033 (2)0.032 (2)0.053 (3)0.0008 (19)0.007 (2)0.0002 (19)
C20.037 (2)0.036 (2)0.056 (3)0.008 (2)0.003 (2)0.001 (2)
C30.050 (3)0.0244 (18)0.049 (2)0.0002 (16)0.007 (2)0.0020 (19)
C40.044 (3)0.031 (2)0.057 (3)0.002 (2)0.007 (2)0.004 (2)
C50.038 (2)0.029 (2)0.041 (2)0.0023 (19)0.007 (2)0.0004 (18)
C60.034 (2)0.034 (2)0.062 (3)0.006 (2)0.006 (2)0.003 (2)
C70.031 (2)0.036 (2)0.064 (3)0.0017 (19)0.001 (2)0.002 (2)
C80.030 (2)0.034 (2)0.040 (2)0.0034 (18)0.0011 (19)0.0040 (19)
C90.028 (2)0.0321 (19)0.041 (2)0.003 (2)0.004 (2)0.0025 (16)
C100.029 (2)0.032 (2)0.040 (2)0.0030 (16)0.0012 (17)0.0006 (17)
C110.029 (2)0.033 (2)0.061 (3)0.0011 (17)0.005 (2)0.003 (2)
C120.029 (2)0.032 (2)0.059 (3)0.002 (2)0.005 (2)0.0023 (18)
C130.028 (2)0.031 (2)0.040 (2)0.0033 (16)0.0020 (18)0.0032 (17)
C140.032 (2)0.034 (2)0.042 (2)0.0021 (18)0.0021 (19)0.0067 (19)
C150.033 (2)0.035 (2)0.058 (3)0.0007 (19)0.003 (2)0.009 (2)
C160.032 (2)0.032 (2)0.043 (2)0.0039 (18)0.0040 (19)0.0086 (18)
C170.032 (2)0.030 (2)0.041 (2)0.0015 (18)0.0055 (19)0.0051 (18)
C180.040 (2)0.038 (2)0.050 (3)0.002 (2)0.012 (2)0.0044 (19)
C190.046 (3)0.038 (2)0.050 (3)0.001 (2)0.005 (2)0.0005 (19)
C200.034 (2)0.031 (2)0.051 (3)0.0049 (18)0.003 (2)0.0046 (18)
C210.041 (3)0.033 (2)0.069 (3)0.004 (2)0.002 (3)0.001 (2)
C220.046 (3)0.032 (2)0.041 (2)0.001 (2)0.003 (2)0.0031 (19)
C230.071 (4)0.029 (2)0.050 (3)0.001 (2)0.001 (3)0.003 (2)
C23A0.092 (5)0.039 (3)0.063 (4)0.015 (3)0.006 (4)0.000 (2)
C23B0.083 (5)0.057 (4)0.119 (6)0.034 (3)0.003 (4)0.007 (4)
C240.111 (5)0.035 (3)0.066 (3)0.009 (4)0.026 (4)0.010 (2)
C250.135 (7)0.056 (4)0.098 (5)0.005 (5)0.048 (5)0.025 (4)
C260.209 (12)0.062 (5)0.083 (5)0.015 (6)0.053 (7)0.033 (4)
C270.188 (11)0.085 (6)0.136 (8)0.008 (7)0.084 (8)0.048 (6)
C300.035 (3)0.045 (3)0.061 (3)0.002 (2)0.006 (2)0.008 (2)
C310.072 (4)0.054 (3)0.058 (3)0.000 (3)0.012 (3)0.021 (3)
Cl10.87 (2)0.186 (5)0.237 (6)0.123 (9)0.347 (11)0.054 (4)
Cl20.547 (19)0.378 (12)0.269 (8)0.110 (13)0.089 (11)0.049 (8)
C320.46 (4)0.134 (13)0.211 (16)0.07 (2)0.07 (2)0.087 (13)
Geometric parameters (Å, º) top
Br1—C31.977 (5)C2—H2B0.9700
Cl1—C321.94 (3)C2—H2A0.9700
Cl2—C321.62 (2)C3—H30.9800
O6—C61.205 (6)C4—H4B0.9700
O16—C301.329 (6)C4—H4A0.9700
O16—C161.457 (6)C5—H50.9800
O22—C221.221 (6)C7—H7B0.9700
O26—C23A1.365 (8)C7—H7A0.9700
O26—C261.460 (13)C8—H80.9800
O30—C301.203 (7)C9—H90.9800
C1—C101.547 (6)C11—H11B0.9700
C1—C21.541 (7)C11—H11A0.9700
C2—C31.507 (7)C12—H12B0.9700
C3—C41.503 (7)C12—H12A0.9700
C4—C51.537 (7)C14—H140.9800
C5—C61.492 (7)C15—H15B0.9700
C5—C101.563 (6)C15—H15A0.9700
C6—C71.513 (7)C16—H160.9800
C7—C81.541 (6)C17—H170.9800
C8—C141.512 (7)C18—H18B0.9600
C8—C91.546 (6)C18—H18A0.9600
C9—C101.546 (7)C18—H18C0.9600
C9—C111.531 (6)C19—H19B0.9600
C10—C191.532 (7)C19—H19C0.9600
C11—C121.539 (7)C19—H19A0.9600
C12—C131.532 (7)C20—H200.9800
C13—C181.538 (6)C21—H21B0.9600
C13—C141.536 (6)C21—H21A0.9600
C13—C171.550 (6)C21—H21C0.9600
C14—C151.530 (7)C23B—H23C0.9600
C15—C161.554 (7)C23B—H23B0.9600
C16—C171.553 (6)C23B—H23A0.9600
C17—C201.549 (7)C24—H24A0.9700
C20—C221.542 (7)C24—H24B0.9700
C20—C211.536 (7)C25—H250.9800
C22—C231.465 (7)C26—H26A0.9700
C23—C241.507 (10)C26—H26B0.9700
C23—C23A1.344 (9)C27—H27B0.9600
C23A—C23B1.478 (11)C27—H27C0.9600
C24—C251.518 (9)C27—H27A0.9600
C25—C271.562 (15)C31—H31C0.9600
C25—C261.491 (16)C31—H31A0.9600
C30—C311.502 (8)C31—H31B0.9600
C1—H1A0.9700C32—H32A0.9700
C1—H1B0.9700C32—H32B0.9700
C16—O16—C30117.9 (4)H7A—C7—H7B108.00
C23A—O26—C26116.7 (6)C7—C8—H8109.00
C2—C1—C10113.1 (4)C9—C8—H8109.00
C1—C2—C3109.8 (4)C14—C8—H8109.00
Br1—C3—C2109.3 (3)C8—C9—H9106.00
Br1—C3—C4109.5 (3)C10—C9—H9106.00
C2—C3—C4113.2 (4)C11—C9—H9106.00
C3—C4—C5109.9 (4)C9—C11—H11A109.00
C4—C5—C6112.6 (4)C9—C11—H11B109.00
C4—C5—C10113.4 (4)C12—C11—H11A109.00
C6—C5—C10111.3 (4)C12—C11—H11B109.00
O6—C6—C5122.9 (4)H11A—C11—H11B108.00
O6—C6—C7121.3 (5)C11—C12—H12A109.00
C5—C6—C7115.8 (4)C11—C12—H12B109.00
C6—C7—C8114.5 (4)C13—C12—H12A109.00
C7—C8—C9110.0 (4)C13—C12—H12B109.00
C7—C8—C14111.5 (4)H12A—C12—H12B108.00
C9—C8—C14109.2 (4)C8—C14—H14107.00
C8—C9—C10111.4 (4)C13—C14—H14107.00
C8—C9—C11111.8 (4)C15—C14—H14107.00
C10—C9—C11114.2 (4)C14—C15—H15A111.00
C1—C10—C5106.8 (4)C14—C15—H15B111.00
C1—C10—C9110.4 (4)C16—C15—H15A111.00
C1—C10—C19109.9 (4)C16—C15—H15B111.00
C5—C10—C9107.1 (4)H15A—C15—H15B109.00
C5—C10—C19110.6 (4)O16—C16—H16110.00
C9—C10—C19112.0 (4)C15—C16—H16110.00
C9—C11—C12112.9 (4)C17—C16—H16110.00
C11—C12—C13111.6 (4)C13—C17—H17106.00
C12—C13—C14106.9 (4)C16—C17—H17106.00
C12—C13—C17116.5 (4)C20—C17—H17106.00
C12—C13—C18110.3 (4)C13—C18—H18A109.00
C14—C13—C1799.2 (3)C13—C18—H18B109.00
C14—C13—C18112.7 (4)C13—C18—H18C109.00
C17—C13—C18110.7 (4)H18A—C18—H18B109.00
C8—C14—C13114.9 (4)H18A—C18—H18C109.00
C8—C14—C15118.0 (4)H18B—C18—H18C109.00
C13—C14—C15103.6 (4)C10—C19—H19A109.00
C14—C15—C16103.9 (4)C10—C19—H19B109.00
O16—C16—C15111.9 (4)C10—C19—H19C109.00
O16—C16—C17108.3 (4)H19A—C19—H19B109.00
C15—C16—C17105.8 (4)H19A—C19—H19C109.00
C13—C17—C16103.6 (4)H19B—C19—H19C109.00
C13—C17—C20119.5 (4)C17—C20—H20110.00
C16—C17—C20113.7 (4)C21—C20—H20110.00
C17—C20—C21111.5 (4)C22—C20—H20110.00
C17—C20—C22109.7 (4)C20—C21—H21A109.00
C21—C20—C22106.7 (4)C20—C21—H21B109.00
O22—C22—C20118.4 (4)C20—C21—H21C109.00
O22—C22—C23124.3 (5)H21A—C21—H21B110.00
C20—C22—C23117.3 (4)H21A—C21—H21C109.00
C22—C23—C23A120.2 (5)H21B—C21—H21C109.00
C22—C23—C24118.2 (5)C23A—C23B—H23A109.00
C23A—C23—C24121.5 (5)C23A—C23B—H23B109.00
O26—C23A—C23122.9 (6)C23A—C23B—H23C109.00
O26—C23A—C23B108.4 (6)H23A—C23B—H23B109.00
C23—C23A—C23B128.6 (6)H23A—C23B—H23C109.00
C23—C24—C25112.0 (6)H23B—C23B—H23C109.00
C24—C25—C26108.2 (8)C23—C24—H24A109.00
C24—C25—C27111.3 (7)C23—C24—H24B109.00
C26—C25—C27114.1 (8)C25—C24—H24A109.00
O26—C26—C25113.6 (7)C25—C24—H24B109.00
O16—C30—O30124.0 (5)H24A—C24—H24B108.00
O16—C30—C31112.2 (5)C24—C25—H25108.00
O30—C30—C31123.9 (5)C26—C25—H25108.00
C2—C1—H1A109.00C27—C25—H25108.00
C2—C1—H1B109.00O26—C26—H26A109.00
C10—C1—H1A109.00O26—C26—H26B109.00
C10—C1—H1B109.00C25—C26—H26A109.00
H1A—C1—H1B108.00C25—C26—H26B109.00
C1—C2—H2A110.00H26A—C26—H26B108.00
C1—C2—H2B110.00C25—C27—H27A109.00
C3—C2—H2A110.00C25—C27—H27B110.00
C3—C2—H2B110.00C25—C27—H27C109.00
H2A—C2—H2B108.00H27A—C27—H27B109.00
Br1—C3—H3108.00H27A—C27—H27C109.00
C2—C3—H3108.00H27B—C27—H27C110.00
C4—C3—H3108.00C30—C31—H31A110.00
C3—C4—H4A110.00C30—C31—H31B110.00
C3—C4—H4B110.00C30—C31—H31C110.00
C5—C4—H4A110.00H31A—C31—H31B109.00
C5—C4—H4B110.00H31A—C31—H31C109.00
H4A—C4—H4B108.00H31B—C31—H31C109.00
C4—C5—H5106.00Cl1—C32—Cl2110.5 (13)
C6—C5—H5106.00Cl1—C32—H32A110.00
C10—C5—H5106.00Cl1—C32—H32B110.00
C6—C7—H7A109.00Cl2—C32—H32A110.00
C6—C7—H7B109.00Cl2—C32—H32B109.00
C8—C7—H7A109.00H32A—C32—H32B108.00
C8—C7—H7B109.00
C30—O16—C16—C17154.6 (4)C9—C11—C12—C1355.2 (5)
C30—O16—C16—C1589.2 (5)C11—C12—C13—C17166.1 (4)
C16—O16—C30—O305.1 (7)C11—C12—C13—C1866.6 (5)
C16—O16—C30—C31174.6 (4)C11—C12—C13—C1456.3 (5)
C23A—O26—C26—C2538.4 (10)C18—C13—C14—C861.4 (5)
C26—O26—C23A—C23B173.4 (7)C18—C13—C14—C1568.8 (5)
C26—O26—C23A—C233.5 (10)C12—C13—C17—C16157.1 (4)
C2—C1—C10—C1964.4 (5)C12—C13—C17—C2075.2 (5)
C2—C1—C10—C9171.6 (4)C14—C13—C17—C1642.9 (4)
C10—C1—C2—C357.2 (5)C18—C13—C17—C1675.8 (4)
C2—C1—C10—C555.6 (5)C12—C13—C14—C15169.9 (4)
C1—C2—C3—Br1178.7 (3)C18—C13—C17—C2051.9 (5)
C1—C2—C3—C456.4 (6)C12—C13—C14—C860.0 (5)
C2—C3—C4—C555.9 (5)C14—C13—C17—C20170.6 (4)
Br1—C3—C4—C5178.1 (3)C17—C13—C14—C8178.6 (4)
C3—C4—C5—C1056.0 (5)C17—C13—C14—C1548.4 (4)
C3—C4—C5—C6176.5 (4)C13—C14—C15—C1635.0 (5)
C4—C5—C6—C7179.4 (4)C8—C14—C15—C16163.2 (4)
C6—C5—C10—C1176.6 (4)C14—C15—C16—O16125.2 (4)
C4—C5—C6—O63.4 (7)C14—C15—C16—C177.5 (5)
C10—C5—C6—O6132.0 (5)C15—C16—C17—C1322.3 (4)
C6—C5—C10—C958.4 (5)C15—C16—C17—C20153.6 (4)
C6—C5—C10—C1963.9 (5)O16—C16—C17—C2033.4 (5)
C4—C5—C10—C1964.3 (5)O16—C16—C17—C1397.8 (4)
C4—C5—C10—C9173.4 (4)C13—C17—C20—C2174.3 (5)
C10—C5—C6—C750.7 (6)C16—C17—C20—C21162.8 (4)
C4—C5—C10—C155.2 (5)C13—C17—C20—C22167.7 (4)
O6—C6—C7—C8137.9 (5)C16—C17—C20—C2244.8 (5)
C5—C6—C7—C844.8 (6)C17—C20—C22—C23142.1 (4)
C6—C7—C8—C946.2 (6)C21—C20—C22—C2397.0 (5)
C6—C7—C8—C14167.5 (4)C21—C20—C22—O2280.6 (5)
C7—C8—C9—C11173.9 (4)C17—C20—C22—O2240.4 (6)
C14—C8—C9—C10179.6 (4)O22—C22—C23—C23A10.1 (8)
C7—C8—C14—C13179.4 (4)C20—C22—C23—C2411.3 (7)
C14—C8—C9—C1151.3 (5)O22—C22—C23—C24166.2 (5)
C7—C8—C14—C1557.9 (6)C20—C22—C23—C23A172.5 (5)
C7—C8—C9—C1057.0 (5)C24—C23—C23A—O269.0 (9)
C9—C8—C14—C1357.7 (5)C24—C23—C23A—C23B174.8 (6)
C9—C8—C14—C15179.6 (4)C22—C23—C23A—C23B1.3 (10)
C11—C9—C10—C153.5 (5)C22—C23—C23A—O26174.9 (6)
C8—C9—C10—C1958.5 (5)C23A—C23—C24—C2513.2 (9)
C11—C9—C10—C1969.3 (5)C22—C23—C24—C25163.0 (6)
C11—C9—C10—C5169.3 (4)C23—C24—C25—C2644.2 (8)
C8—C9—C10—C562.9 (4)C23—C24—C25—C27170.3 (7)
C8—C9—C10—C1178.7 (4)C24—C25—C26—O2657.9 (9)
C10—C9—C11—C12179.4 (4)C27—C25—C26—O26177.7 (7)
C8—C9—C11—C1251.8 (5)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5···O22i0.982.543.491 (6)165
C18—H18C···O30ii0.962.593.545 (7)173
C27—H27B···Cl2iii0.962.322.957 (18)124
C32—H32A···O6iv0.972.233.00 (2)135
C32—H32B···Cl1v0.972.162.89 (3)130
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x+1, y, z; (iii) x+2, y1/2, z+1/2; (iv) x+1, y1/2, z+1/2; (v) x+1/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC31H45BrO5·CH2Cl2
Mr662.51
Crystal system, space groupOrthorhombic, P212121
Temperature (K)293
a, b, c (Å)7.4423 (1), 15.6578 (2), 26.8496 (3)
V3)3128.79 (7)
Z4
Radiation typeMo Kα
µ (mm1)1.52
Crystal size (mm)0.15 × 0.10 × 0.08
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
37310, 7934, 5668
Rint0.088
(sin θ/λ)max1)0.676
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.068, 0.181, 1.03
No. of reflections7934
No. of parameters362
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.75, 0.68
Absolute structureFlack (1983), 3453 Friedel pairs
Absolute structure parameter0.031 (13)

Computer programs: COLLECT (Nonius, 1999), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009), WinGX (Farrugia, 2012).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5···O22i0.982.543.491 (6)165
C18—H18C···O30ii0.962.593.545 (7)173
C27—H27B···Cl2iii0.962.322.957 (18)124
C32—H32A···O6iv0.972.233.00 (2)135
C32—H32B···Cl1v0.972.162.89 (3)130
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x+1, y, z; (iii) x+2, y1/2, z+1/2; (iv) x+1, y1/2, z+1/2; (v) x+1/2, y+1/2, z.
 

Acknowledgements

The authors thank CONACYT for financial support and the Consejo Superior de la Investigación Científica in Spain for the award of a license for the use of the Cambridge Structural Database. Thanks are due to Marco A. Leyva-Ramírez (CINVESTAV-IPN) for helpful discussions.

References

First citationAllen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2. pp. S1–19.  CrossRef
First citationCastro-Méndez, A., Sandoval-Ramírez, J. & Bernès, S. (2002). Acta Cryst. E58, o606–o608.  Web of Science CSD CrossRef IUCr Journals
First citationCorey, E. J. & Suggs, J. W. (1975). Tetrahedron Lett. 16, 2647–2650.  CrossRef
First citationCremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358.  CrossRef CAS Web of Science
First citationFarrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854.  Web of Science CrossRef CAS IUCr Journals
First citationFlack, H. D. (1983). Acta Cryst. A39, 876–881.  CrossRef CAS Web of Science IUCr Journals
First citationHostettmann, K. & Marston, A. (1995). Saponins. Cambridge University Presss.
First citationIglesias-Arteaga, M. A., Pérez Gil, R., Leliebre Lara, V., Coll Manchado, F. & Pérez Martínez, C. S. (1998). Synth. Commun. 28, 75–81.  Web of Science CrossRef
First citationLee, S., LaCour, T. G. & Fuchs, P. L. (2009). Chem. Rev. 109, 2275–2314.  Web of Science CrossRef PubMed CAS
First citationLee, E., Liu, Y. T., Solomon, P. H. & Nakanishi, K. (1976). J. Am. Chem. Soc. 98, 1634–1635.  CrossRef PubMed CAS Web of Science
First citationMonroe, E. W. & Serota, S. (1956). J. Am. Chem. Soc. 78, 1747–1750.
First citationNonius (1999). KappaCCD Server Software. Nonius BV, Delft, The Netherlands.
First citationOtwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.
First citationPettit, G. R., Inoue, M., Kamano, Y., Herald, D. L., Arm, C., Dufresne, C., Christie, N. D., Schmidt, J. M., Doubek, D. L. & Krupa, T. S. (1988). J. Am. Chem. Soc. 110, 2006-2007.  CSD CrossRef CAS Web of Science
First citationPhillips, S. T. & Shair, M. D. (2007). J. Am. Chem. Soc. 129, 6589–6598.  Web of Science CSD CrossRef PubMed CAS
First citationRincón, S., del Río, R. E., Sandoval-Ramírez, J., Meza-Reyes, S., Montiel-Smith, S., Fernández, M. A., Farfán, N. & Santillan, R. (2006). Tetrahedron, 62, 2594–2602.
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals
First citationSteele, J. A. & Mosettig, E. (1963). J. Org. Chem. 28, 571–572.  CrossRef CAS Web of Science

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Volume 68| Part 12| December 2012| Pages o3260-o3261
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