organic compounds
of 3-methoxycarbonyl-2-(4-methoxyphenyl)-8-oxo-1-azaspiro[4.5]deca-1,6,9-trien-1-ium-1-olate
aLaboratory of Synthesis of Natural Products and Drugs, Institute of Chemistry, University of Campinas, PO Box 6154 – 13083-970, Campinas, SP, Brazil, bLaboratory of Single Crystal X-Ray Diffraction, Institute of Chemistry, University of Campinas, PO Box 6154 – 13083-970, Campinas, SP, Brazil, and cLaboratory of Structural Biology and Crystallography, Institute of Chemistry, University of Campinas, PO Box 6154 – 13083-970, Campinas, SP, Brazil
*Correspondence e-mail: aparicio@iqm.unicamp.br
The title compound, C18H17NO5, was prepared by a synthetic strategy based on the Heck reaction from Morita–Baylis–Hillman adducts. The five-membered ring adopts a slightly twisted conformation on the Ca—Cm (a = aromatic and m = methylene) bond. The dihedral angle between the five-membered ring and the spiro aromatic ring is 89.35 (7)°; that between the five-membered ring and the 4-methoxybenzene ring is 4.65 (7)°. Two short intramolecular C—H⋯O contacts occur. In the crystal, molecules are linked by C—H⋯O hydrogen bonds to generate a three-dimensional network.
CCDC reference: 1030399
1. Related literature
For compounds that contain a spirohexadienone moiety in their structures, see: Wright & König (1993); König et al. (1990); Beil et al. (1998) and for their biological activities, see: Glushkov et al. (2010); Pereira et al. (2007). For strategies for the synthesis of spiro-hexadienones from Morita–Baylis–Hillman adducts, see: Coelho et al. (2002); Ferreira et al. (2009); Pirovani et al. (2009); Martins et al. (2014). For the biological activity of compounds containing a nitrone group, see: Fangour et al. (2009); Floyd et al. (2008); Halliwell & Gutteridge (1999); Fevig et al. (1996). For a discussion about non-classical hydrogen bonds, see: Desiraju (2005).
2. Experimental
2.1. Crystal data
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2.3. Refinement
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Data collection: APEX2 (Bruker, 2010); cell SAINT (Bruker, 2010); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: WinGX (Farrugia, 2012) and PLATON (Spek, 2009); software used to prepare material for publication: publCIF (Westrip, 2010).
Supporting information
CCDC reference: 1030399
10.1107/S1600536814023277/hb7301sup1.cif
contains datablocks I, New_Global_Publ_Block. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814023277/hb7301Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536814023277/hb7301Isup3.cdx
Supporting information file. DOI: 10.1107/S1600536814023277/hb7301Isup4.cml
Natural products, isolated both from terrestrial or marine sources, display great structural diversity and exhibit remarkable biological activities, many of them bearing in their structures a spiro-hexadienone moiety (Wright & König (1993); Beil et al. (1998)). Owing to the high conjugation, provided by the presence of a carbonyl group and two double bonds, this structural moiety acts as an efficient Michael acceptor and this chemical property is routinely associated with some biological activities, such as cytotoxic (Pereira et al. (2007); Glushkov et al. (2010)).
Compounds presenting a nitrone group in their structures can present biological activity related to radical trapping in chemical systems (Fangour et al. (2009); Floyd et al. (2008); Halliwell et al. (1999)). The presence of radicals is normally associated to several type of pathologies. Our interest in preparing spiro-hexadienones with great structural diversity combinated with the biological effect that can be associated to nitrone groups stimulated us to synthesize new
containing a nitrone group into their structures and evaluate the biological profiles of these new compounds.A strategy for the synthesis of spiro-hexadienones from Morita-Baylis-Hillman aducts had been developed. This strategy is based on the Heck reaction, followed by phenolic oxidation of functionalized b-ketoester mediated by a hypervalent iodine reagent (Coelho et al. (2002); Ferreira et al. (2009); Floyd et al. (2008); Halliwell et al. (1999)). As far as we know, we synthesized for the first time new functionalized azaspiro compounds from Morita-Baylis-Hillman.
Some β-ketoesters, prepared from Morita-Baylis-Hillman adducts, were treated with hydroxylamine hydrochloride to furnish a diastereomeric mixture of in which the E isomer cyclizes spontaneously to the corresponding isoxazoles. The Z oxime was treated with PIFA [phenyliodine(III) bis(trifluoroacetate)] to furnish the new azaspiro compounds in moderate overall yield (3-17%). The obtained 3-(Methoxycarbonyl)-2-(4-methoxyphenyl)-8-oxo-1-azaspiro[4.5]deca-1,6,9-trien-1-ium-1-olate (33 mg, 0.1 mmol) was dissolved in absolute chloroform-D1 (1 mL), followed by stirring until total dissolution was achieved. The solution was kept in the freezer. After two weeks, the resulting solution was filtered using a vacuum, washed with small portions of cold chloroform and dried in a desiccator to furnish colourless prisms.
A riding model was used to calculate the positions of included H atoms, with aromatic and methyl C—H bond lengths of 0.95 and 0.98 A °, respectively. The isotropic displacement parameters values (Uiso(H)) were fixed at 1.5Ueq(C) for methyl H atoms and 1.2Ueq(C) for all other attached H atoms.
Data collection: APEX2 (Bruker, 2010); cell
SAINT (Bruker, 2010); data reduction: SAINT (Bruker, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: WinGX (Farrugia, 2012) and PLATON (Spek, 2009); software used to prepare material for publication: publCIF (Westrip, 2010).The molecular structure of the title compound with 50% probability displacement ellipsoids. Crystal packing of the title compound, showing hydrogen bonding interactions. |
C18H17NO5 | Z = 2 |
Mr = 327.32 | F(000) = 344 |
Triclinic, P1 | Dx = 1.391 Mg m−3 |
Hall symbol: -P 1 | Cu Kα radiation, λ = 1.54178 Å |
a = 6.0916 (11) Å | Cell parameters from 109 reflections |
b = 8.7713 (16) Å | θ = 9.0–38.4° |
c = 15.167 (3) Å | µ = 0.85 mm−1 |
α = 80.255 (6)° | T = 100 K |
β = 81.703 (6)° | Prismatic, colourless |
γ = 80.122 (6)° | 0.47 × 0.20 × 0.17 mm |
V = 781.3 (2) Å3 |
Bruker APEXII CCD diffractometer | 2771 independent reflections |
Radiation source: fine-focus sealed tube | 2727 reflections with I > 2σ(I) |
Detector resolution: 8.3333 pixels mm-1 | Rint = 0.033 |
ϕ and ω scans | θmax = 67.7°, θmin = 3.0° |
Absorption correction: multi-scan (SADABS; Bruker, 2010) | h = −5→7 |
Tmin = 0.813, Tmax = 1.000 | k = −10→10 |
14656 measured reflections | l = −18→17 |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.042 | w = 1/[σ2(Fo2) + (0.0542P)2 + 0.3281P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.105 | (Δ/σ)max < 0.001 |
S = 1.11 | Δρmax = 0.28 e Å−3 |
2771 reflections | Δρmin = −0.35 e Å−3 |
220 parameters | Extinction correction: SHELXL2014 (Sheldrick, 2014), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.043 (2) |
C18H17NO5 | γ = 80.122 (6)° |
Mr = 327.32 | V = 781.3 (2) Å3 |
Triclinic, P1 | Z = 2 |
a = 6.0916 (11) Å | Cu Kα radiation |
b = 8.7713 (16) Å | µ = 0.85 mm−1 |
c = 15.167 (3) Å | T = 100 K |
α = 80.255 (6)° | 0.47 × 0.20 × 0.17 mm |
β = 81.703 (6)° |
Bruker APEXII CCD diffractometer | 2771 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2010) | 2727 reflections with I > 2σ(I) |
Tmin = 0.813, Tmax = 1.000 | Rint = 0.033 |
14656 measured reflections |
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.105 | H-atom parameters constrained |
S = 1.11 | Δρmax = 0.28 e Å−3 |
2771 reflections | Δρmin = −0.35 e Å−3 |
220 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
O2 | 0.20642 (16) | 0.89397 (12) | 0.62486 (6) | 0.0247 (3) | |
O5 | 0.19082 (18) | 0.28804 (12) | 0.01392 (7) | 0.0309 (3) | |
O1 | 0.19910 (14) | 0.44109 (11) | 0.32280 (6) | 0.0199 (2) | |
O4 | 0.91693 (15) | 0.79511 (11) | 0.19091 (7) | 0.0228 (3) | |
O3 | 0.54105 (16) | 0.85337 (11) | 0.19863 (7) | 0.0281 (3) | |
N1 | 0.38917 (17) | 0.48769 (12) | 0.29230 (7) | 0.0166 (3) | |
C8 | −0.0287 (2) | 0.92550 (17) | 0.65513 (10) | 0.0252 (3) | |
H1A | −0.1106 | 0.9720 | 0.6036 | 0.038* | |
H1B | −0.0535 | 0.9985 | 0.6991 | 0.038* | |
H1C | −0.0827 | 0.8276 | 0.6833 | 0.038* | |
C5 | 0.2673 (2) | 0.80731 (16) | 0.55566 (9) | 0.0202 (3) | |
C4 | 0.1260 (2) | 0.72330 (16) | 0.52570 (9) | 0.0200 (3) | |
H3 | −0.0222 | 0.7203 | 0.5551 | 0.024* | |
C3 | 0.2017 (2) | 0.64391 (15) | 0.45269 (9) | 0.0189 (3) | |
H4 | 0.1048 | 0.5855 | 0.4333 | 0.023* | |
C2 | 0.4179 (2) | 0.64816 (15) | 0.40712 (9) | 0.0177 (3) | |
C1 | 0.4981 (2) | 0.57613 (15) | 0.32644 (9) | 0.0173 (3) | |
C13 | 0.4972 (2) | 0.44582 (15) | 0.20162 (9) | 0.0180 (3) | |
C14 | 0.3688 (2) | 0.55382 (15) | 0.13203 (9) | 0.0186 (3) | |
H8 | 0.3569 | 0.6635 | 0.1312 | 0.022* | |
C15 | 0.2712 (2) | 0.50353 (16) | 0.07177 (9) | 0.0202 (3) | |
H9 | 0.1934 | 0.5777 | 0.0293 | 0.024* | |
C16 | 0.2811 (2) | 0.33526 (16) | 0.06944 (9) | 0.0216 (3) | |
C7 | 0.5596 (2) | 0.73034 (16) | 0.44026 (9) | 0.0207 (3) | |
H11 | 0.7083 | 0.7332 | 0.4114 | 0.025* | |
C6 | 0.4867 (2) | 0.80683 (16) | 0.51396 (9) | 0.0223 (3) | |
H12 | 0.5863 | 0.8593 | 0.5363 | 0.027* | |
C18 | 0.4924 (2) | 0.27616 (15) | 0.20004 (9) | 0.0197 (3) | |
H13 | 0.5580 | 0.2010 | 0.2454 | 0.024* | |
C17 | 0.4002 (2) | 0.22581 (16) | 0.13799 (9) | 0.0213 (3) | |
H14 | 0.4117 | 0.1164 | 0.1379 | 0.026* | |
C12 | 0.7367 (2) | 0.48121 (15) | 0.20051 (9) | 0.0196 (3) | |
H15A | 0.7956 | 0.5274 | 0.1394 | 0.024* | |
H15B | 0.8389 | 0.3846 | 0.2199 | 0.024* | |
C9 | 0.7139 (2) | 0.59949 (15) | 0.26787 (9) | 0.0186 (3) | |
H16 | 0.8422 | 0.5732 | 0.3049 | 0.022* | |
C10 | 0.7081 (2) | 0.76464 (16) | 0.21684 (9) | 0.0195 (3) | |
C11 | 0.9377 (3) | 0.93704 (17) | 0.12808 (10) | 0.0270 (3) | |
H18A | 0.8704 | 0.9329 | 0.0738 | 0.040* | |
H18B | 1.0968 | 0.9470 | 0.1118 | 0.040* | |
H18C | 0.8601 | 1.0274 | 0.1561 | 0.040* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O2 | 0.0232 (5) | 0.0323 (6) | 0.0211 (5) | −0.0051 (4) | −0.0046 (4) | −0.0084 (4) |
O5 | 0.0324 (6) | 0.0323 (6) | 0.0319 (6) | −0.0051 (5) | −0.0150 (5) | −0.0066 (4) |
O1 | 0.0130 (5) | 0.0267 (5) | 0.0208 (5) | −0.0079 (4) | −0.0007 (4) | −0.0017 (4) |
O4 | 0.0166 (5) | 0.0233 (5) | 0.0272 (5) | −0.0063 (4) | 0.0016 (4) | −0.0003 (4) |
O3 | 0.0188 (5) | 0.0246 (5) | 0.0372 (6) | −0.0016 (4) | −0.0037 (4) | 0.0044 (4) |
N1 | 0.0128 (5) | 0.0199 (5) | 0.0161 (5) | −0.0027 (4) | −0.0024 (4) | 0.0005 (4) |
C8 | 0.0252 (7) | 0.0298 (7) | 0.0210 (7) | −0.0038 (6) | −0.0018 (6) | −0.0061 (6) |
C5 | 0.0233 (7) | 0.0216 (7) | 0.0158 (6) | −0.0023 (5) | −0.0067 (5) | −0.0005 (5) |
C4 | 0.0179 (6) | 0.0231 (7) | 0.0183 (6) | −0.0047 (5) | −0.0025 (5) | 0.0008 (5) |
C3 | 0.0180 (6) | 0.0209 (6) | 0.0184 (6) | −0.0057 (5) | −0.0048 (5) | 0.0004 (5) |
C2 | 0.0163 (6) | 0.0187 (6) | 0.0174 (6) | −0.0028 (5) | −0.0051 (5) | 0.0022 (5) |
C1 | 0.0143 (6) | 0.0185 (6) | 0.0182 (6) | −0.0023 (5) | −0.0051 (5) | 0.0019 (5) |
C13 | 0.0139 (6) | 0.0229 (7) | 0.0166 (6) | −0.0016 (5) | −0.0014 (5) | −0.0023 (5) |
C14 | 0.0140 (6) | 0.0202 (6) | 0.0190 (6) | −0.0005 (5) | 0.0006 (5) | −0.0004 (5) |
C15 | 0.0148 (6) | 0.0250 (7) | 0.0184 (6) | −0.0002 (5) | −0.0023 (5) | 0.0011 (5) |
C16 | 0.0156 (6) | 0.0280 (7) | 0.0214 (7) | −0.0036 (5) | −0.0017 (5) | −0.0039 (6) |
C7 | 0.0153 (6) | 0.0238 (7) | 0.0229 (7) | −0.0043 (5) | −0.0045 (5) | −0.0001 (5) |
C6 | 0.0199 (7) | 0.0245 (7) | 0.0246 (7) | −0.0054 (5) | −0.0094 (5) | −0.0019 (5) |
C18 | 0.0159 (6) | 0.0216 (7) | 0.0195 (6) | 0.0000 (5) | −0.0017 (5) | 0.0000 (5) |
C17 | 0.0180 (7) | 0.0208 (7) | 0.0243 (7) | −0.0027 (5) | −0.0017 (5) | −0.0021 (5) |
C12 | 0.0136 (6) | 0.0226 (7) | 0.0219 (7) | −0.0013 (5) | −0.0027 (5) | −0.0017 (5) |
C9 | 0.0130 (6) | 0.0218 (7) | 0.0204 (6) | −0.0021 (5) | −0.0037 (5) | −0.0006 (5) |
C10 | 0.0159 (6) | 0.0231 (7) | 0.0197 (7) | −0.0041 (5) | −0.0013 (5) | −0.0033 (5) |
C11 | 0.0275 (8) | 0.0252 (7) | 0.0277 (7) | −0.0109 (6) | 0.0023 (6) | 0.0002 (6) |
O2—C5 | 1.3705 (17) | C13—C14 | 1.5066 (18) |
O2—C8 | 1.4339 (17) | C13—C12 | 1.5395 (17) |
O5—C16 | 1.2301 (17) | C14—C15 | 1.3289 (19) |
O1—N1 | 1.2905 (14) | C14—H8 | 0.9500 |
O4—C10 | 1.3345 (16) | C15—C16 | 1.473 (2) |
O4—C11 | 1.4462 (17) | C15—H9 | 0.9500 |
O3—C10 | 1.2059 (17) | C16—C17 | 1.4732 (19) |
N1—C1 | 1.3121 (17) | C7—C6 | 1.380 (2) |
N1—C13 | 1.5121 (16) | C7—H11 | 0.9500 |
C8—H1A | 0.9800 | C6—H12 | 0.9500 |
C8—H1B | 0.9800 | C18—C17 | 1.332 (2) |
C8—H1C | 0.9800 | C18—H13 | 0.9500 |
C5—C4 | 1.3908 (19) | C17—H14 | 0.9500 |
C5—C6 | 1.393 (2) | C12—C9 | 1.5519 (18) |
C4—C3 | 1.3884 (19) | C12—H15A | 0.9900 |
C4—H3 | 0.9500 | C12—H15B | 0.9900 |
C3—C2 | 1.3996 (19) | C9—C10 | 1.5197 (18) |
C3—H4 | 0.9500 | C9—H16 | 1.0000 |
C2—C7 | 1.4067 (18) | C11—H18A | 0.9800 |
C2—C1 | 1.4554 (19) | C11—H18B | 0.9800 |
C1—C9 | 1.5014 (18) | C11—H18C | 0.9800 |
C13—C18 | 1.4977 (19) | ||
C5—O2—C8 | 116.78 (10) | C16—C15—H9 | 119.3 |
C10—O4—C11 | 115.74 (11) | O5—C16—C15 | 121.67 (13) |
O1—N1—C1 | 128.90 (11) | O5—C16—C17 | 121.42 (13) |
O1—N1—C13 | 116.85 (10) | C15—C16—C17 | 116.89 (12) |
C1—N1—C13 | 114.09 (10) | C6—C7—C2 | 121.25 (12) |
O2—C8—H1A | 109.5 | C6—C7—H11 | 119.4 |
O2—C8—H1B | 109.5 | C2—C7—H11 | 119.4 |
H1A—C8—H1B | 109.5 | C7—C6—C5 | 120.13 (12) |
O2—C8—H1C | 109.5 | C7—C6—H12 | 119.9 |
H1A—C8—H1C | 109.5 | C5—C6—H12 | 119.9 |
H1B—C8—H1C | 109.5 | C17—C18—C13 | 123.01 (12) |
O2—C5—C4 | 124.47 (12) | C17—C18—H13 | 118.5 |
O2—C5—C6 | 115.89 (12) | C13—C18—H13 | 118.5 |
C4—C5—C6 | 119.64 (12) | C18—C17—C16 | 121.73 (13) |
C3—C4—C5 | 119.90 (12) | C18—C17—H14 | 119.1 |
C3—C4—H3 | 120.1 | C16—C17—H14 | 119.1 |
C5—C4—H3 | 120.1 | C13—C12—C9 | 105.07 (10) |
C4—C3—C2 | 121.34 (12) | C13—C12—H15A | 110.7 |
C4—C3—H4 | 119.3 | C9—C12—H15A | 110.7 |
C2—C3—H4 | 119.3 | C13—C12—H15B | 110.7 |
C3—C2—C7 | 117.62 (12) | C9—C12—H15B | 110.7 |
C3—C2—C1 | 123.04 (12) | H15A—C12—H15B | 108.8 |
C7—C2—C1 | 119.31 (12) | C1—C9—C10 | 112.58 (11) |
N1—C1—C2 | 125.30 (12) | C1—C9—C12 | 103.83 (10) |
N1—C1—C9 | 110.32 (11) | C10—C9—C12 | 109.86 (11) |
C2—C1—C9 | 124.32 (11) | C1—C9—H16 | 110.1 |
C18—C13—C14 | 113.42 (11) | C10—C9—H16 | 110.1 |
C18—C13—N1 | 109.22 (10) | C12—C9—H16 | 110.1 |
C14—C13—N1 | 106.44 (10) | O3—C10—O4 | 124.52 (12) |
C18—C13—C12 | 112.45 (11) | O3—C10—C9 | 125.53 (12) |
C14—C13—C12 | 113.17 (11) | O4—C10—C9 | 109.87 (11) |
N1—C13—C12 | 101.15 (10) | O4—C11—H18A | 109.5 |
C15—C14—C13 | 123.35 (12) | O4—C11—H18B | 109.5 |
C15—C14—H8 | 118.3 | H18A—C11—H18B | 109.5 |
C13—C14—H8 | 118.3 | O4—C11—H18C | 109.5 |
C14—C15—C16 | 121.39 (12) | H18A—C11—H18C | 109.5 |
C14—C15—H9 | 119.3 | H18B—C11—H18C | 109.5 |
D—H···A | D—H | H···A | D···A | D—H···A |
C8—H1C···O1i | 0.98 | 2.59 | 3.4941 (18) | 153 |
C4—H3···O1i | 0.95 | 2.38 | 3.1345 (16) | 136 |
C3—H4···O1 | 0.95 | 2.22 | 2.8725 (17) | 125 |
C14—H8···O3 | 0.95 | 2.57 | 3.3431 (18) | 138 |
C15—H9···O5ii | 0.95 | 2.56 | 3.3821 (17) | 146 |
C18—H13···O2iii | 0.95 | 2.54 | 3.4309 (17) | 155 |
C17—H14···O3iv | 0.95 | 2.38 | 3.2408 (18) | 151 |
C12—H15A···O5v | 0.99 | 2.60 | 3.5402 (18) | 159 |
C9—H16···O1vi | 1.00 | 2.31 | 3.2045 (16) | 148 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x, −y+1, −z; (iii) −x+1, −y+1, −z+1; (iv) x, y−1, z; (v) −x+1, −y+1, −z; (vi) x+1, y, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C8—H1C···O1i | 0.98 | 2.59 | 3.4941 (18) | 153 |
C4—H3···O1i | 0.95 | 2.38 | 3.1345 (16) | 136 |
C3—H4···O1 | 0.95 | 2.22 | 2.8725 (17) | 125 |
C14—H8···O3 | 0.95 | 2.57 | 3.3431 (18) | 138 |
C15—H9···O5ii | 0.95 | 2.56 | 3.3821 (17) | 146 |
C18—H13···O2iii | 0.95 | 2.54 | 3.4309 (17) | 155 |
C17—H14···O3iv | 0.95 | 2.38 | 3.2408 (18) | 151 |
C12—H15A···O5v | 0.99 | 2.60 | 3.5402 (18) | 159 |
C9—H16···O1vi | 1.00 | 2.31 | 3.2045 (16) | 148 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x, −y+1, −z; (iii) −x+1, −y+1, −z+1; (iv) x, y−1, z; (v) −x+1, −y+1, −z; (vi) x+1, y, z. |
Acknowledgements
The authors acknowledge Dr Cristiane Storck Schwalm for the data collection and preliminary data processing and structure
and thank the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2009/18390–4 and 2009/51602–5), the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support. RA is the recipient of a research grant from CNPq.References
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