organic compounds
(1S,3R,8R)-9-(1-Aminoethylidene)-2,2-dichloro-3,7,7-trimethyltricyclo[6.4.0.01,3]undecan-10-one
aLaboratoire de Chimie Biomoléculaires, Substances Naturelles et Réactivité, URAC16, Faculté des Sciences, Semlalia, BP 2390 Bd My Abdellah, 40000 Marrakech, Morocco, and bUniversité Blaise Pascal, Laboratoire des Matériaux Inorganiques, UMR CNRS 6002, 24 Avenue des Landais, 63177 Aubière, France
*Correspondence e-mail: elassaba@gmail.com
The title compound, C16H23Cl2NO, was synthesised from β-himachalene (3,5,5,9-tetramethyl-2,4a,5,6,7,8-hexahydro-1H-benzocycloheptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The molecule contains a seven membered ring, which is fused to a five- and a three-membered ring. The five-membered ring has a twisted conformation, whereas the seven-membered ring displays a chair conformation. The dihedral angle between the five- and seven-membered rings is 45.26 (9)°. The was established unambiguously from effects. In the crystal, molecules are linked into chains propagating along the b axis by intermolecular N—H⋯O hydrogen bonds; an intramolecular N—H⋯O link also occurs.
Related literature
For the isolation of β-himachalene, see: Joseph & Dev (1968); Plattier & Teisseire (1974). For the reactivity of β-himachalene, see: Lassaba et al. (1998); Chekroun et al. (2000); El Jamili et al. (2002); Dakir et al. (2004). For the biological activity of β-himachalene, see: Daoubi et al. (2004). For see: Cremer & Pople (1975).
Experimental
Crystal data
|
Data collection
|
Data collection: APEX2 (Bruker, 2009); cell SAINT-Plus (Bruker, 2009); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S1600536811005307/fj2396sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811005307/fj2396Isup2.hkl
To a solution of enone 1 g (3.32 mmol) in 20 ml of trifluoroacetic acid at 10 °C was added with stirring 1 g (15.38 mmol) of NaN3. After being stirred at room temperature for 24 h, the reaction mixture was neutralized with a solution of Na2CO3 (10%) and extracted three time with diethylether (3x20ml). The combined organic phases were dried on Na2SO4, filtred and concentrated at reduced pressure to give the crude product which was chromatographed on a silica gel column with hexane- ether as
(20/80) to give 630 mg(1.99 mmol) of (1S, 3R, 8R)-9-(1-aminoethylidene)-2,2-dichloro-3,7,7-trimethyltricyclo [6.3.0.01,3]undecan -10-one.The title compound was recrystallized in diethylether.except H1 and H2,all H atoms were fixed geometrically and treated as riding with C—H = 0.96 Å (methyl), 0.97 Å (methylene), 0.98Å (methine) with Uiso(H) = 1.2Ueq (methylene, methine) or Uiso(H) = 1.5Ueq (methyl).
Data collection: APEX2 (Bruker, 2009); cell
SAINT-Plus (Bruker, 2009); data reduction: SAINT-Plus (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999).C16H23Cl2NO | F(000) = 336 |
Mr = 316.25 | Dx = 1.308 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2yb | Cell parameters from 4954 reflections |
a = 7.7570 (7) Å | θ = 3.4–26.4° |
b = 9.7041 (9) Å | µ = 0.40 mm−1 |
c = 10.6901 (10) Å | T = 298 K |
β = 93.432 (3)° | Prism, colourless |
V = 803.25 (13) Å3 | 0.41 × 0.33 × 0.26 mm |
Z = 2 |
Bruker APEXII CCD diffractometer | 2297 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.015 |
Graphite monochromator | θmax = 26.4°, θmin = 3.4° |
ω and ϕ scans | h = −9→9 |
4954 measured reflections | k = −12→6 |
2355 independent reflections | l = −12→13 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.028 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.080 | w = 1/[σ2(Fo2) + (0.0528P)2 + 0.0821P] where P = (Fo2 + 2Fc2)/3 |
S = 1.08 | (Δ/σ)max = 0.001 |
2355 reflections | Δρmax = 0.24 e Å−3 |
193 parameters | Δρmin = −0.22 e Å−3 |
1 restraint | Absolute structure: Flack & Bernardinelli (2000), 614 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.02 (5) |
C16H23Cl2NO | V = 803.25 (13) Å3 |
Mr = 316.25 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 7.7570 (7) Å | µ = 0.40 mm−1 |
b = 9.7041 (9) Å | T = 298 K |
c = 10.6901 (10) Å | 0.41 × 0.33 × 0.26 mm |
β = 93.432 (3)° |
Bruker APEXII CCD diffractometer | 2297 reflections with I > 2σ(I) |
4954 measured reflections | Rint = 0.015 |
2355 independent reflections |
R[F2 > 2σ(F2)] = 0.028 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.080 | Δρmax = 0.24 e Å−3 |
S = 1.08 | Δρmin = −0.22 e Å−3 |
2355 reflections | Absolute structure: Flack & Bernardinelli (2000), 614 Friedel pairs |
193 parameters | Absolute structure parameter: −0.02 (5) |
1 restraint |
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. |
x | y | z | Uiso*/Ueq | ||
H2 | 1.000 (3) | −0.257 (3) | 0.553 (2) | 0.042 (6)* | |
H1 | 0.933 (3) | −0.125 (4) | 0.502 (3) | 0.050 (7)* | |
Cl1 | 0.88492 (8) | 0.36063 (7) | 0.85606 (7) | 0.06081 (18) | |
Cl2 | 0.79425 (7) | 0.12962 (6) | 1.00496 (4) | 0.05055 (16) | |
C9 | 0.7491 (2) | −0.0408 (2) | 0.66044 (16) | 0.0293 (4) | |
O1 | 0.8629 (2) | 0.07077 (17) | 0.48287 (13) | 0.0448 (4) | |
C8 | 0.6205 (2) | 0.0004 (2) | 0.75543 (15) | 0.0274 (4) | |
H8 | 0.6565 | −0.0383 | 0.8375 | 0.033* | |
C1 | 0.6443 (2) | 0.15793 (19) | 0.75843 (15) | 0.0297 (4) | |
C12 | 0.8402 (2) | −0.16350 (19) | 0.65295 (17) | 0.0321 (4) | |
C10 | 0.7797 (2) | 0.0713 (2) | 0.57971 (17) | 0.0333 (4) | |
N1 | 0.9341 (3) | −0.1878 (2) | 0.5548 (2) | 0.0444 (4) | |
C7 | 0.4310 (2) | −0.0475 (2) | 0.71640 (17) | 0.0357 (4) | |
C3 | 0.5434 (3) | 0.2575 (2) | 0.83808 (17) | 0.0362 (4) | |
C2 | 0.7312 (2) | 0.2285 (2) | 0.87178 (18) | 0.0363 (4) | |
C4 | 0.4090 (3) | 0.2029 (3) | 0.9238 (2) | 0.0462 (5) | |
H4A | 0.4656 | 0.1417 | 0.9852 | 0.055* | |
H4B | 0.3620 | 0.2797 | 0.9688 | 0.055* | |
C16 | 0.4318 (3) | −0.2036 (3) | 0.6976 (2) | 0.0451 (5) | |
H16A | 0.5082 | −0.2267 | 0.6333 | 0.068* | |
H16B | 0.3171 | −0.2344 | 0.6731 | 0.068* | |
H16C | 0.4707 | −0.2478 | 0.7745 | 0.068* | |
C11 | 0.7012 (3) | 0.2010 (2) | 0.62976 (17) | 0.0386 (5) | |
H11A | 0.6033 | 0.2311 | 0.5759 | 0.046* | |
H11B | 0.7855 | 0.2747 | 0.6371 | 0.046* | |
C14 | 0.4943 (4) | 0.3966 (3) | 0.7812 (2) | 0.0543 (6) | |
H14A | 0.5823 | 0.4261 | 0.7276 | 0.082* | |
H14B | 0.4834 | 0.4629 | 0.8469 | 0.082* | |
H14C | 0.3863 | 0.3887 | 0.7330 | 0.082* | |
C5 | 0.2612 (3) | 0.1259 (3) | 0.8557 (2) | 0.0551 (6) | |
H5A | 0.2260 | 0.1757 | 0.7798 | 0.066* | |
H5B | 0.1637 | 0.1242 | 0.9084 | 0.066* | |
C6 | 0.3060 (3) | −0.0212 (3) | 0.8212 (2) | 0.0491 (5) | |
H6A | 0.1986 | −0.0681 | 0.7975 | 0.059* | |
H6B | 0.3545 | −0.0657 | 0.8966 | 0.059* | |
C15 | 0.3604 (3) | 0.0199 (3) | 0.5944 (2) | 0.0512 (6) | |
H15A | 0.3540 | 0.1178 | 0.6058 | 0.077* | |
H15B | 0.2472 | −0.0157 | 0.5721 | 0.077* | |
H15C | 0.4358 | −0.0003 | 0.5287 | 0.077* | |
C13 | 0.8492 (3) | −0.2716 (3) | 0.7522 (2) | 0.0488 (5) | |
H13A | 0.9673 | −0.2981 | 0.7700 | 0.073* | |
H13B | 0.7832 | −0.3504 | 0.7236 | 0.073* | |
H13C | 0.8028 | −0.2358 | 0.8268 | 0.073* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.0562 (3) | 0.0361 (3) | 0.0907 (4) | −0.0136 (3) | 0.0093 (3) | −0.0118 (3) |
Cl2 | 0.0568 (3) | 0.0510 (3) | 0.0424 (2) | 0.0037 (3) | −0.0094 (2) | −0.0038 (2) |
C9 | 0.0310 (8) | 0.0247 (9) | 0.0331 (8) | −0.0017 (7) | 0.0087 (6) | −0.0004 (7) |
O1 | 0.0579 (9) | 0.0357 (8) | 0.0439 (7) | −0.0015 (7) | 0.0276 (6) | 0.0035 (6) |
C8 | 0.0315 (8) | 0.0246 (9) | 0.0266 (7) | −0.0005 (7) | 0.0060 (6) | 0.0011 (6) |
C1 | 0.0335 (8) | 0.0239 (10) | 0.0326 (8) | 0.0028 (7) | 0.0085 (6) | 0.0003 (7) |
C12 | 0.0317 (8) | 0.0242 (11) | 0.0406 (9) | −0.0021 (7) | 0.0043 (7) | −0.0033 (7) |
C10 | 0.0380 (9) | 0.0274 (10) | 0.0354 (8) | −0.0023 (8) | 0.0103 (7) | 0.0017 (7) |
N1 | 0.0467 (10) | 0.0312 (10) | 0.0571 (11) | 0.0074 (9) | 0.0187 (8) | −0.0038 (10) |
C7 | 0.0328 (9) | 0.0380 (11) | 0.0365 (9) | −0.0049 (8) | 0.0048 (7) | −0.0009 (8) |
C3 | 0.0429 (10) | 0.0292 (10) | 0.0372 (9) | 0.0069 (8) | 0.0097 (7) | −0.0042 (8) |
C2 | 0.0410 (10) | 0.0262 (10) | 0.0419 (9) | −0.0012 (8) | 0.0055 (8) | −0.0051 (8) |
C4 | 0.0469 (11) | 0.0492 (14) | 0.0444 (10) | 0.0094 (10) | 0.0175 (8) | −0.0066 (10) |
C16 | 0.0449 (11) | 0.0412 (13) | 0.0493 (11) | −0.0131 (10) | 0.0039 (9) | −0.0024 (10) |
C11 | 0.0546 (12) | 0.0245 (10) | 0.0382 (9) | 0.0020 (8) | 0.0159 (8) | 0.0049 (8) |
C14 | 0.0698 (15) | 0.0353 (13) | 0.0589 (13) | 0.0194 (11) | 0.0119 (11) | −0.0001 (11) |
C5 | 0.0365 (10) | 0.0652 (17) | 0.0656 (12) | 0.0064 (12) | 0.0196 (9) | −0.0057 (14) |
C6 | 0.0361 (10) | 0.0549 (15) | 0.0579 (12) | −0.0084 (10) | 0.0156 (9) | −0.0035 (11) |
C15 | 0.0459 (12) | 0.0577 (16) | 0.0484 (11) | 0.0006 (11) | −0.0093 (9) | 0.0019 (11) |
C13 | 0.0531 (12) | 0.0324 (12) | 0.0613 (12) | 0.0075 (10) | 0.0052 (10) | 0.0115 (10) |
Cl1—C2 | 1.766 (2) | C4—C5 | 1.517 (4) |
Cl2—C2 | 1.762 (2) | C4—H4A | 0.9700 |
C9—C12 | 1.389 (3) | C4—H4B | 0.9700 |
C9—C10 | 1.418 (3) | C16—H16A | 0.9600 |
C9—C8 | 1.519 (2) | C16—H16B | 0.9600 |
O1—C10 | 1.253 (2) | C16—H16C | 0.9600 |
C8—C1 | 1.539 (3) | C11—H11A | 0.9700 |
C8—C7 | 1.574 (2) | C11—H11B | 0.9700 |
C8—H8 | 0.9800 | C14—H14A | 0.9600 |
C1—C2 | 1.515 (3) | C14—H14B | 0.9600 |
C1—C11 | 1.528 (2) | C14—H14C | 0.9600 |
C1—C3 | 1.533 (2) | C5—C6 | 1.519 (4) |
C12—N1 | 1.334 (3) | C5—H5A | 0.9700 |
C12—C13 | 1.490 (3) | C5—H5B | 0.9700 |
C10—C11 | 1.509 (3) | C6—H6A | 0.9700 |
N1—H2 | 0.84 (3) | C6—H6B | 0.9700 |
N1—H1 | 0.83 (3) | C15—H15A | 0.9600 |
C7—C16 | 1.528 (3) | C15—H15B | 0.9600 |
C7—C15 | 1.531 (3) | C15—H15C | 0.9600 |
C7—C6 | 1.546 (3) | C13—H13A | 0.9600 |
C3—C2 | 1.506 (3) | C13—H13B | 0.9600 |
C3—C14 | 1.520 (3) | C13—H13C | 0.9600 |
C3—C4 | 1.524 (3) | ||
C12—C9—C10 | 121.23 (16) | C5—C4—H4B | 108.7 |
C12—C9—C8 | 128.39 (17) | C3—C4—H4B | 108.7 |
C10—C9—C8 | 110.19 (16) | H4A—C4—H4B | 107.6 |
C9—C8—C1 | 101.12 (14) | C7—C16—H16A | 109.5 |
C9—C8—C7 | 112.64 (14) | C7—C16—H16B | 109.5 |
C1—C8—C7 | 114.08 (16) | H16A—C16—H16B | 109.5 |
C9—C8—H8 | 109.6 | C7—C16—H16C | 109.5 |
C1—C8—H8 | 109.6 | H16A—C16—H16C | 109.5 |
C7—C8—H8 | 109.6 | H16B—C16—H16C | 109.5 |
C2—C1—C11 | 117.28 (17) | C10—C11—C1 | 103.64 (15) |
C2—C1—C3 | 59.21 (12) | C10—C11—H11A | 111.0 |
C11—C1—C3 | 120.82 (16) | C1—C11—H11A | 111.0 |
C2—C1—C8 | 120.85 (16) | C10—C11—H11B | 111.0 |
C11—C1—C8 | 107.05 (14) | C1—C11—H11B | 111.0 |
C3—C1—C8 | 124.93 (16) | H11A—C11—H11B | 109.0 |
N1—C12—C9 | 120.03 (19) | C3—C14—H14A | 109.5 |
N1—C12—C13 | 115.56 (19) | C3—C14—H14B | 109.5 |
C9—C12—C13 | 124.34 (17) | H14A—C14—H14B | 109.5 |
O1—C10—C9 | 127.82 (19) | C3—C14—H14C | 109.5 |
O1—C10—C11 | 122.38 (17) | H14A—C14—H14C | 109.5 |
C9—C10—C11 | 109.76 (15) | H14B—C14—H14C | 109.5 |
C12—N1—H2 | 120.9 (16) | C4—C5—C6 | 113.71 (19) |
C12—N1—H1 | 115.2 (19) | C4—C5—H5A | 108.8 |
H2—N1—H1 | 123 (2) | C6—C5—H5A | 108.8 |
C16—C7—C15 | 108.37 (18) | C4—C5—H5B | 108.8 |
C16—C7—C6 | 105.49 (18) | C6—C5—H5B | 108.8 |
C15—C7—C6 | 109.80 (18) | H5A—C5—H5B | 107.7 |
C16—C7—C8 | 108.48 (17) | C5—C6—C7 | 119.6 (2) |
C15—C7—C8 | 112.35 (17) | C5—C6—H6A | 107.4 |
C6—C7—C8 | 112.04 (16) | C7—C6—H6A | 107.4 |
C2—C3—C14 | 118.5 (2) | C5—C6—H6B | 107.4 |
C2—C3—C4 | 118.56 (17) | C7—C6—H6B | 107.4 |
C14—C3—C4 | 112.69 (18) | H6A—C6—H6B | 107.0 |
C2—C3—C1 | 59.77 (12) | C7—C15—H15A | 109.5 |
C14—C3—C1 | 117.47 (17) | C7—C15—H15B | 109.5 |
C4—C3—C1 | 120.35 (18) | H15A—C15—H15B | 109.5 |
C3—C2—C1 | 61.01 (12) | C7—C15—H15C | 109.5 |
C3—C2—Cl2 | 120.86 (14) | H15A—C15—H15C | 109.5 |
C1—C2—Cl2 | 119.26 (15) | H15B—C15—H15C | 109.5 |
C3—C2—Cl1 | 119.40 (16) | C12—C13—H13A | 109.5 |
C1—C2—Cl1 | 121.53 (14) | C12—C13—H13B | 109.5 |
Cl2—C2—Cl1 | 108.41 (11) | H13A—C13—H13B | 109.5 |
C5—C4—C3 | 114.04 (18) | C12—C13—H13C | 109.5 |
C5—C4—H4A | 108.7 | H13A—C13—H13C | 109.5 |
C3—C4—H4A | 108.7 | H13B—C13—H13C | 109.5 |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H2···O1i | 0.85 (3) | 2.03 (3) | 2.865 (3) | 170 (2) |
N1—H1···O1 | 0.83 (4) | 1.98 (4) | 2.672 (3) | 140 (3) |
Symmetry code: (i) −x+2, y−1/2, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C16H23Cl2NO |
Mr | 316.25 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 298 |
a, b, c (Å) | 7.7570 (7), 9.7041 (9), 10.6901 (10) |
β (°) | 93.432 (3) |
V (Å3) | 803.25 (13) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.40 |
Crystal size (mm) | 0.41 × 0.33 × 0.26 |
Data collection | |
Diffractometer | Bruker APEXII CCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4954, 2355, 2297 |
Rint | 0.015 |
(sin θ/λ)max (Å−1) | 0.625 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.080, 1.08 |
No. of reflections | 2355 |
No. of parameters | 193 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.24, −0.22 |
Absolute structure | Flack & Bernardinelli (2000), 614 Friedel pairs |
Absolute structure parameter | −0.02 (5) |
Computer programs: APEX2 (Bruker, 2009), SAINT-Plus (Bruker, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2009), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H2···O1i | 0.85 (3) | 2.03 (3) | 2.865 (3) | 170 (2) |
N1—H1···O1 | 0.83 (4) | 1.98 (4) | 2.672 (3) | 140 (3) |
Symmetry code: (i) −x+2, y−1/2, −z+1. |
Acknowledgements
We thank the National Center of Scientific and Technological Research (CNRST) which supports our scientific research.
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The essential oil of the Alas cedar (Cedrus atlantica) consist mainly (50%) of a bicyclic hydrocarbon called β-himachalene (Joseph & Dev (1968); Plattier & Teisseire(1974)). The reactivity of this sesquiterpene and its derivatives has been studied extensively by our team in order to prepare new products having biological proprieties (Lassaba et al., 1998; Chekroun et al., 2000; El Jamili et al., 2002; Dakir et al., 2004). Indeed, these compounds were tested, using the food poisoning technique, for their potential antifungal activity against phytopathogen Botrytis cinerea (Daoubi et al., 2004). Thus the action of one equivalent of dichlorocarbene, generated in situ from chloroform in the presence of sodium hydroxide as base and n-benzyltriethylammonium chloride as catalyst, on β-himachalene produces only (1S,3R,8R)-2,2-dichloro-3,7,7,10- tetramethyltricyclo[6.4.0.01,3] dodec-9-ene (El Jamili et al., 2002). Treatment of the latter by two equivalents of N-bromosccinimide (NBS) give (1S, 3R, 8R, 11R)-2,2-dichloro-3,7,7,10-tetralethyltricyclo[6.4.0.01,3] dodec-9-en-11-one(Dakir et al., 2004). This enone was treated with the sodium azide in trifluoroacetic acide medium, give with a yield (60%) (1S, 3R, 8R) -9-(1-aminoethylidene)-2,2-dichloro-3,7,7- trimethyltricyclo[6.3.0.01,3]undecan -10-one. The structure of this new product was determined by NMR spectral analysis of 1H, 13 C and mass spectroscopy and confirmed by its single-crystal X-ray structure. The molecule is built up from two fused five-membered and seven-membered rings (Fig. 1). The five-membered ring adopts a twisted conformation,as indicated by Cremer & Pople (1975) puckering parameters Q = 0.2822 (2) Å and ϕ = 199.2 (4)°. The seven-membered ring displays a chair conformation with QT = 0.7470 (2) Å, θ2 = 27.72 (2)°, ϕ2 = -51.85 (14)° and ϕ3 =-78.15 (2)°. In the crystal structure, molecules are linked into chains (Fig. 2) running along the b axis by intermolecular N—H···O hydrogen bonds (Table 1) involving the O1 and N atoms. Owing to the presence of Cl atoms, the absolute configuration could be fully confirmed, by refining the Flack parameter (Flack & Bernardinelli (2000)) as C1(S), C3(R)and C8(R).