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Acta Crystallogr Sect E Struct Rep Online. 2010 November 1; 66(Pt 11): o2850.
Published online 2010 October 20. doi:  10.1107/S1600536810040699
PMCID: PMC3009175

(4S)-(−)-4-Benzyl-2,2-dimethyl-3-o-toluoyl-1,3-oxazolidine

Abstract

The absolute configuration of the title compound, C20H23NO2, has been confirmed as 4S. The benzyl residue and H atom at the asymmetric C-atom centre occupy pseudo-axial and bis­ectional positions, respectively. The oxazolidine ring adopts an envelope conformation. In the crystal structure, the mol­ecular packing is stabilized by non-classical C—H(...)O hydrogen bonds.

Related literature

For details of the synthesis, see: Chrzanowska & Dreas (2004 [triangle]); Chrzanowska et al. (2005 [triangle]). For bond-length data, see: Allen et al. (1987 [triangle]). For a description of the Cambridge Structural Database, see: Allen (2002 [triangle]). For ring puckering parameters, see: Cremer & Pople (1975 [triangle]).

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Object name is e-66-o2850-scheme1.jpg

Experimental

Crystal data

  • C20H23NO2
  • M r = 309.39
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-66-o2850-efi2.jpg
  • a = 10.9951 (2) Å
  • b = 17.2768 (3) Å
  • c = 9.1899 (2) Å
  • V = 1745.71 (6) Å3
  • Z = 4
  • Cu Kα radiation
  • μ = 0.59 mm−1
  • T = 130 K
  • 0.30 × 0.20 × 0.09 mm

Data collection

  • Oxford Diffraction SuperNova Single source at offset Atlas diffractometer
  • Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009 [triangle]) T min = 0.882, T max = 1.000
  • 9043 measured reflections
  • 3332 independent reflections
  • 3315 reflections with I > 2σ(I)
  • R int = 0.013

Refinement

  • R[F 2 > 2σ(F 2)] = 0.027
  • wR(F 2) = 0.073
  • S = 1.05
  • 3332 reflections
  • 211 parameters
  • H-atom parameters constrained
  • Δρmax = 0.14 e Å−3
  • Δρmin = −0.13 e Å−3
  • Absolute structure: Flack (1983 [triangle]), 1301 Friedel pairs
  • Flack parameter: 0.11 (16)

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 [triangle]); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 [triangle]); software used to prepare material for publication: WinGX (Farrugia, 1999 [triangle]) and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810040699/bt5373sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810040699/bt5373Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

(4S)-2,2-Dimethyl-3-o-toluoyl-4-benzyloxazolidine has been succesfully used as a building block and chiral auxiliary in the asymmetric synthesis of (S)-(-)-O-methylbharatamine, a protoberberine derivative. The key step of the synthesis, in which a new stereogenic centre was created, involved the addition of latherally lithiated chiral o-toluamide to imine. This addition proceeded stereoselectively for cyclic imine as well as acyclic imine (Chrzanowska & Dreas, 2004); Chrzanowska et al., 2005). The title chiral o-toluamide was obtained from commercially available o-toluoyl chloride and (S)-phenylalaninol, followed by protection of functional NH and OH groups in the form of oxazolidine derivative. In order to obtain confirmation of the absolute configuration of the title compound, a single X-ray diffraction study has been undertaken.

The results obtained for the title compound confirm the absolute 4S configuration (Fig. 1). The benzyl residue and H atom at the stereogenic C4 centre occupy a pseudo-axial and bisectional positions, respectively, as seen in the angles of the C4—C17 and C4—H4 bond vectors to the Cremer & Pople oxazolidine ring plane normal of 16.52 (7)° and 53.11 (4)° (Cremer & Pople, 1975).

The mutual arrangement of the benzyl and oxazolidine systems is described by the torsion angles C18—C17—C4—N3 177.06 (8)° and C18—C17—C4—C5 66.22 (11)° indicating an antiperiplanar and synclinal conformation of the C18 atom in the phenyl group with respect to the N3 and C5 atom of the oxazolidine ring, respectively. Furthermore, the dihedral angle made by the mean planes of the above mentioned six- and five-membered systems amounts to 49.66 (4)°.

In the solid state, the oxazolidine ring has an envelope conformation [puckering parameters (Cremer & Pople, 1975) Q = 0.379 (1) Å and [var phi] = 330.13 (16)°], with atom C5 deviating from the planar system defined by the other four atoms by 0.5776 (15) Å.

The C=O group of the amide group is synperiplanar with respect to the C2—N3 bond [the torsion angle O9—C8—N3—C2: 3.59 (15)°]. We assume that this atom arrangement is stabilized by the three-centre intramolecular C6—H6B···O9···H7B—C7 hydrogen bond (Fig. 1, Table 1). The nearly planar tertiary amide group (C2/N3/C4/C8/O9, r.m.s. = 0.010) and the benzene ring (C10—C15) are not conjugated, the dihedral angle between their mean planes being 88.60 (3)°. Simultaneously, the C8—C10 bond distance of 1.5060 (14) Å is comparable with the normal length of the unconjugated (N—)C(=O)—Car bond of 1.500 (5) Å (Allen et al., 1987). The C8–N3 bond distance of 1.3460 (13) Å is the same as the normal C—N tertiary amide distance [1.346 (5) Å; Allen et al., 1987].

The internal bond lengths and angles in 2,2-dimethyloxazolidine ring are close to those observed in other dimethyloxazolidine derivatives denoted by the following refcodes EBETUA, PIBSAV, VUMMOF, VUMNEW, WAVPUE (CSD Cambridge, version 5.31, Allen, 2002; R≤ 0.050).

The molecular packing in the crystal lattice is stabilized by possible C4—H4···O9i non-classical intermolecular hydrogen bonds which links molecules into chains parallel to the b axis. (Fig. 2, Table 1).

Experimental

(4S)-2,2-Dimethyl-3-o-toluoyl-4-benzyloxazolidine has been synthesized from o-toluoyl chloride and (S)-phenylalaninol, according to literature procedure of Chrzanowska and Dreas (2004). Crystals were obtained after crystallization from diethyl ether, mp. 361—363 K, [α]D = -36.35 [c 1.0, CHCl3].

Refinement

All H atoms were positioned geometrically and were refined in a riding-model approximation with Uiso constrained to be 1.2 (1.5 for methyl groups) times Ueq of the parent atom. The methyl H atoms were refined as rigid groups, which were allowed to rotate. The range of C—H distances was 0.93–0.98 Å. The absolute configuration of the title compound was established by refinement of the Flack (1983) parameter. The rather large s.u. of the Flack parameter is due to the small contribution of atoms with measurable anomalous dispersion effects; refinement of the inverse structure leads to a value close to 1 [x = 0.89 (16)], which provides additional proof of the correct assignment of the absolute configuration.

Figures

Fig. 1.
The molecular structure of (I), showing the atomic labelling scheme. Non-H atoms are drawn as 30% probability displacement ellipsoids; H atoms are shown as small spheres of arbitrary radius.
Fig. 2.
The hydrogen bonding in the crystal structure of (I). Dotted lines indicate hydrogen bonds. Symmetry code: (i) -1/2 + x, 1.5 - y, 1 - z. The H atoms not involved in hydrogen bonds have been omitted for clarity.

Crystal data

C20H23NO2Dx = 1.177 Mg m3
Mr = 309.39Melting point = 361–363 K
Orthorhombic, P21212Cu Kα radiation, λ = 1.54184 Å
Hall symbol: P 2 2abCell parameters from 8954 reflections
a = 10.9951 (2) Åθ = 2.6–75.3°
b = 17.2768 (3) ŵ = 0.59 mm1
c = 9.1899 (2) ÅT = 130 K
V = 1745.71 (6) Å3Prism, colourless
Z = 40.30 × 0.20 × 0.09 mm
F(000) = 664

Data collection

Oxford Diffraction SuperNova Single source at offset Atlas diffractometer3332 independent reflections
Radiation source: SuperNova (Cu) X-ray Source3315 reflections with I > 2σ(I)
mirrorRint = 0.013
Detector resolution: 5.2679 pixels mm-1θmax = 75.5°, θmin = 4.8°
ω scansh = −9→13
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)k = −21→21
Tmin = 0.882, Tmax = 1.000l = −11→11
9043 measured reflections

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.027H-atom parameters constrained
wR(F2) = 0.073w = 1/[σ2(Fo2) + (0.0438P)2 + 0.2282P] where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max = 0.001
3332 reflectionsΔρmax = 0.14 e Å3
211 parametersΔρmin = −0.13 e Å3
0 restraintsAbsolute structure: Flack (1983), 1301 Friedel pairs
Primary atom site location: structure-invariant direct methodsFlack parameter: 0.11 (16)

Special details

Experimental. Absorption correction: CrysAlis Pro (Oxford Diffraction, 2009); Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.
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)

xyzUiso*/Ueq
O10.44508 (7)0.78744 (5)0.89260 (8)0.03235 (18)
C20.54700 (10)0.81054 (6)0.80707 (11)0.0279 (2)
N30.54307 (8)0.75492 (5)0.68336 (9)0.02318 (18)
C40.43450 (9)0.70515 (6)0.69370 (11)0.0233 (2)
H40.39500.69970.59860.028*
C50.35771 (10)0.75411 (6)0.79567 (12)0.0289 (2)
H5A0.31420.79390.74260.035*
H5B0.29960.72240.84820.035*
C60.65962 (11)0.80040 (7)0.90053 (13)0.0381 (3)
H6A0.65160.83070.98760.057*
H6B0.72990.81730.84730.057*
H6C0.66870.74680.92590.057*
C70.53116 (12)0.89341 (7)0.75407 (14)0.0384 (3)
H7A0.45630.89770.70100.058*
H7B0.59790.90700.69170.058*
H7C0.52930.92780.83610.058*
C80.62546 (9)0.75504 (6)0.57504 (11)0.0249 (2)
O90.71397 (7)0.79867 (5)0.57306 (9)0.03526 (19)
C100.60464 (9)0.69888 (6)0.45222 (11)0.0259 (2)
C110.53690 (10)0.72128 (6)0.33042 (11)0.0280 (2)
C120.52701 (11)0.66930 (7)0.21500 (12)0.0351 (3)
H120.48310.68330.13270.042*
C130.58144 (11)0.59718 (8)0.22089 (15)0.0399 (3)
H130.57330.56320.14300.048*
C140.64789 (12)0.57531 (7)0.34174 (14)0.0385 (3)
H140.68420.52670.34550.046*
C150.65998 (10)0.62643 (6)0.45739 (13)0.0318 (2)
H150.70520.61220.53860.038*
C160.47766 (11)0.79954 (7)0.32189 (13)0.0365 (3)
H16A0.43680.80480.23010.055*
H16B0.53860.83910.33070.055*
H16C0.41970.80480.39940.055*
C170.46564 (9)0.62539 (6)0.75855 (12)0.0273 (2)
H17A0.52330.59960.69510.033*
H17B0.50460.63280.85220.033*
C180.35598 (10)0.57400 (6)0.77822 (12)0.0260 (2)
C190.27740 (11)0.55825 (7)0.66370 (13)0.0346 (3)
H190.29170.58000.57270.042*
C200.17747 (12)0.51009 (7)0.68425 (16)0.0432 (3)
H200.12520.50030.60690.052*
C210.15498 (11)0.47678 (6)0.81733 (17)0.0428 (3)
H210.08850.44420.82980.051*
C220.23189 (11)0.49212 (7)0.93230 (16)0.0413 (3)
H220.21740.46981.02270.050*
C230.33108 (10)0.54099 (6)0.91312 (13)0.0331 (2)
H230.38160.55180.99170.040*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0323 (4)0.0396 (4)0.0251 (4)0.0008 (3)0.0023 (3)−0.0044 (3)
C20.0275 (5)0.0295 (5)0.0267 (5)−0.0001 (4)−0.0019 (4)−0.0035 (4)
N30.0208 (4)0.0241 (4)0.0246 (4)−0.0013 (3)−0.0005 (3)0.0001 (3)
C40.0186 (5)0.0263 (5)0.0249 (4)−0.0017 (4)−0.0005 (4)0.0020 (4)
C50.0232 (5)0.0333 (5)0.0301 (5)0.0017 (4)0.0027 (4)0.0000 (4)
C60.0360 (6)0.0437 (6)0.0346 (6)−0.0030 (5)−0.0113 (5)−0.0059 (5)
C70.0435 (7)0.0281 (5)0.0437 (6)0.0016 (5)−0.0014 (6)−0.0028 (5)
C80.0214 (5)0.0265 (4)0.0267 (5)0.0005 (4)−0.0007 (4)0.0044 (4)
O90.0286 (4)0.0387 (4)0.0385 (4)−0.0101 (3)0.0048 (3)−0.0005 (4)
C100.0216 (5)0.0292 (5)0.0267 (5)−0.0013 (4)0.0054 (4)0.0018 (4)
C110.0235 (5)0.0316 (5)0.0287 (5)−0.0025 (4)0.0028 (4)0.0025 (4)
C120.0305 (6)0.0446 (6)0.0302 (5)−0.0032 (5)−0.0006 (5)−0.0029 (5)
C130.0387 (7)0.0406 (6)0.0405 (7)−0.0029 (5)0.0039 (5)−0.0132 (5)
C140.0374 (6)0.0311 (5)0.0471 (7)0.0041 (5)0.0071 (6)−0.0036 (5)
C150.0295 (5)0.0319 (5)0.0340 (6)0.0040 (5)0.0036 (4)0.0030 (4)
C160.0356 (6)0.0368 (6)0.0372 (6)0.0035 (5)−0.0058 (5)0.0040 (5)
C170.0218 (5)0.0286 (5)0.0313 (5)0.0000 (4)−0.0004 (4)0.0047 (4)
C180.0220 (5)0.0220 (4)0.0341 (5)0.0027 (4)0.0012 (4)−0.0007 (4)
C190.0346 (6)0.0323 (5)0.0370 (6)−0.0013 (4)−0.0036 (5)−0.0028 (5)
C200.0326 (6)0.0342 (6)0.0627 (8)−0.0016 (5)−0.0125 (6)−0.0102 (6)
C210.0258 (5)0.0251 (5)0.0774 (9)−0.0036 (4)0.0050 (6)−0.0030 (5)
C220.0361 (6)0.0337 (6)0.0542 (7)−0.0049 (5)0.0087 (6)0.0100 (6)
C230.0298 (6)0.0315 (5)0.0379 (6)−0.0022 (5)−0.0004 (5)0.0071 (5)

Geometric parameters (Å, °)

O1—C21.4258 (13)C12—C131.3834 (18)
O1—C51.4311 (13)C12—H120.9300
C2—N31.4892 (13)C13—C141.3820 (18)
C2—C61.5172 (15)C13—H130.9300
C2—C71.5224 (15)C14—C151.3882 (17)
N3—C81.3460 (13)C14—H140.9300
N3—C41.4742 (12)C15—H150.9300
C4—C51.5187 (14)C16—H16A0.9600
C4—C171.5398 (14)C16—H16B0.9600
C4—H40.9800C16—H16C0.9600
C5—H5A0.9700C17—C181.5082 (14)
C5—H5B0.9700C17—H17A0.9700
C6—H6A0.9600C17—H17B0.9700
C6—H6B0.9600C18—C191.3886 (16)
C6—H6C0.9600C18—C231.3918 (15)
C7—H7A0.9600C19—C201.3911 (17)
C7—H7B0.9600C19—H190.9300
C7—H7C0.9600C20—C211.374 (2)
C8—O91.2310 (12)C20—H200.9300
C8—C101.5060 (14)C21—C221.379 (2)
C10—C151.3926 (15)C21—H210.9300
C10—C111.3990 (15)C22—C231.3905 (16)
C11—C121.3940 (16)C22—H220.9300
C11—C161.5029 (16)C23—H230.9300
C2—O1—C5107.28 (7)C13—C12—C11121.11 (11)
O1—C2—N3102.56 (8)C13—C12—H12119.4
O1—C2—C6107.28 (9)C11—C12—H12119.4
N3—C2—C6112.42 (9)C14—C13—C12120.42 (11)
O1—C2—C7110.47 (10)C14—C13—H13119.8
N3—C2—C7111.06 (9)C12—C13—H13119.8
C6—C2—C7112.53 (10)C13—C14—C15119.47 (11)
C8—N3—C4126.41 (8)C13—C14—H14120.3
C8—N3—C2122.96 (8)C15—C14—H14120.3
C4—N3—C2110.53 (8)C14—C15—C10120.25 (11)
N3—C4—C599.50 (8)C14—C15—H15119.9
N3—C4—C17111.52 (8)C10—C15—H15119.9
C5—C4—C17112.53 (9)C11—C16—H16A109.5
N3—C4—H4110.9C11—C16—H16B109.5
C5—C4—H4110.9H16A—C16—H16B109.5
C17—C4—H4110.9C11—C16—H16C109.5
O1—C5—C4103.59 (8)H16A—C16—H16C109.5
O1—C5—H5A111.0H16B—C16—H16C109.5
C4—C5—H5A111.0C18—C17—C4113.29 (8)
O1—C5—H5B111.0C18—C17—H17A108.9
C4—C5—H5B111.0C4—C17—H17A108.9
H5A—C5—H5B109.0C18—C17—H17B108.9
C2—C6—H6A109.5C4—C17—H17B108.9
C2—C6—H6B109.5H17A—C17—H17B107.7
H6A—C6—H6B109.5C19—C18—C23118.19 (10)
C2—C6—H6C109.5C19—C18—C17121.46 (10)
H6A—C6—H6C109.5C23—C18—C17120.35 (10)
H6B—C6—H6C109.5C18—C19—C20120.38 (12)
C2—C7—H7A109.5C18—C19—H19119.8
C2—C7—H7B109.5C20—C19—H19119.8
H7A—C7—H7B109.5C21—C20—C19120.90 (12)
C2—C7—H7C109.5C21—C20—H20119.6
H7A—C7—H7C109.5C19—C20—H20119.6
H7B—C7—H7C109.5C20—C21—C22119.41 (11)
O9—C8—N3122.95 (10)C20—C21—H21120.3
O9—C8—C10120.24 (9)C22—C21—H21120.3
N3—C8—C10116.81 (8)C21—C22—C23120.03 (12)
C15—C10—C11120.57 (10)C21—C22—H22120.0
C15—C10—C8119.15 (9)C23—C22—H22120.0
C11—C10—C8120.15 (9)C22—C23—C18121.07 (11)
C12—C11—C10118.17 (10)C22—C23—H23119.5
C12—C11—C16120.40 (10)C18—C23—H23119.5
C10—C11—C16121.42 (10)
C5—O1—C2—N3−28.52 (10)C15—C10—C11—C12−0.25 (15)
C5—O1—C2—C6−147.11 (9)C8—C10—C11—C12175.64 (9)
C5—O1—C2—C789.91 (10)C15—C10—C11—C16−179.28 (10)
O1—C2—N3—C8−179.07 (9)C8—C10—C11—C16−3.39 (15)
C6—C2—N3—C8−64.17 (13)C10—C11—C12—C130.67 (16)
C7—C2—N3—C862.91 (13)C16—C11—C12—C13179.71 (11)
O1—C2—N3—C44.37 (10)C11—C12—C13—C14−0.47 (18)
C6—C2—N3—C4119.27 (10)C12—C13—C14—C15−0.17 (19)
C7—C2—N3—C4−113.65 (10)C13—C14—C15—C100.58 (18)
C8—N3—C4—C5−157.19 (9)C11—C10—C15—C14−0.37 (16)
C2—N3—C4—C519.22 (10)C8—C10—C15—C14−176.31 (10)
C8—N3—C4—C1783.88 (12)N3—C4—C17—C18177.06 (8)
C2—N3—C4—C17−99.71 (9)C5—C4—C17—C1866.22 (11)
C2—O1—C5—C441.88 (10)C4—C17—C18—C1953.80 (13)
N3—C4—C5—O1−35.86 (9)C4—C17—C18—C23−126.17 (10)
C17—C4—C5—O182.31 (10)C23—C18—C19—C20−0.61 (16)
C4—N3—C8—O9179.58 (9)C17—C18—C19—C20179.41 (10)
C2—N3—C8—O93.59 (15)C18—C19—C20—C21−0.49 (18)
C4—N3—C8—C100.08 (14)C19—C20—C21—C220.75 (18)
C2—N3—C8—C10−175.92 (9)C20—C21—C22—C230.10 (18)
O9—C8—C10—C1586.97 (13)C21—C22—C23—C18−1.22 (18)
N3—C8—C10—C15−93.51 (11)C19—C18—C23—C221.46 (16)
O9—C8—C10—C11−88.98 (12)C17—C18—C23—C22−178.56 (10)
N3—C8—C10—C1190.54 (11)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C4—H4···O9i0.982.543.4487 (13)154
C6—H6B···O90.962.553.0683 (15)114
C7—H7B···O90.962.513.0800 (15)118

Symmetry codes: (i) x−1/2, −y+3/2, −z+1.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5373).

References

  • Allen, F. H. (2002). Acta Cryst. B58, 380–388. [PubMed]
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