(–)-(4R,5S)-4-Methyl-3-[2(R)-(4-methyl­phen­yl)propion­yl]-5-phenyl­oxazolidin-2-one

Chavda, S.; Eames, J.; Flinn, A.; Motevalli, M.; Malatesti, N.

doi:10.1107/S1600536806031825

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 62| Part 9| September 2006| Pages o4037-o4038

https://doi.org/10.1107/S1600536806031825

(–)-(4R,5S)-4-Methyl-3-[2(R)-(4-methylphenyl)propionyl]-5-phenyloxazolidin-2-one

Sameer Chavda,^a Jason Eames,^b ^* Anthony Flinn,^c Majid Motevalli ^a and Nela Malatesti ^d

^aDepartment of Chemistry, Queen Mary, University of London, Mile End Road, London E1 4NS, England, ^bDepartment of Chemistry, University of Hull, Cottingham Road, Kingston-upon-Hull HU6 7RX, England, ^cOnyx Scientific Limited, Units 97-98, Silverbriar, Sunderland Enterprise Park East, Sunderland SR5 2TQ, England, and ^dDepartment of Chemistry, J. J. Strossmayer University of Osijek, Trg Sv. Trojstva 3, Osijek 31000, Croatia
^*Correspondence e-mail: j.eames@hull.ac.uk

(Received 27 June 2006; accepted 12 August 2006; online 23 August 2006)

In the title compound, C₂₀H₂₁NO₃, formed from enantiomerically pure (+)-(4R,5S)-4-methyl-5-phenyl-2-oxazolidinone and racemic 2-(4-methylphenyl)propanoyl chloride, the two carbonyl groups are oriented anti to each other, and the methyl group of the (4-methylphenyl)propionyl substituent lies close to the mean plane of the five-membered ring.

Comment

The title compound is the third in a series of structurally related compounds, introduced in our earlier report (Coumbarides, Eames et al., 2006 ). With R¹ = 4-(CH₃)C₆H₄, the reaction shown in that report yielded the anti–syn and syn–syn diastereomers in 38 and 38% yields, respectively. The title compound, (I), is the anti–syn diastereomer (Fig. 1). In the crystal structure, the conformation of the central portion of the molecule is closely comparable with that in the previously reported derivatives (Coumbarides, Eames et al., 2006; Coumbarides, Dingjan et al., 2006 ); in the twisted five-membered ring, atoms C1 and C2 lie, respectively, 0.245 (4) Å above and −0.202 (4) Å below the plane defined by atoms O1, O2, N1 and C3. The carbonyl groups (C3=O2 and C11=O3) are oriented anti to each other, with the torsion angle O3—C11—N1—C3 = −169.3 (2)°. The orientation of the 4-(CH₃)C₆H₄ substituent resembles most closely that in the 4-(ⁱBu)C₆H₄ derivative (Coumbarides, Dingjan et al., 2006), with the C19 methyl group lying close to the mean plane of the five-membered ring [deviating by 0.138 (8) Å from it] and the torsion angle N1—C11—C12—C13 = 78.7 (3)°.

Figure 1
The molecular structure of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms have been omitted.

Experimental

The experimental procedure is comparable with that reported previously (Coumbarides, Eames et al., 2006). The actual quantities used for the preparation of (I) were: n-butyllithium (15.45 ml, 2.5 M in hexanes, 38.6 mmol) and (R,S)-oxazolidinone (4.89 g, 27.6 mmol) in 60 ml tetrahydrofuran (THF), combined with a solution of (rac)-2-(4-methylphenyl)propanoyl chloride (5.02 g, 27.6 mmol) in 10 ml THF. The crude residue was purified by flash column chromatography on silica gel, eluting with light petroleum (b.p. 313–333 K)/diethyl ether (1:1), to give a separable diastereoisomeric mixture in the ratio anti–syn:syn,syn 50:50. The anti–syn diastereomer was obtained as colourless crystals (3.39 g, 38% yield, m.p. 341–343 K, R_F 0.71 [light petroleum (b.p 313–333 K)/diethyl ether, 7:3]. Spectroscopic analysis: [α]²⁰_D = −164.5 (CHCl₃, 293 K, concentration 0.18 g per 100 ml); IR (CHCl₃, ν_max/cm⁻¹): 1779 (C=O), 1710 (C=O); ¹H NMR (270 MHz; CDCl₃): δ 7.36–7.24 (9H, m, 9 × CH; Ar and Ph), 5.46 (1H, d, J = 6.9 Hz, CHO), 5.07 (1H, q, J = 7.1 Hz, ArCH), 4.65 (1H, m, NCHCH₃), 2.31 (3H, s, CH₃; Ar), 1.46 (3H, d, J = 7.1 Hz, CH₃CH), 0.91 (3H, d, J = 6.9 Hz, CH₃CHN); ¹³C NMR (67.5 MHz; CDCl₃): δ 174.8 (NC=O), 152.9 (OC=O), 137.7, 137.1, 133.9 (3 × i-C; Ar and Ph), 129.7, 129.1, 128.3, 128.3, 126.1 (5 × CH; Ar and Ph), 79.1 (PhCHO), 55.0 (CHN), 43.6 (ArCH), 21.4 (CH₃; Ar), 19.8 (CH₃CH), 14.5 (CH₃CHN); found: MH⁺ 324.1187; C₂₀H₂₂NO₃ requires 324.1194.

Crystal data

C₂₀H₂₁NO₃
M_r = 323.38
Monoclinic, P 2₁
a = 13.066 (8) Å
b = 9.509 (8) Å
c = 7.201 (4) Å
β = 102.95 (4)°
V = 871.9 (10) Å³
Z = 2
D_x = 1.232 Mg m⁻³
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 160 (2) K
Prism, colourless
0.40 × 0.30 × 0.30 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
ω/2θ scans
Absorption correction: none
1743 measured reflections
1630 independent reflections
1417 reflections with I > 2σ(I)
R_int = 0.010
θ_max = 25.0°
2 standard reflections every 100 reflections intensity decay: 1%

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.032
wR(F²) = 0.078
S = 1.06
1630 reflections
220 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.04P)² + 0.0761P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.12 e Å⁻³
Δρ_min = −0.16 e Å⁻³

H atoms were placed in geometrically idealised positions and constrained to ride on their parent atoms, with C—H = 0.95–1.00 Å and U_iso(H) = 1.2U_eq(C) or 1.5U_eq(methyl C). The methyl groups were allowed to rotate about their local threefold axes. In the absence of significant anomalous scattering effects, the few measured Friedel pairs have been merged. The absolute configuration is assigned on the basis of the known configuration of the starting material (Coumbarides, Eames et al., 2006).

Data collection: CAD-4-PC (Enraf–Nonius, 1994 ); cell refinement: CAD-4-PC; data reduction: XCAD4 (Harms & Wocadlo, 1995 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536806031825/bi2030sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806031825/bi2030Isup2.hkl

Computing details top

Data collection: CAD-4-PC (Enraf–Nonius, 1994); cell refinement: CAD-4-PC; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

(-)-(4R,5S)-4-Methyl-3-[2(R)-(4-methylphenyl)propionyl]- 5-phenyloxazolidin-2-one top

Crystal data top

C₂₀H₂₁NO₃	F(000) = 344
M_r = 323.38	D_x = 1.232 Mg m⁻³
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 25 reflections
a = 13.066 (8) Å	θ = 9.4–12.7°
b = 9.509 (8) Å	µ = 0.08 mm⁻¹
c = 7.201 (4) Å	T = 160 K
β = 102.95 (4)°	Prism, colourless
V = 871.9 (10) Å³	0.40 × 0.30 × 0.30 mm
Z = 2

Data collection top

Enraf–Nonius CAD-4 diffractometer	R_int = 0.010
Radiation source: fine-focus sealed tube	θ_max = 25.0°, θ_min = 1.6°
Graphite monochromator	h = 0→15
ω/2θ scans	k = −2→11
1743 measured reflections	l = −8→8
1630 independent reflections	2 standard reflections every 100 reflections
1417 reflections with I > 2σ(I)	intensity decay: 1%

Refinement top

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)] = 0.032	H-atom parameters constrained
wR(F²) = 0.078	w = 1/[σ²(F_o²) + (0.04P)² + 0.0761P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max < 0.001
1630 reflections	Δρ_max = 0.12 e Å⁻³
220 parameters	Δρ_min = −0.16 e Å⁻³
1 restraint	Absolute structure: assigned on the basis of known starting material
Primary atom site location: structure-invariant direct methods

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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

1.7659 (0.0199) x + 8.7456 (0.0092) y + 2.3685 (0.0098) z = 8.8989 (0.0127)

* -0.0015 (0.0008) N1 * 0.0050 (0.0024) C3 * -0.0014 (0.0007) O1 * -0.0020 (0.0010) O2 - 0.2450 (0.0044) C1 0.2015 (0.0043) C2 - 0.1382 (0.0075) C19

Rms deviation of fitted atoms = 0.0029

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

	x	y	z	U_iso*/U_eq
C1	0.51015 (17)	0.6695 (3)	0.8013 (3)	0.0308 (5)
H1	0.4841	0.7159	0.9065	0.037*
C2	0.49740 (18)	0.7696 (3)	0.6297 (3)	0.0339 (6)
H2	0.4978	0.8686	0.6766	0.041*
C3	0.66853 (19)	0.6938 (3)	0.6989 (3)	0.0393 (6)
C4	0.4596 (2)	0.5268 (3)	0.7589 (4)	0.0407 (7)
H4A	0.4778	0.4676	0.8729	0.061*
H4B	0.4850	0.4825	0.6548	0.061*
H4C	0.3832	0.5377	0.7213	0.061*
C5	0.40230 (19)	0.7494 (3)	0.4694 (3)	0.0325 (6)
C6	0.31243 (19)	0.8228 (3)	0.4763 (4)	0.0409 (7)
H6	0.3128	0.8867	0.5779	0.049*
C7	0.2213 (2)	0.8044 (4)	0.3365 (4)	0.0492 (8)
H7	0.1594	0.8547	0.3433	0.059*
C8	0.2208 (2)	0.7140 (4)	0.1891 (4)	0.0524 (8)
H8	0.1581	0.6999	0.0946	0.063*
C9	0.3109 (3)	0.6431 (4)	0.1769 (4)	0.0547 (8)
H9	0.3106	0.5817	0.0727	0.066*
C10	0.4023 (2)	0.6610 (3)	0.3167 (4)	0.0430 (7)
H10	0.4646	0.6128	0.3076	0.052*
C11	0.67809 (18)	0.6052 (3)	1.0290 (3)	0.0316 (6)
C12	0.79737 (18)	0.6083 (3)	1.0771 (3)	0.0342 (6)
H12	0.8225	0.5842	0.9596	0.041*
C13	0.83601 (17)	0.7545 (3)	1.1413 (3)	0.0320 (6)
C14	0.80485 (19)	0.8201 (3)	1.2912 (3)	0.0378 (6)
H14	0.7535	0.7766	1.3467	0.045*
C15	0.8470 (2)	0.9478 (3)	1.3615 (4)	0.0400 (7)
H15	0.8241	0.9904	1.4644	0.048*
C16	0.92221 (18)	1.0146 (3)	1.2845 (4)	0.0371 (6)
C17	0.9518 (2)	0.9500 (3)	1.1328 (4)	0.0415 (7)
H17	1.0024	0.9943	1.0762	0.050*
C18	0.90949 (19)	0.8226 (3)	1.0614 (4)	0.0381 (6)
H18	0.9311	0.7812	0.9563	0.046*
C19	0.8401 (2)	0.4990 (3)	1.2299 (4)	0.0430 (7)
H19A	0.8174	0.5225	1.3470	0.064*
H19B	0.9170	0.4985	1.2555	0.064*
H19C	0.8133	0.4059	1.1853	0.064*
C20	0.9695 (2)	1.1532 (3)	1.3630 (4)	0.0509 (8)
H20A	0.9370	1.2298	1.2792	0.076*
H20B	1.0453	1.1520	1.3701	0.076*
H20C	0.9569	1.1676	1.4908	0.076*
N1	0.62582 (14)	0.6602 (2)	0.8523 (3)	0.0317 (5)
O1	0.59164 (13)	0.7465 (2)	0.5591 (2)	0.0458 (5)
O2	0.75664 (14)	0.6802 (3)	0.6804 (3)	0.0566 (6)
O3	0.62656 (13)	0.5637 (2)	1.1380 (2)	0.0410 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0269 (12)	0.0347 (14)	0.0304 (12)	0.0006 (11)	0.0059 (10)	0.0005 (11)
C2	0.0341 (12)	0.0297 (15)	0.0364 (13)	0.0000 (11)	0.0047 (10)	0.0028 (11)
C3	0.0340 (13)	0.0503 (18)	0.0333 (13)	−0.0036 (13)	0.0072 (11)	0.0092 (13)
C4	0.0420 (14)	0.0369 (17)	0.0410 (15)	−0.0050 (13)	0.0045 (12)	0.0059 (12)
C5	0.0359 (13)	0.0299 (14)	0.0293 (12)	0.0035 (12)	0.0024 (10)	0.0040 (11)
C6	0.0400 (14)	0.0450 (17)	0.0367 (13)	0.0085 (13)	0.0066 (11)	−0.0018 (13)
C7	0.0388 (15)	0.059 (2)	0.0459 (16)	0.0094 (14)	0.0013 (13)	0.0002 (15)
C8	0.0463 (16)	0.063 (2)	0.0398 (15)	−0.0029 (16)	−0.0075 (13)	0.0010 (15)
C9	0.072 (2)	0.054 (2)	0.0334 (14)	−0.0040 (17)	0.0015 (14)	−0.0114 (14)
C10	0.0502 (15)	0.0382 (16)	0.0402 (14)	0.0102 (14)	0.0089 (12)	−0.0017 (14)
C11	0.0335 (13)	0.0340 (14)	0.0281 (12)	0.0014 (11)	0.0082 (11)	0.0020 (11)
C12	0.0281 (13)	0.0404 (15)	0.0335 (13)	0.0030 (12)	0.0057 (11)	0.0062 (12)
C13	0.0242 (11)	0.0404 (15)	0.0304 (12)	0.0045 (11)	0.0037 (10)	0.0105 (12)
C14	0.0336 (13)	0.0448 (17)	0.0359 (14)	−0.0009 (13)	0.0097 (11)	0.0079 (13)
C15	0.0431 (16)	0.0410 (16)	0.0362 (14)	0.0035 (13)	0.0094 (12)	0.0003 (12)
C16	0.0271 (12)	0.0394 (16)	0.0403 (14)	0.0044 (12)	−0.0022 (11)	0.0101 (13)
C17	0.0312 (13)	0.0447 (17)	0.0499 (15)	−0.0052 (12)	0.0122 (12)	0.0109 (13)
C18	0.0322 (13)	0.0438 (16)	0.0412 (14)	0.0019 (13)	0.0141 (11)	0.0044 (13)
C19	0.0358 (14)	0.0401 (16)	0.0500 (16)	0.0021 (13)	0.0031 (12)	0.0103 (15)
C20	0.0460 (16)	0.0429 (17)	0.0593 (18)	−0.0005 (14)	0.0023 (14)	0.0079 (15)
N1	0.0270 (10)	0.0392 (12)	0.0294 (9)	0.0004 (9)	0.0070 (8)	0.0067 (9)
O1	0.0333 (9)	0.0650 (14)	0.0383 (10)	0.0015 (10)	0.0059 (8)	0.0214 (10)
O2	0.0325 (10)	0.0970 (18)	0.0426 (10)	0.0018 (11)	0.0134 (8)	0.0239 (12)
O3	0.0350 (9)	0.0568 (13)	0.0323 (9)	−0.0019 (9)	0.0098 (8)	0.0099 (9)

Geometric parameters (Å, º) top

C1—N1	1.476 (3)	C11—O3	1.210 (3)
C1—C4	1.510 (4)	C11—N1	1.403 (3)
C1—C2	1.539 (3)	C11—C12	1.519 (3)
C1—H1	1.000	C12—C13	1.515 (4)
C2—O1	1.450 (3)	C12—C19	1.525 (4)
C2—C5	1.507 (4)	C12—H12	1.000
C2—H2	1.000	C13—C14	1.385 (4)
C3—O2	1.195 (3)	C13—C18	1.385 (3)
C3—O1	1.349 (3)	C14—C15	1.381 (4)
C3—N1	1.382 (3)	C14—H14	0.950
C4—H4A	0.980	C15—C16	1.386 (4)
C4—H4B	0.980	C15—H15	0.950
C4—H4C	0.980	C16—C17	1.381 (4)
C5—C6	1.377 (4)	C16—C20	1.510 (4)
C5—C10	1.383 (4)	C17—C18	1.382 (4)
C6—C7	1.388 (4)	C17—H17	0.950
C6—H6	0.950	C18—H18	0.950
C7—C8	1.365 (4)	C19—H19A	0.980
C7—H7	0.950	C19—H19B	0.980
C8—C9	1.377 (4)	C19—H19C	0.980
C8—H8	0.950	C20—H20A	0.980
C9—C10	1.389 (4)	C20—H20B	0.980
C9—H9	0.950	C20—H20C	0.980
C10—H10	0.950

N1—C1—C4	111.9 (2)	N1—C11—C12	117.8 (2)
N1—C1—C2	99.08 (18)	C13—C12—C11	110.0 (2)
C4—C1—C2	115.4 (2)	C13—C12—C19	111.2 (2)
N1—C1—H1	110.0	C11—C12—C19	110.0 (2)
C4—C1—H1	110.0	C13—C12—H12	108.5
C2—C1—H1	110.0	C11—C12—H12	108.5
O1—C2—C5	109.3 (2)	C19—C12—H12	108.5
O1—C2—C1	103.90 (18)	C14—C13—C18	117.7 (3)
C5—C2—C1	117.3 (2)	C14—C13—C12	121.0 (2)
O1—C2—H2	108.7	C18—C13—C12	121.1 (2)
C5—C2—H2	108.7	C15—C14—C13	121.3 (2)
C1—C2—H2	108.7	C15—C14—H14	119.4
O2—C3—O1	122.1 (2)	C13—C14—H14	119.4
O2—C3—N1	129.5 (2)	C14—C15—C16	121.1 (3)
O1—C3—N1	108.4 (2)	C14—C15—H15	119.4
C1—C4—H4A	109.5	C16—C15—H15	119.4
C1—C4—H4B	109.5	C17—C16—C15	117.5 (3)
H4A—C4—H4B	109.5	C17—C16—C20	121.4 (3)
C1—C4—H4C	109.5	C15—C16—C20	121.2 (3)
H4A—C4—H4C	109.5	C16—C17—C18	121.7 (2)
H4B—C4—H4C	109.5	C16—C17—H17	119.2
C6—C5—C10	119.2 (2)	C18—C17—H17	119.2
C6—C5—C2	118.1 (2)	C17—C18—C13	120.8 (3)
C10—C5—C2	122.7 (2)	C17—C18—H18	119.6
C5—C6—C7	120.7 (3)	C13—C18—H18	119.6
C5—C6—H6	119.7	C12—C19—H19A	109.5
C7—C6—H6	119.7	C12—C19—H19B	109.5
C8—C7—C6	119.8 (3)	H19A—C19—H19B	109.5
C8—C7—H7	120.1	C12—C19—H19C	109.5
C6—C7—H7	120.1	H19A—C19—H19C	109.5
C7—C8—C9	120.2 (3)	H19B—C19—H19C	109.5
C7—C8—H8	119.9	C16—C20—H20A	109.5
C9—C8—H8	119.9	C16—C20—H20B	109.5
C8—C9—C10	120.1 (3)	H20A—C20—H20B	109.5
C8—C9—H9	119.9	C16—C20—H20C	109.5
C10—C9—H9	119.9	H20A—C20—H20C	109.5
C5—C10—C9	119.9 (3)	H20B—C20—H20C	109.5
C5—C10—H10	120.1	C3—N1—C11	127.54 (19)
C9—C10—H10	120.1	C3—N1—C1	111.17 (19)
O3—C11—N1	118.8 (2)	C11—N1—C1	120.77 (19)
O3—C11—C12	123.4 (2)	C3—O1—C2	110.07 (18)

N1—C1—C2—O1	25.9 (2)	C12—C13—C14—C15	174.1 (2)
C4—C1—C2—O1	−93.7 (2)	C13—C14—C15—C16	−0.1 (4)
N1—C1—C2—C5	146.7 (2)	C14—C15—C16—C17	1.2 (4)
C4—C1—C2—C5	27.0 (3)	C14—C15—C16—C20	−179.1 (2)
O1—C2—C5—C6	−151.5 (2)	C15—C16—C17—C18	−0.9 (4)
C1—C2—C5—C6	90.6 (3)	C20—C16—C17—C18	179.4 (2)
O1—C2—C5—C10	28.2 (4)	C16—C17—C18—C13	−0.5 (4)
C1—C2—C5—C10	−89.7 (3)	C14—C13—C18—C17	1.5 (4)
C10—C5—C6—C7	2.7 (4)	C12—C13—C18—C17	−173.8 (2)
C2—C5—C6—C7	−177.6 (3)	O2—C3—N1—C11	2.4 (5)
C5—C6—C7—C8	−0.8 (5)	O1—C3—N1—C11	−178.6 (2)
C6—C7—C8—C9	−1.3 (5)	O2—C3—N1—C1	−169.2 (3)
C7—C8—C9—C10	1.3 (5)	O1—C3—N1—C1	9.7 (3)
C6—C5—C10—C9	−2.6 (4)	O3—C11—N1—C3	−169.9 (3)
C2—C5—C10—C9	177.7 (3)	C12—C11—N1—C3	13.2 (4)
C8—C9—C10—C5	0.6 (5)	O3—C11—N1—C1	1.0 (4)
O3—C11—C12—C13	−98.0 (3)	C12—C11—N1—C1	−175.8 (2)
N1—C11—C12—C13	78.7 (3)	C4—C1—N1—C3	99.9 (3)
O3—C11—C12—C19	24.8 (4)	C2—C1—N1—C3	−22.4 (3)
N1—C11—C12—C19	−158.5 (2)	C4—C1—N1—C11	−72.5 (3)
C11—C12—C13—C14	55.6 (3)	C2—C1—N1—C11	165.3 (2)
C19—C12—C13—C14	−66.6 (3)	O2—C3—O1—C2	−171.9 (3)
C11—C12—C13—C18	−129.2 (2)	N1—C3—O1—C2	9.0 (3)
C19—C12—C13—C18	108.7 (3)	C5—C2—O1—C3	−148.9 (2)
C18—C13—C14—C15	−1.3 (4)	C1—C2—O1—C3	−22.9 (3)

Acknowledgements

We are grateful to the Royal Society and the University of London Central Research Fund for their financial support to JE, and the EPSRC National Mass Spectrometry Service (Swansea) for accurate mass determination.

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