6,7-Dimeth­oxy-3-meth­oxy­carbonyl-1-(2-meth­oxy­phen­yl)-3,4-dihydro­isoquinoline 2-oxide

Naicker, T.; Govender, T.; Kruger, H.G.; Maguire, G.E.M.

doi:10.1107/S1600536811016539

organic compounds

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ISSN: 2056-9890

Volume 67| Part 6| June 2011| Page o1352

doi:10.1107/S1600536811016539

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6,7-Dimethoxy-3-methoxycarbonyl-1-(2-methoxyphenyl)-3,4-dihydroisoquinoline 2-oxide

Tricia Naicker,^a Thavendran Govender,^a Hendrik G. Kruger ^b and Glenn E. M. Maguire ^b ^*

^aSchool of Pharmacy and Pharmacology, University of KwaZulu Natal, Durban 4000, South Africa, and ^bSchool of Chemistry, University of KwaZulu Natal, Durban 4000, South Africa
^*Correspondence e-mail: maguireg@ukzn.ac.za

(Received 26 April 2011; accepted 2 May 2011; online 7 May 2011)

In the title compound, C₂₀H₂₁NO₆, an N-oxide-based organocatalyst, the N-containing six-membered ring adopts a twisted half-chair conformation. No hydrogen bonding or π–π stacking was found within the crystal structure.

Related literature

For related structures, see: Naicker et al. (2010 , 2011 ).

Experimental

Crystal data

C₂₀H₂₁NO₆
M_r = 371.38
Monoclinic, P 2₁ /n
a = 5.4765 (1) Å
b = 21.9984 (6) Å
c = 15.0007 (4) Å
β = 92.774 (2)°
V = 1805.08 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 173 K
0.25 × 0.18 × 0.15 mm

Data collection

Bruker APEXII diffractometer
7815 measured reflections
3959 independent reflections
3092 reflections with I > 2σ(I)
R_int = 0.016

Refinement

R[F² > 2σ(F²)] = 0.053
wR(F²) = 0.157
S = 1.06
3959 reflections
245 parameters
H-atom parameters constrained
Δρ_max = 0.92 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811016539/hg5031sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811016539/hg5031Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811016539/hg5031Isup3.cml

checkCIF report

Comment top

The title compound is a novel N-oxide based catalyst containing a tetrahydroisoquinoline (TIQ) backbone. This is the first X-ray crystal structure report of this type of organocatalyst within this TIQ class of molecules. This compound and its derivatives are currently being tested in our laboratory as novel organocatalysts for asymmetric allylation reactions (Naicker et al. 2010).

From the crystal structure it is evident that the N-containing six membered ring assumes a twisted half chair conformation (Fig. 1). This differs from a similar structure that we recently reported which displays a twisted half boat conformation (Naicker et al. 2011). A possible reason for the change is the introduction of the oxygen atom O2 onto the sp2 hybridized nitrogen atom. All our previous examples have either a hydrogen or methyl group at that position.

Interestingly there is no classic hydrogen bonding within the crystal packing however, there are various intermolecular and intramolecular short contact interactions that link the molecules together within the crystal lattice. The N-oxide oxygen O2 displays two potential hydrogen bond interactions to C16—H16 and C20A—H20A which are 3.36 Å and 3.34 Å respectively. These interactions result in a layered packing within the crystal stucture as shown along the (100) axis in Fig. 2. A centroid distance of 7.156 Å indicated that there is no π-π stacking within the crystal matrix.

Related literature top

For related structures, see: Naicker et al. (2010, 2011).

Experimental top

(S)-methyl 6,7-dimethoxy-1-(2-methoxyphenyl)-3,4-dihydroisoquinoline-3-carboxylate (1.30 g, 3.7 mmol) was dissolved in dry methylene chloride (50 ml). Potassium carbonate (1.0 g, 7.5 mmol) was added and the reaction cooled to -78 °C. Meta-chloroperbenzoic acid (0.86 g of 75% pure, net 0.65 g, 3.7 mmol) was then added, and the reaction was allowed to stir at -78 °C for 3 h. At this time, the reaction was allowed to warm to room temperature. After stirring for a further 2 h at room temperature, methylene chloride (50 ml) was added to dilute the reaction and celite (500 mg) was added to aid filtration. The reaction was filtered, and the methylene chloride concentrated to dryness affording the crude product which was purified by column chromatography (methylene chloride:methanol, 99:1, R_f = 1/5) (1.20 g, 87% yield).

Melting point 423 K. [α]²⁰_D 5.128 (c 0.13 in CHCl₃).

IR (neat): 2923, 1742, 1508, 1285, 729 cm^-1.

¹H NMR (400 MHz, CDCl₃) δ 7.55 (dd, J = 7.5, 1.7 Hz, 1H), 7.51 – 7.42 (m, 1H), 7.20 – 6.97 (m, 3H), 6.74 (d, J = 6.5 Hz, 1H), 6.27 (d, J = 13.6 Hz, 1H), 4.94 (dt, J = 5.8, 2.9 Hz, 1H), 3.90 (d, J = 1.8 Hz, 4H), 3.77 (d, J = 4.3 Hz, 3H), 3.73 – 3.54 (m, 6H), 3.49 – 3.33 (m, 1H).

¹³C NMR (101 MHz, CDCl₃) δ 168.74, 157.23, 149.52, 148.17, 131.24, 131.12, 130.43, 122.89, 121.93, 121.49, 121.01, 120.80, 119.71, 112.05, 111.50, 110.64, 110.60, 110.08, 109.50, 77.34, 77.03, 76.71, 70.84, 70.72, 56.17, 56.11, 56.05, 55.93, 55.62, 53.24, 53.10, 30.80, 30.73.

Recrystallization from ethyl acetate at room temperature afforded colourless crystals suitable for X-ray analysis.

Computing details top

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 40% probability level. Hydrogen atoms have been omitted for clarity.
	Fig. 2. A partial projection of the title compound, viewed along [100] plane.

6,7-dimethoxy-3-(methoxycarbonyl)-1-(2-methoxyphenyl)- 3,4-dihydroisoquinolin-2-ium-2-olate top

Crystal data top

C₂₀H₂₁NO₆	F(000) = 784
M_r = 371.38	D_x = 1.367 Mg m⁻³
Monoclinic, P2₁/n	Melting point: 423 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 5.4765 (1) Å	Cell parameters from 7815 reflections
b = 21.9984 (6) Å	θ = 2.3–27.1°
c = 15.0007 (4) Å	µ = 0.10 mm⁻¹
β = 92.774 (2)°	T = 173 K
V = 1805.08 (8) Å³	Block, colourless
Z = 4	0.25 × 0.18 × 0.15 mm

Data collection top

Bruker APEXII diffractometer	3092 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.016
Graphite monochromator	θ_max = 27.1°, θ_min = 2.3°
1.2° ϕ and ω scans	h = −7→7
7815 measured reflections	k = −28→28
3959 independent reflections	l = −19→19

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)] = 0.053	H-atom parameters constrained
wR(F²) = 0.157	w = 1/[σ²(F_o²) + (0.080P)² + 1.0977P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max < 0.001
3959 reflections	Δρ_max = 0.92 e Å⁻³
245 parameters	Δρ_min = −0.33 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0055 (19)

Crystal data top

C₂₀H₂₁NO₆	V = 1805.08 (8) Å³
M_r = 371.38	Z = 4
Monoclinic, P2₁/n	Mo Kα radiation
a = 5.4765 (1) Å	µ = 0.10 mm⁻¹
b = 21.9984 (6) Å	T = 173 K
c = 15.0007 (4) Å	0.25 × 0.18 × 0.15 mm
β = 92.774 (2)°

Data collection top

Bruker APEXII diffractometer	3092 reflections with I > 2σ(I)
7815 measured reflections	R_int = 0.016
3959 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.053	0 restraints
wR(F²) = 0.157	H-atom parameters constrained
S = 1.06	Δρ_max = 0.92 e Å⁻³
3959 reflections	Δρ_min = −0.33 e Å⁻³
245 parameters

Special details top

Experimental. Half sphere of data collected using COLLECT strategy (Nonius, 2000). Crystal to detector distance = 30 mm; combination of ϕ and ω scans of 1.0°, 40 s per °, 2 iterations.

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) top

	x	y	z	U_iso*/U_eq
O1	0.2176 (3)	0.22907 (6)	0.35593 (9)	0.0354 (3)
O2	0.6006 (2)	−0.03624 (6)	0.11617 (9)	0.0322 (3)
O3	0.2824 (3)	−0.10179 (6)	0.19301 (9)	0.0344 (3)
O4	0.5317 (3)	0.12825 (8)	0.45676 (10)	0.0441 (4)
O5	0.2474 (3)	0.07631 (8)	0.52628 (10)	0.0485 (4)
O6	0.2093 (3)	0.16305 (7)	0.07924 (9)	0.0391 (4)
N1	0.2146 (3)	0.17212 (7)	0.33291 (10)	0.0251 (3)
C1	0.3125 (3)	0.14938 (8)	0.26149 (11)	0.0246 (4)
C2	0.3023 (3)	0.08366 (8)	0.24573 (11)	0.0228 (4)
C3	0.4608 (3)	0.05630 (8)	0.18643 (11)	0.0247 (4)
H3	0.5749	0.0806	0.1567	0.030*
C4	0.4517 (3)	−0.00558 (8)	0.17115 (11)	0.0246 (4)
C5	0.2793 (3)	−0.04178 (8)	0.21365 (12)	0.0260 (4)
C6	0.1259 (3)	−0.01473 (8)	0.27287 (12)	0.0262 (4)
H6	0.0115	−0.0390	0.3025	0.031*
C7	0.1370 (3)	0.04758 (8)	0.28959 (11)	0.0238 (4)
C8	−0.0255 (3)	0.07830 (8)	0.35355 (12)	0.0283 (4)
H8A	−0.0748	0.0488	0.3991	0.034*
H8B	−0.1752	0.0932	0.3210	0.034*
C9	0.1083 (3)	0.13129 (8)	0.39883 (12)	0.0259 (4)
H9	−0.0107	0.1550	0.4335	0.031*
C10	0.3260 (4)	0.11235 (9)	0.46255 (13)	0.0344 (5)
C11	0.4434 (5)	0.06056 (13)	0.59251 (17)	0.0572 (7)
H11A	0.3780	0.0341	0.6382	0.086*
H11B	0.5086	0.0978	0.6206	0.086*
H11C	0.5744	0.0393	0.5629	0.086*
C12	0.4564 (3)	0.19020 (8)	0.20530 (12)	0.0278 (4)
C13	0.6553 (3)	0.22127 (8)	0.24385 (14)	0.0314 (4)
H13	0.6881	0.2188	0.3065	0.038*
C14	0.8070 (4)	0.25591 (9)	0.19251 (17)	0.0410 (5)
H14	0.9427	0.2770	0.2195	0.049*
C15	0.7571 (4)	0.25908 (10)	0.10160 (17)	0.0455 (6)
H15	0.8616	0.2823	0.0660	0.055*
C16	0.5593 (4)	0.22943 (10)	0.06094 (15)	0.0418 (5)
H16	0.5270	0.2328	−0.0017	0.050*
C17	0.4075 (4)	0.19452 (8)	0.11258 (13)	0.0323 (4)
C18	0.1512 (5)	0.16733 (12)	−0.01499 (14)	0.0520 (6)
H18A	0.0059	0.1428	−0.0303	0.078*
H18B	0.2892	0.1523	−0.0479	0.078*
H18C	0.1187	0.2098	−0.0311	0.078*
C19	0.7699 (4)	−0.00092 (10)	0.06834 (13)	0.0351 (5)
H19A	0.8650	−0.0278	0.0311	0.053*
H19B	0.8806	0.0207	0.1108	0.053*
H19C	0.6803	0.0286	0.0303	0.053*
C20	0.0983 (4)	−0.13944 (9)	0.22980 (15)	0.0364 (5)
H20A	0.1191	−0.1815	0.2100	0.055*
H20B	−0.0640	−0.1248	0.2094	0.055*
H20C	0.1140	−0.1378	0.2951	0.055*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0496 (8)	0.0207 (7)	0.0370 (7)	−0.0003 (6)	0.0121 (6)	−0.0065 (6)
O2	0.0374 (7)	0.0271 (7)	0.0335 (7)	0.0029 (6)	0.0143 (6)	−0.0035 (5)
O3	0.0425 (8)	0.0194 (6)	0.0422 (8)	−0.0021 (6)	0.0122 (6)	−0.0042 (6)
O4	0.0335 (8)	0.0543 (10)	0.0441 (9)	0.0016 (7)	−0.0020 (6)	−0.0001 (7)
O5	0.0505 (10)	0.0559 (10)	0.0386 (8)	−0.0023 (8)	−0.0030 (7)	0.0157 (7)
O6	0.0542 (9)	0.0366 (8)	0.0261 (7)	0.0019 (7)	−0.0020 (6)	0.0010 (6)
N1	0.0295 (8)	0.0213 (7)	0.0247 (7)	−0.0006 (6)	0.0040 (6)	−0.0014 (6)
C1	0.0292 (9)	0.0223 (8)	0.0223 (8)	0.0019 (7)	0.0024 (7)	−0.0001 (7)
C2	0.0256 (9)	0.0225 (8)	0.0202 (8)	0.0007 (7)	0.0006 (6)	0.0006 (6)
C3	0.0279 (9)	0.0240 (9)	0.0225 (8)	−0.0005 (7)	0.0038 (7)	0.0002 (7)
C4	0.0275 (9)	0.0256 (9)	0.0211 (8)	0.0031 (7)	0.0034 (7)	−0.0019 (7)
C5	0.0315 (9)	0.0203 (8)	0.0261 (9)	0.0002 (7)	−0.0003 (7)	−0.0012 (7)
C6	0.0277 (9)	0.0250 (9)	0.0260 (9)	−0.0032 (7)	0.0033 (7)	0.0002 (7)
C7	0.0251 (8)	0.0240 (9)	0.0225 (8)	0.0010 (7)	0.0016 (6)	−0.0010 (7)
C8	0.0286 (9)	0.0269 (9)	0.0299 (9)	−0.0014 (7)	0.0071 (7)	−0.0023 (7)
C9	0.0304 (9)	0.0247 (9)	0.0230 (9)	0.0025 (7)	0.0074 (7)	0.0003 (7)
C10	0.0522 (13)	0.0269 (10)	0.0245 (9)	0.0061 (9)	0.0068 (8)	−0.0033 (7)
C11	0.0544 (15)	0.0673 (17)	0.0485 (14)	−0.0081 (13)	−0.0119 (11)	0.0216 (13)
C12	0.0350 (10)	0.0195 (8)	0.0294 (9)	0.0038 (7)	0.0081 (7)	0.0010 (7)
C13	0.0341 (10)	0.0227 (9)	0.0379 (10)	0.0024 (7)	0.0063 (8)	0.0016 (8)
C14	0.0370 (11)	0.0267 (10)	0.0603 (14)	−0.0005 (8)	0.0124 (10)	0.0053 (9)
C15	0.0492 (13)	0.0313 (11)	0.0583 (14)	0.0040 (9)	0.0258 (11)	0.0149 (10)
C16	0.0611 (14)	0.0319 (11)	0.0339 (11)	0.0092 (10)	0.0179 (10)	0.0106 (9)
C17	0.0436 (11)	0.0242 (9)	0.0296 (10)	0.0070 (8)	0.0071 (8)	0.0017 (7)
C18	0.0755 (17)	0.0523 (14)	0.0275 (11)	0.0137 (13)	−0.0059 (11)	−0.0040 (10)
C19	0.0360 (11)	0.0378 (11)	0.0325 (10)	0.0011 (8)	0.0132 (8)	−0.0016 (8)
C20	0.0423 (11)	0.0236 (9)	0.0438 (12)	−0.0061 (8)	0.0059 (9)	−0.0007 (8)

Geometric parameters (Å, º) top

O1—N1	1.2995 (19)	C8—H8B	0.9900
O2—C4	1.366 (2)	C9—C10	1.549 (3)
O2—C19	1.429 (2)	C9—H9	1.0000
O3—C5	1.356 (2)	C11—H11A	0.9800
O3—C20	1.436 (2)	C11—H11B	0.9800
O4—C10	1.187 (3)	C11—H11C	0.9800
O5—C10	1.329 (3)	C12—C13	1.388 (3)
O5—C11	1.468 (3)	C12—C17	1.407 (3)
O6—C17	1.362 (3)	C13—C14	1.388 (3)
O6—C18	1.437 (2)	C13—H13	0.9500
N1—C1	1.320 (2)	C14—C15	1.380 (3)
N1—C9	1.476 (2)	C14—H14	0.9500
C1—C2	1.466 (2)	C15—C16	1.381 (4)
C1—C12	1.484 (2)	C15—H15	0.9500
C2—C7	1.393 (2)	C16—C17	1.394 (3)
C2—C3	1.408 (2)	C16—H16	0.9500
C3—C4	1.381 (2)	C18—H18A	0.9800
C3—H3	0.9500	C18—H18B	0.9800
C4—C5	1.411 (3)	C18—H18C	0.9800
C5—C6	1.386 (3)	C19—H19A	0.9800
C6—C7	1.394 (2)	C19—H19B	0.9800
C6—H6	0.9500	C19—H19C	0.9800
C7—C8	1.501 (2)	C20—H20A	0.9800
C8—C9	1.520 (2)	C20—H20B	0.9800
C8—H8A	0.9900	C20—H20C	0.9800

C4—O2—C19	117.10 (15)	O5—C11—H11A	109.5
C5—O3—C20	117.19 (15)	O5—C11—H11B	109.5
C10—O5—C11	112.08 (18)	H11A—C11—H11B	109.5
C17—O6—C18	117.57 (18)	O5—C11—H11C	109.5
O1—N1—C1	125.52 (15)	H11A—C11—H11C	109.5
O1—N1—C9	114.13 (14)	H11B—C11—H11C	109.5
C1—N1—C9	120.15 (15)	C13—C12—C17	119.13 (18)
N1—C1—C2	119.40 (16)	C13—C12—C1	119.27 (16)
N1—C1—C12	118.66 (15)	C17—C12—C1	121.42 (17)
C2—C1—C12	121.51 (15)	C12—C13—C14	121.2 (2)
C7—C2—C3	119.32 (16)	C12—C13—H13	119.4
C7—C2—C1	120.45 (16)	C14—C13—H13	119.4
C3—C2—C1	120.23 (16)	C15—C14—C13	118.7 (2)
C4—C3—C2	120.54 (16)	C15—C14—H14	120.6
C4—C3—H3	119.7	C13—C14—H14	120.6
C2—C3—H3	119.7	C14—C15—C16	121.8 (2)
O2—C4—C3	124.72 (16)	C14—C15—H15	119.1
O2—C4—C5	115.23 (15)	C16—C15—H15	119.1
C3—C4—C5	120.05 (16)	C15—C16—C17	119.4 (2)
O3—C5—C6	125.37 (16)	C15—C16—H16	120.3
O3—C5—C4	115.48 (16)	C17—C16—H16	120.3
C6—C5—C4	119.13 (16)	O6—C17—C16	124.20 (18)
C5—C6—C7	121.00 (16)	O6—C17—C12	116.05 (17)
C5—C6—H6	119.5	C16—C17—C12	119.8 (2)
C7—C6—H6	119.5	O6—C18—H18A	109.5
C2—C7—C6	119.92 (16)	O6—C18—H18B	109.5
C2—C7—C8	117.68 (15)	H18A—C18—H18B	109.5
C6—C7—C8	122.40 (16)	O6—C18—H18C	109.5
C7—C8—C9	110.07 (15)	H18A—C18—H18C	109.5
C7—C8—H8A	109.6	H18B—C18—H18C	109.5
C9—C8—H8A	109.6	O2—C19—H19A	109.5
C7—C8—H8B	109.6	O2—C19—H19B	109.5
C9—C8—H8B	109.6	H19A—C19—H19B	109.5
H8A—C8—H8B	108.2	O2—C19—H19C	109.5
N1—C9—C8	111.39 (14)	H19A—C19—H19C	109.5
N1—C9—C10	105.07 (14)	H19B—C19—H19C	109.5
C8—C9—C10	114.19 (15)	O3—C20—H20A	109.5
N1—C9—H9	108.7	O3—C20—H20B	109.5
C8—C9—H9	108.7	H20A—C20—H20B	109.5
C10—C9—H9	108.7	O3—C20—H20C	109.5
O4—C10—O5	124.7 (2)	H20A—C20—H20C	109.5
O4—C10—C9	125.50 (18)	H20B—C20—H20C	109.5
O5—C10—C9	109.75 (18)

O1—N1—C1—C2	177.89 (16)	O1—N1—C9—C8	146.52 (15)
C9—N1—C1—C2	3.4 (2)	C1—N1—C9—C8	−38.4 (2)
O1—N1—C1—C12	5.3 (3)	O1—N1—C9—C10	−89.34 (17)
C9—N1—C1—C12	−169.18 (15)	C1—N1—C9—C10	85.72 (18)
N1—C1—C2—C7	17.8 (2)	C7—C8—C9—N1	51.46 (19)
C12—C1—C2—C7	−169.84 (16)	C7—C8—C9—C10	−67.4 (2)
N1—C1—C2—C3	−161.82 (16)	C11—O5—C10—O4	3.0 (3)
C12—C1—C2—C3	10.6 (3)	C11—O5—C10—C9	−175.79 (18)
C7—C2—C3—C4	0.5 (3)	N1—C9—C10—O4	−0.3 (3)
C1—C2—C3—C4	−179.88 (16)	C8—C9—C10—O4	122.1 (2)
C19—O2—C4—C3	−2.9 (3)	N1—C9—C10—O5	178.51 (15)
C19—O2—C4—C5	176.99 (16)	C8—C9—C10—O5	−59.1 (2)
C2—C3—C4—O2	−178.80 (16)	N1—C1—C12—C13	56.9 (2)
C2—C3—C4—C5	1.3 (3)	C2—C1—C12—C13	−115.55 (19)
C20—O3—C5—C6	5.5 (3)	N1—C1—C12—C17	−128.06 (19)
C20—O3—C5—C4	−175.62 (16)	C2—C1—C12—C17	59.5 (2)
O2—C4—C5—O3	−1.0 (2)	C17—C12—C13—C14	−0.6 (3)
C3—C4—C5—O3	178.87 (16)	C1—C12—C13—C14	174.57 (17)
O2—C4—C5—C6	177.95 (15)	C12—C13—C14—C15	0.0 (3)
C3—C4—C5—C6	−2.2 (3)	C13—C14—C15—C16	0.8 (3)
O3—C5—C6—C7	−179.98 (17)	C14—C15—C16—C17	−1.0 (3)
C4—C5—C6—C7	1.2 (3)	C18—O6—C17—C16	−1.3 (3)
C3—C2—C7—C6	−1.5 (2)	C18—O6—C17—C12	178.88 (18)
C1—C2—C7—C6	178.87 (16)	C15—C16—C17—O6	−179.39 (19)
C3—C2—C7—C8	178.87 (15)	C15—C16—C17—C12	0.4 (3)
C1—C2—C7—C8	−0.7 (2)	C13—C12—C17—O6	−179.81 (16)
C5—C6—C7—C2	0.7 (3)	C1—C12—C17—O6	5.1 (3)
C5—C6—C7—C8	−179.74 (16)	C13—C12—C17—C16	0.4 (3)
C2—C7—C8—C9	−33.2 (2)	C1—C12—C17—C16	−174.66 (17)
C6—C7—C8—C9	147.19 (17)

Experimental details

Crystal data
Chemical formula	C₂₀H₂₁NO₆
M_r	371.38
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	173
a, b, c (Å)	5.4765 (1), 21.9984 (6), 15.0007 (4)
β (°)	92.774 (2)
V (Å³)	1805.08 (8)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.25 × 0.18 × 0.15

Data collection
Diffractometer	Bruker APEXII diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	7815, 3959, 3092
R_int	0.016
(sin θ/λ)_max (Å⁻¹)	0.641

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.053, 0.157, 1.06
No. of reflections	3959
No. of parameters	245
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.92, −0.33

Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), OLEX2 (Dolomanov et al., 2009).

Acknowledgements

The authors wish to thank Dr Hong Su of the Chemistry Department, University of Cape Town, for her assistance with the crystallographic data collection.

References

Bruker (2006). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Naicker, T., Govender, T., Kruger, H. G. & Maguire, G. E. M. (2011). Acta Cryst. E67, o883. Web of Science CSD CrossRef IUCr Journals Google Scholar
Naicker, T., Petzold, K., Singh, T., Arvidsson, P. I., Kruger, H. G., Maguire, G. E. M. & Govender, T. (2010). Tetrahedron Asymmetry, 21, 2859–2867. Web of Science CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar

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