2,3,4,6-Tetra-O-acetyl-α-D-gluco­pyranosyl azide

The Cu^I-catalysed 1,3-dipolar cyclo­addition of an azide and a terminal alkyne is becoming an increasingly popular tool for synthetic chemists. This is the most representative of the so-called `click reactions' and it is used to generate 1,4-di­substituted triazoles in high yield. During studies on such cyclo­addition reactions, a reduced reactivity of an α-glucosyl azide with respect to the corresponding β-anomer was observed. With the aim of understanding this phenomenon, the structure of the title compound, C₁₄H₁₉N₃O₉, has been determined at 140 K. The glucopyranosyl ring appears in a regular ⁴C₁ chair conformation with all the substituents in equatorial positions, except for the anomeric azide group, which adopts an axial orientation. The observed bond lengths are consistent with a strong anomeric effect, which is reflected in a change in dipolar character and hence reduced reactivity of the α-glucosyl azide.

S1. Comment

Glycosyl azides represent important and versatile building blocks in carbohydrate chemistry (Györgydeák & Thiem, 2006). They have been widely used as synthetic intermediates for the preparation of glycosyl amines, asparagine-linked glycopeptides (Herzner et al., 2000) and, more recently, triazole-linked neoglycoconjugates (Dedola et al., 2007; Dondoni, 2007). These last became available as a result of the discovery of the highly efficient Cu^I-catalysed cycloaddition reaction between azides and terminal alkynes (Rostovtsev et al., 2002; Tornøe et al., 2002), which is commonly referred to as `click chemistry'. This cycloaddition process has been extensively used for the synthesis of a variety of neoglycoconjugates (Dedola et al., 2007; Dondoni, 2007). In the course of our work on the synthesis of starch-like molecules, we experienced major problems with stereocontrol in the synthesis of inter-sugar chain glycosidic linkages (Marmuse et al., 2005a). We therefore resorted to the preparation of pseudo-starch fragments based on glucosyl triazole linkages (Marmuse et al., 2005b; Nepogodiev et al., 2007). Initial studies were based on the immediately accessible β-linked sugar azides, which do not mirror the anomeric stereochemistry of starch. Here, we report the structural analysis of the title compound, (I) (Bianchi & Bernardi, 2006). The X-ray structure of the corresponding β-linked anomer, 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl azide, (II), has already been reported (Temelkoff et al., 2004). Crystals of (I) suitable for X-ray crystallographic analysis were obtained by recrystallization from methanol [Ethanol in prep - which is correct?].

The six-membered pyranose ring in (I) adopts a chair conformation, with all exocyclic substituents adopting an equatorial arrangement, except the anomeric azide which has the expected axial orientation (Fig. 1). Compared with the structure of the corresponding β-anomer, (II) (Temelkoff et al., 2004), the geometry of the pyranose ring and the orientation of the acetate groups of (I) are very similar. However, whereas the length of the C1—O5 bond in (I) [1.423 (3) Å] is the same as in (II) [1.420 (2) Å], the C1—N11 [1.510 (3) versus 1.460 (2) Å] and C5—O5 [1.459 (3) versus 1.432 (2) Å] distances in (I) are significantly longer than in (II). As in the β-anomer, (II), the azido group in (I) appears as a nearly linear fragment [N11—N12—N13 = 173.0 (3)°, compared with 171.4 (2)° for the β-anomer] and shows a very similar C1—N11—N12 bond angle [113.7 (2) versus 113.74 (14)° for the β-anomer].

However, the N—N bond lengths for the azide group and C1—N11 distances in (I) and (II) are different. The structural differences between the anomeric glucosyl azides are all in keeping with the expected influence of the anomeric effect (Briggs et al., 1984; Wolfe et al., 1979). For the β-azide, (II), the terminal N12—N13 bond [1.119 (3) Å] is shorter than the N11—N12 bond [1.243 (2) Å], whereas in the α-azide, (I), these are similar [1.195 (4) and 1.165 (3) Å, respectively]. One might therefore anticipate a significant reactivity difference between compounds (I) and (II) in dipolar cycloaddition chemistry, which we have indeed observed: a much lower reactivity of α-azide (I) compared with β-azide (II) is evident in the Cu^I-catalysed synthesis of triazoles. This is consistent with other experimental observations (Wilkinson et al., 2006) and in accord with computational studies, which show the crucial role that a partial negative charge on atom N11 plays in the mechanism of the Cu^I-catalysed cycloaddition of azides and alkynes (Himo et al., 2005).

S2. Experimental

2,3,4,6-Tetra-O-acetyl-α-D-glucopyranosyl azide, (I), was prepared along with the β-anomer, (II), in a 9:1 ratio (determined by ¹H NMR spectroscopy), as described previously (Bianchi & Bernardi, 2006), using tetra-O-acetyl-β-D-glucopyranosyl chloride (Korytnyk & Mills, 1959) and Me₃SiN₃ (Soli et al., 1999). Single isomers were obtained using purification by silica-gel column chromatography. Crystals of (I) suitable for X-ray diffraction analysis were obtained as colourless blocks by recrystallization from ethanol [Methanol in comment - which is correct?].

S3. Refinement

Non-H atoms were refined with anisotropic displacement parameters, except those in the CH₂OCOMe group of C6 where there is suspected disorder; the major [79.9 (5)%] component C6/O6/C61/O61/C62 was refined anisotropically, but the minor [20.1 (5)%] component C7/O7/C71/O71/C72 was not fully resolved and its C and O atoms were refined isotropically; the methyl C atom represented by C62/C72 was found to be common to both orientations and was refined with full occupancy for that site, using the EXYZ and EADP restraints in SHELXL97 (Sheldrick, 2008).

H atoms were included in idealized positions, with C—H distances for the methyl, methylene and methine groups set to 0.96, 0.97 and 0.98 Å, respectively, and with U_iso(H) = 1.5U_eq(C) for the methyl group and 1.2U_eq(C) for the remaining groups.

The absolute configuration of the C atoms cannot be determined from the X-ray data; its assignment was based on the known configuration of the starting material.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2008).

Figures

Fig. 1. A view of the molecular structure of (I), showing the atom-numbering scheme. For clarity, only the major component of the disordered CH2OCOMe group at C6 is shown. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as capped sticks.

2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl azide

Crystal data

C14H19N3O9	F(000) = 392
Mr = 373.32	Dx = 1.387 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
a = 10.806 (4) Å	Cell parameters from 474 reflections
b = 7.9840 (13) Å	θ = 3.9–25°
c = 11.0107 (8) Å	µ = 0.12 mm^−1
β = 109.742 (2)°	T = 140 K
V = 894.1 (3) Å^3	Block, colourless
Z = 2	0.45 × 0.43 × 0.30 mm

Data collection

Oxford Diffraction Xcalibur3/CCD diffractometer	3125 independent reflections
Radiation source: Enhance (Mo) X-ray Source	2216 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.039
Detector resolution: 16.0050 pixels mm^-1	θmax = 25.0°, θmin = 3.9°
Thin–slice ϕ and ω scans	h = −12→12
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	k = −9→9
Tmin = 0.940, Tmax = 1.060	l = −13→13
8905 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.039	H-atom parameters constrained
wR(F^2) = 0.087	w = 1/[σ^2(Fo^2) + (0.0523P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.90	(Δ/σ)max = 0.007
3125 reflections	Δρmax = 0.15 e Å^−3
257 parameters	Δρmin = −0.16 e Å^−3
1 restraint	Absolute structure: Flack (1983), with how many Friedel pairs?
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.6 (12)

Special details

Experimental. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	0.4935 (2)	0.4785 (3)	0.8762 (3)	0.0365 (7)
H1	0.5258	0.4275	0.9622	0.044*
N11	0.60522 (19)	0.5749 (3)	0.8561 (2)	0.0316 (5)
N12	0.6708 (2)	0.6454 (3)	0.9479 (3)	0.0450 (6)
N13	0.7454 (3)	0.7240 (4)	1.0341 (3)	0.0659 (8)
C2	0.4493 (2)	0.3376 (3)	0.7762 (3)	0.0346 (7)
H2	0.3942	0.2595	0.8041	0.041*
O2	0.56490 (15)	0.2480 (2)	0.77214 (17)	0.0392 (4)
C21	0.5704 (3)	0.0787 (3)	0.7919 (2)	0.0360 (6)
O21	0.4879 (2)	0.0022 (2)	0.8188 (2)	0.0533 (5)
C22	0.6916 (3)	0.0095 (4)	0.7734 (3)	0.0522 (8)
H22A	0.6873	−0.1106	0.7717	0.078*
H22B	0.7676	0.0450	0.8434	0.078*
H22C	0.6974	0.0497	0.6934	0.078*
C3	0.3714 (2)	0.3984 (3)	0.6407 (3)	0.0327 (6)
H3	0.4293	0.4535	0.6012	0.039*
O3	0.30652 (14)	0.2529 (2)	0.56419 (16)	0.0338 (4)
C31	0.3639 (2)	0.1759 (3)	0.4855 (2)	0.0342 (6)
O31	0.46248 (16)	0.2268 (3)	0.46931 (18)	0.0490 (5)
C32	0.2893 (2)	0.0208 (3)	0.4269 (3)	0.0412 (7)
H32A	0.3232	−0.0728	0.4831	0.062*
H32B	0.2992	0.0001	0.3448	0.062*
H32C	0.1979	0.0357	0.4153	0.062*
C4	0.2630 (2)	0.5170 (3)	0.6461 (2)	0.0345 (6)
H4	0.1975	0.4553	0.6719	0.041*
O4	0.20107 (15)	0.5914 (2)	0.51965 (17)	0.0390 (5)
C41	0.0706 (3)	0.5590 (3)	0.4578 (3)	0.0416 (7)
O41	0.0051 (2)	0.4730 (3)	0.5040 (2)	0.0624 (6)
C42	0.0191 (3)	0.6445 (4)	0.3296 (3)	0.0522 (8)
H42A	−0.0734	0.6646	0.3081	0.078*
H42B	0.0337	0.5746	0.2648	0.078*
H42C	0.0639	0.7493	0.3336	0.078*
C5	0.3220 (2)	0.6586 (3)	0.7430 (2)	0.0393 (7)
H5	0.3891	0.7159	0.7168	0.047*
O5	0.38603 (16)	0.5849 (2)	0.87015 (17)	0.0418 (5)
C6	0.2211 (3)	0.7870 (5)	0.7490 (5)	0.0398 (11)	0.799 (5)
H6A	0.2612	0.8682	0.8164	0.048*	0.799 (5)
H6B	0.1869	0.8459	0.6674	0.048*	0.799 (5)
O6	0.1157 (2)	0.6995 (3)	0.7761 (3)	0.0445 (8)	0.799 (5)
C61	0.1025 (4)	0.7172 (6)	0.8924 (4)	0.0472 (10)	0.799 (5)
O61	0.1712 (3)	0.8089 (4)	0.9752 (3)	0.0785 (11)	0.799 (5)
C62	−0.0065 (3)	0.5920 (7)	0.9073 (4)	0.0917 (15)	0.799 (5)
H62A	−0.0263	0.6202	0.9835	0.138*	0.799 (5)
H62B	0.0259	0.4792	0.9142	0.138*	0.799 (5)
H62C	−0.0848	0.6013	0.8331	0.138*	0.799 (5)
C7	0.212 (2)	0.746 (2)	0.7968 (18)	0.038 (5)*	0.201 (5)
H7A	0.2557	0.8233	0.8661	0.046*	0.201 (5)
H7B	0.1497	0.8095	0.7278	0.046*	0.201 (5)
O7	0.1410 (9)	0.6185 (14)	0.8444 (10)	0.037 (3)*	0.201 (5)
C71	0.020 (2)	0.653 (3)	0.856 (2)	0.057 (6)*	0.201 (5)
O71	−0.0305 (15)	0.793 (2)	0.8063 (16)	0.111 (6)*	0.201 (5)
C72	−0.0065 (3)	0.5920 (7)	0.9073 (4)	0.0917 (15)	0.201 (5)
H72A	−0.1008	0.5942	0.8797	0.138*	0.201 (5)
H72B	0.0289	0.6348	0.9937	0.138*	0.201 (5)
H72C	0.0229	0.4789	0.9053	0.138*	0.201 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0354 (14)	0.0290 (15)	0.0456 (17)	0.0025 (13)	0.0145 (13)	0.0054 (13)
N11	0.0273 (11)	0.0258 (11)	0.0417 (14)	−0.0030 (10)	0.0117 (10)	0.0006 (11)
N12	0.0411 (14)	0.0472 (15)	0.0514 (16)	0.0132 (13)	0.0218 (13)	0.0147 (14)
N13	0.0573 (16)	0.079 (2)	0.0597 (18)	−0.0045 (16)	0.0172 (14)	−0.0126 (18)
C2	0.0320 (14)	0.0252 (14)	0.0511 (19)	−0.0006 (12)	0.0200 (14)	0.0003 (13)
O2	0.0339 (9)	0.0233 (10)	0.0623 (12)	0.0041 (8)	0.0188 (8)	0.0064 (9)
C21	0.0505 (16)	0.0229 (14)	0.0330 (15)	0.0022 (14)	0.0120 (13)	0.0009 (12)
O21	0.0709 (14)	0.0283 (10)	0.0710 (14)	−0.0057 (10)	0.0373 (12)	0.0012 (10)
C22	0.0528 (17)	0.0314 (16)	0.069 (2)	0.0097 (14)	0.0164 (16)	−0.0013 (16)
C3	0.0293 (13)	0.0267 (14)	0.0442 (16)	−0.0024 (12)	0.0151 (12)	−0.0009 (12)
O3	0.0323 (9)	0.0259 (10)	0.0468 (11)	−0.0047 (8)	0.0182 (8)	−0.0061 (9)
C31	0.0329 (14)	0.0278 (14)	0.0424 (16)	0.0069 (13)	0.0137 (12)	−0.0004 (13)
O31	0.0463 (11)	0.0441 (12)	0.0677 (14)	−0.0058 (10)	0.0336 (10)	−0.0126 (10)
C32	0.0415 (15)	0.0352 (16)	0.0476 (17)	0.0022 (13)	0.0160 (13)	−0.0073 (14)
C4	0.0298 (13)	0.0262 (14)	0.0465 (16)	−0.0018 (12)	0.0117 (12)	−0.0030 (13)
O4	0.0295 (9)	0.0314 (10)	0.0525 (12)	−0.0004 (8)	0.0092 (8)	−0.0023 (9)
C41	0.0317 (16)	0.0282 (16)	0.0619 (19)	0.0046 (13)	0.0120 (14)	−0.0100 (14)
O41	0.0361 (10)	0.0660 (15)	0.0792 (15)	−0.0098 (11)	0.0118 (10)	0.0055 (13)
C42	0.0436 (16)	0.0457 (18)	0.0595 (19)	0.0044 (14)	0.0072 (14)	−0.0100 (16)
C5	0.0308 (13)	0.0336 (15)	0.0493 (18)	0.0032 (13)	0.0079 (13)	−0.0047 (14)
O5	0.0415 (10)	0.0376 (10)	0.0496 (12)	0.0028 (9)	0.0197 (9)	−0.0038 (10)
C6	0.038 (2)	0.040 (3)	0.041 (3)	0.0038 (18)	0.013 (2)	−0.002 (2)
O6	0.0362 (14)	0.0508 (19)	0.0487 (18)	0.0012 (13)	0.0172 (12)	−0.0135 (15)
C61	0.050 (2)	0.050 (3)	0.042 (2)	0.001 (2)	0.016 (2)	−0.006 (2)
O61	0.098 (2)	0.083 (2)	0.061 (2)	−0.0313 (19)	0.0354 (18)	−0.0252 (18)
C62	0.064 (2)	0.147 (5)	0.064 (3)	0.018 (3)	0.021 (2)	−0.009 (3)
C72	0.064 (2)	0.147 (5)	0.064 (3)	0.018 (3)	0.021 (2)	−0.009 (3)

Geometric parameters (Å, º)

C1—O5	1.423 (3)	C4—H4	0.9800
C1—N11	1.510 (3)	O4—C41	1.367 (3)
C1—C2	1.533 (4)	C41—O41	1.214 (4)
C1—H1	0.9800	C41—C42	1.496 (4)
N11—N12	1.165 (3)	C42—H42A	0.9600
N12—N13	1.195 (4)	C42—H42B	0.9600
C2—O2	1.453 (3)	C42—H42C	0.9600
C2—C3	1.523 (4)	C5—O5	1.459 (3)
C2—H2	0.9800	C5—C6	1.514 (4)
O2—C21	1.367 (3)	C5—C7	1.652 (18)
C21—O21	1.198 (3)	C5—H5	0.9800
C21—C22	1.497 (4)	C6—O6	1.450 (5)
C22—H22A	0.9600	C6—H6A	0.9700
C22—H22B	0.9600	C6—H6B	0.9700
C22—H22C	0.9600	O6—C61	1.343 (5)
C3—O3	1.467 (3)	C61—O61	1.209 (5)
C3—C4	1.522 (3)	C61—C62	1.595 (7)
C3—H3	0.9800	C62—H62A	0.9600
O3—C31	1.369 (3)	C62—H62B	0.9600
C31—O31	1.209 (3)	C62—H62C	0.9600
C31—C32	1.499 (4)	C7—O7	1.47 (2)
C32—H32A	0.9600	C7—H7A	0.9700
C32—H32B	0.9600	C7—H7B	0.9700
C32—H32C	0.9600	O7—C71	1.39 (2)
C4—O4	1.453 (3)	C71—O71	1.28 (2)
C4—C5	1.538 (3)
O5—C1—N11	111.7 (2)	O4—C4—C3	109.2 (2)
O5—C1—C2	110.69 (19)	O4—C4—C5	108.27 (19)
N11—C1—C2	109.9 (2)	C3—C4—C5	109.90 (18)
O5—C1—H1	108.2	O4—C4—H4	109.8
N11—C1—H1	108.2	C3—C4—H4	109.8
C2—C1—H1	108.2	C5—C4—H4	109.8
N12—N11—C1	113.7 (2)	C41—O4—C4	117.6 (2)
N11—N12—N13	173.0 (3)	O41—C41—O4	123.2 (3)
O2—C2—C3	108.9 (2)	O41—C41—C42	124.7 (2)
O2—C2—C1	108.71 (18)	O4—C41—C42	112.1 (2)
C3—C2—C1	113.9 (2)	C41—C42—H42A	109.5
O2—C2—H2	108.4	C41—C42—H42B	109.5
C3—C2—H2	108.4	H42A—C42—H42B	109.5
C1—C2—H2	108.4	C41—C42—H42C	109.5
C21—O2—C2	118.3 (2)	H42A—C42—H42C	109.5
O21—C21—O2	123.2 (2)	H42B—C42—H42C	109.5
O21—C21—C22	127.1 (2)	O5—C5—C6	110.3 (2)
O2—C21—C22	109.7 (2)	O5—C5—C4	108.7 (2)
C21—C22—H22A	109.5	C6—C5—C4	113.1 (2)
C21—C22—H22B	109.5	C4—C5—C7	112.3 (8)
H22A—C22—H22B	109.5	O5—C5—H5	108.2
C21—C22—H22C	109.5	C6—C5—H5	108.2
H22A—C22—H22C	109.5	C4—C5—H5	108.2
H22B—C22—H22C	109.5	C1—O5—C5	113.63 (18)
O3—C3—C4	106.88 (18)	O6—C6—C5	108.1 (3)
O3—C3—C2	108.0 (2)	O6—C6—H6A	110.1
C4—C3—C2	109.8 (2)	C5—C6—H6A	110.1
O3—C3—H3	110.7	O6—C6—H6B	110.1
C4—C3—H3	110.7	C5—C6—H6B	110.1
C2—C3—H3	110.7	H6A—C6—H6B	108.4
C31—O3—C3	119.25 (17)	C61—O6—C6	119.3 (3)
O31—C31—O3	123.5 (2)	O61—C61—O6	123.2 (4)
O31—C31—C32	125.9 (2)	O61—C61—C62	126.1 (3)
O3—C31—C32	110.5 (2)	O6—C61—C62	110.6 (4)
C31—C32—H32A	109.5	O7—C7—C5	111.1 (12)
C31—C32—H32B	109.5	O7—C7—H7A	109.4
H32A—C32—H32B	109.5	C5—C7—H7A	109.4
C31—C32—H32C	109.5	O7—C7—H7B	109.4
H32A—C32—H32C	109.5	C5—C7—H7B	109.4
H32B—C32—H32C	109.5	H7A—C7—H7B	108.0
O5—C1—N11—N12	80.0 (3)	C4—O4—C41—O41	0.6 (4)
C2—C1—N11—N12	−156.8 (2)	C4—O4—C41—C42	179.4 (2)
O5—C1—C2—O2	171.38 (19)	O4—C4—C5—O5	−179.26 (17)
N11—C1—C2—O2	47.6 (3)	C3—C4—C5—O5	−60.1 (2)
O5—C1—C2—C3	49.8 (3)	O4—C4—C5—C6	58.0 (3)
N11—C1—C2—C3	−73.9 (2)	C3—C4—C5—C6	177.1 (3)
C3—C2—O2—C21	−110.9 (2)	O4—C4—C5—C7	83.3 (7)
C1—C2—O2—C21	124.6 (2)	C3—C4—C5—C7	−157.6 (7)
C2—O2—C21—O21	−4.0 (4)	N11—C1—O5—C5	65.7 (3)
C2—O2—C21—C22	175.6 (2)	C2—C1—O5—C5	−57.0 (3)
O2—C2—C3—O3	73.3 (2)	C6—C5—O5—C1	−172.6 (2)
C1—C2—C3—O3	−165.26 (18)	C4—C5—O5—C1	62.9 (2)
O2—C2—C3—C4	−170.52 (19)	C7—C5—O5—C1	176.4 (8)
C1—C2—C3—C4	−49.1 (3)	O5—C5—C6—O6	−67.0 (3)
C4—C3—O3—C31	144.5 (2)	C4—C5—C6—O6	54.9 (4)
C2—C3—O3—C31	−97.4 (2)	C7—C5—C6—O6	−38 (2)
C3—O3—C31—O31	−4.4 (3)	C5—C6—O6—C61	109.1 (4)
C3—O3—C31—C32	174.2 (2)	C6—O6—C61—O61	3.2 (6)
O3—C3—C4—O4	−70.7 (2)	C6—O6—C61—C62	−172.4 (3)
C2—C3—C4—O4	172.40 (19)	O5—C5—C7—O7	−58.9 (12)
O3—C3—C4—C5	170.7 (2)	C6—C5—C7—O7	148 (3)
C2—C3—C4—C5	53.8 (3)	C4—C5—C7—O7	51.2 (13)
C3—C4—O4—C41	117.6 (2)	C5—C7—O7—C71	−159.7 (14)
C5—C4—O4—C41	−122.8 (2)	C7—O7—C71—O71	9 (3)