Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270108020702/bm3053sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270108020702/bm3053Isup2.hkl |
CCDC reference: 700033
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?].
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 Uiso(H) = 1.5Ueq(C) for the methyl group and 1.2Ueq(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.
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).
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) Å3 | Block, colourless |
Z = 2 | 0.45 × 0.43 × 0.30 mm |
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 on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.039 | H-atom parameters constrained |
wR(F2) = 0.087 | w = 1/[σ2(Fo2) + (0.0523P)2] where P = (Fo2 + 2Fc2)/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) |
C14H19N3O9 | V = 894.1 (3) Å3 |
Mr = 373.32 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 10.806 (4) Å | µ = 0.12 mm−1 |
b = 7.9840 (13) Å | T = 140 K |
c = 11.0107 (8) Å | 0.45 × 0.43 × 0.30 mm |
β = 109.742 (2)° |
Oxford Diffraction Xcalibur3/CCD diffractometer | 3125 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | 2216 reflections with I > 2σ(I) |
Tmin = 0.940, Tmax = 1.060 | Rint = 0.039 |
8905 measured reflections |
R[F2 > 2σ(F2)] = 0.039 | H-atom parameters constrained |
wR(F2) = 0.087 | Δρmax = 0.15 e Å−3 |
S = 0.90 | Δρmin = −0.16 e Å−3 |
3125 reflections | Absolute structure: Flack (1983), with how many Friedel pairs? |
257 parameters | Absolute structure parameter: 0.6 (12) |
1 restraint |
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. |
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) |
U11 | U22 | U33 | U12 | U13 | U23 | |
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) |
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) |
Experimental details
Crystal data | |
Chemical formula | C14H19N3O9 |
Mr | 373.32 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 140 |
a, b, c (Å) | 10.806 (4), 7.9840 (13), 11.0107 (8) |
β (°) | 109.742 (2) |
V (Å3) | 894.1 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.12 |
Crystal size (mm) | 0.45 × 0.43 × 0.30 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur3/CCD diffractometer |
Absorption correction | Multi-scan (CrysAlis RED; Oxford Diffraction, 2006) |
Tmin, Tmax | 0.940, 1.060 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8905, 3125, 2216 |
Rint | 0.039 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.039, 0.087, 0.90 |
No. of reflections | 3125 |
No. of parameters | 257 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.15, −0.16 |
Absolute structure | Flack (1983), with how many Friedel pairs? |
Absolute structure parameter | 0.6 (12) |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2007), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 2008), Mercury (Macrae et al., 2006), SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2008).
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 CuI-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 CuI-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 CuI-catalysed cycloaddition of azides and alkynes (Himo et al., 2005).