Conformational disorder in the crystal structure of methyl 2-acetamido-2-de­oxy-β-d-gluco­pyranosyl-(1→4)–2-acetamido-2-de­oxy-β-d-gluco­pyran­oside (methyl β-chitobioside) methanol monosolvate

Shit, P.; Tetrault, T.; Zhang, W.; Yoon, M.-K.; Oliver, A.G.; Serianni, A.S.

doi:10.1107/S2053229624005199

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Conformational disorder in the crystal structure of methyl 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→4)–2-acetamido-2-deoxy-β-D-glucopyranoside (methyl β-chitobioside) methanol monosolvate

P. Shit, T. Tetrault, W. Zhang, M.-K. Yoon, A. G. Oliver and A. S. Serianni

Methyl 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranoside (methyl β-chitobioside), (IV), crystallizes from aqueous methanol at room temperature to give a structure (C₁₇H₃₀N₂O₂₂·CH₃OH) containing conformational disorder in the exocyclic hydroxymethyl group of one of its βGlcNAc residues. As observed in other X-ray structures of disaccharides containing β-(1→4) O-glycosidic linkages, inter-residue hydrogen bonding between O3H of the βGlcNAc bearing the OCH₃ aglycone and O5 of the adjacent βGlcNAc is observed based on the 2.79 Å internuclear distance between the O atoms. The structure of (IV) was compared to that determined previously for 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranose (β-chitobiose), (III). The O-glycosidic linkage torsion angles, phi (ϕ) and psi (ψ), in (III) and (IV) differ by 6–8°. The N-acetyl side chain conformation in (III) and (IV) shows some context dependence, with the C1—C2—N—C_car torsion angle 10–15° smaller for the βGlcNAc residue involved in the internal O-glycosidic linkage. In (IV), conformational disorder is observed in the exocyclic hydroxymethyl (–CH₂OH) group in the βGlcNAc residue bearing the OCH₃ aglycone, and a fitting of the electron density indicates an approximate 50:50 distribution of the gauche–gauche (gg) and gauche–trans (gt) conformers in the lattice. Similar behavior is not observed in (III), presumably due to the different packing structure in the vicinity of the –CH₂OH substituent that affects its ability to hydrogen bond to proximal donors/acceptors. Unlike (IV), a re-examination of the previously reported electron density of (III) revealed conformational disorder in the N-acetyl side chain attached to the reducing-end βGlcNAc residue caused by rotation about the C2—N bond.

Keywords: crystal structure; methyl β-chitobioside; hydrogen bonding; conformational analysis.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S2053229624005199/dg3055sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S2053229624005199/dg3055Isup2.hkl Contains datablock I
	Portable Document Format (PDF) file https://doi.org/10.1107/S2053229624005199/dg3055sup3.pdf Synthesis of Me-β:-chitobioside

CCDC reference: 2359730

Computing details top

Methyl 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranoside methanol monosolvate top

Crystal data top

C₁₇H₃₀N₂O₁₁·CH₄O	F(000) = 504
M_r = 470.47	D_x = 1.376 Mg m⁻³
Monoclinic, P2₁	Cu Kα radiation, λ = 1.54178 Å
a = 4.7599 (1) Å	Cell parameters from 9983 reflections
b = 14.3223 (5) Å	θ = 2.7–71.9°
c = 16.6515 (5) Å	µ = 0.99 mm⁻¹
β = 90.022 (2)°	T = 260 K
V = 1135.18 (6) Å³	Needle, colourless
Z = 2	0.26 × 0.04 × 0.02 mm

Data collection top

Bruker Venture diffractometer	4462 independent reflections
Radiation source: Incoatec Diamond micro-focus	4410 reflections with I > 2σ(I)
HELIOS Multi-layer monochromator	R_int = 0.048
Detector resolution: 7.41 pixels mm^-1	θ_max = 72.7°, θ_min = 2.7°
combination of ω and φ–scans	h = −5→5
Absorption correction: numerical (SADABS2016; Krause et al., 2015)	k = −17→17
T_min = 0.825, T_max = 1.0	l = −20→20
20006 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.031	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.080	w = 1/[σ²(F_o²) + (0.0524P)² + 0.0431P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max = 0.003
4462 reflections	Δρ_max = 0.19 e Å⁻³
330 parameters	Δρ_min = −0.14 e Å⁻³
1 restraint	Absolute structure: Twinning involves inversion, so Flack parameter cannot be determined
Primary atom site location: dual

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refined as a 2-component inversion twin

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
O1	0.6613 (6)	0.38954 (17)	1.01553 (14)	0.0445 (6)
O3	0.6528 (6)	0.37365 (16)	0.73265 (14)	0.0412 (5)
O5	0.7299 (6)	0.52182 (15)	0.94317 (12)	0.0396 (5)
O6	0.9612 (16)	0.7071 (5)	0.9453 (4)	0.0641 (17)	0.5
H6O	0.875712	0.697805	0.987275	0.096*	0.5
O6A	0.538 (2)	0.6967 (5)	0.8715 (6)	0.097 (3)	0.5
H6AO	0.528968	0.753853	0.871180	0.145*	0.5
O8	0.3233 (5)	0.2240 (2)	0.9067 (2)	0.0590 (8)
N1	0.7583 (5)	0.27620 (17)	0.87908 (16)	0.0299 (5)
H1N	0.932 (8)	0.266 (2)	0.8755 (19)	0.017 (7)*
C1	0.7936 (7)	0.4255 (2)	0.94888 (17)	0.0330 (6)
H1A	0.997167	0.416705	0.953441	0.040*
C2	0.6822 (6)	0.37358 (19)	0.87507 (18)	0.0293 (5)
H2A	0.476738	0.378155	0.874899	0.035*
C3	0.7936 (6)	0.4179 (2)	0.79753 (17)	0.0298 (6)
H3A	0.995667	0.405910	0.793219	0.036*
C4	0.7431 (7)	0.52381 (19)	0.79937 (17)	0.0296 (5)
H4A	0.540824	0.536263	0.796932	0.036*
C5	0.8640 (8)	0.5658 (2)	0.87643 (17)	0.0379 (6)
H5A	1.066193	0.553185	0.878652	0.046*
C6	0.8160 (12)	0.6693 (3)	0.8831 (2)	0.0593 (11)
H6A	0.873382	0.699202	0.833542	0.071*	0.5
H6B	0.617058	0.681054	0.890635	0.071*	0.5
H6C	0.876044	0.689708	0.935970	0.071*	0.5
H6D	0.932925	0.700711	0.843857	0.071*	0.5
C7	0.8083 (12)	0.4062 (3)	1.0894 (2)	0.0541 (10)
H7A	0.723974	0.370095	1.131539	0.081*
H7B	0.797678	0.471347	1.102649	0.081*
H7C	1.001519	0.388351	1.083378	0.081*
C8	0.5760 (6)	0.2082 (2)	0.8968 (2)	0.0372 (7)
C9	0.6950 (8)	0.1115 (3)	0.9016 (3)	0.0536 (9)
H9A	0.609485	0.078600	0.945515	0.080*
H9B	0.894259	0.114941	0.910051	0.080*
H9C	0.657534	0.078887	0.852381	0.080*
O1'	0.8809 (4)	0.57052 (15)	0.73397 (12)	0.0298 (4)
O3'	0.7196 (5)	0.74058 (15)	0.48957 (14)	0.0367 (5)
H3'O	0.567 (12)	0.759 (4)	0.471 (3)	0.052 (13)*
H3O	0.715 (10)	0.398 (3)	0.685 (3)	0.046 (11)*
O4'	0.4803 (6)	0.56213 (19)	0.42887 (16)	0.0499 (6)
H4'O	0.551 (11)	0.605 (4)	0.393 (3)	0.052 (12)*
O5'	0.8318 (5)	0.49753 (14)	0.61404 (12)	0.0297 (4)
O6'	0.7734 (5)	0.32150 (16)	0.54828 (16)	0.0395 (5)
H6'O	0.909 (16)	0.295 (5)	0.540 (4)	0.08 (2)*
O7'	1.1510 (5)	0.7998 (2)	0.6826 (2)	0.0559 (7)
N1'	0.7139 (5)	0.74593 (17)	0.66216 (15)	0.0287 (5)
H1N'	0.522 (8)	0.758 (2)	0.6661 (18)	0.020 (7)*
C1'	0.7340 (6)	0.5731 (2)	0.66160 (16)	0.0280 (5)
H1'A	0.531861	0.566904	0.671392	0.034*
C2'	0.7956 (5)	0.66437 (18)	0.61688 (16)	0.0267 (5)
H2'A	0.997740	0.667805	0.606156	0.032*
C3'	0.6387 (6)	0.6623 (2)	0.53637 (17)	0.0293 (6)
H3'A	0.436964	0.667216	0.547368	0.035*
C4'	0.6892 (6)	0.5726 (2)	0.48892 (16)	0.0317 (6)
H4'A	0.874727	0.575294	0.463538	0.038*
C5'	0.6709 (6)	0.48547 (19)	0.54181 (17)	0.0299 (6)
H5'A	0.474313	0.472657	0.555322	0.036*
C6'	0.7956 (8)	0.4029 (2)	0.49838 (19)	0.0373 (7)
H6'A	0.696242	0.392679	0.448283	0.045*
H6'B	0.991389	0.415061	0.486059	0.045*
C7'	0.8984 (6)	0.8097 (2)	0.6888 (2)	0.0330 (6)
C8'	0.7740 (8)	0.8961 (2)	0.7253 (2)	0.0461 (8)
H8'A	0.846644	0.950160	0.698249	0.069*
H8'B	0.822429	0.898956	0.781168	0.069*
H8'C	0.573311	0.894426	0.719681	0.069*
O1S	0.5403 (7)	0.6821 (2)	0.3019 (2)	0.0632 (8)
H1S	0.474933	0.734452	0.294896	0.095*
C1S	0.8289 (14)	0.6839 (6)	0.2880 (3)	0.091 (2)
H1SA	0.900524	0.621240	0.287904	0.136*
H1SB	0.919732	0.719208	0.329534	0.136*
H1SC	0.865150	0.712465	0.236866	0.136*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0584 (14)	0.0455 (13)	0.0297 (11)	−0.0091 (12)	0.0059 (10)	0.0026 (10)
O3	0.0594 (15)	0.0319 (10)	0.0324 (11)	−0.0080 (10)	−0.0036 (11)	−0.0007 (9)
O5	0.0583 (14)	0.0326 (11)	0.0280 (9)	0.0049 (10)	0.0080 (10)	−0.0016 (8)
O6	0.094 (4)	0.052 (3)	0.046 (3)	−0.032 (3)	0.010 (3)	−0.018 (3)
O6A	0.141 (7)	0.046 (3)	0.103 (6)	0.048 (4)	0.061 (6)	0.013 (4)
O8	0.0259 (12)	0.0619 (17)	0.089 (2)	−0.0020 (12)	0.0048 (13)	0.0188 (15)
N1	0.0206 (11)	0.0304 (12)	0.0387 (12)	0.0011 (9)	0.0013 (10)	0.0028 (10)
C1	0.0382 (15)	0.0302 (14)	0.0307 (13)	0.0011 (12)	0.0014 (13)	0.0019 (11)
C2	0.0243 (11)	0.0288 (13)	0.0348 (14)	0.0002 (10)	0.0010 (12)	0.0034 (11)
C3	0.0308 (14)	0.0298 (13)	0.0287 (12)	0.0002 (11)	0.0019 (11)	−0.0009 (10)
C4	0.0324 (13)	0.0272 (12)	0.0292 (12)	0.0011 (11)	0.0042 (12)	0.0014 (11)
C5	0.0537 (17)	0.0316 (14)	0.0285 (13)	−0.0022 (14)	0.0044 (14)	−0.0013 (12)
C6	0.114 (4)	0.0319 (16)	0.0321 (16)	−0.002 (2)	0.003 (2)	−0.0041 (14)
C7	0.088 (3)	0.0457 (17)	0.0290 (14)	0.0033 (19)	−0.0018 (18)	0.0021 (13)
C8	0.0280 (15)	0.0366 (15)	0.0472 (17)	−0.0027 (12)	0.0007 (13)	0.0083 (13)
C9	0.0460 (19)	0.0336 (16)	0.081 (3)	−0.0041 (15)	0.0046 (19)	0.0092 (17)
O1'	0.0318 (9)	0.0296 (9)	0.0280 (9)	−0.0027 (9)	−0.0009 (8)	0.0015 (8)
O3'	0.0347 (12)	0.0325 (10)	0.0429 (11)	−0.0005 (9)	−0.0012 (9)	0.0122 (9)
O4'	0.0624 (16)	0.0430 (13)	0.0442 (12)	−0.0106 (13)	−0.0234 (12)	0.0060 (11)
O5'	0.0345 (9)	0.0254 (8)	0.0291 (9)	0.0054 (7)	−0.0038 (9)	−0.0015 (7)
O6'	0.0369 (11)	0.0269 (10)	0.0547 (14)	0.0000 (9)	−0.0015 (10)	−0.0045 (10)
O7'	0.0233 (11)	0.0536 (15)	0.091 (2)	−0.0022 (11)	0.0001 (12)	−0.0168 (14)
N1'	0.0191 (11)	0.0274 (11)	0.0396 (12)	0.0016 (9)	0.0012 (9)	−0.0023 (9)
C1'	0.0288 (12)	0.0257 (11)	0.0294 (12)	0.0003 (12)	0.0010 (10)	−0.0003 (11)
C2'	0.0239 (11)	0.0238 (11)	0.0323 (12)	−0.0001 (10)	0.0029 (11)	0.0029 (11)
C3'	0.0229 (12)	0.0262 (12)	0.0389 (14)	0.0009 (11)	−0.0014 (11)	0.0072 (12)
C4'	0.0345 (13)	0.0332 (13)	0.0274 (12)	−0.0025 (13)	−0.0044 (11)	0.0022 (12)
C5'	0.0308 (14)	0.0275 (13)	0.0314 (13)	−0.0032 (11)	−0.0061 (12)	−0.0009 (10)
C6'	0.0444 (17)	0.0323 (14)	0.0353 (14)	0.0014 (13)	−0.0044 (14)	−0.0053 (12)
C7'	0.0313 (15)	0.0301 (14)	0.0376 (16)	−0.0011 (12)	−0.0037 (12)	0.0011 (12)
C8'	0.0425 (17)	0.0369 (15)	0.0587 (19)	0.0027 (14)	−0.0063 (16)	−0.0160 (16)
O1S	0.0670 (18)	0.0633 (19)	0.0594 (16)	0.0089 (16)	−0.0009 (15)	0.0201 (15)
C1S	0.070 (3)	0.141 (6)	0.061 (3)	−0.016 (4)	0.007 (3)	0.022 (3)

Geometric parameters (Å, º) top

O1—C1	1.376 (4)	C9—H9C	0.9600
O1—C7	1.435 (5)	O1'—C1'	1.394 (3)
O3—C3	1.420 (4)	O3'—C3'	1.419 (3)
O3—H3O	0.91 (5)	O3'—H3'O	0.83 (6)
O5—C1	1.416 (3)	O4'—C4'	1.418 (4)
O5—C5	1.428 (4)	O4'—H4'O	0.92 (5)
O6—C6	1.356 (8)	O5'—C1'	1.420 (3)
O6—H6O	0.8200	O5'—C5'	1.436 (4)
O6A—C6	1.393 (12)	O6'—C6'	1.436 (4)
O6A—H6AO	0.8200	O6'—H6'O	0.76 (8)
O8—C8	1.235 (4)	O7'—C7'	1.215 (4)
N1—C8	1.338 (4)	N1'—C7'	1.342 (4)
N1—C2	1.443 (4)	N1'—C2'	1.444 (4)
N1—H1N	0.84 (4)	N1'—H1N'	0.93 (4)
C1—C2	1.531 (4)	C1'—C2'	1.533 (4)
C1—H1A	0.9800	C1'—H1'A	0.9800
C2—C3	1.534 (4)	C2'—C3'	1.535 (4)
C2—H2A	0.9800	C2'—H2'A	0.9800
C3—C4	1.536 (3)	C3'—C4'	1.527 (4)
C3—H3A	0.9800	C3'—H3'A	0.9800
C4—O1'	1.437 (4)	C4'—C5'	1.530 (4)
C4—C5	1.529 (4)	C4'—H4'A	0.9800
C4—H4A	0.9800	C5'—C6'	1.508 (4)
C5—C6	1.503 (5)	C5'—H5'A	0.9800
C5—H5A	0.9800	C6'—H6'A	0.9700
C6—H6A	0.9700	C6'—H6'B	0.9700
C6—H6B	0.9700	C7'—C8'	1.501 (4)
C6—H6C	0.9700	C8'—H8'A	0.9600
C6—H6D	0.9700	C8'—H8'B	0.9600
C7—H7A	0.9600	C8'—H8'C	0.9600
C7—H7B	0.9600	O1S—C1S	1.393 (7)
C7—H7C	0.9600	O1S—H1S	0.8200
C8—C9	1.499 (5)	C1S—H1SA	0.9600
C9—H9A	0.9600	C1S—H1SB	0.9600
C9—H9B	0.9600	C1S—H1SC	0.9600

C1—O1—C7	113.9 (3)	H9A—C9—H9C	109.5
C3—O3—H3O	109 (3)	H9B—C9—H9C	109.5
C1—O5—C5	112.7 (2)	C1'—O1'—C4	116.0 (2)
C6—O6—H6O	109.5	C3'—O3'—H3'O	103 (3)
C6—O6A—H6AO	109.5	C4'—O4'—H4'O	98 (3)
C8—N1—C2	123.5 (2)	C1'—O5'—C5'	112.6 (2)
C8—N1—H1N	121 (2)	C6'—O6'—H6'O	103 (5)
C2—N1—H1N	115 (2)	C7'—N1'—C2'	123.1 (2)
O1—C1—O5	108.7 (3)	C7'—N1'—H1N'	119 (2)
O1—C1—C2	107.9 (2)	C2'—N1'—H1N'	117 (2)
O5—C1—C2	110.2 (2)	O1'—C1'—O5'	107.3 (2)
O1—C1—H1A	110.0	O1'—C1'—C2'	110.3 (2)
O5—C1—H1A	110.0	O5'—C1'—C2'	108.4 (2)
C2—C1—H1A	110.0	O1'—C1'—H1'A	110.2
N1—C2—C1	110.2 (2)	O5'—C1'—H1'A	110.2
N1—C2—C3	110.6 (2)	C2'—C1'—H1'A	110.2
C1—C2—C3	110.8 (2)	N1'—C2'—C1'	112.6 (2)
N1—C2—H2A	108.4	N1'—C2'—C3'	109.9 (2)
C1—C2—H2A	108.4	C1'—C2'—C3'	108.3 (2)
C3—C2—H2A	108.4	N1'—C2'—H2'A	108.6
O3—C3—C2	107.0 (2)	C1'—C2'—H2'A	108.6
O3—C3—C4	112.5 (2)	C3'—C2'—H2'A	108.6
C2—C3—C4	109.8 (2)	O3'—C3'—C4'	109.7 (2)
O3—C3—H3A	109.2	O3'—C3'—C2'	109.4 (2)
C2—C3—H3A	109.2	C4'—C3'—C2'	113.1 (2)
C4—C3—H3A	109.2	O3'—C3'—H3'A	108.2
O1'—C4—C5	106.3 (2)	C4'—C3'—H3'A	108.2
O1'—C4—C3	111.9 (2)	C2'—C3'—H3'A	108.2
C5—C4—C3	110.3 (2)	O4'—C4'—C3'	110.1 (3)
O1'—C4—H4A	109.4	O4'—C4'—C5'	106.3 (2)
C5—C4—H4A	109.4	C3'—C4'—C5'	112.3 (2)
C3—C4—H4A	109.4	O4'—C4'—H4'A	109.4
O5—C5—C6	108.0 (3)	C3'—C4'—H4'A	109.4
O5—C5—C4	108.1 (3)	C5'—C4'—H4'A	109.4
C6—C5—C4	113.1 (3)	O5'—C5'—C6'	106.6 (2)
O5—C5—H5A	109.2	O5'—C5'—C4'	110.7 (2)
C6—C5—H5A	109.2	C6'—C5'—C4'	109.9 (3)
C4—C5—H5A	109.2	O5'—C5'—H5'A	109.8
O6—C6—C5	111.9 (5)	C6'—C5'—H5'A	109.8
O6A—C6—C5	114.3 (5)	C4'—C5'—H5'A	109.8
O6—C6—H6A	109.2	O6'—C6'—C5'	109.3 (3)
C5—C6—H6A	109.2	O6'—C6'—H6'A	109.8
O6—C6—H6B	109.2	C5'—C6'—H6'A	109.8
C5—C6—H6B	109.2	O6'—C6'—H6'B	109.8
H6A—C6—H6B	107.9	C5'—C6'—H6'B	109.8
O6A—C6—H6C	108.7	H6'A—C6'—H6'B	108.3
C5—C6—H6C	108.7	O7'—C7'—N1'	122.7 (3)
O6A—C6—H6D	108.7	O7'—C7'—C8'	121.4 (3)
C5—C6—H6D	108.7	N1'—C7'—C8'	115.9 (3)
H6C—C6—H6D	107.6	C7'—C8'—H8'A	109.5
O1—C7—H7A	109.5	C7'—C8'—H8'B	109.5
O1—C7—H7B	109.5	H8'A—C8'—H8'B	109.5
H7A—C7—H7B	109.5	C7'—C8'—H8'C	109.5
O1—C7—H7C	109.5	H8'A—C8'—H8'C	109.5
H7A—C7—H7C	109.5	H8'B—C8'—H8'C	109.5
H7B—C7—H7C	109.5	C1S—O1S—H1S	109.5
O8—C8—N1	121.8 (3)	O1S—C1S—H1SA	109.5
O8—C8—C9	122.0 (3)	O1S—C1S—H1SB	109.5
N1—C8—C9	116.1 (3)	H1SA—C1S—H1SB	109.5
C8—C9—H9A	109.5	O1S—C1S—H1SC	109.5
C8—C9—H9B	109.5	H1SA—C1S—H1SC	109.5
H9A—C9—H9B	109.5	H1SB—C1S—H1SC	109.5
C8—C9—H9C	109.5

C7—O1—C1—O5	−81.3 (3)	C5—C4—O1'—C1'	−154.8 (2)
C7—O1—C1—C2	159.2 (3)	C3—C4—O1'—C1'	84.7 (3)
C5—O5—C1—O1	178.7 (3)	C4—O1'—C1'—O5'	−95.8 (3)
C5—O5—C1—C2	−63.3 (3)	C4—O1'—C1'—C2'	146.2 (2)
C8—N1—C2—C1	105.6 (3)	C5'—O5'—C1'—O1'	172.6 (2)
C8—N1—C2—C3	−131.5 (3)	C5'—O5'—C1'—C2'	−68.3 (3)
O1—C1—C2—N1	−64.1 (3)	C7'—N1'—C2'—C1'	115.7 (3)
O5—C1—C2—N1	177.4 (2)	C7'—N1'—C2'—C3'	−123.4 (3)
O1—C1—C2—C3	173.1 (2)	O1'—C1'—C2'—N1'	−60.3 (3)
O5—C1—C2—C3	54.6 (3)	O5'—C1'—C2'—N1'	−177.6 (2)
N1—C2—C3—O3	64.8 (3)	O1'—C1'—C2'—C3'	177.8 (2)
C1—C2—C3—O3	−172.7 (2)	O5'—C1'—C2'—C3'	60.6 (3)
N1—C2—C3—C4	−172.9 (2)	N1'—C2'—C3'—O3'	63.7 (3)
C1—C2—C3—C4	−50.4 (3)	C1'—C2'—C3'—O3'	−172.8 (2)
O3—C3—C4—O1'	−69.8 (3)	N1'—C2'—C3'—C4'	−173.7 (2)
C2—C3—C4—O1'	171.2 (2)	C1'—C2'—C3'—C4'	−50.2 (3)
O3—C3—C4—C5	172.1 (2)	O3'—C3'—C4'—O4'	−75.0 (3)
C2—C3—C4—C5	53.1 (3)	C2'—C3'—C4'—O4'	162.6 (2)
C1—O5—C5—C6	−172.0 (3)	O3'—C3'—C4'—C5'	166.9 (2)
C1—O5—C5—C4	65.3 (3)	C2'—C3'—C4'—C5'	44.4 (3)
O1'—C4—C5—O5	179.4 (2)	C1'—O5'—C5'—C6'	−179.4 (2)
C3—C4—C5—O5	−59.1 (3)	C1'—O5'—C5'—C4'	61.1 (3)
O1'—C4—C5—C6	59.8 (4)	O4'—C4'—C5'—O5'	−167.9 (2)
C3—C4—C5—C6	−178.7 (3)	C3'—C4'—C5'—O5'	−47.5 (3)
O5—C5—C6—O6	69.8 (5)	O4'—C4'—C5'—C6'	74.5 (3)
C4—C5—C6—O6	−170.6 (4)	C3'—C4'—C5'—C6'	−165.1 (3)
O5—C5—C6—O6A	−68.4 (5)	O5'—C5'—C6'—O6'	60.7 (3)
C4—C5—C6—O6A	51.3 (6)	C4'—C5'—C6'—O6'	−179.2 (3)
C2—N1—C8—O8	4.1 (5)	C2'—N1'—C7'—O7'	−6.3 (5)
C2—N1—C8—C9	−177.5 (3)	C2'—N1'—C7'—C8'	172.3 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O6^a—H6^Oa···O8ⁱ	0.82	2.04	2.823 (7)	160
N1—H1N···O8ⁱⁱ	0.84 (4)	2.02 (4)	2.829 (4)	160 (3)
C9—H9A···O5ⁱⁱⁱ	0.96	2.59	3.525 (5)	165
C9—H9B···O8ⁱⁱ	0.96	2.57	3.398 (5)	144
O3′—H3′O···O6′^iv	0.83 (6)	1.88 (6)	2.692 (3)	165 (5)
O3—H3O···O5′	0.91 (5)	1.94 (5)	2.789 (3)	155 (4)
O3—H3O···O6′	0.91 (5)	2.55 (5)	3.212 (4)	130 (4)
O4′—H4′O···O1S	0.92 (5)	1.88 (5)	2.739 (4)	155 (5)
O6′—H6′O···O3′^v	0.76 (8)	1.99 (8)	2.750 (4)	173 (7)
N1′—H1N′···O7′^vi	0.93 (4)	1.88 (4)	2.808 (3)	171 (3)
C6′—H6′A···O7′^v	0.97	2.66	3.366 (5)	130
C8′—H8′C···O7′^vi	0.96	2.50	3.347 (5)	147
O1S—H1S···O3^iv	0.82	2.13	2.950 (4)	173
C1S—H1SC···O8^iv	0.96	2.56	3.371 (7)	142

Symmetry codes: (i) −x+1, y+1/2, −z+2; (ii) x+1, y, z; (iii) −x+1, y−1/2, −z+2; (iv) −x+1, y+1/2, −z+1; (v) −x+2, y−1/2, −z+1; (vi) x−1, y, z.

Cremer–Pople puckering parameters for GlcNAc pyranosyl rings in (II)–(V) top

Compound^a	θ (°)	φ (°)	Q (Å)	q₂ (Å)	q₃ (Å)	Conformer^b
(II) residue a	0.6 (3)	52.5 (3)	0.572 (3)	0.006 (3)	0.572 (3)	^B_C1,C4
(II) residue b	2.9 (3)	96.5 (6)	0.580 (3)	0.029 (3)	0.580 (3)	^C5S_C1
(III) residue a	4.4 (3)	18.5 (4)	0.568 (3)	0.044 (3)	0.566 (3)	^C3S_C1
(III) residue b	8.8 (3)	338.1 (2)	0.577 (3)	0.088 (9)	0.570 (3)	^O5S_C2
(IV) residue a	5.2 (3)	324 (3)	0.581 (3)	0.055 (3)	0.579 (3)	^O5S_C2
(IV) residue b	12.1 (3)	45.8 (14)	0.564 (3)	0.121 (3)	0.552((3)	B_C1,C4
(V_A)	11.4 (3)	302.0 (12)	0.595 (3)	0.117 (3)	0.583 (3)	B_C2,C5
(V_B)	7.6 (2)	0.6 (2)	0.585 (3)	0.078 (2)	0.580 (3)	^C3,O5B

(a) See Fig. 1 for the definitions of residues a and b in disaccharides (II)–(IV). (b) B = boat and S = twist-boat or skew. Parameters shown for (II), (III) and (V) were extracted from crystal structures reported in Mo & Jensen (1978), Mo (1979), and Hu et al. (2011), respectively.

Selected structural parametersa in X-ray crystal structures of (II)–(V) top

Structural parameter	Disaccharides					Monosaccharides
	βGlcNAcOCH₃ (IV) (residue A)^b	βGlcNAcOR (IV) (residue B)	βGlcNAcOH (III) (residue A)	βGlcNAcOR (III) (residue B)	βGlcNAcOH (II) (residue A)	αGlcNAcOR (II) (residue B)	βGlcNAcOCH₃ (V_A)^c	βGlcNAcOCH₃ (V_B)^c
Bond lengths (Å)
C1—C2	1.531	1.533	1.522	1.522	1.526	1.515	1.533	1.531
C2—C3	1.534	1.535	1.521	1.531	1.527	1.517	1.530	1.534
C3—C4	1.536	1.527	1.531	1.516	1.520	1.516	1.527	1.525
C4—C5	1.529	1.530	1.536	1.507	1.519	1.537	1.526	1.523
C5—C6	1.503	1.508	1.501	1.499	1.512	1.516	1.519	1.514
C1—O1	1.376	1.394	1.389	1.389	1.361	1.395	1.389	1.387
C1—O5	1.416	1.420	1.427	1.429	1.418	1.414	1.418	1.423
C2—N1	1.443	1.444	1.450	1.446	1.450	1.460	1.456	1.455
C3—O3	1.420	1.419	1.430	1.424	1.421	1.431	1.430	1.424
C4—O4/O1'	1.437	1.418	1.448	1.425	1.448	1.422	1.424	1.425
C5—O5	1.428	1.436	1.429	1.436	1.438	1.427	1.443	1.435
C6—O6	f	1.436	1.413	1.415	1.419	1.423	1.430	1.430
O1—CH₃	1.435						1.445	1.439
N1—C_car	1.338	1.342	1.332	1.321	1.345	1.317	1.342	1.343
C_car—O_car	1.235	1.215	1.243	1.246	1.231	1.230	1.237	1.235
C_car—C_Me	1.499	1.501	1.497	1.495	1.490	1.506	1.508	1.510
O3^···O5'	2.789		2.796		3.311
O3^···O1'	3.022		3.099		2.886
O3^···O6'	3.212		2.875		4.828

Bond angles (°)
C5—O5—C1	112.73	112.59	112.59	112.13	114.49	112.92	111.9	111.8
O5—C1—O1	108.71	107.32	107.71	106.87	112.46	107.68	107.64	107.76
C1—O1—CH₃	113.95						112.39	112.43
C1'—O1'—C4		116.03		117.07		116.34
C2—N1—C_car	123.48	123.11	122.90	124.91	124.83	123.89	122.6	121.8
N1—C_car—C_Me	116.08	115.86	116.33	115.91	115.29	115.80	116.1	116.4
N1—C_car—O_car	121.85	122.69	121.49	121.26	123.94	123.89	122.6	122.9
O_car—C_car—C_Me	122.05	121.43	122.17	122.73	120.73	120.24	121.3	120.7
O3—H···O5'	154.85		132.75		142.95

Torsion angles (°)
C1—C2—C3—C4	-50.35	-50.20	-52.05	-48.16	-54.44	-56.66	-47.9	-50.1
C1—O5—C5—C4	65.26	61.07	61.82	67.41	60.36	59.12	69.3	66.5
C3—C4—C5—O5	-59.09	-47.51	-54.82	-58.61	-55.73	-54.68	-63.90	-56.56
O5—C5—C6—O6	e	60.73 (gt)	-60.61 (gg)	58.55 (gt)	-74.59 (gg)	-65.53 (gg)	64.3 (gt)	65.2 (gt)
C1—C2—N1—C_car	105.61	115.67	100.50	113.72	138.69	100.49	108.2	100.0
C3—C2—N1—C_car	-131.52	-123.42	-135.18	-122.48	-98.90	-136.95	-128.1	-137.2
C2—N1—C_car—C_Me	-177.54	172.27	-173.70	178.39	-179.61	-173.90	179.1	-179.1
H2—C2—N1—C_car	-12.83	-4.69	-12.50	-6.73	24.94	-16.95	-9.80	-19.20
C2—N1—C_car—O_car	4.14	-6.30	5.16	-5.28	-2.07	2.94	-1.2	0.8
C2—C3—O3—H	-179.52	-136.70	-148.65	-152.13	143.25	-51.20	-157.87	-112.65
C4—C3—O3—H	59.88	98.72	91.57		23.13
H3—C3—O3—H	–61.48	-19.09	-31.91		-97.92
C3—C4—O4—H		77.12		125.98		99.93	70.45	56.71
C5—C6—O6—H	f	-143.44	80.71	-178.65	88.34	-91.61	-80.28	-80.95
C2—C1—O1—CH₃/H (φ_a)^a	159.18		161.75		–163.57		169.48	175.49
O5—C1—O1—CH₃/H (φ_b)	–81.33		–80.33		74.69		–71.05	-66.63
H1—C1—O1—CH₃/H (φ_c)	39.18		40.24		–42.50		49.18	54.04
C2'—C1'—O1'—C4 (φ_a)		146.23		151.65		161.49
O5'—C1'—O1'—C4 (φ_b)		–95.82		–90.28		–79.57
H1'—C1'—O1'—C4 (φ_c)		24.26		30.20		36.30
C1'—O1'—C4—C3 (ψ_a)		84.73		77.27		133.47
C1'—O1'—C4—C5 (ψ_b)		–154.81		–162.31		–106.89
C1'—O1'—C4—H4 (ψ_c)		–36.73		–44.86		11.69

Notes: (a) O-glycosidic torsion angles ϕ', ϕ and ψ, which specify the rotational properties of the C1—O1, C1'—O1' and O1'—C4 bonds, respectively, in (II)–(IV) can be defined by three different vicinal pathways, which are distinguished by the a–c subscripts. (b) See Fig. 1 for the definitions of residues A and B in (II)–(IV). For simplicity, C_car and C_Me are used in place of the N-acetyl side-chain atom labeling in (IV) shown in Fig. 2. (c) (V_A) and (V_B) refer to the two molecules of (V) observed in the reported crystal structure (Hu et al., 2011). (d) Data for (II), (III) and (V) were taken from Mo & Jensen (1978), Mo (1979), and Hu et al. (2011), respectively. (e) This torsion angle is disorderd in the crystal; approximately equal populations of gg and gt. (f) Could not be determined due to disorder of the O5—C5—C6—O6 torsion angle.

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Conformational disorder in the crystal structure of methyl 2-acetamido-2-de­oxy-β-D-gluco­pyranosyl-(1→4)–2-acetamido-2-de­oxy-β-D-gluco­pyran­oside (methyl β-chitobioside) methanol monosolvate

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Conformational disorder in the crystal structure of methyl 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→4)–2-acetamido-2-deoxy-β-D-glucopyranoside (methyl β-chitobioside) methanol monosolvate