Conformational analysis of the disaccharide methyl α-d-manno­pyranosyl-(1→3)-2-O-acetyl-β-d-manno­pyran­oside monohydrate

Zhang, W.; Wu, Q.; Oliver, A.G.; Serianni, A.S.

doi:10.1107/S2053229619004728

Conformational analysis of the disaccharide methyl α-D-mannopyranosyl-(1→3)-2-O-acetyl-β-D-mannopyranoside monohydrate

W. Zhang, Q. Wu, A. G. Oliver and A. S. Serianni

The crystal structure of methyl α-D-mannopyranosyl-(1→3)-2-O-acetyl-β-D-mannopyranoside monohydrate, C₁₅H₂₆O₁₂·H₂O, (II), has been determined and the structural parameters for its constituent α-D-mannopyranosyl residue compared with those for methyl α-D-mannopyranoside. Mono-O-acetylation appears to promote the crystallization of (II), inferred from the difficulty in crystallizing methyl α-D-mannopyranosyl-(1→3)-β-D-mannopyranoside despite repeated attempts. The conformational properties of the O-acetyl side chain in (II) are similar to those observed in recent studies of peracetylated mannose-containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in (II) elongates by ∼0.02 Å upon O-acetylation. The phi (φ) and psi (ψ) torsion angles that dictate the conformation of the internal O-glycosidic linkage in (II) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated (II) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ∼16°) than for φ (Δ = ∼6°).

Keywords: disaccharide; conformational analysis; crystal structure; α-D-mannopyranosyl; β-D-mannopyranoside; glycobiology.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S2053229619004728/qs3082sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S2053229619004728/qs3082Isup2.hkl Contains datablock I
	Portable Document Format (PDF) file https://doi.org/10.1107/S2053229619004728/qs3082sup3.pdf NMR chemical shifts in disaccharide (II)

CCDC reference: 1908451

Computing details top

Data collection: APEX3 (Bruker, 2015); cell refinement: SAINT (Bruker, 2015); data reduction: SAINT (Bruker, 2015); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010) and PLATON (Spek, 2009).

Methyl α-D-mannopyranosyl-(1-3)-2-O-Acetyl-β-D-mannopyranoside monohydrate top

Crystal data top

C₁₅H₂₆O₁₂·H₂O	D_x = 1.472 Mg m⁻³
M_r = 416.37	Cu Kα radiation, λ = 1.54184 Å
Hexagonal, P6₅	Cell parameters from 9714 reflections
a = 7.8682 (3) Å	θ = 6.5–72.2°
c = 52.555 (3) Å	µ = 1.13 mm⁻¹
V = 2817.7 (3) Å³	T = 120 K
Z = 6	Block, colourless
F(000) = 1332	0.30 × 0.23 × 0.14 mm

Data collection top

Bruker APEXII diffractometer	3719 independent reflections
Radiation source: Incoatec micro-focus	3719 reflections with I > 2σ(I)
Detector resolution: 8.33 pixels mm^-1	R_int = 0.021
combination of ω and φ–scans	θ_max = 72.6°, θ_min = 5.1°
Absorption correction: numerical (SADABS; Krause et al., 2015)	h = −9→9
T_min = 0.816, T_max = 0.907	k = −9→9
37134 measured reflections	l = −64→64

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.022	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.058	w = 1/[σ²(F_o²) + (0.0341P)² + 0.5721P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max = 0.001
3719 reflections	Δρ_max = 0.20 e Å⁻³
287 parameters	Δρ_min = −0.16 e Å⁻³
1 restraint	Absolute structure: Flack x determined using 1835 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: dual	Absolute structure parameter: 0.028 (14)

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.

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

	x	y	z	U_iso*/U_eq
O1	1.05807 (18)	1.00809 (19)	0.54669 (3)	0.0230 (3)
O2	0.76178 (17)	0.62776 (18)	0.54504 (2)	0.0167 (2)
O4	0.31695 (19)	0.68238 (19)	0.50809 (2)	0.0177 (3)
H4O	0.216 (4)	0.636 (4)	0.5168 (5)	0.030 (7)*
O5	0.75643 (17)	0.97678 (18)	0.54738 (2)	0.0166 (3)
O6	0.3921 (3)	0.8446 (3)	0.57154 (3)	0.0380 (4)
H6O	0.338 (4)	0.879 (5)	0.5823 (6)	0.039 (8)*
O7	0.9678 (2)	0.5185 (2)	0.53482 (3)	0.0325 (3)
C1	0.8953 (2)	0.9597 (3)	0.53176 (3)	0.0173 (3)
H1	0.932708	1.050903	0.516908	0.021*
C2	0.8101 (2)	0.7488 (2)	0.52257 (3)	0.0157 (3)
H2	0.906976	0.734740	0.511761	0.019*
C3	0.6224 (3)	0.6899 (2)	0.50786 (3)	0.0144 (3)
H3	0.655673	0.773981	0.492323	0.017*
C4	0.4795 (2)	0.7205 (2)	0.52397 (3)	0.0142 (3)
H4	0.433840	0.628109	0.538762	0.017*
C5	0.5825 (2)	0.9338 (2)	0.53345 (3)	0.0152 (3)
H5	0.621069	1.023095	0.518385	0.018*
C6	0.4526 (3)	0.9744 (3)	0.55047 (3)	0.0191 (3)
H6A	0.525433	1.111930	0.556524	0.023*
H6B	0.336352	0.955685	0.540846	0.023*
C7	1.1834 (3)	1.2161 (3)	0.54980 (4)	0.0271 (4)
H7A	1.280757	1.241343	0.563074	0.041*
H7B	1.104304	1.275216	0.554727	0.041*
H7C	1.250786	1.273739	0.533717	0.041*
C8	0.8604 (2)	0.5337 (3)	0.54988 (4)	0.0182 (3)
C9	0.8169 (3)	0.4518 (3)	0.57627 (4)	0.0239 (4)
H9A	0.852907	0.349586	0.577821	0.036*
H9B	0.676564	0.395113	0.579779	0.036*
H9C	0.892892	0.556861	0.588507	0.036*
O1'	0.53187 (18)	0.48920 (18)	0.50014 (2)	0.0163 (2)
O2'	0.27523 (19)	0.22351 (19)	0.44429 (2)	0.0177 (3)
H2'O	0.172 (4)	0.119 (4)	0.4428 (5)	0.032 (7)*
O3'	0.27615 (19)	−0.08114 (18)	0.47211 (3)	0.0212 (3)
H3'O	0.301 (3)	−0.151 (4)	0.4816 (5)	0.018 (5)*
O4'	0.6920 (2)	0.05956 (19)	0.46951 (2)	0.0216 (3)
H4'O	0.753 (5)	0.048 (5)	0.4571 (7)	0.047 (8)*
O5'	0.66923 (17)	0.51175 (17)	0.46008 (2)	0.0148 (2)
O6'	0.8987 (2)	0.4274 (2)	0.42393 (3)	0.0251 (3)
H6'O	0.816 (5)	0.456 (5)	0.4197 (6)	0.044 (8)*
C1'	0.4947 (2)	0.4615 (2)	0.47384 (3)	0.0146 (3)
H1'	0.441294	0.546391	0.467925	0.017*
C2'	0.3387 (2)	0.2467 (2)	0.47017 (3)	0.0158 (3)
H2'	0.224819	0.214483	0.481598	0.019*
C3'	0.4230 (3)	0.1157 (2)	0.47688 (3)	0.0163 (3)
H3'	0.455995	0.130532	0.495416	0.020*
C4'	0.6097 (3)	0.1767 (2)	0.46164 (3)	0.0162 (3)
H4'	0.577373	0.155603	0.443093	0.019*
C5'	0.7577 (2)	0.3936 (2)	0.46646 (3)	0.0152 (3)
H5'	0.795964	0.412690	0.484833	0.018*
C6'	0.9407 (3)	0.4712 (3)	0.45016 (4)	0.0202 (4)
H6'A	1.019956	0.615329	0.452287	0.024*
H6'B	1.020419	0.413976	0.456212	0.024*
O1W	−0.1202 (2)	−0.1001 (2)	0.43620 (3)	0.0220 (3)
H1WA	−0.133 (4)	−0.130 (4)	0.4204 (7)	0.041 (8)*
H1WB	−0.174 (5)	−0.207 (5)	0.4430 (6)	0.043 (8)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0166 (6)	0.0188 (6)	0.0343 (7)	0.0093 (5)	−0.0071 (5)	−0.0058 (5)
O2	0.0181 (6)	0.0186 (6)	0.0172 (6)	0.0120 (5)	0.0012 (5)	0.0010 (5)
O4	0.0141 (6)	0.0217 (6)	0.0157 (6)	0.0076 (5)	−0.0007 (5)	0.0009 (5)
O5	0.0170 (6)	0.0193 (6)	0.0161 (6)	0.0110 (5)	−0.0027 (5)	−0.0041 (5)
O6	0.0642 (11)	0.0549 (10)	0.0193 (7)	0.0481 (10)	0.0177 (7)	0.0105 (7)
O7	0.0292 (7)	0.0345 (8)	0.0446 (9)	0.0241 (7)	0.0147 (7)	0.0118 (7)
C1	0.0140 (7)	0.0173 (8)	0.0202 (8)	0.0075 (6)	0.0004 (6)	−0.0010 (6)
C2	0.0170 (8)	0.0160 (8)	0.0160 (8)	0.0098 (7)	0.0039 (6)	0.0012 (6)
C3	0.0172 (8)	0.0127 (7)	0.0126 (7)	0.0070 (6)	0.0015 (6)	−0.0003 (6)
C4	0.0146 (7)	0.0161 (8)	0.0115 (7)	0.0074 (6)	−0.0006 (6)	0.0002 (6)
C5	0.0156 (7)	0.0165 (8)	0.0154 (8)	0.0095 (6)	−0.0018 (6)	−0.0004 (6)
C6	0.0225 (9)	0.0220 (8)	0.0175 (8)	0.0146 (7)	0.0003 (6)	−0.0027 (7)
C7	0.0165 (9)	0.0195 (9)	0.0417 (12)	0.0063 (7)	−0.0015 (8)	−0.0094 (8)
C8	0.0110 (7)	0.0158 (8)	0.0270 (9)	0.0061 (6)	−0.0024 (6)	−0.0032 (7)
C9	0.0276 (9)	0.0255 (9)	0.0241 (10)	0.0174 (8)	−0.0072 (8)	−0.0029 (7)
O1'	0.0219 (6)	0.0141 (6)	0.0119 (6)	0.0083 (5)	0.0007 (5)	−0.0017 (4)
O2'	0.0167 (6)	0.0173 (6)	0.0134 (6)	0.0044 (5)	−0.0020 (4)	0.0017 (4)
O3'	0.0218 (6)	0.0135 (6)	0.0222 (6)	0.0043 (5)	−0.0049 (5)	0.0018 (5)
O4'	0.0291 (7)	0.0228 (6)	0.0201 (6)	0.0183 (6)	0.0052 (5)	0.0039 (5)
O5'	0.0168 (6)	0.0134 (5)	0.0135 (5)	0.0070 (5)	0.0026 (4)	0.0007 (4)
O6'	0.0249 (7)	0.0293 (7)	0.0202 (7)	0.0130 (6)	0.0075 (5)	−0.0021 (5)
C1'	0.0165 (8)	0.0151 (7)	0.0121 (7)	0.0079 (6)	0.0021 (6)	0.0007 (6)
C2'	0.0151 (8)	0.0173 (8)	0.0119 (7)	0.0059 (7)	0.0011 (6)	0.0008 (6)
C3'	0.0173 (8)	0.0131 (8)	0.0147 (8)	0.0048 (7)	−0.0008 (6)	−0.0002 (6)
C4'	0.0203 (8)	0.0150 (8)	0.0142 (7)	0.0096 (7)	−0.0004 (6)	−0.0006 (6)
C5'	0.0172 (8)	0.0156 (8)	0.0139 (8)	0.0090 (7)	−0.0014 (6)	−0.0024 (6)
C6'	0.0175 (8)	0.0195 (8)	0.0219 (9)	0.0081 (7)	0.0018 (7)	−0.0013 (7)
O1W	0.0264 (7)	0.0186 (7)	0.0197 (7)	0.0102 (6)	−0.0002 (5)	0.0010 (5)

Geometric parameters (Å, º) top

O1—C1	1.383 (2)	C9—H9A	0.9800
O1—C7	1.437 (2)	C9—H9B	0.9800
O2—C8	1.337 (2)	C9—H9C	0.9800
O2—C2	1.444 (2)	O1'—C1'	1.407 (2)
O4—C4	1.428 (2)	O2'—C2'	1.429 (2)
O4—H4O	0.83 (3)	O2'—H2'O	0.82 (3)
O5—C1	1.426 (2)	O3'—C3'	1.417 (2)
O5—C5	1.435 (2)	O3'—H3'O	0.84 (3)
O6—C6	1.417 (2)	O4'—C4'	1.428 (2)
O6—H6O	0.83 (3)	O4'—H4'O	0.84 (4)
O7—C8	1.207 (2)	O5'—C1'	1.422 (2)
C1—C2	1.524 (2)	O5'—C5'	1.452 (2)
C1—H1	1.0000	O6'—C6'	1.419 (2)
C2—C3	1.520 (2)	O6'—H6'O	0.82 (4)
C2—H2	1.0000	C1'—C2'	1.525 (2)
C3—O1'	1.429 (2)	C1'—H1'	1.0000
C3—C4	1.520 (2)	C2'—C3'	1.521 (2)
C3—H3	1.0000	C2'—H2'	1.0000
C4—C5	1.537 (2)	C3'—C4'	1.524 (2)
C4—H4	1.0000	C3'—H3'	1.0000
C5—C6	1.508 (2)	C4'—C5'	1.531 (2)
C5—H5	1.0000	C4'—H4'	1.0000
C6—H6A	0.9900	C5'—C6'	1.517 (2)
C6—H6B	0.9900	C5'—H5'	1.0000
C7—H7A	0.9800	C6'—H6'A	0.9900
C7—H7B	0.9800	C6'—H6'B	0.9900
C7—H7C	0.9800	O1W—H1WA	0.86 (3)
C8—C9	1.495 (3)	O1W—H1WB	0.81 (4)

C1—O1—C7	113.08 (14)	C8—C9—H9A	109.5
C8—O2—C2	119.09 (13)	C8—C9—H9B	109.5
C4—O4—H4O	109.2 (18)	H9A—C9—H9B	109.5
C1—O5—C5	111.68 (12)	C8—C9—H9C	109.5
C6—O6—H6O	110 (2)	H9A—C9—H9C	109.5
O1—C1—O5	107.16 (14)	H9B—C9—H9C	109.5
O1—C1—C2	108.81 (14)	C1'—O1'—C3	113.60 (13)
O5—C1—C2	110.15 (14)	C2'—O2'—H2'O	109 (2)
O1—C1—H1	110.2	C3'—O3'—H3'O	106.5 (17)
O5—C1—H1	110.2	C4'—O4'—H4'O	108 (2)
C2—C1—H1	110.2	C1'—O5'—C5'	114.20 (12)
O2—C2—C3	108.63 (13)	C6'—O6'—H6'O	108 (2)
O2—C2—C1	106.63 (13)	O1'—C1'—O5'	111.09 (13)
C3—C2—C1	108.94 (14)	O1'—C1'—C2'	106.59 (13)
O2—C2—H2	110.8	O5'—C1'—C2'	111.97 (13)
C3—C2—H2	110.8	O1'—C1'—H1'	109.0
C1—C2—H2	110.8	O5'—C1'—H1'	109.0
O1'—C3—C4	109.51 (14)	C2'—C1'—H1'	109.0
O1'—C3—C2	110.66 (13)	O2'—C2'—C3'	112.14 (14)
C4—C3—C2	110.58 (13)	O2'—C2'—C1'	107.36 (13)
O1'—C3—H3	108.7	C3'—C2'—C1'	109.84 (14)
C4—C3—H3	108.7	O2'—C2'—H2'	109.1
C2—C3—H3	108.7	C3'—C2'—H2'	109.1
O4—C4—C3	107.27 (13)	C1'—C2'—H2'	109.1
O4—C4—C5	110.30 (13)	O3'—C3'—C2'	107.83 (14)
C3—C4—C5	108.98 (13)	O3'—C3'—C4'	112.47 (14)
O4—C4—H4	110.1	C2'—C3'—C4'	110.07 (14)
C3—C4—H4	110.1	O3'—C3'—H3'	108.8
C5—C4—H4	110.1	C2'—C3'—H3'	108.8
O5—C5—C6	108.35 (14)	C4'—C3'—H3'	108.8
O5—C5—C4	110.08 (13)	O4'—C4'—C3'	108.75 (14)
C6—C5—C4	112.36 (14)	O4'—C4'—C5'	109.48 (14)
O5—C5—H5	108.7	C3'—C4'—C5'	109.90 (14)
C6—C5—H5	108.7	O4'—C4'—H4'	109.6
C4—C5—H5	108.7	C3'—C4'—H4'	109.6
O6—C6—C5	109.25 (14)	C5'—C4'—H4'	109.6
O6—C6—H6A	109.8	O5'—C5'—C6'	105.90 (14)
C5—C6—H6A	109.8	O5'—C5'—C4'	109.51 (14)
O6—C6—H6B	109.8	C6'—C5'—C4'	113.28 (14)
C5—C6—H6B	109.8	O5'—C5'—H5'	109.4
H6A—C6—H6B	108.3	C6'—C5'—H5'	109.4
O1—C7—H7A	109.5	C4'—C5'—H5'	109.4
O1—C7—H7B	109.5	O6'—C6'—C5'	113.09 (15)
H7A—C7—H7B	109.5	O6'—C6'—H6'A	109.0
O1—C7—H7C	109.5	C5'—C6'—H6'A	109.0
H7A—C7—H7C	109.5	O6'—C6'—H6'B	109.0
H7B—C7—H7C	109.5	C5'—C6'—H6'B	109.0
O7—C8—O2	123.98 (18)	H6'A—C6'—H6'B	107.8
O7—C8—C9	125.89 (17)	H1WA—O1W—H1WB	102 (3)
O2—C8—C9	110.13 (15)

C7—O1—C1—O5	−79.07 (18)	C2—O2—C8—C9	168.49 (15)
C7—O1—C1—C2	161.85 (15)	C4—C3—O1'—C1'	112.13 (15)
C5—O5—C1—O1	178.65 (13)	C2—C3—O1'—C1'	−125.72 (15)
C5—O5—C1—C2	−63.13 (18)	C3—O1'—C1'—O5'	77.51 (16)
C8—O2—C2—C3	128.63 (15)	C3—O1'—C1'—C2'	−160.26 (13)
C8—O2—C2—C1	−114.09 (16)	C5'—O5'—C1'—O1'	61.63 (17)
O1—C1—C2—O2	58.60 (17)	C5'—O5'—C1'—C2'	−57.43 (18)
O5—C1—C2—O2	−58.59 (17)	O1'—C1'—C2'—O2'	170.46 (13)
O1—C1—C2—C3	175.67 (14)	O5'—C1'—C2'—O2'	−67.87 (17)
O5—C1—C2—C3	58.48 (18)	O1'—C1'—C2'—C3'	−67.36 (16)
O2—C2—C3—O1'	−60.93 (16)	O5'—C1'—C2'—C3'	54.31 (18)
C1—C2—C3—O1'	−176.72 (13)	O2'—C2'—C3'—O3'	−58.14 (17)
O2—C2—C3—C4	60.60 (17)	C1'—C2'—C3'—O3'	−177.43 (13)
C1—C2—C3—C4	−55.19 (17)	O2'—C2'—C3'—C4'	64.88 (18)
O1'—C3—C4—O4	−63.88 (16)	C1'—C2'—C3'—C4'	−54.41 (18)
C2—C3—C4—O4	173.92 (13)	O3'—C3'—C4'—O4'	−63.40 (18)
O1'—C3—C4—C5	176.70 (13)	C2'—C3'—C4'—O4'	176.35 (13)
C2—C3—C4—C5	54.50 (17)	O3'—C3'—C4'—C5'	176.78 (13)
C1—O5—C5—C6	−174.48 (14)	C2'—C3'—C4'—C5'	56.52 (18)
C1—O5—C5—C4	62.30 (17)	C1'—O5'—C5'—C6'	−179.33 (14)
O4—C4—C5—O5	−174.52 (13)	C1'—O5'—C5'—C4'	58.19 (17)
C3—C4—C5—O5	−57.00 (17)	O4'—C4'—C5'—O5'	−176.17 (13)
O4—C4—C5—C6	64.63 (18)	C3'—C4'—C5'—O5'	−56.79 (18)
C3—C4—C5—C6	−177.85 (14)	O4'—C4'—C5'—C6'	65.87 (19)
O5—C5—C6—O6	−63.86 (19)	C3'—C4'—C5'—C6'	−174.75 (15)
C4—C5—C6—O6	58.0 (2)	O5'—C5'—C6'—O6'	−69.90 (18)
C2—O2—C8—O7	−11.7 (3)	C4'—C5'—C6'—O6'	50.1 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O4—H4O···O7ⁱ	0.83 (3)	1.94 (3)	2.764 (2)	175 (3)
O6—H6O···O2′ⁱⁱ	0.83 (3)	1.96 (3)	2.793 (2)	173 (3)
O2′—H2′O···O1W	0.82 (3)	2.10 (3)	2.902 (2)	165 (3)
O3′—H3′O···O4ⁱⁱⁱ	0.84 (3)	1.96 (3)	2.7820 (19)	168 (2)
O4′—H4′O···O1W^iv	0.84 (4)	2.17 (3)	2.9463 (19)	153 (3)
O6′—H6′O···O6^v	0.82 (4)	2.06 (4)	2.819 (2)	153 (3)
O1W—H1WA···O1^vi	0.86 (3)	2.58 (3)	3.224 (2)	133 (3)
O1W—H1WA···O5^vi	0.86 (3)	2.23 (3)	3.0838 (18)	170 (3)
O1W—H1WB···O5′^vii	0.81 (4)	2.12 (4)	2.9303 (19)	177 (3)

Symmetry codes: (i) x−1, y, z; (ii) y, −x+y+1, z+1/6; (iii) x, y−1, z; (iv) x+1, y, z; (v) x−y+1, x, z−1/6; (vi) x−y, x−1, z−1/6; (vii) x−1, y−1, z.

Selected bond lengths, bond angles, and torsion angles in methyl α-D-mannopyranosyl-(1→3)-2-O-acetyl-β-D-mannopyranoside monohydrate, (II), and methyl α-D-mannopyranoside, (III) top

Structural parameter		Compound/residue
	(II) (R1)^a	(II) (R2)^d	(III)^c
Bond lengths (Å)
C1—C2	1.524	1.525	1.524
C2—C3	1.520	1.520	1.529
C3—C4	1.520	1.525	1.519
C4—C5	1.537	1.531	1.529
C5—C6	1.508	1.517	1.518
C1—O1	1.383	1.407	1.400
C1—O5	1.426	1.422	1.415
C2—O2	1.444	1.429	1.415
C3—O1'	1.429
C3—O3		1.417	1.422
C4—O4	1.428	1.427	1.430
C5—O5	1.435	1.452	1.435
C6—O6	1.418	1.419	1.413
O1—CH₃	1.437		1.423

Bond angles (°)
C5—O5—C1	111.68
C5'—O5'—C1'	114.21		114.29
C1'—O1'—C3	113.60
C1—O1—CH₃	113.07		113.91
C2—O2—C_car^b	119.10
O2—C_car—C_Me	110.11
O2—C_car—O_car	123.98
O_car—C_car—C_Me	125.91

Bond torsions (°)
C1—C2—C3—C4	-55.19
C1—O5—C5—C4	62.31
C1'—C2'—C3'—C4'	-54.43		-53.37
C1'—O5'—C5'—C4'	58.17		59.13
C2—C1—O1—CH₃ (φ)	161.86
O5—C1—O1—CH₃ (φ)	-79.07
H1—C1—O1—CH₃ (φ)	40.93
C2'—C1'—O1'—C3 (φ')	-160.30		-177.69
O5'—C1'—O1'—C3 (φ')	77.49		60.51
H1'—C1'—O1'—C3 (φ')	-42.68		-56.22
C1'—O1'—C3—C2 (ψ')	-125.73
C1'—O1'—C3—C4 (ψ')	112.12
C1'—O1'—C3—H3 (ψ')	-6.43
O5—C5—C6—O6	-63.82 (gg)
O5'—C5'—C6'—O6'	-69.88 (gg)		-65.10 (gg)
C1—C2—O2—C_car	-114.10
H2—C2—O2—C_car	6.63
C3—C2—O2—C_car	128.62
C2—O2—C_car—C_Me	168.48
C2—O2—C_car—O_car	-11.69

Notes: (a) R1 and R2 denote the βMan and αMan residues in disaccharide (II)), respectively; see structure in text. The primed atoms in R2 are shown as unprimed for the bond lengths to simplify the table. (b) C_car is the carbonyl C atom of the 2-O-acetyl side chain of (II), O_car is the carbonyl O atom of the side chain and C_Me is the methyl C atom of the side chain. (c) Bond angles and torsions in (III) are listed in some cases with primed atoms to allow visual comparison with the αMan residue (R2) of (II); data were taken from Jeffrey et al. (1977). (d) Bonds are shown with unprimed atoms in residue R2 of (II) to simplify structural comparisons in the table. gg = gauche–gauche.

Cremer–Pople puckering parameters for aldohexopyranosyl residues in (II) and (III) top

Compound/residue	θ (°)	φ (°)	Q (Å)	q₂ (Å)	q₃ (Å)
(II): βMan (R1)	2.00 (18)	16 (5)	0.5893 (18)	0.0208 (18)	0.5889 (18)
(II): αMan (R2)	2.78 (18)	230 (2)	0.5659 (18)	0.0303 (18)	0.5653 (18)
(III): αMan^a	1.2	286	0.557	0.0118	0.5569

Note: (a) errors were not reported for structure (III); data were taken from Jeffrey et al. (1977).

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Conformational analysis of the disaccharide methyl α-D-manno­pyranosyl-(1→3)-2-O-acetyl-β-D-manno­pyran­oside monohydrate

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Conformational analysis of the disaccharide methyl α-D-mannopyranosyl-(1→3)-2-O-acetyl-β-D-mannopyranoside monohydrate