Structures of furanosides: geometrical analysis of low-temperature X-ray and neutron crystal ­structures of five crystalline methyl ­pentofuranosides

Crystal structures of all five crystalline methyl D-pentofuranosides, methyl α-D-arabinofuranoside (1), methyl β-D-arabinofuranoside (2), methyl α-D-lyxofuranoside (3), methyl β-D-ribofuranoside (4) and methyl α-D-xylofuranoside (5) have been determined by means of cryogenic X-ray and neutron crystallography. The neutron diffraction experiments provide accurate, unbiased H-atom positions which are especially important because of the critical role of hydrogen bonding in these systems. This paper summarizes the geometrical and conformational parameters of the structures of all five crystalline methyl pentofuranosides, several of them reported here for the first time. The methyl pentofuranoside structures are compared with the structures of the five crystalline methyl hexopyranosides for which accurate X-ray and neutron structures have been determined. Unlike the methyl hexopyranosides, which crystallize exclusively in the C₁ chair conformation, the five crystalline methyl pentofuranosides represent a very wide range of ring conformations.

S1. Comment

submitted separately

Computing details

Data collection: maXus (Nonius, 1998) for baraf_xray; 'custom software (Schultz, 1987)' for baraf_neutron; ILL programs Hklgen and Mad for axylf_neutron, alyxf_neutron. Cell refinement: maXus (Nonius, 1998) for baraf_xray; 'GSAS (Larson & Von Dreele, 1994)' for baraf_neutron; ILL program Rafd19 for axylf_neutron, alyxf_neutron. Data reduction: maXus (Nonius, 1998) for baraf_xray; 'GSAS (Larson & Von Dreele, 1994)' for baraf_neutron; 'ILL program Retreat (Wilkinson et al., 1988)' for axylf_neutron, alyxf_neutron. Program(s) used to solve structure: 'SHELXS97 (Sheldrick, 1990)' for baraf_xray, axylf_neutron, alyxf_neutron; 'from x-ray structure' for baraf_neutron. Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997) for baraf_xray, axylf_neutron, alyxf_neutron; 'GSAS (Larson & Von Dreele, 1994)' for baraf_neutron. For all compounds, molecular graphics: PLATON (A.L.Spek ,2000). Software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) for baraf_xray, axylf_neutron, alyxf_neutron; manual for baraf_neutron.

Figures

(baraf_xray) Methyl-beta-D-arabinofuranoside

Crystal data

C6H12O5	Dx = 1.401 Mg m^−3
Mr = 164.16	Mo Kα radiation, λ = 0.71070 Å
Orthorhombic, P212121	Cell parameters from 600 reflections
a = 5.906 (1) Å	θ = 8–25°
b = 10.845 (3) Å	µ = 0.12 mm^−1
c = 12.154 (3) Å	T = 100 K
V = 778.5 (2) Å^3	Rectangular prism, clear blank white
Z = 4	0.4 × 0.1 × 0.1 mm
F(000) = 352

Data collection

Nonius Kappa-CCD diffractometer	2219 reflections with > 4σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.000
Graphite monochromator	θmax = 30.9°, θmin = 2.5°
combination of psi and phi oscillations scans	h = 0→8
2313 measured reflections	k = 0→15
2313 independent reflections	l = −16→17

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.076	w = 1/[σ^2(Fo^2) + (0.0517P)^2 + 0.0636P] where P = (Fo^2 + 2Fc^2)/3'
S = 1.00	(Δ/σ)max = 0.017
1365 reflections	Δρmax = 0.24 e Å^−3
148 parameters	Δρmin = −0.20 e Å^−3
0 restraints	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.6 (6)

Special details

Experimental. The crystal was flash-frozen in Paratone-N oil.

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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.20919 (12)	0.19581 (6)	0.19598 (5)	0.02242 (14)
O3	0.33979 (11)	0.44942 (6)	0.45934 (5)	0.02032 (14)
H13	0.427 (3)	0.4119 (14)	0.5017 (16)	0.045 (4)*
O4	0.10562 (11)	0.40443 (6)	0.19685 (5)	0.02090 (14)
O2	0.12255 (12)	0.18433 (6)	0.41985 (5)	0.02161 (14)
H12	0.242 (4)	0.1437 (17)	0.3963 (17)	0.052 (5)*
O5	0.49691 (14)	0.55965 (7)	0.11385 (6)	0.02812 (17)
H15	0.402 (3)	0.5439 (13)	0.0673 (13)	0.033 (4)*
C4	0.28720 (14)	0.45762 (8)	0.26152 (7)	0.01753 (15)
H4	0.239 (2)	0.5406 (11)	0.2836 (10)	0.015 (3)*
C3	0.31500 (14)	0.37593 (7)	0.36319 (6)	0.01674 (15)
H3	0.450 (2)	0.3202 (11)	0.3540 (10)	0.017 (3)*
C2	0.10185 (15)	0.29605 (8)	0.36129 (7)	0.01803 (15)
H2	−0.017 (2)	0.3430 (11)	0.3926 (11)	0.021 (3)*
C5	0.50361 (15)	0.46571 (8)	0.19544 (7)	0.02094 (17)
H5A	0.620 (2)	0.4858 (12)	0.2471 (12)	0.024 (3)*
H5B	0.532 (2)	0.3814 (12)	0.1625 (11)	0.023 (3)*
C1	0.05974 (15)	0.28475 (8)	0.23740 (8)	0.01961 (17)
H1	−0.092 (2)	0.2685 (12)	0.2172 (11)	0.023 (3)*
C6	0.1762 (2)	0.17174 (10)	0.08154 (8)	0.0301 (2)
H6A	0.303 (3)	0.1109 (14)	0.0595 (15)	0.036 (4)*
H6B	0.179 (3)	0.2490 (15)	0.0388 (13)	0.038 (4)*
H6C	0.024 (3)	0.1348 (14)	0.0673 (13)	0.038 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0260 (3)	0.0235 (3)	0.0177 (3)	0.0037 (3)	−0.0007 (2)	−0.0024 (2)
O3	0.0245 (3)	0.0216 (3)	0.0148 (3)	0.0024 (2)	−0.0025 (2)	0.0001 (2)
O4	0.0205 (3)	0.0218 (3)	0.0204 (3)	−0.0002 (2)	−0.0045 (2)	0.0053 (2)
O2	0.0242 (3)	0.0188 (3)	0.0217 (3)	0.0021 (2)	0.0076 (2)	0.0052 (2)
O5	0.0283 (3)	0.0365 (4)	0.0196 (3)	−0.0128 (3)	−0.0052 (3)	0.0118 (3)
C4	0.0200 (4)	0.0165 (3)	0.0160 (3)	0.0008 (3)	−0.0011 (3)	0.0010 (3)
C3	0.0186 (4)	0.0169 (3)	0.0148 (3)	0.0020 (3)	0.0010 (3)	0.0018 (3)
C2	0.0187 (3)	0.0167 (3)	0.0187 (4)	0.0020 (3)	0.0032 (3)	0.0023 (3)
C5	0.0212 (4)	0.0253 (4)	0.0164 (4)	−0.0030 (3)	−0.0003 (3)	0.0049 (3)
C1	0.0186 (4)	0.0197 (4)	0.0204 (4)	−0.0001 (3)	−0.0009 (3)	0.0019 (3)
C6	0.0376 (5)	0.0350 (5)	0.0179 (4)	−0.0016 (4)	−0.0009 (4)	−0.0049 (4)

Geometric parameters (Å, º)

O1—C1	1.4010 (11)	C4—H4	0.981 (12)
O1—C6	1.4286 (12)	C3—C2	1.5283 (12)
O3—C3	1.4221 (10)	C3—H3	1.005 (12)
O3—H13	0.836 (19)	C2—C1	1.5310 (12)
O4—C1	1.4145 (11)	C2—H2	0.949 (14)
O4—C4	1.4494 (10)	C5—H5A	0.955 (14)
O2—C2	1.4105 (10)	C5—H5B	1.012 (13)
O2—H12	0.88 (2)	C1—H1	0.943 (14)
O5—C5	1.4223 (10)	C6—H6A	1.035 (16)
O5—H15	0.816 (17)	C6—H6B	0.987 (16)
C4—C5	1.5121 (12)	C6—H6C	0.999 (19)
C4—C3	1.5292 (11)
C1—O1—C6	112.93 (8)	C3—C2—H2	107.5 (8)
C3—O3—H13	107.3 (12)	C1—C2—H2	108.5 (8)
C1—O4—C4	108.54 (6)	O5—C5—C4	112.86 (7)
C2—O2—H12	109.6 (13)	O5—C5—H5A	108.4 (8)
C5—O5—H15	110.6 (10)	C4—C5—H5A	105.7 (9)
O4—C4—C5	111.13 (7)	O5—C5—H5B	112.1 (8)
O4—C4—C3	106.68 (7)	C4—C5—H5B	107.3 (8)
C5—C4—C3	111.84 (7)	H5A—C5—H5B	110.4 (11)
O4—C4—H4	107.4 (7)	O1—C1—O4	112.69 (7)
C5—C4—H4	109.7 (7)	O1—C1—C2	107.83 (7)
C3—C4—H4	109.9 (7)	O4—C1—C2	103.78 (7)
O3—C3—C2	114.51 (7)	O1—C1—H1	112.0 (8)
O3—C3—C4	110.51 (6)	O4—C1—H1	105.2 (8)
C2—C3—C4	103.16 (7)	C2—C1—H1	115.1 (8)
O3—C3—H3	110.3 (7)	O1—C6—H6A	105.6 (10)
C2—C3—H3	108.0 (7)	O1—C6—H6B	110.8 (9)
C4—C3—H3	110.1 (7)	H6A—C6—H6B	113.1 (13)
O2—C2—C3	114.07 (7)	O1—C6—H6C	111.4 (9)
O2—C2—C1	116.20 (7)	H6A—C6—H6C	110.6 (12)
C3—C2—C1	101.19 (6)	H6B—C6—H6C	105.4 (13)
O2—C2—H2	108.8 (7)

(baraf_neutron) Methyl-beta-D-arabinofuranoside

Crystal data

C6H12O5	Z = 4
Mr = 164.16	Dx = 1.409 Mg m^−3
Orthorhombic, P212121	Neutron radiation, λ = 0.7-4.2 Å
a = 5.901 (1) Å	µ = wavelength-dependent mm^−1
b = 10.791 (2) Å	T = 20 K
c = 12.151 (2) Å	Rectangular prism, clear blank white
V = 773.8 (2) Å^3	2.0 × 2.0 × 1.0 mm

Data collection

'position-sensitive, 6-Li-glass area detector' diffractometer	4688 independent reflections
Radiation source: spallation source (IPNS)	2977 reflections with > 3σ(I)
time–of–flight histogram analysis (Jacobson, 1986) scans	θmax = 61.0°, θmin = 1.0°
Absorption correction: for a sphere ?	h = 0→8
Tmin = ?, Tmax = ?	k = 0→15
4688 measured reflections	l = 0→17

Refinement

Refinement on F^2	Primary atom site location: from X-ray
Least-squares matrix: full	Secondary atom site location: from X-ray
R[F^2 > 2σ(F^2)] = 0.100	Hydrogen site location: structure-invariant direct methods
wR(F^2) = 0.117	All H-atom parameters refined
S = 1.10	Weighting scheme based on measured s.u.'s SigmaFoSq = SigmaFoSq + (.002*FoSq)^2 Wght = 1.0/(SigmaFoSq)^2 All single crystal weights were scaled by Min(Fo/Fc,Fc/Fo)^4
4688 reflections	(Δ/σ)max = 0.001
226 parameters	Extinction correction: Wavelength-dependent spherical absorption correction using cross-sections from Sears (1986), followed by a secondary extinction correction (Type-II) during final refinement.
0 restraints	Extinction coefficient: 0.0002958

Special details

Experimental. The atomic and magnetic scattering factors for 3 types of atoms were: Atom b-len a(1) b(1) a(2) b(2) a(3) b(3) a(4) b(4) c O. 581 3.04850 13.27710 2.28680 5.70110 1.54630. 32390. 86700 32.90890. 25080

C. 665 2.31000 20.84390 1.02000 10.20750 1.58860. 56870. 86500 51.65120. 21560

H -.374. 49300 10.51090. 32291 26.12570. 14019 3.14236. 04081 57.79970. 00304

Refinement. Symmetry-related reflections were not averaged since different extinction factors are applicable to reflections measured at different wavelengths.

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

	x	y	z	Uiso*/Ueq
O1	0.2069 (3)	0.19567 (14)	0.19516 (14)	0.0081
O2	0.1172 (3)	0.18482 (14)	0.41910 (13)	0.0063
O3	0.3368 (3)	0.45047 (16)	0.45886 (13)	0.0067
O4	0.1037 (3)	0.40547 (14)	0.19599 (13)	0.0067
O5	0.4990 (3)	0.56000 (16)	0.11330 (13)	0.0088
C1	0.0565 (2)	0.28563 (13)	0.23639 (11)	0.0059
C2	0.0965 (2)	0.29667 (12)	0.36087 (11)	0.0052
C3	0.3121 (2)	0.37679 (12)	0.36319 (11)	0.0047
C4	0.2866 (3)	0.45931 (12)	0.26050 (11)	0.0058
C5	0.5044 (3)	0.46645 (13)	0.19501 (12)	0.0068
C6	0.1748 (3)	0.17180 (14)	0.08093 (12)	0.0101
H1	−0.1200 (6)	0.2630 (4)	0.2123 (3)	0.0186
H2	−0.0459 (6)	0.3489 (3)	0.3963 (3)	0.0176
H3	0.4581 (6)	0.3142 (3)	0.3539 (3)	0.0180
H4	0.2332 (6)	0.5533 (3)	0.2849 (3)	0.0187
H5A	0.6459 (6)	0.4885 (4)	0.2503 (3)	0.0215
H5B	0.5384 (8)	0.3749 (4)	0.1583 (3)	0.0227
H6A	0.3039 (9)	0.1070 (4)	0.0563 (3)	0.0281
H6B	0.1939 (10)	0.2564 (4)	0.0334 (3)	0.0289
H6C	0.0105 (8)	0.1319 (5)	0.0656 (4)	0.0301
H12	0.2583 (7)	0.1414 (3)	0.4011 (3)	0.0184
H13	0.4393 (7)	0.4052 (4)	0.5093 (3)	0.0197
H15	0.3833 (7)	0.5439 (4)	0.0578 (3)	0.0213

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0101 (6)	0.0075 (5)	0.0067 (5)	0.0012 (5)	−0.0007 (6)	−0.0006 (4)
O2	0.0075 (5)	0.0058 (5)	0.0055 (5)	−0.0001 (5)	0.0002 (5)	0.0019 (4)
O3	0.0073 (5)	0.0080 (5)	0.0050 (5)	0.0017 (5)	−0.0010 (5)	−0.0002 (4)
O4	0.0072 (5)	0.0072 (5)	0.0057 (5)	0.0003 (5)	0.0001 (5)	0.0017 (4)
O5	0.0100 (6)	0.0114 (6)	0.0050 (5)	−0.0033 (6)	−0.0024 (6)	0.0027 (4)
C1	0.0067 (4)	0.0064 (5)	0.0045 (4)	−0.0004 (4)	−0.0005 (4)	0.0014 (3)
C2	0.0055 (4)	0.0046 (4)	0.0054 (4)	0.0008 (4)	0.0012 (4)	0.0005 (3)
C3	0.0053 (4)	0.0053 (4)	0.0036 (4)	−0.0010 (4)	0.0010 (4)	0.0002 (3)
C4	0.0070 (5)	0.0052 (4)	0.0052 (4)	−0.0001 (4)	0.0007 (4)	0.0001 (3)
C5	0.0077 (4)	0.0091 (5)	0.0037 (4)	−0.0003 (4)	−0.0004 (5)	0.0015 (4)
C6	0.0130 (6)	0.0115 (5)	0.0059 (5)	0.0004 (5)	−0.0015 (5)	−0.0014 (4)
H1	0.0137 (12)	0.0220 (14)	0.0201 (14)	−0.0023 (11)	−0.0051 (12)	0.0007 (10)
H2	0.0167 (12)	0.0186 (13)	0.0175 (12)	0.0038 (11)	0.0037 (12)	−0.0007 (10)
H3	0.0169 (12)	0.0187 (13)	0.0185 (12)	0.0033 (11)	−0.0015 (13)	−0.0039 (11)
H4	0.0228 (15)	0.0124 (11)	0.0208 (14)	−0.0027 (12)	0.0003 (13)	−0.0030 (9)
H5A	0.0186 (13)	0.0274 (16)	0.0185 (13)	−0.0042 (14)	−0.0041 (13)	0.0047 (12)
H5B	0.0283 (18)	0.0179 (14)	0.0219 (15)	0.0008 (14)	0.0033 (15)	−0.0028 (11)
H6A	0.032 (2)	0.0311 (18)	0.0215 (15)	0.0163 (18)	−0.0003 (17)	−0.0033 (13)
H5B	0.0283 (18)	0.0179 (14)	0.0219 (15)	0.0008 (14)	0.0033 (15)	−0.0028 (11)
H6A	0.032 (2)	0.0311 (18)	0.0215 (15)	0.0163 (18)	−0.0003 (17)	−0.0033 (13)
H6B	0.042 (2)	0.0244 (16)	0.0200 (14)	−0.0064 (19)	0.004 (2)	0.0070 (13)
H6C	0.0215 (16)	0.044 (3)	0.0245 (18)	−0.0094 (19)	−0.0034 (16)	−0.0098 (17)
H12	0.0203 (14)	0.0157 (13)	0.0191 (13)	0.0064 (11)	0.0027 (13)	0.0034 (10)
H13	0.0220 (15)	0.0232 (15)	0.0138 (11)	0.0016 (14)	−0.0063 (12)	0.0024 (11)
H15	0.0200 (13)	0.0258 (15)	0.0181 (13)	−0.0027 (14)	−0.0059 (13)	0.0033 (12)

Geometric parameters (Å, º)

O1—C1	1.407 (2)	C2—H2	1.099 (4)
O1—C6	1.424 (2)	C3—C4	1.5404 (19)
O2—C2	1.404 (2)	C3—H3	1.100 (4)
O2—H12	0.981 (4)	C4—C5	1.513 (2)
O3—C3	1.416 (2)	C4—H4	1.103 (4)
O3—H13	0.990 (4)	C5—H5A	1.098 (4)
O4—C1	1.411 (2)	C5—H5B	1.102 (4)
O4—C4	1.455 (2)	C6—H6A	1.077 (5)
O5—C5	1.416 (2)	C6—H6B	1.086 (4)
O5—H15	0.975 (4)	C6—H6C	1.077 (5)
C2—C1	1.5355 (19)	H1—C1	1.109 (4)
C2—C3	1.5387 (19)
C1—O1—C6	112.75 (10)	C3—C2—H2	110.25 (16)
C3—O3—H13	107.38 (12)	C1—C2—H2	108.08 (18)
C1—O4—C4	108.9 (3)	O5—C5—C4	112.70 (14)
C2—O2—H12	112.1 (3)	O5—C5—H5A	107.0 (2)
C5—O5—H15	110.2 (3)	C4—C5—H5A	109.6 (3)
O4—C4—C5	111.53 (12)	O5—C5—H5B	113.1 (3)
O4—C4—C3	106.15 (12)	C4—C5—H5B	108.5 (3)
C3—C4—C5	111.85 (11)	H5A—C5—H5B	108.8 (3)
O4—C4—H4	107.5 (2)	O1—C1—O4	112.59 (13)
C3—C4—H4	110.0 (2)	O1—C1—C2	107.90 (12)
C5—C4—H4	109.7 (2)	O4—C1—C2	103.97 (12)
O3—C3—C2	114.56 (13)	O1—C1—H1	110.3 (2)
O3—C3—C4	110.52 (12)	O4—C1—H1	107.2 (2)
C2—C3—C4	103.24 (11)	C2—C1—H1	114.9 (2)
O3—C3—H3	111.27 (19)	O1—C6—H6A	107.1 (3)
C2—C3—H3	107.1 (2)	O1—C6—H6B	110.6 (3)
C4—C3—H3	110.1 (3)	O1—C6—H6C	111.1 (3)
O2—C2—C3	113.69 (13)	H6A—C6—H6B	108.9 (4)
O2—C2—C1	116.29 (12)	H6A—C6—H6C	109.2 (4)
C1—C2—C3	100.87 (11)	H6B—C6—H6C	109.7 (4)
O2—C2—H2	108.43 (17)

(axylf_neutron) Methyl-alpha xylofuranoside

Crystal data

C6H12O5	F(000) = 48
Mr = 164.16	Dx = 1.488 Mg m^−3
Monoclinic, P21	Neutron radiation, λ = 0.95284 Å
a = 6.2238 (2) Å	Cell parameters from 1577 reflections
b = 8.1389 (2) Å	θ = 3–50°
c = 7.3637 (2) Å	µ = 2.56 mm^−1
β = 101.1465 (17)°	T = 20 K
V = 365.97 (2) Å^3	Rectangular block, clear blank white
Z = 2	3.5 × 1.12 × 1.11 mm

Data collection

'4x64 deg. position-sensitive detector (Thomas et. al., 1983) diffractometer	1949 reflections with > 4σ(I)
Radiation source: neutron reactor at ILL	Rint = 0.043
Ge (117) monochromator	θmax = 50.1°, θmin = 3.8°
'ω scans in equatorial geometry'	h = −3→9
Absorption correction: analytical ?	k = −5→13
Tmin = 0.699, Tmax = 0.783	l = −11→11
2323 measured reflections	3 standard reflections every 50 reflections
2323 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.040	All H-atom parameters refined
wR(F^2) = 0.102	' w = 1/[σ^2(Fo^2) + (0.0729P)^2 + 0.7096P] where P = (Fo^2 + 2Fc^2)/3'
S = 1.11	(Δ/σ)max = 0.003
1619 reflections	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
209 parameters	Extinction coefficient: 0.040 (6)
1 restraint	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0 (10)

Special details

Experimental. Atomic scattering factors were taken from Sears (1992).

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 (Ų)

	x	y	z	Uiso*/Ueq
C1	0.0947 (2)	0.36155 (15)	0.69963 (15)	0.0055 (2)
H1	−0.0841 (5)	0.3840 (4)	0.6814 (4)	0.0181 (5)
C2	0.19469 (19)	0.40631 (15)	0.53273 (16)	0.0054 (2)
H2	0.1235 (5)	0.5224 (4)	0.4743 (4)	0.0167 (5)
C3	0.43401 (19)	0.43370 (15)	0.62512 (16)	0.0054 (2)
H3	0.5108 (5)	0.3118 (4)	0.6547 (4)	0.0163 (5)
C4	0.41324 (19)	0.51615 (15)	0.80960 (16)	0.0058 (2)
H4	0.5367 (5)	0.4684 (4)	0.9256 (4)	0.0182 (5)
C5	0.4280 (2)	0.70172 (15)	0.81958 (16)	0.0067 (2)
H5A	0.5955 (5)	0.7422 (4)	0.8162 (5)	0.0201 (5)
H5B	0.3906 (6)	0.7377 (4)	0.9542 (4)	0.0222 (6)
C6	0.0258 (2)	0.13438 (17)	0.87799 (18)	0.0087 (2)
H6A	0.0639 (7)	0.2035 (6)	1.0071 (5)	0.0290 (7)
H6B	0.0728 (8)	0.0069 (5)	0.9033 (7)	0.0306 (8)
H6C	−0.1517 (6)	0.1376 (7)	0.8236 (6)	0.0297 (8)
O1	0.1421 (2)	0.19638 (18)	0.74350 (18)	0.0067 (2)
O2	0.1612 (2)	0.28913 (19)	0.38810 (19)	0.0068 (2)
H12	0.2496 (5)	0.1911 (4)	0.4279 (4)	0.0197 (5)
O5	0.2872 (2)	0.78399 (19)	0.6721 (2)	0.0080 (2)
H15	0.1332 (5)	0.7667 (5)	0.6791 (5)	0.0212 (6)
O3	0.5571 (2)	0.52824 (19)	0.51914 (19)	0.0073 (2)
H13	0.6138 (5)	0.4522 (4)	0.4349 (4)	0.0193 (5)
O4	0.1974 (2)	0.46977 (17)	0.83997 (19)	0.0066 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0060 (4)	0.0057 (4)	0.0052 (4)	−0.0003 (3)	0.0020 (3)	−0.0005 (3)
H1	0.0100 (10)	0.0220 (13)	0.0221 (12)	0.0016 (9)	0.0025 (8)	0.0002 (10)
C2	0.0055 (4)	0.0048 (4)	0.0059 (4)	0.0002 (3)	0.0011 (3)	0.0002 (3)
H2	0.0204 (11)	0.0117 (10)	0.0181 (11)	0.0051 (10)	0.0040 (9)	0.0031 (9)
C3	0.0054 (4)	0.0047 (4)	0.0061 (4)	−0.0002 (4)	0.0012 (3)	−0.0003 (3)
H3	0.0185 (11)	0.0112 (10)	0.0191 (11)	0.0029 (9)	0.0035 (9)	0.0014 (8)
C4	0.0068 (4)	0.0050 (4)	0.0053 (4)	−0.0003 (4)	0.0004 (3)	0.0004 (3)
H4	0.0188 (11)	0.0168 (12)	0.0174 (10)	0.0032 (9)	−0.0008 (9)	0.0021 (9)
C5	0.0079 (5)	0.0053 (4)	0.0069 (4)	−0.0009 (4)	0.0015 (3)	−0.0005 (3)
H5A	0.0136 (11)	0.0198 (12)	0.0266 (13)	−0.0048 (10)	0.0035 (9)	0.0041 (10)
H5B	0.0323 (15)	0.0202 (13)	0.0150 (11)	0.0003 (12)	0.0068 (11)	−0.0052 (10)
C6	0.0107 (5)	0.0078 (5)	0.0081 (5)	−0.0013 (4)	0.0027 (4)	0.0017 (4)
H6A	0.0414 (19)	0.0324 (18)	0.0154 (11)	−0.0086 (16)	0.0108 (12)	−0.0068 (12)
H6B	0.042 (2)	0.0148 (13)	0.0392 (19)	0.0049 (14)	0.0184 (16)	0.0097 (13)
H6C	0.0160 (13)	0.044 (2)	0.0283 (15)	−0.0050 (13)	0.0025 (11)	0.0077 (15)
O1	0.0086 (5)	0.0052 (5)	0.0065 (5)	0.0001 (4)	0.0021 (4)	−0.0004 (4)
O2	0.0074 (5)	0.0067 (5)	0.0058 (5)	−0.0007 (4)	0.0004 (4)	−0.0013 (4)
H12	0.0243 (13)	0.0117 (11)	0.0215 (12)	0.0047 (10)	0.0002 (10)	−0.0020 (9)
O5	0.0081 (5)	0.0063 (5)	0.0098 (5)	0.0014 (4)	0.0025 (4)	0.0023 (4)
H15	0.0138 (11)	0.0249 (15)	0.0246 (13)	0.0006 (10)	0.0026 (10)	0.0043 (11)
O3	0.0075 (5)	0.0063 (5)	0.0087 (5)	−0.0012 (4)	0.0027 (4)	−0.0010 (4)
H13	0.0231 (13)	0.0172 (12)	0.0195 (11)	0.0005 (11)	0.0091 (10)	−0.0053 (10)
O4	0.0081 (5)	0.0062 (5)	0.0063 (5)	−0.0021 (4)	0.0033 (4)	−0.0015 (4)

Geometric parameters (Å, º)

C1—O1	1.4007 (19)	C4—H4	1.104 (3)
C1—O4	1.4132 (18)	C5—O5	1.4240 (19)
C1—C2	1.5252 (16)	C5—H5A	1.098 (3)
C1—H1	1.110 (3)	C5—H5B	1.101 (3)
C2—O2	1.4147 (18)	C6—O1	1.4271 (19)
C2—C3	1.5295 (17)	C6—H6A	1.091 (4)
C2—H2	1.096 (3)	C6—H6B	1.085 (4)
C3—O3	1.4209 (19)	C6—H6C	1.101 (4)
C3—C4	1.5428 (17)	O2—H12	0.982 (3)
C3—H3	1.105 (3)	O5—H15	0.980 (3)
C4—O4	1.4535 (18)	O3—H13	0.989 (3)
C4—C5	1.5140 (18)
O1—C1—O4	112.59 (11)	O4—C4—H4	108.4 (2)
O1—C1—C2	108.32 (11)	C5—C4—H4	106.69 (19)
O4—C1—C2	104.06 (10)	C3—C4—H4	111.35 (19)
O1—C1—H1	110.4 (2)	O5—C5—C4	114.16 (11)
O4—C1—H1	106.7 (2)	O5—C5—H5A	106.8 (2)
C2—C1—H1	114.75 (19)	C4—C5—H5A	110.3 (2)
O2—C2—C1	114.95 (11)	O5—C5—H5B	110.8 (2)
O2—C2—C3	114.98 (11)	C4—C5—H5B	106.7 (2)
C1—C2—C3	100.98 (9)	H5A—C5—H5B	107.9 (3)
O2—C2—H2	107.22 (19)	O1—C6—H6A	111.7 (2)
C1—C2—H2	109.00 (19)	O1—C6—H6B	107.5 (2)
C3—C2—H2	109.5 (2)	H6A—C6—H6B	109.7 (4)
O3—C3—C2	114.62 (11)	O1—C6—H6C	110.3 (2)
O3—C3—C4	113.20 (11)	H6A—C6—H6C	109.8 (4)
C2—C3—C4	102.41 (9)	H6B—C6—H6C	107.7 (4)
O3—C3—H3	109.6 (2)	C1—O1—C6	112.75 (12)
C2—C3—H3	107.70 (19)	C2—O2—H12	109.3 (2)
C4—C3—H3	108.91 (18)	C5—O5—H15	110.9 (2)
O4—C4—C5	107.51 (11)	C3—O3—H13	107.5 (2)
O4—C4—C3	105.05 (10)	C1—O4—C4	110.51 (11)
C5—C4—C3	117.51 (10)

(alyxf_neutron) 'Methyl alpha-D lyxofuranoside'

Crystal data

C6H9.783D2.217O5	Dx = 1.506 Mg m^−3
Mr = 166.2	Neutron radiation, λ = 0.95284 Å
Orthorhombic, P212121	Cell parameters from 1949 reflections
a = 10.332 (3) Å	θ = 3–50°
b = 15.446 (2) Å	µ = 2.14 mm^−1
c = 4.614 (1) Å	T = 20 K
V = 736.3 (3) Å^3	Rectangular needle, clear blank white
Z = 4	6.7 × 1.3 × 1.1 mm
F(000) = 221

Data collection

'4x64 deg. position-sensitive detector (Thomas et. al., 1983) diffractometer	1949 reflections with > 4σ(I)
Radiation source: neutron reactor at ILL	Rint = 0.040
Ge (117) monochromator	θmax = 52.1°, θmin = 3.2°
'ω scans in equatorial geometry'	h = −4→17
Absorption correction: analytical ?	k = −5→25
Tmin = 0.665, Tmax = 0.829	l = −2→7
2791 measured reflections	3 standard reflections every 50 reflections
2036 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.042	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.085	w = 1/[σ^2(Fo^2) + (0.0141P)^2 + 4.2536P] where P = (Fo^2 + 2Fc^2)/3
S = 1.23	(Δ/σ)max < 0.001
2036 reflections	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
215 parameters	Extinction coefficient: 0.0161 (11)
3 restraints	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0 (10)

Special details

Experimental. Atomic scattering factors were taken from Sears (1992).

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	−0.71775 (10)	0.15156 (7)	0.2425 (3)	0.00489 (16)
H1	−0.7137 (3)	0.11884 (18)	0.0302 (7)	0.0178 (4)
C2	−0.58410 (10)	0.17232 (7)	0.3689 (3)	0.00498 (17)
H2	−0.5925 (3)	0.1698 (2)	0.6066 (6)	0.0179 (5)
C3	−0.56211 (10)	0.26672 (7)	0.2821 (3)	0.00504 (17)
H3	−0.4906 (3)	0.29905 (19)	0.4196 (7)	0.0177 (5)
C4	−0.69916 (11)	0.30098 (7)	0.3245 (2)	0.00512 (17)
H4	−0.7204 (3)	0.30436 (19)	0.5602 (6)	0.0180 (5)
C5	−0.72594 (11)	0.38786 (7)	0.1845 (3)	0.00629 (18)
H5A	−0.7060 (3)	0.3847 (2)	−0.0481 (7)	0.0214 (5)
H5B	−0.6603 (3)	0.43621 (18)	0.2816 (9)	0.0227 (6)
C6	−0.89127 (11)	0.05315 (7)	0.3225 (3)	0.0089 (2)
H6A	−0.9648 (3)	0.0956 (2)	0.2300 (11)	0.0281 (7)
H6B	−0.8563 (4)	0.0083 (2)	0.1579 (10)	0.0313 (8)
H6C	−0.9336 (4)	0.0167 (2)	0.5002 (10)	0.0296 (7)
O1	−0.78588 (13)	0.10159 (8)	0.4427 (3)	0.0072 (2)
O2	−0.48778 (12)	0.11402 (8)	0.2712 (3)	0.00614 (19)
H12	−0.4336 (2)	0.09936 (16)	0.4396 (6)	0.0142 (7)	0.259 (10)
D2	−0.4336 (2)	0.09936 (16)	0.4396 (6)	0.0142 (7)	0.741 (8)
O3	−0.53067 (13)	0.27315 (9)	−0.0162 (3)	0.0070 (2)
H13	−0.4392 (2)	0.26271 (17)	−0.0454 (6)	0.0144 (7)	0.265 (9)
D3	−0.4392 (2)	0.26271 (17)	−0.0454 (6)	0.0144 (7)	0.735 (8)
O4	−0.77866 (12)	0.23423 (8)	0.1956 (3)	0.00618 (19)
O5	−0.85566 (12)	0.41635 (8)	0.2337 (3)	0.0067 (2)
H15	−0.9083 (2)	0.40055 (17)	0.0658 (6)	0.0148 (7)	0.259 (10)
D5	−0.9083 (2)	0.40055 (17)	0.0658 (6)	0.0148 (7)	0.741 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0043 (3)	0.0045 (3)	0.0058 (4)	−0.0009 (3)	−0.0004 (3)	0.0003 (3)
H1	0.0202 (10)	0.0170 (10)	0.0163 (10)	0.0016 (9)	−0.0010 (10)	−0.0046 (9)
C2	0.0045 (4)	0.0048 (3)	0.0057 (4)	0.0002 (3)	−0.0001 (3)	0.0000 (3)
H2	0.0187 (10)	0.0226 (11)	0.0123 (10)	0.0025 (9)	−0.0001 (9)	0.0015 (9)
C3	0.0040 (3)	0.0049 (3)	0.0062 (4)	0.0001 (3)	−0.0003 (3)	−0.0002 (3)
H3	0.0166 (10)	0.0185 (10)	0.0179 (11)	−0.0031 (9)	−0.0045 (9)	−0.0031 (9)
C4	0.0049 (4)	0.0045 (3)	0.0060 (4)	0.0005 (3)	0.0008 (3)	−0.0003 (3)
H4	0.0226 (11)	0.0194 (10)	0.0121 (9)	0.0008 (9)	0.0030 (9)	−0.0006 (9)
C5	0.0056 (4)	0.0054 (3)	0.0079 (4)	0.0006 (3)	0.0007 (3)	0.0004 (3)
H5A	0.0232 (12)	0.0261 (12)	0.0148 (10)	0.0057 (11)	0.0054 (10)	0.0038 (10)
H5B	0.0165 (10)	0.0153 (9)	0.0362 (17)	−0.0032 (8)	−0.0055 (12)	−0.0021 (11)
C6	0.0061 (4)	0.0065 (4)	0.0140 (5)	−0.0011 (3)	0.0007 (4)	0.0005 (4)
H6A	0.0185 (10)	0.0198 (11)	0.046 (2)	0.0033 (9)	−0.0111 (14)	0.0028 (14)
H6B	0.0258 (13)	0.0282 (14)	0.040 (2)	−0.0032 (12)	0.0049 (15)	−0.0195 (16)
H6C	0.0281 (15)	0.0282 (15)	0.0324 (17)	−0.0146 (13)	0.0028 (14)	0.0088 (14)
O1	0.0060 (4)	0.0065 (4)	0.0090 (5)	−0.0015 (4)	0.0002 (4)	0.0012 (4)
O2	0.0059 (4)	0.0061 (4)	0.0064 (5)	0.0020 (3)	−0.0003 (4)	0.0002 (4)
H12	0.0138 (10)	0.0159 (11)	0.0130 (10)	0.0041 (7)	−0.0027 (7)	0.0018 (8)
D2	0.0138 (10)	0.0159 (11)	0.0130 (10)	0.0041 (7)	−0.0027 (7)	0.0018 (8)
O3	0.0054 (4)	0.0081 (4)	0.0076 (5)	0.0006 (4)	0.0017 (4)	0.0017 (4)
H13	0.0082 (9)	0.0177 (11)	0.0174 (11)	0.0008 (7)	0.0027 (8)	−0.0016 (9)
D3	0.0082 (9)	0.0177 (11)	0.0174 (11)	0.0008 (7)	0.0027 (8)	−0.0016 (9)
O4	0.0036 (4)	0.0047 (4)	0.0102 (5)	−0.0004 (3)	−0.0011 (4)	0.0013 (4)
O5	0.0052 (4)	0.0064 (4)	0.0085 (5)	0.0012 (3)	0.0001 (4)	0.0002 (4)
H15	0.0121 (10)	0.0177 (11)	0.0145 (11)	0.0010 (7)	−0.0029 (7)	−0.0013 (8)
D5	0.0121 (10)	0.0177 (11)	0.0145 (11)	0.0010 (7)	−0.0029 (7)	−0.0013 (8)

Geometric parameters (Å, º)

C1—O1	1.3943 (17)	C2—H2	1.101 (3)
C1—O4	1.4399 (16)	C3—H3	1.094 (3)
C1—C2	1.5329 (16)	C4—H4	1.111 (3)
C2—O2	1.4159 (17)	C5—H5A	1.094 (4)
C2—C3	1.5292 (16)	C5—H5B	1.104 (3)
C3—O3	1.4178 (19)	O5—D5	0.977 (3)
C3—C4	1.5242 (16)	O2—D2	0.984 (3)
C4—O4	1.4461 (17)	O3—D3	0.968 (3)
C4—C5	1.5148 (16)	O5—H15	0.977 (3)
C5—O5	1.4289 (18)	O2—H12	0.984 (3)
C6—O1	1.4328 (18)	O3—H13	0.968 (3)
C1—H1	1.103 (3)
O1—C1—O4	111.70 (11)	O4—C1—H1	106.82 (19)
O1—C1—C2	108.57 (10)	C2—C1—H1	113.55 (19)
O4—C1—C2	105.39 (9)	O2—C2—H2	110.50 (19)
O2—C2—C3	114.74 (10)	C1—C2—H2	107.50 (19)
O2—C2—C1	112.27 (10)	C3—C2—H2	107.84 (19)
C3—C2—C1	103.51 (9)	O3—C3—H3	112.1 (2)
O3—C3—C4	108.24 (10)	C2—C3—H3	112.56 (19)
O3—C3—C2	110.81 (10)	C4—C3—H3	113.22 (19)
C4—C3—C2	99.17 (9)	O4—C4—H4	108.90 (18)
O4—C4—C5	110.65 (10)	C3—C4—H4	109.00 (18)
O4—C4—C3	103.14 (9)	C5—C4—H4	109.87 (18)
C5—C4—C3	114.99 (9)	O5—C5—H5A	110.3 (2)
O5—C5—C4	112.11 (10)	O5—C5—H5B	107.67 (19)
C1—O1—C6	114.60 (12)	C4—C5—H5A	110.15 (19)
C1—O4—C4	108.80 (10)	C4—C5—H5B	108.3 (2)
C2—O2—D2	107.15 (19)	O1—C6—H6A	111.5 (2)
C2—O2—H12	107.15 (19)	O1—C6—H6B	110.5 (2)
C3—O3—D3	110.3 (2)	O1—C6—H6C	106.5 (2)
C3—O3—H13	110.3 (2)	H5A—C5—H5B	108.2 (3)
C5—O5—D5	108.61 (18)	H6A—C6—H6B	109.9 (4)
C5—O5—H15	108.61 (18)	H6A—C6—H6C	109.1 (3)
O1—C1—H1	110.72 (18)	H6B—C6—H6C	109.3 (3)