2-Amino-8-(2-de­oxy-2-fluoro-β-D-arabinofuranos­yl)imidazo[1,2-a][1,3,5]triazin-4(8H)-one monohydrate, a 2′-deoxy­guanosine analogue with an altered Watson–Crick recognition site

The title compound, C₁₀H₁₂FN₅O₄·H₂O, shows an anti glycosyl orientation [χ = −123.1 (2)°]. The 2-de­oxy-2-fluoro­ara­bino­furanosyl moiety exhibits a major C2′-endo sugar puckering (S-type, C2′-endo–C1′-exo, ²T₁), with P = 156.9 (2)° and τ_m = 36.8 (1)°, while in solution a predominantly N conformation of the sugar moiety is observed. The conformation around the exocyclic C4′—C5′ bond is −sc (trans, gauche), with γ = −78.3 (2)°. Both nucleoside and solvent mol­ecules participate in the formation of a three-dimensional hydrogen-bonding pattern via inter­molecular N—H...O and O—H...O hydrogen bonds; the N atoms of the heterocyclic moiety and the F substituent do not take part in hydrogen bonding.

S1. Comment

Among base-modified nucleosides, the 5-aza-7-deazapurine (imidazo[1,2-a]-1,3,5-triazine) compounds are of considerable interest as they form orthogonal base pairs (purine numbering is used throughout this discussion). 2-Amino-8-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)imidazo[1,2-a]-1,3,5-triazin-4(8H)-one (5-aza-7-deaza-2'-deoxy-2'-fluoroguanosine), (I), is a fluorinated analogue of 5-aza-7-deaza-2'-deoxyguanosine, (IIIa), which can be considered a structural analogue of both 2'-deoxyguanosine and 7-deaza-2'-deoxyguanosine (see first scheme) (Rosemeyer & Seela, 1987). Compound (IIIa) shows an altered Watson–Crick recognition site due to the absence of the H atom at N1, and is therefore the purine counterfeit of 2'-deoxyisocytidine (iC_d; see second scheme, motif II) (Seela & Melenewski, 1999; Seela & Rosemeyer, 2002). Compound (IIIa) (β-D-anomer) forms a parallel-stranded duplex under neutral conditions when placed opposite dG [dG is ? Please define]. It was observed that this `purine–purine' base pair (see second scheme, motif I) is remarkably stable, thereby expanding the pairing modes of synthetic DNA (Seela & Melenewski, 1999). Parallel DNA can be generated either by changing the Watson–Crick recognition site of the nucleobase, as is the case for the above-mentioned 2'-deoxyisocytidine and compound (IIIa), or by changing the anomeric configuration from β-D to α-D (Morvan et al., 1987; Seela & He, 2002). Base-pair motifs illustrating this point are shown in the second scheme . Parallel-stranded DNA is not only conceptional [Meaning not clear - please rephrase] for synthetic biology applications but also demonstrates the polymorphic structures of DNA.

Recently, the 2'-deoxy-2'-fluoroarabino nucleoside of 5-aza-7-deazaguanosine, (I), has been synthesized and its conformational properties investigated in solution (Glaçon & Seela, 2004). The introduction of a 2'-arabinofluoro substituent has been found to confer potent antiviral activity which is enhanced compared with the unmodified counterparts (Pankiewicz, 2000). The presence of the F atom does not lead to significant steric perturbations in the shape of the molecule due to its small van der Waals radius (1.47 Å; Bondi, 1964). At the same time, an F atom is the substituent with the highest electronegativity (3.98, versus 3.44 for O). Therefore, its presence gives rise to essential changes in the electronic state and conformational behaviour of the pentofuranose ring.

We have now studied the conformation and hydrogen-bonding of the monohydrate of (I), the title compound (Ia), in the crystalline state and compared it with the related molecules of 5-aza-7-deazaguanosine, (IIIb) (Kojić-Prodić et al., 1982), and the α-anomer of 5-aza-7-deaza-2'-deoxyguanosine, (IV) (Seela et al., 2002). The three-dimensional structure of (Ia) is shown in Fig. 1 and selected geometric parameters are listed in Table 1.

The 5-aza-7-deazapurine ring system of (Ia) is nearly planar. The deviations of the ring atoms from the least-squares plane (N1/C2/N3/C4/N5/C6–C8/N9) range from -0.021 (2) Å (atom N5) to 0.018 (2) Å (atom N1), with an r.m.s. deviation of 0.014 Å. The C1' substituent and atom O6 of (Ia) lie 0.317 (3) and 0.041 (3) Å, respectively, above this plane, while atom N2 lies 0.074 (3) Å below it. The C2—N2 bond length of the amino group is 1.329 (2) Å, which is very close to the value observed for the amino group of the related 7-deaza-2'-deoxyguanosine [1.343 (4) Å; Seela et al., 2005].

For purines, the orientation of the nucleobase relative to the sugar moiety (syn/anti) is defined by the torsion angle χ (O4'—C1'—N9—C4) (IUPAC–IUB Joint Commission on Biochemical Nomenclature, 1983). In the crystalline state of (Ia), the glycosyl bond torsion angle is in the anti range, with χ = -123.1 (2)°. The ribonucleoside (IIIb) also adopts an anti conformation (Kojić-Prodić et al., 1982), while the 2'-deoxyribonucleoside α-anomer, (IV), adopts a high-anti conformation, with χ = 87.5 (3)° (Seela et al., 2002). The glycosyl N9—C1' bond in (Ia) is 1.447 (2) Å, which is shorter than the corresponding bonds in both (IIIb) [1.462 (4) Å] and the α-anomer, (IV), lacking the 2'-fluoro substituent [1.461 (4) Å].

The conformation about the exocyclic C4'—C5' bond, defined by the torsion angle γ (O5'—C5'—C4'—C3'), is -78.3 (2)° for (Ia), corresponding to a -sc (trans, gauche) conformation. This conformation was also observed for the hydroxyl group of the α-anomer, (IV) (Seela et al., 2002). In contrast, for the ribonucleoside (IIIb) a -gauche conformation about the C4'—C5' bond was reported, which corresponds to ap (gauche, trans) according to Saenger (1984). The F2'—C2' length of (Ia) is 1.398 (2) Å, similar to the C—F bonds found in other 2'-fluoro `up' nucleosides (Birnbaum et al., 1982; He et al., 2003; Seela et al., 2006) and 2'-fluoro `down' nucleosides (Suck et al., 1974; Hakoshima et al., 1981). Moreover, the F2'—C2' bond length is notably close to the C2'-O2' distance observed in the parent compound (IIIb) [1.400 (4) Å; Kojić-Prodić et al., 1982].

The C2'-endo (south, S) and C3'-endo (north, N) puckerings are the most frequently observed sugar-ring conformations of nucleosides. The sugar moiety of (Ia) shows an S-type conformation, with a major C2'-endo puckering (C2'-endo-C1'-exo, ²T₁) and a pseudorotation phase angle P = 156.9 (2)°, with the maximum amplitude τ_m = 36.8 (1)°. Its conformation is close to that of the non-fluorinated ribonucleoside (IIIb) (S-type, C2'-endo, ²E, P = 164.2°; Kojić-Prodić et al., 1982). The 2'-deoxyribonucleoside α-anomer, (IV), also adopts an S sugar conformation, with P = 177.43° and τ_m = 30.5° (C2'-endo-C3'-exo, ²T₃; Seela et al., 2002).

In contrast with its behaviour in the solid state, the spatial conformation of the sugar moiety dynamically interconverts between north and south in solution. For the fluorinated compound (I), this ratio was determined from the vicinal ³J(H,H) and ³J(H,F) coupling constants of ¹H NMR spectra measured in DMSO-d₆ containing one drop of D₂O, using the PSEUROT6.3 program (Van Wijk et al., 1999). The presence of the F atom shifts the sugar population of (I) towards the north conformation (54% N) compared with compound (IIIa) (37% N) (Glaçon & Seela, 2004). The same observation can also be made in the case of fluorinated (II) (50% N) and the unmodified 2'-deoxyguanosine (29% N) (Tennilä et al., 2000). Thus, in solution, the presence of the F atom in an `up' position (arabino configuration) enhances the population of the N conformers. It is interesting to note that the sugar conformation of compound (I) favours N puckering in solution, while in the crystalline state (Ia) adopts an S-type sugar conformation.

The crystalline structure of nucleoside (Ia) forms an infinite three-dimensional network which is stabilized by several intermolecular hydrogen bonds involving the nucleoside and water molecules (Table 2 and Figs. 2 and 3). If layers are selected, perpendicular to the b axis, it can be seen that the nucleobases of (Ia) stack into columns with alternating orientations.

Hydrogen bonds are formed within each layer as well as between adjacent layers. The nucleosides are linked by three intermolecular hydrogen bonds. Both H atoms of the amino group act as donors, forming hydrogen bonds with atom O6 of a neighbouring base moiety (N2—H2B···O6ⁱⁱ) and atom O4' of a neighbouring sugar residue (N2—H2A···O4^'i (see Table 2 for symmetry codes and geometry). Moreover, adjacent sugar residues form strong hydrogen bonds (O3'—H3'··· O5'ⁱⁱⁱ). To connect molecules of adjacent layers, the water molecule acts as a donor (O10—H10A···O6 and O10—H10B···O3'ⁱ) as well as an acceptor (O5'—H5'···O10^iv), as illustrated in Fig. 3. Neither the heterocyclic ring N atoms nor the F substituent take part in hydrogen bonding.

Earlier, we reported the crystal structure of the closely related α-anomer of 5-aza-7-deaza-2'-deoxyguanosine, (IV), albeit lacking the 2'-fluoro substituent (Seela et al., 2002). Interestingly, compound (IV) crystallizes in the same space group (monoclinic, P2₁) with one water molecule in the asymmetric unit, as found for (Ia) (Seela et al., 2002). However, closer inspection of the crystal packing of (IV) reveals several differences from the molecular packing of (Ia). In the crystal structure of (IV), the 5-aza-7-deazaguanine moieties form double layers and are arranged in a reverse orientation to each other (Seela et al., 2002). A distance of 3.508 Å between nucleobases within a layer was calculated. Moreover, individual double layers are spatially displaced. In contrast, the 5-aza-7-deazaguanine moieties of (Ia) form highly regular layers, with a distance of 3.354 Å between the nucleobases. As in (IV), the nucleobases of (Ia) are alternating, although with different orientations of the sugar moieties, as shown in Fig. 2. In addition, the hydrogen-bonding network of the two compounds is different. Conspicuously, none of the heterocyclic ring N atoms of (Ia) is involved in hydrogen bonding, which is in contrast with (IV), where atoms N1 and N3 function as acceptor sites (Seela et al., 2002).

S2. Experimental

Compound (I) was synthesized as previously reported (Glaçon & Seela, 2004). Slow crystallization from water afforded (Ia) as colourless plates (decomposition above 503 K). For the diffraction experiment, a single crystal was mounted on a MiTeGen MicroMounts fibre in a thin smear of oil.

S3. Refinement

In the absence of suitable anomalous scattering, Friedel equivalents could not be used to determine the absolute structure. Refinement of the Flack parameter (Flack, 1983) led to an inconclusive value [0.3 (6)]. Therefore, Friedel equivalents (1512) were merged before the final refinement. The known configuration of the parent molecule was used to define the enantiomer employed in the refined model.

All H atoms were found in a difference Fourier synthesis. In order to maximize the data/parameter ratio, the H atoms were placed in geometrically idealized positions (C—H = 0.93–0.98 Å and N—H = 0.86 Å) and constrained to ride on their parent atoms, with U_iso(H) = 1.2U_eq(C) or U_eq(N). The OH groups were refined as rigid groups allowed to rotate but not tip, with O—H = 0.82 Å and U_iso(H) = 1.5U_eq(O). The water H atoms were located in a difference map and their parameters were initially refined freely. Due to the low reflection/refined parameter ratio, the O—H distances were constrained to 0.87 Å and U_iso(H) = 1.5U_eq(O) in the final cycle of refinement.

Computing details

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures

	Fig. 1. A perspective view of molecule (Ia), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The dashed line indicates the hydrogen bond to the water molecule. [Please check added text]
	Fig. 2. The crystal packing of the β-anomer, (Ia), showing the intermolecular hydrogen-bonded network (dashed lines) The projection is parallel to the ac plane.
	Fig. 3. A detailed view of the hydrogen-bonded network (dashed lines) of the water molecules.

2-amino-8-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)imidazo[1,2-a]- 1,3,5-triazin-4(8H)-one monohydrate

Crystal data

C10H12FN5O4·H2O	F(000) = 316
Mr = 303.26	Dx = 1.596 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 7510 reflections
a = 7.3752 (6) Å	θ = 2.8–28.5°
b = 6.3516 (4) Å	µ = 0.14 mm^−1
c = 13.8654 (11) Å	T = 130 K
β = 103.648 (4)°	Plate, colourless
V = 631.18 (8) Å^3	0.34 × 0.20 × 0.04 mm
Z = 2

Data collection

Bruker APEXII CCD area-detector diffractometer	1813 independent reflections
Radiation source: fine-focus sealed tube	1680 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.041
ϕ and ω scans	θmax = 29.0°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −10→10
Tmin = 0.947, Tmax = 0.995	k = −8→8
20880 measured reflections	l = −18→18

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.079	H-atom parameters constrained
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0432P)^2 + 0.149P] where P = (Fo^2 + 2Fc^2)/3
1813 reflections	(Δ/σ)max < 0.001
192 parameters	Δρmax = 0.31 e Å^−3
1 restraint	Δρmin = −0.24 e Å^−3

Special details

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. 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
N1	0.5766 (2)	0.6888 (3)	0.37504 (10)	0.0130 (3)
C2	0.4377 (2)	0.6943 (3)	0.42394 (12)	0.0113 (3)
N2	0.2648 (2)	0.6948 (3)	0.36752 (11)	0.0137 (3)
H2A	0.2465	0.6916	0.3039	0.016*
H2B	0.1712	0.6982	0.3946	0.016*
N3	0.4558 (2)	0.7004 (3)	0.52370 (10)	0.0113 (3)
C4	0.6315 (2)	0.6914 (3)	0.57294 (12)	0.0116 (3)
N5	0.78107 (19)	0.6759 (3)	0.53167 (11)	0.0127 (3)
C6	0.7530 (2)	0.6785 (3)	0.42729 (12)	0.0132 (3)
O6	0.89169 (17)	0.6721 (3)	0.39218 (9)	0.0186 (3)
C7	0.9460 (2)	0.6694 (3)	0.60650 (13)	0.0153 (4)
H7A	1.0670	0.6596	0.5978	0.018*
C8	0.8954 (2)	0.6801 (4)	0.69317 (13)	0.0157 (4)
H8A	0.9758	0.6793	0.7559	0.019*
N9	0.6998 (2)	0.6927 (3)	0.67269 (10)	0.0133 (3)
C1'	0.5913 (3)	0.7512 (3)	0.74295 (13)	0.0130 (4)
H1'A	0.4679	0.8003	0.7071	0.016*
C2'	0.5697 (3)	0.5823 (3)	0.81722 (13)	0.0140 (4)
H2'A	0.4632	0.4896	0.7913	0.017*
F2'	0.73675 (16)	0.4705 (2)	0.84754 (8)	0.0189 (3)
C3'	0.5417 (2)	0.7172 (3)	0.90412 (13)	0.0138 (4)
H3'A	0.5832	0.6436	0.9676	0.017*
O3'	0.3520 (2)	0.7807 (2)	0.88751 (11)	0.0190 (3)
H3'O	0.2908	0.6861	0.9048	0.028*
C4'	0.6605 (2)	0.9128 (3)	0.89895 (12)	0.0130 (4)
H4'A	0.5923	1.0390	0.9106	0.016*
C5'	0.8528 (3)	0.9121 (4)	0.96939 (13)	0.0164 (4)
H5'A	0.9088	0.7739	0.9694	0.020*
H5'B	0.9324	1.0133	0.9469	0.020*
O5'	0.8398 (2)	0.9643 (2)	1.06734 (9)	0.0185 (3)
H5'O	0.8531	0.8575	1.1015	0.028*
O4'	0.6894 (2)	0.9187 (2)	0.79973 (9)	0.0160 (3)
O10	0.8418 (2)	0.6453 (3)	0.18785 (11)	0.0270 (4)
H10A	0.8411	0.6635	0.2499	0.040*
H10B	0.7727	0.5344	0.1700	0.040*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0127 (7)	0.0144 (7)	0.0125 (6)	−0.0011 (7)	0.0042 (5)	−0.0010 (7)
C2	0.0141 (8)	0.0068 (8)	0.0138 (7)	−0.0004 (7)	0.0047 (6)	−0.0003 (7)
N2	0.0123 (7)	0.0188 (8)	0.0104 (6)	0.0015 (7)	0.0034 (5)	−0.0024 (7)
N3	0.0122 (6)	0.0110 (7)	0.0109 (6)	−0.0004 (6)	0.0030 (5)	−0.0018 (6)
C4	0.0151 (8)	0.0081 (8)	0.0124 (7)	−0.0010 (8)	0.0048 (6)	−0.0021 (7)
N5	0.0104 (6)	0.0146 (8)	0.0131 (6)	0.0000 (7)	0.0029 (5)	−0.0001 (7)
C6	0.0148 (8)	0.0122 (8)	0.0133 (7)	−0.0009 (8)	0.0050 (6)	−0.0009 (8)
O6	0.0125 (6)	0.0282 (8)	0.0167 (6)	−0.0013 (6)	0.0068 (5)	−0.0010 (6)
C7	0.0106 (8)	0.0168 (9)	0.0169 (8)	0.0000 (8)	−0.0003 (6)	−0.0016 (8)
C8	0.0125 (8)	0.0174 (9)	0.0158 (8)	−0.0001 (8)	0.0002 (6)	−0.0004 (8)
N9	0.0127 (7)	0.0158 (8)	0.0111 (6)	0.0013 (7)	0.0019 (5)	−0.0010 (7)
C1'	0.0158 (8)	0.0128 (9)	0.0103 (8)	−0.0006 (7)	0.0031 (6)	−0.0006 (7)
C2'	0.0133 (8)	0.0146 (10)	0.0141 (8)	−0.0009 (7)	0.0033 (7)	0.0002 (7)
F2'	0.0212 (6)	0.0158 (6)	0.0199 (5)	0.0053 (5)	0.0052 (4)	0.0034 (5)
C3'	0.0146 (8)	0.0155 (10)	0.0119 (7)	0.0007 (7)	0.0041 (6)	0.0013 (7)
O3'	0.0146 (6)	0.0193 (8)	0.0245 (7)	−0.0005 (6)	0.0075 (6)	0.0050 (6)
C4'	0.0164 (8)	0.0147 (9)	0.0090 (7)	0.0008 (7)	0.0049 (6)	0.0007 (7)
C5'	0.0167 (8)	0.0189 (10)	0.0141 (8)	0.0002 (8)	0.0043 (7)	−0.0029 (8)
O5'	0.0253 (7)	0.0178 (7)	0.0109 (6)	0.0039 (6)	0.0013 (5)	−0.0016 (6)
O4'	0.0263 (7)	0.0141 (7)	0.0085 (5)	−0.0055 (6)	0.0059 (5)	−0.0020 (5)
O10	0.0416 (9)	0.0250 (9)	0.0157 (6)	−0.0108 (7)	0.0095 (6)	−0.0009 (6)

Geometric parameters (Å, º)

N1—C6	1.333 (2)	C1'—C2'	1.521 (3)
N1—C2	1.356 (2)	C1'—H1'A	0.9800
C2—N2	1.329 (2)	C2'—F2'	1.398 (2)
C2—N3	1.358 (2)	C2'—C3'	1.532 (3)
N2—H2A	0.8600	C2'—H2'A	0.9800
N2—H2B	0.8600	C3'—O3'	1.421 (2)
N3—C4	1.316 (2)	C3'—C4'	1.532 (3)
C4—N9	1.356 (2)	C3'—H3'A	0.9800
C4—N5	1.361 (2)	O3'—H3'O	0.8200
N5—C7	1.401 (2)	C4'—O4'	1.441 (2)
N5—C6	1.413 (2)	C4'—C5'	1.521 (3)
C6—O6	1.233 (2)	C4'—H4'A	0.9800
C7—C8	1.342 (2)	C5'—O5'	1.423 (2)
C7—H7A	0.9300	C5'—H5'A	0.9700
C8—N9	1.405 (2)	C5'—H5'B	0.9700
C8—H8A	0.9300	O5'—H5'O	0.8200
N9—C1'	1.447 (2)	O10—H10A	0.8700
C1'—O4'	1.416 (2)	O10—H10B	0.8700
C6—N1—C2	119.03 (14)	N9—C1'—H1'A	109.6
N2—C2—N1	116.04 (15)	C2'—C1'—H1'A	109.6
N2—C2—N3	116.71 (15)	F2'—C2'—C1'	109.64 (15)
N1—C2—N3	127.26 (16)	F2'—C2'—C3'	108.70 (14)
C2—N2—H2A	120.0	C1'—C2'—C3'	101.14 (15)
C2—N2—H2B	120.0	F2'—C2'—H2'A	112.3
H2A—N2—H2B	120.0	C1'—C2'—H2'A	112.3
C4—N3—C2	112.06 (14)	C3'—C2'—H2'A	112.3
N3—C4—N9	127.78 (15)	O3'—C3'—C4'	108.34 (16)
N3—C4—N5	125.57 (15)	O3'—C3'—C2'	109.98 (15)
N9—C4—N5	106.65 (15)	C4'—C3'—C2'	103.40 (14)
C4—N5—C7	109.82 (14)	O3'—C3'—H3'A	111.6
C4—N5—C6	119.50 (14)	C4'—C3'—H3'A	111.6
C7—N5—C6	130.60 (14)	C2'—C3'—H3'A	111.6
O6—C6—N1	125.54 (16)	C3'—O3'—H3'O	109.5
O6—C6—N5	117.99 (15)	O4'—C4'—C5'	106.71 (14)
N1—C6—N5	116.46 (14)	O4'—C4'—C3'	106.31 (14)
C8—C7—N5	106.58 (15)	C5'—C4'—C3'	115.16 (16)
C8—C7—H7A	126.7	O4'—C4'—H4'A	109.5
N5—C7—H7A	126.7	C5'—C4'—H4'A	109.5
C7—C8—N9	108.13 (15)	C3'—C4'—H4'A	109.5
C7—C8—H8A	125.9	O5'—C5'—C4'	110.46 (15)
N9—C8—H8A	125.9	O5'—C5'—H5'A	109.6
C4—N9—C8	108.81 (14)	C4'—C5'—H5'A	109.6
C4—N9—C1'	123.85 (15)	O5'—C5'—H5'B	109.6
C8—N9—C1'	125.63 (14)	C4'—C5'—H5'B	109.6
O4'—C1'—N9	106.04 (15)	H5'A—C5'—H5'B	108.1
O4'—C1'—C2'	105.94 (14)	C5'—O5'—H5'O	109.5
N9—C1'—C2'	115.93 (16)	C1'—O4'—C4'	109.87 (14)
O4'—C1'—H1'A	109.6	H10A—O10—H10B	104.5
C6—N1—C2—N2	−177.01 (19)	C7—C8—N9—C1'	−166.0 (2)
C6—N1—C2—N3	3.3 (3)	C4—N9—C1'—O4'	−123.1 (2)
N2—C2—N3—C4	177.60 (18)	C8—N9—C1'—O4'	40.3 (3)
N1—C2—N3—C4	−2.7 (3)	C4—N9—C1'—C2'	119.7 (2)
C2—N3—C4—N9	−179.6 (2)	C8—N9—C1'—C2'	−76.9 (2)
C2—N3—C4—N5	−0.5 (3)	O4'—C1'—C2'—F2'	−78.78 (18)
N3—C4—N5—C7	−179.8 (2)	N9—C1'—C2'—F2'	38.5 (2)
N9—C4—N5—C7	−0.6 (2)	O4'—C1'—C2'—C3'	35.88 (17)
N3—C4—N5—C6	3.0 (3)	N9—C1'—C2'—C3'	153.17 (15)
N9—C4—N5—C6	−177.77 (18)	F2'—C2'—C3'—O3'	−162.07 (14)
C2—N1—C6—O6	179.8 (2)	C1'—C2'—C3'—O3'	82.56 (17)
C2—N1—C6—N5	−0.5 (3)	F2'—C2'—C3'—C4'	82.41 (17)
C4—N5—C6—O6	177.3 (2)	C1'—C2'—C3'—C4'	−32.95 (17)
C7—N5—C6—O6	0.8 (3)	O3'—C3'—C4'—O4'	−97.00 (16)
C4—N5—C6—N1	−2.3 (3)	C2'—C3'—C4'—O4'	19.67 (18)
C7—N5—C6—N1	−178.8 (2)	O3'—C3'—C4'—C5'	145.07 (15)
C4—N5—C7—C8	0.3 (2)	C2'—C3'—C4'—C5'	−98.26 (17)
C6—N5—C7—C8	177.0 (2)	O4'—C4'—C5'—O5'	164.03 (15)
N5—C7—C8—N9	0.1 (3)	C3'—C4'—C5'—O5'	−78.3 (2)
N3—C4—N9—C8	179.9 (2)	N9—C1'—O4'—C4'	−148.59 (15)
N5—C4—N9—C8	0.7 (2)	C2'—C1'—O4'—C4'	−24.86 (19)
N3—C4—N9—C1'	−14.3 (3)	C5'—C4'—O4'—C1'	126.35 (17)
N5—C4—N9—C1'	166.45 (18)	C3'—C4'—O4'—C1'	2.96 (19)
C7—C8—N9—C4	−0.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···O4′^i	0.86	2.37	2.989 (2)	129
N2—H2B···O6^ii	0.86	2.06	2.8553 (19)	153
O3′—H3′O···O5′^iii	0.82	1.80	2.617 (2)	175
O5′—H5′O···O10^iv	0.82	1.82	2.624 (2)	168
O10—H10A···O6	0.87	1.92	2.7748 (19)	167
O10—H10B···O3′^i	0.87	1.93	2.792 (2)	169

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