8-Aza-7-deaza-7-propynyladenosine methanol solvate

In the title compound, 4-amino-3-propynyl-1-(β-D-ribofur­anosyl)-1H-pyrazolo[3,4-d]pyrimidine methanol solvate, C₁₃H₁₅N₅O₄·CH₃OH, the torsion angle of the N-glycosylic bond is between anti and high-anti [χ = −101.8 (5)°]. The ribofuranose moiety adopts the C3′-endo (³T₂) sugar conformation (N-type) and the conformation at the exocyclic C—C bond is +sc (gauche, gauche). The propynyl group is out of the plane of the nucleobase and is bent. The compound forms a three-dimensional network which is stabilized by several hydrogen bonds (O—H...O and O—H...N). The nucleobases are stacked head-to-tail. The methanol solvent mol­ecule forms hydrogen bonds with both the nucleobase and the sugar moiety.

S1. Comment

Among the various groups introduced into nucleosides to stabilize oligonucleotide duplexes, the propynyl group has attracted particular attention. This group has been introduced into the 5-position of pyrimidines or the 7-position of 7-deazapurine nucleosides (Froehler et al., 1992; Sági et al., 1993; Seela & Thomas, 1995; Seela & Zulauf, 1999; Barnes & Turner, 2001a,b; He & Seela, 2002a,b) (purine numbering is used throughout). Recently, the single-crystal X-ray structure of 7-deaza-2'-deoxy-7-propynylguanosine, (II), was published (Seela et al., 2004). We now report the crystal structure of the related ribonucleoside 4-amino-3-propynyl-1- (β-D-ribofuranosyl)-1H-pyrazolo[3,4-d]pyrimidine methanol solvate (8-aza-7-deaza-7-propynyladenosine methanol solvate, C₁₃H₁₅N₅O₄·CH₃OH), (I). The synthesis of compound (I) is described in the Experimental section and the structure is shown in Fig. 1. Selected geometric parameters are in Table 1.

The N-glycosylic bond of compound (I) shows a conformation between anti and high-anti, with a C4—N9—C1'—O4' torsion angle χ = −101.8 (5)° (IUPAC–IUB Joint Commission on Biochemical Nomenclature, 1983). By comparison, 8-aza-7-deazaadenosine [8-azatubercidin, (III)], without the substitution of the propynyl group, exhibits the high-anti conformation (χ = −77.6°; Sprang et al., 1978).

The ribofuranosyl ring in (I) adopts the C3'-endo (³T₂) sugar puckering (N conformation), with the pseudorotation phase angle P = 6.3 (4)°, and the maximum amplitude of puckering τ_m = 36.5 (2)° (Rao et al., 1981). This is in contrast with the ribofuranose moiety of compound (III), which exhibits an S-type pucker (²₁T Or ²T₁?), with P = 141.9° and τ_m = −41.9°. The conformation at the C4'—C5' bond in (I) is syn (+sc; gauche, gauche) with a C3'—C4'—C5'—O5' torsion angle of 55.5 (5)°), which is different from the trans conformation usually observed for 8-azapurine and purine nucleosides, such as in (III). In solution, the sugar moiety of (I) is in the N \rightleftharpoons S pseudorotational equilibrium, but is also slightly biased to the N-conformation (54%), as calculated by the PSEUROT program (Van Wijk & Altona, 1993).

In compound (I), the nucleobase ring and the exocyclic N6 (amino) and C1' (sugar) atoms are nearly coplanar, the r.m.s. deviation of the least-squares plane being 0.0152 Å and the maximum deviation being −0.024 (4) Å for atom N1. Atom C71 of the propynyl group lies above the heterocyclic plane, with a deviation of 0.100 (7) Å. This group is slightly bent, with the C72—C71—C7 bond angle being 173.1 (5)°, and is inclined by nearly 4° to the 8-aza-7-deazapurine moiety. This inclination is larger than that observed in 1-(β-D-arabinofuranosyl)-5-propynyluracil (3.7°; Cygler et al., 1984), but smaller than that in 7-deaza-7-propynyl-2'-deoxyguanosine, (II), in which we also found that the propynyl group is inclined by about 4.6° (Seela et al., 2004). The triple-bond length of (I) is within the usual range (Cygler et al., 1984), indicating that this bond is not in conjugation with the nucleobase.

The nucleoside forms a 1:1 complex with methanol via hydrogen bonds (Fig. 2, Table 2). The nucleobases are aligned head to tail, with a plane-to-plane distance of 3.664 Å. This is close to the distance observed for the stacked nucleobases in B-DNA. Some other intermolecular hydrogen bonds are formed in the crystal of (I) (Table 2 and Fig. 2). The amino group does not participate in the hydrogen-bonding pattern, while a hydrogen bond is formed between the H atom of the methyl group of the propynyl side chain and the O atom of the O5'—H group of the sugar moiety (Table 2 and Fig. 2).

S2. Experimental

Compound (I) was synthesized by treatment of a degassed suspension of 7-iodo-8-aza-7-deazaadenosine (200 mg, 0.5 mmol) and CuI (9.6 mg, 0.05 mmol) in anhydrous dimethylformamide (3 ml) with Pd(PPh₃)₄ (29 mg, 0.025 mmol), triethylamine (0.14 ml, 1 mmol) and propyne gas at room temperature overnight. The reaction mixture was diluted with methanol (50 ml) and dichloromethane (50 ml), and Dowex 1X8 (100–200 mesh, 500 mg, bicarbonate form) was introduced. After stirring for 45 min, the mixture was filtered and the filtrate evaporated. Crystallization from methanol furnished compound (I) (80 mg, 47%, m.p. 463–464 K). Analysis: R_f (methanol–dichloromethane, 1:9): 0.21; ¹H NMR (250 MHz, DMSO-d₆, δ, p.p.m.): 2.15 (m, 3H, CH₃), 3.44, 3.54 (2 m, 2H, C5'-H), 3.90 (q, 1H, C4'-H, J = 4.74 Hz), 4.19 (q, 1H, C3'-H, J = 4.84 Hz), 4.55 (q, 1H, C2'-H, J = 5.11 Hz), 4.84 (d, 1H, C5'-OH, J = 5.60 Hz), 5.14 (d, 1H, C3'-OH, J = 5.34 Hz), 5.39 (d, 1H, C2'-OH, J = 5.80 Hz), 6.07 (d, 1H, C1'-H, J = 4.59 Hz), 6.73, 7.98 (2 br, 2H, NH₂), 8.22 (s, 1H, C2—H); ¹³C NMR (62.5 MHz, DMSO-d₆, δ, p.p.m.): 4.40 (C73), 62.3 (C5'), 70.8 (C2'), 71.1 (C72), 73.0 (C3'), 85.2 (C4'), 88.3 (C1'), 93.1 (C71), 100.6 (C5), 127.6 (C7), 154.0 (C6), 156.6 (C2), 157.7 (C4); analytical data for C₁₃H₁₅N₅O₄, M_r = 305.29: calculated: C 51.14, H 4.95, N 22.94%; found C 51.15, H 4.88, N 22.80%. For the diffraction experiment, a single-crystal was fixed at the top of a Lindemann capillary with epoxy resin.

S3. Refinement

In the absence of suitable anomalous scattering, Friedel equivalents could not be used to determine the absolute structure. Therefore, Friedel equivalents were merged before the final refinements. The known configuration of the parent molecule was used to define the enantiomer of the final model. All H atoms were initially 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, O—H = 0.82 Å and N—H = 0.86 Å) and constrained to ride on their parent atoms, with U_iso(H) = 1.2U_eq(C,N) and 1.5U_eq(O).

Computing details

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: SHELXTL (Sheldrick, 1997); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 1999).

Figures

	Fig. 1. A perspective view of the molecule of (I), with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are represented as small spheres of an arbitrary size.
	Fig. 2. The crystal packing of (I), viewed down the a axis, showing the intermolecular hydrogen-bonded network.

4-amino-3-propynyl-1-(β-D-ribofuranosyl)-1H-pyrazolo[3,4-d]pyrimidine methanol solvate

Crystal data

C13H15N5O4·CH4O	F(000) = 712
Mr = 337.34	Dx = 1.391 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 65 reflections
a = 7.3269 (11) Å	θ = 3.7–17.1°
b = 10.0790 (16) Å	µ = 0.11 mm^−1
c = 21.813 (3) Å	T = 293 K
V = 1610.8 (4) Å^3	Needle, colourless
Z = 4	0.56 × 0.20 × 0.15 mm

Data collection

Bruker P4 diffractometer	Rint = 0.030
Radiation source: fine-focus sealed tube	θmax = 27.0°, θmin = 2.2°
Graphite monochromator	h = −9→1
2θ/ω scans	k = −12→1
2707 measured reflections	l = −1→27
2032 independent reflections	3 standard reflections every 97 reflections
1542 reflections with I > 2σ(I)	intensity decay: 5%

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)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.164	H-atom parameters constrained
S = 1.10	w = 1/[σ^2(Fo^2) + (0.081P)^2 + 0.4152P] where P = (Fo^2 + 2Fc^2)/3
2032 reflections	(Δ/σ)max < 0.001
223 parameters	Δρmax = 0.36 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

Special details

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
N1	0.6542 (6)	0.6251 (4)	0.56017 (15)	0.0539 (10)
C2	0.6438 (7)	0.5652 (4)	0.50607 (19)	0.0507 (10)
H2	0.6301	0.4736	0.5078	0.061*
N3	0.6498 (6)	0.6157 (3)	0.44964 (14)	0.0446 (8)
C4	0.6696 (6)	0.7487 (4)	0.45150 (17)	0.0383 (8)
C5	0.6875 (6)	0.8258 (4)	0.50385 (16)	0.0405 (8)
N6	0.6916 (6)	0.8202 (5)	0.61465 (14)	0.0670 (12)
H6A	0.6844	0.7759	0.6483	0.080*
H6B	0.7071	0.9048	0.6157	0.080*
C6	0.6786 (6)	0.7577 (5)	0.56080 (17)	0.0482 (11)
C7	0.7064 (6)	0.9577 (4)	0.48273 (17)	0.0428 (9)
C71	0.7397 (7)	1.0758 (4)	0.51865 (18)	0.0476 (10)
C72	0.7791 (7)	1.1640 (4)	0.55130 (19)	0.0492 (10)
C73	0.8323 (8)	1.2747 (5)	0.5920 (2)	0.0694 (15)
H73A	0.8942	1.2402	0.6274	0.104*
H73B	0.7252	1.3221	0.6048	0.104*
H73C	0.9123	1.3339	0.5704	0.104*
N8	0.6979 (5)	0.9619 (3)	0.42185 (14)	0.0453 (8)
N9	0.6759 (5)	0.8331 (3)	0.40305 (13)	0.0430 (8)
C1'	0.6721 (6)	0.8006 (4)	0.33815 (15)	0.0390 (9)
H1'	0.6264	0.7099	0.3332	0.047*
O2'	0.4835 (5)	0.8182 (3)	0.25073 (13)	0.0522 (8)
H2'	0.4607	0.8680	0.2220	0.078*
C2'	0.5533 (6)	0.8937 (4)	0.30117 (16)	0.0397 (9)
H2'A	0.4559	0.9337	0.3258	0.048*
O3'	0.6391 (5)	1.0630 (3)	0.22474 (12)	0.0518 (8)
H3'	0.5891	1.1331	0.2337	0.078*
C3'	0.6918 (5)	0.9960 (4)	0.27901 (16)	0.0384 (9)
H3'A	0.7152	1.0607	0.3116	0.046*
O4'	0.8523 (4)	0.8083 (3)	0.31315 (11)	0.0461 (7)
C4'	0.8623 (6)	0.9134 (4)	0.26794 (17)	0.0423 (9)
H4'	0.8548	0.8739	0.2270	0.051*
O5'	1.0660 (6)	1.0436 (4)	0.32977 (17)	0.0784 (11)
H5'	1.0556	0.9889	0.3574	0.118*
C5'	1.0404 (7)	0.9819 (6)	0.2740 (2)	0.0637 (13)
H5'A	1.1373	0.9177	0.2680	0.076*
H5'B	1.0504	1.0478	0.2418	0.076*
O10	0.6800 (6)	0.4196 (4)	0.35338 (14)	0.0664 (10)
H10	0.6693	0.4871	0.3741	0.100*
C10	0.8228 (8)	0.3418 (6)	0.3769 (3)	0.0768 (16)
H10A	0.9189	0.3985	0.3913	0.115*
H10B	0.8690	0.2849	0.3452	0.115*
H10C	0.7781	0.2888	0.4103	0.115*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.074 (3)	0.054 (2)	0.0334 (16)	−0.011 (2)	−0.0010 (18)	0.0098 (16)
C2	0.071 (3)	0.042 (2)	0.040 (2)	−0.011 (2)	−0.004 (2)	0.0084 (19)
N3	0.064 (2)	0.0346 (16)	0.0357 (16)	−0.0056 (18)	−0.0044 (18)	0.0035 (14)
C4	0.048 (2)	0.0390 (19)	0.0284 (16)	−0.0022 (18)	−0.0023 (18)	0.0029 (16)
C5	0.046 (2)	0.044 (2)	0.0312 (17)	−0.0026 (18)	−0.0005 (18)	−0.0020 (17)
N6	0.102 (3)	0.069 (3)	0.0299 (16)	−0.015 (3)	0.005 (2)	−0.0042 (18)
C6	0.053 (3)	0.059 (3)	0.0318 (19)	−0.009 (2)	−0.0011 (19)	0.0021 (19)
C7	0.054 (2)	0.041 (2)	0.0336 (19)	−0.002 (2)	0.0011 (17)	−0.0030 (16)
C71	0.058 (3)	0.048 (2)	0.037 (2)	0.001 (2)	0.0021 (18)	−0.0046 (19)
C72	0.064 (3)	0.038 (2)	0.045 (2)	0.007 (2)	0.000 (2)	−0.006 (2)
C73	0.091 (4)	0.052 (3)	0.065 (3)	0.008 (3)	−0.019 (3)	−0.016 (2)
N8	0.065 (2)	0.0357 (17)	0.0347 (16)	−0.0032 (17)	−0.0005 (17)	−0.0029 (14)
N9	0.066 (2)	0.0329 (16)	0.0305 (14)	−0.0064 (18)	−0.0056 (16)	0.0013 (13)
C1'	0.056 (2)	0.0323 (18)	0.0285 (16)	−0.0034 (19)	−0.0030 (17)	0.0005 (15)
O2'	0.071 (2)	0.0443 (15)	0.0415 (14)	−0.0128 (16)	−0.0199 (14)	0.0054 (14)
C2'	0.049 (2)	0.0375 (19)	0.0327 (18)	0.0016 (18)	−0.0057 (17)	−0.0032 (17)
O3'	0.076 (2)	0.0423 (15)	0.0367 (14)	0.0037 (17)	−0.0071 (15)	0.0116 (12)
C3'	0.051 (2)	0.0333 (18)	0.0307 (18)	0.0004 (17)	−0.0053 (17)	0.0010 (15)
O4'	0.0585 (17)	0.0414 (15)	0.0385 (13)	0.0131 (15)	−0.0020 (13)	0.0028 (13)
C4'	0.050 (2)	0.049 (2)	0.0284 (17)	0.000 (2)	0.0003 (17)	0.0021 (17)
O5'	0.087 (3)	0.079 (2)	0.069 (2)	−0.024 (2)	−0.021 (2)	0.009 (2)
C5'	0.057 (3)	0.081 (3)	0.054 (3)	−0.009 (3)	−0.007 (2)	0.011 (3)
O10	0.086 (3)	0.061 (2)	0.0522 (17)	0.012 (2)	−0.0246 (19)	−0.0126 (16)
C10	0.080 (4)	0.075 (4)	0.076 (3)	0.010 (3)	−0.014 (3)	−0.001 (3)

Geometric parameters (Å, º)

N1—C2	1.327 (5)	C1'—C2'	1.513 (5)
N1—C6	1.349 (6)	C1'—H1'	0.9800
C2—N3	1.332 (5)	O2'—C2'	1.432 (5)
C2—H2	0.9300	O2'—H2'	0.8200
N3—C4	1.349 (5)	C2'—C3'	1.525 (6)
C4—N9	1.358 (5)	C2'—H2'A	0.9800
C4—C5	1.388 (5)	O3'—C3'	1.417 (4)
C5—C7	1.414 (6)	O3'—H3'	0.8200
C5—C6	1.421 (5)	C3'—C4'	1.521 (6)
N6—C6	1.336 (5)	C3'—H3'A	0.9800
N6—H6A	0.8600	O4'—C4'	1.449 (5)
N6—H6B	0.8600	C4'—C5'	1.482 (7)
C7—N8	1.330 (5)	C4'—H4'	0.9800
C7—C71	1.445 (6)	O5'—C5'	1.379 (6)
C71—C72	1.175 (6)	O5'—H5'	0.8200
C72—C73	1.479 (6)	C5'—H5'A	0.9700
C73—H73A	0.9600	C5'—H5'B	0.9700
C73—H73B	0.9600	O10—C10	1.405 (6)
C73—H73C	0.9600	O10—H10	0.8200
N8—N9	1.371 (5)	C10—H10A	0.9600
N9—C1'	1.453 (4)	C10—H10B	0.9600
C1'—O4'	1.431 (5)	C10—H10C	0.9600
C2—N1—C6	117.8 (4)	C2'—C1'—H1'	108.9
N1—C2—N3	130.3 (4)	C2'—O2'—H2'	109.5
N1—C2—H2	114.9	O2'—C2'—C1'	106.6 (3)
N3—C2—H2	114.9	O2'—C2'—C3'	110.7 (3)
C2—N3—C4	110.8 (3)	C1'—C2'—C3'	101.8 (3)
N3—C4—N9	127.1 (4)	O2'—C2'—H2'A	112.4
N3—C4—C5	126.3 (4)	C1'—C2'—H2'A	112.4
N9—C4—C5	106.6 (3)	C3'—C2'—H2'A	112.4
C4—C5—C7	105.6 (3)	C3'—O3'—H3'	109.5
C4—C5—C6	116.4 (4)	O3'—C3'—C4'	110.6 (3)
C7—C5—C6	138.1 (4)	O3'—C3'—C2'	113.9 (3)
C6—N6—H6A	120.0	C4'—C3'—C2'	103.1 (3)
C6—N6—H6B	120.0	O3'—C3'—H3'A	109.6
H6A—N6—H6B	120.0	C4'—C3'—H3'A	109.6
N6—C6—N1	119.1 (4)	C2'—C3'—H3'A	109.6
N6—C6—C5	122.5 (4)	C1'—O4'—C4'	110.2 (3)
N1—C6—C5	118.4 (4)	O4'—C4'—C5'	108.9 (3)
N8—C7—C5	110.5 (3)	O4'—C4'—C3'	104.5 (3)
N8—C7—C71	121.5 (4)	C5'—C4'—C3'	117.0 (4)
C5—C7—C71	127.9 (3)	O4'—C4'—H4'	108.7
C72—C71—C7	173.1 (5)	C5'—C4'—H4'	108.7
C71—C72—C73	178.9 (6)	C3'—C4'—H4'	108.7
C72—C73—H73A	109.5	C5'—O5'—H5'	109.5
C72—C73—H73B	109.5	O5'—C5'—C4'	114.1 (4)
H73A—C73—H73B	109.5	O5'—C5'—H5'A	108.7
C72—C73—H73C	109.5	C4'—C5'—H5'A	108.7
H73A—C73—H73C	109.5	O5'—C5'—H5'B	108.7
H73B—C73—H73C	109.5	C4'—C5'—H5'B	108.7
C7—N8—N9	105.9 (3)	H5'A—C5'—H5'B	107.6
C4—N9—N8	111.4 (3)	C10—O10—H10	109.5
C4—N9—C1'	128.0 (3)	O10—C10—H10A	109.5
N8—N9—C1'	120.5 (3)	O10—C10—H10B	109.5
O4'—C1'—N9	110.0 (3)	H10A—C10—H10B	109.5
O4'—C1'—C2'	107.1 (3)	O10—C10—H10C	109.5
N9—C1'—C2'	113.0 (3)	H10A—C10—H10C	109.5
O4'—C1'—H1'	108.9	H10B—C10—H10C	109.5
N9—C1'—H1'	108.9
C6—N1—C2—N3	−1.6 (8)	C7—N8—N9—C4	0.3 (5)
N1—C2—N3—C4	0.0 (7)	C7—N8—N9—C1'	−176.4 (4)
C2—N3—C4—N9	−178.1 (4)	C4—N9—C1'—O4'	−101.8 (5)
C2—N3—C4—C5	1.9 (7)	N8—N9—C1'—O4'	74.3 (5)
N3—C4—C5—C7	179.4 (5)	C4—N9—C1'—C2'	138.6 (4)
N9—C4—C5—C7	−0.7 (5)	N8—N9—C1'—C2'	−45.3 (5)
N3—C4—C5—C6	−1.9 (7)	O4'—C1'—C2'—O2'	88.8 (4)
N9—C4—C5—C6	178.0 (4)	N9—C1'—C2'—O2'	−149.9 (3)
C2—N1—C6—N6	−179.3 (4)	O4'—C1'—C2'—C3'	−27.2 (4)
C2—N1—C6—C5	1.4 (7)	N9—C1'—C2'—C3'	94.0 (4)
C4—C5—C6—N6	−179.2 (5)	O2'—C2'—C3'—O3'	42.7 (4)
C7—C5—C6—N6	−1.1 (9)	C1'—C2'—C3'—O3'	155.6 (3)
C4—C5—C6—N1	0.2 (7)	O2'—C2'—C3'—C4'	−77.3 (4)
C7—C5—C6—N1	178.3 (5)	C1'—C2'—C3'—C4'	35.7 (4)
C4—C5—C7—N8	0.9 (5)	N9—C1'—O4'—C4'	−115.5 (3)
C6—C5—C7—N8	−177.3 (5)	C2'—C1'—O4'—C4'	7.7 (4)
C4—C5—C7—C71	−176.1 (4)	C1'—O4'—C4'—C5'	141.2 (4)
C6—C5—C7—C71	5.6 (9)	C1'—O4'—C4'—C3'	15.4 (4)
C5—C7—N8—N9	−0.8 (5)	O3'—C3'—C4'—O4'	−154.1 (3)
C71—C7—N8—N9	176.5 (4)	C2'—C3'—C4'—O4'	−31.9 (4)
N3—C4—N9—N8	−179.8 (5)	O3'—C3'—C4'—C5'	85.3 (4)
C5—C4—N9—N8	0.3 (5)	C2'—C3'—C4'—C5'	−152.5 (4)
N3—C4—N9—C1'	−3.4 (7)	O4'—C4'—C5'—O5'	−62.6 (5)
C5—C4—N9—C1'	176.7 (4)	C3'—C4'—C5'—O5'	55.5 (5)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2′—H2′···O10^i	0.82	2.01	2.764 (4)	153
O3′—H3′···O2′^i	0.82	1.97	2.776 (4)	168
O5′—H5′···N1^ii	0.82	2.25	3.012 (5)	154
O10—H10···N3	0.82	2.10	2.891 (4)	162
C73—H73B···O5′^iii	0.96	2.29	3.173 (6)	153

Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) x+1/2, −y+3/2, −z+1; (iii) x−1/2, −y+5/2, −z+1.