2,6-Di­chloro-9-(2′,3′,5′-tri-O-acetyl-β-d-ribo­furanos­yl)-9H-purine

Novosjolova, I.; Stepanovs, D.; Bizdēna, Ē.; Mishnev, A.; Turks, M.¯

doi:10.1107/S1600536813034521

organic compounds

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ISSN: 2056-9890

Volume 70| Part 2| February 2014| Pages o108-o109

doi:10.1107/S1600536813034521

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2,6-Dichloro-9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-9H-purine

Irina Novosjolova,^a ^* Dmitrijs Stepanovs,^b Ērika Bizdēna,^a Anatoly Mishnev ^b and Māris Turks ^a

^aDepartment of Material Science and Applied Chemistry, Riga Technical University, 14/24 Azenes street, Riga, LV-1007, Latvia, and ^bLatvian Institute of Organic Synthesis, 21 Aizkraukles street, Riga, LV-1006, Latvia
^*Correspondence e-mail: irina.novosjolova@rtu.lv

(Received 9 December 2013; accepted 23 December 2013; online 4 January 2014)

The title synthetic analog of purine nucleosides, C₁₆H₁₆Cl₂N₄O₇, has its acetylated β-furanose ring in a 3′β-envelope conformation, with the corresponding C atom deviating by 0.602 (5) Å from the rest of the ring. The planar part of the furanose ring forms a dihedral angle of 65.0 (1)° with the mean plane of the purine bicycle. In the crystal, molecules form a three-dimensional network through multiple C—H⋯O and C—H⋯N hydrogen bonds and C—H⋯π interactions.

CCDC reference: 968101

Related literature

For applications of 9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine in synthesis, see: Caner & Vilarrasa (2010 ); Korboukh et al. (2012 ). For the synthesis, see: Vorbrüggen (1995 ); Robins & Uznański (1981 ); Nair & Richardson (1982 ); Francom et al. (2002 ); Francom & Robins (2003 ); Gerster & Robins (1966 ). The conditions were improved by using our previous studies (Kovalovs et al., 2013 ; Novosjolova et al., 2013 ). For the biological activity of purine nucleosides, their anticancer and antiviral activity and use as agonists and antagonists of adenosine receptors, see: Lech-Maranda et al. (2006 ); Robak et al. (2009 ); Gumina et al. (2003 ); Fredholm et al. (2011 ); Elzein & Zablocki (2008 ). For the structure of another 2,6-dichloropurine ribonucleoside, 9-(2′-deoxy-3′,5′-di-O-4-methoxybenzoyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine, see:Yang et al. (2012 ). The purine heterocycle is known to form π–π stacking interactions in related structures, see: Sternglanz & Bugg (1975 ). For standard bond lengths, see: Allen et al. (1987 ). The nature of hydrogen bonding is described by Gilli (2002 ). For a description of the Cambridge Structural Database, see: Allen (2002 ).

Experimental

Crystal data

C₁₆H₁₆Cl₂N₄O₇
M_r = 447.23
Monoclinic, P 2₁
a = 10.1324 (2) Å
b = 9.6887 (3) Å
c = 10.5399 (2) Å
β = 106.537 (2)°
V = 991.90 (4) Å³
Z = 2
Mo Kα radiation
μ = 0.37 mm⁻¹
T = 296 K
0.38 × 0.32 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer
3898 measured reflections
3898 independent reflections
2846 reflections with I > 2σ(I)

Refinement

R[F² > 2σ(F²)] = 0.046
wR(F²) = 0.107
S = 1.02
3898 reflections
265 parameters
H-atom parameters constrained
Δρ_max = 0.22 e Å⁻³
Δρ_min = −0.20 e Å⁻³
Absolute structure: Flack (1983 ), 1518 Friedel pairs
Absolute structure parameter: 0.00 (7)

Table 1
Hydrogen-bond geometry (Å, °)

Cg is the centroid of the C4/C5/N7/C8/N9 imidazole ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8⋯O15′	0.93	2.52	3.265 (4)	137
C8—H8⋯O14′ⁱ	0.93	2.56	3.350 (4)	143
C1′—H1⋯N1ⁱⁱ	0.98	2.48	3.355 (5)	148
C9′—H9B⋯O18′ⁱⁱⁱ	0.96	2.51	3.434 (4)	161
C13′—H13B⋯N7^iv	0.96	2.54	3.502 (5)	175
C5′—H5A⋯Cgⁱ	0.97	2.69	3.454	136
Symmetry codes: (i) $[-x+2, y+{\script{1\over 2}}, -z+2]$ ; (ii) $[-x+2, y+{\script{1\over 2}}, -z+1]$ ; (iii) x-1, y, z-1; (iv) x-1, y, z.

Data collection: KappaCCD Server Software (Nonius, 1997 ); cell refinement: SCALEPACK (Otwinovski & Minor, 1997 ); data reduction: DENZO (Otwinovski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012 ) and Mercury (Macrae et al., 2008 ); software used to prepare material for publication: SHELXL97, PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 968101

Crystal structure: contains datablock I. DOI: 10.1107/S1600536813034521/ld2116sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536813034521/ld2116Isup2.hkl

checkCIF report

1. Comment top

Purine nucleosides are well known of their biological activity: anticancer and antiviral activities, and as agonists and antagonists of adenosine receptors (Lech-Maranda et al. (2006), Robak et al. (2009), Gumina et al. (2003), Fredholm et al. (2011), Elzein & Zablocki (2008).

There is only one example of similar crystal structure of 2,6-dichloropurine ribonucleoside (9-(2'-deoxy-3',5'-di-O-4-methoxybenzoyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine) in literature (Yang et al., 2012, CSD refcode KEBWOF). Search of the Cambridge Structural Database (CSD, Version 1.15; Allen, 2002) indicated that there are only 4 (CSD refcodes: CLPURB, JEMHUF, PUPZAC, ZEXWEE) entries of 2- or 6-chloro substituted derivatives from over 300 crystal structures of 9-(ribofuranosyl)-9H-purines. The bond lengths (Allen et al., 1987) and angles in the molecule of are close to standard values. The furanose cycle adopts an envelope conformation. Atoms C2', C1', O6' and C4' of furanose lie in same plane (denoted as plane A), 2'- and 5'-O-acetyl groups are on opposite sides of the A plane, while 3'-O-acetyl group lies close to the A plane. The C3' deviates from the A by 0.602 (5) Å. The dihedral angle between the least-square planes of the purine system and four planar atoms (C2', C1', O6' and C4') of furanose cycle is 65.0 (1)°. The main torsion angles describing the location of purine system in respect to furanose ring are: C8—N9—C1'—O6' (6.9 (4)°); C8—N9—C1'—C2' (-111.1 (3)°); C4—N9—C1'—O6' (-168.8 (3)°); C4—N9—C1'—C2' (73.2 (4)°). Regardless of the fact that purine heterocycle is known to form π–π stacking interactions in related structures (Sternglanz & Bugg, 1975), such interaction was not observed in the crystals of the title compound. Moderate hydrogen bonds type C—H···O and C— H···N are present to form and stabilize three-dimensional architecture (Table 1).

The 9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine 1 was synthesized by method of Vorbrüggen glycosylation of 2,6-dichloropurine (Vorbrüggen, 1995). The conditions were improved by using our previous studies (Kovalovs et al., 2013; Novosjolova et al., 2013).

2. Experimental top

Single crystals of 9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine were grown from an ethanol solution by slow evaporation in ambient temperature. ¹H-NMR and ¹³C-NMR spectra were recorded at 300 MHz and at 75.5 MHz, respectively. The proton signals for residual non-deuterated solvents (δ 7.26 for CDCl₃) and carbon signals (δ 77.1 for CDCl₃) were used as an internal references for ¹H-NMR and ¹³C-NMR spectra, respectively. Coupling constants are reported in Hz. Analytical thin layer chromatography (TLC) was performed on Kieselgel 60 F254 glass plates precoated with a 0.25 mm thickness of silica gel. Dry MeCN was obtained by distillation over CaH₂. Commercial reagents were used as received.

9-(2',3',5'-Tri-O-acetyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine (3). N,O-Bis(trimethylsilyl)acetamide (5.60 mL, 22.7 mmol) was added to a stirred suspension of 2,6-dichloropurine (2) (4.02 g, 21.2 mmol) in dry acetonitrile (50 mL). The resulting mixture was stirred at 40 °C for 30 min until a clear solution was obtained. Solution of tetra-O-acetyl-D-ribofuranose (1) (6.77 g, 21.3 mmol) in dry acetonitrile (35 mL) was then added, followed by TMSOTf (0.80 mL, 4.4 mmol). The resulting reaction mixture was stirred at 75-80 °C for 2.5-3 h (TLC control). Then it was cooled to ambient temperature and ethanol (1 mL) was added and the mixture was stirred for 15 min at the same temperature followed by evaporation under reduced pressure. The residue was dissolved in CH₂Cl₂ (100 mL) washed with saturated aqueous solution of NaHCO₃ (3 × 25 mL) and water (1 × 25 mL), dried over anh. Na₂SO₄. Evaporation under reduced pressure provided product 3 (8.95 g, 95%) as a slightly yellow powder. The title compound was crystallized from ethanol, mp 158-160 °C [lit.: 159-161 °C (Gerster & Robins, 1966)]. The other analytical data of 9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine are consistent with those reported earlier (Francom et al., 2002; Caner & Vilarrasa, 2010). R_f=0.45 (Toluene/EtOAc 1:2), IR (KBr), ν, cm^-1: 2976, 2924, 1773, 1742, 1593, 1560, 1381, 1367, 1245, 1229, 1200, 1137, 1100, 1061; ¹H-NMR (300 MHz, CDCl₃) δ (ppm): 8.29 (s, 1H, H—C(8)), 6.21 (d, 1H, ³J_1'-2' = 5.6 Hz, H—C(1')), 5.79 (t, 1H, ³J_1'-2' = ³J_2'-3' = 5.6 Hz, H—C(2')), 5.57 (dd, 1H, ³J_2'-3' = 5.6 Hz, ³J_3'-4' = 4.4 Hz, H—C(3')), 4.47 (quartet, 1H, ³J_3'-4' = ³J_4'-5' = 4.4 Hz, H—C(4')), 4.41 (d, 2H, ³J_4'-5' = 4.4 Hz, H—C(5')), 2.16, 2.14, 2.09 (3s, 9H, H₃COOC-C(2',3',5')); ¹³C-NMR (75.5 MHz, CDCl₃) δ (ppm): 170.2, 169.5, 169.4, 153.3, 152.6, 152.2, 143.9, 131.3, 86.5, 80.8, 73.2, 70.5, 62.8, 20.7, 20.5, 20.3.

3. Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 1. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were positioned geometrically with C—H distances ranging from 0.93 Å to 0.98 Å and refined as riding on their parent atoms with U_iso (H) = 1.5U_eq (C) for methyl groups and U_iso (H) = 1.2U_eq (C) for others.

Related literature top

For applications of 9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine in synthesis, see: Caner & Vilarrasa (2010); Korboukh et al. (2012). For the synthesis, see: Vorbrüggen (1995); Robins & Uznański (1981); Nair & Richardson (1982); Francom et al. (2002); Francom & Robins (2003); Gerster & Robins (1966). The conditions were improved by using our previous studies (Kovalovs et al., 2013; Novosjolova et al., 2013). For the biological activity of purine nucleosides, their anticancer and antiviral activity and use as agonists and antagonists of adenosine receptors, see: Lech-Maranda et al. (2006); Robak et al. (2009); Gumina et al. (2003); Fredholm et al. (2011); Elzein & Zablocki (2008). For the structure of another 2,6-dichloropurine ribonucleoside, 9-(2'-deoxy-3',5'-di-O-4-methoxybenzoyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine, see:Yang et al. (2012). The purine heterocycle is known to form π–π stacking interactions in related structures, see: Sternglanz & Bugg (1975). For standard bond lengths, see: Allen et al. (1987). The nature of hydrogen bonding is described by Gilli (2002). For a description of the Cambridge Structural Database, see: Allen (2002).

Structure description top

Refinement details top

Computing details top

Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: SCALEPACK (Otwinovski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinovski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Figures top

	Fig. 1. The asymmetric unit of the title compound showing 50% probability displacement ellipsoids and the atom-numbering (hydrogen atoms are shown as small spheres of arbitrary radii)
	Fig. 2. Packing diagram of the title compound viewed down the b axis

2,6-Dichloro-9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-9H-purine top

Crystal data top

C₁₆H₁₆Cl₂N₄O₇	F(000) = 460
M_r = 447.23	D_x = 1.497 Mg m⁻³
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 17407 reflections
a = 10.1324 (2) Å	θ = 1.0–27.5°
b = 9.6887 (3) Å	µ = 0.37 mm⁻¹
c = 10.5399 (2) Å	T = 296 K
β = 106.537 (2)°	Prism, colorless
V = 991.90 (4) Å³	0.38 × 0.32 × 0.15 mm
Z = 2

Data collection top

Nonius KappaCCD diffractometer	2846 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.000
Graphite monochromator	θ_max = 27.5°, θ_min = 2.0°
CCD scans	h = −13→13
3898 measured reflections	k = −11→12
3898 independent reflections	l = −13→13

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.046	H-atom parameters constrained
wR(F²) = 0.107	w = 1/[σ²(F_o²) + (0.0352P)² + 0.3514P] where P = (F_o² + 2F_c²)/3
S = 1.02	(Δ/σ)_max < 0.001
3898 reflections	Δρ_max = 0.22 e Å⁻³
265 parameters	Δρ_min = −0.20 e Å⁻³
0 restraints	Absolute structure: Flack (1983), 1518 Friedel pairs
0 constraints	Absolute structure parameter: 0.00 (7)
Primary atom site location: structure-invariant direct methods

Crystal data top

C₁₆H₁₆Cl₂N₄O₇	V = 991.90 (4) Å³
M_r = 447.23	Z = 2
Monoclinic, P2₁	Mo Kα radiation
a = 10.1324 (2) Å	µ = 0.37 mm⁻¹
b = 9.6887 (3) Å	T = 296 K
c = 10.5399 (2) Å	0.38 × 0.32 × 0.15 mm
β = 106.537 (2)°

Data collection top

Nonius KappaCCD diffractometer	2846 reflections with I > 2σ(I)
3898 measured reflections	R_int = 0.000
3898 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.046	H-atom parameters constrained
wR(F²) = 0.107	Δρ_max = 0.22 e Å⁻³
S = 1.02	Δρ_min = −0.20 e Å⁻³
3898 reflections	Absolute structure: Flack (1983), 1518 Friedel pairs
265 parameters	Absolute structure parameter: 0.00 (7)
0 restraints

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
N1	1.0850 (3)	0.1139 (3)	0.4785 (3)	0.0535 (8)
C2	0.9650 (4)	0.1787 (4)	0.4602 (3)	0.0508 (9)
N3	0.9178 (3)	0.2553 (3)	0.5399 (2)	0.0458 (6)
C4	1.0170 (3)	0.2704 (3)	0.6574 (3)	0.0404 (7)
C5	1.1477 (3)	0.2135 (4)	0.6915 (3)	0.0429 (8)
C6	1.1761 (4)	0.1309 (4)	0.5952 (3)	0.0510 (9)
N7	1.2211 (3)	0.2508 (3)	0.8196 (3)	0.0506 (7)
C8	1.1331 (3)	0.3266 (4)	0.8596 (3)	0.0473 (8)
H8	1.1540	0.3671	0.9430	0.057*
N9	1.0071 (2)	0.3404 (3)	0.7669 (2)	0.0405 (6)
Cl10	1.32958 (12)	0.04548 (15)	0.62312 (11)	0.0892 (4)
Cl11	0.85038 (11)	0.15549 (12)	0.30379 (9)	0.0733 (3)
C1'	0.8877 (3)	0.4205 (4)	0.7769 (3)	0.0409 (7)
H1	0.8574	0.4827	0.7008	0.049*
C2'	0.7695 (3)	0.3282 (4)	0.7845 (3)	0.0397 (7)
H2	0.7642	0.2421	0.7344	0.048*
C3'	0.8034 (3)	0.3062 (3)	0.9343 (3)	0.0385 (7)
H3	0.8772	0.2380	0.9639	0.046*
C4'	0.8537 (3)	0.4472 (3)	0.9862 (3)	0.0382 (7)
H4	0.7733	0.5063	0.9786	0.046*
C5'	0.9455 (3)	0.4570 (4)	1.1251 (3)	0.0432 (8)
H5A	0.9788	0.5509	1.1437	0.052*
H5B	0.8946	0.4325	1.1870	0.052*
O6'	0.9264 (2)	0.4982 (2)	0.89486 (18)	0.0402 (5)
O7'	0.6460 (2)	0.4081 (2)	0.74576 (19)	0.0490 (6)
C8'	0.5479 (3)	0.3728 (4)	0.6337 (3)	0.0520 (9)
C9'	0.4297 (4)	0.4704 (5)	0.6096 (4)	0.0696 (12)
H9A	0.4616	0.5627	0.6031	0.104*
H9C	0.3895	0.4651	0.6816	0.104*
H9B	0.3620	0.4462	0.5285	0.104*
O10'	0.5636 (3)	0.2809 (4)	0.5649 (3)	0.0967 (11)
O11'	0.6883 (2)	0.2701 (2)	0.9804 (2)	0.0458 (6)
C12'	0.6474 (4)	0.1370 (4)	0.9636 (3)	0.0504 (9)
C13'	0.5286 (4)	0.1098 (5)	1.0189 (5)	0.0826 (15)
H13A	0.5188	0.0122	1.0288	0.124*
H13B	0.4456	0.1462	0.9597	0.124*
H13C	0.5455	0.1538	1.1037	0.124*
O14'	0.7012 (3)	0.0544 (3)	0.9110 (3)	0.0775 (8)
O15'	1.0599 (2)	0.3644 (2)	1.13994 (18)	0.0441 (5)
C16'	1.1551 (3)	0.3677 (4)	1.2595 (3)	0.0499 (8)
C17'	1.2746 (4)	0.2794 (4)	1.2628 (3)	0.0618 (10)
H17A	1.3570	0.3342	1.2865	0.093*
H17B	1.2630	0.2393	1.1770	0.093*
H17C	1.2816	0.2075	1.3270	0.093*
O18'	1.1385 (3)	0.4370 (4)	1.3478 (2)	0.0909 (10)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.063 (2)	0.055 (2)	0.0498 (17)	0.0015 (15)	0.0270 (14)	−0.0050 (14)
C2	0.064 (2)	0.052 (2)	0.0376 (17)	−0.0083 (19)	0.0173 (14)	−0.0028 (16)
N3	0.0551 (17)	0.0437 (17)	0.0444 (15)	0.0010 (13)	0.0239 (12)	0.0023 (13)
C4	0.0511 (19)	0.0378 (19)	0.0362 (16)	−0.0014 (15)	0.0189 (13)	0.0051 (14)
C5	0.0451 (19)	0.046 (2)	0.0406 (16)	0.0016 (15)	0.0166 (13)	0.0040 (15)
C6	0.057 (2)	0.050 (2)	0.0533 (19)	0.0053 (17)	0.0275 (16)	0.0000 (17)
N7	0.0465 (16)	0.0552 (19)	0.0495 (15)	0.0014 (14)	0.0126 (12)	−0.0009 (14)
C8	0.050 (2)	0.048 (2)	0.0437 (17)	−0.0015 (16)	0.0143 (14)	−0.0012 (15)
N9	0.0450 (15)	0.0425 (16)	0.0363 (13)	0.0033 (12)	0.0154 (11)	0.0016 (12)
Cl10	0.0712 (7)	0.1099 (11)	0.0907 (7)	0.0324 (7)	0.0299 (6)	−0.0156 (7)
Cl11	0.0824 (7)	0.0903 (9)	0.0433 (5)	−0.0046 (6)	0.0118 (4)	−0.0139 (5)
C1'	0.0501 (18)	0.0420 (19)	0.0319 (14)	0.0100 (15)	0.0137 (12)	0.0040 (14)
C2'	0.0413 (17)	0.0406 (19)	0.0364 (15)	0.0043 (14)	0.0096 (12)	−0.0049 (14)
C3'	0.0383 (16)	0.0419 (19)	0.0366 (15)	0.0032 (14)	0.0130 (12)	−0.0013 (14)
C4'	0.0405 (16)	0.0397 (19)	0.0357 (14)	0.0054 (14)	0.0129 (12)	−0.0043 (14)
C5'	0.0492 (18)	0.044 (2)	0.0364 (15)	0.0030 (15)	0.0116 (13)	−0.0055 (14)
O6'	0.0493 (12)	0.0367 (13)	0.0371 (11)	−0.0013 (10)	0.0162 (9)	−0.0035 (9)
O7'	0.0426 (12)	0.0597 (17)	0.0380 (11)	0.0133 (11)	0.0005 (9)	−0.0104 (10)
C8'	0.044 (2)	0.060 (3)	0.0451 (18)	−0.0044 (17)	0.0028 (14)	−0.0038 (18)
C9'	0.047 (2)	0.084 (3)	0.065 (2)	0.011 (2)	−0.0044 (16)	−0.006 (2)
O10'	0.079 (2)	0.096 (3)	0.089 (2)	0.0098 (18)	−0.0174 (16)	−0.048 (2)
O11'	0.0382 (12)	0.0531 (16)	0.0492 (12)	−0.0009 (11)	0.0174 (9)	0.0004 (11)
C12'	0.044 (2)	0.054 (2)	0.0484 (18)	−0.0001 (18)	0.0050 (14)	0.0148 (18)
C13'	0.053 (3)	0.109 (4)	0.087 (3)	−0.016 (2)	0.022 (2)	0.027 (3)
O14'	0.0762 (19)	0.0504 (18)	0.112 (2)	−0.0012 (16)	0.0364 (17)	0.0004 (17)
O15'	0.0455 (12)	0.0469 (14)	0.0356 (10)	0.0033 (10)	0.0049 (9)	−0.0040 (10)
C16'	0.051 (2)	0.048 (2)	0.0401 (18)	−0.0036 (17)	−0.0029 (14)	−0.0044 (17)
C17'	0.056 (2)	0.062 (3)	0.057 (2)	0.006 (2)	0.0006 (16)	0.0030 (19)
O18'	0.087 (2)	0.120 (3)	0.0482 (14)	0.026 (2)	−0.0101 (13)	−0.0346 (18)

Geometric parameters (Å, º) top

N1—C6	1.321 (4)	C4'—C5'	1.497 (4)
N1—C2	1.333 (4)	C4'—H4	0.9800
C2—N3	1.308 (4)	C5'—O15'	1.439 (4)
C2—Cl11	1.740 (3)	C5'—H5A	0.9700
N3—C4	1.363 (4)	C5'—H5B	0.9700
C4—N9	1.367 (4)	O7'—C8'	1.354 (4)
C4—C5	1.384 (4)	C8'—O10'	1.187 (4)
C5—C6	1.386 (4)	C8'—C9'	1.489 (5)
C5—N7	1.391 (4)	C9'—H9A	0.9600
C6—Cl10	1.712 (4)	C9'—H9C	0.9600
N7—C8	1.314 (4)	C9'—H9B	0.9600
C8—N9	1.376 (4)	O11'—C12'	1.351 (5)
C8—H8	0.9300	C12'—O14'	1.190 (4)
N9—C1'	1.466 (4)	C12'—C13'	1.502 (5)
C1'—O6'	1.409 (4)	C13'—H13A	0.9600
C1'—C2'	1.515 (5)	C13'—H13B	0.9600
C1'—H1	0.9800	C13'—H13C	0.9600
C2'—O7'	1.429 (4)	O15'—C16'	1.352 (3)
C2'—C3'	1.532 (4)	C16'—O18'	1.198 (4)
C2'—H2	0.9800	C16'—C17'	1.475 (5)
C3'—O11'	1.429 (3)	C17'—H17A	0.9600
C3'—C4'	1.505 (5)	C17'—H17B	0.9600
C3'—H3	0.9800	C17'—H17C	0.9600
C4'—O6'	1.455 (3)

C6—N1—C2	116.3 (3)	C5'—C4'—C3'	117.7 (3)
N3—C2—N1	131.2 (3)	O6'—C4'—H4	108.3
N3—C2—Cl11	114.5 (3)	C5'—C4'—H4	108.3
N1—C2—Cl11	114.3 (2)	C3'—C4'—H4	108.3
C2—N3—C4	109.5 (3)	O15'—C5'—C4'	108.9 (2)
N3—C4—N9	127.5 (3)	O15'—C5'—H5A	109.9
N3—C4—C5	126.6 (3)	C4'—C5'—H5A	109.9
N9—C4—C5	105.9 (3)	O15'—C5'—H5B	109.9
C4—C5—C6	115.0 (3)	C4'—C5'—H5B	109.9
C4—C5—N7	110.9 (3)	H5A—C5'—H5B	108.3
C6—C5—N7	134.1 (3)	C1'—O6'—C4'	109.7 (2)
N1—C6—C5	121.2 (3)	C8'—O7'—C2'	118.5 (3)
N1—C6—Cl10	117.4 (2)	O10'—C8'—O7'	122.0 (3)
C5—C6—Cl10	121.4 (3)	O10'—C8'—C9'	127.8 (3)
C8—N7—C5	103.5 (3)	O7'—C8'—C9'	110.1 (3)
N7—C8—N9	113.8 (3)	C8'—C9'—H9A	109.5
N7—C8—H8	123.1	C8'—C9'—H9C	109.5
N9—C8—H8	123.1	H9A—C9'—H9C	109.5
C4—N9—C8	105.9 (3)	C8'—C9'—H9B	109.5
C4—N9—C1'	125.7 (2)	H9A—C9'—H9B	109.5
C8—N9—C1'	128.2 (3)	H9C—C9'—H9B	109.5
O6'—C1'—N9	108.5 (2)	C12'—O11'—C3'	116.1 (3)
O6'—C1'—C2'	107.2 (2)	O14'—C12'—O11'	122.6 (3)
N9—C1'—C2'	111.8 (3)	O14'—C12'—C13'	126.0 (4)
O6'—C1'—H1	109.8	O11'—C12'—C13'	111.5 (4)
N9—C1'—H1	109.8	C12'—C13'—H13A	109.5
C2'—C1'—H1	109.8	C12'—C13'—H13B	109.5
O7'—C2'—C1'	107.8 (3)	H13A—C13'—H13B	109.5
O7'—C2'—C3'	106.9 (2)	C12'—C13'—H13C	109.5
C1'—C2'—C3'	100.8 (2)	H13A—C13'—H13C	109.5
O7'—C2'—H2	113.5	H13B—C13'—H13C	109.5
C1'—C2'—H2	113.5	C16'—O15'—C5'	115.2 (2)
C3'—C2'—H2	113.5	O18'—C16'—O15'	121.1 (3)
O11'—C3'—C4'	108.8 (2)	O18'—C16'—C17'	127.1 (3)
O11'—C3'—C2'	114.8 (2)	O15'—C16'—C17'	111.8 (3)
C4'—C3'—C2'	101.7 (2)	C16'—C17'—H17A	109.5
O11'—C3'—H3	110.4	C16'—C17'—H17B	109.5
C4'—C3'—H3	110.4	H17A—C17'—H17B	109.5
C2'—C3'—H3	110.4	C16'—C17'—H17C	109.5
O6'—C4'—C5'	109.5 (2)	H17A—C17'—H17C	109.5
O6'—C4'—C3'	104.5 (2)	H17B—C17'—H17C	109.5

C6—N1—C2—N3	−2.3 (6)	O6'—C1'—C2'—O7'	82.0 (3)
C6—N1—C2—Cl11	178.7 (3)	N9—C1'—C2'—O7'	−159.2 (2)
N1—C2—N3—C4	3.0 (5)	O6'—C1'—C2'—C3'	−29.8 (3)
Cl11—C2—N3—C4	−178.0 (2)	N9—C1'—C2'—C3'	89.0 (3)
C2—N3—C4—N9	−178.6 (3)	O7'—C2'—C3'—O11'	44.0 (4)
C2—N3—C4—C5	−0.9 (5)	C1'—C2'—C3'—O11'	156.5 (3)
N3—C4—C5—C6	−1.5 (5)	O7'—C2'—C3'—C4'	−73.3 (3)
N9—C4—C5—C6	176.6 (3)	C1'—C2'—C3'—C4'	39.2 (3)
N3—C4—C5—N7	180.0 (3)	O11'—C3'—C4'—O6'	−157.0 (2)
N9—C4—C5—N7	−1.9 (4)	C2'—C3'—C4'—O6'	−35.5 (3)
C2—N1—C6—C5	−0.8 (5)	O11'—C3'—C4'—C5'	81.3 (3)
C2—N1—C6—Cl10	178.4 (3)	C2'—C3'—C4'—C5'	−157.2 (2)
C4—C5—C6—N1	2.4 (5)	O6'—C4'—C5'—O15'	−65.6 (3)
N7—C5—C6—N1	−179.6 (4)	C3'—C4'—C5'—O15'	53.4 (3)
C4—C5—C6—Cl10	−176.8 (3)	N9—C1'—O6'—C4'	−112.7 (3)
N7—C5—C6—Cl10	1.2 (6)	C2'—C1'—O6'—C4'	8.2 (3)
C4—C5—N7—C8	0.9 (4)	C5'—C4'—O6'—C1'	144.5 (2)
C6—C5—N7—C8	−177.2 (4)	C3'—C4'—O6'—C1'	17.6 (3)
C5—N7—C8—N9	0.4 (4)	C1'—C2'—O7'—C8'	115.0 (3)
N3—C4—N9—C8	−179.9 (3)	C3'—C2'—O7'—C8'	−137.4 (3)
C5—C4—N9—C8	2.0 (3)	C2'—O7'—C8'—O10'	−2.6 (5)
N3—C4—N9—C1'	−3.4 (5)	C2'—O7'—C8'—C9'	−178.7 (3)
C5—C4—N9—C1'	178.5 (3)	C4'—C3'—O11'—C12'	−168.0 (2)
N7—C8—N9—C4	−1.6 (4)	C2'—C3'—O11'—C12'	78.9 (3)
N7—C8—N9—C1'	−177.9 (3)	C3'—O11'—C12'—O14'	−1.6 (5)
C4—N9—C1'—O6'	−168.8 (3)	C3'—O11'—C12'—C13'	178.4 (3)
C8—N9—C1'—O6'	6.9 (4)	C4'—C5'—O15'—C16'	176.9 (3)
C4—N9—C1'—C2'	73.2 (4)	C5'—O15'—C16'—O18'	4.7 (5)
C8—N9—C1'—C2'	−111.1 (3)	C5'—O15'—C16'—C17'	−174.8 (3)

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the C4/C5/N7/C8/N9 imidazole ring.

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···O15′	0.93	2.52	3.265 (4)	137
C8—H8···O14′ⁱ	0.93	2.56	3.350 (4)	143
C1′—H1···N1ⁱⁱ	0.98	2.48	3.355 (5)	148
C9′—H9B···O18′ⁱⁱⁱ	0.96	2.51	3.434 (4)	161
C13′—H13B···N7^iv	0.96	2.54	3.502 (5)	175
C5′—H5A···Cgⁱ	0.97	2.69	3.454	136

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

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the C4/C5/N7/C8/N9 imidazole ring.

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···O15'	0.93	2.52	3.265 (4)	137
C8—H8···O14'ⁱ	0.93	2.56	3.350 (4)	143
C1'—H1···N1ⁱⁱ	0.98	2.48	3.355 (5)	148
C9'—H9B···O18'ⁱⁱⁱ	0.96	2.51	3.434 (4)	161
C13'—H13B···N7^iv	0.96	2.54	3.502 (5)	175
C5'—H5A···Cgⁱ	0.97	2.69	3.454	136

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

Acknowledgements

IN thanks the European Social Fund within the project `Support for the implementation of doctoral studies at Riga Technical University' for a scholarship and ERDF project 2DP/2.1.1.2.0/10/APIA/VI4AA/003 for the opportunity to present this work at the 14th Tetrahedron Symposium.

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Volume 70| Part 2| February 2014| Pages o108-o109

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