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The title compound, C13H14N5O+·Cl-, belongs to the group of aromatic cytokinins. These compounds affect a variety of important physiological processes in plants and animals as well as in bacteria, including cell division, differentiation and senescence. The structure consists of a 6-(4-methoxy­benzyl­amino)­purinium cation and a Cl- anion. The cation moiety exists as the N3-protonated N7 tautomer. The cation contains nearly planar benzene and purine ring systems, with a dihedral angle of 77.46 (5)°. The crystal structure is stabilized by Namino-H...Npurine hydrogen bonds connecting two adjacent mol­ecules, thus forming centrosymmetric dimers.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104016749/tr1094sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104016749/tr1094Isup2.hkl
Contains datablock I

CCDC reference: 251323

Comment top

Cytokinins are an important class of plant growth regulators, defined by their ability to promote cell division in tissue culture in the presence of auxins. Virtually all naturally occurring cytokinins identified to date are adenine derivatives, substituted at the N6 position with an isoprenoid or aromatic side-chain (Letham & Palni, 1983). They occur widely in plants, as well as in animals and bacteria, and affect a variety of important physiological processes, including cell division, differentiation and senescence. One very active and easily obtainable cytokinin is 6-benzylaminopurine (Bap), widely used in plant biotechnology (Strnad, 1997). Nevertheless, Bap has disadvantages in some crops, such as heterogeneity in growth and inhibition of rooting. One way of finding an alternative to Bap is to test Bap derivatives (Werbrouck et al., 1996).

However, Bap and its derivatives are important compounds not only for plant biotechnology and agriculture. An additional modification of a cytokinin molecule could lead to a dramatic change of its action in growth and development control. Surprisingly, additionally C2,N9-substituted Bap derivatives have been discovered, which specifically inhibit Cdc-2 and related kinases. One of the inhibited kinases, the p34cdc2/cyclin B kinase, is a key mitotic factor, which is highly conserved and strongly implicated in cell cycle transition in all eucaryotic cells. The compounds have a strong inhibitory function, with the ability to arrest cells at specific points of the cell cycle (Veselý et al., 1994). The total lack of inhibitory effect of C2,N9-substituted Bap derivatives on major kinases, such as cAMP– and cGMP-dependent kinases, protein kinase C and others, suggests that they might be useful tools for cell cycle studies. These cytokinin derivatives also exhibit strong antimitotic and anticancer activities, based on their ability to block plant and animal cell division at specific levels (G1/S, G2/M) of the cell cycle. This specificity can result in the development of a new class of cytostatic agents, plant cytokinin analogues, which are especially potent towards cell lines with a dysfunction of the endogenous CDK inhibitors (Havlíček et al., 1997; Kryštof et al., 2002). Thus, the development of new cytokinin derivatives might consequently be of a great practical importance. Our recent search for naturally occurring aromatic cytokinins in plants led to the discovery of four new very active endogenous plant hormone substances. These compounds were identified as 6-(2-methoxybenzylamino)purine (ortho-methoxytopolin), 6-(3-methoxybenzylamino)purine (meta-methoxytopolin) and their 9-β-D-ribofuranosyl derivatives (Tarkowská et al., 2003). Subsequently, a group of their synthetic analogues has been prepared in order to study various aspects of their biological activity. One of these is the title compound presented in this study, (I). \sch

The crystal structure of (I) consists of a 6-(4-methoxybenzylamino)purinium cation and a Cl anion (Fig. 1, Table 1). The structure of the cation is similar to those determined for 6-benzylaminopurinium bromide (BapH; Umadevi et al., 2001), 6-(3-chlorobenzylamino)purinium chloride (3ClBapH; Maloň et al., 2001) and 6-(4-chlorobenzylamino)purinium perchlorate (4ClBapH; Maloň et al., 2002). The cation contains nearly planar benzene (A) and pyrimidine (B) ring systems and an ideally planar imidazole (C) ring, with maximum deviations from the planes of six-membered ring A, six-membered ring B and five-membered ring C of 0.0083 (19), 0.0105 (18) and 0.0019 (18) Å, respectively, For which atoms? (Nardelli, 1995). The atoms of the purine ring system (B+C) deviate slightly from planarity, the greatest deviation being 0.0200 (18) Å For which atom?. Rings B and C are nearly coplanar, with a dihedral angle of 1.50 (6)°, whilst the dihedral angles between planes A and B, and A and the purine ring system (B+C), are 77.89 (6) and 77.46 (5)°, respectively.

The cation of (I) is protonated at the N3 and N7 positions of the purine ring, in contrast with the free base, where the protonation occurs on the N9 position. This change in protonation causes changes in the interatomic parameters within the purine ring, mainly in the C—N—C angles. To date, 31 structures of both organic and organometallic compounds with the 6-benzylaminopurine moiety have been deposited with the Cambridge Structural Database (Version 5.25; Allen, 2002), of which only three organic structures represent the N3-protonated N7 tautomer (Umadevi et al., 2001; Malon et al., 2001, 2002). The C2—N3—C4, C8—N7—C5 and C8—N9—C4 angles in the molecular structure of (I) are 117.01 (16), 106.58 (16) and 103.02 (15)°, respectively. These values are comparable with those found for BapH and 3ClBapH (Table 3). On the other hand, these angles differ significantly from those found for Bap (Raghunathan et al., 1983) and 6-(2-chlorobenzylamino)purine (2ClBap) (Maloň et al., 2001), i.e. in the N9-protonated electroneutral forms. The torsion angles C6—N6—C9—C10, C9—N6—C6—C5 and N6—C9—C10—C15 are −129.5 (2), 178.99 (17) and 49.7 (3)°, respectively.

The positive charge of the cation of (I) is neutralized by a Cl anion. The crystal structure is stabilized by N3—H3···N9i hydrogen bonds connecting two adjacent cation molecules [Fig. 2, Table 2; symmetry code: (i) −x, 2 − y, 1 − z], thus forming centrosymmetric dimers. Further hydrogen bonds connect H6···Cl1 and H7···Cl1 (Fig. 1).

Experimental top

The title compound was synthesized by a procedure similar to that described in the literature by Tarkowská et al. (2003). Colourless crystals of (I) suitable for single-crystal X-ray analysis were obtained by recrystallization from 2M HCl. Elemental analysis (ThermoFinnigen Flash EA 1112 CHN Analyzer), calculated for C13H14Cl1N5O1: C 53.52, H 4.84, N 24.01%; found: C 53.45, H 4.80, N 23.94%.

Refinement top

All H atoms were found from difference Fourier maps and refined using a riding model, with C—H distances of 0.95 and 0.99 Å and N—H distances of 0.88 Å, and with Uiso(H) = 1.2Ueq(CH, CH2 and NH) or 1.5Ueq(CH3).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2003); cell refinement: CrysAlis RED (Oxford Diffraction, 2003); data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altamore, 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Johnson & Burnett, 1996); software used to prepare material for publication: SHELXL97 and PARST (Nardelli, 1995).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing the atom-numbering scheme and the hydrogen bonding. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Intramolecular hydrogen bonds are shown as dashed lines. Please check added text.
[Figure 2] Fig. 2. Part of the crystal structure of (I), showing the hydrogen bonding and molecular pairing [symmetry code: (i) −x, 2 − y, 1 − z].
6-(4-Methoxybenzylamino)purin-3-ium chloride top
Crystal data top
C13H14N5O+·ClF(000) = 608
Mr = 291.74Dx = 1.450 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 3161 reflections
a = 20.224 (5) Åθ = 2.7–29.0°
b = 4.991 (5) ŵ = 0.29 mm1
c = 13.365 (5) ÅT = 100 K
β = 97.727 (5)°Prism, colourless
V = 1336.8 (15) Å30.30 × 0.30 × 0.20 mm
Z = 4
Data collection top
Oxford Diffraction Xcalibur2, with Sapphire2 CCD area-detector
diffractometer
1858 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.030
Enhance (Oxford Diffraction) monochromatorθmax = 25.0°, θmin = 3.4°
Detector resolution: 16.3 pixels mm-1h = 2424
rotation method, ω scansk = 55
7109 measured reflectionsl = 1315
2327 independent reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.035Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.082H-atom parameters constrained
S = 1.02 w = 1/[σ2(Fo2) + (0.044P)2]
where P = (Fo2 + 2Fc2)/3
2327 reflections(Δ/σ)max = 0.001
181 parametersΔρmax = 0.20 e Å3
0 restraintsΔρmin = 0.16 e Å3
Crystal data top
C13H14N5O+·ClV = 1336.8 (15) Å3
Mr = 291.74Z = 4
Monoclinic, P21/cMo Kα radiation
a = 20.224 (5) ŵ = 0.29 mm1
b = 4.991 (5) ÅT = 100 K
c = 13.365 (5) Å0.30 × 0.30 × 0.20 mm
β = 97.727 (5)°
Data collection top
Oxford Diffraction Xcalibur2, with Sapphire2 CCD area-detector
diffractometer
1858 reflections with I > 2σ(I)
7109 measured reflectionsRint = 0.030
2327 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0350 restraints
wR(F2) = 0.082H-atom parameters constrained
S = 1.02Δρmax = 0.20 e Å3
2327 reflectionsΔρmin = 0.16 e Å3
181 parameters
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
xyzUiso*/Ueq
Cl10.15243 (2)0.03615 (9)0.24172 (3)0.02263 (15)
O10.43391 (7)0.4342 (3)0.10113 (9)0.0256 (3)
N10.20897 (8)0.7716 (3)0.52425 (11)0.0200 (4)
C20.16698 (10)0.9361 (4)0.55981 (14)0.0204 (4)
H20.18531.05970.61010.024*
N30.10076 (8)0.9459 (3)0.53172 (11)0.0193 (4)
H30.07551.06300.55810.023*
C40.07424 (9)0.7660 (4)0.46028 (13)0.0177 (4)
C50.11531 (9)0.5839 (4)0.42227 (13)0.0168 (4)
N60.22591 (8)0.4162 (3)0.41782 (12)0.0208 (4)
H60.20830.29720.37350.025*
C60.18474 (9)0.5866 (4)0.45388 (13)0.0178 (4)
N70.07388 (7)0.4363 (3)0.35346 (11)0.0191 (4)
H70.08550.30320.31630.023*
C80.01208 (9)0.5348 (4)0.35390 (13)0.0200 (4)
H80.02600.46600.31260.024*
N90.00938 (8)0.7380 (3)0.41775 (12)0.0210 (4)
C90.29810 (9)0.4105 (5)0.44587 (14)0.0259 (5)
H9A0.31070.24860.48680.031*
H9B0.31220.56940.48770.031*
C100.33380 (9)0.4089 (4)0.35378 (14)0.0195 (4)
C110.38376 (9)0.2250 (4)0.34437 (14)0.0227 (5)
H110.39450.09450.39570.027*
C120.41862 (9)0.2270 (4)0.26143 (14)0.0220 (5)
H120.45330.10110.25680.026*
C130.40229 (9)0.4137 (4)0.18584 (14)0.0202 (4)
C140.35157 (10)0.5958 (4)0.19325 (15)0.0252 (5)
H140.34000.72300.14100.030*
C150.31775 (10)0.5935 (4)0.27601 (15)0.0252 (5)
H150.28300.71940.28020.030*
C160.47948 (10)0.2236 (4)0.08540 (16)0.0292 (5)
H16A0.49910.25880.02350.044*
H16B0.45560.05230.07900.044*
H16C0.51500.21540.14300.044*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0210 (3)0.0241 (3)0.0231 (3)0.0028 (2)0.00371 (19)0.0031 (2)
O10.0273 (8)0.0308 (8)0.0200 (7)0.0029 (6)0.0079 (6)0.0024 (6)
N10.0217 (9)0.0214 (9)0.0177 (8)0.0003 (7)0.0056 (7)0.0013 (7)
C20.0259 (11)0.0200 (11)0.0161 (10)0.0008 (9)0.0055 (8)0.0007 (8)
N30.0210 (9)0.0174 (8)0.0206 (8)0.0049 (7)0.0073 (7)0.0010 (7)
C40.0200 (10)0.0165 (10)0.0177 (10)0.0007 (8)0.0064 (8)0.0042 (8)
C50.0189 (10)0.0166 (10)0.0156 (9)0.0008 (8)0.0045 (8)0.0017 (8)
N60.0175 (9)0.0256 (10)0.0193 (8)0.0047 (7)0.0028 (7)0.0047 (7)
C60.0205 (10)0.0195 (10)0.0143 (9)0.0009 (8)0.0051 (8)0.0037 (8)
N70.0192 (9)0.0186 (9)0.0200 (8)0.0018 (7)0.0046 (7)0.0022 (7)
C80.0165 (10)0.0232 (11)0.0205 (10)0.0019 (8)0.0032 (8)0.0015 (9)
N90.0194 (9)0.0219 (9)0.0224 (9)0.0039 (7)0.0054 (7)0.0021 (7)
C90.0174 (11)0.0398 (13)0.0201 (11)0.0063 (9)0.0013 (8)0.0034 (9)
C100.0157 (10)0.0233 (11)0.0186 (10)0.0004 (8)0.0009 (8)0.0049 (8)
C110.0236 (11)0.0249 (11)0.0197 (10)0.0048 (9)0.0031 (8)0.0038 (9)
C120.0183 (10)0.0250 (11)0.0232 (11)0.0063 (8)0.0048 (8)0.0007 (9)
C130.0191 (10)0.0246 (11)0.0168 (10)0.0045 (8)0.0019 (8)0.0037 (8)
C140.0249 (11)0.0268 (12)0.0234 (11)0.0033 (9)0.0009 (9)0.0064 (9)
C150.0193 (10)0.0267 (12)0.0289 (12)0.0073 (9)0.0015 (9)0.0015 (9)
C160.0339 (13)0.0291 (13)0.0274 (12)0.0007 (10)0.0147 (10)0.0049 (9)
Geometric parameters (Å, º) top
O1—C131.377 (2)C8—H80.9500
O1—C161.432 (2)C9—C101.508 (3)
N1—C21.315 (2)C9—H9A0.9900
N1—C61.361 (2)C9—H9B0.9900
C2—N31.342 (2)C10—C111.383 (3)
C2—H20.9500C10—C151.394 (3)
N3—C41.367 (2)C11—C121.391 (3)
N3—H30.8800C11—H110.9500
C4—N91.365 (2)C12—C131.382 (3)
C4—C51.374 (3)C12—H120.9500
C5—N71.372 (2)C13—C141.384 (3)
C5—C61.411 (3)C14—C151.376 (3)
N6—C61.325 (2)C14—H140.9500
N6—C91.458 (2)C15—H150.9500
N6—H60.8800C16—H16A0.9800
N7—C81.344 (2)C16—H16B0.9800
N7—H70.8800C16—H16C0.9800
C8—N91.331 (2)
C13—O1—C16116.45 (15)C10—C9—H9A109.4
C2—N1—C6118.89 (17)N6—C9—H9B109.4
N1—C2—N3126.17 (18)C10—C9—H9B109.4
N1—C2—H2116.9H9B—C9—H9B108.0
N3—C2—H2116.9C11—C10—C15118.04 (18)
C2—N3—C4117.02 (16)C11—C10—C9120.90 (17)
C2—N3—H3121.5C15—C10—C9121.05 (17)
C4—N3—H3121.5C10—C11—C12121.50 (18)
N9—C4—N3128.55 (17)C10—C11—H11119.2
N9—C4—C5111.90 (17)C12—C11—H11119.2
N3—C4—C5119.55 (17)C13—C12—C11119.36 (18)
N7—C5—C4104.94 (16)C13—C12—H12120.3
N7—C5—C6134.38 (17)C11—C12—H12120.3
C4—C5—C6120.63 (17)O1—C13—C12124.03 (17)
C6—N6—C9125.13 (17)O1—C13—C14116.15 (17)
C6—N6—H6117.4C12—C13—C14119.82 (18)
C9—N6—H6117.4C15—C14—C13120.34 (18)
N6—C6—N1120.07 (17)C15—C14—H14119.8
N6—C6—C5122.24 (17)C13—C14—H14119.8
N1—C6—C5117.70 (16)C14—C15—C10120.91 (18)
C8—N7—C5106.58 (16)C14—C15—H15119.5
C8—N7—H7126.7C10—C15—H15119.5
C5—N7—H7126.7O1—C16—H16A109.5
N9—C8—N7113.56 (17)O1—C16—H16B109.5
N9—C8—H8123.2H16A—C16—H16B109.5
N7—C8—H8123.2O1—C16—H16C109.5
C8—N9—C4103.01 (15)H16A—C16—H16C109.5
N6—C9—C10111.28 (15)H16B—C16—H16C109.5
N6—C9—H9A109.4
C6—N1—C2—N31.7 (3)N7—C8—N9—C40.3 (2)
N1—C2—N3—C40.8 (3)N3—C4—N9—C8179.99 (18)
C2—N3—C4—N9178.57 (18)C5—C4—N9—C80.3 (2)
C2—N3—C4—C51.1 (2)C6—N6—C9—C10129.5 (2)
N9—C4—C5—N70.2 (2)N6—C9—C10—C11130.7 (2)
N3—C4—C5—N7179.89 (15)N6—C9—C10—C1549.7 (3)
N9—C4—C5—C6177.63 (16)C15—C10—C11—C121.8 (3)
N3—C4—C5—C62.1 (3)C9—C10—C11—C12177.82 (18)
C9—N6—C6—N11.3 (3)C10—C11—C12—C131.1 (3)
C9—N6—C6—C5178.99 (17)C16—O1—C13—C129.2 (3)
C2—N1—C6—N6179.12 (17)C16—O1—C13—C14171.13 (17)
C2—N1—C6—C50.6 (3)C11—C12—C13—O1179.50 (18)
N7—C5—C6—N62.0 (3)C11—C12—C13—C140.1 (3)
C4—C5—C6—N6179.09 (17)O1—C13—C14—C15179.02 (17)
N7—C5—C6—N1178.30 (18)C12—C13—C14—C150.6 (3)
C4—C5—C6—N11.2 (3)C13—C14—C15—C100.1 (3)
C4—C5—N7—C80.02 (19)C11—C10—C15—C141.2 (3)
C6—C5—N7—C8177.4 (2)C9—C10—C15—C14178.35 (19)
C5—N7—C8—N90.2 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3···N9i0.882.052.883 (2)158
N6—H6···Cl10.882.353.226 (2)171
N7—H7···Cl10.882.233.063 (2)158
Symmetry code: (i) x, y+2, z+1.

Experimental details

Crystal data
Chemical formulaC13H14N5O+·Cl
Mr291.74
Crystal system, space groupMonoclinic, P21/c
Temperature (K)100
a, b, c (Å)20.224 (5), 4.991 (5), 13.365 (5)
β (°) 97.727 (5)
V3)1336.8 (15)
Z4
Radiation typeMo Kα
µ (mm1)0.29
Crystal size (mm)0.30 × 0.30 × 0.20
Data collection
DiffractometerOxford Diffraction Xcalibur2, with Sapphire2 CCD area-detector
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
7109, 2327, 1858
Rint0.030
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.082, 1.02
No. of reflections2327
No. of parameters181
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.20, 0.16

Computer programs: CrysAlis CCD (Oxford Diffraction, 2003), CrysAlis RED (Oxford Diffraction, 2003), CrysAlis RED, SIR97 (Altamore, 1999), SHELXL97 (Sheldrick, 1997), ORTEPIII (Johnson & Burnett, 1996), SHELXL97 and PARST (Nardelli, 1995).

Selected geometric parameters (Å, º) top
N1—C21.315 (2)C5—N71.372 (2)
N1—C61.361 (2)C5—C61.411 (3)
C2—N31.342 (2)N6—C61.325 (2)
N3—C41.367 (2)N6—C91.458 (2)
C4—N91.365 (2)N7—C81.344 (2)
C4—C51.374 (3)C8—N91.331 (2)
C2—N1—C6118.89 (17)C4—C5—C6120.63 (17)
N1—C2—N3126.17 (18)C8—N7—C5106.58 (16)
C2—N3—C4117.02 (16)N9—C8—N7113.56 (17)
N9—C4—C5111.90 (17)C8—N9—C4103.01 (15)
N3—C4—C5119.55 (17)
C9—N6—C6—C5178.99 (17)N6—C9—C10—C1549.7 (3)
C6—N6—C9—C10129.5 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3···N9i0.882.052.883 (2)158
N6—H6···Cl10.882.353.226 (2)171
N7—H7···Cl10.882.233.063 (2)158
Symmetry code: (i) x, y+2, z+1.
Comparative geometrical parameters (°) for selected cytokinin derivatives containing the 6-benzylaminopurine moiety top
CompoundC2-N3-C4C8-N7-C5C8-N9-C4
4MeOBapHa117.02 (16)106.58 (16)103.01 (15)
BapHb118.2 (7)107.4 (6)103.5 (6)
3ClBapHc117.6 (2)106.8 (2)102.60 (18)
2ClBapd111.32 (14)103.68 (15)106.19 (14)
Bape110.70103.90106.41
Notes: (a) this work [4MeOBapH is the 6-(4-methoxybenzylamino)purinium cation]; (b) Umadevi et al. (2001) (BapH is the 6-benzylaminopurinium cation); (c) Maloň et al. (2001) [3ClBapH is the 6-(3-chlorobenzylamino)purinium cation]; (d) Maloň et al. (2001) [2ClBap is 6-(2-chlorobenzylamino)purine]; (e) Raghunathan et al. (1983) (Bap is 6-benzylaminopurine).
 

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