Click chelators - The behavior of platinum and palladium complexes in the presence of guanosine and DNA

Article abstract of DOI:10.1002/ejic.201000183

Triazole chelators, synthesized by click chemistry, are convenient ligands for palladium(II) and platinum(II). Conformational changes induced by the complexation of these PdII and Pt^II complexes with guanosine are similar to those of cisplatin.

Full text of DOI:10.1002/ejic.201000183

FULL PAPER
DOI: 10.1002/ejic.201000183
Click Chelators – The Behavior of Platinum and Palladium Complexes in the
Presence of Guanosine and DNA
Aurélien Chevry,[a] Marie-Laure Teyssot,[a] Aurélie Maisonial,[a] Pascale Lemoine,*[b]
Bernard Viossat,[b] Mounir Traïkia,[a] David J. Aitken,[a][‡] Georges Alves,[c]
Laurent Morel,[c] Lionel Nauton,[a] and Arnaud Gautier*[a]
Keywords: Platinum / Palladium / Click chemistry / Conformation analysis / DNA / Antitumor agents
Triazole chelators, synthesized by click chemistry, are conve-
nient ligands for palladium(II) and platinum(II). Conforma-
tional changes induced by the complexation of these PdII and
PtII complexes with guanosine are similar to those of cispla-
tin. In addition, these complexes behave like cisplatin with
regard to the relaxation of supercoiled plasmid DNA.
the well known platinum-based anticancer compounds
share the general formula cis-[PtX2(NH2R)2] in which R is
an organic subunit, and X is a leaving group, usually a chlo-
ride. We have reported the chelation properties of the in-
verse and regular bidentate chelators such as (1,2,3-triaz-
olyl)methylamine 1 for platinum(II) (Figure 1).[5] Our find-
ings are in agreement with previous literature results, and
show, in our hands, that complexes form easily from regular
free aliphatic amine ligands; conversely, complexations from
the corresponding inverse ligands are scarce, probably due
to the lower electronic density at the C3 atom of the 1,2,3-
triazole moiety.[4,5] The N,N regular complexes of PtII exhi-
bit an IC50 that is greater than that of the regular N,O com-
plexes according to well known structure activity relation-
ships of platinum complexes.[7] Our main concern now fo-
cuses on the propensity of 1 to form palladium chelates
and to evaluate the behavior of the palladium and platinum
chelates 2 and 3 in the presence of nucleotides and DNA.
Introduction
The emergence of “click chemistry” as a new paradigm
for organic synthesis, invoking only simple, high-yielding
and easily workable transformations, has facilitated an ex-
traordinary expansion of the number of molecules available
for medicinal chemistry.[1] Among these click reactions is
the copper-catalyzed Huisgen [2+3] cycloaddition, also de-
noted as copper(I)-catalyzed azide–alkyne cycloaddition
(CuAAC), which has received unrivalled attention, and has
furnished an impressive array of new biologically relevant
compounds.[2] In general, 1,2,3-triazole has proven itself
useful for metal binding, and it is not surprising that such
ligands find use in bioinorganic chemistry.[3] Schibli and co-
workers take advantage of the binding properties of 1,2,3-
triazole in a “click to chelate” approach to synthesize stable
complexes of radionuclides that target tumors.[4] We also
used the 1,2,3-triazole subunit to chelate platinum(II), and
reported the cytotoxicity of this cisplatin analogue on can-
cerous cell lines.[5]
Anticancer platinum drugs have enjoyed a long history
since the discovery of cisplatin {cis-diaminedichloro-
platinum(II)} by Rosenberg et al. in the 1960s.[6] Most of
[a] Clermont-Université, SEESIB, UMR CNRS 6504, Université
Blaise Pascal,
24 avenue des Landais, 63177 Aubière Cedex, France
E-mail: Arnaud.Gautier@univ-bpclermont.fr
[b] Université Paris 5, Faculté de Pharmacie, Laboratoire de
cristallographie et RMN biologiques CNRS UMR-8015
4, avenue de l’observatoire, 75270 Paris Cedex 06, France
E-mail: pascale.lemoine@univ-paris5.fr
[c] Clermont-Université, Université Blaise Pascal, GReD UMR
6247 CNRS, INSERM U931,
Figure 1. Schematic representation of regular and inverse click li-
gands and targeted complexes (C represents the chelating atom).
24 avenue des Landais, 63177 Aubière Cedex, France
[‡] Present address: Université Paris-Sud XI, Laboratoire de
Synthèse Organique et Méthodologie, UMR8182 CNRS
15, rue Georges Clemenceau, 91405 Orsay Cedex, France
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000183.
Indeed, even if palladium complexes have received less
attention than their platinum analogs, recent studies have
proved that this metal still retains some interest as depicted
in Figure 2.[8]
Eur. J. Inorg. Chem. 2010, 3513–3519
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3513

P. Lemoine, A. Gautier et al.
FULL PAPER
We succeeded in growing a single crystal of 2 by slow
diffusion of ethanol into a saturated DMF solution of the
complex, which was analyzed by X-ray diffraction. The
ORTEP view presented in Figure 5 unambiguously proves
the formation of a five-membered palladium chelate ring.
Selected bond lengths and angles are summarized in
Table 1. Similar to the platinum analog, the PdII centre
presents a distorted square-planar geometry, with an angle
of 2° between the planes defined by N1–Pd–N4 and Cl1–
Pd–Cl2. The metal center bond lengths and angles fall into
the usual ranges, although nonequivalence of the N–Pd
bonds [N1–Pd: 2.000(2) Å; N4–Pd: 2.038(2) Å] and Pd–Cl
bonds [Cl2–Pd: 2.270(1) Å; Cl1–Pd: 2.302(1) Å] is observed.
The plane formed by the triazole ring atoms forms an angle
of 7° with the plane defined by N1–Pd–N8.
Figure 2. Some anticancer palladium(II) complexes.
Herein, we report the synthesis of the palladium complex
2 and its structural characteristics. We then determine if the
candidates 2 and 3 behave like cisplatin in the presence of
guanosine in terms of complexation, conformational behav-
ior, and DNA affinity.
Results and Discussion
Ligand Synthesis
The synthesis of 1 has been described previously, and
uses tris(3-hydroxypropyltriazolylmethyl)amine (THPTA)/
CuSO4/ascorbic acid] or [CuCl(SIMes)] – SIMes: 1,3-
Figure 5. ORTEP plot (50% thermal probability ellipsoids) of 2.
bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene
–
as catalysts.[5] Alternatively, 1 can be easily synthesized from
[CuCl(Phen)(SIMes)] – Phen: 1,10-phenanthroline – in
good yields (Figure 3).[9]
Table 1. Selected bond lengths and angles of complex 2.
Distances [Å]
N1–Pd
N4–Pd
Cl1–Pd
2.000(2)
2.038(2)
2.302(1)
Cl2–Pd
2.270(1)
3.07(8)
3.30(3)
H8–H10a
H8–H10b
Angles [°]
N4–Pd–Cl2
N4–Pd–Cl1
N4–Pd–N1
90.35(5)
176.90(5)
81.69(7)
N1–Pd–Cl1
N1–Pd–Cl2
Cl1–Pd–Cl2
95.96(5)
171.94(5)
92.06(2)
Figure 3. Synthesis of ligand 1.
Complexation
We were satisfied to observe that exposure of K2PdCl4
to an aqueous solution of 1·HCl resulted in the rapid for-
mation of the expected neutral N2Cl2 palladium complex 2,
which precipitated spontaneously from the reaction mixture
(Figure 4). The reaction does not require the presence of
the free amine 1 as was the case for the platinum complex
3.[5]
Guanosine Adducts of 2 and 3
The reaction of the activated aqua form of the complexes
2 and 3 with guanosine was investigated. A suspension of
each complex in water was reacted for two days in the pres-
ence of 2 equiv. of AgNO3, then filtered, and the resulting
pale yellow solution was added to a suspension of 2.5 equiv.
of guanosine in water (Figure 6). The solution was stirred
overnight and filtered. For the palladium complex 4, the
product was used without further purification. In the case
of the platinum complex 5, the mixture was separated by
preparative HLPC [MeOH/AcONH4 (0.1 ), pH = 5.5; iso-
cratic conditions], and the resulting platinum adduct was
desalted with a dialysis membrane (cut-off 500).
Figure 4. Formation of complex 2.
3514
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 3513–3519

Pt and Pd Complexes in the Presence of Guanosine and DNA
describe the system unambiguously: the coordinates are
[PN, ΦN, (1 – X)] and (PS, ΦS, X), where X is the molar
fraction of the south component. The coordinates are cal-
culated by a nonlinear regression calculation method based
on NMR measurements of the time-averaged vicinal cou-
pling constants (Pseurot program).[12]
Figure 6. Formation of complexes 4 and 5.
1
The structures of complexes 4 and 5 were proved by H
NMR spectroscopy (vide infra) and mass spectrometry.
Peaks at m/z (z = +2) 430 and 474 for compounds 4 (M =
860.19) and 5 (M = 949.25) respectively, were found in the
mass spectra, accompanied by their isotopic signatures.
Conformational Analysis
The pseudorotation model describes the conformational
behavior of a nucleotide in solution by a fast equilibrium
between two discrete conformers. T represents a twisted
form, E an envelope form, and the superscript and sub-
script numbers refer to the atom in endo or exo configura-
tion relative to C5 of the sugar, respectively, Figure 7.[10] In
practice, a substituted five-membered ring rarely adopts a
pure T or E form because of the asymmetric surroundings
induced by the substituents. Each of the two conformers is
mathematically characterized by two pseudorotation pa-
rameters, one phase coordinate (P) and one puckering coor-
Figure 7. Discrete model and pseudorotational wheel of nucleos-
dinate (Φmax).[11] Several vectors in three-dimensional space ides.
1
Figure 8. H NMR of complex 5 in D2O (300 K).
Eur. J. Inorg. Chem. 2010, 3513–3519
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3515

P. Lemoine, A. Gautier et al.
(1)
FULL PAPER
-H2Ј
-H2Ј
-H4Ј
)
Ps = JH1Ј /(JH1Ј
+ JH3Ј
Plavec and Chattopadhyaya have reported a quantitative
conformational study of the cisplatin–guanosine adduct.[13]
They have demonstrated that, upon platination, the change
of electronic character of the nucleobase is transmitted ac-
ross the sugar ring and results in a shift of the north↔south
(C3Јendo↔C2Јendo) equilibrium as well as a reorientation
of the nucleobase.
where Ps represents the population of the south conformer.
This calculation affords a south population of 49% (see
data in Table 3), yielding close to a 1:1 ratio between the
north and south conformers, a situation relatively close to
that found for the cisplatin adduct.
With regard to the nucleobases orientations, the ROESY
experiment reveals a strong correlation between the two
guanosine H8 signals and the two overlapping signals of the
anomeric H1Ј.[14] Based on the average distance for CH2–N
and Htriazole (3.19 Å) as a standard extracted from the X-
ray data of 2, the values of the two H8–H2Ј distances were
found to be close to 2.6–2.7 Å, implying that each nucleo-
base is largely oriented to an anti conformation (80–90%)
as found in the parent cisplatin adduct.
Overall, the parameters for the guanosine–cisplatin ad-
duct and free guanosine are depicted in Table 2.
Table 2. Pseudorotational parameters and conformational equilib-
rium of the guanosine–cisplatin adduct.
PN
Φmax S PS
Φmax S
%
%
sS
anti
Guanosine
Cisplatin adduct
15
16
32
32
157
161
32
32
80
55
29
92
With the NMR observation in hand, a geometry optimi-
zation (Gaussian 03) for 4 was performed by DFT calcula-
tions [B3LYP/ 6-311G (C, N, O, H)/SDD (Pd)] in the gas
phase to access its conformational parameters.[15] The
choice of the basis set was dictated by the necessity to in-
clude the anomeric effect, which is taken into account by
6-311G, and to include the palladium atom that is not
treated in this basis set, we used the Stuttgart/Dresden basis
set (SDD) to gain a correspondence between the two triple-
ζ basis.[16] For clarity purposes, each nucleoside was named
according to its geometrical position from the triazole sub-
unit in the square-planar complex. Thus, we named the nu-
cleotide trans T and the nucleotide cis C according to Fig-
ure 6. Each possible conformer (T north C north, T north
C south, T south C north, T south C south) was optimized,
starting from anti-anti conformation of the two guanosine
groups. The T north C north is presented in Figure 9 as a
typical example and all the data of interest are collected in
Tables 4 and 5.
A detailed conformational analysis was undertaken on
adducts 4 and 5 by NMR spectroscopy. The NMR spec-
trum of the platinum complex 5, which is similar to that of
complex 4, is presented in Figure 8. It can be seen that a
1:2 (metal/guanosine) adduct forms almost exclusively. The
spectrum displays two separate sets of signals for the nu-
cleotides due to the asymmetry of the palladium complex
(this nonequivalence is not observed in the case of the sym-
metrical cisplatin adduct).[13]
In terms of coupling constants, the two 1H NMR spectra
reveal identical behavior for both sugars. We then at-
tempted to assign each NMR peak for 4 and 5 using COSY,
COSY-DQF (double-quantum filtered) and ROESY NMR
experiments. Unfortunately, the lack of correlation between
the nucleosides and the triazole subunit did not allow us to
discriminate between the cis and trans sugar signals. How-
ever, each signal, regardless the nature of the sugar, was
successfully assigned.
Conformational Behavior of Complex 4
The coupling constants extracted from the NMR spec-
trum are collated in Table 3.
Table 3. Coupling constants of interest of complex 4.
Coupling constants [Hz]
Ј
Ј
1Ј-H2Ј
1Ј-H2Ј
2Ј-H3Ј
2Ј-H3Ј
3Ј-H4Ј
JH
JH
JH
JH
JH
JH3 -H4
4.8
4.8
4.8
4.8
4.9
4.9
Because of the presence of multiple overlapping signals
due to the asymmetry of the ligand, we were unable to cor-
rectly extract the 1H-1H coupling constants of the furanose
ring at different temperatures. This did not allow us to take
advantage of the PSEUROT program to exactly determine
the pseudorotational parameters and the equilibrium con-
stants of the north and south conformers.[12] In order to
Figure 9. Geometry optimization of the T north C north conformer
of 4.
The results of the calculations reveal that palladium(II)
gain a qualitative observation of the ribose conformational retains its square-planar geometry correlating to bond
behavior, we used the simplest Altona–Sundaralingam lengths and angles already found in the structure of 2. The
-H2Ј
-H4Ј
and JH3Ј
equation that correlates the observed JH1Ј
H1Ј–H8 distances calculated are in good agreement with the
coupling constants to the north↔south equilibrium, see values found by the ROESY experiment and fall in the
Equation (1).[11b] range typically found in the literature.[17]
3516
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 3513–3519

Pt and Pd Complexes in the Presence of Guanosine and DNA
Table 4. Calculated distances and angles of the palladium adduct
4.
With regard to the nucleobase orientations, results sim-
ilar to those for 4 were found for compound 5 using the
ROESY experiment. The distance of the two protons H8–
H1Ј is found to be close to 2.6–2.7 Å, implying again that
each nucleobase is largely oriented to an anti conformation
(80–90%).
Distances [Å]
N1–Pd
N4–Pd
H1Ј–H8 (T) H1Ј–H8 (C)
T north, C north 2.02
2.09
2.09
2.09
2.09
2.44
2.44
2.42
2.42
2.42
2.40
2.39
2.42
T north, C south 2.01
T south, C south 2.02
T south, C north 2.02
Action of Complexes 2 and 3 on Supercoiled DNA
Angles [°]
N1–Pd–N4 N7–Pd–N7Ј
To ensure that DNA is also a target for these chelates,
we examined the genotoxicity of 2 and 3 in vitro with the
aid of the supercoiled pcDNA4TO plasmid. It is well
known that upon platinum binding, a relaxation of the
structure – easily visualized on gel electrophoresis – takes
place. The behavior of our complexes was compared to that
of cisplatin by agarose gel electrophoresis. Figure 10 pres-
ents the electrophoresis gel with the supercoiled plasmid as
a blank in line 1. The endonuclease BamH1 was used to
linearize the plasmid in line 2. Line 3 shows the effect of
cisplatin, which is known to relax the supercoiled structure.
Lines 4 and 5 depict the action of complexes 2 and 3 on
the supercoiled plasmid respectively. From this experiment
it is seen that the two complexes are able to relax the su-
percoiled structure of the plasmid.
T north, C north 80.6
93.8
94.2
93.8
93.5
T north, C south 80.6
T south, C south 80.6
T south, C north 80.7
Table 5. Calculated pseudorotational parameters of complex 4.
Pseudorotational parameters [°]
P(trans)
Φmax (trans) P(cis)
Φmax (cis)
T north, C north
T north, C south
T south, C south
T south, C north
46
46
153
152
39
39
35
35
45
38
40
40
39
164
164
44
Although some deviations from the cisplatin analogue
are found, the computed pseudorotational parameters are
in reasonable agreement with those found in literature.[13]
Conformational Behavior of Complex 5
The data extracted from the NMR spectra are collected
in Table 6. There is no overlap of signals over a range of
20 °C, allowing us to extract nine coupling constants at
three different temperatures.
Table 6. Coupling constants of interest in complex 5.
1Ј-H2Ј
2Ј-H3Ј
3Ј-H4Ј
[Hz]
JH
[Hz]
JH
[Hz]
JH
293 K
303 K
313 K
4.85
4.66
4.59
5.01
4.92
4.88
5.01
4.92
4.88
Figure 10. Action of 2 and 3 on plasmid DNA (1% agarose gel).
Line 1: supercoiled plasmid blank, line 2: linearized plasmid by
endonuclease BamH1, line 3: effect of cisplatin, line 4: effect of 2,
line 5: effect of 3. (The blanks corresponding to water/NaClO4 and
water/DMF/NaClO4 used for solubilising cisplatin and complexes
2 and 3 are similar to line 1).
We then have nine physical data; a number superior to
the seven parameters to be determined (PN, ΦN, PS, ΦS and
the three percentages). This gives an over-determined sys-
tem and application of PSEUROT 6.3 furnishes the follow-
ing pseudorotational and equilibrium parameters (Table 7).
Conclusions
Table 7. Pseudorotational and equilibrium parameters for complex
In conclusion, we have found that regular click chelators
containing palladium or platinum can behave similar to cis-
platin. Thus, guanosine adducts form easily and the confor-
mational change produced by such complexation resembles
that of cisplatin. Relaxation of DNA also takes place like
the action of cisplatin.
5.
Pseurorotational parameters
PN
ΦN
PS
ΦS
5.9
35
150
35.8
Equilibrium parameters
T [K]
293
49
0.09
303
48
0.02
313
48
0.07
% south
RMS [Hz][a]
Experimental Section
[a] RMS: root mean square.
General: The following procedures were used in all reactions unless
otherwise noted. Reactions were stirred with a Teflon®-coated mag-
netic stirring bar. Removal of solvents was accomplished by evapo-
ration on a Buchi rotary evaporator (water bath at 40 °C). All com-
The results are similar to those found for the preceding
palladium complex 4 and for the cisplatin adduct with a
good overall root mean square (0.06 Hz).
Eur. J. Inorg. Chem. 2010, 3513–3519
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3517

P. Lemoine, A. Gautier et al.
FULL PAPER
mercially available reagents were used as received. NMR spectra
were recorded in Fourier Transform mode with Bruker AVANCE
400 and 500 spectrometers at 25 °C. Chemical shifts are reported
in ppm. Spin multiplicity is described by means of the following
abbreviations: s = singlet, d = doublet, m = multiplet, and br. =
broad. Coupling constants (J) are reported in Hertz (Hz). Diffrac-
tion data were collected with an Enraf–Nonius CAD4 dif-
fractometer at 293 K. The data collection and reduction were car-
ried out with the CAD4 Express Enraf–Nonius CAD4 program
package. All data were corrected for Lorentz-polarization effects
and absorption corrections were made with Multi-Scan. The struc-
tures were solved through direct and Fourier methods and refined
by full-matrix least-square methods based on F2 with the SIR92
and SHELXL-97 programs. Hydrogen atoms were located from a
difference Fourier map and the same isotropic thermal parameters
were then refined. The final least-square refinements (R1) based on
IϾ2σ(I) converged to 0.0226. All calculations were conducted
using DFT as implemented in the Gaussian 03 program. Geometry
optimizations were performed using the restricted B3LYP exchange
and correlation function and the triple-ζ 6-311G(d,p) basis set for
all atoms except for Pd (SDD basis set) [B3LYP/ 6-311G (C, N, O,
H)/SDD (Pd)]. Harmonic frequency analysis based on analytical
second derivatives was used to characterize the optimized geome-
tries as local minima. Diffraction intensity data were collected at
T = 293 K with an Oxford-Diffraction XCALIBUR diffractometer
[Mo-Kα radiation (λ = 0.7107 Å)] with data collection and re-
duction by using the CrysAlis program package.[18] Data were cor-
rected for Lorentz-polarization effects and empirical absorption
corrections by using SCALE3 ABSPACK.[19] The structure was
solved by direct methods with SIR-92[20] and refined by least-
squares methods on F2 with SHELXL-97[21] incorporated in the
WinGX package.[22] Hydrogen atoms were inserted at calculated
positions with isotropic thermal parameters constrained to be 1.2
times the Ueq of the carrier atoms. The molecule was drawn by
using CAMERON.[23]
0.31 mmol, 2.4 equiv.) in the absence of light for 2 d. The reaction
mixture was passed through a Millipore filter to yield a pale yellow
solution that was added to guanosine (89.9 mg, 0.31 mmol,
2.5 equiv.). The suspension was stirred for 24 h, and passed through
1
a Millipore filter before being analyzed by H NMR spectroscopy.
1H NMR (D2O): δ = 8.60 (s, 1 H, H8); 8.45 (s, 1 H, H8) 8.35 (s, 1
H, triazole), 7.60–7.48 (m, 3 H, Ar), 7.35 (m, 2 H, Ar), 6.05 (d, J
= 4.5 Hz, 1 H, H1Ј), 6.01 (d, J = 4.5 Hz, 2 H, H1Ј), 5.62 (s, 2 H,
CH2), 4.75 (t, J = 4.5 Hz, 1 H, H2Ј), 4.72 (t, J = 4.5 Hz, 1 H, H2Ј),
4.47 (t, J = 4.5 Hz, 1 H, H3Ј), 4.40 (t, J = 4.5 Hz, 1 H, H3Ј),4.36
(m, 2 H, CH2), 4.33 (m, 2 H, CH2), 4.10–3.80 (m, 6 H, H4Ј, H5Ј,
H5Ј of the two riboses) ppm.
Platinum Complex 5: Compound 3 (50.0 mg, 0.11 mmol, 1.0 equiv.)
was stirred in H2O (2.0 mL) in the presence of AgNO3 (47.0 mg,
0.28 mmol, 2.5 equiv.) in the absence of light for 3 d. The reaction
mixture was passed through a Millipore filter to yield a pale yellow
solution that was added to guanosine (77.9 mg, 0.28 mmol,
2.5 equiv.). The suspension was stirred 24 h and passed through a
Millipore filter. The solution was then lyophilized, the mixture
purified by C-18 preparative HPLC [MeOH/AcONH4 (0.1 ):
75:25, pH = 5.5; isocratic conditions], and the fractions containing
the adduct 5 were lyophilized. The resulting solid was dissolved in
water (20 mL) and desalted using a dialysis membrane (cut-off:
1
500) to yield pure adduct 5 (30 mg). H NMR (D2O): δ = 8.55 (s,
1 H, H8); 8.25 (s, 1 H, H8) 8.05 (s, 1 H, triazole), 7.30–7.25 (m, 3
H, Ar), 7.10 (m, 2 H, Ar), 5.80 (d, J = 4.5 Hz, 1 H, H1Ј), 5.75 (d,
J = 4.5 Hz, 2 H, H1Ј), 5.35 (s, 2 H, CH2), 4.45 (t, J = 4.5 Hz, 1 H,
H2Ј), 4.42 (t, J = 4.5 Hz, 1 H, H2Ј), 4.25 (t, J = 4.5 Hz, 1 H, H3Ј),
4.20 (t, J = 4.5 Hz, 1 H, H3Ј),3.90 (m, 2 H, CH2), 3.85 (m, 2 H,
CH2), 3.75–3.70 (m, 6 H, H4Ј, H5Ј, H5Ј of the two riboses) ppm.
DNA Gel Electrophoresis: Three solutions (3ϫ10–4 ) of 2, 3 and
cisplatin were prepared in DMF and water. 1 µL of each solution
was added to 1.4 µg of plasmid pcDNA 4T0 in the presence of
30 µL NaClO4 (10–2 ) and incubated for 24 h at 37 °C. Samples
were then analyzed by agarose (1%) electrophoresis and DNA was
revealed with BET under UV light.
Procedures and Compounds
1·HCl:[5] Benzyl azide (266 mg, 2 mmol, 1.0 equiv.) and propar-
gylamine hydrochloride (218 mg, 2.4 mmol, 1.2 equiv.) were mixed
Supporting Information (see also the footnote on the first page of
1
1
this article): H, 13C, and mass spectra of complexes 2 and 4, H,
in
a mixture of tert-butyl alcohol/H2O (2:1, 4 mL). 16 mg
HPLC profile, and mass spectra of adduct 5.
(0.04 mmol, 2 mol-%) of [CuCl(SIMes)] and 7.2 mg (0.04 mmol,
2 mol-%) of 1,10-phenanthroline were added sequentially. A color
change to orange was observed, and the reaction was stirred for
12 h. The solvent was removed, and the resulting solid was taken
up in ethanol. The resulting white solid was collected by filtration,
and washed with diethyl ether to yield the desired pure triazole
hydrochloride (358 mg, 80%).
CCDC-647394 contains the supplementary crystallographic data.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
Acknowledgments
Palladium Complex 2: 1·HCl (74.2 mg, 0.32 mmol, 1.0 equiv.) was
dissolved in water (3 mL), and added to K2PdCl4 (108 mg,
0.32 mmol, 1.0 equiv.) dissolved in water (2 mL). After a few min-
utes, a red brownish precipitate formed and the reaction was stirred
24 h. The precipitate was collected by filtration, washed with water
(3ϫ5 mL), MeOH (2ϫ5 mL), ether (5 mL), and the resulting solid
was dried in air to yield pure complex 2 (104 mg, 86%). Crystals
were obtained by dissolving 2 in a minimum amount of DMF.
Crystals were grown by slow diffusion of ethanol in a closed desic-
cator kept at 35 °C for two weeks. 1H NMR ([D6]DMSO): δ = 8.29
(s, 1 H, triazole), 7.40 (m, 5 H, Ar), 5.68 (s, 2 H, CH2), 5.58 (m, 2
H, CH2), 3.68 (m, 2 H, NH2) ppm. 13C NMR ([D6]DMSO): δ =
152.0, 134.6, 128.8, 128.6, 128.2, 122.3, 54.6, 40.4 ppm.
C10H12Cl2N4Pd (365.6): calcd. C 32.86, H 3.31, N 15.33; found C
33.44, H 3.49, N 15.56.
We thank Aurélie Job for the purification of compound 5 and Ber-
trand Legeret for mass analysis.
[1] H. C. Kolb, M. G. Finn, K. B. Sharpless, Angew. Chem. Int.
Ed. 2001, 40, 2004–2021.
[2] a) C. W Tornøe, M. Meldal, Peptides: The wave of the future
(Eds.: M. Lebl, R. A. Houghten); Kluwer Academic Publish-
ers, Dordrecht, 2001, pp. 263–264; b) . C. W. Tornøe, C. Chris-
tensen, M. Meldal, J. Org. Chem. 2002, 67, 3057–3064; c) M.
Meldal, C. W. Tornøe, Chem. Rev. 2008, 108, 2952–3015; d)
V. D. Bock, H. Hiemstra, J. H. van Maarseveen, Eur. J. Org.
Chem. 2006, 51–68; e) H. C. Kolb, K. B. Sharpless, Drug Des.
Today 2003, 8, 1128–1137.
[3] For an excellent review, see: H. Struthers, T. L. Mindt, R. Schi-
bli, Dalton Trans. 2010, 39, 675–696.
[4] a) T. L. Mindt, H. Struthers, L. Brans, T. Anguelov, C.
Schweinsberg, V. Maes, D. Tourwé, R. Schibli, J. Am. Chem.
Palladium Complex 4: Compound 2 (46 mg, 0.13 mmol, 1.0 equiv.)
was stirred in D2O (2.5 mL) in the presence of AgNO3 (53.9 mg,
3518
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 3513–3519

Pt and Pd Complexes in the Presence of Guanosine and DNA
Soc. 2006, 128, 15096–15097; b) T. L. Mindt, C. Müller, M.
Melis, M. de Jong, M. R. Schibli, Bioconjugate Chem. 2008, 19,
1689–1695; c) H. Struthers, B. Spingler, T. L. Mindt, R. Schibli,
Chem. Eur. J. 2008, 14, 6173–6183. Other examples: d) A.
Nadler, C. Hain, U. Diederichsen, Eur. J. Org. Chem. 2009, 27,
4593–4599; e) M. L. Bowen, C. Orvig, Chem. Commun. 2008,
41, 5077–5091; f) R. M. Meudtner, M. Ostermeier, R. God-
dard, C. Limberg, S. Hecht, Chem. Eur. J. 2007, 13, 9834–9840;
g) Interestingly, a collection of inverse click ligands has been
amassed, but to date no studies of transition metals complex-
ation were reported; for example see: D. Urankar, J. Kosmrlj,
J. Comb. Chem. 2008, 10, 981–985.
For part I, see: A. Maisonial, P. Serafin, M. Traïkia, E. Deb-
iton, V. Théry, D. J. Aitken, P. Lemoine, B. Viossat, A. Gautier,
Eur. J. Inorg. Chem. 2008, 298–305.
B. Rosenberg, L. van Camp, T. Krigas, Nature 1965, 205, 698–
699.
R. W. Jeanloz, J. Am. Chem. Soc. 1984, 106, 811–813; b) A.
Bax, D. G. Davis, J. Magn. Reson. 1985, 63, 207–213; c) T. L.
Wang, A. J. Shaka, J. Magn. Res. A 1992, 114, 3157–3159. For
the determination of the distances, see: d) E. Ammalahti, M.
Bardet, D. Dalko, J. Cadet, J. Magn. Res. A 1996, 122, 230–
232.
[15] a) M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R.
Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morok-
uma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzew-
ski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K.
Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V.
Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B.
Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A.
Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Re-
vision D.01, Gaussian, Inc., Wallingford, CT, 2004; b) for
B3LYP method: A. J. Cohen, N. C. Handy, Mol. Phys. 2001,
99, 607.
[5]
[6]
[7]
[8]
a) M. J. Cleare, J. D. Hoeschele, Bioinorg. Chem. 1973, 2, 187–
210; b) J. Reedijk, Inorg. Chim. Acta 1992, 873, 198–200.
a) E. J. Gao, Q. T. Liu, L. Y. Duan, Russ. J. Coord. Chem. 2007,
33, 120–123; b) A. Jackson, J. Davis, R. J. Pither, A. Rodger,
M. J. Hannon, Inorg. Chem. 2001, 40, 3964–3973; c) S. Ray,
R. Mohan, J. K. Singh, M. K. Samantaray, M. M. Shaikh, D.
Panda, P. Ghosh, J. Am. Chem. Soc. 2007, 129, 15042–15053;
d) S. Fakih, W. C. Tung, D. Eierhoff, C. Mock, B. Krebs, Z.
Anorg. Allg. Chem. 2005, 631, 1397–1402; e) G. Zhao, H. Lin,
S. Zhu, H. Sun, Y. Chen, J. Inorg. Biochem. 1998, 70, 219–226;
f) E. Amtmann, W. Friebolin, G. Schilling, A pharmaceutical
preparation containing palladium complex compounds and the
uses thereof for treating cancer and autoimmune disease, WO
Patent 018043, 2004.
[16] For calculation of the anomeric effect using the Gaussian pro-
gram, see: C. Thibaudeau, P. Acharya, J. Chattopadhyaya,
Stereoelectronic Effects in Nucleotides and Nucleosides and
Their Structural Implications; Uppsala University Press,
Uppsala, 2002.
[9]
M.-L. Teyssot, A. Chevry, M. Traïkia, M. El-Ghozzi, D.
Avignant, A. Gautier, Chem. Eur. J. 2009, 15, 6322–6326.
[17] H. Rosemeyer, G. Toth, B. Golankiewicz, Z. Kazimierczuk, W.
Bourgeois, U. Kretschmer, H. P. Muth, F. Seela, J. Org. Chem.
1990, 55, 5784–5790.
[10] a) C. A. G. Haasnoot, F. A. A. M. de Leeuw, C. Altona, Tetra-
hedron 1980, 36, 2783–2792; b) C. Altona, Recl. Trav. Chim. [18] CrysAlis RED, Oxford Diffraction Ltd., version 1.171.31.5 (rel.
Pays-Bas 1982, 101, 413–433.
28-08-2006, CrysAlis171.NET) (compiled August 28, 2006,
13:05:05).
[11] a) C. Altona, M. Sundaralingam, J. Am. Chem. Soc. 1972, 94,
8205–8212; b) C. Altona, M. Sundaralingam, J. Am. Chem.
Soc. 1973, 95, 2333–2344.
[19] N. Walker, D. Stuart, Acta Crystallogr., Sect. A 1983, 39, 158–
166.
[12] J. van Wijk, C. A. G. Haasnoot, F. A. A. M. de Leeuw, B. D. [20] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi,
Huckriede, A. W. Hoekzema, C Altona, PSEUROT 6.3, Le-
iden Institute of Chemistry, Leiden University, Leiden, The
Netherlands, 1999.
M. C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr.
1994, 27, 435–436.
[21] G. M. Sheldrick, SHELXL-97: Program for Crystal Structure
Refinement, University of Göttingen, Germany, 1997.
[22] WinGX-version1.63.02: L. J. Farrugia, J. Appl. Crystallogr.
1999, 32, 837–838.
[23] D. J. Watkin, C. K. Prout, L. J. Pearce, CAMERON, Chemical
Crystallography Laboratory, Oxford, UK, 1996.
Received: February 15, 2010
[13] M. Polak, J. Plavec, A. Trifonova, A. Földesi, J. Chatto-
padhyaya, J. Chem. Soc. Perkin Trans. 1 1999, 2835–2843.
[14] The classical NOESY experiments were not adapted due to the
molecular weight of 5 (M = 891 g/mol). Indeed, on routine
spectrometers, the NOE experiment in not effective for com-
pounds of M = 500–1000 g/mol, and ROESY should be used.
See: a) A. A. Bothner-By, R. L. Stephens, J. Lee, C. D. Warren,
Published Online: June 21, 2010
Eur. J. Inorg. Chem. 2010, 3513–3519
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3519