Novel melphalan and chlorambucil derivatives of 2,2,6,6-tetramethyl-1- piperidinyloxy radicals: Synthesis, characterization, and biological evaluation in vitro

Article abstract of DOI:10.1248/cpb.58.332

A series of spin-labeled melphalan and chlorambucil derivatives, coupling the alkylating agents with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radicals, were synthesized, characterized, and their biological properties in vitro were evaluated. These com

Full text of DOI:10.1248/cpb.58.332

332
Chem. Pharm. Bull. 58(3) 332—335 (2010)
Vol. 58, No. 3
Novel Melphalan and Chlorambucil Derivatives of 2,2,6,6-Tetramethyl-1-
piperidinyloxy Radicals: Synthesis, Characterization, and Biological
Evaluation in Vitro
Hongli ZHAO,a,b Xianjiang MENG,a Huihui YUAN,a,b and Minbo LAN*,a,c
a Key Laboratory for Advanced Materials, and Research Center of Analysis and Test, East China University of Science and
Technology; b The Institute of Applied Chemistry, East China University of Science and Technology; and c Key Laboratory
for Ultrafine Materials of Ministry of Education, East China University of Science and Technology; Shanghai 200237, P. R.
China. Received September 14, 2009; accepted October 21, 2009; published online December 11, 2009
A series of spin-labeled melphalan and chlorambucil derivatives, coupling the alkylating agents with 2,2,6,6-
tetramethyl-1-piperidinyloxy (TEMPO) radicals, were synthesized, characterized, and their biological properties
in vitro were evaluated. These compounds showed much higher cytotoxic activity against human leukemia cell
line K562 in vitro than their parent compounds.
Key words melphalan; chlorambucil; 2,2,6,6-tetramethyl-1-piperidinyloxy radical; cytotoxic activity
In recent years nitroxide free radicals have attracted a bucil compounds were obtained through 1-ethyl-3-(3-
great deal of attention in many research fields because, com- dimethyllaminopropyl) carbodiimide hydrochloride (EDC·
pared to most other free radicals, they exhibit a chemical in- HCl) coupling reaction, in which the carboxylic group of
ertness and are wildly used in biological and pathological melphalan (1)/chlorambucil (2) was conjugated with the hy-
areas.1,2) At present, the stable nitroxide radicals such as droxyl or amino group of 4-hydroxyl-2,2,6,6-tetramethyl-1-
2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and its deriv- piperidinyloxy (4-OH-TEMPO)/4-amino-2,2,6,6-tetramethyl-
atives are intensively studied in such fields as spin label/trap- 1-piperidinyloxy (4-NH2-TEMPO). Before the coupling re-
ping in electron paramagnetic resonance (EPR) spectroscopy,2) action occurred, the amino group of the melphalan was pro-
ionizing radiation prevention,3,4) cancer prevention,5—7) hy- tected by 9-fluorenylmethyl chloroformate (Fmoc-Cl) and
pertension,8,9) and chemical synthetic studies.10,11)
then the N-(9-fluorenylmethoxycarbonyl) (N-Fmoc) deriva-
Alkylating agents are one of the oldest anticancer agents tives were formed, followed by the esterification or acylation
in clinical use. Melphalan and chlorambucil, two members of
this family, are employed in various cancer treatments.12)
However, these alkylating agents have numerous drawbacks
because of their high reactivity and the ability to kill cells at
whole using stage,13—15) both of which greatly hinder their
benefits. In an attempt to address their weaknesses, one of
the most effective methods is to design and synthesize novel
compounds by introducing functional groups into the molec-
ular structures of alkylating agents.16,17) TEMPO radical de-
rivatives have demonstrated anticancer activities and can
induce apoptosis of tumor cells in some ways.18) Also, based
on their chemical structures, the new nitroxide compounds
can be designed easily. Furthermore, TEMPO radicals, as
less toxic stable free radicals, can improve the properties of
new compounds, such as the toxicity, antioxidant capability
Reagents and conditions: a: Fmoc-Cl, dioxane, NaHCO3 solution, 0 °C, 8 h
(88.6%); b: (1) EDC·HCl, HOBT, 4-NH2-TEMPO, CH2Cl2, 8 h (85.0%), (2)
EDC·HCl, DMAP, 4-OH-TEMPO, CH2Cl2, 8 h (62.0%); c: piperidine, DMF,
room temperature, 1 h (6: 83.0%, 7: 86.0%).
and anticancer activities. In our lab, a series of novel melpha-
lan and chlorambucil derivatives conjugating TEMPO radi-
cals were designed in order to improve the properties of
Chart 1. Synthesis of Compounds 6 and 7
those anticancer drugs.
In this paper we wish to report our work on synthesis and
characterization, and in vitro cytotoxic activity of the TEMPO
conjugates of melphalan and chlorambucil. Although Prab-
hutendolkar et al.19) reported the synthesis of one chloram-
bucil-tempol (2,2,6,6-tetramethylpiperidin-N-oxyl-4-yl-{4-
[bis(2-chloroethyl)amino]phenyl}butanoate) adduct, its bio-
logical properties were not evaluated. In our investigation,
more novel melphalan/chlorambucil-TEMPO spin-labeled
compounds were synthesized and studied. Through the com-
bination of the two different anticancer mechanisms, we hope
to obtain novel drugs possessing more potency.
Reagents and conditions: a: (1) EDC·HCl, HOBT, 4-NH2-TEMPO, CH2Cl2, 8 h
(87.0%), (2) EDC·HCl, DMAP, 4-OH-TEMPO, CH2Cl2, 8 h (72.0%).
Chemistry Novel spin-labeled melphalan and chloram-
Chart 2. Synthesis of Compounds 8 and 9
© 2010 Pharmaceutical Society of Japan
∗ To whom correspondence should be addressed. e-mail: minbolan@ecust.edu.cn

March 2010
333
Table 1. Physicochemical Properties and Cytotoxic Activities of the Com-
pounds
reaction. In dichloromethane solution, the N-protected mel-
phalan and the chlorambucil reacted with 4-NH2-TEMPO in
the presence of EDC·HCl·1-hydroxybenzotriazole (HOBT)
and 4-OH-TEMPO in EDC·HCl·4-dimethylaminopyridine
(DMAP), respectively. Finally, the N-Fmoc derivatives of the
melphalan were deprotected in the piperidine/N,N-dimethyl-
formamide (DMF) with a very high yield. (Charts 1, 2).
Cytotoxic activities/
K562/IC50 (mM)
Compound
log P
KH/minꢁ1ꢂ103
1
2
6
7
8
9
ꢁ0.97
2.78
0.22
1.34
3.13
2.94
9.08
16.28
11.60
9.45
11.53
9.24
65.66
134.4
36.26
20.03
47.53
38.61
Results and Discussion
Partition Coefficient In our assays, the partition coeffi-
cient (log P) values of the studied compounds were obtained
from the n-octane/water system (Table 1).20) The log P values
of compounds 6 and 7 were much bigger than their parent
melphalan, and similarly, compounds 8 and 9 exhibited in-
creasing lipophilicity compared to chlorambucil. The results
indicated that the introduction of the TEMPO radical led to
an increase of the lipophilicity of the novel compounds. Be-
cause the carboxyl groups of the parent melphalan and chlo-
rambucil were replaced during the reaction of esterification
or amidation by the TEMPO group which has much weaker
polarity, the lipophilicity of the novel compounds increased.
Kinetics of Hydrolysis In our experiment, a water/ace-
tone hydrolysis system was selected, and the hydrolysis was
conducted mainly under a neutral environment because the
rate of the hydrolysis is temperature and pH dependent.21)
The major hydrolytic pathway of the alkylating agents was
the formation of the aziridinium ion, followed by a rapid hy-
Fig. 1. Effects of the Studied Compounds on Viability of K562 Cell
drolysis to yield the monohydroxy, and subsequently the di- valent adducts with DNA via the formation of a transient
hydroxy products. All hydrolysis profiles were found to ex- aziridinium species that attack the nucleophilic N7 position
hibit linear relationships (Rꢀ0.96) in our assays. The kinet- of guanine nucleotides.13) When the parent drugs were modi-
ics of the hydrolysis could be approximated by consecutive fied by TEMPO radicals, the active groups in the structures
first-order kinetics, and the pseudo-first-order rate constants of melphalan and chlorambucil were protected before they
(KH) of the hydrolysis reaction are given in Table 1. The at- reached the target DNA. This way greatly reduced the
tachment of TEMPO moiety to the melphalan and the chlo- chances of the hydrolyzation and the reactions with other
rambucil introduced an ester or amide bond which is also biomolecules in the body. Finally, as known, the piperidine
easily hydrolyzed in the aqueous solution, and the hydrolysis nitroxides can exhibit anticancer ability to a certain ex-
reaction process could be demonstrated by HPLC. But ac- tent.7,23,24) Therefore, we concluded that the combination of
cording to the rate constants KH shown in Table 1, the hydrol- the nitroxide radicals and melphalan/chlorambucil bearing
ysis rate of the modified compounds did not greatly change, two different anti-cancer mechanisms would improve the an-
compared with the counterpart parent drugs. The results tiproliferative potency, compared to each single compound.
showed that the introduction of TEMPO moiety to melphalan
or chlorambucil exerted very little effect on the hydrolysis Conclusion
rate of the parent drugs, and the pathway of hydrolysis that
they underwent may be similar under a neutral environment.
A series of novel spin-labeled melphalan and chlorambucil
derivatives were synthesized and characterized in our lab.
Cytotoxicity Studies The cytotoxic activities of the The novel compounds obviously held the properties of both
compounds in vitro against human leukemia cell line K562 the alkylations and the TEMPO radicals through the physico-
were measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5- chemical measurements and biological evaluation. Because
diphenyltetrazolium bromide (MTT) assay.14) Figure 1 gives the hydrolysis pathway of the alkylations and their TEMPO
the results of the assays. According to our measurements, conjugations was similar, the attachment of the TEMPO radi-
compared to the parent drugs melphalan and chlorambucil, cals to melphalan and chlorambucil had very little effect on
their derivatives modified by TEMPO radicals exhibited im- the hydrolytic stability of the parent compounds. Further-
proved anti-leukemia activities. For human leukemia cell line more, the results of cytotoxic assays in vitro indicated that
K562, IC50 values could be obtained from the assay results the novel compounds functionalized by TEMPO could exert
(Table 1) according to the median effect equation described a strong effect on the cytotoxic potency and improve this po-
by Chou.22) Consequently, the IC50 values of the TEMPO de- tency against the human leukemia K562 cell line.
rivatives were almost twice as low as those of the parent
Experimental
drugs. The results, firstly, may be related to the introduction
of the TEMPO moiety which led to an increase of the
lipophilicity known by our measurements of log P of the
compounds, enhancing the ability to cross the cell mem-
1
General Methods and Materials The H-NMR spectra were recorded
with a Bruker AM-500 NMR Spectrometer and the traditional 1H-NMR
spectra were of very limited help in detecting the final compounds because
the spectra of the nitroxide-containing molecules are broad.1) Melting points
brane. Secondly, we know that the alkylating agents form co- were determined by an X-5 micro-melting point apparatus and uncorrected.

334
Vol. 58, No. 3
KBr
max
EI-mass spectra were obtained on a Micromass GCT TOF GC/MS spec-
trometer. Elemental analyses were realized with an elementar vario EL III
analyser. IR spectra were measured on a Nicolet AVATAR360 FT-IR spec-
trophotometer. The UV–visible spectra were recorded on a UNICO UV-
2102PC spectrophotometer. Analytical thin-layer chromatography (TLC)
was conducted on precoated silica gel plates (Merck silica gel F254,
0.25 mm thick) with detection both by ultraviolet light and visualization with
iodine. EPR measurements were performed at X-band, 9.85 GHz, using a
Bruker EMX EPR spectrometer and the measurement of g-factors of the
compounds was carried out in contrast to a standard g-marker valued of
1.9800 provided by the Bruker Company. High performance liquid chro-
matography (HPLC) was conducted on an Agilent Technologies 1200 Series
HPLC using a 0.4ꢂ30 cm p-Bondapak C-18 column (Agilent Eclipse XDB-
C18, Agilent Ltd. Company, U.S.A.).
Melphalan and chlorambucil used as building block-drugs in this study
were purchased from Beijing Lunarsun Pharmaceutical Co., Ltd. 4-Amino-
2,2,6,6-tetramethyl-1-piperidinyloxy (4-NH2-TEMPO, 97%) radical and 4-
hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (4-OH-TEMPO, 99.9%) radi-
cal were commercially available and were bought from Sigma Corp. All sol-
vents and reagents obtained from commercial sources were analytical
reagent (AR) grade and used without further purification. New compounds
synthesized were tracked by TLC. Human leukemia cell line K562 was pur-
chased from the Institute of Biochemistry and Cell Biology, SIBS, CAS.
Chemistry 1) N-(9-Fluorenylmethoxycarbonyl)-4-[bis(2-chloroethyl)
amino]phenylalanine (3): Ten milliliters of saturated NaHCO3 solution was
added to an ice-cooled solution of melphalan 1 (2 g, 6.55 mmol) and 9-fluo-
renylmethyl chloroformate (Fmoc-Cl, 1.69 g, 6.55 mmol) in dioxane (20 ml).
After stirring for 8 h at room temperature (r.t.), the reaction mixture was
diluted with brine (200 ml), and extracted with ethyl acetate (200 ml). The
aqueous layer was acidified to a pH of 2 and extracted with ethyl acetate
(200 ml) again. The combined organic extracts were dried and concentrated.
The solid residue was purified by column chromatography (hexane : ethyl
g
(cmꢁ1): 3375.3 (N–H); 2973.4, 2945.6 (C–H); 1680.8 (CꢃO); 1620.4,
1521.8 (CꢃC); 1369.6 (ꢃN–O) cmꢁ1. MS m/e: [M]ꢄꢃ457.3. EPR: aN in
·
CH2Cl2: 15.54G; g valueꢃ2.0073. Anal. Calcd for C22H35Cl2N4O2 : C,
57.64; H, 7.70; N, 12.22. Found: C, 57.67; H, 7.95; N, 12.33.
5) 1-Oxyl-4-{4-[bis(2-chloroethyl)amino]phenylalanyl}oxo-2,2,6,6-
tetramethylpiperidine (7): Under similar conditions to the synthesization of
6, compound 7 was prepared as an orange solid, yield 86% and mp 117—
KBr
max
118 °C. IR g
(cmꢁ1): 2972.7, 2932.8 (C–H); 1731.4 (CꢃO); 1614.6,
1519.1, 1462.3 (CꢃC); 1359.4 (ꢃN–O); 1179.4 (C–O–C) cmꢁ1. MS m/e:
[M]ꢄꢃ459.2. EPR: aN in CH2Cl2: 15.54G; g valueꢃ2.0073. Anal. Calcd for
·
C22H34Cl2N3O3 : C, 57.51; H, 7.46; N, 9.15. Found: C, 57.46; H, 7.26; N,
9.03.
6) 1-Oxyl-4-{4-[bis(2-chloroethyl)amino] phenylbutanoyl}amino-2,2,6,6-
tetramethyl-piperidine (8): 4-NH2-TEMPO (562.12 mg, 3.28 mmol), HOBT
(444.21 mg, 3.28 mmol) and EDC·HCl (630.17 mg, 3.28 mmol) were suc-
cessively added to a solution of chlorambucil 2 (1 g, 3.28 mmol) in CH2Cl2
(20 ml) at 0 °C. After stirring for 8 h at r.t., the mixture was concentrated,
and the residue was taken up in brine and extracted with ethyl acetate. The
organic phase was dried and purified by column chromatography (hexane:
ethyl acetateꢃ4 : 1, v/v) to yield an oil and then crystallized with diethyl
ether to give the orange solid 8 (1.3 g, 87%), mp 97—98 °C. IR gmKaBxr (cmꢁ1):
3310.3 (N–H); 2937.5, 2875.5 (C–H); 1642.4 (CꢃO); 1547.5, 1525.4,
1460.6 (CꢃC); 1375.4 (ꢃN–O) cmꢁ1. MS m/e: [M]ꢄꢃ457.3. EPR: aN in
·
CH2Cl2: 14.96G; g valueꢃ2.0073. Anal. Calcd for C23H36Cl2N3O2 : C, 60.39;
H, 7.93; N, 9.19. Found: C, 60.48; H, 7.64; N, 9.06.
7) 1-Oxyl-4-{4-[bis(2-chloroethyl)amino] phenylbutanoyl}oxo-2,2,6,6-
tetramethyl-piperidine (9): Using the procedure employed for the synthesis
of compound 8 and starting from 4-OH-TEMPO (1.7 g , 9.84 mmol), DMAP
(40 mg, 0.328 mmol), EDC·HCl (693.19 mg, 3.608 mmol) and chlorambucil
2 (1 g, 3.28 mmol) in CH2Cl2 (20 ml) at 0 °C, compound 9 was prepared, and
purified by column chromatography (hexane : ethyl acetateꢃ1 : 10, v/v) to
yield an oil and then crystallized with diethyl ether to give the orange solid 9
KBr
max
(cmꢁ1): 3437.5 (N–H); 2973.5, 2932.5
acetateꢃ3 : 1, v/v) to give the compound 3 (3.06 g, 88.6%) as white solid,
(1.1 g, 72%), mp 59—61 °C. IR g
KBr
max
mp 116—118 °C. IR g
(cmꢁ1): 3330.23 (N–H, O–H), 2950.2 (C–H);
(
C–H); 1731.5 (CꢃO); 1615.4, 1520.5, 1465.4 (CꢃC); 1350.6 (ꢃN–O);
1184.5 (C–O–C) cmꢁ1. MS m/e: [M]ꢄꢃ458.2. EPR: aN in CH2Cl2: 15.25G;
1708.7 (CꢃO); 1520.0, 1445.5 (CꢃC); 1350.6 (ꢃN–O); 1047.9 (C–O–C)
cmꢁ1. MS m/e: [M]ꢄꢃ526.2. 1H-NMR (CDCl3) d: 3.0 (m, 2H, CH2Ph),
3.5—3.7 (m, 8H, N(CH2CH2)2), 4.3 (1H, t, CH[Fmoc]), 4.4 (2H, m,
CH2[Fmoc]), 5.2 (1H, d, NH), 6.8 (d, 2H, arom meta), 7.0 (d, 2H, arom
ortho), 7.2—7.7 (8H, m, Ar[Fmoc]), 9.7 (1H, COOH). Anal. Calcd for
C28H28Cl2N2O4: C, 63.76; H, 5.35; N, 5.31. Found: C, 63.81; H, 5.27; N, 4.96.
2) 1-Oxyl-4-{N-(9-fluorenylmethoxycarbonyl)-4-[bis(2-chloroethyl)
amino]phenylalanyl}amino-2,2,6,6-tetramethylpiperidine (4): 4-NH2-
TEMPO (648.7 mg, 3.79 mmol), 1-hydroxy-benzotriazole (HOBT, 512 mg,
3.79 mmol) and 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide hydro-
chloride(EDC·HCl, 726 mg, 3.79 mmol) was successively added to a solu-
tion of 3 (2 g, 3.79 mmol) in CH2Cl2 (20 ml) at 0 °C. After stirring for 8 h at
r.t., the mixture was concentrated, and the residue was taken up in brine and
extracted with ethyl acetate. The organic phase was dried and purified by
column chromatography (hexane : ethyl acetateꢃ1 : 1, v/v) to yield an oil
·
g valueꢃ2.0073. Anal. Calcd for C23H35Cl2N3O3 : C, 60.26; H, 7.70; N, 6.11.
Found: C, 60.23; H, 7.80; N, 5.98.
Determination of log P Oil/water partition coefficients (log P) of the
drugs in the n-octane/water system were determined by the shake-flask
method as described in the literature25), using a UV–Vis spectrophotometer.
The absorption values (corresponding to the maximum absorption wave-
length) of the two phases were obtained. The distribution ratio of one com-
pound between 1-octanol and water was calculated from the ratio of its ab-
sorption values in the oil phase to that in the water phase. Four separate
measurements for the P values were performed. And the reported values of
log P were the arithmetic averages of the four independent measurements.
The standard deviation of these replicated measurements was taken to be the
estimate of the uncertainty in the reported mean value.
Hydrolysis of the Compounds The studied compounds were dissolved
in dimethyl sulfoxide (DMSO) to make 2 mM solutions, and 50 ml of DMSO
solution was added to 950 ml of 50% acetone/water (w/w) in 1.5-ml capped
microcentrifuge tubes at 66 °C14); 50 ml aliquots of the solution were then
analyzed by HPLC. The system was eluted at 1 ml/min with a mobile phase
of 70% MeOH, 10% CH3CN, and 20% 1 M aqueous ammonium acetate,
containing 1 mM triethylamine and 1 mM heptanesulfonic acid. The ab-
sorbance was monitored at 258 and 436 nm, and peaks corresponding to the
parent alkylating agents, half alkylating agents, and the diol were integrated.
The percentage of parent compound remaining at each time point was deter-
mined and used to calculate a pseudo-first-order rate constant for the hydrol-
ysis reaction.
and then crystallized with diethyl ether to give the golden solid 4 (2.2 g,
KBr
85%), mp 139—140 °C. IR g
(cmꢁ1): 3331.8 (N–H); 2970.4, 2928.7
max
(C–H); 1702.5 (CꢃO); 1674.6, 1520.1, 1450 (CꢃC); 1360 (ꢃN–O);
1250.7, 1185.5, 1040.7 (C–O–C) cmꢁ1. MS m/e: [MꢁFmoc]ꢄꢃ457.3. EPR:
a
N in CH2Cl2: 15.54G; g valueꢃ2.0073.
3) 1-Oxyl-4-{N-(9-fluorenylmethoxycarbonyl)-4-[bis(2-chloroethyl)
amino]phenylalanyl}oxo-2,2,6,6-tetramethylpiperidine (5): Using the same
procedure employed for the synthesis of compound 4 and starting from
4-OH-TEMPO (1.95 g, 11.37 mmol), 4-dimethyl-aminopyridine (DMAP,
92.6 mg, 0.758 mmol), EDC·HCl (1.453 g, 7.58 mmol) and compound 3
(2 g, 3.79 mmol) in CH2Cl2 (20 ml) at 0 °C, compound 5 was synthesized,
and purified by column chromatography (dichloromethane : hexane : ethyl
Cytotoxicity Assays K-562 cells were maintained in exponential growth
phase by subculturing in RPMI 1640 containing 10% fetal calf serum and
2 mM L-glutamine at 37 °C, 5% CO2, 95% air, 100% relative humidity. 1ꢂ
100 cells/well were seeded onto 96-well plates, treated using a range of com-
pound concentrations after 24 h incubation. Then MTT was added to each
well to the final concentration of 0.5 mg/ml and cells were incubated for an
additional 3 h at 37 °C. Formazan crystals were dissolved in DMSO and ab-
sorbance was read at 492 nm using a Universal Microplate Reader 550 (Bio-
Rad Instruments).
acetateꢃ1 : 4 : 1, v/v/v) to yield a golden solid 5 (1.6 g, 62%), mp 62—
KBr
max
63 °C. IR g
(cmꢁ1): 3330.2 (N–H); 2971.4, 2929.8 (C–H); 1723.0 (Cꢃ
O); 1615.5, 1519.2, 1448.0 (CꢃC); 1350.6 (ꢃN–O); 1249.3, 1178.6, 1047.9
(C–O–C) mꢁ1. MS m/e: [M]ꢄꢃ681.3. EPR: aN in CH2Cl2: 15.25G; g
valueꢃ2.0073.
4)
1-Oxyl-4-{4-[bis(2-chloroethyl)amino]phenylalanyl}amino-2,2,6,6-
tetramethylpiperidine (6): Piperidine (2 ml) was added dropwise to a stirred
solution of compound 4 (2 g, 2.94 mmol) in DMF (10 ml) at r.t. After 1 h, the
solvent were removed in vacuo by co-evaporating with toluene, and the
residue was purified by column chromatography (hexane : methanol :
dichloromethaneꢃ5 : 1 : 5, v/v/v) to give an oil and then crystallized with
Acknowledgments This work was supported by the EU Framework
Programme 6 Integrated Project Novel and Improved Nanomaterials,
diethyl ether to give the orange solid 6 (1.1 g, 83%), mp 112—113 °C. IR Chemistries and Apparatus for Nano-biotechnology (NACBO) (contract No.

March 2010
335
500804), the Shanghai Nano-Technology Promotion Center (SNPC) (con-
tract No. 0652nm020), and the Ministry of Science and Technology of the
People’s Republic of China (contract No. 0424).
1995, p. 1233.
13) Drablos F., Feyzi E., Aas P. A., Vaagb C. B., Kavli B., Bratlie M. S.,
DNA Repair, 3, 1389—1407 (2004).
14) Gourdie T. A., Valu K. K., Gravatt G. L., Boritzki T. J., Baguley B. C.,
Wakelin L. P. G., Wilson W. R., Woodgate P. D., Denny W. A., J. Med.
Chem., 33, 1177—1186 (1990).
15) Morris A. D., Atassi G., Guilbaud N., Cordi A. A., Eur. J. Med. Chem.,
32, 343—349 (1997).
References
1) Keana J. F. W., Chem. Rev., 78, 37—64 (1978).
2) Naik N., Braslau R., Tetrahedron, 54, 667—696 (1998).
3) Hahn S. M., Cancer Res., 52, 1750—1753 (1992).
4) Liebmann J., DeLuca A. M., Epstein A., Steinberg S. M., Morstyn G.,
Mitchell J. B., Radiat. Res., 137, 400—404 (1994).
16) Urbaniak M. D., Bingham J. P., Hartley J. A., Woolfson D. N., Caddick
S., J. Med. Chem., 47, 4710—4715 (2004).
5) Gariboldi M. B., Lucchi S., Caserini C., Supino R., Oliva C., Monti E.,
Free Radic. Biol. Med., 24, 913—923 (1998).
6) Gariboldi M. B., Ravizza R., Petterino C., Castagnaro M., Finocchiaro
G., Monti E., Eur. J. Cancer, 39, 829—837 (2003).
7) Mitchell J. B., Xavier S., DeLuca A. M., Sowers A. L., Cook J. A.,
Krishna M. C., Hahn S. M., Russo A., Free Radic. Biol. Med., 34,
93—102 (2003).
17) Chen C. H., Lin Y. W., Zhang X. G., Chou T. C., Tsai T. J., Kapuriya
N., Kakadiya R., Su Ts. L., Eur. J. Med. Chem., 44, 3056—3059
(2009).
18) Gariboldi M. B., Ravizza R., Petterino C., Castagnaro M., Finocchiaro
G., Monti E., Eur. J. Cancer, 39, 829—837 (2003).
19) Prabhutendolkar A., Liu X., Mathias E., Ba Y., Kornfield J., Drug
Deliv., 13, 433—440 (2006).
8) Hahn S. M., DeLuca A. M., Coffin D., Krishna C. M., Mitchell J. B.,
Int. J. Radiat. Oncol. Biol. Phys., 42, 839—842 (1998).
20) Poole S. K., Poole C. F., J. Chromatogr. B, 797, 3—19 (2003).
21) Watson E., Dea P., Chan K. K., J. Pharm. Sci., 74, 1283—1292 (1985).
9) Zollner S., Haseloff R. F., Kirilyuk I. A., Blasig I. E., Rubanyi G. M., 22) Chou T. C., J. Lab. Clin. Med., 132, 6—8 (1998).
J. Biol. Chem., 272, 23076—23080 (1997).
10) Kalman H. K., Ceeilia P. S., J. Heterocycl. Chem., 42, 437—450
(2005).
11) Nakatsuji S., Ikemoto H., Akutsu H., Yamada J., Mori A., J. Org.
Chem., 68, 1708—1714 (2003).
23) Ankel E. G., Lai C., Hopwood L. E., Zivkovic Z., Life Sci., 40, 495—
498 (1987).
24) Schubert R., Erker L., Barlow C., Yakushiji H., Larson D., Russo A.,
Mitchell J. B., Wynshaw-Boris A., Hum. Mol. Genet., 13, 1793—1802
(2004).
12) “Goodman and Gilman’s The Pharmacologic Basis of Therapeutics,” 25) “Structure–Activity Relationships of Drugs,” ed. by Renli L., China
ed. by Chabner B. A., Allegro C. J., Curt G. A., Calabresi P., Gilman
A. G., Rall T. W., Nies A. S., Taylor P., Pergamon Press, New York,
Medical Science Press, Beijing, 2004, pp. 273—274.