4′-Alkoxyl substitution enhancing the anti-mitotic effect of 5-(3′,4′,5′-substituted)anilino-4-hydroxy-8-nitroquinazolines as a novel class of anti-microtubule agents

Article abstract of DOI:10.1016/j.bmcl.2006.08.058

Mitosis inhibitors are powerful anticancer drugs. Based on a novel anti-microtubule agent of 5-(4′-methoxy)anilino-4-hydroxy-8-nitroquinazoline, a series of 5-(3′,4′,5′-substituted)anilino-4-hydroxy-8- nitroquinazolines were designed and synthesized to investigate the effect of the substitution on the inhibitory activity against mitotic progression of tumor cells. The large alkoxyl substitution on the 4′-position of 5-anilino ring is beneficial for the potency. The 5-(3′,4′,5′-trimethoxy)anilino-8-nitroquinazoline (1h) displays an overwhelming activity in arresting the cells at the G2/M phase, providing a promising new template for further development of potent microtubule-targeted anti-mitotic drugs.

Full text of DOI:10.1016/j.bmcl.2006.08.058

Bioorganic & Medicinal Chemistry Letters 16 (2006) 5864–5869
40-Alkoxyl substitution enhancing the anti-mitotic effect
of 5-(30,40,50-substituted)anilino-4-hydroxy-8-nitroquinazolines
as a novel class of anti-microtubule agents
Yi Jin,a Zu-Yu Zhou,a Wei Tian,b Qiang Yua and Ya-Qiu Longa,*
aState Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences,
Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
bThe School of Pharmaceutical Engineering, Shenyang Pharmaceutical University, Liaoning 110016, China
Received 12 May 2006; revised 27 July 2006; accepted 11 August 2006
Available online 30 August 2006
Abstract—Mitosis inhibitors are powerful anticancer drugs. Based on a novel anti-microtubule agent of 5-(40-methoxy)anilino-4-hy-
droxy-8-nitroquinazoline, a series of 5-(30,40,50-substituted)anilino-4-hydroxy-8- nitroquinazolines were designed and synthesized to
investigate the effect of the substitution on the inhibitory activity against mitotic progression of tumor cells. The large alkoxyl sub-
stitution on the 40-position of 5-anilino ring is beneficial for the potency. The 5-(30,40,50-trimethoxy)anilino-8-nitroquinazoline (1h)
displays an overwhelming activity in arresting the cells at the G2/M phase, providing a promising new template for further devel-
opment of potent microtubule-targeted anti-mitotic drugs.
Ó 2006 Elsevier Ltd. All rights reserved.
Quinazolines are a class of fused pyrimidine derivatives
which display diverse range of biological activities.1
Among them, 4-anilinoquinazolines are the most prom-
ising small molecule EGFR tyrosine kinase inhibitors.
For example, the best inhibitors of EGFR tyrosine ki-
nase PD153035 (6,7-dimethoxy-4-(30-bromophenyl)ami-
no-quinazoline) and IRESSATM (gefitinib, ZD1839),2
developed from this compound family, are presently
the only approved and granted drugs by the FDA for
the treatment of advanced non-small-cell lung cancer
(NSCLC). However, the activity of the quinazoline fam-
ily could be greatly modulated by the substitution
change on the quinazoline core structure.3 Recently,
we developed a new class of 5-substituted-4-hydroxy-8-
nitroquinazolines which displayed potent antiprolifera-
tive effect against EGFR or ErbB-2 overexpressing
tumor cell lines but not targeting the EGFR
tyrosine kinase.4 Further study on the molecular mech-
anism disclosed that the 5-(4-methoxy)anilino-4-hy-
droxy-8-nitroquinazoline (LJK-11) functions as an
anti-microtubule agent by inhibiting the microtubule
polymerization.5
Microtubules are critical elements in a variety of funda-
mental cell functions, including formation and mainte-
nance of cell shape, transportation of vesicles and
protein complexes, and regulation of motility and cell
division.6 The essential role of microtubules in mitosis
and cell division makes them and their regulatory pro-
teins important targets for anticancer drugs. Anti-micro-
tubule agents, such as nocodazole, vinorelbine,
colchicines, and paclitaxel (Fig. 1), have been successfully
used in treating a variety of cancers.7,8
Despite the success of taxanes and vinca alkaloids to
inhibit the progression of certain cancers in clinical
use, resistance to anti-microtubule agents is encountered
in many tumor types, particularly during multiple cycles
of therapy.9–11 Therefore, there has been great interest in
identifying and developing novel anti-microtubule
drugs. Our preliminary study has revealed that LJK-11
is a specific cell mitosis blocker, which inhibits microtu-
bule polymerization, arrests cells at early stage of mito-
sis, and induces apoptosis of tumor cells.5
Keywords: Quinazoline; Mitosis inhibitor; Tubulin polymerization;
Anti-microtubule agent; Alkoxyl substitution; Aniline; Antiprolifera-
tive effect; Cell cycle; Tumor cells.
*
Since LJK-11 represents a novel anti-microtubule agent,
we are intrigued to conduct SAR study to explore the
Corresponding author. Tel.: +86 21 50806876; fax: +86 21
50807088; e-mail: yqlong@mail.shcnc.ac.cn
0960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2006.08.058

Y. Jin et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5864–5869
5865
Figure 1. The representative structures of anti-microtubule agents.
pharmacophore and then improve the activity. A fo-
cused library containing 5,8-disubstituted quinazoline
structure was designed. In the present work, we have fo-
cused on investigating the effect of the 30,40-substitution
of the 5-anilino portion on the anti-mitosis activity
(Fig. 2). Thus, a series of 5-(30,40-substituted) anilino-
4-hydroxy-8-nitroquinazoline analogs were designed
and synthesized. The activity to inhibit the growth and
block the mitosis of the tumor cell lines was evaluated.
The alkoxyl substitution on the 30,40-position of the 5-
anilino moiety was found to potentiate the anti-mitotic
potency of this novel class of microtubule polymeriza-
tion inhibitors.
stituent structure was referred to the previous SAR
study of the 5-substituted-4-hydroxy-8-nitroquinazo-
lines as EGFR inhibitors.4 The alkoxyl, alkyl, and ami-
noacyl groups containing a,b-unsaturated carboxyl ester
were incorporated into the 4-position of the 5-anilino
ring, in combination with additional substitution on 3-
and 5-position with chloro and methoxy groups, respec-
tively, in some cases. The general synthesis is similar to
the procedure reported previously,4 starting from the
commercially available 3-chloro-2-methyl aniline and
employing Neimentowski synthesis as the key step
to construct the quinazoline core. As depicted in
Scheme 1, the current effort was focused on the synthesis
of the various 30,40-substituted anilines (3a–h) which
react with the common intermediate 2 to furnish the
desired 5-(30,40-substituted)anilino-4-hydroxy-8-nitro-
quinazolines 1a–h.12
A series of 5-anilino-4-hydroxy-8-nitroquinazolines with
various substitution on 30,40-position of 5-anilino moie-
ty was designed and synthesized. The choice of the sub-
Figure 2. The designed series of 5-(30,40-substituted)anilino-4-hydroxy-8-nitroquinazolines.
Scheme 1.

5866
Y. Jin et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5864–5869
According to the synthetic approaches, there are three
types of 3,4-substituted anilines: one is 3-chloro-4-alk-
oxy-aniline (3a–c), the second is the 4-alkyl or aminoac-
yl-aniline (3d–e), and the third is the alkoxyl linked
functional group as 4-substituent (3f–g). 3,4,5-trimeth-
oxyl-aniline (3h) is a special case. The synthesis is
described in Schemes 2–5, respectively.
Generally speaking, the 3-chloro-4-alkoxy-aniline (3a–c)
was prepared from o-chlorophenol via a selective nitra-
Scheme 2. Reagents and conditions: (a) CH3I, CH2Cl2, Na2CO3, rt, yield 95% for 4a or cyclohexene, BF3ÆEt2O, toluene, rt, yield 49% for 4b; (b)
Bi5O(OH)9(NO3)4/ SOCl2, rt, yield 36% for 5a, 58% for 5b; (c) Fe, NH4Cl, MeOH/H2O, refluxed, yield 98% for 3a, 97% for 3b; (d) NaNO2, NaAc,
AcOH/H2O, rt, 70%; (e) Zn/NH4Cl, MeOH/H2O, refluxed, 98%; (f) (Boc)2O, NaHCO3, THF, rt, 100%; (g) i—BnBr, NaHCO3, THF, rt, 55%;
ii—CF3COOH, CH2Cl2, rt, 100%.
Scheme 3. Reagents and conditions: (a) (Boc)2O, NaHCO3, THF, rt, 100%; (b) ZnBr, DIPEA, 0.05 equiv Pd(PPh3)2Cl2, methyl acrylate, THF, rt,
yield 88% for 6, 51% for 7; (c) CF3COOH, CH2Cl2, rt, 100%; (d) TEA, ClCH2COCl, CH2Cl2, rt, 97%; (e) propan-1-amine, THF, rt, 98%; (f) DIPEA,
4-iodo-benzenesulfonyl chloride THF, rt, 94%; (g) Fe/NH4Cl, MeOH/H2O, refluxed, 80%.
Scheme 4. Reagents and conditions: (a) Na2CO3, OHCH2CH2OH, dioxane, refluxed, 69%; (b) 4-iodobenzoic acid, cat. TsOH, toluene, refluxed,
21%; (c) ZnBr, DIPEA, 0.05 equiv Pd(PPh3)2Cl2, methyl acrylate, THF, rt, 66%; (d) Zn/NH4Cl, MeOH/H2O, refluxed, 30%; (e) Na2CO3, KI,
BrCH2CH2CH2OH, acetone, refluxed, 41%; (f) NBS, PPh3, CH2Cl2, refluxed, 60%; (g) morpholine, cat. DMAP, THF, rt, 62%.

Y. Jin et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5864–5869
5867
tissue origin, including lung adenocarcinoma cell line
A549 and gastrointestinal cancer cell line HGC-27.14
The effect of the compounds 1a–h on the cell prolifera-
tion was evaluated using MTT assay.15 As shown in
Figure 3, compounds 1c and 1f–h, bearing an alkoxyl
substituent on the 5-anilino portion, exhibited potent
inhibition on the growth of HGC-27 cells at the concen-
tration of 50 lM, while compounds 1a, 1b, 1d and 1e
displayed poor potency. Furthermore, this series was
less effective in inhibiting the proliferation of A549 cells,
though compound 1c was still the best inhibitor (Fig. 3).
Scheme 5. Reagents and conditions: (a) SOCl2, CH2Cl2, refluxed,
100%; (b) i—NaN3, H2O/THF, 0 °C; ii—toluene, refluxed; iii—5 N
NaOH, then 6 N HCl, overall yield for three steps 70%.
tion and O-alkylation, followed by the reduction of the
nitro into amino group, as depicted in Scheme 2. The
selective 4-nitration of aniline was achieved with
bismuth subnitrate and thionyl chloride,13 and the
reduction proceeded smoothly with zinc or iron powder
in ammonium chloride solution. But for the synthesis of
4-benzyloxyl substituted-3-chloro-aniline (3c), the
reduction of nitro group should take place prior to the
benzylation of the phenol group.
Previous studies have found that the lipophilic electron-
donating groups such as methoxy or benzyloxy at the 40-
position were beneficial for the 5-(40-substituted)-anili-
no-4-hydroxy-8-nitroquinazoline in inhibiting the
growth of breast cancer cells MDA-MB-468, and 30-
chloro substituent on the aniline ring improved the
inhibitory activity against the SK-BR-3 cell line.4 But
in our case, the simultaneous substitution of 30-chloro-
40-methoxy (compound 1a) resulted in a big loss of the
potency compared to LJK-11 (IC50 = 20 lM for A549
and HGC-27 cells). And the cyclohexyloxy group (com-
pound 1b) is disfavored in 40-position either. However,
the large alkoxy group at 40-position (compounds 1c, f
and g) enhanced the antiproliferative effect against both
HGC-27 and A549 cells. On the contrary, the large alkyl
or amide substituent (compounds 1d and e) is detrimen-
tal to the activity. As expected, the 3,4,5-trimethoxyl
substitution confers an effective inhibitor (compound
1h) for the two tumor cell lines.
For the 4-alkyl or 4-aminoacyl-aniline (3d–e), both con-
tain an a,b-unsaturated carboxyl ester on the 4-substitu-
ent, which was introduced by a Heck coupling reaction,
as depicted in Scheme 3.
As shown in Scheme 4, 4-alkoxyl substituted aniline (3f–
g) was prepared from 1-chloro-4-nitrobenzene via an
SNAr reaction followed by an acylation then a Heck
coupling (3f), or from 1-hydroxy-4-nitrobenzene via an
O-alkylation followed by an SN2 reaction (3g). In this
series, a linker was used to join the anilino group and
another functional group, such as morpholine or 3-
phenyl-acrylic acid methyl ester.
Several lines of evidence have indicated that this 5-(40-
substituted)anilino-8-nitroquinazoline family inhibits
proliferation and induces apoptosis by blocking mitosis
of tumor cells. It functions by inhibiting microtubule
polymerization, similar to that of colchicines.5 So we
would like to examine the effect of these analogs on
the mitosis of tumor cells.16
The special 3,4,5-trimethoxyaniline (3h) was converted
from 3,4,5-trimethoxybenzoic acid via a Curtius rear-
rangement, as indicated in Scheme 5.
Anti-proliferative effect of 5-(30,40,50-substituted)anilino-
4-hydroxy-8-nitro-quinazolines on the tumor cells. We
examined the growth inhibitory activity of the new series
of quinazolines using human tumor cell lines of different
Arresting effect of 5-(30,40,50-substituted)anilino-8-nitro-
quinazolines on the mitosis of tumor cells. We analyzed
5-(3',4',5'-Substituted)anilino-8-nitroquinazolines
(50 μM), MTT (HGC-27 or A549 cell line)
DMSO 1a
1b
1c
1d
1e
1f
1g
1h
Figure 3. Effect of compounds 1a–h on the proliferation of HGC-27 or A549 cells after the incubation of 24 and 48 h, respectively. The cell viability
was measured by MTT assay and is expressed as a percentage of the compound-treated viable cells divided by the viable cells of the untreated control.
The data are means of triplicates SD.

5868
Y. Jin et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5864–5869
0
50
100
150
200
250
0
50
100
150
200
250
0
50
100
150
200
250
Channels (FL2-A)
Channels (FL2-A)
Channels (FL2-A)
DMSO
1c
1h
Figure 4. Flow cytometry analysis of 5-(30,40,50-substituted)anilino-8-nitroquinazoline-treated tumor cells. HGC cells were incubated with 50 lM
concentration of 1c or 1h for 24 h. The cells were then fixed and stained with PI, and analyzed by flow cytometry.
the effect of compounds 1a–h on cell cycle.17 It is clear
5-(3’,4’,5'-Substituted)anilino-8-nitroquinazolines, FCM (A549)
that the treatment with potent inhibitors bearing 40-alk-
oxyl substituent, that is, 1c, 1f, 1g, and 1h induced G2/M
arrest of HGC-27 cells after 24 h of drug exposure (Figs.
4, 5). Especially for 3,4,5-trimethoxylaniline containing
analog 1h, 81% of the cell population was blocked in
G2/M phase when they were exposed to 50 lM of 1h
G1
for 24 h (Fig. 5). The potency to block the mitosis of
the cells is correlated with the activity to inhibit the
growth of the tumor cells. Therefore, this series exhibit-
ed an inferior effect on the mitosis of A549 cells (Fig. 6).
However, the 5-(30,40,50-trimethoxy)anilino-8-nitroqui-
nazoline (1h) displays an overwhelming potency in
arresting the tumor cells at G2/M phase, for both
HGC-27 and A549 cells. Considering the structures of
well known anti-microtubule agents such as colchicine
and combretastatin A4, the 3,4,5-trimethoxyphenyl moi-
ety in common plays an important role in the binding to
the tubuline. The observation could be rationalized by
molecular modeling.
G2/M
DMSO 1a 1b
1c
1d
1e
1f
1g
1h
Figure 6. Percentage of A549 cells in G2/M phase after 24-h treatment
with 50 lM concentration of various 5-anilino-8-nitroquinazolines,
evaluated by the flow cytometry analysis. The data are means of
triplicates SD.
several optional conformations of our inhibitors.19,20
Among them, the lowest binding energy one was select-
ed as the possible binding conformation, as shown in
Figure 7.
Based on the recently reported X-ray crystal structure of
a,b-tubulin complexed with N-deacetyl-N-(2-mercapto-
acetyl) colchicine (DAMA-colchicine) (PDB code
1SA0),18 the automated molecular docking can produce
In the final model, the hydrogen bonds between 1h and
tubulin are as follows: (1) the trimethoxyphenyl (TMP)
is hydrogen bonded to the thiol group of Cys b241; (2)
the 4-OH of quinazolinone is hydrogen bonded to the
carbonyl oxygen atom of Asn b258; (3) of particular sig-
nificance to 1h, the 8-nitro group is involved in the inter-
action with the colchicine site via its oxygen atom
forming hydrogen bond with the terminal NH of Lys
b254. For the diaryl system of 1h, the phenyl plane
and quinazolinone plane have a tilt of 57°, and conform
to the shape of the colchicine site. The TMP moieties of
DAMA-colchicine and 1h occupy similar cartesian
space and are buried in a hydrophobic pocket contain-
ing Leu255, Val238, Cys241, Val318, Ala354, and
Ala317 of the b-tubulin structure. That is, why the
3,4,5-trimethoxy substitution endows a significant anti-
microtubule activity.
5-(3’,4’,5'-Substituted)anilino-8-nitroquinazolines, FCM (HGC)
G1
G2/M
DMSO 1a
1b
1c
1d
1e
1f
1g 1h
Figure 5. Percentage of HGC cells in G2/M phase after 24-h treatment
with fixed concentration of various 5-anilino-8-nitroquinazolines,
examined by the flow cytometry analysis. The data are means of
triplicates SD.
In conclusion, we have synthesized and assessed a series
of 5-(30,40,50-substituted)anilino-8-nitroquinazolines as a

Y. Jin et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5864–5869
5869
4. Jin, Y.; Li, H.-Y.; Lin, L.-P.; Tan, J.; Luo, X.; Ding, J.;
Long, Y.-Q. Bioorg. Med. Chem. 2005, 13, 5613.
5. Qin, L.; Ai, M.; Tian, W.; Jin, Y.; Zhou, Z.-Y.; He, J.;
Long, Y.-Q.; Yu, Q. A novel synthetic analog of 5,8-
disubstituted quinazoline blocks mitosis and induces
apoptosis of tumor cells by inhibiting microtubule poly-
merization. Unpublished results.
6. Margolis, R. L.; Wilson, L. Bioessays 1998, 20, 830.
7. Jordan, M. A.; Wilson, L. Nat. Rev. Cancer 2004, 4, 253.
8. Mani, S.; Macapinlac, M., Jr.; Goel, S.; Verdier-Pinard,
D.; Fojo, T.; Rothenberg, M.; Colevas, D. Anti cancer
Drugs 2004, 15, 553.
9. Rowinsky, E. K.; Tolcher, A. W. Antimicrotubule agents.
In Cancer Principles and Practice; Devita, V. T., Jr.,
Hellman, S., Rosenberg, S. A., Eds., 6th ed.; Lippincott
Williams and Willkins: Philadelphia, 2001; p 431.
10. Gottesman, M. M. Annu. Rev. Med. 2002, 53, 615.
11. Dumontet, C.; Sikic, B. I. J. Clin. Oncol. 1999, 17, 1061.
12. The physicochemical data of selected compounds: 1c, mp:
Figure 7. Binding model of 1h with the a,b-tubulin polypeptide whose
backbones are rendered as brown (b chain) and gray (a chain) ribbons.
Residue side chains at the colchicine site (Thr a179, Val a181, Cys
b241, Lys b254 Leu b255, Asn b258, Thr b314, Ala b316, Val b318,
and Ala b354), 1h is shown in stick with the carbon atoms of tubulin
colored green and the carbon atoms of the 1h cyan, nitrogen atoms are
colored blue, oxygen atoms red, and sulfur atoms yellow. White
dashed lines indicate potential intermolecular hydrogen bonds.
1
152–154 °C. H NMR (DMSO-d6, 300 MHz): d ppm 8.30
(d, 1H), 8.27 (d, J = 9.0, 1H), 7.79 (d, J = 9.0, 1H), 7.47
(m, 5H), 7.19 (s, 1H), 7.09 (d, J = 8.3, 1H), 6.90 (d, J = 8.3,
1H), 5.16 (s, 2H). MS (EI) m/z 422 (M+); Anal. Calcd for
(C21H15ClN4O4) C, H, N: 59.65, 3.58, 13.25. Found:
59.83, 3.42, 13.47. 1h, mp: 125–127 °C. 1HNMR (DMSO-
d6, 300 MHz): d ppm 8.22 (s, 1H), 8.14 (d, J = 8.3, 1h),
7.03 (d, J = 8.3, 1H), 6.28 (s, 2H), 3.65 (s, 6H), 3.58 (s,
3H). MS (EI) m/z 372 (M+); Anal. Calcd for
(C17H16N4O6). C, H, N: 54.84, 4.33, 15.05. Found:
54.76, 4.42, 15.14.
new class of anti-microtubule agents. The effect of the
30,40,50-substitution on the 5-anilino ring was investigat-
ed. The large alkoxyl substitution on the 40-position of
5-anilino portion is beneficial for the inhibitory activity
against the growth and mitosis of the tumor cells. How-
ever, the alkyl or amide substituent at this position is
disfavored. With respect to the antiproliferative effect
and anti-mitosis activity, this series is more potent
against HGC-27 tumor cells than A549 tumor cells. Sig-
nificantly, the 5-(30,40,50-trimethoxyl)anilino-8-nitroqui-
nazoline (1h) displays an overwhelming potency in
arresting the tumor cells at the G2/M phase of the cell
cycle, providing new templates for further development
of potent mitosis inhibitors with therapeutic potential in
treating cancer.
13. Muathen, H. A. Molecules 2003, 8, 593.
14. Cell Growth Inhibition Assay. Two human carcinoma cell
lines, A549 (lung adenocarcinoma) and HGC-27 (gastro-
intestinal carcinoma), were used for the cell proliferation
assay. A549 cells were cultured in RPMI-1640 medium
supplemented with 10% calf serum; HGC-27 cells were
cultured in DMEM supplemented with 10% calf serum.
The growth inhibition was examined by MTT assay.
15. Mossman, T. J. Immunol. Methods 1983, 65, 55.
16. Cell mitosis assay by flow cytometry analysis. Tumor
cells were incubated with indicated concentration of
synthetic inhibitor for 24 h. The harvested cells were
washed with PBS, resuspended in 1 mL of iced 75%
ethanol at ꢀ20 °C. After being left to stand overnight,
cell pellets were collected by centrifugation, resuspended
in 500 lL of hypotonic buffer (0.5% Triton X-100 in
PBS and 0.5 lg/mL RNase), and incubated at 37 °C for
30 min. Then 25 lL of propidium iodide solution (50 lg
/mL) was added, and the mixture was allowed to stand
on ice for 1 h. Fluorescence emitted from the propidi-
um iodide–DNA complex was quantitated after excita-
tion of the fluorescent dye by FAC-Scan cytometry.
The histogram of DNA distribution was modeled as a
Acknowledgment
Financial support from the Ministry of Science and
Technology of China (No. 2004CB518903) is greatly
appreciated.
sum of G1, G2-M,
S phase, and an aneuploid
References and notes
population close to the G1 peak, by using ModFitLT
software.
1. Connolly, D. J.; Cusack, D.; O’Sullivan, T. P.; Guiry, P. J.
Tetrahedron 2005, 61, 10153.
17. Yoshida, D.; Hoshino, S.; Shimura, T.; Tahakashi, H.;
Teramoto, A. J. Neurooncol. 2000, 47, 133.
18. Ravelli, R. B.; Gigant, B.; Curmi, P. A.; Jourdain, I.;
Lachkar, S.; Sobel, A.; Knossow, M. Nature 2004, 428,
198.
19. Morris, G. M.; Goodsell, D. S.; Halliday, R. S.; Huey, R.;
Hart, W. E.; Belew, R. K.; Olson, A. J. J. Comput. Chem.
1998, 19, 1639.
20. Morris, G. M.; Goodsell, D. S.; Huey, R.; Hart, W. E.;
Halliday, R. S.; Belew, R. K.; Olson, A. J. AUTODOCK,
M. Version 3.0.3. The Scripps Research Institute, Molec-
ular Graphics Laboratory, Department of Molecular
Biology, 1999.
2. Ciardiello, F.; Tortora, G. Clin. Cancer Res. 2001, 7, 2958.
3. (a) Ballard, P.; Bradbury, R. H.; Hennequin, L. F. A.;
Hickinson, D. M.; Johnson, P. D.; Kettle, J. G.; Kli-
nowska, T.; Morgentin, R.; Ogilvie, D. J.; Olivier, A.
Bioorg. Med. Chem. Lett. 2005, 15, 4226; (b) Bathini, Y.;
Singh, I.; Harvey, P. J.; Keller, P. R.; Singh, R.; Micetich,
R. G.; Fry, D. W.; Dobrusin, E. M.; Toogood, P. L.
Bioorg. Med. Chem. Lett. 2005, 15, 3881; (c) Gungor, T.;
Chen, Y.; Golla, R.; Ma, Z. P.; Corte, J. R.; Northrop, J.
P.; Bin, B.; Dickson, J. K.; Stouch, T.; Zhou, R.; Johnson,
S. E.; Seethala, R.; Feyen, J. H. M. J. Med. Chem. 2006,
49, 2440.