Organic phenyl arsonic acid compounds with potent antileukemic activity

Article abstract of DOI:10.1016/S0960-894X(02)00928-9

A series of 12 organic arsonic acid compounds has been synthesized and evaluated against human B-lineage (NALM-6) and T-lineage (MOLT-3) acute lymphoblastic leukemia (ALL) cell lines. The lead compounds 2-trichloromethyl-4-[4′-(4″-phenylazo)phenylarsonic acid]aminoquinazoline (compound 19, PHI-P518; IC₅₀=1.1±0.5 μM against NALM-6 and 2.0±0.8 μM against MOLT-3) and 2-methylthio-4-(2′-phenylarsonic acid)aminopyrimidine (compound 15, PHI-P381; IC₅₀=1.5±0.3 μM against NALM-6 and 2.3±0.5 μM against MOLT-3) exhibited potent antileukemic activity at low micromolar concentrations.

Full text of DOI:10.1016/S0960-894X(02)00928-9

Bioorganic & Medicinal Chemistry Letters 13 (2003) 581–583
Organic Phenyl Arsonic Acid Compounds with Potent
Antileukemic Activity
Xing-Ping Liu, Rama Krishna Narla and Fatih M. Uckun*
Parker Hughes Cancer Center, Parker Hughes Institute, 2699 Patton Road, St. Paul, MN 55113, USA
Received 14 December 2001; accepted 23 July 2002
Abstract—A series of 12 organic arsonic acid compounds has been synthesized and evaluated against human B-lineage (NALM-6)
and T-lineage (MOLT-3) acute lymphoblastic leukemia (ALL) cell lines. The lead compounds 2-trichloromethyl-4-[40-(400-phenyl-
azo)phenylarsonic acid]aminoquinazoline (compound 19, PHI-P518; IC50=1.1ꢀ0.5 mM against NALM-6 and 2.0ꢀ0.8 mM against
MOLT-3) and 2-methylthio-4-(20-phenylarsonic acid)aminopyrimidine (compound 15, PHI-P381; IC50=1.5ꢀ0.3 mM against
NALM-6 and 2.3ꢀ0.5 mM against MOLT-3) exhibited potent antileukemic activity at low micromolar concentrations.
# 2002 Elsevier Science Ltd. All rights reserved.
Acute lymphoblastic leukemia (ALL) is the most com-
mon form of childhood cancer. The outcome of ALL
patients who experience a relapse after frontline con-
temporary chemotherapy is dismal.1ꢁ3 Therefore, there
is an urgent need for novel antileukemic agents. The
inorganic arsenic compound arsenic trioxide (As2O3) is
a chemotherapeutic drug that has been used in the
treatment of hematologic malignancies.4ꢁ9 Daily intra-
venous infusion of 10 mg As2O3 induced complete
remission in acute promyelocytic leukemia patients who
are refractory to conventional chemotherapy.5,6 In an
effort aimed at identifying arsenic compounds with
more favorable toxicity profile and more broad-spec-
trum anticancer activity, we decided to synthesize a new
class of organic arsenic compounds by derivatizing the
less toxic pentavalent organic arsenical, phenylarsonic
acid (PAA).10 In the present study, we synthesized a
series of 12 phenlarsonic acids and they were tested for
their antileukemic activity using two leukemia cell lines
(NALM-6 And MOLT-3).
4-Chloro-6, 7-dimethoxyquinazoline, as one of the key
starting materials (5) was prepared as outlined in
Scheme 1. In this procedure, 4,5-dimethoxy-2-nitro-
benzoic acid (1) was treated with thionyl chloride SOCl2
first, then the reaction mixture was directly treated with
ammonia NH4OH to give the 4, 5-dimethoxy-2-nitro-
benzamide (2).11 Compound 2 was reduced with sodium
borohydride NaBH4 and catalyzed by copper sulfate
CuSO4,12,13 to give 2-amino-4,5-dimethoxy-benzamide
(3), which was directly refluxed with formic acid
HCO2H to give 6,7-dimethoxy-4-(3H)-quinazolinone (4).
Scheme 1.
*Corresponding author. Tel.: +1-651-796-5450; fax: +1-651-796-5493; e-mail: fatih_uckun@ih.org
0960-894X/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(02)00928-9

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X.-P. Liu et al. / Bioorg. Med. Chem. Lett. 13 (2003) 581–583
Compound 4 was refluxed with phosphorus oxychloride
POCl3 to provide the key starting material 4-chloro-6, 7-
dimethoxyquinazoline (5) with good yield.11
Another two starting materials 4-chloro-2-methylthio-
pyrimidine (6) and 6-chloropurine (7) were commer-
cially available.
Scheme 2.
The arsonic acid compounds for this study were pre-
pared by the condensation of 4-chloro-6,7-dimethoxy-
quinazoline (5), 4-chloro-2-methylthiopyrimidine (6), 6-
chloropurine (7) or 4-chloro-2-trichloromethylquinazo-
line (9) and phenylarsonic acid (Table 1). In brief, a mix-
ture of 2 mmol of compounds 5, 6, 7, or 9, and 2.2 mmol
of 4-(4-aminophenylazo)phenylarsonic acid (to give 10,
13, 16, and 19), 4-aminophenylarsonic acid (to give 11,
4-Chloro-2-trichloromethylquinazoline as the fourth
key starting material (9) was prepared as outlined in
Scheme 2.
Table 1. Structure and antileukemic activities of phenylarsonic acid derivatives against human leukemia NALM-6 (B-lineage ALL) and MOLT-3
(T-lineage ALL) cell lines
Compd
PHI-P
273
R1
R2
H
R3
IC50 (mM)
NALM-6
MOLT-3
16.9 ꢀ3.4
13.9ꢀ2.6
10
11
12
13
379
378
370
H
H
40-As(O)(OH)2
20-As(O)(OH)2
>100
>100
55.6ꢀ12.4
4.1ꢀ1.7
46.6ꢀ12.4
6.1ꢀ1.6
H
SCH3
14
15
380
381
H
H
SCH3
SCH3
40-As(O)(OH)2
20-As(O)(OH)2
5.6ꢀ2.1
1.5ꢀ0.3
9.1ꢀ3.4
2.3ꢀ0.5
16
17
371
385
H
H
22.5ꢀ6.7
21.6ꢀ4.3
40-As(O)(OH)2
20-As(O)(OH)2
>100
>100
18
19
20
21
386
518
517
516
H
>100
1.1ꢀ0.5
>100
>100
2.0ꢀ0.8
>100
CCl3
CCl3
CCl3
40-As(O)(OH)2
20-As(O)(OH)2
>100
>100
4-(40-Aminophenylazo)phenylarsonic acid
4-Aminophenylarsonic acid
2-Aminophenylarsonic acid
>100
>100
>100
Cells were treated with compounds in Table 1 in 96-well plates and incubated for 48 h at 37 ꢂC. The cytotoxic activity was determined using MTT
assays17 and the IC50 values were calculated using Graphpad Prism software. The starting materials 4-(40-aminophenylazo)phenylarsonic acid,
4-aminophenylarsonic acid and 2-aminophenylarsonic acid were not active (IC50 values>100 mM).

X.-P. Liu et al. / Bioorg. Med. Chem. Lett. 13 (2003) 581–583
583
14, 17, and 20) or 2-aminophenylarsonic acid (to give
12, 15, 18, and 21) in 2-propanol (40–80 mL) was heated
to reflux for 8–24 h in the presence of concentrated HCl
(2–4 drops) as a catalys,14,15 to give the expected com-
pounds. All of compounds gave satisfactory analytical
and spectroscopic data. Selected data were listed.16
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The cytotoxic activities of the compounds were eval-
uated against two ALL cell lines, NALM-6 (B-lineage
ALL) and MOLT-3 (T-lineage ALL) using MTT
assay.17 The IC50 values were determined using Graph-
pad Prism software, version 2.0 (San Diego, CA, USA).
The comparison of the IC50 values (Table 1) revealed
significant information regarding the structure–activity
relationships affecting the antileukemic activity of this
series of compounds. The antileukemic activity of the
phenylarsonic acid-containing compounds was strongly
dependent on the type of ligand (quinazoline, pyri-
midine, and purine) and nature of the arsonic acid sub-
stituent present. Three compounds containing
2-methylthiopyrimidine (13, 14, and 15) showed super-
ior cytotoxic activity than the compounds containing
6,7-dimethoxyquinazoline (10, 11, and 12), purine (16,
17, and 18) or 2-trichloromethylquinazoline (19, 20, and
21). The compounds containing 4-(4-phenylazo)phenyl-
arsonic acid (10, 13, 16, and 19) also showed excellent
cytotoxic activities whose IC50 values ranged from 1.1 to
22.5 mM against NALM-6 cells and from 2.0 to 21.6 mM
against MOLT-3 cells. The presence of arsonic acid at
ortho-position (12, 15, 18, and 21) rather than para-posi-
tion (11, 14, 17, and 20) was associated with significantly
better cytotoxic activity. Although 15 containing
2-methylthiopyrimidine and ortho-position asonic acid
showed excellent cytotoxic activity, other compounds
with ortho-position asonic acid were surprisingly inac-
tive. Combination of 2-trichloromethylquinazoline and
4-phenylazophenylarsonic acid (19) yielded the best
compound with an IC50 value of 1.1ꢀ0.5 mM against
NALM-6 cells and 2.0ꢀ0.8 mM against MOLT-3 cells
(Table 1).
14. Yuki, H.; Kishikawa, T.; Tohira, Y.; Watanabe, K. Chem.
Pharm. Bull. 1967, 15, 1052.
15. Andres, R. J.; Hamilton, C. S. J. Am. Chem. Soc. 1945,
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16. Analytical data for lead compounds:
2-Methylthio-4-(20-phenylarsonic acid)aminopyrimidine (15,
PHI-P381). Yield 86%, mp 225–228 ꢂC. 1H NMR (DMSO-d6)
d 10.94 (s, 1H, –NH), 8.46 (d, 1H, J=8.1 Hz, 5-H), 8.21–7.23
(m, 4H, 30, 40, 50, 60-H), 6.47 (d, 1H, J=8.1 Hz, 6-H), 2.49 (s,
3H,-SCH3), 13C NMR (DMSO-d6) d 170.7 (C-2), 159.0 (C-4),
156.1 (C-6), 141.7 (C-5), 133.9 (C-10), 131.5 (C-60), 123.3,
121.9, 121.0 (C-30, 40, 50), 103.6 (C-20), 13.8 (–SCH3). UV
(MeOH) lmax 243 nm (e=1030). IR (KBr) n,max 3550-3420,
2638, 1664, 1583 cmꢁ1. Found: C, 35.25, H, 3.62, N, 10.93.
.
C11H12AsN3O3S HCl requires: C, 35.01, H, 3.45, N, 11.14%.
acid]-
2-Trichloromethyl-4-[40-(400-phenylazo)phenylarsonic
The p53 deficient NALM-6 cell line was previously
shown to be resistant to multiple chemotherapeutic
agents, including alkylating agents, steroids, topo-
isomerase I inhibitors, topoisomerase II inhibitors, vin-
cristine and taxol.18,19 Therefore, the exquisite
sensitivity of NALM-6 cells to arsonic acid derivatives
is quite encouraging. Thus, further development of these
lead compounds (15 and 19) may provide the founda-
tion for more effective treatment programs for therapy-
refractory or recurrent ALL patients.
aminoquinazoline (19, PHI-P518). Yield 77%, mp>300 ꢂC. 1H
NMR (DMSO-d6) 00 d 10.94 (s, 1H,-NH), 8.45 (d, 2H,
00
00 00
J2 ,3 =9.0 Hz, 2 , 6 -H), 8.08–7.77 (m, 4H, 5, 6, 7, 8-H), 7.95
(s, 4H, 20, 30, 50, 60-H), 6.88 (d, 2H, J3 ,2 =9.0 Hz, 3 , 5 -H).
13C NMR (DMSO-d6) d 159.9 (C-2), 158.4 (C-4), 154.7 (C-10),
154.5 (C-400), 149.1 (C-40), 147.7 (C-100), 132.8 (C-9), 131.7 (C-
10), 131.6 (C-200, 600), 128.6 (C-30), 128.5 (C-50), 126.2 (C-6,7),
123.8 (C-5), 123.1 (C-300, 500), 122.4 (C-20, 60), 122.2 (C-8),
114.4, 97.9 (C–CCl3). UV (MeOH) lmax 205 nm (e=5407). IR
(KBr) nmax 3441.6, 3013.3, 2292.2, 1630.7, 1598.2, 1538.6,
1408.4, 1262.0, 1169.9, 1099.4, 817.5 cmꢁ1. MS (EI) m/z 565
(M+, 5), 564 (M+ꢁ1, 7), 459 (54), 395 (12), 341 (53), 306
(100). Found: C, 35.59, H, 2.66, N, 9.88. C21H15AsCl3-
00
00
00 00
References and Notes
.
N5O3 4HCl requires: C, 35.54, H, 2.68, N, 9.87%.
17. Narla, R. K.; Liu, X. P.; Myers, D. E.; Uckun, F. M. Clin.
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Trigg, M. E.; Tubergen, D. G.; Nachman, J.; Steinherz, P. G.;
Sensel, M. G.; Reaman, G. H. Blood 1997, 90, 28.
2. Uckun, F. M.; Herman-Hatten, K.; Crotty, M. L.; Sensel,
M. G.; Sather, H. N.; Tuel-Ahlgren, L.; Sarquis, M. B.; Bos-
trom, B.; Nachman, J. B.; Steinherz, P. G.; Gaynon, P. S.;
Heerema, N. Blood 1998, 92, 810.
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Waddick, K. G.; Ahlgren, L. T.; Chelstrom, L. M.;
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Aeppli, D.; Sladek, N. E. Leuk. Lymphoma 1994, 13, 417.