Schiff bases of 3-formylchromone as thymidine phosphorylase inhibitors

Article abstract of DOI:10.1016/j.bmc.2009.03.020

3-Formylchromone (1), 3-methyl-7-hydroxychromone (2) and Schiff bases of 3-formylchromone 3-19 have been synthesized and their anti-thymidine phosphorylase inhibitory activity was evaluated. Compounds 1-19 showed a varying degree of thymidine phosphorylase inhibition with IC₅₀ values 19.77 ± 3.25 to 480.21 ± 2.34 μM. Their activity was compared with the standard 7-deazaxanthine (IC₅₀ = 39.28 ± 0.76 μM). Compound 12 showed an excellent thymidine phosphorylase inhibitory activity with an IC₅₀ value of 19.77 ± 3.25 μM, better than the standard. Compound 4 also showed an excellent inhibitory activity (IC₅₀ = 40.29 ± 4.56 μM). The parent 3-formylchromone (1) and 3-methyl-7-hydroxychromone (2) were found to be inactive. The structures of the compounds were elucidated by using spectroscopic techniques, including ¹H NMR, EI MS, IR, UV and elemental analysis.

Full text of DOI:10.1016/j.bmc.2009.03.020

Bioorganic & Medicinal Chemistry 17 (2009) 2983–2988
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Schiff bases of 3-formylchromone as thymidine phosphorylase inhibitors
a
a
b
a
Khalid Mohammed Khan a, , Nida Ambreen , Sajjad Hussain , Shahnaz Perveen , M. Iqbal Choudhary
*
a H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
b PCSIR Laboratories Complex, Karachi, Shahrah-e-Dr. Salimuzzaman Siddiqui, Karachi-75280, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
3-Formylchromone (1), 3-methyl-7-hydroxychromone (2) and Schiff bases of 3-formylchromone 3–19
Received 21 December 2008
Revised 7 March 2009
Accepted 11 March 2009
Available online 14 March 2009
have been synthesized and their anti-thymidine phosphorylase inhibitory activity was evaluated. Com-
pounds 1–19 showed
19.77 3.25 to 480.21 2.34
(IC50 = 39.28 0.76 M). Compound 12 showed an excellent thymidine phosphorylase inhibitory activity
with an IC50 value of 19.77 3.25 M, better than the standard. Compound 4 also showed an excellent
inhibitory activity (IC50 = 40.29 4.56 M). The parent 3-formylchromone (1) and 3-methyl-7-hydrox-
a
varying degree of thymidine phosphorylase inhibition with IC50 values
l
M. Their activity was compared with the standard 7-deazaxanthine
l
l
Keywords:
l
3-Formylchromone
3-Methyl-7-hydroxychromone
Schiff bases
Thymidine phosphorylase inhibition
7-Deazaxanthine
ychromone (2) were found to be inactive. The structures of the compounds were elucidated by using
spectroscopic techniques, including 1H NMR, EI MS, IR, UV and elemental analysis.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
well known example is 5-chloro-6-[1-(2-iminopyrrolidinyl)
methyl] uracil hydrochloride (thymidine phosphorylase inhibitor)
Thymidine phosphorylase (EC 2.4.2.4) is an angiogenic factor
that exerts its angiogenic effect by stimulating the endothelial cell
migration. This has been identified as a potential target in the
development of anti-cancer drugs.1 Thymidine phosphorylase
catalyses the hydrolysis (reversible phosphorylation) of thymidine
into thymine and 2-deoxyribose-1-phosphate. This enzyme also
has a transferase activity, whereby 2-deoxyribose is transferred
from the 20-deoxynucleoside to another base.2 This enzyme is nor-
mally expressed in blood platelets and human placenta, and was
found to be produced by different cell types in culture, such as hu-
man foreskin fibroblasts and vascular smooth muscle cells. Abnor-
mally the level of thymidine phosphorylase is highly expressed in
various pathological disorders including pancreatic, gastric carci-
noma, colon carcinoma, uterine sarcoma, uterine leiomuoma, renal
carcinoma, breast and lung cancers, astrocytic tumors, cervical
intraepithelial neoplasia, gastric carcinoma, carcinomas of the
stomach, colon, ovary and bladder, Kaposi sarcoma, atherosclero-
sis, and in various inflammatory diseases.3 Anti-thymidine phos-
phorylase is a form of targeted therapy that uses drugs or other
substances to stop tumors from inducing the formation of new
blood vessels. Identification of effective inhibitors of thymidine
phosphorylase is, therefore, a need for the treatment of various
types of neoplastic and non-neoplastic diseases.
with IC50 value of 35 nm.4 In the subsequent paper from same
group (Matsushita et al.) showed that thymidine phosphorylase
inhibitor suppresses tumor growth in xenograft nude mice, in-
creased apoptotic index and suppress liver metastasis of KB/TP
cells.5 Based on these studies, thymidine phosphorylase inhibitor
was suggested for combination therapy with trifluorothymidine
(TFT), an anti-tumor agent that is rapidly inactivated by thymidine
phosphorylase.12 The success of TAS-102 (A combination of TPI and
TFT) in phase 1 preclinical trials have encourage us and others to
synthesize and evaluate non-nucleoside based compounds for thy-
midine phosphorylase inhibition that may provide better lead in
drug design against thymidine phosphorylase.
The chromone moiety forms an important component of phar-
macophores of a number of biologically active molecules of syn-
thetic as well as natural origin. Many of them have useful
medicinal applications. Consequently, chromone chemistry contin-
ues to draw considerable attention of synthetic organic and medic-
inal chemists.13 Chromones are widely distributed in nature,
especially in the plant kingdom, and a wide spectrum of useful
properties of biological importance are associated with them.14
Chromone derivatives have been of special interest to organic syn-
thesis due to their biological activities including antimycobacterial,
antifungal, anticonvulsant, antimicrobial and mushroom tyrosi-
nase inhibition activities.15–17 These derivatives also serve as inter-
mediates to many products of fine chemical industries such as
pharmaceuticals, agrochemicals and dyestuffs.18
Several potent thymidine phosphorylase inhibitors have been
reported ranging from micro to nano-molar activities.4–11 The best
As a part of our lead discovery program, we screened a library
of 3-formylchromone and its derivatives for their thymidine
* Corresponding author. Tel.: +92 21 4824910; fax: +92 21 4819018 9.
E-mail addresses: hassaan2@super.net.pk, khalid.khan@iccs.edu (K.M. Khan).
0968-0896/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2009.03.020

2984
K. M. Khan et al. / Bioorg. Med. Chem. 17 (2009) 2983–2988
phosphorylase inhibitory activity. Herein we report 3-formylchro-
mone and its derivatives as a new class of potential thymidine
phosphorylase inhibitors.
O
O
+
H
RNH2
CH NR
O
1
O
O
3-19
2. Results and discussion
2.1. Chemistry
Scheme 2.
related to compound 12 without a para-methyl substitution on
aromatic ring, was found to be completely inactive suggesting that
a para-methyl substitution is essential for activity. Structurally
similar compound 6 in which a meta-methyl group was present in-
stead of a meta-methoxy group and absence of para-methyl group
on the aromatic ring found to be about 3.5 time less active
3-Formylchromone was prepared by the Vilsmeier–Haack syn-
thesis (Scheme 1).19 Schiff bases of 3-formylchromone were pre-
pared by a condensation reaction of 3-formylchromones (1) with
a variety of aromatic and aliphatic amines in ethanol (Scheme 2).
The preparation of Schiff’s bases was carried out by stirring the
mixture of 3-formyl chromone (1) (1 mmol) with substituted aro-
matic and aliphatic amines (1 mmol) in ethanol. The progress of
reaction was monitored by TLC. The resulting product was recrys-
tallized from ethanol.
3-Methyl-7-hydroxychromone (2) was prepared by reacting
resorcinol with ethyl acetoacetate in the presence of phosphorous
pentoxide in refluxing ethanol (Scheme 3). In a typical reaction, to
resorcinol (4.5 mmol) in dry ethanol (10 ml), ethyl acetoacetate
(4.5 mmol) and phosphorus pentoxide (4.5 mmol) was added
slowly with intensive stirring with heating. The solid was filtered
off and filtrate was evaporated to afford crude 3-methyl-7-hydrox-
ychromone (2). The crude solid product was recrystallized from
ethanol.
(IC50 = 67.32 3.56 lM) than compound 12 suggesting that meth-
oxy residue on aromatic ring at particular position plays a vital role
in thymidine phosphorylase inhibitory activity. Comparison of
activity of compounds 4 and 5 demonstrated that the replacement
of an ortho chloro group with carbonyl phenyl moiety results in a
sharp decline in activity.
In conclusion, varyingly substituted Schiff’s bases 3–19 along
with parent 3-formyl chromone (1) and 3-methyl-7-hydroxychro-
mone (2) were synthesized and screened for their thymidine phos-
phorylase inhibitory potential. It was found that compounds 4 and
12 posses excellent activities, where compound 12 showed a better
inhibitory activity than the standard 7-deazaxanthine, whereas,
compound 4 exhibited an activity comparable to the standard.
Apparently substitution on the aromatic ring from amine part
might be responsible for the thymidine phosphorylase inhibitory
activity. Compounds 4 and 12, most active compounds of this ser-
ies, can therefore serve as lead compounds for further studies.
The structures of the synthesized compounds were determined
by using spectroscopic techniques which include 1H NMR, EI MS, IR
and UV spectroscopy. Elemental analysis results were also found to
be satisfactory.
2.2. Biology
2.3. Determination of IC50 assay
3-Formylchromone (1), 3-methyl-7-hydroxychromone (2) and
Schiff’s bases of 3-formylchromone 3–19 were synthesized and
randomly screened for their thymidine phosphorylase inhibitory
potential, according to literature protocol.20
Compounds 1–19 demonstrated a varying degree of thymidine
phosphorylase inhibitory activity with IC50 values in the range of
The concentration of test compounds that inhibited the enzyme
activity by 50% (IC50 values) were determined by monitoring the
effect of increasing concentrations of compounds in the assay de-
scribed below. The IC50 values were calculated from inhibition data
by using EZ-Fit Enzyme Kinetic Program (Perrella Scientific Inc.,
Amherst, USA).
19–480
ing an IC50 value of 39.28 0.76
(IC50 = 19.77 3.25 M) was found to be the most active member
lM, if compared with standard drug 7-deazaxanthine hav-
lM. Compound 12
2.4. Thymidine phosphorylase assay protocol
l
of the series, more potent than the standard. Compound 4 also
showed an excellent anti-thymidine phosphorylase activity with
TP/PD-ECGF (E. coli thymidine phosphorylase (Sigma T6632)
activity was determined by measuring the absorbance at 290 nm
spectrophotometrically. The activity was performed as per manu-
facturer instruction. The original method described by Krenitsky
(Krenitsky et al., 1979)20 was modified. Briefly, total reaction mix-
an IC50 = 40.29 4.56
lM. Compounds 9, 10, 16 and 17 showed
IC50 values greater than 100
lM, therefore considered to be inac-
tive. Remaining compounds 1, 2, 7, 8, 11, 13–15, 18 and 19 were
found to be largely inactive against the enzyme (Table 1).
ture of 200
7.4), 30 l of enzyme (E. coli thymidine phosphorylase (Sigma
T6632) at concentration 0.05 and 0.002 U, respectively, were incu-
bated with 5 l of test materials for 10 min at 25 °C in microplate
reader. After incubation, pre read at 290 nm was taken to deduce
the absorbance of substrate particles. Substrate (20 l, 1.5 mM)
ll contained 145 ll of potassium phosphate buffer (pH
Limited SAR study suggests that the activity of compounds lar-
gely depends upon the substitution on aromatic ring. Compound
12 with the para methyl and meta methoxy substitutions on phe-
nyl ring showed a highest degree of thymidine phosphorylase
inhibitory activity, whereas compound 4 with the ortho and para
dichloro substitutions on phenyl moiety showed an activity similar
to the standard. However, parent compound 3-formylchromone (1)
and chromone 2 found to be completely inactive. The activity pat-
tern suggest that inhibitory potential of 3-formylchromone (1) en-
hances when it converts into Schiff bases. Compound 13 which is
l
l
l
was dissolved in potassium phosphate buffer was immediately
added to plate and continuously read after 10, 20, and 30 min in
microplate reader. All assays were performed in triplicate.
3. Experimental
O
Melting points were determined on a Büchi 434 melting point
apparatus and were uncorrected. NMR was performed on a Bruker
AM 300, 400 and 500 MHz, respectively. CHN analysis was per-
formed on a Carlo Erba Strumentazion-Mod-1106, Italy. Ultraviolet
(UV) spectra were recorded on Perkin–Elmer Lambda-5 UV–vis
spectrometer in MeOH. Infrared (IR) spectra were recorded on JASCO
OH
CH3
Anhydrous DMF, POCl3
CHO
O
O
1
Scheme 1.

K. M. Khan et al. / Bioorg. Med. Chem. 17 (2009) 2983–2988
2985
Table 1
Table 1 (continued)
Thymidine phosphorylase inhibitory activities of 3-formylchromone (1) and its Schiff
bases 3–19
Compound No.
R1
IC50 SEMa
(lM)
Compound No.
R1
IC50 SEMa
(lM)
N
19
N.A.b
O
3
145.56 3.25
40.29 4.56
—
7-Deazaxanthinec
SEM is the standard error of the mean.
N.A.—Not active.
7-Deazaxanthine standard inhibitor for thymidine phosphorylase.
39.28 0.76
-HN
a
Cl
b
c
4
5
Cl
IR-A-302 Spectrometer as KBr disc. Electron impact mass spectra (EI
MS) were recorded on a Finnigan MAT-311A, Germany. Thin layer
chromatography (TLC) was performed on pre-coated silica gel glass
plates (Kieselgel 60, 254, E. Merck, Germany). Chromatograms were
visualized by UV at 254 and 365 nm or by iodine vapors.
Cl
75.93 1.28
O
3.1. Procedure for the synthesis of 3-formylchromones (1)
CH3
6
7
67.32 3.56
N.A.b
To the dry dimethylformamide (12.32 ml) in a three necked
flask, POCl3 (49 mmol) was added slowly with intensive stirring
at 50 °C. Heating and stirring was continued for 2 h at 45–55 °C.
The solution of 2-hydroxyacetophenone (10 mmol) in DMF
(3.57 ml) was then slowly added under stirring at 50 °C. The stir-
ring was continued for 2 h, at 55–60 °C. After cooling, the mixture
was kept over night at room temperature and diluted slowly by
adding crushed ice (300 g) and stirred again for 6 h. The crystals
were filtered off and recrystallized from alcohol.
CH3
H3C
8
9
N.A.b
H3C
H3C
Yield: 82%; mp = 142 °C; Rf: 0.56 (EtOAc/Hex, 3:7); UV (MeOH);
kmax 203.6 (log
e
= 4.41) nm; IR (KBr): mmax 3057.4 (br, ArCH),
768.1, 1697 (C@O) cmꢀ1
.
1H NMR (400 MHz, CD3OD) d: 10.18 (s,
1H, CHO), 8.30 (s, 1H, H-2), 8.14 (d, J5,6 = 7.7 Hz, 1H, H-5), 7.61 (d,
J8,7 = 7.6 Hz, 1H, H-8), 7.57 (t, J7,6 = J7,8 = 7.6 Hz, 1H, H-7), 7.47 (t,
J6,7 = J6,5 = 7.5 Hz, 1H, H-6); EI MS: m/z (rel. abund.%) 174 (M+, 2.3),
145 (100), 120 (31), 104 (53), 92 (31); Anal. Calcd for C10H6O3:
(174) Found: C, 68.96; H, 3.48; Requires: C, 68.97; H, 3.47.
480.21 2.34
O2N
10
11
–(–CH2)2–
–C(CH3)3
149.78 5.21
N.A.b
3.2. Procedure for the synthesis of 3-methyl-7-
hydroxychromone (2)
OCH3
CH3
12
13
14
19.77 3.25
3-Methyl-7-hydroxychromone (2) was prepared by reacting
resorcinol with ethyl acetoacetate in the presence of phosphorous
pentaoxide in refluxing ethanol (Scheme 3). In a typical reaction, to
resorcinol (4.5 mmol) in dry ethanol (10 ml), ethyl acetoacetate
(4.5 mmol) and phosphorus pentaoxide (4.5 mmol) was added into
slowly with intensive stirring with heating. Refluxing and stirring
was continued for 2 h for completion of reaction, the progress of
reaction was monitored by TLC. The solid was filtered off and fil-
trate was evaporated to afford solid crude 3-methyl-7-hydroxychr-
omone (2). The crude product was recrystallized from alcohol.
Yield = 82%; mp = 142 °C; Rf = 0.48 (EtOAc/Hex, 3:7); UV
OCH3
N.A.b
H3CO
N.A.b
NO2
HOOC
15
16
N.A.b
(MeOH); kmax 322.4 (log
e = 4.8) nm; IR (KBr): mmax 1721.5,
3424.2 cmꢀ1 1H NMR (300 MHz, CDCl3) d: 7.62 (d, J5,6 = 8.7 Hz,
;
1H, H-5), 6.81 (dd, J6,8 = 2.3 Hz, J6,5 = 8.7 Hz, 1H, H-6), 6.70 (s, 1H,
H-8), 6.10 (s, 1H, H-2), 2.41 (s, 3H, CH3), EI MS: m/z (rel. abund.%)
176 (M+, 90.67), 148 (100), 120 (16.66), 105 (3.22), 91 (28.22);
Anal. Calcd for C10H8O3: (176) Found: C, 68.19; H, 4.56. Requires:
C, 68.18; H, 4.58.
472.60 3.76
OH
HO
O
17
18
340.01 2.78
HO
OH
HO
O
H3C
P2O5
+
N
C2H5O
EtOH
CH3
O
O
2
N.A.b
N
Scheme 3.

2986
K. M. Khan et al. / Bioorg. Med. Chem. 17 (2009) 2983–2988
106 (100), 91 (34); Anal. Calcd for C17H13NO2: (263) [Found:
C, 77.54; H, 4.96; N, 5.34. Requires: C, 77.55; H, 4.98; N,
5.32].
4. General procedure for the synthesis of Schiff bases of 3-
formylchromones 3–19
The preparation of Schiff bases was carried out by stirring the
mixture of 3-formylchromone (1) (1 mmol) with substituted aro-
matic and aliphatic amines (1 mmol) in ethanol 2–4 h at 50–
100 °C. The progress of reaction was monitored by TLC. The result-
ing products were recrystallized from alcohol to afford the title
compounds 3–19.
4.5. 3-{[(4-Methylphenyl)imino]methyl}-4H-chromen-4-one
(7)
Yield = 52%; mp: 118 °C; Rf = 0.38 (EtOAc/Hex, 5:5); UV
(MeOH); kmax 387.4 (log
CH), 2920 (CH), 1645.3 (C@O) cmꢀ1
8.50 (s, 1H, H-2), 7.42–7.53 (m, 4H, H-5,6,7, 8), 7.07 (d, J2 ,3
e
= 4.8) nm; IR (KBr):
mmax 3066 (Aromatic
,
1H NMR (400 MHz, CDCl3) d:
0
0
=
4.1. N0-[-(4-Oxo-4H-chromen-3-yl) methylidene]
propanohydrazide (3)
J6 ,5 = 7.2 Hz, 2H, H-20,60), 7.00 (d, J3 ,2 = J5 ,6 = 7.2 Hz, 2H, H-30,50),
6.9 (s, 1H, CH@N), 2.35 (s, 3H, CH3); EI MS: m/z (rel. abund.%)
263 (M+, 100), 248 (6.68), 172 (80.17), 146 (86.26), 120 (29.57),
105 (60.21), 91 (82.82); Anal. Calcd for C17H13NO2: (263) [Found:
C, 77.54; H, 4.96; N, 5.33. Requires: C, 77.55; H, 4.98; N, 5.32].
0
0
0
0
0
0
Yield = 46%; mp = 278 °C; Rf = 0.42 (EtOAc/Hex, 3:7); UV
(MeOH); kmax 200.1 (log
e
= 4.15) nm; IR (KBr): mmax 3447.8 (NH),
3050 (ArCH), 2924 (CH3), 2862 (CH2), 1703 (C@O) cmꢀ1
;
1H NMR
(400 MHz, CD3OD) d: 10.43 (s, 1H, N–H), 8.29 (s, 1H, H-2), 8.18
(d, J5,6 = 8.4 Hz, 1H, H-5), 7.81 (td, J7,5 = 1.5 Hz, J7,6 = J7,8 = 8.4 Hz,
1H, H-7), 7.64 (d, J8,7 = 8.4 Hz, 1H, H-8), 7.52 (td, J6,8 = 1.5,
J6,5 = J6,7 = 8.4 Hz, 1H, H-6), 4.50 (s, 1H, CH@N), 2.31–2.36 (m, 2H,
4.6. 3-{[(2,6-Dimethylphenyl)imino]methyl}-4H-chromen-4-
one (8)
Yield = 53%; mp = 84 °C; Rf = 0.61(EtOAc/Hex, 3:7); UV (MeOH);
0
0
CH2), 1.20 (t, J3 ,2 = 7.6 Hz, 3H, CH3); EI MS: m/z (rel. abund.%)
244 (M+, 12), 188 (12), 172 (100), 120 (93), 92 (26), 92 (31); Anal.
Calcd for C13H12N2O3: (244) [Found: C, 69.14; H, 5.37; N, 5.77. Re-
quires: C, 69.12; H, 5.39; N, 5.76].
kmax 203.2 (log
e
= 4.2) nm; IR (KBr): mmax 3066 (ArCH), 2920 (Ali-
phatic CH), 1645.3 (C@O), 1291.1 (C–N) cmꢀ1
;
1H NMR (400 MHz,
CD3OD) d: 8.31 (s, 1H, H-2), 8.18 (d, J5,6 = 8.4 Hz, 1H, H-5) 7.81
(td, J7,5 = 1.4 Hz, J7,6 = J7,8 = 8.4 Hz, 1H, H-7), 7.64 (d, J8,7 = 8.4 Hz,
0
0
1H, H-8), 7.52 (t, J6,5 = J6,7 = 8.4 Hz, 1H, H-6), 7.07 (d, J3 ,4
=
4.2. 3-{[(2, 4-Dichlorophenyl)imino]methyl}-4H-chromen-4-
one (4)
J5 ,4 = 8.5 Hz, 2H, H-30, 50), 6.56 (t, J4 ,3 = J4 ,5 = 8.5 Hz, 1H, H-40),
4.50 (s, 1H, CH@N), 2.35 (s, 6H, 2CH3); EI MS: m/z (rel. abund.%)
276.9 (M+, 64.62), 261.8 (22.85), 172 (57.44), 145.9 (40.40), 120
(100), 105 (67.30); Anal. Calcd for C18H15NO2: (277) [Found: C,
77.95; H, 5.46; N, 5.06. Requires: C, 77.96; H, 5.45; N, 5.05].
0
0
0
0
0
0
Yield = 52%; mp = 132 °C; Rf = 0.48 (EtOAc:Hex, 3:7); UV
(MeOH); kmax 207 (log
1594 (Ar) cmꢀ1 1H NMR (300 MHz, CD3OD) d: 8.70 (s, 1H, H-2),
7.71 (s, 1H, H-30), 7.40–7.90 (m, 4H, H-5,6,7,8), 7.03 (d,
e = 4.19) nm; IR (KBr): mmax 1647.1 (C@O),
;
4.7. 3-{[(2-Methyl-6-nitrophenyl) imino] methyl}-4H-
chromen-4-one (9)
J5 ,6 = 7.5 Hz, 1H, H-50), 6.78 (d, J6 ,5 = 7.5 Hz, 1H, H-60), 5.90 (s,
1H, CH@N); EI MS: m/z (rel. abund.%) 316.8 (M+, 48.92), 281.8
(62.60), 213 (3.97), 172 (100), 146 (24.53), 120.9 (47.83), 91.9
(31.69); Anal. Calcd for C16H9Cl2NO2: (387) [Found: C, 60.42; H,
2.83; N, 22.87. Requires: C, 60.40; H, 2.85; N, 22.89].
0
0
0
0
Yield = 63%; mp = 145 °C; Rf = 0.46 (EtOAc/Hex, 3:7); UV
(MeOH); kmax 216 (log
3050 (ArCH), 2924.1 (CH3) cmꢀ1
8.19 (s, 1H, H-2), 7.81 (dd, J5,7 = 1.9, J5,6 = 8.2 Hz, 1H, H-5), 7.62
e
= 4.24) nm; IR (KBr): mmax 1697 (C@O),
;
1H NMR (300 MHz, CD3OD) d:
(d, J5 ,4 = 8.5 Hz, 1H, H-50), 7.47 (dt, J6,8 = 1.5, J6,5 = J6,7 = 8.2 Hz,
4.3. 3-{[(2-Benzoyl-4-chlorophenyl) imino] methyl}-4H-
chromen-4-one (5)
0
0
0
0
0
0
1H, H-6), 7.28 (d, J8,7 = 7.1 Hz, 1H, H-8), 6.95 (dd, J3 ,5 = 2.3, J3 ,4
=
7.1 Hz, 1H, H-30), 6.93 (s, 1H, CH@N), 6.51 (t, J7,6 = J7,8 = 7.1 Hz,
1H, H-7), 6.30 (d, J4 ,3 = 6.2 Hz, 1H, H-40); EI MS: m/z (rel. abund.%)
292 (M+, 13), 172 (100), 248 (6), 145 (9), 120 (14), 105 (5), 92 (32);
Anal. Calcd for C17H12N2O4: (308) [Found: C, 66.22; H, 3.93; N, 9.08.
Requires: C, 66.23; H, 3.92; N, 9.09].
Yield = 76%; mp = 138 °C; Rf = 0.52 (EtOAc:Hex, 3:7); UV
0
0
(MeOH); kmax 229.4 (log
2920 (CH), 1645.3 (C@O), 1291.1 (CN) cmꢀ1
CDCl3) d: 8.51 (s, 1H, H-2), 8.29 (dd, J5,7 = 1.6, J5,6 = 7.9 Hz, 1H, H-
e
= 4.0) nm; IR (KBr): mmax 3066 (br, CH),
;
1H NMR (400 MHz,
0
0
5), 7.93 (t, J7, 8 = J7,6 = 7.3 Hz, 1H, H-7), 7.81 (d, J6 ,5 = 7.3 Hz, 1H,
H-60), 7.71–7.78 (m, 5H, H-8,30,200,400,600), 7.44–7.48 (m, 3H, Ar-H-
4.8. 3-{[(2-{[-(4-Oxo-4H-chromen-3-yl)methylidene]amino}
ethyl)imino] methyl}-4H-chromen-4-one (10)
6,300,500), 7.36 (d, J5 ,6 = 7.3 Hz, 1H, H-50), 6.91 (s, 1H, CH@N); EI
MS: m/z (rel. abund.%) 386 (M+, 27), 309 (8), 120 (31), 281 (3),
229 (31), 151 (22), 104 (53), 77 (100); Anal. Calcd for C23H14ClNO3:
(387) [Found: C, 71.22; H, 3.65; N, 3.62. Requires: C, 71.23; H, 3.64;
N, 3.61].
0
0
Yield = 23%; mp = 188 °C; Rf = 0.35 (EtOAc/Hex, 3:7); UV
(MeOH); kmax 353 (log
1677.1 (C@N), 3073.7 (Ar C@C) cmꢀ1
d: 8.20 (s, 2H, H-2/20), 7.76 (dd, J5,7 = J5 ,7 = 3.1 Hz, J5,6 = J5 ,6
e
= 4.12) nm; IR (KBr): mmax 1646.1 (C@O),
;
1H NMR (400 MHz, CD3OD)
0
0
0
0
=
0
0
0
0
0
4.4. 3-{[(3-Methylphenyl) imino] methyl}-4H-chromen-4-one
(6)
7.6 Hz, 2H, H-5/50), 7.36 (t, J7,6 = J7,8 = J7 ,6 = J7 ,8 = 7.6 Hz, 2H, H-7/
70), 6.98 (d, J8,7 = J8 ,7 = 8.1 Hz, 2H, H-8/80), 6.83 (t, J6,5 = J6,7 = J6 ,5
=
0
0
0
0
J6 ,7 = 7.4 Hz, 2H, H-6/60), 6.80 (s, 2H, CH@N), 3.89 (s, 4H,
(-CH2CH2); EI MS: m/z (rel. abund.%) 372 (M+, 8.65), 252 (2.49),
216 (80.41), 187 (97.81), 121 (80.22); Anal. Calcd for C22H16N2O4:
(372) [Found: C, 70.94; H, 4.34; N, 7.50. Requires: C, 70.96; H,
4.33; N, 7.52].
0
0
Yield = 60%; mp = 116 °C; Rf = 0.46 (EtOAc/Hex, 3:7); UV
(MeOH); kmax 193 (log
1602.5 (C@N), 3064.9 (Ar C@C) cmꢀ1
d: 8.50 (s, 1H, H-2), 7.71 (dd, J5,7 = 1.5 Hz, J5,6 = 8.4 Hz, 1H, H-5),
e
= 4.2) nm; IR (KBr): mmax 1646.4 (C@O),
;
1H NMR (400 MHz, CDCl3)
0
0
7.49 (t, J7,6 = J7,8 = 8.4 Hz, 1H, H-7), 7.31 (d, J6 ,5 = 7.2 Hz, 1H, H-
60), 7.28 (s, 1H, H-20), 7.11 (dd, J5 ,6 = 0.9 Hz, J5 ,4 = 5.8 Hz, 1H, H-
4.9. 3-[Bis(tert-butylamino)methyl]-4H-chromen-4-one (11)
0
0
0
0
50), 7.04 (d, J4 ,5 = 6.2 Hz, 1H, H-40), 6.91 (d, J8,7 = 8.4 Hz, 1H, H-8),
6.80 (t, J6,5 = J6,7 = 8.4 Hz, 1H, H-6), 5.71 (s, 1H, CH@N), 2.30 (s,
3H, CH3); EI MS: m/z (rel. abund.%) 262 (M+, 10.1), 145 (60.9),
0
0
Yield = 46%; mp = 138 °C; Rf = 0.45 (EtOAc/Hex, 5:5); UV
(MeOH); kmax 202.6 (loge = 4.3); IR (KBr): mmax 1641.1 (C@N),

K. M. Khan et al. / Bioorg. Med. Chem. 17 (2009) 2983–2988
2987
2972 (Ar CH), 3074 (ArCH) cmꢀ1
;
1H NMR (500 MHz, CD3OD) d:
(96.35), 91.9 (100); Anal. Calcd for C17H11NO4: (293) [Found: C,
69.73; H, 3.80; N, 4.75. Requires: C, 69.62; H, 3.78; N, 4.78].
8.30 (s, 1H H-2), 7.98 (dd, J5,7 = 1.0 Hz, J5,6 = 7.6 Hz, 1H, H-5), 7.55
(td, J7,5 = 1.5, J7,6 = J7,8 = 7.8 Hz, 1H, H-7), 7.29 (d, J 8,7 = 7.8 Hz, 1H,
H-8), 7.11 (t, J6,8 = 3.1, J6,7 = J6,5 = 7.8 Hz, 1H, H-6), 5.80 (s, 1H,
CH@N), 1.54 (s, 9H, 3CH3); EI MS: m/z (rel. abund.%) 229 (M+,
16), 200 (47), 172 (75), 121 (96); Anal. Calcd for C14H15NO2:
(229) [Found: C, 73.32; H, 6.58; N, 6.12. Requires: C, 73.34; H,
6.59; N, 6.11].
4.14. 3-{[(1-Benzyl-2-hydroxyethyl)imino]methyl}-4H-
chromen-4-one (16)
Yield = 63%; mp = 110 °C; Rf = 0.52 (EtOAc/Hex, 3:7); UV
(MeOH); kmax 206.8 (log
e
= 4.12) nm; IR (KBr): mmax 3066 (ArCH),
2920 (CH), 1645.3 (C@O) cmꢀ1
,
1H NMR (400 MHz, CDCl3) d: 8.01
4.10. 3-{[(3-Methoxy-4-methylphenyl) imino] methyl}-4H-
(s, 1H, H-2), 7.50–8.24 (m, 4H, ArH), 7.02–7.40 (m, 4H, H-5,6,7,8),
chromen-4-one (12)
6.56 (s, 1H, CH@N), 3.57–3.85 (m, 1H, CH2CHCH2–OH), 3.07 (d,
0
0
J1 ,2 = 5.5 Hz, 2H, CH2CHCH2–OH), 2.91 (m, 2H, CH2–CHCH2OH), EI
MS: m/z (rel. abund.%) 307 (M+, 5.16), 276 (16.85), 215.9 (41.09),
172 (23.12), 159 (50.14), 145.9 (14.37), 120 (59.07), 105 (16.32);
Anal. Calcd for C19H17NO3: (307) [Found: C, 75.49; H, 5.57; N,
5.65. Requires: C, 74.25; H, 5.58; N, 4.56].
Yield = 72%; mp = 86 °C; Rf = 0.42 (EtOAc/Hex, 3:7); UV (MeOH);
kmax 307.6 (log
(ArCH) cmꢀ1 1H NMR (300 MHz, CD3OD) d: 8.50 (s, 1H, H-2),
7.42–7.90 (m, 4H, H-5,6,7,8), 7.03 (d, J5 ,6 = 7.5 Hz, 1H, H-50), 6.93
e = 4.5) nm; IR (KBr): mmax 1648.5 (C@O), 909.7
;
0
0
(s, 1H, H-20), 6.72 (d, J6 ,5 = 7.5 Hz, 1H, H-60), 6.14 (s, 1H, CH@N),
3.7 (s, 3H, OCH3), 1.27 (s, 3H, CH3); EI MS: m/z (rel. abund.%) 292
(M+, 100), 276 (41.09), 188 (18.29), 172 (57.53), 145.8 (55.69),
120.8 (54.16), 90.9 (11.32); Anal. Calcd for C18H15NO3: (293)
[Found: C, 73.70; H, 5.16; N, 4.80. Requires: C, 73.71; H, 5.15; N,
4.78].
0
0
4.15. 3-{[(3-Hydroxy-2-pyridinyl)imino]methyl}-4H-chromen-
4-one (17)
Yield = 62%; mp = 144 °C; Rf = 0.5 (EtOAc/Hex, 3:7); UV (MeOH);
kmax 209.4 (log
e
= 4.3) nm; IR (KBr):
mmax 1645.3 (C@O), 1291.1 (C–
N), 3066 (ArCH) cmꢀ1
;
1H NMR (300 MHz, DMSO-d6) d: 10.30 (s,
0
0
4.11. 3-{[(3-Methoxyphenyl)imino]methyl}-4H-chromen-4-one
(13)
1H, OH), 8.63 (d, J6 ,5 = 7.2 Hz, 1H, H-60), 8.30 (s, 1H, H-2), 7.49 (t,
J7,8 = J7,6 = 8.1 Hz, 1H, H-7), 7.37 (d, J4 ,5 = 7.2 Hz, 1H, H-40), 7.22
(d, J5,6 = 7.5 Hz, 1H, H-5), 7.09 (t, J6,5 = J6,7 = 7.5 Hz, 1H, H-6), 7.04
0
0
0
0
0
0
Yield = 43%; mp = 178 °C; Rf = 0.35 (EtOAc/Hex, 5:5); UV
(d, J8,7 = 8.1 Hz, 1H, H-8), 6.95 (t, J5 ,6 = J5 ,4 = 7.2 Hz, 1H, H-50),
6.93 (s, 1H, CH@N); EI MS: m/z (rel. abund.%) 265 (M+, 28), 262
(7), 248 (3), 237 (24), 210 (7), 172 (48), 146 (4), 120 (30), 95
(88), 77 (16); Anal. Calcd for C15H10N2O3: (265) [Found: C, 67.69;
H, 4.0; N, 10.30. Requires: C, 67.67; H, 3.79; N, 10.52].
(MeOH); kmax 204 (log
e
= 4.5) nm; IR (KBr): mmax 1205.3 (O-CH3
;
stretch), 908.9 (ArCH) cmꢀ1
1H NMR (300 MHz, CDCl3) d: 8.82 (s,
1H, H-2), 7.97 (dd J5,7 = 1.5 Hz, J5,6 = 8.8 Hz, 1H, H-5), 7.52 (t,
J7,6 = J7,8 = 7.5 Hz, 1H, H-7), 7.28 (d, J6 ,5 = 7.2 Hz, 1H, H-60), 7.09
(d, J8,7 = 8.3 Hz, 1H, H-8), 6.92 (t, J6,5 = J6,7 = 7.5 Hz, 1H, H-6), 6.78
0
0
(s, 1H, H-20), 6.75 (t, J5 ,4 = J5 ,6 = 8.3 Hz, 1H, H-50), 6.65–6.73 (m,
1H, H-40), 6.51 (s, 1H, CH@N), 4.01 (s, 3H, OCH3); EI MS: m/z (rel.
abund.%) 278 (M+, 52.6), 264 (4), 250 (43.85), 120 (77); Anal. Calcd
for C17H13NO3: (279) [Found: C, 73.14; H, 4.66; N, 5.03. Requires: C,
73.11; H, 4.69; N, 5.02].
4.16. 3-[(4-Pyridinylimino) methyl]-4H-chromen-4-one (18)
0
0
0
0
Yield = 60%; mp = 140 °C; Rf = 0.34 (EtOAc/Hex, 5:5); UV
(MeOH); kmax 201.9 (log
1284.4 (C–N) cmꢀ1
e = 4.4) nm; IR (KBr): mmax 1645.3 (C@O),
;
1H NMR (400 MHz, CDCl3) d: 8.68 (s, 1H,
CH@N), 8.52 (s, 1H, H-2), 8.17 (s, 1H, H-20), 7.91 (d, J4 ,5 = 7.2 Hz,
0
0
4.12. 3-{[(2-Methoxy-4-nitrophenyl) imino] methyl}-4H-
1H, H-40), 7.72 (t, J7,8 = J7,6 = 7.5 Hz, 1H, H-7), 7.58 (t,
0
0
0
0
0
0
chromen-4-one (14)
J5 ,4 = J5 ,6 = 7.2 Hz, 1H, H-50), 7.47 (d, J6 ,5 = 7.2 Hz, 1H, H-60), 7.22
(d, J5,6 = 7.5 Hz, 1H, H-5), 7.12 (t, J6,5 = J6,7 = 7.5 Hz, 1H, H-6), 7.02
(d, J8,7 = 8.4 Hz, 1H, H-8); EI MS: m/z (rel. abund.%) 249 (M+, 62),
172 (55), 146 (33), 120 (38); Anal. Calcd for C15H10N2O2: (249)
[Found: C, 71.93; H, 4.04; N, 11.18. Requires: C, 71.99; H, 4.03;
N, 11.19].
Yield = 63%; mp = 268 °C; Rf = 0.46 (EtOAc/Hex, 3:7); UV
(MeOH); kmax 217.2 (log
e
= 5.0) nm; IR (KBr): mmax 1655.5 (C@O),
1589.7 (C@N), 3100.2 (ArCH) cmꢀ1
;
1H NMR (400 MHz, CDCl3) d:
8.50 (s, 1H, H-2), 8.21 (d, J5,6 = 8.1 Hz, 1H, H-5), 7.72 (d,
J5 ,6 = 8.5 Hz, 1H, H-50), 7.70 (t, J7,6 = J7,8 = 7.5 Hz, 1H, H-7), 7.61 (s,
0
0
1H, H-30), 7.43 (d, J8,7 = 8.1 Hz, 1H, H-8), 7.42 (s, 1H, CH@N), 7.40
4.17. 3-[(3-Pyridinylimino) methyl]-4H-chromen-4-one (19)
(t, J6,5 = J6,7 = 8.1 Hz, 1H, H-6), 6.61 (d, J6 ,5 = 8.5 Hz, 1H, H-60),
3.90 (s, 3H, OCH3); EI MS: m/z (rel. abund.%) 323 (M+, 9.39), 308
(41.6), 262 (19.87), 234 (3.68), 172 (100), 120 (60.01), 91 (60);
Anal. Calcd for C17H12N2O5: (324) [Found: C, 62.98; H, 3.71; N,
8.62. Requires: C, 62.96; H, 3.73; N, 8.64].
0
0
Yield = 62%; mp = 140 °C; Rf = 0.35 (EtOAc/Hex, 5:5); UV
(MeOH); kmax 201.4 (log
e
;
= 4.3) nm; IR (KBr): mmax 1645.3 (C@O),
1H NMR (400 MHz, CDCl3) d: 8.68 (s,
1291.1 (C-N), 3066 cmꢀ1
1H, H-10), 8.50 (s, 1H, H-2), 7.98 (d, J3 ,2 = J5 ,6 = 7.3 Hz, 2H, H-
0
0
0
0
30,50), 7.72 (t, J7,8 = J7,6 = 7.5 Hz, 1H, H-7), 7.37 (d, J2 ,3 = J6 ,5 = 7.3 Hz,
2H, H-2’,60), 7.22 (d, J5,6 = 7.5 Hz, 1H, H-5), 7.12 (t, J6,5 = J6,7 = 7.5 Hz,
1H, H-6), 7.02 (d, J8,7 = 8.4 Hz, 1H, H-8), EI MS: m/z (rel. abund.%)
249 (M+, 62), 172 (55), 146 (33), 120 (38); Anal. Calcd for
C15H10N2O2: (249) [Found: C, 71.93; H, 4.04; N, 11.18; Requires:
C, 71.99; H, 4.03; N, 11.19].
0
0
0
0
4.13. 2-{[-(4-Oxo-4H-chromen-3-yl) methylidene]
amino}benzoic acid (15)
Yield = 64%; mp = 96 °C; Rf = 0.42 (EtOAc/Hex, 3:7); UV (MeOH);
kmax 232.1 (log
e
= 4.3) nm; IR (KBr): mmax 1646.4 (C@O), 1680.1
(C@N), 3065.9 (ArCH) cmꢀ1
;
1H NMR (400 MHz, CDCl3) d: 8.51 (s,
0
0
1H, H-2), 8.28 (d, J5,6 = 7.6 Hz, 1H, H-5), 8.23 (d, J3 ,4 = 7.3 Hz, 1H,
H-30), 7.80 (dd, J5 ,6 = 1.3 Hz, J5 ,4 = 7.6 Hz, 1H, H-50), 7.49 (t,
J7,8 = J7,6 = 8.5 Hz, 1H, H-7), 7.41 (t, J6,5 = J6,7 = 7.2 Hz, 1H, H-6),
Acknowledgement
0
0
0
0
7.30 (t, J4 ,3 = J4 ,5 = 8.3 Hz, 1H, H-40), 7.01 (d, J8,7 = 7.2 Hz, 1H, H-
This work was supported by the Higher Education Commission
(HEC) Pakistan under the National Research Support Program for
the Universities.
0
0
0
0
8), 6.63 (s, 1H, CH@N), 6.61 (d, J6 ,5 = 7.6 Hz, 2H, H-60); EI MS: m/
z (rel. abund.%) 292 (M+, 22.04), 188 (1.05), 172 (58.29), 120
0
0

2988
K. M. Khan et al. / Bioorg. Med. Chem. 17 (2009) 2983–2988
9. McNally, V. A.; Rajabi, M.; Gbaj, A.; Stratford, I. J.; Edwards, P. N.; Douglas, K. T.;
References and notes
Bryce, R. A.; Jaffar, M.; Freeman, S. J. Pharm. Pharmacol. 2007, 59, 537.
10. Liekens, S.; Balzarini, J.; Hernández, A. I.; De Clercq, E.; Priego, E. M.;
Camarasa, M. J.; Pérez-Pérez, M. J. Nucleosides Nucleotides Nucleic Acids
2006, 25, 975.
11. Casanova, E.; Hernandez, A. I.; Priego, E. M.; Liekens, S.; Camarasa, M. J.;
Balzarini, J.; Pérez-Pérez, M. J. J. Med. Chem. 2006, 49, 5562.
12. Liekens, S.; Bronckaers, A.; Pérez-Pérez, M. J.; Balzarini, J. Biochem. Pharmacol.
2007, 74, 1555.
1. (a) Folkman, J. Exp. Cell Res. 2006, 312, 594; (b) Folkman, J.; Shing, Y. J. Biol.
Chem. 1992, 267, 1031; (c) Akiyama, S.-I.; Furukawa, T.; Sumizawa, T.;
Takebayashi, Y.; Nakajima, Y.; Shimaoka, S.; Haraguchi, M. Cancer Sci. 2004,
95, 851; (d) Moghaddam, A.; Zhang, H.-T.; Fan, T.-P. D.; Hu, D.-E.; Lees, V. C.;
Turley, H.; Fox, S. B.; Gatter, K. C.; Harris, A. L.; Bicknell, R. Proc. Natl. Acad. Sci.
U.S.A. 1995, 92, 998.
2. Shigeto, M.; Takao, N.; Tatsuhiko, F.; Tomoyuki, S.; Avako, T.; Kengo, N.;
Suminori, A.; Kazutaka, M.; Masakazu, F.; Yuji, Y.; Hiroki, Y.; Tamotsu, K.;
Akiyama, S. Cancer Res. 1999, 59, 1911.
3. Focher, F.; Spadari, S. Curr. Cancer Drug Targets 2001, 1, 141.
4. Miyadera, K.; Emura, T.; Suzuki, N.; Akiyama, S.; Fukushima, M.; Yamada, Y.
Proc. Natl. Assoc. Cancer Res. 1998, 39, 609.
5. Matsushita, S.; Nitanda, T.; Furukawa, T.; Sumizawa, T.; Tani, A.; Nishimoto, K.;
Akiba, S.; Miyadera, K.; Fukushima, M.; Yamada, Y.; Yoshida, H.; Kanzaki, T.;
Akiyama, S. Cancer Res. 1999, 59, 1911.
13. Ellis, G. P. In Weissberger, A., Taylor, E. C., Eds.; Chromenes, Chromanones and
Chromones; John Wiley and Sons: New York, 1977; pp 1–10.
14. Kumar, R.; Yousuf, M. ARKIVOC 2006, 9, 239.
15. Athanasellis, G.; Melagraki, G.; Afantitis, A.; Makridima, K.; Igglessi-
Markopoulou, O. ARKIVOC 2006, 10, 28.
16. Singh, G. R.; Singh, N. K.; Girdhar, M. P.; Ishar, S. Tetrahedron 2002, 58,
2471.
17. Piao, L. Z.; Park, H. R.; Park, Y. K.; Lee, S. K.; Park, J. H.; Park, M. K. Chem. Pharm.
Bull. 2002, 50, 309.
18. Harnisch, H. Liebigs Ann. Chem. 1972, 765, 8.
19. Margita, L.; Dusan, L.; Mikulas, F.; Maria, M.; Elshaaer, H. M. Molecules 1998, 3,
149.
20. Krenitsky, T. A.; Bushby, S. R. M. U.S. Patent, 4, 178,212, 1-8, Burroughs
Welcome Co., Research Triangle Park, NC, 1979.
6. Pomeisl, K.; Votruba, I.; Holy, A.; Pohl, R. Nucleosides Nucleotides Nucleic Acids
2007, 26, 1025.
7. Gbaj, A.; Edwards, P. N.; Reigan, P.; Freeman, S.; Jaffar, M.; Douglas, K. T. J.
Enzyme Inhib. Med. Chem. 2006, 21, 69.
8. Nencka, R.; Votruba, I.; Hrebabecky, H.; Jansa, P.; Tloustova, E.; Horska, K.;
Masojidkova, M.; Holy, A. J. Med. Chem. 2007, 50, 6016.