Chalcones and flavonoids as anti-tuberculosis agents

Article abstract of DOI:10.1016/S0968-0896(02)00094-9

A series of flavonoids, chalcones and chalcone-like compounds were evaluated for inhibitory activity against Mycobacterium tuberculosis H37Rv. Among them, eight compounds exhibited >90% inhibition on the growth of the bacteria at a concentration of 12.5 μg/mL. Chalcones 1-(2-hydroxyphenyl)-3-(3-chlorophenyl)-2-propen-1-one (22) and 1-(2-hydroxyphenyl)-3-(3-iodophenyl)-2-propen-1-one (37) demonstrated 90 and 92% inhibition, respectively. Chalcone-like compounds (heterocyclic ring-substituted 2-propen-1-one) 1-(4-fluorophenyl)-3-(pyridin-3-yl)-2-propen-1-one (48), 1-(3-hydroxyphenyl)-3-(phenanthren-9-yl)-2-propen-1-one (49), 1-(pyridin-3-yl)-3-(phenanthen-9-yl)-2-propen-1-one (50) and 1-(furan-2-yl)-3-phenyl-2-propen-1-one (51) exhibited 98, 97, 96 and 96% inhibition, respectively. The actual minimum inhibitory concentrations (MIC), defined as the lowest concentration inhibiting 99% of the inoculum, for 22, 37, 48, 49, 50 and 51 were 20.3, 31.5, 48.3, >35.7, 6.8 and 19.2, respectively. A hydrophobic substituent on one aromatic ring, and a hydrogen-bonding group on the other aromatic ring resulted in increased anti-TB activity of the chalcones and chalcone-like compounds. Flavones and flavanones are more geometrically constrained than the corresponding chalcone analogues. The decreased activity of the flavones with respect to the chalcones may be due to the confinement of the terminal aromatic rings to the same plane.

Full text of DOI:10.1016/S0968-0896(02)00094-9

Bioorganic & Medicinal Chemistry 10 (2002) 2795–2802
Chalcones and Flavonoids as Anti-Tuberculosis Agents
Yuh-Meei Lin,a Yasheen Zhou,a Michael T. Flavin,*,a Li-Ming Zhou,a
Weiguo Niea and Fa-Ching Chenb
aMediChem Life Sciences, 2501 Davey Road, Woodridge, IL 60517, USA
bDepartment of Chemistry, National Taiwan University, Taipei, Taiwan
Received 12 September 2001; accepted 9 January 2002
Abstract—A series of flavonoids, chalcones and chalcone-like compounds were evaluated for inhibitory activity against Myco-
bacterium tuberculosis H37Rv. Among them, eight compounds exhibited >90% inhibition on the growth of the bacteria at a con-
centration of 12.5 mg/mL. Chalcones 1-(2-hydroxyphenyl)-3-(3-chlorophenyl)-2-propen-1-one (22) and 1-(2-hydroxyphenyl)-3-(3-
iodophenyl)-2-propen-1-one (37) demonstrated 90 and 92% inhibition, respectively. Chalcone-like compounds (heterocyclic ring-
substituted 2-propen-1-one) 1-(4-fluorophenyl)-3-(pyridin-3-yl)-2-propen-1-one (48), 1-(3-hydroxyphenyl)-3-(phenanthren-9-yl)-2-
propen-1-one (49), 1-(pyridin-3-yl)-3-(phenanthen-9-yl)-2-propen-1-one (50) and 1-(furan-2-yl)-3-phenyl-2-propen-1-one (51)
exhibited 98, 97, 96 and 96% inhibition, respectively. The actual minimum inhibitory concentrations (MIC), defined as the lowest
concentration inhibiting 99% of the inoculum, for 22, 37, 48, 49, 50 and 51 were 20.3, 31.5, 48.3, >35.7, 6.8 and 19.2, respectively.
A hydrophobic substituent on one aromatic ring, and a hydrogen-bonding group on the other aromatic ring resulted in increased
anti-TB activity of the chalcones and chalcone-like compounds. Flavones and flavanones are more geometrically constrained than
the corresponding chalcone analogues. The decreased activity of the flavones with respect to the chalcones may be due to the con-
finement of the terminal aromatic rings to the same plane. # 2002 Elsevier Science Ltd. All rights reserved.
Introduction
(anti-TB) activities of biflavonoids. In this more recent
study, we present the anti-TB screening results with a
variety of chalcones, chalcone-like compounds, flavones
and flavanones.
Tuberculosis (TB), caused by Mycobacterium tuberculosis
(Mtb), a facultative intracellular bacillus, is the world’s
number one killer among infectious diseases and the
leading cause of death among women of reproductive
age.1 Even though improved methods of prevention,
detection, diagnosis and treatment have greatly reduced
the number of people who contract the disease and die
from it, the emergence of multidrug-resistant (MDR)
strains and the global human immunodeficiency virus
(HIV) pandemic have amplified the incidence of TB.2ꢀ5
Results
Synthesis
Chalcones (1,3-diaryl-2-propen-1-ones) and chalcone-like
compounds (1,3-heteroaromatic ring-substituted 2-propen-
1-ones). Chalcones and chalcone-like compounds were
prepared by base-catalyzed condensation of appro-
priately substituted ketones with substituted benzalde-
hydes or heterocylic aldehydes (Scheme 1). To a mixture
of the substituted acetophenone and substituted ben-
zaldehyde in alcohol was added a 60% solution of
potassium hydroxide dropwise with stirring. The reac-
tion mixture was kept at 0 ꢁC for 2 days, then diluted
with water and acidified with acetic acid. The pre-
cipitated chalcone was collected and recrystallized from
alcohol to yield pure chalcone.7
Because of this, there is an urgent need for anti-TB drugs
with improved properties such as enhanced activity
against MDR strains, reduced toxicity, shortened duration
of therapy, rapid mycobactericidal mechanism of action
and the ability to penetrate host cells and exert anti-
mycobacterial effects in the intracellular environment.
In our efforts to discover novel anti-tuberculosis agents,
we screened a series of chalcones and flavonoids. In a
previous paper,6 we have reported the anti-tuberculosis
Flavones. Flavones were synthesized by treating the
corresponding chalcones with selenium dioxide in amyl
*Corresponding author. Tel.: +1-630-783-4600; fax: +1-630-783-
4949; e-mail: mflavin@medichem.com
0968-0896/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(02)00094-9

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Y.-M. Lin et al. / Bioorg. Med. Chem. 10 (2002) 2795–2802
inactive. Flavones, flavonols and flavanones were inactive
or weakly to moderately active.
Chalcones (1,3-Diaryl-2-propen-1-ones). The results of
anti-TB screening of chalcones are displayed in Table 1.
Chalcones with a 2-hydroxyl groupin the B ring and a
3-iodo- or 3-chloro-groupin the A ring, 22 and 37,
respectively, demonstrated the strongest activity among
this series of compounds, with 90 and 92% inhibition,
respectively, against Mtb at a drug concentration of 12.5
mg/mL. Chalcones without halogen substitution in the
molecule exhibited less activity compared to those with
a halogen substitution.
Scheme 1. Preparation of chalcones, chalcone-like compounds,
flavones and flavanones.
The activity of 20-hydroxy-chalcone 5 (61% inhibition)
was enhanced by introducing a chloro- or a methoxy-
groupat the 4 -position of the B-ring, such as com-
0
alcohol (Scheme 1). Thus, 20-, 30- and 40-monohalogeno-
flavones were prepared as usual by condensation of
hydroxyacetophenone with o-, m- and p-halogenobenz-
aldehydes to provide the chalcones. This was followed
by cyclization of the chalcones with selenium dioxide in
amyl alcohol.8ꢀ13 6-Fluoro-, 6-chloro- and 6-bromo-
flavones and related compounds were prepared from 2-
hydroxy-5-halogenoacetophenones.13
pounds 23 (89%) and 1 (78%). A bromo-, or an iodo-
substituent at the 40-position of ring B led to decreased
activity [e.g., 32 (57%) and 42 (21%)]. The bromo-sub-
stituent at the 30-position of the B-ring of 20-hydroxy-
chalcone (5) slightly increased the activity [29 (79%) vs
5 (61%)]. The effect of various substituents at the 50-
position of the B-ring on anti-TB activity was as fol-
lows: phenyl (3, 68%)=Br (31, 68%)ꢂCl (24, 67%)>H
(5, 61%)>I (39, 51%)>NH2 (12, 6%). The anti-TB
activity was also affected by a halogen-substituent on
the B-ring of 20-hydroxychalcone. A rank of the inhibi-
tory activities of compounds with a halogen substituent
on the B ring is outlined as follows: 40-Cl (23, 89%)>50-
Cl (24, 67%); 30-Br (29, 79%)>50-Br (31, 68%)>40-Br
(32, 57%); and 50-I (39, 52%)>40-I (42, 21%)>30-I (44,
0%). Introducing an additional substituent on either the
A- or B-ring of the above 20-hydroxychalcones resulted
in a significant decrease or loss of activity. This effect
was shown in compounds 23 (40-Cl–, 89%) versus 26 (40-
Cl-4-OCH3–, 57%); 1 (40-OCH3–, 78%) versus 7 (4,40,6-
(OCH3)3–, 40%); 31 (50-Br–, 68%) versus 34 (50-Br-4-
OCH3–, 23%) and 36 (50-Br-2-NH2–, 8%); 24 (50-Cl-,
67%) versus 27 (50-Cl-4-OCH3–, 20%); 32 (4-Br-, 57%)
versus 33 (4-Br-4-OCH3–, 25%) and 35 (4-Br-2-NH2–,
12%), 37 (3-I–, 92%) versus 40 (3-I-40-OCH3, 47%) and
39 (50-I–, 51%) versus 45 (5-I-4-OCH3–, 0%).
Flavonols (3-hydroxyflavones). Flavonols were prepared
by treating the corresponding chalcones with a 16%
solution of aqueous sodium hydroxide and 15% hydrogen
peroxide solution (v/v 1:1) (Scheme 1). The 6-halogeno-
flavonols were prepared in good yield by cyclization of
the corresponding chalcones in cold alkaline hydrogen
peroxide.14,15
Flavanones. Flavanones were prepared by refluxing the
corresponding chalcones with phosphoric acid in alcohol
for 2–3 days (Scheme 1). Generally, 2-hydroxy-5-halo-
genoacetophenones condensed smoothly with benzalde-
hyde or p-anisaldehyde in the presence of alcoholic alkali,
giving chalcones, which were cyclized in phosphoric acid
to obtain 6-halogenoflavanones.16
Anti-tuberculosis activity
Forty-seven chalcones (1–47), 21 chalcone-like com-
pounds (48–69), 54 flavones (70–124) and 17 flavanones
(125–142) were screened against Mtb H37Rv at a drug
concentration of 12.5 mg/mL. Among the chalcones and
chalcone-like compounds screened, two chalcones (22
and 23) and four chalcone-like compounds (48–51)
demonstrated >90% inhibitory activity. Twenty-two
compounds exhibited activity between 50 and 89%
(four, 80–89%; five, 70–79%; eight, 60–69%; five, 50–
59%) and 25 compounds displayed activity less than
50% (five, 40–49%; three, 30–39%; five, 20–29%; six,
10–19%; six, 1–9%). The remaining 16 compounds were
The substitution of a halogen groupon the A-ring of 2 0-
hydroxychalcone led to an increase in anti-TB activity.
Compounds with a halogen substituent at the 3-position
demonstrated stronger anti-TB activity than those with a
halogen substituent at the 2- or 4-position. Compounds
with a 3-, 2- and 4-iodo substituent exhibited 92% (37,
3-I–), 41% (41, 2-I–) and 21% (43, 4-I–) inhibition
against Mtb, respectively. Compound 28, 2-bromo-20-
hydroxychalcone, demonstrated an inhibitory activity of
83% while compound 30 with a 4-bromo substituent
exhibited an anti-TB activity of 70%. The activities of

Y.-M. Lin et al. / Bioorg. Med. Chem. 10 (2002) 2795–2802
Table 1. Anti-tuberculosis activity of chalcones
2797
B-ring
40–
A-ring
Compd
20–
30–
50–
60–
2–
3–
4–
5–
Activity
% inhibition
at 12.5 mg/mL
MIC
(mg/mL)
RMP
1
2
3
4
5
6
7
8
0.125–0.25
a
OH
OH
OH
OCH3
NO2
78
75
68
62
61
53
40
39
32
18
11
6
—
OCH3
OCH3
OCH3
OCH3
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
20.3
—
—
—
—
—
—
—
—
—
—
—
—
—
—
31.5
—
—
—
—
—
—
—
—
—
—
Phenyl
OH
OH
OCH2
O
OCH3
OH
OH
OH
OH
OH
OH
OCH3
OCH3
OCH3
9
OCH3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
OH
NH2
NH2
NH2
EtO
OCH3
5
0
0
0
OH
OH
OH
OH
F
EtO
OH
OCH3
OCH3
OCH3
OCH3
COOH
NHCOCH3
0
OCH3
OCH3
OCH3
OCH3
82
66
63
45
90
89
67
67
57
20
83
79
70
68
57
25
23
12
8
92
88
51
47
41
21
21
0
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
F
F
F
Cl
Cl
Cl
Cl
Cl
Cl
OCH3
OCH3
Br
Br
Br
Br
Br
Br
OCH3
OCH3
Br
Br
Br
NH2
NH2
I
I
NH2
I
I
OH
OH
OH
OH
OH
OH
OH
OH
OH
I
OCH3
I
I
I
I
I
OCH3
OCH3
0
0
0
COOH
I
a12.5 and not determined.
compounds 22 (3-chloro-20-hydroxychalcone) and 25 (4-
chloro-20-hydroxychalcone) are 90 and 67%, respec-
tively. Since there was no example of fluoro compounds
tested, it was not possible to predict which halogen
would contribute most to the activity.
comparing the activities of compounds 40 (47%, 40-
methoxy-2-hydroxy-3-iodochalcone) and 47 (0%, 50-carb-
oxyl-20-hydroxy-3-iodochalcone) to that of the parent
compound 37 (92%, 20-hydroxy-3-iodochalcone).
Chalcone-like compounds (1,3-heteroaromatic ring-sub-
stituted 2 - propen - 1 - ones). Chlacone-like compounds
demonstrated the most significant anti-TB activity
among all the compounds evaluated. As presented in
Table 2, compounds 48, 49, 50, and 51 inhibited 98, 97,
Introduction of an additional substituent, such as a
methoxy, bromo or carboxyl groupon the B-ring of 2 -
0
hydroxy-3-iodochalcone (37) led to a dramatic decrease
or a complete loss of activity. This was concluded by

2798
Y.-M. Lin et al. / Bioorg. Med. Chem. 10 (2002) 2795–2802
Table 2. Anti-tuberculosis activity of chalcone-like compounds
Compd
R
R0
Activity % inhibition
at 12.5 mg/mL
MIC (m/mL)
RMP
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
0.125–0.25
48.3
31.5
4-Fuorophenyl-
3-Hydroxyphenyl-
Pyridin-3-yl-
Pyridin-3-yl-
Phenanthren-9-yl-
Phenanthren-9-yl-
3-Phenyl-
2-Aminopyridino-3-yl-
2-Aminopyridino-3-yl-
Pyridin-2-yl-
98
97
96
96
74
53
42
37
16
17
12
3
7
1
0
0
0
0
0
0
6.8
19.2
Furan-2-yl-
a
Phenanthren-2-yl-
3-Fluorenyl-
Pyridin-2-yl-
Naphthalen-1-yl-
Pyridin-2-yl-
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
Phenyl-
4-Dimethylaminophenyl-
Furan-2-yl-
Indol-2-yl-
4-Bromo-2-hydroxyphenyl-
Pyridin-4-yl-
2-Hydroxy-4-methoxyphenyl-
4-Aminophenyl-
Pyridin-4-yl-
2-Hydroxy-5-methoxyphenyl-
4-Methoxyphenyl-
4-Methoxyphenyl-
2-Hydroxy-5-chlorophenyl-
4-Aminophenyl-
3-Hydroxynaphthalen-2-yl-
Furan-2-yl-
Pyridin-2-yl-
Furan-2-yl-
2-Aminopyridin-3-yl-
4-Dimethylaminophenyl-
Furan-2-yl-
Pyridin-4-yl-
Pyridin-3-yl-
2-Aminopyridin-3-yl-
2-Aminopyridin-3-yl-
2-Aminopyridin-3-yl-
Pyridin-4-yl-
0
0
4-Methoxyphenyl-
a>12.5 and not determined.
96, and 96% growth, respectively, of Mtb H37Rv at a drug
concentration of 12.5 mg/mL. The common structural
feature is that all four compounds have a heteroaro-
matic ring or a phenyl ring with a hydrophilic group
substituent on one side of the molecule, and an aromatic
ring, such as phenyl or phenanthrenyl, with or without a
hydrophobic substitution on the other side.
flavonol (80 and 78) did not affect the activity. However,
the substitution of a 7- or 8-iodo group, a 6-fluoro or 6-
bromo groupor a 6-carboxy groupon 4 0-methoxy-
flavonol resulted in a significant decrease or a complete
loss of activity.
Flavanones. Eighteen flavanones were evaluated for
anti-TB activity. The results are listed in Table 4.
5-Methoxy-8-bromoflavanone (125) demonstrated the
most significant activity among these flavanones, with
87% inhibition against Mtb. The substitution of a
bromo groupon the B-ring demonstrated higher activity
than that of a halogen-substituted A-ring [3-bromo-flava-
none (126), 73%, vs 7-bromo-flavanone (128), 53%]. Due
to the small sample size and the lack of diversity, it is
difficult to provide a structure–activity relationship
interpretation.
Additional hydrophilic substituents, such as methoxyl,
hydroxyl and amino groups resulted in a dramatic
decrease or complete loss of activity. From the above
results, it was concluded that the active compounds may
require a lipophilic group on one side and a hydrophilic
group on the other side of 2-propen-1-one.
Flavones. The anti-TB activities of the flavones studied
are presented in Table 3. All flavones tested, including
carboxylated, halogenated, hydroxylated and methoxy-
lated flavones were only moderately to weakly active or
inactive, while halogenated flavones or halogenated fla-
vonols (3-hydroxyflavones) demonstrated moderate activ-
ity. Flavones bearing an 8-bromo or 8-chloro substituent
displayed 66% (72) and 62% (73) growth inhibition at a
dose of 12.5 mg/mL against Mtb. Flavones with a halogen
substitution at the 3-position (120), a 6-, 7- or 8-halogen
substituent on ring A (95, 98, 99, 105, 107, 115, 116, and
117) and 20-, 30- or 40-halogen substituent on ring B (77,
90, 92, 93, 94, 104, and 114) were weakly active or
inactive. Flavonol (3-hydroxyflavone) (85) exhibited a
low potency of 38% inhibition. The presence of a 40-
methoxyl groupon flavonol ( 81) led to a slight, 10%
increase in inhibitory activity. Further modification,
Discussion
SAR analysis and pharmacophore mapping analysis
Two chalcone compounds (22 and 37) and four chal-
cone-like compounds (48, 49, 50, and 51) exhibited
greater than 90% inhibition of the TB bacteria. The
common structural feature of these six compounds is
that they have two aromatic rings, one ring substituted
with a heteroatom, and the other with or without
hydrophobic substitutions. The presence of additional
heteroatoms on the aromatic ring, such as methoxyl,
hydroxyl and amino groups, results in decreased activ-
ity. With the exception of 48, these compounds have a
0
including a 6-chloro or 7-fluoro groupon 4 -methoxy-

Y.-M. Lin et al. / Bioorg. Med. Chem. 10 (2002) 2795–2802
Table 3. Anti-tuberculosis activity of flavones
2799
Compd
3
5
6
7
8
20
30
40
Activity % inhibition
at 12.5 mg/mL
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
Br
Cl
66
62
64
60
58
58
52
51
50
50
48
48
44
43
43
38
29
29
28
28
26
24
23
22
22
20
19
18
15
15
15
13
12
12
7
7
6
5
2
1
0
0
0
0
0
0
0
0
0
0
0
OH
OH
OH
OH
OH
I
Br
Cl
Cl
Br
I
OH
OAc
OH
F
F
OCH3
OCH3
OCH3
OCH3
Cl
Br
OH
OCH3
OH
OH
F
I
OCH3
OH
OCH3
OCH3
Cl
OCH3
Br
OCH3
OH
Br
F
NO2
OH
Br
Br
I
I
I
OCH3
Br
Cl
OH
F
Br
I
OCH3
OCH3
Cl
Br
OCH3
OCH3
Benzoyl
Benzoyl
F
OH
I
I
OCH3
OCH3
COOH
OH
OCH3
F
OCH3
OCH3
OCH3
OCH3
F
Cl
I
Cl
Br
I
OCH3
OCH3
OCH3
OCH3
I
OCH3
OCH3
I
I
OCH3
OCH3
OCH3
OH
0
0
0
0
OH
Br
COOH
OCH3
OCH3
OCH3
OCH3
hydrogen-bonding substituent on the B ring, while the
A ring maintains its hydrophobicity. Although 48 has a
heteroatom on the A ring with a hydrophobic sub-
stituent on the B ring, the A ring and B ring of 48 can be
superimposed with the B ring and A ring, respectively,
of the remaining compounds. An example of this
superimposition model is shown in Figure 1 with
compounds 48 and 51.
Flavones and flavanones can be viewed as geometrically
constrained chalcone analogues. These structural con-
straints may be the cause of the decreased activity with

2800
Y.-M. Lin et al. / Bioorg. Med. Chem. 10 (2002) 2795–2802
Table 4. Anti-tuberculosis activity of flavanones
Compd
3
5
6
7
8
30
40
50
Activity% inhibition
at 12.5 mg/mL
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
OCH3
Br
87
73
63
53
48
30
27
16
9
8
7
0
0
Br
Cl
OH
Br
OCH3
Cl
Cl
I
Br2
OCH3
OCH3
OCH3
I
OCH3
OCH3
OCH3
OCH3
Br
F
OCH3
OCH3
NO2
OCH3
OCH3
COOH
COOH
0
0
0
0
OCH3
I
Br2
Br2
OCH3
0
Conclusion
Two chalcones (22 and 37) and four chalcone-like com-
pounds (48, 49, 50, and 51) exhibited greater than 90%
inhibitory activity against Mtb. The common structural
feature for these six compounds is the two aromatic rings,
one ring substituted with a heteroatom, and the other with
or without hydrophobic substitutions. The presence of
additional hydrophilic substituents, such as methoxyl,
hydroxyl and amino groups, results in decreased activity.
With the exception of 48, all compounds have a hydro-
phobic A ring and a hydrogen-bonding substituent on
the B ring. Structural superimposition analysis indicated
that compound 48 could be inversely superimposed to
the remaining five compounds.
Figure 1. Superimposition of compounds 48 and 51.
respect to their chalcone counterparts. Compared to
flavanones, flavones are less active, and are structurally
more constrained, with the two terminal aromatic rings
in the same plane. The activity relationship of chalcones
and their corresponding flavones is illustrated by the
following examples: when chalcone 41 was converted to
flavone 93, the activity decreased from 41 to 22%.
Similar activity relationships for chalcones and flavones
were observed between other compounds including 41
(41%) to 93 (22%); 28 (83%) to 92 (23%); 30 (70%) to 90
(26%); 22 (90%) to 114 (0%) and 25 (67%) to 104 (7%).
The exception to this trend is the activity relationship
between chalcone 43 (21%) and flavone 77 (51%). How-
ever, there is no corresponding flavanone compound to
determine the activity relationshipwith the active chal-
cone. It is worth mentioning that the important features
in the active chalcone and the chalcone-like compounds
described above do not exist in any of the flavone or
flavanone compounds currently tested.
Experimental
General
Melting points were determined in open glass capillary
tubes and are uncorrected. 1H NMR and 13C NMR
spectra were recorded on a Varian XL300 NMR spec-
trometer in CDCl3, DMSO-d6 or acetone-d6 as speci-
fied, using TMS as an internal standard. Chemical shifts
are expressed in parts per million (d, ppm). IR spectra
were recorded using a Perkin-Elmer 1000 FT-IR spec-
trometer. Mass spectral data were recorded using a
Finnegan LCQ mass spectrometer. Analytical thin-layer
chromatography (TLC) was carried out on precoated
plates (Silica gel F254 from EM Science). Column chro-
matography was performed with silica gel 60 (70–230
mesh from EM Science). The structure and purity of
compounds were confirmed by TLC profiles as well as
IR, NMR and MS spectra.

Y.-M. Lin et al. / Bioorg. Med. Chem. 10 (2002) 2795–2802
2801
3-Chloro-20-hydroxychalcone (22). To a solution of 2-
hydroxyacetophenone (1.5 g, 11 m mol) and 3-chloro-
benzaldehyde (1.32 g, 9 mmol) in EtOH (10 mL) was
added a 60% of KOH (10 g) solution dropwise at 0 ꢁC.
The reaction was stirred at 0 ꢁC for 1 day. Cool water was
added and the reaction mixture was neutralized with cold
acetic acid. The yellow precipitate was collected, washed
with water and recrystallized from EtOH to yield yellow
needles (1.8 g, yield 76%), mp108–108.5 ꢁC, APCIMS
m/z 257.3 [MꢀH]+ (relative intensity 100%), 259.2
[MꢀH+2]+ (isotope) (58%); IR (KBr) cmꢀ1: 3091,
3060, 3017 (aromatic CH, ¼C–H), 3010–2800 (br, –O–
H), 1647 (chalcone C¼O), 1582, 1492 (arom); 1H NMR
(CDCl3) d 12.710 (1H, s, OH-20), 7.923 (1H, dd, J=8.1
Hz, 1.5 Hz, H-60), 7.846 (1H, d, J=15.6 Hz, H-b), 7.657
(1H, d, J=1.5 Hz, H-2), 7.651 (1H, d, J=15.6 Hz, H-a),
7.552–7.749 (2H, m, H-50,6), 7.45–7.35 (2H, m, H-4,5),
7.043 (1H, dd, J=8.1 Hz, 1.2 Hz, H-30), and 6.967 (1H,
ddd, J=8.1 Hz, 6.9 Hz, 1.2 Hz, H-40); 13C NMR (CDCl3)
d 193.598 (>C¼O), 163,792 (¼C<), 143.783 (¼CH–),
136.756 (¼CH–), 136.521 (¼C<), 135.165 (¼C<),
130.784 (¼CH–), 130.382 (¼CH–), 129.760 (¼CH–),
128.106 (¼CH–), 127.119 (¼CH–), 121.521 (¼CH–),
119.956 (¼CH–), 119.030 (¼C<), and 118.780 (¼CH–).
acetophenone and phenanthrene-9-carboxaldehyde by
the same method described above, mp212–213 ꢁC;
1
APCIMS m/z 325.1 [M+H]+; H NMR (acetone-d6) d
8.926 (1H, m, H-8), 8.86 (1H, d, J=8.1 Hz, H-5), 8.781
(bs, OH), 8.643 (1H, d, J=15.6 Hz, H-b), 8.478 (1H, s,
H-10), 8.360 (1H, m, H-4), 8.09 (1H, dd, J=7.8, 1.8 Hz,
H-1), 7.964 (1H, d, J=15.5 Hz, H-a), 7.818–7.643 (6H, m,
H-2,3,6,7,20,60), 7.442 (1H, t, J=7.8 Hz, H-50), 7.167
(1H, dt, J=7.2 Hz, H-40); 13C NMR (acetone-d6) d
190.016 (>C¼O), 158.956 (¼C<), 140.729 (¼C<),
141.905 (¼CH–), 132.465 (¼C<), 132.276 (¼C<),
132.207 (¼C<), 131.562 (¼C<), 131.373 (¼C<), 130.910
(¼CH–), 130.432 (¼CH–), 128.944 (¼CH–), 128.383
(¼CH–), 128.163 (¼CH–), 128.231 (¼CH–), 127.768
(¼CH–), 126.425 (¼CH–), 125.226 (¼CH¼), 124.467
(¼CH–), 123.799 (¼CH–), 121.143 (¼CH–), 121.022
(¼CH–), 115.892 (¼CH–).
1-(Furan-2-yl)-3-phenyl-2-propen-1-one (51).18 Com-
pound 51 was prepared from 2-acetylfuran and benzal-
ꢁ
dehyde as colorless crystals, mp94–95 C. APCIMS m/z
1
199.1 [M+H]+. H NMR (CDCl3) d 7.890 (1H, d, J=
15.9 Hz, H-b), 7.661 (1H, dd, J=1.5, 0.9 Hz, H-50).
7.659 (2H, m, H-2,6), 7.46 (1H, d, J=15.6 Hz, H-a),
7.421 (3H, m, H-3,4,5), 7.341 (1H, dd, J=3.3, 0.9 Hz,
H-30), 6.603 (1H, dd, J=3.6 Hz, 1.5 Hz, H-40); 13C
NMR (CDCl3) d 178.195 (>C¼O), 153.822 (¼C<, C-
20), 146.636 (¼CH–, C-50), 144.101 (C-b), 134.814
(¼C<, C-1), 130.686 (¼CH–, C-4), 129.016 (¼CH–, C-
3,5), 128.607 (¼CH–, C-2,6), 121.216 (¼CH–, C-40),
117.566 (¼CH–, C-a), 112.596 (¼CH–, C-30).
3-Iodo-20-hydroxychalcone (37). Compound 37 was pre-
pared from 2-hydroxyacetophenone and 3-iodobenz-
aldeꢁhyde by the procedure described above, mp 161–
163 C; APCIMS m/z 349.1 [MꢀH]+; IR (KBr) cmꢀ1
:
3010–2800 (br, –O–H), 1638 (chalcone C¼O), 1564,
1485 (arom); 1H NMR (CDCl3) d 12.712 (1H, s, OH-20),
8.019 (1H, d, J=1.5 Hz, H-2), 7.923 (1H, dd, J=8.1, 1.5
Hz, H-6), 7.898 (1H, d, J=15.6 Hz, H-b), 7.756 (1H, dd,
J=7.5, 1.5 Hz, H-6), 7.625 (1H, d, J=15.6 Hz, H-a),
7.603 (1H, dd, J=7.8, 1.2 Hz, H-60), 7.519 (1H, t,d, J=
7.8, 1.2 Hz, H5), 7.179 (1H, t, J=8.4 Hz, H-50), 7.040 (1H,
dd, J=7.2, 1.2 Hz, H-30), 6.966 (1H, ddd, J=8.2, 7.2 Hz,
1.2 Hz, H-40); 13C NMR (CDCl3) d 193.578 (>C¼O),
163.818 (>C¼), 143.649 (¼CH–), 139.665 (¼CH–),
137.070 (¼CH–), 136.903 (>C¼), 136.774 (¼CH–),
130.764 (¼CH–), 129.816 (¼CH–), 128.184 (¼CH–),
121.431 (¼CH–), 119.982 (>C¼), 119.056 (¼CH–),
118.805 (¼CH–), 94.880 (>C¼).
5 - Methoxy - 8 - bromo - flavanone (125). 50-Methoxy-80-
bromo-chalcone was prepared from 5-methoxy-8-
bromo-acetophenone and benzaldehyde by the usual
method. A solution of the chalcone (0.5 g) and phos-
phoric acid (10 g) in EtOH (150 mL) was refluxed for 10
days. Concentration of the solution and dilution with
water gave colorless needles (0.12 g), mp134–165 ꢁC,
APCIMS m/z 333.1 [M]+ (relative intensity 100%), 335.0
[M+2]+ (94%). 1H NMR (CDCl3) d 7.656 (1H, d, J=8.7
Hz, H-6), 7.511 (2H, dt, J=7.5, 1.8 Hz, H-20,60), 7.526–
7.360 (5H, m, B-ring protons), 6.495 (1H, d, J=9.0 Hz,
H-7), 5.572 (1H, m, H-2), 3.030 (2H, m, H-3a and H-3b);
13C NMR (CDCl3) d 190.132 (>C¼O), 160.211 (¼C<),
158.959 (¼C<), 138.964 (¼CH–), 138.296 (¼C<),
128.887 (¼CH–), 128.652 (¼CH–), 125.844 (¼CH–),
112.474 (¼C<), 105.326 (¼CH–), 102.534 (¼C<),
78.034 (>CH–, C-2), 58.353 (–CH3, 5-OCH3), and
45.297 (>CH2, C-3).
1-(4-Fluorophenyl)-3-(pyridin-3-yl)-2-propen-1-one (48).17
Compound 48 was prepared from 4-fluoroaceto-
phenone and 3-pyridinecarboxyaldehyde by the proce-
dure described above, mp126–127 ꢁC; APCIMS m/z
228.2 [M+H]+; 1H NMR (CDCl3) d 8.866 (1H, d,
J=1.8 Hz, H-2), 8.638 (1H, dd, J=4.8 Hz, 1.5 Hz, H-4),
8.0 (2H, ddd, J=9, 5.4 Hz, 2.1 Hz, H-20,60), 7.958 (1H,
dt, J=8.1, 2.1 Hz, H-6), 7.805 (1H, d, J=15.9 Hz, H-b),
7.580 (1H, d, J=15.9 Hz, H-a), 7.380 (1H, dd, J=7.8, 4.8
Hz, H-5), 7.203 (ddd, H=9.0 Hz, 8.1 Hz, 2.1 Hz, H-30,50);
13C NMR (CDCl3) d 188.321 (¼C<), 167.628 (¼C<),
164.236 (¼C<), 151.314 (¼CH–), 150.061 (¼CH–),
141.252 (¼CH–), 134.726 (¼CH–), 134.180 (¼C<),
131.319 (¼CH–), 131.198 (¼CH–), 130.638 (¼C<),
123.867 (¼CH–), 123.435 (¼CH–), 116.105 (¼CH–),
115.817 (¼CH–).
In vitro evaluation of anti-tuberculosis activity.19 The
screening was conducted on a drug concentration of
12.5 mg/mL against Mtb H38Rv in BACTEC 12B med-
ium using the BACTEC 460 radiometric system. The
assay procedure was carried out according to the
method described previously.23 Compounds were solu-
bilized in dimethylsulfoxide at 1 mg/mL and sterilized
by passage through 0.22 mm PFTE filters. Fifty micro-
liters was added to 4 mL BACTEC 12B medium (Bec-
ton Dickinson) to achieve a final concentration of 12.5
mg/mL. Approximately 4ꢃ105 colony forming units of
M. tuberculosis H37Rv ATCC 27294 were added and
1-(3-Hydroxyphenyl)-3-phenanthren-9-yl-2-propen-1-one
(49). The compound was synthesized from 3-hydroxy-

2802
Y.-M. Lin et al. / Bioorg. Med. Chem. 10 (2002) 2795–2802
the cultures were incubated at 37 ꢁC. Starting on the
second day of incubation, the Growth Index (GI, 1 GI
unit=0.0025 dpm 14CO2) was determined daily until the
controls (drug-free) achieved a GI of 999. The percent
inhibition was calculated as 1ꢀ (test sample GIꢄcontrol
GI)ꢃ100.
3. Pablos-Mendez, A.; Raviglione, M. C.; Laszlo, A.; Binkin,
N.; Rieder, H. L.; Bustreo, F.; Cohn, D. L.; Lambregts-van
Weezenbeek, C. S. B.; Kim, S. J.; Chaulet, P.; Nunn, P. N.
Eng. J. Med. 1998, 338, 1641.
4. Murray, C. J. L.; Styblo, K.; Rouillon, A. In Disease Con-
trol Priorities in Developing Countries; Jamison, D. T., Mosely,
W. H., Eds.; Oxford: New York, 1993; p233.
5. Styblo, K. Bull. Int. Union Tuberc. 1990, 65, 24.
6. Lin, Y.-M.; Flavin, M. T.; Cassidy, C. S.; Mar, A.; Chen,
F.-C. Bioorg. Med. Chem. Lett. 2001, 11, 2101.
7. Ariyan, Z. S.; Suschitzky, H. J. Chem. Soc. 1961, 2242.
8. Chen, F. C.; Yang, C. H.; Hsu, K. K. J. Formosan Sci.
1953, 7, 51.
9. Chen, F. C.; Hsu, K. K. J. Formosan Sci. 1953, 7, 54.
10. Chen, F. C.; Lai, P. C.; Hsieh, H. C. J. Formosan Sci.
1953, 7, 57.
11. Chen, F. C.; Lin, C.; Lai, S. C. J. Formosan Sci. 1953, 7,
63.
12. Chen, F. C.; Lin, C.; Tu, T. T. J. Formosan Sci. 1954, 8,
71.
13. Chang, C. T.; Chen, F. C.; Chen, T. S.; Hsu, K. K.; Ueng,
T.; Hung, M. J. Chem. Soc. 1961, 3414.
Acknowledgements
The authors thank Dr. Robert C. Reynolds, Southern
Research Institute, Tuberculosis Antimicrobial Acquisi-
tion & Coordinating Facility (TAACF), National Insti-
tute of Allergy and Infectious Diseases, for administrative
arrangement of the activity tests, and Dr. Constance S.
Cassidy for editing the manuscript. Antimycobacterial
data are provided by the Tuberculosis Antimicrobial
Acquisition and Coordinating Facility (TAACF) through
a research and development contract with the US
National Institute of Allergy and Infectious Diseases.
14. Chen, F. C.; Chang, C. T. J. Formosan Sci. 1954, 8, 74.
15. Chen, F. C.; Hsu, K. K. J. Taiwan Pharm. Assoc. 1953, 5,
49.
16. Chen, F. C.; Chang, C. T. J. Chem. Soc. 1958, 146.
17. Chen, F. C.; Chen, Y. H.; Chen, C. Y. J. Formosan Sci.
1972, 26, 52.
References and Notes
1. Lopez, A. In Disease Control Priorties in Developing Coun-
tries; Jamison, D. T., Mosely, W. H., Eds.; Oxford: New
York, 1993; p35.
18. Chen, F. C.; Chen, Y. H.; Chen, L. S. J. Formosan Sci.
1972, 26, 50.
2. Nivin, B.; Nicholas, P.; Gayer, M.; Frieden, T. R.; Fuji-
wara, P. I. Clin. Infect. Dis. 1998, 26, 303.
19. Collins, L. S.; Franzblau, S. G. Antimicrob. Agents Che-
mother. 1997, 41, 1004.