Synthesis of substituted triazolyl curcumin mimics that inhibit RANKL-induced osteoclastogenesis

Article abstract of DOI:10.1016/j.bmcl.2011.04.106

Some promising new antiresorptive agents of potential utility for treating osteoporosis were uncovered in a curcumin mimics library possessing a substituted triazole moiety, which is synthesized by the Cu(I)-catalyzed Huisgen 1,3-cycloaddition reaction be

Full text of DOI:10.1016/j.bmcl.2011.04.106

Bioorganic & Medicinal Chemistry Letters 21 (2011) 3573–3577
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of substituted triazolyl curcumin mimics that inhibit
RANKL-induced osteoclastogenesis
Sang-Kyu Park a, , Sangtae Oh b, , Hye Kyoung Shin c, Seong Hwan Kim c, Jungyeob Ham d,
Jae-Seok Song e, Seokjoon Lee b,
⇑
a Department of Biochemistry, Kwandong University College of Medicine, Gangneung 210-701, Republic of Korea
b Department of Basic Science, Kwandong University College of Medicine, Gangneung 210-701, Republic of Korea
c Laboratory of Chemical Genomics, Pharmacology Research Center, Bio-organic Science Division, Korea Research Institute of Chemical Technology, Daejeon 305-600, Republic of Korea
d Marine Chemomics Laboratory, Medicine Center, Korea Institute of Science and Technology, Gangneung 210-340, Republic of Korea
e Department of Preventive Medicine, Kwandong University College of Medicine, Gangneung 210-701, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Some promising new antiresorptive agents of potential utility for treating osteoporosis were uncovered
in a curcumin mimics library possessing a substituted triazole moiety, which is synthesized by the Cu(I)-
catalyzed Huisgen 1,3-cycloaddition reaction between two azido intermediates (9 and 10) and various
alkynes (a–k). A tartarate-resistant acid phosphatase (TRAP) activity assay was carried out with
RANKL-induced osteoclastogenesis of mouse monocyte/macrophage RAW264.7 cells; the results indi-
cated that the curcumin mimics derived from intermediate 10 exhibited stronger inhibitory activity than
9. In particular, curcumin mimics 12h, 13c, and 13e strongly inhibited osteoclast differentiation.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 29 March 2011
Revised 20 April 2011
Accepted 25 April 2011
Available online 28 April 2011
Bone tissue undergoes continuous renewal throughout life
through bone remodeling,1 a process that is tightly regulated by
a sequence of osteoclast-mediated bone resorption and osteo-
blast-mediated bone formation.2 The unbalance of resorption and
formation due to aging and hormone problems causes bone mass
to decrease3 and eventually results in bone disease including oste-
oporosis, which leads to an increased susceptibility to fracture.4
There are two kinds of treatment against osteoporosis: antiresorp-
tive therapy that inhibits bone resorption and anabolic therapy
that increases bone formation.5 Examples of antiresorptive agents
include bisphosphonate, which is a first-line treatment for osteo-
porosis patients,6 and estrogen analogs7 such as Raloxifene8 and
Calcitonin.9 On the other hand, the recombinant parathyroid hor-
mone (PTH) teriparatide is an anabolic agent that stimulates new
bone formation,10 although PTH treatment should not exceed
two years because it may cause increased incidence of osteosar-
coma depending on dose and treatment duration.11 Among the
pathogenic factors in osteoporosis that increase bone resorption,
macrophage RAW264.7 cells. In this Letter, we report the synthesis
of a curcumin mimics library and their inhibitory efficacy against
osteoclast differentiation.
Curcumin (diferuloyl methane, 1) isolated from the root of
Curcuma longa L. showed diverse biologic activity; that is, it is anti-
inflammatory, antioxidant, antiviral, and has chemopreventive ef-
fects, anti-infectious activities, and wound-healing properties.13
We have previously found that various curcumin mimics (2), with
asymmetric units possessing alkyl amide and aryl amide functional
groups, have an antiangiogenesis effect14 and multidrug resistance
(MDR) reversal activity.15,16 In addition, sulfonyl amide-linked cur-
cumin derivatives (3) also exhibited a vasodilatation effect on the
basilar artery induced by high K+ ion.17 (Fig. 1) Our research results
on curcumin mimics based on the diverse biologic activity of cur-
cumin indicate that it is a promising natural product for potential
treatment of human diseases. Moreover, Hanazawa and co workers
reported that curcumin promoted apoptosis of rabbit osteoclast,18
and Aggarwal and co workers reported that curcumin suppressed
RANKL signaling and eventually inhibited RANKL-induced osteo-
clastogenesis in RAW 264.7 cells, a murine monocytic cell line.19
Curcumin was also reported to improve bone microarchitecture
and enhance mineral density in APP/PS1 transgenic mice.20 Based
on continuous reports on the antiosteoporosis property of curcu-
min, we are convinced that the feruloyl scaffold may have the
potential to show antiosteoclastogenesis activity. Thus, we de-
signed novel structures for antiosteoporosis drug candidates and
synthesized substituted triazolyl curcumin mimics (4) using
Cu(I)-catalyzed Huisgen 1,3-cycloaddition21,22 as a key reaction.
(Fig. 1).
the receptor activator of NF-jB ligand (RANKL) plays a critical role
in osteoclast differentiation and activation.12 Therefore, the inhibi-
tion of RANKL is one promising therapy to effectively control
osteoclastogenesis. During our research for novel drug candidates
against osteoporosis from natural products or their mimics, we dis-
covered that curcumin mimics showed potent inhibitory activities
in the RANKL-induced osteoclastogenesis of mouse monocyte/
⇑
Corresponding author. Tel.: +82 33 649 7454; fax: +82 33 641 1074.
E-mail address: sjlee@kwandong.ac.kr (S. Lee).
These authors are equally contributed on this work.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.04.106

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S.-K. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3573–3577
O
H
N
O
O
H3CO
HO
R
H3CO
HO
OCH3
OH
O
1
3
2
N
O
O
N
H
N
R
H3CO
HO
R
O2
H3CO
HO
N
S
4
Figure 1. Structures of curcumin and synthetic curcumin mimics.
To obtain important synthetic intermediates (E)-1-(3-azidophe-
nyl)-3-(4-hydroxy-3-methoxyphenyl)prop-2-en-1-one (9) and (E)-
1-(3-azidophenyl)-3-(3-hydroxy-4-methoxyphenyl)prop-2-en-1-
one (10) for the curcumin mimics library, we explored two synthetic
routes. Route A started with the synthesis of 1-(3-aminophenyl)-3-
(4-hydroxy-3-methoxyphenyl)propenone (8) from the reaction of
4-hydroxy-3-methoxybenzaldehyde (5) with 3-acetylaniline (7) in
thepresenceofabasiccatalyst(40%KOH)inethanolatroomtemper-
aturefor10 h.17 Inourpreviousstudy,wefoundthatcompound8was
a useful intermediate to construct a curcumin mimics library with
substituted amide or sulfonamide functionalities, which showed
interesting MDR reversal activity and vasodilatation effect, respec-
tively.16,17 The double bond in the feruloyl structure was conformed
to the trans configuration because of a large coupling constant
(approximately J = 15 Hz) between its two protons. The amine group
of compound 8 was transformed by diazotization with 18% hydro-
chloric acid solution and sodium nitrite (1 equiv) in ice bath to pro-
duce a diazonium ion, which subsequently reacted with sodium
azide (2 equiv) to form the azido group of 9 (Scheme 1 Route A).23,24
However, because it was difficult to separate compound 9 from the
starting material (8), we synthesized the azido intermediate 9 from
thealdolreactionof5with1-(3-azidophenyl)ethanone(11)obtained
from7(Scheme1RouteB),whichallowedeasierpurificationofprod-
uct9fromunreactedstartingmaterials5and11.Usingthismoreeffi-
cient synthetic route, we also obtained the 3-hydroxy-4-methoxy
synthetic intermediate (10), a regioisomer of 9.24
In order to discover novel small molecular inhibitors derived
from curcumin mimics against RANKL-induced osteoclastogenesis
of mouse monocyte/macrophage RAW264.7 cells, we attempted a
tartrate-resistant acid phosphatase (TRAP) activity assay; the
inhibitory activity is summarized in Table 1.26 Between the two
synthetic intermediates 9 and 10, the latter showed approximately
three times more potent inhibitory effect against osteoclastogene-
sis. Positions of the methoxy and hydroxyl moieties of intermedi-
ate 10 are different from those of the parent compound (1),
indicating that the position of these substituents in the curcumin
mimics affects the inhibition of osteoclast differentiation induced
by RANKL. For compounds having 2-hydroxypropyl (a) and prope-
nyl (b) triazol groups, inhibitory activity of 12a and 12b (IC50
19.79 and 9.79 M, respectively) was slightly decreased relative
to 9, while the inhibition potency of 13a and 13b (IC50, 17.09 and
7.76 M, respectively) derived from intermediate 10 greatly de-
,
l
l
creased. Postulating that the slightly stronger hydrophobic prop-
erty of the propenyl (b) group improved the inhibition activity of
12b and 13b compared to 12a and 13a, respectively, we synthe-
sized 12c and 13c with a more hydrophobic phenyl group. The
inhibition effect of 12c was not improved; however the inhibitory
activity of 13c increased to a similar potency level as that of 10.
Based on this structure–activity relationship, which suggests that
improved hydrophobic property might improve the effect on the
osteoclastogenesis, we constructed additional curcumin mimics
possessing substituted aromatic triazoles. Substitution of hydrogen
with fluoride, an isostere of hydrogen, in the phenyl group of 12d
and 13d resulted in an improvement of in the inhibitory effect for
12d only. For compounds with electro-donating groups (e, f, or g)
to the phenyl ring, only 12g possessing a 4-pentylphenyl group and
13e having a 4-methylphenyl group showed increased inhibitory
activity compared to the intermediates 9 and 10, respectively.
Interestingly, among the curcumin mimics derived from
To construct a curcumin mimics library with substituted traiz-
olyl groups (12a–12k and 13a–13k), we attempted the Huisgen
1,3-cycloaddition reaction21,22 between various alkynes (a–k) and
the two azide intermediates (9 and 10), with CuSO4 and sodium
ascorbate in a solution mixture of chloroform, ethanol, and water
(5:3:1).25 The yields of triazole products are summarized in
Scheme 2.
O
O
(a)
R1
R2
NH2
NH2
Route A
O
7
8
R1: OCH3, R2: OH
R1
+
H
(b)
(b)
O
Route B
O
R2
5
6
R1: OCH3, R2: OH
R1: OH, R2: OCH3
R1
R2
N3
N3
(a)
11
9
R1: OCH3, R2: OH
10 R1: OH,
R2: OCH3
Scheme 1. Reagents and conditions: (a) 40% KOH, EtOH, rt, 10 h; (b) NaNO2 (1 equiv), 18% HCl, 0 °C, and then NaN3 (2 equiv); isolated yields for 8, 47%; 9, 28% from route A;
58% from route B; 11, 73%; 10, 40%.

S.-K. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3573–3577
3575
N
O
O
N
R
R1
R2
N3
R1
R2
N
(a)
+
R
alkyne a-k
12a-12k R1: OCH3, R2: OH
13a-13k R1: OH,
9
R1: OCH3, R2: OH
R2: OCH3
10 R1: OH,
R2: OCH3
F
OH
OCH3
F
c
a
d
b
e
f
R:
F3C
Cl
(CH2)4CH3
Br
F
g
j
k
i
h
Scheme 2. Reagents and conditions: (a) Sodium ascorbate (2.5 equiv), CuSO4 (1 equiv), chloroform/EtOH/H2O = 5:3:1, rt, 5 h; isolated yields for 12a, 43%; 12b, 64%; 12c, 74%;
12d, 73%; 12e, 80%; 12f, 45%; 12g, 90%; 12h, 95%; 12i, 63%; 12j, 63%; 12k, 92%; 13a, 25%; 13b, 52%; 13c, 52%; 13d, 49%; 13e, 60%; 13f, 50%; 13g, 58%; 13h, 46%; 13i, 55%; 13j,
54%; 13k, 30%.
Table 1
RANKL-induced osteoclast differentiation. Other curcumin mimics
having electron-withdrawing functionalities (h, i, j, or k) showed
only moderate potency against osteoclastogenesis. Four curcumin
mimics, 12h, 10, 13c, and 13e, strongly inhibited osteoclast differ-
entiation induced by RANKL in a dose-dependent manner shown in
Figure 2.
In conclusion, we synthesized a novel curcumin mimics library
by the Cu(I)-catalyzed Huisgen 1,3-cycloaddition reaction between
two azido intermediates (9 and 10) and various alkynes (a–k) with
the intention of discovering the new antiosteoporosis drug candi-
dates. Based on the TRAP activity screening using mouse mono-
cyte/macrophage RAW264.7 cells, we found that curcumin mimics
library possessing various substituted triazole moieties exhibited
moderate to strong inhibitory activity against the osteoclastogene-
sis induced by RANKL. Considering the preliminary structure–activ-
ity relationship, between the two synthetic intermediates 9 and 10,
we found that (3-hydroxy-4-methoxyphenyl)propenone (10)
showed more promise as a template for novel antiresorptive agents
RANKL-induced TRAP activity of curcumin mimics
IC50
(
l
M)
IC50 (lM)
9
7.11 0.50
19.79 0.43
9.79 3.66
16.81 1.13
6.45 0.48
15.42 0.99
7.90 2.43
5.78 0.22
5.07 0.38
14.27 3.91
19.08 3.48
22.75 2.12
10
1.96 0.67
17.09 1.24
7.76 0.41
1.51 0.96
2.50 0.08
1.70 0.42
6.29 0.21
>30
9.12 0.37
6.61 0.07
6.57 0.29
7.14 0.59
12a
12b
12c
12d
12e
12f
12g
12h
12i
12j
12k
13a
13b
13c
13d
13e
13f
13g
13h
13i
13j
13k
intermediate 9, 12h with an electron-withdrawing o-trifluorophe-
nyl triazole group showed the strongest inhibitory activity against
Figure 2. Effect of compounds (12h, 10, 13c, and 13e) on RANKL-induced TRAP activity in RAW264.7 cells in a dose-dependent manner ⁄p<0.001.

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S.-K. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3573–3577
123.9, 122.6, 120.0, 119.8, 118.8, 116.7, 114.9, 114.4, 110.0, 56.3, 56.1 ppm;
compound 12g: 1H NMR (300 MHz, CDCl3) d 8.39 (t, J = 1.8 Hz, 1H), 8.27 (s, 1H),
8.19 (m, 2H), 7.85 (m, 3H), 7.69 (t, J = 8.07 Hz, 1H), 7.41 (d, J = 15.45 Hz, 1H),
7.27 (m, 3H), 7.17 (d, J = 1.83 Hz, 1H), 6.98 (d, J = 8.2 Hz, 1H), 6.02 (br, 1H, –OH),
3.98 (s, 3H, –OCH3), 2.65 (t, J = 7.5 Hz, 2H), 1.34 (m, 6H), 0.90 (t, J = 6.8 Hz, 3H)
ppm; 13C NMR (75 MHz, CDCl3) d 189.0, 148.8, 148.7, 146.9, 146.5, 143.6,
140.0, 137.4, 130.1, 129.0, 128.3, 127.3, 127.1, 125.8, 124.1, 123.9, 119.9, 118.8,
117.2, 114.9, 114.3, 110.0, 56.1, 35.7, 31.4, 31.0 ppm; compound 12h: 1H NMR
(300 MHz, CDCl3) d 8.41 (t, J = 1.7 Hz, 1H), 8.30 (s, 1H), 8.09 (m, 3H), 7.77 (m,
4H), 7.54 (t, J = 7.5 Hz, 1H), 7.42 (m, 1H), 7.23 (d, J = 1.8 Hz, 1H), 7.17 (d,
J = 1.8 Hz, 1H), 6.98 (d, J = 8.1 Hz, 1H), 6.04 (br, 1H, –OH), 3.98 (s, 3H, –OCH3)
ppm; 13C NMR (75 MHz, CDCl3) d 189.0, 148.7, 146.9, 146.6, 140.2, 132.1,
131.8, 130.2, 128.7, 128.6, 127.1, 126.3, 126.2, 124.3, 124.0, 120.3, 118.8, 110.0,
56.1 ppm; compound 12i: 1H NMR (300 MHz, CDCl3) d 8.38 (t, J = 1.9 Hz, 1H),
8.33 (s, 1H), 8.08 (m, 2H), 7.93 (s, 1H), 7.81 (m, 2H), 7.70 (t, J = 7.9 Hz, 1H), 7.43
(m, 2H), 7.37 (m, 2H), 7.16 (d, J = 1.8 Hz, 1H), 7.04 (d, J = 8.4 Hz, 1H), 6.26 (br,
1H, –OH), 3.96 (s, 3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 190.9, 151.6,
148.8, 148.8, 147.1, 146.6, 140.1, 137.2, 134.9, 130.2, 129.9, 128.6, 127.5, 125.9,
124.1, 123.9, 119.9, 118.7, 118.0, 114.9, 114.3, 110.1, 108.7, 56.1, ppm;
compound 12j: 1H NMR (300 MHz, CDCl3) d 8.33 (t, J = 1.7 Hz, 1H), 8.03 (m, 3H),
7.83 (d, J = 15.5 Hz, 1H), 7.68 (t, J = 8.0 Hz, 1H), 7.42 (m, 3H), 7.03 (d, J = 8.4 Hz,
1H), 6.98 (d, J = 8.2 Hz, 1H), 6.24 (s, 1H), 5.87 (s, 1H), 5.21 (t, J = 1.5 Hz, 1H),
3.97 (s, 3H, –OCH3), 2.21 (s, 3H, CH3) ppm; 13C NMR (75 MHz, CDCl3) d 190.8,
151.6, 148.7, 147.1, 146.5, 130.1, 128.3, 127.5, 124.1, 123.9, 119.8, 118.8, 114.9,
114.3, 110.0, 108.7, 77.4, 77.0, 76.6, 56.1, 20.6 ppm; compound 12k: 1H NMR
(300 MHz, CDCl3) d8.38 (t, J = 1.7 Hz, 1H), 8.33 (s, 1H), 8.09 (m, 2H), 7.85 (d,
J = 15.6 Hz, 1H), 7.72 (t, J = 8.0 Hz, 1H), 7.45 (m, 1H), 7.28 (m, 1H), 7.17 (d,
J = 1.8 Hz, 1H), 7.06 (s, 1H), 7.03 (s, 1H), 6.98 (d, J = 8.2 Hz, 1H), 6.83 (m, 1H),
6.20 (br, 1H, –OH), 3.97 (s, 3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 190.8,
151.6, 148.8, 147.1, 146.9, 146.7, 140.2, 130.2, 129.9, 128.7, 127.5, 127.1, 124.2,
123.9, 120.0, 118.7, 118.4, 114.9, 114.3, 110.1, 108.9, 108.6, 56.1 ppm;
compound 13a: 1H NMR (300 MHz, CDCl3) d 8.29 (s, 1H), 8.03 (m, 3H), 7.80
(d, J = 15.6 Hz, 1H), 7.66 (t, J = 7.9 Hz, 1H), 7.40 (d, J = 15.6 Hz, 1H), 7.31 (d,
J = 2.0 Hz, 1H), 7.16 (dd, J = 1.8, 8.4 Hz, 1H), 6.88 (d, J = 8.3 Hz, 1H), 5.88 (br, 1H,
–OH), 3.95 (s, 3H, –OCH3), 1.73 (s, 6H) ppm; 13C NMR (75 MHz, CDCl3) d 188.8,
149.0, 146.1, 146.0, 139.9, 137.5, 130.1, 128.3, 128.1, 124.3, 123.1, 119.9, 119.2,
110.6, 56.0, 30.4 ppm; compound 13b: 1H NMR (300 MHz, CDCl3) d 8.30 (t,
J = 1.8 Hz, 1H), 8.05 (m, 3H), 7.80 (d, J = 15.6 Hz, 1H), 7.66 (t, J = 7.9 Hz, 1H),
7.40 (d, J = 15.6 Hz, 1H), 7.31 (d, J = 2.0 Hz, 1H), 7.16 (dd, J = 2.0, 8.2 Hz, 1H),
6.88 (d, J = 8.4 Hz, 1H), 5.87 (br, 1H, –OH), 5.20 (s, 1H), 3.95 (s, 3H, –OCH3), 2.21
(s, 3H) ppm; 13C NMR (75 MHz, CDCl3) d 188.9, 149.6, 149.2, 146.1, 146.0,
139.9, 137.4, 132.9, 130.1, 128.2, 128.1, 124.2, 123.1, 119.6, 119.3, 113.5, 113.1,
110.6, 56.0, 20.6 ppm; compound 13c: 1H NMR (300 MHz, CDCl3) d 8.36 (t,
J = 1.8 Hz, 1H), 8.33 (s, 1H), 8.10 (m, 2H), 7.95 (m, 1H), 7.82 (d, J = 15.5 Hz, 1H),
7.70 (t, J = 7.9 Hz, 1H), 7.46 (m, 5H), 7.32 (dd, J = 2.2, 8.6 Hz, 1H), 7.18 (dd,
J = 2.2, 8.6 Hz, 1H), 6.90 (d, J = 8.4 Hz, 1H), 5.73 (br, 1H, –OH), 3.96 (s, 3H, –
OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 189.0, 149.2, 146.1, 146.0, 130.2,
128.9, 128.5, 128.1, 125.9, 124.3, 123.1, 119.7, 119.3, 113.1, 110.6, 56.0 ppm;
compound 13d: 1H NMR (300 MHz, CDCl3) d 8.35 (t, J = 1.8 Hz, 1H), 8.28 (s, 1H),
8.11 (m, 2H), 7.92 (m, 2H), 7.83 (d, J = 15.6 Hz, 1H), 7.71 (t, J = 7.9 Hz, 1H), 7.44
(m, 2H), 7.32 (d, J = 2.0 Hz, 1H), 7.17 (m, 1H), 6.97 (d, J = 8.7 Hz, 1H), 5.74 (br,
1H, –OH), 3.96 (s, 3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 189.0, 147.8,
146.2, 146.1, 145.9, 139.9, 130.2, 128.2, 127.7, 127.6, 124.6, 119.8, 116.2, 115.8,
114.1, 113.0, 110.7, 110.6, 56.0 ppm; compound 13e: 1H NMR (300 MHz, CDCl3)
d 8.36 (t, J = 2.0 Hz, 1H), 8.3 (s, 1H), 8.10 (m, 2H), 7.82 (m, 2H), 7.70 (t, J = 7.9 Hz,
1H), 7.45 (m, 1H), 7.27 (m, 4H), 7.18 (dd, J = 2.6, 8.4 Hz, 1H), 6.90 (d, J = 8.4 Hz,
1H), 5.73 (br, 1H, –OH), 3.96 (s, 3H, –OCH3), 2.41 (s, 3H, –CH3) ppm; 13C NMR
(75 MHz, CDCl3) d 189.1, 149.2, 146.1, 146.0, 130.2, 128.9, 128.5, 128.1, 125.9,
124.3, 123.1, 119.7, 119.3, 118.8, 117.0, 113.1, 110.6, 56.0, 21.2 ppm;
compound 13f: 1H NMR (300 MHz, CDCl3) d 8.35 (t, J = 1.8 Hz, 1H), 8.23 (s,
1H), 8.08 (m, 2H), 7.89 (m, 2H), 7.81 (d, J = 15.5 Hz, 1H), 7.69 (t, J = 8.0 Hz, 1H),
7.45 (m, 2H), 7.32 (d, J = 2.0 Hz, 1H), 7.18 (dd, J = 2.0, 8.43 Hz, 1H), 7.02 (d,
J = 9.0 Hz, 1H), 6.89 (d, J = 8.4 Hz, 1H), 5.76 (br, 1H, –OH), 3.96 (s, 3H, –OCH3),
3.87 (s, 3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 188.9, 149.1, 145.9, 128.1,
127.2, 124.2, 123.1, 119.3, 114.3, 113.1, 110.5, 100.5, 56.0, 55.3 ppm; 13g: 1H
NMR (300 MHz, CDCl3) d 8.34 (t, J = 1.7 Hz, 1H), 8.29 (s, 1H), 8.06 (m, 2H), 7.81
(m, 3H), 7.65 (t, J = 7.9 Hz, 1H), 7.40 (d, J = 15.5 Hz, 1H), 7.28 (m, 3H), 7.14 (dd,
J = 2.0, 8.4 Hz, 1H), 6.86 (d, J = 8.4 Hz, 1H), 6.03 (br, 1H, –OH), 3.92 (s, 3H, –
OCH3), 2.66 (t, J = 7.5 Hz, 2H), 1.64 (m, 2H), 1.31 (m, 4H), 0.90 (t, J = 6.8 Hz, 3H)
ppm; 13C NMR (75 MHz, CDCl3) d 188.8, 149.3, 148.7, 146.1, 146.0, 143.5,
139.8, 137.4, 130.1, 129.0, 128.3, 128.1, 127.3, 125.8, 124.2, 123.1, 119.6, 119.2,
117.2, 113.2, 110.6, 56.0, 35.7, 31.4, 31.0, 22.5, 14.0 ppm; compound 13h: 1H
NMR (300 MHz, CDCl3) d 8.39 (t, J = 1.8 Hz, 1H), 8.30 (s, 1H), 8.08 (m, 3H), 7.80
(m, 2H), 7.68 (m, 2H), 7.53 (t, J = 7.7 Hz, 1H), 7.41 (m, 1H), 7.30 (d, J = 2.0 Hz,
1H), 7.15 (dd, J = 2.0, 8.4 Hz, 1H), 6.89 (d, J = 8.3 Hz, 1H), 5.89 (br, 1H, –OH),
3.93 (s, 3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 188.9, 146.2, 140.0, 137.2,
132.1, 131.8, 130.2, 128.7, 128.6, 128.1, 126.3, 126.2, 124.5, 124.4, 123.0, 120.1,
119.3, 114.0, 113.2, 110.6, 110.2, 56.0 ppm; compound 13i: 1H NMR (300 MHz,
CDCl3) d 8.35 (t, J = 1.7 Hz, 1H), 8.34 (s, 1H), 8.10 (m, 2H), 7.94 (t, J = 1.6 Hz, 1H),
7.82 (m, 2H), 7.71 (t, J = 7.9 Hz, 1H), 7.39 (m, 4H), 7.18 (dd, J = 2.0, 8.3 Hz, 1H),
6.90 (d, J = 8.2 Hz, 1H), 5.72 (br, 1H, –OH), 3.96 (s, 3H, –OCH3) ppm; 13j: 1H
NMR (300 MHz, CDCl3) d 8.34 (t, J = 1.8 Hz, 1H), 8.32 (s, 1H), 8.10 (m, 2H), 7.81
(m, 4H), 7.70 (t, J = 7.9 Hz, 1H), 7.60 (m, 2H), 7.42 (d, J = 15.4 Hz, 1H), 7.32 (d,
J = 2.2 Hz, 1H), 7.16 (dd, J = 2.2, 8.4 Hz, 1H), 6.90 (d, J = 8.4 Hz, 1H), 5.73 (br, 1H,
–OH), 3.96 (s, 3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 188.9, 148.8, 146.1,
146.0, 140.0, 132.1, 130.2, 128.5, 128.1, 127.4, 124.3, 123.2, 119.2, 117.6, 113.1,
to treat osteoporosis. In addition, curcumin mimics such as 12h, 13c,
and 13e showed strong inhibitory activity against
osteoclastogenesis.
References and notes
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Endocr. Rev. 1999, 20, 345.
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24. Spectral data for 9: 1H NMR (300 MHz, CDCl3) d 7.75 (m, 2H), 7.64 (s, 1H), 7.47
(t, J = 10.3 Hz, 1H), 7.31 (d, J = 15.6 Hz, 1H), 7.21 (d, J = 8.1 Hz, 1H), 7.12 (s, 1H),
6.95 (d, J = 8.2 Hz, 1H), 6.07 (br, 1H, -OH), 3.95 (s, 3H, -OCH3) ppm; 13C NMR
(75 MHz, CDCl3) d 189.5, 148.5, 146.8, 145.9, 140.7, 140.0, 129.9, 127.1, 124.7,
123.5, 122.8, 119.1, 118.7, 114.8, 110.0, 55.9 ppm; compound 10: 1H NMR
(300 MHz, CDCl3): d 7.75 (2H), 7.65 (t, J = 1.8 Hz, 1H), 7.48 (t, J = 8.0 Hz, 1H),
7.33 (d, J = 15.6 Hz, 1H), 7.28 (1H), 7.23 (m, 2H), 7.14 (dd, J = 2.1, 8.6 Hz, 1H),
6.88 (d, J = 8.3 Hz, 1H), 5.74 (br, 1H, –OH), 3.95 (s, 3H, –OCH3) ppm; 13C NMR
(75 MHz, CDCl3) d 189.4, 149.0, 145.9, 145.5, 140.8, 140.1, 129.9, 128.3, 124.8,
123.0, 122.9, 119.7, 118.7, 113.0, 110.6, 56.0 ppm.
25. Spectral data for 12a: 1H NMR (300 MHz, CDCl3) d 8.30 (t, J = 1.7 Hz, 1H), 7.99
(3H), 7.80 (d, J = 15.5 Hz, 1H), 7.65 (t, J = 7.9 Hz, 1H), 7.36 (d, J = 15.6 Hz, 1H),
7.24 (dd, J = 1.9, 8.3 Hz, 1H), 7.15 (d, J = 1.7 Hz, 1H), 6.96 (d, J = 8.3 Hz, 1H), 3.96
(s, 3H, –OCH3), 1.72 (s, 6H, –CH3) ppm; 13C NMR (75 MHz, CDCl3) d 189.0,
148.8, 146.9, 146.6, 140.0, 137.4, 130.1, 128.3, 127.2, 124.2, 123.9, 120.0, 118.7,
115.0, 110.1, 68.6, 56.1, 31.0, 30.4, 29.6 ppm; compound 12b: 1H NMR
(300 MHz, CDCl3) d 8.33 (t, J = 1.7 Hz, 1H), 8.03 (m, 3H), 7.83 (d, J = 15.5 Hz,
1H), 7.68 (t, J = 8.0 Hz, 1H), 7.42 (m, 3H), 7.03 (d, J = 8.4 Hz, 1H), 6.98 (d,
J = 8.2 Hz, 1H), 6.24 (s, 1H), 5.87 (s, 1H), 5.21 (t, J = 1.5 Hz, 1H), 3.97 (s, 3H, –
OCH3), 2.21 (s, 3H, CH3) ppm; 13C NMR (75 MHz, CDCl3) d 190.8, 151.6, 148.7,
147.1, 146.5, 130.1, 128.3, 127.5, 124.1, 123.9, 119.8, 118.8, 114.9, 114.3, 110.0,
108.7, 77.4, 77.0, 76.6, 56.1, 20.6 ppm; compound 12c: 1H NMR (300 MHz,
CDCl3) d 8.38 (t, J = 1.7 Hz, 1H), 8.32 (s, 1H), 8.07 (m, 2H), 7.92 (m, 3H), 7.83 (d,
J = 15.6 Hz, 1H), 7.68 (t, J = 7.8 Hz, 1H), 7.40 (m, 5H), 7.24 (dd, J = 1.6, 8.3 Hz,
1H), 7.15 (d, J = 1.83 Hz, 1H), 6.97 (d, J = 8.1 Hz, 1H), 6.15 (br, 1H, –OH), 3.96 (s,
3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 189.0, 148.8, 148.7, 146.9, 146.5,
140.0, 137.4, 130.1, 129.9, 128.9, 128.6, 128.4, 127.1, 125.9, 124.1, 123.9, 119.9,
118.7, 117.6, 114.9, 114.4, 110.1, 56.1 ppm; compound 12d: 1H NMR (300 MHz,
CDCl3) d 8.38 (t, J = 1.9 Hz, 1H), 8.28 (s, 1H), 8.08 (m, 2H), 7.90 (m, 3H), 7.70 (t,
J = 8.0 Hz, 1H), 7.40 (d, J = 15.5 Hz, 1H), 7.16 (m, 4H), 6.98 (d, J = 8.2 Hz, 1H),
6.04 (br, 1H, –OH), 3.98 (s, 3H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 188.9,
148.8, 146.9, 146.6, 140.1, 130.2, 128.4, 127.7, 127.1, 124.1, 123.9, 119.9, 118.7,
117.4, 116.1, 115.8, 114.9, 110.1, 56.1 ppm; compound 12e: 1H NMR (300 MHz,
CDCl3) d 8.36 (s, 1H), 8.27 (s, 1H), 8.05 (m, 2H), 7.81 (m, 2H), 7.66 (t, J = 7.9 Hz,
1H), 7.40 (m, 1H), 7.25 (m, 4H), 7.14 (s, 1H), 6.96 (d, J = 8.3 Hz, 1H), 6.24 (br, 1H,
–OH), 3.95 (s, 3H, –OCH3), 2.39 (s, 3H, –CH3) ppm; 13C NMR (75 MHz, CDCl3) d
189.0, 148.8, 148.7, 146.9, 146.5, 140.0, 138.5, 137.4, 130.1, 129.6, 128.3, 127.1,
125.7, 124.1, 123.9, 119.8, 118.7, 117.3, 115.0, 110.2, 56.0, 21.3 ppm;
compound 12f: 1H NMR (300 MHz, CDCl3) d 8.38 (t, J = 1.7 Hz, 1H), 8.32 (s,
1H), 8.08 (m, 2H), 7.92 (m, 2H), 7.83 (d, J = 15.6 Hz, 1H), 7.68 (t, J = 8.0 Hz, 1H),
7.43 (m, 3H), 7.25 (dd, J = 1.9, 8.5 Hz, 1H), 7.15 (d, J = 1.8 Hz, 1H), 6.96 (d,
J = 8.1 Hz, 1H), 6.14 (br, 1H, –OH), 3.96 (6H) ppm; 13C NMR (75 MHz, CDCl3) d
189.0, 159.9, 148.7, 148.6, 146.9, 146.5, 137.4, 130.4, 128.3, 127.2, 127.1, 124.1,

S.-K. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3573–3577
3577
110.6, 56.0 ppm; compound 13k: 1H NMR (300 MHz, CDCl3) d 8.25 (m, 1H), 8.21
(s, 1H), 8.04 (m, 2H), 7.72 (m, 1H), 7.61 (m, 1H), 7.45 (m, 1H), 7.27 (m, 1H),
6.98–7.12 (m, 3H), 6.83 (m, 1H), 6.73 (m, 1H), 6.56 (d, J = 12.6 Hz, 1H), 5.73 (br,
1H, –OH), 3.99 (s, 1H, –OCH3) ppm; 13C NMR (75 MHz, CDCl3) d 191.0, 151.6,
148.8, 147.1, 146.1, 140.2, 130.2, 129.9, 128.7, 127.5, 127.1, 124.2, 123.9, 120.0,
118.7, 118.4, 114.9, 114.3, 110.1, 108.9, 108.6, 56.2 ppm.
with 10% FBS in the presence of 100 ng/ml RANKL (R&D Systems Inc., MN). The
following day, serially diluted chemicals were added into cells to make a final
concentration of 0.3–30 lM. On day 4, multinucleated osteoclasts were
visualized by TRAP staining using a leukocyte acid phosphatase kit 387-A
(Sigma, MO); (c) TRAP activity assay. The multinucleated cells were fixed with
10% formalin for 10 min and 95% ethanol for 1 min, and then dried. To measure
26. (a) Cell culture. All materials used for cell culture were purchased from HyClone
(UT). RAW264.7 cells were purchased from American Type Culture Collection
(VA) and cultured in Dulbecco’s Modified Eagle’s Medium (DMEM)
supplemented with 10% fetal bovine serum (FBS), 100 U/ml penicillin, and
TRAP activity, 100 ll of citrate buffer (50 mM, pH 4.6) containing 10 mM
sodium tartrate and 5 mM p-nitrophenylphosphate (Sigma) was added to the
dried cell-containing wells of 96-well plates. After incubation for 30 min, the
enzyme reaction mixtures were transferred into the well of fresh plates
containing an equal volume of 0.1 N NaOH. Absorption was measured at
410 nm with Wallac EnVision HTS microplate reader (PerlinElmer, Finland);
(d) Statistical analysis. Significance was determined using the Student’s t-test
and differences were considered significant when p <0.05.
100 mg/ml streptomycin with
a change of medium every 3 days in a
humidified atmosphere of 5% CO2 at 37 °C; (b) Osteoclast differentiation
assay. RAW264.7 cells were plated in a 96-well plate at the density of 1 Â 103
cells/well and cultured in a-minimal essential medium (MEM) supplemented