Synthesis and evaluation of electron-rich curcumin analogues

Article abstract of DOI:10.1016/j.bmc.2008.10.057

The natural product curcumin has long been recognized for its medicinal properties and is utilized for the treatment of many diseases. However, it remains unknown whether this activity is based on its presumably promiscuous scaffold, or if it results from the Michael acceptor properties of the α,β-unsaturated 1,3-diketone moiety central to its structure. To probe this issue, electron-rich pyrazole and isoxazole analogues were prepared and evaluated against two breast cancer cell lines, which resulted in the identification of several compounds that exhibit low micromolar to mid nanomolar anti-proliferative activity. A conjugate addition study was also performed to compare the relative electrophilicity of the diketone, pyrazole and isoxazole analogues.

Full text of DOI:10.1016/j.bmc.2008.10.057

Bioorganic & Medicinal Chemistry 17 (2009) 360–367
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and evaluation of electron-rich curcumin analogues
*
Michael W. Amolins , Laura B. Peterson , Brian S. J. Blagg
Department of Medicinal Chemistry, The University of Kansas, 1251 Wescoe Hall Drive, Malott 4070, Lawrence, KS 66045-7563, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The natural product curcumin has long been recognized for its medicinal properties and is utilized for the
treatment of many diseases. However, it remains unknown whether this activity is based on its presum-
ably promiscuous scaffold, or if it results from the Michael acceptor properties of the a,b-unsaturated 1,3-
diketone moiety central to its structure. To probe this issue, electron-rich pyrazole and isoxazole
analogues were prepared and evaluated against two breast cancer cell lines, which resulted in the iden-
tification of several compounds that exhibit low micromolar to mid nanomolar anti-proliferative activity.
A conjugate addition study was also performed to compare the relative electrophilicity of the diketone,
pyrazole and isoxazole analogues.
Received 10 September 2008
Revised 24 October 2008
Accepted 25 October 2008
Available online 29 October 2008
Keywords:
Curcumin
Cancer
Pyrazole
Isoxazole
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
Turmeric has been utilized for centuries in Eastern medicine as
a topical treatment for wounds, inflammation, and tumors.1 The
active component was identified as curcumin (1, Fig. 1), and its iso-
lation from the rhizome of Curcuma longa L. (Zingiberaceae) over
two centuries ago eventually allowed for structural identification
and testing against various diseases.2 Properties exhibited by cur-
cumin include anti-inflammatory, anti-oxidant, anti-viral, cutane-
ous wound healing, hypocholesterolemic effects in diabetic
patients, anti-angiogenic, and stimulatory response to stress-in-
duced biological activity.3,4 Curcumin has demonstrated preventa-
tive activity against Ab aggregation in Alzheimer’s models5, and
several studies have shown that curcumin manifests anti-prolifer-
ative activity against various cancers, including leukemia, colon, li-
ver, breast, and prostate cancers.4,6–8 However, the truly unique
feature of this molecule is its lack of toxicity. Large quantities of
curcumin can be consumed without toxicity, suggesting this mol-
ecule may serve as a valuable scaffold for therapeutic develop-
ment. Three phase I clinical trials have demonstrated tolerances
as high as 12 g per day.9,10 These distinctive properties make cur-
cumin a valuable lead compound for drug development, and it re-
mains the focus of several clinical trials.4,11
Figure 1. Curcumin.
to hinder pathways responsible for inflammatory cascades through
down regulation of the nuclear transcription factor-jB (NF-jB),
activator protein-1 (AP-1), and by decreasing levels of prostaglan-
din E2 synthase (PGE2).3,12 Curcumin manifests anti-oxidant activ-
ity by scavenging superoxides and hydrogen peroxide, and by
decreasing levels of nitric oxide synthase activity through its elec-
tron rich, aromatic appendages composed of masked catechols.3,13
Its anti-viral activity is most notably recognized by its ability to in-
hibit type I Human Immunodeficiency Virus (HIV), and its wound
healing properties result from the increased biosynthesis of TGF-
b1.3 Curcumin also promotes apoptosis in cancer cells by suppress-
ing cyclin D and endothelial growth factor receptor (EGFR) func-
tion, while simultaneously decreasing levels of phosphokinase B
(AKT), c-myc, and phospho-AKT (pAKT).13
In total, there are 97 previously reported biological targets for
curcumin, ranging from transcription factors to various enzymes
and receptors.4 However, it is not known whether these activities
are due to covalent modification of targets through its Michael
acceptor properties or general promiscuity resulting from the
moderately simple scaffold. It has been postulated that conversion
The ability of curcumin to exhibit such versatility can be at-
tested to the large number of biological targets that are affected
in response to administration of this compound. Anti-inflamma-
tory activity has been ascribed to result from curcumin’s ability
of the
a,b-unsaturated 1,3-diketone moiety into an electron-rich
ring system would lessen the potential for nucleophilic addition.14
Therefore, it was proposed that modification of the 1,3-diketone
into a comparatively electron-rich isoxazole moiety that contains
* Corresponding author. Tel.: +1 785 864 2288; fax: +1 785 864 5326.
E-mail address: bblagg@ku.edu (B.S.J. Blagg).
These authors contributed equally to this work.
0968-0896/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2008.10.057

M. W. Amolins et al. / Bioorg. Med. Chem. 17 (2009) 360–367
361
Scheme 1. Synthesis of 1,3-diketone angalogues.
two adjacent hydrogen bond acceptors in similar proximity to the
original ketones would accomplish this objective. Furthermore,
since the 1,3-diketone can tautomerize into the corresponding
enol15, it was proposed that a pyrazole aromatic nucleus would
represent an electron-rich mimetic of this hydrogen-bonding net-
work and also serve to suppress nucleophilic addition to the adja-
cent, conjugated olefins. Identification of previously reported
curcumin analogues that exhibit increased anti-proliferative,16,17
anti-malarial,18 anti-oxidant, and anti-inflammatory activity,19
as well as improved anti-neurodegenerative properties20,21
provided the basis for the heteroaromatic species reported in this
article.
amine hydrochloride (Scheme 2). After discovering the instability
of allylic alcohol 11 to these cyclization conditions, an alternative
pathway was utilized in which the
a,b-unsaturated ethyl ester
analogue (9) was first cyclized, and subsequently reduced with so-
dium borohydride to give the cyclized allylic alcohol, 20.
2.3. Electrophilicity of curcumin and analogues
To compare the electrophilicity of curcumin to the electron-rich
pyrazole and isoxazole analogues, 1,4-conjugate addition of benzyl
mercaptan to the benzylic olefins was monitored over time by 1H
NMR. After incubating an equimolar mixture of curcumin and ben-
zyl mercaptan for 1 h, new aliphatic protons began to appear at
d2.96 and d4.17 (Fig. 2), indicative of conjugate addition. Addition-
ally, the appearance of a multiplet at d3.57 was attributed to the
2. Results and discussion
a-methylene group adjacent to sulfur in the conjugated product.
2.1. Synthesis of 1,3-diketone analogues
Furthermore, two singlets appeared at d3.76 and d3.83 correspond-
ing to the disulfide product of benzyl mercaptan and the desym-
metrization of the curcumin scaffold, respectively.
Chemistry developed by Lin et al.16,17 was utilized and ex-
panded upon to prepare 1,3-diketone analogues for the purpose
of determining structure–activity relationships (Scheme 1). A com-
plex was formed between boric anhydride and 2,4-pentanedione,
facilitating a 1,5-bis-aldol condensation with 3,4-dimethoxybenz-
aldehyde to afford dimethylcurcumin, 4. Similar methodology
was used to derive compounds 5, 6, and 7 from their respective
3,4-disubstituted benzaldehydes and 3-substituted pentanediones.
Compounds 8, 9, and 10 were obtained from dimethylcurcumin (4)
via Michael addition with methyl propiolate, ethyl propiolate, and
Quantitative addition to the olefin was not observed due to com-
peting disulfide formation, however, integration of the emerging ali-
phatic protons with respect to the aromatic methoxy protons (Table
1) indicated 53% addition after 24 h. Additionally, mass spectrome-
try data provided evidence that addition of benzyl mercaptan to cur-
cumin resulted in both mono- and di-conjugate-addition products,
as masses were observed for both products. In contrast, when the re-
lated isoxazole and pyrazole analogues were incubated with benzyl
mercaptan for 48 h, no change in the 1H NMR was observed (see Sup-
porting Information), indicating that these species were not as sus-
ceptible to nucleophilic attack by benzyl mercaptan.
propiolamide, respectively. Reduction of the a,b-unsaturated ethyl
ester 9 with diisobutyl aluminum hydride at ꢀ78 °C produced the
allylic alcohol 11, in good yield.
This observation can be explained by the electron rich and het-
eraromatic nature of the pyrazole and isoxazole rings as compared
to the diketone species.22 The benzylic olefin is less susceptible to
Michael addition due to decreased electrophilicity and because the
mechanism by which such a transformation occurs involves a non-
aromatic intermediate. The electron-rich and heteroaromatic prop-
erties of the pyrazole and isoxazole rings suggest these compounds
2.2. Synthesis of pyrazole and isoxazole analogues
The completed diketone species were used to prepare pyrazole
analogues through an acid-catalyzed condensation with hydrazine
hydrochloride, while stirring at reflux for forty hours. The isoxazole
analogues were prepared in similar fashion enlisting hydroxyl-

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M. W. Amolins et al. / Bioorg. Med. Chem. 17 (2009) 360–367
Scheme 2. Synthesis of pyrazole and isoxazole analogues.
Table 1
Relative integrationa of protons resulting from 1,4-conjugate addition to curcumin.
Elapsed time
d 2.96 (d, J = 7.7,
a-CH2)
d 4.16 (t, J = 7.8, b-CH)
10 min
1 h
5 h
14 h
24 h
0.08
0.22
0.37
0.91
1.06
0.03
0.12
0.21
0.56
0.62
a
Integrations relative to aromatic OCH3 substituents (6H).
2.4. Growth inhibitory activity by curcumin and analogues
The data shown in Table 2 represent the growth inhibitory
activity of curcumin and its analogues against MCF-7 (ER+) and
SKBr-3 (ER-, HER2 overexpressing) breast cancer cell lines. The re-
sults indicate that compounds 4, 7, 8, 9, and 11 represent the most
potent analogues, manifesting submicromolar to low micromolar
IC50 values against both cell lines. Upon analysis of the anti-prolif-
eration data for these analogues, it is evident that in most cases,
IC50 values for the parent dione are better than the pyrazole and
isoxazole analogues. This can be attributed to the promiscuity of
the
a,b-unsaturated ketone, as well as conformational differences
between the 6-membered hydrogen-bonding network created by
the enol form of the diketone species and the rigid, more conform-
ationally constrained 5-membered ring derivatives. Additionally,
the pyrazole analogues exhibited lower IC50 values than the corre-
sponding isoxazole analogues, highlighting the potential signifi-
cance of a hydrogen bond donor on the pyrazole ring and its
related nature to the corresponding enol form of the diketone spe-
cies. Another interesting observation is the difference in IC50 values
between analogues with 3,4-dimethoxy substitution on each of the
Figure 2. 1H NMR spectra for the addition of benzyl mercaptan to curcumin (a)
10 min (b) 1 h (c) 5 h (d) 14 h (e) 24 h after addition.
are less electrophilic and therefore, less promiscuous than curcu-
min as a ‘‘general” alkylating agent within the cell.

M. W. Amolins et al. / Bioorg. Med. Chem. 17 (2009) 360–367
363
Table 2
inhibitory activity for curcumin and analogues. In fact, both the isox-
azole and pyrazole analogues displayed only slightly lower activities
than the related diketone species, with the pyrazole species mani-
festing slightly better activity than the related isoxazole. These stud-
ies highlighted the importance of the hydrogen-bonding network
demonstrated by curcumin in its enol form, which corresponds
favorably to pyrazoles H-bond donor/acceptor moieties. Curcumin
analogues with diminished electrophilicity that maintain anti-
proliferative activity are exciting and potentially viable targets for
future drug development.
Anti-proliferative activities of curcumin and analoguesa.
Compound
MCF-7 (IC50
,
l
M)b
SKBR3 (IC50
, lM)
1
4
5
6
7
5.58 0.97
1.07 0.05
1.96 0.35
>100
2.11 0.09
0.955 0.145
4.38 1.18
>100
1.09 0.03
1.02 0.05
0.564 0.020
1.96 0.65
9.83 1.12
1.24 0.58
0.258 0.034
1.58 0.46
5.60 1.24
11.7 0.5
>100
8
9
0.512 0.004
1.28 0.14
5.35 0.28
0.796 0.067
4.19 1.59
12.7 0.3
6.01 0.39
10.1 0.7
8.16 3.73
49.5 2.9
11.4 0.5
39.9 2.6
>100
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
4. Experimental
4.1. (1E,16E)-1,7-Bis(3,4-dimethoxyphenyl)hepta-1,6-diene-
3,5-dione (4)
>100
5.99 0.61
52.6 7.8
>100
4.00 0.13
>100
13.9 1.9
>100
42.5 12.2
2,4-Pentanedione (0.32 mL, 3.0 mmol) and boric anhydride
(0.15 g, 2.1 mmol) were dissolved in EtOAc (3.0 mL). The solution
was stirred for 30 min at 40 °C before 3,4-dimethoxybenzaldehyde
(1.0 g, 6.0 mmol) and tributyl borate (1.64 mL, 6.0 mmol) were
added and stirred for 30 min at 40 °C. n-Butylamine (0.45 mL,
4.5 mmol) was dissolved in EtOAc (3.0 mL), and added dropwise
over 15 min. The reaction mixture stirred for 24 h at 40 °C, at
which point it was quenched by the addition of 4 N HCl (10 mL).
The mixture was stirred at 60 °C for 30 min, and then the aqueous
layer extracted with EtOAc (3ꢁ 50 mL). The combined organic lay-
ers were washed with saturated aqueous NaHCO3 and saturated
aqueous NaCl, dried (Na2SO4), filtered, and concentrated. The resi-
due was purified by flash chromatography (SiO2, 2:3 EtOAc in hex-
anes, then 3:2 EtOAc in hexanes) to afford 4 (438.1 mg, 37%) as a
yellow amorphous solid: 1H NMR (CDCl3, 500 MHz) d 3.86 (d,
J = 6.20 Hz, 12H), 5.76 (s, 1 H), 6.43 (d, J = 15.8 Hz, 2H), 6.81 (d,
J = 8.35 Hz, 2H), 7.01 (d, J = 1.85 Hz, 2H), 7.08 (dd, J = 1.90 Hz,
8.30 Hz, 2H), 7.54 (d, J = 15.8 Hz, 2H); 13C NMR (CDCl3, 125 MHz)
d 55.9 (2C), 56.0 (2C), 77.3, 101.4 (2C), 109.6 (2C), 111.1 (2C),
122.0, 122.7, 128.0 (2C), 140.4 (2C), 149.2 (2C), 151.0 (2C), 183.3
(2C); IR (film) vmax 3001, 2959, 2934, 2912, 2837, 1624, 1582,
1556, 1512, 1462, 1454, 1441, 1421, 1339, 1300, 1263, 1232,
1198, 1159, 1136, 1022, 966 cmꢀ1; HRMS (ES+) m/z: [M+H] calcd
for C23H24O6 397.1651; found 397.1640.
1.76 0.39
59.5 6.5
13.2 1.6
>100
55.7 5.7
a
Values represent mean standard error for at least two separate experiments
performed in triplicate.
b
IC50 is defined as the concentration of compound necessary to inhibit cellular
growth by 50%.
aromatic rings and the analogues with the 3-methoxy-4-hydroxy
substitution, which is similar to the natural product. The diketone
species with a 3,4-dimethoxy substitution generally manifested
lower IC50 values than the analogues that contain phenols. In con-
trast, the pyrazole and isoxazole derivatives exhibited the opposite
trend, as the phenolic analogues exhibited lower IC50 values than
analogues with dimethoxy substitution. This can be attributed to
the electronic effect induced by the pyrazole and isoxazole rings,
which impacts the hydrogen bond capability and pKa of the phe-
nols as compared to the diketo species.23 Finally, the difference
in IC50 values between the diketo species with substitutions at
the
ing moiety generally lowers the IC50 value, as observed with com-
pounds and 11. Compound 6, containing 3,4-dimethoxy
a position indicates that an unsaturated and oxygen-contain-
8
4.2. (E)-Ethyl 7-(4-hydroxy-3-methoxyphenyl)-4-((E)-3-(4-
substitution and a saturated R2 substituent (Scheme 2) displayed
no anti-proliferative activity at the concentrations tested. Further
SAR is required to elucidate the origin of this effect as no other
compounds in this library shared this group of functionalities. It
should be noted that similar compounds bearing the unsaturated
amide substituent also manifested decreased activity, indicating
that nitrogen-bearing substituents may be detrimental to their
anti-proliferative activity. In summary, it was observed that the
most active analogues were those that contained a 3,4-dimethoxy
aromatic substitution and unsaturated, oxygen-containing substit-
hydroxy-3-methoxyphenyl)acryloyl)-5-oxohept-6-enoate (5)
Compound 5 was prepared following the same procedure used
for the preparation of 4. The residue was purified by flash chroma-
tography (SiO2, 5:3:2Hexanes:EtOAc:CH2Cl2) to afford 5 (490.0 mg,
32%) as an orange amorphous solid: 1H NMR (CDCl3, 500 MHz) d
1.18 (t, J = 9.5 Hz, 3H), 2.48 (t, J = 8 Hz, 2H), 2.87 (t, J = 9.5 Hz,
2H), 3.90 (s, 6H), 4.06 (q, J = 7.15 Hz, 2H), 5.82 (s, 2H), 6.87 (s,
1 H), 6.88–6.89 (m, 2H), 6.92 (s, 1 H), 7.02 (d, J = 2Hz, 2H), 7.10
(d, J = 8.25 Hz, 2H), 7.64 (d, J = 15.3 Hz, 2H); 13C NMR (CDCl3,
125 MHz) d 14.2, 21.7, 36.6, 56.0 (2C), 60.7, 109.5, 110.1 (2C),
114.9 (2C), 117.8 (2C), 122.9 (2C), 128.0 (2C), 142.2 (2C), 146.8
(2C), 147.9 (2C), 173.0, 182.9 (2C); IR (film) mmax 3400, 3074,
2961, 2926, 2852, 2400, 1722, 1663, 1618, 1587, 1514, 1454,
1429, 1393, 1377, 1275, 1207, 1186, 1161, 1124, 1101, 1032,
976, 945 cmꢀ1; HRMS (ES+) m/z: [M+Na] calcd for C26H28O8
491.1682; found 491.1677.
uents flanking the
molar IC50 values.
a position, which exhibited low to sub micro-
3. Conclusion
We havecompleteda libraryof curcuminanaloguesin an effortto
elucidate structure–activity relationships, as well as to determine
the relevance of curcumin’s Michael acceptor properties and its abil-
ity to act as an anti-cancer agent. Anti-proliferative data from two
breast cancer cell lines were obtained, which led to identification
of several compounds that exhibit increased growth inhibitory
activity versus the natural product. Furthermore, it was determined
that the Michael acceptor properties were not critical to retention of
4.3. (E)-Ethyl-7-(3,4-dimethoxyphenyl)-4-((E)-3-(3,4-
dimethoxyphenyl)acryloyl)-5-oxohept-6-enoate (6)
Compound 6 was prepared following the same procedure used
for the preparation of 4. The residue was purified by flash chroma-

364
M. W. Amolins et al. / Bioorg. Med. Chem. 17 (2009) 360–367
tography (SiO2, 5:3:2Hexanes:EtOAc:CH2Cl2) to afford 6 (351.1 mg,
23%) as a yellow amorphous solid: 1H NMR (CDCl3, 500 MHz) As a
mixture of tautomers: d 1.26 (t, J = 7.2 Hz, 3H), 1.26 (t, J = 7.2Hz,
3H), 2.36 (t, J = 6.9 Hz, 2H), 2.40 (t, J = 6.9, 2H), 2.57 (t, J = 7.4 Hz,
2H), 2.97 (t, J = 7.3 Hz, 2H), 3.93 (12H), 3.97 (12H), 4.15 (q,
J = 7.1 Hz, 2H), 4.15 (q, J = 7.1 Hz, 2H), 4.26 (t, J = 7.1 Hz, 1H), 6.73
(d, J = 15.9 Hz, 2H), 6.87 (d, J = 8.3 Hz, 2H), 6.90 (d, J = 8.3 Hz, 2H),
7.01 (d, J = 15.3 Hz, 2H), 7.07 (d, J = 1.8 Hz, 2H), 7.14 (d, J = 1.7 Hz,
2H), 7.16 (dd, J1 = 8.4 Hz, J2 = 1.8 Hz, 2H), 7.20 (dd, J1 = 8.4 Hz,
J2 = 1.6 Hz, 2H), 7.67 (d, J = 15.9 Hz, 2H), 7.74 (d, J = 15.3 Hz, 2H);
13C NMR (CDCl3, 125 MHz) As a mixture of tautomers d 14.1,
14.2, 23.3, 29.7, 31.6, 36.6, 56.0 (4C), 60.6 (2C), 63.5, 108.9,
109.6, 109.9, 110.2, 110.4, 111.0 (2C), 111.1 (2C), 118.0, 121.7
(2C), 122.7 (2C), 123.9, 126.9 (2C), 127.1 (3C), 128.4 (2C), 142.1,
145.0, 149.2 (4C), 151.1 (2C), 151.8 (2C), 172.9 (2C), 182.9, 190.9,
194.9 (2C); IR (film) mmax 3061, 2959, 2930, 2853, 2617, 2357,
2029, 1732, 1681, 1666, 1639, 1593, 1574, 1556, 1514, 1504,
1454, 1444, 1421, 1377, 1339, 1308, 1263, 1231, 1186, 1161,
1138, 1109, 1022, 984, 945 cmꢀ1; HRMS (ES+) m/z: [M+Na] calcd
for C28H32O8 519.1995; found 519.1944.
118.8, 121.9, 123.0, 128.0 (2C), 139.3 (2C), 143.0, 149.3 (2C),
151.5 (2C), 167.3, 183.8 (2C); IR (film) mmax 2999, 2949, 2935,
2910, 2837, 2604, 2359, 1715, 1614, 1597, 1580, 1508, 1437,
1420, 1342, 1308, 1261, 1225, 1190, 1161, 1138, 1022, 1001,
982, 964, 932 cmꢀ1; HRMS (ES+) m/z: [M + Na] calcd for C27H28O8
503.1682; found 503.1667.
4.6. (2E,6E)-Ethyl-7-(3,4-dimethoxyphenyl)-4-((E)-3-(3,4-
dimethoxyphenyl)acryloyl)-5-oxohepta-2,6-dienoate (9)
Compound 9 was prepared following the same procedure used
for the preparation of 8. The residue was purified by flash chroma-
tography (SiO2, 1:199 MeOH in CH2Cl2, then 1:66 MeOH in CH2Cl2)
to afford 9 (636.0 mg, 94.4%) as a red amorphous solid: 1H NMR
(CDCl3, 500 MHz) d 1.35 (t, J = 7.16 Hz, 3H), 3.95 (s, 12H), 4.30 (q,
J = 7.12Hz, 2H), 5.98 (d, J = 15.64 Hz, 1 H), 6.91 (d, J = 8.34 Hz,
2H), 7.00 (d, J 15.42Hz, 2H), 7.09 (d, J = 1.84 Hz, 2H), 7.21 (dd,
J = 1.84, 8.34 Hz, 2H), 7.78 (d, J = 15.42 Hz, 2H), 7.91 (d,
J = 15.64 Hz, 1 H); 13C NMR (CDCl3, 125 MHz) d 14.6, 56.17 (2C),
56.24 (2C), 60.8, 110.2 (3C), 110.5 (2C), 111.4 (2C), 119.2, 122.7,
123.3, 128.3 (2C), 139.2 (2C), 143.1, 149.5 (2C), 151.6 (2C), 167.1,
183.9 (2C); IR (film) vmax 3061, 2978, 2961, 2935, 2907, 2872,
2837, 2598, 2033, 1715, 1614, 1595, 1580, 1512, 1464, 1443,
1421, 1367, 1308, 1265, 1161, 1140, 1097, 1024, 976 cmꢀ1; HRMS
(ES+) m/z: [M+Na] calcd for C28H30O8 517.1838; found 517.1826.
4.4. (1E,6E)-1,7-Bis(3,4-dimethoxyphenyl)-4-methylhepta-1,6-
diene-3,5-dione (7)
Compound 7 was prepared following the same procedure used
for the preparation of 4. The residue was purified by flash chroma-
tography (SiO2,1:1Hexanes:EtOAc) to afford 7 (573.7 mg, 44%) as a
dark yellow amorphous solid: 1H NMR (CDCl3, 400 MHz) As a mix-
ture of tautomers: d 1.51(d, J = 6.9 Hz, 3H), 2.19(s, 3H), 3.92–
3.96(24H), 6.72(d, J = 15.9 Hz, 2H), 6.89(d, J = 8.4 Hz, 2H), 6.99(d,
J = 15.3 Hz, 2H), 7.06(d, J = 1.68, 2H), 7.10(s, 2H), 7.16(dd, J1 = 8.5,
J2 = 1.9, 2H), 7.19(d, J = 8.2, 2H), 7.43(s, 1H), 7.48(dd, J1 = 8.1,
J2 = 2.2, 1 H), 7.65(d, J = 16.0 Hz, 2H), 7.70(d, J = 15.4, 2H); 13C
NMR (CDCl3, 125 MHz) As a mixture of tautomers d 12.1 29.7,
55.9 (4C), 56.0 (4C), 59.0, 105.7, 109.9, 110.0, 110.1, 110.4, 111.0,
111.0, 111.1, 111.2, 116.6, 118.7 (2C), 121.4 (2C), 122.5, 123.7,
124.4, 127.1 (2C), 128.5, 141.3, 144.7, 146.2 (2C), 149.2 (2C),
149.2 (2C), 151.0 (2C), 151.7, 152.0, 182.5, 191.0, 196.1, 196.8; IR
(film) mmax 3412, 3059, 2999, 2959, 2928, 2853, 2839, 2613,
2598, 2536, 2359, 2035, 1713, 1668, 1591, 1514, 1464, 1454,
1443, 1421, 1377, 1340, 1308, 1265, 1238, 1198, 1161, 1140,
1107, 1045, 1024, 982, 947, 924 cmꢀ1; HRMS (ES+) m/z: [M+H]
calcd for C24H26O6 411.1808; found 411.1800.
4.7. (2E,6E)-7-(3,4-Dimethoxyphenyl)-4-((E)-3-(3,4-
dimethoxyphenyl)acryloyl)-5-oxohepta-2,6-dienamide (10)
Concentrated aqueous ammonia (6.5 mL) was cooled in a dry
ice-isopropyl alcohol bath. Methyl propiolate (2.0 mL, 22.4 mmol)
was added dropwise, and after 10 min, the organic layer was ex-
tracted with EtOAc (3ꢁ 5 mL), dried over Na2SO4, and concen-
trated, affording crystalline propiolamide (quantitative).
Compound
4 (600.0 mg, 1.52 mmol) was dissolved in THF
(10.0 mL) and stirred at rt before NaH (54.52 mg, 60% wt in mineral
oil, 1.36 mmol) was added. The solution was stirred for 30 min at
rt. In a separate flask, propiolamide (209.3 mg, 3.03 mmol) was dis-
solved in THF (6.0 mL) and stirred at rt. Contents from the first flask
were slowly added via cannula to the propiolamide solution over
10 min, and subsequently stirred at rt for 24 h. The reaction was
quenched by addition of 5% sulfuric acid (25 mL) and the aqueous
layer extracted with EtOAc (3ꢁ 50 mL). The combined organic lay-
ers were washed with saturated aqueous NaHCO3 and saturated
aqueous NaCl, dried (Na2SO4), filtered, and concentrated. The resi-
due was recrystallized from EtOAC/hexanes to afford 10 (557.7 mg,
88%) as an orange amorphous solid: 1H NMR (CDCl3, 500 MHz) d
3.94 (d, J = 1.9 Hz, 12H), 5.45 (s, -NH2), 5.95 (d, J = 15.2Hz, 1H),
6.90 (d, J = 8.4 Hz, 2H), 6.98 (d, J = 15.4 Hz, 2H), 7.07 (d, J = 1.9 Hz,
2H), 7.21 (dd, J = 1.9, 8.4 Hz, 2H), 7.76 (d, J = 15.4 Hz, 2H), 7.90 (d,
J = 15.2 Hz, 1H); 13C NMR (CDCl3, 125 MHz) d 55.9 (2C), 56.0 (2C),
110.1 (3C), 110.3 (2C), 111.1 (2C), 118.8, 122.9, 124.1, 128.0 (2C),
137.2 (2C), 142.6, 149.2 (2C), 151.3 (2C), 166.9, 183.4 (2C); IR (film)
vmax 3412, 3323, 3292, 3215, 2999, 2943, 2837, 1663, 1614, 1597,
1582, 1510, 1466, 1441, 1421, 1385, 1342, 1308, 1263, 1225, 1161,
1140, 1111, 1020, 1001, 978, 966 cmꢀ1; HRMS (ESꢀ) m/z: [MꢀH]
calcd for C26H27NO7 464.1709; found 464.1731.
4.5. (2E,6E)-Methyl-7-(3,4-dimethoxyphenyl)-4-((E)-(3,4-
dimethoxyphenyl)acryloyl)-5-oxohepta-2,6-dienoate (8)
Compound 4 (500.0 mg, 1.26 mmol) was dissolved in THF
(6.0 mL) and stirred at rt before NaH (45.4 mg, 60% wt in mineral
oil, 1.17 mmol) was added. The solution was stirred for 30 min at
rt. In a separate flask, methyl propiolate (0.17 mL, 1.95 mmol)
was dissolved in THF (9.0 mL) and stirred at room temperature.
Contents from the first flask were slowly added via cannula to
the methyl propiolate solution over 10 min, and subsequently stir-
red at rt for 24 h. The reaction was quenched by addition of 5% sul-
furic acid (25 mL) and the aqueous layer extracted with EtOAc (3ꢁ
50 mL). The combined organic layers were washed with saturated
aqueous NaHCO3 and saturated aqueous NaCl, dried (Na2SO4), fil-
tered, and concentrated. The residue was purified by flash chroma-
tography (SiO2, 2:3 EtOAc in hexanes, then 3:2 EtOAc in hexanes)
to afford 8 (291.0 mg, 53%) as an orange amorphous solid: 1H
NMR (CDCl3, 500 MHz) d 3.85 (s, 3H), 3.96 (d, J = 1.65, 12H), 6.00
(d, J = 11.7 Hz, 1H), 6.92 (d, J = 11.7 Hz, 2H), 7.00 (d, J = 11.6 Hz,
2H), 7.09 (s, 2H), 7.22 (d, J = 6.15 Hz, 2H), 7.79 (d, J = 11.6 Hz,
2H), 7.93 (d, J = 11.7 Hz, 1H); 13C NMR (CDCl3, 125 MHz) d 51.8,
56.02 (2C), 56.04 (2C), 109.9, 110.0 (2C), 110.5 (2C), 111.2 (2C),
4.8. (1E,6E)-1,7-Bis(3,4-dimethoxyphenyl)-4-((E)-3-
hydroxyprop-1-enyl)hepta-1,6-diene-3,5-dione (11)
Compound 9 (500.0 mg, 1.0 mmol) was dissolved in CH2Cl2
(10.0 mL) and cooled to ꢀ78 °C before dibal-H (3.0 mL, 1 M in
CH2Cl2, 3.0 mmol) was added drop wise. After 30 min, the solution
was warmed to rt and stirred for an additional 1.5 h. The solution
was quenched using saturated aqueous sodium potassium tartrate

M. W. Amolins et al. / Bioorg. Med. Chem. 17 (2009) 360–367
365
(Rochelle’s salt) and the aqueous layer extracted with CH2Cl2 (3ꢁ
50 mL). The combined organic layers were washed with saturated
aqueous NaCl, dried (Na2SO4), and concentrated. The residue was
6.93 (dd, J1 = 8.2 Hz, J2 = 1.6 Hz, 2H), 7.06 (d, J = 16.5 Hz, 2H); 13C
NMR (CDCl3, 125 MHz) d 14.2, 18.8, 35.5, 55.8 (2C), 60.6, 108.4
(2C), 113.9, 114.6 (2C), 115.3 (2C), 120.5 (2C), 129.4 (2C), 130.1
(2C), 144.0 (2C), 145.9 (2C), 146.8 (2C), 173.0; IR (film) mmax
3323, 3041, 3034, 2957, 2924, 2851, 2320, 1724, 1661, 1593,
1556, 1514, 1464, 1429, 1375, 1277, 1238, 1205, 1159, 1124,
1099, 1068, 1034, 962 cmꢀ1; HRMS (ES+) m/z: [M+H] calcd for
C26H28N2O6 465.2026; found 465.2005.
purified
by
flash
chromatography
(SiO2,
1:5:9:10
MeOH:CH2Cl2:EtOAc:hexanes) to afford 11 (301.3 mg, 66%) as a
red amorphous solid: 1H NMR (CDCl3, 500 MHz) d 3.92 (d,
J = 3.9 Hz, 12H), 4.40 (d, J = 4.6 Hz, 2H), 5.88 (dt, J = 5.7, 15.6 Hz,
1H), 6.58 (dt, J = 1.4, 15.6 Hz, 1H), 6.87 (d, J = 8.3 Hz, 2H), 6.97 (d,
J = 15.6 Hz, 2H), 7.05 (d, J = 1.8 Hz, 2H), 7.16 (dd, J = 1.8, 8.4 Hz,
2H), 7.67 (d, J = 15.6 Hz, 2H); 13C NMR (CDCl3, 125 MHz) d 55.94,
55.98, 56.0 (2C), 63.6, 110.4, 111.0 (2C), 111.1 (2C), 111.5 (2C),
119.7, 122.5, 124.2, 128.4 (2C), 136.5 (2C), 141.2, 149.2 (2C),
151.0 (2C), 182.5 (2C); IR (film) vmax 3458, 3443, 2997, 2926,
2874, 2853, 2835, 1620, 1595, 1580, 1556, 1510, 1464, 1454,
1435, 1421, 1337, 1306, 1261, 1192, 1159, 1138, 1094, 1022,
959, 930 cmꢀ1; HRMS (ESꢀ) m/z: [MꢀH] calcd for C26H28O7
451.1757; found 451.1766.
4.12. Ethyl 3-(3,5-bis(3,4-dimethoxystyryl)-1-H-pyrazol-4-
yl)propanoate (15)
Compound 15 was prepared following the same procedure used
for the preparation of 12. The residue was purified by flash chro-
matography (SiO2, 5:3:2 Hexanes:EtOAc:CH2Cl2) to afford 15
(43.0 mg,73%) as a yellow–orange amorphous solid: 1H NMR
(CDCl3, 500 MHz) d 1.23 (t, J = 7.1 Hz, 3H), 2.58 (t, J = 7.7 Hz, 2H),
3.03 (t, J = 7.8 Hz, 2H), 3.87 (12H), 4.12 (q, J = 4.1 Hz, 2H), 6.77
(m, 2H), 6.85 (m, 2H), 6.93 (d, J = 8.25 Hz, 2H), 6.97 (s, 2H), 7.07
(m, 2H); 13C NMR (CDCl3, 125 MHz) 14.2, 18.8, 35.6, 55.9 (4C),
60.6, 108.2 (2C), 111.1, 114.3 (2C), 115.4 (2C), 120.1 (2C), 129.3
(2C), 129.7 (2C), 129.9 (2C), 149.1 (2C), 149.1 (2C), 173.0; IR (film)
mmax 3333, 3173, 3078, 3030, 2957, 2924, 2851, 1728, 1666, 1601,
1583, 1556, 1514, 1464, 1443, 1420, 1373, 1335, 1265, 1234, 1159,
1138, 1095, 1068, 1026, 962 cmꢀ1; HRMS (ES+) m/z: [M+H] calcd
for C28H32N2O6 493.2339; found 493.2321.
4.9. 4,40-(1E,10E)-2,20-(1-H-Pyrazole-3,5-diyl)bis(ethene-2,1-
diyl)bis(2-methoxyphenol) (12)
Compound 1 (300.0 mg, 0.81 mmol) was dissolved in absolute
EtOH (5.0 mL). Hydrazine hydrochloride (66.9 mg, 0.984 mmol)
was added followed by a catalytic amount of glacial acetic acid
(1.0 mL). The solution stirred at reflux for 40 h. The crude reaction
mixture was concentrated in vacuo and redissolved in EtOAc
(200 mL). The organic layer was washed with saturated aqueous
NaHCO3 and saturated NaCl, dried (Na2SO4), filtered, and concen-
trated in vacuo. The residue was purified by column chromatogra-
phy (SiO2, 5:3:2 hexanes:EtOAc:CH2Cl2) to afford compound 12
(262.0 mg, 87%) as a dark orange amorphous solid: 1H NMR (CDCl3
w/MeOD, 500 MHz) d 3.79 (s, 6H), 6.43 (s, 1H), 6.72 (s, 2H), 6.73 (s,
1H), 6.75 (s, 1H), 6.85 (dd, J1 = 8.2 Hz, J2 = 1.8 Hz, 2H), 6.90(d,
J = 8.3 Hz, 2H), 6.92(d, J = 6.4 Hz, 2H); 13C NMR (CDCl3 w/MeOD,
125 MHz) d 55.4 (2C), 98.8, 108.6 (2C), 114.8 (2C), 115.3 (2C),
120.1 (2C), 127.6 (2C), 128.8 (2C), 130.5 (2C), 146.1 (2C), 147.3
(2C); IR (film) mmax 3383, 2359, 2341, 2332, 1593, 1558, 1512,
1456, 1429, 1277, 1259, 1231, 1211, 1155, 1122 cmꢀ1; HRMS(ES+)
m/z: [M+H] calcd for C21H20N2O4 365.1505; found 365.1484.
4.13. 3,5-Bis(3,4-dimethoxystyryl)-4-methyl-1-H-pyrazole (16)
Compound 16 was prepared following the same procedure used
for the preparation of 12. The residue was purified by flash chro-
matography (SiO2, 2:3:5 (CH2Cl2, EtOAc, hexanes)) to afford 16
(60.8 mg, 58%) as a yellow–orange amorphous solid: 1H NMR
(CDCl3, 500 MHz) d 2.22 (s, 3H), 3.82 (s, 6H), 3.82 (s, 6H), 6.73 (d,
2H, J = 8.8 Hz), 6.81 (d, 2H, J = 16.5 Hz), 6.92 (m, 4H), 6.97 (d, 2H,
J = 16.5 Hz); 13C NMR (CDCl3, 125 MHz) d 9.1, 55.8 (2C), 55.9
(2C), 108.6, 108.7 (2C), 111.1 (2C), 112.2 (2C), 115.1 (2C), 119.9
(2C), 129.5 (2C), 130.1 (2C), 149.1 (2C), 149.1 (2C); IR (film) mmax
3416, 3240, 3229, 3111, 2999, 2957, 2932, 2835, 2359, 1636,
1601, 1514, 1464, 1420, 1333, 1265, 1238, 1159, 1138, 1024,
4.10. 3,5-Bis(3,4-dimethoxystyryl)-1-H-pyrazole (13)
960 cmꢀ1 HRMS (ES+) m/z: [M+H] calcd for C24H26N2O4
;
407.1971; found 407.1954.
Compound 13 was prepared following the same procedure used
for the preparation of 12. The residue was purified by flash chro-
matography (SiO2, 2:3:5 (CH2Cl2, EtOAc, hexanes)) to afford 13
(54.0 mg, 90%) as a yellow-orange amorphous solid: 1H NMR
(CDCl3, 500 MHz) d 3.85 (d, J = 15.5 Hz, 12H), 6.62 (s, 1H), 6.74
(d, J = 8.10 Hz, 2H), 6.95 (m, 6H), 7.05 (d, J = 16.5 Hz, 2H); 13C
NMR (CDCl3, 125 MHz) d 55.6 (2C), 55.8 (2C), 99.4, 99.9 (2C),
108.5 (2C), 111.0 (2C), 115.8 (2C), 119.9 (2C), 129.6 (2C), 130.6
(2C), 149.0 (2C), 149.1 (2C); IR (film) vmax 3331, 3177, 3126,
3078, 3065, 2999, 2959, 2934, 2910, 2835, 1599, 1583, 1558,
1514, 1464, 1441, 1420, 1331, 1311, 1265, 1196, 1157, 1138,
4.14. (E)-Methyl 3-(3,5-bis(3,4-dimethoxystyryl)-1-H-pyrazol-4-
yl)acrylate (17)
Compound 17 was prepared following the same procedure used
in the preparation of compound 12. The residue was purified by
flash chromatography (SiO2, 1:1 Hexanes:EtOAc) to afford 17
(43.3 mg,15%) as a yellow–orange amorphous solid: 1H NMR
(CDCl3, 500 MHz) d 3.76 (s, 3H), 3.83 (s, 6H), 3.84 (s, 6H), 6.15 (d,
J = 16.0 Hz, 1H), 6.75 (d, J = 8.1 Hz, 2H), 6.86 (d, J = 16.3 Hz, 2H),
6.93 (d, J = 2.5 Hz, 2H), 6.95 (d, J = 1.7 Hz, 2H), 7.09 (d, J = 16.3,
2H), 7.81 (d, J = 16.0 Hz, 2H); 13C NMR (CDCl3, 125 MHz) d 51.7,
56.0 (4C), 109.0 (2C), 111.1, 113.0 (2C), 113.5 (2C), 117.8 (2C),
120.6 (2C), 129.3 (2C), 132.6 (2C), 135.2 (2C), 149.2 (2C), 149.7
1103, 1024, 960 cmꢀ1
;
HRMS (ES+) m/z: [M+H] calcd for
C23H24N2O4 393.1814; found 393.1801.
4.11. Ethyl 3-(3,5-bis(4-hydroxy-3-methoxystyryl)-1-H-pyrazol-
(2C), 167.9; IR (film) mmax3317, 2923, 2849, 2837, 1701, 1624,
4-yl)propanoate (14)
1601, 1582, 1514, 1464, 1437, 1420, 1310, 1265, 1198, 1159,
1138, 1024, 960, 933 cmꢀ1; HRMS (ES+) m/z: [M+H] calcd for
C27H28N2O6 477.2026; found 477.1993.
Compound 14 was prepared following the same procedure used
for the preparation of 12. The residue was purified by flash chro-
matography (SiO2, 5:3:2 Hexanes:EtOAc:CH2Cl2) to afford 14
(63.5 mg, 81%) as a yellow-orange amorphous solid: 1H NMR
(CDCl3, 500 MHz) d 1.23 (t, J = 7.1 Hz, 3H), 2.57 (t, J = 7.8 Hz, 2H),
3.01 (t, J = 7.8 Hz, 2H), 3.83 (s, 6H), 4.12 (q, J = 7.2 Hz, 2H), 6.82
(d, J = 16.6 Hz, 2H), 6.85 (d, J = 8.3 Hz, 2H), 6.89 (d, J = 1.5 Hz, 2H),
4.15. (E)-Ethyl-3-(3,5-bis(3,4-dimethoxystyryl)-1-H-pyrazol-4-
yl)acrylate (18)
Compound 18 was prepared following the same procedure used
for the preparation of 12. The residue was purified by flash chro-

366
M. W. Amolins et al. / Bioorg. Med. Chem. 17 (2009) 360–367
matography (SiO2, 1:7.5:15:26.5 MeOH:CH2Cl2:EtOAc:hexanes) to
0.83 mmol) was added followed by a catalytic amount of glacial
acetic acid (750 L). The solution stirred at reflux for 40 h. The
afford 18 (37.5 mg, 76%) as a yellow–orange amorphous solid: 1H
l
NMR (CDCl3, 500 MHz)
d
1.35 (t, J = 7.15 Hz, 3H), 3.93 (d,
crude reaction mixture was concentrated in vacuo and redissolved
in EtOAc (200 mL). The organic layer was washed with saturated
aqueous NaHCO3 and saturated NaCl, dried (Na2SO4), filtered, and
concentrated in vacuo. The residue was purified by column chro-
matography (SiO2, 5:3:2 hexanes:EtOAc:CH2Cl2) to afford 21
(218.0 mg, 89%) as a dark orange amorphous solid: 1H NMR (d-
DMSO, 500 MHz) d 3.89 (s, 6H), 6.85 (d, J = 8.1 Hz, 1H), 6.87 (d,
J = 8.1 Hz, 1H), 6.92 (s, 1H), 7.10 (dd, J1 = 8.3 Hz, J2 = 1.9 Hz, 1H),
7.13 (d, J = 12.4 Hz, 1H), 7.13 (dd, J1 = 8.3 Hz, J2 = 1.8 Hz, 1 H),
7.16 (d, J = 12.3 Hz, 1 H), 7.33–7.37 (m, 4H), 9.45 (s, 1H), 9.51 (s,
1H); 13C NMR (CDCl3, 125 MHz) d 55.6, 55.6, 97.8, 109.9, 110.2,
110.3, 112.6, 115.5, 115.5, 121.3, 121.7, 126.9, 127.3, 134.7,
136.4, 147.8, 147.9, 147.9, 148.1, 162.2, 168.3; IR (film) mmax
3402, 2961, 2924, 2851, 2359, 2341, 2332, 1645, 1605, 1593,
1562, 1514, 1464, 1433, 1375, 1279, 1231, 1207, 1188, 1159,
J = 8.30 Hz, 12H), 4.29 (q, J = 7.15 Hz, 2H), 6.23 (d, J = 16.0 Hz,
1H), 6.86 (d, J = 8.20 Hz, 2H), 6.96 (d, J = 16.3 Hz, 2H), 7.04 (d,
J = 1.80 Hz, 2H), 7.06 (dd, J = 1.80, 8.25 Hz, 2H), 7.17 (d,
J = 16.3 Hz, 2H), 7.89 (d, J = 16.0 Hz, 2H); 13C NMR (CDCl3,
125 MHz) 14.4, 55.90 (2C), 55.92 (2C), 60.5, 108.9 (2C), 111.1
(2C), 113.0, 113.6, 118.3 (2C), 120.5 (2C), 129.2 (2C), 132.4 (2C),
134.9 (2C), 149.06, 149.11 (2C), 149.6 (2C), 167.5; IR (film) vmax
3321, 2995, 2957, 2935, 2835, 1701, 1684, 1624, 1601, 1583,
1558, 1514, 1464, 1443, 1420, 1394, 1367, 1308, 1263, 1240,
1159, 1140, 1094, 1026, 962 cmꢀ1; HRMS (ES+) m/z: [M+H] calcd
for C28H30N2O6 491.2182; found 491.2168.
4.16. (E)-3-(3,5-Bis(3,4-dimethoxystyryl)-1-H-pyrazol-4-
yl)acrylamide (19)
1122, 1032, 960 cmꢀ1
;
HRMS (ES+) m/z: [M+H] calcd for
Compound 19 was prepared following the same procedure used
for the preparation of 12. The residue was purified by flash chro-
matography (SiO2, 1:99 MeOH in CH2Cl2) to afford 19 (41.7 mg,
C21H19NO5 366.1342; found 366.1348.
4.19. 3,5-Bis(3,4-dimethoxystyryl)isoxazole (22)
84%) as
a
yellow-orange amorphous solid: 1H NMR (CDCl3,
500 MHz) d 3.92 (s, 12H), 5.62 (s, -NH2), 6.34 (d, J = 15.6 Hz, 1H),
6.87 (d, J = 8.2 Hz, 2H), 6.92 (d, J = 16.4 Hz, 2H), 7.03 (d,
J = 16.4 Hz, 2H), 7.04 (d, J = 1.7 Hz, 2H), 7.10 (dd, J = 1.7, 8.2 Hz,
2H), 7.60 (d, J = 15.6 Hz, 1H); 13C NMR (CDCl3, 125 Hz) d 55.88
(2C), 55.98 (2C), 105.4 (2C), 109.6 (2C), 111.0 (2C), 111.1(2C),
111.2, 117.1 (2C), 120.1, 122.3 (2C), 127.4 (2C), 142.5 (2C), 149.1
(2C), 150.8, 168.0; IR (film) vmax3339, 3325, 3198, 3186, 2999,
2957, 2935, 2912, 2835, 1717, 1668, 1634, 1595, 1514, 1464,
1441, 1420, 1394, 1337, 1308, 1265, 1186, 1159, 1140, 1024,
978, 968; HRMS (ES+) m/z: [M+H] calcd for C26H27N3O5
462.2029; found 462.2010.
Compound 22 was prepared following the same procedure used
for the preparation of 21. The residue was purified by flash chro-
matography (SiO2, 2:3:5 (CH2Cl2, EtOAc, hexanes)) to afford 22
(54.0 mg, 90%) as a yellow-orange amorphous solid: 1H NMR
(CDCl3, 500 MHz) d 3.85 (d, J = 2.55 Hz, 6H), 3.88 (d, J = 4.20 Hz,
6H), 6.37 (s, 1 H), 6.77 (d, J = 16.35, 1H), 6.81 (dd, J = 3.75,
8.20 Hz, 2H), 6.94 (d, J = 16.4 Hz, 1H), 7.03 (m, 5H), 7.23 (d,
J = 16.4 Hz, 1H); 13C NMR (CDCl3, 125 Hz) d 55.89, 55.93, 55.98,
56.0, 97.8, 108.6, 108.9, 111.0, 111.1, 114.2 (2C), 120.9, 121.2,
128.6, 128.9, 134.7, 135.4, 149.2 (2C), 149.9, 150.1, 162.2, 168.5;
IR (film) vmax 2995, 2953, 2932, 2916, 2835, 1643, 1599, 1583,
1512, 1504, 1462, 1427, 1416, 1265, 1225, 1159, 1140, 1024,
964 cmꢀ1; HRMS (ES+) m/z: [M+H] calcd for C23H23NO5 394.1655;
found 394.1649.
4.17. (E)-3-(3,5-Bis(3,4-dimethoxystyryl)-1-H-pyrazol-4-
yl)prop-2-en-1-ol (20)
Compound 18 (80.0 mg, 0.16 mmol) was dissolved in anhy-
drous MeOH (5.0 mL) and stirred at rt. NaBH4 (61.7 mg, 1.6 mmol)
was added and the solution stirred at reflux. After 1 h, additional
NaBH4 (61.7 mg, 1.6 mmol) was added, and the solution stirred
at reflux for 15.5 h. The reaction was quenched by the addition of
H2O, resulting in the formation of a white solid. The precipitate
was dissolved by the addition of 10% HCl (10 mL) and the aqueous
layer was extracted with CH2Cl2 (3ꢁ 20 mL). The combined organic
layers were washed with saturated aqueous NaHCO3 and saturated
aqueous NaCl, dried (Na2SO4), filtered, and concentrated. The resi-
due was purified by flash chromatography (SiO2, 1:7.5:15:26.5
MeOH:CH2Cl2:EtOAc:hexanes) to afford 20 (41.0 mg, 83%) as a yel-
low-orange amorphous solid: 1H NMR (CDCl3, 500 MHz) d 3.84 (s,
2H), 3.87 (d, J = 9.7 Hz, 12H), 6.21 (d, J = 16.0 Hz, 1H), 6.76 (d,
J = 8.45 Hz, 2H), 6.89 (d, J = 16.3 Hz, 2H), 6.92 (m, 4H), 7.16 (d,
J = 16.3 Hz, 2H), 7.87 (d, J = 16.0 Hz, 1H); 13C NMR (CDCl3,
125 Hz) d 51.7, 55.84 (2C), 55.87 (2C), 108.8 (2C), 111.0 (2C),
112.9, 113.3, 117.6 (2C), 120.6 (2C), 129.1 (2C), 132.6 (2C), 135.2
(2C), 149.0, 149.6 (2C), 167.9 (2C); IR (film) vmax 3315, 3153,
3059, 2999, 2949, 2935, 2835, 1713, 1626, 1601, 1583, 1514,
1464, 1441, 1421, 1312, 1265, 1198, 1161, 1140, 1097, 1026,
960, 933 cmꢀ1; HRMS (ES+) m/z: [M+H] calcd for C26H28N2O5
449.2076; found 449.2096.
4.20. Ethyl 3-(3,5-bis(4-hydroxy-3-methoxystyryl)isoxazol-4-
yl)propanoate (23)
Compound 23 was prepared following the same procedure used
for the preparation of 21. The residue was purified by flash chro-
matography (SiO2, 2:3:5 (CH2Cl2, EtOAc, hexanes)) to afford 23
(60.7 mg, 76%) as a yellow amorphous solid: 1H NMR (CDCl3,
500 MHz) d 1.23 (t, J = 7.2 Hz, 3H), 2.60 (t, J = 7.6 Hz, 2H), 2.97 (t,
J = 7.6 Hz, 2H), 3.96 (s, 6H), 4.13 (q, J = 7.2 Hz, 2H), 5.90 (bs, 2H),
6.79 (d, J = 16.5 Hz, 1H), 6.80 (d, J = 16.3 Hz, 1H), 6.94 (d,
J = 8.1 Hz, 1H), 6.94 (d, J = 8.2 Hz, 1H), 7.05 (d, J = 1.8 Hz, 1H),
7.06 (d, J = 1.7 Hz, 1H), 7.08 (dd, J1 = 8.3 Hz, J2 = 1.8 Hz, 1H), 7.11
(dd, J1 = 8.3 Hz, J2 = 1.8 Hz, 1H), 7.31 (d, J = 16.3 Hz, 1H), 7.37 (d,
J = 16.5 Hz, 1H) 13C NMR (CDCl3, 125 MHz) d 14.2, 17.9, 34.6, 56.0
(2C), 60.9, 108.7, 108.9, 109.4, 112.1, 112.3, 114.7, 114.8 (2C),
121.3, 128.5, 128.8, 133.9, 135.2, 146.7, 146.8, 146.8 (2C), 160.0,
164.7, 172.5; IR (film) mmax 3499, 3416, 3049, 2962, 2935, 2872,
2853, 2758, 2748, 2644, 2590, 2548, 2311, 2060, 1728, 1634,
1593, 1514, 1450, 1439, 1373, 1275, 1236, 1207, 1184, 1159,
1122, 1095, 1063, 1032, 964, 939 cmꢀ1, HRMS (ES+) m/z: [M+H]
calcd for C26H27NO7 466.1866; found 466.1860.
4.21. Ethyl 3-(3,5-bis(3,4-dimethoxystyryl)isoxazol-4-
yl)propanoate (24)
4.18. 4,40-(1E,10E)-2,20-(Isoxazole-3,5-diyl)bis(ethene-2,1-
diyl)bis(2-methoxyphenol) (21)
Compound 24 was prepared following the same procedure used
for the preparation of 21. The residue was purified by flash chro-
matography (SiO2, 2:3:5 (CH2Cl2, EtOAc, hexanes)) to afford 24
(64.4 mg, 61%) as a dark yellow amorphous solid: 1H NMR (CDCl3,
Compound 1 (250 mg, 0.69 mmol) was dissolved in absolute
EtOH
(5.0 mL).
Hydroxylamine
hydrochloride
(56.6 mg,

M. W. Amolins et al. / Bioorg. Med. Chem. 17 (2009) 360–367
367
500 MHz) d 1.15 (t, J = 7.2 Hz, 3H), 2.52 (t, 7.5 Hz, 2H), 2.91 (t,
J = 7.5 Hz, 2H), 3.86 (m, 12H), 4.05 (q, J = 7.15 Hz, 2H), 6.73 (d,
J = 4.15 Hz, 1H), 6.75 (d, J = 4.0 Hz, 1H), 6.79–6.82 (m, 2H), 7.01–
7.06 (m, 4H), 7.21 (d, J = 19.0 Hz, 1H), 7.31 (d, J = 16 Hz, 1H); 13C
NMR (CDCl3, 125 MHz) d 14.2, 17.9, 34.6, 56.0, 60.8, 109.0, 109.1,
109.7, 111.1, 111.2, 112.4, 112.5, 120.9, 121.0, 129.0, 133.8,
135.1, 149.2 (2C), 149.9, 150.0, 160.0, 164.7, 172.5; IR (film) mmax
3541, 3435, 3053, 2959, 2930, 2853, 2839, 2598, 2033, 1728,
1674, 1634, 1591, 1514, 1454, 1443, 1421, 1375, 1339, 1263,
1236, 1159, 1140, 1094, 1063, 1024, 966 cmꢀ1; HRMS (ES+) m/z:
[M+H] calcd for C28H31NO7 494.2179; found 494.2163.
1H), 6.59 (d, J = 15.9 Hz, 1H), 6.74 (d, J = 11.2 Hz, 2H), 6.77 (d,
J = 15.8 Hz, 2H), 6.83 (d, J = 8.2 Hz, 2H), 7.11 (dd, J1 = 1.9, J2 = 8.3,
2H), 7.16 (dd, J1 = 1.9 Hz, J2 = 8.3 Hz, 2H), 7.23 (m, 3H), 7.30 (d,
J = 8 Hz, 2H), 7.32 (m, 5H), 7.46 (d, J = 15.8 Hz, 1H), 7.56 (d,
J = 16 Hz, 2H), 8.97 (s, 1H) 9.68 (s, 2H) 10.07 (s, 1H); 13C NMR
(d6-DMSO, 500 MHz) d 34.8, 34.8, 34.8, 43.1, 43.1, 44.0, 48.8,
55.5, 55.6, 79.1, 101.2 101.3, 111.1, 111.5, 111.6, 115.1, 115.6,
119.4, 120.0, 120.1, 120.1, 126.8, 128.3, 128.8, 131.6, 131.7,
131.9, 138.1, 140.5, 145.6, 145.6, 145.7, 147.4, 147.5, 149.3,
156.3, 156.4, 177.5, 190.7, 196.7, 202.1; IR (film) mmax 3028,
2959, 2930, 2916, 1601, 1574, 1556, 1514, 1494, 1452, 1429,
1367, 1360, 1269, 1236, 1209, 1177, 1153, 1121, 1070, 1032,
916 cmꢀ1. Similar experiments were carried out with the pyrazole
and isoxazole derivatives of curcumin, compounds 12 and 21,
respectively.
4.22. 3,5-Bis(3,4-dimethoxystyryl)-4-methylisoxazole (25)
Compound 25 was prepared following the same procedure used
for the preparation of 21. The residue was purified by flash chro-
matography (SiO2, 2:3:5 (CH2Cl2, EtOAc, hexanes)) to afford 25
(59.2 mg, 59%) as a yellow–orange amorphous solid: 1H NMR
(CDCl3, 500 MHz) 2.18 (s, 3H), 3.85 (s, 3H), 3.85 (s, 3H), 3.88 (s,
3H), 3.89 (s, 3H), 6.70 (d, J = 16.3 Hz, 1H), 6.79–6.83 (3H), 6.99–
7.05 (4H), 7.22 (d, J = 16.4 Hz, 1H), 7.26 (d, J = 16.7 Hz, 1H); 13C
NMR (CDCl3, 125 MHz) d 29.7, 55.9 (2C), 56.0 (2C), 108.8, 109.0,
109.2, 110.0, 111.1, 111.2, 113.5, 120.8, 129.1, 129.3, 133.2,
134.9, 149.2 (2C), 149.8, 149.9, 160.5, 164.2; IR (film) mmax 3541,
3445, 3194, 3051, 2999, 2959, 2930, 2853, 2837, 2600, 2361,
2322, 2280, 2033, 1682, 1645, 1634, 1593, 1514, 1506, 1454,
1441, 1421, 1387, 1339, 1312, 1263, 1236, 1196, 1159, 1138,
Supporting information
Characterization for all compounds and spectra for the benzyl
mercaptan addition studies. This material is available via the Inter-
net at http://www.sciencedirect.com.
Acknowledgments
The authors gratefully acknowledge the support of this project
by NIH CA125392 and the NIH Training Grant (T32 GM008545)
on Dynamic Aspects in Chemical Biology (L.B.P.). M.W.A. is a Mad-
ison and Lila Self Predoctoral Fellow.
;
1092, 1024, 964 cmꢀ1 HRMS (ES+) m/z: [M+H] calcd for
C24H25NO5 408.1811; found 408.1797.
References and notes
4.23. Anti-proliferation assays
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MCF-7 and SKBr3 cells were maintained in a 1:1 mixture of Ad-
vanced DMEM/F12 (Gibco) supplemented with non-essential ami-
no acids, L-glutamine (2 mM), streptomycin (500 lg/mL), penicillin
(100 units/mL), and 10% FBS. Cells were grown to confluence in a
humidified atmosphere (37 °C, 5% CO2), seeded (2000/well,
100 lL) in 96-well plates, and allowed to attach overnight. Com-
pound or geldanamycin at varying concentrations in DMSO (1%
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per the manufacturer’s instructions. Cells incubated in 1% DMSO
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formed in triplicate using GraphPad Prism.
4.24. Benzyl mercaptan addition studies
In a 1 dram vial, 15.0 mg curcumin (4) (0.041 mmol) was dis-
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was then added, marking time zero. The contents of the vial were
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