Synthesis, cytotoxicity, and structure-activity insight of NH- and N-methyl-3,5-bis-(arylidenyl)-4-piperidones

Article abstract of DOI:10.1007/s00044-013-0557-9

Twenty-one NH- and N-methyl-3,5-bis-(arylidenyl)-4-piperidone analogs of curcumin, 12 of which are novel, were synthesized and evaluated for their cytotoxicity against B16 (murine melanoma) and L1210 (murine lymphoma) cells grown in culture. These curcumi

Full text of DOI:10.1007/s00044-013-0557-9

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-013-0557-9
ORIGINAL RESEARCH
Synthesis, cytotoxicity, and structure–activity insight
of NH- and N-methyl-3,5-bis-(arylidenyl)-4-piperidones
•
Matthew Gregory Armaan Dandavati Megan Lee
•
•
•
Samuel Tzou Mia Savagian Kimberly A. Brien
•
•
•
Vijay Satam Pravin Patil Moses Lee
•
Received: 29 December 2012 / Accepted: 20 February 2013
Ó Springer Science+Business Media New York 2013
¨
Abstract Twenty-one NH- and N-methyl-3,5-bis-(ary-
lidenyl)-4-piperidone analogs of curcumin, 12 of which are
novel, were synthesized and evaluated for their cytotoxicity
against B16 (murine melanoma) and L1210 (murine lym-
phoma) cells grown in culture. These curcumin analogs are
related to a known anticancer STAT3 inhibitor 3,5-bis-(4-
fluorobenzyl)-4-piperidone (3). The compounds showed
remarkable cytotoxicity, especially against B16 cells. The
dimethoxy substituted analogs 4e and 4f and dihydroxy
analog 4i emerged as the most active compounds with IC50
values in the range of 0.2–2.3 lM. 4e, f, and i were about
10-times more cytotoxic against both cell lines than 3.
Analysis of the results demonstrates that the position of the
hydroxyl group is crucial for cytotoxicity. Amino-con-
taining analogs are generally less active than their halo-
genated and oxygen-containing analogs, and N-substitution
in the 4-piperidone moiety adds value to the cytotoxicity of
the compounds.
possesses promising antitumor (Strofer et al., 2011;
Aggarwal and Shishodia, 2006; Choi et al., 2006), anti-
oxidant, antiarthritic, antiamyloid, antiischemic (Shukla
et al., 2008), and anti-inflammatory (Stix, 2007) properties.
Curcumin has also been reported to be highly effective
against acute polycystic kidney disease (Bello-Reuss and
Lee, 2009). The mechanism of action of curcumin is
presently unclear; however, several models have been
proposed. These include inhibition of tubulin polymeriza-
tion (Gupta et al., 2006), inhibition of the mTOR complex
(Beevers et al., 2009), modulation of signaling pathways
including cell proliferation pathways (cyclin D1, c-myc),
cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, and
c-IAP1), caspase activation pathway (caspase-8, 3, 9),
tumor suppressor pathway (p53, p21), death receptor
pathway (DR4, DR5), mitochondrial pathways, and protein
kinase pathway (JNK, Akt, and AMPK) (Ravindran et al.,
2009). Curcumin effectively inhibits tumor cell prolifera-
tion, induces apoptosis, as well as blocks cancer cell
migration and invasion through interference with the
STAT3 signaling pathway (Senft et al., 2010; Glienke
et al., 2010). In spite of having significant biological
properties the clinical usefulness of curcumin is limited
because of its poor bioavailability due to glucuronidation
and sulfation of the hydroxyl groups (Anand et al., 2007).
Hence, there are efforts underway to design curcuminoids
that have improved bioavailability.
Keywords Curcuminoids Á 4-Piperidones Á Cytotoxicity Á
STAT3 Á Cancer Á B16 Á L1210
Introduction
Curcumin (1 or diferuloylmethane, Fig. 1) is a naturally
occurring and biologically active compound isolated from
the root of turmeric (Curcuma longa). A number of in vitro
as well as in vivo studies have demonstrated that curcumin
A plethora of curcumin derivatives that display potent
anticancer activity have been reported to date. One such
curcumin derivative is bis-(3,4,5-trimethoxyphenylidenyl)
cyclohexanone 2 (Fig. 1). It was reported to possess sub-lM
cytotoxicity against B16 and L1210 cells grown in culture
even though it did not affect microtubule depolymerization
(Davis et al., 2008). The structurally similar 4-piperidone
analog of compound 2, 3,5-bis-(4-fluorobenzyl)-4-piperidone
M. Gregory Á A. Dandavati Á M. Lee Á S. Tzou Á M. Savagian Á
K. A. Brien Á V. Satam Á P. Patil Á M. Lee (&)
Division of Natural and Applied Sciences, Department
of Chemistry, Hope College, Holland, MI 49423, USA
e-mail: lee@hope.edu
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Med Chem Res
Fig. 1 Structures of curcumin
1, 3,5-bis-(3,4,5-
O
H3CO
H3CO
OCH3
O
OH
trimethoxyphenylidenyl)-4-
phenylcyclohexanone 2, 3,5-bis-
(4-fluorobenzyl)-4-piperidone 3,
and general structures of the
curcumin analogs 4(a–o) and
5(a–e) derived from NH- and N-
methyl-4-piperidones
H3CO
HO
OCH3
OH
OCH3
OCH3
OCH3
1
2
O
F
N
H
F
3
O
O
R'
R'
R'
R'
N
H
4(a-o)
N
CH3
5(a-e)
(3 or H-4073, Fig. 1), was also reported to be significantly
cytotoxic toward the A2780 human epithelial ovarian cancer
cells grown in culture and as a xenograft in nude mice
(Selvendiran et al., 2010; Tierney et al., 2012). It was also
disclosed that compound 3 was an effective inhibitor of the
JAK/STAT3 pathway and downregulation of the STAT3-
targeting proteins both in vitro and in vivo (Selvendiran et al.,
2010; Tierney et al., 2012). Theoretical modeling studies
using Auto-Dock demonstrated that the 3,5-bis-(arylideny)-4-
piperidoneshavehighdockingaffinityfortheSTAT3dimerat
the DNA binding domain of the molecule. This in turn pre-
vents binding of the activated STAT3 molecule with DNA,
thereby inhibiting transcription of downstream signaling
follows: (i) expand the range of substituents on the bis-
(arylidene) segment in the NH- and N-methyl-4-piperi-
dones series of compounds, and (ii) discover analogs that
have superior cytotoxicity against B16 and L1210 cells
than the reported compound 3 (Selvendiran et al., 2010;
´
Tierney et al., 2012; Kalai et al., 2011).
Results and discussion
Synthesis of curcumin analogs
As depicted in Scheme 1, the 4-piperidone containing
curcuminoid analogs 3, 4(a–o), and 5(a–e) were synthe-
sized using either an acid or base catalyzed aldol conden-
sation of the appropriately substituted aryl aldehydes with
the corresponding NH- or N-methyl-4-piperidone. Twelve
of the products have not been reported according to a
search on SciFinder Scholar. The reactions proceeded
smoothly at room temperature to afford the products in fair
to good yields. The crude compounds were readily purified
by recrystallization. The structures of the curcumin analogs
´
(Kalai et al., 2011).
Encouraged by the potent anticancer properties of cur-
cumin analogs 2 and 3 as well as the importance of STAT3
as a target in anticancer drug discovery (Ren et al., 2010), a
variety of 4-piperidone-based curcuminoids have been
synthesized and evaluated for their anticancer activity (Das
et al., 2009; Makarov et al., 2009; Das et al., 2007; Adams
et al., 2004; Dimmock et al., 2001; Pati et al., 2008;
Makarov et al., 2012). In our laboratory, we designed and
synthesized twenty curcumin analogs containing a 4-pip-
eridone (4) and N-methyl-4-piperidone (5) core for evalu-
ation of their cyctotoxic properties against murine B16
(melanoma) and L1210 (lymphoma) cells. We envisaged
that the curcumin analogs derived from 4-piperidones 4
and 5 would possess potent cytotoxicity and should have a
similar mechanism of action to 2 and 3. Single crystal
X-ray structures of related 3,5-bis-(arylideny)-4-piperi-
dones have revealed that the alkene functionalities in these
molecules orient in the E-configuration with the b-protons
aligned syn to the carbonyl group (Pati et al., 2008;
Makarov et al., 2012). We anticipate that compounds
derived from 4-piperidones 4 and 5 will adopt a similar
configuration and conformation. Our goal in this study is as
1
were confirmed by infrared, H NMR spectroscopy, and
mass spectrometry. The products were ascertained as
homogeneous according to TLC and NMR analyses.
Besides broadly dividing the compounds in two catego-
ries, NH-3,5-bis-(arylidenyl)-4-piperidones and N-methyl-
3,5-bis-(arylidenyl)-4-piperidones, the target compounds
were further subdivided into four different groups. Group I
comprised mono- and di-halogenated compounds; Group II
comprised oxygen-containing compounds that are not
hydroxylated; Group III contained specifically hydroxylated
compounds; and Group IV possessed nitro- and amino-
containing compounds. Within each group, the substituents
were varied to gain further insight into possible structure and
substitution-related activity relationships. The previously
123

Med Chem Res
Scheme 1 Synthetic pathway
of curcumin analogs 4(a–o) and
5(a–e) derived from
4-piperidone (4) and N-methyl-
4-piperidone (5)
O
O
dry HCl / CH3COOH
or
20% aq. NaOH/ethanol
O
O
R'
R'
H
R'
R'
H
N
R
N
R
a-o
rt, 18 h
a-o
4: R=H,
5: R=CH3
4(a-o)-5(a-e)
R1
n: R' =
a-m: R' =
o: R' =
R2
R3
N
OCH3
O
O
N
CH3
CH3
R5
R4
R=H
R=CH3
4a: R1=H, R2=H, R3=Cl, R4=H, R5=H
4b: R1=H, R2=Cl, R3=Cl, R4=H, R5=H
4c: R1=H, R2=Br, R3=H, R4=H, R5=H
4d: R1=H, R2=OCH3, R3=H, R4=H, R5=H
4e: R1=H, R2=OCH3, R3=H, R4=OCH3, R5=H
4f: R1=OCH3, R2=H, R3=H, R4=OCH3, R5=H
5a: R1=H, R2=H, R3=F, R4=H, R5=H
5b: R1=H, R2=H, R3=Cl, R4=H, R5=H
5c: R1=H, R2=Br, R3=H, R4=H, R5=H
5d: R1=H, R2=H, R3=N(CH3)2, R4=H, R5=H
5e: R1=H, R2=H, R3=N(CH2CH3)2, R4=H, R5=H
4g: R1=OCH3, R2=H, R3=OCH3, R4=H, R5=OCH3
4h: R1=H, R2-R3=OCH2CH2O, R4=H, R5=H
4i: R1=H, R2=OH, R3=H, R4=H, R5=H
4j: R1=H, R2=H, R3=OH, R4=H, R5=H
4k: R1=H, R2=NO2, R3=OH, R4=H, R5=H
4l: R1=H, R2=H, R3=N(CH3)2, R4=H, R5=H
4m: R1=H, R2=H, R3=N(CH2CH3)2, R4=H, R5=H
reported 3,5-bis-(4-fluorobenzyl)-4-piperidone 3 was syn-
thesized to provide a basis of comparison for assessing the
cytotoxicity of target compounds.
L1210 lymphoma cells. Compound 5c, which gave an IC50
value of 2.1 lM against B16 cells, was found to be most
potent in Group I.
The IC50 values of the oxygen-containing, but non-
hydroxylated curcumin, analogs in Group II are displayed
in Table 2. This group of compounds was most active
among the compounds included in this study, both against
the B16 and L1210 cells. The dimethoxylated compounds
4e and 4f were definitely more active against both B16 and
L1210 cells than their monomethoxy and trimethoxy
counterparts. In fact, compound 4f gave the same IC50
value (0.3 lM) for each cell line. Trimethoxy substitution,
as in analog 4g, dramatically lowered the cytotoxicity. The
dioxymethylene-substituted analog 4h showed lower
activity, particularly against L1210 cells than dimethoxy
substituted analogs. The 2-methoxypyridyl analog 4n was
equally active against both B16 and L1210 cell lines. The
extra nitrogen atom was introduced to aid water solubility
by means of its polarity.
Cytotoxicity of curcumin analogs
The cytotoxicity of twenty-one 4-piperidone-curcuminoid
analogs 3, 4(a–o), and 5(a–e) was assessed on murine
melanoma (B16) and murine lymphoma (L1210) cells
using a 72-h continuous exposure MTT assay technique
(Davis et al., 2008). The experiments were performed in
triplicate and the concentrations at which 50 % of cell
growth was inhibited (IC50, lM) were determined for each
compound. The results are presented in Tables 1, 2, 3, and
4. For comparison, the reported IC50 values for the cur-
cumin analog 2, obtained under similar conditions, were
0.51 and 1.2 lM, respectively (Davis et al., 2008).
Table 1 presents IC50 values determined for the mono-
and dihalogenated curcumin analogs in Group I. All the
compounds in this group were found to be cytotoxic against
both cell lines except compound 5c, which was inactive
against L1210 cells. In particular, compounds 4b, 4c, 5a,
and 5b were highly active against both cell lines. The results
also demonstrated that the cytotoxicity against B16 cells
remained consistent regardless of the type of halogen and
N-substitution in 4-piperidone moiety. The N-methyl-4-
piperidone-containing analogs 5a and 5b were more active
than their 4-piperidone-containing counterparts against the
Table 3 lists the cytotoxicity results of the hydroxylated
curcumin analogs in Group III. The results demonstrate
that the relative position of the hydroxyl group on the aryl
moiety has a striking effect on cytotoxicity. Analog 4i,
which has a hydroxyl group in the meta-position of the
phenyl ring, was remarkably active with IC50 values of 0.7
and 2.3 lM for B16 and L1210 cells, respectively. In
contrast, its para-hydroxy counterpart 4j had IC50 values
[100 lM.
123

Med Chem Res
Table 1 IC50 values of the halogenated curcumin analogs belonging to Group I
Sr. no.
Compound
IC50 (lM)
B16
L1210
24.5
1 Glienke et al., (2010)
O
3.8
6.5
4
F
N
H
F
3
O
2
31
F
N
F
CH3
5a
O
3
7
Cl
N
H
Cl
4a
O
4
5
6
3.8
4.1
3.3
10
Cl
N
Cl
CH3
5b
O
3.6
Cl
Cl
Cl
N
H
Cl
4b
O
5.0
Br
Br
N
CH3
5c
O
7
2.1
[100
Br
Br
N
H
4c
123

Med Chem Res
Table 2 IC50 values of the oxygen-containing non-hydroxylated curcumin analogs belonging to Group II
Sr. no.
Compound
IC50 (lM)
B16
L1210
4.3
8
1.9
O
H3CO
OCH3
N
H
4d
9
0.2
1.1
OCH3
O
OCH3
H3CO
N
OCH3
OCH3 H3CO
H
4g
10
0.3
0.3
O
H3CO
OCH3
N
OCH3
H
OCH3
4e
11
25
12.5
O
O
O
O
O
N
H
4h
12
3.0
26.5
OCH3
O
OCH3
OCH3
N
H
OCH3
4f
13
3.6
2.8
O
H3CO
N
N
H
N
OCH3
4n
Finally, Table 4 presents cytotoxicity results of the
amino- and nitro-containing analogs in Group IV. In gen-
eral, compared to compounds in Group I, II, and III, the
compounds in Group IV exhibited weaker cytotoxicity
against both B16 and L1210 cell lines. A highly fluorescent
coumarin-containing compound 4o was found to have good
activity against the B16 cancer cell line. The fluorescent
property was introduced into the molecule to provide a
potential probe for tracking the compound as it travels
through the cell and localizes at the target. The 4-hydroxy-
3-nitro compound 4k gave appreciable activity despite
having a 4-hydroxy functionality. The meta-nitro group
must contribute to the activity of the compound since
without it compound 4j was totally inactive.
123

Med Chem Res
Table 3 IC50 values of the hydroxylated curcumin analogs belonging to Group III
Sr. no.
Compound
IC50 (lM)
B16
L1210
2.3
14
0.7
O
HO
OH
N
H
4i
15
[100
[100
O
HO
N
H
OH
4j
Table 4 IC50 values from cytotoxicity studies of Group IV amino- and nitro-containing compounds
Sr. no.
Compound
IC50 (lM)
B16
32.5
L1210
42.5
O
16
CH3
H3C
N
N
H
N
CH3
CH3
4l
O
17
18
19
23.5
1.5
33
28.5
CH3
H3C
N
N
N
CH3
CH3
CH3
5d
O
35
C2H5
C2H5
N
N
H
N
C2H5
C2H5
4m
O
3.3
C2H5
C2H5
N
N
N
C2H5
CH3
C2H5
5e
123

Med Chem Res
Table 4 continued
Sr. no.
Compound
IC50 (lM)
B16
L1210
29
O
20
44
C2H5
N
C2H5
O
O
N
H
O
O
N
C2H5
C2H5
4o
O
O2N
HO
NO2
OH
21
7.3
2.0
N
H
4k
Conclusion
et al., 2012), 4a (Abaee et al., 2007), 4b (Bazzaro et al.,
2011), 4g (Abaee et al., 2007), and 4l (Odinets et al.,
2008), as well as 5a (Makarov et al., 2008), 5b (Mod-
zelewska et al., 2006), 5d (Makarov et al., 2008), and 5e
(Makarov et al., 2008) were previously reported and they
came up as ‘‘Hits’’ according to a SciFinder Scholar search
conducted on December 22, 2012. Since these are known
compounds only the synthesis and characterization of the
12 new compounds are reported. Compounds 3, 4(a–e),
4(h–o), and 5(a–e) were synthesized according to Method
A:
From the twenty-one 4-piperidone- and N-methyl-4-piper-
idone-containing curcumin analogs synthesized and
reported herein, the dimethoxy-substituted analogs as
exemplified by 4e and 4f emerged as most cytotoxic
against L1210 and B16 cells when compared to the key
reported compounds 2 and 3. Structure–activity analysis of
the results demonstrated that hydroxylated compounds can
be just as active, e.g., 4i, but the position of attachment is
crucial. Also, introduction of a nitro group next to the para-
hydroxy group in the benzene ring enhanced cytotoxicity.
The compounds containing amino substitution were gen-
erally less active than their halogenated and oxygen-con-
taining analogs. Furthermore, the results indicate that
N-substitution in the 4-piperidone moiety adds value to the
cytotoxicity of the compounds. Thus, in future work,
derivatization of the N-position of 4-piperidone can be
investigated. Even though the biological mechanism of
action of these compounds is not reported herein, based on
the report on STAT3 inhibitory activity of 3,5-bis-(4-flu-
Method A
The appropriate aryl aldehyde (2.0 equiv) was added to the
solution of 4-piperidone hydrate hydrochloride or
N-methyl-4-piperidone (1.0 equiv) in acetic acid. Dry
hydrogen chloride gas was purged into the clear solution
for 15 min. The reaction mixture was stirred at room
temperature for 18 h and then filtered through a Bu¨chner
funnel. The precipitate obtained was washed with cold
methanol. The resulting solid was stirred in water. To the
reaction mixture, saturated solution of sodium bicarbonate
in water was added until pH was 9–10. The crude com-
pound was filtered, washed with water, dried under vac-
uum, and purified by recrystallization in ethyl acetate.
´
orobenzyl)-4-piperidone 3 (Kalai et al., 2011; Selvendiran
et al., 2010; Tierney et al., 2012) and the ability of analog 2
to inhibit STAT3 in cells (private communication), it is
possible that the compounds described in this paper also act
by blocking the STAT3 pathway.
Compound 4c Yellow solid (26 %); mp: 253–257 °C; 1H
NMR (DMSO-d6): d 9.50 (s, 1H), 7.85 (s, 2H), 7.78 (s, 2H),
7.70 (d, J = 8.0 Hz, 2H), 7.53 (d, J = 8.0 Hz, 2H), 7.48 (t,
J = 8.0 Hz, 2H), 4.49 (s, 4H); 13C NMR (DMSO-d6): d
182.2, 137.7, 136.0, 132.7, 132.6, 130.9, 129.3, 129.1,
122.1, 43.7; IR (ATR): t 1681, 1611, 1575, 1557, 1506,
1177, 1089, 946, 796, 787; MS: ESI (m/z) 433 (M?H)?.
Experimental
Synthesis of the 4-piperidone containing curcumin
analogs
´
Curcuminoids 3 (Abaee et al., 2007; Kalai et al., 2011;
Lagisettya et al., 2010; Selvendiran et al., 2010; Tierney
123

Med Chem Res
1
Compound 4d Yellow solid (16 %); mp:194–196 °C; H
J = 8.0 Hz, 4H), 6.77 (d, J = 8.0 Hz, 4H), 4.43 (s, 4H),
3.44 (q, J = 4.0 Hz, 8H), 1.13 (t, J = 4.0 Hz, 12H); 13C
NMR (DMSO-d6): d 181.2, 148.8, 139.2, 133.2, 122.0,
120.4, 111.3, 44.2, 43.8, 12.4; IR (ATR): t 3020, 2969,
1572, 1556, 1513, 1486, 1467, 1437, 1403, 1372, 1352,
1329, 1312, 1273, 1174, 1152, 1126, 1094, 1071, 1009,
976, 926, 814, 758, 729; MS: ESI (m/z) 418 (M?H)?.
NMR (DMSO-d6): d 7.80 (s, 2H), 7.44 (t, J = 8.0 Hz, 4H),
7.06 (m, 6H), 4.40 (s, 4H), 3.81 (s, 6H); 13C NMR (DMSO-d6):
d 182.9, 159.4, 138.6, 135.1, 130.0, 129.0, 122.6, 115.8, 115.7,
55.3, 44.3; IR (ATR): t 2356, 1558, 1539, 1506, 1486, 1218,
1088, 1099, 1039, 942, 798; MS: ESI (m/z) 335 (M?H)?.
1
Compound 4e Yellow solid (7 %); mp: 145–147 °C; H
Compound 4n (27 %); mp: 203–205 °C; 1H NMR
(DMSO-d6): d 8.35 (s, 2H), 7.85 (d, J = 8.0 Hz, 2H), 7.55
(s, 2H), 6.91 (d, J = 8.0 Hz, 2H), 3.97 (s, 4H), 3.90 (s,
6H); 13C NMR (DMSO-d6): d 187.0, 163.4, 149.7, 140.4,
135.4, 130.3, 124.6, 110.5, 53.5, 47.5; IR (ATR): t 1660,
1595, 1568, 1557, 1494, 1388, 1348, 1316, 1292, 1259,
1194, 1131, 1091, 1021, 1010, 982, 968, 944, 925, 896,
871, 842, 827, 805, 773, 746, 733; MS: ESI (m/z) 338
(M?H)?.
NMR (DMSO-d6): d 7.51 (s, 2H), 6.61 (s, 4H), 6.56 (s,
2H), 3.99 (s, 4H), 3.78 (s, 12H); 13C NMR (DMSO-d6): d
187.6, 160.4, 136.7, 136.4, 133.8, 108.2, 101.2, 55.3, 47.5;
IR (ATR): t 1586, 1456, 1424, 1333, 1307, 1263, 1233,
1206, 1153, 1058, 1018, 993, 933, 920, 831, 763, 741; MS:
ESI (m/z) 396 (M?H)?.
Compound 4h Yellow solid (41 %); mp: 218–220 °C; 1H
NMR (DMSO-d6): d 7.49 (s, 2H), 7.05 (s, 2H), 7.01 (s,
4H), 6.10 (s, 4H), 3.95 (s, 4H); 13C NMR (DMSO-d6): d
187.3, 148.0, 147.6, 134.5, 133.5, 129.1, 125.7, 110.0,
108.5, 101.5, 47.6; IR (ATR): t 3313, 1646, 1621, 1603,
1580, 1550, 1501, 1490, 1365, 1328, 1270, 1231, 1142,
1099, 1033, 985, 867, 945, 823, 805, 789, 777, 758; MS:
ESI (m/z) 364 (M?H)?.
Compound 4o Dark red solid (15 %); mp: 198–202 °C;
1H NMR (DMSO-d6): d 7.90 (s, 2H), 7.59 (d, J = 4.0 Hz,
4H), 6.76 (d, J = 8.0 Hz, 2H), 6.56 (s, 2H), 3.98 (s, 4H),
3.47 (q, J = 7.0 Hz, 8H), 1.14 (t, J = 7.0 Hz, 12H); 13C
NMR (DMSO-d6): d 185.8, 161.0, 156.0, 151.3, 143.5,
135.6, 130.7, 127.9, 114.0, 109.5, 108.1, 96.3, 47.9, 44.2,
12.3; IR (ATR): t 2966, 2926, 1716, 1615, 1568, 1506,
1413, 1372, 1353, 1322, 1251, 1189, 1130, 1072, 1039,
978, 919, 817, 780, 761, 734, 720; MS: ESI (m/z) 554
(M?H)?.
1
Compound 4i Yellow solid (60 %); mp: 226–230 °C; H
NMR (DMSO-d6): d 9.62 (s br, 2H), 7.47 (s, 2H), 7.26 (t,
J = 8.0 Hz, 2H), 6.90 (d, J = 8.0 Hz, 2H), 6.85 (s, 2H),
6.80 (d, J = 8.0 Hz, 2H), 3.96 (s, 4H); 13C NMR (DMSO-
d6): d 187.6, 157.4, 136.1, 135.9, 133.8, 129.6, 121.5,
116.7, 116.2, 47.6; IR (ATR): t 3315, 1614, 1586, 1559,
1449, 1312, 1288, 1167, 1033, 991, 941, 857, 808, 792,
775, 743; MS: ESI (m/z) 308 (M?H)?.
Compound 5c Orange solid (99 %); mp: 118–121 °C; 1H
NMR (DMSO-d6): d 7.70 (s, 2H), 7.62 (m, 2H), 7.56 (s,
2H), 7.50 (m, 2H), 7.45 (d, J = 8.0 Hz, 2H), 3.72 (s, 4H),
2.38 (s, 3H); 13C NMR (DMSO-d6): d 186.3, 136.95,
134.9, 133.2, 132.7, 131.8, 130.8, 129.1, 122.0, 45.1, 25.2;
IR (ATR): t 3413, 3288, 3058, 2935, 2846, 2778, 1668,
1611, 1584, 1556, 1470, 1456, 1278, 1176, 1133, 1106,
1091, 1073, 1059, 993, 973, 944, 921, 875, 858, 778, 723;
MS: ESI (m/z) 447 (M?H)?.
Compound 4j Yellow solid (35 %); mp: [250 °C; 1H
NMR (DMSO-d6): d 10.30 (s, 2H), 9.50 (s br, 1H), 7.79 (s,
2H), 7.40 (d, J = 8.0 Hz, 4H), 6.92 (d, J = 8.0 Hz, 4H),
4.45 (s, 4H); 13C NMR (DMSO-d6): d 182.0, 159.6, 139.1,
133.0 124.7, 124.6, 116.0, 44.0; IR (ATR): t 3115, 2919,
2809, 1668, 1603, 1578, 1557, 1510, 1443, 1356, 1315,
1271, 1223, 1169, 1107, 1074, 1052, 980, 961, 951, 788,
738; MS: ESI (m/z) 308 (M?H)?.
Compounds 4f and 4g were synthesized according to
Method B:
Method B
1
Compound 4k Yellow solid (35 %); mp: [250 °C; H
NMR (DMSO-d6): d 10.20 (s br, 3H), 8.03 (d, 2H,
J = 2.0 Hz), 7.75 (s, 2H), 7.66 (dd, 2H, J = 8.6, 2.0 Hz),
7.19 (d, 2H, J = 2.0 Hz), 4.40 (s, 4H); 13C NMR (DMSO-
d6): d 182.2, 153.7, 137.4, 136.8, 134.1, 127.5, 127.5,
124.3, 119.7, 44.1; IR (ATR): t 3250, 3010, 2960, 1601,
1524, 1495, 1461, 1422, 1355, 1297, 1263, 1242, 1162,
989, 948, 931, 908, 846, 746; MS: ESI (m/z) 398 (M?H)?.
The appropriate aryl aldehyde (2.0 equiv) was added to a
solution of 4-piperidone hydrate hydrochloride (1.0 equiv) in
ethanol. To the clear solution, 20 % aqueous sodium
hydroxide solutionwasadded dropwise. Thereactionmixture
was stirred at room temperature for 18 h and then filtered
through Buchner funnel. The separated solid was washed with
cold methanol. The resulting solid was stirred in water (5.0) at
room temperature for 15 min and the filtered again. The crude
solid was washed with water and dried under vacuum. The
crude compound was recrystallized in ethyl acetate.
¨
Compound 4m Purple solid (63 %); mp: 218–222 °C; 1H
NMR (DMSO-d6): d 9.36 (s br, 1H), 7.72 (s, 2H), 7.35 (d,
123

Med Chem Res
Compound 4f Yellow solid (36 %); mp: 133–137 °C; 1H
NMR (DMSO-d6): d 7.72 (s, 2H), 7.02 (d, J = 8.0 Hz,
2H), 6.98 (dd, J = 4.0, 8.0 Hz, 2H), 6.79 (d, J = 4.0 Hz,
2H), 3.88 (d br, J = 4.0 Hz, 4H), 3.79 (s, 6H,), 3.74 (s,
6H); 13C NMR (DMSO-d6): d 187.6, 160.4, 136.7, 136.4,
133.8, 108.2, 101.2, 55.3, 47.5; IR (ATR): t 3317, 2932,
2832, 1658, 1594, 1561, 1491, 1443, 1302, 1280, 1268,
1223, 1206, 1187, 1161, 1038, 1005, 946, 936, 921, 861,
806, 781; MS: ESI (m/z) 395 (M?H)?.
Dimmock JR, Padmanilayam MP, Puthucode RN, Nazarali AJ,
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Acknowledgments The authors thank Conjura, LLC for support for
this research.
´
Kalai T, Kuppusamy ML, Balog M, Selvendiran K, Rivera BK,
Kuppusamy P, Hideg K (2011) Synthesis of N-substituted 3,5-
bis(arylidene)-4-piperidones with high antitumor and antioxidant
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