Synthesis and evaluation of (E)-2-(acrylamido)cyclohex-1-enecarboxylic acid derivatives as HCA1, HCA2, and HCA3 receptor agonists

Article abstract of DOI:10.1016/j.bmc.2014.05.011

2-(3-(Naphthalen-2-yl)propanamido)cyclohex-1-enecarboxylic acid and its 6-hydroxynaphthalen-2-yl analogue are well-known hydroxyl-carboxylic acid (HCA) receptor HCA2 agonists. A series of novel aryl derivatives of 2-amidocyclohex-1-ene carboxylic acid tha

Full text of DOI:10.1016/j.bmc.2014.05.011

Bioorganic & Medicinal Chemistry 22 (2014) 3654–3669
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and evaluation of (E)-2-(acrylamido)cyclohex-1-
enecarboxylic acid derivatives as HCA1, HCA2, and HCA3 receptor
agonists
Olga Bobileva a, Rasma Bokaldere a, Vija Gailite a, Ilze Kaula a, Martins Ikaunieks a, Gunars Duburs a,
Ramona Petrovska b, Ilona Mandrika b, Janis Klovins b, Einars Loza a,
⇑
a Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
b Biomedical Research and Study Centre, Ratsupites 1, Riga LV-1067, Latvia
a r t i c l e i n f o
a b s t r a c t
Article history:
2-(3-(Naphthalen-2-yl)propanamido)cyclohex-1-enecarboxylic acid and its 6-hydroxynaphthalen-2-yl
analogue are well-known hydroxyl-carboxylic acid (HCA) receptor HCA2 agonists. A series of novel aryl
derivatives of 2-amidocyclohex-1-ene carboxylic acid that contained rigidity elements, such as an E-dou-
ble bond, triple bond, and trans or cis-substituted cyclopropane rings, instead of the saturated ethane lin-
ker in the amide part of the molecules were designed and synthesized, and the derivatives’ potency for
the activation of HCA1, HCA2, and HCA3 receptors by 30–50-cyclic adenosine monophosphate (cAMP)
assay were evaluated. The SAR studies revealed that the rigidifying of appropriate molecules enabled
modulation of the potency and selectivity of the HCA2 receptor activation.
Received 9 December 2013
Revised 15 April 2014
Accepted 9 May 2014
Available online 17 May 2014
Keywords:
GPR109A
HCA2
Niacin
Ó 2014 Elsevier Ltd. All rights reserved.
Dyslipidemia
Agonist
cAMP
2-Acrylamidocyclohex-1-ene
1. Introduction
In 2003, several groups identified GPR109A as a high affinity
receptor of the antidyslipidemic drug niacin, which is expressed
The beneficial role of niacin (nicotinic acid, one of the vitamin
B3 forms) in the regulation of lipid profiles and its anti-athero-
sclerotic properties has been recognized since 1955 due to a
publication by Altschul et al.1 Human clinical trials showed that
niacin treatment decreases the morbidity and mortality of
patients with coronary diseases and slows the progression of
atherosclerosis.2–4
Niacin reduces free fatty acid (FFA), very low-density lipopro-
tein (VLDL) cholesterol, low-density lipoprotein (LDL) cholesterol,
triglyceride (TG), and lipoprotein a (Lp-a) levels in plasma, while
effectively increasing the high-density lipoprotein (HDL) choles-
terol in plasma.5–9
in adipocytes, keratinocytes and immune cells. The highly related
GPR109B, which shares 95% identity and is only expressed in
humans and chimpanzees, was also identified as a low affinity
receptor for niacin.10–12
GPR109A and GPR109B, together with GPR81, which shares
52% identity with GPR109A, form a G-protein coupled receptor
(GPCR) subfamily. Recently, for all these receptors, endogenous
ligands have been described. Because a common feature of these
ligands is that they are hydroxyl-carboxylic acid metabolites,
naming the corresponding receptors hydroxyl-carboxylic
acid (HCA) receptors was proposed.13 The HCA1 receptor
(GPR81) is activated by 2-hydroxy-propionate (lactate), the
HCA2 (GPR109A) by 3-hydroxy-butyrate, and the HCA3 receptor
(GPR109B) is activated by 3-hydroxy-octanoate. The HCA1,
HCA2, and HCA3 receptors are predominantly expressed in adi-
pocytes and they mediate antilipolytic effects through coupling
to Gi-type G proteins. Moreover, the HCA2 and HCA3 receptors
expressed in immune cells reduces proinflammatory function
by inhibiting proinflammatory cytokine and chemokine
production.14
Abbreviations: FFA, free fatty acid; VLDL, very low-density lipoprotein; LDL, low-
density lipoprotein; TG, triglyceride; Lp-a, lipoprotein a; HDL, high-density
lipoprotein; cAMP, 30–50-cyclic adenosine monophosphate; SAR, structure–activity
relationship; GPCR, G-protein coupled receptor; DIPEA, diisopropylethylamine; Py,
pyridine; TMS, trimethylsilyl; TBS, tert-butyltrimethylsilyl.
⇑
Corresponding author. Tel./fax: +371 67014883.
E-mail address: einars@osi.lv (E. Loza).
http://dx.doi.org/10.1016/j.bmc.2014.05.011
0968-0896/Ó 2014 Elsevier Ltd. All rights reserved.

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3655
Activation of HCA2 in adipose tissue mediates an antilipolytic
response by lowering the intracellular 30–50-cyclic adenosine
monophosphate (cAMP) levels, leading to reduced protein kinase
A activity, which in turn results in a decrease in lipase activity
and a reduction in intracellular TG hydrolysis. Reduction in
intracellular lipolysis decreases FFA secretion into plasma and ulti-
mately reduces the hepatic FFA available for TG synthesis. It has
been postulated that the decreased availability of FFA in the liver
directly reduces the production of hepatic TG and VLDL.15,16 The
mechanism by which niacin increases HDL cholesterol is not fully
understood, but it seems that it could affect the apolipoprotein A1
levels17 and/or limit the cholesterol ester transfer protein
mediated exchange of cholesterol from HDL cholesterol to VLDL
cholesterol and of TG from VLDL to HDL.18
However, the attractive properties of niacin are spoiled due to
the intense cutaneous flushing that accompanies niacin treatment
at therapeutic concentrations. It is postulated that a possible cause
of the flushing could be that HCA2 in epidermal Langerhans cells
mediates the niacin-induced release of prostaglandins D2 and
E2.15,19 The activation of the HCA1 and HCA3 receptors possesses
the antilipolytic activity but avoids the flushing side effect of
niacin, suggesting that these receptors could be a new target for
dyslipidemia treatment.20,21
To evaluate the possible agonist properties of the synthesized
compounds towards human HCA1, HCA2, and HCA3 receptors, for-
skolin-stimulated cAMP accumulation assays10 were arranged. In
these assays, Flp-In-293 cells, which express the recombinant
human HCA1, HCA2, and HCA3, were utilized.
2. Chemistry
Most compounds in Table 1 were synthesized according to the
general strategy shown in Scheme 1. Commercial ethyl 2-oxocyclo-
hexanecarboxylate (32) was treated with 7 N ammonia solution in
methanol and converted into ethyl 2-aminocyclohex-1-enecarb-
oxylate (33),30 which was further acylated using 2-bromoacetyl
bromide to yield 2-bromoacetamido derivative 34. Compound 34
was refluxed with triphenylphosphine in benzene to give stable,
crystalline triphenylphosphonium bromide 35. The salt 35 was
used for in situ preparation of the corresponding phosphorane,
which was condensed with the appropriate aldehydes to give the
expected E-alkenes 36a–p. The ethyl ester groups of compounds
36a–p were hydrolyzed to afford the corresponding target carbox-
ylic acids 3, 8–13, 15–18, and 21–26 (Scheme 1 and Table 1).
In general, the applied reaction conditions for transformations
did not change the structure of the aldehyde part R. However, in
the case of 2-chloroquinoline-3-carbaldehyde upon alkaline hydro-
lysis of the intermediate ester 36n and in the presence of metha-
nol, an exchange of a 2-Cl atom to a methoxy group in the
quinoline part was observed, and the 2-methoxy-3-quinolinyl-
acrylamide derivative 16 was isolated from the reaction mixture.
Only by avoiding methanol upon hydrolysis were we able to pre-
pare target compound 17 with the 2-Cl atom intact (Scheme 1).
Although the Wittig olefination reaction of compound 35 with
aldehydes in all cases formed E-alkenes 36 in overwhelming
excess, the detectable amounts of the corresponding Z-isomers of
the ester intermediates 36n, o (E:Z = 87:13, based on analysis of
the 1H NMR spectra) were observed. After the hydrolysis step
and purification procedures were performed on compounds 36n,
o, the target carboxylic acids 17 and 18 were free of the Z isomer.
The substituted ethyl acrylamidocyclohex-1-ene carboxylates
36j, k,l, o were selectively hydrogenated in a THF–MeOH (1:1) mix-
ture in the presence of 10% Pd (C) catalyst into the corresponding
ethyl propanamidocyclohex-1-ene carboxylates 37a–d. The subse-
quent hydrolysis of compounds 37a–d using 10 N NaOH–THF–
MeOH solutions yielded the expected propanamidocyclohex-1-
enecarboxylic acid derivatives 27–30 (Scheme 1 and Table 1).
The synthesis sequence of hydroxyaryl acrylamides 4 and 14, in
contrast to the general strategy outlined in Scheme 1, included
extra protection and deprotection steps of the hydroxy groups
(Scheme 2). Commercial 6-hydroxy-2-naphthaldehyde (38a) and
8-hydroxyquinoline-2-carbaldehyde (38b) using TBS-chloride/
imidazole treatment were converted into known TBS ethers
39a31 and 39b,32 which were condensed using triphenylphospho-
nium salt 35 in the presence of K2CO3 to give the expected amido-
cyclohex-1-ene carboxylates 40a, b. After the removal of the TBS
protection with tetrabutylammonium fluoride and alkaline hydro-
lysis of the ester function of the hydroxy derivatives 41a, b, the
target carboxylic acids 4 and 14 were obtained.
Since the discovery of these niacin pharmacologic targets,
extensive efforts have been devoted to the search for HCA2
receptor agonists as new drugs with improved pharmacological
properties, including reduced flushing.22–25
Merck chemists developed tetrahydroanthranilic acid deriva-
tives as potent and selective high affinity HCA2 full agonists.26–28
They demonstrated that a 2-propanamidocyclohex-1-enecarboxy-
lic acid scaffold can be used to develop compounds superior to nia-
cin for HCA2 activation with more attractive pharmacological
profiles, for example, 2-(3-(naphthalen-2-yl)propanamido)cyclo-
hex-1-enecarboxylic acid (I) possesses a good pharmacokinetic
profile and in vitro activity, and these parameters can be improved
by placing an extra hydroxyl group at the C-6 position of the naph-
thalene ring, as in compound II (Fig. 1).26 Based on the 2-propa-
namidocyclohex-1-enecarboxylic acid scaffold,
a
preclinical
candidate biaryl cyclohexene carboxylic acid MK-6892 (Fig. 1) as
a potent and selective high affinity HCA2 receptor full agonist with
reduced flushing profiles in animals was developed.27 The authors
demonstrated that the biological activity profile of 3-substituted
propanamidocyclohex-1-enecarboxylic acids can be modulated
by adding extra substituents on the cyclohexene ring29 and the sat-
urated side linker.27
Because the incorporation of rigidity elements in the side linker
could help to pre-organize the molecule in a favorable bioactive
conformation, we were interested to see what type of biological
response could exert a change in the saturated and flexible linker
part of similar molecules to more rigid and constrained linker con-
structs, for example, unsaturated bonds or 1,2-cyclopropyl groups
in compounds III (Fig. 1).
With the aim of testing the possible biological responses, a series
of 2-amidocyclohex-1-enecarboxylic acid analogues of structure III
containing E-double bonds, triple bond, or 1,2-disubstituted cis- and
trans-cyclopropane cycle were prepared (Table 1).
O
O
O
Ar = aryl
y
HN
X
N
Ar
X-Y =
HN
HN
OH
HOOC
HOOC
HOOC
O
N
N
R
(
)
I, R = H
II, R = OH
III
(
)
MK-6892
Figure 1. Structures of known HCA2 receptor agonists I, II, and MK-6892 and envisaged modifications III of the linker part.

3656
O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
Table 1
Potency of the synthesized compounds in the HCA1, HCA2, and HCA3 receptor cAMP assay
O
HN
R
HOOC
No
R
HCA2
HCA3
HCA1
inh.b (%)
inh.b (%)
EC50 (lM)
Emax (%)
Inh.b (%)
a
c
1
8.3 2.4
97
5
66
4
41
4
4
3
2
3
4
1.9 0.9
4.5 1.2
1.4 0.1
97
94
96
4
3
7
26
14
NA
OH
NA
NA
OH
OH
5
6
7
0.9 0.5
98
96
2
5
NA
40
12.5 5.0
55 15
5
(
)
34 18
NA
NA
(
)
8
NA
NA
NA
26 10
NA
O
9
NA
N
N
10
11
4.1 1.4
99
4
NA
NA
N
NA
54 10
NA
12
13
68 10
NA
39 19
NA
24 10
NA
N
N
OH
N
N
14
15
27 13
53 21
NA
NA
O
O
61
8
38 13
O

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3657
Table 1 (continued)
No
R
HCA2
HCA3
HCA1
inh.b (%)
inh.b (%)
a
c
EC50
(l
M)
Emax (%)
Inh.b (%)
59 11
16
17
18
58 11
52 13
NA
27 11
O
N
N
N
27.4 3.5
6.3 4.1
79
86
6
8
37 13
Cl
O
21
7
Cl
19
3.6 1.6
90
7
56 10
NA
O
20
21
5.8 4.2
6.8 3.7
83
93
7
8
26
7
NA
NA
O
O
66 16
O
22
23
51 13
58
6
31 14
36 22
O
O
Cl
O
26.3 4.5
95
4
48 10
O
O
24
25
17
24
9
7
59
6
34 15
NA
O
O
Cl
Br
54 14
O
O
26
27
23 12
46
55
3
6
NA
NA
O
Br
N
60
6
28
29
30
31
70 14
60 15
54 17
26
23
7
6
N
N
36.4 11.2
4.1 2.9
82
91
85
5
6
4
O
53
62
7
3
24 10
Cl
N
O
O
51.6 4.2
28
7
NA—not active up to the 50
l
M concentration tested.
a
Each value represents the mean SD calculated from at least three experiments, each performed in duplicate.
Inhibition (%) of forskolin-stimulated intracellular accumulation of cAMP using 50
100%.
b
lM solution of the tested compound. The forskolin-stimulated cAMP levels were set to
c
Maximal inhibition (%) of forskolin-stimulated cAMP.

3658
O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
O
O
P+Ph3
Br
Br-
O
NH2
HN
HN
COOEt
a
COOEt
c
b
COOEt
COOEt
32
33
34
35
d
O
O
O
O
HN
HN
R
HN
R
R
HN
R
f
HOOC
e
EtOOC
EtOOC
HOOC
e
3, 8-13, 15-18, 21-26
37a-d
27-30
36a-p
No
R
No
R
No
R
No
R
12
28
36k
37b
13
29
36l
37c
Cl
O
O
17
36n
3
36a
23
36e
N
Cl
N
18
30
36o
37d
O
O
8
36b
24
36f
N
CH3
O
O
Cl
N
Cl
N
O
O
O
O
O
15
36m
9
36i
21
36d
25
36g
O
O
Br
N
O
N
22
36p
10
36c
26
36h
16
O
O
O
N
O
Br
11
27
N
36j
37a
Scheme 1. Synthesis of (E)-2-(acrylamido)cyclohex-1-enecarboxylic acid derivatives using a strategy based on the Wittig reaction. Reagents and conditions: (a) NH3, MeOH,
97%; (b) BrCH2COBr, Py, THF, 88%; (c) PPh3, 86%; (d) (1) K2CO3, 18-crown-6, DCM (for 36a–h) or t-BuOK, DMSO (for 36i–p), (2) R2CHO; (e) NaOH, iso-PrOH or MeOH–THF; (f)
H2, Pd(C) (for 37a–c) or H2, Raney Ni (for 37d).
The carboxylic acid 4 was converted into propanamido ana-
logue 2 (Scheme 2 and Table 1) via the selective, Pd-catalyzed
hydrogenation of the linker double bond.
The target acrylamide with an extra triple bond 19 was
prepared from a-bromocinnamaldehyde (42) using a similar reac-
tion sequence to Scheme 1. The resulting ester 43 was converted
into 19 via the alkaline hydrolysis conditions, which eliminated
HBr (Scheme 3).
Another set of compounds in Table 1 was prepared using a
strategy similar to the one used by Raghavan et al.,26 which was
based on acylation reactions of vinylamine 33 (Scheme 4). The
appropriate carboxylic acids 44a–d were converted in situ into
the corresponding chlorides using oxalyl chloride and were
condensed with vinylamine 33 to give the substituted ethyl
amidocyclohex-1-ene carboxylates 45a–d. Saponification of ethyl
esters 45a–d using a 10 N NaOH–THF–MeOH solution yielded
compounds 1, 5, 7, and 20.
44c, precursors for the synthesis of target compounds 5 and 7,
respectively, were prepared as follows: The reaction of the above
prepared TBS ether 39a with CBr4–PPh3 yielded geminal dib-
romoalkene 46. Treatment of alkene 46 with n-BuLi was used
for the in situ generation of lithium acetylenide, which was fur-
ther quenched with solid CO2 to provide the necessary carboxylic
acid 44b (Scheme 4).
The Z-selective Horner–Emmons reaction of methyl 2-(bis(o-
tolyloxy)phosphoryl)acetate3347 with 2-naphthaldehyde provided
(Z)-methyl acrylate 48 (Z:E = 100:8). The palladium-mediated
cyclopropanation reaction34 of the (Z)-acrylate 48 with diazometh-
ane afforded cis-( ) cyclopropane carboxylate 49,35 which was free
of the minor E-isomer product after chromatographic purification.
Compound 49 was hydrolyzed to the desired carboxylic acid 44c
(Scheme 4).
The palladium-mediated cyclopropanation reaction34 of
3-naphthyl substituted acrylamidocyclohexene carboxylate 36a
(synthesis shown in Scheme 1) with diazomethane yielded
trans-( ) cyclopropane carboxamido derivative 45e,35 which was
hydrolyzed as above to the desired product 7 (Scheme 4).
Carboxylic acids 44a and 44d, which are necessary for the
preparation of target compounds 1 and 20, respectively, were
obtained from commercial sources. Carboxylic acids 44b and

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3659
O
R2
R2
R2
X
c
HN
X
CHO
X
CHO
b
a
EtOOC
R1
R1
R1
1
2
39a, R1=OTBS, R2=H, X=CH
39b, R1=H, R2=OTBS, X=N
40a
40b
38a, R1=OH, R2=H, X=CH
38b, R1=H, R2=OH, X=N
, R =OTBS, R =H, X=CH
1
2
, R =H, R =OTBS, X=N
R2
O
R2
O
X
X
HN
d
HN
EtOOC
HOOC
R1
R1
4, R1=OH, R2=H, X=CH
14, R1=H, R2=OH, X=N
41a, R1=OH, R2=H, X=CH
41b, R1=H, R2=OH, X=N
e
4
with
OH
O
HN
HOOC
2
Scheme 2. Synthesis of hydroxyaryl analogues 2, 4, and 14. Reagents and conditions: (a) TBSCl, imidazole, DMF, 99% (39a), 80% (39b); (b) 35, K2CO3, 18-crown-6, DCM, 79%
(40a), 85% (40b); (c) TBAF, THF, 69% (41a), 94% (41b); (d) 5 N NaOH, iso-PrOH, 65 °C, 47% (4), 58% (14); (e) H2, Pd(C), MeOH–THF (1:1), 54%.
O
O
HN
Ph
HN
CHO
a
EtOOC
Br
HOOC
Ph
b
Br
43
-bromocinnamaldehyde (42). Reagents and conditions: (a) 35, t-BuOH, DMSO, 80%; (b) 10% NaOH, THF, MeOH, 29%.
19
42
Scheme 3. Synthesis of carboxylic acid 19 from
a
COOMe
CHO
(o-Tol-O)2P
g
O
COOMe
HOOC
TBSO
TBSO
48
47
39a
O
d
e
O
O
HN
Br
COOMe
31
Br
c
49
20
with
46
h
f
O
O
HN
R
HN
R
O
EtOOC
a
b
HOOC
R
OH
O
44a-d
45a-e
1
,
5 7 20
- ,
HN
d
EtOOC
36a
R
R
No.
No.
44a→45a→1
39a→46→44b→45b→5
36a→45e→6
47 48 49 44c 45c
(
(
)
)
7
→
→
→
→
→
1
OR
44b, 45b: R1 =TBS
5: R' =H
O
O
44d→45d→20
Scheme 4. Preparation of target compounds 1, 5–7, 20, 31 via the acylation of vinylamine 33 using the appropriate carboxylic acids 44a–d and cyclopropanation of the
acrylamido intermediate 36a. Reagents and conditions: (a) (1) (COCl)2, DCM, (2) 33; (b) aq NaOH, THF, 50 °C; (c) H2, Pd(C), MeOH–THF (1:1), 54% (d) CH2N2, Pd(OAc)2, DCM,
96% (45e), 36% (49); (e) CBr4, PPh3, DCM, 89%; (f) (1) n-BuLi, THF, ꢀ78 °C, (2) CO2, ꢀ78 °C, 50%; (g) (1) t-BuOH, DMSO, (2) 2-naphthylaldehyde, 88%; (h) 10 N NaOH, THF–
MeOH (1:1), 50 °C.

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O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
The carboxylic acid 20 was converted into propanamido ana-
logue 31 via the selective Pd-catalyzed hydrogenation of the linker
double bond (Scheme 4 and Table 1).
To increase the diversity of (E)-2-(3-aryl acrylamido)cyclohex-
1-enecarboxylic acids, a series with various quinolines at the 3-
position of the linker were synthesized and tested for activity
(compounds 9–18). Among the prepared 4-quinolinyl (9), 2-quin-
olinyl (10), 8-quinolinyl (11), and 6-quinolinyl (12) derivatives,
only compound 10 exhibits considerable potency with HCA2
2.1. Biological activity and structure–activity relationship (SAR)
The known structures
I
(h-3H-niacin IC50 = 38 nM, hGTP
c
S
(EC50 = 4.1 1.4 lM), while its activity towards HCA1 and HCA3
EC50 = 690 nM)26 and II (h-3H-Niacin IC50 = 8 nM, hGTP
cS EC50 = 76 -
is negligible. Further attempts to modulate the activity by attach-
ing additional functional groups to the quinoline heterocycle
revealed that the prepared molecules are very sensitive to minor
changes in the structure. Thus, 6-quinolinyl compound 12 com-
pletely lost its weak activity towards HCA2 (68% cAMP decrease
nM)29 were used as reference compounds for the comparison in our
studies. The corresponding EC50 values for I (1 in Table 1) and II (2
in Table 1) in our cAMP assay were 8.3 2.4 and 1.9 0.9 lM, respec-
tively. Thus, 6-OH derivative 2 exhibited increased activity in all
assays compared to the unsubstituted analogue 1.
by a 50-lM solution) due to the addition of an extra methyl group
Merk scientists recognized36 that the activity of anthranilides in
both the binding and functional assays can be greatly reduced in
the presence of 4% human serum. In our work, all of the cAMP
assays were performed in the presence of 2% bovine serum albu-
min (BSA). We have also performed some additional experiments
where compounds 3, 5, 6, 19, 20, and 30 (Table 1) were preincu-
bated with 5% BSA for 30–45 min and then used in the cAMP assay
in a buffer with 2% BSA. We did not observe significant differences
in the cAMP level inhibition between the experiments.
2-Naphthalenyl analogues with E-double bond 3 and 4, triple
bond 5, and cis and trans ( )cyclopropane groups 6 and 7 incorpo-
rated in the linker part of molecules. Our first experiments
revealed that a change of the saturated ethyl linker of reference
compound 1 to the E-double bond resulted in active structure 3
next to the quinoline N-atom (compound 13). An extra hydroxyl
group at the C-8 position of the 2-quinolinyl cycle reduced the
activity of compound 10 (EC50 = 4.1 1.4
lM) to 27% cAMP
decrease by a 50- M solution of compound 14. 4,5,6-Trimeth-
l
oxy-2-quinolinyl analogue 15 possesses weak activation of all
three receptors HCA1, HCA2, and HCA3. We had starting materials
for the synthesis of 3-quinolinyl derivatives with extra substitu-
ents only. Thus, the weak activity of 2-methoxy-3-quinolinyl deriv-
ative 16 (59% cAMP decrease by a 50-
placing a chlorine atom instead of the methoxy group at the C-2
position (compound 17, EC50 = 27.4 3.5 M) and even better
potency is achieved in the case of 2-chloro-6-methoxy-3-quinoli-
nyl analogue 18 (EC50 = 6.3 4.1 M).
lM solution) is improved by
l
l
Interestingly, (E)-2-acrylamidocyclohex-1-enecarboxylic acid
(EC50 for 3 is 4.5 1.2 lM versus 8.3 2.4 lM for 1 as measured
derivative 19 containing a phenylethynyl group attached to the E-
by the cAMP assay). The introduction of the hydroxyl group at
the C-6 position of the naphthalene ring, as in 1 and 2, improves
double bond exhibits comparable activation of HCA2 (EC50
3.6 1.6 M) to bicyclic 2-napthalenyl analogue 3 (EC50 = 4.5
1.2 M).
Benzo[1,3]dioxole analogue 20 exhibits a strong preference for
HCA2 activation (EC50 = 5.8 4.2 M). A change in the methylene
bridge of the adjoining oxa groups in compound 20 to ethylene
produces the equally potent compound 21 (EC50 = 6.8 3.7 M);
however, the activity sharply drops upon addition of extra chlorine
or bromine atoms at the 6-position of the benzole ring (compounds
24 and 25) or disconnecting the bridge, as in the case of 3,4-dime-
=
l
the activity of compound 4 (EC50 = 1.4 0.1
lM). Further increases
l
in activity are induced by changing the E-double bond in 6-
hydroxy-2-napthalenyl derivative 4 to the triple bond as in com-
pound 5 (EC50 = 0.9 0.5 lM). It is noteworthy that the selectivity
of the E-doublebond and triple bond analogues 3–5 towards HCA2
increases compared with the corresponding saturated structures.
Thus, the reference structures 1 and 2 exhibit low affinity towards
l
l
HCA1 and HCA3 (ca. 50% cAMP decrease by 50-lM solutions) but
the E-double bond and triple bond 6-hydroxy-2-napthalenyl ana-
logues 4 and 5 do not have detectable effects on HCA1 and
HCA3. Only the E-double bond analogue 3 with unsubstituted 2-
napthalenyl group shows some inhibition with HCA1 (13.7% cAMP
thoxy derivative 22 (51% cAMP decrease by a 50-lM solution).
Although there is some increase in the activity upon addition of
an extra chlorine atom at the C-2 position of 3,4-dimethoxyphenol
(compound 23, EC50 = 26.3 4.5 lM), a bromine atom substituted
decrease by a 50
lM solution). Because we are interested in the
at the C-5 position is not beneficial (compound 26).
effects of the linker rigidity of 2-naphthalenyl derivatives, an
attempt to incorporate trans- and cis-cyclopropyl groups in the lin-
ker was made. A change in the saturated linker in structure 1 to a
trans ( ) cyclopropyl group, as in compound 6, decreases the activ-
Because we are interested in the activity of 2-naphthenyl
substituted propanamido-cyclohexene, carboxylic acids 1 and 2
can be favorably modified in terms of activation and selectivity
towards HCA2 by replacing the saturated propanamido group of
the molecules with an (E)-acrylamido linker; in this way, an
attempt to evaluate the universality of this transformation was
performed. Thus, (E)-2-acrylamido cyclohexene carboxylic acids
11–13 and 20 were selectively hydrogenated into the correspond-
ing saturated propanamido derivatives 27–31, respectively. In the
case of the compound pair 20?31, the ability to activate HCA2 sig-
nificantly decreased for the saturated structure 31. The activities of
the pairs 18?30 and 12?28 do not change, and the initially inac-
tive compounds were transformed to weakly or moderately active
compounds by hydrogenation in the case of the pairs 11?27 and
13?29.
ity with HCA2 (EC50 = 12.5 5.0 lM). Because compound 6 was
prepared as a racemate, this value reflects the combined effect of
both enantiomers. A further drop in activity was observed in the
case of the cis ( ) cyclopropane analogue 7 (34% cAMP decrease
by a 50-lM solution).
(E)-2-(3-Substitued acrylamido)cyclohex-1-enecarboxylic acids:
Encouraged by the finding that a change of the saturated linker
in reference molecules 1 and 2 to the E-double bond leads to
HCA2-active 2-naphthalenyl analogues 3 and 4, brief studies to
obtain SARs for diverse (E)-2-(3-substitued acrylamido)cyclohex-
1-enecarboxylic acids were undertaken.
Limited studies of the impact of the substituents attached to the
naphthalene ring of compound 3 were performed. As it was already
stated, the presence of a 6-hydroxyl group on the naphthalene ring
is beneficial for potency and increases the activation of HCA2 by 4.
In contrast, the placement of a methoxy group at the C-6 position
in compound 8 is detrimental to the activation of HCA2 and HCA3,
while maintaining weak agonist activity towards HCA1 only (26%
3. Conclusions
We designed and synthesized a series of novel aryl derivatives
of 2-amidocyclohex-1-ene carboxylic acids, which contained rigid-
ity elements of E-double bonds, triple bonds, and trans- or
cis-substituted cyclopropane rings in the amide part of the mole-
cules that connects the cyclohexene and aromatic moieties. Also,
cAMP decrease by a 50-lM solution of 8).

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3661
we evaluated their potency for the activation of HCA1, HCA2 and
HCA3 receptors using a cAMP assay. The SAR studies revealed that
in the case of naphthalen-2-yl derivatives, the potency and
selectivity towards HCA2 receptors increases in the order: cis-( )-
cyclopropane (7) << trans-( )-cyclopropane (6) < single bond
(1) ꢁ E-double bond (3). For 6-hydroxynaphthalen-2-yl analogues
2 and 4, the series was expanded to include a compound with a tri-
ple bond (5); all of these compounds (2, 4, and 5) had comparable
potencies.
Among the synthesized (E)-2-(3-aryl)acrylamido)cyclohex-1-
enecarboxylic acids with diverse aryl substituents, several
compounds, such as quinolin-2-yl (10), 2-chloro-6-methoxyquino-
lin-3-yl (18), phenylpropynyl (19), benzo[d][1,3]dioxol-5-yl (20),
and 2,3-dihydrobenzo[b][1,4]dioxin-6-yl (21), exhibited compara-
ble potencies for the activation of HCA2 receptor as the known
agonist, the saturated 2-naphthalenyl analogue 1.
175 mmol) was stirred in a closed vessel at room temperature
for 24 h. The solvent was evaporated and the residue was dried
in vacuo over P2O5 to give 3.30 g (97%) of known31 compound 33
as yellow crystalline substance which was immediately utilized
in the next step. 1H NMR (CDCl3) d: 1.26 (t, J = 7.1 Hz, 3H), 1.55–
1.67 (m, 4H), 2.16–2.27 (m, 4H), 4.13 (q, J = 7.1 Hz, 2H), 6.00 (br
s, 2H). GCMS m/z: 169.1 M+.
4.1.2. Ethyl 2-(2-bromoacetamido)cyclohex-1-enecarboxylate
(34)
To a solution of ethyl 2-aminocyclohex-1-enecarboxylate (33)
(3.33 g, 19.7 mmol) and pyridine (2.33 g, 29.5 mmol) in dry THF
(50 ml) at ꢀ5 °C slowly within 1 h 2-bromoacetyl bromide
(3.93 g, 19.5 mmol) was added. The reaction mixture was stirred
at the same temperature for 45 min. and partitioned between ethyl
acetate (50 ml) and satd NaHCO3 (50 ml). The water phase was
extracted with ethyl acetate (3 ꢂ 30 ml). The organic extracts were
combined, and successively washed with satd NaHCO3 solution
(50 ml), water (2 ꢂ 50 ml), satd NaCl solution (50 ml), and dried
(Na2SO4). The solvent was evaporated, the residue was mixed with
ethyl acetate (50 ml), and the solid material was filtered off. The
filtrate was evaporated to dryness and the residue was dried in
vacuo over P2O5 to give 5.00 g (88%) of compound 34 as a brown
oil, which was immediately utilized in the next step. 1H NMR
(CDCl3) d: 1.30 (t, J = 7.1 Hz, 3H), 1.55–1.68 (m, 4H), 2.30–2.36
(m, 2H), 2.90–2.96 (m, 2H), 3.86 (s, 2H), 4.21 (q, J = 7.1 Hz, 2H),
12.08 (br s, 1H). GCMS m/z: 289.0 M+.
The extended studies of the compound pairs, consisting of 2-(3-
(aryl)propanamido)cyclohex-1-enecarboxylic
acid
and
the
corresponding double bond analogues (E)-2-(3-aryl)acrylami-
do)cyclohex-1-enecarboxylic acid revealed that the modulation of
the activity and selectivity is critically dependent on the aromatic
part of the molecule. Thus, in the case of the benzo[d][1,3]dioxol-
5-yl substituent, the increase in the activity due to changes in the
saturated linker in 31 to the E-double bond in 20 results in the
simultaneous increase of the selectivity towards HCA2 receptor.
The naphthalen-2-yl (1), 6-hydroxynaphthalen-2-yl (2), and
2-chloro-6-methoxyquinolin-3-yl (30) derivatives and their
respective E-double bond analogues, 3, 4, and 18, are almost
equally potent, but in the case of the moderately active 2-methyl-
quinolin-6-yl derivative 29, the corresponding E-double bond
analogue is completely inactive.
4.1.3. (2-((2-(Ethoxycarbonyl)cyclohex-1-en-1-yl)amino)-2-
oxoethyl)triphenylphosphonium bromide (35)
A solution of ethyl 2-(2-bromoacetamido)cyclohex-1-enecarb-
oxylate (34) (4.99 g, 17.2 mmol) and triphenylphosphine (4.52 g,
17.2 mmol) in dry benzene (35 ml) was refluxed for 3 h. The mixture
was allowed to cool to room temperature, the precipitate was
filtered, washed with benzene (50 ml), and dried in vacuo over
P2O5 to give 8.20 g (86%) of compound 35 as white crystals. Mp
124–126 °C. 1H NMR (CDCl3) d: 1.21 (t, J = 7.1 Hz, 3H), 1.49–1.57
(m, 4H), 2.25–2.31 (m, 2H), 2.39–2.46 (m, 2H), 4.10 (q, J = 7.1 Hz,
2H), 5.44 (d, J = 13.7 Hz, 2H), 7.60–7.68 (m, 6H), 7.71–7.78 (m, 3H),
7.82–7.91 (m, 6H), 11.09 (s, 1H). 13C NMR (CDCl3) d: 14.2, 21.5,
4. Experimental
4.1. Chemistry
NMR spectra were recorded at ambient temperature with Varian
400 OXFORD NMR spectrometer (400 MHz). Chemical shifts are
reported in parts per million (d) and referenced to hexame-
thyldisiloxane (HMDSO, d = 0.055 ppm) as an internal standard.
LCMS was performed on an Acquity UPLC system (Waters) con-
nected to the Micromass Q-TOF micro hybrid quadrupole time of
flight mass spectrometer operating in the electrospray ionization
(ESI) positive ion mode and using reverse-phase Acquity UPLC BEH
1
21.6, 24.9, 28.8, 34.8 [d, J(P,C) = 59.3 Hz], 60.4, 114.1, 118.5 [d,
1J(P,C) = 89.0 Hz] 130.1 [d, 2J(P,C) = 13.1 Hz], 134.1 [d, 3J(P,C) = 10.5 Hz],
134.8 [d, 4J(P,C) = 2.9 Hz], 143.9, 161.0 [d, 2J(P,C) = 4.2 Hz], 168.4. LCMS
(ESI) m/z: 473.2 [MꢀBrꢀ]+. Anal. Calcd for C29H31BrNO3P: C 63.05, H
5.66, N 2.54. Found: C 62.90, H 6.01, N 2.27. The obtained ethyl ester
34 may contain up to 3–5% of the corresponding methyl ester impu-
rity (LCMS (ESI) m/z: 458.2 [MꢀBrꢀ]+) coming from the synthesis of
compound 33.
C18 column (1.7
lm, 2.1 ꢂ 50 mm) on a gradient of 5–98% acetoni-
trile–water 0.1% formic acid. HRMS was carried out on a Micromass
Q-Tof micro mass spectrometer. The purity of the compounds of
Table 1 was confirmed to be P95% with Waters Alliance LC systems
equipped with 2695 separation module with quaternary pump,
degasser, autosampler, column thermostat, and Apollo C18
(4.6 ꢂ 150 mm) column. Waters 2489 dual absorbance detector
was used for the analysis. Elemental analyses were obtained with
a Carlo Erba EA 1108 instrument. Melting points were measured
on Gallenkamp or OptiMelt melting point apparatus and are
uncorrected. Various reagents and solvents were purchased from
Sigma–Aldrich, Acros Organic, Alfa Aesar, and Apollo Scientific.
Chromatographical purifications of compounds were performed
by column chromatography using silica gel, 0.035–0.070 mm,
(Acros) or prepacked columns on a Biotage Isolera One Purification
system. Reaction conditions and yields were not optimized. All the
solvents were purified before use by routine techniques.
4.1.4. Synthesis of (E)-(2-acrylamido)cyclohex-1-ene carboxylic
acid esters 36a–p and 43
4.1.4.1. General procedure of the synthesis of (E)-(2-acrylami-
do)cyclohex-1-ene carboxylic acid esters 36a–h. A mixture of (2-
((2-(ethoxycarbonyl)cyclohex-1-en-1-yl)amino)-2-oxoethyl)tri-
phenylphosphonium bromide (35) (1.2 mmol), K2CO3 (1.2 mmol),
18-crown-6 (0.03 mmol), and appropriate aldehyde (1 mmol) in
dichloromethane (10 ml) at room temperature was stirred until
the starting aldehyde disappeared (ca. 24 h). The mixture was sup-
plemented with dichloromethane (20 ml) and washed successively
with satd NH4Cl solution (2 ꢂ 20 ml), water (20 ml), brine (20 ml),
and dried (Na2SO4). The solvent was evaporated and the residue
was mixed with petroleum ether–ethyl acetate, 6:1 (5–10 ml).
The solid material was filtered, washed with petroleum ether
(5 ml) and purified by flash chromatography on silica gel with
4.1.1. Ethyl 2-aminocyclohex-1-enecarboxylate (33)
A mixture of ethyl 2-oxocyclohexanecarboxylate (32) (3.43 g,
20.2 mmol) and ca. 7 N ammonia solution in methanol (25 ml, ca.

3662
O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
chloroform or chloroform–ethyl acetate as eluent to give com-
pounds 36a–g as white or slightly colored solids.
(s, 1H), 7.97 (d, J = 15.5 Hz, 1H), 11.89 (s, 1H). LCMS (ESI) m/z:
438.2 [M+H]+.
4.1.4.1.1. (E)-Ethyl 2-(3-(naphthalen-2-yl)acrylamido)cyclohex-
1-enecarboxylate (36a). Compound 36a was obtained from 2-
naphthaldehyde, yield 73%. 1H NMR (CDCl3) d: 1.33 (t, J = 7.2 Hz,
3H), 1.56–1.72 (m, 4H), 2.33–2.39 (m, 2H), 3.08–3.14 (m, 2H),
4.22 (q, J = 7.2 Hz, 2H), 6.63 (d, J = 15.6 Hz, 1H), 7.47–7.52 (m,
2H), 7.68 (dd, J = 8.6, 1.7 Hz, 1H), 7.80 (d, J = 15.6 Hz, 1H), 7.79–
7.87 (m, 3H), 7.94 (s, 1H), 11.96 (s, 1H). LCMS (ESI) m/z: 350.3
[M+H]+.
4.1.4.1.2. (E)-Ethyl 2-(3-(6-methoxynaphthalen-2-yl)acrylami-
do)cyclohex-1-enecarboxylate (36b). Compound 36b was obtained
from 6-methoxy-2-naphthaldehyde, yield 60%. 1H NMR (CDCl3) d:
1.32 (t, J = 7.1 Hz, 3H), 1.58–1.71 (m, 4H), 2.33–2.39 (m, 2H),
3.07–3.14 (m, 2H), 3.92 (s, 3H), 4.22 (q, J = 7.1 Hz, 2H), 6.58 (d,
J = 15.6 Hz, 1H), 7.12 (d, J = 2.5 Hz, 1H), 7.15 (dd, J = 8.9, 2.5 Hz,
1H), 7.65 (dd, J = 8.6, 1.7 Hz, 1H), 7.71 (d, J = 8.6 Hz, 1H), 7.75 (d,
J = 8.9 Hz, 1H), 7.77 (d, J = 15.6 Hz, 1), 7.87 (s, 1H), 11.93 (s, 1H).
LCMS (ESI) m/z: 380 [M+H]+.
4.1.4.1.3. (E)-Ethyl 2-(3-(quinolin-2-yl)acrylamido)cyclohex-1-
enecarboxylate (36c). Compound 36c was obtained from quino-
line-2-carbaldehyde, yield 48%. 1H NMR (CDCl3) d: 1.33 (t,
J = 7.1 Hz, 3H), 1.58–1.72 (m, 4H), 2.33–2.39 (m, 2H), 3.08–3.15
(m, 2H), 4.23 (q, J = 7.1 Hz, 2H), 7.18 (d, J = 15.4 Hz, 1H), 7.54
(ddd, J = 8.1, 6.9, 1.2 Hz, 1H), 7.58 (d, J = 8.5 Hz, 1H), 7.73 (ddd,
J = 8.5, 6.9, 1.5 Hz, 1H), 7.80 (dd, J = 8.1, 1.5 Hz, 1H), 7.83 (d,
J = 15.4 Hz, 1H), 8.11 (d, J = 8.5 Hz, 1H), 8.16 (d, J = 8.5 Hz, 1H),
12.03 (s, 1H). LCMS (ESI) m/z: 351 [M+H]+.
4.1.4.2. General procedure of the synthesis of (E)-(2-acrylamido)
cyclohex-1-ene carboxylic acid esters 36i–p and 43. To a solution
of phosphonium salt 35 (1.2 equiv) and t-BuOK (1.2 equiv) in
DMSO (1 ml/mmol) was added appropriate aldehyde (1.0 equiv)
and the mixture was stirred at ambient temperature until the
starting aldehyde disappeared (ca. 2 h). The reaction mixture was
diluted with water, the organics were extracted with CHCl3, dried
(Na2SO4), concentrated, and purified by column chromatography
to give compounds 36i–p and 43 as white or slightly colored solids.
4.1.4.2.1. (E)-Ethyl 2-(3-(quinolin-4-yl)acrylamido)cyclohex-1-
enecarboxylate (36i). Compound 36h was obtained from quino-
line-4-carbaldehyde (eluent petroleum ether-ethyl acetate, 1:1),
yield 68%. 1H NMR (CDCl3) d: 1.32 (t, J = 7.1 Hz, 3H), 1.59–1.73
(m, 4H), 2.34–2.39 (m, 2H), 3.08–3.14 (m, 2H), 4.21 (q, J = 7.1 Hz,
2H), 6.71 (d, J = 15.5 Hz, 1H), 7.56 (d, J = 4.6 Hz, 1H), 7.61 (ddd,
J = 8.4, 6.9, 1.3 Hz, 1H), 7.75 (ddd, J = 8.5, 6.9, 1.3 Hz, 1H), 8.14
(dd, J = 8.5, 1.3 Hz, 1H), 8.18 (dd, J = 8.4, 1.3 Hz, 1H), 8.38 (d,
J = 15.5 Hz, 1H), 8.92 (d, J = 4.6 Hz, 1H), 12.10 (s, 1H). LCMS (ESI)
(m/z): 351 [M+H]+.
4.1.4.2.2. (E)-Ethyl 2-(3-(quinolin-8-yl)acrylamido)cyclohex-1-
enecarboxylate (36j). Compound 36j was obtained from quino-
line-8-carbaldehyde (eluent petroleum ether-ethyl acetate,
gradient from 4:1 to 3:1), yield 69%. 1H NMR (CDCl3) d: 1.32 (t,
J = 7.1 Hz, 3H), 1.58–1.71 (m, 4H), 2.33–2.38 (m, 2H), 3.10–3.15
(m, 2H), 4.21 (q, J = 7.1 Hz, 2H), 6.94 (d, J = 15.9 Hz, 1H), 7.44 (dd,
J = 8.3, 4.2 Hz, 1H), 7.54 (t, J = 7.7 Hz, 1H), 7.83 (dd, J = 8.2, 1.3 Hz,
1H), 7.98 (ddd, J = 7.3, 1.3, 0.5 Hz, 1H), 8.15 (dd, J = 8.3, 1.8 Hz,
1H), 8.83 (d, J = 15.9 Hz, 1H), 8.98 (dd, J = 4.2, 1.8 Hz, 1H), 11.95
(s, 1H). 13C NMR (CDCl3) d: 14.4, 21.9, 22.1, 24.5, 28.9, 60.4,
104.9, 121.6, 125.1, 126.4, 128.3, 128.6, 129.8, 133.7, 136.3,
138.9, 146.5, 150.3, 152.9, 164.5, 170.3. LCMS (ESI) m/z: 351.3
[M+H]+.
4.1.4.1.4.
(E)-Ethyl
2-(3-(2,3-dihydrobenzo[b][1,4]dioxin-6-
yl)acrylamido)cyclohex-1-enecarboxylate (36d). Compound 36d
was obtained from 2,3-dihydrobenzo[b][1,4]dioxine-6-carbalde-
hyde, yield 67%. 1H NMR (CDCl3) d: 1.31 (t, J = 7.1 Hz, 3H), 1.56–
1.69 (m, 4H), 2.30–2.37 (m, 2H), 3.04–3.11 (m, 2H), 4.20 (q,
J = 7.1 Hz, 2H), 4.23–4.30 (m, 4H), 6.35 (d, J = 15.5 Hz, 1H), 6.84
(d, J = 8.4 Hz, 1H), 7.02–7.07 (m, 2H), 7.52 (d, J = 15.5 Hz, 1H),
11.85 (s, 1H). LCMS (ESI) m/z: 358.2 [M+H]+.
4.1.4.2.3. (E)-Ethyl 2-(3-(quinolin-6-yl)acrylamido)cyclohex-1-
enecarboxylate (36k). Compound 36k was obtained from quino-
line-6-carbaldehyde (eluent chloroform–methanol, gradient from
100:3 to 20:1). The product was washed with ethyl acetate, yield
68%. 1H NMR (CDCl3) d: 1.33 (t, J = 7.1 Hz, 3H), 1.59–1.71 (m, 4H),
2.33–2.39 (m, 2H), 3.08–3.13 (m, 2H), 4.22 (q, J = 7.1 Hz, 2H),
6.65 (d, J = 15.5 Hz, 1H), 7.42 (dd, J = 8.3, 4.3 Hz, 1H), 7.80 (d,
J = 15.5 Hz, 1H), 7.92 (d, J = 1.9 Hz, 1H), 7.92 (dd, J = 9.3, 1.9 Hz,
1H), 8.08 (d, J = 9.3 Hz, 1H), 8.17 (dd, J = 8.3, 1.6 Hz, 1H), 8.91 (dd,
J = 4.3, 1.6 Hz, 1H), 12.00 (s, 1H). LCMS (ESI) m/z: 351.2 [M+H]+.
4.1.4.2.4. (E)-Ethyl 2-(3-(2-methylquinolin-6-yl)acrylamido)cyclo-
hex-1-enecarboxylate (36l). Compound 36l was obtained from 2-
methylquinoline-6-carbaldehyde (eluent petroleum ether-ethyl
acetate, 1:1), yield 69%. 1H NMR (CDCl3) d: 1.32 (t, J = 7.1 Hz, 3H),
1.59–1.72 (m, 4H), 2.33–2.39 (m, 2H), 2.74 (s, 3H), 3.08–3.13 (m,
2H), 4.22 (q, J = 7.1 Hz, 2H), 6.62 (d, J = 15.5 Hz, 1H), 7.31 (d,
J = 8.4 Hz, 1H), 7.79 (d, J = 15.5 Hz, 1H), 7.88 (s, 1H), 7.89 (dd,
J = 9.0, 2.0 Hz, 1H), 7.99 (d, J = 9.0 Hz, 1H), 8.05 (d, J = 8.4 Hz, 1H),
11.99 (s, 1H). 13C NMR (CDCl3) d: 14.4, 21.8, 22.0, 24.5, 25.6,
28.8, 60.5, 105.3, 122.8, 123.1, 126.6, 127.8, 128.8, 129.5, 132.2,
136.6, 141.7, 148.8, 152.7, 160.2, 164.0, 170.4. LCMS (ESI) m/z:
365.3 [M+H]+.
4.1.4.2.5. (E)-Ethyl 2-(3-(5,6,7-trimethoxyquinolin-2-yl)acrylami-
do)cyclohex-1-enecarboxylate (36m). Compound 36m was
obtained from 5,6,7-trimethoxyquinoline-2-carbaldehyde and
purified by chromatography on a Biotage purification system
(SNAP column, eluent EtOAc–petroleum ether, gradient 5–60%),
yield 33%. 1H NMR (CDCl3) d: 1.32 (t, J = 7.1 Hz, 3H), 1.58–1.71
(m, 4H), 2.33–2.39 (m, 2H), 3.09–3.14 (m, 2H), 3.99 (s, 3H), 4.03
(s, 3H), 4.05 (s, 3H), 4.22 (q, J = 7.1 Hz, 2H), 7.15 (d, J = 15.5 Hz,
1H), 7.26 (s, 1H), 7.44 (d, J = 8.5 Hz, 1H), 7.78 (d, J = 15.5 Hz, 1H),
4.1.4.1.5. (E)-Ethyl 2-(3-(2-chloro-3,4-dimethoxyphenyl)acrylami-
do)cyclohex-1-enecarboxylate (36e). Compound 36e was obtained
from 2-chloro-3,4-dimethoxybenzaldehyde, yield 56%. 1H NMR
(CDCl3) d: 1.31 (t, J = 7.1 Hz, 3H), 1.57–1.70 (m, 4H), 2.30–2.39
(m, 2H), 3.06–3.12 (m, 2H), 3.86 (s, 3H), 3.90 (s, 3H), 4.20 (q,
J = 7.1 Hz, 2H), 6.40 (d, J = 15.6 Hz, 1H), 6.83 (d, J = 8.7 Hz, 1H),
7.40 (d, J = 8.7 Hz, 1H), 8.01 (d, J = 15.6 Hz, 1H), 11.91 (s, 1H). LCMS
(ESI) m/z: 394.3 [M+H]+.
4.1.4.1.6. (E)-Ethyl 2-(3-(6-chlorobenzo[d][1,3]dioxol-5-yl)acry
lamido)cyclohex-1-enecarboxylate (36f). Compound 36f was
obtained from 6-chlorobenzo[d][1,3]dioxole-5-carbaldehyde, yield
77%. 1H NMR (CDCl3) d: 1.31 (t, J = 7.1 Hz, 3H), 1.56–1.70 (m, 4H),
2.31–2.37 (m, 2H), 3.05–3.12 (m, 2H), 4.20 (q, J = 7.1 Hz, 2H),
6.01 (s, 2H), 6.33 (d, J = 15.5 Hz, 1H), 6.86 (s, 1H), 7.08 (s, 1H),
7.99 (d, J = 15.5 Hz, 1H), 11.92 (s, 1H). LCMS (ESI) m/z: 378.3
[M+H]+.
4.1.4.1.7. (E)-Ethyl 2-(3-(6-bromobenzo[d][1,3]dioxol-5-yl)acry-
lamido)cyclohex-1-enecarboxylate (36g). Compound 36g was
obtained from 6-bromobenzo[d][1,3]dioxole-5-carbaldehyde, yield
66%. 1H NMR (CDCl3) d: 1.31 (t, J = 7.1 Hz, 3H), 1.56–1.70 (m, 4H),
2.30–2.38 (m, 2H), 3.05–3.12 (m, 2H), 4.20 (q, J = 7.1 Hz, 2H),
6.01 (s, 2H), 6.30 (d, J = 15.5 Hz, 1H), 7.04 (s, 1H), 7.09 (s, 1H),
7.96 (d, J = 15.5 Hz, 1H), 11.93 (s, 1H). LCMS (ESI) m/z: 422.2
[M+H]+.
4.1.4.1.8. (E)-Ethyl 2-(3-(3-bromo-4,5-dimethoxyphenyl)acrylam-
ido)cyclohex-1-enecarboxylate
(36h). Compound
36h
was
obtained from 3-bromo-4,5-dimethoxybenzaldehyde, yield 73%.
1H NMR (CDCl3) d: 1.32 (t, J = 7.1 Hz, 3H), 1.57–1.71 (m, 4H),
2.31–2.39 (m, 2H), 3.06–3.12 (m, 2H), 3.89 (s, 3H), 3.93 (s, 3H),
4.20 (q, J = 7.1 Hz, 2H), 6.34 (d, J = 15.5 Hz, 1H), 7.05 (s, 1H), 7.08

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3663
8.34 (d, J = 8.5 Hz, 1H), 12.01 (s, 1H). 13C NMR (CDCl3) d: 14.4, 21.8,
22.0, 24.5, 28.8, 56.3, 60.5, 61.4, 61.7, 104.5, 105.5, 119.2, 119.5,
127.1, 131.0, 141.5, 141.8, 146.2, 146.9, 152.5, 152.8, 156.5,
163.8, 170.2. LCMS (ESI) m/z: 441.4 [M+H]+.
water (25 ml), and at ice-bath temperature the pH of the medium
was decreased to 2–3 by adding 6 N HCl. The precipitate was
filtered and the solid material was purified by column chromatog-
raphy on silica gel with chloroform-methanol (gradient up to
85:15) as eluent to give compounds 3, 8–10, 21, and 23–26 as
white or slightly yellowish crystalline substances.
4.1.4.2.6. (E)-Ethyl 2-(3-(2-chloroquinolin-3-yl)acrylamido)cyclo-
hex-1-enecarboxylate (36n). Compound 36n was obtained from
2-chloroquinoline-3-carbaldehyde (eluent EtOAc–petroleum ether,
gradient 1:3 to 1:2), yield 76%. 1H NMR (CDCl3) d: 1.33 (t, J = 7.1 Hz,
3H), 1.59–1.72 (m, 4H), 2.33–2.39 (m, 2H), 3.08–3.14 (m, 2H), 4.22
(q, J = 7.1 Hz, 2H), 6.64 (d, J = 15.6 Hz, 1H), 7.59 (t, J = 7.6 Hz, 1H),
7.75 (ddd, J = 8.3, 7.1, 1.2 Hz, 1H), 7.85 (d, J = 8.1 Hz, 1H), 8.01 (d,
J = 8.3 Hz, 1H), 8.10 (d, J = 15.6 Hz, 1H), 8.40 (s, 1H), 12.06 (s, 1H).
Compound contains ca. 13% of the corresponding Z-isomer—1H
NMR (CDCl3) d: 1.23 (t, J = 7.1 Hz, 3H), 1.59–1.72 (m, 4H), 2.22–
2.27 (m, 2H), 2.90–2.98 (m, 2H), 4.08 (q, J = 7.1 Hz, 2H), 6.27 (d,
J = 12.2 Hz, 1H), 7.10 (d, J = 12.2 Hz, 1H), 7.53 (t, J = 7.5 Hz, 1H),
7.70 (t, J = 7.7 Hz, 1H), 7.81 (d, J = 8.3 Hz, 1H), 7.98 (d, J = 8.5 Hz,
1H), 8.44 (s, 1H), 11.80 (s, 1H). LCMS (ESI) m/z: 385.2 [M+H]+.
4.1.4.2.7. (E)-Ethyl 2-(3-(2-chloro-6-methoxyquinolin-3-yl)acry-
lamido)cyclohex-1-enecarboxylate (36o). Compound 36o was
4.1.5.1.1.
(E)-2-(3-(Naphthalen-2-yl)acrylamido)cyclohex-1-
enecarboxylic acid (3). Compound 3 was obtained from ester
36a, yield 78%. Mp 153–156 °C. HPLC purity 95.0%. 1H NMR
(DMSO-d6) d: 1.51–1.69 (m, 4H), 2.25–2.31 (m, 2H), 2.92–2.98
(m, 2H), 6.86 (d, J = 15.7 Hz, 1H), 7.54–7.59 (m, 2H), 7.68 (d,
J = 15.7 Hz, 1H), 7.89 (dd, J = 8.6, 1.5 Hz, 1H), 7.91–7.98 (m, 3H),
8.18 (s, 1H), 11.85 (s, 1H), 12.58 (br s, 1H). 13C NMR (DMSO-d6)
d: 21.4, 21.5, 24.5, 28.2, 105.8, 122.8, 124.1, 126.7, 127.1, 127.6,
128.4, 128.4, 129.4, 131.9, 132.9, 133.6, 141.4, 150.6, 163.2,
171.1. HRMS m/z calcd for C20H19NO3Na [M+Na]+, 344.1263, found,
344.1280.
4.1.5.1.2. (E)-2-(3-(6-Methoxynaphthalen-2-yl)acrylamido)cyclo-
hex-1-enecarboxylic acid (8). Compound 8 was obtained from
ester 36b, yield 35%. Mp 174 °C. HPLC purity 95.0%. 1H NMR
(DMSO-d6) d: 1.51–1.65 (m, 4H), 2.24–2.33 (m, 2H), 2.91–2.97
(m, 2H), 3.89 (s, 3H), 6.77 (d, J = 15.6 Hz, 1H), 7.20 (dd, J = 8.9,
2.5 Hz, 1H), 7.36 (d, J = 2.5 Hz, 1H), 7.64 (d, J = 15.6 Hz, 1H), 7.83
(m, 2H), 7.87 (d, J = 9.0 Hz, 1H), 8.10 (s, 1H), 11.93 (br s, 1H),
12.59 (br s, 1H). HRMS m/z calcd for C21H21NO4Na [M+Na]+,
374.1368, found, 374.1342.
4.1.5.1.3. (E)-2-(3-(Quinolin-4-yl)acrylamido)cyclohex-1-enecarb-
oxylic acid (9). Compound 9 was obtained from ester 36i (the pH
of the medium upon the isolation procedure was decreased to 4
with AcOH) and purified by column chromatography (eluent chlo-
roform–methanol, 9:1), yield 20%. Mp 176.7–179.6 °C. HPLC purity
99.0%. 1H NMR (CDCl3) d: 1.52–1.67 (m, 4H), 2.27–2.33 (m, 2H),
2.92–2.97 (m, 2H), 7.01 (d, J = 15.6 Hz, 1H), 7.70 (ddd, J = 8.4, 6.9,
1.2 Hz, 1H), 7.83 (ddd, J = 8.4, 6.9, 1.2 Hz, 1H), 7.90 (d, J = 4.5 Hz,
1H), 8.09 (d, J = 8.4 Hz, 1H), 8.26 (d, J = 15.6 Hz, 1H), 8.26 (d,
J = 8.4 Hz, 1H), 8.94 (d, J = 4.5 Hz, 1H), 11.95 (s, 1H), 12.70 (br s,
1H). HRMS m/z calcd for C19H19N2O3 [M+H]+, 323.1396, found,
323.1389.
obtained
from
2-chloro-6-methoxyquinoline-3-carbaldehyde
(eluent chloroform-methanol, gradient from 100:1 to 20:1), yield
82%. 1H NMR (CDCl3) d: 1.32 (t, J = 7.1 Hz, 3H), 1.59–1.72 (m, 4H),
2.34–2.39 (m, 2H), 3.08–3.13 (m, 2H), 3.94 (s, 3H), 4.22 (q,
J = 7.1 Hz, 2H), 6.62 (d, J = 15.6 Hz, 1H), 7.09 (d, J = 2.8 Hz, 1H),
7.39 (dd, J = 9.3, 2.8 Hz, 1H), 7.89 (d, J = 9.3 Hz, 1H), 8.08 (d,
J = 15.6 Hz, 1H), 8.30 (s, 1H), 12.06 (s, 1H). Compound contains
ca. 12% of the corresponding Z-isomer—1H NMR (CDCl3) d: 1.24
(t, J = 7.1 Hz, 3H), 1.59–1.72 (m, 4H), 2.23–2.28 (m, 2H), 2.91–
2.97 (m, 2H), 3.91 (s, 3H), 4.09 (q, J = 7.1 Hz, 2H), 6.25 (d,
J = 12.2 Hz, 1H), 7.07 (d, J = 1.8 Hz, 1H), 7.08 (d, J = 12.2 Hz, 1H),
7.34 (dd, J = 9.2, 2.8 Hz, 1H), 7.86 (d, J = 9.2 Hz, 1H), 8.37 (s, 1H),
11.79 (s, 1H). 13C NMR (CDCl3) d: 14.4, 21.8, 22.0, 24.5, 28.7,
55.8, 60.6, 105.3, 105.8, 124.3, 126.6, 127.9, 128.3, 129.9, 134.7,
137.4, 144.0, 147.8, 152.6, 158.6, 163.0, 170.4. LCMS (ESI) m/z:
415.2 [M+H]+.
4.1.4.2.8. (E)-Ethyl 2-(3-(3,4-dimethoxyphenyl)acrylamido)cyclo-
hex-1-enecarboxylate (36p). Compound 36p was obtained from
3,4-dimethoxybenzaldehyde (eluent chloroform–methanol, 20:1),
yield 73%. 1H NMR (CDCl3) d: 1.32 (t, J = 7.1 Hz, 3H), 1.57–1.70
(m, 4H), 2.32–2.38 (m, 2H), 3.06–3.11 (m, 2H), 3.91 (s, 3H), 3.93
(s, 3H), 4.21 (q, J = 7.1 Hz, 2H), 6.37 (d, J = 15.5 Hz, 1H), 6.85 (d,
J = 8.3 Hz, 1H), 7.06 (d, J = 1.9 Hz, 1H), 7.11 (dd, J = 8.3, 1.9 Hz,
1H), 7.59 (d, J = 15.5 Hz, 1H), 11.83 (s, 1H). LCMS (ESI) m/z: 360.3
[M+H]+.
4.1.4.2.9. Ethyl 2-((2E,4Z)-4-bromo-5-phenylpenta-2,4-dienami-
do)cyclohex-1-enecarboxylate (43). Compound 43 was obtained
from alpha-bromocinnamaldehyde (42) (eluent petroleum ether–
ethyl acetate, 2:1), yield 80%. 1H NMR (CDCl3) d: 1.31 (t,
J = 7.1 Hz, 3H), 1.57–1.70 (m, 4H), 2.32–2.37 (m, 2H), 3.03–3.08
(m, 2H), 4.20 (q, J = 7.1 Hz, 2H), 6.43 (d, J = 14.2 Hz, 1H), 7.26 (s,
1H), 7.33–7.42 (m, 3H), 7.44 (d, J = 14.2 Hz, 1H), 7.74–7.78 (m,
2H), 11.86 (s, 1H). 13C NMR (CDCl3) d: 14.4, 21.8, 22.0, 24.5, 28.7,
60.5, 105.6, 120.6, 127.1, 128.4, 129.4, 130.1, 134.9, 138.6, 142.9,
152.3, 163.5, 170.1. LCMS (ESI) m/z: 404.1 [M+H]+.
4.1.5.1.4. (E)-2-(3-(Quinolin-2-yl)acrylamido)cyclohex-1-enecarb-
oxylic acid (10). Compound 10 was obtained from ester 36c, yield
27%. Mp 184 °C (dec.). HPLC purity 98.5%. 1H NMR (DMSO-d6) d:
1.52–1.66 (m, 4H), 2.26–2.33 (m, 2H), 2.90–2.96 (m, 2H), 7.19 (d,
J = 15.7 Hz, 1H), 7.64 (ddd, J = 8.1, 6.9, 1.2 Hz, 1H), 7.68 (d,
J = 15.7 Hz, 1H), 7.81 (ddd, J = 8.4, 6.9, 1.5 Hz, 1H), 7.94 (d,
J = 8.6 Hz, 1H), 8.00 (d, J = 8.1 Hz, 1H), 8.06 (d, J = 8.4 Hz, 1H),
8.43 (d, J = 8.6 Hz, 1H), 12.05 (s, 1H). HRMS m/z calcd for
C
19H19N2O3 [M+H]+, 323.1396, found, 323.1419.
4.1.5.1.5. (E)-2-(3-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)acrylami-
do)cyclohex-1-enecarboxylic acid (21). Compound 21 was
obtained from ester 36d, yield 64%. Mp 168 °C. HPLC purity
99.0%. 1H NMR (DMSO-d6) d: 1.50–1.63 (m, 4H), 2.22–2.30 (m,
2H), 2.87–2.94 (m, 2H), 4.23–4.30 (m, 4H), 6.56 (d, J = 15.6 Hz,
1H), 6.88 (d, J = 8.4 Hz, 1H), 7.17 (dd, J = 8.4, 1.9 Hz, 1H), 7.24 (d,
J = 1.9 Hz, 1H), 7.40 (d, J = 15.6 Hz, 1H), 11.73 (s, 1H), 12.55 (br s,
1H). 13C NMR (DMSO-d6) d: 21.4, 2 1.5, 24.5, 28.2, 63.9, 64.3,
105.4, 116.6, 117.4, 120.5, 121.9, 127.8, 141.2, 143.5, 145.2,
150.7, 163.4, 171.1. LCMS (ESI) m/z: 330.2 [M+H]+.
4.1.5.1.6. (E)-2-(3-(2-Chloro-3,4-dimethoxyphenyl)acrylamido)cyc
lohex-1-enecarboxylic acid (23). Compound 23 was obtained from
ester 36e, yield 61%. Mp 168 °C. HPLC purity 99.0%. 1H NMR
(DMSO-d6) d: 1.51–1.64 (m, 4H), 2.23–2.31 (m, 2H), 2.88–2.95
(m, 2H), 3.76 (s, 3H), 3.89 (s, 3H), 6.67 (d, J = 15.6 Hz, 1H), 7.12
(d, J = 8.9 Hz, 1H), 7.73 (d, J = 8.9 Hz, 1H), 7.77 (d, J = 15.6 Hz, 1H),
11.84 (s, 1H), 12.61 (br s, 1H). 13C NMR (DMSO-d6) d: 21.3, 21.5,
24.5, 28.2, 56.2, 60.1, 105.9, 111.8, 123.3, 123.5, 125.1, 128.2,
4.1.5. The hydrolysis of amidocyclohex-1-ene carboxylic acid
esters 36a–p and 43 to the corresponding acids 3, 8–13, 15–19,
and 21–26
4.1.5.1. General procedure of the synthesis of amidocyclohex-1-
ene carboxylic acids 3, 8–10, 21, and 23–26. To a suspension of
substituted acrylamidocyclohex-1-ene carboxylic acid ethyl ester
(36a–i) (0.5 mmol) in isopropanol (15 ml) 5 N NaOH solution
(0.4 ml, 2.0 mmol) was added and the resulting mixture was stir-
red at 62–65 °C until the starting material disappeared (ca.
40 min). The solvent was evaporated, the residue was mixed with

3664
O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
136.3, 144.9, 150.5, 154.7, 163.0, 171.1. LCMS (ESI) m/z: 364.2
[MꢀH]ꢀ.
d: 1.52–1.65 (m, 4H), 2.25–2.31 (m, 2H), 2.91 (s, 3H), 2.91–2.96
(m, 2H), 6.98 (d, J = 15.6 Hz, 1H), 7.72 (d, J = 15.6 Hz, 1H), 7.87 (d,
J = 8.2 Hz, 1H), 8.24 (d, J = 8.7 Hz, 1H), 8.40 (d, J = 8.7 Hz, 1H),
8.51 (s, 1H), 8.84 (d, J = 8.2 Hz, 1H), 11.88 (s, 1H), 12.62 br s, 1H).
LCMS (ESI) m/z: 337 [M+H]+.
4.1.5.1.7. (E)-2-(3-(6-Chlorobenzo[d][1,3]dioxol-5-yl)acrylamido)
cyclohex-1-enecarboxylic acid (24). Compound 24 was obtained
from ester 36f, yield 24%. Mp 187 °C. HPLC purity 98.9%. 1H NMR
(DMSO-d6) d: 1.50–1.63 (m, 4H), 2.23–2.31 (m, 2H), 2.87–2.96
(m, 2H), 6.13 (s, 2H), 6.72 (d, J = 15.5 Hz, 1H), 7.17 (s, 1H), 7.61
(s, 1H), 7.75 (d, J = 15.5 Hz, 1H), 11.84 (s, 1H), 12.59 (br s, 1H).
LCMS (ESI) m/z: 348.3 [MꢀH]ꢀ.
4.1.5.2.4.
(E)-2-(3-(5,6,7-Trimethoxyquinolin-2-yl)acrylamido)
cyclohex-1-enecarboxylic acid (15). Compound 15 was obtained
from ester 36m and purified by column chromatography (eluent
chloroform–methanol, 20:1) followed by washing with methanol,
yield 38%. Mp 146–148 °C. HPLC purity 98.4%. 1H NMR (DMSO-
d6) d: 1.52–1.66 (m, 4H), 2.25–2.32 (m, 2H), 2.90–2.97 (m, 2H),
3.89 (s, 3H), 3.98 (s, 6H), 7.14 (d, J = 15.5 Hz, 1H), 7.31 (s, 1H),
7.64 (d, J = 15.5 Hz, 1H), 7.76 (d, J = 8.6 Hz, 1H), 8.35 (d, J = 8.6 Hz,
1H), 11.96 (s, 1H), 12.66 (br s, 1H). LCMS (ESI) m/z: 413.3 [M+H]+.
4.1.5.2.5. (E)-2-(3-(2-Methoxyquinolin-3-yl)acrylamido)cyclohex-
1-enecarboxylic acid (16). Compound 16 was obtained from ester
36n and purified by column chromatography (eluent chloroform–
methanol, 20:1), yield 26%. Mp 193–194 °C. HPLC purity 98.1%. 1H
NMR (DMSO-d6) d: 1.52–1.64 (m, 4H), 2.25–2.31 (m, 2H), 2.91–
2.96 (m, 2H), 4.08 (s, 3H), 6.94 (d, J = 15.7 Hz, 1H), 7.47 (ddd,
J = 8.0, 6.9, 1.1 Hz, 1H), 7.71 (ddd, J = 8.2, 6.9, 1.3 Hz, 1H), 7.76 (d,
J = 15.7 Hz, 1H), 7.78 (d, J = 8.2 Hz, 1H), 7.92 (d, J = 8.0 Hz, 1H),
8.74 (s, 1H), 11.92 (s, 1H), 12.63 (br s, 1H). LCMS (ESI) m/z: 353
[M+H]+.
4.1.5.2.6. (E)-2-(3-(2-Chloroquinolin-3-yl)acrylamido)cyclohex-1-
enecarboxylic acid (17). Compound 17 was prepared from ester
36n (instead of tetrahydrofuran–methanol, 1:1 mixture pure tetra-
hydrofuran was used) and purified by column chromatography
(eluent chloroform–methanol, 20:1), yield 60%. Mp 179–181 °C.
HPLC purity 98.8%. 1H NMR (DMSO-d6) d: 1.52–1.65 (m, 4H), 2.26–
2.32 (m, 2H), 2.91–2.97 (m, 2H), 6.99 (d, J = 15.4 Hz, 1H), 7.71 (t,
J = 7.6 Hz, 1H), 7.84–7.90 (m, 2H), 7.97 (d, J = 8.4 Hz, 1H), 8.08 (d,
J = 8.1 Hz, 1H), 9.07 (s, 1H), 12.03 (s, 1H), 12.68 (br s, 1H). 13C NMR
(DMSO-d6) d: 21.3, 21.5, 24.5, 28.2, 106.4, 126.7, 126.9, 127.1,
127.6, 127.8, 128.6, 131.8, 135.4, 137.2, 147.0, 149.2, 150.3, 162.3,
171.2. LCMS (ESI) m/z: 357.2 [M+H]+.
4.1.5.2.7. (E)-2-(3-(2-Chloro-6-methoxyquinolin-3-yl)acrylamido)
cyclohex-1-enecarboxylic acid (18). Compound 18 was obtained
from ester 36o and purified by column chromatography (eluent
chloroform–methanol, 20:1) followed by washing with ethyl ace-
tate, yield 22%. Mp 158–160 °C. HPLC purity 95.6%. 1H NMR
(DMSO-d6) d: 1.52–1.65 (m, 4H), 2.26–2.31 (m, 2H), 2.91–2.97
(m, 2H), 3.91 (s, 3H), 6.93 (d, J = 15.6 Hz, 1H), 7.37 (d, J = 2.7 Hz,
1H), 7.50 (dd, J = 9.0, 2.7 Hz, 1H), 7.84 (d, J = 15.6 Hz, 1H), 7.87 (d,
J = 9.0 Hz, 1H), 8.22 (s, 1H), 12.04 (s, 1H), 12.68 (br s, 1H). LCMS
(ESI) m/z: 387 [M+H]+.
4.1.5.2.8. (E)-2-(5-Phenylpent-2-en-4-ynamido)cyclohex-1-ene-
carboxylic acid (19). Compound 19 was obtained from ester 43
and purified by column chromatography (eluent chloroform–
methanol, 20:1) followed by washing with ethyl acetate, yield
29%. Mp 157–158 °C. HPLC purity 97.2%. IR: 3079, 3018, 2929,
2617, 2197, 1649, 1609, 1488, 1234, 952, 756, 688 cmꢀ11H NMR
(CDCl3) d: 1.60–1.72 (m, 4H), 2.37–2.43 (m, 2H), 3.05–3.11 (m,
2H), 6.40 (d, J = 15.4 Hz, 1H), 6.97 (d, J = 15.4 Hz, 1H), 7.31–7.38
(m, 3H), 7.46–7.50 (m, 2H), 10.79 (br s, 1H), 11.58 (s, 1H). LCMS
(ESI) m/z: 294 [MꢀH]ꢀ.
4.1.5.1.8. (E)-2-(3-(6-Bromobenzo[d][1,3]dioxol-5-yl)acrylamido)
cyclohex-1-enecarboxylic acid (25). Compound 25 was obtained
from ester 36g, yield 43%. Mp 185 °C. HPLC purity 98.2%. 1H NMR
(DMSO-d6) d: 1.49–1.64 (m, 4H), 2.23–2.30 (m, 2H), 2.87–2.95
(m, 2H), 6.13 (s, 2H), 6.69 (d, J = 15.5 Hz, 1H), 7.30 (s, 1H), 7.60
(s, 1H), 7.72 (d, J = 15.5 Hz, 1H), 11.88 (s, 1H), 12.60 (br s, 1H).
13C NMR (DMSO-d6) d: 21.3, 21.5, 24.5, 28.2, 102.5, 105.9, 106.9,
112.6, 117.0, 123.7, 127.0, 138.9, 147.9, 149.8, 150.5, 163.0,
171.1. LCMS (ESI) m/z: 392.2 [MꢀH]ꢀ.
4.1.5.1.9.
(E)-2-(3-(3-Bromo-4,5-dimethoxyphenyl)acrylamido)
cyclohex-1-enecarboxylic acid (26). Compound 26 was obtained
from ester 36h, yield 43%. Mp 188 °C. HPLC purity 98.4%. 1H
NMR (DMSO-d6) d: 1.51–1.64 (m, 4H), 2.24–2.31 (m, 2H), 2.88–
2.96 (m, 2H), 3.82 (s, 3H), 3.85 (s, 3H), 6.77 (d, J = 15.5 Hz, 1H),
7.22 (s, 1H), 7.45 (s, 1H), 7.73 (d, J = 15.5 Hz, 1H), 11.81 (s, 1H),
12.57 (br s, 1H). 13C NMR (DMSO-d6) d: 21.4, 21.5, 24.5, 28.3,
56.0, 56.0, 105.8, 110.2, 115.5, 116.3, 123.2, 125.6, 139.1, 148.6,
150.6, 151.1, 163.2, 171.0. LCMS (ESI) m/z: 408.3 [MꢀH]ꢀ.
4.1.5.2. General procedure of the synthesis of amidocyclohex-1-
ene carboxylic acids 11–13, 15–19, and 22. To a solution of appro-
priate acrylamidocyclohex-1-ene carboxylate 36j–p, and 43
(1.0 mmol) in THF/MeOH mixture 1:1 (10 ml) 10 N NaOH solution
(0.5 ml, 5.0 mmol) was added. The reaction mixture was stirred at
50 °C until the starting ester disappeared (3–12 h). The reaction
mixture was concentrated; the residue was dissolved in H2O, and
acidified to pH 2 with 6 N HCl. The precipitate was filtered off or
extracted with CHCl3, dried and purified by column chromatogra-
phy to yield compounds 11–13, 15–19, and 22 as white or slightly
yellowish crystalline substances.
4.1.5.2.1. (E)-2-(3-(Quinolin-8-yl)acrylamido)cyclohex-1-enecarb-
oxylic acid (11). Compound 11 was obtained from ester 36j in a
sufficiently pure state to avoid further chromatographical purifica-
tion procedure, yield 75%. Mp 145–146 °C. HPLC purity 94.6%. 1H
NMR (DMSO-d6) d: 1.53–1.66 (m, 4H), 2.26–2.31 (m, 2H), 2.94–
2.99 (m, 2H), 7.02 (d, J = 16.0 Hz, 1H), 7.62 (dd, J = 8.3, 4.2 Hz,
1H), 7.67 (t, J = 7.8 Hz, 1H), 8.07 (dd, J = 8.2, 1.1 Hz, 1H), 8.28 (dd,
J = 7.3, 1.1 Hz, 1H), 8.43 (dd, J = 8.3, 1.8 Hz, 1H), 8.77 (d,
J = 16.0 Hz, 1H), 9.00 (dd, J = 4.2, 1.8 Hz, 1H), 11.94 (s, 1H), 12.61
(br s, 1H). 13C NMR (DMSO-d6) d: 21.4, 21.5, 24.5, 28.3, 105.7,
121.9, 124.1, 126.5, 127.9, 128.2, 130.3, 132.0, 136.7, 137.3,
145.3, 150.5, 150.8, 163.4, 171.2. LCMS (ESI) m/z: 323 [M+H]+.
4.1.5.2.2. (E)-2-(3-(Quinolin-6-yl)acrylamido)cyclohex-1-enecarb-
oxylic acid (12). Compound 12 was obtained from ester 36k and
purified by column chromatography (eluent chloroform–methanol,
gradient from 20:1 to 10:1), yield 28%. Mp 179–182 °C. 1H NMR
(DMSO-d6) d: 1.51–1.65 (m, 4H), 2.26–2.31 (m, 2H), 2.91–2.97
(m, 2H), 6.91 (d, J = 15.7 Hz, 1H), 7.57 (dd, J = 8.3, 4.2 Hz, 1H),
7.70 (d, J = 15.7 Hz, 1H), 8.02 (d, J = 8.8 Hz, 1H), 8.15 (dd, J = 8.8,
1.8 Hz, 1H), 8.23 (d, J = 1.5 Hz, 1H), 8.38 (d, J = 8.3 Hz, 1H), 8.92
(dd, J = 4.2, 1.6 Hz, 1H), 11.92 (s, 1H), 12.62 (br s, 1H). LCMS (ESI)
m/z: 323 [M+H]+.
4.1.5.2.9. (E)-2-(3-(3,4-Dimethoxyphenyl)acrylamido)cyclohex-1-
enecarboxylic acid (22). Compound 22 was obtained from ester
36p and purified by column chromatography (eluent chloroform–
methanol, gradient from 50:1 to 20:1), yield 47%. Mp 146–
148 °C. HPLC purity 98.7%. 1H NMR (DMSO-d6) d: 1.50–1.63 (m,
4H), 2.23–2.30 (m, 2H), 2.88–2.95 (m, 2H), 3.79 (s, 3H), 3.81 (s,
3H), 6.63 (d, J = 15.5 Hz, 1H), 6.98 (d, J = 8.3 Hz, 1H), 7.20 (dd,
J = 8.3, 1.7 Hz, 1H), 7.33 (d, J = 1.7 Hz, 1H), 7.45 (d, J = 15.5 Hz,
1H), 11.74 (s, 1H), 12.52 (br s, 1H). 13C NMR (DMSO-d6) d: 21.4,
4.1.5.2.3. (E)-2-(3-(2-Methylquinolin-6-yl)acrylamido)cyclohex-1-
enecarboxylic acid (13). Compound 13 was obtained from ester
36l and purified by column chromatography (eluent chloroform–
methanol, 20:1), yield 46%. Mp 231–233 °C. 1H NMR (DMSO-d6)

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3665
21.5, 24.5, 28.3, 55.5, 55.6, 105.2, 110.4, 111.5, 119.9, 122.7, 127.2,
4.1.7. Synthesis of (E)-2-(3-(8-hydroxyquinolin-2-yl) acrylami
141.8, 148.9, 150.7, 150.9, 163.6, 171.1. LCMS (ESI) m/z: 332.2
do)cyclohex-1-enecarboxylic acid (14)
[M+H]+.
4.1.7.1. 8-((tert-Butyldimethylsilyl)oxy)quinoline-2-carbaldehy
de (39b)32. Known32 compound 39b was prepared from 8-
hydroxyquinoline-2-carbaldehyde (38b) by the same protocol as
compound 39a as an oil, yield 80%. 1H NMR (CDCl3) d: 0.29 (s,
6H), 1.10 (s, 9H), 7.25 (dd, J = 7.6, 1.4 Hz, 1H), 7.48 (dd, J = 8.2,
1.4 Hz, 1H), 7.56 (dd, J = 8.2, 7.6 Hz, 1H), 7.99 (d, J = 8.5 Hz, 1H),
8.25 (dd, J = 8.5, 0.9 Hz, 1H), 10.23 (d, J = 0.9 Hz, 1H). 13C NMR
(CDCl3) d: ꢀ4.0, 18.8, 25.8, 117.3, 119.0, 120.5, 130.0, 131.5,
137.2, 141.9, 151.4, 153.7, 193.6. LCMS (ESI) m/z: 288.2 [M+H]+.
4.1.6. Synthesis of (E)-2-(3-(6-hydroxynaphthalen-2-yl)acrylam
ido)cyclohex-1-enecarboxylic acid (4)
4.1.6.1. 6-((tert-Butyldimethylsilyl)oxy)-2-naphthaldehyde (39a)31. To
a solution of tert-butyldimethylsilyl chloride (0.63 g, 4.18 mmol)
in DMF (4 ml) were added 6-hydroxy-2-naphthlaldehyde (38a)
(0.60 g, 3.48 mmol) and imidazole (0.47 g, 6.91 mmol). The resulting
mixture was stirred at ambient temperature for 1 h. The reaction
mixture was diluted with diethyl ether (20 ml), washed with water
(3 ꢂ 15 ml), and dried (Na2SO4). The solvent was evaporated and the
residue (1.1 g) was purified by column chromatography (eluent
EtOAc–petroleum ether, 1:6) to afford 0.99 g (99%) of known31 com-
pound 39a as an oil. 1H NMR (CDCl3) d: 0.27 (s, 6H), 1.02 (s, 9H), 7.16
(dd, J = 8.8, 2.4 Hz, 1H), 7.22 (d, J = 2.4 Hz, 1H), 7.75 (d, J = 8.6 Hz, 1H),
7.88 (d, J = 8.8 Hz, 1H), 7.89 (dd, J = 8.6, 1.5 Hz, 1H), 8.25 (s, 1H),
4.1.7.2. (E)-Ethyl 2-(3-(8-((tert-butyldimethylsilyl)oxy)quinolin-
2-yl)acrylamido)cyclohex-1-enecarboxylate
(40b). Compound
40b was obtained from phosphonium salt 35 and carbaldehyde
39b by general procedure Section 4.1.4.1 and purified by column
chromatography (eluent dichloromethane), yellowish crystals,
yield 85%. 1H NMR (CDCl3) d: 0.30 (s, 6H), 1.11 (s, 9H), 1.31 (t,
J = 7.1 Hz, 3H), 1.58–1.72 (m, 4H), 2.32–2.39 (m, 2H), 3.08–3.14
(m, 2H), 4.21 (q, J = 7.1 Hz, 2H), 7.11 (d, J = 15.6 Hz, 1H), 7.14–
7.19 (m, 1H), 7.36–7.43 (m, 2H), 7.59 (d, J = 8.5 Hz, 1H), 7.83 (d,
J = 15.6 Hz, 1H), 8.10 (d, J = 8.5 Hz, 1H), 12.14 (s, 1H). 13C NMR
(CDCl3) d: ꢀ4.1, 14.3, 18.8, 21.7, 21.9, 24.3, 25.9, 28.6, 60.3,
105.5, 118.6, 120.2, 120.6, 127.3, 127.7, 129.5, 136.5, 141.8,
142.1, 152.0, 152.2, 153.0, 163.8, 170.0. LCMS (ESI) m/z: 481.3
[M+H]+.
t
10.08 (s, 1H). GCMS m/z: 201.1 [MꢀC4H8ꢀCO]+, 229.1 [Mꢀ Bu]+,
286.1 M+.
4.1.6.2. (E)-Ethyl 2-(3-(6-((tert-butyldimethylsilyl)oxy)naphtha-
len-2-yl)acrylamido)cyclohex-1-enecarboxylate (40a). Compound
40a was obtained from phosphonium salt 35 and aldehyde 39a by
general procedure Section 4.1.4.1 and purified by column chroma-
tography (eluent dichloromethane), white solid, yield 79%. 1H
NMR (CDCl3) d: 0.25 (s, 6H), 1.01 (s, 9H), 1.32 (t, J = 7.1 Hz, 3H),
1.57–1.72 (m, 4H), 2.32–2.38 (m, 2H), 3.08–3.14 (m, 2H), 4.22 (q,
J = 7.1 Hz, 2H), 6.57 (d, J = 15.5 Hz, 1H), 7.08 (dd, J = 8.9, 2.3 Hz,
1H), 7.16 (d, J = 2.3 Hz, 1H), 7.63 (dd, J = 8.7, 1.5 Hz, 1H), 7.66 (d,
J = 8.7 Hz, 1H), 7.73 (d, J = 8.9 Hz, 1H), 7.77 (d, J = 15.5 Hz, 1H), 7.86
(s, 1H), 11.93 (s, 1H). 13C NMR (CDCl3) d: ꢀ4.3, 14.3, 18.3, 21.7,
21.9, 24.4, 25.7, 28.7, 60.3, 104.8, 115.0, 121.3, 122.7, 124.2, 127.3,
129.0, 129.5, 130.1, 130.2, 135.5, 142.6, 152.8, 154.7, 164.3, 170.2.
LCMS (ESI) m/z: 480.5 [M+H]+.
4.1.7.3. (E)-Ethyl 2-(3-(8-hydroxyquinolin-2-yl)acrylamido)cycl
ohex-1-enecarboxylate (41b). Compound 41bwas obtained from
compound 40b by a similar protocol to 41a as a yellowish solid,
yield 69%. 1H NMR (CDCl3) d: 1.33 (t, J = 7.1 Hz, 3H), 1.58–1.72
(m, 4H), 2.33–2.39 (m, 2H), 3.07–3.13 (m, 2H), 4.23 (q, J = 7.1 Hz,
2H), 7.08 (d, J = 15.5 Hz, 1H), 7.18 (dd, J = 7.6, 1.2 Hz, 1H), 7.31
(dd, J = 8.3, 1.2 Hz, 1H), 7.45 (dd, J = 8.3, 7.6 Hz, 1H), 7.60 (d,
J = 8.5 Hz, 1H), 7.79 (d, J = 15.5 Hz, 1H), 8.15 (d, J = 8.5 Hz, 1H),
8.19 (br s, 1H), 12.06 (s, 1H). 13C NMR (CDCl3) d: 14.3, 21.6, 21.9,
24.4, 28.7, 60.4, 105.7, 110.5, 117.7, 121.6, 127.5, 128.3, 128.5,
136.8, 138.1, 140.8, 151.0, 152.3, 152.4, 163.4, 170.1. LCMS (ESI)
m/z: 367.2 [M+H]+.
4.1.6.3. (E)-Ethyl 2-(3-(6-hydroxynaphthalen-2-yl)acrylamido)
cyclohex-1-enecarboxylate (41a). To a solution of compound
40a (0.380 g, 0.8 mmol) in tetrahydrofuran (15 ml) at 10 °C was
added 1 M solution of tetra-n-butylammonium fluoride in tetrahy-
drofuran (1 ml, 1 mmol) and the reaction mixture was stirred at
ambient temperature for 1 h. The reaction mixture was supple-
mented with ethyl acetate (40 ml), successively washed with
water (20 ml), satd NH4Cl solution (2 ꢂ 20 ml), brine, and dried
(Na2SO4). The solvents were removed and the residue was dried
in vacuo to give 0.200 g (69%) of compound 41a as white crystal-
line substance. 1H NMR (DMSO-d6) d: 1.24 (t, J = 7.1 Hz, 3H),
1.52–1.65 (m, 4H), 2.31–2.36 (m, 2H), 2.89–2.95 (m, 2H), 4.17 (q,
J = 7.1 Hz, 2H), 6.79 (d, J = 15.6 Hz, 1H), 7.11 (dd, J = 8.7, 2.4 Hz,
1H), 7.14 (d, J = 2.4 Hz, 1H), 7.63 (d, J = 15.6 Hz, 1H), 7.70 (d,
J = 8.7 Hz, 1H), 7.77 (dd, J = 8.7, 1.6 Hz, 1H), 7.80 (d, J = 8.7 Hz,
1H), 8.05 (s, 1H), 9.98 (s, 1H), 11.41 (s, 1H). LCMS (ESI) m/z: 366
[M+H]+.
4.1.7.4. (E)-2-(3-(8-Hydroxyquinolin-2-yl)acrylamido)cyclohex-
1-enecarboxylic acid (14). Compound 14 was obtained from the
ester 41b by general procedure Section 4.1.5.1, yield 58%. Mp
191 °C (dec.). HPLC purity 99.0%. 1H NMR (DMSO-d6) d: 1.52–1.66
(m, 4H), 2.27–2.34 (m, 2H), 2.93–2.99 (m, 2H), 7.11 (dd, J = 7.5,
1.4 Hz, 1H), 7.39 (dd, J = 8.1, 1.4 Hz, 1H), 7.46 (dd, J = 8.1, 7.5 Hz,
1H), 7.52 (d, J = 15.4 Hz, 1H), 7.71 (d, J = 15.4 Hz, 1H), 7.88 (d,
J = 8.6 Hz, 1H), 8.35 (d, J = 8.6 Hz, 1H), 9.87 (s, 1H), 11.94 (s, 1H),
12.65 (br s, 1H). HRMS m/z calcd for
339.1345, found, 339.1346.
C
19H19N2O4 [M+H]+,
4.1.8. General procedure of the synthesis of substituted ethyl
amidocyclohex-1-ene carboxylates 45a–d
To a solution of appropriate carboxylic acid 44a–d (1.0 mmol) in
dichloromethane (6 ml) oxalylchloride (3.0 mmol) and a drop of
DMF were added. The reaction mixture was stirred at ambient
temperature for 40 min and the solvent was removed in vacuo. The
residue was dissolved in dichloromethane (6 ml), and under argon
to the obtained solution was added a mixture of ethyl 2-aminocyclo-
hex-1-enecarboxylate (33) (1.1 mmol) and triethylamine (1.1 mmol)
in dichloromethane (3 ml). The reaction mixture was stirred at room
temperature for 2 h. The mixture was diluted with dichloromethane,
washed successively with NaHCO3 solution, brine, and dried (Na2
SO4). The solvent was removed and the residue was purified as
indicated below to give crystalline compounds 45a–d.
4.1.6.4. (E)-2-(3-(6-Hydroxynaphthalen-2-yl)acrylamido)cyclo-
hex-1-enecarboxylic acid (4). Compound 4 was obtained from
the ester 41a by general procedure Section 4.1.5.1, yield 47%. Mp
189 °C (dec.). HPLC purity 94.8%. 1H NMR (DMSO-d6) d: 1.51–
1.64 (m, 4H), 2.25–2.31 (m, 2H), 2.90–2.98 (m, 2H), 6.73 (d,
J = 15.7 Hz, 1H), 7.11 (dd, J = 8.7, 2.3 Hz, 1H), 7.13 (d, J = 2.3 Hz,
1H), 7.62 (d, J = 15.7 Hz, 1H), 7.70 (d, J = 8.6 Hz, 1H), 7.76 (dd,
J = 8.6, 1.5 Hz, 1H), 7.80 (d, J = 8.7 Hz, 1H), 8.03 (s, 1H), 9.97 (s,
1H), 11.83 (s, 1H), 12.56 (br s, 1H). HRMS m/z calcd for C20H19NO4-
Na [M+Na]+, 360.1212, found, 360.1212.

3666
O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
4.1.8.1. Ethyl 2-(3-(naphthalen-2-yl)propanamido)cyclohex-1-
enecarboxylate (45a). Compound 45a was obtained from com-
mercial carboxylic acid 44a; the product was purified by column
chromatography (eluent petroleum ether–ethyl acetate, 5:1), yield
76%. 1H NMR (CDCl3) d: 1.27 (t, J = 7.1 Hz, 3H), 1.52–1.65 (m, 4H),
2.25–2.30 (m, 2H), 2.69–2.75 (m, 2H), 2.93–2.99 (m, 2H), 3.11–
3.17 (m, 2H), 4.13 (q, J = 7.1 Hz, 2H), 7.35 (dd, J = 8.4, 1.8 Hz, 1H),
7.38–7.46 (m, 2H), 7.65 (s, 1H), 7.74–7.81 (m, 3H), 11.63 (s, 1H).
13C NMR (CDCl3) d: 14.4, 21.8, 22.0, 24.3, 28.8, 31.5, 40.1, 60.4,
104.7, 125.4, 126.1, 126.6, 127.3, 127.7, 127.7, 128.2, 132.3,
133.7, 138.3, 152.3, 170.1, 170.7. LCMS (ESI) m/z: 352.3 [M+H]+.
diluted with methanol (4 ml) and again concentrated in vacuo. The
residue was dissolved in dichloromethane (15 ml) and to the
obtained solution at ice bath temperature a drop of DMF followed
by oxalylchloride (1.85 ml, 21.6 mmol) was added. The mixture
was stirred at ambient temperature for 3 h and concentrated in
vacuo. The residue was dissolved in tetrahydrofuran (10 ml) and
to the obtained solution at ice bath temperature a solution of o-cre-
sol (1.33 g, 12.3 mmol) in tetrahydrofuran (10 ml) and triethyl-
amine (1.82 ml, 13.0 mmol) were added. The mixture was stirred
at ambient temperature for 1 h and quenched with saturated
NaHCO3. The mixture was extracted with ethyl acetate; the organic
layer was washed with water, brine, and dried (Na2SO4). The solvents
were evaporated and the residue was purified by column chromatog-
raphy (eluent ethyl acetate–petroleum ether, gradient from 1:3 to
1:2) to give 1.12 g (54%) of known33 compound 47. 1H NMR (CDCl3)
d: 2.24 (s, 6H), 3.33 (d, J = 21.7 Hz, 2H), 3.75 (s, 3H), 7.07 (tt, J = 7.3,
1.1 Hz, 2H), 7.12 (dt, J = 1.8, 7.7 Hz, 2H), 7.18 (d, J = 7.3 Hz, 2H), 7.27
(td, J = 1.2, 8.1 Hz, 2H). LCMS (ESI) m/z: 333.1 [MꢀH]ꢀ.
4.1.8.2. Synthesis of ethyl 2-(3-(6-((tert-butyldimethylsilyl)
oxy)naphthalen-2-yl)propiolamido)cyclohex-1-enecarboxylate
(45b4.)1..8.2.1. tert-Butyl((6-(2,2-dibromovinyl)naphthalen-2-yl)oxy)
dimethylsilane (46). To a solution of triphenylphosphine (1.78 g,
6.78 mmol) and carbon tetrabromide (1.13 g, 3.41 mmol) in dichlo-
romethane (5 ml) was added compound 39a (0.65 g, 2.27 mmol).
The resulting mixture was stirred at ambient temperature for
1.5 h. The reaction mixture was concentrated, the residue was trit-
urated with ethyl acetate and petroleum ether mixture (1:8)
(5 ꢂ 10 ml), and the obtained solution was concentrated. The resi-
due was purified by column chromatography (eluent petroleum
ether–ethyl acetate, 10:1) to afford 0.89 g (89%) of compound 46
as an oil which solidified on standing in the refrigerator. 1H NMR
(CDCl3) d: 0.24 (s, 6H), 1.01 (s, 9H), 7.07 (dd, J = 8.8, 2.4 Hz, 1H),
7.15 (d, J = 2.4 Hz, 1H), 7.58 (dd, J = 8.6, 1.7 Hz, 1H), 7.58 (s, 1H),
7.65 (d, J = 8.6 Hz, 1H), 7.72 (d, J = 8.8 Hz, 1H), 7.93 (s, 1H). GCMS
4.1.8.3.2. (Z)-Methyl 3-(naphthalen-2-yl)acrylate (48). To
a
solution of compound 47 (0.59 mg, 1.76 mmol) in tetrahydrofuran
(19 ml) at 3 °C was added solid t-BuOK (0.22 g, 1.96 mmol) and the
mixture was stirred for 5 min, and cooled to ꢀ78 °C. To the reac-
tion mixture at ꢀ78 °C under argon was added a solution of 2-
naphthaldehyde (0.25 g, 1.60 mmol) in tetrahydrofuran (2 ml).The
mixture was stirred at ꢀ78 °C for 1.5 h and quenched with satu-
rated NaHCO3. The mixture was extracted with ethyl acetate; the
organic layer was washed with water, brine, and dried (Na2SO4).
The solvents were evaporated and the residue was purified by Bio-
tage Purification system (SNAP column, eluent EtOAc–petroleum
ether, gradient 3–18%) to afford 0.30 g (88%) of compound 48 con-
taining ca. 8% of the corresponding E-isomer as an impurity. 1H
NMR (CDCl3) d: 3.72 (s, 3H), 6.03 (d, J = 12.7 Hz, 1H), 7.10 (d,
J = 12.7 Hz, 1H), 7.44–7.52 (m, 2H), 7.72 (dd, J = 8.6, 1.6 Hz, 1H),
7.78–7.87 (m, 3H), 8.04 (s, 1H). 13C NMR (CDCl3) d: 51.6, 119.6,
126.4, 127.0, 127.1, 127.6, 127.8, 128.7, 130.1, 132.5, 133.1,
133.6, 143.5, 166.8. LCMS (ESI) m/z: 213.0 [M+H]+.
4.1.8.3.3. cis-( )-Methyl 2-(naphthalen-2-yl)cyclopropanecarboxy-
late (49). To a solution of compound 48 (0.245 g, 1.15 mmol) and
Pd(OAc)2 (26 mg, 0.12 mmol) in dichloromethane (2 ml) at ice bath
temperature over 20 min ca. 1 M diazomethane solution in diethyl
ether (25 ml, 25 mmol) was added and the resulting mixture was
stirred for 1 h. To the mixture a drop of acetic acid was added,
the mixture was filtered through a pad of silica gel and concen-
trated. The residue was purified by column chromatography (elu-
ent petroleum ether–ethyl acetate, gradient from 8:1 to 6:1) to
afford 0.09 g (34%) of compound 49. 1H NMR (CDCl3) d: 1.42
(ddd, J = 8.6, 8.0, 5.1 Hz, 1H), 1.84 (td, J = 5.4, 7.5 Hz, 1H), 2.17
(ddd, J = 9.2, 8.0, 5.6 Hz, 1H), 2.72 (q, J = 8.5 Hz, 1H), 3.38 (s, 3H),
7.38 (dd, J = 8.4, 1.8 Hz, 1H), 7.38–7.45 (m, 2H), 7.70–7.80 (m,
4H). GCMS m/z: 226.1 M+.
t
m/z: 385 [Mꢀ Bu]+, 442 M+.
4.1.8.2.2. 3-(6-((tert-Butyldimethylsilyl)oxy)naphthalen-2-yl)pro-
piolic acid (44b). To a solution of compound 46 (0.88 g, 2.0 mmol,
1 equiv) in dry tetrahydrofuran (12 ml) at ꢀ78 °C under argon was
added 2 M solution of n-BuLi in hexane (2.2 ml, 4.4 mmol). After
stirring for 40 min at ꢀ78 °C, the reaction mixture was warmed
to 0 °C, and then cooled to ꢀ70 °C. To this solution solid carbon
dioxide (7 g) was added and the mixture was allowed to warm to
room temperature. The mixture was partitioned between ethyl
acetate (20 ml) and 1% HCl solution (20 ml), the organic part was
washed with 1% HCl (15 ml), and dried (Na2SO4). The solvent was
evaporated and the residue was purified by column chromatogra-
phy (eluent MeOH–CHCl3, 1:5) to afford 0.32 g (49%) of compound
44b as a white solid. IR: 2958, 2928, 2858, 2584, 2206, 1667, 1622,
1419, 1302, 1271, 1262, 1172, 963, 916, 852, 783 cmꢀ11H NMR
(CDCl3) d: 0.26 (s, 6H), 1.01 (s, 9H), 7.12 (dd, J = 8.8, 2.4 Hz, 1H),
7.17 (d, J = 2.4 Hz, 1H), 7.53 (dd, J = 8.6, 1.6 Hz, 1H), 7.67 (d,
J = 8.6 Hz, 1H), 7.72 (d, J = 8.8 Hz, 1H), 8.11 (s, 1H). 13C NMR (CDCl3)
d: ꢀ4.3, 18.3, 25.6, 90.1, 90.1, 113.9, 115.0, 123.3, 127.2, 128.3,
128.8, 129.9, 134.7, 136.7, 155.7. LCMS (ESI) m/z: 327 [M+H]+.
4.1.8.2.3. Ethyl 2-(3-(6-((tert-butyldimethylsilyl)oxy)naphthalen-
2-yl)propiolamido)cyclohex-1-enecarboxylate
(45b). Compound
45b was obtained from carboxylic acid 44b by general procedure
4.1.8 and purified by column chromatography (eluent petroleum
ether–ethyl acetate, 4:1), yield 39%. 1H NMR (CDCl3) d: 0.25 (6H,
s), 1.01 (s, 9H), 1.32 (t, J = 7.1 Hz, 3H), 1.57–1.70 (m, 4H), 2.32–
2.37 (m, 2H), 2.99–3.04 (m, 2H), 4.22 (q, J = 7.1 Hz, 2H), 7.10 (dd,
J = 8.8, 2.4 Hz, 1H), 7.15 (d, J = 2.4 Hz, 1H), 7.52 (dd, J = 8.5,
1.7 Hz, 1H), 7.64 (d, J = 8.5 Hz, 1H), 7.70 (d, J = 8.8 Hz, 1H), 8.06
(s, 1H), 11.91 (s, 1H). LCMS (ESI) m/z: 478 [M+H]+.
4.1.8.3.4. cis-( )-2-(Naphthalen-2-yl)cyclopropanecarboxylic acid
(44c). To a solution of compound 49 (0.094 g, 0.41 mmol) in tetra-
hydrofuran (2 ml) and methanol (1 ml) was added a solution of KOH
(0.070 g, 1.25 mmol) in water (4 ml). The mixture was stirred for
21 h at 50 °C and concentrated. The residue was dissolved in water
(2 ml) and acidified to pH 1 with 20% HCl. The mixture was extracted
with chloroform, washed with brine, and dried (Na2SO4). The solvent
was evaporated and the residue was dried in vacuo to afford 0.087 g
(99%) of compound 44c. 1H NMR (CDCl3) d: 1.43 (ddd, J = 8.6, 7.8,
5.1 Hz, 1H), 1.78 (td, J = 5.3, 7.7 Hz, 1H), 2.09 (ddd, J = 9.2, 7.8,
5.6 Hz, 1H), 2.75 (q, J = 8.5 Hz, 1H), 7.34 (dd, J = 8.5, 1.6 Hz, 1H),
7.39–7.46 (m, 2H), 7.68 (s, 1H), 7.68 (d, J = 8.3 Hz, 1H), 7.73–7.79
(m, 2H), ꢃ9 (br s, 1H). LCMS (ESI) m/z: 213.0 [M+H]+.
4.1.8.3. Synthesis of cis-( )-ethyl 2-(2-(naphthalen-2-yl)cyclo-
propanecarboxamido)cyclohex-1-enecarboxylate (45c). 4.1.8.3.1.
Methyl [bis(o-methoxyphenyl)phosphono]acetate (47)33
.
To a solu-
tion of trimethyl phosphonoacetate (1.25 g, 6.86 mmol) in dichloro-
methane (4 ml) at ice bath temperature was added
bromotrimethylsilane (2.0 ml, 15.2 mmol) and the mixture was stir-
red at ambient temperature for 5 h. The mixture was concentrated,
4.1.8.3.5. cis-( )-Ethyl 2-(2-(naphthalen-2-yl)cyclopropanecarbox-
amido)cyclohex-1-enecarboxylate (45c). Compound 45c was
obtained from carboxylic acid 44c by general procedure 4.1.8 and

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3667
purified by chromatography on a Biotage Purification system
(SNAP column, eluent ethyl acetate–petroleum ether, gradient 1–
28%), yield 38%. 1H NMR (CDCl3) d: 1.30 (t, J = 7.1 Hz, 3H), 1.38
(ddd, J = 8.6, 7.8, 5.1 Hz, 1H), 1.36–1.48 (m, 4H), 1.88 (td, J = 5.4,
7.4 Hz, 1H), 2.13 (ddd, J = 9.2, 7.8, 5.6 Hz, 1H), 2.15–2.26 (m, 2H),
2.50–2.70 (m, 2H), 2.68 (q, J = 8.5 Hz, 1H), 4.18 (q, J = 7.1 Hz, 2H),
7.36–7.43 (m, 3H), 7.66–7.79 (m, 4H), 11.78 (s, 1H). LCMS (ESI)
m/z: 364.3 [M+H]+.
obtained from ester 45e by general procedure Section 4.1.5.2 and
purified by column chromatography (eluent chloroform–methanol,
gradient from 50:1 to 20:1), yield 58%. Mp 156–159 °C. HPLC purity
96.7%. 1H NMR (CDCl3) d: 1.45 (ddd, J = 8.2, 6.6, 4.5 Hz, 1H), 1.55–
1.69 (m, 4H), 1.67 (td, J = 4.7, 9.3 Hz, 1H), 1.84 (ddd, J = 8.2, 5.0,
4.2 Hz, 1H), 2.31–2.37 (m, 2H), 2.69 (ddd, J = 9.3, 6.6, 4.2 Hz, 1H),
2.95–3.10 (m, 2H), 7.22 (dd, J = 8.5, 1.7 Hz, 1H), 7.41 (ddd, J = 8.0,
6.9, 1.4 Hz, 1H), 7.45 (ddd, J = 8.2, 6.9, 1.6 Hz, 1H), 7.56 (unresolved
d, J = 1.7 Hz, 1H), 7.74–7.80 (m, 3H), 9.40 (br s, 1H), 11.69 (s, 1H).
13C NMR (DMSO-d6) d: 16.3, 21.4, 21.5, 24.4, 25.6, 27.9, 28.2,
105.1, 124.3, 124.7, 125.4, 126.2, 127.3, 127.5, 127.9, 131.8,
132.9, 137.9, 150.3, 169.5, 171.1. LCMS (ESI) m/z: 334.2 [MꢀH]ꢀ.
4.1.8.4. (E)-Ethyl 2-(3-(benzo[d][1,3]dioxol-5-yl)acrylamido)cycl
ohex-1-enecarboxylate (45d). Compound 45d was obtained from
commercial carboxylic acid 44d; the product was purified by
washing with ethyl acetate, yield 51%. 1H NMR (CDCl3) d: 1.31
(t, J = 7.1 Hz, 3H), 1.60–1.70 (m, 4H), 2.32–2.36 (m, 2H), 3.05–
3.10 (m, 2H), 4.20 (q, J = 7.1 Hz, 2H), 5.99 (s, 2H), 6.33 (d,
J = 15.5 Hz, 1H), 6.79 (d, J = 8.0 Hz, 1H), 7.01 (dd, J = 8.0, 1.7 Hz,
1H), 7.05 (d, J = 1.7 Hz, 1H), 7.54 (d, J = 15.5 Hz, 1H), 11.86 (s,
1H). LCMS (ESI) m/z: 344.2 [M+H]+.
4.1.10.4. cis-( )-2-(2-(Naphthalen-2-yl)cyclopropanecarboxami-
do)cyclohex-1-enecarboxylic acid (7). Compound 7 was obtained
from ester 45c by general procedure Section 4.1.5.2 and purified by
column chromatography (eluent chloroform–methanol, gradient
from 100:1 to 33:1) followed by crystallization from ethyl acetate,
yield 83%. Mp 137–140 °C. HPLC purity 98.7%. 1H NMR (CDCl3) d:
1.40 (ddd, J = 8.8, 7.9, 5.2 Hz, 1H), 1.39–1.54 (m, 4H), 1.89 (td,
J = 5.4, 7.4 Hz, 1H), 2.12 (ddd, J = 9.1, 7.9, 5.6 Hz, 1H), 2.25–2.31
(m, 2H), 2.53–2.74 (m, 2H), 2.72 (q, J = 8.5 Hz, 1H), 2.36–2.45 (m,
3H), 7.69–7.74 (m, 2H), 7.74–7.79 (m, 2H), 9.72 (br s, 1H), 11.57
(s, 1H). 13C NMR (DMSO-d6) d: 10.2, 21.2, 24.2, 25.3, 25.4, 27.8,
104.0, 125.4, 125.9, 127.0, 127.3, 127.4, 127.7, 131.2, 132.4,
134.6, 150.6, 167.3, 171.2. LCMS (ESI) m/z: 336.2 [M+H]+.
4.1.9. trans-( )-Ethyl 2-(2-(naphthalen-2-yl)cyclopropanecarbo
xamido)cyclohex-1-enecarboxylate (45e)
To a solution of compound 36a (0.14 g, 0.40 mmol) in dichloro-
methane (2.5 ml) was added Pd(OAc)2 (4.0 mg, 0.02 mmol) and the
mixture was cooled in an ice bath. To the reaction mixture over
10 min was added an excess of ca. 1 M diazomethane solution in
diethyl ether (7.5 ml, 7.5 mmol) and the mixture was stirred for
30 min at ambient temperature. The reaction mixture was filtered
through silica gel, the eluate was evaporated and the residue was
dried in vacuo to afford 0.14 g (96%) of compound 45e. 1H NMR
(CDCl3) d: 1.27 (t, J = 7.1 Hz, 3H), 1.42 (ddd, J = 8.3, 6.5, 4.6 Hz, 1H),
1.54–1.68 (m, 4H), 1.68 (ddd, J = 9.2, 5.1, 4.6 Hz, 1H), 1.89 (ddd,
J = 8.3, 5.1, 4.1 Hz, 1H), 2.28–2.35 (m, 2H), 2.67 (ddd, J = 9.2, 6.5,
4.1 Hz, 1H), 2.92–3.08 (m, 2H), 4.15 (q, J = 7.1 Hz, 2H), 7.20 (dd,
J = 8.5, 1.8 Hz, 1H), 7.38–7.47 (m, 2H), 7.55 (unresolved d, J = 1.8 Hz,
1H), 7.73- 7.77 (m, 2H), 7.78 (dd, J = 7.7, 1.5 Hz, 1H), 11.95 (s, 1H).
13C NMR (CDCl3) d: 14.4, 17.1, 21.8, 22.0, 24.3, 26.4, 28.5, 28.8, 60.4,
104.4, 124.7, 124.8, 125.5, 126.3, 127.5, 127.7, 128.2, 132.4, 133.5,
138.0, 152.4, 170.2, 170.7. LCMS (ESI) m/z: 364.2 [M+H]+.
4.1.10.5. (E)-2-(3-(Benzo[d][1,3]dioxol-5-yl)acrylamido)cyclo-
hex-1-enecarboxylic acid (20). Compound 20 was obtained from
ester 45d by general procedure Section 4.1.5.2 and purified by col-
umn chromatography (eluent chloroform–methanol, 20:1), yield
60%. Mp 163–164 °C. HPLC purity 97.5%. 1H NMR (DMSO-d6) d:
1.50–1.63 (m, 4H), 2.23–2.30 (m, 2H), 2.88–2.94 (m, 2H), 6.07 (s,
2H), 6.59 (d, J = 15.5 Hz, 1H), 6.94 (d, J = 8.1 Hz, 1H), 7.16 (dd,
J = 8.1, 1.6 Hz, 1H), 7.40 (d, J = 1.6 Hz, 1H), 7.43 (d, J = 15.5 Hz,
1H), 11.74 (s, 1H), 12.54 (br s, 1H). LCMS (ESI) m/z: 314.2
([MꢀH]ꢀ).
4.1.11. Synthesis of substituted propanamido-cyclohex-1-
enecarboxylic acids 2 and 27–31
4.1.10. Synthesis of cyclohex-1-enecarboxylic acids 1, 5–7, and
20
4.1.11.1. General procedure for hydrogenation of acrylamido-
cyclohex-1-ene derivatives 36j–l, and 36o into propanamido-
cyclohex-1-enecarboxylate derivatives 37a–d. Hydrogen gas was
bubbled through a mixture of appropriate acrylamidocyclohex-1-
ene carboxylate derivative 36j–l or 36o (1 mmol) and 10% Pd/C
(20 wt %) in THF–MeOH, 1:1 mixture (10 ml) for 40 min to 2 h.
The reaction mixture was filtered through silica gel, concentrated
in vacuo, and purified if necessary as indicated, to yield compounds
37a–d as white solids, accordingly.
4.1.11.1.1. Ethyl 2-(3-(quinolin-8-yl)propanamido)cyclohex-1-
enecarboxylate (37a). Compound 37a was obtained from
acrylamidocyclohexene derivative 36j and purified by column
chromatography (eluent petroleum ether–ethyl acetate, 3:1), yield
54%. 1H NMR (CDCl3) d: 1.25 (t, J = 7.1 Hz, 3H), 1.52–1.65 (m, 4H),
2.25–2.30 (m, 2H), 2.86 (t, J = 7.7 Hz, 2H), 2.94–3.00 (m, 2H), 3.61
(t, J = 7.7 Hz, 2H), 4.11 (q, J = 7.1 Hz, 2H), 7.38 (dd, J = 8.3, 4.2 Hz,
1H), 7.44 (dd, J = 8.1, 7.1 Hz, 1H), 7.60 (d, J = 7.1 Hz, 1H), 7.67 (dd,
J = 8.1, 1.3 Hz, 1H), 8.12 (dd, J = 8.3, 1.8 Hz, 1H), 8.93 (dd, J = 4.2,
1.8 Hz, 1H), 11.52 (s, 1H). LCMS (ESI) m/z: 353.3 [M+H]+.
4.1.11.1.2. Ethyl 2-(3-(quinolin-6-yl)propanamido)cyclohex-1-
enecarboxylate (37b). Compound 37b was obtained from acry-
lamidocyclohexene derivative 36k and purified by chromatogra-
4.1.10.1. 2-(3-(Naphthalen-2-yl)propanamido)cyclohex-1-ene-
carboxylic acid (1)26. Known26 compound 1 was obtained from
ester 45a by general procedure Section 4.1.5.2 and purified by col-
umn chromatography (eluent chloroform–methanol, 10:1), yield
28%. Mp 135–137 °C. HPLC purity 99.0%. 1H NMR (CDCl3) d:
1.53–1.68 (m, 4H), 2.27–2.36 (m, 2H), 2.70 (t, J = 7.7 Hz, 2H),
2.96–3.02 (m, 2H), 3.13 (t, J = 7.7, 2H), 7.33 (dd, J = 8.4, 1.5 Hz,
1H), 7.40 (dt, J = 1.6, 6.9 Hz, 1H), 7.44 (dt, J = 1.7, 6.9 Hz, 1H), 7.64
(s, 1H), 7.74–7.80 (m, 3H), 10.2 (br s, 1H), 11.38 (s, 1H). LCMS
(ESI) m/z: 324 [M+H]+.
4.1.10.2. 2-(3-(6-Hydroxynaphthalen-2-yl)propiolamido)cyclo-
hex-1-enecarboxylic acid (5). Compound 5 was obtained from
ester 45b by general procedure Section 4.1.5.2 and purified by col-
umn chromatography (eluent chloroform–methanol–acetic acid,
100:10:1) followed by washing with a chloroform–methanol mix-
ture (10:1), yield 45%. Mp 196–198 °C. IR: 3158, 2965, 2872, 2212,
1673, 1607, 1508, 1462, 1215, 999, 902, 812, 725 cmꢀ11H NMR
(DMSO-d6) d: 1.49–1.65 (m, 4H), 2.21–2.32 (m, 2H), 2.79–2.89
(m, 2H), 7.12–7.22 (m, 2H), 7.47 (dd, J = 8.5, 1.5 Hz, 1H), 7.75 (d,
J = 8.5 Hz, 1H), 7.85 (d, J = 9.4 Hz, 1H), 8.15 (s, 1H), 10.18 (br s,
1H), 12.07 (s, 1H), 12.76 (br s, 1H). LCMS (ESI) m/z: 334 ([MꢀH]ꢀ).
phy on
a Biotage Purification system (SNAP column, eluent
petroleum ether–ethyl acetate, gradient from 100:0 to 50:50),
yield 82%.1H NMR (CDCl3) d: 1.27 (t, J = 7.1 Hz, 3H), 1.52–1.65 (m,
4H), 2.25–2.30 (m, 2H), 2.73 (t, J = 7.7 Hz, 2H), 2.93–2.98 (m, 2H),
4.1.10.3. trans-( )-2-(2-(Naphthalen-2-yl)cyclopropanecarbox-
amido)cyclohex-1-enecarboxylic acid (6). Compound
6 was

3668
O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3.17 (t, J = 7.7 Hz, 2H), 4.13 (q, J = 7.1 Hz, 2H), 7.37 (dd, J = 8.3,
4.2 Hz, 1H), 7.59 (dd, J = 8.6, 1.9 Hz, 1H), 7.63 (s, 1H), 8.02 (d,
J = 8.6 Hz, 1H), 8.09 (dd, J = 8.3, 1.7 Hz, 1H), 8.86 (dd, J = 4.2,
1.7 Hz, 1H), 11.64 (s, 1H). 13C NMR (CDCl3) d: 14.3, 21.8, 22.0,
24.3, 28.7, 31.3, 39.8, 60.4, 104.8, 121.3, 126.5, 128.6, 129.7,
130.9, 135.8, 139.2, 147.4, 150.0, 152.2, 170.1, 170.5. LCMS (ESI)
m/z: 353.3 [M+H]+.
1.4 Hz, 1H), 11.61 (s, 1H), 12.52 (br s, 1H). 13C NMR (DMSO-d6) d:
21.3, 21.4, 24.3, 28.1, 30.4, 38.6, 104.8, 121.4, 126.3, 127.8, 128.8,
130.8, 135.5, 139.1, 146.6, 149.9, 150.5, 169.8, 171.1. LCMS (ESI)
m/z: 325 [M+H]+.
4.1.11.5. 2-(3-(2-Methylquinolin-6-yl)propanamido)cyclohex-1-
enecarboxylic acid (29). Compound 29 was obtained from ester
37c by general procedure Section 4.1.5.2 and purified by column
chromatography (eluent chloroform–methanol, 20:1) followed by
washing with methanol, yield 52%. Mp 180–181 °C. HPLC purity
99.0%. 1H NMR (DMSO-d6) d: 1.45–1.57 (m, 4H), 2.18–2.23 (m,
2H), 2.63 (s, 3H), 2.69 (t, J = 7.6 Hz, 2H), 2.77–2.82 (m, 2H), 3.03
(t, J = 7.6 Hz, 2H), 7.37 (d, J = 8.4 Hz, 1H), 7.60 (dd, J = 8.6, 1.9 Hz,
1H), 7.71 (d, J = 1.9 Hz, 1H), 7.82 (d, J = 8.6 Hz, 1H), 8.15 (d,
J = 8.4 Hz, 1H), 11.61 (s, 1H), 12.52 (br s, 1H). 13C NMR (DMSO-
d6) d: 21.3, 21.4, 24.3, 24.8, 28.1, 30.3, 38.7, 104.8, 122.1, 126.0,
126.1, 128.1, 130.6, 135.6, 138.1, 146.2, 150.5, 158.0, 169.8,
171.1. LCMS (ESI) m/z: 339 [M+H]+.
4.1.11.1.3.
Ethyl
2-(3-(2-methyl-quinolin-6-yl)propanamido)
cyclohex-1-enecarboxylate (37c). Compound 37c was obtained
from acrylamidocyclohexene derivative 36l and purified by chro-
matography on a Biotage Purification system (SNAP column, eluent
petroleum ether–ethyl acetate, gradient from 15:85 to 5:95%),
yield 88%. 1H NMR (CDCl3) d: 1.26 (t, J = 7.1 Hz, 3H), 1.52–1.65
(m, 4H), 2.25–2.30 (m, 2H), 2.72 (s, 3H), 2.72 (t, J = 7.8 Hz, 2H),
2.93–2.98 (m, 2H), 3.14 (t, J = 7.8 Hz, 2H), 4.13 (q, J = 7.1 Hz, 2H),
7.25 (d, J = 8.4 Hz, 1H), 7.55 (dd, J = 8.6, 2.0 Hz, 1H), 7.58 (unre-
solved d, J = 2.0 Hz, 1H), 7.92 (d, J = 8.6 Hz, 1H), 7.97 (d, J = 8.4 Hz,
1H), 11.63 (s, 1H). 13C NMR (CDCl3) d: 14.3, 21.8, 21.9, 24.3, 25.4,
28.7, 31.2, 39.9, 60.4, 104. 8, 122.2, 126.2, 126.6, 128.8, 130.8,
135.9, 138.2, 146.9, 152.2, 158.5, 170.1, 170.6. LCMS (ESI) m/z:
367.4 [M+H]+.
4.1.11.1.4. Ethyl 2-(3-(2-chloro-6-methoxy-quinolin-3-yl)propa-
namido)cyclohex-1-enecarboxylate (37d). Compound 37d was
obtained from acrylamidocyclohexene derivative 36o (Raney
nickel was used instead of Pd/C catalyst and the duration of hydro-
genation was 9 h) and purified by column chromatography (eluent
petroleum ether-ethyl acetate, 3:1), yield 58%. 1H NMR (CDCl3) d:
1.27 (t, J = 7.1 Hz, 3H), 1.53–1.65 (m, 4H), 2.25–2.30 (m, 2H), 2.77
(t, J = 7.5 Hz, 2H), 2.92–2.98 (m, 2H), 3.22 (t, J = 7.5 Hz, 2H), 3.91
(s, 3H), 4.14 (q, J = 7.1 Hz, 2H), 7.03 (d, J = 2.8 Hz, 1H), 7.32 (dd,
J = 9.3, 2.8 Hz, 1H), 7.87 (d, J = 9.3 Hz, 1H), 7.95 (s, 1H), 11.66 (s,
1H). 13C NMR (CDCl3) d: 14.3, 21.8, 21.9, 24.3, 28.7, 28.9, 37.5,
55.7, 60.4, 104.9, 105.0, 122.6, 128.7, 129.7, 132.6, 137.1, 142.7,
148.7, 152.0, 158.2, 170.0, 170.1. LCMS (ESI) m/z: 417.3 [M+H]+.
4.1.11.6. 2-(3-(2-Chloro-6-methoxyquinolin-3-yl)propanamido)
cyclohex-1-enecarboxylic acid (30). Compound 30 was obtained
from ester 37d by general procedure Section 4.1.5.2 and purified
by column chromatography (eluent chloroform–methanol, 20:1)
followed by washing with methanol, yield 56%. Mp 165–167 °C.
HPLC purity 95.3%. 1H NMR (DMSO-d6) d: 1.46–1.59 (m, 4H),
2.18–2.24 (m, 2H), 2.73 (t, J = 7.6 Hz, 2H), 2.78–2.84 (m, 2H), 3.08
(t, J = 7.6 Hz, 2H), 3.89 (s, 3H), 7.37 (d, J = 2.7 Hz, 1H), 7.39 (dd,
J = 9.0, 2.7 Hz, 1H), 7.83 (d, J = 9.0 Hz, 1H), 8.22 (s, 1H), 11.65 (s,
1H), 12.55 (br s, 1H). LCMS (ESI) m/z: 389 [M+H]+.
4.1.11.7. 2-(3-(Benzo[d][1,3]dioxol-5-yl)propanamido)cyclohex-
1-enecarboxylic acid (31). Compound 31 was obtained from car-
boxylic acid 20 by general procedure 4.1.11.1 and purified by col-
umn chromatography (eluent chloroform–methanol, 20:1), yield
36%. Mp 114–115 °C. HPLC purity 97.8%. 1H NMR (DMSO-d6) d:
1.46–1.58 (m, 4H), 2.18–2.24 (m, 2H), 2.52 (t, J = 7.6 Hz, 2H), 2.76
(t, J = 7.6 Hz, 2H), 2.76–2.82 (m, 2H), 5.95 (s, 2H), 6.66 (dd, J = 7.9,
1.6 Hz, 1H), 6.79 (d, J = 7.9 Hz, 1H), 6.81 (d, J = 1.6 Hz, 1H), 11.57
(s, 1H), 12.52 (br s, 1H). 13C NMR (DMSO-d6) d: 21.4, 21.5, 24.3,
28.1, 30.2, 39.3, 100.6, 104.7, 108.1, 108.7, 121.1, 134.5, 145.4,
147.2, 150.5, 169.9, 171.2. LCMS (ESI) m/z: 318 [M+H]+.
4.1.11.2. 2-(3-(6-Hydroxynaphthalen-2-yl)propanamido)cyclo-
hex-1-enecarboxylic acid (2)29. Known29 compound
2 was
obtained from carboxylic acid 4 by general procedure 4.1.11.1
and purified by column chromatography (eluent chloroform–
methanol–acetic acid, 100:5:1), yield 54%. Mp 159 °C (dec.). HPLC
purity 99.0%. 1H NMR (DMSO-d6) d: 1.45–1.58 (m, 4H), 2.17–2.24
(m, 2H), 2.63 (t, J = 7.6 Hz, 2H), 2.77–2.83 (m, 2H), 2.95 (t,
J = 7.6 Hz, 2H), 7.04 (dd, J = 8.7, 2.3 Hz, 1H), 7.06 (d, J = 2.3 Hz,
1H), 7.27 (dd, J = 8.4, 1.7 Hz, 1H), 7.56 (s, 1H), 7.59 (d, J = 8.4 Hz,
1H), 7.66 (d, J = 8.7 Hz, 1H), 9.61 (s, 1H), 11.62 (s, 1H), 12.48 (br
s, 1H). LCMS (ESI) m/z: 338.2 [MꢀH]ꢀ. HRMS m/z calcd for C20H21-
NNaO4 [M+Na]+, 362.1368, found, 362.1381.
4.2. Biology
4.2.1. Generation of HCA receptor stable cell line
The human HCA1, HCA2 and HCA3 receptor genes were amp-
lified from genomic reference DNA. PCR products were cloned into
pcDNA5/FRT (Invitrogen) using the HindIII–XhoI (HCA2 and HCA3)
and NheI–NotI (HCA1) cloning sites. All constructs were verified by
sequencing.
4.1.11.3. 2-(3-(Quinolin-8-yl)propanamido)cyclohex-1-enecarb-
oxylic acid (27). Compound 27 was obtained from ester 37a by
general procedure Section 4.1.5.2, yield 62%. Mp 129–131 °C. HPLC
purity 95.0%. 1H NMR (DMSO-d6) d: 1.47–1.59 (m, 4H), 2.18–2.24
(m, 2H), 2.73 (t, J = 7.7 Hz, 2H), 2.79–2.85 (m, 2H), 3.46 (t,
J = 7.7 Hz, 2H), 7.52 (dd, J = 8.1, 7.1 Hz, 1H), 7.54 (dd, J = 8.3,
4.1 Hz, 1H), 7.63 (dd, J = 7.1, 1.2 Hz, 1H), 7.84 (dd, J = 8.1, 1.2 Hz,
1H), 8.35 (dd, J = 8.3, 1.8 Hz, 1H), 8.93 (dd, J = 4.1, 1.8 Hz, 1H),
11.58 (s, 1H), 12.47 (br s, 1H). LCMS (ESI) m/z: 325 [M+H]+.
Flp-In-293 cells (Invitrogen) were maintained in DMEM med-
ium supplemented with 10% fetal bovine serum, penicillin and
streptomycin (100
and 5% CO2.
lg/ml each) and 100 lg/ml zeocin at 37 °C
For the generation of stable cell lines, Flp-In-293 cells were
seeded into 6-well plate at 70% confluency and transfected with
HCA1-3 receptor expressing plasmids using Turbofect (ThermoSci-
entific) reagent. After 48 h the medium was supplemented with
4.1.11.4. 2-(3-(Quinolin-6-yl)propanamido)cyclohex-1-enecarb-
oxylic acid (28). Compound 28 was obtained from ester 37b by
general procedure Section 4.1.5.2 and purified by crystallization
from methanol, yield 34%. Mp 167–169 °C. HPLC purity 99.0%. 1H
NMR (DMSO-d6) d: 1.45–1.57 (m, 4H), 2.17–2.23 (m, 2H), 2.71 (t,
J = 7.6 Hz, 2H), 2.77–2.83 (m, 2H), 3.06 (t, J = 7.6 Hz, 2H), 7.49
(dd, J = 8.2, 4.1 Hz, 1H), 7.67 (dd, J = 8.6, 1.6 Hz, 1H), 7.78 (s, 1H),
7.93 (d, J = 8.6 Hz, 1H), 8.28 (d, J = 8.2 Hz, 1H), 8.84 (dd, J = 4.1,
200
lg/ml of hygromycin for selection of antibiotic resistant cell
clones. For the maintenance of cell lines stably expressing HCA
receptors hygromycin concentration were reduced to 100 lg/ml.
4.2.2. Intracellular cAMP assay
Cells stably expressing HCA receptors were distributed into a
384-well white microplate at a density 10,000 cells/well and stim-
ulated with the indicated compounds in the presence of 3 lM

O. Bobileva et al. / Bioorg. Med. Chem. 22 (2014) 3654–3669
3669
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Acknowledgments
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Our studies were supported by Latvian State Research Program
BIOMEDICINE.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmc.2014.05.011.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
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