Structural modifications of (Z)-3-(2-aminoethyl)-5-(4-ethoxybenzylidene) thiazolidine-2,4-dione that improve selectivity for inhibiting the proliferation of melanoma cells containing active ERK signaling

Article abstract of DOI:10.1039/c3ob40199e

We herein report on the pharmacophore determination of the ERK docking domain inhibitor (Z)-3-(2-aminoethyl)-5-(4-ethoxybenzylidene)thiazolidine-2,4- dione, which has led to the discovery of compounds with greater selectivities for inhibiting the proliferation of melanoma cells containing active ERK signaling. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ob40199e

Organic &
Biomolecular Chemistry
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PAPER
Structural modifications of (Z)-3-(2-aminoethyl)-
5-(4-ethoxybenzylidene)thiazolidine-2,4-dione that
improve selectivity for inhibiting the proliferation of
melanoma cells containing active ERK signaling
Cite this: Org. Biomol. Chem., 2013, 11,
3706
Kwan-Young Jung,†a Ramin Samadani,†a Jay Chauhan,a Kerrick Nevels,a
Jeremy L. Yap,a Jun Zhang,a Shilpa Worlikar,a Maryanna E. Lanning,a Lijia Chen,a
Mary Ensey,b Sagar Shukla,a Rosene Salmo,c Geoffrey Heinzl,a Caryn Gordon,d
Troy Dukes,e Alexander D. MacKerell, Jr.,a,f Paul Shapiro*a,f and Steven Fletcher*a,f
Received 30th January 2013,
Accepted 9th April 2013
We herein report on the pharmacophore determination of the ERK docking domain inhibitor (Z)-
3-(2-aminoethyl)-5-(4-ethoxybenzylidene)thiazolidine-2,4-dione, which has led to the discovery of com-
pounds with greater selectivities for inhibiting the proliferation of melanoma cells containing active ERK
signaling.
DOI: 10.1039/c3ob40199e
www.rsc.org/obc
Significant efforts in developing anti-cancer therapies have
focused on targeted inhibition of the ERK1/2 pathway in the
Introduction
The extracellular signal-regulated kinases-1 and 2 (ERK1/2) are context of cancers containing activating mutations in
ubiquitous mediators of intracellular signaling events and are upstream RTK, Ras and B-Raf proteins.3 The utility of many of
regulated in response to a variety of membrane receptors these targeted compounds has been limited due to issues with
including receptor tyrosine kinases (RTK), G-protein coupled lack of efficacy, toxicity, and the development of drug resist-
receptors, and cytokine receptors.1 Activated receptors ance through mutations or activation of alternative survival
promote the sequential activation of the Ras G-proteins, Raf pathways.3l,4 Promising new drugs that target the mutated and
kinases, M̲AP or E̲RK k̲inases 1 and 2 (MEK1/2), and finally active form of B-Raf in melanoma cells have clinical limit-
ERK1/2. MEK1/2 are thought to be the primary kinases that ations due to the unanticipated activation of the ERK1/2
directly activate ERK1/2 through phosphorylation of a threo- pathway through alternative mechanisms and the activation of
nine and a tyrosine located in a TXY motif found in MAP compensatory signaling pathways that lead to drug resistance.5
kinase family members.1b The ERK proteins may phosphory-
While constitutive activation of the ERK1/2 proteins func-
late and regulate the activity of hundreds of different substrate tion in sustaining cancer cell proliferation and survival, regu-
proteins found in both the cytoplasm and nucleus.1b,2 As such, lated activity of ERK1/2 serves integral roles in normal cell
many extracellular signals use ERK1/2 to transmit information processes. Thus, in the absence of discriminating between
to regulate a variety of cellular functions including prolifer- cancer and normal cells, inhibitors that completely block
ation, survival, differentiation, and migration.
ERK1/2 signaling are destined to have off-target toxicity to
normal cells. Given that ERK proteins may have nearly 300
interacting partners with over half of these being phosphory-
lated substrates,2 the identification of molecules that disrupt
ERK1/2 interactions with substrates relevant to cancer cell pro-
liferation and survival may have a significant impact on the
development of novel inhibitors that prevent the phosphory-
lation and regulation of ERK substrates involved in disease pro-
cesses while preserving ERK functions in normal cells. In the
current studies, we describe the optimization of compounds
that are predicted to target ERK substrate docking sites and
their selective inhibition of melanoma cancer cells containing
constitutively activated ERK signaling. Moreover, we show that
aDepartment of Pharmaceutical Sciences, University of Maryland School of
Pharmacy, 20 N Pine St., Baltimore, MD 21201, USA.
E-mail: sfletche@rx.umaryland.edu, pshapiro@rx.umaryland.edu;
Fax: +1 410 706 5017; Tel: +1 410 706 6361
bNotre Dame of Maryland University, 4701 N Charles Street, Baltimore,
MD 21212, USA
cIndiana University Purdue University Indianapolis, 420 University Boulevard
Indianapolis, IN 46202, USA
dUniversity of Maryland, College Park, MD 20742, USA
eAntioch Diploma Plus High School, 2555 Harford Road, Baltimore, MD 21218, USA
fUniversity of Maryland Greenebaum Cancer Center, Baltimore, MD 21201, USA
†These authors contributed equally to this work.
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optimized compounds are effective at inhibiting melanoma
cells that have become resistant to B-Raf targeted therapies.
Chemistry
We previously reported the successful use of computer-aided
drug design (CADD) to search for low-molecular-weight
docking domain inhibitors of ERK.6 One of the compounds,
identified as 76, binds ERK2 with a Kd value of 5 μM and
blocks phosphorylation of the downstream ERK targets RSK-1
and Elk-1. Moreover, 76 inhibit2 growth of HeLa cervical carci-
noma and A549 lung carcinoma cells as assessed by colony for-
mation assay in a dose dependent manner with IC50 values of
∼20 μM.6b Compound 76 was predicted by CADD to target a
polar cleft within the D-recruitment site (DRS), which facili-
tates ERK interactions with substrates containing D domains
Scheme 1 (a) 4-Ethoxybenzaldehyde, cat. piperidine, EtOH, reflux, 16 h, 77%;
(b) HOCH2CH2NHTr, PPh3, DIAD, THF, rt, 16 h, 75%; (c) TFA–CH2Cl2, 1 : 1, rt,
30 min, 99%.
(also referred to as the DEJL motif or D
̲ocking site for E̲RK or
J
̲
̲
the common docking (CD) and threonine residues in ED
docking sites.8 It was proposed that the primary amino group
of 76 was engaged in salt bridge interactions with Asp316 and
Asp319 of the CD site and was within 5–7 Å of Thr157 and
Thr158 of the ED site.6b In addition, commercially available
analogues of 76 obtained from a structure-based similarity
search showed activity in preliminary experiments (not
shown), indicating the compound to be a suitable lead for
additional optimization.9 To determine the pharmacophore of
76, which would help direct future optimization efforts, we
embarked on a structure–activity relationship (SAR) study.
Comprised of three distinct components – a 4-ethoxybenzy-
lidene group, a thiazolidine-2,4-dione (TZD) core and an ethyl-
amine tail (Fig. 1) – compound 76 was re-synthesized in just
three linear steps (Scheme 1). Briefly, a Knoevenagel conden-
sation of thiazolidine-2,4-dione (1) with 4-ethoxybenzaldehyde
afforded benzylidene 2. Alkylation of the acidic imide NH of 2
was then accomplished via Mitsunobu conditions (diisopropyl
azodicarboxylate (DIAD) and triphenylphosphine (PPh3)) with
N-trityl-ethanolamine to give 3, which, upon brief treatment
with TFA, furnished the lead compound 76.
furnished a dual inhibitor of the Raf/MEK/ERK and PI3K/Akt
signaling pathways.11 In the present work, a cell-based SAR
analysis of 76 focused on the TZD component and ethylamine
moiety, in which cancer cells with activated ERK signaling
were employed. Additionally, further novel analogs that
explored the SAR of the 4-ethoxyphenyl group were also pre-
pared, directly complementing the aforementioned studies.10
Thiazolidine-2,4-dione (TZD) SAR. In order to determine the
contribution of the TZD portion of 76 to the inhibition of ERK,
we prepared all of the TZD analogues (6, 9, 13, 17 and 20)
depicted in Scheme 2. First, to examine its role, the benzy-
lidene CvC double bond of 76 was chemoselectively reduced
with LiBH4 as shown in Scheme 2A to deliver compound 4, the
imide nitrogen of which was alkylated with N-Boc-2-bromoethyl-
amine to give 5, and then TFA-mediated removal of the Boc
group furnished target molecule 6. In order to generate the rhod-
anine analogue (9) of 76, the chemistry carried out was the
same as that set forth in Scheme 1, substituting 1for rhodanine
(7). For the cyclic imide derivative 13, reaction of maleimide
(10) with PPh3 afforded the stabilized phosphorane 11, which
underwent a Wittig reaction with 4-ethoxybenzaldehyde to
furnish benzylidene 12. N-Alkylation of 12 with N-Boc-2-bromo-
ethylamine, and subsequent removal of the Boc group gave the
imide-functionalized product 13. Acetylation of pyrrolidin-2-
one (14), followed by a modified Knoevenagel condensation
reaction with 4-ethoxybenzaldehyde yielded benzylidene 16. In
this case, the amide NH of 16 was insufficiently acidic to
undergo the Mitsunobu reaction with N-trityl-ethanolamine (5);
instead, N-trityl-ethanolamine was first activated as its O-mesy-
late and then conjugated to the amide anion of 16. Deprotec-
tion of the Tr group by treatment with TFA afforded the target
molecule 17. Finally, to investigate the importance of the cyclic
nature of the TZD ring of 76, we constructed the acyclic analog
20. Once more, a Knoevenagel condensation played a key role
in the synthesis, conjugating malonic acid (18) to 4-ethoxybenz-
aldehyde to furnish the cinnaminic acid derivative 19, which
Recently, Li et al. conducted an SAR analysis of the 4-ethoxy-
phenyl moiety of 76.10 It was found that shifting the 4-ethoxy
group to the 2-position of the phenyl ring led to increased
inhibition of human leukemia U937 cell proliferation. In a
subsequent study, removal of the 4-ethoxy group and extension
of the benzylidene moiety to a 3-phenylpropylidene moiety
Fig. 1 A retrosynthetic analysis reveals the structural components of lead com-
pound 76.
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Scheme 2 (a) LiBH4, THF–pyridine, 80 °C, 12 h, 77%; (b) BrCH2CH2NHBoc, K2CO3, DMF, rt, 16 h, 43–53%; (c) TFA–CH2Cl2, 1 : 1, rt, 1 h, 43–99%; (d) 4-ethoxybenz-
aldehyde, cat. piperidine, EtOH, reflux, 1–16 h, 77–93%; (e) PPh3, acetone, reflux, 1 h, 83%; (f ) Ac2O, THF, reflux, 2 h, 77%; (g) 4-ethoxybenzaldehyde, NaOtBu, 0 °C
to 55 °C, THF, 1 h, 45%; (h) MsOCH2CH2NHTr, NaH, rt, DMF, 16 h, 58%; (i) 4-ethoxybenzaldehyde, piperidine, pyridine, 120 °C, 4 h, 99%; ( j) BocNHCH2CH2NH2,
HBTU, DIPEA, DMF, rt, 3 h, 99%.
was then coupled to N-Boc-ethylenediamine and subsequently the appropriate bromide or alcohol, respectively, to afford
deprotected to give acrylamide derivative 20.
N-Boc or N-Tr intermediates 21, as shown in Scheme 3, which
Ethylamine SAR. The ethylamine group of 76 was modu- were then deprotected under acidic conditions to deliver the
lated to a variety of alternative groups; these can be divided final products 22 as their TFA salts. For the basic N-functiona-
into three categories: alkylamino substitutions, N-functiona- lized ethylamino substitutions (Scheme 4), 76 was converted to
lized ethylamino substitutions, which may be further sub- secondary amines 23a–e either through mono-reductive amin-
divided into basic and non-basic substitutions, and, finally, ation conditions or de novo syntheses, and tertiary amines
alkyl and benzylic substitutions. For the alkylamino substi- 24a–c through one-pot, double-reductive aminations. In the
tutions, which were designed to investigate the optimal spacer course of our work, we discovered that the neutral N-Boc-pro-
between the TZD ring and the basic amino group, as well as tected derivative of 76 exhibited some activity in the cellular
the identity of the basic group itself, benzylidene 2 was pre- assays. Presumably, this molecule exhibits a different binding
pared as earlier described. The imide NH of 2 was next alkyl- mode to the parent compound that carries a basic, primary
ated via classical conditions or the Mitsunobu reaction with amine. Nonetheless, we elected to investigate further
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Scheme 3 (a) Br-X-NHBoc, K2CO3, DMF, rt, 3 h, 16–79% or HO-X-NHTr, PPh3, DIAD, THF, 45 °C, 16 h, 99%; (b) TFA–CH2Cl2, 1 : 1, rt, 1 h, 36–97%.
Scheme 4 (a) R2CHO, NaBH(OAc)3, CH2ClCH2Cl, rt, 16 h, 38–69%; (b) 1. HOCH2CH2N(R)Tr, PPh3, DIAD, THF, rt, 16 h; 2. TFA–CH2Cl2, rt, 30 min, 28–37% (two steps);
(c) excess R2CHO, NaBH(OAc)3, CH2ClCH2Cl, rt, 16 h, 69–93%; (d) (RCO)2O, CH2Cl2, DIPEA, rt, 16 h, 81–92% or 4-cyanobenzoic acid, HBTU, DIPEA, DMF, rt, 16 h,
92%; (e) ROCOCl, DIPEA, CH2Cl2, rt, 16 h, 96–98%; (f) RSO2Cl, DIPEA, CH2Cl2, rt, 16 h, 92–98%.
substitutions of this ethylamino group that included
additional non-basic derivatives. Compound 76 was thus sub-
jected to a variety of acylations, alkoxycarbonylations and sul-
fonylations to furnish the corresponding amides (25a–d),
carbamates (26a–e) and sulfonamides (27a–c), respectively,
according to standard chemistry outlined in Scheme 4. Finally,
Scheme 5 (a) HO-X-NHTr, PPh3, DIAD, THF, 45 °C, 12 h, 61–95%; (b) RBr,
for the non-amino-based alkyl and benzylic substitutions, the
imide NH of 3 was functionalized using classical conditions
with K2CO3 and the appropriate alkyl or benzylic bromide or
chloride at room temperature, 60 °C or 100 °C, depending on
the reactivity of the halide, to afford compounds 28a–s
(Scheme 5).
K2CO3, DMF, rt or 100 °C, 3 h, 78–99% or RCl, K2CO3, DMF, 60 °C, 3 h, 93–96%.
Knoevenagel condensations with a variety of aldehydes, and
then subsequently deprotected under acidic conditions to
furnish the final molecules 30a–l.
4-Ethoxyphenyl SAR. Variation of the 4-ethoxyphenyl com-
ponent of 76 was accomplished via the chemistry described in
Biology
Scheme 6. Briefly, after a Mitsunobu reaction of 1 with N-trityl- For initial phenotypic screening, we evaluated the activity of 76
ethanolamine, resulting compound 29 was subjected to analogues on proliferation of A375 and SK-MEL-28 melanoma
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studied.14 All compounds were initially tested at 100 μM for
their abilities to inhibit cell proliferation, and data are pre-
sented as a percentage of the vehicle-treated control (100%).
Table 1 shows the cell data for analogues of 76 in which the
TZD core was varied. As compared to the parent compound 76,
which showed selective inhibition of melanoma cells,
reduction of the benzylidene double bond (compound 6) led
to almost complete loss of growth inhibition activity in all cell
lines, indicating this double bond plays either a structural role
to maintain 76 in a β-strand-like structure15 and/or is function-
ally significant as a Michael acceptor. That is, the biological
activity of 76 may derive, in part, from its ability to act as an
irreversible inhibitor through covalent alkylation of amino
acid side chains, particularly cysteines, on the surface of the
ERK1/2 proteins. The isosteric replacement of the 2-carbonyl
oxygen with a sulfur atom (compound 9) resulted both in a
Scheme 6 (a) HOCH2CH2NHTr, PPh3, DIAD, THF, rt, 16 h, 75%; (b) 1. ArCHO,
cat. piperidine, EtOH, reflux, 16 h; 2. RBr or RI, K2CO3, DMF, 70 °C, 12 h; 3. TFA–
CH2Cl2, 1 : 1, rt, 30 min, 20–73% (two or three steps).
cell lines, which have constitutively active ERK1/2 due to a reduction of inhibitory activity and a reduction in selectivity
homozygous mutation in B-Raf that drives proliferation and for melanoma cells. The endocyclic sulfur appears to be impor-
survival.12 In addition, compounds were tested in RPMI-7951 tant, since its replacement with an isosteric methylene group
cells, which also contain mutated B-Raf and are resistant to (compound 13) resulted in a less potent and selective inhibitor
B-Raf inhibitors due to the overexpression of MAP3K8 (the of cells containing B-Raf or N-Ras mutations compared to the
gene encoding COT/Tpl2) that provides an alternative mechan- parent compound 76, indicating the sulfur atom may function
ism to indirectly or directly activate ERK proteins.5c,13 We also as a hydrogen bond acceptor. Removal of the carbonyl group
studied the compounds’ effects on HL-60 leukemic cells that of 13 that is juxtaposed to the endocyclic sulfur in 76 resulted
are p53 defective and have an activating mutation in N-Ras, in compound 17 that was almost completely bereft of inhi-
and, therefore, also demonstrate upregulation of ERK1/2. For bitory activity (Table 1). Furthermore, deletion of the two endo-
comparison, HeLa cervical carcinoma and Jurkat T-cell leuke- cyclic methylene groups of 17 afforded the non-cyclic
mia cells, which are p53 defective cancer cell lines but contain compound 20, which exhibited little inhibition of any of the
no known activating mutations in the ERK pathway, were cells. Taken together, these data confirm the importance of
Table 1 Cell viability SAR of thiazolidine-2,5-dione (TZD) ring of 76 at 100 μM
Cell viability (% of vehicle)
Compound number
Structure
SK-MEL-28
A375
2.1
RPMI-7951
0.3 0.02
HL-60
HeLa
Jurkat
59
76
11
88
45
65
7
3
7
4
2
4.4
1
53
90
26
75
3
5
6
92
6
70
3.3
19
5
41 17
4
6
2
108 10
9
21 10
2
7.9
3
52
4
13
29
3
5
58 28
100 10
17
20
79
83
6
4
95
81
2
5
96
93
3
9
73
9
89
94
4
5
92
89
2
7
59 25
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the benzylidene double bond and the TZD core towards
Some of the greatest variation in inhibitory potency and
effective inhibition of cell lines harboring constitutive ERK selectivity was seen upon changes in the 4-ethoxyphenyl group
activation. of 76 (Table 5). First, the importance of the 4-ethoxy moiety
Analysis of the results in Table 2 reveals that, with the was established by synthesizing and testing unsubstituted
exception of the longer 3-propylamine derivative 22a, modifi- compound 30a, which showed some inhibition only in the
cation of the ethyl portion of the ethylamine tail of 76 led to HL-60 cell line. Moreover, the location of the ethoxy group
either a reduction in activity and/or selectivity against mela- proved significant, since shifting it from the para (compound
noma cells (compare data for 76 with that for 22a–e). Alkyl- 76) to the meta or ortho positions (compounds 30b and 30c,
ation of the primary amino group of 76 to afford secondary respectively) resulted in reduced growth inhibition and selec-
amines resulted in a drop in inhibitory activity with small tivity for melanoma cells with activating mutations in the ERK
groups (e.g. methyl, 23a) that could be recovered with bulkier pathway, although inhibition of HL-60 cells was maintained.
groups (e.g. isobutyl, 23c; benzyl, 23d). However, selective inhi- Comparison of the data for the para-substituted isosteres 30d
bition of cell lines containing activating B-Raf or N-Ras and 30f reveal that a polar group at this position is preferred
mutations was largely lost. The corresponding tertiary amines to deliver both potency and, particularly, selectivity for inhibit-
24a–c exhibited no inhibition of any of the cell lines. Collec- ing melanoma and HL-60 cells. This is supported by compar-
tively, these findings demonstrate the significance of the ing the data for isosteres 76 and 30e, wherein the latter,
primary amino group of 76, suggesting it may engage in mul- although a potent inhibitor of the melanoma cell proliferation,
tiple hydrogen bonds. The corresponding tertiary amines 24a–c exhibited 10 fold less selectivity for HL-60 cells, which must
exhibited no inhibition of any of the cell lines. Similarly, be attributed to the replacement of the para-oxygen with
little inhibition of cell proliferation was observed upon replace- a para-methylene group. The addition of further hydrophobi-
ment of the ethylamine group (pKa ∼ 10) with the less basic city to the para-hydroxyl of 30f also generated potent and
imidazole derivative 28a (pKa ∼ 7) or the 2-aminopyridine selective inhibitors with para-benzyloxy and para-isobutoxy
derivative 28b (pKa ∼ 6), the latter of which could be envisaged derivatives 30g and 30h, respectively, completely inhibiting
to engage in hydrogen-bonded chelates with Asp316 or Asp319 proliferation of melanoma and HL-60 cells and demonstrating
through its tautomeric pyridin-2(1H)-imine. However, growth excellent selectivity over HeLa and Jurkat cell lines. Given that
inhibitory activity was observed with the considerably more Li et al. had discovered substitution at the ortho position of
basic (pKa ∼ 12) guanidine derivative 28c, although there was the phenyl ring of 76 resulted in compounds with potent
no apparent selectivity for the melanoma cells over HL-60, activity against the proliferation of human leukemia U937
HeLa or Jurkat cells. A finely-tuned basic group, therefore, is cells,10 we prepared the focused set of ortho-functionalized
required at the terminus of the ethyl group of 76 to confer congeners 30j–l. Indeed, this led to a series of highly cytotoxic
both potency and selectivity against cells with constitutive ERK compounds. However, at the same time, selectivity at 100 μM
activation.
In general, data in Table 3 demonstrate that blockade of lost.
the amino group of 76 as neutral amides, carbamates and sul-
for the ERK-dependent melanoma cell lines appeared to be
In summary, our findings indicate that the pharmacophore
fonamides (25a–27c) afforded compounds with little to no of 76 requires a 4-alkoxyphenyl group connected to a TZD ring
inhibitory activity, underscoring the importance of the basic by virtue of a Z-double bond, along with an ethyl linker con-
character of the primary amino group of 76, which is consist- necting a primary amine to the imide nitrogen of the TZD
ent with binding acidic residues, such as Asp316 and Asp319, ring. Whilst the endocyclic sulfur appears to be important, the
in salt bridge interactions, as originally proposed.6b An excep- Z-double bond is not. Functionalization of the primary amino
tion is the Fmoc derivative 26e, which demonstrated selective group of 76 was detrimental to its biological activity,
inhibition of melanoma cells.
As shown in Table 4, removal of (3) and replacement of the gen bonding interactions are important for inhibitory activity.
ethylamine moiety with non-basic groups (28d–s) for the most The initial screening of compounds suggested several new
suggesting its basicity and capacity to engage in several hydro-
part eliminated selectivity and potency in inhibiting mela- compounds that were selective inhibitors of cancer cell lines
noma cell proliferation, reinforcing the significance of this with activated ERK signaling. To further examine the effects of
component of lead compound 76 that was established above potential lead compounds, we performed dose-response assays
(Tables 2 and 3). In sharp contrast, para-substituted benzoic to determine GI50 values on a select number of compounds
acid derivative 28q proved highly selective for inhibiting A375 that showed selectivity for inhibiting proliferation of cells with
cells but not the other melanoma cell lines with mutated B-Raf activated ERK signaling. An example of the dose response
suggesting this compound may have other cellular targets. curve for compound 30h and the B-Raf inhibitor PLX4032 for
Furthermore, we discovered that the location of the carboxylic inhibiting the growth of melanoma cell lines is shown in
acid function of 28q is significant, as evidenced by the meta Fig. 2. Importantly, these data demonstrate that 30h is equally
(28r) and ortho (28s) isomers, which had reduced inhibition effective at inhibiting melanoma cells that have become resist-
of, and selectivity towards, A375 cells. Given its lack of basic ant to PLX4032 as it is against PLX4032-sensitive cells. A
character, 28q may also target a different binding site than the summary of GI50 values for select lead compounds along with
lead compound 76.
comparisons to known ERK pathway inhibitors in various cell
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Table 2 Cell viability SAR of basic replacements of ethylamine tail of 76 at 100 μM
Cell viability (% of vehicle)
Compound number
R
SK-MEL-28
A375
2.1
RPMI-7951
HL-60
HeLa
Jurkat
76
11
7
2
0.3 0.02
0.6 0.1
4.4
1
53
3
59
5
22a
22b
0.5 0.01
0.7 0.1
8.0 72
12
49
2
7
9.0
2
32
28
4
4
25
4
16
1
7.3
3
58 10
22c
22d
13
2
22
3
8.1
3
45
87
7
4
54 10
33
32
9
2
41 11
1.8 0.1
25
11
5
100
81
5
22e
19
4
25
3
4
62
2
9
6
23a
23b
23c
91
1
95
51
2
4
54
60
7
4
17 11
85
81
4
2
83
63 10
14
10
4
4
69 10
1.3 0.1
1.0 0.1
1.0 0.1
2.5 0.3
3.7 0.4
2.5 0.1
23d
23e
25
96
6
6
13
89
1
3
5.0
2
37
88
1
2
89
98
4
5
96
5
75 25
24a
24b
101 0.3
115
122
2
7
130
120
4
3
110 14
109 24
90
92
5
9
95
1
104
4
104
2
2
24c
28a
107
3
115
101
1
108
70
9
4
108 16
97
80
8
4
100
74
6
2
1
2
6
123 20
107 26
106
105
6
5
28b
28c
86
55
3
6
111
31
101
42
87
17
6
2
4
20
6
6.5 0.5
lines is shown in Table 6. These data highlight several key relevant B-Raf and MEK inhibitors. As shown in Table 6, 30h is
points of these SAR studies. First, TZD-containing compounds about three times as potent as the MEK inhibitor AZD6244 in
have been identified as selective inhibitors of cancer cell lines preventing growth of the drug-resistant RPMI7951 melanoma
containing activated ERK signaling. Second, changes in the cell line. Lastly, 30h is as potent as the ATP-competitive pyrazo-
4-ethoxyphenyl component of the parent compound 76 lylpyrrole ERK inhibitor (N-(1-(3-chloro-4-fluorophenyl)-
improve selectivity and potency for inhibiting melanoma cell 2-hydroxyethyl)-4-(4-(3-chlorophenyl)-1H-pyrazol-5-yl)-1H-pyrrole-
growth. Third, compound 30h is a potent inhibitor of mela- 2-carboxamide, "ERK Inhibitor")16 in preventing melanoma
noma cell lines that have become resistant to the clinically cell proliferation and provides an alternative non-ATP-
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Table 3 Cell viability SAR of N-functionalization of ethylamine tail of 76 at 100 μM
Cell viability (% of vehicle)
Compound number
R
SK-MEL-28
A375
121
RPMI-7951
HL-60
HeLa
Jurkat
25a
105
105
73
2
2
4
4
124
127
62
5
3
106 23
100 11
105
103
92
8
6
25b
25c
118
101 23
98 11
1
84
2
7
31
5
81
99
1
7
25d
103
2
118
3
122 10
101 12
9
102
7
26a
26b
26c
88
83
94
3
5
1
96
4
3
102
67
4
104 31
95 21
80 28
84
88
95
4
5
3
97
7
88
4
111
110
9
4
102
4
3
75 12
26d
26e
97
29
1
7
103
43
54
27
6
3
85 27
98
85
6
4
112
5
3
103 13
139 14
27a
27b
87
95
2
3
94
2
68
99
3
4
82 44
82
90
1
4
85
3
109
6
2
101 52
103
3
27c
92
5
107
118
6
51 31
91
5
97
4
dependent approach to target cancer cells that are dependent further supported by the selective inhibition of the SRE pro-
on active ERK signaling.
moter activity by compound 22a (Fig. 3B).
To further demonstrate that the test compounds were tar-
geting the ERK signaling pathway, we examined the activity of
the activator protein-1 (AP-1) promoter and the serum
response element (SRE), which are regulated by the ERK sub-
Conclusions
strates c-Fos and Elk-1, respectively.17 Compounds 76 and 30g The current study provides a comprehensive structure–func-
were both potent inhibitors of AP-1 and SRE promoter activity tion analysis of TZD-based compounds and their ability to
with estimated IC50 values around 5 μM or less (Fig. 3A and B). inhibit the proliferation of cancer cells containing activated
Interestingly, 30h also inhibited ERK-mediated AP-1 and SRE ERK signaling. These compounds support the utility of deve-
promoter activity but was less potent than compounds 76 and loping novel TZD compounds that have been recognized to
30g at lower concentrations. This suggests differences in how have potential applications for treating cancers such as mela-
these compounds inhibit ERK signaling functions, which is noma.18 We have identified several chemical features (Fig. 4)
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Table 4 Cell viability SAR of non-basic ethylamine replacements of 76 at 100 μM
Cell viability (% of vehicle)
Compound number
R
SK-MEL-28
A375
RPMI-7951
HL-60
HeLa
Jurkat
2
103
1
3
110 10
144
2
103 16
98 13
104
4
28d
28e
101
91
119
116
5
4
116 10
80 26
91 19
96
91
4
2
101
101
5
4
1
3
137
128
110
8
3
3
28f
97
113
117
9
7
99 14
95 18
87
88
4
7
99
5
28g
101
2
108
3
3
4
7
28h
28i
28j
106
90
1
122
110
124
6
4
6
133
9
97 27
104
95
3
108
105
101
3
3
114 20
65
1
4
5
95
114
5
89 31
89
28k
28l
79
79
97
4
3
7
105
4
102
102
106
2
3
8
65 12
82 54
86 37
80
81
95
2
5
3
98
2
105 12
96 11
28m
108
117
3
3
103 11
28n
28o
28p
104
94
3
119 13
102 23
97 23
86 21
98 24
97
9
9
101
97
9
2
5
119
119
6
1
89
7
105
3
122
34
1
100
6
101
28q
28r
28s
59 13
2.0 0.5
3
6
8
84 37
41 22
31 15
64
75
61
2
4
4
85
80
46
3
3
1
83
49
7
8
59
39
1
1
83
45
in compounds such as 30h that promote selective and potent that their mechanisms of action involves inhibition of ERK sig-
inhibition of cancer cells lines containing active ERK signaling naling and not general toxicity. Moreover, these compounds
as a result of B-Raf or N-Ras mutations. Essential for activity is are potent inhibitors of ERK-regulated transcription and
a TZD core, the imide nitrogen of which should be functiona- further support ERK as the molecular target. Of particular
lized with an ethyl moiety terminating in a primary amino importance is the ability for several compounds to inhibit
group. Furthermore, the acidic methylene of the TZD ring melanoma cell lines that have become resistant to clinically
must be linked to a para-alkoxy-substituted phenyl ring relevant B-Raf inhibitors. Recent studies support the use of
through a Z-double bond. Given that other transformed cell ERK-targeted compounds to overcome alternative signaling
lines are not affected by the compounds, our findings suggests pathways that contribute to drug resistance.19 Future studies
3714 | Org. Biomol. Chem., 2013, 11, 3706–3732
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Table 5 Cell viability SAR of 4-ethoxyphenyl moiety of 76 at 100 μM
Cell viability (% of vehicle)
Compound number
R
SK-MEL-28
A375
RPMI-7951
89 17
HL-60
HeLa
Jurkat
30a
88
11
7
7
82
9
28 20
82 10
88
59
4
5
76
2.1
2
0.3 0.02
4.4
4.8
1
2
53
40
3
1
30b
36
6
19
3
30
2
54
66
5
5
30c
52 11
22
23
9
6
45
23
2
1
8.9
4
39
3
30d
30e
30f
31
7
4.8
5.9
2
2
54
11
3
2
71
16
96
6
8
3
0.6 0.4
0.6 0.1
0.7 0.1
38
3
8.8
2
24
5
17 12
63 10
30g
30h
0.8 0.2
1.8 0.5
0.6 0.4
0.3 0.04
0.2 0.04
5.0
5.2
2
2
48
59
3
3
91
87
8
5
1.0
85
1
30i
30j
9
78
3
102 10
24
8
68
3
99
5
1.0 0.1
0.8 0.02
0.6 0.03
1.0 0.04
9.5 3.4
8.3 3.4
0.8 0.1
0.6 0.1
1.8 0.1
1.5 0.1
30k
30l
0.6 0.04
0.9 0.1
0.5 0.01
0.5 0.04
0.6 0.03
5.7
2
8.0
2
6.7
1
will be important to provide a more comprehensive biological grade and purchased from Sigma-Aldrich, Alfa Aesar, Oakwood
characterization of the lead compounds identified in these Chemicals and TCI America. 1H and 13C NMR spectra were
studies and the ERK substrates they affect.
recorded on Varian INOVA 400 MHz and Varian INOVA
500 MHz NMR spectrometers at 25 °C. Chemical shifts are
reported in parts per million (ppm). The residual solvent peak
was used as an internal reference. The mass spectra were
obtained on an Electrospray TOF (ESI-TOF) mass spectrometer
Experimental
Unless otherwise stated, all reactions were performed under an (Bruker amaZon X). Prior to biological testing, final com-
inert (N2) atmosphere. Reagents and solvents were reagent pounds were confirmed to be >95% pure by HPLC
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Fig. 3 Effects of test compounds on AP-1 and SRE promoter activity. ERK-
mediated promoter activity was tested in HeLa cells transfected with AP-1 (A) or
SRE (B) promoter constructs driving luciferase expression. The ERK pathway was
stimulated with EGF (25 ng mL−1) in the presence or absence of the indicated
concentrations of each test compound and luciferase activity was determined
after 6 hours. The MEK inhibitor, U0126, was used as a positive control.
Fig. 2 Melanoma cell growth inhibition dose response curves for PLX4032 and
lead compound 30h. Melanoma cells (A375, SK-MEL-28, and RPMI7951) were
seeded at a density of 5000 per well in 96-well plate. After overnight incubation,
cells were treated with varying doses of PLX4032 (A) or 31 h (B) for two days.
Cell viability was determined by the addition of Cell Titer-Blue Reagent (20 μL
per well) followed by 2 hours of incubation at 37 °C after which fluorescence
was recorded (555/585 nm). Cell viability was expressed as percentage of
vehicle control and data represent the average of three individual experiments.
Fig. 4 Pharmacophore of 76 that elicits cytotoxicity towards melanoma cells
Table 6 GI50 values (μM) of select lead compounds. ND = not determined
harboring constitutive ERK activation.
Compound
A375
SK-MEL-28
RPMI7951
HeLa
Jurkat
76
22a
30g
30h
PLX4032
AZD6244
ERK Inhibitor
29
24
22
7.0
0.07
0.03
5.0
34
46
36
9.0
0.38
0.17
4.0
46
17
11
7.0
11
20
11
>50
ND
∼100
>100
>10
>10
>10
>100
ND
>100
>100
>10
>10
>10
gradient of 75% A to 100% B over 32 min, Atlantis; (II) a gradi-
ent of 50% A to 100% B over 22 min, Symmetry; (III) a gradient
of 75% A to 100% B over 62 min, Atlantis; (IV) a gradient of
100% A to 100% B over 30 min, Atlantis; (V) a gradient of
75% A to 100% B over 52 min, Atlantis; (VI) a gradient of 50%
A to 100% B over 30 min, Atlantis; (VII) a gradient of 100% A
to 100% B over 52 min, Atlantis; (VIII) a gradient of 50% A
to 100% B over 52 min, Atlantis; (IX) a gradient of 100% A to
100% B over 22 min, Symmetry; (X) a gradient of 50% C to
100% D, X-Bridge; (XI) a gradient of 100% E to 100% F over
22 min, X-Bridge; (XII) a gradient of 25% E to 100% F over
22 min, X-Bridge; (XIII) an isocratic gradient of 100% F for
5 min followed by a gradient of 100% E to 100% F over 22 min,
X-Bridge.
chromatography using a Waters 1525 analytical/preparative
HPLC fitted with a C18 reversed-phase column (Atlantis T3:
4.6 mm × 150 mm; Symmetry: 4.6 mm × 150 mm; X-Bridge:
4.6 mm × 150 mm) according to the following conditions with
solvents (A) H2O/0.1% TFA, (B) CH3CN–H2O, 9 : 1 with 0.1%
TFA, (C) H2O, (D) CH3CN–H2O, 9 : 1, (E) H2O/0.1% NH4OH, (F)
CH3CN–H2O, 9 : 1 with 0.1% NH4OH at 1 ml min−1: (I) a
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1
(Z)-5-(4-Ethoxybenzylidene)thiazolidine-2,4-dione (2)
yield as a colorless oil. H-NMR (CDCl3, 500 MHz) δ 9.07 (1H,
bs, NH), 7.17 (2H, d, J = 8.5 Hz, Ar), 6.88 (2H, d, J = 8.5 Hz, Ar),
4.53 (1H, dd, J = 3.5 Hz, J = 10.0 Hz, CHS), 4.06 (2H, q, J =
8.0 Hz, OCH2CH3), 3.52 (1H, m, CH2), 3.12 (1H, dd, J = 4.5 Hz,
J = 10.0 Hz, CH2), 1.44 (3H, t, J = 8.0 Hz, OCH2CH3).
4-Ethoxybenzaldehyde (2.78 mL, 20.0 mmol) and 2,4-thiazoli-
dinedione 1 (3.75 g, 32.0 mmol) were dissolved in 80 mL of
anhydrous ethanol at room temperature and piperidine
(0.60 mL, 6.0 mmol) was added to the reaction flask. The reac-
tion mixture was stirred at 75 °C for 1 day and then allowed to
cool down to room temperature until a yellow crystalline pre-
cipitate formed, collected by filtration, washed with water and
dried to afford compound 3 in 77.0% (3.84 g) yield as a yellow
tert-Butyl (2-(5-(4-ethoxybenzyl)-2,4-dioxothiazolidin-3-yl)ethyl)-
carbamate (5)
Potassium carbonate (1.40 g, 9.68 mmol) was added to a solu-
tion of compound 4 (303 mg, 1.21 mmol) in 4 mL of an-
hydrous DMF at 0 °C. After stirring the reaction mixture for
20 min, a solution of tert-butyl (2-bromoethyl)carbamate
(268 mg, 1.21 mmol) in anhydrous DMF (2 mL) was added
and then the reaction mixture was stirred at room temp-
erature for 3 h. The reaction was quenched by adding water
and then extracted with ethyl acetate. The ethyl acetate layer
was washed with 10% NH4Cl aqueous solution followed by
water and dried over anhydrous Na2SO4, filtered, concentrated
and purified by silica column chromatography (20% ethyl
acetate in hexanes) to afford compound 5 in 53.1% (253 mg)
as a colorless oil. 1H-NMR (CDCl3, 500 MHz) δ 7.14 (2H, d,
J = 7.5 Hz, Ar), 6.85 (2H, d, J = 7.5 Hz, Ar), 4.51 (1H, m,
CH2CHS), 4.43 (1H, m, NH), 4.02 (2H, q, J = 6.5 Hz, OCH2CH3),
3.68 (2H, t, J = 5.5 Hz, NCH2), 3.43 (1H, m, CH2CH), 3.26
(2H, m, CH2NH), 3.12 (1H, m, CH2CH), 1.43 (9H, s, C(CH3)3),
1.40 (3H, t, J = 8.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6,
125 MHz) δ 173.8, 171.0, 157.6, 155.7, 130.2, 130.1, 128.5,
114.4, 114.3, 77.8, 62.9, 51.1, 51.0, 41.5, 37.0, 36.4, 28.2, 28.1,
14.6, 14.5.
1
solid. H-NMR (CDCl3, 500 MHz) δ 7.83 (1H, s, CH), 7.46 (2H,
d, J = 9.0 Hz, Ar), 6.98 (2H, d, J = 9.0 Hz, Ar), 4.10 (2H, q, J =
6.5 Hz, OCH2CH3), 1.43 (3H, d, J = 6.5 Hz, OCH2CH3);
MS (ESI) m/z Calcd for C12H11NO3S (M+): 249.0. Found: 250.0
(M + H+); HPLC purity (condition I), 99.2% (tR, 14.60 min),
HPLC purity (condition V), 98.5% (tR, 6.49 min).
(Z)-3-(2-Aminoethyl)-5-(4-ethoxybenzylidene)thiazolidine-
2,4-dione (3)
Compound 2 (1.26 g, 5.08 mmol), 2-(tritylamino)ethanol
(2.00 g, 6.60 mmol) and triphenylphosphine (1.80 g,
6.86 mmol) were dissolved in 51 mL of anhydrous THF, and
stirred at room temperature for 5 min. DIAD (1.3 mL,
6.60 mmol) was added to the reaction mixture and then stirred
overnight at 45 °C. The reaction mixture was diluted with ethyl
acetate and washed with sat’d NH4Cl aqueous solution. The
organic layer was collected, dried over anhydrous Na2SO4,
filtered, concentrated and purified by silica column chromato-
graphy (30% ethyl acetate in hexanes) to afford 3 (75.0%,
2.71 g) as a white solid.
3-(2-Aminoethyl)-5-(4-ethoxybenzyl)thiazolidine-2,4-dione (6)
(Z)-3-(2-Aminoethyl)-5-(4-ethoxybenzylidene)thiazolidine-
Compound 5 (80 mg, 0.20 mmol) was dissolved in 50% TFA in
dichloromethane (2 mL) and then stirred at room temperature
for 1 h. The solvent was removed by evaporation and the
residue was dissolved in dioxane (2 mL), and evaporated again.
The solid was collected by filtration, washed with ethyl ether,
and dried to afford compound 6 in 58.5% (48 mg) yield as a
white solid. 1H-NMR (CD3OD, 500 MHz) δ 7.17 (2H, d, J =
9.0 Hz, Ar), 6.86 (2H, d, J = 9.0 Hz, Ar), 4.72 (1H, dd, J = 3.5 Hz,
J = 8.5 Hz, CH2CHS), 4.01 (2H, q, J = 6.5 Hz, OCH2CH3), 3.83
(2H, t, J = 5.5 Hz, NCH2), 3.45 (1H, dd, J = 3.5 Hz, J = 14.5 Hz,
CH2CH), 3.13–3.06 (3H, m, CH2CH + CH2NH2), 1.37 (3H, t, J =
6.5 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 174.0,
171.4, 157.6, 130.2, 130.1, 128.4, 114.4, 114.3, 62.9, 51.4, 38.7,
2,4-dione (76)
The title compound 76 was prepared from
2.68 mmol) in a manner to that described for 6 in 72.0%
(1.09 g) as a white solid. H-NMR (DMSO-d6, 400 MHz) δ 8.06
(2H, bs, NH2), 7.85 (1H, s, CH), 7.56 (2H, d, J = 8.4 Hz, Ar), 7.07
(2H, d, J = 8.4 Hz, Ar), 4.08 (2H, q, J = 6.4 Hz, OCH2CH3), 3.87
(2H, m, CH2), 3.05 (2H, m, CH2), 1.31 (3H, t, J = 6.4 Hz,
OCH2CH3); 13C-NMR (DMSO-d6, 100 MHz) δ 167.9, 166.0,
160.5, 132.8, 132.2, 132.1, 125.2, 118.2, 115.4, 115.3, 63.5,
36.9, 14.5.
3 (1.43 g,
1
5-(4-Ethoxybenzyl)thiazolidine-2,4-dione (4)
To a suspension of lithium borohydride (0.22 g, 10.04 mmol) 36.6, 36.2, 14.6; MS (ESI) m/z Calcd for C14H18N2O3S (M+):
in 40 mL of THF–pyridine (ratio 1 : 1), compound 3 (1.00 g, 294.1, Found: 295.0 (M + H+); HPLC purity (condition IX),
4.02 mmol) was added at 0 °C. The reaction mixture was 96.2% (tR, 3.31 min), HPLC purity (condition XI), 94.6%
stirred at 80 °C for 12 h and then cooled to 0 °C. 21 mL of 4 N (tR, 3.97 min).
HCl aqueous solution was added carefully and the resulting
suspension was stirred at 0 °C for 10 min, and refluxed for 1 h.
(Z)-5-(4-Ethoxybenzylidene)-2-thioxothiazolidin-4-one (8)
After cooling down at room temperature, the solvent was 4-Ethoxybenzaldehyde (2.78 mL, 20.00 mmol) and rhodanine
removed by evaporation. The residue was dissolved in ethyl 7 (3.75 g, 32.0 mmol) were dissolved in 80 mL of anhydrous
acetate and washed with water. The organic layer was col- ethanol at room temperature, and piperidine (0.60 mL,
lected, dried over anhydrous Na2SO4, filtered, concentrated 6.0 mmol) was added to the reaction flask. The reaction
and purified by silica column chromatography (50% ethyl mixture was stirred at 75 °C for 1 day and then allowed to cool
acetate in hexanes) to afford compound 4 in 76.6% (0.77 g) down to room temperature until a yellow crystalline precipitate
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formed, and the solid was collected by filtration, washed with (96 mg, 0.43 mmol) in anhydrous DMF (1 mL) was added and
water and ethyl acetate, and dried to afford compound 8 in then the reaction mixture was stirred at room temperature for
80.0% (2.99 g) yield as a yellow solid. 1H-NMR (DMSO-d6, 3 h. The reaction was quenched by adding water and extracted
400 MHz) δ 13.74 (1H, bs, NH), 7.59 (1H, s, CH), 7.54 (2H, d, with ethyl acetate. The ethyl acetate layer was washed with
J = 8.4, Ar), 7.08 (2H, d, J = 8.4, Ar), 4.10 (2H, q, J = 7.2, 10% NH4Cl aqueous solution followed by water and dried over
CH2CH3), 1.34 (3H, t, J = 7.2, CH2CH3); 13C-NMR (DMSO-d6, anhydrous Na2SO4, filtered, concentrated and purified by silica
100 MHz) δ 169.3, 160.3, 160.2, 139.4, 127.9, 126.6, 123.8, column chromatography (20% ethyl acetate in hexanes) to
122.6, 87.0, 32.8.
afford 70 mg (43.2%) of Boc-protected 13 as a white solid.
1H-NMR (CDCl3, 500 MHz) δ 7.56 (1H, s, CH), 7.44 (2H, d, J =
8.0 Hz, Ar), 6.96 (2H, d, J = 8.0 Hz, Ar), 4.87 (1H, bs, NH), 4.08
(2H, q, J = 6.5 Hz, OCH2CH3), 3.77 (2H, m, CH2), 3.54 (2H, s,
(Z)-3-(2-Aminoethyl)-5-(4-ethoxybenzylidene)-
2-thioxothiazolidin-4-one (9)
To compound 8 (50 mg, 0.18 mmol), HOCH2CH2NHTr (54 mg, CH2), 3.40 (2H, m, CH2), 1.44 (3H, t, J = 6.5 Hz, OCH2CH3),
0.18 mmol) and triphenylphosphine (73 mg, 0.28 mmol) dis- 1.38 (9H, s, C(CH3)3); 13C-NMR (CDCl3, 125 MHz) δ 174.6,
solved in 15 mL of anhydrous THF was added DIAD (55 μL, 171.6, 160.7, 156.2, 134.5, 132.2, 126.8, 120.5, 115.2, 79.6, 63.8,
0.28 mmol) and stirred for 12 h. Reaction was reduced in vacuo 39.3, 39.0, 34.2, 28.4, 14.8.
and purified by column chromatography (10% ethyl acetate in
Step 2. The title compound 13 was prepared from Boc-pro-
hexanes) to give 67 mg (67.7%) of a yellow oil. Deprotection tected 13 (47 mg, 0.13 mmol) in a manner similar to that
following the procedure of compound 6 gave the title com- described for 6 in 92.0% (45 mg) yield as a white solid.
pound 9 as a yellow solid (53%, 40 mg). 1H-NMR (DMSO-d6, 1H-NMR (DMSO-d6, 500 MHz) δ 7.94 (2H, s, NH2), 7.62 (2H, d,
500 MHz) δ 7.90 (2H, bs, NH2), 7.80 (1H, s, CH), 7.63 (2H, d, J = 9.0 Hz, Ar), 7.44 (1H, s, CH), 7.03 (2H, d, J = 9.0 Hz, Ar), 4.10
J = 8.0, Ar), 7.13 (2H, d, J = 8.0, Ar), 4.29 (2H, t, J = 6.0, CH2), (2H, q, J = 6.0 Hz, OCH2CH3), 3.76 (2H, m, CH2), 3.61 (2H, m,
4.14 (2H, q, J = 7.0, CH2CH3), 3.21–3.13 (2H, m, CH2), 1.36 CH2), 3.04 (2H, m, CH2), 1.34 (3H, t, J = 6.0 Hz, OCH2CH3);
(3H, t, J = 7.0, CH2CH3); 13C-NMR (DMSO-d6, 125 MHz) 13C-NMR (DMSO-d6, 125 MHz) δ 174.6, 170.9, 159.9, 132.1,
δ 193.8, 167.5, 160.8, 133.1, 132.8, 125.2, 119.1, 115.5, 63.6, 132.0, 126.5, 122.2, 114.9, 63.3, 36.9, 35.8, 33.9, 14.5; MS (ESI)
41.7, 36.4, 14.4; MS (ESI) m/z Calcd for C14H16N2O2S2 (M+): m/z Calcd for C15H18N2O3 (M+): 274.1, Found: 275.0 (M + H+);
308.1, Found: 309.0 (M + H+); HPLC purity (condition IX), HPLC purity (condition IX), 97.8% (tR, 3.24 min), HPLC purity
99.0% (tR, 3.62 min), HPLC purity (condition X), 95.2% (condition X), 98.1% (tR, 3.54 min).
(tR, 5.94 min).
(E)-3-(4-Ethoxybenzylidene)pyrrolidin-2-one (16)
3-(Triphenylphosphoranylidene)pyrrolidine-2,5-dione (11)
4-Ethoxybenzaldehyde (633 mg, 4.22 mmol) and 15 (596 mg,
Maleimide (0.60 g, 6.05 mmol) and triphenylphosphine 4.69 mmol) were dissolved in 6 mL of anhydrous THF, and
(1.57 g, 5.97 mmol) were dissolved in 40 mL of acetone and potassium tert-butoxide (631 mg, 5.62 mmol) was added to the
the reaction mixture was stirred at 65 °C for 1 h. After cooling reaction flask. The reaction mixture was stirred at 55 °C for 1 h
down to room temperature, the solid was collected by fil- and then allowed to cool down to room temperature until a
tration, washed with acetone, and dried to afford compound yellow crystalline precipitate formed, and the solid was col-
1
11 in 82.5% (1.77 g) yield as a white solid. H-NMR (DMSO-d6, lected by filtration, washed with water and ethyl acetate, and
500 MHz) δ 9.74 (1H, s, NH), 7.73–7.62 (15H, m, 3× Ar), 2.97 dried to afford compound 16 in 45.0% (411 mg) as a yellow
1
(2H, s, CH2).
solid. H-NMR (DMSO-d6, 400 MHz) δ 8.03 (1H, bs, NH), 7.46
(2H, d, J = 8.8, Ar), 7.03 (1H, s, CH), 6.97 (2H, d, J = 8.8, Ar),
4.05 (2H, q, J = 6.8, CH2CH3), 3.39–3.32 (2H, m, CH2),
(E)-3-(4-Ethoxybenzylidene)pyrrolidine-2,5-dione (12)
The title compound 12 was prepared from 4-ethoxybenzalde- 3.39–2.98 (2H, m, CH2), 1.33 (3H, t, J = 6.8, CH2CH3); 13C-NMR
hyde (0.22 mL, 1.60 mmol) and compound 11 (1.03 g, (DMSO-d6, 100 MHz) 170.9, 158.5, 130.9, 129.7, 128.1, 127.5,
2.88 mmol) in a manner similar to that described for 3 in 114.6, 63.1, 38.7, 25.7, 14.6.
92.5% (342 mg) yield as a yellow solid. 1H-NMR (CDCl3,
(E)-1-(2-Aminoethyl)-3-(4-ethoxybenzylidene)pyrrolidin-2-one
500 MHz) δ 7.53 (1H, s, CH), 7.44 (2H, d, J = 8.5 Hz, Ar), 6.96
(17)
(2H, d, J = 8.5 Hz, Ar), 4.08 (2H, q, J = 6.5 Hz, OCH2CH3), 1.44
(3H, t, J = 6.5 Hz, OCH2CH3); 13C-NMR (CDCl3, 125 MHz) To compound 16 (50 mg, 0.23 mmol) in 7 mL of anhydrous
δ 174.8, 171.8, 160.9, 135.0, 132.3, 126.6, 121.4, 115.3, 63.9, DMF was added sodium hydride (10 mg, 0.23 mmol) and
35.3, 14.8.
stirred for 1 h. MsOCH2CH2NHTr (174 mg, 0.46 mmol) was
added and stirred overnight. Reaction was reduced in vacuo
and the product was purified by column chromatography (10%
ethyl acetate in hexanes) to give 67 mg (58%) of clear oil.
(E)-1-(2-Aminoethyl)-3-(4-ethoxybenzylidene)pyrrolidine-
2,5-dione (13)
Step 1. Potassium carbonate (180 mg, 1.30 mmol) was added Deprotection following the procedure of compound 6 gave the
to a solution of compound 12 (100 mg, 0.43 mmol) in 3 mL of title compound 17 as a yellow solid (45%, 33 mg). 1H-NMR
anhydrous DMF at 0 °C. After stirring the reaction mixture for (DMSO-d6, 500 MHz) δ 7.82 (2H, bs, NH2), 7.50 (2H, d, J = 7.8,
20 min, a solution of tert-butyl (2-bromoethyl)carbamate Ar), 7.10 (1H, s, CH), 6.99 (2H, d, J = 7.8, Ar), 4.06 (2H, q, J = 7.0,
3718 | Org. Biomol. Chem., 2013, 11, 3706–3732
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CH2CH3), 3.57 (2H, t, J = 6.0, CH2), 3.49 (2H, t, J = 6.0, CH2), (Z)-tert-Butyl (3-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
3.09–2.95 (4H, m, 2× CH2), 1.36 (3H, t, J = 7.0, CH2CH3); propyl)carbamate (21a)
13C-NMR (DMSO-d6, 125 MHz) δ 169.3, 158.7, 131.0, 129.3,
Potassium carbonate (350 mg, 2.53 mmol) was added to a
solution of compound 2 (210 mg, 0.84 mmol) in 4 mL of an-
hydrous DMF at 0 °C. After stirring of reaction mixture for
20 min, a solution of tert-butyl (3-bromopropyl)carbamate
128.2, 127.9, 114.7, 63.2, 44.0, 40.5, 36.7, 24.1, 14.7; MS (ESI)
m/z Calcd for C15H20N2O2 (M+): 260.2, Found: 261.1 (M + H+);
HPLC purity (condition IX), 97.8% (tR, 3.00 min), HPLC purity
(condition X), 99.1% (tR, 3.97 min).
(200 mg, 0.84 mmol) in anhydrous DMF (3 mL) was added and
then the reaction mixture was stirred at room temperature for
(E)-3-(4-Ethoxyphenyl)acrylic acid (19)
3 h. The reaction was quenched by adding water and extracted
with ethyl acetate. The ethyl acetate layer was washed with
10% NH4Cl aqueous solution followed by water and dried over
anhydrous Na2SO4, filtered, concentrated and purified by silica
column chromatography (20% ethyl acetate in hexanes) to
afford compound 21a (78.8%, 270 mg) as a white solid.
1H-NMR (CDCl3, 500 MHz) δ 7.85 (1H, s, CH), 7.46 (2H, d, J =
9.0 Hz, Ar), 6.98 (2H, d, J = 9.0 Hz, Ar), 5.02 (1H, m, NH), 4.11
(2H, q, J = 6.5 Hz, OCH2CH3), 3.84 (2H, t, J = 6.5 Hz, CH2),
3.12 (2H, m, CH2), 1.85 (2H, t, J = 6.5 Hz, CH2), 1.44 (9H, s,
C(CH3)3), 1.23 (3H, d, J = 6.5 Hz, OCH2CH3).
A solution of 4-ethoxybenzaldehyde (1.00 mL, 7.20 mmol) and
piperidine (0.11 mL, 1.08 mmol) in 40 mL of pyridine was
heated to 120 °C. A solution of malonic acid (1.50 g,
14.40 mmol) in 40 mL of pyridine was added dropwise over
30 min and the reaction solution was stirred at 120 °C for 4 h.
After cooling down to 0 °C, excess amount of concentrated
HCl was added carefully to make ∼pH 1. A white crystalline
precipitate formed, and the solid was collected by filtration,
washed with 0.1 N HCl aqueous solution, and dried to afford
compound 19 in 99.5% (1.40 g) of pure 19 as a white
solid. 1H-NMR (DMSO-d6, 500 MHz) δ 12.14 (1H, s, CO2H),
7.62 (2H, d, J = 9.0 Hz, Ar), 7.56 (1H, d, J = 15.5 Hz, CH),
6.95 (2H, d, J = 9.0 Hz, Ar), 6.38 (1H, d, J = 15.5 Hz, CH),
4.07 (2H, q, J = 6.5 Hz, OCH2CH3), 1.33 (3H, t, J = 6.5 Hz,
OCH2CH3).
(Z)-tert-Butyl (1-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
propan-2-yl)carbamate (21b)
The title compound 21b was prepared from compound 2
(260 mg, 1.04 mmol) and tert-butyl (1-bromopropan-2-yl)carba-
mate (247 mg, 1.04 mmol) in a manner similar to that
described for 21a. Yield = 22.5%, 95.0 mg; 1H-NMR (CDCl3,
500 MHz) δ 7.85 (1H, s, CH), 7.46 (2H, d, J = 9.0 Hz, Ar), 6.98
(2H, d, J = 9.0 Hz, Ar), 4.60 (1H, m, NH), 4.10 (3H, q, J = 7.0 Hz,
OCH2CH3 + CHCH3), 3.73 (1H, m, NCH2), 1.45 (3H, t, J = 8.0
Hz, OCH2CH3), 1.36 (9H, s, C(CH3)3), 1.21 (3H, d, J = 6.5 Hz,
CHCH3); 13C-NMR (CDCl3, 125 MHz) δ 168.7, 167.0, 161.0,
155.5, 134.0, 132.4, 125.9, 118.4, 115.4, 79.6, 63.9, 47.1, 45.2,
28.4, 18.7, 14.8.
(E)-N-(2-Aminoethyl)-3-(4-ethoxyphenyl)acrylamide (20)
Step 1. To a mixture of compound 19 (120 mg, 0.63 mmol),
HBTU (360 mg, 0.94 mmol), tert-butyl (2-aminoethyl)carba-
mate (100 mg, 0.63 mmol) and DIPEA (163 μL, 0.94 mmol) was
added 6 mL of DMF at room temperature. The reaction
mixture was stirred for 3 h at room temperature and then the
reaction was quenched by adding water. The white solid was
collected by filtration, washed with water and ethyl ether, and
dried to afford 208 mg (99.5%) of Boc-protected 20 as a white
(Z)-tert-Butyl (2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)propyl)carbamate (21c)
1
solid. H-NMR (DMSO-d6, 500 MHz) δ 8.04 (1H, m, NH), 7.51
(2H, d, J = 8.0 Hz, Ar), 7.39 (1H, d, J = 15.5 Hz, CH), 6.97
(2H, d, J = 8.0 Hz, Ar), 6.85 (1H, m, NH), 6.47 (1H, d, J =
15.5 Hz, CH), 4.07 (2H, q, J = 6.5 Hz, OCH2CH3), 3.21 (2H, q,
J = 6.0 Hz, CH2NH), 3.04 (2H, q, J = 6.0 Hz, NHCH2), 1.39
(9H, s, C(CH3)3), 1.34 (3H, t, J = 6.5 Hz, OCH2CH3); 13C-NMR
(DMSO-d6, 125 MHz) δ 165.4, 159.5, 155.6, 138.3, 129.0, 127.3,
119.6, 114.7, 77.6, 63.1, 38.8, 28.2, 14.5.
Step 2. The title compound 20 was prepared from Boc-pro-
tected 20 (60 mg, 0.18 mmol) in a manner similar to that
described for 6 in 75.0% (47 mg) yield as a white solid.
1H-NMR (DMSO-d6, 500 MHz) δ 8.30 (1H, m, NH), 7.88 (2H, m,
NH2), 7.53 (2H, d, J = 8.0 Hz, Ar), 7.44 (1H, d, J = 15.5 Hz, CH),
6.98 (2H, d, J = 8.0 Hz, Ar), 6.50 (1H, d, J = 15.5 Hz, CH), 4.08
(2H, q, J = 7.0 Hz, OCH2CH3), 3.43 (2H, m, CH2NH2), 2.94 (2H,
m, NHCH2), 1.35 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR
The title compound 21c was prepared from compound 2
(300 mg, 1.20 mmol) and tert-butyl (2-bromopropyl)carbamate
(286 mg, 1.20 mg) in a manner similar to that described for
1
21a. Yield = 15.4%, 75 mg; H-NMR (CDCl3, 500 MHz) δ 7.84
(1H, s, CH), 7.45 (2H, d, J = 8.5 Hz, Ar), 6.97 (2H, d, J = 8.5 Hz,
Ar), 4.67 (1H, m, NH), 4.11 (1H, m, CHCH3), 4.09 (2H, q, J =
7.0 Hz, OCH2CH3), 3.75 (2H, m, CHCH2), 1.45 (3H, d, J =
6.5 Hz, CH3CH), 1.35 (9H, s, C(CH3)3), 1.20 (3H, t, J = 6.5 Hz,
OCH2CH3); 13C-NMR (CDCl3, 125 MHz) δ 168.4, 167.0, 161.0,
156.0, 134.0, 133.7, 132.4, 125.9, 115.4, 79.7, 63.9, 51.4, 47.1,
45.2, 42.7, 28.4, 18.7, 15.2, 14.8.
(S,Z)-Methyl 2-((tert-butoxycarbonyl)amino)-3-(5-(4-
ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)propanoate (21d)
(DMSO-d6, 125 MHz) δ 166.1, 159.7, 138.9, 129.1, 127.1, 119.1, Compound 2 (285 mg, 1.15 mmol), (S)-methyl 2-((tert-butoxy-
114.8, 66.3, 63.2, 38.8, 36.7, 14.5; MS (ESI) m/z Calcd for carbonyl)amino)-3-hydroxypropanoate (251 mg, 1.15 mmol)
C13H18N2O2 (M+): 234.1, Found: 235.0 (M + H+); HPLC purity and triphenylphosphine (452 mg, 1.72 mmol) were dissolved
(condition IX), 99.0% (tR, 3.10 min), HPLC purity (condition in 11 mL of anhydrous THF, and stirred at room temperature
XIII), 99.8% (tR, 3.29 min).
for 5 min. DIAD (338 μL, 1.72 mmol) was added to the reaction
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mixture and then stirred overnight at 45 °C. The reaction (Z)-3-(1-Aminopropan-2-yl)-5-(4-ethoxybenzylidene)-
mixture was diluted with ethyl acetate and washed with sat’d thiazolidine-2,4-dione (22c)
NH4Cl aqueous solution. The organic layer was collected,
The title compound 22c was prepared from compound 21c
dried over anhydrous Na2SO4, filtered, concentrated and puri-
(64 mg, 0.16 mmol) in a manner similar to that described for
fied by silica column chromatography (30% ethyl acetate in
6 in 71.4% (48 mg) yield as a white solid. 1H-NMR (CDCl3
+
hexanes) to afford compound 21d (99.5%, 517 mg) as a white
solid. 1H-NMR (CDCl3, 500 MHz) δ 7.86 (1H, s, CH), 7.46
(2H, d, J = 9.0 Hz, Ar), 6.98 (2H, d, J = 9.0 Hz, Ar), 5.31 (1H, d,
J = 8.5 Hz, NH), 4.69 (1H, m, CHNH), 4.17–4.03 (4H, m,
NCH2 + OCH2CH3), 3.79 (3H, s, OCH3), 1.44 (3H, t, J = 8.0 Hz,
OCH2CH3), 1.39 (9H, s, C(CH3)3).
CD3OD, 500 MHz) δ 7.85 (1H, s, CH), 7.44 (2H, d, J = 7.5 Hz,
Ar), 6.97 (2H, d, J = 7.5 Hz, Ar), 4.08 (2H, q, J = 6.5 Hz,
OCH2CH3), 4.00 (1H, m, NCH), 3.88 (1H, m, CH2NH2), 3.67
(1H, m, CH2NH2), 2.70 (2H, s, NH2), 1.44 (3H, t, J = 6.5 Hz,
OCH2CH3), 1.37 (3H, d, J = 8.0 Hz, CHCH3); 13C-NMR (CDCl3,
125 MHz) δ 167.8, 165.9, 160.4, 132.9, 132.6, 132.2, 125.3,
118.1, 115.4, 63.5, 48.4, 45.4, 44.3, 16.2, 15.4, 14.5; MS (ESI)
m/z Calcd for C15H18N2O3S (M+): 306.1, Found: 307.0 (M + H+);
HPLC purity (condition IX), 98.5% (tR, 3.59 min).
(Z)-Di-tert-butyl (2-(5-(4-ethoxybenzylidene)-2,4-
dioxothiazolidin-3-yl)propane-1,3-diyl)dicarbamate (21e)
The title compound 21e was prepared from compound 2
(292 mg, 1.17 mmol) and di-tert-butyl (2-bromopropane-1,3-
diyl)dicarbamate (413 mg, 1.17 mg) in a manner similar to
that described for 21a. Yield = 23.9%, 130 mg; 1H-NMR
(CDCl3, 500 MHz) δ 7.85 (1H, s, CH), 7.46 (2H, d, J = 9.0 Hz,
Ar), 6.98 (2H, d, J = 9.0 Hz, Ar), 5.07 (1H, m, NH), 4.90 (1H, m,
NH), 4.10 (2H, q, J = 7.0 Hz, OCH2CH3), 4.01 (1H, m,
CH(CH2)2), 3.87 (1H, m, CH2NH), 3.80 (1H, m, CH2NH), 3.28
(2H, m, CH2NH), 1.56 (3H, t, J = 7.0 Hz, OCH2CH3), 1.45 (9H, s,
C(CH3)3), 1.38 (9H, s, C(CH3)3); 13C-NMR (CDCl3, 125 MHz)
δ 168.7, 167.0, 161.2, 156.7, 155.9, 134.4, 132.5, 125.8, 118.1,
115.4, 94.9, 80.0, 79.9, 64.0, 50.5, 43.4, 42.1, 28.5, 28.4, 14.8.
(S,Z)-Methyl 2-amino-3-(5-(4-ethoxybenzylidene)-
2,4-dioxothiazolidin-3-yl)propanoate (22d)
The title compound 22d was prepared from compound 21d
(120 mg, 0.27 mmol) in a manner similar to that described for
6 in 35.5% (44 mg) yield as a light-yellow solid. 1H-NMR
(DMSO-d6, 500 MHz) δ 8.62 (2H, s, NH2), 7.91 (1H, s, CH), 7.61
(2H, d, J = 9.0 Hz, Ar), 7.12 (2H, d, J = 9.0 Hz, Ar), 4.33 (1H, t,
J = 7.0 Hz, CHNH2), 4.14–4.06 (4H, m, NCH2 + OCH2CH3), 3.75
(3H, s, OCH3), 1.35 (3H, t, J = 8.0 Hz, OCH2CH3); 13C-NMR
(DMSO-d6, 125 MHz) δ 167.7, 167.6, 165.8, 160.6, 133.4, 132.3,
125.1, 117.6, 115.5, 115.4, 94.3, 63.6, 53.2, 50.0, 40.6, 14.5,
14.4; MS (ESI) m/z Calcd for C16H18N2O5S (M+): 350.1, Found:
(Z)-3-(3-Aminopropyl)-5-(4-ethoxybenzylidene)thiazolidine-
2,4-dione (22a)
351.0 (M
+
H+); HPLC purity (condition IX), 94.6%
(tR, 3.45 min), HPLC purity (condition XI), 99.2% (tR, 5.13 min).
The title compound 22a was prepared from compound 21a
(157 mg, 0.39 mmol) in a manner similar to that described for
6 in 90.3% (148 mg) yield as a white solid. H-NMR (CD3OD,
(Z)-3-(1,3-Diaminopropan-2-yl)-5-(4-ethoxybenzylidene)-
thiazolidine-2,4-dione (22e)
1
500 MHz) δ 7.79 (1H, s, CH), 7.45 (2H, d, J = 8.5 Hz, Ar), 6.97
(2H, d, J = 8.0 Hz, Ar), 4.04 (2H, q, J = 7.5 Hz, OCH2CH3), 3.79
(2H, t, J = 7.0 Hz, CH2), 2.90 (2H, t, J = 7.5 Hz, CH2), 1.94 (2H,
m, CH2), 1.35 (3H, t, J = 7.5 Hz, OCH2CH3); 13C-NMR (CD3OD,
125 MHz) δ 167.6, 165.9, 160.5, 132.9, 132.2, 125.2, 117.9,
115.3, 63.5, 38.7, 36.6, 25.6, 14.4; MS (ESI) m/z Calcd for
C15H18N2O3S (M+): 306.1, Found: 307.0 (M + H+); HPLC
purity (condition IX), 99.8% (tR, 3.75 min), HPLC purity (con-
dition X), 98.5% (tR, 4.71 min).
The title compound 22e was prepared from compound 21e
(70 mg, 0.13 mmol) in a manner similar to that described for
6 in 96.7% (55 mg) yield as a light-yellow solid. 1H-NMR
(CDCl3, 500 MHz) δ 7.84 (1H, s, CH), 7.40 (2H, d, J = 9.0 Hz,
Ar), 6.91 (2H, d, J = 9.0 Hz, Ar), 4.11 (1H, m, NCH), 4.09 (2H, q,
J = 6.5 Hz, OCH2CH3), 3.47 (2H, m, CH2), 3.43 (2H, m, CH2),
3.21–2.65 (4H, bs, 2× NH2), 1.19 (3H, t, J = 6.5 Hz, OCH2CH3);
13C-NMR (CDCl3, 125 MHz) δ 168.3, 166.2, 160.6, 133.1, 133.0,
132.2, 125.2, 118.2, 118.0, 115.9, 115.5, 115.3, 63.5, 47.7, 47.6,
41.2, 14.5, 14.4; MS (ESI) m/z Calcd for C15H19N3O3S (M+):
321.1, Found: 322.0 (M + H+); HPLC purity (condition IX),
95.3% (tR, 3.14 min), HPLC purity (condition X), 91.0% (tR,
4.33 min).
(Z)-3-(2-Aminopropyl)-5-(4-ethoxybenzylidene)thiazolidine-
2,4-dione (22b)
The title compound 22b was prepared from compound 21b
(57 mg, 0.14 mmol) in a manner similar to that described for
6 in 76.5% (45 mg) yield as a white solid. 1H-NMR (CDCl3,
500 MHz) δ 7.88 (1H, s, CH), 7.45 (2H, d, J = 8.0 Hz, Ar), 6.99
(2H, d, J = 8.0 Hz, Ar), 4.11 (2H, m, OCH2CH3), 3.98 (1H, m,
(Z)-5-(4-Ethoxybenzylidene)-3-(2-(methylamino)ethyl)-
thiazolidine-2,4-dione (23a)
NH2), 3.90 (1H, m, NH2), 3.69 (1H, m, CHNH2), 3.48 (2H, m, To a solution of compound 76 (122 mg, 0.30 mmol) in 4 mL of
CH2CH), 1.46 (3H, d, J = 6.5 Hz, CHCH3), 1.21 (3H, t, J = 1,2-dichloroethane was added triethylamine (84 μL,
6.5 Hz, OCH2CH3); 13C-NMR (CDCl3, 125 MHz) δ 168.1, 166.2, 0.60 mmol), aqueous formaldehyde (37%, 24 μL, 0.30 mmol)
160.55, 132.9, 132.2, 125.2, 118.1, 115.4, 66.3, 63.5, 45.4, 44.3, and sodium triacetoxyborohydride (254 mg, 1.20 mmol). The
16.2, 14.5; MS (ESI) m/z Calcd for C15H18N2O3S (M+): 306.1, reaction mixture was allowed to stir overnight at room temp-
Found: 307.0 (M + H+); HPLC purity (condition IX), 94.8% erature. The reaction was quenched by adding sat’d aqueous
(tR, 3.71 min), HPLC purity (condition X), 94.8% (tR, 4.94 min). NaHCO3 and stirred at room temperature for 20 min. The
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reaction mixture was partitioned between ethyl acetate and (Z)-3-(2-(Benzylamino)ethyl)-5-(4-ethoxybenzylidene)-
sat’d aqueous NaHCO3, the organic layer was washed with thiazolidine-2,4-dione (23d)
brine, collected, dried over anhydrous Na2SO4, filtered, con-
centrated and purified by silica column chromatography using
The title compound 23d was prepared from compound 76
(204 mg, 0.70 mmol), benzaldehyde (71 μL, 0.70 mmol)
and sodium triacetoxyborohydride (445 mg, 2.10 mmol)
dichloromethane–methanol–NH4OH (ratio: 92/7/1) to afford
compound 23a (38.1%, 35 mg) as a yellow solid. 1H-NMR
in a manner similar to that described for 23a in 46.0%
(DMSO-d6, 400 MHz) δ 9.88 (1H, bs, NH), 7.86 (1H, s, CH), 7.57
(2H, d, J = 8.4 Hz, Ar), 7.08 (2H, d, J = 8.4 Hz, Ar), 4.08 (2H, q,
(123 mg) yield as a light-yellow solid. 1H-NMR (DMSO-d6,
500 MHz) δ 7.86 (1H, s, CH), 7.58 (2H, d, J = 8.0 Hz, Ar),
J = 6.8 Hz, OCH2CH3), 3.97 (2H, m, CH2), 3.53 (2H, m, CH2),
7.28–7.19 (5H, m, Ar), 7.09 (2H, d, J = 8.0 Hz, Ar), 4.11 (2H, q,
2.82 (3H, m, CH3), 1.31 (3H, t, J = 6.8 Hz, OCH2CH3); 13C-NMR
J = 7.0 Hz, OCH2CH3), 3.75 (2H, t, J = 6.0, CH2), 3.67
(DMSO-d6, 100 MHz) δ 168.3, 166.4, 160.9, 133.5, 132.7, 125.6,
(2H, m, CH2), 2.72 (2H, t, J = 6.0 Hz, CH2), 1.34 (3H, t, J =
118.4, 115.8, 63.9, 54.2, 42.7, 37.0, 14.9; MS (ESI) m/z Calcd for
7.0 Hz, OCH2CH3).
C15H18N2O3S (M+): 306.1, Found: 307.0 (M + H+); HPLC
purity (condition IX), 94.8% (tR, 4.25 min), HPLC purity (con-
dition II), 90.7% (tR, 7.39 min).
(Z)-4-(((2-(5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
ethyl)amino)methyl)benzonitrile (23e)
(Z)-5-(4-Ethoxybenzylidene)-3-(2-(ethylamino)ethyl)-
thiazolidine-2,4-dione (23b)
The title compound 23e was prepared from compound 76
(146 mg, 0.50 mmol), 4-cyanobenzaldehyde (37 μL,
0.50 mmol) and sodium triacetoxyborohydride (318 mg,
1.50 mmol) in a manner similar to that described for 23a
in 69.0% (140 mg) yield as a light-yellow solid. 1H-NMR
(DMSO-d6, 500 MHz) δ 9.07 (1H, s, NH), 7.95 (2H, d, J =
8.0 Hz, Ar), 7.90 (1H, s, CH), 7.67 (2H, d, J = 8.0 Hz, Ar), 7.60
(2H, d, J = 8.0 Hz, Ar), 7.10 (2H, d, J = 8.0 Hz, Ar), 4.30 (2H, m,
CH2), 4.11 (2H, q, J = 7.0 Hz, OCH2CH3), 3.98 (2H, m, CH2),
3.27 (2H, m, CH2), 1.34 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR
(DMSO-d6, 100 MHz) δ 168.3, 166.4, 161.0, 133.5, 133.1, 132.7,
131.2, 125.5, 118.8, 118.4, 115.8, 112.2, 64.0, 49.9, 44.8,
38.2, 14.9.
To compound 3 (225 mg, 0.91 mmol), HOCH2CH2N(Et)Tr
(300 mg, 0.91 mmol) and triphenylphosphine (357 mg,
1.36 mmol) dissolved in anhydrous THF (20 mL) was added
DIAD (268 μL, 1.36 mmol) and stirred for 12 h. Reaction was
reduced in vacuo and column chromatography to give 276 mg
of a yellow solid. Deprotection following the procedure of com-
pound 6 gave the title compound 23b as a yellow solid (28.0%,
83 mg). 1H-NMR (DMSO-d6, 500 MHz) δ 8.61 (1H, bs, NH), 7.91
(1H, s, CH), 7.61 (2H, d, J = 7.5, Ar), 7.11 (2H, d, J = 7.5, Ar),
4.12 (2H, q, J = 7.0, OCH2CH3), 3.94 (2H, t, J = 6.0, CH2),
3.26–3.19 (2H, m, CH2), 3.00 (2H, q, J = 6.5, NCH2CH3), 1.35
(3H, t, J = 7.0, OCH2CH3), 1.17 (3H, t, J = 6.5, NCH2CH3);
13C-NMR (DMSO-d6, 125 MHz) δ 167.8, 166.0, 165.6, 133.1,
132.3, 125.2, 118.0, 115.4, 63.6, 44.0, 42.1, 38.0, 14.5, 10.8;
MS (ESI) m/z Calcd for C16H20N2O3S (M+): 320.1, Found: 321.1
(M + H+); HPLC purity (condition IX), 99.4% (tR, 3.66 min),
HPLC purity (condition X), 98.8% (tR, 5.07 min).
(Z)-3-(2-(Dimethylamino)ethyl)-5-(4-ethoxybenzylidene)-
thiazolidine-2,4-dione (24a)
To a solution of compound 76 (122 mg, 0.30 mmol) in 4 mL of
1,2-dichloroethane was added triethylamine (84 μL,
0.60 mmol), aqueous formaldehyde (37%, 24 μL, 0.30 mmol)
and sodium triacetoxyborohydride (254 mg, 1.20 mmol). The
(Z)-5-(4-Ethoxybenzylidene)-3-(2-(isobutylamino)ethyl)-
thiazolidine-2,4-dione (23c)
To compound 3 (90 mg, 0.36 mmol), HOCH2CH2N(iBu)Tr reaction mixture was allowed to stir overnight at room temp-
(130 mg, 0.36 mmol) and triphenylphosphine (142 mg, erature. The reaction was quenched by adding sat’d aqueous
0.54 mmol) dissolved in anhydrous THF (20 mL) was added NaHCO3 and stirred at room temperature for 20 min. The reac-
DIAD (107 μL, 0.54 mmol) and stirred for 12 h. Reaction was tion mixture was partitioned between ethyl acetate and sat’d
reduced in vacuo and column chromatography to give 130 mg aqueous NaHCO3, the organic layer was washed with brine,
of a yellow foam. Deprotection following the procedure of com- collected, dried over anhydrous Na2SO4, filtered, concentrated
pound 6 gave the title compound 23c as a yellow solid (37.1%, and purified by silica column chromatography using dichloro-
46 mg). 1H-NMR (DMSO-d6, 500 MHz) δ 8.49 (1H, bs, NH), 7.92 methane–methanol–NH4OH (ratio: 92/7/1) to afford compound
(1H, s, CH), 7.61 (2H, d, J = 8.0, Ar), 7.11 (2H, d, J = 8.0, Ar), 24a (76.2%, 73 mg) as a yellow solid. 1H-NMR (DMSO-d6,
4.12 (2H, q, J = 7.0, CH2CH3), 3.98 (2H, t, J = 5.5, CH2), 400 MHz) δ 7.83 (1H, s, CH), 7.56 (2H, d, J = 8.4 Hz, Ar), 7.05
3.26–3.17 (2H, m, CH2), 2.88–2.79 (2H, m, CH2), 1.97–1.88 (2H, d, J = 8.4 Hz, Ar), 4.08 (2H, q, J = 6.4 Hz, OCH2CH3), 3.64
(1H, m, CH(CH3)2), 1.35 (3H, t, J = 7.0, CH2CH3), 0.93 (6H, d, (2H, m, CH2), 3.31 (6H, s, 2 × CH3), 3.23 (2H, m, CH2), 1.31
J = 7.0, 2× CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.8, 166.0, (3H, t, J = 6.4 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 100 MHz)
160.6, 133.1, 132.3, 125.2, 118.0, 115.4, 63.6, 53.8, 44.8, 37.5, δ 170.0, 168.0, 166.3, 160.8, 132.9, 132.6, 125.7, 118.5, 115.7,
25.5, 19.9, 14.5; MS (ESI) m/z Calcd for C18H24N2O3S (M+): 63.9, 41.9, 36.5, 22.9, 14.9; MS (ESI) m/z Calcd for C16H20N2O3S
348.2, Found: 349.1 (M + H+); HPLC purity (condition IX), (M+): 320.1, Found: 321.0 (M + H+); HPLC purity (condition
99.2% (tR, 3.75 min), HPLC purity (condition X), 98.7% IX), 98.5% (tR, 5.72 min), HPLC purity (condition II), 96.0%
(tR, 6.71 min).
(tR, 8.71 min).
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(Z)-3-(2-(Dibenzylamino)ethyl)-5-(4-ethoxybenzylidene)-
(Z)-N-(2-(5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
thiazolidine-2,4-dione (24b)
ethyl)-2,2,2-trifluoroacetamide (25b)
The title compound 24b was prepared from compound 76 To a solution of compound 76 (81 mg, 0.20 mmol) in 4 mL of
(117 mg, 0.40 mmol), benzaldehyde (82 μL, 0.80 mmol) dichloromethane was added potassium carbonate (83 mg,
and sodium triacetoxyborohydride (254 mg, 1.20 mmol) 0.60 mmol) followed by trifluoroacetic anhydride (31 μL,
in a manner similar to that described for 23a in 93.1% 0.22 mmol). After being stirred at room temperature for 3 h,
(176 mg) yield as a light-yellow solid. 1H-NMR (DMSO-d6, the reaction solution was diluted with 50 mL of dichloro-
400 MHz) δ 7.72 (1H, s, CH), 7.59 (2H, d, J = 8.4 Hz, Ar), methane, washed with water, collected the organic layer, dried
7.20–7.16 (8H, m, Ar), 7.12–7.07 (4H, m, Ar), 4.08 (2H, q, J = over Na2SO4, filtered, concentrated and purified by silica
6.8 Hz, OCH2CH3), 3.75 (2H, m, CH2), 3.32 (4H, s, 2× CH2), column chromatography (6% ethyl acetate in dichloro-
2.54 (2H, m, CH2), 1.32 (3H, t, J = 6.8 Hz, OCH2CH3); 13C-NMR methane) to afford 62 mg (81.0%) of the title compound 25b
(DMSO-d6, 100 MHz) δ 167.6, 165.9, 160.8, 139.4, 133.1, 132.6, as a light-yellow solid. 1H-NMR (DMSO-d6, 500 MHz) δ 9.56
128.8, 128.5, 127.2, 125.8, 118.3, 115.8, 63.9, 57.7, 50.1, 14.9; (1H, m, NH), 7.88 (1H, s, CH), 7.60 (2H, d, J = 8.5 Hz, Ar), 7.10
MS (ESI) m/z Calcd for C28H28N2O3S (M+): 472.2, Found: 473.1 (2H, d, J = 8.5 Hz, Ar), 4.11 (2H, q, J = 7.0 Hz, OCH2CH3), 3.79
(M + H+).
(2H, t, J = 6.0 Hz, CH2), 3.45 (2H, m, CH2), 1.34 (3H, t, J =
7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.6,
165.9, 160.4, 156.8, 132.7, 132.2, 125.2, 118.0, 116.9, 115.4,
114.6, 63.5, 40.5, 37.0, 14.5; MS (ESI) m/z Calcd for
C16H15F3N2O4S (M+): 388.1, Found: 389.0 (M + H+); HPLC
purity (condition I), 97.1% (tR, 21.01 min), HPLC purity (con-
dition III), 98.3% (tR, 21.70 min).
(Z)-3-(((4-Cyanobenzyl)(2-(5-(4-ethoxybenzylidene)-2,4-
dioxothiazolidin-3-yl)ethyl)amino)methyl)benzonitrile (24c)
The title compound 24c was prepared from compound 76
(88 mg, 0.30 mmol), 4-cyanobenzaldehyde (79 mg, 0.60 mmol)
and sodium triacetoxyborohydride (190 mg, 0.90 mmol)
in a manner similar to that described for 23a in 68.5%
(110 mg) yield as a yellow solid. 1H-NMR (CDCl3, 400 MHz)
(Z)-tert-Butyl (2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)ethyl)carbamate (25c)
δ 7.72 (1H, s, CH), 7.52–7.50 (6H, m, Ar), 7.53–7.34 (4H, m, Ar), To a solution of compound 76 (101 mg, 0.25 mmol) in 3 mL of
7.02 (2H, d, J = 8.0 Hz, Ar), 4.11 (2H, q, J = 6.8 Hz, OCH2CH3), dichloromethane was added DIPEA (131 μL, 0.75 mmol) fol-
3.84 (2H, m, CH2), 3.58 (4H, s, 2× CH2), 2.69 (2H, m, CH2), 1.44 lowed by pivaloyl chloride (34 μL, 0.28 mmol). After being
(3H, t, J = 6.8 Hz, OCH2CH3); 13C-NMR (CDCl3, 100 MHz) stirred at room temperature overnight, the reaction solution
δ 167.9, 166.1, 161.2, 144.2, 134.0, 132.4, 132.2, 129.3, 125.3, was diluted with 50 mL of dichloromethane, washed with
118.7, 117.6, 115.4, 111.1, 63.8, 58.0, 50.7, 39.2, 29.6, 14.6; water, collected the organic layer, dried over Na2SO4, filtered,
MS (ESI) m/z Calcd for C30H26N4O3S (M+): 522.2, Found: 523.1 concentrated and purified by silica column chromatography
(M + H+).
(10% ethyl acetate in hexanes) to afford 89 mg (90.8%) of the
title compound 25c as a yellow solid. 1H-NMR (DMSO-d6,
500 MHz) δ 7.84 (1H, s, CH), 7.64 (1H, t, J = 5.5 Hz, NH), 7.58
(2H, d, J = 8.0 Hz, Ar), 7.09 (2H, d, J = 8.0 Hz, Ar), 4.11 (2H, q,
J = 7.0 Hz, OCH2CH3), 3.69 (2H, m, CH2), 3.30 (2H, m, CH2),
1.34 (3H, t, J = 7.0 Hz, OCH2CH3), 1.01 (9H, s, C(CH3)3);
13C-NMR (DMSO-d6, 125 MHz) δ 177.6, 167.5, 165.9, 160.3,
132.2, 132.1, 125.3, 118.3, 115.3, 63.5, 41.4, 37.9, 36.3,
27.3, 14.5; MS (ESI) m/z Calcd for C19H24N2O5S (M+): 392.1,
Found: 393.1 (M + H+); HPLC purity (condition I), 98.7%
(tR, 20.59 min), HPLC purity (condition VIII), 99.2%
(tR, 11.43 min).
(Z)-N-(2-(5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
ethyl)acetamide (25a)
To a solution of compound 76 (101 mg, 0.25 mmol) in 5 mL
of dichloromethane was added triethylamine (105 μL,
0.75 mmol) and acetic anhydride (26.0 μL, 0.28 mmol).
After being stirred at room temperature overnight, the reaction
solution was diluted with 50 mL of dichloromethane,
washed with water, collected the organic layer, dried over
Na2SO4, filtered, concentrated and purified by silica column
chromatography (33% dichloromethane in ethyl acetate) to
afford 74 mg (88.6%) of the title compound 25a as a light-
yellow solid. 1H-NMR (DMSO-d6, 500 MHz) δ 7.99 (1H, t, J =
(Z)-4-Cyano-N-(2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)ethyl)benzamide (25d)
6.0 Hz, NH), 7.86 (1H, s, CH), 7.59 (2H, d, J = 9.0 Hz, Ar), To a solution of 4-cyanobenzoic acid (46 mg, 0.31 mmol) in
7.10 (2H, d, J = 9.0 Hz, Ar), 4.11 (2H, q, J = 7.0 Hz, OCH2CH3), 3 mL of DMF was added DIPEA (131 μL, 0.75 mmol) followed
3.68 (2H, t, J = 6.0 Hz, CH2), 3.27 (2H, m, CH2), 1.72 by HBTU (114 mg, 0.30 mmol). After being stirred at room
(3H, s, CH3), 1.34 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR temperature for 1 h, compound 76 (101 mg, 0.25 mmol) was
(DMSO-d6, 125 MHz) δ 169.5, 167.5, 165.9, 160.4, 132.5, added and then the reaction mixture was stirred at room temp-
132.2, 125.3, 118.1, 115.3, 63.5, 41.4, 36.0, 22.4, 14.5; MS (ESI) erature overnight. The reaction solution was diluted with
m/z Calcd for C16H18N2O4S (M+): 334.1, Found: 335.0 (M + H+); 50 mL of ethyl acetate and washed with water (30 mL × 5), col-
HPLC purity (condition I), 97.5% (tR, 3.38 min), HPLC purity lected the organic layer, dried over Na2SO4, filtered, concen-
(condition III), 99.5% (tR, 4.82 min).
trated and purified by silica column chromatography (15%
3722 | Org. Biomol. Chem., 2013, 11, 3706–3732
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ethyl acetate in hexanes) to afford 97 mg (92.1%) of the title J = 5.5 Hz, NCH2), 3.81 (2H, d, J = 6.5 Hz, C(vO)OCH2), 3.49
compound 25d as a light-yellow solid. 1H-NMR (DMSO-d6, (2H, m, CH2N), 1.87 (1H, m, CH(CH3)2), 1.43 (3H, t, J = 7.5 Hz,
500 MHz) δ 8.89 (1H, t, J = 6.0 Hz, NH), 7.96 (2H, d, J = 9.0 Hz, OCH2CH3), 0.88 (6H, d, J = 6.5 Hz, CH(CH3)2); 13C-NMR
Ar), 7.87 (1H, s, CH), 7.86 (2H, d, J = 9.0 Hz, Ar), 7.59 (2H, d, J = (CDCl3, 125 MHz) δ 168.6, 166.9, 161.1, 157.0, 134.3, 132.5,
9.0 Hz, Ar), 7.10 (2H, d, J = 9.0 Hz, Ar), 4.11 (2H, q, J = 7.0 Hz, 125.8, 118.1, 115.4, 71.4, 64.0, 41.6, 39.6, 28.1, 19.1, 14.8;
OCH2CH3), 3.84 (2H, m, CH2), 3.54 (2H, m, CH2), 1.34 (3H, t, MS (ESI) m/z Calcd for C19H24N2O5S (M+): 392.1, Found: 393.0
J = 7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.7, (M + H+); HPLC purity (condition I), 98.2% (tR, 23.71 min),
166.0, 165.4, 160.4, 138.4, 132.6, 132.4, 132.2, 127.9, 125.3, HPLC purity (condition III), 97.7% (tR, 36.64 min).
118.3, 118.1, 115.3, 113.5, 63.5, 41.3, 37.0, 14.5; MS (ESI) m/z
(Z)-Benzyl (2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)ethyl)carbamate (26d)
Calcd for C22H19N3O4S (M+): 421.1, Found: 422.1 (M + H+);
HPLC purity (condition I), 99.1% (tR, 20.25 min), HPLC purity
(condition III), 98.3% (tR, 6.85 min).
The title compound 26d was prepared from compound 76
(70 mg, 0.17 mmol), benzyl chloroformate (27 μL, 0.19 mmol)
and DIPEA (75 μL, 0.43 mmol) in a manner similar to that
(Z)-Methyl (2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)ethyl)carbamate (26a)
described for 25a in 95.5% (70 mg) yield as a light-yellow
1
The title compound 26a was prepared from compound 76 solid. H-NMR (CDCl3, 500 MHz) δ 7.83 (1H, s, CH), 7.44 (2H,
(101 mg, 0.25 mmol), methyl chloroformate (21 μL, d, J = 8.5 Hz, Ar), 7.32–7.25 (5H, m, Ar), 6.97 (2H, d, J = 8.5 Hz,
0.28 mmol) and DIPEA (131 μL, 0.75 mmol) in a manner Ar), 5.07 (3H, s, C(vO)OCH2 + NH), 4.10 (2H, q, J = 7.5 Hz,
similar to that described for 25a in 98.2% (86 mg) yield as a OCH2CH3), 3.92 (2H, m, NCH2), 3.51 (2H, m, CH2N), 1.44 (3H,
1
yellow solid. H-NMR (DMSO-d6, 500 MHz) δ 7.87 (1H, s, CH), t, J = 7.5 Hz, OCH2CH3); 13C-NMR (CDCl3, 125 MHz) δ 168.6,
7.59 (2H, d, J = 8.0 Hz, Ar), 7.27 (1H, m, NH), 7.10 (2H, d, J = 166.9, 161.2, 156.6, 136.6, 134.4, 132.5, 128.6, 128.2, 125.8,
8.0 Hz, Ar), 4.10 (2H, q, J = 7.0 Hz, OCH2CH3), 3.70 (2H, m, 118.0, 115.4, 67.0, 64.0, 41.5, 39.7, 14.8; MS (ESI) m/z Calcd for
CH2), 3.50 (3H, s, CH3), 3.22 (2H, m, CH2), 1.35 (3H, t, J = C22H22N2O5S (M+): 426.1, Found: 427.0 (M + H+); HPLC purity
7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.5, (condition I), 97.3% (tR, 23.84 min), HPLC purity (condition
165.9, 160.4, 156.8, 132.5, 132.2, 125.3, 118.2, 115.3, 63.5, 51.3, III), 92.3% (tR, 38.28 min).
41.5, 37.8, 14.5; MS (ESI) m/z Calcd for C16H18N2O5S (M+):
(Z)-(9H-Fluoren-9-yl)methyl (2-(5-(4-ethoxybenzylidene)-
2,4-dioxothiazolidin-3-yl)ethyl)carbamate (26e)
350.1, Found: 351.0 (M + H+); HPLC purity (condition I),
100% (tR, 16.80 min), HPLC purity (condition V), 94.6%
(tR, 5.75 min).
The title compound 26e was prepared from compound 76
(101 mg, 0.25 mmol), Fmoc chloride (71 mg, 0.28 mmol) and
DIPEA (131 μL, 0.75 mmol) in a manner similar to that
described for 25a in 96.4% (124 mg) yield as a yellow solid.
(Z)-tert-Butyl (2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)ethyl)carbamate (26b)
The title compound 26b was prepared from compound 76 1H-NMR (CDCl3, 400 MHz) δ 7.79 (1H, s, CH), 7.73 (2H, d, J =
(405 mg, 0.50 mmol), di-tert-butyl dicarbonate (153 mg, 7.2 Hz, Fmoc), 7.56 (2H, d, J = 8.0 Hz, Ar), 7.37 (4H, m, Fmoc),
0.70 mmol) and DIPEA (261 μL, 1.50 mmol) in a manner 7.27 (2H, m, Fmoc), 6.92 (2H, d, J = 8.0 Hz, Ar), 5.17 (1H, m,
similar to that described for 25a in 97.9% (192 mg) yield as a NH), 4.32 (2H, d, J = 6.8 Hz, CH2-Fomc), 4.18 (1H, m, CH-Fomc),
light-yellow solid. 1H-NMR (CDCl3, 400 MHz) δ 7.83 (1H, s, 4.06 (2H, q, J = 6.8 Hz, OCH2CH3), 3.93 (2H, m, CH2), 3.52 (2H,
CH), 7.44 (2H, d, J = 7.6 Hz, Ar), 6.96 (2H, d, J = 7.6 Hz, Ar), m, CH2), 1.42 (3H, t, J = 6.8 Hz, OCH2CH3); 13C-NMR (CDCl3,
4.78 (1H, m, NH), 4.08 (2H, q, J = 6.4 Hz, OCH2CH3), 3.87 (2H, 100 MHz) δ 168.4, 166.7, 160.9, 156.4, 143.9, 141.2, 134.3,
m, CH2), 3.40 (2H, m, CH2), 1.44 (3H, t, J = 6.4 Hz, OCH2CH3), 132.3, 127.5, 127.0, 125.4, 125.1, 119.8, 117.7, 115.1, 67.0, 63.7,
1.37 (9H, s, C(CH3)3); 13C-NMR (CDCl3, 100 MHz) δ 168.3, 47.1, 41.3, 39.5, 14.6; MS (ESI) m/z Calcd for C29H26N2O5S
166.7, 160.9, 155.9, 133.9, 132.2, 125.6, 118.0, 115.1, 79.6, 63.7, (M+): 514.2, Found: 515.1 (M + H+); HPLC purity (condition I),
41.6, 38.8, 20.2, 14.6; MS (ESI) m/z Calcd for C19H24N2O5S 97.0% (tR, 28.04 min), HPLC purity (condition V), 96.0%
(M+): 392.1, Found: 393.1 (M + H+); HPLC purity (condition I), (tR, 44.48 min).
98.3% (tR, 23.74 min), HPLC purity (condition V), 98.1%
(Z)-N-(2-(5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
(tR, 36.56 min).
ethyl)methanesulfonamide (27a)
(Z)-Isobutyl (2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)ethyl)carbamate (26c)
The title compound 27a was prepared from compound 76
(101 mg, 0.25 mmol), methylsulfonyl chloride (21 μL,
The title compound 26c was prepared from compound 76 028 mmol) and DIPEA (131 μL, 0.75 mmol) in a manner
(70 mg, 0.17 mmol), isobutyl chloroformate (25 μL, similar to that described for 25a in 96.2% (89 mg) yield as a
1
0.19 mmol) and DIPEA (75 μL, 0.43 mmol) in a manner yellow solid. H-NMR (DMSO-d6, 500 MHz) δ 7.86 (1H, s, CH),
similar to that described for 25a in 96.4% (65 mg) yield as a 7.59 (2H, d, J = 9.0 Hz, Ar), 7.28 (1H, t, J = 6.0 Hz, NH), 7.10
light-yellow solid. 1H-NMR (CDCl3, 500 MHz) δ 7.84 (1H, s, (2H, d, J = 9.0 Hz, Ar), 4.11 (2H, q, J = 7.0 Hz, OCH2CH3), 3.74
CH), 7.45 (2H, d, J = 9.0 Hz, Ar), 6.97 (2H, d, J = 9.0 Hz, Ar), (2H, t, J = 6.0 Hz, CH2), 3.22 (2H, m, CH2), 2.88 (3H, s, CH3),
4.97 (1H, s, NH), 4.09 (2H, q, J = 7.5 Hz, OCH2CH3), 3.91 (2H, t, 1.34 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6,
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Organic & Biomolecular Chemistry
125 MHz) δ 167.5, 165.8, 160.4, 132.6, 132.2, 125.3, 118.1, dichloromethane and the reaction mixture was stirred at room
115.3, 63.5, 41.8, 14.5; MS (ESI) m/z Calcd for C15H18N2O5S2 temperature for 1 h. The solvent was removed by evaporation
(M+): 370.1, Found: 371.0 (M + H+); HPLC purity (condition II), and the precipitate was collected by filtration, washed with
95.2% (tR, 14.41 min), HPLC purity (condition III), 99.5% (tR, ethyl ether, and dried to afford 61 mg (84.8%) of pure 28a
5.31 min).
as a light-yellow solid. 1H-NMR (DMSO-d6, 500 MHz) δ 8.76
(1H, s, Im), 7.79 (1H, s, CH), 7.50 (1H, s, Im), 7.47 (2H, d, J =
7.5 Hz, Ar), 6.98 (2H, d, J = 7.5 Hz, Ar), 4.77 (2H, s, NCH2), 3.99
(2H, q, J = 6.0 Hz, OCH2CH3), 1.22 (3H, t, J = 6.0 Hz,
(Z)-4-Cyano-N-(2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)ethyl)benzenesulfonamide (27b)
The title compound 27b was prepared from compound 76 OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.1, 165.2,
(101 mg, 0.25 mmol), 4-cyano-benzenesulfonyl chloride 160.6, 134.6, 133.4, 132.3, 127.9, 125.1, 117.7, 115.4, 63.5, 35.6,
(55 mg, 0.28 mmol) and DIPEA (131 μL, 0.75 mmol) in a 14.4; MS (ESI) m/z Calcd for C16H15N3O3S (M+): 329.1, Found:
manner similar to that described for 25a in 92.0% (105 mg) 330.0 (M
+
H+); HPLC purity (condition IX), 97.5%
yield as a light-yellow solid. 1H-NMR (DMSO-d6, 500 MHz) δ (tR, 3.57 min), HPLC purity (condition X), 95.4% (tR, 6.74 min).
8.24 (1H, t, J = 6.0 Hz, NH), 8.07 (2H, d, J = 9.0 Hz, Ar), 7.91
(Z)-3-((6-Aminopyridin-2-yl)methyl)-5-(4-ethoxybenzylidene)-
(2H, d, J = 9.0 Hz, Ar), 7.84 (1H, s, CH), 7.58 (2H, d, J = 9.0 Hz,
thiazolidine-2,4-dione (28b)
Ar), 7.10 (2H, d, J = 9.0 Hz, Ar), 4.10 (2H, q, J = 7.0 Hz,
OCH2CH3), 3.68 (2H, t, J = 6.0 Hz, CH2), 3.10 (2H, m, CH2), Step 1. Potassium carbonate (131 mg, 0.95 mmol) was added
1.34 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6, to a solution of compound 2 (78 mg, 0.32 mmol) in 3 mL of
125 MHz) δ 167.4, 165.7, 160.4, 144.6, 133.5, 132.7, 132.2, anhydrous DMF at 0 °C. After stirring of the reaction mixture
127.1, 125.2, 117.9, 117.6, 115.3, 114.9, 63.5, 41.4, 14.5; MS for 20 min, a solution of tert-butyl (6-(bromomethyl)pyridin-
(ESI) m/z Calcd for C21H19N3O5S2 (M+): 457.1, Found: 458.0 2-yl)carbamate (90 mg, 0.32 mmol) in 1 mL of anhydrous DMF
(M + H+); HPLC purity (condition I), 97.7% (tR, 21.40 min), was added and then the reaction mixture was stirred at room
HPLC purity (condition III), 97.9% (tR, 24.19 min).
temperature for 3 h. The reaction was quenched by adding
water and extracted with ethyl acetate. The ethyl acetate layer
was washed with 10% NH4Cl aqueous solution followed by
water and dried over anhydrous Na2SO4, filtered, concentrated
(Z)-N-(2-(5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
ethyl)-1-methyl-1H-imidazole-4-sulfonamide (27c)
The title compound 27c was prepared from compound 76 and purified by silica column chromatography (20% ethyl
(101 mg, 0.25 mmol), 1-methylimidazole-4-sulfonyl chloride acetate in hexanes) to afford 112 mg (78.1%) of Boc-protected
(50 mg, 0.28 mmol) and DIPEA (131 μL, 0.75 mmol) in a 28b as a yellow solid. 1H-NMR (CDCl3, 500 MHz) δ 7.88
manner similar to that described for 25a in 98.0% (108 mg) (1H, s, CH), 7.86 (1H, d, J = 8.0 Hz, Py), 7.64 (1H, d, J =
yield as a light-yellow solid. 1H-NMR (DMSO-d6, 500 MHz) δ 8.0 Hz, Py), 7.48 (2H, d, J = 9.0 Hz, Ar), 6.99 (2H, d, J = 8.0 Hz,
7.83 (1H, s, CH), 7.74 (1H, m, NH), 7.68 (1H, s, Im), 7.66 (1H, s, Ar), 6.94 (1H, d, J = 8.0 Hz, Py), 4.94 (2H, s, NCH2), 4.10
Im), 7.58 (2H, d, J = 9.0 Hz, Ar), 7.10 (2H, d, J = 9.0 Hz, Ar), 4.10 (2H, q, J = 7.0 Hz, OCH2CH3), 1.50 (9H, s, C(CH3)3), 1.44 (3H, t,
(2H, q, J = 7.0 Hz, OCH2CH3), 3.69 (2H, t, J = 6.0 Hz, CH2), 3.67 J = 7.0 Hz, OCH2CH3).
(3H, s, Im-CH3), 3.10 (2H, m, CH2), 1.33 (3H, t, J = 7.0 Hz,
Step 2 (cleavage of Boc group). The title compound 28b was
OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.4, 165.7, prepared from Boc-protected 28b (60 mg, 0.13 mmol) in a
160.4, 139.5, 132.4, 132.2, 125.3, 123.9, 118.2, 115.3, 63.5, 41.6, manner similar to that described for 6 in 78.0% (48 mg) yield
33.4, 14.5; MS (ESI) m/z Calcd for C18H20N4O5S2 (M+): 436.1, as a yellow solid. H-NMR (DMSO-d6, 500 MHz) δ 7.93 (1H, s,
1
Found: 437.0 (M + H+); HPLC purity (condition IV), 100% (tR, CH), 7.68 (1H, t, J = 8.0 Hz, Py), 7.62 (2H, d, J = 9.0 Hz, Ar), 7.12
5.74 min), HPLC purity (condition II), 100% (tR, 8.67 min).
(2H, d, J = 8.0 Hz, Ar), 6.73 (1H, d, J = 8.0 Hz, Py), 6.64 (1H, d,
J = 8.0 Hz, Py), 4.84 (2H, s, NCH2), 4.12 (2H, q, J = 7.0 Hz,
OCH2CH3), 1.35 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR
(DMSO-d6, 125 MHz) δ 167.4, 165.4, 160.6, 155.9, 133.6, 132.4,
(Z)-3-((1H-Imidazol-5-yl)methyl)-5-(4-ethoxybenzylidene)-
thiazolidine-2,4-dione (28a)
Step 1. To a solution of compound 2 (150 mg, 0.60 mmol) in 125.2, 117.6, 115.4, 115.3, 110.9, 109.5, 63.5, 42.6, 14.4; MS
20 mL of anhydrous THF was added (1-trityl-1H-imidazol-5-yl)- (ESI) m/z Calcd for C18H17N3O3S (M+): 355.1, Found: 356.0
methanol (205 mg, 0.60 mmol), triphenylphosphine (237 mg, (M + H+); HPLC purity (condition IX), 99.1% (tR, 3.88 min),
0.90 mmol) and DIAD (178 μL, 0.90 mmol). The reaction HPLC purity (condition X), 97.4% (tR, 11.28 min).
mixture was stirred at 45 °C overnight. The solvent was
(Z)-1-(2-(5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
ethyl)guanidine (28c)
removed by evaporation and the residue was dissolved in ethyl
acetate, and washed with sat’d aqueous NH4Cl. The organic
layer was collected, dried over anhydrous Na2SO4, filtered, con- The title compound 28c was prepared from compound 2
centrated and purified by silica column chromatography (30% (101 mg, 0.25 mmol), N,N′-di-Boc-1H-pyrazole-1-carboxamidine
ethyl acetate in hexanes) to afford trityl-protected 28a in 61.1% (85 mg, 0.27 mmol) and DIPEA (65 μL, 0.38 mmol) in a
(210 mg) yield as a white solid.
manner similar to that described for 28b in 81.1% (108 mg)
Step 2 (cleavage of trityl group). The trityl-protected 28a yield as a yellow solid. 1H-NMR (DMSO-d6, 400 MHz) δ 7.84
(90 mg, 0.16 mmol) was dissolved in 20% TFA solution in (1H, s, CH), 7.70 (1H, m, NH), 7.56 (2H, d, J = 8.4 Hz, Ar),
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7.34–7.28 (3H, bs, NH + NH2), 7.07 (2H, d, J = 8.4 Hz, Ar), 4.06 6.96 (2H, d, J = 8.4 Hz, Ar), 4.08 (2H, q, J = 6.8 Hz, OCH2CH3),
(2H, q, J = 6.8 Hz, OCH2CH3), 3.72 (2H, m, CH2), 3.38 (2H, m, 4.06 (2H, m, CH2), 3.74 (2H, t, J = 5.2 Hz, CH2), 1.42 (3H, t,
CH2), 1.31 (3H, t, J = 6.8 Hz, OCH2CH3); 13C-NMR (DMSO-d6, J = 6.8 Hz, OCH2CH3); 13C-NMR (CDCl3, 100 MHz) δ 167.9,
100 MHz) δ 168.0, 166.2, 160.9, 157.3, 133.2, 132.6, 125.6, 166.1, 161.0, 134.4, 132.3, 125.4, 117.5, 115.2, 63.8, 42.6,
118.4, 115.8, 63.9, 41.1, 38.7, 14.9; MS (ESI) m/z Calcd for 39.8, 14.6; MS (ESI) m/z Calcd for C14H14ClNO3S (M+): 311.0,
C15H18N4O3S (M+): 334.1, Found: 335.1 (M + H+); HPLC purity Found: 312.0 (M + H+); HPLC purity (condition I), 98.9%
(condition IX), 100% (tR, 4.14 min), HPLC purity (condition II), (tR, 24.50 min), HPLC purity (condition III), 96.8% (tR,
98.5% (tR, 6.38 min).
38.45 min).
(Z)-5-(4-Ethoxybenzylidene)-3-propylthiazolidine-2,4-dione
(28d)
(Z)-tert-Butyl 2-(5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)acetate (28g)
Potassium carbonate (93 mg, 0.60 mmol) was added to a solu-
tion of compound 2 (75 mg, 0.30 mmol) in 3 mL of anhydrous
DMF at 0 °C. After stirring of the reaction mixture for 20 min,
a solution of 1-bromopropane (30 μL, 0.33 mmol) in 1 mL of
anhydrous DMF was added and then the reaction mixture was
stirred at room temperature overnight. The reaction was
quenched by adding water and extracted with ethyl acetate.
The ethyl acetate layer was washed with water (4 × 20 mL) and
dried over anhydrous Na2SO4, filtered, concentrated and puri-
fied by silica column chromatography (15% ethyl acetate in
hexanes) to afford 82 mg (93.9%) as a light-yellow solid.
1H-NMR (DMSO-d6, 500 MHz) δ 7.86 (1H, s, CH), 7.57 (2H, d,
J = 8.0 Hz, Ar), 7.09 (2H, d, J = 8.0 Hz, Ar), 4.11 (2H, q, J =
7.0 Hz, OCH2CH3), 3.60 (2H, NCH2), 1.59 (2H, m, CH2), 1.34
(3H, t, J = 7.0 Hz, OCH2CH3), 0.85 (3H, t, J = 8.0 Hz, CH2CH3);
13C-NMR (DMSO-d6, 125 MHz) δ 167.4, 165.8, 160.4, 132.9,
132.2, 125.3, 117.8, 115.3, 63.5, 43.0, 20.5, 14.4, 11.0; MS (ESI)
m/z Calcd for C15H17NO3S (M+): 291.1, Found: 292.0 (M + H+);
HPLC purity (condition I), 99.5% (tR, 26.10 min), HPLC purity
(condition III), 98.6% (tR, 44.36 min).
The title compound 28g was prepared from compound 2
(249 mg, 1.00 mmol), tert-butyl bromoacetate (215 mg,
1.10 mmol) and potassium carbonate (276 mg, 2.00 mmol) in
a manner similar to that described for 28d in 99.0% (360 mg)
yield as a pale-yellow solid. 1H-NMR (DMSO-d6, 500 MHz)
δ 7.95 (1H, s, CH), 7.62 (2H, d, J = 9.0 Hz, Ar), 7.11 (2H, d, J =
9.0 Hz, Ar), 4.37 (2H, s, NCH2), 4.12 (2H, q, J = 7.0 Hz,
OCH2CH3), 1.42 (9H, s, C(CH3)3), 1.35 (3H, t, J = 7.0 Hz,
OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 166.9, 165.6,
165.1, 160.7, 134.0, 132.5, 125.0, 117.0, 115.4, 115.3, 94.2, 82.4,
63.6, 42.8, 27.6, 27.5, 14.5; MS (ESI) m/z Calcd for C18H21NO5S
(M+): 363.1, Found: 364.0 (M + H+); HPLC purity (condition I),
97.3% (tR, 25.73 min), HPLC purity (condition III), 98.9%
(tR, 47.53 min).
(Z)-2-(5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)acetic
acid (28h)
The title compound 28h was prepared by deprotection of tert-
butyl group of compound 28g (300 mg, 0.82 mmol). Deprotec-
tion following the procedure of compound 6 gave the title com-
pound 28h as a yellow solid (93.4%, 235 mg). 1H-NMR (DMSO-
d6, 500 MHz) δ 13.40 (1H, bs, CO2H), 7.94 (1H, s, CH), 7.61
(2H, d, J = 8.0 Hz, Ar), 7.11 (2H, d, J = 8.0 Hz, Ar), 4.37 (2H, s,
NCH2), 4.12 (2H, q, J = 7.0 Hz, OCH2CH3), 1.34 (3H, t, J = 7.0
Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 168.0, 167.0,
165.1, 160.7, 133.9, 132.4, 125.0, 117.2, 115.4, 63.5, 42.2, 14.4;
MS (ESI) m/z Calcd for C14H13NO5S (M+): 307.1, Found: 308.0
(M + H+); HPLC purity (condition I), 100% (tR, 16.91 min),
HPLC purity (condition III), 98.3% (tR, 5.25 min).
(Z)-5-(4-Ethoxybenzylidene)-3-(2-hydroxyethyl)thiazolidine-
2,4-dione (28e)
The title compound 28e was prepared from compound 2
(249 mg, 1.00 mmol), ethane-1,2-diol (111 μL, 2.00 mmol), tri-
phenylphosphine (524 mg, 2.00 mmol) and DIAD (394 μL,
2.00 mmol) in a manner similar to that described for 9 in
95.2% (279 mg) yield as a white solid. 1H-NMR (DMSO-d6,
400 MHz) δ 7.83 (1H, s, CH), 7.55 (2H, d, J = 8.0 Hz, Ar), 7.06
(2H, d, J = 8.0 Hz, Ar), 4.07 (2H, q, J = 6.4 Hz, OCH2CH3), 3.68
(2H, m, CH2), 3.54 (2H, m, CH2), 1.32 (3H, t, J = 6.4 Hz,
OCH2CH3); 13C-NMR (DMSO-d6, 100 MHz) δ 167.4, 165.9,
160.4, 132.6, 132.3, 125.4, 117.5, 115.2, 63.5, 44.1, 39.9, 14.5;
(Z)-3-Benzyl-5-(4-ethoxybenzylidene)thiazolidine-2,4-dione
(28i)
MS (ESI) m/z Calcd for C14H15NO4S (M+): 293.1, Found: 294.0 The title compound 28i was prepared from compound 2
(M + H+); HPLC purity (condition I), 98.8% (tR, 3.55 min), (75 mg, 0.30 mmol), benzyl bromide (39 μL, 0.33 mmol) and
HPLC purity (condition VIII), 96.3% (tR, 6.54 min).
potassium carbonate (83 mg, 0.60 mmol) in a manner similar
to that described for 28d in 99.6% (101 mg) yield as a white
solid. 1H-NMR (DMSO-d6, 500 MHz) δ 7.92 (1H, s, CH),
7.59 (2H, d, J = 9.0 Hz, Ar), 7.35 (2H, d, J = 7.0 Hz, Ar), 7.31
(Z)-3-(2-Chloroethyl)-5-(4-ethoxybenzylidene)thiazolidine-
2,4-dione (28f)
The title compound 28f was prepared from compound 2 (3H, m, Ar), 7.10 (2H, d, J = 9.0 Hz, Ar), 4.83 (2H, s, NCH2), 4.11
(249 mg, 1.00 mmol), 2-chloroethanol (100 μL, 1.50 mmol), tri- (2H, q, J = 7.0 Hz, OCH2CH3), 1.34 (3H, t, J = 7.0 Hz,
phenylphosphine (393 mg, 1.50 mmol) and DIAD (295 μL, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.3, 165.6,
1.50 mmol) in a manner similar to that described for 9 in 160.5, 135.5, 133.5, 132.3, 128.6, 127.7, 127.6, 125.2, 117.6,
1
88.5% (276 mg) yield as a light-yellow solid. H-NMR (CDCl3, 115.3, 63.5, 44.5, 14.4; MS (ESI) m/z Calcd for C19H17NO3S
400 MHz) δ 7.85 (1H, s, CH), 7.42 (2H, d, J = 8.4 Hz, Ar), (M+): 339.1, Found: 340.1 (M + H+); HPLC purity (condition I),
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100% (tR, 25.50 min), HPLC purity (condition III), 99.7% 100% (tR, 4.62 min), HPLC purity (condition II), 98.1% (tR,
(tR, 48.88 min).
11.57 min).
(Z)-4-((5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
methyl)benzonitrile (28m)
(Z)-5-(4-Ethoxybenzylidene)-3-(pyridin-2-ylmethyl)thiazolidine-
2,4-dione (28j)
The title compound 28m was prepared from compound 2
(75 mg, 0.30 mmol), p-cyanobenzyl bromide (65 mg,
0.33 mmol) and potassium carbonate (83 mg, 0.60 mmol) in a
manner similar to that described for 28d in 81.5% (89 mg)
yield as a light-yellow solid. 1H-NMR (DMSO-d6, 500 MHz)
δ 7.93 (1H, s, CH), 7.84 (2H, d, J = 9.0 Hz, Ar), 7.61 (2H, d, J =
9.0 Hz, Ar), 7.51 (2H, d, J = 9.0 Hz, Ar), 7.11 (2H, d, J = 9.0 Hz,
Ar), 4.92 (2H, s, NCH2), 4.12 (2H, q, J = 7.0 Hz, OCH2CH3), 1.35
(3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz)
δ 167.4, 165.6, 160.6, 141.0, 133.7, 132.6, 132.4, 128.3, 125.2,
118.6, 117.6, 115.4, 110.5, 94.3, 63.5, 44.2, 14.5; MS (ESI) m/z
Calcd for C20H16N2O3S (M+): 364.1, Found: 365.1 (M + H+);
HPLC purity (condition I), 99.7% (tR, 26.08 min), HPLC purity
(condition III), 98.9% (tR, 42.43 min).
The title compound 28j was prepared from compound 2
(75 mg, 0.30 mmol), 2-picolyl chloride·HCl (54 mg,
0.33 mmol), sodium iodide (45 mg, 0.30 mmol) and potassium
carbonate (104 mg, 0.75 mmol) in a manner similar to that
described for 28d in 97.5% (99 mg) yield as a white solid.
1H-NMR (DMSO-d6, 500 MHz) δ 8.50 (1H, d, J = 4.0 Hz, Py),
7.92 (1H, s, CH), 7.84 (1H, t, J = 8.0 Hz, Py), 7.61 (2H, d, J =
8.0 Hz, Ar), 7.46 (1H, d, J = 8.0 Hz, Py), 7.34 (1H, t, J = 6.0 Hz,
Py), 7.11 (2H, d, J = 8.0 Hz, Ar), 4.99 (2H, s, NCH2), 4.12 (2H, q,
J = 7.0 Hz, OCH2CH3), 1.35 (3H, t, J = 7.0 Hz, OCH2CH3);
13C-NMR (DMSO-d6, 125 MHz) δ 167.3, 165.6, 160.5, 153.7,
148.7, 137.5, 133.4, 132.3, 125.2, 122.9, 121.7, 117.8, 115.3,
94.3, 63.5, 45.3, 14.4; MS (ESI) m/z Calcd for C18H16N2O3S
(M+): 340.1, Found: 341.0 (M + H+); HPLC purity (condition
IV), 99.0% (tR, 6.02 min), HPLC purity (condition II), 99.2%
(tR, 13.35 min).
(Z)-5-(4-Ethoxybenzylidene)-3-(4-nitrobenzyl)thiazolidine-
2,4-dione (28n)
The title compound 28n was prepared from compound 2
(150 mg, 0.60 mmol), p-nitrobenzyl bromide (143 mg,
0.66 mmol) and potassium carbonate (166 mg, 1.20 mmol) in a
manner similar to that described for 28d in 99.5% (229 mg)
yield as a white solid. 1H-NMR (DMSO-d6, 500 MHz) δ 8.22 (2H,
d, J = 9.0 Hz, Ar), 7.94 (1H, s, CH), 7.61 (2H, d, J = 9.0 Hz, Ar),
7.58 (2H, d, J = 9.0 Hz, Ar), 7.11 (2H, d, J = 9.0 Hz, Ar), 4.97 (2H,
s, NCH2), 4.12 (2H, q, J = 7.0 Hz, OCH2CH3), 1.36 (3H, t, J =
7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.9,
166.0, 161.0, 147.4, 143.5, 134.1, 132.8, 131.3, 129.2, 129.0,
125.6, 124.4, 124.2, 118.0, 115.8, 64.0, 44.4, 14.9; MS (ESI) m/z
Calcd for C19H16N2O5S (M+): 384.1, Found: 385.0 (M + H+);
HPLC purity (condition I), 97.4% (tR, 26.75 min), HPLC purity
(condition III), 94.7% (tR, 45.74 min).
(Z)-5-(4-Ethoxybenzylidene)-3-(pyridin-3-ylmethyl)thiazolidine-
2,4-dione (28k)
The title compound 28k was prepared from compound 2
(75 mg, 0.30 mmol), 3-picolyl chloride·HCl (54 mg,
0.33 mmol), sodium iodide (45 mg, 0.30 mmol) and potassium
carbonate (124 mg, 0.90 mmol) in a manner similar to that
described for 28d in 93.1% (95 mg) yield as a white solid.
1H-NMR (DMSO-d6, 500 MHz) δ 8.73 (1H, s, Py), 8.67 (1H, d,
J = 3.5 Hz, Py), 8.07 (1H, d, J = 8.0 Hz, Py), 7.92 (1H, s, CH),
7.65 (1H, d, J = 8.0 Hz, Py), 7.59 (2H, d, J = 9.0 Hz, Ar), 7.10
(2H, d, J = 9.0 Hz, Ar), 4.95 (2H, s, CH2), 4.11 (2H, q, J = 7.0 Hz,
OCH2CH3), 1.34 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR
(DMSO-d6, 125 MHz) δ 167.5, 165.6, 160.6, 146.1, 146.0, 139.4,
133.5, 132.8, 132.3, 125.2, 125.0, 117.7, 115.4, 94.3, 63.5, 42.0,
14.4; MS (ESI) m/z Calcd for C18H16N2O3S (M+): 340.1, Found: (Z)-3-(4-Aminobenzyl)-5-(4-ethoxybenzylidene)thiazolidine-
341.0 (M + H+); HPLC purity (condition IV), 100% (tR, 2,4-dione (28o)
4.47 min), HPLC purity (condition II), 97.1% (tR, 11.96 min).
To a solution of compound 28n (100 mg, 0.26 mol) in 10 mL
of chloroform–ethanol co-solvent (ratio, 4 : 1) was added tin(II)
chloride·dihydrate (293 mg, 1.30 mmol). The reaction mixture
was stirred at 45 °C overnight. The reaction mixture was
(Z)-5-(4-Ethoxybenzylidene)-3-(pyridin-4-ylmethyl)thiazolidine-
2,4-dione (28l)
The title compound 28l was prepared from compound 2 diluted with dichloromethane and washed with sat’d aqueous
(75 mg, 0.30 mmol), 4-picolyl chloride·HCl (54 mg, NaHCO3, collected the organic layer, dried over anhydrous
0.33 mmol), sodium iodide (45 mg, 0.30 mmol) and potassium Na2SO4, filtered, concentrated and purified by silica column
carbonate (124 mg, 0.90 mmol) in a manner similar to that chromatography (10% ethyl acetate in dichloromethane) to
described for 28d in 96.1% (98 mg) yield as a white solid. afford 88 mg (97.0%) of pure 28o as a yellow-orange solid.
1H-NMR (DMSO-d6, 500 MHz) δ 8.72 (2H, d, J = 8.0 Hz, Py), 1H-NMR (DMSO-d6, 500 MHz) δ 7.91 (1H, s, CH), 7.59 (2H, d,
7.95 (1H, s, CH), 7.68 (2H, d, J = 8.0 Hz, Py), 7.61 (2H, d, J = J = 8.0 Hz, Ar), 7.27 (2H, d, J = 8.0 Hz, Ar), 7.10 (2H, d, J = 8.0
9.0 Hz, Ar), 7.12 (2H, d, J = 9.0 Hz, Ar), 5.02 (2H, s, CH2), 4.13 Hz, Ar), 7.02 (2H, d, J = 8.0 Hz, Ar), 4.77 (2H, s, NCH2), 4.11
(2H, q, J = 7.0 Hz, OCH2CH3), 1.35 (3H, t, J = 7.0 Hz, (2H, q, J = 7.0 Hz, OCH2CH3), 1.34 (3H, t, J = 7.0 Hz,
OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.5, 165.5, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.3, 165.6,
160.6, 149.7, 146.1, 133.7, 132.4, 125.1, 123.5, 117.6, 115.4, 160.5, 138.3, 133.4, 132.3, 130.2, 129.0, 128.8, 128.5, 125.2,
63.5, 43.6, 14.4; MS (ESI) m/z Calcd for C18H16N2O3S (M+): 119.5, 118.2, 117.6, 115.3, 63.5, 44.2, 14.4; MS (ESI) m/z Calcd
340.1, Found: 341.0 (M + H+); HPLC purity (condition IV), for C19H18N2O3S (M+): 354.1, Found: 355.1 (M + H+); HPLC
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purity (condition IV), 100% (tR, 4.94 min), HPLC purity (con- 6.5 Hz, OCH2CH3), 1.58 (9H, s, C(CH3)3), 1.44 (3H, t, J = 6.5 Hz,
dition II), 97.3% (tR, 14.30 min).
OCH2CH3); 13C-NMR (CDCl3, 125 MHz) δ 168.1, 166.4, 165.5,
161.2, 135.6, 134.4, 132.7, 132.5, 129.8, 129.4, 128.8, 125.8,
118.2, 115.4, 81.4, 64.0, 45.0, 28.3, 14.8.
(Z)-tert-Butyl 4-((5-(4-ethoxybenzylidene)-2,4-dioxothiazolidin-
3-yl)methyl)benzoate (28p)
Step 2 (cleavage of tert-butyl group). The title compound 28r
The title compound 28p was prepared from compound 2 was prepared from tert-butyl-protected-28r (60 mg, 0.14 mmol)
(75 mg, 0.30 mmol), tert-butyl 4-(bromomethyl)benzoate in a manner similar to that described for 6 in 62.0% (42 mg)
(106 mg, 0.39 mmol) and potassium carbonate (83 mg, yield as a white solid. 1H-NMR (DMSO-d6, 500 MHz) δ 13.07
0.60 mmol) in a manner similar to that described for 28d in (1H, bs, CO2H), 7.93 (1H, s, CH), 7.89 (2H, d, J = 8.0 Hz, Ar),
96.4% (127 mg) yield as a white solid. 1H-NMR (DMSO-d6, 7.59 (2H, d, J = 8.0 Hz, Ar), 7.58 (1H, s, Ar), 7.49 (1H, t, J =
500 MHz) δ 7.93 (1H, s, CH), 7.88 (2H, d, J = 8.0 Hz, Ar), 7.60 8.0 Hz, Ar), 7.09 (2H, d, J = 8.0 Hz, Ar), 4.90 (2H, s, CH2), 4.11
(2H, d, J = 8.0 Hz, Ar), 7.42 (2H, d, J = 8.0 Hz, Ar), 7.10 (2H, d, (2H, q, J = 7.0 Hz, OCH2CH3), 1.34 (3H, t, J = 7.0 Hz,
J = 8.0 Hz, Ar), 4.89 (2H, s, CH2), 4.11 (2H, q, J = 7.0 Hz, OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.4, 166.9,
OCH2CH3), 1.52 (9H, s, C(CH3)3), 1.34 (3H, t, J = 7.0 Hz, 165.6, 160.6, 136.0, 133.7, 132.4, 132.2, 131.1, 129.0, 128.7,
OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.3, 165.5, 128.5, 125.1, 117.5, 115.3, 63.5, 44.3, 14.4; MS (ESI) m/z Calcd
164.6, 160.6, 140.4, 133.6, 132.4, 130.7, 129.3, 127.6, 125.2, for C20H17NO5S (M+): 383.1, Found: 384.0 (M + H+); HPLC
117.5, 115.4, 80.7, 63.5, 44.3, 27.7, 14.4; MS (ESI) m/z Calcd for purity (condition I), 97.4% (tR, 22.14 min), HPLC purity (con-
C24H25NO5S (M+): 439.1, Found: 440.0 (M + H+); HPLC purity dition III), 94.9% (tR, 32.36 min).
(condition VI), 100% (tR, 28.77 min), HPLC purity (condition
(Z)-2-((5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
III), 98.6% (tR, 51.92 min).
methyl)benzoic acid (28s)
(Z)-4-((5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
methyl)benzoic acid (28q)
Step 1. The compound tert-butyl-protected-28s was prepared
from compound 2 (290 mg, 1.16 mmol), tert-butyl 2-(bromo-
The title compound 28q was prepared by deprotection of tert- methyl)benzoate (314 mg, 1.16 mmol) and potassium carbon-
butyl group of compound 28p (100 mg, 0.23 mmol). Deprotec- ate (480 mg, 3.48 mmol) in a manner similar to that described
tion following the procedure of compound 6 gave the title com- for 28r (step 1) in 61.8% (315 mg) yield as a white-yellow solid.
1
pound 28q as a white solid (85 mg, 97.3%). H-NMR (DMSO- 1H-NMR (CDCl3, 500 MHz) δ 7.93 (1H, d, J = 7.5 Hz, Ar),
d6, 500 MHz) δ 12.92 (1H, bs, CO2H), 7.94 (1H, s, CH), 7.91 7.89 (1H, s, CH), 7.48 (2H, d, J = 8.5 Hz, Ar), 7.41 (1H, t, J =
(2H, d, J = 8.0 Hz, Ar), 7.60 (2H, d, J = 8.0 Hz, Ar), 7.42 (2H, d, 7.5 Hz, Ar), 7.30 (1H, t, J = 7.5 Hz, Ar), 7.09 (1H, d, J =
J = 8.0 Hz, Ar), 7.10 (2H, d, J = 8.0 Hz, Ar), 4.90 (2H, s, CH2), 7.5 Hz, Ar), 6.98 (2H, d, J = 8.5 Hz, Ar), 5.40 (2H, s, CH2), 4.10
4.11 (2H, q, J = 7.0 Hz, OCH2CH3), 1.34 (3H, t, J = 7.0 Hz, (2H, q, J = 8.0 Hz, OCH2CH3), 1.63 (9H, s, C(CH3)3), 1.44 (3H, t,
OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.4, 166.9, J = 8.0 Hz, OCH2CH3); 13C-NMR (CDCl3, 125 MHz) δ 168.1,
165.6, 160.6, 140.3, 133.6, 132.4, 130.2, 129.6, 127.5, 125.2, 166.6, 166.4, 161.1, 136.3, 134.4, 132.5, 132.2, 131.2, 127.5,
117.5, 115.3, 63.5, 44.3, 14.4; MS (ESI) m/z Calcd for 126.3, 125.8, 118.2, 115.4, 82.0, 64.0, 43.5, 28.4, 14.8.
C20H17NO5S (M+): 383.1, Found: 384.0 (M + H+); HPLC purity
(condition I), 99.1% (tR, 22.22 min), HPLC purity (condition was prepared from tert-butyl-protected-28s (100 mg,
Step 2 (cleavage of tert-butyl group). The title compound 28s
VII), 96.9% (tR, 38.40 min).
0.23 mmol) in a manner similar to that described for 6 in
67.1% (76 mg) yield as a white solid. 1H-NMR (DMSO-d6,
500 MHz) δ 13.21 (1H, s, CO2H), 7.95 (1H, d, J = 8.0 Hz, Ar),
7.93 (1H, s, CH), 7.62 (2H, d, J = 9.0 Hz, Ar), 7.53 (1H, t, J =
(Z)-3-((5-(4-Ethoxybenzylidene)-2,4-dioxothiazolidin-3-yl)-
methyl)benzoic acid (28r)
Step 1. Potassium carbonate (166 mg, 1.20 mmol) was added 8.0 Hz, Ar), 7.40 (1H, t, J = 8.0 Hz, Ar), 7.29 (1H, t, J =
to a solution of compound 2 (100 mg, 0.40 mmol) in 4 mL of 7.5 Hz, Ar), 7.11 (2H, d, J = 9.0 Hz, Ar), 5.22 (2H, s, CH2), 4.12
anhydrous DMF at 0 °C. After stirring of the reaction mixture (2H, q, J = 7.0 Hz, OCH2CH3), 1.34 (3H, t, J = 7.0 Hz,
for 20 min, a solution of tert-butyl 3-(bromomethyl)benzoate OCH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 168.1, 167.5,
(110 mg, 0.40 mmol) in 1 mL of anhydrous DMF was added 165.8, 160.5, 136.2, 133.5, 132.5, 132.3, 130.8, 129.2, 127.4,
and then the reaction mixture was stirred at room temperature 125.7, 125.2, 117.8, 115.4, 63.5, 43.2, 14.5; MS (ESI) m/z Calcd
for 3 h. The reaction was quenched by adding water and for C20H17NO5S (M+): 383.1, Found: 384.0 (M + H+); HPLC
extracted with ethyl acetate. The ethyl acetate layer was washed purity (condition I), 98.6% (tR, 22.48 min), HPLC purity (con-
with 10% NH4Cl aqueous solution followed by water and dried dition XI), 98.7% (tR, 18.85 min).
over anhydrous Na2SO4, filtered, concentrated and purified by
silica column chromatography (10% ethyl acetate in hexanes)
3-(2-(Tritylamino)ethyl)thiazolidine-2,4-dione (29)
to afford 116 mg (66.0%) of tert-butyl-28r as a light-yellow To a solution of compound 1 (900 mg, 7.69 mmol) in 80 mL
solid. 1H-NMR (CDCl3, 500 MHz) δ 8.02 (1H, s, CH), 7.92 of anhydrous THF was 2-(tritylamino)ethanol (3.03 g,
(1H, d, J = 7.5 Hz, Ar), 7.86 (1H, s, Ar), 7.57 (1H, d, J = 10.00 mmol), triphenylphosphine (2.72 g, 10.40 mmol) and
7.5 Hz, Ar), 7.45 (2H, d, J = 9.0 Hz, Ar), 7.38 (1H, d, J = 7.5 Hz, Ar), DIAD (1.97 mL, 10.00 mmol). The reaction mixture was stirred
6.97 (2H, d, J = 9.0 Hz, Ar), 4.93 (2H, s, NCH2), 4.08 (2H, q, J = at room temperature overnight. The solvent was removed by
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evaporation and the residue was dissolved in ethyl acetate, and (2H, m, CH2), 1.38 (3H, t, J = 7.0 Hz, OCH2CH3); 13C-NMR
washed with sat’d aqueous NH4Cl. The organic layer was col- (DMSO-d6, 125 MHz) δ 168.0, 166.0, 157.4, 132.6, 128.6, 127.6,
lected, dried over anhydrous Na2SO4, filtered, concentrated 121.5, 121.4, 120.9, 112.8, 94.2, 64.0, 36.9, 14.5; MS (ESI) m/z
and purified by silica column chromatography (20% ethyl Calcd for C14H16N2O3S (M+): 292.1, Found: 293.0 (M + H+);
acetate in hexanes) to afford 29 in 75.0% (2.31 g) yield as a HPLC purity (condition IX), 98.3% (tR, 3.69 min), HPLC purity
white solid. 1H-NMR (CDCl3, 500 MHz) δ 7.43–7.21 (15H, m, (condition X), 99.2% (tR, 4.57 min).
Trt), 4.08 (2H, s, thiazolidine-CH2), 3.52 (2H, t, J = 7.0 Hz,
(Z)-3-(2-Aminoethyl)-5-(4-methylbenzylidene)thiazolidine-
NCH2), 2.61 (2H, m, CH2NH).
2,4-dione (30d)
(Z)-3-(2-Aminoethyl)-5-benzylidenethiazolidine-2,4-dione (30a)
The title compound 30d was prepared from 4-methylbenzalde-
Benzaldehyde (63 μL, 0.62 mmol) and compound 29 (250 mg, hyde (73 μL, 0.62 mmol), compound 29 (250 mg, 0.62 mmol)
0.62 mmol) were dissolved in 10 mL of anhydrous ethanol at and piperidine (7.0 μL, 0.062 mmol) in a manner similar to
room temperature, and piperidine (7 μL, 0.062 mmol) was that described for 30a in 36.0% (83 mg) yield as a cream solid.
added to the reaction solution. The reaction mixture was 1H-NMR (DMSO-d6, 400 MHz) δ 8.02 (2H, bs, NH2), 7.90 (1H, s,
stirred at 75 °C for 1 day and then allowed to cool down to CH), 7.54 (2H, d, J = 8.0, Ar), 7.37 (2H, d, J = 8.0, Ar), 3.95–3.87
room temperature until a yellow crystalline precipitate formed, (2H, m, CH2), 3.14–3.03 (2H, m, CH2), 2.37 (3H, s, CH3);
and the solid was collected by filtration, washed with water 13C-NMR (DMSO-d6, 100 MHz) δ 167.8, 166.0, 141.0, 132.8,
and ethyl acetate, and dried to afford the trityl-protected form 130.2, 130.2, 130.1, 120.4, 39.2, 36.9, 21.1; MS (ESI) m/z Calcd
of the title compound ("trityl-30a") as a white solid. Deprotec- for C13H14N2O2S (M+): 262.1, Found: 263.0 (M + H+); HPLC
tion of the trityl group with TFA according to the procedure for purity (condition IX), 95.4% (tR, 3.32 min), HPLC purity (con-
compound 6 gave the title compound 30a as a white solid dition X), 97.6% (tR, 4.59 min).
(48.1%, 74 mg). 1H-NMR (DMSO-d6, 500 MHz) δ 7.91 (1H, s,
CH), 7.87 (2H, bs, NH2), 7.62 (2H, d, J = 9.0 Hz, Ar), 7.52–7.47
(Z)-3-(2-Aminoethyl)-5-(4-propylbenzylidene)thiazolidine-
2,4-dione (30e)
(3H, m, Ar), 3.88 (2H, t, J = 5.6, CH2), 3.09 (2H, t, J = 5.6, CH2);
13C-NMR (DMSO-d6, 125 MHz) δ 168.2, 166.3, 133.3, 133.1, The title compound 30e was prepared from 4-propylbenzalde-
131.1, 130.4, 129.9, 122.0, 39.6, 37.3; MS (ESI) m/z Calcd for hyde (92 mg, 0.62 mmol), compound 29 (250 mg, 0.62 mmol)
C12H12N2O2S (M+): 248.1, Found: 249.0 (M + H+). HPLC purity and piperidine (7.0 μL, 0.062 mmol) in a manner similar to
(condition IX), 99.8% (tR, 3.56 min), HPLC purity (condition that described for 30a in 38.0% (95 mg) yield as a white solid.
II), 98.0% (tR, 4.54 min).
1H-NMR (DMSO-d6, 400 MHz) δ 8.03 (2H, bs, NH2), 7.91 (1H, s,
CH), 7.56 (2H, d, J = 8.4, Ar), 7.38 (2H, d, J = 8.4, Ar), 3.91 (2H,
t, J = 5.6, CH2), 3.14–3.05 (2H, m, CH2), 2.61 (2H, t, J = 7.2,
CH2CH2CH3), 1.61 (2H, sept, J = 7.2, CH2CH2CH3), 0.90 (3H, t,
(Z)-3-(2-Aminoethyl)-5-(3-ethoxybenzylidene)thiazolidine-2,4-
dione (30b)
The title compound 30b was prepared from 3-ethoxybenzalde- J = 7.2, CH2CH2CH3); 13C-NMR (DMSO-d6, 100 MHz) δ 167.9,
hyde (87 μL, 0.62 mmol) and compound 29 (250 mg, 166.0, 145.6, 132.8, 130.5, 130.2, 129.5, 120.5, 39.2, 37.1, 36.9,
0.62 mmol) and piperidine (7.0 μL, 0.062 mmol) in a manner 23.8, 13.6; MS (ESI) m/z Calcd for C15H18N2O2S (M+): 290.1,
similar to that described for 30a in 20.4% (50 mg) yield as a Found: 291.1 (M + H+); HPLC purity (condition IX), 99.3%
white solid. 1H-NMR (DMSO-d6, 500 MHz) δ 7.96 (2H, bs, (tR, 3.78 min), HPLC purity (condition X), 99.6% (tR, 6.24 min).
NH2), 7.91 (1H, s, CH), 7.46 (1H, t, J = 8.4, Ar), 7.22 (2H, m, Ar),
(Z)-3-(2-Aminoethyl)-5-(4-hydroxybenzylidene)thiazolidine-
7.08 (1H, d, J = 8.4, Ar), 4.08 (2H, q, J = 6.8, CH2CH3), 3.91 (2H,
2,4-dione (30f)
t, J = 5.6, CH2), 3.09 (2H, t, J = 5.6, CH2), 1.35 (3H, t, J = 6.8,
CH2CH3); 13C-NMR (DMSO-d6, 125 MHz) δ 167.7, 165.9, 159.0, The title compound 30f was prepared from 4-hydroxybenzalde-
134.3, 132.8, 130.6, 121.9, 121.7, 116.9, 115.9, 63.3, 36.9, 14.6; hyde (76 mg, 0.62 mmol), compound 29 (250 mg, 0.62 mmol)
MS (ESI) m/z Calcd for C14H16N2O3S (M+): 292.1, Found: 293.0 and piperidine (20.0 μL, 0.19 mmol) in a manner similar to
(M + H+); HPLC purity (condition IX), 91.4% (tR, 3.51 min), that described for 30a in 43.0% (102 mg) yield as a yellow solid
HPLC purity (condition X), 97.3% (tR, 4.78 min).
1H-NMR (DMSO-d6, 400 MHz) δ 10.4 (1H, bs, OH), 7.91–7.78
(3H, bs, NH2 + CH), 7.51 (2H, d, J = 8.8, Ar), 6.94 (2H, d, J = 8.8,
Ar), 3.89 (2H, t, J = 6.0, CH2), 3.07 (2H, t, J = 6.0, CH2);
13C-NMR (DMSO-d6, 100 MHz) δ 168.0, 166.1, 160.2, 133.3,
(Z)-3-(2-Aminoethyl)-5-(2-ethoxybenzylidene)thiazolidine-2,4-
dione (30c)
The title compound 30c was prepared from 2-ethoxybenzalde- 132.6, 123.8, 116.9, 116.5, 37.0, 22.4; MS (ESI) m/z Calcd for
hyde (87 μL, 0.62 mmol) and compound 29 (250 mg, C12H12N2O3S (M+): 264.1, Found: 265.0 (M + H+); HPLC purity
0.62 mmol) and piperidine (7.0 μL, 0.062 mmol) in a manner (condition IX), 97.4% (tR, 2.88 min).
similar to that described for 30a in 35.4% (64 mg) yield as a
1
(Z)-3-(2-Aminoethyl)-5-(4-isobutoxybenzylidene)thiazolidine-
2,4-dione (30g)
white solid. H-NMR (DMSO-d6, 500 MHz) δ 8.16 (1H, s, CH),
7.96 (2H, bs, NH2), 7.48 (1H, t, J = 6.5 Hz, Ar), 7.42 (1H, t, J =
6.5 Hz, Ar), 7.17 (1H, t, J = 6.5 Hz, Ar), 7.10 (1H, t, J = 6.5 Hz, To tritylated-30f (100 mg, 0.20 mmol) and potassium carbo-
Ar), 4.17 (2H, q, J = 7.0 Hz, OCH2CH3), 3.89 (2H, m, CH2), 3.08 nate (82 mg, 0.60 mmol) in 3 mL of anhydrous DMF was added
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isobutyl iodide (54 μL, 0.40 mmol). The reaction was allowed (Z)-3-(2-Aminoethyl)-5-(2-isobutoxybenzylidene)thiazolidine-
to stir at 70 °C for 12 h. The reaction solution was diluted with 2,4-dione (30j)
ethyl acetate and washed with water, brine, collected the
To tritylated-30i (100 mg, 0.20 mmol) and potassium carbo-
organic phase, dried over anhydrous Na2SO4, filtered, concen-
nate (82 mg, 0.60 mmol) in 3 mL of anhydrous DMF was added
trated and purified by silica column chromatography. Depro-
isobutyl iodide (54 μL, 0.40 mmol). The reaction was allowed
to stir at 70 °C for 12 h. The reaction solution was diluted with
ethyl acetate and washed with water, brine, collected the
organic phase, dried over anhydrous Na2SO4, filtered, concen-
tection following the procedure for compound 6 gave the title
compound 30g as a yellow solid (65.2%, 56 mg). 1H-NMR
(DMSO-d6, 400 MHz) δ 7.92 (2H, bs, NH2), 7.90 (1H, s, CH),
7.60 (2H, d, J = 8.4, Ar), 7.12 (2H, d, J = 8.4, Ar), 3.90 (2H, t, J =
trated and purified by silica column chromatography. Depro-
5.6, CH2), 3.83 (2H, t, J = 6.8, CH2iPr), 3.13–3.03 (2H, m, CH2),
tection following the procedure for compound 6 gave the title
2.03 (1H, sept, J = 6.8, CHMe2), 0.98 (6H, t, J = 6.8, 2 × CH3);
compound 30j as a yellow solid (73.7%, 64 mg). 1H-NMR
13C-NMR (DMSO-d6, 100 MHz) δ 167.9, 166.1, 160.8, 132.9,
(DMSO-d6, 500 MHz) δ 8.18 (1H, s, CH), 7.97 (2H, s, NH2), 7.49
132.3, 125.3, 118.2, 115.5, 74.0, 36.9, 27.6, 19.0; MS (ESI) m/z
(1H, t, J = 8.0 Hz, Ar), 7.42 (1H, d, J = 8.0 Hz, Ar), 7.17 (1H, d,
J = 8.0 Hz, Ar), 7.10 (1H, t, J = 8.0 Hz, Ar), 3.91 (2H, m, OCH2),
Calcd for C16H20N2O3S (M+): 320.1, Found: 321.1 (M + H+);
HPLC purity (condition IX), 97.6% (tR, 3.97 min), HPLC purity
3.87 (2H, m, NCH2), 3.09 (2H, m, CH2), 2.08 (1H, m,
(condition X), 99.8% (tR, 6.47 min).
CH(CH3)2), 1.02 (6H, d, J = 7.0 Hz, CH(CH3)2); 13C-NMR
(DMSO-d6, 125 MHz) δ 167.9, 166.0, 157.7, 132.7, 128.2, 127.0,
(Z)-3-(2-Aminoethyl)-5-(4-(benzyloxy)benzylidene)thiazolidine-
2,4-dione (30h)
121.5, 121.3, 121.0, 113.0, 74.3, 36.9, 27.7, 18.9; MS (ESI) m/z
Calcd for C16H20N2O3S (M+): 320.1, Found: 321.0 (M + H+);
HPLC purity (condition IX), 99.4% (tR, 3.81 min), HPLC purity
(condition II), 99.2% (tR, 5.29 min).
To tritylated-30f (100 mg, 0.20 mmol) and potassium carbon-
ate (82 mg, 0.60 mmol) in 3 mL of anhydrous DMF was added
benzyl bromide (50 μL, 0.40 mmol). The reaction was allowed
to stir at room temperature for 3 h. The reaction solution was
diluted with ethyl acetate and washed with water, brine, col-
lected the organic phase, dried over anhydrous Na2SO4, fil-
tered, concentrated and purified by silica column
chromatography. Deprotection following the procedure for
compound 6 gave the title compound 30h as a yellow solid
(Z)-3-(2-Aminoethyl)-5-(2-(benzyloxy)benzylidene)thiazolidine-
2,4-dione (30k)
To tritylated-30i (100 mg, 0.20 mmol) and potassium carbo-
nate (82 mg, 0.60 mmol) in 3 mL of anhydrous DMF was
added benzyl bromide (50 μL, 0.40 mmol). The reaction was
allowed to stir at room temperature for 3 h. The reaction solu-
tion was diluted with ethyl acetate and washed with water,
brine, collected the organic phase, dried over anhydrous
Na2SO4, filtered, concentrated and purified by silica column
chromatography. Deprotection following the procedure for
compound 6 gave the title compound 30k as a pale-yellow
solid (95.1%, 89 mg). 1H-NMR (DMSO-d6, 500 MHz) δ 8.15
(1H, s, CH), 7.92 (2H, s, NH2), 7.47 (5H, m, Ar), 7.42 (1H, t,
J = 8.0 Hz, Ar), 7.37 (1H, t, J = 8.0 Hz, Ar), 7.28 (1H, t, J =
8.0 Hz, Ar), 7.13 (1H, t, J = 8.0 Hz, Ar), 5.26 (2H, s, CH2), 3.88
(2H, m, CH2), 3.07 (2H, m, CH2); 13C-NMR (DMSO-d6,
125 MHz) δ 167.9, 166.0, 157.2, 136.5, 132.6, 128.5, 128.4,
128.1, 127.7, 127.3, 121.7, 121.6, 121.3, 113.4, 69.9, 36.9;
MS (ESI) m/z Calcd for C19H18N2O3S (M+): 354.1, Found: 355.0
(M + H+); HPLC purity (condition IX), 99.3% (tR, 4.13 min),
HPLC purity (condition X), 99.6% (tR, 5.87 min).
1
(97.0%, 91 mg). H-NMR (DMSO-d6, 400 MHz) δ 8.29 (2H, bs,
NH2), 7.88 (1H, s, CH) 7.61 (2H, d, J = 9.2, Ar), 7.46 (2H, d, J =
7.2, Ar), 7.40 (2H, d, J = 7.2, Ar), 7.34 (1H, d, J = 7.2, Ar), 7.19
(2H, d, J = 9.2, Ar), 5.19 (2H, s, CH2), 3.91 (2H, t, J = 6.0, CH2),
3.09–2.99 (2H, m, CH2); 13C-NMR (DMSO-d6, 100 MHz) δ 167.9,
166.0, 160.2, 136.5, 132.6, 132.2, 128.5, 128.1, 127.9, 125.6,
118.6, 115.9, 69.5, 36.5; MS (ESI) m/z Calcd for C19H18N2O3S
(M+): 354.1, Found: 355.1 (M + H+); HPLC purity (condition
IX), 98.6% (tR, 3.91 min), HPLC purity (condition X), 97.1%
(tR, 6.40 min).
(Z)-3-(2-Aminoethyl)-5-(2-hydroxybenzylidene)thiazolidine-
2,4-dione (30i)
The title compound 30i was prepared from 2-hydroxybenzalde-
hyde (76 mg, 0.62 mmol), compound 29 (250 mg, 0.62 mmol)
and piperidine (20.0 μL, 0.19 mmol) in a manner similar to
that described for 30a in 50.0% (117 mg) yield as a yellow
(Z)-4-((2-((3-(2-Aminoethyl)-2,4-dioxothiazolidin-5-ylidene)-
methyl)phenoxy)methyl)benzonitrile (30l)
1
solid. H-NMR (DMSO-d6, 500 MHz) δ 10.75 (1H, s, OH), 8.13
(1H, s, CH), 7.98 (2H, s, NH2), 7.36 (1H, d, J = 8.0 Hz, Ar), 7.32 To tritylated-30i (100 mg, 0.20 mmol) and potassium carbo-
(1H, d, J = 8.0 Hz, Ar), 7.00 (1H, d, J = 8.0 Hz, Ar), 6.94 (1H, d, nate (82 mg, 0.60 mmol) in 3 mL of anhydrous DMF was added
J = 8.0 Hz, Ar), 3.89 (2H, m, CH2), 3.08 (2H, m, CH2); 13C-NMR 4-cyanobenzyl bromide (78 mg, 0.40 mmol). The reaction was
(DMSO-d6, 125 MHz) δ 168.1, 166.1, 157.4, 132.5, 128.4, 128.2, allowed to stir at room temperature overnight. The reaction
119.9, 119.8, 119.7, 116.2, 39.0, 36.9; MS (ESI) m/z Calcd for solution was diluted with ethyl acetate and washed with water,
C12H12N2O3S (M+): 264.1, Found: 265.0; MS (ESI) m/z Calcd for brine, collected the organic phase, dried over anhydrous
C12H12N2O3S (M+): 264.1, Found: 265.1 (M + H+); HPLC purity Na2SO4, filtered, concentrated and purified by silica column
(condition IX), 97.9% (tR, 3.19 min), HPLC purity (condition chromatography. Deprotection following the procedure for
X), 96.8% (tR, 3.86 min).
compound 6 gave the title compound 30l as a light-yellow
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Organic & Biomolecular Chemistry
solid (79.1%, 78 mg). 1H-NMR (DMSO-d6, 500 MHz) δ 8.15
(1H, s, CH), 7.91 (2H, s, NH2), 7.89 (2H, d, J = 8.0 Hz, Ar), 7.66
(2H, d, J = 8.0 Hz, Ar), 7.48 (2H, t, J = 8.0 Hz, Ar), 7.23 (1H, d,
J = 8.0 Hz, Ar), 7.15 (1H, t, J = 8.0 Hz, Ar), 5.38 (2H, s, CH2),
3.89 (2H, m, CH2), 3.08 (2H, m, CH2); 13C-NMR (DMSO-d6,
125 MHz) δ 167.9, 165.9, 156.8, 142.2, 132.5, 128.6, 128.1,
127.1, 122.0, 121.8, 121.6, 118.6, 113.3, 110.8, 69.0, 36.9;
MS (ESI) m/z Calcd for C20H17N3O3S (M+): 379.1, Found: 380.1
(M + H+); HPLC purity (condition IX), 96.1% (tR, 3.80 min),
HPLC purity (condition X), 98.4% (tR, 5.43 min).
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water soluble tetrazolium-1 (WST-1) assay as previously
described.20 Briefly, cells (∼5000 per well) were seeded in 96
well plates, allowed to recover for 16–20 hours, and then
treated with the indicated test compound for 48 hours. After
incubation, WST-1 reagent was added and absorbance was
read at 450 nm with background subtraction taken at 650 nm.
Values were normalized to the control (DMSO only treated)
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Luciferase assay. HeLa cells were seeded in 24-well plates
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∼60–70% confluent. Cells were transfected with activator
protein-1 (pAP1(PMA)-TA-Luc; Clontech) or the serum
response element (pGL4.33-SRE; Promega) luciferase reporter
plasmids (250 ng per well) using Lipofectamine™ (Invitrogen).
After 16 hours, cells were treated with increasing amount of
compounds as indicated for 20 minutes, followed by stimu-
lation with EGF (25 ng mL−1) for 4.5 h. The luciferase activity
in the cell extracts was determined with a Dual Luciferase
Assay System (Promega) according to the manufacturer’s
instructions. Luciferase activities were monitored with a
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Acknowledgements
We thank the National Institutes of Health (CA120215 to
P. S. and A. D. M., GM100693 to R. S.), the University of Mary-
land Computer-Aided Drug Design Center and the University
of Maryland School of Pharmacy (S. F.) for financial support of
this work.
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