1-Oxo-3-substitute-isothiochroman-4-carboxylic acid compounds: Synthesis and biological activities of FAS inhibition

Article abstract of DOI:10.1016/j.bmcl.2008.12.010

A new series 1-oxo-3-substitute-isothiochroman-4-carboxylic acid compounds have been designed and synthesized. Screening of these molecules for FAS inhibition in vitro has indicated that compounds 2c and 2d showed more effective FAS inhibition activities

Full text of DOI:10.1016/j.bmcl.2008.12.010

Bioorganic & Medicinal Chemistry Letters 19 (2009) 770–772
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
1-Oxo-3-substitute-isothiochroman-4-carboxylic acid compounds: Synthesis
and biological activities of FAS inhibition
Xiaokui Wang a, Guoming Zhao a, Yao Chen a,b, Xiaowei Xu a,c, Wu Zhong a, Lili Wang a, Song Li a,
*
a Beijing Institute of Pharmacology & Toxicology, Taiping Road 27, Beijing 100850, PR China
b School of Pharmaceutical Engineering, Shenyang Pharmaceutical University, Shenyang 110016, PR China
c Inner Mongolia Medical College, Hohht 010059, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series 1-oxo-3-substitute-isothiochroman-4-carboxylic acid compounds have been designed and
synthesized. Screening of these molecules for FAS inhibition in vitro has indicated that compounds 2c
and 2d showed more effective FAS inhibition activities and higher therapeutic index than C75.
Ó 2008 Elsevier Ltd. All rights reserved.
Received 30 October 2008
Revised 2 December 2008
Accepted 4 December 2008
Available online 7 December 2008
Keywords:
Fatty acid synthase
Anti-obesity
1-Oxo-3-substitute-isothiochroman-4-
carboxylic acid
Obesity has emerged as a worldwide health, economy and so-
cial psychology problem. It has been one of the most common met-
abolic pathologies in contemporary society, that is, associated with
increased risk of type II diabetes, cardiovascular and cerebrovascu-
lar diseases.1
Fatty acid synthase (FAS) is the key enzyme in de novo lipogen-
esis from acetyl-CoA, malonyl-CoA and NADPH, which has been
proved to be a new appetite and body weight regulation target in
mice. FAS is a multi-enzyme complex containing seven proteins
as functional domains.2 Among the seven moieties of FAS, the
ketoacyl synthase domain (KS) is the potential target of C75 (1 in
Fig. 1), which has been known as a novel inhibitor of FAS and it
can lead a distinct decrease of food intake and body weight of mice
without significant toxity.3
conc. sulfuric acid and methanol. Compound 5 reacted with NaH
in THF at 0 °C for 1 h, followed by the addition of heptaldehyde
keeping on stirring for another 4–6 h at same temperature, after
usual acidification and purification, provided the expected com-
pound 6a as a white solid in 90% yields (Scheme 1). The reaction
has been used generally in organic synthesis named aldol
reactions.4
1,4-Addition of thioacetic acid to the compound 6a gave the
corresponding product 7a according to Holmberg (Scheme 1).5
A
solution of 6a and thioacetic acid (1:2) was stirred at 80–85 °C in
dry pyridine for 3 days, intermediates 7a was obtained as a thick
liquid. The liquid was hydrolyzed from acetylthio group to the thiol
in HCl solution (6 mol/L) without purification, and then it was cy-
clized to the mixture of two diastereomers by refluxing with TFA
for 24 h. The mixture of 8a and 9a, the trans- and cis-isomers, were
obtained as a white solid in total 48% yield (Scheme 2).
Our interest was initially kindled by the novel mechanism and
the structure of C75. We have planned to introduce a benzene ring
to replace the unstable
a-methylene moiety, which has been
known as a key pharmacophore of C75. Some different carbon-
chains and sulfur atom have also been introduced based on bio-
isosteric rule to investigate structure–function relationship of FAS
inhibitors. The rationally designed molecules (2a–f in Fig. 1) has
been synthesized and evaluated for their FAS inhibitory activities.
The synthesis of the compounds 2a and 3a has been described
as a sample. Commercially available 2-Carboxymethyl-benzoic
acid 4 was transferred to the dimethylester 5 by reaction with
* Corresponding author. Tel.: +86 010 66931250.
E-mail address: wxkcaptain@yahoo.com.cn (S. Li).
Figure 1.
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.12.010

X. Wang et al. / Bioorg. Med. Chem. Lett. 19 (2009) 770–772
771
Table 2
Classical complement inhibition, cytotoxicity and apoptosis assay results for
compounds 2a–f
a
a
Compound
IC50
(lM)
TC50 (lM)
T.I.b
5.61
C75
2a
2b
2c
2d
2e
2f
15.53( 2.26)
36.73( 4.03)
26.86( 3.76)
12.32( 1.80)
8.29( 1.24)
4.11( 1.03)
3.62( 0.46)
87.09( 14.25)
>200
>200
84.18( 15.37)
88.58( 15.77)
11.99( 2.26)
9.67( 2.23)
6.83
10.69
2.92
2.67
a
Values are means of three experiments, standard deviation is given in
parentheses.
b
Scheme 1. Reagents and conditions: (a) CH3OHÁH2SO4, 90%; (b) NaH/THF,
n-C6H13CHO, 90%; (c) CH3COSH/pyridine, 80–85 °C/3days, 57%.
In vitro therapeutic index (TC50/IC50).
with the cytotoxic estimated by the MTT method of HLF cell (Table
2). Finally, it will be a favorite substituent when the carbon-chain at
C5 position is n-C8H17– or n-C9H19–, and compounds 2c and 2d
showed more effective FAS inhibition activities and higher thera-
peutic index than C75.
The crystal structure of KS of human FAS has not been reported.
In order to investigate the interactions of these compounds in the
active site of KS, the three-dimensional structure of KS domain
(402 amino acid residues) of human FAS was modeled preliminary
on InsightII/Homology module using the X-ray structure of Esche-
richia coli. KASII protein (PDB code 1FJ8) and Synechocystis SP KASII
protein (PDB code 1E5M) as template. The scores of Profile 3D is
149.4, and the RMS deviation of protein backbone is 0.25.
We carried out docking of compounds C75 and 2c in the target
by means of the Affinity modular of InsightII. The result indicated
that these molecules can fit in the KS active site in the same fash-
ion, and the RMS deviation is 0.35 and 0.40 (Fig. 2). The active site
includes a hydrophobic pocket (13–15 Å) formed by residues
Ala162, Tyr224, Val263, Phe202, Phe258, Glu335, etc., and a hydro-
philic pocket formed by residues Ser114, Cys163, Pro336, Phe397,
etc.
Scheme 2. Reagents and conditions: (a) HCl (6 mol/L), reflux, TFA in CH2Cl2/reflux,
48%.
The mixture of 8a and 9a were easily hydrolyzed by LiOH
(1 mol/L) in CH3OH–H2O (1:2) on stirring at room temperature
overnight (Scheme 3),6 and the products 2a and 3a were obtained
in the ratio of 3:1 by the usual workup and chromatography sepa-
ration. The cis- and trans-isomer was determinated by the coupling
constant of hydrogen atoms of C5 and C6 position (J = 3.08 Hz in
cis-isomer and J = 3.36 Hz in trans-isomer).7 Each isomer was ob-
tained as racemates. Compounds 2b–f and 3b–f were synthesized
by the same procedure using different aldehydes.
Compound 2a–f and 3a–f have been evaluated for in vitro FAS
inhibitory activities using purified FAS from SD rat liver.8 All these
compounds have showed comparatively activities of FAS inhibitory
in vitro (Table 1). Just like C75, the trans-isomers perform higher
inhibitory activities than cis-isomers, but the distinction become
unremarkable in 2e/3e and 2f/3f. Otherwise, the enhancement of
activities has been found following by the elongation of carbon-
chain at the C5 position from n-C6H13– (2a) to n-C11H23– (2f). The
inhibitory activities rised immensely when the carbon-chain of
substituent arrived at n-C10H21–, and it was probably correlated
In C75, the hydroxyl H atom of carboxy is present at a distance
of 2.16 Å from the oxygen of carbonyl moiety of Pro336, and the
distance is 1.95 Å in compound 2c, which interacts through H-
bond formation. Further, the
aromatic moiety of Phe397 at a distance of 2.45 Å, which indicates
that a effect would be present. In compound 2c, the benzene
ring performs a similar effect with Phe397 residue to C75 at
a distance of 4 Å (Fig. 3).
a-methylene group approaches the
p–p
p–p
While similar types of interactions are observed during the
docking of compounds 2a–f in the active site of KS. The thiobuty-
Scheme 3. Reagents and conditions: (a) LiOH (1 mol/L), 85%.
Table 1
In vitro FAS inhibitory activities of compounds 2a–f, 3a–f and C75 in 60 lmol
Compound
% Inhibition SD
Compound
% Inhibition SD
C75
2a
2b
2c
2d
2e
2f
52.75 2.51
40.44 4.26
43.07 2.84
50.93 6.51
77.54 2.46
90.98 3.76
96.72 1.42
3a
3b
3c
3d
3e
3f
11.03 3.76
11.59 4.53
40.16 1.42
43.48 2.08
90.18 3.42
95.65 3.40
Figure 2. C75 (blue) and compound 2c (green) docked in the active site with
similar fashion in the modulated structure of KS. Figure was generated with Ds
ViewPro 5.0 (http://www.accelrys.co).

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X. Wang et al. / Bioorg. Med. Chem. Lett. 19 (2009) 770–772
and 2d showed more remarkable FAS inhibition activities and
higher therapeutic index than C75. The substituent such as
n-C8H17– and n-C9H19– at C5 position and trans-configuration will
be favorite for high activity and low toxicity, and this research
would lead to the discovery of new compounds for further investi-
gations and also support the design of these molecules.
Acknowledgment
We are grateful to the National Natural Science Foundation of
China (30672534) for financial supports.
References and notes
1. (a) Firdaus, M.; Mathew, M. K.; Wright, J. Geriatrics 2006, 61, 18; (b) Fonseca, V.
A. Clin. Cornerstone 2005, 7, 61; (c) Jacobs, D. R., Jr. Am. J. Clin. Nutr. 2006, 83, 189.
2. (a) Wakil, S. J. Biochemistry 1989, 28, 4523; (b) Wakil, S. J.; Stoops, J. K.; Joshi, V.
C. Ann. Rev. Biochem. 1983, 52, 537.
3. (a) Kuhajda, F. P.; Pizer, E. S.; Li, J. N., et al Proc. Natl. Acad. Sci. U.S.A. 2000, 97,
3450; (b) Thupari, J. N.; Landree, L. E.; Ronnett, G. V., et al Proc. Natl. Acad. Sci.
U.S.A. 2002, 99, 9498.
Figure 3. C75 and compound 2c docked in the active site: some important amino
acid residues in hydrophobic pocket (green), hydrophilic pocket (red), H-bond
interactions (Pro336) and p–p effect (Phe397, blue) are present.
4. Owton, W. M.; Gallagher, P. T., et al Synth. Commun. 1993, 23, 2119.
5. (a) Stanetty, P.; Kremslehner, M.; V.öllenkle, H. J. Chem. Soc., Perkin Trans. 1 1998,
853; (b) Garbiras, B. J.; Marburg, S. Synthesis 1999, 2, 270.
rolactones structure can fit in the hydrophilic pocket just like C75,
and the hydrophobic pocket have enough space to hold a linear
carbon-chain containing 6–11 carbon atoms. Compounds 3a–f
are devoid of H-bond interactions because of the cis-configuration.
In conclusion, a novel series of 1-oxo-3-substitute-isothiochro-
man-4-carboxylic acid compounds were designed and synthesized,
and these compounds performed similar interactions to C75 in the
active site of KS, which was modeled preliminary. Compounds 2c
6. McNamara, J. M.; Leazer, J. L.; Bhupathy, M., et al J. Org. Chem. 1989, 54, 3718.
7. Selected data for compound 2a: 1H NMR (400 MHz, CD3Cl) d = 7.98 (d, 1H,
J = 6.72 Hz); 7.57 (m, 1H); 7.49 (m, 1H); 7.25 (d, 1H, J = 6.16 Hz); 4.06 (d, 1H,
J = 3.36 Hz); 3.83 (m, 1H); 1.63 (m, 2H); 1.1–1.6 (m, 8H); 0.88 (t, 3H, J = 6.72 Hz).
MS (FAB) [M+1]+: m/z = 293.1.Compound 3a: 1H NMR (400 MHz, CD3Cl) d = 7.98
(dd, 1H, J = 7.84, 1.40 Hz); 7.53 (m, 1H); 7.47 (m, 1H); 7.27 (d, 1H, J = 9.52 Hz);
4.10 (d, 1H, J = 3.08 Hz); 3.93 (m, 1H); 1.99 (m, 1H); 1.84 (m, 1H); 1.1–1.6 (m,
8H); 0.88 (t, 3H, J = 6.72 Hz). MS (FAB) [M+1]+: m/z = 293.1.
8. Linn, T. Arch. Biochem. Biophys. 1981, 209, 613.