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