Study of acylhydrazone derivatives with deoxygenated seven-membered rings as potential β-ketoacyl-acyl carrier protein synthase III (FabH) inhibitors

Article abstract of DOI:10.1039/c6md00263c

Fatty acid biosynthesis is essential for bacterial survival. FabH, β-ketoacyl-acyl carrier protein (ACP) synthase III, is a particularly attractive target, since it is central to the initiation of fatty acid biosynthesis and highly conserved among Gram-positive and Gram-negative bacteria. Following previous studies, a series of acylhydrazone derivatives with deoxygenated rings were synthesized in this work. For all of the 36 analogues synthesized, studies using H NMR, C NMR, MS and elemental analyses were conducted. Their biological activities were also evaluated against two Gram-negative bacterial strains: E. coli and P. aeruginosa, and two Gram-positive bacterial strains: B. subtilis and S. aureus by the MTT method as potential FabH inhibitors. The resulting compound F18 showed the highest antibacterial activity with MIC values of 1.56-3.13 μg mL^-1 against the tested bacterial strains and was found to be the most potent E. coli FabH inhibitor with an IC₅₀ value of 2.0 μM. Molecular modeling simulation studies were performed in order to predict the biological activities of compound F18 into the E. coli FabH active site.

Full text of DOI:10.1039/c6md00263c

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RESEARCH ARTICLE
Study of acylhydrazone derivatives with
deoxygenated seven-membered rings as potential
β-ketoacyl-acyl carrier protein synthase III (FabH)
inhibitors†‡
Cite this: DOI: 10.1039/c6md00263c
*
Yang Zhou,§ Yin Luo,§ Yu-Shun Yang, Liang Lu and Hai-Liang Zhu
Fatty acid biosynthesis is essential for bacterial survival. FabH, β-ketoacyl-acyl carrier protein (ACP) synthase
III, is a particularly attractive target, since it is central to the initiation of fatty acid biosynthesis and highly
conserved among Gram-positive and Gram-negative bacteria. Following previous studies, a series of acyl-
hydrazone derivatives with deoxygenated rings were synthesized in this work. For all of the 36 analogues
synthesized, studies using H NMR, C NMR, MS and elemental analyses were conducted. Their biological ac-
tivities were also evaluated against two Gram-negative bacterial strains: E. coli and P. aeruginosa, and two
Gram-positive bacterial strains: B. subtilis and S. aureus by the MTT method as potential FabH inhibitors.
The resulting compound F18 showed the highest antibacterial activity with MIC values of 1.56–3.13 μg mL−1
against the tested bacterial strains and was found to be the most potent E. coli FabH inhibitor with an IC50
value of 2.0 μM. Molecular modeling simulation studies were performed in order to predict the biological
activities of compound F18 into the E. coli FabH active site.
Received 13th May 2016,
Accepted 11th July 2016
DOI: 10.1039/c6md00263c
www.rsc.org/medchemcomm
Due to these previous discoveries, serious attention has
been paid to enzymes with key roles in the FAS cycle as po-
Introduction
Fatty acid synthesis (FAS) is a necessary metabolic process
for the viability and growth of all living organisms.1–3 The
enzymes that catalyze fatty acid biosynthesis in prokaryotes
and eukaryotes are classified into two types since they have
some differences.4 The type I system is found in animals
and humans, and FAS involves a single polypeptide com-
posed of several distinct enzyme domains.5–7 The type II
system is found in bacteria, plants and protozoa, and the
FAS components are present as discrete proteins.8,9 The cor-
responding enzymes of the two FAS systems are related in
structure and function, but lack overall sequence homology.
Thus, the FAS bacterial system represents a potential target
for selective inhibition by broad-spectrum antibiotics.10,11
Significant efforts and progress have been made in the
search for small-molecule inhibitors of the type II FAS sys-
tem. Fig. 1 illustrates several compounds, both natural
products and synthetic analogues, that inhibit several steps
in the FAS cycle.9,10,12
tential targets for antibiotic inhibition. β-ketoacyl-acyl car-
rier protein synthase III (FabH) is the bacterial condensing
enzyme in Gram-positive and -negative bacteria which initi-
ates the FAB cycle by catalyzing the first condensation step
between acetyl-CoA and malonyl-ACP. FabH uses acetyl-CoA
as the primer for subsequent condensations, and cause the
feedback inhibition of fatty acid synthesis by the final prod-
uct palmitoyl-ACP to finally stop the circulation.13–15 How-
ever, other condensing enzymes FabB and FabF, function-
ing later in the cycle, both use acyl-ACP as the primer for
subsequent
condensations
and
are
hence
non-
State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University,
Nanjing 210023, People's Republic of China. E-mail: zhuhl@nju.edu.cn;
Fax: +86 25 83592672; Tel: +86 25 83592572
† The authors declare no competing interests.
‡ Electronic supplementary information (ESI) available. See DOI: 10.1039/
c6md00263c
Fig. 1 Several reported inhibitors targeting the fatty acid synthesis
§ These authors contributed equally to this work.
(FAS) pathway.
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Fig. 2 Several reported antibacterial agents targeting FabH.
Scheme 1 Design strategy: a lead compound (YKAs3003) initiates a series of novel antibiotic agents with deoxygenated seven-membered rings
and N-acylhydrazone.
redundant.16,17 Furthermore, FabH proteins are highly con-
served at the sequence and structural level in both Gram-
positive and -negative bacteria, while there are no signifi-
cantly homologous proteins in humans.18 More importantly,
there are essentially no differences between the amino acid
residues of the FabH active sites of Gram-positive and
Gram-negative bacteria. Thus, all lines of evidence indicate
that FabH plays a critical role in the fatty acid biosynthesis
pathway and provides a valid and unexploited target for the
development of broad-spectrum antibiotics.
Due to the above advantages of FabH, many research
groups including our group have been committed to the
development of antibacterial agents targeting FabH, and
some potential FabH inhibitors with high antibacterial ac-
tivity have been invented (Fig. 2).19–24 Apparently, some of
hydrazine and Schiff base moieties, the privileged structure,
N-acylhydrazone (–CO–NH–NCH–), was chosen as the ba-
sis for the design of novel FabH inhibitors. Moreover, acyl-
hydrazones have aroused considerable attention due to
their particular physical, chemical, and biological character-
istics. Based on their unique properties and characteristics,
they are known to possess a wide spectrum of biological ac-
tivities, such as antibacterial activity.25–27
From our previous research, four novel Schiff bases de-
rived from YKAs3003 (ref. 20) that retain the structure of
the cyclohexylamine moiety were designed. The Schiff base
with a deoxygenated seven-membered ring was the most
suitable for the development of new FabH inhibitors via
molecular docking. In this series of compounds, the com-
pound containing 16 aliphatic substituents (compound 5 in
Scheme 1) was found to be the most potent E. coli FabH
inhibitor with an IC50 value of 1.6 μM.28 Considering the
excellent properties of acylhydrazones and our previous
these compounds exhibited
a hydrazine moiety (–NH–
NCH–) or a Schiff base moiety (–CN–) in their core
structures as shown in Fig. 2. Considering the instability of
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Scheme 2 General synthesis of acylhydrazone derivatives (F1–F36). Reagents and conditions: I) H2SO4, MeOH, refluxing, overnight; II) 1,3-
dibromopropane, K2CO3, 100 °C, 13 h; III) hydrazine hydrate, EtOH, refluxing, 1 day; IV) RCHO, AcOH, EtOH, refluxing, 5 h.
research results, our new design strategy is to replace the
Schiff base moiety with an N-acylhydrazone moiety in the
core structures, while keeping the deoxygenated seven-
membered ring (Scheme 1).
Then, hydrazide D was yielded by reacting C with hydrazine
hydrate in ethanol. The synthesis of compounds F1–F36 was
accomplished by reaction of D with various aldehydes E in
ethanol with 75–98% yield. Details of the whole synthesis
process are shown in the experimental section. The struc-
tures of all synthetic compounds were fully characterized by
spectroscopic methods and elemental analysis. All the details
of the compounds are in the ESI.‡
Results and discussion
Chemistry
In this study, 36 acylhydrazone derivatives (F1–F36) were syn-
thesized. The synthetic route to compounds F1–F36 is shown
in Scheme 2. These compounds were synthesized from 3,4-
dihydroxybenzoic acid (A). Esterification of 4-hydroxy-3-
methoxybenzoic acid by methanol and concentrated sulfuric
acid afforded the corresponding ester B with 98% yield. Com-
pound C was obtained from the reaction of ester B and 1,3-
dibromopropane in DMF solvent and using K2CO3 as a base.
Biological activity
Ethics statement. These experiments were conducted in
accordance with the guideline issued by the State Food and
Drug Administration (SFDA of China). The cell lines were
cultured and passaged in accordance with the guidelines
established by the National Science Council of the Republic
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Table 1 Antibacterial activity of synthesized compounds
MIC [μg mL−1
]
Gram-negative
Gram-positive
Compda
R
E. coli
P. aeruginosa
B. subtilis
S. aureus
F1
F2
F3
F4
F5
F6
F7
H
4-CH3
3-CH3
2-CH3
2-OH
2-Cl
2-Br
50
50
50
>100
50
50
50
25
50
50
50
25
>100
50
50
>100
12.5
>100
25
>100
>100
>100
>100
25
25
50
50
50
F8
2-CHO
25
25
50
25
F9
4-NIJCH3)2
4-NO2
6.25
25
12.5
25
6.25
25
6.25
50
F10
F11
F12
F13
F14
F15
F16
F17
F18
F19
F20
F21
F22
F23
F24
F25
F26
F27
F28
F29
F30
F31
F32
F33
F34
F35
F36
Kanamycin B
DMSO
4-CF3
4-F
4-I
4-Ph
4-OH
4-OCH3
25
12.5
25
3.13
50
25
12.5
25
25
6.25
25
25
50
12.5
6.25
25
12.5
25
6.25
12.5
12.5
25
6.25
3.13
6.25
25
25
50
25
6.25
12.5
6.25
25
6.25
6.25
3.13
12.5
6.25
6.25
>100
>100
>100
1.56
>100
12.5
3.13
3.13
6.25
12.5
12.5
25
12.5
3.13
6.25
6.25
25
6.25
6.25
3.13
12.5
3.13
6.25
25
>100
>100
3.13
>100
50
3,4-OCH3
3,4,5-OCH3
3,5-OCH3; 4-OH
3,4-OH
3-NO2; 4-OH
2-OH; 5-Cl
2-OH; 4-NIJCH3)2
2-OH; 5-NO2
2-OH; 3,5-Cl
2,4-Cl
2-Cl; 6-F
3-NO2; 4-F
3-NO2; 4-Cl
3-NO2; 6-Cl
2-F; 5-NO2
β-Naphthalene
α-Naphthalene
Allyl benzene
5-Methylfuran
Thiophene
—
3.13
1.56
3.13
12.5
6.25
12.5
12.5
6.25
12.5
6.25
12.5
12.5
3.13
3.13
6.25
6.25
3.13
50
3.13
1.56
3.13
25
12.5
25
50
3.13
6.25
12.5
50
6.25
3.13
6.25
12.5
3.13
6.25
50
>100
>100
3.13
>100
>100
>100
1.56
>100
—
a
The compounds tested for antibacterial activity are consistent with the description in the Experimental section.
of China. The primary cell lines were purchased from ATCC.
All experimental protocols were approved by the Academic
Committee of Nanjing University.
All the synthesized acylhydrazone derivatives F1–F36 were
evaluated for their antimicrobial activity against two Gram-
negative bacterial strains: E. coli ATCC 25922 and Pseudomo-
nas aeruginosa ATCC 27853, and two Gram-positive bacterial
strains: Staphylococcus aureus ATCC 6538 and Bacillus subtilis
ATCC 530 utilizing the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide) assay. The minimum inhibitory
concentrations (MIC) of these compounds against these bac-
teria are presented in Table 1. The results were compared
with those provided by the known antibiotic kanamycin un-
der identical conditions, which exhibited significant anti-
bacterial activities among most synthesized compounds.
DMSO was added as the negative control within the biologi-
cal testing. All tested compounds were divided into three
groups according to their biological activity: high activity
(F14, F17–F19, F24, F29, F30, F32, F33), medium activity
(F9–F13, F15, F16, F20–F23, F25–F28, F31), and low activity
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Table 2 E. coli FabH inhibitory activity of synthesized compounds
Compda
E. coli FabH IC50 [μM]
PSAb [Å2]
Hemolysis LCc [mg mL−1
]
Cytotoxicity IC50 [μM]
F9
7.2 0.4
17.6 1.5
12.4 0.9
32.5 3.1
6.9 0.5
4.7 0.3
38.7 2.7
24.1 1.6
4.1 0.3
2.0 0.1
3.9 0.3
7.8 0.6
8.9 0.5
13.2 0.8
6.7 0.2
3.5 0.1
5.4 0.4
4.3 0.2
20.6 1.8
5.1 0.3
4.4 0.2
3.9 0.3
9.5 0.6
4.6 0.2
5.2 0.3
5.6 0.4
62.646
102.117
59.294
59.294
59.294
59.294
80.110
68.224
77.154
122.933
97.970
100.925
122.933
80.110
83.462
122.933
80.110
59.294
59.294
102.117
102.117
102.117
102.117
59.294
59.294
282.615
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
134.8 11.5
185.1 9.8
104.2 6.5
125.9 11.7
200.6 12.6
146.1 8.5
178.3 10.4
131.6 12.8
125.8 6.4
120.5 8.8
147.3 13.1
101.8 5.2
198.0 14.7
110.6 10.3
203.3 16.9
156.8 11.4
184.2 10.6
197.5 13.9
163.6 15.1
130.9 9.6
147.1 12.0
172.5 10.4
168.3 7.9
114.4 10.3
129.7 9.5
139.6 12.3
F10
F11
F12
F13
F14
F15
F16
F17
F18
F19
F20
F21
F22
F23
F24
F25
F26
F27
F28
F29
F30
F31
F32
F33
Kanamycin B
a
b
The compounds tested for antibacterial activity are consistent with the description in the Experimental section. Molecular polar surface
area (PSA); calculated with Discovery Studio 3.1.29 c Lytic concentration 30%.
Fig. 3 (a) 2D model of the interaction between compound F18 and the 1HNJ binding site. (b) 3D molecular docking model of compound F18 with
1HNJ. The H-bond was displayed as a dotted line and the amino acid it acts on was labeled in green. Other important residues were labeled in
yellow.
(F1–F8, F34–F36). All compounds in the high-activity group
demonstrated excellent inhibitory activity against Gram-
negative and Gram-positive bacteria. Especially, compound
F18 showed comparable activity to the positive control kana-
mycin B (MIC = 3.13, 3.13, 1.56 and 1.56 μg mL−1, respec-
tively; Table 1). Most small molecules of the medium-activity
group showed modest antibacterial activities against the four
pathogenic strains, and the remaining compounds of the last
group had little or no bioactivity for any strains.
into two groups: compounds (F1–F31) which contain various
substituents on an aromatic ring, and compounds (F32–F36)
which contain a naphthalene ring/heterocyclic ring. To deter-
mine how the substituents on the benzene ring affected the
antimicrobial activity, compound F1 without any substituent
groups on the benzene ring was first evaluated, which showed
lower antimicrobial activity with MIC values of 50, 50, more
than 100 μg mL−1 and more than 100 μg mL−1 against E. coli,
P. aeruginosa, B. subtilis and S. aureus, respectively. Introducing
electron-donating groups like the methyl group (F2, F3, F4)
was disadvantageous to the biological activity, regardless of
In order to discuss the structure–activity relationships
(SARs) of these compounds, the compounds were classified
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Fig. 4 (a) Compound F18 mimicking the original ligand in steric conformation. (b) The receptor surface model of compound F18 embedded in
FabH.
the position of the substituent on the benzene ring. More-
over, compounds F5–F8 with only an -ortho substituent with
a slightly lower activity suggest that this -ortho substitution
weakened the inhibitory activity. Para-substitution on the ring
strengthened the activity (F9–F16), while electron-
withdrawing groups at the para-position had no distinct ef-
fect on the activity. Compounds F9 and F14 with larger steric
substituents on the para-position presented higher activities
than others. By increasing the number of –OCH3 substituents
on the benzene ring, the activities of the compounds
(F16–F19) were enhanced. This caused compound F18 owing
3 –OCH3, to have the maximum activity with MIC values of
1.56, 3.13, 1.56 and 3.13 μg mL−1 against E. coli, P.
aeruginosa, B. subtilis and S. aureus, respectively. Besides, this
phenomenon still occurred when the substituent was –Cl (F6,
F26) or –OH (F5, F15, F20). When the ortho-position of the
benzene ring had a –OH (F22–F25) or –Cl (F26 and F27) sub-
stituent, while the other positions were substituted by other
electron-withdrawing groups, the activities were not obviously
enhanced. Furthermore, the MIC values of compounds with
–NO2 on the meta-position were in the range of 3.13–12.5 μg
mL−1; these results indicated that introducing strong
electron-withdrawing groups like –NO2 (F21, F24, F28–F31)
into the meta-position of benzene increased the probability
of possessing antibacterial activity.
For the other group, compounds with α- and
β-naphthalene rings (F32, F33) strengthened the antimicro-
bial effects, which suggests that the large steric substituents
contributed to the antibacterial activity of our compounds. Fi-
nally, the benzene ring of F1 was replaced with allyl benzene,
a furan ring or a thiophene ring (F34–F36, respectively),
which resulted in a significant decrease in potency with MIC
values of 25 to >100 μg mL−1. This suggested that the ben-
zene ring contributed to the antibacterial activity of the syn-
thesized compounds.
The compounds synthesized were then evaluated for their
E. coli FabH inhibitory activity (F9–F33), and the results are
listed in Table 2. All compounds showed potent E. coli FabH
inhibition, and compound F18 showed the highest activity
against E. coli FabH with an IC50 value of 2.0 μM. This re-
sult supports the potent antibacterial activities of com-
pound F18, which is the most potent FabH inhibitor in
this series of compounds. Compound F18 possessing three
methoxyl groups on the benzene ring which induce larger
steric effects, are more beneficial for inhibitory activity
as compared to two or one methoxyl group (F16, F17).
Nitro (–NO2) on the meta-position of the benzene ring
strengthened the FabH inhibitory activity and the IC50
values of compounds F21, F24 and F28–F31 were in the
range of 3.5–9.5 μM. Moreover, compounds F14, F32 and
F33 bearing a diphenyl or naphthalene ring also presented
higher activity with IC50 values of 4.7, 4.6 and 5.2 μM, re-
spectively. Developing various compounds with –NO2 on
the meta-position of the benzene ring or large steric groups
was another strategy to produce more potent compounds
with antibacterial activity. Molecular polar surface area
(PSA) is also calculated in Table 2, which is a very useful
parameter for prediction of drug transport properties, re-
lated to the binding affinity and the cell permeability of
FabH inhibitors.30 Because the molecular polar surface
areas (PSA) of these compounds were in the range of
59.294–122.933 Å2, therefore this molecular property cannot
significantly account for the results obtained. The PSA
value for compound F18 is 122.933 Å2, which meets Veber
rules (<140 Å2). In summary, the results for the E. coli
FabH inhibitory activity of the test compounds described
above generally corresponded to the SARs of their anti-
bacterial activities. This demonstrates that the potent anti-
bacterial activities of the selected compounds are probably
correlated with their FabH inhibitory activities.
The compounds selected above were also tested for their
hemolytic activity. Additionally, they were also tested for their
cytotoxic activity on a mouse embryonic fibroblast cell line
(NIH-3 T3) using the MTT assay.31 The results are summa-
rized in Table 2. All the compounds displayed low hemolytic
activities. The cytotoxicity assay determined the selectivity of
our compounds for bacterial over mammalian cells. Interpre-
tation of the cytotoxicity data indicates that the compounds
possessing inhibitory activity were shown to have low toxicity.
To determine the interaction binding mode between the
target protein and small molecules, molecular docking of the
most active compound F18 and E. coli FabH was performed
on a binding model based on the E. coli FabH–CoA complex
structure (PDB: 1HNJ).32 The corresponding result is shown
in Fig. 3, which was composed of two interaction maps. The
docking study was performed using the CDOCKER protocol.29
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The 2D optimal conformation and the 3D diagram of the
interaction with the FabH active site are presented in
Fig. 3a and b, respectively. The main chain of ARG151 forms
two hydrogen bonds (HE–O, 2.27 Å, 111.676°; HE–O, 2.18 Å,
165.173°) with two oxygen atoms of compound F18.
These interactions were vital for the stabilization of the
binding mode. As shown in Fig. 4a, inheriting the advantage
of mimicking the original ligand malonyl-CoA, compound
F18 exhibited more powerful interactions with the active site.
The receptor surface model in Fig. 4b also suggests that F18
embedded deeply into the active site of FabH. Thus, com-
pound F18 could be expected as a potential inhibitor of
E. coli FabH with potent antibacterial activity.
2 J. Wang, S. M. Soisson, K. Young, W. Shoop, S. Kodali and A.
Galgoci, Nature, 2006, 441, 358–361.
3 H. Song, G. Z. Ao and H. Q. Li, Expert Opin. Ther. Pat.,
2014, 24, 19–27.
4 D. J. Payne, P. V. Warren, D. J. HoImes, Y. Ji and J. T.
Lonsdale, Drug Discovery Today, 2001, 6, 537–544.
5 C. Y. Lai and J. E. Cronan, J. Biolumin. Chemilumin.,
2003, 19, 51494–51503.
6 Y. J. Lu, Y. M. Zhang and C. O. Rock, Biochem. Cell Biol.,
2004, 82, 145–155.
7 S. Natarajan, J. K. Kim, T. K. Jung, T. T. Ngoc Doan, H. P. T.
Ngo, M. K. Hong, S. Kim, V. P. Tan, S. J. Ahn, S. H. Lee, Y.
Han, Y. J. Ahn and L. W. Kang, Mol. Cells, 2011, 33, 19–25.
8 S. W. White, J. Zheng, Y. M. Zhang and C. O. Rock, Annu.
Rev. Biochem., 2005, 74, 791–831.
Conclusions
9 R. Veyron-Churlet, O. Guerrini, L. Mourey, M. Daffé and D.
Zerbib, Mol. Microbiol., 2004, 54, 1161–1172.
In this paper, we synthesized 36 novel derivatives with
N-acylhydrazone and deoxygenated seven-membered fused
rings, and evaluated their antibacterial activities against
E. coli FabH for the first time. Several compounds (F14,
F17–F19, F24, F29, F30, F32, F33) presented potent anti-
Gram-negative and -positive bacterial activities. Compound
F18 showed the most potent antibacterial activity with MIC
values of 1.56–3.13 μg mL−1 against the tested bacterial
strains and exhibited the most potent E. coli FabH inhibitory
activity with an IC50 of 2.0 μM. Preliminary structure–activity
relationships and molecular modeling studies provided fur-
ther insight into the interactions between the enzyme and its
ligands. This study showed F18 was a potential inhibitor of
E. coli FabH with potent antibacterial activity. Moreover, it
provided valuable information for the designing E. coli FabH
inhibitors as antibacterial agents in the future. With these
promising results, we will be utilizing the structure of com-
pound F18 as the basis for further compound design and
SAR development in the future. Moreover, the development
of similar novel compounds based on this core structure
containing nitrogen heterocyclic or alkane chains instead of
a benzene ring on the right side will be investigated in future
studies.
10 H. Q. Li, Y. Luo and H. L. Zhu, Bioorg. Med. Chem., 2011, 19,
4454–4459.
11 Y. Wang and S. Ma, ChemMedChem, 2013, 8, 1589–1608.
12 R. A. Daines, I. Pendrak, K. Sham, G. S. Van Aller, A. K.
Konstantinidis, J. T. Lonsdale, C. A. Janson, X. Qiu, M.
Brandt, S. S. Khandekar, C. Silverman and M. S. Head,
J. Med. Chem., 2003, 46, 5–8.
13 K. S. Gajiwala, S. Margosiak, J. Lu, J. Cortez, Y. Su, Z. Nie
and K. Appelt, FEBS Lett., 2009, 583, 2939–2946.
14 R. J. Heath, S. White and C. O. Rock, Appl. Microbiol.
Biotechnol., 2002, 58, 695–703.
15 J. Beld, J. L. Blatti, C. Behnke, M. Mendez and M. D.
Burkart, J. Appl. Phycol., 2014, 24, 1619–1629.
16 R. J. Heath and C. O. Rock, J. Biolumin. Chemilumin.,
1996, 271, 1833–1836.
17 G. E. Schujman, S. Altabe and D. D. Mendoza, Mol.
Microbiol., 2008, 68, 987–996.
18 Z. Nie, C. Perretta, J. Lu, Y. Su, S. Margosiak, K. S. Gajiwala,
J. Gortez, V. Nikulin, K. M. Yager, K. Appelt and S. S. Chu,
J. Med. Chem., 2005, 48, 1596–1609.
19 L. Shi, R. Q. Fang, Z. W. Zhu, Y. Yang, K. Cheng, W. Q.
Zhong and H. L. Zhu, Eur. J. Med. Chem., 2010, 45,
4358–4364.
Experimental section
20 J. Lee, K. Jeong, J. Lee, D. Kang and Y. Kim, Bioorg. Med.
Chem., 2009, 17, 1506–1513.
21 J. Y. Lee, K. W. Jeong, S. Shin, J. U. Lee and Y. Kim, Eur. J.
Med. Chem., 2012, 47, 261–269.
All laboratory instruments, methods and data of this article
are in the ESI.‡
22 P. C. Lv, J. Sun, Y. Luo, Y. Yang and H. L. Zhu, Bioorg. Med.
Chem. Lett., 2010, 20, 4657–4660.
Acknowledgements
23 Y. Li, C. P. Zhao, H. P. Ma, M. Y. Zhao, Y. R. Xue, X. M.
Wang and H. L. Zhu, Bioorg. Med. Chem., 2013, 21,
3120–3126.
24 P. C. Lv, K. R. Wang, Y. Yang, W. J. Mao, J. Chen, J. Xiong
and H. L. Zhu, Bioorg. Med. Chem. Lett., 2009, 19,
6750–6754.
We thank Mr. Chong Zhang of Hohai University (Changzhou
213022, Jiangsu) for the synthesis of compounds F4–F10 in
this paper. This work was financed by the China Postdoctoral
Science Foundation and was supported by Public Science &
Technology Research Funds Projects of Ocean (No. 201505023).
25 A. J. M. Rasras, T. H. Al-Tel, A. F. Al-Aboudi and R. A. Al-
Qawasmeh, Eur. J. Med. Chem., 2010, 45, 2307–2313.
26 A. M. Kamel, M. A. Lobna, M. L. El-Sayed, I. H. Mohamed
and H. B. Rania, Bioorg. Med. Chem., 2006, 14, 8675–8682.
References
1 R. J. Heath and C. O. Rock, J. Biolumin. Chemilumin.,
1996, 271, 1833–1836.
This journal is © The Royal Society of Chemistry 2016
Med. Chem. Commun.

View Article Online
Research Article
MedChemComm
27 X. L. Wang, Y. B. Zhang, J. F. Tang, Y. S. Yang, R. Q. Chen, F.
Zhang and H. L. Zhu, Eur. J. Med. Chem., 2012, 57, 373–382.
28 Y. Zhou, Q. R. Du, J. Sun, J. R. Li, F. Fang, D. D. Li, Y. Qian,
H. B. Gong, J. Zhao and H. L. Zhu, ChemMedChem, 2013, 8,
433–441.
30 P. Ertl, B. Rohde and P. Selzer, J. Med. Chem., 2000, 43,
3714–3717.
31 J. Y. Lee, K. W. Jeong, S. Shin, J. U. Lee and Y. Kim, Eur. J.
Med. Chem., 2012, 47, 261–269.
32 X. Qiu, C. A. Janson, W. W. Smith, M. Head, J. Lonsdale
and A. K. Konstantinidis, J. Mol. Biol., 2001, 307,
341–356.
29 Discovery Studio 3.1, Accelrys Software Inc., San Diego, CA,
USA, 2011.
Med. Chem. Commun.
This journal is © The Royal Society of Chemistry 2016