Synthesis and antibacterial evaluation of novel 4-alkyl substituted phenyl β-aldehyde ketone derivatives

Article abstract of DOI:10.1016/j.ejmech.2008.03.010

A series of novel 4-alkylphenyl β-aldehyde ketones and their derivatives were designed and synthesized on the basis of the chemical structures of Houttuynin and β-lactam antibiotics. Antibacterial activities of these compounds were investigated. The results demonstrated that most of the compounds tested had moderate antibacterial activities against Gram-positive pathogen Staphylococcus aureus (ATTC-25923) than Houttuynin, and Gram-positive bacteria were more susceptible to the compounds than Gram-negative bacteria. Compound 23 was found to be the most potent compound with MIC of 1.0 μg/mL against S. aureus. Particularly, compounds 16, 22 and 23 showed more active antibacterial activities against the clinically important pathogenic bacteria, methicillin-resistant S. aureus (MRSA) than Houttuynin and levofloxacin. The preliminary structure-activity relationship (SAR) analysis suggested that (1) the introduction of appropriate alkyl substituents into position 4 of phenyl ring enhanced antibacterial activities of these compounds, and isopropyl substituent might be more favorable; (2) the presence of ketone carbonyl moiety might play a vital role in determining significant antibacterial activities of these compounds.

Full text of DOI:10.1016/j.ejmech.2008.03.010

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 44 (2009) 1737e1744
http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and antibacterial evaluation of novel 4-alkyl substituted
phenyl b-aldehyde ketone derivatives
Jinbing Liu a, Rihui Cao a, Qifeng Wu c, Chunming Ma a, Zihou Wang b,
a,
c,**
, Huacan Song
*
Wenlie Peng
a School of Chemistry and Chemical Engineering, Sun Yat-Sen University, 135 Xin Gang Xi Road, Guangzhou 510275, PR China
b Centre for Drug Evaluation, State Drug Administration, Beijing 100050, PR China
c School of Life Science, Sun Yat-Sen University, 135 Xin Gang Xi Road, Guangzhou 510275, PR China
Received 8 January 2008; received in revised form 18 February 2008; accepted 13 March 2008
Available online 27 March 2008
Abstract
A series of novel 4-alkylphenyl b-aldehyde ketones and their derivatives were designed and synthesized on the basis of the chemical
structures of Houttuynin and b-lactam antibiotics. Antibacterial activities of these compounds were investigated. The results demonstrated
that most of the compounds tested had moderate antibacterial activities against Gram-positive pathogen Staphylococcus aureus (ATTC-
25923) than Houttuynin, and Gram-positive bacteria were more susceptible to the compounds than Gram-negative bacteria. Compound 23
was found to be the most potent compound with MIC of 1.0 mg/mL against S. aureus. Particularly, compounds 16, 22 and 23 showed more active
antibacterial activities against the clinically important pathogenic bacteria, methicillin-resistant S. aureus (MRSA) than Houttuynin and
levofloxacin. The preliminary structureeactivity relationship (SAR) analysis suggested that (1) the introduction of appropriate alkyl substituents
into position 4 of phenyl ring enhanced antibacterial activities of these compounds, and isopropyl substituent might be more favorable; (2) the
presence of ketone carbonyl moiety might play a vital role in determining significant antibacterial activities of these compounds.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Houttuynin; b-Ketone aldehyde; Synthesis; Antibacterial activity
1. Introduction
have a b-aldehyde ketone unit as an important pharmacological
moiety. Previous researches showed that Houttuynin possesses
broad spectrum pharmacological properties including antibac-
terial, antivirus, anti-inflammation and enhanced immunity
[13]. Sodium houttuyfonate (Fig. 1), derived from Houttuynin,
has been clinically used in antimicrobial medications for many
years in China [13e16]. Sodium houttuyfonate was mainly
dependent on the hydrophobic interaction with membrane
proteins or lipid of bacteria to inhibit bacteria growth [17]. In
vitro experiments suggested that modifying the structure of
cell membrane would be one of the important factors of sodium
houttuyfonate exerting the pharmaceutical effects [14]. On the
other hand, most of the b-lactam antibiotics (Fig. 2), such as
cefuroxime axetil and cefotaxime sodium, contained O-alkyl
oxime unit which played an important role in enhancing their
antibacterial activities. Stimulated by the above knowledge of
The increasing incidence of bacterial resistance to currently
available antibacterial agents represents one of the major grow-
ing global health problems [1e6]. Obviously, there is an urgent
need for the discovery and development of novel and effective
antibacterial drugs, which can inhibit or kill bacteria by novel
mechanisms, rather than analogues of existing antibiotics
[7e12]. Houttuynin (Fig. 1), n-nonyl-b-oxo-aldehyde, was first
isolated from Houttuynia cordata Thunb as the major active
constituent, and its structure was characterized and shown to
* Corresponding author. Tel.: þ86 20 84110918; fax: þ86 20 84112245.
** Corresponding author.
E-mail addresses: pengwl@mail.sysu.edu.cn (W. Peng), yjhxhc@mail.
sysu.edu.cn (H. Song).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.03.010

1738
J. Liu et al. / European Journal of Medicinal Chemistry 44 (2009) 1737e1744
O
O
2.2. Antibacterial activity in vitro
H3C
All the synthesized compounds were tested for their in vitro
antibacterial activities against both Gram-positive bacteria
Staphylococcus aureus (ATTC-25923) and Gram-negative
bacteria Escherichia coli (ATTC-25922) and Pseudomonas
aeruginosa (ATTC-27853). The antibacterial activity was
reported as the minimum inhibitory concentration (MIC) in
mg/mL that was determined by the agar dilution method as rec-
ommended by the NCCLS (National Committee for Clinical
Laboratory Standards) [18]. The MICs are summarized in
Table 1 along with the data of levofloxacin, clarithromycin
and Houttuynin for comparison.
As shown in Table 1, most of the compounds had moderate
antibacterial activities against Gram-positive pathogen S.
aureus, but compounds 16, 17 and 26 only showed weak
activity against the Gram-negative pathogens E. coli and P.
aeruginosa. Particularly, compound 23 was found to be the
most potent compound with MIC of 1.0 mg/mL against S.
aureus. These results indicated that Gram-positive bacteria
were more susceptible to the newly synthesized compounds
than Gram-negative bacteria.
Houttuynin
O
OH
H3C
SO3Na
Sodium Houttuyfonate
Fig. 1. The chemical structure of Houttuynin and sodium houttuyfonate.
sodium houttuyfonate and b-lactam antibiotics in the present
investigation, we attempted to combine the O-alkyl oxime
unit of b-lactam antibiotics with b-aldehyde ketone of Houttuy-
nin and sodium houttuyfonate to design and synthesize novel
promising antibacterial drugs. The present investigation aimed
at (1) elucidating the preliminary structureeactivity relation-
ships; (2) probing structural requirements for the potent
antibacterial activities of these compounds; (3) discovering
and developing novel and potent antibacterial drugs with novel
action mechanism. To the best of our knowledge, all 4-
alkylphenyl b-aldehyde ketones and their derivatives except
compounds 5, 6 and 16 are novel.
Among all the compounds investigated, the oxime (13 and 15)
and oxime-alkylether derivatives (14 and 16e29) exhibited more
active antibacterial activity than other compounds, which impli-
cated that oxime and O-alkyl oxime moiety might play an impor-
tant role in enhancing antibacterial activities of these compounds.
Unfortunately, 3-oxo-3-phenylpropanal (5), 3-(4-methylphenyl)
-3-oxopropanal (6) and sodium 1-hydroxy-3-(4-alkylphenyl)-3-
oxopropane-1-sulfonate (7e8) failed to exhibit the antibacterial
activity against the three strains investigated at the concentration
of 64 mg/mL. Similarly, the semicarbazones and thiosemicarba-
zone derivatives (9e12) were also inactive.
In order to examine the effect of alkyl substituents attached
to the phenyl ring on the antibacterial activities of the
compounds, a series of 3-phenyl b-aldehyde ketone derivatives
bearing different alkyl substituents at position 4 of phenyl ring
were synthesized. As shown in Table 1, compound 14 having no
substituent at position 4 of phenyl ring showed weak antibacte-
rial activity. Introducing a short chain alkyl substituent into
position 4 of phenyl ring led to compounds 16 (methyl), 18
(ethyl), 22 (isopropyl) and 26 (n-pentyl), which all exhibited
better antibacterial activities against the Gram-positive patho-
gen S. aureus than their parent compound 14. Similarly,
compounds 17 (methyl), 19 (ethyl), 23 (isopropyl) and 27
(n-pentyl) also displayed more potent antibacterial activities
than compound 14. Interestingly, compounds 22 and 23 which
bearing the same isopropyl substituents at position 4 of phenyl
ring demonstrated more prominent antibacterial activities than
other 4-alkylphenyl derivatives, and compound 23 was found to
be the best compound with MIC of 1.0 mg/mL against S. aureus.
These results indicated that the introduction of appropriate al-
kyl substituents into position 4 of phenyl ring enhanced antibac-
terial activities of these compounds, and isopropyl substituent
might be more favorable.
2. Results and discussion
2.1. Chemistry
The general procedure for the synthesis of 3-(4-alkylphenyl)-
3-oxopropanal and their derivatives are described in Scheme 1.
In brief, the reaction of 40- alkylacetophenone with 2.0 equiv of
ethyl formate and 1.5 equiv of sodium ethoxide or metal sodium
in dry toluene at room temperature gave the corresponding
intermediate, sodium salt of phenyl-3-hydroxyprop-2-en-1-one
(1) and 4-alkylphenyl-3-hydroxyprop-2-en-1-one (2e4).
Compounds 1 and 2 were acidified with 5% hydrochloric acid
to give the 3-phenyl-3-oxopropanal (5) and 3-(4-alkylphenyl)-
3-oxopropanal (6) in 65e76% overall yields. Compounds 3
and 4 were treated with saturated sodium bisulfite at room tem-
perature to give sodium 1-hydroxy-3-(4-alkylphenyl)-3-oxopro-
pane-1-sulfonate (7e8). Reaction of 3-phenyl-3-oxopropanal
(5) and 3-(4-alkylphenyl)-3-oxopropanal (6) with semicarba-
zide, and thiosemicarbazide in EtOH, respectively, gave the
corresponding Schiff base (9e12) in 52e91% overall yield.
Compounds 13e29 were obtained by the treatment of sodium
salts of 3-(4-alkylphenyl)-3-oxopropanal with hydroxylamine
hydrochloride, methoxyamine hydrochloride, ethoxyamine
hydrochloride, respectively.
NOR2
H
S
N
R1
O
N
O
O
R4
O
OR3
Cefuroxime axetil, R1 = 2-furanyl, R2 = CH3, R3 = 1-acetoxyethyl, R4 = aminoformyl
Cefotaxime sodium, R1 = 4-(2-aminothiazolyl), R2= CH3, R3 = Na, R4 = acetyl
To explore the influence of the ketone carbonyl on antibac-
terial activities of the 4-alkylphenyl b-aldehyde ketone
Fig. 2. The chemical structure of b-lactam antibiotics.

J. Liu et al. / European Journal of Medicinal Chemistry 44 (2009) 1737e1744
R1
1739
R2
R
13-29
v
O
O
O
O
ONa
ii
CH3
i
R
R
5 R = H
6 R = CH3
R
1 R = H
2 R = CH3
3 R = CH(CH3)2
4 R = CH2CH2CH2CH2CH3
iv
iii
SO3Na
OH
O
R1 R2
R
R
9-12
7 R = CH(CH3)2
8 R = CH2CH2CH2CH2CH3
9 R = H, R1 = O, R2 = NNHCONH2
10 R = H, R1 = O, R2 = NNHCSNH2
12 R = CH3, R1 = O, R2 = NNHCSNH2
14 R = H, R1 = O, R2 = NOCH3
11 R = CH3, R1 = O, R2 = NNHCONH2
13 R = H, R1 = O, R2= NOH
15 R = CH3, R1 = O, R2= NOH;
16 R = CH3, R1 = O, R2 = NOCH3
18 R = CH2CH3, R1 = O, R2 = NOCH3
20 R = CH2CH3, R1 = R2 = NOCH3
22 R = (CH3)2CH, R1 = O, R2 = NOCH3
24 R = (CH3)2CH , R1 = R2 = NOCH3
26 R = CH3(CH2)4, R1 = O, R2 = NOCH3
28 R = CH3(CH2)4 , R1 = R2 = NOCH3
17 R = CH3, R1 = O, R2 = NOCH2CH3
19 R = CH2CH3, R1 = O, R2 = NOCH2CH3
21 R = CH2CH3, R1 = R2 = NOCH2CH3
23 R = (CH3)2CH, R1 = O, R2 = NOCH2CH3
25 R = (CH3)2CH, R1 = R2 = NO CH2CH3
27 R = CH3(CH2)4, R1 = O, R2 = NO CH2CH3
29 R = CH3(CH2)4 , R1 = R2 = NOCH2CH3
Scheme 1. Synthesis of 4-alkylphenyl b-aldehyde ketones and their derivatives. Reagents: (i) ethyl formate/Na/toluene, (ii) 5% HCl, (iii) saturated sodium bisulfite
solution, (iv) NH2NHCSNH2 or NH2NHCSNH2/EtOH/reflux, (v) NH2OH$HCl or NH2OR$HCl/EtOH/RT.
derivatives, the dioxime-alkylethers were designed and synthe-
sized, and their antibacterial activities in vitro against Gram-
positive bacteria and Gram-negative bacteria were also
investigated. As shown in Table 1, the 4-alkylphenyl b-
aldehyde ketone monooxime-alkylether derivatives (18e19,
22e23 and 26e27) displayed 8e32 times more active against
S. aureus than the corresponding dioxime-alkylether deriva-
tives (20e21, 24e25 and 28e29). These results indicated
that the presence of ketone carbonyl moiety might play a vital
role in determining significant antibacterial activities of these
compounds.
With the purpose of further corroborating the prominent an-
tibacterial activities, compound 23 was selected to investigate
the antibacterial activities against 10 strains of clinical isolates
of S. aureus and the results are summarized in Table 2. As
shown in Table 2, compound 23 exhibited prominent antibac-
terial activities.
Furthermore, three compounds (16, 22 and 23) were
selected to test the antibacterial activities in vitro against
important pathogenic methicillin-resistant S. aureus (MRSA)
and the results are summarized in Table 3. As shown in Table
3, compounds 16, 22 and 23 displayed moderate antibacterial
activities against MRSA, which are slightly superior to the
Houttuynin and levofloxacin.
3. Conclusions
The present investigation reported, for the first time, that
4-alkylphenyl b-aldehyde ketone derivatives had potent anti-
bacterial activities, and Gram-positive pathogens were more
susceptible to these compounds. Of all the investigated
compounds, compounds 22 and 23 bearing the isopropyl
substituents at position 4 of phenyl ring demonstrated more
prominent antibacterial activities than other 4-alkylphenyl
substituted derivatives. Interestingly, compounds 16, 22 and
23 exhibited more potent antibacterial activities against
clinically important pathogenic bacteria MRSA than Hout-
tuynin and levofloxacin. The preliminary structureeactivity
relationship (SAR) analysis suggested that (1) the introduc-
tion of appropriate alkyl substituents into position 4 of
phenyl ring enhanced antibacterial activities of these com-
pounds, and isopropyl substituent might be more favorable;
(2) the presence of ketone carbonyl moiety might play a vital
role in determining significant antibacterial activities of these
compounds.
We have explored the influence of substituents at position 4
of phenyl ring on the ability of these compounds against
Gram-positive pathogens. To acquire more information about
the structural requirements for the possible improvement of

1740
J. Liu et al. / European Journal of Medicinal Chemistry 44 (2009) 1737e1744
Table 1
In vitro antibacterial activities of 4-alkylphenyl b-aldehyde ketones and their
derivatives
4. Experimental
4.1. Reagents and general methods
Compounds
MIC (mg/mL)
Staphylococcus
aureus
(ATTC-25923)
Escherichia
coli
(ATTC-25922)
Pseudomonas
aeruginosa
(ATTC-27853)
Most chemical reagents were purchased from Darui
Chemical Co. (Shanghai, PR China) and 1-(4-alkylphenyl)
ethanones were prepared by the FeC acylation reaction
according to the methods described by Wang [19]. Toluene
was dried over molecular sieve. The other commercially avail-
able reagents and solvents were used without further purifica-
tion. All reactions were monitored by TLC (Merck Kieselgel
60, F254). Melting points (mp) were determined with WRS-
1B melting point apparatus and are uncorrected. NMR spectra
were recorded on Mercury-Plus300 spectrometers at 25 ꢀC us-
ing CDCl3 or DMSO-d6 as a solvent. All chemical shifts (d)
were quoted in parts per million downfield from TMS and cou-
pling constants (J ) are given in hertz. Abbreviations used in
the splitting pattern were as follows: s ¼ singlet, d ¼ doublet,
t ¼ triplet, m ¼ multiplet, br ¼ broad. Infrared (IR) spectra
were recorded on a PerkineElmer Infracord 221 spectrometer
and reported in cmꢁ1. LCeMS spectra were recorded using
the LCMS-2010A. Elemental analyses were performed on
a Vario EL instrument.
5
>64
>64
>64
>64
>64
>64
>64
>64
64
>64
>64
>64
>64
>64
>64
>64
>64
>64
>64
>64
64
>64
>64
>64
>64
>64
>64
>64
>64
>64
>64
>64
64
6
7
8
9
10
11
12
13
14
64
64
15
16
4
17
18
4
64
64
4
>64
>64
>64
>64
>64
>64
>64
>64
64
>64
>64
>64
>64
>64
>64
>64
>64
64
19
20
4
32
21
22
32
2
23
24
1
32
25
26
32
4
4.2. General procedures for 4-alkylphenyl
b-aldehyde ketone (5, 6) [20]
27
28
4
64
>64
>64
>64
32
>64
>64
>64
>64
0.5
29
64
Clarithromycin
Levofloxacin
Houttuynin
0.12
0.25
32
1-(4-Alkylphenyl) ethanone (0.05 mol) was dissolved in dry
toluene and the mixture was stirred in the ice bath. Sodium
(0.075 mol) was added to the solution and the mixture was
stirred for 30 min in the ice bath. Ethyl formate was then added
dropwise to the reaction mixture, which was maintained at
<5 ꢀC, after the addition, the reaction mixture was stirred for
another 2 h and allowed to warm to room temperature, then
stirred overnight (about 15 h). Water (150 mL) was added to
the slurry mixture, and the reaction was stirred for an additional
30 min and then partitioned between organic layer and water.
Water layer was extracted with dichloromethane (2 ꢂ 50 mL).
These extracts were discarded and pooled. The aqueous phase
was acidified with 5% hydrochloric acid and extracted with di-
chloromethane (3 ꢂ 50 mL). This extract was washed with wa-
ter and brine, dried over anhydrous sodium sulfate, and the
solvent was removed under reduced pressure to give yellow
oil. 3-Oxo-3-phenylpropanal (5) was purified further by recrys-
tallization from hexane to afford the solid product.
0.025
e
e
the antibacterial properties, synthesis of additional new b-
aldehyde ketone derivatives is desirable. Further biological
evaluation required to confirm these 4-alkyl substituted phenyl
b-aldehyde ketone derivatives in animal models are in prog-
ress in our laboratories. Moreover, the molecular mechanisms
of these compounds are ongoing to further design and develop
more potent compounds.
Table 2
MIC of compound 23, sodium houttuyfonate, and levofloxacin against strains
of Staphylococcus aureus
Strains
MIC (mg/mL)
Compound 23
Levofloxacin
Houttuynin
S. aureus 1
S. aureus 2
S. aureus 3
S. aureus 4
S. aureus 5
S. aureus 6
S. aureus 7
S. aureus 8
S. aureus 9
S. aureus 10
MIC50
4
16
4
0.25
0.5
64
64
64
64
32
64
64
64
64
32
64
64
Table 3
MIC of compounds 16, 22 and 23 against strains of methicillin-resistant
Staphylococcus aureus (MRSA)
0.25
0.25
0.125
0.5
2
1
Compounds MIC (mg/mL)
MRSA1 MRSA2 MRSA3 MRSA4 MRSA5
MIC50 MIC90
4
8
0.25
0.25
0.25
0.5
8
16
22
8
8
8
8
8
8
8
8
8
4
8
8
8
8
4
4
23
Levofloxacin
16
8
8
8
16
16
16
8
8
16
16
16
4
0.25
0.5
8
16
16
16
16
16
16
16
MIC90
8
Houttuynin 16

J. Liu et al. / European Journal of Medicinal Chemistry 44 (2009) 1737e1744
1741
4.2.1. 3-Oxo-3-phenylpropanal (5)
Yield 76%, yellow solid; mp 109e110 ꢀC. IR (KBr): 3059,
2923, 1657, 1591, 1249, 1005, 701 cmꢁ1 1H NMR (300
4.4. General procedure for the preparation of
semicarbazone and thiosemicarbazone of 4-alkylphenyl
b-aldehyde ketone (9e12) [21e23]
.
MHz, CDCl3): d 8.27 (d, J ¼ 4.2 Hz, 1H, ]CH), 7.81 (d, J ¼
8.4 Hz, 2H, PhH), 7.63 (t, J ¼ 7.5 Hz, 1H, PhH), 7.51 (t,
J ¼ 8.1 Hz, 2H, PhH), 6.19 (d, 1H, J ¼ 4.2 Hz, ]CH). 13C
NMR (75 MHz, CDCl3): d 198.6, 172.9, 138.6, 134.0, 130.5,
129.4, 97.1. ESI-MS m/z: 149 (M þ 1).
The corresponding 4-alkylphenyl b-keto aldehyde (5
mmol) was dissolved in anhydrous ethanol (10 mL). Semicar-
bazide or thiosemicarbazide (5 mmol) was added to the
solution. The mixture was stirred for 5e8 h under refluxing
conditions. The reaction mixture was cooled to RT and the
precipitates were filtered.
4.2.2. 3-(4-Methylphenyl)-3-oxopropanal (6)
Yield 65%, yellow oil. IR (KBr): 2963, 1683, 1607, 1417,
1
1056, 843 cmꢁ1. H NMR (300 MHz, CDCl3): d 8.35 (d, J ¼
4.4.1. 3-Oxo-3-phenylpropanal semicarbazone (9)
5.1 Hz, 1H, ]CH), 7.80 (d, J ¼ 8.1 Hz, 2H, PhH), 7.07 (d,
J ¼ 8.1 Hz, 2H, PhH), 6.16 (d, J ¼ 5.1 Hz, H, ]CH), 2.36 (s,
3H, CH3). 13C NMR (75 MHz, CDCl3): d 197.8, 172.5, 152.6,
134.4, 129.1, 126.7, 97.8, 23.8. ESI-MS m/z: 163 (M þ 1).
Yield 52%, yellow solid; mp 170e172 ꢀC. IR (KBr): 3342,
3336, 1685, 1593, 1451, 1068, 745 cmꢁ1. 1H NMR (300 MHz,
DMSO-d6): d 11.31 (br s, 1H, NH), 7.92 (d, J ¼ 7.9 Hz, 2H,
PhH), 7.80 (br s, 1H, NH), 7.62 (t, J ¼ 5.4 Hz, 1H, ]CH),
7.59 (br s, 1H, NH), 7.51 (t, J ¼ 7.5 Hz, 1H, PhH), 7.32 (t, J ¼
8.0 Hz, 2H, PhH), 4.02 (d, J ¼ 5.4 Hz, 2H, CH2). 13C NMR
(75 MHz, CDCl3): d 193.8, 158.2, 154.8, 137.6, 134.3,
129.5, 128.4, 36.2. ESI-MS m/z: 206 (M þ 1).
4.3. General procedure for the preparation
of sodium 1-hydroxy-3-(4-alkylphenyl)-3-
oxopropane-1-sulfonate (7, 8)
1-(4-Alkylphenyl) ethanone (0.05 mol) was dissolved in
dry toluene and stirred in the ice bath. Sodium (0.075
mol) was added to the solution and the mixture was stirred
for 30 min in the ice bath. Ethyl formate was then added drop-
wise to the reaction mixture, which was maintained at <5 ꢀC,
after the addition, the mixture was stirred for another 2 h. Then
the reaction mixture was warmed to RT and stirred overnight
(about 15 h). The precipitates were separated by filtration and
dried to afford the corresponding sodium salt of 4-alkylphenyl-
3-hydroxyprop-2-en-1-one. The treatment of sodium salt of 4-
alkylphenyl-3-hydroxyprop-2-en-1-one with saturated solution
of sodium bisulfite at RT for 2 h, the precipitates were separated
by filtration and crystallized from 50% ethanol to afford sodium
1-hydroxy-3-(4-alkylphenyl)-3-oxopropane-1-sulfonate.
4.4.2. 3-Oxo-3-phenylpropanal thiosemicarbazone (10)
Yield 91%, yellow solid; mp 180e181 ꢀC. IR (KBr): 3369,
3265, 1650, 1593, 1065, 748 cmꢁ1 1H NMR (300 MHz,
.
DMSO-d6): d 11.62 (br s, 1H, NH), 8.28 (br s, 1H, NH),
7.86 (d, J ¼ 8.7 Hz, 2H, PhH), 7.70 (t, J ¼ 5.7 Hz, 1H,
]CH), 7.56 (br s, 1H, NH), 7.48 (t, J ¼ 8.1 Hz, 1H, PhH),
7.28 (t, J ¼ 7.6 Hz, 2H, PhH), 4.46 (d, J ¼ 5.7 Hz, 2H, CH2).
13C NMR (75 MHz, CDCl3): d 196.4, 183.1, 154.7, 130.8,
129.6, 129.2, 127.6, 35.8. ESI-MS m/z: 222 (M þ 1).
4.4.3. 3-Oxo-3-p-tolylpropanal semicarbazone (11)
Yield 72%, yellow solid; mp 183e185 ꢀC. IR (KBr): 3241,
3178, 2920, 1713, 1599, 1438, 807 cmꢁ1. 1H NMR (300 MHz,
DMSO-d6): d 10.01 (br s, 1H, NH), 8.22 (br s, 1H, NH2), 7.87
(d, J ¼ 8.4 Hz, 2H, PhH), 7.51 (br s, 1H, NH2), 7.34 (d,
J ¼ 8.4 Hz, 2H, PhH), 7.25 (t, J ¼ 5.4 Hz, 1H, CH), 6.18 (br s,
1H, NH2), 3.96 (d, J ¼ 5.4 Hz, 2H, CH2), 2.37 (s, 3H, CH3).
13C NMR (75 MHz, CDCl3): d 195.6, 159.1, 154.7, 139.9,
133.3, 129.3, 128.4, 35.2, 23.4. ESI-MS m/z: 220 (M þ 1).
4.3.1. Sodium 1-hydroxy-3-(4-isopropylphenyl)-
3-oxopropane-1-sulfonate (7)
Yield 63%, white solid; mp 192e194 ꢀC. IR (KBr): 3449,
2960, 1683, 1606, 1411, 1361, 1060, 827 cmꢁ1. 1H NMR (300
MHz, DMSO-d6): d 7.80 (d, J ¼ 6.6 Hz, 2H, PhH), 7.33 (d,
J ¼ 6.6 Hz, 2H, PhH), 5.28 (t, 1H, CH), 4.88 (s, 1H, OH),
3.35 (d, 2H, CH2), 2.86e2.89 (m, 1H, CH), 1.12 (d, 6H,
2CH3). 13C NMR (75 MHz, CDCl3): d 194.5, 152.8, 136.7,
129.5, 126.1, 81.4, 56.8, 36.7, 23.2. ESI-MS m/z: 271 (M ꢁ 23).
4.4.4. 3-Oxo-3-p-tolylpropanal thiosemicarbazone (12)
Yield 58%, yellow solid; mp 158e159 ꢀC. IR (KBr): 3250,
.
3171, 1664, 1594, 1167, 827 cmꢁ1 1H NMR (300 MHz,
DMSO-d6): d 11.26 (br s, 1H, NH), 8.16 (br s, 1H, NH2),
7.87 (d, J ¼ 8.1 Hz, 2H, PhH), 7.63 (br s, 1H, NH2), 7.59 (t,
J ¼ 5.7 Hz, 1H, CH), 7.34 (d, J ¼ 8.1 Hz, 2H, PhH), 4.01 (d, J
¼ 5.7 Hz, 2H, CH2), 2.38 (s, 3H, CH3). 13C NMR (75 MHz,
CDCl3): d 191.6, 183.1, 154.9, 138.5, 130.8, 129.6, 128.0,
34.3, 24.3. ESI-MS m/z: 236 (M þ 1).
4.3.2. Sodium 1-hydroxy-3-oxo-3-(4-pentylphenyl)
propane-1-sulfonate (8)
Yield 46%, white solid; mp 179e181 ꢀC. IR (KBr): 3424,
3238, 2925, 1677, 1599, 1412, 1053, 829 cmꢁ1 1H NMR
.
(300 MHz, DMSO-d6): d 7.84 (d, J ¼ 8.1 Hz, 2H, PhH), 7.31
(d, J ¼ 8.1 Hz, 2H, PhH), 4.91 (t, 1H, CH), 4.72 (s, 1H,
OH), 3.18 (d, 2H, CH2), 2.59 (t, 2H, CH2), 1.87e1.89 (m,
4H, 2CH2), 1.53e1.55 (m, 2H, CH2), 0.75 (t, J ¼ 6.3 Hz,
3H, CH3). 13C NMR (75 MHz, CDCl3): d 192.4, 143.5,
134.7, 129.1, 128.6, 82.8, 54.7, 36.1, 31.9, 31.1, 23.0, 14.6.
ESI-MS m/z: 299 (M ꢁ 23).
4.5. General procedure for the preparation of
oxime and oxime-ether of 4-alkyl-phenyl
b-aldehyde ketone (13e29)
The sodium salt of 4-alkylphenyl-3-hydroxyprop-2-en-1-one
(5 mmol) was added to 20 mL anhydrous ethanol and the

1742
J. Liu et al. / European Journal of Medicinal Chemistry 44 (2009) 1737e1744
mixture was stirred at RT. The corresponding hydroxylamine hy-
drochloride, methoxyamine hydrochloride or ethoxyamine hy-
drochloride (5 mmol or 10 mmol) were added to the reaction
mixture. The mixture was stirred at RT for 6e9 h. After comple-
tion of the reaction as indicated by TLC, the solution was con-
centrated in vacuo. The residue was dissolved in methylene
chloride and washed with water. The organic phase was dried
over anhydrous sodium sulfate, filtered and evaporated. The re-
sulting oil obtained was purified by silica gel column chromatog-
raphy to give first the dioxime and dioxime-ether derivatives
followed by the oxime and oxime-ether derivatives.
J ¼ 6.9 Hz, 3H, CH3). 13C NMR (75 MHz, CDCl3): d 195.4,
145.0, 143.8, 133.9, 129.6, 128.5, 69.9, 39.5, 22.0, 15.0.
ESI-MS m/z: 206 (M þ 1). Anal. Calcd for C12H15NO2: C,
70.22; H, 7.37; N, 6.82. Found: C, 70.54; H, 7.22; N, 6.47.
4.5.6. 3-(4-Ethylphenyl)-3-oxopropanal
oxime-methyl ether (18)
Yield 64%, yellow oil. IR (KBr): 2967, 2937, 1684, 1607,
1
1413, 1346, 1042, 821 cmꢁ1. H NMR (300 MHz, CDCl3):
d 7.90 (d, J ¼ 7.2 Hz, 2H, PhH), 7.67 (t, J ¼ 4.8 Hz, 1H,
CH), 7.30 (d, J ¼ 7.2 Hz, 2H, PhH), 4.00, 3.86 (dd, J ¼ 4.8,
8.1 Hz, 2H, CH2), 3.93 (s, 3H, CH3), 2.67e2.75 (m, 2H,
CH2), 1.29 (t, J ¼ 7.5 Hz, 3H, CH3). 13C NMR (75 MHz,
CDCl3): d 194.6, 150.8, 145.3, 134.1, 128.6, 128.4, 62.1,
39.3, 29.3, 15.5. ESI-MS m/z: 206 (M þ 1). Anal. Calcd for
C12H15NO2: C, 70.22; H, 7.37; N, 6.82. Found: C, 69.85; H,
7.10; N, 6.75.
4.5.1. 3-Oxo-3-phenylpropanal oxime (13)
Yield 58%, yellow solid; mp 135e136 ꢀC. IR (KBr): 3427,
1640, 1605, 1150 cmꢁ1. 1H NMR (300 MHz, CDCl3): d 7.86 (d,
J ¼ 7.9 Hz, 2H, PhH), 7.77 (t, J ¼ 5.4 Hz, 1H, CH), 7.49 (t, J
¼ 7.1 Hz, 1H, PhH), 7.31 (t, J ¼ 7.5 Hz, 2H, PhH), 3.45 (d,
J ¼ 5.4 Hz, 2H, CH2). 13C NMR (75 MHz, CDCl3): d 195.8,
154.2, 137.8, 127.0, 124.4, 124.3, 34.6. ESI-MSm/z: 164 (M þ 1).
4.5.7. 3-(4-Ethylphenyl)-3-oxopropanal
oxime-ethyl ether (19)
Yield 68%, yellow oil. IR (KBr): 2971, 2932, 1684, 1602,
4.5.2. 3-Oxo-3-phenylpropanal oxime-methyl ether (14)
Yield 62%, yellow solid; mp 73e75 ꢀC. IR (KBr): 2947,
.
1657, 1595, 1149, 1005, 768 cmꢁ1 1H NMR (300 MHz,
1
1411, 1333, 1046, 824 cmꢁ1. H NMR (300 MHz, CDCl3):
d 7.90 (d, J ¼ 8.0 Hz, 2H, PhH), 7.64 (t, J ¼ 3.9 Hz, 1H, CH),
7.28 (d, J ¼ 8.0 Hz, 2H, PhH), 4.09e4.18 (m, 2H, CH2), 4.00,
3.86 (dd, J ¼ 3.9, 6.3 Hz, 2H, CH2), 2.66e2.73 (m, 2H, CH2),
1.23e1.29 (m, 6H, 2CH3). 13C NMR (75 MHz, CDCl3):
d 193.9, 149.1, 144.2, 130.6, 129.6, 125.4, 69.9, 38.4, 29.2,
16.3, 14.8. ESI-MS m/z: 220 (M þ 1). Anal. Calcd for
C13H17NO2: C, 71.21; H, 7.81; N, 6.39. Found: C, 71.51; H,
7.90; N, 6.59.
CDCl3): d 7.83 (d, J ¼ 8.3 Hz, 2H, PhH), 7.63 (t, J ¼ 6.0 Hz,
1H, CH), 7.51 (t, J ¼ 8.1 Hz, 1H, PhH), 7.35 (t, J ¼ 7.5 Hz,
2H, PhH), 3.92, 3.75 (dd, J ¼ 6.0, 6.9 Hz, 2H, CH2), 3.71 (s,
3H, CH3). 13C NMR (75 MHz, CDCl3): d 192.7, 142.3,
133.8, 131.0, 128.7, 127.9, 61.0, 34.1. ESI-MS m/z: 178
(M þ 1). Anal. Calcd for C10H11NO2: C, 67.78; H, 6.26; N,
7.90. Found: C, 68.12; H, 6.39; N, 7.78.
4.5.3. 3-Oxo-3-p-tolylpropanal oxime (15)
Yield 46%, yellow solid; mp 176e178 ꢀC. IR (KBr): 3592,
4.5.8. 3-(4-Ethylphenyl)-3-oxopropanal
dioxime-methyl ether (20)
Yield 31%, yellow oil. IR (KBr): 2965, 2820, 1684, 1571,
3083, 1642, 1607, 1458, 829 cmꢁ1 1H NMR (300 MHz,
.
CDCl3): d 7.71 (t, J ¼ 5.1 Hz, 1H, CH), 7.53 (d, J ¼ 8.1 Hz,
2H, PhH), 7.25 (d, J ¼ 8.1 Hz, 2H, PhH), 3.45 (d, J ¼
5.1 Hz, 2H, CH2), 2.32 (s, 3H, CH3). 13C NMR (75 MHz,
CDCl3): d 192.7, 154.3, 137.8, 132.6, 127.3, 124.1, 34.6,
19.3. ESI-MS m/z: 178 (M þ 1).
1
1425, 1335, 1048, 837 cmꢁ1. H NMR (300 MHz, CDCl3):
d 7.60 (d, J ¼ 8.4 Hz, 2H, PhH), 7.42 (t, J ¼ 5.4 Hz, 1H, CH),
7.21 (d, J ¼ 8.4 Hz, 2H, PhH), 3.92e4.00 (m, 6H, 2CH3),
3.77, 3.63 (dd, J ¼ 5.4, 6.3 Hz, 2H, CH2), 2.64e2.70 (m, 2H,
CH2), 1.27 (t, J ¼ 7.5 Hz, 3H, CH3). 13C NMR (75 MHz,
CDCl3): d 153.6, 146.1, 132.7, 128.7, 128.1, 126.5, 62.5, 62.1,
29.0, 25.2, 15.8. ESI-MS m/z: 235 (M þ 1). Anal. Calcd for
C13H18N2O2: C, 66.64; H, 7.74; N, 11.96. Found: C, 66.87; H,
7.93; N, 11.91.
4.5.4. 3-Oxo-3-p-tolylpropanal oxime-methyl ether (16)
Yield 68%, yellow oil. IR (KBr): 2939, 1648, 1574, 1419,
1
1047, 819 cmꢁ1. H NMR (300 MHz, CDCl3): d 7.68 (t, J ¼
5.1 Hz, 1H, CH), 7.58 (d, J ¼ 8.1 Hz, 2H, PhH), 7.21 (d, J ¼
8.1 Hz, 2H, PhH), 4.01 (s, 3H, CH3), 4.00, 3.85 (dd, J ¼ 5.1,
8.1 Hz, 2H, CH2), 2.31 (s, 3H, CH3). 13C NMR (75 MHz,
CDCl3): d 195.3, 145.3, 144.1, 133.9, 129.6, 128.5, 62.1,
39.3, 22.0. ESI-MS m/z: 192 (M þ 1). Anal. Calcd for
C11H13NO2: C, 69.09; H, 6.85; N, 7.32. Found: C, 69.34; H,
6.67; N, 7.71.
4.5.9. 3-(4-Ethylphenyl)-3-oxopropanal
dioxime-ethyl ether (21)
Yield 28%, yellow oil. IR (KBr): 2972, 2933, 2820, 1682,
.
1577, 1382, 1337, 1048, 832 cmꢁ1 1H NMR (300 MHz,
CDCl3): d 7.61 (d, J ¼ 8.4 Hz, 2H, PhH), 7.49 (t, J ¼ 4.5 Hz,
1H, CH), 7.21 (d, J ¼ 8.4 Hz, 2H, PhH), 4.08e4.30 (m, 4H,
2CH2), 3.81, 3.67 (dd, J ¼ 4.5, 5.7 Hz, 2H, CH2), 2.63e2.70
(m, 2H, CH2), 1.23e1.37 (m, 9H, 3CH3). 13C NMR
(75 MHz, CDCl3): d 153.3, 145.9, 133.1, 128.6, 128.2,
126.4, 70.2, 69.4, 29.0, 25.4, 15.9, 15.2, 14.9. ESI-MS m/z:
263 (M þ 1). Anal. Calcd for C15H22N2O2: C, 68.67; H,
8.45; N, 10.68. Found: C, 68.87; H, 8.27; N, 10.47.
4.5.5. 3-Oxo-3-p-tolylpropanal oxime-ethyl ether (17)
Yield 57%, yellow oil. IR (KBr): 2977, 1614, 1515, 1382,
1
1046, 820 cmꢁ1. H NMR (300 MHz, CDCl3): d 7.89 (d, J ¼
7.8 Hz, 2H, PhH), 7.66 (t, J ¼ 4.8 Hz, 1H, CH), 7.28 (d, J ¼
7.8 Hz, 2H, PhH), 4.10e4.19 (m, 2H, CH2), 4.02, 3.63 (dd,
J ¼ 5.1, 8.1 Hz, 2H, CH2), 2.42 (s, 3H, CH3), 1.29 (t,

J. Liu et al. / European Journal of Medicinal Chemistry 44 (2009) 1737e1744
1743
4.5.10. 3-(4-Isopropylphenyl)-3-oxopropanal
oxime-methyl ether (22)
Yield 77%, yellow oil. IR (KBr): 2963, 2821, 1684, 1606,
(m, 4H, 2CH2), 0.92 (t, J ¼ 6.3 Hz, 3H, CH3). 13C NMR
(75 MHz, CDCl3): d 193.9, 149.7, 145.3, 134.1, 129.0,
128.6, 62.1, 39.4, 36.3, 31.8, 31.1, 22.9, 14.4. ESI-MS m/z:
248 (M þ 1). Anal. Calcd for C15H21NO2: C, 72.84; H, 8.56;
N, 5.66. Found: C, 72.64; H, 8.46; N, 5.49.
1
1417, 1364, 1054, 853 cmꢁ1. H NMR (300 MHz, CDCl3):
d 7.92 (d, J ¼ 7.3 Hz, 2H, PhH), 7.66 (t, J ¼ 4.8 Hz, 1H, CH),
7.34 (d, J ¼ 7.3 Hz, 2H, PhH), 4.01, 3.87 (dd, J ¼ 4.8, 7.5 Hz,
2H, CH2), 3.94 (s, 3H, CH3), 2.96e3.00 (m, 1H, CH), 1.30 (d,
J ¼ 6.6 Hz, 6H, 2CH3). 13C NMR (75 MHz, CDCl3): d 194.3,
154.6, 148.2, 134.5, 128.7, 127.8, 61.7, 39.0, 31.3, 19.5. ESI-
MS m/z: 220 (M þ 1). Anal. Calcd for C13H17NO2: C, 71.21;
H, 7.81; N, 6.39. Found: C, 71.52; H, 7.97; N, 6.22.
4.5.15. 3-Oxo-3-(4-pentylphenyl)propanal
oxime-ethyl ether (27)
Yield 64%, yellow oil. IR (KBr): 2957, 2931, 2858, 1683,
.
1606, 1573, 1415, 1045, 875 cmꢁ1 1H NMR (300 MHz,
CDCl3): d 7.91 (d, J ¼ 8.1 Hz, 2H, PhH), 7.67 (t, J ¼ 4.8 Hz,
1H, CH), 7.28 (d, J ¼ 8.1 Hz, 2H, PhH), 4.22 (m, 2H, CH2),
4.02, 3.87 (dd, J ¼ 4.8, 6.0 Hz, 2H, CH2), 2.69 (t,
J ¼ 7.8 Hz, 2H, CH2), 1.62e1.69 (m, 2H, CH2), 1.24e1.35
(m, 7H, 2CH2, CH3), 0.92 (t, J ¼ 6.6 Hz, 3H, CH3). 13C
NMR (75 MHz, CDCl3): d 194.8, 149.6, 145.0, 134.1, 129.2,
128.6, 69.6, 39.6, 36.3, 31.8, 31.1, 22.9, 15.0, 14.4. ESI-MS
m/z: 262 (M þ 1). Anal. Calcd for C16H23NO2: C, 73.53; H,
8.87; N, 5.36. Found: C, 73.21; H, 8.46; N, 5.40.
4.5.11. 3-(4-Isopropylphenyl)-3-oxopropanal
oxime-ethyl ether (23)
Yield 81%, yellow oil. IR (KBr): 2966, 2870, 1683, 1605,
1
1413, 1387, 1047, 822 cmꢁ1. H NMR (300 MHz, CDCl3):
d 7.93 (d, J ¼ 8.4 Hz, 2H, PhH), 7.68 (t, J ¼ 4.8 Hz, 1H, CH),
7.34 (d, J ¼ 8.4 Hz, 2H, PhH), 4.15e4.22 (m, 2H, CH2), 4.11,
3.89 (dd, J ¼ 4.8, 6.3 Hz, 2H, CH2), 2.91e3.03 (m, 1H, CH),
1.30 (d, 9H, 3CH3). 13C NMR (75 MHz, CDCl3): d 193.7,
149.8, 143.9, 131.2, 128.6, 126.1, 69.7, 38.4, 29.1, 16.8, 14.5.
ESI-MS m/z: 234 (M þ 1). Anal. Calcd for C14H19NO2: C,
72.07; H, 8.21; N, 6.00. Found: C, 72.37; H, 8.39; N, 5.86.
4.5.16. 3-Oxo-3-(4-pentylphenyl)propanal
dioxime-methyl ether (28)
Yield 32%, yellow oil. IR (KBr): 2932, 2862, 1576, 1427,
1
1336, 1048, 852 cmꢁ1. H NMR (300 MHz, CDCl3): d 7.59
4.5.12. 3-(4-Isopropylphenyl)-3-oxopropanal
dioxime-methyl ether (24)
(d, J ¼ 8.1 Hz, 2H, PhH), 7.45 (t, J ¼ 5.1 Hz, 1H, CH), 7.19
(d, J ¼ 8.1 Hz, 2H, PhH), 4.00 (s, 3H, CH3), 3.93 (s, 3H,
CH3), 3.77, 3.63 (dd, J ¼ 5.1, 6.0 Hz, 2H, CH2), 2.64 (t, 2H,
CH2), 1.59e1.64 (m, 2H, CH2), 1.31e1.33 (m, 4H, 2CH2),
0.92 (t, J ¼ 6.6 Hz, 3H, CH3). 13C NMR (75 MHz, CDCl3):
d 153.6, 146.1, 144.7, 132.6, 128.8, 126.5, 62.4, 61.8, 36.0,
31.8, 31.4, 28.5, 22.9, 14.4. ESI-MS m/z: 277 (M þ 1). Anal.
Calcd for C16H24N2O2: C, 69.53; H, 8.75; N, 10.14. Found:
C, 69.88; H, 8.35; N, 9.82.
Yield 22%, yellow oil. IR (KBr): 2961, 2820, 1574, 1417,
1339, 1051, 837 cmꢁ1. 1H NMR (300 MHz, CDCl3): d 7.61 (d,
J ¼ 8.4 Hz, 2H, PhH), 7.43 (t, J ¼ 4.8 Hz, 1H, CH), 7.24 (d,
J ¼ 8.4 Hz, 2H, PhH), 3.83e4.00 (m, 6H, 2CH3), 3.77, 3.63
(dd, J ¼ 4.8, 6.3 Hz, 2H, CH2), 2.87e2.94 (m, 1H, CH), 1.27 (d,
J ¼ 6.6 Hz, 6H, 2CH3). 13C NMR (75 MHz, CDCl3): d 153.4,
146.0, 133.1, 128.9, 128.5, 126.2, 62.9, 62.2, 29.3, 24.9, 15.2.
ESI-MS m/z: 249 (M þ 1). Anal. Calcd for C14H20N2O2: C,
67.71; H, 8.12; N, 11.28. Found: C, 68.12; H, 8.25; N, 11.21.
4.5.17. 3-Oxo-3-(4-pentylphenyl)propanal
dioxime-ethyl ether (29)
Yield 35%, yellow oil. IR (KBr): 2931, 1514, 1381, 1336,
.
1045, 865 cmꢁ1 1H NMR (300 MHz, CDCl3): d 7.60 (d,
J ¼ 8.1 Hz, 2H, PhH), 7.47 (t, J ¼ 5.1 Hz, 1H, CH), 7.20 (d,
J ¼ 8.1 Hz, 2H, PhH), 4.04e4.29 (m, 4H, 2CH2), 3.79, 3.67
(dd, J ¼ 5.1, 6.0 Hz, 2H, CH2), 2.64 (t, J ¼ 7.5 Hz, 2H, CH2),
1.57e1.66 (m, 2H, CH2), 1.31e1.35 (m, 6H, 2CH3), 1.21e
1.31 (m, 4H, 2CH2), 0.92 (t, J ¼ 6.6 Hz, 3H, CH3). 13C NMR
(75 MHz, CDCl3): d 153.5, 145.9, 144.1, 132.6, 128.2, 126.4,
70.2, 69.4, 36.1, 31.7, 31.0, 29.0, 22.4, 15.9, 15.7, 14.5. ESI-
MS m/z: 305 (M þ 1). Anal. Calcd for C18H28N2O2: C, 71.02;
H, 9.27; N, 9.20. Found: C, 71.08; H, 9.35; N, 9.25.
4.5.13. 3-(4-Isopropylphenyl)-3-oxopropanal
dioxime-ethyl ether (25)
Yield 18%, yellow oil. IR (KBr): 2968, 2933, 2880, 1570,
1
1417, 1384, 1046, 837 cmꢁ1. H NMR (300 MHz, CDCl3):
d 7.60 (d, J ¼ 7.3 Hz, 2H, PhH), 7.48 (t, J ¼ 5.1 Hz, 1H,
CH), 7.23 (d, J ¼ 7.3 Hz, 2H, PhH), 4.08e4.27 (m, 4H,
2CH2), 3.80, 3.64 (dd, J ¼ 5.1, 6.3 Hz, 2H, CH2), 2.88e2.94
(m, 1H, CH), 1.25e1.37 (m, 12H, 4CH3). 13C NMR
(75 MHz, CDCl3): d 153.6, 145.8, 132.8, 128.6, 128.1,
126.6, 70.5, 69.7, 29.2, 25.0, 15.9, 15.1, 14.7. ESI-MS m/z:
277 (M þ 1). Anal. Calcd for C16H24N2O2: C, 69.53; H,
8.75; N, 10.14. Found: C, 69.28; H, 8.79; N, 10.13.
4.6. In vitro antibacterial activity assays
4.5.14. 3-Oxo-3-(4-pentylphenyl)propanal
oxime-methyl ether (26)
Yield 69%, yellow oil. IR (KBr): 2957, 2932, 2858, 1684,
All the synthesized compounds were tested for their antibac-
terial activity against both Gram-positive (S. aureus) and Gram-
negative (E. coli and P. aeruginosa) bacteria strains. The test
was performed by the agar dilution method according to the
Clinical and Laboratory Standard Institute (CLSI) (formerly
National Committee for Clinical Laboratory Standards) [18].
Twofold serial dilutions of the compounds and reference drugs
1606, 1570, 1414, 1042, 863 cmꢁ1 1H NMR (300 MHz,
.
CDCl3): d 7.90 (d, J ¼ 8.1 Hz, 2H, PhH), 7.67 (t, J ¼ 4.8 Hz,
1H, CH), 7.29 (d, J ¼ 8.1 Hz, 2H, PhH), 4.01, 3.87 (dd,
J ¼ 4.8, 6.0 Hz, 2H, CH2), 3.93 (s, 3H, CH3), 2.69 (t,
J ¼ 8.1 Hz, 2H, CH2), 1.60e1.67 (m, 2H, CH2), 1.32e1.35

1744
J. Liu et al. / European Journal of Medicinal Chemistry 44 (2009) 1737e1744
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were prepared in MuellereHinton agar (MHA). The overnight
cultures (after 16e18 h of incubation at 37 ꢀC) of all the bacte-
ria were used for the assay and adjusted to the turbidity of a 0.5
McFarland Standard. The stock solution (1 mg/mL) of all the
test chemicals was prepared by dissolving 1 mg of the test
chemical in 1 mL of dimethylsulfoxide (DMSO), and DMSO
was used as control for all the test compounds. Twenty
milliliters of MHA and 500 mL of each test bacterial culture
of 16e18 h incubation adjusted at 0.5 McFarland were mixed
and poured into sterilized and labeled plates. The wells of
6 mm diameter were punched in the solidified agar plates.
Test chemicals of 100 mL were added to individual wells. The
loaded plates were incubated at 37 ꢀC for 24 h. The diameter
of zone of growth inhibition around each well was measured
after incubation using a Vernier Caliper. The MIC value is the
lowest concentration of the antimicrobial agent that prevents
the development of viable growth after16e18 h incubation.
MIC values (mg/mL) were determined on MuellereHinton
(MH) agar with medium containing dilutions of antibacterial
agents by the literature method [3,24]. Stock solution of 4 mg/
mL was prepared in DMSO and was appropriately diluted to
get final concentrations of 64, 32, 16, 8, 4, 2, 1, 0.5, 0.25 and
0.12 mg/mL. Levofloxacin (purchased from Darui Chemical
Co.), clarithromycin (purchased from Hisunpharm Co.) and
Houttuynin (purchased from Guangzhou Qingping Group
Corporation Limited) were used as positive control.
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