Design, synthesis and biological evaluation of 3-(4-halophenyl)-3- oxopropanal and their derivatives as novel antibacterial agents

Article abstract of DOI:10.1248/cpb.58.1127

In continuing our program aimed to search for potent drugs for bacterial infections, a series of 3-(4-halophenyl)-3-oxopropanal and their derivatives were designed, synthesized and their antibacterial activities in vitro against both Gram-positive bacteri

Full text of DOI:10.1248/cpb.58.1127

September 2010
Regular Article
Chem. Pharm. Bull. 58(9) 1127—1131 (2010)
1127
Design, Synthesis and Biological Evaluation of 3-(4-Halophenyl)-3-
oxopropanal and Their Derivatives as Novel Antibacterial Agents
Jinbing LIU, ,a,b Wei YI,b Jianming HU,a Fengyan WU,a Liangzhong ZHAO,a Huacan SONG,b and
*
c
Zhihou WANG
a Department of Biology and Chemical Engineering, Shaoyang University; Shao Shui Xi Road, Shaoyang 422100, P. R.
China: b School of Chemistry and Chemical Engineering, Sun Yat-sen University; 135 Xin Gang Xi Road, Guangzhou
510275, P. R. China: and c Centre for Drug Evaluation, State Drug Administration; Beijing 100050, P. R. China.
Received January 15, 2010; accepted June 6, 2010; published online June 11, 2010
In continuing our program aimed to search for potent drugs for bacterial infections, a series of 3-(4-
halophenyl)-3-oxopropanal and their derivatives were designed, synthesized and their antibacterial activities in
vitro against both Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli
and Pseudomonas aeruginosa were evaluated. Compounds 7, 8, 13—16, 21 and 22 had moderate antibacterial ac-
tivities against Staphylococcus aureus (minimal inhibitory concentration (MIC) Ͻ16 mg/ml), suggesting that the
introduction of mono-methoxyamine or ethoxyamine moiety might play an important role in determining the po-
tent antibacterial activities. Furthermore, the antibacterial activities of select compounds 7, 15 and 16 against
the clinically important pathogenic bacteria-methicillin-resistant Staphylococcus aureus (MRSA) were also inves-
tigated. Results showed that these compounds exhibited more potent activities than the well-known antibacterial
agents Houttuynin and Levofloxacin.
Key words synthesis; 3-(4-halophenyl)-3-oxopropanal; derivative; antibacterial activity; structure–activity relationship analysis
The increasing incidence of bacterial resistance to cur- crobial medicine in clinical practice because of better activity
rently available antibacterial agents is a growing global and lower side effect than Houttuynin.9—11) These results in-
health problem. Therefore, modern medicine is engaged in dicated that the modification of aldehyde group of Hout-
an eager quest for new antibiotics, which can treat the infec- tuynin might facilitate the antibacterial activity.
tions caused by constantly emerging antibiotic resistant bac-
More recently, our group described that 3-(4-alkylphenyl)-
teria.1—3) So far, many efforts have been spent in the search 3-oxopropane derivatives showed moderate antibacterial ac-
for effective and safe antibacterial drugs, and a large number tivities against Gram-positive pathogen Staphylococcus au-
of naturally occurring and synthetic antibiotics have already reus (ATTC-25923). The preliminary structure–activity rela-
been reported. However, most of them are not potent enough tionship (SAR) analysis showed that the introduction of ap-
to put into practical use due to their weak individual activi- propriate substituent into position 4 of phenyl ring enhanced
ties or safety concerns. For example, due to undesirable side antibacterial activities of these compounds.12) In addition,
effects, Grepafloxacin and Ttrovafloxacin were withdrawn some literatures also reported that the introduction of halo-
from the market and their use is now prohibited in several gen could significantly increased the antibacterial activity.13)
countries.4—6) Obviously, this is still needed to search and de-
velop novel antibacterial drugs with better activities together vestigation, a series of 3-(4-halophenyl)-3-oxopropanal and
with lower side effects. their derivatives were designed, synthesized and their anti-
Taking advantage of above information, in the present in-
Houttuynin, n-nonyl-b-oxo-aldehyde (Fig. 1), was origi- bacterial activities against Gram-negative and Gram-positive
nally isolated as one of the main active constituents from bacteria in vitro were evaluated. Furthermore, the SAR was
Houttuynina cordata THUNB, which has been used as antibi- also discussed. The purpose of this study was to investigate
otic drug for a long time in China.7) Recently studies have the antibacterial effect of 3-(4-halophenyl)-3-oxopropanal
showed that Houttuyfonate homologues (HOU-Cn) derived derivatives, with the ultimate aim of developing novel potent
from Houttuynin could improve the immune ability of mice antibacterial drugs with better activities and lower side ef-
and inhibit the growth of Staphylococcus aureus and Bacillus fects.
subtilis efficiently.8) In addition, it was worthy noted that,
Experimental
sodium houttuyfonate (Fig. 1), the addition compound of
Chemistry Most chemical reagents were purchased from Darui Chemi-
sodium bisulfite and Houttuynin, has been used as an antimi-
cal Co. (Shanghai, China), some 1-(4-halophenyl)ethanones were prepara-
tion by the Friedel–Crafts reaction according to the methods described by
Wang and Liang14) tetrahydrofuran (THF) and toluene were dried over mo-
lecular sieve. The other commercially available reagents and solvents were
used without further purification. All reactions were monitored by TLC
(Merck Kieselgel 60, F254). Melting points (mp) were determined with
Shanghai Precision & Scientific Instrument WRS-1B melting point appara-
tus and are uncorrected. NMR spectra were recorded on Varian Mercury-
Plus300 spectrometers at 25 °C using CDCl3 or DMSO-d6 as a solvent. All
chemical shifts (d) are quoted in ppm downfield from tetramethylsilicane
(TMS) and coupling constants (J) are given in Hz. Abbreviations used in the
splitting pattern were an follows: sϭsinglet, dϭdoublet, tϭtriplet, qϭquin-
tet, mϭmultiplet, bϭbroad. Infrared (IR) spectra were recorded on a Perkin-
Elmer Infracord 221 spectrometer and reported in cmϪ1. LC-MS spectra
Fig. 1. The Chemical Structure of Houttuynin and Sodium Houttuyfonate
∗ To whom correspondence should be addressed. e-mail: xtliujb@yahoo.com.cn
© 2010 Pharmaceutical Society of Japan

1128
Vol. 58, No. 9
were recorded using the Shimadzu LCMS-2010A. Elemental analyses were ing 3-(4-halophenyl)-3-oxopropanal (5 mmol) was dissolved in anhydrous
performed on a Vario EL instrument. ethanol (10 ml). Semicarbazide, thiosemicarbazide (5 mmol) was added to
Synthesis. General Procedures for 3-(4-Halophenyl)-3-oxopropane the solution. The mixture was stirred for 5—8 h under refluxing conditions.
(1—3)15) 1-(4-Halophenyl)ethanone (0.05 mol) was dissolved in dry THF The reaction mixture was cooled to room temperature, the precipitate was
or toluene, and stirred in the ice bath. Sodium (0.075 mol) was added to the
solution, the mixture was stirred for 30 min in the ice bath. Ethyl formate
separated by filtration.
Procedure: The corresponding 3-(4-halophenyl)-3-oxopropanal (5
B
was then added dropwise to the reaction mixture, which was maintained at mmol) was dissolved in anhydrous ethanol (10 ml), methoxyamine or
Ͻ5 °C, after the addition, the reaction mixture was stirred for another 2 h. ethoxyamine (5 mmol or 10 mmol) was added to the reaction mixture. The
The reaction mixture was warmed to room temperature and stirred overnight reaction carried out at room temperature for 6—9 h, and the reaction process
(about 15 h). Water (150 ml) was added to the slurry mixture, and the reac-
tion was stirred for an additional 30 min and then portioned between organic
was monitored by TLC. After completion of the reaction, the reaction mix-
ture was concentrated in vacuo, diluted with dichloromethane, washed with
layer and water. Water layer was extracted with two 50 ml portions of water, dried over anhydrous sodium sulfate, concentrated in vacuo. The
dichloromethane. These extracts were discarded. The aqueous phase was residue was workup by chromatography on silica gel to give product.
acidified with acetic acid or 5% hydrochloric acid, and extracted with
3-(4-Fluorophenyl)-3-oxopropanal Oxime-methyl Ether (7): Yield 80%;
dichloromethane (3ϫ50 ml). This extract was washed with water and brine, yellow solid, mp 65—67 °C; IR (KBr) nmax, cmϪ1: 2947, 2911, 1669, 1598,
dried over anhydrous sodium sulfate, and the solvent was removed by rotary 1509, 1215, 829; 1H-NMR (300 MHz, CDCl3) d: 8.01 (d, 2H, Jϭ8.4 Hz,
evaporation under reduced pressure to give thick yellow oil, which was puri- PhH), 7.66 (t, 1H, Jϭ6.0 Hz, CH), 7.18 (d, 2H, Jϭ8.4 Hz, PhH), 4.01 (dd,
fied by crystallization from hexane to afford the 3-(4-halophenyl)-3-oxo- 2H, Jϭ6.0, 6.9 Hz, CH2), 3.87 (s, 3H, CH3); 13C-NMR (75 MHz, CDCl3) d:
propane or by chromatography on silica gel to give product.
194.2, 164.5, 144.9, 132.7, 131.2, 116.3, 61.9, 39.4; ESI-MS m/z: 196
3-(4-Fluorophenyl)-3-oxopropanal (Enolic, 1): Yield 76%, yellow solid, (Mϩ1); Anal. Calcd for C10H10FNO2: C, 61.53; H, 5.16; N, 7.18. Found: C,
mp 53—54 °C; IR (KBr): 1679, 1599, 1232, 845; 1H-NMR (300 MHz,
CDCl3) d: 8.20 (d, 1H, Jϭ4.5 Hz, ϭCH), 7.92 (d, 2H, Jϭ7.6 Hz, PhH), 7.17
(d, 2H, Jϭ7.6 Hz, PhH), 6.18 (d, 1H, Jϭ4.5 Hz, ϭCH); 13C-NMR(75 MHz,
61.59; H, 5.51; N, 7.57.
3-(4-Fluorophenyl)-3-oxopropanal Oxime-ethyl Ether (8): Yield 68%;
yellow solid, mp 55—56 °C; IR (KBr) nmax, cmϪ1: 2983, 2892, 1676, 1597,
CDCl3) d: 188.4, 172.2, 153.6, 132.2, 129.9, 114.8, 96.6; electrospray ion- 1390, 1050, 830; 1H-NMR (300 MHz, CDCl3) d: 8.01 (d, 2H, Jϭ8.5 Hz,
ization-mass spectrometry (ESI-MS) m/z: 167 (Mϩ1); Anal. Calcd for PhH), 7.66 (t, 1H, Jϭ4.8 Hz, CH), 7.17 (d, 2H, Jϭ8.5 Hz, PhH), 4.20—4.10
C9H7FO2: C, 65.06; H, 4.25. Found: C, 65.23; H, 4.11.
(m, 2H, CH2), 4.01 (dd, 2H, Jϭ4.8, 6.0 Hz, CH2), 1.31(t, 3H, Jϭ6.6 Hz,
3-(4-Bromophenyl)-3-oxopropanal (Enolic, 2): Yield 64%, yellow solid, CH3); 13C-NMR (75 MHz, CDCl3) d: 194.2, 164.4, 144.5, 132.8, 131.2,
1
mp 79—80 °C; IR (KBr): 1665, 1585, 837; H-NMR (300 MHz, CDCl3) d: 116.2, 69.7, 39.6, 14.8; ESI-MS m/z: 210 (Mϩ1); Anal. Calcd for
8.27 (d, 1H, Jϭ4.2 Hz, ϭCH), 7.78 (d, 2H, Jϭ7.6 Hz, PhH), 7.62 (d, 2H,
C11H12FNO2: C, 63.15; H, 5.78; N, 6.69. Found: C, 62.89; H, 5.63; N, 6.92.
3-(4-Fluorophenyl)-3-oxopropanal Semicarbazone (9): Yield 80%; yellow
Jϭ7.6 Hz, PhH), 6.19 (d, 1H, Jϭ4.2 Hz, ϭCH); 13C-NMR (75 MHz, CDCl3)
d: 189.5, 172.6, 135.2, 132.2, 129.7, 127.8, 97.9; ESI-MS m/z: 228 (Mϩ1); solid, mp 166—167 °C; IR (KBr) nmax, cmϪ1: 3342, 3336, 1685, 1583, 1451,
1
Anal. Calcd for C9H7BrO2: C, 47.61; H, 3.11. Found: C, 47.96; H, 3.43.
1068, 825; H-NMR (300 MHz, DMSO-d6) d: 9.59 (bs, 1H, NH), 8.06 (d,
3-(4-Iodophenyl)-3-oxopropanal (Enolic, 3): Yield 58%, yellow oil; IR 2H, Jϭ6.8 Hz, PhH), 7.85 (bs, 2H, NH2), 7.67 (t, 1H, Jϭ5.4 Hz, CH), 7.33
(KBr): 1675, 1591, 839; 1H-NMR (300 MHz, CDCl3) d: 8.29 (d, 1H, (d, 2H, Jϭ6.8 Hz, PhH), 3.95 (d, 2H, Jϭ5.4 Hz, CH2); 13C-NMR (75 MHz,
Jϭ4.2 Hz, ϭCH), 7.83 (d, 2H, Jϭ8.4 Hz, PhH), 7.67 (d, 2H, Jϭ8.4 Hz, DMSO-d6) d: 194.3, 158.2, 154.6, 144.3, 132.6, 130.8, 115.7, 35.8; ESI-MS
PhH), 6.21 (d, 1H, Jϭ4.2 Hz, ϭCH); 13C-NMR (75 MHz, CDCl3) d: 189.5, m/z: 224 (Mϩ1); Anal. Calcd for C10H10FN3O2: C, 53.81; H, 4.52; N, 18.83.
172.6, 138.2, 135.8, 129.5, 102.1, 98.5; ESI-MS m/z: 275 (Mϩ1); Anal.
Found: C, 53.89; H, 5.13; N, 18.92.
Calcd for C9H7IO2: C, 39.44; H, 2.57. Found: C, 39.63; H, 2.61.
3-(4-Fluorophenyl)-3-oxopropanal Thiosemicarbazone (10): Yield 82%;
General Procedure for the Preparation of Sodium 1-Hydroxy-3-(4- yellow solid, mp 176—178 °C; IR (KBr) nmax, cmϪ1: 3439, 3260, 1674,
halophenyl)-3-oxopropane-1-sulfonate (4—6) 1-(4-Halophenyl)ethanone 1585, 1408, 827; 1H-NMR (300 MHz, DMSO-d6) d: 11.29 (bs, 1H, NH),
(0.05 mol) was dissolved in dry THF or toluene, and stirred in the ice bath.
Sodium (0.075 mol) was added to the solution, the mixture was stirred for
30 min in the ice bath. Ethyl formate was then added dropwise to the reac-
tion mixture, which was maintained at Ͻ5 °C, after the addition, the reaction
8.07 (d, 2H, Jϭ8.4 Hz, PhH), 7.85 (bs, 2H, NH2), 7.67 (t, 1H, Jϭ5.7 Hz,
CH), 7.35 (d, 2H, Jϭ8.4 Hz, PhH), 4.04 (d, 2H, Jϭ5.7 Hz, CH2); 13C-NMR
(75 MHz, DMSO-d6) d: 195.9, 178.5, 155.6, 142.3, 133.5, 131.8, 116.4,
42.8; ESI-MS m/z: 240 (Mϩ1); Anal. Calcd for C10H10FN3OS: C, 50.20; H,
mixture was stirred for another 2 h. The reaction mixture was warmed to 4.21; N, 17.56. Found: C, 50.56; H, 4.08; N, 17.72.
room temperature and stirred overnight (about 15 h). The precipitates was
separated by filtration, the corresponding enolic sodium was obtained. The
treatment of enolic sodium with saturated sodium bisulfite and acetic acid at
3-(4-Fluorophenyl)-3-oxopropanal Dioxime-methyl Ether (11): Yield
56%; yellow oil; IR (KBr) nmax, cmϪ1: 2940, 2903, 1605, 1512, 1429, 840;
1H-NMR (300 MHz, CDCl3) d: 7.67 (d, 2H, Jϭ8.7 Hz, PhH), 7.66 (t, 1H,
room temperature for 2 h, the precipitates was separated by filtration, which Jϭ5.2 Hz, CH), 7.08 (d, 2H, Jϭ8.7 Hz, PhH), 4.01 (s, 3H, CH3), 3.93 (s, 3H,
was purified by crystallization from 50% ethanol to afford the sodium 1-hy- CH3), 3.76 (dd, 2H, Jϭ5.2, 6.2 Hz, CH2); 13C-NMR (75 MHz, CDCl3) d:
droxy-3-(4-halophenyl)-3-oxopropane-1-sulfonate.
Sodium 1-Hydroxy-3-(4-fluorophenyl)-3-oxopropane-1-sulfonate (4):
158.3, 153.2, 146.0, 128.5, 127.6, 116.6, 62.4, 62.3, 30.6; ESI-MS m/z: 225
(Mϩ1); Anal. Calcd for C11H13FN2O2: C, 58.92; H, 5.84; N, 12.49. Found:
Yield 56%; yellow solid, mp 190—192 °C; IR (KBr): 3239, 1679, 1600, C, 58.87; H, 5.62; N, 12.58.
1
1260, 807; H-NMR (300 MHz, D2O) d: 7.91 (d, 2H, Jϭ8.4 Hz, PhH), 7.68
(d, 2H, Jϭ8.4 Hz, PhH), 5.26 (t, 1H, Jϭ4.2 Hz, CH), 3.40 (d, 2H, Jϭ4.2 Hz,
3-(4-Fluorophenyl)-3-oxopropanal Dioxime-ethyl Ether (12): Yield 62%;
yellow oil; IR (KBr) nmax, cmϪ1: 2987, 2891, 1592, 1384, 1051, 832; 1H-
CH2); 13C-NMR (75 MHz, D2O) d: 192.4, 144.6, 132.7, 131.2, 116.3, 81.4, NMR (300 MHz, CDCl3) d: 7.68 (d, 2H, Jϭ8.4 Hz, PhH), 7.46 (t, 1H,
39.8; ESI-MS m/z: 247 (MϪ23); Anal. Calcd for C9H8FNaO5S: C, 40.00; H, Jϭ5.2 Hz, CH), 7.07 (d, 2H, Jϭ8.4 Hz, PhH), 4.29—4.09 (m, 4H, 2CH2),
2.98. Found: C, 40.32; H, 3.16.
3.78 (dd, 2H, Jϭ5.2, 6.1 Hz, CH2), 1.21—1.36 (m, 6H, 2CH3); 13C-NMR
(75 MHz, CDCl3) d: 162.7, 152.3, 145.5, 128.5, 128.2, 115.8, 70.4, 69.5,
Sodium 1-Hydroxy-3-(4-bromophenyl)-3-oxopropane-1-sulfonate (5):
Yield 33%; yellow solid, mp 204—205 °C; IR (KBr): 3226, 2913, 1679, 28.8, 15.1, 14.8; ESI-MS m/z: 253 (Mϩ1); Anal. Calcd for C13H17FN2O2: C,
1582, 1402, 820; 1H-NMR (300 MHz, D2O) d: 7.85 (d, 2H, Jϭ8.7 Hz, PhH),
7.73 (d, 2H, Jϭ8.7 Hz, PhH), 5.71 (t, 1H, Jϭ4.2 Hz, CH), 3.27 (d,
61.89; H, 6.79; N, 11.10. Found: C, 61.97; H, 6.62; N, 11.23.
3-(4-Chlorophenyl)-3-oxopropanal Oxime-methyl Ether (13): Yield 52%;
2H, Jϭ4.2 Hz, CH2); 13C-NMR (75 MHz, D2O) d: 192.8, 135.2, 132.3, yellow oil; IR (KBr) nmax, cmϪ1: 2971, 2884, 1670, 1584, 1346, 1052, 819;
130.1, 129.5, 81.2, 39.6; ESI-MS m/z: 308 (MϪ23); Anal. Calcd for 1H-NMR (300 MHz, CDCl3) d: 7.68 (d, 2H, Jϭ8.4 Hz, PhH), 7.49 (d, 2H,
C9H8BrNaO5S: C, 32.65; H, 2.44. Found: C, 32.84; H, 2.81.
Jϭ8.4 Hz, PhH), 7.40 (t, 1H, Jϭ4.8 Hz, CH), 3.94 (s, 3H, CH3), 3.69 (dd,
Sodium 1-Hydroxy-3-(4-iodophenyl)-3-oxopropane-1-sulfonate (6): Yield 2H, Jϭ4.8,6.5 Hz, CH2); ESI-MS m/z: 212 (Mϩ1); Anal. Calcd for
45%; yellow solid, mp 238—239 °C; IR (KBr): 3235, 2912, 1678, 1589, C10H10ClNO2: C, 56.75; H, 4.76; N, 6.62. Found: C, 56.53; H, 4.63; N, 6.45.
815; 1H-NMR (300 MHz, D2O) d: 7.74 (d, 2H, Jϭ7.8 Hz, PhH), 7.68 (d, 2H,
Jϭ7.8 Hz, PhH), 5.42 (t, 1H, Jϭ4.5 Hz, CH), 3.18 (d, 2H, Jϭ4.5 Hz, CH2);
13C-NMR (75 MHz, D2O) d: 193.2, 138.2, 135.4, 130.0, 102.1, 81.2, 36.9;
3-(4-Chlorophenyl)-3-oxopropanal Oxime-ethyl Ether (14): Yield 56%;
yellow crystals, mp 94—95 °C; IR (KBr) nmax, cmϪ1: 2936, 2815, 1718,
1
1597, 1484, 1394, 1052, 832; H-NMR (300 MHz, CDCl3) d: 7.99 (d, 2H,
ESI-MS m/z: 355 (MϪ23); Anal. Calcd for C9H8INaO5S: C, 28.59; H, 2.13. Jϭ8.4 Hz, PhH), 7.61 (d, 2H, Jϭ8.4 Hz, PhH), 7.54 (t, 1H, Jϭ4.3 Hz, CH),
Found: C, 28.22; H, 2.43.
General Procedure for the Preparation of Schiff Bases of 3-(4- Jϭ7.0 Hz, CH3); ESI-MS m/z: 226 (Mϩ1); Anal. Calcd for C11H12ClNO2:
Halophenyl)-3-oxopropanal (7—24)16—18) A Procedure: The correspond-
C, 58.54; H, 5.36; N, 6.21. Found: C, 58.50; H, 5.24; N, 6.35.
4.10 (q, 2H, Jϭ7.0 Hz, CH2), 4.08 (dd, 2H, Jϭ4.3, 6.0 Hz, CH2), 1.20 (t, 3H,

September 2010
1129
yellow oil; IR (KBr) nmax, cmϪ1: 2971, 2927, 1671, 1580, 1406, 1054, 824;
1H-NMR (300 MHz, CDCl3) d: 7.70 (d, 2H, Jϭ7.8 Hz, PhH), 7.43 (d, 2H,
Jϭ7.8 Hz, PhH), 7.40 (t, 1H, Jϭ4.9 Hz, CH), 4.29—4.13 (m, 4H, 2CH2),
3.76 (dd, 2H, Jϭ4.9, 6.0 Hz, CH2), 1.35—1.21 (m, 6H, 2CH3); 13C-NMR
(75 MHz, CDCl3) d: 155.2, 144.9, 138.1, 135.2, 129.6, 98.0, 69.7, 69.2,
28.8, 14.9, 14.5; ESI-MS m/z: 361 (Mϩ1); Anal. Calcd for C13H17IN2O2: C,
43.35; H, 4.76; N, 7.78. Found: C, 43.68; H, 4.97; N, 7.43.
In Vitro Antibacterial Tests All of the compounds were evaluated for
their antibacterial activity using conventional agar-dilution method. Twofold
serial dilutions of the compounds and reference drugs were prepared in
Mueller–Hinton agar. Drugs (6.4 mg) were dissolved in dimethylsulfoxide
(DMSO, 1 ml) and the solution was diluted with water (9 ml) without precip-
itation. Further progressive double dilution with melted Mueller–Hinton
agar was performed to obtain the required concentrations of 4, 2, 1, 0.5,
0.25, 0.125, 0.06, 0.03, and 0.015 mg/ml. Petri dishes were incubated with
1—5ϫ104 colony forming units (cfu) and incubated at 37 °C for 18 h. The
minimal inhibitory concentration (MIC) was the lowest concentration of the
test compound, which resulted in no visible growth on the plate. To ensure
that the solvent had no effect on bacterial growth, a control test was per-
formed with test medium supplemented with DMSO at the same dilutions as
used in the experiment. For the minimal bactericidal concentration assay
(MBC) assay, aliquots (10 ml) of each culture without visible growth were
transferred to 90 ml of Mueller–Hinton broth. Incubation, reading and inter-
pretation were performed according to MIC specifications.19)
3-(4-Bromophenyl)-3-oxopropanal Oxime-methyl Ether (15): Yield 80%;
yellow solid, mp 68—70 °C; IR (KBr) nmax, cmϪ1: 2935, 1674, 1579, 1391,
1042, 807; 1H-NMR (300 MHz, CDCl3) d: 7.82 (d, 2H, Jϭ7.8 Hz, PhH),
7.63 (d, 2H, Jϭ7.8 Hz, PhH), 7.19 (t, 1H, Jϭ5.0 Hz, CH), 3.63 (dd, 2H,
Jϭ5.0, 6.2 Hz, CH2), 3.93 (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: 257
(Mϩ1); Anal. Calcd for C10H10BrNO2: C, 46.90; H, 3.94; N, 5.47. Found: C,
47.22; H, 4.28; N, 5.41.
3-(4-Bromophenyl)-3-oxopropanal Oxime-ethyl Ether (16): Yield 69%;
yellow solid, mp 68—69 °C; IR (KBr) nmax, cmϪ1: 2978, 2891, 1673, 1579,
1391, 1059, 813; 1H-NMR (300 MHz, CDCl3) d: 7.84 (d, 2H, Jϭ8.4 Hz,
PhH), 7.60 (d, 2H, Jϭ8.4 Hz, PhH), 7.18 (t, 1H, Jϭ4.9 Hz, CH), 4.21—4.12
(m, 2H, CH2), 4.00 (dd, 2H, Jϭ4.9, 6.0 Hz, CH2), 1.30 (t, 3H, Jϭ7.6 Hz,
CH3); 13C-NMR (75 MHz, CDCl3) d: 194.8, 144.3, 135.0, 132.3, 130.0,
129.1, 69.7, 39.7, 14.8; ESI-MS m/z: 271 (Mϩ1); Anal. Calcd for
C11H12BrNO2: C, 48.91; H, 4.48; N, 5.19. Found: C, 48.98; H, 4.56; N, 5.02.
3-(4-Bromophenyl)-3-oxopropanal Semicarbazone (17): Yield 49%; yel-
low solid, mp 170—172 °C; IR (KBr) nmax, cmϪ1: 3440, 3339, 1686, 1589,
1455, 1070, 821; 1H-NMR (300 MHz, DMSO-d6) d: 9.96 (bs, 1H, NH), 7.89
(d, 2H, Jϭ7.4 Hz, PhH), 7.51 (bs, H, NH2) 7.32 (t, 1H, Jϭ5.4 Hz, CH), 7.26
(d, 2H, Jϭ7.4 Hz, PhH), 6.24 (s, H, NH2), 3.92 (d, Jϭ5.4 Hz, 2H, CH2); 13C-
NMR (75 MHz, DMSO-d6) d: 194.7, 157.2, 154.7, 136.3, 132.1, 130.9,
127.6, 36.8; ESI-MS m/z: 285 (Mϩ1); Anal. Calcd for C10H10BrN3O2: C,
42.27; H, 3.55; N, 14.79. Found: C, 42.36; H, 3.68; N, 14.85.
3-(4-Bromophenyl)-3-oxopropanal Thiosemicarbazone (18): Yield 72%;
yellow solid, mp 182—183 °C; IR (KBr) nmax, cmϪ1: 3369, 3266, 1675,
1644, 1582, 1161, 800; 1H-NMR (300 MHz, DMSO-d6) d: 11.2 (bs, 1H,
NH), 7.92 (d, 2H, Jϭ7.1 Hz, PhH), 7.66 (d, 2H, Jϭ7.1 Hz, PhH), 7.60 (bs,
Results and Discussion
Synthetic Chemistry The synthesis of of 3-(4-halo-
H, NH2), 7.59 (t, 1H, Jϭ5.7 Hz, CH), 7.55 (bs, H, NH2), 3.98 (d, 2H, phenyl)-3-oxopropanal and their derivatives are shown in
Jϭ5.7 Hz, CH2); 13C-NMR (75 MHz, DMSO-d6) d: 196.6, 178.5, 154.6,
Chart 1. In brief, the reaction of 4Ј-haloacetophenone with
2.0 eq of ethyl formate and 1.5 eq of metal sodium in dry
toluene gave the corresponding intermediate sodium salt of
142.1, 132.5, 130.8, 128.4, 42.8; ESI-MS m/z: 301 (Mϩ1); Anal. Calcd for
C10H10BrN3OS: C, 40.01; H, 3.36; N, 14.00. Found: C, 40.41; H, 3.42; N,
14.15.
1-(4-halophenyl)-3-hydroxyprop-2-en-1-one (Chart 1-i). This
intermediate sodium salt was acidified with 5% hydrochlo-
ric acid or acetic acid to give the 3-(4-halophenyl)-3-oxo-
propanal (1—3) in 62—78% overall yield (Chart 1-ii).15) The
corresponding sodium salt was treated with saturated sodium
bisulfite at room temperature to give sodium 1-hydroxy-3-(4-
halophenyl)-3-oxopropane-1-sulfonate (4—6) (Chart 1-iii).
Reaction of 3-(4-halophenyl)-3-oxopropanal (1—3) with
methoxyamine, ethoxyamine, semicarbazide, and thiosemi-
carbazide, respectively, in EtOH gave the corresponding com-
pound (7—24) in 71—86% overall yield (Chart 1-iv).16—18)
Biology The antibacterial activities in vitro of all the ob-
tained compounds were tested against both Gram-positive
bacteria Staphylococcus aureus (ATTC-25923) and Gram-
negative bacteria Escherichia coli (ATTC-25922) and
3-(4-Bromophenyl)-3-oxopropanal Dioxime-methyl Ether (19): Yield
58%; yellow oil; IR (KBr) nmax, cmϪ1: 2937, 2901, 1591, 1427, 1049, 828;
1H-NMR (300 MHz, CDCl3) d: 7.57 (d, 2H, Jϭ8.1 Hz, PhH), 7.49 (d, 2H,
Jϭ8.1 Hz, PhH), 7.43 (t, 1H, Jϭ4.8 Hz, CH), 4.00 (ds, 6H, 2CH3), 3.74 (d,
2H, Jϭ4.8, 6.1 Hz, CH2); 13C-NMR (75 MHz, CDCl3) d: 152.5, 145.2,
134.1, 131.8, 128.1, 123.9, 62.7, 61.8, 28.2; ESI-MS m/z: 286 (Mϩ1); Anal.
Calcd for C11H13BrN2O2: C, 46.33; H, 4.60; N, 9.82. Found: C, 46.45; H,
4.68; N, 9.66.
3-(4-Bromophenyl)-3-oxopropanal Dioxime-ethyl Ether (20): Yield 56%;
yellow oil; IR (KBr) nmax, cmϪ1: 2985, 2893, 1590, 1381, 1055, 831; 1H-
NMR (300 MHz, CDCl3) d: 7.51 (d, 2H, Jϭ7.8 Hz, PhH), 7.06 (d, 2H,
Jϭ7.8 Hz, PhH), 6.89 (t, 1H, Jϭ5.0 Hz, CH), 4.25—4.10 (m, 4H, 2CH2),
3.96 (dd, 2H, Jϭ5.0, 6.2 Hz, CH2), 1.38—1.22 (m, 6H, 2CH3); 13C-NMR
(75 MHz, CDCl3) d: 156.9, 145.9, 133.8, 132.0, 128.1, 123.7, 69.7, 69.2,
28.1, 14.9, 14.3; ESI-MS m/z: 314 (Mϩ1); Anal. Calcd for C13H17BrN2O2:
C, 49.85; H, 5.47; N, 8.94. Found: C, 50.17; H, 5.91; N, 8.71.
3-(4-Iodophenyl)-3-oxopropanal Oxime-methyl Ether (21): Yield 59%;
yellow solid, mp 103—104 °C; IR (KBr) nmax, cmϪ1: 2929, 1673, 1575,
1389, 1044, 800; 1H-NMR (300 MHz, CDCl3) d: 7.86 (d, 2H, Jϭ7.8 Hz, Pseudomonas aeruginosa (ATTC-27853). It was reported as
PhH), 7.69 (d, 2H, Jϭ7.8 Hz, PhH), 7.63 (t, 1H, Jϭ4.8 Hz, CH), 4.00 (dd,
the minimum inhibitory concentration (MIC) in mg/ml that
was determined by the agar dilution method as recommended
2H, Jϭ4.8, 6.0 Hz, CH2), 3.93 (s, 3H, CH3); 13C-NMR(75 MHz, CDCl3) d:
194.6, 143.5, 138.4, 135.6, 129.8, 102.0, 62.2, 35.3; ESI-MS m/z: 304
by the NCCLS (National Committee for Clinical Laboratory
(Mϩ1); Anal. Calcd for C10H10INO2: C, 39.63; H, 3.33; N, 4.62. Found: C,
39.71; H, 3.38; N, 4.55.
Standards).19) The obtained MIC values, together with the
3-(4-Iodophenyl)-3-oxopropanal Oxime-ethyl Ether (22): Yield 61%; yel-
low solid, mp 105—106 °C; IR (KBr) nmax, cmϪ1: 2973, 2936, 1672, 1580,
1391, 1052, 809; 1H-NMR (300 MHz, CDCl3) d: 7.86 (d, 2H, Jϭ8.1 Hz,
PhH), 7.70 (d, 2H, Jϭ8.1 Hz, PhH), 7.63 (t, 1H, Jϭ4.9 Hz, CH), 4.26—4.03
(m, 2H, CH2), 3.99 (dd, 2H, Jϭ4.9, 6.0 Hz, CH2), 1.30 (t, 3H, Jϭ6.9 Hz,
CH3); 13C-NMR (75 MHz, CDCl3) d: 195.1, 144.3, 138.3, 135.5, 129.8,
102.0, 69.7, 39.6, 14.9; ESI-MS m/z: 318 (Mϩ1); Anal. Calcd for
C11H12INO2: C, 41.66; H, 3.81; N, 4.42. Found: C, 41.57; H, 3.82; N, 4.28.
3-(4-Iodophenyl)-3-oxopropanal Dioxime-methyl Ether (23): Yield 54%;
yellow oil; IR (KBr) nmax, cmϪ1: 2937, 2899, 2818, 1683, 1586, 1329, 1047,
data of the reference antibacterial agents Levofloxacin, Clar-
ithromycin and Houttuynin for comparison are summarized
in Table 1.
As shown in Table 1, Compounds 7, 8, 13—16, 21 and 22
had moderate antibacterial activities against Staphylococcus
aureus (MICϽ16 mg/ml). Especially, compound 21 was
found to be most active antibacterial agent with MIC of
1.0 mg/ml against Staphylococcus aureus. However, of all the
synthesized samples, only compounds 15 and 21 showed the
weak and same activities against Escherichia coli and
Pseudomonas aeruginosa (MICϭ64 mg/ml). The results in-
dicated that Gram-positive bacteria were more sensitive to
newly prepared compounds than Gram-negative bacteria.
From the results of the antibacterial activity of the synthe-
1
827; H-NMR (300 MHz, CDCl3) d: 7.71 (d, 2H, Jϭ8.1 Hz, PhH), 7.43 (d,
2H, Jϭ8.1 Hz, PhH), 7.37, 6.67 (t, 1H, Jϭ5.0 Hz, CH), 4.01 (s, 3H, CH3),
3.92 (s, 3H, CH3), 3.73 (dd, 2H, Jϭ5.0, 6.1 Hz, CH2); 13C-NMR (75 MHz,
CDCl3) d: 152.7, 145.3, 137.8, 134.7, 128.2, 95.9, 62.7, 61.8, 28.1; ESI-MS
m/z: 333 (Mϩ1); Anal. Calcd for C11H13IN2O2: C, 39.78; H, 3.95; N, 8.43.
Found: C, 40.12; H, 4.29; N, 8.22.
3-(4-Iodophenyl)-3-oxopropanal Dioxime-ethyl Ether (24): Yield 51%;

1130
Vol. 58, No. 9
7. XϭF, R1ϭNOCH3, R2ϭO;
9. XϭF, R1ϭNNHCONH2, R2ϭO;
11. XϭF, R1ϭR2ϭNOCH3;
8. XϭF, R1ϭNOEt, R2ϭO;
10. XϭF, R1ϭNNHCSNH2, R2ϭO;
12. XϭF, R1ϭR2ϭNOEt;
13. XϭCl, R1ϭNOCH3, R2ϭO;
15. XϭBr, R1ϭNOCH3, R2ϭO;
17. XϭBr, R1ϭNNHCONH2, R2ϭO;
19. XϭBr, R1ϭR2ϭNOCH3;
21. XϭI, R1ϭNOCH3, R2ϭO;
23. XϭI, R1ϭR2ϭNOCH3;
14. XϭCl, R1ϭNOEt, R2ϭO
16. XϭBr, R1ϭNOEt, R2ϭO;
18. XϭBr, R1ϭNNHCSNH2, R2ϭO;
20. XϭBr, R1ϭR2ϭNOEt;
22. XϭI, R1ϭNOEt, R2ϭO;
24. XϭI, R1ϭR2ϭNOEt
Reagents: (i) ethyl formate/Na/toluene, (ii) 5% HCl or acetic acid, (iii) saturating sodium bisulfite solution, (iv)
NH2NHCSNH2, NH2NHCONH2, NH2OCH3, NH2OCH2CH3/EtOH, (v) NH2OCH3·HCl or NH2OCH2CH3·HCl/EtOH.
Chart 1. Synthesis of 3-(4-Halophenyl)-3-oxopropanal and Their Derivatives
ous conclusion which reported that the introduction of appro-
priate substituents into position 4 of phenyl ring enhanced
antibacterial activities of these compounds.
Table 1. Antibacterial Activity of 3-(4-Halophenyl)-3-oxopropanal and
Their Derivatives in Comparison with Clarithromycin, Levofloxacin and
Houttuynine
(2) Compounds 21—24, having iodine substitution at
position 4 of phenyl ring, showed more profound antibacter-
ial activity than other halogen substituted homologous ones.
The results suggested that the antibacterial activity of 3-(4-
halophenyl)-3-oxopropanal and their derivatives might be as-
sociated with the electronic character of the halogen atom on
the 4-position of benzene. In the present investigation, the
halogen substitution for improving the antibacterial activity
strength followed the order: IϾBrϾClϾF.
(3) Among all the compounds investigated, the oxime-
methyl ether (7, 13, 15, 21) and oxime-ethyl ether derivatives
(8, 14, 16, 22) exhibited potent antibacterial activities with
MIC values ranging from 1 to 16 mg/ml. However, sodium 1-
hydroxy-3-(4-halophenyl)-3-oxopropane-1-sulfonates (4—6)
and the semicarbazones and thiosemicarbazone derivatives
failed to exhibit the antibacterial activity at the concentration
of 64 mg/ml. It implicated that the O-methyl and O-ethyl
oxime moiety might play an important role in improving the
potent antibacterial activities.
(4) When an additional O-methyl or O-ethyl oxime moi-
ety was introduced to the active compounds 7, 8, 13—16, 21
and 22, the obtained corresponding dioxime-methyl ether or
ethyl ether derivatives were nearly inactive at the concentra-
tion of 16 mg/ml. The results suggested that the presence of
ketone carbonyl moiety might be absolutely necessarily for
determining the antibacterial activity of these compounds.
The above SAR results were summarized in Fig. 2.
MIC (mg/ml)
Compds.
Staphylococcal
aureus
(ATTC-25923)
Escherichia
coli
(ATTC-25922)
Pseudomonas
aeruginosa
(ATTC-27853)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
16
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
64
Ͼ64
Ͼ64
Ͼ64
32
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
64
Ͼ64
Ͼ64
Ͼ64
Ͼ64
0.5
8
Ͼ64
Ͼ64
Ͼ64
Ͼ64
8
8
2
8
Ͼ64
Ͼ64
64
Ͼ64
1
4
32
64
24
Clarithromycin
Levofloxacin
Houttuynin
0.12
0.25
32
0.025
—
—
Furthermore, three compounds (7, 15, 16) were selected to
test the antibacterial activities in vitro against the clinically
important pathogenic bacteria, methicillin-resistant Staphylo-
sized 3-(4-halophenyl)-3-oxopropanal and their derivatives, coccus aureus (MRSA) and the results were summarized in
the following SAR could be derived: Tables 2 and 3. As shown in Table 2, compounds 7, 15 and
(1) In general, it was observed that most of the com- 16 displayed more potent antibacterial activities against
pounds with halogen substituted phenyl rings at position 4 MRSA than the Houttuynin and Levofloxacin, suggesting
showed better antibacterial activity than the ones with a non- that further development of such compounds may be of inter-
substituted phenyl ring.12) This further supported our previ- est.

September 2010
1131
Table 2. MIC of Compounds 7, 15 and 16 against Strains of Methicillin-Resistant Staphylococcus aureus (MRSA)
MIC (mg/ml)
Compds.
MIC50
MIC90
MRSA1
MRSA2
MRSA3
MRSA4
MRSA5
7
15
8
4
8
8
8
8
8
4
4
8
8
8
8
8
16
8
8
8
4
8
8
16
Levofloxacin
Houttuynin
8
16
8
16
16
16
16
16
Ͼ16
16
16
16
Ͼ16
16
Table 3. MBC of Compounds 7, 15 and 16 against Strains of Methicillin-Resistant Staphylococcus aureus (MRSA)
MBC (mg/ml)
Compds.
MIC50
MIC90
MRSA1
MRSA2
MRSA3
MRSA4
MRSA5
7
15
16
512
128
64
Ͼ16
32
Ͼ512
128
128
Ͼ16
128
512
128
256
Ͼ16
64
Ͼ512
256
128
Ͼ16
32
512
128
64
Ͼ16
64
512
128
128
Ͼ16
64
Ͼ512
128
256
Ͼ16
128
Levofloxacin
Houttuynin
Acknowledgment This work was supported by the Foundation of Edu-
cation Department of Hunan Province, China (09B091).
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Conclusion
The present investigation for the first time reported that 3-
(4-halophenyl)-3-oxopropanal and their derivatives had po-
tent antibacterial activities, and Gram-positive pathogens
were more susceptible to these compounds. Of all the investi-
gated compounds, compound 24 was found to be most active
antibacterial agent with MIC of 1.0 mg/ml against Staphylo-
coccus aureus. SAR analysis indicated that (1) the introduc-
tion of appropriate substituents into position 4 of phenyl ring
enhanced antibacterial activities. (2) The antibacterial activ-
ity of these compounds might be associated with the elec-
tronic character of the halogen atom on the 4-position of ben-
zene. (3) The O-methyl and O-ethyl oxime moiety might play
an important role in determining the potent antibacterial ac-
tivities. (4) The presence of ketone carbonyl moiety might be
absolutely necessarily for improving the antibacterial activity
of these compounds. Furthermore, the antibacterial activities
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Dilution Antimicrobial Susceptability Tests for Bacteria that Grow
ties than the well-known antibacterial agents Houttuynin and
Levofloxacin, suggesting that further development of such
compounds may be of interest.
Aerobically-Third Edition; approved Standard; NCCLS Document
M7-A3 (ISBN 1-56238-209-8),” NCCLS, Villanova, PA 1993.