Synthesis of new nanocopolymer containing β-lactams

Article abstract of DOI:10.1007/s13738-013-0277-6

Several new monocyclic β-lactam monomers bearing the NO₂ group 2a-g were synthesized via a [2 + 2] ketene-imine cycloaddition reaction (Staudinger reaction). Calculation of coupling constant of H-3 and H-4, and the X-ray crystallography of β-la

Full text of DOI:10.1007/s13738-013-0277-6

J IRAN CHEM SOC
DOI 10.1007/s13738-013-0277-6
ORIGINAL PAPER
Synthesis of new nanocopolymer containing b-lactams
•
Aliasghar Jarrahpour Roghayeh Heiran
Received: 16 April 2013 / Accepted: 17 May 2013
Ó Iranian Chemical Society 2013
Abstract Several new monocyclic b-lactam monomers
bearing the NO2 group 2a–g were synthesized via a [2 ? 2]
ketene–imine cycloaddition reaction (Staudinger reaction).
Calculation of coupling constant of H-3 and H-4, and the
X-ray crystallography of b-lactam 2e confirmed the cis ste-
reochemistry of these b-lactams. Then aminophenyl b-lac-
tams were synthesized by the reduction of NO2 to NH2 group
inthepresenceofRaneyNiandhydrazinehydrate. Treatment
of these aminophenyl b-lactams with acryloyl chloride and
sodium bicarbonate (NaHCO3), afforded the monomers
bearing the NHCOCH=CH2 group. These acrylated b-lactam
monomersweredissolvedin a warm mixtureofbutyl acrylate
and styrene and then were converted to the corresponding
polyacrylate nano b-lactams by emulsion polymerization in
water. A unique feature of this methodology is the ability to
incorporate water-insoluble compounds directly into the
nanoparticle framework. Structures of the synthesized com-
pounds were confirmed by physical and spectral analyses.
Dynamic light scattering analysis and transmission electron
microscopy of the finalemulsions show that the nanoparticles
were about 50–70 nm in diameter.
been done on the synthesis of new potent antifungal and
antibacterial 2-azetidinones [1, 2]. The biological activity
of the 2-azetidinone framework is believed to be associated
with the chemical reactivity of 2-azetidinone ring and on
the substituents, especially at nitrogen of the 2-azetidinone
ring [3]; therefore, functionalization of the 2-azetidinone
framework is significant for the development of new b-
lactam antibiotics [4].
The body distribution, effectiveness, and specificity of a
drug can be modified when it is incorporated within a
carrier. In recent years, there have been a number of efforts
on the development of polymeric micelles as carriers
of hydrophobic drugs because of their unique properties
[5–8].
Nano-delivery systems of appropriate stability, size, and
surface properties offer the possibility of increasing the
therapeutic index of the known or new drug molecules by
increasing their efficiency and decreasing their toxicity
against physiological tissues [9, 10].
Several groups have reported on the preparation and
antibacterial testing of different ampicillin- or penicillin-
entrapped polycyanoacrylates, carbohydrate- and antibi-
otic-conjugated polyacrylate nanoparticles formed by
anionic emulsion polymerization in water [11–17].
Turos et al. [6, 7, 16, 17] have reported the preparation
and in vitro microbiological properties of polyacrylate-
based nanoparticle emulsions that contain water-insoluble
antibiotic drugs, such as penicillin or N-thiolated b-lac-
tam. These nanoparticles were prepared by free radical
emulsion polymerization in water. Easy preparation, facile
control of nanoparticle size, and enhanced anti-MRSA
activity of the nanoparticle polymers versus the nonpo-
lymerized form were some essential features of these
nanoparticles. In this paper, we report the synthesis of
some new nano b-lactams.
Keywords 2-Azetidinone Á [2 ? 2] Cycloaddition Á
Staudinger reaction Á Polyacrylate nanoparticles
Introduction
2-Azetidinones (b-lactams) show a wide range of activity
on different pathogens and a considerable research has
A. Jarrahpour (&) Á R. Heiran
Department of Chemistry, College of Sciences,
Shiraz University, 71454 Shiraz, Iran
e-mail: jarrah@susc.ac.ir
123

J IRAN CHEM SOC
1
Experimental
(CO, b-lactam); H-NMR (CDCl3)d (ppm): 3.68 (OMe, s,
3H), 5.87 (H-4, d, J = 5.0 Hz, 1H), 5.93 (H-3, d,
J = 5.0 Hz, 1H), 6.79–8.13 ArH, m, 13H); 13C-NMR d
(ppm) 55.2 (OMe), 59.9 (C-4), 80.7 (C-3), 114.6, 115.0,
118.4, 122.0, 123.2, 129.4, 129.4, 129.7, 141.3, 148.1,
156.1, 156.1 (aromatic carbons), 161.7 (CO, b-lactam);
GC–MS m/z = 390 [M?]; Anal. calcd for C22H18N2O5: C,
67.69; H, 4.65; N, 7.18 %. Found: C, 67.65; H, 4.61; N,
7.16 %.
General
All required chemicals were purchased from the Fluka,
Merck, and Acros chemical companies. CH2Cl2 and Et3N
were dried by distillation over CaH2 and then stored over
4 A molecular sieves. 1H-NMR and 13C-NMR spectra
˚
were recorded in CDCl3 or DMSO-d6 using a Bruker
Avance DPX instrument (operating at 250 MHz for 1H and
62.9 MHz for 13C). Chemical shifts were reported in ppm
(d) downfield from TMS. All the coupling constants (J) are
in Hertz. IR spectra were run on a Shimadzu FT-IR 8300
spectrophotometer. The mass spectra were recorded on a
Shimadzu GC–MS QP 1000 EX instrument. Elemental
analyses were run on a Thermo Finnigan Flash EA-1112
series. Melting points were determined in open capillaries
with a Buchi 510 melting point apparatus and are not
corrected. The distribution morphology of the product was
analyzed by CM10 transmission electron microscope
(TEM; Philips 120 kV). Sample size and distribution of the
products were checked by dynamic light scattering using a
HORIBA DLS instrument. Column chromatography was
performed on Merck Kieselgel (230–270 mesh). Thin layer
chromatography (TLC) was carried out on silica gel 254
analytical sheets obtained from Fluka.
3-(2,4-Dichlorophenoxy)-1-(4-methoxyphenyl)-4-
(4-nitrophenyl)azetidin-2-one (2b)
White crystals from EtOAc (yield 61 %); mp: 196–198 °C;
IR (KBr, cm-1): 1,346, 1,521 (NO2), 1,754 (CO, b-lactam);
1H-NMR (CDCl3) d (ppm): 3.70 (OMe, s, 3H), 5.43 (H-4,
d, J = 5.0 Hz, 1H), 5.48 (H-3, d, J = 5.0 Hz, 1H),
6.74–8.18 (ArH, m, 11H); 13C-NMR d (ppm): 55.5 (OMe),
60.5 (C-4), 81.9 (C-3), 114.7, 116.8, 118.8, 123.7, 124.1,
127.7, 128.1, 129.0, 129.6, 130.1, 140.0, 148.0, 151.2,
157.0 (aromatic carbons), 161.3 (CO, b-lactam); GC–MS
m/z = 458 [M?]; Anal. calcd for C22H16Cl2N2O5: C,
57.53; H, 3.51; N, 6.10 %. Found: C, 57.53; H, 3.49; N,
6.11 %.
3-(4-Chlorophenoxy)-1-(4-methoxyphenyl)-4-
(4-nitrophenyl)azetidin-2-one (2c)
General procedure for the preparation of Schiff bases
1a–g
White crystals from EtOAc (yield 66 %); mp: 128–130 °C;
IR (KBr, cm-1): 1,349, 1,527 (NO2), 1,749 (CO, b-lactam);
1H-NMR (CDCl3) d (ppm): 3.76 (OMe, s, 3H), 5.47 (H-4,
d, J = 4.9 Hz, 1H), 5.57 (H-3, d, J = 4.9 Hz, 1H),
6.73–8.20 (ArH, m, 12H); 13C-NMR d (ppm) 55.5 (OMe),
60.9 (C-4), 81.3 (C-3), 114.6, 116.8, 118.7, 123.7, 127.7,
128.9, 129.4, 129.7, 140.3, 148.2, 155.1, 156.9 (aromatic
carbons), 161.5 (CO, b-lactam); GC–MS m/z = 424 [M?];
Anal. calcd for C22H17ClN2O5: C, 62.20; H, 4.03; N,
6.59 %. Found: C, 62.19; H, 4.00; N, 6.59 %.
A mixture of a substituted aniline (10.0 mmol) and an
aromatic aldehyde (10.0 mmol) was refluxed in ethanol for
appropriate time. After cooling of solution, the precipitate
was filtered and washed with ethanol to afford Schiff bases
1a–g.
General procedure for the synthesis of b-lactams 2a–g
A mixture of Schiff base (1.00 mmol), triethylamine
(5.00 mmol), acetic acid derivative (1.5 mmol) and p-tol-
uenesulfonyl chloride (1.5 mmol) in dry CH2Cl2 (50 mL)
was stirred at room temperature overnight. After the reac-
tion completion (TLC monitoring), the mixture was washed
with HCl (1 N), saturated sodium bicarbonate solution,
brine, dried (Na2SO4) and the solvent was evaporated under
vacuum to afford the crude b-lactams 2a–g. Then they were
purified by recrystallization from EtOAc.
3-(2,4-Dichlorophenoxy)-1-(4-methoxyphenyl)-4-
(3-nitrophenyl)azetidin-2-one (2d)
White crystals from EtOAc (yield 53 %); mp: 156–158 °C;
IR (KBr, cm-1): 1,344, 1,522 (NO2), 1,763 (CO, b-lactam);
1H-NMR (CDCl3) d (ppm): 3.76 (OMe, s, 3H), 5.51 (H-4,
d, J = 5.1 Hz, 1H), 5.56 (H-3, d, J = 5.1 Hz, 1H),
6.82–8.29 (ArH, m, 11H); 13C-NMR d (ppm) 55.5 (OMe),
60.4 (C-4), 81.6 (C-3), 114.7, 116.6, 118.8, 123.3, 123.9,
127.7, 127.9, 129.7, 129.7, 130.0, 130.1, 133.9, 135.0,
148.3, 151.1, 156.9 (aromatic carbons), 161.3 (CO, b-lac-
tam); GC–MS m/z = 458 [M?]; Anal. calcd for
C22H16Cl2N2O5: C, 57.53; H, 3.51; N, 6.10 %. Found: C,
57.50; H, 3.52; N, 6.10 %.
1-(4-Methoxyphenyl)-4-(4-nitrophenyl)-3-phenoxyazetidin-
2-one (2a)
Light yellow crystals from EtOAc (yield 64 %); mp:
142–144 °C; IR (KBr, cm-1): 1,352, 1,521 (NO2), 1,770
123

J IRAN CHEM SOC
1-(4-Methoxyphenyl)-4-(3-nitrophenyl)-3-
phenoxyazetidin-2-one (2e)
4-(4-Aminophenyl)-1-(4-methoxyphenyl)-3-
phenoxyazetidin-2-one (3a)
White crystals from EtOAc (yield 47 %); mp: 142 °C; IR
(KBr, cm-1): 1,350, 1,527 (NO2), 1,739 (CO, b-lactam);
1H-NMR (CDCl3) d (ppm): 3.75 (OMe, s, 3H), 5.48 (H-4,
d, J = 4.8 Hz, 1H), 5.63 (H-3, d, J = 4.8 Hz, 1H),
6.75–8.23 (ArH, m, 13H); 13C-NMR d (ppm) 55.5 (OMe),
61.0 (C-4), 81.0 (C-3), 114.6, 115.4, 118.8, 122.6, 123.3,
123.8, 129.5, 129.5, 129.8, 133.9, 135.4, 148.1, 156.4,
156.8 (aromatic carbons), 161.9 (CO, b-lactam); GC–MS
m/z = 390 [M?]; Anal. calcd for C22H18N2O5: C, 67.69;
H, 4.65; N, 7.18 %. Found: C, 67.65; H, 4.61; N, 7.16 %.
White crystal purified by column chromatography (eluent
5:1 CHCl3/EtOAc) (yield 63 %); mp: 150–152 °C; IR
(KBr, cm-1): 1,736 (CO, b-lactam), 3,361, 3,446 (NH2);
1H-NMR (DMSO) d (ppm): 3.66 (OMe, s, 3H), 5.03 (NH2,
s, 2H), 5.43 (H-4, d, J = 4.5 Hz, 1H), 5.67 (H-3, d,
J = 4.5 Hz, 1H), 6.36–7.48 (ArH, m, 13H); 13C-NMR d
(ppm); 55.1 (OMe), 61.1 (C-4), 80.4 (C-3), 113.4, 114.3,
115.0, 118.4, 119.1, 121.5, 128.9, 129.2, 130.2, 148.6,
155.7, 156.6 (aromatic carbons), 162.2 (CO, b-lactam);
GC–MS m/z = 360 [M?]; Anal. calcd for C22H20N2O3: C,
73.32; H, 5.59; N, 7.77 %. Found: C, 73.29; H, 5.57; N,
7.79 %.
1-(4-Methoxyphenyl)-3-(naphthalen-2-yloxy)-4-(3-
nitrophenyl)azetidin-2-one (2f)
4-(4-Aminophenyl)-3-(2,4-dichlorophenoxy)-1-(4-
methoxyphenyl)-azetidin-2-one (3b)
Light green powder from EtOAc (yield 72 %); mp:
158 °C; IR (KBr, cm-1): 1,342, 1,527 (NO2), 1,743 (CO,
b-lactam); H-NMR (CDCl3) d (ppm): 3.76 (OMe, s, 3H),
1
White crystal purified by column chromatography (eluent
5:1 CHCl3/EtOAc) (yield 67 %); mp: 150–152 °C; IR
(KBr, cm-1): 1,757 (CO, b-lactam), 3,372, 3,458 (NH2);
1H-NMR (DMSO) d (ppm): 3.67 (OMe, s, 3H), 5.06 (NH2,
s, 2H), 5.46 (H-4, d, J = 4.3 Hz, 1H), 5.82 (H-3, d,
J = 4.3 Hz, 1H), 6.36–7.42 (ArH, m, 11H); 13C-NMR d
(ppm); 55.1 (OMe), 59.7 (C-4), 80.4 (C-3), 113.4, 114.3,
115.0, 115.0, 118.4, 119.1, 121.5, 128.9, 129.2, 129.2,
130.2, 148.6, 155.7, 156.6 (aromatic carbons), 162.2 (CO,
b-lactam); GC–MS m/z = 428 [M?]; Anal. calcd for
C22H18Cl2N2O3: C, 61.55; H, 4.23; N, 6.53 %. Found: C,
61.49; H, 4.25; N, 6.55 %.
5.53 (H-4, d, J = 4.8 Hz, 1H), 5.74 (H-3, d, J = 4.8 Hz,
1H), 6.82–8.28 (ArH, m, 15H); 13C-NMR d (ppm) 55.5
(OMe), 61.0 (C-4), 81.0 (C-3), 109.1, 114.6, 118.0, 118.8,
123.2, 123.8, 124.5, 126.7, 126.9, 127.6, 129.5, 129.6,
129.8, 129.8, 133.8, 133.9, 135.34, 148.2, 154.3, 156.9
(aromatic carbons), 161.8 (CO, b-lactam); GC–MS m/
z = 440 [M?]; Anal. calcd for C26H20N2O5: C, 70.90; H,
4.58; N, 6.36 %. Found: C, 70.93; H, 4.56; N, 6.35 %.
1-(4-Chlorophenyl)-4-(4-nitrophenyl)-3-phenoxyazetidin-
2-one (2 g)
White powder from EtOAc (yield 51 %); mp: 206–208 °C;
IR (KBr, cm-1): 1,350, 1,527 (NO2), 1,743 (CO, b-lactam);
1H-NMR (CDCl3) d (ppm): 5.50 (H-4, d, J = 4.9 Hz, 1H),
5.66 (H-3, d, J = 4.9 Hz, 1H), 6.76–8.19 (ArH, m, 13H);
13C-NMR d (ppm); 60.1 (C-4), 80.9 (C-3), 115.0, 118.7,
122.1, 123.2, 128.3, 128.3, 128.3, 129.4, 135.1, 140.7, 147.4,
156.0 (aromatic carbons), 162.5 (CO, b-lactam); GC–MS m/
z = 394 [M?]; Anal. calcd for C21H15ClN2O4: C, 63.89; H,
3.83; N, 7.10 %. Found: C, 63.86; H, 3.84; N, 7.11 %.
4-(4-Aminophenyl)-3-(4-chlorophenoxy)-1-(4-
methoxyphenyl)-azetidin-2-one (3c)
White powder purified by column chromatography (eluent
5:1 CHCl3/EtOAc) (yield 63 %); mp: 150–152 °C; IR
(KBr, cm-1): 1,745 (CO, b-lactam), 3,388, 3,475 (NH2);
1H-NMR (DMSO) d (ppm): 3.67 (OMe, s, 3H), 5.07 (NH2,
s, 2H), 5.44 (H-4, d, J = 4.5 Hz, 1H), 5.70 (H-3, d,
J = 4.5 Hz, 1H), 6.37–7.23 (ArH, m, 12H); 13C-NMR d
(ppm); 55.1 (OMe), 60.9 (C-4), 80.4 (C-3), 113.4, 114.4,
116.7, 118.50, 118.8, 125.2, 128.8, 128.9, 130.1, 148.7,
155.3, 155.7 (aromatic carbons), 161.8 (CO, b-lactam);
GC–MS m/z = 394 [M?]; Anal. calcd for C22H19ClN2O3:
C, 66.92; H, 4.85; N, 7.09 %. Found: C, 66.86; H, 4.87; N,
7.13 %.
General procedure for the synthesis of b-lactams 3a–g
b-Lactams 2a–g (1 mmol) was dissolved in 80 mL of EtOH:
H2O (9:1) by heating to reflux. Then the temperature was
reduced to 60 °C and hydrazine hydrate (2.34 mmol) and
Raney-Ni (1 g) were added. The mixture was refluxed for
several minutes until complete conversion of b-lactams 2a–
g to 3a–g (TLC monitoring). The cold mixture was filtered
and the solvent was evaporated under the reduced pressure.
The crude products were purified by silica gel chromatogra-
phy (eluent 5:1 CHCl3/EtOAc) to yield pure b-lactams 3a–g.
4-(3-Aminophenyl)-3-(2,4-dichlorophenoxy)-1-(4-
methoxyphenyl)-azetidin-2-one (3d)
White crystal purified by column chromatography (eluent
5:1 CHCl3/EtOAc) (yield 93 %); mp: 142–144 °C; IR
123

J IRAN CHEM SOC
(KBr, cm-1): 1,747 (CO, b-lactam), 3,358, 3,441 (NH2);
1H-NMR (DMSO) d (ppm): 3.68 (OMe, s, 3H), 5.03 (NH2,
s, 2H), 5.47 (H-4, d, J = 4.6 Hz, 1H), 5.86 (H-3, d,
J = 4.6 Hz, 1H), 6.39–7.43 (ArH, m, 11H); 13C-NMR d
(ppm); 60.3 (OMe), 65.9 (C-4), 85.8 (C-3), 117.9, 119.2,
119.6, 120.9, 121.3, 123.5, 127.4, 130.7, 132.7, 133.6,
134.3, 135.2, 138.1, 153.5, 156.1, 161.1 (aromatic car-
bons), 166.4 (CO, b-lactam); GC–MS m/z = 429 [M?];
Anal. calcd for C22H18Cl2N2O3: C, 61.55; H, 4.23; N,
6.53 %. Found: C, 61.57; H, 4.19; N, 6.56 %.
80.6 (C-3), 113.4, 115.0, 118.5, 118.7, 121.6, 127.8, 128.9,
129.1, 129.2, 135.6, 148.8, 156.5 (aromatic carbons), 163.1
(CO, b-lactam); GC–MS m/z = 364 [M?]; Anal. calcd for
C21H17ClN2O2: C, 69.14; H, 4.70; N, 7.68 %. Found: C,
69.13; H, 4.72; N, 7.64 %.
General procedure for the synthesis of b-lactams 4a–g
b-Lactams 3a–g (0.50 mmol) were dissolved in 10 mL dry
CH2Cl2, NaHCO3 (0.05 g, 0.06 mmol) was added and the
mixture was cooled in an ice bath for 20 min, then acryloyl
chloride (0.04 mL, 0.50 mmol) was added and the mixture
was stirred at 0 °C for 1 h. The crude product was purified
by silica gel chromatography (eluent 4:1 CHCl3/EtOAc) to
yield pure b-lactams 4a–g.
4-(3-Aminophenyl)-1-(4-methoxyphenyl)-3-
phenoxyazetidin-2-one (3e)
White powder purified by column chromatography (eluent
5:1 CHCl3/EtOAc) (yield 92 %); mp: 200 °C; IR (KBr,
cm-1): 1,739 (CO, b-lactam), 3,359, 3,436 (NH2); 1H-
NMR (DMSO) d (ppm): 3.68 (OMe, s, 3H), 5.04 (NH2, s,
2H), 5.45 (H-4, d, J = 4.7 Hz, 1H), 5.73 (H-3, d,
J = 4.7 Hz, 1H), 6.52–7.24 (ArH, m, 13H); 13C-NMR d
(ppm); 55.2 (OMe), 61.3 (C-4), 80.6 (C-3), 112.7, 113.9,
114.4, 115.2, 115.8, 118.3, 121.7, 128.6, 129.2, 130.2,
133.7, 148.4, 155.8, 156.7 (aromatic carbons), 162.2 (CO,
b-lactam); GC–MS m/z = 360 [M?]; Anal. calcd for
C22H20N2O3: C, 73.32; H, 5.59; N, 7.77 %. Found: C,
73.45; H, 5.54; N, 7.80 %.
N-(4-(1-(4-Methoxyphenyl)-4-oxo-3-phenoxyazetidin-2-yl)
phenyl) acrylamide (4a)
White powder purified by thin layer chromatography
(eluent 4:1 CHCl3/EtOAc) (yield 72 %); mp: 168 °C; IR
(KBr, cm-1): 1,663 (CO, amide), 1,742 (CO, b-lactam),
1
3,300 (NH); H-NMR (DMSO) d (ppm): 3.66 (OMe, s,
3H), 5.61 (H-4, d, J = 4.7 Hz, 1H), 5.67 (vinylic, d,
J = 10.0 Hz, 1H), 5.78 (H-3, d, J = 4.7 Hz, 1H), 6.16
(vinylic, d, J = 16.8 Hz, 1H), 6.33 (vinylic, dd, J = 10.0,
16.8 Hz, 1H), 6.78–7.54 (ArH, m, 13H), 10.09 (NH, s, 1H);
13C-NMR d (ppm); 55.1 (OMe), 60.5 (C-4), 80.4 (C-3),
114.4, 114.9, 118.4, 118.9, 121.7, 126.8, 127.9, 128.6,
129.2, 130.0, 131.7, 138.9, 155.8, 156.4 (aromatic and
vinylic carbons), 162.0 (CO, b-lactam), 163.0 (CO, amide);
GC–MS m/z = 414 [M?]; Anal. calcd for C25H22N2O4: C,
72.45; H, 5.35; N, 6.76 %. Found: C, 72.43; H, 5.34; N,
6.76 %.
4-(3-Aminophenyl)-1-(4-methoxyphenyl)-3-(naphthalen-2-
yloxy) azetidin-2-one (3f)
Light brown powder purified by column chromatography
(eluent 5:1 CHCl3/EtOAc) (yield 83 %); mp: 222–224 °C;
IR (KBr, cm-1): 1,745 (CO, b-lactam), 3,359, 3,456 (NH2);
1H-NMR (DMSO) d (ppm): 3.68 (OMe, s, 3H), 5.02 (NH2,
s, 2H), 5.55 (H-4, d, J = 4.4 Hz, 1H), 5.89 (H-3, d,
J = 4.4 Hz, 1H), 6.34–7.79 (ArH, m, 15H); 13C-NMR d
(ppm); 60.4 (OMe), 66.5 (C-4), 85.8 (C-3), 114.1, 118.0,
119.2, 119.7, 121.2, 123.2, 123.6, 129.3, 131.7, 131.9,
132.7, 133.8, 134.1, 134.4, 135.5, 138.9, 138.9, 153.6,
159.7, 161.1 (aromatic carbons), 167.3 (CO, b-lactam);
GC–MS m/z = 410 [M?]; Anal. calcd for C26H22N2O3: C,
76.08; H, 5.40; N, 6.82 %. Found: C, 76.08; H, 5.38; N,
6.85 %.
N-(4-(3-(2,4-Dichlorophenoxy)-1-(4-methoxyphenyl)-4-
oxoazetidin-2-yl) phenyl) acrylamide (4b)
White crystal purified by thin layer chromatography (eluent
4:1 CHCl3/EtOAc) (yield 71 %); mp: 192 °C; IR (KBr,
cm-1): 1,666 (CO, amide), 1,735 (CO, b-lactam), 3,332
(NH); 1H-NMR (DMSO) d (ppm): 3.67 (OMe, s, 3H), 5.62
(H-4, d, J = 4.6 Hz, 1H), 5.71 (vinylic, d, J = 9.8 Hz,
1H), 5.79 (H-3, d, J = 4.6 Hz, 1H), 6.15 (vinylic,
J = 16.9 Hz, d, 1H), 6.31 (vinylic, dd, J = 9.8, 16.9 Hz,
1H), 6.79–7.84 (ArH, m, 11H), 10.10 (NH, s, 1H); 13C-
NMR d (ppm); 55.1 (OMe), 60.6 (C-4), 80.4 (C-3), 114.4,
114.9, 118.4, 118.4, 118.9, 121.7, 126.9, 127.9, 128.6,
129.2, 129.2, 130.0, 131.6, 138.9, 155.8, 156.4 (aromatic
and vinylic carbons), 162.0 (CO, b-lactam), 163.0 (CO,
amide); GC–MS m/z = 483 [M?]; Anal. calcd for
C25H20Cl2N2O4: C, 62.12; H, 4.17; N, 5.80 %. Found: C,
62.10; H, 4.18; N, 5.81 %.
4-(4-Aminophenyl)-1-(4-chlorophenyl)-3-phenoxyazetidin-
2-one (3 g)
White powder purified by column chromatography (eluent
5:1 CHCl3/EtOAc) (yield 62 %); mp: 210–212 °C; IR
(KBr, cm-1): 1,745 (CO, b-lactam), 3,301, 3,379 (NH2);
1H-NMR (DMSO) d (ppm): 5.08 (NH2, s, 2H), 5.50 (H-4,
d, J = 4.6 Hz, 1H), 5.74 (H-3, d, J = 4.6 Hz, 1H),
6.38–7.41 (ArH, m, 13H); 13C-NMR d (ppm); 61.2 (C-4),
123

J IRAN CHEM SOC
N-(4-(3-(4-Chlorophenoxy)-1-(4-methoxyphenyl)-4-
oxoazetidin-2-yl) phenyl) acrylamide (4c)
163.0 (CO, amide); GC–MS m/z = 414 [M?]; Anal. calcd
for C25H22N2O4: C, 72.45; H, 5.35; N, 6.76 %. Found: C,
72.40; H, 5.33; N, 6.75 %.
White powder purified by thin layer chromatography
(eluent 4:1 CHCl3/EtOAc) (yield 73 %); mp: 198–200 °C;
IR (KBr, cm-1): 1,666 (CO, amide 1,743 (CO, b-lactam)),
N-(3-(1-(4-Methoxyphenyl)-3-(naphthalene-2-yloxy)-4-
oxoazetidin-2-yl) phenyl) acrylamide (4f)
1
3,332 (NH); H-NMR (DMSO) d (ppm): 3.67 (OMe, s,
3H), 5.62 (H-4, d, J = 4.4 Hz, 1H), 5.71 (vinylic, d,
J = 9.7 Hz, 1H), 5.81 (H-3, d, J = 4.4 Hz, 1H), 6.18
(vinylic, J = 17.0 Hz, d, 1H), 6.26 (vinylic, dd, J = 9.7,
17.0 Hz, 1H), 6.82–7.55 (ArH, m, 12H), 10.12 (NH, s, 1H);
13C-NMR d (ppm); 55.1 (OMe), 60.3 (C-4), 80.4 (C-3),
114.5, 116.7, 118.4, 118.9, 125.4, 126.9, 127.6, 128.6,
129.0, 129.9, 131.6, 138.9, 155.1, 155.9 (aromatic and
vinylic carbons), 161.6 (CO, b-lactam), 163.0 (CO, amide);
GC–MS m/z = 448 [M?]; Anal. calcd for C25H21ClN2O4:
C, 66.89; H, 4.72; N, 6.24 %. Found: C, 66.86; H, 4.70; N,
6.21 %.
White powder purified by thin layer chromatography
(eluent 4:1 CHCl3/EtOAc) (yield 60 %); mp: 190 °C; IR
(KBr, cm-1): 1,689 (CO, amide), 1,743 (CO, b-lactam),
1
3,332 (NH); H-NMR (DMSO) d (ppm): 3.68 (OMe, s,
3H), 5.71 (vinylic, d, J = 9.9 Hz, 1H), 5.74 (H-4, d,
J = 4.7 Hz, 1H), 5.97 (H-3, d, J = 4.7 Hz, 1H), 6.17
(vinylic, d, J = 17.2 Hz, 1H), 6.25 (vinylic, dd, J = 9.9,
17.2 Hz, 1H), 6.90–7.78 (ArH, m, 12H), 10.10 (NH, s, 1H);
13C-NMR d (ppm); 55.2 (OMe), 60.8 (C-4), 80.5 (C-3),
108.8, 114.5, 117.8, 118.1, 118.4, 119.1, 123.7, 124.1,
126.5, 126.7, 126.9, 127.4, 128.6, 128.9, 129.3, 130.0,
131.6, 133.5, 133.9, 138.9, 154.1, 155.9 (aromatic and
vinylic carbons), 161.9 (CO, b-lactam), 163.0 (CO, amide);
GC–MS m/z = 464 [M?]; Anal. calcd for C29H24N2O4: C,
74.98; H, 5.21; N, 6.03 %. Found: C, 74.97; H, 5.18; N,
6.04 %.
N-(3-(3-(2,4-Dichlorophenoxy)-1-(4-methoxyphenyl)-4-
oxoazetidin-2-yl) phenyl) acrylamide (4d)
White powder purified by thin layer chromatography
(eluent 4:1 CHCl3/EtOAc) (yield 78 %); mp: 166–168 °C;
IR (KBr, cm-1): 1,651 (CO, amide), 1,738 (CO, b-lactam),
3,294 (NH); 1H-NMR (CDCl3) d (ppm): 3.66 (OMe, s,
3H), 5.28 (H-4, d, J = 4.9 Hz, 1H), 5.41 (H-3, d,
J = 4.9 Hz, 1H), 5.64 (vinylic, d, J = 10.1 Hz, 1H), 6.22
(vinylic, dd, J = 10.1, 16.7 Hz, 1H), 6.31 (vinylic, d,
J = 16.7 Hz, 1H), 6.69–7.60 (ArH, m, 11H), 7.53 (NH, s,
1H); 13C-NMR d (ppm); 54.4 (OMe), 60.3 (C-4), 80.5 (C-
3), 113.4, 113.4, 115.6, 117.8, 117.8, 118.2, 119.3, 123.1,
126.4, 127.0, 128.2, 128.9, 129.0, 130.0, 132.2, 137.1,
150.3, 155.6 (aromatic and vinylic carbons), 160.6 (CO, b-
lactam), 162.6 (CO, amide); GC–MS m/z = 482 [M?];
Anal. calcd for C25H20Cl2N2O4: C, 62.12; H, 4.17; N,
5.80 %. Found: C, 62.13; H, 4.20; N, 5.79 %.
N-(4-(1-(4-Chlorophenyl)-4-oxo-3-phenoxyazetidin-2-yl)
phenyl) acrylamide (4 g)
White powder purified by thin layer chromatography
(eluent 4:1 CHCl3/EtOAc) (yield 56 %); mp: 228 °C; IR
(KBr, cm-1): 1,666 (CO, amide), 1,738 (CO, b-lactam),
3,317 (NH); 1H-NMR (DMSO) d (ppm): 5.68 (H-4, d,
J = 4.7 Hz, 1H), 5.73 (vinylic, d, J = 9.8 Hz, 1H), 5.84
(H-3, d, J = 4.7 Hz, 1H), 6.13 (vinylic, d, J = 17.0 Hz,
1H), 6.33 (vinylic, dd, J = 9.8, 17.0 Hz, 1H), 6.79–7.89
(ArH, m, 13H), 10.11 (NH, s, 1H); 13C-NMR d (ppm); 60.7
(C-4), 80.6 (C-3), 114.9, 118.7, 118.9, 121.8, 126.9, 127.4,
128.0, 128.6, 129.2, 129.3, 131.6, 135.4, 139.0, 156.3
(aromatic and vinylic carbons), 162.8 (CO, b-lactam),
163.0 (CO, amide); GC–MS m/z = 418 [M?]; Anal. calcd
for C24H19ClN2O3: C, 68.82; H, 4.57; N, 6.69 %. Found:
C, 68.80; H, 4.58; N, 6.69 %.
N-(3-(1-(4-Methoxyphenyl)-4-oxo-3-phenoxyazetidin-2-yl)
phenyl) acrylamide (4e)
White powder purified by thin layer chromatography
(eluent 4:1 CHCl3/EtOAc) (yield 89 %); mp: 160 °C; IR
(KBr, cm-1): 1,674 (CO, amide), 1,743 (CO, b-lactam),
Preparation of the polyacrylate nanoparticle emulsions
1
3,317 (NH); H-NMR (DMSO) d (ppm): 3.67 (OMe, s,
Poly(butyl acrylate-styrene) nanoparticles were prepared by
emulsion polymerization. b-Lactams 4a, 4c or 4d (30 mg,
3 % wt/wt) were dissolved in a 7:3 (wt/wt) mixture of butyl
acrylate (108.5 mg), styrene (46.5 mg) at 70 °C and heated
for 10 min under Ar atmosphere. Deionized water (8.0 mL)
was then added to the solution, followed by appropriate
amount of sodium dodecyl sulfate (10 mg) and potassium
persulfate (5 mg) as surfactant and radical initiator,
respectively. The mixture was then stirred for 7 h at 70 °C
3H), 5.63 (H-4, d, J = 4.7 Hz, 1H), 5.68 (vinylic, d,
J = 9.8 Hz, 1H), 5.82 (H-3, d, J = 4.7 Hz, 1H), 6.23
(vinylic, d, J = 17.0 Hz, 1H), 6.39 (vinylic, dd, J = 9.8,
17.0 Hz, 1H), 6.79–7.65 (ArH, m, 13H), 10.05 (NH, s, 1H);
13C-NMR d (ppm); 55.1 (OMe), 60.9 (C-4), 80.5 (C-3),
114.5, 115.1, 118.2, 118.3, 119.1, 121.8, 123.6, 126.9,
128.6, 129.3, 130.0, 131.6, 133.9, 138.9, 155.9, 156.4
(aromatic and vinylic carbons), 162.0 (CO, b-lactam),
123

J IRAN CHEM SOC
Table 1 Structure of
monocyclics b-lactams 2a–g,
3a–g, and 4a–g
Entry Structures of 2a-g
Yield
(%) a
Structures of 3a-g
Yield
(%) a
Structures of 4a-g
Yield
(%) a
1
64
63
72
2a
4a
4b
3a
3b
3c
2
61
66
67
63
71
73
2b
3
2c
4c
4
53
47
93
92
78
89
4d
2d
3d
3e
5
4e
2e
6
72
51
83
62
60
56
2f
3f
4f
7
4g
2g
3g
a
Isolated yields
and cooled to room temperature. The samples were purified
and characterized to determine their shape and average size.
Purification of the above emulsion was performed by
continuous extraction using ethyl acetate followed by cen-
trifugation on a bench top centrifuge, and then samples were
filtered with cellulose acetate membrane (0.2 lm).
123

J IRAN CHEM SOC
Analysis of the emulsions of nanoparticles
stacking interactions. Furthermore, a p–p interaction helps
to stabilize the crystal structure.
Sample size and distribution of the emulsions were
checked by dynamic light scattering (DLS) using a HOR-
IBA DLS instrument equipped with a laser Beam at
550 nm. The sample was pre-diluted with distilled water
(0.3 mL of emulsion in 24.7 mL of water). Transmission
electron microscopy (TEM) of the samples was captured
by placing a drop of diluted emulsion (1 mL of emulsion in
10 mL of the distilled water and sonicated) onto a formvar-
coated copper grid and evaporating the solvent by air
blowing, then the grid was viewed on the microscope.
Then b-lactams 2a–g containing the nitro group at para or
meta position of the phenyl ring on C-4 of 2-azetidinone were
reduced easily to aminophenyl b-lactams 3a–g by Raney Ni
and hydrazine hydrate in EtOH/H2O (9:1) in good to excel-
lent yields (Scheme 1; Table 1). In the presence of Raney
nickel, hydrazine hydrate decomposed to nitrogen, hydrogen
and ammonia [20] but in this condition b-lactam ring has not
been affected by hydrazine or ammonia.
Then aminophenyl b-lactams 3a–g were dissolved in
CH2Cl2 and in the presence of acryloyl chloride and NaHCO3
as basic catalysts were converted to b-lactam monomers 4a–
g in moderate to good yields (Scheme 1; Table 1).
Results and discussion
Preparation of emulsified polyacrylate nanoparticles as
antibacterial drug carriers have been investigated [6, 7, 16].
These nanopolymeric emulsions can be prepared easily in
water by radical-induced emulsion polymerization using an
acrylated derivative of the b-lactam as a comonomer in a
warmed mixture of butyl acrylate and styrene. For this, the
solubility of acrylated b-lactam monomers 4a–g was
examined in a 7:3 (w:w) mixture of butyl acrylate and
styrene. It was found that b-lactam monomers 4a, 4c, and
4d were readily dissolved to homogeneity in the mixture of
butyl acrylate and styrene at 70 °C under Ar atmosphere.
The mixture was then pre-emulsified in deionized water
and sodium dodecyl sulfate (SDS) (1 weight %) as sur-
factant. After about 30 min, the homogenous solution was
treated with potassium persulfate (0.5 weight %) to start
free radical polymerization for 7 h (Scheme 1).
The Staudinger reaction ([2 ? 2] ketene–imine cycload-
dition reaction) is one of the most common methods for the
synthesis of monocyclic 2-azetidinones [18]. Cycloaddition
reactions of imines 1a–g with different substituted acetic
acids in the presence of p-toluenesulfonyl chloride and
triethylamine afforded cis 2-azetidinones 2a–g in moderate
to good yields (Scheme 1; Table 1). The cis stereochem-
istry of these b-lactams was confirmed from the coupling
constant of H-3 and H-4, which was calculated to be
J3,4 = 4.3–5.1 Hz for the cis stereoisomers.
The X-ray crystallography of 2e [19] (Fig. 1) showed
that the b-lactam ring (N1/C8–C10) is nearly planar, with a
˚
maximum deviation of 0.023 (2) A for N1. Its mean plane
makes dihedral angles of 11.61 (19), 74.5 (2), and 72.3
(2)°, respectively, with three aromatic rings (C1–C6),
(C11–C16), and (C17–C22). A weak intramolecular C–
HÁÁÁO hydrogen bond contributes to the stability of the
molecular configuration. The crystal structure is stabilized
by intermolecular C–HÁÁÁO hydrogen-bonding and C–HÁÁÁp
Then the nanopolymeric emulsions were purified by
continuous extraction using ethyl acetate followed by
centrifugation on a bench top centrifuge, to remove minor
impurities, such as excess surfactant or residual monomers
without altering the physical characteristics of the
Fig. 1 X-ray crystal structure
of 2e
123

J IRAN CHEM SOC
Scheme 1 Synthesis of
monocyclic b-lactams and
nano-b-lactams
of 5c is shown in Fig. 2, and as it is seen in the image, the
nanoparticles were essentially perfectly spherical, which
was similar to the size distribution profile obtained by DLS
analysis (Fig. 3). DLS analysis of the final emulsion
showed that the average diameter of the 5a, 5c, and 5d is
uniformly about 56.6, 62, and 66.9 nm, respectively, with
size distributions spanning from about 20–150 nm.
Conclusions
In this study, several polyacrylate nano b-lactams have
been synthesized from the corresponding monomeric b-
lactams by emulsion polymerization. The polyacrylated b-
lactam nanoparticles showed average diameter of
50–70 nm.
Fig. 2 TEM image of 5c
Acknowledgments The authors thank the Shiraz University
Research Council for financial support (Grant No. 90-GR-SC-23).
References
1. N.S. Vatmurge, B.G. Hazra, V.S. Pore, F. Shirazi, P.S. Chavan,
M.V. Deshpande, Bioorg. Med. Chem. Lett. 18, 2043 (2008)
2. R.J. Shah, N.R. Modi, M.J. Patel, L.J. Patel, B.F. Chauhan, M.M.
Patel, Med. Chem. Res. 20, 587 (2011)
3. P.D. Mehta, N.P.S. Sengar, A.K. Pathak, Eur. J. Med. Chem. 45,
5541 (2010)
4. S.S.B. Reshma, A. Bhalla, G. Hundal, Tetrahedron 65, 10060
(2009)
5. S.J. Douglas, S.S. Davis, L. Illum, Int. J. Pharm. 34, 145 (1986)
6. E. Turos, J.-Y. Shim, Y. Wang, K. Greenhalgh, G.S.K. Reddy, S.
Dickey, D.V. Lim, Bioorg. Med. Chem. Lett. 17, 53 (2007)
7. J.C. Garay-Jimenez, D. Gergeres, A. Young, D.V. Lim, E. Turos,
Nanomedcine: NBM 5, 443 (2009)
8. A.L.Z. Lee, S. Venkataraman, S.B.M. Sirat, S. Gao, J.L. Hedrick,
Y.Y. Yang, Biomaterials 33, 1921 (2012)
9. A. Mahmud, X.-B. Xiong, A. Lavasanifar, Eur. J. Pharm. Biop-
harm. 69, 923 (2008)
Fig. 3 DLS of 5c
nanoparticles in the emulsion [21]. Then the samples were
filtered with cellulose acetate membrane (0.2 lm) to
remove any large scale particles.
The morphology and the particle size analysis of the
emulsions were performed by TEM and DLS. TEM image
123

J IRAN CHEM SOC
10. K.N. Kontogiannopoulos, A.N. Assimopoulou, S. Hatziantoniou,
K. Karatasos, C. Demetzos, V.P. Papageorgiou, Int. J. Pharm.
422, 381 (2012)
11. S.H. Michelland, M.J. Alonso, A. Andremont, P. Maincen, J.
Sauzieres, P. Couvreur, Int. J. Pharm. 35, 121 (1987)
12. G. Fontana, G. Pitarresi, V. Tomarchio, B. Carlisi, P.L. San
Biagio, Biomaterials 19, 1009 (1998)
13. G. Fontana, M. Licciardi, S. Mansueto, D. Schillaci, G. Giam-
mona, Biomaterials 22, 2857 (2001)
14. N.S. Santos-Magalhaes, A. Pontes, V.M.W. Pereira, M.N.P.
Caetano, Int. J. Pharm. 208, 71 (2000)
15. S.C. Abeylath, E. Turos, Carbohydr. Polym. 70, 32 (2007)
16. J.C. Garay-Jimenez, E. Turos, Bioorg. Med. Chem. Lett. 21, 4589
(2011)
17. E. Turos, G.S.K. Reddy, K. Greenhalgh, P. Ramaraju, S.C.
Abeylath, S. Jang, S. Dickeyc, D.V. Lim, Bioorg. Med. Chem.
Lett. 17, 3468 (2007)
18. G.I. Georg, P. He, J. Kant, J. Mudd, TetrahedronLett. 31, 451(1990)
19. Z. Baktır, M. Akkurt, A. Jarrahpour, R. Heiran, Acta Cryst. E67,
o537 (2011)
20. N.R. Ayyangar, A.G. Lugade, P.V. Nikrad, V.K. Sharma, Syn-
thesis 11, 640 (1981)
21. J. Garay-Jimenez, A. Young, D. Gergeres, K. Greenhalgh, E.
Turos, Nanomedicine: NBM 4, 98 (2008)
123