Synthesis and antimicrobial/antimalarial activities of novel naphthalimido trans-β-lactam derivatives

Article abstract of DOI:10.1007/s00044-017-1920-z

This paper describes for the first time the synthesis and microbiological assessment of some new β-lactam derivatives containing a 1,8-naphthalimide functional group. These compounds were obtained through a [2 + 2] cyclocondensation (Staudinger reaction)

Full text of DOI:10.1007/s00044-017-1920-z

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-017-1920-z
ORIGINAL RESEARCH
Synthesis and antimicrobial/antimalarial activities of novel
naphthalimido trans-β-lactam derivatives
Javad Ameri Rad1 Aliasghar Jarrahpour1 Christine Latour2 Veronique Sinou2
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Jean Michel Brunel3 Hsaine Zgou4 Yahia Mabkhot5 Taibi Ben Hadda6
Edward Turos7
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Received: 20 December 2016 / Accepted: 13 May 2017
© Springer Science+Business Media New York 2017
1
Abstract This paper describes for the first time the synth-
esis and microbiological assessment of some new β-lactam
characterized by FT-Infra Red, H NMR, 13C NMR, mass
spectrometry, elemental analyses, and X-ray crystal-
lography, and then individually evaluated for antibacterial
and antimalarial activities. Two of the β-lactams, 3c and 3l,
afforded IC50 values of 3 and 5 µM, respectively, against
Plasmodium falciparum K1 resistant strain.
derivatives containing
a 1,8-naphthalimide functional
group. These compounds were obtained through a [2 + 2]
cyclocondensation (Staudinger reaction) of a ketene derived
from 2-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl) acetic
acid (Alrestatin) and various N-arylimines. The reaction
was totally diastereoselective leading exclusively to the
formation of trans-β-lactam adducts 3a–l, which were
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Keywords β-Lactam 1,8-Naphthalimide Staudinger
reaction Alrestatin Antimalarial
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Electronic supplementary material The online version of this article
(doi:10.1007/s00044-017-1920-z) contains supplementary material,
which is available to authorized users.
Introduction
* Aliasghar Jarrahpour
aliasghar6683@yahoo.com
jarrah@susc.ac.ir
The β-lactam ring (2-azetidinone) is the important functional
group responsible for the incomparable effectiveness of the
most widely employed antibacterial agents, such as the
penicillins and cephalosporins, (Coates et al. 2005; Morin
and Gorman 1982) and as synthetic intermediates and
building blocks in organic synthesis (Alcaide et al. 2007;
Alcaide et al. 2008). β-Lactams have been investigated for a
broad range of biological (Jarrahpour et al. 2016) and
pharmacological applications, such as cholesterol absorption
inhibitors, (Rosenblum et al. 1998) human cytomegalovirus
protease inhibitors, (Mehta et al. 2010) thrombin inhibitors,
(Sutton et al. 2004) anti-hyperglycemic, (Goel et al. 2004)
anti-tumor, (Chen et al. 2008; Frezza et al. 2008, Banik
et al. 2010) anti-HIV, (Sperka et al. 2005) anti-
inflammatory analgesic, (Saturnino et al. 2000) anti-
malarial, (Ebrahimi et al. 2016; Jarrahpour et al. 2012;
Jarrahpour et al. 2014) anti-fungal, (O’Driscoll et al. 2008)
anti-proliferative, (O’Boyle et al. 2011) anti-tubercular,
(Sharma et al. 2011) anti-oxidant, (Nagarajan et al. 2012),
1
Department of Chemistry, College of Sciences, Shiraz University,
Shiraz 71946-84795, Iran
2
Aix-Marseille Université, UMR-MD3 Relation hôte-parasites,
Physiopathologie & Pharmacologie, Faculté de pharmacie, Bd
Jean Moulin, F-13385 Marseille, France
3
Centre de Recherche en Cancérologie de Marseille (CRCM),
CNRS, UMR7258, Institut Paoli Calmettes, Aix-Marseille
Université, UM 105, Inserm, U1068, Faculté de Pharmacie, Bd
Jean Moulin, F-13385 Marseille, France
4
Ibn Zohr University, Polydisciplinary Faculty, 45000 Ouarzazate,
Morocco
5
Department of Chemistry, College of Science, King Saud
University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
6
LCM Laboratory, FSO, University of Mohammed Premier,
Faculty of Sciences, 60000 Oujda, Morocco
7
Center for Molecular Diversity in Drug Design, Discovery, and
Delivery, Department of Chemistry, University of South Florida,
CHE 205, 4202 East Fowler Avenue, Tampa, FL 33620, USA

Med Chem Res
and insecticidal activities (Cao et al. 2011), as well as
serine-dependent enzyme inhibitors (Konaklieva 2002).
Despite the large number of β-lactam compounds that
have already been prepared and evaluated for these prop-
erties, a dire need still remains for new antibiotic com-
pounds to counter the rapid rise in drug resistance seen
among various pathogenic bacteria (Chu et al. 1996). A
plethora of synthetic methods have been developed over
the last century for the formation of the β-lactam ring,
including cyclization reactions, carbene insertion reactions
and rearrangement of heterocyclic compounds, Refor-
matsky reaction, and the Staudinger imine-ketene cycload-
dition (Soengas et al. 2011). The most fundamental and
versatile method for the synthesis of β-lactams (Singh 2003;
Coates et al. 2005) remains the Staudinger imine-ketene
cycloaddition reaction, which is used commonly in the
pharmaceutical and synthetic chemistry arenas (Southgate
1994).
Cyclic imides have likewise received considerable
attention due to their diverse pharmaceutical applications
(Zhang and Zhou 2011). In particular, isoquinolinedione
(naphthalimide) derivatives are cyclic imides of special
interest because of their photophysical and biological
properties as free radical scavengers, (Zhang et al. 2011)
photoredox anticancer agents, (MacIntyre et al. 2010)
fluorescent labels, (Sawa et al. 2006) photosensitizers,
(Rogers and Kelly 1999) and medical imaging agents
(Alcala et al. 2011). The promising anticancer activity of
some naphthalimide-containing compounds is related to
the planarity and optimal size of the 1,8-naphthalimide
ring that enable for efficient intercalation into duplex DNA
(El-Betany and McKeown 2012). In addition, 1,8-naph-
thalimide derivatives exhibit diverse non-biological
applications as fluorescent pigments and dyes, (Stolarski
2009) components in fluorescent sensors for specific metal
cations, (Xu et al. 2009) visible pH indicators, (Georgiev
et al. 2011) as well as optical switches, (Ferreira et al.
2009) organic luminescent devices, (Jung et al. 2009)
coloration of polymers, (Bojinov et al. 2008) light emitting
diodes (Bouche et al. 1996) and fluorescence switchers
(El-Betany and McKeown 2012). The use of a naphthali-
mide precursor has been crucial for the development of
new anticancer drugs such as Amonafide (Wu et al. 2009)
discovered by Brana and Ramos in 2001, (Brana and
Ramos 2001) leading to the development of a series of
other drug candidates such as mitonafide, elinafide, and
bisnafide (Brider and Gellerman 2012; Malviya et al.
1992; Robinson and Castaner 1996). Our interest in the
biological applications of β-lactams and naphthalimides
led us to assess molecular constructs that contain both
bioactive moieties, in terms of their syntheses, as well as
investigations into their potential microbiological
activities.
Materials and methods
General information
All needed chemicals were purchased from Merck, Fluka
and Acros chemical companies and used without further
purification. All reagents and solvents were dried prior to
use according to standard methods (Armarego and Chai
2003). IR spectra were run on a Shimadzu FT-Infra Red
8300 spectrophotometer using potassium bromide pellets (ʋ
in cm−1). 1H-NMR and 13C-NMR spectra were recorded in
dimethylsulfoxide-d6 (DMSO-d6) using a Bruker Avance
DPX instrument (1H NMR 250 MHz, 13C NMR 62.5 MHz).
Chemical shifts are reported in parts per million (δ)
downfield from tetramethylsilane. All of the coupling con-
stants (J) are in hertz (Hz). Splitting patterns are indicated as
s: singlet, d: doublet, t: triplet, q: quartet, m: multiplet, dd:
doublet of doublet. 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 obtained on a Buchi 510 melting
point apparatus and are uncorrected. X-ray data were col-
lected on a Bruker APEX-II CCD diffractometer.
General procedure for the synthesis of Alrestatin
A mixture of 1,8-naphthalic anhydride (1.00 mmol) and
glycine (1.10 mmol) was added in DMF (5 mL) and the
mixture was stirred at 60 °C for several hours (TLC control
in a 2:1 n-hexane:ethyl acetate solvent mixture). After
cooling to room temperature, 20 mL water was added and
the solid Alrestatin was separated. The product was purified
by recrystallization from ethanol and used for the next step
(Donkor et al. 1998).
General procedure for the β-lactams preparation
(Staudinger reaction)
The appropriate aromatic imine (Schiff base) (1.00 mmol),
triethylamine (5.00 mmol), 2-(1,3-dioxo-1H-benzo[de]iso-
quinolin-2(3H)-yl) acetic acid (1.50 mmol), and tosyl
chloride (1.50 mmol) were added to anhydrous CH2Cl2
(5 mL) stirred at 0 °C, and the mixture was allowed to warm
to room temperature for further stirring for 24 h (TLC
control in a 7:3 n-hexane:ethyl acetate solvent mixture). The
mixture was then washed twice with 1N aqueous HCl
solution (20 mL), and once with saturated aqueous NaHCO3
solution (50 mL) and brine (20 mL). The organic layer was
dried over anhydrous Na2SO4 and the solvent removed to
produce the product as a crystal, which was then purified by
recrystallization from ethyl acetate and acetone in a 3:2
volumetric ratio.

Med Chem Res
2-(1-(4-Ethoxyphenyl)-2-(4-nitrophenyl)-4-oxoazetidin-3-
yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (3a)
β-lactam), 55.0 (CH3–O); GC-MS m/z = 548 [M+]; Ana-
lysis calculated for C36H24N2O4: C, 78.82; H, 4.41; N,
5.11%. Found: C, 76.53; H, 4.45; N, 5.81%.
White solid (Yield 75%); Rf = 0.86 (n-hexane: ethyl acet-
ate = 7:3) Mp: 255–257 °C; IR (KBr, cm−1): 1774 (CO β-
lactam), 1704 (CO Naph), 1666 (CO Naph); 1H-NMR (250
MHz, DMSO-d6) δ 1.27 (3H, t, J = 6.7 Hz, CH3), 3.95 (2H,
q, J = 6.7 Hz, CH2), 5.69 (1H, d, J = 2.7 Hz, H-4), 5.94
(1H, d, J = 2.7 Hz, H-3), 6.91 (2H, d, J = 9.0 Hz, ArH),
7.19 (2H, d, J = 9.0 Hz, ArH), 7.79–7.89 (4H, m, ArH),
8.24 (2H, d, J = 9.0 Hz, ArH), 8.43–8.50 (4H, m, ArH);
13C-NMR (62.5 MHz, DMSO-d6) δ 163.2 (CO β-lactam),
162.1 (CO Naph), 155.0, 147.4, 144.8, 134.8, 131.2, 131.1,
130.5, 128.1, 127.4, 127.3, 123.9, 121.5, 118.2, 115.0,
(aromatic carbons), 63.4 (C β-lactam), 63.1 (C β-lactam),
58.0 (CH2-O), 14.5 (CH3); GC-MS m/z = 507 [M+]; Ana-
lysis calculated for C29H21N3O6: C, 68.63; H, 4.17; N,
8.28%. Found: C, 68.20; H, 4.60; N, 8.51%.
2-(2-(4-Chlorophenyl)-4-oxo-1-(p-tolyl)azetidin-3-yl)-1H
benzo[de]isoquinoline-1,3(2H)-dione (3d)
White solid (Yield 68%); Rf = 0.94 (n-hexane: ethyl acet-
ate = 7:3); Mp: 263–265 °C; IR (KBr, cm−1): 1759 (CO β-
lactam), 1705 (CO Naph), 1666 (CO Naph); 1H-NMR (250
MHz, DMSO-d6) δ: 2.23 (3H, s, CH3), 5.54 (1H, d, J = 2.5
Hz, H-4), 5.91 (1H, d, J = 2.5 Hz, H-3), 7.13–7.18 (4H, m,
ArH), 7.44 (2H, d, J = 8.5 Hz, ArH), 7.55 (2H, d, J = 8.5
Hz, ArH), 7.87 (2H, t, J = 7.7 Hz, ArH), 8.44–8.50 (4H, m,
ArH); 13C-NMR (62.5 MHz, DMSO-d6) δ 168.4 (CO β-
lactam), 167.8 (CO Naph), 141.3, 140.1, 140.1, 138.2,
138.2, 136.4, 136.4, 134.8, 134.0, 133.9, 132.6, 132.5,
126.7, 122.0 (aromatic carbons), 68.7 (C β-lactam), 63.3 (C
β-lactam), 25.6 (CH3); GC-MS m/z = 468 [M+, 37Cl], 466
[M+, 35Cl]; Analysis calculated for C28H19ClN2O3: C,
72.30; H, 4.10; N, 6.00%. Found: C, 71.67; H, 3.98; N,
6.11%.
2-(2-(4-Chlorophenyl)-1-(4-methoxyphenyl)-4-oxoazetidin-
3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (3b)
White solid (Yield 70%); Rf = 0.91 (n-hexane: ethyl acet-
ate = 7:3); Mp: 272–273 °C; IR (KBr, cm−1): 1766 (CO β-
lactam), 1704 (CO Naph), 1666 (CO Naph); 1H-NMR (250
MHz, DMSO-d6) δ: 3.69 (3H, s, CH3), 5.53 (1H, d, J = 2.5
Hz, H-4), 5.90 (1H, d, J = 2.5 Hz, H-3), 5.91 (2H, d, J =
9.0 Hz, ArH), 7.19 (2H, d, J = 9.0 Hz, ArH), 7.43 (2H, d, J
= 8.5 Hz, ArH), 7.55 (2H, d, J = 8.5 Hz, ArH), 7.85 (2H, d,
J = 8.0 Hz, ArH), 8.43–8.48 (4H, m, ArH); 13C-NMR
(62.5 MHz, DMSO-d6) δ 163.2 (CO β-lactam), 162.3 (CO
Naph), 155.6, 136.0, 134.9, 133.0, 131.2, 130.6, 128.8,
128.7, 127.4, 127.3, 121.5, 118.2, 117.1, 114.4 (aromatic
carbons), 63.9 (C β-lactam), 63.4 (C β-lactam), 55.2
(CH3–O); GC-MS m/z = 484 [M+, 37Cl], 482 [M+, 35Cl];
Analysis calculated for C28H19ClN2O4: C, 69.64; H, 3.97;
N, 5.80%. Found: C, 68.24; H, 4.05; N, 5.83%.
2-(1-(4-(Diethylamino)phenyl)-2-(4-nitrophenyl)-4-
oxoazetidin-3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione
(3e)
Red solid (Yield 69%); Rf = 0.91 (n-hexane: ethyl acetate
= 7:3); Mp: 254–256 °C; IR (KBr, cm−1): 1759 (CO β-
lactam), 1705 (CO Naph), 1674 (CO Naph); 1H-NMR (250
MHz, DMSO-d6) δ: 1.02 (6H, t, J = 7.0 Hz, 2CH3), 3.26
(4H, q, J = 7.0 Hz, 2CH2–N), 5.62 (1H, d, J = 2.5 Hz, H-4),
5.88 (1H, d, J = 2.5 Hz, H-3), 6.62 (2H, d, J = 8.0 Hz,
ArH), 7.08 (2H, d, J = 8.0 Hz, ArH), 7.76–7.83 (2H, m,
ArH), 7.86–7.92 (2H, m, ArH), 8.22–8.25 (2H, m, ArH),
8.46–8.52 (4H, m, ArH); 13C-NMR (62.5 MHz, DMSO-d6)
δ 163.2 (CO β-lactam), 161.6 (CO Naph), 147.4, 145.2,
144.5, 134.8, 131.2, 131.1, 128.0, 127.4, 127.3, 126.1,
123.9, 121.6, 118.6, 111.9 (aromatic carbons), 63.2 (C β-
lactam), 57.9 (C β-lactam), 43.6 (CH2–N), 12.2 (CH3); GC-
MS m/z = 534 [M+]; Analysis calculated for C31H26N4O5:
C, 69.65; H, 4.90; N, 10.48%. Found: C, 68.36; H, 4.79; N,
10.80%.
2-(2-(Anthracen-9-yl)-1-(4-methoxyphenyl)-4-oxoazetidin-
3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (3c)
Yellow solid (Yield 80%); Rf = 0.88 (n-hexane: ethyl
acetate = 7:3); Mp: 185–187 °C; IR (KBr, cm−1): 1751 (CO
1
β-lactam), 1704 (CO Naph), 1666 (CO Naph); H-NMR
(250 MHz, DMSO-d6) δ: 3.57 (3H, s, CH3), 6.73–6.79 (4H,
m, ArH and H-4), 6.97 (2H, d, J = 2.5 Hz, H-3), 7.09 (2H,
d, J = 8.7 Hz, ArH), 7.49–7.57 (4H, m, ArH), 7.81–7.90
(2H, m, ArH), 8.16 (2H, d, J = 7.7 Hz, ArH), 8.42–8.51
(6H, m, ArH), 8.51(1H, s, ArH); 13C-NMR (62.5 MHz,
DMSO-d6) δ 163.8 (CO β-lactam), 162.1 (CO Naph),
155.7, 134.9, 131.3, 131.1, 131.0, 130.9, 130.0, 129.8,
129.7, 127.5, 127.4, 127.2, 125.1, 124.1, 122.5, 121.4,
117.7, 114.5 (aromatic carbons), 62.1 (C β-lactam), 55.5 (C
2-(1-(Naphthalen-1-yl)-2-(naphthalen-2-yl)-4-oxoazetidin-
3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (3f)
White solid (Yield 63%); Rf = 0.89 (n-hexane: ethyl acet-
ate = 7:3); Mp: 309–311 °C; IR (KBr, cm−1): 1766 (CO β-
lactam), 1704 (CO Naph), 1666 (CO Naph); 1H-NMR (250
MHz, DMSO-d6): 6.10 (1H, d, J = 2.5 Hz, H-4,), 6.38 (1H,
d, J = 2.5 Hz, H-3,), 7.41–7.49 (4H, m, ArH), 7.54–7.69
(2H, m, ArH), 7.71–7.74 (1H, m, ArH), 7.78–7.94 (7H, m,

Med Chem Res
ArH), 8.10 (1H, s, ArH), 8.46–8.59 (5H, m, ArH); 13C-
NMR (62.5 MHz, DMSO-d6) δ 164.0 (CO β-lactam), 163.3
(CO Naph), 134.9, 134.3, 133.8, 132.5, 132.4, 131.3, 131.3,
128.5, 127.6, 127.6, 127.5, 127.3, 127.2, 126.6, 126.5,
126.4, 126.3, 126.2, 124.5, 121.5 (aromatic carbons), 62.0
(C β-lactam), 60.0 (C β-lactam); GC-MS m/z = 518 [M+];
Analysis calculated for C35H22N2O3: C, 81.07; H, 4.28;
N, 5.40%. Found: C, 80.95; H, 4.11; N, 5.53%.
MHz, DMSO-d6): 3.67 (6H, s), 5.94 (1H, d, J = 1.0 Hz, H-
4), 5.68 (1H, d, J = 1.0 Hz, H-3), 6.51 (1H, d, J = 8.0 Hz,
ArH), 6.88 (1H, d, J = 8.0 Hz, ArH), 7.12 (1H, s, ArH),
7.80–7.91 (4H, m, ArH), 8.24 (2H, d, J = 8.0 Hz, ArH),
8.49 (4H, t, J = 7.0 Hz, ArH); 13C-NMR (62.5 MHz,
DMSO-d6) δ 163.2 (CO β-lactam), 162.1 (CO Naph),
149.1, 147.4, 145.4, 144.7, 134.9, 131.2, 131.1, 130.8,
128.1, 127.4, 127.3, 123.9, 121.5, 112.3, 108.2, 102.1
(aromatic carbons), 63.3 (C β-lactam), 58.2 (C β-lactam),
55.7 (O–CH3), 55.4 (O–CH3); GC-MS m/z = 523 [M+];
Analysis calculated for C29H21N3O7: C, 66.54; H, 4.04; N,
8.03%. Found: C, 66.83; H, 3.98; N, 8.22%.
2-(2-(4-Nitrophenyl)-4-oxo-1-(p-tolyl)azetidin-3-yl)-1H-
benzo[de]isoquinoline-1,3(2H)-dione (3g)
White solid (Yield 65%); Rf = 0.94 (n-hexane: ethyl acet-
ate = 7:3); Mp: 290–291 °C; IR (KBr, cm−1): 1774 (CO β-
lactam), 1705 (CO Naph), 1666 (CO Naph); 1H-NMR (250
MHz, DMSO-d6): 2.24 (3H, s), 5.70 (1H, d, J = 2.7 Hz, H-
4), 5.95 (1H, d, J = 2.7 Hz, H-3), 7.14-7.17 (4H, m, ArH),
7.81 (2H, d, J = 9.0 Hz, ArH), 7.88 (2H, t, J = 8.0 Hz,
ArH), 8.24 (2H, d, J = 9.0 Hz, ArH), 8.28 (4H, t, J = 8.0
Hz, ArH); 13C-NMR (62.5 MHz, DMSO-d6) δ 168.4 (CO β-
lactam), 167.6 (CO Naph), 152.7, 150.0, 140.1, 140.0,
138.4, 136.5, 136.4, 134.9, 134.3, 133.3, 132.5, 129.2,
126.8, 122.0(aromatic carbons), 68.6 (C β-lactam), 63.2 (C
β-lactam), 25.6 (CH3); GC-MS m/z = 477 [M+]; Analysis
calculated for C28H19N3O5: C, 70.43; H, 4.01; N, 8.80%.
Found: C, 69.32; H, 4.61; N, 8.57%.
2-(1-(2,4-Dimethoxyphenyl)-2-(2-nitrophenyl)-4-
oxoazetidin-3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-
dione (3j)
White solid (Yield 55%); Rf = 0.92 (n-hexane: ethyl acet-
ate = 7:3); Mp: 249–251 °C; IR (KBr, cm−1): 1759 (CO β-
lactam), 1697 (CO Naph), 1666 (CO Naph); 1H-NMR (250
MHz, DMSO-d6): 3.71 (3H, s), 3.83 (3H, s), 6.41 (1H, d, J
= 2.5 Hz, H-4), 6.45 (1H, d, J = 2.5 Hz, H-3), 6.59–6.61
(1H, m, ArH), 7.56–7.75 (2H, m, ArH), 7.85–8.04 (3H, m,
ArH), 8.39–8.56 (6H, m, ArH), 9.50 (1H, s, ArH); 13C-
NMR (62.5 MHz, DMSO-d6) δ 165.2 (CO β-lactam), 163.2
(CO Naph), 151.1, 141.1, 140.6, 138.4, 136.1, 134.5, 131.7,
131.2, 130.8, 130.6, 130.3, 128.8, 127.2, 123.2, 121.7,
119.9, 103.9, 98.7 (aromatic carbons), 68.6 (C β-lactam),
63.5 (C β-lactam), 55.6 (O–CH3), 55.1 (O–CH3); GC-MS
m/z = 523 [M+]; Analysis calculated for C29H21N3O7: C,
66.54; H, 4.04; N, 8.03%. Found: C, 66.83; H, 4.27; N,
8.22%.
2-(1-(Benzo[d][1,3]dioxol-5-yl)-2-(4-nitrophenyl)-4-
oxoazetidin-3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-
dione (3h)
Gray solid (Yield 68%); Rf = 0.90 (n-hexane: ethyl acetate
= 7:3); Mp: 242–244 °C; IR (KBr, cm−1): 1766 (CO β-
lactam), 1705 (CO Naph), 1666 (CO Naph); 1H-NMR (250
MHz, DMSO-d6): 5.67 (1H, d, J = 2.5 Hz, H-4), 5.93 (1H,
d, J = 2.5 Hz, H-3), 5.94–5.98 (2H, m, ArH), 6.59 (2H, d, J
= 7.7 Hz, ArH), 6.82–6.98 (2H, m, ArH), 7.79–7.91 (4H,
m, ArH), 8.22–8.51 (5H, m, ArH); 13C-NMR (62.5 MHz,
DMSO-d6) δ 168.5 (CO β-lactam), 167.5 (CO Naph),
152.8, 152.7, 149.8, 148.9, 140.1, 136.5, 136.4, 133.4,
132.5, 129.1, 126.8, 114.8, 113.8, 106.5, 104.4, 102.4
(aromatic carbons), 87.7 (O–CH2–O), 68.5 (C β-lactam),
63.6 (C β-lactam); GC-MS m/z = 507 [M+]; Analysis cal-
culated for C28H17N3O7: C, 66.27; H, 3.38; N, 8.28%.
Found: C, 66.27; H, 4.11; N, 8.57%.
2-(1-(Benzo[d][1,3]dioxol-5-yl)-2-(3,4-dimethoxyphenyl)-
4-oxoazetidin-3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-
dione (3k)
Yellow solid (Yield 80%); Rf = 0.91 (n-hexane: ethyl
acetate = 7:3); Mp: 239–241 °C; IR (KBr, cm−1): 1759 (CO
1
β-lactam), 1712 (CO Naph), 1666 (CO Naph); H-NMR
(250 MHz, DMSO-d6): 3.69 (3H, s), 3.73 (3H, s), 5.40 (1H,
d, J = 2.7 Hz, H-4), 5.95 (1H, d, J = 2.7 Hz, H-3),
5.96–6.03 (2H, m, O–CH2–O), 6.63 (1H, dd, J1 = 8.2 Hz,
J2 = 2.0 Hz, ArH), 6.84–6.95 (2H, m, ArH), 7.04 (1H, dd,
J1 = 8.2 Hz, J2 = 1.7 Hz, ArH), 7.12–7.22 (1H, m, ArH),
7.86 (2H, t, J = 7.7 Hz, ArH), 8.41–8.54 (3H, m, ArH);
13C-NMR (62.5 MHz, DMSO-d6) δ 163.1 (CO β-lactam),
162.8 (CO Naph), 155.5, 148.9, 148.8, 147.4, 143.4, 134.8,
132.1, 131.2, 128.9, 127.3, 121.5, 118.9, 111.8, 110.5,
109.6, 108.4, 101.1, 99.0 (aromatic carbons), 82.4
(O–CH2–O), 63.5 (C β-lactam), 59.3 (C β-lactam), 55.4 (O–
CH3), 55.3 (O–CH3); GC-MS m/z = 522 [M+]; Analysis
2-(1-(3,4-Dimethoxyphenyl)-2-(4-nitrophenyl)-4-
oxoazetidin-3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-
dione (3i)
White solid (Yield 72%); Rf = 0.93 (n-hexane: ethyl acet-
ate = 7:3); Mp: 178–180 °C; IR (KBr, cm-1): 1766 (CO β-
lactam), 1704 (CO Naph), 1666 (CO Naph); 1H-NMR (250

Med Chem Res
calculated for C30H22N2O7: C, 68.96; H, 4.24; N, 5.36%.
Found: C, 68.31; H, 4.35; N, 5.29%.
concentration were determined using ICESTIMATOR
(Kaddouri et al. 2006; Le Nagard et al. 2011).
2-(1-(2,4-Dimethoxyphenyl)-2-(3,4-dimethoxyphenyl)-4-
oxoazetidin-3-yl)-1H-benzo[de]isoquinoline-1,3(2H)-
dione (3l)
Results and discussion
Yellow solid (Yield 85%); Rf = 0.92 (n-hexane: ethyl
acetate = 7:3); Mp: 191–193 °C; IR (KBr, cm−1): 1755 (CO
β-lactam),1705 (CO Naph), 1666 (CO Naph); 1H-NMR
(250 MHz, DMSO-d6): 3.65–3.71 (12H, m, 4 CH3), 5.61
(1H, d, J = 2.2 Hz, H-4), 5.87 (1H, d, J = 2.2 Hz, H-3), 6.53
(2H, d, J = 8.7 Hz, ArH), 6.84 (1H, d, J = 8.2 Hz, ArH),
6.93 (1H, d, J = 8.0 Hz, ArH), 7.03 (1H, s, ArH), 7.45 (1H,
d, J = 8.2 Hz, ArH), 7.86 (2H, t, J = 7.7 Hz, ArH), 8.47
(4H, d, J = 7.7 Hz, ArH,); 13C-NMR (62.5 MHz, DMSO-
d6) δ 163.2 (CO β-lactam), 163.1 (CO Naph), 158.2, 153.3,
148.6, 148.5, 134.8, 131.2, 130.0, 127.4, 127.3, 127.2,
124.4, 121.5, 118.8, 117.7, 111.6, 110.3, 104.9, 99.4 (aro-
matic carbons), 63.4 (C β-lactam), 61.7 (C β-lactam), 56.0
(O–CH3), 55.7 (O–CH3), 55.3 (O–CH3), 55.3 (O–CH3);
GC-MS m/z = 538 [M+]; Analysis calculated for
C31H26N2O7: C, 69.14; H, 4.87; N, 5.20%. Found: C,
68.93; H, 4.50; N, 5.37%.
All new trans-β-lactams were synthesized by the reaction
between an appropriate aromatic imine and 2-(1,3-dioxo-
1H-benzo[de]isoquinolin-2(3H)-yl) acetic acid in the pre-
sence of tosyl chloride and triethylamine in anhydrous
CH2Cl2, stirred at 0 °C to room temperature for 24 h
(Scheme 1). The reaction products were purified by
recrystallization and fully characterized by spectral and
elemental analyses. These experimental conditions afforded
exclusively the trans-β-lactams 3a–l in isolated yields
varying from 55 to 85%. The trans stereochemistry of each
new β-lactam compound was assigned from the coupling
constants of the two β-lactam ring protons, H-3 and H-4
(J3,4 ≤ 2.75 Hz) (Bandyopadhyay et al. 2012; Banik et al.
2010; Duguet et al. 2010; Wild and Georg 1993; Zarei
2013). X-ray single crystal analysis on 3b and 3c (Fig. 1)
(Celik et al. 2015a, 2015b) confirmed the trans disubstitu-
tion of the β-lactam rings.
Performing the cycloaddition reaction at −78 °C or in
different solvents did not lead to improvement in yield or
changes in diastereoselectivity, although the use of toluene
at reflux had a detrimental effect on the isolated yield.
β-Lactams 3a–l were evaluated for antimicrobial activ-
ities using a standard in vitro microbiological assay. None
of the compounds possess significant antimicrobial activ-
ities against the Gram-positive Staphylococcus aureus or
the Gram-negative bacteria Escherichia coli or Pseudomo-
nas aeruginosa, except for derivative 3f which has an MIC
of 1.5 µg/mL against S. aureus. An assessment was subse-
quently performed for their anticancer activities against a
SUM149 breast cancer cell line, but in no case was an IC50
lower than 50 µM obtained for the twelve compounds.
However, moderate to excellent antimalarial activities were
found for some of the compounds against chloroquine-
resistant P. falciparum K1 strain, as outlined in Table 1.
IC50 values varying from 3 µM up to 125 µM were obtained.
The substituents on the phenyl group at C4 position are
responsible for these differences in bioactivity. Indeed, the
presence of a nitro group is detrimental, leading to low
antimalarial activities (Table 1, compounds 3a, 3e, 3g, 3h,
3i) whereas a phenyl group bearing a chloro, a methoxy or
an anthracenyl group each gave better in vitro bioactivity
(Table 1, compounds 3b, 3c, 3d, 3k, 3l). Although the
mode of antimalarial action has not yet been identified, the
observed anti-Plasmodium bioactivity found among just
this small library of compounds is intriguing and worthy of
further investigation.
General procedure for antimalarial activity
measurements
The chloroquine-resistant P. falciparum strain K1 (South-
east Asia) was in vitro cultured in complete medium con-
sisting of RPMI 1640 (In Vitrogen) supplemented with
27.5 mM NaHCO3, 20 mg/L gentamycin, and 10% human
serum. Parasites were grown at 37 °C in human O + red
blood cells at a 6% hematocrit under a 5% CO2, 10% O2,
and 85% N2 atmosphere. Cultures were synchronized by
sorbitol treatments (Noedl et al. 2005). Stock solutions of
lactam derivatives were prepared in sterile DMSO (10 mM)
and later dilutions were with complete culture medium.
Increasing concentrations of lactam derivatives (100 µL/
well, top concentration = 50 µM) were distributed in a 96-
well plate; DMSO (0.5% vol/vol, top concentration) was
distributed for control. Then, 100 µL from a culture con-
taining >95% ring (0–20 h post-invasion) at a 0.8% para-
sitemia and 3% hematocrit in complete medium was added
per well. The plates were incubated at 37 °C in presence of
5% CO2, 85% N2 and 10% O2 for 72 h. After culture the
plates were frozen at −20 °C. Parasite susceptibility was
tested in parallel against chloroquine diphosphate (Sigma-
Aldrich) (final concentrations: 6.25–3200 nM). Parasite
growth inhibition was quantified using a homemade HRP2
ELISA assay based on pfHRP2 detection. Dose-response
curves and drug concentrations inhibiting parasite growth
by 50% (IC50) using duplicate-well data for each drug

Med Chem Res
Scheme 1 Synthesis of 3-
naphthalimido trans-β-lactams
3a–l
Fig. 1 ORTEP images of the single crystal X-ray structures for 3-naphthalimido trans-β-lactams 3b and 3c, respectively. (CCDC reference
1044874 and CDCC reference 1048898)

Med Chem Res
Table 1 Antimalarial activities of trans-β-lactams 3a–l against
chloroquine-resistant P. falciparum K1 strain
Armarego W, Chai C (2003) Purification of laboratory chemicals, 5th
edn. Butter Worth, Oxford
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Banik BK, Banik I, Becker FF (2010) Asymmetric synthesis of
anticancer β-lactams via Staudinger reaction: Utilization of chiral
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Bojinov VB, Georgiev NI, Nikolov PS (2008) Synthesis and photo-
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Product
IC50 (µM)
Product
IC50 (µM)
3a
3b
3c
3d
3e
3f
>125
11.93
3.03
3g
3h
3i
31.17
>125
35.27
NTb
24.60
5.18
–
8.22
3j
3k
3l
44.78
NTb
Chla
0.97
–
Bouche C-M, Berdague P, Facoetti H, Robin P, Le Barny P, Schott M
(1996) Side-chain electroluminescent polymers. Synth Met
81:191–195
a
Chl: Chloroquine (reference antibiotic)
b
Brana M, Ramos A (2001) Naphthalimides as anticancer agents:
synthesis and biological activity. Curr Med Chem-Anti-Cancer
Agent 1:237–255
Brider T, Gellerman G (2012) A two-step synthesis of medicinally-
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NT: Not Tested due to insufficient solubility in DMSO
Conclusion
In this study, we have described the synthesis of a series of
naphthalimido-substituted trans-β-lactams by a stereo-
selective ketene-imine cycloaddition (Staudinger reaction).
To the best of our knowledge, this is the first time that
Alrestatin ketene has been used for the synthesis of 2-
azetidinones. This novel ketene afforded good to excellent
yields of the desired β-lactams and with exclusive trans
diastereoselectivity. Additionally we have been able to
demonstrate the potent use of such derivatives as anti-
malarial agents against a chloroquine-resistant strain with an
IC50 of 3 µM for compound 3c. Further studies are being
focused on the synthesis of additional analogs to enhance
anti-Plasmodium bioactivity and drug-like properties of the
β-lactams, as well as to better understand the basis for the
observed antimalarial properties.
Cao XF, Wang YS, Li SW, Chena CS, Ke SY (2011) Synthesis and
biological activity of a series of novel N‐Substituted β‐Lactams
derived from natural gallic acid. J Chin Chem Soc 58:35–40
Celik I, Akkurt M, Jarrahpour A, Ameri Rad J, Celik O (2015a)
Crystal structure of 2-[4-(4-chlorophenyl)-1-(4-methoxyphenyl)-
2-oxoazetidin-3-yl]benzo[de]isoquinoline-1,3-dione
dimethyl
sulfoxide monosolvate. Acta Crystallogr Sect E 71:o129–o130
Celik I, Akkurt M, Jarrahpour A, Ameri Rad J, Celik O (2015b)
Crystal structure of 2-[(3S,4S)-4-(anthracen-9-yl)-1-(4-methox-
yphenyl)-2-oxoazetidin-3-yl]-2-aza-2H-phenalene-1,3-dione
unknown solvate. Acta Crystallogr Sect E 71:o184–o185
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Acknowledgements The authors would like to thank the Shiraz
University Research Council for financial support (Grant No. 95-GR-
SC-23). T.B.H. and Y.N.M. extend their sincere appreciation to the
Deanship of Scientific Research at King Saud University for funding
this Prolific Research Group (PRG-1437-29).
Compliance with ethical standards
Conflict of interest The authors declare that they have no competing
interests.
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properties of macromolecular components based on 1, 8-
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