Synthesis and in vitro antileishmanial efficacy of novel quinazolinone derivatives

Article abstract of DOI:10.1111/cbdd.13790

Currently available drugs being used to treat leishmaniasis have several shortcomings, including high toxicity, drug administration that requires hospitalization, and the emergence of parasite resistance against clinically used drugs. As a result, there is a dire need for the development of new antileishmanial drugs that are safe, affordable, and efficient. In this study, two new series of synthesized quinazolinone derivatives were investigated as potential future antileishmanial agents, by assessing their activities against the Leishmania (L.) donovani and L.?major species. The cytotoxicity profiles of these derivatives were assessed in vitro on Vero cells. The compounds were found to be safer and without any toxic activities against mammalian cells, compared to the reference drug, halofuginone, a clinical derivative of febrifugine. However, they had demonstrated poor antileishmanial growth inhibition efficacies. The two compounds that had been found the most active were the mono quinazolinone 2d and the bisquinazolinone 5b with growth inhibitory efficacies of 35% and 29% for the L.?major and L.?donovani 9515 promastigotes, respectively. These outcomes had suggested structural redesign, inter alia the inclusion of polar groups on the quinazolinone ring, to potentially generate novel quinazolinone derivatives, endowed with effective antileishmanial potential.

Full text of DOI:10.1111/cbdd.13790

PROFESSOR DAVID N'DA (Orcid ID : 0000-0002-2327-0551)
Article type
: Research Article
Synthesis and in vitro antileishmanial efficacy of novel quinazolinone derivatives
Izak F. Prinsloo1, Nonkululeko H. Zuma2, Janine Aucamp2, David D. N’Da *2
1Pharmaceutical chemistry, School of Pharmacy, North-West University, Potchefstroom 2520, South Africa.
2Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom 2520, South
Africa.
*Corresponding author: David.nda@nwu.ac.za; Tel.: +2718 299 2256;
ORCID ID: 0000-0002-2327-0551
Running title: Novel antileishmanial quinazolinone derivatives
Abstract
Currently available drugs being used to treat leishmaniasis have several shortcomings, including
high toxicity, drug administration that requires hospitalization, and the emergence of parasite
resistance against clinically used drugs. As a result, there is a dire need for the development of
new antileishmanial drugs that are safe, affordable and efficient. In this study, two new series of
synthesized quinazolinone derivatives were investigated as potential future antileishmanial
agents, by assessing their activities against the Leishmania (L.) donovani and L. major species.
The cytotoxicity profiles of these derivatives were assessed in vitro on Vero cells. The
compounds were found to be safer and without any toxic activities against mammalian cells,
compared to the reference drug, halofuginone, a clinical derivative of febrifugine. However, they
had demonstrated poor antileishmanial growth inhibition efficacies. The two compounds that had
been found the most active were the mono quinazolinone 2d and the bisquinazolinone 5b with
growth inhibitory efficacies of 35% and 29% for the L. major and L. donovani 9515 promastigotes,
respectively. These outcomes had suggested structural redesign, inter alia the inclusion of polar
groups on the quinazolinone ring, to potentially generate novel quinazolinone derivatives,
endowed with effective antileishmanial potential.
This article has been accepted for publication and undergone full peer review but has not been
through the copyediting, typesetting, pagination and proofreading process, which may lead to
differences between this version and the Version of Record. Please cite this article as doi:
10.1111/CBDD.13790
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Keywords: Leishmaniasis; promastigote; febrifugine; halofuginone; quinazolinone
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1.
Introduction
Leishmania is a kinetoplastid parasite, member of Trypanosomatida family. It has negatively
impacted humankind for centuries, with records showing parasitic evidence from as early as
1,500 – 2,500 BCE (Steverding, 2017). Leishmaniasis refers to the disease being caused by the
Leishmania parasite, of which there are in excess of twenty known species that can infect
humans (WHO, 2019a). The L. donovani and L. major species are the most problematic,
accounting for the highest disease burden, due to these two species being the causative agents
of visceral and cutaneous leishmaniasis, respectively (WHO, 2010). The disease is endemic to
ninety-eight countries (WHO, 2019b), with its distribution ever increasing. In 2019, around
600,000 - 1 million new cases of cutaneous leishmaniasis, and some 50,000 - 90,000 new cases
of the visceral form of the disease, were reported to have occurred worldwide (WHO, 2020). The
clinical forms of the disease include: (i) the disfiguring mucocutaneus (ML) form, which causes a
partial or complete loss of the mucous membranes in the mouth, nose and throat; (ii) the
cutaneous (CL) form, which presents with ulcers and skin lesions across exposed body parts;
and (iii) the life threatening visceral (VL) form, characterized by fevers, weight loss, fatigue, an
enlarged spleen and liver, with a 95% fatal rate if left untreated (WHO, 2019c).
Currently available chemotherapies for the treatment of leishmaniasis consist of a handful of
drugs, namely pentavalent antimonials, amphotericin B, pentamidine, paromomycin and
miltefosine (Fig. 1). Despite their use having spanned over decades, painful intravenous (IV) and
intramuscular (IM) administration, high toxicity and the need for hospitalization during drug
administration have resulted in their misuse and in low patient compliance. Consequently, these
drugs have become sub-standard, due to an increasing loss in efficacy. Furthermore, the
emergence of drug resistant strains of the causative pathogens has rendered these drugs even
more inefficient, hence the need to increase dosages to achieve therapeutic effects (Sundar &
Chakravarty, 2013), which has further accentuated toxicity and perpetuated patient non-
compliance.
Figure 1
Drug combination therapies is an intervention being used to combat drug resistance, which aims
at lowering the dosages of each drug that’s included in treatment regimens to lower their toxicity
levels (Sundar & Chakravarty, 2015). However, as this approach has proven to only serve as a
momentary solution to an urgent problem, there is a need for alternative, effective, safe and
affordable chemical agents for use as antileishmanial drugs (Bekhit et al., 2018).
A large library of quinazolinone derivatives have previously been screened for a variety of
biological activities, emphasizing the value of these derivatives to the health industry (Khan et al.,
2016). Quinazolinones are the building blocks for over a hundred-and-fifty naturally occurring
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alkaloids. An example of one such alkaloid is methaqualone (Fig. 2), well known for its sedative-
hypnotic effects (Mhaske & Argade, 2006).
Febrifugine and its analogue, halofuginone, are also eminent quinazolinone derivatives that
possess potent antiprotozoal activity, including antileishmanial activity (Pandey et al., 2017;
Wong, 2017). Febrifugine was first isolated from the Chinese medicinal plant, Dichroa febrifuga
and has been used for the treatment of malaria related fevers for over 2,000 years (Batista, Silva,
& de Oliveira, 2009). Its clinical introduction as a modern medicinal agent has, however, been
unsuccessful, due to severe adverse effects being reported during its initial clinical testing for
possible antimalarial use, including vomiting, nausea and liver toxicity (Burns, 2008). Since then,
further derivatives of febrifugine have been synthesized and despite potent antileishmanial
activities, they reportedly also present with poor safety profiles, but with less severe adverse
effects (McLaughlin, Evans, & Pines, 2014; Wong, 2017). Subsequently, many studies have
been conducted to improve the pharmacological characteristics of febrifugine and halofuginone.
A study by Jiang and co-workers (Jiang et al., 2005) suggested that the modification of the
piperidine moiety would lead to a complete loss in antiprotozoal activity. Later studies by Zhu et
al. (Zhu, Chandrashekar, Meng, Robinson, & Chatterji, 2012; Zhu et al., 2010) concluded that
modification of the carbonyl linker and piperidine ring had no bearing on the antiprotozoal
activities of the compounds (Fig. 2). Thus, no clear consensus hence exists regarding the
potential impact that modification of the piperidine moiety would have of the biological activity of
febrifugine.
We hypothesized that modifications, such as the replacement of the 2-methylpiperidin-3-ol moiety
with a cycloamine, or substitution of the piperidin-3-ol with another quinazolinone ring might
reduce the adverse effects of both agents, while preserving the antiprotozoal activity of
febrifugine. To date, we have investigated in vitro the antileishmanial activities of two series of
quinazolinone derivatives, namely febrifugine analogues bearing acetylamide side chains, as well
as bisquinazolinones of which the piperidin-3-ol group had been replaced by another
quinazolinone ring.
Bisquinazolinones are synthetic structures in which two quinazolinone moieties are linked
together. Very limited literature is available on these compounds. Reddy and colleagues
reported on the antimicrobial, antifungal and antifeedant activities of bisquinazolinone derivatives
(L. M. Reddy, Reddy, & Reddy, 2002; P. Reddy, Mittapelli, & Reddy, 2010). Furthermore,
Elshahawi and co-workers reported on the insecticidal activities of bis-benzoxazin-4-one
bisquinazolinones (Fig. 2) (Elshahawi, EL‐Ziaty, Morsy, & Aly, 2016). Liu and co-workers also
described the green synthesis of bisquinazolinones but the biological activity has yet to be
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disclosed (Liu, Lu, Zhou, & Wang, 2014). Notably, all these synthesized bisquinazolinones are
linked at the C-2 atom of the quinazolinone ring through a carbon−carbon covalent bond (Fig. 2).
Figure 2
In this study, we propose easy synthetic routes for generating novel quinazolinone derivatives.
Bisquinazolinone (N-3 substituted quinazolinone) and febrifugine derivatives were synthesized,
as depicted in Schemes 1 and 2. The design of these derivatives had been inspired by the
potent antileishmanial activities of quinazolinone related derivatives, as reported in previous
studies (Elshahawi et al., 2016; Pandey et al., 2017).
We herein report on the synthesis of these compounds and their antileishmanial growth inhibition
efficacies, as well as on their cytotoxicities on mammalian cells.
2.
Material and methods
Materials
2.1.
Solvents: dichloromethane (DCM), hexane, diethyl ether (Et2O), ethanol (EtOH), ethyl acetate
(EtOAc) and methanol (MeOH) were obtained from ACE Chemicals (Johannesburg, South
Africa). Bases: potassium carbonate and sodium hydroxide were acquired from ACE Chemicals
(Johannesburg, South Africa), whereas triethylamine was acquired from Sigma-Aldrich
(Johannesburg, South Africa).
Reagents, such as morpholine, thiomorpholine, 1-
formamide, 1,3-dichloro-2-propanol, triethyl
methylpiperazine, 1-acetylpiperazine,
orthopropionate, triethyl orthoacetate, triethyl orthoformate, anthranilic acid and
dimethylformamide (DMF) were all acquired from Sigma-Aldrich (Johannesburg, South Africa); 4-
piperidone monohydrate hydrochloride, 2-aminobenzamide, 2-amino-4-chlorobenzoic acid, 2-
amino-4,5-dimethoxybenzoic acid, 2-aminobenzenesulfonamide, piperidone ethylene ketal, 1-
(tetrahydro-2-furoyl)piperazine, 1-(2-pyridyl)piperazine were all acquired from AK Scientific
(California, USA), while chloroacetyl chloride was acquired from Fluka Analytical (Johannesburg,
South Africa).
2.2.
General procedures
Nuclear magnetic resonance (NMR) spectra of 1H and 13C were recorded on a Bruker AvanceTM
III spectrometer, in solution of deuterated dimethyl sulfoxide (DMSO-d6) ((CD3)2SO). Chemical
shifts (δ) are reported in parts per million (ppm) and the 1H chemical shifts are reported downfield
of tetramethylsilane (TMS), with internal reference to the residual proton in (CD3)2SO (2.5 ppm).
13C chemical shifts were internally referenced to the (CD3)2SO resonances (40.0 ppm). The
splitting patterns are abbreviated as follows: singlet (s), doublet (d), doublet of doublets (dd),
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doublet of doublets of doublets (ddd), triplet (t) and multiplet (m). The coupling constant J is
reported in herz (Hz). Spectra were analyzed with MestReNova software, version 5.3.2-4936.
High resolution mass spectrometry (HRMS) was recorded on a Bruker MicroTOF Q II mass
spectrometer, equipped with an ESI source set at 180 °C, using Bruker Compass DataAnalysis
4.0 software. A full scan from m/z 50 to 1500 was performed at a capillary voltage of 4 500 V, an
end plate offset voltage of -500 V, with the nebulizer set at 0.4 Bar, r, and a collision cell RF
voltage of 100 Vpp.
Infrared (IR) spectra were recorded on a Bruker Alpha-P FTIR (ATR) instrument. Melting points
(mp) were determined with a Büchi melting point B-545 instrument and were uncorrected.
Column chromatography was performed, using high purity grade silica gel (pore size 60 Å, 70 -
230 mesh, 63 – 200 m) from Sigma Aldrich and thin layer chromatography was performed, using
silica gel plates (60F254) from Merck (Johannesburg, South Africa).
2.3.
Synthesis
2.3.1. Quinazolinone intermediates 1a-f
The syntheses of intermediates 1a, 4-(3H)quinazolinone and 1b, 2H-benzo[e][1,2,4]thiadiazine
1,1-dioxide, 1c, 7-chloroquinazolin-4(3H)-one, 1d, 6,7-dimethoxyquinazolin-4(3H)-one, 1e, 2-
methylquinazolin-4(3H)-one and 1f, 2-ethylquinazolin-4(3H)-one,
are described in the
Supplementary Information file.
2.3.2. 2-Chloroacetylamide intermediates
The synthesis of these intermediates is described in the Supplementary Information file.
2.3.3. Febrifugine analogues 2a-g and 3a-d
These compounds were synthesized by adapting a known method (Pedgaonkar et al., 2014)
described as follows: To a two-neck, round bottom flask, containing anhydrous DMF (10 mL),
were added 4-quinazolinone intermediate 1a-f (1.0 eq.), 2-chloroacetylamide intermediate (1.2
eq.) and K2CO3 (1.5 eq.). The reaction mixture was refluxed for 24 h. Upon cooling to 60 °C,
saturated ammonium chloride (NH4Cl) (20 mL) was added to trap most of the DMF into the
aqueous phase, followed by extraction with DCM (3× 100 mL). The organic phase was dried
over MgSO4 and then evaporated in vacuo. The residue was then dissolved in EtOAc (20 mL)
and allowed to precipitate upon addition of hexane at 4 °C to afford the target febrifugine
analogue 2a-g and 3a-d.
3-(2-Morpholino-2-oxoethyl)quinazolin-4(3H)-one 2a
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The reaction of 1a (4-(3H)quinazolinone) (0.9 g, 6.08 mmol) with 2-chloro-1-morpholinoethanone
(1.2 g, 7.3 mmol) afforded 2a as white crystals (0.68 g, 2.49 mmol, 41%). m.p. 236.1 °C. IR
1
(ATR)°ѵmax/cm-1: 1672 (C=O), 1648 (C=O), 1605 (C=N), 1245 (C−N), 1105 (C−O). H NMR (600
MHz, DMSO-d6) δ (ppm): 8.25 (s, 1H, H-2), 8.14 (d, J = 7.9 Hz, 1H, H-5), 7.85 (t, J = 7.9 Hz, 1H,
H-6), 7.70 (d, J = 8.1 Hz, 1H, H-8), 7.56 (t, J = 8.1 Hz, 1H, H-7), 4.95 (s, 2H, H-1’), 3.68 (s, 2H, H-
5’a), 3.59 (d, J = 3.8 Hz, 4H, H-4’a, H-5’), 3.46 (s, 2H, H-4’). 13C NMR (151 MHz, DMSO-d6) δ
(ppm): 165.70 (C-2’), 160.63 (C-4), 148.98 (C-8a), 148.51 (C-2), 134.92 (C-7), 127.68 (C-6),
127.57 (C-5), 126.50 (C-8), 121.92 (C-4a), 66.46 (C-5’a), 66.41 (C-5’), 46.99 (C-1’), 45.20 (C-
4’a), 42.51 (C-4’). Purity: 98%. HRMS-ESI m/z [M+H]+ 274.1177 (calc. for C14H15N3O3 :
+
274.1186).
3-{2-Oxo-2-[4-(pyridin-2-yl)piperazin-1-yl]ethyl}quinazolin-4(3H)-one 2b
The reaction of 1a (4-(3H)quinazolinone) (0.79 g, 5.38 mmol) with 2-chloro-1-[4-(pyridin-2-
yl)piperazin-1-yl]ethanone (1.55 g, 6.45 mmol) gave 2b as a yellowish white powder (0.82 g,
mmol, 2.35 mmol, 44%). m.p. 194.5 °C. IR (ATR)°ѵmax/cm-1: 1671 (C=O), 1650 (C=O), 1608
1
(C=N), 1471 (C−N), 1236 (C−N). H NMR (600 MHz, DMSO-d6) δ (ppm): 8.27 (s, 1H, H-2), 8.15
(d, J = 6.5 Hz, 2H, H-9’, H-5), 7.85 (t, J = 8.1 Hz, 1H, H-7), 7.71 (d, J = 8.1 Hz, 1H, H-8), 7.57 (dd,
J = 13.5, 6.5 Hz, 2H, H-11’, H-6), 6.88 (d, J = 8.5 Hz, 1H, H-12’), 6.69 (t, J = 5.9 Hz, 1H, H-10’),
5.01 (s, 2H, H-1’), 3.68 (dd, J = 24.3, 3.8 Hz, 4H, H-5’, H-5’a), 3.56 (dd, J = 34.0, 3.8 Hz, 4H, H-
4’, H-4’a). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 165.69 (C-2’), 160.64 (C-4), 159.13 (C-7’),
149.01 (C-8a), 148.52 (C-2), 148.06 (C-9’), 138.15 (C-11’), 134.92 (C-7), 127.69 (C-6), 127.57
(C-8), 126.51 (C-5), 121.94 (C-4a), 113.86 (C-10’), 107.80 (C-12’), 47.13 (C-1’), 44.99 (C-4’),
44.78 (C-4’a), 44.34 (C-5’), 41.84 (C-5’a). Purity: 97%. HRMS-ESI m/z [M+H]+ 350.1617 (calc. for
+
C19H19N5O2 : 350.1612).
3-[2-(4-Acetylpiperazin-1-yl)-2-oxoethyl]quinazolin-4(3H)-one 2c
The reaction 1a (4-(3H)quinazolinone) (0.67 g, 4.55 mmol) with 1-(4-acetylpiperazin-1-yl)-2-
chloroethanone (1.12 g, 5.46 mmol) afforded 2c as a light brown powder (0.07 g, 0.23 mmol,
5%). m.p.: 185.2 °C. IR (ATR)°ѵmax/cm-1: 1648 (C=O), 1629 (C=O), 1608 (C=N), 1242 (C−N),
1
1223 (C−N). H NMR (600 MHz, DMSO-d6) δ (ppm): 8.25 (s, 1H, H-2), 8.14 (d, J = 7.9 Hz, 1H,
H-5), 7.85 (t, J = 8.1 Hz, 1H, H-7), 7.70 (d, J = 8.1 Hz, 1H, H-8), 7.56 (t, J = 7.9 Hz, 1H, H-6), 4.98
(d, J = 3.3 Hz, 2H, H-1’), 3.54 (dd, J = 67.4, 36.0 Hz, 8H, H-4’, H-4’a, H-5’, H-5’a), 2.05 (d, J =
17.1 Hz, 3H, H-8’). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 169.05 (C-7’), 165.72 (C-2’), 160.63
(C-4), 148.96 (C-8a), 148.51 (C-2), 134.93 (C-7), 127.69 (C-6), 127.58 (C-8), 126.50 (C-5),
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121.92 (C-4a), 47.10 (C-1’), 45.97-39.58 (C-4’, C-4’a, C-5’, C-5’a), 21.79-21.68 (C-8’). Purity:
99%. HRMS-ESI m/z [M+H]+ 315.1464 (calc. for C16H18N4O3 : 315.1452).
+
3-[2-Oxo-2-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)ethyl]quinazolin-4(3H)-one 2d
The reaction of 1a (4-(3H)quinazolinone) (0.65 g, 4.42 mmol) with 2-chloro-1-(1,4-dioxa-8-
azaspiro[4.5]decan-8-yl)ethanone (1.17 g, 5.3 mmol) produced 2d as grey-brown crystals (0.67 g,
2.03 mmol, 46%). m.p.: 279.8 °C. IR (ATR)°ѵmax/cm-1: 1672 (C=O), 1639 (C=O), 1606 (C=N),
1
1094 (C−O). H NMR (600 MHz, DMSO-d6) δ (ppm): 8.26 (s, 1H, H-2), 8.14 (d, J = 7.9 Hz, 1H,
H-5), 7.85 (t, J = 7.9 Hz, 1H, H-6), 7.70 (d, J = 8.1 Hz, 1H, H-8), 7.56 (t, J = 8.1 Hz, 1H, H-7), 4.97
(s, 2H, H-1’), 3.93 (s, 4H, H-8’, H-8’a), 3.60 (s, 2H, H-4’a), 3.53 (s, 2H, H-4’), 1.72 (d, J = 51.5 Hz,
2H, H-5’a), 1.59 (d, J = 5.0 Hz, 2H, H-5’). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 165.29 (C-2’),
160.63 (C-4), 149.05 (C-8a), 148.53 (C-2), 134.89 (C-7), 127.67 (C-6), 127.53 (C-8), 126.49 (C-
5), 121.94 (C-4a), 106.70 (C-6’), 64.37 (C-8’, C-8’a), 53.73 (C-1’), 47.04 (C-4’a), 42.94 (C-4’),
35.35 (C-5’a), 34.79 (C-5’). Purity 95%. HRMS-ESI m/z [M+H]+ 330.1427 (calc. for C17H19N3O4 :
+
330.1448).
3-(2-Oxo-2-thiomorpholinoethyl)quinazolin-4(3H)-one 2e
1a (4-(3H)quinazolinone) (0.61 g, 4.17 mmol) and 2-chloro-1-thiomorpholinoethanone (0.9 g, 5.0
mmol) provided 2e as a cream-white powder (0.63 g, 2.17 mmol, 52%). m.p.: 194.2 °C. IR
1
(ATR)°ѵmax/cm-1: 1670 (C=O), 1648 (C=O), 1608 (C=N), 1170 (C−N). H NMR (600 MHz, DMSO-
d6) δ (ppm): 8.26 (s, 1H, H-2), 8.14 (d, J = 7.5 Hz, 1H, H-5), 7.85 (t, J = 7.5 Hz, 1H, H-6), 7.70 (d,
J = 8.1 Hz, 1H, H-7), 7.56 (t, J = 8.1 Hz, 1H, H-8), 4.94 (s, 2H, H-1’), 3.83 (s, 2H, H-4’a), 3.73 (s,
2H, H-4’), 2.75 (s, 2H, H-5’a), 2.58 (s, 2H, H-5’). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 165.57
(C-2’), 160.63 (C-4), 149.02 (C-8a), 148.530 (C-2), 134.92 (C-7), 127.68 (C-6), 127.56 (C-8),
126.50 (C-5), 121.92 (C-4a), 47.68 (C-1’), 47.22 (C-4’a), 44.94 (C-4’), 27.33 (C-5’a), 26.86 (C-5’).
Purity: 93%. HRMS-ESI m/z [M+H]+ 290.0948 (calc. for C14H15N3O2S+: 290.0958).
3-[2-Oxo-2-(4-oxopiperidin-1-yl)ethyl]quinazolin-4(3H)-one 2f
The reaction of 1a (4-(3H)quinazolinone) (0.59 g, 4.05 mmol) with 1-(2-chloroacetyl)piperidin-4-
one (0.85 g, 4.86 mmol, 1.2 eq.) resulted in 2f as a cream-yellow powder (0.21 g, 0.73 mmol,
1
18%). m.p. 224.6 °C. IR (ATR)°ѵmax/cm-1: 1697 (C=O), 1662 (C=O), 1602 (C=N). H NMR (600
MHz, DMSO-d6) δ (ppm): 7.98 (s, 1H, H-2), 7.88 (d, J = 7.8 Hz, 1H, H-5), 7.72 (t, J = 8.5 Hz, 1H,
H-7), 7.51 (t, J = 7.8 Hz, 1H, H-6), 7.26 (d, J = 8.5 Hz, 1H, H-8), 5.17 (s, 2H, H-1’), 3.93 (s, 4H, H-
4’, H-4’a), 3.55 (d, J = 20.9 Hz, 4H, H-5’, H-5’a). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 164.55
(C-6’), 152.49 (C-2’), 136.28 (C-4), 133.60 (C-8a), 127.12 (C-2), 124.63 (C-7), 123.08 (C-6),
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117.13 (C-5), 106.70 (C-8), 64.37 (C-1’), 51.12 (C-4’a), 42.92 (C-4’), 35.18 (C-5’a), 34.71 (C-5’).
Purity: 95%. HRMS-ESI m/z [M+H]+ 286.1217 (calc. for C15H15N3O3 : 286.1186).
+
3-{2-Oxo-2-[4-(tetrahydrofuran-2-carbonyl)piperazin-1-yl]ethyl}quinazolin-4(3H)-one 2g
The reaction of 1a (4-(3H)quinazolinone) (0.8 g, 5.47 mmol), 2-chloro-1-[4-(tetrahydrofuran-2-
carbonyl)piperazin-1-yl]ethanone (1.71 g, 6.564 mmol) and TEA (instead of K2CO3) (1.14 mL,
8.71 mmol) afforded 2g as a yellowish power (0.76 g, 2.08 mmol, 38%). m.p. 203.3 °C. IR
1
(ATR)°ѵmax/cm-1: 1676 (C=O), 1649 (C=O), 1607 (C=N), 1244 (C−N), 1019 (C−O). H NMR (600
MHz, DMSO-d6) δ (ppm): 8.24 (s, 1H, H-2), 8.14 (d, J = 7.8 Hz, 1H, H-5), 7.85 (t, J = 7.8 Hz, 1H,
H-6), 7.70 (d, J = 8.1 Hz, 1H, H-8), 7.56 (t, J = 8.1 Hz, 1H, H-7), 4.97 (d, J = 10.2 Hz, 2H, H-1’),
4.76 – 4.65 (m, 1H, H-8’), 3.80 – 3.73 (m, 2H, H-10’), 3.64 – 3.49 (m, 6H, H-4’, H-4’a, H-5’a), 3.46
(d, J = 34.6 Hz, 2H, H-5’), 2.04 – 1.77 (m, 4H, H-11’, H-12’). 13C NMR (151 MHz, DMSO-d6) δ
170.15 (C-7’), 165.75 (C-2’), 160.63 (C-4), 148.96 (C-8a), 148.51 (C-2), 134.93 (C-7), 127.69 (C-
6), 127.58 (C-8), 126.51 (C-5), 121.92 (C-4a), 75.38 (C-8’), 68.71 (C-10’), 47.10 (C-1’) 45.17-
41.57 (C-4’, C-4’a, C-5’, C-5’a), 28.34 (C-12’), 25.69 (C-11’). Purity: 82%. HRMS-ESI m/z [M+H]+
+
371.1710 (calc. for C19H22N4O4 : 371.1714).
2-(1,1-Dioxido-2H-benzo[e][1,2,4]thiadiazin-2-yl)-1-morpholinoethanone 3a
The reaction of 1b (2H-Benzo[e][1,2,4]thiadiazine 1,1-dioxide) (0.7 g, 3.84 mmol) with 2-chloro-1-
morpholinoethanone (0.75 g, 4.61 mmol) afforded 3a as a brownish powder (0.58 g, 1.88 mmol,
49%). m.p. 264.4 °C. IR (ATR)°ѵmax/cm-1: 1660 (C=O), 1615 (C=N), 1467 (S=O), 1278 (C−N),
1
1166 (C−O). H NMR (600 MHz, DMSO-d6) δ (ppm): 7.98 (s, 1H, H-2), 7.89 (d, J = 7.9 Hz, 1H,
H-5), 7.73 (t, J = 7.9 Hz, 1H, H-6), 7.52 (t, J = 8.6 Hz, 1H, H-7), 7.28 (d, J = 8.6 Hz, 1H, H-8), 5.17
(s, 2H, H-1’), 3.71 (s, 2H, H-5’a), 3.60 (s, 2H, H-5’), 3.55 (s, 2H, H-4’a), 3.45 (s, 2H, H-4). 13C
NMR (151 MHz, DMSO-d6) δ (ppm): 165.02 (C-2’), 152.44 (C-2), 136.25 (C-8a), 133.61 (C-7),
127.17 (C-4a), 124.66 (C-5), 123.10 (C-6), 117.10 (C-8), 66.43 (C-5’a), 66.32 (C-5’), 45.96 (C-
4’a), 45.20 (C-4’), 42.53 (C-1’). Purity: 91%. HRMS-ESI m/z [M+H]+ 310.0851 (calc. for
C13H15N3O4S+: 310.0856).
2-(1,1-Dioxido-2H-benzo[e][1,2,4]thiadiazin-2-yl)-1-[4-(pyridin-2-yl)piperazin-1-yl]ethenone 3b
1b (2H-Benzo[e][1,2,4]thiadiazine 1,1-dioxide) (0.7 g, 3.84 mmol) and 2-chloro-1-[4-(pyridin-2-
yl)piperazin-1-yl]ethanone (0.94 g, 4.61 mmol) afforded 3b as a brownish powder (0.15 g,
0.38 mmol, 10%). m.p. 264.4 °C. IR (ATR)°ѵmax/cm-1: 1655 (C=O), 1591 (C=N), 1474 (S=O),
1
1233 (C−N), 1148 (C−N). H NMR (600 MHz, DMSO-d6) δ (ppm): 8.15 (d, J = 4.6 Hz, 1H, H-9’),
7.99 (s, 1H, H-2), 7.89 (d, J = 7.9 Hz, 1H, H-5), 7.72 (t, J = 7.9 Hz, 1H, H-6), 7.58 (t, J = 7.8 Hz,
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1H, H-11’), 7.52 (t, J = 8.6 Hz, 1H, H-7), 7.29 (d, J = 8.6 Hz, 1H, H-8), 6.89 (d, J = 8.5 Hz, 1H, H-
12’), 6.69 (t, J = 5.8 Hz, 1H, H-10’), 5.22 (s, 2H, H-1’), 3.68 (d, J = 12.8 Hz, 4H, H-5’, H-5’a), 3.56
(d, J = 13.5 Hz, 4H, H-4’, H-4’a). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 165.02 (C-2’), 159.12
(C-7’), 152.46 (C-9’), 148.08 (C-2), 138.17 (C-8a), 136.27 (C-11’), 133.62 (C-7), 127.17 (C-4a),
124.66 (C-5), 123.11 (C-6), 117.15 (C-8), 113.86 (C-10’), 107.82 (C-12’), 51.18 (C-1’), 44.86 (C-
4’a), 44.77 (C-4’), 44.29 (C-5’a), 41.82 (C-5’). Purity: 92%. HRMS-ESI m/z [M+H]+ 386.1252
(calc. for C18H19N5O3S+: 386.1281).
1-(4-Acetylpiperazin-1-yl)-2-(1,1-dioxido-2H-benzo[e][1,2,4]thiadiazin-2-yl)ethanone 3c
1b (2H-Benzo[e][1,2,4]thiadiazine 1,1-dioxide) (0.7 g, 3.84 mmol) and 1-(4-acetylpiperazin-1-yl)-
2-chloroethanone (0.94 g, 4.61 mmol) afforded 3c as a cream-white powder (0.65 g, 1.84 mmol,
48%), m.p. 248.8 °C. IR (ATR)°ѵmax/cm-1: 1662 (C=O), 1629 (C=O), 1618 (C=N), 1481 (S=O),
1
1145 (C−N). H NMR (600 MHz, DMSO-d6) δ (ppm): 7.97 (s, 1H, H-2), 7.89 (d, J = 7.9 Hz, 1H,
H-5), 7.72 (t, J = 7.9 Hz, 1H, H-6), 7.52 (t, J = 8.6 Hz, 1H, H-7), 7.28 (d, J = 8.6 Hz, 1H, H-8), 5.19
(s, 2H, H-1’), 3.63 – 3.43 (m, 8H, H-4’, H-4’a, H-5’, H-5’a), 2.06 (d, J = 19.7 Hz, 3H, H-8’). 13C
NMR (151 MHz, DMSO-d6) δ (ppm): 169.07 (C-7’), 165.03 (C-2’), 152.43 (C-2), 136.25 (C-8a),
133.60 (C-7), 127.18 (C-4a), 124.67 (C-5), 123.10 (C-6), 117.14 (C-8), 51.14 (C-1’), 45.81-40.94
(C-4’, C-4’a, C-5’, C-5’a), 21.81-21.68 (C-8’). Purity: 95%. HRMS-ESI m/z [M+H]+ 351.1119
(calc. for C15H18N4O4S+: 351.1122).
2-(1,1-Dioxido-2H-benzo[e][1,2,4]thiadiazin-2-yl)-1-(4-methylpiperazin-1-yl)ethanone 3d
The reaction of 1b (2H-Benzo[e][1,2,4]thiadiazine 1,1-dioxide) (0.7 g, 3.84 mmol) with 2-chloro-1-
(4-methylpiperazin-1-yl)ethanone (0.81 g, 4.61 mmol) afforded 3d as a grey-white powder (0.31
g, 0.96 mmol, 25%). m.p. 204.5 °C. IR (ATR)°ѵmax/cm-1: 1662 (C=O), 1476 (S=O), 1277 (C−N).
1H NMR (600 MHz, DMSO-d6) δ (ppm): 8.25 (s, 1H, H-2), 8.14 (d, J = 7.9 Hz, 1H, H-5), 7.85 (t, J
= 7.9 Hz, 1H, H-6), 7.70 (d, J = 8.1 Hz, 1H, H-8), 7.56 (t, J = 8.1 Hz, 1H, H-7), 4.98 (d, J = 3.4 Hz,
2H, H-1’), 3.62 (s, 1H, H-4’a), 3.57 (s, 3H, H-4’), 3.52 (s, 1H, H-5’a), 3.45 (s, 3H, H-5’), 2.05 (d, J
= 17.1 Hz, 3H, H-7’). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 165.72 (C-2’), 148.96 (C-2),
148.51 (C-8a), 134.94 (C-7), 127.69 (C-4a), 127.58 (C-5), 126.50 (C-6), 121.92 (C-8), 47.12 (C-
7’), 47.10 (C-1’), 45.98-44.46 (C-5’a, C-5’), 42.29-40.94 (C-4’, C-4’a). Purity: 98%.
2.3.4. Bisquinazolinones
2.3.4.1. Bisquinazolinone alcohols 4a-f
1a-f (4-(3H)quinazolinone) (1eq.) and base (NaOH or K2CO3) (1.5 eq.) were dissolved in MeOH
or DMF (10-40 mL) upon stirring at room temperature. Alcohol (0.9-1.1 eq.) was added to the
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quinazolinone solution, and the resulting mixture was stirred for 24 h at room temperature.
Afterwards, the solvent was evaporated under vacuum and the residue was recrystallized to
afford the target bisquinazolinone alcohol 4a-f.
3,3'-(2-Hydroxypropane-1,3-diyl)bis(quinazolin-4(3H)-one) 4a
The reaction of 1a (4-(3H)quinazolinone) (3.6 g, 24.64 mmol), NaOH (1.5 g, 37.5 mmol, 1.5 eq.)
and 1,3-dichloropropan-2-ol (2.25 mL, 25.87 mmol, 1.05 eq.) followed by recrystallization in
H2O:EtOH (9:1, v/v) afforded 4a as cream-white crystals (1.11 g, 3.2 mmol, 13%). m.p. 342.7 °C.
1
IR (ATR)°ѵmax/cm-1: 3408 (O−H), 1647 (C=O), 1601 (C=O), 1106 (C−N). H NMR (600 MHz,
DMSO-d6) δ (ppm): 8.26 (s, 2H, H-2), 8.16 (d, J = 8.0 Hz, 2H, H-5), 7.85 – 7.80 (m, 2H, H-6), 7.67
(d, J = 8.1 Hz, 2H, H-8), 7.55 (t, J = 8.1 Hz, 2H, H-7), 5.59 (d, J = 5.9 Hz, 1H, H-2’), 4.29 (dd, J =
13.6, 3.4 Hz, 2H, H-1’), 4.20 – 4.14 (m, 1H, H-4’), 3.82 (dd, J = 13.6, 8.5 Hz, 2H, H-3’). 13C NMR
(151 MHz, DMSO-d6) δ (ppm): 160.58 (C-4), 148.73 (C-2), 148.04 (C-8a), 134.47 (C-7), 127.22
(C-6), 127.11 (C-8), 126.18 (C-5), 121.65 (C-4a), 65.90 (C-2’), 49.77 (C-1’, C-3’). Purity: 99%.
+
HRMS-ESI m/z [M+H]+ 349.1299 (calc. for C19H16N4O3 : 349.1301).
3,3'-(2-Hydroxypropane-1,3-diyl)bis(7-chloroquinazolin-4(3H)-one) 4b
The reaction of 1c (7-chloroquinazolin-4(3H)-one) (1 g, 5.54 mmol), K2CO3 (1.15 g, 8.31 mmol,
1.5 eq.) and 1,3-dichloropropan-2-ol (0.53 mL, 6.1 mmol, 1.1 eq.) in DMF (10 mL) followed by
precipitation in H2O provided 4b as a cream-white powder (0.68 g, 1.61 mmol, 29%), m.p.
234.7°C. IR (ATR)°ѵmax/cm-1: 3453 (O−H), 1649 (C=O), 1598 (C=O), 1552 (C=N), 1135 (C−N).
1H NMR (600 MHz, DMSO-d6) δ (ppm): 8.30 (s, 2H, H-2), 8.13 (d, J = 8.6 Hz, 2H, H-5), 7.72 (s,
2H, H-8), 7.57 (d, J = 8.6 Hz, 2H, H-6), 5.69 (d, J = 5.8 Hz, 1H, H-2’), 4.27 (dd, J = 13.5, 2.5 Hz,
2H, H-1’), 4.14 (s, 1H, H-4’), 3.83 (dd, J = 13.5, 8.6 Hz, 2H, H-3’). 13C NMR (151 MHz, DMSO-d6)
δ (ppm): 160.03 (C-4), 150.11 (C-8a), 149.05 (C-2), 139.13 (C-7), 128.32 (C-5), 127.43 (C-6),
126.30 (C-8), 120.41 (C-4a), 65.68 (C-2’), 49.74 (C-1’, C-3’). Purity: 99%. HRMS-ESI m/z
+
[M+H]+ 417.0497 (calc. for C19H14Cl2N4O3 : 417.0521).
3,3'-(2-Hydroxypropane-1,3-diyl)bis(6,7-dimethoxyquinazolin-4(3H)-one) 4c
The reaction of 1d (6,7-dimethoxyquinazolin-4(3H)-one) (0.8 g, 3.88 mmol), K2CO3 (0.85 g, 5.82
mmol, 1.5 eq.) and 1,3-dichloropropa-2-ol (0.37 mL, 4.27 mmol, 1.1 eq.) in DMF (10 mL) followed
by recrystallization in EtOH provided 4c as a yellow-brown powder (0.64 g, 1.36 mmol, 35%).
m.p. 310.4 °C. IR (ATR)°ѵmax/cm-1: 3425 (O−H), 1664 (C=O), 1608 (C=N), 1498 (C−O), 1282
1
(C−N). H NMR (600 MHz, DMSO-d6) δ (ppm): 8.18 (s, 2H, H-2), 7.45 (s, 2H, H-5), 7.13 (s, 2H,
H-8), 5.59 (d, J = 6.1 Hz, 1H, H-2’), 4.26 (dd, J = 13.5, 3.6 Hz, 2H, H-1’), 4.12 (s, 1H, H-4’), 3.90
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(s, 6H, H-9), 3.87 (s, 6H, H-10), 3.81 (dd, J = 13.5, 8.2 Hz, 2H, H-3’). 13C NMR (151 MHz,
DMSO-d6) δ (ppm): 159.51 (C-4), 154.32 (C-7), 148.52 (C-2), 147.01 (C-6), 143.99 (C-8a),
114.46 (C-4a), 107.68 (C-8), 104.94 (C-5), 65.97 (C-2’), 55.83 (C-9), 55.58 (C-10), 49.37 (C-1’,
C-3’). Purity: 96%. HRMS-ESI m/z [M+H]+ 469.1738 (calc. for C23H24N4O7 : 469.1723).
+
3,3'-(2-Hydroxypropane-1,3-diyl)bis(7-chloroquinazolin-4(3H)-one) 4d
The reaction of 1e (2-methylquinazolin-4(3H)-one) (1.0 g, 6.24 mmol), K2CO3 (1.5 g, 10.85 mmol,
1.74 eq.) and 1,3-dichloropropa-2-ol (0.5 mL, 5.75 mmol, 0.92 eq.) in DMF (10 mL) followed by
recrystallization in EtOAc presented 4d as off white beads (0.21 g, 0.56 mmol, 9%). m.p. 194.3
1
°C. IR (ATR)°ѵmax/cm-1: 3287 (O−H), 1712 (C=O), 1677 (C=O), 1646 (C=N). H NMR (600 MHz,
DMSO-d6) δ (ppm): 8.08 (dd, J = 8.5, 1.3 Hz, 2H, H-5), 7.76 (ddd, J = 8.5, 7.2, 1.5 Hz, 2H, H-6),
7.56 (d, J = 8.1 Hz, 2H, H-8), 7.48 – 7.44 (m, 2H, H-7), 4.29 - 4.25 (m, 2H, H-2’, H-4’), 3.88 (dt, J
= 6.8, 5.9 Hz, 4H, H-1’, H-3’), 2.64 (s, 6H, H-9). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 161.91
(C-4), 156.65 (C-2), 147.45 (C-8a), 134.59 (C-7), 126.67 (C-6), 126.47 (C-8), 126.44 (C-5),
120.40 (C-4a), 69.34-64.54 (C-2’), 48.06 (C-1’, C-3’), 23.85 (C-9). Purity: 98%. HRMS-ESI m/z
+
[M+H]+ 377.1642 (calc. for C21H20N4O3 : 377.1614).
3,3'-(2-Hydroxypropane-1,3-diyl)bis(2-ethylquinazolin-4(3H)-one) 4e
The reaction of 1f (2-ethylquinazolin-4(3H)-one) (1.0 mg, 5.74 mmol), K2CO3 (1.5 g, 10.85 mmol,
1.89 eq.) and 1,3-dichloropropa-2-ol (0.5 mL, 5.75 mmol, 1.0 eq.) in DMF (10 mL) and
subsequent recrystallization in EtOAc afforded 4e as a white powder (0.38 g, 0.92 mmol, 16%).
m.p. 179.1°C. IR (ATR)°ѵmax/cm-1: 3332 (O−H), 1649 (C=O), 1608 (C=O), 1584 (C=N), 1120
1
(C−N). H NMR (600 MHz, DMSO-d6) δ (ppm): 8.10 (dd, J = 7.9, 1.4 Hz, 2H, H-5), 7.79 – 7.76
(m, 2H, H-6), 7.60 (d, J = 8.2 Hz, 2H, H-8), 7.49 – 7.45 (m, 2H, H-7), 4.29 (d, J = 3.4 Hz, 1H, H-
2’), 4.27 (d, J = 3.4 Hz, 1H, H-4’), 3.92 (dd, J = 13.8, 9.1 Hz, 4H, H-1’, H-3’), 3.86 (ddd, J = 14.2,
5.1, 3.5 Hz, 4H, H-9), 1.26 (t, J = 7.3 Hz, 6H, H-10). 13C NMR (151 MHz, DMSO-d6) δ (ppm):
161.50 (C-4), 159.13 (C-2), 146.75 (C-8a), 134.02 (C-7), 126.37 (C-6), 125.96 (C-8), 125.90 (C-
5), 119.79 (C-4a), 68.82-63.98 (C-2’), 46.45 (C-1’, C-3’), 27.47 (C-9), 10.75 (C-10). Purity: 92%.
+
HRMS-ESI m/z [M+H]+ 405.1960 (calc. for C23H24N4O3 : 405.1927).
2,2'-(2-Hydroxypropane-1,3-diyl)bis(2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide) 4f
The reaction of 1b (10 g, 54.88 mmol), NaOH (3.3 g, 82.5 mmol, 1.5 eq.) and 1,3-dichloropropan-
2-ol (2.5 mL, 28.9 mmol, 1.05 eq.) followed by recrystallization in EtOH afforded 4f as a fine white
powder (6.07 g, 14.27 mmol, 26%). m.p. 319.5 °C. IR (ATR)°ѵmax/cm-1: 3428 (O−H), 1613 (C=O),
1593 (C=N), 1468 (S=O), 1413 (S=O), 1163 (C−N), 1141 (C−N). 1H NMR (600 MHz, DMSO-d6) δ
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(ppm): 7.98 (s, 2H, H-2), 7.89 (s, 2H, H-5), 7.78 (s, 4H, H-6-8), 7.54 (s, 2H, H-7), 5.96 (s, 1H, H-
2’), 4.52 (d, J = 14.0 Hz, 2H, H-1’), 4.02 (s, 1H, H-4’), 3.97 (d, J = 11.9 Hz, 2H, H-3’). 13C NMR
(151 MHz, DMSO) δ (ppm): 151.58 (C-2), 135.22 (C-8a), 133.33 (C-7), 126.99 (C-4a), 124.68 (C-
5), 123.12 (C-6), 116.64 (C-8), 64.39 (C-2’), 52.78 (C-1’-3’). Purity: 93%. HRMS-ESI m/z [M+H]+
+
421.0648 (calc. for C17H16N4O5S2 : 421.0640).
2.3.4.2. Bisquinazolinone ketones 5a-c
A solution of bisquinazolinone alcohol 4a,b,f (1 eq.) and acetic anhydride (21 eq.) in DMSO (4
mL) was stirred for 24 h at room temperature. Afterwards, the solution was diluted with EtOH (10
mL), and the resulting precipitate was filtered off and recrystallized in EtOH or H2O to afford the
target bisquinazolinone ketone 5a-c
3,3'-(2-Oxopropane-1,3-diyl)bis(quinazolin-4(3H)-one) 5a
The of 4a [3,3'-(2-hydroxypropane-1,3-diyl)bis(quinazolin-4(3H)-one)] (0.5 g, 1.44 mmol) with
acetic anhydride (2.85 mL, 30.32 mmol, 21 eq.) followed by recrystallization in EtOAc afforded 5a
as grey-white flakes (0.23 g, 47%). m.p. 340.7 °C. IR (ATR)°ѵmax/cm 1: 1663 (C=O), 1605 (C=O),
1
1560 (C=N), 1236 (C−N), 1220 (C−N). H NMR (600 MHz, DMSO-d6) δ (ppm): 8.28 (s, 1H, H-2),
8.17 (dd, J = 8.0, 1.1 Hz, 1H, H-5), 7.85 – 7.81 (m, 1H, H-6), 7.68 (d, J = 7.5 Hz, 1H, H-8), 7.55 (t,
J = 7.5 Hz, 1H, H-7), 4.30 (dd, J = 13.6, 3.5 Hz, 1H, H-1’), 3.84 (dd, J = 13.6, 8.4 Hz, 1H, H-3’).
13C NMR (151 MHz, DMSO-d6) δ (ppm): 160.39 (C-4), 148.60 (C-8a), 147.97 (C-2), 134.26 (C-7),
127.11 (C-6), 126.90 (C-8), 126.04 (C-5), 121.56 (C-4a), 65.78 (C-2’), 49.62 (C-1’, C-3’). Purity:
+
90%. HRMS-ESI m/z [M+H]+ 347.1133 (calc. for C19H14N4O3 : 347.1144).
3,3'-(2-Oxopropane-1,3-diyl)bis(7-chloroquinazolin-4(3H)-one) 5b
The reaction of 4b [3,3'-(2-hydroxypropane-1,3-diyl)bis(7-chloroquinazolin-4(3H)-one)] (0.52 g,
1.23 mmol) with acetic anhydride (2.45 mL, 25.9 mmol, 21 eq.) followed by recrystallization in
H2O afforded 5b as brown flakes (0.05 g, 0.12 mmol, 10%). m.p. 226.8 °C. IR (ATR)°ѵmax/cm-1:
1667 (C=O), 1602 (C=O). 1H NMR (600 MHz, DMSO-d6) δ (ppm): 8.35 (d, J = 15.4 Hz, 2H, H-2),
8.16 (s, 2H, H-5), 7.76 (s, 2H, H-8), 7.60 (s, 2H, H-6), 4.31 (d, J = 34.4 Hz, 2H, H-1’), 4.06 (s, 2H,
H-3’). 13C NMR (151 MHz, DMSO-d6) δ (ppm): 159.80 (C-2’a), 149.66 (C-8a), 148.85 (C-2),
138.85 (C-7), 128.09 (C-5), 127.21 (C-6), 126.17 (C-8), 120.20 (C-4a), 47.14 (C-1’), 46.53 (C-3’).
+
Purity: 83%. HRMS-ESI m/z [M+H]+ 415.0390 (calc. for C19H12Cl2N4O3 : 415.0365).
1,3-Bis(1,1-dioxido-2H-benzo[e][1,2,4]thiadiazin-2-yl)propan-2-one 5c
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The reaction of 4f [2,2'-(2-hydroxypropane-1,3-diyl)bis(2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide]
(0.5 g, 1.19 mmol) with acetic anhydride (2.36 mL, 25 mmol, 21 eq.) followed by recrystallization
in EtOAc afforded 5c as cream-white flakes (0.3 g, 0.71 mmol, 60%). m.p. 321.1 °C. IR
1
(ATR)°ѵmax/cm-1: 1611 (C=O), 1590 (C=N), 1470 (S=O), 1166 (C−N). H NMR (600 MHz, DMSO-
d6) δ (ppm): 8.06 (s, 2H, H-2), 7.87 (d, J = 7.9 Hz, 2H, H-5), 7.83 (d, J = 3.0 Hz, 4H, H-6, H-8),
7.56 (dd, J = 8.1, 3.0 Hz, 2H, H-7), 4.69 (d, J = 13.5 Hz, 2H, H-1’), 4.37 – 4.32 (m, 2H, H-3’). 13C
NMR (151 MHz, DMSO-d6) δ (ppm): 169.05 (C-2’), 151.37 (C-2), 134.86 (C-8a), 133.22 (C-7),
127.07 (C-4a), 124.44 (C-5), 122.85 (C-6), 116.38 (C-8), 66.88, 49.83 (C-1’, C-3’), 19.75. Purity:
90%. HRMS-ESI m/z [M+H]+ 419.0489 (calc. for C17H14N4O5S2 : 419.0484).
+
2.4.
In vitro biological assays
2.4.1. Antileishamanial assay
The anti-promastigote activities of the synthesized compounds were evaluated, using the
resazurin assay, also known as the AlamarBlue® assay, on three Leishmania strains. The assay
involves the irreversible enzymatic reduction of oxidized blue resazurin dye into a pink, highly
fluorescent resorufin, by viable cells (Czekanska, 2011). This non-toxic reagent serves as an
effective tool for assessing cell proliferation and drug toxicity.
L. donovani (strains 1S (MHOM/SD/62/1S) and 9515 (MHOM/IN/95/9515)) and L. major (strain
IR-173 (MHOM/IR/-173)) promastigotes were cultured in M199 with Hank’s salts and 0.68 mM L-
glutamine (Sigma Aldrich), supplemented with 4.2 mM sodium bicarbonate, 25 mM Hepes, 10%
fetal bovine serum and 50 U/mL penicillin/streptomycin solution, and the pH adjusted to 7.3 - 7.4.
The promastigotes were maintained at 26 °C. For the resazurin assay, logarithmic phase
promastigotes (1.25 × 105 cells/mL, final volume 100 μL/well) were seeded in 96-well plates
(Nunc, Thermofisher Scientific) in the presence of (i) 10 μM of compound for activity screening, or
(ii) twelve x two-fold dilution concentrations of compounds for minimum inhibitory concentration
(IC50) determinations. Amphotericin B (10 μM) served as the standard drug, while growth
medium without any parasites served as the blank. The plates were incubated for 72 h at 26 oC
in a humidified atmosphere. After incubation, 50 μL of resazurin solution (0.01% in phosphor
buffered saline (PBS, Sigma-Aldrich)) was added to each well and the plates further incubated at
26 oC in the dark for 2 h (1S promastigotes) to 4 h (9515 and IR-173 promastigotes).
Absorbances were measured at 570 nm and 600 nm, using the Thermofisher Scientific GO
Multiscan plate reader. Data analysis was performed for each biological replicate, using SkanIt
4.0 Research Edition software. The background absorbance of resazurin (600 nm) was
subtracted from the absorbance values of resorufin (570 nm). The mean absorbance, the
percentage growth inhibition and cell viability were determined by the following equations:
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Growth inhibition % = [(Δ Abs neg control – Δ Abs blank) - (Δ Abs sample – Δ Abs blank)] / (Δ
Abs neg control – Δ Abs blank) x 100
Cell viability % = (Δ Abs sample – Δ Abs blank) / (Δ Abs neg control – Δ Abs blank) x 100
The IC50 and Z-score were determined for each compound’s three biological replicates, using
GraphPad Prism 5. The mean IC50 of the biological replicates served as the final value of each
compound.
2.4.2. Cytotoxicity assay
The cytotoxicities of the synthesized compounds were evaluated, using the resazurin assay (Jain,
Sahu, Walker, & Tekwani, 2012). Vero (Cellonex, South Africa) cells were cultured in Hyclone
Dulbecco’s modified Eagle’s medium with high glucose (Separations), supplemented with 10%
fetal bovine serum (Thermofisher Scientific) and 1% L-glutamine, penicillin-streptomycin,
amphotericin B and non-essential amino acids (Lonza). The cells were maintained in a
humidified atmosphere at 37 °C and 5% CO2. For the resazurin assay, 96-well plates were
prepared with 200 μL of cell suspension (30,000 cells/mL) and incubated for 24 h. The cells were
then treated with: (i) 100 μL of emetine dihydrochloride (Sigma Aldrich) solution, diluted with
growth medium to the necessary concentrations (positive control); (ii) 80 μL of growth medium
and 20 μL of solvent (negative control to compensate for possible solvent effects); (iii) 80 μL of
growth medium and 20 μL of diluted experimental compound solutions. The blank controls
contained growth medium without cells. The treated plates were incubated for 48 h.
To initiate the resazurin assay, 50 μL of sterile-filtered resazurin sodium salt (Sigma Aldrich)
solution (0.01% in PBS) was added and the plates incubated for 2 h. Absorbances were
measured at 570 nm and 600 nm, using the Thermofisher Scientific GO Multiscan plate reader.
Data analysis was performed for each biological replicate, using SkanIt 4.0 Research Edition
software. The background absorbance (600 nm) was subtracted from the absorbance values
(570 nm), the mean absorbance calculated and the percentage cell viability was determined by
the following equation:
Cell viability % = (Δ Abs sample – Δ Abs blank) / (Δ Abs neg control – Δ Abs blank) x 100
The IC50 and Z-score were determined for each compound’s three biological replicates, using
GraphPad Prism 5. The mean IC50 of the biological replicates served as the final value with
standard error of the means (SEM) of each compound (Table 3).
3.
Results and discussion
Chemistry
3.1.
3.1.1. Febrifugine analogues
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A straightforward, three-step process was used to synthesize the target derivatives
(2a-f, 3a-d) (Table 1). Firstly, a condensation reaction was used for the synthesis of the 4-
(3H)quinazolinones (1a,c-f) and 2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide (1b). Intermediates
1a,c-f were produced from aminobenzoic acid derivatives (e.g. anthranilic acid, 2-amino-4-
chlorobenzoic acid, 2-amino-4,5-dimethoxybenzoic acid and 2-aminobenzamide) and formamide
(Juvale, Gallus, & Wiese, 2013), while the reaction of 2-aminobenzenesulfonamide and triethyl
orthoformate resulted in 1b (Scheme 1) (Bozdag et al., 2017). The 4-(3H)quinazolinone
intermediates were obtained in average yield (40-50%), whereas 1b (2H-
benzo[e][1,2,4]thiadiazine 1,1-dioxide), a thiazine derivative in which a sulfone group had
replaced the carbonyl at C-4 of the 4-(3H)quinazolinone, was isolated in good yield (81%).
Scheme 1
Table 1
The structure of each compound was confirmed through routine analytical techniques, such as
NMR, HRMS and IR spectra. The IR spectra of intermediates 1a,c-f and 1b showed a distinctive
N−H (amide) peak between 3198 – 2616 cm-1, and a medium C=N peak at 1610 − 1600 cm-1.
Additionally, 1a,c-f had a distinctive carbonyl (C=O) peak in the 1700 − 1650 cm-1 region,
1
whereas 1b displayed the strong bend of S=O stretching ca. 1400 cm-1. Furthermore, H NMR
confirmed the presence of 1a-f as characterized by three to five aromatic protons of the
quinazolinone/benzothiadiazine-1,1-dioxide ring, between 7.29 − 8.13 ppm, in addition to a
prominent singlet peak for H-2 (except for 1e and 1f) within this region, which was an indication of
the successful ring closure. Additionally, one proton downfield in the region of 12.5 – 12.0 ppm
was indicative of the presence of the acidic proton H-3. 13C NMR provided the correct number of
carbon peaks, with the distinctive C-2 peak between 150 – 145 ppm for both compounds. The
distinctive C-4 (C=O) peak in the region of 165 – 160 ppm was also present for 1a,c-f.
Intermediates 1a,b were subsequently used to synthesize compounds 2a-g and 3a-d,
respectively.
Secondly, the acylation of cycloamines with chloroacetyl chloride (Scheme 1) produced 2-
chloroacetylamide intermediates. Thirdly, the chloroacetylamides (without further purification)
were reacted with intermediates 1a and 1b through nucleophilic substitution (SN2) (Scheme 1)
(Lee et al., 2015) in the presence of the mineral base (K2CO3) to generate the quinazolinone
derivatives, 2a-g and 3a-d, as shown in Table 1.
Compounds 2a-g were obtained in poor (5%) to average (52%) yields. The below average yields
were ascribed to difficulties in the purification process, using silica gel chromatography, as some
of the compounds had been found sparingly soluble in common organic solvents, such
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dichloromethane, methanol, ethyl acetate, initially employed as mobile phases. IR spectra of
each of the 2a-g compound showed two strong and distinctive carbonyl (C=O) peaks between
1700 − 1600 cm-1, a medium C=N peak at 1610 − 1600 cm-1, while the broad N−H peak found
between 3198 – 2616 cm-1 in the spectra of 1a and 1b had disappeared from those of 2a-g.
IR spectroscopy performed on compounds 3a-d resulted in spectra presented with a distinctive
sulfone (S=O) peak between 1481 – 1467 cm-1, and the medium C=N peak at 1610 − 1600 cm-1,
while the broad N−H peak between 3255 – 3019 cm-1 had also disappeared. The lack of N−H
peaks was confirmative of the successful substitution reaction. 1H spectra supported the
structural findings, with the distinctive H-2 at 8.0 – 7.5 ppm, H-1’ at 5.0 – 4.5 ppm and the
acetylamide substituent peaks, H-4’, H-4’a, H-5 and H-5’a in the 4.0 − 2.5 ppm range, with the
lack of the N−H peak at 13 − 12 ppm for all compounds. The 13C NMR spectra further confirmed
the structures of the compounds by presenting the distinctive C-4 peak at 165 – 160 ppm for
compounds 2a-g, the C-2’ peak at 170 – 165 ppm and C-2 at 150 – 145 ppm for compounds 2a-
g and 3a-d. The structures were further confirmed by HRMS data, with the presence of the
expected molecular ions in the form of [M+H]+ fragments in the ESI spectra.
3.1.2. Bisquinazolinones
The alcohols 4a-f and ketones 5a-c (Table 2) were synthesized in two- and three-step processes,
respectively. The multi-step process of compounds 4a-f included a condensation and a
nucleophilic substitution (SN2) reaction. The first step in this process was the condensation of
anthranilic acid with formamide (Juvale et al., 2013) to yield unsubstituted 4-(3H)quinazolinone
1a, while the condensation of various substituted benzamides with formamide/triethoxymethane
(Bozdag et al., 2017), as depicted in Scheme 2, produced the substituted 4-(3H)quinazolinone
intermediates 1c-f.
The nucleophilic substitution (SN2) of 4-(3H)quinazolinone or 2H-
benzo[e][1,2,4]thiadiazine 1,1-dioxide derivatives at its N-3 position with 1,3-dichloropropan-2-ol
in DMF in the presence of potassium carbonate, resulted in the formation of secondary
bisquinazolinone alcohols, 4a-f (Scheme 2). The Albright-Goldman oxidation (Albright &
Goldman, 1965), in which DMSO/acetic anhydride serves as the oxidizing agent, was applied to
4a, 4b and 4f to generate the bisquinazolinone ketones, 5a-c.
Scheme 2
Table 2
Compounds 4a-f were isolated in poor yields of 9 – 35%. Ketones 5a-c were synthesized
through the oxidation of the secondary alcohols, 4a, 4b and 4f. Although, the synthesis of the
ketones was simple to perform, their purification by either recrystallization or column
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chromatography on silica gel proved to be tedious, due to their insolubility in commonly used
organic solvents, especially that of 5b (10% yield). IR Spectra (Supplementary Information) of
the bisquinazolinones commonly had no N−H stretching at 3300 − 3100 cm-1, which was
indicative of the disappearance of H-3 and hence of the successful SN2. Distinctive broad peaks
of O−H between 3450 − 3250 cm-1, and strong C=O peaks at 1700 − 1600 cm-1 were present for
the alcohols and ketone functional groups, respectively.
1H spectra accounted for all of the expected H protons, while the distinctive peaks of protons H-
1’, H-2’, H-3’, H-4’ and aromatic protons between 8.5 – 7.0 ppm were also confirmed. It should
be noted that the methylene protons, H-1’ and H-3’ on the α carbons in compounds 4a-f are not
equivalent, due to the chirality of C-2’. This resulted in a doublet of doublets (dd) for each of H-1’
and H-3’ protons. In compound 4d, H-2’ and H-4’ overlapped to form a multiplet. The 13C spectra
1
of 4d and 4e presented with two peaks for the chiral carbon (C-2’) in the 70 - 65 ppm region. H
spectra of the ketones accounted for the expected number of protons. However, residual traces
of precursor alcohol, as indicated by H-4’ proton peaks, were present in the spectra.
3.2.
Pharmacology
The synthesized compounds, including the intermediates, were screened for in vitro
antileishmanial activity and cytotoxicity. Halofuginone (HF) was used as reference drug.
Leishmania species have two developmental forms, i.e. the promastigotes and amastigotes.
Promastigotes are responsible for the infective stage (insect), while amastigotes account for the
clinical stage (mammalian host, human or animal). Since the amastigotes are liable for the clinical
manifestations of the disease, they are clinically relevant. In this study, the quinazolinone
derivatives were screened primarily against L. promastigotes of various strains, using
amphotericin B (AMB) as standard drug in a two-stage process, involving the determination of the
parasite growth inhibition percentage at a single concentration, followed by an activity
assessment through IC50 determination. The cytotoxicity profiles of the derivatives were
evaluated, using Vero cells with emetine (EM), known for its high toxicity, as a standard. The
biological results are presented in Table 3.
Table 3
All synthesized compounds were found to be non-toxic to the mammalian cells, with IC50 values
above 100 μM.
The literature suggests a 70% parasite growth inhibition threshold (at 100 μM) for antileishmanial
IC50 determinations (Siqueira-Neto et al., 2010). However, none of the synthesized compounds
had reached that threshold. Subsequently, in order to accommodate all derivatives, the threshold
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was lowered and arbitrarily set at 25% to allow for more derivatives qualifying for IC50
determinations.
Intermediates 1a and 1b had poor growth inhibition against all three strains. However, both
compounds showed a higher percentage growth inhibition against L. major, 32% and 27%,
respectively, with 1a being slightly more active (7 – 15%) against L. donovani parasites.
Similarly, all the febrifugine derivatives 2a-g showed higher growth inhibition (27 − 35%) against
L. major, compared to the L. donovani strains. The best performers were 2d and 2e, with 35%
and 32%, respectively despite poor inhibition (<15%) of the L. donovani parasite. It is noteworthy
that compounds with a distal electron withdrawing group (2a, 2d, 2e and 2f) on the quinazolinone
ring had better growth inhibition values (>28%). A comparison of quinazolinone (2a, 2b and 2c)
and thiadiazine 1,1-dioxide (3a, 3b and 3c) derivatives revealed that the sulfone containing
compounds had slightly higher growth inhibition (3 – 10%) against L. donovani parasites, but a
lower inhibitory effect against L. major (18 – 25%), compared to their carbonyl counterparts (23 –
28%).
Contrary, all bisquinazolinones (except 4c) had no inhibitory effect on the growth of L. major
promastigotes. Against donovani parasites, however, the hydroxyl-functionalized (4b and 4c)
and the carbonyl tethered 5b bisquinazolinones possessed better growth inhibition, especially
against the L. donovani 9515 strain (>20%). These were also the only bisquinazolinone
derivatives featuring an electron withdrawing group (EWG), namely chlorine (4b and 5b)
substituents in position C-6. This suggests the presence of an EWG on the quinazolinone ring as
an influential factor in producing biologically active quinazolinone derivatives. This finding is
supported by the reported high growth inhibition (100%) of halofuginone, which has two EWGs
(6-Cl and 7-Br), regardless of the species and strain being considered (Table 3). However, the
high toxicity of halofuginone, almost twice that of toxic emetine (IC50 0.03 vs. 0.05 μM) on Vero
cells, suggests that the excellent observed performance of halofuginone is not entirely intrinsic,
but may have basal toxicity as a contributor.
On contrary, a polar substituent on the quinazolinone moiety, as a means to increase solubility,
had seemed necessary for imparting a derivative with biological activity. This was supported by
the complete inactivity of compounds 4a, 4f, 5a and 5c, all devoid of polar substituents at the C-6
and/or C-7 positions.
Moreover, the introduction of a methyl (4d) or ethyl (4e) group at C-2 had improved growth
inhibition towards the L. donovani strains.
Overall, the quinazolinones, despite poor growth inhibition, were more active against L. major (25
- 35% growth inhibition) than against L. donovani promastigotes. Thus, derivatives 1a, 1b, 2a,
2b, 2d, 2e, 2f, 2g, and 5c, with parasite growth inhibitions higher than 25%, were selected for
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IC50 determinations. They all were also non-cytotoxic to Vero cells, with IC50 > 100 μM (Adewusi,
Steenkamp, Fouche, & Steenkamp, 2013; Fu, Chen, Soroka, Warin, & Sang, 2014). However,
they were found to be inactive against L. major promastigotes, with IC50 >100 μM. Plausible
explanations to this fact could be: (i) the removal of the piperidine ring of febrifugine, which
corroborates the importance of this moiety for antiprotozoal activity, as previously reported (Jiang
et al., 2005); (ii) substituting a second quinazolinone moiety at N-3, instead of C-2, as per the
literature (P. Reddy et al., 2010), and (iii) the reduction in the total number of distal electron
withdrawing groups on the quinazolinone ring.
4.
Conclusion
There are currently limited new drugs in the pipeline for the treatment of patients suffering from
leishmaniasis infections. Additionally, existing therapeutic agents in clinical use possess
limitations, including inadequate modes of administration, high toxicity levels and the emergence
of drug resistant strains of the causative pathogens. In this study, quinazolinone derivatives,
wherein the 2-methylpiperidin-3-ol moiety of febrifugine was replaced by an acetylamide, or the
piperidin-3-ol by another quinazolinone ring, were investigated as potential new antileishmanial
agents. None of the synthesized compounds provided significant growth inhibition against
Leishmania parasites. However, all the derivatives proved to be safer than halofuginone, with no
demonstrated toxicity on the mammalian cells. The outcome of this study suggests a structural
redesign in order to generate more biologically active quinazolinone derivatives. Thus, future
work will entail the introduction of more electron withdrawing groups on the quinazolinone ring,
replacement of the biologically critical piperidine ring with a bioisostere (e.g. piperazine ring) and
derivatization on the C-2 position of the quinazolinone moiety.
Contributions
Conceptualization: [David D. N’Da]; Methodology: [Izak F. Prinsloo, Janine Aucamp, Nonkululeko
H. Zuma]; Formal analysis and investigation: [David D. N’Da, Janine Aucamp and Izak F.
Prinsloo]; Writing - original draft preparation: [Izak F. Prinsloo and Nonkululeko H. Zum]; Writing -
review and editing: [David D. N’Da]; Funding acquisition: [David D. N’Da]; Resources: [David D.
N’Da]; Supervision: [David D. N’Da].
Acknowledgements
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This work was based upon research financially supported by the National Research Foundation
(NRF) (UID 98937 and IFRR 115349) and the North-West University. The authors wish to thank
Dr. JHL Jordaan for MS analysis, Dr. D Otto for NMR analysis.
The following reagents were obtained through BEI Resources, NIAID, NIH:
Leishmania donovani, Strain 1S (MHOM/SD/62/1S), NR-48821
Leishmania donovani, Strain 9515 (MHOM/IN/95/9515), NR-48822
Leishmania major, Strain IR173 (MHOM/IR/-173), NR-48816
Disclaimer
Any opinions, findings and conclusions, or recommendations expressed in this material are those
of the authors and therefore the NRF does not accept any liability in regard thereto.
Declaration of competing Interest
The authors declare that they have no conflict of interest
Ethics
Ethics approval for this study was obtained from the Human Research Ethics Committee of the
North-West University (NWU-00944-19-A1).
Availability of data and material
All data generated or analyzed during this study are included in this article and its supplementary
information file.
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Synthesis and in vitro antileishmanial efficacy of novel
quinazolinone derivatives
Izak F. Prinsloo1, Nonkululeko H. Zuma, Janine Aucamp2, David D. N’Da *2
1Pharmaceutical chemistry, School of Pharmacy, North-West University, Potchefstroom 2520, South
Africa.
2Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom 2520,
South Africa.
*Corresponding author: David.nda@nwu.ac.za; Tel.: +2718 299 2256;
ORCID ID: 0000-0002-2327-0551
Table 1. Acetylamide substituted of quinazolinones 2a-g and 3a-d
Compound
R
Compound
R
2a
2b
3a
3b
2c
2d
3c
3d
2e
2f
2g
This article is protected by copyright. All rights reserved

Synthesis and in vitro antileishmanial efficacy of novel
quinazolinone derivatives
Izak F. Prinsloo1, Nonkululeko H. Zuma, Janine Aucamp2, David D. N’Da *2
1Pharmaceutical chemistry, School of Pharmacy, North-West University, Potchefstroom 2520, South
Africa.
2Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom 2520,
South Africa.
*Corresponding author: David.nda@nwu.ac.za; Tel.: +2718 299 2256;
ORCID ID: 0000-0002-2327-0551
Table 2. Bisquinazolinones 4a-f and 5a-c
Substituents
X2
Compound
Functional group D
X1
X3
4a
4b
4c
4d
4e
4f
C=O
H
H
H
“
“
Cl
“
“
OCH3 OCH3
“
CH3
“
H
“
H
“
“
CH2CH3
H
O=S=O
“
“
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5a
5b
5c
C=O
C=O
H
“
H
Cl
H
H
“
O=S=O
“
“
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Synthesis and in vitro antileishmanial efficacy of novel
quinazolinone derivatives
Izak F. Prinsloo1, Nonkululeko H. Zuma, Janine Aucamp2, David D. N’Da *2
1Pharmaceutical chemistry, School of Pharmacy, North-West University, Potchefstroom 2520, South
Africa.
2Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom 2520,
South Africa.
*Corresponding author: David.nda@nwu.ac.za; Tel.: +2718 299 2256;
ORCID ID: 0000-0002-2327-0551
Table 3. Leishmania promastigote growth inhibition and cytotoxicity of synthesized compounds
Growth inhibition (%)a
Cytotoxicity, IC50 (μM)b
Compd.
Veroc
L. donovani L. donovani L. major
1S
9515
IR-173
7.2
14.7
32.1
> 100
> 100
> 100
1a
0
5.9
3.6
26.8
28.0
1b
6.8
2a
0
4.6
26.9
> 100
2b
0
3.6
22.9
34.5
> 100
> 100
2c
2d
5.6
14.4
3.0
0
6.3
5.3
31.5
28.3
> 100
> 100
2e
2f
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4.2
8.9
2.9
10.3
9.5
26.6
23.6
17.8
> 100
> 100
> 100
2g
3a
5.9
3b
0
8.3
24.6
> 100
3c
0
2.1
11.3
0
1.7
2.9
16.9
2.2
> 100
> 100
> 100
> 100
> 100
3d
4a
20.3
22.2
16.6
0.7
4b
4c
14.6
0.7
5.7
4d
8.12
18.5
4.2
> 100
4e
4f
0
0
0
4.3
0
> 100
> 100
> 100
> 100
0.2
0.7
0
5a
29.4
0
3.7
3.9
5b
5c
AMB
HF
100
100
100
100
100
100
nd
0.03
0.05
EM
a
b
Expressed as a mean percentage from duplicate biological experiments.
represented as the mean from the triplicate
biological experiments. c African green monkey kidney epithelial cells. AMB (Amphotericin B deoxycholate); HF (halofuginone
hydrochloride) and EM (Emetine dihydrochloride hydrate).
This article is protected by copyright. All rights reserved

Synthesis and in vitro antileishmanial efficacy of novel
quinazolinone derivatives
Izak F. Prinsloo1, Nonkululeko H. Zuma, Janine Aucamp2, David D. N’Da *2
1Pharmaceutical chemistry, School of Pharmacy, North-West University, Potchefstroom 2520, South
Africa.
2Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom 2520, South
Africa.
*Corresponding author: David.nda@nwu.ac.za; Tel.: +2718 299 2256;
ORCID ID: 0000-0002-2327-0551
Scheme 1. Synthesis of quinazolinones 1a,b, 2a-g and 3a-d.
Reagents and conditions: (i): 1a: anthranilic acid (1 eq.), formamide (20.5 eq.), reflux, 5 h. 1b:
2-aminobenzenesulfonamide (1 eq.), trimethyl orthoformate (9.8 eq.), 100°C reflux, 17 h. (ii):
cycloamine (1 eq.), CAC (1.2 eq.), DCM, TEA (1.5 eq.), 24 h, 0 °C - r.t. (iii): 2a-g: 4-
(3H)quinazolinone (1 eq.), 2-chloroacetylamide intermediate (1.2 eq.), K2CO3/TEA (1.5 eq.),
DMF, 24 h, 90 °C reflux. 3a-d: 2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide (1 eq.), 2-
chloroacetylamide intermediate (1.2 eq.), K2CO3 (1.5 eq.), DMF, 24 h, 90 °C reflux.