Synthesis and anthelmintic activity of some novel (E)-2-methyl/propyl-4-(2-(substitutedbenzylidene)hydrazinyl)-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines

Article abstract of DOI:10.1007/s00044-020-02586-5

A series of some novel (E)-2-methyl/propyl-4-[(2-(substitutedbenzylidene)hydrazinyl]-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines was synthesized and characterized by adopting an appropriate synthetic scheme. The effect of electron withdrawing and

Full text of DOI:10.1007/s00044-020-02586-5

MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research
https://doi.org/10.1007/s00044-020-02586-5
ORIGINAL RESEARCH
Synthesis and anthelmintic activity of some novel (E)-2-methyl/
propyl-4-(2-(substitutedbenzylidene)hydrazinyl)-5,6,7,8-
tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines
1
Satya Sri Chitikina1 Praveen Buddiga1 Pran Kishore Deb2 Raghu Prasad Mailavaram
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Katharigatta N. Venugopala3,4 Anroop B. Nair3 Bilal Al-Jaidi5 Supratik Kar6
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Received: 1 April 2020 / Accepted: 3 June 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
A series of some novel (E)-2-methyl/propyl-4-[(2-(substitutedbenzylidene)hydrazinyl]-5,6,7,8-tetrahydrobenzo[4,5]thieno
[2,3-d]pyrimidines was synthesized and characterized by adopting an appropriate synthetic scheme. The effect of electron
withdrawing and electron donating groups at the aromatic ring in presence of methyl and propyl substituents at the 2-position
of the scaffold was evaluated for anthelmintic activity against adult Indian earthworms (Pheretima posthuma). Among 2-
methyl-thieno[2,3-d]pyrimidine analogs, compounds with electron donating methoxy group either at para-position or at
meta and para-positions of the aromatic ring showed potent anthelmintic activity at 100 μg/ml (284 and 261.8 μM
concentrations) for compounds 5g and 5h with a mean paralytic time of 2.32, 2.22 min, and helminthicidal time of 22.38,
19.43 min, respectively. In contrast, the presence of electron withdrawing chloro group at ortho and para-position of the
aromatic ring was found to be favorable for the anthelminthic activity of the compounds 5n and 5o (at concentration of
259.7 μM) with propyl group at the 2-position of the thieno[2,3-d]pyrimidine scaffold, exhibiting mean paralytic time of
2.5 min, 2.81 min and helminthicidal time of 21, 20.03 min, respectively. Anthelmintic activities of these four compounds
5g, 5h, 5n, and 5o (at the concentrations of 284, 261.8, 259.7, and 259.7 μM, respectively) were found to be on par with the
standard drug piperazine adipate (time for paralysis and death at 6.25 and 24.5 min, respectively) at concentration of 100 μg/
ml (431.03 μM). Overall, the potency of these compounds (5g, 5h, 5n, and 5o) is better than standard drug as they exhibited
the same activity at 259.7–284 μM as that of a standard drug (which has shown the same activity at 431.03 μM). Further, the
predicted ADME properties of all the synthesized compounds were found to be in the satisfactory ranges as predicted by
SwissADME software and found to have drug-like properties. Thus, further modification of these compounds might lead to
the discovery of more potent analogs.
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Keywords Anthelmintics Thienopyrimidines Benzylidenehydrazines ADME properties by SwissADME software
* Raghu Prasad Mailavaram
Pharmacy, King Faisal University, Al-Ahsa 31982, Saudi Arabia
raghumrp@rediffmail.com
4
5
6
Department of Biotechnology and Food Technology, Durban
University of Technology, Durban 4001, South Africa
1
Department of Pharmaceutical Chemistry, Shri Vishnu College of
Pharmacy, Vishnupur, West Godavari Dist., Bhimavaram, AP 534
202, India
Faculty of Pharmacy, Yarmouk University, P.
O. Box 566, Irbid 21163, Jordan
2
Interdisciplinary Center for Nanotoxicity, Department of
Chemistry, Physics and Atmospheric Sciences, Jackson State
University, Jackson, MS 39217, USA
Department of Pharmaceutical Sciences, Faculty of Pharmacy,
Philadelphia University, P.O. Box 1, Amman 19392, Jordan
3
Department of Pharmaceutical Sciences, College of Clinical

Medicinal Chemistry Research
Introduction
et al. 2016; Lanusse et al. 2018; Martin et al. 2018). It should
be noted that anthelmintic drugs mainly acting on the GIT are
structurally different showing different mechanism of actions.
In recent years, many plants, herbal extracts, and novel che-
mical compounds belonging to diverse heterocyclic scaffolds
have been explored for their antiparasitic and anthelmintic
activities (Zajíčková et al. 2020; Romero-Benavides et al.
2017; ba Ndob et al. 2016; Santos et al. 2019; Bauri et al. 2015;
Keiser et al. 2016; Preston et al. 2017; Preston and Gasser
2018; Taylor et al. 2013; Tyagi et al. 2018). Interestingly, some
of the recently reported molecules with thieno[2,3-d]pyrimidine
scaffold have shown promising anthelmintic activities (Meyer
et al. 2009; Mavrova et al. 2018; Bahashwan et al. 2013;
Partridge et al. 2018). These encouraging results gave us an
impetus to synthesize and evaluate the anthelmintic activities
Helminthiasis is one of the most common parasitic
infections and a neglected tropical disease, mainly
affecting the poor people and livestock of developing
countries due to inadequate sanitation and unhygienic
conditions (Knox et al. 2012; Woods et al. 2007; Le et al.
2019; Idris et al. 2019). The helminth parasites mainly
reside in the gastrointestinal tract (GIT) of the host, but
their larvae can also invade the liver and other organs of
the body (Tripathi 2013; Stear et al. 2007). They are
harmful to the host by causing malnutrition, anemia,
secreting toxins and if untreated, then they can also
result in chronic infections by regulating immune-
mediated inflammation (Elliott and Weinstock 2012;
Jones and Berkley 2014; Helmby 2015). Furthermore,
the fecal elimination of helminth eggs from the infected
people and animals can contaminate the soils in areas
with poor sanitation conditions leading to the reinfection
in environment (Chander et al. 2014; Idris et al. 2019).
The World Health Organization (WHO) estimates that
more than 1.5 billion people, or 24% of the world’s
population harbor soil-transmitted worm infections
worldwide, including more than 267 million preschool-
age children and over 568 million school-age children as
well as women of child bearing age, pregnant women
including and occupational groups like fishermen and
irrigation field workers for schistosomiasis https://www.
who.int/neglected_diseases/news/nobel_prize_2019/en/
(accessed on 15/1/2019).
Anthelmintic drugs can either kill (vermicides) or expel the
worms from the GIT and other parts of the body. There are four
major classes of common anthelmintics viz. benzimidazoles
(e.g., mebendazole, albendazole, fenbendazole, and flubenda-
zole), imidazothiazoles (levamisole), piperazines (phosphate,
citrate, and adipate), piperidines (pyrantel and oxantel), mac-
rocyclic lactones (ivermectin and moxidectin), and the amino-
acetonitrile derivative, monepantel available for the treatment
of nematodes infections (Taman and Azab 2014; Geary et al.
2015). Surprisingly, many of these marketed drugs available
for human treatment were first developed as veterinary medi-
cines (Zajíčková et al. 2020). However, most of these drugs are
associated with undesirable side effects in the GIT (nausea,
vomiting, and abdominal pain), liver, and kidney, including
allergic reactions, alopecia, hypotension, and body ache among
others. In addition, helminths have been gaining resistance
against many drugs including the latest drug monepentel and
moxidectin, thereby imposing a big challenge to the chemists
for the discovery and development of alternative drugs with
improved efficacy, pharmacokinetic and pharmacodynamics
properties, devoid of side effects of existing anthelmintic drugs
(Kotze and Prichard 2016; Geary 2012; Shalaby 2013; Raza
of
a
novel series of (E)-2-methyl/propyl-4-(2-(sub-
stitutedbenzylidene)hydrazinyl)-5,6,7,8-tetrahydrobenzo[4,5]
thieno[2,3-d]pyrimidines.
Materials and methods
Chemistry
Experimental
Reactions were routinely monitored by thin layer chroma-
tography (TLC) on silica gel (precoated F254 Merck plates)
and the spots were visualized under UV light (254 nm).
Melting points were recorded in open capillaries on
LABINDIA melting point apparatus and were uncorrected.
IR spectra were recorded on Bruker FT-IR Spectrometer
1
(Spectrum RX I) using the KBr pellet technique. H NMR
spectra were determined in CDCl3 or DMSO-d6 with a
Bruker Avance II [400 MHz (1H)] and signals were recor-
ded in parts per million (δ) downfield from tetra-
methylsilane (TMS) as an internal standard. Mass spectra
(ESI) were recorded on Waters Micromass Q-TOF Micro.
General procedure for the synthesis of compounds
2-Amino-3-carbethoxy-4,5,6,7-tetrahydrobenzo[b]thiophene (1)
(Gewald et al. 1966; Gewald 1965; Rao et al. 2013), 4-hydroxy-
2-methyl/propyl-5,6,7,8-tetrahydrobenzo[4,5]thieno [2,3-d]pyr-
imidines (2a and 2b) (Prasad et al. 2001; Prasad and Kishore
2007a), 4-chloro-2-methyl/propyl-5,6,7,8-tetrahydrobenzo[4,5]
thieno[2,3-d]pyrimidines (3a and 3b) (Deb et al. 2018;
Prasad et al. 2001), 4-hydrazino-2-methyl/propyl-5,6,7,8-tetra-
hydrobenzo[4,5]thieno[2,3-d]pyrimidines (4a and 4b) (Prasad
et al. 2008, 2007b) were prepared by following reported
procedures.

Medicinal Chemistry Research
General procedure for the synthesis of 2-methyl/propyl-4-
(2-(substitutedbenzylidene)hydrazinyl)-5,6,7,8-
yellow solid, yield: 75%, M.P.: 198–199 °C, IR (KBr) νmax
:
3350.07, 2932.93, 1629.25, 1521.53 cm−1 1H NMR
;
tetrahydrobenzo[4,5]thieno[2,3-d] pyrimidines (5a–p)
(DMSO-d6, 400 MHz) δ = 11.37 (1H, s, HN–N=CH–),
8.78 (1H, s, HN–N=CH), 8.55 (1H, s, ArH), 8.44–8.46
(1H, d, J = 8.2 Hz, ArH), 8.22–8.24 (1H, d, J = 8.2 Hz,
ArH), 7.71–7.76 (1H, t, J = 8.2, ArH), 2.99–3.01 (2H, m,
CH2), 2.74–2.76 (2H, m, CH2), 2.45 (3H, s, –CH3),
1.78–1.79 (4H, d, J = 4.8, 2CH2) ppm; MS (ESI) m/z (%):
367 (M+, 100); 368 (M + H, 20); Elemental analysis: calcd.
For C18H17N5O2S: C, 58.86; H, 4.63; N, 19.07%. Found:C,
58.87; H, 4.65; N, 19.20%.
Compounds 4a and 4b (0.002 M, 0.5 g) and appropriate
aldehyde (0.002 M) were taken in a round bottom flask
containing 20 ml ethanol and 2 drops of glacial acetic acid
was added and kept in stirring for about 2 h. The reaction
was monitored using TLC. After completion of the reaction
the reaction mixture was kept at room temperature over-
night. The precipitate formed was filtered, dried and
recrystallized with acetone to get the final products 5a–p.
(E)-4-(2-(4-chlorobenzylidene)hydrazinyl)-2-methyl-5,6,7,8-
tetrahydrobenzo[4,5] thieno[2,3-d]pyrimidine (5e) Light
(E)-4-(2-benzylidenehydrazinyl)-2-methyl-5,6,7,8-tetrahy-
drobenzo[4,5]thieno[2,3-d] pyrimidine(5a) White solid,
yield: 73%, M.P.: 122–123 °C, IR (KBr) νmax: 3433.94,
yellow solid, yield: 81%, M.P.: 170–171 °C, IR (KBr) νmax
:
3335.58, 2923.26, 1625.61, 726.79 cm−1 1H NMR
;
2931.10, 2833.56, 1628.42, 1544.92 cm−1
;
1H NMR
(DMSO-d6, 400 MHz) δ = 11.19 (1H, s, HN–N=CH–),
8.41 (1H, s, HN–N=CH), 8.01–8.03 (2H, d, J = 8.0 Hz,
2ArH), 7.49–7.51 (2H, d, J = 8.4 Hz, 2ArH), 2.97–2.99
(2H, m, CH2), 2.73–2.75 (2H, m, CH2), 2.42 (3H, s, –CH3),
1.78–179 (4H, m, 2CH2) ppm; MS (ESI) m/z (%): 357 (M+,
100); Elemental analysis: calcd. For C18H17ClN4S: C,
60.50; H, 4.76; N, 15.69%. Found: C, 60.54; H, 4.80; N,
15.72%.
(DMSO-d6, 400 MHz) δ = 11.13 (1H, s, HN–N=CH–),
8.41 (1H, s, HN–N=CH),7.98–7.99 (2H, d, J = 6.4 Hz,
2ArH), 7.41–7.46 (3H, q, J = 7.4 Hz, 2ArH), 2.98–3.00
(2H, m, CH2), 2.73–2.75 (2H, m, CH2), 2.42 (3H, s, CH3),
1.79–1.82 (4H, m, 2CH2) ppm; MS (ESI) m/z (%): 322
(M+, 100); 323 (M + H, 30); Elemental analysis: calcd. For
C18H18N4S: C, 67.08; H, 5.59; N, 17.39%. Found: C, 67.10;
H, 5.61; N, 17.41%.
(E)-4-(2-(2-chlorobenzylidene)hydrazinyl)-2-methyl-5,6,7,8-
tetrahydrobenzo[4,5] thieno[2,3-d]pyrimidine (5f) Light
(E)-4-((2-(2-methyl-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-
d]pyrimidin-4-yl)hydrazono)methyl)phenol
solid, yield: 70%, M.P.: 215–216 °C, IR (KBr) νmax
3379.02, 2935.74, 1565.62, 1415.74 cm−1 1H NMR
(5b) White
brown solid, yield: 77%, M.P.: 154–156 °C, IR (KBr) νmax
:
:
3323.23, 2920.41, 1625.57, 752.91 cm−1 1H NMR
;
;
(DMSO-d6, 400 MHz) δ = 11.27 (1H, s, HN–N=CH–),
8.67 (1H, s, HN–N=CH–) 8.53–8.51 (1H, m, ArH),
7.52–7.50 (1H, m, ArH), 7.44–7.42 (2H, m, ArH),
2.98–2.99 (2H, m, CH2), 2.73–2.74 (2H, m, CH2), 2.43
(3H, s, –CH3), 1.79–1.81 (4H, m, 2CH2) ppm; MS (ESI) m/
z (%): 356 (M+, 100); 357 (M + H, 30); Elemental analysis:
calcd. For C18H17ClN4S: C, 60.50; H, 4.76; N, 15.69%.
Found: C, 60.48; H, 4.80; N, 15.70%.
(DMSO-d6, 400 MHz) δ = 10.62 (s, 1H, OH), 8.57 (1H, s,
HN–N=CH–), 8.19 (1H, s, HN–N=CH–), 7.55–7.57 (2H,
d, J = 8.2 Hz, 2ArH), 6.73–6.75 (2H, d, J = 8.4 Hz, 2ArH),
2.67 (3H, s, –CH3), 2.62–2.67 (2H, m, CH2), 2.25–2.2.58
(2H, m, CH2), 1.70–1.75 (4H, m, 2CH2) ppm; MS (ESI) m/z
(%): 338 (M+, 100); 339 (M + H, 40); Elemental analysis:
calcd. For C18H18N4OS: C, 63.90; H, 5.33; N, 16.57%.
Found: C, 63.92; H, 5.35; N, 16.60%.
(E)-4-(2-(4-methoxybenzylidene)hydrazinyl)-2-methyl-
5,6,7,8-tetrahydrobenzo[4,5] thieno[2,3-d]pyrimidine (5g)
Light brown solid, yield: 72%, M.P.: 98–99 °C, IR (KBr)
(E)-2-methyl-4-(2-(4-nitrobenzylidene)hydrazinyl)-5,6,7,8-
tetrahydrobenzo[4,5] thieno[2,3-d]pyrimidine (5c) Light
1
yellow solid, yield: 76%, M.P.: 210–211 °C, IR (KBr) νmax
:
νmax: 3393.00, 2934.19, 2835.85, 1609.44 cm−1; H NMR
3319, 2931.96, 1622.62, 1556.97 cm−1; 1H NMR (Acetone-
d6, 400 MHz) δ = 10.95 (1H, s, HN–N=CH–), 8.38 (1H, s,
HN–N=CH), 8.11–8.14 (2H, d, J = 8.8, 2ArH), 7.95–7.97
(2H, d, J = 8.4, 2ArH), 2.92–2.94 (2H, m, CH2), 2.66–2.68
(2H, m, CH2), 2.31 (3H, s, –CH3), 1.72–1.77 (4H, m, 2CH2)
ppm; MS (ESI) m/z (%): 367 (M+ 100); 368 (M + H, 20);
Elemental analysis: calcd. For C18H17N5O2S: C, 58.86; H,
4.63; N, 19.07%. Found: C, 58.89; H, 4.66; N, 19.17%.
(DMSO-d6, 400 MHz) δ = 11.05 (1H, s, HN–N=CH–),
8.35 (1H, s, HN–N=CH–) 7.91–7.93 (2H, d, J = 8.0 Hz,
2ArH), 6.99–7.01 (2H, d, J = 8.4 Hz, 2ArH), 3.81 (3H, s,
–OCH3), 2.97–2.99 (2H, m, CH2), 2.72–2.74 (2H, m, CH2),
2.40 (3H, s, –CH3), 1.78–1.79 (4H, m, 2CH2) ppm; MS
(ESI) m/z (%): 352 (M+, 100); 353 (M + H, 30); Elemental
analysis: calcd. For C19H20N4OS: C, 64.78; H, 5.68; N,
15.91%. Found: C, 64.82; H, 5.72; N, 15.95%.
(E)-2-methyl-4-(2-(3-nitrobenzylidene)hydrazinyl)-5,6,7,8-
tetrahydrobenzo[4,5] thieno[2,3-d]pyrimidine (5d) Light
(E)-4-(2-(3,4-dimethoxybenzylidene)hydrazinyl)-2-methyl-
5,6,7,8-tetrahydrobenzo [4,5]thieno[2,3-d]pyrimidine (5h)

Medicinal Chemistry Research
Light brown solid, yield: 73%, M.P.: 120–121 °C, IR (KBr)
νmax: 3359.82, 2938.52, 2825, 1601.50 cm−1 1H NMR
For C20H21N5O2S: C, 60.76, H, 5.32; N, 17.72%. Found: C,
60.72, H, 5.30; N, 17.70%.
;
(DMSO-d6, 400 MHz) δ = 11.10 (1H, s, HN–N=CH–),
8.34 (1H, s, HN–N=CH–) 7.68–7.69 (1H, d, J = 8.6 Hz,
ArH), 7.38–7.39 (1H, s, ArH), 7.00–7.02 (1H, d, J =
8.4 Hz, ArH), 3.86 (3H, s, –OCH3), 3.81 (3H, s, –OCH3),
3.86 (3H, s, –OCH3), 2.97–2.98 (2H, m, –CH2), 2.72–2.74
(2H, m, –CH2), 2.40 (3H, s, –CH3), 1.78–1.80 (4H, m,
2CH2) ppm; MS (ESI) m/z (%): 382 (M+, 100); 383 (M +
H, 30); Elemental analysis: calcd. For C20H22N4O2S: C,
62.83; H, 5.76; N, 14.66%. Found: C, 62.87; H, 5.78; N,
14.70%.
(E)-4-(2-(3-nitrobenzylidene)hydrazinyl)-2-propyl-5,6,7,8-
tetrahydrobenzo [4,5]thieno[2,3-d]pyrimidine (5l) Light
brown solid, yield: 87%, M.P.: 160–161 °C, IR (KBr) νmax
:
3338.05, 1629.44, 2935.38, 1539.96 cm−1 1H NMR
;
(DMSO-d6, 400 MHz) δ = 11.24 (1H, s, HN–N=CH–),
8.76 (1H, s, HN–N=CH–), 8.55 (1H, s, ArH), 8.44–8.46
(1H, d, J = 8.0 Hz, ArH), 8.21–8.24 (1H, m, ArH),
8.09–8.11 (1H, d, J = 7.6 Hz, ArH), 2.73–2.77 (4H, m,
2CH2), 1.78–1.82 (4H, m, CH2CH2CH3), 1.70–1.74 (3H t,
m, CH2CH2CH3), 0.92–0.98 (4H, t, m, 2CH2) ppm; MS
(ESI) m/z (%): 395 (M+, 100); Elemental analysis: calcd.
For C20H21N5O2S: C, 60.76, H, 5.32; N, 17.72%. Found: C,
60.80, H, 5.35; N, 17.76%.
(E)-4-(2-benzylidenehydrazinyl)-2-propyl-5,6,7,8-tetrahy-
drobenzo[4,5]thieno[2,3-d] pyrimidine (5i) Light brown
solid, yield: 72%, M.P.: 102–103 °C, IR (KBr) νmax
:
3348.85, 1628.86, 1583.73, 1545.31, 2926.67, 2956.35
1
cm−1; H NMR (DMSO-d6, 400 MHz) δ = 11.02 (1H, s,
(E)-4-(2-(2-nitrobenzylidene)hydrazinyl)-2-propyl-5,6,7,8-
tetrahydrobenzo [4,5]thieno[2,3-d]pyrimidine (5m) Light
HN–N=CH–), 8.41 (1H, s, HN–N=CH–), 7.41–7.46 (1H,
m, ArH), 7.67–7.70 (2H, d, J = 7.6 Hz, ArH), 7.97–7.98
(2H, d, J = 7.2 Hz, 2ArH), 2.98–3.02 (2H, m,
–CH2CH2CH3), 2.77–2.79 (2H, m, –CH2CH2CH3),
1.69–1.78 (8H, m, 4CH2), 0.94–0.98 (3H, m,
–CH2CH2CH3) ppm; MS (ESI) m/z (%): 350 (M+, 100);
Elemental analysis: calcd. For C20H22N4S: C, 68.57; H,
6.29; N, 16.00%. Found: C, 68.60; H, 6.32; N, 16.10%.
brown solid, yield: 83%, M.P.: 134–136 °C, IR (KBr) νmax
:
3324.05, 1629.84, 2926.21, 1528.50 cm−1 1H NMR
;
(DMSO-d6, 400 MHz) δ = 11.12 (1H, s, HN–N=CH–),
8.64 (1H, s, HN–N=CH–), 8.53–8.55 (1H, m, ArH),
8.01–8.04 (1H, m, ArH), 7.80–7.82 (1H, m, ArH), 7.64 (1H
m, ArH), 2.71–2.76 (4H, q, J = 6.6 Hz, 2CH2), 1.76–1.82
(4H, q, J = 8.1 Hz, –CH2CH2CH3), 1.70–1.74 (3H, t, J =
7.6 Hz, –CH2CH2CH3), 0.92–0.98 (4H m, 2CH2) ppm; MS
(ESI) m/z (%): 395 (M+, 100); Elemental analysis: calcd.
For C20H21N5O2S: C, 60.76, H, 5.32; N, 17.72%. Found: C,
60.82, H, 5.36; N, 17.78%.
(E)-4-((2-(2-propyl-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-
d]pyrimidin-4-yl) hydrazono)methyl)phenol (5j) Light
brown solid, yield: 76%, M.P.: 210–212 °C, IR (KBr) νmax
:
3370.58, 1414.54, 1603.84, 2946.17 cm−1 1H NMR
;
(Acetone-d6, 400 MHz) δ = 10.53 (1H, s, OH), 8.53 (1H, s,
HN–N=CH–), 8.19 (1H, s, HN–N=CH–),7.54–7.56 (2H,
d, J = 8.0 Hz, 2ArH), 6.74–6.76 (2H, d, J = 8.4 Hz, 2ArH),
2.90–2.92 (2H, m, CH2), 2.68–2.70 (2H, m, CH2CH2CH3),
2.63–2.65 (2H, m, CH2CH2CH3), 1.63–1.70 (6H, m, 3CH2),
0.85–0.88 (3H, t, J = 7.2 Hz, CH2CH2CH3) ppm; MS (ESI)
m/z (%): 366 (M+, 100); Elemental analysis: calcd. For
C20H22N4OS: C, 65.57; H, 6.01; N, 15.30%. Found: C,
65.61; H, 6.21; N, 15.35%.
(E)-4-(2-(4-chlorobenzylidene)hydrazinyl)-2-propyl-5,6,7,8-
tetrahydrobenzo [4,5]thieno[2,3-d]pyrimidine(5n) Light
brown solid, yield: 83%, M.P.: 132–134 °C, IR (KBr) νmax
:
1
3268, 1625.84, 2934.2, 2950.27, 743.83 cm−1; H NMR
(DMSO-d6, 400 MHz) δ = 11.07 (1H, s, HN–N=CH–),
8.41 (1H, s, HN–N=CH–), 8.00–8.02 (2H, d, J = 8.4 Hz,
2ArH), 7.50–7.52 (2H, d, J = 8.2 Hz, 2ArH), 2.79–2.80
(2H, m, CH2CH2CH3), 2.70–2.77 (2H, m, CH2CH2CH3),
1.69–1.78 (8H, m, 4CH2), 0.94–0.98 (3H, m, CH2CH2CH3)
ppm; MS (ESI) m/z (%): 385 (M+, 100); Elemental ana-
lysis: calcd. For C20H21ClN4S: C, 62.34; H, 5.46, N,
14.55%. Found: C, 62.40; H, 5.48, N, 14.58%.
(E)-4-(2-(4-nitrobenzylidene)hydrazinyl)-2-propyl-5,6,7,8-
tetrahydrobenzo [4,5]thieno[2,3-d]pyrimidine (5k) Light
brown solid, yield: 80%, M.P.: 180–182 °C, IR (KBr) νmax
:
3343.75, 1623.1, 2918.06, 2931.27, 1530.45 cm−1 1H
;
(E)-4-(2-(2-chlorobenzylidene)hydrazinyl)-2-propyl-5,6,7,8-
tetrahydrobenzo [4,5]thieno[2,3-d]pyrimidine(5o) Light
NMR (DMSO-d6, 400 MHz) δ = 10.83 (1H, s,
HN–N=CH–), 8.38 (1H, s, HN–N=CH–), 8.11–8.13 (2H,
d, J = 8.8 Hz, 2ArH), 7.94–7.96 (2H, d, J = 8.4 Hz, 2ArH),
2.92 (2H, m, CH2), 2.66–2.67 (2H, m, -CH2CH2CH3),
2.57–2.61 (2Hm, –CH2CH2CH3), 1.63–1.70 (6H, m,
3CH2), 0.85–0.88 (3H, t, J = 7.4, –CH2CH2CH3) ppm; MS
(ESI) m/z (%): 395 (M+, 100); Elemental analysis: calcd.
brown solid, yield: 75%, M.P.: 110–112 °C, IR (KBr) νmax
:
3354.05, 1624.7, 2930.78, 2955.28, 750.72 cm−1; 1H NMR
(DMSO-d6, 400 MHz) δ = 11.16 (1H, s, HN–N=CH–),
8.67 (1H, s, HN–N=CH–), 8.48–8.51 (1H t, J = 4.6 Hz,
ArH), 7.50–7.54 (1H, m, ArH), 7.42–7.44 (2H, t, J =
4.6 Hz, 2ArH), 2.71–2.75 (4H, t, J = 7.4 Hz, 2CH2),

Medicinal Chemistry Research
1.75–1.82 (4H, m, CH2CH2CH3), 1.69–1.73 (3H, t, J =
7.4 Hz, CH2CH2CH3), 0.92–0.97 (4H, m, 2CH2) ppm; MS
(ESI) m/z (%): 385 (M+, 100); Elemental analysis: calcd.
For C20H21ClN4S: C, 62.34; H, 5.46, N, 14.55%. Found: C,
62.38; H, 5.50, N, 14.60%.
observation of complete lack of any movement of worms
upon vigorous shaking followed by dipping in warm water
(50 °C). T-test was run for the biological data of all the
compounds. Results of anthelmintic activities are listed in
Table 1.
(E)-4-(2-(3,4-dimethoxybenzylidene)hydrazinyl)-2-propyl-
5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine (5p)
Light brown solid, yield: 86%, M.P.: 130–132 °C, IR (KBr)
Results and discussion
1
νmax:3346.95, 1627.2, 2926.32, 2946.97, 2846.74 cm−1; H
Chemistry
NMR (DMSO-d6, 400 MHz) δ = 10.99 (1H, s,
HN–N=CH–), 8.34 (1H, s, HN–N=CH-), 8.24 (1H, s,
ArH), 7.67–7.68 (1H, d, J = 7.6 Hz, ArH), 7.01–7.03 (1H,
d, J = 8.0 Hz, ArH), 3.86 (3H, s, OCH3), 3.81 (3H, s,
–OCH3), 2.67–2.75 (4H, m, CH2), 1.75–1.83 (4H, m,
–CH2CH2CH3), 1.69–1.73 (3H, m, –CH2CH2CH3),
0.92–0.97 (4H, m, 2CH2) ppm; MS (ESI) m/z (%): 410
(M+100); 411 (M+H, 30); Elemental analysis: calcd. For
C22H26N5O2S: C, 64.39; H, 6.34; N, 17.07%. Found: C,
64.41; H, 6.37; N, 17.10%.
As illustrated in Fig. 1, the compound 2-amino-3-car-
bethoxy-4,5,6,7-tetrahydrobenzo[4,5]thiophene (1) was
synthesized by stirring molar quantities of cyclohexanone,
ethylcyanoacetate and sulfur in ethanol for one hour under
basic conditions following the reported procedure (Gewald
et al. 1966; Gewald 1965). Compounds (2a) and (2b) were
prepared by condensing compound (1) with acetonitrile and
butyronitrile, respectively, in the presence of dry hydrogen
chloride. Chlorination of compounds 2a and 2b with
phosphorous oxychloride at 110 °C for 6 h under anhydrous
conditions resulted in the formation of 4-chloro-2-methyl/
propyl-5,6,7,8-tetrahydrobenzo[b]thieno[2,3-d]pyrimidines
(3a and 3b), which upon further treatment with
hydrazine hydrate resulted in the formation of key inter-
mediate compounds 4-hydrazino-2-methyl/propyl-5,6,7,8-
tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines (4a and 4b).
Compounds 2a, 2b, 3a, 3b, 4a, and 4b were also synthe-
sized by following our previously reported procedure and
their melting points were corroborated well with the melting
point of these compounds (Prasad et al. 2001, 2008).
Compounds 4a and 4b were treated with various aldehydes
to obtain the target compounds 5a–p, which were char-
acterized based on their spectrometric analysis.
Anthelmintic assay
All the target compounds (5a–p) were screened for
anthelmintic activity as per the reported method (Ajaiyeoba
et al. 2008; Garg et al. 2014) by using Indian earthworms
(Pheretima posthuma), because of their anatomical and
physiological similarity with human intestinal roundworm.
All adult Indian earthworms of ~5–8 cm long and
0.4–0.8 mm diameter were collected from local Ram-
lakshmi vermi compost yard, Palakol. Earthworms were
washed with normal saline water and kept in different
groups of Petri dishes labeled as control, standard and tests,
containing six worms in each plate. Piperazin adipate
(37.0% w/w) was used as a standard drug at a concentration
of 100 μg/ml (431.03 μM). The dose of piperazine adipate
was optimized by carrying out its activity using different
concentrations (10, 20, 50, 80, and 100 μg/ml). At 100 μg/
ml, it showed activity and thus selected as standard dose.
Dimethyl sulphoxide (DMSO) 1% was used as control. Test
solutions of all the target compounds (5a–p) prepared with
1% DMSO were evaluated at four different concentrations
of 20 μg/ml (48.7–62.1 μM), 50 μg/ml (122.0–155.2 μM),
Anthelmintic activity
All the target compounds (5a–p) were screened for their
preliminary anthelmintic activity (Table 1) following the
reported method (Ajaiyeoba et al. 2008) by using adult
Indian earthworms (P. posthuma) because of its anatomical
and physiological similarity with the human intestinal
roundworm parasites. Piperazine adipate was used as a
standard at 100 μg/ml (431.03 μM) concentration. All the
synthesized compounds were evaluated at four different
concentrations of 20 (48.7–62.1 μM) 50 (122.0–155.2 μM),
80 (195.1–248.4 μM), and 100 (243.9–310.5 μM) μg/ml.
Six worms were used for each concentration and the time
taken for paralysis and death were recorded in minutes. The
standard drug piperazine adipate (100 μg/ml, 431.03 μM)
showed paralytic activity at a mean time of 6.25 min. At the
same concentration [100 μg/ml (243.9–295.8 μM)], com-
pounds 5b, 5e, 5f, 5g, 5h, 5k, 5l, 5m, 5n, 5o, 5p paralyzed
80 μg/ml
(195.1–248.4 μM),
and
100 μg/ml
(243.9–310.5 μM), respectively. Petri plates of the test
groups were treated individually with 20 ml of test solutions
of each concentration. Motility of worms was recorded after
incubating them in a humid chamber with a thermostat at
37 °C (Mavrova et al. 2018). Time taken for complete
paralysis and death of earthworms were recorded. Time
taken for earthworms to become motionless (except vigor-
ous shaking) was considered as the time of paralysis;
whereas the time of death was ascertained based on the

Medicinal Chemistry Research
Table 1 Anthelmintic activity of (E)-2-methyl/propyl-4-(2-(substitutedbenzylidene)hydrazinyl)-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]
pyrimidines 5a–5p
Comp.
R1
R2
H
Concentration
(µg/ml)
Concentration
(µM)
Time taken for
paralysis in
minutes (Mean
and S.E.M.)
Time taken for
death in minutes
(Mean and S.E.
M.)
5a
–CH3
20
50
62.1
155.2
248.4
310.5
59.2
30.06 0.006
33.37 0.065
14.03 0.114
06.36 0.174
–
110.35 0.076
80.74 0.205
49.91 0.153
40.22 0.217
–
80
100
20
5b
5c
5d
5e
5f
–CH3
–CH3
–CH3
–CH3
–CH3
–CH3
–CH3
–C3H7
p-OH
p-NO2
m-NO2
p-Cl
50
147.9
236.6
295.8
54.5
11.46 0.170
09.96 0.290
04.24 0.045
42.83 1.740
36.77 1.007
15.60 0.887
08.92 1.655
40.46 0.119
34.14 0.051
14.35 0.272
08.72 0.141
40.39 0.065
34.14 0.051
07.20 0.057
05.58 0.153
21.44 1.147
27.85 2.310
06.38 0.314
05.43 0.569
–
40.60 0.748
57.85 1.298
38.19 0.045
112.16 4.020
102.66 2.216
49.19 3.619
25.31 0.811
110.45 0.076
100.31 0.117
48.49 0.026
24.98 0.177
110.58 0.153
100.19 0.067
93.04 0.579
35.71 0.202
99.14 1.360
100.50 1.176
83.18 8.226
30.55 2.576
–
80
100
20
50
136.2
218.0
272.4
54.5
80
100
20
50
136.2
218.0
272.4
56.0
80
100
20
50
140.0
224.0
280.1
56.0
80
100
20
o-Cl
50
140.0
224.0
280.1
56.8
80
100
20
5g
5h
5i
p-
OCH3
50
142.0
227.3
284.0
52.3
09.58 0.153
05.35 0.012
02.32 0.007
–
38.60 0.200
28.86 0.190
22.38 0.144
–
80
100
20
m,p-
di-
OCH3
50
130.9
209.4
261.8
57.1
09.2 0.608
05.18 0.464
02.22 0.236
33.81 0.580
34.57 1.095
21.88 0.28
19.43 0.168
96.86 0.435
80
100
20
H

Medicinal Chemistry Research
Table 1 (continued)
Comp.
R1
R2
Concentration
(µg/ml)
Concentration
(µM)
Time taken for
paralysis in
minutes (Mean
and S.E.M.)
Time taken for
death in minutes
(Mean and S.E.
M.)
50
80
142.9
228.6
33.16 0.468
09.81 0.183
72.16 0.557
63.13 0.416
100
20
285.7
54.6
06.08 0.179
43.00 2.708
10.45 0.062
06.43 0.042
08.00 1.366
28.79 1.691
23.06 3.424
13.37 1.274
05.39 0.337
35.87 0.212
22.08 0.591
13.01 0.189
05.49 0.286
33.26 0.358
24.97 0.346
14.10 0.312
05.41 0.046
36.00 0.620
05.31 0.065
03.98 0.150
02.50 0.058
36.45 1.970
05.40 0.236
03.81 0.321
02.81 0.273
33.08 1.012
29.73 0.615
08.71 0.237
05.33 0.193
06.25 0.062
49.55 1.079
75.15 1.306
96.49 1.891
81.89 0.740
73.55 3.060
75.49 9.086
62.26 6.232
47.59 7.507
39.90 7.745
86.08 0.453
61.67 1.021
52.88 1.109
43.36 1.184
84.09 0.741
56.60 1.720
51.75 0.487
43.66 0.455
63.53 0.305
43.25 0.349
24.00 0.428
21.00 0.546
69.35 5.519
44.76 2.364
23.40 2.346
20.03 2.745
86.60 0.711
63.25 0.493
57.25 0.730
37.65 0.387
24.50 1.057
5j
–C3H7
–C3H7
–C3H7
–C3H7
–C3H7
–C3H7
-C3H7
–
p-OH
p-NO2
m-NO2
o-NO2
p-Cl
50
136.6
218.6
273.2
50.6
80
100
20
5k
5l
50
126.6
202.5
253.2
50.6
80
100
20
50
126.6
202.5
253.2
50.6
80
100
20
5m
5n
5o
5p
50
126.6
202.5
253.2
51.9
80
100
20
50
129.9
207.8
259.7
51.9
80
100
20
o-Cl
50
129.9
207.8
259.7
48.7
80
100
20
m,p-
di-
OCH3
50
122.0
195.1
243.9
431.03
80
100
100
Piperazine
adipate
–

Medicinal Chemistry Research
O
O
Cl
N
Fig. 1 Synthesis of (E)-2-
methyl/propyl-4-
[(substitutedbenzylidene)
hydrazinyl]-5,6,7,8-
tetrahydrobenzo[4,5]theino[2,3-
d]pyrimidines (5a–p). Reagents
and conditions: (i) RCN, dry
HCI gas 6 h; (ii) POCI3, 110 °C,
2–8 h (iii) N2H4·H2O, C2H5OH,
80 °C; (iv) R2-C6H4CHO,
stirring room temperature
NH
N
OC2H5
NH2
(i)
(ii)
R1
R1
N
S
[3a,b]
S
[1]
S
,b]
[2a
Comp. No.
R1
R2
--
--
--
--
--
--
H
(iii)
2a
2b
3a
3b
4a
4b
5a
5b
5c
5d
5e
5f
-CH3
-C3H7
-CH3
-C3H7
-CH3
-C3H7
-CH3
-CH3
-CH3
-CH3
-CH3
-CH3
-CH3
-CH3
-C3H7
-C3H7
-C3H7
-C3H7
-C3H7
-C3H7
-C3H7
-C3H7
H2NHN
N
R1
N
S
p-OH
p-NO2
m-NO2
p-Cl
[4a,b]
o-Cl
(iv)
5g
5h
5i
p-OCH3
m,p-di-OCH3
H
5j
5k
5l
p-OH
p-NO2
m-NO2
o-NO2
p-Cl
R2
N
5m
5n
5o
5p
HN
o-Cl
N
m,p-di-OCH3
S
N
R1
[5a-p]
20 µg/ml
50 µg/ml
80 µg/ml
100 µg/ml
20 µg/ml
50 µg/ml
80 µg/ml
100 µg/ml
140
120
100
80
50
40
30
20
10
0
60
40
20
0
Target compounds
Target compounds
Fig. 3 Time of death of target compounds 5a–p. Each value is
expressed as mean (n = 6) SEM
Fig. 2 Time of paralysis of target compounds 5a–p. Each value is
expressed as mean (n = 6) SEM
the worms in 4.24, 5.58, 5.43, 2.32, 2.22, 5.39, 5.49, 5.41,
2.5, 2.81 and 5.33 min, respectively; whereas at 80 μg/ml
(207.8–227.3 μM) concentration, compounds 5g, 5h, 5n, 5o
paralyzed the worms in a mean time of 5.35, 5.18, 3.98 and
3.81 min, respectively. Similarly, at 100 μg/ml (431.03 μM)
mean lethal time for the standard drug and compounds 5g,
5h, 5n, 50 (284.0, 261.8, 259.7, and 259.7 μM respectively)
were found to be 24.5, 22.38, 19.43, 21 and 20.03 min,
respectively. The t-test was run for all the compounds using
graph pad prism. Compounds 5b, 5d, 5e, 5g, 5h, 5j, 5l, 5m,
5n, 5o, and 5p have shown significant variation in inducing
paralysis (p value < 0.05) at all the test concentrations and
the compounds 5a, 5b, 5e, 5i, 5j, 5l, 5m, 5n, 5o, and 5p
have shown significant helminthicidal activity (p value <
0.05) at all the test concentrations when compared with that
of the standard drug (100 μg/ml, 431.03 μM). At 50 μg/ml
of test concentration, all the drugs have shown moderate
paralytic as well as helminthicidal activity when compared
with that of the standard. Finally, it can be concluded from
the results that the compounds 5g, 5h, 5n, 5o have shown
potent anthelminthic activity at 100 μg/ml (284.0, 261.8,
259.7, and 259.7 μM, respectively) with a mean paralytic
time of 2.32, 2.22, 2.5, 2.81 min and helminthicidal time of
22.38, 19.43, 21, 20.03 min, respectively, when compared
with that of the standard (6.25 and 24.5 min time for
paralysis and death) as shown in Figs. 2 and 3.
Prediction of ADME properties and drug-likeness
The ADME (absorption, distribution, metabolism, and excre-
tion) parameters like physicochemical properties, lipophilicity,
water solubility, pharmacokinetics, and drug-like nature of the
molecules (5a–p) were tested employing SwissADME soft-
ware (http://swissadme.ch/) (Daina et al. 2017). The details of
the calculated parameters are presented in Table 2. Except
compounds 5n and 5o, all the compounds satisfied the

Medicinal Chemistry Research
Table 2 Predicted physicochemical properties, pharmacokinetics and drug-likeness of (E)-2-methyl/propyl-4-(2-(substitutedbenzylidene)
hydrazinyl)-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines (5a–p) and piperazine adipate
Molecule
Piperazine
adipate
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
MW
232.28
5
322.4 338.4 367.4 367.4 356.8 356.8 352.4 382.4 350.4 366.4 395.4 395.4 395.4 384.9 384.9 410.5
RB
3
3
1
3
4
2
4
5
1
4
5
1
3
3
1
3
3
1
4
4
1
5
5
1
5
3
1
5
4
2
6
5
1
6
5
1
6
5
1
5
3
1
5
3
1
7
5
1
HBA
HBD
MR
F-Csp3
TPSA
iLOGP
6
4
67.16
0.8
97.3 99.3 106.1 106.1 102.3 102.3 103.8 110.3 106.9 108.9 115.7 115.7 115.7 111.9 111.9 119.9
0.28 0.28 0.28 0.28 0.28 0.28 0.32 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.41
78.4 98.6 124.2 124.2 78.4 78.4 87.6 96.9 78.4 98.6 124.2 124.2 124.2 78.4 78.4 96.9
98.66
1.67
3.25 2.84 2.82 2.78 3.41 3.48 3.3
5.13 4.78 4.96 4.96 5.76 5.76 5.1
3.59 3.63 3.28 3.29 3.23 3.32 3.85 3.96 4.08
5.08 5.92 5.57 5.75 5.75 5.75 6.55 6.55 5.87
XLOGP3 −5.34
Log S
GIA
HS
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
PS
PS
PS
High
No
High High High High High High High High High High Low Low Low High High High
BBB-P
Pgp-S
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes Yes No
Yes No
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
No No No No No No No Yes No Yes No No No No No Yes
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
CYP1A2i No
CYP2C9i No
CYP2D6i No
CYP3A4i No
Yes Yes Yes Yes Yes Yes Yes No
Yes Yes Yes Yes Yes No
Lipinski
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
violations
Ghose
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
violations
BS
0.55
0
0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55
PAINS-A
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
MW molecular weight, RB rotatable bonds, HBA H-bond acceptor, HBD: H-bond donor, MR molar refractivity, F-Csp3 fraction Csp3 to identify the
saturation, iLOGP, HS highly soluble, MS moderately soluble, PS poorly soluble, GIA GI absorption, BBB-P BBB permeant, Pgp-S Pgp substrate,
i inhibitor for all CYP, BS bioavailability score, PAINS-A Pan Assay interference structure alerts
Lipinski’s rule of five (5). On the contrary, all molecules
successfully passed the Ghose drug-like filter. To display the
drug-likeness of the identified most active molecules according
to anthelmintic assay and activity evaluation, six physico-
chemical properties have been taken into consideration: lipo-
philicity, size, polarity, solubility, flexibility, and saturation
(Expressed as Lipo, Size, Polar, Insolu, Flex, and Insatu,
respectively in Fig. 4), generated Bioavailability Radar plots. A
physicochemical range on each axis was defined by descriptors
and the pink area in which the radar plot of the compound has
to stay completely to be identified as a drug-like molecule.
Here, the pink prepared with the optimum range for individual
properties (size: MW between 150 and 500 g/mol, polarity:
TPSA between 20 and 130 Å2, solubility: lipophilicity:
XLOGP3 between −0.7 and +5.0, log S not higher than 6,
flexibility: no more than 9 rotatable bonds and saturation: the
fraction of carbons in the sp3 hybridization not less than 0.25. It
can be evident from the plots in Fig. 4 that in case of the most
active compounds (5g, 5h, 5n, and 5o), major drug-likeness
properties are staying within the acceptable specified pink area
which make them probable future lead molecules for
anthelmintic activity. To compare the predicted parameters of
the synthesized compounds with the standard drug, we have
predicted the similar features for piperazine adipate. Interest-
ingly, we found almost similar bioavailability score for piper-
azine adipate and all the synthesized compounds (5a–p). The
predicted parameters strongly support the obtained outcomes
from the anthelmintic assay and activity of the synthesized
compounds (5a–p).
Conclusion
A series of some novel (E)-2-methyl/propyl-4-(2-(sub-
stitutedbenzylidene)hydrazinyl)-5,6,7,8-tetrahydrobenzo
[4,5]thieno[2,3-d]pyrimidines was synthesized and char-
acterized. Two different series of compounds having a
methyl (5a–h) and propyl (5i–p) substituents at the 2-
position of the thieno[2,3-d]pyrimidine scaffold with dif-
ferent electron withdrawing and electron donating groups
at the aromatic ring were evaluated for their preliminary
anthelmintic activity against adult Indian earthworms (P.

Medicinal Chemistry Research
Fig. 4 Bioavailability Radar
plots of the most active
compounds 5g, 5h, 5n, and 5o
posthuma). Interestingly, compounds 5g and 5h having
methyl group at the 2-position of the scaffold with electron
donating methoxy group at para-position and dimethoxy
group at meta and para-positions of the aromatic ring
showed potent anthelmintic activity at 100 μg/ml (284.0
and 261.8 μM) with a mean paralytic time of 2.32,
2.22 min, and helminthicidal time of 22.38, 19.43 min,
respectively. In contrast, the presence of electron with-
drawing chloro group at ortho and para-position of the
aromatic ring was found to be favorable for the anthel-
minthic activity of the compounds 5n and 5o with propyl
group at the 2-position of the thieno[2,3-d]pyrimidine
scaffold, exhibiting mean paralytic time of 2.5, 2.81 min
and helminthicidal time of 21, 20.03 min, respectively, at
the same concentration (100 μg/ml, 259.7 μM). Anthel-
mintic activities of these four compounds 5g, 5h, 5n, and
5o were found to be on par with the standard drug piper-
azine adipate (100 μg/ml, 431.03 μM), that showed the
time for paralysis and death at 6.25, and 24.5 min,
respectively. Overall, the potency of these compounds (5g,
5h, 5n, and 5o) is better than standard drug as they
exhibited the same activity at 259.7–284 μM as that of the
standard drug (which has shown the same activity at
431.03 μM). The experimental outcomes are strongly
supported by their satisfactory ADME and drug-like
properties as predicated by the SwissADME software.
Thus, further modification of these compounds might lead
to the discovery of more potent analogs.
Acknowledgements Authors thank Sri K.V. Vishnu Raju, Chairman-
Sri Vishnu Educational Society, Dr. D.B. Raju, Director and Dr. K.
Prasad, Principal-Shri Vishnu College of Pharmacy for their constant
support and encouragement. They also thank Lila Impex Ltd for
spectral and elemental analysis.
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
Ethical approval We declare that all the co-authors are aware of and
approve of the submission.
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
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