Synthesis, antimycobacterial evaluation and docking studies of some 7-Methyl-5,6,7,8-tetrahydropyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4(3H)-ones

Article abstract of DOI:10.1248/cpb.c17-00999

Two series of 3-substituted-7-methyl-5,6,7,8-tetrahydropyrido[4',3':4,5] thieno[2,3-d]pyrimidin-4(3H)- one (6a-k) and 3-substituted-7,2-dimethyl-5,6,7,8-tetrahydropyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4(3H)- one (7a-k) derivatives were synthesized and c

Full text of DOI:10.1248/cpb.c17-00999

Vol. 66, No. 10
Chem. Pharm. Bull. 66, 923–931 (2018)
923
Regular Article
Synthesis, Antimycobacterial Evaluation and Docking Studies of Some
7-Methyl-5,6,7,8-tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-
ones
Narender Malothu,a Umasankar Kulandaivelu,b Malathi Jojula,c Shravan Kumar Gunda,d and
,a,†
Raghuram Rao Akkinepally*
a Medicinal Chemistry Division, University College of Pharmaceutical Sciences; Kakatiya University,
b
Warangal-506009, India: KL College of Pharmacy, KLEF Deemed to Be University; Vaddeswaram, Guntur-522502,
c
India: Department of Microbiology, Sri Shivani College of Pharmacy; Warangal-506009, India: and d Bioinformatics
Division, Osmania University; Hyderabad-500007, India.
Received December 12, 2017; accepted July 10, 2018
Two series of 3-substituted-7-methyl-5,6,7,8-tetrahydropyrido[4′,3′:4,5] thieno[2,3-d]pyrimidin-4(3H)-
one (6a–k) and 3-substituted-7,2-dimethyl-5,6,7,8-tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-
1
one (7a–k) derivatives were synthesized and characterized using spectral data i.e., IR, H-, 13C-NMR, Mass
and CHN elemental analyses. The synthesized compounds were evaluated for antibacterial activity against
each of two strains of Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Esch-
erichia coli and Klebsiella pneumoniae) bacteria and antimycobacterial activity screened against two strains
i.e., Mycobacterium tuberculosis (MTB) H37Rv and an isoniazid-resistant clinical sample. Further to validate
potentiality of our design was analyzed using molecular docking studies by taking crystal structure of MTB
pantothenate synthetase (MTB-PS) (PDB: 3IVX). In this study, some compounds 6k (Minimum Inhibitory
Concentration (MIC): MIC-22µM), 7d (MTB: MIC-22µM) and 7k (MTB: MIC-11µM) showed potential anti-
bacterial and antimycobacterial activities.
Key words antimycobacterial activity; isoniazid; Mycobacterium tuberculosis H37Rv; pantothenate synthe-
tase; 5,6,7,8-tetrahydropyrido[4′,3′:4,5]thieno(2,3-d)pyrimidine-4(3H)-one
Tuberculosis (TB) is considered as a serious public health such as 6-benzyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-
threat worldwide, as current therapy is limited due to the carboxamide (A, SID 92104095; IC50=3.3 µg/mL),6) 6-acetyl-
emergence of multi-drug resistance (MDR) and extensively 4,5,6,7-tetrahydro thieno[2,3-c]pyridine-3-carboxamide (B,
drug resistance (XRD), regimen therapy, and severe side SID 92097880; IC50=0.5µg/mL))6) derivatives, as de-
effects of existing drugs and long duration of therapy.1,2) scribed earlier.5) In addition, Rashmi et al. reported po-
Moreover, TB is more widespread due to its coincidence tentiality of some thieno[2,3-d]pyrimidines (C) on My-
with AIDS and Human Immunodeficiency Virus (HIV) co- cobacterium.7) Narayana et al. reported the antibacterial
infection.3) Development of drug resistance (MDR and XDR) activity of some 4,5,6,7-tetrahydro[1]benzothieno[2,3-d]-
to widely used first line drugs is an obstacle in the treatment pyridimidine-4(3H)-ones (D).8) These studies proved the
and control programs of this disease. Resistance to isoniazid essentiality of 4,5,6,7-tetrahydrothieno[2,3-c]pyridine (A, B)
(INH) is more predominant in MDR TB as about 30% of nucleus and arylidineamino side chain at 3rd or 4th posi-
clinical isolates found to be resistant to it, worldwide. Several tion in C and D in their antibacterial and antimycobacterial
decades of extensive research resulted in identification and activity (Fig. 1). In the design of molecules, both the struc-
development of only few drugs such as bedaquiline and dela- tural features were adopted. The 3-amino-7-methyl-5,6,7,8-
manide, which were approved as drugs of choice in drug re- tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one
sistant (MDR and XDR) TB. Several other novel drug candi- was considered as a key structure for the synthesis. The bulky
dates for drug resistant TB such as oxazolidinones (linezolid), (benzyl) group present in the previous series5) was substituted
nitroimidazoles (PA-824) and ethylenediamines (SQ-109) etc., with a small (methyl) group at 7th position of 5,6,7,8-tetra-
are currently under clinical development.4) There is an urgent hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidine nucleus. Au-
need of shorter and simple regimens, effective, safe and well relio et al. also reported the allosteric modulation effects
tolerated drugs for drug-resistant and drug-susceptible TB.
of 2-amino-4,5,6,7-tetrahydrothieno[2,3-c]pyridines on A1
In view of development of hetero-fused thieno[2,3-d]- adenosine receptor.9) Modifications at 7th position with small
pyrimidine-4(3H)-one analogues various recent reports and medium pharmacophores such as N-methyl, N-benzyl
prompted us to continue our studies by retaining and N-ethoxycarbonyl resulted differences in their biologi-
4,5,6,7-tetrahydrothieno[2,3-c]pyridine as basic nucleus.5) cal activity. As per their studies, it was due to increase in
It was a common feature in some reported Mycobacterium basicity with N-methyl substitution. Although, the structure
tuberculosis Pantothenate synthetase (MTB-PS) inhibitors activity relationship was described for A1 adenosine receptor
modulation, the significance of 7th substitution was consid-
† Present address: National Institute of Pharmaceutical Education and Re-
ered in this study and attempted with these modifications
perhaps it could show a better antimycobacterial activity. In
search (NIPER), Sector 67; S.A.S. Nagar (Mohali)-160 062, Punjab, India.
*To whom correspondence should be addressed. e-mail: raghumed@gmail.com
© 2018 The Pharmaceutical Society of Japan

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Chem. Pharm. Bull.
Vol. 66, No. 10 (2018)
this direction our studies are continued on the development reported procedure9,10) which gave the product in 85% of yield.
of novel hetero-fused thieno[2,3-d]pyrimidine analogues The compound 3 was converted to iminoester derivatives
against drug-resistant TB (INH-resistant TB).5) Two series by heating under reflux in triethylorthoformate and triethy-
of molecules 7-methyl-3-(substituted-aryledineamino)-5,6,7,8- lorthoacetate, which gave thick brown oily products 4a and
tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-ones 4b, respectively. Compounds 4a and 4b were treated with
(6a–k)
and
2,7-dimethyl-3-(substituted-aryledineamino)- hydrazine hydrate5,11–13) to get their cyclized products 5a and
2-methyl-5,6,7,8-tetrahydropyrido [4′,3′:4,5]thieno[2,3-d]pyrim 5b. In IR spectrum compound 5b showed two characteristic
idin-4(3H)-ones (7a–k) have been synthesized and evaluated signals at 3450cm−1 and 3300cm−1 assignable to N–H stretch-
for their antitubercular activity. Initial antibacterial screening ing for 3-NH2 group and another signal at 1670cm−1 assign-
was performed against each of two Gram-positive (Bacillus able to C=O stretching of carbonyl group of pyrimidine ring.
subtilis and Staphylococcus aureus) and Gram-negative (Esch- The 1H-NMR spectrum of compound 5b showed a singlet
erichia coli and Klebsiella pneumonia) bacteria. The antimy- at δ=2.20ppm which could be assignable to methyl (2-CH3)
cobacterial activity was conducted for selected compounds group of pyrimidinone ring. The presence of another broad
based on results obtained in initial antibacterial screening. singlet at the δ=5.13ppm could be assignable to primary
Mycobacterium tuberculosis (MTB) H37Rv and an INH-resis- amino functionality.
tant clinical sample were used as standard and test organisms.
Further, in silico binding interactions of these analogues
Table 1. Physical Data of Synthesized Compounds 6a–k and 7a–k
were studied using target protein MTB-PS (PDB: 3IVX) with
the help of Molegro Virtual Docker (MVD) software. These
investigations indicated that some of the compounds expressed
promising in vitro antibacterial and antimycobacterial activi-
ties against the test strains.
Comp.
Code
Mol. Wt. Melting range Yield
R
R1
Results and Discussion
Chemistry The synthesis
(M)
(°C)
(%)
of
target
compounds
6a
6b
6c
6d
6e
6f
H
H
H
H
H
H
H
H
H
H
H
-C6H5
324
358
343
350
354
340
414
369
330
314
392
338
372
355
363
368
354
428
383
312
328
406
164–166
196–198
180–182
236–238
168–170
220–222
192–194
159–161
120–122
156–158
190–192
185–187
153–155
230–232
200–202
173–175
218–220
198–200
154–156
178–180
172–174
181–183
87
78
64
67
80
65
67
72
66
80
82
85
71
65
68
82
76
70
78
70
79
80
7-methyl-3-(substituted-aryledineamino)-5,6,7,8-tetra-
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-ones (6a–
k) and 2,7-dimethyl-3-(substituted-aryledineamino)-5,6,7,8-
tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-ones
(7a–k) was achieved as shown in Chart 1.
The requisite key starting material 3 was synthesized by
Gewald Reaction (GR) using N-methyl-4-piperidone (1),
elemental sulphur and ethylcyanoacetate (2) by following a
4-ClC6H4
4-FC6H4
4-CNC6H4
4-OCH3C6H4
4-OHC6H4
6g
6h
6i
3,4,5-(OCH3)3C6H2
2-NO2C6H4
Thiophene-2-yl
Furan-2-yl
6j
6k
7a
7b
7c
7d
7e
7f
2,6-Cl2C6H3
CH3 -C6H5
CH3 4-ClC6H4
CH3 4-FC6H4
CH3 4-CNC6H4
CH3 4-OCH3C6H4
CH3 4-OHC6H4
CH3 3,4,5-(OCH3)3C6H2
CH3 2-NO2C6H4
CH3 Thiophene-2-yl
CH3 Furan-2-yl
CH3 2,6-Cl2C6H3
7g
7h
7i
7j
Fig. 1. General Structures of Some Potent Antibacterial Agents (A, B:
MTB-PS Inhibitors)
7k
i) S8, morpholine, ethanol, reflux, 1–2h; ii) Triethylorthoformate/triethylorthoacetate, reflux, 2–4h; iii) NH2NH2H2O, ethanol, stir, 1–2h; iv) R1CHO, glacial CH3COOH,
ethanol, reflux, 12h.
Chart 1. General Chart for Synthesis of Compounds 6a–k and 7a–k

Vol. 66, No. 10 (2018)
Chem. Pharm. Bull.
925
Table 2. Antibacterial Activity (MIC) Data of Test Compounds 6a–k and 7a–k
MIC (µM)
Comp. Code
R
R1
S. aureus
B. subtilis
E. coli
K. pneumoniae
MTCC 96
MTCC 441
MTCC 443
MTCC 109
6a
6b
6c
6d
6e
6f
H
-C6H5
NA
43.64
46
NA
43.64
46
NA
21.82
23
NA
87.29
46
H
4-ClC6H4
H
4-FC6H4
H
4-CNC6H4
4-OCH3C6H4
4-OHC6H4
3,4,5-(OCH3)3C6H2
2-NO2C6H4
Thiophene-2-yl
Furan-2-yl
2,6-Cl2C6H3
-C6H5
48
48
24
48
H
44.1
NA
NA
84
88.2
NA
NA
84
44.1
NA
NA
84
NA
NA
NA
84
H
6g
6h
6i
H
H
H
48
48
24
48
6j
H
98
98
98
<98
22
6k
7a
7b
7c
7d
7e
7f
H
22
22
11
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
—
NA
44
NA
44
NA
22
NA
44
4-ClC6H4
4-FC6H4
46
46
23
46
4-CNC6H4
4-OCH3C6H4
4-OHC6H4
3,4,5-(OCH3)3C6H2
2-NO2C6H4
Thiophene-2-yl
Furan-2-yl
2,6-Cl2C6H3
—
24
24
12
24
44
44
22
44
NA
NA
162
28
NA
NA
162
28
NA
NA
162
28
NA
NA
162
28
7g
7h
7i
7j
50
50
50
50
7k
Std
Ctrl
21
21
10
21
<1
NA
<1
NA
<1
NA
<1
NA
—
—
Std.=Streptomycin; Ctrl=N,N-dimethylformamide (DMF) in water (25% v/v); NA=Not active.
In the last step different arylidineamino analogues 6a–k and (MTCC-109) using streptomycin as a reference. Broth micro
7a–k were prepared by condensation of 5a and 5b with differ- dilution method15,16) was employed for determination of mini-
ently substituted aromatic aldehydes following some reported mum inhibitory concentration (MIC) for all test compounds.
protocols.5,7,8,14) The IR spectra of compound 6a–k and 7a–k The MIC (µM) data of all the compounds were tabulated in
showed characteristic signals of C=O stretching and C=N Table 2.
stretching (-imine). The loss of strong N–H stretching signals
Among all the synthesized compounds, 6b, 6c, 6d, 6i,
of 3-NH2 group was noticeable which revealed the formation 6k, 7b, 7c, 7d and 7k exhibited good activity with MIC
1
of imine. The H-NMR spectra for compounds 6a–k showed in the range of 11–24µg/mL against E. coli and rest of the
characteristic singlet at δ=9.4–10.2ppm could be assignable compounds showed moderate to less activity. The structure
for single proton of imine (–N=CH) and another sharp singlet activity relationship reveals that presence of thieno(2,3-d)-
at δ=8.2–8.3ppm could be assignable to single proton (2-H) pyrimidine-4-one ring with 3-arylidineamino side chain skel-
of pyrimidinone ring. Compounds 7a–k showed singlet at eton is crucial for biological activity. In general, the arylidin-
δ=9.2–10.2ppm could be assignable for single proton of imine eamino side chain bearing substituted phenyl and heterocyclic
(–N=CH) and another singlet at δ=2.59–2.63ppm could be groups showed more activity over unsubstituted analogues.
assignable for methyl (2-CH3) protons of pyrimidinone ring. Phenyl ring substituted with electron withdrawing groups such
The mass spectra (Electron Spray Ionization (ESI) and Elec- as chloro (4-Cl: 6b, 7b; 2,6-dichloro: 6k, 7k), flouro (4-F: 6c,
tron Impact (EI) mode) showed the molecular ion (M+, M++1, 7c) (excepting 4-methoxy: 6e, 7e) and also with thiophene
M++2) peaks for all the compounds. The halogenated com- (6i, 7i) system exhibited better activity when compared to
pounds showed the isotopic peaks (M++1 and M++2), which electron donating groups such as hydroxyl (4-OH: 6f, 7f), 3,
further confirms the presence of chlorine (Cl) as a substituent, 4, 6-trimethoxyl (6g, 7g). However nitro (2-NO2) containing
in compounds 6b, 6k, 7b and 7k. The physical data of all the compounds (6h, 7h) showed less activity. Compounds possess-
final compounds was shown in Table 1.
ing 2,6-dichloro (6k, 7k) substitution on phenyl ring exhibited
Antibacterial Activity All the newly synthesized com- potent activity on all the test organisms (Gram-positive and
pounds 6a–k and 7a–k were assessed for their in vitro Gram-negative bacteria) used. Variations in the phenyl substi-
antibacterial activity against S. aureus (MTCC-96), B. sub- tution might have altered the lipophilic character of molecules
tilis (MTCC-441), E. coli (MTCC-443) and K. pneumoniae which is an important feature for permeability across the

926
Chem. Pharm. Bull.
Vol. 66, No. 10 (2018)
Table 3. Antimycobacterial Activity (in Vitro) of Test Compounds
MIC (µM)
Comp. Code
R
R1
MTB H37Rv
Clinical sample of MTB
14d
21d
14d
21d
6b
6c
H
4-ClC6H4
4-FC6H4
4-CNC6H4
2,6-Cl2C6H3
4-ClC6H4
4-FC6H4
4-CNC6H4
4-OCH3C6H4
Thiophene-2-yl
2,6-Cl2C6H3
—
46
88
180
22
24
25
22
84
98
11
46
88
180
22
24
25
22
84
98
11
46
88
180
22
24
25
22
84
98
11
4
46
88
180
22
24
25
22
84
98
11
4
H
6d
H
6k
H
7b
CH3
CH3
CH3
CH3
CH3
CH3
—
7c
7d
7e
7i
7k
Std1
Std2
Std3
Std4
Ctrl
0.1
0.1
—
—
2
4
2
2
2
—
—
4
4
4
—
—
0.09
NA
0.09
2
2
—
—
NA
NA
NA
Std1=INH; Std2=Streptomycin; Std3=Ethambutol; Std4=Rifampicin; Ctrl=DMF in water (25% v/v); NA=Not active.
Table 4. H-Bond Interactions of Biologically Active Ligands 6k, 7d and 7k
Comp code
Residue
Atom ID
PDB atom name
Ligand name
Distance
6k
Gly 158
Val 187
Thr 186
Gly 158
Val 187
Gly 158
Val 187
1163
1397
1386
1163
1397
1163
1397
N (d)
N (d)
O (d+a)
N (d)
N (d)
N (d)
N (d)
O (a)
N (a)
N (a+d)
O (a)
N (a)
O (a)
N (a)
2.93
2.70
3.14
1.65
3.09
2.60
3.11
7d
7k
bacterial cell membrane. The 4-hydroxyl (activating group) 7k, 6k instead monochloro (4-Cl) substitution in 6b, 7b en-
substituted compounds (6f and 7f) were found to be less po- hanced the biological activity. Compounds, 6c, 6d, 7e and 7i
tent might be due to their poor lipophilicity. On overall assess- exhibited poor in potency and their MIC range was observed
ment most of the compounds showed activity against E. coli at ≥46µM. The antimycobacterial activity (MIC in µM) data is
(Gram-negative bacteria). Methyl substitution at 2nd position tabulated in Table 3.
of pyrimidine ring relatively enhanced the biological activity.
Molecular Modeling The molecular docking studies
Antimycobacterial Activity Few compounds randomly were performed on target protein MTB-PS, which has been
selected for antimycobacterial studies by considering the proven to be valid drug target for rational design of new ana-
preliminary antibacterial activity data. The MTB H37Rv and logues for TB by several reports.18,19) The crystal structure of
an INH-resistant clinical sample were taken as reference and MTB-PS was retrieved from protein data bank ((PDB: 3IVX)
test organisms, respectively. The MIC was determined on (http://www.rcsb.org/pdb/explore.do?structure Id=3ivx). Li-
Middlebrook 7H9 medium supplemented with OADC using gands possessing 4-flouro (6c), 4-hydroxy (6f), 2-nitro (6h),
broth micro dilution method with the help of four well known 4-methoxy (7e) and 2,4-dichloro (6k, 7k) substitution on
drugs (INH, Streptomycin, Rifampicin and Ethambutol) as phenyl ring of arylidineamino side chain showed best docking
reference.17 The test samples were prepared by serial dilu- scores, i.e., −118.43, −118.42, −122.87, −121.03, −120.68 and
tion method in different strengths in DMF in water (25% v/v) −115.63, respectively.
as diluent. Among all the tested compounds 7k, bearing 2,
The carbonyl (C=O, H-bond acceptor) group at 4th po-
6-dichloro substitution on arylidineamino side chain showed sition in pyrimidine ring showed strong hydrogen bond
greater activity with MIC-11µM against MTB H37Rv and also interaction with Gly 158 (H-bond donor) amino acid resi-
clinical sample (INH-resistant). Other compounds bearing due in all (6a–k and 7a–k) the ligands. Another H-bond
2,6-dichloro (6k), 4-Cl (7b), 4-F (7c) and 4-CN (7d) showed interaction was observed at nitrogen (7-N) atom of the
activity in the MIC range of 22–25µM on both the strains. The 5,6,7,8-tetrahydrothieno[2,3-d]pyridine ring with Val 187
additional chloro (Cl) group at 2nd position of phenyl ring in amino acid residue (Table 4).

Vol. 66, No. 10 (2018)
Chem. Pharm. Bull.
927
Fig. 2. Snapshots of the Typical Binding Interactions of Ligands 7b (A) and 7k (B) with Active Site of MTB-PS, Hydrogen Bond Interactions of
C=O Group with Residue of Gly 158 and Nitrogen (7-N) with Val 187
Additionally, the steric interactions observed for all the by s (singlet), d (doublet), t (triplet), q (quartet), brs (broad sin-
molecules with amino acid residues such as Leu 50, Val 184, glet), dd (double doublet) and m (multiplet). MS were recorded
Pro 185, Gln164 and Pro 38. All these molecules 6a–k and on ESI and EI mode using QSTARXL hybrid MS/MS system
7a–k lack additional π–π stacking and van der Waals interac- (Applied Bio-systems, U.S.A.), Central Instrumentation Labo-
tions due to presence of N-methyl group at 7th position, hence ratory, Indian Institute of Chemical Technology, Hyderabad,
they showed less potency compared to N-benzyl analogues.5) India. Elemental analysis was carried out using vario MICRO
The binding mode and orientation pattern at active site were CUBE Elementar (2mgChem80s method), Kakatiya Univer-
analyzed for all molecules. The docking poses of the experi- sity, Warangal. All the chemicals used in the synthesis were
mentally more potent molecules 7b and 7k were showed in procured from Aldrich Company Ltd. (Bengaluru, India) and
Fig. 2.
Himedia Chemicals (Mumbai, India). All the solvents used
were purchased from SD Fine Chemicals Ltd. (Mumbai, India)
and were employed without further purification.
Conclusion
In conclusion this study deals with the design
Ethyl-2-amino-6-methyl-4,5,6,7-tetrahydrothieno[2,3-c]-
and synthesis of novel analogues of 7-methyl-5,6,7,8- pyridine-3-carboxylate (3) N-Methyl-4-piperidone (1) (5g,
tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-ones. 26.42mmol), ethyl cyanoacetate (2) (3.09mL, 29.06mmol)
Among all the compounds 6a, 6b, 6c, 6d, 6k, 7b, 7c, 7d, 7e and sulphur (1.02g, 31.70mmol) were suspended in ethanol
and 7k showed promising antibacterial activity against E. coli (55mL). Morpholine (4.62mL, 52.84mmol) was added and the
in the MIC range 10–24µM and compounds 6k, 7b, 7c, 7d mixture was heated under reflux gently with stirring for 2h.
and 7k further showed antimycobacterial activity in the MIC The cooled solution was diluted with water and extracted with
range 10–25µM against MTB H37Rv and an INH-resistant dichloromethane (3×50mL). The combined organic layers
clinical sample. Among these compound 7k was found to be were washed with water, then brine, dried (MgSO4), filtered
more potent (MIC-11µM). Further the molecular docking stud- and concentrated. The resultant residue was triturated with hot
ies helped in knowing the binding modes of core structure methanol (20mL) and washed with ice cold methanol to afford
with active sites and the docking scores obtained were cor- the desired product as an off white powder.
related with the MIC values (µM) of most of the compounds.
Yield, 7.1g (85%). mp 110–111°C. IR (KBr) cm−1: 3344,
Further investigations are in progress on enzyme inhibitory 3254 (N–H, str), 2986, 2878 (C–H, str), 1685 (C=O, str).
activity, cytotoxicity and pharmacokinetic properties to vali- 1H-NMR (CDCl3) δ (ppm): 6.03 (2H, brs, 2-NH2), 4.27 (2H, q,
date these results.
J=7.2Hz, CH2 of carboxylate), 3.39 (2H, s, 7-CH2), 2.85 (2H,
t, J=5.7Hz, 5-CH2), 2.68 (2H, t, J=5.8Hz, 4-CH2), 2.45 (3H,
s, 7-NCH3), 1.34 (3H, t, J=7.2Hz, –CH3 of carboxylate). ESI-
Experimental
Chemistry Melting points of all the compounds were MS (m/z; %): 241 (M++1; 100).
determined in open capillaries on melting point apparatus
3-Amino-7-methyl-5,6,7,8-tetrahydropyrido[4′,3′:4,5]-
(Biotechniques India-BTI-34), and are uncorrected. Purity thieno[2,3-d]pyrimidin-4(3H)-one (5a) A solution of 3
and homogeneity was verified by pre-coated TLC plates (E. (1⋅10g, 57mmol) in triethylorthoformate (5mL) was heated
Merck silica gel 60F254). IR spectra were recorded using KBr under reflux for 2–4h. Excess triethylorthoformate was re-
pellet method on Bruker spectrophotometer and Perkin-Elmer moved in vacuo. The residue was treated with ethyl acetate in
1
FTIR 240-C (υmax in cm−1). The H-NMR and 13C-NMR was hexane (20% v/v) and dried to obtain light brown oily product
recorded on a Bruker spectrometer 500MHz and 400MHz (4a). It was used directly in next step without purification. A
respectively using tetramethylsilane (TMS) as internal stan- mixture of 4a and hydrazine hydrate (1mL) in 10mL of ab-
dard, Central Instrumentation Laboratory, Indian Institute of solute ethanol was stirred at room temperature for 1–2h. The
Chemical Technology, Hyderabad, India. The chemical shifts separated fine solid was filtered, washed with ethanol and pu-
(δ) are reported in part per million (ppm) relative to TMS rified by recrystallization from ethanol to afford analytically
using CDCl3 as solvent. Signal multiplicities are represented pure pale yellow granules.

928
Chem. Pharm. Bull.
Vol. 66, No. 10 (2018)
Yield, 0.76g (71%). mp 194–196°C. IR (KBr) cm−1: 3450, 2.56 (3H, s, 7-NCH3), 2.79 (2H, t, J=5.12Hz, 5-CH2), 3.18
1
3300 (N–H, str), 2910 (C–H, str), 1670 (C=O, str). H-NMR (2H, t, J=5.22Hz, 6-CH2), 3.66 (2H, s, 8-CH2), 7.78 (2H, d,
(CDCl3) δ (ppm): 2.50 (3H, s, 7-NCH3), 2.80 (2H, t, J=6Hz, J=8.86Hz, 3′,5′-Ar-H), 7.94 (2H, d, J=8.84Hz, 2′,6′-Ar-H),
5-CH2), 3.20 (2H, t, J=6Hz, 6-CH2), 3.67 (2H, s, 8-CH2), 5.13 8.28 (1H, s, 2-H of pyrimidinone), 9.92 (1H, s, N=CH).
(2H, brs, 3-NH2), 8.20 (1H, s, 2-H pyrimidinone). ESI-MS 13C-NMR (CDCl3) δ (ppm): 26.12, 45.47, 51.84, 53.73, 115.24,
(m/z; %): 236 (M++1; 100).
118.08, 122.87, 128.76, 130.23, 132.51, 132.61, 137.44, 146.02,
3-Amino-2,7-dimethyl-5,6,7,8-tetrahydropyrido[4′,3′:4,5]- 156.76, 159.70, 160.69. ESI-MS (m/z; %): 350 (M++1; 100).
thieno[2,3-d]pyrimidin-4(3H)-one (5b) A solution of 3 Anal. Calcd for C18H15N5OS: C, 61.87; H, 4.33; N, 20.04.
(1⋅10g, 57mmol) in triethylorthoacetate (5mL) was heated Found: C, 61.58; H, 4.76; N, 19.82.
under reflux for 2–4h. Excess triethyorthoacetate was re-
3-((4-Methoxybenzylidene)amino)-7-methyl-5,6,7,8-tetra-
moved in vacuo. The residue was treated with ethyl acetate in hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (6e)
hexane (20% v/v) and dried to obtain light brown oily product [El-Kashef et al.].11)
(4b). It was used directly in next step without purification. A
3-((4-Hydroxybenzylidene)amino)-7-methyl-5,6,7,8-tetra-
mixture of 4b and hydrazine hydrate (1mL) in 10mL of ab- hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (6f)
solute ethanol was stirred at room temperature for 1–2h. The [El-Kashef et al.].11)
separated fine solid was filtered, washed with ethanol and pu-
7-Methyl-3-((3,4,5-trimethoxybenzylidene)amino)-5,6,7,8-
rified by recrystallization from ethanol to afford analytically tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one
pure pale yellow granules.
(6g)
Yield, 0.84g (74%). mp 200–202°C. IR (KBr) cm−1: 3450,
Yield, 0.28g (67%). mp 192–194°C. IR (KBr) cm−1: 3059
1
3300 (N–H, str), 2910 (C–H, str), 1670 (C=O, str). H-NMR (aromatic C–H, str), 2937, 2776 (aliphatic C–H, str), 1672
(CDCl3) δ (ppm): 2.20 (3H, s, 2-CH3 of pyrimidinone), 2.50 (C=O, str), 1576 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.52
1
(3H, s, 7-NCH3), 2.80 (2H, t, J=5.82Hz, 5-CH2), 3.20 (2H, (3H, s, 7-NCH3), 2.81 (2H, t, J=5.86Hz, 5-CH2), 3.22 (2H, t,
t, J=5.73Hz, 6-CH2), 3.67 (2H, s, 8-CH2), 5.13 (2H, brs, J=5.89Hz, 6-CH2), 3.69 (2H, s, 8-CH2), 3.94 (6H, s, 3′,5′-Ar-
3-NH2). ESI-MS (m/z; %): 250 (M++1; 85).
OCH3), 3.96 (3H, s, 4′-Ar-OCH3), 7.12 (2H, s, 2′,6′-Ar-H), 8.26
7-Methyl-3-(substituted-aryledineamino)-5,6,7,8-tetra- (1H, s, 2-H of pyrimidinone), 9.44 (1H, s, N=CH). ESI-MS
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (m/z; %): 415 (M++1; 100). Anal. Calcd for C20H22N4O4S: C,
(6a–k)
General Method
57.96; H, 5.35; N, 13.52. Found: C, 57.92; H, 5.46; N, 13.68.
7-Methyl-3-((2-nitrobenzylidene)amino)-5,6,7,8-tetra-
A
mixture of 5a (0.001M) and appropriate aldehyde hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (6h)
(0.001M) in catalytic amount of glacial acetic acid in 10mL of
Yield, 0.27g (72%). mp 159–161°C. IR (KBr) cm−1: 3019
absolute ethanol was heated under reflux for 2–6h. On cool- (aromatic C–H, str), 2932, 2774 (aliphatic C–H, str), 1686
ing, the separated solid was filtered, washed with cold ethanol (C=O, str), 1524 (C=N, str). 1H-NMR (CDCl3) δ (ppm):
and recrystallized from acetic acid: ethanol to afford desired 2.51 (3H, s, 7-NCH3), 2.79 (2H, t, J=5.88Hz, 5-CH2), 3.18
product.
(2H, t, J=5.88Hz, 6-CH2), 3.67 (2H, s, 8-CH2), 7.72 (1H, dt,
3-(Benzylideneamino)-7-methyl-5,6,7,8-tetrahydropyrido J=8.02Hz, 4′-Ar-H), 7.78 (1H, dt, J=8.02Hz, 5′-Ar-H), 8.18
[4′,3′:4,5]thieno[2,3-d]pyrimidin-4 (3H)-one (6a) [El-Kashef (2H, dd, J=8.12, 1.52Hz, 3′,6′-Ar-H), 8.28 (1H, s, 2-H of py-
et al.].11)
rimidinone),10.18 (1H, s, N=CH). 13C-NMR (CDCl3) δ (ppm):
3-((4-Chlorobenzylidene)amino)-7-methyl-5,6,7,8-tetrahy- 26.04, 45.43, 51.84, 53.72, 122.94, 124.86, 128.49, 129.42,
dropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (6b) [El- 130.36, 131.97, 132.28, 133.73, 145.57, 148.86, 156.20, 159.57,
Kashef et al.].11)
160.75. ESI-MS (m/z; %): 370 (M++1; 100). Anal. Calcd for
3-((4-Fluorobenzylidene)amino)-7-methyl-5,6,7,8- C17H15N5O3S: C, 55.27; H, 4.09; N, 18.96. Found: C, 55.42; H,
tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one 4.46; N, 18.88.
(6c)
7-Methyl-3-((thiophen-2-ylmethylene)amino)-5,6,7,8-
Yield, 0.22g (64%). mp 180–182°C. IR (KBr) cm−1: 3069, tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one
3031 (aromatic C–H, str), 2919 (aliphatic C–H, str), 1672 (6i)
(C=O, str), 1601 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.59
Yield, 0.22g (66%). mp 120–122°C. IR (KBr) cm−1: 3051
1
(3H, s, 7-CH3), 2.79 (2H, t, J=5.88Hz, 5-CH2), 3.18 (2H, t, (aromatic C–H, str), 2938, 2785 (aliphatic C–H, str), 1683
1
J=5.94Hz, 6-CH2), 3.67 (2H, s, 8-CH2), 7.18 (2H, t, J=8.62Hz, (C=O, str), 1581 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.51
3′,5′-Ar-H), 7.85 (2H, dd, J=5.4, 5.4Hz, 2′,6′-Ar-H), 8.24 (1H, (3H, s, 7-NCH3), 2.81 (2H, t, J=5.88Hz, 5-CH2), 3.19 (2H, t,
s, 2-H of pyrimidinone), 9.53 (1H, s, N=CH). 13C-NMR J=5.79Hz, 6-CH2), 3.68 (2H, s, 8-CH2), 7.26 (1H, dt, J=5,
(CDCl3) δ (ppm): 26.12, 45.48, 51.89, 53.76, 116.34–116.34 (d), 1.12Hz, 4′-Ar-H of thiophene), 7.54 (1H, dd, J=3.88, 1.53Hz,
122.92, 129.31–129.34 (d), 130.13, 130.71–130.80 (d), 132.07, 3′-Ar-H of thiophene), 7.58 (1H, dd, J=5.01, 3.12Hz, 5′-Ar-H
145.57, 156.37, 160.86, 162.43, 164.01, 166.53. ESI-MS (m/z; of thiophene), 8.25 (1H, s, 2-H of pyrimidinone), 9.78 (1H,
%): 343 (M++1; 100). Anal. Calcd for C17H15FN4OS: C, 59.63; s, N=CH). 13C-NMR (CDCl3) δ (ppm): 25.80, 49.87, 51.64,
H, 4.42; N, 16.36. Found: C, 58.92; H, 4.46; N, 16.88.
62.01, 112.54, 118.74, 127.36, 128.44, 129.14, 130.28, 137.96,
4-(((7-Methyl-4-oxo-5,6,7,8-tetrahydropyrido[4′,3′:4,5]- 146.90, 153.58, 155.08, 161.19. ESI-MS (m/z; %): 331 (M++1;
thieno[2,3-d]pyrimidin-3(4H)-yl)imi no)methyl)benzonitrile 100). Anal. Calcd for C15H14N4OS2: C, 54.52; H, 4.27; N, 16.96.
(6d)
Found: C, 54.82; H, 4.46; N, 16.88.
3-((Furan-2-ylmethylene)amino)-7-methyl-5,6,7,8-tetra-
Yield, 0.23g (67%). mp 236–238°C. IR (KBr) cm−1: 3099
(aromatic C–H, str), 2955 (aliphatic C–H, str), 2229 (CN, str), hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (6j)
1
1674 (C=O, str), 1545 (C=N, str). H-NMR (CDCl3) δ (ppm):
Yield, 0.25g (80%). mp 156–158°C. IR (KBr) cm−1: 3104

Vol. 66, No. 10 (2018)
Chem. Pharm. Bull.
929
(aromatic C–H, str), 2920, 2841 (aliphatic C–H, str), 1662
(C=O, str), 1539 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.54 hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (7c)
(3H, s, 7-NCH3), 2.82 (2H, t, J=5.82Hz, 5-CH2), 3.20 (2H, t,
3-((4-Fluorobenzylidene)amino)-2,7-dimethyl-5,6,7,8-tetra-
1
Yield, 0.23g (65%). mp 230–232°C. IR (KBr) cm−1: 3069
J=5.83Hz, 6-CH2), 3.68 (2H, s, 8-CH2), 6.58 (1H, dd, J=3.48, (aromatic C–H, str), 2919 (aliphatic C–H, str), 1672 (C=O,
1
1.76Hz, 4′-Ar-H of furan), 7.02 (1H, d, J=3.22Hz, 5′-Ar-H of str), 1601 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.50 (3H,
furan), 7.69 (1H, d, J=1.55Hz, 3′-Ar-H of furan), 8.29 (1H, s, s, 7-CH3), 2.59 (3H, s, 2-CH3 of pyrimidinone), 2.77 (2H, t,
2-H of pyrimidinone), 9.54 (1H, s, N=CH). EI-MS (m/z; %): J=6Hz, 5-CH2), 3.13 (2H, t, J=6Hz, 6-CH2), 3.63 (2H, s,
314 (M+; 62), 315 (M++1; 12). Anal. Calcd for C15H14N4O2S: 8-CH2), 7.18 (2H, t, J=8.8Hz, 3′,5′-ArH), 7.90 (2H, dd, J=5.6,
C, 57.31; H, 4.49; N, 17.82. Found: C, 57.72; H, 4.46; N, 16.18. 5.6Hz, 2′,6′-Ar-H), 8.91 (1H, s, N=CH). 13C-NMR (CDCl3)
3-((2,4-Dichlorobenzylidene)amino)-7-methyl-5,6,7,8-tetra- δ (ppm): 22.52, 25.97, 45.50, 51.94, 53.73, 116.14–116.36 (d),
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (6k)
120.85, 128.90–128.93 (d), 129.87, 130.24, 131.00–131.09 (d),
Yield, 0.32g (82%). mp 190–192°C. IR (KBr) cm−1: 153.99, 155.51, 161.19, 164.19, 165.76, 166.72. EI-MS (m/z; %):
3083 (aromatic C–H, str), 2938, 2783 (aliphatic C–H, str), 356 (M+; 38), 234 (M+-C7H4Cl2N; 45), 192 (M+-C9H4Cl2NO;
1
1681(C=O, str), 1582 (C=N, str). H-NMR (CDCl3) δ (ppm): 100). Anal. Calcd for C17H15FN4OS: C, 59.63; H, 4.42; N,
2.50 (3H, s, 7-NCH3), 2.79 (2H, t, J=5.98Hz, 5-CH2), 3.19 16.36. Found: C, 59.22; H, 4.86; N, 16.06.
(2H, t, J=5.56Hz, 6-CH2), 3.71 (2H, s, 8-CH2), 7.34 (1H, dd,
4-(((2,7-Dimethyl-4-oxo-5,6,7,8-tetrahydropyrido[4′,3′:4,5]-
J=1.6, 2.5Hz, 5′-Ar-H), 7.47 (1H, d, J=2Hz, 3′-Ar-H), 8.13 thieno[2,3-d]pyrimidin-3(4H)-yl)imino)methyl)benzonitrile
(1H, d, J=8.2Hz, 6′-Ar-H), 8.23 (1H, s, 2-H of pyrimidinone), (7d)
10.09 (1H, s, N=CH). 13C-NMR (CDCl3) δ (ppm): 26.14,
Yield, 0.25g (68%). mp 200–202°C. IR (KBr) cm−1: 3050
45.44, 51.84, 53.73, 122.93, 127.74, 128.45, 129.60, 129.98, (aromatic C–H, str), 2981 (aliphatic C–H, str), 2234 (CN,
1
130.30, 132.17, 136.80, 138.56, 145.80, 156.40, 158.37, 160.67. str), 1676 (C=O, str), 1550 (C=N, str). H-NMR (CDCl3) δ
ESI-MS (m/z; %): 394 (M++2; 35), 392 (M+; 100). Anal. Calcd (ppm): 2.52 (3H, s, 7-NCH3), 2.63 (3H, s, 2-CH3 of pyrimidi-
for C17H14Cl2N4OS: C, 51.92; H, 3.59; N, 14.25. Found: C, none), 2.79 (2H, t, J=5.22Hz, 5-CH2), 3.14 (2H, t, J=5.54Hz,
51.72; H, 3.46; N, 14.48.
6-CH2), 3.64 (2H, s, 8-CH2), 7.79 (2H, d, J=8.82Hz,
2,7-Dimethyl-3-(substituted-aryledineamino)-5,6,7,8- 3′,5′-Ar-H), 8.01 (2H, d, J=8.89Hz, 2′,6′-Ar-H), 9.22 (1H,
tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)- s, N=CH). 13C-NMR (CDCl3) δ (ppm): 22.64, 25.98, 45.48,
one (7a–k)
51.88, 53.69, 115.56, 118.02, 120.87, 129.02, 129.96, 130.68,
General Method
132.63, 136.97, 153.66, 155.65, 161.10, 163.32. ESI-MS (m/z;
A mixture of 5b (0.001M) and appropriate aldehyde %): 364 (M++1; 100). Anal. Calcd for C19H17N5OS: C, 62.79;
(0.001M)) in catalytic amount of glacial acetic acid in 10mL H, 4.71; N, 19.27. Found: C, 62.42; H, 4.86; N, 19.66.
of absolute ethanol was heated under reflux for about 2–6h.
3-((4-Methoxybenzylidene)amino)-2,7-dimethyl-5,6,7,8-
On cooling, the separated solid was filtered, washed with cold tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one
ethanol and recrystallized from acetic acid: ethanol to afford (7e)
desired product.
3-(Benzylideneamino)-2,7-dimethyl-5,6,7,8-tetra- (aromatic C–H, str), 2921 (aliphatic C–H, str), 1684 (C=O,
Yield, 0.31g (82%). mp 173–175°C. IR (KBr) cm−1: 3095
1
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (7a)
str) 1567 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.53 (3H, s,
Yield, 0.29g (85%). mp 185–187°C. IR (KBr) cm−1: 3066 7-NCH3), 2.60 (3H, s, 2-CH3 of pyrimidinone), 2.80 (2H, t,
(aromatic C–H, str), 2957 (aliphatic C–H, str), 1640 (C=O, J=5.82Hz, 5-CH2), 3.16 (2H, t, J=5.79Hz, 6-CH2), 3.66 (2H,
1
str), 1547 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.53 (3H, s, 8-CH2), 3.91 (3H, s, Ar-OCH3), 7.01 (2H, d, J=8.81Hz,
s, 7-NCH3), 2.62 (3H, s, 2-CH3 of pyrimidinone), 2.80 (2H, t, 3′,5′-Ar-H), 7.86 (2H, d, J=8.80Hz, 2′,6′-Ar-H), 8.75 (1H,
J=5.83Hz, 5-CH2), 3.16 (2H, t, J=5.81Hz, 6-CH2), 3.65 (2H, s, N=CH). 13C-NMR (CDCl3) δ (ppm): 22.66, 26.10, 45.46,
s, 8-CH2), 7.51 (2H, t, J=7.38Hz, 3′,5′-Ar-H), 7.56 (1H, dt, 51.91, 53.76, 55.44, 114.43, 122.92, 125.47, 130.07, 130.57,
J=2.67, 1.85Hz, 4′-Ar-H), 7.90 (2H, d, J=7.07Hz, 2′,6′-Ar-H), 131.76, 145.28, 156.19, 160.93, 163.12, 164.29. EI-MS (m/z; %):
8.94 (1H, s, N=CH). EI-MS (m/z; %): 338 (M+; 31), 339 368 (M+ ; 18), 192 (M+-C10H9O2N; 15), 57 (M+-C16H13N3O2S;
(M++1; 6). Anal. Calcd for C17H16N4OS: C, 62.94; H, 4.97; N, 100). Anal. Calcd for C19H20N4O2S: C, 61.94; H, 5.47; N, 15.21.
17.27. Found: C, 63.06; H, 4.66; N, 17.16.
Found: C, 61.58; H, 5.12; N, 15.06.
3-((4-Chlorobenzylidene)amino)-2,7-dimethyl-5,6,7,8-tetra-
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (7b)
Yield, 0.26g (71%). mp 153–155°C. IR (KBr) cm−1: 3069
3-((4-Hydroxybenzylidene)amino)-2,7-dimethyl-5,6,7,8-tetra-
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (7f)
Yield, 0.27g (76%). mp 218–220°C. IR (KBr) cm−1: 3250
(aromatic C–H, str), 2919 (aliphatic C–H, str), 1672 (C=O, (aromatic C–H, str), 2949 (aliphatic C–H, str), 1647 (C=O,
1
1
str), 1546 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.50 (3H, str), 1546 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.41 (3H,
s, 7-NCH3), 2.61 (3H, s, 2-CH3 of pyrimidinone), 2.84 (2H, s, 7-NCH3), 2.48 (3H, s, 2-CH3 of pyrimidinone), 2.71 (2H,
t, J=5.88Hz, 5-CH2), 3.18 (2H, t, J=5.91Hz, 6-CH2), 3.68 t, J=5.86Hz, 5-CH2), 2.97 (2H, t, J=5.80Hz, 6-CH2), 3.59
(2H, s, 8-CH2), 7.39 (2H, d, J=7.89Hz, 3′,5′-Ar-H), 7.50 (2H, (2H, s, 8-CH2), 6.98 (2H, d, J=5.14Hz, 3′,5′-Ar-H), 7.84 (2H,
d, J=7.98Hz, 2′,6′-Ar-H), 10.42 (1H, s, N=CH). 13C-NMR d, J=8.32Hz, 2′,6′-Ar-H), 8.67 (1H, s, N=CH), 10.47 (1H,
(CDCl3) δ (ppm): 22.52, 26.10, 45.45, 51.87, 53.74, 122.91, s, Ar-OH). 13C-NMR (CDCl3) δ (ppm): 22.51, 26.13, 45.48,
129.29, 129.72, 130.15, 131.62, 132.12, 138.41, 145.68, 156.46, 51.90, 53.77, 122.91, 129.32, 129.76, 130.18, 131.64, 132.15,
160.81, 161.98. ESI-MS (m/z; %): 374 (M++2; 33), 372 (M+; 138.45, 145.70, 156.49, 160.85, 162.03. ESI-MS (m/z; %): 355
100). Anal. Calcd for C17H15ClN4OS: C, 56.90; H, 4.21; N, (M++1; 100). Anal. Calcd for C18H18N4O2S: C, 61.00; H, 5.12;
15.61. Found: C, 56.52; H, 4.16; N, 15.16.
N, 15.81. Found: C, 61.38; H, 4.96; N, 16.12.

930
Chem. Pharm. Bull.
Vol. 66, No. 10 (2018)
1
2,7-Dimethyl-3-((3,4,5-trimethoxybenzylidene)amino)- str), 1582 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.54 (3H,
5,6,7,8-tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin- s, 7-NCH3), 2.63 (3H, s, 2-CH3 of pyrimidinone), 2.80 (2H,
4(3H)-one (7g)
t, J=5.79Hz, 5-CH2), 3.17 (2H, t, J=5.82Hz, 6-CH2), 3.66
Yield, 0.3g (70%). mp 198–200°C. IR (KBr) cm−1: 3059 (2H, s, 8-CH2), 7.39 (1H, dd, J=8.51, 1.50Hz, 5′-Ar-H), 7.51
(aromatic C–H, str), 2937 (aliphatic C–H, str), 1672 (C=O, (1H, d, J=1.99Hz, 3′-Ar-H), 8.17 (1H, d, J=8.48Hz, 6′-Ar-H),
str), 1576 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.53 (3H, 9.42 (1H, s, N=CH). 13C-NMR (CDCl3) δ (ppm): 22.51, 26.14,
1
s, 7-NCH3), 2.62 (3H, s, 2-CH3 of pyrimidinone), 2.80 (2H, 45.44, 51.84, 53.73, 122.93, 127.74, 128.45, 129.60, 129.98,
t, J=5.81Hz, 5-CH2), 3.16 (2H, t, J=5.76Hz, 6-CH2), 3.66 130.30, 132.17, 136.80, 138.56, 145.80, 156.40, 158.37, 166.67.
(2H, s, 8-CH2), 3.94 (6H, s, 3′,5′-Ar-OCH3), 3.96 (3H, s, EI-MS (m/z; %): 408 (M++2, 14), 406 (M+; 20), 234 (M+−
4′-Ar-OCH3), 7.16 (2H, s, 2′,6′-Ar-H), 8.77 (1H, s, N=CH). C7H4Cl2N; 45), 192 (M+−C9H4Cl2NO; 100). Anal. Calcd for
13C-NMR (CDCl3) δ (ppm): 22.48, 25.97, 45.47, 51.93, 53.71, C18H16Cl2N4OS: C, 53.08; H, 3.96; N, 13.76. Found: C, 52.86;
56.29, 60.99, 106.28, 120.81, 127.60, 129.85, 130.15, 142.29, H, 3.67; N, 14.52.
153.36, 153.60, 155.49, 161.21, 167.28. ESI-MS (m/z; %): 429
(M++1; 100). Anal. Calcd for C21H24N4O4S: C, 58.86; H, 5.65; were screened for their in vitro antibacterial activity against
N, 13.07. Found: C, 58.58; H, 5.26; N, 13.12. mentioned strains of Gram-positive and Gram-negative bac-
2,7-Dimethyl-3-((2-nitrobenzylidene)amino)-5,6,7,8-tetra- teria. The MIC values were determined by employing similar
Antibacterial Activity The synthesized final compounds
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (7h)
techniques of our studies,5) and the results were compared
Yield, 0.3g (78%). mp 154–156°C. IR (KBr) cm−1: with standard (streptomycin). The MIC values were expressed
3019 (aromatic C–H, str), 2932 (aliphatic C–H, str), 1686 in micro moles (µM) and the results were listed in Table 1.
(C=O, str), 1524 (C=N, str). 1H-NMR (CDCl3) δ (ppm):
Antimycobacterial Activity The MTB H37Rv and an
2.51 (3H, s, 7-NCH3), 2.62 (3H, s, 2-CH3 of pyrimidinone), INH-resistant clinical sample of Mycobacteria were used for
2.79 (2H, t, J=6Hz, 5-CH2), 3.24 (2H, t, J=6Hz, 6-CH2), screening and the MIC values were determined using a broth
3.67 (2H, s, 8-CH2), 7.66 (1H, dt, J=8.12Hz, 4′-Ar-H), micro dilution method as described in our previous protocols.5)
7.80 (1H, dt, J=8.12Hz, 5′-Ar-H), 8.20 (2H, dd, J=8.34, The stock solution of all compounds was prepared in the con-
1.46Hz, 3′,6′-Ar-H), 9.44 (1H, s, N=CH). ESI-MS (m/z; %): centration of 1mg/mL dissolved in DMF in water (25% v/v).
384 (M++1; 26), 340 (M+−C2H3O; 100). Anal. Calcd for About ten test concentrations ranging from 1000–1µg/mL
C18H17N5O3S: C, 56.38; H, 4.47; N, 18.27. Found: C, 56.48; H, were used to assess the efficacy of each compound.
4.91; N, 17.98.
Molecular Docking The molecular docking studies were
2,7-Dimethyl-3-((thiophen-2-ylmethylene)amino)-5,6,7,8- performed using Molegro Virtual Docker (MVD) tools24 on
tetrahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one targeted protein MTB-PS (PDB: 3IVX).
(7i)
Yield, 0.24g (70%). mp 178–180°C. IR (KBr) cm−1: 3051
Acknowledgments One of the authors (MN) thanks
(aromatic C–H, str), 2938, 2785 (aliphatic C–H, str), 1683 UGC-BSR (No. F.7-106/2007) for providing a merit scholar-
1
(C=O, str), 1581 (C=N, str). H-NMR (CDCl3) δ (ppm): 2.53 ship. The authors are thankful to the Principal, University
(3H, s, 7-NCH3), 2.62 (3H, s, 2-CH3 of pyrimidinone), 2.80 College of Pharmaceutical Sciences (UCPSc), Kakatiya Uni-
(2H, t, J=5.82Hz, 5-CH2), 3.16 (2H, t, J=5.80Hz, 6-CH2), versity for providing facilities and also Principal and Manage-
3.65 (2H, s, 8-CH2), 7.18 (1H, dd, J=5.00, 3.70Hz, 4′-Ar-H), ment, Sri Shivani College of Pharmacy, Warangal for permit-
7.58 (1H, dd, J=3.67, 1.01Hz, 5′-Ar-H), 7.61 (1H, td, J=4.97, ting to carry out the biological activity.
0.90Hz, 3′-Ar-H), 9.13 (1H, s, N=CH). 13C-NMR (CDCl3) δ
(ppm): 22.51, 25.76, 49.83, 51.59, 61.96, 112.49, 118.66, 127.33,
Conflict of Interest The authors declare no conflict of
128.40, 129.10, 130.25, 137.92, 146.85, 153.55, 155.02, 155.53, interest.
161.16. ESI-MS (m/z; %): 315 (M+−CO; 92), 344.9 (M++1;
45). Anal. Calcd for C16H16N4OS2: C, 55.79; H, 4.68; N, 16.27.
Found: C, 55.88; H, 4.61; N, 16.32.
Supplementary Materials The online version of this ar-
ticle contains supplementary materials.
3-((Furan-2-ylmethylene)amino)-2,7-dimethyl-5,6,7,8-tetra-
hydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidin-4(3H)-one (7j)
Yield, 0.26g (79%). mp 172–174°C. IR (KBr) cm−1: 3123
(aromatic C–H, str), 2936, 2803 (aliphatic C–H, str), 1671
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