Synthesis of some new C2 substituted dihydropyrimidines and their electrophysiological evaluation as L-/T-type calcium channel blockers

Article abstract of DOI:10.1016/j.bioorg.2019.04.009

Drugs targeting different calcium channel subtypes have strong therapeutic potential for future drug development for cardiovascular disorders, neuropsychiatric diseases and cancer. This study aims to design and synthesize a new series of C2 substituted di

Full text of DOI:10.1016/j.bioorg.2019.04.009

Accepted Manuscript
Synthesis of some new C2 substituted dihydropyrimidines and their electro-
physiological evaluation as L-/T-type Calcium Channel blockers
Mohamed Teleb, Ola H. Rizk, Fang-Xiong Zhang, Frank R. Fronczek, Gerald
W. Zamponi, Hesham Fahmy
PII:
S0045-2068(18)31478-0
DOI:
https://doi.org/10.1016/j.bioorg.2019.04.009
YBIOO 2915
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
15 December 2018
22 March 2019
6 April 2019
Please cite this article as: M. Teleb, O.H. Rizk, F-X. Zhang, F.R. Fronczek, G.W. Zamponi, H. Fahmy, Synthesis
of some new C2 substituted dihydropyrimidines and their electrophysiological evaluation as L-/T-type Calcium
Channel blockers, Bioorganic Chemistry (2019), doi: https://doi.org/10.1016/j.bioorg.2019.04.009
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Synthesis of some new C2 substituted dihydropyrimidines and their
electrophysiological evaluation as L-/T-type Calcium Channel blockers
a,b
b,c
d
e
Mohamed Teleb , Ola H. Rizk , Fang-Xiong Zhang , Frank R. Fronczek ,
d
a,*
Gerald W. Zamponi , Hesham Fahmy
a
Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State
University, Brookings, SD 57007, USA
b
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Alexandria University,
Alexandria 21521, Egypt
c
Department of Pharmaceutical chemistry, Faculty of Pharmacy and drug manufacturing,
Pharos University in Alexandria, Alexandria 21311, Egypt.
d
Department of Physiology & Pharmacology, Hotchkiss Brain Institute, University of
Calgary, 3330 Hospital Drive NW, Calgary T2N 4N1, Canada
e
Department of Chemistry, College of Science, Louisiana State University, Baton Rouge,
LA 70803, USA
ABSTRACT
Drugs targeting different calcium channel subtypes have strong therapeutic potential for
future drug development for cardiovascular disorders, neuropsychiatric diseases and cancer.
This study aims to design and synthesize a new series of C2 substituted dihydropyrimidines
to mimic the structure features of third generation long acting dihydropyridine calcium
channel blockers and dihydropyrimidines analogues. The target compounds have been
evaluated as blockers for Ca
technique. Among the tested compounds, compound 7a showed moderate calcium channel
blockade activity against Ca 3.2. Moreover, the predicted physicochemical properties and
V
1.2 and Ca
V
3.2 utilizing the whole-cell patch clamp
V
pharmacokinetic profiles of the target compounds recommend that they can be considered
as drug-like candidates. The results highlight some significant information for the future
design of lead compounds as calcium channel blockers.

Corresponding author: E-mail: Hesham.Fahmy@sdstate.edu (Hesham Fahmy)
Keywords: Calcium channels; T-type calcium channel blockers; L-type calcium channel blockers
Whole patch clamp technique; Dihydropyrimidines; 1,4-Dihydropyridines.
1

1
. Introduction
Recent studies showed that various calcium channel isoforms have been
associated with many disorders ranging from cardiovascular and neuronal diseases [1,2]
to cancer development and progression [3]. Hence, they are considered new attractive
molecular targets for therapeutic intervention for such disorders. Within this approach,
the design of selective calcium channel modulators is currently in progress. Over the last
few years, many calcium channel blockers (CCBs) with varying channel isoform
selectivity have been reported [4-8]. Among different CCBs, selective T-type (Ca 3)
V
blockers are emerging as non-traditional therapeutic avenues for different
neuropsychiatric disorders such as Parkinson disease, epilepsy, pain, autism, anxiety and
addiction [2,9]. Furthermore, there is a growing body of evidence that selective T-type
calcium channel blockers can specifically affect calcium homeostasis and signaling in
cancer cells, without harming normal tissues thus supporting normal cell proliferation,
survival, and resistance to treatment [3]. This may provide new insights in cancer therapy
especially in cases in which currently available treatments are limited due to serious side
effects or resistance [10]. In cardiovascular system, T-type calcium channels upregulation
triggers increased aldosterone secretion [11]. Clinical studies also reported that combined
L- and T-types calcium channel blockade avoids cardio-renal injuries associated with
traditional L-type CCBs [12]. Accordingly, T-type calcium channel modulation hold
promise for better hypertension management [13,14] than traditional L-type CCBs which
are still recommended by the 2018 European Society of Hypertension (ESH) / European
Society of Cardiology (ESC) Guidelines for the management of arterial hypertension
[
15].
Along these lines, diverse molecules targeting various calcium channel isoforms
have been reported [4-8,16,17]. Structure activity relationships were studied to
understand their respective activity and selectivity profiles. Among different CCBs,
dihydropyridines (DHPs) are the best known class with well-established structure activity
relationship data. Since the introduction of nifedipine [18]; the prototype DHP, the 1,4-
DHP scaffold has been modified at almost every position introducing higher generations
with improved potency, pharmacokinetic and safety profiles to the market [19-23].
Among various structural modifications, C2-substitution attracted considerable interest to
confer optimized activity and desirable pharmacokinetics. Structure activity relationship
studies of DHPs showed systematic modifications at C2 leading to the third generation
long acting DHP CCB; amlodipine [20] (Figure 1). Furthermore, bioisosteric
replacement of the dihydropyridine core leads to potent dihydropyrimidne (DHPM)
mimics adopting similar molecular conformation [24]. This modification eventually
paved the way for further exploration of more potent DHPM analogs. Numerous valuable
reviews described the importance of DHPMs as CCBs [25-27] (Figure 1)
2

In view of the above-mentioned findings, and as a continuation of our effort [6-8]
to identify new potent calcium channel blockers, the current study aimed at designing and
synthesizing DHPM derivatives with various functionalities at C2 linked to the DHPM
core via variable spacer nature and size. Most of the synthesized compounds were
evaluated as blockers for Ca
technique.
V
1.2 and Ca 3.2 by applying the whole-cell patch clamp
V
Fig.1. DHPs in clinical use, lead C2 substituted DHPM mimics and target DHPMs.
. Results and discussion
2
2
.1. Chemistry
The synthetic strategies adopted for the synthesis of the intermediate and target
compounds are depicted in Schemes 1 and 2. In scheme 1, the 1,4-
3

Dihydropyrimidinethione 1 was synthesized by multi-components one-pot Biginelli
reaction of thiourea, 3-nitrobenzaldehyde and ethyl acetoacetate in boiling ethanol
containing 37% HCl [28]. Conversion of the 2(3H)-thioxo derivative 1 to the
corresponding 2-aroylmethylsulfanyl derivatives 2a, b was achieved via stirring with
phenacyl bromides in dry acetone at reflux temperature. IR spectra of 2a, b showed new
stretching absorption band for ketone C=O of the aroyl side chain. The 2-aryl-2-
hydroxyvinyl derivatives 3a, b were prepared according to the method reported by
Eschenmoser which illustrated that the thione derivative 1 readily underwent sulfide
2
contraction through selective alkylation of the C sulfur with α-bromoketones followed
by subsequent elimination of the bridged sulfur assisted by addition of a thiophilic agent
(
triphenylphosphine) to furnish the desired C=C coupled products 3a,b [29]. IR spectra
-1
showed the expected OH stretching absorption band at 3314-3309 cm , beside usual
bands assigned for NH, ester C=O, C=N, NO and C-O-C detected at their expected
2
frequencies. Reaction of 1 with N-(3-bromo-propyl)phthalimide under mild basic
conditions afforded the corresponding 1,3-dioxoisoindolin-2-ylpropylsulfanyl derivative
4
in a good yield (75%). IR spectrum lacked the NHC=S stretching absorption bands
characteristic for its precursor 1 and showed an additional C=O stretching absorption
-1
band at 1768 cm corresponding to the isoindolinyl carbonyl groups. Attempts to prepare
the free amino derivative 5 by cleavage of the phthalimido intermediate (4) with
methylamine were unsuccessful [20]. Compound 1 was also alkylated under mild basic
conditions with 3-bromopropanol to the corresponding 3-hydroxypropylsulfanyl
derivative 6. Structure of the obtained product was confirmed by spectral data. Its IR
spectrum lacked the NHC=S stretching absorption bands originally present in its
-
1 1
precursor 1 and showed a new OH stretching absorption band at 3150 cm . H-NMR
spectrum of 6 displayed two characteristic D O-exchangeable broad singlets assigned for
OH and N-H at 4.93 and 6.97 ppm respectively.
2
In scheme 2, Stirring a solution of the alcohol derivative 6 in anhydrous pyridine
with acetyl chloride at room temperature afforded the corresponding acetyl derivative 7a
[
30,31]. Carbonate 7b was also synthesized by treating 6 with 1.2 equivalent of ethyl
chloroformate under similar reaction conditions [32]. Structures of 7a,b were confirmed
by spectral data and by HMBC for 7a (Figure 2) and by X-ray crystallography for 7b
(
Figure 3). IR spectra of 7a,b lacked the high frequency OH and NH stretching
absorption bands present in their precursor alcohol 6 and showed a new C=O stretching
3
absorption band attributed to side chain carbonyl of carbonate and amide. N acylation
regioselectivity was unequivocally established by HMBC of compound 7a and X-ray
crystallography of compound 7b. HMBC of compound 7a showed a correlation between
4
C -H of the DHPM core at 6.58 ppm and the carbonyl carbon of the acetamido group at
3
1
70.88 ppm (Figure 2) confirming direct connectivity between N and the acetyl group.
Stirring a mixture of alcohol 6 and benzenesulfonyl chloride in dry pyridine overnight at
room temperature didn’t afford the expected phenylsulfonate ester derivative 8, the ethyl
8
-methyl-6-(3-nitrophenyl)-3,4-dihydro-2H,6H-pyrimido[2,1-b][1,3]thiazine-7-
carboxylate 9 was obtained instead. The spectral analysis of this purified product
indicated that the intermediate sulfonate ester underwent in situ cyclization. Spectral data
4

1
13
(
IR, H-NMR, C-NMR) lacked the ring core NH and the side chain phenylsulfonate
moiety confirming the cyclic structure. The structure of the compound 9 obtained in the
above reaction was confirmed by X-ray crystallography (Figure 4) and HMBC spectral
data (Figure 5). Cyclization regioselectivity of compound 9 was unequivocally
6
established by HMBC. As evidenced from the spectrum, the methine C -H of the DHPM
core at 5.31 ppm showed interaction with the side chain methylene carbon NCH at 48.96
2
ppm confirming structure 9 (Figure 5). Carbamates are known to be readily prepared by
treating the appropriate alcohol with different isocyanates under neutral reaction
conditions [33]. Herein, stirring a mixture of the alcohol derivative 6 and the substituted
isocyanate derivative in anhydrous dichloromethane at room temperature afforded the
corresponding carbamates 10a-c. Unexpectedly, attempts to synthesize the corresponding
thiocarbamates 11a-c following the same reaction conditions utilizing the appropriate
isothiocyanates were unsuccessful. Structures of the obtained products 10a-c were
confirmed by spectral analyses. IR spectra lacked the high frequency OH stretching
absorption band and showed new NH and C=O stretching absorption bands attributed to
-1
1
side chain carbamate ester at 3296-3294 and 1699-1679 cm respectively. H-NMR of
0a-c showed two downfield D O-exchangeable singlets at 7.20-9.75 and 8.77-9.83 ppm
1
2
1
which were attributed to carbamate-NH and N -H protons respectively.
Reagents : (i) HCl, ethanol, reflux; (ii) appropriate phenacyl bromide, acetone, reflux;
(
(
iii) K
iv) K
2
CO
CO
3
, acetone, appropriate phenacyl bromide, stirring at R.T., then PPh
, KI, N-(3-bromopropyl)phthalimide, reflux (v) methylamine; (vi) K
3
, reflux;
CO , 3-
2
3
2
3
Bromopropanol, reflux.
5

Scheme 1: Synthetic pathways for compounds 1-6
Reagents: (i) acetyl chloride or ethyl chloroformate, anhydrous pyridine, stirring at R.T.,
under N
2
atmosphere; (ii) benzenesulphonyl chloride, anhydrous pyridine; (iii)
appropriate phenylisocyanate, anhydrous DCM, stirring at R.T.; (iv) appropriate
phenylisothiocyanate, anhydrous DCM, stirring at R.T.
Scheme 2: Synthetic pathways for compounds 7-10
6

Fig. 2. HMBC spectrum of Compound 7a
a)
b)
Fig. 3. a) Compound 7b with 50% ellipsoids and crystallographic numbering; b)
Crystal packing of compound 7b in the unit cell
7

a)
b)
Fig. 4. a) Compound 9 with 50% ellipsoids and crystallographic numbering; b)
Crystal packing of compound 9 in the unit cell.
Fig. 5. HMBC spectrum of Compound 9
8

2
.2. Electrophysiology
Most of the synthesized compounds were evaluated for their calcium
channel blocking activities by a whole-cell patch clamp recording assay using Ca 1.2 and
3.2 channels (Figure 6). Currents from tsA-201 cells transiently transfected with rat
1.2 (L-type) and ancillary calcium channel β1b and α2δ subunit cDNA were
V
Ca
Ca
V
V
recorded, and % inhibition by each test compound (at a concentration of 10 mM) was
determined to measure the resting state block. (Figure 6a) shows that compounds
mediated less than 50% block. Results recorded from similar experiments with cells
transfected with the Ca 3.2 (T-Type) α1 subunit are represented in (Figure 6b).
V
Compound 7a showed moderate blockade, the remainder of the test compounds were less
active.
a)
b)
9

Fig. 6 (a) Tonic block of rat Ca
test compounds (n =4-5 per channel). (b) Tonic block of human Ca
same compounds (n =4-5 per channel, at 10 μM). Error bars reflect standard errors
v
1.2 (L-type) induced by a 10 micromolar application of
v
3.2 (T-type) with the
2
.3. In silico prediction of physicochemical properties and drug-likeness data for the
new compounds
Oral bioavailability represents important role in the generation of bioactive
molecules into therapeutic agents [34]. So, it was essential to apply a computational study
to assess whether our compounds possess the right parameters to exhibit drug-likeness or
not. Molinspiration [35] online software was used to calculate molecular descriptors that
were used by Lipinski in formulating his rule of five [36] (Table 1). Molsoft software
[
37] was applied to predict drug likeness and solubility parameters (Table 2) in order to
analyze their overall potential to meet the requirements for a drug and to also compare
them to the reference drug; amlodipine. Lipinski’s rule of five [36] states that cell
permeability and oral bioavailability are likely to occur if at least three of the following
rules are obeyed: molecular weight (M.W)≤500 Da, n-octanol-water partition coefficient
(
log P)≤5, number of hydrogen bond acceptors (HBA)≤10, number of hydrogen bond
donors (HBD)≤5. The results revealed that five compounds (2a, 6, 7a, 9 and 10a) are in
full accordance to Lipinski’s rule of five with no single violation. Two compounds (3a
and 4)
Moreover, the number of rotatable bonds (NROTB) and topological polar surface area
TPSA) have been reported as very good descriptors of oral bioavailability of drugs [38].
showed one violation. Other compounds displayed additional violations.
(
10

2
Also, it has been stated that compounds with TPSA < 140 Å are predicted to have good
oral bioavailability [39,40]. Results showed that TPSA of all compounds were in the
2
acceptable range (below 150 Å ). Besides, TPSA was used to calculate percentage of
absorption (%ABS = 109-0.345 TPSA). All the tested compounds displayed reasonable
%
ABS in the range of 57.39–78.73% indicating a good predicted oral bioavailability. In
silico physicochemical properties data are listed in Table 1.
It was reported that 80% of drugs in the market have predictable solubility above
0
.0001 mg/L. The results illustrated that all tested compounds accomplished the
solubility requirement. Drug-likeness model score is expressed by a numerical value
which determines whether a particular molecule can behave as a drug or not the more
positive the numerical value the more it is likely for a compound to act as a drug [41]. As
shown in (Table 2), all compounds have positive drug likeness values which indicates
that they have good predicted drug-likeness prospective. Finally, compounds (2a, 6, 7a, 9
and 10a) can be considered as drug-like candidates as they presented reasonable
physicochemical properties with good predicted drug-likeness values.
11

Table 1: In silico physicochemical properties of the tested compounds as predicted
by Molinspiration
a
b
c
d
Lipinski’s
Violation
e
f
Volumes
(A)
g
Code
LogP M.Wt HBA HBD
TPSA %ABS
3
NROTB
2
a
4.24 439.49
5.19 407.43
4.58 508.56
2.74 379.44
3.04 463.51
4.27 523.56
3.47 361.42
4.92 498.56
5.37 512.59
8
8
10
8
10
12
7
10
10
7
1
2
1
2
0
0
0
2
2
3
0
1
1
0
0
2
0
0
2
0
113.59 69.81
116.75 68.72
135.60 62.21
116.75 68.72
131.11 63.76
149.57 57.39
379.66
361.18
434.19
330.89
403.32
454.90
312.41
434.65
451.21
363.90
9
7
3a
4
6
10
9
11
15
5
12
12
10
7a
7b
9
87.73
78.73
1
1
0a
0c
134.85 62.47
134.85 62.47
Amlodipine 2.58 408.88
99.89
74.54
a
LogP: logarithm of compound partition coefficient between n-octanol and water.
M.Wt: molecular weight.
b
c
HBA: number of hydrogen bond acceptors.
d
HBD:number of hydrogen bond donors.
TPSA: polar surface area.
e
e
%ABS: percentage of absorption.
g
NROTB: number of rotatable bonds
Table 2: In silico drug-likeness data of the tested compounds as predicted by Molsoft
a
Code
S (mg/L) Drug-likeness
model score
2
3
4
6
7
a
a
0.40
1.18
0.37
57.56
43.95
7.53
8.10
0.41
0.15
26.53
0.06
0.28
0.64
0.24
0.21
0.23
0.27
0.34
0.36
0.94
a
7b
9
1
1
0a
0c
Amlodipine
a
S aqueous solubility
12

3
. Conclusion
This study deals with the synthesis of dihydropyrimidine derivatives with various
functionalities at C2 linked to the dihydropyrimidine core via variable spacer nature and
size. The newly synthesized compounds have been evaluated as blockers for Ca 1.2 and
Ca 3.2 utilising the whole-cell patch clamp technique. Among the tested compounds,
compound 7a showed moderate calcium channel activity against Ca 3.2. Additionally,
V
V
V
the physicochemical properties and pharmacokinetic profiles of the target compounds
were predicted using Molinspiration and Molsoft softwares. Computational results
showed that such type of compounds could be considered as drug-like candidates.
a
Compound 7a showed an aqueous solubility (S ) value of 43.95 and a “Drug-likeness
model score” value of 0.21. These results may have a value in guiding further structural
modification of C2 substituted dihydropyrimidine to develop potent calcium channel
blockers.
4
. Experimental
4
.1. Chemistry
All chemicals were purchased from commercial sources. Flash column
chromatography separation was performed using Acros organics silica gel 40-60 µm, 60
Å using combination of ethyl acetate and hexanes. Preparative thin layer chromatography
TM
was performed using UNIPLATE 1500µm silica gel plates with UV 254 preparative
layer. Whatman and sigma TLC plates were utilized for thin layer chromatography and
visualization was done using UV fluorescence at 254 nm. Melting points were recorded
on a Mel-Temp, Laboratory devices, Inc and are uncorrected. %CHN Analyzer by
combustion/ TCD and %S by O flask combustion/IC were used for elemental analysis of
final compounds and performed by Micro Analysis Inc., Wilmington DE, USA and are
1
13
within 0.4%. H and C NMR spectra were obtained on a Bruker Avance 400 MHz &
1
6
00MHz instrument using DMSO-d6 as solvent unless otherwise stated. H NMR Spectra
are reported in order; multiplicity, number of protons and signals were characterized as s
singlet), d (doublet), dd (doublet of doublet), t (triplet), m (multiplet), br s (broad signal),
(
q (quartet). Chemical shifts are relative to TMS as an internal standard. Mass spectra
were recorded on ThermoFinnigan MAT95XL high resolution magnetic sector mass
spectrometer, using electrospray ionization method. The IR spectra were recorded on
-1
ZnSe crystal at 8 cm resolution in Nicolet 380 ATR-FTIR spectrophotometer (Thermo
electron Corporation, Madison, WI). 1,4-Dihydropyrimidinethione (1) was prepared
according to previously published reaction conditions [28].
Ethyl 2-(aroylmethylsulfanyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydropyrimidine-5-
carboxylates (2a,b)
13

The appropriately substituted phenacyl bromide (1.0 mmol) was added to a stirred
suspension of the 1,4-dihydropyrimidinethione 1 (0.32 g, 1.0 mmol) in dry acetone (50
mL) and stirring was continued at reflux temperature for 1-3 h. The separated product
was filtered, washed with dry acetone and dried without need for further purification.
Ethyl 2-(benzoylmethylsulfanyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydropyrimidine-
o
-1
5
1
-carboxylates (2a). Yield: 0.3 g (79%); MP: 210-12 C; IR (KBr, cm ): 3056 (NH),
1
722, 1687 (C=O), 1600 (C=N), 1524, 1323 (NO
, 400 MHz) δ ppm: 0.97-1.10 (m, 3H, OCH
.25 (m, 4H, SCH & OCH CH ), 5.38, 5.57 (2s, 1H, C -H), 6.86-7.09 (m, 2H, ArHs),
.43-8.18 (m, 7H, ArHs), 8.55 (s, br, 1H, NH, D O-exchangeable); C-NMR (DMSO-d ,
2
), 1195, 1094 (C-O-C); H-NMR
6
(
DMSO-d
6
2
CH
3
), 2.47 (s, 3H, C -CH ), 3.85-
3
4
4
7
1
1
1
2
2
3
1
3
2
6
00.63 MHz) δ ppm: 13.61, 17.17, 39.84, 43.46, 55.68, 56.07, 60.73, 97.50, 99.79,
05.33, 122.08, 123.48, 125.85, 127.03, 127.64, 128.96, 129.13, 130.17, 133.82, 142.04,
+
.
46.67, 163.32, 166.32; HRMS (ESI) calcd. for C22
40.1275.
H
22
N
3
O S [M+1] : 440.1275; Found:
5
4
Ethyl
2-(4-fluorobenzoylmethylsulfanyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydro
o
-1
pyrimidine-5-carboxylates (2b). Yield: 0.4 g (89%); MP: 218-20 C; IR (KBr, cm ):
1
3
069 (NH), 1726, 1673 (C=O), 1596 (C=N), 1523, 1324 (NO
NMR (DMSO-d , 400 MHz) δ ppm: 0.92-1.13 (m, 3H, OCH
.86-4.25 (m, 4H, SCH & OCH CH ), 5.33, 5.56 (2s, 1H, C -H), 6.79-8.18 (m, 8H,
ArHs), 8.63 (s, br, 1H, NH, D O-exchangeable); HRMS (ESI) calcd. for C22
M+1] : 458.1180; Found: 458.1189.
2
), 1192, 1089 (C-O-C); H-
6
6
2
CH
3
), 2.45 (s, 3H, C -CH ),
3
4
3
2
2
3
2
H21FN
3
5
O S
+
.
[
Ethyl 2-(2-aryl-2-hydroxyvinyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydropyrimidine
5-carboxylates (3a,b)
-
A stirred suspension of the dihydropyrimidinethione 1 (0.32 g, 1.0 mmol) in dry
acetone (50 mL) was treated with K CO (0.2 g, 1.5 mmol) and the appropriate phenacyl
2
3
bromide (1 mmol) at room temperature. After stirring for 30 min (monitored by TLC),
triphenylphosphine (0.39 g, 1.5 mol) was added in one portion, and the reaction
temperature was raised to reflux. Stirring was continued for additional 10 h for
completion of the reaction followed by evaporation of the solvent to dryness under
reduced pressure. The obtained residue was purified by flash chromatography or
preparative TLC with gradient eluents of 0-90% EtOAc/hexane to produce the desired
product.
Ethyl
2-(2-phenyl-2-hydroxyvinyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydro
-1
pyrimidine -5-carboxylates (3a). Yield: 0.29 g (71%); MP: oil; IR (KBr, cm ): 3314
1
(
OH), 3187 (NH), 1682 (C=O), 1630 (C=N), 1525, 1346 (NO
NMR (CDCl , 400 MHz) δ ppm: 1.11 (t, J = 8.0 Hz, 3H, OCH
), 3.95-4.10 (m, 2H, OCH CH ), 5.29 (s, 1H, vinylic CH=C-OH), 5.35, 5.40 (2s,
2
), 1201, 1057 (C-O-C); H-
3
2
CH ), 2.24, 2.31 (2s, 3H,
3
6
C -CH
3
2
3
14

4
1
2
H, C -H), 7.16-7.34 (m, 4H, Ar-Hs), 7.47 (d, J = 8.0 Hz, 2H, Ar-, 7.52 (d, J = 8.0 Hz,
H, Ar-H), 7.61 (d, J = 8.0 Hz, 1H, Ar-H), 7.96 (t, J = 6.0, 1H, Ar-H), 8.04 (s, 1H, Ar-
H), 8.60 (s, 1H, NH, D
exchangeable); C-NMR (CDCl , 100.63 MHz) δ ppm: 14.18, 18.71, 19.48, 51.99,
2
O-exchangeable), 11.40, 12.79 (2s, 1H, vinylic OH, D
2
O-
1
3
3
5
1
1
2.31, 60.42, 60.50, 78.98, 101.40, 101.84, 121.66, 121.86, 122.83, 126.53, 126.61,
28.23, 128.30, 129.69, 129.92, 130.64, 130.79, 132.83, 132.93, 139.94, 140.20, 145.04,
45.39, 145.82, 146.08, 148.04, 148.30, 154.34, 154.80, 165.07, 165.20, 186.61, 187.02;
+
.
HRMS (ESI) calcd. for C22
H
22
N
3
5
O [M+1] : 408.1554; Found: 408.1558.
Ethyl 2-(2-[4-fluorophenyl]-2-hydroxyvinyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydro
-1
pyrimidine -5-carboxylates (3b). Yield: 0.3 g (70%); MP: oil; IR (KBr, cm ): 3309
1
(
OH), 3191 (NH), 1701 (C=O), 1630 (C=N), 1527, 1346 (NO
2
), 1197, 1058 (C-O-C); H-
CH ), 2.47, 2.49 (2s, 3H,
), 5.61, 5.66 (2s, 1H, C -H), 5.73 (s, 1H, vinylic
CH=COH), 7.08-8.26 (m, 8H, ArHs), 9.38 (s, 1H, NH, D O-exchangeable), 11.65, 13.14
O-exchangeable); HRMS (ESI) calcd. for C22 Na
M+Na] : 448.1279; Found: 448.1282.
NMR (Acetone-d , 400 MHz) δ ppm: 1.17-1.24 (m, 3H, OCH
C -CH
6
2
4
3
6
3
), 4.04-4.15 (m, 2H, OCH
2
CH
3
2
(
[
2s, 1H, vinylic OH, D
2
H20FN
3
O
5
+
.
Ethyl 2-(3-(1,3-dioxoisoindolin-2-yl)propylsulfanyl)-6-methyl-4-(3-nitrophenyl)-1,4-
dihydropyrimidine-5-carboxylate (4)
A suspension of the dihydropyrimidinethione 1 (0.32 g, 1.0 mmol) in dry acetone
(
50 mL) was treated with K
2
CO (0.2 g, 1.5 mmol) and stirred at room temperature for 30
3
min. KI (40 mg) and N-(3-bromopropyl)phthalimide (0.3 g, 1.2 mmol) were then added
in one portion and the reaction temperature was raised to reflux. Stirring was continued
for additional 5-6 h until completion of the reaction followed by evaporation of the
solvent to dryness under reduced pressure. The obtained residue was purified by flash
chromatography with gradient eluents of 0-90% EtOAc/hexane to offer the desired
-1
product. Yield: 0.38 g (75 %); MP: 150-2°C; IR (KBr, cm ): 3272 (NH), 1768, 1693
1
(
C=O), 1647 (C=N), 1531, 1349 (NO
2
), 1163, 1100 (C-O-C); H-NMR (CDCl
CH ), 1.97 (quint, J = 8.0 Hz, 2H,
), 2.94, 3.09 (2 quint, J = 8.0 Hz, 2H, SCH ), 3.71, (t,
), 5.69 (s, 1H, C -H), 6.64 (s,
O-exchangeable), 7.43 (t, J = 8.0 Hz, 1H, Ar-H), 7.61 (d, J = 8.0, 1H, Ar-H),
.69-7.74 (m, 2H, Ar-Hs), 7.79-7.86 (m, 2H, Ar-Hs), 8.04 (d, J = 8.0, 1H, Ar-H), 8.08 (s,
3
, 400
MHz) δ ppm: 1.22 (t, J = 6.0 Hz, 3H, OCH
SCH
J = 6.0 Hz, 2H, CH
1
7
1
5
1
2
3
6
2
CH
2
CH
2
), 2.34 (s, 3H, C -CH
N), 4.12 (q, J = 8.0 Hz, 2H, OCH
3
2
4
2
2
CH
3
H, NH, D
2
1
3
H, Ar-H); C-NMR (CDCl
9.21, 60.06, 99.80, 121.99, 123.25, 123.32, 129.17, 131.96, 133.44, 134.03, 145.34,
46.25, 146.84, 148.22, 150.00, 166.36, 168.33; HRMS (ESI) calcd. for C25 O S
3
, 100.63 MHz) δ ppm: 14.25, 18.80, 28.03, 28.70, 36.67,
H
25
N
4
6
+
.
[
M+1] : 509.1489; Found: 509.1491.
Ethyl 2-(3-hydroxypropylsulfanyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydro
pyrimidine-5-carboxylate (6)
15

A suspension of the dihydropyrimidinethione 1 (0.32 g, 1.0 mmol) in dry acetone
50 mL) was treated with K CO (0.2 g, 1.5 mmol) and stirred at RT for 30 min. 3-
(
2
3
Bromoethanol (0.16 g, 0.11 mL, 1.2 mmol) was then added in one portion and the
reaction temperature was raised to reflux. Stirring was continued for additional 20 h until
completion of the reaction followed by evaporation of the solvent to dryness under
reduced pressure. The obtained residue was diluted with H
2
O, extracted with EtOAc (3 x
SO and evaporated under
5
0 mL), washed with H O and brine, dried over anhydrous Na
2
2
4
reduced pressure. The obtained residue was purified by flash chromatography with
gradient eluents of 0-90% EtOAc/hexane to afford the desired product. Yield: 0.37 g (97
-
1
%
1
8
CH
); MP: 107-9 °C; IR (KBr, cm ): 3150 (OH), 3113 (NH), 1696 (C=O), 1638 (C=N),
1
532, 1355 (NO
.0 Hz, 3H, OCH
CH CH ), 2.37 (s, 3H, C -CH
.57- 3.74 (m, 2H, CH -OH), 4.08-4.16 (m, 2H, OCH
exchangeable), 5.77 (s, 1H, C -H), 6.97 (s, br, 1H, NH, D
.0 Hz, 1H, Ar-H), 7.67 (d, J = 8.0 Hz, 1H, Ar-H), 8.10-8.17 (m, 2H, Ar-H); HRMS
2
), 1191, 1079 (C-O-C); H-NMR (CDCl
CH ), 1.63-1.73 (m, 1H, S-CH CH
), 3.05-3.11 (m, 1H, SCH), 3.19-3.27 (m, 1H, SCH),
CH ), 4.93 (s, br, 1H, OH, D O-
O-exchangeable), 7.48 (t, J =
3
, 400 MHz) δ ppm: 1.22 (t, J =
2
3
2
2
CH ), 1.90-1.98 (m, 1H, S-
2
6
2
2
2
3
3
2
2
3
2
4
2
6
+
.
(
ESI) calcd. for C17
H
22
N
3
O S [M+1] : 380.1275; Found: 380.1277.
5
Ethyl 2-(3-substituted propylsulfanyl)-3-acetyl-6-methyl-4-(3-nitrophenyl) -3,4-
dihydropyrimidine-5-carboxylate (7a,b)
A mixture of DHPM alcohol 5 (0.38 g, 1.0 mmol) and acetyl chloride (0.09 g, 1.2
mmol) or ethyl chloroformate (0.13 g, 1.2 mmol) in anhydrous pyridine (3mL) was
stirred overnight at room temperature under N
diluted with H O (100 mL), extracted with ethyl acetate (3 x 100 mL) and the combined
organic layers were washed with H O and brine, dried over anhydrous sodium sulphate
2
atmosphere. The reaction mixture was
2
2
and evaporated under reduced pressure. The pure compounds were isolated by flash
chromatography utilizing gradient eluents of 0-90% EtOAc / hexane.
Ethyl
2-(3-acetoxypropylsulfanyl)-3-acetyl-6-methyl-4-(3-nitrophenyl)-3,4-
-1
dihydropyrimidine-5-carboxylate (7a). Yield: 0.32 g (70 %); MP: oil; IR (KBr, cm ):
1
1
738, 1693 (C=O), 1609 (C=N), 1527, 1349 (NO
2
), 1227, 1077 (C-O-C); H-NMR
, 400 MHz) δ ppm: 1.25 (t, J = 6.0 Hz, 3H, OCH CH ), 1.94-2.02 (m, 2H, S-
), 2.49 (s, 3H, OCOCH ), 2.52 (s, 3H, NCOCH ),
), 4.07-4.13 (m, 2H, OCH CH ), 4.21 (t, J = 8.0 Hz, 2H,
), 6.58 (s, 1H, C -H), 7.50 (t, J = 8.0 Hz, 1H, Ar-H,), 7.61 (t, J = 8.0 Hz,
(
CDCl
3
2
3
6
CH
2
CH
2
CH
2
), 2.05 (2s, 3H, C -CH
3
3
3
3
.18 (t, J = 8.0 Hz, 2H, S-CH
2
2
3
4
CH
2
-OCOCH
3
1
3
1
1
1
1
H, Ar-H,), 8.06 (s, dist, 1H, Ar-H), 8.14 (d, J = 8.0 Hz, 1H, Ar-H); C-NMR (CDCl ,
00.63 MHz) δ ppm: 14.21, 20.87, 20.97, 25.00, 27.89, 28.65, 52.15, 60.79, 62.71,
11.49, 121.97, 123.23, 129.65, 133.35, 140.66, 148.41, 153.02, 156.29, 165.49, 169.89,
70.88; HRMS (ESI) calcd. for C21
3
+.
H
26
N
3
O S [M+1] : 464.1486; Found: 464.1491.
7
Ethyl 2-(3-ethoxycarbonyloxypropylsulfanyl)-3-ethoxycarbonyl-6-methyl-4-
16

(
3-nitrophenyl)-3,4-dihydropyrimidine dicarboxylate (7b). Yield: 0.38 g (73 %); MP:
-1
7
1
0-2 °C; IR (KBr, cm ): 1744, 1732, 1708 (C=O), 1623 (C=N mixed with C=C Ar),
1
506-1495 (C=C Ar), 1535, 1349-1356 (NO
, 400 MHz) δ ppm: 1.26 (t, J = 8.0 Hz, 3H, OCH
H, NCOOCH CH ), 1.39 (t, 3H, J = 8.0 Hz, OCOOCH CH
CH CH CH ), 2.45 (s, 3H, C -CH ), 3.07, 3.24 (2 quint, J = 7.0 Hz, 2H, S-CH
.24 (m, 6H, OCH CH , carbamate NCOOCH CH & carbonate CH CH OCO), 4.34 (q,
H, J = 8.0 Hz, carbonate OCOOCH CH ), 6.33 (s, 1H, C -H), 7.50 (d, J = 8.0 Hz, 1H,
2
), 1193, 1254, 1072, 1014 (C-O-C); H-
CH ,), 1.31 (t, J = 8.0 Hz,
), 1.96-2.09 (m, 2H, S-
), 4.16-
NMR (CDCl
3
3
2
3
2
3
2
3
6
2
2
2
3
2
4
2
2
3
2
3
2
2
4
2
3
1
3
Ar-H), 7.60 (d, J = 8.0 Hz, 1H, Ar-H), 8.13-8.16 (m, 2H, Ar-H); C-NMR (CDCl ,
3
1
1
1
00.63 MHz) δ ppm: 14.22, 14.27, 21.61, 28.01, 28.33, 54.16, 60.74, 64.02, 64.14, 66.25,
09.63, 122.22, 123.29, 129.68, 133.15, 141.76, 148.38, 152.60, 152.88, 155.06, 157.12,
+
.
65.70; HRMS (ESI) calcd. for C23
H
30
N
3
9
O S [M+1] : 524.1697; Found: 524.1698.
Ethyl 8-methyl-6-(3-nitrophenyl)- 3,4-dihydro-2H,6H-pyrimido[2,1-b][1,3]thiazine-
-carboxylate (9)
7
A mixture of DHPM alcohol 5 (0.38 g, 1.0 mmol) and benzenesulfonyl chloride
0.35 g, 0.25 mL, 2.0 mmol) in dry pyridine (5 mL) was stirred at room temperature for
an overnight. The reaction mixture was diluted with H O and extracted with ethyl acetate
3 x 50 mL). The combined organic extracts were washed with H O and brine, dried over
(
2
(
2
anhydrous sodium sulphate and evaporated under reduced pressure. The residue left was
purified by preparative TLC with gradient eluent of 0-90% EtOAc/hexane to give the
-1
desired product. Yield: 0.3 g (83 %); MP: 126-8°C; IR (KBr, cm ): 1685 (C=O), 1589
1
(
(
C=N), 1526, 1347 (NO
t, J = 8.0 Hz, 3H, OCH
2
), 1227, 1075 (C-O-C); H-NMR (CDCl
CH ), 2.05-2.20 (m, 1H, S-CH CH CH
), 2.92-3.04 (m, 2H, S-CH ), 3.21-3.28 (m, 1H, N-
), 4.05-4.15 (m, 2H, OCH CH ), 5.31 (s, 1H, C -H), 7.54
3
, 400 MHz) δ ppm: 1.23
2
3
2
2
2
), 2.24-2.30 (m, 1H, S-
6
CH
CH
2
CH
2
CH
2
), 2.35 (s, 3H, C -CH
3
2
4
2
), 3.40-3.45 (m, 1H, N-CH
2
2
3
(
t, J = 8.0 Hz, 1H, Ar-H), 7.79 (d, J = 8.0 Hz, 1H, Ar-H), 8.16 (d, J = 8.0 Hz, 1H, Ar-H ),
1
3
8
2
1
3
.20 (s, dist, 1H, Ar-H); C-NMR (DMSO-d
6
, 100.63 MHz) δ ppm: 14.29, 22.90, 24.36,
7.03, 48.96, 59.93, 63.40, 102.29, 122.03, 123.26, 130.17, 133.37, 144.12, 148.14,
+
.
55.82, 160.02, 166.18; HRMS (ESI) calcd. for C17
62.1165.
H
20
N
3
O S [M+1] : 362.1169; Found:
4
Ethyl 2-(3-arylcarbamoyloxypropylsulfanyl)-6-methyl-4-(3-nitrophenyl)-1,4-
dihydropyrimidine-5-carboxylates (10a-c)
A solution of DHPM alcohol 5 (0.38g, 1.0 mmol) in anhydrous dichloromethane
(
5 mL), was treated with the appropriate isocyanate derivative (1.0 mmol). After
overnight stirring at room temperature, the reaction was concentrated under reduced
pressure and the residue left was purified by flash chromatography using gradient eluents
of 0-90% EtOAc/hexane to afford the pure carbamates.
17

Ethyl 2-(3-phenylcarbamoyloxypropylsulfanyl)-6-methyl-4-(3-nitrophenyl)-
1
,4- dihydropyrimidine-5-carboxylates (10a). Yield: 0.35 g (70 %); MP: oil; IR (KBr,
-1
cm ): 3294 (NH), 1702, 1679 (C=O), 1650 (C=N), 1526, 1347 (NO
2
), 1218, 1087 (C-O-
, 400 MHz) δ ppm: 1.19 (t, J = 6.0 Hz, 3H, OCH CH ), 1.94-
), 3.01-3.19 (m, 2H, S-CH ), 4.03-4.23
OCONH), 5.80 (s, 1H, C -H), 7.01 (t, J = 8.0 Hz, 1H, Ar-H),
1
C); H-NMR (Acetone-d
.06 (m, 2H, S-CH CH CH
m, 4H, OCH CH & CH
6
2
3
6
2
(
2
2
2
), 2.36 (s, 3H, C -CH
3
2
4
2
3
2
7
8
.28 (t, J = 8.0 Hz, 2H, Ar-Hs), 7.54-7.58 (m, 3H, Ar-H), 7.77 (d, J = 8.0 Hz, 1H, Ar-H),
.07 (d, J = 8.0 Hz, 1H, Ar-H,), 8.18 (s, 1H, Ar-H), 8.59, 8.77 (2s, 2H, NH & carbamate
1
3
NH, D
2
O-exchangeable); C-NMR (acetone-d , 100.63 MHz) δ ppm: 14.54, 18.11,
6
2
1
C
0.83, 27.38, 59.88, 60.23, 63.71, 99.47, 119.09, 122.32, 123.35, 129.53, 130.35, 134.26,
40.11, 147.32, 148.63, 149.10, 151.57, 154.30, 166.87, 170.94; HRMS (ESI) calcd. for
+.
24
H
27
N
4
6
O S [M+1] : 499.1646; Found: 499.1649.
Ethyl
2-(3-[4-bromophenyl]carbamoyloxypropylsulfanyl)-6-methyl-4-(3-
nitrophenyl)-1,4- dihydropyrimidine-5-carboxylates (10b). Yield: 0.3 g (52 %); MP:
-
1
oil; IR (KBr, cm ): 3296 (NH), 1700, 1679 (C=O), 1650 (C=N), 1526, 1347 (NO
2
),
1
1
216, 1077 (C-O-C); H-NMR (CDCl
OCH CH ), 1.87-1.99 (m, 2H, S-CH CH
S-CH ), 3.96-4.24 (m, 4H, CH OCOAr& OCH
H, ArHs), 7. 59 (t, J = 8.0 Hz, 1H, Ar-H,), 7.67 (d, J = 8.0 Hz, 1H, Ar-H,), 8.02 (s, 1H,
Ar-H), 8.07 (d, J = 8.0 Hz, 1H, Ar-H,), 9.75, 9.83 (2s, 2H, NH & OCONHAr, D O-
S [M+1] : 577.0751; Found:
S [M+1] : 579.0730; Found: 579.0738
3
, 400 MHz) δ ppm: 1.14 (2t, J = 4.0 Hz, 3H,
6
2
3
2
2
CH
2
), 2.26 (s, 3H, C -CH
3
), 2.96- 3.13 (m, 2H,
4
2
2
2
CH ), 5.65 (s, 1H, C -H), 7.41-7.50 (m,
3
4
2
+.
exchangeable); HRMS (ESI) calcd. for C24
H26BrN
4
O
6
+
5
77.0735. C24
H
26[81]BrN
4
O
6
Ethyl 2-(3-[p-tolyl]carbamoyloxypropylsulfanyl)-6-methyl-4-(3-nitrophenyl)-
1
,4- dihydropyrimidine-5-carboxylates (10c). Yield: 0.4 g (78 %); MP: oil; IR (KBr,
-1
cm ): 3296 (NH), 1702, 1679 (C=O), 1651 (C=N), 1526, 1347 (NO
2
), 1160, 1092 (C-O-
, 400 MHz) δ ppm: 1.21 (t, J = 8.0 Hz, 3H, OCH CH ), 1.89-1.92
), 2.94-3.15 (m, 2H,
1
C); H-NMR (CDCl
m, 2H, S-CH CH CH
S-CH ,), 4.07-4.17 (m, 4H, OCH
.0 Hz, 2H, Ar-Hs), 7.20-7.28 (m, 3H, Ar-H & NH, D
Hz, 1H, Ar-H), 7.64-7.66 (m, 2H, Ar-H & OCONHAr, D
3
2
3
6
(
2
2
2
), 2.27 (s, 3H, tolyl-CH
CH & CH OCOAr), 5.79 (s, 1H, C -H), 7.06 (d, J =
O-exchangeable), 7.41 (t, J = 8.0
O-exchangeable), 8.03 (d, J =
3
), 2.29 (s, 3H, C -CH
3
4
2
2
3
2
8
2
2
+.
8
.0 Hz, 1H, Ar-H), 8.16 (s, 1H, Ar-H); HRMS (ESI) calcd. for C25
H N
29 4
6
O S [M+1] :
5
13.1802; Found: 513.1780.
4
.2. Calcium channel antagonism
4
.2.1. Chemicals
Stock solutions of 10 or 30 mM concentrations of the test compounds were
prepared in DMSO. The stock solutions were diluted before the experiments so that the
18

concentration of DMSO was 0.1% or less in the final dilution. Calcium channel currents
are not affected by a concentration of 0.1% DMSO or less.
4
.2.2. Cell culture and transient transfection
Human embryonic kidney cells (HEK) tsA-201 cells were grown to 80-90%
confluence at 37 °C (5% CO2) in Dulbecco's modiEed Eagle's medium (Life
Technologies, Grand Island, NY). They were supplemented with 10% (vol/vol) fetal
bovine serum (HyClone, Thermo Scientific, Pittsburgh, PA), 200 U/ml penicillin, and 0.2
mg/mL streptomycin (Life Technologies, Grand Island, NY). Cells were then suspended
with 0.25% trypsin/ethylenediaminetetraacetic acid and plated onto glass coverslips in
1
0-cm culture dishes (Corning, Corning, NY) at 10% confluence 6 h before transfection.
Calcium channel (5 µg) and green fluorescent protein marker (0.5 µg) DNAs were
transfected into the cells with calcium phosphate. For Ca 1.2, the additional Ca β1b (5
µg) and Ca α2δ1 (5 µg) subunits were co-expressed. Cells were then transferred to 30 °C
V
V
V
1
6-18 h later following transfection and stored for two days before recording.
4
.2.3. Electrophysiology
Cells on a glass coverslip were transferred into an external bath solution of 20
mM BaCl , 1 mM MgCl , 40 mM TEACl, 65 mM CsCl, 10 mM HEPES, 10 mM
glucose, pH 7.4. Borosilicate glass pipettes (Sutter Instrument Co., Novato, CA, 3e5 MU)
were filled with internal solution containing 140 mM CsCl, 2.5mM CaCl ,1mM MgCl , 5
2
2
2
2
mM EGTA, 10 mM HEPES, 2 mM Na-ATP and 0.3 mM Na-GTP, pH 7.3. Whole-cell
patch clamp recordings were carried out using an EPC 10 amplifier (HEKA Elektronik,
Bellmore, NY) linked to a personal computer equipped with Pulse (V8.65) software
(
HEKA Elektronik, Bellmore, NY). After seal formation, the membrane beneath the
pipette was ruptured and the pipette solution was allowed to dialyze into the cell for 2-5
min before recording. Voltage-dependent currents were leak corrected with an online P/4
subtraction paradigm. Data were recorded at 10 kHz and filtered at 2.9 kHz. T-type
_
calcium currents were produced by depolarization from a holding potential of 110 mV to
_
a test potential of 20 mV. L-type calcium currents were produced by depolarization from
_
a holding potential of 90 mV to a test potential of +20 mV, with an inter-pulse interval
of 20 s. The duration of the test pulse typically was 100 ms.
4
.2.4. Data analysis and statistics
Data analysis was carried out using online analysis built-in Pulse software
(
(
HEKA Elektronik, Bellmore, NY). All graphs were prepared using GraphPad Prism 5
GraphPad Software, La Jolla, CA). All data are given as mean values ± standard errors.
4
.3. X-ray crystallography
19

The crystal structure of 7b was determined using X-ray data collected at 90K with
MoKα radiation (λ=0.71073 Å), on a Bruker Kappa Apex-II DUO diffractometer.
C
23
H
29
N
3
O S, triclinic space group P-1, a=8.1914(9), b=9.4010(9), c=16.1918(16) Å,
9
-3
α=95.372(6), β= 96.356(6), γ=93.378(6)°, Z =2, Dcalcd=1.413 g cm . A total of 16372
data was collected at to θ=28.7°, R=0.039 for 4842 data with I > 2σ(I) of 6200 unique
data (Rint =0.025) and 329 refined parameters. The CIF has been deposited at the
Cambridge Crystallographic Data Centre, CCDC 1885031.
The crystal structure of 9 was determined using X-ray data collected at 90K with MoKα
radiation (λ=0.71073 Å), on a Bruker Kappa Apex-II DUO diffractometer. C17
orthorhombic space group P2 , a=7.7908(5), b=13.5778(9), c=16.0974(10) Å, Z=4,
calcd=1.410 g cm . A total of 18313 data was collected at to θ=30.6°, R=0.041 for 4404
H
19
N
3
4
O S,
1
2
2
1 1
-3
D
data with I >2σ(I) of 5208 unique data (Rint =0.050) and 229 refined parameters. The CIF
has been deposited at the Cambridge Crystallographic Data Centre, CCDC 1885032.
Acknowledgment
This research project was funded by The Egyptian Ministry of Higher Education
and Scientific Research and the Department of Pharmaceutical Sciences, College of
Pharmacy, South Dakota State University. Gerald W. Zamponi is supported by a
Foundation Grant of the Canadian Institutes of Health Research and by a grant from
Alberta Innovates holds a Canada Research Chair.
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22

Graphical Abstract
New series of C2 substituted dihydropyrimidines were designed and synthesized to mimic the
structure features of third generation long acting dihydropyridine calcium channel blockers
and dihydropyrimidines analogues. They are evaluated as blockers for Ca
utilising the whole-cell patch clamp technique. Compound 7a showed moderate calcium
channel activity against Ca 3.2.
V
1.2 and Ca
V
3.2
V

Highlights


New series of C2 substituted dihydropyrimidines were designed and synthesized.
The target compounds have been evaluated as blockers for Ca
utilising the whole-cell patch clamp technique.
V
1.2 and Ca
V
3.2


Compound 7a showed moderate calcium channel activity against Ca
The predicted physicochemical properties and pharmacokinetic profiles of the
target compounds recommend that they can be considered as drug-like candidates.
V
3.2.