Synthesis, antimicrobial and hypoglycemic activities of novel N-(1-adamantyl)carbothioamide derivatives

Article abstract of DOI:10.3390/molecules20058125

The reaction of 1-adamantyl isothiocyanate 4 with the various cyclic secondary amines yielded the corresponding N-(1-adamantyl)carbothioamides 5a-e, 6, 7, 8a-c and 9. Similarly, the reaction of 4 with piperazine and trans-2,5-dimethylpiperazine in 2:1 molar ratio yielded the corresponding N,N′-bis(1-adamantyl)piperazine-1,4-dicarbothioamides 10a and 10b, respectively. The reaction of N-(1-adamantyl)-4-ethoxycarbonylpiperidine-1-carbothioamide 8c with excess hydrazine hydrate yielded the target carbohydrazide 11, in addition to 4-(1-adamantyl)thiosemicarbazide 12 as a minor product. The reaction of the carbohydrazide 11 with methyl or phenyl isothiocyanate followed by heating in aqueous sodium hydroxide yielded the 1,2,4-triazole analogues 14a and 14b. The reaction of the carbohydrazide 11 with various aromatic aldehydes yielded the corresponding N′-arylideneamino derivatives 15a-g. The compounds 5a-e, 6, 7, 8a-c, 9, 10a, 10b, 14a, 14b and 15a-g were tested for in vitro antimicrobial activity against certain strains of pathogenic Gram-positive and Gram-negative bacteria and the yeast-like fungus Candida albicans. The compounds 5c, 5d, 5e, 6, 7, 10a, 10b, 15a, 15f and 15g showed potent antibacterial activity against one or more of the tested microorganisms. The oral hypoglycemic activity of compounds 5c, 6, 8b, 9, 14a and 15b was determined in streptozotocin (STZ)-induced diabetic rats. Compound 5c produced significant reduction of serum glucose levels, compared to gliclazide.

Full text of DOI:10.3390/molecules20058125

Molecules 2015, 20, 8125-8143; doi:10.3390/molecules20058125
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis, Antimicrobial and Hypoglycemic Activities of Novel
N-(1-Adamantyl)carbothioamide Derivatives
1
1
2
3
Ebtehal S. Al-Abdullah , Hanaa M. Al-Tuwaijri , Hanan M. Hassan , Monirah A. Al-Alshaikh ,
Elsayed E. Habib 4,5 and Ali A. El-Emam 1,*
1
Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University,
Riyadh 11451, Saudi Arabia; E-Mails: ealabdullah@ksu.edu.sa (E.S.A.-A.);
haltuwajri@ksu.edu.sa (H.M.A.-T.)
2
Department of Pharmaceutical Sciences, College of Pharmacy, Princess Nourah Bint Abdulrahman
University, Riyadh 11671, Saudi Arabia; E-Mail: hananhafila@hotmail.com
3
Department of Chemistry, College of Sciences, King Saud University, Riyadh 11451, Saudi Arabia;
E-Mail: mshaikh@ksu.edu.sa
4
Department of Microbiology, Faculty of Pharmacy, University of Mansoura, Mansoura 35516,
Egypt; E-Mail: sayedhabib@hotmail.co.jp
5
Department of Pharmaceutics and Pharmaceutical Technology (Microbiology),
College of Pharmacy, Taibah University, Almadinah Almunawwarah 11344, Saudi Arabia
*
Author to whom correspondence should be addressed; E-Mail: aelemam@ksu.edu.sa;
Tel.: +966-11-4677350; Fax: +966-11-4676220.
Academic Editor: Derek J. McPhee
Received: 23 April 2015 / Accepted: 5 May 2015 / Published: 6 May 2015
Abstract: The reaction of 1-adamantyl isothiocyanate 4 with the various cyclic secondary
amines yielded the corresponding N-(1-adamantyl)carbothioamides 5a–e, 6, 7, 8a–c and 9.
Similarly, the reaction of 4 with piperazine and trans-2,5-dimethylpiperazine in 2:1 molar
ratio yielded the corresponding N,N'-bis(1-adamantyl)piperazine-1,4-dicarbothioamides 10a
and 10b, respectively. The reaction of N-(1-adamantyl)-4-ethoxycarbonylpiperidine-1-
carbothioamide 8c with excess hydrazine hydrate yielded the target carbohydrazide 11, in
addition to 4-(1-adamantyl)thiosemicarbazide 12 as a minor product. The reaction of the
carbohydrazide 11 with methyl or phenyl isothiocyanate followed by heating in aqueous
sodium hydroxide yielded the 1,2,4-triazole analogues 14a and 14b. The reaction of
the carbohydrazide 11 with various aromatic aldehydes yielded the corresponding
N'-arylideneamino derivatives 15a–g. The compounds 5a–e, 6, 7, 8a–c, 9, 10a, 10b, 14a,

Molecules 2015, 20
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1
4b and 15a–g were tested for in vitro antimicrobial activity against certain strains of
pathogenic Gram-positive and Gram-negative bacteria and the yeast-like fungus Candida
albicans. The compounds 5c, 5d, 5e, 6, 7, 10a, 10b, 15a, 15f and 15g showed potent
antibacterial activity against one or more of the tested microorganisms. The oral
hypoglycemic activity of compounds 5c, 6, 8b, 9, 14a and 15b was determined in
streptozotocin (STZ)-induced diabetic rats. Compound 5c produced significant reduction of
serum glucose levels, compared to gliclazide.
Keywords: adamantane derivatives; carbothioamides; antimicrobial activity; hypoglycemic
activity
1
. Introduction
Derivatives of adamantane have long been known for their multifarious pharmacological activities.
The incorporation of an adamantyl moiety into several molecules results in compounds with relatively
high lipophilicity, which in turn can modify the biological availability of these molecules. The
adamantyl-bearing compound are more lipophilic than their des-adamantyl analogues. Beyond
increasing the partition coefficient, the adamantyl group positively modulates the therapeutic index of
many experimental compounds through a variety of mechanisms [1,2]. After the discovery of
amantadine in 1960 as potent antiviral drug for the treatment of Influenza A infection [3–5] and as
antiparkinsonian drug [6,7], adamantane derivatives attracted the attention of several scientists as
potential chemotherapeutic agents. Further studies based on amantadine resulted in the discovery of
more potent antiviral drugs as Rimantadine [8] and Tromantadine [9]. Several adamantane derivatives
were also proved to possess marked inhibitory activity against human immunodeficiency viruses
(
HIV) [10–13]. 6-[3-(1-Adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437), a
synthetic retinoid derivative, was developed as a potent inducer of apoptosis in human head and neck
squamous cell carcinoma [14]. Several adamantane derivatives were recognized as potent bactericidal
and fungicidal agents [15–25]. In addition, the adamantane-based drugs, Vildagliptin [26] and
Saxagliptin [27] are members of a new class of oral hypoglycemic agents known as dipeptidyl peptidase
IV (DPP-IV) inhibitors, which were approved for the treatment of type 2 diabetes. Adamantane
derivatives constitutes the major class of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1)
inhibitor, which are considered important therapy for controlling non-insulin-dependent diabetes,
hyperglycemia, obesity, insulin resistance, hyperlipidemia, hypertension and other symptoms associated
with excessive body cortisol [28–30]. Moreover, anti-inflammatory activity was reported to several
adamantane-containing molecules [19–22,31–33]. In view of the reported chemotherapeutic and
hypoglycemic activities of the N-(1- and 2-adamantyl)carboxamides [29,34–36] and the diverse
biological activities of several N-(substituted)carbothioamides [37,38], it was of interest to synthesize
series of N-(1-adamanty)carbothioamide derivatives, structurally-related to the previously reported
adamantane derivatives, for evaluation as antimicrobial and hypoglycemic agents.

Molecules 2015, 20
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2
. Results and Discussion
2.1. Chemical Synthesis
1
-Adamantyl isothiocyanate 4, required as starting material, was prepared in good yield via
modification of the previously described methods [39,40]. Thus, 1-adamantylamine 1 was reacted with
carbon disulfide and trimethylamine, in ethanol, to yield the dithiocarbamate salt 2, followed by addition
of di-tert-butyl dicarbonate (Boc O) to yield the intermediate 3, which was converted to the target
2
product 4 via stirring with catalytic amount of 4-dimethylaminopyridine (DMAP). 1-Adamantyl
isothiocyanate 4 was reacted with the cyclic secondary amines namely, 1-substituted piperazines,
morpholine, pyrrolidine, 4-substituted piperdines and 1,2,3,4-tetrahydroisoquinoline, in boiling ethanol,
to yield the corresponding N-(1-adamantyl)carbothioamides 5a–e, 6, 7, 8a–c and 9, respectively. The
reaction was found to proceed smoothly and the products were precipitated from the reaction mixture in
good yields after two hours. 1-Adamantyl isothiocyanate 4 was similarly reacted with piperazine and
trans-2,5-dimethylpiperazine in 2:1 molar ratio to yield the corresponding N,N'-bis(1-
adamantyl)piperazine-1,4-dicarbothioamide derivatives 10a and 10b in high yields (Scheme 1, Table 1).
The structures of compounds 5a–e, 6, 7, 8a–c, 9, 10a and 10b were confirmed by elemental analyses, in
1
13
addition to the H-NMR, C-NMR, and ESI-MS mass spectral data which were in full agreement with
their structures, in addition to the X-ray spectrum of compound 9 [41].
S
CS / Et N
2
3
NH2
-
+
N
S HN Et
2
3
H
1
Boc O
2
S
O
N
H
S
OC H (tert)
4
9
S
3
N
N
DMAP
O
H
O
HN
6
S
HN
N
R
HN
S
N
N
H
N
NCS
N
N
5
a-e
R
H
4
5
5
5
5
5
a: R = C H
7
2
5
H
b: R = COOC H
N
2
5
R
R
c: R = C H
6
5
d: R = 2-CH OC H
HN
3
6
4
e: R = C H CH
NH
NH
6
5
2
R
S
S
S
R
N
N
N
H
N
H
N
N
9
H
H
8
a-c
a: R = H
b: R = C H
R
N
N
8
8
8
10a,b
0a: R = H
R
S
6
5
1
1
c: R = COOC H
2
5
0b: R = CH3
Scheme 1. Synthesis of the target N-(1-adamanty)carbothioamides 5a–e, 6, 7, 8a–c, 9, 10a
and 10b.

Molecules 2015, 20
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Table 1. Crystallization solvents, melting points, yield percentages, molecular formulae and
molecular weights of compounds 5a–e, 6, 7, 8a–c, 9, 10a, 10b, 14a, 14b and 15a–g.
Mp
Yield
(%)
77
68
91
95
95
88
74
78
90
78
88
89
92
38
44
65
61
54
48
43
44
58
Molecular Formula
(Mol. Wt.)
Comp. No.
R
Cryst. Solv.
(°C)
5
a
C
2
H
5
2
5
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
DMF
DMF
EtOH
DMF
EtOH
150–152
121–123
174–176
137–139
146–148
139–141
175–177
145–147
137–139
166–168
147–149
227–229
232–234
200–202
>300
C
17
18
21
22
22
15
H
29
29
29
31
31
24
N
3
S (307.50)
S (351.51)
S (355.54)
OS (385.57)
S (369.57)
OS (280.43)
5
b
COOC
H
5
C
H
N
3
O
2
5
c
C
6
H
C
H
N
3
5
d
2-CH
3
OC
6
H
4
C
H
N
3
5
e
C
6
H
5
-
-
CH
2
C
H
N
3
6
C
H
N
2
7
C
15
C
16
C
22
H
24
H
26
H
30
N
2
N
2
N
2
S (264.43)
S (278.46)
S (354.55)
8
a
H
8
b
C
6
H
5
8
c
COOC
2
H
5
C
19
H
30
20
26
28
19
24
24
N
2
O
2
S (350.52)
9
-
C
H
26
N
2
S (326.5)
10a
10b
14a
14b
15a
15b
H
C
H
40
44
N
4
S
2
2
(472.75)
(500.81)
(391.6)
CH
3
C
H
N
4
S
CH
3
C
H
29
31
32
N
S
5 2
C
6
H
5
C
H
N
5
S
2
(453.67)
S (440.6)
2-OH
196–198
237–237
199–201
154–156
128–130
170–172
194–196
C
H
N
4
O
2
3,4-Cl
2,6-Cl
2
EtOH/CHCl
EtOH
3
C
24
H
30Cl
30Cl
2
2
N
4
OS (493.49)
OS (493.49)
1
5c
5d
5e
5f
5g
2
C
24
H
N
4
1
3,4-(OCH
3,4,5-(OCH
2-OH-5-OCH
3-OC H -4-OH EtOH/CHCl
3
)
2
EtOH
C
26
H
36
H
38
H
34
H
36
N
4
N
4
N
4
N
4
O
3
O
4
O
3
O
3
S (484.65)
S (514.68)
S (470.63)
S (484.65)
1
3
)
3
EtOH
C
27
C
25
C
26
1
3
EtOH/CHCl
3
3
1
2
5
N-(1-Adamantyl)-4-ethoxycarbonylpiperidine-1-carbothioamide 8c was reacted with excess
hydrazine hydrate, in ethanol, at reflux temperature, to get the target carbohydrazide derivative 11. On
monitoring the reaction with thin layer chromatography (TLC), it was observed that the target product
was formed after few minutes in addition to a minor product which was further identified as
4
-(1-adamantyl)thiosemicarbazide 12. It was also observed that prolongation of the reaction time results
in higher ratios of the side product 12. The reaction time was optimized at 20 min to yield 72% of 11
and 18% of 12. The formation of the side product could be explained as a result of hydrazinolysis of the
thiocarboxamide function of the major product 11. The structure of the side product 12 was assigned
1
13
based on the H-NMR and C-NMR data, in addition to ESI-MS mass spectra and elemental analyses.
The reaction of the carbohydrazide 11 with equimolar amount of methyl or phenyl isothiocyanate, in
ethanol for 6 h yielded the intermediate 1,4-disubstituted-3-thiosemicarbazides 13a or 13b. Dehydrative
cyclization of compounds 13a and 13b was achieved by heating in 10% aqueous sodium hydroxide
solution for 2 h, followed by acidification with hydrochloric acid to yield the target 1,2,4-triazole
derivatives 14a and 14b in 38% and 44% overall yields, respectively. Attempted reaction of the
carbohydrazide 11 with various aromatic aldehydes via prolonged heating in ethanol yielded fair yields
of the corresponding arylideneamino derivatives. On the other hand, carrying out the reaction in the
higher boiling solvent N,N-dimethylformamide (DMF) greatly improved the yield. Thus, the reaction of

Molecules 2015, 20
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the carbohydrazide 11 with certain aromatic aldehydes via heating in DMF for two hours yielded the
target compounds 15a–g in relatively higher yields (43%–71%).
The structures of compounds 11, 12, 14a, 14b and 15a–g (Scheme 2, Table 1) were confirmed by
1
13
elemental analyses, in addition to the H-NMR, C-NMR, and ESI-MS mass spectral data, which were
in full agreement with their structures.
S
N
N
H
O
8c
O
NH NH
2
2
EtOH
S
S
N
N
+
H
N
NHNH
2
H
N
H
NH2
1
2 (18%)
1
1 (72%)
O
R
N
C
S
E
tO
H
S
S
N
N
H
H
N
N
N
S
N
H
H
R
N
R
O
13a,b
N
N
1
1
1
1
1
1
1
5a: R = 2-OH
5b: R = 3,4-Cl2
5c: R = 2,6-Cl2
H
H
O
15a-g
1
1
3a,14a: R = CH3
1. NaOH, H O
2. HCl
2
3b,14b: R = C H
5d: R = 3,4-(OCH3)2
6
5
5e: R = 3,4,5-(OCH3)3
5f: R = 2-OH-5-OCH3
5g: R = 3-OC H -4-OH
2
5
S
N
H
N
R
N
SH
1
4a,b
N
N
Scheme 2. Synthesis of the target N-(1-adamanty)carbothioamides 14a,b and 15a–h.
.2. In Vitro Antimicrobial Activity
2
The synthesized compounds 5a–e, 6, 7, 8a–c, 9, 10a, 10b, 14a, 14b and 15a–g were tested for in vitro
inhibitory activity against the standard pathogenic strains of the Institute of fermentation of Osaka (IFO)
namely; Staphylococcus aureus IFO 3060, Bacillus subtilis IFO 3007, Micrococcus luteus IFO 3232
(Gram-positive bacteria), Escherichia coli IFO 3301, Pseudomonas aeuroginosa IFO 3448 (Gram-negative
bacteria), and the yeast-like pathogenic fungus Candida albicans IFO 0583. The primary screening was
carried out using the agar disc-diffusion method using Müller-Hinton agar medium [42]. The results of
the preliminary antimicrobial screening of the synthesized compounds (200 μg/disc), the antibacterial
antibiotics Ampicillin trihydrate, Gentamicin (100 μg/disc) and the potent antifungal drug Clotrimazole

Molecules 2015, 20
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(
100 μg/disc) and the calculated log P values (Clog P) of the tested compounds (calculated using the CS
ChemOffice Ultra version 8.0, CambridgeSoft, Cambridge, MA, USA) are presented in Table 2.
Table 2. Antimicrobial activity of compounds 5a–e, 6, 7, 8a–c, 9, 10a, 10b, 14a, 14b and
15a–g (200 μg/8 mm disc), the broad spectrum antibacterial drugs Gentamicin (100 μg/8 mm
disc), Ampicillin (100 μg/8 mm disc) and the antifungal drug Clotrimazole (100 μg/8 mm
disc) against Staphylococcus aureus IFO 3060 (SA), Bacillus subtilis IFO 3007 (BS),
Micrococcus luteus IFO 3232 (ML), Escherichia coli IFO 3301 (EC), Pseudomonas
aeuroginosa IFO 3448 (PA), and Candida albicans IFO 0583 (CA).
Diameter of Growth Inhibition Zone (mm) a
Comp.
No.
Clog P
SA
-
BS
-
ML
EC
PA
CA
5
a
4.32
4.32
4.77
4.79
5.52
3.23
4.06
4.62
6.03
4.01
5.48
6.86
7.90
3.40
5.29
5.07
5.77
4.70
4.41
4.03
5.14
4.79
-
-
-
-
5
b
-
-
-
-
-
-
b
b
b
b
b
b
b
5
c
20 (8)
19 (4)
15
24 (2)
22 (4)
19 (8)
20 (1)
20 (2)
14
16
15
14
-
5
d
17
12
-
-
5
e
12
15
12
-
b
b
b
b
6
22 (2)
18 (8)
12
19 (4)
15
12
-
7
18 (4)
15
13
-
8
a
12
-
-
-
8
b
16
16
14
-
-
-
8
c
12
13
-
-
-
-
9
-
-
-
-
-
-
b
b
b
10a
10b
14a
14b
15a
15b
25 (32)
26 (32)
-
28 (16)
24 (8)
-
20 (32)
18
16
-
b
b
b
b
23 (32)
19 (64)
12
-
-
-
-
-
-
-
-
15
-
-
-
b
b
18 (16)
12
22 (2)
12
12
-
-
-
-
-
-
-
1
5c
5d
5e
5f
5g
14
17
12
-
-
-
1
-
-
-
-
-
1
-
-
-
-
13
-
-
b
b
b
b
b
1
22 (8)
19 (8)
26 (2)
23 (2)
NT
27 (1)
25 (2)
25 (2)
19 (8)
18 (8)
18 (2)
19 (2)
11
11
13
NT
NT
21 (2)
b
b
b
b
b
b
1
12
12
b
b
b
Gentamicin
Ampicillin
20 (0.5)
19 (1)
16 (2)
NT
b
b
21 (0.5)
NT
17 (2)
NT
b
Clotrimazole
NT
a
b
(
-): Inactive (inhibition zone < 10 mm); (NT): Not tested; The figures shown in parentheses represent the
MIC values (μg/mL).
The antimicrobial activity results revealed that the tested compounds exhibited various degrees of
inhibition against the tested microorganisms. Potent antibacterial activity was displayed by the
compounds 5c–e, 6, 7, 10a, 10b, 15a, 15f and 15g which produced growth inhibition zones ≥ 18 mm
against one or more of the tested bacteria. In addition, the derivatives 8a, 8b and 15c showed moderate
activity (growth inhibition zones 14–17 mm), the derivatives 8c and 15b produced weak activity (growth

Molecules 2015, 20
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inhibition zones 10–13 mm) and the derivatives 5a, 5b, 9, 14a, 14b, 15d and 15e were practically
inactive (growth inhibition zones < 10 mm) against the tested microorganisms.
The Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus and to a lesser extent
Micrococcus luteus are considered the most sensitive among the tested microorganisms. Meanwhile, the
activity against the tested Gram-negative bacteria was generally lower than that of the Gram-positive
bacteria, only compound 10a and 10b were found strongly active against Escherichia coli and
moderately or weakly active against Pseudomonas aeuroginosa. The inhibitory activity of the
compounds against Candida albicans was rather lower than their antibacterial activity, only compounds
1
5f and 15g displayed marginal activity compared to Clotrimazole. In addition, the antimicrobial activity
of the compounds were not correlated to their lipophilicity.
The N-(1-adamantyl)carbothioamides 5c–e, 6, 7 and 8a–c showed marked activity against the tested
Gram-positive bacteria and weak to moderate activity against the tested Gram-negative bacteria, in
addition to the absence of antifungal activity. The antibacterial activity was dependent on the nature of
the precursor cyclic secondary amine. Among the piperazine derivatives 5a–e, the 4-aryl and benzyl
derivatives 5c, 5d and 5e were highly active and the ethyl and the ethoxycarbonyl derivatives 5a and 5b
were inactive. The morpholine and pyrrolidine derivatives 6 and 7 were highly active against the
Gram-positive bacteria and retained moderate activity against Escherichia coli and weak activity against
Pseudomonas aeuroginosa. The antibacterial activity of the piperidine derivatives 8a–c was lower
than their morpholine and pyrrolidine analogues with moderate to weak activity against the tested
Gram-positive bacteria. The tetrahydroisoquinoline derivative 9 totally lacked antimicrobial activity.
The N,N'-bis(1-adamantyl)piperazine-1,4-dicarbothioamides 10a and 10b exhibited potent
broad-spectrum antibacterial activity against the tested Gram-positive bacteria and Escherichia coli in
addition moderate activity and weak activity against Pseudomonas aeuroginosa. The N-(1-
adamantyl)piperidine-4-(5-mercapto-4-phenyl-1,2,4-triazol-3-yl)-1-carbothioamides 14a and 14b totally
lacked antimicrobial activity. Concerning the antimicrobial activity of the N'-(arylidene)piperidine-4-
carbohydrazides 15a–g, it was observed that the activity mainly dependent on the arylidene moiety. The
phenolic derivatives 15a, 15f and 15g displayed potent antibacterial activity against the tested
Gram-positive bacteria and endowed marginal activity against Candida albicans.
The minimal inhibitory concentrations (MIC) [43] for the most active compounds 5c, 5d, 5e, 6, 7,
1
0a, 10b, 15a, 15f and 15g which are shown in Table 2, were in accordance with the results obtained in
the primary screening. Despite the potent broad-spectrum antibacterial activity of compounds 10a and
0b, the MIC values were higher than expected. The high MIC values of compounds 10a and 10b may
1
be attributed high lipophilicity and the poor water solubility in the aqueous Müller-Hinton Broth and
Sabouraud Liquid Medium.
2
.3. In Vivo Hypoglycemic Activity
The oral hypoglycemic activity of compounds 5c, 6, 8b, 9, 14a and 15b was determined in
streptozotocin (STZ)-induced diabetic rats. The compounds were tested at 10 and 20 mg/kg dose levels.
The diabetogenic effect of STZ is the direct result of irreversible damage to the pancreatic beta cells,
resulting in degranulation and loss of insulin secretion [44,45].

Molecules 2015, 20
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The results of oral hypoglycemic activity compounds 5c, 6, 8b, 9, 14a and 15b (10 and 20 mg/kg)
and the potent hypglycemic drug gliclazide in STZ-induced diabetic rats (10 mg/kg) are listed in
Table 3. The highest activity was shown by compound 5c, which produced significant strong
dose-independent reduction of serum glucose levels in STZ-induced diabetic rats, compared to gliclazide
at 10 mg/kg dose level (Potency ratio 92.48%). Compound 6 displayed good hypoglycemic at 20 mg/kg
dose level and weak activity at 10 mg/kg dose level.
Table 3. Oral hypoglycemic activity of compounds 5c, 6, 8b, 9, 14a, 15b (10 and 20 mg/kg)
and gliclazide (10 mg/kg) in STZ-induced diabetic rats.
Results
24 (mg/dL) a
Treatment
C
0
(mg/dL) a
302.6 ± 11.64
C
% Glucose Reduction b
5.09%
Group 1 c
Group 2 d
287.2 ± 16.85
295.4 ± 17.52 183.0 ± 13.38 *
291.6 ± 15.23 189.0 ± 22.16 *
319.6 ± 7.85 207.0 ± 13. 84 *
38.05%
5
5
c (10 mg/kg)
c (20 mg/kg)
35.19% (92.48)
35.23% (46.30)
7.05% (18.52)
33.92% (44.58)
2.57% (6.75)
4.05% (5.32)
2.48% (6.52)
4.20% (5.52)
0.95% (2.50)
5.24% (6.89)
−2.06%
6
(10 mg/kg)
(20 mg/kg)
283.8 ± 11.16
263.8 ± 16.66
6
296.6 ± 12.92 196.0 ± 9.67 *
8
8
b (10 mg/kg)
b (20 mg/kg)
264.2 ± 5.49
303.3 ± 16.35
282.8 ± 13.90
276.2 ± 14.17
257.4 ± 9.45
291.2 ± 8.18
275.8 ± 15.52
264.6 ± 7.35
277.4 ± 7.19
271.4 ± 21.85
287.8 ± 13.37
286.8 ± 17.16
9
(10 mg/kg)
(20 mg/kg)
9
1
1
1
1
4a (10 mg/kg) 274.8 ± 14.59
4a (20 mg/kg) 286.4 ± 24.56
5b (10 mg/kg) 282.0 ± 14.21
5b (20 mg/kg) 293.2 ± 15.66
2.18% (2.87)
a
b
Results are expressed as mean ± S.E.M. (n = 5); The figures shown in parentheses are the relative potency
c
compared with glicalzide; Treated with a single oral dose of 0.5% (w/v) aqueous CMC solution (5 mL/kg);
d
Treated with 10 mg/kg gliclazide in 0.5% (w/v) aqueous CMC; * Significant difference at p < 0.01 compared
with the corresponding control.
The hypoglycemic activity of the tested N-adamantyl carbothioamides 5c, 6, 8b, 9, 14a and 15c
greatly influenced by the nature of the carbothioamide moiety. The piperazine and morpholine
carbothioamides 5c and 6 retained good potency, while the corresponding piperidine and
tetrahydroisoquinoline analogs 8b, 9, 14a and 15c were almost inactive.
2
.4. Oral Acute Toxicity Testing of Compound 5c
The method of Litchfield and Wilcoxon was adopted for measuring the acute oral toxicity of
compound 5c which possessed the highest hypoglycemic activity [46]. The oral LD50 of compound 5c
in normal albino mice was found to be 298 ± 15.50 mg/kg. The oral LD50 of gliclazide was reported to
be >3000 mg/kg in mice [47]. Although the oral acute toxicity of compound 5c is higher than that of
gliclazide, the compound induces its hypoglycemic activity at safe doses.

Molecules 2015, 20
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3. Experimental Section
3.1. General
Melting points (°C) were measured in open glass capillaries using a Branstead 9100 Electrothermal
melting point apparatus and are uncorrected. NMR spectra were obtained on a Bruker AC 500 Ultra
1
Shield NMR spectrometer (Fällanden, Switzerland) operating at 500.13 MHz for H and 125.76 MHz
1
3
for C, the chemical shifts are expressed in δ (ppm) downfield from tetramethylsilane (TMS) as internal
standard; coupling constants (J) are expressed in Hz. Electrospray ionization mass spectra (ESI-MS)
were recorded on an Agilent 6410 Triple Quad tandem mass spectrometer at 4.0 and 3.5 kV for positive
and negative ions, respectively. Elemental analyses (C, H, N & S) were in agreement with the proposed
structures within ±0.4% of the theoretical values. Monitoring the reactions and checking the purity of
the final products were carried out by thin layer chromatography (TLC) using silica gel precoated
aluminum sheets (60 F254, Merck) and visualization with ultraviolet light (UV) at 365 and 254 nm. The
bacterial strains and Candida albicans fungus were obtained from the Institute of Fermentation of Osaka
(
IFO), Osaka, Japan. The reference drugs Ampicillin trihydrate (CAS 7177-48-2), Gentamicin sulfate
CAS 1405-41-0), Clotrimazole (CAS 23593-75-1) and Gliclazide (CAS 21187-98-4) were purchased
(
from Sigma-Aldrich Chemie GmbH, Taufkirchen, Germany. The Sprauge-Dawley rats and the normal
albino mice were purchased from local animal house (Abu-Rawash, Giza, Egypt). The animal
experiments for the determination of the hypoglycemic activity and acute toxicity were carried out in
agreement with the pertinent legal and ethical standards of the international guidelines.
3
.2. Synthesis of N-(1-Adamantyl)-4-substituted piperazine-1-carbothioamides 5a–e, N-(1-
Adamantyl)morpholine-4-carbothioamide 6, N-(1-Adamantyl)pyrrolidine-1-carbothioamide 7, N-(1-
Adamantyl)-4-substituted piperidine-1-carbothioamides 8a–c and N-(1-Adamantyl)-1,2,3,4-
tetrahydroisoquinoline-2-carbothioamide 9
A mixture of 1-adamantyl isothiocyanate 4 (387 mg, 2 mmol) and 2.0 mmol of the appropriate cyclic
secondary amine (1-substituted piperazines, morpholine, pyrrolidine, piperidine, 4-phenylpiperidine,
ethyl isonipecotate or 1,2,3,4-tetrahydroisoquinoline), in ethanol (15 mL), was heated under reflux for
2
h. On cooling, the precipitated crude product were filtered, washed with cold ethanol, dried, and
crystallized from ethanol.
1
5
a: H-NMR (DMSO-d
6
): δ 1.0 (t, 3H, CH
2
CH
3
, J = 7.0 Hz), 1.62 (s, 6H, Adamantane-H), 1.97–2.03
CH
), 29.06, 39.15,
), 51.35, 52.14 (Piperazine-C), 180.21 (C=S). ESI-MS,
(
m, 3H, Adamantane-H), 2.24 (s, 6H, Adamantane-H), 2.32 (s, 4H, Piperazine-H), 3.34 (q, 2H, CH
2
3
,
1
3
J = 7.0 Hz), 3.68 (s, 4H, Piperazine-H), 6.52 (s, 1H, NH). C-NMR: δ 11.90 (CH
3
CH
2
3
9.97, 40.90 (Adamantane-C), 47.18 (CH CH
2
3
m/z: 308.3 (M+H)+.
1
5
b: H-NMR (DMSO-d
6
): δ 1.18 (t, 3H, CH
2
CH , J = 7.0 Hz), 1.58–1.62 (m, 6H, Adamantane-H), 1.78
3
(
s, 3H, Adamantane-H), 2.25 (s, 6H, Adamantane-H), 3.34–3.39 (m, 4H, Piperazine-H), 3.73 (s, 4H,
1
3
Piperazine-H), 4.04 (q, 2H, CH
2
CH
3
, J = 7.0 Hz), 6.57 (s, 1H, NH). C-NMR: δ 14.54 (CH
3
CH ), 29.09,
2

Molecules 2015, 20
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3
6.08, 39.06, 40.06 (Adamantane-C), 46.72, 53.84 (Piperazine-C), 60.69 (CH
80.53 (C=S). ESI-MS, m/z: 352.4 (M+H)+.
2
CH
3
), 154.63 (C=O),
1
1
5
c: H-NMR (DMSO-d
6
): δ 1.63 (s, 6H, Adamantane-H), 1.96–2.05 (s, 3H, Adamantane-H), 2.27 (s,
6
H, Adamantane-H), 3.16–3.20 (m, 4H, Piperazine-H), 3.84–3.88 (m, 4H, Piperazine-H), 6.64 (s, 1H,
13
NH), 6.77–6.80 (m, 1H, Ar-H), 6.92–6.94 (m, 2H, Ar-H), 7.21–7.24 (m, 2H, Ar-H). C-NMR: δ 29.08,
6.08, 40.90, 46.96 (Adamantane-C), 47.66, 53.80 (Piperazine-C), 115.15, 118.82, 128.95, 150.48
3
(
Ar-C), 180.41 (C=S). ESI-MS, m/z: 356.4 (M+H)+.
1
5
6
5
4
1
d: H-NMR (CDCl
3
): δ 1.58–1.66 (m, 6H, Adamantane-H), 1.90–2.05 (s, 3H, Adamantane-H), 2.24 (s,
), 3.84–3.88 (m, 4H, Piperazine-H),
H, Adamantane-H), 3.03 (s, 4H, Piperazine-H), 3.80 (s, 3H, OCH
.23 (s, 1H, NH), 6.81–6.86 (m, 3H, Ar-H), 6.95–6.96 (m, 1H, Ar-H). C-NMR: δ 29.76, 35.54, 36.44,
1.92 (Adamantane-C), 47.29, 53.18 (Piperazine-C), 55.44 (OCH ), 111.38, 118.36, 121.10, 123.51,
3
1
3
3
40.48, 152.24 (Ar-C), 180.49 (C=S). ESI-MS, m/z: 386.4 (M+H)+.
1
5
6
1
5
3
e: H-NMR (DMSO-d
6
): δ 1.62 (s, 6H, Adamantane-H), 1.97–2.03 (s, 3H, Adamantane-H), 2.24 (s,
), 3.70 (s, 4H, Piperazine-H), 6.52 (s,
H, NH), 7.27–7.34 (m, 5H, Ar-H). C-NMR: δ 29.06, 36.07, 39.05, 40.91 (Adamantane-C), 47.21,
H, Adamantane-H), 2.34 (s, 4H, Piperazine-H), 3.49 (s, 2H, CH
2
1
3
2.27 (Piperazine-C), 61.68 (CH
70.4 (M+H)+.
2
), 126.98, 128.16, 128.92, 137.72 (Ar-C), 180.19 (C=S). ESI-MS, m/z:
6
: 1H-NMR (DMSO-d
): δ 1.63 (s, 6H, Adamantane-H), 1.97–2.05 (s, 3H, Adamantane-H), 2.26 (s, 6H,
6
1
3
Adamantane-H), 3.57 (s, 4H, Morpholine-H), 3.67 (s, 4H, Morpholine-H), 6.57 (s, 1H, NH). C-NMR:
δ 29.08, 36.08, 40.85, 47.69 (Adamantane-C), 53.78, 65.79 (Morpholine-C), 180.87 (C=S). ESI-MS,
m/z: 281.3 (M+H)+.
1
7
: H-NMR (CDCl
3
): δ 1.68–1.73 (m, 7H, 3 Adamantane-H & 4 Pyrrolidine-H), 1.98–2.02 (m, 3H,
Adamantane-H), 2.09–2.12 (s, 3H, Adamantane-H), 2.22–2.23 (m, 6H, Adamantane-H), 3.55–3.57 (m,
1
3
4
4
H, Pyrrolidine-H), 4.98 (s, 1H, NH). C-NMR: δ 25.52, 54.50 (Pyrrolidine-C), 29.83, 36.37, 41.99,
2.14 (Adamantane-C), 176.68 (C=S). ESI-MS, m/z: 265.3 (M+H)+.
1
8
a: H-NMR (CDCl
3
): δ 1.52–1.66 (m, 12H, Piperidine & Adamantane-H), 2.04 (s, 3H, Adamantane-H),
1
3
2
.22–2.23 (m, 6H, Adamantane-H), 3.65 (t, 4H, Piperidine-H, J = 5.5 Hz), 5.14 (s, 1H, NH). C-NMR:
δ 23.83, 25.38, 48.46 (Piperidine-C), 29.65, 36.45, 42.02, 43.77 (Adamantane-C), 179.75 (C=S).
ESI-MS, m/z: 279.3 (M+H)+.
1
8
b: H-NMR (CDCl
3
): δ 1.57–1.68 (m, 8H, 6 Adamantane-H & 2 Piperidine-H), 1.89–1.90 (m, 1H,
Piperidine-H), 2.10 (s, 3H, Adamantane-H), 2.23–2.24 (m, 6H, Adamantane-H), 2.65–2.71 (m, 2H,
Piperidine-H), 2.91–2.97 (m, 2H, Piperidine-H), 3.18–3.22 (m, 2H, Piperidine-H), 5.23 (s, 1H, NH),
1
3
7
.12–7.16 (m, 3H, Ar-H), 7.22–7.25 (m, 2H, Ar-H). C-NMR: δ 29.23, 42.71, 48.12 (Piperidine-C),
2
9.78, 32.88, 36.46, 42.0 (Adamantane-C), 126.55, 126.78, 128.49, 145.04 (Ar-C), 179.99 (C=S).
ESI-MS, m/z: 355.4 (M+H)+.

Molecules 2015, 20
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1
8
c: H-NMR (CDCl
3 2 3
): δ 1.18 (t, 3H, CH CH , J = 7.0 Hz), 1.50–2.21 (m, 4H, Piperidine-H), 1.58–1.62
(
m, 8H, 6 Adamantane-H & 2 Piperidine-H), 2.04 (s, 3H, Adamantane-H), 2.25–2.27 (m, 6H,
Adamantane-H), 2.47–2.58 (m, 1H, Piperidine-H), 3.0–3.14 (m, 2H, Piperidine-H), 4.06 (q, 2H,
1
3
CH
2
CH
3
, J = 7.0 Hz), 5.18 (s, 1H, NH). C-NMR: δ 14.21 (CH
2
CH ), 29.74, 36.41, 40.60, 41.91
3
(
Adamantane-C), 35.53, 43.76, 46.63 (Piperidine-C), 66.6 (CH
2
CH ), 174.17 (C=O), 180.14 (C=S).
3
9
: 1H-NMR (CDCl
H, Adamantane-H), 2.85 (t, 2H, J = 6.0 Hz, tetrahydroisoquinoline-CH
), 4.80 (s, 2H, tetrahydroisoquinoline-CH ), 5.15 (s, 1H, NH), 7.08–7.15 (m,
3
): δ 1.60–1.67 (m, 6H, Adamantane-H), 2.05 (s, 3H, Adamantane-H), 2.25–2.26 (m,
), 3.81 (t, 2H, J = 6.0 Hz,
6
2
tetrahydroisoquinoline-CH
2
2
1
3
4H, Ar-H). C-NMR: δ 29.68, 32.88, 35.56, 42.01 (Adamantane-C), 29.24, 48.12, 54.82, 126.49,
127.08, 128.33, 129.14, 133.43, 135.50 (tetrahydroisoquinoline-C), 179.46 (C=S). ESI-MS, m/z:
3
27.4 (M+H)+.
3.3. Synthesis of N,N'-Bis(1-adamantyl)piperazine-1,4-dicarbothioamide 10a and trans-N,N'-Bis(1-
adamantyl)-2,5-dimethylpiperazine-1,4-dicarbothioamide 10b
A mixture of 1-adamantyl isothiocyanate 4 (774 mg, 4 mmol) and anhydrous piperazine or trans-2,5-
dimethylpiperazine (2.0 mmol), in ethanol (20 mL), was heated under reflux for 2 h. On cooling, the
precipitated crude product were filtered, washed with cold ethanol, dried, and crystallized from DMF.
1
1
1
3
0a: H-NMR (CDCl
3
): δ 1.25–1.45 (m, 12H, Adamantane-H), 1.49–1.66 (m, 6H, Adamantane-H),
1
3
.87–2.09 (m, 12H, Adamantane-H), 3.08 (s, 8H, Piperazine-H), 9.81 (s, 2H, NH). C-NMR: δ 27.98,
5.44, 40.08, 41.98 (Adamantane-C), 51.38, 52.08 (Piperazine-C), 179.98 (C=S). ESI-MS, m/z: 471.4
(
M−H, 100)−.
1
1
0b: H-NMR (CDCl
3
): δ 0.86 (d, 6H, CH , J = 5.0 Hz), 1.08–1.23 (m, 12H, Adamantane-H),
3
1
.46–1.47 (m, 6H, Adamantane-H), 1.86–2.09 (m, 12H, Adamantane-H), 2.25–2.66 (m, 2H, Piperazine
1
3
H), 3.43–3.54 (m, 2H, Piperazine-H), 3.70–3.76 (m, 2H, Piperazine-H), 9.83 (s, 2H, NH). C-NMR: δ
4.15 (CH ), 28.14, 35.41, 41.38, 42.70 (Adamantane-C), 50.32, 57.41 (Piperazine-C), 180.01 (C=S).
ESI-MS, m/z: 499.5 (M−H, 100)−.
1
3
3
.4. Synthesis of 1-(1-Adamantylthiocarbamoyl)piperidine-4-carbohydrazide 11 and 4-(1-Adamanty)-
-thiosemicarbazide 12
3
Hydrazine hydrate (98%, 10 mL) was added to a hot solution of compound 8c (3.5 g, 0.01 mol) in
ethanol (20 mL) and the mixture was heated under reflux with stirring for 20 min. On cooling, the
precipitated crude product was filtered, washed with cold ethanol, dried and crystallized from ethanol to
yield 2.42 g (72%) of compound 11. The filtrate was evaporated under reduced pressure and the residue
was crystallized from water to yield 0.4 gm (18%) of compound 12.
1
1
1: Mp. 216–217 °C. H-NMR (DMSO-d
6
): δ 1.55–1.96 (m, 10H, 6 Adamantane-H & 4 Piperidine-H),
2
.06–2.18 (m, 9H, Adamantane-H), 2.32 (m, 1H, Piperidine-H), 2.68–2.92 (m, 4H, Piperidine-H), 5.50
1
3
(d, 2H, NH , J = 9.5 Hz), 8.08 (t, 1H, NH, J = 9.5 Hz), 8.36 (s, 1H, NH). C-NMR: δ 28.0, 36.05, 40.75,
2

Molecules 2015, 20
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4
4.95 (Adamantane-C), 30.85, 41.35, 48.0 (Piperidine-C), 172.80 (C=O), 181.88 (C=S). ESI-MS, m/z:
37.3 (M+H, 100)+.
3
1
1
2: Mp. 195–197 °C. H-NMR (DMSO-d
, J = 10.5 Hz), 7.42 (t, 1H, NH, J = 10.5 Hz), 8.36 (s, 1H, NH). C-NMR:
δ 28.99, 35.95, 39.85, 51.91 (Adamantane-C), 179.08 (C=S). ESI-MS, m/z: 226.2 (M+H, 100)+.
6
): δ 1.64–2.02 (m, 6H, Adamantane-H), 2.12–2.18 (m, 9H,
13
Adamantane-H), 4.50 (d, 2H, NH
2
3
.5. Synthesis of N-(1-Adamantyl)piperidine-4-(5-mercapto-4-phenyl-1,2,4-triazol-3-yl)-1-
carbothioamide 14a,b
A mixture of 1-(1-adamantylthiocarbamoyl)piperidine-4-carbohydrazide 11 (673 mg, 2 mmol),
methyl or phenyl isothiocyanate (2 mmol), in ethanol (10 mL), was heated under reflux for 6 h. The
solvent was then distilled off in vacuo to yield the crude products 13a,b which were used in the second
step without further purification.
Aqueous sodium hydroxide solution (10%, 10 mL) was added to the crude product 13a or 13b and
the mixture was heated under reflux for 2 h, then filtered hot. The filtrate was acidified with 37% HCl
to pH 1–2 and the precipitated crude products 14a,b were filtered, washed with water and crystallized.
1
1
4
8
2
3
4a: H-NMR (DMSO-d
6
): δ 1.67–1.69 (m, 9H, Adamantane-H), 1.92–2.16 (m, 10H, 6 Adamantane-H &
),
), 28.92, 36.08, 39.88, 41.90 (Adamantane-C),
Piperidine-H), 2.22–2.24 (m, 1H, Piperidine-H), 2.62–2.64 (m, 4H, Piperidine-H), 3.42 (s, 3H, CH
3
13
.30 (s, 1H, NH), 9.88 (s, 1H, SH). C-NMR: δ 22.50 (CH
3
7.80, 35.05, 51.30 (Piperidine-C), 163.52, 179.95 (Triazole C-3 & C-5), 180.23 (C=S). ESI-MS, m/z:
90.4 (M−H, 100)−.
1
1
2
1
4b: H-NMR (DMSO-d
6
): δ 1.64–1.65 (m, 9H, Adamantane-H), 2.01–2.06 (m, 6H, Adamantane-H),
.16–2.22 (m, 5H, Piperidine-H), 2.51–2.52 (m, 4H, Piperidine-H), 7.14–7.51 (m, 5H, Ar-H), 8.32 (s,
1
3
H, NH), 9.63 (s, 1H, SH). C-NMR: δ 28.94, 35.88, 39.87, 40.03 (Adamantane-C), 28.98, 35.95, 53.31
(
Piperidine-C), 124.80, 124.86, 128.18, 139.0 (Ar-C), 161.50, 180.50 (Triazole C-3 & C-5), 181.90
(
C=S). ESI-MS, m/z: 452.4 (M−H, 100)−.
3
.6. Synthesis of 1-[(1-Adamantyl)thiocarbamoyl)]-N'-(arylidene)piperidine-4-carbohydrazides 15a–g
A mixture of 1-(1-adamantylthiocarbamoyl)piperidine-4-carbohydrazide 11 (673 mg, 2 mmol), the
appropriate aromatic aldehyde (2 mmol), in DMF (6 mL), was heated under reflux for 2 h. On cooling,
water (10 mL) was gradually added with stirring and the mixture was allowed to stand for 1 h. The
precipitated crude products were filtered, washed with water, dried and crystallized.
1
1
9
1
4
1
5a: H-NMR (DMSO-d
6
): δ 1.65–1.67 (m, 9H, Adamantane-H), 1.95–2.40 (m, 15H, 6 Adamantane-H &
Piperidine-H), 6.83–6.89 (m, 2H, Ar-H), 7.21–7.23 (m, 1H, Ar-H), 7.47 (s, 1H, NH), 7.68–7.70 (m,
1
3
H, Ar-H), 8.32 (s, 1H, NH), 8.39 (s, 1H, OH), 11.27 (s, 1H, CH=N). C-NMR: δ 29.01, 35.91, 39.03,
0.98 (Adamantane-C), 30.63, 40.03, 52.92 (Piperidine-C), 116.12, 119.35, 120.29, 125.84, 131.07,
56.51 (Ar-C), 138.50 (CH=N), 162.0 (C=O), 174.54 (C=S). ESI-MS, m/z: 439.4 (M−H, 100)−.

Molecules 2015, 20
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1
1
5
9
5b: H-NMR (CDCl
3
): δ 1.65–1.67 (m, 9H, Adamantane-H), 1.91–2.26 (m, 11H, 6 Adamantane-H &
Piperidine-H), 2.82–2.89 (m, 4H, Piperidine-H), 7.19–7.66 (m, 4H, Ar-H & NH), 8.48 (s, 1H, NH),
1
3
.29 (s, 1H, CH=N). C-NMR: δ 29.23, 36.33, 40.67, 41.48 (Adamantane-C), 29.64, 43.78, 54.47
(
Piperidine-C), 126.18, 127.70, 128.50, 130.87, 133.33, 133.52 (Ar-C), 138.35 (CH=N), 160.26 (C=O),
+
+
+
1
74.81 (C=S). ESI-MS, m/z (Rel. Int.): 498.4 (M+4+H, 9) , 496.4 (M+2+H, 54) , 494.40 (M+H, 100) .
1
1
5c: H-NMR (DMSO-d
6
): δ 1.64–1.66 (m, 9H, Adamantane-H), 2.05–3.31 (m, 15H, 6 Adamantane-H & 9
Piperidine-H), 7.40 (t, 1H, Ar-H, J = 8.0 Hz), 7.56 (d, 2H, Ar-H, J = 8.0 Hz), 7.47 (s, 1H, NH),
1
3
7
.68–7.70 (m, 1H, Ar-H), 8.34 (s, 1H, NH), 8.39 (s, 1H, CH=N). C-NMR: δ 28.99, 35.96, 39.04, 41.38
(
Adamantane-C), 28.94, 40.86, 52.96 (Piperidine-C), 129.05, 129.70, 130.80, 133.68 (Ar-C), 135.65
+
(CH=N), 161.50 (C=O), 174.94 (C=S). ESI-MS, m/z (Rel. Int.): 498.4 (M+4+H, 11) , 496.4 (M+2+H,
+
+
6
1) , 494.40 (M+H, 100) .
1
1
5d: H-NMR (CDCl
3
): δ 1.58–1.72 (m, 9H, Adamantane-H), 1.90–2.27 (m, 11H, 6 Adamantane-H &
), 3.91 (s, 3H,
), 6.84 (d, 1H, Ar-H, J = 8.5 Hz), 7.18–7.20 (m, 1H, Ar-H), 7.48 (s, 1H, Ar-H), 8.54 (s, 1H, NH),
5
Piperidine-H), 2.81–2.88 (m, 4H, Piperidine-H), 3.14 (s, 1H, NH), 3.86 (s, 3H, OCH
3
OCH
.85 (s, 1H, CH=N). C-NMR: δ 28.96, 35.54, 41.25, 41.53 (Adamantane-C), 29.74, 43.77, 54.97
Piperidine-C), 55.99 (OCH ), 56.0 (OCH ), 108.83, 110.70, 124.05, 127.20, 149.42, 151.91 (Ar-C),
3
1
3
8
(
3
3
1
38.55 (CH=N), 161.21 (C=O), 174.81 (C=S). ESI-MS, m/z: 485.4 (M+H, 100)+.
1
1
5e: H-NMR (CDCl
3
): δ 1.63–1.67 (m, 9H, Adamantane-H), 1.90–2.27 (m, 11H, 6 Adamantane-H &
), 3.83 (s, 6H, OCH ), 3.87 (s, 1H,
5
Piperidine-H), 2.80–2.86 (m, 4H, Piperidine-H), 3.82 (s, 3H, OCH
3
3
1
3
NH), 6.77 (s, 2H, Ar-H), 8.60 (s, 1H, NH), 9.16 (s, 1H, CH=N). C-NMR: δ 29.64, 35.54, 36.33, 41.49
Adamantane-C), 29.22, 43.77, 54.22 (Piperidine-C), 56.20 (2xOCH ), 56.30 (OCH ), 104.35, 128.79,
41.04, 153.57 (Ar-C), 140.23 (CH=N), 161.67 (C=O), 174.69 (C=S). ESI-MS, m/z: 515.4 (M+H, 100)+.
(
3
3
1
1
1
5f: H-NMR (CDCl
3
): δ 1.59–2.23 (m, 20H, 15 Adamantane-H & 5 Piperidine-H), 2.81–2.89 (m, 4H,
), 6.44–6.46 (m, 3H, Ar-H & NH), 7.15–7.19 (s, 2H, Ar-H & NH),
Piperidine-H), 3.78 (s, 3H, OCH
3
1
3
8
3
1
.52 (s, 1H, OH), 11.27 (s, 1H, CH=N). C-NMR: δ 29.03, 35.87, 41.24, 42.10 (Adamantane-C), 29.88,
6.07, 54.93 (Piperidine-C), 55.50 (OCH ), 101.23, 107.50, 111.12, 122.0, 162.82, 163.88 (Ar-C),
33.50 (CH=N), 161.77 (C=O), 174.50 (C=S). ESI-MS, m/z: 469.4 (M−H, 100)−.
3
1
1
5g: H-NMR (CDCl
3
): δ 1.40 (t, 3H, CH
2
CH
3
, J = 7.0 Hz), 1.63–2.26 (m, 20H, 15 Adamantane-H & 5
CH , J = 7.0 Hz), 5.5 (br. s, 1H, NH),
.85–6.87 (m, 1H, Ar-H), 7.03–7.05 (m, 2H, Ar-H), 7.30 (s, 1H, NH), 7.66 (s, 1H, NH), 9.28 (s, 1H,
Piperidine-H), 2.25–2.27 (m, 4H, Piperidine-H), 4.07 (q, 2H, CH
2
3
6
1
3
CH=N). C-NMR: δ 14.84 (CH
2
CH
), 109.39, 114.68, 121.96, 125.80, 146.17, 148.14 (Ar-C), 141.84
CH=N), 161.20 (C=O), 174.33 (C=S). ESI-MS, m/z: 483.4 (M−H, 100)+.
3
), 29.54, 36.34, 40.56, 41.56 (Adamantane-C), 30.64, 41.66, 54.15
(
Piperidine-C), 64.65 (CH
2
CH
3
(
3.7. Determination of the in Vitro Antimicrobial Activity (Agar Disc-Diffusion Method)
Sterile filter paper discs (8 mm diameter) were moistened with the compound solution in
dimethylsulphoxide of specific concentration (200 μg/disc), the antibacterial antibiotics Gentamicin and
Ampicillin trihydrate (100 μg/disc) and the antifungal drug Clotrimazole (100 μg/disc) were carefully

Molecules 2015, 20
8138
placed on the agar culture plates that had been previously inoculated separately with the microorganisms.
The plates were incubated at 37 °C, and the diameter of the growth inhibition zones were measured after
2
4 h in case of bacteria and 48 h in case of Candida albicans.
3
.8. Determination of the Minimal Inhibitory Concentration (MIC)
Compounds 5c, 5d, 5e, 6, 7, 10a, 10b, 15f and 15g Gentamicin and Ampicillin trihydrate were
dissolved in dimethylsulphoxide at concentration of 128 μg/mL. The twofold dilutions of the solution
were prepared (128, 64, 32, …, 0.5 μg/mL). The microorganism suspensions at 106 CFU/mL (colony
forming unit/mL) concentrations were inoculated to the corresponding wells. The plates were incubated
at 36 °C for 24 h. The MIC values were determined as the lowest concentration that completely inhibited
visible growth of the microorganism as detected by unaided eye.
3
.9. Determination of the in Vivo Hypoglycemic Activity
Animals: Locally bred male Sprauge-Dawley rats (250 ± 30 g body weight) were obtained from Abu
Rawash, Giza, Egypt. The rats were housed in wire-bottomed cages at 22 ± 2 °C. A standard pellet diet
and tap water were supplied ad libitium. The animals were acclimatized to these conditions for 15 days
before the experiment.
Induction of experimental diabetes: Rats were fasted for 16 h before the induction of diabetes with
STZ (Sigma Chemical Co., St. Louis, MO, USA). The animals were injected intraperitoneally with
0
.22–0.25 mL of a freshly prepared solution STZ (60 mg/mL in 0.01 M citrate buffer, pH 4.5) at a final
dose of 60 mg/kg body weight. Only rats with serum glucose levels greater than 250 mg/dL were used
in experiments.
Design of the experiment: Uniform suspensions of the compounds 5c, 6, 8b, 9, 14a and 15b and the
oral hypoglycemic drug gliclazide (positive control) in 0.5% (w/v) aqueous carboxymethyl cellulose
(
CMC) solution were prepared at specific concentration of 10 mg/mL in case of the test compounds and
gliclazide. 48 h post STZ injection, the hypoglycemic activity of the compounds 5c, 6, 8b, 9, 14a and
5b was assessed, the diabetic rats were fasted for 16 h and divided into 14 groups each of 5 animals
n = 5) and the serum glucose level was determined for each group and considered as initial fasting
serum glucose (C ). Group 1, which served as the negative diabetic control group, received only a single
1
(
0
oral dose of 0.5% (w/v) aqueous CMC solution (5 mL/kg). Groups 2 was treated with 10 mg/kg
gliclazide in 0.5% (w/v) aqueous CMC (positive control). Groups 3–14 were treated with either a single
oral dose of the 10 or 20 mg/kg of the test compounds. All treatments were administered by oral gavage.
2
4 h after treatment, the blood samples were collected and the serum glucose level (C24) was determined
for each group.
Determination of serum glucose: Blood samples from the tail vein were collected, allowed to clot,
centrifuged at 2000 r.p.m. for 10 min. The serum was separated and used in the same day for the
measurement of serum glucose levels using commercial glucose oxidase (GO) assay kit (Sigma-Aldrich
Co., St. Louis, MO, USA). Blood glucose levels were expressed in mg/dL as mean ± SEM. The data
were statistically analyzed using ANOVA with Tukey’s multiple comparison test. The values of p < 0.01
were considered as significant. The percentage of serum glucose reduction for each group was calculated
in relation to the initial serum glucose level as follows:

Molecules 2015, 20
8139
%
Serum glucose reduction = [(C
is the mean initial fasting serum glucose level, C24 is the mean serum glucose level 24 h
after treatment.
0
− C24/C
0
)] × 100
where C
0
3.10. Determination of the Oral Acute Toxicity of Compound 5c
Freshly prepared suspensions of compound 5c in concentrations of 1%, 3%, 4%, 6%, 8% and 12% in
0
.5% aqueous carboxymethyl cellulose solution were prepared. Each compound was given to six groups
each of 6 normal albino mice of both sexes by oral intubation in doses of 250, 500, 750, 1000, 1250 and
500 mg/kg. The percentage mortality was recorded 24 h after compound administration and the oral
lethal dose LD50 was calculated.
1
4
. Conclusions
In this study, series of N-(1-adamantyl)carbothioamides were synthesized and their in vitro
antimicrobial activity was determined. Compounds 5c, 5d, 5e, 6, 7, 10a, 10b, 15a, 15f and 15g displayed
marked antibacterial activity. In addition, the in vivo oral hypoglycemic activity of compounds 5a–e, 6,
7
, 8a–c, 10a, 10b, 14a, 14b and 15a–g was determined in streptozotocin (STZ)-induced diabetic rats.
Compound 5c produced significant hypoglycemic activity compared gliclazide at a safe dose. The active
compounds are considered to be good candidates as newer antibacterial and hypoglycemic agents,
further studies such as molecular docking for the exploration of the mechanism of their biological
activity are required for optimization of the activity are being undertaken.
Supplementary Materials
Supplementary materials can be accessed at: http://www.mdpi.com/1420-3049/20/05/8125/s1.
Acknowledgments
The authors would like to extend their appreciation to the Deanship of Scientific Research at King
Saud University for funding this study through the research group project No. RGP-1435-362.
Author Contributions
Ebtehal S. Al-Abdullah and Ali A. El-Emam designed the study; Hanaa M. Al-Tuwaijri, Monirah A.
Al-Alshaikh, Ebtehal S. Al-Abdullah and Ali A. El-Emam synthesized the intermediate and target
compounds and performed the interpretation of spectral data; Hanan M. Hassan conducted the
hypoglycemic activity testing; Elsayed E. Habib performed the antimicrobial testing. All the authors
participated in the preparation of the manuscript.
Conflicts of Interest
The authors declare no conflicts of interest in this study.

Molecules 2015, 20
8140
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Sample Availability: Samples of the all compounds are available from the correspondent author.
©
2015 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
http://creativecommons.org/licenses/by/4.0/).
(