Synthesis and antimicrobial evaluation of some new cyclooctanones and cyclooctane-based heterocycles

Article abstract of DOI:10.1002/ardp.201100186

The versatile synthon (E)-2-((dimethyl amino)methylene)cyclooctanone (2) was used as a key intermediate for the synthesis of cyclooctanones and cyclooctane-based heterocycles with pyrazole, isoxazole, pyrimidine, pyrazolopyrimidine, triazolopyrimidine and

Full text of DOI:10.1002/ardp.201100186

Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
231
Full Paper
Synthesis and Antimicrobial Evaluation of Some New
Cyclooctanones and Cyclooctane-Based Heterocycles
Korany A. Ali1, Hanaa M. Hosni2, Eman A. Ragab3, and Sherein I. Abd El-Moez4
1 Applied Organic Chemistry Department, National Research Center, Dokki-Cairo, Egypt
2 Pesticides Chemistry Department, National Research Center, Dokki-Cairo, Egypt
3 Chemistry Department, Faculty of Science, University of Cairo, Giza, Egypt
4 Microbiology and Immunology Department, National Research Center, Dokki-Cairo, Egypt
The versatile synthon (E)-2-((dimethyl amino)methylene)cyclooctanone (2) was used as a key
intermediate for the synthesis of cyclooctanones and cyclooctane-based heterocycles with
pyrazole, isoxazole, pyrimidine, pyrazolopyrimidine, triazolopyrimidine and imidazopyrimidine
derivatives via its reactions with several nitrogen nucleophiles. The newly synthesized compounds
were screened in vitro for their antimicrobial activity against pathogenic microorganisms (Listeria
monocytogenes, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus aureus, Pseudomonas
aeruginosa and Candida albicans). Most of the tested compounds showed moderate to high
antibacterial and antifungal effects against the tested pathogenic microorganisms. Among the
synthesized compounds, 2-((p-sulfonamidophenyl)methylene)cyclooctanone (5) showed excellent
activity against Listeria monocytogenes.
Keywords: Cyclooctanone / Pyrazole / Pyridine / Pyrimidine / Listeria monocytogenes / Methicillin-resistant
Staphylococcus aureus (MRSA)
Received: May 23, 2011; Revised: July 13, 2011; Accepted: July 18, 2011
DOI 10.1002/ardp.201100186
Introduction
Cyclooctane rings are frequently found in the skeleton of
many natural products that have different biological activi-
ties [4]. On the other hand, many of nitrogen-containing
saturated heterocycles have been found to play fundamental
roles in biological process [5].
Bacteria are the cause of some deadly diseases and wide-
spread epidemics of human civilization. For example,
Listeria monocytogenes is a facultatively anaerobe, intracellular
bacterium that is the causative agent of listeriosis. It is one of
the most virulent foodborne pathogens with 20 to 30 percent
of clinical infections resulting in death [1]. Annually, lister-
iosis is the leading cause of death among foodborne bacterial
pathogens with fatality rates exceeding even Salmonella and
Clostridium botulinum [2]. Furthermore, methicillin-resistant
Staphylococcus aureus (MRSA) is a bacterium responsible for
several difficult-to-treat infections in humans. MRSA is
thought to be one of the resident microbes, which is a
harmless to healthy people, but intractable in immunosup-
pressed patients [3].
In view of the above-mentioned facts and in continuation
of our interest in the synthesis of a variety of heterocyclic
systems for biological and pharmacological evaluations
[6–13], we report herein our procedure for the synthesis of
cyclooctanones and cyclooctane-based heterocycles with a
different substitution pattern starting from (E)-2-((dimethyl
amino)methylene)cyclooctanone (2) and evaluating their
selectivity towards pathogenic microorganisms (Listeria mono-
cytogenes, methicillin-resistant Staphylococcus aureus (MRSA),
Staphylococcus aureus, Pseudomonas aeruginosa and Candida
albicans).
Results and discussion
Correspondence: Korany A. Ali, Applied Organic Chemistry Department,
National Research Center, Dokki-Cairo 12622, Egypt.
E-mail: kornykhlil@yahoo.com
Fax: þ20233370931
Chemistry
The synthetic strategies adopted to obtain the target com-
pounds are outlined in schemes (1–5). The starting compound
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

232
K. A. Ali et al.
Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
(E)-2-((dimethylamino)methylene)cyclooctanone (2) could be
synthesized through treatment of cyclooctanone 1 with
dimethylformamide-dimethylacetal (DMF-DMA) under reflux
condition (Scheme 1). The structure of compound 2 and
their analytical confirmations have been well described
[14–16].
one isolable product, identified as 4,5,6,7,8,9-hexahydro-1-
1
phenyl-1H-cycloocta[c]pyrazole (7b) (Scheme 2). The H NMR
spectrum of compound 7a showed characteristic singlet sig-
nals at 7.39 and 12.10 ppm for H-3 of pyrazole and NH
protons, respectively [20–22]. The formation of compounds
7a,b is assumed to take place via a Michael-type addition of
the amino group of hydrazines to the enamine double bond
in 2 or 3 followed by interamolecular cyclization via the loss
of dimethylamine or morpholine and water molecules
(Scheme 2). In a similar manner, enaminone derivatives 2
or 3 was reacted with hydroxylamine hydrochloride in reflux-
ing ethanol, in the presence of anhydrous sodium acetate, to
give only one isolable product identified as 4,5,6,7,8,9-hexa-
hydrocycloocta[d]isoxazole (8) rather than isomeric form 9
(Scheme 2). The structure of compound 8 was assigned as the
correct structure on the basis of the 1H NMR spectrum of the
product, where a resonance for H-3 of isoxazole appeared
typically at d 8.41 ppm. The isomeric product was ruled out
as H-5 of isoxazole would be expected to resonate at lower
filed around d 9.30 ppm [23, 24].
Enaminones are highly reactive building blocks and their
utility in organic synthesis has recently earned considerable
attention [17–19]. The reactivity of the enaminone 2 towards
some nitrogen nucleophiles was investigated. Thus, treat-
ment of enaminone 2 with morpholine and piperidine in
refluxing ethanol affords in each case only one isolable prod-
uct identified as (E)-2-(morpholinomethylene)cyclooctanone
(3) and (E)-2-((piperidin-1-yl)methylene)cyclooctanone (4),
respectively (Scheme 1). The structures of the isolated prod-
ucts were assigned based on their elemental analysis and
spectral data. For example, the 1H NMR spectrum of com-
pound 3 displayed signals at d 2.97–3.98 and 7.45 character-
–
istic for morpholine and C CH protons, respectively.
–
When the enaminone 2 or the morpholinyl derivative 3
was treated with p-sulfonamide under reflux condition, it
afforded 2-((p-sulfonamidophenyl)methylene)cyclooctanone
(5). The 1H NMR spectrum of the latter product exhibited
characteristic two doublet signals at d 7.81 and 11.72 (D2O-
The enaminone derivatives 2 or 3 reacted also with guani-
dine in refluxing ethanol, to give a high yield of a single
product (as examined by TLC) identified as 5,6,7,8,9,10-hexa-
hydrocycloocta[d]pyrimidin-2-amine (10) according to its
1
–
exchangeable) characteristic for C CH and NH protons,
–
respectively.
elemental analysis and spectral data. The H NMR spectrum
of the latter product exhibited characteristic signals at d 4.88
(D2O-exchangeable) and at d 7.96 due to amino and C–H
pyrimidine protons, respectively.
Treatment of the enaminone 2 or the morpholinyl deriva-
tive 3 with hydrazine hydrate in refluxing ethanol afforded a
single product isolated after chromatography as pale yellow
oil identified as 4,5,6,7,8,9-hexahydro-1H-cycloocta[c]pyrazole
(7a). Similarly, the enaminone 2 or 3 was reacted with phenyl
hydrazine in ethanol at refluxing temperature to afford only
The reactivity of enaminone 2 towards some heterocyclic
amines was also investigated. Thus, treatment of the enam-
inone 2 with 5-amino-3-phenyl pyrazole (11), 3-amino-1,2,4-
triazole (14) and 2-amino benzimidazole 17, in refluxing
CH3
O
O
O
H
N
CH3
OMe
OMe
Xylene
CH3
N
N
H
+
reflux
5h
CH3
2E
2Z
1
O
S
O
O
EtOH
reflux
NH2
EtOH
reflux
EtOH
reflux
H2N
N
N
H
H
O
O
O
O
S
O
N
N
HN
NH2
O
5
3
4
EtOH
reflux
O
S
O
Scheme 1. Synthetic pathway for the forma-
tion of compounds 2, 3, 4, and 5.
NH2
H2N
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
Synthesis and Antimicrobial Evaluation of Some New Cyclooctanones
233
R
N
O
NHNHR
N
7a R= H
7a R=Ph
NH2NHR
-HY
H
-H2O
6a,b
O
N
O
H
NH2OH
Y
8
N
O
-HY
-H2O
2 or 3
//
9
NH2
N
NH
N
NH2
H2N
N
O
Y=NMe2 or
-HY
-H2O
Scheme 2. Synthetic pathway for the forma-
tion of compounds 7a,b, 8 and 10.
10
ethanol in the presence of a catalytic amount of piperidine,
gave, in each case, a single product identified as 1-phenyl-
5,6,7,8,9,10-hexahydrocycloocta[20,10-e]pyrazolo[1,5-a]pyrimi-
dine (13), 5,6,7,8,9,10-hexahydrocycloocta[20,10-e]triazolo[1,5-
a]pyrimidine (16) and 5,6,7,8,9,10-hexahydrocycloocta[20,10-
e]pyrimido[1,2-a]benzimidazole (19), respectively on the basis
of their elemental analysis and spectral data. The reaction of
heterocyclic amines 11, 14 and 17 with enaminone 2 is
assumed to take place via initial Michael-type addition of
amino group to the enamine double bound followed by
elimination of the dimethyl amine and water molecules
(Scheme 3). Further evidence of the proposed structure 13
Ph
1
NMe2
N
N
N
H
20
DMF-DMA
NH2
Ph
Ph
N
N
Ph
N
N
O
N
H
11
Ph
N
N
HO
H
N
N
H
H
N
N
-H2O
-HNMe2
13
12b
12a
N
N
N
H
14
N
N
N
N
N
O
NH2
O
N
N
N
N
HO
H
N
N
H
CH3
H
N
N
-H2O
CH3
-HNMe2
2
16
15b
15a
N
NH2
N
N
H
N
N
N
N
O
H
N
N
N
17
H
H
HO
N
-H2O
-HNMe2
Scheme 3. Synthetic pathway for the forma-
tion of compounds 13, 16 and 19.
18a
19
18b
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

234
K. A. Ali et al.
Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
absorption band at v 1651 cmꢀ1. Furthermore, the product
21 was further confirmed by an independent synthesis from
cyanoacetamide and enaminone 2. The two reaction products
were identical in all respects (mp, TLC and spectra) [see
experimental part]. Compound 21 has been reported by
another synthetic route from the condensation of cyanoacet-
amide with sodium salt of 2-formyl-cycloalkanone [26]
Reaction of enaminone 2 with acetyl acetone and ethyl
acetoacetate in glacial acetic acid in the presence of
ammonium acetate gave cycloocta[b]pyridine derivatives 24
and 25, respectively (Scheme 5). The structures of the isolated
products were assigned based on their elemental analysis and
spectral data. For example, the 1H NMR spectra of compounds
24 and 25 showed a singlet signals at d 7.98 and 8.57 ppm
respectively, characteristic for H-4 of pyridine. In addition,
the mass spectra of compounds 24 and 25 revealed bands at
m/z 217 and 247 respectively, corresponding to their molecu-
lar ion peak. On the other hand, compounds 24 and 25 have
been previously reported by another synthetic route from 2-
aminomethylene-cyclooctanone [27].
NH
O
O
CN
CN
NC
//
CN
EtONa/EtONa
22
O
HN
CH3
N
CH3
O
21
2
NC
NH2
NH2
O
CN
EtONa/EtONa
//
23
Scheme 4. Synthetic pathway for the formation of compound 21.
was obtained by an independent synthesis via the reaction
of N-(N,N-dimethylaminomethylene)imino-3-phenyl-1-H-pyra-
zole (20) with cyclooctanone 1 in refluxing acetic acid to
afford a product identical in all respects (mp, TLC and spec-
tral data) with that obtained from the reaction of 2 with 11 as
shown in Scheme 3.
Biological testing
Antimicrobial activity
Eight of the newly synthesized target compounds were eval-
uated for their in vitro antibacterial activity against patho-
genic bacteria such as Gram positive bacteria: L.
monocytogenes, methicillin-resistant Staphylococcus aureus
(MRSA), S. aureus; and Gram negative bacteria: Ps. aeruginosa;
and anti-fungal activity against C. albicans. The minimum
inhibitory concentration (MIC) (mg/mL) and inhibition zone
diameters values are recorded in Table 1. The results depicted
in Table 1 revealed that most of tested compounds of this
investigation have moderate to good activity against most of
the tested pathogenic bacteria. As compared to the standard
drug (ciprofloxacin) with MICs 0.19, 0.097 and 0.39 mg/mL
against L. monocytogenes, S. aureus, Ps. aeruginosa respectively,
As previously reported, enaminones can be used also as
potential precursors for the synthesis of fused pyridine sys-
tems when reacting with active methylene compounds [25].
Thus, treatment of enaminone 2 with malononitrile in
refluxing sodium ethoxide solution afforded a pale yellow
product for which two possible structures 21 and 22 can be
formulated (Scheme 4). Structure 22 was ruled out based on
the 1H NMR and IR spectral data of the product. The 1H NMR
spectrum of the latter product showed the presence of amidic
NH at d 12.39 ppm and the absence of imine signal around d
3.0 ppm [25]. Also, its IR spectrum revealed amidic carbonyl
CH3
O
N
H3C
CH3
CH3
O
O
CH3COOH/CH3COONH4
reflux
O
H
24
CH3
CH3
O
N
N
CH3
H3C
O
C2H5
C2H5
O
O
O
2
CH3COOH/CH3COONH4
reflux
Scheme 5. Synthetic pathway for the forma-
tion of compounds 24 and 25.
25
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
Synthesis and Antimicrobial Evaluation of Some New Cyclooctanones
235
Table 1. Inhibition zone (mm) and minimal inhibitory concentrations (MIC, mg/mL) of some newly synthesized compounds.
Compound no
Zone of inhibition in (mm) and MIC in (mg/mL)
Gramþve Bacteria GramSve Bacteria
Fungi
MRSA
L. monocytogenes
S. aureus
Ps. aeruginosa
C. albicans
5
8
10
13
16
19
21
10 (25)
12 (12.5)
11 (12.5)
9 (50)
12 (12.5)
9 (50)
11 (100)
9 (50)
18 (12.5)
N
28 (0.097)
12 (6.25)
14 (1.56)
13 (3.125)
13 (3.125)
13 (3.125)
N
11 (12.5)
13 (3.12)
13 (3.12)
N
11 (3.12)
12 (12.5)
12 (6.25)
10 (25)
10 (25)
N
N
N
11 (12.5)
13 (3.125)
12 (6.25)
12 (6.25)
N
11 (25)
11 (50)
9 (25)
10 (25)
9 (25)
11 (50)
11 (25)
N
24
N
N
N
N
Vancomycin
Ciprofloxacin
Fluconazole
28 (0.19)
–
28 (0.097)
–
25 (0.39)
–
–
19 (1.5)
–
MIC: Minimal inhibitory concentration value with SEM ¼ 0.02
N, not tested
2-(p-sulfonamidophenyl)methylene cyclooctanone (5) showed Experimental section
very promising activity with MICs 0.097 and 3.12 mg/mL
against L. monocytogenes and Ps. aeruginosa respectively.
Compound 10 shows significant antibacterial activity against
L. monocytogenes with MIC 1.56 mg/mL. As compared to the
standard drug (vancomycin) with MIC 12.5 mg/mL against
methicillin-resistant Staphylococcus aureus (MRSA), compounds
8, 10 and 16 showed promising activity with MICs 12.5 mg/mL.
The anti-fungal data (Table 1) revealed that some of tested
compounds of this investigation have moderate activity
against the tested pathogenic fungi (C. albicans) as compared
to the standard drug fluconazole.
Chemistry
General
All melting points were measured on a Gallenkamp melting
point apparatus (Weiss Gallenkamp, London, UK). The infra-
red spectra were recorded in potassium bromide disks on pye
Unicam SP 3300 and Shimadzu FT IR 8101 PC infrared
spectrophotometers (Pye Unicam Ltd. Cambridge, England
and Shimadzu, Tokyo, Japan, respectively). The NMR spectra
were recorded on a Varian Mercury VX-300 NMR spec-
trometer (Varian, Palo Alto, CA, USA). 1H spectra were run
at 300 MHz and 13C spectra were run at 75.46 MHz in
deuterated chloroform (CDCl3) or dimethyl sulphoxide
(DMSO-d6). Chemical shifts are given in parts per million
and were related to that of the solvent. Mass spectra were
recorded on a Shimadzu GCMS-QP 1000 EX mass spec-
trometer (Shimadzu) at 70 eV. Elemental analyses were car-
ried out at the Micro-analytical Centre of Cairo University,
Giza, Egypt. All reactions were followed by TLC (Silica gel,
Aluminum Sheets 60 F254, Merck).
From the antimicrobial activity and structural activity
relationship (SAR) of compound 5, we can conclude that
the sulfonamide moiety is essential for the activity
against pathogenic bacteria L. monocytogenes and Ps. aeruginosa.
On the other hand the good bacterial activity against
methicillin-resistant Staphylococcus aureus (MRSA), exhibited
by compounds 8, 10 and 16 might be due to the
presence of isoxazole and pyrimidine moieties. It is
interesting to note that an alteration in the molecular
configuration of investigated compounds may have a pro-
nounced effect on anti-microbial screening, e.g. compound
16 having fused triazolo[1,5-a]pyrimidine moiety showed
good antibacterial activity against methicillin-resistant
Staphylococcus aureus (MRSA) than compound 19 with
pyrimido[1,2-a]benzimidazole moiety.
Material and reagents
Hydrazine hydrate, phenyl hydrazine, guanidine hydrochlo-
ride, acetyl acetone ethylacetoacetate, 2-amiobenzimidazole,
3-aminotriazole were purchased from Aldrich Chemical CO.
Triethylamine, morpholine and piperidine, were purchased
from British Drug Houses (BDH). Dimethylformamide-
dimethylacetal (DMF-DMA) was obtained from Merck CO,
Germany. Hydrochloric acid and potassium carbonate
were purchased from El-Nasr Pharmaceutical and
Chemical CO. (ADWIC). 3-Phenyl-1H-pyrazol-5-amine (11)
From structure activity relationship (SAR) point of
view, the attachment of phenyl sulfonamide moiety to
cyclooctanone ring can be considered as breakthrough
in developing new antibiotic agents against Listeria
monocytogenes.
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

236
K. A. Ali et al.
Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
and (E)-N,N-dimethyl-N’-(3-phenyl-1H-pyrazol-5-yl)formamidine (20)
were prepared according to literature procedures [28, 29].
Compounds 24 and 25 have been previously reported by another
synthetic route from 2-aminomethylene-cyclooctanone [27].
was distilled off under reduced pressure and the residual
brown solid was taken in methanol. The solid product so
formed was filtered off, washed thoroughly with methanol,
dried and finally recrystallized from ethanol to afford com-
pound 5.
Preparation of (E)-2-((dimethylamino)methylene)-
cyclooctanone (2)
Yield (1.15 g, 75%); pale yellow crystals (ethanol); mp:
–
179–1808C. IR (KBr): v 3360, 3161 (NH, NH ), 1644 (C O)
–
2
A
mixture of cyclooctanone
1
(1.26 g, 10 mmol) and
cmꢀ1 1H NMR (DMSO-d6): d 1.20–3.11 (m, 12H, 6CH2),
.
dimethylformamide-dimethylacetal (DMF-DMA) (1.33 mL,
10 mmol) was refluxed for 5h, and then allowed to cool.
The reaction product was isolated after chromatography to
give compound 2 as pale yellow oil. An analytical pure sample
was obtained by crystallization [14–16]. Yield (1.61 g, 85%);
7.15–7.55 (m, 4H, ArH’s, 2H, NH2-SO2, D2O-exchangeable),
7.81 (d, 1H, CH-enamine), 11.72 (d, 1H, NH, D2O-exchange-
able). MS m/z (%): 308 [Mþ] (59), 266 (30), 211 (98), 130 (100),
91 (46). Anal. Calcd for C15H20N2O3S (308.40): C, 58.42; H, 6.54;
N, 9.08. Found: C, 58.52; H, 6.57; N, 9.10.
–
colorless crystal (hexane), mp: 39–418C. IR (KBr): v 1680 (C O)
–
cmꢀ1
.
1H NMR (DMSO-d6): d 1.12–2.91 (m, 12H, 6CH2), 3.41
Reaction of compounds 2 and 3 with hydrazines
To a solution of the enaminone derivative 2 or 3 (5 mmol) in
absolute ethanol (20 mL) was added (5 mmol) of the appro-
priate hydrazines. The reaction mixture was refluxed for
several hours. The solvent was distilled off at reduced pres-
sure and the residual viscous liquid was taken in methanol
and isolated by chromatography (chloroform) to afford the
corresponding pyrazole derivatives 7a,b. The synthesized
compounds together with their physical and spectral data
are listed below:
þ
–
–
(s, 6H, 2CH ), 7.52 (s, 1H, CH C). MS m/z (%): 181 [M ] (75),
3
145 (100). Anal. Calcd. for C11H19NO (181.27): C, 72.88;
H, 10.56; N, 7.73. Found: C, 72.92; H, 10.51; N, 7.80.
Preparation of compounds 3 and 4
To a solution of the enaminone 2 (0.90 g, 5 mmol) in ethanol
(15 mL) was added morpholine (0.42 g, 5 mmol) or piper-
idine (0.43 g, 5 mmol). The reaction mixture was refluxed
for several hours and the progress of the reaction was moni-
tored by TLC. The solvent was evaporated under reduced
pressure and the oil residue was isolated by chromatography
(chloroform/methanol, 9:1) to give compound 3 and 4 as pale
yellow oil. Analytical pure samples were obtained by crystal-
lization to give colorless crystals of compounds 3 and 4,
respectively.
4,5,6,7,8,9-Hexahydro-1H-cycloocta[c]pyrazole (7a)
Yield (0.51 g, 68%); colorless crystal (hexane); mp: 49–518C. IR
(KBr): v 3320 (NH) cmꢀ1 1H NMR (DMSO-d6): d 1.30–3.01
.
(m, 12H, 6CH2), 7.39 (s, 1H, CH pyrazole), 12.10 (s, 1H, NH,
D2O-exchangeable). MS m/z (%): 150 [Mþ] (100). Anal. Calcd. for
C9H14N2 (150.22): C, 71.96; H, 9.39; N, 18.65. Found: C, 71.90;
H, 9.42; N, 18.71.
(E)-2-(Morpholinomethylene)cyclooctanone (3)
Yield (0.80 g, 72%); colorless crystal (hexane); mp: 42–448C. IR
ꢀ1
(KBr): v 1667 (C O) cm
.
1H NMR (CDCl3): d 1.15–2.93
4,5,6,7,8,9-Hexahydro-1-phenyl-1H-cycloocta[c]-
pyrazole (7b)
–
–
(m, 12H, 6CH2), 2.97 (t, 4H, 2CH2 morpholine), 3.98 (t, 4H,
þ
–
2CH , morpholine), 7.45 (s, 1H, CH C). MS m/z (%): 223 [M ]
–
(75), 151 (51), 126 (100), 113 (43), 59 (70). Anal. Calcd for
Yield (0.81 g, 72%); pale yellow crystal (hexane); mp: 55–578C.
1H NMR (DMSO-d6): d 1.39–3.61 (m, 12H, 6CH2), 7.45 (s, 1H,
CH-pyrazole), 6.98–7.30 (m, 5H, ArH’s). MS m/z (%): 226 [Mþ]
(24), 183 (21), 170 (17), 77 (100). Anal. Calcd for C15H18N2
(226.32): C, 79.61; H, 8.02; N, 12.38. Found: C, 79.57; H, 7.97;
N, 12.35.
2
C
13H21NO2 (223.31): C, 69.92; H, 9.48; N, 6.27. Found: C,
69.94; H, 9.44; N, 6.33.
(E)-2-((Piperidin-1-yl)methylene)cyclooctanone (4)
Yield (0.90 g, 82%); colorlesꢀs1 crystal (hexane); mp: 45–478C.
–
IR (KBr): v 1664 (C O) cm
.
1H NMR (CDCl3): d 1.1þ4–3.93
Reaction of (E)-2-dimethylaminomethylene cyclooctanone
with hydroxylamine hydrochloride and guanidine
–
(m, 22H, 11CH ), 7.45 (s, 1H, CH C). MS m/z (%): 221 [M ] (25),
–
–
178 (13), 151 (21), 125 (35), 86 (83), 60 (100). Anal. Calcd. for
2
C
14H23NO (221.34): C, 75.97; H, 10.47; N, 6.33. Found: C, 75.91;
General procedure
H, 10.44; N, 6.37.
To a mixture of the enaminone 2 or 3 (5 mmol) and hydroxyl-
amine hydrochloride or guanidine hydrochloride (5 mmol)
in ethanol (10 mL) was added anhydrous potassium carbon-
ate (5 mmol). The resulting mixture was refluxed for 5 h and
allowed to cool to room temperature then diluted with water
(30 mL). The solid products that formed were collected by
2-((p-Sulfonamidophenyl)methylene)cyclooctanone (5)
To a solution of the enaminone derivative 2 or 3 (5 mmol) in
ethanol (10 mL) was added p-sulfonamide (0.86 g, 5 mmol).
The reaction mixture was refluxed for 8 h, then the solvent
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
Synthesis and Antimicrobial Evaluation of Some New Cyclooctanones
237
filtration, washed with water, dried and recrystallized from the
6.91–7.43 (m, 5H, ArH0s), 8.00 (s, 1H, pyrazole-H), 8.37 (s, 1H,
pyrimidine-H). MS m/z (%): 277 [Mþ] (100), 149 (83). Anal. Calcd.
for C18H19N3 (277.36): C, 77.95; H, 6.90; N, 15.15. Found: C,
77.85; H, 6.94; N, 15.11.
proper solvent to afford compounds 8 and 10, respectively.
4,5,6,7,8,9-Hexahydrocycloocta[d]isoxazole (8)
Yield (0.55 g, 73%); white solid (ethanol/dioxane); mp: 250–
1
2528C. H NMR (DMSO-d6): d 1.37–3.52 (m, 12H, 6CH2), 8.41
5,6,7,8,9,10-Hexahydrocycloocta[20,10-e]triazolo[1,5-a]-
pyrimidine (16)
(s, 1H, CH-isoxazole). MS m/z (%): 151 [Mþ] (35), 69 (100). Anal.
Calcd. for C9H13NO (151.21): C, 71.49; H, 8.67; N, 9.26. Found:
C, 71.43; H, 8.70; N, 9.23.
Yield (0.80 g, 79%); pale yellow crystals (ethanol); mp:
121–1228C. 1H NMR (CDCl3): d 1.31–3.28 (m, 12H, 6CH2),
8.57 (s, 1H, pyrimidine-H), 8.68 (s, 1H, triazole-H). 13C NMR
(CDCl3): d 25.77, 25.88, 26.24, 26.38, 27.14, 31.86 (6 CH2),
122.93, 149.22, 154.65, 155.45, 155.62 (triazole and pyrimi-
dine carbons). MS m/z (%): 202 [Mþ] (100), 174 (89), 159 (62),
146 (43). Anal. Calcd. for C11H14N4 (202.26): C, 65.32; H, 6.98;
N, 27.70. Found: C, 65.26; H, 6.88; N, 27.63.
5,6,7,8,9,10-Hexahydrocycloocta[d]pyrimidin-2-amine (10)
Yield (0.84 g, 95%); pale yellow crystals (ethanol); mp: 173–
.
1748C. IR (KBr): v 3336, 3160 (NH2) cmꢀ1 1H NMR (CDCl3):
d 1.24–2.73 (m, 12H, 6CH2), 4.88 (s, 2H, NH2, D2O-exchange-
able), 7.96 (s, 1H, CH-pyrimidine). 13C NMR (CDCl3): d 25.73,
25.99, 28.34, 29.85, 32.29, 33.90 (6 CH2), 123.66, 157.57,
162.03, 170.52 (pyrimidine carbons). MS m/z (%): 177 [Mþ]
(73), 149 (89), 95 (100). Anal. Calcd. for C10H15N3 (177.25):
C, 67.76; H, 8.53; N, 23.71. Found: C, 67.71; H, 8.59; N, 23.67.
5,6,7,8,9,10-Hexahydrocycloocta[20,10-e]pyrimido [1,2-a]-
benzimidazole (19)
Yield (0.90 g, 72%); yellow crystals (ethanol); mp: 133–1348C.
1H NMR (CDCl3): d 1.25–3.35 (m, 12H, 6CH2), 7.25–7.55 (m, 4H,
ArH0s), 8.48 (s, 1H, pyrimidine-H). 13C NMR (CDCl3): 25.83,
25.92, 29.32, 29.78, 32.96, 35.30 (6 CH2), 110.44, 120.32,
121.19, 125.88, 126.80, 130.02, 144.49, 150.94, 170.91
(aromatic, imidazole and pyrimidine carbons). MS m/z (%):
251 [Mþ] (100), 222 (25), 77 (15). Anal. Calcd. for C16H17N3
(251.33): C, 76.46; H, 6.82; N, 16.72. Found: C, 76.39; H, 6.78; N,
16.84.
Reaction of (E)-2-dimethylaminomethylene cyclooctanone
with heterocyclic amines: Preparation of compounds 13,
16 and 19.
Method A
General procedure: To a mixture of the enaminone 2 (0.90 g,
5 mmol) and the appropriate heterocyclic amines 11, 14 and
17 (5 mmol) in ethanol (20 mL), a catalytic amount of piper-
idine was added. The reaction mixture was refluxed for
several hours (the reactions were followed by TLC). The
solvent was distilled off at reduced pressure and the residual
viscous liquid was taken in methanol and the resulting solid
was collected by filtration, washed thoroughly with ethanol,
dried and finally crystallized from ethanol to afford
compounds 13, 16 and 19, respectively. The synthesized com-
pounds 13, 16 and 19 together with their physical and
spectral data are listed below.
1,2,5,6,7,8,9,10-Octahydro-2-oxocycloocta[b]-
pyridine-3-carbonitrile (21)
To a solution of 2 or 3 (5 mmol) in ethanolic sodium ethoxide
[prepared from sodium metal (0.11g) and absolute ethanol
(20 mL)] was added malononitrile or cyanoacetamide
(5 mmol). The reaction mixture was refluxed for 5 h, and
then poured into ice-cold water. The solution was acidified
with diluted HCl. The formed solid was collected by filtration,
washed with water, dried and finally recrystallized from
ethanol/dioxane, to afford the same product 21 identical
in all respects (TLC, mp and spectral data), yield (75%, 71%,
respectively), Brown crystals (ethanol/dioxane); mp:
Method B
A mixture of cyclooctanone 1 (10 mmol) and an equivalent
molar ratio of 5-N-(N,N-dimethylaminomethylene)amino-3-
methyl-1H-pyrazole (20) in acetic acid (20 mL) was heated
under reflux for 6 h. The solvent was removed by distillation
under reduced pressure and the remainder was left to cool.
The precipitated solid product was collected by filtration.
Crystallization from ethanol afforded product identical in
all respects (mp, mixed mp, TLC, IR, and mass spectra with 13).
–
252–2548C. IR (KBr): v 3410 (NH), 2219 (CN), 1651 (C O)
–
cmꢀ1 1H NMR (DMSO-d6): d 1.11–3.28 (m, 12H, 6CH2), 7.98
.
(s, 1H, pyridine-H), 12.39 (s, 1H, D2O-exchangeable, NH).
MS m/z (%): 202 [Mþ] (100), 187 (17), 173 (39), 159 (63), 146
(21). Anal. Calcd. for C12H14N2O (202.25): C, 71.26; H, 6.98,
13.85. Found: C, 71.35; H, 7.12; .N, 13.73.
Reaction of (E)-2-dimethylaminomethylene cyclooctanone
(2) with acetyl acetone and ethyl acetoacetate
1-Phenyl-5,6,7,8,9,10-hexahydrocycloocta[20,10-e]-
pyrazolo[1,5-a]pyrimidine (13)
Yield (1.03 g, 75%); pale yellow crystals (ethanol); mp:
General procedure: To a mixture of 2 or 3 (5 mmol) and
ammonium acetate (0.5 g) in glacial acetic acid (20 mL),
was added acetyl acetone or ethyl acetoacetate (5 mmol).
1
125–1268C. H NMR (DMSO-d6): d 1.22–3.78 (m, 12H, 6CH2),
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

238
K. A. Ali et al.
Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
The reaction mixture was refluxed for several hours and
followed by TLC. The solvent was evaporated under reduced
pressure, the oil residue was isolated with chromatography
on silica gel using chloroform and the product was isolated
as pale yellow oil. An analytical pure sample was obtained
by crystallization to give the corresponding pyridine deriva-
tive 24 and 25. The synthesized compounds 24 and 25 together
with their physical and spectral data are listed below.
Ciprofloxacin, vancomycin and fluconazole were used as
reference drugs (Oxoid).
Antimicrobial activity
Antibacterial as well as antifungal activity of eight tested
compounds in DMSO (100 mg/mL) was in vitro evaluated using
agar well diffusion method [30, 31]. The results were recorded
for each tested compound as the average diameter of
inhibition zones of bacterial or fungal growth around the
disks in mm. Vancomycin against MRSA and ciprofloxacin
(100 mg/mL) were used as positive control standard antibac-
terial, fluconazole (100 mg/mL) was used as standard
antifungal.
1-(5,6,7,8,9,10-Hexahydro-2-methylcycloocta[b]-
pyridin-3-yl)ethanone (24)
Yield (0.83 g, 77%); colorless crystal (hexane); mp: 55–578C. IR
ꢀ1
–
–
(KBr): v 1685 (C O) cm
.
1H NMR (CDCl3): d 1.19–3.37
(m, 12H, 6CH2), 2.66, 2.69 (s, 6H, 2CH3), 7.98 (s, 1H,
CH-pyridine). 13C NMR (CDCl3): d 20.26 (CH3), 25.76, 25.81,
29.32, 30.38, 34.40, 32.01, 34.47, (6 CH2 and acetyl CH3),
130.61, 133.27, 137.68, 155.32, 163.49 þ(pyridine carbons),
Using microtiter dilution plate method [32], the minimum
inhibitory concentration (MIC) considered as quantitative
method was used for evaluation of the antibacterial activity
of the synthesized compounds against inhibited organisms.
MIC gives more details about the quantitative hindrance
ability of the tested compounds against the tested bacterial
strains: MRSA, Ps. aeruginosa, L. monocytogenes and S. aureus. The
results of the agar well diffusion test and MIC of tested
compounds to reveal their antibacterial and antifungal
activities are shown in Table 1.
–
200.42 (acetyl C O). MS m/z (%): 217 [M ] (25), 202 (31), 81
–
(100), 67 (93). Anal. Calcd. for C14H19NO (217.31): C, 77.38; H,
8.81; N, 6.45. Found: C, 77.43; H, 8.73; N, 6.47.
Ethyl-5,6,7,8,9,10-hexahydro-2-
methylcycloocta[b]pyridine-3-carboxylate (25)
Yield (0.90 g, 73%); colorless crystal (hexane); mp: 61–638C. IR
ꢀ1
–
–
(KBr): v 1721 (C O) cm
.
1H NMR (CDCl3): d 1.15–3.36
Methods
(m, 12H, 6CH2), 1.23 (t, J ¼ 8 Hz, 3H, CH3), 2.93 (s, 3H,
CH3), 4.32 (q, J ¼ 8 Hz, 2H, CH2), 8.57 (s, 1H, CH-pyridine).
13C NMR (CDCl3): d 14.26 (CH3CH2), 24.19, 25.74, 25.78, 30.39,
31.19, 34.44, 40.82 (6 CH2 and CH3), 60.91 (CH3CH2), 123.21,
133.21, 138.75, 156.65, 163.83 þ(pyridine carbons), 166.86
Preparation of bacterial suspensions
Suspension of the above mentioned microorganisms was
prepared by inoculating fresh stock cultures into separate
broth tubes, each containing (7 mL) of Muller Hinton broth
for bacterial strains and Sabouraud dextrose broth for fungal
strain. The inoculated tubes were incubated at 378C and 288C
for 24 h for bacterial and fungal strains respectively.
Muller Hinton agar and Sabouraud dextrose agar (Oxiod)
were melted and poured each in empty sterile Petri dishes
(15 mm) and left for 24 h. Wells of diameter 6 mm were
formed in wells using sterile Pasteur pipette. A specific cul-
ture of each organism was spread with a dry sterile swab on
the surface of the previously prepared plates. 50 mL of
solutions of the tested compound were then placed onto
the wells. Also, antimicrobial standard were put in the centre
of the plate agar and incubated at 37–288C for 24 h for
bacterial and fungal strains, respectively. After incubation,
the plates were examined visually and the zone of inhibition
was measured. The test was repeated three times for each
compound.
–
(ester C O). MS m/z (%): 247 [M ] (100), 216 (73), 174 (23),
–
81 (71), 67 (92). Anal. Calcd. for C15H21NO2 (247.33): C, 72.84;
H, 8.56; N, 5.66. Found: C, 72.73; H, 8.62; N, 5.72.
Biological screening
Material and reagents
Tested strains include: bacterial strains as Gram positive
bacteria; Methicillin resistant S. aureus (MRSA) from fecal
sample of dead mare due to toxic shock syndrome containing
mec-A gene isolated and completely identified by biochemical
identification including coagulase test, antibiotic resistance
test as well as molecular analysis. L. monocytogenes and S. aureus
isolated from mastitic cow milk and were identified using
biochemical analysis. Gram negative bacterium; Ps. aeruginosa
was isolated from mastitic cow milk and completely ident-
ified by biochemical analysis using indole test, methyl red,
Voges-Proskauer, Simon citrate test and production of hydro-
gen sulphide on triple sugar iron agar media. Fungal strain;
C. albicans isolated from vaginal swab of dead mare due to
MRSA. Tested strains isolated and identified at the depart-
ment of microbiology and immunology, veterinary division,
National Research Centre (NRC), Dokki, Egypt.
Determination of the minimum inhibitory concentration
(MIC)
Determination of MIC of compounds against tested strains
was achieved using 96-well sterile micro plates. The plates
were incubated at 37–288C for 24 h for bacterial and fungal
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

Arch. Pharm. Chem. Life Sci. 2012, 345, 231–239
Synthesis and Antimicrobial Evaluation of Some New Cyclooctanones
239
[11] K. A. Ali, M. A. Elsayed, H. S. Abdalghfar, Arkivoc, 2011, ii,
103–114.
strains respectively. After incubation, the plates were
examined visually for bacterial or fungal growth precipi-
tation and the experiment was repeated three times.
It was carried out for the tested compounds with initial
concentration 100 mg/mL, two fold serial dilutions of the
tested compounds, reference antibiotic (vancomycin and
ciprofloxacin) and fluconazole were prepared using
Muller Hinton broth. The tubes were then incubated with
the tested organisms, grown in their suitable broth at 378C
for 24 h for bacteria and at 288C for 24 h for fungi (about
1 ꢁ 105 cells/mL), each well receiving 100 mL of the above
inoculums and incubated at 37–288C for 24–48 h for bac-
terial and mycotic growth, respectively. The lowest concen-
tration that showed no growth was taken as MIC.
[12] M. A. Radwan, E. A. Ragab, N. M. Sabry, S. M. El-Shenawyc,
Bioorg. Med. Chem, 2007, 15, 3832–3841.
[13] K. A. Ali, Y. M. Elkholy, A. M. Farag, J. Het. Chem, 2008, 45, 279–
283.
[14] Z. Jin-Cong, Magnetic Resonance in Chemistry 1996, 34 (8), 595–
602.
[15] B. Francesco, B. Olga, L. Eleonora, M. Giulia, M. Luisa,
Synthesis, 1997, 1169–1174.
[16] B. Alberto, C. Sergio, S. Pietro, J. Het. Chem, 1977, 14 (2), 249–
251.
[17] S. M. Riyadh, I. A. Abdelhamid, H. M. Al-Matar, N. M. Hilmy,
M. H. Elnagdi, Heterocycles 2008, 75, 1849 –1904.
[18] G. Negri, C. Kascheres, A. J. Kascheres, J. Het. Chem, 2004, 461–
491.
[19] A. A. Elassar, A. A. El-Khair, Tetrahedron, 2003, 59, 8463–
8480.
The authors have declared no conflict of interest.
[20] C. E. Grothaus, F. B. Dains, J. Am. Chem. Soc, 1936, 58,
1334.
References
[21] D. J. Anderson, C. R. Muchmore, J. Het. Chem, 1995, 32, 1189–
1196.
[1] V. Ramaswamy, V. M. Cresence, J. S. Rejitha, M. U. Lekshmi,
K. S. Dharsana, S. P. Prasad, H. M. Vijila, J. Microbiol. Immunol.
Infect, 2007, 40, 4–13.
[22] S. O. Abdallah, N. H. Metwally, H. F. Anwar, M. H. Elnagdi,
J. Het. Chem, 2005, 42, 781–786.
[2] Vaishali. Dharmarha, ‘‘A Focus on Listeria Monocytogenes’’
National Agricultural Library, Food Safety Research
Information Office 2008 Retrieved January 28, 2009.
[23] A. Z. A. Hassanien, S. A. S. Ghozlan, M. H. Elnagdi, J. Chin.
Chem. Soc, 2004, 51, 575–579.
[24] E. Dominguez, E. Ibeas, E. M. Demarigort, J. K. Palacios, R.
San Martin, J. Org. Chem, 1996, 5435–5439.
[3] M. Michel, L. Gutmann, Lancet, 1997, 349, 1901 –1906.
[4] M. S. Dane, B. Amy, Y. Bing, E. Margaret, J. T. Joanne, J. B.
Sorenson, D. Kenneth, D. J. Thomas, F. Joan, Eur. J. Med. Chem,
2007, 42, 109–113.
[25] T. A. Farghaly, N. A. Abdel Hafez, E. A. Ragab, H. M. Awad,
M. M. Abdallad, Eur J of Med. Chem, 2010, 45, 492–500.
[26] G. E. H. Elgemeie, A. M. E. Attia, B. A. W. Hussain, Nucleosides
& Nucleotides 1998, 17 (5), 855–868.
[5] M. Vargas, Y. Leonor, V. Kouznetsov, Het. Comm, 2011, 4, 341–
344.
[27] B. Gerhard, S. H. Karl, B. Eberhard, Chemische. Berichte, 1973,
106 (6), 1736–1742.
[6] A. M. Farag, K. A. Ali, A. S. Mayhoub, T. M. Abdalla, A. E. Amr,
N. Abdel-Hafez, M. M. Abdalla, Eur. J. Med. Chem, 2010, 45,
5887–5898.
[28] G. R. Allen, J. Org. React, 1973, 20, 337.
[29] K. M. Al-Zaydi, M. A. Al-Shiekh, E. A. Hafez, J. Chem. Res, 2000,
13, 167–173.
[7] A. M. Farag, A. S. Mayhoub, T. M. Abdalla, A. E. Amr, K. A. Ali,
N. Abdel-Hafez, M. M. Abdalla, Arch. Pharm, 2010, 343, 384–
396.
[30] D. Sgouras, P. Maragkoudakis, K. Petraki, B. Martinez-
Gonzalez, E. Eriotou, S. Michopoulos, G. Kalantzopoulos,
E. Tsakalidou, A. Mentis, Appl. Environ. Microbiol, 2004, 70,
518–526.
[8] A. E. Amr, K. A. Ali, M. M. Abdalla, Eur. J. Med. Chem, 2009, 44,
901–907.
[9] M. S. Mohamed, M. M. Kamel, E. M. Kassem, N. Abotaleb,
S. A. El-moez, M. F. Ahmed, Eur. J. Med. Chem, 2010, 45, 3311–
3319.
[31] C. Wiart, Oxford J. Med. 2007, 4, 299–311.
[32] K. Oldenburg, Comb. Chem. High Throughput Screen, 2005, 8,
499–512.
[10] K. A. Ali, Arkivoc 2010, xi, 55–63.
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com