Stereoselective synthesis and antimicrobial activity of benzofuran-based (1E)-1-(piperidin-1-yl)-N2-arylamidrazones

Article abstract of DOI:10.1016/j.ejmech.2009.09.002

The reaction of 2-oxo-N-arylpropanehydrazonoyl chlorides 3a-e with 3-methyl-2-benzofurancarboxylic acid hydrazide (7) furnished N-(aryl)propanehydrazonoyl chlorides 8a-e. X-Ray of 8c revealed the (1Z,2E) configuration of structure 8. Nucleophilic substitu

Full text of DOI:10.1016/j.ejmech.2009.09.002

European Journal of Medicinal Chemistry 44 (2009) 4985–4997
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Stereoselective synthesis and antimicrobial activity of benzofuran-based
(1E)-1-(piperidin-1-yl)-N2-arylamidrazones
,
b
Hatem A. Abdel-Aziz a , Amal A.I. Mekawey
*
a Applied Organic Chemistry Department, National Research Center, Dokki, Cairo 12622, Egypt
b Regional Center of Mycology and Biotechnology, Al-Azhar University, Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of 2-oxo-N-arylpropanehydrazonoyl chlorides 3a–e with 3-methyl-2-benzofurancarboxylic
acid hydrazide (7) furnished N-(aryl)propanehydrazonoyl chlorides 8a–e. X-Ray of 8c revealed the
(1Z,2E) configuration of structure 8. Nucleophilic substitution reaction of 8a or 8d with piperidine
resulted in the formation of 1-(piperidin-1-yl)-N2-arylamidrazones 9a, b. The X-ray diffraction of 9b
showed its (1E,2E) configuration and it confirmed the stereoselectivity of the latter reaction. (1E,2Z,3E)-
Received 6 August 2009
Received in revised form
28 August 2009
Accepted 1 September 2009
Available online 6 September 2009
1-(Piperidin-1-yl)-1-(arylhydrazono)-2-[(3-methylbenzofuran-2-oyl)hydrazono]-4-arylbut-3-enes
11
were synthesized in stereoselective reaction from 8 or alternatively from 9. X-ray analysis of 11b showed
a conversion of configuration respect to 8d or 9b. X-Ray analysis of 9b and 11b revealed the role of
hydrogen interactions in the stereochemistry of their solid state structure. The in vitro antimicrobial
activity of the newly synthesized compounds demonstrated an excellent growth inhibition of
compounds 9 and 11 against clinically isolated strains of human fungal pathogens and exhibited
a significant potency against Gram-positive bacteria. Griseofulvin and Amoxicilline were used as refer-
ences for antifungal and antibacterial screening. The effect of most potent antifungal compound 9b on
morphological features of Aspergillus fumigatus and Candida albicans using image analyzer was studied.
Furthermore, the effect of 9b on the ultra-structures of the latter fungi was occurred by transmission
electron microscope.
Keywords:
Benzofurans
Propanehydrazonoyl chlorides
Amidrazones
Sterioselectivity
X-ray crystallography
Antimicrobial activity
Ó 2009 Elsevier Masson SAS. All rights reserved.
1. Introduction
corporis, Tinea pedis, Tinea cruris, Tinea barbae, Tinea capitis, Tinea
unguium) [16].
Benzofurans with substituent(s) at C-2 and/or C-3 have attrac-
ted strong interest due to their widespread in a large number of
natural products and for their useful biological and pharmacolog-
ical properties [1–7]. The antifungal agent Cicerfuran, obtained from
the roots of wild species of chickpea, Cicer bijugum, reported to be
a major factor in the defense system against Fusarium wilt [8]. In
addition, Benzbromarone is potent uricosuric agent used in the
treatment of gout, especially when Allopurinol, a first-line treat-
ment, fails [9]. Furthermore, the highly effective antiarrhythmic
drug Amiodarone [10] and the unique anti-depression agent
R-(–)-1-(benzofuran-2-yl)-2-propylaminopentane [11] are impor-
tant benzofuran synthetic pharmaceutics. However, a huge number
amongst the natural and synthetic benzofurans have established
potency as antifungal agents [12–16] such as the fungistatic
benzofuran derivative Griseofulvin. It is generally given for fungal
infections that involve the scalp, hair, nails and skin (e.g. Tinea
Although the invasive fungal diseases are now more frequent
than the first half of last century, they are still difficult to diagnose
clinically and present more complicate therapeutic problems with
increasing incidence of chronic, often fatal, mycoses in immuno-
compromised patients. Fungi divided to three classes; (a) derma-
tophytes (superficial mycoses), (b) subcutaneous (deep mycoses)
and (c) saprophytic and opportunistic fungi. Dermatophytes fungi,
class a, or ringworm fungi fitted by evolution to attack the human
protein keratin such as epidermis, hair and nail keratin causing
fungal diseases such as T. pedis, T. corporis or T. capidis [17]. Gris-
eofulvin used to treat ringworm infections. It binds to keratin in
keratin precursor cells and makes them resistant to fungal infec-
tions [16].
Moreover, the deep mycoses fungus Candida albicans, class b, is
endogenous inhabitant of the alimentary tract and the mucocuta-
neous regions of the body. Although it is not usually found in large
numbers on normal human skin, it rapidly colonizes the skin after
an injury [18]. C. albicans, have been isolated from infections in
every area of the human body (skin, nails, mucous membranes, in
* Corresponding author. Tel.: þ202 3371635; fax: þ202 7601877.
E-mail address: hatem_741@yahoo.com (H.A. Abdel-Aziz).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.09.002

4986
H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
addition to gasterointestinal, respiratory, vaginal, esophageal and
urinary tracts) causing an enormous diversity of clinical syndromes
[19]. Myristoyl-CoA:protein N-myristoyltransferase (Nmt) is
a monomeric enzyme that catalyzes the transfer of the fatty acid
myristate from myristoyl-CoA to the N-terminal glycine residue of
a variety of eukaryotic proteins such as C. albicans proteins. Genetic
and biochemical studies have established that Nmt is an attractive
target for antifungal drugs. A series of inhibitors having a benzo-
furan core such as RO-09-4609 and RO-09-4879 exhibited high
inhibitory activity against C. albicans N-myristoyltransferase
(CaNmt) and, subsequently, exhibited potent in vivo antifungal
activity [20].
However, because of the high number of therapy-resistant for
fungal infections and the growing number of life-threatening
invasive mycoses, there is still a great need for the development of
antifungal agents with a new biological spectrum [20,21].
On the other hand, amidrazones were found to possess inter-
esting biological activities [22–25]. Some of amidrazone-containing
hetererocycles have been demonstrated potent in vitro antimicro-
bial activity. Amidrazone-substructural fragments were found to be
the antifungal pharmacophore of the latter compounds [26–28].
Additionally, amidrazones have been reported as precursors of
some effective antifungal azoles [29]. Consequently, the efficient
construction of these molecules has received significant attention
[30–34].
On the other hand, the reactions of hydrazonoyl chlorides 5 with
various secondary amines to form oxanilino-N2-amidrazones 6
have been explored firstly by Shawali [42]. It is worthy to mention
that, most structures of N2-arylamidrazones determined by X-ray
diffraction analysis were found to be Z-configured [43,44] (Fig. 1).
Recently, Frohberg et al. have been reported the first success-
fully attempts on the separation and fully characterization of
E-isomers 6B beside Z-isomers 6A of some oxanilo-N2-arylami-
drazones 6 to correlate their exact stereochemistry with their
biological activity [31]. From the latter data, it is important to
combine our present study with X-ray diffraction analysis to
determine the stereochemistry of the new class N-arylpropanehy-
drazonoyl chlorides 8a–e and their reaction products 1-(piperidin-
1-yl)-N2-arylamidrazones 9a, b and 11a–c.
Thus, the reaction of 2-oxo-N-arylpropanehydrazonoyl chlorides
3a–e with 3-methyl-2-benzofurancarboxylic acid hydrazide (7) in
refluxing THF afforded, in each case, a single yellow product. IR
spectra of the latter products revealed a carbonyl absorption band
in the region 1683–1680 cmꢀ1 in addition to the absorption bands
of 2NH functions in the region 3372–3238 cmꢀ1. Their 1H NMR
spectra exhibited two D2O exchangeable signals of 2NH groups in
the regions
signals of two methyl groups in the region
carbons of the latter methyl groups appeared at
d
8.59–10.19 and
d
10.70–11.27 in addition to two singlet
2.31–2.58. The two sp3
8.8 and 13.7 in 13
d
d
C
NMR spectra. The latter spectroscopic data of the reaction products
and their satisfactory elemental analyses supported the structure
2-{[(3-methylbenzofuran-2-yl)carbonyl]hydrazono}-N-(aryl)pro-
panehydrazonoyl chlorides as postulated in Scheme 1. However,
X-ray diffraction of 8c (Fig. 2) indicated without doubt that the
reaction product is the stereoisomer (1Z,2E)-8 and ruled out the
other possible stereoisomers (3 isomers). Characteristic bond
lengths of 8c and the torsion angles of its two essential double
bonds 1Z and 2E are listed in Table 1. There is no intra- or
intermolecular hydrogen interactions were detected in 8c.
Next, the reactivity of 8a or 8d towards piperidine was exam-
ined. Heating each of the latter 8 in ethanol resulted in elimination
of hydrogen chloride and the formation of a single product, in each
case, as evidenced by TLC analysis of the crude product. Elemental
analysis, 1H NMR and the mass spectral data were compatible with
the assigned structure 9a, b in Scheme 1 (see experimental). The X-
ray diffraction (Fig. 3a and 3b) showed the (1E,2E) configuration of
9b and confirmed the sterioselectivity of the latter reaction. It is
In view of the above facts and in continuation of our interest in
the synthesis of bioactive benzofurans as antimicrobial agents [35–
39], we hope to report herein, a convenient synthesis of a new class
of benzofuran-based (1Z,2E)-N-arylpropanehydrazonoyl chlorides
with highly synthetic potency for stereoselective synthesis of the
title compounds for their antimicrobial evaluation.
2. Results and discussion
2.1. Chemistry
The reaction of
a-chloroketones 1 with acid hydrazides to give
the corresponding
a-chlorohydrazone derivatives 2 was reported
[40]. Although the hydrazone derivative of 1, 2-oxo-N-arylpropa-
nehydrazonoyl chlorides 3 have been known for more than one
century [41], their reaction with acid hydrazides to afford the highly
functionalized propanehydrazonoyl chlorides 4 not yet reported.
Cl
Cl
O
Cl
O
Cl
H
N
H
N
O
N
O
N
R
R
N
H
R1
N
Ar
R1
N
H
N
N
Ar
Me
Me
Me
Me
4
2
3
1
N
Cl
N
H
N
H
N
H
N
H
H
N
N
R2
N
HN
R2
N
Ar
NNH-Ar
R2
R2
NNH-Ar
O
O
(1Z)-
O
O
Ar
6A
6B
(1E)-
5
6
(E)
Ar
N
O
N
Cl
Me
N
O
Me
O
Me
N
H
H
(E)
(E)
(E)
N
N
H
N
N
(E)
N
H
(Z)N
Ar
N
N
H
N(Z)
Ar1
O
O
Me
Me
HN
O
Ar
8
(1Z,2E)-
(1E,2E)-9
(1E,2Z,3E)-11
Fig. 1.

H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
4987
N
O
Me
O
NH2
NNHPh
10
N
H
Me
(c)
O
7
Cl
O
(a)
NNHAr
3
Me
O
Me
N
(E)
Cl
O
Me
(E)
H
N
(b)
(E)
N
N
H
N
N
Ar
(Z)
N
N
H
O
Me HN
stereoselective reaction
Me
Ar
Ar
O
1Z
1E
(1E,2E)-
9
(1Z,2E)-
8
9
a
b
8
a
b
c
Ar
Ph
Ph
4-NO2C6H4
one-pot stereoselective reaction
(e)
4-MeC6H4
4-MeOC6H4
4-NO2C6H4
4-BrC6H4
stereoselective reaction
(d)
1Z
2E
1E
2Z
2E
2Z
d
e
(E)
Ar
N
N
Me
O
N
H
H
N
(E)
N (Z)
Ar1
O
Ar1
(1E,2Z,3E)-11
O
N
(E)
(E)
N
11 Ar
Ar1
Ph
N
H
N
Ph
a
b
c
O
Me
HN
Ar
4-NO2C6H4 Ph
4-BrC6H4 4-ClC6H4
(1E,2E)-12
Scheme 1. Reagents and conditions: (a) THF, reflux 9-12 h, 77–83%; (b) piperidine, EtOH, heating 30 min at 100 ꢁC, 65–72%; (c) for 9a, THF, reflux 18 h, 23%; (d) bezaldehyde, EtOH,
piperidine (2 equ.), reflux 8 h, 68–70%; (e) bezaldehyde or 4-chlorobezaldehyde, EtOH, piperidine (4 equ.), reflux 8 h, 70–76%.
noteworthy to mention here that some (1E)-N2-arylamidrazones
were prepared by stereochemical rearrangement in polar solvents
through the preparation and/or recrystallization [31]. However, the
single crystal of 9b suitable for X-ray analysis was obtained by slow
evaporation, at room temperature, for ethanol solution of 9b and it
was found to have two independent molecules in the asymmetric
unit with the same stereochemistry. Essential bond distances of
(1E,2E)-9b and the torsion angle of its double bonds 1E and 2E were
given in Table 1.
An alternative synthesis of 9a was explored. Thus, refluxing
a mixture of acid hydrazide 7 with 1-(2-phenylhydrazono)-1-
(piperidin-1-yl)propan-2-one 10 in THF for 18 h afforded 23% yield
of 9a (Scheme 1).
Surprisingly, upon attempts to condense benzaldehyde with 9a,
b to prepare compounds 12a, b, where the methyl function of 3-
methybenzofurans have been reported as C-nucleophile toward
aromatic aldehydes or ketones in basic condition [45], the
condensation occurred at methyl group of hydrazone chain to
afford compounds 11a, b not the expected 12a, b (Scheme 1). Thus,
the reaction of (1Z,2E)-isomer 9a, b with benzaldehyde in refluxing
ethanol, in the presence of piperidine, resulted in the formation of
a reaction product precipitated, in each case, during reflux. The IR
spectra of the latter products exhibited, in each case, a band in the
region 1683–1680 cmꢀ1 due to the carbonyl absorption whereas
the absorption bands of 2NH functions appeared in the region
3372–3238 cmꢀ1. Their 1H NMR spectra were characterized by the
Fig. 2. X-ray structure of (1Z,2E)-8c.

4988
H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
Table 1
Characteristic bond lengths [Å] and torsion angles [ꢁ] of (1Z,2E)-8c, (1E,2E)-9b (A) and (1E,2Z,3E)-11b.
(1Z,2E)-8c
(1E,2E)-9b(A)
(1E,2Z,3E)-11b
5
6
1
5
7
(E)
N
N
3
Cl
13
O
N
N
O
19
(E)
15
N
17
H
H
N
6
6
( Z)
4
(E)
H
8
(E)
4
23
N
(Z)
(E)
N
3
24
20
N
N
16
14
N
34
23
N
17
8
H
N
32
Me
41
7
Ph
H
1
10
Me
21
HN
16
27
O
2
bond length [Å]
C8–N6
N6–N7
1.415(3)
1.340(3)
1.284(3)
1.730(3)
1.471(4)
1.287(3)
1.372(3)
1.369(4)
1.208(3)
1.490(4)
N16–C21
N14–N16
N14–C34
N19–C34
C32–C34
N6–C32
N4–N6
N4–C23
O3–C23
C32–C41
1.352(4)a
1.402(4)b
1.297(4)c
1.376(4)d
1.497(5)e
1.277(4)
1.386(3)
1.366(4)
1.216(4)
1.486(5)
C13–N7
N7–N5
N5–C17
C17–N6
C17–C8
C8–N1
N1–N3
N3–C16
C16–O2
C8–C10
1.358(3)a
1.385(2)b
1.280(3)c
1.382(3)d
1.500(3)e
1.289(3)
1.377(2)
1.366(3)
1.217(3)
1.440(3)
1.328(3)
N7–C20
C20–Cl1
C20–C17
C17–N15
N15–N4
N4–C24
C24–O5
C17–C27
C10–C23
torsion angles [ꢁ]
(1Z)
N6–N7–C20–Cl1
(2E)
(1E)
(1E)
0.2(2)f
N16–N14–C34–N19
(2E)
N4–N6–C32–C34
168.5(10)g
N6–C17–N5–N7
(2Z)
N3–N1–C8–C17
(3E)
ꢀ170.0(6)g
ꢀ3.4(4)f
C20–C17–N15–N4
179.2(4)g
ꢀ179.8(10)g
C8–C10–C23–C25
175.8(8)g
a
The bond lengths of (1E,2E)-9b(A) and (1E,2Z,3E)-11b are well within the range that typically occurred in other amidrazone derivatives: 1.391(2)–1.396(3) Å.
b
c
d
e
f
1.342(4)–1.351(2) Å.
1.286(3)–1.294(2) Å.
1.373(3)–1.405(4) Å.
1.491(4)–1.511(3) Å[31].
The torsion angles of (1Z,2E)-8c, (1E,2E)- 9b(A) and (1E,2Z,3E)-11b are well within the range that typically reported for Z ¼ 0ꢁ/ ꢂ 30ꢁ.
g
E ¼ ꢂ150ꢁ / 180.
presence of two signals in the regions
assigned to the 2 NH groups in addition to singlet signal charac-
teristic to benzofuran C-3 methyl group in the region 2.57–2.58.
The 13C NMR spectra showed a signal of sp3 carbon at
8.8 of
benzofuran C-3 methyl carbon in addition to the other sp3 signals of
piperidine carbons in the region
23.8–48.6. Moreover, the 1H NMR
spectrum of 9a revealed a two douplets at 6.91 and 7.23 due to the
protons of olefinic bond with J ¼ 16.5 Hz consistent with the trans
olefinic vicinal coupling constant. The above mentioned spectro-
scopic data provided support for 11a–c (Scheme 1). X-Ray analysis
of amidrazone 11b (Fig. 4a and 4b) showed that, the stereochemical
structure of 11 is (1E,2Z,3E) geometrical structure and excluded the
other possible stereoselective isomers (7 isomers) or the site
selective product 12 as postulated in Scheme 1. Selected bond
distances in (1E,2Z,3E)-11b and the torsion angle of its essential
double bonds 1E, 2Z and 3E were given in Table 1.
Interestingly, treatment of 8a, 8d with benzaldehyde refluxing
in ethanol, in the presence of four molar ratio of piperidine, affor-
ded a reaction product identical to compound 11a, b that were
obtained above. Similar reaction of 8e with 4-chloro benzaldehyde
furnished amidrazone 11c.
X-Ray diffraction of 9b showed a network of three intermolec-
ular hydrogen contacts between the independent molecules A and
B (Fig. 5). The latter three H-bonds tided the hydrazide part with
amidrazone skeleton and linked the two molecules (A and B) into
a dimer, these findings suggested that the hydrazide part played
a unique role in the stereochemistry of amidrazone skeleton.
d
8.37–8.56 and 10.60–10.88,
Beside to the intramolecular hydrogen bond N3–H3/N6, three
intermolecular hydrogen contacts N7–H7/N1, N7–H7/O2 and
C9–H9/O2 stabilized the structure (1E,2Z,3E)-11b. The importance
of hydrogen bonds as an auxiliary binding and, in some cases, as the
dominant factor in determining crystal packing [46] or molecular
conformation [47] has received wide attention in biological
systems [48]. However, hydrogen bonds played a crucial role in
directing the molecular assembly of 11 in the solid state. The
hydrogen interactions in 9b and 11b were outlined in Fig. 5. The
hydrogen interaction between ortho-proton of benzene moiety and
H–bond acceptors (N or O) was already known [49] (C33–H33/O2
and C28–H28/O3 in case of 9b, and C9–H9—O2 in case of 11b). The
hydrogen bond geometry of (1E,2E)-9b and (1E,2Z,3E)-11b repre-
sented in Table 2.
The preliminary antimicrobial test showed an excellent activity for
9b as promising antifungal agent. The latter findings stimulated our
interest to investigate the reactivity of 8d towards sodium benzene-
sulfinate and hydroxylaminewith the followingobjective in mind. We
thought it interesting to explore the utility of the 8d as a synthon for
new potent antimicrobial agents. Firstly, 8d reacted with sodium
benzenesulfinate in refluxing ethanol, yielding 3-methyl-N’-1-
methyl-2-[(4-nitrophenyl)hydrazono-2-(phenylsulfonyl)ethylidene]-
1-benzofuran-2-carbohydrazide (13) as shown in Scheme 2.
Secondly, the reactions of 8d with hydroxylamine hydrochloride,
in refluxing ethanol, resulted in the formation of N-hydroxy-2-
{[(3-methyl-1-benzofuran-2-yl)carbonyl]hydrazono}-N’-(4-nitrophe
nyl)propanehydrazonamide (14) (Scheme 2). Each of the latter
d
d
d
d

H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
4989
Fig. 3. (a) X-ray structure of (1E,2E)-9b. (b) View of (1E,2E)-9b, Hydrogen atoms are omitted for clarity.
reactions was found to give a single product as evidenced by
2.2. Biological activity
TLC analysis. The structure of compound 13 or 14 was estab-
lished on the basis of their elemental analysis and spectral
data (see experimental). It would be of great support to get an
evidence for one of their possible isomeric structures by
carrying out a single crystal X-ray analysis of the reaction
product, however all attempts to get such crystals for X-ray
diffraction were failed Scheme 3
In an attempt to understanding the potentiality of 9a, b and 11a–
c in antimicrobial test and to shed some light on their preliminary
SAR, we synthesized hydrazones 15a, b. Thus, the reaction of acid
hydrazide 7 with acetaldehyde or E-cinnamaldehyde, in refluxing
ethanol, afforded the corresponding (E)-hydrazones 15a and 15b,
respectively. Their 1H NMR spectra revealed, in each case, a singlet
All synthesized compounds were screened for their antifungal
and antibacterial activities at 100 g concentration against two
m
filamentous fungi (Aspergillus fumigatus and Syncephalastrum
racemosum), two yeast (C. albicans and Geotrihum candidium), two
Gram-positive (Staphylococcus aureus and Bacillus subtilis) and two
Gram-negative (Escherichia coli and Pseudomonas aeruginosa)
bacteria. Griseofulvin and Amoxicilline were used as a standard
antifungal and antibacterial agent, respectively. Some of the newly
synthesized compounds showed excellent antimicrobial activities
with respect to the control drugs. Most of active compounds have
a significant antifungal potency more than antibacterial potency.
The results of the antifungal and antibacterial activities were
shown in Tables 3 and 4, respectively. Susceptibilities of the fungal
and bacterial isolates to our synthesized benzofurans were inves-
tigated by measuring their inhibitory effect on the growth of
microorganisms compared to the solvent used.
signal in the region
d 8.50–8.54 characteristic for the azomethyne
proton and showed D2O-exchangeable singlet signal integrating for
one proton of ]NNH– function.
The compounds containing arylidene–hydrazide structure may
exist as E/Z geometrical isomers about –C]N– double bond and
cis–trans amide conformers. These compounds were present in
higher percentage in DMSO-d6 in the form of geometrical E isomer
about –C]N– bond [50]. In the present study, the spectral data
were obtained in DMSO-d6 and neither the signal of Z isomer nor
these of cis–trans conformers of E isomer were observed.
2.2.1. Antifungal activity
Data in Table 3 revealed a remarkable activity of compounds 9a,
b and 11a–c as antifungal agents. Compound 9b exhibited the
highest potency against all tested fungal organisms with respect to
reference drug Griseofulvin, it is an antibiotic fungistatic drug

4990
H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
Fig. 4. (a)X-ray structure of (1E,2Z,3E)-11b. (b) View of (1E,2Z,3E)-11b, Hydrogen atoms were omitted for clarity.
administered orally in the treatment of dermatophyte and ring-
worm infections [16].
well as hydrazones 15a, b showed varied antifungal activity against
C. albicans with potencies ranged from 0.5 to 1.2 and revealed no
ability against most of other fungal species. On the other hand,
sulfone 13 and hydroxymoyl 14 revealed potencies 1.5 and 1.05
against C. albicans and S. racemosum, respectively.
C. albicans was the most sensitive fungus with potency 1.8 of
Griseofulvin followed by A. fumigatus, G. candidum and S. racemosum
with potencies 1.28, 1.2 and 1.16, respectively. The order of activity
of compounds 9a, b and 11a–c against tested fungal strains from
higher to lower was 9b, 11a, 11b, 9a then 11c. Compounds 8a–e as
G. candidum have been isolated from infections in debilitated,
from human lung, and respiratory tract, gut, and skin tissue and
Interam. H bond
Interm. H bond
O2N
O2N
N
H
N
N
O
N
H
N
H
N
H
H
Me
O
N
N
N
H
B
N
N
O
A
H
N
N
Ph
O
Ph
Me
N
N
H
N
H
H
N
H
N
H
N
N
NO2
NO2
9b
(1E,2E)-
11b
(1E,2Z,3E)-
Fig. 5. Intera- and intermolecular hydrogen bonds (dashed lines) of (1E,2E)-9b and (1E,2Z,3E)-11b.

H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
4991
Table 2
Intra- and intermolecular hydrogen bonds of (1E,2E)-9b and (1E,2Z,3E)- 11.
(1E,2E)-9b
D–H (A)/A (B)
Intermolecular
N16dH16/N13
N16dH16/O2
C33dH33/O2
D–H (B)/A (A)
Intermolecular
N11–H11/N6
N11–H11/O3
C28–H28/O3
D–H
H/A
D/A
<(DHA)
0.960 (3)
0.960 (3)
0.960 (3)
D–H
2.550
2.253
2.740
H/A
3.227
3.149
3.480
D/A
127.70
154.96
134.39
<(DHA)
0.960 (3)
0.960 (3)
0.960 (3)
2.509
2.503
2.645
3.196
3.370
3.467
128.47
150.06
143.95
(1E,2Z,3E)-11b
D–H/A
D–H
H/A
D/A
<(DHA)
Intramolecular
N3–H3/-N6
Intermolecular
N7–H7/-N1
N7–H7/-O2
C9–H9/-O2
0.960(2)
2.410
2.986
118.2
0.960(2)
0.960(2)
0.960(2)
2.522(2)
2.520(2)
2.643(2)
3.415
3.202
3.271
149.9
125.4
123.4
Distances (D–H, H/A, D/A) are given in Å, angles in ꢁ, D: donor, A: acceptor.
immunocompromised patients in cases of vaginitis, thrush, bron-
chitis, diabetic and cutaneous infections. The general term for these
infections is geotrichosis [51]. Although, G. candidum was recorded
the highest resistance for tested compounds, 9b showed a potency
of 1.2 against this fungus.
inhibitory effects against the Gram-negative bacterium E. coli 9b
whereas they revealed no effect, or very weak, against P. aerogenosa
which emerged as one of the most problematic Gram-negative
pathogens, with the alarminglyhigh antibiotics resistance rates[52].
It has been estimated that over one-half of all therapeutic agents
consist of heterocyclic compounds. The heterocyclic ring system in
many cases comprised the very core of the active moiety or phar-
macophore. Nevertheless, the bicyclic array in the therapeutic
agents based on the benzofuran ring played the role of a rigid
support for functional groups. In our present study, varying
substitution at C-2 of benzofuran moiety in the newly synthesized
compounds especially 9b, 11b, 13, 14, 15a and 15b (Fig. 6), and
subsequent their antimicrobial results identified the functionality
for optimal antimicrobial property in this class of compounds.
According to structure–activity relationships (SAR), it can be
concluded that both of piperidine moiety and 4-nitro-
phenylhydazone functions were essential for the antimicrobial
activity. The piperidines, which are so frequently found in the side
chains of therapeutic agents, are not usually associated with
pharmacophores; they simply serve as surrogates for open-chain
tertiary amines.
2.2.3. Minimum inhibitory concentration (MIC)
The minimum inhibitory concentration (MIC) of 9b was
measured against the most sensitive fungi A. fumigatus and
C. albicans, and against the most effective bacterial strain S. aureus.
Compound 9b showed low MIC (25
revealed MIC of 75 g/ml against C. albicans respect to that of
Griseofulvin which showed 50 and 75 g/ml against A. fumigatus
and C. albicans, respectively. On the other hand, 9b exhibited high
MIC 75 g/ml against S. aureus respect to Amoxicilline (50 g/ml) as
mg/ml) against A. fumigatus and
m
m
m
m
reference drugs. The minimum inhibitory concentration (MIC) of 9b
against highly inhibited organisms reported in Table 5.
2.2.4. Effect of 9b on the morphological features of A. fumigatus and
C. albicans
Prompted by the antifungual potentialities of compound 9b, it
was selected for further assessment. The effect of 9b on A. fumigatus
and C. albicans was carried out using image analyzer in the RCMB
center, Al-Azhar University. Image analysis studies showed that, the
size of all morphological features of A. fumigatus was reduced by
Griseofulvin and 9b respect to their original measurements.
Furthermore, many of chlamydospores were obtained after incu-
2.2.2. Antibacterial activity
Although, the synthesized compounds showed
a variable
potencies against tested bacteria, their activity were lower than that
of standard drug Amoxicilline. From the results in Table 4 Gram-
positive bacteria were highly susceptible where Bacillus subtilis was
the most affected strain against tested compounds followed by
S. aureus. Alternatively, the tested compounds exhibited weak
bation of A. fumigatus with 100 mL of 9b. On the other hand, Gris-
eofulvin caused aggregation of C. albicans cells while 9b caused
elongation and swollen for the same cells with great reduction in
their number.
O
Cl
Me
H
N
N
N
N
H
(b)
(a)
O
Me
9b
NO2
O
O
Ph
N
OH
N
O
O
S
HN
Me
Me
H
N
H
N
N
N
N
H
N
H
O
Me
Me
14
O
NO2
NO2
13
Scheme 2. Reagents and conditions: (a) PhSO2Na.2H2O, reflux 10 h, 53%; (b) NH2OH.HCl, K2CO3, EtOH, reflux 45 min, 47%.

4992
H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
O
biological activity and structure of such class of compounds.
Me
NH2
However, to confirm this suggestion, further study for similar
compounds is in progress and their biological evaluations are
currently underway.
N
H
O
7
(a)
4. Experimental
4.1. Chemistry
O
Me
O
Me
(E)
R
N
(Z)
H
N
N
H
15
R
N
H
4.1.1. General
H
O
a
b
-Me
R
O
Melting points were measured with a Gallenkamp apparatus. IR
spectra were recorded on Shimadzu FT-IR 8101 PC infrared spec-
trophotometer. The NMR spectra were recorded on a Varian
Mercury VX-300 NMR spectrometer. 1H spectra were run at
300 MHz and 13C spectra of compounds 8a, 8c, 8d, 9a, b and 11a,
b were run at 75.46 MHz in deuterated dimethylsulphoxide (DMSO-
d6). Chemical shifts (dH) are reported relative to TMS as internal
standard. All coupling constant (J) values are given in hertz.
Chemical shifts (dC) are reported relative to DMSO-d6 as internal
standards. The abbreviations used are as follows: s, singlet; d,
doublet; m, multiplet; D2O exch., exchanged with D2O; all the NH
exchanged with D2O. Mass spectra were measured on a GCMS-
QP1000 EX spectrometer at 70 e V. Elemental analyses were carried
out at the Microanalytical center of Cairo University. X-Ray crys-
tallography was carried out on a Kappa CCD Enraf Nonius FR 590
diffractometer, National Research Center, Dokki, Cairo, Egypt. The
X-ray diffraction measurements of compounds 8c, 9b and 11b were
made using maXus (Bruker Nonius, Delft & Mac Science, Japan) [53],
Ph
15
16
Scheme 3. Reagents and conditions: (a) R–CHO, EtOH, reflux 4 h, 62–78%.
2.2.5. Effect of 9b on the ultra-structures of A. fumigatus and
C. albicans
Effect of DMSO, Griseofulvin and 9b on the ultra-structures of
A. fumigatus and C. albicans was occurred by transmission electron
microscope at 25,000 magnifications. The results revealed a great
effect of 9b against both of A. fumigatus and C. albicans such as
shrinking of cell membrane, distortion of most of sub-organs,
aggregation of lysised mitochondria in groups and most cells
became semi-empty. In hyphae cell, cell wall and cell membrane
increased in thickness in both of A. fumigatus and C. albicans.
3. Conclusion
In conclusion, we described an efficient synthesis of functionally
(1Z,2E)-N-(aryl)propanehydrazonoyl chlorides bearing active
methyl group used as C-nucleophiles. These derivatives were used
in economical and versatile synthetic approach for stereoselective
synthesis of the title derivatives. The results of the present study
showed that, some of the newly synthesized benzofuran-based
(1E)-1-(piperidin-1-yl)-N2-arylamidrazones have significant anti-
fungal potencies and can be consider very promising in the
perspective of new drugs discovery with respect to the medical
importance of the tested fungal strains. Accordingly, generalization
of the latter established method can be widely used in synthesis of
library of (1E)-N2-arylamidrazones with expected biological
activity. In this regard as well as in the light of interesting structural
and biological results the situation definitely calls for some addi-
tional research towards understanding the relation between
at wavelength
l
¼ 0.71073 Å and a graphite monochromator was
used for data collection. 3-Methylbenzofuran-2-carboxylic acid
hydrazide (7) [54], 2-oxo-N-arylpropanehydrazonoyl chlorides 3a–e
[41], and 1-(2-phenylhydrazono)-1-(piperidin-1-yl)propan-2-one
(10) [22] were prepared according to the literature procedures.
4.1.2. Synthesis of (1Z,2E)-2-{[(3-methylbenzofuran-2-yl)carbonyl]
hydrazono}-N-(aryl)propanehydrazonoyl chlorides 8a–e
A mixture of 3-methyl-2-benzofurancarboxylic acid hydrazide
(7) (1.9 g, 10 mmol) and the appropriate 2-oxo-N-arylpropanehy-
drazonoyl chloride 3a-e (10 mmol) in dry THF (50 mL) was heated
under refluxing temperature. The reaction was controlled by TLC
and continued until the starting substrates were completely
consumed (9–12 h), then left to cool to room temperature.
The solvent was removed, in each case, under reduced pressure and
Table 3
In vitro antifungal activity of the synthesized compounds.
Compound
Aspergillus fumigatus
Syncephalastrum
racemosum
Candida albicans
Geotrichum candidum
I.Z.a
P.b
I.Z.a
P.b
I.Z.a
P.b
I.Z.a
P.b
8a
8b
8c
8d
8e
9a
9b
11a
11b
11c
13
–
–
–
0
0
0
0.56
0
1.12
1.28
0.84
0
0
0
–
–
–
–
0
0
0
0
6 ꢂ 0.5
6 ꢂ 0.5
10 ꢂ 0.5
12 ꢂ 0.8
10 ꢂ 1
0.6
0.6
1
1.2
1
1.4
1.8
1.5
1.7
1.4
1.5
0.9
0.8
0.5
1
–
–
–
0
0
0
0.5
0
0
1.2
0
0
0
14 ꢂ 1.3
5 ꢂ 0.5
–
5 ꢂ 0.5
16 ꢂ 1.2
22 ꢂ 1.2
19 ꢂ 1.4
21 ꢂ 1.7
20 ꢂ 1.8
–
0.26
0.84
1.16
1
1.1
1.05
0
1.05
0
0
–
–
28 ꢂ 2.2
14 ꢂ 0.9
18 ꢂ 1.3
14 ꢂ 1
32 ꢂ 2.5
12 ꢂ 0.8
21 ꢂ 2
–
–
–
–
–
–
–
–
–
–
–
–
–
17 ꢂ 1.4
14 ꢂ 1.1
15 ꢂ 1
0
0
0
0
14
0
0
0
1
20 ꢂ 1.5
9 ꢂ 0.8
8 ꢂ 0.5
5 ꢂ 0.5
10 ꢂ 0.7
15a
15b
Grisofulvin
–
–
25 ꢂ 2.3
19 ꢂ 1.6
1
10 ꢂ 0.8
1
a
Inhibition zone in mm.; –: not detected.
potency ¼ I.Z. of compound / I.Z. of Grisofulvin.
b

H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
4993
Table 4
In vitro antibacterial activity of the synthesized compounds.
Compound
Staphylococcus aureus
Bacillus subtilis
Escherichia coli
Pseudomonas aeruginosa
I.Z.a
Pb
I.Z.a
Pb
I.Z.a
Pb
I.Z.a
Pb
8a
–
0
–
0
–
0
–
0
8b
8c
–
–
0
0
7 ꢂ 0.5
0.29
0
–
–
0
0
–
–
0
0
–
8d
8e
9a
9b
11a
11b
11c
13
12 ꢂ 1
0.4
0
0.5
0.87
0.53
0
0.33
0.27
0
6 ꢂ 0.5
9 ꢂ 0.5
–
20 ꢂ 1.5
15 ꢂ 1.6
–
16 ꢂ 1.5
10 ꢂ 1.3
–
0.25
0.38
0
0.83
0.63
0
0.67
0.42
0
10 ꢂ 0.8
0.36
0
5 ꢂ 0.5
0.25
0
0
0.35
0
0
0
0
0
–
–
–
15 ꢂ 1.2
26 ꢂ 1.7
16 ꢂ 1
–
10 ꢂ 1
8 ꢂ 1
–
17 ꢂ 1.1
20 ꢂ 1
14 ꢂ 1
8 ꢂ 0.7
10 ꢂ 0.8
6 ꢂ 0.5
–
0.61
0.71
0.5
0.29
0.36
0.21
0
–
7 ꢂ 0.5
–
–
–
–
14
–
15a
15b
Amoxicilline
16 ꢂ 1.5
0.53
0
1
–
0
0.33
1
20 ꢂ 1.6
0.71
0
1
–
–
0
0
1
–
8 ꢂ 0.6
–
30 ꢂ 2.5
24 ꢂ 2
28 ꢂ 2
20 ꢂ 2.2
a
Inhibition zone in mm.; –: not detected.
b
potency ¼ I.Z. of compound / I.Z. of Amoxicilline.
the residue was triturated with ethanol to give yellow colored
product. The solid products that formed were filtered off, washed
with ethanol and recrystallized from EtOH/DMF to afford the cor-
responding (1Z,2E)-N-arylpropanehydrazonoyl chlorides 8a–e in
77–83% yields.
152.9; MS m/z (%) 370 (Mþ þ 2, 3.0), 369 (Mþ þ 1, 2.5), 368 (Mþ,
8.6), 159 (100), 77 (12.4). Anal. Calcd for C19H17ClN4O2: C, 61.87; H,
4.65; N, 15.19%. Found: C, 62.03; H, 4.51; N, 15.27%.
4.1.2.2. (1Z,2E)-2-{[(3-Methylbenzofuran-2-yl)carbonyl]hydrazono}-
N-(4-tolyl)propanehydrazonoyl chloride (8b). Reaction time 9.5 h,
4.1.2.1. (1Z,2E)-2-{[(3-Methylbenzofuran-2-yl)carbonyl]hydrazono}-
N-phenylpropanehydrazonoyl chloride (8a). Reaction time 11 h, pale
yellow crystals (3.10 g, 77%); mp 208–210 ꢁC; IR (KBr)
n
3302,
1H NMR (DMSO-d6)
d 2.31 (s, 3H, CH3), 2.34 (s, 3H, CH3), 2.57 (s, 3H, CH3), 7.28–7.85
3256 (2NH), 1682 (C]O), 1612 (C]N) cmꢀ1
;
yellow crystals (2.84 g, 79%); mp 200–202 ꢁC; IR (KBr)
n
3371, 3248
1H NMR (DMSO-d6)
2.43
(s, 3H, CH3), 2.57 (s, 3H, CH3), 6.90–7.78 (m, 9H, ArH), 10.19 (s, D2O
exch., 1H,]NNH–), 10.75 (s, D2O exch., 1H, –CONH–); 13C NMR
8.8
(2NH), 1682 (C]O), 1605 (C]N) cmꢀ1
;
d
(m, 8H, ArH), 8.59 (s, D2O exch., 1H,]NNH–), 10.77 (s, D2O exch.,
1H, –CONH–); MS m/z (%) 384 (Mþ þ 2, 8.3), 383 (Mþ þ 1, 4.8),
382 (Mþ, 25.9), 159 (100), 77 (17.4). Anal. Calcd for
C20H19ClN4O2: C, 62.74; H, 5.00; N, 14.63%. Found: C, 62.60; H,
5.12; N, 14.55%.
d
(1C of benzofuran CH3), 13.7 (1C of propane CH3), 111.7, 113.8, 114.8,
121.0, 121.2, 122.6, 123.4, 127.5, 128.8, 129.1, 129.2, 142.3, 143.4,
O
Me
Cl
H
N
N
N
H
N
O
Me
NO2
8d
NO2
O
Me
N
N
N
N
Me
N
H
N
H
N
H
O
Me HN
N
N
11b
Ph
O
9b
O
NO2
H
OH
N
O
Ph
N
N
O
O
Me
O
S
Me
H
H
N
N
N
N
N
N
H
H
O
Me
14
O
Me
13
NO2
NO2
O
O
Me
Me
Me
N
Ph
N
N
H
N
H
O
O
15a
15b
Fig. 6. Structure features of compounds 8d, 9b, 11b, 13, 14, 15a and 15b.

4994
H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
Table 5
1 mmol) was added. The reaction mixture was refluxed for 18 h
then left to cool. The precipitated product was filtered off, washed
with ethanol and dried. Recrystallization from EtOH afforded 0.1 g
(23% yield) of compound 9a.
Minimum inhibitory concentration (MIC) of 9b.
Compound MIC ( g/ml)
Aspergillus fumigatus Candida albicans Staphylococcus aureus
m
9b
Standard
25
75
75
4.1.3.1. (1E,2E)-1-(Piperidin-1-yl)-1-phenylhydrazono-2-[(3-methyl-
50 (Grisofulvin)
75 (Grisofulvin)
50 (Amoxicilline)
benzofuran-2-oyl)hydrazono]propane (9a). Orange needles in yield
(0.54 g, 65%) ; mp 206–208 ꢁC; IR (KBr)
n
3362, 3215 (2NH), 1682
4.1.2.3. (1Z,2E)-2-{[(3-Methylbenzofuran-2-yl)carbonyl]hydrazono}-
(C]O), 1599 (C]N) cmꢀ1; 1H NMR (DMSO-d6)
d
1.61 (m, 6H, 3CH2
N-(4-methoxyphenyl)propanehydrazonoyl chloride (8c). Reaction
of piperidine), 2.22 (s, 3H, CH3), 2.61 (s, 3H, CH3), 3.16 (m, 4H, 2CH2
of piperidine), 7.02–8.04 (m, 9H, ArH), 9.74 (s, D2O exch.,
time 9 h, yellow crystals (3.27 g, 82%); mp 217–219 ꢁC; IR (KBr)
n
3346, 3238 (2NH),1680 (C]O),1604 (C]N) cmꢀ1; 1H NMR (DMSO-
d6) 2.36 (s, 3H, CH3), 2.57 (s, 3H, CH3), 3.67 (s, 3H, –OCH3), 7.28–
7.87 (m, 8H, ArH), 8.89 (s, D2O exch., 1H,]NNH–), 10.70 (s, D2O
exch., 1H, –CONH–); 54.8, 13C NMR
8.8 (1C of benzofuran CH3),
1H,]NNH–), 10.42 (s, D2O exch., 1H, –CONH–) ppm; 13C NMR
d 8.7
d
(1C of benzofuran CH3), 13.6 (1C of propane CH3), 23.7 (1C of
piperidine), 25.3 (2C of piperidine), 48.7 (2C of piperidine), 111.6,
113.7, 115.0, 121.0, 121.2, 122.6, 123.4, 127.2, 128.7, 130.1, 143.3, 147.5,
152.5; MS m/z (%), 418 (Mþ þ 1, 9.1), 417 (Mþ, 34.7), 159 (100). Anal.
Calcd for C24H26N6O4: C, 69.04; H, 6.52; N, 16.77%. Found: C, 68.88;
H, 6.64; N, 16.70%.
d
13.7 (1C of propane CH3), 56.1 (1C of –OCH3), 111.5, 114.1, 114.4,
121.0, 121.4, 122.6, 123.8, 127.8, 128.4, 129.2, 129.4, 129.8, 141.8,
143.7, 153.1; MS m/z (%) 400 (Mþ þ 2, 12.3), 399 (Mþ þ 1, 7.9), 398
(Mþ, 39.6), 159 (100). Anal. Calcd for C20H19ClN4O3: C, 60.23; H,
4.80; N, 14.05%. Found: C, 60.44; H, 4.67; N, 14.13%. The purified
product 8c was dissolved in ethanol/DMF (v/v ¼ 3/1) and yellow
single crystals were separated after 3 days. Crystal data for
compound 8c: C20H19ClN4O3, Mr, 398.850; system, monoclinic;
Space group, P21/c; unit cell dimensions, a 12.9456 (5) Å, b 11.2257
4.1.3.2. (1E,2E)-1-(Piperidin-1-yl)-1-[(4-nitrophenyl)hydrazono]-2-
[(3-methylbenzofuran-2-oyl)hydrazono]propane (9b). Red crystals
in yield (0.67 g, 72%) ; mp 232–234 ꢁC; IR (KBr)
n
3370, 3219 (2NH),
1680 (C]O), 1597 (C]N) cmꢀ1; 1H NMR (DMSO-d6)
d
1.62 (m, 6H,
3CH2 of piperidine), 2.22 (s, 3H, CH3), 2.60 (s, 3H, CH3), 3.18 (m, 4H,
2CH2 of piperidine), 6.98–8.07 (m, 8H, ArH), 9.70 (s, D2O exch.,
(6) Å, c 13.5705 (6) Å,
a b
90.00ꢁ, 95.137 (4)ꢁ; V, 1964.2 (2) Å3; Z, 4;
Dx,1.349 mg.mꢀ3
;
q
range for data collection, 2.910–19.980ꢁ;
m(Mo-
1H,]NNH–), 10.55 (s, D2O exch., 1H, –CONH–) ppm; 13C NMR
d 8.7
Ka), 0.22 mmꢀ1; T, 298 K; measured reflections, 2999; independent
reflections, 1807; observed reflections, 1453; Rint, 0.026; R(all),
(1C of benzofuran CH3), 13.7 (1C of propane CH3), 23.7 (1C of
piperidine), 25.3 (2C of piperidine), 48.8 (2C of piperidine), 111.6,
113.7, 114.8, 120.9, 121.1, 122.6, 123.4, 127.3, 128.7, 130.0, 143.1, 147.2,
152.9; MS m/z (%) 464 (Mþ þ 2, 22.3), 463 (Mþ þ 1, 52.1), 462 (Mþ,
71.3), 288 (21.7), 159 (58.1), 84 (100). Anal. Calcd for C24H26N6O4: C,
62.33; H, 5.67; N, 18.17%. Found: C, 62.26; H, 5.48; N, 18.15%. The red
single crystal of 9b was cultured from EtOH by slow evaporation at
room temperature. Crystal data for compound 9b: C48H52N12O8, Mr,
925.020; system, triclinic; Space group, P1; unit cell dimensions,
0.048; wR(ref), 0.077; wR(all), 0.079; S(ref), 1.359; S(all), 1.577;
D/
smax, 0.046; Drmax, 0.17 eÅ3, Drmin, –0.16 eÅ3.
4.1.2.4. (1Z,2E)-2-{[(3-Methylbenzofuran-2-yl)carbonyl]hydrazono}-
N-(4-nitrophenyl)propanehydrazonoyl chloride (8d). Reaction time
12 h, yellow powder (3.43 g, 83%); mp 238–240 ꢁC; IR (KBr)
n
3367,
1H NMR (DMSO-d6)
2.34 (s, 3H, CH3), 2.58 (s, 3H, CH3), 7.11–7.89 (m, 8H, ArH), 9.12 (s,
D2O exch., 1H,]NNH–), 11.27 (s, D2O exch., 1H, –CONH–); 13C NMR
8.8 (1C of benzofuran CH3), 13.7 (1C of propane CH3), 111.7, 112.6,
3250 (2NH), 1683 (C]O), 1600 (C]N) cmꢀ1
;
d
a 9.6172 (4) Å, b 14.1318 (5) Å, c 18.7384 (9) Å,
a
72.960 (3)ꢁ,
range for
(Mo-Ka), 0.09 mmꢀ1; T, 298 K;
b
84.802 (2)ꢁ; V, 2407.5 (2) Å3; Z, 2; Dx, 1.276 mg.mꢀ3
; q
d
data collection, 2.910–19.980ꢁ;
m
114.7, 120.9, 121.12, 122.56, 123.4, 127.4, 128.8, 129.1, 129.3, 129.4,
142.3, 142.5, 143.4, 152.9; MS m/z (%) 415 (Mþ þ 2, 23.2), 414
(Mþ þ 1, 13.9), 413 (Mþ, 68.8), 287 (15.7), 159 (100). Anal. Calcd for
C19H16ClN5O4: C, 55.15; H, 3.90; N, 16.92%. Found: C, 55.03; H, 4.02;
N, 16.83%.
measured reflections, 7451; independent reflections, 5088;
observed reflections, 2130; Rint, 0.042; R(all), 0.127; wR(ref), 0.081;
wR(all), 0.104; S(ref), 1.864; S(all), 2.002;
D/smax, 0.048; Drmax,
0.41 eÅ3, Drmin, ꢀ0.37 eÅ3.
4.1.4. Synthesis of (1E,2Z,3E)-1-(piperidin-1-yl)-1-(arylhydrazono)-
2-[(3-methylbenzofuran-2-oyl)hydrazono]-4-(aryl1)
but-3-enes 11a–c
Method A. To a solution of the appropriate amidrazone 9a or 9b
(1 mmol) in ethanol (50 mL), piperidine (0.17 g, 2 mmol) and
benzaldehyde (0.1 g, 1 mmol) were added. The reaction mixture
was refluxed for 8 h. The precipitated product was filtered off,
washed with ethanol and dried. Recrystallization from EtOH/DMF
afforded compounds 11a and 11b, respectively.
Method B. To a solution of propanehydrazonoyl chloride 8a, 8d
or 8e (1 mmol) in ethanol (50 mL), piperidine (0.34 g, 4 mmol) and
the appropriate aldehyde (1 mmol) were added. The reaction
mixture was refluxed for 8 h. The precipitated product was filtered
off, washed with ethanol and dried. Recrystallization from EtOH
/DMF afforded compounds 11a–c, respectively.
4.1.2.5. (1Z,2E)-2-{[(3-Methylbenzofuran-2-yl)carbonyl]hydrazono}-
N-(4-bromophenyl)propanehydrazonoyl chloride (8e). Reaction time
11 h, Yellow needles (3.58 g, 80%); mp 235–237 ꢁC; IR (KBr)
n
3372,
1H NMR (DMSO-d6)
2.44 (s, 3H, CH3), 2.57 (s, 3H, CH3), 7.24–7.62 (m, 8H, ArH), 8.89 (s,
3257 (2NH), 1680 (C]O), 1600 (C]N) cmꢀ1
;
d
D2O exch., 1H,]NNH–), 10.58 (s, D2O exch., 1H, –CONH–); MS m/z
(%) 449 (Mþ þ 2, 9.6), 448 (Mþ þ 1, 9.5), 447 (Mþ, 10.1), 446 (10.3),
159 (100). Anal. Calcd for C19H16Cl2N4O2: C, 50.97; H, 3.60; N,
12.51%. Found: C, 50.76; H, 3.62; N, 12.34%.
4.1.3. Synthesis of (1E,2E)-1-(Piperidin-1-yl)-1-(arylhydrazono)-2-
[(3-methylbenzofuran-2-oyl)hydrazono]propanes 9a, b
Method A. To a solution of propanehydrazonoyl chloride 8a or 8d
(2 mmol) in ethanol (50 mL), piperidine (0.32 g, 4 mmol) was
added. The reaction mixture was heated 30 min at 100 ꢁC then left
to cool at room temperature overnight. The precipitated product
was filtered off, washed with ethanol and dried. Recrystallization
from EtOH afforded compounds 9a and 9b, respectively.
Method B (for 9a). To a solution of 3-methyl-2-benzofur-
ancarboxylic acid hydrazide (7) (0.19 g, 1 mmol) in THF (50 mL), 1-
(2-phenylhydrazono)-1-(piperidin-1-yl)propan-2-one (10) (0.25 g,
4.1.4.1. (1E,2Z,3E)-1-(Piperidin-1-yl)-1-(phenylhydrazono)-2-[(3-
methylbenzofuran-2-oyl)hydrazono]-4-phenylbut-3-ene (11a).
Orange needles (0.35 g, 70% method A; 0.38 g, 76%, method B); mp
208–210 ꢁC; IR (KBr)
cmꢀ1; 1H NMR (DMSO-d6)
3H, CH3), 3.28 (m, 4H, 2CH2 of piperidine), 6.61(m, 1H, ArH), 6.91
n
3375, 3254 (2NH), 1681 (C]O), 1603 (C]N)
1.63 (m, 6H, 3CH2 of piperidine), 2.58 (s,
d

H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
4995
(d, J ¼ 16.5 Hz, 1H, olefinic]CH–), 6.98–7.11 (m, 4H, ArH), 7.23
4.1.6. N-Hydroxy-2-{[(3-methyl-1-benzofuran-2-yl)
carbonyl]hydrazono}-N’-(4-nitrophenyl)
propanehydrazonamide (14)
(d, J ¼ 16.5 Hz, 1H, olefinic]CH–), 7.33–7.52 (m, 7H, ArH), 7.62
(d, J ¼ 8.1 Hz,1H, ArH), 7.79 (d, J ¼ 8.1 Hz,1H, ArH), 8.37 (s, D2O exch.,
1H,]NNH–), 10.70 (s, D2O exch., 1H, –CONH–); 13C NMR
d
8.8 (1C of
A mixture of 8d (0.41 g, 1 mmol), of hydroxylamine hydrochlo-
ride (0.11 g, 1.5 mmol) and anhydrous potassium carbonate (0.21 g,
1.5 mmol) in ethanol (50 mL) was refluxed for 45 min, then left to
cool. The reaction mixture was poured into cold water and the solid
product was filtered off, washed with water, dried and finally
recrystallized from EtOH/DMF to afford 14 as yellow fibers in 0.19 g
benzofuran CH3), 23.83 (1C of piperidine), 25.2 (2C of piperidine),
48.6 (2C of piperidine), 111.8, 113.7, 114.9, 121.4, 121.9, 122.6, 123.3,
123.6, 124.5, 127.6, 128.3, 128.9, 129.3, 130.1, 138.6, 139.0, 142.4, 143.4,
148.8, 154.7; MS m/z (%) 507 (Mþ þ 2, 6.3), 506 (Mþ þ 1, 31.5), 505
(Mþ, 23.7), 159 (100), 77 (10.7). Anal. Calcd for C31H31N5O2: C, 73.64;
H, 6.18; N, 13.85%. Found: C, 73.52; H, 6.16; N, 13.62%.
(47 %) yield; mp 286–288 ꢁC; IR (KBr)
n
3390–3150 (3NH þ OH),
1686 (C]O), 1588 (C]N) cmꢀ1 1H NMR (DMSO-d6)
;
d
2.38 (s, 3H,
4.1.4.2. (1E,2Z,3E)-1-(Piperidin-1-yl)-1-[(4-nitrophenyl)hydrazono]-
2-[(3-methylbenzofuran-2-oyl)hydrazono]-4-phenylbut-3-ene
(11b). Red crystals (0.37 g, 68%, method A; 0.4 g, 72%, method B);
CH3), 2.58 (s, 3H, CH3), 5.72 (s, D2O exch., 1H, –OH), 7.02–7.05 (m,
1H, ArH), 7.08 (s, D2O exch., 1H, –NH–OH), 7.2–7.81 (m, 7H, ArH),
9.70 (s, D2O exch., 1H,]NNH–), 10.60 (s, D2O exch., 1H, –CONH–);
MS m/z (%) 411 (Mþ þ 1, 15.5), 410 (Mþ, 68.0), 159 (100). Anal. Calcd
for C19H18N6O5: C, 55.61; H, 4.42; N, 20.48%. Found: C, 55.49; H,
4.48; N, 20.36%.
mp 261–263 ꢁC; IR (KBr)
n
3367, 3252 (2NH), 1684 (C]O), 1604
1.61 (m, 6H, 3CH2 of piperidine),
(C]N) cmꢀ1; 1H NMR (DMSO-d6)
d
2.58 (s, 3H, CH3), 3.18 (m, 4H, 2CH2 of piperidine), 6.99–7.53 (m, 6H,
ArH), 7.56–7.66 (m, 5H, ArH), 7.68 (d, J ¼ 8.1 Hz, 1H, ArH), 8.00 (d,
J ¼ 8.1 Hz, 1H, ArH), 9.34 (s, D2O exch., 1H,]NNH–), 10.88 (s, D2O
4.1.7. Synthesis of hydrazones 15a, b
exch., 1H, –CONH–); 13C NMR
d
8.8 (1C of benzofuran CH3), 23.7 (1C
A mixture of 3-methyl-2-benzofurancarboxylic acid hydrazide
(7) (0.19 g, 1 mmol) and acetaldehyde or E-cinnamaldehyde
(1 mmol) in absolute ethanol (30 mL) was refluxed for 4 h then left
to cool. The solid product so formed was collected by filtration,
washed with ethanol and dried. Recrystallization from the proper
solvent afforded the corresponding hydrazones 15a, b.
of piperidine), 25.2 (2C of piperidine), 48.6 (2C of piperidine), 111.7,
113.7,114.8, 121.2, 121.3, 122.6, 123.0, 123.4, 124.5,127.6, 128.3, 129.1,
129.3, 138.3, 138.7, 142.5, 143.4, 148.8, 154.1; MS m/z (%) 552
(Mþ þ 2, 7.2), 551 (Mþ þ 1, 33.0), 550 (Mþ, 28.3), 159 (100). Anal.
Calcd for C31H30N6O4: C, 67.62; H, 5.49; N, 15.26%. Found: C, 67.56;
H, 5.42; N, 15.20%. The red single crystal of 11b was cultured from
a mixture solution of CH3CN/DMF (v/v ¼ 5/1) by slow evaporation
at room temperature. Crystal data for compound 11b:
C31H30ClN6O4, Mr, 480.524; system, monoclinic; Space group, P21/c;
unit cell dimensions, a 13.8406 (7) Å, b 12.1451 (6) Å, c 20.5992
4.1.7.1. N’-[(1E)-Ethylidene]-3-methyl-1-benzofuran-2-carbohydrazide
(15a). White powder (0.13 g, 62%); mp.170–172 ꢁC (EtOH); IR (KBr)
n
3217 (NH),1659 (C]O),1605 (C]N) cmꢀ1; 1H NMR (DMSO-d6)
d 2.14
(s, 3H, CH3), 2.58 (s, 3H, CH3), 7.30–7.82 (m, 4H, ArH), 8.50 (s, 1H,
–CH]N–), 11.95 (s, D2O exch., 1H,]NNH–); MS m/z (%) 217 (Mþ þ 1,
7.0), 216 (Mþ, 58.8), 159 (100). Anal. Calcd for C12H12N2O2: C, 66.65;
H, 5.59; N, 12.96%. Found: C, 66.73; H, 6.06; N, 13.08%.
(13) Å,
a b
90.00ꢁ, 124.282 (18)ꢁ; V, 2861.1 (3) Å3; Z, 4; Dx,
1.278 mg.mꢀ3
; q m(Mo-Ka),
range for data collection, 2.910–25.350ꢁ;
0.09 mmꢀ1; T, 298 K; measured reflections, 9015; independent
reflections, 6216; observed reflections, 1700; Rint, 0.044; R(all),
0.291; wR(ref), 0.087; wR(all), 0.133; S(ref), 1.894; S(all), 2.125;
D
/
4.1.7.2. 3-Methyl-N’-[(1E,2E)-3-phenylprop-2-en-1-ylidene]-1-benzo-
furan-2-carbohydrazide (15b). White fibers (0.24 g, 78%); mp 195–
smax, 0.025; Drmax, 0.55 eÅ3, Drmin, –0.67 eÅ3.
197 ꢁC (EtOH/DMF); IR (KBr)
n
3225 (NH), 1664 (C]O), 1603 (C]N)
4.1.4.3. (1E,2Z,3E)-1-(Piperidin-1-yl)-1-[(4-bromophenyl)hydrazono]-
2-[(3-methylbenzofuran-2-oyl)hydrazono]-4-(4-chlorophenyl)but-3-
ene (11c). Orange needles (0.43 g, 70%, method B); mp 256–258 ꢁC;
cmꢀ1; 1H NMR (DMSO-d6)
d
2.57 (s, 3H, CH3), 6.88 (d, J ¼ 16.4 Hz, 1H,
olefinic]CH–), 6.96–7.15 (m, 4H, ArH), 7.25 (d, J ¼ 16.5 Hz, 1H,
olefinic]CH–), 7.29–7.78 (m, 5H, ArH), 8.54 (s, 1H, –CH]N–), 12.20
(s, D2O exch., 1H,]NNH–); MS m/z (%) 305 (Mþ þ 1, 8.2), 304 (Mþ,
38.9), 159 (100). Anal. Calcd for C19H16N2O2: C, 74.98; H, 5.30; N,
9.20%. Found: C, 74.82; H, 5.46; N, 9.33%.
IR (KBr)
NMR (DMSO-d6)
n ;
3364, 3245 (2NH), 1684 (C]O), 1558 (C]N) cmꢀ1 1H
d
1.61 (m, 6H, 3CH2 of piperidine), 2.57 (s, 3H,
CH3), 3.18 (m, 4H, 2CH2 of piperidine), 6.85–6.96 (m, 2H, ArH), 7.09–
7.23 (m, 2H, ArH), 7.32–7.56 (m, 6H, ArH), 7.64 (d, J ¼ 8.1 Hz, 1H,
ArH), 7.77 (d, J ¼ 8.1 Hz, 1H, ArH), 8.56 (s, D2O exch., 1H,]NNH–),
10.60 (s, D2O exch.,1H, –CONH–); MS m/z (%) 620 (Mþ þ 2,17.4), 619
(Mþ þ 1, 18.5), 618 (Mþ, 13.1), 617 (13.4), 444 (34.9), 175 (36.8), 159
(100). Anal. Calcd for C31H29BrClN5O2: C, 60.16; H, 4.72; N, 11.31%.
Found: C, 59.97; H, 4.78; N, 11.36%.
4.2. Antimicrobial activity
4.2.1. Culture media
Two specific media were used for detecting the antimicrobial
activity, malt extract agar (MEA) for fungal isolates [malt extract,
20 g; bacteriological peptone, 5 g; agar, 20 g, the pH was adjusted to
5.4 ꢂ 0.2 at 25 ꢂ 2 ꢁC] while nutrient agar medium was used for
bacterial growth [beef extract, 3 g; bacteriological peptone, 5 g;
agar, 20 g, the pH was adjusted to 6.2 ꢂ 0.2 at 25 (ꢂ 2) ꢁC ]. Each
medium was prepared by dissolving the solid ingredients in 1 L of
cold distilled water and then heated to 60–70 ꢁC with stirring.
Media were sterilized by autoclaving at 121 ꢁC (1.5 atm) for 15–
20 min [55].
4.1.5. 3-Methyl-N’-1-methyl-2-[(4-nitrophenyl)hydrazono-2-
(phenylsulfonyl)ethylidene]-1-benzofuran-2-carbohydrazide (13)
To a solution of 8d (0.41 g, 1 mmol) in absolute ethanol (50 mL),
sodium benzenesulfinate dihydrate (0.4 g, 2 mmol) was added. The
mixture was refluxed for 10 h, then left to cool. The reaction
mixture was poured into cold water and the solid product filtered
off, washed with water, dried and finally recrystallized from EtOH/
DMF to afford sulfone 13 as yellow fibers in 0.28 g (53%) yield; mp
>300 ꢁC; IR (KBr)
n
3345, 3256 (2NH), 1674 (C]O), 1588 (C]N)
2.45 (s, 3H, CH3), 2.57 (s, 3H, CH3),
cmꢀ1 1H NMR (DMSO-d6)
;
d
4.2.2. Microorganisms
6.78–7.01 (m, 4H, ArH), 7.09–7.89 (m, 9H, ArH), 8.48 (s, D2O exch.,
1H,]NNH–), 9.98 (s, D2O exch., 1H, –CONH–); MS m/z (%) 520
(Mþ þ 1, 11.3), 519 (Mþ, 35.0), 159 (100). Anal. Calcd for
C25H21N5O6S: C, 57.80; H, 4.07; N,13.48; S, 6.17%. Found: C, 57.68; H,
4.11; N, 13.60; S, 6.13%.
Eight clinical strains employed for this investigation include two
filamentous fungi (A. fumigatus, S. racemosum), two yeast (C. albi-
cans and G. candidum), two Gram-positive (S. aureus and Bacillus
subtilis) and two Gram-negative (E. coli and P. aeruginosa) bacteria.
All strains were kindly provided from culture collection of the

4996
H.A. Abdel-Aziz, A.A.I. Mekawey / European Journal of Medicinal Chemistry 44 (2009) 4985–4997
Regional Center for Mycology and Biotechnology (RCMB), Al-Azhar
University, Cairo, Egypt.
Appendix. Supplementary data
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.ejmech.2009.09.002.
4.2.3. Antimicrobial assays
By diffusion agar technique, the antifungal and antibacterial
potentialities against the tested species were expressed as the
measurement of diameter of their inhibition zone. Hole-plate
diffusion method was used; six equidistant (1 cm diameter) holes
were made using sterile cork borer in Malt extract agar and
Nutrient agar sterile plates (10 ꢃ 10 cm), which had previously
been seeded with tested fungal and bacterial isolates. Holes were
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Acknowledgement
One of the authors (HAA) is deeply indebted to National
Research Center, Cairo, Egypt for financially supporting.

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