Demonic axe-like conjugated alkynes in combating microbes

Article abstract of DOI:10.1016/j.ejmech.2013.07.013

A new series of disubstituted alkynes was obtained by microwave induced internal splitting of the corresponding β-oxo- alkylidenetriphenylphosphoranes. The antimicrobial potential of these conjugated alkynes and phosphoranes was assayed in vitro against three Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis), three Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae) and five fungal strains (Aspergillus niger, Candida albicans, Aspergillus flavus, Candida rugosa, Saccharomyces cerevisiae). The 3-pyridylalkyne derivatives viz., 3-(6-chloropyridin-3-yl)propynenitrile (6a), 3-(2-chloropyridin-3-yl)propynenitrile (6b), ethyl 3-(6-chloropyridin-3-yl) propiolate (6c), iso-propyl 3-(6-chloropyridin-3-yl)propiolate (6d) and 3-(2,6-dichloro-5-fluoropyridin-3-yl)propynenitrile (6e) were found to be highly potent towards all tested microorganisms except E. coli.

Full text of DOI:10.1016/j.ejmech.2013.07.013

European Journal of Medicinal Chemistry 68 (2013) 132e138
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Demonic axe-like conjugated alkynes in combating microbes
Jayaram Reddy Komsani a, Satish Koppireddi a, Sreenivas Avula a,
,
Pranay Kumar Koochana b, Rambabu Yadla a
*
a Fluoroorganics Division, CSIR-Indian Institute of Chemical Technology (IICT), Tarnaka, Hyderabad 500607, Andhra Pradesh, India
b Biology Division, CSIR-IICT, Hyderabad 500607, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series of disubstituted alkynes was obtained by microwave induced internal splitting of the corre-
sponding b-oxo-alkylidenetriphenylphosphoranes. The antimicrobial potential of these conjugated al-
Received 12 February 2013
Received in revised form
22 July 2013
Accepted 27 July 2013
Available online 8 August 2013
kynes and phosphoranes was assayed in vitro against three Gram-positive bacteria (Staphylococcus aureus,
Bacillus subtilis, Staphylococcus epidermidis), three Gram-negative bacteria (Escherichia coli, Pseudomonas
aeruginosa, Klebsiella pneumoniae) and five fungal strains (Aspergillus niger, Candida albicans, Aspergillus
flavus, Candida rugosa, Saccharomyces cerevisiae). The 3-pyridylalkyne derivatives viz., 3-(6-chloropyridin-
3-yl)propynenitrile (6a), 3-(2-chloropyridin-3-yl)propynenitrile (6b), ethyl 3-(6-chloropyridin-3-yl)pro-
piolate (6c), iso-propyl 3-(6-chloropyridin-3-yl)propiolate (6d) and 3-(2,6-dichloro-5-fluoropyridin-3-yl)
propynenitrile (6e) were found to be highly potent towards all tested microorganisms except E. coli.
Ó 2013 Elsevier Masson SAS. All rights reserved.
Keywords:
iso-Propyl
bromotriphenylphosphoranylacetic acid
ester
b
a
-Oxo-alkylidene-triphenylphosphoranes
-Nicotinoyl- -(alkoxycarbonyl)
a
methylenetriphenylphosphoranes
Halopyridylpropynenitrile
Alkyl halopyridylpropynoic acid ester
Antimicrobial activity
1. Introduction
antimicrobial agents effective against pathogenic microorganisms
resistant to currently available treatments. Our continued interest in
Development of new antimicrobial drugs would remain a
continuous activity to address the problems caused by rapid devel-
opmentofmicrobial resistance to mostof theknownantibiotics[1]. If
suitable new drugs were not made available, the drug resistance
caused by mutations in the microbial genomes would subject the
immunocompromised patients who have undergone bone-marrow
transplantation, or those suffering from AIDS or diabetes and
receiving chemotherapy to greater risk [2]. The resistance of candi-
diasis, a common fungal infection found in both adults and infants
caused by Candida albicans, to treatment with azole antifungal drugs
is currently a burning problem [3,4]. Most of the available antifungal
agents could be classified into polyenes, nucleoside analogs, echi-
nocandins and azoles [5] and their longer term use in treatment was
fraught with severe side effects. Forexample, the useof amphotericin
B (a polyene antifungal drug) has been restricted due to its adverse
side effects like renal toxicity [5,6]. Such a scenario demands a
renewed global effort seeking continuous development of new
the synthesis and conversion of disubstituted acetylenes into various
heterocyclic compounds [7,8] has prompted us to prepare a new
series of propynenitriles and alkyl propynoic acid esters having a
bulky substituent attached directly to the acetylenic carbon atom for
evaluating their antimicrobial efficacy. Acetylenic carboxylic acid
esters and alkynenitriles were not properly investigated for their
antimicrobial potential. Conjugated alkynenitriles and acetylenic
carboxylic acid esters with their ability to undergo nucleophilic
addition reactions are good synthons for preparing heterocyclic
compounds [9]. Several pyridine and furan ring containing hetero-
cyclic compounds have found use in pharmaceutical and agro-
chemical applications [10]. For example, a chloronicotinyl insecticide
like imidacloprid is used worldwide for controlling pests due to its
broad spectrum of activity and low mammalian toxicity [11]. The
present investigation was aimed at preparing a new series of con-
jugated alkynes with a bulky group attached to the sp-carbon atom,
by an elegant process involving microwave induced intramolecular
Wittig reaction of the corresponding
b-oxo-alkylidenetriphenyl-
phosphoranes, for assaying their antibacterial and antifungal po-
tential. Conjugated alkynenitriles are rod like compounds, having all
the atoms forming the two adjacent and rigid triple bonds along with
* Corresponding author. Tel.: þ91 40 27193171; fax: þ91 40 27193943.
E-mail addresses: ryadla@yahoo.com, rambabu@iict.res.in (R. Yadla).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.07.013

J.R. Komsani et al. / European Journal of Medicinal Chemistry 68 (2013) 132e138
133
Table 1
the carbon directly attached to the sp-carbon atom in a straight line.
With a planar and bulky substituent like 2-chloropyridin-3-yl- or 6-
chloropyridin-3-yl- moiety attached to the sp-carbon atom, these
conjugated alkynenitriles and the corresponding acetylenic carbox-
ylic acid esters resemble a demonic axe with the chloropyridinyl
substituent mimicking the axe-head and the linear part of the
molecule forming thehandle. The chloropyridinyl moietyattached to
the stick-like alkynes could possibly interact with microbial DNA and
inhibit the growth as reported earlier in the case of pyrimidones [12]
and pyridinium compounds [13].
List of b-oxo-ylides synthesized.
i. NEt3, DCM,150C
Z
Ph3PCH2Z X
Ph3P
5a-p
ii. RCOCl, RT, 9 h
COR
3
4
S. No.
R
Z
Isolated yield, %
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
6-Chloropyridin-3-yl
CN
95
89
92
91
88
94
93
84
90
90
91
87
87
89
85
82
2-Chloropyridin-3-yl
CN
6-Chloropyridin-3-yl
6-Chloropyridin-3-yl
2,6-Dichloro-5-fluoropyridin-3-yl
CO2Et
CO2iPr
CN
2. Results and discussion
o-Tolyl
o-Tolyl
t-Butyl
CN
2.1. Chemistry
CO2Et
CO2Et
CO2Et
CO2Et
CO2iPr
CO2Et
CO2iPr
CN
2-Chloropyridin-3-yl
2,6-Dichloro-5-fluoropyridin-3-yl
2,6-Dichloro-5-fluoropyridin-3-yl
Triphenylphosphine (1) was reacted with chloroacetonitrile (2a)
in refluxing toluene for 7 h to obtain cyanomethyltriphenyl
phosphonium chloride (3a) in quantitative yield [7,8]. The reaction
of alkyl chloro/bromoacetate (2b) with 1 in dry dichloromethane
has resulted in the corresponding alkyl bromo/chloro-triphenyl
phosphoranylacetic acid ester (3b). Treatment of cyanomethyl-
triphenylphosphonium chloride salt (3a) or alkyl bromo/chloro-
triphenylphosphoranylacetic acid ester (3b) with triethylamine
2-Furyl
2-Furyl
2-Furyl
t-Butyl
t-Butyl
CN
CO2iPr
has resulted in quantitative formation of the respective a-(cyano/
alkoxycarbonyl)methylenetriphenylphosphorane [7,8]. These reac-
tive phosphorous ylides, without isolation, were acylated in the
same reaction flask with the corresponding carboxylic acid chloride
The phosphoranes 5aep were characterized with the help of IR,
NMR (1H & 13C) and mass spectroscopy. The IR spectra of the nitrile
group containing oxo-ylides (5aeb, 5eef, 5n and 5o) showed sharp
nitrile stretching absorption band in the region of 2164e2186 cmꢀ1
.
(4aep) under transylidation conditions to afford the desired
ylides (5aep) in high yield. The reaction sequence was depicted in
Scheme 1. Thus, a series of -cyanomethylenetriphenylphosphor-
anes and -(ethoxy/iso-propyloxycarbonyl)methylenetriphenyl-
b-oxo-
The alkyl ester containing oxo-ylides (5ced, 5i, 5jek, 5geh, 5lem
and 5p) showed strong ester carbonyl stretching IR absorption
a
a
band in the region of 1656e1692 cmꢀ1. The
b-keto stretching ab-
phosphoranes (5aep) having 6-chloronicotinoyl-, 2-chloro-
nicotinoyl-, 2,6-dichloro-5-fluoronicotinoyl-, o-toluoyl-, 2-furoyl-
or t-butyroyl-substituent on the ylide carbon were synthesized in
high yield (Table 1). The chloronicotinoyl-substituted phosphorus
ylides (5aee, 5iek) along with the o-toluoyl- (5f), furoyl- (5m) and
pivaloyl- (5oep) derivatives were prepared for the first time. The
sorption band of the oxo-ylides 5aep was shifted to 1532e
1577 cmꢀ1 region due to delocalization of electrons involving the
ylide carbon. Also present was a sharp absorption band each in
1435e1440 and 995e1095 cmꢀ1 regions, a common feature
observed in compounds containing phosphorus linked to aryl
group [17e19]. The 13C NMR signal for the ylide carbon of phos-
phoranes 5aep appeared as a doublet (1J(CeP) ¼ 122e127 Hz) be-
a
-(ethoxycarbonyl)methylenetriphenylphosphoranes containing
o-toluoyl- (5g), t-butyroyl- (5h), 2-furoyl- (5l) substituent, and the
-(2-furoyl)- -cyanomethylenetriphenylphosphorane (5n) were
tween
d 50e70 ppm, indicating greater localization of negative
a
a
charge on this carbon and imparting partial ionic character to P]C
bond. The signals due to the eighteen carbon atoms present in three
phenyl rings attached to P-atom were observed as four distinct
previously reported [14e16]. However, IR, 1H NMR, 13C NMR and
Mass spectral data was not available for the stabilized ylide 5n.
The oxo-ylides 5aeh were converted into disubstituted conju-
gated alkynes (6aeh) via intramolecular Wittig reaction under
microwave irradiation conditions. All these alkynes containing a
bulky substituent were screened against six bacterial strains viz.,
Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis,
Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae,
and five fungal species viz., Aspergillus niger, Aspergillus flavus,
C. albicans, Candida rugosa, Saccharomyces cerevisiae to obtain their
MIC values and zone of inhibition, respectively.
1
2
3
doublets in the range
d 123e133 ppm with J(CeP), J(CeP), J(CeP),
4J(CeP) values of 93e94 Hz, 9e10 Hz, 11e13 Hz and 3e4 Hz,
respectively. The spectral data was presented in Experimental
section.
Thermal decomposition of keto-ylides at elevated temperatures
to obtain alkynes was prior art [20]. The heat sensitive alkynes
formed in this reaction have to be distilled simultaneously under
high vacuum, resulting in their lower isolated yield. We have
overcome this drawback by applying microwave energy under
i. NEt3, DCM,15 0C
Z
DCM, RT, 72 h
Ph3P + XCH2Z
Ph3P
Ph3PCH2Z X
3a-b
or
Toluene,
ii. RCOCl,RT, 9 h
COR
1
2a-b
5a-p
4
Reflux,7 h
MW
9 min
X = Cl or Br ,
Z = CN (2a and 3a),
Z = COOEt, COOiPr (2b and 3b).
-
Ph3PO
7
Z
R
Ph3P
O
]
[
R
C C Z
6a-h
Scheme 1. Reaction sequence leading to alkynes (6).

134
J.R. Komsani et al. / European Journal of Medicinal Chemistry 68 (2013) 132e138
Table 2
appeared at
acetylenic carboxylic acid esters (6ced, 6geh) was seen around
153 ppm.
d 105 ppm, while the signal due to ester carbonyl of the
List of conjugated alkynes synthesized.
Z
d
9 min.
M.W.,
R
C C Z
Ph3P
5a-h
(Ph3PO)
COR
2.2. Biological activity
6a-h
An in vitro antimicrobial assay was carried out in respect of all
the synthesized phosphorous ylides 5aep and conjugated alkynes
6aeh against six bacterial strains (B. subtilis, S. aureus,
S. epidermidis, E. coli, P. aeruginosa, K. pneumoniae) and five fungal
strains (A. niger, A. flavus, C. albicans, C. rugosa, S. cerevisiae). Sta-
bilized phosphorus ylides containing substituted benzoyl moiety
on the ylide carbon were reported [23] to exhibit high antibacterial
and moderate antifungal activity in vitro. In contrast to this report,
no effectiveness was exhibited by the oxo-ylides 5aep against all
the tested bacterial strains, with their MIC values higher than
S. No.
R
Z
Isolated yield (%)
MW
Thermal
6a
6b
6c
6d
6e
6f
6-Cloropyridin-3-yl
2-Cloropyridin-3-yl
6-Cloropyridin-3-yl
6-Cloropyridin-3-yl
CN
CN
CO2Et
COi2Pr
CN
CN
CO2Et
CO2Et
76
73
79
78
71
81
83
59
52
55
56
49
52
59
61
31
2,6-Dichloro-5-fluoropyridin-3-yl
o-Tolyl
o-Tolyl
t-Butyl
6g
6h
150
mg/mL. They did not show any noticeable antifungal activity
either, with a near zero mm zone of inhibition even at 100
mg/mL
concentration against all the five fungal species studied. However,
the 3-pyridinyl-substituted acetylenic compounds (6aee) were
more effective against all the tested microorganisms except E. coli,
suggesting a crucial role for the 3-pyridyl moiety in enhancing the
antimicrobial properties of this class of compounds.
controlled conditions over a shorter duration to facilitate intra-
molecular Wittig reaction of the oxo-ylides at relatively lower
temperature and obtained the conjugated alkynes (6aeh) in good
yield (Table 2). The 3-(6-chloropyridin-3-yl)prop-2-ynenitrile (6a),
3-(2-chloropyridin-3-yl) prop-2-ynenitrile (6b), ethyl 3-(6-chloro
pyridin-3-yl)prop-2-ynoic acid ester (6c), iso-propyl 3-(6-chloro
pyridin-3-yl)prop-2-ynoic acid ester (6d) and 3-(2,6-dichloro-5-
fluoropyridin-3-yl)prop-2-ynenitrile (6e) were new compounds,
while 3-(2-methylphenyl)prop-2-ynenitrile (6f) was prepared by
this method for the first time. Compound 6f was obtained earlier by
a different route involving cyanation of alkyne [21]. The preparation
of ethyl 3-(2-methylphenyl)prop-2-ynoic acid ester (6g) and ethyl
4,4-dimethylpent-2-ynoate (6h) was also reported earlier [14,22].
2.2.1. Antibacterial activity of conjugated alkynes (6aeh)
3-(6-Chloropyridin-3-yl)propynenitrile (6a), 3-(2-chloropyri-
din-3-yl)propynenitrile (6b), ethyl 3-(6-chloropyridin-3-yl)pro-
piolate (6c), iso-propyl 3-(6-chloropyridin-3-yl)propiolate (6d) and
3-(2,6-dichloro-5-fluoropyridin-3-yl)propynenitrile (6e) were very
potent in vitro towards all tested Gram-positive microorganisms
(B. subtilis, S. aureus & S. epidermidis) and two Gram-negative K.
pneumoniae & P. aeruginosa bacterial strains. Their effectiveness
was comparable to the standards used viz., streptomycin and
penicillin. However, they were not so effective against E. coli. The
aryl- and t-butyl-substituted acetylenes (6feh) were ineffective
against all the tested microorganisms. Compounds 6aed, with
minimum inhibitory concentration (MIC) value ranging from 0.78
The 2-chloronicotinoyl containing
a-(alkoxycarbonyl)methylene-
triphenylphoshoranes 5iek did not undergo triphenylphosphine
oxide (7) extrusion under the controlled microwave irradiation
conditions and failed to give the corresponding alkynes. The
disubstituted acetylenes (6aeh) were thoroughly characterized
with the help of IR, 1H NMR, 13C NMR and mass spectroscopic data.
The IR spectra of the conjugated alkynenitriles (6aeb, 6eef) con-
tained sharp nitrile stretching absorption band at 2265e2271 cmꢀ1
and the alkyne triple bond absorption band at 2140e2148 cmꢀ1
region. The IR absorption band due to acetylene function of the
alkyl acetylenic carboxylic acid esters has appeared in the region of
2206e2227 cmꢀ1. The characteristic ester carbonyl stretching ab-
sorption band of the acetylenic carboxylic acid esters (6c, 6d, 6g
and 6h) was seen in 1701e1708 cmꢀ1 region. The 13C NMR spectra
to 1.56
mg/mL against P. aeruginosa, were comparable in their
antibacterial activity to streptomycin and considerably more potent
than penicillin. The antibacterial activity of conjugated alkynes
(6aeh) and the standards was shown in Table 3.
2.2.2. Antifungal activity of conjugated alkynes (6aeh)
The 3-(halopyridin-3-yl)alkynes (6aee) have displayed very
good zone of inhibition values of 10e44 mm at 50 mg/mL concen-
tration against A. niger, A. flavus, C. albicans, C. rugosa and
S. cerevisiae. The in vitro antifungal activity of 3-(2/6-chloropyridin-
3-yl)alkynenitriles (6aeb) against A. niger, A. flavus, C. albicans and
contained signals due to acetylenic carbons in the
d 70e85 ppm
region. The nitrile carbon signal in alkynenitriles (6aeb, 6eef)
Table 3
In vitro antibacterial activity assay of acetylenic compounds 6aeh.
Compound
MIC (mg/mL)
Gram-positive
Gram-negative
B. subtilis
S. aureus
S. epidermidis
E. coli
P. aeruginosa
K. pneumoniae
6a
6b
6c
6d
6e
6f
6g
6h
1.56
3.125
6.25
50
6.25
>150
>150
>150
1.562
6.25
1.56
6.25
1.56
1.56
6.25
50
50
1.56
25
>150
>150
>150
3.125
3.125
100
100
100
100
0.78
0.78
0.78
1.56
3.125
12.5
6.25
12.5
12.5
˃150
˃150
˃150
6.25
3.125
12.5
100
100
>150
>150
>150
1.562
6.25
>150
>150
>150
12.5
6.25
>150
>150
>150
12.5
Penicillin
Streptomycin
1.562

J.R. Komsani et al. / European Journal of Medicinal Chemistry 68 (2013) 132e138
135
C. rugosa was slightly better than that of amphotericin B (standard).
However, they were ineffective against S. cerevisiae. Ethyl 3-(6-
chloropyridin-3-yl)propynoate (6c) was very potent towards
S. cerevisiae and A. niger and its activity was comparable to
amphotericin B. The aryl- and t-butyl-substituted acetylenic
compounds 6feh were ineffective against all tested fungal strains.
The antifungal assay of conjugated alkynes 6aeh was displayed in
Table 4.
spectrometry (HRMS) experiments were performed using a quad-
rupole time-of-flight mass spectrometer (QSTAR XL).
4.1.1. General procedure for the synthesis of b-oxo-
alkylidenetriphenylphosphoranes (5aep)
The general protocol followed for preparing
described here taking -(6-chloronicotinoyl)-
enetriphenylphosphorane (5a) as an example. The remaining
b
-oxo-ylides was
a
a-(cyano)methyl-
b-oxo-ylides (5bep) were prepared in a similar manner.
Triethylamine (1.06 g, 0.01 mol) was added drop wise to a stir-
3. Conclusions
red suspension of cyanomethyltriphenylphosphonium chloride
(3a, 1.68 g, 0.005 mol) in 10 mL dry CH2Cl2 at 10e15 ꢁC under N2
atmosphere. The reaction mixture was stirred at room temperature
for 30 min and a solution of 6-chloronicotinoyl chloride (4a, 0.88 g,
0.005 mol) in 5 mL CH2Cl2 was added drop wise in about 15 min.
After vigorous stirring for 12 h at room temperature, the reaction
mixture was diluted with 10 mL CH2Cl2 and washed with 3 ꢂ 10 mL
water. The organic layer was separated, dried over anhydrous so-
dium sulfate and the solvent was removed on rotavapor. The crude
product was recrystallized from a 1:4 mixture of CH2Cl2 and hexane
Conjugated alkynes containing a bulky
synthesized in high yield from -oxo-alkylidenetriphenyl-phos-
b-substituent were
b
phoranes via microwave induced intramolecular Wittig reaction
and tested in vitro for their antimicrobial activity against three
Gram-positive and three Gram-negative bacteria, along with five
fungal species. Halopyridin-3-yl substituted acetylenes have dis-
played very good broad spectrum antimicrobial activity, a first
observation for disubstituted acetylenes. The antibacterial efficacy
of 3-(6-chloropyridin-3-yl)propynenitrile, 3-(2-chloropyridin-3-yl)
propynenitrile and ethyl 3-(6-chloropyridin-3-yl)propynoic acid
ester against B. subtilis, S. aureus, P. aeruginosa and K. pneumoniae
was comparable to penicillin and streptomycin. The same com-
pounds have also exhibited good antifungal activity comparable to
amphotericin B against A. niger, C. albicans, A. flavus, C. rugosa,
S. cerevisiae. However, they were less affective against E. coli. The
results indicated that conjugated alkynenitriles and acetylenic
carboxylic acid esters armed with a suitable bioactive scaffold have
the potential to become a new class of antimicrobial agents.
to obtain
a-(6-chloronicotinoyl)-a-(cyano)methylenetriphenylpho
sphorane (5a). Yield: 2.09 g (95%).
4 .1.1.1.
triphenylphosphorane (5a). Colorless solid; mp 175e177 ꢁC; 1H
NMR (
ppm in CDCl3, 500 MHz): 7.34 (1H, d, J ¼ 7.8 Hz, PyeH),
a- ( 6 - C h l o ron i c o t i n o yl ) - a - ( c ya n o ) m e t hyl e n e -
d
7.54e7.60 (6H, m, AreHs), 7.64e7.71 (9H, m, AreHs), 8.30 (1H, dd,
J ¼ 1.9, 7.8 Hz, PyeH), 8.93 (1H, d, J ¼ 1.9 Hz, PyeH); 13C NMR (
d
1
ppm in CDCl3, 75 MHz): 50.4 (d, JCeP ¼ 125.1 Hz, P]C), 121.5
2
1
(d, JCeP ¼ 15.3 Hz, eCN), 122.5 (d, JCeP ¼ 94.4 Hz, PePh), 129.3
3
4
(d, JCeP ¼ 10.9 Hz, PePh), 133.4 (d, JCeP ¼ 3.4 Hz, PePh), 133.6
(d, 2JCeP ¼ 10.9 Hz, PePh), 128.7, 132.0, 138.3, 149.6, 153.0, 186.3 (d,
4. Experimental protocols
2JCeP ¼ 4.3 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3055, 2176, 1573, 1482,
1437, 1356, 1128, 1105, 1014, 938; ESI-MS m/z (M þ H)þ: 441; HRMS
4.1. Chemistry
m/z calcd for C26H19ON2ClP [M þ H]þ : 441.0918; found: 441.0903.
All the reagents and solvents were purchased from commercial
sources. The solvents were redistilled and dried before use. Melting
points were determined on the veego (VMP-MP) melting point
apparatus and were uncorrected. Thin layer chromatography was
carried out on Merck 60 F254 silica gel coated glass sheets. The
acetylenic compounds were purified by column chromatography on
silica gel (60e120 mesh). Infrared spectra were recorded on Perkine
Elmer FT-IR 1600 spectrometer. 1H and 13C nuclear magnetic reso-
nance spectra were recorded on Bruker Avance 300 MHz and Inova
500 MHz spectrometer with TMS as internal standard. Chemical
4.1.1. 2.
triphenylphosphorane (5b). Colorless solid; mp 135e137 ꢁC; 1H
NMR (
a- (2 -C hlo ro ni c ot i no yl) -a -(c yan o) m ethylen e-
d
ppm in CDCl3, 300 MHz): 7.25 (1H, dd, J ¼ 4.5, 7.5 Hz,
PyridineeH), 7.41e7.49 (9H, m, AreHs), 7.62e7.70 (6H, m, AreHs),
7.80 (1H, dd, J ¼ 2.2, 7.5 Hz, PyridineeH), 8.39 (1H, dd, J ¼ 2.2,
4.5 Hz, PyridineeH); IR (KBr)
y
cmꢀ1: 3054, 2186, 1568, 1481, 1437,
1338, 1188, 1114, 1064, 997; ESI-MS m/z (M þ H)þ: 441; HRMS m/z
calcd for C26H19ON2ClP [M þ H]þ: 441.0918; found: 441.0905.
4.1.1.3.
a-(6-Chloronicotinoyl)-a-(ethoxycarbonyl)methylene-
shifts (d) were given in parts per million and coupling constants
were given as absolute values expressed in Hertz. Mass spectral
analysis using electrospray ionization (ESI) and high resolution mass
triphenylphosphorane (5c). Colorless solid; mp 165e167 ꢁC;
1H NMR (
d
ppm in CDCl3, 300 MHz): 0.68 (3H, t, J ¼ 6.7 Hz, eCH3),
Table 4
Invitro antifungal activity data of acetylenic compounds 6a h.
Compound
C.albicans
C.rugosa
S.cerevisiae
A.niger
A.flavus
Zone of inhibition (mm)
50a
100a
50a
100a
50a
100a
50a
100a
50a
100a
6a
6b
6c
6d
6e
6f
35
23
15
13
11
0
40
28
20
19
16
0
33
23
10
0
0
0
28
29
15
11
11
0
0
0
25
11
0
10
11
29
17
10
0
39
26
25
17
20
0
43
30
29
23
24
0
44
35
20
12
20
0
47
39
25
19
25
0
0
6g
0
0
0
0
0
0
0
0
0
0
6h
0
0
0
0
0
0
0
0
0
0
Amphote-ricin-B
23.5
21
22
25
25
a
Concentration of compound in g/mL.

136
J.R. Komsani et al. / European Journal of Medicinal Chemistry 68 (2013) 132e138
3.69 (2H, q, J ¼ 6.7 Hz, eCH2), 7.26 (1H, d, J ¼ 8.3 Hz, PyeH), 7.44e
7.60 (9H, m, AreHs), 7.68e7.77 (6H, m, AreHs), 7.85 (1H, dd, J ¼ 2.2,
J ¼ 1.5, 7.5 Hz, PyeH), 8.28 (1H, dd, J ¼ 1.5, 4.5 Hz, PyeH); IR (KBr)
y
cmꢀ1: 3053, 2975, 1655, 1532, 1482, 1436, 1187, 995; ESI-MS m/z
8.3 Hz, PyeH), 8.64 (1H, d, J ¼ 2.2 Hz, PyeH); 13C NMR (
d
ppm in
(M þ Na)þ: 510; HRMS m/z calcd for C28H23O3NClNaP [M þ Na]þ:
CDCl3,125 MHz): 13.6, 54.1 (d, 1JCeP ¼ 127.3 Hz, P]C), 58.6,125.4 (d,
510.0994; found: 510.1007.
3
1JCeP ¼ 92.2 Hz, PePh), 128.9 (d, JCeP ¼ 10.9 Hz, PePh), 132.1 (d,
4JCeP ¼ 3.4 Hz, PePh), 133.3 (d, 2JCeP ¼ 10.9 Hz, PePh) 128.4, 132.0,
138.7,149.6,151.5,164.9 (d, 2JCeP ¼ 14.3 Hz, ester carbonyl),183.7 (d,
4.1.1.9.
ylenetriphenylphosphorane (5j). Colorless solid; mp 133e135 ꢁC; 1H
NMR (
ppm in CDCl3, 300 MHz): 0.65 (3H, t, J ¼ 7.1 Hz, eCH3), 3.69
(2H, q, J ¼ 7.1 Hz, eCH2), 7.35 (1H, d, J ¼ 7.1 Hz, PyeH), 7.46e7.60
a-(2,6-Dichloro-5-fluoronicotinoyl)-a-(ethoxycarbonyl)meth-
2JCeP ¼ 4.3 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3053, 2975, 1655, 1575,
d
1482, 1441, 1326, 1256, 1083, 1023, 895; ESI-MS m/z (M þ Na)þ: 510;
HRMS m/z calcd for C28H23O3NClNaP [M þ Na]þ: 510.0996; found:
510.1009.
(9H, m, AreHs), 7.69e7.79 (6H, m, AreHs); 13C NMR (
d ppm in
CDCl3, 75 MHz): 13.3, 50.0 (d, 1JCeP ¼ 121.8 Hz, P]C), 58.8, 124.4 (d,
3
1JCeP ¼ 93.3 Hz, PePh), 128.6 (d, JCeP ¼ 12.6 Hz, PePh), 131.9 (d,
4.1.1.4.
triphenylphosphorane (5d). Colorless solid; mp120e122 ꢁC; 1H
NMR (
a
-(6-Chloronicotinoyl)-
a
-(isopropyloxycarbonyl)methylene-
4JCeP ¼ 4.3 Hz, PePh), 133.2 (d, 2JCeP ¼ 9.8 Hz, PePh), 125.0, 129.9,
133.7, 135.0, 154.1, 166.7 (d, 2JCeP ¼ 13.1 Hz, ester eC]O), 185.1 (d,
d
ppm in CDCl3, 500 MHz): 0.65 (6H, d, J ¼ 5.5 Hz, two CH3
2JCeP ¼ 6.5 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3055, 2985, 1664, 1547,
groups), 4.56e4.62 (1H, m, eCH), 7.26 (1H, d, J ¼ 2.7 Hz, PyeH),
1479, 1439, 1385, 1327, 1256, 1104, 900; ESI-MS m/z (M þ H)þ: 540;
HRMS m/z calcd for C28H22O3NCl2FP [M þ H]þ: 540.0692; found:
540.0708.
7.39e7.51 (9H, m, AreHs), 7.64e7.70 (6H, m, AreHs), 7.79 (1H, dd,
J ¼ 2.7,1.8 Hz, PyeH), 8.58 (1H, d, J ¼ 1.8 Hz, PyeH); 13C NMR (
d ppm
in CDCl3, 125 MHz): 21.4, 50.1 (d, 1JCeP ¼ 127.3 Hz, P]C), 66.0, 125.5
(d, 1JCeP ¼ 92.2 Hz, PePh), 128.9 (d, 3JCeP ¼ 10.9 Hz, PePh), 131.7 (d,
4JCeP ¼ 3.2 Hz, PePh), 133.2 (d, 2JCeP ¼ 10.9 Hz, PePh), 128.4, 137.5,
138.7, 149.7, 151.5, 166.7 (d, 2JCeP ¼ 13.1 Hz, ester carbonyl), 179.1 (d,
4.1.1.10 .
triphenylphosphorane (5l). Red color solid; mp 100e102 ꢁC; 1H
NMR (
a-(2-Furo yl)-a-(ethoxycarbonyl)methylene-
d
ppm in CDCl3, 300 MHz): 0.65 (3H, t, J ¼ 6.9 Hz, eCH3), 3.64
2JCeP ¼ 4.3 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3055, 2976, 1656, 1577,
(2H, q, J ¼ 6.9 Hz, eCH2), 6.40 (1H, dd, J ¼ 2.2, 3.0 Hz, FuraneH), 7.12
1444, 1358, 1324, 1256, 1095, 924; ESI-MS m/z (M þ H)þ: 502;
HRMS m/z calcd for C29H26O3NClP [M þ H]þ: 502.1333; found:
502.1328.
(1H, d, J ¼ 3.0 Hz, FuraneH), 7.40 (1H, d, J ¼ 2.2 Hz, FuraneH), 7.41e
7.55 (9H, m, AreHs), 7.67e7.76 (6H, m, AreHs); 13C NMR (
d ppm in
CDCl3, 125 MHz): 13.8, 49.6 (d, 1JCeP ¼ 125.1 Hz, P]C), 58.8, 126.1
(d, 1JCeP ¼ 94.4 Hz, PePh), 128.6 (d, 3JCeP ¼ 13.1 Hz, PePh), 131.7 (d,
2
4.1.1.5.
a
-(2,6-Dichloro-5-fluoro-nicotinoyl)-
a
-(cyano)methylene-
4JCeP ¼ 3.7 Hz, PePh), 133.3 (d, JCeP ¼ 8.7 Hz, PePh), 110.9, 114.4,
triphenylphosphorane (5e). Colorless solid; mp 205e207 ꢁC;
131.8, 143.0, 167.2 (d, 2JCeP ¼ 13.1 Hz, ester carbonyl), 179.2 (d, 2JCe
1H NMR (
d
ppm in CDCl3, 500 MHz): 7.57 (1H, m, PyeH), 7.58e7.62
¼ 6.5 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3058, 2981, 1671, 1575, 1473,
P
(6H, m, AreHs), 7.67e7.74 (9H, m, AreHs); 13C NMR
(d
1438, 1326, 1260, 1077, 1012, 933; ESI-MS m/z (M þ Na)þ: 465;
HRMS m/z calcd for C27H23O4NaP [M þ Na]þ: 465.1226; found:
465.1252.
1
ppm in CDCl3, 75 MHz): 52.6 (d, JCeP ¼ 122.0 Hz, P]C), 120.7
2
1
(d, JCeP ¼ 15.2 Hz, eCN), 122.1 (d, JCeP ¼ 93.0 Hz, PePh), 129.6
3
4
(d, JCeP ¼ 13.7 Hz, PePh), 133.5 (d, JCeP ¼ 3.7 Hz, PePh), 133.8
(d, 2JCeP ¼ 10.6 Hz, PePh), 126.1, 137.9, 139.2, 141.2, 154.5, 185.3 (d,
4.1.1.11.
triphenylphosphorane (5m). Colorless solid; mp 145e147 ꢁC; 1H
NMR (
a-(2-Furoyl)-a-(isopropyloxycarbonyl)methylene-
2JCeP ¼ 6.1 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3062, 2180, 1578, 1481,
1438, 1391, 1108; ESI-MS m/z (M þ H)þ: 493; HRMS m/z calcd for
d
ppm in CDCl3, 300 MHz): 0.82 (6H, d, J ¼ 6.4 Hz, two eCH3
C
26H17ON2Cl2FP ([M þ H]þ): 493.0434; found: 493.0441.
groups), 4.69e4.78 (1H, m, eCH), 6.42 (1H, dd, J ¼ 1.7, 3.3 Hz,
FuraneH), 7.13 (1H, dd, J ¼ 0.9, 3.3 Hz, FuraneH), 7.42 (1H, dd,
J ¼ 0.9, 1.7 Hz, FuraneH), 7.44e7.54 (9H, m, AreHs), 7.64e7.81 (6H,
4.1.1.6.
a
-(o-Toluoyl)-
a
-(cyano)methylenetriphenylphosphorane (5f).
Colorless solid; mp 125e127 ꢁC; 1H NMR (
d
ppm in CDCl3,
m, AreHs); IR (KBr) y
cmꢀ1: 3067, 2976, 1692, 1668, 1512, 1475,
300 MHz): 2.40 (3H, s, AreCH3), 7.15 (2H, t, J ¼ 6.7 Hz, AreHs), 7.19
(1H, d, J ¼ 2.2 Hz, AreH), 7.21 (1H, d, J ¼ 2.2 Hz, AreH), 7.50e7.60
(9H, m, AreHs), 7.60e7.71 (6H, m, AreH); ESI-MS m/z (M þ H)þ:
420; HRMS m/z calcd for C28H23ONP [M þ H]þ: 420.1511; found:
420.1499.
1435, 1363, 1254, 1106, 1071, 1002, 932; ESI-MS m/z (M þ H)þ: 457;
HRMS m/z calcd for C28H26O4P [M þ H]þ: 457.1563; found:
457.1555.
4.1.1.12.
Colorless solid; mp 167e169 ꢁC; 1H NMR (
300 MHz): 1.35 (9H, s, three eCH3 groups), 7.45e7.54 (9H, m, Are
a
-(Pivaloyl)-
a-(cyano)methylenetriphenylphosphorane (5o).
d
ppm in CDCl3,
4.1.1.7.
a
-(Pivaloyl)-
a
-(ethoxycarbonyl)methylenetriphenylphosphor-
ppm in CDCl3,
ane (5h). Colorless solid; mp 149e150 ꢁC; 1H NMR (
d
Hs), 7.55e7.62 (6H, m, AreHs); 13C NMR (
d ppm in CDCl3,
300 MHz): 0.68 (3H, t, J ¼ 6.7 Hz, eCH3), 1.27 (9H, s, three eCH3
75 MHz): 26.9, 42.5 (d, 3JCeP ¼ 6.5 Hz, tBuequaternary carbon), 51.2
groups), 3.58 (2H, q, J ¼ 6.7 Hz, eCH2), 7.35e7.50 (9H, m, AreHs),
(d, 1JCeP ¼ 127.3 Hz, P]C), 122.5 (d, 2JCeP ¼ 17.5 Hz, eCN), 123.9 (d,
7.55e7.65 (6H, m, AreHs); 13C NMR (
d
ppm in CDCl3, 75 MHz): 13.6,
1JCeP ¼ 94.4 Hz, PePh), 128.7 (d, JCeP ¼ 13.1 Hz, PePh), 132.5
3
3
t
4
2
27.2, 42.5 (d, JCeP ¼ 6.5 Hz, Buequaternary carbon), 50.5 (d, 1JCe
(d, JCeP ¼ 4.3 Hz, PePh), 133.1 (d, JCeP ¼ 8.7 Hz, PePh), 202.5 (d,
1
¼ 125.3 Hz, P]C), 58.5, 128.0 (d, JCeP ¼ 94.4 Hz, PePh), 128.5
2JCeP ¼ 4.3 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3052, 2164, 1565, 1479,
P
(d, 3JCeP ¼ 13.1 Hz, PePh), 131.1 (d, 4JCeP ¼ 2.9 Hz, PePh), 132.7 (d,
1437, 1327, 1160, 1105, 1027, 996; ESI-MS m/z (M þ H)þ: 386; HRMS
2JCeP ¼ 10.9 Hz, PePh), 202.3 (d, 2JCeP ¼ 4.3 Hz, eC]O); IR (KBr)
y
m/z calcd for C25H25ONP [M þ H]þ: 386.1668; found: 386.1665.
cmꢀ1: 3048, 2940, 1662, 1537, 1483, 1438, 1329, 1251, 1075; ESI-MS
m/z (M þ H)þ: 433; HRMS m/z calcd for C27H30O3P [M þ H]þ:
433.1927; found: 433.1919.
4.1.1.13.
triphenylphosphorane (5p). Colorless solid; mp 145e147 ꢁC; 1H
NMR (
ppm in CDCl3, 300 MHz): 0.72 (6H, d, J ¼ 6.2 Hz, two eCH3
groups), 1.27 (9H, s, three CH3 groups), 4.58e4.69 (1H, m, eCH),
7.35e7.47 (9H, m, AreHs), 7.56e7.66 (6H, m, AreHs); 13C NMR (
a-(Pivaloyl)-a-(isopropyloxycarbonyl)methylene-
d
4.1.1.8.
triphenylphosphorane (5i). Colorless solid; mp 123e125 ꢁC; 1H
NMR (
a-(2-Chloronicotinoyl)-a-(ethoxycarbonyl)methylene-
d
3
t
d
ppm in CDCl3, 300 MHz): 0.65 (3H, t, J ¼ 6.7 Hz, eCH3),
ppm in CDCl3, 75 MHz): 21.4, 27.2, 42.6 (d, JCeP ¼ 6.5 Hz, Bue
1
3.69 (2H, q, J ¼ 6.7 Hz, eCH2), 7.20 (1H, dd, J ¼ 4.5, 7.5 HZ, PyeH),
quaternary carbon), 51.5 (d, JCeP ¼ 125.3 Hz, P]C), 65.6, 128.0
7.44e7.60 (9H, m, AreHs), 7.68e7.77 (6H, m, AreHs), 7.80 (1H, dd,
(d, 1JCeP ¼ 92.2 Hz, PePh), 128.4 (d, 3JCeP ¼ 13.1 Hz, PePh), 131.1 (d,

J.R. Komsani et al. / European Journal of Medicinal Chemistry 68 (2013) 132e138
137
4JCeP ¼ 2.3 Hz, PePh), 132.7 (d, 2JCeP ¼ 8.7 Hz, PePh), 202.4 (d, 2JCe
IR (KBr) y
cmꢀ1: 3377, 3035, 2985, 2928, 2223, 1701, 1578, 1545,
¼ 6.5 Hz, eC]O); IR (KBr)
y
cmꢀ1: 3050, 2974, 1655, 1526, 1483,
1455, 1291, 1204, 1099; ESI-MS m/z (M þ H)þ: 224; HRMS m/z calcd
for C11H11O2NCl [M þ H]þ: 224.0300; found: 224.0317; Anal.
(C11H10O2NCl): C 59.07%, H 4.51%, N 6.26%; found: C 59.02%, H
4.72%, N 6.15%.
P
1437, 1354,1254, 1083, 1075, 998; ESI-MS m/z (M þ H)þ: 447; HRMS
m/z calcd for C28H32O3P [M þ H]þ: 447.2083; found: 447.2076.
4.1.2. General procedure for the synthesis of conjugated acetylenes
(6aeh)
4.1.2.7. 3-(2,6-Dichloro-5-fluoropyridin-3-yl)prop-2-ynenitrile (6e).
4.1.2.1. Microwave irradiation method. The
b
-oxo-ylide (5, 0.045
Colorless solid; mp 87e89 ꢁC; 1H NMR (
d
ppm in CDCl3): 7.65 (1H,
mol) was taken in a sealed tube and subjected to microwave irra-
diation (CEM discover, 250 W,120 ꢁC, 25 psi) for 6e10 min. The dark
brown reaction mixture was dissolved in 10 mL CH2Cl2 and purified
by column chromatography using silica gel (60e120 mesh). Initial
fractions, eluted with pet ether, on solvent removal have afforded
the corresponding conjugated alkynes. The fractions eluted with
ethyl acetate and pet ether (1:9) contained the unreacted phos-
phorane (5) followed by triphenylphosphine oxide (7).
d, J ¼ 7.1 Hz, PyridineeH); IR (KBr)
y
cmꢀ1: 3057, 2924, 2854, 2229,
1727, 1617, 1551, 1404, 1241, 1125, 1061, 824, 721; ESI-MS m/z
(M þ H)þ: 215; HRMS m/z calcd for C8H2N2Cl2F [M þ H]þ: 214.9579;
found: 214.9577; Anal. (C8H1N2Cl2F): C 44.69%, H 0.47%, N 13.03%;
found: C 44.62%, H 0.53%, N 12.98%.
4.1.2.8. 3-(2-Methylphenyl)prop-2-ynenitrile (6f). Light yellow co-
lor liquid; 1H NMR (
d ppm in CDCl3, 300 MHz): 2.48 (3H, S, eCH3),
7.20 (1H, d, J ¼ 7.5 Hz, AreH), 7.27 (1H, d, J ¼ 6.7 Hz, AreH), 7.41 (1H,
4.1.2.2. Thermal decomposition method. The
b
-oxo-ylide (0.045
t, J ¼ 6.7, 7.5 Hz, AreH), 7.56(1H, d, J ¼ 6.7 Hz, AreH); 13C NMR (
d
mol) was taken in a short path distillation flask and heated at 250e
260 ꢁC under 1 mm vacuum for 25 min and the distillate was
collected in a cold trap. The distillate and the dark brown reaction
mass consisting of disubstituted acetylene (6) and triphenylphos-
phine oxide (7) was dissolved in CH2Cl2 (20 mL) and subjected to
column chromatography as described above to obtain the pure
alkyne.
ppm in CDCl3): 20.4, 82.3, 85.0, 105.5, 117.4, 126.0, 130.0, 131.7,
134.0, 143.9; IR (KBr)
y
cmꢀ1: 3065, 2924, 2265, 2140, 760; ESI-MS
m/z (M þ H)þ:142; HRMS m/z calcd for C10H8N ([M þ H]þ):
142.0657; found: 142.0649; Anal. (C10H7N): C 85.08%, H 5.00%, N
9.92%; found: C 85.02%, H 5.08%, N 9.79%.
4.1.2.9. Ethyl 3-(2-methylphenyl)prop-2-ynoate (6g). Light yellow
color liquid; 1H NMR (
d ppm in CDCl3, 300 MHz): 1.35 (3H, t,
4.1.2.3. 3-(6-Chloropyridin-3-yl)prop-2-ynenitrile
(6a).
ppm in CDCl3,
J ¼ 7.1 Hz, eCH3), 2.48 (3H, s, eCH3), 4.30 (2H, q, J ¼ 7.1 Hz, eCH2),
Colorless solid; mp 118e120 ꢁC; 1H NMR (
d
7.14e7.35 (3H, m, AreHs), 7.53 (1H, d, J ¼ 6.9 Hz, AreH); 13C NMR (
d
300 MHz): 7.40 (1H, d, J ¼ 8.3 Hz, PyeH), 7.84 (1H, dd, J ¼ 2.2,
ppm in CDCl3): 13.6, 20.0, 61.5, 83.9, 84.6, 119.0, 125.2, 129.2, 130.0,
8.3 Hz, PyeH), 8.64 (1H, d, J ¼ 2.2 Hz, PyeH); 13C NMR (
d
ppm in
132.9, 141.7, 153.7; IR (KBr) y
cmꢀ1: 3399, 2983, 2206, 1708, 1187,
CDCl3): 72.6, 78.3, 104.7, 115.9, 124.5, 142.4, 151.2, 153.9; IR (KBr)
y
765; ESI-MS m/z (M þ H)þ: 189; HRMS m/z calcd for C12H13O2
([M þ H]þ): 189.0916; found: 189.0912; Anal. (C12H12O2): C 76.57%,
H 6.43%; found: C 76.65%, H 6.50%.
cmꢀ1: 3421, 3090, 3038, 2925, 2855, 2364, 2270, 2148, 1974, 1874,
1710, 1578, 1534, 1456, 1114, 1024, 848; ESI-MS m/z (M þ H)þ: 163;
HRMS m/z calcd for C8H4N2Cl [M þ H]þ: 163.0036; found:
163.0040; Anal. (C8H3N2Cl): C 59.10%, H 1.86%, N 17.23%; found: C
59.03%, H 1.98%, N 17.15%.
4.1.2.10. Ethyl 4,4-dimethylpent-2-ynoate (6h). Red color liquid; 1H
NMR (
d
ppm in CDCl3, 300 MHz): 0.71 (3H, t, J ¼ 7.1 Hz, eCH3), 1.27
(9H, S, three eCH3 groups), 3.59 (2H, q, J ¼ 7.1 Hz, eCH2); IR (KBr)
y
4.1.2.4. 3-(2-Chloropyridin-3-yl)prop-2-ynenitrile
(6b). Colorless
cmꢀ1: 2926, 2852, 2227,1725; ESI-MS m/z (M þ H)þ:155; HRMS m/z
calcd for C9H15O2 [M þ H]þ: 155.0982; found: 155.0979; Anal.
(C9H14O2): C 70.10%, H 9.15%; found: C 70.08%, H 9.21%.
solid; mp 96e98 ꢁC; 1H NMR (
d
ppm in CDCl3, 300 MHz): 7.31 (1H,
dd, J ¼ 2.2, 7.5 Hz, PyridineeH), 7.92 (1H, dd, J ¼ 1.5, 7.5 Hz, Pyri-
dineeH), 8.51 (1H, dd, J ¼ 2.2,1.5 Hz, Pyridine-H); 13C NMR (
d ppm in
CDCl3): 69.2, 77.1, 104.7, 115.7, 122.0, 143.4, 151.3, 153.9; IR (KBr)
y
4.2. Biology
cmꢀ1: 3422, 3079, 2923, 2853, 2271, 2145, 1735, 1571, 1447, 1397,
1089, 808, 735; ESI-MS m/z (M þ H)þ: 163; HRMS m/z calcd for
C8H4N2Cl [M þ H]þ: 163.0057; found: 163.0061; Anal. (C8H3N2Cl): C
59.10%, H 1.86%, N 17.23%; found: C 59.05%, H 1.92%, N 17.18%.
All the test organisms used for antimicrobial activity study were
obtained from Microbial Type Culture Collection and Gene Bank
(MTCC), IMTECH, Chandigarh, India.
4.1.2.5. Ethyl
3-(6-chloropyridin-3-yl)
prop-2-ynoate
ppm in CDCl3, 300 MHz):
(6c).
4.2.1. Antibacterial activity
Colorless solid; mp 72e74 ꢁC; 1H NMR (
d
The minimum inhibitory concentration (MIC) of various syn-
thetic compounds (5aep, 6aeh) were obtained against three
representative Gram-positive microorganisms viz., B. subtilis (MTCC
441), S. aureus (MTCC 96), S. epidermidis (MTCC 435) and Gram-
negative microorganisms viz., E. coli (MTCC 443), P. aeruginosa
(MTCC 741), and K. pneumoniae (MTCC 618) using broth dilution
method recommended by National Committee for Clinical Labo-
ratory (NCCL) standards [24,25].
1.37 (3H, t, J ¼ 7.1 Hz, eCH3), 4.29 (2H, q, J ¼ 7.1 Hz, eCH2), 7.35 (1H,
d, J ¼ 8.3 Hz, PyridineeH), 7.80 (1H, dd, J ¼ 2.2, 8.3 Hz, PyridineeH),
8.59 (1H, d, J ¼ 2.2 Hz, PyridineeH); 13C NMR (
d ppm in CDCl3):
14.0, 62.3, 80.8, 84.4, 115.8, 124.2, 142.0, 151.2, 152.9, 153.2; IR (KBr)
y
cmꢀ1: 3395, 3092, 3039, 2983, 2928, 2855, 2235, 2206, 1985, 1707,
1577, 1544, 1458, 1366, 1291, 1188, 1101; ESI-MS m/z (M þ H)þ: 210;
HRMS m/z calcd for C10H9O2NCl [M þ H]þ: 210.0316; found:
210.0319; Anal. (C10H8O2NCl): C 57.29%, H 3.85%, N 6.68%; found: C
56.98%, H 3.89%, N 6.48%.
Standard antibacterial agents like penicillin and streptomycin
were also screened under identical conditions for comparison.
4.1.2.6. Propan-2-yl 3-(6-chloropyridin-3-yl)prop-2-ynoate (6d).
4.2.2. Antifungal activity
Colorless solid; mp 58e60 ꢁC; 1H NMR (
d
ppm in CDCl3, 300 MHz):
The in vitro antifungal efficacy of all the synthesized phos-
phoranes (5aep) and alkynes (6aeh) was determined against five
fungal strains viz., C. albicans (MTCC 227), C. rugosa (NCIM 3462),
S. cerevisiae (MTCC 36), A. niger (MTCC 344), A. flavus (MTCC 277) by
agar well diffusion method. The fungal strains were obtained from
1.34 (6H, d, J ¼ 6.2 Hz, two eCH3 groups), 5.08e5.18 (1H, m, eCH),
7.36 (1H, d, J ¼ 8.3 Hz, PyridineeH), 7.80 (1H, dd, J ¼ 2.2, 8.3 Hz,
PyridineeH), 8.59 (1H, d, J ¼ 2.2 Hz, PyridineeH); 13C NMR (
d ppm
in CDCl3): 21.1, 70.1, 80.0, 84.3, 115.5, 123.7, 141.5, 151.2, 152.3, 152.7;

138
J.R. Komsani et al. / European Journal of Medicinal Chemistry 68 (2013) 132e138
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