Synthesis and antimicrobial screening of some novel chalcones and flavanones substituted with higher alkyl chains

Article abstract of DOI:10.1007/s00044-013-0876-x

As a part of our program to generate some novel flavonoid frameworks substituted with higher alkyl groups as possible antimicrobial agents, we have in total synthesized twelve novel chalcones (11-16) and their corresponding flavanones (17-22) substituted with either nonyl or dodecyl chains in ring B in very good to excellent yields. The synthesized compounds have been screened for their antimicrobial potential against six bacterial and four fungal strains. The tested compounds, in general, showed significant antibacterial and comparable antifungal activities. While the chalcone (16) with a dodecyl chain showed highly promising antibacterial activity against almost all the organisms tested, the chalcone (13) with nonyl chain showed promising antifungal activity against Candida rugosa and Aspergillus niger strains.

Full text of DOI:10.1007/s00044-013-0876-x

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-013-0876-x
ORIGINAL RESEARCH
Synthesis and antimicrobial screening of some novel chalcones
and flavanones substituted with higher alkyl chains
•
Uppuluri Venkata Mallavadhani
•
Laxmidhar Sahoo Koochana Pranay Kumar
•
Upadyayula Suryanarayana Murty
Received: 19 June 2013 / Accepted: 7 November 2013
Ó Springer Science+Business Media New York 2013
Abstract As a part of our program to generate some novel
flavonoid frameworks substituted with higher alkyl groups as
possible antimicrobial agents, we have in total synthesized
twelve novel chalcones (11–16) and their corresponding
flavanones (17–22) substituted with either nonyl or dodecyl
chains in ring B in very good to excellent yields. The syn-
thesized compounds have been screened for their antimicro-
bial potential against six bacterial and four fungal strains. The
testedcompounds, ingeneral, showed significantantibacterial
and comparable antifungal activities. While the chalcone (16)
with a dodecyl chain showed highly promising antibacterial
activity against almost all the organisms tested, the chalcone
(13) with nonyl chain showed promising antifungal activity
against Candida rugosa and Aspergillus niger strains.
diverse functions including defense and UV protection
(Buer et al., 2010). These compounds are reported to exhibit
a wide spectrum of biological activities such as antimicro-
bial, antiviral, antihypertensive, antioxidant, anti-inflam-
matory, and cytotoxic (Nowakowska, 2007). Especially,
their antimicrobial activity is gaining importance and
increasingly documented. The antimicrobial effectiveness
of chalcones and flavanones depends on their abilities to
form complexes with both extracellular and soluble proteins
as well as bacterial membranes, penetration into cell
membranes, and the maintenance of intercellular concen-
trations in infecting species (Fowler et al., 2011). The
antimicrobial activity of these compounds mainly attributed
to the presence of phenolic hydroxyl groups, phenyl rings,
and a,b-unsaturated ketones or benzopyrone rings, which
have high affinity to proteins and thus may inhibit microbial
enzymes (Cushnie and Lamb, 2005). It has been realized
that certain degree of lipophilicity enhances the antimicro-
bial activity. The lipophilicity of chalcones and flavanones
can be increased by substituting with higher alkyl chains
(Cushnie and Lamb 2011). The two retrochalcones of
liquorice viz. licochalcone A and licochalcone C, with 1,1-
dimethallyl and 3,3-dimethally groups, respectively, were
reported to exhibit potent antibacterial activity against
Bacillus subtilis, Staphylococcus aureus, and Micrococcus
luteus (Haraguchi et al., 1998). Kromann et al. (2004)
reported that the introduction of an hexyl group in licoch-
alcone A significantly enhances its antibacterial activity
against S. aureus. They further reported that a clear positive
correlation is seen when the Clog P values are compared
with antibacterial activity (Kromann et al., 2004). Stapleton
et al. (2004) also reported that substitution with C8 and C10
alkyls enhances the activity of some flavonoids against
S. aureus. Chalcones and flavanones substituted with higher
alkyl chains especially in ring B are novel and expected to
Keywords Chalcones ꢀ Flavanones ꢀ Nonyl chalcones ꢀ
Nonyl flavanones ꢀ Dodecyl chalcones ꢀ
Dodecyl flavanones ꢀ Antibacterial activity ꢀ
Antifungal activity
Introduction
Chalcones and flavanones, the two important sub groups of
flavonoids, are ubiquitous in the plant kingdom with many
U. V. Mallavadhani (&) ꢀ L. Sahoo
Natural Products Chemistry Division, CSIR-Indian Institute of
Chemical Technology, Tarnaka, Hyderabad 500 607, India
e-mail: uvmavadani@yahoo.com
Present Address:
L. Sahoo
Sai Life Sciences, Hyderabad, India
K. P. Kumar ꢀ U. S. Murty
Biology Division, CSIR-Indian Institute of Chemical
Technology, Tarnaka, Hyderabad 500607, India
123

Med Chem Res
exhibit potent antimicrobial activities. To synthesize these
frameworks, the alkyl substitution has to come from the
benzaldehyde core. For this purpose, 2-hydroxy-5-nonyl-
benzaldehyde and 5-dodecyl-2-hydroxy-benzaldehyde were
found to be the highly attractive templates. In fact, these two
benzaldehydes are the key precursors for the synthesis of
liquid ion exchange reagents, which are highly useful in
hydrometallurgy for extraction of precious metals like Cu
and Ni (Sperline et al., 1998; Cheng et al., 2000; Gordon
et al., 2008; Pouramini and Moradi, 2012). Further, these
two benzaldehydes can be conveniently prepared from the
commercially available 4-nonyl-phenol and 4-dodecyl-
phenol respectively. With this background, we have now
synthesized a series of twelve rings B substituted nonyl and
dodecyl chalcones and flavanones from the two key 4-alkyl-
phenols and screened for their antimicrobial potential.
4-nonyl and 4-dodecyl phenols by modified Duff method
using hexamine and trifluoroacetic acid (Blazevic et al.,
1979). In this connection, it is to mention here that the
commercial 4-nonyl-phenol and 4-dodecyl-phenol contain
both the ring and side-chain isomers. Repetitive chro-
matographic purification of these two phenols removes the
ring impurities completely and afforded pure nonyl and
dodecyl phenols with the alkyl substituents as inseparable
linear and branched isomeric mixtures. Hence, the purified
4-nonyl-phenol and 4-dodecyl- phenol with mixed isomeric
chains have been taken up for the synthesis. Thus the two
synthesized o-hydroxybenzaldehydes or their correspond-
ing O-alkyl ethers on condensation with an appropriate
2-hydroxyacetophenone in the presence of 60 % ethanolic
KOH yielded the chalcones substituted with nonyl or
dodecyl groups in ring B. The resulting chalcones on acid
catalyzed cyclization afforded the corresponding flava-
nones (Marais et al., 2006). In total, 6 flavanones with three
different frameworks, such as i) 20-methoxy, ii) 20-allyloxy,
and iii) 20,5-dimethoxy, were synthesized from their cor-
responding chalcones (Scheme 1).
Results and discussion
Chemistry
All the synthesized compounds have been characterized
1
The two key precursor benzaldehydes viz. 2-hydroxy-5-
nonyl-benzaldehyde and 5-dodecyl-2-hydroxy-benzalde-
hyde were prepared from the commercially available
by their spectroscopic data (IR, H, and 13C NMR and
Mass) (Mandge et al., 2007; Hwang et al., 2011; Yoon
et al., 2011). While chalcones 11–16 showed characteristic
Scheme 1 Synthesis of novel
alkyl substituted chalcones and
flavanones
H
O
H
O
OR1
r
B
H
C
O
CHO
exam ne
H i
CH3 I or
TFA
K2CO3, Acetone
R
R
R
:
=
=
=
=
R H
C
1
:
=
=
:
=
=
5 R
:
H19
C9
1 R
H19
3 R
H19
C9
H25
C12
;
;
;
C9
3
:
:
=
CH3
2 R
H25
C12
4 R
6 R C12H25
R
1
:
=
R1
7 R
H19
C9
:
=
=
R
1
8 R C12H25
;
H
O
:
=
=
9 R2
H
OC
i)
:
10 R2
H
3
R2
O
ii)
Ethanol - KOH
R
5'
R
5
6'
8
5
6
a
8
O
2
3'
H
β
O
2'
7
6
4'
Ethanol - HCl
1'
4'
5'
4
1
3
α
3'
2'
a
5
3
2
R
4
O
1O
1'
R
1O
6R' 2
R2
O
:
=
=
=
=
=
=
=
=
=
H R H19
C9
;
17 R1
H
H
R
C
C
;
;
3
2
:
=
=
=
=
=
=
=
H R
;
=
=
11 R1
H
R
H19
C9
C
;
;
3
2
:
=
H25
C12
18 R1
R
H R
;
3
2
:
=
12 R1
H
C
R
H R
;
H25
C12
3
2
:
=
=
R2 H R
C9
19 R1
H19
;
;
;
:
=
=
13 R1
R
H R
;
H19
C9
;
;
2
:
=
=
R
R
20 R1
R
H R
H25
C12
;
2
:
=
=
R
R
14 R1
R
H R
;
H25
H19
C12
2
:
=
=
=
=
21 R1
H
H
R
R
H
H19
C9
H25
C12
C
C
OC
OC
;
;
;
;
3
2
2
3
3
:
=
=
=
15 R1
H
C
R
H
OC
;
3
H
OC
3
C9
;
;
3
2
2
:
22 R1
H
3
:
=
H25
C12
16 R1
H
R
C
;
3
123

Med Chem Res
a,b-unsaturated carbonyl absorptions around 1640–
1630 cm-1 in IR and a and b protons as doublets around
7.75–7.90 and d 8.2–8.1, respectively, with coupling con-
16, 17, 18, 22 (ii) S. aureus—15, 16 (iii) S. epidermidis—
16, 21, 22 (iv) E. coli—16 (v) P. aeruginosa—16 (vi)
K. pneumoniae—16. From this analysis, it is evident that
the nonyl and dodecyl chalcones with 2,60-dimethoxy-20-
hydroxy substitution patterns such as compounds 15 and 16
are highly active than the other synthesized compounds.
Further, it is interesting to note that the dodecyl chalcone
(16) is the most active one and showed promising anti-
bacterial activity against all the six organisms tested.
1
stants of 16 Hz each in H NMR, the flavanones 17–22
showed the carbonyl absorption around 1690 cm-1 in IR
and H-2 and H-3 protons around d 5.9–5.80 and 3.0–2.9,
respectively, in 1H NMR and C2 and C3 around
d 75.0–74.0 and 45.0–44.0, respectively, in 13C NMR. The
nonyl and dodecyl chains (mixed isomers) showed the
characteristic peaks in NMR between 0.6 and 1.8 (1H) and
8.40–52.70 (13C).
Antifungal screening
Antibacterial screening
The twelve synthesized novel chalcones and flavanones
have been subjected to antifungal screening against four
fungal strains such as Candida albicans, Candida rugosa,
Saccharomyces cerevisiae, and Aspergillus niger by
employing Agar cup method (Linday, 1962) with ampho-
tericin-B as standard. The organisms were obtained from
Institute of Microbial Technology, Chandigarh, India.
Cultures of test organisms were maintained on Potato
Dextrose Agar (PDA) slants and were sub cultured in Petri
dishes prior to testing. The antifungal activity was
expressed in terms of inhibition of zones, expressed in mm
diameters, and the results are presented in Table 2;
(Fig. 2).
The twelve synthesized chalcones and flavanones (11–22)
have been subjected to antibacterial screening against six
bacterial strains such as B. subtilis, S. aureus, Staphylo-
coccus epidermidis, Escherichia coli, Pseudomonas aeru-
ginosa, Klebsiella pneumoniae by employing broth dilution
method (Clinical and Laboratory standards Institute, 2008)
with penicillin G and streptomycin as standards. The
microorganisms were obtained from the Institute of
Microbial Technology, Chandigarh, India. Cultures of test
organism were maintained on nutrient agar (Himedia labs,
Mumbai) slants and were sub cultured in Petri dishes prior
to testing the antimicrobial activity was expressed in terms
of MIC values, which are the lowest concentrations able to
inhibit the bacterial growth. The results are presented in
Table 1 (Fig. 1). All the tested compounds, in general,
showed significant antibacterial activity. The highly active
compounds for each organism are: (i) B. subtilis—11, 12,
Surprisingly, compounds 12, 13, and 19 only showed
antifungal activity. While compounds 13 and 19 showed
significant activity against 2 organisms, compound 12
showed moderate activity against one organism. Com-
pounds 13 and 19 are the allyloxy-nonyl substituted chal-
cone and its corresponding flavanone, respectively.
Table 1 Antibacterial activity of alkyl substituted chalcones and flavanones
MIC(lg/mL)
Compound
Bacillus
subtilis
Staphylococcus
aureus
Staphylococcus
epidermidis
Escherichia
coli
Pseudomonas
aeruginosa
Klebsiella
pneumoniae
11
75
37.5
150
150
150
150
150
150
75
150
150
150
150
150
37.5
150
150
150
150
150
150
2.5
150
150
150
150
150
37.5
150
150
150
150
150
75
150
150
150
150
150
75
12
75
13
150
150
150
75
150
14
150
15
18.75
18.75
37.5
75
16
17
75
150
150
150
150
75
150
150
150
150
150
150
6.25
3.125
18
75
19
150
150
150
75
150
20
150
21
75
22
37.5
1.562
6.25
75
Penicillin
Streptomycin
1.562
6.25
3.125
3.125
12.5
1.562
6.25
123

Med Chem Res
Fig. 1 Antibacterial activity of
alkyl substituted chalcones and
flavanones
Compound Code
Table 2 Antifungal activity of alkyl substituted chalcones and flavanones
Zone of Inhibition (mm)
Compound
Candida albicans
Candida rugosa
100 lg 150 lg
Saccharomyces cerevisiae
Aspergillus niger
100 lg
150 lg
100 lg
150 lg
100 lg
150 lg
12
0
0
0
0
9
0
0
0
0
0
0
0
13
0
11
9
16
13
0
8
12
12
19
0
0
8
Amphotericin-B (50 lg)
23.5
21
22
25
Compounds 11, 14–18 and 20–22 did not show any antifungal activity
Fig. 2 Antifungal activity of
alkyl substituted chalcones and
flavanones
Interestingly, these two compounds also found selective in
exhibiting antifungal activity against C. rugosa and
A. niger. The highest antifungal activity (16 mm zone
inhibition) was found with Compound 13, when tested
against the organism C. rugosa at 150 lg concentration.
Conclusion
In conclusion, a series of 12 novel nonyl and dodecyl ring
B substituted chalcones and flavanones were synthesized
from the two precursor aldehydes viz. 2-hydroxy-5-nonyl-
123

Med Chem Res
benzaldehyde and 5-dodecyl-2-hydroxy-benzaldehyde in
very good to excellent yields. The synthesized compounds
have been screened against six bacterial and four fungal
strains. In general, the synthesized compounds showed
significant antibacterial activity and comparable antifungal
activity. Significantly, the chalcone (16) with a dodecyl
chain showed highly promising antibacterial activity
against almost all the organisms tested. Whereas, the
chalcone (13) with nonyl chain showed promising anti-
fungal activity against the C. rugosa and A. niger strains.
Thus the two compounds 13 and 16 can be considered as
lead compounds and can be fine tuned further to develop
some highly potent antimicrobial agents.
51.41–8.47 (C9H19: mixed side-chain isomers). ESI-Mass
(m/z): 249 (M??H).
5-Dodecyl-2-hydroxy-benzaldehyde (4)
To a mixture of 4-dodecylphenol (10 g, 0.038 mol) and
hexamine (10.68 g, 0.067 mol), trifluoroacetic acid
(29 mL, 0.381 mol) was added drop wise. The resulting
reaction mixture was heated on a water bath at 75 °C for
10 h. After work up followed by silica gel column chro-
matography gave 5-dodecyl-2-hydroxybenzaldehyde as
pale reddish oil (4.42 g, 40 %). IR (Neat, cm-1): 2961,
1
1658, 1485, 1284 and 756; H NMR (CDCl3): d 0.4–1.8
(m, 25 H), 6.9 (d, J = 8.9 Hz, 1H, Ar–H), 7.25–7.60 (m,
2H, Ar–H), 9.9 (s, 1H, –CHO) and 10. 90 (s, 1H, –OH). 13
C
Experimental
NMR (300 Hz) (CDCl3): 196.68 (–CHO), 159.20 (C2),
139.51 (C5), 135.78 (C1), 135.19 (C4), 130.65 (C6), 116.90
(C3), 51.40-8.45 (C12H25: mixed side-chain isomers). ESI-
Mass (m/z): 291 (M??H).
General
4-Nonylphenol and 4-dodecylphenol were procured from
Herdillia Chemicals Ltd., Mumbai, India and purified by
column chromatography before use. All the reagents and
solvents were purchased from commercial suppliers and
used after purification (distillation/crystallization). Purity
of the compounds was routinely checked by thin layer
chromatography (TLC) and 1H NMR. TLC was performed
on silica gel-coated plates, and the components were
visualized under UV light or exposing to Iodine vapors or
by spraying with methanolic sulfuric acid (5 % v/v) fol-
lowed by heating the plates at *105 °C in an oven/hot
plate. IR spectra were recorded on JASCO FT IR- 5300 or
Perkin Elmer Spectrum 1000 spectrophotometers. 1H NMR
and 13C NMR spectra were recorded on a Bruker Avance
360 and DPX-300 Spectrometers using TMS as internal
standard. Positive ion electronspray mass spectra and high
resolution mass spectra were obtained with Micromass
Quattro II triple quadrupole spectrometer and Micromass
Q-Tof 2 Mass spectrometer.
2-Methoxy-5-nonyl-benzaldehyde (5)
A mixture of 2-hydroxy-5-nonyl-benzldehyde (3, 700 mg,
2.82 mmol), methyl iodide (0.27 mL, 4.23 mmol), and
anhydrous K2CO3 (778 mg, 5.64 mmol) in dry acetone
(10 mL) was refluxed over night. The solvent acetone was
removed under reduced pressure, and crushed ice was
added to the residue. The resulting product was extracted
with ethyl acetate (3 9 25 ml), the organic layer washed
with water, dried over anhydrous sodium sulfate, and
concentrated under reduced pressure. The crude product
was purified by silica gel column chromatography with
hexane–ethyl acetate (98:2) as eluent to yield compound 5
as colorless oil, 591 mg (yield: 80 %). Rf: 0.23 (n-hexane–
ethyl acetate 95:5); IR (Neat, cm-1): 1640 (C=O). 1HNMR
(200 MHz) (CDCl3) :d 0.6–1.7 (m, 19H, alkyl chain), 3.95
(s, –OCH3, 3H), 6.90 (d, J = 12.0 Hz, 1H0, 7.54 (m, 1H),
7.78 (m, 1H), 10.45 (s, –CHO, 1H). 13C NMR (300 Hz)
(CDCl3): 190.15 (–CHO), 159.67 (C2), 134.21 (C5), 133.85
(C4), 125.64 (C1), 124.06 (C6), 111.04 (C3), 55.45
(–OCH3), 51.44–8.50 (C9H19: mixed side-chain isomers).
ESI-Mass (m/z): 263 (M??H).
2-Hydroxy-5-nonyl-benzaldehyde (3)
To a mixture of 4-nonylphenol (10 g, 0.045 mol) and
hexamine (12.7 g, 0.090 mol), trifluoroacetic acid
(34.98 mL, 0.454 mol) was added drop wise. The resulting
reaction mixture was heated on a water bath at 75 °C for
10 h. After work up followed by silica gel column chro-
matography gave 2-hydroxy-5-nonyl-benzaldehyde as pale
reddish oil (4.5 g, 40 %), IR (Neat, cm-1): 2961, 1658,
1485, 1284 and 756; 1H NMR (CDCl3): d 0.4–1.8 (m, 19 H),
6.9 (d, J = 8.9 Hz, 1H, Ar–H), 7.25–7.60 (m, 2H, Ar–H),
9.9 (s, 1H, –CHO) and 10. 90 (s, 1H, –OH). 13C NMR
(300 Hz) (CDCl3): 196.73 (–CHO), 159.24 (C2), 139.46
(C5), 135.75 (C1), 135.24 (C4), 130.68 (C6), 116.96 (C3),
5-Dodecyl-2-methoxy-benzaldehyde (6)
This compound was prepared from the aldehyde 4 as per
the above procedure. Obtained as colorless oil, yield: 83 %,
1H NMR (CDCl3, 200 MHz): d 0.6–1.8 (m, 25H, alkyl
chain), 3.95 (s, –OCH3, 3H), 6.98 (d, J = 8.4 Hz, 1H),
7.54 (m, 1H), 7.82(m, 1H), 10.48 (s, –CHO, 1H). Mass
(m/z): 304 [M?H]?. 13C NMR (300 Hz) (CDCl3): 190.20
(–CHO), 159.79 (C2), 134.36 (C5), 133.67 (C4), 126.72
(C1), 123.94 (C6), 111.04 (C3), 55.59 (–OCH3), 50.40–8.50
123

Med Chem Res
(C12H25: mixed side-chain isomers). ESI-Mass (m/z): 305
(M??H).
under reduced pressure. The crude product was purified by
column chromatography with hexane–ethyl acetate (98:2)
as eluent to yield compound 11 as a colorless oil, 360 mg
(Yield: 60 %), Rf: 0.21 (n-hexane–ethyl acetate 95:5). IR
2-Allyloxy-5-nonyl-benzaldehyde (7)
1
(Neat, cm-1): 1640 (C=O). H NMR (CDCl3, 200 MHz):
d 0.6–1.8 (m, 19H, alkyl chain), 3.96 (s, 3H, –OMe), 6.80
(t, 2H), 7.06 (d, J = 8.0 Hz, 1H), 7.38 (m, 1H), 7.54 (t,
2H), 7.85 (d, J = 16.0, 1H), 7.85 (d, J = 8.0, 1H), 8.10 (d,
J = 16, 1H), 13.0 (s, 1H, OH). 13C NMR (300 Hz)
(CDCl3): 190.33 (–C=O), 110.67 (C1), 156.73 (C2), 118.46
(C3), 129.72 (C4), 136.03 (C5), 129.72 (C6), 142.25 (a-C),
A mixture of 2-hydroxy-5-nonyl-benzldehyde (3, 1.0 g,
4.0 mmol), allyl bromide (0.34 mL, 4.0 mmol), and
anhydrous K2CO3 (1.1 g, 8.0 mmol) in dry acetone
(10 mL) was refluxed for 8 h on a water bath. The com-
pletion of the reaction was monitored by TLC. The solvent
acetone was removed under reduced pressure, and crushed
ice was added to the residue. The resulting product was
extracted with ethyl acetate (3 9 25 ml); the organic layer
was washed with water, dried over anhydrous sodium
sulfate, and concentrated under reduced pressure. The
crude product was purified by silica gel column chroma-
tography with hexane–ethyl acetate (98:2) as eluent to
yield compound 7 as colorless oil, 1.0 gm (yield: 86 %).
Rf: 0.43 (n-hexane–ethyl acetate 95:5); IR (Neat, cm-1):
0
0
0
120.57 (b-C), 120.57 (C1 ), 163.48 (C2 ), 118.68 (C3 ),
0
0
0
136.03 (C4 ), 120.57 (C5 ), 129.72 (C6 ), 55.52 (2–OCH3),
52.20–8.50 (C9H19: mixed side-chain isomers). ESI-Mass
(m/z): 381.1 (M??H). Anal. calcd for C25H32O3: C, 78.89;
H, 8.48. Found: C, 78.92; H, 8.52.
1-(20-Hydroxy-phenyl)- 3-(5-dodecyl-2-methoxy-phenyl)-
propen-1-one (12)
1
1680, 1640. H NMR (CDCl3, 200 MHz): d 0.5–1.8 (s,
19H, alkyl chain), 4.70 (d, J = 6 Hz, 2H), 5.40 (m, 2H),
6.10 (m, 1H), 6.90 (d, J = 10 Hz, 1H), 7.45 (m, 1H), 7.8
(m, 1H), 10.50 (s, 1H). 13C NMR (300 Hz) (CDCl3):
190.10 (–CHO), 158.75 (C2), 134.35 (C5), 134.05 (C4),
133.85 (C6), 133.49 (C1), 132.52 (=CH2), 117.75 (–CH=),
112.30 (C3), 69.10 (–OCH2–), 50.65–8.50 (C9H19: mixed
side-chain isomers). ESI-Mass (m/z): 289.1 (M??H).
This compound was prepared from the aldehyde 6 as per the
1
above procedure. Yield: 54 %, IR (Neat, cm-1): 1640. H
NMR (CDCl3, 200 MHz): d 0.6–1.6 (m, 25H, alkyl chain),
3.94 (s, 3H, –OCH3), 6.90 (m, 3H), 6.96 (d, J = 8.4 Hz, 1H),
7.42–7.56 (m, 1H), 7.78 (d, J = 10.0 Hz, 1H), 7.92 (d,
J = 8.0 Hz, 1H), 8.20 (d, J = 16.0 Hz, 1H), 13.00 (s, 1H,
OH). 13C NMR (300 Hz) (CDCl3): 194.49 (–C=O), 110.68
(C1), 156.92 (C2), 118.48 (C3), 129.72 (C4), 136.01 (C5),
0
2-Allyloxy-5-dodecyl-benzaldehyde (8)
129.72 (C6) 142.39 (a-C), 120.58 (b-C), 120.21 (C1 ), 163.52
0
0
0
0
0
(C2 ), 118.68 (C3 ), 136.01 (C4 ), 120.58 (C5 ), 129.72 (C6 ),
55.53 (–OCH3), 52.49–8.64 (C12H25: mixed side-chain iso-
mers). ESI-Mass (m/z): 423 (M??H). Anal. calcd for
C28H38O3: C, 79.07; H, 9.28. Found: C, 79.11; H, 9.32.
This compound was prepared from the aldehyde 4 as per the
above procedure. It was obtained as colorless oil, (Yield:
1
88 %), IR: (Neat, cm-1): 1680, 1640. H NMR (CDCl3,
200 MHz): d 0.4–1.7 (s, 25H, alkyl chain), 4.62 (d, J = 6 Hz,
2H), 5.38 (dd, J = 16, 8.7 Hz, 1H), 5.41 (m, 1H), 6.15 (m,
1H), 6.91 (d, J = 8.6 Hz, 1H), 7.47 (m, 1H), 7.8 (d,
J = 9.4 Hz, 1H), 10.50 (s, 1H). 13C NMR (300 Hz) (CDCl3):
190.02(–CHO),158.79(C2),134.40(C5),134.09(C4),133.82
(C1), 133.50 (C6), 132.52 (=CH2), 117.78 (–CH=), 112.34
(C3), 69.09 (–OCH2–), 50.64–8.53 (C12H25: mixed side-chain
isomers). ESI-Mass (m/z): 331 (M??H).
1-(20-Hydroxy-phenyl)-3-(2-allyloxy-5-nonyl-phenyl)-
propen-1-one (13)
This compound was prepared from the aldehyde 7 as per
the above procedure. Yield: 60 %, 1H NMR (CDCl3,
200 MHz) : d 0.6–1.8 (m, 19H, alkyl chain), 2.34 (d,
J = 8.0 Hz, 2H), 4.60 (d, J = 5.0 Hz, 2H), 5.40 (m, 2H),
6.20 (m, 1H), 6.90 (m, 3H), 7.02 (d, J = 8.0 Hz, 1H), 7.48
(d, J = 5.0 Hz, 1H), 7.54 (s,1H), 7.90 (d, J = 16 Hz, 2H),
8.20 (d, J = 16.0 Hz, 1H), 13.0 (s, 1H, OH). 13C NMR
(300 Hz) (CDCl3): 194.60 (–C=O), 111.86 (C1), 155.25
(C2), 118.07 (C3), 129.65 (C4), 136.54 (C5), 129.65 (C6),
1-(20-Hydroxy-phenyl)-3-(2-methoxy-5-nonyl-phenyl)-
propen-1-one (11)
A
mixture of 2-hydroxyacetophenone (9,186 mg,
0
0
1.37 mmol) and 2-methoxy-5-nonyl- benzaldehyde (5,
400 mg, 1.52 mmol) was stirred in 10 mL of 60 % etha-
nolic KOH for 48 h. Ethanol was removed under reduced
pressure. The reaction mixture was neutralized with dilute
HCl and extracted with EtOAc. The organic layer was
dried over anhydrous sodium sulfate and concentrated
142.15 (a-C), 120.50 (b-C), 121.15 (C1 ), 163.55 (C2 ),
0
0
0
0
118.35 (C3 ), 136.54 (C4 ), 121.15 (C5 ), 129.65 (C6 ),
132.95 (=CH2), 118.64 (–CH=), 69.28 (–OCH2–),
52.70–8.40 (C9H19: mixed side-chain isomers). ESI-Mass
(m/z): 407.3 (M??H). Anal. calcd for C27H34O3: C, 79.75;
H, 8.43. Found: C, 79.78; H, 8.47.
123

Med Chem Res
1-(20-Hydroxy-phenyl)-3-(2-allyloxy-5-dodecyl-phenyl)-
2,3-Dihydro-2-(20-methoxy-50-nonyl-phenyl)-4H-1-
propen-1-one (14)
benzopyran-4-one (17)
This compound was prepared from the aldehyde 8 as per
the above procedure. Yield : 55 %, 1H NMR (CDCl3,
200 MHz): d 0.6–1.6 (m, 25H, alkyl chain), 4.62 (d,
J = 8.0 Hz, 2H), 5.48 (m, 2H), 6.20 (m, 1H), 6.82 (d,
J = 8.6 Hz, 2H), 7.04 (m, 1H), 7.55 (m, 2H), 7.94 (m, 3H),
13.0 (s, 1H, -OH). 13C NMR (300 Hz) (CDCl3): 194.42
(–C=O), 111.96 (C1), 155.93 (C2), 118.17 (C3), 129.70
(C4), 136.04 (C5), 129.70 (C6), 142.45 (a-C), 120.23 (b-C),
A mixture of chalcone 11 (125 mg, 0.328 mmol) and conc.
HCl (1 mL) in ethanol (10 mL) was refluxed for 48 h on a
water bath. Ethanol was distilled off under reduced pres-
sure, and the resulting residue was extracted with ethyl
acetate (3 9 25 mL). The combined ethyl acetate extract
was dried over anhydrous sodium sulfate and concentrated
under reduced pressure. The crude product was purified by
column chromatography with hexane–ethyl acetate (98:2)
as eluent to yield compound 17 as colorless oil, 60 mg
(yield: 48 %), Rf: 0.23 (n-hexane–ethyl acetate 95:5). IR
0
120.95 (C1 ), 163.46 (C2 ), 118.47 (C3 ), 136.04 (C4 ),
0
0
0
0
0
120.95 (C5 ), 129.70 (C6 ), 132.95 (=CH2), 118.64 (–CH=),
69.28 (–OCH2–), 52.70–8.44 (C12H25: mixed side-chain
isomers). ESI-Mass (m/z): 449.2 (M??H). Anal. calcd for
C30H40O3: C, 80.30; H, 8.99. Found: C, 80.32; H, 8.92.
1
(Neat, cm-1): 1695. H NMR (CDCl3, 200 MHz): d
0.6–1.8 (m, 19H, alkyl chain), 2.96 (d, J = 8.2 Hz, 2H),
3.82 (s. 3H), 5.84 (t, 1H), 6.82 (d, J = 8.8 Hz 1H), 7.04
(m, 2H), 7.52 (m, 3H), 7.98 (d, J = 7.8 Hz, 1H). 13C NMR
(200 Hz) (CDCl3): 193.00 (–C=O), 75.00 (C2), 44.00 (C3),
127.13 (C5), 121.33 (C6), 135.97 (C7), 118.13 (C8), 121.33
1-(20-Hydroxy-60-methoxy-phenyl)-3-(2-methoxy-5-
nonyl-phenyl)-propen-1-one (15)
0
(C5a), 162.20 (C8a), 127.13 (C1 ), 152.60 (C2 ), 109.94
0
0
0
0
0
This compound was prepared from the aldehyde 5 and the
acetophenone 10 as per the above procedure. Yield: 75 %, IR
(C3 ), 129.75 (C4 ), 135.97 (C5 ), 129.75 (C6 ), 55.50
(20-OCH3), 52.50–8.55 (C9H19: mixed side-chain isomers).
ESI-Mass (m/z): 381 (M??H). Anal. calcd for C25H32O3:
C, 78.89; H, 8.48. Found: C, 78.92; H, 8.52.
1
(Neat, cm-1): 1684, 1640. H NMR (CDCl3, 200 MHz): d
0.6–1.8 (m, 19H), 3.90 (s. 3H), 3.95 (s, 3H), 6.40 (d,
J = 8.4 Hz, 1H), 6.62 (d, J = 8.4 Hz 1H), 6.86 (d,
J = 8.4 Hz, 1H), 7.40 (t, 2H), 7.54 (m, 1H), 7.95 (d,
J = 16.0 Hz, 1H), 8.15 (d, J = 16.0 Hz), 13.29 (s, 1H, OH).
13C NMR (300 Hz) (CDCl3): 194.82 (–C=O), 111.17 (C1),
156.59 (C2), 111.17 (C3), 129.94 (C4), 135.72 (C5), 127.84
2,3-Dihydro-2-(50-dodecyl-20-methoxy-phenyl)-4H-1-
benzopyran-4-one (18)
This compound was prepared from the chalcone 12 as per
the above procedure. Yield: 83 %, IR (Neat, cm-1): 1695.
1H NMR (CDCl3, 200 MHz): d 0.6–1.7 (m, 25H, alkyl
chain), 2.95 (d, J = 8.0 Hz, 2H), 3.80 (s, 3H, –OCH3),
5.90 (t, J = 8.0 Hz, 1H), 6.80 (d, J = 8.0 Hz, 1H), 7.04
(m, 2H), 7.50 (m, 3H), 7.90 (d, J = 8.0 Hz, 1H). 13C:
192.47 (–C=O), 74.90 (C2), 43.80 (C3), 126.42 (C5), 121.15
(C6), 135.70 (C7), 118.06 (C8), 121.15 (C5a), 161.98 (C8a),
0
0
(C6), 139.65 (a-C), 123.27 (b-C), 111.17 (C1 ), 164.84 (C2 ),
0
0
0
0
112.40 (C3 ), 135.72 (C4 ), 101.53 (C5 ), 160.81 (C6 ), 55.65
(20-OCH3), 55.42 (2-OCH3), 51.67-8.61 (C9H19: mixed side-
chain isomers). ESI-Mass (m/z):411 (M??H). Anal. calcd for
C26H34O4: C, 76.35; H, 8.35. Found: C, 76.37; H, 8.37.
1-(20-Hydroxy-60-methoxy-phenyl)-3-(5-dodecyl-2-
0
0
0
0
methoxy-phenyl)-propen-1-one (16)
126.42 (C1 ), 153.35 (C2 ), 109.75 0 (C3 ), 126.90 (C4 ),
0
0
135.70 (C5 ), 126.90 (C6 ), 55.24 (2 –OCH3), 52.00-8.67
(C12H25: mixed side-chain isomers). ESI-Mass (m/z): 423
(M??H). Anal. calcd for C28H38O3: C, 79.07; H, 9.28.
Found: C, 79.11; H, 9.32.
This compound was prepared from the aldehyde 6 and the
acetophenone 10 as per the above procedure. Yield: 54 %.
1
IR (Neat, cm-1): 1635. H NMR (CDCl3, 200 MHz): d
0.6–1.6 (m, 25H), 3.90 (s, 3H), 3.94 (s. 3H), 6.40 (d,
J = 16 Hz, 1H), 6.60 (d, J = 16 Hz 1H), 6.84 (d,
J = 8.4 Hz, 1H), 7.26 (m, 2H), 7.60 (m, 1H), 7.95 (d,
J = 16 Hz, 1H), 8.10 (d, J = 16 Hz), 13.29 (s, 1H, OH).
13C NMR (300 Hz) (CDCl3): 194.84 (–C=O), 111.19 (C1),
156.78 (C2), 111.19 (C3), 129.60 (C4), 135.56 (C5), 127.68
2,3-Dihydro-2-(20-allyloxy-50-nonyl-phenyl)-4H-1-
benzopyran-4-one (19)
This compound was prepared from the chalcone 13 as per
the above procedure. Yield: 45 %,1H NMR (CDCl3,
200 MHz): d 0.54–1.8 (m, 19H, alkyl chain), 3.0 (d,
J = 8.0 Hz, 2H), 4.60 (d, J = 5.0 Hz, 2H), 5.30 (m, 2H),
5.90 (t, 1H), 6.0 (m, 1H), 6.80 (d, J = 4.6 Hz, 1H), 7.16
(m, 3H), 7.52 (m, 2H), 8.00 (d, J = 8.2 Hz, 1H). 13C NMR
(300 Hz) (CDCl3): 192.50 (–C=O), 74.92 (C2), 43.62 (C3),
126.60 (C5), 121.00 (C6), 133.06 (C7), 117.55 (C8), 121.40
0
(C6), 139.78 (a-C), 123.29 (b-C), 111.19 (C1 ), 164.85
0
0
0
0
0
(C2 ), 112.41 (C3 ), 135.56 (C4 ), 101.54 (C5 ), 161.00 (C6 ),
55.68 (20-OCH3), 55.46 (2–OCH3), 51.77–8.63 (C12H25:
mixed side-chain isomers). ESI-Mass (m/z): 453 (M??H).
Anal. calcd for C29H40O4: C, 76.94; H, 8.91. Found: C,
76.96; H, 8.93.
123

Med Chem Res
0
(C5a), 162.10 (C8a), 126.39 (C1 ), 152.50 (C2 ), 111.11
0
(200 MHz) (CDCl3) : 191.66 (–C=O), 74.38 (C2), 45.18
(C3), 160.78 (C5), 103.77 (C6), 135.54 (C7), 103.77 (C8),
0
0
0
0
(C3 ), 126.92 (C4 ), 135.85 (C5 ), 126.92 (C6 ), 133.06
(=CH2), 118.18 (–CH=), 68.82 (–OCH2–), 50.95-8.70
(C9H19: mixed side-chain isomers). ESI-Mass (m/z): 407.3
(M??H). Anal. calcd for C27H34O3: C, 79.75; H, 8.43.
Found: C, 79.78; H, 8.47.
0
111.52 (C5a), 163.83 (C8a), 126.46 (C1‘), 153.54 (C2 ),
0
0
0
0
110.92 (C3 ), 127.69 (C4 ), 135.54 (C5 ), 127.69 (C6 ),
56.19 (20–OCH3), 55.34 (5–OCH3), 52.00–8.69 (C12H25:
mixed side-chain isomers). ESI-Mass (m/z): 453 (M??H).
Anal. calcd for C29H40O4: C, 76.94; H, 8.91. Found: C,
76.96; H, 8.93.
2,3-Dihydro-2-(20-allyloxy-50-dodecyl-phenyl)-4H-1-
benzopyran-4-one (20)
Antibacterial activity
This compound was prepared from the chalcone 14 as per
the above procedure. Yield: 50 %,1H NMR (CDCl3,
200 MHz): d 0.6–1.7 (m, 25H, alkyl chain), 3.0 (d,
J = 8.0 Hz, 2H), 4.60 (d, J = 8.5 Hz, 2H), 5.3 (t, 1H), 5.4
(m, 21H), 5.88 (t, 1H), 6.0 (m, 1H), 6.82 (d, J = 8.6 Hz,
1H), 7.10 (m, 3H), 7.52 (m, 2H), 7.96 (d, J = 8.0 Hz, 1H).
13C NMR (300 Hz) (CDCl3): 192.64 (–C=O), 74.94 (C2),
43.82 (C3), 126.65 (C5), 121.03 (C6), 133.06 (C7), 117.34
The minimum inhibitory concentrations (MIC) of the
synthesized compounds were determined against three
representative gram-positive organisms viz. B. subtilis
(MTCC 441), S. aureus (MTCC 96), S. epidermidis and
three Gram-negative organisms viz E. coli (MTCC 443),
P. aeruginosa (MTCC 741), K. pneumoniae (MTCC 618)
by micro dilution method recommended by CLSI Standard
Protocol in liquid medium (Nutrient agar) distributed in
96-well plates. Serial dilutions of the tested compounds
were performed (concentrations from 150 to 0.97 lg/mL)
in a 200 lL culture medium; afterward each well was
seeded with a 50 lL microbial suspension of 0.5 Mac-
Farland density. In each test, a microbial culture control
and a sterility control (negative) were performed. The
plates were incubated for 24 h at 37 °C. The lowest con-
centration which inhibited the visible microbial growth was
considered as the MIC (lg/mL) value for the tested com-
pound. Spectrophotometer has been used for quantitative
measurement of microbial growths. Penicillin and Strep-
tomycin were used as standard drugs. The experiments
were carried out in triplicate. The MIC values are presented
in the Table 1.
0
(C8), 121.29 (C5a), 162.09 (C8a), 126.49 (C1 ), 152.42 (C2 ),
0
0
0
0
0
111.01 (C3 ), 126.97 (C4 ), 135.89 (C5 ), 126.97 (C6 ),
133.06 (=CH2), 118.18 (–CH=), 68.82 (–OCH2),
50.92–8.76 (C12H25: mixed side-chain isomers). ESI-Mass
(m/z): 449.2 (M??H). Anal. calcd for C30H40O3: C, 80.30;
H, 8.99. Found: C, 80.32; H, 8.92.
2,3-Dihydro-2-(20-methoxy-50-nonyl-phenyl)-5-methoxy-
4H-1-benzopyran-4-one (21)
This compound was prepared from the chalcone 15 as per
the above procedure. Yield: 53 %, IR (Neat, cm-1): 1680,
1
1690. H NMR (CDCl3, 200 MHz): d 0.6–1.8 (m, 19H,
alkyl chain), 2.95 (d, J = 8.8 Hz), 3.85 (s. 3H), 3.95 (s,
3H), 5.80 (t, 1H), 6.54 (d, J = 8.4 Hz 1H), 6.72 (d,
J = 8.4 Hz, 1H), 6.82 (d, J = 8.8 Hz, !H), 7.2 (m, 1H),
7.42 (m, 2H). 13C NMR (200 MHz) (CDCl3) : 191.00
(–C=O), 74.00 (C2), 45.00 (C3), 161.45 (C5), 103.45 (C6),
136.27 (C7), 103.45 (C8), 111.23 (C5a), 162.20 (C8a),
Antifungal activity
In vitro, antifungal activity of the newly synthesized
compounds was studied against the fungal strains,
C. albicans (MTCC 227), C. rugosa (NCIM 3467), Sac-
charomyces cervisiae (MTCC 36), and A. niger (MTCC
282) by Agar Well Diffusion method. The PDA medium
was suspended in distilled water (39 g in 1000 mL) and
heated to boiling until it dissolved completely; the medium
and Petri dishes were autoclaved at a pressure of 15 lb/inc2
for 20 min. Agar well bioassay was employed for testing
antifungal activity. The medium was poured into sterile
petri dishes under aseptic conditions in a laminar air flow
chamber. When the medium in the plates solidified, 0.5 mL
of (week old) culture of test organism was inoculated and
uniformly spread over the agar surface with a sterile
L-shaped rod. Solutions were prepared by dissolving the
compound in DMSO and Chloroform, and different con-
centrations were made. After inoculation, wells were
0
0
0
0
126.50 (C1 ), 154.20 (C2 ), 111.00 (C3 ), 127.50 (C4 ),
0
0
0
136.27 (C5 ), 127.50 (C6 ), 56.67 (2 –OCH3), 55.89 (5–
OCH3), 52.00-8.50 (C9H19: mixed side-chain isomers).
ESI-Mass (m/z):0.411.2 (M??H). Anal. calcd for
C26H34O4: C, 76.35; H, 8.35. Found: C, 76.37; H, 8.37.
2,3-dihydro-2-(50-dodecyl-20-methoxy-phenyl) -5-methoxy-
4H-1-benzopyran-4-one (22)
This compound was prepared from the chalcone 16 as per
the above procedure. Yield: 40 %, IR (Neat, cm-1): 1692.
1H NMR (CDCl3, 200 MHz): d 0.6–1.64 (m, 25H, alkyl
chain), 2.95 (d, J = 6.8 Hz, 2H), 3.80 (s, 3H, –OCH3),
3.98 (s, 3H, –OCH3), 5.80 (dd, 8.4 Hz, 1H), 6.58 (d,
J = 8.4 Hz, 1H),6.74 (d, J = 8.0 Hz, 1H), 6.82 (d,
J = 8.0 Hz, 1H), 7.38 (t, 2H), 7.56 (m, 1H). 13C NMR
123

Med Chem Res
Gordon RJ, Campbell J, Henderson DK, Henry DCR, Swart RM,
Tasker PA, White FJ, Wood JL, Yellowlees LJ (2008) Polyac-
idic multiloading metal extractants. Chem Commun 4801–4803
Haraguchi H, Tanimoto K, Tamura Y, Mizutani K, Kinoshita T
(1998) Mode of antibacterial action of retrochalcones from
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Hwang D, Hyun J, Jo G, Koh D, Lim Y (2011) Synthesis and
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scooped out with 6 mm sterile cork borer, and the lids of
the dishes were replaced. To each well, different concen-
trations of test solutions were added. Controls were main-
tained. The treated and the controls were kept at 27 °C for
48 h. Inhibition zones were measured, the diameter cal-
culated in millimeter. The experiments were carried out in
triplicate. The results were presented in Table 2.
Kromann H, Larsen M, Boesen T, Schonning K, Nielsen SF (2004)
Synthesis of prenylated benzaldehydes and their use in the
synthesis of analogues of licochalcone A. Eur J Med Chem
39:993–1000
Acknowledgments We are highly thankful to the Director, CSIR-
IICT, Hyderabad, India for support and encouragement.
Linday ME (1962) Practical introduction to microbiology. E and F.N.
Spon Ltd., London 177
Mandge S, Singh HP, Gupta SD, Moorthy NSHN (2007) Synthesis
and characterisation of some chalcone derivatives. Tren Appl Sci
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