Green synthesis and antiviral activity of novel triarylmethane derivatives via Friedel-Crafts alkylation by polyethylene glycol (PEG-400)

Article abstract of DOI:10.14233/ajchem.2016.19122

A series of novel triarylmethane derivatives (3a-j) were synthesized by a one-pot, two-component method via Friedel-Crafts alkylation of various electron-rich arenes (1a-j) with a wide variety of aldehydes (2a-j) in presence of the polyethylene glycol (PEG-400) as a green solvent at 50-60 °C in good to excellent yields (76-96 %). Their structures were confirmed by FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry and elemental analysis. All the triarylmethanes were tested and evaluated for their antiviral and antifungal activities. Compounds 3b, 3f, 3g and 3i exhibited highest antiviral activities against tobacco mosaic virus (TMV).

Full text of DOI:10.14233/ajchem.2016.19122

Asian Journal of Chemistry; Vol. 28, No. 3 (2016), 473-478
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2016.19122
Green Synthesis and Antiviral Activity of Novel Triarylmethane Derivatives via
Friedel-Crafts Alkylation by Polyethylene Glycol (PEG-400)
1,*
1
2
N. REVAPRASADU , C. SAMPATH and P. HARIKA
1Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa, KwaZulu-Natal 3886, South Africa
2Department of Chemistry, Andhra Loyola Institute of Engineering and Technology, Vijayawada-520 008, India
*Corresponding author: E-mail: sevaprasaduN@unizulu.ac.za
Received: 19 February 2015;
Accepted: 27 October 2015;
Published online: 5 December 2015;
AJC-17633
A series of novel triarylmethane derivatives (3a-j) were synthesized by a one-pot, two-component method via Friedel-Crafts alkylation of
various electron-rich arenes (1a-j) with a wide variety of aldehydes (2a-j) in presence of the polyethylene glycol (PEG-400) as a green
solvent at 50-60 °C in good to excellent yields (76-96 %). Their structures were confirmed by FT-IR, 1H NMR, 13C NMR, mass spectrometry
and elemental analysis. All the triarylmethanes were tested and evaluated for their antiviral and antifungal activities. Compounds 3b, 3f,
3g and 3i exhibited highest antiviral activities against tobacco mosaic virus (TMV).
Keywords: Triarylmethanes, Friedel-Crafts alkylation, Green synthesis, Antiviral activity.
found widespread application in the chemical industry [8].
Methods for the synthesis of triarylmethanes have been
developed [9,10] which centred mainly on Friedel-Crafts
alkylation of electron-rich arenes with aldehydes usingAuCl3/
AgOTf [11], [Ir(COD)Cl]2-SnCl4 [12], Cu(OTf)2 and Sc(OTf)3
[13]as the Lewis acids. However, the quest for low-cost, environ-
mentally friendly catalysts and mild reaction conditions in
which to synthesize these compounds remains a major challenge.
Polyethylene glycol (PEG) is a biodegradable polymer used
in several organic transformations as catalyst and medium.
Polyethylene glycol has received growing attention in the field
of green chemistry because of its excellent features such as non-
toxic, inexpensive, easily recoverable and thermally stable [14].
In this contribution, we disclose a highly efficient and
practical synthesis of triarylmethanes (TRAMs) derivatives
from aromatic aldehydes and electron-rich arenes by using
polyethylene glycol (PEG-400) as a recyclable reaction medium
via Friedel-Crafts alkylation. Mild reaction conditions and
using an environmental-friendly solvent make this transfor-
mation an attractive option for the straight forward preparation
of triarylmethanes. In addition, all the triarylmethanes were
evaluated for antiviral activity.
INTRODUCTION
Viral plant diseases can be found worldwide and are a
serious threat to modern agriculture. Although, plant viruses
are genetically rather simple, they are difficult to prevent or
control and have devasting impact on crop growth. So plant
virus is a type of plant disease, known as “plant cancer”. In
recent years, the impact of climate anomalies and the areas of
crops affected by plant virus disease are on the rise resulting
in tremendous economic losses in the world. The tobacco
mosaic virus (TMV) is one of the most important classes of
common diseases occurring in tobacco growing all over the
world. This virus seriously affects the quality and yield of
tobacco. It is estimated that each year an economic loss worth
one billion U.S. dollars [1] is encountered worldwide only by
the prevalence of tobacco mosaic virus disease in agricultural
fields. As a result, development of efficient, environmentally
friendly antiviral agents through chemical synthesis has become
the core area of research for eradication of and/or prevention of
attack by tobacco mosaic virus. Ningnanmycin can inhibit virus
replication effectively and suppress virus symptoms.
Friedel-Crafts alkylation is one of the important C-C bond
forming reactions in organic chemistry [2]. These reactions
are usually assisted by either protic acids or Lewis acid catalysts.
Triarylmethanes (TRAMs) have attracted considerable
attention [3] due to their varied biological activity as antiviral
[4], antitumour [5], antitubercular [6], antifungal [7], anti-
inflammatory agents [7]. Moreover, these compounds have
EXPERIMENTAL
Melting points were determined in open capillaries on a
Mel-Temp apparatus and are uncorrected. All reagents were
from Sigma-Aldrich and were used without further purification.

474 Revaprasadu et al.
Asian J. Chem.
Thin-layer chromatography (TLC) was performed using Merck
aluminium-backed plates (Kieselgel 60 F254) and visualization
was achieved by UV light. Crude products were purified by
column chromatography on silica gel of 60-120 mesh. The
infrared spectra were recorded on a Perkin-Elmer FT-IR 240C
spectrophotometer using KBr optics. NMR spectra were
recorded in CDCl3 on a Bruker 300 MHz spectrometer for 1H
NMR and 13C NMR using tetramethylsilane (TMS) as an
internal standard. Chemical shifts (δ) are expressed in parts
per million (ppm) and coupling constants (J) in hertz (Hz).
Mass spectra were recorded on an ESI-MS mass spectrometer
and elemental analysis was performed on a Thermo Finnegan
instrument.
General procedure for the synthesis of triarylmethane
derivatives (3a-j): To a 50 mL round bottomed flask, 1,3-
dimethoxybenzene (1a, 2 mol), benzaldehyde (2a, 1 mol) and
PEG-400 (15 mL) were successively added and then the mix-
ture was magnetically stirred at 50-60 °C for the appropriate
time specified in Scheme-I. The progress of the reaction was
monitored by thin-layer chromatography (TLC) (ethyl acetate:
hexane, 3:7). After completion of the reaction, the crude
mixture was worked up in ice-cold water. The product that
separated out was filtered and the filtrate was evaporated to
remove water, leaving behind polyethylene glycol. The same
polyethylene glycol was utilized to synthesize further triaryl-
methane derivatives. The resulting product, though seen as a
single compound by TLC, was further purified by passing it
over a column of silica gel (60-120 mesh) using ethyl acetate:
hexane (3:7) as an eluent to afford the analytically pure compound,
4,4'-(phenylmethylene)bis(1,3-dimethoxy-benzene) (3a). All
other compounds 3b-j were synthesized according to the same
experimental procedure.
3.69 (s, 3H), 3.66 (s, 6H); 13C NMR (CDCl3, 300 MHz): δ
158.9, 157.9, 157.1, 133.0, 129.7, 129.3, 126.7, 125.0, 119.7,
110.5, 103.1, 98.5, 55.6, 55.5, 55.0, 35.7; ESI-MS: (m/z, %):
394 (M+, 100); Anal. calcd. for C24H26O5: C, 73.08; H, 6.64.
Found: 73.19; H, 6.58.
4-[Bis(2,4-dimethoxyphenyl)methyl]phenol (3c): White
solid; yield 79 %; m.p. 161-163 °C; IR (KBr, νmax, cm-1): 3089,
2923, 1618, 1522, 1507, 1340, 1210, 836; 1H NMR (CDCl3,
300 MHz): δ 9.86 (s, 1H), 7.81(d, J = 8.6 Hz, 2H), 6.96 (d, J
= 8.5 Hz, 2H), 6.90 (d, J = 8.3 Hz, 1H), 6.66-6.71 (m, 3H),
6.45 (d, J = 2.4 Hz, 1H), 6.36 (dd, J = 2.4 Hz, 1H), 5.94 (s,
1H), 3.78 (s, 6H), 3.67 (s, 6H); 13C NMR (CDCl3, 300 MHz):
δ 162.3, 160.6, 158.9, 157.8, 153.4, 136.3, 132.6, 130.2, 130.1,
125.7, 116.0, 114.7, 106.1, 103.6, 98.9, 55.6, 55.2, 41.2; ESI-
MS: (m/z, %): 403 (M+Na, 100);Anal. calcd. for C23H24O5: C,
72.61; H, 6.36. Found: C, 72.55; H, 6.41.
4,4'-[(3-Nitrophenyl)methylene]bis(1,3-dimethoxy-
benzene) (3d):Yellow solid; yield 91 %; m.p. 153-155 °C; IR
(KBr, νmax, cm-1): 3079, 2922, 1611, 1528, 1507, 1352, 1203,
827; 1H NMR (CDCl3, 300 MHz): δ 7.14-8.16 (m, 4H), 7.06
(d, J = 7.1 Hz, 2H), 6.55 (s, 2H), 6.42 (s, 2H), 6.07 (s, 1H),
3.89 (s, 6H), 3.63 (s, 6H); 13C NMR (CDCl3, 300 MHz): δ
151.4, 147.8, 144.1, 142.5, 128.8, 127.8, 125.6, 124.3, 114.4,
98.1, 58.8, 55.8, 42.3; ESI-MS :m/z, %): 432 (M+Na, 95);
Anal. calcd. for C23H23NO6 : C, 67.47; H, 5.66; N, 3.42. Found:
C, 67.52; H, 5.57; N, 3.48.
4,4'-[(4-Methoxyphenyl)methylene]bis(1,3-dimethoxy-
benzene) (3e): White solid; yield 81 %; m.p. 134-136 °C; IR
(KBr, νmax, cm-1): 3085, 2921, 1622, 1523, 1505, 1346, 1206,
827; 1H NMR (CDCl3, 300 MHz): δ 6.38-6.44 (m, 2H), 6.20-
6.24 (m, 2H), 6.12-6.18 (m, 2H), 5.88-5.92 (m, 2H), 5.78-
5.83 (m, 2H), 5.44 (s, 1H), 3.19 (s, 6H), 3.18 (s, 3H), 3.10 (s,
6H); 13C NMR (CDCl3, 300 MHz): δ 158.9, 157.6, 157.2,
136.2, 129.9, 129.7, 125.2, 112.9, 103.1, 98.3, 55.1, 54.7, 54.6,
41.0); ESI-MS: (m/z, %): 394 (M+, 100); Anal. calcd. for
C24H26O5: C, 73.08; H, 6.64. Found: C, 73.11; H, 6.73.
4-[Bis(2,4-dimethoxyphenyl)methyl]benzonitrile (3f):
White solid; yield 96 %; m.p. 169-171 °C; IR (KBr, νmax, cm-1):
Ar
Ar
PEG-400
50-60 °C
2Ar–H
1a-j
+
RCHO
2a-j
R
3a-j
1
3076, 2933, 1632, 1526, 1508, 1342, 1211, 834; H NMR
Scheme-I: Synthesis of novel triarylmethanes (3a-j)
(CDCl3, 300 MHz): δ 7.51 (d, J = 8.3 Hz, 2H), 7.13 (d, J = 8.3
Hz, 2H), 6.62 (d, J = 8.3 Hz, 2H), 6.46 (d, J = 2.0 Hz, 2H),
6.37 (dd, J = 2.0 Hz, 8.3 Hz, 2H), 6.01 (s,1H), 3.78 (s, 6H),
3.67 (s, 6H); 13C NMR (CDCl3, 300 MHz): δ 159.4, 157.8,
159.8, 131.6, 130.2, 129.6, 123.4, 119.2, 109.2, 103.5, 98.6,
55.4, 55.1, 42.5; ESI-MS: (m/z, %): 389 (M+, 100);Anal. calcd.
for C24H23NO4: C, 74.02; H, 5.95; N, 3.60. Found: C, 74.13;
H, 5.85; N, 3.71.
4,4'-(Phenylmethylene)bis(1,3-dimethoxybenzene)
(3a): White solid; yield 95 %; m.p. 142-144 °C; IR (KBr, νmax
,
cm-1): 3081, 2928, 1615, 1525, 1500, 1349, 1200, 830; H
NMR (CDCl3, 300 MHz): δ 7.49 (d, J = 8.0 Hz, 2H), 7.04 (d,
J = 7.0 Hz, 2H), 6.68 (d, J = 8.3 Hz, 1H), 6.45 (d, J = 2.4 Hz,
2H), 6.36 (dd, J = 2.4 Hz, 8.3 Hz, 2H), 6.01 (s, 1H), 3.77 (s,
6H), 3.67 (s, 6H); 13C NMR (CDCl3, 300 MHz): δ 159.0, 157.9,
144.5, 133.7, 130.3, 130.1, 129.0, 128.4, 127.7, 125.5, 125.2,
103.2, 98.6, 55.5, 55.1, 42.0; ESI-MS: (m/z, %): 387 (M+Na,
95); Anal. calcd. for C23H24O4: C, 75.80; H, 6.64. Found: C,
75.69; H, 6.67.
1
2-[Bis(2,4-dimethoxyphenyl)methyl]naphthalene (3g):
White solid; yield 90 %; m.p. 156-157 °C; IR (KBr, νmax, cm-1):
1
3077, 2932, 1640, 1528, 1506, 1354, 1206, 836; H NMR
(CDCl3, 300 MHz): δ 7.93-8.00 (m, 1H), 7.81 (t, J = 6.2 Hz,
1H), 7.69 (t, J = 7.1 Hz, 1H), 7.27-7.41 (m, 3H), 6.93 (s, 1H),
6.63-7.75 (m, 3H), 6.49 (d, J = 7.7 Hz, 2H), 6.28-6.34 (m,
2H), 3.75 (s, 6H), 3.68 (s, 6H); 13C NMR (CDCl3, 300 MHz):
δ 159.1, 157.7, 140.9, 133.8, 131.9, 130.4, 128.3, 126.5, 125.5,
125.0, 124.7, 124.5, 103.3, 98.5, 55.5, 55.0, 38.1; ESI-MS:
(m/z, %): 437 (M+Na, 90);Anal. calcd. for C27H26O4: C, 78.24;
H,6.32. Found: C, 78.33; H, 6.21.
4,4'-[(2-Methoxyphenyl)methylene]bis(1,3-dimethoxy-
benzene) (3b): White solid; yield 76 %; m.p. 137-139 °C; IR
(KBr, νmax, cm-1): 3087, 2931, 1618, 1520, 1504, 1353, 1206,
837; 1H NMR (CDCl3, 300 MHz): δ 7.14-7.19 (m, 1H), 6.84
(d, J = 8.0 Hz, 1H), 6.79 (d, J = 7.4 Hz, 1H), 6.75 (dd, J = 1.6
Hz, 7.6 Hz, 2H), 6.64 (d, J = 8.3 Hz, 2H), 6.44 (d, J = 2.4 Hz,
2H), 6.33 (dd, J = 2.4, 8.3 Hz, 2H), 6.23 (s, 1H), 3.77 (s, 6H),

Vol. 28, No. 3 (2016)
Green Synthesis and Antiviral Activity of Novel Triarylmethane Derivatives 475
2,2'-(Phenylmethylene)bis(1,3,5-trimethoxybenzene)
(3h): White solid; yield 92 %; m.p. 165-137 °C; IR (KBr, νmax
where,A =Average local lesion numbers of control (not treated
with compound; B = Average local lesion numbers smeared
with drugs.
,
cm-1): 3087, 2921, 1610, 1528, 1506, 1352, 1203, 828; H
NMR (CDCl3, 300 MHz): δ 8.12 (d, J = 7.7 Hz, 2H), 7.61 (t,
J = 7.4 Hz, 1H), 7.48 (t, J = 7.7 Hz, 2H), 7.14 (t, J = 7.4 Hz,
1H), 7.05 (d, J = 6.7 Hz, 2H), 6.11 (s, 1H), 6.09 (s, 1H), 3.78
(s, 6H), 3.49 (s, 12H); 13C NMR (CDCl3, 300 MHz): δ 171.9,
159.9, 159.7, 159.0, 145.5, 133.6, 130.0, 129.2, 128.3, 127.6,
126.8, 124.4, 114.1, 92.7, 91.7, 55.9, 55.1, 54.9, 36.9; ESI-
MS: (m/z, %): 424 (M+, 95);Anal. calcd. for C25H28O6: C, 70.74;
H, 6.65. Found: C, 70.78; H, 6.71.
1
RESULTS AND DISCUSSION
The reaction of various electron-rich arenes 1a-j with a
wide variety of aldehydes 2a-j in the presence of PEG-400 by
one-pot, two-component method via Friedel-Crafts alkylation
at 50-60 °C led to the formation of triarylmethane derivatives
3a-j in good to excellent yields (Scheme-I).
5,5'-[(3-Nitrophenyl)methylene]bis(1,2,4-trimethoxy-
benzene) (3i):Yellow solid; yield 95 %; m.p. 148-150 °C; IR
(KBr, νmax, cm-1): 3078, 2929, 1616, 1522, 1507, 1344, 1205,
833; 1H NMR (CDCl3, 300 MHz): δ 7.14-7.26 (m, 4H), 6.55
(s, 2H), 6.42 (s, 2H), 6.07 (s, 1H), 3.89 (s, 6H), 3.66 (s, 6H),
3.63 (s, 6H); 13C NMR (CDCl3, 300 MHz): δ 151.4, 147.8,
144.1, 142.5, 128.8, 127.8, 125.6, 124.3, 114.4, 98.1, 58.8,
55.8, 42.3; ESI-MS: (m/z, %): 492 (M+Na, 95); Anal. calcd.
for C25H27NO8: C, 63.96; H, 5.80; N, 2.80. Found: C, 63.92;
H, 5.72; N, 2.84.
Previously, toxic solvents such as chloroform, dichloro-
methane and benzene have been used in the synthesis of triaryl-
methanes (TRAMs). Polyethylene glycol has gained impor-
tance as a ‘green’ reaction medium in view of environmental
perception [17]. In this perspective, polyethylene glycol has
become a ‘green’solvent as an alternative reaction medium to
perform organic synthesis due to its inherent advantages over
toxic solvents. Furthermore, polyethylene glycol is inexpensive,
easy to handle, thermally stable, non-toxic and recyclable. As
depicted in Scheme-I, the nature of substituents on the aromatic
aldehyde molecules has a significant effect on the yields and
time of the reactions. In the presence of PEG-400, various
electron-rich arenes reacted with a number of aromatic
aldehydes. The aromatic aldehydes with electron-withdrawing
groups such as NO2, CN and CHO increased the yields and
reduced the reaction times (Scheme-I), whereas electron-
donating substituents such as the OH and OCH3 groups behaved
differently in the synthesis of triarylmethanes (Scheme-I).
The chemical structures of all the triarylmethanes 3a-j
were confirmed by elemental analysis, IR, 1H NMR, 13C NMR
and mass spectral data. All the compounds displayed charac-
teristic IR stretching absorptions at 3089, 2931, 1618, 1522
and 1504 cm-1 respectively. The 1H and 13C NMR spectral data
for all compounds 3a-j showed characteristic chemical shifts
in the expected region. The ESI mass spectra of 3a-j agreed
with the proposed structures.
Antiviral activity: The newly synthesized derivatives 3a-
j were evaluated for their antiviral activity against tobacco
mosaic virus (TMV) by Gooding and Hebert method [15]. It
is clear that the compounds 3a-j showed a certain degree of
antiviral activity against tobacco mosaic virus (TMV). The struc-
tural modification caused by changing the substituents (R) on
the aromatic aldehydes has a wide impact on antiviral activity
of the final synthesized compounds. Among the compounds
screened, 3b, 3f, 3g and 3i displayed high antiviral activities
against the virus. The other compounds showed reasonably
moderate to good antiviral activity (Table-2).
2,2'-[(3-Chlorophenyl)methylene]bis(1,3,5-trimethoxy-
benzene) (3j): White solid; yield 84 %; m.p. 159-162 °C; IR
(KBr, νmax, cm-1): 2933, 2832, 1593, 1461, 1379, 1348, 1211,
1
1174, 1039, 955, 817; H NMR (CDCl3, 300 MHz): δ 7.10-
7.06 (m, 2H), 7.03-6.94 (m, 2H), 6.18 (s, 1H), 6.11 (s, 4H),
3.79 (s, 6H), 3.53 (s, 12H); 13C NMR (CDCl3, 300 MHz): δ
159.6, 159.4, 148.2, 131.9, 127.8, 127.1, 125.4, 124.0, 113.0,
91.4, 55.8, 55.2, 36.7; ESI-MS: (m/z, %): 492 (M+Na, 95);
Anal. calcd. for C25H27O6Cl: C, 65.43; H, 5.93. Found: C, 65.53;
H, 5.81.
Antiviral bioassay
Purification of tobacco mosaic virus (TMV): Using
Gooding’s method [15], upper leaves of Nicotiana tabacum L
inoculated with tobacco mosaic virus were selected and ground
in phosphate buffer, then filtered through a double-layer pledget.
The filtrate was centrifuged at 10,000 g, treated with polyethylene
glycol and centrifuged again. The whole experiment was carried
out at 4 °C.Absorbance values were measured at 260 nm using
an ultraviolet spectrophotometer.
(A260 × Dilution ratio)
E1cm (0.1 %,260 nm)
Virus concentration =
×100
Curative effect of compounds against tobacco mosaic
virus in vivo: Growing leaves of Nicotiana tabacum L of the
same age was selected. Tobacco mosaic virus (concentration
of 6 × 10-3 mg/mL) was dipped and inoculated on the whole
leaves, which were then washed with water and dried. The
compound solution was smeared on the left side and the solvent
was smeared on the right side for control.The local lesion numbers
were counted and recorded 3-4 days after inoculation [16].
For each compound, three repetitions were measured. The rates
of inhibition for the compounds 3a-i are shown in Table-1.
The inhibition rates of the compounds were then calculated
according to the following formula:
Conclusion
We have developed a mild and highly efficient one-pot
protocol for the ‘green’ synthesis of triarylmethanes (TRAMs)
from aromatic aldehydes and electron-rich arenes by using
PEG-400 as a recyclable reaction medium and as a catalyst
via Friedel-Crafts alkylation in good to excellent yields (76-
96 %). Moreover, the compounds 3b, 3f, 3g and 3i displayed
high antiviral activity against tobacco mosaic virus. Environ-
mental acceptability, excellent yields, simple work-up procedure,
A − B
A
Inhibition rate (%) =
×100

476 Revaprasadu et al.
Asian J. Chem.
TABLE-1
SYNTHESIS OF NOVEL TRIARYLMETHANES (3a-j)
Compound
Ar-H
RCHO
Product
Time (h)
Yield (%)
OCH3
OCH3
OCH3
OCH3
H3CO
OCH3
CHO
2
95
76
79
3a
H3CO
OCH3
OCH3
CHO
H3CO
OCH3
3
3b
H3CO
OCH3
OCH3
OCH3
OCH3
H3CO
OCH3
HO
CHO
3
3c
H3CO
HO
OCH3
OCH3
OCH3
CHO
H3CO
OCH3
2
91
3d
H3CO
O2N
OCH3
NO2
OCH3
OCH3
H3CO
OCH3
H3CO
CHO
3
81
3e
H3CO
H3CO
OCH3
OCH3
OCH
OCH3
3
H3CO
OCH3
NC
CHO
2
96
3f
H3CO
NC
OCH3

Vol. 28, No. 3 (2016)
Green Synthesis and Antiviral Activity of Novel Triarylmethane Derivatives 477
OCH3
H3CO
OCH3
OCH3
2
90
3g
H3CO
CHO
OCH3
OCH3
H3CO
H3CO
OCH3
OCH3
OCH3
CHO
H3CO
2
92
3h
H3CO
OCH3
OCH3
OCH3
OCH3
H3CO
OCH3
CHO
H3CO
2
95
3i
H3CO
O2N
OCH3
NO2
OCH3
OCH3
H3CO
H3CO
OCH3
OCH3
CHO
H3CO
OCH3
3
84
3j
Cl
OCH3
OCH3
Cl
TABLE-2
cleaner reaction profiles, eco-friendly solvent, shorter reaction
time, inexpensive and recyclable non-ionic solvent are the addi-
tional notable features of this protocol to synthesize potentially
useful antiviral products.
ANTIVIRAL INHIBITORY ACTIVITY OF
NOVEL TRIARYLMETHANES (3a-j)
AGAINST TOBACCO MOSAIC VIRUS
Compound
Concentration (µg/mL)
Inhibition rate (%)
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
37.21
43.12
35.67
31.00
36.22
42.40
44.08
34.65
41.19
38.11
54.51
3a
3b
3c
3d
3e
3f
3g
3h
ACKNOWLEDGEMENTS
The authors are grateful to National Research Foundation
(NRF), SouthAfrica and University of Zululand, SouthAfrica
for financial support. The authors are also grateful to Andhra
Loyola Institute of Engineering and Technology, Vijayawada,
Andhra Pradesh, India for the encouragement.
REFERENCES
3i
3j
Ningnanmycina
1. Y.F. Wu, R. Cao, N.S. Wei and G.H. Zhou, World Agr., 35, 229 (1995).
2. M. Bandini, A. Melloni and A. Umani-Ronchi, Angew. Chem. Int. Ed.,
43, 550 (2004).
aNingnanmycin was used a standard.

478 Revaprasadu et al.
Asian J. Chem.
3. (a) V. Nair, S. Thomas, S.C. Mathew and K.G. Abhilash, Tetrahedron,
62, 6731 (2006); (b) M.S. Shchepinov and V.A. Korshun, Chem. Soc.
Rev., 32, 170 (2003); (c) M.B. Dinger and M.J. Scott, J. Chem. Soc.
Perkin Trans. II, 1741 (2000).
10. (a) Z. Tu, B. Rama Raju, T.-R. Liou, V. Kavala, C.-W. Kuo, Y. Jang, Y.-H.
Shih, C.-C. Wang and C.-F. Yao, Tetrahedron, 65, 2436 (2009); (b)
C.M. Chu, W.J. Huang, J.T. Liu and C.F. Yao, Tetrahedron Lett., 48,
6881 (2007).
4. (a) N. Mibu, K. Yokomizo, M. Uyeda and K. Sumoto, Chem. Pharm.
Bull. (Tokyo), 53, 1171 (2005); (b) N. Mibu, K. Yokomizo, M. Uyeda
and K. Sumoto, Chem. Pharm. Bull. (Tokyo), 51, 1325 (2003).
5. M.R. Lewis and P.P. Goland, Cancer Res., 12, 130 (1952).
6. (a) M.K. Parai, G. Panda, V. Chaturvedi, Y.K. Manju and S. Sinha,
Bioorg. Med. Chem. Lett., 18, 289 (2008); (b) G. Panda, J.K. Shagufta,
V. Mishra, V. Chaturvedi, A.K. Srivastava, R. Srivastava and B.S.
Srivastava, Bioorg. Med. Chem., 12, 5269 (2004).
7. S. Podder, J. Choudhury, U.K. Roy and S.J. Roy, Org. Chem., 72, 3100
(2007).
8. R. Muthyala,A.R. Katritzky and X. Lan, Dyes Pigments, 25, 303 (1994).
9. (a) S. Lin and X. Lu, J. Org. Chem., 72, 9757 (2007); (b) S. Shirakawa
and S. Kobayashi, Org. Lett., 9, 311 (2007).
11. V. Nair, K.G. Abhilash and N. Vidya, Org. Lett., 7, 5857 (2005).
12. J. Choudhury, S. Podder and S. Roy, J. Am. Chem. Soc., 127, 6162
(2005).
13. J. Esquivias, R. Gómez Arrayás and J.C. Carretero, Angew. Chem. Int.
Ed., 45, 629 (2006).
14. K.U.M. Rao, S.H. Jayaprakash, S.K. Nayak and C.S. Reddy, Catal.
Sci. Technol., 1, 1665 (2011).
15. G.V. Jr Gooding and T. T. Hebert, Phytopathology, 57, 1285 (1967).
16. B.A. Song, H.P. Zhang, H. Wang, S. Yang, L.H. Jin, D.Y. Hu, L.L.
Pang and W.J. Xue, Agric. Food Chem., 53, 7886 (2005).
17. (a) G. Kamalakar, K. Komura and Y. Sugi, Ind. Eng. Chem. Res., 45,
6118 (2006); (b) H. Weingartner and E.U. Franck, Angew. Chem. Int.
Ed., 44, 2672 (2005).