Design, synthesis, and anti-influenza viral activities of 1,3-diarylprop-2-en-1-ones: A novel class of neuraminidase inhibitors

Article abstract of DOI:10.1007/s12272-012-0406-2

A series of 1,3-diarylprop-2-en-1-one derivatives 3a-v have been synthesized and evaluated for their ability to inhibit neuraminidase (NA). Among the prepared compounds, the less lipophilic derivative 3k showed the most potent in vitro inhibitory activity against NA with an IC50 value of 1.5 μM.

Full text of DOI:10.1007/s12272-012-0406-2

Arch Pharm Res Vol 35, No 4, 633-638, 2012
DOI 10.1007/s12272-012-0406-2
Design, Synthesis, and Anti-influenza Viral Activities of 1,3-Diarylprop-
2-en-1-ones: A Novel Class of Neuraminidase Inhibitors
Mayank Kinger1, Yong Dae Park1, Jeong Hoon Park1, Min Goo Hur1, Hyung Jae Jeong2, Su-Jin Park2,
Woo Song Lee2, Sang Wook Kim3, and Seung Dae Yang1
2
1Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongup 580-185, Korea, Infection
3
Control Research Center and AI Control Research Center, KRIBB, Jeongup 580-185, Korea, and Department of Nano-
material Chemistry, College of Science & Technology, Dongguk University, Gyeongju 780-714, Korea
(Received June 15, 2011/Revised August 16, 2011/Accepted September 15, 2011)
A series of 1,3-diarylprop-2-en-1-one derivatives 3a-v have been synthesized and evaluated for
their ability to inhibit neuraminidase (NA). Among the prepared compounds, the less lipo-
philic derivative 3k showed the most potent in vitro inhibitory activity against NA with an
IC50 value of 1.5
µM.
Key words: Anti-influenza activity, Synthesis, Neuraminidase, 1,3-Diarylprop-2-en-1-ones
infected host cells but also in their movement through
the upper respiratory tract by taking charge of cata-
INTRODUCTION
The pandemic influenza virus has been identified as lyzing the cleavage of neuraminic acid residues (Von
the cause of a widespread outbreak of febrile respira- Itzstein, 2007). NA cleaves -ketosidic linkages between
α
tory infection (Jamieson et al., 2009). It is particularly sialic acid and the adjacent sugar residues. The removal
dangerous to the very young, the elderly and debili- of sialic acid lowers the viscosity of the virus particle,
tated patients, and those who have suppressed im- thus permitting the entry of the virus into epithelial
mune systems are at an especially high risk to develop cells. The replication of virus particles is blocked by
severe complications that lead to high morbidity and the application of NA inhibitors, which have the ability
mortality rates (Hien et al., 2004). The influenza virus to fit into the active site of the enzyme and thus inhibit
is an RNA virus belonging to the Orthomyxoviridae the cleavage of the connection between the host cell
family, which is subdivided into three serologically and newly built virions (Moscona, 2005). Therefore, it
distinct types: A, B and C. Among these, only influ- is possible to block an influenza virus infection by
enza viruses A and B are responsible for the spread of inhibiting NA. The current anti-influenza drugs osel-
seasonal flu epidemics every year (Von Itzstein, 2007). tamivir (Tamiflu) and zanamivir are successful ex-
Advances in understanding the molecular and amples, and both exert their antiviral effects through
cellular biology of influenza have led to the identi- the inhibition of NA in the influenza A and B viruses
fication of several molecular targets to combat these (Kim et al., 1997). The identification of novel struc-
pathogens. Neuraminidase (NA;a EC 3.2.1.18) is one tures that can be potentially useful in designing new,
of two major surface glycoproteins of both type A and potent, selective and less toxic anti-viral agents is still
B influenza viruses and is essential for viral repli- a major challenge to researchers.
cation in vitro (Air and Laver, 1989). The NA protein
In the present investigation, we began our studies
plays a key role not only in the release of virions from by focusing on 1,3-diarylprop-2-en-1-one compounds.
The class of compounds with a 1,3-diarylprop-2-en-1-
one framework has been known for over a century.
Correspondence to: Seung Dae Yang, Advanced Radiation Tech-
These natural compounds occur mainly as petal
nology Institute, Korea Atomic Energy Research Institute, Jeon-
pigments and are found in variety of trees and plants,
gup 580-185, Korea
and have been found to show good inhibitory activity
against the influenza virus. Recently, Grienke et al.
Tel: 82-63-570-3570, Fax: 82-63-570-3549
E-mail: sdyang@kaeri.re.kr
633

634
M. Kinger et al.
isolated and investigated six candidates from the seed
J
= 4.8, 1.1 Hz), 7.80 (2H, m); 13C-NMR (125 MHz,
extract of Alpinia katsumadai and found an active CDCl3, δ, ppm): 40.2, 111.8, 116.3, 122.5, 128.1, 130.5,
compound against influenza virus that contains a 130.9, 132.9, 145.0, 146.4, 152.1, 182.2.
prop-2-en-1-one moiety (Grienke et al., 2010). In a
related study, Ryu et al. isolated several polyphenols, 1-(Thien-2-yl)-3-(2,6-difluorophenyl)prop-2-en-1-
comprising chalcones, flavonoids, coumarins, and one (3b)
polybenzofuran responsible for NA inhibitory activity Yield 95%; IR (
found in extracts of Glycyrrhiza uralensis (Ryu et al., calcd for C13H18F2OS: 250.0264. Found: 250.0262; 1H-
2010). In this article, we describe our initial optimi- NMR (500 MHz, CDCl3, , ppm): 6.96 (2H, m), 7.18
zation studies for a series of new 1,3-diarylprop-2-en- (1H, dd, = 4.8, 3.7 Hz), 7.32 (1H, m), 7.71 (2H, m),
1-ones to determine their antiviral activities and 7.85 (1H, dd, = 3.7, 1.1 Hz), 7.91 (1H, d, = 16.0 Hz);
identify the compound with the highest NA inhibition 13C-NMR (125 MHz, CDCl3,
, ppm): 111.9, 127.2,
ν
max, KBr): 1635 cm−1 (C=O); HRMS
δ
J
J
J
δ
potency.
128.3, 129.9, 131.2, 132.2, 134.3, 145.4, 161.0, 163.0,
182.2.
MATERIALS AND METHODS
General experimental procedures
1-(Thien-2-yl)-3-(4-fluorophenyl)prop-2-en-1-one
(3c)
1H-NMR and 13C-NMR were measured downfield Yield 68%; IR (
ν
max, KBr): 1636 cm−1 (C=O); HRMS
1
relative to tetramethylsilane in CDCl3 unless other- calcd for C13H9OSF: 230.0358. Found: 230.0355; H-
wise noted (value in ppm); coupling constants
reported in hertz, and conducted on a JNM-ECA 500 (1H, dd,
spectrometer (Jeol). IR spectra (KBr) were recorded (2H, m), 7.66 (1H, m), 7.79 (1H, d,
with a Bruker-Vector22 instrument (Bruker). High (1H, m); 13C-NMR (125 MHz, CDCl3,
J
are NMR (500 MHz, CDCl3,
δ, ppm): 7.09 (2H, m), 7.16
J
= 4.8, 3.7 Hz), 7.32 (1H, d,
J
= 15.7 Hz), 7.62
= 15.7 Hz), 7.84
J
δ, ppm); 116.0,
resonance mass spectra (HRMS) were recorded on 121.2, 128.3, 130.5, 131.0, 131.9, 134.0, 142.8, 145.5,
JMS-700 (Jeol) and measured at Gyeongsang National 163.0, 181.9.
University (Chinju). The stationary phases used for
column chromatography (Silica gel 60, 70-230 mesh), 1-(Thien-2-yl)-3-(phenyl)prop-2-en-1-one (3d)
and TLC plates (Silical-gel 60 F254) were purchased Yield 70%; IR (
ν
max, KBr): 1635 cm−1 (C=O); HRMS
form Merck KGaA. Spots were detected under UV calcd for C13H10OS: 214.0452. Found: 214.0453; H-
1
radiation. All the reagent-grade chemicals were pur- NMR (500 MHz, CDCl3,
chased from the Sigma-Aldrich.
δ
, ppm): 7.18 (1H, dd,
3.7 Hz), 7.41 (4H, m), 7.64 (2H, m), 7.67 (1H, dd,
4.8, 1.1 Hz), 7.85 (2H, m); 13C-NMR (125 MHz, CDCl3,
, ppm); 121.6, 128.3, 128.6, 129.0, 130.7, 131.9, 134.0,
134.7, 144.1, 147.5, 182.
J = 4.8,
J =
δ
General procedure for synthesis of 1,3-diaryl-
prop-2-en-1-ones derivatives 3a-v
To a solution of appropriate ketone (10 mmol) and
aldehyde (10 mmol) in ethanol was added aqueous 1-(Thien-2-yl)-3-(2,4-dichlorophenyl)prop-2-en-1-
sodium hydroxide (12 mmol) at 0ºC. The reaction one (3e)
mixture was stirred for 7-8 h at room temperature Yield 68%; IR (
until the disappearance of the starting materials. On calcd for C13H8OSCl2: 281.9673. Found: 281.9705; 1H-
completion, the reaction mixture was poured into ice NMR (500 MHz, CDCl3, , ppm): 7.18 (1H, dd, = 4.8,
cold water and adjusted to pH 6 with 0.1 N HCl. The 4.0 Hz), 7.29 (1H, m), 7.35 (1H, d, = 15.7 Hz), 7.46
precipitate was filtered, and washed with ethanol. The (1H, d, = 2.4 Hz), 7.66 (1H, d, = 8.6 Hz), 7.70 (1H,
crude product was subjected to purification through dd,
= 5.1, 1.1 Hz), 7.85 (1H, dd, = 3.8, 1.1 Hz), 8.13
silica gel column chromatography (
-hexane-ethyl (1H, d,
= 15.5 Hz); 13C-NMR (125 MHz, CDCl3,
ν
max, KBr): 1637 cm−1 (C=O); HRMS
δ
J
J
J
J
J
J
n
J
δ,
acetate = 3:1) to afford 3a-v in 53-95% yields.
ppm); 124.7, 127.6, 128.4, 128.6, 130.2, 131.7, 132.2,
134.4, 136.2, 136.6, 138.7, 145.1, 181.6.
1-(Thien-2-yl)-3-(4-dimethylaminophenyl)prop-2-
en-1-one (3a)
1-(Thien-2-yl)-3-(4-chlorophenyl)prop-2-en-1-one
Yield 92%; IR (
calcd for C15H15NOS: 257.0874. Found: 257.0873; H- Yield 92%; IR (
NMR (500 MHz, CDCl3,
ν
max, KBr): 1636 cm−1 (C=O); HRMS (3f)
1
ν
max, KBr): 1636 cm−1 (C=O); HRMS
1
δ
, ppm): 3.03 (6H, s), 6.67 (2H, calcd for C13H9OSCl: 248.0063. Found: 248.0068; H-
d,
d,
J
J
= 8.8 Hz), 7.14 (1H, dd,
= 15.4 Hz), 7.53 (2H, d,
J
J
= 4.8, 3.7 Hz), 7.21 (1H, NMR (500 MHz, CDCl3,
= 8.8 Hz), 7.60 (1H, dd, (1H, dd, = 5.2, 3.7 Hz), 7.34 (1H, d,
δ
, ppm): 7.11 (2H, m), 7.18
J
J
= 15.4 Hz), 7.63

Anti-influenza Viral Activities of 1,3-Diarylprop-2-en-1-ones
635
(2H, m), 7.68 (1H, dd,
15.5 Hz), 7.86 (1H, dd,
MHz, CDCl3, , ppm); 122.1, 128.4, 129.3, 129.7, 132.0, 111.8, 116.1, 118.4, 122.7, 130.4, 144.2, 152.0, 153.0,
J
J
= 4.8, 1.1 Hz), 7.81 (1H, d,
J
=
7.55 (2H, d,
J
= 8.6 Hz), 7.80 (1H, d,
J
= 15.5 Hz); 13C-
= 4.0, 1.1 Hz); 13C-NMR (125 NMR (125 MHz, CDCl3,
δ, ppm): 14.2, 40.2, 109.1,
δ
133.2, 134.2, 136.5, 142.6, 145.4, 181.8.
157.4, 177.7.
1-(Thien-2-yl)-3-(4-methoxyphenyl)prop-2-en-1-
one (3g)
1-(5-Methylfuran-2-yl)-3-(3-hydroxyphenyl)prop-
2-en-1-one (3l)
Yield 68%; IR (
ν
max, KBr): 1635 cm−1 (C=O); HRMS Yield 60%; IR (
ν
max, KBr): 1635 cm−1 (C=O); HRMS
1
1
calcd for C14H12O2S: 244.0558. Found: 244.0556; H- calcd for C16H17O2N: 255.1259. Found: 255.1257; H-
NMR (500 MHz, CDCl3,
δ
, ppm): 3.84 (3H, s), 6.92 NMR (500 MHz, CDCl3,
δ
, ppm): 2.38 (3H, s), 6.17 (1H,
= 8.0, 1.4 Hz), 7.10 (2H, m), 7.19
= 15.7 Hz), 7.73 (1H, d, = 15.7
, ppm): 14.3, 109.6,
, ppm): 55.3, 114.5, 119.3, 127.5, 128.2, 130.3, 115.2, 117.8, 120.1, 121.0, 121.5, 130.2, 136.4, 143.5,
(2H, d,
(1H, d,
J
J
= 8.8 Hz), 7.16 (1H, dd,
= 15.4 Hz), 7.59 (2H, d,
J
= 4.8, 3.7 Hz), 7.29 m), 6.88 (1H, dd,
J
J
= 8.6 Hz), 7.64 (1H, (2H, m), 7.30 (1H, d,
J
J
dd,
J
= 4.8, 1.1 Hz), 7.82 (2H, m); 13C-NMR (125 MHz, Hz); 13C-NMR (125 MHz, CDCl3,
δ
CDCl3,
δ
131.5, 133.6, 144.0, 145.8, 161.8, 182.1.
152.4, 156.3, 159.2, 179.0.
1-(Thien-2-yl)-3-(4-nitrophenyl)prop-2-en-1-one
(3h)
1-(5-Methylfuran-2-yl)-3-(4-hydroxyphenyl)prop-
2-en-1-one (3m)
Yield 68%; IR (ν ν
max, KBr): 1636 cm−1 (C=O); HRMS Yield 58%; IR ( max, KBr): 1638 cm−1 (C=O), 3279 cm−1
calcd for C13H9OSNO2: 259.0303. Found: 259.0300; 1H- (OH); HRMS calcd for C14H12O3: 228.0786. Found:
1
NMR (500 MHz, CDCl3,
(1H, d, = 15.7 Hz), 8.05 (2H, m), 8.13 (2H, d,
Hz), 8.25 (2H, d, = 8.3 Hz), 8.36 (1H, d, = 3.7 Hz); m), 7.38 (2H, d,
13C-NMR (125 MHz, CDCl3, , ppm): 124.4, 126.3, 129.6, 9.14 (1H, s); 13C-NMR (125 MHz, CDCl3,
δ
, ppm): 7.31 (1H, m), 7.77 228.0786; H-NMR (500 MHz, CDCl3,
δ
, ppm): 2.30
= 8.6 Hz), 7.09 (2H,
= 8.6 Hz), 7.64 (1H, d, = 15.4 Hz),
, ppm): 14.25,
J
J = 8.9 (3H, s), 6.07 (1H, m), 6.76 (2H, d, J
J
J
J
J
δ
δ
130.4, 135.0, 136.9, 140.8, 141.5, 145.6, 148.6, 181.9.
109.86, 116.3, 118.9, 121.0, 126.1, 131.0, 143.0, 152.6,
158.5, 160.5, 176.4.
1-(Thien-2-yl)-3-(4-methylphenyl)prop-2-en-1-one
(3i)
1-(5-Methylfuran-2-yl)-3-(4-methylphenyl)prop-2-
Yield 85%; IR (
calcd for C14H12OS: 228.0609. Found: 228.0611; H- Yield 72%; IR (
NMR (500 MHz, CDCl3,
dd, = 4.9, 4.0 Hz), 7.22 (2H, d,
= 15.4 Hz), 7.53 (2H, d, = 8.0 Hz), 7.66 (1H, dd, s), 6.21 (1H, m), 7.22 (3H, m), 7.34 (1H, d,
= 4.8, 1.1 Hz), 7.83 (2H, m); 13C-NMR (125 MHz, 7.54 (2H, d, = 15.7 Hz); 13C-
= 8.3 Hz), 7.83 (1H, d,
, ppm); 21.6, 120.6, 128.3, 128.6, 129.8, 131.7, NMR (125 MHz, CDCl3, , ppm): 14.3, 21.6, 109.3,
ν
max, KBr): 1636 cm−1 (C=O); HRMS en-1-one (3n)
1
ν
max, KBr): 1635 cm−1 (C=O); HRMS
1
δ
, ppm): 2.38 (3H, s), 7.17 (1H, calcd for C15H14O2: 226.0994. Found: 226.0992; H-
J
J
= 8.0 Hz), 7.37 (1H, NMR (500 MHz, CDCl3,
δ
, ppm): 2.38 (3H, s), 2.43 (3H,
d,
J
J
J
= 15.7 Hz),
J
J
J
CDCl3,
δ
δ
132.1, 133.8, 141.2, 144.2, 145.7, 182.2.
119.5, 120.3, 128.5, 129.7, 132.2, 141.0, 143.4, 152.6,
158.1, 177.4.
1-(Thien-2-yl)-3-(naphtha-2-yl)prop-2-en-1-one (3j)
Yield 94%; IR (
ν
max, KBr): 1637 cm−1 (C=O); HRMS 1-(5-Methylfuran-2-yl)-3-(4-methoxyphenyl)prop-
1
calcd for C17 H12OS: 264.0609. Found: 264.0601; H- 2-en-1-one (3o)
NMR (500 MHz, CDCl3,
3.7 Hz), 7.53 (3H, m), 7.69 (1H, dd,
7.78 (1H, m), 7.87 (4H, m), 8.02 (2H, m); 13C-NMR NMR (500 MHz, CDCl3,
(125 MHz, CDCl3, , ppm): 121.8, 123.7, 126.8, 127.5, s), 6.20 (1H, m), 6.93 (2H, d,
127.8, 128.3, 128.7, 128.8, 130.8, 131.9, 132.2, 133.4, 7.60 (2H, d, = 8.8 Hz), 7.82 (1H, d,
NMR (125 MHz, CDCl3, , ppm): 14.2, 55.4, 109.3,
δ
, ppm): 7.20 (1H, dd,
J
= 4.8, Yield 67%; IR (
ν
max, KBr): 1636 cm−1 (C=O); HRMS
1
J
= 4.9, 1.1 Hz), calcd for C15H14O3: 242.0943. Found: 242.0940; H-
δ
, ppm): 2.44 (3H, s), 3.85 (3H,
= 8.8 Hz), 7.24 (2H, m),
= 15.5 Hz ); 13C-
δ
J
J
J
133.9, 134.5, 144.2, 145.7, 182.1.
δ
114.4, 119.0, 119.2, 127.6, 130.3, 143.1, 152.7, 157.9,
161.6, 177.4.
1-(5-Methylfuran-2-yl)-3-(4-dimethylaminophe-
nyl)prop-2-en-1-one (3k)
Yield 86%; IR (
ν
max, KBr): 1635 cm−1 (C=O); HRMS 1-(5-Methylfuran-2-yl)-3-(naphtha-2-yl)prop-2-
1
calcd for C14H12O3: 228.0786. Found: 228.0786; H- en-1-one (3p)
NMR (500 MHz, CDCl3,
s), 6.18 (1H, m), 6.68 (2H, d,
δ
, ppm): 2.42 (3H, s), 3.03 (6H, Yield 96%; IR (
ν
max, KBr): 1635 cm−1 (C=O); HRMS
1
J
= 8.9 Hz), 7.17 (2H, m), calcd for C18H14O2: 262.0994. Found: 262.0992; H-

636
M. Kinger et al.
NMR (500 MHz, CDCl3,
δ
, ppm): 2.46 (3H, s), 6.23 (1H, Yield 53%; IR (
ν
max, KBr): 1638 cm−1 (C=O), 3436 cm−1
m), 7.29 (1H, d,
m), 8.02 (3H, m); 13C-NMR (125 MHz, CDCl3,
14.3, 109.4, 119.6, 121.5, 123.8, 126.8, 127.4, 127.8, (3H, s), 3.99 (2H, m), 4.12 (2H, m), 6.22 (1H, m), 6.96
128.7, 130.7, 132.4, 133.4, 134.4, 143.4, 152.6, 158.3, (1H, m), 7.25 (5H, m), 7.79 (1H, d,
= 15.7 Hz); 13C-
, ppm): 14.2, 61.4, 69.4, 109.5,
J = 3.45 Hz), 7.50 (2H, m), 7.83 (4H, (OH); HRMS calcd for C16H16O4: 272.1049. Found:
1
δ
, ppm): 272.1048; H-NMR (500 MHz, CDCl3, δ, ppm): 2.45
J
177.3.
NMR (125 MHz, CDCl3, δ
114.2, 115.2, 119.9, 120.6, 121.7, 130.0, 136.3, 143.1,
152.5, 158.4, 159.0, 177.2.
1-(5-Methylfuran-2-yl)-3-(4-chlorophenyl)prop-2-
en-1-one (3q)
Yield 94%; IR (
ν
max, KBr): 1635 cm−1 (C=O); HRMS 1-(5-Methylfuran-2-yl)-3-(4-(2-hydroxyethoxy)
1
calcd for C15H14O2Cl: 246.0448. Found: 246.0446; H- phenyl)prop-2-en-1-one (3v)
NMR (500 MHz, CDCl3,
m), 7.24 (1H, m), 7.36 (3H, m), 7.56 (2H, d,
7.78 (1H, d,
= 15.7 Hz); 13C-NMR (125 MHz, CDCl3, 272.1050; H-NMR (500 MHz, CDCl3,
, ppm): 14.3, 109.5, 119.8, 121.8, 129.2, 129.6, 133.4, (3H, s), 3.97 (2H, m), 4.11 (2H, m), 6.18 (1H, m), 6.92
δ
, ppm): 2.44 (3H, s), 6.22 (1H, Yield 56%; IR (
ν
max, KBr): 1637 cm−1 (C=O), 3432 cm−1
J
= 8.6 Hz), (OH); HRMS calcd for C16H16O4: 272.1049. Found:
1
J
δ, ppm): 2.45
δ
136.3, 141.8, 152.5, 158.4, 177.0.
(2H, d,
Hz), 7.79 (1H, d,
CDCl3, , ppm): 14.2, 61.3, 69.4, 109.4, 115.0, 116.2,
J
= 8.3 Hz), 7.24 (2H, m), 7.57 (2H, d,
J = 8.3
J
= 15.7 Hz); 13C-NMR (125 MHz,
1-(5-Methylfuran-2-yl)-3-(2,4-dichlorophenyl)
prop-2-en-1-one (3r)
δ
119.2, 127.9, 130.3, 143.1, 152.6, 158.1, 160.7, 177.5.
Yield 75%; IR (
calcd for C14H10O2Cl2: 280.0058. Found: 280.0058; 1H-
NMR (500 MHz, CDCl3, , ppm): 2.43 (3H, s), 6.21 (1H,
m), 7.26 (2H, m), 7.32 (1H, d, = 15.7 Hz), 7.45 (1H,
m), 7.67 (1H, d, = 8.6 Hz), 8.12 (1H, d,
13C-NMR (125 MHz, CDCl3,
, ppm): 14.3, 109.6, 120.1, In general, 4-methylumbelliferyl-a-D-N-acetylneura-
124.4, 127.5, 128.5, 130.1, 131.9, 136.1, 136.3, 137.8, minic acid sodium salt hydrate (SIGMA, M8639) 0.125
ν
max, KBr): 1636 cm−1 (C=O); HRMS
Neuraminidase (Clostridium perfringens) inhib-
ition assay
δ
J
The enzyme assay was performed as previously
J
J = 15.7 Hz); reported with slight modifications (Potier et al., 1979).
δ
152.3, 158.5, 176.7.
mM in 50 mM sodium acetate buffer (pH 5.0) was
used as a substrate. Neuraminidase 0.1 U/mL in acet-
ate buffer was used as the enzyme source. The isolated
compounds were dissolved in MeOH and diluted to
1-(5-Methylfuran-2-yl)-3-(4-fluorophenyl)prop-2-
en-1-one (3s)
Yield 71%; IR (
ν
max, KBr): 1637 cm−1 (C=O); HRMS appropriate concentrations in acetate buffer. Enzyme
1
calcd for C15H11O2F: 230.0743. Found: 230.0745; H- (15
µ
L) was added to 15
L) in a cuvette, and 60
= 15.7 Hz), strate was added at 37oC. 4-Methylumbelliferone was
= 15.7 Hz); 13C-NMR (125 immediately quantified by fluorometrically by LS-55
, ppm): 14.2, 109.4, 116.0, 119.6, 121.1, luminescence. The excitation wavelength was 365 nm,
µ
L of sample solution mixed
NMR (500 MHz, CDCl3,
m), 7.08 (2H, m), 7.24 (1H, m), 7.30 (1H, d,
7.61 (2H, m), 7.79 (1H, d,
MHz, CDCl3,
δ
, ppm): 2.43 (3H, s), 6.20 (1H, with buffer (510
µ
µL of sub-
J
J
δ
130.3, 131.2, 142.0, 152.5, 158.2, 163.0, 177.1.
with the excitation slits set at 2.5 nm, and the emis-
sion wavelength was 450 nm, with the emission slits
set at 20 nm. For the determination of enzyme activity,
we used a time-driven protocol with initial velocity
1-(5-Methylfuran-2-yl)-3-(2-(2-hydroxyethoxy)
phenyl)prop-2-en-1-one (3t)
Yield 54%; IR (
(OH); HRMS calcd for C16H16O4: 272.1049. Found: analyzed using a nonlinear regression program (Sigma
ν
max, KBr): 1638 cm−1 (C=O), 3432 cm−1 recorded over a range of concentrations and the data
1
272.1049; H-NMR (500 MHz, CDCl3,
(3H, s), 4.04 (2H, m), 4.15 (2H, m), 6.16 (1H, m), 6.90
(1H, d, = 8.3 Hz), 6.96 (1H, m), 7.24 (1H, m), 7.31
δ, ppm): 2.41 Plot; SPCC Inc.).
J
Activity (%) = 100[1/(1 + [I]/IC50)]]
(1H, m), 7.51 (1H, d,
1.7 Hz), 8.12 (1H, d,
CDCl3, δ, ppm): 14.2, 61.4, 69.9, 109.4, 112.2, 119.8,
J
J
= 16.0 Hz), 7.60 (1H, dd,
J = 7.7,
= 15.7 Hz); 13C-NMR (125 MHz,
RESULTS AND DISCUSSION
121.1, 122.1, 124.0, 129.4, 131.8, 138.8, 152.7, 158.0,
158.2, 178.0.
In this study, the 1,3-diarylprop-2-en-1-one deriva-
tives 3a-v were synthesized according to the method
shown in Scheme 1. To prepare the target compounds,
the appropriate commercially available ketones and
aldehydes were suspended in ethanol with sodium
1-(5-Methylfuran-2-yl)-3-(3-(2-hydroxyethoxy)
phenyl)prop-2-en-1-one (3u)

Anti-influenza Viral Activities of 1,3-Diarylprop-2-en-1-ones
637
Scheme 1. Synthesis of derivatives 3a-v. Reagents and
conditions: (1) EtOH, NaOH, 0oC
Table I. Neuraminidase inhibitory activities of 1,3-diaryl-
prop-2-en-1-one derivatives 3a-v
% Inhibition
Compd
X
R1
R2
IC50 (µ
M)a
at 25
µM
3a
3b
3c
3d
3e
3f
3g
3h
3i
S
S
S
S
S
S
S
S
S
H
H
H
H
H
H
H
H
H
H
4-N(CH3)2-Ph
2,6-di-F-Ph
4-F-Ph
78.8
7.4
8.6
3.8
6.7
9.9
54.6
1.6
25.4
8.0
3.2 ± 0.31
Ph
2,4-di-Cl-Ph
4-Cl-Ph
4-OCH3-Ph
4-NO2-Ph
4-CH3-Ph
Naphtha-2-yl
Fig. 1. Effects of compounds 3a
,
3g
,
3k
,
3m and 3v on
neuraminidase hydrolysis of neuraminic acid (compound 3a
; compound 3g ; compound 3k ; compound 3m
compound 3v ).
,
23.2 ± 1.82
●
,
○
,
▼
, ▽
;
,
■
3j
S
of the substituent on the phenyl ring. As shown in
Table I, the lead compound 3a with -dimethylamino
at para position of the phenyl group showed good
3k
3l
O
O
O
O
O
O
O
O
O
O
O
O
CH3 4-N(CH3)2-Ph
CH3 3-OH-Ph
CH3 4-OH-Ph
85.1
30.0
62.5
18.5
33.3
11.1
18.0
9.4
29.4
21.6
35.8
54.4
1.5 ± 0.28
N,N
3m
3n
3o
3p
3q
3r
3s
3t
18.4 ± 1.21
potency (IC50 = 3.2 µM), but replacing the substituents
CH3 4-CH3-Ph
at R2 resulted in a decrease in activity. Among the
CH3 4-OCH3-Ph
CH3 Naphtha-2-yl
CH3 4-Cl-Ph
CH3 2,4-di-Cl-Ph
CH3 4-F-Ph
CH3 2-O(CH2)2OH-Ph
CH3 3-O(CH2)2OH-Ph
CH3 4-O(CH2)2OH-Ph
compounds, the 4-methoxy-substituted 3g showed mod-
erate activity (IC50 = 23.2 µM), whereas fluoro-, chloro-,
methyl-, NO2-, and naphthyl-substituted analogues
resulted in a significant loss of potency. The analogues
that had more lipophilic groups generally showed greater
decrease in potency compared with the corresponding
analogues containing less lipophilic groups. Based on
the above results, further simple modification of the
structure did not show further enhancements in activity.
We envisioned that more potent inhibitors would be
obtained by replacing the thiophene to the 5-methylfuran
ring with substitutions at R2. Various functional groups,
3u
3v
22.3 ± 2.5
aAll compounds were examined in a set of experiments
repeated three times; IC50 values of compounds represent
the concentration that caused 50% enzyme activity loss;
Oseltamivir was used as a positive control (IC50 value =
1.59 nM)
.
such as methyl,
hydroxide at 0oC. The chemical structures of these naphthyl, and fluoro groups were introduced at R2 to
compounds were determined using several spectro- give compounds 3k . The analogues containing more
scopic analyses including IR, 1H-NMR, 13C-NMR, and lipophilic groups, such as methyl (3n), 4-chloro (3q),
N,N-dimethylamino, hydroxyl, chloro,
-s
mass spectrometry.
The prepared compounds 3a
2,4-dichloro (3r), 4-fluoro (3s), and naphthyl (3p),
were tested for their resulted in a significant loss in potency. The position
-v
enzymatic inhibitory activities against NA from Clo- effect of the hydroxyl group was examined. The intro-
stridium perfringens. The enzyme assay was based on duction of a hydroxyl group at the 4-position resulted
a previously described procedure with some modifi- in a moderate potency (3m, IC50 value of 18.4 µM).
cations (Potier et al., 1979). We examined the inhibi- However, the 3-hydoxyl-substituted derivative 3l re-
tory effects of 1,3-diarylprop-2-en-1-one derivatives on sulted in decreased potency compared with 3m. For
the release of 4-methylumbelliferone from 20-(4-methy- the 4-methoxy group at the R2 position, compound 3o
lumbelliferyl)-a-
a well known NA inhibitor, was used as a positive con- corresponding analogues containing thiophene. How-
trol (IC50 = 1.59 nM). We initially examined the effect ever, the introduction of an -dimethylamino group
D-N-acetylneuraminic acid. Oseltamivir, demonstrated decreased potency compared with the
N,N

638
M. Kinger et al.
at para position of the phenyl group in compound 3k
resulted in a two-fold improvement in inhibitory
activities compared with 3a, with an IC50 values of 1.5
REFERENCES
Air, G. M. and Laver, W. G., The neuraminidase of influenza
virus. Proteins, 6, 341-356 (1989).
µM. Next, attention was focused on changing the
Grienke, U., Schmidtke, M., Kirchmair, J., Pfarr, K., Wutzler,
P., Dürrwald, R., Wolber, G., Liedl, K. R., Stuppner, H.,
and Rollinger, J. M., Antiviral potential and molecular
insight into neuraminidase inhibiting Diarylheptanoids
from Alpinia katsumadai. J. Med. Chem., 53, 778-786
(2010).
hydroxyl group to 2-hydroxyethyl ether because of the
result from compound 3m. Introduction of 2-hydroxy-
ethyl ether at the 2-, 3-, or 4-positions of the phenyl
ring resulted in decreased potency. However, com-
pound 3v, containing a 2-hydroxylethyl ether at the 4-
position of the phenyl ring, was equipotent to 3m
,
Hien, T. T., Liem, N. T., Dung, N. T., San, L. T., Mai, P. P.,
Chau, N. V., Suu, P. T., Dong, V. C., Mai, L. T. Q., Thi, N.
T., Khpa, D. B., Phat, L. P., Truong, N. T., Long, H. T.,
Tung, C. V., Giang, L. T., Tho, N. D., Nga, L. H., Tien, N.
T. K., San, L. H., Tuan, L. V., Dolecek, C., Thanh, T. T.,
Jong, M., Schultsz, C., Cheng, P., Lim, W., Horby, P., and
Farrar, J., Avian influenza A (H5N1) in 10 patients in
Vietnam. N. Engl. J. Med., 350, 1179-1188 (2004).
Jamieson, D. J., Honein, M. A., Rasmussen, S. A., Williams,
J. L., Swerdlow, D. L., Biggerstaff, M. S., Lindstrom, S.,
Louie, J. K., Christ C, M., Bohm, S. R., Fonseca, V. P.,
Ritger, K. A., Kuhles, D. J., Eggers, P., Bruce, H.,
Davidson, H. A., Lutterloh, E., Harris, M. L., Burke, C.,
Cocoros, N., Finelli, L., MacFarlane, K. F., Shu, B., and
Olsen, S. J., H1N1 2209 influenza virus infection during
pregnancy in the USA. Lancet, 374, 451-458 (2009).
Jeong, H. J., Ryu, Y. B., Park, S. J., Kim, J. H., Kwon, H. J.,
Kim, J. H., Park, K. H., Rho, M. C., and Lee, W. S.,
Neuraminidase inhibitory activities of flavonols isolated
from Rhodiola rosea roots and their in vitro anti-influenza
viral activities. Bioorg. Med. Chem., 17, 6816-6823 (2009).
Kim, C. U., Lew, W., Williams, M. A., Liu, H., Zhang, L.,
Swaminathan, S., Bischofberger, N., Chen, M. S., Mendel,
D. B., Tai, C. Y., Laver, W. G., and Stevens, R. C.,
Influenza neuraminidase inhibitors possessing a novel
hydrophobic interaction in the enzyme active site: design,
synthesis, and structural analysis of carbocyclic sialic acid
analogues with potent anti-influenza activity. J. Am.
Chem. Soc., 119, 681-690 (1997).
Moscona, A., Neuraminidase inhibitors for influenza. N.
Engl. J. Med., 353, 1363-1373 (2005).
Potier, M., Mameli, L., Belisle, M., Dallaire, L., and Melancon,
S. B., Fluorometric assay of neuraminidase with sodium
(4-methylumbelliferyl-α-D-N-acetylneuraminiate) substrate.
Anal. Biochem., 94, 287-296 (1979).
Ryu, Y. B., Kim, J. H., Park, S. J., Chang, J. S., Rho, M. C.,
Bae, K. H., Park, K. H., and Lee, W. S., Inhibition of
neuraminidase activity by polyphenol compounds isolated
from the roots of Glycyrrhiza uralensis. Bioorg. Med.
Chem. Lett., 20, 971-974 (2010).
Von Itzstein, M., The war against influenza: discovery and
development of sialidase inhibitors. Nat. Rev. Drug Discov.,
6, 967-974 (2007).
with an IC50 value of 22.3 M. This suggests that the
µ
4-position of the substituent on the phenyl ring is
crucial and plays an important role in the inhibitory
effect of these compounds.
Previous reports have suggested that naturally
isolated diarylheptanoids containing a prop-2-en-1-
one core moiety were able to inhibit NA in an enzyme
test (Grienke et al., 2010). The report revealed that
the two peripheral phenyl groups, with a spacer re-
presented by the heptyl chain, seemed to contribute to
NA inhibitory activity. In this study, we examined the
NA and influenza virus inhibitory activities of our
series of 1,3-diarylprop-2-en-1-one derivatives (3a-v).
We conducted a SAR study with the compounds to
determine the optimal structure and position of the
substituent for significant and specific NA inhibitory
activities. To our knowledge, this is the first demon-
stration of a small-molecule inhibitor of NA. Com-
pound 3k, with an
tion on the phenyl ring, was found to have especially
effective inhibitory activities (an IC50 value of 1.5 M).
N,N-dimethylamino at the 4-posi-
µ
The analogues that have more lipophilic groups gener-
ally showed decreased potency compared with the
corresponding, less lipophilic analogues. This would
indicate that the increase in potency of the NA inhibi-
tory activity is related to a more substantial interac-
tion with the enzyme and influenced by lipophilicity.
Jeong and co-workers also suggested that the presence
of the less lipophilic group in the B-ring of flavonoids
is essential for their potent inhibitory activity against
NA (Jeong et al., 2009). In summary, these preliminary
data demonstrate that 1,3-diarylprop-2-en-1-ones deri-
vatives might be considered as a potential therapeutic
agent in the treatment of influenza virus infections.
ACKNOWLEDGEMENTS
This work was supported by Nuclear R&D Program
from the Ministry of Education, Science and Technol-
ogy (MEST).