Synthesis of E- and Z-Pyrazolylacrylonitriles and their evaluation as novel antioxidants

Article abstract of DOI:10.1016/S0968-0896(99)00056-5

A facile synthesis of (Z)- and (E)-2-(5-arylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitriles and (Z)-2-(1,3-diarylpyrazol-5-yl)-3-(pyrrol-2-yl)acrylonitriles, and isomerisation of (Z)-2-(5-arylpyrazolyl)acrylonitriles to (E)-2-(5-arylpyrazolyl)acrylonitriles under basic conditions have been reported. (Z)-2-(1,3-Diarylpyrazolyl)acrylonitriles did not undergo isomerisation under the similar conditions. New compounds were identified on the basis of their spectral data (¹H-, ¹³C-, ¹H-¹H COSY, NOESY, NOE, HMQC NMR, IR, UV and EI mass). The structures of one acrylonitrile and five of their precursor 6-arylpyran-2-ones and cyanomethylpyrazoles were confirmed by X-ray crystallographic studies. Effects of pyrazolylacrylonitriles and their precursors on rat liver-microsomal lipid peroxidation were evaluated in vitro with a view to establish structure-activity relationship and to identify a lead compound. Copyright (C) 1999 Elsevier Science Ltd.

Full text of DOI:10.1016/S0968-0896(99)00056-5

Bioorganic & Medicinal Chemistry 7 (1999) 1425±1436
Synthesis of E- and Z-Pyrazolylacrylonitriles and their Evaluation
as Novel Antioxidants
Virinder S. Parmar,a,* Ajay Kumar,a Ashok K. Prasad,a Sanjay K. Singh,a
Naresh Kumar,a Shubhasish Mukherjee,a Hanumantharao G. Raj,b
Sanjay Goel,b William Erringtonc and Mohindar S. Puard
aDepartment of Chemistry, University of Delhi, Delhi-110 007, India
bDepartment of Biochemistry, VP Chest Institute, University of Delhi, Delhi-110 007, India
cDepartment of Chemistry, University of Warwick, Coventry CV4 7AL, England
dStructural Chemistry Division, Schering Plough Research Institute, Kenilworth, NJ 07033-0539, USA
Received 16 November 1998; accepted 13 February 1999
AbstractÐA facile synthesis of (Z)- and (E)-2-(5-arylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitriles and (Z)-2-(1,3-diarylpyrazol-5-yl)-3-
(pyrrol-2-yl)acrylonitriles, and isomerisation of (Z)-2-(5-arylpyrazolyl)acrylonitriles to (E)-2-(5-arylpyrazolyl)acrylonitriles under
basic conditions have been reported. (Z)-2-(1,3-Diarylpyrazolyl)acrylonitriles did not undergo isomerisation under the similar
1
conditions. New compounds were identi®ed on the basis of their spectral data (1H-, 13C-, H-1H COSY, NOESY, NOE, HMQC
NMR, IR, UV and EI mass). The structures of one acrylonitrile and ®ve of their precursor 6-arylpyran-2-ones and cyano-
methylpyrazoles were con®rmed by X-ray crystallographic studies. E€ects of pyrazolylacrylonitriles and their precursors on rat
liver-microsomal lipid peroxidation were evaluated in vitro with a view to establish structure±activity relationship and to identify a
lead compound. # 1999 Elsevier Science Ltd. All rights reserved.
Introduction
biological cells, are basically involved in detoxi®cation
of invading organisms and chemicals, but stray ROS
also initiate lipid peroxidation in healthy cells leading to
diverse pathologies such as Alzheimer's disease, athero-
sclerosis, diabetes, Parkinson's disease, etc.21 Thus,
reduction of the rate of these life-limiting metabolic
processes by use of chemicals22±24 has been a subject of
current research. In recent years, we have reported the
synthesis of several new pyrazoles,25 pyrazolylcoumar-
ins26 and isoxazoles,27 and studied their biological
activities.28 In continuation, we wish to report herein
the synthesis of Z- and E-pyrazolylacrylonitriles and
their e€ects on NADPH-catalysed liver-microsomal
lipid peroxidation.
Pyrazoles and their derivatives are widely used as medi-
cines, e.g. as antipyretic,1,2 antiin¯ammatory,3 gastric
secretion stimulatory,4 antidepressant,5 against rheu-
matoid arthritis,6,7 antihypercholesterolemic agents,8
antibacterial agents,9 anticonvulsant agents,10 anti-
®larial agents,11 etc. Along with the medicinal applica-
tions, this class of compounds are also useful as
agrochemicals, e.g. as herbicides,12,13 fungicides,14 pes-
ticides15 and insecticides,15 and as dyestu€s,16±18 in
sunscreen materials19 and as analytical reagents.20 Very
few pyrazole derivatives are naturally occurring, may be
due to the diculty of living organisms to construct the
N N bond. Owing to the widespread applications,
synthesis and biological activity evaluation of pyrazoles
and their derivatives have been a subject of intensive
investigations as revealed by enormous literature covering
the subject.
Results and Discussion
(Z)-2-(5-Arylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitriles
4a±4h were prepared by coupling of pyrrole-2-carbox-
aldehyde with the corresponding 5-aryl-3-cyano-
methylpyrazoles 3a±3h27,29 in quantitative yields
according to the procedure outlined in Scheme 1 and
described in detail in the Experimental. Arylpyrazoles
3a±3h, in turn were prepared in four steps starting
with the condensation of ethyl cyanoacetate with
carbon disul®de in sodium ethoxide, methylation of
Considerable progress has been made in recent years in
relating ageing to oxidation in biological cells. The
reactive oxygen species (ROS), cause of oxidation in
Key words: Arylpyrazoles; pyrazolylacrylonitriles; isomerisation;
antioxidants; lipid peroxidation.
* Corresponding author. Tel.: +91-11-725-6555/7206; fax: +91-11-
725 7206; e-mail: vparmar.duchem@axcess.net.in
0968-0896/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(99)00056-5

1426
V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
Scheme 1. Reagents and conditions: (i) EtOH, Na, 0ꢀC, stirring 5±6 h; (ii) CH3I, MeOH, 0ꢀC, stirring 2±3 h; (iii) DMF, appropriately substituted
acetophenone, KOH, 30ꢀC, stirring 6 h; (iv) MeOH, NH2NH2, re¯uxing 5±6 h; (v) EtOH, NaOBut, pyrrole-2-carboxaldehyde, stirring 4±5 h; (vi)
EtOH, NaOBut, pyrrole-2-carboxaldehyde, re¯uxing 20±25 h.
the disodio salt, condensation of resulted ethyl 2-
cyano-3,3-bis-methylthioacrylate (1) with corresponding
acetophenones a€ording pyranones 2a±2h, followed by
reaction with hydrazine in methanol27,30 (Scheme 1).
(Z)-Pyrazolylacrylonitriles were well characterised by
the same reaction mixture when re¯uxed at 90±100ꢀC
for 20±24 h a€orded the thermodynamically stable E-
isomers, i.e. (E)-2-(5-arylpyrazol-3-yl)-3-(pyrrol-2-yl)
acrylonitriles 5a±5h in 52 to 60% yields along with the
corresponding (Z)-isomers 4a±4h as minor products
(25±30% yields); the composition of equilibrium mix-
tures of (Z)- and (E)-pyrazolylacrylonitriles thus formed
did not change on further continuation of the reaction.
An attempt to isomerise (Z)-acrylonitriles by re¯uxing
their solution in methanol failed, whereas addition of
NaOBut in the reaction mixture and continuation of
re¯uxing allowed the isomerisation of (Z)-pyr-
azolylacrylonitriles to the corresponding (E)-isomers.
The reaction condition of isomerisation indicates that
the base deprotonates the more acidic NH proton of
pyrazole ring of acrylonitriles leading to di€erent reso-
nance structures and to single bond character across the
double bond; rotation through corresponding single
bond results in isomerisation (Scheme 2). The other less
plausible explanation of isomerisation of (Z)-pyr-
azolylacrylonitriles to the corresponding E-isomers is
via deprotonation of the pyrrolic nitrogen or reversible
addition of ethoxide ion to acrylonitrile-double bond.
1
analysis of their spectral data. The H NMR spectra of
4a and 4b exhibited resonances for all the protons
including the two D2O-exchangeable broad singlets at
around d 11.50 and 13.40 due to two acidic NH. The
proton NMR spectral assignments for compounds 4b
1
and 4e were con®rmed by H-1H COSY NMR. Thus,
1
peaks resonating at d 6.33 and 7.15 in the H NMR
spectrum of 4b assigned to C-4000H, and C-3000H and C-
5000H of pyrrole moiety, respectively, showed expected
1
cross peaks in its H-1H COSY NMR spectrum. Simi-
1
larly, peaks at d 7.29 and 7.70 in the H NMR of 4b,
assigned to C-300H and C-500H, and C-200H and 600H,
respectively were con®rmed by expected cross peaks in
1
its H-1H COSY NMR spectrum. The assignment of
13C NMR spectral values in case of (Z)-pyr-
azolylacrylonitrile 4a was done on the basis of selective
INEPT experiment and carbons of compounds 4b±4h
were assigned accordingly (Table 4).
The coupling reaction of pyrrole-2-carboxaldehyde with
3-cyanomethylpyrazoles 3a±3h in the presence of NaO-
But is highly temperature dependent. Thus, the reaction
carried out at room temperature (25±30ꢀC) a€orded
exclusively the kinetically controlled (Z)-isomers, i.e. the
compounds 4a±4h in 88 to 95% yields in 4±5 h, whereas
The structures of (Z)- and (E)-acrylonitriles 4a±4h and
5a±5h were unambiguously ascertained on the basis of
their TLC behaviour, UV spectra and NMR experi-
ments. The close inspection of the models of (Z)- and
(E)-acrylonitriles indicated that the pyrazole and pyr-
role moieties are in trans position in Z-isomer, which

V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
1427
Scheme 2. Proposed mechanism of isomerisation of (Z)-pyrazolylacrylonitriles to (E)-pyrazolylacrylonitriles.
Table 1. Comparison of salient features in the NMR and the UV
spectral data of (Z)- and (E)-arylpyrazolylacrylonitriles 4a±4h and 5a±
5h
reduces steric hindrance between two bulky groups
hence it is a favoured product of reaction at room tem-
perature. In basic conditions, the double bond in the
acrylonitrile moiety develops a single bond character
and at high temperature, when the molecule gets su-
cient energy to cross over the energy barrier of steric
hindrance, (E)-isomers are formed and stabilised by
intramolecular interaction between NH of pyrrole moi-
ety and nitrogen of pyrazole moiety as both the moieties
come closer to each other in space (Scheme 2). This
interaction is revealed by TLC behaviour of isomers as
well, e.g. Rf values of (Z)- and (E)-isomers (ethyl acet-
ate:benzene, 1:9) are between 0.40±0.42 and between
0.60±0.64, respectively, indicating that the E-isomer is
less polar than Z-isomer due to involvement of NH
proton in hydrogen bonding intramolecularly. In their
UV spectrum, the -CHˆC(CN)- chromophore of E-iso-
mer absorbs at lower wavelength (353±356 nM) than
that of the Z-isomer (360±363 nM) which is indicative of
the fact that in E-isomers, the two bulky groups are cis
to each other and because of the steric hindrance of the
two bulky groups, the planarity necessary for extension
of conjugation is disrupted leading to the hypsochromic
shift (Table 1). This electronic e€ect is also observed in
Compounds
N-10 N-1000 C-3H C-2
H(d) H(d) (d) (d)
lmax
CHˆC(CN)
(
)
Z-isomers
4a
4b
4c
4d
4e
4f
13.50 11.55 7.81 112.0
13.30 11.60 7.78 111.8
13.20 11.47 7.74 111.9
13.40 11.49 7.74 112.0
13.51 11.50 7.75 111.9
13.50 11.52 7.73 112.1
13.43 11.48 7.75 112.2
13.50 11.51 7.73 112.2
362
362
362
362
363
362
362
360
4g
4h
E-isomers
5a
5b
5c
5d
5e
5f
13.36 14.02 7.39 121.4
13.32 13.90 7.31 119.5
13.34 13.90 7.32 121.5
13.24 13.90 7.34 121.5
13.20 14.10 7.34 121.2
13.20 13.90 7.35 121.2
13.27 13.90 7.34 121.2
13.10 13.90 7.35 121.1
353
356
356
353
356
356
356
356
5g
5h
E-isomers. This interaction is not possible in Z-isomers
because pyrazole and pyrrole moieties are trans to each
other. The structures of (Z)- and (E)-acrylonitriles were
also supported by NOESY and NOE experiments.
Thus, the NH groups of pyrrole and pyrazole moieties
gave a cross peak in the NOESY spectrum of (E)-acry-
lonitriles 5a, 5b and 5e indicating that they are close to
each other in space (cis geometry). No NH NH cross
peak was observed in the NOESY spectrum of (Z)-
acrylonitrile 4b indicating that they are too far away in
space (trans geometry) to exhibit the dipolar coupling.
All other expected cross peaks were observed in the
NOESY spectra of the acrylonitriles 4b, 5a, 5b and 5e.
Again, irradiation of C-40H in compound 4b gave 4.0%
and 9.1% NOE on C-3H and, C-200H and C-600H,
1
the resonance position of C-3H in the H NMR spectra
and resonance position of C-2 in the 13C NMR spectra
of (E)- and (Z)-acrylonitriles. Smooth extension of
conjugation through C-2 and C-3 double bond increases
s-character and hence electronegativity of these two sp2-
hybridised carbons resulting in the lowering of chemical
shift values of C-3 protons in Z-isomers, C-3H in Z-iso-
mers appears between d 7.73±7.81, while in E-isomers, it
is exhibited at between d 7.31±7.39 (Table 1). Again, in
1
the H NMR spectra of acrylonitrites, the pyrrolic NH
of Z-isomers resonated at lower d values (d11.47±11.60)
than the E-isomers (d13.90±14.10) indicating that the
proton of pyrrolic NH is involved in H-bonding type of
interaction with the nitrogen of pyrazole in the case of

1428
V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
respectively indicating that these protons are closer to
each other in space. Similarly, irradiation of C-3H gave
5.2% NOE on C-40H and 1.4% NOE on C-3000H and C-
5000H (Table 2). These results clearly indicate that C-40H
and C-3H are situated on the same side of the double
bond in compound 4b. Contrary to this, irradiation of C-
40H or C-3H in compound 5e (E-isomer) showed no
NOE on each other (Table 2) indicating that they are on
The Z- and E- structural assignments and proposed
driving force for isomerisation of (Z)-acrylonitriles to
(E)-acrylonitriles is supported by the synthesis of (Z)-
1,3-diarylpyrazolylacrylonitriles 7a±7d by coupling of
pyrrole-2-carboxaldehyde with corresponding 5-cyano-
methyl-1,3-diarylpyrazoles 6a±6d in quantitative yields
(Scheme 3). The compounds 6a±6d were prepared by
condensation of appropriate arylhydrazines with the
corresponding pyranones 2a, 2b, 2e and 2f (Scheme 3) in
45 to 52% yields and identi®ed on the basis of their
spectral analysis. In the diarylpyrazolylacrylonitriles 7a±
7d, the N-1 of pyrazole ring bears an aryl group and
hence pyrrolic NH can not form hydrogen bonding (a
driving force for isomerisation). This indicates that the
E-form will not be an energetically favoured form. The
expected result was observed when a solution of the (Z)-
acrylonitriles 7a±7d in methanol was re¯uxed in the
presence of NaOBut for 48 h without formation of any
traces of (E)-isomers. This proves that the lowering of
energy due to interaction of NH of pyrrole moiety with
the nitrogen of pyrazole moiety is a necessary driving
force for the isomerisation. The structures of (Z)-dia-
rylpyrazolylacrylonitriles 7a±7d were established on the
basis of their spectral analysis. Thus, the 1H NMR
spectra of 7a±7d showed the presence of one D2O-
exchangeable proton as a broad singlet and peaks in the
aromatic region due to two aryl groups. The assign-
ments of 1H NMR spectral signals of compound 7d
were con®rmed by the presence of expected cross peaks
1
the opposite side of the double bond. The H NMR
spectral peak assignments of (E)-acrylonitriles 5b and 5e
were con®rmed by presence of expected cross peaks in
1
their H-1H COSY NMR spectra. The 13C NMR spec-
tral signals of (E)-acrylonitrile 5a were carefully assigned
1
by H-13C correlation (HMQC) experiment (Table 3)
and selective INEPT experiment. The assignments of
carbon signals in the 13C NMR spectra of the (E)-acry-
lonitriles 5b±5h were made accordingly (Table 5).
Table 2. NOE results of compounds 4b, 5e and 7d
Compounds
Proton
irradiated
%
Enhancement
C-200 C-600 C-3H C-3000 C-40 C-5000 N-1000
H
H
H
H
H
H
4b
5e
C-40H
C-3H
9.1 9.1 4.0
Ð
1.4 5.2 1.4
Ð
Ð
Ð
Ð
Ð
2.1
Ð
Ð
Ð
8.5 8.5
Ð Ð
25 25
Ð
Ð
Ð
Ð
Ð
C-40H
C-3H
Ð
7.8
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Ð
N-1000H
C-40H
7d
7.4 7.4 2.9
Ð
1
in its H-1H COSY NMR spectrum. The Z-con®gura-
tion across the double bond in compound 7d was
proved by NOE experiment. Thus, irradiation of signal
at d 6.80 due to C-40H gave 2.9% and 7.4% NOE on C-
3H and, C-200H and C-600H, respectively (Table 2). This
proves that the C-40H and the C-3H are on the same
side of the double bond, i.e. geometry across the double
bond is Z(trans). The observed NOE between C-3H
and C-40H is also con®rmed by the presence of a cross
peak in the NOESY spectrum of 7d due to dipolar cou-
pling of these two protons. The structures of diarylpyr-
azoles 6a±6d and (Z)-diarylpyrazolylacrylonitriles 7a±7d
were also supported by the presence of all relevant
peaks in their 13C NMR spectra (Table 6). All the 5-
Table 3. 1H and 13C correlation (HMQC) for compound 5a
Proton irradiated
Carbon observed
C-4000H (s, 6.38)
C-3000H (6.81)
C-40H (6.96)
C-4000(110.0)
C-3000(119.4)
C-40(102.3), C-30(146.0), C-100(127.9)
and C-2 (121.9)
C-5000H (7.30)
C-3H (7.39)
C-400H (7.42)
C-5000(124.4)
C-3 (131.2), C-1 (93.8) and C-2000(128.1)
C-400(128.8)
C-300H and C-500H(7.51) C-300 and C-500 (129.1)
C-200H and C-600H(7.90) C-200 and C-600(125.6), and C-50(143.5)
Table 4. 13C NMR Chemical-shift values of compounds 4a-4h (Z-
isomers)
Table 5. 13C NMR Chemical-shift values of compounds 5a±5h (E-
isomers)
Carbon No.
4a
4b
4c
4d
4e
4f
4g
4h
Carbon No.
5a
5b
5c
5d
5e
5f
5g
5h
C-1
C-2
95.5 95.5 93.8 93.6 95.2 95.3 93.8 95.5
112.0 111.8 111.9 112.0 111.9 112.1 122.2 112.2
130.9 130.7 131.0 131.3 130.9 131.1 131.4 131.1
147.6 147.4 145.8 148.0 147.6 147.6 145.8 147.4
99.0 98.5 98.0 99.1 99.4 99.6 99.4 100.0
143.6 143.6 143.4 142.6 142.4 143.0 143.5 143.6
128.3 127.1 130.7 130.9 127.6 127.1 124.6 127.0
125.2 125.1 126.6 127.3 126.9 127.1 117.9 130.9
128.9 129.4 114.4 115.8 128.2 131.8 159.8 122.3
128.2 137.8 159.3 163.9 132.8 121.3 111.3 124.2
128.2 129.4 114.4 115.8 128.2 131.8 130.4 130.9
125.2 125.1 126.6 127.3 126.9 127.7 114.9 127.6
127.1 125.1 127.0 127.4 127.0 127.0 127.2 127.6
118.4 118.3 118.3 119.5 118.3 118.2 119.6 118.2
111.1 111.0 111.0 111.1 111.0 111.1 110.6 111.1
123.0 122.9 124.3 124.7 123.1 123.3 124.6 124.2
C-1
C-2
93.8 93.8 93.9 93.7 93.5 93.5 93.7 93.5
121.9 119.5 121.5 121.5 121.2 121.2 121.2 121.1
131.2 131.3 131.3 131.5 131.4 131.9 131.2 131.1
146.0 146.0 146.0 146.2 146.1 146.1 145.9 145.9
102.3 102.0 101.6 102.5 102.7 102.7 102.5 103.1
143.5 143.7 143.6 142.8 142.4 142.4 143.4 142.0
127.9 127.9 128.0 128.1 127.7 127.7 124.4 127.7
125.6 125.2 127.2 127.9 127.3 127.5 117.7 131.4
129.1 129.7 114.6 116.1 129.1 131.9 159.7 122.4
128.8 138.6 159.8 163.9 133.3 121.9 110.9 124.5
129.1 129.7 114.6 116.4 129.1 131.9 130.1 131.7
125.6 125.2 127.2 127.9 127.3 127.5 114.7 130.3
128.1 125.2 127.2 128.1 127.3 127.7 127.8 128.0
119.4 121.4 119.6 119.7 119.4 119.4 119.3 119.4
110.0 111.1 111.1 111.2 111.0 110.9 110.7 110.9
124.4 124.6 124.6 124.8 124.5 124.5 129.3 124.5
C-3
C-30
C-3
C-30
C-400
C-400
C-500
C-100
C-200
C-300
C-400
C-500
C-6
C-500
C-100
C-200
C-300
C-400
C-500
C-6
C-2000
C-3000
C-4000
C-5000
CH3/OCH3
C-2000
C-3000
C-4000
C-5000
CH3/OCH3
Ð
20.7 55.4
Ð
Ð
Ð
55.4
Ð
Ð
20.8 55.4
Ð
Ð
Ð
55.2
Ð

V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
1429
Scheme 3. Reagents and conditions: (i) PhNHNH2 HCl/p-FC6H4NHNH2HCl, MeOH/ pyridine, re¯uxing 5-6 hrs; (ii) EtOH, NaOBut, pyrrole-2-
carboxaldehyde, re¯uxing 4-5 hrs.
Table 6. 13C NMR Chemical-shift values of compounds 6a±6d and
7a±7d
crystallographic studies. Similarly, the structures of the
three lactones, 3-cyano-6-(4-¯uorophenyl)-4-methylthio-
2H-pyran-2-one (2d), 3-cyano-6-(3-methoxyphenyl)-4-
methylthio-2H-pyran-2-one (2g) and 6-(3-bromophe-
nyl)-3-cyano-4-methylthio-2H-pyran-2-one (2h), and a
Carbon
No.
6a
6b
6c
6d Carbon 7a
No.
7b
7c
7d
C-3
C-4
152.8 152.8 151.5 151.6 C-1 119.0 119.3 119.3 119.0
105.7 105.6 105.7 105.7 C-2 90.6 91.0 91.0 89.9
pyrazole,
3-cyanomethyl-5-(4-methylphenyl)pyrazole
(3b) were ®nally con®rmed by X-ray crystallographic
studies. The schematic representation of the molecular
structures of the pyran-2-one 2d, pyrazole 3b and (E)-
acrylonitrile 5h are shown in Figures 1±3, respectively;
the structures of 2g,31 2h,27 5h32 and 6b25 have been
reported elsewhere. The crystal structure of (E)-acrylo-
nitrile 5h depicted in Figure 3 clearly exhibits the E-
geometry across the acrylonitrile double bond and also
reveals that in the solid state, an additional tautomer is
possible in which the proton at N-10 has migrated to N-20
(Fig. 3). Con®rmation of the spectroscopically established
structures of lactones 2d, 2g and 2h, pyrazoles 3b and 6b,
and of acrylonitrile 5h by X-ray crystallography supports
the structure deduction of all other acrylonitriles and their
precursors.
C-5
C-6
C-7
133.2 133.1 133.1 131.6 C-3 136.2 136.0 136.2 136.4
16.7 16.7 16.7 16.6 C-30 152.1 152.0 151.5 152.1
116.1 116.1 116.1 115.8 C-40 105.9 105.3 105.3 105.2
112.8 124.4 124.4 117.4 C-50 133.1 138.6 139.7 132.3
129.2 129.9 129.4 127.7 C-100 125.6 125.5 125.9 127.8
125.7 125.7 127.5 132.3 C-200 126.3 129.9 129.9 137.3
128.8 130.5 134.5 122.9 C-300 129.2 126.9 127.5 127.7
125.7 125.7 127.5 132.3 C-400 128.8 129.9 134.5 122.8
129.2 129.9 129.4 127.7 C-500 129.2 126.9 127.5 127.7
138.1 138.1 134.4 133.6 C-600 126.3 129.9 129.4 132.3
130.1 130.1 130.2 127.9 C-1000 138.1 138.6 138.9 135.6
126.2 126.1 125.7 117.0 C-2000 129.9 129.9 129.9 128.0
129.4 129.3 129.5 165.5 C-3000 126.0 126.0 126.0 116.7
126.2 126.1 125.7 117.0 C-4000 129.0 129.0 127.5 163.0
130.1 130.1 130.2 127.9 C-5000 126.0 126.0 126.0 116.7
C-10
C-20
C-30
C-40
C-500
C-600
C-100
C-200
C-300
C-4
C-500
C-600
CH3
Ð
21.8
Ð
Ð
C-6000 129.9 129.9 129.9 128.0
C-20000 139.4 139.7 139.7 139.1
C-30000 120.6 120.5 120.9 121.1
C-40000 111.6 111.6 111.7 111.8
C-50000 125.8 127.0 127.5 125.9
Antioxidant activity studies
CH3
Ð
20.5
Ð
Ð
Five pyranones, i.e. 2a, 2b, 2d, 2g and 2h, seven 5-aryl-
pyrazoles 3a±3f and 3h, three 1,3-diarylpyrazoles 6a±6c
and all twenty acrylonitrites 4±4h, 5a±5h and 7a±7d
have been tested for their e€ect on NADPH-catalysed
rat liver-microsomal lipid peroxidation. Svingen et al.33
have demonstrated that NADPH-dependent lipid per-
oxidation proceeds through the formation of lipid
hydroperoxides, called initiation step followed by pro-
pagation step which involves the breakdown of hydro-
peroxides yielding reactive radicals and oxidised
products. We have investigated the e€ect of above pyr-
anones and pyrazole derivatives at both initiation and
propagation steps. NADPH-dependent liver microsomal
arylpyrazolylacrylonitriles 4a±4h and 5a±5h, 1,3-dia-
rylpyrazoles 6a±6d and 1,3-diarylpyrazolylacrylonitriles
7a±7d have been found to be new compounds.
X-ray crystallography
The structures determined on the basis of spectral ana-
lysis of the new pyrazole, 5-cyanomethyl-3-(4-methyl-
phenyl)-1-phenylpyrazole (6b), and the new pyrazo-
lylacrylonitrile (E)-2-[5-(3-bromophenyl)pyrazol-3-yl]3-
(pyrrol-2-yl)acrylonitrile (5h) were con®rmed by X-ray

1430
V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
Table 7. Inhibitory e€ect of pyranones and cyanomethylpyrazoles on
lipid peroxidation in rat liver microsomes initiated by NADPH
Compound
% Inhibition
of initiation
Compound
% Inhibition
of initiation
2a
2b
2d
2g
2h
3a
3b
3c
3
14
4
14
18
33
31
35
3d
3e
3f
3h
6a
6b
6c
27
33
10
18
33
33
26
Table 8. Inhibitory e€ect of 2-pyrazolyl-3-(pyrrol-2-yl)acrylonitriles
on lipid peroxidation in rat liver microsomes initiated by NADPH
Figure 1. X-ray crystal structure of 3-cyano-6-(4-¯ourophenyl)-4-
methylthio-2H-pyran-2-one (2d).
Compound
% Inhibition
of initiation
Compound
% Inhibition
of initiation
4a
5a
4b
5b
4c
5c
4d
5d
4e
5e
53
73
69
95
52
67
20
62
42
69
4f
5f
42
68
27
90
77
68
36
48
87
80
4g
5g
4h
5h
7a
7b
7c
7d
Figure 2. X-ray crystal structure of 3-cyanomethyl-5-(4-methylphe-
nyl)pyrazole (3b).
the activity over its precursor pyrazole 6c, activity of
compounds 7a and 7b remained comparable to their
precursor pyrazoles 6a and 6b, respectively.
Normally the antioxidant property of a compound is
attributed to its (a) oxygen radical scavenging ability,
(b) ability to inhibit cellular microsomal P-450-linked
mixed function oxidation (MFO) reaction and (c) abil-
ity to suppress the formation of reactive oxygen species
(ROS). Pyrazolylacrylonitriles have neither radical
scavenging ability nor can they inhibit MFO (data not
shown). But there exists the possibility of pyr-
azolylacrylonitriles forming a stable mixed ligand com-
plex with ADP and Fe2+ (see Experimental) thereby
preventing the production of ADP-perferryl radical
responsible for ROS formation as we have shown earlier
in the case of dioxygenated 4-methylcoumarins.35±37 E-
Isomers of acrylonitriles have demonstrated much
higher antioxidant activity than Z-isomers, possibly
because they can form more stable mixed ligand com-
plex with ADP and Fe2+ as compared to those formed
by the corresponding Z-isomers.
Figure 3. (E)-2-[5-(3-Bromophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)-acry-
lonitrile (5h).
lipid peroxidation was assayed by the method of Ernster
and Nordenbrand.34 All activity testings have been car-
ried out at 100 mM concentrations. The results (Table 7)
illustrate that the pyranones 2a, 2b, 2d, 2g and 2h do not
exhibit signi®cant activity to inhibit the initiation of
NADPH-catalysed peroxidation of lipids of rat liver-
microsomes. Whereas conversion of pyranones to 3-
arylpyrazoles 3a±3f and 3h and to 1,3-diarylpyrazoles
6a±6c increases the activity by 0 to 11 fold in di€erent
cases, the maximum increase in activity has been
observed in pyrazoles with unsubstituted phenyl ring/
rings derived from the corresponding pyranones. The
antioxidant activity of 5-arylpyrazoles and 1,3-dia-
rylpyrazoles are comparable. Z- and E-Pyrazolylacry-
lonitriles (4a±4h and 5a±5h) showed 3±4 fold increase in
their antioxidant activity over the activity of the
respective precursor (Table 8). Though diarylpyr-
azolylacrylonitrile 7c exhibits a signi®cant increase in
Among all lactones and pyrazole derivatives tested for
their antioxidant activity, (E)-2-[5-(4-methylphenyl)
pyrazol-3-yl]-3-(pyrrol-2-yl)acrylonitrile (5b) and (E)-2-
[5-(3-methoxyphenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)acry-
lonitrile (5g) exhibit very high degree of inhibition, i.e.
95 and 90%, respectively of the NADPH-catalysed lipid
peroxidation in rat liver microsomes at the initiation
stage (Table 8). The IC50 values for inhibition of lipid-
hydroperoxide formation (Table 9) and activity of inhi-
bition at propagation stage of NADPH-catalysed lipid

V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
1431
Table 9. Antioxidant potential of 2-pyrazolyl-3-(pyrrol-2-yl)acrylo-
nitriles
and IR spectra were recorded on Beckmann DU-2
spectrophotometer and Shimadzu model 435 spectro-
photometer, respectively. The 1H NMR spectra were
recorded either at Perkin±Elmer 200, Bruker AC-250 or
XL-400 instruments at 200, 250 or 400 MHz, respec-
tively. The 13C NMR spectra were recorded on same
Compound
aIC50 (m moles)
Compound
aIC50 (m moles)
4b
4h
5a
5b
5c
5d
9.1
2.1
18.3
8.7
18.1
31.6
5e
5f
5g
5h
7c
7d
12.6
8.7
5.8
12.0
6.6
15.4
1
instruments as for H NMR spectral recordings either
at 50, 62.8 or 100 MHz. TMS has been used as an
1
internal standard for both H and 13C NMR spectral
recordings. The chemical shift values are on d scale and
the coupling constants (J) are in Hz. The 1H-1H COSY,
NOE, NOESY and HMQC NMR studies were per-
formed on a XL-400 or GE-400 spectrometer. The EI
mass spectra were recorded either on a varian MAT
311A or Jeol AX 505W mass spectrometer at 70 eV.
Analytical TLCs were performed on silica gel coated on
5Â20 cm glass plates and/or on precoated Merck silica
gel 60 F254 plates. Solvent systems used for Rf measure-
ments were A (ethyl acetate:benzene, 1:9) and B (ethyl
acetate:benzene, 1:19). The developing agents were
alcoholic FeCl3 solution (3%) or iodine vapours. Reac-
tions were monitored on Shimadzu LC-10AS HPLC
instrument with SPD-10A UV±vis detector and Shim-
pack CLC-ODS (4.6Â150 mm) reverse phase column.
Solvent system used for HPLC was methanol:water
mixture (7:3) at the ¯ow rate of 0.75 mL/min and mon-
itored at 254 nM. 6-Aryl-3-cyano-4-thiomethyl-2H-
pyran-2-ones 2a±2h were prepared according to the
procedure given in our earlier publication27 in three
steps starting with the condensation of carbon disul®de
and ethyl cyanoacetate and dimethylation of disodio
salt leading to 1, followed by condensation with corre-
sponding acetophenones.
aIC50 values are calculated only for those compounds who have shown
more than 60% inhibition at initiation step.
Table 10. Inhibitory e€ect of 2-pyrazolyl-3-(pyrrol-2- yl)acrylonitriles
on linoleic acid hydroperoxide induced lipid peroxidation
Compound
% Inhibition of
propagation
Compound
% Inhibition of
propagation
4b
4h
5a
5b
5c
5d
72.3
11.2
11.2
30.6
29.8
5.6
5e
5f
5g
5h
7c
7d
10.0
37.1
19.5
26.2
11.1
37.8
peroxidation in rat liver microsomes (Table 10) have
been evaluated only for those compounds which have
shown more than 60% inhibition of lipid peroxidation at
the initiation stage. The minimum IC50 value, i.e. 2.1 has
been measured for (Z)-2-[5-(3-bromophenyl)pyrazol-3-yl]
-3-(pyrro-2-yl)acrylonitrile (4h) for the inhibition at
initiation stage.
General method of preparation of 5-aryl-3-cyanomethyl-
pyrazoles 3a±3h. To a solution of 6-aryl-3-cyano-4-
methylthio-2H-pyran-2-ones (2a±2h, 6 mmol) in metha-
nol (30 ml), hydrazine monohydrate (9 mmol) was added
and the reaction mixture was re¯uxed for 5±6 h. The
progress of the reaction was monitored on HPLC and/
or on TLC. The reaction mixture was concentrated on
completion under reduced pressure, poured over cru-
shed ice (200 g) and stirred vigorously until a brownish-
yellow solid precipitated out. It was ®ltered, washed
with water (2Â25 mL), dried, and column chromato-
graphed over silica gel using ethyl acetate±petroleum
ether as eluent to a€ord 3a±3h27 as white solids, which
were crystallised from ethyl acetate to white shining
needles in 50 to 60% yields.
Conclusion
A facile synthetic procedure has been developed for the
synthesis of a new class of heterocyclic compounds, i.e.
(Z)- and (E)-2-(5-arylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylo
nitriles and (Z)-2-(1,3-diarylpyrazol-5-yl)-3-(pyrrol-2-
yl)acrylonitriles. The mechanism of isomerisation of (Z)-
2-(5-arylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitriles into
the corresponding E-isomers has been proposed on the
basis of investigations carried out. In total twenty four
new/novel compounds have been synthesised and sub-
jected to screening of their activity as antioxidants for
inhibition of NADPH-catalysed peroxidation of rat
liver microsomes which led to the identi®cation of aryl-
pyrazolylacrylonitriles 5b, 5g and 4h as highly potent
compounds. Again, this activity evaluation has revealed
that methyl- or methoxyphenylpyrazolylacrylonitriles
5b and 5g are better antioxidants than unsubstituted, or
¯uoro- or chloro substituted phenylpyrazolylacryloni-
triles. These acrylonitriles may be of signi®cance for the
development of a clinical antioxidant agent.
General method of preparation of (Z)-2-(5-arylpyrazol-
3-yl)-3-(pyrrol-2-yl)acrylonitriles 4a±4h. To a solution
of 5-aryl-3-cyanomethylpyrazoles27 3a±3h (1.5 mmol) in
ethanol (20 mL), NaOBut (1.5 mmol) was added, and
reaction mixture was stirred for 15 min at 25±30ꢀC
followed by addition of pyrrole-2-carboxaldehyde
(1.5 mmol) in one lot. Stirring was continued for 4±5 h
and progress of the reaction was monitored on HPLC
and/or on TLC. The reaction mixture was con-
centrated on completion under reduced pressure and
poured over crushed ice (50 g), when a yellow solid pre-
cipitated out. It was ®ltered, washed with water
(2Â25 mL), dried over P2O5 in a vacuum desiccator and
Experimental
Melting points were determined either in a bath or on a
Mettler FP62 instrument and are uncorrected. The UV

1432
V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
crystallised to a€ord pure acrylonitriles 4a±4h in almost
quantitative yields.
m/z (% rel. int.): 278 [M+] (100), 277(47), 250(15),
249(8), 222(5), 194(2), 183(2), 156(10), 139(3), 129(5),
122(4), 95(5), 75(3) and 39(2).
(Z)-2-(5-Phenylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitrile
(4a). Crystallised from acetone as a yellow powder
(351 mg, 90%), mp 209±10 ꢀC; Rf 0.40 (solvent A); IR
(Nujol): 3594, 3490, 3420, 3139, 2208, 1728, 1682, 1608,
1538, 1497, 1325, 1124, 1096, 1029, 972, 880 and
742 cm 1; UV (MeOH): 206, 248 and 362 nM; 1H NMR
(400 MHz, DMSO-d6): d 6.38 (1H, brs, C-4000H), 6.91
(1H, s, C-40H), 7.15 (1H, brs, C-3000H), 7.20 (1H, brs, C-
5000H), 7.39 (1H, m, C-400H), 7.49 (2H, m, C-300H and C-
500H), 7.81 (3H, m, C-3H, C-200H and C-600H), 11.55
(1H, brs, N-1000H) and 13.50 (1H, brs, N-10H); 13C
NMR (100 MHz, DMSO-d6): Table 4; EIMS, m/z (rel.
int.): 260 [M+](100), 259(51), 232(18), 217(44), 204(12),
183(4), 177(5), 156(17), 149(9), 130(7), 129(10), 104(13),
89(9), 77(25), 51(18) and 43(36).
(Z)-2-[5-(4-Chlorophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylonitrile (4e). Crystallised from acetone as a yellow
powder (409 mg, 94%), mp 243±46 ꢀC; Rf 0.41 (solvent
A); IR (Nujol): 3402, 3316, 3191, 2729, 2360, 2228,
1
1727, 1271, 1253, 1208, 1150, 840, 780 and 729 cm
;
UV (MeOH): 206, 254 and 363 nM; 1H NMR
(250 MHz, DMSO-d6): d 6.33 (1H, brs, C-4000H), 6.92
(1H, s, C-40H), 7.14 (2H, brs, C-3000H and C-5000H), 7.54
(2H, d, J=8.1 Hz, C-300H and C-500H), 7.75 (1H, s, C-
3H), 7.82 (2H, d, J=8.1 Hz, C-200H and C-600H), 11.50
(1H, brs, N-1000H) and 13.51 (1H, brs, N-10H); 13C
NMR (62.8 MHz, DMSO-d6): Table 4; EIMS, m/z (%
rel. int.): 296 [M++2](33), 295(31), 294 [M+] (100),
293(41), 266(4), 258(3), 238(1), 231(15), 204(4), 183(2),
176(2), 156(12), 138(5), 129(7), 111(4), 88(3), 75(6) and
55(4).
(Z)-2-[5-(4-Methylphenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylonitrile (4b). Crystallised from acetone as a yellow
powder (369 mg, 90%), mp 215 ꢀC; Rf 0.42 (solvent A);
IR (Nujol): 3603, 3176, 2361, 2219, 1726, 1598, 1533,
1342, 1118, 1037, 1020, 908, 789 and 730 cm 1; UV
(Z)-2-[5-(4-Bromophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylonitrile (4f). Crystallised from acetone as a yellow
powder (467 mg, 91%), mp 233±35 ꢀC; Rf 0.42 (solvent
A); IR (Nujol): 3402, 3316, 2228, 1600, 1520, 1320,
1295, 1195, 1120, 1100, 1040, 980, 835, 800 and
740 cm 1; UV (MeOH): 209, 257 and 362 nM; 1H NMR
(250 MHz, DMSO-d6): d 6.34 (1H, brs, C-4000H), 6.92
(1H, s, C-40H), 7.14 (2H, brs, C-3000H and C-5000H), 7.67
(2H, d, J=8.5 Hz, C-300H and C-500H), 7.73 (1H, s, C-
3H), 7.77 (2H, d, J=8.5 Hz, C-200H and C-600H), 11.52
(1H, brs, N-1000H), 13.50 (1H, brs, N-10H); 13C NMR
(62.8 MHz, DMSO-d6): Table 4; EIMS, m/z (% rel.
int.): 340 [M++2] (94), 339(47), 338 [M+](100),
337(34), 310(3), 261(14), 250(7), 231(26), 204(11),
183(3), 176(9), 156(25), 149(19), 129(15), 109(36),
89(11), 77(35) and 43(51).
1
(MeOH): 209, 254 and 362 nM; H NMR (400 MHz,
DMSO-d6: 2.34 (3H, s, CH3), 6.33 (1H, brs, C-4000H),
6.82 (1H, s, C-40H), 7.15 (2H, brs, C-3000H and C-5000H),
7.29 (2H, d, J=7.8 Hz, C-300H and C-500H) 7.70 (2H, d,
J=7.8 Hz, C-200H and C-600H), 7.78 (1H, s, C-3H), 11.60
(1H, brs, N-1000H) and 13.30 (1H, brs, N-10H); 13C
NMR (62.8 MHz, DMSO-d6): Table 4; EIMS, m/z (%
rel. int.): 274[M+](100), 273(49), 258(4), 246(8), 231(4),
204(1), 183(1), 156(7), 137(4), 129(3), 118(3), 91(3),
77(1) and 39(2).
(Z)-2-[5-(4-Methoxyphenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylonitrile (4c). Crystallised from acetone as a yellow
powder (395 mg, 91%), mp 210±11 ꢀC. Rf 0.42 (solvent
A); IR (Nujol): 3604, 3321, 3175, 2360, 2219, 1725,
1605, 1270, 1133, 1020, 965, 816, 783 and 728 cm 1. UV
(Z)-2-[5-(3-Methoxyphenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylonitrile (4g). Crystallised from acetone as a yellow
powder (391 mg, 90%), mp 158±60 ꢀC; Rf 0.42 (solvent
A); IR (Nujol): 3605, 3404, 2360, 2208, 1726, 1607,
1588, 1537, 1328, 1311, 1274, 1169, 1128, 1097, 1038,
970, 940, 864, 832 and 772 cm 1; UV (MeOH): 209, 251
1
(MeOH): 206, 260 and 362 nM, H NMR (250 MHz,
DMSO-d6): d 3.81 (3H, s, OCH3), 6.33 (1H, brs, C-
4000H), 6.77 (1H, s, C-40H), 7.04 (2H, d, J=8.5 Hz, C-
300H and C-500H), 7.13 (2H, brs, C-3000H and C-5000H),
7.72 (2H, d, J=8.5 Hz, C-200H and C-600H), 7.74 (1H, s,
C-3H), 11.47 (1H, brs, N-1000H) and 13.20 (1H, brs, N-
10H); 13C NMR (62.8 MHz, DMSO-d6): Table 4; EIMS,
m/z (% rel. int.): 290 [M+](100), 289(38), 274(3), 262(6),
247(2), 231(2), 191(1), 183(7), 156(5), 145(5), 134(2),
129(3), 102(1), 77(1) and 39(2).
1
and 362 nM; H NMR (400 MHz, DMSO-d6): d 3.83
(3H, s, OCH3), 6.33 (1H, brs, C-4000H), 6.91 (1H, s, C-
40H), 6.94 (1H, m, C-400H), 7.13 (2H, brs, C-3000H and
C-5000H), 7.37±7.38 (3H, m, C-200H, C-500H and (C-600H),
7.75 (1H, s, C-3H), 11.48 (1H, brs, N-1000H) and 13.43
(1H, s, N-10H); 13C NMR (62.8 MHz, DMSO-d6):
Table 4; EIMS, m/z (% rel. int.): 290 [M+](100),
289(91), 274(8), 262(10), 247(5), 217(5), 191(4), 183(2),
162(10), 156(7), 145(5), 129(3), 102(2), 95(1), 77(2) and
39(2).
(Z)-2-[5-(4-Fluorophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylotnitrile (4d). Crystallised from acetone as yellow
needles (370 mg, 88%), mp 210 ꢀC; Rf 0.40 (solvent A);
IR (Nujol): 3500, 3310, 2342, 2210, 1726, 1608, 1500,
1
1155, 1120, 1102, 1020, 965, 880, 835, 800 and 735 cm
;
(Z)-2-[5-(3-Bromophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylonitrile (4h). Crystallised from acetone as yellow
plates (484mg, 95%), mp 239 ꢀC; Rf 0.42 (solvent A); IR
(Nujol): 3631, 3429, 2361, 2206, 1726, 1611, 1579, 1170,
1123, 1103, 1036, 1020, 969, 876, 723 and 679 cm 1; UV
(MeOH): 208, 254 and 360 nM; 1H NMR (250MHz,
DMSO-d6): d 6.33 (1H, brs, C-4000H), 6.99 (1H, s, C-400H),
7.14 (2H, brs, C-3000 and C-5000H), 7.42 (1H, t, J=7.9 Hz, C-
UV (MeOH): 208, 245 and 362 nM; 1H NMR
(250 MHz, DMSO-d6): d 6.33 (1H, brs, C-4000H), 6.87
(1H, s, C-40H), 7.13 (2H, brs, C-3000 and C-5000H), 7.31
(2H, t, J=8.6 Hz, C-300H and C-500H), 7.74 (1H, s, C-
3H), 7.85 (2H, dd, J=5.5 and 8.6 Hz, C-200H and C-
600H), 11.49 (1H, brs, N-1000H) and 13.40 (1H, brs, N-
10H); 13C NMR (62.8 MHz, DMSO-d6): Table 4; EIMS,

V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
1433
500H), 7.55 (1H, d, J=7.9 Hz, C-400H), 7.73 (1H, s, C-3H),
7.80 (1H, d, J=7.9 Hz, C-600H), 8.04 (1H, brs, C-200H),
11.51 (1H, brs, N-1000H) and 13.50 (1H, brs, N-10H); 13C
NMR (62.8 MHz, DMSO-d6): Table 4; EIMS, m/z (% rel.
int.): 340 [M++2] (2), 338 [M+] (3), 256(4), 250(5),
218(57), 205(3), 185(5), 156(1), 154(8), 125(5), 109(100),
77(50) and 39(44).
(1H, brs, N-1000H); 13C NMR (62.8 MHz, DMSO-d6):
Table 5; EIMS, m/z (% rel. int.): 274 [M+](100), 273(59),
258(5), 246(11), 137(4), 231(5), 203(1),183(1), 182(1),
156(9), 137(4), 129(4), 118(4), 115(3), 91(5), 73(2), 65(41)
and 43(7).
(E)-2-[5-(4-Methoxyphenyl)pyrazol-3-yl]-3-(pyrrol-2-
yl) acrylonitrile (5c). Crystallised from acetone as a yel-
low powder (239 mg, 55%), mp 159 ꢀC; Rf 0.64 (solvent
A); IR (Nujol): 3325, 3174, 2342, 2219, 1726, 1605,
1270, 1163, 1133, 1049, 1024, 964, 901, 883, 815, 774
General method for isomerisation of (Z)-acrylonitriles 4a±
4h to (E)-acrylonitriles 5a±5h. (Z)-2-(5-Arylpyrazol-3-yl)-
3-(pyrrol-2-yl)acrylonitrile 4a±4h (0.15 mmol) was added
to a solution of NaOBut (48 mg, 0.5 mmol) in ethanol
(20 mL) and the solution re¯uxed for 24h. The TLC
showed almost complete conversion of the Z-isomer to E-
isomer. The reaction mixture was concentrated under
reduced pressure, poured over crushed ice, when a yellow
solid precipitated out. It was ®ltered, washed with water
and dried over P2O5 in a vacuum desicator, puri®cation of
the crude product by column chromatography a€orded
5a±5h in 80±85% yields.
1
and 724 cm 1; UV (MeOH): 209, 260 and 356 nM; H
NMR (250 MHz, DMSO-d6): d 3.81 (3H, s, OCH3),
6.33 (1H, brs, C-4000H), 6.78 (1H, brs, C-3000H), 6.81 (1H,
s, C-40H), 7.05 (2H, d, J=8.8 Hz, C-300H and C-500H),
7.28 (1H, brs, C-5000H), 7.32 (1H, s, C-3H), 7.79 (2H, d,
J=8.8 Hz, C-200H and C-600H), 13.34 (1H, brs, N-10H)
and 13.90 (1H, brs, N-1000H); 13C NMR (62.8 MHz,
DMSO-d6). Table 5; EIMS, m/z (% rel. int.): 290 [M+]
(100), 289(39), 274(3), 262(7), 246(2), 231(3), 183(1),
156(6), 145(3), 134(3), 129(3), 73(5), 60(6) and 43(7).
General method of preparation of (E)-2-(5-arylpyrazol-3-
yl)-3-(pyrrol-2-yl)acrylonitriles 5a±5h. To a solution of
5-aryl-3-cyanomethylpyrazole 3a±3h (1.5 mmol) in
ethanol (20 mL), NaOBut (1.5 mmol) was added fol-
lowed by addition of pyrrole-2-carboxaldehyde
(1.5 mmol) and the reaction mixture was re¯uxed for 20±
25 h. The progress of the reaction was monitored on
HPLC and/or on TLC, the reaction was worked up as in
the case of preparation of Z-isomers; yellow crude pro-
duct obtained was puri®ed by column chromatography
with a solvent system of petroleum ether and ethyl ace-
tate. Elution of the column with 5% and 10% ethyl ace-
tate in petroleum ether a€orded compounds 5a±5h and
4a±4h as the major and minor products, respectively.
(E)-2-[5-(4-Fluorophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)-
acrylonitrile (5d). Crystallised from acetone as a yellow
powder (216mg, 52%), mp 188 ꢀC; Rf 0.60 (solvent A); IR
(Nujol): 3200, 3190, 2228, 1600, 1400, 1340, 1320, 1255,
1235, 1140, 1080, 1035, 980, 835, 780 and 720 cm 1; UV
(MeOH): 209, 248 and 353 nM; 1H NMR (250MHz,
DMSO-d6): d 6.33 (1H, brs, C-4000H), 6.79 (1H, brs, C-
3000H), 6.91 (1H, s, C-40H), 7.28 (1H, brs, C-5000H), 7.34
(1H, s, C-3H), 7.37 (2H, d, J=8.5 Hz, C-300H and C-500H),
7.90 (2H, d, J=8.5 Hz, C-200H and C-600H), 13.24 (1H, brs,
N-10H) and 13.90 (1H, brs, N-1000H); 13C NMR
(62.8 MHz, DMSO-d6: Table 5; EIMS, m/z (% rel. int.):
278 [M+] (100), 277(47), 250(15), 249(6), 222(4), 208(1),
194(1), 183(1), 156(10), 139(3), 129(5), 122(4), 102(1),
95(4), 75(3) and 41(6).
(E)-2-(5-Phenylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitrile
(5a). Crystallised from acetone as a light yellow powder
(206 mg, 53%), mp 165±66 ꢀC; Rf 0.62 (solvent A); IR
(Nujol): 3316, 3191, 2729, 2360, 2228, 1783, 1727, 1600,
1410, 1339, 1150, 1088, 1039, 986, 959, 871, 840, 799, 770
(E)-2-[5-(4-Chlorophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)-
acrylonitrile (5e). Crystallised from acetone as a yellow
powder (266 mg, 60%), mp 226±29 ꢀC. Rf 0.61 (solvent
A); IR (Nujol): 3593, 3245, 2725, 2359, 2216, 1724,
1599, 1269, 1153, 829, 787 and 725 cm 1; UV (MeOH):
1
and 729 cm 1; UV (MeOH): 209, 248 and 353 nM; H
NMR (400 MHz, DMSO-d6): d 6.38 (1H, brs, C-4000H),
6.81 (1H, brs, C-3000H), 6.96 (1H, s, C-40H), 7.30 (1H,
brs, C-5000H), 7.39 (1H, s, C-3H), 7.42 (1H, m, C-400H),
7.51 (2H, m, C-300H and C-500H), 7.90 (2H, d, J=7.0 Hz,
C-200H and C-600H), 13.36 (1H, brs, N-10H), 14.02 (1H,
brs, N-1000H); 13C NMR (100 MHz, DMSO-d6): Table 5;
EIMS, m/z (% rel. int.): 260 [M+](100), 259(53), 232(18),
204(10), 183(4), 176(5), 156(17), 140(2), 130(7), 129(12),
104(13), 90(4), 77(33), 51(23) and 43(32).
1
209, 260 and 356 nM; H NMR (250 MHz, DMSO-d6):
d 6.32 (1H, brs, C-4000H), 6.79 (1H, brs, C-3000H), 6.97
(1H, s, C-40H), 7.28 (1H, brs, C-5000H), 7.34 (1H, s, C-
3H), 7.57 (2H, d, J=8.5 Hz, C-300H and C-500H), 7.89
(2H, d, J=8.5 Hz, C-200H and C-600H), 13.20 (1H, brs,
N-10H) and 14.10 (1H, brs, N-1000H); 13C NMR
(62.8 MHz, DMSO-d6): Table 5; EIMS, m/z (% rel.
int.): 296 [M++2](34), 295(32), 294 [M+](100), 293(43),
278(4), 266(4), 258(4), 243(10), 231(15), 203(7), 183(2),
156(14), 138(7), 149(20), 129(8), 111(6), 83(6), 75(11)
and 43(73).
(E)-2-[5-(4-Methylphenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)
acrylonitrile (5b). Crystallised from acetone as yellow
needles (234 mg, 57%), mp 173 ꢀC; Rf 0.60 (solvent A);
IR (Nujol): 3272, 2360, 2211, 1726, 1605, 1583, 1533,
1
(E)-2-[5-(4-Bromophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)-
acrylonitrile (5f) . Crystallised from acetone as a yellow
powder (305 mg, 60%), mp 225 ꢀC; Rf 0.62 (solvent A);
IR (Nujol): 3254, 2200, 1600, 1340, 1126, 1060, 1020,
993, 820, 780, 743 and 720 cm 1; UV (MeOH): 209, 260
1342, 1120, 1093, 1035, 986, 906, 786 and 723 cm
;
UV (MeOH): 206, 254 and 356 nM; 1H NMR
(400 MHz, DMSO-d6): d 2.35 (3H, s, CH3), 6.34 (1H,
brs, C-4000H), 6.80 (1H, brs, C-3000H), 6.88 (1H, s, C-40H),
7.30 (1H, brs, C-5000H), 7.31 (1H, s, C-3), 7.33 (2H, d,
J=8.1 Hz, C-300H and C-500H), 7.75 (2H, d, J=8.1 Hz,
C-200H and C-600H), 13.32 (1H, brs, N-10H) and 13.90
1
and 356 nM; H NMR (250 MHz, DMSO-d6): d 6.33
(1H, t, J=2.9 Hz, C-4000H), 6.77 (1H, brs, C-3000H), 6.97
(1H, s, C-40H), 7.28 (1H. brs, C-5000H), 7.35 (1H, s, C-

1434
V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
3H), 7.68 (2H, d, J=8.5Hz, C-300H and C-500H), 7.81 (2H,
d, J=8.6 Hz, C-200H and C-600H), 13.20 (1H, brs, N-10H)
and 13.90 (1H, brs, N-1000H); 13C NMR (62.8 MHz,
DMSO-d6): Table 5; EIMS, m/z (% rel. int.): 340 [M++2]
(96), 339(50), 338 [M+](100), 337(35), 310(3), 358(14),
231(25), 203(7), 183(3), 176(5), 156(21), 151(4), 129(13),
102(10), 88(8), 75(11) and 39(8).
C-600H); 13C NMR (50 MHz, CDCl3): Table 6; EIMS, m/z
(% rel. int.): 259[M+] (100), 231(59), 219(20), 204(5),
180(7), 155(25), 129(10), 116(30), 89(22) and 77(60).
5-Cyanomethyl-3-(4-methylphenyl)-1-phenylpyrazole (6b).
Crystallised from acetone as white needles (737mg,
45%), mp 115±16 ꢀC; Rf 0.54 (solvent B); IR (Nujol):
2724, 2341, 1712, 1595, 1377, 795 and 723 cm 1; UV
(MeOH): 213 and 265 nM; 1H NMR (200MHz, CDCl3):
d 2.37 (3H, s, CH3), 3.77 (2H, s, C-6H), 6.82 (1H, s, C-4H),
7.24 (2H, d, J=8.0 Hz, C-30H and C-50H), 7.45±7.56 (5H,
m, Ar00H) and 7.73 (2H, d, J=8.0 Hz, C-20H and C-60H),
13C NMR (50 MHz, CDCl3): Table 6; EIMS, m/z (% rel.
int.): 273 [M+] (100), 259(18), 245(45), 233(25), 194(5),
155(20), 130(20), 116(18), 91(20) and 77(37).
(E)-2-[5-(3-Methoxyphenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)-
acrylonitrile (5g). Crystallised from acetone as a light
yellow powder (243 mg, 56%), mp 155 ꢀC; Rf 0.64
(solvent A); IR (Nujol): 3253, 2359, 2212, 1727, 1592,
1573, 1533, 1308, 1271, 1145, 1092, 1048, 980, 901, 857,
842, 785 and 766 cm 1; UV (MeOH): 212, 254 and
1
356 nM; H NMR (400MHz, DMSO-d6): d 3.84 (3H, s,
OCH3), 6.33 (1H, brs, C-4000H), 6.79 (1H, brs, C-3000H), 6.96
(1H, s, C-40H), 6.98 (1H, d, J=8.4 Hz, C-40H), 7.28 (1H,
brs, C-5000H), 7.34 (1H, s, C-3H), 7.36±7.44 (3H, m, C-200H,
C-500H and C-600H), 13.27 (1H, brs, N-10H) and 13.90
(1H, brs, N-1000H); 13C NMR (62.8MHz, DMSO-d6):
Table 5; EIMS, m/z (% rel. int.): 290 [M+](100), 289(53),
274(5), 262(7), 246(3), 217(3), 203(1), 190(2), 183(1),
156(8), 145(5), 134(3), 129(4), 102(2), 73(7) and 44(9).
5-Cyanomethyl-3-(4-chlorophenyl)-1-phenylpyrazole (6c).
Crystallised from acetone as white needles (814mg, 46%),
mp 83±84 ꢀC; Rf 0.50 (solvent B); IR (Nujol): 2359, 1597,
1500, 830, 804, 785, 763 and 699 cm 1; UV (MeOH): 212
and 265 nM; 1H NMR (200MHz, CDCl3): d 3.77 (2H, s,
C-6H), 6.82 (1H, s, C-4H), 7.39 (2H, d, J=8.4 Hz, C-30H
and C-50H), 7.44±7.51 (5H, m, H) and 7.78 (2H, d,
J=8.4Hz, C-20H and C-60H); 13C NMR (50 MHz,
CDCl3): Table 6; EIMS, m/z (% rel. int.): 295 [M++2]
(30), 293 [M+] (100), 277(25), 265(18), 231(23), 198(5),
155 (6), 116(4), 91(3) and 77(18).
(E)-2-[5-(3-Bromophenyl)pyrazol-3-yl]-3-(pyrrol-2-yl)-
acrylonitrile (5h). Crystallised from acetone as yellow
needles (274 mg, 54%), mp 210±11 ꢀC; Rf 0.62 (solvent A);
IR (Nujol): 3224, 2360, 2342, 2225, 1726, 1596, 1306, 1148,
1
1118, 1090, 1037, 1020, 967, 898, 884, 730 and 686 cm
;
3-(4-Bromophenyl)-5-cyanomethyl-1-(4-¯uorophenyl)-
pyrazole (6d). Crystallised from acetone as white needles
(1.107 g, 52%), mp 145±46 ꢀC; Rf 0.50 (solvent B); IR
(Nujol): 2359, 2254, 1598, 1511, 1377, 1215, 957, 838,
798, 772, 719 and 610; UV (MeOH): 209 and 265 nM;
1H NMR (200 MHz, CDCl3): d 3.74 (2H, s, C-6H), 6.79
(1H, s, C-4H), 7.24 (2H, d, J=8.6 Hz, C-30H and C-
50H), 7.43 and 7.47 (2H, 2d, J=4.8 Hz each, C-300H and
C-500H), 7.53 (2H, d, J=8.5 Hz, C-200H and C-600H) and
7.70(2H, d, J=8.6 Hz, C-20H and C-60H); 13C NMR
(50 MHz, CDCl3): Table 6; EIMS, m/z (% rel. int.): 357
[M++2] (96), 355[M+](100), 329(10), 315(5), 276(6),
249(6), 196(2), 173(9), 134(15), 107(7) and 95(15).
UV (MeOH): 212, 257 and 356nM; 1H NMR (250MHz,
DMSO-d6): d 6.33 (1H, brs, C-4000H), 6.79(1H, brs, C-
3000H), 7.05(1H, s, C-40H), 7.29(1H, brs, C-5000H), 7.35(1H,
brs, C-3H), 7.45(1H, t, J=7.9 Hz, C-500H), 7.60(1H, d,
J=8.2 Hz, C-400H), 7.88 (1H, d, J=7.9 Hz, C-600H), 8.14
(1H, brs, C-200H), 13.10(1H, brs, N-10H) and 13.90 (1H,
brs, N-1000H); 13C NMR (62.8 MHz, DMSO-d6): Table 5;
EIMS, m/z (% rel. int.): 340 [M++2] (19), 338 [M+] (20),
337(5), 289(31), 287(31), 250(17), 229(3), 218(75), 185(7),
156(2), 154(8), 125(26), 109(100), 77(59), 65(37) and 39(29).
General method of preparation of 5-cyanomethyl-1,3-dia-
rylpyrazoles 6a-6d. To a solution of 6-aryl-3-cyano-4-
methylthio-2H-pyran-2-one 2a, 2b, 2e and 2f (6.0 mmol)
in methanol/pyridine (30 mL), phenylhydrazine/p-¯uor-
ophenylhydrazine hydrochloride (9.0 mmol) was added
and the reaction mixture was re¯uxed for 5±6 h. The
progress of the reaction was monitored on HPLC and/or
on TLC. The reaction mixture was concentrated on
completion under reduced pressure, poured over crushed
ice (200 g) and stirred vigorously until a brownish yellow
solid precipitated out. It was ®ltered, washed with water,
dried and column chromatographed over silica gel using
ethyl acetate-petroleum ether as eluent to a€ord 6a±6d as
yellowish white solids which crystallised from ethyl ace-
tate as white shining needles in 45% to 52% yields.
General method of synthesis of (Z)-2-(1,3-diarylpyrazol-
5-yl)-3-(pyrrol-2-yl)acrylonitriles 7a±7d. To a solution of
5-cyanomethyl-1,3-diarylpyrazoles 6a±6d (1.5 mmol) in
ethanol (20mL), NaOBut (1.5 mmol) was added and the
reaction mixture was stirred for 15 min at 25±30ꢀC fol-
lowed by addition of pyrrole-2-carboxaldehyde (1.5 mmol)
in one lot. Stirring was continued for 4±5 h and progress
of the reaction was monitored on HPLC and/or on TLC.
The reaction mixture was concentrated on completion
under reduced pressure and poured over crushed ice
(50 g). The yellow solid that precipitated out was ®ltered,
dried over P2O5 in a vacuum dessicator and the crude
product was puri®ed by column-chromatography using
ethyl acetate:petroleum ether (1:49) as eluent and ®nally
crystallised to a€ord 7a±7d in almost quantitative yields.
5-Cyanomethyl-1,3-diphenylpyrazole (6a). Crystallised
from acetone as white needles (745mg, 48%), mp 71ꢀC; Rf
0.50 (solvent B); IR (Nujol): 2361, 2342, 2254, 1766, 1598,
1548, 1504, 759, 723 and 685 cm 1; UV (MeOH): 212 and
(Z)-2-(1,3-Diphenylpyrazol-5-yl)-3-(pyrrol-2-yl)acrylo-
nitrile (7a). Crystallised from acetone as yellow needles
(441 mg, 87%), mp 120±23 ꢀC; Rf 0.60 (solvent B); IR
(Nujol): 3403, 2727, 2360, 2207, 1592, 1126, 1039, 976,
767, 749 and 732 cm 1; UV (MeOH): 218, 252 and
1
260 nM; H NMR (200MHz, CDCl3): d 3.75 (2H, s, C-
6H), 6.84 (1H, s, C-4H), 7.36±7.52 (8H, m, C-300H, C-400H,
C-500H and Ar0H) and 7.84 (2H, d, J=6.9 Hz, C-200H and

V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
1435
359 nM; 1H NMR (200MHz, CDCl3): d 6.33 (1H, brs, C-
40000H), 6.63 (1H, brs, C-30000H), 6.84 (1H, s, C-40H), 7.05
(2H, s, C-3H and C-50000H), 7.35±7.55 (8H, m, C-3000H and
C-5000H and Ar00H), 7.88 (2H, d, J=6.9 Hz, C-2000H and C-
6000H), 9.75 (1H, brs, NH); 13C NMR (50 MHz, CDCl3):
Table 6; EIMS, m/z (% rel, int): 336 [M+] (100), 335(95),
308(6), 269(58), 233(50), 205(15), 168(18), 154(3), 129(10),
104(15) and 91(40).
3-Cyano-6-(4-¯uorophenyl)-4-methylthio-2H-pyran-2-one
(2d). C13H8FNO2S, M=265.26, T=180(2)K, l=0.71073
A. Monoclinic a=38.0091(10), b=4.90430(10), c=14.46
090(10) A, b=108.478(2)ꢀ, V=2556.66(9) A3, space
1
group C2/c, Z=8, Dx=1.378Mg/m3, m=0.260mm
,
F(000)=1088. Crystal size 0.40Â0.40Â0.06mm; y range
for data collection 2.26±24.99ꢀ, limiting indices
49<h<43, 6<k<6, 19<l<16; re¯ections collected
5993; independent re¯ections 2232 [R(int) =0.0394;
re®nement method full-matrix least-squares on F2; data/
restraints/parameters 2232/0/173; goodness-of-®t on F2
(Z)-2-[3-(4-Methylphenyl)-1-phenylpyrazol-5-yl]-3-(pyr-
rol-2-yl)acrylonitrile (7b). Crystallised from acetone as
yellow needles (472 mg, 90%), mp 176±78 ꢀC; Rf 0.64
(solvent B); IR (Nujol). 3403, 2726, 2360, 2208, 1642,
1590, 1323, 1127, 1041, 776, 752, 723 and 700 cm 1; UV
(MeOH): 209, 253 and 363 nM; 1H NMR (200MHz,
CDCl3): d 2.39 (3H, s, CH3), 6.33 (1H, brs, C-40000H), 6.62
(1H, brs, C-30000H), 6.81 (1H, s, C-40H), 7.04 (2H, s, C-3H
and C-50000H), 7.24 (2H, d, J=8.0 Hz, C-300H and C-500H),
7.46±7.58 (5H, m, Ar000H), 7.77 (2H, d, J=8.0 Hz, C-200H
and C-600H) and 9.70 (1H, brs, NH); 13C NMR (50 MHz,
CDCl3): Table 6; EIMS, m/z (% rel. int.): 350 [M+] (100),
349(95), 335(25), 322(5), 283(45), 258(15), 233(47),
194(14), 154(5), 119(99), 91(60) and 77(25).
1.046; R(F)[I>2s(I)]=0.0624; wR(F2)= 0.1664; largest
3
di€. peak and hole 0.596 and 0.238 e A
.
3-Cyanomethyl-5-(4-methylphenyl)pyrazole (3b). C12H11
N3, M=197.24, T=180(2)K, l=0.71073A. Monoclinic
a=12.5575(7), b=14.4585(3), c=5.8342 (3)A, b=
103.097(2)ꢀ, V=1031.72(8)A3, space group P21/c, Z=4,
Dx=1.270Mg/m3, m=0.079mm 1, F(000) =416. Crystal
size 0.42Â0.34Â0.10mm; y range for data collection 1.66
to 23.00ꢀ; index range
16<h<16,
18<k<18,
7<l<6; re¯ections collected 3433; independent re¯ec-
tions 1418 [R(int)=0.1336]; re®nement method full-
matrix least-squares on F2; data/restraints/parameters
1418/0/138; goodness-of-®t on F2 0.997; R(F)[I>
(Z)-2-[3-(4-Chlorophenyl)-1-phenylpyrazol-5-yl]-3-(pyr-
rol-2-yl)acriylonitrile (7c). Crystallised from acetone as
yellow needles (526 mg, 95%), mp 175±77 ꢀC; Rf 0.62
(solvent B); IR (Nujol): 3403, 2726, 2360, 2208, 1642,
1589, 1323, 1126, 1041, 781, 752 and 723 cm 1; UV
(MeOH): 216, 252 and 365 nM; 1H NMR (200MHz,
CDCl3): d 6.34 (1H, brs, C-40000H), 6.62 (1H, brs, C-30000M),
6.81 (1H, s, C-40H), 7.04 (2H, s, C-3H and C-50000H), 7.40
(2H, d, J=8.6Hz, C-300H and C-500H), 7.44±7.57 (5H, m,
Ar000H), 7.81 (2H, d, J=8.6 Hz, C-200H and C-600H) and
9.69 (1H, brs, NH); 13C NMR (50 MHz, CDCl3): Table 6;
EIMS, m/z (% rel. int.): 373 [M++2] (33), 371 [M+]
(100), 370(80), 333(7), 303(40), 268(15), 233(45), 205(20),
129(10), 91(51), 77(43) and 67(22).
2s[I]=0.0940; wR(F2)=0.2285; largest di€. peak and
3
hole 0.323 and 0.344 e A
.
E€ect of pyrazolylacrylonitriles and their precursors on
NADPH-catalysed liver microsomal lipid peroxidation.
a) Assay for inhibition of lipid peroxidation
Detailed assay procedure has been described in our
earlier commnunication.35 In short, rat liver micro-
somes (1 mg protein) were preincubated with Tris±HCl
(0.025M, pH 7.5) and test compound (100 mM in
DMSO) was added at 37 ꢀC for 10 min, followed by the
addition of ADP (3 mM) and FeCl3 (0.15 mM). The
reaction for inhibition of enzymatic lipid peroxidation
was started by the addition of NADPH (0.5 mM) and
incubation of the reaction mixture continued for 10 min.
The products of lipid peroxidation were quanti®ed by
the estimation of thiobarbituric acid reactive substances
(TBARS) thus formed as described earlier.35 The inhi-
bitory potential of various pyrazolylacrylonitriles was
assessed by determining the inhibitor concentration for
50% inhibition of lipid peroxidation (IC50).
(Z)-2-[3-(4-Bromophenyl)-1-(4-¯uorophenyl)pyrazol-5-yl]
-3-(pyrrol-2-yl)acrylonitrile (7d). Crystallised from ace-
tone as yellow needles (605 mg, 93%), mp 197±201 ꢀC,
Rf 0.60 (solvent B); IR (Nujol): 3413, 2725, 2360, 2203,
1659, 1643, 1589, 1325, 1223, 1169, 1154, 1124, 1041,
980, 847, 783, 750, 723 and 692 cm 1; UV (MeOH): 211,
1
259 and 364 nM; H NMR (200 MHz, CDCl3): d 6.36
(1H, brs, C-40000H), 6.65 (1H, brs, C-30000H), 6.80 (1H, s,
C-40H), 7.07 (1H, brs, C-50000H), 7.09 (1H, s, C-3H), 7.21
(2H, d, J=9.0 Hz, C-300H and C-500H), 7.45±7.60 (4H,
m, Ar000H), 7.75 (2H, d, J=9.0 Hz, C-200H and C-600H)
and 9.70 (1H, brs, NH); 13C NMR (50 MHz, CDCl3):
Table 6; EIMS, m/z (% rel. int.): 434 [M++2] (98), 432
[M+] (100), 431(45), 406(3), 367(15), 351(40), 324(20),
276(20), 251(80), 229(25), 176(23), 156(18), 129(23),
109(90), 95(46), 81(25), 69(44) and 57(23).
b) Assay for inhibition of propagation of lipid perox-
idation
For this purpose, linoleic acid hydroperoxide was incu-
bated with EDTA and FeSO4 in order to propagate the
lipid peroxidation as described by Sato et al.40 The test
compound at a concentration of 100 mM was added to
the reaction mixture to determine the e€ect of linoleic
acid-induced lipid peroxidation.
X-ray crystallography. The crystallographic measure-
ments on compounds 2d and 3b were made using a Sie-
mens SMART area-detector di€ractometer. Graphite
monochromated Mo-Ka radiation was used in all cases.
The structures were solved using SHELXTL-PLUS38
and re®ned with SHELXL-96.39 The crystal data of
compounds 2d and 3b are given below.
Acknowledgements
The authors thank the Danish International Develop-
ment Agency (DANIDA, Denmark), the Council of
Scienti®c and Industrial Research (CSIR, New Delhi,

1436
V. S. Parmar et al. / Bioorg. Med. Chem. 7 (1999) 1425±1436
India) and the University Grants Commission (UGC,
New Delhi, India) for ®nancial assistance.
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