Isoxazole-based derivatives from Baylis-Hillman chemistry: Assessment of preliminary hypolipidemic activity

Article abstract of DOI:10.1016/S0968-0896(03)00105-6

The synthesis of isoxazole-based derivatives utilizing Baylis-Hillman chemistry and results of their preliminary bioevaluation as hypolipidemic agents in triton model are described.

Full text of DOI:10.1016/S0968-0896(03)00105-6

Bioorganic & Medicinal Chemistry 11 (2003) 2269–2276
Isoxazole-Based Derivatives from Baylis–Hillman Chemistry:
Assessment of Preliminary Hypolipidemic Activityy
A. Patra,a S. Batra,a,* A. P. Bhaduri,a A. Khanna,b R. Chanderb and M. Dikshitc
aMedicinal Chemistry Division, Central Drug Research Institute, PO Box, 173, Lucknow 226001, India
bBiochemistry Division, Central Drug Research Institute, PO Box, 173, Lucknow 226001, India
cPharmacology Division, Central Drug Research Institute, PO Box, 173, Lucknow 226001, India
Received 19 December 2002;accepted 6 February 2003
Abstract—The synthesis of isoxazole-based derivatives utilizing Baylis–Hillman chemistry and results of their preliminary bioeva-
luation as hypolipidemic agents in triton model are described.
# 2003 Elsevier Science Ltd. All rights reserved.
The Baylis–Hillman (BH) chemistry has been expoun-
ded tremendously in the last couple of years. This has
been mainly due to the unique property of this C–C
bond forming reaction to furnish multifunctional deri-
vatives that can be modified as per the requirement.1
Towards this objective various workers have exempli-
fied the use of BH reaction for the synthesis of a wide
spectrum of biodynamic heterocycles and intermediates
for natural products.2 The problem of unusually slow
reaction rate associated with BH reaction has been
almost overcome by the use of Lewis acids,3 additives,4
sonication,5 supercritical liquid6 etc. Despite the
aggressive exploitation of this reaction for its synthetic
utility, only few reports addressing the medicinal use of
derivatives obtained from the BH chemistry exist.7 This
could be attributed to the limited spectrum of substrate,
which undergoes this reaction. Our interest in the BH
chemistry has been mainly associated with our finding
that 5-isoxazolecarboxaldehyde undergoes unusually
fast DABCO- or Lewis acid-mediated BH reaction.8 In
the present era of developing chemical libraries using
combinatorial ways, our major aim is to develop isox-
azole-based libraries both in solution and solid phase
and screen them in appropriate bioassays. As isoxazole
form component of various bioactive molecules, an easy
BH reaction of 5-isoxazolecarboxaldehyde has provided
a good platform to achieve our objectives.
The cardiovascular diseases affect large populations
both in developed and developing countries.9 Athero-
sclerosis caused by lipid disorders that in turn results
from high levels of cholesterol and oxidized LDL forms
the major share of such diseases. The statins have been
an excellent choice for control of cholesterol, and LDL
indirectly. However, the side effects due to the long-term
use have led researchers to look for better options.10
Toward these objectives we have earlier reported the
synthesis and bioevaluation of 3 amino-hex-2-ene-3-one
derivatives as hypolipidemic agents.11 However their
toxicity in vivo at higher doses led us to discard further
optimization and evaluation of those derivatives.12 We
reasoned among ourselves that the isoxazole nucleus
imbibed those hexenone derivatives in a manner that for
now the keto and amino group are in a rigid geometry
and the position between the two have swapped (Fig. 1).
In addition, the isoxazole-based amide derivatives have
earlier been reported to show inhibition of ACAT
enzyme that in turn results in decrease of cholesterol
levels.13 Using this information we have evaluated var-
ious derivatives obtained from BH chemistry for hypo-
lipidemic activity in the triton model. The details of
synthesis and preliminary bioevaluation of these com-
pounds are presented in this communication.
yCDRI Communication No. 6340.
*Corresponding author. Tel.: 91-522-2212411-18 x4368;fax: 91-522-
2223405, 2223938;e-mail: batra_san@yahoo.co.uk
Figure 1.
0968-0896/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0968-0896(03)00105-6

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A. Patra et al. / Bioorg. Med. Chem. 11 (2003) 2269–2276
Scheme 1. Reagents and conditions: (a) DABCO (20 mol%), CH2¼CHCO2Me (1.0 equiv), rt, 30 min;(b) AcCl (1.5 equiv), Pyridine (1.3 equiv),
DCM, rt, 3 h;(c) NaBH 4 (2.0 equiv), MeOH, rt, 1 h;(d) KOH (2.0 equiv), MeOH: H 2O (4:1), rt, 2 h;(e) R’NH 2 (1.0 equiv), DIC (1.0 equiv), HOBt
(1.0 equiv), DCM, rt, 3–4 h.
Chemistry
with amines yielded amides 6–8a–d. The E-stereo-
chemistry of amides was confirmed on the basis of NOE
studies.
The compounds described herein were obtained from
four different synthetic strategies. The amide deriva-
tives (6–8a–d) were obtained as described in Scheme 1.
The various 3-substituted phenyl-5-isoxazolecarbox-
aldehydes were subjected to BH reaction with methyl
acrylate to obtain the BH adducts (2a–d). These were
then acetylated using acetyl chloride to obtain acetates
(3a–d), which upon reduction with sodium borohydride
reaction yielded compounds (4a–d). The potassium
hydroxide-mediated hydrolysis of compounds 4a–d
furnished the acids 5a–d, which upon coupling reactions
In another strategy compounds 9a–d were directly
obtained from the BH reactions of acrylamide with
the aldehydes 1a–d in excellent yields (Scheme 2).
The BH reaction using acrylamide has been descri-
bed14 to be complete within 12–48 h depending on the
aldehyde employed, but in the case of 5-isoxazole-
carboxaldehydes this reaction was completed within
5–7 h.
The compounds 10–12a–d and 15a–d were
obtained through the synthetic methodologies that
have been reported earlier8b,c and have been sum-
marized in Schemes 3 and 4. Here it is essential
to state that though we have obtained the E- and
Z-isomers of compound 15, only compounds hav-
ing E-stereochemistry were subjected to biological
screening.
Scheme 2. Reagents and conditions: (a) DABCO (0.5 equiv), acryl-
amide (1.0 equiv) Dioxane–water (3:2), rt, 5–7 h.
Scheme 3. Reagents and conditions: (a) Cyclohexenone (1.5 equiv), TiCl4 (1.0 equiv), DCM, rt, 1.5 h;(b) Cyclopentenone (1.5 equiv), TiCl (1.0
4
equiv), DCM, rt, 1.5 h.
Scheme 4. Reagents and conditions: (a) DABCO (20 mol%), tert-Butyl acrylate (1.0 equiv), rt 30 min;(b) AcCl (1.5 equiv), Pyridine (1.3 equiv),
DCM, rt, 2 h;(c) Acetylacetone (2.0 equiv), K 2CO3 (1.5 equiv), EtOH, reflux, 2 h;(d) TFA (25%) in DCM, rt, 6 h;(e) HTIB (1.0 equiv), DCM, rt,
16 h.

A. Patra et al. / Bioorg. Med. Chem. 11 (2003) 2269–2276
2271
Results and Discussion
were observed as 86.29 (ꢀ4.78), 86.73 (ꢀ6.49) and
81.28 (ꢀ9.63) mg/dL, respectively. The level of these
parameters after the addition of triton was recorded as
285.41 (ꢀ22.96), 248.07 (ꢀ35.91) and 266.49 (ꢀ51.03)
showing an increase of 3.3, 2.86 and 3.27 fold, respec-
tively. It was found that the amides described in Scheme
1 showed significant biological activity. The effect was
The hypolipidemic activity data of various compounds
is summarized in Tables 1 and 2. The compound gug-
gulsterone, which is the active constituent of the hypo-
lipidemic drug Guggulipid was used as standard for the
present study. The plasma levels of TC, PL and TG
Table 1. Hypolipidemic activity data of new compounds
Compd. No.
Bioactivitya
Cholesterol (TC)
Phospholipids (PL)
Triglycerides (TG)
Guggulsterone
42
6*
8**
17**
20*
18**
7**
23**
10**
14**
30*
12**
16**
16**
23**
28*
14**
17**
14**
6**
34
35
12
12
20
24
34
21
9
17
29
10
16
12
28
29
21
15
27
2
24
33
10
8
22
29
2
23
8
9
4a
4b
4c
4d
5a
5b
5c
5d
6a
6b
6c
6d
7a
7b
7c
7d
8a
8b
8c
8d
9a
9b
9c
9d
30
7
18
22
24
26
19
15
22
7
19
28
18
17
20
16*
25**
24*
33*
28*
12
25
22
12
11
P**<0.01;*0.001.
aTriton fed group was compared with control and triton plus compound treated and the values are the % decrease obtained from levels that are
meanꢀS.D. of six rats.
Table 2. Hypolipidemic activity data of reported compounds8a,8c
Compd. No
Bioactivitya
Cholesterol (TC)
Phospholipids (PL)
Triglycerides (TG)
10a
10b
10c
10d
11a
11b
11c
11d
12a
12b
12c
12d
14a
14b
14c
14d
15a
15b
15c
15d
6**
9**
7**
17**
28**
8**
28*
36*
17**
20**
9**
14**
18**
14*
39*
34*
ND
38*
10
8
8
17
24
6
21
33
15
19
34
10
24
19
22
33
ND
20
22
14
12
8
18
5
23
9
28
37
15
18
18
9
29
16
30
33
ND
28
30
16
34*
13**
P**<0.01;*0.001.
aTriton fed group was compared with control and triton plus compound treated and the values are the % decrease obtained from levels that are
meanꢀS.D. of six rats.

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A. Patra et al. / Bioorg. Med. Chem. 11 (2003) 2269–2276
pronounced in the compound having 2-chlorophenyl at
position 3 of the isoxazole nucleus and benzyl moiety on
the NH of the amide (7c). Increasing the lipophilicity
(8a–d) led to total loss in activity. Therefore, it was
decided to synthesize the simple amide derivatives uti-
lizing the acrylamide in BH reaction. This led to sig-
nificant increase in the cholesterol lowering profile of
nearly all the derivatives (9a–d) though phospholipid
and triglycerides were not lowered in proportion. Out of
the earlier reported derivatives, the BH adducts derived
from cyclohexenone or cyclopentenone did not show
any activity but the hemiacetals that were obtained in
significant yields elicit potent biological response. The
hemiacetal (11d) having 4-benzyloxy substitution in the
isoxazole moiety was observed to have better hypolipi-
demic profile. On the other hand for acrylic acids (14)
and furanones (15) in Scheme 4, the biological activity was
more concentrated in compounds with 2-chloro substitu-
tion on the phenyl ring of the isoxazole. During our stud-
ies with 5-isoxazolecarboxaldehyde derivatives we have
discovered that these compounds elicit significant in vivo
antithrombotic activity,15 therefore we subjected some of
the amides for this activity. However, none of the deriva-
tives show potent biological activity (Table 3).
shifts in d values, J in Hz). The EIMS were recorded on
JEOL-D-300 mass spectrometer at 70 eV while FABMS
were recorded on JEOL/SX-102 spectrometer. Ele-
mental analyses were performed on a Carlo Erba 1108
microanalyzer.
General method for acetates
See ref 8b.
2-[Acetoxy-(3-phenyl-isoxazol-5-yl)-methyl]-acrylic acid
methyl ester (3a). 96.7% as yellow oil;IR (Neat)
(cmꢁ1) 1700 (CO2CH3), 1730 (OCOCH3); 1H NMR
(CDCl3, 200 MHz) 2.17 (s, 3H, CH3), 3.78 (s, 3H, CH3),
6.11 (s, 1H, ¼CH2), 6.58 (s, 1H, ¼CH), 6.60 (s, 1H,
¼CH2), 6.88 (s, 1H, CH), 7.43–7.46 (m, 3H, Ar–H),
7.76–7.81 (m, 2H, Ar–H);mass (EIMS) m/z 301 (M+).
Anal. calcd. for C16H15NO5 C, 63.78;H, 5.02;N, 4.65.
Found C, 63.62;H, 5.22;N, 4.68.
2-[Acetoxy-(3-p-tolyl-isoxazol-5-yl)-methyl]-acrylic acid
methyl ester (3b). 82% as white solid, m.p. 97–98 ꢂC;
1
IR (KBr) (cmꢁ1) 1709 (CO2CH3) 1745 (OCOCH3); H
NMR (CDCl3, 200 MHz) 2.17 (s, 3H, CH3), 2.39 (s, 3H,
Ar–CH3), 3.77 (s, 3H, CH3), 6.10 (s, 1H, ¼CH2), 6.56 (s,
1H, ¼CH2), 6.58 (s, 1H, CH), 6.87 (s, 1H, ¼CH), 7.24
(d, 2H, J=8.0 Hz, Ar–H), 7.67 (d, 2H, J=8.0 Hz, Ar–H);
Mass (EIMS) m/z 315 (M+). Anal. calcd. for
C17H17NO5 C, 64.75;H, 5.43;N, 4.44. Found C, 64.65;
H, 5.28;N, 4.20%.
Conclusion
In conclusion, we have described the preliminary hypo-
lipidemic activity profile of various products derived
from the BH chemistry of 5-isoxazolecarbox-aldehydes.
During this study it was encouraging to note that
hemiacetals and acrylamides show good biological
response and their further optimization to modulate
and optimize the hypolipidemic activity is under pro-
gress.
2-{Acetoxy-[3-(2-chloro-phenyl)-isoxazol-5-yl]-methyl}-
acrylic acid methyl ester (3c). 90% as yellow oil;IR
(Neat) (cmꢁ1) 1703 (CO2CH3), 1739 (OCOCH3); 1H
NMR (CDCl3, 200 MHz) 2.18 (s, 3H, CH3), 3.78 (s, 3H,
CH3), 6.11 (s, 1H, ¼CH2), 6.56 (s, 1H, ¼CH2), 6.58 (s,
1H, ¼CH), 6.74 (s, 1H, CH), 7.32–7.49 (m, 3H, Ar–H),
7.71–7.74 (m, 1H, Ar–H);Mass (EIMS) m/z 335 (M+).
Anal. calcd. for C16H14ClNO5 C, 57.24;H, 4.20;N,
4.17. Found C, 57.45;H, 3.99;N, 4.08%.
Experimental
2 - {Acetoxy - [3 - (4 - benzyloxy - phenyl) - isoxazol - 5 - yl] -
methyl}-acrylic acid methyl ester (3d). 95% as white
solid, m.p. 95–97 ꢂC;IR (KBr) (cm ꢁ1) 1709 (CO2CH3),
General. Melting points are uncorrected and were
determined in capillary tubes on a hot stage apparatus
containing silicon oil. IR spectra were recorded using
Perkin Elmer’s Spectrum RX I FTIR spectrophoto-
meter. H NMR spectra were recorded either on a Bru-
ker Avance DRX-300 or Bruker DPX-200 FT spectro-
meters, using TMS as an internal standard (chemical
1
1744 (OCOCH3); H NMR (CDCl3, 200 MHz) 2.16 (s,
3H, OCOCH3), 3.77 (s, 3H, CO2CH3), 5.11 (s, 2H,
CH2), 6.10 (s, 1H, ¼CH2), 6.52 (s, 1H, ¼CH2), 6.56 (s,
1H, ¼CH), 6.86 (s, 1H, CH), 7.03 (d, 2H, J=8.8 Hz,
Ar–H), 7.32–7.46 (m, 5H, Ar–H), 7.72 (d, 2H, J=8.8
Hz, Ar–H);Mass (EIMS) m/z 407 (M+). Anal. calcd.
for C23H21NO6 C, 67.80;H, 5.20;N, 3.44. Found C,
67.92;H, 5.34;N, 3.56%.
1
Table 3. In vivo antithrombotic activity of amides at 30 mmol/kg
Compound
Protection (%)
Compound
Protection (%)
General procedure for sodium borohydride reduction
6a
6b
6c
6d
7a
7b
7c
7d
0
20
0
0
0
20
0
0
8a
8b
8c
8d
9a
9b
9c
9d
20
0
20
ND
0
0
40
0
To a solution of appropriate compound from 3a–d (4
mmol) in methanol (5 mL) was added NaBH4 (0.76 g, 8
mmol) with stirring at 0–5 ꢂC. After 15 min. the reaction
was decomposed with water and extracted with ethyl
acetate (2ꢃ30 mL). The organic phase was separated
and washed with brine (40 mL), dried (Na2SO4) and
concentrated in vacuo. The residue upon trituration
with hexane furnished the pure product (4a–d) as solids.
Acetylsalicylic acid was used as standard that gives % of protection of
40.

A. Patra et al. / Bioorg. Med. Chem. 11 (2003) 2269–2276
2273
2-Methyl-3-(3-phenyl-isoxazol-5-yl)-acrylic acid methyl
ester (4a). 81% as white solid, mp 88–90 ꢂC;IR (KBr)
200 MHz) d 2.35 (s, 3H, CH3), 2.41 (s, 3H, CH3), 6.75 (s,
1H, ¼CH), 7.28 (d, 2H, J=8.0 Hz, Ar–H), 7.62 (s, 1H,
¼CH), 7.73 (d, 2H, J=8.0 Hz, Ar–H);mass (EIMS) m/z
243 (M+). Anal. calcd for C14H13NO3 C, 69.12;H, 5.38;
N, 5.75. Found C, 69.35;H, 5.27;N, 5.20%.
1
(cmꢁ1) 1714 (CO2CH3); H NMR (CDCl3, 200 MHz) d
2.33 (s, 3H, CH3), 3.85 (s, 3H, CH3), 6.73 (s, 1H, ¼CH),
7.52 (s, 1H, ¼CH), 7.72 (d, 2H, J=8.0 Hz, 3ꢃAr–H and
¼CH), 7.84 (m, 2H, Ar–H);mass (EIMS) m/z 243
(M+). Anal. calcd for C14H13NO3.H2O C, 64.36;H,
5.79;N, 4.83. Found C, 64.62;H, 5.55;N: 5.06%.
3-[3-(2-Chloro-phenyl)-isoxazol-5-yl]-2-methyl-acrylic
acid (5c). 99.5% as white solid, mp 155–156 ꢂC;IR
(KBr) (cmꢁ1) 1695 (CO), 3440 (OH); 1H NMR (CDCl3,
200 MHz) d 2.35 (s, 3H, CH3), 6.95 (s, 1H, ¼CH), 7.50
(m, 3H, Ar–H), 7.65 (s, 1H, ¼CH), 7.77 (m, 1H, Ar–H);
mass (EIMS) m/z 263 (M+). Anal. calcd for
C13H10ClNO3 C, 59.17;H, 3.81;N, 5.30. Found C,
59.32;H, 4.06;N, 5.22%.
2-Methyl-3-(3-p-tolyl-isoxazol-5-yl)-acrylic acid methyl
ester (4b). 84% as white solid, mp 105–106 ꢂC;IR
(KBr) (cmꢁ1) 1708 (CO2CH3); 1H NMR (CDCl3,
200 MHz) d 2.33 (s, 3H, CH3), 2.41 (s, 3H, Ar–CH3),
3.85 (s, 3H, CH3), 6.69 (s, 1H, ¼CH), 7.28 (d, 2H,
J=8.0 Hz, Ar–H), 7.52 (s, 1H, ¼CH), 7.72 (d, 2H,
J=8.0 Hz, Ar–H);mass (EIMS) m/z 206 (M+-41).
Anal. calcd for C15H15NO3 C, 70.02;H, 5.88;N, 5.44.
Found C, 70.21;H, 6.09;N, 5.35%.
3-[3-(4-Benzyloxy-phenyl)-isoxazol-5-yl]-2-methyl-acrylic
acid (5d). 98.5% as white solid, mp 156–158 ꢂC;IR
(KBr) (cmꢁ1) 1687 (CO), 3440 (OH); 1H NMR (CDCl3,
200 MHz) d 2.31 (s, 3H, CH3), 5.13 (s, 2H, CH2), 6.66
(s, 1H, ¼CH), 7.07 (d, 2H, J=8.0 Hz, Ar–H), 7.38 (m,
5H, Ar–H), 7.54 (s, 1H, ¼CH), 7.74 (d, 2H, J=8.0 Hz,
Ar–H);mass (EIMS) m/z 335 (M+). Anal. calcd for
C20H17NO4 C, 71.63;H, 5.11;N, 4.18. Found C, 71.86;
H, 5.27;N, 4.30%.
3-[3-(2-Chloro-phenyl)-isoxazol-5-yl]-2-methyl-acrylic
acid methyl ester (4c). 88% as white solid, mp 90–
92 ꢂC;IR (KBr) (cm ꢁ1) 1719 (CO2CH3); 1H NMR
(CDCl3, 200 MHz) d 2.33 (s, 3H, CH3), 3.86 (s, 3H,
CH3), 6.90 (s, 1H, ¼CH), 7.49 (m, 4H, 3ꢃAr–H and
¼CH), 7.76 (m, 1H, Ar–H);mass (FABMS+) m/z 278
(M++1). Anal. calcd for C14H12ClNO3 C, 60.55;H,
4.36;N, 5.04. Found C, 60.21;H, 4.29;N: 5.35%.
General procedure for the synthesis of amides
To a solution of appropriate compound from 5a–d (4
mmol) in a mixture of dry dichloromethane (10 mL)
and dry DMF (1 mL) and was added DIC (0.6 mL, 4
mmol) followed by HOBt (0.5 g, 4 mmol). After 25 min
appropriate amine was added dropwise under stirring.
The reaction was continued for 3–4 h followed by cool-
ing of the mixture to 0 ꢂC in ice-salt mixture. The sepa-
rated solid was filtered and the filtrate was washed with
5% aqueous HCl followed by 5% sodium bicarbonate
solution. The filtrate was then washed with water and
the organic layer after usual work up furnished a resi-
due that was column chromatographed on neutral alu-
mina using hexane–ethyl acetate (3:7, v/v) as eluent to
furnish the pure product as colourless solid or oil.
3-[3-(4-Benzyloxy-phenyl)-isoxazol-5-yl]-2-methyl-acrylic
acid methyl ester (4d). 77% as white solid, mp 128–
130 ꢂC;IR (KBr) (cm ꢁ1) 1710 (CO2CH3); 1H NMR
(CDCl3, 200 MHz) d 2.32 (s, 3H, CH3), 3.84 (s, 3H,
CH3), 5.12 (s, 2H, CH2), 6.66 (s, 1H, ¼CH), 7.03 (d, 2H,
J=8.0 Hz, Ar–H), 7.42 (m, 6H, 5ꢃAr–H and ¼CH),
7.76 (d, 2H, J=8.0 Hz, Ar–H);mass (FABMS+) m/z
350 (M++1). Anal. calcd for C21H19NO4 C, 72.19;H,
5.48;N, 4.00. Found C, 71.84;H, 5.73;N: 3.67%.
General procedure for hydrolysis
To a solution of appropriate compound from 4a–d (4
mmol) in 80% aqueous methanol (5 ml) was added
KOH (0.38 g, 8 mmol) with stirring at rt. After 1 h the
reaction was neutralized with cold aqueous HCl (30%)
keeping the temperature of reaction mixture below
20 ꢂC. The separated solid was isolated, dried and
recrystallized from ethanol, to furnish the pure acid as
colourless solid.
N-sec-Butyl-2-methyl-3-(3-phenyl-isoxazol-5-yl)-acrylam-
ide (6a). 84% as white solid, mp 130–132 ꢂC;IR (KBr)
(cmꢁ1) 1624 (CO), 3299 (NH); 1H NMR (CDCl3,
200 MHz) d 0.96 (t, 3H, J=7.4 Hz, CH3), 1.21 (d, 3H,
J=7.4 Hz, CH3), 1.62 (m, 2H, CH2), 2.33 (s, 3H, CH3),
4.04 (m, 1H, CH), 5.70 (brs, 1H, NH), 6.65 (s, 1H,
¼CH), 7.16 (s, 1H, ¼CH), 7.47 (m, 3H, Ar–H), 7.83 (m,
2H, Ar–H); 13C NMR (CDCl3, 75.46 MHz) 10.3, 20.2,
29.5, 47.2, 103.5, 117.6, 126.7, 128.6, 128.9, 130.1, 137.4,
162.4, 167.5 ppm;mass (EIMS) m/z 284 (M+). Anal.
calcd for C17H20N2O2 C, 71.81;H, 7.09;N, 9.85. Found
C, 72.07;H, 6.89;N, 10.14%.
2-Methyl-3-(3-phenyl-isoxazol-5-yl)-acrylic acid (5a).
99.5% as white solid, mp 180–182 ꢂC;IR (KBr) (cm
ꢁ1
)
1
1685 (CO), 3445 (OH); H NMR (CDCl3, 200 MHz) d
2.36 (s, 3H, CH3), 6.78 (s, 1H, ¼CH), 7.48 (m, 3H, Ar–
H), 7.54 (s, 1H, ¼CH), 7.83 (m, 2H, Ar–H); 13C NMR
(CDCl3, 75.46 MHz) d 20.6, 65.8, 99.1, 125.8, 125.9,
128.1, 128.8, 129.2, 139.2, 141.3, 161.2, 167.9, 172.6;
mass (EIMS) m/z 229 (M+). Anal. calcd for C13H11NO3
C, 68.11;H, 4.83;N, 6.11. Found C, 67.84;H, 5.06;N,
5.82%.
N-sec-Butyl-2-methyl-3-(3-p-tolyl-isoxazol-5-yl)-acrylam-
ide (6b). 92.5% as white solid, mp 160–161 ꢂC;IR (KBr)
(cmꢁ1) 1622 (CO), 3276 (NH); 1H NMR (CDCl3,
200 MHz) d 0.95 (t, 3H, J=7.8 Hz, CH3), 1.20 (d, 3H,
J=6.6 Hz, CH3), 1.63 (m, 2H, CH2), 2.33 (s, 3H, CH3),
2.34 (s, 3H, CH3), 4.03 (m, 1H, CH), 5.69 (brd, 1H,
J=7.8 Hz, NH), 6.63 (s, 1H, ¼CH), 7.08 (s, 1H, ¼CH),
7.28 (d, 2H, J=8.0 Hz, Ar–H), 7.81 (d, 2H, J=8.0 Hz,
2-Methyl-3-(3-p-tolyl-isoxazol-5-yl)-acrylic acid (5b).
98.5% as white solid, mp 204–205 ꢂC (d);IR (KBr)
(cmꢁ1) 1687 (CO), 3420 (OH); 1H NMR (CDCl3,

2274
A. Patra et al. / Bioorg. Med. Chem. 11 (2003) 2269–2276
Ar–H);mass (EIMS) m/z 298 (M+). Anal. calcd for
C18H22N2O2 C, 72.16;H, 7.43;N, 9.39. Found C, 72.18;
H, 7.56;N, 9.14%.
NMR (CDCl3, 200 MHz) d 2.35 (s, 3H, CH3), 4.59 (d,
2H, J=4.8 Hz, CH2), 5.12 (s, 2H, CH2), 6.25 (brs, 1H,
NH), 6.67 (s, 1H, ¼CH), 7.05 (d, 2H, J=8.0 Hz, Ar–
H), 7.36 (m, 6H, 5ꢃAr–H and ¼CH), 7.41 (m, 5H, Ar–
H), 7.74 (d, 2H, J=8.0 Hz, Ar–H);mass (FABMS+)
m/z 425 (M++1). Anal. calcd for C27H24N2O3 C,
76.39;H, 5.70;N, 6.60. Found C, 76.57;H, 5.85;N,
6.82%.
N-sec-Butyl-3-[3-(2-chloro-phenyl)-isoxazol-5-yl]-2-
methyl-acrylamide (6c). 80.5% as white solid, mp 110–
112 ꢂC;IR (KBr) (cm ꢁ1) 1618 (CO), 3285 (NH); 1H
NMR (CDCl3, 200 MHz) d 0.96 (t, 3H, J=7.4 Hz,
CH3), 1.21 (d, 3H, J=7.4 Hz, CH3), 1.58 (m, 2H, CH2),
2.34 (s, 3H, CH3), 4.06 (m, 1H, CH), 5.75 (brd, 1H,
J=7.2 Hz, NH), 6.82 (s, 1H, ¼CH), 7.19 (s, 1H, ¼CH),
7.36–7.52 (m, 3H, Ar–H), 7.72–7.77 (m, 1H, Ar–H);
mass (FABMS+) m/z 319 (M++1). Anal. calcd for
C17H19ClN2O2 C, 64.06;H, 6.01;N, 8.78. Found C,
64.16;H, 6.38;N, 8.52%.
2-Methyl-N-nonyl-3-(3-phenyl-isoxazol-5-yl)-acrylamide
(8a). 98% as white solid, mp 90–92 ꢂC;IR (KBr)
(cmꢁ1) 1614 (CO), 3296 (NH); 1H NMR (CDCl3,
200 MHz) d 0.88 (t, 3H, J=6.8 Hz, CH3), 1.29 (m, 12H,
6ꢃCH2), 1.58 (m, 2H, CH2), 2.34 (s, 3H, CH3), 3.38 (m,
2H, CH2), 6.13 (brs, 1H, NH), 6.65 (s, 1H, ¼CH), 7.21
(s, 1H, ¼CH), 7.46 (m, 3H, Ar–H), 7.82 (m, 2H, Ar–H);
13C NMR (CDCl3, 75.46 MHz) d 14.0, 15.1, 22.3, 22.6,
23.4, 26.9, 29.1, 29.2, 29.4, 31.8, 40.2, 41.8, 103.6, 117.8,
126.7, 128.6, 128.9, 130.1, 137.2, 157.2, 162.4, 167.6,
168.1;mass (FABMS+) m/z 355 (M++1). Anal. calcd
for C22H30N2O2 C, 72.69;H, 8.59;N, 7.77. Found C,
72.74;H, 8.79;N, 7.57%.
3-[3-(4-Benzyloxy-phenyl)-isoxazol-5-yl]-N-sec-butyl-2-
methyl-acrylamide (6d). 70.6% as white solid, mp 122–
124 ꢂC;IR (KBr) (cm ꢁ1) 1621 (CO), 3285 (NH); 1H
NMR (CDCl3, 200 MHz) d 0.95 (t, 3H, J=7.4 Hz, CH3),
1.14 (d, 3H, J=6.2 Hz, CH3), 1.58 (m, 2H, CH2), 2.31 (s,
3H, CH3), 3.84 (m, 1H, CH), 5.12 (s, 2H, CH2), 5.78 (brd,
1H, J=7.2 Hz, NH), 6.66 (s, 1H, ¼CH), 7.08 (d, 2H,
J=8.0 Hz, Ar–H), 7.17 (s, 1H, ¼CH), 7.40 (m, 5H, Ar–
H), 7.76 (d, 2H, J=8.0 Hz, Ar–H);mass (FABMS+) m/z
391 (M++1). Anal. calcd for C24H26N2O3 C, 73.82;H,
6.71;N, 7.17. Found C, 73.57;H, 6.81;N, 7.17%.
2-Methyl-N-nonyl-3-(3-p-tolyl-isoxazol-5-yl)-acrylamide
(8b). 95% as white solid, mp 118–120 ꢂC;IR (KBr)
(cmꢁ1) 1612 (CO), 3298 (NH); 1H NMR (CDCl3,
200 MHz) d 0.88 (t, 3H, J=6.8 Hz, CH3), 1.27 (m, 14H,
7ꢃCH2), 2.34 (s, 3H, CH3), 2.40 (s, 3H, CH3), 3.37 (m,
2H, CH2), 6.13 (brs, 1H, NH), 6.62 (s, 1H, ¼CH), 7.20
(s, 1H, ¼CH), 7.28 (d, 2H, J=8.0 Hz, Ar–H), 7.71 (d,
2H, J=8.0 Hz, Ar–H);mass (EIMS) m/z 368 (M+).
Anal. calcd for C23H32N2O2 C, 74.96;H, 8.75;N, 7.60.
Found C, 74.76;H, 8.59;N, 7.70%.
N-Benzyl-2-methyl-3-(3-phenyl-isoxazol-5-yl)-acrylamide
(7a). 90% as white solid, mp 120–121 ꢂC;IR (KBr)
(cmꢁ1) 1624 (CO), 3292 (NH); 1H NMR (CDCl3,
200 MHz) d 2.37 (s, 3H, CH3), 4.58 (d, 2H, J=5.6 Hz,
CH2), 6.21 (brs, 1H, NH), 6.66 (s, 1H, ¼CH), 7.30 (s,
1H, ¼CH), 7.33 (m, 5H, Ar–H), 7.46 (m, 3H, Ar–H), 7.82
(m, 2H, Ar–H); 13C NMR (CDCl3, 75.46 MHz) d 15.1,
44.0, 103.8, 118.2, 126.7, 127.5, 127.7, 128.0, 128.5, 128.9,
130.1, 136.7, 137.8, 162.4, 167.4, 168.0;mass (EIMS) m/z
318 (M+). Anal. calcd for C20H18N2O2 C, 75.45;H, 5.69;
N, 8.79. Found C, 75.17;H, 5.87;N, 8.83%..
3-[3-(2-Chloro-phenyl)-isoxazol-5-yl]-2-methyl-N-nonyl-
acrylamide (8c). 89% as colourless oil;IR (Neat)
(cmꢁ1) 1614 (CO), 3302 (NH); 1H NMR (CDCl3,
200 MHz) d 0.88 (t, 3H, J=6.8 Hz, CH3), 1.27 (m, 12H,
6ꢃCH2), 1.58 (m, 2H, CH2), 2.34 (s, 3H, CH3), 3.37 (m,
2H, CH2), 6.01 (brs, 1H, NH), 6.82 (s, 1H, ¼CH), 7.21
(s, 1H, ¼CH), 7.45 (m, 3H, Ar–H), 7.75 (m, 1H, Ar–H);
mass (FABMS+) m/z 389 (M++1). Anal. calcd for
C22H29ClN2O2 C, 67.94;H, 7.52;N, 9.12. Found C,
67.59;H, 7.38;N, 9.12%.
N-Benzyl-2-methyl-3-(3-p-tolyl-isoxazol-5-yl)-acrylamide
(7b). 92% as white solid, mp 148–150 ꢂC;IR (KBr)
1
(cmꢁ1) 1625 (CONH), 3301 (NH); H NMR (CDCl3,
200 MHz) d 2.36 (s, 3H, CH3), 2.40 (s, 3H, CH3), 4.58 (d,
2H, J=5.6 Hz, CH2), 6.22 (brs, 1H, NH), 6.63 (s, 1H,
¼CH), 7.29 (m, 3H, 2ꢃAr–H and ¼CH), 7.35 (m, 5H,
Ar–H), 7.71 (d, 2H, J=8.0 Hz, Ar–H);mass (EIMS) m/z
332 (M+). Anal. calcd for C21H20N2O2 C, 75.88;H, 6.06;
N, 8.42. Found C, 75.76;H, 6.22;N, 8.45%.
3-[3-(4-Benzyloxy-phenyl)-isoxazol-5-yl]-2-methyl-N-
nonyl-acrylamide (8d). 74% as white solid, mp 135–
136 ꢂC;IR (KBr) (cm ꢁ1) 1616 (CO), 3286 (NH); 1H
NMR (CDCl3, 200 MHz) d 0.88 (t, 3H, J=6.8 Hz,
CH3), 1.27 (m, 12H, 6ꢃCH2), 1.61 (m, 2H, CH2), 2.33
(s, 3H, CH3), 3.32–3.42 (m, 2H, CH2), 5.12 (s, 2H,
CH2), 6.13 (brs, 1H, NH), 6.66 (s, 1H, ¼CH), 7.05 (d,
2H, J=8.0 Hz, Ar–H), 7.19 (s, 1H, ¼CH), 7.40 (m, 5H,
Ar–H), 7.75 (d, 2H, J=8.0 Hz, Ar–H);mass
(FABMS+) m/z 461 (M++1). Anal. calcd for
C29H36N2O2 C, 75.62;H, 7.88;N, 6.08. Found C, 75.76;
H, 7.97;N, 5.96%.
N-Benzyl-3-[3-(2-chloro-phenyl)-isoxazol-5-yl]-2-methyl-
acrylamide (7c). 89% as white solid, mp 130–131 ꢂC;IR
(KBr) (cmꢁ1) 1656 (CO), 3289 (NH); 1H NMR (CDCl3,
200 MHz) d 2.36 (s, 3H, CH3), 4.58 (d, 2H, J=5.6 Hz,
CH2), 6.25 (brs, 1H, NH), 6.82 (s, 1H, ¼CH),), 7.41 (m,
4H, 3ꢃAr–H and ¼CH), 7.52 (m, 5H, Ar–H), 7.74 (m,
1H, Ar–H);mass (EIMS) m/z 352 (M+). Anal. calcd for
C20H17ClN2O2 C, 68.08;H, 4.85;N, 7.93. Found C,
67.97;H, 5.16;N, 7.74%.
General procedure for BH reaction with acrylamide
N-Benzyl-3-[3-(4-benzyloxy-phenyl)-isoxazol-5-yl]-2-
methyl-acrylamide (7d). 84% as white solid, mp 140–
142 ꢂC;IR (KBr) (cm ꢁ1) 1628 (CO), 3278 (NH); 1H
A mixture of appropriate compound from 1a–d (4
mmol), DABCO (20 mol%) and acrylamide (4 mmol) in
5 mL of dioxane–water (3: 2, v/v) mixture was stirred at

A. Patra et al. / Bioorg. Med. Chem. 11 (2003) 2269–2276
2275
rt for 5–7 h. Thereafter the reaction mixture was
extracted with ethyl acetate. The usual work up of the
organic layer furnished a residue that upon filtration
through a small band of silica gel using hexane–ethyl
acetate (4: 6, v/v) as eluent yielded the pure products as
solids. The compound 9d was obtained as colourless
solid directly from the reaction mixture
and blood was withdrawn from retro-orbital plexus.
Serum was separated by centrifugation at low speed and
assayed for total cholesterol, phospholipid and trigly-
cerides by standard procedure reported earlier.11,16
.
Antithrombotic. All the new amides were evaluated for
their antithrombotic activity in vivo. Swiss mice (20–25 g,
from CDRI animal colony) were used in a group of at
least 10 animals each. Thrombosis was induced by infu-
sion of a mixture of 15 mg collagen and 5 mg adrenaline in
a volume of 100 mL into the tail vein of each mouse. This
resulted in either death or hind limb paralysis of 100%
animals. The compounds were administered at 30 mmol/
kg by oral route 1 h prior to the thrombotic challenge.
The antithrombotic effects of these compounds were
assessed by the percentage protection offered by these
agents to mice from death or paralysis following throm-
botic challenge using acetylsalicyclic acid as a standard.
2-[Hydroxy-(3-phenyl-isoxazol-5-yl)-methyl]-acrylamide
(9a). 85% as white solid, mp 127–128 ꢂC;IR (KBr)
1
(cmꢁ1) 1625 (CO), 3386 (OH), 3200 (NH2); H NMR
(CDCl3, 200 MHz) d 4.72 (d, 1H, J=7.4 Hz, OH), 5.62
(d, 1H, J=7.4 Hz, CH), 5.78 (s, 1H ¼CH2), 5.99 (s, 1H
¼CH2), 6.65 (s, 1H, ¼CH), 7.47 (m, 3H, Ar–H), 7.79
(m, 2H, Ar–H); 13C NMR (CDCl3, 75.46 MHz) d 103.4,
120.8, 125.8, 127.6, 128.0, 129.2, 133.2, 161.5, 166.6,
168.0;mass (FABMS+) m/z 245 (M++1). Anal. calcd.
for C13H12N2O3 C, 59.53, H, 5.38;N 10.68. Found C,
59.26;H, 5.37;N, 10.48%.
2-[Hydroxy-(3-p-tolyl-isoxazol-5-yl)-methyl]-acrylamide
(9b). 90% as white solid, mp 144–145 ꢂC;IR (KBr)
Acknowledgements
1
(cmꢁ1) 1624 (CO), 3382 (OH), 3200 (NH2); H NMR
One of the authors (AP) gratefully acknowledges the
financial support from CSIR, India in the form of
fellowship.
(CDCl3, 200 MHz) d 2.38 (s, 3H, CH3), 4.81 (s, 1H,
OH), 5.63 (s, 1H, CH), 5.78 (s, 1H ¼CH2), 6.02 (s, 1H
¼CH2), 6.61 (s, 1H, ¼CH), 7.24 (d, 2H, J=8.0 Hz, Ar–
H), 7.71 (d, 2H, J=8.0 Hz, Ar–H);mass (FAB+) m/z
259 (M++1). Anal. calcd. for C14H14N2O3 C, 65.11;H,
5.46;N, 10.85. Found C, 64.99;H, 5.61;N, 10.81%.
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1
(KBr) (cmꢁ1) 1679 (CO), 3360 (OH), 3204 (NH2); H
NMR (CDCl3, 200 MHz) d 4.72 (d, 1H, J=7.4 Hz,
OH), 5.62 (d, 1H, J=7.4 Hz, CH), 5.78 (s, 1H ¼CH2),
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methyl}-acrylamide (9d). 88% as white solid, mp 150–
152 ꢂC;IR (KBr) (cm ꢁ1) 1625 (CO), 3390 (OH), 3201
(NH2); 1H NMR (CDCl3, 200 MHz) d 5.10 (d, 2H,
J=8.0 Hz, s of OCH2 merged with d of OH), 5.69 (d,
1H, J=6.0 Hz, CH), 5.77 (s, 1H ¼CH2), 6.13 (s, 1H
¼CH2), 6.53 (s, 1H, ¼CH), 7.03 (d, 2H, J=8.0 Hz, Ar–
H), 7.37 (m, 5H, Ar–H), 7.71 (d, 2H, J=8.0 Hz, Ar–H);
mass (FAB+) m/z 359 (M++1). Anal. calcd for
C20H18N2O4 C, 68.56;H, 5.18;N, 8.00. Found C, 68.81;
H, 5.31;N, 7.88%.
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