Synthesis and antimicrobial studies of some new 3-isoxazoline substituted phthalazine methylsulfonyl oxadiazoles

Article abstract of DOI:10.1155/2011/356437

A series of new 3-isoxazoline substituted phthalazine methylsulfonyloxadiazoles were prepared from methyl 2-(4-oxo-3,4- dihydrophthalazin-1-yl) acetate. The structure of synthesized compounds were characterized by spectral data and screened for their anti

Full text of DOI:10.1155/2011/356437

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2011, 8(3), 1022-1029
http://www.e-journals.net
Synthesis and Antimicrobial Studies of
Some New 3-Isoxazoline Substituted
Phthalazine Methylsulfonyl Oxadiazoles
A.M. SRIDHARA§, K. R. VENUGOPALA REDDY*, J. KESHAVAYYA¶,
#
D.S. AMBIKA , SANATHKUMAR GOUD§ and S.K. PEETHAMBAR
§Advinus Therapeutics Ltd, 21 & 22
Peenya II Phase, Bangalore-560058, India
*Department of Studies in Industrial Chemistry
Kuvempu University, Shankaragatta -577 451, Karnataka, India
¶Department of studies in Chemistry
Kuvempu University, Shankaragatta-577 451, Karnataka, India
#Dept. of Plant Pathology,
G.K.V.K, UAS, Bangalore-65, India
Department of Biochemistry, Kuvempu University
Shankaragatta-577 451, Karnataka, India
venurashmi30@rediffmail.com
Received 25 August 2010; Revised 19 November 2010; Accepted 15 December 2010
Abstract: A series of new 3-isoxazoline substituted phthalazine methylsulfonyl-
oxadiazoles were prepared from methyl 2-(4-oxo-3,4-dihydrophthalazin-1-yl)
acetate. The structure of synthesized compounds were characterized by
spectral data and screened for their antimicrobial activities against various
bacteria and fungi strains. Several of these compounds showed antimicrobial
activity.
Keywords: Phthalazin-1(2H)-one, 1,3,4-Oxadiazole, Isoxazoline, Phthalazine acetic acid
Introduction
Phthalazin-1(2H)-ones, methylsulfanyl oxadiazoles and isoxazolines serves as some
important building blocks for biological active molecules. Figure 1 has been revealed by
these three important biological active pharmacophore component systems.

1023
K. R. V. REDDY et al.
N
N
Methylsulfonyloxadiazole
SCH3
N
O
R
N
N
O
Isoxazoline
O
Phthalazin-1(2H)-one
Figure 1. Phthalazine isoxazolines scaffold
Phthalazin-1(2H)-one derivatives are of considerable interest due to their antidiabatic1
antiallergic2, antiasthmatic3, antihypertensive4, vasorelaxant5, aldose reductase inhibitor6,
and antimicrobial7 activities. Moreover a number of established drug molecules like
hydralazine8, budralazine9, azelastine10, ponalrestat11 and zopolrestat12 are accessible starting
from the corresponding phthalazinones. The second pharmacophore component is
isoxazoline, which represents an important class of heterocyclic compounds with broad
spectrum of biological activities. Substituted isoxazolines have revealed anti-influenza
virus13, antifungal14, antitubercular15, spermicidal and anti-HIV16, β-adrenergic receptor
antagonist properties17. Similarly the third pharmacophore methylsulfanyl oxadiazole unit is
also one of important biologically active building block. The substituted methylsulfanyl-
oxadiazoles have been found to exhibit diverse biological activities such as inhibitors of
glycogen synthase kinase-3β18, antifungal19, antibacterial and anti-HIV20, insecticidal21, anti-
inflammatory and analgesic22, anticonvulsants and muscle relaxants23.
The diverse biological activities of these pharmacophores; phthalazin-1(2H)-one,
methylsulfanyl oxadiazole and isoxazoline pharmacophores, encouraged us to discover a
new lead compounds, which contains all these pharmocophores in a single molecules, that
may exhibit higher pharmacological activities. By combining these pharmacophore
components in a single molecule, to give a compact system, we designed and synthesized a
series of phthalazin-1(2H)-one derivatives containing methylsulfanyl oxadiazole and
isoxazoline moieties. The synthesized new phthalazin-1(2H)-one derivatives were
characterized by mass, IR and NMR spectral data’s.
Experimental
NMR spectra were recorded on 400 MHz Varian-AS NMR spectrometer using TMS as an
internal standard. IR spectra were recorded by using Perkin Elmer Spectrum 100 Series FT-IR
spectrometer. Mass spectra were recorded on Agilent 1200 Series LC/MSD VL system.
Melting points were determined by using Buchi melting point B-545 instrument and are
uncorrected. All reactions were monitored by thin layer chromatography (TLC) using Merck
pre-coated TLC silica gel plates. The crude compounds were purified by using
CombiFlash® Companion® flash chromatography system, Teledyne Isco, Inc USA. BPL
Sanyo domestic microwave oven was used for reactions.
Preparation of methyl 2-(3-allyl-4-oxo-3,4-dihydrophthalazin-1-yl)acetate (2)
Allyl bromide (60.5 g, 0.5 mol) was added to a stirred solution of methyl 2-(4-oxo-3,4-
dihydrophthalazin-1-yl)acetate (1)24 (21.8 g, 0.10 mol) in dimethylformamide (250 mL) and

Synthesis and Antimicrobial Studies of Some New 3-Isoxazoline
1024
o
potassium carbonate (69.0 g, 0.5 mol) at room temperature and heated to 60-65 C for 6 h.
After completion of reaction, filtered the inorganics, the filtrate obtained was distilled
o
completely under reduced pressure at 60-65 C. The residue obtained was diluted with ice
water (500 mL) and stirred for 30 minutes. The precipitated product was filtered, dried and
recrystallized using isopropyl alcohol to yield compound 2 as white solid. M.p.: 90.2-95.8 oC;
1
MS: m/z=259.1 (M++1); IR (KBr) ν cm-1: 3012, 1708, 1675, 1599; H NMR (400 MHz,
DMSO-d6) δ: 3.64 (s, 3H, CH3), 4.11 (s, 2H, CH2), 4.73-4.74 (d, J=5.6 Hz, CH2), 5.08-5.19
(m, 2H, CH2), 5.94-6.04 (m, 1H, CH2), 7.87-7.92 (m, 3H, Ar-H), 8.30-8.32 (m, 1H, Ar-H).
Preparation of 2-(3-allyl-4-oxo-3,4-dihydrophthalazin-1-yl)acetohydrazide (3)
To a solution of phthalazin-1(2H)-one acetic acid methyl ester (2), (20.0 g, 0.077 mol) in
ethanol (300 mL) was added hydrazine hydrate (11.5 g, 0.22 mol). The reaction mixture was
heated under reflux for 10 h. Cooled the reaction mixture to room temperature, the precipitate
obtained was filtered, dried to yield compound 3 (11.5 g) as white solid. Yield: 74.6%; M.p.:
o
1
201.4-207.9 C; MS: m/z=259.1(M+1); IR (KBr) ν cm-1: 3202, 1758, 1673; H NMR (400
MHz, DMSO-d6): δ 1H NMR (DMSO-d6, 400 MHz) δ: 3.75 (s, 2H, CH2), 4.26-4.27 (d, J=4.0
Hz, 2H, CH2), 4.72-4.73 (d, J=5.6 Hz, 2H, NH2), 5.11-5.19 (m, 2H, CH2), 5.94-6.04 (m, 1H,
CH), 7.85-7.94 (m, 3H, Ar-H), 8.28-8.30 (d, J=8.0, 1H, Ar-H), 9.32 (s, 1H, NH).
Preparation of 2-allyl-4-((5-mercapto-1,3,4-oxadiazol-2-yl)methyl)phthalazin-1
(2H)-one (4)
Compound 3 (11.0 g, 0.042 mol) was added to a solution of KOH (3.8 g, 0.07 mol) in
anhydrous ethanol (160 mL). A solution of CS2 (8.2 g, 0.113 mol) in anhydrous ethanol
(40 mL) was added drop wise to the vigorously stirred mixture, which was refluxed for 10 h.
After completion of reaction, cooled and evaporated the solvent under reduced pressure. The
residue obtained was dissolved in water (200 mL) and acidified to pH 5~6 with hydrochloric
acid. The precipitated product was isolated by filtration and drying to yield compound 4
o
(8.5 g) as white solid. Yield: 66.6%; M.p.: 195.2-199.3 C; MS: m/z= 301.1 (M++1); IR
(KBr) νcm-1: 2540, 1754, 1672; 1H NMR (400 MHz, DMSO-d6) δ: 4.59 (s, 2H, CH2), 4.70-
4.72(d, J=5.6 Hz, 2H, CH2), 5.09-5.19 (m, 2H, CH2), 5.92-6.02 (m, 1H, CH), 7.88–8.27
(m, 3H, Ar-H), 8.27-8.33 (m, 1H, Ar-H), 14.37 (s, 1H, SH).
Preparation of 2-allyl-4-((5-(methylthio)-1,3,4-oxadiazol-2-yl)methyl) phthalazin-
1(2H) - one (5)
The compound 4 (8.0 g, 0.026 mol) was dissolved in 10% potassium hydroxide in water
(100 mL). To the clear solution, methyl iodide (4.4 g, 0.03 mol) was added and stirred for 4 h
at room temperature. After completion of reaction (checked by TLC), precipitated product
was filtered, washed with water, dried to get compound 5 (7.5 g) as white solid. Yield:
88.3%; M.p.: 119.9-125.5 oC; MS: m/z=315.1 (M++1); IR (KBr) cm−1: 2935, 1711, 1652; 1H
NMR (400 MHz, DMSO-d6) δ: 2.60 (s, 3H, S-CH3), 4.69 (s, 2H, CH2), 4.71-4.72 (d, J=5.6
Hz, 2H, CH2) 5.07-5.18 (m, 2H, CH2), 5.91-6.00 (m, 1H, CH), 7.89–8.03 (m, 3H, Ar-H),
8.31-8.33 (d, J=7.6 Hz, 1H, Ar-H).
General method for the preparation of 3-substituted phthalazin-1(2H)-one
derivatives 6(a-i)
An equimolar mixture of aldoxime (10.0 mmol) and N-chlorosuccinimide (10.0 mmol) were
made paste with dimethylformamide (2 mL) and alumina (2 g) in a 10 mL beaker. The
mixture was irradiated at 600 W for 2 min in domestic microwave oven. After adding

1025
K. R. V. REDDY et al.
compound (5) (9 mmol), the reaction mixture was irradiated further for 6 min. After
completion of reaction, diluted with water (25 mL) and extracted with ethyl acetate (3x50 mL).
The organic layer was washed with water (10 mL) and then with saturated sodium chloride
solution. After drying with anhydrous sodium sulphate and filtration, the solvent was
evaporated to get crude product, which was purified by using flash chromatography eluting
with ethyl acetate / hexane (1: 5) to get the corresponding phthalazin-1(2H)-ones 6(a-i).
2-((3-Methyl-4,5-dihydroisoxazol-5-yl)methyl)-4-((5-(methylthio)-1,3,4-oxadiazol-
2-yl)methyl)phthalazin-1(2H)-one (6a)
o
1
White solid; Yield: 52.1%; M.p.: 119.3-121.9 C; MS: m/z =372.1 (M++1); H NMR
(400 MHz, DMSO-d6) δ: 1.92 (s, 3H, C-CH3), 2.65 (s, 3H, S-CH3), 3.29-3.45 (m, 2H, CH2),
4.34-4.39 (dd, J=6.8 Hz, 13.4 Hz, 1H, CH2), 4.45-4.55 (m, 3H, two CH2), 5.22-5.26 (m, 1H,
oxazole-CH), 7.61-7.91 (m, 3H, Ar-H), 8.29-8.31 (m, 1H, Ar-H); 13C NMR (400 MHz,
DMSO-d6) δ: 163.7, 159.7, 156.1, 139.9, 141.9, 140.0, 134.35, 132.9, 132.7, 128.9, 127.6,
127.0, 126.0, 124.7, 50.9, 29.1, 10.68; IR (KBr) cm−1: 2937, 1712, 1658, 1514.
4-((5-(Methylthio)-1,3,4-oxadiazol-2-yl)methyl)-2-((3-phenyl-4,5-dihydroisoxazol-
5-yl)methyl)phthalazin-1(2H)-one (6b)
Yield: 65.6%; M.p.: 144.6-148.3 oC; MS: m/z =434.1 (M++1); 1H NMR (400 MHz, DMSO-d6)
δ: 2.65 (s, 3H, S-CH3), 3.29-3.45 (m, 2H, CH2), 4.34-4.39 (dd, J=6.8, 13.4 Hz, 1H, CH2),
4.45-4.55 (m, 3H, two CH2), 5.22-5.26 (m, 1H, oxazole-CH), 7.38-7.39 (m, 3H, Ar-H), 7.67-
7.87 (m, 5H, Ar-H), 8.45-8.47 (d, J=7.2 Hz, 1H, Ar-H); 13C NMR (400 MHz, DMSO-d6) δ:
166.1, 163.9, 159.5, 156.5, 139.9, 133.6, 132.0, 130.1, 129.2, 128.6, 128.5, 127.5, 126.8,
124.3, 78.1, 77.4, 77.0, 76.7, 53.5, 38.4, 29.7, 14.4; IR (KBr) cm−1: 2998, 1673, 1532.
2-((3-(4-Chlorophenyl)-4,5-dihydroisoxazol-5-yl)methyl)-4-((5-(methylthio)-
1,3,4-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (6c)
White solid; Yield: 53.2%; M.p.: 122.3-127.9 oC; MS: m/z = 468.1 (M++1); 1H NMR (400 MHz,
DMSO-d6): δ 2.67 (s, 3H, S-CH3), 3.28-3.43 (m, 2H, CH2), 4.32-4.37 (dd, J=6.8, 13.4 Hz,
1H, CH2), 4.48-4.58 (m, 3H, two CH2), 5.23-5.27 (m, 1H, oxazole-CH), 7.34-7.36 (d, J=8.0 Hz,
2H, Ar-H), 7.76-7.88 (m, 3H, Ar-H), 8.43-8.45 (d, J=7.6 Hz, 1H, Ar-H); 13C NMR (400 MHz,
DMSO-d6) δ: 166.0, 163.9, 159.4, 155.6, 140.0, 136.0, 133.7, 132.0, 129.1, 128.6, 128.0, 127.7,
127.4, 124.3, 78.4, 77.4, 77.1, 76.8, 53.3, 38.2, 29.6, 14.4; IR (KBr) cm−1: 2989, 1681, 1542.
2-((3-(4-Fluorophenyl)-4,5-dihydroisoxazol-5-yl)methyl)-4-((5-(methylthio)-
1,3,4-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (6d)
o
1
Yield: 53.8%; White solid; M.p.: 130.2-133-8 C; MS: m/z = 452.1 (M++1); H NMR
(400 MHz, DMSO-d6) δ: 2.67 (s, 3H, S-CH3), 3.28-3.43 (m, 2H, CH2), 4.32-4.37 (dd, J=6.8,
13.4 Hz, 1H, CH2), 4.48-4.58 (m, 3H, two CH2), 5.23-5.27 (m, 1H, oxazole-CH), 7.34-7.36
(d, J=8.0 Hz, 2H, Ar-H), 7.56-7.62 (d, J=8.0 Hz, 2H, Ar-H), 7.76-7.88 (m, 3H, Ar-H), 8.43-
8.45 (d, J=7.6 Hz, 1H, Ar-H); 13C NMR (400 MHz, DMSO-d6) δ: 166.0, 163.9, 159.4,
155.6, 140.0, 136.0, 1133.7, 132.0, 129.1, 128.5, 128.0, 127.7, 127.4, 124.3, 78.4, 77.4,
77.1, 76.8, 53.3, 38.2, 29.6, 14.4; IR (KBr) cm−1: 2989, 1752, 1681, 1542.
2-((3-(4-Methoxyphenyl)-4,5-dihydroisoxazol-5-yl)methyl)-4-((5-(methylthio)-
1,3,4-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (6e)
o
1
Yield: 59.3%; White solid; M.p.: 151.6-155.8 C; MS: m/z= 464.1 (M++1); H NMR
(400 MHz, DMSO-d6) δ: 2.65 (s, 3H, S-CH3), 3.27-3.42 (m, 2H, CH2), 3.82 (s, 3H, -OCH3),

Synthesis and Antimicrobial Studies of Some New 3-Isoxazoline
1026
4.30-4.35 (dd, J= 6.4 Hz, 1H, CH2), 4.46-4.52 (m, 3H, two CH2), 5.18-5.21 (m, 1H, oxazole-CH),
6.88 (dd, J=8.8 Hz, 2H, Ar-H), 7.58-7.60 (d, J=8.8 Hz, 2H, Ar-H), 7.75-7.87 (m, 3H,
Ar-H), 8.42 (d, J=7.6 Hz, 1H, Ar-H); 13C NMR (400 MHz, DMSO-d6) δ: 166.0, 163.9,
161.0, 159.4, 156.1, 139.9, 133.6, 131.9, 129.3, 128.2, 127.3, 124.3, 122.3, 114.0, 77.5,
76.9, 55.3, 53.4, 38.6, 36.3, 29.6, 14.4; IR (KBr) cm−1: 2988, 1753, 1657, 1545.
2-((3-(3,4-Dimethoxyphenyl)-4,5-dihydroisoxazol-5-yl)methyl)-4-((5-(methylthio)-
1,3,4-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (6f)
o
1
Yield: 45.0%; White solid; M.p.: 146.0-149.8 C; MS m/z = 494.1 (M++1); H NMR
(400 MHz, DMSO-d6) δ: 2.68 (s, 3H, S-CH3), 3.25-3.45 (m, 1H, CH2), 3.74 (m, 1H, CH2),
3.91 (s, 6H, two -OCH3), 4.37-4.48 (dd, J= 6.4 Hz, 1H, CH2), 4.52-4.57 (m, 3H, two CH2),
5.18-5.24 (m, 1H, oxazole-CH), 6.93-6.95 (dd, J=8.0 Hz, 2H, Ar-H), 7.05-7.14 (d, J=8.8 Hz,
2H, Ar-H), 7.38-7.40 (m, 1H, Ar-H), 7.57-7.7.99 (m, 2H, Ar-H), 8.47-8.49 (d, J=7.2 Hz,
1H, Ar-H); 13C NMR (400 MHz, DMSO-d6) δ: 166.0, 163.9, 161.0, 159.4, 156.1, 139.9,
133.6, 131.9, 129.3, 128.4, 128.2, 127.3, 124.3, 122.3, 121.6, 114.0, 77.7, 77.5, 77.2, 76.9,
55.3, 53.4, 38.6, 36.3, 29.6, 14.4; IR (KBr) cm−1: 2979, 17650, 1673, 1545.
2-((3-(3-(4-Fluorophenoxy)phenyl)-4,5-dihydroisoxazol-5-yl)methyl)-4-(5-methylthio)-
1,3,4-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (6g)
o
1
Yield: 52.8%; White solid; M.p.: 171.1-174.9 C; MS: m/z = 544.1 (M++1); H NMR
(400 MHz, DMSO-d6) δ: 2.66 (s, 3H, S-CH3), 3.24-3.40 (m, 2H, CH2), 4.34-4.39 (dd, J=6.8,
13.4 Hz, 1H, CH2), 4.45-4.56 (m, 3H, CH2), 5.20-5.34 (m, 1H, oxazole-CH), 6.98-7.00
(d, J=7.6 Hz, 2H, Ar-H), 7.09-7.11 (t, J=7.6, 7.2 Hz, 1H, Ar-H), 7.21-7.23 (m, 1H, Ar-H),
7.33-7.45 (m, 4H, Ar-H), 7.78-7.88 (m, 3H, Ar-H), 8.45-8.47 (m, 1H, Ar-H); 13C NMR
(400 MHz, DMSO-d6) δ: 166.1, 163.9, 159.5, 156.7, 155.2, 153.9, 144.2, 139.9, 133.7,
132.0, 129.8, 128.5, 127.8, 127.5, 126.4, 123.6, 123.3, 119.7, 117.6, 117.2, 78.4, 77.4, 77.1,
76.8, 53.4, 38.3, 29.6, 14.1; IR (KBr) cm−1: 2979, 1775, 1673, 1544.
4-((5-(Methylthio)-1,3,4-oxadiazol-2-yl)methyl)-2-((3-(thiophen-2-yl)-4,5-dihydro
isoxazol-5-yl)methyl)phthalazin-1(2H)-one (6h)
o
1
Yield: 70.2%; Off-white solid; M.p.: 139.5-143.1 C; MS: m/z = 440.1 (M++1); H NMR
(400 MHz, DMSO-d6) δ: 1.091.23 (m, 1H, CH2), 2.66 (s, 3H, S-CH3), 3.51-3.58 (dd, J=10.4,
16.8 Hz, 1H, CH2), 4.05-4.13 (m, 1H, CH2), 4.41-4.54 (m, 1H, CH2), 4.71-4.87 (m, 2H,
CH2), 5.08-5.12 (m, 1H, Oxazole CH), 7.17-7.22 (m, 1H, Ar-H), 7.38-7.39 (d, J=3.6 Hz, 1H,
Ar-H), 7.70-7.71 (d, J=4.8 Hz, 1H, Ar-H), 7.85-8.15 (m, 3H, Ar-H), 8.32-8.34 (d, J=7.6 Hz,
1H, Ar-H). 13C NMR (400 MHz, DMSO-d6) δ: 159.4, 155.6, 140.0, 136.0, 133.7, 132.0,
129.1, 128.9, 128.6, 128.4, 127.7, 127.7, 124.3, 77.4, 77.1, 76.8, 53.4, 38.3, 29.6, 14.1; IR
(KBr) cm−1: 2989, 1760, 1681, 1542.
2-((3-(2-Hydroxyphenyl)-4,5-dihydroisoxazol-5-yl)methyl)-4-((5-(methylthio)-
1,3,4-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (6i)
o
1
Yield: 45.6%; White solid; M.p.: 169.2-172.9 C; MS: m/z = 450.1 (M++1); H NMR
(400 MHz, DMSO-d6) δ: 2.66 (s, 3H, S-CH3), 3.41-3.48 (m, 1H, CH2), 3.60-3.67 (dd,
J=10.4, 17.2 Hz, 1H, CH2),4.16-4.20 (dd, J=5.6, 13.6 Hz, 1H, CH2), 4.39-4.44 (q, J=7.6,
13.4 Hz, 1H, CH2), 4.66-4.75 (m, 2H, CH2), 5.07-5.11 (m, 1H, oxazole-CH), 6.90-6.97
(q, J=7.2, 8.4, 17.8 Hz, 2H, Ar-H). 7.31-7.35 (t, J=7.2, 7.6 Hz, 1H, Ar-H), 7.42-7.44
(d, J=7.6 Hz, 1H, Ar-H), 7.90-8.05 (m, 3H, Ar-H), 8.32-8.34 (d, J=8.0 Hz, 1H, Ar-H), 9.84
(s, 1H, OH); 13C NMR (400 MHz, DMSO-d6) δ: 166.1, 163.9, 159.5, 156.5, 139.9, 133.6,
132.0, 130.1, 129.2, 128.6, 128.5, 127.5, 126.8, 124.3, 78.1, 77.4, 77.0, 76.7, 53.5, 38.4,
29.7, 14.4; IR (KBr) cm−1: 3326, 2975, 1675.

1027
K. R. V. REDDY et al.
Results and Discussion
The key intermediate in the synthesis of new phthalazine-1(2H)-one isoxazolines 6(a-i) is
methyl 2-(4-oxo-3,4-dihydrophthalazin-1-yl)acetate (1), which was prepared from phthalic
anhydride in good yield24.
O
O
O
O
O
NH
NH2
Allyl bromide / DMF /K2CO3
60-65 oC
NH2NH2.H2O
N
N
N
N
N
NH
Ethanol / reflux
1
O
2
O
O
3
i)CS2 / KOH /
N
O
Methanol
ii) HCl
N
SH
N
N
N
N
SCH3
SH
O
O
N
N
R-C=NOH / NBS
DMF / K2CO3
KOH / Water / CH3I
N
N
N
N
6(a-i)
O
O
5
O
4
N
O
R
R = a) Methyl, b) Phenyl, C) 4-Chlorophenyl, d) 4-Fluorophenyl, e) 4-methoxyphenyl, f) 3-4-
Dimethoxyphenyl, g) 4-Fluoro(3-phenoxy)phenyl, h) Thiophene-2yl, i) 2-hydroxyphenyl
Scheme 1. Synthesis of phthalazine isoxazoline derivatives 6(a-i)
N-allylation of compound (1) with allyl bromide in presence of potassium carbonate
gave methyl 2-(3-allyl-4-oxo-3,4-dihydrophthalazin-1-yl)acetate (2). The compound 2 on
reaction with hydrazine hydrate afford hydrazide 3. Oxadiazolinethione (4) was prepared
from reaction of the hydrazide 3 with carbon disulphide and potassium hydroxide, in
ethanol, followed by acidification. On treatment with methyl iodide, the compound (4) gave
2-allyl-4-(5-mercapto-1,3,4-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (5). Allyl function
of compound (5) undergoes 1,3 dipolar cyclization25 with aldoximes26 via nitrile oxide in
presence of N-chlorosuccinimide, potassium carbonate and dimethylformamide gave desired
compounds 6(a-i). The synthesised new compounds were characterised by mass, IR, NMR
and elemental analysis studies.
Biological screening
The in vitro antimicrobial activity was carried out against 24 h old cultures of two bacteria
and two fungi by cup-plate method in duplicate. Compounds (6a-i) has been tested for their
antimicrobial activity against E. coli and S. aureus and antifungal activity against M. gypsum
and A. flavus at a concentration of 100 µg/mL in DMSO using cup plate diffusion method.
Nutrient agar and potato dextrose agars were used to culture the bacteria and fungus
respectively. The solution of Amoxicillin 100 µg/mL and metronidazole at 100 µg/mL were
prepared in DMSO and used as standard for comparison of antibacterial and antifungal
activities respectively the results were discussed in Table 1.

Synthesis and Antimicrobial Studies of Some New 3-Isoxazoline
1028
Table 1. Antimicrobial activity of compounds 6(a-i)
Zone of Inhibition measured in mm
Antibacterial activity
Escherichia Staphylococcus
Antifungal activity
Microsporum Aspergillus
Synthesized
compounds
Coli S.D
100 µg/mL
2.50 0.70
6.50 0.70
5.00 0.00
3.00 0.00
3.50 0.70
7.50 0.70
8.50 0.70
6.00 0.70
3.00 0.00
-
Aureus S.D
100 µg/mL
4.50 0.70
8.5 0.70
7.5 0.70
4.50 0.70
3.00 0.00
8.00 0.00
11.50 0.70
7.50 0.70
3.00 0.00
-
Gypsum S.D
100 µg/mL
4.50 0.70
3.50 0.70
4.50 0.70
5.50 0.70
3.00 0.00
2.50 0.70
7.00 0.00
4.50 0.70
3.00 0.00
17.50 0.70
-
flavusd S.D
100 µg/mL
4.50 0.70
11.50 0.70
7.50 0.70
5.50 0.70
5.00 0.00
7.50 0.70
11.00 0.00
4.50 0.70
5.00 0.00
17.50 0.70
-
6a
6b
6c
6d
6e
6f
6g
6h
6i
Metronidazole
Amoxicillin
9.00 0.00
15.50 0.70
The compounds 6b and 6f-g exhibiting good activity against E. coli and compounds 6b, 6c, 6f and 6g
show good activity of against S. Aureus. Similarly the compounds 7g showed good activity against
M.gypsum and the compounds 6b and 6g showed activity against A. and all remaining compounds
exhibiting moderate activity against all the four organisms used for screening
Conclusion
In this article we report the synthesis of (6a-i), new phthalazine isoxazolines substituted at
C4 position with methylsulfonyl oxadiazole starting from commercially available phthalic
anhydride. Investigation of their antimicrobial activity revealed that isoxazolines with
substitution with thiophene (6h) shows the most active compound although it was
significantly less than that of positive control. The fact that the compounds prepared in this
study are chemically unrelated to the current medication suggests that the further work is
clearly warranted.
Acknowledgment
The author A.M.Sridhara thankful to Advinus Therapeutics Pvt.Ltd Bangalore, Chairman,
Department of Industrial Chemistry, Kuvempu University for supporting the research.
References
1.
Boland O M, Blackwell C C, Clarke B F and Ewing D J, Diabetes, 1993, 42(2),
336-340.
2.
3.
Hamamoto Y, Nagai K, Muto M and Asagami C, Exp Dermatol., 1993, 2(5), 231-235.
Yamaguchi M, Kamei K, Koga T, Akima M, Maruyama A, Kuroki T and Ohi N, J
Med Chem., 1993, 36(25), 4061-4068.
4.
5.
6.
7.
Ono K, Saito T, Sasano H, Moroi R, Sano M and Akimoto T, Xenobiotica, 1979, 9,
227-236.
Del Olmo E, Barboza B, Ybarra M I, Lopez-Perez J L, Carron R, Sevilla M A, Boselli C
and San Feliciano A, Bioorg Med Chem Lett., 2006, 16(10-15), 2786-2790.
Kashima K, Sato N, Sato K, Shimizu H and Mori M, Endocrinol., 1998, 139(8),
3404-3408.
Khalil A M, Berghot M A and Gouda M A, Eur J Med Chem., 2009, 44, 4448-4454.

1029
K. R. V. REDDY et al.
8.
9.
Leenen F H H, Smith D L, Faraks R M, Reeves R A and Marquez-Julio A, Am J
Med., 1987, 82, 969-978.
Tanaka S, Tanaka M and Akashi A, Stroke, 1989, 20, 1724-1729.
10. Kemp J P, Meltzer E O, Orgel H A, Welch M J, Bucholtz G A, Middleton Jr E,
Spector S L, Newton J J and Perhach Jr J L, J Allergy Clin Immunol., 1987, 79,
893-899.
11. Kador P F, Kinoshita J H and Sharpless N E, J Med Chem., 1985, 28(7), 841-849.
12. Mylari B L, Larson E R, Beyer T A, Zembrowski W J, Aldinger C E, Dee M F,
Siegel T W and Singleton D H, J Med Chem., 1991, 34, 108-122.
13. Kai H, Matsumoto H, Hattori N, Takase A, Fujiwara T and Sugimoto H, Bioorg Med
Chem Lett., 2001, 11(5), 1997-2000.
14. Basappa, Sadashiva M P, Mantelingu K, Swamy S N and Rangappa K S, Bioorg Med
Chem., 2003, 11, 4539-4544.
15. Tangallapally R P, Sun D, Rakesh N, Budha N, Lee R E B, Lenaerts A J M, Meibohm B
and Lee R E, Bioorg Med Chem Lett., 2007, 17(23), 6638-6642.
16. Srivastava S, Bajpai L K, Batra S, Bhaduri A P, Maikhuri J P, Gupta G and Dhar J D,
Bioorg Med Chem., 1999, 7, 2607-2613.
17. Conti P, Dallanoce C, Amici M D, Micheli C D and Klotz K N, Bioorg Med Chem.,
1998, 6, 401-419.
18. Saitoh M, Kunitomo J, Kimura E, Hayase Y, Kobayashi H, Uchiyama N, Kawamoto T,
Tanaka T, Mol C D, Dougan D R, Textor G S, Snell G P and Itoh F, Bioorg Med
Chem., 2009, 17(5), 2017-2029.
19. Chen C J, Song B A, Yang S, Xu G F, Bhadury P S, Jin L H, Hu D Y, Li Q Z, Liu F,
Xue W, Lu P and Chen Z, Bioorg Med Chem., 2007, 15, 3981-3989.
20. Iqbal R, Zareef M, Ahmed S, Zaidi J H, Arfan M, Shafique M and Al-Masoudi N A, J
Chin Chem Soc., 2006, 53, 689-696.
21. Ram V J and Vlietinck A J, J Heterocycl Chem., 1988, 25, 253-256.
22. Kalsi R, Bhalla T N, Parmar S S and Barthwal J P, Pharmacol., 1989, 39, 103-108.
23. Almasirad A, Vousooghi N, Tabatabai S A, Kebriaeezadeh A and Shafiee A, Acta
Chim Slov., 2007, 54, 317-324.
24. Sinay Jr Terry G and Sysko Robert J, U.S. Patent 4904782, 1990.
25. Huisgen R, Angew Chem Int Ed Engl., 1963, 2, 565-598.
26. Liu K C, Shelton B R and Howe R K, J Org Chem., 1980, 45, 3916-3918.

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