Synthesis and antimicrobial activities of some novel quinoxalinone derivatives

Article abstract of DOI:10.3390/50600864

Condensation of 4-benzoyl-1,2-phenylenediamine with sodium pyruvate in acetic acid furnished two products which were identified as 6-benzoyl and 7-benzoyl-3-methyl-2(1H)quinoxalinones (1a,b). Fusion of 1a with aromatic aldehydes furnished the styryl derivatives 2a-c. Alkylation of 1a,b with dimethyl sulphate or ethyl chloroacetate produced the N-alkyl derivatives 3a,b and 4a,b. Hydrazinolysis of the ester derivative 4a with hydrazine hydrate afforded the hydrazide derivative 5 which underwent condensation with aldehydes to give the corresponding hydrazone derivatives 6a,b. In addition, chlorination of 1a with thionyl chloride afforded the 2-chloro derivative 7 which was subjected to reaction with sodium azide and n-butylamine to yield the corresponding tetrazolo (8) and n-butylamino (9) derivatives, respectively. The structures of the compounds prepared were confirmed by analytical and spectral data. Also, some of the synthesized compounds were screened for antimicrobial activity.

Full text of DOI:10.3390/50600864

Molecules 2000, 5, 864-873
molecules
ISSN 1420-3049
http://www.mdpi.org
Synthesis and Antimicrobial Activities of Some Novel
Quinoxalinone Derivatives
M.M. Ali1, M.M.F. Ismail2, M.S.A. El-Gaby3, M. A. Zahran1 and Y.A. Ammar1*
1Department of Chemistry, Faculty of Science, Al-Azhar University, Nasr-City 11884, Cairo, Egypt
Fax: 002(02)2629356, E-mail: yossry@yahoo.com
2Department of Pharmaceutical Chemistry, Faculty of Pharmacy (Girl’s), Al-Azhar University,
Nasr-City, Cairo, Egypt
3Department of Chemistry, Faculty of Science, Al-Azhar University at Assiut, Assiut 71524, Egypt
Fax: 002(088)325436, E-mail: m_elgaby@hotmail.com
Received: 29 April 2000 / Accepted: 13 June 2000 / Published: 18 June 2000
Abstract: Condensation of 4-benzoyl-1,2-phenylenediamine with sodium pyruvate in acetic
acid furnished two products which were identified as 6-benzoyl and 7-benzoyl-3-methyl-
2(1H)quinoxalinones (1a,b). Fusion of 1a with aromatic aldehydes furnished the styryl de-
rivatives 2a-c. Alkylation of 1a,b with dimethyl sulphate or ethyl chloroacetate produced the
N-alkyl derivatives 3a,b and 4a,b. Hydrazinolysis of the ester derivative 4a with hydrazine
hydrate afforded the hydrazide derivative 5 which underwent condensation with aldehydes to
give the corresponding hydrazone derivatives 6a,b. In addition, chlorination of 1a with
thionyl chloride afforded the 2-chloro derivative 7 which was subjected to reaction with so-
dium azide and n-butylamine to yield the corresponding tetrazolo (8) and n-butylamino (9)
derivatives, respectively. The structures of the compounds prepared were confirmed by ana-
lytical and spectral data. Also, some of the synthesized compounds were screened for antimi-
crobial activity.
Keywords: Quinoxalinones, 4-benzoyl-1,2-phenylenediamine, antimicrobial activity.
© 2000 by MDPI (http://www.mdpi.org). Reproduction is permitted for noncommercial purposes.

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Molecules 2000, 5
Introduction
Numerous quinoxaline derivatives are important as antibacterial, antifungal, anticancer, antidepres-
sant and antiinflammatory agents [1-3]. From this point of view and in continuation of our interest on
the chemistry of quinoxaline [4-9], it was of interest to synthesized some quinoxalinone derivatives with
the aim of investigating their antimicrobial properties.
Results and Discussion
Condensation of 4-benzoyl-1,2-phenylenediamine with sodium pyruvate in acetic acid at room tem-
perature furnished two products which showed analytical and spectral data in good agreement with the
3-methylquinoxalinone structures 1a,b. The reaction proceeds due to the (–R) effect of the benzoyl
group which deactivates the p-amino group, thus the m-amino group initiates the reaction to give 6-
benzoyl-3-methyl-2(1H)quinoxalinone 1a as the main product (60%). The second isomer was obtained
1
in 30% yield and identified as 7-benzoyl-3-methyl-2(1H)quinoxalinone 1b (Scheme 1). The H NMR
spectrum of 1a in DMSO-d6 exhibited signals at 2.6 (3H, s, CH3), 8.21 (1H, broad, NH; cancelled with
D2O). Also, the mass spectrum displayed a molecular ion peak at m/z 264 (70%). The proposed frag-
mentation pattern of 1a is illustrated in Scheme 2.
O
H
N
O
Ph
(b)
(a)
(b)
N
CH3
O
O
NH2
NH2
OH
1b
C
C
+
O
CH3
H
N
O
Ph
(a)
O
N
CH3
Ph
1a
ArCHO
H
N
O
O
N
CH=CHAr
Ph
2a-c
a; Ar= C6H4.Cl-p
; Ar= C H .OCH -p
b
c; Ar= C66H24(OCH33)3-3,4,5
Scheme 1.

866
Molecules 2000, 5
+
.
H
N
O
.
.
B
m/z 265
(12.2 %)
-Ph
+ H
m/z 187
(19.6 %)
A
Ph
N
CH3
O
m/z 195
(1.4 %)
.
m/z 264
(70.0 %)
-B
+
O
+
- CO
.
Ph
Ph C
-A
m/z 77
(41.4 %)
m/z 105
(37.9%)
+
+
.
H
N
H
N
O
-CH3CN
m/z 118
(3.4 %)
CH3
Ph
N
N
CH3
O
m/z 236
(5.6 %)
m/z 159
(100%; base peak)
.
- CO
.
+
+
.
H
N
H
N
.
- CH3
- CH3CN
m/z 235
(6.8 %)
m/z 90
(7.1 %)
CH3
N
N
m/z 131
(23.5%)
m/z 116
(1.9 %)
Scheme 2. Fragmentation pattern of compound 1a.
6-Benzoyl-3-substituted styryl-2(1H)quinoxalinones 2a-c were obtained via fusion of 1a with aro-
matic aldehydes in the presence of piperidine at 1600C. The 1H NMR of 2b in DMSO-d6 showed signals
at 4.2 (3H, s, OCH3), 7.20, 7.65 (2H, 2s, CH=CH). The coupling constant of the styryl protons is 14-15
Hz, indicating trans isomerism at the double bond.
It was reported that quinoxalinone was alkylated using dimethyl sulphate to furnish the correspond-
ing N-methyl derivative [10]. In a similar fashion compounds 1a,b were alkylated with dimethyl sul-
phate in the presence of sodium hydroxide to afford the 6-and 7-benzoyl-1,3-dimethyl-
1
2(1H)quinoxalinones 3a,b, respectively (Scheme 3). The H NMR spectrum of 3a in CDCl3 showed
signals at 2.6 (3H, s, CH3), 3.6 (3H, s, N-CH3). Also, when compounds 1a,b were alkylated with ethyl
chloroacetate in acetone using potassium carbonate as catalyst, the ester derivatives 4a,b were pro-
1
duced. The H NMR spectrum of 4a in CDCl3 showed 1.4 (3H, t, CH3-ester), 2.4 (3H, s, CH3), 4.2
(2H, q, OCH2–ester), 4.9 (2H, s, N-CH2).
Hydrazinolysis of 4a with hydrazine hydrate afforded 1-[6-benzoyl-3-methyl-2(1H)-quinoxali-
none]acetic acid hydrazide (5). Its mass spectrum showed a molecular ion peak at m/z 336 (M+, 1.6%)

867
Molecules 2000, 5
and 321[M+-15 (CH3.)]. Refluxing of the hydrazide derivative 5 with aromatic aldehydes in ethanol fur-
1
nished the corresponding 1-[6-benzoyl-3-methyl-2(1H)quinoxalinone]acetic hydrazones 6a,b. The H
NMR spectrum of 6b showed signals 2.6 (3H, s, CH3), 4.0 (3H, s, OCH3) and 9.0 (1H, s, N=CH).
CH2COOEt
CH3
N
N
O
O
(CH3)2SO4
ClCH2COOEt
1a,b
R
R
N
CH3
N
CH3
3a, R= 6-benzoyl
b, R= 7-benzoyl
, R= 6-benzoyl
b, R= 7-benzoyl
4a
4a
+
NH2NH2
CH2CONHN=CHAr
CH2CONHNH2
N
O
N
O
ArCHO
O
O
N
CH3
N
CH3
Ph
6a, Ar = C6H5
Ph
5
, Ar = C H OCH -p
b
6
4
3
Scheme 3.
In addition, chlorination of 1a with thionyl chloride furnished 6-benzoyl-2-chloro-3-methyl-
quinoxaline (7) (Scheme 4).
H
N
N C4H9-n
CH3
N
Cl
SOCl2
n-Butylamine
1a
O
O
N
N
CH3
Ph
Ph
9
7
NaN3
N
N
N
N
N
N
N3
O
O
N
CH3
CH3
Ph
Ph
8
Scheme 4.

868
Molecules 2000, 5
Its IR spectrum revealed the disappearance of the NH band, present in the parent compound. Also,
its mass spectrum showed m/z 267 [M+-15 (CH3), 56.1%]. When the chloro derivative 7 was reacted
with sodium azide in ethanol, the 7-benzoyl-4-methyltetrazolo[1,5-a]quinoxaline (8) was obtained
which was found to be in tautomeric equlibrium with the 2-azido derivative [11]. Its IR spectrum dis-
played absorption bands at 1700 (C=O) and the characteristic absorption band for the azido group at
2240 cm-1 [12]. Also, its mass spectrum displayed a molecular ion peak m/z at 289 (M+, 1.6%). Finally,
condensation of 7 with n-butylamine in DMF furnished 6-benzoyl-2-butylamino-3-methylquinoxaline
(9). Its IR spectrum showed a NH band at 3250 cm-1.
Anitmicrobial activities
The antimicrobial activities of the synthesized compounds 1a,b, 2b, 4a,b, 5 and 6b were determined
by the agar diffusion technique [13]. The organisms tested were Staphyloccus aureus (NCTC 7447),
Bacillus cereus (ATCC-14579), Serratia marcescens (IMRU 70), Proteus merabitis (NCTC-289), As-
pergillus ochraceus Wilhelm (AUCC-230) and Penicillium chrysogenum Thom (AUCC-530). The agar
media were inoculated with test organisms and a solution of the tested compound in DMSO (250
mg/ml) was placed separately in cups (8 mm diameter) in the agar medium. Streptomycin (25 mg) and
mycostatin (30 mg) were used as a reference for the antibacterial and antifungal activities, respectively.
The inhibition zones were measured after 24 hr. incubation. The results of the antimicrobial activity
tests are summarized in Table 1.
Table 1. Antimicrobial activity of some synthesized compounds.
Compd. Staphyloccus
Bacillus
cereus
Serratia
Proteus
Aspergillus
ochraceus
Penicillium
chrysogenum
Thom
No.
aureus
marcesens
merabitis
(NCTC 7447) (NCTC 14579) (IMRU-70) (NCTC-289) Wilhelm
(AUCC-230) (AUCC-530)
1a
1b
2b
4a
4b
5
+++
++
++
+++
++
+++
++
++
++
+
++
++
+
+++
++
++
+++
++
++
+++
+++
++
++
+++
++
+
++
++
+++
R
+++
++
++
++
+++
R
++
+
6b
+++
+++
+++
+++
Key: R : Resistant
+ : Less active (0.2-0.5 mm)
++ : Moderately active (0.6-1.4 mm)
+++ : Highly active (1.5-2.0 mm)

869
Molecules 2000, 5
Most of the synthesized compounds were found to possess varied antibacterial activities towards all
the microorganisms used with minimal inhibitory concentration (MIC). However, none of the tested
compounds showed superior activity than the reference drugs.
Experimental
General
Melting points were determined by an Electrothermal melting point apparatus and are uncorrected.
Elemental analyses were carried out by Microanalytical Unit, Faculty of Science, Cairo University. IR
1
spectra were recorded on a Shimadzu 440 spectrophotometer using KBr disks. H NMR spectra were
measured on a Varian EM-360 90 MHz spectrophotometer (Varian, UK) using TMS as internal stan-
dard. The mass spectra were run by a Shimadzu-GC-MS-GP 100 EX using the direct inlet system.
3-Methyl-2(1H)quinoxalinones (1a,b)
A solution of 4-benzoyl-1,2-phenylenediamine (0.01mol) in acetic acid (50 mL) was treated with a
solution of sodium pyruvate (0.01mol) in a minimum amount of water. The reaction mixture was stirred
at room temperature for 2 hr and the solid thus obtained was subjected to fractional crystallization to
give products 1a,b (Table 2). Spectral data: 1a: IR (cm-1): 3320 (NH), 2950 (CH-aliphatic), 1690
1
(C=O); H NMR (ppm, DMSO-d6): of 1a; 2.47 (3H, s, CH3), 6.72-7.82 (8H, m, Ar-H), 8.43 (1H,
broad, NH; exchangeable with D2O). Mass spectrum (m/z): 264 (M, 70%), 236 (5.6%), 235 (6.8%),
195 (1.4%), 187 (19.6%), 159 (100%), 131 (23.5%), 118 (3.4%), 116 (1.9%), 105 (37.3%) and 77
(41.4%). 1b: 1H NMR (ppm, DMSO-d6): 2.6 (3H, s, CH3), 8.21 (1H, broad, NH), 6.8-7.4 (8H, m, Ar-
H).
6-Benzoyl-3-substituted styryl-2(1H)quinoxalines (2a-c)
A mixture of (1a, 0.01mol), the requisite aldehyde (0.01mol) and piperidine (0.5mL) was fused at
160oC for 2 hr. The obtained product was crystallized from the appropriate solvent (Table 2) to afford
compounds 2a-c.
6-Benzoyl-3-(4-chlorostyryl)-2(1H)quinoxaline (2a)
IR (cm-1): 3340 (NH), 1680, 1650 (C=O). 1H NMR spectrum of 2a in DMSO-d6 exhibited signals at
7.16. 7.78 (2H, 2s, CH=CH), 7.89-8.20 (12H, m, Ar-H), 8.72 (1H, broad, NH; exchangeable with
D2O).

870
Molecules 2000, 5
6-Benzoyl-3-(4-methoxystryryl)-2-(1H)quinoxaline (2b)
IR (cm-1): 3080 (NH), 1682, 1645 (C=O). 1H NMR spectrum of 2b in DMSO-d6 exhibited signals at
4.2 (3H, s, OCH3), 7.20, 7.65 (2H, 2s, CH=CH), 7.90-8.4 (12H, m, Ar-H), 8.6 (1H, s, NH; exchange-
able with D2O).
6-Benzoyl-3-(3,4,5-trimethoxystryryl)-2-(1H)quinoxaline (2c)
IR (cm-1): 3320 (NH), 1690, 1635 (C=O). 1H NMR spectrum of 2c in DMSO-d6 exhibited signals at
3.91 (6H, s, 2OCH3), 4.1 (3H, s, OCH3), 7.30, 7.42 (2H, 2s, CH=CH), 7.82-8.32 (10H, m, Ar-H), 9.21
(1H, s, NH; exchangeable with D2O).
6-Benzoyl or 7-benzoyl-1,3-dimethyl-2(1H)quinoxalines (3a,b)
Dimethyl sulphate (0.022 mol) was added to a solution of (1a or 1b; 0.01 mol) in sodium hydroxide
solution (10%, 50 mL). The reaction mixture was stirred at 60oC for 3 hr and the obtained solid was
recrystallized to give (3a,b; Table 2). IR spectrum of 3a revealed bands at 2980 (CH-aliphatic) and
1695, 1644 (CO), also 1H NMR spectrum of 3a in CDCl3 showed signals at 2.6 (3H, s, CH3), 3.6 (3H,
s, N-CH3), 7.9-8.5 (8H, m, Ar-H). IR (cm-1) spectrum of 3b: 2950 (CH-aliphatic), 1693, 1638 (C=O).
1H NMR spectrum of 3b in CDCl3 showed signals at 2.46 (3H, s, CH3), 3.71 (3H, s, N-CH3), 7.82-8.31
(8H, m, Ar-H).
Ethyl [6-or 7-benzoyl-3-methyl-2(1H)quinoxalinon-1-yl]acetate (4a,b)
A mixture of (1a or 1b; 0.01 mol), ethyl chloroacetate (0.01 mol) and potassium carbonate (2 g) in
acetone (50 ml) was refluxed for 6 hr. The obtained product was crystallized from the proper solvent to
13
furnish (4a,b; Table 2). IR spectrum of 4a: 2982 (CH-aliphatic), 1735, 1680 (C=O). C NMR of 4a
DMSO-d6 showed 15.3 (CH3-ester), 21.2 (CH3), 45.4 (N-CH2), 58.3 (OCH2-ester), 119-148.6 (13 C
sp2 carbon atoms) and 168.2, 170.4, 175.8 (3 C=O groups). IR spectrum of 4b afforded bands at 2985
(CH-aliphatic) and 1730, 1695 (C=O). 1H NMR spectrum of 4b in CDCl3 showed signals at 1.2 (3H, t,
CH3-ester), 2.4 (3H, s, CH3), 4.2 (2H, q, OCH2-ester), 4.9 (2H, s, N-CH2) and 7.1-8.0(8H, m, Ar-H).
[6-Benzoyl-3-methyl-2-quinoxalinon-1-yl]acetic acid hydrazide (5)
To a solution of (4a, 0.01mol) in ethanol (50 ml), hydrazine hydrate (0.012 mol) was added. The re-
action mixture was refluxed for 10 hr and the obtained product was crystallized from the suitable sol-
vent to yield (5; Table 2). Its IR spectrum showed bands at 3300, 3200 (NH, NH2), 1690, 1675 (C=O).
Also its mass spectrum showed m/z 336 (1.6%), 321 (15.8%), 305 (84.8%), 277 (5.6%), 264 (5.0%),
249 (100%), 235 (3.1%), 216 (4.5%), 188 (2.2%), 130 (2.3%), 116 (2.3%), 105 (52.4%) and 77

871
Molecules 2000, 5
(53.1%).
[6-Benzoyl-3-methyl-2(1H)quinoxalinon-1-yl]acetic acid hydrazones (6a,b)
A solution of the hydrazide derivative 5 (0.01mol) in ethanol (30 mL) was treated with benzaldehyde
or p-methoxybenzaldehyde (0.01 mol). The reaction mixture was refluxed for 4 hr and the product that
obtained after filtration was crystallized from the proper solvent to afford (6a,b; Table 2). IR spectrum
of 6a showed bands at 2990 (CH-aliphatic) and 1690, 1670 (C=O). 1H NMR spectrum of 6a in CDCl3
exhibited signals at 2.45 (3H, s, CH3), 4.83 (2H, s, N-CH2), 7.40-8.22 (13H, m, Ar-H), 8.62 (1H,
1
broad, NH; exchangeable with D2O) and 9.10 (1H, s, N=CH). H NMR spectrum of 6b in CDCl3 ex-
hibited signals at 2.6 (3H, s, CH3), 4.0 (3H, s, OCH3), 4.8 (2H, s, N-CH2), 7.2-8.1 (12H, m, Ar-H), 8.5
(1H, broad, NH) and 9.0 (1H, s, N=CH).
6-Benzoyl-2-chloro-3-methylquinoxaline (7)
To a solution of 1a, 0.01mol) in dioxane (20 mL) and DMF (5 mL), thionyl chloride (10 mL) was
added. The reaction mixture was refluxed for 4 hr and the obtained solid was crystallized from the
proper solvent to afford compound 7 (Table 2). Its mass spectrum showed m/z at 267 [M+-15 (CH3);
56.1%], 254 (8.1%), 242 (14.3%), 240 (10.4%), 225 (8.8%), 184 (2.6%), 162 (100%), 105 (COPh;
3.6%) and 77 (73.2).
7-Benzoyl-4-methyltetrazolo[1,5-a]quinoxaline (8)
To a solution of 7 (0.01mol) in ethanol (50 mL), sodium azide (0.01 mol) was added and the reac-
tion mixture was refluxed for 6 hr. The product obtained after filtration was crystallized from a suitable
solvent to furnish 8 (Table 2). Its IR spectrum exhibited the following bands: 2943 (CH-aliphatic), 2240
(N3), 1700 (C=O), 1609 (N=N), 1586 (C=N). 1H NMR spectrum of 8 in CDCl3 exhibited signals at 2.57
(3H, s, CH3), 7.67-8.21 (8H, m, Ar-H). Also, its mass spectrum showed a molecular ion peak at m/z
289 (M+, 1.6%), 235 (1.2%), 185 (12.4%), 139 (1.5%), 105 (COPh, 100%) and 77 (Ph, 77.2%).
6-Benzoyl-2-(n-butylamino)-3-methylquinoxaline (9)
A mixture of 7 (0.01mol) and n-butylamine (0.01 mol) in DMF (20 mL) was heated under reflux for
3 hr. After allowing the reaction mixture to cool to room temperature, it was poured into cooled water
(100mL). The insoluble material was filtered off and crystallized from the appropriate solvent to give 9
(Table 1). Its IR spectrum revealed bands at 3250 (NH), 2995 (CH-aliphatic) and 1688 (C=O). Mass
spectrum of 9 exhibited a molecular ion peak at m/z 319 (25%) together with base peak at m/z 105
(100%).

872
Molecules 2000, 5
Table 2. Physical data of the compounds prepared.
Compd.
No.
M.P.
(oC)
Solvent
Cryst.
Yield
(%)
60
Mol. Formula
(M.wt)
Analyses,%
H
C
N
1a
148-50 DMF/H2O
C16H12N2O2
(264)
72.73 4.55 10.61
72.80 4.40 10.70
72.73 4.55 10.61
72.60 4.50 10.60
1b
2a
2b
2c
3a
3b
4a
4b
5
265-7
178-80
158-60
220-1
158-60
134-6
155-7
180-2
278-9
194-5
172-3
135-7
140-2
168-70
Ethanol
Ethanol
Ethanol
DMF/H2O
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
DMF/H2O
DMF/H2O
Benzene
Ethanol
Ethanol
30
72
73
60
64
58
65
62
73
71
74
78
67
60
C16H12N2O2
(264)
C23H15N2O2Cl 71.41 3.88
7.25
7.10
7.33
7.20
6.33
6.10
(386.5)
C24H18N2O3
(382)
71.50 3.90
75.39 4.71
75.30 4.80
70.59 4.98
70.60 5.00
C26H22N2O3
(442)
C17H14N2O2
(278)
73.38 5.04 10.07
73.40 5.00 10.10
73.38 5.04 10.07
73.30 5.20 10.10
C17H14N2O2
(278)
C20H18N2O4
(350)
68.57 5.14
68.60 5.20
68.57 5.14
68.40 5.10
8.00
8.10
8.00
8.10
C20H18N2O4
(350)
C18H16N4O3
(336)
64.29 4.76 16.67
64.10 4.80 16.70
70.76 4.72 13.21
70.80 5.00 13.20
68.72 4.85 12.34
68.60 4.74 12.45
6a
6b
7
C25H20N4O3
(424)
C26H22N4O4
(454)
C16H11N2OCl 67.96 3.89
9.91
(282.5)
C16H11N5O
(289)
67.80 3.90 10.00
66.44 3.81 24.22
66.58 3.70 24.14
75.24 6.58 13.17
75.40 6.72 13.00
8
9
C20H21N3O
(319)

873
Molecules 2000, 5
References and Notes
1. Kaneko, C.; Katagiri, S. Asahi Glass Co. Ltd., Japan Kokai Tokkyo Koho JP 1988, 62, 207, 264
(Chem.Abs., 1988, 109, 231061).
2. Sarges, R.; Howard, H.R.; Browne, R.C.; Label, L.A.; Seymour, P.A. J. Med. Chem. 1990, 33,
2240.
3. Kinashi, H.; Otten, S. L.; Dunkan, J. S.; Hutchinson, C. R. J.Antibiot. 1988, 41, 642.
4. Ammar, Y.A.; Ismail, I.M.;.El-Sharief, A.M.Sh.; Mohamed, Y. A.; Amer, R. M. J. Prakt.Chem.
1988, 330, 821.
5. Ammar, Y.A.; Ismail, I. M.; El-Sharief, A. M. Sh.; Mohamed, Y. A.; Amer, R. M. J. Indian Chem.
Soc. 1989, 66, 124.
6. Ammar, Y. A. J. Serb. Chem. Soc. 1990, 55, 9, 515.
7. Ammar, Y.A.; Mohamed, Y.A.; El-Sharief, A.M.Sh.; Zahran, M.A. Egypt J.Chem. 1991, 34, 4,
361.
8. Mohamed, Y. A.; Ammar, Y. A.; El-Sharief, A. M. Sh.; Zahran, M. A. Affinidad 1993, 444, 123.
9. El-Shrief, A. M. Sh.; Ali, M.M.; Ammar, Y.A.; Abd Salam, A. A. Pak. J. Sci. Ind. Res. 1996, 1-4,
5.
10. Basr, M. Z. A.; Mahgoub, S. A.; Abd El-Latif, F.F.; Fahmy, A.M.; Moustafa, O. S. J. Ind. Chem.
Soc. 1990, 67, 216.
11. Stole, R.; Hasuch, F. J. Prakt. Chem. 1933, 136, 9.
12. Khalil, Z. H.; Geies, A. A. Phosphorous, Sulfur and Silicon 1990, 60, 223.
13. Carrod, L. P.; Grady, F. D. Antibiotics and Chemotherapy, 3rd. ed.; Churchill Livingstone: Edin-
burgh, 1972; p. 477.
Samples Availability: Available from the authors.
© 2000 by MDPI (http://www.mdpi.org). Reproduction is permitted for noncommercial purposes.