Physicochemical and biological characterization of novel macrocycles derived from o-phthalaldehyde

Article abstract of DOI:10.1016/j.ejmech.2008.09.035

A series of novel macrocyclic compounds were synthesized by the condensation of o-phthalaldehyde with aromatic amino alcohols followed by treatment with 1,2-dibromoethane or 1,3-dibromopropane in non-template method. The structural features of the isolate

Full text of DOI:10.1016/j.ejmech.2008.09.035

European Journal of Medicinal Chemistry 44 (2009) 2621–2625
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Physicochemical and biological characterization of novel macrocycles derived
from o-phthalaldehyde
,
b
b
b,
**
P. Muralidhar Reddy a, Yen-Peng Ho a , Kanne Shanker , Rondla Rohini , Vadde Ravinder
*
a Department of Chemistry, National Dong Hwa University, Hualien, Taiwan
b Department of Chemistry, Kakatiya University, Warangal 506 009, AP, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 March 2008
Received in revised form 6 September 2008
Accepted 11 September 2008
Available online 7 October 2008
A series of novel macrocyclic compounds were synthesized by the condensation of o-phthalaldehyde
with aromatic amino alcohols followed by treatment with 1,2-dibromoethane or 1,3-dibromopropane in
non-template method. The structural features of the isolated macrocycles have been determined from
the microanalytical, IR, 1H, 13C NMR and mass spectral studies. Antimicrobial activities of these macro-
cyclic compounds were tested against the Gram-positive (Bacillus subtilis, Staphylococcus aureus) and
Gram-negative (Escherichia coli, Klebsiella pneumoniae) bacteria and found to exhibit potential antibac-
terial activity. The macrocycles were also tested in vitro to evaluate their activity against fungi, namely,
Aspergillus flavus (A. flavus) and Fusarium species.
Keywords:
Physicochemical
o-Phthalaldehyde
Macrocyclic compounds
Antimicrobial activity
Ó 2008 Elsevier Masson SAS. All rights reserved.
1. Introduction
demetallation from the macrocyclic complex [2,21]. Secondly,
template synthesis from dicarbonyl compounds and diamines
Macrocyclic compounds possessing heteroatoms are valuable
compounds with broad spectrum of pharmacological activities [1–4]
apart from their potential application in the field of molecular
catalysis. More importantly, macrocyclic Schiff bases and the rele-
vant transition metal complexes are of great interest in coordination
chemistry, although this subject has been extensively studied [5–7].
These compounds exhibit biological activity as antibiotics, antiviral,
antitumour, antifungal, antibacterials and anticancer agents because
of their specific structures [8–11]. Interest in the chemistry and
biological activity of tetradentate macrocyclic compounds and its
complexes has increased in recent years, mainly due to their rele-
vance to the bioorganic and bioinorganic chemistry of metal
complexes [12–16]. Particular attention has been devoted to their
correlation with the active sites of metalloenzymes and metal-
loproteins and to mimicing the activity of such biomolecules [17–20].
Macrocyclic Schiff bases provide a method of establishing
multiple N2O2 donor sites capable of forming multimetallic
complexes. Template synthesis with metal ions is the usually
employed route to get macrocyclic Schiff bases. However, template
synthesis has two substantial disadvantages. Firstly, more complete
the template condensation, stronger the metal ion bound in the
macrocyclic cavity. Hence it is difficult to isolate the free ligand by
usually affords symmetric macrocyclic complexes and thus other
starting building blocks have to be used to obtain nonsymmetric
macrocyclic Schiff bases [22–25]. To the best of our knowledge, no
work has been done on the condensation of o-phthalaldehyde with
aromatic amino alcohols by non-template methods. Hence, we
report here the non-template synthesis of new macrocyclic
compounds with characterization, antibacterial and antifungal
activity. These compounds behave as tetradentate ligands by
donating four lone pairs of electrons two each from nitrogen atoms
and other two each from oxygen atoms.
2. Results and discussion
2.1. Chemistry
The macrocyclic compounds were derived from the condensa-
tion reaction of o-phthalaldehyde with aromatic amino alcohols
followed by ring closure with aliphatic dihaloalkane compounds.
The condensation reaction occurred efficiently in a water–meth-
anol (1:1) suspension medium [26] without using any acid catalyst
and the products were isolated by simple filtration.
The intermediates required for the synthesis of the new mac-
rocycles, the diimine–dihydroxy compounds, were prepared by
condensation reaction between 1 mol of o-phthaladehyde 1 and
2 mol of aromatic aminoalcohol viz. o-aminophenol 2, 3-hydroxy-
2-aminopyridine 3, 3-amino-2-naphthol 4, 2-amino-m-cresol 5 or
* Corresponding author.
** Corresponding author. Tel.: þ91 9390100594.
E-mail address: ravichemku@rediffmail.com (V. Ravinder).
0223-5234/$ – see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.09.035

2622
P. Muralidhar Reddy et al. / European Journal of Medicinal Chemistry 44 (2009) 2621–2625
2-amino-p-cresol 6. The reactions afforded diimines 7–11, respec-
tively. Subsequently, [1 þ1] reaction of the diimines, 7–11 with 1,2-
dibromoethane (12) or 1,3-dibromopropane (13) in the presence of
sodium hydroxide in aqueous methanol resulted in the isolation of
pure macrocycles 14–23 in high yields (Scheme 1).
number of different types of protons present. A signal arising from
CH]N protons appeared in the range of 8.41–8.80 ppm suggesting
the condensation of OPA with primary amines [30]. The formation
of Ar–O–C linkage was further supported by the presence of signals
in the range of 3.90–4.37 ppm corresponding to methylenic protons
adjacent to phenolic oxygen [31,32]. Multiplets observed in the
range of 6.00–7.90 ppm have been assigned to the aromatic protons
[23].
2.1.1. Infrared spectral analysis
The appearance of a strong intensity band in the IR spectra of
macrocyclic ligands (14–23), in the range of 1622–1608 cmꢀ1
attributable to nC]N provides a strong evidence for the condensa-
tion [27]. Similarly, the disappearance of bands corresponding to
nO–H (aromatic) and nC–Br in the range of 3512–3430 and 700–
600 cmꢀ1 [28] suggests the cyclization by the reaction between
phenolic groups and alkyl dihalide. This fact was further supported
by the appearance of bands in the range of 1208–1140 cmꢀ1
corresponding to nC–O–C modes [29]. Aromatic ring stretching
frequencies were observed for all the ligands around 1400 cmꢀ1
region and wagging frequencies were observed around 3050 cmꢀ1
region [23].
13C NMR spectra of all the ligands contain signals in the range of
165.0–170.2 ppm confirming the presence of carbon, which is
doubly bonded to nitrogen [33]. The signals in the range of 60.0–
67.4 ppm due to methylenic carbon adjacent to oxygen atoms
indicate the presence of O–CH2 linkage [34]. The aryl carbons are
resonated in the range of 107.6–153.0 ppm [30].
2.1.3. FAB mass analysis
All the macrocyclic ligands displayed a single peak in ESI–MS
suggesting the purity of the macrocycles. The FAB mass spectrum of
compound 14 shows a parent peak at m/z (Mþ) 342 (16.7%) corre-
sponding to the molecular formula C22H18N2O2. The mass spectrum
shows major fragments at m/z values of 315 (100%), 312 (74.5%),
282 (62.6%), 249 (52.1%), 222 (48.2%), 212 (31.2%), 179 (23.4%) and 43
(10.4%).
2.1.2. 1H and 13C NMR spectral analysis
In the 1H NMR spectra of macrocyclic ligands (14–23), the
integral intensities of each signal were found to agree with the
Scheme 1. Synthetic route of macrocyclic compounds.

P. Muralidhar Reddy et al. / European Journal of Medicinal Chemistry 44 (2009) 2621–2625
2623
2.2. Antimicrobial activity
Brucker WH 270 (67.93 MHz) spectrometers were used for 1H NMR
and 13C NMR measurements. ESI and FAB MS were used to obtain
mass spectra. Hot air oven (Instrument and equipment Pvt. Ltd.,
Mumbai), incubator (Instrument and equipment Pvt. Ltd., Mum-
bai), laminar airflow unit (Clas laminar technologies Pvt. Ltd.
Secunderabad), autoclave (Medica instrument Mfg. Co., Mumbai)
were used in the present investigations. Organisms like Bacillus
subtilis (MTCC-619, IMTECH, Chandigarh), Staphylococcus aureus
(MTCC–96, IMTECH, Chandigarh), Escherichia coli (MTCC-722,
IMTECH, Chandigarh), Klebsiella pneumonia (MTCC-109, IMTECH,
Chandigarh), Aspergillus flavus (A. flavus) (MGM Hospital,
Warangal), Fusarium (MGM Hospital, Warangal), were used in the
present investigations.
Antibacterial activities of the macrocyclic compounds (14–23)
were studied along with existing antibacterial drugs viz. Strepto-
mycin, Ampicillin and Rifampicin. Preliminary screening for ten
macrocycles was performed at fixed concentrations of 1000 mg/ml
(Table 1). All the compounds were found to be acting on two types
each of Gram-positive (Bacillus subtilis and Staphylococcus aureus)
and Gram-negative (Escherichia coli and Klebsiella pneumonia)
bacteria. Out of ten macrocycles, only two compounds 16, 17 were
found to be very effective based on the obtained values of relative
zone of inhibition. In addition, the above two macrocycles were
found to be effective at different dilutions based on the activity. The
minimum inhibitory concentration [35,36] of these macrocycles
was also verified by the liquid dilution method in which the
effectiveness was observed at lower concentrations. The activity of
these two macrocycles against Gram-positive (Bacillus subtilis and
Staphylococcus aureus) and Gram-negative (Escherichia coli and
Klebsiella pneumonia) bacteria were compared with the activity of
existing antibacterial drugs like Streptomycin, Ampicillin and
Rifampicin and these macrocycles were found to be very active
than the Streptomycin and Ampicillin (Table 2). The compounds 16,
17 could show very good efficacy on clinical resistant strains.
3.1. Typical procedure for the preparation of macrocyclic
compounds (14–23)
In a typical procedure, to a suspension of ortho-phthalaldehyde
(1.34 g, 1 mmol) in 15 ml of 1:1 aqueous methanol solution was
added to a 15 ml solution of o-aminophenol (2.18 g, 2 mmol), 2-
amino-3-hydroxy pyridine (2.20 g, 2 mmol), 3-amino-2-naphthol
(3.18 g, 2 mmol), 2-amino-m-cresol (2.46 g, 2 mmol), 2-amino-p-
cresol (2.46 g, 2 mmol), with constant stirring at 60 ꢁC. The reaction
mixture was continuously stirred for 30 min to separate the solid
from reaction mixture and cooled. The solid was filtered and
washed with diethyl ether and recrystallized from methanol. The
intermediate compounds 7–11 (1 equiv.), in methanol solution
(30 ml) were added to an aqueous sodium hydroxide (1 equiv.)
solution. This solution was heated and 1,2-dibromoethane or
1,3-dibromopropane (1 equiv.) in methanol (20 ml) was added to it.
The solution was refluxed under nitrogen atmosphere for 4 h and
then cooled to 0 ꢁC. The crystals obtained were filtered and washed
with methanol and water. The corresponding products were
recrystallized from methanol and found to be TLC-pure in chloro-
form and methanol mixture. The yield, analytical data and the
spectral data are given below.
2.3. Antifungal activity
The macrocyclic compounds were also tested in vitro to evaluate
their activity against fungi, namely, Aspergillus flavus (A. flavus) and
Fusarium species. Though there is sufficient increase in the fungicidal
activity of macrocyclic compounds, it could not reach the effectiveness
of the conventional fungicide Amphotericin and Bavistin. The general
trend of growth of inhibition against the fungui were found to lie in the
order: 16 > 17 > 20 > 18 ¼ 22 > 19 ¼ 21 >14 > 23 > 15 for A. flavus
(500
vus (1000
Fusarium (500
m
g/ml), 16 > 17 > 20 > 18 ¼ 21 ¼ 22 > 19 ¼ 23 > 14 >15 for A. fla-
m
g/ml), 17 > 16 > 20 > 22 > 14 ¼19 ¼ 21 > 23 > 18 > 15 for
mg/ml) 17 > 16 > 20 > 19 ¼ 22 >14 > 21 >23 >18 > 15
The advantages of synthetic procedure are: (1) the process is
a simple two-step reaction involving inexpensive starting mate-
rials; (2) the process is shorter; (3) using water–methanol (1:1) as
solvent allows the formation of imines without the need for
catalysis and (4) yields are high and reactions are fast, and products
can be isolated by filtration.
for Fusarium (1000 mg/ml). The results are presented in Fig. 1.
3. Experimental
o-Phthalaldehyde and substituted aromatic amino alcohols
were obtained from Aldrich, USA and all other compounds are
analytical grade products from Merck. The solvents were distilled
and stored over molecular sieves. Purity of the compounds
was checked by TLC using Merck 60F254 silica gel plates. The
percentages of carbon, hydrogen, nitrogen in macrocyclic metal
compounds were determined using a Perkin–Elmer CHN analyzer
at 240C. The IR spectra were recorded in KBr pellets on a Perkin–
Elmer 283 spectrophotometer. Brucker WH 300 (200 MHz) and
3.1.1. 6,7-Dihydrotribenzo[e,i,m][1,4,7,12]dioxadiazacyclotetradecine
(14)
Yield 81%; mp 181; IR 1622, 1141, 3040w, 1498, 1420, 1350 cmꢀ1
;
1H NMR (200 MHz, CDCl3)
Ar-H), 8.50 (2H, s, CH]N); 13C NMR (67.93 MHz, CDCl3)
d
4.20 (4H, s, O–CH2), 6.60–7.80 (12H, m,
64.0 (2C, O–
d
CH2–CH2–O), 110.0, 128.0, 129.0, 133.0, 138.0, 153.0 (18C, Ar-C), 165.0
(2C, CH]N); mass spectrum, m/z 342 (6% Mþ). Anal. found: C, 77.10;
H, 5.40; N, 8.20%. Calcd for C22H18N2O2: C, 77.17; H, 5.30; N, 8.18%.
Table 1
Zone of inhibition of macrocyclic compounds against four different bacteria.
3.1.2. 13,14-Dihydro-12H-tribenzo[b,f,j][1,12,4,9]
dioxadiazacyclopentadecine (15)
Entry Empirical formula (1000
m
g/ml) Zone of inhibition (mm)
MTCC-619 MTCC-96 MTCC-722 MTCC-109
Yield 74%; mp 178; IR 1620, 1171, 3040w, 1490, 1420, 1350 cmꢀ1
;
1H NMR (200 MHz, CDCl3)
t, O–CH2), 6.80–7.80 (12H, m, Ar-H), 8.50 (2H, s, CH]N); 13C NMR
(67.93 MHz, CDCl3) 30.0 (1C, C–CH2–C), 67.0 (2C, O–CH2), 127.0,
d 2.30–2.50 (2H, m, C–CH2–C), 3.90 (4H,
STD 1 Streptomycin
STD 2 Ampicillin
STD 3 Rifampicin
10
11
51
11
10
38
35
15
13
12
13
14
13
12
13
49
12
11
35
30
15
14
14
15
12
14
6
8
6
7
48
10
11
40
32
14
13
11
12
13
11
45
12
12
32
29
14
11
12
11
10
12
d
14
15
16
17
18
19
20
21
22
23
C22H18N2O2
C23H20N2O2
C20H16N4O2
128.0, 129.0, 139.0, 152.0 (18C, Ar-C), 166.0 (2C, CH]N); mass
spectrum, m/z 356(8% Mþ). Anal. found: C, 77.05; H, 5.33; N, 7.96%.
Calcd for C23H20N2O2: C, 77.51; H, 5.66; N, 7.86%.
C
21H18N4O2
C30H22N2O2
C31H24N2O2
C24H22N2O2
C25H24N2O2
C24H22N2O2
C25H24N2O2
3.1.3. 6,7-Dihydrobenzo[i]dipyrido[3,2-e:2,3-
m][1,4,7,12]dioxadiazacyclotetradecine (16)
Yield 78%; mp 193; IR 1625, 1584, 1206, 3042w, 1445, 1403.8,
1391 cmꢀ1 1H NMR (200 MHz, CDCl3)
; d 4.10 (4H, s, O–CH2),

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P. Muralidhar Reddy et al. / European Journal of Medicinal Chemistry 44 (2009) 2621–2625
Table 2
MIC of the macrocyclic compounds and existing antibiotics.
Entry
Bacteria
Range of concentration (
m
g/ml)
Absorbance of suspension
Compound 16
Compound 17
Streptomycin
Ampicillin
Rifampicin
1
2
3
4
MTCC-619
MTCC-96
MTCC-722
MTCC-109
10
5
1
10
2
2
2
–
–
–
–
–
–
–
10
0.620
0.395
0.765
1.13
0.25
0.25
0.25
2
2
6.00–7.00 (8H, m, Ar-H), 7.80 (2H, s, CH]N in pyridine), 8.80 (2H, s,
CH]N); 13C NMR (67.93 MHz, CDCl3)
60.0 (2C, O–CH2), 120.0,
found: C, 81.54; H, 5.30; N, 6.20%. Calcd for C31H24N2O2: C, 81.56;
H, 5.36; N, 6.14%.
d
121.0, 133.0, 137.0, 142.0, 143.0 (16C, Ar–C), 151.0 (2C, Ar–CH]N),
168.0 (2C, CH]N); mass spectrum, m/z 344 (7% Mþ) Anal. found: C,
68.94; H, 4.89; N, 16.01%. Calcd for C20H16N4O2: C, 69.74; H, 4.68; N,
16.27%.
3.1.7. 1,12-Dimethyl-6,7-dihydrotribenzo[e,i,m][1,4,7,12]
dioxadiazacyclotetradecine (20)
Yield 84%; mp 184; IR 1622, 1141, 3040w, 1488, 1430,
1364 cmꢀ1
;
1H NMR (200 MHz, CDCl3)
d
2.16 (6H, s, –CH3), 4.02
(4H, s, O–CH2), 6.72–7.46 (10H, m, Ar-H), 8.45 (2H, s, CH]N); 13C
NMR (67.93 MHz, CDCl3) 9.2 (2C, –CH3), 64.6 (2C, O–CH2–CH2–
3.1.4. 13,14-Dihydro-12H-benzo[f]dipyrido[3,2-b:2,3-j]
[1,12,4,9]dioxadiaza-cyclopentadecine (17)
d
Yield 75%; mp 186; IR 1620, 1585, 1200, 3042w, 1446, 1400,
O), 107.6, 123.4, 125.2, 128.8, 133.1, 133.9, 136.0, 137.7, 146.7 (18C,
Ar-C), 164.8 (2C, CH]N); mass spectrum, m/z 370 (12% Mþ). Anal.
found: C, 77.72; H, 6.05; N, 7.60%. Calcd for C24H22N2O2: C, 77.81;
H, 5.99; N, 7.56%.
1380 cmꢀ1; 1H NMR (200 MHz, CDCl3)
d 2.20–2.30 (2H, m, C–CH2–
C), 3.92 (4H, t, O–CH2), 7.80 (2H, s, CH]N in pyridine), 6.40–7.40
(8H, m, Ar-H), 8.60 (2H, s, CH]N); 13C NMR (67.93 MHz, CDCl3)
d
30.2 (1C, C–CH2–C), 67.4 (2C, O–CH2), 122.7, 123.6, 133.5, 142.5
(16C, Ar-C), 155.2 (2C, Ar–CH]N), 170.2 (2C, CH]N); mass spec-
trum, m/z 358(4% Mþ). Anal. found: C, 70.32; H, 5.12; N, 15.61%.
Calcd for C21H18N4O2: C, 70.38; H, 5.06; N, 15.63%.
3.1.8. 7,19-Dimethyl-13,14-dihydro-12H-tribenzo[b,f,j][1,12,4,9]
dioxadiazacyclopentadecine (21)
Yield 82%; mp 179; IR 1620, 1141, 3040w, 1487, 1430,
1363 cmꢀ1
;
1H NMR (200 MHz, CDCl3)
d
2.18 (6H, s, –CH3), 2.33–
2.38 (2H, m, C–CH2–C), 3.91–3.95 (4H, t, O–CH2), 6.58–7.33 (10H,
m, Ar-H), 8.41 (2H, s, CH]N); 13C NMR (67.93 MHz, CDCl3)
19.4
3.1.5. 21,22-Dihydrobenzo[i]dinaphtho[2,3-e:2,3-m]
[1,4,7,12]dioxadiaza-cyclotetradecine (18)
d
Yield 76%; mp 225; IR 1608.2, 1158.9, 3060.0w, 1497.4, 1449.9,
(2C, –CH3), 31.4 (1C, C–CH2–C), 68.1 (2C, O–CH2–CH2–O), 107.9,
124.0, 125.8, 129.1, 133.5, 133.8, 136.7, 137.6, 146.7 (18C, Ar-C),
165.2 (2C, CH]N); mass spectrum, m/z 384 (7% Mþ). Anal. found:
C, 78.13; H, 6.28; N, 7.26%. Calcd for C25H24N2O2: C, 78.10; H, 6.29;
N, 7.29%.
1372.9 cmꢀ1; 1H NMR (200 MHz, CDCl3)
d
4.37 (4H, s, O–CH2), 7.00–
7.50 (16H, m, Ar-H), 8.40 (2H, s, CH]N); 13C NMR (67.93 MHz,
CDCl3) 64.0 (2C, O–CH2), 109.0, 124.0, 126.0, 126.0, 127.0, 133.0,
d
134.0, 140.0, 149.0 (26C, Ar-C), 167.0 (2C, CH]N); mass spectrum,
m/z 442(9% Mþ). Anal found: C, 81.89; H, 5.21; N, 6.07%. Calcd for
C30H22N2O2: C, 81.43; H, 5.01; N, 6.33%.
3.1.9. 2,11-Dimethyl-6,7-dihydrotribenzo[e,i,m][1,4,7,12]
dioxadiazacyclotetradecine (22)
3.1.6. 15,16-Dihydro-14H-benzo[f]binaphthol[2,3-b:2,3-j]
[1,12,4,9]dioxadiazacyclopenta decine (19)
Yield 76%; mp 182; IR 1622, 1141, 3042w, 1488, 1431,
1363 cmꢀ1
;
1H NMR (200 MHz, CDCl3)
d
2.27 (6H, s, –CH3), 4.05
(4H, s, O–CH2), 6.49–7.47 (10H, m, Ar-H), 8.42 (2H, s, CH]N); 13C
NMR (67.93 MHz, CDCl3) 21.0 (2C, –CH3), 64.1 (2C, O–CH2–CH2–
Yield 79%; mp 216; IR 1610, 1208, 3040w, 1490, 1449,
1360 cmꢀ1
;
1H NMR (200 MHz, CDCl3)
d
2.30–2.40 (2H, m, C–
CH2–C), 3.92 (4H, t, O–CH2), 7.20–7.90 (16H, m Ar-H), 8.50 (2H, s,
CH]N); 13C NMR (67.93 MHz, CDCl3)
30.2 (1C, C–CH2–C), 66.8
d
O), 113.7, 125.6, 129.4, 131.3, 133.0, 133.5, 133.8, 138.3, 150.2 (18C,
Ar-C), 165.4 (2C, CH]N); mass spectrum, m/z 370(14% Mþ). Anal.
found: C, 77.72; H, 6.05; N, 7.60%. Calcd for C24H22N2O2: C, 77.81;
H, 5.99; N, 7.56%.
d
(2C, O–CH2), 125.9, 126.2, 126.3, 127.0, 133.8, 148.5 (26C, Ar-C),
164.8 (2C, CH]N); mass spectrum, m/z 456 (15% Mþ). Anal.
3.1.10. 8,18-Dimethyl-13,14-dihydro-12H-tribenzo[b,f,j][1,12,4,9]
dioxadiaza cyclopentadecine (23)
70
Yield 78%; mp 176; IR 1622, 1140, 3040w, 1487, 1432, 1362 cmꢀ1
;
A-500
1H NMR (200 MHz, CDCl3)
CH2–C), 3.94–3.98 (4H, t, O–CH2), 6.64–7.62 (10H, m, Ar-H), 8.48
(2H, s, CH]N); 13C NMR (67.93 MHz, CDCl3)
21.0 (2C, –CH3), 30.3
d 2.24 (6H, s, –CH3), 2.33–2.39 (2H, m, C–
60
A-1000
50
40
30
20
10
0
F-500
d
(1C, C–CH2–C), 68.0 (2C, O–CH2–CH2–O), 113.7, 126.1, 129.7, 131.2,
133.1, 133.6, 134.8, 138.6, 150.0 (18C, Ar-C), 166.0 (2C, CH]N); mass
spectrum, m/z 384 (11% Mþ). Anal. found: C, 78.13; H, 6.28; N, 7.26%.
Calcd for C25H24N2O2: C, 78.10; H, 6.29; N, 7.29%.
F-1000
3.2. Antimicrobial testing by agar diffusion
Antimicrobial testing was done by cup plate method [37]. 27 ml
of molten agar was added to sterile Petri dishes and allowed to
solidify for 1 h. Then 50 ml of the 24 h culture of a test organism
was spread evenly onto the agar plate with the sterile cotton swab.
Six millimetre wide bores were made on the agar using a borer. The
14 15 16 17 18 19 20 21 22 23 D-1 D-2
Macrocyclic Compounds & Drugs
Fig. 1. Comparison of zone of inhibition of macrocyclic compounds and existing drug
molecules against two different fungi.

P. Muralidhar Reddy et al. / European Journal of Medicinal Chemistry 44 (2009) 2621–2625
2625
solutions of the macrocyclic compounds were added into each of
References
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prepared by replacing macrocycle by Streptomycin sulphate. This
was taken as a standard against bacteria. These dishes were then
incubated at 37 ꢁC for 24 h. The zones of growth inhibition were
found. The activities of compounds were interpreted either active
or inactive. The minimum inhibitory concentration required was
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