Synthesis of novel carbazole based macrocyclic amides as potential antimicrobial agents

Article abstract of DOI:10.1016/j.ejmech.2008.07.031

A series of carbazole based macrocyclic diamides with thia and oxy linkages have been synthesized and the inhibitory activity of the cyclophane amides against human pathogenic bacteria and plant pathogenic fungi are documented. (S)-1,10-Bi-2-naphthol [(S)

Full text of DOI:10.1016/j.ejmech.2008.07.031

European Journal of Medicinal Chemistry 44 (2009) 3040–3045
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis of novel carbazole based macrocyclic amides as potential
antimicrobial agents
,
a
b
b
Perumal Rajakumar a , Karuppannan Sekar , Vellasamy Shanmugaiah , Narayanasamy Mathivanan
*
a Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025, India
b Biocontrol and Microbial Metabolites Lab, Center for Advanced Studies in Botany, University of Madras, Guindy Campus, Chennai 600 025, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of carbazole based macrocyclic diamides with thia and oxy linkages have been synthesized and
the inhibitory activity of the cyclophane amides against human pathogenic bacteria and plant pathogenic
fungi are documented. (S)-1,10-Bi-2-naphthol [(S)-BINOL] based chiral carbazolophane amide emerged
as the most interesting compound in this series exhibiting excellent antibacterial and antifungal
activities.
Received 7 March 2008
Received in revised form 11 July 2008
Accepted 17 July 2008
Available online 31 July 2008
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords:
Carbazolophanes
(S)-1,10-Bi-2-naphthol [(S)-BINOL]
Antibacterial activity
Antifungal activity
1. Introduction
macrocycles with antibacterial activity [15] and cyclophane amides
with anti-inflammatory activity [16]. However, to the best of our
Synthesis of new supramolecules architecturally novel and of
potential importance in the context of designing simple models for
studying biomolecular interactions stimulates the imaginative skill
of synthetic chemists. Replacement of the oxygen donor atom in
the crown ether with sulfur and/or nitrogen atom and by intro-
ducing functional groups viz., amide, ester in the ring would make
them as models of protein–metal binding sites in biological systems
[1–3]. Synthetic development of new macrocyclic peptide antibi-
otics against bacteria has undergone dramatic changes during the
last few years including biphenomycin B [4], vancomycine type
glycopeptide antibiotics [5] and 1,10-binaphthyl carbazole linked
cyclic peptides [6,7]. Cyclic peptides with open pores are useful as
transport vehicles for biologically important ions and neutral
molecules [8]. Synthetic biphenyl based cyclic amides have been
reported for anion complexation [9], and cyclic tetraamide recep-
tors having barbiturate binding domain have also been reported
[10]. Supramolecular amides are also used as molecular receptors
[11] and in molecular recognition [12] of biologically interacting
substrates including anti-HIV active macrocyclic amides [13].
Copper complexes of macrocyclic compounds exhibit increased
antibacterial and antifungal activities than the uncomplexed
macrocyclic compounds [14]. We have recently reported the
synthesis of permanent fluorescence sensing chiral fluorophoric
knowledge, no carbazole based amide macrocycles have been
reported. Herein, we report the synthesis of carbazolophane
amides 1–6 along with their antibacterial and antifungal activities.
2. Chemistry
Six new carbazole based macrocyclic amides (1–6) were
synthesized, which include possible combinations of benzene,
pyridine, biphenyl and chiral binaphthyl unit (Schemes 1–4). One
equivalent of isophthaloyl dichloride (12), pyridine 2,6-dicarbox-
ylicacid chloride (13), biphenicacid chloride (14), and the extended
diacid chlorides 15, 19 and 23 react with 1 equiv. of thia bridged
carbazole diamine 11 (prepared by the reaction of 3,6-bis
(bromomethyl)-9-ethylcarbazole (10) [17] with 2-aminothiophenol
in the presence of KOH) to give the carbazolophane amides 1–6 in
27–40% yield and the rest of the yield contained unidentified
products. All the new compounds gave satisfactory IR, 1H and 13C
NMR, mass spectral and elemental analysis.
3. Biology
Antimicrobial activities of compounds were tested using disc
diffusion assay [18]. Tested microorganism strains: human patho-
genic bacteria such as Proteus mirabilis, Proteus vulgaris, Staphylo-
coccus aureus, and Salmonella typhi; plant pathogenic fungi such as
Rhizoctonia solani, Macrophomina phaseolina, Curvularia lunata and
* Corresponding author. Tel.: þ91 4422351269; fax: þ91 4422352494.
E-mail address: perumalrajakumar@hotmail.com (P. Rajakumar).
0223-5234/$ – see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.07.031

P. Rajakumar et al. / European Journal of Medicinal Chemistry 44 (2009) 3040–3045
3041
O
O
O
O
O
O
N
HN
NH
HN
NH
HN
NH
S
S
S
S
S
S
N
Et
N
Et
2
N
Et
1
3
O
O
O
O
O
O
O
O
O
O
NH
HN
O
O
NH
S
HN
NH
HN
S
S
S
S
S
N
Et
N
Et
N
Et
4
6
5
NH2
H2N
R
R
iv
i
S
S
N
N
Et
Et
7
N
Et
11
8 R = CHO
ii
9 R = CH2OH
iii
10 R = CH2Br
Scheme 1. Reagents and conditions: (i) POCl3/DMF, DCE, reflux, 48 h, 8 (55%); (ii) NaBH4, THF–EtOH (1:1), rt, 12 h, 9 (80%); (iii) 48% HBr (aq.), 0 ꢀC, 5 h, 10 (72%); (iv) 2-amino-
thiophenol, KOH, TBAB, toluene–H2O (1:1), reflux, 5 h, 11 (80%).
Alternaria alternata (obtained from the culture collections of
Biocontrol and Microbial Metabolites Lab, Center for Advanced
Studies in Botany, University of Madras, Chennai, India) under in
vitro conditions. The observed data on the antimicrobial activity of
the compounds and control drugs are given in Tables 1 and 2 in the
form of minimum inhibitory concentration (MIC).
4. Results and discussion
The precursor diamine 11 for the synthesis of cyclophane
amides 1–6 was synthesized as follows. Diamine 11 was prepared
in 80% yield by the reaction of 3,6-bis(bromomethyl)-9-ethyl-
carbazole (10) [17] with 2-aminothiophenol in the presence of KOH
and TBAB as phase transfer catalyst in toluene–water (1:1) system
under refluxing conditions. The dibromide 10 was obtained from
the diol 9 using aq. HBr at 0 ꢀC. The dialcohol 9 in turn was obtained
in 80% yield by the reduction of the dialdehyde 8 with NaBH4 in
THF–EtOH (1:1) mixture. Formylation of N-ethylcarbazole (7) with
DMF and POCl3 in 1,2-dichloroethane afforded the dialdehyde 8
after purification by column chromatography using SiO2 in 55%
yield (Scheme 1).
In order to test the synthetic utility of precyclophane 11 for the
synthesis of amide carbazolophanes, 1 equiv. of precyclophane 11
was coupled with 1 equiv. of isophthaloyl dichloride (12), pyridine
2,6-dicarboxylicacid chloride (13), biphenicacid chloride (14) and
diacid chloride 15 [19] (prepared from corresponding diacid) to
give the carbazolophane amides 1, 2, 3 and 4 in 40%, 32%, 28%, and
37% yields, respectively, after purification by column
O
O
O
O
4
O
Cl
Cl
O
Cl
15
1
12
Cl
i
i
O
11
O
Cl
13
N
Cl
O
Cl
Cl
14
O
i
i
2
3
Scheme 2. Reagents and conditions: (i) TEA, CHCl3 (dry), 12 h, 1 (40%), 2 (32%), 3 (28%),
4 (37%).

3042
P. Rajakumar et al. / European Journal of Medicinal Chemistry 44 (2009) 3040–3045
O
O
i
O
O
ii
Br
Br
CO2Me
CO2Me
R
R
16
17
18
R = CO2H
R = COCl
iii
19
iv
5
Scheme 3. Reagents and conditions: (i) p-hydroxymethylbenzoate, K2CO3, KI, CH3CN, reflux, 12 h, 17 (92%); (ii) 25% KOH, MeOH, reflux, 18 (85%); (iii) SOCl2, TEA, DCM, reflux, 3 h, 19
(82%); (iv) 11 (1 equiv.), TEA, CHCl3 (dry), rt, 12 h, 5 (27%).
chromatography and the rest of the yield contained unidentified
products (Scheme 2). The structure of cyclophanes 1–4 was
confirmed from spectroscopic and analytical data.
cyclophane amide 5 in 27% yield and the remaining are
unidentified products (Scheme 3).
1H NMR spectrum of carbazolophane amide 5 displayed a three
1H NMR spectrum of carbazolophane amide 1 displayed a three
proton triplet at
a singlet at 4.20. The NCH2 and OCH2 protons appeared as
a quartet at 4.89, respectively.
4.42 (J ¼ 7.2 Hz) and as a singlet at
A two proton singlet at 9.01 for amide NH protons appeared in
addition to 26 aromatic protons. In 13C NMR spectrum methyl and
methylene carbon of N-ethyl moiety appeared at 12.5, and 36.8,
respectively. The SCH2 and OCH2 methylene carbons appeared at
41.6 and 64.5 and carbonyl carbon appeared at 160.0 in
addition to aromatic carbons.
d
1.47 (J ¼ 7.2 Hz) and SCH2 protons appeared as
proton triplet at
N-ethyl moiety, and singlet at
quartet at
4.01 (J ¼ 7.2 Hz) for methylene protons of the N-ethyl
unit, and a two proton singlet at 8.97 for amide NH protons
appeared in addition to the aromatic protons. 13C NMR spectrum of
1 showed a peak at 13.9 and 37.5 for methyl and methylene
carbon of ethyl unit, respectively. The SCH2 carbons appeared at
44.2 and a peak at 163.0 for carbonyl carbon in addition with 16
aromatic carbons.
d
1.28 (J ¼ 7.2 Hz) for methyl proton present in the
d
d
3.94 for SCH2 protons. A two proton
d
d
d
d
d
d
d
d
d
d
d
d
d
d
Introductionofopticallyactive(S)-1,10-bi-2-naphthol [(S)-BINOL]
spacer into such cyclophane amides would give chiral carbazolo-
phane. Modifications on compounds with bridged binaphthyl
diether linkage have been previously studied [21].
In order to explore the utility of the diamine 11 for the synthesis
of chiral carbazolophane amide, the diamine 11 was stirred with
1 equiv. (S)-1,10-bi-2-naphthol [(S)-BINOL] based chiral diacid
chloride 23 in the presence of triethylamine in dry CHCl3 to give the
chiral carbazolophane amide 6 in 32% yield and the remaining are
unidentified products. The chiral diacid 22 was obtained by the
reaction of (S)-1,10-bi-2-naphthol [(S)-BINOL] with 2.1 equiv. of
Large cavity carbazolophanes with amide linkages using diacid
chloride 19 was synthesized as follows. The diacid chloride 19
was obtained by the reaction of o-xylene dibromide with
2.1 equiv. p-hydroxymethylbenzoate in the presence of K2CO3 and
KI in dry CH3CN to give the diester 17 [20] in 92% yield, which on
hydrolysis gave the corresponding diacid 18. Diacid 18 was then
smoothly converted into the diacid chloride 19 in 82% yield by
using thionyl chloride. Reaction of 1 equiv. diamine 11 with
1 equiv. of diacid chloride 19 in the presence of 2.1 equiv. of
triethylamine in CHCl3 for 12 h at room temperature gave
i
ii
OEt
Cl
O
O
O
O
O
OH HO
O
iii
O
O
O
R
R
OEt
EtO
20
21
22
R = OH
R = Cl
23
iv
6
Scheme 4. Reagents and conditions: (i) K2CO3, KI, CH3CN, reflux, 12 h, 21 (82%); (ii) 25% KOH, MeOH, reflux, 22 (55%); (iii) SOCl2, TEA, DCM, reflux, 4 h, 20 (63%); (iv) 11, TEA, CHCl3
(dry), rt, 12 h, 6 (32%).

P. Rajakumar et al. / European Journal of Medicinal Chemistry 44 (2009) 3040–3045
3043
Table 1
ranged between 5 and 80 mg/ml. The chiral carbazolophane amide 6
In vitro antibacterial activity against human pathogens (minimum inhibitory
concentration in mg/ml) for amide carbazolophanes
shows remarkable antibacterial activity against tested pathogens
namely, P. mirabilis, P. vulgaris, S. aureus and S. typhi compared to
rest of the cyclophane amides and commercial antibiotic, tetracy-
Carbazolophane amides
P. mirabilis
P. vulgaris
S. aureus
S. typhi
1
2
3
4
5
6
50
5
40
20
10
5
60
30
40
60
40
5
20
10
70
40
30
10
20
NI
50
30
60
30
20
10
15
NI
cline at lowest concentration ranging from 5 to 10
m
g/ml, followed
by cyclophanes 2 and 5 (ranging from 5 to 30 g/ml and 10–40
m
mg/
ml, respectively) compared with reference control. The minimum
inhibitory concentration (MIC) values are relatively low for carba-
zolophane amides 1, 3, 4 and 5 as compared with reference control
(Table 1).
Tetracycline
Control
20
NI
35
NI
NI: no inhibition.
4.2. Effect of carbazolophane amides on the growth of plant
pathogenic fungi
ethyl chloroacetate in the presence of potassium carbonate
followed by the hydrolysis of the resulting chiral diethylester 21 to
give the corresponding diacid 22, which was then reacted with
thionyl chloride to give diacid chloride 23 (Scheme 4).
Similar to antibacterial activity, all the six carbazolophane
amides exhibited different levels of antifungal activity against the
four-tested plant pathogenic fungi compared to DMSO control.
Further, the antifungal activity of the test compounds was dose
dependent and was remarkable at higher concentrations. The
minimum inhibitory concentrations (MICs) of the carbazolophanes
1–6 against fungal plant pathogens as determined by well diffusion
1H NMR spectrum of carbazolophane 6 displayed a three proton
triplet and two proton quartet at
d
1.15 (J ¼ 7.2 Hz) and
d 4.10
(J ¼ 7.2 Hz) for methyl and methylene proton of N-ethyl unit,
respectively. The SCH2 and OCH2 protons attached to the (S)-1,10-
bi-2-naphthol [(S)-BINOL] unit as well as those attached to the
method ranged between 10 and 45
phanes tested, chiral cyclophane amide 6 (ranging from 10 to 20
m
g/ml. Among the six cyclo-
g/
carbazole unit appeared as two doublets at
d 3.65 (d, 2H,
m
J ¼ 12.6 Hz), 3.78 (d, 2H, J ¼ 12.3 Hz) and 4.20 (d, 2H, J ¼ 15 Hz), 4.45
(d, 2H, J ¼ 15 Hz) due to the atropisomerism of the (S)-1,10-bi-2-
naphthol [(S)-BINOL] unit, in addition to the aromatic protons. In
13C NMR spectrum N-ethyl unit of methyl and methylene carbon
ml) significantly inhibited all the four plant pathogens namely, R.
solani, M. phaseolina, C. lunata and A. alternata compared to rest of
the cyclophanes and commercial fungicide, carbendazim. Carba-
zolophane 2 was rated as the second best cyclophane amide with
appeared at
carbons appeared at
at 165.5 in addition to aromatic carbons.
In the present study, antimicrobial activities of six different
d
17.0, and
d
37.5, respectively. The SCH2 and OCH2
antifungal activity (ranging from 10 to 20 mg/ml) compared with
d
42.1 and
d
67.3 and carbonyl carbon appeared
reference control. The minimum inhibitory concentration (MIC)
values are relatively low for cyclophanes 1, 3, 4 and 5 as compared
with reference control (Table 2).
d
newly synthesized amide carbazolophanes were evaluated against
four human pathogenic bacteria such as P. mirabilis, P. vulgaris, S.
aureus, and S. typhi. Antifungal activity of these compounds was
also tested against four plant pathogenic fungi viz., R. solani, M.
phaseolina, C. lunata and A. alternata under in vitro conditions. The
biological screening results of carbazolophane amides with 10%
DMSO as control and with commercial antibiotics viz., tetracycline
(for human pathogenic bacteria), carbendazim (for plant patho-
genic fungi) are tabulated (Tables 1 and 2) in the form of minimum
inhibitory concentration (MIC).
The results obtained have clearly indicated that (S)-1,10-bi-2-
naphthol [(S)-BINOL] based chiral carbazolophane 6 acts as an
excellent antibacterial and antifungal agent as compared to other
cyclophanes. This may be due to the rigid and restricted confor-
mational behavior of macrocyclic carbazole amides in the presence
of (S)-1,10-bi-2-naphthol [(S)-BINOL] unit [22]. In molecular orbital
(MO) calculation carried out using MOPAC (PM3) method on chiral
carbazolophane amide 6, the minimization energy (MM2) of chiral
4.1. Effect of carbazolophane amides on the growth of human
pathogens
All the six cyclic carbazole amides exhibited different levels of
antibacterial activity against the four-tested human pathogenic
bacteria compared to DMSO as control. Further, the antibacterial
activity of the test compounds was dose dependent and was
remarkable at higher concentrations. The minimum inhibitory
concentration (MIC) of carbazolophane amides 1–6 against bacte-
rial human pathogens as determined by well diffusion method
Table 2
In vitro antifungal activity against plant pathogens (minimum inhibitory concen-
tration in mg/ml) for amide carbazolophanes
Carbazolophane amides
R. solani
M. phaseolina
C. lunata
A. alternata
1
2
3
4
5
6
30
20
20
50
40
20
25
NI
30
10
15
45
50
15
18
NI
20
15
20
35
20
10
15
NI
15
15
25
25
15
10
12
NI
Carbendazim
Control
Fig. 1. Energy minimization of cyclophane amide 6. Heat of formation of cyclophane
amide 6 is 5.8242 kcal/mol.
NI: no inhibition.

3044
P. Rajakumar et al. / European Journal of Medicinal Chemistry 44 (2009) 3040–3045
carbazolophane amide was found to be 5.8242 kcal/mol. Fig. 1
shows that molecule has good rigidity and two naphthyl rings are
in twisted form.
6.2.3. Carbazolophane 2
Yield 32%; mp 221 ꢀC; IR (KBr, cmꢂ1): 3330, 1672, 1577; 1H NMR
(300 MHz, CDCl3)
d
: 1.27 (t, 3H, J ¼ 7.2 Hz), 3.96 (s, 4H), 4.00 (q, 2H,
J ¼ 7.2 Hz), 6.61 (d, 2H, J ¼ 7.7 Hz,), 6.83–6.91 (m, 3H), 7.10 (t, 2H,
J ¼ 7.2 Hz), 7.29 (d, 2H, J ¼ 7.6 Hz), 7.39 (t, 2H, J ¼ 7.8 Hz), 7.56 (s,
2H), 7.70 (d, 2H, J ¼ 6.9 Hz), 8.42 (d, 2H, J ¼ 8.1 Hz), 8.94 (s, 2H); 13C
5. Conclusion
In conclusion, the carbazolophanes 2 and 6 exhibited good
antibacterial and antifungal activities against all the four human
pathogenic bacteria and plant pathogenic fungi. Chiral carbazolo-
phane 6 may be developed as antimicrobial drug as it showed
superior activity against all the tested pathogens than the other
compounds including tetracycline and carbendazim. Molecular
recognition studies of various biologically important anions with
these carbazolophane amides are under investigation.
NMR (75 MHz, CDCl3) d: 13.6, 37.4, 44.1, 108.2, 119.1, 119.6, 122.5,
124.0, 124.3, 125.3, 126.0, 127.5, 128.4, 130.0, 131.0, 137.1, 139.1, 141.1,
162.0; MS (EI) m/z: 600 (Mþ). Elemental Anal. Calcd for
C35H28N4O2S2: C, 69.97; H, 4.70; N, 9.33. Found: C, 69.82; H, 4.82; N,
9.49.
6.2.4. Carbazolophane 3
Yield 28%; mp 252 ꢀC; IR (KBr, cmꢂ1): 3326, 1664, 1566, 1505; 1H
NMR (300 MHz, CDCl3)
d
: 1.33 (t, 3H, J ¼ 7.2 Hz), 4.16 (s, 4H), 4.23 (q,
6. Experimental
2H, J ¼ 7.2 Hz), 6.80 (t, 2H, J ¼ 7.5 Hz), 6.99–7.06 (m, 6H), 7.11–7.17
(m, 8H), 7.46 (dd, 2H, J ¼ 7.8 Hz, J ¼ 1.2 Hz), 7.74 (s, 2H), 8.04 (d, 2H,
6.1. Chemistry
J ¼ 8.1 Hz), 9.02 (s, 2H); 13C NMR (75 MHz, CDCl3)
d: 13.7, 37.6, 41.0,
107.7,120.7,122.5, 123.1,125.1,126.5,126.9,127.4,128.0,128.7,129.8,
130.0, 132.7, 136.0, 138.3, 139.4, 139.7, 168.1; MS (EI) m/z: 676 (Mþ).
Elemental Anal. Calcd for C42H33N3O2S2: C, 74.64; H, 4.92; N, 6.22.
Found: C, 74.81; H, 4.81; N, 6.35.
All the reagents and solvents employed were of the best grade
available and were used without further purification. The melting
points were determined using a Toshniwal melting point apparatus
by open capillary tube method and were uncorrected. Spectro-
scopic data were recorded by the following instruments IR: FTIR-
8300 spectrophotometer; NMR Bruker 300 MHz; MS: EI-MS
spectra on Jeol DX-303 mass spectrometer and FAB-MS spectra Jeol
SX 102/DA-6000 mass spectrometer. The elemental analyses for the
compounds were carried out using the Perkin–Elmer 240B
elemental analyzer.
6.2.5. Carbazolophane 4
Yield 37%; mp 248 ꢀC; IR (KBr, cmꢂ1): 3390, 1683, 1581, 1510; 1H
NMR (300 MHz, CDCl3)
d
: 1.29 (t, 3H, J ¼ 7.2 Hz), 3.93 (s, 4H), 4.13 (s,
4H), 4.19 (q, 2H, J ¼ 7.2 Hz), 6.51 (dd, 2H, J ¼ 8.1 Hz, J ¼ 2.4 Hz), 6.60
(t, 1H, J ¼ 2.4 Hz), 6.85 (dd, 2H, J ¼ 8.4 Hz, J ¼ 1.5 Hz), 7.04–7.13 (m,
5H), 7.33 (td, 2H, J ¼ 7.8 Hz, J ¼ 1.2 Hz), 7.68 (dd, 2H, J ¼ 9.3 Hz,
J ¼ 1.2 Hz), 7.79 (d, 2H, J ¼ 1.2 Hz), 8.37 (dd, 2H, J ¼ 8.2 Hz,
6.2. General procedure for the synthesis of carbazolophane amides
(1–6)
J ¼ 1.2 Hz), 9.60 (s, 2H); 13C NMR (75 MHz, CDCl3)
d: 13.6, 37.6, 42.8,
67.6, 103.5, 107.4, 108.0, 119.5, 120.5, 122.8, 123.0, 124.6, 126.7, 127.0,
130.3, 130.6, 136.5, 139.6, 139.8, 158.6, 165.7; MS (EI) m/z: 660 (Mþ).
Elemental Anal. Calcd for C38H33N3O4S2: C, 69.17; H, 5.04; N, 6.37.
Found: C, 69.27; H, 5.18; N, 6.59.
A solution of the corresponding diacid chlorides (0.5 mmol) in
dry chloroform (100 ml) and a solution of diamine 11 (0.5 mmol)
and triethylamine (1.1 mmol) in dry chloroform (100 ml) were
simultaneously added drop wise to a well-stirred solution of
chloroform (500 ml) for 6 h. After the addition was complete, the
reaction mixture was stirred for another 6 h. The solvent was
removed at reduced pressure and the residue obtained was then
dissolved in chloroform (300 ml), washed with water (2 ꢁ 100 ml)
to remove triethylamine hydrochloride and then dried over sodium
sulfate. Removal of the chloroform under reduced pressure gave
cyclophane as a crude material, which was purified by column
chromatography (SiO2).
6.2.6. Carbazolophane 5
Yield 27%; mp 140 ꢀC; IR (KBr, cmꢂ1): 3367, 1676, 1596, 1498; H
1
NMR (300 MHz, CDCl3)
d
: 1.47 (t, 3H, J ¼ 7.2 Hz), 4.20 (s, 4H), 4.42 (q, 2H,
J ¼ 7.2 Hz), 4.89 (s, 4H), 6.81 (d, 4H, J ¼ 8.7 Hz), 6.92–7.12 (m, 8H), 7.35–
7.56 (m, 8H), 7.69–7.86 (m, 4H), 8.00 (s, 2H), 9.01(s, 2H); 13C NMR
(75 MHz, CDCl3) d: 12.5, 36.8, 41.7, 64.5, 107.7, 108.0, 113.0, 113. 2, 119.0,
119.3, 121.4, 123.0, 125.1, 125.7, 127.4, 127.6, 127.7, 129.4, 131.2, 132.9,
138.3, 165.5; m/z (FAB-MS): 812 (Mþ). Elemental Anal. Calcd for
C50H41N3O4S2: C, 73.96; H, 5.09; N, 5.17. Found: C, 73.82; H, 5.17; N, 5.28.
6.2.1. Diamine 11
6.2.7. Carbazolophane 6
25
Yield 80%; mp 114 ꢀC; IR (KBr, cmꢂ1): 3382; 1H NMR (300 MHz,
Yield 32%; mp 110 ꢀC; [
a]
ꢂ112.14, (c 0.01, CHCl3); IR (KBr,
D
CDCl3)
2H, J ¼ 7.2 Hz), 6.57–6.71 (m, 4H), 7.07–7.13 (m, 2H), 7.13–7.26 (m,
6H), 7.79 (s, 2H); 13C NMR (75 MHz, CDCl3)
: 13.8, 37.6, 40.3, 108.3,
d
: 1.38 (t, 3H, J ¼ 7.2 Hz), 3.50 (br s, 4H), 4.10 (s, 4H), 4.29 (q,
cmꢂ1): 3328, 1689, 1583, 1517; 1H NMR (300 MHz, CDCl3)
d: 1.15 (t,
3H, J ¼ 7.2 Hz), 3.65 (d, 2H, J ¼ 12.6 Hz), 3.78 (d, 2H, J ¼ 12.3 Hz), 4.10
(q, 2H, J ¼ 7.2 Hz), 4.20 (d, 2H, J ¼ 15 Hz), 4.45 (d, 2H, J ¼ 15 Hz), 6.68
(d, 2H, J ¼ 8.1 Hz), 6.93 (d, 2H, J ¼ 8.4 Hz), 6.99 (t, 2H, J ¼ 7.2 Hz), 7.15
(d, 2H, J ¼ 7.5 Hz), 7.20 (d, 2H, J ¼ 6.0 Hz), 7.23–7.35 (m, 4H), 7.42 (d,
2H, J ¼ 9.0 Hz), 7.51 (d, 2H, J ¼ 6.9 Hz), 7.69 (s, 2H), 7.86 (d, 2H,
J ¼ 7.2 Hz), 8.02 (d, 2H, J ¼ 8.1 Hz), 8.07 (d, 2H, J ¼ 9.0 Hz), 9.00 (s,
d
114.9, 118.1, 118.5, 120.7, 122.8, 126.8, 128.5, 129.8, 136.3, 139.4,
148.4; MS (EI) m/z: 469 (Mþ). Elemental Anal. Calcd for C28H27N3S2:
C, 71.60; H, 5.79; N, 8.95. Found: C, 71.48; H, 5.91; N, 8.82.
6.2.2. Carbazolophane 1
2H); 13C NMR (75 MHz, CDCl3)
d: 14.0, 37.5, 42.1, 67.3, 107.4, 114.8,
Yield 40%; mp 243 ꢀC; IR (KBr, cmꢂ1): 3344, 1679, 1577, 1510; 1H
119.7,120.4,122.6,122.9,124.2,124.7,125.3,125.6,126.7,127.0,127.2,
127.8, 128.2, 129.7, 130.4, 130.9, 133.9, 136.0, 139.6, 153.3, 165.5; m/z
(QIT-MS): 836 (Mþ). Elemental Anal. Calcd for C52H41N3O4S2: C,
74.71; H, 4.94; N, 5.03. Found: C, 74.88; H, 5.11; N, 5.17.
NMR (300 MHz, CDCl3)
d: 1.28 (t, 3H, J ¼ 7.2 Hz), 3.94 (s, 4H), 4.01
(q, 2H, J ¼ 7.2 Hz), 6.65 (d, 2H, J ¼ 7.8 Hz), 6.89–6.93 (m, 3H), 7.12 (t,
2H, J ¼ 7.5 Hz), 7.32 (d, 2H, J ¼ 7.8 Hz), 7.43 (t, 2H, J ¼ 7.8 Hz), 7.58 (s,
2H), 7.67 (s, 1H), 7.73 (d, 2H, J ¼ 6.9 Hz), 8.49 (d, 2H, J ¼ 8.1 Hz), 8.97
(s, 2H); 13C NMR (75 MHz, CDCl3)
d: 13.9, 37.5, 44.2, 108.3, 119.3,
6.3. Biological activity
119.8,122.7,124.0,124.4,125.4,126.2,127.7,128.6,130.1,131.0,133.6,
137.2, 139.3, 141.2, 163.0; MS (EI) m/z: 599 (Mþ). Elemental Anal.
Calcd for C36H29N3O2S2: C, 72.09; H, 4.87; N, 7.01. Found: C, 72.21;
H, 4.73; N, 7.19.
6.3.1. Antibacterial studies
Test organisms and their maintenance: the human pathogenic
bacterial cultures such as P. mirabilis, P. vulgaris, S. aureus and S. typhi

P. Rajakumar et al. / European Journal of Medicinal Chemistry 44 (2009) 3040–3045
3045
were obtained from the culture collections of Biocontrol and Micro-
bial Metabolites Lab, Center for Advanced Studies in Botany, Univer-
sity of Madras, Chennai, India and the biological screening of
carbazolophane amides was performed there itself. The human
bacterial pathogens viz., P. mirabilis, P. vulgaris, S. aureus and S. typhi
were maintained on nutrient agar (NA) consisting of the following (g/
l): beef extract 1.0; yeast extract 2.0; peptone 5.0; NaCl 5.0; agar 15.0;
distilled H2O 1 L; pH 7.2 in slants or petriplates at room temperature
(28 ꢃ 2 ꢀC). Effect of carbazolophane amides on the growth of human
pathogens: the minimal inhibitory concentration (MIC) was deter-
minedforcompounds1–6bywelldiffusionassay [17]. Thecompound
compound that showed prominent inhibition of fungal growth
after 3 days of incubation at 37 ꢀC.
Acknowledgments
K.S. thanks CSIR for the award of SRF. The author thanks CSIR,
India, for financial assistance, DST-FIST for providing NMR facility to
the department, SAIF, CDRI, Lucknow for FAB-MS spectra.
References
at the concentration range of 5–100 mg/ml in 10% DMSO was used in
[1] M.W. Hosseini, J.M. Lehn, S.R. Du, K. Gu, M.P. Mertes, J. Org. Chem. 52 (1987) 1662.
[2] J.M. Lehn, Science (Washington, D.C.) 227 (1985) 849.
[3] P.G. Yohannes, M.P. Mertes, K.B. Mertes, J. Am. Chem. Soc. 107 (1985) 8288.
[4] R. Le¨pine, J. Zhu, Org. Lett. 14 (2005) 2981.
[5] K.C. Nicolaou, C.N.C. Boddy, S. Bra¨se, N. Winssinger, Angew. Chem., Int. Ed. 38
(1999) 2096.
this study with tetracycline as reference control. The minimum
inhibitory concentration (MIC) value was taken as the lowest
concentration of compound that showed prominent inhibition of
bacterial growth after 24 h of incubation at 37 ꢀC.
[6] J.B. Bremner, J.A. Coates, D.R. Coghlan, D.M. David, P.A. Keller, S.G. Pyne, New J.
Chem. 26 (2002) 1549.
6.3.2. Antifungal studies
Test organisms and their maintenance: the plant pathogenic
fungi viz., R. solani, M. phaseolina, C. lunata and A. alternata were
obtained from the culture collections of Biocontrol and Microbial
Metabolites Lab, Center for Advanced Studies in Botany, Univer-
sity of Madras, Chennai, India and the biological screening of
carbazolophane amides was performed there itself. The plant
pathogens viz., R. solani, M. phaseolina, C. lunata and A. alternata
were maintained on potato dextrose agar (PDA) containing the
following (g/l): potato 200 g; dextrose 20 g; agar 15 g; distilled
H2O; 1 L; pH 6.5 in slants or Petriplates at room temperature
(28 ꢃ 2 ꢀC). Effect of carbazolophane amides on the growth of plant
pathogenic fungi: similar to antibacterial activity, the minimum
inhibitory concentration (MIC) was determined for cyclic amides
1–6 by well diffusion assay. The compound at the concentration
[7] J.B. Bremner, J.A. Coates, P.A. Keller, S.G. Pyne, H.M. Witchard, Synlett (2002)
219–222.
[8] H. Kataoka, T. Katagi, Tetrahedron 43 (1987) 4519.
[9] A.M. Costero, M.J. Banuls, M.J. Aurell, M.D. Ward, S. Argent, Tetrahedron 60
(2004) 9471.
[10] R. Brian, E. Unai, S. Troels, J. Chem. Soc., Perkin Trans. 1 (2002) 1723.
[11] A.H. Christopher, H.P. Duncan, Angew. Chem., Int. Ed. Engl. 31 (1992) 792.
[12] C.S. Kyu, V.E. Donna, F. Erkang, D.H. Andrew, J. Am. Chem. Soc. 113 (1991) 7640.
[13] B.S. Jhaumeer-Laulloo, Asian J. Chem. 12 (2000) 775.
[14] C. Sulekh, T. Sangeetika, T. Shalini, Trans. Metal Chem. 29 (2004) 925.
[15] P. Rajakumar, S. Selvam, V. Shanmugaiah, M. Mathivanan, Bioorg. Med. Chem.
Lett. 17 (2007) 5270.
[16] P. Rajakumar, A.M. Abdul Rasheed, A.I. Rabia, D. Chamundeeswari, Bioorg.
Med. Chem. Lett. 16 (2006) 6019.
[17] K. Tani, Y. Tohda, K. Hisada, M. Yamamoto, Chem. Lett. (1996) 145.
[18] A. Pandurangan, N. Mathivanan, V.R. Prabavathy, V. Kabilan, V. Murugesan,
K. Murugesan, Indian J. Exp. Biol. 33 (1995) 357.
[19] D.M. Purohit, V.H. Shah, Indian J. Chem. 38 (1999) 618.
[20] P. Rajakumar, R. Kanagalatha, Tetrahedron 62 (2006) 9735.
[21] J.J.G.S. Van Es, H.A.M. Biemans, E.W. Meijer, Tetrahedron: Asymmetry 8 (1997)
1825.
range of 5–100 mg/ml in 10% DMSO was used in this study with
carbendazim as reference control. Minimum inhibitory concen-
tration (MIC) value was taken as the lowest concentration of
[22] P. Rajakumar, M. Srisailas, Tetrahedron 57 (2001) 9749.