Synthesis, optical, and antioxidant studies of anthraquinone-core-based dendrimers with N-phenylcarbazole as surface group

Article abstract of DOI:10.1071/CH13521

Synthesis of hyperbranched dendrimers up to third generation with N-phenylcarbazole as surface group and anthraquinone as the core unit has been achieved. The fluorescence decay studies of the dendrimers indicate that generation growth alters the relaxati

Full text of DOI:10.1071/CH13521

CSIRO PUBLISHING
Aust. J. Chem. 2014, 67, 636–643
Full Paper
http://dx.doi.org/10.1071/CH13521
Synthesis, Optical, and Antioxidant Studies of
Anthraquinone-core-based Dendrimers with
N-Phenylcarbazole as Surface Group
A D
,
A
Perumal Rajakumar,
Nagarathinam Venkatesan,
B
C
Karuppannan Sekar, Subramani Nagaraj,
C
and Ramasamy Rengasamy
A
Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai
600 025, India.
B
Department of Chemistry, Anna University University College of Engineering,
]
Dindigul 624 622, India.
C
Centre for Advanced Studies in Botany, University of Madras, Guindy Campus,
Chennai 600 025, India.
D
Corresponding author. Email: perumalrajakumar@gmail.com
Synthesis of hyperbranched dendrimers up to third generation with N-phenylcarbazole as surface group and anthraquinone
as the core unit has been achieved. The fluorescence decay studies of the dendrimers indicate that generation growth alters
the relaxation time. The highly branched third-generation dendrimer has a longer relaxation time than the zero-, first-,
and second-generation dendrimers. Similarly, higher-generation dendrimers show better antioxidant behaviour with
1,1-diphenyl-2-picryl hydrazyl than the lower-generation dendrimers.
Manuscript received: 28 September 2013.
Manuscript accepted: 22 November 2013.
Published online: 6 January 2013.
Introduction
acidic conditions and hence they cannot function as permanent
fluorescent sensing materials under highly acidic conditions.
Very few hyperbranched dendritic architectures with permanent
sensing fluorescence property have been reported in the litera-
ture.[13] Recently, we reported the synthesis of hyperbranched
dendritic architecture with permanent sensing fluorescence and
with either bactericidal efficacy[14] or an axially chiral enan-
tiopure nature.[15] Compounds with antioxidant properties are
attractive as they are useful in protecting from the process of
ageing and for protection of the human body from oxidative
degradation. The search for a better antioxidant material with a
non-permeable matrix is of much interest. Though antioxidant
dendrimers with carbazole as the surface group have been
reported recently,[16] inconsistent antioxidant behaviour was
observed. However, to the best of our knowledge, Fre´chet-type
antioxidant dendrimers with N-phenylcarbazole as surface group
and with fluorescent anthraquinone as the core unit have not been
reported so far. The presence of the fluorescent anthraquinone
core in the antioxidant dendrimers can act as a fluorescent tag in
biomedical applications. Herein, we describe the convergent
synthesis, optical, electrochemical properties and antioxidant
study of anthraquinone-core-based novel dendrimers 1a, 1b, 1c,
and 1d incorporating N-phenylcarbazole dendrons (Fig. 1).
Dendrimers are globular monodisperse macromolecules con-
taining branched repeating units emanating from a core unit.
The three-dimensional scaffold in dendrimers allows additional
control over the structure and morphology of the materials.
Dendrimers with carbazole-based dendritic wedges are inter-
esting because of their role both in biological as well as in
electrochemical devices, such as electroxerography and photo-
electrochemical appliances[1] for photonic application[2] and for
their practical use as photo sensitisers,[3] microcavity photo-
conduction, and as hole-transporting materials.[4] The search for
bioactive dendrimers of nanomolecular dimension is of great
interest because of their role in various biomedical applications
such as drug delivery,[5] gene transfection,[6] and imaging.[7]
The dendrimer surface provides an excellent platform for drug
delivery for treatments against cancer[8] as well as bacteria and
viruses.[9] Recently, it has been shown that some surface-
modified dendrimers themselves act as nanodrugs against
viruses.[10] Moreover, the lone pair of electrons of the carbazole
nitrogen at the surface of the dendrimers can be easily lost by an
oxidation process and hence such carbazole-containing den-
drimers may exhibit interesting antioxidant properties in the
biomedicinal field. Dendrimers with fluorescent tags play an
important role in biology.[11] Anthraquinone-based dendrimers
are fascinating owing to their high fluorescence activity, and
hence their mobility in biological systems can be easily moni-
tored. Though some fluorescent dendrimers have been repor-
ted,[12] the dendritic core loses fluorescence activity under
Results and Discussion
Synthesis of Dendritic Arms
The synthesis of the dendritic arms for all the generations of
dendrimers was carried out by the reported procedure.[16]
Journal compilation Ó CSIRO 2014
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Anthraquinone-core-based carbazole dendrimers
637
bromide 3. Reaction of methyl 3,5-dihydroxybenzoate with 2.1
equivalents of dendritic bromide 3 afforded the methylcarbox-
ylate 5 in 72 % yield. Reduction of the methylcarboxylate 5 with
lithium aluminium hydride (LAH) in dry THF gave the dendritic
alcohol 6 [G-1]-CH2OH, which on further treatment with SOCl2
in dry dichloromethane (DCM) at 08C resulted in the formation
of the dendritic chloride 7 [G-1]-CH2Cl in 80 % yield. Similarly,
reaction of methyl 3,5-dihydroxybenzoate with 2.1 equivalents
of dendritic chloride 7 [G-1]-CH2Cl gave the second-generation
methyl carboxylate 8 [G-2]-CO2Me, which by a similar
sequence to that mentioned above gave the second-generation
dendritic chloride 10 [G-2]-CH2Cl in 72 % yield through the
second-generation dendritic alcohol 9 [G-2]-OH. Through a
similar sequence, the third-generation dendritic chloride 13
[G-3]-CH2Cl was obtained in 75 % yield from the second-
generation dendritic chloride 10 [G-2]-CH2Cl (Scheme 1).
N
N
O
O
N
O
O
O
O
O
O
O
O
O
O
N
N
N
1a
1b
Synthesis of Dendrimers
N
Reaction of 2.1 equivalents of the dendritic bromide 3 with 1.0
equivalent of 1,5-dihydroxy anthraquinone 4 in the presence of
K2CO3 in dry DMF afforded the zero-generation dendrimer 1a
N
O
N
1
O
O
in 53 % yield (Scheme 2). In the H NMR spectrum, 1a dis-
N
O
O
O
O
played a singlet for the methylene protons at d 5.45 ppm in
addition to the signals for the aromatic proton, and in 13C NMR
spectrum, the methylene carbon and the carbonyl carbon
appeared at d 70.7 and 182.4 ppm respectively in addition to the
signals for the aromatic carbons. The structure of dendrimer 1a
was further confirmed from the satisfactory elemental analysis
and by the appearance of a molecular ion at m/z 750 (Mþ) in the
FAB (fast-atom bombardment) mass spectrum. Similarly, the
reaction of 2.1 equivalents of dendritic chlorides 7 (G-1)-CH2Cl,
10 (G-2)-CH2Cl and 13 (G-3)-CH2Cl with each 1.0 equivalent
of the dihydroxyanthraquinone 4 in the presence of K2CO3 in
dry DMF afforded the first-, second-, and third-generation
dendrimers 1b, 1c, and 1d in 65, 61, and 68 % yields respectively
(Scheme 2).
In the 1H NMR spectrum, dendrimer 1b displayed two sharp
singlets for methylene protons at d 5.16 and 5.22 integrating for
eight and four protons respectively in addition to the signals for
the aromatic protons, and in 13C NMR spectrum, the two types
of methylene carbons and the carbonyl carbon appeared at d
69.8, 70.8 and 182.4 respectively in addition to the signals for
the aromatic carbons. The structure of the first-generation
dendrimer 1b was further confirmed by the appearance of a
molecular ion at m/z 1506 (Mþ) in the FAB mass spectrum and
from satisfactory elemental analysis.
In the 1H NMR spectrum, dendrimer 1c displayed three
methylene protons as a singlet at d 5.08 integrating for 28
protons in addition to the signals for the aromatic protons. In
the 13C NMR spectrum, three different methylene carbons and
the carbonyl carbons appeared at d 69.6, 69.9, 70.5 and 182.2
respectively in addition to the signals for the aromatic carbon. In
the MALDI-TOF (matrix-assisted laser desorption–ionisation
time-of-flight) mass spectrum, the molecular ion peak appeared
at m/z 3038 (M þ Naþ) and the structure of dendrimer 1c was
further confirmed from elemental analysis.
In the 1H NMR spectrum, dendrimer 1d showed four differ-
ent singlets at d 4.95, 4.98, 5.01 and 5.10 for four different
methylene protons integrating for 4, 8, 16 and 32 protons
respectively in addition to the signals for the aromatic protons.
In the 13C NMR spectrum, the methylene and carbonyl carbons
appeared at d 69.7, 69.9, 70.0, and 182.3 in addition to the
signals for the aromatic carbons. The structure of the dendrimer
O
O
O
O
O
O
N
O
O
N
O
N
N
1c
N
N
N
N
N
O
O
N
O
O
O
O
O
O
O
O
N
O
O
N
O
O
O
O
O
O
O
O
N
O
O
N
O
O
O
O
O
O
O
O
N
O
O
N
N
N
N
N
1d
Fig. 1. Structures of the dendrimers 1a d.
]
Copper-catalysed N-arylation of carbazole with 4-iodotoluene
to give N-p-tolyl carbazole 2 was used for the synthesis
of dendrimers in the present study.[17] p-Bromomethyl-N-
phenylcarbazole 3 required for the synthesis of phenylcarba-
zole-based dendrimers was obtained in 84 % yield by the radical
bromination of N-p-tolyl carbazole 2. The first-generation
dendritic chloride 7 [G-1]-CH2Cl required for the synthesis of
first-generation dendrimer 1b was obtained from the dendritic

638
P. Rajakumar et al.
ii
ii
Z ϭ -p-C6H4CH4 2
Z ϭ -C6H4CH2Br
3 [G-0] CH2Br
i
R
R ϭ CO2Me 5 [G-1]-CO2Me
R ϭ CH2OH 6 [G-1]-CH2OH
R ϭ CH2CI 7 [G-1]-CH2CI
R ϭ CO2Me 8 [G-2]-CO2Me
R ϭ CH2OH 9 [G-2]-CH2OH
R ϭ CH2CI 10 [G-2]-CH2CI
iv
iii
iv
ii
R ϭ CO2Me 11 [G-3]-CO2Me
R ϭ CH2OH 12 [G-3]-CH2OH
R ϭ CH2CI 13 [G-3]-CH2CI
iii
iv
Scheme 1. Synthesis of dendrons. Reagents and conditions: (i) N-bromosuccinimide (NBS), CCl4, benzoyl peroxide (Bz2O2), reflux,
6 h, 84 %; (ii) methyl 3,5-dihydroxybenzoate (0.5 equiv.), K2CO3, 18-crown-6, DMF, 808C, 48 h, 5 72 %, 8 70 %, 11 73 %; (iii) lithium
aluminium hydride (LAH), THF, reflux, 6 h, 6 67 %; 9 71 %; 12 70 %; (iv) SOCl2, pyridine, dichloromethane (DCM), 08C to room
temperature, 3 h, 7 80 %; 10 72 %; 13 75 %.
1.6
1a
1b
1a
1b
1c
1d
1.4
1.2
1.0
0.8
0.6
0.4
3
7
i
i
O
OH
OH
O
13
10
4
i
i
1c
1d
325
330
335
340
345
350
355
Scheme 2. Synthesis of dendrimers 1a d. Reagents and conditions:
]
(i) K2CO3, 18-crown-6, DMF, 608C, 48 h; 1a 53 %; 1b 65 %; 1c 61 %;
1d 68 %.
Wavelength [nm]
Fig. 2. UV-vis absorption spectra of dendrimers 1a d (1.0 ꢁ 10ꢀ5 M)
]
in DMF.
1d was further confirmed by the appearance of a molecular ion
peak at m/z 6058 (M þ Naþ) in the MALDI-TOF mass spectrum
as well as by satisfactory elemental analysis.
bands were observed at 326 and 339 nm (Fig. 2). The intensity of
both the bands at 326 and 339 nm increases as the generation of
the dendrimer increases from lower to higher for the same
Optical and Fluorescence Studies
concentration of dendrimers 1a d. Neither bathochromic nor
]
hypsochromic shifts could be observed on changing the solvent
from DMF to CHCl3. Protonation of the carbonyl chromophore
The UV-vis absorption spectra of dendrimers 1a, 1b, 1c, and 1d
were recorded at a concentration of 10ꢀ5 mol Lꢀ1 and two main

Anthraquinone-core-based carbazole dendrimers
639
Table 1. Bi- and tri-exponential fluorescence analysis of the
800
600
400
200
0
1a
1b
1c
1d
dendrimers 1a d in DMF
]
Dendrimer Analysis
Life-time [ns]
Amplitudes [%]
t1
t2
t3
A1
A2
A3
1a
1b
1c
1d
Bi-exponential 2.14 7.83
–
61.25 38.75
–
Tri-exponential 1.12 3.71 7.31
6.85 51.57 41.28
Tri-exponential 4.36 8.41 1.15 34.27 53.53 12.19
Tri-exponential 1.53 4.28 9.96 25.41 39.53 35.03
80
70
60
50
40
30
20
10
0
400
450
500
550
600
650
Wavelength [nm]
Fig. 3. Fluorescence emission spectra of dendrimers 1a d (1.0 ꢁ 10ꢀ5 M)
]
in DMF.
1a
1b
1c
1d
in the anthraquinone moiety could lead to a change in lmax.
However, on adding ethanoic acid, TFA, and HCl up to 5 M for
1 ꢁ 10ꢀ5 M of the dendrimer, no shift in lmax could be observed.
Dendrimer 1a exhibited a fluorescence emission band at
425 nm. Similarly, dendrimers 1b, 1c, and 1d showed fluores-
cence emission at 441, 427, and 426 nm respectively (Fig. 3).
Hence, fluorescence quenching did not occur even after adding
ethanoic acid, TFA, and HCl to the dendrimers, which shows
that the dendrimers 1a, 1b, 1c, and 1d can function as permanent
fluorescence-sensing materials even under highly acidic
conditions.
20
40
60
80
100
250
500 1000
Concentration [μg mLϪ1
]
Fig. 4. 1,1-Diphenyl-2-picryl hydrazyl (DPPH) scavenging activity
spectrometric assay of various concentration of the dendrimers 1a, 1b, 1c,
and 1d.
other dendrimers and hence the highly branched third-genera-
tion dendrimer could be a better fluorescent material than the
zero-, first-, and second-generation dendrimers. A smooth
correlation between fluorescence properties and increase in
dendrimer generation was observed. Hence, by synthesising
higher-generation dendrimers, very efficient free radical-
stabilised and highly fluorescent organic nanomaterial can be
easily obtained.
Fluorescence Decay Analysis
Fluorescence decay of the dendrimers 1a d was recorded
]
using the time-correlated photon-counting (TCSPC) method
with the following setup. A diode-pumped Millena CW 532-
nm laser was used to pump a Ti : sapphire rod in a Tsunami
picosecond-mode locked laser system. The 750-nm (80-MHz)
output was taken from the Ti : sapphire laser and passed through
a pulse picker to generate a 4-MHz pulse. The second harmonic
output (375 nm) was generated by a flexible harmonic generator.
The vertically polarised 375-nm laser was used to excite the
sample. The fluorescence emission at the magic angle (54.78)
was dispersed in a monochromator (f/3 aperture), counted by a
microchannel plate photomultiplier tube (Hamamatsu R 3809),
and processed through computational fluid dynamics, text
analysis conference, and a multichannel analyser. The instru-
ment response function for this system is ,52 ns; the fluores-
cence decay was analysed using the software provided by
Interessengemeinschaft Bensberger Handel (DAS-6). The fluo-
rescence decay of dendrimer 1a was bi-exponential with a life-
time of 2.14 and 7.83 ns in DMF, whereas dendrimers 1b, 1c,
and 1d were tri-exponential with life-times of 1.12, 3.71, 7.31;
4.36, 8.41, 1.15, and 1.53, 4.28, 9.96 ns. The life-times and
relative amplitudes are shown in Table 1.
Antioxidant Studies of Dendrimers 1a–d
The antioxidant activity of all the dendrimers was tested with
1,1-diphenyl-2-picryl hydrazyl (DPPH) by a free radical-
scavenging technique using a spectrometric assay method.
Samples at different concentrations were prepared and tested for
free radical-scavenging activity using DPPH. The percentage
inhibition was calculated and the antioxidant activity of the
dendrimers and standard antioxidants like ascorbic acid, a-
tocopherol, and butylated hydroxyanisole (BHA) was recorded
and compared. The antioxidant activity and IC50 (concentration
producing 50 % inhibition) values of the dendrimers along with
standard drugs are shown in Figs 4 and 5 respectively.
Methodology
DPPH has a violet colour and absorbs at 517 nm in ethanol.
When DPPH is mixed with the dendrimers, which can donate
free electrons, DPPH loses its colour and undergoes reduction to
give diphenyl picryl hydrazine.[18] Dendrimers 1a–d were dis-
solved in CHCl3 with concentrations of 20, 40, 60, 80, 100, 250,
500 and 1000 mg mLꢀ1 and used for the study. The test solutions
Among all the dendrimers, dendrimer 1d exhibited the
longest relaxation time t3, with an amplitude of 39.53 (A2).
The dendrimer 1d exhibited a bi-exponential delay with a life-
time (t2) of 7.83 ns. From the life-time (t) and amplitude (A)
measurements of dendrimers 1a d, it is clear that dendrimer 1d
]
is the best fluorescence-sensing material. In conclusion, the
third-generation dendrimer has a longer relaxation time than the
of dendrimers 1a d (0.1 mL) in CHCl were added to a solution
]
of DPPH (0.5 mL) in ethanol and absorption was measured at
3

640
P. Rajakumar et al.
100
80
60
40
20
0
Ascarbic acid
α-Tocopherol
BHA
Dendrimer 1c
Dendrimer 1d
0
20
40
60
80
100
C
1a
1b
1c
1d
IC50 [μg mLϪ1
]
0
5
10
15
Time [min]
20
25
Fig. 5. 1,1-Diphenyl-2-picryl hydrazyl (DPPH) scavenging capacities
(concentration producing 50 % inhibition; IC50) of dendrimers 1c and 1d
with standard drugs.
Fig. 6. 1,1-Diphenyl-2-picryl hydrazyl (DPPH) reaction kinetics of each
dendrimer with time (up to 25 min) using methanol as control.
517 nm. Percentage activity was calculated from the following
equation:
reported herein have a highly fluorescent anthraquinone core
and hence fluorescent tagging can be carried out in order to
monitor their presence in biological systems. Further, the
carbazole-based dendrimers may have good biocompatibility,
cytotoxicity, and bioavailability. In our earlier work,[16] incon-
sistent antioxidant behaviour was observed on increasing the
dendrimer generation. However, in the present investigation, a
smooth correlation was observed with respect to the dendrimer
generation and antioxidant behaviour. The antioxidant proper-
ties gradually increased as the dendrimer generation increased.
Hence, it is possible to synthesise superior antioxidant materials
by simply increasing the dendrimer generation. Moreover,
within the given generation, the opportunity to increase the
number of carbazole units is also possible, which could result in
the formation of excellent antioxidant nanomaterials.
% Activity ¼ ½As ꢀ Ab=Acꢂ ꢁ 100
where As ¼ absorbance of DPPH test solution along with
dendrimers, Ab ¼ absorption of blank solution without DPPH
and with dendrimers, and Ac ¼ control DPPH solution with
DPPH solution and without dendrimer. Fig. 4 shows the per-
centage of DPPH reduction with change in the concentration of
dendrimers 1a–d.
Results
The third-generation dendrimer 1d showed excellent activity
at concentration ranges of 40 to 1000 mg mLꢀ1. The antioxidant
properties of all the dendrimers, 1a, 1b, 1c, and 1d, increased
with an increase in concentration of the dendrimers in the test
solution. In fact, zero-generation dendrimer 1a is the weakest
antioxidant. Antioxidant strength gradually increases with
increasing dendrimer generation from zero to third and hence
the second- and third-generation dendrimers 1c and 1d show
better antioxidant properties than 1a and 1b, which could be due
to a higher number of carbazole groups on the surface, generally
termed as a multivalent effect.[19] IC50 values were determined
in order to confirm the reducing activity of the dendrimers
synthesised. Scavenging activity of 50 % was observed at 70 and
52 mg mLꢀ1 for dendrimers 1c and 1d respectively (Fig. 5). The
antioxidant activity is significant when compared with standard
antioxidant drugs[20] like ascorbic acid, a-tocopherol, and BHA
(with IC50s of 15, 25, and 29 mg mLꢀ1 respectively). Variations
in antioxidant behaviour with reference to time delay were also
assessed by the DPPH assay method. Each of the dendrimers
was tested for radical-scavenging activity against DPPH for up
to 25 min using methanol as control, and all the four dendrimers
Conclusion
Using a convergent strategy, anthraquinone-core-based zero-,
first-, second-, and third-generation fluorescent dendrimers
containing N-phenylcarbazole as surface groups were synthe-
sised. Fluorescence studies indicated that even under highly
acidic conditions, fluorescence quenching did not occur and the
highly branched dendrimer 1d exhibited the longest relaxation
time in fluorescence decay analysis. Though all the synthesised
dendrimers exhibited antioxidant activity, dendrimers 1c and 1d
showed excellent antioxidant properties with significant IC50
values. The second- and third-generation dendrimers 1c and 1d
could be further developed as antioxidant materials with activity
comparable with that of commercially available substances.
Further, the synthesis of higher-generation dendrimers and their
cytotoxicity, biocompatibility, bioavailability and in vivo
studies are under way.
(1a d) exhibited rapid radical-scavenging activity for the first
]
20 min, with later activity remaining almost constant (Fig. 6).
Among all the dendrimers, the third-generation dendrimer 1d
showed excellent radical scavenging and only 20 % of DPPH
radical remained even after 25 min, which shows that it could act
as an excellent antioxidant material. Though the antioxidant
properties of syringaldehyde[21] can be compared with that of
the dendrimers reported in the current investigation, the corro-
sive phenolic unit prevents its application as a non-toxic
antioxidant material. Further, the antioxidant dendrimers
Experimental
General
All the reagents and solvents employed were of the best grade
available and used without further purification. The melting
points, determined using a Toshniwal melting point apparatus
by open capillary tube method, are uncorrected. Spectroscopic
data were recorded with the following instruments: UV-vis,
Shimadzu 260 spectrophotometer, and emission spectra,

Anthraquinone-core-based carbazole dendrimers
641
Perkin–Elmer LS-5B fluorescence spectrophotometer; IR,
Fourier-transform (FT)IR-8300 spectrometer (Model 8300;
Shimadzu); NMR, Bruker 300 MHz; MS, FAB-MS spectra, Jeol
SX 102/DA-600 mass spectrometer, and MALDI-TOF MS,
Voyager DE-PRO Biospectrometry workstation (Applied Bio-
systems). The elemental analysis of the dendrimers was carried
out using a Perkin–Elmer CHNS2400 elemental analyser. Col-
umn chromatography was performed on silica gel (ACME, 100–
200 mesh). Routine monitoring of the reaction was carried out
using thin-layer chromatography developed on glass plates
coated with silica gel-G (ACME) of 25-mm thickness and
visualised with iodine.
poured into ice water. The resulting precipitate was filtered,
washed thoroughly with water, and dissolved in CHCl3
(150 mL), washed with water (50 mL), brine (50 mL), and then
dried (anhydrous Na2SO4). Removal of the solvent under
reduced pressure gave the dendrimer as a crude material, which
was purified by column chromatography (SiO2).
Compound 2
9-p-Tolylcarbazole was prepared according to the Buchwald
procedure.[17] To a mixture of CuI (0.87 g, 0.46 mmol), K3PO4
(12.17 g, 5.72 mmol), and carbazole (3.6 g, 2.18 mmol) in tolu-
ene (100 mL) was added p-iodotoluene (5.0 g. 2.29 mmol) and
(ꢃ)-trans-1,2-diaminocyclohexane (1.05 g, 0.92 mmol) under
nitrogen. The reaction mixture was heated on an oil bath at
1108C for 12 h. The reaction mixture was filtered and the solvent
was evaporated under vacuum, and the residue thus obtained
was dissolved in CHCl3. The organic phase was washed with
water (2 ꢁ 150 mL) and brine (1 ꢁ 100 mL) and was dried
(Na2SO4). The crude product obtained after evaporating the
solvent was purified by column chromatography (SiO2) in
hexane to give 2 as a white solid in 92 % yield (5.43 g); mp
148–1508C. dH (300 MHz, CDCl3) 2.42 (s, 3H), 7.21–7.27 (m,
2H), 7.31–7.40 (m, 8H), 8.10 (d, 2H, J 7.5). dC (75 MHz, CDCl3)
21.3, 109.9, 119.9, 120.4, 123.4, 125.9, 127.1, 130.6, 135.1,
137.4, 141.2. Anal. Calc. for C19H15N: C 88.68, H 5.88, N 5.44.
Found: C 88.64, H 5.93, N 5.46 %.
General Procedure for the Synthesis of Dendritic Esters (A)
A mixture of the appropriate dendritic bromide or chloride
(2.1 equiv.), methyl 3,5-dihydroxybenzoate (1.0 equiv.), anhy-
drous potassium carbonate (3.0 equiv.), and 18-crown-6
(0.1 equiv.) in dry DMF (30 mL) was vigorously stirred at 808C
for 48 h under a nitrogen atmosphere. The reaction mixture was
then allowed to cool to room temperature and poured into ice
water. The resulting precipitate was filtered, washed thoroughly
with water and dissolved in CHCl3 (150 mL). The organic layer
was separated, washed with brine (1 ꢁ 150 mL), dried
(anhydrous Na2SO4), and evaporated to give the crude ester,
which was purified by column chromatography (SiO2) using a
mixture of hexane and CHCl3 as the eluent.
Compound 3
General Procedure for the Reduction of the Dendritic Ester
Freshly recrystallised NBS (1.64 g, 0.93 mmol) was added in
three equal portions at 0.5-h intervals to a solution of 9-p-
tolylcarbazole (2.0 g, 0.78 mmol) in dry CCl4 (100 mL) heated at
reflux; each portion was immediately followed by adding a few
milligrams of benzoyl peroxide. After heating under reflux for a
total of 3 h, the reaction mixture was cooled and the precipitated
succinimide was removed by filtration. The residue obtained
after evaporation of the solvent was chromatographed (SiO2)
with hexane/CHCl3 (1 : 1) as eluent to give the bromide 3 as a
highly viscous oil (2.19 g). Yield: 84 %. dH (300 MHz, CDCl3)
4.56 (s, 2H), 7.25–7.31 (m, 2H), 7.37–7.39 (m, 4H), 7.49–7.52
(m, 2H), 7.55–7.58 (m, 2H), 8.12 (d, 2H, J 7.8). dC (75 MHz,
CDCl3) 32.8, 109.8, 120.2, 120.4, 123.6, 126.1, 127.3, 130.6,
136.9, 137.9, 140.7. Anal. Calc. for C19H14BrN: C 67.87, H
4.20, N 4.17. Found: C 67.44, H 4.16, N 4.12 %.
into the Corresponding Alcohol (B)
To a stirred suspension of LAH (2.5 equiv.) in dry THF (20 mL),
a solution of the appropriate dendritic ester (1.0 equiv.) in dry
THF (30 mL) was added dropwise at room temperature under a
nitrogen atmosphere. The reaction mixture was heated under
reflux for 6 h, after which it was cooled to 108C and the excess
LAH was quenched cautiously by adding 10 % NaOH solution
dropwise. Anhydrous Na2SO4 was added to the reaction mix-
ture, which was stirred and filtered. THF (20 mL) was added to
the residue, and the mixture was kept on steam bath for 10 min
and then filtered. The process was repeated four or five times.
The combined THF fractions were evaporated to give the crude
alcohol, which was purified by column chromatography (SiO2).
General Procedure for the Conversion of the Dendritic
Alcohol into the Corresponding Chloride (C)
Dendrimer 1a
To a stirred solution of the appropriate dendritic alcohol
(1.0 equiv.) in dry CH2Cl2 (10 mL) was added dropwise a
solution of SOCl2 (3.0 equiv.) in dry CH2Cl2 (30 mL) in the
presence of pyridine (1.2 equiv.) at 08C. The reaction mixture
was stirred at room temperature for 3 h and then quenched by the
addition of ice water (5 mL). The organic layer was separated,
washed with water (2 ꢁ 25 mL), dried (anhydrous Na2SO4), and
evaporated to give the crude compound, which was purified by
column chromatography (SiO2) using hexane and CH2Cl2(1 : 1)
as eluent.
Dendrimer 1a (0.29 g) was obtained as an orange-coloured
solid from dihydroxyanthraquinone (0.17 g, 0.07 mmol) and the
[G-0]-bromide 3 (0.5 g, 0.15 mmol) using the general procedure
D. Yield: 53 %; mp 157–1598C. Rf.0.16 (CHCl3/methanol,
9 : 1). nmax (KBr)/cmꢀ1 1655 cmꢀ1. dH (300 MHz, CDCl3) 5.45
(s, 4H), 7.29–7.32 (m, 6H), 7.41–7.43 (m, 10H), 7.73–7.78 (m,
4H), 7.89–7.92 (m, 4H), 8.03 (d, 2H, J 7.5), 8.15 (d, 4H, J 7.5).
dC (75 MHz, CDCl3) 70.7, 109.8, 118.7, 119.9, 120.1, 120.3,
123.4, 125.9, 127.4, 128.4, 128.7, 135.1, 135.5, 137.4, 137.6,
140.9, 158.8, 182.4. m/z (FAB) 750 (Mþ). Anal. Calc. for
C52H34N2O4: C 83.18, H 4.56, N 3.73. Found: C 83.14, H
4.54, N 3.75 %.
General Procedure for the Synthesis of Dendrimers (D)
A mixture of the appropriate dendritic bromide or chloride
(2.2 equiv.), dihydroxyanthraquinone (1.0 equiv.), 18-crown-6
(0.1 equiv.), and potassium carbonate (5.0 equiv.) in dry DMF
(25 mL) was stirred at 608C for 48 h under nitrogen. The reaction
mixture was then allowed to cool to room temperature and
Dendritic Ester 5 {[G-1]-CO2Me}
Dendritic ester 5 (2.2 g) was obtained as colourless solid
from methyl 3,5-dihydroxy benzoate (480 mg, 2.85 mmol)
and [G-0]-bromide 3 (3.00 g, 5.97 mmol) using the general

642
P. Rajakumar et al.
procedure A; yield: 72 %; mp 150–1528C. nmax
(KBr)/cmꢀ1 1722 cmꢀ1. dH (300 MHz, CDCl3) 3.88 (s, 3H),
5.14 (s, 4H), 6.87 (t, 1H, J 2.4), 7.17–7.24 (m, 4H), 7.30–7.37
(m, 10H), 7.53 (d, 4H, J 8.4), 7.61 (d, 4H, J 8.4), 8.07 (d, 4H, J
7.8). dC (75 MHz, CDCl3) 52.4, 69.9, 107.4, 108.6, 109.8, 120.0,
120.3, 123.5, 125.9, 127.3, 129.1, 132.4, 135.2, 137.6, 140.8,
159.8, 166.7. m/z (EI) 678 (Mþ). Anal. Calc. for C46H34N2O4:
C 81.40, H 5.05, N 4.13. Found: C 81.45, H 5.01, N 4.09 %.
m/z (FAB) 1433 (Mþ). Anal. Calc. for C98H72N4O8: C 82.10,
H 5.06, N 3.91. Found: C 82.12, H 5.08, N 3.87 %.
Dendritic Alcohol 9 {[G-2]-CH2OH}
Dendritic alcohol 9 (1.04 g) was obtained as a colourless
solid by reducing the dendritic ester 8 (1.5 g, 0.72 mmol) with
LAH (81 mg, 2.14 mmol) using the general procedure B. Yield:
71 %; mp 125–1278C. Rf.0.21 (hexane/CHCl3, 1 : 4). nmax
(KBr)/cmꢀ1 3420 cmꢀ1. dH (300 MHz, CDCl3) 4.64 (s, 2H),
5.05 (s, 4H), 5.17 (s, 8H), 6.62 (s, 1H), 6.66 (s, 2H), 6.70 (s, 2H),
6.78 (s, 4H), 7.27 (s, 4H), 7.29 (s, 2H), 7.36–7.42 (m, 18H), 7.58
(d, 8H, J 8.4), 7.66 (d, 8H, J 8.4), 8.13 (d, 8H, J 7.8). dC (75 MHz,
CDCl3) 65.3, 69.8, 70.0, 101.5, 101.7, 105.9, 106.6, 109.7,
120.0, 120.3, 123.4, 126.0, 127.2, 129.1, 135.9, 137.6, 139.6,
140.8, 143.6, 160.2, 160.2. m/z (FAB) 1405 (Mþ). Anal. Calc.
for C97H72N4O7: C 82.88, H 5.16, N 3.99. Found: C 82.85,
H 5.18, N 3.96 %.
Dendritic Alcohol 6 {[G-1]-CH2OH}
Dendritic alcohol 6 (1.61 g) was obtained as colourless solid
by reducing the dendritic ester 5 (2.5 g, 1.98 mmol) with LAH
(188 mg, 4.95 mmol) using the general procedure B. Yield:
67 %; mp 102–1048C. Rf.0.21 (hexane/CHCl3, 1 : 4). nmax
(KBr)/cmꢀ1 3421 cmꢀ1. dH (300 MHz, CDCl3) 4.63 (s, 2H),
5.10 (s, 4H), 6.61 (s, 1H), 6.66 (s, 2H), 7.19–7.23 (m, 8H), 7.34
(s, 4H), 7.52 (d, 4H, J 7.8), 7.59 (d, 4H, J 7.8), 8.06 (d, 4H, J 7.5).
dC (75 MHz, CDCl3) 65.3, 69.7, 101.5, 106.0, 109.7, 120.0,
120.3, 123.4, 125.9, 127.2, 129.0, 136.0, 137.5, 140.8, 143.7,
160.2. m/z (EI) 650 (Mþ). Anal. Calc. for C45H34N2O3: C 83.05,
H 5.27, N 4.30. Found: C 83.07, H 5.25, N 4.27 %.
Dendritic Chloride 10 {[G-2]-CH2Cl}
Dendritic chloride 10 (0.72 g) was obtained as white solid
from the dendritic alcohol 9 (1.0 g, 0.48 mmol) and SOCl2
(0.14 mL, 1.45 mmol) using the general procedure C. Yield:
72 %; mp 137–1398C. Rf.0.56 (hexane/CH2Cl2, 3 : 2). dH
(300 MHz, CDCl3) 4.49 (s, 2H), 5.01 (s, 4H), 5.12 (s, 8H),
6.63–6.69 (m, 6H), 6.76 (s, 3H), 7.22–7.28 (m, 8H), 7.33–7.38
(m, 16H), 7.55 (d, 8H, J 8.4), 7.61 (d, 8H, J 8.4), 8.10 (d, 8H,
J 7.5). dC (75 MHz, CDCl3) 46.4, 69.8, 70.1, 101.8, 102.3, 106.7,
107.8, 109.8, 120.1, 120.4, 123.5, 126.0, 127.3, 128.6, 129.1,
135.9, 137.6, 139.4, 140.8, 160.1, 160.3. m/z (FAB) 1423 (Mþ).
Anal. Calc. for C97H71ClN4O6: C 81.81, H 5.03, N 3.93. Found:
C 81.83, H 5.05, N 3.97 %.
Dendritic Chloride 7 {[G-1]-CH2Cl}
Dendritic chloride 7 (0.8 g) was obtained as a white solid
from the alcohol 6 (1.0 g, 0.15 mmol) and SOCl2 (0.13 mL,
0.18 mmol) using the general procedure C. Yield: 80 %; mp
168–1708C. Rf 0.56 (hexane/CH2Cl2, 3 : 2). dH (300 MHz,
CDCl3) 4.58 (s, 2H), 5.18 (s, 4H), 6.71 (t, 1H, J 2.4), 6.75
(d, 2H, J 2.1), 7.26–7.31 (m, 4H), 7.37–7.42 (m, 8H), 7.60
(d, 4H, J 8.7), 7.67 (d, 4H, J 8.7), 8.14 (d, 4H, J 7.5). dC (75 MHz,
CDCl3) 46.3, 69.8, 102.3, 107.9, 109.8, 120.0, 120.4, 123.5,
125.9, 127.3, 129.1, 135.8, 137.6, 139.9, 140.8, 160.1. m/z (EI)
668 (Mþ). Anal. Calc. for C45H33ClN2O2: C 80.76, H 4.97,
N 4.19. Found: C 80.71, H 4.95, N 4.23 %.
Dendrimer 1c
Dendrimer 1c (0.32 g) was obtained as an orange-coloured
solid from dihydroxyanthraquinone (40 mg, 0.01 mmol) and the
dendritic chloride 10 (0.5 g, 0.03 mmol) using the general
procedure D. Yield: 61 %; mp 141–1438C. Rf.0.16 (CHCl3/
methanol, 9 : 1). nmax (KBr)/cmꢀ1 1658 cmꢀ1. dH (300 MHz,
CDCl3) 5.08 (bs, 28H), 6.64 (s, 4H), 6.77 (s, 8H), 6.92 (s, 4H),
7.03 (s, 2H), 7.22–7.23 (m, 22H), 7.35 (s, 32H), 7.54 (d, 30H,
J 7.5), 7.85 (d, 2H, J 7.5), 8.09 (d, 16H, J 6.6). dC (75 MHz,
CDCl3) 69.6, 69.9, 70.5, 101.7, 105.5, 106.5, 109.7, 118.2,
120.0, 120.3, 121.2, 123.4, 125.9, 127.1, 129.0, 134.7, 135.9,
137.4, 139.0, 140.7, 158.2, 160.1, 160.2, 182.2. m/z (MALDI-
TOF) 3038 (M þ Naþ). Anal. Calc. for C208H148N8O16: C 82.85,
H 4.95, N 3.72. Found: C 82.82,H 4.98, N 3.75 %.
Dendrimer 1b
Dendrimer 1b (0.34 g) was obtained as an orange-coloured
solid from dihydroxyanthraquinone (80 mg, 0.03 mmol) and the
[G-1]-chloride 7 (0.5 g, 0.07 mmol) using the general procedure
D. Yield: 65 %; mp 148–1508C. Rf.0.16 (CHCl3/methanol,
9 : 1). nmax (KBr)/cmꢀ1 1656 cmꢀ1. dH (300 MHz, CDCl3) 5.16
(s, 8H), 5.22 (s, 4H), 6.63 (s, 2H), 6.96 (s, 4H), 7.16–7.21 (m,
16H), 7.24–7.34 (m, 8H), 7.48–7.63 (m, 20H), 7.86 (d, 2H, J
7.8), 8.04 (d, 8H, J 7.5). dC (75 MHz, CDCl3) 69.8, 70.8, 101.9,
105.8, 109.8, 118.5, 120.0, 120.2, 120.3, 121.5, 123.4, 126.0,
127.2, 129.2, 135.0, 136.1, 137.5, 137.5, 139.2, 140.8, 158.5,
160.3, 182.4. m/z (FAB) 1506 (Mþ). Anal. Calc. for
C104H72N4O8: C 82.96, H 4.82, N 3.72. Found: C 82.92,
H 4.78, N 3.69 %.
Dendritic ester 11 {[G-3]-CO2Me}
Dendritic ester 11 (0.89 g) was obtained as a colourless solid
from methyl-3,5-dihydroxybenzoate (100 mg, 0.59 mmol) and
the second-generation dendritic chloride 10 {[G-2]-CH2Cl}
(1.25 g, 1.19 mmol) using the general procedure A. Yield:
Dendritic Ester 8 {[G-2]-CO2Me}
Dendritic ester 8 (0.89 g) was obtained as colourless solid
from methyl 3,5-dihydroxybenzoate (100 mg, 0.59 mmol) and
the first-generation dendritic chloride 7 [G-1]-CH2Cl (1.25 g,
1.19 mmol) using the general procedure A. Yield: 70 %; mp
121–1238C. nmax (KBr)/cmꢀ11720 cmꢀ1. dH (300 MHz, CDCl3)
3.89 (s, 3H), 5.08 (s, 4H), 5.17 (s, 8H), 6.71 (s, 2H), 6.79 (s, 6H),
6.87 (s, 1H), 7.25–7.40 (m, 24H), 7.57 (d, 8H, J 9.0), 7.66 (d, 8H,
J 9.0), 8.12 (d, 8H, J 9.0). dC (75 MHz, CDCl3) 52.3, 69.8, 70.2,
101.8, 106.6, 108.5, 109.7, 120.0, 120.3, 123.4, 125.9, 127.2,
129.0, 135.9, 137.5, 139.1, 140.8, 141.2, 141.4, 159.7, 160.2.
73 %; mp 132–1348C. nmax (KBr)/cmꢀ1 1722 cmꢀ1
. dH
(300 MHz, CDCl3) 3.88 (s, 3H), 5.05 (s, 4H), 5.11 (s, 8H),
5.16 (s, 16H),6.36 (s, 1H), 6.43 (s, 2H), 6.48 (s, 2H), 6.56 (s, 4H),
6.60 (s, 4H), 6.67 (s, 8H), 7.13–7.18 (m, 16H), 7.28–7.34 (m,
32H), 7.47 (d, 16H, J 8.4), 7.51 (d, 16H, J 8.1), 8.11 (d, 16H,
J 7.5). dC (75 MHz, CDCl3) 52.4, 69.9, 70.2, 70.5102.2, 107.2,
107.7, 108.8, 109.8, 120.0, 120.3, 123.5, 126.0, 127.1, 129.0,
135.8, 137.4, 139.0, 140.8, 141.1, 141.3, 141.7, 159.7, 160.0,
166.5. m/z (MALDI-TOF) 2954 (M þ Naþ). Anal. Calc. for

Anthraquinone-core-based carbazole dendrimers
643
C202H148N8O16: C 82.43, H 5.07, N 3.81. Found: C 82.40,
H 5.01, N 3.79 %.
References
[1] (a) J. F. Ambrose, R. F. Nelson, J. Electrochem. Soc. 1968, 115, 1159.
doi:10.1149/1.2410929
Dendritic Alcohol 12 {[G-3]-CH2OH}
(b) F. Ambrose, L. L. Carpenter, R. F. J. Nelson, Electrochem. Soc.
1975, 122, 876. doi:10.1149/1.2134365
Dendritic alcohol 12 (1.04 g) was obtained as a colourless
solid by reducing the dendritic ester 11 (1.5 g, 0.72 mmol) with
LAH (81 mg, 2.14 mmol) using the general procedure B. Yield:
70 %; mp 141–1438C. Rf.0.21 (hexane/CHCl3, 1 : 4). nmax
(KBr)/cmꢀ1 3420 cmꢀ1. dH (300 MHz, CDCl3) 4.46 (s, 2H),
4.87 (s, 4H), 4.93 (s, 8H), 4.97 (s, 16H), 6.43 (s, 1H), 6.48 (s,
2H), 6.54 (s, 2H), 6.58 (s, 4H), 6.62 (s, 4H), 6.67 (s, 8H), 7.14–
7.19 (m, 16H), 7.29 (s, 32H), 7.45 (d, 16H, J 8.1), 7.52 (d, 16H, J
8.1), 8.02 (d, 16H, J 7.8). dC (75 MHz, CDCl3) 69.7, 70.0, 101.3,
101.7, 105.7, 106.4, 106.5, 109.7, 120.0, 120.3, 123.4, 126.0,
127.2, 128.6, 128.8, 129.1, 135.8, 137.5, 139.5, 140.7, 143.6,
160.0, 160.2. m/z (MALDI-TOF) 2938 (M þ Naþ). Anal. Calc.
for C201H148N8O15: C 82.81, H 5.12, N 3.84. Found: C 82.84,
H 5.10, N 3.79 %.
[2] (a) P. Furuta, J. Brooks, M. E. Thompaon, J. M. J. J. Fre´chet, Am.
Chem. Soc 2003, 125, 13165. doi:10.1021/JA0371348
(b) T. W. Kwon, M. M. Alam, S. A. Jenekhe, Chem. Mater. 2004, 16,
4657. doi:10.1021/CM0494711
(c) S. M. Grayson, J. M. J. Fre´chet, Chem. Rev. 2001, 101, 3819.
doi:10.1021/CR990116H
[3] (a) M. Sangermano, G. Malucelli, A. Priola, S. Lengvinaite,
J. Simokaitiene, J. V. Grazulevicius, Eur. Polym. J. 2005, 41, 475.
doi:10.1016/J.EURPOLYMJ.2004.10.030
(b) Z. Gomurashvili, Y. Hua, J. V. Crivello, Macromol. Chem. Phys.
2001, 202, 2133. doi:10.1002/1521-3935(20010701)202:11,2133::
AID-MACP2133.3.0.CO;2-D
(c) D. R. Prudhomme, Z. Wang, C. J. Rizzo, J. Org. Chem. 1997, 62,
8257. doi:10.1021/JO971332Y
[4] (a) Y. Shirota, J. Mater. Chem. 2000, 10, 1. doi:10.1039/A908130E
(b) J. Kido, K. Hongawa, K. Okuyama, K. Nagai, Appl. Phys. Lett.
1993, 63, 2627. doi:10.1063/1.110402
Dendritic Chloride 13 {[G-3]-CH2Cl}
[5] (a) U. Boas, P. M. H. Heegaard, Chem. Commun. 1996, 1523.
(b) L. Balogh, D. R. Swanson, D. A. Tomalia, G. L. Hagnauer, A. T.
McManus, Nano Lett. 2001, 1, 18. doi:10.1021/NL005502P
[6] J. Recker, D. J. Tomcik, J. R. Parquette, J. Am. Chem. Soc. 2000, 122,
10298. doi:10.1021/JA001225C
Dendritic chloride 13 (0.75 g) was obtained as a white solid
from the dendritic alcohol 12 (1.0 g, 0.48 mmol) and SOCl2
(0.14 mL, 1.45 mmol) using the general procedure C. Yield:
75 %; mp 157–1598C. Rf.0.56 (hexane/CH2Cl2, 3 : 2). dH
(300 MHz, CDCl3) 4.44 (s, 2H), 4.94 (s, 4H), 5.01 (s, 8H),
5.11 (s, 16H), 6.53 (s, 1H), 6.59 (s, 2H), 6.63 (s, 2H), 6.67 (s,
4H), 6.70 (s, 4H), 6.72 (s, 8H), 7.22–7.29 (m, 16H), 7.32–7.39
(m, 32H, Ar), 7.53 (d, 16H, J 8.4), 7.61 (d, 16H, J 8.4), 8.10 (d,
16H, J 7.5). dC (75 MHz, CDCl3) 69.7, 70.0, 101.7, 102.2, 106.6,
107.7, 109.7, 120.1, 120.4, 123.4, 126.0, 127.2, 128.6, 129.1,
135.9, 137.5, 139.3, 139.5, 139.7, 140.8, 160.0, 160.2. m/z
(MALDI-TOF) 2956 (M þ Naþ). Anal. Calc. for
C201H147ClN8O14: C 82.29, H 5.05, N 3.82. Found: C 82.34,
H 5.03, N 3.79 %.
[7] (a) B. P. Hay, E. J. Werner, K. N. Raymond, Bioconjug. Chem. 2004,
15, 1496. doi:10.1021/BC0498370
(b) M. Doubrovin, I. Serganova, P. Mayer-Kuckuk, V. Ponomarev, R.
G. Blasberg, Bioconjug. Chem. 2004, 15, 1376. doi:10.1021/
BC0498572
[8] K. Kono, M. Liu, J. M. J. Fre´chet, Bioconjug. Chem. 1999, 10, 1115.
doi:10.1021/BC990082K
[9] Y. Y. Cheng, J. R. Wang, T. L. Roa, X. X. He, T. W. Xu, Front. Biosci.
2008, 13, 1447. doi:10.2741/2774
[10] D. Tyssen, S. A. Henderson, A. Johnson, J. Sterjovski, K. Moore, J. La,
M. Zanin, S. Sonza, P. Karellas, M. P. Giannis, G. Krippner,
S. Wesselingh, T. McCarthy, P. R. Gorry, P. A. Ramsland, R. Cone,
J. R. A. Paull, G. R. Lewis, G. Tachedjian, PLoS ONE 2010, 5, e12309.
doi:10.1371/JOURNAL.PONE.0012309
Dendrimer 1d
Dendrimer 1d (0.26 g) was obtained as an orange-coloured
solid from dihydroxyanthraquinone (16 mg, 0.07 mmol) and the
dendritic chloride 13 (0.4 g, 0.14 mmol) using the general
procedure D. Yield: 68 %; mp 162–1648C. Rf.0.16 (CHCl3/
methanol, 9 : 1). nmax (KBr)/cmꢀ1 1656 cmꢀ1. dH (300 MHz,
CDCl3) 4.95 (s, 8H), 5.01 (s, 16H), 5.03 (s, 4H), 5.10 (s, 32H),
6.51 (s, 2H), 6.56 (s, 4H), 6.59 (s, 4H), 6.62 (s, 8H), 6.66 (s, 8H),
6.70 (s, 16H), 7.22–7.27 (m, 34H), 7.35–7.37 (m, 64H), 7.46 (s,
2H), 7.53 (d, 32H, J 8.1), 7.60 (d, 32H, J 8.4), 7.98 (s, 2H), 8.10
(d, 32H, J 7.8). dC (75 MHz, CDCl3) 69.7, 69.9, 70.0, 101.7,
106.5, 109.7, 120.0, 120.3, 123.4, 125.9, 127.2, 128.8, 129.1,
135.8, 137.5, 139.5, 140.7, 160.1, 182.3. m/z (MALDI-TOF)
6058 (M þ Naþ). Anal. Calc. for C416H300N16O32: C 82.79, H
5.01, N 3.71. Found: C 82.83, H 4.99, N 3.74 %.
[11] M. Sakamoto, A. Veno, H. Mihare, Chem. Commun. 2000, 1741.
doi:10.1039/B003786I
[12] S. Ghosh, K. A. Banthia, Tetrahedron Lett. 2002, 43, 6457.
doi:10.1016/S0040-4039(02)01323-0
[13] P. Rajakumar, K. Ganesan, Synlett 2004, 2236. doi:10.1055/S-2004-
830872
[14] P. Rajakumar, K. Ganesan, S. Jayavelu, K. Murugesan, Synlett 2005,
1121. doi:10.1055/S-2005-865201
[15] P. Rajakumar, K. Ganesan, Tetrahedron Asymmetry 2005, 16, 2295.
doi:10.1016/J.TETASY.2005.06.009
[16] P. Rajakumar, N. Venkatesan, K. Sekar, S. Nagaraj, R. Rengasamy,
Eur. J. Med. Chem. 2010, 45, 1220. doi:10.1016/J.EJMECH.2009.
11.051
[17] J. C. Antilla, A. Klapars, S. L. Buchwald, J. Am. Chem. Soc. 2002, 124,
11684. doi:10.1021/JA027433H
[18] H. Fenglin, K. Ruili, H. Bao, M. Liang, Fitoterapia 2004, 75, 14.
doi:10.1016/J.FITOTE.2003.07.003
[19] Y. Li, Y. Y. Cheng, T. W. Xu, Curr. Drug Discov. Technol. 2007, 4,
Acknowledgements
The authors thank the Council of Scientific and Industrial Research (CSIR)
New Delhi for financial assistance; the Department of Science and Tech-
nology (DST) Fund for Improvement of S&T Infrasture in Higher Educa-
tional Institutions (FIST) for providing the NMR facility to the department;
Sophisticated Analytical Instrument Facility (SAIF), Central Drug Research
Institute (CDRI), Lucknow, and SAIF, Indian Institute of Technology
(IITM) Chennai, for mass spectral data; and the National Centre for Ultra-
fast Processes, University of Madras, for fluorescence studies. NV thanks
DST and CSIR, New Delhi, for fellowships.
246. doi:10.2174/157016307783220503
[20] Y. Rajeshwar, G. P. Senthil Kumar, M. Gupta, U. K. Mazumdar, Eur.
Bull. Drug Res. 2005, 13, 31.
[21] C. Y. Lee, A. Sharma, J. E. Cheong, J. L. Nelson, Bioorg. Med. Chem.
Lett. 2009, 19, 6326. doi:10.1016/J.BMCL.2009.09.088