Synthesis and antioxidant studies of novel bi-, tri-, and tetrapodal 9-aryl-1,8-dioxo-octahydroxanthenes

Article abstract of DOI:10.1016/j.tetlet.2015.01.162

Compounds bearing two, three, and four 9-aryl-1,8-dioxo-octahydroxanthenes units were synthesized by regioselective O-alkylation of monopodal xanthenes with bis-, tris-, and tetrakis(bromomethyl)benzenes as alkylating agents using K₂CO₃

Full text of DOI:10.1016/j.tetlet.2015.01.162

Tetrahedron Letters 56 (2015) 1401–1406
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthesis and antioxidant studies of novel bi-, tri-, and tetrapodal
9-aryl-1,8-dioxo-octahydroxanthenes
⇑
P. Iniyavan, S. Sarveswari, V. Vijayakumar
Centre for Organic and Medicinal Chemistry, School of Advanced Sciences, VIT University, Vellore 632 014, Tamil Nadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Compounds bearing two, three, and four 9-aryl-1,8-dioxo-octahydroxanthenes units were synthesized by
regioselective O-alkylation of monopodal xanthenes with bis-, tris-, and tetrakis(bromomethyl)benzenes
as alkylating agents using K2CO3 as base and DMF as solvent in moderate temperature. All the synthe-
sized compounds were characterized by NMR and mass spectral data and then tested for antioxidant
activity, as reflected by free radical scavenging, increased with increasing number of xanthene units.
Ó 2015 Elsevier Ltd. All rights reserved.
Received 22 December 2014
Revised 23 January 2015
Accepted 24 January 2015
Available online 31 January 2015
Keywords:
Xanthenes
Bipodal–tripodal–tetrapodal
Antioxidant
DPPH
Xanthenes are common natural products and an important
motif in a variety of biologically active and useful compounds.1
Compounds carrying the xanthene moiety exhibit promising bio-
logical activities, such as anticancer,2 analgesic,3 anti-inflamma-
tory,4 and antibacterial5 activities. In addition, xanthene
derivatives can be used as pH sensitive fluorescent materials for
the visualization of bio-molecular assemblies,6 as bactericides in
agriculture7 and in laser technologies.8 Some of the xanthene
based compounds have found applications as antagonists of
zoxalamine and in photodynamic therapy.9 In particular,
naphtha-pyranopyrimidines have been reported to be antagonists
for the neuropeptide S receptor (NPSR)10 that is a novel drug target
for the treatment of respiratory, sleep, anxiety, and addiction
disorders.11
storage systems.20 The conjugated chromophores of bis- and
tris(indolyl)methanes are used as pH indicators and calorimetric
chemosensors for transition metals.21
So far, mostly monopodal xanthenes have been studied while
reports on polypodal xanthenes are rare. According to the factors
mentioned and our continuous interest in synthesis of bi-, tri-,
and tetrapodal organic compounds,22 we report herein the first
successful synthesis of bi-, tri-, and tetrapodal 9-aryl-1,8-dioxo-
octahydroxanthenes and its antioxidant properties.
The basic building block 9-aryl-1,8-dioxo-octahydroxanthenes
5, 6, and 723 were synthesized through condensation reaction of
dimedone (4) and hydroxy benzaldehydes (1–3) using ethanol as
solvent in the presence of catalytic amount of BF3/OEt224 (Table 1)
(Scheme 1).
Organic compounds like dendrimers containing repeating
structural motifs have found application in macromolecular chem-
istry, by light harvesting,12 by photodynamic therapy,13 as dyes,14
as catalysts,15 for molecular encapsulation,16 for multivalent
diagnostics by magnetic resonance imaging17 and for blood
substitution.18 Moreover, the tripodal derivative of 1,3,5-tris(N-
alkylaminomethyl)benzene has drawn much attention as an effi-
cient building block for the synthesis of functional moieties such
as molecular receptors, since its aryl ring acts as a tiny inflexible
platform for receptor synthesis.19 Similarly the bipodal and
tetrapodal moieties of trimethyne thiacarbocyanine dyes and
fluoromethyl pyrroles (FMPs) have found applications in energy
The synthetic pathways leading to bipodal, tripodal, and tetra-
podal xanthenes using 5, 6, and 7 are outlined in Schemes 2–4
respectively. Synthesis of compounds 14–28 was achieved by reg-
ioselective O-alkylation of 9-aryl-1,8-dioxo-octahydroxanthenes 5,
6, and 7 with bis-, tris-, and tetrakis(bromomethyl)benzenes 8–13
Table 1
Synthesis of monopodal xanthenes
Product
R1
R2
R3
Time (h)
T (°C)
Yield (%)
5
6
7
–H
–OCH3
–H
–OH
–OH
–OCH3
–H
–OCH3
–OH
4
3
3
50
50
50
92
93
93
Dimedone (2.1 mmol), benzaldehydes (1 mmol), BF3/OEt2 (10 mol %) in ethanol at
50 °C.
⇑
Corresponding author. Tel.: +91 09443916746.
E-mail address: kvpsvijayakumar@gmail.com (V. Vijayakumar).
http://dx.doi.org/10.1016/j.tetlet.2015.01.162
0040-4039/Ó 2015 Elsevier Ltd. All rights reserved.

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P. Iniyavan et al. / Tetrahedron Letters 56 (2015) 1401–1406
R2
was observed that the yields were better with DMF and hence,
DMF was considered as a suitable solvent (Table 2).
R1
O
R3
O
O
R2
Bipodal derivatives of xanthenes were synthesized through the
reaction of 1 equiv of different bis(bromomethyl)benzenes 8, 9,
and 10 with 2 equiv of xanthenes 5, 6, and 7 in the presence of
K2CO3 in DMF under stirring for 48 h at 70 °C (Table 3). The 1H
NMR spectrum of bipodal derivative 1629 showed two singlets at
d 0.99 and d 1.09 for 24 methyl protons, a sharp singlet at d 4.96
for 4 O-methylene protons, a sharp singlet at d 4.69 for 2 methine
protons in addition to the aromatic protons. The 13C NMR spectrum
of compound 16 displayed three peaks at d 40.89, d 69.69, and d
196.53 for methine, O-methylene, and carbonyl carbons in addition
to olefinic and aromatic carbons. The m/z value observed at
835.4199 in the HRMS spectrum also confirmed the formation of
the bipodal derivative 16.
BF3:OEt2
Ethanol
R1
R3
O
O
5-7
4
O
1-3
Scheme 1. Synthesis of monopodal xanthenes.
as alkylating agents in the presence of K2CO3 in DMF under stirring
for 48 h at 70 °C.28
Initially, the reaction was attempted with different bases like
K2CO3, KOH, t-BuOK, and Et3N to increase the yield of the product.
The reaction was found to be good with K2CO3, a mild base which
afforded the desired product in a high yield. Different solvents such
as DMF, DMSO, THF, and acetonitrile were also examined and it
A similar synthetic strategy was adopted to synthesize the
trimers by the reaction of 1 equiv of 1,3,5-tris(bromomethyl)
benzenes (11, 12) with 3 equiv of xanthenes 5, 6, and 7 in presence
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
18
O
O
O
O
O
Br
Br
Br
Br
16
Br
Br
O
13
8
OH
10
O
O
O
O
O
O
Br
Br
Br
O
O
O
O
5
Br
14
Br
9
Br
O
O
11
Br
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
17
15
Scheme 2. Synthesis of bi-, tri-, and tetrapodal derivatives of xanthene 5.

P. Iniyavan et al. / Tetrahedron Letters 56 (2015) 1401–1406
1403
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
21
O
O
O
O
O
O
O
23
Br
Br
Br
Br
Br
O
13
10
Br
OH
O
O
O
O
O
O
O
O
O
O
Br
Br
8
Br
O
O
O
O
O
6
Br
O
19
9
Br
Br
O
O
12
O
Br
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
22
20
Scheme 3. Synthesis of bi-, tri-, and tetrapodal derivatives of xanthene 6.
of K2CO3 in DMF (Table 3). The 1H NMR spectrum of the tripodal
derivative 2230 showed two singlets at d 1.01 and d 1.10 integrating
for 36 methyl protons, a broad singlet at d 3.77 for 18 methoxy
protons, a sharp singlet at d 4.72 for 3 methine protons, a sharp
singlet at d 4.90 for 6 O-methylene protons in addition to
aromatic protons. The 13C NMR spectrum of compound 23
displayed four peaks at d 40.92, d 56.21, d 74.94, and d 196.49 for
methine, methoxy, O-methylene and carbonyl carbons in addition
to olefinic and aromatic carbons. The m/z value observed at
1393.6500 in the HR-MS spectrum also confirmed the formation
of the trimer.
Likewise the tetramers of xanthenes were synthesized from the
reaction of 1 equiv of 1,2,4,5-tetrakis(bromomethyl)benzene (13)
with 4 equiv of building blocks 5, 6, and 7 under the same reaction
conditions (Table 3). The 1H NMR spectrum of tetrapodal derivative
1831 showed two singlet peaks at d 0.99 and d 1.09 for 48 methyl
group protons, a sharp singlet at d 5.02 for eight O-methylene pro-
tons, a sharp singlet at d 4.69 for four methine protons in addition
to the aromatic protons. The 13C NMR spectrum of compound 16
displayed three peaks at d 40.87, d 67.43, and d 196.56 for methine,
O-methylene, and carbonyl carbons in addition to olefinic and aro-
matic carbons. The m/z value observed at 1631 [M+K]+ in the
MALDI-TOF mass spectrum also confirmed the formation of the
target molecule.
Antioxidant activity
Radical scavenging activity is very important due to the delete-
rious role of free radicals in foods and in biological systems. The
antioxidant activity of the synthesized compounds was investi-
gated using DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical
scavenging assay with respect to the standard BHT (butylated
hydroxy toluene) using the literature method.25 All compounds
14–28 were dissolved in DMSO with concentration of 10, 50,
100, 250, 500, and 1000
lg/ml then mixed with freshly prepared
2 ml of 0.1 mM DPPH solution and left in dark for 30 min.

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P. Iniyavan et al. / Tetrahedron Letters 56 (2015) 1401–1406
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
26
O
Br
Br
Br
O
O
28
10
Br
Br
13
Br
H
O
O
O
O
O
O
O
O
O
8
Br
Br
O
O
O
O
O
7
O
Br
24
Br
9
O
Br
12
Br
O
O
Br
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
27
O
O
25
Scheme 4. Synthesis of bi-, tri-, and tetrapodal derivatives of xanthene 7.
Table 2
Inhibitionð%Þ ¼ ½1 ꢀ ðAsample=AcontrolÞꢁ ꢂ 100
Synthesis of bipodal derivative 16 in different conditions
where Acontrol is the absorbance of the control (blank, without com-
pound) and Asample is the absorbance of the compounds. The per-
centage of inhibition is shown in Figure 1 which reveals the
radical scavenging activity of xanthenes on DPPH radicals increases
with increase in concentration. Moreover, the activity of xanthenes
gradually increases from dimers to trimers, which could be due to
the more number of xanthene units in the trimers, generally termed
as multivalent effect.26 Based on the similar trend, tetramers should
show much greater antioxidant property.
However, trimers and tetramers showed more or less the same
activity due to crowding effect which causes serious steric hin-
drance and decrease the availability of xanthene units to exhibit
antioxidant property.27
Entry
Base
Solvent
Time (h)
T (°C)
Yield (%)
1
2
4
5
6
7
8
9
K2CO3
KOH
t-BuOK
Et3N
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
DMF
DMF
DMF
DMF
DMSO
THF
acetonitrile
DMF
DMF
DMF
48
48
48
48
48
48
48
36
60
48
48
70
70
70
70
70
70
70
70
70
RT
90
81
37
12
44
67
8
19
38
81
6
10
11
12
DMF
72
1,4-Bis(bromomethyl)benzene 10 (1 mmol), xanthene 5 (2 mmol) under the above
conditions.
Among all the compounds, the tripodal derivative (22) of
xanthene 6 showed maximum activity at a concentration of
1000 lg/ml.
Subsequently, the absorbance was measured at 517 nm and the
observed values are given in Table 4. Percentage activity of the
compounds was calculated using the following equation.
In conclusion, the monopodal xanthenes served as building
blocks for the construction of novel bi-, tri-, and tetrapodal

P. Iniyavan et al. / Tetrahedron Letters 56 (2015) 1401–1406
1405
Table 3
Synthesis of xanthenes using various alkylating agents
Entry
Alkylating agent
Xanthenes
Product
Yielda (%)
1
2
3
4
5
6
7
8
1,4-Bis(bromomethyl)benzene 10
1,3-Bis(bromomethyl)benzene 9
1,2-Bis(bromomethyl)benzene 8
1,4-Bis(bromomethyl)benzene 10
1,3-Bis(bromomethyl)benzene 9
1,2-Bis(bromomethyl)benzene 8
1,4-Bis(bromomethyl)benzene 10
1,3-Bis(bromomethyl)benzene 9
1,2-Bis(bromomethyl)benzene 8
2,4,6-Tris(bromomethyl)mesitylene 11
1,3,5-Tris(bromomethyl)benzene 12
1,3,5-Tris(bromomethyl)benzene 12
1,2,4,5-Tetrakis(bromomethyl)benzene 13
1,2,4,5-Tetrakis(bromomethyl)benzene 13
1,2,4,5-Tetrakis(bromomethyl)benzene 13
5
5
5
6
6
6
7
7
7
5
6
7
5
6
7
16
15
14
21
20
19
26
25
24
17
22
27
18
23
28
81
75
77
83
85
80
81
75
74
63
71
62
58
62
56
9
10
11
12
13
14
15
a
The yields refer to the isolated pure products.
Table 4
Antioxidant activity for the compounds 14–28 by DPPH method
S. no.
Concentration
10
l
g/ml
50
l
g/ml
100
l
g/ml
250
lg/ml
500
l
g/ml
1000 lg/ml
A
I
A
I
A
I
A
I
A
I
A
I
BHT
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Control
0.212
0.848
0.847
0.829
0.81
0.801
0.830
0.821
0.801
0.792
0.792
0.856
0.830
0.82
77
8
8
0.066
0.755
0.764
0.737
0.672
0.635
0.727
0.709
0.711
0.635
0.645
0.726
0.718
0.727
0.654
0.626
93
18
17
20
27
31
21
23
23
31
30
21
22
21
29
32
0.055
0.636
0.626
0.598
0.543
0.525
0.598
0.595
0.58
0.543
0.562
0.635
0.608
0.582
0.506
0.516
94
31
32
35
41
43
35
35
37
41
39
31
34
37
45
44
0.046
0.571
0.589
0.525
0.267
0.258
0.545
0.552
0.516
0.322
0.35
0.534
0.516
0.517
0.258
0.248
95
38
36
43
71
72
41
40
44
65
62
42
44
44
72
73
0.039
0.541
0.488
0.497
0.211
0.193
0.497
0.506
0.442
0.193
0.211
0.535
0.453
0.442
0.221
0.211
96
41
47
46
77
79
46
45
52
79
77
42
51
52
76
77
0.016
0.534
0.461
0.442
0.175
0.165
0.451
0.423
0.413
0.147
0.193
0.497
0.442
0.414
0.156
0.175
98
42
50
52
81
82
51
54
55
84
79
46
52
55
83
81
10
12
13
10
11
13
14
14
7
10
11
14
15
0.791
0.783
0.9215
A—absorbance I—inhibition percentage.
Figure 1. DPPH radical scavenging activity of various concentrations of the bi-, tri-, and tetrapodal compounds (14–28) of xanthenes 5, 6, and 7.
xanthenes by conventional methodology. The antioxidant activity
of the synthesized compounds was also studied and it showed that
the efficiency is concentration dependent as well as it depends on
the size of the compounds.
Acknowledgements
Authors are thankful to the Administration, VIT University, Vel-
lore, India for providing facilities to carry research work and also

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P. Iniyavan et al. / Tetrahedron Letters 56 (2015) 1401–1406
22. (a) Rajesh, K.; Palakshi Reddy, B.; Vijayakumar, V. Can. J. Chem. 2011, 89, 1236–
1244; (b) Rajesh, K.; Palakshi Reddy, B.; Vijayakumar, V. Ultrason. Sonochem.
2012, 19, 522–531; (c) Balaji, G. L.; Rajesh, K.; Venkatesh, M.; Sarveswari, S.;
Vijayakumar, V. RSC Adv. 2014, 4, 39–46.
23. (a) Verma, G. K.; Raghuvanshi, K.; Verma, R. K.; Dwivedi, P.; Singh, M. S.
Tetrahedron 2011, 67, 3698–3704; (b) Mohammadpoor-Baltork, I.; Moghadam,
M.; Mirkhani, V.; Tangestaninejad, S.; Reza Tavakoli, H. Chin. Chem. Lett. 2011,
22, 9–12; (c) Bayat, M.; Imanieh, H.; Hossieni, S. H. Chin. J. Chem. 2009, 27,
2203–2206.
thankful to the SIF-Chemistry, VIT University and SAIF, IIT-Madras
for providing NMR and MASS spectral facilities. Author P. Iniyavan
is thankful to the VIT University for providing Research
Associateship.
Supplementary data
24. Sethukumar, A.; Vithya, V.; Udhaya Kumar, C.; Arul Prakasam, B. J. Mol. Struct.
2012, 1008, 8–16.
25. Vijesh, A. M.; Isloor, A. M.; Peethambar, S. K.; Shivananda, K. N.; Arulmoli, T.;
Isloor, N. A. Eur. J. Med. Chem. 2011, 46, 5591–5597.
26. Li, Y.; Cheng, Y. Y.; Xu, T. W. Curr. Drug Discovery Technol. 2007, 4, 246–254.
27. Rajakumar, P.; Venkatesan, N.; Sekar, K.; Nagaraj, S.; Rengasamy, R. Eur. J. Med.
Chem. 2010, 45, 1220–1224.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2015.01.
162.
References and notes
28. General procedure for synthesis of bi-, tri-, and tetrapodal xanthenes (14–28):
To a solution of 1 equiv of xanthenes 5, 6, and 7 in 5 ml of dry DMF, 2 equiv
of powdered K2CO3 was added, stirred well for 30 min at room temperature.
To that, alkylating agent (0.5 equiv in case of dimers; 0.333 equiv in case of
trimers; 0.25 equiv in case of tetramers dissolved in minimum amount of
DMF was added drop wise for 1 h with stirring at 50 °C. After the complete
addition, the reaction mixture was stirred at 70 °C for 48 h. After completion
of the reaction as indicated by TLC, the reaction mixture was poured into a
beaker containing ice cold water and stirred well. The precipitate was
collected and, if necessary, purified by column chromatography on silica gel
(60–120 mesh). (The bipodal derivatives were purified using hexane/
ethylacetate (75:25) solvent mixture whereas tripodal and tetrapodal
derivatives were purified using the chloroform/methanol (99.7:0.3) solvent
mixture as eluent).
1. (a) Li, J.; Hu, M.; Yao, S. Q. Org. Lett. 2009, 11, 3008–3011; (b) Antony, L. A. P.;
Slanina, T.; Sebej, P.; Šolomek, T.; Klan, P. Org. Lett. 2013, 15, 4552–4555.
2. Mulakayala, N.; Murthy, P. V. N. S.; Rambabu, D.; Aeluri, M.; Adepu, R.; Krishna,
G. R.; Reddy, C. M.; Prasad, K. R. S.; Chaitanya, M.; Kumar, C. S.; Basaveswara
Rao, M. V.; Pal, M. Bioorg. Med. Chem. Lett. 2012, 22, 2186–2191.
3. Hafez, H. N.; Hegab, M. I.; Ahmed-Farag, I. S.; El-Gazzar, A. B. A. Bioorg. Med.
Chem. Lett. 2008, 18, 4538–4543.
4. Poupelin, J. P.; Saint-Ruf, G.; Foussard-Blanpin, O.; Marcisse, G.; Uchida-
Earnauf, G.; Lacroix, R. Eur. J. Med. Chem. 1978, 13, 67–71.
5. Evangelinou, O.; Hatzidimitriou, A. G.; Velali, E.; Pantazaki, A. A.; Voulgarakis,
N.; Aslanidis, P. Polyhedron 2014, 72, 122–129.
6. Mungra, D. C.; Patel, M. P.; Rajani, D. P.; Patel, R. G. Eur. J. Med. Chem. 2011, 46,
4192–4200.
29. Bipodal derivative: 9,9’-(4,4’-(1,4-phenylenebis(methylene)) bis(oxy)bis(4,1-
phenylene))bis (3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-
dione) (16): White solid; mp 236–237 °C; 1H NMR (400 Hz, CDCl3) d 0.99,
1.09 (s, 24H, CH3), 2.21 (q, J = 9.2 Hz, 8H, CH2), 2.45 (s, 8H, CH2), 4.69 (s, 2H,
CH), 4.96 (s, 4H, CH2), 6.81 (d, J = 8 Hz, 4H, ArH), 7.21 (d, J = 8.0 Hz, 4H, ArH),
7.38 (m, 4H, ArH); 13C NMR (100 Hz, CDCl3) d 27.41, 29.28, 30.99, 32.23, 40.89,
50.80, 69.69, 114.36, 115.18, 115.80, 127.74, 129.37, 136.80, 136.90, 157.29,
162.11, 196.53. DEPT-135 (100 MHz, CDCl3): d 27.41 (CH3, C-11, 110), 29.27
(CH3, C-12, 120), 30.98 (CH, C-4), 40.88 (CH2, C-7, 70), 50.79 (CH2, C-9, 90), 69.69
(CH2, C-17), 114.36 (CH, C-15, 150), 127.74 (CH, C-19, 190, 20, 200), 129.37 (CH,
C-14, 140) ppm; HRMS (m/z): calcd 835.4210 (M+). Found: 835.4199.
30. Tripodal derivative: 9,9’,9’’-(4,4’,4’’-(benzene-1,3,5-triyltris(methylene))tris(oxy)
tris(3,5-dimethoxybenzene-4,1-diyl))tris(3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-
1H-xanthene-1,8(2H)-dione) (22): White solid; mp 140–142 °C; 1H NMR (400 Hz,
CDCl3) d1.01, 1.10 (s, 36H, CH3), 2.22 (s, 12H, CH2), 2.46 (s, 12H, CH2), 3.77(s, 18H,
7. Hideo, T.; Tokkyo Koho, J. Chem Abstr. 1981, 95, 80922b JP 56005480.
8. Naya, A.; Ishikawa, M.; Matsuda, K.; Ohwaki, K.; Saeki, T.; Noguchi, K.; Ohtake,
N. Bioorg. Med. Chem. 2003, 11, 875–884.
9. (a) Ion, R. M. Prog. Catal. 1997, 2, 55–76; (b) Ion, R. M.; Planner, A.;
Wiktorowicz, K.; Frackowiak, M. D. Acta Biochim. Polon. 1998, 45, 833–845.
10. McCoy, J. G.; Marugan, J. J.; Liu, K.; Zheng, W.; Southall, N.; Huang, W.; Heilig,
M.; Austin, C. P. ACS Chem. Neurosci. 2010, 1, 559–574.
11. Pañeda, C.; Huitron-Resendiz, S.; Frago, L. M.; Chowen, J. A.; Picetti, R.; de
Lecea, L.; Roberts, A. J. J. Neurosci. 2009, 29, 4155–4161.
12. (a) Rajakumar, P.; Anandhan, R. Eur. J. Med. Chem. 2011, 46, 4687–4695; (b) Lo,
S. C.; Burn, P. L. Chem. Rev. 2007, 107, 1097–1116; (c) Adronov, A.; Fréchet, J. M.
J. Chem. Commun. 2000, 1701–1710.
13. (a) Nishiyama, N.; Jang, W. D.; Kataoka, K. New J. Chem. 2007, 31, 1074–1082;
(b) Nishiyama, N.; Stapert, H. R.; Zhang, G. D.; Takasu, D.; Jiang, D. L.; Nagano,
T.; Aida, T.; Kataoka, K. Bioconjugate chem. 2002, 14, 58–66.
14. Zhu, S.; Zhang, J.; Vegesna, G. K.; Pandey, R.; Luo, F. T.; Green, S. A.; Liu, H. Chem.
Commun. 2011, 3508–3510
15. Feng, L.; Maass, J. S.; Luck, R. L. Inorg. Chim. Acta 2011, 373, 85–92.
16. Rajakumar, P.; Satheeshkumar, C.; Ravivarma, M.; Ganesan, S.; Maruthamuthu,
P. J. Mater. Chem. A 2013, 1, 13941–13948.
OCH3), 4.72 (s, 3H, CH), 4.90 (s, 6H, CH2), 6.50 (s, 6H, ArH), 7.53 (s, 3H, ArH); 13
C
NMR (100 Hz, CDCl3) d 27.20, 29.38, 30.95, 31.63, 32.21, 40.92, 50.75, 56.21,
74.94, 105.95, 115.66, 127.17, 136.18, 137.91, 139.62, 153.14, 162.35, 196.49.
HRMS (m/z): calcd 1393.6543 (M+). Found: 1393.6500.
31. Tetrapodal
derivative:
9,9’,9’’,9’’’-(4,4’,4’’,4’’’-(benzene-1,2,4,5-tetrayltetrakis
(methylene))tetrakis(oxy)tetrakis(benzene-4,1-diyl))tetrakis(3,3,6,6-tetramethyl-
3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione) (18): White solid; mp 137–
139 °C; 1H NMR (400 Hz, CDCl3) d 0.99, 1.09 (s, 48H, CH3), 2.19 (s, 16H, CH2),
2.45 (s, 16H, CH2), 4.69 (s, 4H, CH), 5.02 (s, 8H, CH2), 6.79 (d, J = 6 Hz, 8H, ArH),
7.18 (d, J = 4.4 Hz, 8H, ArH), 7.58 (s, 2H, ArH); 13C NMR (100 Hz, CDCl3) d 27.51,
29.22, 30.92, 32.23, 40.87, 50.79, 67.43, 114.42, 115.79, 129.36, 135.22, 136.89,
157.10, 162.13, 196.56. MALDI-TOF-MS (m/z): calcd 1631.9552 (M+K). Found:
1631.
17. Villaraza, A. J. L.; Bumb, A.; Brechbiel, M. W. Chem. Rev. 2010, 110, 2921–2959.
18. Tappenden, J. JR Army Med. Corps. 2007, 153, 3–9.
19. (a) Hennrich, G.; Anslyn, E. V. Chem. Eur. J. 2002, 8, 2219–2224; (b) Ruiz, H. L.;
Hernandez, M. C.; Lima, S. R.; Hopflz, H. J. Mex. Chem. Soc. 2011, 55, 168–175.
20. (a) Avakyan, V. G.; Shapiro, B. I.; Alfimov, M. V. Dyes Pigments 2014, 109, 21–33;
(b) Nikoofard, H.; Sabzyan, H. J. Fluorine Chem. 2007, 128, 668–673.
21. Ghorbani-Vaghei, R.; Veisi, H.; Keypour, H.; Dehghani-Firouzabadi, A. A. Mol.
Divers. 2009, 14, 87–96.