Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for photodynamic therapy application

Article abstract of DOI:10.1016/j.tet.2016.12.037

In the present work, we describe a successful strategy centered on the use of click chemistry to synthesize mono-, di- and triporphyrin building blocks named [ZnTPP]₁, [ZnTPP]₂and [ZnTPP]₃. The number of photosensitizers (

Full text of DOI:10.1016/j.tet.2016.12.037

Tetrahedron xxx (2016) 1e10
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Synthesis of mono-, di- and triporphyrin building blocks by click
chemistry for photodynamic therapy application
, b,
Amirah Mohd Gazzali a c, Ludovic Colombeau b, Philippe Arnoux b, Habibah A. Wahab c,
b
a
a, *
ꢀ
ꢀ
Celine Frochot , Regis Vanderesse , Samir Acherar
a
ꢀ
ꢀ
Laboratoire de Chimie Physique Macromoleculaire, Universite de Lorraine-CNRS, UMR 7375, 1 Rue Grandville, BP 20451, 54001, Nancy Cedex, France
b
ꢀ
ꢀ
ꢀ ꢀ
ꢀ
Laboratoire Reactions et Genie des Procedes, Universite de Lorraine-CNRS, UMR 7274, 1 Rue Grandville, BP 20451, 54001, Nancy Cedex, France
c School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia
a r t i c l e i n f o
a b s t r a c t
Article history:
In the present work, we describe a successful strategy centered on the use of click chemistry to syn-
thesize mono-, di- and triporphyrin building blocks named [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3. The number
of photosensitizers (ZnTPP unit) coupled to the building blocks does not seem to dramatically modify the
photophysical properties of the photosensitizer in terms of fluorescence and singlet oxygen formation,
quantum yields and lifetime. These building blocks, obtained in high yield, could be combined with a
targeting agent (vector) to create new photosensitizer-vector conjugates to investigate the optimum ratio
of photosensitizer needed for maximum photodynamic therapy efficiency.
Received 22 September 2016
Received in revised form
15 December 2016
Accepted 17 December 2016
Available online xxx
Keywords:
Photosensitizer
Porphyrin
© 2016 Elsevier Ltd. All rights reserved.
Click chemistry
Microwaves
Photodynamic therapy
1. Introduction
present several drawbacks such as poor light absorption in the red,
cutaneous photosensitivity and lack of tumor specificity. To over-
Photodynamic therapy (PDT) is a promising treatment involving
the concomitant action of: 1) a photoactivatable molecule, the
photosensitizer (PS), 2) light of a suitable wavelength, and 3) oxy-
gen present naturally in the biological medium. After photosensi-
tizer excitation by light, energy transfer to the oxygen allows the
generation of reactive oxygen species (ROS), and particularly
reactive singlet oxygen, which leads to cell death.1 This technique
has proved to be highly effective for the treatment of some types of
diseases in various therapeutic fields such as oncology,2 vascular
cardiology,3 dermatology,4 gynecology5,6 or malaria.7
come these disadvantages, second and third generations of pho-
tosensitizers were developed, for example such as in oncology, a
new porphyrin (Visudyne®), chlorins (Foscan®, Talaporfin® or
Photochlor®) and phthalocyanine (Photosens®).10
One of the proposed strategies for increasing the photodynamic
efficiency of photosensitizers is to combine them with a vector
capable of selectively binding to specific receptors overexpressed
on tumor cell membranes. The various vectors which have been
used by members of our team are, among others, peptides and folic
acid (FA).11 FA is specific for the folate receptor alpha (FR
a), which is
Among the various potential photosensitizers that are available,
porphyrins have been extensively studied in the field of photody-
namic therapy (PDT).8 Porphyrinic molecules have an aromatic
planar architecture capable of developing attractive photophysical
properties for PDT applications (Fig. 1), and several exist in nature.9
Photofrin®, a mixture of porphyrin oligomers, is the most popular
one used clinically in PDT and corresponds to the first generation
photosensitizers. However, first generation photosensitizers
overexpressed in many human cancers (ovary, brain, kidney, breast,
myeloid cells, and lung) while peptides (ATWLPPR and DKPPR)12,13
were used for targeting vascular endothelial growth factor (VEGF)
receptor or its co-receptor neuropilin-1 (NRP-1), both over-
expressed by tumor cells. These new PS-vector conjugates devel-
oped by our team are depicted in Fig. 2.
In the literature, several strategies to synthesize porphyrin
conjugates are described14 but click chemistry appears to be the
most effective method and its use in various fields such as
biochemistry, and medicinal or surface chemistry, continues to
increase year after year. “Click Chemistry” was an idiom introduced
in 2001 by Sharpless to cover all organic reactions that could be
* Corresponding author.
E-mail address: samir.acherar@univ-lorraine.fr (S. Acherar).
http://dx.doi.org/10.1016/j.tet.2016.12.037
0040-4020/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Gazzali AM, et al., Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for
photodynamic therapy application, Tetrahedron (2016), http://dx.doi.org/10.1016/j.tet.2016.12.037

2
A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
diverse opportunities to combine two building blocks that are
difficult to connect by conventional coupling techniques. Recently,
the use of a microwave was reported, opening wider applications in
the field of click chemistry. In 2015 we published a recapitulative
review about the synthesis of porphyrin, chlorine or phthalocya-
nine conjugates by azide-alkyne click chemistry, and their related
applications.19
The mild condition of the CuAAC reaction is compatible with the
peptidic chemistry and offers the possibility to develop new
peptide-based drugs, which could be potentially useful therapeu-
tically.20 Furthermore, the 1,2,3-triazole ring is highly stable against
hydrolysis and could ensure delivery of the conjugated drugs to
their targeted receptors.21
Fig. 1. Typical structure of a porphyrin which can be functionalized at their
meso-positions.
b- and
The main goal of this work is to establish a strategy centered on
the use of click chemistry to synthesize mono-, di- and tri-
porphyrin building blocks abbreviated to [ZnTPP]1, [ZnTPP]2 and
[ZnTPP]3 respectively, for easier reading. These building blocks
could be combined with a targeting agent (vector) to create new
PS-vector conjugates to investigate the optimum ratio of PS needed
for maximum PDT efficiency.
2. Results and discussion
2.1. Synthesis of clickable porphyrin scaffold bearing a propargyl
group
Our approach was first based on the synthesis of a structurally
related derivative of zinc tetraphenylporphyrin (ZnTPP) 2 bearing a
propargyl group for linkage upon the CuAAC reaction (Scheme 1),
using a protocol similar to that which we reported previously with
zinc tetraphenylchlorin (ZnTPC).22 The metallation of TPP is
essential, to avoid copper metallation of the porphyrin ring during
the subsequent CuAAC reaction.
5-(4-carbonylphenyl)-10,15,20-triphenyl-21H,23H-porphyrin
(TPP-COOH) was used as starting material and prepared according
to the protocol previously described by our team.23 The TPP-COOH
was converted into the propargyl derivative (1) in a one-pot two-
steps reaction by a classical peptide method (Scheme 1). The first
step is the in situ activation of the carboxyl group of TPP-COOH by
Fig. 2. New PS-vector conjugates developed by our team for PDT applications.
dicyclohexylcarbodiimide (DCC,
ysuccinimide (NHS, 2 equivalents) followed by a coupling reaction
with an excess of propargylamine (10 equivalents). Several
1 equivalent) and N-hydrox-
described as modular, wide in scope, high yielding, easy to perform
and stereospecific. The reactions must use harmless or easily
disposed solvents and have to generate only by-products that can
be removed by simple purification techniques.15
Among the reactions that are considered as “Click Chemistry”,
the most commonly used is the copper-catalyzed azide-alkyne
cycloaddition (CuAAC) reaction. The azide-alkyne cycloaddition
was first studied by Huisgen et al. in 1968 and the authors' findings
showed the slow formation of a mixture of both 1,4- and 1,5-
disubstituted 1,2,3-triazole regioisomers (Fig. 3).16 In 2002, Sharp-
less and Meldal simultaneously found that the use of the Cu(I)
catalyst helps to increase the reaction rate and to obtain only the
1,4-disubstituted regioisomer even at sub-ambient-temperature
(Fig. 3).17,18
The introduction of the CuAAC reaction has opened up new and
Fig. 3. Huisgen's reaction.
Scheme 1. Synthesis of alkyne-functionalized ZnTPP 2.
Please cite this article in press as: Gazzali AM, et al., Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for
photodynamic therapy application, Tetrahedron (2016), http://dx.doi.org/10.1016/j.tet.2016.12.037

A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
3
conditions (temperature and reaction time) were tested and those
used are summarized in Table 1. The best yield (96%, trial A6) was
obtained after one day at 40 ꢀC for both activating and coupling
steps. Finally, the porphyrin ring of molecule 1 was metallated with
Zn(OAc)2 to provide the alkyne-functionalized ZnTPP 2 in a quan-
titative yield.
2.2. Synthesis of clickable aromatic scaffolds bearing one, two or
three azide groups
To synthesize [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building blocks
by the CuAAC reaction, we created platforms bearing one, two or
three azide groups. To achieve this goal, we chose to use
commercially available hydroxy and polyhydroxy derivatives of
methyl benzoate (Fig. 4).
The methyl benzoate derivatives substituted by 1e3 hydroxy
groups (Fig. 4) were functionalized through their hydroxy groups
with an azide functional group 4 derived from diethylene glycol
(Scheme 2). We decided to use diethylene glycol as the spacer unit
to improve the hydrophilicity of our clickable aromatic scaffolds 6,
8 and 10. 2-(2-azidoethoxy)ethyl methanesulfonate 4 was synthe-
sized in two steps from diethylene glycol with 63% overall yield
(Scheme 2). This two-steps procedure involved mesylation of both
hydroxy groups using mesyl chloride (4 equivalents) to provide
dimesylate intermediate 3, followed by nucleophilic substitution of
one mesylate group of 3 with a sodium azide (1 equivalent). The last
step has already been described by Sirion et al.24 under similar
conditions but we were able to significantly improve the yield (77%
instead of 40%).
Fig. 4. Chemical structures of hydroxy and polyhydroxy derivatives of methyl benzoate
used in this work.
The resulting azide- and mesylate-functionalized diethylene
glycol 4 were used to elaborate clickable aromatic scaffolds 6, 8 and
10 bearing one, two or three azide groups and the same two-steps
approach was adopted for their synthesis (Scheme 2). To achieve
this goal, we decided to use experimental conditions similar to
those previously employed by Chen et al.25 for the synthesis of
products 9 and 10. The first step of this approach is based on the
nucleophilic substitution of the mesylate group of product 4 by the
hydroxy groups present in the methyl benzoate derivatives repre-
sented in Fig. 4, to provide the corresponding mono-, di- and tri-
azide derivatives of methyl benzoates 5, 7 and 9 in high yields (Step
A in Scheme 2). Finally, the saponification of the ester group of 5, 7
and 9 led to clickable aromatic scaffolds 6, 8 and 10 respectively
with yields of up to 90% (Step B in Scheme 2), opening the way for
the synthesis of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building blocks by
click chemistry (Fig. 5).
Scheme 2. Synthesis of clickable aromatic scaffolds 6, 8 and 10.
2.3. Synthesis of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building blocks by
click chemistry
alkyne-functionalized ZnTPP 2 to the three azide-functionalized
aromatic scaffolds 6, 8 and 10, through click chemistry. These
various conjugations led to the elaboration of the desired [ZnTPP]1,
The last part of this article is dedicated to the conjugation of the
Table 1
Several trials for the one-pot preparation of alkyne-functionalized TPP 1 via Scheme 1.
Trial
Step 1 conditions
Temperature (ꢀC)
Step 2 conditions
Temperature (ꢀC)
Yield (%)a
Reaction time (h)
Reaction time (h)
A1
A2
A3
A4
A5
A6
A7
rtb
rtb
rtb
rtb
40
40
40
4
rtb
rtb
40
40
40
40
40
24
24
24
24
24
24
2.5
58
67
68
67
69
96
66
24
24
4
4
24
0.5
a
Yields calculated after purification by flash chromatography.
rt ¼ room temperature.
b
Please cite this article in press as: Gazzali AM, et al., Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for
photodynamic therapy application, Tetrahedron (2016), http://dx.doi.org/10.1016/j.tet.2016.12.037

4
A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
N
N
Zn
N
O
OH
N
Zn
N
N
N
N
O
O
O
NH
NH
N
N
O
N
N
N
N
N
O
O
O
N
O
O
O
O
N
HO
O
HO
O
N
N
N
N
O
N
[ZnTPP]2
O
N
Zn
O
HN
O
N
NH
O
N
N
N
[ZnTPP]3
N
N
N
N
N
N
NH
NH
Zn
O
O
N
N
Zn
N
N
N
N
N
Zn
N
N
[ZnTPP]1
Fig. 5. Chemical structures of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building blocks.
[ZnTPP]2 and [ZnTPP]3 building blocks represented in Fig. 5.
In the first phase, we investigated the synthesis of the [ZnTPP]1
building block by appending the alkyne-clickable porphyrin 2 (1
equivalent) onto the monoazide-functionalized aromatic scaffold 6
(1 equivalent) through the CuAAC reaction. The active Cu(I) catalyst,
needed to drive the reaction, is generated from CuSO4.5H2O (0.1
equivalent) and sodium ascorbate (0.5 equivalent). With the aim of
obtaining the best conditions for this reaction, several trials were
conducted by changing 5 parameters i.e. solvent (DMF or THF/H2O),
method (magnetic stirring or microwave), temperature (rt, 50 ꢀC or
80 ꢀC), time of reaction and under nitrogen or not. The results of
these trials are summarized in Table 2.
An examination of the results shown in Table 2 demonstrated
that the reaction yield is better with the microwave technique than
with magnetic stirring, giving higher yields in a shorter time
(compare B3/B7 or B4/B8 trials), in THF/H2O than in DMF (compare
B4/B12 or B6/B14 trials), at 80 ꢀC than 50 ꢀC (compare B10/B11 and
B5/B6 trials) and under nitrogen (compare B5/B7 or B6/B8 trials).
Table 2
Several trials for the synthesis of [ZnTPP]1.
CuSO4.5H2O (0.1 equiv.)
2
+
6
[ZnTPP]1
Na ascorbate (0.5 equiv.)
(1 equiv.)
(1 equiv.)
Trial
Solvent
Method
Temperature (ꢀC)
Reaction time
Nitrogen
Yield (%)a
B1
B2
B3
B4
B5
B6
B7
B8
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
THF/H2O (4:1)
THF/H2O (4:1)
THF/H2O (4:1)
THF/H2O (4:1)
THF/H2O (4:1)
THF/H2O (4:1)
THF/H2O (4:1)
THF/H2O (4:1)
Magnetic stirring
Magnetic stirring
Magnetic stirring
Magnetic stirring
Microwave
Microwave
Microwave
Microwave
Magnetic stirring
Magnetic stirring
Magnetic stirring
Magnetic stirring
Microwave
Microwave
Microwave
Microwave
rtb
rtb
50
80
50
80
50
80
rtb
rtb
80
80
80
80
80
80
Overnight
Overnight
Overnight
Overnight
No
7
Yes
Yes
Yes
No
11
75
75
43
60
86
89
10
20
55
96
88
97
92
97
2 roundsc of 45 min
2 roundsc of 45 min
2 roundsc of 45 min
2 roundsc of 45 min
Overnight
No
Yes
Yes
No
Yes
Yes
Yes
No
No
No
No
B9
B10
B11
B12
B13
B14
B15
B16
Overnight
3 h
Overnight
1 round of 45 min
2 roundsc of 45 min
1 round of 90 min
2 roundsc of 90 min
a
Yields calculated after purification by flash chromatography.
rt ¼ room temperature.
b
c
CuSO4.5H2O (0.1 equiv.) and Na ascorbate (0.5 equiv.) were added again at the end of the first round microwave.
Please cite this article in press as: Gazzali AM, et al., Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for
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A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
5
Moreover, the addition of a second dose of CuSO4.5H2O and sodium
ascorbate contributes positively to increase the reaction yield
(compare B13/B14 or B15/B16 trials). In summary, the [ZnTPP]1
building block is provided at a very high yield (97%, trials B14 and
B16).
reaction yield. Trial B18 allowed us to obtain [ZnTPP]3 but at a lower
yield (18%) than in trial B17, reflecting the importance of microwave
initiation on reaction yield. In short, despite the clear negative
impact of the steric hindrance of scaffold 10 in the triple CuAAC
reaction (compare trials B14/B17), [ZnTPP]3 was obtained at a good
yield (77%, trial B17).
Encouraged by these results, we decided to undertake the
preparation of the [ZnTPP]3 building block directly, to examine the
steric effects exerted by the triazide-functionalized aromatic scaf-
fold 10 in the triple CuAAC reaction. For the synthesis of the
[ZnTPP]3 building block by the reaction of scaffold 10 with three
equivalents of molecule 2, we chose to use the best result for each
of the following conditions: 1) DMF with magnetic stirring (trial
B4), 2) DMF with microwave (trial B8), 3) THF/H2O with magnetic
stirring (trial B12) and, 4) THF/H2O with microwave (trial B14). For
the CuAAC reaction, the amount of the catalyst (CuSO4.5H2O and
sodium ascorbate) is tripled. The results are described in Table 3.
As can be seen from Table 3, none of the four attempts (B4, B8,
B12 and B14) were successful. [ZnTPP]3 is only present in trace
amounts and it is impossible to detect it by NMR. However, a weak
spot of [ZnTPP]3 was observed on a TLC plate (CH2Cl2/MeOH, 95/5,
Rf ¼ 0.21) with a slightly better intensity in the case of the B14 trial.
Based on these findings, the result of the B14 trial was placed under
a nitrogen atmosphere with magnetic stirring at room temperature
for 5 days (named trial B17) and this gave a 77% yield of [ZnTPP]3.
Finally, we carried out a last triple CuAAC reaction (named trial B18)
under nitrogen, in THF/H2O, at room temperature, with magnetic
stirring, for 5 days to evaluate whether microwave initiation in trial
B17, due to the B14 trial conditions, plays a significant role in the
Concerning the synthesis of the [ZnTPP]2 building block, we
used the same four conditions (trials B4, B8, B12 and B14 of Table 1)
as for [ZnTPP]3 synthesis. The formation of [ZnTPP]2 requires a
double CuAAC reaction between the diazide-functionalized aro-
matic scaffold 8 and two equivalents of 2, and this time, by doubling
the amount of the catalyst (CuSO4.5H2O and sodium ascorbate)
compared to the [ZnTPP]1 synthesis. The results illustrated in
Table 4 indicate that the double CuAAC reaction does not occur in
THF/H2O, but in DMF under magnetic stirring (58%, trial B4) and
microwave (38%, trial B8). To check whether the negative impact of
the steric hindrance of 8 is still present, as previously observed for
[ZnTPP]3 synthesis, the results of the trials B4 and B8 were placed
separately under magnetic stirring at room temperature until
completion (3 days) under a nitrogen atmosphere (named trials
B19 and B20 respectively). These conditions enabled us to improve
the reaction yield, to reach a maximum of 93% (trial B19).
The successful synthesis of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3
building blocks through the CuAAC reaction paves the way for the
development of new PS-vector conjugates. These new conjugates
may be synthesized via a peptide coupling reaction between the
carboxylic acid function of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building
blocks and a targeting agent (vector) such as folic acid or ATLWLPR
Table 3
Several trials for the synthesis of [ZnTPP]3.
CuSO4.5H2O (0.3 equiv.)
2
+
10
(1 equiv.)
[ZnTPP]3
Na ascorbate (1.5 equiv.)
(3 equiv.)
Trial
Solvent
Method
Temperature (ꢀC)
Reaction time
Nitrogen
Yield (%)a
B4
B8
B12
B14
B17
B18
DMF
DMF
THF/H2O (4:1)
THF/H2O (4:1)
Magnetic stirring
Microwave
Magnetic stirring
Microwave
80
80
80
80
Overnight
Yes
Yes
Yes
No
ndc
ndc
ndc
ndc
77
2 roundsb of 45 min
Overnight
2 roundsb of 45 min
B14 followed by magnetic stirring at rtd during 5 days under nitrogen atmosphere
THF/H2O (4:1)
Magnetic stirring
rtd
5 days
Yes
18
a
Yields calculated after purification by flash chromatography.
CuSO4.5H2O (0.3 equiv.) and Na ascorbate (1.5 equiv.) were added again at the end of the first round microwave.
b
c
nd ¼ not determined.
d
rt ¼ room temperature.
Table 4
Several trials for the synthesis of [ZnTPP]2.
CuSO4.5H2O (0.2 equiv.)
Na ascorbate (1 equiv.)
2
+
8
[ZnTPP]2
(2 equiv.)
(1 equiv.)
Trial
Solvent
Method
Temperature (ꢀC)
Reaction time
Nitrogen
Yield (%)a
B4
B8
B12
B14
B19
B20
DMF
DMF
THF/H2O (4:1)
THF/H2O (4:1)
Magnetic stirring
Microwave
Magnetic stirring
Microwave
80
80
80
80
Overnight
Yes
Yes
Yes
No
59
2 roundsb of 45 min
Overnight
38
ndc
ndc
93
2 roundsb of 45 min
B4 followed by magnetic stirring at rtd during 3 days under nitrogen atmosphere
B8 followed by magnetic stirring at rtd during 3 days under nitrogen atmosphere
81
a
Yields calculated after purification by flash chromatography.
CuSO4.5H2O (0.2 equiv.) and Na ascorbate (1 equiv.) were added again at the end of the first round microwave.
b
c
nd ¼ not determined.
d
rt ¼ room temperature.
Please cite this article in press as: Gazzali AM, et al., Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for
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A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
[ZnTPP]1
N
N
N
N
HN
O
N
O
Zn
N
O
N
O
OH
1.1. EDC.HCl, NHS, CH2Cl2/MeOH (4:1)
Microwave, 300 W, 40°C, 90 minutes
72%
N3
H N
1.2.
2
Microwave, 300 W, 60°C, 120 minutes
N
N
N
N
HN
O
N3
N
O
Zn
N
O
N
O
HN
[ZnTPP]1-N3
Scheme 3. Azide-functionalization of [ZnTPP]1.
and DKPPR peptides (Fig. 2) to investigate the optimum ratio of PS
needed for maximum PDT efficiency. However, to take the best
advantage of the click chemistry, it would be interesting to develop
new PS-vector conjugates through the CuAAC reaction. To reach
that goal, we have shown that it is possible to functionalize the
carboxylic acid moiety of our building blocks (only [ZnTPP]1 is used
as an example) with commercially available 3-azido-1-
propanamine. The azide-functionalization of [ZnTPP]1 provides
the corresponding [ZnTPP]1-N3 in a 72% yield (Scheme 3).
3. Conclusion
Our goal was to synthesize three building blocks named
[ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 having one, two or three PS units in
their structures, respectively. Starting from the use of click chem-
istry (and more specifically the CuAAC reaction), we described the
synthesis of these three building blocks with high yields. The
presence of one or more PS units did not seem to result in profound
changes in the photophysical properties of the PS (i.e. fluorescence
and singlet oxygen formation, quantum yields and lifetime). These
photophysical results pave the way for the potential conjugation of
[ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building blocks with a targeting
agent (vector) for the elaboration of new PS-vector conjugates to
investigate the optimum ratio of PS needed for maximum PDT
efficiency.
2.4. Photophysical properties of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3
building blocks
Photophysical properties of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3
building blocks are shown in Fig. 6 and summarized in Table 5.
Typical porphyrin absorption spectra were recorded and exhibited
a Soret band at 414 nm and four Q-bands. The fluorescence spec-
trum is typical of a porphyrin with two maxima at around 650 nm
and 720 nm. As we already showed in a previous study,22 the
addition of Zn induced a shift of 1) the Soret band from 414 nm to
421 nm and 2) the maximum of fluorescence from 650 nm to
610 nm for the first and 720 nme660 nm for the second band. It
also induced a decrease of the fluorescence lifetime from 10.0 ns to
2.1 ns. Surprisingly, the fluorescence quantum yield did not
decrease as has often been described in the literature.22,26 DeRosa
et al. reported that the introduction of Zn into TPP increased the
singlet oxygen quantum yield in benzene from 0.63 to 0.83.27 In our
case, the introduction of Zn into TPP-propargyl increases the singlet
oxygen quantum yield in ethanol from 0.49 to 0.72.
4. Experimental
4.1. General
Unless other stated, all chemicals were purchased as the highest
purity commercially available and were used without further pu-
rifications. All reactions involving porphyrin compounds were
performed in the dark. All microwave reactions were conducted in
oven-dried glass tube using CEM Discover microwave synthesizer
(North Carolina, USA). Reactions were monitored by thin-layer
chromatography (TLC) using aluminium-backed silica gel plates
(Macharey-Nagel ALUGRAM® SIL > G/UV254). TLC spots were
viewed under ultraviolet light and by heating the plate after
treatment with a staining solution of phosphomolybdic acid.
Product purifications were performing using Silica Gel 60
(230e400 mesh) for column chromatography and Geduran 60 H
Silica Gel (63e200 mesh) for flash column chromatography. 1H
NMR spectra were recorded on a Brucker Advance spectropho-
tometer operating at 300 MHz. The spectra were recorded in CDCl3
The addition of a Zn-porphyrin to the structure does not seem to
modify drastically the photophysical properties of the photosensi-
tizer in terms of fluorescence and singlet oxygen formation quan-
tum yields or lifetime. However, [ZnTPP]3 presents two different
fluorescence lifetimes. This might be due to a partial lost of Zn.
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A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
7
Fig. 6. Photophysical properties of TPP-COOH, [ZnTPP]1, [ZnTPP]2, [ZnTPP]3 and [ZnTPP]1-N3. (a) Absorption spectra at a single concentration of DMSO (1 mg mLꢁ1) and (b)
fluorescence emission spectra at a single concentration of EtOH (equal Soret bands at 0.2 0.05 by dilution). (c) Fluorescence decay, (d) singlet oxygen emission spectra and (e)
singlet oxygen decay after excitation (lexc. ¼ 414 nm and 421 nm) at a constant EtOH concentration (equal Soret bands at 0.2 0.05 by dilution).
and DMSO-d6 solvents at room temperature (T ¼ 298 K) using TMS
¼ 0 ppm) or DMSO residual peak ( ¼ 2.5 ppm) as internal ref-
erences respectively. Chemical shifts ( ) are given in parts per
million (ppm), and coupling constants (J) are given in hertz (Hz).
Multiplicities are reported as follow: s ¼ singlet, d ¼ doublet,
t ¼ triplet, q ¼ quadruplet, m ¼ multiplet, br ¼ broad and
Ar. ¼ aromatic. Electron spray ionization mass spectra (ESI-MS)
were recorded on a Brucker MicroTof-Q HR spectrometer in the
France) double beam UVevisible spectrophotometer. Fluorescence
spectra were recorded on a Fluorolog-3 spectrofluorimeter FL3-222
(Horiba Jobin Yvon, Longjumeau, France) with a thermostated cell
compartment (25 ꢀC) using a 450 W Xenon lamp. Fluorescence
quantum yield (ff) were determined using tetraphenyl porphyrin
(TPP) solution in toluene as fluorescence standard (ff ¼ 0.11).28
Singlet oxygen quantum yield (fD) were determined by direct
measurement of the infrared luminescence using Rose Bengal in
EtOH as a reference (fD ¼ 0.68).29 The absorbance value at the
excitation wavelength of the reference and the sample solutions
were set around 0.2.
(d
d
d
ꢀ
ꢀ
“Service commun de Spectrometrie de Masse”, Faculte des Sciences
ꢁ
et Technologies (Vandœuvre-les-Nancy, France). Absorption spectra
were recorded on a Perkin-Elmer Lambda EZ210 (Courtaboeuf,
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8
A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
Table 5
Photophysical data for the porphyrin derivatives.
d
f
Compound
Absorption lmaxa (nm) (ε)b - Soret band
ffc
fD
tfe
tD
TPP-COOH
414 (166993)
414 (126289)
421 (290200)
421 (211587)
421 (226551)
421 (329375)
421 (201286)
0.08
0.09
0.07
0.08
0.07
0.06
0.08
0.60
0.49
0.72
0.54
0.43
0.46
0.65
10.1
10.0
2.1
1.9
1.9
16
16
15
18
16
16
17
TPP-propargyl 1
ZnTPP-propargyl 2
[ZnTPP]1
[ZnTPP]2
[ZnTPP]3
2.2e10.6
2.0
[ZnTPP]1-N3
a
Maximum absorption or fluorescence in EtOH.
ε in L/mol.cm.
Fluorescence quantum yield determined in EtOH, relative to fluorescence of TPP as standard (lexc. ¼ 414 nm and 421 nm).
Singlet oxygen production quantum yield in EtOH, relative to the emission of Rose Bengal (lexc. ¼ 414 nm and 421 nm).
Fluorescence lifetime (ns).
b
c
d
e
f
Singlet oxygen lifetime (ms).
4.2. Synthesis of clickable porphyrin scaffold bearing a propargyl
126.5 (6 CH Ar), 127.5 (3 CH Ar), 131.4 (C Ar), 132.0 (2 CH,
b
-posi-
group (2)
tion), 132.1 (4 CH, b-position), 132.3 (2 CH, b-position), 134.4 (6 CH
Ar), 134.5 (2 CH Ar), 142.8 (4 C Ar), 149.6 (2 C), 150.1 (2 C), 150.2
4.2.1. 5-(4-propargylamidocarboxyphenyl)-10,15,20-triphenyl-21H,
23H-porphyrin (1)
(2 C), 150.3 (2 C), 165.6 (C]O); HRMS (ESI) calculated for
C
48H31N5OZn [MþH]þ m/z 758.1898, found 758.3737.
In the absence of light and under N2, dicyclohexylcarbodiimide
(DCC, 31 mg, 0.15 mmol, 1.0 equiv) and N-hydroxysuccinimide
(NHS, 35 mg, 0.30 mmol, 2.0 equiv) were added successively to a
solution of TPP-COOH (100 mg, 0.15 mmol, 1.0 equiv) in CH2Cl2
(20 mL). The mixture was stirred at room temperature during a
specified period of time (see Table 1) to afford the succinimide
4.3. Synthesis of azide-terminated diethylene glycol linker (4)
4.3.1. 2-(2-methylsulfonyloxyethoxy)ethyl methanesulfonate (3)
To a solution of diethylene glycol (10.6 g, 100 mmol, 1.0 equiv) in
CH2Cl2 (200 mL) at ꢁ10 ꢀC was added Et3N (22.3 g, 220 mmol, 2.2
equiv) and the mixture was stirred during 1 h. Methanesulfonyl
chloride (34.3 g, 300 mmol, 3.0 equiv) was then added dropwise
over a period of 0.5 h and the resulting mixture was stirred for 24 h
at room temperature under nitrogen atmosphere. The reaction
progress was monitored by TLC and after complete disappearance
of starting material, the reaction mixture was concentrated under
reduced pressure and compound 3 was recrystallized in hot MeOH
and white crystals were obtained with a 82% yield (21.5 g,
82 mmol). TLC (CH2Cl2/MeOH, 95/5): Rf ¼ 0.67; 1H NMR (300 MHz,
intermediate. An excess of propargylamine (100 mL, 1.5 mmol, 10
equiv) was then added and the reaction was allowed to continue for
several hours (see Table 1). The solvent was evaporated in vacuo
and the resulting crude material was purified by flash chromatog-
raphy (CH2Cl2/EtOH, 97/3) to afford 1 (101 mg, 0.145 mmol) as
purple solid in 96% of maximum yield (Trial A6). TLC (CH2Cl2/EtOH,
97/3): Rf ¼ 0.72; 1H NMR (300 MHz, CDCl3)
d
ꢁ2.89 (s, 2H, 2 NH),
2.38 (t, J ¼ 2.7 Hz, 1H, CH alkyne), 4.39 (dd, J ¼ 5.1, 2.7 Hz, 2H, CH2),
6.55 (t, J ¼ 5.4 Hz, 1H, NH), 7.70e7.79 (m, 9H, 9 CH), 8.14e8.22 (m,
8H, 8 CH), 8.33 (d, J ¼ 8.1 Hz, 2H, 2 CH), 8.77 (d, J ¼ 4.8 Hz, 2H, 2 CH),
CDCl3)
d
3.06 (s, 6H, 2 CH3), 3.79 (t, 4H, J ¼ 4.5 Hz, 2 CH2eO), 4.37 (t,
8.83e8.90 (m, 6H, 6 CH); 13C NMR (75 MHz, CDCl3)
d 29.9 (CH2),
4H, J ¼ 4.5 Hz, 2 CH2-OMs); 13C NMR (75 MHz, CDCl3)
d 38.3 (2 CH3),
72.2 (CH alkyne), 79.3 (C alkyne), 121.3 (C, meso-position), 121.4
(3 C, meso-position), 125.2 (2 CH Ar), 126.4 (6 CH Ar), 127.7 (3 CH
69.4 (2 CH2), 69.7 (2 CH2); HRMS (ESI) calculated for C6H16O7S2
[MþH]þ m/z 265.0415, found 264.9863.
Ar), 131.4 (C Ar), 131.9 (2 CH,
b-position), 132.0 (4 CH, b-position),
132.3 (2 CH, -position), 134.5 (6 CH Ar), 134.8 (2 CH Ar), 143.0 (4 C
b
4.3.2. 2-(2-Azidoethoxy)ethyl methanesulfonate (4)
Ar), 149.5 (2 C), 150.1 (2 C), 150.2 (2 C), 150.3 (2 C), 165.8 (C]O);
HRMS (ESI) calculated for C48H33N5O [MþH]þ m/z 696.2763, found
696.2812.
To solution of 3 (5.24 g, 20 mmol, 1.0 equiv) in CH3CN (50 mL)
was added NaN3 (1.30 mg, 20 mmol,1.0 equiv), and the mixture was
stirred at 70 ꢀC for 40 h under nitrogen atmosphere. The precipitate
was cooled at room temperature, filtered off, and the filtrate was
evaporated and purified by flash column chromatography (EtOAc/
petroleum ether, 35/65) to give 4 in 77% yield (3.22 g, 15.4 mmol) as
a colorless oil. TLC (CH2Cl2/MeOH, 95/5): Rf ¼ 0.69 (visualization by
10% PPh3 followed by dipping in ninhydrin stain); 1H NMR
4.2.2. Zinc 5-(4-propargylamidocarboxyphenyl)-10,15,20-
triphenylporphyrin (2)
In the absence of light and under N2, zinc acetate dihydrate
(114 mg, 0.51 mmol, 3.6 equiv) was added to a solution of 1
(100 mg, 0.14 mmol, 1 equiv) in THF (15 mL) and refluxed for 2 h.
The metallation was monitored by UVevisible spectrometry
(350e800 nm) and TLC (CH2Cl2/EtOH, 97/3). After cooling to room
temperature, THF was removed in vacuo and the crude material was
dissolved in CH2Cl2 (50 mL), washed with water (5 ꢂ 20 mL) and
dried over MgSO4. After evaporation of CH2Cl2, compound 2 was
obtained as purple microcrystalline solid in quantitative yield
(106 mg, 0.14 mmol). TLC (CH2Cl2/EtOH, 97/3): Rf ¼ 0.81; 1H NMR
(300 MHz, CDCl3)
d
3.04 (s, 3H, CH3), 3.38 (t, 2H, J ¼ 4.8 Hz,
CH2eN3), 3.68 (t, 2H, J ¼ 4.8 Hz, CH2eO), 3.76 (t, 2H, J ¼ 4.5 Hz,
CH2eO), 4.36 (t, 2H, J ¼ 4.5 Hz, CH2-OMs)); 13C NMR (75 MHz,
CDCl3)
d 37.9 (CH3), 51.0 (CH2eN3), 69.3 (CH2), 69.5 (CH2), 70.5
(CH2); HRMS (ESI) calculated for C5H11N3O4S [MþH]þ m/z 210.0548,
found 209.9914.
4.4. Synthesis of clickable aromatic scaffolds bearing one, two or
three azide groups (6, 8 and 10)
(300 MHz, CDCl3)
d
2.39 (t, J ¼ 2.7 Hz, 1H, CH alkyne), 4.45 (dd,
J ¼ 5.1, 2.7 Hz, 2H, CH2), 6.59 (t, J ¼ 5.4 Hz, 1H, NH), 7.71e7.79 (m,
9H, 9 CH), 8.16e8.23 (m, 8H, 8 CH), 8.31 (d, J ¼ 8.1 Hz, 2H, 2 CH),
8.77 (d, J ¼ 4.8 Hz, 2H, 2 CH), 8.84e8.88 (m, 6H, 6 CH); 13C NMR
4.4.1. General method for nucleophilic substitution reaction (Step A)
To a solution of commercially available methyl benzoate deriv-
ative (10 mmol, 1.0 equiv) in DMF (40 mL) was added K2CO3 (3.3
equiv per hydroxy group) and 4 (1.1 equiv per hydroxy group) and
(75 MHz, CDCl3)
d 29.7 (CH2), 72.1 (CH alkyne), 79.4 (C alkyne),
121.2 (C, meso-position), 121.4 (3 C, meso-position), 125.0 (2 CH Ar),
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A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
9
the mixture was stirred overnight at 80 ꢀC. After completion of the
reaction as monitored by TLC, the mixture was cooled at room
temperature, washed with saturated NaHCO3 (2 ꢂ 50 mL) and dried
over MgSO4. After evaporation of DMF, the resulting crude material
was purified by flash column chromatography (EtOAc/petroleum
ether, 50/50) to afford the corresponding compound (5, 7 or 9) as
light-yellowish oil in yield up to 93%. Compounds 5, 7 and 9 were
characterized as reported below.
CH2eO), 3.88 (t, 4H, J ¼ 4.5 Hz, 2 CH2eO), 4.17 (t, 4H, J ¼ 4.5 Hz, 2
CH2eOeAr), 6.77 (s, 1H, CHpara Ar), 7.27 (s, 2H, 2 CHortho Ar); 13C
NMR (75 MHz, CDCl3) d 51.1 (2 CH2eN3), 68.3 (2 CH2), 70.0 (2 CH2),
70.7 (2 CH2), 108.2 (CH Ar), 109.1 (2 CH Ar), 131.6 (C Ar), 160.3 (2 C
Ar), 171.9 (C]O); HRMS (ESI) calculated for C15H20N6O6 [MþH]þ m/
z 381.1522, found 381.1443.
4.4.2.3. 3,4,5-Tris-[2-(2-Azidoethoxy)-ethoxy]-benzoic acid (10).
TLC (EtOAc/petroleum ether, 40/60): Rf ¼ 0.32; 1H NMR (300 MHz,
4.4.1.1. Methyl 4-[2-(2-Azidoethoxy)-ethoxy]-benzoate (5). TLC
(EtOAc/petroleum ether, 40/60): Rf ¼ 0.71; 1H NMR (300 MHz,
CDCl3) d 3.37e3.43 (m, 6H, 3 CH2eN3), 3.73e3.77 (m, 6H, 3 CH2eO),
3.83e3.91 (m, 6H, 3 CH2eO), 4.22e4.30 (m, 6H, 3 CH2eOeAr), 7.38
CDCl3)
d
3.41 (t, 2H, J ¼ 4.8 Hz, CH2eN3), 3.75 (t, 2H, J ¼ 4.8 Hz,
(s, 2H, 2 CHortho Ar); 13C NMR (75 MHz, CDCl3)
d
51.2 (CH2eN3), 51.3
CH2eO), 3.88 (s, 3H, OCH3), 3.89 (t, 2H, J ¼ 4.8 Hz, CH2eO), 4.20 (t,
2H, J ¼ 4.8 Hz, CH2eOeAr), 6.94 (d, 2H, J ¼ 9.0Hz, 2 CHmeta Ar), 7.99
(CH2eN3), 51.4 (CH2eN3), 69.3 (2 CH2), 69.4 (2 CH2), 70.4 (CH2),
70.7 (2 CH2), 71.2 (CH2), 73.0 (CH2), 110.2 (2 CH Ar), 124.8 (C Ar),
143.7 (C Ar), 152.8 (2 C Ar), 171.6 (C]O); HRMS (ESI) calculated for
(d, 2H, J ¼ 9.0 Hz, 2 CHortho Ar); 13C NMR (75 MHz, CDCl3)
d 51.2
(CH2eN3), 52.3 (OCH3), 68.1 (CH2), 70.0 (CH2), 70.8 (CH2), 114.8 (2
CH Ar), 123.4 (C Ar), 132.1 (2 CH Ar), 163.1 (C Ar), 167.2 (C]O);
HRMS (ESI) calculated for C12H15N3O4 [MþH]þ m/z 266.1140, found
266.0941.
C
19H27N9O8 [MþH]þ m/z 510.2060, found 510.1973.
4.5. Synthesis of [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building blocks
4.5.1. Magnetic stirring method (Tables 2e4)
4.4.1.2. Methyl 3,5-Bis-[2-(2-Azidoethoxy)-ethoxy]-benzoate (7).
TLC (EtOAc/petroleum ether, 40/60): Rf ¼ 0.60; 1H NMR (300 MHz,
To a solution of clickable aromatic scaffold 6, 8 or 10 (0.1 mmol,
1.0 equiv.) and ZnTPP 2 (1.0 equiv per azide function) in appropriate
solvent (5 mL) was added CuSO4.5H2O (0.1 equiv per azide func-
tion) and Na ascorbate (0.5 equiv per azide function). The mixture
was stirred at appropriate temperature for some time under a ni-
trogen atmosphere or not (see Tables 2e4). At the end of the re-
action and after cooling to room temperature, the mixture was
washed with water (3 ꢂ 20 mL), dried over MgSO4 and concen-
trated under reduced pressure. The crude product was purified by
column chromatography using a stepwise gradient of MeOH in
CH2Cl2 (2e10%, v/v) to provide the corresponding building block
([ZnTPP]1, [ZnTPP]2 or [ZnTPP]3) as dark purplish powder.
CDCl3)
d
3.40 (t, 4H, J ¼ 4.8 Hz, 2 CH2eN3), 3.74 (t, 4H, J ¼ 4.8 Hz, 2
CH2eO), 3.86 (t, 4H, J ¼ 4.8 Hz, 2 CH2eO), 3.88 (s, 3H, OCH3), 4.15 (t,
4H, J ¼ 4.8 Hz, 2 CH2eOeAr), 6.71 (t, 1H, J ¼ 2.1 Hz, CHpara Ar), 7.20
(d, 2H, J ¼ 2.1 Hz, 2 CHortho Ar); 13C NMR (75 MHz, CDCl3)
d 51.2 (2
CH2eN3), 52.7 (OCH3), 68.3 (2 CH2), 70.1 (2 CH2), 70.8 (2 CH2), 107.5
(CH Ar), 108.7 (2 CH Ar), 132.5 (C Ar), 160.3 (2 C Ar), 167.2 (C]O);
HRMS (ESI) calculated for C16H22N6O6 [MþH]þ m/z 395.1679, found
395.1585.
4.4.1.3. Methyl 3,4,5-Tris-[2-(2-Azidoethoxy)-ethoxy]-benzoate (9).
TLC (EtOAc/petroleum ether, 40/60): Rf ¼ 0.58; 1H NMR (300 MHz,
CDCl3)
d
3.36e3.42 (m, 6H, 3 CH2eN3), 3.70e3.76 (m, 6H, 3 CH2eO),
4.5.2. Microwave method (Tables 2e4)
3.80e3.89 (m, 9H, 3 CH2eO, OCH3), 4.18e4.26 (m, 6H, 3 CH2e
Clickable aromatic scaffold 6, 8 or 10 (0.05 mmol, 1.0 equiv.),
ZnTPP 2 (1.0 equiv per azide function), CuSO4.5H2O (0.1 equiv per
azide function), Na ascorbate (0.5 equiv per azide function) and
appropriate solvent (2.5 mL) were mixed in a microwave tube with
a magnetic stir bar. The reaction tube was then fitted with its screw
OeAr), 7.30 (s, 2H, 2 CHortho Ar); 13C NMR (75 MHz, CDCl3)
d
51.4 (3
CH2eN3), 51.5 (OCH3), 69.4 (CH2), 69.5 (CH2), 70.3 (2 CH2), 70.5
(CH2), 70.9 (2 CH2), 71.3 (CH2), 73.0 (CH2), 109.7 (2 CH Ar), 125.8 (C
Ar), 143.1 (C Ar), 152.9 (2 C Ar), 167.1 (C]O); HRMS (ESI) calculated
for C20H29N9O8 [MþH]þ m/z 524.2217, found 524.2024.
cap, and stirred under
a nitrogen atmosphere or not (see
Tables 2e4). The reaction was carried out under microwave irra-
diation at 300 W and appropriate temperature for 45 or 90 min per
round (see Tables 2e4). After cooling to room temperature, the
crude reaction mixture was treated and purified in the same way as
magnetic stirring method.
4.4.2. General method for saponification reaction (Step B)
To a solution of methyl ester derivative 5, 7 or 9 (3 mmol, 1.0
equiv) in MeOH (30 mL) was added KOH (6 mmol, 2.0 equiv) and
the mixture was refluxed for 24 h. The crude material was cooled at
room temperature, neutralized with Amberlite IR 120 ion exchange
resin. The reaction was filtered and the resin was washed with
MeOH (3 ꢂ 10 mL). The filtrate was concentrated under reduced
pressure to give the desired clickable aromatic scaffold (6, 8 or 10)
as light-yellowish oil in yield up to 90%. Compounds 6, 8 and 10
were characterized as reported below.
4.5.3. [ZnTPP]1, [ZnTPP]2 and [ZnTPP]3 building blockswere
characterized as reported below
4.5.3.1. [ZnTPP]1 building block. TLC (CH2Cl2/MeOH, 95/5):
Rf ¼ 0.38; 1H NMR (300 MHz, DMSO-d6)
d
3.83 (t, 2H, J ¼ 5.1 Hz,
CH2eO), 3.94 (t, 2H, J ¼ 5.1 Hz, CH2eO), 4.18 (t, 2H, J ¼ 5.1 Hz,
CH2eOeAr), 4.60 (t, 2H, J ¼ 5.1 Hz, OeCH2eCH2-triazole), 4.68 (d,
2H, J ¼ 5.7 Hz, triazole-CH2-NH), 7.04 (d, 2H, J ¼ 8.7 Hz, 2 CHmeta of
the benzoic acid unit), 7.78e7.81 (m, 9H, 9 CH), 7.89 (d, 2H,
J ¼ 8.7 Hz, 2 CHortho of the benzoic acid unit), 8.16e8.33 (m, 11H, 10
CH, CH triazole ring), 8.74e8.79 (m, 8H, 8 CH), 9.38 (t,1H, J ¼ 5.7 Hz,
NHeCH2-triazole), 12.4 (br s, 1H, CO2H); 13C NMR (75 MHz, DMSO-
4.4.2.1. 4-[2-(2-Azidoethoxy)-ethoxy]-benzoic acid (6). TLC (EtOAc/
petroleum ether, 40/60): Rf ¼ 0.46; 1H NMR (300 MHz, CDCl3)
d
3.43 (t, 2H, J ¼ 4.8 Hz, CH2eN3), 3.77 (t, 2H, J ¼ 4.8 Hz, CH2eO),
3.91 (t, 2H, J ¼ 4.8 Hz, CH2eO), 4.23 (t, 2H, J ¼ 4.8 Hz, CH2eOeAr),
6.98 (d, 2H, J ¼ 9.0 Hz, 2 CHmeta Ar), 8.07 (d, 2H, J ¼ 9.0 Hz, 2 CHortho
Ar); 13C NMR (75 MHz, CDCl3)
d
51.4 (CH2eN3), 68.3 (CH2), 70.2
d6) d 35.2 (CH2eNH), 49.4 (CH2-triazole), 67.4 (CH2), 68.7 (CH2),
(CH2), 71.0 (CH2), 115.0 (2 CH Ar), 122.6 (C Ar), 133.0 (2 CH Ar), 163.9
(C Ar), 172.6 (C]O); HRMS (ESI) calculated for C11H13N3O4 [MþH]þ
m/z 252.0984, found 252.0747.
69.1 (CH2), 114.5 (2 CH Ar), 119.4 (C, meso-position), 120.6 (2 C,
meso-position), 120.7 (C, meso-position), 123.4 (C Ar), 123.6 (CH,
triazole ring), 125.7 (2 CH Ar), 126.8 (6 CH Ar), 127.7 (3 CH Ar), 131.5
(6 CH, b-position), 131.8 (2 CH, b-position), 131.9 (2 CH Ar), 133.3 (C
4.4.2.2. 3,5-Bis-[2-(2-Azidoethoxy)-ethoxy]-benzoic
acid
(8).
Ar), 134.3 (8 CH Ar), 142.9 (3 C Ar), 145.3 (C, triazole ring), 145.9 (C
Ar), 149.1 (2 C), 149.5 (4 C), 149.6 (2 C), 162.1 (C Ar), 166.4 (C]O),
167.2 (C]O); HRMS (ESI) calculated for C59H44N8O5Zn [MþH]þ m/z
TLC (EtOAc/petroleum ether, 40/60): Rf ¼ 0.38; 1H NMR (300 MHz,
CDCl3)
d
3.42 (t, 4H, J ¼ 4.8 Hz, 2 CH2eN3), 3.76 (t, 4H, J ¼ 4.8 Hz, 2
Please cite this article in press as: Gazzali AM, et al., Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for
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10
A.M. Gazzali et al. / Tetrahedron xxx (2016) 1e10
1009.2804, found 1009.3010.
J ¼ 5.1 Hz, CH2eO), 3.94 (t, 2H, J ¼ 5.1 Hz, CH2eO), 4.16 (t, 2H,
J ¼ 5.1 Hz, CH2eOeAr), 4.60 (t, 2H, J ¼ 5.1 Hz, OeCH2eCH2-triazole),
4.68 (d, 2H, J ¼ 5.7 Hz, triazole-CH2-NH), 7.02 (d, 2H, J ¼ 8.7 Hz, 2
CHmeta of the p-hydroxybenzamide unit), 7.77e7.84 (m,11H, 9 CH, 2
CHortho of the p-hydroxybenzamide unit), 8.12e8.35 (m, 12H,10 CH,
CH triazole ring, NHeCH2eCH2), 8.75e8.78 (m, 8H, 8 CH), 9.41 (t,
1H, J ¼ 5.7 Hz, NHeCH2-triazole); 13C NMR (75 MHz, DMSO-d6)
4.5.3.2. [ZnTPP]2 building block. TLC (CH2Cl2/MeOH, 95/5):
Rf ¼ 0.26; 1H NMR (300 MHz, DMSO-d6)
d
3.72 (t, 4H, J ¼ 5.1 Hz, 2
CH2eO), 3.87 (t, 4H, J ¼ 5.1 Hz, 2 CH2eO), 4.09 (t, 4H, J ¼ 5.1 Hz, 2
CH2eOeAr), 4.53 (t, 4H, J ¼ 5.1 Hz, 2 OeCH2eCH2-triazole), 4.64 (d,
4H, J ¼ 5.7 Hz, 2 triazole-CH2eNH)), 6.72 (br s, 1H, CHpara of the
benzoic acid unit), 7.08 (br s, 2H, 2 CHortho of the benzoic acid unit),
7.76e7.80 (m, 18H, 18 CH), 7.95e8.31 (m, 22H, 20 CH, 2 CH triazole
ring), 8.72e8.77 (m, 16H, 16 CH), 9.41 (t, 2H, J ¼ 5.7 Hz, 2 NHeCH2-
d
28.4 (CH2), 36.5 (CH2eNH), 43.6 (CH2),48.5 (CH2eN3), 49.3 (CH2-
triazole), 67.1 (CH2), 68.6 (CH2), 68.9 (CH2), 113.9 (2 CH Ar), 119.2 (C,
meso-position), 120.4 (2 C, meso-position), 120.5 (C, meso-position),
123.5 (CH, triazole ring), 125.5 (2 CH Ar), 126.6 (6 CH Ar), 126.8 (C
triazole); 13C NMR (75 MHz, DMSO-d6)
d 35.0 (2 CH2eNH), 49.2
(CH2-triazole), 49.9 (CH2-triazole), 67.3 (2 CH2), 68.8 (2 CH2), 69.3
(2 CH2), 107.4 (CH Ar), 107.7 (2 CH Ar), 119.2 (2 C, meso-position),
120.4 (4 C, meso-position), 120.5 (2 C, meso-position), 123.5 (2 CH,
triazole ring), 125.6 (4 CH Ar), 126.6 (12 CH Ar), 127.5 (6 CH Ar),
Ar),127.5 (3 CH Ar),131.4 (6 CH, b-position),131.6 (2 CH, b-position),
131.7 (2 CH Ar), 133.1 (C Ar), 134.1 (8 CH Ar), 142.7 (3 C Ar), 145.1 (C,
triazole ring), 145.7 (C Ar), 148.9 (2 C), 149.3 (4 C), 149.4 (2 C), 160.6
(C Ar), 165.7 (C]O), 166.2 (C]O); HRMS (ESI) calculated for
131.3 (2 CH,
b-position), 131.6 (6 CH,
b
-position), 131.7 (8 CH,
b
-
C
62H50N12O4Zn [MþH]þ m/z 1091.3447, found 1091.3380.
position), 133.1 (3 C Ar), 134.1 (16 CH Ar), 142.7 (6 C Ar), 145.1 (2 C,
triazole ring), 145.7 (2 C Ar), 148.9 (4 C), 149.3 (8 C), 149.4 (4 C),
159.3 (2 C Ar), 166.3 (2 C]O), 167.1 (C]O); HRMS (ESI) calculated
for C111H82N16O8Zn2 [MþH]þ m/z 1895.5162, found 1895.4825.
Acknowledgements
Amirah Mohd Gazzali was supported by Kementerian Pendi-
dikan Malaysia and Universiti Sains Malaysia under their Academic
Staff Training Scheme (ASTS) scholarship. The authors acknowledge
Mrs M. Achard for performing Mass experiments and Mr O. Favre
for running NMR experiments.
4.5.3.3. [ZnTPP]3 building block. TLC (CH2Cl2/MeOH, 95/5):
Rf ¼ 0.21; 1H NMR (300 MHz, DMSO-d6)
d 3.73e3.84 (m, 6H, 3
CH2eO), 3.89e3.98 (m, 6H, 3 CH2eO), 4.08e4.19 (m, 6H, 3
CH2eOeAr), 4.53e4.60 (m, 6H, 3 OeCH2eCH2-triazole), 4.62e4.69
(m, 6H, 3 triazole-CH2-NH), 7.25 (s, 2H, 2 CHortho of the benzoic acid
unit), 7.72e7.79 (m, 27H, 27 CH), 8.09e8.30 (m, 33H, 30 CH, 3 CH
triazole ring), 8.74e8.77 (m, 24H, 24 CH), 9.36 (t, 3H, J ¼ 5.7 Hz, 3
Appendix A. Supplementary data
NHeCH2-triazole); 13C NMR (75 MHz, DMSO-d6)
d 32.5 (3
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2016.12.037.
CH2eNH), 49.2 (CH2-triazole), 49.8 (CH2-triazole), 49.9 (CH2-tri-
azole), 68.9 (2 CH2), 69.0 (2 CH2), 69.5 (CH2), 69.8 (2 CH2), 70.3
(CH2), 72.9 (CH2), 108.7 (2 CH Ar), 118.9 (2 C, meso-position), 120.1
(6 C, meso-position), 120.4 (4 C, meso-position), 123.5 (CH, triazole
ring), 123.8 (2 CH, triazole ring), 124.2 (C Ar), 125.6 (2 CH Ar), 125.9
(4 CH Ar), 126.6 (6 CH Ar), 127.0 (12 CH Ar), 127.5 (3 CH Ar), 128.1 (6
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95/5): Rf ¼ 0.56; 1H NMR (300 MHz, DMSO-d6)
d 1.49e1.56 (m, 2H,
CH2eCH2eCH2), 3.21e3.40 (m, 4H, CH2eCH2eCH2eN3), 3.80 (t, 2H,
Please cite this article in press as: Gazzali AM, et al., Synthesis of mono-, di- and triporphyrin building blocks by click chemistry for
photodynamic therapy application, Tetrahedron (2016), http://dx.doi.org/10.1016/j.tet.2016.12.037