Efficient synthesis of dendritic architectures by one-pot double click reactions

Article abstract of DOI:10.1071/CH09052

Dendritic macromolecules with 8 and 16 hydroxy end-groups on the periphery have been synthesized using double click reactions (Cu-catalyzed azide/alkyne click chemistry, i.e., CuAAC and DielsAlder [4 + 2] cycloaddition reactions) with a one-pot technique.

Full text of DOI:10.1071/CH09052

Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2009, 62, 1371–1377
Efficient Synthesis of Dendritic Architectures
by One-Pot Double Click Reactions
Xing Quan XiongA
ACollege of Materials Science & Engineering, Huaqiao University, Xiamen 361021, China.
Email: xxqluli@hqu.edu.cn
Dendritic macromolecules with 8 and 16 hydroxy end-groups on the periphery have been synthesized using double
click reactions (Cu-catalyzed azide/alkyne click chemistry, i.e., CuAAC and Diels–Alder [4 + 2] cycloaddition reactions)
1
with a one-pot technique. The structure of the dendrimers was characterized by H and 13C NMR spectroscopy, and
matrix-assisted laser desorpton–ionization time-of-flight mass spectrometry. The purity was determined by size exclusion
chromatography.
Manuscript received: 24 January 2009.
Manuscript accepted: 5 March 2009.
Introduction
cycloaddition reactions. These two different kinds of reactions,
in which orthogonal reactive groups are ‘clicked’ together with
high efficiency, have been extensively applied to polymer chem-
istry, to produce a range of polymeric materials varying from
dendrimers,[31–35] to block polymers,[36–39] star polymers,[40–45]
and other complex polymers.[46–51]
Dendrimers[1–3] are a class of monodispersed macromolecules
with a regular and highly branched three-dimensional archi-
tecture. The size, the number of end groups, and the func-
tionality are tailored, which enables their properties to be
tuned precisely. Therefore, dendrimers have emerged as attrac-
tive nanometer-scale subjects for various applications such
as molecular light harvesting,[4,5] drug delivery,[6–10] homo-
geneous catalysis,[11–15] etc. In recent years, another important
application of dendrimers is to use well-defined dendrons as
the building blocks to construct dendronized polymers with a
one-dimensional structure in macromolecular chemistry.[16–20]
In general, there are two synthetic strategies to synthe-
size dendrimers. The first route is known as the divergent
growth approach,[21,22] i.e., the divergent generation of den-
drons through repetitive growth and activation steps from a
central core. The second route is a convergent approach.[23] By
this strategy, perfect dendrons are coupled onto a preformed
functional centre. However, with the generation increase, these
two synthetic strategies face the shortcomings of incomplete
grafting and low yields, respectively. Fortunately, by the combi-
nation of divergent and convergent approaches, namely using an
orthogonal procedure, one can produce dendrimers with defect-
free structures in good yields. Chemical reactions with highly
efficient selection, strong tolerance of functional groups, and
quantitative yield are usually employed in this strategy.
The orthogonal combination of CuAAC and Diels–Alder
[4 + 2] cycloaddition reactions (namely double click reac-
tions) has received great attention from academia.[52–54]
Herein, we report an orthogonal approach to defect-free
dendrimer derivatives of the classical Fréchet-type and
2,2-bis(methylol)propionic acid (bis-MPA) dendritic macro-
molecules using double click reactions with a one-pot technique.
As shown in Scheme 1, the whole synthetic process of this work
is carried out through the following steps: (i) preparation of
an alkyne-modified central core by Williamson etherification;
(ii) attachment of anthracene groups onto the central core by
CuAAC and then postmodification of the anthracene functional
core through a Diels–Alder [4 + 2] cycloaddition with a one-pot
technique; and (iii) mild and efficient cleavage of the isopropy-
lidene protecting groups on the periphery of the intermediates
6a and 6b. By this strategy, bis-MPA dendrons may be grafted
onto the functional dendrimers through an accelerated method
and this process can also be monitored easily using UV and flu-
orescence measurements. The details of the above procedures
and the results obtained will be discussed in the next section.
Recently, the ‘click’reaction concept, mainly exemplified by
Cu-catalyzed azide/alkyne click chemistry, i.e., CuAAC,[24,25]
has attracted considerable attention in polymer chemistry
because it meets the requirement for the orthogonal syn-
thesis of polymeric materials through accelerated synthetic
strategies.[26,27] For example, linear and mikto-arm star poly-
mers have been synthesized by combining CuAAC and con-
trolled radical polymerization (CRP), such as atom transfer
radical polymerization (ATRP),[28,29] and nitroxide-meditated
polymerization (NMP).[30]
Results and Discussion
Synthesis of Alkyne-Modified Fréchet-Type Dendron 3
Compound 3 was synthesized by the Williamson etherification
of bisphenol-A with an excess of Fréchet-type [G1]-Br in the
presence of K2CO3 in acetone (see Scheme S1 in the Accessory
Publication for the synthesis of 3). The structure of 3 was con-
1
firmed by H and 13C NMR spectroscopy and matrix-assisted
laser desorption–ionization time-of-flight (MALDI-TOF) mass
1
spectrometry. In the H NMR spectrum of 3, the single peak
More importantly, the orthogonality of CuAAC has also
allowed the reaction to be combined with Diels–Alder [4 + 2]
at 2.50 ppm corresponded to the proton of –C≡CH. The single
peaks at 1.63, 4.65, and 4.97 ppm, respectively, were assigned
© CSIRO 2009
10.1071/CH09052
0004-9425/09/101371

1372
X. Q. Xiong
O
O
O
O
N
O
O
N3
O
CH3
C
O
O
O
O
5a
O
O
C
O
O
O
O
O
CH3
O
O
N
C
O
3
O
4
O
O
5b
3
ϩ
4
5a or 5b
ϩ
CuBr,
PMDETA
DMF
25ЊC to 110ЊC
OH
O
6a or 6b
HO
OH
O
O
HO
Hϩ resin
THF/MeOH
(3/1, v/v)
O
O
N
N
O
N
N
O
O
N
O
CH3
C
N
N
O
O
N
O
O
O
N
CH3
N
N
N
N
N
O
O
N
7a
or
N
O
O
O
O
HO
HO
OH
OH
O
O
OH
HO
O
O
OH
HO
O
C
OH
O
HO
OH
C
O
HO
C
C
O
O
O
O
O
O
O
O
O
N
N
N
N
N
O
O
N
O
CH3
C
N
N
N
O
O
O
O
N
CH3
O
N
N
N
N
O
O
N
O
N
O
7b
O
O
O
O
C
O
O
OH
O
O
O
OH
OH
C
C
O
O
HO
OH
C
HO
O
HO
HO
Scheme 1. Structure of building blocks and strategy to prepare hydroxy-group modified dendrimers 7a and 7b by one-pot double click reactions.

Synthesis of Dendritic Architectures
1373
O
O
O
O
O
O
O
O
O
N
N
O
N
N
N
O
O
1
CH
O
2
3
N
N
N
O
O
O
N
N
C
O
O
CH
3
3
4
N
N
5
N
N
14
10
12
O
6
O
N
N
O
O
O
8
O
O
7
O
O
13
O
11
9
O
O
H-9,13
H-3
H-7,8,11
H-Ar
H-1
H-6
H-10,12
H-2
H-14
H-Ar
H-4
*
H-5
H-8,11
9
8
7
6
5
4
3
2
1
0
ppm
Fig. 1. 1H NMR spectrum of dendrimer 6a in CDCl3 with assignment.
to the protons of –CH3, –OCH2C≡CH, and –CH2O. The car-
bon signals of the –C≡C group were observed at 76.68 and
79.21 ppm in the 13C NMR spectrum. The signal at 56.83 ppm
was assigned to the carbon of C-4 of –OCH2C≡CH. The carbon
signal of C-1 of the methyl appeared in the 13C NMR spectrum at
31.93 ppm. The carbon signal at 70.57 ppm corresponded to C-3
of –OCH2Ar. The other correlative signals could be assigned to
the corresponding protons and carbons of 3 as shown in Figs S1
and S2 of the Accessory Publication.
6a and 6b, respectively). As can be seen from Fig. 1, the peaks
between 7.60 and 8.40 ppm, characteristic for aromatic protons
of anthracene, completely disappear, which clearly indicates the
quantitative efficiency of the process. It reveals the loss of the
aromaticity of the central phenyl units of anthracene as a result of
the Diels–Alder cycloaddition.At the same time, the single peak
at 2.50 ppm also completely disappears, which represented the
–C≡CH proton. Furthermore, a double peak appeared at approx-
imately 4.74 ppm, which is attributable to the bridgehead proton
of the cycloadduct H-14. The peaks at 3.56 and 4.10 ppm were
assigned to H-8 and H-11 of the bis-MPA dendron, respectively.
The distinct signals at 1.13, 1.33, and 1.37 ppm correspond to
H-9 and H-13 of the methyl groups in the bis-MPA dendron.
These results reveal that the synthesis of dendrimer 6a by a
one-pot double click reaction was achieved efficiently.
The Diels–Alder [4 + 2] cycloaddition was monitored by UV
spectroscopy. In order to obtain a direct comparison easily, the
intermediate anthracene derivative 4ꢀ of the CuAAC reaction
was isolated, whose detailed structural analysis is shown in Figs
S6–S7. In the UV spectra (Fig. 2 for 4ꢀ and 6a, and Fig. S8 for 4ꢀ
and 6b), although compound 4ꢀ displayed a characteristic five-
finger absorbance in the range of 300–400 nm, the dendrimer 6a
showed no absorbance in the same region (Fig. 2b), which was
caused by the loss of the aromaticity of the central phenyl unit
of anthracene.
One-Pot Synthesis of Dendrimers 6a and 6b
by a Double Click Reaction
In this step, compound 3, azide-functionalized anthracene 4, and
bis-MPA dendrons 5a or 5b were reacted in one pot in order to
produce the corresponding dendrimer 6a or 6b by double click
reactions (Scheme 1). During the process, excess amounts of
4 (3.5 mmol, 1.1 equiv.) and 5a or 5b (6.4 mmol, 2.0 equiv.)
are used compared with that of 3 (0.8 mmol). A click reaction
was accomplished between the azide of 4 and the alkyne group
of dendron 3 catalyzed by CuBr/pentamethyldiethylenetriamine
(PMDETA) in N,N-dimethylformamide (DMF) at room temper-
ature. When the reaction was completed, the reaction mixture
washeatedto110◦Candcontinuedtostirfor3h. Duringthispro-
cess, a Diels–Alder [4 + 2] reaction was accomplished between
the anthracene group of the intermediate and the bis-MPA
dendrons 5a or 5b.
Fluorescence spectra might also provide further evidence for
the efficiency of the Diels–Alder reaction (Fig. 2 for 4ꢀ and 6a,
and Fig. S9 for 4ꢀ and 6b). Fig. 2 (right) shows the fluores-
cence spectra of the intermediate 4ꢀ before and after reaction
with the bis-MPA dendron. The characteristic fluorescent band
of the anthracene group between 350 and 500 nm disappears
Evidence for the occurrence of the double click reactions was
obtained from 1H NMR, 13C NMR, UV, and fluorescence spec-
1
troscopy. The H NMR spectrum of dendrimer 6a is shown in
Fig. 1 (see Fig. S3 in the Accessory Publication for the 1H NMR
spectrum of 6b, and see Figs S4–S5 for the 13 C NMR spectra of

1374
X. Q. Xiong
completely after the Diels–Alder reaction. Based on the above
results of 1H NMR, UV, and fluorescence measurements, it
is clear that a quantitative Diels–Alder reaction has occurred
between the anthracene and bis-MPA dendron. That is to say,
the bis-MPA dendrons have been attached to the central core
successfully by a Diels–Alder reaction between anthracene and
maleimide derivatives.
which were assigned to H-1 and H-2 of the methyl group (see
Fig. S10 for the 1H NMR spectrum of 7b). Furthermore, no sig-
nals for C-1, 2, and 3 of the protective groups at 23.03, 25.11, and
98.94 ppm in the 13C NMR spectrum were found (Fig. S11b),
which indicates that the protective groups were removed com-
pletely from the dendrimer 6a (see Fig. S12 for the 13C NMR
spectrum of 7b).
Size exclusion chromatography (SEC) was applied to charac-
terize the purity of the building blocks (3, 5b) and the dendrimers
(6b, 7b). As demonstrated in Fig. 4, monodisperse peaks were
obtained (1.01 ≤ Mw/Mn ≤ 1.08), which indicates that the click
reaction and separation were efficient (see Fig. S13 for the SEC
traces of 3, 5a, 6a, and 7a). The actual molar masses were deter-
mined by MALDI-TOF mass spectrometry, and the observed
molecular weight agreed with the theoretical values. For exam-
ple, the MALDI-TOF mass spectrum of 7b (Fig. 5) showed a
single peak at m/z 3538, which is the molecular ion peak with
Deprotection of Dendrimers 6a and 6b
The isopropylidene groups of –OH groups in two dendrimers
could be removed using Dowex H+ resin in a mixture of tetra-
hydrofuran (THF) and MeOH. The hydrolyzed products were
confirmed by 1H and 13C NMR spectroscopy.
The partial 1H NMR spectra (Fig. 3b) confirmed that the iso-
propylidene groups have been completely removed based on the
disappearance of the resonance of signals at 1.33 and 1.37 ppm,
0.9
750
600
(a)
0.6
450
300
150
0
(a)
(b)
0.3
(b)
0.0
320
360
400
440
400
450
500
550
600
Wavelength [nm]
Wavelength [nm]
Fig. 2. Comparison of UV/Vis (left) and fluorescence spectra (right, λexc 350 nm) of 4ꢀ (a) and 6a (b) in THF (5.0 × 10−5 M for UV/Vis and 2.0 × 10−5 M
for fluorescence spectra, 25◦C).
O
O
O
OH
3
O
3
1
O
Hϩ resin
O
N
N
OH
2
O
O
O
O
H-3
ϪOH
(b)
H-1,2
H-3
(a)
5
4
3
2
1
ppm
Fig. 3. The partial 1H NMR spectra of 6a (a) and 7a (b) in CDCl3.

Synthesis of Dendritic Architectures
1375
sodium [M + Na]+ (see Fig. S14 for the MALDI-TOF mass
spectrum of 7a). Detailed characterization information of 6a,
6b, 7a, and 7b is collected in Table 1.
were used without further purification. Compounds 5a and
5b were prepared (all of purity ≥98%) according to literature
procedures.[20]
Instruments
Conclusions
NMR spectra were acquired in CDCl3 on a Bruker DMX-400
In this work, we have demonstrated a versatile synthesis of den-
drimers that contain functional groups, such as hydroxy groups,
on the dendritic periphery, by efficiently combining CuAAC
and Diels–Alder [4 + 2] cycloaddition strategies with a one-
pot technique. Based on NMR, mass spectrometry, SEC, and
fluorescence analysis, we confirm the formation of a class of
defect-free dendrimers. This facile modular synthetic method
can, furthermore, afford the production of dendrimers with
different compositions and functions.
1
spectrometer at 400 MHz for H NMR and 100 MHz for 13C
NMR, the chemical shifts are given in δ values from tetramethyl-
silane (TMS) as an internal standard. SEC using polystyrene as a
standard was performed on a Waters 2414 instrument with THF
as an eluent at a flow rate of 1.0 mL min−1. Fluorescence spec-
tra were recorded on a Varian Cary-Eclipse spectrophotometer.
MALDI-TOF mass spectrometry was performed on a Bruker
Biflex III spectrometer equipped with a 337 nm nitrogen laser.
Mass spectra were acquired in positive reflector mode using an
acceleration voltage of 19 kV.
Experimental
Materials
Synthesis of Alkyne-Modified Fréchet-Type Dendron 3
Bisphenol-A (tech 97%, Alfa), 9-anthracenemethanol (tech
98%, Alfa), propargyl bromide (80% in toluene, Alfa), sodium
azide (AR, Beijing Chemicals Co.), lithium tetrahydroalumi-
nate (typically 97%, Alfa), and sodium hydride (60% dispersed
in mineral oil, Aldrich) were used as received. Maleic an-
hydride (MAn) was recrystallized from benzene. Other reagents
Bisphenol-A (0.71 g, 3.01 mmol), anhydrous potassium carbon-
ate (2.0 g, 14.5 mmol), [G1]-Br (1) (2.0 g, 7.16 mmol), and
potassium iodide (120 mg, 0.72 mmol) were refluxed in dry ace-
tone (20 mL) under N2 for 48 h. The solution was evaporated to
dryness, and the residue partitioned between dichloromethane
(DCM, 100 mL) and water (100 mL). The organic layer was sep-
arated, and the aqueous phase extracted with DCM (3 × 20 mL).
The combined organic phase was dried (Na2SO4), filtered, and
evaporated to give a fawn product. The crude product was puri-
fied by column chromatography (SiO2, DCM/petroleum ether
(PE), 1/4, v/v). The alkyne-modified compound 3 was isolated
as a white solid (1.34 g, 70%). δH 1.63 (s, 6H, 2 × CH3), 2.50
c
b
a
d
Table 1. Characterization data of molar masses and polydispersities
from mass spectra (MALDI-TOF) and SEC of 6a, 6b, 7a, and 7b
Sample Calcd molar massA
m/z ([M + Na]+) Polydispersity index
6a
6b
7a
7b
2747.1
3836.2
2586.7
3515.7
2747.4B/2770.4
3859.2/3875.2C
2609.1
1.05
1.05
1.05
1.08
20
22
24
26
28
30
3538.0
Time [min]
ACalculated according to the atom weight.
B[M]+.
Fig. 4. Size exclusion chromatography traces of building blocks 3 (trace b),
5b (trace a), and the dendrimers 6b (trace c), and 7b (trace d).
C[M + K]+.
600
400
200
0
m/z
2000
2500
3000
3500
4000
4500
5000
5500
6000
Fig. 5. Matrix-assisted laser desorpton–ionization time-of-flight mass spectrometry spectrum of 7b.

1376
X. Q. Xiong
(s, 4H, 4 × C≡CH), 4.65 (s, 8H, 4 × OCH2C≡CH), 4.97 (s, 4H,
2 × CH2O), 6.55–7.14 (m, 14H, H-Ar). δC 31.93 (2C, CH3),
42.60 (1C, C(CH3)2), 56.83 (4C, OCH2C≡CH), 70.57 (2C,
OCH2Ar), 76.68 (4C, C≡CH), 79.21 (4C, C≡CH), 102.54,
107.70, 115.10, 128.66, 140.76, 144.37, 157.36, 159.72 (C-Ar).
m/z (MALDI-TOF) 647.0 [M + Na]+, 663.0 [M + K]+.
Compound 7a: δH 0.99 (s, 12H, 4 × CH3), 1.60 (s, 6H,
2 × CH3), 3.12–3.34 (m, 24H, H-6, 10, 12, and –OH), 3.63–
3.71 (m, 24H, H-7, 8, and 11), 4.71 (s, 4H, H-14), 4.88 (s, 4H,
H-2), 5.14 (s, 8H, H-3), 5.86 (dd, 8H, H-5), 6.57–7.31 (m, 42H,
H-Ar), 8.19 (s, 4H, H-4), 8.37 (s, 4H, H-Ar). δC 17.31, 31.10,
37.74, 45.82, 46.22, 47.62, 48.20, 49.16, 49.66, 61.74, 62.09,
67.29, 69.80, 106.90, 114.26, 121.38, 124.10, 124.83, 125.72,
126.55, 126.92, 127.18, 127.34, 127.52, 127.89, 128.90, 131.23,
138.93, 139.17, 140.05, 141.89, 143.49, 143.61, 156.51, 159.59,
175.32, 176.54. m/z (MALDI-TOF) 2609.1 [M + Na]+.
One-Pot Synthesis of Dendritic Architectures
Compound
3
(0.50 g, 0.80 mmol), azide-functionalized
anthracene 4 (0.82 g, 3.50 mmol), and bis-MPA dendron 5a or
5b (6.40 mmol, 2.0 equiv.) were dissolved in nitrogen-purged
DMF (10 mL) in a Schlenk flask, CuBr (46.0 mg, 0.32 mmol,
0.1 equiv.) and PMDETA (55.4 mg, 0.32 mmol, 0.1 equiv.) were
added, and the reaction mixture was degassed by three freeze–
pump–thaw cycles and left under nitrogen and stirred at room
temperature for 12 h. The reaction mixture was then stirred at
110◦C for 3 h. When the reaction was completed, the mixture
was evaporated under high vacuum. The crude product obtained
was then dissolved in 5.0 mL of THF and passed through an
alumina column to remove the copper salt. The solution was
evaporated to give a crude product, which was purified by col-
umn chromatography (SiO2, DCM/PE, 1/3, v/v). The dendrimer
6a or 6b was isolated as a white solid (the yields were 73 and
65%, respectively).
Compound 6a: δH 1.13 (s, 12H, 4 × CH3), 1.33 (s, 12H,
4 × CH3), 1.37 (s, 12H, 4 × CH3), 1.62 (s, 6H, 2 × CH3), 3.14–
3.28 (m, 8H, H-10, 12), 3.37 (t, J 5.50, 8H, 4 × NCH2), 3.56
(d, J 11.80, 8H, H-8, 11), 3.61 (t, J 5.45, 8H, H-7), 4.10 (d, J
11.80, 8H, H-8, 11), 4.74 (d, J 2.90, 4H, H-14), 4.92 (s, 4H,
H-2), 5.16 (s, 8H, H-3), 5.86 (dd, 8H, H-5), 6.67–7.35 (m,
42H, H-Ar), 8.25 (s, 4H, H-4), 8.35 (s, 4H, H-Ar). δC 19.43,
23.53, 25.51, 26.50, 31.94, 38.09, 42.60, 46.66, 47.02, 48.40,
48.98, 49.93, 61.96, 62.88, 66.70, 66.75, 68.86, 70.59, 98.95,
107.55, 115.01, 122.20, 124.86, 125.65, 126.56, 127.08, 127.74,
127.96, 128.15, 128.36, 128.66, 139.71, 139.85, 140.85, 142.64,
144.33, 160.45, 174.72, 176.70, 177.04. m/z (MALDI-TOF)
2747.4 [M]+•, 2768.4 [M + Na]+.
Compound 7b: δH ((D6)DMSO) 1.02 (s, 24H, 8 × CH3), 1.16
(s, 12H, 4 × CH3), 1.57 (s, 6H, 2 × CH3), 3.24 (s, 8H, H-10, 12),
3.40–3.49 (m, 40H, H-7, 8, 11, and –OH), 4.10–4.30 (m, 40H,
H-7, 8, 11, 15, and –OH), 4.81 (s, 4H, H-14), 4.99 (s, 4H, H-2),
5.18 (s, 8H, H-3), 5.90 (dd, 8H, H-5), 6.73–7.85 (m, 42H, H-Ar),
8.28 (s, 4H, H-4), 8.53 (s, 4H, H-Ar). δC ((D6)DMSO) 17.30,
17.63, 36.89, 40.45, 45.34, 46.51, 46.70, 47.67, 48.18, 50.88,
61.65, 64.32, 65.32, 79.70, 114.69, 122.36, 124.69, 125.71,
126.44, 127.08, 127.25, 127.42, 127.59, 128.00, 139.68, 139.91,
141.24, 142.93, 143.05, 159.82, 172.57, 174.69, 176.48. m/z
(MALDI-TOF) 3538.0 [M + Na]+.
Accessory Publication
Scheme S1 of the synthesis of alkyne-modified compound 3,
Figs S1–S2 of the H and 13C NMR spectra of compound 3,
1
1
Fig. S3 of the H NMR spectrum of 6b, Fig. S4 of the 13C
NMR spectrum of 6a, Fig. S5 of the 13C NMR spectrum of
1
6b, Figs S6–S7 of the H and 13C NMR spectra of compound
4ꢀ, Figs S8–S9 of the UV/vis and fluorescence spectra of 4ꢀ
1
and 6b, Fig. S10 of the H NMR spectrum of 7b, Fig. S11 of
the partial 13C NMR spectra of 6a and 7a, Fig. S12 of the 13
C
NMR spectrum of 7b, Fig. S13 of the SEC traces of 3, 5a, 6a,
and 7a, and Fig. S14 of the MALDI-TOF MS spectrum of 7a
are available from the Journal’s website.
Acknowledgements
Financial support by the Special Foundation for Young Scientists of Fujian
Province, China (Grant No. 2008F3067) and the Scientific Research Starting
Foundation of Huaqiao University, China (Grant No. 08BS213) are greatly
acknowledged. The author is grateful to Professor Yongming Chen at CAS
for his useful discussions in this work and for help with GPC and NMR
characterization.
Compound 6b: δH 1.09 (s, 12H, 4 × CH3), 1.10 (s, 12H,
4 × CH3), 1.25 (s, 24H, 8 × CH3), 1.27 (s, 12H, 4 × CH3),
1.36 (s, 12H, 4 × CH3), 1.37 (s, 12H, 4 × CH3), 1.62 (s, 6H,
2 × CH3), 3.23 (d, 4H, J 8.48, H-10), 3.31–3.36 (m, 12H,
4 × NCH2, H-12), 3.56–3.60 (m, 24H, H-8, 11, 15, and 17),
4.08–4.27 (m, 32H, H-7, 8, 11, 15, and 17), 4.74 (d, J 2.68, 4H,
H-14), 4.91 (s, 4H, H-2), 5.15 (s, 8H, H-3), 5.90 (dd, 8H, H-5),
6.67–7.35 (m, 42H, H-Ar), 8.18 (s, 4H, H-4), 8.34 (s, 4H,
H-Ar). δC 12.30, 14.99, 15.19, 18.38, 19.35, 19.40, 20.31, 21.30,
22.63, 22.69, 23.50, 23.51, 26.20, 29.92, 32.45, 42.21, 42.89,
42.92, 46.67, 47.59, 48.55, 49.02, 62.82, 62.84, 66.09, 66.81,
98.94, 115.00, 122.29, 124.83, 125.63, 126.50, 127.16, 127.66,
127.89, 128.07, 128.27, 128.64, 135.12, 139.86, 139.99, 140.97,
142.70, 144.22, 157.39, 160.51, 172.96, 174.45, 176.94, 177.20.
m/z (MALDI-TOF) 3859.2 [M + Na]+, 3875.2 [M + K]+.
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