One-pot synthesis of hyperbranched poly(amido amine) clicked with a sugar shell via Michael addition polymerization and thiol click reaction

Article abstract of DOI:10.1007/s11426-010-4050-8

This paper reports the production of glycopolymers via a simple and flexible method. A novel glycopolymer with a hyperbranched poly(amido amine) core and a sugar shell (HPAA-GLc) was synthesized by using thiol-ene click reaction via facile one-pot method. Hyperbranched poly(amido amine) with vinyl terminals was first synthesized by Michael addition polymerization of N,N′-methylene bisacrylamide (MBA) with 1-(2-aminoethyl) piperazine (AEPZ). Subsequently, thiol-ene click reaction between vinyl units of hyperbranched poly(amido amine) and thio-glucose was performed in situ. Based on the NMR result, all the vinyl groups reacted with thiol-glucose in 120 min. Strong photoluminescence emission was observed from the aqueous solution of HPAA-GLc. Science China Press and Springer-Verlag Berlin Heidelberg 2010.

Full text of DOI:10.1007/s11426-010-4050-8

SCIENCE CHINA
Chemistry
August 2010 Vol.53 No.8: 1663–1668
doi: 10.1007/s11426-010-4050-8
• ARTICLES •
· SPECIAL TOPIC · Advances in Principles of Polymerization
One-pot synthesis of hyperbranched poly(amido amine)
clicked with a sugar shell via Michael addition
polymerization and thiol click reaction
YU ZhiQiang, CUI MengMeng, YAN JunJie & YOU YeZi*
CAS Key Lab of Soft Matter Chemistry; Department of Polymer Science and Engineering,
University of Science and Technology of China, Hefei 230026, China
Received May 14, 2010; accepted June 24, 2010
This paper reports the production of glycopolymers via a simple and flexible method. A novel glycopolymer with a hyper-
branched poly(amido amine) core and a sugar shell (HPAA-GLc) was synthesized by using thiol-ene click reaction via facile
one-pot method. Hyperbranched poly(amido amine) with vinyl terminals was first synthesized by Michael addition polymeri-
zation of N,N′-methylene bisacrylamide (MBA) with 1-(2-aminoethyl) piperazine (AEPZ). Subsequently, thiol-ene click reac-
tion between vinyl units of hyperbranched poly(amido amine) and thio-glucose was performed in situ. Based on the NMR re-
sult, all the vinyl groups reacted with thiol-glucose in 120 min. Strong photoluminescence emission was observed from the
aqueous solution of HPAA-GLc.
thiol-ene click reaction, glycopolymers, hyperbranched poly(amido amine), photoluminescence
biomimetic properties and significance in biological appli-
1 Introduction
cations. Two different approaches have been developed to
synthesize polymers with pendent sugar moieties: polym-
erization of a sugar-containing monomer and post-func-
tionalization of preformed polymers using sugar-containing
reagents. The latter approach is relatively simple and con-
venient because the synthesis of sugar-containing mono-
mers often requires tedious multi-step reactions. However,
the method frequently results in polymers having less regu-
lar structures because of incomplete reactions due to steric
hindrance [14, 15]. In recent years, click reaction has been
used to produce polymers with pendent sugar moieties. The
most representative example is the construction of glyco-
polymers from alkyne backbone-functional polymers via
Cu-catalyzed azide-alkyne click chemistry [16, 17] and
thiol-ene click reaction [6, 7] under mild reaction conditions.
Although great progress has been achieved in the synthesis
of polymers with pendent sugar moieties, simple and flexi-
ble methods are still desirable for their preparation, espe-
cially one-pot method.
Thiol-ene click chemistry has attracted significant attention
in the material field [1–4]. The reaction of thiols with enes
is performed under various conditions including acid/base
catalyzed thiol-Michael reaction and radical mediated radi-
cal thiol-ene reaction. The reaction displays many charac-
teristics of click reaction [5], such as high efficiency, simple
orthogonal reactions and biologically friendly nature (metal
free). It has been very attractive in the synthesis of func-
tional polymers, especially bio-related polymers [6, 7].
Glycopolymers are synthetic polymers with pendent
sugar moieties [8, 9]. The pendent sugar moieties play a
significant role in a number of significant biological proc-
esses including inflammation, cell-cell contacts, signal
transmission and fertilization [10–13]. Therefore, polymers
with sugar moieties have been of interest due to their
*Corresponding author (email: yzyou@ustc.edu.cn)
*Corresponding author (email: yzyou@ustc.edu.cn)
*Corresponding author (email: yzyou@ustc.edu.cn)
© Science China Press and Springer-Verlag Berlin Heidelberg 2010
chem.scichina.com
www.springerlink.com

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YU ZhiQiang, et al. Sci China Chem August (2010) Vol.53 No.8
Herein, we report a facile one-pot approach to synthesize
argon for 5 min and sealed. Then, hydrogen bromide (40%
in acetic acid, 60 mL) was injected, and the reaction mixture
was stirred at room temperature for 2.5 h. After the reaction
finished, the reaction mixture was partitioned between di-
chloromethane (200 mL) and water (200 mL), and the
aqueous layer was re-extracted with dichloromethane (3 ×
100 mL). The combined organic layers were washed with
saturated sodium hydrogen carbonate aqueous solution,
washed with brine (400 mL), dried over magnesium sulfate,
filtered and evaporated in vacuum. Crystallization from
ethyl acetate/petroleum ether afforded 2,3,4,6-tetra-O-ace-
tyl--D-glucopyranosyl bromide (8.80 g, 84%) as a white
crystalline solid. 1H NMR (300 MHz, CDCl3):  2.04, 2.06,
2.10, 2.11 (4s, 12H, COCH3), 4.10–4.19 (m, 1H, H-6’),
4.26–4.36 (m, 2H, H-5/H-6), 4.81–4.87 (dd, 1H, H-2),
5.13–5.20 (t, 1H, H-4), 5.53–5.60 (t, 1H, H-3), 6.58–6.64 (d,
1H, H-1) ppm.
hyperbranched poly(amido amine) (HPAA) with a sugar
shell by using click chemistry. Hyperbranched poly(amido
amine) with vinyl terminals (HPAA-vinyl) was synthesized
using Michael addition polymerization of N,N′-methylene
bisacrylamide (MBA) with 1-(2-aminoethyl) piperazine
(AEPZ). The vinyl terminals subsequently reacted with
thio-glucose in situ via thiol-ene click reaction under base
catalysis with 100% conversion in a short time. HPAA
clicked with a sugar shell shows strong photoluminescence
emission.
2 Experimental
2.1 Materials
Pentaacetyl--D-glucopyranose (99%), 1-(2-aminoethyl)
piperazine (AEPZ, 99%) and N,N′-methylene bisacrylamide
(MBA, 99%) were purchased from Aldrich. Hydrogen bro-
mide (HBr, 33% in acetic acid) was obtained from Xiangfan
Wan Weiyang Chemical Co., Ltd. Thiourea, triethylamine
(TEA, 99%), sodium metabisulphite (Na2S2O5, 98%), and
sodium methoxide (50% in methanol) were purchased from
Sinopharm Chemical Reagent Co., Ltd. Cation exchange
resin 7120H was purchased from Tianyuan Group Shanghai
Resin Factory Co., Ltd. The resin was washed with metha-
nol and water, and finally acidified with 10% hydrochloric
acid. Other chemicals and solvents were purchased from
Shanghai Lingfeng Chemical Reagent Co., Ltd. and used as
received without further purification.
2,3,4,6-Tetra-O-acetyl--D-glucopyranosyl-1-isothiouroniu
m) bromide (3)
Thiourea (2.4 g, 32.1 mmol, 1.5 equiv) and compound 2
(8.80 g, 21.4 mmol, 1 equiv) were dissolved in acetone
(100 mL) under argon. The reaction was preformed at 60 °C
under stirring. After 30 min, a white solid appeared, and
was collected by filtration and the filtrate returned to reflux.
This process was repeated until the solid ceased to precipi-
tate. The combined precipitates were re-crystallized from
acetone/petroleum ether to afford 2,3,4,6-tetra-O-acetyl--
D-glucopyranosyl-1-isothiouronium bromide (4.91 g, 47 %)
as a white crystalline solid. 1H NMR (300 MHz, d6-DMSO):
1.98, 2.00, 2.02, 2.06 (4s, 12H, COCH3), 4.06–4.12 (m,
1H, H-6’), 4.17–4.24 (m, 2H, H-5/H-6), 5.08–5.14 (m, 2H,
H-2/H-4), 5.25–5.38 (m, 1H, H-3), 5.66–5.71 (m, 1H, H-1),
9.17 (s, 4H, NH2) ppm.
2.2 Characterization
1H NMR spectra (300 MHz) and 13C NMR spectra (75 MHz)
were recorded on a Bruker AV 300 spectrometer. The number-
average molecular weight (Mn) and polydispersity index of
polymers were determined by size exclusion chromatogra-
phy (SEC) using a Waters 2690 apparatus with two columns
in series (Waters Styragel HR 4E and 5E) and polystyrene
as standards. The SEC system was equipped with a mini-
DAWN multiangle light scattering detector. DMF was used
as the eluent at a flow rate of 1.0 mL/min and a temperature
of 35 °C. SEC data were analyzed using Astra 4.50 software
from Wyatt Technology. Excitation spectra and emission
spectra were obtained on a Perkin-Elmer LS 55 lumines-
cence spectrometer with a slit width of 5 nm using a 10-
mm-path quartz cell under xenon discharge lamp excitation.
2,3,4,6-Tetra-O-acetyl-1-thio--D-glucopyranoside (4)
Sodium metabisulphite (2.85 g, 15.0 mmol, 1.5 equiv) and
compound 3 (4.90 g, 10.0 mmol, 1 equiv) were dissolved in
dichloromethane (45 mL) and water (25 mL). The reaction
mixture was heated to reflux under argon for 4 h. Then it
was cooled to room temperature, and the phases separated.
The aqueous layer was re-extracted with dichloromethane
(3 × 60 mL), dried over magnesium sulfate, filtered and
concentrated in vacuum to afford 2,3,4,6-tetra-O-acetyl-1-
thio--D-glucopyranoside (3.73 g, 100%) as a white crystal-
1
line solid. H NMR (300 MHz, CDCl3):  2.01, 2.03, 2.08,
2.10 (4s, 12H, COCH3), 2.20–2.40 (d, 1H, SH), 3.70–3.76
(ddd, 1H, H-5), 4.09–4.20 (dd, 1H, H-6’), 4.24–4.4.28 (dd,
1H, H-6), 4.52–4.59 (t, 1H, H-1), 4.94–5.01 (t, 1H, H-2),
5.07–5.14 (t, 1H, H-4), 5.16–5.23 (t, 1H, H-3) ppm.
2.3 Synthesis of 1-thio--D-glucose (-GlcSH)
2,3,4,6-Tetra-O-acetyl--D-glucopyranosyl bromide (2)
1-Thio--D-glucose (-GlcSH) (5)
Sodium methoxide (50% in methanol, 880 mg, 8.2 mmol,
1.5 equiv) was added into a solution of 2,3,4,6-tetra-O-acetyl-
Pentaacetyl--D-glucopyranose 1 (10.0 g, 25.6 mmol, 1
equiv) was added in to a 250 mL flask and dissolved in di-
chloromethane (75 mL). The solution was bubbled with

YU ZhiQiang, et al. Sci China Chem August (2010) Vol.53 No.8
1665
1-thio--D-glucopyranoside (2.0 g, 5.4 mmol, 1 equiv) in
methanol (25 mL). The reaction mixture was stirred at room
temperature for 30 min. The reaction mixture was acidified
with 7120H cation exchange resin, filtered and concentrated
in vacuum to afford 1-thio--D-glucose (-GlcSH) (1.10 g,
1
96 %) as a pale yellow oil. H NMR (300 MHz, D2O): 
3.20 (t, 1H, H-4), 3.40 (m, 3H, H-2/H-3/H-5) 3.64 (dd, 1H,
H-6’), 3.82 (d, 1H, H-6), 4.50 (d, 1H, H-1) ppm; MS: calcd.
for C6H12O9S (MH+) 195.03, found 195.04. The final
product contains ~10% 1-thio--D-glucose (-GlcSH) based
on 1H NMR results.
Scheme 1 Synthesis of 1-thio--D-glucose. Reaction conditions: (a) HBr
(40% in acetic acid), dichloromethane (84%); (b) thiourea, acetone, 60 °C
(47%); (c) Na2S2O5, dichloromethane/water (100%); (d) MeONa, MeOH
(96%).
2.4 One-pot synthesis of HPAA with a sugar shell
MBA (2.467 g, 16.0 mmol) was added into a solution of
AEPZ (1.038 g, 8.0 mmol) in a 24 mL solvent mixture
(methanol/water = 70/30, v/v). After fully mixing, the reac-
tion mixture was stirred at 50 °C until 25% of the total vinyl
salt, followed by mild hydrolysis with sodium metabisul-
phite and Zémplen deacetylation. All the compounds were
confirmed by 1H NMR.
1
groups were left (monitored by H NMR spectroscopy, a
portion of the reaction solution was taken out and concen-
trated under a reduced pressure, followed by precipitating
into cold acetone and drying in vacuum for measure). Then,
predetermined -GlcSH (The molar ratio to double bonds is
2.0) and TEA were added to the reaction mixture, and some
of the solution was transferred to the NMR tube. The spec-
tra were taken at different time intervals for the kinetic
study. After 100% conversion of the double bonds (120 min),
the reaction solution was concentrated under a reduced
pressure, followed by precipitating into cold acetone and
drying in vacuum.
3.2 Synthesis of HPAA with vinyl terminals (HPAA-vinyl)
HPAA-vinyl was synthesized using Michael addition po-
lymerization of MBA with AEPZ at a molar ratio of 2/1
(Scheme 2). Based on the Michael addition reaction mecha-
nism, the resulting HPAA contains the residual 25 mol%
vinyl groups after polymerization, which was confirmed by
1H NMR spectroscopy of the reaction solution after 96 h
reaction as shown in Figure 1(a). This residual vinyl groups
1
value is 24% calculated from eq. (1) according to the H
NMR spectrum.
2.5 Effect of feed ratios on thiol click reactions
Residual vinyl groups value %  I
3I4.264.49 100%


5.486.49
To further investigate the effect of -GlcSH concentration,
the thiol click reactions of HPAA-vinyl with different
amounts of -GlcSH (The molar ratios to double bonds are
1.0 and 1.4) were performed at room temperature for dif-
ferent reaction time. Typically, a predetermined amount of
AEPZ and MBA reaction solution (0.25 mmol double bonds,
1.0 equiv) was added into a vial. -GlcSH (49.0 mg, 0.25
mmol, 1.0 equiv) and 50 L TEA were added under argon,
and the reaction was performed at room temperature for 5 or
24 h. The final polymer was obtained via precipitating in
cool acetone and drying under vacuum at room temperature.
(1)
where I5.486.49 and I4.264.49 are integral values of the signals
at 5.486.49 ppm attributed to vinyl protons and those at
4.264.49 ppm attributed to methylene protons from MBA
in Figure 1(a), respectively. The resulting poly(amido amine)
with a hyperbranched structure was confirmed by the ap-
pearance of peaks at 50–51 ppm in its 13C NMR as shown in
Figure 1(b). However, it is difficult to obtain the degree of
1
branching from H NMR and 13C NMR, which is similar to
the previous findings [20–22].
3.3 Synthesis of HPAA with a sugar shell via thiol-ene
click reactions
3 Results and discussion
3.1 Synthesis of 1-thio--D-glucose
The vinyl ends of HPAA are activated species which could
easily react with -GlcSH via thiol-ene click reaction under
base-catalysis. Considering that thiol-ene click reactions
could be performed in a wide range of solvents, here we
synthesized HPAA with a sugar shell by hydrothiolation of
vinyl groups in situ using one-pot method as shown in
-GlcSH could be easily synthesized following standard
coupling methods [18, 19] at the anomeric center (Scheme 1).
First, compound 1 was treated with HBr to afford the gly-
cosyl halides (compound 2). Then 2 was converted into 5
through treatment with thiourea to afford the isothiouronium

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YU ZhiQiang, et al. Sci China Chem August (2010) Vol.53 No.8
Scheme 2 Synthetic strategy for preparation of HPAA with a sugar shell.
Figure 1 (a) 1H NMR spectrum of 1-(2-aminoethyl) piperazine (AEPZ) and N,N′-methylene bisacrylamide (MBA) reaction solution in d6-DMSO. (b) 13C
NMR spectrum of hyperbranched poly(amido amine) with vinyl terminals in d6-DMSO.

YU ZhiQiang, et al. Sci China Chem August (2010) Vol.53 No.8
1667
Scheme 2. For better understanding of the kinetics of
thiol-ene click reaction at room temperature, HPAA react-
cates that the -GlcSH concentration has a significant effect
on thiol click reactions. Only 85% conversion was achieved
even when the reaction was performed for 24 h. The low
conversion may be attributed to three factors: the high steric
hindrance of -GlcSH, insufficient reaction time and some
of the -GlcSH oxidized to dimers. However, by increasing
the feed ratio of -GlcSH to vinyl to 1.4, complete conver-
sion was achieved in 5 h.
1
1
ing with -GlcSH was monitored by H NMR. In its H
NMR, the integral value of vinyl double bond peaks de-
creases with the increase of reaction time as shown in Fig-
ure 2. The conversion of the vinyl was calculated from eq.
(2) according to the 1H NMR spectrum.
Conversion %  0.25 I
3I4.304.50 0.25100%




5.486.49
(2)
3.5 Photoluminescence properties of HPAA-GLc
where I5.486.49 and I4.304.50 are integral values of the signals
at 5.486.49 ppm attributed to vinyl protons and those at
4.304.50 ppm attributed to methylene protons from MBA.
A conversion of 50% was achieved in 30 min and a com-
plete conversion was achieved within 120 min.
HPAA with a sugar shell was obtained via precipitating
from cool acetone. The Mn of HPAA with vinyl terminals is
19600, and the Mn of HPAA with a sugar shell is 28800,
further confirming the success of the thiol-click reaction.
Figure 3 shows the excitation and emission fluorescence
spectra of HPAA-vinyl, HPAA-GLc1, HPAA-GLc2 and
HPAA-GLc3 recorded at room temperature. The preformed
polymer HPAA-vinyl exhibited very weak photolumines-
cence, but after clicked with -GlcSH, HPAA-GLc1,
HPAA-GLc2 and HPAA-GLc3 showed enhanced fluores-
cence emission with an emission band at 380 nm and an
excitation band at 320 nm. This indicates that the -GlcSH
groups hydrothiolation to HPAA plays a significant role in
the fluorescent properties. Those crowed terminal -GlcSH
groups may make the overall structure of HPAA much
tighter and change the structure and the microenvironment
of the fluorescence species, therefore enhancing the fluo-
rescence emission. The fluorescence intensity was stronger
with increasing conversion of vinyl, which further con-
firmed the above mechanism.
3.4 Effect of feed ratios on thiol click reactions
Post-functionalization of preformed polymers using sugar-
containing reagents often results in incomplete conversion
of the post-functional groups due to steric hindrance. Our
research results show that quantitative conversion of the
vinyl could be achieved within 2 h with the molar ratio of
-GlcSH to vinyl being 2.0. To further investigate the effect
of -GlcSH concentration on thiol click reactions, several
control reactions were performed. The reaction conditions
and results are shown in Table 1. A 78% conversion was
obtained in 5 h at the feed molar ratio of 1.0, which indi-
4 Conclusions
In summary, hyperbranched poly(amido amine) clicked
with a sugar shell was synthesized via the thiol-ene click
reaction between HPAA-vinyl and -GlcSH in one pot. The
highly efficient and simple reaction process is very suitable
for large-scale synthesis of glycopolymers. The investigation
of their potential applications in gene delivery and bio-
imaging is underway.
Figure 2 1H NMR spectra of thiol-ene click reaction at different time.
Table 1 Reaction conditions and results of thiol click reaction between
HPAA-vinyl and -GlcSH
Feed molar ratio
-GlcSH: vinyl
Reaction time
(h)
Conversion of
vinyl (%) a)
Sample
HPAA-GLc1
HPAA-GLc2
HPAA-GLc3
1.0
1.0
1.4
5
24
5
78
85
100
Figure 3 Fluorescence excitation and emission spectra of HPAA-vinyl,
HPAA-GLc1, HPAA-GLc2 and HPAA-GLc3.
a) Calculated according to eq. (2).

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