N-glycosylation approach to glucose-functionalized diamine and its use for protection-free synthesis of polyurea bearing glucoside pendant

Article abstract of DOI:10.1002/pola.26376

A glucose-functionalized diamine was prepared and used as a new monomer for polyurea synthesis. The diamine was prepared by N-glycosylation of 1,6-hexamethylenediamine with D-glucose. Upon adding diisocyanates to the diamine, isocyanate reacted selectively with the amino groups, not with the hydroxyl groups of the glucose-derived structure, to give the corresponding polyureas. The polyureas exhibited highly hydrophilic nature due to the presence of the glucose-derived side chain. A ternary system consisting of the glucose-functionalized diamine, piperazine, and diisocyanate gave the corresponding polyureas, where content of the glucose-derived moiety was tunable by feed ratio between the diamine and piperazine.

Full text of DOI:10.1002/pola.26376

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N-Glycosylation Approach to Glucose-Functionalized Diamine and Its Use
for Protection-Free Synthesis of Polyurea Bearing Glucoside Pendant
Atsushi Sudo, Shou Sugita
Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, Kowakae 3-4-1, Higashi-Osaka,
Osaka 577-8502, Japan
Correspondence to: A. Sudo (E-mail: asudo@apch.kindai.ac.jp)
Received 7 August 2012; accepted 6 September 2012; published online 28 September 2012
DOI: 10.1002/pola.26376
ABSTRACT: A glucose-functionalized diamine was prepared and
used as a new monomer for polyurea synthesis. The diamine was
prepared by N-glycosylation of 1,6-hexamethylenediamine with
D-glucose. Upon adding diisocyanates to the diamine, isocyanate
reacted selectively with the amino groups, not with the hydroxyl
groups of the glucose-derived structure, to give the corresponding
polyureas. The polyureas exhibited highly hydrophilic nature due
to the presence of the glucose-derived side chain. A ternary
system consisting of the glucose-functionalized diamine, pipera-
zine, and diisocyanate gave the corresponding polyureas, where
content of the glucose-derived moiety was tunable by feed ratio
C
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between the diamine and piperazine.
2012 Wiley Periodicals,
Inc. J Polym Sci Part A: Polym Chem 51: 298–304, 2013
KEYWORDS: D-glucose; hydrophilic polymers; N-glycosylation;
renewable resources; step-growth polymerization
INTRODUCTION Monosaccharides are attractive building
blocks for synthesizing various polymer materials.1–6 They
possess plural hydroxyl groups, of which regioselective reac-
tions permit incorporation of monosaccharide-derived struc-
tures into materials in well-defined manners, so that those
materials inherit various virtues such as affinity to biomole-
cules, hydrophilicity, and self-assembling nature from mono-
saccharides.7–11 In addition, those hydroxyl groups are
located in specifically defined orientations, and thus efficient
use of them will lead to precise construction of three dimen-
sional macromolecular architectures.12,13 Monosaccharides
have another important reactive site, that is, the anomeric
position, to which various functional groups can be intro-
duced.14 N-Glycosides are a class of compounds synthesized
by introduction of amines to the anomeric position of mono-
saccharides. So far, they have attracted much attention due
to their bioactivity,15–18 molecular recognition,19 and their
potential applicability to surfactants.20–22 N-glycosides can
be synthesized quite simply, just by mixing monosaccharides
and the corresponding amines in bulk or in alcohol solutions.
This simple method as well as the structural diversity of
amines has prompted the development of functional N-glyco-
side derivatives.
important monomers for polymer synthesis based on their
reactions with electrophilic molecules involving isocyanates,
epoxides, and acrylates that afford practically important class
of polymers such as polyureas, polyamines, and polyami-
noesters. Modification of diamines by N-glycosylation can
afford the corresponding ‘‘sugar-functionalized’’ amines, of
which utilization as new monomers for polymer synthesis
will open a new window for development of sugar-function-
alized polymers with unique properties. So far, sugar-
functionalized diamines have been synthesized,23,24 and their
biological activity25–27 and ability to form metal com-
plexes28,29 have been evaluated; however, to the best of our
knowledge, there have been no reports on their application
as monomers for polymer synthesis.
Herein, we report a polyaddition system with exploiting a
bifunctional N-glycoside, which can be easily prepared by
N-glycosylation of diamine with glucose (Scheme 1). In this
system, protection of the glucose-derived hydroxyl group can
be avoided based on the difference in intrinsic nucleophilic-
ity between hydroxyl and amino groups, leading to the for-
mation of polymers bearing glucose moiety in the side chain.
EXPERIMENTAL
The focus of the present work is utilization of N-glycosides
as a new class of monosaccharide-derived monomers. More
specifically, our interest is exploitation of N-glycosylation as
a convenient method for modifying amines into ‘‘sugar-func-
tionalized’’ amine-type monomers. Diamines are highly
Materials
D-Glucose (Glu), hexamethylenediamine (HMDA), butylamine,
and lithium chloride were purchased from Kishida Chemical
Co. and used as received. Phenyl isocyanate, methylenediphenyl
Additional Supporting Information may be found in the online version of this article.
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3.66–3.61 (m, 2H), 3.43–3.35 (m, 1H), 3.14–3.06 (m, 1H),
3.15–3.08 (m, 2H), 2.89–2.81 (m, 1H), 2.82–2.75 (m, 1H),
2.13 (br s, 1H), 1.41–1.25 (m, 4H), 0.86 (t, J ¼ 7.4 Hz, 3H);
13C NMR (DMSO-d6, d): 90.78, 77.61, 77.44, 73.51, 70.54,
61.39, 45.19, 32.14, 19.93, 13.97.
Reaction of 1 with Phenyl Isocyanate
To a solution of 1 (0.941 g; 4.00 mmol) and lithium chloride
(0.424 g; 10.0 mmol) in DMF (24 ꢂmL), phenyl isocyanate
(0.476 g; 4.00 mmol) was added at 0 C. The resulting solution
was allowed to warm to room temperature and was stirred for
24 h. DMF was removed under reduced pressure, and the
resulting residue was passed through a short pad of silica gel
[eluent ¼ ethyl acetate/methanol (4/1)] to remove a highly po-
lar fraction. The corresponding adduct 2 thus obtained was
used in the next reaction step without further purification. The
characteristic spectroscopic data of 2 are as follows:
1
ꢂ
H NMR (DMSO-d6, at 60 C, d): 8.30 (s, 1H), 7.46 (d, J ¼ 8.3
Hz, 2H), 7.20 (t, J ¼ 7.8 Hz, 2H), 6.92 (t, J ¼ 7.3 Hz, 1H),
5.30 (br s, 1H), 4.95 (br s, 1H), 4.88 (d, J ¼ 8.3 Hz, 2H), 4.41
(br s, 1H), 3.68 (d, J ¼ 11 Hz, 1H), 3.57 (d, J ¼ 11 Hz, 1H),
3.46–3.38 (m, 3H), 3.34–3.22 (m, 3H), 3.19 (br s, 1H), 3.11
(br s, 1H), 2.50 (s, 1H), 1.59–1.50 (m, 2H), 1.36–1.24 (m,
2H), 0.89 (t, J ¼ 7.3 Hz, 3H); 13C NMR (DMSO-d6, at 60 ꢂC,
d): 154.9, 139.9, 128.2, 121.3, 119.2, 86.17, 78.38, 70.72,
69.51, 60.51, 42.79, 31.10, 19.23, 13.31.
SCHEME 1 The concept of this work: modification of diamine
with glucose and utilization of the modified diamine for poly-
mer synthesis.
4,40-diisocyanate (MDI), and 2,6-tolylenediisocyanate (TDI)
were purchased from Tokyo Chemical Industry Co. and distilled
prior to use. N, N-Dimethylformamide was purchased from
Wako Pure Chemical Industries Co. and distilled prior to use.
Other reagents and solvents were purchased from Wako Pure
Chemical Industries Co. and used as received.
Acetylation of Hydroxyl Groups of 2
To a solution of crude 2 obtained as mentioned above in
pyridine (20 mL), acetic anhydride (10 mL) was added and
stirred at room temperature. After 24 h, the volatiles were
removed under reduced pressure. The resulting residue was
fractionated by silica gel column chromatography [eluent ¼
hexane/ethyl acetate (1/1)] to obtain tetraacetate 3 (1.67 g;
3.20 mmol; 80% from 1) as a white powder. IR (KBr): m ¼
1756, 1674.
Instruments
NMR spectra (400 MHz for 1H; 100.6 MHz for 13C) were
recorded on a JEOL NMR spectrometer model JNM-AL400.
Chemical shift d and coupling constant J are given in parts
per million and Hertz, respectively. IR spectra were obtained
on a JASCO FT/IR-470 and wave number m is given in cmꢀ1
.
Number average molecular weight (Mn) and weight average
molecular weight (Mw) were estimated by size exclusion
chromatography (SEC), performed on a Tosoh chromato-
graph model HLC-8120GPC equipped with Tosoh TSK gel-
Super HM-H styrogel columns (6.0 mm u ꢁ 15 cm), using N,
1
ꢂ
H NMR (DMSO-d6, at 80 C, d): 8.12 (s, 1H), 7.43 (d, J ¼ 8.3
Hz, 2H), 7.27 (t, J ¼ 8.1 Hz, 2H), 7.00 (t, J ¼ 7.3 Hz, 1H),
5.59 (d, J ¼ 9.3Hz, 1H), 5.34 (t, J ¼ 9.3 Hz, 1H), 5.23 (t, J ¼
9.3 Hz, 1H), 5.06 (t, J ¼ 9.5 Hz, 1H), 4.17 (d, J ¼ 4.4 Hz, 2H),
4.10–4.00 (m, 1H), 3.40–3.18 (m, 2H), 2.02 (s, 3H), 2.01 (s,
3H), 1.95 (s, 3H), 1.94 (s, 3H), 1.57–1.45 (m, 2H), 1.36–1.25
(m, 2H), 0.89 (t, J ¼ 7.3 Hz, 3H); 13C NMR (DMSO-d6, at 60
ꢂC, d): 169.3, 168.9, 168.7, 168.5, 154. 1, 139.2, 127.8, 122.1,
120.2, 86.87, 78.32, 72.49, 68.29, 68.04, 61.59, 42.64, 31.06,
19.88, 19.83, 19.72, 19.03, 13.12.
N-dimethylformamide (DMF) containing
1 wt% lithium
bromide as an eluent at the flow rate of 0.6 mL/min after
calibration with polystyrene standards. Thermogravimetric
analysis (TGA) was performed with a SEIKO Instruments
TG/DTA model EXSTAR6000 under nitrogen flow.
Synthesis of N-Butyl-b-glucopyranosylamine 1
To a suspension of Glu (18.02 g; 100.0 mmol) in methanol
(8 mL), butylamine (10.97 g; 150.0 mmol) was added and
heated at 60 C for 30 min. Addition of hot ethanol (60 mL)
to the solution and cooling to room temperature resulted in
gelation of the mixture, and the gel was divided into small
pieces. Toluene (30 mL) was added to the gel, and the mix-
ture was stirred at room temperature, filtered with suction,
washed with toluene, and then dried under vacuum to
obtain 1 (17.37 g; 73.83 mmol, 74%) as a white powder.
One-Pot Model Reactions
A mixture of butylamine (0.228 g; 3.12 mmol), Glu (0.65 g;
3.6 mmol), triethylamine ꢂ(0.40 mL; 3.0 mmol), and methanol
(4 mL) was stirred at 60 C for 20 min. The resulting solution
was concentrated under reduced pressure. The residual white
solid was dried under vacuum, and then dissolved in DMF
(10 mL) containing lithium chloride (0.33 g; 7.8 mmol). To
the solution, a solution of phenylisocꢂyanate (0.372 g; 3.13
mmol) in DMF (5 mL) was added at 0 C and stirred at room
temperature under argon. After 12 h, pyridine (10 mL) and
acetic anhydride (5 mL) were added successively, and the
ꢂ
1H NMR (DMSO-d6, d): 4.83 (d, J ¼ 4.9 Hz, 1H), 4.79 (d, J ¼
4.4 Hz, 1H), 4.45 (d, J ¼ 3.9 Hz, 1H), 4.35 (t, J ¼ 5.9 Hz, 1H),
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solution was stirred at room temperature for 7 h. The vola-
tiles were removed under reduced pressure, and the resulting
residue was dissolved in ethyl acetate (20 mL). The resulting
solution was washed with 10 mL of water three times, dried
over sodium sulfate, filtered, and concentrated under reduced
pressure. The residue was fractionated by silica gel column
chromatography (eluent: hexane/ethyl acetate ¼ 2/1) to
obtain 3 (1.40 g; 2.68 mmol; 86%) as a white solid.
solid was dissolved in ethyl acetate (50 mL) and the solution
was poured into diethyl ether (200 mL). The resulting white
precipitate was isolated by filtration with suction, dried under
vacuum. This precipitation process with using ethyl acetate/
ether was repeated once to obtain polymer 8a (2.11 g; 71%).
IR (KBr): m ¼ 1744, 1662.
Synthesis of Polyurea 8b and Isolation of Its Precursor 7b
From HMDA (0.357 g; 3.07 mmol), Glu (1.33 g; 7.38 mmol),
PZ (0.264 g; 3.07 mmol), and MDI (1.536 g; 6.14 mmol), pol-
yurea 8b was synthesized and isolated according to the pro-
cedure described above for the synthesis of polyurea 8a. As
a result, polyurea 8b (2.51 g; 60%) was obtained as a pale
yellow solid. IR (KBr): m ¼ 1658.
Synthesis of Polyurea 6a
To a solution of HMDA (0.305 g; 2.63 mmol) in methanol (10
mL), Glu (1.14 g; 6.33 mmol) and triethylamine (0.38 mL; 2.6
mmol) were ꢂadded successively. The resulting mixture was
stirred at 60 C for 20 min. The volatiles were removed under
reduced pressure to obtain a mixture of bifunctional N-glyco-
side 4 and Glu. To this mixture, lithium chloride (0.55 g; 13
mmol) and DMF (23 mL) were added and stirred for 30 min
at room temperature. To the resulting solution, a solution of
MDI (0.657 g; 2.63 mmol) in DMF (3 mL) was added and
stirred at room temperature. After 12 h, pyridine (10 mL)
and acetic anhydride (5 mL) were added and stirred at room
temperature for 12 h. The resulting solution was concentrated
under reduced pressure and diluted with methanol (20 mL).
To this mixture, water (10 mL) was added to precipitate the
target polymer 6a. The resulting yellow precipitate was iso-
lated by filtration with suction and dried under vacuum. The
obtained solid was dissolved in ethyl acetate (50 mL) and the
solution was poured into diethyl ether (200 mL). The result-
ing white precipitate was isolated by filtration with suction,
dried under vacuum. This precipitation process with using
ethyl acetate/ether was repeated once to obtain polymer 6a
(1.97 g; 70%). IR (KBr): m ¼ 1753, 1664.
Polyurea 7b, of which treatment with acetic anhydride and
pyridine gave 8b, was synthesized and isolated as follows:
From HMDA (0.370 g; 3.19 mmol), Glu (1.38 g; 7.66 mmol),
PZ (0.274 g; 3.19 mmol), and MDI (1.60 g; 6.37 mmol), poly-
urea 7b was synthesized according to the procedure
described above for the synthesis of polyurea 8a. The result-
ing solution of 7b in DMF (50 mL) was poured into water
(300 mL). The resulting viscous precipitate was isolated by
ꢂ
decantation and dried under vacuum at 85 C for 10 days to
give 7b (2.54 g, 78%) as a pale yellow solid. IR (KBr): m ¼
1755, 1659.
Synthesis of Polyurea 9
To a solution of PZ (0.258 g; 3.00 mmol) in DMF (10 mL), a
solution of MDI (0.751 g; 3.00 mmol) in DMF (5 mL) was
added, and the resulting solution was stirred at room tem-
perature. After 12 h, the mixture became a gel. With using
60 mL of DMF, the formed gel was transferred into a 500-
mL flask, and ethyl acetate (400 mL) was added to it. The
resulting precipitate was isolated by filtration with suction
and dried under vacuum to obtain polyurea 9 (0.979 g,
97%). IR (KBr): m ¼ 1642.
Synthesis of Polyurea 6b
From HMDA (0.341 g; 2.93 mmol), Glu (1.27 g; 7.04 mmol),
and TDI (0.522 g; 3.00 mmol), polyurea 6b was synthesized
and isolated according to the procedure described above for
the synthesis of polyurea 6a. As a result, polyurea 6b (1.07
g; 38%) was obtained as a white solid. IR (KBr): m ¼ 1752,
1666.
RESULTS AND DISCUSSION
Model System
As a model system for the designed polyaddition, we investi-
gated a sequence of reactions starting from butylamine
(Scheme 2). N-glycoside 1 was readily obtained by the N-gly-
cosylation of butylamine with D-glucose (Glu) according to
the reported procedure for the selective synthesis of b-iso-
mer of N-glycosides.21 Supporting Information Figures S1
Synthesis of Polyurea 8a
To a solution of HMDA (0.301 g; 2.59 mmol) in methanol (8
mL), Glu (0.65 g; 3.6 mmol) and triethylamine (0.30 mL; 2.1
mmol) were ꢂadded successively. The resulting mixture was
stirred at 60 C for 20 min. The volatiles were removed under
reduced pressure to obtain a mixture of bifunctional N-glyco-
side 4 and Glu. To this mixture, lithium chloride (0.55 g; 13
mmol), piperazine (PZ; 74.6 mg; 0.866 mmol) and DMF (35
mL) were added successively and stirred for 30 min at room
temperature. To the resulting solution, a solution of MDI
(0.864 g; 3.46 mmol) in DMF (3 mL) was added and stirred
at room temperature. After 12 h, pyridine (10 mL) and acetic
anhydride (5 mL) were added and stirred at room tempera-
ture for 12 h. The resulting solution was concentrated under
reduced pressure and diluted with methanol (20 mL). To this
mixture, water (10 mL) was added to precipitate the target
polymer 8a. The resulting yellow precipitate was isolated by
filtration with suction and dried under vacuum. The obtained
1
and S2 show H and 13C NMR spectra of 1, respectively. The
obtained N-glycoside 1 was treated with an equimolar
amount of phenyl isocyanate in DMF at room temperature.
Addition of lithium chloride was quite effective to enhance
the solubility of 1, as is often the case with polysaccharide
chemistry. After 6 h, the mixture was analyzed by TLC to
confirm the complete consumption of 1 as well as formation
of a UV-detectable compound as a sole product. This product
was passed through a short silica gel column and analyzed
by NMR. The resulting spectra are shown in Supporting
Information Figure S3. These spectra confirmed the success-
ful formation of compound 2 by the reaction of the amino
group of 1 with phenyl isocyanate. The absence of any
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ity.30–32 In addition, selective N-acylation of N-glycosides with
acyl halide or acid anhydride have been also reported.17,20,21
For further detailed analysis of the adduct 2, it was treated
with acetic anhydride and pyridine to convert it into the cor-
responding tetraacetate 3. Figures 1(a) and 2(a) show the
1H and 13C NMR spectra, respectively, where all the signals
were completely assigned to all the protons and carbon
atoms that constitute 3. The assignment was made concrete
by its 13C NMR analysis with distortionless enhancement by
1
polarization transfer with 135ꢂ pulse (DEPT135), H–1H cor-
relation spectroscopy (HH-COSY), and 13C–1H correlation
spectroscopy (CH-COSY). The resulting spectra are shown in
Supporting Information Figures S4–S6. The IR spectrum of 3
indicated two strong absorptions at 1756 and 1674 cmꢀ1
,
which were attributable to ester C¼¼O and urea C¼¼O,
respectively.
Next, the abovementioned reaction sequence was performed
in one pot. N-glycoside 1 was prepared by treating butyla-
mine with a slightly excess amount of Glu in methanol, fol-
lowed by concentration under reduced pressure and drying
under vacuum. The resulting mixture of 1 and Glu was dis-
solved in DMF with the aid of addition of lithium chloride,
then phenylisocyanate was added to the solution. TLC analy-
sis of the reaction mixture confirmed selective formation of
2, which implied reaction of phenyl isocyanate with the
hydroxyl groups of 1 and Glu was negligible. The final step
SCHEME 2 A cascade of model reactions.
byproducts implied that phenyl isocyanate reacted with the
amino group exclusively, without reacting with the hydroxyl
groups of 1. There have been a few reports on similar reac-
tions of N-glycosides and isocyanates with high N-selectiv-
FIGURE 1 1H NMR spectra (in DMSO-d6 at 80 ꢂC) of model compound 3 and polyurea 6a.
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FIGURE 2 13C NMR spectra (in DMSO-d6 at 80 ꢂC) of model compound 3 and polyurea 6a.
was acetylation of the hydroxyl groups with acetic anhydride
and pyridine, which gave 3 and D-glucose pentaacetate.
These two products were separated by column chromatogra-
phy leading to the successful isolation of 3 in 86% yield.
neous throughout, suggesting that the target linear polyurea
5a was formed without its crosslinking due to the reaction
of the side chain hydroxyl groups with MDI. We attempted
precipitation of 5a from water to remove lithium chloride;
Polyaddition System
The high selectivity and efficiency demonstrated in the
model system prompted us to perform the corresponding
polyaddition system consisting of a bifunctional N-glycoside
4 and diisocyanate (Scheme 3). What we expected was an
exclusive reaction of isocyanate with the amino groups of 4
that affords a linear polyurea 5 without contamination of its
structure by reaction of isocyanate with the hydroxyl groups.
A similar polyurea synthesis with using 2,6-diamino-2,6-
dideoxy-D-glucose as a diamine-type monomer has been
reported.33 A bifunctional N-glycoside 4 was prepared just
by mixing HMDA with Glu in a 1:2 molar ratio in methanol.
The details of the preparation and isolation of 4 are
described in Supporting Information. It was characterized by
1H and 13C NMR (Supporting Information Figures S1 and S2,
respectively). These spectra clarified 4 was contaminated by
a significant amount of methanol, presumably due to the
high polarity of 4. Heating 4 under vacuum to remove meth-
anol completely resulted in gradual decomposition of 4. To
avoid this problematic issue, we decided to prepare 4 in situ
and use it without further purification: HMDA and Glu were
mixed in a 1:2.4 molar ratio, to ensure the complete modifi-
cation of the amino groups. The resulting mixture of 4 and
Glu was dried under vacuum, dissolved in DMF containing
lithium chloride, and then treated with MDI (Table 1, Entry
1). During the polymerization, the system remained homoge-
SCHEME 3 Synthesis of polyureas with using glucose-modi-
fied diamine 4.
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TABLE 1 Polyaddition of Bifunctional N-Glycoside 4 and Diisocyanate with Using PZ as a Comonomer
Composition
(4-Derived Unit:
PZ-Derived Unit)a
Entry
Diisocyanate
[4]0:[PZ]0
Polymer
Yield (%)a
Mn (Mw/Mn)b
1
2
3
4
5
a
MDI
TDI
100:0
100:0
75:25
50:50
0:100
6a
6b
8a
8b
9
70
38
71
60
97
–
6300 (1.87)
2940 (1.76)
8870 (3.39)
8060 (2.47)
–
MDI
MDI
MDI
5:5
3:7
c
c
–
–
Determined by 1H NMR.
Not determined because of the insolubility of 9.
c
b
Estimated by SEC (eluent ¼ DMF containing 1 wt % lithium bromide,
PSt-standards).
however, addition of the DMF solution of 5a to an excess
amount of water led to emulsification, presumably due to
the amphiphilicity of 5a. To avoid such difficulty in isolation
of 5a, it was treated with acetic anhydride and pyridine to
convert the hydroxyl groups into less polar acetate. The
resulting polymer 6a became immiscible with water and
thus easily isolated by precipitation from water. The isolated
6a was further purified by precipitation from ether. Figures
1(b) and 2(b) show the 1H and 13C NMR spectra of 6a,
which clarified the structural similarity between the repeat-
ing unit of 6a and the model compound 3. The IR spectrum
of 6a indicated two strong absorptions at 1753 and 1664
cmꢀ1, which were attributable to ester C¼¼O and urea C¼¼O,
respectively. By SEC, the number average molecular weight
(Mn) and weight average molecular weight (Mw) of 6b were
estimated to be 6300 and 11,800, respectively. In a similar
way, polyaddition of 4 and tolylene-2,4-diisocyanate (TDI)
was performed (Table 1, Entry 2). The resulting polymer
was treated by acetic anhydride and pyridine, and thus the
corresponding polyurea 6b was obtained successfully.
should exhibit similar reactivity to those of a secondary dia-
mine 4 leading to statistic compositions of copolymers. Dia-
mine 4, prepared by the abovementioned procedure, was
mixed with PZ in feed ratios in 75:25 and 50:50, and these
diamine mixtures were dissolved in DMF containing lithium
chloride and treated with MDI to perform polyaddition (Ta-
ble 1, entries 3 and 4). The polyureas 7a and 7b formed in
situ were converted into 8a and 8b, respectively, by acetyla-
tion of the hydroxyl groups. These polymers were isolated
by precipitation from water. The compositions were deter-
1
mined by H NMR. As a typical example, the spectrum of 8b
is shown in Figure 3. The signals attributable to the MDI-
derived structures and those attributable to the 4-derived
structures were observed. By comparing the intensities of
these signals, the degrees of introduction of 4-derived com-
ponent were calculated. The resulting values were lower
than those expected from the feed ratios, implying that the
reaction of the amino groups of 4 with isocyanate was steri-
cally more hindered than that of PZ, presumably due to the
presence of bulky glucose-derived moieties. Isolation of poly-
urea 7a by precipitation from water was not successful due
to emulsification, while polyurea 7b with a smaller content
of 4-derived unit was isolated by precipitation from water
successfully. As can be expected from the presence of plural
hydroxyl groups in the side chain, 7b was hygroscopic and
thus removal of water from it by vacuum drying was not
easy. Besides the copolymerizations, polycondensation of PZ
Upon succeeding in the utilization of the sugar-modified dia-
mine 4 for polyurea synthesis, we examined synthesis of pol-
yureas with controlling content of the D-glucose-derived
structure by employing PZ as a comonomer (Scheme 4). The
reason why PZ was chosen from a wide variety of conven-
tional diamines was that PZ is a secondary diamine that
SCHEME 4 Synthesis of polyureas based on 4-PZ-MDI ternary
system.
FIGURE 3 1H NMR spectrum of 8b.
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13 Kaneko, Y.; Kadokawa, J.-I. J. Biomater. Sci. Polym. Ed.
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urea 9 (Table 1, Entry 5).
Properties of Polyureas
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The polyureas 6a, 6b, 7b, 8a, and 8b were soluble in DMSO
and DMF containing lithium chloride, while they were insolu-
ble in water, methanol, DMF, tetrahydrofuran, acetone, ethyl
acetate, and ether. Polyurea 9 was insoluble in water and all
the organic solvents tested for the other polyureas.
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Thermal stability of the polyureas was investigated by TGA.
The resulting profiles are shown in Figure 4. The profiles of
6a and 6b were similar to each other, as can be expected
from the structural similarity. The profiles of 8a and 8b
clarified that they were thermally more stable than 6a. Poly-
urea 9 obtained by polyaddition of MDI and PZ was ther-
mally most stable to imply the intrinsic high thermal stabil-
ity of urea-derivatives of PZ. The higher thermal stability of
8a and 8b than 6a can be attributable to the incorporation
of PZ-derived urea function.
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hexamethylene diamine by treatment with D-glucose and was
employed as a new diamine-type monomer with glucose-
derived moieties bearing unprotected hydroxyl groups. The
difference in intrinsic nucleophilicity between amino group
and hydroxyl group permitted the selective reaction of the
former with diisocyanate to give the corresponding polyureas
with endowing the side chains with the glucose-derived struc-
ture bearing plural hydroxyl groups. The present work has
proven the feasibility of our concept ‘‘utilization of N-glycosy-
lation as a method for facile modification of various amines
into the corresponding amine-type monomers.’’ Further exploi-
tation of the present methodology to development of unique
monosaccharide-derived polymers will be continued.
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