Synthesis and characterization of a new methacrylic glycomonomer

Article abstract of DOI:10.3906/kim-1103-63

The carbohydrate containing monomer 3-O-(2′-hydroxy-3′- methacryloyloxypropyl)-1,2: 5,6-di-O-isopropylidene-α-D-glucofuranose was easily prepared from D-glucose and methacrylic acid in 4 steps. The structure of the new methacrylic monomer was confirmed using FTIR, NMR (including ¹H-NMR, ¹³C-NMR, COSY, HMQC and HMBC), and HPLC-MS. This work is part of our groups effort to obtain new polymers based on renewable resources with enhanced biodegradability and biocompatibility.

Full text of DOI:10.3906/kim-1103-63

Turk J Chem
35 (2011) , 757 – 767.
¨
˙
c
ꢀ TUBITAK
doi:10.3906/kim-1103-63
Synthesis and characterization of a new methacrylic
glycomonomer
1
2
1
ˇ
Liliana Marinela S¸TEFAN , Ana-Maria PANA , Mihai-Cosmin PASCARIU
Eugen S¸IS¸U3, Geza BANDUR1 and Lucian-Mircea RUSNAC1,∗
1University of Timi¸soara, Faculty of Industrial Chemistry and Environmental Engineering,
6 Carol Telbisz, 300001, Timi¸soara-ROMANIA
e-mail: lucian.rusnac@chim.upt.ro
2Technical University, Faculty of Chemical Engineering and Environmental Protection, 73
Prof. dr. docent Dimitrie Mangeron, 70050, Ia¸si-ROMANIA
3Institute of Chemistry, 24 Mihai Viteazul Blvd, 300223, Timi¸soara-ROMANIA
Received: 05.03.2011
The carbohydrate containing monomer 3-O-(2ꢀ -hydroxy-3ꢀ -methacryloyloxypropyl)-1,2:5,6-di-O-isoprop-
ylidene-α-D-glucofuranose was easily prepared from D-glucose and methacrylic acid in 4 steps. The structure
of the new methacrylic monomer was confirmed using FTIR, NMR (including 1 H-NMR, 13 C-NMR, COSY,
HMQC and HMBC), and HPLC-MS. This work is part of our group’s effort to obtain new polymers based
on renewable resources with enhanced biodegradability and biocompatibility.
Key Words: D-glucose, glycomonomer, biodegradability, methacrylic acid, epoxidation
Introduction
The field of biodegradable polymers represents one of the important industrial achievements of the 20th century,
but the current rising consumption of petrochemical raw materials associated with polymer production has
motivated many researchers to find alternative starting materials.1,2 It is predicted that by 2040 ground biomass
will be a cheaper raw material than petroleum hydrocarbons. The progressive transition of the chemical industry
toward renewable feedstock is emerging as an inevitable necessity.3 Therefore, carbohydrates are an excellent
substitute for products of fossil origin for industrial development.4−7 Polymers containing carbohydrate moieties
∗Corresponding author
757

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
have also proved to be biodegradable and biocompatible, and so this could be a viable alternative for developing
environmental friendly products.
Synthetic carbohydrate polymers are being increasingly investigated as biodegradable, biocompatible,
and biorenewable materials for use, among others, as water absorbents, chromatographic supports, and medical
devices.8,9 Moreover, polymers with pendant carbohydrate moieties have been useful in clinical diagnostic
applications, and for targeted gene therapies. Applications of these polymers are essential in surgery, for
prosthetic systems and in pharmacology.10−14
This paper presents the synthesis of a new D-glucose based glycomonomer, namely 3-O-(2ꢀ -hydroxy-3ꢀ -
methacryloyloxypropyl)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (4). Starting with D-glucose, this prod-
uct can be easily prepared in 4 steps involving isopropylidenation, allylation, epoxidation, and acylation of the
resulting “epoxy” diacetonated sugar (3) with methacrylic acid (Figure 1). (+)-D-glucose was submitted to di-
isopropylidenation according to the literature.15,16 The resulting 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose
(1) was protected with allyl chloride in anhydrous DMF using NaH as catalyst.17,18
Epoxides can be prepared by reacting vinyl groups with peroxy acids. From the various methods used
for this conversion, the one using meta-chloroperbenzoic acid (MCPBA) at low temperature seemed the most
appropriate for the preparation of compound 3.19 The oxirane or epoxy ring can be further homopolymerized or
reacted with active hydrogen containing compounds such as amines, phenols, or acids.20 We chose methacrylic
acid to construct a biocompatible vinylic monomer.21 The structure of the monomer 4 thus obtained was proved
using IR and NMR analyses while HPLC-MS confirmed its molecular weight.
6
6
5
O
O
4
1
9
HO
HO
O
5
O
4
O
O
1
9
7
12
O
OH
OH
O
a
b
12
7
O
8
3 2
10
O
8
O
3 2
10
14
O
11
HO
HO
11
13
15
D-Glucose
(1)
(2)
c
6
O
9
5
6
O
4
1
O
5
O
O
7
4
1
12
O
9
O
d
7
12
8
O
10
3
2
O
O
8
11
10
3 2
O
O
O
15
14
17
18
11
14
13
13
O
16
15
O
19
OH
(3)
(4)
Figure 1. Preparation of D-glucose monomer: (a) acetone, H2 SO4 ; (b) AllCl, NaH, DMF; (c) MCPBA, CHCl3 ; (d)
methacrylic acid, TEA.
758

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
Experimental
Materials and methods
All reagents were used as purchased. The syntheses were monitored using thin-layer chromatography performed
on silica gel plates, Merck silica gel 60 F254 aluminum sheets.
The FTIR spectra were recorded on a Jasco FT/IR-410 spectrometer. The FTIR analyses were done
using KBr plates for liquid samples (530-4000 cm−1) and KBr pellets for solids (400-4000 cm−1). NMR spectra
were recorded on a Bruker Avance DRX 400 spectrometer using TMS as reference and CDCl3 as solvent.
Chemical shifts are given in ppm; coupling constants (J) are in Hz. Atom numbering is given in Figure 1.
Mass spectrometry experiments were performed using a quadrupole time-of-flight mass spectrometer, equipped
with an electrospray ion source (Agilent 6520 Accurate Mass Q-ToF LC/MS). The samples were dissolved in
a chloroform/methanol mixture (6:4). The solutions were introduced into the ESI source via a syringe pump
at a flow rate of 0.2 mL/min. The electrospray interface was set in positive ionization mode with the capillary
voltage at 4000 V and the heat source at 325 ˚C, in full scan spectra (m/z 100-1000). Nitrogen was used as a
drying and nebulizing gas (7 L/min, 35 psi). Data were collected and processed using MassHunter Workstation
software.
Synthesis of compounds 1-4
1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (1)
This compound was synthesized according to the literature.15 White crystals; mp 105-107 ˚C; Rf (hexane/ethyl
acetate 2:1) 0.28; IR (cm−1): 3429, 2985, 2952, 2903, 2872, 1457, 1376, 1318, 1249, 1222, 1162, 1069, 1030,
847, 784; data are consistent with the values reported in the literature.22
3-O-allyl-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (2)
This compound was synthesized according to the literature.17,18 Colorless syrup; Rf (hexane/ethyl acetate
6:1) 0.3; IR (cm−1): 3082, 2990, 2935, 2894, 1737, 1649, 1649, 1457, 1428, 1373, 1255, 1214, 1166, 1078, 1023;
1 H-NMR and 13 C-NMR are according to the literature.23
3-O-(2ꢀ ,3ꢀ -epoxypropyl)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (3)
3-O-allyl-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (2) (1.00 g, 3.33 mmol) in 5 mL CHCl3 was cooled to
0 ˚C. MCPBA (2.29 g, 13.27 mmol, 4 equiv.) was added. The reaction mass was stirred for 24 h. The mixture
was diluted with CHCl3 and washed with brine. The organic phase was dried over Na2 SO4 and concentrated
under vacuum. The product was purified by recrystallization from cyclohexane. White crystals; 0.895 g (85%
yield); Rf (hexane/ethyl acetate 2:1) 0.40; IR (cm−1): 3055, 2987, 2934, 2892, 1734, 1457, 1374, 1255, 1214,
1166, 1079, 1020, 849, 759, 637, 537; 1 H-NMR (δ, ppm): 1.32 (s, 3H, H-12, H-12ꢀ ), 1.35 (s, 3H, H-10, H-10ꢀ ),
1.43 (s, 3H, H-9, H-9ꢀ ), 1.50 (s, 3H, H-11, H-11’), 2.62 (dd, J=4.8, 2.8, H-15b’), 2.65 (dd, J=5.0, 2.6, H-15b),
2.80 (t, J=4.6, H-15a), 2.82 (t, J=4.6, H-15a’), 3.15 (H-14, H-14ꢀ ), 3.48 (dd, J=11.6, 6.4, 0.37H, H-13b’), 3.64
759

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
(dd, J=11.8, 5.0, 0.61H, H-13b), 3.89 (H-13a), 3.95 (H-13a’), 4.00 (H-6b, H-6b’, H-3, H-3ꢀ ), 4.11 (H-4, H-4ꢀ ,
H-6a, H-6a’), 4.31 (H-5, H-5ꢀ ), 4.55 (d, J=3.6, H-2), 4.60 (d, J=3.6, H-2ꢀ ), 5.88 (d, J=3.6, H-1), 5.89 (d, J=3.6,
H-1’); 13 C-NMR (δ, ppm): 25.4 (C-10, C-10ꢀ ), 26.2 (C-12, C-12ꢀ ), 26.8 and 26.9 (C-9, C-9ꢀ , C-11, C-11’),
44.1 (C-15), 44.4 (C-15ꢀ ), 50.5 (C-14), 50.7 (C-14ꢀ ), 67.4 (C-6, C-6ꢀ ), 70.6 (C-13), 72.1 (C-13ꢀ ), 72.4 (C-5),
72.4 (C-5ꢀ ), 81.1 (C-4, C-4ꢀ ), 82.5 (C-2ꢀ ), 82.6 (C-2), 82.9 (C-3), 82.9 (C-3ꢀ ); 105.2 and 105.2 (C-1, C-1’), 109.1
(C-7, C-7ꢀ ), 111.8 (C-8, C-8ꢀ ); ESI-MS: calcd. for [C15 H24 O7 Na]+m/z = 339.15, found: m/z = 339.10
[M+Na]+ (95%); calcd. for [C15 H24 O7 K]+ 355.10, found 355.07 [M+K]+ (5%).
D-glucose monomer (4)
To a solution of 3 (2 g, 6.32 mmol) in 10 mL of DMF were added methacrylic acid (4.29 mL, 4.36 g, 50.6 mmol)
and triethylamine (0.7 mL, 0.51 g, 5.06 mmol) dropwise. The mixture was stirred vigorously while being heated
to 65 ˚C. After 24 h, the mixture was cooled by adding distilled water. The resulting product was extracted
into CH2 Cl2 , then washed with water, and dried over Na2 SO4 . The product was purified by silica gel column
chromatography (hexane/ethyl acetate 1:1). Brownish viscous syrup; 1.65 g (65% yield); Rf (hexane/ethyl
acetate) (1:1) 0.38; IR (cm−1): 3482, 2987, 2934, 2896, 1719, 1637, 1459, 1375, 1216, 1167, 1076, 1020, 946,
848, 637, 540; 1 H-NMR (δ, ppm): 1.32 (s, 3H, H-12), 1.37 (s, 3H, H-10), 1.44 (s, 3H, H-9), 1.50 (s, 3H,
H-11), 1.95 (s, 3H, H-19), 2.90 and 2.97 (OH, OH’), 3.46 (H-13b), 3.62 (H-13b’), 3.81 (H-13a’), 3.90 (H-13a),
4.02 (H-6b), 4.03 (H-14), 4.06 (H-3), 4.11 (H-4), 4.16 (H-6a), 4.21 (H-15), 4.330 (H-5); 4.38 (H-15ꢀ ), 4.57 (H-2),
5.60 (t, 0.78 H, H-18b), 5.66 (t, 0.24 H, H-18b’), 5.90 (H-1), 6.14 (s, 0.77 H, H-18a), 6.22 (s, 0.22 H, H-18a’);
13 C-NMR (δ, ppm): 18.0 (C-19ꢀ ), 18.3 (C-19), 25.1 (C-10ꢀ ), 25.1 (C-10), 26.2 (C-12, C-12ꢀ ), 26.8, 26.8 and
26.9 (C-9, C-9ꢀ , C-11, C-11’); 65.0 (C-15), 65.1 (C-15ꢀ ); 67.9 and 67.9 (C-6, C-6ꢀ ), 69.5 (C-14, C-14ꢀ ), 71.0
(C-13ꢀ ), 72.9 (C-13), 72.9 (C-5, C-5ꢀ ), 81.3 (C-4, C-4ꢀ ), 82.6 (C-2, C-2ꢀ ), 83.1 (C-3ꢀ ), 84.5 (C-3), 105.6 (C-1),
105.7 (C-1’), 109.5 (C-7ꢀ ), 109.5 (C-7), 112.1 and 112.1 (C-8, C-8ꢀ ), 126.1 (C-18), 127.3 (C-18ꢀ ), 135.9 (C-17),
136.0 (C-17ꢀ ), 167.3 (C-16), 171.2 (C16ꢀ ); ESI-MS: calcd. for [C19 H30 O9 Na]+ m/z = 425.19, found: m/z
= 425.09 [M+Na]+ (100%).
Results and discussion
FT-IR study
Allylation of 1 was readily proven from the FTIR spectra. The intense O-H bond stretching absorption band
at 3429 cm−1 disappeared in the product 2 spectrum. The medium intensity νas C=CH2 appeared at 3082
cm−1 while ν C=C revealed itself at 1645 cm−1 , both belonging to the allylic residue from the third OH of
the furanosic ring. Both signals disappeared in the compound 3 spectrum as the epoxidic structure was formed;
this and the epoxidic ν O-CH from 3055 cm−1 confirmed the oxidation of the double bond.
The FTIR spectrum of 4 confirms the structure of the D-glucose monomer. While the C=O from the
esteric group shows a strong absorption band at 1719 cm−1 , the signal corresponding to νas C-O esteric bond
overlaps with the acetal bands that appear around 1160 cm−1 in all mentioned compounds. The broad peak
from 3482 cm−1 confirms the generated OH, while the signal at 1637 cm−1 is characteristic of the C=C bond
from the methacrylic moiety.
760

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
NMR study
The NMR spectroscopy also confirmed the D-glucose derivatives structure. From 1 H-NMR spectroscopy we
could observe that the singlet at 3.024 ppm corresponding to the free hydroxyl proton from 1 had disappeared
(Figure 2). This confirms that O-allylation was achieved. Figure 3 displays the 1 H-NMR spectrum of allylated
product. The synthesized compound 2 shows a shift value increase of 7-8 ppm at the alkylated carbon, typical
for the conversion of a hydroxyl group into an alkoxyl.24 The attached proton suffers a displacement in the
opposite direction (from 4.305 to 3.947 ppm)
The 1 H-NMR spectrum of the epoxidated product 3 indicated the formation of both cis- and trans-
epoxides (∼ 3:2 ratio using protons 15b/15b’) (Figure 4). The presence of the 2 diastereomers increased the
complexity of this NMR spectrum (and also in the case of 4) by doubling the 13 C and 1 H signals. As expected,
the signals corresponding to the double bond protons of compound 2 (5.893 ppm and 5.254 ppm) are replaced
by those of the epoxy group in compound 3 (2.708 ppm and 3.154 ppm, in this particular order). The allylic
protons also suffer a similar shift to the right, and also an increase in the difference of magnetic vicinity. An
increase in the magnetic shielding could be observed for carbons 14 (from 134.16 to 50.71/50.51) and 15 (from
117.32 to 44.43/44.07) of compound 3 when compared to compound 2.
6.0
5.0
4.0
3.0
2.0
1.0
PPM
Figure 2. 1 H-NMR spectrum of 1.
761

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
7.5
7.5
7.0
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
ppm
Figure 3. 1 H-NMR spectrum of 2.
7.5
7.5
7.0
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0 ppm
Figure 4. 1 H-NMR spectrum of 3.
762

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
The 1 H spectrum of the D-glucose monomer (4) is presented in Figure 5 and shows the specific double
bond protons in 2 groups (5.5-6.5 ppm) and the methyl (1.95 ppm) from the methacrylic moiety. From protons
18a/18a’ and 18b/18b’ we obtained a 3:1 ratio between the 2 diastereomers. The protons 14 and 15 move to
higher values when compared with the same positions in compound 3. Hydroxylic protons show faint signals
at about 2.9 ppm. The esteric carbon atom gives a typical signal at about 170 ppm, while both double bond
carbon atoms appear near 130 ppm in the 13 C spectrum of compound 4. C-14 and C-15 move approximately
20 ppm to higher values when compared to compound 3.
7.5
7.5
7.0
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5 ppm
Figure 5. 1 H-NMR spectrum of 4.
MS analysis
Soft ionization methods in mass spectrometry are now widely available for structure elucidation of natural
products, particularly for glycoconjugates.25−27 This is why we performed HPLC-ESI-MS analyses on our
products. These were detected as Na or K adducts. The mass spectrum for compound 2 is presented in Figure
6. The peak observed at m/z = 323.11 is associated with the presence of the single-charge sodium adduct.
The peak at m/z = 623.25 corresponds to the dimeric sodium adduct [2M+Na]+ . Furthermore, other ions of
m/z = 363.14 (the base peak), 379.33, and 703.31 could be attributed to sodium adducts [M+C3 H4 +Na)]+
[M+C3 H4 O+Na)]+ , and [2(M+C3 H4)+Na)]+
,
.
763

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
Figure 6. ESI mass spectrum of 2.
Figure 7 displays the mass spectrum for 3. The most abundant ion corresponds to single-charge sodium
adduct at m/z = 339.10. The peaks observed at m/z = 317.09 and m/z = 355.08 are associated with [M+H]+
and the presence of the potassium adduct [M+K]+ , respectively. The peaks accompanying the base peak are
[2M+C3 H6 O2 +Na]+ at m/z= 729.36 and [2(M+C3 H6 O2)+Na]+ at m/z= 803.48, corresponding to the
dimeric adduct with sodium and C3 H6 O2 . Moreover, an additional peak can be observed at m/z = 413.22
and can be associated with [M+C3 H6 O2 +Na]+ . CID MS/MS of the sodium adduct at 339.10 displayed 2 M
= 58 losses (at m/z = 281.06 and 223.02), assigned to the cleavage of the isopropylidene protecting groups.
The epoxidic oxygen loss can be clearly seen at m/z = 323.80, while the peak at m/z = 144.98 indicates the
leaving of both acetal groups and of the epoxidic 3 carbon atom chain (Figure 8).
Figure 7. ESI mass spectrum of 3.
764

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
Figure 8. MS/MS spectrum of 3.
Figure 9 displays the mass spectrum for 4. The base peak is observed at m/z = 425.09 and is associated
with the presence of the single-charge sodium adduct. Another ion of m/z = 464.02 is also detectable and
can be attributed to the sodium adduct [M+C3 H3 +Na)]+ . The peaks at m/z = 287.04 and m/z = 345.08
indicate the loss of the 2 isopropylidene units, while the peak at m/z = 143.03 was associated with the cleavage
of the glycosidic moiety at C-13.
Figure 9. ESI mass spectrum of the D-glucose monomer 4.
765

Synthesis and characterization of a new..., L. M. S¸TEFAN, et al.
Acknowledgments
This work was partially supported by the strategic grant POSDRU/88/1.5/S/50783, Project ID50783 (2009),
co-financed by the European Social Fund - Investing in People, within the Sectoral Operational Programme
Human Resources Development 2007/2013.
This paper was supported by the project PERFORM-ERA ”Postdoctoral Performance for Integration in
the European Research Area” (ID-57649), financed by the European Social Fund and the Romanian Govern-
ment.
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