Convenient synthesis of glucosamine and mannosamine starting from glucose

Full text of DOI:10.1002/bkcs.10349

Note
DOI: 10.1002/bkcs.10349
BULLETIN OF THE
S.-J. Kim and H. Cho
KOREAN CHEMICAL SOCIETY
Convenient Synthesis of Glucosamine and Mannosamine
Starting from Glucose
*
Se-Jin Kim and Hyeongjin Cho
Department of Chemistry, College of Natural Sciences, Inha University, Incheon 402-751, Korea.
*E-mail: hcho@inha.ac.kr
Received February 24, 2015, Accepted March 18, 2015, Published online June 25, 2015
Keywords: Glucosamine, Mannosamine, L-Glucosamine, L-Mannosamine
Glucosamine and mannosamine are 2-amino-2-deoxyhexoses
that contain an amino group replacing 2-hydroxyl group of
glucose and mannose, respectively. Glucosamine is the build-
ing unit of chitin, a major component in the exoskeletons of
arthropods, and an important precursor in the glycosylation
of proteins and lipids. Mannosamine, 2-epimer of glucosa-
mine, is a biosynthetic precursor of sialic acid; enzymatic con-
densation of N-acetyl mannosamine and pyruvate produces
sialic acid. Increased interest in the biochemical function of
glucosamine and mannosamine raised the need for the
L-isomers or isotope-labeled forms of these aminosugars,
and led us to study the convenient synthetic route for those.1–4
Glucosamine is mostly obtained by hydrolysis of naturally
occurring chitin. Mannosamine can be obtained by enzymatic
cleavage ofsialicacidinasmallquantity.5,6 Mannosaminecan
also be obtained by alkaline epimerization of 2-hydroxyl
group of a glucosamine derivative.7 A classical strategy for
the synthesis of mannosamine is to replace 2-hydroxyl group
of mannitol derivatives with an amino group followed by
selective oxidation to obtain an aldose.8,9 Chemical
approaches to prepare 2-aminohexose include introduction
of an azido function followed by reduction of the azido group
into amine. Xue and Guo used 2,3-epoxide of a glucose deriv-
ative for nucleophilic ring opening with an azide.10 Another
widely used strategy is azidonitration of tri-acetyl glycal,
which was found more convenient for our purpose and
adopted in this study.11,12
Tri-O-acetyl-D-glucal is commercially available and the
synthetic protocol is well established.9 The literature proce-
dure was reproduced in this study to start from L-glucose
the synthesis of L-isomers of glucosamine and mannosamine.
Isotope-labeled D-glucose could also be the starting point for
the labeled forms of these aminosugars. Preparation of tri-O-
acetyl-D-glucal can be accomplished in three sequential reac-
tion steps, including peracetylation of glucose, substitution of
1-acetoxy group with bromide, and reductive elimination of
acetoxy bromide. These reactions can be performed in one
pot without separation of the intermediate products and we
obtained the tri-acetyl glucal (2) in a 72% overall yield.13
The overall synthetic strategy is as shown in Figure 1. Azi-
donitration of tri-acetyl glucal with sodium azide and ceric
ammonium nitrate (CAN) produced a mixture of 3 and 4,
which appear as a single spot on thin-layer chromatography
(TLC). After acetolysis of the nitrates, the products 5 and 6
were separable on TLC. Equatorial orientation of all of the
acetoxy groups of tri-acetyl glucal (2) did not discriminate
the two faces of the double bond of 2 and resulted in the for-
mation of 5 and 6 in a comparable ratio. 1H NMR spectrum of
the crude product shows the presence of both α and β anomers
of 5 and 6 (Figure 2). The peaks at δ 5.57, 5.86, 6.14, and
6.31 correspond to 1-H of the pyranosides as assigned in
Figure 2(a). Difficulties were found in the chromatographic
separation of 5 and 6 due to low solubility of 6 in chromato-
graphic solvent systems and it was circumvented by isolating
part of 6 by recrystallization prior to column purification. The
crystallized form of 6 contained only the α anomer of 6
(Figure 2(b)). When the mother liquor was purified by column
chromatography, 5 and 6 was separated from each other, both
as mixtures of α and β anomers. When the α/β mixture of 6 in
MeOH was kept on a shelf for days, the β anomer isomerizes to
α form with crystallization of the α isomer. Compound 6 can
be thus obtained as an α form, but 5 as a α/β mixture. Isolated
yields of 5 and 6 were 37 and 31%, respectively. Separation of
5 and 6 affords the divergence point for the two isomeric ami-
nosugars. Removal of acetoxy groups followed by reduction
of the azido function afforded glucosamine and mannosamine
as hydrochloride salts.
Some of the previous procedures leading to 2-amino func-
tionality in hexose required tedious processes or, in some
cases, they were hardly reproducible in our laboratory. The
present procedure is a combination of known reactions and
offers an expedient route to glucosamine and mannosamine
producing good yields consistently. With the procedures
developed in this study, we synthesized L-isomers of glucosa-
mine and mannosamine starting from L-glucose. Current pro-
cedure also provides a convenient route for isotope-labeled
forms of the aminosugars which would be valuable tools for
biochemical research.
Experimental
Tri-O-acetyl-D-glucal (2).13 D-Glucose (5.0 g, 28 mmol) was
added to a stirred mixture of acetic anhydride (20 mL) and
60% HClO4 (0.14 mL) at 40 ꢀC during 20 min and maintained
Bull. Korean Chem. Soc. 2015, Vol. 36, 1916–1918
© 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Figure 2. 1H NMR spectra of (a) a mixture of 5 and 6 (both α/β anom-
ers) in the crude product, (b) 6 obtained by recrystallization, (c) 6
obtained from column chromatography, and (d) 5 from column
chromatography.
Figure 1. Strategy for the synthesis of D-glucosamine and D-manno-
samine. Reagents and conditions: (a) (i) Ac2O, cat. HClO4, 40 ꢀC, 20
min, (ii) Br2, P, H2O, room temperature, 3 h, (iii) Zn powder, AcOH/
NaOAc, CuSO4Á5H2O, H2O, 0 ꢀC, 3 h, 72% in three steps; (b) NaN3,
CAN, CH3CN, −15 ꢀC, overnight; (c) AcOH, NaOAc, 100 ꢀC, 1.5 h,
recrystallizationandcolumnchromatography, 37%5and31%6from
2; (d) 4 M HCl, 40 ꢀC, overnight; (e) H2 (1 atm), 10% Pd/C, MeOH-
H2O-4 M HCl = 27:2:1, room temperature, 1 day, 61% 8 from 5, 61%
10 from 6.
solution was extracted six times with CHCl3 (10 mL). The
CHCl3 extracts were combined and washed with cold H2O
(20 mL), cold half-saturated Na2CO3 solution (20 mL), and
cold H2O (20 mL). It was then dried, concentrated, and puri-
fied with column chromatography (SiO2, hexane:EtOAc =
2:1) to obtain tri-O-acetyl-D-glucal as a syrup (5.6 g, 72%).
1H NMR (400 MHz, CDCl3) δ 2.04 (s, 3H), 2.07 (s, 3H),
2.09 (s, 3H), 4.19 (dd, 1H, J = 12.0 Hz, 3.2 Hz), 4.22–4.27
(m, 1H), 4.39 (dd, 1H, J = 6.4 Hz, 3.6 Hz), 4.84 (dd, 1H, J
= 6.4 Hz, 3.6 Hz), 5.22 (dd, 1H, J = 7.6 Hz, 6.0 Hz),
4.32–4.35 (m, 1H), 6.46 (dd, J = 6.4 Hz, 1.2 Hz).
at that temperature for 40 min. After addition of red phospho-
rus (1.5 g, 48 mmol), the reaction flask was cooled to 0 ꢀC and
Br2 (9 g, 56 mmol) was added during 40 min. H2O (1.5 mL)
was then added during 20 min. The reaction mixture was stir-
red at room temperature for 3 h. The mixture was filtered with
suction through a celite pad, which was washed with
CH3CO2H (2 mL). The filtered solution containing tetra-O-
acetyl-α-D-glucopyranosyl bromide was saved to be used in
the next step.
CH3CO2NaÁ3H2O (20 g) was dissolved in H2O (29 mL)
and CH3CO2H (20 mL) in 500 mL Erlenmeyer flask and the
solution was cooled in an ice-salt bath. Zinc dust (11 g, 168
mmol) and then a solution of CuSO4Á5H2O (1.1 g) in H2O
(4 mL) were added into the solution and stirred for 5 min. Into
theresulting suspension wasaddedthebromide solutionsaved
previously over a period of 2 h while cooling in an ice-salt
bath. After stirring for an additional 3 h at 0 ꢀC, the mixture
was filtered and the filter paper was washed with 50% acetic
acid (20 mL). H2O (50 mL) was added into the filtrate, and the
Compounds 5 and 6.12 A solution of tri-O-acetyl-D-glucal
(5.65 g, 20.8 mmol)inanhydrousCH3CN(70 mL)wascooled
at −15 ꢀC and added into a solution of NaN3 (2.02 g, 31.1
mmol) and CAN (34.1 g, 62.2 mmol) in anhydrous CH3CN
(40 mL) at −15 ꢀC. After stirring overnight at −15 ꢀC, the reac-
tion mixture was mixed with cold EtOAc (150 mL) and H2O
(100 mL). The separated organic layer was washed with cold
H2O (3 × 35 mL), dried over Na2SO4, and concentrated to
obtain a mixture of 3 and 4 as a syrup (7.5 g). The mixture
of3and4wasmixedwithCH3CO2H(50 mL)andsodiumace-
tate (3.3 g), and heated at 100 ꢀC for 1.5 h. The reaction mix-
turewaspouredintocoldEtOAc(260 mL)andH2O(200 mL).
The organic layer was separated, washed with cold saturated
NaHCO3 solution (3 × 50 mL) and cold H2O (100 mL) suc-
cessively, dried over Na2SO4 and concentrated to obtain a
mixture of 5 and 6 as a thick syrup (8.6 g). The syrup was dis-
solved in MeOH (20 mL) and stored at −20 ꢀC overnight to
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KOREAN CHEMICAL SOCIETY
obtain 1.3 g of amorphous solids. The solids were recrystal-
lized in MeOH to obtain 6 (1.0 g) as crystals. The mother
liquors were combined and purified by SiO2 column chroma-
tography (hexane:EtOAc = 3:1) to obtain 5 (2.90 g, 36.5%)
and 6 (2.44 g including the recrystallization product,
30.8%). Combined yield was 67% from tri-O-acetyl glucal.
Compound 5. Rf = 0.40 (hexane-EtOAc 2:1); mp
D-Mannosamine hydrochloride. The procedure for D-
glucosamine hydrochloride was repeated starting with 6
(435 mg, 1.14 mmol) except the recrystallization step. After
hydrogenation, the reaction mixture was filtered and concen-
trated to obtain a syrup (370 mg). It was dissolved in 95%
EtOH (1.5 mL) and kept at −20 ꢀC. Scratching the surface
of the flask helps crystal formation. The yield was 151
mg (61%).
1
114–116 ꢀC; H NMR (400 MHz, CDCl3) δ 2.00 (s), 2.02
(s), 2.05 (s), 2.07 (s), 2.08 (s), 2.17 (s), 3.62–3.80 (m),
3.76–3.80 (m), 4.01–4.08 (m), 4.25–4.30 (m), 4.99–5.11
(m), 5.43 (dd, J = 10.4 Hz, J = 9.2 Hz), 5.53 (d, J = 8.4 Hz),
6.27 (d, J = 4.0 Hz); 13C NMR (100 MHz, CDCl3) δ 20.70,
20.81, 21.02, 21.07, 60.46, 61.59, 62.75, 67.97, 68.07,
69.92, 70.92, 72.84, 72.87, 90.13, 92.72, 168.66, 168.70,
169.68, 169.77, 169.92, 170.19, 170.67.
Acknowledgments. This study was supported by Inha Uni-
versity and the Basic Science Research Program through the
National Research Foundation of Korea (NRF) funded by
the Ministry of Education, Science and Technology (2010-
0022853).
1
Supporting Information. H and 13C NMR spectra for com-
Compound 6 (α-anomer). Rf = 0.25 (hexane-EtOAc 2:1);
mp 130–132 ꢀC; 1H NMR (400 MHz, CDCl3) δ 2.05 (3H, s),
2.09(3H, s), 2.11(3H, s), 2.16(3H, s), 4.00–4.03(2H, m), 4.09
(1H, dd, J = 12.4 Hz, 2.4 Hz), 4.24 (1H, dd, J = 12.8 Hz, 4.8
Hz), 5.35–5.42 (2H, m), 6.11 (1H, d, J = 2.0 Hz); 13C NMR
(100 MHz, CDCl3) δ 20.68, 20.78, 20.88, 21.05, 60.71,
61.98, 65.52, 70.74, 70.95, 91.56, 168.37, 169.55,
170.23, 170.87.
D-Glucosamine hydrochloride. The suspension of 5 (749
mg, 1.96 mmol) in 4 M HCl (8 mL) was stirred overnight at
40 ꢀC. The solids dissolve slowly as the reaction proceeds.
Activated carbon (200 mg) was added and stirred for 10
min. After filtration to remove carbon, 1-butanol was added
and evaporatedin vacuotoobtain 7 asa syrup (371 mg). Crude
7 was dissolved in a mixture of MeOH-H2O-4 M HCl (27:2:1)
and hydrogenated at room temperature and 1 atm of H2 in the
presence of 10% Pd/C. After 1 day, the reaction mixture was
filtered over a celite pad, concentrated to ca. 1 g, mixed with
EtOH (1.5 mL), and left at 4 ꢀC overnight. Solids thus
obtained were recrystallized again in a mixture of EtOH-
H2O (4:1) to obtain crystals of D-glucosamine hydrochloride
(118 mg, 0.547 mmol, 28%). Combined mother liquor was
used to harvest additional products (140 mg, 33%) by repeated
recrystallization in EtOH.
pounds 5, 6, 8, and 10 are available.
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Bull. Korean Chem. Soc. 2015, Vol. 36, 1916–1918
© 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de 1918