New efficient synthesis of β-glucosylamines of mono- and disaccharides with the use of ammonium carbamate

Full text of DOI:10.1023/A:1015428720733

Doklady Chemistry, Vol. 383, Nos. 4–6, 2002, pp. 89–92. Translated from Doklady Akademii Nauk, Vol. 383, No. 4, 2002, pp. 500–503.
Original Russian Text Copyright © 2002 by Likhosherstov, Novikova, Shibaev.
CHEMISTRY
New Efficient Synthesis of b-Glucosylamines of Mono-
and Disaccharides with the Use of Ammonium Carbamate
L. M. Likhosherstov, O. S. Novikova, and V. N. Shibaev
Presented by Academician N. K. Kochetkov January 8, 2002
Received January 9, 2002
In recent years, strategies to synthesize different amounts of the volatile salt restricts, however, the appli-
neoglucoconjugates used for studying the specificity of cation of the method in preparative syntheses. More-
biological interactions with the participation of carbo- over, glucosylamines are unstable in aqueous solutions
hydrate residues and for targeted transport of different and undergo fast hydrolysis at pH 1.5 to 9.0 and pro-
pharmaceuticals in organisms have been extensively duce diglucosylamines in concentrated solutions. The
developed. Glucosylamines of mono- and oligosaccha- rate of these reactions, which occur upon the isolation
rides are promising starting compounds for the synthe- of glucosylamines, depends considerably on the nature
sis of similar compounds. However, the available meth- of the sugar used, which strongly affects the yield and
ods for the synthesis of these compounds need purity of the resulting glucosylamines.
improvement.
Variation of the glucosylamine synthesis based on
the use of a saturated aqueous solution of (NH4)2CO3
Classical methods based on the reaction of
[7], as well as aqueous [8] or methanolic solutions [9]
monosaccharides with NH3 in a methanol solution (see
of NH3 in the presence of small amounts of (NH4)2CO3,
reviews [1, 2]) require a very long time for the reaction
were proposed later. The two last modifications made it
to be completed. Poor solubilities of oligosaccharides
possible to reduce the reaction time; however, they
in methanol hinder the application of this method, and
could not serve as general methods for preparing these
attempts to obtain glucosylamine from 2-acetamido-2-
compounds.
deoxy-D-glucose have resulted in many side reactions
[3]. In 1986, we put forward an efficient method for the
In this paper, we report on a new synthesis of β-glu-
synthesis of β-glucopyranosylamines from 2-aceta- cosylamines which provides a rather fast preparation of
mido-2-deoxyhexoses and their derivatives, which is derivatives of hexoses, pentoses, 2-acetamido-2-deoxy-
based on the use of a saturated aqueous solution of hexoses, and a number of disaccharides with high
NH4HCO3 [4]; the method was widely applied subse- yields in preparative amounts. The synthesis is carried
quently to the preparation of derivatives of hexoses, out with the use of mixtures of ammonium carbamate
6-deoxyhexoses, and oligosaccharides with different and an aqueous NH3 solution and involves intermediate
chain lengths [3, 5, 6]. The necessity of having a pro- isolation of the salts of glucosylamines with carbamic
longed and labor-consuming procedure for the evapora- acid, which are rather stable upon storage. Scheme 1
tion of aqueous solutions to remove considerable shows the reaction processes.
NH+4 + NH2COO–
2NH3 + CO2
(H2O)
NH2COONH4
NH3
NH2COONH4
Sug–OH
Sug(β)NH2
Sug(β)NH2 HOOCNH2
1b–9b
(H2O)
1a–9a
+CO2
–NH3 +NH3
–CO2
–NH3
[Sug(β)]2NH
1d–9d
Sug(β)NHCOONH4
1c–9c
Sug = D-Glcp (1), D-Galp (2), D-GlcNAcp (3),
Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Leninskii pr. 47, Moscow, 119991 Russia
0012-5008/02/0004-0089$27.00 © 2002 åÄIä “Nauka /Interperiodica”

90
LIKHOSHERSTOV et al.
D-Xylp (4), D-Ribp (5), D-Galp(β1–4)-D-Glcp (6),
D-Galp(α1–6)-D-Glcp (7), D-Glcp(β1–4)-D-Glcp (8),
D-Glcp(β1–6)-D-Glcp (9)
Scheme 1.
Optimum conditions were found using the reaction pylethylamine to prevent the hydrolysis of glucosyl-
with D-glucose as an example (Table 1). After keeping amine (method A).
a solution of the monosaccharide in a methanol–
NH4OH mixture with 2 equiv. of ammonium carbamate
(24 h at 37°C), the initial compound virtually com-
pletely transforms into glucosylamine 1a according to
electrophoresis data. Cooling of the reaction mixture
resulted in the precipitation of salt 1b, whose composi-
tion was confirmed by elemental analysis. The 1H NMR
spectrum of a DMSO-d6 solution of the compound
obtained showed only the signals characteristic for
β-glucopyranosylamine. At the same time in the region
of anomeric protons, the 1H NMR spectrum of a solu-
tion of the same compound in D2O (Table 2) showed a
rather intense signal from H-1 of N-(β-glucosyl)car-
bamate 1c (δ 4.68 ppm, cf. [6]) along with a signal from
H-1 of 1a (δ 4.08 ppm) and a weak signal correspond-
ing to H-1 of di-β-glucosylamine 1d. The formation of
compound 1c in an aqueous solution could be
explained by the hydrolysis of the salt, the decarboxy-
lation of the resulting carbamic acid, and the reaction of
the liberated glucosylamine with CO2 (Scheme 1). The
conversion of 1b into 1c also occurs on adding water to
a solution of 1b in DMSO (see note to Table 2).
Similar reaction conditions proved to be suitable for
preparing glucosylammonium carbamates 2b–9b
derived from a series of mono- and disaccharides
(Table 1). The ratio of methanol to concentrated
NH4OH in a reaction mixture and the reaction duration
were selected in a series of preliminary experiments
taking into account the solubility of initial sugars and
reaction products. The formation of derivatives of pen-
toses D-xylose (4b) and D-ribose (5b) proceeds mark-
edly faster than the synthesis of derivatives of hexoses
D-glucose (1b) and D-galactose (2b). The derivatives
of monosaccharides 2b–5b, lactose 6b, and gentiobiose
9b were precipitated from the reaction mixture, while
the glucosylammonium carbamates of melibiose 7b
and cellobiose 8b were precipitated by adding 2-pro-
panol.
By example of the preparation of 2-acetamido-2-
deoxy-D-glucopyranosylammonium carbamate (3b),
we demonstrated that the reaction could be carried out
without addition of concentrated NH4OH, although the
molar ratio of ammonium carbamate to sugar and the
reaction duration should be increased. Such a proce-
dure may be very useful for the synthesis of glucosy-
lamine derivatives from carbohydrates that are unstable
in the presence of aqueous ammonia solutions.
A facile transformation of salt 1b into unstable glu-
cosylcarbamate 1c was used for regeneration of free
glucosylamine 1a, which was isolated in quantitative
yield by concentrating a solution of the salt in methanol
1
The H NMR spectra of glucosylammonium car-
containing a small amount of water and N,N-diisopro- bamates 2b–9b in D2O (Table 2) always show signals
Table 1. Conditions of the synthesis of glucosylammonium carbamates 1b–9b and their transformation into free glucosyla-
mines 1a–9a
Reaction conditions*
Method of
Glucosylammonium
Yield, %
preparation of
Initial sugar
Volume ratio
concentration, M MeOH/conc. NH4OH
carbamate
Reaction time, h*
amine from salt**
1b
2b
3b
4b
5b
6b
7b
8b
9b
89
93
83
93
94
85
87
82
85
0.4
0.4
0.4
0.8
0.8
0.4
0.4
0.4
0.4
19
24
15
48
5
A
A
B
C
A
C
C
C
C
4
59***
19
19
4
3
20
10
25
12
4
1
4
* All reactions were carried out at 37°C and at an ammonium carbamate/sugar ratio of 2.0.
** See Experimental.
*** Water was used instead of concentrated NH OH; the ammonium carbamate/sugar ratio was 4.0.
4
DOKLADY CHEMISTRY Vol. 383 Nos. 4–6 2002

NEW EFFICIENT SYNTHESIS
91
1
Table 2. H NMR data for solutions of carbamates 1b–9b in D2O
Signals of H-1 (δ, ppm)a
corresponding to β-glucopyranosylamines 2a–9a and
β-glucosylcarbamates 2c–9c whose ratio depends on
the sugar nature and sometimes signals indicating a
slight admixture of diglucosylamines. As shown using
compounds 3b and 6b, as examples, only signals corre-
sponding to glucosylamines were observed in DMSO-
d6 solutions, while the addition of D2O resulted in the
emergence of signals indicating their partial transfor-
mation into glucosylcarbamates 3c and 6c.
Along with the above method A for the regeneration
of glucosylamine from its carbamate, we developed
two other simpler but not universal variants of the pro-
cess. One of them (method B with 3b as an example) is
based on the evaporation of methanolic solutions with-
out base added and is suitable for salts soluble in meth-
anol. In the other variant (method C with 4b and 6b–9b
as examples), aqueous salt solutions are treated with tri-
ethylamine, followed by precipitation of glucosyl-
amines via addition of alcohols.
Ratio
of a/c
Admixture
Carbamate
of d, %
a
c
d
1b
2b
3b
4b
5b
6b
7b
8b
9b
2.0b
2.0
2
3
4.08
4.02
4.68
4.65
4.72
4.61
4.87
4.72
4.74
4.73
4.70
4.29
4.23
–
4.16
–
3.3c not detectedd 4.13
1.3
0.6
3
4.02
not detected 4.27
2.0e not detected 4.11
–
1.1
1.5
2.0
5
2
4.14
4.13
4.31
4.32
–
not detected 4.10
a
All signals are doublets with J = 8.6–9.0 Hz.
b
Only 1a in DMSO-d (signal from H-1 at δ 3.77 ppm), a mixture
of 1a and 1c (4 : 1, signals of H-1 at 3.76 and 4.41 ppm, respecti-
vely) in DMSO-d –D O (4 : 1).
6
6
2
c
Thus, we developed a method for the synthesis of β-
glucosylamines with the use of ammonium carbamate
which provides an opportunity to obtain relatively stable
salts of these compounds with carbamic acid on a prepar-
ative scale in a rather simple manner; the salts may be
further converted into the corresponding glucosy-
lamines. The suggested method seems to be very prom-
ising for the preparation of these important compounds.
Only 3a in DMSO-d (signal from H-1 at δ 3.82 ppm), a mixture
6
of 3a and 3c (4 : 1, signals of H-1 at 3.85 and 4.49 ppm, respecti-
vely) in DMSO-d –D O (6 : 1).
6
2
d
e
Not detected.
Only 6a (signal from H-1 at δ 3.80 ppm) in DMSO-d , a mixture
6
of 6a and 6c (6 : 1, signals of H-1 at 3.81 and 4.46 ppm, respecti-
vely) in DMSO-d –D O (4 : 1).
6
2
EXPERIMENTAL
(10 mmol) of powdered 2-acetamido-2-deoxy-D-glu-
cose and 3.12 g (40 mmol) of ammonium carbamate in
24.6 mL of methanol and 0.42 mL of water was kept for
48 h at 37°C and 16 h at 5°ë. The resultant precipitate
was separated by filtration, washed with methanol and
ether, and dried to give 2.32 g (83%) of salt 3b.
1H and 13C NMR spectra were recorded in D2O at
24–30°ë on a Bruker WM-250 spectrometer (operating
at 250 MHz for 1H and 75 MHz for 13C) relative to ace-
tone or residual protons of the solvent (as an internal
standard). Electrophoresis was performed on Filtrak
FN1 paper in a 6% HCOOH solution (12 V cm–1, 1 h).
The compounds were detected by ninhydrin staining
and with the reagent sequence KIO4–AgNO3–KOH.
The reactions were carried out in screw-capped tubes.
Solutions were concentrated in vacuum on a water bath
at <30°C.
Transformation of Glucosylammonium Carbamates
into Glucosylamines
Method A. An 8-mL volume of methanol and
0.022 mL of N,N-diisopropylethylamine were added to
a solution of 50 mg of salt 1b, 2b, or 5b in 0.2 mL of
water. The solution was concentrated at 90 mmHg to
1 mL, and 3 mL of 2-propanol was added. The resulting
mixture was evaporated to dryness at 12 mmHg. The
residue was dried to produce glucosylamines 1a, 2a,
and 5a in ~100% yield.
b-D-Glucopyranosylammonium
carbamates
(general procedure). Methanol was added to a solu-
tion of hexose, pentose, or disaccharide and ammonium
carbamate in concentrated NH4OH, and the mixture
was kept at 37°C (see Table 1). Carbamates 1b, 2b, 4b–
6b, and 9b precipitated upon cooling the mixtures (5 to
−10°C, 1–16 h). Carbamates 7b and 8b were precipi-
tated from the reaction mixtures by 2-propanol (1.2 vol-
umes), and the resulting oily sediment was allowed to
stand for 3 h at –10°C and, then, was separated and trit-
urated with a methanol–2-propanol mixture (1 : 1) until
powder formation. The product was separated by filtra-
tion, washed with cold methanol and ether, and dried to
give salts 1b, 2b, and 4b–9b in a yield from 82 to 94%
(Table 1).
Method B. A 7-mL volume of methanol was added
to 50 mg of salt 3b, and the salt was dissolved at 50°C.
The solution was concentrated at 90 mmHg to 1 mL;
then, 2 mL of methanol was added and the mixture was
concentrated at 90 mmHg to 0.5 mL. Then, another
2 mL of methanol was added and the mixture was con-
centrated at 12 mmHg to dryness to leave 38.8 mg
(99%) of amorphous glucosylamine 3a.
Method C. (a) Triethylamine (0.04 mL), 0.25 mL of
2-Acetamido-2-deoxy-b-D-glucopyranosylam- methanol, and 0.5 mL of absolute ethanol were added
monium carbamate (3b). A mixture containing 2.21 g under stirring to a solution of 50 mg of salt 4b in 0.1 mL
DOKLADY CHEMISTRY Vol. 383 Nos. 4–6 2002

92
LIKHOSHERSTOV et al.
Table 3. Properties of glucosylammonium carbamates 1b–9b and glucosylamines 1a–9a
Elemental analysis data, found/calculated, %
Molecular
formula
[α]D
Gluco-
[α]D
[α]D
Carbamate
(c 1, water) sylamine (c 1, water) (reference)
C
H
N
1b
2b
3b
4b
5b
6b
7b
8b
9b
C7H16N2O7
C7H16N2O7
C9H19N3O7
C6H14N2O6
C6H14N2O6
34.99/35.00
34.90/35.00
38.43/38.43
34.73/34.29
34.58/34.29
6.65/6.71
6.73/6.71
7.20/6.81
6.84/6.71
6.76/6.71
6.63/6.51
6.78/6.72
7.03/6.51
6.86/6.51
11.35/11.66
+5.3°
1a
+19.8°
+52.2°
–5.2°
+20.8° [10]
+62.2° [10]
–4.7°[4]
–17.0°[9]
–17.4° [11]
+38.5° [12]
–
11.61/11.66 +28.6°
2a
14.73/14.94
13.36/13.33
13.24/13.33
6.81/6.96
+1.3°
–12.1°
–18.3°
+27.4°
+84.9°
+12.0°
–13.5°
3a
4a
–13.8°
–23.3°
+38.4°
+100.1°
+17.7°
–5.4°
5a
C13H26N2O12 38.57/38.81
C13H28N2O13* 36.67/37.14
C13H26N2O12 38.87/38.81
C13H26N2O12 37.98/38.81
6a
6.88/6.66
7a**
8a
7.31/6.96
+20.0° [12]
–
7.05/6.96
9a
* For monohydrate. Content of H O: found (%): 3.56, calculated (%): 4.28.
2
** The substance contains 5% of 7d according to the NMR spectrum in D O.
2
2. Isbell, H.S. and Frush, H.L., Methods in Carbohydrate
Chemistry, New York: Academic, 1980, vol. 8,
pp. 255−259.
of water, and the resulting mixture was kept for 16 h at
5°C. The resulting precipitate was separated by filtra-
tion, washed with a methanol–absolute ethanol (1 : 1)
mixture and ether, and dried to yield 29.2 mg (94%) of
glucosylamine 4a.
3. Manger, I.D., Rademacher, T.W., and Dwek, R.A., Bio-
chemistry, 1992, vol. 31, pp. 10724–10732.
4. Likhosherstov, L.M., Novikova, O.S., Derevitskaya, V.A.,
and Kochetkov, N.K., Carbohydr. Res., 1986, vol. 146,
pp. C1–C5.
(b) Triethylamine (0.042 ml) and 0.6 mL of metha-
nol were added under stirring to a solution of 80 mg of
salts 6b–9b in 0.1 mL of water, and absolute ethanol
was added under stirring until the appearance of intense
turbidity. The mixture was kept for 16 h at 5°C. The
resulting precipitate was separated by filtration, washed
with absolute ethanol and ether, and dried to produce
60–65 mg (88–95%) of glucosylamines 6a–9a.
5. Urge, L., Otvos, L., Lang, E., Wroblewski, K., Laczko, I.,
and Hollosi, M., Carbohydr. Res., 1992, vol. 235,
pp. 83–93.
6. Kallin, E., Lonn, H., Norberg, T., and Elofsson, M.,
J. Carbohydr. Chem., 1989, vol. 8, no. 4, pp. 597–611.
1
The data of H NMR spectra for the compounds
obtained are presented in Table 2, and elemental analy-
ses and optical rotation data are listed in Table 3.
7. Vetter, D. and Gallop, M.A., Bioconjugate Chem., 1995,
vol. 6, pp. 316–318.
8. Lubineau, A., Auge, J., and Drouillat, B., Carbohydr.
Res., 1995, vol. 266, no. 2, pp. 211–219.
9. Likhosherstov, L.M., Novikova, O.S., Shibaev, V.N., and
Kochetkov, N.K., Izv. Akad. Nauk, Ser. Khim., 1996,
no. 7, pp. 1848–1851.
ACKNOWLEDGMENTS
This work was supported by the Russian Foundation
for Basic Research, project no. 01–03–33267.
10. Isbell, H.S. and Frush, H.L., J. Org. Chem., 1958,
vol. 23, no. 9, pp. 1309–1319.
REFERENCES
1. Monsigny, M., Quetard, C., Bourgerie, S., Delay, D.,
11. Tipson, R.S., J. Org. Chem., 1961, vol. 26, no. 7,
pp. 2462–2465.
Pichon, C., Midoux, P., Mayer, R., and Roche, A.C., Bio- 12. Micheel, F., Frier, R., Plate, E., and Hiller, A., Chem.
chimie, 1998, vol. 80, pp. 99–108.
Ber., 1952, vol. 85, no. 11, pp. 1092–1096.
DOKLADY CHEMISTRY Vol. 383 Nos. 4–6 2002