Direct oxidative amidation of aldoses by iodine in ammonia water

Article abstract of DOI:10.1002/jccs.200300018

Aldopentoses, aldohexoses and the benzylated derivatives reacted with iodine in ammonia water at room temperature to give their corresponding saccharide amides in high yields. The reactions proceeded with oxidation of the aldose hemiacetals by iodine to g

Full text of DOI:10.1002/jccs.200300018

Journal of the Chinese Chemical Society, 2003, 50, 129-133
129
Direct Oxidative Amidation of Aldoses by Iodine in Ammonia Water
Ming-Yi Chena (
Jiun-Jie Shieb (
), Jue-Liang Hsub (
),
) and Jim-Min Fangb* (
)
aDepartment of General Education, Taipei Nursing College, Taipei, Taiwan, R.O.C.
bDepartment of Chemistry, National Taiwan University, Taipei 106, Taiwan, R.O.C.
Aldopentoses, aldohexoses and the benzylated derivatives reacted with iodine in ammonia water at room
temperature to give their corresponding saccharide amides in high yields. The reactions proceeded with oxi-
dation of the aldose hemiacetals by iodine to generate the saccharide lactone intermediates, which underwent
ammonolysis in situ to give the saccharide amides.
Keywords: Aldoses; Amides; Iodine; Ammonia.
N
INTRODUCTION
We have recently found a direct method, using iodine in
O
H
C
CH2
CH2
i) I2, aq. NH3, r.t.
ii) Ac2O, py
OH
OAc
ammonia water, for transformation of aldehydes to nitriles.1
This transformation often occurs at room temperature within
a short period (< 1 h) in an efficient manner. A variety of alde-
hydes, including aromatic, heterocyclic, aliphatic, conju-
gated and polyhydroxy aldehydes, have thus been treated
with I2 in aqueous NH3 to afford their corresponding nitriles
with high yields (83-97%). The polyhydroxy aldehydes such
as 2-deoxy-D-ribose (1a) and 2,3,4,5,6-penta-O-benzyl-D-
glucose (1b) are especially attractive substrates, because they
are water-soluble and no protection of the hydroxyl groups is
required (Eqs. 1 and 2).
OH
OH
OAc
OAc
(1)
1a
2a (83%)
N
C
O
H
OBn
OBn
I2, aq. NH3, r.t.
BnO
BnO
OBn
OBn
OBn
OBn
OBn
(2)
OBn
1b
2b (85%)
In order to apply this simple, economic and environ-
mentally benign method to carbohydrate chemistry, we in-
vestigated further the reactions of aldoses with iodine in am-
monia water.
O
H
O
NH2
O
NH2
OH
OH
OH
OH
OH
OH
OH
OH
OAc
OAc
OAc
OAc
I2, aq. NH3, r.t.
Ac2O, py
(3)
RESULTS AND DISCUSSION
3a
4a
5a (71%)
should exhibit a signal around d 120 for the cyano group. In-
stead, the 13C NMR spectrum fit a structure of ribonamide
(4a)2 with the amido group displaying at d 178.6 (Eq. 3). Sub-
sequent peracetylation of this crude product (Ac2O, pyridine,
25 °C, 6 h) afforded 2,3,4,5-O-tetraacetyl-D-ribonamide (5a)
with full structural characterization.3
When D-ribose (1 mmol) was treated with iodine (1.2
mmol) in ammonia water (10 mL of 28% solution), the dark
solution became colorless after stirring at room temperature
for 6 h. The reaction mixture was concentrated under reduced
pressure to give a practically pure product. The 13C NMR
spectrum (CD3OD, 75 MHz) of this product showed five sig-
nals at d 63.0, 69.0, 69.4, 70.8 and 178.6. None of these sig-
nals could be attributed to the putative nitrile product, which
The aldopentoses and aldohexoses examined in this
study all reacted similarly with iodine in ammonia water to
Dedicated to Professor Fa-Ching Chen on the occasion of his ninetieth birthday.
* Corresponding author. E-mail: jmfang@ccms.ntu.edu.tw

130 J. Chin. Chem. Soc., Vol. 50, No. 1, 2003
Chen et al.
Table 1. Reactions of Aldoses with Iodine in Ammonia Water at Room Temperature, Giving Saccharide Amides
Aldose
Cosolvent
Reaction time (h)
Amide product (yield, %)
D-ribose (3a)
D-arabinose (3b)
D-xylose (3c)
D-glucose (3d)
D-galactose (3e)
D-fucose (3f)
2,3,4,6-tetra-O-benzyl-D-glucose (6a)
2,3,4,6-tetra-O-benzyl-D-galactose (6b)
2,3,4,6-tetra-O-benzyl-D-mannose (6c)
-
-
6
10
9
3
3
2
15
2
5aa (71)b, c
5ba (62)b, c
5ca (78)b, c
5da (87)b
5ea (85)b
5fa (90)b
7a (82)
-
-
-
-
THF
THF
THF
7b (85)
7c (89)
7
a The final product of two steps: (i) reaction with I2 in aqueous NH3, and (ii) acetylation with Ac2O in pyridine.
b The overall yield of two steps.
c Though the reaction with I2 in aqueous NH3 was clean as shown by the 13C NMR analysis, the overall yield
decreased due to incomplete acetylation.
afford the corresponding saccharide amides in good yields
(Table 1). These aldopentoses and aldohexoses usually exist
as the hemiacetal forms by linkage of the C-4 or C-5 hydroxyl
groups with the C-1 aldehyde groups. Our current method
thus provided a way to modify aldose derivatives, particu-
larly at the C-4 and C-5 positions. For example, a THF solu-
tion of 2,3,4,6-tetra-O-benzyl-D-glucose (6a) was treated
with iodine in ammonia water to give 2,3,4,6-tetra-O-ben-
zyl-D-gluconamide (7a) in 82% yield. The unprotected hy-
droxyl group at C-5 has been subjected to Moffatt or Swern
oxidation to give a saccharide ketoamide as a pivotal precur-
sor for the preparation of glyconolactams, azasugars and
L-aldohexoses.4,5 On the one hand, this ketoamide can be re-
duced by NaBH4 to give the saccharide amide with 5S-
chirality that eventually leads to L-aldohexoses.5 On the other
hand, this ketoamide can be converted to O-benzylated glu-
conolactam by consecutive condensation with NH3/MeOH
and reduction with Me3SiH/BF3.4a Reduction of the O-ben-
zylated gluconolactam with LiAlH4, followed by hydro-
genolysis of the benzyl groups, has been achieved to afford
deoxynojirimycin, an azasugar possessing glucosidase inhib-
iting activity.4d
Saccharide amides can be formed either by hydration of
saccharide nitriles,6 or by ammonolysis of saccharide lac-
tones4,5 as shown in Fig. 1. In order to discern these two possi-
ble reaction pathways, we prepared the saccharide lactone
8a4d and nitrile 9a.6d Lactone 8a was obtained by Moffatt or
Swern oxidation [Me2SO, (COCl)2] of tetrabenzylglucose
6a.4d,5a On the other hand, 6a reacted with hydroxylamine to
give an oxime, which underwent dehydration on treatment
with Ph3P/CBr4 to give nitrile 9a.6d Ammonolysis of lactone
8a in I2/NH3
solution proceeded rapidly (< 20 min),
(aq)
whereas complete hydration of nitrile 9a under the same con-
O
NH2
OR
OBn
OBn
O
NH2
O
NH2
OR
5
ammonolysis
O
[O]
O
BnO
BnO
5
O
Bn
RO
RO
O
OH
BnO
BnO
OR
OH
OR
OR
OR
OR
RO
O
BnO
NH2
OBn
5
OR
OR
8a
6a
5
BnO
4b R = H
5b R = Ac
4c R = H
5c R = Ac
5d R = Ac
7a R = Bn
N
C
OBn
OH
O
H
5
OBn
OBn
oxidative
amination
OBn
O
NH2
O
NH2
OR
O
NH2
OAc
BnO
BnO
7a
BnO
BnO
hydration
OBn
OH
OBn
OH
RO
RO
AcO
AcO
5
5
OBn
OH
OBn
OBn
OH
OR
OAc
9a
6a
OBn
CH3
Fig. 1. Two possible reaction pathways for the conver-
sion of aldoses to saccharide amides.
5e R = Ac
7b R = Bn
5f
7c

Direct Oxidative Amidation of Aldoses by Iodine in Ammonia Water
J. Chin. Chem. Soc., Vol. 50, No. 1, 2003 131
ditions required a prolonged period (18 h).7 On the other
hand, 2,3,4,6-tetrabenzyloxy-5-oxohexanenitrile, the ketoni-
trile prepared by Swern oxidation of 9a, did not show any ap-
parent hydration product on stirring in I2/NH3 (aq) solution for
24 h.7
moval of volatiles from the reaction mixture. The products of
D-sugar amides are applicable to the preparations of biologi-
cally active azasugars and L-sugars.4,5 As the amide group
can be transformed into other functional groups, for example
via Hofmann rearrangement to an amino group, the saccha-
ride amides are potentially used as chiral precursors in or-
ganic synthesis.
It is known that aldoses can be oxidized to aldonol-
actones by using Br2 or I2 as the oxidizing agents.8 For exam-
ple, N-acetylglucosamine and N-acetylgalactosamine are ox-
idized by bromine water to give saccharide lactones.8a,b
Perbenzyl-maltotriose and maltotetrose react with I2 in alka-
line conditions (KOH, MeOH, 40 °C, 50 min) to give the cor-
responding lactones.8c Peracetylmannose reacts sluggishly
(10 days at room temperature) with N-iodosuccinimide in
CH2Cl2 solution to produce mannono-1,5-lactone.8d On the
basis of these reports and our experimental results, formation
of saccharide amides was attributed to ammonolysis of the in-
termediate lactones. The aldopentoses and aldohexoses used
in this study tended to exist as cyclic hemiacetals, which
could be oxidized by I2 (or INH2)9 in ammonia water to give
saccharide lactones.
EXPERIMENTAL SECTION
Representative Procedure for the Reactions of Saccha-
rides with Iodine in Ammonia Water
CAUTION: It is known that iodine reacts with ammo-
nia water under certain conditions to give a black powder of
nitrogen triiodide monoamine (NI3 NH3).8b The dry powder
.
explodes readily by mechanical shock, heat or irradiation.
Although we did not have any incidents when handling the
reactants in this study, one should avoid using excess reagent.
A solution of 2,3,4,6-tetra-O-benzyl-D-glucose (1
mmol) and iodine (1.2 mmol) in ammonia water (10 mL of
28% solution) and THF (1 mL) was stirred at room tempera-
ture for the indicated time as monitored by TLC analyses.
The dark solution became colorless at the end of reaction.
The reaction mixture was charged with aqueous Na2S2O3 (0.5
mL of 5% solution), followed by extraction with Et2O (2 × 15
mL), to give a practically pure product of 2,3,4,6-tetra-O-
benzyl-D-gluconamide in 82% yield. For the water-soluble
substrates, such as D-ribose, the cosolvent (THF) is not
needed in the reaction. After the aldose was completely con-
sumed, the reaction mixture was concentrated under reduced
pressure, instead of extraction with Et2O, to give exclusively
the desired D-ribonamide2 (4a) as shown by the 13C NMR
analysis. Peracetylation of 4a with Ac2O in pyridine was car-
ried out to give 2,3,4,5-O-tetraacetyl-D-ribonamide (5a) for
full characterization.3
This reaction mode for conversion of aldoses to saccha-
ride amides via the intermediacy of aldolactones is different
from that found in our previous study1 for conversion of com-
mon aldehydes to nitriles. Except for 2-deoxy-D-ribose, the
aldehydes used in our previous study1 are not in hemiacetal
forms. The aldehyde groups may easily condense with NH3 to
form aldimines, which are subsequently oxidized by iodine to
give N-iodo aldimine intermediates.10 These N-iodo aldimine
intermediates may also be formed by condensation of the al-
dehydes with INH2. Elimination of HI from these intermedi-
ates in ammonia solution would occur rapidly to give the cor-
responding nitrile products. It is unclear why the reaction of
2-deoxy-D-ribose with I2/NH3 (aq) gives a nitrile product, but
not the corresponding amide.
In summary, our current method provides a convenient
way to convert aldopentoses, aldohexoses and their deriva-
tives to the corresponding saccharide amides by a direct oxi-
dative amidation in I2/NH3 (aq). This method shows distinct
advantageous features over the previously reported two-step
methods:5,6 (i) The transformation is realized in a simple
one-pot procedure, without primary preparations of the inter-
mediary saccharide lactones via Moffatt or Swern oxidations;
(ii) Iodine is utilized as a convenient and mild oxidizing
agent; (iii) Ammonia water (readily available) is used instead
of liquid ammonia; (iv) No organic solvent is required in the
reactions with water-soluble aldoses; (v) Protection of the
hydroxyl groups in aldoses is not mandatory in this transfor-
mation; and (vi) Practically pure saccharide amides are ob-
tained in high yields by extraction with ether or simply by re-
All the products 4a-c, 5a-f and 7a-c are known com-
pounds.
D-Ribonamide2 (4a)
13C NMR (CD3OD, 75 MHz) d 63.0, 69.0, 69.4, 70.8,
178.6.
D-Arabinamide2 (4b)
13C NMR (D2O, 75 MHz) d 64.7, 72.2, 72.4, 73.0,
180.0.
D-Xylonamide2 (4c)
13C NMR (D2O, 75 MHz) d 63.8, 70.8, 73.8, 74.1,

132 J. Chin. Chem. Soc., Vol. 50, No. 1, 2003
Chen et al.
180.0.
5.29 (1H, dd, J = 9.9, 1.9 Hz), 5.64 (1H, dd, J = 10.0, 1.9 Hz),
6.10 (1H, br s), 6.33 (1H, br s). 13C NMR (CDCl3, 100 MHz) d
20.3, 20.4, 20.5, 20.6, 20.7, 62.0, 67.3, 67.4, 67.8, 70.7,
168.9, 169.3, 169.6, 169.7, 170.3, 170.4. HRMS calcd for
C16H24NO11 (M + H) 406.1349; found 406.1332.
2,3,4,5-Tetra-O-acetyl-D-ribonamide3 (5a)
[a]D25 -32.6 (c 2.0, CHCl3), lit.3 -35.5 (CHCl3). 1H NMR
(CDCl3, 200 MHz) d 2.04 (3H, s), 2.06 (3H, s), 2.08 (3H, s),
2.10 (3H, s), 3.84 (1H, dd, J = 11.7, 7.4 Hz), 4.27 (1H, dd, J =
11.7, 5.1 Hz), 5.21-5.35 (2H, m), 5.71 (1H, dd, J = 10.3, 2.1
Hz), 5.90 (1H, br s, NH), 5.98 (1H, br s, NH). 13C NMR
(CDCl3, 50 MHz) d 20.1, 20.2, 20.3, 20.5, 61.4, 68.1, 71.8,
72.0, 167.9, 169.1, 169.5, 169.6, 170.1.
2,3,4,5-Tetra-O-acetyl-D-fuconamide11 (5f)
1H NMR (DMSO-d6, 400 MHz) d 1.05 (3H, d, J = 6.5
Hz), 1.95 (3H, s), 1.96 (3H, s), 2.06 (3H, s), 2.07 (3H, s), 4.99
(1H, m), 5.07 (1H, dd, J = 9.8, 2.0 Hz), 5.51 (1H, dd, J = 9.8,
2.0 Hz), 7.32 (1H, br s), 5.79 (1H, br s). 13C NMR (DMSO-d6,
75 MHz) d 16.0, 20.3 (2 ×), 20.6, 20.9, 66.6, 68.2, 70.0, 70.6,
168.1, 168.6, 169.6 (2 ×), 169.8.
2,3,4,5-Tetra-O-acetyl-D-arabonamide6a,6c (5b)
[a]D25 +21.2 (c 3.0, CHCl3), lit.6a +24.3 (CHCl3). IR
(KBr) 3454, 1750, 1699, 1374 cm-1. H NMR (CDCl3, 200
1
MHz) d 1.97 (3H, s), 1.98 (3H, s), 2.01 (3H, s), 2.11 (3H, s),
4.02 (1H, dd, J = 12.7, 4.9 Hz), 4.16 (1H, dd, J = 12.7, 2.7
Hz), 5.08 (1H, m), 5.35 (1H, d, J = 2.4 Hz), 5.62 (1H, dd, J =
9.0, 2.4 Hz), 6.27 (1H, br s), 6.58 (1H, br s). 13C NMR
(CDCl3, 50 MHz) d 20.3, 20.4, 20.5, 20.6, 61.6, 67.8, 68.9,
70.8, 169.0, 169.4, 169.5, 169.7, 170.5.
2,3,4,6-Tetra-O-benzyl-D-gluconamide4a,4d (7a)
1H NMR (CDCl3, 300 MHz) d 3.60 (1H, dd, J = 9.9, 5.2
Hz), 3.67 (1H, dd, J = 9.9, 3.0 Hz), 3.88 (1H, dd, J = 7.3, 5.6
Hz), 3.94 (1H, m), 4.10 (1H, dd, J = 5.0, 3.3 Hz), 4.26 (1H, d,
J = 3.3 Hz), 4.48-4.67 (5H, m), 4.70 (1H, d, J = 8.2 Hz), 4.74
(1H, d, J = 8.2 Hz), 5.92 (1H, br s), 6.63 (1H, br s), 7.23-7.43
(20H, m). 13C NMR (CDCl3, 75 MHz) d 71.1, 71.3, 73.3,
73.7, 74.1, 75.2, 77.7, 79.7, 80.5, 127.6, 127.6, 127.7, 127.8,
127.9, 128.2, 128.3, 128.4, 128.5, 136.7, 137.7, 138.0, 138.2,
174.2.
2,3,4,5-Tetra-O-acetyl-D-xylonamide6a,6c (5c)
IR (KBr) 3449, 1750, 1699, 1375 cm-1. 1H NMR (CDCl3,
200 MHz) d 1.95 (3H, s), 1.97 (3H, s), 2.02 (3H, s), 2.13 (3H,
s), 3.96 (1H, dd, J = 12.1, 6.0 Hz), 4.24 (1H, dd, J = 12.1, 4.3
Hz), 5.19-5.27 (2H, m), 5.51 (1H, dd, J = 6.1, 4.1 Hz), 6.47
(1H, br s), 6.55 (1H, br s). 13C NMR (CDCl3, 50 MHz) d 20.2,
20.3, 20.4, 20.5, 61.7, 69.1, 69.4, 71.2, 169.0, 169.4, 169.5,
169.9, 170.4.
2,3,4,6-Tetra-O-benzyl-D-galactonamide4d (7b)
1H NMR (CDCl3, 300 MHz) d 3.53 (1H, dd, J = 9.3, 6.4
Hz), 3.60 (1H, dd, J = 9.3, 6.4 Hz), 3.90 (1H, dd, J = 8.0, 1.2
Hz), 4.16 (1H, dd, J = 7.3, 5.4 Hz), 4.20 (2H, s), 4.35-4.72
(8H, m), 5.93 (1H, br s), 6.64 (1H, br s), 7.18-7.34 (20H, m).
13C NMR (CDCl3, 75 MHz) d 69.2, 71.4, 73.1, 73.2, 73.6,
75.0, 77.2, 79.4, 79.8, 127.4, 127.7, 127.8, 128.0, 128.1,
128.3, 128.6, 136.7, 137.8, 137.9, 13.8.0, 174.5.
2,3,4,5,6-Penta-O-acetyl-D-gluconamide6a,6b (5d)
Mp 181-183 °C, lit.6b 184-185 °C. [a]2D5 +26.1 (c 1.25,
CHCl3), lit.6b +23.6 (CHCl3). IR (KBr) 3414, 1758, 1699,
1377 cm-1. 1H NMR (CDCl3, 300 MHz) d 2.01 (3H, s), 2.03
(3H, s), 2.04 (3H, s), 2.09 (3H, s), 2.20 (3H, s), 4.12 (1H, dd, J
= 12.3, 5.6 Hz), 4.33 (1H, dd, J = 12.3, 3.9 Hz), 5.05 (1H, m),
5.32 (1H, d, J = 5.1 Hz), 5.46 (1H, dd, J = 6.2, 5.1 Hz), 5.65
(1H, t, J = 5.1 Hz), 5.86 (1H, br s), 6.16 (1H, br s). 13C NMR
(CDCl3, 75 MHz) d 20.2, 20.4 (2 ×), 20.6 (2 ×), 20.7, 61.6,
68.8, 69.4, 71.2, 168.6, 169.3, 169.6, 169.9 (2 ×), 170.7.
HRMS calcd for C16H24NO11 (M + H) 406.1349; found
406.1330.
2,3,4,6-Tetra-O-benzyl-D-mannonamide4d (7c)
1H NMR (CDCl3, 300 MHz) d 3.64-3.68 (2H, m), 3.88
(1H, dd, J = 7.1, 5.7 Hz), 4.02 (1H, m), 4.13 (1H, dd, J = 5.5,
3.8 Hz), 4.33 (1H, d, J = 3.8 Hz), 4.49 (1H, dd, J = 5.7, 3.3
Hz), 4.50-4.54 (4H, m), 4.57-4.68 (2H, m), 4.72 (2H, s), 5.73
(1H, br s), 6.59 (1H, br s), 7.17-7.39 (20H, m). 13C NMR
(CDCl3, 75 MHz) d 70.9, 71.2, 72.7, 73.4, 74.4, 74.6, 78.9,
80.0, 81.2, 127.6, 127.7, 127.8, 127.9, 128.0, 128.3, 128.4,
128.5, 137.1, 138.1, 138.3, 173.4.
2,3,4,5,6-Penta-O-acetyl-D-galactonamide6a,6b (5e)
Mp 169-170 °C, lit.6a 166-167 °C. [a]2D5 +25.6 (c 1.8,
CHCl3), lit.6a +27 (CHCl3). IR (KBr) 3441, 1750, 1679, 1378
cm-1. 1H NMR (CDCl3, 400 MHz) d 1.99 (3H, s), 2.03 (3H, s),
2.04 (3H, s), 2.05 (3H, s), 2.15 (3H, s), 3.80 (1H, dd, J = 11.6,
7.3 Hz), 4.22 (1H, dd, J = 11.6, 5.1 Hz), 5.19-5.22 (2H, m),
ACKNOWLEDGMENTS
We thank the National Science Council for financial
support and Dr. Chun-Chen Lin (Institute of Chemistry, Aca-

Direct Oxidative Amidation of Aldoses by Iodine in Ammonia Water
J. Chin. Chem. Soc., Vol. 50, No. 1, 2003 133
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