Selection of protecting groups and synthesis of a β-1,4-GlcNAc-β- 1,4-GlcN unit

Article abstract of DOI:10.1007/s00706-009-0172-0

The synthesis of the disaccharide tert-butyldimethylsilyl (4-O-acetyl-2-azido-3,6-di-O-benzyl-2-deoxy-β-d-glucopyranosyl)-3, 6-di-O-benzyl-2-deoxy-2-phthalimido-β-d-glucopyranoside, designed as a repeating unit appearing in oligo- and polysaccharides, whi

Full text of DOI:10.1007/s00706-009-0172-0

Monatsh Chem (2009) 140:1245–1250
DOI 10.1007/s00706-009-0172-0
ORIGINAL PAPER
Selection of protecting groups and synthesis
of a b-1,4-GlcNAc-b-1,4-GlcN unit
Toshinari Kawada Æ Yuko Yoneda
Received: 28 March 2009 / Accepted: 29 July 2009 / Published online: 1 September 2009
Ó Springer-Verlag 2009
Abstract The synthesis of the disaccharide tert-butyldi-
methylsilyl (4-O-acetyl-2-azido-3,6-di-O-benzyl-2-deoxy-
b-D-glucopyranosyl)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-
b-D-glucopyranoside, designed as a repeating unit appearing
in oligo- and polysaccharides, which exhibits a distinguished
‘‘obverse–reverse’’ property in b-1,4-glucan chain, was
accomplished. This disaccharide was synthesized by glyco-
sylation of a phthalimido sugar with an azido sugar. A
selective removal of the two different protecting groups atC-2
for obtaining 2-acetamido-4-O-(2-amino-2-deoxy-b-D-glu-
copyranosyl)-2-deoxy-b-D-glucopyranose indicates that the
selection and combination, using phthalimido and azido as
protecting groups, are an excellent strategy for synthesizing
such target disaccharides.
nano-materials, since two different properties can be
attached on alternate sides [1].
For synthesizing b-1,4-glucans having two faces origi-
nating from the monosaccharide residue, it is a prerequisite
that one of the constituents of the disaccharide unit has two
kinds of protecting groups that can be cleaved selectively.
Both protecting groups should be stable under the reaction
conditions for the introduction and/or cleavage of the
alternate protecting group and during the glycosylation
reaction applied for extension of the glucan chain.
Chitin/chitosan, one of typical b-1,4-glucans, show
higher nucleophilicity for attachment of a variety of func-
tional groups by means of acetamido/free amino groups at
the C-2 position. Hence, oligo- and polysaccharides
repeating 2-amino-2-deoxy-D-glucose (D-glucosamine) and
2-acetamido-2-deoxy-D-glucose (N-acetyl-D-glucosamine)
alternatively are interesting target molecules, which present
model compounds of de-acetylated chitin having randomly
distributed acetyl groups (degree of substitution = 0.5) [2].
In this manuscript, the selection of two protecting
groups, the synthesis of a repeating disaccharide unit and
suitable de-protection conditions are described.
Keywords Carbohydrates ꢀ Drug research ꢀ Glycosides ꢀ
Oligosaccharides
Introduction
The b-1,4-glucan chain consists of monosaccharide resi-
dues turning in
a ‘‘obverse–reverse’’ manner, thus
potentially exhibits two faces. The potential two faces
cannot be recognized in the original chain, but would be
distinguished by introducing the same functional group at
the same carbon position in each monosaccharide moiety
of the two neighboring residues. This b-1,4-glucan pre-
senting two faces is one of the most promising novel
Results and discussion
The repeating disaccharide unit contains two kinds of
D-glucosamine residues with different protecting groups at
C-2, finally converted into free amino and acetamido
groups, respectively. The acetamido group itself is a potential
protecting group, but it easily forms an oxazoline under
glycosylation conditions and leads to complex product
mixtures [3–5]. After promising preliminary reactions and
searching the literature [6], the azido and phthalimido
groups were selected as protecting groups. The azido group
T. Kawada (&) ꢀ Y. Yoneda
Graduate School of Life and Environmental Sciences,
Kyoto Prefectural University, Shimogamo, Sakyo-ku,
Kyoto 606-8522, Japan
e-mail: kawada@kpu.ac.jp
123

1246
T. Kawada, Y. Yoneda
is known to be stable under several conditions, though its
introduction process is crucial. The phthaloyl group is also
stable under various conditions and usually can be easily
introduced and cleaved [7]. Both azido and phthalimido
groups can be converted into free amino groups and/or
acetamido groups [8].
tert-Butyldimethylsilyl 2-deoxy-3,6-di-O-benzyl-2-phtha-
limido-b-D-glucopyranoside (4) was prepared from
established compound 1 [12–14] via benzylidenation,
benzylation, and selective reductive ring-opening reaction
of the benzylidene moiety. The glycosylation reaction
between phthalimido acceptor 4 and azido donor 5 was
conducted under trimethylsilyl trifluoromethanesulfonate
(TMSOTf) promotion in dichloromethane at -20 °C using
the same molar amount of 4 and 5. The imidate 5 was
consumed within 2 h, and a mixture of a- and b-glycosides
was produced. The anomers were separated with flash col-
umn chromatography (ethyl acetate:toluene = 1:15, v/v) to
obtain b-glycoside 6 (26%). Normally the glycosylation
reaction in acetonitrile preferentially gives b-glycosides;
however, in this case many by-products were observed. Other
catalysts, such as boron trifluoride–diethyl etherate, trifluo-
romethanesulfonic acid, silver trifluoromethanesulfonate and
tin (II) trifluoromethanesulfonate, afforded lower yields than
The phthalimido group at C-2 performs neighboring
group participation [4, 9] to ensure b-selective glycoside
formation for a gluco-type donor. In the case of glycosyl-
ation reactions using azido donors, the stereochemical
outcome and yield highly depend on reaction conditions
and reaction partners [10, 11]. Based on the knowledge
above, a phthalimido moiety, not an azido moiety, is
advantageous for use as a glycosyl donor. However, if the
phthalimido donor is used in our case, the synthesized
disaccharide equips an azido group at its reducing end,
which indicates disadvantages for the following glysosy-
lation reaction used as a glycosyl donor. Hence, a
disaccharide 6 was designed to have the phthalimido group
at the neighboring position, albeit the azido donor is used
as a glycosyl donor.
1
that obtained with TMSOTf. The H NMR spectrum of 6
shows two doublets for anomeric protons at d = 4.48 and
5.34 ppm, having coupling constants 8.3 and 8.1 Hz,
respectively, thus indicating that both glycosidic bonds are
b-configured.
The synthetic route for the repeating disaccharide unit is
presented in Scheme 1.
Scheme 1
OH
O
HO
HO
OTBDMS
NPhth
1
OBn
N3
O
BnO
AcO
O
PhCH(OMe)2,
OTBDMS
NPhth
BnO
O
-TsOH, diox.
p
6
OBn
O
Ph
Ph
(1) H NCH CH NH , -BuOH
n
2
2
2
(2) Ac2O, Pyrid2ine
O
O
OTBDMS
NPhth
HO
2
OBn
O
N3
BnO
O
OTBDMS
PhCH2Br, NaH,
TBAI, THF
AcO
BnO
O
OBn
NHAc
7
O
O
NaOMe, MeOH
O
OTBDMS
BnO
NPhth
3
OBn
O
N3
BnO
HO
O
TES, TFA,
CH2Cl2
OTBDMS
BnO
O
OBn
NHAc
8
OBn
TBAF, THF
O
HO
OTBDMS
BnO
4
NPhth
OBn
O
N3
BnO
HO
O
BnO
OH
O
OBn
TMSOTf,
CH2Cl2
NHAc
9
10% Pd-C,
THF/EtOH/water
N3
OC(=NH)CCl3
BnO
AcO
OH
O
O
OBn
NH2
5
HO
HO
O
HO
O
OH
OH
NHAc
10
123

Selection of protecting groups
1247
(dd, 1H, J1, 2 = 8.0 Hz, J2, 3 = 10.6 Hz, H-2), 4.28 (dd,
Disaccharide 6 was treated with ethylenediamine in n-
butanol [15] for 8 h until all starting material 6 was con-
sumed. The crude reaction product was directly used in the
acetylation reaction to obtain acetamido disaccharide 7 in
53% yield over two steps. The acetyl and tert-butyldi-
methylsilyl (TBDMS) groups were sequentially cleaved to
afford compound 9 in 82% yield. Subsequently, the azido
and benzyl groups were converted to the free amino and
hydroxyl groups, respectively, by hydrogenation using
10% palladium–carbon at normal pressure to give disac-
charide 10 in 72% yield. We were able to establish a
straightforward method for the preparation of disaccharide
repeating units, using suitable protecting groups.
1H, J5,
1H, J2, = 10.6 Hz, J3, = 8.7 Hz, H-3), 5.42 (d, 1H,
= 4.6 Hz, J6a,
= 10.1 Hz, H-6a), 4.67 (dd,
6b
6a
3
4
J1, 2 = 8.0 Hz, H-1), 5.54 (s, 1H, CHPh), 7.32–7.51 (m, 5H,
Ph), 7.60–7.82 (m, 4H, Phthaloyl) ppm; 13C NMR (125 MHz,
CDCl3): d = -5.7, -4.0 (2 9 SiMe), 17.3 (Cq), 25.1 (t-Bu),
58.8 (C-2), 66.1 (C-5), 68.0 (C-3), 68.5 (C-6), 82.2 (C-4), 93.7
(C-1), 101.7 (CHPh), 123.2 (Phthaloyl), 126.3, 128.2, 129.1,
131.4, 137.0 (Ph) ppm; [a]D = -33.0°cm3g-1dm-1 (c = 1.0,
CHCl3).
tert-Butyldimethylsilyl 3-O-benzyl-4,6-O-benzylidene-2-
deoxy-2-phthalimido-b-D-glucopyranoside
(3, C34H39NO7Si)
To a stirred solution of 25.0 g 2 (48.9 mmol) in 145 cm3
anhydrous THF 2.35 g sodium hydride dispersed in
mineral oil (60%, 58.7 mmol) and 812 mg tetra-n-butyl-
ammonium iodide (TBAI, 2.20 mmol) were added at 0 °C.
After 30 min 6.89 cm3 benzyl bromide (58.7 mmol) was
added to the reaction mixture, and stirring was continued at
room temperature for 2 h. Finally, the reaction mixture was
filtered through a pad of Celite and worked up to give a
yellow solid. Recrystallization from EtOH gave 22.8 g
(78%) 3 as colorless crystals. Rf = 0.54 (EtOAc/n-hexane,
Experimental
General methods
Nuclear magnetic resonance (NMR) spectra were measured
with tetramethylsilane as an internal standard. The
assignments of the signals were determined using H–1H
1
correlated spectroscopy and/or 13C–1H heteronuclear mul-
tiple-quantum correlation technique. Coupling constants
(J) are given in Hz. Anhydrous dichloromethane and tet-
rahydrofuran were prepared by distilling from phosphorus
pentoxide and sodium/benzophenone. Flash column chro-
matography was performed on silica gel (Wakogel FC-40).
Preparative thin-layer chromatography (TLC) was done on
silica gel plates (Kieselgel 60 F254, Merck). Results of
elemental analyses agreed favorably with calculated val-
ues. Unless otherwise indicated, the usual workup for each
reaction mixture consists of extraction with ethyl acetate,
washing with brine, drying over sodium sulfate, and
evaporation in vacuo.
1
1:4, v/v); H NMR (500 MHz, CDCl3): d = -0.12, 0.13
(s, 6H, 2 9 SiMe), 0.67 (s, 9H, t-Bu), 3.65 (ddd, 1H, J4, 5
= 9.0 Hz, J5, 6a = 5.1 Hz, J5, 6b = 10.1 Hz, H-5), 3.83 (t,
1H, J3, 4 = 9.0 Hz, J4, 5 = 9.0 Hz, H-4), 3.86 (t, 1H, J5, 6b
= 10.1 Hz, J6a, 6b = 10.1 Hz, H-6b), 4.18 (dd, 1H, J1, 2
8.3 Hz, J2, = 10.6 Hz, H-2), 4.35 (dd, 1H, J5,
=
=
3
6a
5.1 Hz, J6a,
= 10.6 Hz, J3, = 9.0 Hz, H-3), 4.50–4.80 (m, 2H,
= 10.1 Hz, H-6a), 4.45 (dd, 1H, J2,
6b
3
4
CH2Ph), 5.42 (d, 1H, J1, 2 = 8.3 Hz, H-1), 5.62 (s, 1H,
CHPh), 6.88–7.54 (m, 10H, Ph), 7.70–7.73 (m, 4H,
Phthaloyl) ppm; 13C NMR (125 MHz, CDCl3): d =
-5.6, -4.3 (2 9 SiMe), 17.5 (Cq), 25.2 (t-Bu), 58.0 (C-2),
66.2 (C-5), 68.8 (C-6), 73.9–74.3 (2 9 CH2Ph), 74.3 (C-3),
83.2 (C-4), 93.9 (C-1), 101.3 (CHPh), 123.2 (Phthaloyl),
126.1, 127.3, 128.0–129.0, 133.8, 138.0 (2 9 Ph) ppm;
[a]D = ?28.0°cm3 g-1 dm-1 (c = 1.0, CHCl3).
tert-Butyldimethylsilyl 4,6-O-benzylidene-2-deoxy-2-
phthalimido-b-D-glucopyranoside (2, C27H33NO7Si)
A solution of 23.8 g TBDMS 2-deoxy-2-phthalimido-b-
D-glucopyranoside (1, 56.2 mmol) [12–14], 16.9 cm3
benzaldehyde dimethyl acetal (113.0 mmol) and 214 mg
p-toluenesulfonic acid monohydrate (1.10 mmol) in
357 cm3 1,4-dioxane was agitated under reduced pressure
(30 mmHg) at 30 °C for 13 h. The reaction mixture was
neutralized with sodium bicarbonate and filtered. The
filtrate was concentrated in vacuo to give crude crystals.
Recrystallization from ethanol gave 25.0 g derivative 2
(87%) as colorless crystals. Rf = 0.53 (EtOAc/n-hexane,
tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-phthali-
mido-b-D-glucopyranoside (4, C34H41NO7Si)
To a stirred solution of 6.10 g 3 (10.1 mmol) in 48.8 cm3
anhydrous CH2Cl2 8.00 cm3 triethylsilane (TES,
50.1 mmol) and 3.86 cm3 trifluoroacetic acid (50.1 mmol)
were added at 0 °C. After stirring at room temperature for
5 h, the reaction mixture was worked up to give an oily
residue. The residue was purified by flash column chro-
matography using a solvent mixture of EtOAc/toluene (1:7,
v/v) to give 4.50 g (74%) 4 as a colorless oil. Rf = 0.47
1
1:2, v/v); H NMR (500 MHz, CDCl3): d = -0.10, 0.14
(s, 6H, 2 9 SiMe), 0.69 (s, 9H, t-Bu), 3.19 (br s, 1H, 3-OH),
3.55 (t, 1H, J3, 4 = 8.7 Hz, J4, 5 = 8.7 Hz, H-4), 3.57 (ddd,
1H, J4, 5 = 8.7 Hz, J5, 6a = 4.6 Hz, J5, 6b = 10.1 Hz, H-5),
3.78 (t, 1H, J5, 6b = 10.1 Hz, J6a, 6b = 10.1 Hz, H-6b), 4.15
1
(EtOAc/n-hexane, 1:2, v/v); H NMR (500 MHz, CDCl3):
d = -0.11, 0.03 (s, 6H, 2 9 SiMe), 0.65 (s, 9H, t-Bu),
3.04 (br s, 1H, 4-OH), 3.65 (ddd, 1H, J4, 5 = 9.6 Hz, J5, 6a
123

1248
T. Kawada, Y. Yoneda
= 5.0 Hz, J5, 6b = 4.6 Hz, H-5), 3.78 (dd, 1H, J5, 6b
=
tert-Butyldimethylsilyl 2-acetamido-4-O-(4-O-acetyl-2-
azido-3,6-di-O-benzyl-2-deoxy-b-D-glucopyranosyl)-3,6-
di-O-benzyl-2-deoxy-b-D-glucopyranoside
4.6 Hz, J6a,
= 5.0 Hz, J6a, 6b = 10.1 Hz, H-6a), 3.83 (dd, 1H, J3, 4
= 10.1 Hz, H-6b), 3.82 (dd, 1H, J5,
6a
6b
=
8.3 Hz, J4, 5 = 9.6 Hz, H-4), 4.12 (dd, 1H, J1, 2 = 8.3 Hz,
J2, 3 = 11.0 Hz, H-2), 4.28 (dd, 1H, J2, 3 = 11.0 Hz, J3, 4
= 8.3 Hz, H-3), 4.54–4.76 (m, 2H, CH2Ph), 5.36 (d, 1H,
J1, 2 = 8.3 Hz, H-1), 7.67–7.80 (m, 4H, Phthaloyl) ppm;
13C NMR (125 MHz, CDCl3): d = -5.6, -4.3 (2 9
SiMe), 17.4 (Cq), 25.2 (t-Bu), 57.5 (C-2), 70.8 (C-6),
73.7 (2 9 CH2Ph), 74.1 (C-5), 74.2 (C-4), 78.4 (C-3), 93.3
(C-1), 123.0–123.2 (Phthaloyl), 127.3, 127.6–128.2, 128.4,
129.0, 131.6, 133.7, 137.7, 138.2 (2 9 Ph) ppm; [a]D =
?21.0°cm3 g-1 dm-1 (c = 1.0, CHCl3).
(7, C50H64N4O11Si)
To a solution of 100 mg compound 6 (0.10 mmol) in
5 cm3 n-butanol 270 mm3 ethylenediamine (3.96 mmol)
was added dropwise at 0 °C. The reaction mixture was
stirred at 90 °C for 8 h, and finally the solvent was
removed by co-evaporation with EtOH to afford a yellow-
ish residue. The residue was re-dissolved in 3 cm3 pyridine
and 5 cm3 acetic anhydride was added at 0 °C. The
reaction mixture was stirred overnight at room temperature.
After workup a yellowish residue was obtained, which was
purified by flash column chromatography using a solvent
mixture of EtOAc/n-hexane (1:2, v/v) to yield 47.0 mg
(53%) 7 as a colorless oil. Rf = 0.61 (EtOAc/n-hexane,
tert-Butyldimethylsilyl 4-O-(4-O-acetyl-2-azido-3,6-di-
O-benzyl-2-deoxy-b-D-glucopyranosyl)-3,6-di-O-benzyl-2-
deoxy-2-phthalimido-b-D-glucopyranoside
1
1:2, v/v); H NMR (500 MHz, CDCl3): d = 0.07, 0.11 (s,
6H, 2 9 SiMe), 0.87 (s, 9H, t-Bu), 1.80, 1.82 (s, 6H,
(6, C56H64N4O12Si)
To a stirred solution of 3.4 g trichloroacetoimidoyl
4-O-acetyl-2-azido-3,6-di-O-benzyl-2-deoxy-a/b-D-glucopy-
ranoside (5, 6.0 mmol) [16–18] and 3.6 g 4 (6.0 mmol) in
40 cm3 anhydrous CH2Cl2 22 mm3 TMSOTf (120 lmol)
were added dropwise at -20 °C. After stirring for 1 h, the
reaction mixture was neutralized with triethylamine and
worked up to afford a yellow oily residue. The residue
was purified by flash column chromatography using a
solvent mixture of EtOAc/toluene (1:15, v/v) to give a
colorless oil that was crystallized from EtOH to obtain
1.56 g (26%) colorless crystals of 6. Rf = 0.52 (EtOAc/n-
hexane, 1:2, v/v); 1H NMR (500 MHz, CDCl3): d =
-0.10, 0.04 (s, 6H, 2 9 SiMe), 0.67 (s, 9H, t-Bu), 1.83 (s,
0
0
0
0
2 9 CH3CO), 3.28 (t, 1H, J2 , 3 = 9.6 Hz, J3 , 4 = 9.6 Hz,
H-30), 3.31–3.36 (m, 2H, H-50, H-60b), 3.35 (ddd, 1H,
J1,
0
J1 ,
= 7.6 Hz, J2, = 8.8 Hz, H-2), 3.40 (dd, 1H,
3
2
= 8.3 Hz, J2 , = 9.6 Hz, H-20), 3.44 (dd, 1H,
20
30
0
0
0
0
0
J
5 , 6 a = 3.5 Hz, J6 a, 6 b = 10.3 Hz, H-60a), 3.57 (ddd, 1H,
J4, 5 = 8.8 Hz, J5, 6a = 3.2 Hz, J5, 6b = 2.1 Hz, H-5), 3.79
(dd, 1H, J5, 6b = 2.1 Hz, J6a, 6b = 11.0 Hz, H-6b), 3.90
(dd, 1H, J5, 6a = 3.2 Hz, J6a, 6b = 11.0 Hz, H-6a), 4.01 (t,
1H, J2, 3 = 8.8 Hz, J3, 4 = 8.8 Hz, H-3), 4.07 (t, 1H, J3, 4
= 8.8 Hz, J4,
= 8.8 Hz, H-4), 4.29–4.39 (m, 4H,
20
5
CH2Ph), 4.45 (d, 1H, J1 , = 8.3 Hz, H-10), 4.53–4.87
0
0
0
0
0
(m, 4H, CH2Ph), 4.98 (t, 1H, J3 , 4 = 9.6 Hz, J4 , 5 =
9.6 Hz, H-40), 5.01 (d, 1H, J1, 2 = 7.6 Hz, H-1), 5.47 (br s,
1H, NH), 7.22–7.30 (m, 20H, 4 9 Ph) ppm; 13C NMR
(125 MHz, CDCl3): d = -5.3, -4.3 (2 9 SiMe), 17.9(Cq),
20.7, 23.5 (2 9 CH3CO), 25.6 (t-Bu), 58.5 (C-2), 66.5 (C-20),
68.4 (C-6), 69.5 (C-60), 71.1 (C-40), 73.3 (C-50), 73.4, 73.5,
73.8, 74.9 (4 9 CH2Ph), 74.6 (C-5), 76.8 (C-3), 78.1 (C-4),
80.5 (C-30), 95.0 (C-1), 100.8 (C-10), 127.4–128.4, 137.6–
139.0 (4 9 Ph), 169.6, 169.9 (2 9 CH3CO) ppm; [a]D =
-14.0°cm3 g-1 dm-1 (c = 1.0, CHCl3).
0
0
40
= 9.6 Hz, J3 ,
30
3H, CH3CO), 3.31 (t, 1H, J2 ,
= 9.6 Hz, H-30), 3.35–3.39 (m, 2H, H-50, H-60b), 3.43
(dd, 1H, J1 , = 8.3 Hz, J2 , = 9.6 Hz, H-20), 3.47–
0
0
20
30
3.50 (m, 1H, H-60a), 3.66 (ddd, 1H, J4, 5 = 9.7 Hz, J5, 6a
= 3.3 Hz, J5, 6b = 1.2 Hz, H-5), 3.79 (dd, 1H, J5, 6b
1.2 Hz, J6a, = 11.0 Hz, H-6b), 3.98 (dd, 1H, J5,
= 3.3 Hz, J6a, 6b = 11.0 Hz, H-6a), 4.15 (dd, 1H, J1, 2
=
6b
6a
=
8.1 Hz, J2, = 10.9 Hz, H-2), 4.16 (dd, 1H, J3,
3
4
3
= 8.7 Hz, J4, = 9.7 Hz, H-4), 4.32 (dd, 1H, J2,
5
= 10.9 Hz, J3, = 8.7 Hz, H-3), 4.35–4.59 (m, 6H,
4
tert-Butyldimethylsilyl 2-acetamido-4-O-(2-azido-3,6-di-
O-benzyl-2-deoxy-b-D-glucopyranosyl)-3,6-di-O-benzyl-2-
deoxy-b-D-glucopyranoside (8, C48H62N4O10Si)
CH2Ph), 4.48 (d, 1H, J1 , = 8.3 Hz, H-10), 4.56–4.81
0
20
0
0
= 9.6 Hz, J4 ,
40
(m, 2H, CH2Ph), 4.99 (t, 1H, J3 ,
50
= 9.6 Hz, H-40), 5.34 (d, 1H, J1, = 8.1 Hz, H-1),
To a solution of 240 mg 7 (0.26 mmol) in 3 cm3 methanol
15.0 mm3 sodium methoxide solution in methanol (28%,
0.27 mmol) was added dropwise at 0 °C. The reaction
mixture was stirred at room temperature for 9 h and
afterwards was neutralized with DOWEX 50W-X8 (H?)
resin. The resin was filtered off; the filtrate was concen-
trated in vacuo and purified by flash column
chromatography using a solvent mixture of EtOAc/n-
hexane (1:2, v/v) to yield 182 mg (78%) 8 as a colorless
oil. Rf = 0.57 (EtOAc/n-hexane, 1:2, v/v); 1H NMR
2
6.83–7.40 (m, 20H, 4 9 Ph), 7.59–7.78 (m, 4H, Phthaloyl)
ppm; 13C NMR (125 MHz, CDCl3): d = -5.6, -4.3
(2 9 SiMe), 17.5 (Cq), 20.7 (CH3CO), 25.3 (t-Bu), 57.8
(C-2), 66.9 (C-20), 68.1 (C-6), 69.4 (C-60), 71.1 (C-40),
73.3 (C-50), 73.7–74.7, 76.6 (4 9 CH2Ph), 74.9 (C-5),
76.7 (C-3), 78.2 (C-4), 80.6 (C-30), 93.4 (C-1), 101.0
(C-10), 123.0 (Phthaloyl), 127.4–128.4, 131.5–131.6,
133.6, 137.6–138.6 (4 9 Ph), 169.6 (CH3CO) ppm;
[a]D = -1.0°cm3 g-1 dm-1 (c = 1.0, CHCl3).
123

Selection of protecting groups
1249
0
0
(500 MHz, CDCl3): d = 0.07, 0.11 (s, 6H, 2 9 SiMe),
0
0.87 (s, 9H, t-Bu), 1.80 (s, 3H, CH3CO), 2.97 (d, 1H, J4 ,
4.03–4.07 (m, 2H, H-2, H-5), 4.24 (d, 1H, J1 , 2 = 8.2 Hz,
H-10), 4.40–4.86 (m, 8H, CH2Ph), 5.08 (m, 1H, H-1a) 5.22
(t, 1H, J1, 2 = 7.4 Hz, H-1b), 5.45 (d, 1H, J2, NH = 8.7 Hz,
NH), 7.22–7.42 (m, 20H, 4 9 Ph) ppm; 13C NMR
(125 MHz, CDCl3): d = 23.2 (CH3CO), 52.9 (C-2), 66.1
(C-20), 68.2 (C-6), 70.3 (C-5), 70.8 (C-60), 73.8 (C-40), 72.9
(C-50), 73.2–73.6 (4 9 CH2Ph), 76.9 (C-4), 77.2 (C-3),
82.6 (C-30), 91.6 (C-1), 101.0 (C-10), 127.3–128.5
(4 9 Ph), 170.4 (CH3CO) ppm; [a]D = ?16.0°cm3
g-1 dm-1 (c = 1.0, CHCl3).
0
= 1.9 Hz, 4-OH), 3.18 (t, 1H, J2 , 3 = 9.7 Hz, J3 , 4
0
0
0
OH
= 9.7 Hz, H-30), 3.21 (ddd, 1H, J4 , 5 = 9.7 Hz, J5 , 6 a
=
0
0
0
0
= 5.5 Hz, H-50), 3.31 (dd, 1H, J1 ,
0
5.1 Hz, J5 ,
0
0
6 b
20
= 8.3 Hz, J2 , = 9.7 Hz, H-20), 3.36 (ddd, 1H, J1,
= 7.4 Hz, J2, 3 = 9.0 Hz, J2, NH = 7.8 Hz, H-2), 3.50 (dd,
0
30
2
1H, J5 , 6 b = 5.5 Hz, J6 a, 6 b = 10.1 Hz, H-60b), 3.56 (ddd,
1H, J4, 5 = 9.0 Hz, J5, 6a = 3.7 Hz, J5, 6b = 2.3 Hz, H-5),
0
0
0
0
3.59 (dd, 1H, J5 , 6 a = 5.1 Hz, J6 a, 6 b = 10.1 Hz, H-60a),
0
0
0
0
3.64 (t, 1H, J3 , 4 = 9.7 Hz, J4 , 5 = 9.7 Hz, H-40), 3.76
(dd, 1H, J5, 6b = 2.3 Hz, J6a, 6b = 11.0 Hz, H-6b), 3.89
(dd, 1H, J5, 6a = 3.7 Hz, J6a, 6b = 11.0 Hz, H-6a), 3.97 (t,
1H, J2, 3 = 9.0 Hz, J3, 4 = 9.0 Hz, H-3), 4.03 (t, 1H, J3, 4
0
0
0
0
0
2-Acetamido-4-O-(2-amino-2-deoxy-b-D-glucopyranosyl)-
2-deoxy-b-D-glucopyranose (10, C14H26N2O10)
Compound 9 (289 mg, 0.38 mmol) was dissolved in
15 cm3 of a solvent mixture (THF/EtOH/H2O = 1:1:0.5)
containing 145 mg 10% palladium on carbon, and the
resulting mixture was stirred under hydrogen for 24 h at
25 °C. The catalyst was removed by filtration, and the
filtrate was evaporated to dryness. The residue was purified
by flash column chromatography using a solvent mixture of
MeOH/CH2Cl2/H2O (6:4:1, v/v/v) to give 104 mg (72%)
10 as a colorless oil. Rf = 0.40 (MeOH/CH2Cl2/H2O,
6:4:1, v/v/v); 13C NMR (125 MHz, CD3OD): d = 22.6
(CH3CO), 55.6 (C-2), 58.5 (C-20), 62.1 (C-60), 62.5 (C-6),
70.8 (C-5), 71.5 (C-3), 71.5 (C-40), 77.6 (C-30), 78.4 (C-50),
81.2 (C-4), 92.2 (C-1), 104.4 (C-10), 173.5 (CH3CO) ppm;
[a]D = -13.0°cm3 g-1 dm-1 (c = 1.0, MeOH).
5
20
= 9.0 Hz, J4, = 9.0 Hz, H-4), 4.40 (d, 1H, J1 ,
= 8.3 Hz, H-10), 4.42–4.99 (m, 8H, CH2Ph), 4.99 (d, 1H,
J1, 2 = 7.4 Hz, H-1), 5.45 (d, 1H, J2, NH = 7.8 Hz, NH),
7.21–7.40 (m, 20H, 4 9 Ph) ppm; 13C NMR (125 MHz,
CDCl3): d = -5.3, -4.3 (2 9 SiMe), 17.9 (CH3CO), 25.6
(t-Bu), 58.3 (C-2), 66.2 (C-20), 68.5 (C-6), 70.7 (C-60), 73.1
(C-40), 73.2 (C-50), 73.2–73.6 (4 9 CH2Ph), 74.6 (C-5),
77.3 (C-4), 78.1 (C-3), 82.6 (C-30), 95.0 (C-1), 100.8
(C-10), 127.3–128.5 (4 9 Ph), 169.2 (CH3CO) ppm;
[a]D = -13.0°cm3 g-1 dm-1 (c = 1.0, CHCl3).
2-Acetamido-4-O-(2-azido-3,6-di-O-benzyl-2-deoxy-b-
D-glucopyranosyl)-3,6-di-O-benzyl-2-deoxy-b-D-glucopyra-
nose (9, C42H48N4O10)
To a stirred solution of 110 mg 8 (0.12 mmol) in 1 cm3
anhydrous THF 3.70 mm3 acetic acid (61.6 lmol) and
180 mm3 tetra-n-butylammonium fluoride solution (TBAF,
1.0 M in THF, 0.18 mmol) were added at 0 °C. After
stirring at room temperature for 24 h, another portion of
180 mm3 TBAF solution (0.18 mmol) was added, then the
reaction mixture was heated to 50 °C, and stirring was
continued for 10 h. The reaction mixture was worked up to
give a colorless residue, which was purified by flash
column chromatography using a solvent mixture of EtOAc/
n-hexane (1:1, v/v) to give a colorless oil that was
crystallized from EtOH to yield 76.0 mg (82%) colorless
crystals of 9. Rf = 0.21 (EtOAc/toluene, 2:1, v/v); 1H
NMR (500 MHz, CDCl3): d = 1.78 (s, 3H, CH3CO), 3.01
Acknowledgments This research was conducted with the support of
a Grant-in-Aid for Scientific Research (18658133) from the Japan
Society for the Promotion of Science (JSPS).
References
1. Waldmann TA (1991) Science 252:1657
2. Vaorumb KJ, Anthonsen MA, Grasdalen H, Smidsrod O (1991)
Carbohydr Res 217(1):19
3. Heidelas JE, Lees WJ, Pale P, Whitesides GM (1992) J Org
Chem 57(1):146
4. Banoub J, Boullanger P, Lafont D (1992) Chem Rev 92:1167
5. Macmillan D, Daines AM, Bayrhuber M, Flitsch SL (2002) Org
Lett 4(9):1467
6. Greene TW, Wuts PGM (1991) Protective groups in organic
synthesis, 2nd edn. Wiley, New York, pp 309–405, 437–440
7. Bamford MJ, Pichel JC, Husman W, Potel B, Storer R, Wier NG
(1995) J Chem Soc Perkin Trans I 9:1181
8. Figueroa-Perez S, Verez-Bencomo V (1998) Tetrahedron Lett
39(50):9143
0
0
OH
30
(d, 1H, J4 ,
= 2.3 Hz, 4-OH), 3.12 (dd, 1H, J2 ,
40
= 10.1 Hz, J3 , = 9.2 Hz, H-30), 3.30 (dd, 1H, J1 ,
0
0
20
= 8.2 Hz, J2 , 3 = 10.1 Hz, H-20), 3.47 (dd, 1H, J5 , 6 b
=
0
0
0
0
6.0 Hz, J6 a, 6 b = 10.1 Hz, H-60b), 3.54 (dd, 1H, J5 , 6 a
=
0
0
0
0
9. Schmidt RR (1998) Pure Appl Chem 70(2):397
10. Schmidt RR, Kinzy W (1994) Adv Carbohydr Chem Biochem
50:21
= 10.1 Hz, H-60a), 3.62 (t, 1H, J3 ,
0
4.6 Hz, J6 a,
0
0
6 b
40
= 9.2 Hz, J4 , = 9.2 Hz, H-40), 3.62 (ddd, 1H, J4 ,
0
0
50
50
= 9.2 Hz, J5 , 6 a = 4.6 Hz, J5 , 6 b = 6.0 Hz, H-50), 3.69
(dd, 1H, J5, 6b = 2.3 Hz, J6a, 6b = 11.0 Hz, H-6b), 3.70
(dd, 1H, J2, 3 = 8.3 Hz, J3, 4 = 9.4 Hz, H-3), 3.90 (dd, 1H,
J5, 6a = 3.7 Hz, J6a, 6b = 11.0 Hz, H-6a), 3.99 (t, 1H, J3, 4
0
0
0
0
11. Belen Cid M, Fransisco A, Marint-Lomas M (2005) Chem Eur J
11(3):928
12. Ito H, Ishida H, Waki H, Ando S, Kiso M (2000) Glycoconj J
16(10):585
13. Chung R, Moquist P, Finney
339(8):1531
N
(2004) Carbohydr Res
= 9.4 Hz, H-4), 4.10 (d, 1H, J1,
= 3.2 Hz, 1-OH),
OH
123

1250
T. Kawada, Y. Yoneda
14. Yang G, Henning L, Findeisen M, Oehme R, Giesa S, Welzel P
(2004) Helv Chim Acta 87(7):1794
17. Martin-Lomas M, Khiar N, Gracia S, Koessler JL, Nieto PM,
Rademacher TW (2000) Chem Eur J 6(19):3608
15. Demchenko AV, Boons GJ (2001) J Org Chem 66:2547
16. Jacquine JC (1990) Carbohydr Res 199(2):153
18. Fraser-Reid B, Anikumar G, Nair LG, Olsson LM, Mercedes G,
Daniel J (2000) Isr J Chem 40(3–4):252
123