Preparation of α and β anomers of 1,2,3,6-tetra-O-acetyl-4- chloro-4-deoxy-D-galactopyranose based upon anomerization and kinetic acetylation

Article abstract of DOI:10.1016/j.carres.2004.11.028

4-Chloro-4-deoxy-α-d-galactopyranose, 1,2,3,6-tetra-O-acetyl-4- chloro-4-deoxy-α-d-galactopyranose and 1,2,3,6-tetra-O-acetyl-4-chloro-4- deoxy-β-d-galactopyranose were readily prepared from 1,4:3,6-dianhydro- β-d-fructofuranosyl 4-chloro-4-deoxy-α-d-galactopyranoside. In the study, we found an interesting anomerization phenomenon of 4-chloro-4-deoxy-d- galactose. The molar ratio of α and β anomers in solution is about 1:2 when the anomerization reaches a dynamic equilibrium, and the β anomer could completely convert to the α anomer in the process of crystallization and precipitation. The acetylation of 4-chloro-4-deoxy-d-galactopyranose is kinetically controlled, and the configuration of the starting galactose determines the configuration of the resulting acetates. The influence of the chloro group at C-4 and the O-acetyl group at the anomeric carbon on the galactopyranose ring conformations is discussed, based upon the crystallographic data for the α and β anomers of 1,2,3,6-tetra-O-acetyl-4-chloro-4- deoxy-d-galactopyranose.

Full text of DOI:10.1016/j.carres.2004.11.028

Carbohydrate
RESEARCH
Carbohydrate Research 340 (2005) 489–495
Note
Preparation of a and b anomers of
1,2,3,6-tetra-O-acetyl-4-chloro-4-deoxy-D-galactopyranose
based upon anomerization and kinetic acetylation
Feng-Wu Liu, Yan-Bing Zhang, Hong-Min Liu* and Xiao-Ping Song
Department of Chemistry, Zhengzhou University, Zhengzhou 450052, PR China
Received 15 September 2004; accepted 30 November 2004
Abstract—4-Chloro-4-deoxy-a-D-galactopyranose, 1,2,3,6-tetra-O-acetyl-4-chloro-4-deoxy-a-D-galactopyranose and 1,2,3,6-tetra-
O-acetyl-4-chloro-4-deoxy-b-D-galactopyranose were readily prepared from 1,4:3,6-dianhydro-b-D-fructofuranosyl 4-chloro-4-
deoxy-a-D-galactopyranoside. In the study, we found an interesting anomerization phenomenon of 4-chloro-4-deoxy-D-galactose.
The molar ratio of a and b anomers in solution is about 1:2 when the anomerization reaches a dynamic equilibrium, and the b ano-
mer could completely convert to the a anomer in the process of crystallization and precipitation. The acetylation of 4-chloro-4-
deoxy-D-galactopyranose is kinetically controlled, and the configuration of the starting galactose determines the configuration of
the resulting acetates. The influence of the chloro group at C-4 and the O-acetyl group at the anomeric carbon on the galactopyr-
anose ring conformations is discussed, based upon the crystallographic data for the a and b anomers of 1,2,3,6-tetra-O-acetyl-4-
chloro-4-deoxy-D-galactopyranose.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: Acetylation; Anomerization; 4-Chloro-4-deoxy-D-galactopyranose; Conformation; X-Ray analysis
Carbohydrates and their derivatives are potentially use-
ful substrates in the chemical and biological fields. To
improve the function of compounds with new and
attractive characteristics, structural modifications of
the sugars are often required.1,2 Structural modifications
can occur by substitution with O-acetyl, phosphate, sul-
fate, or chloro, and other groups. Variation of the sub-
stitution greatly alters the characteristics of saccharides
and the conformation adopted by a sugar ring. The ring
conformational analysis of carbohydrates is also of
interest in regard to biological activities, as well as
chemical and physical properties determined by the
adopted conformations of the compounds.3
side (1) has been reported in our earlier paper.5 To
our knowledge, although the synthesis of anhydrosu-
crose derivatives have been extensively investigated, no
further utilization of anhydrosucrose in organic synthe-
sis has been reported. We attempted to hydrolyze 1 to
prepare new monosaccharides and successfully obtained
4-chloro-4-deoxy-a-D-galactopyranose (4). In the study,
we found an interesting anomerization phenomenon for
the new halogenated monosaccharides. On the basis of
the anomerization, the a and b anomers of the acetates
of the monosaccharides were synthesized.
We report herein the preparation and the unique ano-
merization of 4-chloro-4-deoxy-a-D-galactopyranose,
and the respective preparation of the a and b ano-
mers of 1,2,3,6-tetra-O-acetyl-4-chloro-4-deoxy-D-galac-
topyranose based on the anomerization via different
processes. The galactopyranose ring conformations of
a and b anomers were analyzed also based on the
crystallographic data and Cremer–Pople puckering
parameters.
Within sucrochemistry, the synthetic methods for var-
ious anhydrosucrose derivatives have been developed
previously,4 and the synthesis of 1,4:3,6-dianhydro-b-
D-fructofuranosyl 4-chloro-4-deoxy-a-D-galactopyrano-
*
Corresponding author. Tel./fax: +86 371 7767200; e-mail:
liuhm@zzu.edu.cn
0008-6215/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2004.11.028

490
F.-W. Liu et al. / Carbohydrate Research 340 (2005) 489–495
Table 1. 13C NMR spectral data of compound 2–5
Hydrolysis of 1,4:3,6-dianhydro-b-D-fructofuranosyl
4-chloro-4-deoxy-a-D-galactopyranoside (1)5 with dilute
sulfuric acid, followed by concentration to dryness under
diminished pressure and fractionation by chromatogra-
phy, afforded 4-chloro-4-deoxy-D-galactopyranose with
a melting point of 147–150 ꢁC (dec) and an optical rota-
tion of +134.0ꢁ (c 0.726, MeOH). The smaller J12 value
(4.0 Hz) observed in the 1H NMR spectrum of the galac-
topyranose, based upon 2D NMR spectra, showed it as
the a anomer 4. Acetylation of 4 with acetic anhydride
in pyridine resulted in the product (compound 2, needles)
with a melting point of 76–78 ꢁC and an optical rotation
2a
3a
4b
5b
1
2
3
4
5
6
89.6
92.2
92.7
68.0
68.7
65.6
69.0
61.0
97.9
72.0
72.1
64.2
73.4
60.9
66.1
68.3
67.3
71.7
58.4
68.9
57.3
71.9
63.0
20.5
62.7
20.62
20.69
20.72
20.81
169.0
169.1
170.1
170.3
AcO
(CH3)
20.7
20.8
20.9
168.7
169.6
170.35
170.38
AcO
(C@O)
of +146.5ꢁ (c 1.03, CHCl3). H and 13C NMR spectral
1
data indicated that 2 is pure 1,2,3,6-tetra-O-acetyl-4-
chloro-4-deoxy-a-D-galactopyranose. In our previous
study, acetylation of D-galactose under the same condi-
tions yielded almost pure b anomer acetate. It is obvious
that the introduction of chlorine into C-4 of galactopyr-
anose ring has altered the feature of acetylation. Further-
more, the dry concentrated residue without fraction
(intermediate residue) was acetylated directly and ex-
tracted with ethyl acetate, followed fractionation by
chromatography, giving a mixture of a and b anomers
of 1,2,3,6-tetra-O-acetyl-4-chloro-4-deoxy-D-galactopyra-
nose (a:b ꢀ 1:2, mol/mol). The anomeric acetates were
separated by recrystallization from absolute ethanol to
afford the b anomer (compound 3) as needles (as shown
in Scheme 1) with a melting point of 176–177 ꢁC and an
a In CDCl3.
b In Me2SO-d6.
Table 2. 1H NMR spectral data of compound 2–5
2a
3a
4b
5b
1
6.37(d)
5.69(d)
4.95(d)
3.48(m)
3.84(m)
4.36(d)
4.08(t)
4.31(d)
3.23(t)
3.60(dd)
4.26(d)
3.65(t)
3.48(t)
2
5.45(dd)
5.32(dd)
4.62(d)
4.43(t)
4.27(dd)
4.20(dd)
2.03
5.44(dd)
5.05(dd)
4.53(d)
4.11(t)
4.31(dd)
4.24(dd)
2.06
3
4
5
6a
3.48(m)
6b
CH3CO
2.08
2.14
2.09
2.128
1
optical rotation of +64.8ꢁ (c 0.58, CHCl3). The H and
2.16
3.6
2.132
8.4
13C NMR spectral data for the three compounds are
shown in Tables 1 and 2. Single-crystal X-ray analysis
after recrystallization from absolute ethanol established
the structure of 2 and 3 as shown in Figure 1.
J1,2
J2,3
4.0
7.2
9.2
3.6
6.4
10.6
10.0
J3,4
3.6
6.4
3.6
6.0
2.4
6.4
J5,6
J6a,6b
11.4
11.2
In order to investigate the reason for the different re-
1
sults of the two acetylations, we utilized H NMR tech-
a In CDCl3.
b In Me2SO-d6.
nology to trace the anomerization of 4 in solution.
Compound 4 was dissolved in deuterated Me2SO, and
1
the H NMR spectrum was recorded immediately. The
deuterated Me2SO was replaced by CD3OD, a similar
anomerization was shown to exist. Therefore, 4 was dis-
solved in a solution of 5:1 methanol–pyridine and
heated to reflux for 10 h, followed by evaporation of
the methanol. Acetylation of the residual solution con-
taining pyridine with acetic anhydride gave a mixture of
a and b anomers of acetates in a ratio of 1:1.92, almost
same result as the direct acetylation of the intermediate
residue. On the basis of the experiments described
1
recorded H NMR spectrum indicated the presence of
only a anomer at first. The a anomer converted gradu-
ally to the b anomer (5, as shown in Tables 1 and 2) with
the passage of time, and the 1H NMR spectrum showed
the ratio of a to b anomers was 1:2 when the anomeriza-
tion reached a dynamic equilibrium (as shown in
Scheme 2). This ratio is in accord with that of the ano-
meric acetates from the intermediate residue. When the
Cl
HO
OH
O
Cl
AcO
OAc
O
Cl
AcO
OAc
O
O
(1)
(2)
O
OAc
HO
AcO
AcO
O
OAc
O
2
3
1
Scheme 1. Preparation of a and b anomers of 1,2,3,6-tetra-O-acetyl-4-chloro-4-deoxy-D-galactopyranose. Reagents and conditions: (1) (a) 0.37 N
H2SO4, 60 ꢁC, 2 h; (b) separation by chromatography; (c) Ac2O, pyridine; (2) (a) 0.37 N H2SO4, 60 ꢁC, 2 h; (b) Ac2O, pyridine; (c) separation by
chromatography; (d) recrystallization from EtOH.

F.-W. Liu et al. / Carbohydrate Research 340 (2005) 489–495
491
2
3
Figure 1. ORTEP of compounds 2 and 3, hydrogens omitted.
Since the intermediate residue is a mixture, why is the
final product obtained in the hydrolysis of 1 only the a
anomer of 4-chloro-4-deoxy-D-galactopyranose? The
solution of 4 in methanol was heated to reflux and kept
for 24 h. At the end of this time the solvent was allowed
to evaporate slowly and naturally to dryness, giving a
Cl
HO
OH
O
Cl
HO
OH
O
OH
HO
HO
OH
(~34%)
(~66%)
4
5
1
product as a white solid. The H NMR spectrum of
Scheme 2. Anomerization of 4-chloro-4-deoxy-D-galactopyranose in
Me2SO.
the product indicated that the product was pure 4-
chloro-4-deoxy-a-D-galactopyranose, while the solution
of 4 in CD3OD after keeping at 55 ꢁC for 20 h contained
two anomers (a:b ꢀ 1:1.1). It is obvious that the conver-
sion from the b anomer to the a anomer takes place in
the process of crystallization or precipitation, and the
b anomer disappears at last.
above, we could conclude that there are a and b ano-
mers in the intermediate residue; acetylation of 4-
chloro-4-deoxy-D-galactopyranose is
controlled process, that is, the anomeric configuration
of the starting galactose determines the configuration
of the resulting acetates.
a
kinetically
Crystal data summary and refinement results for com-
pound 2 and 3 are contained in Table 3. Single-crystal
Table 3. Crystal data summary and refinement results for compound 2 and 3
2
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
C
733.48
28H38Cl2O18
C14H19ClO9
366.74
291(2)
291(2)
Orthorhombic
P212121
Orthorhombic
P212121
Space group
Unit cell dimensions
˚
a (A)
9.3626(19)
10.239(2)
38.098(8)
3652.3(13)
4
5.7960(12)
14.472(3)
21.532(4)
1806.1(6)
4
˚
b (A)
˚
c (A)
3
˚
V (A )
Z
Dcalcd (Mg/m3)
1.334
0.250
1.349
0.253
Absorption coefficient (mmꢁ1
F (000)
)
1536
0.20 · 0.20 · 0.18
1.07–25.00
768
0.20 · 0.18 · 0.18
1.70–27.49
Crystal size (mm3)
h Range for data collection (ꢁ)
Index ranges
0 6 h 6 11, ꢁ12 6 k 6 12, ꢁ45 6 l 6 45
9195/5585 [R(int) = 0.0533]
Full-matrix least-squares on F2
5585/0/435
ꢁ7 6 h 6 7, 0 6 k 6 18, ꢁ27 6 l 6 27
5025/3192 [R(int) = 0.0747]
Full-matrix least-squares on F2
3192/0/218
Reflections collected/unique
Refinement method
Data/restraints/parameters
Final R indices [I > 2r(I)]
R indices (all data)
Goodness-of-fit on F2
R1 = 0.0568
wR2 = 0.1284
1.049
R1 = 0.0531
wR2 = 0.1641
1.035
ꢁ3
ꢁ3
˚
˚
Largest diff. peakand hole
0.186 and ꢁ0.152 e A
0.320 and ꢁ0.312 e A

492
F.-W. Liu et al. / Carbohydrate Research 340 (2005) 489–495
X-ray analysis revealed that two rotamers are present in
4
an asymmetric unit and that the C1 conformations of
weakH-bonds between O(5) of carbonyl group in one
molecule and H at C(1) as well as H at C(3) in the pyra-
nose ring of another molecule (distance C(1)–Hꢂ ꢂ ꢂO-5
pyranose rings exist in the solid state of the acetate 2.
The primary hydroxyl groups of two rotamers in 2 are
in the tg position (O(1)–C(5)–C(6)–O(8) = ꢁ178.2ꢁ)
and the gt position (O(1A)–C(5A)–C(6A)–O(8A) =
66.5ꢁ), respectively, being the two favored orientations
for sugars with the galacto configuration.6 For acetate
3, one asymmetric unit contains only one molecule with
the primary hydroxyl group in the gt position (O(1)–
C(5)–C(6)–O(8) = 78.3ꢁ) and the pyranose ring existing
in the 4C1 conformation. The regular intermolecular
˚
˚
2.559 A, C(3)–Hꢂ ꢂ ꢂO-5 2.572 A; angle 1-C–Hꢂ ꢂ ꢂO-5
140.1ꢁ, 3-C–Hꢂ ꢂ ꢂO-5 140.3ꢁ) result in the closer packing
of acetate 3 (as shown in Fig. 2). Then despite the pres-
ence of more kinds and higher numbers of supramole-
cular bonds, including C–Hꢂ ꢂ ꢂO, C–Hꢂ ꢂ ꢂCl, and
C@Oꢂ ꢂ ꢂCl, in acetate 2 than in acetate 3, most of the
atoms involved in the bonds are at carbon atoms outside
pyranose rings (as shown in Fig. 3), which could not
allow the close packing of molecules. It seems that the
Figure 2. The weakH-bonds of 3.
Figure 3. The supramolecular bonds of 2.

F.-W. Liu et al. / Carbohydrate Research 340 (2005) 489–495
493
presence of the two molecules rotated with respect to
each other in one asymmetric unit lead to a relatively
ÔirregularÕ and ÔlooserÕ packing of 2, which is also indi-
of 1,2,3,6-tetra-O-acetyl-4-chloro-4-deoxy-D-galactose.
Meanwhile, the different orientation of the O-acetyl
groups at the anomeric carbon resulted in the greater
difference of melting points and optical rotation between
the a and b anomers of 1,2,3,6-tetra-O-acetyl-4-chloro-
4-deoxy-D-galactose as described above.
In conclusion, the paper describes the preparation, the
unique anomerization, and the acetylation of the 4-
chloro-4-deoxy-D-galactopyranose as well as the separa-
tion of the a and b anomers of the tetraacetates. The
influence of the chlorine atom at C-4 and the O-acetyl
group at anomeric carbon on the conformation of the
pyranose ring of both the a and b anomers of 1,2,3,6-
tetra-O-acetyl-4-chloro-4-deoxy-D-galactopyranose are
also discussed. Through the above study, we developed
a facile approach to 4-chloro-4-deoxy-a-D-galactopyra-
nose and the two anomers of 1,2,3,6-tetra-O-acetyl-4-
chloro-4-deoxy-D-galactopyranose.
3
˚
rectly confirmed by the difference of 40 A between the
cell volumes of the two anomers (V(2) and 2V(3) in Ta-
ble 3). In turn, this probably explains the significant dif-
ference of 100 ꢁC between the melting points of 2 and 3
as well as the exclusive crystallization of 3 from solution
of a mixture of the two anomers.
According to the literature,7 the a-D-galactopyranose
pentaacetate has a pyranose ring close to a perfect chair
with nearly equal (but with opposite sign) values for the
three pairs of torsion angles, and the magnitudes of the
torsion angles are 50.3–59.1ꢁ. The value of h8 (2.7ꢁ) and
the magnitudes of the torsion angles (52.0–58.5ꢁ) for 2
clearly reveals the pyranose ring with a slight distortion.
Comparing the C–O bond lengths around the anomeric
carbon in 2 within the a-D-galactopyranose pentaace-
tate, we found that both the exocyclic C(1)–O(2) bond
and the endocyclic C(1)–O(1) bond are shorter in com-
pound 2 than in galactopyranose pentaacetate (1.424,
1. Experimental
˚
˚
1.399 A vs 1.441, 1.406 A). In contrast to compound 2,
the pyranose ring of 3 is much greater distorted away
from the perfect chair of b-D-galactopyranose pentaace-
tate.1 This is shown by the larger value of h (8.1ꢁ) and
the larger magnitude of the torsion angles of the pyra-
nose ring in 3 (48.4–65.2ꢁ). b-D-Galactopyranose penta-
acetate has a relatively smaller magnitude of the torsion
angles (53.3–61.5ꢁ). Both the exocyclic C(1)–O(2) bond
and the endocyclic C(1)–O(1) bond around the anomeric
1.1. General methods
1H and 13C NMR spectra were acquired on a Bruker
AVANCE DPX-400 spectrometer with chemical shifts
(d) given in parts per million relative to Me4Si as an
internal standard. Melting points were determined on
a WC-1 melting-point apparatus and are uncorrected.
Optical rotations were measured on a Perkin–Elmer
341 Polarimeter.
˚
carbon are longer in compound 3 (1.438, 1.432 A) than
˚
in b-D-galactopyranose pentaacetate (1.408, 1.408 A).
Table 4 contains some critical bond lengths, torsion
angles and Cremer–Pople puckering parameters for 2
and 3. From the above comparison we could conclude
that the equatorial O-acetyl group at the anomeric
carbon caused greater distortion of the pyranose ring
1.2. Single-crystal X-ray analysis
A single crystal suitable for data collection was mounted
on a Rigaku RAXIS-IV single-crystal X-ray diffracto-
meter. The X-ray diffraction data were collected using
˚
Mo Ka radiation (k = 0.71073 A) at a temperature of
291(2) K and corrected for Lorentz-polarization effects.
The structure was solved via direct methods and ex-
panded using the Fourier technique. The nonhydrogen
atoms were refined with anisotropic thermal parameters.
All hydrogen atoms were refined isotropically. The final
cycle of full-matrix least-squares refinement was based
on 5585 reflections and 435 variable parameters for
the crystal of 2, and 3192 reflections and 218 variable
parameters for the crystal of 3. All calculations were
performed using the SHELX-97 crystallographic software
package.9 Final atomic coordinates and equivalent iso-
tropic displacement parameters for compound 2 and 3
are given in Tables 5 and 6.
˚
Table 4. Critical bond lengths (A) and torsion angles (ꢁ) and Cremer–
Pople puckering parameters for 2 and 3
2
3
C(1)–C(2)
C(2)–C(3)
1.531(6)
1.516(6)
1.520(6)
1.525(6)
1.444(5)
1.399(5)
1.424(5)
1.514(6)
1.509(6)
1.531(6)
1.527(6)
1.429(5)
1.432(5)
1.438(4)
C(3)–C(4)
C(4)–C(5)
O(1)–C(5)
O(1)–C(1)
O(2)–C(1)
C(5)–O(1)–C(1)–C(2)
C(1)–O(1)–C(5)–C(4)
C(1)–C(2)–C(3)–C(4)
C(2)–C(3)–C(4)–C(5)
C(3)–C(4)–C(5)–O(1)
O(1)–C(1)–C(2)–C(3)
ꢁ58.5(4)
57.9(4)
ꢁ62.0(4)
65.2(4)
ꢁ53.7(4)
52.0(4)
ꢁ48.4(4)
49.3(4)
ꢁ52.7(4)
55.9(5)
ꢁ57.4(4)
53.5(4)
4-Chloro-4-deoxy-a-D-galactopyranose (4): Concen-
trated sulfuric acid (0.4 mL) was added to a solution
of 1 (3.24 g, 10 mmol) in H2O (40 mL). The mixture
was heated to 60 ꢁC and kept for 2 h, followed by con-
centration to dryness under diminished pressure and
Puckering parameters
˚
Q (A)
0.548(4)
2.7(4)
0.563(4)
8.1(4)
h (ꢁ)

494
F.-W. Liu et al. / Carbohydrate Research 340 (2005) 489–495
Table 5. Selected atomic coordinates (·104) and equivalent isotropic
displacement parameters (A · 10 ) for compound 2
221. Anal. Calcd for C6H11ClO5: C, 36.29; H, 5.58.
Found: C, 36.06; H, 5.69.
2
3
˚
x
y
z
U (equiv)
1,2,3,6-Tetra-O-acetyl-4-chloro-4-deoxy-a-D-galactose
(2): Compound 4 obtained above (1.81 g, 9.1 mmol) was
mixed with pyridine (15 mL), Ac2O (10 mL), and cata-
lytic amount of DMAP. The mixture was stirred at
ambient temperature and monitored by TLC. After
the disappearance of starting sugar, absolute EtOH
(10 mL) was added. The mixture was continued to stir
for 20 min, then partitioned by EtOAc and H2O. The
EtOAc layer was washed with water (20 mL · 2), dried
over anhyd Na2SO4 and evaporated, affording com-
pound 2 as a white solid (3.00 g, 82% yield from 1).
Cl(1)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
7636(2)
8039(3)
7431(3)
6414(5)
4933(3)
3480(4)
5995(3)
7401(4)
798(1)
1336(3)
ꢁ259(3)
783(4)
268(1)
71(1)
56(1)
57(1)
104(1)
63(1)
88(1)
57(1)
87(1)
67(1)
93(1)
56(1)
49(1)
49(1)
48(1)
50(1)
62(1)
67(1)
80(2)
66(1)
111(2)
60(1)
86(2)
66(1)
90(2)
1099(1)
1502(1)
1952(1)
1162(1)
1170(1)
513(1)
458(1)
565(1)
408(1)
1260(1)
986(1)
775(1)
617(1)
903(1)
774(1)
1848(1)
2055(1)
1239(1)
1422(2)
385(1)
138(1)
390(1)
195(1)
ꢁ801(3)
928(4)
ꢁ1519(3)
ꢁ3260(3)
683(3)
11,115(3)
12,095(4)
6901(5)
6001(4)
6926(5)
8199(4)
8987(5)
10,130(5)
7128(6)
7782(6)
3693(6)
2694(6)
6339(6)
5188(7)
12,074(5)
13,118(6)
2578(4)
684(4)
ꢁ38(4)
Recrystallization from absolute EtOH gave a needle
ꢁ964(4)
ꢁ256(4)
496(4)
20
D
product: mp 76–78 ꢁC, ½aꢃ +146.5 (c 1.03, CHCl3).
ESIMS: [M+Na]+ 389. Anal. Calcd for C14H19ClO9:
C, 45.85; H, 5.22. Found: C, 45.66; H, 5.37.
1413(4)
ꢁ108(5)
ꢁ1158(5)
ꢁ192(5)
ꢁ1089(6)
ꢁ2689(4)
ꢁ3139(5)
1415(5)
586(6)
1,2,3,6-Tetra-O-acetyl-4-chloro-4-deoxy-b-D-galactose
(3): Concentrated H2SO4 (0.4 mL) was added to a
solution of 1 (3.24 g, 10 mmol) in H2O (40 mL). The
mixture was heated to 60 ꢁC and kept for 2 h, followed
by concentration to dryness under diminished pressure.
The residue obtained was acetylated directly in the pres-
ence of a catalytic amount of DMAP with Ac2O in pyr-
idine. After completion of the acetylation, absolute
EtOH (10 mL) was added. The mixture was allowed to
stir for 20 min, then partitioned by EtOAc and H2O.
The EtOAc layer was washed with H2O (20 mL · 2),
concentrated, and fractioned by chromatography with
10:1 CHCl3–EtOAc to give a mixture of a and b ano-
mers of acetates in a ratio of 1:2. The anomeric acetates
were separated by crystallization from hot absolute
U (equiv) is defined as one third of the trace of the orthogonalized Uij
tensor.
Table 6. Selected atomic coordinates (·104) and equivalent isotropic
displacement parameters (A · 10 ) for compound 3
2
3
˚
x
y
z
U (equiv)
Cl(1)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
6207(2)
4134(5)
6365(5)
3411(6)
6340(4)
6662(1)
4864(2)
4124(2)
3129(2)
5757(2)
5759(3)
7352(2)
8377(3)
4755(3)
3904(4)
4870(3)
5745(3)
6601(3)
6541(3)
5618(3)
5457(3)
3269(3)
2593(3)
5758(3)
5759(3)
8214(3)
8904(4)
4022(4)
3360(5)
251(1)
862(1)
77(1)
56(1)
54(1)
92(1)
52(1)
78(1)
63(1)
101(1)
74(1)
131(2)
47(1)
51(1)
49(1)
55(1)
51(1)
64(1)
63(1)
70(1)
55(1)
71(1)
65(1)
79(2)
74(1)
98(2)
1588(1)
1775(2)
2332(1)
2268(2)
1562(2)
1576(2)
97(2)
EtOH to afford compound 3 as needles (1.86 g, 51%
20
yield from 1): mp 176–177 ꢁC, ½aꢃ +64.8 (c 0.58,
D
10,190(5)
6394(6)
3480(7)
ꢁ13(6)
CHCl3). ESIMS: [M+Na]+ 389. Anal. Calcd for
C14H19ClO9: C, 45.85; H, 5.22. Found: C, 45.69; H,
5.45.
1790(9)
4755(6)
6063(7)
4762(7)
3876(7)
2634(7)
1803(8)
5504(10)
7312(9)
8405(7)
8296(9)
5517(9)
7422(10)
178(10)
ꢁ1782(11)
ꢁ613(3)
1505(2)
1664(2)
1471(2)
802(2)
2. Supplementary materials
Complete crystallographic data for the structural analy-
sis have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC 250116 (compound 2)
and CCDC 250117 (compound 3). Copies of this infor-
mation may be obtained free of charge from the Direc-
tor, Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge, CB2 1EZ, UK. (fax: +44
718(2)
68(2)
1723(2)
1817(3)
2575(2)
3275(2)
1619(2)
1703(3)
ꢁ254(3)
ꢁ139(3)
1223 336033, deposit@ccdc.cam.ac.ukor
www.ccdc.cam.ac.uk).
http://
U (equiv) is defined as one third of the trace of the orthogonalized Uij
tensor.
Acknowledgements
fractionation by chromatography with 8:1 CHCl3–
MeOH, afforded 4 (1.81 g, 91% yield): mp 147–150 ꢁC
We are grateful to NNSF of PR China (No. 20272054)
for financial support of this work.
20
(dec), ½aꢃ +134.0 (c 0.726, MeOH). ESIMS: [M+Na]+
D

F.-W. Liu et al. / Carbohydrate Research 340 (2005) 489–495
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