Synthesis of β-d-arabinofuranosides: stereochemical differentiation between d- and l-enantiomers

Article abstract of DOI:10.1016/j.carres.2008.09.006

The glycosylation of 3,5-O-di-tert-butylsilylene-protected d-thioarabinofuranosides with a range of glycosyl acceptors using NIS/AgOTf as promoters proceeded in a stereoselective manner to give the corresponding β-d-arabinofuranosides in high yields.

Full text of DOI:10.1016/j.carres.2008.09.006

Carbohydrate Research 343 (2008) 3100–3106
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Note
Synthesis of b-D-arabinofuranosides: stereochemical
differentiation between D- and L-enantiomers
*
Yingxi Wang, Samuel Maguire-Boyle, Ravindra T. Dere, Xiangming Zhu
Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
a r t i c l e i n f o
a b s t r a c t
Article history:
The glycosylation of 3,5-O-di-tert-butylsilylene-protected
D-thioarabinofuranosides with a range of
Received 28 February 2008
Received in revised form 22 August 2008
Accepted 4 September 2008
Available online 10 September 2008
glycosyl acceptors using NIS/AgOTf as promoters proceeded in a stereoselective manner to give the
corresponding b- -arabinofuranosides in high yields.
D
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
b-D-Arabinofuranoside
Glycosylation
Thioglycoside
Protecting groups
Arabinosides are important constituents of proteoglycans, glyco-
proteins, and polysaccharides, and are widely distributed in living
glycosylation,4 has been used to introduce a b-
D-arabinofuranoside
moiety. Also, Lowary and co-workers3c successfully employed
2,3-anhydrofuranoyl donors as glycosylating agents to construct
organisms, including plants.1 Both
D
- and
-form being the major component of mycobacte-
rial cell walls and the -form being an important component of
plant cell walls. Although -arabinofuranosides are more prevalent
in both - and -series, b-arabinofuranosides occur often at the
L-arabinofuranosides are
found, with the
D
b-D-arabinofuranosidic linkages, in which the oxirane of the
glycosylation products could be opened in a regioselective manner
L
a
using lithium benzyl alkoxide in the presence of (ꢀ)-sparteine. The
D
L
b-D-arabinofuranoside selectivity has also been improved by deac-
nonreducing end of the polysaccharides and may play pivotal roles
in a number of biological events. For example, arabinogalactan, a
major polysaccharide found in mycobacterial cell wall, contains
tivation of the glycosyl donor and acceptor.5
Recently, Boons and co-workers6 achieved the direct b-
L-arabi-
nofuranosylation of different glycosyl acceptors using a 3,5-O-di-
tert-butylsilylene (DTBS)-protected -thioarabinofuranoside as gly-
b-
D-arabinofuranosides at its nonreducing termini. Galactans in
L
plant cell walls are also often modified by b-
L
-arabinofuranosides
cosyl donor on the basis of locking the donor in a conformation, in
which nucleophilic attack from the b face was favored. This con-
formationally constrained donor gave excellent b-selectivity in a
range of glycosylations with glycosyl acceptors having primary
and secondary alcohols, and was successfully employed to synthe-
size an arabinogalactan fragment derived from the plant cell wall.
Interestingly, soon after, Ito and co-workers7 investigated the gly-
at their nonreducing termini and side chains. Therefore, the syn-
thesis of b-arabinofuranosides,2 particularly the development of
effective b-arabinofuranosylating agents,3 has received significant
interest.
In contrast to a-arabinofuranosides, which are readily obtained
through neighboring group participation, the stereoselective syn-
thesis of b-arabinofuranosides is still a great challenge in carbo-
hydrate chemistry. The use of arabinofuranosyl donors with a
nonparticipating group at C-2 gives in general glycosides with poor
cosylation property of an analogous DTBS-protected D-thioarabino-
furanosides under the same activation conditions (NIS/AgOTf), and
reported the predominant formation of b-glycosides but with a
lower selectivity. Surprisingly, in their work an excellent b-selec-
tivity was obtained in the activation of another conformationally
less constrained donor, the 3,5-O-tetraisopropyldisiloxanylidene-
protected thioglycoside. These results raised the question of
anomeric selectivity, and a-anomers are often the major products
due to both stereoelectronic and steric effects. Hence, several indi-
rect approaches have been developed to synthesize b-arabinofur-
anosides. For example, the intramolecular aglycone delivery
method, in which a glycosyl acceptor was first tethered to the
C-2 hydroxyl group of an arabinofuranosyl donor followed by
whether our procedure is applicable to
subsequent report by Crich et al. suggested that the DTBS-pro-
tected -thioarabinofuranoside showed no significant b-selectivity
D-arabinofuranosides. A
D
on activation with BSP/Tf2O or Ph2SO/Tf2O in the presence of differ-
ent acceptors, while its enantiomer, that is, the corresponding
* Corresponding author. Tel.: +353 17162386; fax: +353 17162501.
E-mail address: Xiangming.Zhu@ucd.ie (X. Zhu).
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.09.006

Y. Wang et al. / Carbohydrate Research 343 (2008) 3100–3106
3101
acetate 110, as shown in Scheme 1. Reaction of 1 with thiophenol in
the presence of boron trifluoride etherate provided thioglycoside 2
in 78% yield. Subsequently, deacetylation of 2 with sodium meth-
oxide followed by silylation with di-tert-butylsilane bis(trifluoro-
methanesulfonate) under the action of lutidine produced the
3-O-unprotected arabinofuranoside 3 in 81% yield. The 2-hydroxyl
group of 3 was then benzylated in high yield to give the donor 4 by
reaction with benzyl bromide in the presence of silver oxide. It is
worth mentioning here that although compound 4 was expected
to be mainly in a 3E envelope conformation based on the previous
computational work,6 a recent X-ray study of the analogous p-tolyl
thioglycoside indicated that the furanosyl ring may adopt an E4
conformation.11
L
-thioglycoside, showed an excellent b-selectivity under NIS/AgOTf
conditions.8 However, they did not explore the reaction property of
the
-thioglycoside under the action of NIS/AgOTf.9
Based on our previous results,6 in order to investigate the
glycosylating property of DTBS-protected -thioglycosides, such
as compound (Scheme 1), particularly under NIS/AgOTf
D
D
4
conditions, we decided to conduct some glycosylation reactions
using compound 4 as the glycosyl donor, and wish to report
here the observed stereochemical differentiation between
D- and
L-arabinofuranosylations.
The excellent b-selectivity obtained in
L-arabinofuranosylation
reactions prompted us to investigate the applicability of the 3,5-
di-O-tert-butylsilylene protecting group as a stereocontrolling ele-
ment in D
-arabinofuranosylations. In light of our previous work,6
Having the glycosyl donor 4 in hand, attention was focused on
the fused silylene ring in thioglycoside 4 would result in an
oxocarbenium ion being locked into a 3E conformation, in which
C-3 is displaced above the plane formed by C-4, O(endo), C-1 and
the glycosylation of
a range of different glycosyl acceptors
(Fig. 1). Thus, coupling of the donor 4 with the galactosyl acceptor
712 in the presence of NIS/AgOTf was first performed, but unex-
pectedly, the desired b-linked disaccharide 14 (Table 1, entry 1)
C-2. Thus, nucleophilic attack from the
a face of this structure
would be disfavored due to unfavorable steric interaction with
H-2, while b attack will encounter only staggered substituents,
and thus be the favored mode of reaction. In the alternative E3 con-
formation, the silylene ring would be distorted inducing consider-
able ring strain.
was produced with a modest selectivity (b/
the previous exclusive b-selectivity obtained in the corresponding
-arabinofuranosylation reaction.6 Fortunately, the
/b-isomers
could be readily separated by flash column chromatography. We
reasoned that there must be a ‘mismatch’ effect13 in the donor–
acceptor pair in the glycosidation reaction. For a specific glycosyl
a 5:1), compared with
L
a
Synthesis of the glycosyl donor 4 was initiated from
D-arabi-
nose, which was first transformed into the known arabinose tetra-
acceptor,
L
-thioarabinofuranoside donors, such as the enantiomer
-thioarabi-
of compound 4, could give a better b-selectivity than
D
nofuranosides. As reported in the literature and in our previous
work, the anomeric stereochemistry of the disaccharides was con-
firmed by the chemical shift of the anomeric carbon and the cou-
AcO
AcO
OAc
O
AcO
O
a
OAc
Ref.
3
D-Arabinose
pling constant JH1–H2 value (the same hereinafter): b-isomer,
SPh
3
d(C-1) 97–104 ppm, JH1–H2 = 4–6 Hz;
a-isomer, d(C-1) 104–
OAc
OAc
3
111 ppm, JH1–H2 = 1–3 Hz.
1
2
Donor 4 was also reacted with acceptors 814 under the same
activation conditions, giving rise to disaccharide 15 in 83% yield
and very good b-selectivity (Table 1, entry 2). Similarly, mannosyl
acceptor 915 was also glycosylated with donor 4 in a b-selective
manner to give compound 16 in 88% yield (Table 1, entry 3). To ob-
tain more information on the glycosylation property of this donor,
acceptors 1016 and 1117 having secondary hydroxyl groups were
also coupled with 4, and not unexpectedly, the corresponding
disaccharides 17 and 18 were both generated in high yield and
modest selectivity (Table 1, entries 4 and 5). The commercially
available acceptor 12 was also glycosylated smoothly with donor
4, leading to disaccharide 19 in high yield and b-selectivity (Table
1, entry 6). In addition, glycosylation of benzyl-protected acceptor
1314 with donor 4 gave also the corresponding disaccharide 20 in
very good yield and modest b-selectivity (Table 1, entry 7).
b
O
OBn
O
OH
O
O
t
c
Bu
t
Bu
Si
SPh
Si
SPh
t
O
Bu
t
O
Bu
4
3
e
d
O
O
CF3
S
O
OBn
O
O
O
O
O
t
Bu
t
Bu
Si
CCl3
NH
Si
SPh
t
O
Bu
t
O
Bu
5
6
In spite of the above modest selectivities, donor 4 could still gly-
cosylate all the acceptors under the present conditions (NIS/AgOTf)
in a selective manner in favor of the formation of b-glycosides.
Moreover, all the glycosylation products were isolated in very high
yields as indicated in Table 1, and more often, the pure b-anomers
Scheme 1. Synthesis of DTBS-protected D-arabinofuranosyl donors 4–6. Reagents
and conditions: (a) PhSH, BF3ꢁEt2O, CH2Cl2, 78%; (b) NaOMe, MeOH, then
tBu2Si(OTf)2, 2,6-lutidine, DMF–CH2Cl2, 81% (2 steps); (c) BnBr, Ag2O, CH2Cl2, 83%;
(d) o-trifluoromethylbenzenesulfonyl chloride, KI, Ag2O, collidine, CH2Cl2, 70%; (e)
NBS, acetone–H2O, then Cl3CCN, DBU, CH2Cl2, 45% (two steps).
AcO
AcO
OH
OH
OBz
HO
BzO
O
O
O
BzO
BzO
OMe
BzO
OAc
BzO
8
OMe
OMe
7
9
OH
O
OH
OAc
O
HO
AcO
O
O
Ph
O
O
O
BnO
BnO
OMe
O
HO
O
BzO
O
BnO
13
OMe
OAc
OMe
10
11
12
Figure 1. Selected glycosyl acceptors 7–13.

3102
Y. Wang et al. / Carbohydrate Research 343 (2008) 3100–3106
Table 1
D-Arabinofuranosylation of DTBS-protected donors 4–6 with acceptors 7–11
Entry
1
Donor
Acceptor
Product
Yielda (%)
90
b:a
Ratiob
O
OBn
O
O
AcO
t
Bu
O
4
7
5:1
Si
OMe
t
AcO
O
Bu
OAc
14
O
OBn
O
O
O
O
t
Bu
BzO
2
3
4
4
8
9
83
88
8:1
3:1
Si
BzO
BzO
t
O
O
OMe
Bu
15
OBn
O
OBz
O
O
t
Bu
BzO
Si
BzO
t
OMe
Bu
16
O
O
Ph
O
O
O
O
t
BnO
4
5
4
4
10
11
72
88
3:1
4:1
Bu
BzO
OMe
Si
17
t
O
O
Bu
O
O
OAc
O
t
BnO
Bu
O
Si
OMe
AcO
t
Bu
OAc
18
O
O
BnO
O
t
Bu
O
Si
O
6
4
12
78
6:1
t
O
O
Bu
O
O
O
19
OBn
O
O
O
O
t
Bu
BnO
7
8
4
5
13
8
75
84
2:1
4:1
Si
BnO
BnO
t
OMe
Bu
20
15
CF3
O
O
S
O
O
O
t
Bu
O
9
6
12
75
2:1
O
Si
O
t
O
Bu
O
O
O
21
a
Isolated yield.
Determined by integration of proton signals in the 1H NMR spectrum after chromatographic purification or by MS of the isolated pure isomers.
b
could be separated from the reaction mixture by flash column
chromatography. From the fact that there are only very few conve-
donors is one of the most fundamental parameters responsible
for the selectivity of glycosylation reactions. Glycosylation of 5
with acceptor 8 was then performed under the normal Schmidt
glycosylation conditions;19 however, the b-selectivity of this reac-
tion even dropped slightly, compared with entry 2 in Table 1. Also,
the 2-hydroxyl protecting group of donor 4 was altered from the
present electron-donating benzyl group to the strong electron-
withdrawing trifluorobenzenesulfonyl group with the hope of
nient methods available in the literature for the synthesis of b-
arabinofuranosides, donor 4 and its analogues can yet be regarded
as an efficient b- -arabinofuranosylating agent. This has been
D-
D
demonstrated very recently by Lowary and co-workers in the
impressive synthesis of the arabinan domains of mycobacterial
arabinogalactan and lipoarabinomannan, in which two b-D-arabin-
ofuranosidic linkages were constructed at the same time by use of
making a-glycosyl triflate the reaction intermediate, which could
the corresponding p-tolyl thioglycoside of 4.18
then undergo an SN2 reaction to produce b-glycosides.20 It should
be noted that 2-sulfonyl protecting groups are generally thought
as non-participating in glycosylation reactions, and have often
been employed in the synthesis of 1,2-cis-glycosides.21 Hence,
compound 3 was then treated with commercially available o-tri-
fluorobenzenesulfonyl chloride in the presence of KI–Ag2O and col-
lidine, as described previously,20 to give sulfonate 6 in 70% yield.
In this report, structural alteration of compound 4 with a view
to enhancing further its glycosylation selectivity has also been
made, but unfortunately, this turned out to be not very successful.
For instance, glycosyl trichloroacetimidate 5 was prepared from
thioglycoside 4 by a standard two-step procedure, as shown in
Scheme 1, considering the fact that the leaving group of glycosyl

Y. Wang et al. / Carbohydrate Research 343 (2008) 3100–3106
3103
Unfortunately, the reaction of donor 6 with acceptor 12 did not
bring any higher b-selectivity either (Table 1, entry 7).
of the crude phenyl 1-thio-
a
-
D
-arabinofuranoside (1.0 g,
ꢂ4.13 mmol) in a mixture of CH2Cl2 (35 mL) and DMF (7 mL) at
0 oC were added 2,6-lutidine (2.1 mL, 18 mmol) and di-tert-butyl-
silyl bis(trifluoromethanesulfonate) (1.5 mL, 4.12 mmol). The
resulting mixture was stirred for 2 h, after which it was concen-
trated under diminished pressure, diluted with EtOAc, and
washed successively with water and brine. The organic layer
was dried over MgSO4 and concentrated under diminished pres-
sure to give a residue that was purified by flash column chroma-
tography (6:1 cyclohexane–EtOAc) to give 3 (1.15 g, 73%) as a
In summary, the glycosylation property of the conformationally
constrained
toward a range of different glycosyl acceptors as a continuation
of our previous work.6 The results indicated that b-
-arabinofur-
D-arabinofuranosyl donor 4 has been investigated
D
anosides could be synthesized from this donor in modest to high
selectivities, though overall the selectivities were lower than those
obtained in
lenge in synthesizing b-
be regarded as an efficient b-
L
-arabinofuranosylation reactions. In view of the chal-
-arabinofuranosides, compound 4 may yet
-arabinofuranosylating agent. Struc-
D
D
white amorphous solid: [
a]
+182.8 (c 0.7 CHCl3); 1H NMR
D
tural modification of this compound has also been carried out in
the hope of further enhancement of the glycosylation selectivity
and this will continue to be our interest.
(400 MHz, CDCl3): d 7.51 (m, 2H, PhH), 7.30 (m, 3H, PhH), 5.32
(d, J 5.7 Hz, 1H, H-1), 4.34 (q, J 3.6 Hz, 1H, H-5a), 4.15 (t, J
6.6 Hz, 1H, H-2), 4.02 (dd-like, J 12.0, 7.2 Hz, 1H, H-3), 3.94 (m,
2H, H-4, H-5b), 2.48 (br s, 1H, OH), 1.06 (s, 9H, tBu), 0.99 (s,
t
9H, Bu); 13C NMR (75 MHz, CDCl3): d 134.5, 131.7, 129.3, 127.8
1. Experimental
(Ph), 91.4 (C-1), 81.3 (C-3), 81.2 (C-2), 74.0 (C-4), 67.6 (C-5),
27.7 (Me3C), 27.3 (Me3C), 22.9 (Me3C), 20.4 (Me3C); ESIMS: m/z
405.3 [M+Na]+, 421.3 [M+K]+; HRESIMS: calcd for C19H31O4SSi
[M+H]+ 383.1712, found 383.1725.
1.1. General methods
Unless otherwise stated, all moisture-sensitive reactions were
performed in oven-dried glassware under an argon atmosphere
using dry solvents. These were evaporated under diminished
pressure while maintaining the water bath temperature below
40 °C. All reactions were monitored by TLC using Silica Gel 60
F254 coated on aluminum sheet and the compounds were visual-
ized by UV or by treatment with 8% H2SO4 in MeOH followed
by heating. Flash chromatography was performed with the indi-
1.4. Phenyl 2-O-benzyl-3,5-O-(di-tert-butylsilanediyl)-
1-thio-a-D-arabinofuranoside (4)
BnBr (0.11 mL, 0.93 mmol) and Ag2O (327 mg, 1.41 mmol) were
added to a soln of 3 (183 mg, 0.48 mmol) in CH2Cl2 (5 mL), and the
reaction was stirred vigorously at room temperature for 72 h, after
which the mixture was filtered through a pad of silica gel. The fil-
trate was concentrated to give a residue, which was purified by
flash chromatography (100:0?60:1 cyclohexane–EtOAc) to afford
cated solvent system using 40–60 lm silica gel. Optical rotations
were measured at 20 °C with a Perkin–Elmer 343 polarimeter
(1 dm cell). CDCl3 and tetramethylsilane were used as solvent,
and internal standard, respectively, for 1H NMR (300 MHz and
400 MHz) spectra. 13C NMR spectra were recorded at 75 MHz
and 100 MHz by using CDCl3 as solvent, and the signals were as-
signed with the aid of DEPT, HSQC. Yields refer to chromatograph-
ically pure compounds and are calculated based on reagents
consumed.
the title compound 4 (170 mg, 75%) as a pale yellow oil: [a]
D
+126.8 (c 0.5 CHCl3); 1H NMR (300 MHz, CDCl3): d 7.44–7.19 (m,
10H, ArH), 5.43 (d, J 5.1 Hz, 1H, H-1), 4.78 (AB peak, J 12.0 Hz,
2H, PhCH2), 4.32 (q-like, J 3.9 Hz, 1H, H-5a), 4.14 (t-like, J 8.1 Hz,
t
1H, H-3), 3.96 (m, 3H, H-2, H-4, H-5b), 1.07 (s, 9H, Bu), 0.98 (s,
t
9H, Bu); 13C NMR (75 MHz, CDCl3) d 137.8, 134.7, 131.4, 129.1,
128.5, 128.1, 128.0, 127.9, 127.8, 127.5 (Ar), 90.1 (C-1), 87.1 (C-2
or C-4), 81.4 (C-3), 73.9 (C-2 or C-4), 72.4 (PhCH2), 67.5 (C-5),
27.7 (Me3C), 27.3 (Me3C), 22.8 (Me3C), 20.3 (Me3C); ESIMS: m/z
495.3 [M+Na]+; HRESIMS: calcd for C26H37O4SSi [M+H]+
473.2182, found 473.2186.
1.2. Phenyl 2,3,5-tri-O-acetyl-1-thio-
a
-
D
-arabinofuranoside (2)
To a stirred soln of penta-O-acetyl-
D
-arabinofuranose (1.0 g,
3.10 mmol) in CH2Cl2 (10 mL) was added thiophenol (0.5 mL,
4.88 mmol). BF3ꢁOEt2 (0.23 mL, 1.83 mmol) was then added drop-
wise at 0 oC. After stirring at 0 °C for 3 h, the reaction was
quenched by the addition of Et3N (0.6 mL, 4.30 mmol), and the
mixture was concentrated under diminished pressure. The residue
was diluted with EtOAc, washed successively with water and brine,
dried over MgSO4, and then concentrated under diminished pres-
sure. The residue was purified by flash chromatography
(3:1?2:1 cyclohexane–EtOAc,) to afford the desired product 2
1.5. 2-O-Benzyl-3,5-O-(di-tert-butylsilanediyl)-
a-
D-arabinofuranosyl trichloroacetimidate (5)
To a soln of 4 (160 mg, 0.34 mmol) in acetone (6.7 mL) and
water (0.3 mL) was added NBS (120 mg, 0.67 mmol), and the mix-
ture was stirred at room temperature for 1 h. The reaction was
then quenched by the addition of solid NaHCO3, and concentrated
under diminished pressure. The residue was purified by flash chro-
matography (7:1 cyclohexane–EtOAc,) to afford the hemiacetal
(822 mg, 72%) as a colorless syrup: [a]
+155.8 (c 0.9 CHCl3); 1H
D
NMR (300 MHz, CDCl3): d 7.51 (m, 2H, PhH), 7.31 (m, 3H, PhH),
5.54 (d-like, J 2.1 Hz, 1H, H-1), 5.28 (t, J 2.1 Hz, 1H, H-2), 5.08
(dd, J 5.4, 2.1 Hz, 1H, H-3), 4.48 (q, J 5.4 Hz, 1H, H-4), 4.40 (dd, J
12.0, 3.9 Hz, 1H, H-5a), 4.29 (dd, J 12.0, 5.4 Hz, 1H, H-5b), 2.11,
2.09, 2.08 (3s, 9H, Ac); 13C NMR (75 MHz, CDCl3): d 170.5, 170.0,
169.6 (3MeCO), 133.6, 132.2, 129.1, 127.9 (Ph), 90.9 (C-1), 81.6
(C-2), 80.2 (C-4), 77.3 (C-3), 62.9 (C-5), 20.8 (CH3CO); ESIMS: m/z
391.1 [M+Na]+; HRESIMS: calcd for C17H20NaO7S [M+Na]+
391.0827, found 391.0819.
intermediate (78 mg, 60%) as an
a/b mixture. A soln of the hemiac-
etal (50 mg, 0.13 mmol), CCl3CN (72
lL, 0.72 mmol), and catalytic
DBU in CH2Cl2 (5 mL) was stirred at room temperature for
30 min, after which the solvent was removed under diminished
pressure, and the resulting residue was purified by flash column
chromatography (8:1 cyclohexane–EtOAc + 1% Et3N) to give the
title compound
5 (51 mg, 75%) as a
white foam: 1H NMR
(300 MHz, CDCl3): d 8.61 (s, 1H, NH), 7.36–7.29 (m, 5H, PhH),
6.19 (d, J 2.7 Hz, 1H, H-1), 4.79 and 4.72 (AB peak, J 12.0 Hz, 2H,
PhCH2), 4.39 (dd, J 4.0 Hz, J 8.0 Hz, 1H, H-2), 4.28–4.10 (m,
1.3. Phenyl 3,5-O-(di-tert-butylsilanediyl)-1-thio-a-D-
arabinofuranoside (3)
t
2H, H-3, H-4), 4.10–3.95 (m, 2H, H-5), 1.08 (s, 9H, Bu), 1.00 (s,
Compound 2 was deacetylated following a standard proce-
9H, tBu). Imidate 5 was immediately used in the next step without
further characterization.
dure, and the product was used without purification. To a soln

3104
Y. Wang et al. / Carbohydrate Research 343 (2008) 3100–3106
1.6. Phenyl 3,5-O-(di-tert-butylsilanediyl)-2-O-
(dd, J 10.2, 3.6 Hz, 1H, H-3), 4.80 (d, J 3.2 Hz, 1H, H-10), 4.67 and
4.53 (AB, J 12.0 Hz, 2H, PhCH2), 4.31 (d, J 8.0 Hz, 1H, H-1), 4.29
(m, 1H, H-50a), 4.00 (t, J 8.0 Hz, 1H, H-40), 3.84 (m, 3H, H-20, H-30,
H-50a), 3.81 (t, J 6.8 Hz, 1H, H-5), 3.73 (dd, J 10.0, 6.4 Hz, 1H,
H-6a), 3.43 (s, 3H, OMe), 3.41 (overlapped with OMe, 1H, H-6b),
(2-trifluoromethylbenzenesulfonyl)-1-thio-
arabinofuranoside (6)
a-D-
To a stirred soln of 3 (92 mg, 0.24 mmol) in CH2Cl2 (20 mL) were
added s-collidine (62 l, 0.47 mmol), KI (62 mg, 0.37 mmol), Ag2O
(88 mg, 0.38 mmol), and o-trifluoromethylbenzenesulfonyl chlo-
ride (36
L, 0.23 mmol) at 0 oC. The reaction mixture was stirred
t
l
2.04, 1.99, 1.92 (3s, 9H, Ac), 0.99, 0.93 (2s, 18H, Bu); 13C NMR
(100 MHz, CDCl3): d 170.42, 170.36, 169.8 (3MeCO), 138.0, 128.6,
128.1, 128.0 (Ph), 107.8 (C-10), 102.3 (C-1), 88.0 (C-20), 81.6
(C-40), 74.2 (C-30), 72.3 (PhCH2), 71.8 (C-5), 71.4 (C-3), 69.3 (C-2),
67.7 (C-50), 67.6 (C-4), 66.4 (C-6), 57.2 (OCH3), 27.7, 27.3 (2Me3C),
22.8 (Me3C), 21.1, 20.92, 20.85 (3MeCO), 20.3 (Me3C); ESIMS: m/z
700.4 [M+H2O+], 705.3 [M+Na+]; HRESIMS: calcd for C33H50NaO13Si
[M + Na]+ 705.2918, found m/z 705.2904.
l
at 0 oC for 1 h, allowed to warm up to room temperature and stir-
red for another 36 h, after which the mixture was diluted with
CH2Cl2 and filtered through a pad of Celite. The filtrate was washed
successively with saturated aq NaHCO3 and brine, dried over
MgSO4, and concentrated under diminished pressure to give a res-
idue, which was then purified by flash column chromatography
(10:1 cyclohexane–EtOAc) to give 6 (99 mg, 70%) as a colorless
1.7.2. Methyl 2-O-benzyl-3,5-O-(di-tert-butylsilanediyl)-
oil: [a
]
D
+54.3 (c 2.1 CHCl3); 1H NMR (400 MHz, CDCl3): d 8.26
a
/b-
glucopyranoside (15)
/b-Mixture: 55 mg (white amorphous solid). Spectral data for
D-arabinofuranosyl-(1?6)-2,3,4-tri-O-benzoyl-a-D-
(d-like, J 8.8 Hz, 1H, ArH), 7.86 (d-like, J 8.8, 1H, ArH), 7.67 (m,
2H, ArH), 7.42 (m, 2H, ArH), 7.23 (m, 3H, ArH), 5.38 (d, J = 4.8 Hz,
1H, H-1), 4.72 (dd, J 7.2, 4.8 Hz, 1H, H-2), 4.22 (q-like, J 3.6 Hz,
1H, H-5a), 4.03 (dd, J 8.8, 7.2 Hz, 1H, H-3), 3.80 (m, 2H, H-5b,
H-4), 0.81 (s, 9H, tBu), 0.77 (s, 9H, tBu); 13C NMR (100 MHz, CDCl3):
d 135.0, 134.0, 133.1, 132.8, 132.7, 132.5, 129.3, 128.9 (q, JC–F
6.1 Hz, 1C), 128.4 (Ar), 122.5 (q, JC–F 273.0 Hz, 1C, CF3), 88.8
(C-1), 88.4 (C-2), 79.2 (C-3), 73.4 (C-4), 67.1 (C-5), 27.3, 27.1
(2Me3C), 22.7, 20.2 (2Me3C); ESIMS: m/z 613.7 [M+Na]+; HRESIMS:
calcd for C26H33F3O6S2Si [M+Na]+ 613.1338, found 613.1352.
a
the major b-isomer: 1H NMR (400 MHz, CDCl3) d 7.98–7.26 (m,
20H, Ar), 6.12 (t, J 10.0 Hz, 1H, H-3), 5.47 (t, J 10.0 Hz, 1H, H-4),
5.20 (m, 2H, H-1, H-2), 5.09 (d, J 5.6 Hz, 1H, H-10), 4.81 (AB, J
12.4 Hz, 2 H, PhCH2), 4.35–4.22 (m, 3H, H-5, H-30, H-5a0 ), 3.96–3.85
(m, 3H, H-6a, H-20, H-5b0 ), 3.71 (m, 1H, H-6b), 3.61 (m, 1H, H-40),
3.39 (s, 3H, OMe), 1.06 (s, 9H, tBu), 0.98 (s, 9H, tBu); 13C NMR
(100 MHz, CDCl3) d 166.02, 165.98, 165.5 (3PhCO), 138.3, 133.6,
133.5, 133.2, 130.2, 130.1, 130.0, 128.6, 128.48, 128.46, 128.1,
127.8 (Ar), 101.4 (C-10), 96.9 (C-1), 81.1 (C-20), 79.0 (C-30), 73.6 (C-
40), 72.4 (PhCH2), 71.9 (C-4), 70.8 (C-3), 69.8 (C-2), 69.5 (C-50),
68.5 (C-5), 67.8 (C-6), 55.7 (OCH3), 27.8, 27.4 (2Me3C), 22.8, 20.3
(2Me3C); ESIMS: m/z 886.6 [M+H2O]+, 891.5 [M+Na]+; HRESIMS:
calcd for C48H56NaO13Si [M+Na]+ 891.3388, found m/z 891.3400.
1.7. General procedure for the synthesis of disaccharides 14–21
A mixture of the thioglycoside 4 or 6 (0.18 mmol) and the cor-
responding sugar alcohol (0.12 mmol) in CH2Cl2 (10 mL) was stir-
red at room temperature in the presence of 4 Å molecular sieves
(500 mg) for 20–30 min. After the mixture was cooled to ꢀ20 °C,
NIS (61 mg, 0.27 mmol) followed by a soln of AgOTf (23 mg,
1.7.3. Methyl 2-O-benzyl-3,5-O-(di-tert-butylsilanediyl)-
a
/b-
mannopyranoside (16)
/b-Mixture: 28 mg (white amorphous solid). Spectral data for
D-arabinofuranosyl-(1?6)-2,3,4-tri-O-benzoyl-a-D-
90 lmol) in toluene (0.2 mL) was added. The reaction mixture
was warmed slowly to room temperature, and stirring was contin-
ued for 10–20 min. The reaction was quenched by the addition of
Et3N. The suspension was diluted with EtOAc and filtered through
a pad of silica gel, and the filtrate was washed successively with
saturated aq Na2S2O3 and brine. The organic layer was dried over
MgSO4 and concentrated under diminished pressure to give a res-
idue, which was purified by flash column chromatography (10:1
cyclohexane–EtOAc) to afford the corresponding disaccharide.
a
the major b-isomer: 1H NMR (400 MHz, CDCl3): d 8.09 (d, J
7.2 Hz, 2H, Ar), 7.95 (d, J 7.2 Hz, 2H, Ar), 7.81 (d, J 7.2 Hz, 2 H,
Ar), 7.60–7.23 (m, 14H, Ar), 5.84 (dd, J 10.0, 3.2 Hz, 1H, H-3),
5.76 (t, J 10.0 Hz, 1H, H-4), 5.63 (dd, J 3.2, 2.0 Hz, 1H, H-2), 5.12
(d, J 5.6 Hz, 1H, H-10), 4.93 (d, J 1.2 Hz, H-1), 4.80 (AB, J 12.4 Hz,
2H, PhCH2), 4.35–4.21 (m, 3 H, H-5, H-30, H-5a0 ), 3.94–3.77 (m,
4H, H-6, H-20, H-50b), 3.61 (m, 1H, H-40), 3.43 (s, 3H, OMe), 1.03
(s, 9H, tBu), 0.97 (s, 9H, tBu); 13C NMR (100 MHz, CDCl3): d
165.83, 165.80, 165.7 (3PhCO), 138.2, 133.7, 133.6, 133.3, 130.2,
130.04, 129.95, 128.8, 128.7, 128.48, 128.46, 128.2 (Ar), 101.3
(C-10), 98.5 (C-1), 81.0 (C-20), 79.0 (C-30), 73.8 (C-40), 71.8 (PhCH2),
70.73 (C-2), 70.67 (C-5), 70.3 (C-3), 68.6 (C-50), 68.0 (C-6), 67.7
(C-4), 55.5 (OCH3), 27.7, 27.4 (2Me3C), 22.8, 20.3 (2Me3C); ESIMS:
m/z 891.5 [M+Na]+; HRESIMS: calcd for C48H56NaO13Si [M+Na]+
891.3388, found m/z 891.3390.
1.7.1. Methyl 2-O-benzyl-3,5-O-(di-tert-butylsilanediyl)-
a/b-D-arabinofuranosyl-(1?6)-2,3,4-tri-O-acetyl-b-D-
galactopyranoside (14)
b-Isomer: 42 mg (white amorphous solid): [
a
]
D
ꢀ43.0 (c 1.2
CHCl3); 1H NMR (400 MHz, CDCl3): d 7.34–7.19 (m, 5H, ArH),
5.33 (d, J 2.4 Hz, 1H, H-4), 5.09 (dd, J 10.4, 8.0 Hz, 1H, H-2), 4.93
(dd, J 10.4, 3.6 Hz, 1H, H-3), 4.86 (d, J 5.6 Hz, 1H, H-10), 4.72 (AB,
J 12.4 Hz, 2H, PhCH2), 4.27 (d, J 8.0 Hz, 1H, H-1), 4.23 (t, J
10.4 Hz, H-30), 4.18 (dd, J 8.8, 4.8 Hz, 1H, H-50a), 3.82 (m, 3H, H-20,
H-50b, H-5), 3.67 (dd, J 10.4, 5.2 Hz, 1H, H-6a), 3.53 (m, 2H, H-40,
H-6b), 3.37 (s, 3H, OMe), 2.03, 1.98, 1.90 (3s, 9H, Ac), 1.01, 0.91
1.7.4. Methyl 2-O-benzyl-3,5-O-(di-tert-butylsilanediyl)-
a
/b-
-glucopyranoside (17)
b-Isomer: 37 mg (white foam): [
D-arabinofuranosyl-(1?3)-2-O-benzoyl-4,6-O-benzylidene-
a-
D
t
(2s, 18H, Bu); 13C NMR (100 MHz, CDCl3): d 170.3, 170.2, 169.8
a
]
D ꢀ43.0 (c 1.2 CHCl3); 1H NMR
(3MeCO), 138.1, 128.6, 128.2, 128.0 (Ph), 102.2 (C-1), 100.9 (C-
10), 80.7 (C-20), 78.6 (C-30), 74.0 (C-40), 72.5 (C-5), 71.9 (PhCH2),
71.3 (C-3), 69.3 (C-2), 68.4 (C-50), 67.9 (C-4), 67.0 (C-6), 57.2
(OCH3), 27.8, 27.4 (2Me3C), 22.8 (Me3C), 21.0, 20.9, 20.8 (3MeCO),
20.3 (Me3C); ESIMS: m/z 700.4 [M+H2O+], 705.3 [M+Na+]; HRE-
SIMS: calcd for C33H50NaO13Si [M + Na]+ 705.2918, found m/z
705.2903.
(400 MHz, CDCl3): d 8.11 (d, J = 8.0 Hz, 2H, ArH), 7.63 (t, J = 7.6 Hz,
1H, ArH), 7.50–7.38 (m, 7H, ArH), 7.14 (m, 3H, ArH), 7.01 (d, J 7.6
Hz, 2H, ArH), 5.53 (s, 1H, PhCH), 5.28 (d, J 4.8 Hz, 1H, H-10), 5.23
(dd, J 9.6, 3.6 Hz, 1H, H-2), 5.08 (d, J 3.2 Hz, 1H, H-1), 4.59 and
4.39 (AB peak, J 12.6 Hz, 2H, PhCH2), 4.49 (t, J 9.6 Hz, 1H, H-3),
4.32 (m, 2H, H-30, H-5a0 ), 3.95 (m, 2H, H-5, H-6a), 3.77 (m, 3H,
H-4, H-20, H-5b0 ), 3.56 (m, 2H, H-40, H-6b), 3.39 (s, 3H, OMe), 0.94
t
t
a
-Isomer: 8 mg (white amorphous solid): [
a
]
D
+10.6 (c 1.2
(s, 9H, Bu), 0.92 (s, 9H, Bu); 13C NMR (100 MHz, CDCl3): d 165.8
(PhCO), 137.7, 137.5, 133.6, 130.0, 129.7, 129.4, 128.9, 128.4,
128.3, 127.63, 127.57, 126.6 (Ar), 102.4 (PhCH), 99.8 (C-10), 98.0
CHCl3); 1H NMR (400 MHz, CDCl3): d 7.32–7.19 (m, 5H, ArH),
5.41 (d, J 3.2 Hz, 1H, H-4), 5.13 (dd, J 10.4, 8.0 Hz, 1H, H-2), 4.95

Y. Wang et al. / Carbohydrate Research 343 (2008) 3100–3106
3105
(C-1), 80.3 (C-20), 79.7 (C-4), 77.9 (C-30), 74.7 (C-2), 74.6 (C-40), 72.6
(C-3), 71.4 (PhCH2), 69.2 (C-50), 68.2 (C-6), 63.0 (C-5), 55.5 (OCH3),
27.6, 27.3 (2Me3C), 22.6, 20.2 (2Me3C); ESIMS: m/z 771.6 [M+Na]+;
HRESIMS: calcd for C41H53O11Si [M+H]+ 749.3357, found m/z
749.3372.
(m, 1H, H-5), 3.97–3.85 (m, 3H, H-50a, H-20, H-6a), 3.71 (dd, J 11.6,
6.8 Hz, H-6b), 3.64 (m, 1H, H-40), 1.47, 1.43, 1.32, 1.31 (4s, 12H,
4Me), 1.07 (s, 9H, tBu), 0.98 (s, 9H, tBu); 13C NMR (100 MHz, CDCl3):
d 138.3, 128.4, 128.1, 127.7 (Ar), 109.4, 108.7 (2Me2C), 100.6 (C-10),
96.5 (C-1), 80.8 (C-20), 78.7 (C-3’), 73.9 (C-40), 71.7 (PhCH2), 71.3 (C-
4), 70.8 (C-2), 70.7 (C-3), 68.7 (C-50), 67.9 (C-5), 67.0 (C-6), 27.8,
27.4 (2Me3C), 26.3, 26.2, 25.2, 24.6 (4Me), 22.8, 20.3 (2Me3C);
ESIMS: m/z 645.6 [M+Na]+; HRESIMS: calcd for C32H50NaO10Si
[M+Na]+ 645.3071, found m/z 645.3079.
a-Isomer: 13 mg (colorless syrup): [a]
+72.0 (c 1.0 CHCl3); 1H
D
NMR (400 MHz, CDCl3): d 8.13 (d, J 7.6 Hz, 2H, ArH), 7.60 (t, J
7.6 Hz, 1H, ArH), 7.47 (m, 4H, ArH), 7.32–7.20 (m, 6H, ArH), 7.11
(m, 2H, ArH), 5.60 (s, 1H, PhCH), 5.35 (br s, J 1.6 Hz, 1H, H-10),
5.17 (dd, J 9.6, 3.6 Hz, 1H, H-2), 4.99 (d, J 3.6 Hz, 1H, H-1), 4.54
(AB peak, J 11.6 Hz, 2H, PhCH2), 4.41 (t, J 9.6 Hz, 1H, H-3), 4.33
(dd, J 10.0, 4.8 Hz, H-50a), 3.93 (m, 2H, H-30, H-40), 3.88 (dd-like, J
7.2, 1.6 Hz, H-20), 3.84–3.75 (m, 3H, H-5b0 , H-4, H-6a), 3.72 (t, J
10.0 Hz, 1H, H-6b), 3.56 (td, J 10.0, 5.6 Hz, 1H, H-5), 3.40 (s, 3H,
OMe), 0.96 (s, 9H, tBu), 0.70 (s, 9H, tBu); 13C NMR (100 MHz,
CDCl3): d 166.0 (PhCO), 138.1, 137.2, 133.7, 130.1, 129.7, 129.2,
128.7, 128.5, 128.4, 127.8, 127.6, 126.2 (Ar), 107.8 (C-10), 101.9
(PhCH), 98.4 (C-1), 88.5 (C-20), 82.3 (C-4), 81.5 (C-3’ or C-40), 73.8
(C-3), 73.7 (C-5), 72.1 (PhCH2), 71.8 (C-2), 69.2 (C-50), 67.6 (C-6),
62.5 (C-40 or C-30), 55.7 (OCH3), 27.6, 27.1 (2Me3C), 22.7, 20.0
(2Me3C); ESIMS: m/z 771.5 [M+Na]+; HRESIMS: calcd for
C41H53O11Si [M+H]+ 749.3357, found m/z 749.3391.
a
-Isomer: 14 mg (colorless syrup): [
a]
D ꢀ102.3 (c 0.9 CHCl3); 1H
NMR (400 MHz, CDCl3): d 7.40–7.28 (m, 5H, PhH), 5.53 (d, J 5.2 Hz,
1H, H-1), 5.01 (d, J 3.2 Hz, 1H, H-10), 4.73 (AB peak, J 12.0 Hz, 2H,
PhCH2), 4.62 (dd, J 8.0, 2.4 Hz, 1H, H-3), 4.32 (m, 2H, H-50 , H-2),
a
4.26 (dd, J 8.0, 2.0 Hz, H-4), 4.09 (dd, J 9.2, 7.2 0Hz, 1H, H-30), 4.01
(m, 2H, H-5, H-20), 3.97–3.89 (m, 2H, H-40, H-5b), 3.80 (dd, J 10.4,
6.4 Hz, 1H, H-6a), 3.69 (dd, J 10.4, 7.2 Hz, H-6b), 1.51, 1.44, 1.33,
t
t
1.26 (4s, 12H, 4Me), 1.06 (s, 9H, Bu), 0.99 (s, 9H, Bu); 13C NMR
(100 MHz, CDCl3): d 138.2, 128.5, 128.0, 127.9 (Ar), 109.5, 108.8
(2Me2C), 107.9 (C-10), 96.6 (C-1), 87.9 (C-20), 81.5 (C-30), 74.1 (C-
40), 72.2 (PhCH2), 71.1 (C-4), 70.9 (C-2 and C-3), 67.8 (C-5’), 67.5
(C-6), 66.3 (C-5), 27.7, 27.4 (2Me3C), 26.3, 26.2, 25.2, 24.7 (4Me),
22.9, 20.4 (2Me3C); ESI-MS: m/z 645.6 [M+Na]+; HRESIMS: calcd
for C32H50NaO10Si [M+Na]+ 645.3071, found m/z 645.3079.
1.7.5. Methyl 2-O-benzyl-3,5-O-(di-tert-butylsilanediyl)-
a/b-
D-arabinofuranosyl-(1?4)-2,3,6-tri-O-acetyl-b-
D-
1.7.7. Methyl 2-O-benzyl-3,5-O-(di-tert-butylsilanediyl)-
galactopyranoside (18)
a/b-D-arabinofuranosyl-(1?6)-2,3,4-tri-O-benzyl-a-D-
b-Isomer: 74 mg (white foam): [
a
]
D ꢀ41.2 (c 1.2 CHCl3); 1H NMR
glucopyranoside (20)
(400 MHz, CDCl3): d 7.47 (d, J 6.8 Hz, 2H, ArH), 7.34 (t, J 7.4 Hz, 2H,
ArH), 7.28 (m, 1H, ArH), 5.40 (dd, J 10.4, 8.0 Hz, 1H, H-2), 5.11 (d, J
5.2 Hz, 1H, H-10), 5.02 (dd, J 10.4, 2.8 Hz, 1H, H-3), 4.96 and 4.76
(AB peak, J 12.8 Hz, 2H, PhCH2), 4.41 (d, J 7.6 Hz, 1H, H-1), 4.32
(t, J 10.2 Hz, 1H, H-30), 4.22 (m, 3H, H-5a0 , H-6a, H-6b), 4.11 (d, J
2.4 Hz, 1H, H-4), 3.93 (m, 2H, H-50a, H-20), 3.78 (t, J = 6.2 Hz, 1H,
H-5), 3.58 (m, 1H, H-40), 3.49 (s, 3H, OMe), 2.06, 2.05, 2.03 (3s,
b-Isomer: 49 mg (colorless syrup): [
a
]
D
ꢀ14.5 (c 1.1 CHCl3); 1H
NMR (300 MHz, CDCl3): d 7.29 (m, 20H, ArH), 5.00 (d, J 5.4 Hz,
1H, H-10), 4.97 (d, J 11.1 Hz, 1H, PhCHaHb), 4.87–4.62 (m, 7H,
PhCH2), 4.59 (d, J 3.0 Hz, 1H, H-1), 4.35 (t, J 9.0 Hz, 1H, H-30),
4.27 (dd, J 9.3, 5.1 Hz, 1H, H-50a), 4.01–3.88 (m, 4H, H-20, H-50b,
H-3, H-6a), 3.80–3.47 (m, 5H, H-5, H-40, H-6b, H-4, H-2), 3.32 (s,
3H, OMe), 1.05, 0.98 (2s, 18H, Bu); 13C NMR (75 MHz, CDCl3): d
t
t
t
9H, 3Ac), 1.07 (s, 9H, Bu), 0.98 (s, 9H, Bu); 13C NMR (100 MHz,
CDCl3): d 170.5, 170.0, 169.3 (3MeCO), 138.2, 128.2, 127.6, 127.3
(Ar), 101.7 (C-1), 100.3 (C-10), 80.5(C-20), 78.0 (C-30), 73.7 (C-40),
73.5 (C-3), 71.84 (C-5), 71.80 (C-4), 71.2 (PhCH2), 69.2 (C-2), 67.9
(C-50), 63.3 (C-6), 56.4 (OCH3), 27.5, 27.1 (2Me3C), 22.6 (Me3C),
20.81, 20.78, 20.76 (3MeCO), 20.0 (Me3C); ESIMS: m/z 705.3
[M+Na]+, 721.5 [M+K]+; HRESIMS: calcd for C33H50NaO13Si
[M+Na]+ 705.2918, found m/z 705.2923.
139.1, 138.7, 138.4, 138.2, 128.7, 128.6, 128.5, 128.3, 128.2,
128.1, 127.9, 127.85, 127.80 (Ph), 101.2 (C-1’), 98.2 (C-1), 82.4
(C-20), 81.0 (C-3), 80.2 (C-2), 79.2 (C-3’), 78.2 (C-4), 75.9, 75.1
(PhCH2), 73.64 (C-40), 73.57, 71.7 (PhCH2), 70.5 (C-5), 68.5 (C-50),
67.6 (C-6), 55.3 (OCH3), 27.8, 27.4 (2Me3C), 22.8, 20.3 (2Me3C);
ESIMS: m/z 844.9 [M+H2O+]; HRESIMS: calcd for C48H62NaO10Si
[M+Na]+ 849.4010, found m/z 849.4030.
a
-Isomer: 24 mg (colorless syrup): [
a
]
ꢀ52.0 (c 1.2 CHCl3); 1H
D
a-Isomer: 18 mg (white foam): [
a
]
D +27.2 (c 1.2 CHCl3); 1H NMR
NMR (300 MHz, CDCl3) d 7.30 (m, 20H, ArH), 5.03 (d, J 3.0 Hz, 1H,
(400 MHz, CDCl3): d 7.36–7.26 (m, 5H, Ar), 5.25 (dd, J 10.4, 8.0 Hz,
1H, H-2), 4.89 (d, J 2.8 Hz, 1H, H-10), 4.71 and 4.67 (AB peak, J
11.6 Hz, 2H, PhCH2), 4.69 (dd, J 10.0, 3.2 Hz, 1H, H-3), 4.44 (dd, J
10.2, 6.0 Hz, 1H, H-6a), 4.34 (d, J 7.6 Hz, 1H, H-1), 4.26 (dd, J 10.4,
4.4 Hz, 1H, H-50a), 4.13–4.05 (m, 5H, H-4, H-20, H-30, H-40, H-6b),
3.91 (t, J 9.4 Hz, 1H, H-50a), 3.74 (t, J 7.2 Hz, 1H, H-5), 3.49 (s, 3H,
H-1’), 4.98 (d, J 10.8 Hz, 1H, PhCHaHb), 4.88–4.73 (m, 4H, PhCH2),
4.67–4.60 (m, 4H, PhCH2, H-1), 4.19 (m, 1H, H-50 ), 4.08 (t-like, J
a
8.1 Hz, 1H, H-30), 4.02–3.88 (m, 5H, H-20, H-5b0 , H-3, H-40, H-6a),
3.75 (m, 1H, H-5), 3.65–3.55 (m, 2H, H-6b, H-4), 3.53 (dd, J 9.6,
t
3.6 Hz, 1H, H-2), 3.36 (s, 3H, OMe), 1.05, 0.95 (2s, 18H, Bu); 13C
NMR (75 MHz, CDCl3)
d 139.0, 138.5, 138.4, 138.0, 128.70,
t
OMe), 2.06, 2.02, 2.00 (3s, 9H, 3Ac), 1.05 (s, 9H, Bu), 1.02 (s, 9H,
128.66, 128.58, 128.30, 128.26, 128.1, 128.00, 127.95, 127.87
(Ph), 107.5 (C-1’), 98.3 (C-1), 88.0 (C-20), 82.3 (C-3), 81.8 (C-30),
80.3 (C-2), 78.0 (C-4), 76.1, 75.3 (PhCH2), 74.2 (C-40), 73.6, 72.1
(PhCH2), 70.2 (C-5), 67.7 (C-50), 67.0 (C-6), 55.4 (OCH3), 27.7, 27.3
(2Me3C), 22.8, 20.3 (2Me3C); ESIMS: m/z 844.9 [M+H2O+]; HRE-
SIMS: calcd for C48H62NaO10Si [M + Na]+ 849.4010, found m/z
849.4023.
tBu); 13C NMR (100 MHz, CDCl3): d 170.5, 170.2, 169.4 (3MeCO),
137.7, 128.3, 127.9, 127.7 (Ar), 108.7 (C-10), 102.0 (C-1), 87.5 (C-
20), 81.6 (C-30), 74.0, 73.7 (C-4, C-40), 72.2 (C-3), 72.1 (PhCH2),
71.5 (C-5), 68.9 (C-2), 67.6 (C-50), 61.2 (C-6), 56.8 (OCH3), 27.4,
27.1 (2Me3C), 22.6 (Me3C), 20.9, 20.8, 20.7 (3Ac), 20.1 (Me3C);
ESIMS: m/z 705.6 [M+Na]+; HRESIMS: calcd for C33H50NaO13Si
[M+Na]+ 705.2918, found m/z 705.2902.
1.7.8. 3,5-O-(Di-tert-butylsilanediyl)-2-O-(2-
1.7.6. 2-O-Benzyl-3,5-O-(di-tert-butylsilanediyl)-
arabinofuranosyl-(1?6)-1,2;3,4-di-O-isopropylidene-
a
/b-
D
-
trifluoromethylbenzenesulfonyl)-
(1?6)-1,2;3,4-di-O-isopropylidene-
b-Isomer: (38 mg, colorless syrup): [
a
a
/b-
D
-arabinofuranosyl-
-galactopyranose (21)
D +187.7 (c 1.9 CHCl3); 1H
a
-D
-
-D
galactopyranose (19)
a
]
b-Isomer: 80 mg (colorless syrup): [
a]
D +186.6 (c 0.9 CHCl3); 1H
NMR (400 MHz, CDCl3): d 8.23 (d, J 7.2 Hz, 1H, Ar), 7.84 (d, J 7.2 Hz,
1H, Ar), 7.66 (m, 2H, Ar), 5.44 (d, J 4.8 Hz, 1H, H-1), 5.15 (d, J 5.2 Hz,
1H, H-10), 4.63 (dd, J 9.2, 5.2 Hz, 1H, H-20), 4.54 (dd, J 8.0, 2.0 Hz, 1H,
H-3), 4.33 (t, J 9.2 Hz, 1H, H-3’), 4.24–4.18 (m, 3H, H-2, H-4, H-50a),
NMR (400 MHz, CDCl3): d 7.44–7.26 (m, 5H, PhH), 5.54 (d, J 4.8 Hz,
1H, H-1), 5.13 (d, J 5.2 Hz, 1H, H-10), 4.81 (AB peak, J 12.8 Hz, 2H,
PhCH2), 4.57 (dd, J 8.0, 2.4 Hz, 1H, H-3), 4.36 (t, J 9.2 Hz, 1H,
H-30), 4.29 (m, 2 H, H-50a, H-2), 4.24 (dd, J 8.0, 2.0 Hz, H-4), 4.03
3.96 (t-like, J 6.0 Hz, 1H, H-5), 3.81 (m, 2H, H-50 , H-6a), 3.60 (dd, J
b

3106
Y. Wang et al. / Carbohydrate Research 343 (2008) 3100–3106
10.8, 6.0 Hz, H-6b), 3.54 (m, 1H, H-40), 1.50, 1.36, 1.26, 1.19 (4s,
References
12H, 4Me), 0.89 (s, 9H, Bu), 0.77 (s, 9H, Bu); 13C NMR (100 MHz,
CDCl3): d 135.4, 133.9, 132.3, 131.9 (Ar), 129.3 (q, JC–F 33.7 Hz,
1C, Ar), 128.8 (q, JC–F 5.9 Hz, 1C, Ar), 122.5 (q, JC–F 273.0 Hz, 1C,
Ar), 109.3, 109.0 (2Me2C), 99.1 (C-10), 96.5 (C-1), 82.1 (C-2’), 76.0
(C-30), 73.2 (C-40), 71.0 (C-4), 70.84 (C-2), 70.79 (C-3), 68.4 (C-50),
67.2 (C-6), 66.7 (C-5), 27.4, 27.2 (2Me3C), 26.3, 26.2, 25.2,
24.7 (4Me), 22.7, 20.2 (2Me3C); ESIMS: m/z 763.9 [M+Na]+; HRE-
SIMS: calcd for C32H47F3NaO12SSi [M+Na]+ 763.2407, found
763.2414.
t
t
1. (a) Fincher, G. B.; Stone, B. A. Ann. Rev. Plant Physiol. 1983, 34, 47–70; (b) Ridley,
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a
-Isomer: 19 mg (colorless syrup): [a]
+79.3 (c 1.2 CHCl3); 1H
D
NMR (400 MHz, CDCl3): d 8.25 (d, J 6.8 Hz, 1H, Ar), 7.85 (d, J
6.8 Hz, 1H, Ar), 7.68 (m, 2H, Ar), 5.46 (d, J 5.2 Hz, 1H, H-1), 5.10
(d, J 2.8 Hz, 1H, H-1’), 4.65 (dd, J 7.2, 2.4 Hz, 1H, H-20), 4.55 (dd, J
8.0, 2.4 Hz, 1H, H-3), 4.27–4.21 (m, 3H, H-2, H-4, H-50a), 4.00 (t, J
8.4 Hz, 1H, H-3’), 3.95 (t-like, J 7.2 Hz, 1H, H-5), 3.81 (m, 2H,
H-50b, H-40), 3.75 (dd, J 10.4, 6.0 Hz, 1H, H-6a), 3.57 (dd, J 10.8,
7.2 Hz, H-6b), 1.49, 1.37, 1.30, 1.27 (4s, 12H, 4Me), 0.84 (s, 9H,
t
tBu), 0.77 (s, 9H, Bu); 13C NMR (100 MHz, CDCl3): d 134.8, 134.2,
133.0, 132.4 (Ar), 129.3 (q, JC–F 33.7 Hz, 1C, Ar), 128.9 (q, JC–F
6.1 Hz, 1C, Ar), 122.5 (q, JC-F 273.0 Hz, 1C, Ar), 109.5, 108.9
(2Me2C), 106.2 (C-1’), 96.5 (C-1), 89.4 (C-20), 79.4 (C-30), 73.3
(C-40), 70.9 (C-4), 70.81 (C-2), 70.75 (C-3), 68.2 (C-6), 67.4 (C-50),
66.6 (C-5), 27.3, 27.2 (2Me3C), 26.3, 26.2, 25.2, 24.5 (4Me), 22.7,
20.2 (2Me3C); ESI-MS: m/z 763.9 [M+Na]+; HRESIMS: calcd for
C32H47F3NaO12SSi [M+Na]+ 763.2407, found m/z 763.2414.
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Liu, C.; Nacario, R. C.; Schriemer, D. C.; Klassen, J. S.; Peters, T.; Lowary, T. L. J.
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Acknowledgments
Financial support by the School of Chemistry and Chemical
Biology at University College Dublin and by the Research Frontier
Program of Science Foundation Ireland is gratefully acknowledged.
19. Schmidt, R. R.; Kinzy, W. Adv. Carbohydr. Chem. Biochem. 1994, 50, 21–123.
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Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.carres.2008.09.006.