Synthesis of octyl arabinofuranosides as substrates for mycobacterial arabinosyltransferases

Article abstract of DOI:10.1016/S0008-6215(02)00541-4

A panel of octyl oligosaccharides comprised of arabinofuranose rings have been synthesized via efficient and readily scaleable routes. The key glycosylation reactions involved the coupling of octyl glycoside acceptors with the appropriate thioglycosides using N-iodosuccinimide and silver triflate activation. These syntheses were undertaken to provide substrates suitable for use in assays of mycobacterial arabinosyltransferases.

Full text of DOI:10.1016/S0008-6215(02)00541-4

Carbohydrate Research 338 (2003) 581–588
www.elsevier.com/locate/carres
Synthesis of octyl arabinofuranosides as substrates for
mycobacterial arabinosyltransferases
Jeongseok Han, Rajendrakumar Reddy Gadikota, Patrick R. McCarren,
Todd L. Lowary*
Department of Chemistry, The Ohio State Uni6ersity, 100 West 18th A6enue, Columbus, OH 43210, USA
Received 30 October 2002; accepted 10 December 2002
Abstract
A panel of octyl oligosaccharides comprised of arabinofuranose rings have been synthesized via efficient and readily scaleable
routes. The key glycosylation reactions involved the coupling of octyl glycoside acceptors with the appropriate thioglycosides
using N-iodosuccinimide and silver triflate activation. These syntheses were undertaken to provide substrates suitable for use in
assays of mycobacterial arabinosyltransferases. © 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Synthesis; Octyl arabinofuranosides; Mycobacterial arabinosyltransferases
1. Introduction
In an earlier publication, we showed that fragments
of hexasaccharide 1, which were protected at the ‘re-
ducing’ end as a methyl glycoside, were substrates for
mycobacterial AraT’s.6 However, these methyl gly-
cosides are relatively poor substrates when compared to
analogs that are glycosides of longer-chain alcohols
(e.g., octanol and decanol).7 Moreover, the assay used
for evaluating potential substrates and inhibitors of
these enzymes involves a butanol extraction of the
assay mixture, a step that is significantly facilitated
though the use of oligosaccharide substrates with more
lipophilic aglycones. Therefore, in the interest of effi-
ciently screening a wide range of potential inhibitors of
these enzymes, it was necessary to synthesize the octyl
glycoside fragments of 1, which could be used as sub-
strates in these assays. In this paper, we describe the
synthesis of these oligosaccharides (2–7, Fig. 1) via
routes that are slightly modified compared to those
used for the preparation of the corresponding methyl
glycosides.6
The cell wall of mycobacteria, including the pathogens
Mycobacterium tuberculosis and Mycobacterium leprae,
is comprised in large part of two polysaccharides,
lipoarabinomannan (LAM) and arabinogalactan
(AG).1 Although these polysaccharides fulfill different
roles in the cell-wall complex, a feature shared by both
is an arabinan component that contains approx 70
arabinofuranose residues. A key structural motif in this
arabinan is the hexasaccharide 1, which is found at the
non-reducing ends of both polymers. Mycobacterial
viability is critically dependent upon its ability to pro-
duce both polysaccharides, and ethambutol, a drug
used to treat tuberculosis, acts by inhibiting at least one
of the arabinosyltransferases (AraT’s) that assemble the
arabinan portions of AG and LAM.2 The absence of
arabinofuranose-containing oligo- or polysaccharides in
humans (and all mammals) makes these enzymes partic-
ularly attractive drug targets.3 This fact, combined with
the demonstration of the mode of action of ethambutol,
has prompted increasing interest in identifying other
inhibitors of these AraT’s both by our group4 and
others.5
2. Results and discussion
We endeavored to develop synthetic routes to 2–7 that
involved a minimum number of protecting group
classes and readily available monosaccharide building
* Corresponding author
E-mail address: lowary.2@osu.edu (T.L. Lowary).
0008-6215/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0008-6215(02)00541-4

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J. Han et al. / Carbohydrate Research 338 (2003) 581–588
trisaccharide 4, were carried out in two steps each by
reacting the appropriate acceptor (8, 9, or 10) with
thioglycoside 11 in the presence of N-iodosuccinimide
and silver triflate (Scheme 1). The protected oligosac-
charides 14–16 were obtained in 78–92% yields, and
the stereochemistry of the nascent glycosidic bond was
straightforwardly determined through the use of 1H and
13C NMR spectroscopy.9 Deprotection of 14–16 was
done under standard conditions using sodium methox-
ide giving 2–4 in excellent yield. This approach to 15 is
blocks. The monomers chosen for these syntheses were
8–13 (Fig. 2), which were prepared as previously re-
ported.8 We note that we prefer the use of thioglycoside
11 over the corresponding peracetylated derivative6 as
11 is a readily crystalline material, which can be
purified directly from the crude reaction mixture. This
significantly facilitates not only the preparation of large
amounts of 11 but also donors 12 and 13, which can be
prepared in a few steps from 11.
The synthesis of the disaccharides 2 and 3, as well as
Fig. 1. Hexasaccharide motif common to both mycobacterial arabinogalactan and lipoarabinomannan (1); synthetic targets (2–7).
Fig. 2. Monosaccharide building blocks used for the synthesis of (2–7).
Scheme 1. (a) 11, N-iodosuccinimide, AgOSO2CF3, CH2Cl2, 0 °C, 90 (for 8), 92 (for 9), 78% (for 10). (b) NaOCH3, CH3OH, rt,
93 (for 14), 85 (for 15), 84% (for 16).

J. Han et al. / Carbohydrate Research 338 (2003) 581–588
583
Scheme 2. (a) 12, N-iodosuccinimide, AgOSO2CF3, CH2Cl2, 0 °C, 82%. (b) n-Bu4NF, THF, rt, 84%. (c) 11, N-iodosuccinimide,
AgOSO2CF3, CH2Cl2, 0 °C, 80%. (d) BzOH, Ph3P, DEAD, THF, 0 °C“rt, 90%. (e) 11, N-iodosuccinimide, AgOSO2CF3,
CH2Cl2, 0 °C, 88%. (f) NaOCH3, CH3OH, rt, 77 (for 20), 87 (for 21), 88% (for 24). (g) 13, N-iodosuccinimide, AgOSO2CF3,
CH2Cl2, 0 °C, 82%. (h) n-Bu4NF, THF, rt, 88%. (i) 11, N-iodosuccinimide, AgOSO2CF3, CH2Cl2, 0 °C, 87%.
superior to our previously reported route6 to the corre-
sponding methyl glycoside, which employed an accep-
tor with a silyl protecting group on O-5, thus
necessitating a two-step deprotection protocol.
87% yield of trisaccharide 24, which was subsequently
debenzoylated to give 6 (88%).
In conclusion, we have synthesized multi-milligram
quantities of oligosaccharides 2–7 via efficient routes
that are easily scaleable for the preparation of gram-
scale amounts of these glycans. The use of these
oligosaccharides in investigations dedicated to identify-
ing new inhibitors of mycobacterial arabinosyltrans-
ferases is currently in progress.4c
As illustrated in Scheme 2, the remaining targets
(5–7) were synthesized with minimum difficulty, albeit
less directly than 2–4. Glycosylation of alcohol 8 with
12 afforded disaccharide 17 in 82% yield. The siloxane
protecting group was cleaved to give diol 18 (in 84%
yield), which was an intermediate for the preparation of
both 5 and 7. Reaction of 18 with an excess of 11
afforded tetrasaccharide 20 (80%), which was then de-
protected to give 7 (77%). Alternatively, reaction of 18
with benzoic acid under Mitsunobu conditions afforded
disaccharide 19 (90%), which was then glycosylated
with 11 and deprotected providing 5 (77% over two
steps). The final target, trisaccharide 6, was also pre-
pared from monosaccharide 8. Coupling of 8 with 13
provided disaccharide 22 (82%), which was then depro-
tected yielding 23 in 88% yield. Glycosylation of this
disaccharide alcohol with thioglycoside 11 afforded an
3. Experimental
3.1. General procedures
Solvents were distilled from the appropriate drying
agents before use. Unless stated otherwise, all reactions
were carried out at room temperature (rt), under a
positive pressure of argon and were monitored by TLC
on Silica Gel 60 F254 (0.25 mm, E. Merck). Spots were
detected under UV light or by charring with 10%

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J. Han et al. / Carbohydrate Research 338 (2003) 581–588
H2SO4 in EtOH. Solvents were evaporated at reduced
pressure and below 40 °C (bath). Column chromatogra-
phy was performed on silica gel 60 (40–60 mm).
Iatrobeads refers to a beaded silica gel 6RS-8060, which
is manufactured by Iatron Laboratories (Tokyo). The
ratio between silica gel and product ranged from 100 to
50:1 (w/w). Optical rotations were measured at 229
3.4. Octyl 3,5-di-O-(a-D-arabinofuranosyl)-a-D-arabino-
furanoside (4)
Trisaccharide 16 (57 mg, 0.045 mmol) was deacylated
as described for the preparation of 2. The product was
purified by chromatography (10:1 CH2Cl2–CH3OH) to
yield 4 (20 mg, 84%) as an oil: Rf 0.23 (5:1 CH2Cl2–
CH3OH); [h]D +147.6° (c 0.8, CH3OH); 1H NMR (400
MHz, CD3OD): lH 5.00 (d, 1 H, J 1.5 Hz), 4.90 (d, 1
H, J 1.2 Hz), 4.80 (d, 1 H, J 1.2 Hz), 4.08–4.06 (m, 1
H), 4.03 (dd, 1 H, J 2.9, 1.5 Hz), 4.00–3.93 (m, 4 H),
3.89–3.85 (m, 2 H), 3.77 (dd, 2 H, J 6.1, 3.6 Hz), 3.71
(t, 1 H, J 3.1 Hz), 3.69–3.59 (m, 4 H), 3.57 (dd, 1 H, J
5.3, 2.6 Hz), 3.36 (dt, 1 H, J 9.5, 6.5 Hz), 1.54–1.49 (m,
2 H), 1.34–1.25 (m, 10 H), 0.85 (t, 3 H, J 6.8 Hz); 13C
NMR (100 MHz, CD3OD): lC 110.0, 109.9, 109.5,
86.3, 85.9, 84.7, 84.0, 83.5, 82.9, 82.6, 79.3, 79.2, 69.1,
68.1, 63.5, 63.4, 33.4, 31.1, 30.9, 30.8, 27.6, 24.1, 14.8;
ESIMS m/z Calcd for [C23H42O13]Na+: 549.2518.
Found: 549.2469.
1
2 °C. H NMR chemical shifts, dH, were referenced to
Me4Si (lH 0.0, CDCl3), CD3OH (lH 4.78, CD3OD),
HOD (lH 4.78, D2O). 13C chemical shifts, lC, were
referenced to internal CDCl3 (lC 77.00, CDCl3) internal
CD3OD (lC 49.00, CD3OD), or external dioxane (lC
67.40, D2O).
3.2. Octyl 5-O-(a-D-arabinofuranosyl)-a-D-arabinofuran-
oside (2)
Disaccharide 14 (130 mg, 0.14 mmol) was dissolved in
7:3 CH3OH–CH2Cl2 (10 mL), and 1.0 M methanolic
NaOCH3 (2 mL) was added dropwise. After stirring for
6 h, the reaction mixture was neutralized with dry ice
and concentrated. The crude residue was purified by
chromatography (10:1 CH2Cl2–CH3OH) to yield 25f,7,8c
(53 mg, 93%) as an oil: Rf 0.48 (5:1 CH2Cl2–CH3OH);
3.5. Octyl 5-O-[3-O-(a-
D-arabinofuranosyl)-a-D-ara-
binofuranosyl]-a- -arabinofuranoside (5)
D
Trisaccharide 21 (500 mg, 0.39 mmol) was deacylated
as described for the preparation of 2. Purification of the
product was achieved by chromatography on
Iatrobeads (10:1 CH3Cl–CH3OH) to yield 5 (180 mg,
87%) as a foam: Rf 0.27 (5:1, CH2Cl2–CH3OH); [h]D
+156.2° (c 1.0, CH3OH); 1H NMR (400 MHz,
CD3OD): lH 5.11 (d, 1 H, J 1.1 Hz), 5.04 (s, 1 H), 4.91
(d, 1 H), 4.22 (br s, 1 H), 4.14–3.94 (m, 7 H), 3.90–3.74
(m, 4 H), 3.72–3.60 (m, 4 H), 3.46 (ddd, 1 H, J 6.8, 9.6.
9.6 Hz), 1.58–1.52 (m, 2 H), 1.30–1.18 (m, 10 H), 0.82
(t, 3 H, J 6.5 Hz); 13C NMR (100 MHz, D2O): lC
107.8, 107.7, 107.4, 84.2, 83.4, 82.4, 82.0, 81.7, 81.6,
79.6, 76.9, 76.9, 68.6, 66.0, 61.5, 61.4, 32.0, 29.6, 29.5,
29.4, 26.1, 22.8, 14.1; ESIMS m/z Calcd for
[C23H42O13]Na+: 549.2517. Found: 549.2565.
1
[h]D +120.4° (c 1.0, CH3OH); H NMR (400 MHz,
CD3OD): lH 4.90 (d, 1 H, J 1.2 Hz), 4.80 (d, 1 H, J 1.6
Hz), 3.98–3.90 (m, 4 H), 3.85 (dd, 1 H, J 6.4, 3.8 Hz),
3.82–3.78 (m, 2 H), 3.70 (dd, 1 H, J 11.8, 3.3 Hz),
3.68–3.58 (m, 3 H), 3.37 (dt, 1 H, J 9.6, 6.6 Hz),
1.56–1.51 (m, 2 H), 1.34–1.26 (m, 10 H), 0.86 (t, 3 H,
J 6.8 Hz); 13C NMR (100 MHz, CD3OD): lC 109.6,
109.5, 85.9, 83.6, 83.4, 83.1, 79.1, 78.8, 68.9, 68.0, 63.1,
33.0, 30.7, 30.5, 30.4, 27.2, 23.7, 14.4; ESIMS m/z
Calcd for [C18H34O9]Na+: 417.2095. Found: 417.2086.
3.3. Octyl 3-O-(a-D-arabinofuranosyl)-a-D-arabinofuran-
oside (3)
3.6. Octyl 5-O-[5-O-(a-
D-arabinofuranosyl)-a-D-ara-
binofuranosyl]-a- -arabinofuranoside (6)
D
Disaccharide 15 (91 mg, 0.099 mmol) was deacylated as
described for the preparation of 2. The product was
purified by chromatography (10:1 CH2Cl2–CH3OH) to
yield 3 (33 mg, 85%) as an oil: Rf 0.33 (5:1 CH2Cl2–
CH3OH); [h]D +158.3° (c 1.0, CH3OH); 1H NMR (400
MHz, CD3OD): lH 5.02 (d, 1 H, J 1.6 Hz), 4.81 (d, 1
H, J 1.3 Hz), 4.05 (dd, 1 H, J 3.1, 1.5 Hz), 4.00–3.92
(m, 3 H), 3.90–3.86 (m, 1 H), 3.80–3.72 (m, 2 H),
3.70–3.63 (m, 3 H), 3.59 (dd, 1 H, J 11.9, 5.4 Hz), 3.37
(dt, 1 H, J 9.6, 6.5 Hz), 1.57–1.50 (m, 2 H), 1.34–1.26
(m, 10 H), 0.86 (t, 3 H, J 6.8 Hz); 13C NMR (100 MHz,
CD3OD): lC 109.5, 109.0, 85.5, 84.0, 83.7, 83.6, 82.2,
78.6, 68.6, 63.0, 62.8, 33.0, 30.7, 30.5, 30.4, 27.2, 23.7,
14.4; ESIMS m/z Calcd for [C18H34O9]Na+: 417.2095.
Found: 417.2103.
Trisaccharide 24 (450 mg, 0.35 mmol) was deacylated
as described for the preparation of 2. The product was
purified by chromatography on Iatrobeads (3:1
CH3Cl–CH3OH) to yield 6 (162 mg, 88%) as a foam:
Rf 0.24 (5:1, CH2Cl2–CH3OH); [h]D +133.2° (c 1.0,
1
CH3OH); H NMR (400 MHz, CD3OD): lH 5.01 (s, 2
H), 4.96 (d, 1 H, J 1.7 Hz), 4.20–4.10 (m, 1 H),
4.10–3.92 (m, 7 H), 3.90 (dd, 1 H, J 3.3, 5.9 Hz),
3.87–3.62 (m, 7 H), 3.46 (ddd, 1 H, J 6.8, 6.8, 9.6 Hz),
1.58–1.52 (m, 2 H), 1.30–1.18 (m, 10 H), 0.82 (t, 3 H,
J 6.5 Hz); 13C NMR (100 MHz, D2O): lC 108.0, 107.9,
107.7, 84.3, 82.8, 82.1, 81.5, 81.3, 81.2, 68.7, 77.3, 77.1,
76.9, 67.1, 67.0, 61.5, 31.8, 29.4, 29.3, 29.2, 25.9, 22.6,

J. Han et al. / Carbohydrate Research 338 (2003) 581–588
585
14.0; ESIMS m/z Calcd for [C23H42O13]Na+: 549.2517.
Found: 549.2413.
3.9. Octyl 2,5-di-O-benzoyl-3-O-(2,3,5-tri-O-benzoyl-a-
-arabinofuranosyl)-a- -arabinofuranoside (15)
D
D
3.7. Octyl 5-O-[3,5-di-O-(a-D-arabinofuranosyl)-a-D-
arabinofuranosyl]-a-D-arabinofuranoside (7)
Alcohol 9 (60 mg, 0.13 mmol) was glycosylated with 11
(96 mg, 0.17 mmol) using N-iodosuccinimide (38 mg,
0.17 mmol) and silver triflate (10 mg, 0.039 mmol) in
Tetrasaccharide 20 (35 mg, 0.022 mmol) was deacylated
as described for the preparation of 2. The product was
purified by chromatography (10:1 CH2Cl2–CH3OH) to
yield 7 (11 mg, 77%) as an oil: Rf 0.14 (5:1 CH2Cl2–
CH3OH); [h]D +140.0° (c 0.5, CH3OH); 1H NMR (400
MHz, CD3OD): lH 4.99 (d, 1 H, J 1.4 Hz), 4.90 (s, 2
H), 4.16–4.13 (m, 1 H), 4.09 (dd, 1 H, J 2.5, 1.1 Hz),
4.00 (dd, 1 H, J 5.8, 2.6 Hz), 3.98–3.91 (m, 4 H),
3.90–3.85 (m, 4 H), 3.78–3.75 (m, 3 H), 3.72–3.63 (m,
4 H), 3.61–3.56 (m, 3 H), 3.40–3.35 (m, 1 H), 3.29 (s,
1 H), 1.56–1.50 (m, 2 H), 1.34–1.23 (m, 10 H), 0.85 (t,
3 H, J 6.8 Hz); 13C NMR (100 MHz, CD3OD): lC
110.0, 109.9, 109.8, 109.5, 86.3, 86.0, 84.6, 84.0, 83.9,
83.8, 83.5, 83. 4, 82.1, 79.3, 79.2, 79.0, 69.4, 68.1, 67.9,
63.5, 63.4, 33.4, 31.1, 30.9, 30.8, 27.7, 24.1, 14.8; ES-
IMS m/z Calcd for [C28H50O17]Na+: 681.2940. Found:
681.2952.
,
CH2Cl2 (7 mL) with powdered molecular sieves (4 A,
0.2 g) as described for the preparation of 14. The
product was purified by chromatography (3:1 hexanes–
EtOAc) to yield 15 (115 mg, 92%) as an oil: Rf 0.41 (3:1
1
hexanes–EtOAc); [h]D +9.3° (c 1.0, CHCl3); H NMR
(400 MHz, CDCl3) lH 8.15–8.00 (m, 10 H), 7.66–7.58
(m, 3 H), 7.53–7.46 (m, 4 H), 7.45–7.41 (m, 4 H),
7.31–7.25 (m, 4 H), 5.76 (s, 1 H), 5.70 (d, 1 H, J 1.1
Hz), 5.61 (d, 1 H, J 4.0 Hz), 5.44 (s, 1 H), 5.30 (s, 1 H),
4.77 (dd, 2 H, J 10.9, 2.8 Hz), 4.67–4.60 (m, 3 H),
4.56–4.52 (m, 2 H), 3.81 (dt, 1 H, J 9.6, 6.9 Hz), 3.58
(dt, 1 H, J 9.6, 6.6 Hz), 1.73–1.64 (m, 2 H), 1.43–1.39
(m, 2 H), 1.34–1.29 (m, 8 H), 0.90 (t, 3 H, J 6.8 Hz);
13C NMR (100 MHz, CDCl3): lC 166.1 (2 C), 165.6,
165.5 (2 C), 133.5 133.4 (2 C), 133.0 (3 C), 129.8, 129.7,
129.6 (2 C), 129.3, 129.1, 128.5, 128.4, 128.3, 128.2,
105.8, 105.3, 82.6, 81.8, 81.7, 81.1, 80.8, 77.7, 67.7, 63.8,
63.3, 31.8, 29.4, 29.3, 29.2, 26.0, 22.6, 14.0; ESIMS m/z
Calcd for [C53H54O14]Na+: 937.3406. Found: 937.3408.
3.8. Octyl 2,3-di-O-benzoyl-5-O-(2,3,5-tri-O-benzoyl-a-
D-arabinofuranosyl)-a-
D-arabinofuranoside (14)
A mixture of 8 (100 mg, 0.21 mmol) and 11 (155 mg,
,
0.27 mmol), and powdered molecular sieves (4 A, 0.2 g)
3.10. Octyl 2-O-benzoyl-3,5-di-O-(2,3,5-tri-O-benzoyl-
a-D-arabinofuranosyl)-a-D-arabinofuranoside (16)
in dry CH2Cl2 (10 mL) was stirred at 0 °C for 20 min.
To the mixture were added N-iodosuccinimide (61 mg,
0.27 mmol) and silver triflate (16 mg, 0.062 mmol).
After stirring for 30 min at 0 °C, the reaction mixture
was neutralized with Et3N, diluted with CH2Cl2 (100
mL), and filtered through Celite. The filtrate was
washed successively with satd aq Na2S2O3, water, and
brine. The solvent was dried (Na2SO4) and evaporated.
The residue was purified by chromatography (3:1 hex-
anes–EtOAc) to yield 1410 (175 mg, 90%) as an oil: Rf
0.43 (3:1 hexanes–EtOAc); [h]D −0.9° (c 1.0, CHCl3);
1H NMR (400 MHz, CDCl3): lH 8.10–7.98 (m, 10 H),
7.62 (t, 2 H, J 7.4 Hz), 7.56–7.41 (m, 9 H), 7.36–7.28
(m, 4 H), 5.69 (d, 1 H, J 1.0 Hz), 5.68–5.62 (m, 2 H),
5.56 (d, 1 H, J 1.2 Hz), 5.51 (s, 1 H), 5.27 (s, 1 H), 4.88
(dd, 1 H, J 11.8, 3.3 Hz), 4.80 (dd, 1 H, J 8.1, 4.7 Hz),
4.71 (dd, 1 H, J 11.8, 4.7 Hz), 4.50 (dd, 1 H, J 7.6, 4.6
Hz), 4.29 (dd, 1 H, J 11.2, 4.6 Hz), 4.02 (dd, 1 H, J
11.1, 2.9 Hz), 3.80 (dt, 1 H, J 9.4, 6.7 Hz), 3.55 (dt, 1
H, J 9.4, 6.3 Hz), 1.71–1.61 (m, 2 H), 1.47–1.28 (m, 10
H), 0.90 (t, 3 H, J 6.8 Hz); 13C NMR (100 MHz,
CDCl3): lC 166.2, 165.7 (2 C), 165.4, 165.2, 133.4 (3 C),
133.3, 133.0, 129.9, 129.8, 129.3, 129.1, 129.0, 128.5,
128.4, 128.3 (2 C), 105.9, 105.6, 81.9, 81.8 (2 C), 81.2,
77.8, 77.3, 67.4, 66.2, 63.7, 31.8, 29.5, 29.4, 29.2, 26.2,
22.6, 14.0; ESIMS m/z Calcd for [C53H54O14]Na+:
937.3406. Found: 937.3368.
Alcohol 10 (30 mg, 0.082 mmol) was glycosylated with
11 (114 mg, 0.20 mmol) using N-iodosuccinimide (45
mg, 0.20 mmol) and silver triflate (10 mg, 0.039 mmol)
,
in CH2Cl2 (8 mL) with powdered molecular sieves (4 A,
0.2 g) as described for the preparation of 14. The
product was purified by chromatography (2:1 hexanes–
EtOAc) to yield 16 (80 mg, 78%) as an oil: Rf 0.46 (2:1
hexanes–EtOAc); [h]D +18.0° (c 1.1, CHCl3); 1H
NMR (400 MHz, CDCl3): lH 8.09–7.98 (m, 14 H),
7.47–7.26 (m, 21 H), 5.66 (d, 1 H, J 1.2 Hz), 5.60–5.56
(m, 4 H), 5.45 (d, 1 H, J 1.5 Hz), 5.42 (s, 1 H), 5.23 (s,
1 H), 4.83 (dd, 1 H, J 11.0, 2.6 Hz), 4.78 (dd, 1 H, J
8.2, 3.6 Hz), 4.69–4.60 (m, 4 H), 4.56 (dd, 1 H, J 6.1,
0.9 Hz), 4.31–4.40 (m, 1 H), 4.19–4.12 (m, 1 H), 3.95
(dd, 1 H, J 11.4, 2.3 Hz), 3.76 (dt, 1 H, J 9.6, 6.9 Hz),
3.51 (dt, 1 H, J 9.6, 6.6 Hz), 1.66–1.60 (m, 2 H),
1.38–1.27 (m, 10 H), 0.89 (t, 3 H, J 6.8 Hz); 13C NMR
(100 MHz, CDCl3): lC 166.1, 166.0, 165.6 (3 C), 165.1
(2 C), 133.5, 133.4, 133.3 (2 C), 133.0, 129.9 (2 C),
129.8 (2 C), 129.7 (3 C), 128.5, 128.4, 128.3, 128.2,
106.0, 105.8, 105.5, 82.8, 81.7 (3 C), 81.6, 81.3, 80.9,
77.8, 77.7, 67.5, 65.8, 63.7, 63.7, 31.8, 29.4, 29.3, 29.2,
26.0, 25.6, 14.0; ESIMS m/z Calcd for [C72H70O20]Na+:
1277.4353. Found: 1277.4431.

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J. Han et al. / Carbohydrate Research 338 (2003) 581–588
3.11. Octyl 2,3-di-O-benzoyl-5-O-(2-O-benzoyl-3,5-O-
(1,1,3,3-tetraisopropylsiloxane-1,3-diyl)-a- -arabino-
furanosyl)-a- -arabinofuranoside (17)
to 0 °C. Diethylazodicarboxylate (0.2 mL, 1.25 mmol)
was added dropwise over 10 min. The reaction mixture
was brought to rt and was then stirred for 30 min.
After concentration of the reaction mixture to an oil,
the product was purified by chromatography (2:1 hex-
ane–EtOAc) to provide 19 (621 mg, 90%) as an oil: Rf
0.41 (2:1 hexane–EtOAc); [h]D +18.5° (c 1.0, CHCl3);
1H NMR (400 MHz, CDCl3): lH 8.25–7.90 (m, 8 H),
7.75–7.30 (m, 12 H), 5.55 (d, 1 H, J 4.5 Hz), 5.53 (s, 1
H), 5.43 (s, 1 H), 5.26 (s, 1 H), 5.22 (d, 1 H, J 2.1 Hz),
4.63 (dd, 1 H, J 2.8, 10.7 Hz), 4.59–4.40 (m, 3 H),
4.25–4.15 (m, 2 H), 3.96 (dd, 1 H, J 3.2, 10.9 Hz), 3.77
(ddd, 1 H, J 6.7, 6.7, 9.4 Hz), 3.53 (ddd, 1 H, J 6.7, 6.7,
9.4 Hz), 1.55–1.70 (m, 2 H), 1.55–1.19 (m, 10 H), 0.85
(t, 3 H, J 6.7 Hz); 13C NMR (100 MHz, CDCl3): lC
166.4, 166.2, 165.8, 165.4, 133.6, 133.4, 133.0, 130.1,
129.9, 129.8, 129.7, 129.2, 129.1, 129.0, 128.5, 128.4,
128.3, 105.6, 105.2, 85.3, 82.3, 81.9, 81.7, 77.3, 76.7,
67.6, 66.0, 63.8, 31.8, 29.5, 29.4, 29.2, 26.1, 22.6, 14.0;
ESIMS m/z Calcd for [C46H50O13]Na+: 833.3144.
Found: 833.3112.
D
D
Alcohol 8 (800 mg, 1.70 mmol) was glycosylated with
thioglycoside 12 (1.30 g, 2.16 mmol) using N-iodosuc-
cinimide (497 mg, 2.20 mmol) and silver triflate (131
,
mg, 0.51 mmol) in CH2Cl2 (20 mL) containing 4 A
molecular sieves (0.5 g) as described for the preparation
of 14. The product was purified by chromatography
(6:1 hexanes–EtOAc) to provide 17 (1.32 g, 82%) as an
oil: Rf 0.23 (6:1 hexanes–EtOAc); [h]D +4.2° (c 1.0,
1
CHCl3); H NMR (400 MHz, CDCl3): lH 8.04–7.91
(m, 6 H), 7.52–7.34 (m, 9 H), 5.48–5.45 (m, 2 H), 5.40
(d, 1 H, J 1.2 Hz), 5.15 (s, 1 H), 5.09 (d, 1 H, J 1.4 Hz),
4.43–4.40 (m, 2 H), 4.09–3.81 (m, 5 H), 3.71–3.67 (m,
1 H), 3.46–3.40 (m, 1 H), 1.61–1.49 (m, 2 H), 1.38–
0.59 (m, 41 H); 13C NMR (100 MHz, CDCl3): lC 165.6,
165.5, 165.3, 133.3, 133.3, 133.2, 133.0, 130.0, 129.9,
129.8, 129.7, 129.5, 129.3, 129.0, 128.5, 128.4, 128.4,
128.2, 128.2, 128.1, 105.7, 105.6, 84.1, 81.7, 81.6, 81.2,
77.7, 76.0, 67.5, 67.4, 61.5, 31.8, 29.6, 29.5, 29.4, 29.4,
29.3, 26.2, 22.6, 17.4, 17.3, 17.0, 16.9, 16.9, 14.1, 13.5,
13.1, 12.8, 12.4; ESIMS m/z Calcd for [C51H72O13-
Si2]Na+: 971.4404. Found: 971.4459.
3.14. Octyl 5-O-[3,5-di-O-(2,3,5-tri-O-benzoyl-a-
binofuranosyl)-2-O-benzoyl-a- -arabinofuranosyl]-2,3-di-
O-benzoyl-a- -arabinofuranoside (20)
D-ara-
D
D
Alcohol 18 (25 mg, 0.035 mmol) was glycosylated with
11 (5 mg, 0.019 mmol) using N-iodosuccinimide (20
mg, 0.089 mmol) and silver triflate (131 mg, 0.51 mmol)
3.12. Octyl 2,3-di-O-benzoyl-5-O-(2-O-benzoyl-a-
binofuranosyl)-a- -arabinofuranoside (18)
D-ara-
D
,
in CH2Cl2 (8 mL) containing 4 A molecular sieves (0.2
Disaccharide 17 (1.3 g, 1.4 mmol) was dissolved in
THF (20 mL), and the solution was cooled to 0 C
before n-Bu4NF·3H2O (710 mg, 2.7 mmol) was added.
After 15 min, the reaction mixture was concentrated,
and the residue was purified by chromatography (1:3
EtOAc–toluene) to give 18 (811 mg, 84%) as an oil: Rf
0.46 (1:1 EtOAc–toluene); [h]D +51.0° (c 1.0, CHCl3);
1H NMR (400 MHz, CDCl3): lH 8.09–7.98 (m, 6 H),
7.60–7.42 (m, 9 H), 5.55 (d, 1 H, J 5.0 Hz,), 5.51 (d, 1
H, J 1.4 Hz), 5.39 (s, 1 H), 5.26 (s, 1 H), 5.17–5.16 (m,
1 H), 4.47–4.40 (m, 1 H), 4.33–4.30 (m, 1 H), 4.21–
4.13 (m, 2 H), 3.99–3.92 (m, 2 H), 3.81–3.74 (m, 2 H),
3.56–3.46 (m, 1 H), 2.06 (br s, 1 H), 1.78 (br s, 1 H),
1.68–1.61 (m, 2 H), 1.42–1.25 (m, 10 H), 0.86 (t, 3 H,
J 6.7 Hz); 13C NMR (CDCl3, 100 MHz): lC 166.6,
165.9, 165.3, 133.6, 133.5, 129.9, 129.9, 129.8, 129.8,
129.0, 128.5, 128.5, 105.6, 105.1, 86.0, 84.9, 84.5, 83.6,
81.9, 81.7, 67.6, 65.9, 62.2, 31.8, 29.5, 29.4, 29.3, 26.1,
22.6, 14.1; ESIMS m/z Calcd for [C39H46O12]Na+:
729.2881. Found: 729.2875.
g) as described for the preparation of 14. The product
was purified by chromatography (2:1 hexanes–EtOAc)
to yield 20 (44 mg, 80%) as an oil: Rf 0.38 (2:1
hexanes–EtOAc); [h]D +12.3° (c 1.0, CHCl3); 1H
NMR (400 MHz, CDCl3): lH 8.14–7.94 (m, 18 H),
7.64–7.21 (m, 27 H), 5.69 (d, 1 H, J 4.4 Hz), 5.61–5.50
(m, 6 H), 5.45 (d, 2 H, J 1.4 Hz), 5.27 (s, 1 H),
4.87–4.74 (m, 2 H), 4.73–4.59 (m, 6 H), 4.54–4.30 (m,
1 H), 4.23 (dd, 1 H, J 11.2, 4.4 Hz), 4.19–4.14 (m, 2 H),
4.01–3.94 (m, 2 H), 3.80 (dt, 1 H, J 9.4, 6.7 Hz), 3.55
(dt, 1 H, J 9.4, 6.3 Hz), 1.70–1.62 (m, 2 H), 1.46–1.28
(m, 10 H), 0.90 (t, 3 H, J 6.8 Hz); 13C NMR (100 MHz,
CDCl3): lC 166.1, 165.2, 165.6, 165.5 (3 C), 165.4,
165.1, 164.9, 133.3, 129. 9, 129.8 (4 C), 129.7, 129.6,
128.5, 128.4, 128.4, 128.3 (3 C), 128.2 (2 C), 105.9,
105.7, 105.6, 105.4, 82.0, 81.9, 81.9 (2 C), 81.7 (2 C),
81.6, 81.4, 77.8, 77.7, 77.3, 67.5, 65.6, 65.5, 63.7, 63.5,
60.3, 31.8, 29.5, 29.4, 29.2, 26.1, 22.6, 14.0; ESIMS m/z
Calcd for [C91H86O26]Na+: 1618.5333. Found:
1618.5459.
3.13. Octyl 2,3-di-O-benzoyl-5-O-(2,5-di-O-benzoyl-a-
3.15. Octyl 2,3-di-O-benzoyl-5-O-(2,5-di-O-benzoyl-3-
D-arabinofuranosyl)-a-D-arabinofuranoside (19)
O-(2,3,5-tri-O-benzoyl-a-
D-arabinofuranosyl)-a-D-ara-
binofuranosyl)-a- -arabinofuranoside (21)
D
Diol 18 (600 mg, 0.84 mmol), Ph3P (330 mg, 1.25
mmol), and benzoic acid (150 mg, 1.25 mmol) were
dissolved in THF (10 mL), and the solution was cooled
Alcohol 19 (600 mg, 0.74 mmol) was glycosylated with
thioglycoside 11 (500 mg, 0.88 mmol) using N-iodosuc-

J. Han et al. / Carbohydrate Research 338 (2003) 581–588
587
cinimide (200 mg, 0.88 mmol) and silver triflate (57 mg,
EtOAc); [h]D −8.6° (c 1.0, CHCl3); 1H NMR (400
MHz, CDCl3): dH 8.10–7.85 (m, 8 H), 7.60–7.20 (m, 12
H), 5.65 (d, 1 H, J 1.3 Hz), 5.61 (d, 1 H, J 4.9 Hz), 5.51
(d, 1 H, J 1.2 Hz), 5.44 (dd, 1 H, J 0.8, 4.8 Hz), 5.36 (s,
1 H), 5.22 (s, 1 H), 4.51–4.40 (m, 2 H), 4.19 (dd, 1 H,
J 4.5, 11.2 Hz), 3.91–4.07 (m, 3 H), 3.74 (ddd, 1 H, J
6.4, 6.4, 9.5 Hz), 3.49 (ddd, 1 H, J 6.4, 6.4, 9.5 Hz),
1.70–1.50 (m, 2 H), 1.45–1.19 (m, 10 H), 0.83 (t, 3 H,
J 6.7 Hz); 13C NMR (100 MHz, CDCl3): lC 166.1,
165.7, 165.4, 165.1, 133.5, 133.5, 133.4, 133.3, 129.9 (2),
129.8, 129.3, 129.2, 129.1, 129.0, 128.6, 128.5, 128.4,
128.3, 105.8, 105.6, 83.7, 81.9, 81.8, 81.7, 77.8, 77.4,
67.4, 66.2, 62.3, 31.8, 29.5, 29.4, 29.3, 26.2, 22.6, 14.1;
ESIMS m/z Calcd for [C46H50O13]Na+: 833.3149.
Found: 833.3106.
,
0.22 mmol) in CH2Cl2 (10 mL) containing 4 A molecu-
lar sieves (0.3 g) as described for the preparation of 14.
The product was purified by chromatography (4:1 hex-
anes–EtOAc) to provide 21 (0.82 g, 88%) as an oil: Rf
0.22 (4:1 hexanes–EtOAc); [h]D +16.0° (c 1.0, CHCl3);
1H NMR (400 MHz, CDCl3): lH 8.20–7.80 (m, 15 H),
8.60–7.05 (m, 20 H), 5.85–5.56 (m, 2 H), 5.56–5.53 (m,
5 H), 5.10 (s, 1 H), 4.85–4.38 (m, 8 H), 4.23 (d, 1 H, J
9.6 Hz), 3.96 (d, 1 H, J 10.9 Hz), 3.75 (ddd, 1 H, J 6.7,
6.7, 9.4 Hz), 3.50 (ddd, 1 H, J 6.7, 6.7, 9.4 Hz),
1.70–1.50 (m, 2 H), 1.45–1.19 (m, 10 H), 0.83 (t, 3 H,
J 6.7 Hz); 13C NMR (100 MHz, CDCl3): lC 166.1,
165.7, 165.6, 164.9, 133.4, 133.4, 133.3, 132.9, 130.0,
129.9, 129.8, 129.7, 129.6, 128.5, 128.4, 128.3, 105.6,
105.5 (2), 82.7, 82.0, 81.9, 81.8, 81.5, 81.4, 81.3, 77.8,
77.1, 67.5, 65.7, 63.7, 63.0, 31.8, 29.5, 29.4, 29.2, 26.1,
22.6, 14.0; ESIMS m/z Calcd for [C72H70O20]Na+:
1277.4352. Found: 1277.4390.
3.18. Octyl 2,3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-a-
D-arabinofuranosyl-(5-O-(2,3,5-tri-O-benzoyl-a-
D-ara-
binofuranosyl))-a- -arabinofuranoside (24)
D
3.16. Octyl 2,3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-5-
O-tert-butyldiphenylsilyl-a-D-arabinofuranosyl)-a-D-
arabinofuranoside (22)
Alcohol 23 (550 mg, 0.67 mmol) was glycosylated with
thioglycoside 11 (460 mg, 0.81 mmol) using N-iodosuc-
cinimide (180 mg, 0.80 mmol) and silver triflate (52 mg,
,
0.20 mmol) in CH2Cl2 (20 mL) containing 4 A molecu-
Alcohol 8 (500 mg, 1.1 mmol) was glycosylated with 13
(970 mg, 1.4 mmol) using N-iodosuccinimide (311 mg,
1.4 mmol) and silver triflate (81 mg, 0.32 mmol) in
lar sieves (0.5 g) as described for the preparation of 14.
The product was purified by chromatography (4:1 hex-
anes–EtOAc) to provide 24 (0.74 g, 87%) as a solid: Rf
0.34 (4:1 hexanes–EtOAc); [h]D +6.2° (c 0.5, CHCl3);
1H NMR (400 MHz, CDCl3): lH 8.05–7.80 (m, 14 H),
7.55–7.10 (m, 21 H), 5.64–5.59 (m, 4 H), 5.57 (d, 1 H,
J 4.8 Hz), 5.50 (s, 1 H), 5.46 (s, 1 H), 5.41 (s, 1 H), 5.21
(s, 1 H), 4.82 (dd, 1 H, J 3.2, 11.8 Hz), 4.72–4.60 (m,
3 H), 4.43–4.38 (m, 1 H), 4.28–4.15 (m, 2 H), 3.97 (dd,
1 H, J 3.0, 11.3 Hz), 3.92 (dd, 1 H, J 2.8, 11.2 Hz), 3.74
(ddd, 1 H, J 6.6, 6.6, 9.7 Hz), 3.48 (ddd, 1 H, J 6.6, 6.6,
9.7 Hz), 1.70–1.50 (m, 2 H), 1.45–1.19 (m, 10 H), 0.83
(t, 3 H, J 6.7 Hz); 13C NMR (100 MHz, CDCl3): lC
166.2, 165.8, 165.7, 165.5, 165.2, 165.1, 133.4, 133.3,
133.2, 133.0, 129.9, 132.4, 129.8, 129.3, 129.1, 129.1,
128.9, 128.8, 128.4, 128.4, 128.2, 105.9, 105.8, 105.8,
82.0, 81.9, 81.8, 81.7, 81.5, 81.2, 77.8, 77.4, 67.5, 66.0
(2), 63.7, 31.8, 29.5, 29.4, 29.2, 26.2, 22.6, 14.1; ESIMS
m/z Calcd for [C72H70O20]Na+: 1277.4352. Found:
1277.4235.
,
CH2Cl2 (20 mL) containing 4 A molecular sieves (0.5 g)
as described for the preparation of 14. The product was
purified by chromatography (4:1 hexanes–EtOAc) to
provide 22 (910 mg, 82%) as an oil: Rf 0.30 (4:1
1
hexanes–EtOAc); [h]D −2.7° (c 0.8, CHCl3); H NMR
(400 MHz, CDCl3): lH 8.10–7.25 (m, 30 H), 5.45–5.54
(m, 2 H), 5.35 (s, 1 H), 5.25 (s, 1 H), 5.19 (s, 1 H), 4.43
(dd, 1 H, J 4.5, 4.5 Hz), 4.32–4.20 (m, 2 H), 4.14 (dd,
1 H, J 5.0, 11.0 Hz), 3.92 (dd, 1 H, J 3.4, 11.0 Hz), 3.86
(d, 2 H, J 4.5 Hz), 3.76 (ddd, 1 H, J 6.7, 6.7, 9.4 Hz),
3.52 (ddd, 1 H, J 6.7, 6.7, 9.4 Hz), 1.68–1.49 (m, 2 H),
1.45–1.21 (m, 10 H), 1.10–0.90 (m, 9 H), 0.82 (t, 3 H,
J 6.7 Hz); 13C NMR (100 MHz, CDCl3): lC 166.8,
166.2, 165.9, 136.0 (2), 133.9, 133.8, 133.7, 130.4, 130.3,
130.2, 130.1, 129.7, 129.6, 128.9, 128.8, 128.1, 106.0,
105.7, 85.2, 85.6, 82.4, 82.1, 78.0, 77.2, 68.0, 66.4, 63.9,
32.3, 30.0, 29.8, 29.7, 27.2, 26.6, 23.1, 19.7, 14.5; ES-
IMS m/z Calcd for [C62H68O13Si]Na+: 1071.4321.
Found: 1071.4286.
Acknowledgements
3.17. Octyl 2,3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-a-
D
-arabinofuranosyl)-a-D-arabinofuranoside (23)
This work was supported by the National Institutes
of Health (AI 44045) and the National Science Founda-
tion (REU Fellowship to PRM).
Disaccharide 22 (850 mg, 0.81 mmol) was dissolved in
THF (20 mL) and then n-Bu4F·3H2O (254 mg, 0.97
mmol) was added. After stirring for 4 h, the reaction
mixture was concentrated, and the resulting residue was
purified by chromatography (3:1 hexanes–EtOAc) to
give 23 (581 mg, 88%) as an oil: Rf 0.25 (3:1 hexanes–
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