Synthesis of spacer-containing analogs of serogroup 6 pneumococcal oligosaccharides

Article abstract of DOI:10.1016/j.carres.2008.03.035

An efficient convergent strategy for the synthesis of a range of spacer-containing pneumococcal oligosaccharides of serogroup 6 and derivatives thereof has been developed. The spacer-containing oligosaccharides were deprotected and are available for subsequent conjugation and immunological studies, which are underway in our laboratory.

Full text of DOI:10.1016/j.carres.2008.03.035

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 1707–1717
Synthesis of spacer-containing analogs of serogroup
6 pneumococcal oligosaccharides
Archana R. Parameswar, Scott J. Hasty and Alexei V. Demchenko*
Department of Chemistry and Biochemistry, University of Missouri, St. Louis, One University Boulevard, St. Louis, MO 63121, USA
Received 19 February 2008; received in revised form 23 March 2008; accepted 30 March 2008
Available online 4 April 2008
Abstract—An efficient convergent strategy for the synthesis of a range of spacer-containing pneumococcal oligosaccharides of sero-
group 6 and derivatives thereof has been developed. The spacer-containing oligosaccharides were deprotected and are available for
subsequent conjugation and immunological studies, which are underway in our laboratory.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Carbohydrates; Streptococcus pneumoniae; Spacer; Synthetic vaccines; Glycosylation; Oligosaccharides
1. Introduction
entific and clinical insights,5 it still accounts for nearly
20% of all childhood deaths under the age of five that
is translated into two million deaths every year.6
Complex carbohydrates represent a unique family of
multi-functional compounds involved in many biologi-
cal phenomena.1 Our current knowledge about the key
roles of these fascinating natural compounds is not yet
complete. However, thanks to the explosive growth of
the field of glycobiology in the recent years, we already
know that carbohydrates are involved in a broad range
of life threatening processes such as bacterial and viral
infections, development and growth of tumors, metasta-
sis, tissue rejection are only a few to mention. The fact
that many of these processes are directly associated with
pathogenesis of many deadly diseases has already stim-
ulated heated interest for the development of excellent
carbohydrate-based therapeutics.2
Also, the pneumococcal bacterial cell is surrounded
by a polysaccharide capsule, and preventive vaccination
based on the related carbohydrates, which are com-
monly applied as sugar-protein conjugates, has been
found a viable weapon against the bacterial invasion.3
Streptococcus pneumoniae (SPn) have become one of
the most frequent causes of invasive bacterial infections,
particularly in patients with weakened or immature im-
mune system.4 Although the study of the pneumococcal
disease over the last 120 years has led to important sci-
Among 91 elucidated SPn serotypes,7 serogroup 6 has
been consistently ranked second–third most frequent
cause of invasive pneumococcal disease worldwide.8
This fact stimulated extensive structural9 and synthetic
studies10,11 of SPn6 oligosaccharides and derivatives
thereof. Because for the most part relatively small oligo-
saccharide fragments are non-immunogenic, many syn-
thetic targets are equipped with a spacer moiety,
suitable for conjugation to a carrier protein. These con-
jugates were proven to significantly increase the immune
response and are immunogenic even in small children
who are at the greatest risk to infection.12 In continua-
tion of our recent studies toward the stereoselective syn-
thesis of pneumococcal oligosaccharides,13 herein we
report the synthesis of spacer-containing oligosaccha-
rides (1 and 2) and derivatives thereof (3–6, Fig. 1) struc-
turally related to the repeating unit of SPn6. The spacer
moiety is essential for conjugation with a carrier protein
and subsequent immunological studies.
2. Results and discussion
SPn6A and SPn6B repeating units consist of structurally
related complex pseudo-tetrasaccharides, which in the
*
Corresponding author. E-mail: demchenkoa@umsl.edu
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.03.035

1708
A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
building blocks 8–10, whereas the synthesis of the
OH OH
SPn6A
HO
O
spacer-containing ribitol units would require particular
attention (Scheme 1). Efficient chemical synthesis of
the spacer-containing oligosaccharides of SPn6 and
derivatives thereof will help to quickly obtain substan-
tial quantities of pure samples for conjugation and
immunological studies.
The synthesis of the SBox galactose building block
(7a) was carried out from the known precursor ethyl
4-O-anisoyl-2,3,6-tri-O-benzyl-1-thio-b-D-galactopyran-
oside (7)14 via conventional protocol involving bromin-
ation–thioglycosylation sequence.15 2-Benzyl-triacetate
SBox galactoside 7b, which provided excellent results
in our previous work, was also generated for compari-
son studies.15 Known derivatives 8–10 were projected
for the introduction of units B and C and their synthesis
was accomplished as described previously.16
Synthesis of the 3-OH ribitol building block 11 was
carried out from the known precursor 1411 as shown
in Scheme 2. First, diol 14 was subjected to dibutyltin
oxide-mediated alkylation, which was required to ensure
excellent regioselective protection of the primary hydr-
oxyl.17 The resulting compound 15 was obtained in
62% yield; it was then subjected to benzylation to afford
16, and the latter was deallylated using PdCl2 in MeOH
to afford compound 17 in 60% yield. Bromine was then
converted to the corresponding azide via conventional
nucleophilic displacement to provide the requisite glyco-
syl acceptor 11 in 89% yield. For the synthesis of 4-OH
ribitol building block 12, the known precursor 1813 was
alkylated and converted to the azido derivative using
similar reaction conditions as described for the synthesis
of acceptor 11.
Having obtained the key monosaccharide building
blocks, we turned our attention to the oligosaccharide
assembly. For the synthesis of pseudo-disaccharides 5
and 6, per-benzoylated rhamnose building block 9 was
used as a glycosyl donor. Coupling of 9 with ribitol
acceptors 11 and 12 in the presence of NIS–TfOH affor-
ded glycosides 20 and 21 with complete a-selectivity in
NH2
D
O
HO
HO
OH
O
O
C
HO
O
Synthetic Targets:
1: A-B-C-D
3: B-C-D
HO
OH
HO
HO
O
A
O
OH
B
5: C-D
OH
SPn6B
NH2
HO
O
E
OH
O
HO
HO
OH
O
HO
HO
O
C
O
Synthetic Targets:
2: A-B-C-E
4: B-C-E
OH
HO
HO
O
A
O
OH
B
6: C-E
Figure 1.
natural polysaccharide are connected via a phosphate
(5?2000) linkage. In our previous work, we have already
shown that the pseudo-disaccharides, -trisaccharides,
and -tetrasaccharides of SPn6 series could be synthe-
sized via selective activation strategy in the overall excel-
lent yields and complete stereoselectivity.13 Our current
work reports the synthesis of spacer-containing oligo-
saccharides (1–6 ), using a similar approach. Neverthe-
less, some adjustments have been made to the scheme:
while in our previous work, the assembly of ABCD tet-
rasaccharide was performed in (B + C) + A + D fash-
ion, herein the assembly was carried out as follows:
A + B + (C + D). These strategic adjustments required
further optimization of the anomeric selectivity, and
for this purpose two types of galactose building block
have been investigated (7a,b). Our expectation was that
anisoyl group at C-4 of galactose would help to achieve
excellent 1,2-cis stereoselectivity.14 The D-gluco and L-
rhamno units will be introduced by using common
α-D-Gal
Ribitol
OR3
R2O OR1
O
R1O
α
N3
-L-Rha
N
S
BnO
O
O
OBn
OR4 OBn
SEt
α
-D-Glc
7a
: R1= Bn, R2= An
7b: R1=R2= Ac
3
4
O
R1O
11
: R =H, R =Bn
12: R3=Bn, R4=H
R2O
Ph
O
OR1
O
O
9: R1=R2=Bz
SR1
R2O
1
2
10
: R =Bz, R =H
BnO
An =
O
OMe
8a: R1=thiazolinyl, R2=Ac
8b: R1=Et, R2=H
Scheme 1. Retrosynthetic analysis of spacer-containing oligosaccharides of SPn6.

A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
1709
O
O
Br
Bu SnO, Bu NBr,
Br
Br
BnO
OH
BnO
O
2
4
MS 4Å, benzene
OBn
OH
14
RO
OBn
62%
15
: R= H
16: R= Bn
BnBr, NaH
DMF, 84%
PdCl2, MeOH 60%
OH
R
O
BnO
BnO
OBn
NaN3, DMF
89%
17: R= Br
11
: R= N3
OBn
OBn
Br
R
Br
BnO
OH
BnO
O
Bu2SnO, Bu4NBr,
MS 4Å, benzene
60%
OH OBn
OH OBn
18
19: R= Br
NaN3, DMF
80%
12
: R= N3
Scheme 2. Synthesis of ribitol acceptors 11 and 12.
75% and 87% yields, respectively (Scheme 3). The
compounds obtained were then subjected to a two-
step sequential deprotection: deacylation (NaOMe in
MeOH) and hydrogenation using palladium on charcoal
in 5% HCl in EtOH to obtain pseudo-disaccharides 5
and 6 in 85% and 90% yields, respectively.
tively. These rhamnosylations also proceeded with
complete a-stereoselectivity. The protected pseudo-tri-
saccharides 23 and 24 were then subjected to the stan-
dard deprotection sequence, as described above for the
synthesis of 5 and 6, to afford compounds 3 and 4 in
88% and 78% yields, respectively.
For the synthesis of pseudo-trisaccharides 3 and 4, the
S-ethyl anomeric moiety of disaccharide 22, obtained
from 8a and 10 as described previously,13 was activated
with NIS–TfOH for the glycosylation of glycosyl accep-
tors 11 and 12 (Scheme 4). As a result, saccharides 23
and 24 were isolated in 80% and 78% yields, respec-
Finally, we were aiming for the synthesis of pseudo-
tetrasaccharides 1 and 2, the ultimate targets of this
work. For this purpose, galactose derivative 7b was used
as a glycosyl donor; unfortunately, this coupling re-
sulted in a very poor stereoselectivity (a:b = 3:1). This
was a rather unexpected result considering the success
BnO
OBn
BnO
O
N3
O
NIS/TfOH
1. NaOMe, MeOH
9 + 11
5
O
4Å MS, 1,2-DCE
75%
2. H2, Pd/C, HCl
BzO
85%
BzO
20
OBz
OBn
N3
BnO
O
NIS/TfOH
OBn
O
1. NaOMe, MeOH
9 + 12
6
4Å MS, 1,2-DCE
2. H2, Pd/C, HCl
90%
O
BzO
87%
BzO
OBz
21
Scheme 3. Synthesis of spacer-containing pseudo-disaccharides 5 and 6.

1710
A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
BnO
OBn
BnO
O
N3
O
11, NIS/TfOH
1. NaOMe, MeOH
O
BzO
3
4Å
MS, 1,2-DCE
80%
2. H2, Pd/C, HCl
88%
O
OBz
BnO
O
AcO
O
O
SEt
23
Ph
O
BzO
BnO
O
OBz
AcO
O
O
O
Ph
22
OBn
N3
BnO
O
12, NIS/TfOH
OBn
O
4
Å
MS, 1,2-DCE
78%
1. NaOMe, MeOH
O
4
BzO
2. H2, Pd/C, HCl
78%
O
OBz
BnO
AcO
O
O
O
24
Ph
Scheme 4. Synthesis of spacer-containing pseudo-trisaccharides 3 and 4.
7
of our previous galactosylation using the A + BC strat-
egy.13 To improve this, we obtained galactose donor 7a,
containing an anisoyl group at the C-4 position, a
known concept to improve the outcome of a-galactosy-
lations. The SBox leaving group of 7a was then selec-
tively activated over the SEt moiety of glucosyl
acceptor 8b. This reaction was carried out in diethyl
ether–1,2-dichloroethane (5:1) mixture of solvents to
further enhance the stereoselectivity. This fine-tuning
of reaction conditions using the previously elaborated
methodologies allowed us to obtain disaccharide 25 in
99% yield and very good stereoselectivity (a:b = 14:1,
Scheme 5).
For the synthesis of the disaccharide acceptor 26,
rhamnose building block 10 was glycosidated with ribi-
tol acceptor 11 to afford the requisite disaccharide in
65% yield. No self-condensation of compound 10, bear-
ing both leaving and hydroxyl moieties, was detected.
To complete the assembly, the disaccharide donor 25
was coupled with the disaccharide acceptor 26 in the
presence of NIS and catalytic TfOH. As a result, pseu-
do-tetrasaccharide derivative 27 was obtained in 66%
yield. Finally, the deprotection of 27 was carried out
using conventional deacylation–hydrogenation sequence
to afford pseudo-tetrasaccharide 1 in 70%.
10
8
11
AgOTf, 3Å MS
Ether/ DCE 99%
NIS/ TfOH, 4Å MS
Ether/ DCE 65%
BnO
OBn
O
AnO OBn
BnO
O
N3
BnO
O
BnO
O
BnO
O
SEt
O
O
BzO
O
Ph
HO
OBz
25
26
NIS/ TfOH, 4Å MS
Ether/ DCE 66%
BnO
OBn
BnO
O
N3
O
AnO OBn
O
O
BzO
BnO
O
OBz
BnO
O
BnO
O
O
O
Ph
27
(i) NaOMe, MeOH
(ii) H2, Pd/ C, 5% HCl-EtOH
70%
1
Scheme 5. Synthesis of spacer-containing pseudo-tetrasaccharide of
SPn6A 1.
For the synthesis of pseudo-tetrasaccharide 2, corre-
sponding to the carbohydrate part of the repeating unit
of SPn6B, disaccharide acceptor 28 was obtained from
building blocks 10 and 12 in 78% yield. Glycosylation
of 28 with the disaccharide donor 25 led to the fully pro-
tected pseudo-tetrasaccharide 29 in 70% yield with com-
plete a-stereoselectivity. The conventional deprotection
of 29 afforded the target compound 2 in 76% yield
(Scheme 6).

A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
1711
Unless noted otherwise, 1H NMR spectra were recorded
in CDCl3 at 300 MHz (Bruker Avance), 13C NMR spec-
tra and two-dimensional experiments were recorded in
CDCl3 at 75 MHz (Bruker Avance) or at 125 MHz
(Bruker ARX-500). HRMS determinations were made
with the use of JEOL MStation (JMS-700) Mass
Spectrometer.
OBn
N3
10
12
BnO
HO
O
NIS/ TfOH, 4Å MS
Ether/ DCE 78%
O
OBn
O
BzO
OBz
28
25
NIS/ TfOH, 4Å MS
Ether/ DCE 70%
3.2. Benzoxazolyl 4-O-anisoyl-2,3,6-tri-O-benzyl-1-thio-
b-D-galactopyranoside (7a)
OBn
N3
BnO
O
The solution of ethyl 4-O-anisoyl-2,3,6-tri-O-benzyl-1-
thio-b-D-glucopyranoside14 (3.98 g, 6.34 mmol) and
activated molecular sieves (3 A, 3.17 g) in CH2Cl2
O
OBn
˚
AnO OBn
O
O
BnO
BnO
(95 mL) was stirred under argon for 1 h. Freshly pre-
pared solution of Br2 in CH2Cl2 (60 mL, 1:165) was then
added and the reaction mixture was kept for 5 min at rt.
After this, the solid was filtered off and the filtrate was
concentrated in vacuo at rt. Crude residue was then trea-
ted with KSBox (7.6 mmol) and 18-crown-6 (0.76 mmol)
in dry acetone (12 mL) under argon for 16 h at rt. Upon
completion, the mixture was diluted with CH2Cl2, the
solid was filtered off and the residue was washed with
CH2Cl2. The combined filtrate (200 mL) was washed
with 1% aq NaOH (50 mL) and water (3 ꢀ 50 mL).
The organic layer was separated, dried with MgSO4,
and concentrated in vacuo. The residue was purified
by silica gel column chromatography (EtOAc–toluene
gradient elution) to afford 7a as a syrup (2.2 g, 50%).
Analytical data for 7a: Rf = 0.46 (EtOAc–hexanes 3:7);
BnO
O
OBn
BnO
O
O
29
(i) NaOMe, MeOH
O
O
Ph
(ii) H2, Pd/ C, 5% HCl-EtOH
76%
2
Scheme 6. Synthesis of spacer-containing pseudo-tetrasaccharide of
SPn6B 2.
In conclusion, we have developed an efficient conver-
gent strategy for the synthesis of a range of spacer-con-
taining pneumococcal oligosaccharides, serogroup 6
(SPn6). Further studies related to the synthesis of other
spacer-containing oligosaccharides and their conjuga-
tion to the carrier protein and subsequent immunologi-
cal studies are underway in our laboratory.
29
1
½aꢁD +10.8 (c 1.0, CHCl3); H NMR: d 3.40–3.53 (m,
2H, H-6a, 6b), 3.69 (s, 3H, –OCH3), 3.74 (dd, 1H,
J2,3 = 2.8 Hz, H-3), 3.89–3.97 (m, 2H, H-2, 5), 4.18–
4.82 (m, 6H, 4 ꢀ CH2Ph), 5.36 (dd, 1H, J3,4 = 2.3 Hz,
H-4), 6.76–7.98 (m, 25H, aromatic); 13C NMR: d 56.2,
67.5, 68.6, 72.4, 74.3, 76.4, 81.9, 85.7, 110.7, 114.4,
119.7, 122.7, 124.9, 125.1, 128.3, 128.4, 128.5 (ꢀ2),
128.8 (ꢀ4), 128.9, 129.1, 132.7, 138.1, 138.2, 138.3,
142.4, 161.9, 164.2, 165.9. FABMS m/z [M+H]+ calcd
for C42H40NO8S: 718.2475. Found: 718.2452.
3. Experimental
3.1. General
Column chromatography was performed on silica gel 60
(EM Science, 70–230 mesh), reactions were monitored
by TLC on Kieselgel 60 F254 (EM Science). The com-
pounds were detected by examination under UV light
and by charring with 10% sulfuric acid in methanol. Sol-
vents were removed under reduced pressure at <40 °C.
ClCH2CH2Cl was distilled from CaH2 directly prior to
application. Methanol was dried by refluxing with mag-
nesium methoxide, distilled and stored under argon.
Pyridine was dried by refluxing with CaH2 and then dis-
3.3. 3-O-Allyl-2,5-di-O-benzyl-1-O-(4-bromobutyl)-D-
ribitol (15)
To a solution of 3-O-allyl-2,5-di-O-benzyl-D-ribitol 1411
(871 mg, 2.34 mmol) in benzene (18 mL), freshly acti-
˚
vated molecular sieves (4 A, 4 g) were added and the
˚
tilled and stored over molecular sieves (3 A). Anhydrous
mixture was stirred under argon for 1 h. Bu2SnO
(786 mg, 3.2 mmol) and Bu4NBr (784 mg, 2.4 mmol)
were then added followed by the addition of 1,4-dibro-
mobutane (1.3 mL, 14.04 mmol). The reaction mixture
was refluxed for 20 h under argon, then cooled to rt.
Molecular sieves were filtered off through a pad of Cel-
ite, rinsed with toluene (2 ꢀ 5 mL), and the combined
filtrate was then concentrated in vacuo. The residue
was purified by column chromatography on silica gel
DMF (EM Science) and ether were used as is. Molecular
˚
˚
sieves (3 A or 4 A), used for the reactions, were crushed
and activated in vacuo at 390 °C for 8 h in the first in-
stance and then for 2–3 h at 390 °C directly prior to
application. AgOTf (Acros) was first dried by co-evapo-
ration with toluene (3 ꢀ 10 mL) and then placed in
vacuo for 2–3 h directly prior to application. Optical
rotations were measured at ‘Jasco P-1020’ polarimeter.

1712
A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
25
(EtOAc–hexanes gradient elution) to afford 15 as a col-
orless liquid (730 mg, 62% yield). Analytical data for 15:
lytical data for 17: Rf = 0.45 (EtOAc–hexanes 3:7); ½aꢁD
ꢃ3.8 (c 1.0, CHCl3); 1H NMR: d 1.69–1.76 (m, 2H,
CH2sp), 1.80–1.98 (m, 2H, CH2sp), 2.97 (d, 1H, –OH),
3.40–3.47 (m, 4H, 2 ꢀ CH2sp), 3.53–3.63 (m, 3H, H-4,
5), 3.68–3.80 (m, 3H, H-1,2), 4.03–4.06 (m, 1H, H-3),
4.49–4.75 (m, 6H, 3 ꢀ CH2Ph), 7.26–7.33 (m, 15H, aro-
matic); 13C NMR: d 27.2, 28.4, 29.6, 33.9, 70.4, 70.7,
70.9, 71.2 (ꢀ2), 71.8, 72.2 (ꢀ3), 73.7 (ꢀ2), 77.6,
78.1, 127.8, 127.9 (ꢀ2), 128.1 (ꢀ2), 128.5 (ꢀ4), 128.6
(ꢀ2), 138.3, 138.6. FABMS m/z [M+H] + calcd for
C30H38BrO5: 559.1887. Found: 559.1885.
28
Rf = 0.50 (EtOAc–hexanes 2:3); ½aꢁD +70.1 (c 1.0,
1
CHCl3); H NMR: d 1.63–1.68 (m, 2H, CH2sp), 1.84–
1.89 (m, 2H, CH2sp), 2.81 (d, 1H, –OH), 3.33–3.43 (m,
4H, 2 ꢀ CH2sp), 3.54–3.63 (m, 3H, H-3,5), 3.64–3.68
(m, 2H, H-1), 3.77–3.79 (m, 1H, H-2), 3.87–3.91 (m,
1H, H-2), 3.87–3.91 (m, 1H, H-4), 4.00–4.11 (m, 2H,
OCH2), 4.44–4.66 (m, 4H, 2 ꢀ CH2Ph), 5.08–5.18 (m,
2H, CH2@), 5.72–5.87 (m, 1H, @CH–), 7.24–7.28 (m,
10H, aromatic); 13C NMR: d 28.8, 30.2, 34.3, 70.8,
70.9, 71.4, 71.8, 73.0, 73.3, 73.9, 79.3, 79.6, 117.4,
128.1, 128.2, 128.3 (ꢀ2), 128.4 (ꢀ2), 128.9 (ꢀ2), 129.0
(ꢀ2), 135.5, 138.6, 138.9. FABMS m/z [M+Na]+ calcd
for C26H35BrO5Na: 529.1566. Found: 529.1542.
3.6. 1-O-(4-Azidobutyl)-2,4,5-tri-O-benzyl-D-ribitol (11)
Sodium azide (86 mg, 1.75 mmol) was added to a stirring
solution of 17 (0.42 g, 0.75 mmol) in dry DMF (6 mL).
The reaction was heated at 60 °C for 5 h, then poured
in crushed ice (ꢂ30 mL), stirred for 15 min, and ex-
tracted with EtOAc (3 ꢀ 20 mL). The combined organic
extract was dried with anhydrous MgSO4 and concen-
trated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc–hexanes gradient
elution) to afford compound 11 as a colorless syrup
(0.35 g, 89% yield). Analytical data for 11: Rf = 0.48
3.4. 3-O-Allyl-2,4,5-tri-O-benzyl-1-O-(4-bromobutyl)-D-
ribitol (16)
Benzyl bromide (0.3 mL, 2.1 mmol) was added to a stir-
ring solution of 15 (0.73 g, 1.44 mmol) in dry DMF
(10 mL) at 0 °C. Sodium hydride (60% suspension in
mineral oil, 0.12 g, 2.8 mmol) was added slowly until
the evolution of hydrogen gas has seized. The reaction
mixture was stirred for 5 h at rt until complete disap-
pearance of the starting material as indicated by TLC.
The reaction mixture was poured in crushed ice
(ꢂ50 mL), stirred for 15 min, extracted with EtOAc–
ether (1:1, 3 ꢀ 30 mL). The combined organic extract
was dried with anhydrous MgSO4, filtered, and concen-
trated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc–hexanes gradient
elution) to afford compound 16 as a colorless liquid
(0.72 g, 84% yield). Analytical data for 16: Rf = 0.57
29
(EtOAc–hexanes 2:3); ½aꢁD ꢃ4.8 (c 1.0, CHCl3); 1H
NMR: d 1.56 (br s, 4H, 2 ꢀ CH2sp), 2.95 (br s, 1H,
–OH), 3.17–3.24 (m, 2H, CH2sp), 3.33–3.35 (m, 2H,
CH2sp), 3.52–3.60 (m, 2H, H-2, 4), 3.62–3.73 (m, 4H,
H-1, 5), 3.95 (br s, 1H, H-3), 4.40–4.67 (m, 6H,
3 ꢀ CH2Ph), 7.15–7.25 (m, 15H, aromatic); 13C NMR:
d 25.8, 26.9, 51.3, 70.6, 71.3, 71.4, 72.1, 72.4, 73.9, 78.3,
78.4, 127.6 (ꢀ2), 127.7, 127.8 (ꢀ2), 127.9 (ꢀ4), 128.3
(ꢀ5), 128.4 (ꢀ4), 138.2, 138.5. FABMS m/z [M+H]+
calcd for C30H38N3O5: 520.2811. Found: 520.2827.
28
(EtOAc–hexanes 2:3); ½aꢁD ꢃ2.2 (c 1.0, CHCl3); 1H
NMR: d 1.87–2.00 (m, 2H, CH2sp), 2.13–2.27 (m, 2H,
CH2sp), 3.64–3.68 (m, 4H, 2 ꢀ CH2sp), 3.85–4.10 (m,
7H, H-1, 2, 3, 4, 5), 4.38–3.41 (m, 2H, OCH2), 4.75–
5.00 (m, 6H, 3 ꢀ CH2Ph), 5.36–5.50 (m, 2H, CH2@),
6.08–6.13 (m, 1H, @CH–), 7.54–7.65 (m, 15H, aro-
matic); 13C NMR: d 26.6, 28.5, 29.9, 70.3, 70.5, 70.9,
72.3, 72.5, 72.9, 73.5, 78.6, 78.7, 116.5, 127.6, 127.7,
127.8 (ꢀ2), 127.9 (ꢀ4), 128.4 (ꢀ4), 128.5 (ꢀ2), 128.6,
135.2, 135.4, 138.4, 138.6, 138.8. FABMS m/z [M+H]+
calcd for C33H42BrO5: 597.2216. Found: 597.2198.
3.7. 2,3,5-Tri-O-benzyl-1-O-(4-bromobutyl)-D-ribitol (19)
The title compound was obtained from 1813 as described
for the synthesis of compound 15 in 60% yield. Analyt-
29
ical data for 19: Rf = 0.56 (EtOAc–hexanes 2:3); ½aꢁD
1
+16.3 (c 1.0, CHCl3); H NMR: d 1.60–1.65 (m, 2H,
CH2sp), 1.81–1.88 (m, 2H, CH2sp), 2.77 (br s, 1H,
–OH), 3.30–3.39 (m, 4H, 2 ꢀ CH2sp), 3.53–3.61 (m,
3H, H-3, 5), 3.66–3.71 (m, 2H, H-1), 3.84–3.96 (m,
1H, H-2), 4.10–4.12 (m, 1H, H-4), 4.42–4.63 (m, 6H,
3 ꢀ CH2Ph), 7.21–7.29 (m, 15H, aromatic); 13C NMR:
d 28.4, 29.8, 33.9, 70.4, 70.6, 71.0, 71.3, 72.6, 73.5
(ꢀ2), 73.8, 79.0, 79.3, 127.7, 127.8 (ꢀ2), 127.9 (ꢀ2),
128.0, 128.2 (ꢀ2), 128.5 (ꢀ4), 128.6, 138.1, 138.5,
138.6. FABMS m/z [M+H]+ calcd for C30H38BrO5:
559.1887. Found: 559.1885.
3.5. 2,4,5-Tri-O-benzyl-1-O-(4-bromobutyl)-D-ribitol (17)
To a stirring solution of 16 (0.7 g, 1.2 mmol) in MeOH
(7 mL), PdCl2 (0.25 g) was added and the reaction was
stirred at rt for 3 h. The solid was then filtered off
through Celite, rinsed with EtOAc (3 ꢀ 10 mL), and
the combined filtrate was concentrated in vacuo. The
residue was purified by column chromatography on
silica gel (EtOAc–hexanes gradient elution) to afford
compound 17 as a yellow syrup (0.42 g, 60% yield). Ana-
3.8. 1-O-(4-Azidobutyl)-2,3,5-tri-O-benzyl-D-ribitol (12)
The title compound was obtained from 19 as described for
the preparation of compound 11 in 80% yield. Analytical

A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
1713
data for 12: Rf = 0.40 (EtOAc–hexanes 3:7); ½aꢁ29 +29.0 (c
4H, H-1, 5), 3.72–3.75 (m, 1H, H-2), 3.82–3.86 (m,
1H, H-4), 4.20–4.32 (m, 2H, H-3, 50), 4.40–4.60 (m,
6H, 3 ꢀ CH2Ph), 5.21 (s, 1H, H-10), 5.52–5.59 (m, 2H,
D
1.0, CHCl3); 1H NMR: d 1.61 (br s, 4H, 2 ꢀ CH2sp), 2.83
(d, 1H, –OH), 3.19–3.23 (m, 2H, CH2sp), 3.38–3.40 (m,
2H, CH2sp), 3.54–3.58 (m, 3H, H-3, 5), 3.66–3.72 (m,
2H, H-1), 3.82–3.87 (m, 1H, H-2), 3.93 (br s, 1H, H-4),
4.42–4.69 (m, 6H, 3 ꢀ CH2Ph), 7.18–7.29 (m, 15H, aro-
matic); 13C NMR: d 25.9, 27.0, 51.4, 70.4, 70.9, 71.0,
71.3, 72.6, 73.5, 73.9, 79.0, 79.3, 127.7, 127.8 (ꢀ2),
127.9 (ꢀ4), 128.0 (ꢀ2), 128.1 (ꢀ2), 128.5 (ꢀ4), 128.6
(ꢀ2), 138.2, 138.6. FABMS m/z [M+H] + calcd for
C30H38N3O5: 520.2811. Found: 520.2827.
H-20, 40), 5.67 (dd, 1H, J2 ;3 ¼ 3:1 Hz, H-30), 7.17–8.06
(m, 30H, aromatic); 13C NMR: d 18.2, 26.4, 27.5, 51.9,
67.8, 69.0, 70.7, 71.2, 71.3, 71.5, 72.4, 72.6, 72.7, 73.8,
78.3, 98.3, 128.2 (ꢀ3), 128.4 (ꢀ3), 128.5 (ꢀ6), 128.9
(ꢀ6), 129.0 (ꢀ3), 129.2 (ꢀ3), 129.6, 129.8, 130.1, 130.3
(ꢀ4), 130.5 (ꢀ2), 133.7, 133.9, 134.0, 138.8, 139.0,
166.1, 166.2, 166.4. FABMS m/z [M+Na]+ calcd for
C57H59N3O12Na: 1000.3996. Found: 1000.3963.
0
0
3.9. Typical glycosylation procedures: preparation of
pseudo-oligosaccharides
3.11. 1-O-(4-Aminobutyl)-3-O-(a-L-rhamnopyranosyl)-D-
ribitol (5)
3.9.1. Method A. AgOTf-promoted activation of the
SBox glycosyl donors. A mixture of the glycosyl donor
To a solution of 20 (60 mg, 0.06 mmol) in dry methanol
(1.0 mL) was added 1M NaOMe to pH 9 (ꢂ0.1 mL).
The reaction mixture was stirred for 15 h at rt, then neu-
tralized with Dowex (H+), filtered, and concentrated in
vacuo. The crude residue was dissolved in a mixture of
ethanol–HCl (12:0.03) and 10% Pd–C (70 mg) was
added. The reaction mixture was stirred under an atmo-
sphere of H2 for 8 h. When TLC showed the formation
of ninhydrin positive spot on the baseline, the catalyst
was filtered off and the filtrate was neutralized with
Dowex (OHꢃ) resin and concentrated under reduced
pressure. The residue was co-evaporated with water
(2 ꢀ 2 mL) and then purified by column chromatogra-
phy on Sephadex G-15 (water elution) to afford com-
pound 5 as a syrup (19 mg, 85% yield). Analytical data
(0.11 mmol), glycosyl acceptor (0.10 mmol), and freshly
˚
activated molecular sieves (3 A,
200 mg) in
ClCH2CH2Cl (2 mL) was stirred under argon for
1.5 h. Freshly conditioned AgOTf (0.22 mmol) was
added and the reaction mixture was stirred for 15 min
at rt, then diluted with CH2Cl2, the solid was filtered
off and the residue was washed with CH2Cl2. The com-
bined filtrate (30 mL) was washed with 20% aq NaH-
CO3 (15 mL) and water (3 ꢀ 10 mL), the organic
phase was separated, dried over MgSO4, and concen-
trated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc–hexanes gradient
elution) to afford a pseudo-oligosaccharide derivative.
26
1
for 5: ½aꢁD ꢃ24.4 (c 0.5, H2O); H NMR (D2O): d 1.32
3.9.2. Method B. NIS–TfOH-promoted activation of S-
ethyl glycosyl donors. A mixture of the glycosyl
donor (0.13 mmol), glycosyl acceptor (0.10 mmol),
(d, 3H, H-60), 1.72–1.74 (m, 4H, 2 ꢀ CH2sp), 2.99–3.02
(m, 2H, CH2sp), 3.51 (dd, 1H, J3 ;4 ¼ 9:6 Hz, H-40),
3.62–3.65 (m, 2H, CH2sp), 3.69–3.71 (m, 2H, H-1b,
5b), 3.75–3.90 (m, 5H, H-1a, 5a, 3, 30, 50), 3.99–4.03
(m, 2H, H-2, 4), 4.08–4.10 (m, 1H, H-20), 4.99 (d, 1H,
0
0
˚
and freshly activated molecular sieves (4 A, 200 mg) in
ClCH2CH2Cl (2 mL) or ether–DCE was stirred for 1 h
under argon. NIS (0.25 mmol) and TfOH (0.025 mmol)
were added at ꢃ30 °C to 0 °C and the reaction mixture
was stirred for 10 min. Upon completion, the solid was
filtered off and the residue was washed with CH2Cl2.
The combined filtrate (30 mL) was washed with 20%
aq Na2S2O3 (15 mL) and water (3 ꢀ 10 mL). The organ-
ic phase was separated, dried over MgSO4, and concen-
trated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc–hexanes gradient
elution) or Sephadex LH-20 (methanol–CH2Cl2, 1:1)
to afford a pseudo-oligosaccharide derivative.
J1 ;2 ¼ 1:7 Hz, H-10) ppm; 13C NMR (D2O): d 16.9,
24.8, 26.1, 39.8, 62.7, 69.7, 70.3, 70.5, 70.7, 70.8, 71.1,
71.8, 72.2, 80.4, 100.9. FABMS m/z [M+H]+ calcd for
C15H32O9N: 370.2077. Found: 370.2071.
0
0
3.12. 1-O-(4-Azidobutyl)-4-O-(2,3,4-tri-O-benzoyl-a-L-
rhamnopyranosyl)-2,3,5-tri-O-benzyl-D-ribitol (21)
The title compound was obtained by Method B from 9
and 12 in 87% yield. Analytical data for 21: Rf = 0.50
25
(EtOAc–hexanes 3:7); ½aꢁD +61.2 (c 1, CHCl3); 1H
NMR: d 1.07 (d, 3H, H-60), 1.59 (s, 4H, 2 ꢀ CH2sp),
3.13 (d, 2H, CH2sp), 3.41–3.50 (m, 2H, CH2sp), 3.61–
3.67 (m, 3H, H-3, 5), 3.71 (d, 1H, H-2), 3.74–3.80 (m,
2H, H-1), 4.18–4.23 (m, 1H, H-50), 4.28–4.33 (m, 1H,
H-4), 4.37–4.70 (m, 6H, 3 ꢀ CH2Ph), 5.36 (dd, 1H,
3.10. 1-O-(4-Azidobutyl)-3-O-(2,3,4-tri-O-benzoyl-a-L-
rhamnopyranosyl)-2,4,5-tri-O-benzyl-D-ribitol (20)
The title compound was obtained by Method B from 9
and 11 in 75% yield. Analytical data for 20: Rf = 0.50
J1 ;2 ¼ 7:4 Hz, H-10), 5.55 (dd, 1H, J3 ;4 ¼ 9:9 Hz, H-
30), 5.66–5.77 (m, 2H, H-20, 40), 7.11–8.02 (m, 30H, aro-
matic); 13C NMR: d 18.2, 26.5, 27.6, 51.9, 67.7, 70.7,
71.3, 71.5, 71.6, 72.5, 73.4, 74.0, 74.1, 76.4, 78.8, 79.6,
0
0
0
0
29
(EtOAc–hexanes 3:7); ½aꢁD +37.8 (c 1, CHCl3); 1H
NMR: d 1.11 (d, 3H, H-60), 1.58 (br s, 4H, 2 ꢀ CH2sp),
3.18 (s, 2H, CH2sp), 3.36 (d, 2H CH2sp), 3.66–3.70 (d,

1714
A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
97.4, 128.2, 128.3 (ꢀ2), 128.4 (ꢀ3), 128.5 (ꢀ2), 128.7
(ꢀ2), 128.9 (ꢀ2), 129.0 (ꢀ6), 129.2 (ꢀ2), 129.9, 130.1,
130.2, 130.3 (ꢀ4), 130.4 (ꢀ2), 130.6 (ꢀ2), 133.7, 133.9,
134.0, 138.7, 138.8, 139.1, 166.1, 166.2, 166.4. FABMS
m/z [M+Na] + calcd for C57H59N3O12Na: 1000.3996.
Found: 1000.3963.
3.06–3.08 (m, 2H, CH2sp), 3.51 (dd, 1H,
00 00
J4 ;5 ¼ 9:2 Hz, H-400), 3.58–3.65 (m, 4H, H-40, 200, CH
2sp), 3.68–3.72 (m, 2H, H-1b, 5b), 3.77–3.93 (m, 8H,
H-1a, 3, 5a, 30, 50, 300, 6a00, 6b00), 3.99–4.03 (m, 2H, H-
2, 4), 4.09–4.11 (m, 1H, H-500), 4.23 (dd, 1H,
J2 ;3 ¼ 2:6 Hz, H-20), 5.05 (d, 1H, J1 ;2 ¼ 1:7 Hz, H-10),
0
0
0
0
5.15 (d, 1H, J1 ;2 ¼ 3:5 Hz, H-100); 13C NMR (D2O):
00 00
3.13. 1-O-(4-Azidobutyl)-4-O-(a-L-rhamnopyranosyl)-D-
ribitol (6)
d,
17.2, 24.1, 26.1, 39.7, 60.7, 62.7, 62.9, 67.3,
69.7, 69.8, 70.5, 70.7, 71.1, 71.7, 72.0, 72.5, 73.3, 75.7,
80.4, 95.8, 100.5. FABMS m/z [M+H]+ calcd for
C21H42NO14: 532.2605. Found: 532.2606.
The title compound was obtained from 21 using the
same reaction conditions as described for the synthesis
of compound 5 in 90% yield. Analytical data for 6:
3.16. O-(3-O-Acetyl-2-O-benzyl-4,6-O-benzylidene-a-D-
glucopyranosyl)-(1?3)-O-(2,4-di-O-benzoyl-a-L-
rhamnopyranosyl)-(1?4)-1-O-(4-azidobutyl)-2,3,5-tri-O-
benzyl-D-ribitol (24)
26
1
½aꢁD ꢃ81.5 (c 1.0, H2O); H NMR (D2O): d 1.34 (d,
3H, H-60), 1.71–1.82 (m, 4H, 2 ꢀ CH2sp), 3.06–3.09
(m, 2H, CH2sp), 3.52 (dd, 1H, J3 ;4 ¼ 9:7 Hz, H-40),
3.60–3.69 (m, 3H, H-1b, CH2sp ), 3.75–3.85 (m, 4H,
H-2, 3, 30, 50), 3.89–3.95 (m, 4H, H-1a, 4, 5), 4.07 (dd,
0
0
The title compound was obtained by Method B from 22
and 12 in 78% yield. Analytical data for 24: Rf = 0.41
1H, J2 ;3 ¼ 1:7 Hz, H-20), 5.06 (dd, 1H, J1 ;2 ¼ 1:5 Hz,
H-10); 13C NMR (D2O): d 17.1, 24.1, 26.1, 39.7, 59.6,
69.6, 70.6, 70.7, 70.9, 71.7, 72.3, 72.4, 78.6, 100.3; HR-
FAB HR-FAB MS [M+H]+ calcd for C15H32O9N:
370.2077. Found: 370.2071.
0
0
0
0
22
(EtOAc–hexanes 3:7); ½aꢁD +58.7 (c 1, CHCl3); 1H
NMR: d 1.09 (d, 3H, H-60), 1.59 (bs, 4H, 2 ꢀ CH2sp),
1.76 (s, 3H, COCH3), 3.15 (br s, 2H, CH2sp), 3.26 (dd,
1H, J3 ;4 ¼ 9:3 Hz, H-400), 3.38–3.45 (m, 4H, H-3, 200,
00 00
CH2sp), 3.60–3.74 (m, 5H, H-2, 5, 500, 6b00), 3.78–3.86
(m, 3H, H-1, 6a00), 4.12–4.15 (m, 1H, H-50), 4.22–4.28
(m, 1H, H-4), 4.33 (s, 1H, H-30), 4.38–4.70 (m, 8H,
4 ꢀ CH2Ph), 5.12–5.18 (m, 3H, H-100, 300, CHPh), 5.36
3.14. O-(3-O-Acetyl-2-O-benzyl-4,6-O-benzylidene-a-D-
glucopyranosyl)-(1?3)-O-(2,4-di-O-benzoyl-a-L-
rhamnopyranosyl)-(1?3)-1-O-(4-azidobutyl)-2,4,5-tri-
O-benzyl-D-ribitol (23)
(dd, 1H, J1 ;2 ¼ 1:5 Hz, H-10), 5.54 (dd, 1H, J3 ;4
¼
0
0
0
0
9:8 Hz, H-40), 5.66 (d, 1H, J2 ;3 ¼ 2:7 Hz, H-20), 6.95–
8.11 (m, 35H, aromatic); 13C NMR: d 17.9, 20.9, 25.9,
27.1, 51.4, 62.8, 67.6, 68.7, 70.1, 70.4, 71.0, 71.1, 71.7,
72.1, 72.6, 72.9, 73.5, 75.7, 78.6, 79.2, 79.4, 94.4, 96.8,
101.2, 126.5 (ꢀ2), 127.6, 127.7 (ꢀ3), 127.8
(ꢀ2), 127.9 (ꢀ3), 128.0 (ꢀ6), 128.1 (ꢀ3), 128.3 (ꢀ3),
128.5 (ꢀ6), 128.6 (ꢀ3), 128.8, 129.6, 129.7, 129.8,
130.2, 133.2, 133.4, 137.2, 137.9, 138.2, 138.3, 138.5,
165.7, 166.3, 169.3. FABMS m/z [M+Na]+ calcd for
C72H77N3O17Na: 1278.5151. Found: 1278.5138.
0
0
The title compound was obtained by Method B from 22
and 11 in 80% yield. Analytical data for 23: Rf = 0.38
22
(EtOAc–hexanes 3:7); ½aꢁD +50.3 (c 0.8, CHCl3); 1H
NMR: d 1.07 (d, 3H, H-60), 1.55 (br s, 4H, 2 ꢀ CH2sp),
1.73 (s, 3H, COCH3), 3.13–3.19 (m, 2H, CH2sp), 3.22
(dd, 1H, J1a,1b = 9.6 Hz, H-1a), 3.32–3.40 (m, 3H, H-20,
CH2sp), 3.59–3.73 (m, 5H, H-1b, 2, 4, 5), 3.79–3.83 (m,
3H, H-3, 30, 40), 4.14–4.19 (m, 3H, H-50, 500, 6b00), 4.24–
4.30 (m, 1H, H-6a00), 4.39–4.69 (m, 8H, 4 ꢀ CH2Ph),
4.99 (dd, 1H, J1 ;2 ¼ 3:2 Hz, H-10), 5.10–5.17 (m, 3H,
H-100, 300, CHPh), 5.45–5.51 (m, 2H, H-200, 400), 6.94–
7.99 (m, 35H, aromatic); 13C NMR: d 17.8, 20.9, 25.9,
27.1, 51.4, 62.9, 67.6, 68.7, 68.9, 69.0, 70.5, 70.6, 70.8,
70.9, 72.1, 72.2, 72.4, 72.6, 73.4, 79.4, 95.1, 97.8, 101.3,
126.5 (ꢀ2), 127.7 (ꢀ4), 127.8 (ꢀ4), 127.9 (ꢀ4), 128.0
(ꢀ6), 128.3 (ꢀ4), 128.5 (ꢀ6), 128.7 (ꢀ4), 129.6, 129.8,
130.2, 133.3, 133.4, 137.2, 137.9, 138.4, 138.5, 138.6,
165.7, 166.4, 169.3. FABMS m/z [M+Na]+ calcd for
C72H77N3O17Na: 1278.5151. Found: 1278.5138.
0
0
3.17. O-(a-D-Glucopyranosyl)-(1?3)-O-(a-L-rhamno-
pyranosyl)-(1?4)-1-O-(4-aminobutyl)-D-ribitol (4)
The title compound was obtained from 24 as described
for the synthesis of compound 5 in 78% yield. Analytical
27
1
data for 4: ½aꢁD +25.4 (c 0.4, H2O); H NMR (D2O): d
1.35 (d, 3H, H-60), 1.70–1.72 (m, 4H, 2 ꢀ CH2sp),
00 00
2.82–2.84 (m, 2H, CH2sp), 3.51 (dd, 1H, J4 ;5
¼
9:5 Hz, H-400), 3.61–3.65 (m, 4H, H-40, 200, CH2sp),
3.75–3.87 (m, 7H, H-1, 2, 3, 50, 300, 6a00), 3.91–3.95 (m,
5H, H-5, 30, 500, 6b00), 4.01–4.04 (m, 1H, H-4), 4.27 (dd,
3.15. O-(a-D-Glucopyranosyl)-(1?3)-O-(a-L-rhamnopyr-
anosyl)-(1?3)-1-O-(4-aminobutyl)-D-ribitol (3)
1H, J2 ;3 ¼ 2:5 Hz, H-20), 5.12 (d, 1H, J1 ;2 ¼ 1:3 Hz,
0
0
0
0
H-10), 5.18 (d, 1H, J1 ;2 ¼ 3:2 Hz, H-100); 13C NMR
00 00
The title compound was obtained from 23 as described
for the synthesis of compound 5 in 88% yield. Analytical
(D2O): d 17.1, 24.5, 26.2, 40.0, 59.6, 60.6, 67.4, 69.7
(ꢀ2), 70.5 (ꢀ2), 71.2, 71.6, 71.7, 72.0, 72.4, 73.2, 75.9,
25
1
+
data for 3: ½aꢁD +33.2 (c 1.0, H2O); H NMR (D2O): d
78.8, 95.9, 99.9. FABMS m/z [M+H]
calcd for
1.35 (d, 3H, H-60), 1.74–1.79 (m, 4H, 2 ꢀ CH2sp),
C21H42NO14: 532.2605. Found: 532.2606.

A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
1715
3.18. Ethyl O-(4-O-anisoyl-2,3,6-tri-O-benzyl-a-D-galac-
topyranosyl)-(1?3)-2-O-benzyl-4,6-O-benzylidene-1-
thio-b-D-glucopyranoside (25)
2 ꢀ CH2sp), 3.24 (d, 4H, H-6a000, 6b000, CH2sp), 3.38–
3.42 (m, 2H, CH2sp), 3.45–3.53 (m, 2H, H-400, 6a00),
3.59 (dd, 1H, H-200), 3.67–3.70 (m, 5H, H-1, 5, 2000),
3.76–3.80 (m, 3H, H-500, 6b00, 3000), 3.85 (s, 3H, –OCH ),
3
The title compound was obtained by Method A from 7
and 8 in 99% yield. Analytical data for 25: Rf = 0.50
3.88–3.93 (m, 2H, H-2, 4), 3.97–4.05 (m, 1H, H-3),
4.07 (dd, 1H, J3 ;4 ¼ 4:8 Hz, H-300), 4.17–4.28 (m, 4H,
00 00
29
(EtOAc–hexanes 3:7); ½aꢁD +42.7 (c 1, CHCl3); 1H
H-50, 5000, CH2Ph), 4.36–4.40 (m, 3H, H-30, CH2Ph),
NMR: d 1.15 (t, 3H, CH3), 2.77–2.81 (m, 2H, CH2),
4.45–4.77 (m, 10H, 5 ꢀ CH2Ph), 5.08 (d, 1H,
3.16 (dd, 1H, J5 ;6a0 ¼ 5:2 Hz, J6a0;6b ¼ 4:9 Hz, H-6a0),
J1 ;2 ¼ 3:5 Hz, H-100), 5.28 (s, 1H, H-1000), 5.30 (s, 2H,
0
0
00 00
3.34 (dd, 1H, J5 ;6b ¼ 6:9 Hz, H-6b0), 3.46–3.51 (m,
1H, H-4), 3.57 (dd, 1H, J3,4 = 4.9 Hz, H-3), 3.81 (dd,
1H, J6a,6b = 10.3 Hz, H-6b), 3.85–3.91 (m, 4H, H-6a,
H-10, CHPh), 5.52 (dd, 1H, J3
¼ 3:3 Hz, H-4000),
000;4000
0
0
5.62–5.66 (m, 2H, H-20, 40), 6.81–8.09 (m, 55H, aro-
matic); 13C NMR: d 17.9, 25.9, 27.1, 36.8, 51.4, 55.6,
62.6, 67.1, 67.8, 68.0, 68.4, 68.8, 68.9, 69.4, 70.8, 70.9,
71.7, 71.9, 72.1, 72.2, 72.3, 72.4, 72.8, 72.9, 73.2, 73.4,
74.7, 75.9, 77.7, 77.8, 77.9, 82.9, 94.9, 96.8, 97.7, 101.9,
113.6, 123.1, 126.8 (ꢀ 2), 127.3, 127.4, 127.6 (ꢀ2),
127.7 (ꢀ2), 127.9 (ꢀ5), 127.96 (ꢀ3), 128.0 (ꢀ4), 128.1
(ꢀ6), 128.2 (ꢀ2), 128.3 (ꢀ4), 128.5 (ꢀ6), 128.6 (ꢀ3),
128.7, 128.8, 129.2, 129.7, 129.8, 129.9, 130.2, 132.0
(ꢀ4), 133.3, 133.5, 137.4, 137.5, 138.4, 138.5 (ꢀ2),
138.6 (ꢀ2), 138.8, 163.3, 165.6, 165.8, 166.2. FABMS
m/z [M+Na]+ calcd for C105H109N3O23Na: 1802.7344.
Found: 1802.7366.
20, –OCH3), 4.05 (dd, 1H, J3 ;4 ¼ 3:2 Hz, J2 ;3
¼
0
0
0
0
6:9 Hz, H-30), 4.12–4.19 (m, 4H, 2 ꢀ CH2Ph), 4.33–
4.37 (m, 2H, H-5, 50), 4.52 (dd, 1H, J2,3 = 3.2 Hz, H-
2), 4.57–4.83 (m, 4H, 2 ꢀ CH2Ph), 5.05 (dd, 1H,
J1,2 = 7.1 Hz, H-1), 5.45 (dd, 1H, J4 ;5 ¼ 2:6 Hz, H-40),
0
0
0
0
5.50 (s, 1H, CHPh), 5.71 (dd, 1H, J1 ;2 ¼ 3:5 Hz, H-
10), 6.85–7.95 (m, 30H, aromatic); 13C NMR: d 15.3,
25.3, 53.6, 67.5, 68.9 (ꢀ2), 70.1, 72.0, 72.3, 72.9, 74.7,
75.4, 75.8, 76.4, 80.3, 82.6, 85.2, 96.8, 102.1, 113.7
(ꢀ2), 127.4, 127.6 (ꢀ2), 127.7, 127.8 (ꢀ2), 128.1 (ꢀ2),
128.2 (ꢀ5), 128.4 (ꢀ5), 128.5 (ꢀ3), 128.6 (ꢀ3), 128.7
(ꢀ3), 129.5, 132.1 (ꢀ2), 137.3, 137.7, 138.3, 138.6.
FABMS m/z [M+H]+ calcd for C57H61O12S: 969.3883.
Found: 969.3884.
3.21. O-(a-D-Galactopyranosyl)-(1?3)-O-(a-D-glucopyr-
anosyl)-(1?3)-O-(a-L-rhamnopyranosyl)-(1?3)-1-O-(4-
aminobutyl)-D-ribitol (1)
3.19. 1-O-(4-Azidobutyl)-3-O-(2,4-di-O-benzoyl-a-L-
rhamnopyranosyl)-2,4,5-tri-O-benzyl-D-ribitol (26)
The title compound was obtained from 27 in 70% yield
similarly to that described for the synthesis of com-
pound 5, the only difference being pH 12 to ensure
the rapid removal of the anisoyl moiety. Analytical
The title compound was obtained by Method B from 10
and 11 in 65% yield. Analytical data for 26: Rf = 0.57
28
25
(EtOAc–hexanes 2:3); ½aꢁD ꢃ14.9 (c 1, CHCl3); 1H
data for 1: ½aꢁD +80.8 (c 1.0, H2O); H NMR (D2O):
d 1.21 (d, 3H, H-60), 1.71–1.76 (m, 4H, 2 ꢀ CH2sp),
3.04–3.07 (m, 2H, CH2sp), 3.55–3.69 (m, 16H), 3.71–
3.88 (m, 14H), 3.92–4.07 (m, 8H), 4.22–4.27 (m, 2H,
1
NMR: d 1.11 (d, 3H, H-60), 1.59 (br s, 4H, 2 ꢀ CH2sp),
3.18–3.22 (m, 2H, CH2sp), 3.31–3.35 (m, 2H, CH2sp),
3.62–3.73 (d, 4H, H-1, 5), 3.78–3.86 (m, 2H, H-2, 4),
4.15–4.24 (m, 3H, H-3, 30, 50), 4.42–4.63 (m, 6H,
3 ꢀ CH2Ph), 5.13–5.21 (m, 2H, H-10, 40), 5.32–5.34 (m,
1H, H-20), 7.19–8.11 (m, 25H, aromatic); 13C NMR: d
17.7, 25.9, 27.2, 51.5, 67.0, 68.6, 69.3, 70.7, 71.0, 72.1,
72.3, 73.3, 73.5, 75.8, 77.9, 97.5, 127.7 (ꢀ2), 127.9
(ꢀ3), 128.0 (ꢀ6), 128.4 (ꢀ6), 128.7 (ꢀ4), 129.6, 129.7,
130.1 (ꢀ4), 133.7 (ꢀ2), 138.4 (ꢀ2), 138.6, 166.1,
167.4. FABMS m/z [M+Na]+ calcd for C50H55-
N3O11Na: 896.3734. Found: 896.3732.
H-20, 5000), 5.02 (d, 1H, J1 ;2 ¼ 1:8 Hz, H-10), 5.13 (d,
0
0
1H, J1 ;2 ¼ 6:3 Hz, H-100), 5.40 (d, 1H, J1
¼
00 00
000;2000
3:7 Hz, H-1000); 13C NMR. (D2O): d 17.1, 24.1, 26.1,
39.7, 60.5, 61.2, 62.7 (ꢀ2), 67.1, 68.9, 69.5, 69.7,
69.8, 70.1, 70.2, 70.4, 70.7, 71.1, 71.8, 72.4 (ꢀ2),
75.5, 79.9, 80.4, 90.0, 95.7, 99.7, 100.5. FABMS
m/z [M+H]+ calcd for C27H52NO19: 694.3134. Found
694.3141.
3.22. 1-O-(4-Azidobutyl)-4-O-(2,4-di-O-benzoyl-a-L-
rhamnopyranosyl)-2,3,5-tri-O-benzyl-D-ribitol (28)
3.20. O-(4-O-Anisoyl-2,3,6-tri-O-benzyl-a-D-galactopyr-
anosyl)-(1?3)-O-(2-O-benzyl-4,6-O-benzylidene-a-
D-glucopyranosyl)-(1?3)-O-(2,4-di-O-benzoyl-a-L-
rhamnopyranosyl)-(1?3)-1-O-(4-azidobutyl)-2,4,5-tri-
O-benzyl-D-ribitol (27)
The title compound was obtained by Method B from 10
and 12 in 78% yield. Analytical data for 28: Rf = 0.49
29
(EtOAc–hexanes 3:7); ½aꢁD +3.2 (c 0.9, CHCl3); 1H
NMR: d 1.07 (d, 3H, H-60), 1.56 (s, 4H, 2 ꢀ CH2sp),
2.40 (d, 1H, –OH), 3.06–3.09 (m, 2H, CH2sp), 3.38–
3.40 (d, 2H, CH2sp), 3.57–3.65 (m, 3H, H-2, 3, 5),
3.70–3.73 (m, 2H, H-1), 4.00–4.14 (m, 2H, H-30, 50),
4.22 (bs, 1H, H-4), 4.36–4.86 (m, 6H, 3 ꢀ CH2Ph),
The title compound was obtained by Method B from 25
and 26 in 66% yield. Analytical data for 27: Rf = 0.60
28
(EtOAc–hexanes 2:3); ½aꢁD +55.6 (c 1.0, CHCl3); 1H
NMR: d 1.19 (d, 3H, H-60), 1.60–1.64 (m, 4H,

1716
A. R. Parameswar et al. / Carbohydrate Research 343 (2008) 1707–1717
5.14 (dd, 1H, J1 ;2 ¼ 9:8 Hz, H-10), 5.31–5.37 (m, 2H, H-
20, 40), 7.14–8.05 (m, 25H, aromatic); 13C NMR: d 18.2,
26.4, 27.6, 51.8, 67.3, 67.7, 70.9, 71.3, 71.5, 73.1, 74.0,
74.1 (ꢀ2), 76.0, 76.2, 78.5, 79.7, 97.0, 128.2, 128.3
(ꢀ2), 128.4 (ꢀ3), 128.5 (ꢀ2), 128.6 (ꢀ2), 128.9 (ꢀ6),
129.1 (ꢀ2), 129.2 (ꢀ2), 130.2, 130.5 (ꢀ2), 130.6
(ꢀ2), 134.1 (ꢀ2), 138.7, 138.9 (ꢀ2), 166.6, 167.8.
FABMS m/z [M+Na] + calcd for C50H55N3O11Na:
896.3734. Found: 896.3732.
(d, 1H, J1 ;2 ¼ 1:8 Hz, H-10), 5.16 (d, 1H, J1 ;2
¼
0
0
0
0
00 00
3:3 Hz, H-100), 5.45 (d, 1H, J1
¼ 3:7 Hz, H-1000); 13C
000;2000
NMR (D2O): d 17.5, 24.4, 26.1, 39.8, 60.7, 61.4, 62.1,
63.9, 67.0, 68.2, 69.9, 70.4, 70.6 (ꢀ2), 71.1, 71.7, 72.1,
72.8, 72.9, 73.3, 76.5, 79.8, 81.1, 96.8, 100.6, 101.5. FAB-
MS m/z [M+H] + calcd for C27H52NO19: 694.3134.
Found: 694.3141.
Acknowledgments
3.23. O-(4-O-Anisoyl-2,3,6-tri-O-benzyl-a-D-galactopyr-
anosyl)-(1?3)-O-(2-O-benzyl-4,6-O-benzylidene-a-D-
glucopyranosyl)-(1?3)-O-(2,4-di-O-benzoyl-a-L-
rhamnopyranosyl)-(1?4)-1-O-(4-azidobutyl)-2,3,5-tri-O-
benzyl-D-ribitol (29)
The authors thank NSF (CAREER CHE-0547566) for
financial support of this research; NSF for grants to pur-
chase the NMR spectrometer (CHE-9974801) and the
mass spectrometer (CHE-9708640) used in this work;
Dr. R. S. Luo for assistance with 500 MHz 2D NMR
experiments; and Dr. R. E. K. Winter and Mr. J. Kra-
mer for HRMS determinations.
The title compound was obtained by Method B from 25
and 28 in 70% yield. Analytical data for 29: Rf = 0.56
29
(EtOAc–hexanes 2:3); ½aꢁD +54.8 (c 1.0, CHCl3); 1H
NMR: d 1.15 (d, 3H, H-60), 1.64 (br s, 4H, 2 ꢀ CH2sp),
3.21–3.23 (m, 4H, CH2sp, H-6a000, 6b000), 3.40–3.43 (m,
3H, CH2sp, H-6b00), 3.44–3.47 (m, 1H, H-6a00), 3.49–
3.51 (dd, 1H, H-200), 3.57–3.61 (m, 2H, H-2000, H-400),
3.64–3.70 (m, 5H, H-2, 3, 5, 3000), 3.74–3.80 (m, 6H, H-
1, 500, –OCH3), 3.86–3.90 (m, 1H, H-3), 3.96 (dd, 1H,
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1
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