Iterative one-pot syntheses of chitotetroses

Article abstract of DOI:10.1016/j.carres.2006.01.007

Rapid syntheses of chitotetrose derivatives were achieved in good yields using the newly developed reactivity independent iterative one-pot strategy. The protective groups on donors and acceptors were independently evaluated allowing matching of the two p

Full text of DOI:10.1016/j.carres.2006.01.007

Carbohydrate
RESEARCH
Carbohydrate Research 341 (2006) 1669–1679
Iterative one-pot syntheses of chitotetroses
Lijun Huang,a Zhen Wang,a Xiaoning Li,a Xin-shan Yeb and Xuefei Huanga,*
aDepartment of Chemistry, The University of Toledo, 2801 W. Bancroft Street, MS 602, Toledo, OH 43606, USA
bThe State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University,
Xue Yuan Road 38, Beijing 100083, China
Received 7 November 2005; received in revised form 3 January 2006; accepted 8 January 2006
Available online 26 January 2006
Dedicated to Professor Koji Nakanishi on the occasion of his 80th birthday
Abstract—Rapid syntheses of chitotetrose derivatives were achieved in good yields using the newly developed reactivity independent
iterative one-pot strategy. The protective groups on donors and acceptors were independently evaluated allowing matching of the
two partners in glycosylation. No anomeric reactivity adjustments or intermediate purification were necessary thus significantly
improving the overall synthetic efficiency. Only near stoichiometric amounts of building blocks were required for the assembly
of target molecules further highlighting the potential of the iterative one-pot method in complex oligosaccharide synthesis.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Iterative; One-pot synthesis; Chitotetrose; Reactivity independent
1. Introduction
acceptor can be carried out independent of the anomeric
reactivities of donors and acceptors.7 Medium sized oli-
gosaccharides have been assembled in a few hours using
this methodology without the need of intermediate puri-
fication and aglycon adjustments. Our reactivity inde-
pendent one-pot approach represents a significant
advancement in chemoselective glycosylation as the
time-consuming anomeric reactivity adjustment is
unnecessary. To explore the scope of this method, we
have embarked on application of this strategy in assem-
bly of complex oligosaccharides. Herein, we report our
syntheses of chitotetroses, that is, tetrasaccharides con-
taining b-(1!4)-linked glucosamines.
With the recognition of multifaceted biological proper-
ties of oligosaccharides and glyco-conjugates, the devel-
opment of novel methods to expedite oligosaccharide
synthesis has been a major focus of modern synthetic
carbohydrate chemistry.1,2 A popular synthetic strategy
is the reactivity based chemoselective glycosylation
method, where a more reactive armed glycosyl donor is
preferentially activated in the presence of a less reactive
disarmed acceptor.2,3 Many innovative methods have
been developed for tuning anomeric reactivities.3–5 How-
ever, the very need to achieve precise anomeric reactivity
values necessitates extensive and tedious protecting
group and/or aglycon adjustments, which in turn de-
tracts from its broad application and restricts the possi-
bility of matching6 the glycosyl donor with the acceptor.
Recently, we have developed a new iterative one-pot
glycosylation method, by which multiple sequential gly-
cosylations of a thioglycosyl donor by a thioglycosyl
2. Results and discussion
Chitotetroses and their derivatives have diverse biologi-
cal functions such as immunostimulatory,8 antitumor,9
anticoagulant,10 and anti-HIV activities.11 Chemical
synthesis of this class of compounds presents a signifi-
cant challenge due to the well known low nucleophilicity
of 4-hydroxyl group of glucosamine building blocks. To
date, there have been a few reports of step-wise assembly
*
Corresponding author. Tel.: +1 419 530 1507; fax: +1 419 530
4033; e-mail: xuefei.huang@utoledo.edu
0008-6215/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2006.01.007

1670
L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
of these molecules, which are often characterized by
multiple protecting group manipulations and aglycon
leaving group adjustments on oligosaccharide interme-
diates.12,13 A single one-pot synthesis was accomplished
by our group using the reactivity based chemoselective
glycosylation approach.4 Even though building blocks
with multiple levels of anomeric reactivities were conve-
niently generated through post-synthetic modification of
the aglycon of a common intermediate, the need for
reactivity adjustment of our previous one-pot synthesis
prompted us to explore the utility of our reactivity inde-
pendent iterative one-pot method.7
BnO
BnO
O
O
HO
O
HO
O
STol
STol
N
OCH3
N
O
Ac
O
Ac
1
2
OBn
O
OBn
O
HO
BnO
HO
BnO
STol
PhthN
TrocHN
3
4
O
N
Ph
O
O
OCH3
O
N
It is known that the low nucleophilicity of 4-hydroxyl
group of protected N-acetyl glucosamine is mainly due
to the steric hinderance around this secondary hydroxyl
group and the intermolecular hydrogen bonding with
the 2-acetamido moiety.14 The N-protecting group on
a glycosyl acceptor can significantly affect its nucleo-
philicity, with the following order of activities: N3,
NH-Troc > N-Phth > NH-Ac.14,15 Recently, Crich and
Vinod have demonstrated that the usage of oxazolidi-
none protected N-acetyl glucosamine O-glycoside accep-
tor 1 considerably enhanced the glycosylation yield
compared with the corresponding O-glycoside without
the oxazolidinone moiety.16,17 We anticipated that oxa-
zolidinone protected thioglycosyl acceptor 2 may lead to
higher glycosylation yield and the resulting disaccharide
can function as a glycosyl donor.18 To investigate the
influence of N-protecting groups on our glycosylation
methodology, glycosyl acceptors 2, 3, and 4 were pre-
pared. The azido moiety is unsuitable as an N-protecting
group for one-pot synthesis of b-linked oligoglucosam-
ines because it is a well known non-participatory group
favoring the formation of a-anomer when used in a
donor.19
TTBP
N
O
Ac
7
ingly, regioselective reductive opening of the benzylidene
ring by treatment of NaCNBH3 and HCl4 yielded a mix-
ture of a-and b-thioglycoside 2, with 2a as the major
product (40%). This is in line with the observation by
the Crich group where the oxazolidinone bearing O-gly-
coside 7 was epimerized at the anomeric position under
similar reaction conditions.16 Thioglycosyl acceptors
3
21 and 422 were synthesized in a straightforward manner
from building block 5 (Scheme 1b and c).
Glycosylations of thioglycosyl donor 820 with accep-
tors 2 to 4 were carried out following our previously
established pre-activation condition.7 The disarmed gly-
cosyl donor 8 was cleanly activated in the absence of any
acceptors at ꢀ70 °C by the powerful thiophilic promoter
p-TolSOTf, formed in situ by reaction of p-TolSCl23
with AgOTf.7,24 Subsequent addition of the glycosyl
acceptor (0.9 equiv) to the reaction mixture led to the
formation of thioglycosyl disaccharide. The reaction of
N-Phth protected acceptor 3 with donor 8 produced
the desired disaccharide 9 in 56% yield with trace
amount (<5%) of donor elimination product glycal 10
(Table 1, entry 1). It is noteworthy that acceptor 3 has
a higher anomeric reactivity than donor 8. This reversal
of anomeric reactivity, that is, chemoselective glycosyl-
The synthesis of oxazolidinone protected acceptor 2
started from the benzylidene protected glucosamine
derivative 5 (Scheme 1).20 Removal of the phthalimido
group followed by oxazolidinone formation and acetyla-
tion provided the fully protected glucosamine 6. Interest-
BnO
O
O
a)
O
Ph
O
i - iii
O
HO
Ph
iv
O
O
STol
O
STol
O
HO
40%
N
74%
STol
N
NPhth
6
O
5
5
Ac
O
Ac
2α
b)
Ph
BnO
O
v, iv
O
O
O
HO
STol
STol
HO
BnO
80%
NPhth
NPhth
3
c)
BnO
HO
BnO
O
v, i, vi, iv
70%
O
Ph
O
STol
O
STol
HO
NHTroc
4
NPhth
5
Scheme 1. Preparation of acceptors 2–4. Reagents and conditions: (i) ethylene diamine, EtOH, reflux, overnight; (ii) 4-O2NC6H4OCOCl, NaHCO3,
CH3CN/H2O, rt, overnight; (iii) AcCl, DIPEA, DCM, rt, overnight; (iv) NaCNBH3, 1 M HCl in Et2O, 0 °C, 1.5 h; (v) NaH, TBAI, DMF, MS;
BnBr, 2 h, rt; (vi) Troc-Cl, NaHCO3, H2O, THF.

L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
1671
Table 1. Evaluation of N-protective group on glycosylation of various
thioglycosyl acceptors by donor 8
glycosyl acceptor 2a by donor 8. Disappointingly, the
disaccharide product 14 was produced in only 39% yield
with 50% of acceptor 2a recovered after reaction (Table
1, entry 4). The oxazolidinone moiety did not seem to
improve the glycosylation and N-Phth was used as the
N-protecting group in further studies.
1) p-TolSCl, -70 °C
Donor 8 (1 eq) + AgOTf
Product
2) acceptor (0.9 eq)
Entry #
Acceptor
Pdt.
Yield (%)
1
2
3
4
3
9
11
13
14
56
50
50
39
The four-component one-pot assembly of fully pro-
tected tetraglucosamine derivative 16 was performed as
outlined in Scheme 2. Pre-activation of donor 8 by
p-TolSOTf was followed by addition of acceptor 3.
The reaction temperature was raised to ꢀ10 °C in
20 min. After acceptor 3 was completely consumed as
judged by TLC analysis, the reaction mixture was
cooled back down to ꢀ70 °C, followed by sequential
addition of AgOTf, p-TolSCl, acceptor 3, and warming
up to ꢀ10 °C. Subsequently, the reaction temperature
was lowered to ꢀ70 °C again, which was followed by
addition of acceptor 154 and AgOTf/p-TolSCl. Slight
excess of glycosyl donors was employed for the first
two glycosylations to ensure complete consumption of
the acceptor. The excess activated donor decomposed
upon warming up thus not affecting the following reac-
tions. The desired protected chitotetrose 16 was isolated
from the one-pot reaction by flash column chromatogra-
phy in 32% overall yield. It is noteworthy that the same
acceptor 3 was used for the formation of the first and the
second glycosidic linkages without resorting to anomeric
reactivity adjustment.
To enhance the glycosylation yield, we next explored
the protecting groups on the glycosyl donor. From the
readily available alcohol 5,20 benzylation and silylation
gave donor 1721 and 18 in 90% and 85% yields, respec-
tively (Scheme 3a and b). Regioselective opening of
the benzylidene group with TMSOTf and borane
THF26 followed by benzylation produced the benzyl
protected donor 19 in 80% yield for the two steps
(Scheme 3c).
4
12
2a
OBn
AcO
AcO
O
O
O
HO
BnO
AcO
AcO
AcO
S
STol
AcO
NO2
NPhth
NPhth
NPhth
8
10
12
OBn
O
AcO
AcO
AcO
9: R1 = Phth, R2 = Tol
11: R1 = HTroc, R2 = Tol
13: R1 = Phth, R2 = p-NO2-Ph
O
O
BnO
SR2
PhthN
NR1
AcO
AcO
OBn
O
O
O
AcO
O
PhthN
14
N
STol
Ac
O
ation of an armed acceptor with a disarmed donor is not
possible with the traditional reactivity based glycosyla-
tion methods.
The glycosylation of N-Troc protected acceptor 4 by
donor 8 gave a yield of 50% of the disaccharide 11,
along with 20% of regenerated donor 8 even after com-
plete consumption of the donor during pre-activation
(Table 1, entry 2). This is the first time that a substantial
amount of the regenerated donor was observed among
all reactions we carried out so far using the pre-activa-
tion scheme. The donor regeneration is presumably
due to the intermolecular aglycon transfer25 from the
acceptor to the activated donor via S-alkylation instead
of the desired O-alkylation of the hydroxyl group. This
further re-affirms the low nucleophilicity of 4-hydroxyl
group of glucosamine acceptors. The usage of p-nitro
phenyl thioglycosyl acceptor 124 suppressed the aglycon
transfer side reaction, but the disaccharide product 13
was obtained in only 50% yield (Table 1, entry 3). We
examined next the glycosylation of oxazolidinone thio-
With various donors in hand, we began to evaluate
their effects on glycosylation. The benzyl and benzyli-
dene containing donor 17 reacted with acceptor 3 giving
61% of disaccharide 20 (Table 2, entry 1) together with
20% of recovered acceptor 3. Exchange of the benzyl
group in 17 with TBS moiety (donor 18) led to a much
AgOTf
p-TolSCl
3 (0.8 eq)
AgOTf
p-TolSCl
15 (1 eq)
p-TolSCl
3 (0.9 eq)
8 (1 eq)
+ AgOTf
16
15 min
15 min 15 min
20 min 15 min 5 min
20 min
15 min
15 min 90 min
32%
- 10 °C
- 70 °C
- 10 °C
- 10 °C
- 70 °C
- 70 °C
OAc
O
OBn
OBn
O
OBn
O
OBn
O
O
O
BnO
AcO
AcO
O
BnO
HO
BnO
O
BnO
OBn
OBn
PhthN
15
PhthN
PhthN
PhthN
PhthN
16
Scheme 2. One-pot synthesis of chitotetrose 16.

1672
L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
Table 2. Evaluation of donors on glycosylation of acceptor 3
a)
O
Ph
O
i
O
Ph
1) p-TolSCl, -70 °C
2) acceptor 3 (0.9 eq)
Pdt.
O
O
STol
17
O
STol
BnO
Donor (1 eq) + AgOTf
Product
Yield (%)
HO
PhthN
90%
PhthN
5
5
Entry #
Donor
b)
Ph
O
Ph
O
O
O
STol
18
1
2
3
17
18
19
20
21
22
61
74
50
ii
O
O
TBSO
STol
STol
HO
PhthN
85%
PhthN
c)
BnO
BnO
TBSO
OBn
O
O
iii, i
O
O
Ph
Ph
O
O
STol
19
20: R = Bn
21: R = TBS
O
O
O
BnO
STol
RO
TBSO
80%
PhthN
PhthN
PhthN
18
NPhth
BnO
OBn
O
Scheme 3. Preparation of donors 17–19. Reagents and conditions: (i)
NaH, TBAI, DMF, MS; BnBr, 2 h, rt; (ii) TBSOTf, 2,6-lutidine,
DCM, 4 h, 0 °C; (iii) TMSOTf, BH3ÆTHF, 4 h, ꢀ20 to 0 °C.
O
PhthN
O
BnO
O
BnO
STol
22
23
TBSO
PhthN
NPhth
BnO
OTBS
OBn
BnO
O
TBSO
O
cleaner reaction with complete consumption of the
acceptor, producing disaccharide 21 in 74% yield (Table
2, entry 2). Both the TBS and benzylidene groups are
important for high yield, because donor 19, which is
devoid of the benzylidene group, glycosylated acceptor
3 in a lower 50% yield (Table 2, entry 3). 1,10-Linked
disaccharide 23 and glycal 24 were isolated as the major
side products (ꢁ10%) for this reaction. The enhancement
effect of TBS group is currently under investigation.
One-pot sequential reactions of 18, 3, 25,27 and 2613
promoted by p-TolSOTf led to the formation of tetra-
saccharide 27 in 45% yield in less than 6 h (Scheme 4).
This corresponds to an average of 85% yield for each
step of the five synthetic steps carried out in one pot.
The reactivity independent nature of our method al-
lowed us to utilize the PMB containing building block
25 instead of acceptor 3 for the second glycosylation.
To prevent the loss of acid labile PMB group, a steri-
PhthN
OBn
BnO
O
BnO
24
TBSO
NPhth
cally hindered base TTBP28 was added with each accep-
tor. In addition to the desired product 27 and final
acceptor 26 (50%), we have isolated from the final reac-
tion mixture, glucals 28 (18%), 29 (15%), and hemiacetal
30 (24%) as the major side products, which were formed
through elimination or hydrolysis of activated glycosyl
donors due to insufficient nucleophilicity of the accep-
tors. The glucals do not react with the promoter p-Tol-
SOTf at low temperature, which do not affect further
donor activation. In addition, these side products have
sufficiently different polarities from the desired oligosac-
25 (0.7 eq)
+ TTBP
26 (0.9 eq)
+ TTBP
3 (0.9 eq)
+ TTBP
p-TolSCl
p-TolSCl
AgOTf
AgOTf
p-TolSCl
18 (1eq)
+ AgOTf
27
5 min
15 min 5 min
90 min 15 min 5 min
90 min
5 min
5 min 90 min
45%
- 70 °C
- 20 °C - 70 °C
- 20 °C - 70 °C
- 20 °C
OBn
O
OBn
OBn
O
OBn
O
OBn
O
O
Ph
O
O
O
PMBO
HO
PMBO
O
BnO
HO
BnO
STol
O
BnO
O
OCH3
OCH3
TBSO
PhthN
PhthN
PhthN
PhthN
PhthN
PhthN
25
26
27
OBn
O
OBn
OBn
O
O
Ph
O
O
Ph
O
O
O
O
O
O
BnO
O
TBSO
BnO
PMBO
TBSO
PhthN
28
PhthN
PhthN
NPhth
29
NPhth
OBn
OBn
O
O
Ph
O
O
O
PMBO
O
OH
O
TBSO
BnO
PhthN
PhthN
PhthN
30
Scheme 4. One-pot synthesis of chitotetrose 27.

L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
1673
charide 27, thus not interfering with product purification
3.2. p-Tolyl 2-acetamido-4,6-O-benzylidene-2-N-3-O-
carbonyl-2-deoxy-1-thio-b-D-glucopyranoside (6)
by flash chromatography. The PMB and TBS groups in
tetrasaccharide 27 can be selectively removed to allow
for alkylations of alternating 3-hydroxyl groups in the
tetraglucosamine, which are useful intermediates for
peptidoglycan synthesis.29
p-Tolyl
4,6-O-benzylidene-2-deoxy-2-phthalimido-1-
thio-b-D-glucopyranoside 5 (1.5 g, 2.98 mmol, 1 equiv)
and ethylenediamine (9 g, 150 mmol, 50 equiv) were dis-
solved in dry ethanol (15 mL). The mixture was heated
at reflux for 16 h. The reaction mixture was cooled
and neutralized with 2 N HCl until slightly basic. After
concentration, the crude product was dissolved in
EtOAc (10 mL) and washed with H2O, brine, then dried,
and concentrated. Column chromatography (15:1,
CH2Cl2–MeOH) on silica gel afforded the free amine
as a yellow solid (0.98 g, 88%). The obtained amine
(0.98 g, 2.62 mmol, 1 equiv) and NaHCO3 (1.1 g,
13.09 mmol, 5 equiv) were dissolved in H2O/CH3CN
mixture (15 mL/15 mL) and cooled to 0 °C. p-Nitro-
phenyl chloroformate (1.59 g, 7.89 mmol, 3 equiv) in
CH3CN (5 mL) was added slowly and the mixture was
stirred at 0 °C for 3 h. The resulting aqueous mixture
was extracted with EtOAc and the combined extracts
were washed with water, brine, then dried, and concen-
trated. Silica gel column chromatography (2.5:1, hex-
anes–EtOAc) afforded the oxazolidinone protected
glucosamine as a white solid (0.88 g, 84%). The oxazo-
lidinone protected glucosamine (0.42 g, 1.05 mmol,
In conclusion, facile syntheses of chitotetrose deriva-
tives were achieved in good yields using our newly devel-
oped reactivity independent iterative one-pot method.
Unlike solid phase synthesis,30 only near stoichiometric
amounts of building blocks were required. No anomeric
reactivity differentiations between donors and acceptors
were necessary, thus allowing independent evaluation of
protecting groups. As the N-protecting group, the
phthalimido moiety gave the most consistent results,
while the new oxazolidinone group did not improve
the glycosylation. The introduction of benzylidene and
TBS groups onto thioglycosyl donor significantly en-
hanced the yield. Further improvements on this chal-
lenging glycosylation reaction will depend upon the
augmentation of the nucleophilicity of 4-hydroxyl group
of glucosamine acceptors.
3. Experimental
3.1. General procedures
1 equiv) and Hunig’s base (0.92 mL, 5.29 mmol, 5 equiv)
¨
were dissolved in CH2Cl2 (6 mL). Acetyl chloride
(0.38 mL, 5.34 mmol, 5.1 equiv) was added under N2.
The mixture was stirred for 6 h and then poured into
saturated aqueous NaHCO3. The mixture was diluted
with CH2Cl2 (5 mL) and the organic layer was sepa-
rated. The aqueous layer was extracted twice with
CH2Cl2 and the combined extracts were washed with
H2O, brine, then dried, and concentrated. Column chro-
matography (1:1, hexanes–EtOAc) on silica gel afforded
All reactions were carried out under nitrogen with anhy-
drous solvents in flame-dried glassware, unless otherwise
noted. All glycosylation reactions were performed in the
presence of molecular sieves, which were flame-dried
right before the reaction under high vacuum. Glycosyl-
ation solvents were dried using an MBraun solvent puri-
fication system. Chemicals used were reagent grade as
supplied except where noted. Analytical thin-layer chro-
matography was performed using silica gel 60 F254 glass
plates (EM Science); compound spots were visualized by
UV light (254 nm) and by staining with a yellow solu-
1
the product 11 as a white solid (0.39 g, 84%). H NMR
(600 MHz, CDCl3): d 2.33 (s, 3H), 2.58 (s, 3H), 3.50–
3.54 (m, 1H), 3.92 (t, J = 10.2 Hz, 1H), 4.07 (t,
J = 9.3 Hz, 1H), 4.13 (dd, J = 9.0, 10.8 Hz, 1H), 4.27
(dd, J = 4.8, 10.5 Hz, 1H), 4.33 (t, J = 0.5 Hz, 1H),
4.91 (d, J = 9.0 Hz, 1H), 5.59 (s, 1H), 7.11–7.12 (m,
2H), 7.38–7.35 (m, 5H), 7.43–7.44 (m, 2H); 13C NMR
(150 MHz, CDCl3): d 21.42, 25.17, 61.01, 68.46, 73.31,
78.60, 78.97, 88.95, 101.77, 126.35, 128.60, 129.65,
129.87, 130.02, 133.20, 136.45, 138.79, 153.81, 173.54;
HRMS: [M+Na]+ C23H23NNaO6S calcd 464.1144, obsd
464.1181.
tion
containing
Ce(NH4)2(NO3)6
(0.5 g)
and
(NH4)6Mo7O244H2O (24.0 g) in 6% H2SO4 (500 mL).
Flash column chromatography was performed on silica
gel 60 (230–400 Mesh, EM Science). 1H NMR, 13C
NMR, 1H–1H COSY, and 1H–13C HMQC spectra were
recorded on a Varian VXRS-400 or Inova-600 instru-
ment and were referenced using Me4Si (0 ppm), residual
CHCl3 (d 1H NMR 7.26 ppm, 13C NMR 77.0 ppm).
Optical rotations were measured at 25 °C. ESI mass
spectra were recorded on ESQUIRE LC–MS operated
in positive ion mode. High-resolution mass spectra were
recorded on a Micromass electrospray TofTM II (Micro-
mass, Wythenshawe, UK) mass spectrometer equipped
with an orthogonal electrospray source (Z-spray) oper-
ated in positive ion mode, which is located at the Mass
Spectrometry and Proteomics Facility, the Ohio State
University.
3.3. p-Tolyl 2-acetamido-6-O-benzyl-2-N,3-O-carbonyl-
2-deoxy-1-thio-a-D-glucopyranoside (2a)
The mixture of compound 6 (0.11 g, 0.25 mmol,
1 equiv), NaCNBH3 (0.19 g, 3.0 mmol, 12 equiv) in
THF (5 mL) was cooled to 0 °C. One molar of HCl in
Et2O (ꢁ3 mL) was added under N2 until the solution

1674
L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
was slightly acidic. The reaction mixture was stirred at
0 °C for 1.5 h and diluted with 10 mL of CH2Cl2 and
then poured into aqueous NaHCO3. The organic layer
was separated and washed with H2O, brine, then dried,
and concentrated. Column chromatography (1:1, hex-
anes–EtOAc) on silica gel afforded the product 2a as a
white solid (44 mg, 40%). [a]D +176.4 (c, 0.0056 g/mL,
deoxy-2-N-Troc glucopyranoside (1.19 g, 100%). The
desired compound 4 (660 mg, 90%) was then obtained
as a white solid from the 2-deoxy-2-N-Troc glucopyr-
anoside (730 mg, 1.14 mmol) following the same proce-
dure as in the synthesis of compound 3. The overall
yield for synthesis of compound 4 was 70% for the four
steps starting from compound 5. Comparison of the
NMR data with those reported in the literature22 con-
firmed the identity of 4.
1
CH2Cl2); H NMR (600 MHz, CDCl3): d 2.31 (s, 3H),
2.53 (s, 3H), 3.11 (br, 1H), 3.72–3.74 (m, 1H), 3.83–
3.86 (m, 1H), 4.01–4.04 (m, 1H), 4.08–4.11 (m, 1H),
4.16–4.19 (m, 1H), 4.37 (dd, J = 12, 9.6 Hz, 1H), 4.53
(d, J = 12.0 Hz, 1H), 4.61 (d, J = 12 Hz, 1H), 6.07 (d,
J = 4.2 Hz, 1H), 7.08–7.09 (m, 2H), 7.29–7.36 (m, 7H);
13C NMR (150 MHz, CDCl3): d 21.37, 24.06, 59.91,
69.72, 70.70, 72.51, 74.07, 78.41, 86.88, 128.06, 128.31,
128.82, 128.92, 130.21, 133.27, 137.55, 138.70, 153.32,
171.45; HRMS: [M+Na]+ C23H25NNaO6S calcd
466.1300, obsd 466.1271.
3.6. General procedure for single step glycosylation
A solution of donor (0.067 mmol) and freshly activated
˚
molecular sieve MS—4 A (300 mg) in a mixture of
CH2Cl2 and Et2O (1:1, 4 mL) (100% Et2O was used
for donors 18 and 19) was stirred for 30 min, and cooled
to ꢀ70 °C, which was followed by sequential additions
of AgOTf (52 mg, 0.201 mmol) dissolved in Et2O
(1 mL) and p-TolSCl (10.5 lL, 0.067 mmol) through
syringes. After the donor was completely consumed
according to TLC analysis (about 15 min at ꢀ70 °C), a
solution of acceptor (0.060 mmol) in CH2Cl2 (0.5 mL)
was injected via a syringe. The reaction mixture was
warmed to ꢀ10 °C under stirring in 2 h. Then the mix-
ture was diluted with CH2Cl2 (20 mL) and filtered.
The filtrate was washed twice with saturated aqueous
NaHCO3 solution (20 mL) and once with brine
(10 mL). The organic layer was collected and dried over
MgSO4. After removal of the solvent, the residue was
applied to silica gel flash chromatography column using
a mixture of hexanes and EtOAc to afford the desired
disaccharide.
3.4. p-Tolyl 3,6-di-O-benzyl-2-deoxy-2-N-phthalimido-1-
thio-b-D-glucopyranoside (3)
The mixture of compound 17 (1 g, 1.68 mmol), NaC-
NBH3 (1.06 g, 17 mmol), and molecular sieves MS
AW300 in THF (20 mL) was cooled to 0 °C. Two molar
of HCl in Et2O (ꢁ9 mL) was added under N2 until no
more gas evolved from the reaction. The reaction mix-
ture was stirred at 0 °C for 30 min. The reaction was
quenched with Et3N and filtered. The filtrate was diluted
with CH2Cl2 (30 mL) and extracted with saturated solu-
tions of aqueous NH4Cl (20 mL) and NaHCO3 (20 mL).
The organic layer was separated and dried with Na2SO4.
Column chromatography (2:1, hexanes–EtOAc) on sil-
ica gel afforded the product 3 as a white solid in 90%
yield (80% yield for the two steps from compound 5).
Comparison of the NMR data with those reported in
the literature21 confirmed the identity of 3.
3.7. p-Tolyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-
D-glucopyranosyl-(1!4)-3,6-di-O-benzyl-2-deoxy-2-
phthalimido-1-thio-b-D-glucopyranoside (9)
Compound 9 was synthesized from donor 8 and acceptor
3 in 56% yield following the general procedure of single
step glycosylation together with trace amount of glycal
10. Compound 9 [a]D +3.5 (c, 0.058 g/mL, CH2Cl2);
1H NMR (600 MHz, CDCl3): d 1.82 (s, 3H), 1.93 (s,
3H), 1.98 (s, 3H), 2.20 (s, 3H), 3.35 (dd, J = 3.0, 9.6Hz,
1H), 3.44–3.48 (m, 2H), 3.58 (d, J = 10.8 Hz, 1H),
3.89 (dd, J = 2.4, 12.0 Hz, 1H), 4.08–4.22 (m, 4H), 4.30
(dd, J = 8.4, 10.2 Hz, 1H), 4.44 (d, J = 12.6 Hz, 1H),
4.48 (d, J = 11.4 Hz, 1H), 4.54 (d, J = 11.4 Hz, 1H),
4.79 (d, J = 12.6 Hz, 1H), 5.11 (t, J = 9.6 Hz, 1H), 5.26
(d, J = 9.6 Hz, 1H), 5.49 (d, J = 8.4 Hz, 1H), 5.78
(dd, J = 9.0, 10.2 Hz, 1H), 6.79–7.88 (m, 22 H); 13C
NMR (150 MHz, CDCl3): d 20.68, 20.86, 20.86,
21.31, 54.93, 55.46, 60.64, 68.38, 68.96, 70.82, 71.70,
72.94, 74.63, 76.15, 77.89, 78.81, 83.50, 97.03, 127.27–
138.64 (aromatic carbons), 169.75, 170.36, 170.93
(CH3CO); HRMS: [M+Na]+ C55H52N2NaO15S calcd
1035.2986, obsd 1035.2985. Compound 10: [a]D ꢀ22.5
3.5. p-Tolyl 3,6-di-O-benzyl-2-deoxy-1-thio-2-N-trichlo-
roethoxycarbonyl-b-D-glucopyranoside (4)
Compound 17 (1.9 g, mmol) and ethylenediamine
(11.8 mL, 175 mmol, 55 equiv) were dissolved in dry eth-
anol (30 mL). The mixture was heated at reflux for 16 h.
The reaction mixture was evaporated and dissolved in
EtOAc (30 mL), which was neutralized with 1 N
H2SO4 until slightly basic. The resulting suspension
was kept in ice-water for 1 h, and then filtered to afford
the glucosamine sulfate salt (1.53 g, 85%) as a white so-
lid. The solid (1.05 g, 1.86 mmol) was dissolved in a mix-
ture of THF and saturated aqueous NaHCO3 solution
(30 mL) followed by addition of TrocCl (340 lL,
2.51 mmol). The mixture was stirred for 1 h, and then
extracted with EtOAc (60 mL) and saturated aqueous
NaHCO3 (20 mL). The organic layer was dried over
Na2SO4 and purified by silica gel column to give 2-

L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
1675
(c, 0.0067 g/mL, CH2Cl2); 1H NMR (600 MHz, CDCl3):
d 1.92 (s, 3H), 2.12 (s, 3H), 2.14 (s, 3H), 4.36 (dd, J = 4.2,
12.0 Hz, 1H), 4.47–4.58 (m, 2H), 5.31 (t, J = 4.2 Hz, 1H),
5.59 (d, J = 4.2 Hz, 1H), 6.76 (s, 1H), 7.72–7.76 (m, 2H),
7.83–7.88 (m, 2H); HRMS [M+Na]+ C20H19NNaO9
calcd 440.0958, obsd 440.0961.
3.10. p-Tolyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-
D-glucopyranosyl-(1!4)-2-acetamido-6-O-benzyl-2-N-3-
O-carbonyl-2-deoxy-1-thio-a-D-glucopyranoside (14)
Compound 14 was synthesized from donor 8 and accep-
tor 2a in 39% yield following the general procedure of
single step glycosylation together with recovered accep-
1
3.8. p-Tolyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-
D-glucopyranosyl-(1!4)-3,6-di-O-benzyl-2-deoxy-1-thio-
2-N-trichloroethoxycarbonyl-b-D-glucopyranoside (11)
tor 2a (50%). [a]D +98.8 (c, 0.0093 g/mL, CH2Cl2); H
NMR (600 MHz, CDCl3): d 1.86 (s, 3H), 2.04 (s, 3H),
2.14 (s, 3H), 2.29 (s, 3H), 2.52 (s, 3H), 3.39 (m, 1H),
3.49 (dd, J = 4.8 Hz, 13.8 Hz, 1H), 3.88–4.25 (m, 8H),
4.33–4.37 (m, 2H), 4.48 (dd, J = 14.4 Hz, 18.6 Hz, 1H)
5.21 (t, J = 15.0 Hz, 1H), 5.56 (d, J = 13.2 Hz, 1H),
5.78 (dd, J = 13.2 Hz, 15.6 Hz, 1H), 6.05 (d,
J = 6.6 Hz, 1H), 6.98–7.88 (m, 13H); 13C NMR
(150 MHz, CDCl3): d 20.69, 20.89, 21.04, 21.35, 24.12,
54.94, 60.05, 61.93, 67.82, 68.80, 71.03, 72.26, 72.46,
73.20, 75.40, 77.45, 86.45, 97.75, 123.86–138.61 (aro-
matic carbons), 152.98, 169.75, 170.41, 171.12, 171.41;
HRMS: [M+Na]+ C43H44N2NaO15S calcd 883.2360,
obsd 883.2333.
Compound 11 was synthesized from donor 8 and
acceptor 4 in 50% yield following the general proce-
dure of single step glycosylation together with recov-
ered acceptor 4 (20%). [a]D ꢀ10.7 (c, 0.012 g/mL,
CH2Cl2); 1H NMR (600 MHz, CDCl3):
d 1.82
(s, 3H), 1.94 (s, 3H), 1.98 (s, 3H), 2.25 (s, 3H), 3.26
(m, 2H), 3.40 (d, J = 10.2 Hz, 1H), 3.45 (dd, J = 3.6,
10.8Hz, 1H), 3.56 (d, J = 10.2 Hz, 1H), 3.75–3.83
(m, 2H), 4.08 (t, J = 9.0 Hz, 1H), 4.11 (dd, J = 4.2,
12.6 Hz, 1H), 4.27 (dd, J = 9.0, 10.8 Hz, 1H), 4.42
(d, J = 12 Hz, 1H), 4.48 (d, J = 12 Hz, 1H), 4.62–
4.65 (m, 2H), 4.70 (d, J = 12 Hz, 1H), 4.76 (d, J = 4.2
Hz, 1H), 4.91 (d, J = 11.4 Hz, 1H), 5.03 (d, J = 7.8 Hz,
1H), 5.10 (t, J = 9.6 Hz, 1H), 5.50 (d, J = 8.4 Hz, 1H),
5.74 (t, J = 10.2 Hz, 1H), 6.95–7.84 (18, 2H); 13C
NMR (150 MHz, CDCl3): d 20.66, 20.84, 20.89,
21.33, 55.43, 56.30, 61.66, 68.44, 68.86, 70.79, 71.88,
73.00, 74.40, 74.59, 75.33, 78.80, 79.76, 85.62, 97.10,
127.63–138.42 (aromatic carbons), 153.71(carbonyl of
Troc), 169.70, 170.35, 170.88 (CH3CO); HRMS:
[M+Na]+ C50H51Cl3N2NaO15S calcd 1079.1973, obsd
1079.2067.
3.11. Benzyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-
b-D-glucopyranosyl-(1!4)-3,6-di-O-benzyl-2-deoxy-2-
phthalimido-b-D-glucopyranosyl-(1!4)-3,6-di-O-benzyl-
2-deoxy-2-phthalimido-b-D-glucopyranosyl-(1!4)-3,6-
di-O-benzyl-2-deoxy-2-phthalimido-b-D-glucopyranoside
(16)
After the donor 8 (60 mg, 0.11 mmol) and activated
˚
molecular sieve MS—4 A (500 mg) were stirred for
30 min at room temperature in the mixed solvents of
CH2Cl2 and Et2O (1:1) (6 mL), the solution was cooled
to ꢀ70 °C followed by sequential additions of AgOTf
(86 mg, 0.335 mmol) in Et2O (1.5 mL) and p-TolSCl
(17.3 lL, 0.11 mmol). The mixture was vigorously stir-
red for 15 min and a solution of acceptor 3 (59 mg,
0.099 mmol) in CH2Cl2 (0.5 mL) was added. The mix-
ture was stirred for 5 min, then the flask was warmed
to ꢀ10 °C in 15 min. Then the mixture was cooled down
to ꢀ70 °C again followed by sequential additions of
AgOTf (76 mg, 0.297 mmol) in Et2O (1.5 mL) and p-
TolSCl (15.5 lL, 0.099 mmol). After 15 min, a solution
of acceptor 3 (53 mg, 0.089 mmol) in CH2Cl2 (0.5 mL)
was injected though a syringe. The mixture was stirred
for 5 min and warmed to ꢀ10 °C in 15 min by switching
the cold bath. A solution of acceptor 15 (64 mg,
0.11 mmol) in CH2Cl2 (0.5 mL) was added to the reac-
tion mixture, and the resulting mixture was cooled down
to ꢀ70 °C followed by sequential additions of AgOTf
(68 mg, 0.089 mmol) in Et2O (1.5 mL) and p-TolSCl
(14 lL, 0.089 mmol). The reaction mixture was stirred
for 1.5 h from ꢀ70 to 10 °C and then was diluted with
CH2Cl2 (30 mL) followed by filtration and extrac-
tion. The collected organic phase was dried over
Na2SO4, and the residue was applied to flash column
3.9. p-Nitrophenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthal-
imido-b-D-glucopyranosyl-(1!4)-3,6-di-O-benzyl-2-
deoxy-2-phthalimido-1-thio-b-D-glucopyranoside (13)
Compound 13 was synthesized from donor 8 and accep-
tor 12 in 50% yield following the general procedure of
single step glycosylation. [a]D +21.8 (c, 0.010 g/mL,
1
CH2Cl2); H NMR (600 MHz, CDCl3): d 1.84 (s, 3H),
1.94 (s, 3H), 1.99 (s, 3H), 3.49–3.55 (m, 3H), 3.61 (d,
J = 9.6 Hz, 1H), 3.96 (dd, J = 2.4, 12.0 Hz, 1H), 4.19–
4.23 (m, 3H), 4.25 (dd, J = 3.6, 12.0 Hz, 1H), 4.33 (dd,
J = 8.4, 10.8 Hz, 1H), 4.44 (d, J = 12 Hz, 1H), 4.45 (d,
J = 12.6 Hz, 1H), 4.53 (d, J = 11.4 Hz, 1H), 4.82 (d, J =
12.6 Hz, 1H), 5.13 (t, J = 10.2 Hz, 1H), 5.47 (d, 1H,
J = 10.2 Hz, 1H), 5.50 (d, J = 8.4 Hz, 1H), 5.79 (dd,
J = 9.0, 10.8 Hz, 1H), 6.79–7.94 (m, 22H); 13C NMR
(150 MHz, CDCl3): d 20.68, 20.86, 20.87, 54.52, 55.45,
61.69, 68.43, 68.90, 70.77, 71.81, 73.06, 74.89, 76.42,
77.70, 78.79, 82.03, 97.25, 123.94–146.65 (aromatic
carbons), 169.74, 170.36, 170.88 (CH3CO); HRMS:
[M+Na]+ C54H49N3NaO17S calcd 1066.2680, obsd
1066.2742.

1676
L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
chromatography with a mixed solvent system of
CH2Cl2, hexanes, and EtOAc to give the desired tetra-
saccharide 16 (55 mg) in 32% yield as colorless foam.
as white foam (1.07 g, 90%). Comparison of the NMR
data with those reported in the literature21 confirmed
the identity of 17.
1
Its structure was confirmed by H NMR, 13C NMR,
1H–1H COSY experiments, and HRMS. [a]D ꢀ20.0 (c,
0.038 g/mL, CH2Cl2); 1H NMR (600 MHz, CDCl3):
(a, b, c, and d denote the four monosaccharide units
in the sequence of its anomeric proton appearance in
3.13. p-Tolyl 4,6-O-benzylidene-3-O-tert-butyldimethyl-
silyl-2-deoxy-2-phthalimido-1-thio-b-D-glucopyranoside
(18)
1
the H NMR spectrum from the most downfield to the
To a mixture of compound 5 (1 g, 2 mmol) and mole-
˚
most upfield shifted. Monosaccharide unit a is the one
at the non-reducing end) d 1.82 (s, 3H, CH3CO), 1.88
(s, 3H, CH3CO), 1.96 (s, 3H, CH3CO), 2.76 (broad d,
J = 10.2 Hz, 1H, c/d-H5), 2.89 (broad d, J = 10.2 Hz,
1H, b-H5), 3.02 (dd, J = 3.0, 10.2 Hz, 1H, c/d-H6),
3.15 (dd, J = 2.4, 10.2 Hz, 1H, b-H6), 3.18 (dd,
J = 3.0, 10.2 Hz, 1H, c/d-H5), 3.27 (dd, J = 3.6,
10.2 Hz, 1H, c/d-H6), 3.29 (d, J = 10.2 Hz, 1H, c/d-
H6), 3.37–3.42 (m, 2H, a-H5, b-H6), 3.44 (broad d,
J = 10.2 Hz, 1H, c/d-H6), 3.88 (dd, J = 1.8, 12.0 Hz,
1H, a-H6), 3.97–4.10 (m, 7H, b-H2, c-H2, c-H3, c-H4,
d-H2, d-H3, d-H4), 4.14 (dd, J = 9.0, 10.8 Hz, 1H,
a-H3), 4.16 (dd, J = 8.4, 12.0 Hz, 1H, a-H6), 4.24 (d,
J = 9.0 Hz, 1H, a-H4), 4.27–4.44 (m, 10H, 9PhCH2,
a-H2), 4.52 (d, J = 11.4 Hz, 1H, PhCH2), 4.62(d,
J = 12.6 Hz, 1H, PhCH2), 4.67 (d, J = 12.6 Hz, 1H,
PhCH2), 4.81 (d, J = 12.6 Hz, 1H, PhCH2), 4.84 (d,
1H, J = 12.6 Hz, PhCH2), 4.85 (d, J = 8.4 Hz, 1H, d-
H1), 5.01 (m, 1H, c-H1), 5.07 (d, 1H, J = 9.0 Hz, 1H,
b-H1), 5.10 (t, J = 9.0 Hz, a-H4), 5.46 (d, J = 8.4 Hz,
1H, a-H1), 5.75 (dd, J = 9.0, 10.8 Hz, 1H, a-H3), 6.63–
7.91 (m, 51 H); 13C NMR (150 MHz, CDCl3): d 20.68,
20.82, 20.85, 55.49, 55.86, 56.79, 56.82, 61.57, 67.19,
67.27, 68.28, 68.87, 70.64, 70.91, 71.53, 72.35, 72.50,
72.72, 74.18, 74.36, 74.42, 74.60, 74.63, 74.73, 75.47,
75.57, 76.08, 76.54, 96.81, 96.81, 96.91, 97.21, 123.26–
139.00 (aromatic carbons), 167.78–168.41 (phthalimido
carbonyl carbons), 169.74, 170.36, 170.91 (CH3CO);
HRMS: [M+Na]+ C111H102N4NaO28 calcd 1961.6578,
obsd 1961.6393.
cular sieve MS—4 A (300 mg) in anhydrous CH2Cl2
(10 mL) were added 2,6-lutidine (460 lL, 4 mmol) and
tert-butyldimethylsilyl triflate (550 lL, 2.4 mmol) at
0 °C. The mixture was stirred for 4 h. The reaction
mixture was filtered and the filtrate was extracted
with a satd aqueous solution of NH4Cl (20 mL). The
organic layer was separated and dried over Na2SO4.
Column chromatography on silica gel (15% EtOAc in
hexanes) afforded the product 18 as white foam
(1.04 g, 85%). 1H NMR (600 MHz, CDCl3): d ꢀ0.32
(s, 3H), ꢀ0.16 (s, 3H), 0.56 (s, 9H), 2.28 (s, 3H), 3.55
(t, J = 9.6 Hz, 1H), 3.67 (dt, J = 4.8, 9.6 Hz, 1H), 3.80
(t, J = 10.2 Hz, 1H), 4.29 (t, J = 10.2 Hz, 1H), 4.37
(dd, J = 4.8, 10.2 Hz, 1H), 4.61 (t, J = 9.6 Hz, 1H),
5.51 (s, 1H), 5.57 (d, J = 10.2 Hz, 1H), 7.01–7.04
(m, 2H), 7.20–7.35 (m, 7H), 7.75–7.95 (m, 4H); 13C
NMR (150 MHz, CDCl3): d ꢀ5.11, ꢀ3.93, 17.96,
21.39, 25.63, 57.02, 68.92, 70.79, 82.70, 84.86, 102.24,
123.47–138.47 (aromatic carbons), 167.64, 168.61 (car-
bonyl groups of phthalimido); ESI-MS [M+Na]+
C34H39NNaO6SSi calcd 640.8, obsd 640.3.
3.14. p-Tolyl 4,6-di-O-benzyl-3-O-tert-butyldimethylsilyl-
2-deoxy-2-phthalimido-1-thio-b-D-glucopyranoside (19)
To a solution of compound 18 (0.43 g, 0.7 mmol) and
1 M borane THF (7.2 mL) in anhydrous CH2Cl2
(10 mL) was added trimethylsilyl triflate (100 lL,
0.5 mmol) at ꢀ20 °C. After 2 h, trimethylsilyl triflate
(200 lL, 1 mmol) was added again. The mixture was
stirred for 2 h more. The reaction was quenched by
the addition of Et3N, and MeOH was added until no
gas was formed. All solvents were evaporated and the
desired primary alcohol (0.39 g) was purified through
column chromatography on silica gel (25% EtOAc in
hexanes). To a mixture of the primary alcohol (0.3 g,
0.5 mmol), tetrabutyl-ammonium iodide (40 mg,
0.1 mmol) and freshly activated molecular sieve MS—
3.12. p-Tolyl 3-O-benzyl-4,6-O-benzylidene-2-deoxy-2-
phthalimido-1-thio-b-D-glucopyranoside (17)
To a mixture of compound 5 (1 g, 2 mmol), tetrabutyl-
ammonium iodide (0.15 g, 0.4 mmol), and freshly
˚
activated molecular sieve MS—4 A (300 mg) in anhy-
drous DMF (10 mL) was added 95% NaH (80 mg,
3.2 mmol) at 0 °C. The mixture was stirred for 30 min
and benzyl bromide (290 lL, 0.42 g, 2.4 mmol) was
added via a syringe. After 90 min, the reaction was
quenched with acetic acid and filtered. Et2O (40 mL)
was added to the filtrate, which was extracted with
saturated aqueous solutions of NH4Cl (20 mL) and
NaHCO3 (20 mL). The organic layer was separated
and dried over Na2SO4. Column chromatography on
silica gel (3:1, hexanes–EtOAc) afforded the product 17
˚
4 A (100 mg) in anhydrous DMF (5 mL) was added
95% NaH (20 mg, 0.8 mmol) at 0 °C. The mixture was
stirred for 30 min and benzyl bromide (180 lL, 0.26 g,
1.5 mmol) was added via a syringe. After 90 min, the
reaction was quenched by the addition of acetic acid
and filtered. Et2O (10 mL) was added to the filtrate,
which was extracted with saturated aqueous solutions
of NH4Cl (10 mL) and NaHCO3 (10 mL). The organic
layer was separated and dried over Na2SO4. Column

L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
1677
chromatography on silica gel (4:1, hexanes–EtOAc)
afforded the product 19 (0.32 g) as white foam in overall
80% yield for the two steps. 1H NMR (600 MHz,
CDCl3): d ꢀ0.44 (s, 3H), ꢀ0.08 (s, 3H), 0.72 (s, 9H),
2.27 (s, 3H), 3.58 (t, J = 9.6 Hz, 1H), 3.64–3.69 (m,
1H), 3.72–3.80 (m, 2H), 4.27 (t, J = 10.2 Hz, 1H), 4.47
(t, J = 9.0 Hz, 1H), 4.53 (d, J = 12.0 Hz, 1H), 4.59 (d,
J = 12.0 Hz, 1H), 4.65 (d, J = 12.0 Hz, 1H), 4.78 (d,
J = 12.0 Hz, 1H), 5.52 (d, J = 10.2 Hz, 1H), 7.01–7.04
(m, 2H), 7.20–7.35 (m, 12H), 7.75–7.95 (m, 4H); 13C
NMR (150 MHz, CDCl3): d ꢀ4.46, ꢀ3.94, 17.84,
21.35, 25.87, 56.99, 69.18, 73.64, 73.71, 74.70, 79.67,
80.01, 83.69, 123.39, 123.78, 127.25, 127.59, 127.74,
127.87, 127.90, 128.45–128.53, 129.75, 133.34, 134.38,
138.51, 138.52; ESI-MS [M+Na]+, C41H47NNaO6SSi
calcd 732.9, obsd 732.5.
7.71–7.79 (m, 3H), 7.84–7.88 (m, 1H), 7.92–7.94 (m,
1H); 13C NMR (100 MHz, CDCl3): ꢀ5.46, ꢀ4.12,
17.67, 21.07, 25.36, 54.67, 58.29, 65.92, 68.17, 68.75,
69.30, 72.71, 74.56, 76.03, 77.55, 78.74, 82.78, 83.10,
97.60, 101.85, 123.07, 123.19, 123.41, 123.78, 126.34,
127.06, 127.33, 127.50, 127.74, 127.91, 128.05, 128.11,
128.26, 129.03, 129.41, 131.59, 131.65, 131.66, 133.48,
133.61, 133.78, 134.28, 134.33, 137.15, 138.04, 138.33,
138.37, 167.21, 167.63, 167.86, 168.64; HRMS:
[M+Na]+ C62H64N2NaO12SSi calcd 1111.3925, obsd
1111.3877.
3.17. p-Tolyl 4,6-di-O-benzyl-3-O-tert-butyldimethylsilyl-
2-deoxy-2-phthalimido-b-D-glucopyranosyl-(1!4)-3,6-di-
O-benzyl-2-deoxy-2-phthalimido-1-thio-b-D-glucopyrano-
side (22)
3.15. p-Tolyl 3-O-benzyl-4,6-benzylidene-2-deoxy-2-
phthalimido-b-D-glucopyranosyl-(1!4)-3,6-di-O-benzyl-
2-deoxy-2-phthalimido-1-thio-b-D-glucopyranoside (20)
Compound 22 was synthesized from donor 19 and
acceptor 3 in 50% yield following the general procedure
of single step glycosylation together with disaccharide 23
and glycal 24 (10%). [a]D +20.1 (c, 0.035 g/mL,
CH2Cl2); 1H NMR (600 MHz, CDCl3): d ꢀ0.40
(s, 3H), ꢀ0.07 (s, 3H), 0.70 (s, 9H), 2.20 (s, 3H), 3.32–
3.36 (m, 2H), 3.48 (dd, J = 3.6 Hz, 10.8 Hz, 1H), 3.58–
3.70 (m, 4H), 4.10–4.24 (m, 5H), 4.47–4.56 (m, 6H),
4.69 (d, J = 12.0 Hz, 1H), 4.75 (d, J = 11.4Hz, 1H),
4.88 (d, J = 12.6 Hz, 1H), 5.26 (d, J = 10.3 Hz, 1H),
4.30 (d, J = 10.2 Hz, 1H), 6.71–7.89 (m, 32 H); 13C
NMR (150 MHz, CDCl3): d ꢀ4.82, ꢀ3.88, 17.89,
21.32, 25.87, 55.05, 58.59, 68.10, 68.62, 72.21, 72.92,
73.33, 74.37, 74.86, 75.31, 75.46, 77.78, 79.09, 80.11,
83.58, 96.77, 123.24–138.79 (aromatic carbons), 167.51,
167.92, 168.01, 169.25 (carbonyl groups of phthalim-
ido); HRMS: [M+Na]+ C69H72N2NaO12SSi calcd
1203.4473, obsd 1203.4505.
Compound 20 was synthesized from donor 17 and
acceptor 3 in 61% yield following the general procedure
of single step glycosylation. [a]D +17.0 (c, 0.024 g/mL,
1
CH2Cl2); H NMR (600 MHz, CDCl3): d 2.21 (s, 3H),
3.33–3.42 (m, 3H), 3.48–3.52 (m, 2H), 3.70 (t,
J = 9.0 Hz, 1H), 4.10–4.22 (m, 5H), 4.37 (d, J = 20 Hz,
1H), 4.42 (dd, 1H, J = 9.0, 10.2 Hz, 1H), 4.43–4.48 (m,
3H), 4.77 (dd, J = 4.8, 12.6 Hz, 2H), 5.27 (d,
J = 10.2 Hz, 1H), 5.35 (d, J = 8.4 Hz, 1H), 5.50 (s,
1H), 6.86–7.88 (m, 32 H); 13C NMR (150 M Hz,
CDCl3): d 21.32, 54.91, 56.72, 65.95, 68,35, 68.96,
72.92, 74.32, 74.67, 74.80, 76.32, 78.00, 78.93, 83.35,
83.39, 97.95, 101.41, 126.29–138.58 (aromatic carbons);
HRMS: [M+Na]+ C63H56N2NaO12S calcd 1087.3452,
obsd 1087.3494.
3.18. 4,6-di-O-benzyl-3-O-tert-butyldimethylsilyl-2-
deoxy-2-phthalimido-b-D-glucopyranosyl-(1!1)-4,6-di-
O-benzyl-3-O-tert-butyldimethylsilyl-2-deoxy-2-phtha-
limido-D-glucopyranoside (23)
3.16. p-Tolyl 4,6-O-benzylidene-3-O-tert-butyldimethyl-
silyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl-(1!4)-
3,6-di-O-benzyl-2-deoxy-2-phthalimido-1-thio-b-D-gluco-
pyranoside (21)
1
[a]D = 0 (c, 0.013 g/mL, CH2Cl2); H NMR (600 MHz,
Compound 21 was synthesized from donor 18 and
acceptor 3 in 74% yield following the general procedure
of single step glycosylation. [a]D ꢀ4.4 (c, 0.011 g/mL,
CH2Cl2); 1H NMR (600 MHz, CDCl3): d ꢀ0.28 (s,
3H), ꢀ0.14 (s, 3H), 0.56 (s, 9H), 2.21 (s, 3H), 3.32–
3.38 (m, 2H), 3.42 (dd, J = 7.2, 10.8 Hz, 1H), 3.46 (t,
J = 9.0 Hz, 1H), 3.52 (t, J = 10.2 Hz, 1H), 3.54 (t,
J = 10.2 Hz, 1H), 4.08–4.24 (m, 5H), 4.46 (d, J =
12.0 Hz, 1H), 4.49 (d, J = 12.0 Hz, 1H), 4.53 (d,
J = 12.0 Hz, 1H), 4.61 (t, J = 9.6 Hz, 1H), 4.77 (d, J =
12.0 Hz, 1H), 5.27 (d, J = 10.2 Hz, 1H), 5.34 (d, J =
8.4 Hz, 1H), 5.41 (s, 1H), 6.84–6.92 (m, 5H), 7.00–7.03
(m, 2H), 7.16–7.20 (m, 2H), 7.28–7.39 (m, 8H), 7.42–
7.46 (m, 2H), 7.54–7.58 (m, 1H), 7.62–7.69 (m, 2H),
CDCl3): d ꢀ0.48 (s, 6H), ꢀ0.13 (s, 6H), 0.66 (s, 18H),
3.37 (m, 2H), 3.47 (m, 4H), 3.65 (m, 2H), 4.05 (d,
J = 18 Hz, 2H), 4.07 (dd, J = 13.2 Hz, 15.6 Hz, 4H),
4.20 (d, J = 18 Hz, 2H), 4.43 (m, 2H), 4.54 (d,
J = 17.4 Hz, 2H), 4.65 (d, J = 7.4 Hz, 2H), 5.41 (d,
J = 13.2 Hz, 2H), 7.13–7.55 (m, 28H); 13C NMR
(150 MHz, CDCl3): d ꢀ4.55, ꢀ4.04, 17.78, 25.82,
57.48, 69.12, 72.20, 73.72, 74.41, 75.47, 79.62, 96.88,
127.17–138.69 (aromatic carbons); HRMS: [M+Na]+
C68H80N2NaO13Si2 calcd 1211.5096, obsd 1211.5143.
Compound 24 was isolated as a mixture with com-
pound 23, which was characterized by ESI-MS. ESI-
MS: [M+Na]+ C34H39NNaO6Si calcd 608.2, obsd
608.3.

1678
L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
3.19. Methyl 4,6-O-benzylidene-3-O-tert-butyldimethyl-
silyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl-(1!4)-
3,6-di-O-benzyl-2-deoxy-2-phthalimido-b-D-glucopyrano-
syl-(1!4)-6-O-benzyl-2-deoxy-3-O-p-methoxybenzyl-2-
phthalimido-b-D-glucopyranosyl-(1!4)-3,6-di-O-benzyl-
2-deoxy-2-phthalimido-b-D-glucopyranoside (27)
1991.6; HRMS: [M+Na]+ C113H112N4NaO26Si calcd
1991.7231, obsd 1991.7139. Compounds 28, 29, and 30
were characterized by ESI-MS. Compound 28,
C55H56N2NaO12Si [M+Na]+calcd 987.4, obsd 987.6.
Compound 29, C84H83N3NaO19Si [M+Na]+calcd
1488.5, obsd 1488.7. Compound 30, C84H85N3NaO20Si
[M+Na]+calcd 1506.5, obsd 1506.7.
Compound 27 was synthesized in 45% overall yield
using building blocks 18, 3, 25, and 26 in a similar man-
ner as in the assembly of tetrasaccharide 16 with the
exception that pure Et2O was used to dissolve donor
18, and TTBP (1 equiv) was added together with each
acceptor. For reaction time, see Scheme 4. The desired
product was purified by silica gel flash chromatography
using the solvent systems of hexanes–EtOAc (1:1) and
hexanes–CH2Cl2–EtOAc (5:5:3). Its structure was con-
firmed by 1H NMR, 13C NMR, 1H–1H COSY,
1H–13C HMQC experiments, and HRMS. [a]D ꢀ31.4
Acknowledgment
We are grateful for the financial support from the Uni-
versity of Toledo, the National Institutes of Health (R01
GM 72667), and the Pardee Foundation.
Supplementary data
1
(c, 0.013 g/mL, CH2Cl2); H NMR (600 MHz, CDCl3):
1H and 13C NMR spectra of compounds 2a, 6, 9, 11, 13,
14, 16, 20, 21, 22, 23, and 27. Supplementary data asso-
ciated with this article can be found, in the online ver-
sion, at doi:10.1016/j.carres.2006.01.007.
(a, b, c, and d denote the four monosaccharide units in
the sequence of its anomeric proton appearance in the
1H NMR spectrum from the most downfield to the most
upfield shifted) d ꢀ0.31 (s, 3H, SiCH3), ꢀ0.17 (s, 3H,
SiCH3), 0.54 (s, 9H, SiC(CH3)3), 2.76 (broad d,
J = 9.0 Hz, 1H, c-H5), 2.90 (broad d, J = 9.0 Hz, 1H,
b-H5), 3.01 (dd, J = 3.0, 10.8 Hz, 1H, c-H6), 3.12 (dd,
J = 2.4, 10.8 Hz, 1H, b-H6), 3.18–3.24 (m, 1H, d-H4),
3.21 (s, 3H, OCH3), 3.24–3.32 (m, 3H, c-H6, d-H5, d-
H6), 3.37–3.47 (m, 4H, a-H4, a-H6, b-H6, d-H6), 3.54
(s, 3H, ArOCH3), 3.96–4.03 (m, 4H, c-H2, c-H3, d-H2,
d-H3), 4.04–4.12 (m, 3H, a-H6, b-H2, c-H4), 4.13–4.21
(m, 3H, a-H2, a-H5, b-H3), 4.23 (t, J = 8.4 Hz, 1H, b-
H4), 4.29 (d, J = 12.0 Hz, 1H, ArCH2), 4.32–4.42 (m,
6H, 6ArCH2), 4.47 (d, J = 12.0 Hz, 1H, ArCH2), 4.50
(d, J = 12.0 Hz, 1H, ArCH2), 4.59 (t, J = 9.0 Hz, 1H,
a-H3), 4.70 (d, J = 12.6 Hz, 1H, ArCH2), 4.71 (d,
J = 12.6 Hz, 1H, ArCH2), 4.77 (d, J = 7.8 Hz, 1H, d-
H1), 4.82 (d, J = 12.0 Hz, 1H, ArCH2), 5.01–5.04 (m,
1H, c-H1), 5.07 (d, J = 7.8 Hz, 1H, b-H1), 5.33 (d,
J = 8.4 Hz, 1H, a-H1), 5.38 (s, 1H, PhCHbenzylidene),
6.18–6.21 (m, 2H), 6.62–7.96 (m, 48H); 13C NMR
(100 MHz, CDCl3): ꢀ5.18 (SiCH3), ꢀ3.85 (SiCH3),
17.94 (SiC(CH3)3), 25.65 (SiC(CH3)3), 54.88 (ArOCH3),
55.76, 56.60 (OCH3), 56.85 (b-C2), 56.90, 58.58 (a-C2),
66.05, 67.33, 68.30, 68.97, 69.61, 72.45, 72.61, 72.74,
74.36, 74.46, 74.52, 74.72, 75.51, 75.80, 76.26, 76.58,
83.04 (a-C4), 96.75 (b-C1), 96.95 (c-C1), 97.76 (a-C1),
99.18 (d-C1), 102.09 (PhCHbenzylidene), 113.25, 123.05,
123.35, 123.52, 123.79, 123.95, 126.59, 126.88, 127.16,
127.23, 127.48, 127.53, 127.56, 127.59, 127.87, 127.99,
128.11, 128.14, 128.22, 128.27, 128.33, 128.52, 129.25,
129.88, 131.33, 131.77, 131.99, 133.71, 133.73, 133.82,
134.02, 134.19, 134.53, 137.42, 138.53, 138.60, 138.63,
138.88, 138.97, 158.50, 167.82, 167.84, 168.27, 168.38,
168.75 (carbonyl groups of phthalimido); ESI-MS
References
1. (a) Codee, J. D. C.; Litjens, R. E. J. N.; Van den Bos, L. J.;
Overkleeft, H. S.; Van der Marel, G. A. Chem. Soc. Rev.
2005, 34, 769–782; (b) Carbohydrates in Chemistry and
Biology; Wiley-VCH: Weinheim, 2000; Vols. 1–4; (c)
Davis, B. G. J. Chem. Soc., Perkin Trans. 1 2000, 2137–
2160.
2. Yu, B.; Yang, Z.; Cao, H. Curr. Org. Chem. 2005, 9, 179–
194.
3. Koeller, K. M.; Wong, C.-H. Chem. Rev. 2000, 100, 4465–
4493.
4. Huang, L.; Wang, Z.; Huang, X. Chem. Commun. 2004,
1960–1961.
5. (a) Pornsuriyasak, P.; Gangadharmath, U. B.; Rath, N.
P.; Demchenko, A. V. Org. Lett. 2004, 6, 4515–4518; (b)
Lahmann, M.; Oscarson, S. Org. Lett. 2000, 2, 3881–3882;
(c) Geurtsen, R.; Holmes, D. S.; Boons, G.-J. J. Org.
Chem. 1997, 62, 8145–8154.
6. (a) Lopez, J. C.; Agocs, A.; Uriel, C.; Gomez, A. M.;
Fraser-Reid, B. Chem. Commun. 2005, 5088–5090; (b)
Fraser-Reid, B.; Lopez, J. C.; Gomez, A. M.; Uriel, C.
Eur. J. Org. Chem. 2004, 1387–1395.
7. Huang, X.; Huang, L.; Wang, H.; Ye, X.-S. Angew.
Chem., Int. Ed. 2004, 43, 5221–5224.
8. (a) Semenuk, T.; Krist, P.; Pavlicek, J.; Bezouska, K.;
Kuzma, M.; Novak, P.; Kren, V. Glycoconjugate J. 2002,
18, 817–826; (b) Shibata, Y. Rec. Res. Dev. Immun. 1999,
1, 551–558; (c) Bezouska, K.; Sklenar, J.; Dvorakova, J.;
Havlicek, V.; Pospisil, M.; Thiem, J.; Kren, V. Biochem.
Biophys. Res. Commun. 1997, 238, 149–153.
9. (a) Gorbach, V. I.; Kraiskova, I. N.; Lukyanov, P. A.;
Loenko, Y. N.; Soloveva, T. F.; Ovodov, Y. S.; Deev, V.
V.; Pimenov, A. A. Carbohydr. Res. 1994, 260, 73; (b)
Suzuki, K.; Mikami, T.; Okawa, Y.; Tokoro, A.; Suzuki,
S.; Suzuki, M. Carbohydr. Res. 1986, 151, 403–408.
10. Vongchan, P.; Sajomsang, W.; Subyen, D.; Kongtawelert,
P. Adv. Chitin Sci. 2002, 5, 650–655.
C
113H112N4NaO26Si [M+Na]+ calcd 1991.7, found

L. Huang et al. / Carbohydrate Research 341 (2006) 1669–1679
1679
11. (a) Nishimura, S.-I.; Kai, H.; Shinada, K.; Yoshida, T.;
Tokura, S.; Kurita, K.; Nakashima, H.; Yamamoto, N.;
Uryu, T. Carbohydr. Res. 1998, 306, 427–433; (b) Katsu-
raya, K.; Ishikawa, S.; Ichikawa, T.; Goto, K.; Uryu, T.
Seisan Kenkyu 1997, 49, 170–173.
19. (a) Tanaka, H.; Adachi, M.; Takahashi, S. Tetrahedron
Lett. 2004, 45, 1433–1436; (b) Orgueira, H. A.; Bartolozzi,
A.; Schell, P.; Litjens, R. E. J. N.; Palmacci, E. R.;
Seeberger, P. H. Chem. Eur. J. 2003, 9, 140–169; (c)
Paulsen, H.; Stenzel, W. Angew. Chem., Int. Ed. 1975, 14,
558–559.
12. (a) Yamago, S.; Yamada, T.; Maruyama, T.; Yoshida, J.-I.
Angew. Chem., Int. Ed. 2004, 43, 2145–2148; (b) Aly, M. R.
E.; Ibrahim, E. I.; El Ashry, E. S. H.; Schmidt, R. R.
Carbohydr. Res. 2001, 331, 129–142; (c) Hinou, H.;
Umino, A.; Matsuoka, K.; Terunuma, D.; Takahashi, S.;
Esumi, Y.; Kuzuhara, H. Bull. Chem. Soc. Jpn. 2000, 73,
163–171; (d) Kanie, O.; Ito, Y.; Ogawa, T. J. Am. Chem.
Soc. 1994, 116, 12073–12074; (e) Tailler, D.; Jacquinet, J.-
C.; Beau, J.-M. J. Chem. Soc., Chem. Commun. 1994,
1827–1828; (f) Ikeshita, S.; Sakamoto, A.; Nakahara, Y.;
Nakahara, Y.; Ogawa, T. Tetrahedron Lett. 1994, 35,
3123–3126; (g) Wang, L. X.; Li, C.; Wang, Q. W.; Hui, Y.
Z. Tetrahedron Lett. 1993, 34, 7763–7766; (h) Kuyama, H.;
Nakahara, Y.; Nukada, T.; Ito, Y.; Nakahara, Y.; Ogawa,
T. Carbohydr. Res. 1993, 243, C1–C7; (i) Nicolaou, K. C.;
Bockovich, N. J.; Carcanague, D. R.; Hummel, C. W.;
Even, L. F. J. Am. Chem. Soc. 1992, 114, 8701–8702.
13. Schwartz, D. A.; Lee, H.-H.; Carver, J. P.; Krepinsky, J. J.
Can. J. Chem. 1985, 63, 1073–1079.
20. Zhang, Z.; Ollmann, I. R.; Ye, X.-S.; Wischnat, R.;
Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121,
734–753.
21. Wang, Y.; Huang, X.; Zhang, L.-H.; Ye, X.-S. Org. Lett.
2004, 6, 4415–4417.
22. Mong, T. K. K.; Huang, C.-Y.; Wong, C.-H. J. Org.
Chem. 2003, 68, 2135–2142.
23. Barrett, A. G. M.; Dhanak, D.; Graboski, G. G.; Taylor,
S. J. Org. Synth. Coll. 1993, 8, 550.
24. (a) Crich, D.; Sun, S. Tetrahedron 1998, 54, 8321–8348; (b)
Martichonok, V.; Whitesides, G. M. J. Org. Chem. 1996,
61, 1702–1706.
25. (a) Zhu, T.; Boons, G.-J. Carbohydr. Res. 2000, 329, 709–
715; (b) Belot, F.; Jacquinet, J.-C. Carbohydr. Res. 1996,
290, 79–86.
26. Hernandez-Torres, J. M.; Liew, S.-T.; Achkar, J.; Wei, A.
Synthesis 2002, 487–490.
27. Kameyama, A.; Ehara, T.; Yamada, Y.; Ishida, H.; Kiso,
M.; Hasegawa, A. J. Carbohydr. Chem. 1995, 14, 507–
523.
14. Crich, D.; Dudkin, V. J. Am. Chem. Soc. 2001, 123, 6819–
6825.
15. Xue, J.; Khaja, S. D.; Locke, R. D.; Matta, K. L. Synlett
2004, 861–865.
28. Crich, D.; Smith, M.; Yao, Q.; Picione, J. Synthesis 2001,
323–326.
16. Crich, D.; Vinod, A. U. J. Org. Chem. 2005, 70, 1291–
1296.
29. Chowdhury, A. R.; Siriwardena, A.; Boons, G. J. Tetra-
hedron Lett. 2002, 43, 7805–7807.
17. Crich, D.; Vinod, A. U. Org. Lett. 2003, 5, 1297–1300.
18. (a) Boysen, M.; Gemma, E.; Lahmann, M.; Oscarson, S.
Chem. Commun. 2005, 3044–3046; (b) Wei, P.; Kerns, R. J.
J. Org. Chem. 2005, 70, 4195–4198.
30. (a) Seeberger, P. H. Chem. Commun. 2003, 1115–1121; (b)
Plante, O. J.; Palmacci, E. R.; Seeberger, P. H. Science
2001, 291, 1523–1527; (c) Seeberger, P. H.; Haase, W.-C.
Chem. Rev. 2000, 100, 4349–4393.