One-pot synthesis of cyclic oligosaccharides by the polyglycosylation of monothioglycosides

Article abstract of DOI:10.1016/j.carres.2019.107888

Cyclic oligosaccharides such as cyclodextrins (CyDs) have been known as excellent host molecules for the inclusion of various organic guest molecules. The development of new synthetic methods for preparing cyclic oligosaccharides from simple and readily a

Full text of DOI:10.1016/j.carres.2019.107888

Journal Pre-proof
One-pot synthesis of cyclic oligosaccharides by the polyglycosylation of
monothioglycosides
Hidehisa Someya, Takehito Seki, Gota Ishigami, Taiki Itoh, Yutaka Saga, Yasuyuki
Yamada, Shin Aoki
PII:
S0008-6215(19)30632-9
DOI:
https://doi.org/10.1016/j.carres.2019.107888
CAR 107888
Reference:
To appear in: Carbohydrate Research
Received Date: 26 October 2019
Revised Date: 29 November 2019
Accepted Date: 3 December 2019
Please cite this article as: H. Someya, T. Seki, G. Ishigami, T. Itoh, Y. Saga, Y. Yamada, S. Aoki, One-
pot synthesis of cyclic oligosaccharides by the polyglycosylation of monothioglycosides, Carbohydrate
Research (2020), doi: https://doi.org/10.1016/j.carres.2019.107888.
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© 2019 Published by Elsevier Ltd.

One-Pot Synthesis of Cyclic Oligosaccharides by the
Polyglycosylation of Monothioglycosides
Hidehisa Someya,a Takehito Seki,a Gota Ishigami,a Taiki Itoh,a Yutaka Saga,a Yasuyuki Yamada,b,c,d and
Shin Aokia,e,*
a Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510,
Japan
b Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku,
Nagoya 464-8602, Japan
c Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,
Japan
d JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
e Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda,
Chiba 278-8510, Japan,
*Corresponding author. E-mail address: shinaoki@rs.noda.tus.ac.jp (Shin Aoki).
1

ABSTRACT:
Cyclic oligosaccharides such as cyclodextrins (CyDs) have been known as excellent host
molecules for the inclusion of various organic guest molecules. The development of new synthetic
methods for preparing cyclic oligosaccharides from simple and readily available glycosyl donors would
be highly desirable, since the current traditional synthetic routes include multiple reaction steps
(glycosylation reactions and deprotections).
We herein report on the synthesis of cyclic
oligosaccharides by polyglycosylation of monothioglycosides, typically, 2,3,4-protected 1-
thioglycosides. A series of promoters and solvents were tested for the glycosylation of thiogalactosides
that contain a hydroxy group at the 6-position, and glycosylation using a N-iodosuccinimide
(NIS)/trimethylsilyl triflate (TMSOTf) promoter system in dichloromethane afforded cyclic
oligosaccharides which consist of tri~penta galactosides containing repeating β-(1→6) glycosidic
linkage as major products, as evidenced by a single crystal X-ray structure analysis of the cyclic
tetragalactoside. The effect of reaction temperature and reactant concentrations on the glycosylation
products was also investigated. The cyclic glucosides were obtained by the glycosylation of the
thioglucosides. Moreover, protecting groups of the synthesized cyclic tetragalactoside were removed to
obtain deprotected cyclic tetragalactoside.
Keywords:
Glycosylation, Thiogalactoside, Thioglucoside, Cyclic oligosaccharide, β-(1→6)
glycosidic linkage
2

1. Introduction
Cyclic oligosaccharides are ring-shaped molecules which consist of carbohydrate oligomers. The
first paper regarding cyclic oligosaccharides, which are now recognized as cyclodextrins 1
(cyclo(1→4)-α- -glucooligosaccharides) (CyDs) was reported by Villiers in 1891, and Schardinger
D
isolated cyclodextrins followed by elucidation of their structure by Freudenberg in early the1900s [1, 2]
(Scheme 1). In recent studies, Yamada and co-workers achieved a synthesis of the smallest
cyclodextrins, namely CyD3 and CyD4 [3]. CyDs have a unique ability to capture various molecules
within their hydrophobic cavities, resulting in the formation of inclusion complexes [4]. Due to these
properties and their low toxicity, CyDs are used extensively in pharmaceutical science [5], in analytical
chemistry [6], in supramolecular chemistry [7], as well as in foods [8] and cosmetics [9].
Other CyD analogs such as cyclosophorans 2 (cyclo(1→2)-β-
cycloawaodorins (cyclo(1→4)-α- -rhamnooligosaccharides) [11]; cycloinulooligosaccharides
(cyclo(2→1)-β- -fructooligosaccharides) 4 [12] and others [13] have also been reported (Scheme 1).
D-glucooligosaccharides) [10];
3
L
D
Although it is well known that these cyclic oligosaccharides form inclusion complexes with organic
molecules or metal cations [14–16], they are able to recognize different molecules depending on the size
and the shape of their inner cavities as compared to those of CyDs. Therefore, the design and synthesis
of novel CyD analogues with new properties and functions would be highly desirable.
3

Scheme 1. Typical examples of cyclic oligosaccharides.
The major synthetic methods of cyclic oligosaccharides can be classified into the following four
categories: (i) isolation from bacterial products [17–19]; (ii) enzymatic synthesis [20–23]; (iii) chemical
synthesis [3, 11, 13, 24–36]; and (iv) chemoenzymatic synthesis [37–39]. Chemical synthesis has
advantages in the large-scale synthesis of natural and artificial cyclic oligosaccharides and can be
categorized into two approaches. The first method is the stepwise preparation of linear oligosaccharides
4

6 from monomer units 5 followed by their cyclization to afford cyclic oligosaccharides 7 (Scheme 2a).
For instance, the cyclic oligosaccharides including -glucose moieties [3, 25, 27, 30], -glucosamine
moieties [30, 35, 36], 4-deoxy-4-C-methyl- -glucose moieties [33, 34] and -rhamnose moieties [11]
D
D
D
L
were synthesized from the corresponding linear oligosaccharides, which contain a glycosyl bromide,
glycosyl fluoride or thioglycoside unit at the reducing end. The second method is the one-pot
polyglycosylation (polycondensation) [40] of sugar units that function as both glycosyl donors and
glycosyl acceptors such as monosaccharide units (e.g. 1,2-O-(1-cyano)ethylidene derivatives [26] and
thioglycosides [32]) and disaccharide units (e.g. glycosyl bromides [24], 1,2-O-(1-cyano)ethylidene
derivatives [29], glycosyl acetates [28] and thioglycosides [31]).
Although the first approach has been the most commonly employed method for the construction
of cyclic oligosaccharides, it requires tedious processes such as protecting group and/or leaving group
manipulations, glycosylation reactions, and purifications after each synthetic step. In order to extend
the second approach, we attempted to develop the efficient method for the construction of cyclic
oligosaccharides from simple monosaccharides. This manuscript reports on the synthesis of cyclic
oligosaccharides 9 by the glycosylation of the thioglycosides 8 in which functions of a glycosyl donor
and a glycosyl acceptor are contained in the same molecule (Scheme 2b).
5

Scheme 2. Chemical synthesis of cyclic oligosaccharides. (a) Stepwise synthesis of cyclic
oligosaccharides; (b) one-pot polyglycosylation to afford cyclic oligosaccharides (this work). (PG =
protecting group, LG = leaving group, Ar = aryl group)
2. Results and discussion
In conducting the one-pot polyglycosylation of monosaccharides, we focused on the use of
thioglycosides as substrates due to their ease of preparation and derivatization, long shelf life and high
reactivity in the presence of specific promoters [41–46]. Kartha and co-workers recently reported on the
one-pot synthesis of cyclic oligosaccharides obtained as a mixture of stereoisomers from armed
monothioglycosides in which the hydroxy groups were protected by benzyl and trityl groups [32].
These results prompted us to examine the synthesis of cyclic oligosaccharides using benzoylated
monothioglycosides, which would permit the stereochemistry of the products to be controlled. We
6

prepared the thiogalactoside 10 [47] for use in a one-pot polyglycosylation and examined the effects of
glycosylation promoters, reaction solvents, the concentration of 10 and reaction temperature on the
nature of the products (Table 1).
The O-glycosylations of 2,3,4-tri-O-benzoyl-1-tolylthio-β-D-galactoside 10 (corresponding to 8 in
Scheme 2b) were conducted under specific conditions as listed in Table 1 and quenched with water.
Note that the crude reaction mixture was roughly purified by silica gel column chromatography and then
treated with acetic anhydride to acetylate linear saccharides and other byproducts for the easy
purification of the cyclic oligogalactosides (it was difficult to separate and purify linear saccharides for
their characterization). As summarized in Table 1, a series of typical promoters such as N-
iodosuccinimide (NIS)/trimethylsilyl triflate (TMSOTf) [48], p-toluenesulfenyl chloride (p-
TolSCl)/silver triflate (AgOTf) [49–52] and methyl triflate (MeOTf) [53] were examined. The reaction
using NIS/TMSOTf afforded the cyclic oligogalactosides 12–16, whereas the use of a combination of p-
TolSCl and AgOTf gave negligible amounts of cyclic oligosaccharides (entries 1 and 2 of Table 1). The
use of MeOTf furnished a mixture of linear and cyclic saccharides (entry 3). In order to examine the
effect of halonium species, the glycosylation reaction was conducted in the presence of N-
bromosuccinimide (NBS)/TMSOTf [54], as shown in entry 4, in which the isolated yields of cyclic
oligogalactosides 12–16 were slightly lower than those in entry 1 (NIS/TMSOTf). Figure 1a
summarizes the chemical yields of cyclic monogalactoside (1,6-anhydrogalactose) 11 and cyclic
oligogalactosides 12–16, showing that the polyglycosylation of 10 with NIS/TMSOTf and
NBS/TMSOTf gives cyclic trimer 12, cyclic tetramer 13 and cyclic pentamer 14 in higher chemical
yields than other cyclic galactosides. The use of NIS/AgOTf [55] was examined to evaluate the effect
of silver cations, resulting in the formation of the cyclic trisaccharide 12 in higher chemical yield than
those of cyclic tetra~octagalactosides 13–16 (entry 5). The use of N-(p-methylphenylthio)-ε-
caprolactam (NMPTC) [56], an organosulfur reagent, and TMSOTf afforded only negligible amounts of
cyclic oligosaccharides (entry 6). The above results suggest that using a combination of NIS and
TMSOTf is preferred compared to other promoter systems.
7

Table 1. Examination of reaction conditions for synthesis of cyclic oligogalactosides 12–16 by the one-
pot polyglycosylation of 10
Yields (%)
Promoters
(eq.)
Concentration
Entry
Solvent
Temperature Time
Linear
saccharides
of 10
11
3
12
13
-
13
23
-
14
18
-
15
5
-
16
5
-
NIS(3.0)
TMSOTf(1.5)
1
2
CH2Cl2
CH2Cl2
0.01 M
0.01 M
0.01 M
0.01 M
0.01 M
0.01 M
0.01 M
0.01 M
0.01 M
0.01 M
0.001 M
0.1 M
-40 °C
-40 °C
2.5 h
2.5 h
<9
p-TolSCl(2.0)
AgOTf(3.0)
-
<52
<23
<22
<13
<15
<42
3
MeOTf(16) CH2Cl2
0 °C to r.t. 48 h
14 <13 <10 <6
-
-
NBS(3.0)
CH2Cl2
4
-40 °C
2.5 h <2
12
19
-
18
13
-
17
11
-
8
5
-
4
2
-
TMSOTf(1.5)
NIS(3.0)
CH2Cl2
5
-40 to 0 °C
5 h
15
-
AgOTf(1.5)
NMPTC(2.0)
CH2Cl2
6
-40°C to r.t. 24 h
TMSOTf(2.3)
NIS(3.0)
EtCN
7
-40 °C
-40 °C
-40 °C
2.5 h
2.5 h
2.5 h
-
-
<9
<7
-
-
TMSOTf(1.5)
NIS(3.0)
THF
8
No reaction
TMSOTf(1.5)
NIS(3.0)
Toluene
9
-
-
-
-
-
6
-
-
-
-
-
-
<5
<18
<18
<4
TMSOTf(1.5)
NIS(3.0)
Toluene
10
11
12
-40 to 0 °C 3.5 h
<3
28
17
<7
7
TMSOTf(1.5)
NIS(3.0)
CH2Cl2
-40 °C
-40 °C
2.5 h
2.5 h
15
3
5
5
3
6
TMSOTf(1.5)
NIS(3.0)
CH2Cl2
21
TMSOTf(1.5)
8

NIS(3.0)
TMSOTf(1.5)
13
14
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
0.01 M
0.01 M
0.01 M
0.1 M
-78 °C
0 °C
2.5 h
2.5 h
2.5 h
2.5 h
-
-
-
-
-
-
-
<56
NIS(3.0)
TMSOTf(1.5)
21
13
6
22
22
11
13
18
14
6
5
4
3
5
3
-
<12
-
NIS(3.0)
TMSOTf(1.5)
15a
16b
-40 °C
-40 °C
2
-
NIS(3.0)
TMSOTf(1.5)
a Glycosylation was carried out in the presence of 3.0 eq. of LiClO4 against 10.
b Products were isolated without acetylation (second step).
9

(a)
NIS/TMSOTf (Entry 1)
p-TolSCl/AgOTf (Entry 2)
MeOTf (Entry 3)
30
25
20
15
10
NBS/TMSOTf (Entry 4)
NIS/AgOTf (Entry 5)
NMPTC/TMSOTf (Entry 6)
5
0
1
(11)
2
3
(12)
4
(13)
5
(14)
6
(15)
7
8
(16)
Cyclic galactosides (n = 1, 2, 3, 4, 5, 6, 7, 8)
(b)
CH2Cl2 (Entry 1)
30
EtCN (Entry 7)
THF (Entry 8)
25
20
15
10
Toluene (-40 °C) (Entry 9)
Toluene (-40 to 0 °C) (Entry 10)
5
0
1
2
3
4
5
6
7
8
(11)
(12)
(13)
(14)
(15)
(16)
Cyclic galactosides (n = 1, 2, 3, 4, 5, 6, 7, 8)
(c)
(d)
(e)
30
25
0.001 M of 10 (Entry 11)
0.01 M of 10 (Entry 1)
0.1 M of 10 (Entry 12)
20
15
10
5
0
1
2
3
(12)
4
(13)
5
(14)
6
(15)
7
8
(16)
(11)
Cyclic galactosides (n = 1, 2, 3, 4, 5, 6, 7, 8)
30
25
-78 °C (Entry 13)
-40 °C (Entry1)
0 °C (Entry 14)
20
15
10
5
0
1
2
3
(12)
4
(13)
5
(14)
6
(15)
7
8
(16)
(11)
Cyclic galactosides (n = 1, 2, 3, 4, 5, 6, 7, 8)
30
No salt (Entry 1)
LiClO4 (Entry15)
25
20
15
10
5
0
1
(11)
2
3
(12)
4
(13)
5
(14)
6
(15)
7
8
(16)
Cyclic galactosides (n = 1, 2, 3, 4, 5, 6, 7, 8)
10

Figure 1. Relationship between reaction conditions and isolated chemical yields of cyclic
oligogalactosides. Open symbols denote the chemical yield, which include very little amounts of
impurities. The bold numbers under the “n” in each graph indicate the compound number of and cyclic
galactosides (11–16 shown in Table 1). (a) Effect of promoters; (b) solvent effect; (c) effect of the
concentration of 10; (d) effect of reaction temperature; and (e) effect of salts.
The effect of the solvent on the synthesis of cyclic oligosaccharides was studied (entries 1 and
7–10 in Table 1 and Figure 1b). The use of propionitrile gave small amounts of the cyclic
tetragalactoside 13 and cyclic pentagalactoside 14 including unidentified products (entry 7). As shown
in entries 8 and 9, the glycosylations in THF and toluene at -40 °C afforded negligible amounts of cyclic
oligosaccharides. The use of toluene at -40 °C to 0 °C gave the cyclic oligogalactosides 12–14 in lower
chemical yields (entry 10) compared to dichloromethane in entry 1, suggesting that dichloromethane is
better than the other solvents.
The effect of the concentration of reactants on the polyglycosylation of 10 was also examined
(entries 1, 11 and 12 in Table 1 and Figure 1c). Figure 1c suggests that the chemical yields of larger
cyclic oligogalactoside were increased when higher concentrations of 10 were used, possibly because
higher concentration conditions accelerate the intermolecular glycosylation to give a longer linear
oligosaccharide having leaving group (-STol group), followed by intramolecular cyclization.
The effect of reaction temperature on the glycosylation products was also investigated (entries 1,
13 and 14 in Table 1 and Figure 1d). The reaction at -78 °C gave linear saccharides instead of cyclic
saccharides (entry 13), possibly because the activation energy for the cyclization is high. A comparison
of the reactions at -40 °C and 0 °C suggested that, when the reaction was carried out at a lower
temperature, a larger cyclic oligosaccharide is produced in slightly higher yields (entries 1 vs. 14 in
Table 1 and Figure 1d).
The presence of LiClO4 in the reaction was examined, in order to observe the effect of the
presence of a salt in controlling the selectivity of the ring size of cyclic oligogalactosides due to the
interaction between oxygen atoms and lithium cations. However, the result (entry 15 in Table 1) was
11

almost same as that shown in entry 1 (Figure 1e). The reaction without acetylation process was also
checked and the same cyclic oligogalactosides 12–16 were produced as in entry 16.
The structures of cyclic oligosaccharides 12–16 were determined by NMR spectroscopy and
1
mass spectrometry. The assignments of the H NMR spectra of 12–16 (Figure 2) suggested that these
molecules have highly symmetrical structures because the spectra showed simple peak signals
corresponding to the repeating monomer units. The coupling constants associated with the anomeric
proton and the proton at the 2-position (3J H1–H2) of 12–16 were 7.2 to 8.0 Hz, which are reasonable
values compared with common β-galactosides. The formation of 1,6-glycosidic linkages between the
galactose units and/or ester bonds between benzoyl groups and hydroxy groups at the 2- ,3- and 4-
positions were confirmed by the measurement of 1H–13C HMBC (see NMR spectra in the
Supplementary Data).
12

1
Figure 2. The H NMR spectra of cyclic oligogalactosides in CDCl3 at 400 MHz. (a) cyclic
trisaccharide 12; (b) cyclic tetrasaccharide 13; (c) cyclic pentasaccharide 14; (d) cyclic hexasaccharide
15; and (e) cyclic octasaccharide 16.
The number of galactose units constituting 12–16 was determined by ESI-MS as summarized in
Figure 3. The peaks of [M+Na]+ ions were observed for the cyclic tri-, tetra-, and pentagalactosides,
corresponding to 12, 13, and 14 respectively. The cyclic hexagalactoside 15 and the octagalactoside 16
were detected as 2 peaks corresponding to [M+Na]+ and [M+2Na]2+ ions for 15 and [M+2Na]2+ and
[M+3Na]3+ ions for 16. The above results indicate that 12–16 are cyclic oligosaccharide with repeating
D-galactopyranosyl moieties linked by β-(1→6) glycosidic bonds.
13

Figure 3. The ESI-MS spectra of cyclic oligogalactosides 12–16. (a) cyclic trisaccharide 12; (b) cyclic
tetrasaccharide 13; (c) cyclic pentasaccharide 14; (d) cyclic hexasaccharide 15; and (e) cyclic
octasaccharide 16.
We were able to obtain good crystals of the cyclic tetragalactoside 13 that were suitable for a
single crystal X-ray structure analysis by recrystallization from toluene. The stick and stick-CPK
14

models (atoms constituting the inner cavity are presented by CPK model and the other atoms are stick
model) of 13 shown in Figure 4, revealed its structure with the repeating β-(1→6) glycosidic linkage
and a small rectangular-like inner cavity, whose diameter is 2.4~3.3 Å. The ORTEP drawing of 13 and
its typical crystallographic parameters are described in the Supplementary Data (Figure S1 and Table
S1).
(a)
(b)
Top view
Top view
(c)
(d)
Side view
Side view
Figure 4. Crystal structure of 13. (a) Top view of a stick model; (b) top view of a stick-CPK model, in
which only the scaffold forming inner cavity is presented in the CPK model; (c) side view of the stick
model; and (d) side view of the stick-CPK model.
The 6-membered pyranose ring of 13 adopts a nearly 4C1 (chair) conformation, as suggested by
the polar coordinate values, meridian angle (φ), azimuthal angle (θ) and radius (Q), which were
calculated by a Cremer-Pople puckering parameter analysis (Table S2 in the Supplementary Data) [57–
15

60]. Table 2 summarizes representative dihedral angles of galactose units 1~4 of 13 (DAn(x), x =
number of galactose unit in 13, n = 1~3), suggesting that two pairs of two opposite galactose units in 13
adopt two different conformation with respect to the linkages between adjacent galactose units. Namely,
DA1(1) and DA1(3) values are ca. 174~176 °, indicating the conformation of the O5(1 or 3)–C5(1 or 3)
bond and C6(1 or 3)–O6(1 or 3) bond adopt s-trans (antiperiplanar) conformation. On the other hand,
DA1(2) and DA1(4) values are ca. 68~71 ° that correspond to s-cis (synclinal) conformation. DA2(x)
values of C5(x)–C6(x)–O6(x)–C1(x+1) of all the galactose units are ca. -108~-99 °, which means their
s-trans (anticlinal) conformation with respect to C5(x)–C6(x) bond and O6(x)–C1(x+1) bond. The
DA3(1) and DA3(3) values for C6(x)–O6(x)–C1(x+1)–O5(x+1) are ca. 50~57 ° and DA3(2) and DA3(4)
values (note that C1(5) and O5(5) mean C1(1) and O5(1), respectively) are ca. -86~-74 ° that
correspond to s-cis (synclinal) conformation with respect to C6–O6 bond and C1–O5 bond (in the
adjacent galactose unit) in both cases.
Table 2. Representative dihedral angles (DAn(x)) regarding the linkage between galactose units
consisting 13. The benzoyl groups are removed for clearly.
Unit 3
O5(3)
C6(3)
C6(2)
C1(3)
O6(3)
C1(4)
O6(2)
C5(2)
O5(2)
Unit 4
C5(3)
O5(4)
C5(4)
Unit 2
C1(1)
O5(1)
C5(1)
C6(4)
C1(2)
O6(1)
O6(4)
C6(1)
Unit 1 (= Unit 5)
Angle (°)
Galactose Galactose Galactose Galactose
Dihedral angles of specific galactose (x)
(DAn(x))
unit 1–2
(x = 1)
unit 2–3
(x = 2)
unit 3–4
(x = 3)
unit 4–1
(x = 4)
176.4
70.5
173.9
67.9
DA1(x): O5(x)–C5(x)–C6(x)–O6(x)
DA2(x): C5(x)–C6(x)–O6(x)–C1(x+1)
-107.5
-99.0
-100.1
-101.7
16

DA3(x): C6(x)–O6(x)–C1(x+1)–O5(x+1)
50.3
-86.4
57.3
-74.1
We next carried out the glycosylation of thioglucoside 17 [61] to produce the cyclic
oligoglucosides (Table 3). The use of NIS/TMSOTf in the glycosylation of 17 gave the cyclic
monoglucoside (1,6-anhydroglucose) 18 in 18% yield and cyclic diglucoside 19 in 10% yield,
respectively (entry 1). This result was different from the case of the thiogalactoside 10 (entry 1 in Table
1), in which cyclic tri- to octagalactosides 12–16 were obtained, possibly due to the lower reactivity of
the thioglucoside 17 than the thiogalactoside 10 [62]. In entry 2, the use of a combination of p-TolSCl
and AgOTf as promoter system gave negligible amounts of cyclic oligosaccharides (1,6-anhydroglucose
18 and linear saccharides including some impurities were major products), similar the results for entry 2
in Table 1. The reaction in higher concentration of 17 afforded cyclic oligoglucosides with larger ring
sizes such as the cyclic trisaccharide 20, the tetrasaccharide 21, the pentasaccharide 22 and the
hexasaccharide 23 (entry 3). The high reaction temperature (0 °C) for this glycosylation afforded the
1,6-anhydroglucose 18 in higher yield (entry 4) than that of entry 3. The reaction without acetylation
process was also examined in entry 5 and afforded the same products 18–23 as those of entries 3 and 4.
It should be noted that cyclic diglucoside 19 was obtained in 4~14% from 17 (entry 1, 3, 4 and 5 in
Table 3), while cyclic digalactoside was negligibly obtained from 10 (Table 1), possibly due to the steric
hindrance of the benzoyl groups on the axial 4-OH group of thiogalactoside.
Table 3. Polyglycosylation of thioglucoside 17 for the synthesis of cyclic oligoglucosides 19–23.
1) Promoters, CH2Cl2
4Å MS, Temperature, 2.5 h
then H2O, r.t., 30 min
OH
O
O
O
BzO
BzO
BzO
BzO
S
Linear glucosides
O
2) Ac2O, DMAP, Pyridine
0 °C to r.t., Overnight
OBz
Bz
n
Cyclic glucosides
Thioglucoside
17
18: n = 1, 19: n = 2, 20: n = 3,
21: n = 4, 22: n = 5, 23: n = 6
17

Yields (%)
Promoters Concentration
Entry
Temperature
Linear
saccharides
(eq.)
of 17
18
18
25
15
32
8
19
10
-
20
-
21
-
22
-
23
-
NIS(3.0)
TMSOTf(1.5)
1
2
0.01 M
0.01 M
0.1 M
0.1 M
0.1 M
-40 °C
-40 °C
-40 °C
0 °C
<38
p-TolSCl(2.0)
AgOTf(3.0)
-
-
-
-
<18
NIS(3.0)
TMSOTf(1.5)
3
7
16
14
21
22
11
23
5
3
6
3
2
4
-
-
-
NIS(3.0)
TMSOTf(1.5)
4
4
NIS(3.0)
TMSOTf(1.5)
5a
-40 °C
14
a Products were isolated without acetylation (second step).
The glycosylation of the thiogalactoside 24 [63] (Scheme 3), in which the hydroxy group at the 6-
position was protected by trityl group was also conducted, because the use of substrates with a trityl group
for the glycosylation has been reported [26, 29, 32]. As shown in Scheme 3, the glycosylation of 24 gave
the cyclic oligogalactosides 12–16, similar to the products obtained by the glycosylation of thiogalactoside
10 despite the fact that the chemical yields were lower than that using 10 in entry 1 of Table 1.
18

Scheme 3. Glycosylation of thiogalactoside 24 to afford the cyclic oligogalactosides 12–16.
The deprotection of the cyclic tetragalactoside 13 was carried out by treatment with MeNH2 to
afford 25 in 93% yield (Scheme 4).
Scheme 4. Deprotection of 13.
3. Conclusions
We report herein on the one-pot synthesis of cyclic oligosaccharides via the polyglycosylation of simple
and readily available monothioglycosides such as thiogalactoside 10 and thioglucoside 17. Among the
glycosylation promoters and solvents tested, the use of a combination of NIS and TMSOTf in CH2Cl2 in the
glycosylation of 10 was found to give the cyclic oligogalactosides 12–16 in better chemical yields than when
other promoter systems and solvents were used. A study of the effect of the concentration of reactants and
reaction temperature suggested that higher concentrations and lower temperatures (-40 °C vs. 0 °C) afforded
slightly larger cyclic oligogalactosides. The measurement of NMR and mass spectroscopy confirmed the
formation of β-(1→6) glycosidic linkage and the number of the galactose units. The crystal structure of 13 also
supported the construction of β-(1→6) glycosidic linkage and revealed the 4C1-conformation of pyranose ring
and the small inner cavity having inner diameter of 2.4~3.3 Å, by a single crystal X-ray structure analysis. This
method also can be applied to the glycosylation of the thioglucoside 17 to give the corresponding cyclic
oligoglucosides 19–23. The deprotection of cyclic tetragalactoside 13 was also carried out to give the deprotected
19

cyclic tetragalactoside 25. The inclusion of some organic and/or inorganic compounds in these cyclic
oligogalactosides and cyclic oligoglucosides composed of β-(1→6) glycosidic linkages are currently underway.
20

4. Experimental section
4.1. General information
All reagents and solvents were purchased at the highest commercial quality and were used
without further purification. Anhydrous CH2Cl2 was distilled from calcium hydride. Anhydrous EtCN
was prepared by distillation from calcium hydride and successive distillation from phosphorus (V)
oxide. Anhydrous THF was prepared by distillation from sodium and benzophenone. Anhydrous
toluene and pyridine were purchased. All aqueous solutions were prepared using deionized water.
1H (400 MHz) and 13C (100 MHz) NMR spectra were recorded on a JNM-ECZ400S (JEOL,
Tokyo, Japan) spectrometer. Two-dimensional NMR spectra (correlation spectroscopy (COSY),
heteronuclear multiple quantum correlation (HMQC) and heteronuclear multiple bond coherence
(HMBC)) were recorded on a JNM-ECZ400S (JEOL, Tokyo, Japan) spectrometer. Tetramethylsilane
1
(TMS) was used as an internal reference (0 ppm) for H NMR measurements in CDCl3. 3-
(Trimethylsilyl)propionic-2,2,3,3-d4 acid sodium (TSP) was used as an internal reference (0 ppm) for 1H
NMR measurements in D2O. 1,4-Dioxane was used as an internal reference (67.19 ppm) for 13C NMR
measurements in D2O. IR spectra were recorded on a Perkin-Elmer FTIR Spectrum 100 (ATR)
(PerkinElmer, Massachusetts, USA). MS measurements were performed on a JEOL JMS-700 (JEOL,
Tokyo, Japan) and Varian 910-MS (Varian Medical Systems, California, USA) spectrometer. Optical
rotations were determined with a JASCO P-1030 digital polarimeter (JASCO, Tokyo, Japan) in 50 mm
cells using the D line of sodium (589 nm). Thin-layer chromatography (TLC) and preparative thin-layer
chromatography (PTLC) were performed using Merck Silica gel 60 F254 plate (Merck KGaA,
Darmstadt, Germany). Silica gel column chromatography was performed using Fuji Silysia Chemical
FL-100D (Fuji Silysia Chemical, Aichi, Japan). Gel permeation chromatography (GPC) experiments
were carried out using a system consisting of a PUMP P-50 (Japan Analytical Industry Co., Ltd., Tokyo,
Japan), a UV/VIS DETECTOR S-3740 (Soma, Tokyo, Japan), a Manual Sample Injector 7725i
(Rheodyne, Bensheim, Germany) and an MDL-101 1 PEN RECORDER (Japan Analytical Industry Co.,
21

Ltd., Tokyo, Japan), equipped with two GPC columns, JAIGEL-1H and JAIGEL-2H (Japan Analytical
Industry Co., Ltd., Tokyo, Japan) (20φ x 600 mm, No. A605201 and A605204).
4.2. General procedure
4.2.1. Glycosylation of thiogalactoside 10 (Table 1, entry 1)
A mixture of thiogalactoside 10 (24.0 mg, 0.040 mmol), activated 4 Å molecular sieves (400
mg) and anhydrous CH2Cl2 (4.0 mL) was stirred at room temperature for 30 min and then cooled to −40
°C, to which NIS (27.0 mg, 0.12 mmol) and TMSOTf (11.0 µL, 0.061 mmol) were added at the same
temperature. After stirring for 2.5 hr at −40 °C, H2O (1.0 mL) was added to the reaction mixture
followed by stirring for 30 min at room temperature. The reaction mixture was diluted with CHCl3 and
filtered through a Celite pad. The organic layer was washed with 10w/v% aqueous Na2S2O3, saturated
aqueous NaHCO3 and brine, dried over Na2SO4, filtered and concentrated under reduced pressure. The
remaining residue was purified by silica gel column chromatography (hexanes/AcOEt = 10/1–1/1) to
give a crude compound as a colorless solid (21.0 mg). To the solution of this crude compound in
anhydrous pyridine (400 µL), Ac2O (50.0 µL, 0.53 mmol) and DMAP (0.3 mg, 0.0025 mmol) were
added at 0 °C. The reaction mixture was stirred at the same temperature for 30 min and then allowed to
warm to room temperature. After stirring overnight, the reaction mixture was diluted with CHCl3,
washed with 1 M aqueous HCl, saturated aqueous NaHCO3 and brine, dried over Na2SO4, filtered and
concentrated under reduced pressure. The residue was purified by GPC (solvent: CHCl3, flow rate: 3.6
mL/min, retention time (tr): fraction 1: 36~47 min including cyclic tri~octa galactosides, fraction 2:
47~51 min including 1,6-anhydrogalactose) followed by PTLC for the GPC fraction 1 (hexanes/AcOEt
= 2/1 for 5 times, the compounds were extracted with CHCl3) to isolate 1,6-anhydrogalactose 11 (0.6
mg, 3% yield, Rf = 0.87 (hexanes/AcOEt = 2/1 once)), cyclic trigalactoside 12 (2.4 mg, 13% yield, Rf =
0.73 (hexanes/AcOEt = 2/1 for 5 times)), cyclic tetragalactoside 13 (4.3 mg, 23% yield, Rf = 0.58
(hexanes/AcOEt = 2/1 for 5 times)), cyclic pentagalactoside 14 (3.4 mg, 18% yield, Rf = 0.42
(hexanes/AcOEt = 2/1 for 5 times)), cyclic hexagalactoside 15 (1.0 mg, 5% yield, Rf = 0.29
22

(hexanes/AcOEt = 2/1 for 5 times)) and cyclic octagalactoside 16 (0.9 mg, 5% yield, Rf = 0.11
(hexanes/AcOEt = 2/1 for 5 times)).
4.2.2. Glycosylation of thioglucoside 17 (Table 3, entry 3)
The glycosylation and acetylation steps were carried out following the procedure used for the
glycosylation of 10. A mixture of thioglucoside 17 (60.0 mg, 0.10 mmol), activated 4 Å molecular
sieves (100 mg) and anhydrous CH2Cl2 (1.0 mL) was stirred at room temperature for 30 min and then
cooled to −40 °C, to which NIS (67.8 mg, 0.30 mmol) and TMSOTf (27.0 µL, 0.15 mmol) were added
at the same temperature. After stirring for 2.5 hr at −40 °C, H2O (1.0 mL) was added to the reaction
mixture followed by stirring for 30 min at room temperature. The reaction mixture was diluted with
CHCl3 and filtered through a Celite pad. The organic layer was washed with 10w/v% aqueous Na2S2O3,
saturated aqueous NaHCO3 and brine, dried over Na2SO4, filtered and concentrated under reduced
pressure. The remaining residue was purified by silica gel column chromatography (hexanes/AcOEt =
10/1–1/1) to give a crude compound as a colorless syrup (63.3 mg). To the solution of this crude
compound in anhydrous pyridine (1.0 mL), Ac2O (189 µL, 2.00 mmol) and DMAP (1.2 mg, 0.0098
mmol) were added at 0 °C. The reaction mixture was stirred at the same temperature for 30 min and
then allowed to warm to room temperature. After stirring overnight, the reaction mixture was diluted
with CHCl3, washed with 1 M aqueous HCl, saturated aqueous NaHCO3 and brine, dried over Na2SO4,
filtered and concentrated under reduced pressure. The residue was purified by GPC (solvent: CHCl3,
flow rate: 4.6 mL/min, tr: fraction 1: 30~36 min including cyclic tri~hexa glucosides, fraction 2: 36~42
min including 1,6-anhydroglucose and cyclic diglucoside) followed by PTLC for GPC fraction 1 and 2
(hexanes/AcOEt = 3/2 for 5 times, then toluene/AcOEt = 5/1 twice regarding the GPC fraction 1 and
hexanes/AcOEt = 3/1 twice regarding the GPC fraction 2, compounds were extracted with CHCl3) to
isolate 1,6-anhydroglucose 18 (7.2 mg, 15% yield, Rf = 0.40 (hexanes/AcOEt = 3/1 twice)), cyclic
diglucoside 19 (3.2 mg, 7% yield, Rf = 0.20 (hexanes/AcOEt = 3/1 twice)), cyclic triglucoside 20 (7.8
mg, 16% yield, Rf = 0.34 (toluene/AcOEt = 5/1 twice)), cyclic tetraglucoside 21 (10.3 mg, 22% yield,
23

Rf = 0.57 (toluene/AcOEt = 5/1 twice)), cyclic pentaglucoside 22 (2.2 mg, 5% yield, Rf = 0.60
(toluene/AcOEt = 5/1 twice)), cyclic hexaglucoside 23 (1.5 mg, 3% yield, Rf = 0.51 (toluene/AcOEt =
5/1 twice)).
4.3. Spectral data
4.3.1. 1,6-Anhydro-2,3,4-tri-O-benzoyl-β-D-galactopyranose (11)
Colorless syrup: spectroscopic data for the product were identical to previously reported data
[64].
4.3.2. Cyclotris-(1→6)-(2,3,4-tri-O-benzoyl-β-
D
-galactopyranosyl) (12)
1
Colorless solid: H NMR (400 MHz, CDCl3, TMS): = 8.01–7.96 (m, 6H, Ar), 7.95–7.90 (m,
δ
6H, Ar), 7.79–7.72 (m, 6H, Ar), 7.56–7.50 (m, 3H, Ar), 7.49–7.37 (m, 12H, Ar), 7.29–7.14 (m, 12H,
Ar), 5.85 (dd, J = 3.2, 1.6 Hz, 3H, H-4), 5.75 (t, J = 9.2 Hz, 3H, H-2), 5.59 (dd, J = 10.0, 3.2 Hz, 3H, H-
3), 5.12 (d, J = 7.2 Hz, 3H, H-1), 4.48 (dd, J = 12.0, 7.6 Hz, 3H, H-6), 4.27 (d, J = 7.6 Hz, 3H, H-5),
4.03 (d, J = 12.0 Hz, 3H, H-6) ppm; 13C NMR (100 MHz, CDCl3, TMS):
165.2 (C=O), 133.4 (Ar), 129.8 (Ar), 129.2 (Ar), 128.8 (Ar), 128.7 (Ar), 128.6 (Ar), 128.5 (Ar), 128.3
(Ar), 99.4 (C-1), 73.8 (C-5), 71.3 (C-3), 69.3 (C-4), 69.0 (C-2), 67.8 (C-6) ppm; IR (ATR): = 3064,
δ = 165.7 (C=O), 165.4 (C=O),
ν
2935, 2876, 1723, 1601, 1584, 1492, 1451, 1315, 1255, 1176, 1089, 1066, 1025, 1001, 936, 854, 801,
753, 703, 685, 616 cm−1; HRMS (ESI+): m/z calcd. for [M+Na]+, C81H66O24Na, 1445.3836; found,
1445.3812; [α]24 = +132.0 º (c = 1.0, CHCl3).
D
4.3.3. Cyclotetrakis-(1→6)-(2,3,4-tri-O-benzoyl-β-
D
-galactopyranosyl) (13)
= 7.98–7.90 (m, 8H, Ar), 7.88–7.81 (m,
1
Colorless solid: H NMR (400 MHz, CDCl3, TMS):
δ
8H, Ar), 7.70–7.63 (m, 8H, Ar), 7.52–7.34 (m, 20H, Ar), 7.33–7.37–7.27 (m, 8H, Ar), 7.23–7.15 (m, 8H,
Ar), 5.97 (d, J = 2.8 Hz, 4H, H-4), 5.76 (dd, J = 10.2, 8.0 Hz, 4H, H-2), 5.54 (dd, J = 10.4, 3.2 Hz, 4H,
24

H-3), 4.86 (d, J = 8.0 Hz, 4H, H-1), 4.30–4.18 (m, 8H, H-5, H-6), 4.04 (dd, J = 15.8, 7.6 Hz, 4H, H-6)
ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ
= 165.3 (C=O), 165.3 (C=O), 165.2 (C=O), 133.4 (Ar),
133.3 (Ar), 133.1 (Ar), 129.8 (Ar), 129.7 (Ar), 129.2 (Ar), 128.9 (Ar), 128.8 (Ar), 128.5 (Ar), 128.1
(Ar), 101.2 (C-1), 74.8 (C-5), 72.1 (C-3), 68.5 (C-2), 68.3 (C-4), 65.9 (C-6) ppm; IR (ATR): = 3065,
ν
2938, 2878, 1721, 1602, 1585, 1492, 1451, 1315, 1250, 1176, 1088, 1064, 1025, 1002, 936, 855, 801,
753, 701, 685, 616 cm−1; HRMS (ESI+): m/z calcd. for [M+Na]+, C108H88O32Na, 1919.5151; found,
1919.5151; [α]24 = +177.4 º (c = 1.0, CHCl3).
D
4.3.4. Cyclopentakis-(1→6)-(2,3,4-tri-O-benzoyl-β-
D-galactopyranosyl) (14)
Colorless solid: 1H NMR (400 MHz, CDCl3, TMS):
δ
= 7.99–7.92 (m, 10H, Ar), 7.87–7.81 (m,
10H, Ar), 7.76–7.71 (m, 10H, Ar), 7.59–7.53 (m, 5H, Ar), 7.49–7.29 (m, 30H, Ar), 7.25–7.19 (m, 10H,
Ar), 5.82 (d, J = 3.2 Hz, 5H, H-4), 5.66 (dd, J = 10.4, 8.0 Hz, 5H, H-2), 5.51 (dd, J = 10.2, 3.6 Hz, 5H,
H-3), 4.85 (d, J = 8.0 Hz, 5H, H-1), 4.17 (t, J = 6.4 Hz, 5H, H-5), 3.94–3.84 (m, 10H, H-6) ppm; 13C
NMR (100 MHz, CDCl3, TMS):
133.1 (Ar), 129.9 (Ar), 129.8 (Ar), 129.7 (Ar), 129.2 (Ar), 128.9 (Ar), 128.6 (Ar), 128.3 (Ar), 128.2
(Ar), 100.5 (C-1), 72.7 (C-5), 71.6 (C-3), 69.2 (C-2), 67.9 (C-4), 64.8 (C-6) ppm; IR (ATR): = 3065,
δ = 165.4 (C=O), 165.2 (C=O), 165.1 (C=O), 133.5 (Ar), 133.2 (Ar),
ν
2939, 2883, 1722, 1602, 1585, 1492, 1451, 1315, 1251, 1176, 1089, 1065, 1025, 1002, 935, 855, 801,
760, 703, 685, 616 cm−1; HRMS (ESI+): m/z calcd. for [M+Na]+, C135H110O40Na, 2393.6466; found,
2393.6488; [α]25 = +118.1 º (c = 1.0, CHCl3).
D
4.3.5. Cyclohexakis-(1→6)-(2,3,4-tri-O-benzoyl-β-
D-galactopyranosyl) (15)
Colorless solid: 1H NMR (400 MHz, CDCl3, TMS):
δ
= 8.00–7.95 (m, 12H, Ar), 7.94–7.88 (m,
12H, Ar), 7.78–7.72 (m, 12H, Ar), 7.62–7.56 (m, 6H, Ar), 7.49–7.31 (m, 36H, Ar), 7.25–7.19 (m, 12H,
Ar), 5.80 (d, J = 3.2 Hz, 6H, H-4), 5.67 (dd, J = 10.4, 8.0 Hz, 6H, H-2), 5.48 (dd, J = 10.4, 3.2 Hz, 6H,
H-3), 4.81 (d, J = 8.0 Hz, 6H, H-1), 4.13 (t, J = 6.4 Hz, 6H, H-5), 3.90 (dd, J = 10.8, 6.0 Hz, 6H, H-6),
25

13
3.82 (dd, J = 10.8, 6.4 Hz, 6H, H-6) ppm; C NMR (100 MHz, CDCl3, TMS):
δ = 165.3 (C=O), 165.3
(C=O), 165.0 (C=O), 133.7 (Ar), 133.2 (Ar), 133.1 (Ar), 130.0 (Ar), 129.8 (Ar), 129.8 (Ar), 129.3 (Ar),
129.1 (Ar), 129.0 (Ar), 128.5 (Ar), 128.4 (Ar), 128.2 (Ar), 101.5 (C-1), 72.9 (C-5), 71.6 (C-3), 69.5 (C-
2), 67.9 (C-4), 66.7 (C-6) ppm; IR (ATR):
ν = 3067, 2931, 2863, 1721, 1603, 1586, 1492, 1452, 1315,
1251, 1176, 1090, 1065, 1025, 1002, 935, 853, 801, 759, 703, 686, 617 cm−1; HRMS (ESI+): m/z calcd.
for [M+2Na]2+, C162H132O48Na2, 1445.3836; found, 1445.3851; [α]2D6 = +122.6 º (c = 0.2, CHCl3).
4.3.6. Cyclooctakis-(1→6)-(2,3,4-tri-O-benzoyl-β-D-galactopyranosyl) (16)
Colorless solid: 1H NMR (400 MHz, CDCl3, TMS):
δ
= 7.95–7.86 (m, 32H, Ar), 7.76–7.70 (m,
16H, Ar), 7.48–7.38 (m, 24H, Ar), 7.35–7.27 (m, 32H, Ar), 7.23–7.15 (m, 16H, Ar), 5.82 (d, J = 3.2 Hz,
8H, H-4), 5.59 (dd, J = 10.4, 8.0 Hz, 8H, H-2), 5.41 (dd, J = 10.2, 3.2 Hz, 8H, H-3), 4.62 (d, J = 7.6 Hz,
8H, H-1), 4.00–3.88 (m, 8H, H-5), 3.83–3.71 (m, 8H, H-6), 3.60-3.48 (m, 8H, H-6) ppm; 13C NMR (100
MHz, CDCl3, TMS):
129.3 (Ar), 129.3 (Ar), 128.9 (Ar), 128.4 (Ar), 128.2 (Ar), 101.2 (C-1), 72.6 (C-5), 71.7 (C-3), 69.5 (C-
2), 67.9 (C-4), 66.7 (C-6) ppm; IR (ATR): = 3066, 2925, 2853, 1720, 1602, 1585, 1492, 1451, 1315,
δ = 165.3 (C=O), 165.3 (C=O), 165.1 (C=O), 133.2 (Ar), 130.0 (Ar), 129.8 (Ar),
ν
1254, 1176, 1089, 1065, 1025, 1002, 935, 853, 801, 749, 703, 686, 617 cm−1; HRMS (ESI+): m/z calcd.
for [M+2Na]2+, C216H176O64Na2, 1919.5151; found, 1919.5192; [α]2D6 = +79.5 º (c = 0.2, CHCl3).
4.3.7. 1,6-Anhydro-2,3,4-tri-O-benzoyl-β-D-glucopyranose (18)
Colorless solid: spectroscopic data for the product were identical to previously reported data [65].
4.3.8. Cyclobis-(1→6)-(2,3,4-tri-O-benzoyl-β-D-glucopyranosyl) (19)
1
Colorless solid: H NMR (400 MHz, CDCl3, TMS):
δ
= 8.26–8.19 (m, 4H, Ar), 8.13–8.08 (m,
4H, Ar), 8.07–8.02 (m, 4H, Ar), 7.62–7.56 (m, 2H, Ar), 7.55–7.49 (m, 4H, Ar), 7.49–7.44 (m, 4H, Ar),
7.44–7.37 (m, 8H, Ar), 6.80 (dd, J = 10.6, 9.6 Hz, 2H, H-4), 5.76 (dd, J = 9.2, 2.8 Hz, 2H, H-3), 5.43
26

(dd, J = 2.6, 1.6 Hz, 2H, H-2), 5.05 (d, J = 1.2 Hz, 2H, H-1), 4.31–4.20 (m, 4H, H-5, H-6), 3.87 (dd, J =
12.8, 1.2 Hz, 2H, H-6) ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ
= 166.1 (C=O), 165.2 (C=O), 164.2
(C=O), 133.5 (Ar), 133.1 (Ar), 133.1 (Ar), 130.5 (Ar), 130.0 (Ar), 129.9 (Ar), 129.6 (Ar), 129.4 (Ar),
129.3 (Ar), 128.5 (Ar), 128.3 (Ar), 128.3 (Ar), 100.3 (C-1), 75.6 (C-2), 74.0 (C-3), 73.4 (C-5), 71.5 (C-
6), 66.9 (C-4) ppm; IR (ATR):
ν = 3065, 2926, 2856, 1720, 1601, 1584, 1491, 1451, 1363, 1315, 1246,
1176, 1090, 1067, 1025, 976, 939, 843, 801, 704, 686, 616 cm−1; HRMS (FAB+): m/z calcd. for [M+H]+,
C54H45O16, 949.2702; found, 949.2704; [α]24 = +130.2 º (c = 0.3, CHCl3).
D
4.3.9. Cyclotris-(1→6)-(2,3,4-tri-O-benzoyl-β-D-glucopyranosyl) (20)
Colorless solid: 1H NMR (400 MHz, CDCl3, TMS):
δ
= 7.91–7.82 (m, 18H, Ar), 7.53–7.41 (m,
9H, Ar), 7.36–7.27 (m, 18H, Ar), 5.87 (t, J = 9.6 Hz, 3H, H-3), 5.56 (t, J = 9.6 Hz, 3H, H-4), 5.51 (dd, J
= 9.2, 7.2 Hz, 3H, H-2), 5.01 (d, J = 6.8 Hz, 3H, H-1), 4.32 (dd, J = 12.4, 6.8 Hz, 3H, H-6), 4.13 (t, J =
13
6.8 Hz, 3H, H-5), 3.94 (d, J = 11.2 Hz, 3H, H-6) ppm; C NMR (100 MHz, CDCl3, TMS):
δ = 165.9
(C=O), 165.0 (C=O), 164.9 (C=O), 133.2 (Ar), 133.2 (Ar), 133.0 (Ar), 130.1 (Ar), 129.9 (Ar), 129.8
(Ar), 129.8 (Ar), 129.8 (Ar), 129.4 (Ar), 129.1 (Ar), 128.9 (Ar), 128.3 (Ar), 128.3 (Ar), 100.7 (C-1),
74.2 (C-5), 72.4 (C-2), 72.4 (C-3), 69.1 (C-4), 68.7 (C-6) ppm; IR (ATR):
ν = 3064, 2925, 2854, 1725,
1601, 1584, 1492, 1451, 1367, 1315, 1248, 1176, 1089, 1066, 1025, 976, 937, 851, 800, 704, 686, 617
cm−1; HRMS (ESI+): m/z calcd. for [M+Na]+, C81H66O24Na, 1445.3836; found, 1445.3827; [α]2D5 = +8.6
º (c = 0.3, CHCl3).
4.3.10. Cyclotetrakis-(1→6)-(2,3,4-tri-O-benzoyl-β-D-glucopyranosyl) (21)
Colorless solid: spectroscopic data for the product were identical to previously reported data [30].
1H NMR (400 MHz, CDCl3, TMS):
δ
= 7.91–7.78 (m, 24H, Ar), 7.49–7.39 (m, 12H, Ar), 7.35–7.27 (m,
24H, Ar), 5.85 (t, J = 9.6 Hz, 4H, H-3), 5.65–5.57 (m, 8H, H-2, H-4), 5.02 (brs, 4H, H-1), 4.25 (brs, 4H,
H-5), 4.17–4.02 (m, 8H, H-6) ppm; 13C NMR (100 MHz, CDCl3, TMS):
27
δ = 165.9 (C=O), 165.0 (C=O),

164.8 (C=O), 133.2 (Ar), 133.0 (Ar), 129.9 (Ar), 129.8 (Ar), 129.8 (Ar), 129.5 (Ar), 129.1 (Ar), 128.9
(Ar), 128.3 (Ar), 101.0 (C-1), 74.4 (C-5), 73.1 (C-3), 71.4 (C-2), 69.1 (C-4), 67.5 (C-6) ppm; IR (ATR):
ν
= 3064, 2939, 2884, 1723, 1601, 1584, 1492, 1451, 1366, 1315, 1247, 1176, 1088, 1065, 1025, 975,
936, 852, 800, 704, 685, 616 cm−1; HRMS (ESI+): m/z calcd. for [M+Na]+, C108H88O32Na, 1919.5151;
found, 1919.5147; [α]24 = +11.3 º (c = 1.0, CHCl3).
D
4.3.11. Cyclopentakis-(1→6)-(2,3,4-tri-O-benzoyl-β-D-glucopyranosyl) (22)
Colorless solid: 1H NMR (400 MHz, CDCl3, TMS):
δ
= 7.90–7.80 (m, 30H, Ar), 7.50–7.39 (m,
15H, Ar), 7.36–7.27 (m, 18H, Ar), 7.26–7.20 (m, 12H, Ar), 5.84 (t, J = 9.6 Hz, 5H, H-3), 5.54–5.45 (m,
10H, H-2, H-4), 4.87 (d, J = 7.6 Hz, 5H, H-1), 4.23–4.13 (m, 10H, H-5, H-6), 3.98 (dd, J = 11.0, 6.4 Hz,
5H, H-6) ppm; 13C NMR (100 MHz, CDCl3, TMS):
(Ar), 133.1 (Ar), 132.9 (Ar), 129.9 (Ar), 129.6 (Ar), 129.3 (Ar), 129.0 (Ar), 128.3 (Ar), 128.2 (Ar),
100.9 (C-1), 74.0 (C-5), 72.6 (C-3), 71.3 (C-2), 69.4 (C-4), 67.7 (C-6) ppm; IR (ATR): = 3063, 2925,
δ = 165.8 (C=O), 164.9 (C=O), 164.8 (C=O), 133.2
ν
2854, 1726, 1601, 1584, 1491, 1451, 1364, 1315, 1257, 1177, 1090, 1066, 1025, 975, 938, 853, 800,
705, 686, 616 cm−1; HRMS (ESI+): m/z calcd. for [M+2Na]2+, C135H110O40Na2, 1208.3179; found,
1208.3173; [α]24 = -7.9 º (c = 0.2, CHCl3).
D
4.3.12. Cyclohexakis-(1→6)-(2,3,4-tri-O-benzoyl-β-D-glucopyranosyl) (23)
Colorless solid: 1H NMR (400 MHz, CDCl3, TMS): δ = 7.95–7.86 (m, 24H, Ar), 7.80–7.74 (m,
12H, Ar), 7.47–7.40 (m, 6H, Ar), 7.40–7.32 (m, 12H, Ar), 7.32–7.27 (m, 12H, Ar), 7.24–7.20 (m, 12H,
Ar), 7.19–7.13 (m, 12H, Ar), 5.85 (t, J = 9.6 Hz, 6H, H-3), 5.51 (t, J = 8.8 Hz, 6H, H-2), 5.46 (t, J = 9.2
Hz, 6H, H-4), 4.90 (d, J = 7.6 Hz, 6H, H-1), 4.11–4.03 (m, 6H, H-6), 4.02–3.94 (m, 12H, H-5, H-6)
ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ = 165.8 (C=O), 165.0 (C=O), 164.7 (C=O), 133.0 (Ar),
133.0 (Ar), 132.8 (Ar), 130.0 (Ar), 129.9 (Ar), 129.8 (Ar), 129.6 (Ar), 129.2 (Ar), 129.1 (Ar), 128.3
(Ar), 128.2 (Ar), 128.1 (Ar), 100.6 (C-1), 73.7 (C-5), 73.1 (C-3), 71.7 (C-2), 69.7 (C-4), 66.8 (C-6)
28