Synthesis of disaccharide nucleosides utilizing the temporary protection of the 20,30-cis-diol of ribonucleosides by a boronic ester

Article abstract of DOI:10.3390/molecules22101650

Disaccharide nucleosides are an important class of natural compounds that have a variety of biological activities. In this study, we report on the synthesis of disaccharide nucleosides utilizing the temporary protection of the 20,30-cis-diol of ribonucleosides, such as adenosine, guanosine, uridine, 5-metyluridine, 5-fluorouridine and cytidine, by a boronic ester. The temporary protection of the above ribonucleosides permits the regioselective O-glycosylation of the 5'-hydroxyl group with thioglycosides using a p-toluenesulfenyl chloride (p-TolSCl)/silver triflate (AgOTf) promoter system to afford the corresponding disaccharide nucleosides in fairly good chemical yields. The formation of a boronic ester prepared from uridine and 4-(trifluoromethyl)phenylboronic acid was examined by 1H, 11B and 19F NMR spectroscopy.

Full text of DOI:10.3390/molecules22101650

molecules
Article
Synthesis of Disaccharide Nucleosides Utilizing the
Temporary Protection of the 20,30-cis-Diol of
Ribonucleosides by a Boronic Ester
Hidehisa Someya 1, Taiki Itoh 1 and Shin Aoki 1,2,
*
ID
1
Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510,
Japan; 3b17705@ed.tus.ac.jp (H.S.); 3b16703@ed.tus.ac.jp (T.I.)
Imaging Frontier Center, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
Correspondence: shinaoki@rs.noda.tus.ac.jp; Tel.: +81-4-7121-3670
2
*
Received: 8 September 2017; Accepted: 29 September 2017; Published: 1 October 2017
Abstract: Disaccharide nucleosides are an important class of natural compounds that have a variety of
biological activities. In this study, we report on the synthesis of disaccharide nucleosides utilizing the
temporary protection of the 20,30-cis-diol of ribonucleosides, such as adenosine, guanosine, uridine,
5-metyluridine, 5-fluorouridine and cytidine, by a boronic ester. The temporary protection of the
above ribonucleosides permits the regioselective O-glycosylation of the 5’-hydroxyl group with
thioglycosides using a p-toluenesulfenyl chloride (p-TolSCl)/silver triflate (AgOTf) promoter system
to afford the corresponding disaccharide nucleosides in fairly good chemical yields. The formation of
a boronic ester prepared from uridine and 4-(trifluoromethyl)phenylboronic acid was examined by
1H, 11B and 19F NMR spectroscopy.
Keywords: disaccharide nucleoside; glycosylation; boronic ester; temporary protection
1. Introduction
Disaccharide nucleosides, which contain an external sugar moiety linked to one of the
hydroxyl groups of the nucleoside via an O-glycoside bond, constitute an important class of natural
compounds [
antibiotics and other biologically-active compounds [
amicetin analogs [ 17], ezomycin [18] and some candidates for inhibitors of chitin synthase [19]
1
–
7]. They are found in biopolymers, such as tRNA and poly(ADP-ribose), as well as
5
,6,
8–
11]. Adenophostins [12 15], HF-7 [16],
–
6,
are typical examples of disaccharide nucleosides that contain adenine, guanine, cytosine and uracil
moieties, respectively. Therefore, disaccharide nucleosides and their analogs would be expected to be
good drug candidates.
Several strategies for the synthesis of disaccharide nucleosides such as enzymatic O-glycosylation [20
,21],
chemical N-glycosylation [ 16 22 24] and chemical O-glycosylation [ 14 16 18 19 24 37] have been
5
,9
,
,
–
7,
9
,
,
,
,
,
–
reported to date. Chemical O-glycosylation is often useful for the large-scale synthesis of the desired
disaccharide nucleosides in higher chemical yields compared to chemical N-glycosylation. However,
the neutralization of promoters, which are generally Lewis or Brønsted acids, by the nucleobase
moieties would be a possible drawback. Moreover, it is reported that an excess amount of the
glycosyl donor is required for glycosylation at the hydroxyl site to be complete, because it is likely
that glycosylation preferentially proceeds on the nucleobase or other Lewis basic site [18,32,34,36].
Side reactions such as depurination (cleavage of the anomeric C–N bond of nucleosides), anomerization
reaction and trans-purinylation have also been reported [35,38,39].
We previously reported on the synthesis of disaccharide nucleosides
O-glycosylation of 2’-deoxyribonucleoside with the thioglycosyl donor (PG: protecting group)
(Figure 1a) [40]. Among the glycosyl promoters tested, a combination of p-toluenesulfenyl chloride
3 by the direct
2
1
Molecules 2017, 22, 1650; doi:10.3390/molecules22101650
www.mdpi.com/journal/molecules

Molecules 2017, 22, 1650
2 of 21
(p-TolSCl) and silver triflate (AgOTf) was found to give the corresponding products in moderate to high
chemical yields. These results prompted us to investigate the synthesis of disaccharide nucleosides
via the O-glycosylation of ribonucleosides. The synthesis of disaccharide nucleosides using protected
ribonucleosides as glycosyl acceptors, which requires tedious protecting group manipulations, has been
reported in previous studies [7,9,14,16,18,19,24,32–37]. The development of direct and regioselective
O-glycosylation using unprotected or temporarily-protected ribonucleosides would afford a more
convenient synthetic route to prepare various biologically-active derivatives.
In this manuscript, we report on the O-glycosylation of unprotected ribonucleosides
50-hydroxyl group via the temporary protection of the 20,30-cis-diol by a boronic ester
. It has been
reported that boronic and borinic acids are capable of forming the cyclic esters with carbohydrate
derivatives [41 42], and such derivatives have been utilized for regio- and/or stereo-selective alkylation,
acylation, silylation and glycosylation [43 53]. In our strategy, the ribonucleoside is treated
with the boronic acid to prepare in situ, which is
to temporarily protect the 20,30-cis-diol of
then O-glycosylated at the 5‘-hydroxyl group with the glycosyl donor to afford the disaccharide
nucleosides in a regioselective manner (Figure 1b) (in this manuscript, “disaccharide nucleosides”
4 at the
6
,
–
4
5
4
6
7
8
include the glycosylated deoxyribonucleosides and ribonucleosides, due to the generally-used
terminology).
Figure 1.
(a
) O-glycosylation of 20-deoxyribonucleoside with a thioglycosyl donor using the
p-toluenesulfenyl chloride (p-TolSCl)/silver triflate (AgOTf) promoter system; (
O-glycosylation of ribonucleoside at the 5 -OH position via temporary protection of 2 ,3 -cis-diol.
b
) regioselective
0
0
0
2. Results and Discussion
2.1. O-Glycosylation of Nucleosides with Thioglycosyl Donors
We first examined the O-glycosylation of uridine 10 with the thiomannoside
equivalents of p-TolSCl and 6.0 equivalents of AgOTf [55 56] against 10 (i.e., 2.0 equivalents of p-TolSCl
and 4.0 equivalents of AgOTf against according to our previous paper [40]). Thioglycosides are one
9 [54] using 3.0
,
9

Molecules 2017, 22, 1650
3 of 21
of the most popular glycosyl donor due to their ease of preparation and modification, high stability
and the many available activation methods [25 29 57]. After the glycosylation and crude purification,
–
,
the resulting compounds were acetylated to permit the desired products to be purified more easily.
The results for the glycosylation reactions are summarized in Table 1. In Entry 1, the glycosylation
of 10 with
9 without boronic acid derivatives gave a complex mixture. In Entry 2, a mixture of 10
and phenylboronic acid 11a was co-evaporated with pyridine and 1,40-dioxane followed by stirring in
0
1,4-dioxane under reflux conditions [44] to prepare the temporary 2 ,3 -cis-diol-protected intermediate
6
(in Figure 1), to which
9
(corresponding to
7
in Figure 1) was added. The glycosylation of
8 in Figure 1) in 41% (α/β = 1.6/1) in a regioselective
6
proceeded
at its 50-OH to afford 12 (corresponding to
manner. The formation of a 100,50-glycosidic linkage of 12 was confirmed by comparing its 1H NMR
spectrum with that of the authentic sample prepared by another synthetic route, in which the chemical
yield was 20% for four steps from 10 to 12 (excluding the steps required for the preparation of
9; see
Scheme S1 in the Supplementary Materials). In Entry 3, a mixture of 10 and 11a was co-evaporated
9
,
with pyridine and 1,4-dioxane, and the resulting mixture was treated with promoters to give 12 in a
yield nearly similar to that for Entry 2. In the following Entries 4–10, therefore, glycosylation reactions
were conducted using a procedure similar to that used in Entry 3 for easy manipulation.
Table 1. O-glycosylation of uridine 10 with the thiomannoside
9 in the absence and presence of
boronic acid.
Boronic Acid b
Entry
Solvent
Condition
Yield (for 3 Steps) c
◦
1 a
2 a,d
3 a,e
4 a,e
5 a,e
6 a,e
7 a,e
8 a,e
9 a,e
10 e,f
11 a,e
-
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
1,4-Dioxane
CH2Cl2
EtCN
−20 C, 1.5 h
<16% (complex mixture)
41% (α/β = 1.6/1)
45% (α/β = 1.6/1)
39% (α/β = 1.8/1)
51% (α/β = 1.8/1)
46% (α/β = 1.8/1)
27% (α/β = 3.3/1)
trace
◦
PhB(OH)2 (11a)
−20 C, 1.5 h
◦
11a
−20 C, 1.5 h
◦
4-MeOPhB(OH)2 (11b)
4-CF3PhB(OH)2 (11c)
2,4-F2PhB(OH)2 (11d)
−20 C, 1.5 h
◦
−20 C, 1.5 h
◦
−20 C, 1.5 h
11c
11c
11c
11c
r.t., 1.5 h
◦
−40 C, 1.5 h
◦
−40 C, 1.5 h
61% (α/β = 1.6/1)
57% (α/β = 1.5/1)
30% (α/β = 1.6/1)
◦
EtCN
EtCN
−40 C, 1.5 h
◦
4-CH3(CH2)5PhB(OH)2 (11e)
−40 C, 1.5 h
a
Glycosylation reactions were carried out in the presence of 1.5 equivalents of
9, 3.0 equivalents of p-TolSCl and 6.0
equivalents of AgOTf against 10. Acetylation reactions were carried out in the presence of ca. 10 equivalents of
c
Ac2O (acetic anhydride) and catalytic amount of DMAP. b Stoichiometry of 11 was 1.5 equivalents against 10
. The
α
/
β
ratio was determined by 1H NMR. d A mixture of 10 and 11a was co-evaporated with pyridine and 1,4-dioxane,
10 and 11 was co-evaporated with pyridine and
1,4-dioxane and treated with promoters. Glycosylation reactions were carried out in the presence of 1.5 equivalents
e
and then, a solution of
9
in MeCN was added. A mixture of
9,
f
of 9, 1.8 equivalents of p-TolSCl and 3.6 equivalents of AgOTf against 10 as followed by acetylation with Ac2O (ca.
10 equivalents) and DMAP (catalytic amount).
The electrostatic effect of the substituents of the boronic acid was studied in Entries 4–6.
Glycosylations using 4-methoxyphenylboronic acid (4-MeOPhB(OH)2) 11b, 4-(trifluoromethyl)
phenylboronic acid (4-CF3PhB(OH)2) 11c and 2,4-difluorophenylboronic acid (2,4-F2PhB(OH)2) 11d
were conducted to give 12 in 39%, 51% and 46%, respectively, suggesting the positive effect of
electron-withdrawing moieties such as -CF3 and -F on the aromatic ring of the boronic acid.

Molecules 2017, 22, 1650
4 of 21
The solvent effect was also examined in Entries 7–9. It is well known that glycosylation in an
ether-type solvent such as Et2O, THF and 1,4-dioxane enhances -stereoselectivity [58 59]. As shown
in Entry 7, 1,4-dioxane improved the -stereoselectivity of the reaction, while the chemical yield
α
,
α
was unsatisfactory. In Entry 8, CH2Cl2 gave a negligible amount of 12, due to the low solubility of
the substrates. Glycosylation using EtCN gave 12 in higher chemical yield (Entry 9) than those for
1,4-dioxane (Entry 7) and MeCN (Entry 3), and the stereoselectivity was nearly the same as that in
MeCN (Entry 3).
In Entry 10, glycosylation using lower equivalents of promoters (1.8 equivalents of p-TolSCl
and 3.6 equivalents of AgOTf against 10) than those in Entry 9 gave similar results. Therefore,
3.0 equivalents and 6.0 equivalents of p-TolSCl and AgOTf were used in the following O-glycosylations
to complete the reactions. In Entry 11, phenylboronic acid having a C6 alkyl chain 11e was used to
improve the solubility of the boronic ester, albeit the chemical yield was not improved.
The O-glycosylation of adenosine 13 with 9 was examined next. As shown in Entry 1 of Table 2,
O-glycosylation in the absence of boronic acid derivatives gave a complex mixture, as in the case
of uridine (Entry 1 in Table 1). In Entries 2 and 3, in which PhB(OH)2 11a and 4-CF3PhB(OH)2 11c
were used, 14 was produced, but the yields were lower (14% and 11%, respectively) than those of
10 in Entries 3 and 9 of Table 1, which can be attributed to the trans-purinylation of 13 and/or 14
(N-mannosyl adenine 15 was isolated in 6–27%) [36].
Table 2. O-glycosylation of adenosine 13 with thiomannoside
9 in the absence and presence of
boronic acid.
Entry a
Solvent
Condition
Yield of 14 (for 3 Steps) c
Yield of 15 (for 3 Steps)
Boronic Acid b
◦
1
-
MeCN
MeCN
EtCN
−20 C, 1.5 h
<10% (complex mixture)
14% (α/β = 1/1.0)
11% (α/β = 1/1.2)
not isolated
6%
◦
2 d
3 d
PhB(OH)2 (11a)
4-CF3PhB(OH)2
−20 C, 1.5 h
◦
(11c
)
−40 C, 1.5 h
27%
a
Glycosylation reactions were carried out in the presence of 1.5 equivalents of
9, 3.0 equivalents of p-TolSCl and 6.0
equivalents of AgOTf against 13. Acetylation reactions were carried out in the presence of ca. 10 equivalents of
c
Ac2O and the catalytic amount of DMAP. b Stoichiometry of 11 was 1.5 equivalents against 13
.
The
α/β ratio was
determined by 1H NMR. d A mixture of
with promoters.
9, 13 and 11 was co-evaporated with pyridine and 1,4-dioxane and treated
We attempted the O-glycosylations of various nucleosides 10
thiogalactoside 23, in which the hydroxyl groups were protected by benzoyl groups to achieve
-selective O-glycosylation by neighboring group participation at the O2 benzoyl group (Table 3).
The formation of a
-100,50-glycosidic linkage between the galactose moiety and ribonucleoside in the
products 24
32 was confirmed by NNR measurements (1H NMR, 13C NMR, 1H-1H COSY, HMQC and
HMBC). As listed in Table 3, the reaction of the unprotected and N-protected adenosine, 13 and 16 60],
afforded the desired products 24 and 25 in 42% and 30%, respectively (Entries 1 and 2). Note that
, 13 and 16–22 with the
β
β
–
[
β-
β-
the use of unprotected adenosine 13 gave a better yield than that for the protected 16, phenomena
similar to the O-glycosylation of 2’-deoxyadenosine reported by us in a previous study (Figure 1a) [40].

Molecules 2017, 22, 1650
5 of 21
It should also be noted that the reaction of 13 with 23 (Entry 1) gave negligible amounts of N-galactosyl
adenine as a byproduct unlike the use of the mannosyl donor in an O-glycosylation reaction (Entries 2
9
and 3 in Table 2). In Entries 3 and 4, the reaction of the unprotected and N-protected guanosine, 17 and
18 [61], afforded the corresponding products β-26 and β-27 in 12% and 44%, respectively. The higher
yield of
N-protected 18 in EtCN than that from the unprotected 17. In Entry 5, the O-glycosylation of uridine
10 with 23 gave the desired product 28 in 42% yield, and the electrophilic substitution reaction at
the 5-position of the uracil moiety of 10 and/or 28 with the p-toluenesulfenyl cation was observed
(ca. 15%) [62]. In Entries 6 and 7, the O-glycosylation of 5-metyluridine 19 and 5-fluorouridine 20
afforded the corresponding products 29 and 30 in 53% and 61%, respectively. In Entries 8 and 9,
the reaction of the unprotected and N-protected cytidine, 21 and 22 63], afforded 31 and 32 in
31 in slightly
β-27 is possibly due to better solubility of the boronic ester intermediate prepared from the
β-
β-
β-
β-
[
β-
β-
55% and 40%, respectively. It should be noted that the use of the unprotected 21 gave
higher yield than β-32 from the protected 22.
β-
Table 3. O-glycosylation of nucleosides 10, 13 and 16–22 with the thiogalactoside 23.
Entry a
Acceptor
Product
Yield (for 2 Steps)
1
2
3
4
5
6
7
8
9
13 (Ade)
16 (AdeBz
17 (Gua)
β-24
β-25
β-26
β-27
β-28
β-29
β-30
β-31
β-32
42%
30%
12%
44%
)
18 (GuaiBu
10 (Uri)
)
42% (ca. 15%: nucleobase = 5-STol-Uri)
19 (5-Me-Uri)
20 (5-F-Uri)
21 (Cyt)
53%
61%
55%
40%
22 (CytBz
)
a
Glycosylation reactions were carried out in the presence of 1.5 equivalents of 23, 3.0 equivalents of p-TolSCl and
6.0 equivalents of AgOTf against the acceptor (10 13 or 16 22). Stoichiometry of 11c was 1.5 equivalents against
acceptor (10 13 or 16 22). A mixture of 23, acceptor (10 13, or 16 22) and 11c was co-evaporated with pyridine and
1,4-dioxane and treated with promoters.
,
–
,
–
,
–
The O-glycosylation of 5-fluorouridine 20 with glucosyl, galactosyl and mannosyl donors was
also examined. As summarized in Table 4, the glucosyl donor 33 64] and the galactosyl donor 23
afforded the corresponding products 35 and 30 in reasonably acceptable yields, while the use of
the mannosyl donor 34 [65] gave a mixture.
[
β-
β-

Molecules 2017, 22, 1650
6 of 21
Table 4. O-Glycosylation of 5-fluorouridine 20 with thioglycosides 23, 33 and 34.
BzO
OBz
O
BzO
BzO
BzO
OBz
O
OBz
O
BzO
BzO
STol
STol
BzO
OBz
BzO
STol
34 ( -Man)
33 ( -Glc)
23 ( -Gal)
Entry a
Donor
Product Yield (for 2 Steps)
1
2 b
3
33 (β-Glc)
23 (β-Gal)
34 (α-Man)
β-35
β-30
α-36
54%
61%
<39% (mixture)
a
Glycosylation reactions were carried out in the presence of 1.5 equivalents of donor (23
of p-TolSCl and 6.0 equivalents of AgOTf against 20. Stoichiometry of 11c was 1.5 equivalents against 20. A mixture
of donor (23 33 or 34), 20 and 11c was co-evaporated with pyridine and 1,4-dioxane and treated with promoters.
, 33 or 34), 3.0 equivalents
,
b
Taken from Entry 7 of Table 3 in this manuscript.
2.2. O-Glycosylation of Nucleosides with Thioglycosyl Donors Containing the Boronic Acid Moiety on the
Leaving Group
Shen and co-workers recently reported on the 1,2-cis glycosylation of some simple alcohols using
glucosyl donors containing a boronic acid moiety on the leaving group, which is referred to leaving
group-based aglycon delivery [48]. These results prompted us to examine the use of the thioglycosyl
donor 37 containing a boronic acid moiety on the leaving group, which was expected to form a boronic
ester with the 20,30-cis-diol of ribonucleoside 38 to give the intermediate 39 (Figure 2). It was expected
that the O-glycosylation of 39 would produce 40 in a pseudo-intramolecular manner.
Figure 2. Regio- and stereo-selective O-glycosylation of the ribonucleoside utilizing the glycosyl donor
containing a boronic acid moiety.
In Table 5, the results for the O-glycosylation of uridine 10 and adenosine 13 with the glycosyl
donors 41 and 42 (Schemes S2 and S3 in the Supplementary Materials) are summarized. In Entries
1 and 2, the reactions of 10 and 13 with 41 afforded the corresponding products 12 and 14 in 44%

Molecules 2017, 22, 1650
7 of 21
(α/β = 1.9/1) and 16% (
α
/β
= 1.3/1), respectively. In Entries 3 and 4, 42 gave the almost the same
chemical yields and stereoselectivities as those in Entries 1 and 2. These results are similar to Entry 3 in
Table 1 and Entry 2 in Table 2, in which 10 or 13 was reacted with and phenylboronic acid 11a under
9
the same conditions in Table 5, indicating that the introduction of a boronic acid on the thiophenyl
leaving group in our reactions has a negligible effect on the overall reaction.
Table 5. O-glycosylation of uridine 10 and adenosine 13 with thioglycosides 41 and 42.
Entry a
Donor
Acceptor
Product
Yield (for 3 Steps) b
1
2
3
4
41 (Ar = 2-PhB(OH)2) (α form)
41 (Ar = 2-PhB(OH)2) (α form)
10 (Nucleobase = Uri)
13 (Nucleobase = Ade)
10 (Nucleobase = Uri)
13 (Nucleobase = Ade)
12
14
12
14
44% (α/β = 1.9/1)
16% (α/β = 1.3/1)
36% (α/β = 2.1/1)
14% (α/β = 1.1/1)
42 (Ar = 4-PhB(OH)2) (
42 (Ar = 4-PhB(OH)2) (
α
/
β
= 1/1.0)
= 1/1.0)
α
/β
a
Glycosylation reactions were carried out in the presence of 1.5 equivalents of donor (41 or 42), 3.0 equivalents of
p-TolSCl and 6.0 equivalents of AgOTf against the acceptor (10 or 13). A mixture of donor (41 or 42) and acceptor
(
10 or 13) was co-evaporated with pyridine and 1,4-dioxane and treated with promoters. Acetylation reactions were
carried out in the presence of ca. 10 equivalents of Ac2O and a catalytic amount of DMAP. b The
α/β ratio was
determined by 1H NMR.
2.3. Deprotection of the Glycosylation Products
The deprotection of the glycosylation product 12
aqueous LiOH to afford 43 and 43, which were separated by silica gel column chromatography.
The deprotection of the benzyl groups of 43 and 43 under traditional reaction conditions (10%
Pd/C with H2 gas) gave 44 and 44, respectively (Scheme 1a) [66]. The deprotection of 30 by
treatment with MeNH2 [67] afforded β-45 [68] in 62% (Scheme 1b).
(α/β = 1.6/1) involved a treatment with
α
-
β-
α
-
β-
α
-
β-
β-
Scheme 1. Deprotection of 12 (a) and β-30 (b).

Molecules 2017, 22, 1650
8 of 21
2.4. Interaction of Uridine and 4-(Trifluoromethyl)phenylboronic Acid Studied by 1H, 11B and 19
NMR Spectroscopy
F
The temporary protection of the 2’3’-cis-diol of ribonucleoside with a boronic acid was
checked by NMR spectroscopy. The 1H, 11B and 19F NMR measurements of uridine 10
4-(trifluoromethyl)phenylboronic acid 11c and a mixture of 10 and 11c were undertaken in CD3CN
(Figure 3). For the preparation of the third sample, a mixture of 10 and 11c was azeotroped with
pyridine and 1,4-dioxane, followed by stirring in 1,4-dioxane under the reflux conditions for 1
h. For comparison, 11c was azeotroped in a similar manner, and the 11B and 19F NMR spectra
of the resulting mixture were obtained. As shown in Figure 3a,b, the peaks for the 20 and 30
hydroxyl groups disappeared, and the 20 and 30 proton signals were shifted considerably upfield
upon the addition of 11c. In Figure 3c–e, it was assumed that the peaks at 21 ppm, 28 ppm and 32
ppm correspond to a 2,4,6-tris[4-(trifluorometyl)phenyl]boroxine pyridine complex, the proposed
,
structure of which is 49 (some NMR spectra of boroxine pyridine complexes were reported [69
11c or 2,4,6-tris[4-(trifluorometyl)phenyl]boroxine and the desired boronic ester 47, respectively.
In Figure 3f–h, we assumed that the peaks at 63.3 ppm, 63.2 ppm and 62.8 ppm correspond to 47
11c or 2,4,6-tris[4-(trifluorometyl)phenyl]boroxine and 49, respectively.
–71]),
−
−
−
,
Figure 3. Cont.

Molecules 2017, 22, 1650
9 of 21
Figure 3. Possible assignment of intermediates from the reaction of uridine 10 and 4-CF3PhB(OH)2
◦
11c in 1H, 11B and 19F NMR spectra (in CD3CN at 25 C). ( ) 1H NMR of 10; ( ) 1H NMR of a mixture
a b
46; (c) 11B NMR of 11c; (d) 11B NMR of a mixture 48; (e) 11B NMR of a mixture 46; (f) 19F NMR of 11c;
(g) 19F NMR of a mixture 48; (h) 19F NMR of a mixture 46.

Molecules 2017, 22, 1650
10 of 21
3. Materials and Methods
3.1. General Information
Reagents and solvents were commercially purchased, were the highest commercial quality
available and were used without further purification. Anhydrous CH2Cl2 was prepared by distillation
from calcium hydride. Acetonitrile and propionitrile were prepared by distillation from calcium
hydride and the successive distillation from phosphorus (V) oxide. Anhydrous 1,4-dioxane was
prepared by distillation from sodium. All aqueous solutions were prepared using deionized water.
1H (300 and 400 MHz), 11B (128 MHz), 13C (75 and 100 MHz) and 19F (376 MHz) NMR
spectra were recorded on a JEOL Always 300 (JEOL, Tokyo, Japan) and a JEOL Lamda 400
(JEOL, Tokyo, Japan) spectrometer. Tetramethylsilane (TMS) was used as an internal reference
for 1H and 13C NMR measurements in CDCl3, CD3OD, CD3CN, acetone-d6 and DMSO-d6.
3-(Trimethylsilyl)propionic-2,2,3,3-d4 acid sodium (TSP) was used as an internal reference for 1H NMR
measurements in D2O. 1,4-Dioxane was used as an internal reference for 13C NMR measurements in
D2O. 11B and 19F NMR spectra were measured in a quartz NMR tube. The boron trifluoride-diethyl
ether complex (BF3
trifluoroacetic acid (TFA) in CDCl3 was used as an external reference (
·
OEt2) in CDCl3 was used as an external reference (0 ppm) for 11B NMR, and
76.5 ppm) for 19F NMR.
−
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. Elemental analyses were performed on a
Perkin-Elmer CHN 2400 analyzer (PerkinElmer, Massachusetts, USA). Optical rotations were measured
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 silica gel column chromatography were
performed using Merck Silica gel 60 F254 plate (Merck KGaA, Darmstadt, Germany) and Fuji Silica
Chemical FL-100D (Fuji Silysia Chemical, Aichi, Japan), respectively. HPLC experiments were carried
out using a system consisting of a PU-2089 Plus intelligent HPLC pump (JASCO, Tokyo, Japan),
a UV-2075 Plus intelligent UV-visible detector (JASCO, Tokyo, Japan), a Rheodine injector (Model
¯
No. 7125) and a Chromatopak C-R8A (Shimadzu, Kyoto, Japan). For preparative HPLC, a SenshuPak
Pegasil ODS column (Senshu Scientific Co., Ltd., Tokyo, Japan) (20ϕ × 250 mm, No. 0509271H)
was used. GPC experiments were carried out using a system consisting of a POMP 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 Analyrical Industry Co., Ltd., Tokyo, Japan), equipped with two GPC columns, JAIGEL-1H
and JAIGEL-2H (Japan Analyrical Industry Co., Ltd., Tokyo, Japan) (20ϕ × 600 mm, No. A605201
and A605204).
3.2. Synthesis of Compounds
20,30-Di-O-acetyl-50-O-(600-O-acetyl-200,300,400-tri-O-benzyl-
Table 1): A mixture of (28.4 mg, 48.6 mol), 10 (7.9 mg, 32.4
co-evaporated with anhydrous pyridine (three times) and anhydrous 1,4-dioxane (three times) and
dissolved in anhydrous 1,4-dioxane (320 L). This reaction mixture was stirred under reflux conditions
for 1 h and concentrated under reduced pressure. The resulting mixture was stirred with activated 4 Å
molecular sieves (64 mg) in anhydrous EtCN (640 L) at room temperature for 30 min and then cooled
α
/
β
-D-mannopyranosyl)uridine (12) (Entry 9 in
mol) and 11c (9.3 mg, 49.0 mol) was
9
µ
µ
µ
µ
µ
to
−
40 ◦C, to which p-TolSCl (12.8
µ
L, 96.8
µ
mo◦l) and AgOTf (49.9 mg, 194
µmol) were added at the
40 C, the reaction mixture was quenched with saturated
same temperature. After stirring for 1.5 h at
−
aqueous NaHCO3, diluted with CHCl3 and filtered through Celite. The organic layer was washed with
saturated aqueous NaHCO3 and brine, dried over Na2SO4, filtered and concentrated under reduced
pressure. The remaining residue was purified by silica gel column chromatography (CHCl3/MeOH =
1/0–50/1) to give 50-O-(600-O-acetyl-200,300,400-tri-O-benzyl-
α
/β-D-mannopyranosyl)uridine including
a small amount of byproducts as a colorless syrup (15.2 mg). To the resulting crude compound in

Molecules 2017, 22, 1650
11 of 21
anhydrous pyridine (200
µ
L), Ac2O (20.4
µ
L, 21.6◦µmol, 10.0 equiv. based on the crude compound)
and DMAP (catalytic amount) 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 silica gel column chromatography (CHCl3/MeOH = 1/0–90/1) to give 12 as a colorless
1
amorphous solid (15.8 mg, 61% yield for 3 steps,
α
/
β
= 1.6/1): H NMR (300 MHz, CDCl3, TMS):
δ = 8.56 (s, 0.6H), 8.29 (s, 0.4H), 7.89 (d, J = 8.1 Hz, 0.4H), 7.41–7.19 (m, 15.6H), 6.29 (d, J = 7.2 Hz, 0.4H),
6.15–6.05 (m, 0.6H), 5.55 (dd, J = 5.1, 1.2 Hz, 0.4H), 5.39 (dd, J = 8.1, 1.8 Hz, 0.6H), 5.33–5.23 (m, 2H),
5.01–4.86 (m, 2H), 4.80–4.55 (m, 4.6H), 4.46 (s, 0.4H), 4.39–4.21 (m, 3H), 4.13 (dd, J = 10.5, 1.8 Hz, 0.4H),
4.05 (d, J = 2.7 Hz, 0.4H), 3.99–3.84 (m, 2.2H), 3.84–3.68 (m, 1.6H), 3.68–3.57 (m, 1H), 3.44 (dt, J = 9.9, 6.9
Hz, 0.4H), 2.15 (s, 1.2H), 2.12 (s, 1.8H), 2.09 (s, 1.2H), 2.09 (s, 1.8H), 2.06 (s, 1.8H), 2.00 (s, 1.2H) ppm;
13C NMR (100 MHz, CDCl3, TMS):
δ = 170.9, 170.8, 170.1, 169.8, 169.7, 169.6, 162.8, 162.6, 150.8, 150.4,
141.0, 138.8, 138.2, 137.9, 137.8, 137.7, 128.5, 128.5, 128.4, 128.4, 128.1, 128.1, 128.0, 127.9, 127.8, 127.7,
127.6, 103.3, 103.2, 100.0 (C100 , 1JCH = 153.6 Hz, β form), 98.5 (C100 , 1JCH = 171.0 Hz, α form), 86.3, 85.2,
82.8, 82.1, 81.4, 80.1, 77.3, 75.2, 75.2, 75.0, 74.8, 74.7, 74.3, 73.9, 73.7, 73.5, 72.9, 72.8, 72.5, 72.2, 71.9, 71.2,
71.0, 68.6, 66.8, 63.3, 63.2, 20.9, 20.9, 20.7, 20.6, 20.4 ppm; IR (ATR):
ν = 3200, 3065, 3032, 2930, 2877,
1742, 1691, 1498, 1455, 1373, 1310, 1231, 1073, 1042, 1029, 925, 901, 811, 737, 697, 635, 597 cm−1; HRMS
(FAB+): calcd. for [M + H]+, C42H47N2O14, 803.3027; found, 803.3028.
20,30-Di-O-acetyl-50-O-(600-O-acetyl-200,300,400-tri-O-benzyl-
7-N-(60-O-acetyl-20,30,40-tri-O-benzyl-
-D-mannopyranosyl)adenine (15) (Entry 2 in Table 2): A mixture of
(28.4 mg, 48.6 mol), 13 (8.6 mg, 32.2 mol) and 11a (5.9 mg, 48.4 mol) was co-evaporated with
anhydrous pyridine (three times) and anhydrous 1,4-dioxane (three times) and dissolved in anhydrous
1,4-dioxane (320 L). This reaction mixture was stirred under reflux conditions for 1 h and concentrated
under reduced pressure. The resulting mixture was stirred with activated 3 Å molecular sieves (64 mg)
in anhydrous MeCN (640 L) at room temperature for 30 min and then cooled to
20 ◦C, to which
p-TolSCl (12.8 L, 96.8 mol) were added at the same temperature.
After stirring for 1.5 h at
α/β-D-mannopyranosyl)adenosine (14) and
α
9
µ
µ
µ
µ
µ
−
µ
µ
mol) and AgOTf (49.9 mg, 194
20 C, the reaction mixture was quenched with saturated aqueous NaHCO3,
µ
◦
−
diluted with CHCl3 and filtered through Celite. The organic layer was washed with saturated
aqueous NaHCO3 and brine, dried over Na2SO4, filtered and concentrated under reduced pressure.
The resulting residue was purified by silica gel column chromatography (CHCl3/MeOH = 1/0–10/1)
to give 50-O-(600-O-acetyl-200,300,400-tri-O-benzyl-
α
/β
-D-mannopyranosyl)adenosine including a small
amount of byproducts as a colorless syrup (6.3 mg). To the resulting crude compound in anhydrous
pyridine (200 L), Ac2O (8.0 L, 84.9 mol, 10.0 equiv. based on the crude compound) and DMAP
µ
µ
µ
(catalytic amount) 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 aqueous NaHCO3 and brine, dried over Na2SO4, filtered and
concentrated under reduced pressure. The residue was purified by silica gel column chromatography
(CHCl3/MeOH = 1/0–5/1) to give 14 as a colorless amorphous solid (3.8 mg, 14% yield for 3 steps,
α
/β
= 1/1.0) and 15 as a colorless syrup (1.1 mg, 6% yield for 3 steps): 14
(α/β
= 1/1.0); 1H NMR
(300 MHz, CDCl3, TMS): = 8.36 (s, 1H), 8.35 (s, 0.5H), 7.93 (s, 0.5H), 7.42–7.27 (m, 13.5H), 7.16 (t,
δ
J = 2.7 Hz, 1.5H), 6.31 (d, J = 6.0 Hz, 0.5H), 6.20 (d, J = 5.7 Hz,0.5H), 5.92 (t, J = 5.7 Hz, 0.5H), 5.78–5.67
(m, 1H), 5.67–5.52 (m, 2.5H), 4.97–4.83 (m, 3H), 4.77–4.45 (m, 5H), 4.45–4.16 (m, 3H), 4.05–3.82 (m, 3H),
3.82–3.62 (m, 1H), 3.58–3.41 (m, 1H), 2.15 (s, 1.5H), 2.13 (s, 1.5H), 2.07 (s, 1.5H), 2.06 (s, 1.5H), 2.03 (s,
1.5H), 2.01 (s, 1.5H) ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ
= 171.1, 170.9, 169.9, 169.6, 169.4, 169.3,
155.5, 155.4, 153.4, 153.1, 150.0, 150.0, 139.7, 138.7, 138.4, 138.2, 138.1, 138.0, 137.9, 128.4, 128.4, 128.4,
128.4, 128.4, 128.2, 128.1, 127.9, 127.9, 127.8, 127.7, 127.7, 127.6, 127.6, 127.3, 120.1, 119.8, 100.9 (C100
1JCH = 156.9 Hz, form), 98.6 (C100 , 1JCH = 168.5 Hz,
form), 85.7, 85.2, 82.3, 82.2, 81.4, 80.2, 75.3, 75.1,
75.0, 74.5, 74.4, 74.3, 74.1, 73.9, 73.1, 73.0, 72.4, 71.7, 71.1, 70.7, 69.3, 66.6, 63.5, 63.4, 21.0, 20.9, 20.7, 20.6,
20.4, 20.4 ppm; IR (ATR): = 3332, 3171, 3066, 3032, 2927, 2875, 1742, 1635, 1595, 1498, 1473, 1455, 1424,
,
β
α
ν

Molecules 2017, 22, 1650
12 of 21
1366, 1332, 1293, 1234, 1213, 1071, 1042, 1027, 903, 825, 799, 736, 697, 667, 649, 602 cm−1; HRMS (FAB+):
calcd. for [M + H]+, C43H48N5O12, 826.3299; found, 826.3294; 15; 1H NMR (300 MHz, CDCl3, TMS):
δ
= 8.44 (s, 1H), 7.90 (s, 1H), 7.41–7.28 (m, 10H), 7.23–7.19 (m, 1H), 7.18–7.08 (m, 2H), 6.86–6.74 (m,
2H), 5.88 (s, 2H), 5.61 (s, 1H), 4.97 (d, J = 10.8 Hz, 1H), 4.77 (s, 2H), 4.70 (d, J = 6.3 Hz, 1H), 4.66 (d,
J = 6.6 Hz, 1H), 4.45 (dd, J = 12.0, 3.3 Hz, 1H), 4.26 (dd, J = 12.0, 2.4 Hz, 1H), 4.25 (d, J = 11.1 Hz, 1H),
4.11 (t, J = 9.6 Hz, 1H), 3.96 (s, 1H), 3.88 (dd, J = 9.3, 2.7 Hz, 1H), 3.76 (dt, J = 9.6, 3.0 Hz, 1H), 1.98 (s,
3H) ppm; 13C NMR (75 MHz, CDCl3, TMS):
δ = 170.0, 160.7, 153.2, 151.6, 143.0, 137.3, 135.9, 128.7,
128.6, 128.5, 128.5, 128.4, 128.3, 128.3, 128.2, 127.7, 111.8, 85.7, 82.8, 76.7, 76.1, 75.4, 75.1, 73.0, 72.5, 62.2,
20.7 ppm; IR (ATR): ν = 3449, 3371, 3167, 3089, 3064, 3031, 2927, 2873, 1742, 1627, 1587, 1551, 1497,
1475, 1455, 1425, 1389, 1365, 1340, 1296, 1228, 1094, 1019, 966, 909, 887, 825, 736, 695, 602 cm−1; HRMS
(FAB+): calcd. for [M + H]+, C34H36N5O6, 610.2666; found, 610.2668; [α]25 = −20.6 (c = 1.0, CHCl3).
D
50-O-(200,300,400,600-Tetra-O-benzoyl-
of 23 (80.4 mg, 114 mol), 13 (20.4 mg, 76.3
with anhydrous pyridine (three times) and anhydrous 1,4-dioxane (three times) and dissolved in
anhydrous 1,4-dioxane (760 L). This reaction mixture was stirred under reflux conditions for 1 h and
β
-D-galactopyranosyl)adenosine (
β
-
24) (Entry 1 in Table 3): A mixture
mol) was co-evaporated
µ
µmol) and 11c (21.7 mg, 114
µ
µ
concentrated under reduced pressure. The resulting mixture was stirred with activated 4 Å molecular
sieves (150 mg) in anhydrous EtCN (1.50 mL) at room temperature for 30 min and then cooled to
−
40 ◦C, to which p-TolSCl (30.3
same temperature. After stirring for 1.5 h at
µ
L, 229
µ
mol) ◦and AgOTf (117.6 mg, 458
µmol) were added at the
40 C, the reaction mixture was quenched with saturated
−
aqueous NaHCO3, diluted with CHCl3 and filtered through Celite. The organic layer was washed with
saturated aqueous NaHCO3 and brine, dried over Na2SO4, filtered and concentrated under reduced
pressure. The resulting residue was purified by silica gel column chromatography (CHCl3/MeOH =
1
1/0–30/1) to give
β-
24 as a colorless solid (27.4 mg, 42% yield): H NMR (400 MHz, CDCl3, TMS):
δ
= 8.46 (s, 1H), 8.07 (dd, J = 7.6, 2.0 Hz, 2H), 8.02–7.98 (m, 3H), 7.97–7.93 (m, 2H), 7.83–7.79 (m, 2H),
7.57–7.51 (m, 1H), 7.49 (t, J = 7.6 Hz, 1H), 7.45–7.32 (m, 8H), 7.20 (t, J = 8.0 Hz, 2H), 6.47 (brs, 2H), 6.13
(d, J = 6.4 Hz, 1H), 6.04 (d, J = 3.2 Hz, 1H), 5.90 (dd, J = 10.4, 8.0 Hz, 1H), 5.73 (dd, J = 10.4, 3.2 Hz, 1H),
4.92 (d, J = 8.0 Hz, 1H), 4.70 (dd, J = 11.2, 6.4 Hz, 1H), 4.63 (t, J = 5.6 Hz, 1H), 4.47–4.33 (m, 4H), 4.20
(d, J = 4.8 Hz, 1H), 3.77 (d, J = 8.4 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ = 166.1, 166.1,
165.6, 165.5, 155.3, 152.0, 148.8, 139.0, 133.8, 133.5, 133.4, 133.4, 130.0, 129.8, 129.8, 129.7, 129.3, 128.7,
128.7, 128.6, 128.5, 128.4, 119.0, 101.5, 88.3, 83.9, 76.3, 72.5, 71.6, 71.2, 70.1, 70.0, 68.0, 61.8 ppm; IR (ATR):
ν
= 3345, 3203, 3070, 2929, 1721, 1639, 1602, 1585, 1475, 1452, 1421, 1316, 1259, 1177, 1092, 1066, 1025,
1002, 938, 906, 857, 799, 753, 705, 685, 649, 617 cm−1; HRMS (FAB+): calcd. for [M + H]+, C44H40N5O13,
846.2623; found, 846.2626; Anal. Calcd. for C44H39N5O13 1.5H2O: C, 60.55; H, 4.85; N, 8.02; found: C,
·
60.47; H, 4.61; N, 7.98; [α]2D5 = +13.9 (c = 1.0, CHCl3).
0
00 00 00 00
6-N-Benzoyl-5 -O-(2 ,3 ,4 ,6 -tetra-O-benzoyl-
O-Glycosylation using 23 (80.5 mg, 115 mol), 16 (28.4 mg, 76.5
anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3 L, 229 mol), AgOTf (117.8 mg, 458
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-galactopyranosyl)adenosine (
mol), 11c (21.8 mg, 115
mol), 4 Å
β
-
25) (Entry 2 in Table 3):
µ
µ
µmol),
µ
µ
µ
µ
used for the synthesis of
(CHCl3/MeOH = 1/0–50/1) to give
NMR (300 MHz, CDCl3, TMS):
β
-
24. The residue was purified by silica gel column chromatography
1
β-
25 as a colorless solid (21.9 mg, 30% yield for 2 steps): H
δ
= 9.21 (brs, 1H), 8.66 (s, 1H), 8.57 (s, 1H), 8.17-8.08 (m, 2H), 7.90–7.81
(m, 4H), 7.90–7.81 (m, 2H), 7.76 (d, J = 7.5 Hz, 2H), 7.62–7.36 (m, 11H), 7.30 (t, J = 7.8 Hz, 2H), 7.22 (t,
J = 7.8 Hz, 2H), 6.15 (d, J = 5.1 Hz, 1H), 6.01 (d, J = 3.0 Hz, 1H), 5.78 (dd, J = 10.2, 7.5 Hz, 1H), 5.65 (dd,
J = 10.5, 3.3 Hz, 1H), 5.49 (brs, 1H), 4.88 (d, J = 7.8 Hz, 1H), 4.76–4.59 (m, 2H), 4.43 (dd, J = 11.1, 6.3 Hz,
1H), 4.38–4.21 (m, 4H), 3.81 (dd, J = 10.5, 2.7 Hz, 1H), 3.51 (s, 1H) ppm; 13C NMR (75 MHz, CDCl3,
TMS):
129.3, 128.9, 128.8, 128.8, 128.7, 128.6, 128.5, 128.3, 127.9, 122.8, 101.5, 89.4, 84.2, 75.8, 71.8, 71.6, 71.2, 69.9,
69.3, 68.0, 61.9 ppm; IR (ATR): = 3336, 3066, 2938, 1721, 1612, 1603, 1584, 1510, 1489, 1452, 1406, 1316,
1250, 1177, 1092, 1066, 1025, 1002, 938, 901, 858, 824, 798, 755, 704, 685, 644, 616 cm−1; HRMS (FAB+):
δ = 166.1, 165.5, 165.5, 164.6, 152.2, 151.0, 149.4, 141.7, 133.7, 133.5, 133.4, 132.8, 130.2, 129.8, 129.6,
ν

Molecules 2017, 22, 1650
13 of 21
calcd. for [M + H]+, C51H44N5O14, 950.2885; found, 950.2885; Anal. Calcd. for C51H43N5O14
·
1.5H2O:
C, 62.70; H, 4.75; N, 7.17; found: C, 62.80; H, 4.57; N, 7.22; [α]2D5 = +4.88 (c = 1.0, CHCl3).
50-O-(200,300,400,600-Tetra-O-benzoyl-
O-Glycosylation using 23 (80.5 mg, 115
mol), anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-galactopyranosyl)guanosine
mol), 17 (21.6 mg, 76.3
L, 229 mol), AgOTf (117.6 mg, 458
(
β
-
26
)
(Entry
mol), 11c (21.8 mg, 115
mol), 4 Å
3 in Table 3):
µ
µ
µ
µ
µ
µ
µ
used for the synthesis of
(CHCl3/MeOH = 1/0–8/1) to give
(400 MHz, DMSO-d6, TMS):
β
-
24. The residue was purified by silica gel column chromatography
1
β-26 as a colorless solid (8.1 mg, 12% yield for 2 steps): H NMR
δ
= 10.68 (s, 1H), 8.11-8.07 (m, 2H), 8.05 (s, 1H), 7.94 (d, J = 8.4 Hz, 2H),
7.85 (d, J = 8.4 Hz, 2H), 7.76–7.69 (m, 3H), 7.69–7.63 (m, 3H), 7.62–7.48 (m, 4H), 7.43 (t, J = 7.6 Hz, 2H),
7.35 (t, J = 7.6 Hz, 2H), 6.51 (s, 2H), 5.91 (d, J = 3.2 Hz, 1H), 5.86 (dd, J = 10.4, 3.2 Hz, 1H), 5.70 (d,
J = 6.0 Hz, 1H), 5.60 (t, J = 10.0 Hz, 1H), 5.39 (d, J = 6.4 Hz, 1H), 5.22 (d, J = 7.6 Hz, 1H), 5.19 (d, J = 3.6
Hz, 1H), 4.69 (t, J = 6.4 Hz, 1H), 4.52 (dd, J = 11.2, 2.8 Hz, 1H), 4.42 (dd, J = 11.2, 6.8 Hz, 1H), 4.37 (dd,
J = 11.2, 6.0 Hz, 1H), 4.10 (d, J = 8.8, 1H), 4.03 (d, J = 2.8 Hz, 1H), 3.92 (d, J = 2.8 Hz, 1H), 3.82 (dd,
J = 10.8, 4.0 Hz, 1H) ppm; 13C NMR (100 MHz, DMSO-d6, TMS):
153.6, 151.4, 135.1, 133.8, 133.7, 133.5, 133.5, 129.4, 129.2, 129.1, 129.0, 129.0, 128.8, 128.7, 128.7, 128.7,
128.6, 128.6, 128.4, 116.6, 99.9, 86.4, 83.1, 73.8, 71.2, 70.7, 70.0, 69.6, 68.4, 61.7 ppm; IR (ATR): = 3332,
δ = 165.1, 165.1, 165.1, 164.4, 156.8,
ν
3128, 3065, 2935, 1724, 1673, 1638, 1602, 1584, 1572, 1538, 1491, 1452, 1350, 1316, 1261, 1177, 1092, 1067,
1025, 1002, 938, 904, 857, 801, 781, 755, 706, 686, 638, 617 cm−1; HRMS (FAB+): calcd. for [M + H]+,
C44H40N5O14, 862.2572; found, 862.2573; Anal. Calcd. for C44H39N5O14 1.5H2O: C, 59.46; H, 4.76; N,
·
7.88; found: C, 59.52; H, 4.62; N, 7.87; [α]2D4 = +11.3 (c = 1.0, DMSO).
2-N-Isobutyryl-50-O-(200,300,400,600-tetra-O-benzoyl-
Table 3): Glycosylation using 23 (80.5 mg, 115 mol), 18 (27.0 mg, 76.4
anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3 L, 229 mol), AgOTf (117.8 mg, 458
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-galactopyranosyl) guanosine (
mol), 11c (21.8 mg, 115
mol), 4 Å
β
-
27) (Entry 4 in
µ
µ
µmol),
µ
µ
µ
µ
used for the synthesis of
β
-
24. The residue was purified by silica gel column chromatography
1
(CHCl3/MeOH = 1/0–20/1) to give
(300 MHz, CDCl3, TMS):
β-
27 as a colorless solid (31.4 mg, 44% yield for 2 steps): H NMR
δ
= 12.11 (s, 1H), 10.33 (s, 1H), 8.09–7.90 (m, 6H), 7.88 (s, 1H), 7.79–7.67 (m,
2H), 7.58–7.31 (m, 10H), 7.24 (t, J = 7.8 Hz, 2H), 6.20 (brs, 1H), 6.00 (d, J = 3.3 Hz, 1H), 5.79 (dd, J = 10.5,
7.5 Hz, 1H), 5.72–5.60 (m, 2H), 4.98 (d, J = 5.1 Hz, 1H), 4.84 (d, J = 8.1 Hz, 1H), 4.67 (dd, J = 10.5, 5.1
Hz, 1H), 4.42–4.24 (m, 3H), 4.16 (d, J = 2.7 Hz, 1H), 4.05 (brs, 2H), 3.72 (d, J = 8.1 Hz, 1H), 2.62–2.49 (m,
1H), 1.13 (d, J = 6.9 Hz, 3H), 0.94 (d, J = 6.6 Hz, 3H) ppm; 13C NMR (75 MHz, CDCl3, TMS): δ = 179.6,
166.5, 166.0, 165.5, 165.4, 155.6, 148.7, 147.8, 139.4, 133.8, 133.4, 129.9, 129.7, 129.6, 129.2, 128.8, 128.6,
128.5, 128.3, 120.6, 101.8, 89.4, 83.7, 72.5, 71.4, 71.2, 70.1, 69.4, 67.9, 61.6, 36.1, 18.8, 18.5 ppm; IR (ATR):
ν = 3201, 3067, 2974, 2936, 1720, 1677, 1602, 1560, 1475, 1452, 1404, 1376, 1350, 1316, 1258, 1178, 1156,
1092, 1066, 1026, 1002, 949, 908, 856, 802, 784, 752, 706, 687, 642, 617 cm−1; HRMS (FAB+): calcd. for
[M + H]+, C48H46N5O15, 932.2990; found, 932.2990; Anal. Calcd. for C48H45N5O15
·
1.5H2O: C, 60.12;
H, 5.05; N, 7.30; found: C, 60.29; H, 4.86; N, 7.34; [α]2D5 = +25.9 (c = 1.0, CHCl3).
50-O-(200,300,400,600-Tetra-O-benzoyl-
O-Glycosylation using 23 (80.4 mg, 114
mol), anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-galactopyranosyl)uridine
mol), 10 (18.6 mg, 76.2
L, 229 mol), AgOTf (117.6 mg, 458
(
β
-
28
)
(Entry
5 in Table 3):
µ
µmol), 11c (21.7 mg, 114
µ
µ
µ
µ
µmol), 4 Å
used for the synthesis of
(CHCl3/MeOH = 1/0–40/1) to give
NMR (400 MHz, CDCl3, TMS):
β
-
24. The residue was purified by silica gel column chromatography
1
β-
28 as a colorless solid (26.1 mg, 42% yield for 2 steps): H
δ
= 9.91 (s, 1H), 8.10–8.05 (m, 2H), 8.04–7.99 (m, 2H), 7.95–7.86 (m,
3H), 7.79–7.75 (m, 2H), 7.63 (t, J = 7.6 Hz, 1H), 7.59–7.49 (m, 3H), 7.50–7.38 (m, 4H), 7.33 (t, J = 7.6
Hz, 2H), 7.23 (t, J = 7.6 Hz, 2H), 6.02 (d, J = 2.8 Hz, 1H), 5.92–5.84 (m, 2H), 5.77 (dd, J = 10.4, 8.0 Hz,
1H), 5.67 (dd, J = 10.8, 3.6 Hz, 1H), 5.03 (d, J = 4.0 Hz, 1H), 4.91 (d, J = 7.6 Hz, 1H), 4.71 (dd, J = 10.8,
6.0 Hz, 1H), 4.49–4.39 (m, 3H), 4.23 (d, J = 4.4 Hz, 1H), 4.13–4.02 (m, 2H), 3.79 (d, J = 10.0 Hz, 1H),

Molecules 2017, 22, 1650
14 of 21
3.39 (d, J = 5.6 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ
= 166.1, 165.5, 165.5, 165.5, 163.6,
151.3, 140.2, 133.9, 133.6, 133.4, 129.8, 129.8, 129.7, 129.3, 128.9, 128.7, 128.6, 128.6, 128.5, 128.4, 102.6,
101.5, 90.6, 83.4, 75.2, 71.7, 71.2, 70.0, 69.8, 68.2, 68.1, 61.9 ppm; IR (ATR): = 3356, 3069, 2972, 1720,
ν
1687, 1602, 1585, 1492, 1452, 1383, 1316, 1261, 1178, 1093, 1067, 1027, 1002, 907, 858, 806, 763, 706,
686, 617 cm−1; HRMS (FAB+): calcd. for [M + H]+, C43H39N2O15, 823.2350; found, 823.2352; Anal.
Calcd. for C43H38N2O15
H2O: C, 61.43; H, 4.80; N, 3.33; found: C, 61.45; H, 4.70; N, 3.38; [α]2D5 = +50.7
·
(c = 1.0, CHCl3).
5-Metyl-50-O-(200,300,400,600-tetra-O-benzoyl-
O-Glycosylation using 23 (80.5 mg, 115
anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
used for the synthesis of 24. The residue was purified by silica gel column chromatography
(CHCl3/MeOH = 1/0–40/1) to give
29 as a colorless solid (33.8 mg, 53% yield for 2 steps): 1H NMR
(400 MHz, CDCl3, TMS): = 10.04 (s, 1H), 8.09–8.05 (m, 2H), 8.04–8.00 (m, 2H), 7.97–7.93 (m, 2H),
β
-D-galactopyranosyl)uridine (
mol), 19 (19.7 mg, 76.3 mol), 11c (21.8 mg, 115
L, 229 mol), AgOTf (117.6 mg, 458 mol), 4 Å
β
-
29) (Entry 6 in Table 3):
µ
µ
µmol),
µ
µ
µ
µ
β-
β-
δ
7.79–7.74 (m, 2H), 7.67 (s, 1H), 7.61–7.52 (m, 2H), 7.50–7.37 (m, 6H), 7.34 (t, J = 7.6 Hz, 2H), 7.20 (t,
J = 7.6 Hz, 2H), 6.03 (d, J = 3.6 Hz, 1H), 5.88 (d, J = 4.4 Hz, 1H), 5.81 (dd, J = 10.4, 7.6 Hz, 1H), 5.71
(dd, J = 10.4, 3.2 Hz, 1H), 5.08 (s, 1H), 4.90 (d, J = 7.6 Hz, 1H), 4.70 (dd, J = 11.2, 6.4 Hz, 1H), 4.50–4.37
(m, 3H), 4.21 (d, J = 4.4 Hz, 1H), 4.09 (dd, J = 10.0, 4.4 Hz, 1H), 4.01 (dd, J = 10.0, 4.8 Hz, 1H), 3.77 (d,
J = 9.2 Hz, 1H), 3.41 (d, J = 4.8 Hz, 1H), 2.06 (s, 3H) ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ = 166.1,
165.6, 165.6, 165.5, 164.2, 151.3, 136.1, 133.8, 133.6, 133.4, 129.9, 129.8, 129.7, 129.7, 129.3, 128.9, 128.7,
128.6, 128.5, 128.5, 128.3, 111.3, 102.2, 89.8, 83.3, 74.6, 71.8, 71.2, 70.2, 69.8, 69.3, 68.1, 61.9, 12.8 ppm; IR
(ATR): ν = 3385, 3067, 2930, 1720, 1686, 1602, 1585, 1492, 1468, 1452, 1386, 1349, 1316, 1259, 1177, 1092,
1066, 1025, 1002, 937, 909, 858, 802, 793, 755, 705, 685, 616 cm−1; HRMS (FAB+): calcd. for [M + H]+,
C44H41N2O15, 837.2507; found, 837.2510; Anal. Calcd. for C44H40N2O15 H2O: C, 61.82; H, 4.95; N, 3.28;
·
found: C, 61.70; H, 4.85; N, 3.30; [α]2D5 = +28.1 (c = 1.0, CHCl3).
5-Fluoro-50-O-(200,300,400,600-tetra-O-benzoyl-
O-Glycosylation using 23 (80.4 mg, 114
anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-galactopyranosyl)uridine (
mol), 20 (20.0 mg, 76.3 mol), 11c (21.7 mg, 114
L, 229 mol), AgOTf (117.6 mg, 458 mol), 4 Å
β
-
30) (Entry 7 in Table 3):
µ
µ
µmol),
µ
µ
µ
µ
used for the synthesis of
then AcOEt/CHCl3 = 1/1) to give
(300 MHz, CDCl3, TMS):
β
-
24. The residue was purified by silica gel column chromatography (CHCl3
1
β-30 as a colorless solid (38.8 mg, 61% yield for 2 steps): H NMR
δ
= 9.81 (brs, 1H), 8.10 (t, J = 7.2 Hz, 3H), 8.04–7.99 (m, 2H), 7.94–7.89 (m, 2H),
7.78–7.73 (m, 2H), 7.64–7.48 (m, 4H), 7.47–7.37 (m, 4H), 7.33 (t, J = 7.5 Hz, 2H), 7.21 (t, J = 7.2 Hz, 2H),
6.03 (d, J = 3.0 Hz, 1H), 5.88 (d, J = 3.9 Hz, 1H), 5.78 (dd, J = 10.2, 7.5 Hz, 1H), 5.71 (dd, J = 10.2, 3.3 Hz,
1H), 4.86 (d, J = 7.2 Hz, 1H), 4.72 (dd, J = 11.1, 6.3 Hz, 1H), 4.51 (brs, 1H), 4.52–4.33 (m, 3H), 4.27 (d,
J = 3.3 Hz, 1H), 4.19 (t, J = 4.8 Hz, 1H), 4.02 (s, 1H), 3.74 (d, J = 9.6 Hz, 1H), 3.32 (brs, 1H) ppm; 13
C
NMR (100 MHz, CDCl3, TMS): δ
= 166.1, 165.8, 165.7, 165.5, 157.0 (d, 2JCF = 26.4 Hz), 149.9, 140.8 (d,
1JCF = 237.0 Hz), 133.9, 133.7, 133.4, 130.0, 129.8, 129.7, 129.3, 128.8, 128.7, 128.6, 128.5, 128.4, 124.9 (d,
2JCF = 35.5 Hz), 101.7, 90.5, 84.0, 75.3, 71.8, 71.0, 70.9, 69.9, 69.0, 67.9, 61.8 ppm; 19F NMR (376 MHz,
CDCl3, TFA):
δ
=
−
164.57 (s) ppm; IR (ATR): ν = 3447, 3074, 2941, 1715, 1602, 1585, 1493,1452, 1351,
1317, 1258, 1178, 1092, 1066, 1026, 1002, 936, 894, 858, 800, 753, 706, 687, 617 cm−1; HRMS (FAB+): calcd.
for [M + Na]+, C43H37FN2O15Na, 863.2076; found, 863.2072; Anal. Calcd. for C43H37FN2O15
H2O: C,
·
60.14; H, 4.58; N, 3.26; found: C, 60.02; H, 4.41; N, 3.32; [α]2D5 = +37.2 (c = 1.0, CHCl3).
50-O-(200,300,400,600-Tetra-O-benzoyl-
O-Glycosylation using 23 (80.4 mg, 114
mol), anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-galactopyranosyl)cytidine
mol), 21 (18.5 mg, 76.1
L, 229 mol), AgOTf (117.6 mg, 458
(
β
-
31
)
(Entry
mol), 11c (21.7 mg, 114
mol), 4 Å
8
in Table 3):
µ
µ
µ
µ
µ
µ
µ
used for the synthesis of
(CHCl3/MeOH = 1/0–10/1) to give
β
-
24. The residue was purified by silica gel column chromatography
1
β-
31 as a colorless solid (34.1 mg, 55% yield for 2 steps): H

Molecules 2017, 22, 1650
15 of 21
NMR (300 MHz, acetone-d6, TMS):
δ
= 8.13-8.08 (m, 2H), 8.06–8.01 (m, 2H), 7.97–7.92 (m, 2H), 7.88 (d,
J = 7.5 Hz, 1H), 7.76 (dd, J = 8.4, 1.1 Hz, 2H), 7.73-7.65 (m, 1H), 7.65-7.56 (m, 3H), 7.56-7.44 (m, 4H), 7.39
(t, J = 7.2 Hz, 2H), 7.32 (t, J = 7.5 Hz, 2H), 6.90 (brs, 2H), 6.10 (dd, J = 3.0, 0.9 Hz, 1H), 5.97 (d, J = 7.8 Hz
1H), 5.90 (d, J = 7.8 Hz, 1H), 5.87–5.77 (m, 2H), 5.33 (d, J = 7.8 Hz, 1H), 4.78 (t, J = 6.3 Hz, 1H), 4.70 (dd,
J = 10.8, 6.0 Hz, 1H), 4.54 (dd, J = 10.8, 6.6 Hz, 1H), 4.38 (dd, J = 11.1, 1.8 Hz, 1H), 4.19–4.12 (m, 1H),
,
4.06 (t, J = 4.5 Hz, 1H), 4.02–3.93 (m, 2H) ppm; 13C NMR (100 MHz, acetone-d6, TMS):
δ = 166.9, 166.4,
166.3, 166.2, 165.8, 157.0, 142.1, 134.6, 134.3, 134.3, 134.2, 130.7, 130.5, 130.4, 130.3, 130.2, 130.2, 130.1,
129.8, 129.5, 129.4, 129.3, 102.2, 95.4, 91.6, 84.0, 76.4, 72.8, 72.0, 71.1, 70.9, 69.8, 69.7, 62.8 ppm; IR (ATR):
ν
= 3350, 3208, 3072, 2935, 1723, 1642, 1602, 1529, 1486, 1452, 1349, 1316, 1259, 1178, 1092, 1065, 1025,
1002, 940, 909, 857, 788, 753, 705, 685, 616 cm−1; HRMS (FAB+): calcd. for [M + H]+, C43H40N3O14,
822.2510; found, 822.2507; Anal. Calcd. for C43H39N3O14 1.5H2O: C, 60.85; H, 4.99; N, 4.95; found: C,
·
60.87; H, 4.72; N, 4.97; [α]2D5 = +62.4 (c = 1.0, CHCl3).
4-N-Benzoyl-50-O-(200,300,400,600-tetra-O-benzoyl-
O-glycosylation using 23 (80.6 mg, 115 mol), 22 (26.6 mg, 76.6
anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3 L, 229 mol), AgOTf (117.8 mg, 458
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-galactopyranosyl)cytidine (
mol), 11c (21.8 mg, 115
mol), 4 Å
β
-
32) (Entry 9 in Table 3):
µ
µ
µmol),
µ
µ
µ
µ
used for the synthesis of
(CHCl3/MeOH = 1/0–50/1) to give
NMR (400 MHz, CDCl3, TMS):
β
-
24. The residue was purified by silica gel column chromatography
1
β-
32 as a colorless solid (28.0 mg, 40% yield for 2 steps): H
δ
= 8.93 (brs, 1H), 8.28 (d, J = 7.6 Hz, 1H), 8.06–8.01 (m, 4H), 7.91 (dd,
J = 8.4, 1.6 Hz, 2H), 7.87 (d, J = 7.2 Hz, 2H), 7.73 (dd, J = 8.0, 1.6 Hz, 2H), 7.68 (brs, 1H), 7.60–7.53 (m,
2H), 7.53–7.37 (m, 9H), 7.32 (t, J = 8.0 Hz, 2H), 7.19 (t, J = 8.0 Hz, 2H), 6.03 (d, J = 3.2 Hz, 1H), 5.86
(d, J = 3.6 Hz, 1H), 5.76 (dd, J = 10.4, 8.0 Hz, 1H), 5.69 (dd, J = 10.4, 3.6 Hz, 1H), 5.54 (brs, 1H), 4.92
(d, J = 7.6 Hz, 1H), 4.78 (dd, J = 11.6, 6.4 Hz, 1H), 4.48 (dd, J = 11.2, 6.4 Hz, 1H), 4.43–4.35 (m, 3H),
4.14 (t, J = 4.4 Hz, 1H), 4.10 (d, J = 3.6 Hz, 1H), 3.81 (dd, J = 11.6, 2.4 Hz, 1H), 3.66 (brs, 1H) ppm; 13
NMR (100 MHz, CDCl3, TMS): = 166.1, 165.6, 165.5, 165.3, 162.6, 144.7, 133.6, 133.4, 133.4, 133.1,
132.9, 129.9, 129.8, 129.8, 129.7, 129.4, 128.9, 128.8, 128.6, 128.5, 128.4, 128.3, 127.7, 101.7, 97.1, 93.1,
84.8, 76.4, 71.8, 71.3, 71.2, 69.6, 68.7, 68.1, 61.9 ppm; IR (ATR): = 3320, 3066, 2930, 1724, 1645, 1603,
C
δ
ν
1556, 1481, 1452, 1379, 1315, 1248, 1177, 1092, 1066, 1025, 1002, 938, 899, 859, 802, 787, 756, 704, 685,
616 cm−1; HRMS (FAB+): calcd. for [M + H]+, C50H44N3O15, 926.2772; found, 926.2773; Anal. Calcd.
for C50H43N3O15
CHCl3).
·
H2O: C, 63.62; H, 4.81; N, 4.45; found: C, 63.34; H, 4.71; N, 4.56; [α]2D5 = +46.6 (c = 1.0,
5-Fluoro-50-O-(200,300,400,600-tetra-O-benzoyl-
O-Glycosylation using 33 (80.4 mg, 114
anhydrous 1,4-dioxane (760 L), p-TolSCl (30.3
molecular sieves (150 mg) and anhydrous EtCN (1.50 mL) was conducted according to the procedure
β
-D-glucopyranosyl)uridine (
mol), 20 (20.0 mg, 76.2 mol), 11c (21.7 mg, 114
L, 229 mol), AgOTf (117.6 mg, 458 mol), 4 Å
β
-
35) (Entry 1 in Table 4):
µ
µ
µmol),
µ
µ
µ
µ
used for the synthesis of
(CHCl3/MeOH = 1/0–30/1) to give
NMR (300 MHz, CDCl3, TMS):
β
-
24. The residue was purified by silica gel column chromatography
1
β-
35 as a colorless solid (34.5 mg, 54% yield for 2 steps): H
δ
= 9.66 (brs, 1H), 8.09 (d, J = 6.6 Hz, 1H), 8.04-7.98 (m, 2H), 7.91 (d,
J = 8.1 Hz, 4H), 7.87–7.82 (m, 2H), 7.56–7.24 (m, 12H), 5.97 (t, J = 9.9 Hz, 1H), 5.82 (d, J = 3.0 Hz, 1H),
5.69 (t, J = 9.9 Hz, 1H), 5.48 (dd, J = 10.2, 7.8 Hz, 1H), 4.90 (d, J = 8.1 Hz, 1H), 4.70 (dd, J = 12.0, 3.0 Hz,
1H), 4.55 (brs, 1H), 4.52 (dd, J = 12.0, 4.8 Hz, 1H), 4.33 (dd, J = 10.8, 2.1 Hz, 1H), 4.28–4.15 (m, 3H), 4.06
(s, 1H), 3.76 (d, J = 9.6 Hz, 1H), 3.31 (s, 1H) ppm; 13C NMR (100 MHz, CDCl3, TMS):
δ = 166.2, 165.8,
165.5, 165.0, 157.1 (d, 2JCF = 26.4 Hz), 149.8, 140.7 (d, 1JCF = 236.2 Hz), 133.7, 133.5, 133.4, 133.3, 129.9,
129.8, 129.7, 129.4, 128.7, 128.6, 128.5, 128.4, 128.4, 124.8 (d, 2JCF = 34.6 Hz), 100.8, 90.6, 83.9, 75.4, 72.7,
72.3, 71.9, 70.6, 69.6, 68.0, 62.8 ppm; 19F NMR (376 MHz, CDCl3, TFA):
ν
δ
=
−
165.00 (s) ppm; IR (ATR):
= 3426, 3072, 2953, 1716, 1602, 1585, 1493,1452, 1369, 1317, 1260, 1178, 1091, 1068, 1027, 1003, 936, 895,
855, 800, 758, 708, 687, 618 cm−1; HRMS (FAB+): calcd. for [M + H]+, C43H38FN2O15, 841.2256; found,
841.2261; Anal. Calcd. for C43H37FN2O15 1.5H2O: C, 59.52; H, 4.65; N, 3.23; found: C, 59.51; H, 4.47; N,
·
3.26; [α]2D5 = +8.39 (c = 1.0, CHCl3).

Molecules 2017, 22, 1650
16 of 21
O-Glycosylation using glycosyl donors containing boronic acid on leaving group (Entries 1–4 in
Table 5): A mixture of 41 or 42 (30.2 mg, 48.0 mol) and 10 (7.8 mg, 31.9 mol) or 13 (8.6 mg, 32.2 mol)
was co-evaporated with anhydrous pyridine (three times) and anhydrous 1,4-dioxane (three times) and
dissolved in anhydrous 1,4-dioxane (320 L). This reaction mixture was stirred under reflux conditions
for 1 h and concentrated under reduced pressure. O-glycosylation and acetylation were conducted
according to the procedure used for the synthesis of 12 or 14 using p-TolSCl (12.7 L, 96.1 mol),
AgOTf (49.5 mg, 193 mol), 3 Å molecular sieves (64 mg), anhydrous MeCN (640 L), anhydrous
pyridine (200 µL), Ac2O (10.0 equiv. based on the crude compound) and DMAP (catalytic amount).
µ
µ
µ
µ
µ
µ
µ
µ
0
00 00 00
5 -O-(2 ,3 ,4 -Tri-O-benzyl-
α
/
β
-D-mannopyranosyl)uridine (43) (Scheme 1a): To a solution of 12 (25.2 mg,
L), 1 M aqueous LiOH was added at room temperature. After
31.4 mol, = 1.6/1) in THF (400 µ
µ
α
/
β
stirring for 2 h, the reaction mixture was neutralized with 0.1 M aqueous HCl, extracted with CHCl3,
washed with brine, dried over Na2SO4, filtered and concentrated under reduced pressure. The residue
was purified by silica gel column chromatography (CHCl3/MeOH = 20/1) to give
solid (12.1 mg, 57% yield) and 43 as a colorless solid (7.5 mg, 35% yield):
43; 1H NMR (300 MHz,
CDCl3, TMS): = 10.11 (s, 1H), 7.39 (d, J = 8.4 Hz, 1H), 7.36–7.17 (m, 15H), 5.74 (d, J = 2.1 Hz, 1H),
5.43 (d, J = 8.4 Hz, 1H), 4.91 (s, 1H), 4.87 (t, J = 6.3 Hz, 2H), 4.75 (d, J = 12.0 Hz, 1H), 4.67 (d, J = 9.0 Hz
1H), 4.64–4.51 (m, 3H), 4.20 (s, 1H), 4.13 (s, 1H), 4.02 (s, 2H), 3.90–3.74 (m, 4H), 3.73–3.56 (m, 4H),
3.00 (s, 1H) ppm; 13C NMR (100 MHz, CDCl3, TMS):
= 163.7, 151.1, 139.7, 138.0, 137.8, 128.5, 128.4,
128.4, 128.3, 127.9, 127.8, 127.7, 127.6, 102.3, 98.3 (C1”, 1JCH = 169.4 Hz), 90.1, 82.6, 79.7, 75.1, 75.0, 74.8,
74.7, 73.1, 73.0, 72.4, 69.9, 66.6, 62.3 ppm; IR (ATR): = 3384, 3064, 3032, 2924, 2879, 1683, 1497, 1455,
1389, 1364, 1321, 1269, 1210, 1068, 1027, 909, 864, 845, 810, 735, 697 cm−1; HRMS (FAB+): calcd. for
[M + H]+, C36H41N2O11, 677.2710; found, 677.2709; Anal. Calcd. for C36H40N2O11
H2O: C, 62.24;
H, 6.09; N, 4.03; found: C, 62.36; H, 6.01; N, 4.13; [α]2D5 = +42.7 (c = 0.2, CHCl3); 43; 1H NMR (300
MHz, CD3OD, TMS): = 7.96 (d, J = 8.1 Hz, 1H), 7.41–7.20 (m, 15H), 5.96 (d, J = 5.4 Hz, 1H), 5.34 (d,
α-43 as a colorless
β-
α-
δ
,
δ
ν
·
β-
δ
J = 8.1 Hz, 1H), 4.92–4.84 (m, 2H), 4.75–4.55 (m, 5H), 4.28 (t, J = 5.7 Hz, 1H), 4.22 (dd, J = 5.1, 3.3 Hz,
1H), 4.18–4.10 (m, 2H), 4.08 (d, J = 2.1 Hz, 1H), 3.86–3.73 (m, 3H), 3.67 (dd, J = 9.6, 2.7 Hz, 1H), 3.60
(dd, J = 11.7, 6.3 Hz, 1H), 3.35–3.26 (m, 1H) ppm; 13C NMR (100 MHz, CD3OD, TMS):
δ
= 166.1, 152.6,
143.4, 139.8, 139.7, 129.7, 129.4, 129.3, 129.3, 128.9, 128.8, 128.7, 103.0, 101.8 (C1”, 1JCH = 156.1 Hz), 89.9,
85.2, 84.1, 77.9, 76.9, 76.2, 76.0, 75.8, 75.6, 73.0, 72.2, 70.0, 62.8 ppm; IR (ATR): = 3387, 3063, 3032, 2926,
ν
2874, 1673, 1498, 1456, 1401, 1364, 1316, 1274, 1249, 1211, 1179, 1072, 1027, 906, 866, 811, 786, 736, 696
cm−1; HRMS (FAB+): calcd. for [M + H]+, C36H41N2O11, 677.2710; found, 677.2709; Anal. Calcd. for
C36H40N2O11
CH3OH).
·
H2O: C, 62.24; H, 6.09; N, 4.03; found: C, 62.29; H, 5.86; N, 4.20; [α]D23
=
−
67.6 (c = 0.5,
50-O-
Pd/C (19.0 mg) in MeOH (540
atmosphere. The mixture was filtered through Celite with MeOH and H2O, and then, the filtrate
was concentrated under reduced pressure to give 44 as a colorless solid (11.4 mg, 99% yield): 44
1H NMR (300 MHz, D2O, TSP):
= 7.89 (d, J = 8.1 Hz, 1H), 5.96–5.87 (m, 2H), 4.96 (s, 1H), 4.33 (s,
3H), 4.06–3.96 (m, 2H), 3.90 (t, J = 10.5 Hz, 2H), 3.57–3.84 (m, 4H) ppm; 13C NMR (75 MHz, D2O,
1,4-dioxane): = 166.8, 152.1, 142.0, 102.5, 100.3, 90.4, 82.9, 74.6, 73.6, 71.2, 70.6, 69.8, 67.2, 66.3, 61.5
ppm; IR (ATR): = 3289, 2935, 2502, 1666, 1466, 1397, 1273, 1199, 1129, 1104, 1050, 1025, 912, 868, 810,
801, 765, 720, 676, 622 cm−1; HRMS (FAB+): calcd. for [M + Na]+, C15H22N2O11Na, 429.1121; found,
α
/
β
-D-Mannopyranosyl)uridine (44) (Scheme 1a): A mixture of
α-43 (19.2 mg, 28.4 µmol), 10%
µL) was vigorously stirred for 22 h at room temperature under a H2
α
-
α- ;
δ
δ
ν
429.1118; Anal. Calcd. for C15H22N2O11 2.75H2O: C, 39.52; H, 6.08; N, 6.14; found: C, 39.58; H, 5.93; N,
·
5.81; [α]2D4 = +29.3 (c = 0.8, H2O).
Cleavage of benzyl groups using
β
-
43 (17.8 mg, 26.3
µ
mol), 10% Pd/C (18.0 mg) and MeOH
44 to give the 44 as a colorless
= 8.05 (d, J = 8.1 Hz, 1H), 5.96 (d,
(500
µ
L) was conducted according to the procedure for synthesis of
α
-
β-
solid (10.5 mg, 98% yield):
β-
44; 1H NMR (300 MHz, D2O, TSP):
δ
J = 4.2 Hz, 1H), 5.89 (d, J = 8.1 Hz, 1H), 4.74 (s, 1H), 4.49–4.12 (m, 4H), 4.05 (s, 1H), 3.95 (d, J = 12.3 Hz,
1H), 3.88 (d, J = 11.7 Hz, 1H), 3.75 (dd, J = 11.7, 6.6 Hz, 1H), 3.70–3.52 (m, 2H), 3.40 (t, J = 6.6 Hz, 1H)

Molecules 2017, 22, 1650
17 of 21
ppm; 13C NMR (75 MHz, D2O, 1,4-dioxane):
δ
= 167.8, 153.0, 142.7, 103.0, 100.9, 89.7, 83.6, 76.9, 74.4,
73.5, 70.9, 70.4, 69.0, 67.5, 61.7 ppm; IR (ATR):
ν = 3288, 2933, 2503, 1670, 1510, 1465, 1390, 1266, 1133,
1053, 1023, 879, 815, 790, 764, 714, 632, 616 cm−1; HRMS (FAB+): calcd. for [M + Na]+, C15H22N2O11Na,
429.1121; found, 429.1119; Anal. Calcd. for C15H22N2O11 2.6H2O: C, 39.76; H, 6.05; N, 6.18; found: C,
·
40.15; H, 6.00; N, 5.80; [α]2D5 = −10.6 (c = 0.8, H2O).
5-Fluoro-50-O-(
β
-D-galactopyranosyl)uridine ( ◦
β-45) (Scheme 1b): A mixture of β-30 (25.2 mg, 30.0 µmol)
and 10 M MeNH2 in MeOH was stirred at 0 C for 2 h and then allowed to warm to room temperature.
After stirring for 13 h, the reaction mixture was concentrated under reduced pressure. The residue was
dissolved in H2O, and the N-methylbenzamide was removed by successive washing of the aqueous
phase with CH2Cl2. The aqueous layer was concentrated under reduced pressure. The residue was
purified by preparative HPLC (H2O (0.1%TFA)) to give
62% yield): 1H NMR (300 MHz, D2O, TSP):
= 8.18 (d, J = 6.6 Hz, 1H), 5.94 (d, J = 1.8 Hz, 1H),
4.51 (d, J = 7.2 Hz, 1H), 4.48–4.24 (m, 4H), 3.98–3.86 (m, 2H), 3.86–3.77 (m, 2H), 3.77–3.69 (m, 1H),
3.69–3.58 (m, 2H) ppm; 13C NMR (100 MHz, D2O, 1,4-dioxane): = 160.1 (d, 2JCF = 26.4 Hz), 150.8,
141.4 (d, 1JCF = 232.1 Hz), 126.3 (d, 2JCF = 38.1 Hz), 103.7, 89.9, 83.6, 75.9, 74.4, 73.4, 71.5, 69.9, 69.2, 68.9,
β-45 as a colorless amorphous solid (7.9 mg,
δ
δ
61.6 ppm; 19F NMR (376 MHz, D2O, TFA):
δ
=
−
166.73 (s) ppm; IR (ATR): ν = 3357, 3075, 2935, 2827,
1661, 1477, 1398, 1365, 1258, 1202, 1035, 952, 921, 890, 843, 793, 750, 722, 697 cm−1; HRMS (FAB+): calcd.
for [M + Na]+, C15H21FN2O11Na, 447.1027; found, 447.1030; [α]D25 = +17.6 (c = 0.3, H2O).
1H, 11B and 19F NMR measurements of mixtures of uridine (10) and boronic acid (11c) (Figure 3):
A mixture of 10 (34.3 mg, 140 µmol) and 11c (40.0 mg, 211 µmol) was co-evaporated with anhydrous
pyridine (three times) and anhydrous 1,4-dioxane (three times). The resulting residue was dissolved in
anhydrous 1,4-dioxane (1.40 mL) and then stirred under reflux conditions for 1 h. The reaction mixture
(140
(640
µL) was separated and concentrated under reduced pressure. The residue 46 dissolved in CD3CN
µ
conditions as were used to prepare 48 for the 11B and 19F NMR measurements.
L) was measured by a 1H, 11B and 19F NMR spectrometers. 11c was treated under the same
4. Conclusions
We report herein on the synthesis of disaccharide nucleosides utilizing the temporary protection
of the 20,30-cis-diol of ribonucleosides by a boronic ester. The glycosylation of the uridine 10, which is
temporarily protected by a boronic acid, with the thioglycoside 9 using a p-TolSCl/AgOTf promoter
system followed by acetylation gave the disaccharide nucleoside 12 containing a 100,50-glycosidic
linkage in reasonable chemical yield. This synthetic method was applied to the glycosylation
of protected or unprotected adenosine, guanosine, uridine or cytidine, 10, 13, 16–22, with the
galactosyl donor 23 to afford the desired products in moderate chemical yields. O-glycosylations of
5-fluorouridine 20 with the glucosyl donor 33, the galactosyl donor 23 and the mannosyl donor 34
were also conducted. The introduction of a boronic acid on the phenylthio leaving group had only a
negligible effect on the reactivity and stereoselectivity of the system. The deprotection of compounds
12 and
β-30 was also demonstrated to give the corresponding deprotected compounds
α-44 and β-44
from 12 and
β-
45 from 30. Because 5-fluorouridine and 5-fluorouracil have been reported to have
β-
anticancer, antivirus and antibacterial activities [24
new drug candidates.
,68,72–78], β-45 and its analogs represent potentially
Finally, 1H, 11B and 19F NMR measurements of a mixture of uridine 10 and 4-(trifluoromethyl)
phenylboronic acid 11c suggest that the 2’ and 3’ hydroxyl groups of 10 react with 11c to form the cyclic
boronic ester intermediate 47, as expected, resulting in selective O-glycosylation of the ribonucleoside
acceptors at the 5’-position.
These results afford important and useful information regarding the concise and short-step
synthesis of various biologically-active disaccharide nucleoside derivatives via the O-glycosylation of
temporarily-protected nucleosides and related compounds.
Supplementary Materials: Supplementary Materials are available online.

Molecules 2017, 22, 1650
18 of 21
Acknowledgments: This work was supported by grants-in-aid from the Ministry of Education, Culture, Sports,
Science and Technology (MEXT) of Japan (Nos. 22390005, 245900425, 24659011, 24640156 and 15K00408 for S.A.)
and a grant from the Tokyo Biochemical Research Foundation, Tokyo, Japan. We appreciate the assistance of
Fukiko Hasegawa (Faculty of Pharmaceutical Sciences, Tokyo University of Science) for collecting and interpreting
the mass spectral data, Noriko Sawabe for the NMR measurement and Tomoko Matsuo (Research Institute for
Science and Technology, Tokyo University of Science) for the elemental analyses.
Author Contributions: Hidehisa Someya carried out the synthesis of the glycosyl donors and acceptors,
O-glycosylation reactions, deprotection of 12 and 1H, 11B and 19F NMR measurements and prepared the
manuscript. Taiki Itoh synthesized some glycosyl donors and carried out the deprotection of β-30. Shin Aoki
supervised all experiments and the preparation of the manuscript. All of the authors have read and approved the
final version of the manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
2.
3.
4.
Kobayashi, J.; Doi, Y.; Ishibashi, M. Shimofuridin A, a nucleoside derivative embracing an acylfucopyranoside
unit isolated from the okinawan marine tunicate Aplidium multiplicatum. J. Org. Chem. 1994, 59, 255–257.
[CrossRef]
Takahashi, M.; Tanzawa, K.; Takahashi, S. Adenophostins, newly discovered metabolites of penicillium
brevicompactum, act as potent agonists of the inositol 1,4,5-trisphosphate receptor. J. Biol. Chem. 1994, 269,
369–372. [PubMed]
Haneda, K.; Shinose, M.; Seino, A.; Tabata, N.; Tomoda, H.; Iwai, Y.; Omura, S. Cytosaminomycins,
new anticoccidial agents produced by Strevtomvces sp. KO-8119 I. taxonomy, production, isolation and
physico-chemical and biological properties. J. Antibiot. 1994, 47, 774–781. [CrossRef] [PubMed]
Shiomi, K.; Haneda, K.; Tomoda, H.; Iwai, Y.; Omura, S. Cytosaminomycins, new anticoccidial agents
produced by Streptomyces sp. KO-8119 II. structure elucidation of cytosaminomycins A, B, C and D. J. Antibiot.
1994, 47, 782–786. [CrossRef] [PubMed]
5.
6.
Knapp, S. Synthesis of complex nucleoside antibiotics. Chem. Rev. 1995, 95, 1859–1876. [CrossRef]
Efimtseva, E.V.; Kulikova, I.V.; Mikhailov, S.N. Disaccharide nucleosides as an important group of natural
compounds. Mol. Biol. 2009, 43, 301–312. [CrossRef]
7.
8.
Huang, R.M.; Chen, Y.N.; Zeng, Z.; Gao, C.H.; Su, X.; Peng, Y. Marine nucleosides: Structure, bioactivity,
synthesis and biosynthesis. Mar. Drugs 2014, 12, 5817–5838. [CrossRef] [PubMed]
Efimtseva, E.V.; Mikhailov, S.N. Disaccharide nucleosides and oligonucleotides on their basis. New tools
for the study of enzymes of nucleic acid metabolism. Biochemistry (Moscow) 2002, 67, 1136–1144. [CrossRef]
[PubMed]
9.
Mikhailov, S.N.; Efimtseva, E.V. Disaccharide nucleosides. Russ. Chem. Rev. 2004, 73, 401–414.
10. Kimura, K.; Bugg, T.D.H. Recent advances in antimicrobial nucleoside antibiotics targeting cell wall
biosynthesis. Nat. Prod. Rep. 2003, 20, 252–273. [CrossRef] [PubMed]
11. Winn, M.; Goss, R.J.M.; Kimura, K.; Bugg, T.D.H. Antimicrobial nucleoside antibiotics targeting cell wall
assembly: Recent advances in structure-function studies and nucleoside biosynthesis. Nat. Prod. Rep. 2010
27, 279–304. [CrossRef] [PubMed]
,
12. Takahashi, M.; Kagasaki, T.; Hosoya, T.; Takahashi, S. Adenophostins A and B: Potent agonists of
inositol-1,4,5-trisphosphate receptor produced by Penicillium brevicompactum. Taxonomy, fermentation,
isolation, physico-chemical and biological properties. J. Antibiot. 1993, 46, 1643–1647. [CrossRef] [PubMed]
13. Takahashi, S.; Kinoshita, T.; Takahashi, M. Adenophostins A and B: Potent agonists of inositol-1,4,5-
trisphosphate receptor produced by penicillium brevicompactum. Structure elucidation. J. Antibiot. 1994, 47,
95–100. [CrossRef] [PubMed]
14. Hotoda, H.; Takahashi, M.; Tanzawa, K.; Takahashi, S.; Kaneko, M. IP3 receptor-ligand. 1: Synthesis of
adenophostin A. Tetrahedron Lett. 1995, 36, 5037–5040. [CrossRef]
15. Hirota, J.; Michikawa, T.; Miyawaki, A.; Takahashi, M.; Tanzawa, K.; Okura, I.; Furuichi, T.; Mikoshiba, K.
Adenophostin-medicated quantal Ca2+ release in the purified and reconstituted inositol 1,4,5-trisphosphate
receptor type 1. FEBS Lett. 1995, 368, 248–252. [CrossRef]

Molecules 2017, 22, 1650
19 of 21
16. McCormick, J.; Li, Y.; McCormick, K.; Duynstee, H.I.; Van Engen, A.K.; Van der Marel, G.A.; Ganem, B.; Van
Boom, J.H.; Meinwald, J. Structure and total synthesis of HF-7, a neuroactive glyconucleoside disulfate from
the funnel-web spider Hololena curta. J. Am. Chem. Soc. 1999, 121, 5661–5665. [CrossRef]
17. Bu, Y.Y.; Yamazaki, H.; Ukai, K.; Namikoshi, M. Anti-mycobacterial nucleoside antibiotics from a
marine-derived Streptomyces sp. TPU1236A. Mar. Drugs 2014, 12, 6102–6112. [CrossRef] [PubMed]
18. Knapp, S.; Gore, V.K. Synthesis of the ezomycin nucleoside disaccharide. Org. Lett. 2000, 2, 1391–1393.
[CrossRef] [PubMed]
19. Behr, J.B.; Gourlain, T.; Helimi, A.; Guillerm, G. Design, Synthesis and biological evaluation of
hetaryl-nucleoside derivatives as inhibitors of chitin synthase. Bioorg. Med. Chem. Lett. 2003, 13, 1713–1716.
[CrossRef]
20. Binder, W.H.; Kählig, H.; Schmid, W. Galactosylation by use of β-galactosidase: Enzymatic syntheses of
disaccharide nucleosides. Tetrahedron: Asymmetry 1995, 6, 1703–1710. [CrossRef]
21. Ye, M.; Yan, L.-Q.; Li, N.; Zong, M.-H. Facile and regioselective enzymatic 5-galactosylation of pyrimidine
2-deoxynucleosides catalyzed by β-glycosidase from bovine liver. J. Mol. Catal. B 2012, 79, 35–40. [CrossRef]
22. Niedballa, U.; Vorbrüggen, H. A general synthesis of N-glycosides. III. Simple synthesis of pyrimidine
disaccharide nucleosides. J. Org. Chem. 1974, 39, 3664–3667. [CrossRef] [PubMed]
23. Abe, H.; Shuto, S.; Matsuda, A. Synthesis of the C-glycosidic analog of adenophostin A, a potent IP3 receptor
agonist, using a temporary silicon-tethered radical coupling reaction as the key step. Tetrahedron Lett. 2000
41, 2391–2394. [CrossRef]
,
24. Watanabe, K.A.; Matsuda, A.; Halat, M.J.; Hollenberg, D.H.; Nisselbaum, J.S.; Fox, J.J. Nucleosides. 114.
50-O-Glucuronides of 5-fluorouridine and 5-fluorocytidine. Masked precursors of anticancer nucleosides.
J. Med. Chem. 1981, 24, 893–897. [CrossRef] [PubMed]
25. Khan, S.H.; O’Neill, R.A. Modern Methods in Carbohydrate Synthesis; Harwood Academic Publishers:
Amsterdam, The Netherlands, 1996.
26. Lindhorst, T.K. Essentials of Carbohydrate Chemistry and Biochemistry; Wiley-VCH Verlag Gmb-H & Co. KGaA:
Weinheim, Germany, 2007.
27. Demchenko, A.V. Handbook of Chemical Glycosylation; Wiley-VCH Verlag Gmb-H & Co. KGaA: Weinheim,
Germany, 2008.
28. Chen, X.; Halcomb, R.L.; Wang, P.G. Chemical Glycobiology (ACS Symposium Series 990); American Chemical
Society: Washington, WA, USA, 2008.
29. Toshima, K.; Tatsuta, K. Recent progress in O-glycosylation methods and its application to natural products
synthesis. Chem. Rev. 1993, 93, 1503–1531. [CrossRef]
30. Ito, Y. My stroll in the backyard of carbohydrate chemistry. Trend. Glycosci. Glycotechnol. 2010, 22, 119–140.
[CrossRef]
31. Yasomanee, J.P.; Demchenko, A.V. From stereocontrolled glycosylation to expeditious oligosaccharide
synthesis. Trend. Glycosci. Glycotechnol. 2013, 25, 13–41. [CrossRef]
32. Nakamura, M.; Fujita, S.; Ogura, H. Synthesis of disaccharide nucleoside derivatives of 3-deoxy-
D-glycero-D-galacto-2-nonulosonic acid (KDN). Chem. Pharm. Bull. 1993, 41, 21–25. [CrossRef]
33. Mikhailov, S.N.; Rodionov, A.A.; Efimtseva, E.V.; Ermolinsky, B.S.; Fomitcheva, M.V.; Padyukova, N.S.;
Rothenbacher, K.; Lescrinier, E.; Herdewijn, P. Studies on disaccharide nucleoside synthesis. Mechanism
of the formation of trisaccharide purine nucleosides. Nucleosides Nucleotides 1999, 18, 691–692. [CrossRef]
[PubMed]
34. Lichtenthaler, F.W.; Sanemitsu, Y.; Nohara, T. Synthesis of 50-O-glycosyl-ribo-nucleosides. Angew. Chem.
Int. Ed. 1978, 17, 772–774. [CrossRef]
35. Knapp, S.; Gore, V.K. Synthesis of the shimofuridin nucleoside disaccharide. J. Org. Chem. 1996, 61,
6744–6747. [CrossRef] [PubMed]
36. Zhang, Y.; Knapp, S. Glycosylation of nucleosides. J. Org. Chem. 2016, 81, 2228–2242. [CrossRef] [PubMed]
37. Xing, L.; Niu, Q.; Li, C. Practical glucosylations and mannosylations using anomeric benzoyloxy as a leaving
group activated by sulfonium ion. ACS Omega 2017, 2, 3698–3709. [CrossRef]
38. Septak, M. Kinetic studies on depurination and detritylation of CPG-bound intermediates during
oligonucleotide synthesis. Nucl. Acids Res. 1996, 24, 3053–3058. [CrossRef] [PubMed]

Molecules 2017, 22, 1650
20 of 21
39. Gulyaeva, I.V.; Neuvonen, K.; Lönnberg, H.; Rodionov, A.A.; Shcheveleva, E.V.; Bobkov, G.V.; Efimtseva, E.V.;
0
Mikhailov, S.N. Effective anomerisation of 2 -deoxyadenosine derivatives during disaccharide nucleoside
synthesis. Nucleosides Nucleotides Nucleic Acids 2004, 23, 1849–1864. [CrossRef] [PubMed]
40. Aoki, S.; Fukumoto, T.; Itoh, T.; Kurihara, M.; Saito, S.; Komabiki, S. Synthesis of disaccharide nucleosides
by the O-glycosylation of natural nucleosides with thioglycoside donors. Chem. Asian J. 2015, 10, 740–751.
[CrossRef] [PubMed]
41. Ferrier, R.J. 450. The interaction of phenylboronic acid with hexosides. J. Chem. Soc. (Resumed) 1961
2325–2330. [CrossRef]
,
42. Ferrier, R.J. Carbohydrate boronates. Adv. Carbohyd. Chem. Biochem. 1978, 35, 31–80.
43. Duggan, P.J.; Tyndall, E.M. Boron acids as protective agents and catalysts in synthesis. J. Chem. Soc. Perkin
Trans. 1 2002, 1325–1339. [CrossRef]
0
44. Yamada, K.; Hayakawa, H.; Wada, T. Method for preparation of 2 -O-alkylribonucleosides by regioselective
0
0
alkylation of 2 ,3 -O-(arylboronylidene) ribonucleosides. JPN. Patent JP 2009/256335A, 5 November 2009.
45. Lee, D.; Taylor, M.S. Borinic acid-catalyzed regioselective acylation of carbohydrate derivatives. J. Am.
Chem. Soc. 2011, 133, 3724–3727. [CrossRef] [PubMed]
46. Gouliaras, C.; Lee, D.; Chan, L.; Taylor, M.S. Regioselective activation of glycosyl acceptors by a diarylborinic
acid-derived catalyst. J. Am. Chem. Soc. 2011, 133, 13926–13929. [CrossRef] [PubMed]
47. Satoh, H.; Manabe, S. Design of chemical glycosyl donors: Does changing ring conformation influence
selectivity/reactivity? Chem. Soc. Rev. 2013, 42, 4297–4309. [CrossRef] [PubMed]
48. Liu, X.; Zhang, B.; Gu, X.; Chen, G.; Chen, L.; Wang, X.; Xiong, B.; You, Q.-D.; Chen, Y.-L.; Shen, J.
1,2-trans-1-Dihydroxyboryl benzyl S-glycoside as glycosyl donor. Carbohydr. Res. 2014, 398, 45–49. [CrossRef]
[PubMed]
49. Nakagawa, A.; Tanaka, M.; Hanamura, S.; Takahashi, D.; Toshima, K. Regioselective and
1,2-cis-α-stereoselective glycosylation utilizing glycosyl-acceptor-derived boronic ester catalyst. Angew. Chem.
Int. Ed. 2015, 127, 11085–11089. [CrossRef]
50. Tanaka, M.; Nashida, J.; Takahashi, D.; Toshima, K. Glycosyl-acceptor-derived borinic ester-promoted direct
and β-stereoselective mannosylation with a 1,2-anhydromannose donor. Org. Lett. 2016, 18, 2288–2291.
[CrossRef] [PubMed]
51. Nishi, N.; Nashida, J.; Kaji, E.; Takahashi, D.; Toshima, K. Regio- and stereoselective β-mannosylation
using a boronic acid catalyst and its application in the synthesis of a tetrasaccharide repeating unit of
lipopolysaccharide derived from E. Coli O75. Chem. Commun. 2017, 53, 3018–3021. [CrossRef] [PubMed]
52. Mancini, R.S.; Leea, J.B.; Taylor, M.S. Boronic esters as protective groups in carbohydrate chemistry: Processes
for acylation, silylation and alkylation of glycoside-derived boronates. Org. Biomol. Chem. 2017, 15, 132–143.
[CrossRef] [PubMed]
53. Mancini, R.S.; Lee, J.B.; Taylor, M.S. Sequential functionalizations of carbohydrates enabled by boronic esters
as switchable protective/activating groups. J. Org. Chem. 2017, 82, 8777–8791. [CrossRef] [PubMed]
54. Lemanski, G.; Ziegler, T. Synthesis of 4-O-D-mannopyranosyl-α-D-glucopyranosides by intramolecular
glycosylation of 6-O-tethered mannosyl donors. Tetrahedron 2000, 56, 563–579. [CrossRef]
55. Huang, X.; Huang, L.; Wang, H.; Ye, X.-S. Iterative one-pot synthesis of oligosaccharides. Angew. Chem.
Int. Ed. 2004, 43, 5221–5224. [CrossRef] [PubMed]
56. Verma, V.P.; Wang, C.-C. Highly stereoselective glycosyl-chloride-mediated synthesis of 2-deoxyglucosides.
Chem. Eur. J. 2013, 19, 846–851. [CrossRef] [PubMed]
57. Lian, G.; Zhang, X.; Yu, B. Thioglycosides in carbohydrate research. Carbohydr. Res. 2015, 403, 13–22.
[CrossRef] [PubMed]
58. Wulff, G.; Röhle, G. Results and problems of O-glycoside synthesis. Angew. Chem. Int. Ed. 1974, 13, 157–170.
[CrossRef] [PubMed]
59. Demchenko, A.; Stauch, T.; Boons, G.-J. Solvent and other effects on the stereoselectivity of thioglycoside
glycosidations. Synlett 1997, 818–820. [CrossRef]
60. Zhu, X.-F.; Williams, H.J., Jr.; Scott, A.I. An improved transient method for the synthesis of N-benzoylated
nucleosides. Synth. Commun. 2003, 33, 1233–1243. [CrossRef]
61. Eisenführ, A.; Arora, P.S.; Sengle, G.; Takaoka, L.R.; Nowickb, J.S.; Famuloka, M. A ribozyme with michaelase
activity: Synthesis of the substrate precursors. Bioorg. Med. Chem. 2003, 11, 235–249. [CrossRef]

Molecules 2017, 22, 1650
21 of 21
62. Welch, C.J.; Bazin, H.; Heikkilä, J.; Chattopadhyaya, J. Synthesis of C-5 and N-3 arenesulfenyl uridines.
Preparation and properties of a new class of uracil protecting group. Acta Chem. Scand. 1985, B 39, 203–212.
[CrossRef]
0
0
63. Samuels, E.R.; McNary, J.; Aguilar, M.; Awad, A.M. Effective synthesis of 3 -deoxy-3 -azido nucleosides for
antiviral and antisense ribonucleic guanidine (RNG) applications. Nucleosides Nucleotides Nucleic Acids 2013
32, 109–123. [CrossRef] [PubMed]
,
64. France, R.R.; Rees, N.V.; Wadhawan, J.D.; Fairbanks, A.J.; Compton, R.G. Selective activation of glycosyl
donors utilising electrochemical techniques: a study of the thermodynamic oxidation potentials of a range of
chalcoglycosides. Org. Biomol. Chem. 2004, 2, 2188–2194. [CrossRef] [PubMed]
65. Tam, P.-H.; Lowary, T.L. Synthesis of deoxy and methoxy analogs of octyl
(1 6)- -D-mannopyranoside as probes for mycobacterial lipoarabinomannan biosynthesis. Carbohydr. Res.
2007, 342, 1741–1772. [CrossRef] [PubMed]
α-D-mannopyranosyl-
→
α
66. Shuto, S.; Horne, G.; Marwood, R.D.; Potter, B.V.L. Total synthesis of nucleobase-modified adenophostin A
mimics. Chem. Eur. J. 2001, 7, 4937–4946. [CrossRef]
67. Wunderlich, C.H.; Spitzer, R.; Santner, T.; Fauster, K.; Tollinger, M.; Kreutz, C. Synthesis of (6-13C)pyrimidine
nucleotides as spin-labels for RNA dynamics. J. Am. Chem. Soc. 2012, 134, 7558–7569. [CrossRef] [PubMed]
68. Abraham, R.C.; Aman, N.; Borstel, R.V.; Darsley, M.; Kamireddy, B.; Kenten, J.; Morris, G.; Titmas, R.
Conjugates of COL-1 monoclonal antibody and
β-D-galactosidase can specifically kill tumor cells by
generation of 5-fluorouridine from the prodrug
127–133. [CrossRef]
β-D-galactosyl-5-fluorouridine. Cell Biophys. 1994, 24/25,
69. Yalpani, M.; Boeseb, R. The structure of amine adducts of triorganylboroxines. Chem. Ber. 1983, 116,
3347–3358. [CrossRef]
70. McKinley, N.F.; O’Shea, D.F. Efficient synthesis of aryl vinyl ethers exploiting 2,4,6-trivinylcyclotriboroxane
as a vinylboronic acid equivalent. J. Org. Chem. 2004, 69, 5087–5092. [CrossRef] [PubMed]
71. Iovine, P.M.; Fletcher, M.N.; Lin, S. Condensation of arylboroxine structures on Lewis basic copolymers as a
noncovalent strategy toward polymer functionalization. Macromolecules 2006, 39, 6324–6326. [CrossRef]
72. Chen, T.-B.; Huzak, M.; Macura, S.; Vuk-Pavlovic´, S. Somatostatin analogue octreotide modulates metabolism
and effects of 5-fluorouracil and 5-fluorouridine in human colon cancer spheroids. Cancer Lett. 1994, 86,
41–51. [CrossRef]
73. Agudo, R.; Arias, A.; Pariente, N.; Perales, C.; Escarmís, C.; Jorge, A.; Marina, A.; Domingo, E. Molecular
characterization of a dual inhibitory and mutagenic activity of 5-fluorouridine triphosphate on viral RNA
synthesis. Implications for lethal mutagenesis. J. Mol. Biol. 2008, 382, 652–666. [CrossRef] [PubMed]
74. Kirienko, D.R.; Revtovich, A.V.; Kirienko, N.V. A high-content, phenotypic screen identifies fluorouridine as
an inhibitor of pyoverdine biosynthesis and Pseudomonas aeruginosa virulence. mSphre 2016, 1, e00217-16.
75. Wu, Q.; Xia, A.; Lin, X. Synthesis of monosaccharide derivatives and polymeric prodrugs of 5-fluorouridine
via two-step enzymatic or chemo-enzymatic highly regioselective strategy. J. Mol. Catal. B: Enzymatic 2008
54, 76–82. [CrossRef]
,
76. Brusa, P.; Dosio, F.; Coppo, S.; Pacchioni, D.; Arpicco, S.; Crosasso, P.; Cattel, L. In vitro and in vivo antitumor
activity of immunoconjugates prepared by linking 5-fluorouridine to antiadenocarcinoma monoclonal
antibody. Farmaco 1997, 52, 71–81. [PubMed]
77. Ozaki, S.; Akiyama, T.; Morita, T.; Kumegawa, M.; Nagase, T.; Uehara, N.; Hoshi, A.
0
5-Fluorouracil derivatives XX.: Synthesis and antitumor activity of 5 -O-unsaturated acyl-5-fluorouridines.
Chem. Pharm. Bull. 1990, 38, 3164–3166. [CrossRef] [PubMed]
78. Martino, M.M.; Jolimaitre, P.; Martino, R. The prodrugs of 5-fluorouracil. Curr. Med. Chem. Anti-Cancer Agents
2002, 2, 267–310. [CrossRef]
Sample Availability: Sample of the compounds are not available from the authors.
©
2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).