Stereoselective synthesis of pseudoglycosides catalyzed by TeCl4 under mild conditions

Article abstract of DOI:10.1016/j.tet.2012.07.070

Catalytic amounts of tellurium(IV) tetrachloride were used to promote the O-glycosylation of 3,4,6-tri-O-acetyl-d-glucal to give the corresponding 2,3-unsaturated-O-glycosides. With simple alcohols, the desired compounds were obtained in good yields and excellent anomeric selectivity in a short reaction time using only 2 mol % of the catalyst. The application of the method in the synthesis of a small set of glycopyranosides with rigid or flexible linkers gave the corresponding α anomers as products in good yields. Further applications of some of the synthesized compounds in allylation reaction of aldehydes gave the corresponding homoallylic alcohols in good yields.

Full text of DOI:10.1016/j.tet.2012.07.070

Tetrahedron 68 (2012) 8645e8654
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Stereoselective synthesis of pseudoglycosides catalyzed by TeCl4 under mild
conditions
ˇ
a
a
a
b
a
ꢀ
~
Juliano C.R. Freitas , Tulio R. Couto , Antonio A.S. Paulino , Joao R. de Freitas Filho , Ivani Malvestiti ,
Roberta A. Oliveira a, Paulo H. Menezes a
,
*
a Departamento de Química, Universidade Federal de Pernambuco, Av. Jornalista Anibal Fernandes s/n, 50670-901 Recife-PE, Brazil
b Departamento de Química, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros s/n, 52171-900 Recife-PE, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 May 2012
Received in revised form 11 July 2012
Accepted 19 July 2012
Available online 26 July 2012
Catalytic amounts of tellurium(IV) tetrachloride were used to promote the O-glycosylation of 3,4,6-tri-O-
acetyl-D-glucal to give the corresponding 2,3-unsaturated-O-glycosides. With simple alcohols, the de-
sired compounds were obtained in good yields and excellent anomeric selectivity in a short reaction time
using only 2 mol % of the catalyst. The application of the method in the synthesis of a small set of gly-
copyranosides with rigid or flexible linkers gave the corresponding
a anomers as products in good yields.
Further applications of some of the synthesized compounds in allylation reaction of aldehydes gave the
corresponding homoallylic alcohols in good yields.
Keywords:
2,3-Unsaturated O-glycosides
Glycosidation reaction
Tellurium(IV) tetrachloride
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
In addition to their role in energy metabolism, carbohydrates
are also responsible for several functions in cells and organisms.1
For instance, carbohydrates can be found in intra- and extracellu-
lar media bound to proteins and lipids.2 They are also present as
free polysaccharides on cell surfaces and in intercellular space,
which are used by bacteria and virus as attachment sites.3
Pseudoglycosides can also be used as building blocks in the
synthesis of natural products,4 glycopeptides,5 sugars,6 oligosac-
charides,7 and nucleosides.8 Besides, carbohydrates are present as
units in several natural products such as salicin,9 catalpol,10 and
macrolactin O11 (Fig. 1), which present a wide range of biological
activities.
Fig. 1. Representative examples of natural products containing an O-glycosidic bond.
2,3-Unsaturated-O-glycosides are useful intermediates in car-
bohydrate chemistry. They can be easily obtained from the glyco-
sylation reaction or through a Ferrier rearrangement, which
involves a nucleophilic substitution reaction combined with an
allylic shift in a glycal.12 The orientation of the formed glycoside
the cost of the reagents led to a search for a milder procedure for
the preparation of this class of compounds.
Tellurium tetrahalides (TeCl4, TeBr4, and TeI4) are versatile
compounds, since they can react with both Lewis bases and Lewis
acids,15 and this amphoteric behavior can be understood in terms of
the partially ionic TeeX bonding, which can be controlled by the
electronegativity of the halide.
Recently, we described the use of tellurium tetrabromide (IV) to
promote the O-glycosylation of glycals to yield the corresponding
2,3-unsaturated-O-glycosides.14b We describe herein the results
obtained by using tellurium tetrachloride, a less expensive and
more electrophilic Lewis acid choice to promote the O-glycosyla-
bond,
a or b depends on some combination of control elements,
being the most important the ‘kinetic anomeric effect’.13
A number of Lewis acids and oxidizing agents can promote this
reaction14 with some caveats in generality, yields, and selectivity. In
addition, the use of strong acidic or oxidizing conditions, as well as
* Corresponding author. E-mail address: pmenezes@ufpe.br (P.H. Menezes).
tion of 3,4,6-tri-O-acetyl-D-glucal, 1. The method may be useful as
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.07.070

8646
J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
an alternative to the previously described ones, particularly for the
synthesis of glycopyranosides with rigid or flexible linkers, com-
pounds of great interest in chemistry and biology (Fig. 2).16
In an attempt to broaden the scope of our methodology and to
demonstrate its efficiency, we explored the generality of our
method extending the conditions to other alcohols and the results
are summarized in Table 2.
Inspection of Table 2 shows that the reaction worked well for
a variety of alcohols. Both hindered and non-hindered alcohols
gave the desired products in a short reaction time and
a anomeric
selectivity. The reaction with alkynols also gave the corresponding
products after short reaction times with excellent
a selectivity
(Table 2, entries 1e3).
When allylic, homoallylic, and benzylic alcohols were used;
the reaction times were slightly increased without any loss in
the stereoselectivity (Table 2, entries 4e6). The same behavior
was observed for aliphatic and cyclic alcohols (Table 2, entries
7e13). The reaction of glycal 1 with phenol derivatives is de-
scribed to be difficult to proceed,14c but in our case, the product
was obtained in moderate yield and anomeric selectivity (Table
2, entry 14).
The syntheses of molecules bearing multiple carbohydrate
moieties are of great interest in chemistry and biology since these
molecules can mimic ligandereceptor interactions increasing the
affinities to an appropriate target.17 This is particularly true for
soluble proteins (lectins), which possess multiple and often ho-
mologous carbohydrate recognition domains (CRDs).18
Fig. 2. Examples of pseudoglycosides with rigid or flexible linkers.
2. Results and discussion
For preliminary optimization of the reaction conditions, 1
(1.0 mmol) and propargyl alcohol (1.2 mmol) in dichloromethane
(10 mL) were treated at room temperature with different amounts
of TeCl4 and the progress of the reaction was monitored by TLC. The
results are depicted in Table 1.
Table 1
Influence of the amount of TeCl4 in the synthesis of 2,3-unsaturated O-glyco-
a
sidesd2a and 2a0
Our strategy for the synthesis of analogs of this class of com-
pounds was initially based on the use of alkynyl diols in order to
obtain the corresponding alkynyl glycosides. Thus, the reaction of
3,4,6-tri-O-acetyl- -glucal 1 with different alkynyl diols as nucle-
D
ophiles using catalytic amounts of tellurium tetrachloride under
the same conditions described in Table 2 gave the corresponding
glycosides 2oer in good yields, selectivities, and short reaction
times (Table 3).
Entry
TeCl4 (equiv)
Ratioa
(
a
:b
)
Yieldb (%)
In general, the reaction proceeded smoothly with good yield. In
1
2
3
4
0.4
0.2
0.08
0.05
0.02
d
88:12
88:12
89:11
89:11
88:12
d
90
91
92
92
92
d
all cases the a,a isomer was observed as the major compound, with
a slightly decrease in the selectivity when comparing Table 3 to
Table 2. When but-2-yne-1,4-diol was used, compound 2o was
obtained in an excellent yield and moderate
entry 1).
a selectivity (Table 3,
5
6c
The distance between the two glycosidic units was increased
when 1,3-diynes were used. In these cases, the yields were
lower compared to the reaction using but-2-yne-1,4-diol (Table
3, entries 2e4). When a more hindered 1,3-diyne was used,
compound 2q was isolated in a similar yield with a slight in-
crease in the selectivity (Table 3, entry 3). Finally, the use of
a
The anomeric ratios were obtained by 1H NMR and confirmed by gas chroma-
tography for all reactions.
b
Isolated yield.
Product not observed after 360 min.
c
In all cases the reaction proceeded smoothly leading to the
a
homopropargylic alkynyl alcohol gave the corresponding
complete conversion of 1 into the corresponding 2,3-unsaturated
O-glycoside 2a in high yield and with excellent
(Table 1, entries 1e5). It is also interesting to note that when the
amount of TeCl4 was reduced from 0.4 to 0.02 equiv, no decrease in
the yield and anomeric selectivity was observed (Table 1, entries 1
and 5). The stereochemistry of 2a was supported by a NOESY ex-
alkynyl glycoside 2r in moderate yield and with
a selectivity
a selectivity
(Table 3, entry 4).
Given the yields and selectivities obtained when alkynyl diols
were used we turned our attention to alternative procedures to
prepare the alkynyl 2,3-unsaturated O-glycosides in a more selec-
tive way. So, compounds 2aec (Table 2, entries 1e3) were purified
periment. The structure of the
b
anomer has the same stereo-
anomer has opposite
stereochemistry. Thus, it is expected that the interaction between
H1b and H5 in the anomer would produce a positive NOE effect. In
our case, no NOE was observed after irradiation of the signal at
5.22 corresponding to the H1a in the anomer (Fig. 3).
by column chromatography to give the corresponding pure
a iso-
chemistry at both H1 and H5 whereas the
a
b
mers, which were then submitted to a Ni-catalyzed aerobic oxi-
dative coupling reaction19 (Table 4). It is important to mention this
b
oxidative coupling does not isomerizes the anomeric center, so
isomers were obtained exclusively.
a,a
d
a
From Table 3 it can also be observed that compound 2p was
obtained in 76% yield and 77% selectivity (Table 3, entry 2). By
comparison, using the Ni-catalyzed aerobic oxidative coupling
reaction (Table 4, entry 1), the pure isomer of 2p was ob-
a,a
a,a
tained in 70% overall yield after two steps starting from 2a (Table
1, entry 1).
The synthesized compounds are useful intermediates for
preparing aromatic cluster glycosides, through alkyne cyclo-
trimerization reaction,20 which might conceivably serve as guests
in hosteguest chemistry. These systems contain a lipophilic core
Fig. 3. NOE irradiation of 2a.

J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
8647
surrounded by a hydrophilic shell, thus providing an ideal envi-
ronment for inclusion compounds with amphiphilic guests.21
In addition, compounds 2oer might be used in the formation
of homogeneous cross-linked complexes with lectins for
bioconjugations.22
Table 2
TeCl4 promoted synthesis of 2,3-unsaturated O-glycosides 2aen
Dimeric carbohydrates with flexible linkers were also shown to
have higher affinities for some lectins having different kinetics and
organization patterns of the cross-linked lattices.23 Our strategy to
synthesize these class of compounds was based on the glyco-
sidation reaction of 1 with glycols catalyzed by tellurium tetra-
chloride. The corresponding products 2set were obtained in good
Entry
1
Product
Time (min) Ratioa
(
a
:
b
)
Yieldb (%)
92
2a
2b
2c
3
5
3
88:12
91:9
yields and
a selectivities (Table 5).
Starting with ethylene glycol the method gave the correspond-
ing product 2s in good yield and selectivity in a very short reaction
time (Table 5, entry 1). When the distance between the two gly-
cosidic units was increased by the use of diethylene glycol the
corresponding product 2t was obtained in good yield and selec-
tivity, demonstrating that other glycols could be used in the re-
action (Table 5, entry 2).
Finally, the use of glycol ethers gave the corresponding products
2uev in moderate yields and selectivities (Table 6). Generally, an-
alogs of these compounds are prepared by hydrogenolysis of the
corresponding alkynyl derivatives, thus our method is comple-
mentary to the previous described strategies to prepare this class of
compounds.18c
The development of methods focusing on environmentally
benign reaction media has become particularly prominent.24
Thus, advances in the development of aqueous biphasic cataly-
sis25 and the use of supercritical fluids,26 ionic liquids,27 and
fluorous media28 continue to be important areas of in-
vestigation. Study of organometallic reactions using water as
(co)-solvent is still a challenge. However, the use of water as
a solvent seems to be the best option due to its simplicity and
very low cost.
Despite the several existing methods for the allylation of car-
bonyl compounds in aqueous media based on In,29 Sn,30 Zn,31 and
Mg32 derived reagents, organotrifluoroborates have proved to be
very useful due to the good reactivity and excellent stereocontrol
toward 1,2-additions. In this context, several methods for the
allylation of carbonyl compounds using allylic trifluoroborates
promoted by variety of Lewis acids33 or palladium-catalysts34 have
been described.
Thus we were interested in expanding the scope of these re-
actions to include the use of the synthesized compounds as cata-
lysts in the allylation reaction of aldehydes. We first examined the
viability of the reaction of 4-nitro-benzaldehyde 3 and potassium
allyltrifluoroborate 4 in a biphasic reaction medium (CH2Cl2/H2O)
at room temperature using 2sev (10 mol %) as phase transfer cat-
alysts to give the corresponding homoallylic alcohol 5. These results
are presented in Table 7.
In all cases, 5 was obtained in high yields and did not require
further purification by chromatography. In the absence of a phase
transfer catalyst, the product was obtained only in 7% yield after
15 min (Table 7, entry 5).
When 2s and 2t were used as promoters, the corresponding
homoallylic alcohol 5 was obtained in excellent yield after only
10 min. Subsequent conversion of the obtained products of both
reactions into their corresponding Mosher ester derivatives fol-
lowed by 19F analysis did not indicate any enantiomeric excess for
the reaction. Compounds 2uev also gave the corresponding prod-
uct in good yield; however when 2v was used a longer reaction
time was required for the reaction completion This fact may be
explained by the role of cation solvation by the ligand in size
match-selectivity phenomena, which is widely accepted as the
most important factor in controlling metal ion selectivity for
macrocyclic ligands.35
2
93
94
88
89
90
90
91
88
90
87
90
87
3
89:11
87:13
92:8
4
2d 10
2e 15
5
6
2f
20
87:13
87:13
88:12
88:12
89:11
91:9
7
2g 20
2h 25
8
9
2i
2j
10
15
10
11
12
13
2k 15
2l
10
90:10
87:13
2m 15
14
2n
3
60:40
75
a
The anomeric ratios were obtained by 1H NMR and confirmed by gas chroma-
tography for all reactions.
b
Isolated yield.

8648
J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
Table 3
TeCl4 promoted synthesis of alkynyl 2,3-unsaturated O-glycosides 2oer
Entry
R
n
Product
Time
(min)
Ratio
(a:a/a:b/b:b)
Yieldb (%)
a
1
eCH2e
1
2o
10
78:22:trace
89
2
eCH2e
2
2p
10
77:23:trace
76
3
eC(CH3)2
2
2q
10
82:18:trace
71
4
eCH2CH2e
2
2r
10
80:20:trace
70
a
The anomeric ratios were obtained by 1H NMR and confirmed by gas chromatography for all reactions.
Isolated yield.
b
3. Conclusion
Table 4
Synthesis of a,a conjugated diynes from the homocoupling reaction of alkynyl 2,3-
unsaturated O-glycosides
In summary, we have demonstrated that a catalytic amount of
tellurium(IV) tetrachloride can efficiently promote the O-glycosyl-
ation of glycals. The approach is complementary to the previously
described methods for the synthesis of O-glycosides and a com-
parison of the use of a catalytic amount of TeCl4 with literature
methods is described in Table 8. Although the available methods
gave 2a in good yields and selectivities in some cases, our method
gave similar results using shorter reaction times and low catalyst
loading under milder reaction conditions.
In addition, the application of the method in the synthesis of
dimeric glycopyranosides having rigid or flexible linkers, gave the
Entry
Alkyne
Product
Time (h)
Ratioa
(
a
:
a
/
a
:
b
/
b
:
b
)
Yieldb (%)
1
2
3
2a
2b
2c
2p
2q
2r
10
12
10
100:0:0
100:0:0
100:0:0
75
76
72
corresponding products in good yields and
a anomeric selectivity.
Further application of the synthesized compounds in the allylation
reaction of aldehydes using potassium allyltrifluoroborate in
aqueous conditions gave the corresponding homoallylic alcohols in
good yields.
a
The anomeric ratios were obtained by 1H NMR and confirmed by gas chroma-
tography for all reactions.
b
Isolated yield.

J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
8649
Table 5
TeCl4 promoted the reaction of 1 with glycols
Entry
1
HOeReOH
Product
Time (min)
Ratioa
(a
:a
/a
:
b/b
:b
)
Yieldb (%)
2s
15
86:14:Trace
70
2
2t
20
87:13:Trace
67
a
The anomeric ratios were obtained by 1H NMR and confirmed by gas chromatography for all reactions.
Isolated yield.
b
Table 6
Table 8
TeCl4 promoted the reaction of 1 with glycol ethers
Comparison between the use of TeCl4 and other catalysts for the synthesis of 2a and
2a0
Entry
Product
Time (min)
Ratioa
75:25
(a
:
b)
Yieldb (%)
Catalyst
Time (min)
Yield (%)
Ratio 2a/2a0
1
2u
15
86
1
2
3
4
5
6
7
8
TeCl4
TeBr4
3
5
20
720
10
10
390
480
10
150
60
240
69
60
92
92
80
82
88
86
85
78
90
76
76
89
78
97
85
93
88:12
87:13
68:32
80:20
da
14b
14h
Er(OTf)3
HFIP14g
14d
ZnCl2/Al2O3
H3PO4
14e
91:9
14c
AuCl3
87:13
70:30
90:10
88:12
91:9
80:20
60:40
86:14
90:10
90:10
CeCl3$7H2O14n
14o
9
InCl3
2
2v
20
76:24
88
14k
10
11
12
13
14
15
16
Bi(OTf)3eSiO2
14j
HClO4eSiO2
La(NO3)3$6H2O14f
14l
FeCl3
K-1014p
a
The anomeric ratios were obtained by 1H NMR and confirmed by gas chroma-
14i
Mg(ClO4)2
Dy(OTf)3
70
90
tography for all reactions.
14m
b
Isolated yield.
a
The ratio was not given.
Table 7
2,3-unsaturated O-glycosides promote the allylation of aldehydes
4. Experimental section
4.1. Material
All reagents and solvents used were previously purified and
dried in agreement with the literature.36 Tellurium(IV) tetrachlo-
ride was purchased from Aldrich Chemical Co. and used as received.
All other commercially available reagents and solvents were used
as received. Reactions were monitored by thin-layer chromatog-
raphy on 0.25 mm E. Merck silica gel 60 plates (F254) using UV light,
vanillin, and p-anisaldehyde as visualizing agents. Column chro-
matography purification was performed using Silica Gel 60
(230e400 mesh) unless indicated otherwise. All compounds
Entry
Catalyst
Time (min)
Yielda (%)
1
2
3
4
5
2s
2t
2u
2v
d
10
10
5
90
15
91
90
93
92
7
a
Isolated yield.

8650
J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
purified by chromatography were sufficiently pure for use in fur-
1742, 1375, 1239, 1030 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d 5.90 (br d,
ther experiments, unless indicated otherwise.
J3e2¼10.2 Hz, 1H, H-3), 5.82 (dt, J2e3¼10.2 Hz, J2e1¼J2e4¼1.5 Hz, 1H,
H-2), 5.33 (ddd, J4e5¼9.6 Hz, J4e3¼3.0 Hz, J4e2¼1.5 Hz, 1H, H-4),
5.22 (br s, 1H, H-1), 4.29 (d, J¼2.4 Hz, 2H, OCH2), 4.25 (dd,
4.2. Instrumentation
0
0
J6e6 ¼12.4 Hz, J6e5¼5.4 Hz, 1H, H-6), 4.16 (dd, J6 e6¼12.4 Hz,
1H NMR and 13C NMR data were recorded in CDCl3 or DMSO-d6.
J6 e5¼2.4 Hz, 1H, H-60), 4.07 (ddd, J5e4¼9.6 Hz, J5e6¼5.4 Hz,
0
0
The chemical shifts are reported as delta (
d
) units in parts per
J5e6 ¼2.4 Hz, 1H, H-5), 2.07 (t, J¼2.4 Hz, 1H, C^CeH), 2.09 (s, 3H,
million (ppm) relative to the solvent residual peak as the internal
reference. 11B (128 MHz) and 19F (376 MHz) NMR spectra were
recorded in DMSO-d6. Spectra were calibrated using BF3$Et2O
(0.0 ppm) as external reference in the case of 11B NMR and chemical
shifts were referenced to external CF3CO2H (0.0 ppm) in the case of
19F NMR. Coupling constants (J) for all spectra are reported in hertz
(Hz). Further analysis by NOESY was performed to confirm the
stereochemistry and peak assignments. High-resolution mass
spectral analyses were performed on using ESI method. Infrared
spectra were recorded using samples prepared as thin films on salt
plates or as KBr pellets. The melting points (mp) are not corrected.
OAc), 2.07 (s, 3H, OAc); 13C NMR (75 MHz, CDCl3)
d 170.7, 170.2,
129.7, 127.1, 92.7, 78.9, 74.8, 67.1, 65.0, 62.7, 55.0, 20.9, 20.7.
4.3.2.2. 2-Methyl but-3-yn-2-yl 4,6-di-O-acetyl-2,3-dideoxy-a-D-
erythro-hex-2-enopyranoside (2b).38 Isolated as a colorless oil;
20
0.28 g (93%); [
a
]
D
þ51.7 (c 0.50, MeOH); IR (thin film) nmax 3268,
2986, 1743, 1369, 1231, 1027, 887 cmꢁ1 1H NMR (300 MHz, CDCl3)
;
d
5.85 (br d, J3e2¼10.2 Hz, 1H, H-3), 5.77 (ddd, J2e3¼10.2 Hz,
J2e4¼2.7 Hz, J2e1¼1.8 Hz, 1H, H-2), 5.62 (br s, 1H, H-1), 5.26 (ddd,
J4e5¼9.3 Hz, J4e2¼2.7 Hz, J4e3¼1.5 Hz, 1H, H-4), 4.29e4.02 (m, 3H,
H-6, H-60 and H-5), 2.51 (s, 1H, C^CeH), 2.05 (s, 3H, OAc), 2.04 (s,
3H, OAc), 1.56 (s, 3H, OCH3), 1.50 (s, 3H, OCH3); 13C NMR (75 MHz,
4.3. Typical procedure
CDCl3) d 171.2. 170.7, 121.2, 128.9, 91.3, 85.6, 73.8, 72.0, 67.4, 65.4,
63.5, 30.9, 30.2, 21.7, 21.3.
4.3.1. Synthesis of tri-O-acetyl-
bottomed flask containing
D
-glucal (1).37 To a 100 mL round
suspension of -glucose (1.0 g,
a
D
4.3.2.3. But-3-yn-1-yl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-
5.55 mmol) in acetic anhydride (3.60 g; 7.0 mol equiv) was added
a solution of HBr/AcOH [hydrobromic acid 48% (0.5 mL) in acetic
anhydride (2.0 mL)] at room temperature over 1 h period. An ad-
ditional amount of HBr/AcOH [hydrobromic acid 48% (3.0 mL) in
acetic anhydride (12.0 mL)] was added and the mixture was
warmed up to room temperature and stirred overnight. Anhydrous
sodium acetate (2.0 g, 24.4 mmol) was then added and after 0.5 h
was added a suspension of CuSO4$5H2O (0.315 g; 1.3 mmol) and
zinc dust (12.6 g; 200 mmol) in water (10 mL) and acetic acid
(15 mL) containing sodium acetate (9.45 g; 115 mmol). The mixture
was stirred at room temperature for 1.5 h. The solid residue was
filtered off and washed with ethyl acetate (100 mL) and water
(100 mL). The organic phase was washed with a saturated solution
of NaHCO3 (100 mL) and brine (50 mL) before drying over MgSO4.
The organic phase was filtered and concentrated in vacuo. Silica gel
chromatography using hexanes/EtOAc (9:1) provided 1.24 g (90%)
of the title compound as a white solid; mp: 54e55 ꢀC (lit.37
hex-2-enopyranoside (2c).14m Isolated as a colorless oil; 0.26 g;
(94%); [
a]
20 þ91.3 (c 1.00, MeOH) [lit.39c
[
a
]
25 þ45.4 (c 2.50, CHCl3)];
D
D
IR (KBr pellet) nmax 3280, 2917, 1742, 1371, 1230, 1043, 974 cmꢁ1; 1H
NMR (300 MHz, CDCl3)
d
5.87 (br d, J3e2¼10.2 Hz, 1H, H-3), 5.81
(ddd, J2e3¼10.2 Hz, J2e4¼2.7 Hz, J2e1¼1.5 Hz, 1H, H-2), 5.28 (ddd,
J4e5¼9.6 Hz, J4e2¼2.7 Hz, J4e3¼1.8 Hz, 1H, H-4), 5.05 (br s, 1H, H-1),
4.25e4.17 (m, 2H, H-6 and H-60), 4.11 (ddd, J5e4¼9.6 Hz,
0
0
J5e6¼5.4 Hz, J5e6 ¼3.0 Hz, 1H, H-5), 3.83 (dt, J7e7 ¼16.5 Hz,
0
0
J7e8¼6.6 Hz, 1H, OCH2CH2), 3.66 (dt, J7 e7¼16.5 Hz, J7 e8¼6.6 Hz, 1H,
0
OCH2CH2), 2.50 (td, J8e7¼J8e7 ¼6.6 Hz, J8e9¼2.7 Hz, 2H, OCH2CH2),
2.08 (s, 3H, OAc), 2.06 (s, 3H, OAc), 1.97 (t, J9e8¼2.7 Hz, 1H,
C^CeH); 13C NMR (75 MHz, CDCl3)
d 170.7, 170.2, 129.3, 127.4, 94.5,
80.9, 69.4, 66.9, 66.7, 65.1, 62.8, 20.9, 20.7, 20.0.
4.3.2.4. Allyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-
enopyranoside (2d).14c Isolated as a colorless oil; 0.24 g (88%);
20
[a
]
þ101.9 (c 1.00, MeOH) [lit.14g
[
a]
þ91.0 (c 0.80, MeOH)]; IR
D
D
20
25
52e53 ꢀC); [
a
]
ꢁ10.4 (c 1.00, MeOH) [lit.37
[a
]
ꢁ59.0 (c 1.00,
(thin film) nmax 2920, 1743, 1642, 1371, 1235, 1039 cmꢁ1 1H NMR
;
D
D
EtOH)]; IR (KBr pellet) nmax 2959, 1738, 1649, 1373, 1226,
(300 MHz, CDCl3) d 5.98e5.83 (m, 3H, H-2,H-3 and eCH]CH2),
1043 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d
6.45 (d, J1e2¼6.0 Hz, 1H, H-
5.30e5.13 (m, 3H, H-4 and eCH]CH2), 5.05 (br s, 1H, H-1),
1), 5.32 (br s, 1H, H-2), 5.20 (t, J3e2¼J3e4¼5.7 Hz, 1H, H-3),
4.84e4.81 (m, 1H, H-5), 4.38 (dd, J4e5¼12.0 Hz, J4e3¼5.7 Hz, 1H, H-
4), 4.25e4.16 (m, 2H, H-6, H-60), 2.07 (s, 3H, OAc), 2.06 (s, 3H, OAc),
4.26e4.01 (m, 5H, H-5, H-6, H-60 and OCH2), 2.07 (s, 3H, OAc), 2.05
(s, 3H, OAc); 13C NMR (75 MHz, CDCl3)
d 170.7, 170.2, 134.0, 129.2,
127.6, 117.5, 93.5, 69.2, 66.8, 65.1, 62.8, 20.9, 20.7.
2.02 (s, 3H, OAc); 13C NMR (75 MHz, CDCl3)
d
170.5, 170.4, 169.5,
145.6, 98.9, 73.8, 67.4, 67.1, 61.3, 20.9, 20.7, 20.7.
4.3.2.5. But-3-en-1-yl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-
hex-2-enopyranoside (2e).14f Isolated as a colorless oil; 0.25 g (89%);
20
25
4.3.2. General procedure for the synthesis of 2,3-unsaturated O-gly-
copyranosides (2aeo, 2v, and 2w). To a 50 mL round bottomed flask
containing a solution of 1 (272 mg, 1.0 mmol) and appropriate al-
cohol (1.2 mmol) in dichloromethane (10 mL) at 0 ꢀC under argon
was added TeCl4 (5 mg, 2 mol %). The ice bath was removed and the
mixture was stirred for the time indicated in Tables 2 and 6. A
saturated solution of ammonium chloride (5 mL) was then added
and the mixture was extracted with EtOAc (2ꢂ10 mL). The com-
bined organic phases were dried over MgSO4 and the solvents were
removed under reduced pressure followed by purification by a flash
column chromatography [hexanes/EtOAc (95:5)] to yield the cor-
responding 2,3-unsaturated O-glycopyranosides.
[a
]
þ83.5 (c 1.00, MeOH) [lit.14f
[
a]
þ80.9 (c 1.20, CHCl3)]; IR
D
D
(thin film) nmax 2923, 1747, 1648, 1369, 1234, 1041 cmꢁ1 1H NMR
;
(300 MHz, CDCl3)
d
5.86 (br d, J3e2¼10.2 Hz,1H, H-3), 5.83e5.76 (m,
2H, H-2 and eCH]CH2), 5.31e5.26 (m, 1H, H-4), 5.11 (dd, J¼3.0,
1.8 Hz, 1H, eCH]CH2), 5.07e5.04 (m, 1H, eCH]CH2), 5.02 (br s,
0
1H, H-1), 4.25 (dd, J6e6 ¼12.4 Hz, J6e5¼5.4 Hz, 1H, H-6), 4.15 (dd,
J6 e6¼12.4 Hz, J6 e5¼2.4 Hz, 1H, H-60), 4.07 (ddd, J5e4¼9.6 Hz,
0
0
0
J5e6¼5.4 Hz, J5e6 ¼2.4 Hz, 1H, H-5), 3.80 (dt, J¼9.6 Hz, J¼6.9 Hz, 1H,
OCH2), 3.56 (dt, J¼9.6 Hz, J¼6.9 Hz, 1H, OCH2), 2.38 (dt, J¼6.9 Hz,
J¼1.5 Hz, 1H, eCH2CH]C), 2.36 (dt, J¼6.9 Hz, J¼1.5 Hz, 1H,
eCH2CH]C), 2.08 (s, 3H, OAc), 2.06 (s, 3H, OAc); 13C NMR (75 MHz,
CDCl3)
d 170.7, 170.2, 134.9, 129.0, 127.7, 116.5, 94.4, 68.0, 66.8, 65.1,
62.9, 34.1, 20.9, 20.7.
4.3.2.1. Prop-2-yn-1-yl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-
hex-2-enopyranoside (2a).14c White solid; mp: 58e59 ꢀC (lit.14g
4.3.2.6. Benzyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-
20
57e58 ꢀC); [
a
]
þ138.6 (c 1.00, MeOH) [lit.14g
[
a
]
þ110.0 (c 0.80,
enopyranoside (2f).14c Isolated as a colorless oil; 0.29 g (90%);
D
D
20
MeOH)]; 0.25 g (92%); IR (KBr pellet) nmax 3281, 2935, 2893, 2129,
[a
]
þ62.1 (c 1.00, MeOH) [lit.14g
[
a]
þ150.0 (c 0.80, MeOH)]; IR
D
D

J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
8651
(thin film) nmax 3030, 2899, 1745, 1656, 1490, 1451, 1371, 1234, 1042,
696 cmꢁ1 1H NMR (300 MHz, CDCl3)
7.38e7.26 (m, 5H, Haryl),
1104 cmꢁ1
;
1H NMR (300 MHz, CDCl3)
d
5,82 (br d, J¼10.2 Hz, 1H,
;
d
H-3), 5.72 (dt, J2e3¼10.2 Hz, J2e1¼J2e4¼2.7 Hz, 1H, H-2), 5.31 (br s,
1H, H-1), 5.25 (br d, J4e5¼9.6 Hz, 1H, H-4), 4.26e4.10 (m, 3H, H-5,
H-6 and H-60), 2.07 (s, 3H, OAc), 2.05 (s, 3H, OAc), 1.27 (s, 9H,
5.98e5.82 (m, 2H, H-2 and H-3), 5.35e5.31 (m, 1H, H-4), 5.13 (br s,
1H, H-1), 4.78 (d, J¼11.4 Hz, 1H, eOCH2(C6H5)), 4.56 (d, J¼11.4 Hz,
1H, eOCH2(C6H5)), 4.31e4.09 (m, 3H, H-5, H-6 and H-60), 2.10 (s,
eC(CH3)3);13C NMR (75 MHz, CDCl3)
d
170.8, 170.3, 129.5, 128.1,
3H, OAc), 2.07 (s, 3H, OAc); 13C NMR (75 MHz, CDCl3)
d 170.8, 170.3,
88.9, 75.3, 66.4, 65.2, 63.2, 28.7, 20.9, 20.8.
137.6, 129.3, 128.5, 128.0, 127.9, 127.8, 93.6, 70.3, 67.1, 65.3, 62.9,
20.9, 20.8.
4.3.2.12. Cyclohexyl
4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-
hex-2-enopyranoside (2l).14b Isolated as a colorless oil; 0.28 g (90%);
4.3.2.7. Methyl 4,6-di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-hex-2-
[a
]
20 þ86.9 (c 1.00, MeOH) [lit.39b
[
a
]
D
31.7 þ110.7 (c 1.00, CHCl3)]; IR
D
enopyranoside (2g).14i Isolated as a colorless oil; 0.22 g (90%);
(thin film) nmax 2933, 2858, 2659, 2134, 1747, 1450, 1370, 1233, 1187,
[
a]
20 þ126.7 (c 1.00, MeOH) [lit.14g
[
a
]
D þ124.0 (c 1.20, MeOH)]; IR
1036 cmꢁ1
;
1H NMR (300 MHz, CDCl3)
d
5.82 (br d, J¼10.5 Hz, 1H,
D
(thin film) nmax 2969, 2893, 1747, 1443, 1370, 1232, 1182, 1106 cmꢁ1
;
H-3), 5.76 (dt, J2e3¼10.5 Hz, J2e1¼J2e4¼1.5 Hz, 1H, H-2), 5.24 (dd,
J4e5¼9.3 Hz, J4e3¼1.2 Hz, 1H, H-4), 5.12 (br s, 1H, H-1), 4.20 (m, 3H,
H-5, H-6 and H-60), 3.64e3.55 (m, 1H, eOCH(CH2)5), 2.04 (s, 3H,
OAc), 2.03 (s, 3H, OAc), 1.92e1.82 (m, 2H, eOCH(CH2)5), 1.71e1.68
(m, 2H, OCH(CH2)5), 1.52e1.48 (m, 1H, eOCH(CH2)5), 1.37e1.15 (m,
1H NMR (300 MHz, CDCl3)
d
5.91 (br d, J3e2¼10.8 Hz, 1H, H-3), 5.82
(dt, J2e3¼10.8 Hz, J2e1¼J2e4¼1.8 Hz, 1H, H-2), 5.32e5.28 (m, 1H,
0
H-4), 4.92 (br s, 1H, H-1), 4.25 (dd, J6e6 ¼12.3 Hz, J6e5¼5.4 Hz, 1H,
H-6), 4.17 (dd, J6 e6¼12.3 Hz, J6 e5¼2.7 Hz, 1H, H-60), 4.05 (ddd,
0
0
J5e4¼9.9 Hz, J5e6¼5.4 Hz, J5e6 ¼2.7 Hz, 1H, H-5), 3.44 (s, 3H,
5H, eOCH(CH2)5); 13C NMR (75 MHz, CDCl3)
d 170.6, 170.2, 128.6,
0
eOCH3), 2.09 (s, 3H, OAc), 2.07 (s, 3H, OAc); 13C NMR (75 MHz,
128.4, 92.6, 76.6, 66.5, 65.3, 63.0, 33.6, 32.0, 25.4, 24.3, 24.0, 20.9,
20.6.
CDCl3)
20.8.
d 170.8, 170.3, 129.2, 127.6, 95.4, 66.7, 65.1, 62.9, 55.9, 20.9,
4.3.2.13. Cyclopentyl
4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-
4.3.2.8. Ethyl 4,6-di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-hex-2-
hex-2-enopyranoside (2m).40 Isolated as a colorless oil; 0.26 g
enopyranoside (2h).14i Isolated as a colorless oil; 0.23 g (91%); [
a
]
(87%); [
a
]
20 þ80.4 (c 1.00, MeOH) [lit.40
[
a]
25 þ99.0 (c 0.98, CHCl3)];
D
D
D
þ78.7 (c 1.00, MeOH) [lit.14g
[
a
]
D
þ120.0 (c 1.20, MeOH)]; IR (thin
IR (thin film) nmax 2940, 2861, 2673, 2137, 1746, 1456, 1373, 1234,
film) nmax 2978, 2895, 1745, 1446, 1373, 1235, 1185, 1108 cmꢁ1
;
1H
1039 cmꢁ1
;
1H NMR (300 MHz, CDCl3)
d
5.81 (br d, J¼10.5 Hz, 1H,
NMR (300 MHz, CDCl3)
d
5.85 (br d, J3e2¼10.5 Hz, 1H, H-3), 5.80 (dt,
H-3), 5.74 (dt, J2e3¼10.5 Hz, J2e1¼J2e4¼2.4 Hz, 1H, H-2), 5.23 (dd,
J2e3¼10.5 Hz, J2e1¼J2e4¼1.5 Hz, 1H, H-2), 5.29e5.25 (m, 1H, H-4),
J4e5¼9.6 Hz, J4e3¼1.2 Hz, 1H, H-4), 5.04 (br s, 1H, H-1), 4.20 (dd,
0
0
0
5.01 (br s, 1H, H-1), 4.22 (dd, J6e6 ¼12.0 Hz, J6e5¼5.1 Hz, 1H, H-6),
J6e6 ¼12.0 Hz, J6e5¼5.4 Hz, 1H, H-6), 4.12 (dd, J6 e6¼12.0 Hz,
4.14 (dd, J6 e6¼12.0 Hz, J6 e5¼2.4 Hz, 1H, H-60), 4.07 (ddd,
J6 e5¼2.4 Hz, 1H, H-60), 4.06 (ddd, J5e4¼9.6 Hz, J5e6¼5.4 Hz,
0
0
0
0
0
J5e4¼9.6 Hz, J5e6¼5.1 Hz, J5e6 ¼2.4 Hz, 1H, H-5), 3.80 (q, J¼7.2 Hz,
J5e6 ¼2.4 Hz, 1H, H-5), 2.04 (s, 3H, OAc), 2.02 (s, 3H, OAc), 1.76e1.47
1H, eCH2CH3), 3.80 (q, J¼7.2 Hz, 1H, eCH2CH3), 2.06 (s, 3H, OAc),
(m, 9H, eOCH(CH2)4and eOCH(CH2)4); 13C NMR (75 MHz, CDCl3)
2.04 (s, 3H, OAc), 1.21 (t, J¼7.2 Hz, 3H, eCH2CH3); 13C NMR (75 MHz,
d
170.6, 170.2, 128.5, 128.3, 93.5, 80.5, 66.6, 65.2, 62.9, 33.4, 32.2,
CDCl3)
d
170.7, 170.2, 128.9, 127.8, 94.1, 66.7, 65.1, 64.1, 62.9, 20.9,
23.4, 23.0, 20.8, 20.7.
20.8, 15.1.
4.3.2.14. 2-Methoxy-4-methyl-phenyl 4,6-di-O-acetyl-2,3-
4.3.2.9. n-Propyl 4,6-di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-hex-2-
dideoxy-
less oil; 0.26 g (75%); [
a-D-erythro-hex-2-enopyranoside (2n). Isolated as a color-
enopyranoside (2i).39a Isolated as a colorless oil; 0.24 g (88%);
a]
20 þ81.7 (c 0.75, CH2Cl2); IR (thin film) nmax
D
[
a
]
20 þ99.7 (c 1.00, MeOH) [lit.39a
[
a
]
D
31.7 þ118.2 (c 1.00, CHCl3)]; IR
3056, 2955, 2936, 2852, 1741, 1514, 1370, 1237, 1098, 1048,
D
(thin film) nmax 2964, 2881, 1747, 1450, 1371, 1234, 1182, 1105 cmꢁ1
;
736 cmꢁ1 1H NMR (300 MHz, CDCl3) glycal a d 6.91e6.64 (m, 3H,
;
1H NMR (300 MHz, CDCl3)
d
5.92e5.78 (m, 2H, H-2 and H-3),
Haryl), 6.08e5.79 (m, 2H, H-2 and H-3), 5.44e5.27 (m, 2H, H-1 and
H-4), 4.14e4.27 (m, 2H, H-6 and H-60), 4.12e4.06 (m, 1H, H-5), 3.84
(s, 3H, ArOCH3), 2.31 (s, 3H, ArCH3), 2.09 (s, 3H, OAc), 2.08 (s, 3H,
OAc); GCeMS (EI, rel int. %) m/z 350 ([Mþ], 4), 290 (2), 275 (1), 230
(25), 217 (60), 187 (5), 165 (12), 138 (8), 111 (4), 91 (3), 43 (100);
glycal b d 6.91e6.64 (m, 3H, Haryl), 6.08e5.79 (m, 2H, H-2 and H-3),
5.44e5.27 (m, 2H, H-1 and H-4), 4.14e4.27 (m, 2H, H-6 and H-60),
3.95e3.88 (m, 1H, H-5), 3.87 (s, 3H, ArOCH3), 2.36 (s, 3H, ArCH3),
2.06 (s, 3H, OAc), 2.03 (s, 3H, OAc); GCeMS (EI, rel int. %) m/z 350
([Mþ], 2), 311 (1), 290 (5), 279 (8), 262 (2), 230 (11), 217 (17), 167
(31), 149 (59), 138 (5), 71 (19), 57 (43), 43 (100); 13C NMR (75 MHz,
0
5.29e5.25 (m, 1H, H-4), 4.99 (br s, 1H, H-1), 4.21 (dd, J6e6 ¼12.0 Hz,
0
0
J6e5¼5.4 Hz, 1H, H-6), 4.14 (dd, J6 e6¼12.0 Hz, J6 e5¼2.1 Hz, 1H, H-
60), 4.08 (ddd, J5e4¼9.6 Hz, J5e6¼5.1 Hz, J5e6 ¼2.1 Hz, 1H, H-5), 3.68
0
(dt, J¼9.6, 7.5 Hz, 1H, eCH2CH2CH3), 3.45 (dt, J¼9.6, 7.5 Hz, 1H,
eCH2CH2CH3), 2.07 (s, 3H, OAc), 2.05 (s, 3H, OAc), 1.61 (qui,
J¼7.5 Hz, 2H, eCH2CH2CH3), 0.91 (t, J¼7.5 Hz, 3H, eCH2CH2CH3);
13C NMR (75 MHz, CDCl3)
d 170.7, 170.2,128.9, 127.8, 94.2, 70.5, 66.7,
65.2, 62.9, 22.9, 20.9, 20.7, 10.6.
4.3.2.10. iso-Propyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-
2-enopyranoside (2j).14d Isolated as a colorless oil; 0.24 g (90%);
CDCl3) d 170.9, 170.5, 170.3, 170.2, 146.1, 143.6, 132.2, 131.8, 130.1,
20
[
a]
þ96.5 (c 1.00, MeOH) [lit.14g
[
a
]
D
þ97.0 (c 0.70, MeOH)]; IR
129.6, 127.7, 127.3, 125.2, 125.1, 115.3, 114.0, 113.3, 113.0, 90.5, 74.8,
74.5, 70.9, 68.6, 67.3, 65.4, 65.0, 63.7, 62.8, 55.9, 21.0, 20.8, 20.7, 20.6,
18.6, 18.5; HRMS (ESI, MeOH/H2O) calcd for C18H22O7Na [MþNa]þ
373.1263, found 373.1279.
D
(thin film) nmax 2971, 2902, 1745, 1450, 1372, 1317, 1233, 1184,
1127 cmꢁ1
;
1H NMR (300 MHz, CDCl3)
d
5.76 (br d, J¼11.7 Hz, 1H,
H-3), 5.69 (dt, J2e3¼11.7 Hz, J2e1¼J2e4¼1.8 Hz, 1H, H-2), 5.19e5.15
(m, 1H, H-4), 5.02 (br s, 1H, H-1), 4.17e4.01 (m, 3H, H-5, H-6 and H-
60), 3.98e3.84 (m, 1H, eCH(CH3)CH3), 1.98 (s, 3H, OAc), 1.97 (s, 3H,
OAc), 1.14 (d, J¼6.3 Hz, 3H, eCH(CH3)CH3), 1.07 (d, J¼6.0 Hz, 3H,
4.3.2.15. 2-(2-(2-Methoxyethoxy)ethoxy)ethanyl 4,6-di-O-acetyl-
2,3-dideoxy-
a colorless oil; 0.32 g (86%); [
pellet) nmax 2878, 1743, 1453, 1371, 1237, 1048 cmꢁ1
(300 MHz, CDCl3)
5.86 (br s, 2H, H-2, H-3), 5.31 (br d, J4e5¼9.6 Hz,
a-D-erythro-hex-2-enopyranoside (2u). Isolated as
eCH(CH3)CH3); 13C NMR (75 MHz, CDCl3)
d
170.4, 169.9, 128.5,
a]
þ61.3 (c 1.00, MeOH); IR (KBr
20
D
128.2, 92.5, 70.4, 66.5, 65.1, 62.8, 23.2, 21.7, 20.7, 20.5.
;
1H NMR
d
0
4.3.2.11. tert-Butyl 4,6-di-O-acetyl-2,3-dideoxy- -erythro-hex-
a
-
D
1H, H-4), 5.07 (br s, 1H, H-1), 4.25 (dd, J6e6 ¼12.0 Hz, J6e5¼5.1 Hz,
2-enopyranoside (2k).40 Isolated as a colorless oil; 0,25 g (87%);
1H, H-6), 4.16 (dd, J6 e6¼12.0 Hz, J6 e5¼2.1 Hz, 1H, H-60), 4.10 (ddd,
0
0
20
25
0
[
a]
þ146.4 (c 1.00, MeOH) [lit.40
[
a]
þ100.0 (c 1.00, CHCl3)]; IR
J5e4¼9.6 Hz, J5e6¼5.1 Hz, J5e6 ¼2.1 Hz, 1H, H-5), 3.74e3.61 (m, 10H,
D
D
(thin film) nmax 2958, 2904, 2129, 1747, 1463, 1371, 1333, 1234, 1186,
OCH2), 3.55e3.52 (m, 2H, OCH2), 3.34 (s, 3H, OCH3), 2.09 (s, 3H,

8652
J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
OAc), 2.07 (s, 3H, OAc); 13C NMR (75 MHz, CDCl3)
129.1, 127.7, 94.6, 71.9, 70.6, 70.5, 70.3, 67.8, 66.8, 65.2, 62.9, 58.9,
20.9, 20.8; ; HRMS (ESI, MeOH/H2O) calcd for C17H28NaO9 [MþNa]þ
399,1631, found 399.1648.
d
170.8, 170.3,
MeOH/H2O) calcd for C30H38O12Na [MþNa]þ, 613.2261; found,
613.2257.
4.3.3.4. Octa-3,5-diyne-1,8-diyl bis-4,6-di-O-acetyl-2,3-dideoxy-
a-D-erythro-hex-2-enopyranoside (2r). Isolated as a colorless oil;
4.3.2.16. 2-(2-Ethoxyethoxy)ethanyl4,6-di-O-acetyl-2,3-dideoxy-
D
0.19 g (70%); [
a
]
20 þ58.7 (c 1.00, MeOH); IR (KBr pellet) nmax 2889,
D
a
-
-erythro-hex-2-enopyranoside (2v).23c Isolated as a colorless oil;
1742, 1371, 1232, 1106, 1042 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d
5.89
0.30 g (88%); [
a
]
20 þ48.4 (c 1.00, MeOH); IR (KBr pellet) nmax 2973,
(br d, J3e2¼10.5 Hz, 1H, H-3), 5.82 (dt, J2e3¼10.5 Hz,
D
2872, 1743, 1445, 1235, 1110, 1048 cmꢁ1; 1H NMR (300 MHz, CDCl3)
J2e1¼J2e4¼2.1 Hz, 1H, H-2), 5.30 (br d, J4e5¼9.6 Hz, 1H, H-4), 5.05
0
d
5.85 (br s, 2H, H-2, H-3), 5.31 (br d, J4e5¼9.6 Hz, 1H, H-4), 5.07 (br
(br s, 1H, H-1), 4.24 (dd, J6e6 ¼12 Hz, J6e5¼5.4 Hz, 1H, H-6), 4.17 (dd,
s, 1H, H-1), 4.25 (dd, J6e6 ¼13.5 Hz, J6e5¼5.4 Hz, 1H, H-6), 4.16 (dd,
J6 e6¼12 Hz, J6 e5¼2.4 Hz, 1H, H-60), 4.15e4.07 (m, 1H, H-5), 3.83(dt,
0
0
0
J6 e6¼13.5 Hz, J6 e5¼2.7 Hz, 1H, H-60), 4.10 (ddd, J5e4¼9.6 Hz,
J7e7 ¼9.9 Hz, J7e8¼6.6 Hz, 1H, OCH2CH2), 3.70 (dt, J7 e7¼9.9 Hz,
0
0
0
0
0
0
0
J5e6¼5.4 Hz, J5e6 ¼2.7 Hz, 1H, H-5), 3.55e3.69 (m, 8H, OCH2), 3.51
J7 e8¼6.6 Hz, 1H, OCH2CH2), 2.58 (t, J8e7¼J8e7 ¼6.6 Hz, 2H,
(q, J¼6.9 Hz, 2H, OCH2CH3),2.09 (s, 3H, OAc), 2.07 (s, 3H, OAc),1.19 (t,
OCH2CH2), 2.10 (s, 3H, OAc), 2.08 (s, 3H, OAc); 13C NMR (75 MHz,
J¼6.9 Hz, 3H, OCH2CH3); 13C NMR (75 MHz, CDCl3)
d
170.8, 170.3,
CDCl3) d 170.8, 170.3, 129.4, 127.3, 94.6, 74.2, 67.0, 66.5, 66.2, 65.1,
129.1, 127.7, 94.6, 70.6, 70.4, 69.8, 67.8, 66.8, 66.6, 65.2, 62.9, 20.9,
20.8, 15.1.
62.8, 20.9, 20.8; HRMS (ESI, MeOH/H2O) calcd for C28H34O12Na
[MþNa]þ, 585.1948; found, 585.1959.
4.3.3. General procedure for the synthesis of 2,3-unsaturated O-gly-
copyranosides (2oer). To a 50 mL round bottomed flask containing
a solution of 1 (326 mg, 1.2 mmol) and appropriate alcohol
(0.5 mmol) in dichloromethane (10 mL) at 0 ꢀC under argon was
added TeCl4 (5 mg, 2 mol %). The ice bath was removed and the
mixture was stirred for the time indicated in Tables 3 and 5. A
saturated solution of ammonium chloride (5 mL) was then added
and the mixture was stirred until the change in the color. The
mixture was extracted with EtOAc (2ꢂ10 mL) and the combined
organic phases were dried over MgSO4. The solvents were removed
under reduced pressure followed by purification by a flash column
chromatography [hexanes/EtOAc (95:5)] to yield the corresponding
2,3-unsaturated O-glycopyranosides.
4.3.3.5. Ethane-1,2-diyl bis-4,6-di-O-acetyl-2,3-dideoxy-
a-D-er-
ythro-hex-2-enopyranoside (2s). Isolated as a colorless oil; 0.18 g
20
(70%); [
a
]
þ72.8 (c 1.00, MeOH); IR (KBr pellet) nmax 2938, 1742,
D
1371, 1235, 1041, 909 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d
5.93e5.84
(m, 2H, H-2, H-3), 5.33 (br d, J4e5¼9.6 Hz, 1H, H-4), 5.10 (br s, 1H, H-
1), 4.26 (dd, J6 e6¼12.0 Hz, J6 e5¼5.1 Hz, 1H, H-60), 4.18 (dd,
0
0
0
J6e6 ¼12.0 Hz, J6e5¼2.4 Hz, 1H, H-6), 4.12 (ddd, J5e4¼9.6 Hz,
0
0
J5e6¼5.1 Hz, J5e6 ¼2.4 Hz, 1H, H-5), 3.94 (d, J7 e7¼12.3 Hz, 1H,
0
OCH2), 3.76 (d, J7e7 ¼12.3 Hz, 1H, OCH2), 2.11 (s, 3H, OAc), 2.10 (s,
3H, OAc); 13C NMR (75 MHz, CDCl3)
d 170.5, 170.1, 129.6; 127.8; 94.9,
68.0, 67.2, 65.4, 63.2, 21.2, 21.0; HRMS (ESI, MeOH/H2O) calcd for
C22H30O12Na [MþNa]þ, 509.1635; found, 509.1634.
4.3.3.6. 2,20-Oxydiethanyl bis-4,6-di-O-acetyl-2,3-dideoxy-
a-D-
4.3.3.1. But-2-yne-1,4-diyl bis-4,6-di-O-acetyl-2,3-dideoxy-
a
-
D
-
erythro-hex-2-enopyranoside (2t).41 Isolated as
a colorless oil;
erythro-hex-2-enopyranoside (2o).41 Isolated as a colorless oil;
0.18 g (67 %); [
a
]
D
20 þ83.5 (c 0.50, MeOH); IR (KBr pellet) nmax 2961,
0.23 g (89%); [
a
]
D
20 þ95.9 (c 1.00, MeOH); IR (KBr pellet) nmax 2924,
1737, 1369, 1260, 1019, 799 cmꢁ1
;
1H NMR (300 MHz, CDCl3)
2861, 1744, 1375, 1235, 1036, 910, 838 cmꢁ1
;
1H NMR (300 MHz,
d
5.92e5.86 (m, 2H, H-2, H-3), 5.34 (br d, J4e5¼9.6 Hz, 1H, H-4), 5.10
(br s, 1H, H-1), 4.27 (dd, J6 e6¼12.0 Hz, J6 e5¼4.8 Hz, 1H, H-60), 4.16
0
0
CDCl3)
d
5.91 (br d, J3e2¼10.2 Hz, 1H, H-3), 5.81 (dt, J2e3¼10.2 Hz,
0
J2e1¼J2e4¼2.1 Hz, 1H, H-2), 5.43 (br s, 1H, H-1), 5.32 (br d,
(dd, J6e6 ¼12.0 Hz, J6e5¼2.4 Hz, 1H, H-6), 4.11 (ddd, J5e4¼9.6 Hz,
0
0
J4e5¼9.6 Hz,1H, H-4), 4.24 (dd, J6e6 ¼12.3 Hz, J6e5¼5.4 Hz,1H, H-6),
J5e6 ¼4.8 Hz, J5e6¼2.4 Hz, 1H, H-5), 3.94e3.89 (m, 1H, OCH2CH2),
4.17 (dd, J6 e6¼12.3 Hz, J6 e5¼2.4 Hz, 1H, H-60), 4.12e4.05 (m, 1H, H-
3.89e3.68 (m, 3H, OCH2CH2), 2.11 (s, 3H, OAc), 2.09 (s, 3H, OAc); 13
C
0
0
5), 2.09 (s, 2H, OCH2C^C), 2.08 (s, 3H, OAc), 2.07 (s, 3H, OAc); 13C
NMR (75 MHz, CDCl3)
d 171.1, 170.6, 129.5, 127.9, 94.0, 70.7, 68.0,
NMR (75 MHz, CDCl3)
d 170.7, 170.2, 129.7, 127.1, 92.6, 82.0, 67.1,
67.1, 65.4, 63.1, 21.2, 21.1.
65.0, 62.8, 55.2, 20.9, 20.7.
4.3.4. General procedure for the homocoupling reaction of alkynyl
2,3-unsaturated O-glycopyranosides (2aec). In a flask containing
a solution of the appropriate alkynes 2aec (1 mmol) in THF (4 mL)
were added TMEDA (20 mol %), CuI (5 mol %), NiCl2$6H2O (5 mol %),
and Et3N (3 equiv). The mixture was stirred for the time indicated
in Table 4 and then diluted using EtOAc (20 mL). The mixture was
washed with water (5ꢂ50 mL) and the combined organic phases
were dried over MgSO4. The solvents were removed under reduced
pressure and the crude product was purified using a flash column
chromatography [hexanes/EtOAc (6:4)] to yield the corresponding
2,3-unsaturated O-glycopyranosides 2per.
4.3.3.2. Hexa-2,4-diyne-1,6-diyl bis-4,6-di-O-acetyl-2,3-dideoxy-
D
a-
-erythro-hex-2-enopyranoside (2p).23b Isolated as a colorless oil;
0.20 g (76%); [
a
]
20 þ123.8 (c 1.00, MeOH); IR (KBr pellet) nmax 2912,
D
1742, 1233, 1035, 911 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d 5.91 (br d,
J3e2¼10.2 Hz, 1H, H-3), 5.81 (dt, J2e3¼10.2 Hz and J2e4¼J2e1¼2.1 Hz,
1H, H-2), 5.32 (br d, J4e5¼9.6 Hz, 1H, H-4), 5.19 (br s, 1H, H-1), 4.36
0
(s, 2H, OCH2C^C), 4.25 (dd, J6e6 ¼12.3 Hz, J6e5¼5.1 Hz, 1H, H-6),
4.15 (dd, J6 e6¼12.3 Hz, J6 e5¼2.7 Hz, 1H, H-60), 4.05 (ddd,
0
0
0
J5e4¼9.6 Hz, J5e6¼5.1 Hz, J5e6 ¼2.7 Hz, 1H, H-5), 2.08 (s, 3H, OAc),
2.07 (s, 3H, OAc); 13C NMR (75 MHz, CDCl3)
d 170.7, 170.2, 129.9,
126.9, 92.9, 74.9, 70.4, 67.2, 64.9, 62.6, 55.4, 20.9, 20.7.
4.3.5. General procedure for the potassium allyltrifluoroborate
(4).42 To a solution of B(OMe)3 (8.15 mL, 7.59 g, 73.2 mmol) in THF
(40 mL) was added dropwise allylmagnesium chloride (30 mL,
60 mmol, 2.0 M in THF) at ꢁ78 ꢀC. The mixture was stirred for
30 min. The ice bath was removed. The yellow solution with a white
precipitate was allowed to reach the room temperature over a 1 h
period. Then, it was cooled to 0 ꢀC and KHF2 (23.4 g, 300 mmol) was
added in one portion. This was followed by the dropwise addition
of H2O (30 mL). The ice bath was removed. The mixture was stirred
for 30 min and then concentrated under high vacuum. The white
solid was extracted with hot acetone (4ꢂ100 mL). The extracts
4.3.3.3. 2,7-Dimethylocta-3,5-diyne-2,7-diyl bis-4,6-di-O-acetyl-
2,3-dideoxy-
a colorless oil; 0.21 g (71%); [
pellet) nmax 3055, 2987, 2917, 2848, 1742, 1369, 1229, 1025,
738 cmꢁ1; 1H NMR (300 MHz, CDCl3)
a-D-erythro-hex-2-enopyranoside (2q). Isolated as
20
a
]
þ175.1 (c 1.00, MeOH); IR (KBr
D
d
5.88 (br d, J3e2¼10.2 Hz, 1H,
H-3), 5.80 (dt, J2e3¼10.2 Hz, J2e1¼J2e4¼1.8 Hz, 1H, H-2), 5.59 (br s,
1H, H-1), 5.28 (dd, J4e5¼9.6 Hz, J4e2¼1.8 Hz,1H, H-4), 4.29e4.03 (m,
3H, H-5, H-6, H-60), 2.07 (s, 6H, OAc), 1.59 (s, 3H, OCCH3), 1.53 (3H,
OCH3); 13C NMR (75 MHz, CDCl3)
d
170.8, 170.3, 128.7, 128.6, 91.2,
81.3, 72.0, 69.2, 67.0, 65.1, 63.0, 30.2, 29.7, 20.9, 20.7; HRMS (ESI,

J.C.R. Freitas et al. / Tetrahedron 68 (2012) 8645e8654
8653
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were filtered through a Celite pad and the filtrate was concentrated
to afford a white solid. The solid was purified by dissolving in the
minimum amount of hot acetone, followed by cooling to room
temperature and precipitation with Et2O. The solution was allowed
to stand for 20 min to complete precipitation. The precipitate was
collected and dried under high vacuum to yield 3.37 g (38%) of
ꢀ
ꢀ
8. (a) Borrachero-Moya, P.; Cabrera-Escribano, F.; Gomez-Guillen, M.; Peredes-
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Leon, M. R. Carbohydr. Res. 1998, 308, 181e190; (b) Schmidt, R. R.; Angerbauer,
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de Freitas, J. R.; Menezes, P. H. J. Braz. Chem. Soc. 2010, 21, 2169e2172; (c) Bala-
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a powdery white solid. 1H NMR (300 MHz, DMSO-d6)
d 5.85e5.74
(m, 1H, CH2]CH), 4.56 (d, J¼17.2 Hz, 1H, CH2]CH), 4.49 (d,
J¼9.6 Hz,1H, CH2]CH), 0.92 (br s, 2H, CH2BF3K); 13C NMR (75 MHz,
DMSO-d6)
d
142.9, 108.9; 11B NMR (128 MHz, DMSO-d6)
d
d
4.21 (q,
ꢁ136.4
J11B,19F¼61.3 Hz, BF3K); 19F NMR (376 MHz, DMSO-d6)
(J19F,11B¼61.3 Hz, BF3K).
4.3.6. General procedure for the allylation of 4-NO2ebenzaldehyde
(3) with potassium allyltrifluoroborate (4) using 2,3-unsaturated
O-glycosides as catalysts. To a solution of 4-NO2ebenzaldehyde 3
(151 mg, 1.0 mmol) and the appropriate 2,3-unsaturated O-gly-
cosides 2sev (10 mol %) in CH2Cl2 (3 mL) was added potassium
allyltrifluorborate
4 (163 mg, 1.10 mmol) followed by water
(3 mL). The biphasic mixture was stirred for the time indicated in
Table 7 and then diluted with CH2Cl2 (5 mL). The layers were
separated and the aqueous layer was extracted with CH2Cl2
(3ꢂ5 mL) and dried over MgSO4. The solvent was removed under
reduced pressure to yield
5 without the need of further
purification.
15. (a) Narhi, S. M.; Oilunkaniemi, R.; Laitinen, R. S.; Ahlgren, M. Inorg. Chem. 2004,
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16. Lis, H.; Sharon, N. Chem. Rev. 1998, 98, 637e674.
4.3.6.1. 1-(4-Nitrophenyl)but-3-en-1-ol
(300 MHz, CDCl3)
(5).30b 1H
NMR
d
8.21 (d, J¼8.5 Hz, 2H, HAryl), 7.54 (d, J¼8.5 Hz,
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2H, HAryl), 5.86e5.72 (m, 1H, CH]CH2), 5.22e5.16 (m, 2H, CH]
CH2), 4.87 (dd, J¼8.0, 4.7 Hz, CHOH), 2.58e2.42 (m, 2H, CHCH2),
ꢁ
18. (a) Giguere, D.; Sato, S.; St-Pierre, C.; Sirois, S.; Roy, R. Bioorg. Med. Chem. Lett.
2.31 (br s, 1H, OH); 13C NMR (75 MHz, CDCl3)
126.9, 123.9, 119.9, 72.5, 44.2.
d 151.5, 147.5, 133.6,
ꢁ
2006, 1668e1672; (b) Giguere, D.; Patnam, R.; Bellefleur, M.-A.; St-Pierre, C.;
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Acknowledgements
The authors gratefully acknowledge CNPq (484778/2011-0),
FACEPE (APQ-1402-1.06/10), CAPES and INCT-INAMI for financial
support. P.H.M, J.C.R.F., and T.R.C. are thankful to CNPq for their
fellowships.
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Supplementary data
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2012.07.070.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
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T. C.; Roy, R.; Wimmerova, M.; Dubreuil, F.; Varrot, A.; Imberty, A. Glycobiology
2010, 20, 87e98.
ꢀ
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F. J. Biol. Chem. 2005, 280, 8640e8646; (b) Masato, K.; Shull, B. K.; Yang, W.
Water-soluble glycosylated derivatives of 1,2-dithiin compounds. U.S. Patent
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