RuCl3·3H2O as catalyst for Ferrier rearrangement: An efficient procedure for the preparation of pseudoglycosides

Article abstract of DOI:10.1016/j.tet.2013.09.061

By using RuCl₃·3H₂O as catalyst, an improved method for the synthesis of 2,3-unsaturated-glycosides has been established. A series of 2, 3-unsaturated-glucosides were obtained from 2,4,6-tri-O-acetyl-d- glucal or 3,4-di-O-acetyl-6-deoxy-l-glucal in good yield and high anomeric selectivity.

Full text of DOI:10.1016/j.tet.2013.09.061

Tetrahedron 69 (2013) 10045e10051
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
RuCl3$3H2O as catalyst for Ferrier rearrangement: an efficient
procedure for the preparation of pseudoglycosides
,
b
,
a
Peiran Chen a , Lei Lin
*
a Key Laboratory of Eco-Textile, The Ministry of Education, Donghua University, 2999 Renmin Road North, Songjiang District, Shanghai 201620, China
b Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, CAS, Shanghai 200032, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 July 2013
Received in revised form 12 September 2013
Accepted 19 September 2013
Available online 25 September 2013
By using RuCl3$3H2O as catalyst, an improved method for the synthesis of 2,3-unsaturated-glycosides has
been established. A series of 2, 3-unsaturated-glucosides were obtained from 2,4,6-tri-O-acetyl-
D-glucal
or 3,4-di-O-acetyl-6-deoxy- -glucal in good yield and high anomeric selectivity.
L
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Type I Ferrier Rearrangement
RuCl3$3H2O
Tri-O-acetyl-D-glucal
3,4-Di-O-acetyl-6-deoxy-L-glucal
2,3-Unsaturated glycoside
1. Introduction
stoichiometric amount of catalyst, harsh reaction conditions, and
low yields, which leading to extensive work up. We therefore have
interest in finding new efficient catalyst for this reaction for milder
and more efficient synthetic process with good anomeric selectivity
and yield by using stoichiometric amount of nucleophile under low
catalyst load.
2,3-Unsatureted-glycosides are of great importance in synthesis
and have been widely used as chiral intermediates in the prepa-
ration of biologically active compounds1 and functional materials2
since they could provide the regio- and stereo-varieties for the
subsequent reactions. One of the most useful procedures to achieve
2,3-unsaturated glycosides directly and efficiently is Type I Ferrier
Rearrangement, in which glycal is reacted with nucleophile with
the catalysis of various Lewis acid catalysts. This reaction is sup-
posed to proceed through a highly resonance-stabilized cyclic al-
lylic oxocarbonium intermediate, which is formed via removal of
the leaving group at C-3 position of the glycal promoted by catalyst,
followed by the attack of a nucleophile via quasi-equatorial orien-
tation3 (Scheme 1).
In our previous investigation in the Type I Ferrier Rearrange-
4v
ment catalyzed by metal Lewis acid Fe(OTf)3 and TiCl3(OTf),4x
a series of alcohols were reacted with 3,4,6-tri-O-acetyl-D-glucal
affording 2,3-unsaturated O-glycosides in high yield and good
anomeric selectivity. The influence of the inductive and the steric
effects of the nucleophiles on the reaction results has also been
examined. Following our previous work, now we report our results
using RuCl3$3H2O as a new highly efficient catalyst for Type I Fer-
rier Rearrangement of various glucals with alcohols or thiols as
nucleophiles.
Besides some other type of catalysts, Lewis acids have been
reported to be the major catalyst in Type I Ferrier Rearrangement. A
wide range of Lewis acid catalysts, such as BF3$Et2O, FeCl3,
Fe2(SO4)3, Fe(NO3)3, InCl3, BiCl3, CeCl3, ZnCl2, Pd(OAc)2, ZrCl4,
2. Results and discussion
K5CoW12O40$3H2O, Bi(OTf)3, Er(OTf)3, Yb(OTf)3, Fe(OTf)3, TiCl4,
2.1. Role of the counter-ion in the metal chloride catalysts
AuCl3, HBF4eSiO2, ZnCl2/Al2O3, TiCl3(OTf) have been reported in the
literature.4 However, some of those reaction systems suffered from
the drawbacks in terms of large excess of nucleophile,
For comparison of the catalytic activity of different metal
chloride catalysts, a comparative study has been carried out by
using tri-O-acetyl- -glucal (1) and EtOH as the nucleophile in
D
a model system catalyzed by RuCl3$3H2O and some other different
chloride catalyst Lewis acid catalysts, including FeCl3,5a InCl3,5b,c
ZnCl2,4s and TiCl4,4w which have been reported to be used in
* Corresponding author. Tel.: þ86 21 67792594; e-mail address: prchen@dhu.e-
du.cn (P. Chen).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.09.061

10046
P. Chen, L. Lin / Tetrahedron 69 (2013) 10045e10051
..
O
O
Nu
O
R2
R2
R2
..
1
:Nu
2
2
R1
allyloxycarbenium ion
R1
R1
3
LG
3
LA
:
LG = leaving group
LA = Lewis acid catalyst
Scheme 1. Mechanism of Type I Ferrier Rearrangement proposed by R. J. Ferrier.3b,f
Type I Ferrier Rearrangement as catalysts. Results are shown in
Table 1.
By comparison of the results in entry 1 with the others in Table
2, acetonitrile appeared to be the most proper solvent. This might
be attributed to its higher hydrophilic character than those of other
tested solvents.
Table 1
A comparative study of the catalytic effect of different metal chloride Lewis acid
catalysts in the Ferrier Rearrangement of glucal 1a
2.3. Type I Ferrier Rearrangement under the optimized
conditions
OAc
O
OAc
O
MCln Lewis acid
40oC
OAc
+
EtOH
OEt
After the optimization, we have established our reaction con-
ditions: with RuCl3$3H2O (10 mol %) as the catalyst and acetonitrile
as the solvent, the Ferrier Rearrangement was performed between
AcO
AcO
1
Entry
Lewis acid catalyst
Reaction time
Conversion (%)b
a
:
bc
3,4,6-tri-O-acetyl-D-glucal (1 equiv) or 3,4-di-O-acetyl-6-deoxy-L-
glucal (1 equiv) and various nucleophiles (1.5 equiv) at 40 ꢀC. Re-
sults are summarized in Table 3. The structure and stereochemistry
1
2
3
4
5
TiCl4
ZnCl2
SnCl2
FeCl3
24 h
24 h
24 h
24 h
18 h
Trace
N.R.
Trace
N.R.
44
/
/
/
/
of all the glycosidation products were characterized by 1H NMR, 13
NMR, IR, and MS data.
C
RuCl3$3H2O
4:1
Generally, the reaction afforded 2,3-unsaturated glycosides in
high yield with good anomeric selectivity. While using tri-O-acetyl-
-glucal as starting material, the simple alcohols (entries 1e3, Table
3) as the nucleophile gave the products with lower selectivity on
the anomeric center, while those with higher steric hindrance
(entries 4 and 5, Table 3) gave the products, which are good both in
yield and in anomeric selectivity. Thiol (entry 6, Table 3) could be
used as nucleophile in this reaction system and gives the product in
a
Reaction conditions: tri-O-acetyl-D-glucal (1) (188 mg, 0.7 mmol), EtOH (5 mL),
catalyst (10 mol %), 40 ꢀC.
b
Determined by analysis of the 1H NMR spectra of the reaction mixture.
The anomeric ratio was determined by integration of the anomeric hydrogen in
D
c
the 1H NMR spectra.
Results shown in Table 1 demonstrate the obviously different
catalytic activity of the metal chloride catalysts with various
counter-ions in this reaction. Among the tested metal chloride
catalysts, RuCl3$3H2O is the most efficient one in terms of conver-
sion and selectivity, which indicates that Ru(III) anion might attract
the leaving group more effectively to form the intermediate ally-
loxycarbenium ion (Scheme 1).
satisfactory yield and selectivity. If 3,4-di-O-acetyl-6-deoxy-L-glu-
cal was used, even those nucleophiles with relative low steric
hindrance could give the products with high selectivity on the
anomeric center (entries 14e17, Table 3).
The scope of this procedure for the preparation of 2,3-un-
saturated O-glycoside connected with various biologically impor-
tant natural products has also been explored. Formation of two
disaccharides (entries 7 and 8, Table 3), three steroid glycosides
2.2. Optimization of solvent
Solvent played an important role in the reaction. Therefore,
optimization has been carried out. Table 2 shows the results.
(entries 11e13, and 20, Table 3) and two other natural product (L-
menthol and (1R)-endo-(þ)-fenchol) glycosides (entries 9, 10, 18,
and 19, Table 3) in good yield and high selectivity demonstrated the
catalytic capability of RuCl3$3H2O in the synthesis of natural
product analogs by the Ferrier Rearrangement.
Table 2
Optimization of solventa for the RuCl3$3H2O catalyzed Ferrier Rearrangement re-
action system
Rearrangement reaction system
OAc
3. Conclusion
OAc
O
RuCl3 3H2O
(10mmol%)
Solvent,
40oC
O
OAc
+
EtOH
OEt
We have established a practical procedure for Type I Ferrier
Rearrangement with RuCl3$3H2O as the catalyst. Comparing with
the metal Lewis acid Fe(OTf)34v and TiCl3(OTf),4x the reactions time
of Ferrier Rearrangement promoted by RuCl3$3H2O could be re-
duced obviously. As an advantage, nucleophile other than alcohols,
such as thiol, was used in this reaction system and gave satisfactory
AcO
AcO
1
Entry
Solvent
Reaction time
Conversion (%)b
a:
bc
1
2
3
4
Acetonitrile
DCM
THF
30 min
40 min
30 min
50 min
89.5
77
7:1
6:1
5:1
7:1
76
77
result. Besides tri-O-acetyl-D-glucal, 3,4-di-O-acetyl-6-deoxy-L-
Toluene
glucal was tested as another starting material and a series of cor-
responding 2,3-unsaturated glycosides were prepared with good
yield and high selectivity, which meant that compared with our
previous achievement, RuCl3$3H2O, as the catalyst of Type I Ferrier
Rearrangement, was applicable to more kinds of glucals.
a
Reaction conditions: tri-O-acetyl-D-glucal (1) (188 mg, 0.7 mmol), EtOH
(1.3 equiv), RuCl3$3H2O (10 mol %), solvent (5 mL), 40 ꢀC.
b
Determined by analysis of the 1H NMR spectra of the reaction mixture.
The anomeric ratio was determined by integration of the anomeric hydrogen in
c
the 1H NMR spectra.

P. Chen, L. Lin / Tetrahedron 69 (2013) 10045e10051
10047
Table 3
Type I Ferrier Rearrangement reaction of 3,4,6-tri-O-acetyl-
D
-glucal or 3,4-di-O-acetyl-6-deoxy-
L
-glucal (1) with various nucleophiles (2aet) catalyzed by RuCl3$3H2Oa
CH R
2
O
CH R
2
3H O
2
RuCl
3
O
Nucleophile
(1.5eq)
(10mmol%)
MeCN,
40 C
OAc
+
Nu
OAc
o
AcO
1
2a~t
3a~t
R=OAc or H
c
Entry
Glycals (1)
Nucleophiles (2)
Time
Products (3)
Yieldb/(
a:b)
OAc
O
OAc
O
OEt
1
EtOH
10 min
89% (7:1)
OAc
AcO
AcO
3a
OAc
O
OAc
OH
O
O
2
10 min
90% (10:1)
OAc
AcO
AcO
3b
OAc
O
OAc
O
O
OH
AcO
AcO
3
4
10 min
81% (7:1)
OAc
AcO
3c
OAc
O
OAc
O
HO
Br
Br
Br
O
10 min
83% (17:1)
OAc
Br
Br
Br
AcO
3d
Br
OAc
OAc
O
F
F
O
COOEt
5
10 min
55% (12:1)
OAc
O
OH
CF2
EtOOC
Br
AcO
AcO
3e
OAc
O
OAc
SH
O
S
6d
5 h
65% (7:1)
OAc
AcO
AcO
3f
O
O
O
O
OAc
OAc
O
O
O
O
O
7
30 min
50% (a only)
OAc
O
O
O
HO
AcO
AcO
O
3g
O
OAc
O
O
O
OAc
8
10 min
60% (5:1)
O
O
O
O
O
OAc
AcO
HO
O
O
O
AcO
O
(continued on next page)
3h

10048
P. Chen, L. Lin / Tetrahedron 69 (2013) 10045e10051
Table 3 (continued )
c
Entry
Glycals (1)
Nucleophiles (2)
Time
Products (3)
Yieldb/(
a:b)
OAc
OAc
O
O
O
HO
9
30 min
79% (a only)
OAc
AcO
AcO
3i
OAc
O
OAc
O
O
10
5 min
75% (15:1)
OAc
AcO
OH
AcO
3j
O
OAc
O
O
OAc
O
11
12
20 min
70% (6:1)
OAc
AcO
O
AcO
HO
3k
3l
O
OAc
O
O
OAc
O
O
20 min
52% (a only)
OAc
AcO
AcO
HO
O
O
OAc
OAc
O
O
O
13
15 min
55% (10:1)
OAc
AcO
AcO
HO
3m
CH3
O
O
OCH2CH3
14
15
16
17
EtOH
10 min
20 min
20 min
10 min
78% (10:1)
65% (12:1)
OAc
AcO
AcO
AcO
3n
CH3
O
O
O
C14H29-n
n-C14H29OH
OAc
AcO
3o
CH3
O
OH
O
O
64% (
71% (
a
a
only)
only)
OAc
AcO
AcO
AcO
3p
O
CH3
O
O
OH
OAc
AcO
3q
O
CH3
O
O
HO
AcO
18
20 min
68% (
a
only)
OAc
AcO
3r

P. Chen, L. Lin / Tetrahedron 69 (2013) 10045e10051
10049
c
Table 3 (continued )
Entry
Glycals (1)
Nucleophiles (2)
Time
Products (3)
Yieldb/(
a
:b
)
CH3
O
O
O
19
10 min
75% (17:1)
OAc
AcO
OH
AcO
3s
O
O
CH3
20
10 min
40% (13:1)
O
O
OAc
O
AcO
AcO
HO
3t
a
General reaction conditions: tri-O-acetyl-D-glucal (188 mg, 0.7 mmol) or 3,4-di-O-acetyl-6-deoxy-L-glucal (177 mg, 0.7 mmol), nucleophile (2aet) (1.5 equiv), RuCl3$3H2O
(20 mol %), MeCN (5 mL), 40 ꢀC.
b
Isolated yield.
c
The anomeric ratio was determined by integration of the anomeric hydrogen in the 1H NMR spectra.
d
The reaction temperature was ꢃ20 ꢀC.
By using RuCl3$3H2O as catalyst, a series of alcohols and thiols
4.2.1. Ethyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-
were reacted with glucal donor affording 2,3-unsaturated glyco-
sides in high yield and good anomeric selectivity. The influence of
the inductive and the steric effects of the nucleophiles on the re-
action results has also been examined. This reaction system has also
demonstrated its applicability in the synthesis of natural product
analogs of biological interest by the Ferrier Rearrangement.
enopyranoside (3a). Colorless oil; ½a D25
þ112.5 (c 1.67, CHCl3,
ꢂ
a 25
a
:
b
¼7:1) {lit.4x: ½ ꢂD þ82.72 (c 0.83, CHCl3,
a
:
b
¼7:1)}; 1H NMR
(400 MHz, CDCl3)
d
5.89 (q, J¼10.5 Hz, 2H), 5.34 (d, J¼9.7 Hz,
1H), 5.07 (s, 1H), 4.37e4.11 (m, 3H), 3.92e3.80 (m, 1H),
3.68e3.54 (m, 1H), 2.12 (s, 3H), 2.10 (s, 3H), 1.28 (t, J¼7.0 Hz, 3H)
ppm; IR (film, cmꢃ1): 2978, 2896, 2896, 1738, 1642, 1378, 1235,
1142, 1044, 894, 731, MS (ESI) m/z: 280.9 ([MþNa]þ, 75), 212.9
(100), 153.0 (60).
4. Experimental
4.2.2. Cyclohexyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-
4.1. Method and materials
enopyranoside (3b). Colorless oil; ½a D25
þ135.5 (c 1.60, CHCl3,
ꢂ
¼10:1) {lit.4x: ½a D25
ꢂ
þ65.3 (c 0.60, CHCl3,
a
:b
¼8:1)}; 1H NMR
1H and 13C NMR spectra were recorded on a Bruker AV-400
(400 MHz) spectrometer with Me4Si as internal standard. 19F
NMR spectra were obtained on a Bruker AM-300 (282 M Hz)
spectrometer using CFCl3 as an external standard; downfield shifts
a
:
b
(400 MHz, CDCl3)
d
5.83 (q, J¼10.3 Hz, 2H), 5.28 (d, J¼9.4 Hz, 1H),
5.16 (s,1H), 4.18 (dd, J¼17.8, 8.2 Hz, 3H), 3.63 (dd, J¼10.7, 7.2 Hz,1H),
2.08 (s, 3H), 2.07 (s, 3H), 1.97e1.84 (m, 2H), 1.73 (d, J¼4.4 Hz, 2H),
1.54 (d, J¼10.3 Hz, 1H), 1.29 (ddd, J¼28.0, 19.2, 11.1 Hz, 5H) ppm. IR
(film, cmꢃ1):2933, 2851, 1744, 1637, 1372, 1234, 1037, 967. MS (ESI)
m/z: 335.0 ([MþNa]þ, 55); 212.8 (100).
being designated as positive, all chemical shifts (d) were expressed
in parts per million and coupling constants (J) are in Hertz. Mass
spectra were recorded on a Finnigan-MAT-8430 instrument using
EI ionization at 70 eV. High-Resolution mass spectral (ESI) analyses
were performed on a Finnigan-MAT-8430 spectrometer. IR spectra
were recorded on a Nicolet 380 spectrometer. Optical rotations
were measured by WZZ-2 polarimeter. Melting points were mea-
sured on a WRS-2A melting point apparatus. Glucal, epian-
4.2.3. Benzyl 4,6-di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-hex-2-
þ156.2 (c 1.43, CHCl3,
only)}; 1H NMR
enopyranoside (3c). Colorless oil; ½a D25
ꢂ
a
:
b
¼7:1) {lit.4x: ½a D25
ꢂ
þ46.6 (c 0.64, CHCl3,
a
(400 MHz, CHCl3)
d
7.39 (d, J¼3.9 Hz, 5H), 5.91 (q, J¼10.7 Hz, 2H),
5.36 (d, J¼9.5 Hz, 1H), 5.17 (s, 1H), 4.84 (d, J¼11.7 Hz, 1H), 4.63 (d,
J¼11.6 Hz, 1H), 4.36e4.08 (m, 3H), 2.13 (s, 3H), 2.11 (s, 3H) ppm; IR
(film, cmꢃ1):2880, 1743, 1650, 1450, 1143, 1039, 962, 833, 736, 699.
MS (ESI) m/z: 338.0 ([MþNH4]þ, 100); 212.9 (85).
drosterone,
L
-menthol, (1R)-endo-(þ)-fenchol, and the protected
glucose were purchased from Energy-Chemical Company. All the
solvents used in the reaction were purified by re-distillation.
4.2. General experimental procedure of Ferrier rearrange-
4.2.4. 2,2,2-Tribromomethyl ethoxyl 4,6-di-O-acetyl-2,3-dideoxy-a-
ment of 2,4,6-tri-O-acetyl-D-glucal or 3,4-di-O-acetyl-6-deoxy-
D
-erythro-hex-2-enopyranoside (3d). Colorless oil; ½a D25
þ88.7 (c
ꢂ
L-glucal catalyzed with RuCl3$3H2O
2.26, CHCl3,
NMR (400 MHz, CDCl3)
J¼9.7 Hz, 1H), 5.07 (s, 1H), 4.26 (t, J¼3.8 Hz, 2H), 4.15e4.05 (m, 1H),
3.96 (d, J¼9.4 Hz, 1H), 3.57 (s, 6H), 3.52 (d, J¼9.4 Hz, 1H), 2.13 (s, 3H),
2.12 (s, 3H) ppm; IR (film, cmꢃ1):2957, 1743, 1645, 1424, 1375, 1231,
1043, 905, 853, 741, 665, 609. MS (ESI): m/z 555.8 ([MþNH4]þ, 100).
a:b
¼17:1); {lit.4x: ½a D25
ꢂ
þ73 (c 0.65, CHCl3,
a
:
b
¼10:1); 1H
d
5.89 (dd, J¼39.7, 10.2 Hz, 2H), 5.36 (d,
To a stirred solution of tri-O-acetyl-
D-glucal (188 mg, 0.7 mmol)
or 3,4-di-O-acetyl-6-deoxy- -glucal (177 mg, 0.7 mmol) and the
L
corresponding nucleophile (1.5 equiv) in MeCN (5 mL) were added
RuCl3$3H2O (10 mol %) at ambient temperature. The mixture was
stirred under 40 ꢀC for the appropriate amount of time (Table 3),
and the extent of the reaction was monitored by TLC analysis. The
reaction mixture was diluted with cooled sodium bicarbonate
(satd, 20 mL) and extracted with DCM (3ꢁ20 mL). The combined
organics were dried over anhydrous Na2SO4. The solvent was re-
moved under vacuum. All the products were purified by silica gel
4.2.5. Ethyl
2,2-difluoro-3-O-(4,6-di-O-acetyl-2,3-dideoxy-a-D-er-
ythro-hex-2-enopyranosyl)-3-(4-bromophenyl)propanoate
(3e). Colorless oil; ½a D25
ꢂ
þ182.4 (c 0.58, CHCl3,
a
:
b
¼12:1); 1H NMR
(400 MHz, CDCl3)
d
7.55 (t, J¼7.1 Hz, 2H), 7.41e7.30 (m, 2H), 5.95 (d,
J¼10.3 Hz, 1H), 5.80 (dd, J¼21.4, 10.2 Hz, 1H), 5.44e5.25 (m, 2H),
column chromatography (hexane/EtOAc¼8/1 while tri-O-acetyl-
glucal as starting material or hexane/EtOAc¼25/1 while 3,4-di-O-
acetyl-6-deoxy- -glucal as starting material).
D-
5.14 (dd, J¼15.4, 8.1 Hz, 1H), 4.88 (s, 1H), 4.40e4.22 (m, 3H),
4.09e3.99 (m,1H), 2.16 (s, 3H), 2.12 (s, 3H),1.34 (t, J¼7.0 Hz, 3H); 13
C
L

10050
P. Chen, L. Lin / Tetrahedron 69 (2013) 10045e10051
NMR (101 MHz, CDCl3):
d
170.87, 170.56, 170.21, 133.13, 131.88,
8.2 Hz, 3H), 3.66 (s, 1H), 2.47 (dd, J¼19.4, 9.0 Hz, 1H), 2.13 (s, 3H),
2.11 (s, 3H), 1.99e1.67 (m, 7H), 1.59e1.42 (m, 4H), 1.31 (d, J¼20.3 Hz,
6H), 1.18 (d, J¼11.6 Hz, 1H), 0.98 (t, J¼11.9 Hz, 2H), 0.88 (s, 3H), 0.85
(s, 3H), 0.73 (d, J¼10.0 Hz, 1H) ppm; IR (film, cmꢃ1): 2932, 2851,
1743, 1636, 1450, 1377, 1234, 1035; MS (ESI) m/z: 525.2 ([MþNa]þ,
100), 212.8 (8).
130.70, 129.82, 126.47, 124.08, 96.69, 91.21, 67.75, 64.85, 63.20,
62.42, 61.83, 20.96, 20.80, 13.95; 19F NMR (377 MHz, CDCl3)
d
ꢃ119.20 (d, J¼15.4 Hz), ꢃ119.47 (d, J¼16.2 Hz) ppm; IR (film,
cmꢃ1):2944, 1744, 1652, 1483, 1376, 1305, 1299, 908, 860, 741, 647,
609. MS (ESI): m/z 543.0 ([MþNa]þ, 100). HR-ESI C21H23Br1F2Na1O8
[MþNa]þ calcd 543.0439, found 543.0437.
4.2.12. 16-Dehydropregnenolonyl-4,6-di-O-acetyl-2,3-dideoxy-a- -
4.2.6. Cyclohexyl 4,6-di-O-acetyl-2,3-dideoxy-
a
-
-erythro-hex-2-
erythro-hex-2-enopyranoside (3l). White solid; mp 72e73 ꢀC; ½aꢂD2D5
eno-1-thio-
a
-
D
-pyranoside (3f). Colorless oil; ½aꢂ2DD5 þ101.3 (c 1.0,
þ176.3 (c 1.38, CHCl3,
a
only) {lit.4x: ½a D25
ꢂ
þ134 (c 0.51, CHCl3,
CHCl3,
a
:b
¼7:1); {lit.6a: ½a D25
ꢂ
þ78 (c 0.80, CHCl3,
a
only)}, 1H NMR
a d 6.74 (s, 1H), 5.88
only); 71e73 ꢀC}; 1H NMR (400 MHz, CDCl3)
(400 MHz, CDCl3)
d
5.95 (d, J¼10.0 Hz, 1H), 5.78 (d, J¼10.0 Hz, 1H),
(dd, J¼23.8, 10.4 Hz, 2H), 5.39 (s, 1H), 5.33 (d, J¼9.2 Hz, 1H), 5.20 (s,
1H), 4.25 (dt, J¼20.5, 8.1 Hz, 3H), 3.66e3.49 (m, 1H), 2.51e2.35 (m,
3H), 2.29 (s, 3H), 2.13 (s, 3H), 2.11 (s, 3H), 2.05 (d, J¼16.3 Hz, 2H),
1.95e1.86 (m, 2H),1.73e1.26 (m,10H),1.06 (s, 3H), 0.94 (s, 3H) ppm;
IR (film, cmꢃ1): 2939, 1745, 1664, 1439, 1372, 1233, 1037, 971. MS
(ESI) m/z: 549.2 ([MþNa]þ, 100), 213.0 (8).
5.69 (s, 1H), 5.37 (d, J¼9.3 Hz, 1H), 4.43e4.15 (m, 3H), 2.92 (t,
J¼10.2 Hz, 1H), 2.12 (s, 3H), 2.11 (s, 3H), 2.04 (s, 2H),1.77 (s, 2H), 1.62
(d, J¼15.7 Hz, 1H), 1.50e1.25 (m, 5H); IR (film, cmꢃ1):2930, 2854,
1742,1645,1445,1372,1231,1049, 966, 896, 832, 790, 648. MS (ESI):
m/z346.0 ([MþNH4]þ, 100).
4.2.7. 3-O-(4,6-Di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-hex-2-
4.2.13. (5,6-Dihydro-16-dehydropregnenolonyl)-4,6-di-O-acetyl-2,3-
enopyranosyl)-l,2:5,6-di-O-isopropylidene-
a
-
D
-glucofuranose
dideoxy-
a
-
D
-erythro-hex-2-enopyranoside
(3m). White
solid;
(3g). Colorless oil; ½a D25
ꢂ
þ139.8 (c 0.51, CHCl3,
a
only); {lit.4x: ½a D25
ꢂ
mp¼127e129 ꢀC; ½a D25
ꢂ
þ192.4 (c 1.63, CHCl3,
a:b
¼10:1) {lit.4x: ½a D25
ꢂ
þ77 (c 0.56, CHCl3,
a
:
b
¼5:1)}; 1H NMR (400 MHz, CDCl3):
d
5.91
þ76 (c 0.53, CHCl3,
a
only); 124e126 ꢀC}; 1H NMR (400 MHz, CDCl3)
(d, J¼3.2 Hz, 2H), 5.86 (d, J¼10.0 Hz, 1H), 5.29 (s, 2H), 4.65 (d,
J¼3.0 Hz, 1H), 4.34 (d, J¼2.0 Hz, 1H), 4.28e4.06 (m, 6H), 4.00 (dd,
J¼8.0, 4.9 Hz, 1H), 2.14 (s, 3H), 2.11 (s, 3H), 1.51 (s, 3H), 1.42 (s,
3H), 1.34 (s, 3H), 1.33 (s, 3H) ppm; IR (film, cmꢃ1): 2986, 1745,
1630, 1376, 1038, 845. MS (ESI) m/z: 490.1 ([MþNH4]þ, 100);
472.1 (38).
d
6.72 (s,1H), 5.87 (dd, J¼22.7,10.3 Hz, 2H), 5.33 (d, J¼9.4 Hz,1H), 5.20
(s, 1H), 4.22 (dd, J¼18.3, 7.9 Hz, 3H), 3.65 (t, J¼10.8 Hz, 1H), 2.38 (dd,
J¼27.6,15.3 Hz,1H), 2.28(s, 3H), 2.13 (s, 3H), 2.10 (s, 3H), 2.07e1.82 (m,
2H), 1.79e1.56 (m, 6H), 1.44 (d, J¼11.5 Hz, 4H), 1.32 (d, J¼8.6 Hz, 3H),
1.19e0.94 (m, 3H), 0.90 (s, 3H), 0.86 (s, 3H), 0.73 (t, J¼9.3 Hz, 1H). IR
(film, cmꢃ1): 2933, 2847, 1745, 1664, 1443, 1373, 1234,1035, 910, 816,
743; MS (ESI) m/z: 551.2 ([MþNa]þ, 100), 213.0 (8).
4.2.8. 6-O-(4,6-Di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-hex-2-
enopyranosyl)-1,2:3,4-di-O-isopropylidene-
a
-
D
-galactopyranose
4.2.14. Ethyl 4-O-acetyl-6-deoxy-2,3-dideoxy-
a
-
D
-erythro-hex-2-
þ21.9 (c 0.67, CHCl3,
5.87 (t, J¼9.1 Hz, 2H), 5.08
(3h). White solid; mp¼132e134 ꢀC; ½a D25
ꢂ
þ17.6 (c 0.83, CHCl3,
enopyranoside (3n).6b Colorless oil; ½a 2D5
ꢂ
a
:
b
¼5:1); {lit.4x: ½a D25
ꢂ
þ24.2 (c 0.73, CHCl3,
a
:b
¼6:1)}; 1H NMR
a:b
¼10:1); 1H NMR (400 MHz, CDCl3)
d
(400 MHz, CDCl3)
d
5.94e5.81 (m, 2H), 5.55 (d, J¼5.0 Hz, 1H), 5.35
(d, J¼8.9 Hz, 1H), 5.00 (s, 1H), 4.01 (dq, J¼12.6, 6.3 Hz, 1H), 3.85 (dq,
J¼14.5, 7.2 Hz, 1H), 3.71e3.42 (m, 1H), 2.11 (s, 3H), 1.28 (d, J¼7.1 Hz,
3H),1.26e1.24 (m, 3H) ppm; IR (film, cmꢃ1): 2979, 2889,1742, 1690,
1474, 1474, 1382, 1309, 1237, 1045, 927, 640; MS (ESI) m/z: 222.9
([MþNa]þ, 40); 212.4 (15).
(d, J¼12.9 Hz, 1H), 5.12 (s, 1H), 4.64 (d, J¼6.4 Hz, 1H), 4.39e4.24 (m,
3H), 4.17 (d, J¼11.4 Hz, 2H), 4.02 (d, J¼7.1 Hz, 1H), 3.90 (dd, J¼10.2,
6.3 Hz, 1H), 3.78 (dd, J¼9.9, 7.4 Hz, 1H), 2.14 (s, 3H), 2.11 (s, 3H), 1.56
(s, 3H), 1.47 (s, 3H), 1.37 (s, 3H), 1.36 (s, 3H) ppm; IR (film,
cmꢃ1):2996, 2930, 1741, 1638, 1450, 1378, 1226, 1172, 1051, 1004,
892, 645. MS (ESI): m/z 490.1 ([MþNH4]þ, 100).
4.2.15. n-Tetradecyl
4-O-acetyl-6-deoxy-2,3-dideoxy-
a-D-erythro-
hex-2-enopyranoside (3o). Colorless oil; ½a D25
ꢂ
ꢃ140.8 (c 1.16, CHCl3,
4.2.9.
L
-Menthyl 4,6-di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-hex-2-
a
:
b
¼12:1); 1H NMR (400 MHz, CDCl3)
d 5.94e5.79 (m, 2H), 5.07 (d,
enopyranoside (3i). Colorless oil; ½a D25
ꢂ
27.0 (c 0.50, CHCl3, only)
a
J¼8.1 Hz, 1H), 4.97 (s, 1H), 4.09e3.94 (m, 1H), 3.77 (dd, J¼11.5,
4.7 Hz, 1H), 3.55e3.46 (m, 1H), 2.10 (s, 3H), 1.61 (dd, J¼13.5, 6.6 Hz,
3H), 1.26 (d, J¼9.3 Hz, 24H), 0.90 (t, J¼6.7 Hz, 3H); 13C NMR
{lit.4x: ½a 2D5
ꢂ
þ141 (c 0.53, CHCl3,
a
only)}; 1H NMR (400 MHz, CDCl3)
d
5.85 (s, 2H), 5.26 (d, J¼8.9 Hz, 1H), 5.08 (s, 1H), 4.27e4.08 (m, 3H),
3.41 (td, J¼10.4, 3.9 Hz, 1H), 2.19 (t, J¼11.8 Hz, 1H), 2.09 (s, 3H), 2.06
(s, 3H),1.61 (d, J¼9.7 Hz, 3H),1.46e0.93 (m, 5H), 0.90 (s, 3H), 0.88 (s,
3H), 0.76 (d, J¼6.9 Hz, 3H) ppm; IR (film, cmꢃ1): 2952, 2865, 1744,
1634, 1455, 1374, 1234, 1183, 1037, 911; MS (ESI) m/z: 391.0
([MþNa]þ, 100), 212.9 (75).
(101 MHz, CDCl3) d 170.58, 129.52, 127.97, 94.36, 70.97, 68.78, 64.73,
31.94, 29.83, 29.68, 29.68, 29.68, 29.68, 29.68, 29.62, 29.42, 29.38,
26.19, 22.71, 21.11, 18.00, 14.14. IR (film, cmꢃ1):2925, 2857, 1744,
1637, 1460, 1375, 1235, 1099, 1044, 918, 724. MS (ESI): m/z 391.3
([MþNa]þ, 100); HR-ESI:C22H40Na1O4 [MþNa]þ calcd 391.2816,
found 391.2819.
4.2.10. (þ)-endo-Fenacholyl
4,6-di-O-acetyl-2,3-dideoxy-a-D-er-
ythro-hex-2-enopyranoside (3j). White solid; mp¼75e77 ꢀC; ½a D25
ꢂ
4.2.16. Cyclohexyl 4-O-acetyl-6-deoxy-2,3-dideoxy-
a
-
D
-erythro-hex-
ꢃ191 (c 0.63, CHCl3, only)
5.84 (t, J¼11.0 Hz, 2H),
þ132.3.6 (c 1.45, CHCl3,
a
:b
¼15:1); {lit.4x: ½a D25
ꢂ
þ55.1 (c 0.54, CHCl3,
2-enopyranoside (3p). Colorless oil; ½a D25
ꢂ
a
a
only); mp¼74e76 ꢀC}; 1H NMR (400 MHz, CDCl3)
d
5.89 (s, 2H),
{lit.6c
:
a:b
¼6.2:1}; 1H NMR (400 MHz, CDCl3)
d
5.32 (d, J¼9.5 Hz, 1H), 5.01 (s, 1H), 4.34e4.12 (m, 3H), 3.48 (s, 1H),
2.12 (s, 6H), 1.67 (t, J¼19.6 Hz, 4H), 1.54e1.26 (m, 3H), 1.14 (s, 3H),
1.07 (s, 3H), 0.90 (s, 3H) ppm; IR (film, cmꢃ1): 2956, 2876, 1743,
1644, 1461, 1373, 1329, 1228, 1040, 900, 832, 749. MS (ESI) m/z:
389.0 ([MþNa]þ, 70); 212.9 (100).
5.13 (s, 1H), 5.07 (d, J¼9.3 Hz, 1H), 4.05 (dd, J¼9.1, 6.3 Hz, 1H),
3.70e3.51 (m, 1H), 2.10 (s, 3H), 1.92 (d, J¼4.3 Hz, 2H), 1.76 (d,
J¼4.0 Hz, 2H), 1.67e1.50 (m, 2H), 1.35 (s, 2H), 1.31 (s, 2H), 1.24 (d,
J¼6.3 Hz, 3H); IR (film, cmꢃ1):2931, 2856, 1744, 1636, 1450, 1375,
1236, 1096, 1038, 913, 737; MS (ESI): m/z 277.0 ([MþNa]þ, 100).
4.2.11. Epiandrosteronyl-4,6-di-O-acetyl-2,3-dideoxy-
a
-
D
-erythro-
4.2.17. Benzyl 4-O-acetyl-6-deoxy-2,3-dideoxy-
a
-
D
-erythro-hex-2-
ꢃ228 (c 0.51, CHCl3, only)
7.41e7.30 (m, 5H), 5.87
hex-2-enopyranoside (3k). White solid; mp¼125e126 ꢀC; ½a D25
ꢂ
enopyranoside (3q). Colorless oil; ½a D25
ꢂ
a
þ112.7 (c 1.81, CHCl3,
a
:b
¼6:1) {lit.4x: ½a D25
ꢂ
þ106 (c 0.61, CHCl3,
{lit.4q
:
a:b
¼5:1}; 1H NMR (400 MHz, CDCl3):
d
a
:b
¼10:1); mp¼124e126 ꢀC}; 1H NMR (400 MHz, CDCl3)
d
5.89 (t,
(q, J¼10.3 Hz, 2H), 5.09 (s, 2H), 4.81 (d, J¼11.9 Hz, 1H), 4.63 (d,
J¼12.2 Hz, 2H), 5.34 (d, J¼9.7 Hz, 1H), 5.20 (s, 1H), 4.22 (dd, J¼18.4,
J¼11.9 Hz, 1H), 4.04 (dq, J¼12.7, 6.3 Hz, 1H), 2.11 (s, 3H), 1.22 (d,

P. Chen, L. Lin / Tetrahedron 69 (2013) 10045e10051
10051
J¼6.2 Hz, 3H) ppm; IR (film, cmꢃ1): 2980, 2885,1740,1651,1495,1451,
1374, 1237, 1045, 927, 640. MS (ESI) m/z: 280.0 ([MþNH4]þ, 100).
The Natural Science Foundation of Shanghai Municipality (Grant
No. 12ZR1400200) and The Fundamental Research Funds for the
Central Universities.
4.2.18.
L
-Menthyl 4-O-acetyl-6-deoxy-2,3-dideoxy-
a
-
D
-erythro-hex-
2-enopyranoside (3r). Colorless oil; ½a D25
ꢂ
ꢃ354 (c 1.15 CHCl3,
Supplementary data
a
only); 1H NMR (400 MHz, CDCl3)
d
5.80 (dd, J¼47.3, 10.2 Hz, 2H),
5.16 (s, 1H), 5.05 (d, J¼9.6 Hz, 1H), 4.09e3.88 (m, 1H), 3.55 (td,
J¼10.6, 4.0 Hz, 1H), 2.28 (dd, J¼6.9, 5.1 Hz, 1H), 2.11 (s, 3H),
1.73e1.63 (m, 2H), 1.58e1.26 (m, 3H), 1.23 (d, J¼6.2 Hz, 3H),
1.16e0.98 (m, 2H), 0.94 (s, 3H), 0.92 (s, 3H), 0.83 (d, J¼6.9 Hz, 3H),
Supplementary data include 1H NMR, 19F NMR spectra of all the
products; 13C NMR, HRMS of the new compounds are available.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2013.09.061.
0.77 (t, J¼6.5 Hz, 1H); 13C NMR (101 MHz, CDCl3):
d 170.57, 129.46,
128.38, 90.53, 75.84, 70.95, 65.01, 47.91, 40.29, 34.43, 31.43, 25.35,
22.84, 22.32, 21.15, 21.13, 18.02, 15.63; IR (film, cmꢃ1): 2924, 2864,
1745, 1455, 1374, 1325, 1098, 1032, 914, 837, 795; MS (ESI): m/z
333.2 ([MþNa]þ, 100); HR-ESI:C18H30Na1O4 [MþNa]þ calcd
333.2033, found 333.2036.
References and notes
1. For examples, see: (a) Durham, T. B.; Miller, M. J. Org. Lett. 2002, 4, 135; (b)
Williams, D. R.; Heidebrecht, R. W., Jr. J. Am. Chem. Soc. 2003, 125, 1843; (c)
Domon, D.; Fujiwara, K.; Ohtaniuchi, Y.; Takezawa, A.; Takeda, S.; Kawasaki, H.;
Murai, A.; Kawai, H.; Suzuki, T. Tetrahedron Lett. 2005, 46, 8279; (d) Panarese, J.
D.; Waters, S. P. Org. Lett. 2009, 11, 5086; (e) Rusin, A.; Zawisza-Puchalka, J.;
Kujawa, K.; Gogler-Piglowska, A.; Wietrzyk, J.; Switalska, M.; Glowala-Kosinska,
M.; Gruca, A.; Szeja, W.; Krawczyk, Z.; Grynkiewicz, G. Bioorg. Med. Chem. 2011,
19, 295.
4.2.19. (þ)-endo-Fenacholyl
4-O-acetyl-6-deoxy-2,3-dideoxy-a-D-
erythro-hex-2-enopyranoside (3s). Colorless oil; ½a D25
ꢃ203 (c 1.56,
ꢂ
CHCl3,
a
:
b
¼17:1); 1H NMR (400 MHz, CDCl3)
d 5.85 (s, 2H), 5.04 (d,
2. For example, see: Bozell, J. J.; Tice, N. C.; Sanyal, N.; Thompson, D.; Kim, J.-M.;
Vidal, S. J. Org. Chem. 2008, 73, 8763.
J¼9.1 Hz, 1H), 4.92 (s, 1H), 4.00 (dq, J¼12.6, 6.2 Hz, 1H), 3.24 (s, 1H),
2.12 (s, 3H), 1.71 (s, 3H), 1.51e1.30 (m, 3H), 1.25 (d, J¼6.3 Hz, 3H),
1.12 (s, 1H), 1.09 (s, 3H), 1.06 (s, 3H), 0.90 (s, 3H). 13C NMR (101 MHz,
3. (a) Ferrier, R. J.; Sankey, G. H. J. Chem. Soc. C 1966, 2345; (b) Ferrier, R. J.; Prasad,
N. J. Chem. Soc. C 1969, 570; (c) Wieczorek, B.; Thiem, J. J. Carbohydr. Chem. 1998,
17, 785; (d) Csuk, R.; Shaad, M.; Krieger, C. Tetrahedron 1996, 52, 6397; (e) Ferrier,
R. J. Top. Curr. Chem. 2001, 215, 153; (f) Ferrier, R. J. Org. React. 2003, 62, 174; (g)
Ferrier, R. J.; Zubkov, O. A. Org. React. 2004, 62, 569.
CDCl3) d: 170.58, 129.19, 128.00, 96.38, 92.97, 70.95, 64.91, 49.40,
48.07, 41.02, 38.99, 30.40, 26.17, 25.91, 21.66, 21.14, 19.76, 17.89; IR
(film, cmꢃ1): 2927, 2864, 1730, 1638, 1458, 1384, 1233, 1097, 1042,
911, 805, 742; MS (ESI): m/z 331.2 ([MþNa]þ, 100); HR-ESI:
4. (a) Babu, B. S.; Balasubramanian, K. K. Tetrahedron Lett. 2000, 41, 1271; (b)
Masson, C.; Soto, J.; Bessodes, M. Synlett 2000, 1281; (c) Takhi, M.; Rahman, A.;
Adel, A. H.; Schmidt, R. R. Tetrahedron Lett. 2001, 42, 4053; (d) Swamy, N. R.;
Venkateswarlu, Y. Synthesis 2002, 598; (e) Yadav, J. S.; Reddy, B. V. S.; Reddy, K.
B.; Satyanarayana, M. Tetrahedron Lett. 2002, 43, 7009; (f) Bettadaiah, B. K.;
Srinivas, P. Tetrahedron Lett. 2003, 44, 7257; (g) Kim, H.; Men, H.; Lee, C. J. Am.
Chem. Soc. 2004, 126, 1336; (h) Swamy, N. R.; Srinivasulu, M.; Reddy, T. S.; Goud,
T. V.; Venkateswarlu, Y. J. Carbohydr. Chem. 2004, 23, 435; (i) Rafiee, E.; Tan-
gestaninejad, S.; Habibi, M. H.; Mirkhani, V. Bioorg. Med. Chem. Lett. 2004, 14,
3611; (j) Babu, J. L.; Khare, A.; Vankar, Y. D. Molecules 2005, 10, 884; (k) Naik, P.
U.; Nara, J. S.; Harjani, J. R.; Salunkhe, M. M. J. Mol. Catal. A: Chem. 2005, 234, 35;
(l) Procopio, A.; Dalposso, R.; De Nino, A.; Nardi, M.; Oliverio, M.; Russo, B.
Synthesis 2006, 2608; (m) Procopio, A.; Dalpozzo, R.; Nino, A. D.; Maiuolo, L.;
Nardi, M.; Oliverio, M.; Russo, B. Carbohydr. Res. 2007, 342, 2125; (n) Zhang, G.;
Shi, L.; Liu, Q.; Wang, J.; Li, L.; Liu, X. Tetrahedron 2007, 63, 9705; (o) Zhang, G.;
Liu, Q. Synth. Commun. 2007, 37, 3485; (p) Tayama, E.; Otoyama, S.; Isaka, W.
Chem. Commun. 2008, 4216; (q) Baramulugan, R.; Kopollu, S. R. Tetrahedron 2009,
65, 8139; (r) Rodriguez, O. M.; Colinas, P. A.; Bravo, R. D. Synlett 2009, 1154; (s)
Gorityala, B. K.; Lorpitthaya, R.; Bai, Y.; Liu, X.-W. Tetrahedron 2009, 65, 5844; (t)
Nagaraj, P.; Ramesh, N. G. Tetrahedron Lett. 2009, 50, 3970; (u) Ding, F.; William,
R.; Gorityala, B. K.; Ma, J.; Wang, S.; Liu, X.-W. Tetrahedron Lett. 2010, 51, 3146; (v)
Chen, P.-R.; Wang, S.-S. Tetrahedron 2012, 68, 5356; (w) Deshpande, P. P.; Price,
K. N.; Baker, D. C. J. Org. Chem. 1996, 61, 455; (x) Chen, P.-R.; Lin, L. Tetrahedron
2013, 69, 4524.
C
18H28Na1O4 [MþNa]þ calcd 331.1875, found 331.1880.
4.2.20. Epiandrosteronyl-4-O-acetyl-6-deoxy-2,3-dideoxy-
a
-
D
-er-
ythro-hex-2-enopyranoside (3t). Colorless oil; ½a D25
ꢂ
ꢃ64 (c 0.52,
CHCl3,
a:b
¼13:1); 1H NMR (400 MHz, CDCl3)
d 5.93e5.76 (m, 2H),
5.14 (s, 1H), 5.07 (d, J¼9.1 Hz, 1H), 4.04 (dq, J¼12.4, 6.2 Hz, 1H),
3.70e3.47 (m, 1H), 2.46 (dd, J¼19.2, 8.8 Hz, 1H), 2.10 (s, 3H),
1.99e1.86 (m, 2H), 1.79 (dd, J¼25.7, 12.8 Hz, 3H), 1.66 (s, 3H),
1.60e1.49 (m, 3H), 1.32 (dd, J¼13.6, 8.8 Hz, 6H), 1.24 (d, J¼6.3 Hz,
3H), 1.15 (d, J¼11.8 Hz, 1H), 1.01 (dt, J¼12.0, 9.2 Hz, 2H), 0.88 (s, 3H),
0.85 (s, 3H), 0.71 (dd, J¼15.0, 7.3 Hz, 1H) ppm; 13C NMR (101 MHz,
CDCl3):
d 170.60, 129.45, 128.36, 92.59, 71.00, 64.57, 54.45, 54.31,
51.42, 47.81, 44.83, 44.65, 37.12, 35.87, 35.80, 35.04, 34.61, 31.57,
30.91, 29.71, 28.51, 21.79, 21.11, 20.49, 18.02, 13.83, 12.23 ppm; IR
(film, cmꢃ1): 2925, 2852, 1737, 1638, 1451, 1377, 1235, 1102, 1031,
918, 833, 748; MS (ESI) m/z: 467.3 ([MþNa]þ, 100); HR-ESI:
C
27H40O5Na1 [MþNa]þ calcd 467.2761, found 467.2768.
5. (a) Yadav, J. S.; Reddy, B. V. S.; Narasimha, C. D.; Madavi, C.; Kunwar, A. C.
Tetrahedron Lett. 2009, 50, 81; (b) Mukherjee, D.; Yousuf, S. K.; Taneja, S. C.
Tetrahedron Lett. 2008, 49, 4944; (c) Nagaraj, P.; Ramesh, N. G. Tetrahedron 2010,
66, 591.
Acknowledgements
6. (a) Chen, P.-R.; Wang, S.-S. Tetrahedron 2013, 69, 583; (b) Bhate, P.; Horton, D.;
Priebe, W. Carbohydr. Res. 1985, 144, 331; (c) Toshima, K.; Ishizuka, T.; Matsuo, G.;
Masaya Nakata, M.; Kinoshita, M. J. Chem. Soc., Chem. Commun. 1993, 704.
This work is financially supported by a grant of The National
Natural Science Foundation of China (NSFC, Grant No. 21272305),