Facile O-glycosylation of glycals using Glu-Fe3O4-SO3H, a magnetic solid acid catalyst

Article abstract of DOI:10.1039/c6ra03305a

A new glucose derived magnetic solid acid catalyst (Glu-Fe₃O₄-SO₃H) was synthesized in a convenient and ecofriendly manner and well characterized using FTIR, PXRD, EDAX, SEM, and XPS which showed the presence of Fe₃

Full text of DOI:10.1039/c6ra03305a

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Facile O-Glycosylation of Glycals Using Glu-Fe3O4-SO3H, a Magnetic Solid
Acid Catalyst
Raju S. Thombal and Vrushali H. Jadhav*
Department of Organic Chemistry, National Chemical Laboratory (CSIRꢀNCL), Puneꢀ411008, India.
A new glucose derived magnetic solid acid catalyst (GluꢀFe3O4ꢀSO3H) was synthesized in a
convenient and ecofriendly manner and well characterized using FTIR, PXRD, EDAX, SEM,
and XPS which showed the presence of Fe3O4 embedded on the surface of the catalyst along
with ꢀSO3H, ꢀOH and ꢀCOOH functional groups. This new heterogeneous catalyst was
studied for synthesis of 2ꢀdeoxy galactosides/glucosides with good yields and selectivity.
Moreover, the catalyst can be easily separated from the reaction with an external magnetic
force and reused minimum four times without any significant decrease in yields of the
products after every recycle.
Keywords: glycosylation, glycals, magnetic, sulfonated, recycled
1. Introduction
2ꢀdeoxyꢀOꢀglycosides are found widely in number of natural products.1ꢀ2 2ꢀdeoxyꢀOꢀ
glycoside component in any natural product plays an important role as it is responsible for the
bioactivity of a drug. For chemical synthesis of these natural products large quantities of 2ꢀ
deoxyꢀOꢀglycosides are required. Hence, attention has been extensively paid for synthesis of
these glycosides. Till date, number of homogeneous catalyst have been reported for the
synthesis of 2ꢀdeoxyꢀOꢀglycosides by direct addition of alcohols to glycals using protic acids
or Lewis acids.3ꢀ8 They suffer from drawback of corrosion, contamination and needs
neutralization after the reaction and hence the workup is tedious. Such catalysts are difficult
Email: vh.jadhav@ncl.res.in
Tel: +91 (20) 25902275
to separate from the reaction and they cannot be reused. Also one main disadvantage in these
direct glycosylations is the possibility of the Ferrier reaction. Heterogeneous catalysts have
advantages over homogeneous catalyst that they are inexpensive, more efficient, stable, easily
separable and reusable. Hence there is a need to develop mild and efficient catalyst for
glycosylation reactions to overcome the above mentioned problems. Balmond et. al9 in 2012,

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reported selective synthesis of 2ꢀdeoxyꢀOꢀgalactoside using thiourea as a catalyst. Das et. al10
in 2015, reported selective synthesis of 2ꢀdeoxyꢀOꢀglycosides using electron deficient
pyridinium salts. Our continuous interest in this field prompted us to synthesize glucose
derived magnetic solid acid catalyst.11 Herein, we report the synthesis of new GluꢀFe3O4ꢀ
SO3H catalyst and showed its application for tetrahydropyran protection of alcohols and
glycosylation of protected glycals in the synthesis of 2ꢀdeoxyꢀOꢀglycosides (Figure 1).
SO3H
HO
COOH
a) Fe preloading
b) Pyrolysis & Sulfonation
HOOC
OH
sp2 carbons
SO3H
Glu-Fe3O4-SO3H
Glucose
Tetrahydropyran/2ꢀdeoxyꢀ Oꢀglycoside
ROH, Neat/DCM, rt
DihydroPyran/Glycal
Figure 1. Schematic representation for synthesis of Glu-Fe3O4-SO3H catalyst and its application for THP
protection of alcohol and 2-deoxy-O-glycoside synthesis.
2. Experimental
2.1 Catalyst Preparation
5.0 g of glucose and 276 mL of FeCl3 solution with a concentration of 100 mmol/L were
mixed in a flask and stirred for 5 h at rt. Then, the water in the mixture was evaporated, and
the solid residue was dried at 378 K overnight and sieved again to collect the particles with a
size smaller than 120 mesh to obtain the Fe preloaded glucose. Fe preloaded glucose was
0
then stirred with pꢀTSA (5 eq) at 140 C for 24 h under argon atmosphere. The mixture was
then cooled to rt, and then slowly added to a beaker containing 500 mL deionised water. The
suspension mixture was then filtered off and washed repeatedly with deionised water to
2ꢀ
remove all the sulfate ions (SO4 ). The solid was further washed with absolute ethanol to
remove the water, and then dried at 353 K overnight to get a black magnetic material (Gluꢀ
Fe3O4ꢀSO3H).

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2.2 General procedure for THP protection of alcohols using Glu-Fe3O4-SO3H under
neat conditions
Dihydropyran (0.30 mmol), alcohol (0.9 mmol) and catalyst GluꢀFe3O4ꢀSO3H (1 wt %) were
stirred together in a screwꢀcapped vial under argon atmosphere. The mixture was stirred neat
at rt for 2ꢀ5 min. The reaction was monitored by TLC analysis. After completion of the
reaction, DCM was added and the catalyst was separated from the reaction mixture by
applying external magnetic field. DCM layer was decanted and then evaporated to obtain the
product.
2.3 General procedure for glycosylation of protected glycals using Glu-Fe3O4-SO3H.
Glycal (1.2 mmol), alcohol (1.4 mmol) and catalyst GluꢀFe3O4ꢀSO3H (5 wt %) were stirred
together in a screwꢀcapped vial under argon atmosphere neat or in DCM (DCM was used
when the glycal and alcohol both are solids). The mixture was stirred for required
temperatures and required time. The reaction was monitored by TLC. After completion of the
reaction the catalyst was separated from the reaction mixture by applying external magnetic
field (In neat conditions, DCM was added after completion of the reaction). DCM layer was
then decanted and evaporated to obtain the product. The anomeric ratio’s were determined
from the 1H NMR of the products.
3. Results and Discussion
3.1 Characterization of the catalyst
Due to our continuous interest in this field, we have synthesized a magnetic carbonaceous
solid acid catalyst GluꢀFe3O4ꢀSO3H. For preparation of this catalyst, we choose readily
available Dꢀglucose as a carbon precursor, Fe was preloaded on glucose using FeCl3 and pꢀ
TSA was used as a sulphonating agent to create active acidic sites. Initially Fe was preloaded
on glucose using FeCl3. The free ꢀOH groups in glucose easily coordinated with adsorbed Fe
(III) ions and then evaporation of solvent and drying gave black Fe (III) based complex. This

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complex was then pyrolysed and sulfonated simultaneously using pꢀTSA at 140 ºC under
nitrogen. The Fe preloaded on glucose was partly hydrolysed to FeO(OH) during drying.
FeO(OH) was further reduced to Fe3O4 by reducing components like H2, CO2 and CO which
are formed during carbonation process.12 Pyrolysis and sulfonation inꢀsitu leads to formation
of a polycylic aromatic structure embedded with active Fe3O4, –SO3H, –COOH and ꢀOH
sites.
The catalyst thus obtained was characterized with FTꢀIR (Spectrum 400), PXRD
(Panalytical X'Pert Pro), Elemental analysis from EDAX (Nova Nano SEM 450), SEM
(Quanta™ Scanning Electron Microscope), XPS (Prevac Ambient Pressure Photo Electron
Spectroscopy) and BET surface area (Quantachrome ASiQwin). The acid densities were
measured by acid base titration.13 FTꢀIR spectrum (Figure 2a) showed characteristic peaks at
1012 cmꢀ1 and 1040 cmꢀ1 which are attributed to O=S=O stretching vibrations in ꢀSO3H
groups and peak at 1127 cmꢀ1 for SO3H stretching. This indicates that the sulfonic acid
groups have been successively incorporated on the catalyst surface. Peaks at 1645 cmꢀ1
attributed for C=C stretching vibrations in aromatic carbons and peak at 1670 cmꢀ1 attributed
for C=O stretching. Peak at 1714 cmꢀ1 attributed to presence of C=O stretching vibration of –
COOH group. Bands at 2925 cmꢀ1 attributed for CꢀH stretching band. Bands due to OꢀH
stretching were observed at 3410 cmꢀ1.The PXRD (Figure 2b) showed a weak but broad peak
of 2θ at 15ꢀ30º, indicating formation of amorphous carbon having aromatic carbon sheets
oriented in a random fashion. The sharp peaks seen indicates the formation of Fe3O4
crystallite in the pyrolysis process. The energy dispersive Xꢀray analysis (Figure 2c) confirms
that the catalyst surfaces are composed mainly of C, O, Fe and S. Composition of S and Fe is
found to be 7.4% and 7.7% respectively from EDAX. The elemental analysis showed
composition of C to be 50%, H to be 4% and S to be 9%. SEM (Figure 2d)
image shows formation of porous nature of the catalyst. The surface composition of Gluꢀ

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Fe3O4ꢀSO3H was analysed by XPS (Figure 2e). The C 1s spectrum includes six peaks with
different binding energy values. The peaks could be assigned to the carbon atoms in the
forms of CꢀS (283.5 eV), CꢀC (284 and 284.5 eV), CꢀO (285 eV), C=O (285.5 eV), O=CꢀO
(286 eV). The S 2p spectrum showed three different peaks that can be assigned to SꢀC
(186.5), SꢀO (169 eV) and S=O (169.5 eV). O 1s spectrum shows peaks in the range 530ꢀ535
eV indicating the presence of FeꢀO and CꢀOꢀFe groups suggesting the linkage of Fe3O4 with
(b )
2 0 0
1 8 0
1 6 0
1 4 0
am orphous c arbon
1 2 0
F e 3O 4
1 0 0
8 0
6 0
4 0
2 0
0
0
2 0
4 0
6 0
8 0
1 0 0
2 θ /d e g re e
cps/eV
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
S
Fe
C
O
S
Fe
1
2
3
4
5
keV
6
7
8
9
10
Figure 2. a) FTꢀIR of GluꢀFe3O4ꢀSO3H. b) PXRD of GluꢀFe3O4ꢀSO3H. c) EDAX of GluꢀFe3O4ꢀSO3H. d) SEM
image of GluꢀFe3O4ꢀSO3H. e) XPS of GluꢀFe3O4ꢀSO3H
porous carbon. BET surface area, pore size and pore volume was calculated using the
standard BrunauerꢀEmmettꢀTeller (BET) equation and was found to be 3.38 m2/g, 9.53 Aº
and 6.07 m3/g respectively. The total acid density and the sulphonic acid density of Gluꢀ

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Fe3O4ꢀSO3H based on acid base titration was found to be 2.87 mmol/g and 1.46 mmol/g
respectively.
3.2 Effect of catalyst on tetrahydropyran protection of alcohols
Initially we focused our attention on the tetrahydropyranyl (THP) protection of alcohols. As a
first set of experiments, we studied the THP protection of various primary, secondary and
tertiary alcohols like cyclohexanol 2a, isopropanol 2b, benzyl alcohol 2c and tꢀbutanol 2d
with dihydropyran 1 (Table 1).
Table 1. Tetrahydropyran protection of alcohols using GluꢀFe3O4ꢀSO3H catalyst under solvent free conditions at
room temperature
Entry Alcohol
Product
Yielda
(%)
1.
2.
3.
99
89
96
2a
2b
2c
4.
80
2d
[a] Isolated yields
To our delight, the GluꢀFe3O4ꢀSO3H catalyst efficiently catalyzed this reaction under neat
reaction conditions at rt within 2ꢀ5 minutes to obtain THPꢀprotected products 3aꢀ3d using 1
wt% loading of catalyst to give full conversion and high yields. The reaction when performed
without using GluꢀFe3O4ꢀSO3H catalyst, no formation of THP protected product was
observed.
3.3 Effect of catalyst on glycosylation of protected glycals

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After successful establishment of the THP protection of various alcohols, we turned our
attention towards the more challenging glycosylation reaction of different glycals using
various acceptors as alcohols. For this study the required glycal components 3,4,6ꢀtriꢀOꢀ
benzyl, 3,4,6ꢀtriꢀOꢀsilyl and 3,4,6ꢀtriꢀOꢀacetyl galactals (4-6) as well as 3,4,6ꢀtriꢀOꢀbenzyl,
3,4,6ꢀtriꢀOꢀsilyl and 3,4,6ꢀtriꢀOꢀacetyl glucals (7–9) were synthesized by known procedure.10
Glycosyl acceptors choosen for the study were bisacetonideꢀDꢀglucose 2e, (ꢀ) menthol 2f,
cholesterol 2g, octanol 2h, propargyl alcohol 2i and methanol 2j.
Initially, we optimized the reaction conditions for glycosylation of 3,4,6ꢀtriꢀOꢀbenzyl
ꢀgalactal10 4 using bisacetonideꢀ
D
Dꢀglucose 2e using GluꢀFe3O4ꢀSO3H catalyst (Table 2).
Since both reagents are solid, DCM was used as a solvent for glycosylation reaction. The
reaction was studied at various temperatures such as ꢀ20 ºC, 0 ºC, rt and 40 ºC using 10 wt%
of catalyst loading. It was observed that the reaction did not proceed atall at ꢀ20 ºC in DCM
even after 24 h. At 0 ºC, in DCM after 12 h, the reaction did not proceed to completion thus
giving 45% yield of the glycoside 10a in 1:1
α
:
β
anomeric ratio. At rt in DCM, glycosylation
anomeric ratio.
was found to be complete giving 94% yield of the glycoside 10a in 83:17
α:β
When the glycosylation was carried out at 40 ºC in DCM, only 32% of the glycosylated
product 10a was obtained along with the Ferrier rearranged product. Hence the optimum
temperature for the reaction was found to be room temperature. The catalyst loading was
further studied and it was found out that glycosylation of 4 with 5 wt% catalyst in DCM at rt
gave quantitave yield of the glycoside with 83:17 α:β selectivity. When the catalyst loading
was further decreased to 1 wt% at rt, it was observed that the reaction was incomplete. Hence
5 wt% catalyst loading was optimized for further glycosylation reactions that were carried
out. It was also observed that the isopropylidine groups were stable under these catalytic
conditions.

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Table 2. Optimisation of reaction conditions in glycosylation of 3,4,6ꢀtriꢀOꢀbenzylꢀDꢀgalactal 4 and alcohol 2e
in presence of GluꢀFe3O4ꢀSO3H catalysta
Entry
Catalyst loading
(wt %)
Temp Time
Yieldb
(%)
ꢀ
α:β ratioc
(0C)
(h)
1
2
3
4
5
10
10
10
10
5
ꢀ20
0
24
12
3
-
45
50:50
83:17
50:50
83:17
rt
94
40
rt
4
32
3
97
[a] All reactions performed in screwꢀcapped vial on 100 mg scale of 4 and 2e in 2 mL DCM. [b] Isolated yields
[c] Ratio determined from 1H NMR.
Additions of various alcohols 2eꢀ2j on different glycals 4ꢀ9 using GluꢀFe3O4ꢀSO3H
catalyst are reported in Table 3. It was observed that addition of alcohols 2f, 2g and 2h with
3,4,6ꢀtriꢀOꢀbenzylꢀ
and selectivity (Table 3, entries 1ꢀ3). Addition of alcohol 2i gave formation of galactoside in
α: 71:29 ratio (Table 3, entry 4). When methanol 2j was used, selectively αꢀgalactoside was
formed in good yield (Table 3, entry 5). Both primary and secondary alcohols reacted
smoothly to provide the glycoside product. 3,4,6ꢀtriꢀOꢀsilylꢀ ꢀgalactal 5 with alcohol 2e
afforded the glycoside in 91:9 α:β ratio with excellent yield (Table 3, entry 6). 3,4,6ꢀtriꢀOꢀ
acetylꢀ ꢀgalactal 6 did not undergo addition of alcohol 2e even on prolonged time (Table 3,
Dꢀgalactal 4, afforded exclusively the αꢀgalactoside with excellent yields
β
D
D
entry 7). The deactivating effect of acetyl protection in glycosylation has been reported
earlier.14
Table 3. Addition of alcohols to the glycals 4ꢀ9 in the presence magnetic GluꢀFe3O4ꢀSO3H catalyst

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Entry Glycal
Alcohol
2f
Time (h)
Product
10b
10c
10d
10e
10f
10g
-
Yielda (%)
α:β ratiob
1
2
8
6
82
α
4
4
4
4
4
5
6
7
7
7
7
7
7
8
9
89
α
2g
2h
2i
3c
4c
5c
6
4
91
α
3
96
71:29
3
94
α
2j
3
88
91:9
2e
7
5
no reaction
ꢀ
2e
8
3
84
77:23
2e
10h
10i
9
6
80
83:17
2f
10
11c
12c
13c
14
15
6
83
77:23
91: 9d, 50:50e, 90:10f
90: 10d, 50:50e, 83:27f
69: 31d, 38:62e,91:9
91:9
2g
2h
2i
10j
10k
10l
4
80
3
93
94
3.5
3
2j
10m
10n
-
81
2e
6
no reaction
ꢀ
2e
1
[a] Isolated yields [b] Ratio’s determined from H NMR spectroscopy [c] 3 equiv of alcohols were used [d] α:β
ratio of 2ꢀdeoxyꢀOꢀglycoside [e] Ratio of the Ferrier product and 2ꢀdeoxyꢀOꢀglycoside [f] α:β ratio of the Ferrier
product.

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We next turned our attention to glucals 7ꢀ9 for glycosylation. 3,4,6ꢀtriꢀOꢀbenzylꢀDꢀglucal 7,
reacted smoothly with alcohol 2e, 2f and 2g giving α:β glycoside in 77:23, 83:17 and 77:23
ratio respectively (Table 3, entries 8ꢀ10). In case of addition of alcohol 2h to 3,4,6ꢀtriꢀOꢀ
benzylꢀDꢀglucal 7, 2ꢀdeoxyꢀOꢀglycoside and Ferrier product were formed in a ratio of 50:50,
of which 2ꢀdeoxyꢀOꢀglycoside was formed in a α:β ratio of 91:9, whereas Ferrier product was
formed in a α:β ratio of 90:10 (Table 3, entry 11). Similarly in case of addition of alcohols 2i
and 2j to 3,4,6ꢀtriꢀOꢀbenzylꢀ
products (Table 3, entries 12 and 13). 3,4,6ꢀtriꢀOꢀsilyꢀ
gave 91:9 α:β mixture of the glucoside (Table 3, entry 14). 3,4,6ꢀtriꢀOꢀacetylꢀ
D
ꢀglucal 7 gave mixture of 2ꢀdeoxyꢀOꢀglycoside and Ferrier
ꢀglucal 8 on addition of alcohol 2e
ꢀglucal 9 did
D
D
not show formation of any product (Table 3, entry 15) due to deactivating effect of acetyl
group.
Table 4. Effect of catalyst on addition of alcohol to 3,4,6ꢀtriꢀOꢀbenzylꢀ
D
ꢀgalactal 4
Entry
Catalyst
Alcohol
Yield
(%)
α:β ratio of 2ꢀdeoxyꢀOꢀglycoside
1
2
3
4
5
6
TMSONO2
pTSA/[bmim]BF4
Cerric ammonium nitrate
Y zeolites
Cholesterol
MeOH
68
91
78
80
81
94
81:1915
4:116
MeOH
32:117
BnOH
Only Ferrier product18
Only Ferrier product19
Only α
SiO2.H2SO4
MeOH
GluꢀFe3O4ꢀSO3H
MeOH
Comparison of some known catalyst vs. GluꢀFe3O4ꢀSO3H has been shown in Table 4
for addition of alcohols to 3,4,6ꢀtriꢀOꢀbenzylꢀ ꢀgalactal 4. Addition of cholesterol to
galactal 4 in presence of trimethylsilylnitrate gave 81:19 α:β ratio of 2ꢀdeoxyꢀOꢀglycoside
(Table 4, entry 1). Whereas addition of methanol to ꢀgalactal 4 in presence of pꢀ
D
Dꢀ
D
TSA/[bmim]BF4 and CAN gave 4:1 and 32:1 α:β ratio of 2ꢀdeoxyꢀOꢀglycoside respectively
(Table 4, entries 2 and 3). Heterogeneous catalyst such as Y zeolites and SiO2.H2SO4 gave no
formation of 2ꢀdeoxyꢀOꢀglycoside instead gave only Ferrier rearranged product formation

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(Table 4, entries 4 and 5). Whereas, GluꢀFe3O4ꢀSO3H gave addition of methanol to Dꢀgalactal
4 selectively forming αꢀ2ꢀdeoxyꢀOꢀglycoside which indicates good efficiency of the catalyst
for selective formation of 2ꢀdeoxyꢀOꢀglycoside (Table 4, entry 6).
It was observed that addition reaction of alcohols to galactals displayed high αꢀ
stereoselectivity, which is consistent with the anomeric effect. While, addition reaction of
alcohols to glucals generally gave a low α:β ratio along with the Ferrier rearranged products
in some cases. This phenomenon can be explained by the steric hindrance of the bulky
benzyloxy/silyl group at Cꢀ4 position of galactals which prevents the attack of acceptors from
the top face of the sugar ring, thus promoting the formation of major αꢀanomer.
3.4 Resuability of the catalyst
Reusability and isolation of the catalysts are important factors for any practical application. It
is very convenient to recover GluꢀFe3O4ꢀSO3H catalyst in the end of the reaction by
separating it using external magnetic field (Figure 3).
Figure 3. Separation of catalyst GluꢀFe3O4ꢀSO3H using external magnetic field.
The solid catalyst thus separated could be readily reused for the next runs without any
prior activation. It was observed that reuse of GluꢀFe3O4ꢀSO3H catalyst gave no significant
decrease in yield of products in case of THP protection as well as glycosylation of glycals
after four recycles (Table 5).

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Table 5: Reusability of GluꢀFe3O4ꢀSO3H catalyst in THP protection and 2ꢀdeoxyꢀOꢀglycoside synthesis
Entry
Reuse
THP protectiona
(%)
Glycosylationb
(%)
1
2
3
4
1st recycle
99
99
98
96
94
92
91
86
nd
2 recycle
rd
3 recycle
4th recycle
[a] Reaction performed between 1 and 2a. [b] Reaction performed between 4 and 2e
4. Conclusion
In conclusion, a new porous magnetic carbonaceous solid acid catalyst GluꢀFe3O4ꢀSO3H was
efficiently prepared and was found to show excellent catalytic activity for THP protection of
alcohols and synthesis of 2ꢀdeoxyꢀOꢀglycoside under mild reaction conditions giving high
yields and selectivity. The catalyst could also be recovered by external magnetic force and
reused several times without any loss of activity. This catalytic system is environmentally
green and can be used as an ideal method for glycosylation reactions.
Acknowledgements
V.H.J. thanks DST, New Delhi for the INSPIRE Faculty Award (IFA 12, CHꢀ44) and Fast
Track Grant (CSꢀ041/2013). V.H.J also thanks Director, NCL for providing all the infraꢀ
structural facilities.
References
1. X. He, G. Agnihotri and H. W. Liu, Chem Rev., 2000, 100, 4615ꢀ4662.
2. A. Kirsching, A. F. W. Rohr and J. Rohr, Bioorganic Chemistry: Deoxysugars,
Polyketides and Related Classes: Synthesis; Biosynthesis: Enzymes, Springer: Berlin.,
1997, 1ꢀ84.
3. J. S. Yadav, B. V. S. Reddy, K. B. Reddy and M. Satyanarayana, Tetrahedron Lett.,
2002, 43, 7009ꢀ7012.
4. K. Toshima, H. Nagai, Y. Ushiski and S. Matsumura, Synlett., 1998, 1007ꢀ1009.
5. K. Pachamuthu and Y. D. Vankar, J. Org. Chem., 2001, 66, 7511ꢀ7513.

Page 13 of 14
RSC Advances
View Article Online
DOI: 10.1039/C6RA03305A
6. X. K. Cui, M. Zhong, X. B. Meng and Z. J. Li, Carbohydr Res., 2012, 358, 19ꢀ22.
7. T. Kimura, D. Takahashi and K. Toshima, J. Org. Chem., 2015, 80, 9552−9562.
8. C. Masson, J. Soto and M. Bessodes, Synlett., 2000, 1281ꢀ1282.
9. E. I. Balmond, D. M. Coe, M. C. Galan and E. M. McGarrigle, Angew. Chem. Int. Ed.,
2012, 51, 9152ꢀ9155.
10. S. Das, D. Pekel, J. M. Neudcrfl, and A. Berkessel, Angew. Chem. Int. Ed., 2015, 54,
12479ꢀ12483.
11. R. S. Thombal, A. R. Jadhav and V. H. Jadhav, RSC Adv., 2015, 5, 12981ꢀ12986.
12. W. J. Liu, K. Tian, H. Jiang and H. Q. Yu, Nature Sci Rep,, 2013, 3, 2419ꢀ2425.
13. S. Suganuma, K. Nakajima, M. Kitano, D. Yamaguchi, H. Kato, S. Hayashi and M.
Hara, J. Am. Chem. Soc., 2008, 130, 12787ꢀ12793.
14. E. I. Balmond, D. BenitoꢀAlifonso, D. M. Coe, R. W. Alder, E. M. McGarrigle and M.
C. Galan, Angew. Chem. Int. Ed., 2014, 53, 8190ꢀ8194.
15. B. Gopal Reddy and Y. D. Vankar, Arkivoc. 2004, viii, 12ꢀ19.
16. G. Diaz, A. Ponzinibbio, R. D. Bravo, Top Catal., 2012, 55, 644ꢀ648.
17. K. Pachamuthu and Y. D. Vankar, J. Org. Chem., 2001, 66, 7511ꢀ7513.
18. P. Levecque, D. W. Gammon, P. Jacobs, D. De Vos and B. Sels, Green Chem., 2010,
12, 828ꢀ835.
19. J. Zhang, B. Zhang, J. Zhou, H. Chen, J. Li, G. Yang, Z. Wang and J. Tang, J.
Carbohydr. Chem., 2013, 32, 380ꢀ391.

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DOI: 10.1039/C6RA03305A