Zeolite catalyzed selective deprotection of di- and tri-O-isopropylidene sugar acetals

Article abstract of DOI:10.1016/j.carres.2008.05.006

H-Beta zeolite, a microporous solid acid, is demonstrated to be an efficient catalyst for the selective deprotection of cyclic as well as acyclic O-isopropylidene sugar acetals derived from d-glucose, d-xylose, d-mannose, and d-mannitol in aqueous MeOH at room temperature. A notable observation is the conversion of d-mannitol triacetonide into 1,2:3,4-di-O-isopropylidene-d-mannitol (48%) and 3,4-O-isopropylidene-d-mannitol (36%) brought about in 6 h by H-beta zeolite and the non-occurrence of any hydrolysis in the case of H-ZSM-5 catalyzed reaction in 24 h under the same conditions.

Full text of DOI:10.1016/j.carres.2008.05.006

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 1801–1807
Note
Zeolite catalyzed selective deprotection of
di- and tri-O-isopropylidene sugar acetals
Pallooru Muni Bhaskar, Manoharan Mathiselvam and Duraikkannu Loganathan*
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
Received 20 January 2008; received in revised form 25 April 2008; accepted 4 May 2008
Available online 8 May 2008
Dedicated to Professor C. N. Pillai on his 70th birthday
Abstract—H-Beta zeolite, a microporous solid acid, is demonstrated to be an efficient catalyst for the selective deprotection of cyclic
as well as acyclic O-isopropylidene sugar acetals derived from D-glucose, D-xylose, D-mannose, and D-mannitol in aqueous MeOH
at room temperature. A notable observation is the conversion of D-mannitol triacetonide into 1,2:3,4-di-O-isopropylidene-D-man-
nitol (48%) and 3,4-O-isopropylidene-D-mannitol (36%) brought about in 6 h by H-beta zeolite and the non-occurrence of any
hydrolysis in the case of H-ZSM-5 catalyzed reaction in 24 h under the same conditions.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: O-Isopropylidene acetals; Carbohydrates; Hydrolysis; Zeolites and solid acids
Driven by the growing need for developing synthetic
methodologies based on green chemistry, the applica-
tion of inorganic solid acids, such as zeolites and mole-
cular sieves, as heterogeneous catalysts for solution phase
organic transformations is gaining greater attention.1
The advantages of solid acids over the homogeneous
systems include elimination–minimization of (a) hazards
in handling of corrosives, (b) difficulty in separation and
neutralization, and (c) disposal costs. The following un-
ique characteristics set zeolites apart from other solid
acid catalysts: (a) regular pore size and pore architec-
ture, (b) pore widths of molecular dimensions that en-
able shape or size selective catalysis, and (c) acid–base
properties that can be tuned to match substrate reactiv-
ity. Thus zeolites offer exciting opportunities for selec-
tive transformations of multifunctional molecules such
as carbohydrates. Zeolites have been employed, as
acid–base catalysts, in carbohydrate chemistry to cata-
lyze reactions such as the formation of O-isopropylidene
acetals,2 preparation of 5-hydroxymethylfurfural from
fructose and precursors,3 hydrolysis of di- and polysac-
charides,4 and synthesis of alkyl glucoside surfactants.5
Zeolite catalyzed cleavage of sugar acetals has, however,
been hitherto unexplored.
Protection and deprotection of hydroxyl groups rep-
resent important procedures in carbohydrate chemis-
try.6 Selectively protected acetals of sugars, such as
O-isopropylidene derivatives, are useful intermediates
for the synthesis of biologically active molecules.7
Though several homogeneous Lewis/Bronsted catalysts
have been employed for the selective deprotection of
sugar acetals,8 reports on the use of solid acids are
rather limited and include ion-exchange resin9 and
FeCl3/NaHSO4/HClO4 supported on silica gel.10 As
part of our major program on solid acid-catalyzed trans-
formations of carbohydrates and other substrates in the
liquid-phase,11 we report herein on the selective and
complete deprotection of several di- and tri-O-isopro-
pylidene sugar acetals using H-ZSM-5 and H-beta zeo-
lite as catalysts. Both these zeolites share the common
property with their strong Brønsted acid sites. H-
ZSM-5 is a 10 ring medium pore zeolite (approximate
*
Corresponding author. Tel.: +91 44 22574206; fax: +91 44
22570509; e-mail: loganath@iitm.ac.in
Present address: Sanmar Speciality Chemicals Ltd, API Divn., 38 Old
Mahabalipuram Road, Perungudi, Chennai 600 096, India.
˚
d = 5.5 A) containing two perpendicularly intersecting
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.05.006

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P. M. Bhaskar et al. / Carbohydrate Research 343 (2008) 1801–1807
Table 1. Solid acid catalyzed selective cleavage of 1,2:5,6-di-O-
isopropylidene-a-D-glucofuranose (1)
channel systems, whereas H-beta is a 12 ring large pore
zeolite (approximate d = 7.5 A) consisting of two poly-
morphs A and B, each of which contains straight as well
as tortuous channels.12
˚
Entry Catalyst
Solvent
Timea Yield of
2b (%)
1
2
H-ZSM-5
H-Beta
MeOH–H2O (1:1) 16
MeOH–H2O (4:1) 48
92
85
96
94
88
22
Our initial efforts to bring about the selective depro-
tection of the diacetonide 1,2:5,6-di-O-isopropylidene-
a-D-glucofuranose (1a) using H-Y and H-ZSM-5 zeolite
in CCl4–CHCl3 with a stoichiometric amount of water
did not afford any product as shown by the TLC analy-
sis of the reaction mixture. Filtration of the catalyst
followed by evaporation of the solvent gave back the
unreacted starting material. However, extraction of the
recovered catalyst with MeOH under refluxing condi-
tions gave a product whose physical and spectral data
matched well with those of D-glucose. It was suspected
that the adsorbed substrate inside the zeolite pores
underwent partial hydrolysis but the product was not
desorbing and coming out into the relatively non-polar
liquid-phase, thus undergoing complete deprotection
to form D-glucose. By remaining inside the pores, D-glu-
cose also prevented catalytic turn over.
Therefore, it was reasoned that the appropriate med-
ium for the selective hydrolysis should be able to dis-
solve the substrate and also be able to extract the
product from zeolite pores when the reaction is in pro-
gress. Toward this end, aqueous MeOH was chosen as
the medium and selective hydrolysis of 1a was explored
using different solid acids at room temperature (Scheme
1). Following partial/complete conversion after the
specified time, the reaction mixture was worked up
and the product formed was purified by column chro-
matography over silica gel. The isolated yield of pure
product 1,2-O-isopropylidene-a-D-glucofuranose, 2a,
obtained in each of the solid acid catalyzed reactions
is shown in Table 1. H-ZSM-5 and H-beta are found
to be efficient catalysts in 50% aqueous MeOH medium.
A decrease in water content in the medium has led to
longer reaction times and lower yield of 2a in the case
of H-ZSM-5 catalyst. However, there was no significant
difference in reaction time observed with H-beta zeolite.
Even after 48 h of reaction, the conversion in the case of
montmorillonite K-10 was rather poor whereas H-Y
zeolite turned out to be completely ineffective. H-Beta
zeolite catalyzed transformation is much faster as com-
pared to that of H-ZSM-5 as well as that of previously
MeOH–H2O (1:1)
MeOH–H2O (9:1)
MeOH
2
2
4
3
4
Montmorillonite MeOH–H2O (1:1) 48
K-10
H-Y
MeOH–H2O (1:1) 48
—
a All the reactions were performed at room temperature.
b Yield of isolated pure product.
reported heterogeneous Bronsted acid catalysts such as
ion-exchange resin9 and HClO4 supported on silica
gel.10c Total hydrolysis was observed when the reaction
was performed using H-beta zeolite in MeOH–H2O (1:1)
under refluxing conditions for 4 h affording D-glucose in
near quantitative yield (94%). The high efficiency of
H-beta zeolite compared to other zeolites examined may
be due to its greater acid strength coupled with large
pore openings and spacious channel intersections.13
To evaluate the recyclability of the catalyst, H-beta
zeolite was filtered from the selective hydrolysis reaction
mixture containing 2a, washed with hot MeOH three
times, and dried in the oven at 400 °C. Treatment of
1a with the first and the second time recycled catalyst
in separate reactions afforded 2a in 97% and 95% yields,
respectively. H-Beta zeolite also proved to be effective in
bringing about selective deprotection of 2 in the pres-
ence of acid-labile protecting groups such as allyl,
benzyl, and propargyl (Scheme 2). The yield of the 3-
O-substituted derivatives 2b–d obtained based on
recovery of the starting material was greater than 95%
illustrating the stability of these functional groups under
the reaction conditions.
In an effort to evaluate the general application of the
method, selective hydrolysis of di-O-isopropylidene ace-
tals of D-xylose, D-galactose, D-mannose, and D-manni-
tol (Fig. 1) was examined using H-ZSM-5 and H-beta
zeolite in aqueous MeOH at room temperature. The
MeOH–H2O ratio for the reactions was chosen depend-
ing on the solubility of the substrates. Whenever possi-
ble, a 9:1 ratio of MeOH–H2O was chosen to facilitate
O
HO
HO
O
O
Solid Acid
MeOH / H2O, RT
O
OH
OH
O
O
O
O
1a
2a
Scheme 1.

P. M. Bhaskar et al. / Carbohydrate Research 343 (2008) 1801–1807
1803
HO
HO
O
O
H-Beta Zeolite
O
O
OR
OR
MeOH / H2O (9:1)
RT, 48 h
O
O
O
O
R = Allyl (2b, 80%) / Benzyl (2c, 60%)
/ Propargyl (2d, 89%)
1b-1d
Scheme 2.
OH
O
O
O
O
OH
O
O
O
O
O
O
O
OH
O
O
5
4
3
OH
O
HO
HO
O
O
O
O
O
O
O
OH
O
O
OH
O
OH
OAc
7
6
8
O
O
HO
OH
HO
HO
O
O
O
O
O
O
OH
O
O
O
OAc
O
9
10
11
Figure 1.
the easy removal of the medium. 1,2:5,6-Di-O-isopro-
pylidene-a-D-xylofuranose (3) underwent facile conver-
sion in the presence of both H-ZSM-5 and H-beta
zeolite furnishing the monoacetonide 1,2-O-isopropyl-
idene-a-D-xylofuranose (4) in excellent yields (Table 2,
entries 1 and 2). Expectedly, hydrolytic cleavage of the
1,3-dioxane ring in 3 is faster than the 1,3-dioxalane ring
of 1a.8iiia,14
Table 2. Zeolite catalyzed cleavage of various di-O-isopropylidene sugar derivatives
Entry
Substrate
Catalyst
MeOH–H2O ratio
Time (h)
Product (yield, %)a
1
2
3
4
5
6
7
8
9
3
H-ZSM-5
H-Beta
H-Beta
H-ZSM-5
H-Beta
H-Beta
H-ZSM-5
H-Beta
H-ZSM-5
1:1
9:1
9:1
1:1
1:1
1:1
1:1
1:1
1:1
4
1
8
24
24
24
48
24
3
4 (91)
4 (90)
9 (97)
—
3
8
10
10
10
11
11
11
—
D-Galactose (96)b
D-Mannitol (92)
D-Mannitol (96)
D-Mannitol (96)b
a Yield of isolated pure product.
b Reactions were performed at refluxing temperature.

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P. M. Bhaskar et al. / Carbohydrate Research 343 (2008) 1801–1807
The selective hydrolysis of 2,3:5,6-di-O-isopropyl-
Moving forward from di-O-isopropylidene acetals
to tri-O-isopropylidene acetals, the hydrolysis of 1,2:3,
4:5,6-tri-O-isopropylidene-D-mannitol (12) was then
explored (Scheme 3). The triacetonide 12 underwent
facile hydrolysis in the presence of H-beta zeolite in
MeOH–H2O (9:1) to form the 1,2:3,4-di-O-isopropyl-
idene-D-mannitol (13) and 3,4-O-isopropylidene-D-man-
nitol (14) in 48% and 36% yields, respectively (Table 3).
Interestingly, there was no reaction observed when
H-ZSM-5 was used under the above conditions (Table
3, entries 2 and 3). The failure of H-ZSM-5 to effect this
transformation could be ascribed to its small pore open-
ings, making it difficult for the bulky triacetonide to en-
ter into the pores for catalysis to occur. The reported15
crystal structure of 12 lends support to this reasoning.
The selectively protected 1,2:3,4-di-O-isopropylidene
acetal (13) of D-mannitol was known to be a valuable
chiral intermediate for the synthesis of many natural
products and pharmaceutical intermediates.16 The
reported procedure17 for the preparation of 13 from 12
gives lower yields and involves the use of concentrated
hydrochloric acid and tedious work-up. This is the first
report on the use of a solid acid for selective deprotec-
tion of a tri-O-alkylidene sugar derivative.
In conclusion, we have developed an efficient hetero-
geneous catalytic procedure for selective hydrolysis of
di- and tri-O-isopropylidene sugar acetals at room tem-
perature using the proton form of the commercially
available ZSM-5 and beta zeolites. Complete hydrolysis
of di-O-isopropylidene derivatives has also been demon-
strated under refluxing conditions. A notable observa-
tion is the conversion of D-mannitol triacetonide into
1,2:3,4-di-O-isopropylidene-D-mannitol and 3,4-O-iso-
propylidene-D-mannitol in good yields brought about
by H-beta zeolite. The method developed would prove
idene-D-mannofuranose (5) was then examined. Analysis
of reaction mixture involving H-ZSM-5 in MeOH–H2O
(1:1) after 60 h and H-beta in MeOH–H2O (9:1) after 8 h
showed on TLC disappearance of 5 and formation of a
more polar product compared to 5 in each case, which
1
was identified based on H NMR analysis as a mixture
of monoacetonides of D-mannose viz., 2,3-O-isopropyl-
idene-D-mannofuranose (6) and 2,3-O-isopropylidene-
D-mannopyranose (7). Understandably, the substrate 5
was initially transformed by selective hydrolysis to 6,
which underwent ring modification to form 7 resulting
finally in an equilibrium mixture of pyranose and fura-
nose forms. The product complexity problem was solved
by protecting the anomeric hydroxyl function in 5 as the
acetate and subjecting the same to hydrolysis. Treatment
of the monoacetate 8, 1-O-acetyl-2,3:5,6-di-O-isopropyl-
idene-D-mannofuranose, with H-beta zeolite in MeOH–
H2O (9:1) at room temperature for 8 h afforded 1-O-
acetyl-2,3-O-isopropylidene-D-mannofuranose (9) as
the single product in excellent yield (97%).
Having found H-ZSM-5 and H-beta zeolite as effi-
cient catalysts for selective deprotection of di-O-isopro-
pylidene derivatives derived from furanose systems,
their utility for achieving the same with a pyranose
system was examined. 1,2:3,4-Di-O-isopropylidene-a-D-
galactopyranose (10) was allowed to react in the pres-
ence of H-ZSM-5 or H-beta zeolite in MeOH–H2O
(1:1) at room temperature. The substrate remained un-
changed even after 24 h in both cases (entries 4 and 5).
However, when the reaction was performed using
H-beta zeolite in MeOH–H2O (1:1) under refluxing
conditions for 24 h, cleavage of both acetonide groups
occurred affording D-galactose in near quantitative yield
(Table 2, entry 6). In the case of acyclic diacetonide,
1,2:5,6-di-O-isopropylidene-D-mannitol (11), treatment
with H-ZSM-5 at room temperature in MeOH–H2O
(1:1) led to hydrolysis, although not selectively, to form
D-mannitol in excellent yield (Table 2, entry 7). H-Beta
zeolite effected the same transformation in shorter time
(Table 2, entry 8). The reaction time for the H-ZSM-5
catalyzed complete hydrolysis was reduced by perform-
ing the reaction under refluxing condition (Table 2,
entry 9).
Table 3. Zeolite catalyzed cleavage of 1,2:3,4:5,6-tri-O-isopropylidene-
D-mannitol (12)
Entry Catalyst
MeOH–H2O Time Product
ratio
(h)
(yield %)
1
2
3
H-Beta
H-ZSM-5 9:1
H-ZSM-5 1:1
9:1
6
24
24
13 (48) and 14 (36)
No reaction
No reaction
HO
HO
O
HO
HO
O
O
O
O
H-Beta Zeolite
O
O
O
O
OH
OH
O
O
O
MeOH / H2O, RT
12
14
13
Scheme 3.

P. M. Bhaskar et al. / Carbohydrate Research 343 (2008) 1801–1807
1805
to be very useful in providing efficient and convenient
access to several selectively protected sugar acetals that
serve as renewable chiral pools for the synthesis of nat-
ural products.
with MeOH. The filtrate combined with washings was
concentrated under reduced pressure and the residual
water was co-evaporated with EtOH–toluene (1:2)
under reduced pressure to afford a colorless syrup which
on further purification by column chromatography over
silica gel using chloroform–MeOH (9:1) gave a pure
product 4 (yield 0.34 g, 91%).
1. Experimental
1.1. General
1.3.1.
1,2-O-Isopropylidene-a-D-glucofuranose
(2a).
Yield 0.41 g (94%), mp 158–160 °C [lit.19 160–161 °C],
[a]D ꢀ12.4 (c 1.0, H2O) [lit.19 ꢀ11.4 (H2O)]; H NMR
1
Thin layer chromatography was performed on micro
slides coated with silica gel (200–300 mesh) of 0.1 mm
thickness. The components on TLC were visualized by
spraying with 10% H2SO4 in MeOH and heating on a
hot plate. Column chromatography was performed by
gravity method using silica gel (60–120 mesh) using a
mixture of ethyl acetate and hexane. Melting points
were determined on a Toshniwal melting point appara-
tus and are uncorrected. Specific rotations were deter-
mined with JASCO-DIP 200 digital polarimeter. IR
spectra were recorded on a Shimadzu IR-470 spectro-
meter. NMR spectra were recorded with JEOL
GSX-400 or Bruker AV400 spectrometer using TMS
as internal standard. Electrospray ionization mass spec-
tral (ESI-MS) analyses were performed with a Micro-
mass Q-Tof mass spectrometer in the positive ion mode.
(D2O) d 6.02 (d, 1H, J = 3.4 Hz, H-1), 4.70 (d, 1H,
H-2), 4.32 (d, 1H, H-3), 4.10 (dd, 1H, H-4), 3.92 (m,
1H, H-5), 3.80 (dd, 1H, J = 12.2 Hz, 2.9 Hz, H-6), 3.64
(dd, 1H, J = 12.2 Hz, 6.3 Hz, H-60), 1.52 and 1.36 (s
each, 2 ꢁ 3H, 2 ꢁ CH3); 13C NMR (D2O) d 110.9 (s),
102.9 (d, C-1), 82.6 (d, C-2), 78.0 (d, C-4), 71.8 (d,
C-3), 66.6 (d, C-5), 61.7 (t, C-6), 23.7, 23.3 (2q, 2 ꢁ CH3).
1.3.2. 3-O-Allyl-1,2-O-isopropylidene-a-D-glucofuranose
(2b). Yield 0.24 g (80%), syrup, [a]D ꢀ37.2 (c 1.0,
CHCl3) [lit.27 ꢀ30.2 (CHCl3)]; 1H NMR (CDCl3) d
5.92 (d, 1H, J = 3.6 Hz, H-1), 5.98–5.85 (m, 1H,
CH2@CH–), 5.33 and 5.24 (m, each, 2H, CH2@CH–),
4.58 (d, 1H, H-2), 4.23–4.00 (m, 5H, H-3, H-4, H-5
and –CH2–), 3.84 (dd, 1H, J = 3.2 Hz, 11.6 Hz, H-6a),
3.74 (dd, 1H, J = 5.6 Hz, 11.6 Hz, H-6b), 1.49 (s, 3H,
CH3) and 1.32 (s, 3H, CH3).
1.2. Materials
All sugars used were purchased from Sigma–Aldrich
USA or from Pfanstiehl Laboratories Inc. USA and
used as such. Montmorillonite K-10 was obtained from
1.3.3. 3-O-Benzyl-1,2-O-isopropylidene-a-D-glucofura-
nose (2c). Yield 0.19 g (60%), syrup, [a]D ꢀ42.3 (c
1
0.6, CHCl3) [lit.27 ꢀ46.2 (CHCl3)]; H NMR (CDCl3)
Fluka. Beta and ZSM-5 zeolite, obtained from Sud-Che-
¨
d 7.41–7.28 (m, 5H, Ph), 5.94 (d, 1H, J = 3.6 Hz, H-1),
4.73 and 4.56 (AB q, 2H, –CH2Ph), 4.63 (d, 1H,
J = 3.6 Hz, H-2), 4.16–4.07 (m, 2H, H-3 and H-4),
4.03 (m, 1H, H-5), 3.81 (dd,1H, J = 3.2 Hz, 11.6 Hz,
H-6a), 3.70 (dd, 1H, J = 5.6 Hz, 11.6 Hz, H-6b), 1.49
(s, 3H, CH3) and 1.32 (s, 3H, CH3).
mie India Limited New Delhi, and Y-zeolite (H-b, Si/
Al = 101; H-ZSM-5, Si/Al = 454; H-Y, Si/Al = 8.6)
were converted to H-form by using standard proce-
dure.18 All the substrates were prepared according to
the reported procedures: 1,2:5,6-di-O-isopropylidene-
D-glucofuranose (1a),19 3-O-allyl-1,2:5,6-di-O-isopro-
pylidene-D-glucofuranose (1b),20 3-O-benzyl-1,2:5,6-di-
O-isopropylidene-D-glucofuranose (1c),21 3-O-propar-
gyl-1,2:5,6-di-O-isopropylidene-D-glucofuranose (1d),22
1,2:3,5-di-O-isopropylidene-D-xylofuranose (3),23 2,3:5,
6-di-O-isopropylidene-D-mannose (5),19 1-O-acetyl-
1.3.4.
ranose (2d). Yield 0.12 g (89%), syrup, [a]D
3-O-Propargyl-1,2-O-isopropylidene-a-Dꢀ-g5lu4c.6ofu(c-
1
0.6, CHCl3) [lit.28 ꢀ37.7 (CHCl3)]; H NMR (CDCl3)
d
5.91 (d, 1H, J = 3.6 Hz, H-1), 4.61 (d, 1H,
(8)24
J = 3.6 Hz, H-2), 4.38–4.22 (m, 3H, H-3 and –CH2–),
4.17 (dd, 1H, J = 3.2 Hz, 8.4 Hz, 8.4 Hz, H-4), 3.99
(m, 1H, H-5), 3.84 (dd, 1H, J = 5.6 Hz, 11.6 Hz,
H-6a), 3.74 (dd, 1H, J = 5.6 Hz, 11.6 Hz, H-6b), 1.50
(s, 3H, CH3) and 1.32 (s, 3H, CH3).
2,3:5,6-di-O-isopropylidene-a-D-mannofuranose
1,2:3,4-di-O-isopropylidene-a-D-galactopyranose (10),25
1,2:5,6-di-O-isopropylidene-D-mannitol (11),26 and
1,2:3,4:5,6-tri-O-isopropylidene-D-mannitol (12).17
1.3. Typical procedure for the selective hydrolysis
1.3.5.
1,2-O-Isopropylidene-a-D-xylofuranose
(4).
To a solution of 3 (0.46 g, 2 mmol) in MeOH–H2O (9:1)
(20 mL), H-beta zeolite (0.5 g) was added and stirred at
room temperature. TLC analysis of the reaction mixture
showed the disappearance of the substrate after 4 h. The
catalyst was then filtered through Celite pad and washed
Yield, 0.34 g (91%); [a]D ꢀ18.9 (c 1, H2O) [lit.29 ꢀ20.6
(H2O)]; 1H NMR (D2O) d 6.05 (d, 1H, J = 3.9 Hz,
H-1), 4.70 (d, 1H, J = 3.9 Hz, H-2), 4.30 (m, 2H, H-3,
H-4), 3.88 (dd, 1H, H-5), 3.79 (dd, 1H, H-50), 1.54,
1.38 (s each, 2 ꢁ 3H, 2 ꢁ CH3); 13C NMR (D2O) d

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P. M. Bhaskar et al. / Carbohydrate Research 343 (2008) 1801–1807
111.9 (s), 103.8 (d, C-1), 84.1 (d, C-2), 80.5 (d, C-4), 73.2
(d, C-3), 58.7 (t, C-5), 24.9, 24.5 (2 ꢁ q, 2 ꢁ CH3).
mentation Facility (SAIF), IIT Madras for the spectral
data.
1.3.6. 1-O-Acetyl-2,3-O-isopropylidene-a-D-mannofura-
nose (9). Yield 0.51 g (97%); [a]D +70.0 (c 4.0, CHCl3);
IR (neat) cmꢀ1 3392, 2928, 1702, 1641, 1363, 1251, 1235,
Supplementary data
1
1060, 956, 873, 806; H NMR (CDCl3) d 6.14 (s, 1H,
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.carres.
2008.05.006.
H-1), 4.90 (dd, 1H, J = 5.9 Hz, 3.7 Hz, H-3), 4.69 (d,
1H, J = 6.0 Hz, H-2), 4.10 (dd, 1H, J = 8.3 Hz, 3.8 Hz,
H-4), 4.00 (m, 1H, H-5), 3.84 (dd, 1H, J = 11.5 Hz,
3.2 Hz, H-6), 3.70 (dd, 1H, J = 11.5 Hz, 5.4 Hz, H-60),
2.06 (s, 3H, CH3CO), 1.48, 1.33 (s each, 2 ꢁ 3 H,
2 ꢁ CH3); 13C NMR (CDCl3) d 167.8, 111.4, 98.9
(C-1), 82.9, 79.4, 77.9, 68.0, 62.2, 24.2 (CH3CO), 22.9,
19.4 (2 ꢁ CH3); HRMS (ESI) calculated for
C11H18O7Na [M+Na]+: 285.0950, found: 285.0958.
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Acknowledgments
Funding provided by the Department of Science and
Technology, New Delhi, for the purchase of the
400 MHz NMR under IRHPA Scheme and ESI-MS
under the FIST program is gratefully acknowledged.
The authors thank the Sophisticated Analytical Instru-

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