Zeolite-catalyzed Helferich-type glycosylation of long-chain alcohols. Synthesis of acetylated alkyl 1,2-trans glycopyranosides and alkyl 1,2-cis C2-hydroxy-glycopyranosides

Article abstract of DOI:10.1016/j.carres.2006.12.014

Zeolite-catalyzed glycosylation of long-chain alcohols, using the inexpensive and readily available peracetylated β-d-gluco- and galactopyranoses as glycosyl donors under solvent free conditions, has been explored for the first time. Among the various forms (H-, Na-, Fe- and Zn) of β zeolite examined as catalysts in the reaction of 1,2,3,4,6-penta-O-acetyl-β-d-galactopyranose with cetyl alcohol, Fe-β zeolite gave the maximum yield of 63% of cetyl 2,3,4,6-tetra-O-acetyl-β-d-galactopyranoside and cetyl 3,4,6-tri-O-acetyl-α-d-galactopyranoside. Fe-β Zeolite-catalyzed glycosylation was found to be general affording the title compounds in each case in a moderate yield, but with a good stereoselectivity. The yield of synthetically valuable acetylated long-chain alkyl 1,2-cis C2-hydroxy-glycopyranosides obtained in the present single-step procedure is considerably higher than that of the previously reported multi-step method employing the Stork silicon tether approach.

Full text of DOI:10.1016/j.carres.2006.12.014

Carbohydrate Research 342 (2007) 704–709
Zeolite-catalyzed Helferich-type glycosylation of long-chain
alcohols. Synthesis of acetylated alkyl 1,2-trans glycopyranosides
and alkyl 1,2-cis C2-hydroxy-glycopyranosides
Udayanath Aich and Duraikkannu Loganathan*
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
Received 14 August 2006; received in revised form 11 December 2006; accepted 17 December 2006
Available online 22 December 2006
Abstract—Zeolite-catalyzed glycosylation of long-chain alcohols, using the inexpensive and readily available peracetylated b-D-
gluco- and galactopyranoses as glycosyl donors under solvent free conditions, has been explored for the first time. Among the var-
ious forms (H-, Na-, Fe- and Zn) of b zeolite examined as catalysts in the reaction of 1,2,3,4,6-penta-O-acetyl-b-D-galactopyranose
with cetyl alcohol, Fe-b zeolite gave the maximum yield of 63% of cetyl 2,3,4,6-tetra-O-acetyl-b-D-galactopyranoside and cetyl 3,4,6-
tri-O-acetyl-a-D-galactopyranoside. Fe-b Zeolite-catalyzed glycosylation was found to be general affording the title compounds in
each case in a moderate yield, but with a good stereoselectivity. The yield of synthetically valuable acetylated long-chain alkyl 1,2-cis
C2-hydroxy-glycopyranosides obtained in the present single-step procedure is considerably higher than that of the previously
reported multi-step method employing the Stork silicon tether approach.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Carbohydrates; Helferich glycosylation; Fatty alcohols; Alkyl C2-hydroxy-glycoside; b Zeolite; Non-ionic surfactant
1. Introduction
observed for the first time the thermotropic liquid crys-
talline property of hexadecyl b-D-glucopyranoside.
Many chemical8 methods have subsequently been devel-
oped for the synthesis of alkyl glycosides. Among the
different glycosyl donors used for the chemical synthesis
of alkyl glycosides, the sugar peracetates are very inex-
pensive and readily available. The different Lewis acids
employed for the synthesis of alkyl glycosides involving
sugar peracetates as donors include SnCl4, ZnCl2–
POCl3, BF3–Et2O and FeCl3.9 In addition, several pro-
cedures for the synthesis of alkyl glycosides have been
patented.10 Enzymatic11 synthesis of alkyl glycosides
using glycosidases as catalysts has also gained interest
due to their high specificity. However, owing to the lim-
ited availability and high cost of the suitable enzymes,
the enzymatic approach has not been upgraded to indus-
trial levels.1a
Alkyl glycosides have attracted tremendous interest in
recent years in view of their diverse applications as food
emulsifiers, cleaning agents, personal care products and
textile lubricants.1 Alkyl glycosides are also very useful
as antimicrobial agents,2 non-ionic detergents in the iso-
lation of membrane proteins3 and also as drug carriers.4
Synthetic long-chain alkyl maltosides, in particular, are
also known to enhance the absorption of nasal insulin.5
Alkyl glycosides are termed as green surfactants as they
are prepared from naturally occurring renewable
sources (sugars and fatty alcohols) and are easily bio-
degradable. These molecules are also highly stable under
alkaline conditions as compared to the corresponding
sugar fatty acid esters.6
The first synthesis of a long-chain alkyl glucoside was
achieved in 1911 by Fischer and Helferich,7 who also
Thus, there is still a need to develop newer, environ-
mentally friendly as well as economical routes to long-
chain alkyl glycosides based on green chemistry. Hetero-
geneous catalysts such as zeolites have been extensively
*
Corresponding author. Tel.: +91 44 22574206; fax: +91 44
22570509; e-mail: loganath@iitm.ac.in
0008-6215/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2006.12.014

U. Aich, D. Loganathan / Carbohydrate Research 342 (2007) 704–709
705
used for liquid-phase organic transformations.12 As part
of our program on the development of solid acid cata-
lyzed carbohydrate transformations,13 we have earlier
demonstrated H-b zeolite as an efficient catalyst for
the peracetylation of sugars.14 The synthesis of various
aryl glycopyranosides by H-b zeolite-catalyzed Helferich
glycosylation was also reported recently from our labo-
ratory.15 We disclose herein the synthesis of several
long-chain alkyl glycopyranosides under solvent free
conditions using four different forms of b zeolite as cat-
alysts and 1,2,3,4,6-penta-O-acetyl-b-D-glycopyranoses
as the donors.
Table 1. b Zeolite-catalyzed reaction of penta-O-acetyl-b-D-galacto-
pyranose with cetyl alcohol using Na-, H-, Fe- and Zn-b zeolite as
catalyst
Catalyst
Yield of 3a (%) Yield of 5a (%) Total yield (%)
H-b Zeolite
42
19
23
26
17
61
58
63
50
Na-b Zeolite 35
Fe-b Zeolite 37
Zn-b Zeolite 33
characterized based on their physical and spectral data
1
(Table 1). H NMR spectral data of the less polar frac-
tion (Rf = 0.6) (3a) matched well with those reported for
cetyl 2,3,4,6-tetra-O-acetyl-b-D-galactopyranoside.9b
1
The H NMR spectrum of the more polar fraction
2. Results and discussion
(Rf = 0.2) (5a) exhibited
a doublet at 4.98 ppm
(J = 3.8 Hz) assignable to H-1 of an a-D-galactopyrano-
side. The singlets resonating at 2.15 and 2.07 ppm inte-
grating for a total of nine protons revealed the
presence of three acetyl groups. The anomeric proton
The application of zeolites as heterogeneous catalysts
for organic synthesis is an area of intense research.
Among the various zeolites (H-EMT, H-Y, H-ZSM-5,
H-ZSM-12, H-ZSM-22 and H-b zeolite) examined ear-
lier in our laboratory as catalysts for peracetylation of
sugars,14 H-b zeolite proved to be a highly efficient cat-
alyst probably due to its greater acid strength and larger
pore openings and channel intersections. Hence, the
same material was chosen for the present study. H-b
Zeolite-catalyzed synthesis of long-chain alkyl glycopyr-
anosides was initially examined using 1,2,3,4,6-penta-O-
acetyl-b-D-galactopyranose (1) as the donor and cetyl
alcohol (5 equiv) as the acceptor at 140 ꢁC under solvent
free conditions (Scheme 1). After 12 h, when the conver-
sion reached a maximum as shown by TLC analysis
(EtOAc–hexane, 1:2.5) based on the extent of disappear-
ance of peracetylated sugar donor, the reaction mixture
was cooled to room temperature and worked up. Flash
column chromatography of the crude product over silica
gel (230–400 mesh) afforded predominantly cetyl 2,3,4,6-
tetra-O-acetyl-b-D-galactopyranoside (3a, Rf = 0.6; 42%)
as well as cetyl 3,4,6-tri-O-acetyl-a-D-galactopyranoside
(5a, Rf = 0.2; 19%) as the products both of which were
1
signal in the two-dimensional H NMR gradient COSY
spectrum was observed to correlate with a doublet of
doublets appearing at 3.95 ppm (J = 3.8 and 10.4 Hz).
Hence, the latter signal was assigned to H-2. Compari-
son of the reported chemical shift (4.86 ppm) of H-2
of cetyl 2,3,4,6-tetra-O-acetyl-a-D-galactopyranoside9b
with the above data pointed out the upfield shift of H-
2 of 5a by 0.91 ppm due to the absence of an acetyl
group at C-2. The 13C NMR spectrum of compound
5a displayed three acetoxy carbonyl carbon signals at
170.8, 170.4 and 170.2 ppm, while the anomeric carbon
appeared at 98.6 ppm. The high resolution ESI-MS
showed the molecular ion [M+Na]+ peak at m/z
533.3356 consistent with the compound being a tri-O-
acetylated cetyl galactoside. Thus the more polar frac-
tion was characterized as cetyl 3,4,6-tri-O-acetyl-a-D-
galactopyranoside (5a).
To examine the effect of varying Bronsted and Lewis
acidity on the reaction yield and product selectivity,
the above reaction was performed using Na, Fe and
Zn forms of b zeolite under the same reaction condi-
tions. These three reactions also afforded 3a and 5a as
the predominant products (Table 1). However, in case
of Fe-b zeolite, the combined yield of the two products
was found to be the highest. Therefore, all the subse-
quent reactions were carried out by taking Fe-b zeolite
as the catalyst. The reaction of 1 with three other
long-chain alcohols also afforded the fully acetylated
alkyl b-D-galactopyranosides and alkyl 3,4,6-tri-O-ace-
tyl-a-D-galactopyranosides as the major products. The
reaction 1,2,3,4,6-penta-O-acetyl-b-D-glucopyranose (2)
with the four different long-chain alcohols under the
same reaction conditions also led to the same product
selectivity (Table 2), thus demonstrating the gener-
ality of Fe-b zeolite-catalyzed glycosylation of fatty
alcohols.
R1
OAc
O
ROH
+
R2
AcO
a: R = cetyl; b: R = dodecyl
c: R = 2-ethylhexyl; d: R = octyl
OAc
OAc
Gal (1): R1 = OAc, R2 = H
Glc (2): R1 = H, R2 = OAc
β-Zeolite
140 oC, 12 h
R1
OAc
R1
OAc
O
O
+
ROAc
+
R2
AcO
R2
AcO
OR
OAc
OH
OR
5a-d, 6a-d
3a-d, 4a-d
Scheme 1. b Zeolite-catalyzed synthesis of acetylated alkyl 1,2-trans
glycopyranosides and alkyl 1,2-cis C2-hydroxy-glycopyranosides.

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U. Aich, D. Loganathan / Carbohydrate Research 342 (2007) 704–709
Table 2. Fe-b Zeolite-catalyzed synthesis of alkyl glycoside using sugar peracetates as the donors and long-chain fatty alcohols as the acceptors
Sr. no.
Acceptor
Donor
Products
Yield (%)
Products
Yield (%)
Total yield (%)
1
2
3
4
5
6
7
8
Cetyl alcohol
Dodecyl alcohol
2-Ethylhexanol
Octanol
Cetyl alcohol
Dodecyl alcohol
2-Ethylhexanol
Octanol
1
1
1
1
2
2
2
2
3a
3b
3c
3d
4a
4b
4c
4d
37
38
40
43
33
36
37
41
5a
5b
5c
5d
6a
6b
6c
6d
26
28
23
27
24
25
19
24
63
66
63
70
57
61
56
65
All the known peracetylated alkyl b-D-glycopyrano-
sides (3b–d and 4a–d) and octyl 3,4,6-tri-O-acetyl-a-D-
glucopyranoside (6d) were characterized based on com-
parison of their physical and spectral data with those
reported in literature.9,16 All the seven and hitherto
unknown alkyl 3,4,6-tri-O-acetyl-a-D-glycopyranosides,
5a–d and 6a–c, have been fully characterized. A careful
1H NMR analysis of two minor fractions, obtained from
column chromatography of product mixture of each of
the reactions revealed the formation of the fully acetyl-
ated alkyl a-D-glycopyranoside and alkyl 3,4,6-tri-acet-
yl-b-D-glycopyranoside, each in less than 5% yield.
The total yield ranging from 57–70% (Table 2) of the
major products obtained in the present procedure is
quite good. Although the yield (33–43%) of the fully
acetylated alkyl b-D-glycopyranosides is moderate, the
efficiency of the present b zeolite-catalyzed method is
comparable to the enzymatic synthesis of alkyl glyco-
pyranosides both in terms of yield as well as stereoselec-
tivity.11 Incidentally, the yield and stereoselectivity of
the acetylated alkyl 1,2-trans glycopyranosides and alkyl
1,2-cis C2-hydroxy-glycopyranosides observed here
compare well with those of the corresponding aryl
glycopyranosides reported earlier under similar H-b
zeolite-catalyzed conditions.15
cis C2-hydroxy-glycopyranosides. This five-step synthe-
sis starting from b-D-glucose pentaacetate (2) afforded
octyl 3,4,6-tri-O-acetyl-a-D-glucopyranoside (6d) in an
overall yield of only ꢀ11%.
In conclusion, zeolite-catalyzed glycosylation of fatty
alcohols using peracetylated sugars as donors was
demonstrated for the first time. Fe-b zeolite-catalyzed
glycosylation was found to be general for the prepara-
tion of various long-chain alkyl glycopyranosides in a
moderate yield. The single-step synthesis reported here
represents the most efficient methodology developed so
far for acetylated alkyl 1,2-cis C2-hydroxy-glycopyr-
anosides. The present solid acid catalyzed procedure
would prove to be very useful for the preparation of
these selectively functionalized compounds, which are
valuable intermediates for the synthesis of (a) many
naturally occurring oligosaccharides, also, naturally
occurring glycoconjugates containing 1,2-linkages, and
also (b) several alkyl 2-O-sulfo/2-halo-/2-azido/2-deoxy
glycosides for various applications in glycobiology
research.
3. Experimental
Acetylated alkyl C2-hydroxy-glycosides are poten-
tially very useful intermediates for the synthesis of many
biologically and industrially important targets such as
dimeric anti-Shiga like toxin,17a Clarhamnoside (a gly-
cospingolipid containing Gala(1,2)Gal sequence occur-
ring in the marine sponge, Agelas clathrodes),17b
Gemini surfactants17c and kojidextrins.17d In view of
the significance of C2-hydroxy-glycosides, several meth-
ods have been developed for their synthesis.18 However,
each of these methods involve multiple steps. Although
the formation of long-chain alkyl C2-hydroxy-glycopyr-
anosides in trace amount was detected earlier based on
TLC analysis in SnCl4 catalyzed Helferich-type glycosyl-
ation,9b this is the first report on zeolite-catalyzed single-
step synthesis of alkyl C2-hydroxy-glycosides from
sugar peracetates and the yield obtained is also the high-
est. The stereoselective formation of 1,2-cis linkages, in
general, is considerably more challenging. An extension
of the Stork silicon tether approach by Bols,16 represents
the only report on the preparation of alkyl (octyl) 1,2-
3.1. General information
Thin-layer chromatograms were performed on 25 mm
E. Merck silica gel plates (60F-254). Detection was done
by spraying the plates with 10% sulfuric acid in ethanol
and heating on a hot plate. Column chromatography
was performed using silica gel (230–400 mesh) under
flash conditions using a mixture of EtOAc and hexane.
Optical rotations were measured at 30 ꢁC on a JAS-
CO-DIP 200 digital polarimeter using a cell of 10 mm
length. NMR spectra were recorded on a Bruker
AV400 spectrometer. ESI-MS spectra were measured
on a Micromass Q-Tof mass spectrometer. All free sug-
ars used were purchased from Sigma–Aldrich USA or
from Pfanstiehl Laboratories Inc. USA. Sugar perace-
tates were prepared by using NaOAc and Ac2O19 at
100 ꢁC. b Zeolite (Na form) was obtained from Sud-
¨
Chemie India Ltd, New Delhi and activated by heating
to 540 ꢁC prior to converting into various other forms as
described below.

U. Aich, D. Loganathan / Carbohydrate Research 342 (2007) 704–709
707
3.2. Preparation of H-b zeolite
1H, H-5), 4.15–4.09 (m, 2H, H-6a, H-6b), 3.95 (dd,
1H, J = 3.8, 10.4 Hz, H-2), 3.75 (m, 1H, H10a), 3.51
(m, 1H, H10b), 2.15, 2.07, 2.06 (3s, 9H, 3 · COCH3),
1.65 (m, 2H, –CH2), 1.35–1.10 (m, 26H, 13 · –CH2–),
0.89 ppm (m, 3H, –CH3); 13C NMR (100 MHz, CDCl3):
d 170.8, 170.4, 170.2 (3 · –COCH3), 98.6 (C-1), 70.9,
68.9, 68.3, 67.1, 66.7, 61.9 (C-6), 31.9, 29.7, 29.7, 29.6,
29.6, 29.4, 29.4, 29.4, 26.2, 22.7, 20.8, 20.7, 20.6 (3 ·
–COCH3), 14.1 (–CH3); ESI-MS: calcd for C28H50O9Na
[M+Na]+: 553.3353. Found: 553.3356.
Na-b Zeolite (10 g) was suspended in ammonium chlo-
ride solution (0.2 M, 150 mL) and stirred for 6 h at
room temperature. The solid was filtered and washed
several times with deionized water. The exchange oper-
ation was repeated four times. The ammonium-
exchanged zeolite was then calcined at 450 ꢁC for 12 h
under the flow of air to furnish H-b zeolite.
3.3. Preparation of Zn-b zeolite
3.7. Dodecyl 3,4,6-tri-O-acetyl-a-D-galactopyranoside
(5b)
Na-b Zeolite (5 g) was stirred in an aqueous solution of
zinc acetate (0.1 M, 150 mL) at 100 ꢁC for 24 h. The so-
lid was filtered and washed several times with deionized
water. The exchanged zeolite was then calcined at
200 ꢁC for 12 h under the flow of air to furnish Zn-b
zeolite.
1
Syrup; [a]D +52.5 (c 1.0, CHCl3); H NMR (400 MHz,
CDCl3): d 5.41 (m, 1H, H-4), 5.13 (dd, 1H, J = 3.2,
10.4 Hz, H-3), 4.98 (d, 1H, J = 4.0 Hz, H-1), 4.18 (m,
1H, H-5), 4.12–4.07 (m, 2H, H-6a, H-6b), 3.95 (dd,
1H, J = 4.0, 10.4 Hz, H-2), 3.75 (m, 1H, H10a), 3.52
(m, 1H, H10b), 2.15 (s, 3H, COCH3), 2.07 (s, 6H,
2 · COCH3), 1.63 (m, 2H, –CH2), 1.43–1.16 (m, 18H,
9 · –CH2–), 0.88 ppm (t, 3H, –CH3); 13C NMR
(100 MHz, CDCl3): d 170.8, 170.4, 170.2 (3 · –COCH3),
98.5 (C-1), 70.9, 68.9, 68.3, 67.1, 66.7, 61.9 (C-6), 31.9,
29.7, 29.7, 29.6, 29.5, 29.4, 29.4, 29.3, 26.2, 22.7, 20.9,
20.7, 20.7 (3 · –COCH3), 14.1 (–CH3); ESI-MS:
calcd for C24H42O9Na [M+Na]+: 497.2727. Found:
497.2735.
3.4. Preparation of Fe-b zeolite
Na-b Zeolite (5 g) was stirred in an aqueous solution of
ferric nitrate (0.1 M, 150 mL) at 100 ꢁC for 24 h. The-
solid was filtered and processed as mentioned above to
furnish Fe-b zeolite.
3.5. General procedure for synthesis of alkyl 2,3,4,6-tetra-
O-acetyl-b-D-glycopyranosides (3a–d, 4a–d) and alkyl
3,4,6-tri-O-acetyl-a-D-glycopyranosides (5a–d, 6a–d)
3.8. 20-Ethylhexyl 3,4,6-tri-O-acetyl-a-D-galactopyrano-
side (5c)
A
mixture of penta-O-acetyl-b-D-glycopyranose (1
mmol) and long-chain fatty alcohol (5 mmol) was
heated under stirring to form a homogeneous melt. To
this melt, freshly activated b zeolite (0.2 g) was added
and the mixture was heated at 140 ꢁC. The progress of
the reaction was monitored by TLC (EtOAc–hexane,
2:3). After 14 h, the reaction mixture was cooled to
room temperature. To this mixture, chloroform
(40 mL) was added and then heated at reflux for 1 h to
extract the product from zeolite pores. The catalyst
was then filtered and the extraction with chloroform
was repeated twice. The combined filtrate was concen-
trated under reduced pressure to give a residue that
was subjected to flash column chromatography over
silica gel. Initial elution with a mixture of EtOAc and
hexane (9:91) gave the fully acetylated alkyl
glycopyranosides (3a–d and 4a–d), while further elution
with (11:89) mixture of the same solvents afforded the
tri-O-acetylated C2-hydroxy-glycopyranosides (5a–d,
6a–d).
1
Syrup; H NMR (400 MHz, CDCl3): d 5.42 (m, 1H, H-
4), 5.10 (dd, 1H, J = 3.3, 10.3 Hz, H-3), 4.97 (d, 1H,
J = 3.6 Hz, H-1), 4.17 (m, 1H, H-5), 4.15–4.08 (m, 2H,
H-6a, H-6b), 3.97 (dd, 1H, J = 3.6, 10.3 Hz, H-2), 3.71
(m, 1H, H10a), 3.39 (m, 1H, H10b), 2.15, 2.08, 2.07
(3s, 9H, 3 · COCH3), 1.64–1.15 (m, 9H), 0.99–
0.78 ppm (m, 6H, 2 · CH3); 13C NMR (100 MHz,
CDCl3): d 170.8, 170.4, 170.2, 98.7 (C-1), 98.6 (C-1),
71.3, 70.9, 68.3, 67.2, 66.7, 62.0 (C-6), 39.5, 39.4, 31.9,
30.5, 30.4, 29.7, 29.3, 29.0, 23.9, 23.8, 23.0, 22.7, 20.8,
20.6, 20.6, 14.1, 14.0 (–CH3), 11.1, 10.9 (–CH3); ESI-
MS: calcd for C20H34O9Na [M+Na]+: 441.2101. Found:
441.2109.
3.9. Octyl 3,4,6-tri-O-acetyl-a-D-galactopyranoside (5d)
1
Syrup; [a]D +18.8 (c 1.0, CHCl3); H NMR (400 MHz,
CDCl3): d 5.40 (m, 1H, H-4), 5.11 (dd, 1H, J = 3.3,
10.4 Hz, H-3), 4.97 (d, 1H, J = 4.0 Hz, H-1), 4.17 (m,
1H, H-5), 4.14–4.05 (m, 2H, H-6a, H-6b), 3.94 (m, 1H,
H-2), 3.74 (m, 1H, H10a), 3.50 (m, 1H, H10b), 2.15 (s,
3H, COCH3), 2.05 (s, 6H, 2 · COCH3), 1.62 (m, 2H,
–CH2), 1.40–1.17 (m, 10H, 5 · –CH2–), 0.87 ppm (m,
3H, –CH3); 13C NMR (100 MHz, CDCl3): d 170.8,
3.6. Cetyl 3,4,6-tri-O-acetyl-a-D-galactopyranoside (5a)
1
Syrup; [a]D +48.4 (c 1.0, CHCl3); H NMR (400 MHz,
CDCl3): d 5.42 (m, 1H, H-4), 5.13 (dd, 1H, J = 3.2,
10.4 Hz, H-3), 4.98 (d, 1H, J = 3.8 Hz, H-1), 4.19 (m,

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U. Aich, D. Loganathan / Carbohydrate Research 342 (2007) 704–709
170.4, 170.2 (3 · –COCH3), 98.5 (C-1), 70.8, 68.9, 68.3,
67.0, 66.7, 61.9 (C-6), 31.9, 29.7, 29.4, 29.2, 26.1, 22.6,
20.8, 20.7, 20.6 (3 · COCH3), 14.0 (–CH3); ESI-MS:
calcd for C20H34O9Na [M+Na]+: 441.2101. Found:
441.2093.
3.13. Octyl 3,4,6-tri-O-acetyl-a-D-glucopyranoside (6d)
Syrup; [a]D +113 (c 0.2 CH2Cl2); lit.16 [a]D +116 (c 0.2,
1
CH2Cl2); H NMR (400 MHz, CDCl3): d 5.24 (t, 1H,
J = 9.7 Hz, H-3), 5.02 (t, 1H, J = 9.7 Hz, H-4), 4.93
(d, 1H, J = 3.9 Hz, H-1), 4.28 (dd, 1H, J = 4.6,
12.2 Hz, H-6a), 4.11 (dd, 1H, J = 2.1, 12.2 Hz, H-6b),
3.97 (m, 1H, H-5), 3.76 (m, 1H, H10a), 3.70 (dd, 1H,
J = 3.9, 9.7 Hz, H-2), 3.52 (m, 1H, H10b), 2.11, 2.10,
2.05 (3s, 9H, 3 · COCH3), 1.55 (m, 2H, –CH2), 1.42–
1.15 (m, 10H, 5 · –CH2–), 0.89 ppm (m, 3H, –CH3).
3.10. Cetyl 3,4,6-tri-O-acetyl-a-D-glucopyranoside (6a)
1
Syrup; [a]D +18.8 (c 1.0, CHCl3); H NMR (400 MHz,
CDCl3): d 5.25 (t, 1H, 9.6 Hz, H-3), 5.03 (t, 1H,
J = 9.6 Hz, H-4), 4.93 (d, 1H, J = 3.8 Hz, H-1), 4.29
(dd, 1H, J = 4.6, 12.3 Hz, H-6a), 4.09 (dd, 1H,
J = 2.1, 12.3 Hz, H-6b), 3.98 (m, 1H, H-5), 3.76 (m,
1H, H10a), 3.70 (dd, 1H, J = 3.8, 9.6 Hz, H-2), 3.52
(m, 1H, H10b), 2.11 (s, 6H, 2 · COCH3), 2.06 (s, 3H,
COCH3); 1.66 (m, 2H, –CH2), 1.40–1.15 (m, 26H,
13 · –CH2–), 0.88 ppm (m, 3H, –CH3); 13C NMR
(100 MHz, CDCl3): d 170.9, 170.7, 169.6, 98.2 (C-1),
73.6, 70.9, 69.0, 68.0, 67.6, 62.0 (C-6), 31.9, 29.7, 29.7,
29.6, 29.5, 29.4, 29.3, 26.1, 22.7, 20.9, 20.7, 20.6 (3 ·
–COCH3), 14.1 (–CH3); ESI-MS: calcd for C28H50O9Na
[M+Na]+: 553.3353. Found: 553.3356.
Acknowledgements
Funding provided by the Department of Science and
Technology, New Delhi, for the purchase of the
400 MHz NMR under IRPHA Scheme and ESI-MS un-
der the FIST program is gratefully acknowledged. We
gratefully acknowledge the facilities provided by the
Sophisticated Analytical Instrumentation Facility, IIT
Madras. One of us (U.A.) is thankful to the Council
of Scientific and Industrial Research (CSIR), New
Delhi, for award of a Senior Research Fellowship.
3.11. Dodecyl 3,4,6-tri-O-acetyl-a-D-glucopyranoside (6b)
1
Syrup; [a]D +25.2 (c 1.0, CHCl3); H NMR (400 MHz,
CDCl3): d 5.24 (t, 1H, J = 9.6 Hz, H-3), 5.02 (t, 1H,
J = 9.6 Hz, H-4), 4.93 (d, 1H, J = 3.8 Hz, H-1), 4.28
(dd, 1H, J = 4.7, 12.3 Hz, H-6a), 4.10 (dd, 1H,
J = 2.1, 12.3 Hz, H-6b), 3.98 (m, 1H, H-5), 3.75 (m,
1H, H10a), 3.70 (dd, 1H, J = 3.8, 9.6 Hz, H-2), 3.51
(m, 1H, H10b), 2.11, 2.10, 2.05 (3s, 9H, 3 · COCH3);
1.59 (m, 2H, –CH2), 1.39–1.14 (m, 18H, 9 · –CH2–),
0.89 ppm (m, 3H, –CH3); 13C NMR (100 MHz, CDCl3):
d 170.7, 170.3, 170.2 (3 · –COCH3), 98.5 (C-1), 70.9,
68.9, 68.3, 67.1, 66.7, 61.9 (C-6), 31.9, 29.7, 29.6, 29.5,
29.4, 29.3, 26.2, 22.7, 20.8, 20.7, 20.6 (3 · –COCH3),
14.1 (–CH3); ESI-MS: calcd for C24H42O9Na: 497.2727
[M+Na]+. Found: 497.2726.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.carres.
2006.12.014.
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