Amberlyst 15-catalyzed efficient synthesis of 2,3-unsaturated glycosides via Ferrier rearrangement for glycal

Article abstract of DOI:10.1080/00397910601131353

Amberlyst 15 serves as an inexpensive, effective, and environmentally friendly catalyst in converting 3,4,6-tri-O-acetyl-D-glucal (1) into 2,3-unsaturated O- and S-glycosides via Ferrier rearrangement in moderate to excellent yields with high α selectivity. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910601131353

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Amberlyst 15–Catalyzed Efficient Synthesis
of 2,3‐Unsaturated Glycosides via Ferrier
Rearrangement for Glycal
Qiang Tian a , Xing‐Mei Zhu a & Jin‐Song Yang a
a Department of Chemistry of Medicinal Natural Products and Key
Laboratory of Drug Targeting , School of Pharmacy, Sichuan University ,
Chengdu, China
Published online: 10 Mar 2007.
To cite this article: Qiang Tian , Xing‐Mei Zhu & Jin‐Song Yang (2007) Amberlyst 15–Catalyzed Efficient
Synthesis of 2,3‐Unsaturated Glycosides via Ferrier Rearrangement for Glycal, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 37:5, 691-701, DOI:
10.1080/00397910601131353
To link to this article: http://dx.doi.org/10.1080/00397910601131353
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Synthetic Communicationsw, 37: 691–701, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910601131353
Amberlyst 15–Catalyzed Efficient Synthesis
of 2,3-Unsaturated Glycosides via Ferrier
Rearrangement for Glycal
Qiang Tian, Xing-Mei Zhu, and Jin-Song Yang
Department of Chemistry of Medicinal Natural Products and Key
Laboratory of Drug Targeting, School of Pharmacy, Sichuan University,
Chengdu, China
Abstract: Amberlyst 15 serves as an inexpensive, effective, and environmentally
friendly catalyst in converting 3,4,6-tri-O-acetyl-D-glucal (1) into 2,3-unsaturated O-
and S-glycosides via Ferrier rearrangement in moderate to excellent yields with high
a selectivity.
Keywords: Amberlyst 15, Ferrier rearrangement, glycal, glycosidation, 2,3-unsatu-
rated glycoside
Preparation of 2,3-unsaturated glycosides has always received attention
because of their synthetic versatility as potential precursors in the synthesis
of complex carbohydrates, glycoconjugates, and many significant
molecular, such as antibiotics and nucleosides, through subsequent elabor-
ation of 2,3-alkene.[1,2] A conventional approach to 2,3-unsaturated glycosides
involves treatment of glycals with O- or S-nucleophilic species in the presence
of Lewis acids, which is popularly called the Ferrier rearrangement.[3]
Numerous Lewis acids have been developed to drive the reaction, including
[4]
BF3 Et2O, InCl3,[5] SnCl4,[6] Yb(OTf)3,[7] Sc(OTf)3,[8] FeCl3,[9] BiCl3,[10]
.
ZnCl2,[11] LiBF4,[12] clay montmorillionite K-10,[13] Dy(OTf)3,[14] ZrCl4,[15]
Address correspondence to Jin-Song Yang, Department of Chemistry of Medicinal
Natural Products and Key Laboratory of Drug Targeting, School of Pharmacy, Sichuan
University, Chengdu 610041, China. E-mail: yjspharm@yahoo.com.cn
691

692
Q. Tian, X.-M. Zhu, and J.-S. Yang
and Pd(OAc)2.[16] In addition, electron-transfer catalyst K5CoW12O40
3H2O,[17] protic acid HClO4 supported on silica gel,[18] and oxidants such
as 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ)[19] and cerium(V)
ammonium nitrate (CAN)[20] have also been used for the Ferrier reaction.
Although some of these methods were successful for the production of 2,3-
unsaturated glycosides, a number of them are practically inconvenient to
use (most of Lewis acids are air sensitive); employ harsh reaction conditions
.
.
(strong acidity or oxidation conditions, such as BF3 Et2O and DDQ), and
toxic or costly catalysts; and sometimes have low anomeric selectivity.
As part of our research concerning the development of a new promoter in
glycosidation, we have investigated the synthesis of 2,3-unsaturated glyco-
sides under a mild and environmentally benign process. Described herein
is a heterogeneous solid acidic Amberlyst 15–catalyzed synthesis of
2,3-unsaturated O- and S-glycosides via Ferrier rearrangement starting from
3,4,6-tri-O-acetyl-D-glucal (1) in moderate to excellent yields with high selec-
tivity possessing mild reaction conditions, an inexpensive and green catalyst
(Scheme 1).
Initially, different media such as THF, CH2Cl2, MeCN, and PhMe were
screened for the glycosidation of 1 with 1 equiv of isopropanol (1a)
mediated by 20 wt% Amberlyst 15. The results are summarized as entries
1–4 in Table 1 and show that PhMe is the best choice of solvent with
respect to the yield. Our attention was next focused on the effect of the
quantity of Amberlyst 15 on this glycosidation in PhMe. It was demonstrated
that the yield of product 1b was greatly improved with a gradual enhancement
of stereoselectivity through increasing the weight ratio of Amberlyst 15 to 1
(entries 4–6 in Table 1). The best result was achieved with the use of 80
wt% Amberlyst 15 affording 1b in 95% yield and exclusively a-form.
Based on the optimal conditions, the glycosidations of 1 with other O-
nucleophiles were systematically studied to extend the synthetic application
of this reaction. Primary, secondary, allylic, propargyl alcohols, and cholesterol
reacted with 1 with equal ease to produce the corresponding 2,3-unsaturated
O-glycosides in excellent yields with high a-stereoselectivity (entries 1–7,
Table 2). Glycosyl acceptors, such as methyl 2-O-benzoyl-4,6-O-benzyli-
dene-a-D-glucopyranoside (8a, entry 8, Table 2), methyl 2,3,6-tri-O-benzyl-
a-D-glucopyranoside (9a, entry 9, Table 2), 1,2:3,4-di-O-isopropylidene-a-D-
galactopyranose (10a, entry 10, Table 2), and allyl 2,3,4-tri-O-benzyl-a-D-
glucopyranoside (11a, entry 11, Table 2) were also employed to react with 1
Scheme 1.

Synthesis of 2,3-Unsaturated Glycosides
693
Table 1. Screening of solvent and quantity of Amberlyst 15 for the
glycosidation of 1 with isopropanol (1a)a
Wt% of Amberlyst
15 for 1
Isolated yield
of 1b (%)
Entry
Solvent
a/bb
1
2
3
4
5
6
THF
20
20
20
20
50
80
5
20
40
50
75
95
—
—
CH2Cl2
MeCN
PhMe
PhMe
PhMe
a
8/1
10/1
a
aReactions were performed at 25 8C with 1 equiv of 1a for 2h.
bAnomeric distributions were determined by 1H NMR (400 MHz)
spectroscopic analysis.
to furnish exclusively the corresponding 1 ! 3, 1 ! 4, and 1 ! 6-linked
a-disaccharides 8b, 9b, 10b, and 11b in 60%, 52%, 93%, and 89% yields,
respectively, without cleavage of the acid-sensitive protecting groups, benzyli-
dene and isopropylidene. The relative low yields of 8b and 9b were attributed
reasonably to the steric hindrance of the secondary hydroxyls of 8a and 9a.
Likewise, phenol (12a) was readily converted into the corresponding
glycoside 12b in 70% yield (entry 12, Table 2).
Amino acid alcohol 13a[21] derived from threonine was also exposed to
this procedure (entry 13, Table 2). The exclusive product was a-isomer
13b, which can act as a useful glycosylated amino acid building block for
the synthesis of glycopeptide. This procedure therefore provides a new
access to the O-linked glycopeptide framework.
The versatility of the protocol was further evaluated through thioglycosi-
dations of 1 with p-methylthiophenol 14a and ethanethiol 15a. Solvent was
critical for the reactivity and stereoselectivity in these cases. For example, if
run in PhMe, the glycosidation of 1 with 14a gave 60% of 14b as an a/b-
anomeric mixture in a ratio of 1.2:1 (entry 14, Table 2). Fortunately, the
stereochemical outcomes and the yields were considerably improved by the
addition of 1,4-dioxane to the reaction system. As illustrated by entries 15
and 16 in Table 2, highly a-selective formations of the corresponding
thioglycosides 14b and 15b were achieved in 89% and 90% yields, respect-
ively, when the glycosidations were carried out in the mixed solvent of
PhMe/1,4-dioxane (1/3, v/v).
In the cases where inseparable a/b mixtures of 2,3-unsaturated glyco-
sides were obtained, the ratios of two isomers could be determined by inte-
gration of the signals in NMR spectra of the products. The a-configuration
of the major product was established by the chemical shifts of the anomeric
1
protons and coupling constants for J1, 2 and J4, 5 in the H NMR spectra.[22]
nuclear Overhauser effect (NOE) experiments were carried out for further

Table 2. 80 Wt% Amberlyst 15–catalyzed glycosidation of 3,4,6-tri-O-acetyl-D-glucal (1) with alcohols and thiolsa
Entry
1
Acceptor
Glycoside
Time (h)
2
Isolated yield (%)
95
a/bb
Ref.
[9]
Isopropanol 1a
a
2
3
4
5
6
7
n-Butanol 2a
Benzyl alcohol 3a
Cyclohexanol 4a
Allyl alcohol 5a
Propargyl alcohol 6a
Cholesterol 7a
1
96
93
95
95
96
95
8/1
a
[9]
[9]
1.5
1.8
1.5
1.2
2
10/1
20/1
10/1
a
[17]
[8]
[8]
[18]

8
9
2.6
2.8
60
52
a
a
—
[18]
10
3
93
a
[18]
11
12
3
89
70
a
a
—
Phenol 12a
3.5
[7]
(continued)

Table 2. Continued
Entry
13
Acceptor
Glycoside
Time (h)
1
Isolated yield (%)
65
a/bb
Ref.
—
a
14
15c
16c
p-Methylthiophenol 14a
1.5
1.5
1.5
60
89
90
1.2/1
20/1
8/1
[12]
[12]
[15]
14a
14b
Ethanethiol 15a
aReactions were performed at 25 8C with 1 equiv of the acceptors in PhMe, unless otherwise indicated.
1
bAnomeric distributions were determined by H NMR (400 MHz) spectroscopic analysis.
cIn PhMe/1,4-dioxane (1/3, v/v).

Synthesis of 2,3-Unsaturated Glycosides
697
confirmation, in which considerable NOE enhancements were observed
between H-1 and H-4 in all products. These data indicate that H-1 and H-4
are on the same side of the molecule and prove the a-stereochemistry.
It is noteworthy that the workup involves simple filtration, and the
catalyst could be recycled after washing with acetone and air drying. The
recovered Amberlyst 15 could be reused with a gradual loss of activity. For
example, glycosidation of 1 with isopropanol mediated by 80 wt%
recovered catalyst gave 1b in the yields of 96% (2 h, only a-isomer) and
95% (overnight, only a-isomer) over two cycles.
In conclusion, a heterogeneous solid acid Amberlyst 15–catalyzed
efficient and highly a-stereoselective Ferrier glycosidation has been
developed to generate structurally diverse 2,3-unsaturated O- and S-glycosides.
To the best of our knowledge, this is the first application of Amberlyst 15 to
promote the Ferrier glycosidation of glycal.[23] In view of its high level of
stereoselectivity combined with a simple operation, mild reaction conditions,
and the utility of an inexpensive, recyclable resin, this method is convenient,
economically viable, and green.
EXPERIMENTAL
Materials and Methods
3,4,6-Tri-O-acetyl-D-glucal (1) and Amberlyst 15 (dry) ion-exchange resin
were purchased from Acros Chemical. All solvents used in the reactions
were distilled from appropriate drying agents prior to use. Reactions were
monitored by thin-layer chromatography (TLC) using silica-gel GF254
plates with detection by charring with 10% (v/v) H2SO4 in EtOH or by ultra-
violet (UV) detection. Silica gel (100–200 mesh) was used for column chrom-
atography. Optical rotations were measured with a PE-314 automatic
polarimeter at 20 + 18C for solutions in a 1.0-dm cell. ESI-MS spectra
were acquired on a BioTOF Q. Elemental analyses were obtained on a
1
Carlo Erba 1106 instrument. H and 13C NMR spectra were recorded on
Bruker AC-E 200 or Varian Inova-400/54 spectrometers, with TMS as
internal reference. Chemical shifts are expressed in parts per million (ppm)
downfield from the internal Me4Si absorption.
Typical Experimental Protocol
To a stirred 0.2 M solution of 3,4,6-tri-O-acetyl-D-glucal 1 and the acceptor
(1 equiv) in anhydrous solvent (as indicated in Table 2), Amberlyst 15 (80
wt% for 1) was added in one portion at 25 8C. The mixture was stirred for
the desired time (Table 2) until the complete disappearance of the starting
materials as judged by TLC. The reaction mixture was filtered, and the

698
Q. Tian, X.-M. Zhu, and J.-S. Yang
resin was washed with acetone. The combined filtrate and washings were con-
centrated under reduced pressure. The residue was subjected to column
chromatography using petroleum ether–EtOAc as the eluant to afford the cor-
responding products. Following the same reaction conditions, O- and S-
nucleophiles gave the corresponding 2,3-unsaturated glycosides as summar-
ized in Table 2. Glycosides 1b–7b, 9b, 10b, 12b, 14b, and 15b are known
1
compounds, and their H and 13C NMR data matched the reported data in
the cited references (Table 2). Spectral data of new compounds that are not
reported are listed next.
Data
Methyl O-(40,60-di-O-acetyl-20,30-dideoxy-a-D-erythro-hex-20-enopyranosyl)-
(1 ! 3)-2-O-benzoyl-4,6-O-benzylidene-a-D-glucopyranoside (8b). From 1
(54.5 mg), colorless syrup, 71.8 mg (60%); Rf 0.3 (3:1, petroleum ether–
1
EtOAc); [a]2D1C þ 60.1 (c 1.5, CHCl3); H NMR (400 MHz, CDCl3): dH 1.90
(s, 3H, COCH3), 2.10 (s, 3H, COCH3), 3.43 (s, 3H, OCH3), 3.75–4.00
(m, 6H, H-6a, H-6b, H-5, H-6a0, H-6b0 and H-50), 4.34 (dd, J3,4 10.0, J4,5
4.8 Hz, 1H, H-4), 4.59 (t, J2,3, J3,4 9.6 Hz, 1H, H-3), 5.00 (d, J1,2 3.6 Hz, 1H,
0
H-1), 5.20 (dd, J1,2 3.6, J2,3 10.0 Hz, 1H, H-2), 5.24 (dd, J3 , 4 1.6, J4 ,5
0
0
0
9.6 Hz, 1H, H-40), 5.54 (s, 1H, H-10), 5.60 (s, 1H, PhCH), 5.78 (d, J2 ,3
0
0
11.6 Hz, 1H, H-20), 5.82 (dt, J2 ,3 10.4, J3 ,4 2.0 Hz, 1H, H-30), 7.34–8.14
(m, 10H, aromatic); 13C NMR (100 MHz, CDCl3): dC 170.8, 170.0
(2 ꢀ COCH3), 165.8 (PhCO), 137.0, 133.4, 129.8, 129.7, 129.1, 128.7, 128.5,
128.3, 128.2, 127.6, 126.3, 126.0 (aromatic, C-20 and C-30), 101.6 (PhCH),
98.0 (C-1), 94.3 (C-10), 82.7 (C-3), 72.4 (C-2), 71.9 (C-4), 69.0 (C-6), 66.4
(C-40), 64.7 (C-50), 62.4 (C-5), 62.1 (C-60), 55.4 (OCH3), 20.7, 20.6
(2 ꢀ COCH3); HR ESI-MS: calcd. for C31H34O12 [M þ Na]þ: 621.1948;
found: 621.1937. Anal. calcd for C31H34O12: C, 62.20; H, 5.73þ; found: C,
62.39; H, 5.79.
0
0
0
0
Allyl O-(40,60-di-O-acetyl-20,30-dideoxy-a-D-erythro-hex-20-enopyranosyl)-
(1 ! 6)-2,3,4-tri-O-benzyl-a-D-glucopyranoside (11b). From 1 (54.5 mg),
colorless syrup, 122.7 mg (89%); Rf 0.31 (3:1, petroleum ether–EtOAc);
[a]2D1 þ 34.4 (c 18.2, CHCl3); H NMR (400 MHz, CDCl3): dH 1.99 (s, 3H,
1
COCH3), 2.06 (s, 3H, COCH3), 3.53 (dd, J1,2 3.6, J2,3 9.6 Hz, 1H, H-2),
3.59 (t, J2,3, J3,4 9.2 Hz, 1H, H-3), 3.71 (d, J4,5 10.8 Hz, 1H, H-5), 3.83
(d, J3,4 9.6 Hz, 1H, H-4), 3.98–4.06 (m, 5H, OCH2aCH55CH2, H-6a, H-6b,
H-50, and H-6b0), 4.13–4.20 (m, 2H, OCH2bCH55CH2 and H-6a0), 4.64
(d, J 10.8 Hz, 1H, PhCH2), 4.66 (d, J 12.4 Hz, 1H, PhCH2), 4.77 (d, J
14.4 Hz, 1H, PhCH2), 4.80 (d, J
4.4 Hz, 1H, H-1), 4.81 (d, J 12.0 Hz,
1,2
1H, PhCH2), 4.93 (d, J 10.8 Hz, 1H, PhCH2), 5.00 (d, J 10.8 Hz, 1H,
PhCH2), 5.10 (s, 1H, H-10), 5.22 (d, J 10.0 Hz, 1 H, OCH2CH55CH2a),
5.29 (s, 1H, H-40), 5.33 (d, J 10.8 Hz, 1H, OCH2CH55CH2b), 5.85 (s, 2H,

Synthesis of 2,3-Unsaturated Glycosides
699
H-20 and H-30), 5.93 (m, 1H, OCH2CH55CH2), 7.26–7.36 (m, 15H, aromatic);
13C NMR (100 MHz, CDCl3): dC 170.6, 170.2 (2 ꢀ COCH3), 138.7, 138.3,
138.1, 128.9, 128.4, 128.3, 128.1, 128.0, 127.9, 127.8, 127.7, 127.6, 127.5,
127.4 (aromatic, C-20 and C-30), 133.7 (OCH2CH55CH2), 118.2
(OCH2CH55CH2), 95.5 (C-10), 94.7 (C-1), 82.0, 80.0, 77.9 (3 ꢀ PhCH2),
75.7 (C-3), 74.9 (C-2), 73.1 (OCH2CH55CH2), 70.2 (C-5), 68.2 (C-4), 67.0
(C-6), 66.9 (C-50), 65.1 (C-40), 62.7 (C-60), 20.9, 20.7 (2 ꢀ COCH3); HR
ESI-MS: calcd. for C37H41O10 [M þ Na]þ: 668.2597; found: 668.2590.
Anal. calcd. for C37H41O10: C, 68.82; H, 6.40; found: C, 69.02; H, 6.51.
Benzyl N-(benzyloxycarbonyl)threonine 4,6-di-O-acetyl-2,3-dideoxy-a-D-
erythro-hex-2-enopyranoside (13b). From 1 (54.5 mg), colorless syrup,
72.2 mg (65%); Rf 0.25 (3:1, petroleum ether–EtOAc); [a]2D1 2 1.7 (c 12.2,
1
CHCl3); H NMR (400 MHz, CDCl3): dH 1.33 (d, Jb,g 6.4 Hz, 3H, CH3-g),
2.04 (s, 3H, COCH3), 2.05 (s, 3H, COCH3), 3.98 (m, 1H, H-5), 4.13 (d, J5,6
4.0 Hz, 2H, H-6a, H-6b), 4.35 (m, 1H, H-b), 4.41 (dd, Ja, b 9.6, Ja, NH
2.0 Hz, 1H, H-a), 4.69 (s, 1H, NH), 5.12 (d, J 12.0 Hz, 1H, PhCH2), 5.13
(s, 2H, PhCH2), 5.18 (dd, J3,4 1.2, J4,5 9.2 Hz, 1H, H-4), 5.22 (d, J1,2
2.8 Hz, 1H, H-1), 5.24 (d, J 12.0 Hz, 1H, PhCH2), 5.47 (d, J2,3 10.0 Hz, 1H,
H-3), 5.72 (d, J2,3 10.4 Hz, 1H, H-2), 7.30–7.37 (m, 15H, aromatic); 13C
NMR (100 MHz, CDCl3): dC 170.6, 170.2 (2 ꢀ COCH3), 170.3 (COOBn),
156.6 (NHCOOBn), 136.1, 135.1, 128.8, 128.6, 128.5, 128.1, 128.0, 127.2
(aromatic, C-2 and C-3), 95.6 (C-1), 76.3, 67.3 (2 ꢀ PhCH2), 67.2 (C-b),
66.9 (C-5), 65.1 (C-4), 63.0 (C-6), 56.9 (C-a), 20.9, 20.7 (2 ꢀ COCH3),
18.8 (CH3-g); HR ESI-MS: calcd. for C29H33NO10 [M þ Na]þ: 578.2002;
found, 578.1988. Anal. calcd. for C29H33NO10: C, 62.69; H, 5.99; N, 2.52;
found: C, 62.88; H, 6.07; N, 2.65.
ACKNOWLEDGMENT
We are grateful to the National Natural Science Foundation of China (No.
30300434) and the Outstanding Youth Foundation of Sichuan Province,
China (No. 04ZQ026-039) for financial support of this work.
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