Zirconium(IV) chloride catalyzed synthesis of 2,3-unsaturated C, N, O, S, and heteroaromatic glycosylation in the ferrier rearrangement

Article abstract of DOI:10.1081/CAR-200040119

The reaction of tri-O-acetyl-D-glucal with nucleophiles to afford the corresponding 2,3-unsaturated glycopyranosides in excellent yields by zirconium(IV) chloride in acetonitrile at ambient temperature has been demonstrated. Copyright

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Zirconium(IV) Chloride Catalyzed
Synthesis of 2,3‐Unsaturated C, N, O, S,
and Heteroaromatic Glycosylation in the
Ferrier Rearrangement
a
a
Navath Raghavendra Swamy , Masuna Srinivasulu
,
a
a
Thummalapally Srikanth Reddy , Thirumani Venkateshwar Goud
&
a
Yenamandra Venkateswarlu
a
Organic Chemistry Division‐I, Natural Product Laboratory , Indian
Institute of Chemical Technology , Hyderabad, 500 007, India
Published online: 18 Aug 2006.
To cite this article: Navath Raghavendra Swamy , Masuna Srinivasulu , Thummalapally Srikanth
Reddy , Thirumani Venkateshwar Goud & Yenamandra Venkateswarlu (2004) Zirconium(IV) Chloride
Catalyzed Synthesis of 2,3‐Unsaturated C, N, O, S, and Heteroaromatic Glycosylation in the Ferrier
Rearrangement, Journal of Carbohydrate Chemistry, 23:6-7, 435-441, DOI: 10.1081/CAR-200040119
To link to this article: http://dx.doi.org/10.1081/CAR-200040119
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JOURNAL OF CARBOHYDRATE CHEMISTRY
Vol. 23, No. 6&7, pp. 435–441, 2004
Zirconium(IV) Chloride Catalyzed Synthesis of
,3-Unsaturated C, N, O, S, and Heteroaromatic
2
#
Glycosylation in the Ferrier Rearrangement
Navath Raghavendra Swamy, Masuna Srinivasulu,
Thummalapally Srikanth Reddy, Thirumani Venkateshwar Goud,
and Yenamandra Venkateswarlu*
Organic Chemistry Division-I, Natural Product Laboratory, Indian Institute of
Chemical Technology, Hyderabad, India
CONTENTS
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
II. RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . 436
III. EXPERIMENTAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437
ACKNOWLEDGMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
#
IICT Communication No 021011
*
Correspondence: Yenamandra Venkateswarlu, Organic Chemistry Division-I, Natural Product
Laboratory, Indian Institute of Chemical Technology, Hyderabad 500 007, India; Tel.: þ 91-40-
27193167; Fax: þ91-40-27160512; E-mail: luchem@iict.res.in.
4
35
DOI: 10.1081/CAR-200040119
0732-8303 (Print); 1532-2327 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

436
Swamy et al.
ABSTRACT
The reaction of tri-O-acetyl-D-glucal with nucleophiles to afford the corresponding
,3-unsaturated glycopyranosides in excellent yields by zirconium(IV) chloride in
acetonitrile at ambient temperature has been demonstrated.
2
Key Words: Ferrier rearrangement; 2,3-Unsaturated glycopyranosides; Nucleophiles;
Heteroaromatics; Protected amino acids; Zirconium(IV) chloride.
INTRODUCTION
Unsaturated carbohydrates are a versatile class of compounds in synthetic organic
chemistry in which alkyl, aryl 2,3-unsaturated glycosides are important building blocks
[
in many bioactive molecules. C-glycosyl, N-glycosyl reactions are important chiral
1]
[2]
intermediates for the synthesis of biologically active natural products such as anti-
[7]
[
3,4]
[3,4]
[5] [6]
C-glycosyl antibiotics, palytoxin, spongistatin,
virals,
halichondrin,
antitumor agents,
glycopeptides,
[
8]
[9,10]
[11]
glycoprotein modified carbohydrates,
and
[
12]
nucleosides.
Products of C-glycosidation are important intermediates due to their propensity for
further functionalization. For instance, allyl glycosides are amenable to hydroxylation,
epoxidation, amino hydroxylation, and hydrogenation, while glycosyl cyanides are
[
13]
useful chiral intermediates due to the readily transformed cyanide group. Alternatively,
glycosyl azides are important precursors for the synthesis of glycosyl amine.
RESULTS AND DISCUSSION
[
14]
The well-known Ferrier rearrangement,
involving Lewis acid catalyzed allylic
rearrangement, is widely used to obtain 2,3-unsaturated glycosides and thus gives
access to the aforementioned structures. A variety of reagents are used to effect this trans-
[
15,16]
[17,18]
formation, which include strong acids such as BF OEt ,
3
SnCl ,
4
[20]
and
[21]
DDQ,
2
[19]
TMSOTf.
Other reagents such as acidic montmorillonite K-10,
[24]
[22,23]
[25,26]
[27,28]
InCl3,
and BiCl3
triflates such as Sc(OTf)3,
and Yb(OTf)3
are also
known to bring about the Ferrier rearrangement under different conditions. However,
many of these procedures suffer from disadvantages such as strong oxidizing conditions,
high acidity, longer reaction times, unsatisfactory yields, low stereoselectivity, and use of
[9,10]
a large amount of reagent or catalyst. For instance, various amounts of BF OEt
3
are
2
often needed to effect the transformation, while metal triflates can be highly expensive. No
single catalyst is able to perform to carryout C, N, O, S, and heteroaromatic glycosylation
reaction in the Ferrier rearrangement.
Previously, ZrCl has been used as an efficient catalyst in acetalization, dithioaceta-
4
[
29,30]
lization,
thioacetalizations of acetals,
and 1,3-oxathiolanes of carbonyl compounds. Also it has been used in trans-
[
31]
[32]
and in the synthesis of chloromethyl esters.
In view of
the current thrust on catalytic processes, there is merit in developing a truly catalytic
method to prepare 2,3-unsaturated C-glycosyl, glycosyl azide from silylated nucleophiles
such as allyltrimethyl silane, trimethylsilyl cynide, and allyltrimethyl azide using

Zirconium(IV) Chloride Catalyzed Synthesis
437
inexpensive and nonpolluting reagents. Herein, we wish to report zirconium(IV) chloride
catalyzed glycosylation with silylated nucleophiles, heteroaromatics, and protected amino
acids. The reaction proceeds efficiently at ambient temperature and the products are
obtained in excellent yields (Sch. 1). Furthermore, other functionalities such as Bz, Bn,
NHBOC, NHCBz, Ac, OMe, allyl, CN, and N are compatible under the reaction con-
3
ditions. The reaction conditions are very mild and no by-products are observed. We
first examined the reaction of tri-O-acetyl-D-glucal with allyltrimethyl silane in the pre-
sence of zirconium(IV) chloride in acetonitrile at ambient temperatures affording the cor-
responding 2,3-unsaturated glycopyranoside in 95% yield (Tab. 1 entry a). This success
encouraged us to extend the generality of the reaction. The glycosidation of tri-O-acetyl
glucal with trimethylsilyl cyanide, allyltrimethyl azide, and protected amino acids pro-
ceeded smoothly (Tab. 1). These compounds are potential precursors for the synthesis
of glycopeptide building blocks.
In conclusion, the present procedure has the advantages of mild reaction conditions,
high stereoselectivity, reduced reaction time, inexpensive catalyst, high yields of products,
and simple experimental work-up procedure for the preparation of 2,3-unsaturated
glycosylated products. Zirconium(IV) chloride catalyzed Ferrier glycosylation has been
developed to produce structurally diverse C, N, O, S, and heteroaromatic glycosylation
reaction in the Ferrier rearrangement and will be an important addition to the existing
methodologies.
EXPERIMENTAL
General procedure: A solution of glucal (1 mmol) and nucleophiles (1.1 mmol) in
MeCN (10 mL) was treated with zirconium(IV) chloride (5 %mol) and stirred for an
appropriate time (Tab. 1) at rt. After completion of the reaction, the solvent was
removed from the reaction mixture under reduced pressure, water was added and the
reaction contents were extracted into EtOAc. The organic layer was dried over anhyd.
Na SO and concentrated to give the crude product, which was purified by silica gel
2
4
chromatography eluting with ethyl acetate : hexane (2 : 8) to give pure 2,3-unsaturated
glycopyranosides in high yields (Tab. 1).
1
C-Allyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranoside (a):
1
H
NMR (CDCl , 200 MHz): d 2.08 (s, 6H, Ac), 2.35–2.45 (m, 2H, H -1 , H -1 ), 3.95
1
3
a
b
(
dt, 1H, J5,6 ¼ 6.5 and J ¼ 3.7 Hz), 4.10–4.20 (m, 2H, H -6, H -6), 4.25–4.30
5,4
a
b
1
1
m, 1H, H -4), 5.05–5.20 (m, 3H, H -3, H -2, H -2 ), 5.75–5.95 (m, 3H, H -1, H -3 ,
(
a a a a a a
1
þ
H -3 ). FAB-MS: 255 (M þ 1).
b
1
C-Allyl 4,6-di-O-benzyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranoside (c):
1
H
NMR (CDCl , 200 MHz): d 2.21–2.3 (m, 1H, H -1 ), 2.4–2.5 (m, 1H, H -1 ), 3.61 (dd,
1
3
a
b
Scheme 1.

438
Swamy et al.
Table 1.
2
,3-Unsaturated
Glycoside
Time Yield Anomeric ratio
a
b
Entry
a)
Acceptor
(min) (%)
(a/b)
Ref.
60
60
60
60
96
95
96
64
10 : 1
9 : 1
b)
c)
d)
[22,23]
11 : 1
8 : 2
[22,23]
[22,23]
[22,23]
[22,23]
e)
f)
60
30
30
66
56
55
8 : 2
8 : 3
9 : 3
g)
h)
i)
Me Si-CN
3
30
30
45
75
70
81
10 : 1
8 : 3
[24]
[24]
Me Si-N
3
3
j)
7 : 4
k)
45
60
85
87
9 : 2
l)
Ph-SH
10 : 1
[1]
a
Isolated yield as pure anomeric mixtures after purification.
b
The anomeric ratio was determined on the basis of the integration ratios of the anomeric hydrogens
1
in the H NMR spectra at 200 MHz.

Zirconium(IV) Chloride Catalyzed Synthesis
439
2
H, J6,6 ¼ 4 Hz, J ¼ 4 Hz, H -6, H -6), 3.73 (d, 1H, J ¼ 5 Hz, H -5), 3.96 (d, 1H,
5,6
a
b
5,6
a
J4,3 ¼ 5 Hz, H -4), 4.28 (br d, 1H, J ¼ 5 Hz, H-3), 4.4–4.5 (dd, 2H, J ¼ 6 Hz,
a
3,4
1,1
J1,1 ¼ 6 Hz, OCH ), 4.53–4.6 (dd, 2H, J ¼ 6 Hz, J ¼ 6 Hz, OCH ), 5.0 (d, 1H,
2
1
1,1
1,1
2
1
J2,3 ¼ 4 Hz, H -3 ), 5.1 (d, 1H, J ¼ 5 Hz, H -3 ), 5.76–5.82 (m, 2H, H -2, H -1),
a
2,3
b
a
a
þ
5
.83 (d, 1H J ¼ 6 Hz, H -1), 7.2–7.3 (m, 10H, Ar) FAB-MS: 351(M þ 1).
1
,2
a
1
2
-(4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranosyl)furan (d):
H
NMR (CDCl , 200 MHz): d 1.98 (s, 3H, Ac), 2.1 (s, 3H, Ac), 4.03 (dt, 1H, J ¼ 1.8,
3
5,6
J5,4 ¼ 6 Hz, H -3), 4.15 (m, 1H, H -5), 4.30 (m, 2H, OCH , H -6, H -6), 4.81 (t, 1H,
a
a
2
a
b
J2,1 ¼ 6 Hz, J ¼ H -2), 5.07 (dd, 1H, J ¼ 6 Hz, J ¼ 8 Hz, H -4), 6.13 (d, 1H,
2,3
a
4,5
4,3
a
J ¼ 3.5 Hz, H , Aryl), 6.34 (dd, 1H, J ¼ 2.5, J ¼ 3.5 Hz, Hb, Aryl), 6.51 (d, 1H,
a
2,1
2,3
þ
J
¼ 4 Hz, H -1), 7.37 (d,1H, J ¼ 2.5 Hz, H , Aryl) FAB-MS: 281 (M þ 1).
1
,2
a
c
N-(tert-butoxycarbonyl)-O-(4,6-di-O-acetyl 2,3-dideoxy-a-D-erythro-hex-2-eno-
1
2
5
0
pyranosyl)-L-threonine methyl ester (j): [a]
D
þ 42.39 (c ¼ 1, CHCl ): H NMR
3
(
CDCl , 200 MHz): d 1.31 (d, J ¼ 6.3 Hz, 3H CH ), 1.42 (s, 9H, C(CH ) ), 2.08
3
3
3 3
(
s, 6H,OAc), 3.78 (s, 3H, COOMe), 4.08–3.80 (m, 5H, H -5, H -6, H -6, a-CH,
a a b
b-CH), 4.95 (brs, 1H, H -1), 5.15 (d, JNHa ¼ 9.8 Hz,1H, NH), 5.26 (dd J ¼ 1.1 Hz,
a
3,4
þ
J4,5 ¼ 9.8 Hz, 1H, H -4), 5.65 (brs, 1H, H-2), 5.84 (brs, 1H, H-3) FAB-MS: 446 (M þ 1).
a
N-(benzyloxycarbonyl)-O-(4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-eno-
1
pyranoside)-L-serine methyl ester (k): H NMR (CDCl , 200 MHz): d 2.08 (s, 6H,
3
OCOCH3), 3.75 (s, 3H, COOMe), 3.9–4.03 (m, 2H, H -6, H -6), 4.10–4.22 (m, 3H,
a
b
a-CH, b-CH ), 4.42–4.55 (m, 1H H-5), 5.09 (s, 2H, OCH -Ph), 5.20 (d, 1H,
2
2
J ¼ 10 Hz, H-4), 5.72–5.88 (m, 3H, H-1, H-2, H-3), 7.28–3.80 (m, 5H, Ar) FAB-MS:
þ
4
66 (M þ 1).
ACKNOWLEDGMENT
We are thankful to the director of IICT for his constant encouragement and to CSIR,
New Delhi, for the award of fellowship to NRS, MS, and TVG.
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Received July 12, 2004
Accepted July 20, 2004