A facile new procedure for the deprotection of allyl ethers under mild conditions

Article abstract of DOI:10.1139/v00-073

A novel isomerization of O-allyl glycosides into prop-1-enyl glycosides was observed instead of cross-metathesis during an olefin metathesis reaction using Grubbs' ruthenium benzylidene catalyst (Cy₃P)₂RuCl₂=CHPh (1), N-allyltritylamine, and N,N-diisopropylethylamine as necessary auxiliary reagents. In the search for a better catalytic system, it has been found that dichlorotris(triphenylphosphine)ruthenium(II), [(C₆H₅)₃P]₃RuCl₂, (2) was much more efficient for the isomerization of allylic ethers. The labile prop-1-enyl group was easily hydrolyzed using HgCl₂-HgO and the hemiacetals (25-32) were isolated in excellent yields (ca. 90%).

Full text of DOI:10.1139/v00-073

838
A facile new procedure for the deprotection of
allyl ethers under mild conditions
Yun-Jin Hu, Romyr Dominique, Sanjoy Kumar Das, and René Roy
Abstract: A novel isomerization of O-allyl glycosides into prop-1-enyl glycosides was observed instead of
cross-metathesis during an olefin metathesis reaction using Grubbs’ ruthenium benzylidene catalyst
(Cy3P)2RuCl2=CHPh (1), N-allyltritylamine, and N,N-diisopropylethylamine as necessary auxiliary reagents. In the
search for a better catalytic system, it has been found that dichlorotris(triphenylphosphine)ruthenium(II),
[(C6H5)3P]3RuCl2, (2) was much more efficient for the isomerization of allylic ethers. The labile prop-1-enyl group was
easily hydrolyzed using HgCl2–HgO and the hemiacetals (25–32) were isolated in excellent yields (ca. 90%).
Key words: allyl ether, carbohydrate, Grubbs’ catalyst, isomerization, metathesis, deprotection.
Résumé : Au cours d’une réaction de métathèse d’oléfine impliquant du catalyseur de Grubbs, le benzylidène de
ruthénium, (Cy3P)2RuCl2=CHPh (1), de la N-allyltritylamine et du N,N-diisopropyléthylamine comme réactifs
auxiliaires nécessaires, on a observé une nouvelle isomérisation des glycosides de O-allyle en glycosides de
prop-2-ényle. Au cours de nos travaux en vue développer un meilleur système catalytique, on a trouvé que le
dichlorotris(triphénylphosphine)ruthénium(II), [(C6H5)3P]3RuCl2 (2), est beaucoup plus efficace pour l’isomérisation des
éthers allyliques. Le groupe prop-1-ényle labile est hydrolysé facilement à l’aide de HgCl2–H2O et on a isolé les
hémiacétals (25–32) avec d’excellents rendements (environ 90%).
Mots clés : éther allylique, catalyseur de Grubbs, isomérisation, métathèse, déprotection.
[Traduit par la Rédaction] Hu et al. 845
Introduction
benzylidene catalyst (Cy3P)2RuCl2=CHPh 1 or dichloro-
tris(triphenylphosphine)ruthenium(II) (2) in excellent yields
(ca. 90%).
The use of allyl ether protecting groups is of great impor-
tance in carbohydrate chemistry and other natural product
syntheses (1) because of their ready availability and stability
under reasonably strong acidic and basic conditions. Several
methods for the deprotection of allyl ethers have already
been described in the literature (2–11). Most methods in-
volve initial isomerization of allyl to prop-1-enyl ethers with
either a base such as [(CH3)3COK] (2) or transition metals:
Ti(0) (3), Rh(I) (4), Ir(I) (5), Pd-C (6), Pd(PPh3)4 (7),
Pd(OAc)2 (7), H2Ru(PPh3)4 (8), Fe(CO)5 (9). The labile
prop-1-enyl ethers can then be cleaved to the corresponding
alcohols by mineral acids or HgCl2–HgO (10) (Scheme 1).
Direct cleavage of allyl ethers is generally carried out using
stoichiometric amounts of palladium salts or complexes such
as PdCl2(PhCN)2, PdCl2 (11). However, some of these meth-
ods are still less than satisfactory for practical use and some-
times are found to be capricious (12). Herein, we wish to
report a new method for the deprotection of the allyl group
from carbohydrate derivatives using Grubbs’ ruthenium
Results and discussion
Recently we have been interested in the metathesis reac-
tion of O-allyl glycosides using Grubbs’ catalyst
(Cy3P)2Cl2Ru=CHPh (1) (13, 14). However, when the
cross-metathesis reaction between N-allyltritylamine 3 (15)
and allyl 2,3,4,6-tetra-O-acetyl-α-D-galactopyranoside 9 (16)
was carried out with 1, an unexpected isomerization product
17 was isolated in 30% yield instead of the anticipated cross
metathesis compound. Furthermore, neither sugar nor
N-allyltritylamine dimer could be detected. Treatment of 9
with 1,4-diazabicyclo[2,2,2]octane (DABCO) in the presence
of Grubbs’ catalyst 1 afforded only 4% of the isomerized
product 17 together with 40% of allyl α-D-galactopyranoside
homodimer (14). Similar results were obtained when
triethylamine was used as base. Neither isomerization nor
metathesis products were detected when diethylamine or
pyridine were used (Table 1, entries 6 and 7). The isomer-
ized product 17 was obtained with the highest yield when 9
was treated with diisopropylethylamine (DIPEA) in the pres-
ence of Grubbs’ catalyst 1. However, all the isomerization
yields of those reactions were still very low in the absence
of N-allyltritylamine 3 (Scheme 2). When both 3 and 1
equiv. of DIPEA were simultaneously used in the reaction,
the isomerization yield was improved dramatically to 80%
(Table 1, entry 8). Furthermore, there was no self-metathesis
product that could be detected.
Received November 8, 1999. Accepted April 4, 2000.
Published on the NRC Research Press website on June 13,
2000.
Y.-J. Hu, R. Dominique, S.K. Das, and R. Roy.1
Department of Chemistry, University of Ottawa, Ottawa, ON
K1N 6N5, Canada.
1Author to whom correspondence may be addressed.
Telephone: (613) 562-5800, ext 6055. Fax: (613) 562-5170.
e-mail: rroy@science.uottawa.ca
Can. J. Chem. 78: 838–845 (2000)
© 2000 NRC Canada

Hu et al.
839
Table 1. Isomerization of allyl α-D-galactopyranoside 9 with different bases or additives in the presence of
Grubbs’ catalyst (1).
Recycled
glycosides (%)
Self metathesis
sugar dimer (%)
Entry
Base or additive
Isomerization (%)
1
2
3
4
5
6
7
8
9
3
67
55
45
80
35
100
100
16
78
65
—
40
45
12
50
—
—
—
20
30
30
4
3
DABCO
Et3N
NMMa
DIPEA
Diethylamine
Pyridine
3 and DIPEA
4
6
10
—
—
80
—
—
10
5
aNMM: N-methylmorpholine.
More detailed studies showed that the isomerization of
allyl ethers to propenyl ethers with Grubbs’ catalyst pro-
ceeded smoothly in the presence of amine 3 and a stoichio-
metric amount of base such as diisopropylethylamine
(DIPEA). To improve the yield of the isomerization and sup-
press the formation of metathesis products, 1.0 equiv. of
DIPEA and 2.0 equiv. of 3 were treated with different glyco-
sides in the presence of 0.1 equiv. of 1 (toluene, reflux, 4 h).
Good yields were obtained without any metathesis product
being detected in any of these experiments (Table 2).
Scheme 1.
The ratios of the unseparated E and Z stereoisomers in the
Bearing in mind the above observations, alternative bases
which could provide both basicity and olefinic functionality
were explored. To this end, several N-allylated amine deriva-
tives (4–8) that could mimic the structure of amine 3 were
synthesized to test the reaction. It was found that Boc-allyl
carbamate 4 and amine 5 did not catalyze this reaction at all.
Several tertiary amines 6–8 with increasing chain length also
failed to afford the desired isomerization products with 3
and catalyst 1 when they were subjected to the optimum
conditions. This demonstrates that the strong steric hin-
drance of N-allyltritylamine also had an important influence
on the isomerization of 9 as well as its basicity. At this
stage, we believed the presence of the secondary amine 3 as
an auxiliary reagent was crucial for the isomerization to
occur.
pro-1-enyl glycosides were determined from the analysis of
1
the H NMR spectra of the crude mixtures by observation of
3
the JH,H coupling constants of the alkenyl protons (17). In-
terestingly, the cis stereoisomers predominated. Isomeriza-
tion of partially protected glycosides 12 and 15 proceeded in
lower yields, presumably because some of the remaining
free hydroxyl groups of the substrates coordinated to some
extent with the catalyst and reduced or prevented its activity.
When control experiments were performed in the absence of
3 and DIPEA, only the expected self-metathesis products
were obtained in high yields (14).
We noticed that olefin isomerization of allylic ether
and allyl alcohol can be catalyzed by Ru(II)(H2O)6(tos)2
(tos = p-toluenesulfonate) (18) in aqueous solution and
Scheme 2.
© 2000 NRC Canada

840
Can. J. Chem. Vol. 78, 2000
Table 2. Results from the isomerization and hemiacetal transformations (25–32) (HgCl2–HgO) of various allyl glycosides (9–16) into
prop-1-enyl glycosides (17–24) in the presence of Grubbs’ catalyst 1 and amine 3, or catalyst 2 (Ph3P)3Cl2Ru(II) and DIPEA (PhCH3,
reflux, 4 h).
(PPh3)2X2Ru=CH-CH=CPh2 (X = Cl or CF3COO) (19) in
dichloromethane. When compared to existing methodologies,
however, Ru(II)(H2O)6(tos)2, (PPh3)2X2Ru=CH-CH=CPh2, or
Grubbs’ catalyst are relatively expensive and the isomeri-
zation yields are not competitive. We therefore initiated a
search for a better catalyst by screening a family of ruthe-
nium complexes for activity in this reaction. From this in-
vestigation, it was found that the commercially available,
dichlorotris(triphenylphosphine)ruthenium(II) [(PPh3)3RuCl2
(2)] can be used as an efficient catalyst for the deprotection
of allyl group from the glycosides 9–16 following a two-step
procedure.
We began with the isomerization reaction of peracetylated
allyl α-D-galactopyranoside (9) in different aprotic solvents
© 2000 NRC Canada

Hu et al.
841
Scheme 3.
Table 3. [(Ph3P)3RuCl2]-catalyzed isomerization of O-allyl glycosides (9, 11).
Entry
Glycoside
Base
Solvent
Time (h)
Product
Yield (%)
1
2
3
4
5
6
7
8
9
9
9
9
9
9
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
—
Pyridine
NMOb
DABCOc
Et3N
THF
CH3CN
CH2Cl2
2
2
2
1
2
2
6
6
6
2
3
2
17
17
17
17
17
17
17
19
19
19
19
19
0
0
80
96
Toluene
Ethanol:H2O (9:1)
Methanol
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
a
-
-
a
9
9
0
0
54
85
82
94
11
11
11
11
11
10
11
12
DIPEA
aDeacetylation was detected during the isomerization.
bNMO: N-methylmorpholine oxide.
c1,4-Diazabicyclo[2.2.2]octane.
such as tetrahydrofuran, acetonitrile, dichloromethane, and
toluene in the presence of 2 and DIPEA (Table 3). No
isomerization was detected when THF and acetonitrile were
used as solvents. When the reaction was carried out in
refluxing dichloromethane, the isomerized product (17) was
obtained in 80% yield. The best result was obtained when
the reaction was performed in toluene under refluxing condi-
tions. Lower yields were obtained when the reactions were
performed in anhydrous methanol or aqueous ethanol due to
competing de-O-acetylation. It is noteworthy that no iso-
merized product was detected in the absence of catalyst or
base, even under forcing conditions such as prolonged reac-
tion time, higher reaction temperature, and the use of up to
20 mol% of catalyst. Several common organic bases were
examined for activity in the isomerization of 11. No
isomerization product was formed in pyridine. Upon treat-
ment with triethylamine or 1,4-diazabicyclo[2,2,2]octane,
the isomerization reactions proceeded smoothly. It was found
that diisopropylethylamine (DIPEA) was the most suitable
base for the system in terms of the high yields obtained for
both 9 and 11 (Table 3). This novel isomerization reaction
most likely follows the metal hydride addition-elimination
mechanism (18).
cosides (12, 15) with free hydroxyl groups, which were not
suitable for the metathesis reaction because of the coordina-
tion to the metal in the Grubbs’ catalyst, were still good sub-
strates for these isomerization conditions.
As expected, hydrolysis of the enol ethers proceeded rap-
idly under acidic conditions (pH = 2) to provide hemiacetals
(4). Alternatively, treatment of prop-1-enyl ethers with
HgCl2–HgO in aqueous acetone at room temperature for 1 h
gave deprotected products in high yields. The whole proce-
dure could be simplified as a two-step one-pot reaction: after
isomerization of allyl ether, toluene and DIPEA were re-
moved under reduced pressure and the resulting residue was
then subjected to 0.5 equiv. of HgO and 1.0 equiv. of HgCl2
in aqueous acetone (water:acetone – v/v 1:1) at room tem-
perature for 1 h.
The excellent results described above provide a new route
towards the deprotection of O-allyl glycosides in the field of
carbohydrate chemistry. Up to now, there were several meth-
ods reported for the deprotection of O-allyl ethers (2–10,
20–22), however, these methods have been limited by severe
reaction conditions such as: using strong base (2) or strong
acid (20) as catalyst, performing reactions in aqueous alco-
hol (4) or alkaline solution (9), using oxidizing (21) or re-
ducing (22) conditions, and operating under severe
oxygen-free and anhydrous conditions (5). Compared to
Wilkinson’s catalyst (4), which is commonly used for
deprotection of O-allyl ether in carbohydrate chemistry, ru-
thenium (II) complexes have two advantages with similarly
effective performance with respect to promoting the
Various allyl glycosides were subjected to the following
standard conditions: a catalytic amount of 2 (10 mol%) was
utilized as catalyst and a stoichiometric amount of DIPEA as
base and the reactions were performed in refluxing toluene.
Isomerized products were obtained in excellent yields (Ta-
ble 2). It is also noteworthy that even those O-allyl gly-
© 2000 NRC Canada

842
Can. J. Chem. Vol. 78, 2000
isomerization of O-allyl glycosides. First, the ruthenium
(II) complex is more than two times cheaper than
Wilkinson’s catalyst; second, the ruthenium (II) complex
does not reduce the alkene as is sometimes observed when
using (Ph3P)3RhCl (23). As for Felkin’s Ir (I) catalyst, which
is not commercially available, the procedure must be per-
formed under strictly oxygen-free and anhydrous conditions
(5). Our method for the isomerization of allyl groups by
dichlorotris(triphenylphosphine)ruthenium(II) (2) is widely
applicable and easy to perform under mild reaction condi-
tions (Table 2). The isomerization of O-allyl ethers proceeds
readily at refluxing temperature without affecting free
hydroxyl, O-isopropylidene, trityl, acetyl, benzyl, or
p-methoxylbenzyl groups.
flash chromatography on silica gel 60 (230–400 mesh; E.
Merck No. 9385). Solvents were evaporated under reduced
pressure using a rotary evaporator connected to a water aspi-
rator. All chemicals used in experiments were of reagent
grade. Solvents were purified by published procedures.
Compounds 10 and 11 were synthesized by the reported pro-
cedure (26). Compound 12 was prepared by the method
reported by Fraser–Reid et al. (27). Allyl α-L-rhamnopy-
ranosides (13–15) were prepared according to the method re-
ported by Luckas et al. (28). Allyl glycoside 16 was
synthesized by the published procedure (16).
Typical procedure for isomerization of glycosides by
Grubbs’ catalyst (1); procedure A
Saloman and coworkers (24) reported the selective rear-
rangement of diallyl ethers catalyzed by dichlorotris(triphenyl-
To a solution of glycoside (0.1 mmol) in toluene (2 mL),
N-allyltritylamine (3) (0.2 mmol), Grubbs’ catalyst 1
(8.2 mg, 0.01 mmol) and DIPEA (0.1 mmol) were added un-
der a nitrogen atmosphere. The reaction mixture was stirred
under reflux conditions for 4 h. The resulting red solution
was concentrated using a rotary evaporator and the residue
was partitioned between water and dichloromethane. The or-
ganic layer was dried (Na2SO4), concentrated, and purified
by column chromatography.
phosphine)ruthenium(II) (2) involving
a
preliminary
rearrangement to allyl vinyl ethers followed by a Claisen re-
arrangement. However, high temperature (200°C) instead of
an organic base was used in their experiments. A recent re-
port showed that isomerization of O-allyl ethers using 2 at
130°C led to the formation of many byproducts (9), so it
would appear that its use has not been exploited until now.
To the best of our knowledge, there are no other reports of
the application of this catalyst for the deprotection of O-allyl
groups.
The simplicity and mildness of this methodology led us to
explore this procedure for the deprotection of allyl ether
from 6-O-allyl-1,2:3,4-di-O-isopropylidene-α-D-galactopy-
ranose (33). Treatment of 33 with catalyst 2 and DIPEA un-
der the same reaction conditions gave the isomerized
product 34 in 95% yield (Scheme 3).
Typical procedure for isomerization using (Ph3P)3Cl2Ru
(2); procedure B
To a solution of glycosides (0.1 mmol) in toluene (2 mL),
dichlorotris(triphenylphosphine)ruthenium(II)
(9.6
mg,
0.01 mmol) and DIPEA (0.2 mmol) were added under a ni-
trogen atmosphere. The resulting solution was stirred under
reflux conditions for 2 h and then toluene and DIPEA were
removed under reduced pressure. The residue was purified
by silica gel column chromatography to obtain the appropri-
ate isomerized product.
Conclusions
In conclusion, an efficient isomerization of O-allyl glyco-
sides has been achieved in the presence of a catalytic
amount of dichlorotris(triphenylphosphine)ruthenium(II) (2),
from which we have developed a facile method for the
deprotection of O-allyl acetals and ethers. This is
preparatively a very useful method, which is performed
under mild conditions and is compatible with the presence
of various protecting groups. It is also worth noting that the
commercially available polystyrene-anchored (PPh3)2RuCl2
should show similar activity towards the isomerization of
O-allyl glycosides, which would make the actual procedure
even more attractive (25).
Procedure for the deprotection of prop-1-enyl group
The purified isomerization product (0.1 mmol) was dis-
solved in 2 mL of acetone:water (1:1). To the solution, HgO
(10.8 mg, 0.05 mmol) and HgCl2 (27.2 mg, 0.1 mmol) were
added. After stirring for 1 h at room temperature, with moni-
toring by TLC, the deprotected product was extracted with
ethyl acetate and washed with potassium iodide solution to
remove mercuric compounds. Following a usual work-up,
colorless oil was obtained and purified by silica gel column
chromatography to obtain the appropriate product as an α
and β mixture.
Prop-1-enyl 2,3,4,6-tetra-O-acetyl-α -D-galactopyranoside (17):
After silica gel column chromatography with ethyl acetate
and hexane as eluent (1:2), compound 17 (as a mixture of E
and Z isomers in 1:2 ratio) was isolated as a syrup, Rf (hex-
Experimental section
Materials
1H and 13C NMR spectra were recorded at 500 or
200 MHz and 125 or 50 MHz respectively, with tetramethyl-
silane (0.00 ppm) as an internal reference. Thin-layer chro-
matography (TLC) was performed using silica gel 60 F254
aluminum sheets purchased from E. Merck. Reagents used
for developing plates include ceric sulfate (1% w/v) and am-
monium sulfate (2.5% w/v) in 10% (v/v) aqueous sulfuric
acid, iodine, dilute aqueous potassium permanganate, and
UV light. TLC plates were heated to approximately 150°C
when necessary. Purifications were performed by gravity or
1
ane:EtOAc = 2:1): 0.38. For E isomer: H NMR (200 MHz,
CDCl3), δ : 6.13 (dq, 1H, J = 12.3, 1.6 Hz), 5.50–5.35 (m,
2H), 5.36–5.29 (m, 1H), 5.25–5.09 (m, 2H), 4.27–4.15 (m,
1H), 4.12–3.98 (m, 2H), 2.14 (s, 3H), 2.07 (s, 3H), 2.02 (s,
3H), 2.00 (s, 3H), 1.55 (dd, 3H, J = 7.0, 1.6 Hz). For Z iso-
1
mer: H NMR (200 MHz, CDCl3), δ : 6.05 (dq, 1H, J = 6.1,
1.6 Hz), 5.50–5.35 (m, 2H), 5.36–5.29 (m, 1H), 5.25–5.09
(m, 1H), 4.70–4.59 (m, 1H), 4.27–4.15 (m, 1H), 4.12–3.98
(m, 2H), 2.14 (s, 3H), 2.07 (s, 3H), 2.02 (s, 3H), 2.00 (s,
© 2000 NRC Canada

Hu et al.
843
3H), 1.62 (dd, 3H, J = 6.9, 1.6 Hz). HRMS(FAB), calcd. for
6H), 3.91–3.59 (m, 4H), 3.80 (s, 3H), 1.53–1.51 (m, 3H),
1.32 (d, 3H, J = 5.7 Hz). For Z isomer: H NMR (500 MHz,
1
C17H24O10K (M + K+): 427.1007, found: 427.1456.
CDCl3), δ (ppm): 7.40–6.86 (m, 14H), 6.10 (dq, 1H, J = 6.9,
1.6 Hz), 4.96 (d, 1H, J = 1.0 Hz), 4.89–4.56 (m, 6H),
4.55–4.46 (m, 1H), 3.91–3.59 (m, 4H), 3.80 (s, 3H),
1.53–1.51 (m, 3H), 1.32 (d, 3H, J = 5.7 Hz). MS (FAB) m/z:
504 (M+).
Prop-1-enyl 2-acetamido-3,4-di-O-acetyl-2-deoxy-6-O-trityl-
β-D-glucopyranoside (18): Compound 18 (as a Z isomer)
was obtained from 10 as a syrup in 85% yield using Grubbs’
catalyst. The expected product was obtained in 95% yield
using catalyst 2. Rf (hexane:EtOAc = 1:1): 0.23. For Z iso-
1
mer: H NMR (200 MHz, CDCl3), δ (ppm): 7.60–7.00 (m,
Prop-1-enyl 2,3,4-tri-O-acetyl-α-L-rhamnopyranoside (22):
Compound (E:Z = 1:2) was obtained as a syrup in 95% yield
using procedure B, Rf (hexane:EtOAc = 1:4): 0.27. For E
15H), 6.29 (dq, 1H, J = 6.2, 1.7 Hz), 5.54 (d, 1H, J =
9.2 Hz), 5.26–5.23 (m, 2H), 4.83 (d, 1H, J = 8.2 Hz),
4.75–4.68 (m, 1H), 4.20–4.15 (m, 1H), 3.61–3.52 (m, 1H),
3.31–3.12 (m, 2H), 2.07 (s, 3H), 2.02 (s, 3H), 1.78 (s, 3H),
1.68–1.65 (m, 3H). HRMS (FAB), calcd. for C34H37N1O8K
(M + K+): 626.2156, found: 626.2150.
1
isomer: H NMR (200 MHz, CDCl3), δ (ppm): 6.13 (dq, 1H,
J = 12.3, 1.7 Hz), 5.40–5.00 (m, 4H), 4.94 (s, 1H), 3.84 (dq,
1H, J = 9.7, 6.2 Hz), 2.15 (s, 3H), 2.05 (s, 3H), 1.99 (s, 3H),
1.55 (dd, 3H, J = 7.0, 1.7 Hz), 1.21 (d, 3H, J = 6.2 Hz). For
1
Z isomer: H NMR (200 MHz, CDCl3), δ (ppm): 6.07 (dq,
Prop-1-enyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopy-
ranoside (19): Known compound 19 (29) (E:Z = 1:3) was
obtained as a colorless oil in 70% yield using Grubbs’ cata-
lyst and 92% yield using catalyst 2. Rf (hexane:EtOAc =
1H, J = 6.2, 1.7 Hz), 5.40–5.00 (m, 3H), 4.94 (s, 1H),
4.73–4.55 (m, 1H), 3.84 (dq, 1H, J = 9.7, 6.2 Hz), 2.15 (s,
3H), 2.05 (s, 3H), 1.99 (s, 3H), 1.63 (dd, 3H, J = 7.0,
1.7 Hz), 1.21 (d, 3H, J = 6.2 Hz).13C NMR (50 MHz,
CDCl3), δ (ppm): 169.9, 169.9, 169.8, 141.6 (E), 140.7 (Z),
105.3 (E), 105.0 (Z), 97.1 (Z), 96.5 (E), 70.9, 70.8, 69.2,
68.8, 66.8, 20.9, 17.4, 12.4 (E), 9.3 (Z). HRMS (FAB),
calcd. for C15H23O8 (M + 1): 331.1733, found: 331.1749.
1
1:6): 0.34. For E isomer: H NMR (500 MHz, CDCl3), δ
(ppm): 6.19 (m, 1H), 5.62 (d, 1H, J = 8.8 Hz), 5.31 (dd, 1H,
J = 10.2, 9.2 Hz), 5.15–5.05 (m, 2H), 4.83 (d, 1H, J =
8.3 Hz), 4.26 (dd, 1H, J = 12.2, 4.5 Hz), 4.13 (dd, 1H, J =
10.0, 2.3 Hz), 4.03 (m, 1H), 3.78 (m, 1H), 2.08 (s, 3H), 2.04
(s, 3H), 2.02 (s, 3H), 1.95 (s, 3H), 1.55 (dd, 3H, J = 6.8,
1.7 Hz). For Z isomer: 1H NMR (500 MHz, CDCl3), δ
(ppm): 6.15 (dq, 1H, J = 4.5, 1.7 Hz), 5.62 (d, 1H, J =
8.8 Hz), 5.31 (dd, 1H, J = 10.2, 9.2 Hz), 5.10 (m, 1H), 4.83
(d, 1H, J = 8.3 Hz), 4.61 (m, 1H), 4.26 (dd, 1H, J = 12.2,
4.5 Hz), 4.13 (dd, 1H, J = 10.0, 2.3 Hz), 4.03 (m, 1H), 3.78
(m, 1H), 2.08 (s, 3H), 2.04 (s, 3H), 2.02 (s, 3H), 1.95 (s,
3H), 1.56 (dd, 3H, J = 6.9, 1.7 Hz).13C NMR (125 MHz,
CDCl3), δ (ppm): 170.5, 170.4, 170.3, 142.4 (E), 141.2 (Z),
105.7 (E), 105.6 (Z), 95.9 (E), 95.3 (Z), 67.9, 67.7, 67.5,
66.8, 61.4, 20.6, 12.3 (E), 9.2 (Z). HRMS (FAB), calcd. for
C17H26NO9 (M + 1): 388.1608, found: 388.1877.
Prop-1-enyl 4-O-(p-methoxybenzyl)-α -L-rhamnopyranoside (23):
Compound 23 (E:Z = 1:2) was obtained from 15 as colorless
1
oil in 96% yield using catalyst 2. For E isomer: H NMR
(500 MHz, CDCl3), δ (ppm): 7.28 (d, 2H, J = 7.7 Hz), 6.87
(d, 2H, J = 7.7 Hz), 6.16 (dq, 1H, J = 12.2, 1.6 Hz), 5.03 (m,
1H), 4.96 (d, 1H, J = 1.5 Hz), 4.65–4.48 (m, 2H), 3.98–3.63
(m, 3H), 3.75 (s, 3H), 3.32 (dq, 1H, J = 9.4, 4.4 Hz), 2.57
(bs, 1H), 1.54–1.50 (m, 3H), 1.32 (d, 3H, J = 4.4 Hz). For Z
isomer: 7.28 (d, 2H, J = 7.7 Hz), 6.87 (d, 2H, J = 7.7 Hz),
6.08 (dq, 1H, J = 6.1, 1.9 Hz), 4.96 (d, 1H, J = 1.5 Hz),
4.65–4.48 (m, 3H), 3.98–3.63 (m, 3H), 3.75 (s, 3H), 3.32
(dq, 1H, J = 9.4, 4.4 Hz), 2.37 (bs, 1H), 1.54–1.50 (m, 3H),
1.32 (d, 3H, J = 4.4 Hz). 13C NMR (125 MHz, CDCl3), δ
(ppm): 142.4 (E), 141.3 (Z), 129.7, 114.1, 104.5 (E), 103.8
(Z), 99.0 (Z), 98.5 (E), 81.0, 74.7, 71.3, 70.4, 67.9, 55.3,
17.9, 12.4 (E), 9.2 (Z). HRMS (FAB), calcd. for C17H24O6
(M + 1): 324.1573, found: 324.1708.
Prop-1-enyl 3,4-O-isopropylidene-β-D-galactopyranoside (20):
Compound 20 (E:Z = 1:1) was obtained as colorless oil in
20% yield using Grubbs’ catalyst. The expected product 20
was obtained in 92% yield using catalyst 2. Rf (hex-
1
ane:EtOAc = 1:3): 0.32. For E isomer: H NMR (200 MHz,
CDCl3), δ (ppm): 6.24 (dq, 1H, J = 12.3, 1.7 Hz), 5.23–5.10
(m, 1H), 4.41 (d, 1H, J = 8.3 Hz), 4.30–4.07 (m, 2H),
4.06–3.58 (m, 4H), 2.38 (d, 1H, J = 2.4 Hz), 1.62–1.36 (m,
Prop-1-enyl 2,3,4,6-tetra-O-benzyl-α -D-mannopyranoside (24):
Compound 24 (E:Z = 1:1) was obtained as colorless syrup in
84%, Rf (hexane:EtOAc = 4:1): 0.30, E:Z = 1:1. For E iso-
1
9H). For Z isomer: H NMR (200 MHz, CDCl3), δ (ppm):
6.17 (dq, 1H, J = 6.4, 1.6 Hz), 5.23–5.10 (m, 1H), 4.70–4.57
(m, 1H), 4.41 (d, 1H, J = 8.3 Hz), 4.30–4.07 (m, 2H),
4.06–3.58 (m, 4H), 2.38 (d, 1H, J = 2.4 Hz), 1.62–1.36 (m,
9H). 13C NMR (50 MHz, CDCl3), δ (ppm): 143.6 (E), 142.6
(Z), 110.5, 105.0 (E), 104.5 (Z), 101.9 (Z), 101.3 (E), 78.7,
73.8, 73.7, 73.1, 62.2, 28.0, 26.2, 12.2 (E), 9.4 (Z). MS
(FAB) m/z: 260 (M+).
1
mer: H NMR (500 MHz, CDCl3), δ (ppm): 7.46–7.24 (m,
20H), 6.25 (dq, 1H, J = 12.3, 1.6 Hz), 5.18 (br, 1H), 5.16
(m, 1H), 4.98–4.58 (m, 8H), 4.16 (t, 1H, J = 8.6 Hz), 4.06
(dd, 1H, J = 8.6, 1.0 Hz), 3.95–3.78 (m, 4H), 1.61 (m, 3H).
For Z isomer: 1H NMR (500 MHz, CDCl3), δ (ppm):
7.46–7.24 (m, 20H), 6.21 (dq, 1H, J = 6.7, 1.6 Hz), 5.18 (br,
1H), 4.98–4.58 (m, 8H), 4.60 (m, 1H), 4.16 (t, 1H, J =
8.6 Hz), 4.06 (dd, 1H, J = 8.6, 1.0 Hz), 3.95–3.78 (m, 4H),
1.61 (m, 3H). 13C NMR (125 MHz, CDCl3), δ (ppm): 142.5
(E), 141.5 (Z), 138.5, 128.4, 128.3, 128.1, 128.0, 127.8,
127.7, 127.6, 127.5, 104.6 (E), 103.8 (Z), 98.0 (Z), 97.8 (E),
80.1, 75.3, 75.1, 74.7, 73.4, 73.3, 72.4, 72.3, 69.0, 12.5 (E),
9.3 (Z). HRMS (FAB), calcd. for C37H40O6K (M + K+):
619.2462, found: 619.2437.
Prop-1-enyl 2,3-di-O-benzyl-4-O-(p-methoxybenzyl)-α -L-rhamnopy-
ranoside (21): Compound 21 (E:Z = 1:1) was isolated from
13 as a syrup in 77% and 94% yield using Grubbs’ catalyst
(1) and catalyst 2, respectively. Rf (hexane:EtOAc = 10:1):
1
0.40. For E isomer: H NMR (500 MHz, CDCl3), δ (ppm):
7.40–6.86 (m, 14H), 6.12 (dq, 1H, J = 12.4, 1.6 Hz),
5.05–4.95 (m, 1H), 4.96 (d, 1H, J = 1.0 Hz), 4.89–4.56 (m,
© 2000 NRC Canada

844
Can. J. Chem. Vol. 78, 2000
2,3,4,6-Tetra-O-acetyl-α ,β-D-galactopyranose (25) (30): The
purified isomerized product 17 (38.8 mg, 0.1 mmol) was dis-
solved in 2 mL of acetone:water (1:1), then HgO (10.8 mg,
0.05 mmol) and HgCl2 (27.2 mg, 0.1 mmol) were added.
The reaction mixture was stirred for 20 min at room
temperature, monitored by TLC, the deprotected product
was extracted with ethyl acetate and washed with potassium
iodide solution to remove mercuric compounds. Following a
usual work-up, known compound 25 (30) was obtained in
140.2, 132.2, 130.4, 129.1, 129.0, 128.9, 128.7, 128.5,
128.4, 128.2, 128.1, 114.3, 93.0 ( β ), 92.9 (α), 83.9, 81.2,
77.2, 75.4, 73.3, 72.4, 68.2, 55.5, 18. HRMS (FAB), calcd.
for C28H33O6 (M + 1): 465.2277, found: 465.2224.
2,3,4-Tri-O-acetyl-α ,β-L-rhamnopyranose (30):
Known
compound 30 (31) was obtained from 22 as a syrup in 92%
yield, α :β = 13:1. For α anomer: 1H NMR (500 MHz,
CD3COCD3), δ (ppm): 6.02 (d, 1H, J = 4.4 Hz), 5.29 (dd,
1H, J = 10.1, 3.5 Hz), 5.17 (dd, 1H, J = 3.5, 1.8 Hz), 5.09
(dd, 1H, J = 4.4, 1.8 Hz), 4.99 (t, 1H, J = 10.1 Hz), 4.05 (m,
1H), 2.07 (s, 3H), 2.01 (s, 3H), 1.95 (s, 3H), 1.91 (s, 3H),
1.12 (d, 3H, J = 6.3 Hz). 13C NMR (125 MHz, CD3COCD3),
δ (ppm): 170.5, 170.4, 170.3, 92.6, 71.7, 71.4, 69.8, 66.6,
20.7, 17.9. HRMS (FAB), cacld. for C12H19O8 (M + 1):
291.0180, found: 291.0216.
1
92% yield, α:β = 3:1. For α anomer: H NMR (500 MHz,
CDCl3), δ (ppm): 5.47 (dd, 1H, J = 3.4, 3.3 Hz), 5.43 (m,
1H), 5.37 (dd, 1H, J = 10.9, 3.3 Hz), 5.11 (dd, 1H, J = 10.7,
3.4 Hz), 4.43 (t, 1H, J = 6.7 Hz), 4.06 (m, 1H), 4.05 (m,
1H), 3.68 (bs, 1H), 2.11 (s, 3H), 2.05 (s, 3H), 2.01 (s, 3H),
1
1.95 (s, 3H). For β anomer: H NMR (500 MHz, CDCl3), δ
(ppm): 5.43 (m, 1H), 5.37 (dd, 1H, J = 10.9, 3.3 Hz), 5.04
(m, 1H), 4.67 (dd, 1H, J = 7.8, 7.4 Hz), 4.11 (d, 1H,. J =
7.4 Hz), 4.06 (m, 1H), 4.05 (m, 1H), 3.93 (t, 1H, J =
6.7 Hz), 2.11 (s, 3H), 2.05 (s, 3H), 2.01 (s, 3H), 1.95 (s,
3H). 13C NMR (125 MHz, CDCl3), δ (ppm): 171.0, 170.6,
170.5, 170.4, 170.2, 170.1, 170.0, 95.9, 90.6, 71.0, 70.4,
68.3, 68.2, 67.2, 66.1, 61.8, 61.5, 42.4, 20.6. MS (FAB) m/z:
349 (M + 1).
4-O-(p-Methoxybenzyl)-α ,β-L-rhamnopyranose (31): Com-
pound 31 (α :β = 9:1) was obtained as colorless oil in 93%.
1
For α anomer: H NMR (500 MHz, CD3COCD3), δ (ppm):
7.29 (d, 2H, J = 8.7 Hz), 6.87 (d, 2H, J = 8.7 Hz), 5.31 (d,
1H, J = 4.0 Hz), 5.05 (bs, 1H), 4.83 (d, 1H, J = 10.9 Hz),
4.58 (d, 1H, J = 11.0 Hz), 4.00–3.80 (m, 3H), 3.76 (s, 3H),
3.32 (dd, 1H, J = 9.3, 9.0 Hz), 1.16 (d, 3H, J = 6.3 Hz). For
1
β anomer: H NMR (500 MHz, CD3COCD3), δ (ppm): 7.29
2-Acetamido-3,4-di-O-acetyl-2-deoxy-6-O-trityl-α ,β-D-gluco-
pyranose (26): Compound 26 (as an α and β mixture) was
obtained from 18 in 92% yield as colorless oil, Rf (hex-
(d, 2H, J = 8.7 Hz), 6.87 (d, 2H, J = 8.7 Hz), 5.16 (d, 1H, J
= 9.3 Hz), 4.68 (d, 1H, J = 9.3 Hz), 4.83 (d, 1H, J =
10.9 Hz), 4.58 (d, 1H, J = 11.0 Hz), 4.00–3.80 (m, 3H), 3.76
(s, 3H), 3.32 (dd, 1H, J = 9.3, 9.0 Hz), 1.19 (d, 3H, J =
5.8 Hz). 13C NMR (125 MHz, CD3COCD3), δ (ppm): 160.0,
132.4, 130.3, 114.3, 95.0, 82.2, 74.8, 73.2, 72.4, 67.6, 55.5,
14.5. HRMS (FAB), calcd. for C14H20O6K (M + K+):
323.0897, found: 323.1397.
1
ane:EtOAc = 1:1): 0.20. For α anomer: H NMR (200 MHz,
CDCl3), δ (ppm): 7.33 (m, 15H), 5.79 (d, 1H, J = 9.3 Hz),
5.30–5.18 (m, 3H), 4.33–4.12 (m, 2H), 3.55 (d, 1H, J =
2.5Hz), 3.20 (dd, 1H, J = 10.4, 2.1 Hz), 3.04 (dd, 1H, J =
10.4, 4.6 Hz), 1.98 (s, 3H), 1.91 (s, 3H), 1.70 (s, 3H). For β
1
anomer: H NMR (200 MHz, CDCl3), δ (ppm): 7.33 (m,
15H), 5.79 (d, 1H, J = 9.3 Hz), 5.30–5.18 (m, 2H),
4.33–4.12 (m, 3H), 4.12 (m, 1H), 3.55 (d, 1H, J = 2.5Hz),
3.20 (dd, 1H, J = 10.4, 2.1 Hz), 3.04 (dd, 1H, J = 10.4,
4.6 Hz), 1.98 (s, 3H), 1.91 (s, 3H), 1.70 (s, 3H). MS
(FAB) m/z: 471 (M + 1).
2,3,4,6-Tetra-O-benzyl-α ,β-D-mannopyranose (32): Com-
pound 32 (α:β = 3:1) was obtained as colorless oil in 78%
yield, Rf (hexane:EtOAc = 4:1): 0.20. For α anomer: 1H
NMR (500 MHz, CDCl3), δ (ppm): 7.60–7.00 (m, 20H),
5.25 (d, 1H, J = 1.6Hz), 5.05–4.49 (m, 8H), 4.04 (m, 1H),
3.96 (dd, 1H, J = 9.6, 2.8 Hz), 3.86 (t, 1H, J = 9.6 Hz), 3.79
(dd, 1H, J = 2.8, 1.6 Hz), 3.73–3.67 (m, 2H). For β anomer:
1H NMR (500 MHz, CDCl3), δ (ppm): 7.60–7.00 (m, 20H),
5.05–4.49 (m, 9H), 4.04 (m, 1H), 3.96 (dd, 1H, J = 9.6,
2.8 Hz), 3.86 (t, 1H, J = 9.6 Hz), 3.79 (dd, 1H, J = 2.8,
1.6 Hz), 3.73–3.67 (m, 2H). 13C NMR (125 MHz, CDCl3), δ
(ppm): 138.4, 138.4, 138.3, 138.0, 128.5, 128.5, 128.3,
128.3, 128.1, 128.0, 127.9, 127.9, 127.8, 127.8, 127.7,
127.6, 127.6, 127.5, 127.5, 93.7 ( β isomer), 92.7 (α isomer),
79.7, 74.6, 73.3, 72.7, 72.6, 72.2, 71.5, 69.6. MS (FAB) m/z:
541 (M + 1).
3,4-O-Isopropylidene-α ,β-D-galactopyranose (28): Com-
pound 28 (α :β = 2:1) was obtained as a syrup in 90% yield
from 20, Rf (EtOAc): 0.23. For α anomer: 1H NMR
(500 MHz, CDCl3), δ (ppm): 5.61 (bs, 1H), 5.23 (bs, 1H),
4.30–3.5 (m, 6H), 1.49 (s, 3H), 1.30 (s, 3H). For β anomer:
1H NMR (500 MHz, CDCl3), δ (ppm): 6.32 (bs, 1H), 4.65
(bs, 1H), 4.30–3.5 (m, 6H), 1.49 (s, 3H), 1.30 (s, 3H). 13C
NMR (125 MHz, CDCl3), δ (ppm): 110.4 ( β ), 109.8 (α),
95.9 (β isomer), 91.3 (α), 79.1, 75.6, 74.3, 74.1, 73.8, 73.4,
69.2, 68.9, 62.5, 62.2, 28.0, 27.4, 26.3, 25.7. HRMS (FAB),
calcd. for C9H17O6 (M + 1): 221.1025, found: 221.1289.
2,3-Di-O-benzyl-4-O-(p-methoxybenzyl)-α ,β-L-rhamnopyranose
(29): Compound 29 (α :β = 5:1) was obtained as syrup in
91% yield, Rf (hexane:EtOAc = 4:1): 0.25. For α anomer: 1H
NMR (500 MHz, CD3COCD3), δ (ppm): 7.43–7.24 (m,
12H), 6.86 (d, 2H, J = 8.6 Hz), 5.17 (s, 1H), 4.84–4.57 (m,
6H), 3.89 (m, 2H), 3.82 (m, 1H), 3.77 (s, 3H), 3.52 (t, 1H, J
1,2:3,4-Di-O-isopropylidene-6-O-(prop-1-enyl)-α -D-galactopyr-
anose (34): Compound 34 was obtained from 33 (32) in
95% yield as a syrup, Rf (hexane:EtOAc = 1:6): 0.40. E:Z =
1
5:1. For E-isomer, H NMR (500 MHz, CDCl3), δ (ppm):
6.20 (dq, 1H, J = 12.6, 1.6 Hz), 5.50 (d, 1H, J = 5.0 Hz),
4.77 (m, 1H), 4.57 (dd, 1H, J = 7.9, 2.5 Hz), 4.28 (dd, 1H, J
= 5.0, 2.5 Hz), 4.22 (dd, 1H, J = 7.9, 2.0 Hz), 3.99 (m, 1H),
3.80 (dd, 1H, J = 10.3, 5.9 Hz), 3.74 (dd, 1H, J = 10.3,
6.8 Hz), 1.54 (dd, 3H, J = 6.8, 1.7 Hz), 1.41 (s, 3H), 1.30 (s,
3H), 1.29 (s, 6H). 13C NMR (125 MHz, CDCl3), δ (ppm):
146.2, 109.3, 108.6, 98.9, 96.3, 70.6, 70.5, 67.4, 66.1, 25.9,
1
= 9.1 Hz), 1.18 (d, 3H, J = 6.2 Hz). For β anomer: H NMR
(500 MHz, CD3COCD3), δ (ppm): 7.43–7.24 (m, 12H), 6.86
(d, 2H, J = 8.6 Hz), 4.84–4.57 (m, 7H), 3.89 (m, 2H), 3.82
(m, 1H), 3.77 (s, 3H), 3.52 (t, 1H, J = 9.1 Hz), 1.18 (d, 3H,
J = 6.2 Hz). 13C NMR (125 MHz, CD3COCD3), δ (ppm):
© 2000 NRC Canada

Hu et al.
845
U. Moller, N. Debski, and P. Welzel. Tetrahedron Lett. 34,
5871 (1993); (c) B. Yu, B. Li, J. Zhang, and Y. Hui. Tetrahe-
dron Lett. 39, 4871 (1998).
24.9, 24.4, 12.4. HRMS (FAB), calcd. for C15H25O6 (M + 1):
301.1691, found: 301.1624.
1,2:3,4-Di-O-isopropylidene-α -D-galactopyranose (35):
Known compound 352 was obtained from 34 in 91% yield as
colorless oil, Rf (hexane:EtOAc = 1:3): 0.30. 1H NMR
(200 MHz, CDCl3), δ (ppm): 5.55 (d, 1H, J = 5.0 Hz), 4.60
(dd, 1H, J = 7.9, 2.2 Hz), 4.32 (dd, 1H, J = 5.0, 2.2 Hz),
4.25 (dd, 1H, J = 7.9, 1.2 Hz), 3.86–3.80 (m, 4H), 1.51 (s,
3H), 1.44 (s, 3H), 1.32 (s, 6H).
13. (a) S.T. Nguyen, L.K. Johnson, and R.H. Grubbs. J. Am.
Chem. Soc. 114, 3974 (1992); (b) M. Schuster and S. Blechert.
Angew. Chem. Int. Ed. Engl. 36, 2036 (1997); (c) S.K.
Armstrong. J. Chem. Soc. Perkin Trans. 1, 371 (1998); (g)
S.C.G. Biagini, S.E. Gibson, and S.P.J. Keen. J. Chem. Soc.
Perkin Trans. 1, 2485 (1998).
14. For a review see: R. Roy and S. Das. Chem. Commun. 519
(2000).
15. H.E. Applegate, C.M. Cimarusti, J.E. Dolfini, P.T. Funke,
W.H. Koster, M.S. Puar, W.A. Slusarchyk, and M.G. Young. J.
Org. Chem. 44, 811 (1979).
16. F.M. Winnik, J.P. Carver, and J.J. Krepinski. J. Org. Chem. 47,
2701 (1982).
17. D.L. Pavia, G.M. Lampman, and G.S. Kriz. In Introduction to
spectroscopy. Harcourt Brace College Publishers, Washington.
1996.
Acknowledgements
Support of this work by the Natural Sciences and Engi-
neering Research Council of Canada (NSERC) is gratefully
acknowledged.
References
18. D.V. McGrath and R.H. Grubbs. Organometallics, 13, 224
(1994).
19. Z. Wu, S.T. Nguyen, R.H. Grubbs, and J.W. Ziller. J. Am.
Chem. Soc. 117, 5503 (1995).
20. S.P. Chavan, P.K. Zubaidha, S.W. Dantale, A. Keshavaraja, A.
Ramaswamy, and T. Ravindranathan. Tetrahedron Lett. 36, 237
(1995).
21. M. Ochiai, T. Ito, H. Takahashi, A. Nakanishi, M. Toyonari, T.
Sueda, S. Goto, and M. Shiro. J. Am. Chem. Soc. 118, 7716
(1996).
1. (a) T.W. Greene and P.G.M. Wuts. In Protective groups in or-
ganic synthesis. John Wiley and Sons, New York. 1991. p. 42;
(b) R. Gigg and C.D. Warren. J. Chem. Soc. 2205 (1965);
(c) P.A. Gent, R. Gigg, and A.A.E. Penglis. J. Chem. Soc.
Perkin Trans. 1, 1395 (1976).
2. (a) T.J. Prosser. J. Am. Chem. Soc. 83, 1701 (1961); (b) C.C.
Price and W.H. Snyder. J. Am. Chem. Soc. 83, 1773 (1961).
3. S.M. Kadam, S.K. Nayak, and A. Banerji. Tetrahedron Lett.
33, 5129 (1992).
4. (a) E.J. Corey and J.W. Suggs. J. Org. Chem. 38, 3223 (1973);
(b) G.-J. Boons, A. Burton, and S. Isles. Chem. Commun. 141
(1996).
22. R. Beugelmans, S. Bourdet, A. Bigot, and J. Zhu. Tetrahedron
Lett. 35, 4349 (1994).
23. (a) C.D. Warren and R.W. Jeanloz. Carbohydr. Res. 53, 67
(1977); (b) T. Nishiguchi, K. Tachi, and K. Fukuzumi. J. Org.
Chem. 40, 237 (1975); (c) C.A.A. van Boeckel and J.H. van
Boom. Tetrahedron, 3561 (1979).
24. J.M. Reuter and R.G. Salomon. J. Org. Chem. 42, 3360
(1977).
25. A. Zoran and Y. Sasson. J. Org. Chem. 46, 255 (1981).
26. R.T. Lee and Y.C. Lee. Carbohydr. Res. 37, 193 (1974).
27. B. Fraser-Reid, U.E. Udodong, Z. Wu, H. Ottosson, J.R.
Merritt, C.S. Rao, C. Roberts, and R. Madsen. Synlett, 927
(1992).
28. L. Valente, A. Olesker, R. Rabanal, L.E.S. Barata, G. Lukacs,
and T.T. Thang. Tetrahedron Lett. 13, 1153 (1979).
29. M.A. Nashed, C.W. Slife, M. Kiso, and L. Anderson.
Carbohydr. Res. 82, 237 (1980).
5. (a) D. Baudry, M. Ephritikhine, and H. Felkin. Chem.
Commun. 694 (1978); (b) J.J. Oltvoort, C.A.A. van Boeckel,
J.H. DeKoning, and J.H. van Boom. Synthesis, 305 (1981).
6. R. Boss and R. Scheffold. Angew. Chem. Int. Ed. Engl. 15,
588 (1976).
7. M. Honda, H. Morita, and I. Nagakura. J. Org. Chem. 62, 8932
(1997).
8. K.C. Nicolaou, C.W. Hummel, N.J. Bockovich, and C.-H.
Wong. Chem. Commun. 870 (1991).
9. J.V. Crivello and S. Kong. J. Org. Chem. 63, 6745 (1998).
10. R. Gigg and C.D. Warren. J. Chem. Soc. C, 1903 (1968).
11. (a) M. Bruce and Y. Roshan-Ali. J. Chem. Res. Synop., 193
(1981); (b) T. Ogawa, T. Kitajima, and T. Nukada. Carbohydr.
Res. 123, C5 (1983); (c) T. Ogawa and S. Nakabayasi.
Carbohydr. Res. 93, C1 (1981); (d) H.B. Mereyala and S.
Guntha. Tetrahedron Lett. 34, 6929 (1993).
30. M. Mikamo. Carbohydr. Res. 191, 150 (1989).
31. V. Pozsgay and A. Neszmelyi. Carbohydr. Res. 80, 196 (1980).
32. T. Bieg and W. Szeja. J. Carbohyd. Chem. 4, 441 (1985).
12. (a) K. Nakayama, K. Uoto, K. Higashi, T. Soga, and T.
Kusama. Chem. Pharm. Bull. 40, 1718 (1992); (b) J. Luning,
2 The spectral data of 35 were identical with the product from Aldrich Chemical Co.
© 2000 NRC Canada