Regioselective debenzylation of C-glycosyl compounds by boron trichloride

Article abstract of DOI:10.1016/j.carres.2004.12.001

Boron trichloride has been found to promote selective deprotection of 1,2- or 1,3-cis oriented secondary benzyl ethers of per-benzylated C-glycosyl derivatives. The reactivity towards BCl₃ follows the order: C-4 ≥ C-2 > C-6 > C-3 for C-glucopyranosyl derivatives and C-3 ≥ C-4 > C-6 > C-2 for C-galactopyranosyl derivatives. Preparatively useful selective debenzylation at secondary positions was possible after careful control of reaction conditions.

Full text of DOI:10.1016/j.carres.2004.12.001

Carbohydrate
RESEARCH
Carbohydrate Research 340 (2005) 481–487
Note
Regioselective debenzylation of C-glycosyl compounds by
boron trichloride
a
a
Juan Xie,a,b, Mickael Menand and Jean-Marc Valery
*
´
´
¨
a
`
Synthese, Structure et Fonction des Molecules Bioactives, CNRS UMR 7613, Equipe Chimie des Glucides,
´
´
Universite Pierre et Marie Curie, 4 Place Jussieu, F-75005 Paris, France
´
b
´
Laboratoire de Photophysique et Photochimie Supramoleculaires et Macromoleculaires, CNRS UMR 8531, Ecole Normale
´
t
Superieure de Cachan, 61 Avenue du P Wilson, F-94235 Cachan, France
Received 13 October 2004; received in revised form 17 November 2004; accepted 2 December 2004
Available online 29 December 2004
Abstract—Boron trichloride has been found to promote selective deprotection of 1,2- or 1,3-cis oriented secondary benzyl ethers of
per-benzylated C-glycosyl derivatives. The reactivity towards BCl3 follows the order: C-4 P C-2 > C-6 > C-3 for C-glucopyranosyl
derivatives and C-3 P C-4 > C-6 > C-2 for C-galactopyranosyl derivatives. Preparatively useful selective debenzylation at second-
ary positions was possible after careful control of reaction conditions.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Keywords: Boron trichloride; C-Glycosyl compounds; Regioselective debenzylation
C-Glycosyl compounds, especially C-alcenyl derivatives,
are useful precursors not only for the synthesis of meta-
bolically and chemically stable glycoconjugates,1 but
also for the construction of natural products such as
ciguatoxin,2 brevetoxin B,3 hemibrevetoxin B,4,5 gambi-
erol,5,6 maitotoxin,7 prelaureatin,8 okadaic acid,9 verru-
carol10 or ezomycins.11 In these multistep syntheses, the
protection–deprotection strategy is a basic approach.
Among the wide range of protecting groups, the benzyl
ether is frequently used owing to its ease of formation,
inherent stability and variety of methods available for
its deprotection. Selective removal of a benzyl ether
functionality in an easily available per-O-benzylated
precursor would be of considerable interest to minimize
the number of transformations required. Several debenz-
ylation methods (acetolysis, catalytic hydrogenolysis
and Lewis acids such as SnCl4, TiCl4 or CrCl2/LiI) have
been studied for the preparation of partially benzylated
monosaccharides.12 The selective debenzylation has
equally been achieved with TIBAL/DIBAL-H,13
TMSI,12a NIS or a combination of diacetoxyiodobenz-
ene/iodine.14
During the course of our research towards the synthe-
sis of selectively protected C-glycosyl building blocks,
we have recently discovered a new regioselective debenz-
ylation reaction by boron trichloride (Scheme 1). BCl3
has been used in the cleavage of methylene or benzylid-
ene acetals and methyl or benzyl ethers/esters,15 or in the
N3
1) BCl3 (2.5 equiv),
O
CH2Cl2, -78°C
OBn
2) Ac2O, pyridine
98 %
N3
O
AcO
OAc
OBn
2
BnO
N3
O
1) BCl3 (2.5 equiv),
CH2Cl2, -78°C
OBn
1
OBn
2) NaH, MeI
85 %
MeO
OMe
3
*
Corresponding author. Tel.: +33 1 47405339; fax: +33 1 47402454;
e-mail: joanne.xie@ppsm.ens-cachan.fr
Scheme 1.
0008-6215/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2004.12.001

482
J. Xie et al. / Carbohydrate Research 340 (2005) 481–487
regeneration of free amino acids from N-benzyloxycar-
bonyl-5-oxazolidinones and from N-benzyloxycarbon-
ylamino derivatives.16 However, the regioselectivity of
the BCl3 promoted deprotection reaction has never been
reported.17 We describe herein the utility of this reagent
for the regioselective debenzylation of per-benzylated C-
glycosyl compounds.
pounds has been studied and the results are compiled
in Tables 1 and 2. Reaction of b-C-allyl-D-glucosyl
derivative 418 with BCl3 (2.5 equiv) followed by acetyla-
tion led to a mixture of 2,4-di-O-acetyl (5a, 67%) and
2,3,4-tri-O-acetyl (5b, 31%) derivatives, separable by
chromatography on silica gel (entry 4). In the case of
the b-C-vinyl D-glucosyl derivative 6,20 the 4-O-benzyl
ether was split more readily than the 2-O-benzyl group
(entries 5 and 6). On prolonged treatment, 4-O-acetyl
(7a, 25%), 2,4-di-O-acetyl (7b, 38%) and peracetylated
derivatives (7c, 15%) have been isolated (entry 7). Com-
plete deprotection can be achieved with an excess of
BCl3 in 64% yield (entry 8). It is not excluded that the
cis-oriented allyl or vinyl group assisted the 3-O-benzyl
ether cleavage in 4 and 6 as compared to 1. The per-benz-
ylated a-C-glucosyl compound 821 seemed to be more
reactive than the azido derivatives 1 and 6: 1.25 equiv
of BCl3 was sufficient to convert all the starting material
into the 2,4-di-O-acetyl (9a, 70%) and 2,4,6-tri-O-acetyl
derivative (9b, 11%) (entry 9). On prolonged treatment,
compound 9b became predominant (entry 11 vs 10) and
an excess of reagent brought progressively the reaction
to complete deprotection (entries 12 and 13), accompa-
nied by partial decomposition of the product (entry
13). These results show that the ease of cleavage of
Treatment of a-C-allyl-D-glucosyl derivative 118 with
BCl3 at ꢀ78 ꢁC followed by acetylation gave 2 as the
sole product in nearly quantitative yield (Scheme 1).
This debenzylation is optimal with 2.5 equiv of BCl3
(Table 1, entry 1–3). The 3-O-benzyl group is not
cleaved even with an excess of reagent (entry 3). This
remarkable selectivity may be explained by prior com-
plexation of the oxygenophilic boron atom with the
cis-oriented C-2 and C-4 benzyloxy groups, which al-
lowed the subsequent deprotection. It is to be noted that
19
the use of BCl3ÆSMe2 instead of BCl3 led to a mixture
of several debenzylated products. The regioselective
deprotection of 1 can be applied to large-scale prepara-
tions (up to 20 mmol). Other protecting groups can eas-
ily be introduced in 2- and 4-positions: compound 3 was
isolated in 85% overall yield (Scheme 1).
In order to study the scope and regioselectivity of this
reaction, a panel of per-benzylated C-glycosyl com-
Table 1. BCl3-promoted debenzylation of C-glucopyranosyl compounds
OR4
O
OR3
O
N3
N3
N3
O
O
O
R3O
R2O
R2O
R1O
R3O
R2O
R3O
R2O
R3O
R2O
OR1
NHAc
OR1
OR1
OR1
1: R1=R2=R3=Bn
4: R1=R2=R3=Bn
5a: R2=Bn, R1=R3=Ac
5b: R1=R2=R3=Ac
8: R1=R2=R3=R4=Bn
10: R1=R2=R3=Bn
11a: R2=R3=Bn, R1=Ac
11b: R2=Bn, R1=R3=Ac
11c: R1=R2=R3=Ac
6: R1=R2=R3=Bn
2: R2=Bn, R1=R3=Ac
9a: R2=R4=Bn, R1=R3=Ac
9b: R2=Bn, R1=R3=R4=Ac
9c: R1=R2=R3=R4=Ac
7a: R1=R2=Bn, R3=Ac
7b: R2=Bn, R1=R3=Ac
7c: R1=R2=R3=Ac
Entry
Reactant
BCl3 (equiv)
Time (h)
Product (% yield)a
SMb
Glu(OAc)
Glu(OAc)2
Glu(OAc)3
Glu(OAc)4
1
1
1.25
2.5
7.5
2.5
1.25
2.5
2.5
7.5
1.25
2.5
2.5
7.5
7.5
2.5
3.5
3.5
2
2
2
2
2
1
2
1
1
1
2
0.5
2
1
1
2
1c
—
—
—
—
—
—
—
—
2
1
2 (98%)d
2 (85%)d
5a (67%)d
—
3
1
—
—
—
—
—
—
—
4
4
5b (31%)d
—
—
5
6
6 (28%)
6 (12%)
7a (30%)
7a (36%)
—
—
6
6
—
7b (38%)
—
7
6
—
—
7a (25%)
—
7c (15%)
7c (64%)
9b (11%)
9b (20%)
9b (40%)
9b (38%)
—
–
—
8
6
9
8
—
—
—
—
9a (70%)
9a (60%)
9a (35%)
9a (10%)
—
—
—
10
11
12
13
14
15
16
8
8
—
—
—
—
—
8
9c (25%)
9c (44%)
—
8
—
10 (33%)
—
10
10
10
11a (32%)
11a (19%)
—
—
11b (12%)
11b (35%)
—
11c (40%)
11c (55%)
—
—
—
—
a Isolated yield after acetylation and purification by preparative thin-layer chromatography.
b Starting material.
c Majority of the starting material was recovered.
d Isolated yield after flash chromatography on 3 mmol scale.

J. Xie et al. / Carbohydrate Research 340 (2005) 481–487
Table 2. BCl3-promoted debenzylation of a-C-allyl-galactopyranosyl compounds
483
OR4
O
14: R1=R2=R3=R4=Bn
N3
15a: R1=R3=R4=Bn, R2=Ac
15b: R1=R4=Bn, R2=R3=Ac
15c: R1=Bn, R2=R3=R4=Ac
15d: R1=R2=R3=R4=Ac
O
12: R1=R2=R3=Bn
13a: R1=Bn, R2=R3=Ac
13b: R1=R2=R3=Ac
R3O
R2O
R3O
R2O
OR1
OR1
Entry
Reactant
BCl3 (equiv)
Time (h)
Product (% yield)a
SMb
12 (15%)
—
Gal(OAc)
Gal(OAc)2
Gal(OAc)3
Gal(OAc)4
1
2
3
4
5
6
7
12
12
12
14
14
14
14
1.25
2.5
7.5
1.25
2.5
5
2
2
1
2
2
2
2
—
—
13a (51%)
13a (67%)
13a (25%)
15b (42%)
15b (20%)
—
—
—
—
13b (20%)
13b (15%)
15c (28%)
15c (25%)
15c (40%)
15c (20%)
—
14 (17%)
—
15a (5%)
—
—
—
—
—
—
—
—
15d (35%)
15d (53%)
15d (60%)
7.5
—
a Isolated yield after acetylation and purification by preparative thin-layer chromatography.
b Starting material.
per-benzylated C-glucosyl compounds follows the order
C-4 P C-2 > C-6 > C-3.
with other methods. Preparatively useful selective de-
benzylation of per-benzylated C-glycosyl compounds
at secondary positions was possible after careful control
of reagent amount and reaction time. Finally, all the
partially debenzylated products reported are new C-gly-
cosyl derivatives, which should be useful synthetic
intermediates.
However, the 3-O-benzyl group is split first when the
2-O-benzyl ether is replaced by an acetamido group
(compound 10,22 entry 14). Because of the presence of
the acetamido group, 3.5 equiv of BCl3 were necessary
to consume all the starting material (entries 15 and
16). The relative ease of removal of benzyl groups fol-
lows the order C-3 > C-6 > C-4 for the amino C-gluco-
syl compound 10. The regioselective O-debenzylation
by anchimeric assistance has already been observed.23
Table 2 reports on the debenzylation of per-benzy-
lated a-C-allyl-D-galactopyranosyl compounds. Entries
1 and 2 show that the cis-oriented C-3 and C-4 benzyl-
oxy groups of compound 12 are more reactive than
the C-2 substituent. The 3,4-di-O-acetyl compound 13a
can be isolated in 67% yield (entry 2). However, as in
the case of compound 8 (Table 1, entry 13), use of
7.5 equiv of BCl3 led to lower yields of products (entry
3). Concerning the tetra-O-benzylated a-C-galactosyl
compound 14,21 a moderate regioselectivity was ob-
served (entries 4 and 5). Treatment of 14 with more than
5 equivalents of reagent furnished the tri- and tetra-O-
debenzylated derivatives 15c and 15d (entries 6 and 7).
In the light of these results, the reactivity of a-C-galac-
tosyl compounds towards BCl3 follows the order: C-
3 P C-4 > C-6 > C-2. Furthermore, the trans-oriented
C-2 benzyl group in 12 and 14 was only partially
deprotected with an excess of reagent (entries 3, 6
and 7).
1. Experimental
1.1. General methods
1H and 13C NMR spectra were recorded on a Bruker
AGH-250 spectrometer in CDCl3 solns. Optical rota-
tions were measured using a Perkin–Elmer 141 polari-
meter and a 10-cm cell. Column chromatography was
performed on E. Merck Silica Gel 60 (230–400 mesh).
Analytical thin-layer chromatography was performed
on E. Merck aluminum precoated plates of Silica Gel
60F-254 with detection by UV and by spraying with
6 N H2SO4 and heating about 2 min at 300 ꢁC. Dichlo-
romethane and pyridine were distilled over CaH2.
Microanalyses were performed at the Service de Micro-
´
analyse de lꢀUniversite Pierre et Marie Curie.
1.2. General procedure for the debenzylation of per-
benzylated C-glycosyl compounds
To a soln of the per-benzylated C-glycosyl derivative
(0.1 mmol) in dry CH2Cl2 (2 mL) under an argon atmo-
sphere, was added slowly boron trichloride (1 M soln in
CH2Cl2) via a syringe at ꢀ78 ꢁC, and the mixture was
further stirred at this temperature. After the indicated
time (Tables 1 and 2), the reaction was quenched with
1:1 MeOH–CH2Cl2 (2 mL) and concentrated under
diminished pressure. The resulting residue was dissolved
In conclusion, we have reported a new regioselective
debenzylation of C-glycosyl compounds. BCl3 has been
found to be efficient to promote selective deprotection of
1,2- or 1,3-cis oriented secondary benzyl ethers. This
process, with an operationally simple protocol, comple-
ments the already existing methodologies and unravels
possibilities for selectivities that have not been achieved

484
J. Xie et al. / Carbohydrate Research 340 (2005) 481–487
in 2:1 pyridine–Ac2O (1.5 mL) and stirred for 15 h at rt.
After concentration under diminished pressure, the res-
idue was dissolved in EtOAc, washed with water, dried
over MgSO4, concentrated and purified by preparative
TLC (Et2O–cyclohexane or EtOAc–cyclohexane).
(C-3). Anal. Calcd for C18H25N3O4: C, 62.23; H, 7.25;
N, 12.10. Found: C, 62.01; H, 7.33; N, 12.19.
1.2.3.
3-(20,40-Di-O-acetyl-60-azido-30-O-benzyl-60-
deoxy-b-D-glucopyranosyl)-1-propene (5a). [a]D ꢀ8.6
(c 1, CH2Cl2), Rf 0.69 (2:3 EtOAc–cyclohexane); 1H
NMR (CDCl3, 250 MHz) 7.29–7.17 (m, 5H, Ph), 5.89–
5.72 (m, 1H, CH@), 5.07–5.01 (m, 2H, CH2@), 4.92 (t,
J 9.8 Hz, 1H, H-20 or 40), 4.91 (t, J 9.5 Hz, 1H, H-40
or 20), 4.56 (s, 2H, CH2–Ph), 3.63 (t, J 9.3 Hz, 1H, H-
30), 3.52–3.43 (m, 1H, H-50), 3.40–3.34 (m, 1H, H-10),
3.26 (dd, J 13.3, 7.5 Hz, 1H, H-60a), 3.07 (dd, J 13.3,
2.5 Hz, 1H, H-60b), 2.25–2.22 (m, 2H, H-3), 1.95 (s,
3H, Ac), 1.92 (s, 3H, Ac). 13C NMR (CDCl3,
62.9 MHz) d 169.7, 169.6 (CO), 138.0 (Cipso), 133.2
(CH@), 128.6, 127.9, 127.8 (Ph), 117.9 (CH2@), 81.7
(C-30), 77.7 (C-10,50), 74.2 (CH2–Ph), 73.1, 71.4 (C-
20,40), 51.7 (C-60), 36.1 (C-3), 21.0, 20.9 (Me). Anal.
Calcd for C20H25N3O6: C, 59.54; H, 6.25; N, 10.42.
Found: C, 59.09; H, 6.21; N, 10.51.
1.2.1.
3-(20,40-Di-O-acetyl-60-azido-30-O-benzyl-60-
deoxy-a-D-glucopyranosyl)-1-propene (2). [a]D +47.5 (c
0.91, CH2Cl2), Rf 0.62 (2:3 EtOAc–cyclohexane); 1H
NMR (CDCl3, 250 MHz): 7.32–7.23 (m, 5H, Ph),
5.82–5.66 (m, 1H, CH@), 5.14–5.06 (m, 2H, CH2@),
4.91 (dd, J 6.3, 4.0 Hz, 1H, H-20), 4.82 (t, J 6.0 Hz,
1H, H-40), 4.66 (d, J 12.0 Hz, 1H, CH–Ph), 4.57 (d, J
11.8 Hz, 1H, CH–Ph), 4.16-4.06 (m, 1H, H-10), 3.87
(ddd, J 8.1, 5.8, 3.9 Hz, 1H, H-50), 3.75 (t, J 6.3 Hz,
1H, H-30), 3.51 (dd, J 13.1, 8.1 Hz, 1H, H-60a), 3.17
(dd, J 13.1, 3.9 Hz, 1H, H-60b), 2.52–2.35 (m, 1H, H-
3a), 2.33–2.15 (m, 1H, H-3b), 2.02 (s, 3H, Ac), 1.97 (s,
3H, Ac). 13C NMR (CDCl3, 62.9 MHz): d 170.3, 170.1
(CO), 137.9 (Cipso), 133.5 (CH@), 128.9, 128.4, 128.1
(Ph), 118.3 (CH2@), 75.5 (C-30), 74.1 (CH2–Ph), 72.8
(C-50), 70.7 (C-20), 69.9, 69.8 (C-10,40), 50.7 (C-60), 33.1
(C-3), 21.3 (Me). Anal. Calcd for C20H25N3O6: C,
59.54; H, 6.25; N, 10.42. Found: C, 59.88; H, 6.30; N,
10.29.
1.2.4.
3-(20,30,40-Tri-O-acetyl-60-azido-60-deoxy-b-D-
glucopyranosyl)-1-propene (5b). [a]D +7.1 (c 1,
CH2Cl2), Rf 0.54 (2:3 EtOAc–cyclohexane); H NMR
1
(CDCl3, 250 MHz): 5.89–5.78 (m, 1H, CH@), 5.17 (t,
J 9.8 Hz, 1H), 5.11–5.04 (m, 2H, CH2@), 4.97 (t, J
9.8 Hz, 1H), 4.91 (t, J 9.5 Hz, 1H), 3.63 (ddd, J 9.5,
7.0, 3.3 Hz, 1H, H-50), 3.54 (ddd, J 9.8, 7.0, 4.0 Hz,
1H, H-10), 3.29 (dd, J 12.8, 7.0 Hz, 1H, H-60a), 3.21
(dd, J 13.3, 3.0 Hz, 1H, H-60b), 2.34–2.25 (m, 2H, H-
3), 2.04 (s, 3H, Ac), 2.03 (s, 3H, Ac), 2.00 (s, 3H, Ac).
13C NMR: (CDCl3, 62.9 MHz) d 170.6, 169.7 (CO),
132.7 (CH@), 118.3 (CH2@), 77.3, 74.3, 71.7, 69.9
(CH), 51.4 (C-60), 36.0 (C-3), 20.8 (Me). Anal. Calcd
for C15H21N3O7: C, 50.70; H, 5.96; N, 11.83. Found:
C, 50.51; H, 6.01; N, 11.77.
1.2.2.
3-(60-Azido-30-O-benzyl-60-deoxy-20,40-di-O-
methyl-a-D-glucopyranosyl)-1-propene (3). Compound
118 (3.2 g, 6.41 mmol) in dry CH2Cl2 (200 mL) was de-
benzylated with BCl3 (2.5 equiv, 16 mL) during 1 h 30 at
ꢀ78 ꢁC as described above. The reaction mixture was
then quenched with 1:1 MeOH–CH2Cl2 (130 mL) and
concentrated under diminished pressure. The residue
was dissolved in EtOAc and washed with 5% aq NaH-
CO3, water and brine, dried over MgSO4 and concen-
trated. A soln of the resulting residue (2.04 g) in dry
DMF (10 mL) was added to a mixture of NaH
(450 mg, 18.8 mmol) in DMF (15 mL) at 0 ꢁC. After
30 min, MeI (1.1 mL, 18.8 mmol) was added. The mix-
ture was allowed to warm at rt and was then stirred
overnight. After concentration, the residue was diluted
in EtOAc and water and extracted. The organic layer
was washed with brine, dried (MgSO4) and concentrated
to give 3 as an oil (1.88 g, 85%). [a]D +71.6 (c 1,
1.2.5. (40-O-Acetyl-60-azido-20,30-di-O-benzyl-60-deoxy-b-
D-glucopyranosyl)-ethene (7a). [a]D +3.4 (c 0.7,
CH2Cl2), Rf 0.62 (1:2 EtOAc–cyclohexane); H NMR
1
(CDCl3, 250 MHz): 7.36–7.26 (m, 10H, Ph), 6.05–5.91
(m, 1H, CH@), 5.52–5.30 (m, 2H, CH2@), 4.98 (t, J
9.5 Hz, 1H, H-40), 4.88 (d, J 11.5 Hz, 1H, CH–Ph),
4.76 (d, J 10.8 Hz, 1H, CH–Ph), 4.68 (d, J 11.5 Hz,
1H, CH–Ph), 4.66 (d, J 10.8 Hz, 1H, CH–Ph), 3.85
(dd, J 9.5, 5.5 Hz, 1H, H-10), 3.69 (t, J 9.3 Hz, 1H, H-
30), 3.56 (ddd, J 9.5, 6.6, 3.3 Hz, 1H, H-50), 3.38 (t, J
9.3 Hz, 1H, H-20), 3.31 (dd, J 13.5, 6.5 Hz, 1H, H-60a),
3.22 (dd, J 13.3, 3.0 Hz, 1H, H-60b), 1.94 (s, 3H, Ac).
13C NMR (CDCl3, 62.9 MHz): d 169.9 (CO), 138.3,
137.8 (Cipso), 134.4 (CH@), 128.6, 128.2, 128.1, 127.9
(Ph), 118.1 (CH2@), 83.9 (C-30), 82.5 (C-20), 79.7 (C-
10), 77.2 (C-50), 75.4 (CH2–Ph), 71.5 (C-40), 51.7
(C-60), 21.0 (Me). Anal. Calcd for C24H27N3O5: C,
65.89; H, 6.22; N, 9.60. Found: C, 65.74; H, 6.33; N,
9.69.
1
CH2Cl2), Rf 0.47 (1:4 EtOAc–cyclohexane); H NMR
(CDCl3, 250 MHz): d 7.39–7.26 (m, 5H, Ph), 5.92–5.73
(m, 1H, CH@), 5.19–5.10 (m, 2H, CH2@), 4.88 (d, J
11.0 Hz, 1H, CH–Ph), 4.75 (d, J 11.0 Hz, 1H, CH–
Ph), 4.21–4.13 (m, 1H, H-10), 3.65–3.55 (m, 2H, H-
30,50), 3.53 (s, 3H, OMe), 3.47 (s, 3H, OMe), 3.48–3.41
(m, 2H, H-20,60b), 3.34 (dd, J 13.1, 5.3 Hz, 1H, H-60a),
3.15 (dd, J 9.5, 8.5 Hz, 1H, H-40), 2.40–2.38 (m, 2H,
H-3). 13C NMR (CDCl3, 62.9 MHz): d 138.8 (Cipso),
134.4 (CH@), 128.5, 128.0, 127.8 (Ph), 117.2 (CH2@),
81.9, 81.8 (C-20,30), 80.7 (C-40), 75.2 (CH2–Ph), 73.1
(C-10), 71.2 (C-50), 60.9, 58.8 (OMe), 51.8 (C-60), 30.3

J. Xie et al. / Carbohydrate Research 340 (2005) 481–487
485
1.2.6. (20,40-Di-O-acetyl-60-azido-30-O-benzyl-60-deoxy-
b-D-glucopyranosyl)-ethene (7b). Rf 0.44 (1:2 EtOAc–
cyclohexane); H NMR (CDCl3, 250 MHz) d 7.34–7.23
(m, 5H, Ph), 5.83–5.69 (m, 1H, CH@), 5.39–5.24 (m,
2H, CH2@), 5.02 (t, J 9.5 Hz, 1H, H-20), 4.97 (t, J
9.5 Hz, 1H, H-40), 4.62 (s, 2H, CH2–Ph), 3.81 (dd, J
9.7, 6.8 Hz, 1H, H-10), 3.72 (t, J 9.3 Hz, 1H, H-30),
3.59 (ddd, J 9.3, 7.0, 3.0 Hz, 1H, H-50), 3.35 (dd, J
13.5, 6.8 Hz, 1H, H-60a), 3.23 (dd, J 13.5, 3.0 Hz, 1H,
H-60b), 1.99 (s, 3H, Ac), 1.97 (s, 3H, Ac).
169.8 (CO), 137.4 (Cipso), 133.5 (CH@), 128.6, 128.1,
127.8 (Ph), 117.7 (CH2@), 75.2 (C-30), 73.7 (CH2–Ph),
71.3 (C-50), 70.6, 69.5, 68.6 (C-10,20,40), 61.8 (C-60),
32.9 (C-3), 21.0 (Me). Anal. Calcd for C22H28O8: C,
62.85; H, 6.71. Found: C, 62.62; H, 6.84.
1
1.2.10. 3-(30-O-Acetyl-20-N-acetylamino-40,60-di-O-benz-
yl-20-deoxy-a-D-glucopyranosyl)-1-propene (11a). [a]D
+30.0 (c 0.6, CH2Cl2), Rf 0.43 (3:1 EtOAc–cyclohexane);
1H NMR (CDCl3, 250 MHz): d 7.28–7.16 (m, 10H, Ph),
6.15 (d, J 8.8 Hz, 1H, NH), 5.79–5.63 (m, 1H, CH@),
5.07–4.97 (m, 3H, H-30, CH2@), 4.52 (s, 2H, CH2–Ph),
4.51 (d, J 11.8 Hz, 1H, CH–Ph), 4.44 (d, J 12.0 Hz,
1H, CH–Ph), 4.10 (ddd, J 8.8, 6.8, 3.8 Hz, 1H, H-20),
4.03–3.96 (m, 1H, H-10), 3.90 (q, J 5.0 Hz, 1H, H-50),
3.68 (dd, J 10.3, 5.3 Hz, 1H, H-60a), 3.60 (t, J 5.8 Hz,
1H, H-40), 3.56 (dd, J 10.3, 5.3 Hz, 1H, H-60a), 2.35–
2.10 (m, 2H, H-3), 1.89 (s, 3H, Ac), 1.80 (s, 3H, Ac).
13C NMR (CDCl3, 62.9 MHz) d 170.8, 169.9 (CO),
138.0, 137.6 (Cipso), 134.1 (CH@), 128.7, 128.6, 128.2,
127.9 (Ph), 117.4 (CH2@), 73.9 (C-40), 73.5 (C-50,
CH2–Ph), 70.9 (C-30), 70.5 (C-10), 67.9 (C-60), 50.1 (C-
20), 33.4 (C-3), 23.3 (Me), 21.1 (Me). Anal. Calcd for
C27H33NO6: C, 69.36; H, 7.11; N, 3.00. Found: C,
69.55; H, 7.02; N, 2.90.
1.2.7. (20,30,40-Tri-O-acetyl-60-azido-60-deoxy-b-D-gluco-
pyranosyl)-ethene (7c). [a]D +20.3 (c 0.4, CH2Cl2), Rf
0.35 (1:2 EtOAc–cyclohexane); 1H NMR (CDCl3,
250 MHz): 5.81–5.68 (m, 1H, CH@), 5.41–5.30 (m,
2H, CH2@), 5.22 (t, J 9.5 Hz, 1H, H-30), 5.02 (t, J
9.8 Hz, 1H, H-40), 4.92 (t, J 9.5 Hz, 1H, H-20), 3.90
(dd, J 10.0, 6.5 Hz, 1H, H-10), 3.72–3.64 (m, 1H, H-
50), 3.32–3.31 (m, 2H, H-60), 2.03 (s, 3H, Ac), 2.02 (s,
3H, Ac), 2.00 (s, 3H, Ac). 13C NMR (CDCl3,
62.9 MHz): d 170.4, 169.6, 169.5 (CO), 133.0 (CH@),
119.7 (CH2@), 78.9 (C-10), 76.9 (C-50), 73.9 (C-30),
71.4 (C-20), 69.7 (C-40), 51.2 (C-60), 20.7 (Me). Anal.
Calcd for C14H19N3O7: C, 49.27; H, 5.61; N, 12.31.
Found: C, 49.50; H, 5.67; N, 5.50.
1.2.8. 3-(20,40-Di-O-acetyl-30,60-di-O-benzyl-a-D-gluco-
pyranosyl)-1-propene (9a). [a]D +45.0 (c 1, CH2Cl2),
Rf 0.20 (2:3 Et2O–cyclohexane); 1H NMR (CDCl3,
250 MHz): d 7.29–7.16 (m, 10H, Ph), 5.78–5.60 (m, 1H,
CH@), 5.08–4.99 (m, 2H, CH2@), 4.94 (t, J 5.5 Hz, 1H,
H-40), 4.86 (dd, J 6.0, 3.8 Hz, 1H, H-20), 4.58 (s, 2H,
CH2–Ph), 4.44 (s, 2H, CH2–Ph), 4.08–4.00 (m, 1H, H-
10), 3.91 (q, J 5.8 Hz, 1H, H-50), 3.70 (t, J 6.0 Hz, 1H,
H-30), 3.61 (dd, J 10.5, 6.3 Hz, 1H, H-60a), 3.54 (dd, J
10.5, 5.5 Hz, 1H, H-60b), 2.45–2.33 (m, 1H, H-3a),
2.23–2.15 (m, 1H, H-3b), 1.99 (s, 3H, Ac), 1.90 (s, 3H,
Ac). 13C NMR (CDCl3, 62.9 MHz) d 170.1, 169.9
(CO), 137.9 (Cipso), 133.7 (CH@), 128.6, 128.5, 127.9,
127.7 (Ph), 117.7 (CH2@), 75.3 (C-30), 73.5 (CH2–Ph),
72.5 (C-50), 70.6 (C-20), 69.6 (C-10), 69.1 (C-40), 68.5
(C-60), 33.2 (C-3), 21.1 (Me). Anal. Calcd for
C27H32O7: C, 69.21; H, 6.88. Found: C, 69.00; H, 6.95.
1.2.11. 3-(30,60-Di-O-acetyl-20-N-acetylamino-40-O-benz-
yl-20-deoxy-a-D-glucopyranosyl)-1-propene (11b). [a]D
+39.3 (c 0.3, CH2Cl2), Rf 0.33 (3:1 EtOAc–cyclohexane);
1H NMR (CDCl3, 250 MHz) d 7.30–7.23 (m, 5H, Ph),
6.17 (d, J 9.0 Hz, 1H, NH), 5.79–5.63 (m, 1H, CH@),
5.08–4.99 (m, 3H, H-30, CH2@), 4.57 (s, 2H, CH2–Ph),
4.31 (dd, J 11.8, 7.0 Hz, 1H, H-60a), 4.17–4.10 (m, 2H,
H-20,60b), 4.05–3.94 (m, 2H, H-10,50), 3.44 (t, J 4.8 Hz,
1H, H-40), 2.34–2.10 (m, 2H, H-3), 2.01 (s, 3H, Ac),
1.97 (s, 3H, Ac), 1.81 (s, 3H, Ac). 13C NMR (CDCl3,
62.9 MHz): d 170.7, 169.9 (CO), 137.2 (Cipso), 133.9
(CH@), 128.8, 128.4, 128.1 (Ph), 117.6 (CH2@), 73.4
(C-40, CH2–Ph), 72.6 (C-50), 70.3 (C-30), 67.0 (C-10),
61.7 (C-60), 49.7 (C-20), 33.7 (C-3), 23.3 (Me), 21.2
(Me), 20.9 (Me). Anal. Calcd for C22H29NO7: C, 62.99;
H, 6.97; N, 3.34. Found: C, 63.15; H, 7.00; N, 3.26.
1.2.12.
3-(60-Azido-20,30,40-tri-O-benzyl-60-deoxy-a-D-
1.2.9. 3-(20,40,60-Tri-O-acetyl-30-O-benzyl-a-D-glucopyr-
anosyl)-1-propene (9b). [a]D +76.7 (c 0.3, CH2Cl2), Rf
0.11 (2:3 Et2O–cyclohexane); 1H NMR (CDCl3,
250 MHz): d 7.29–7.19 (m, 5H, Ph), 5.76–5.58 (m, 1H,
CH@), 5.07–5.00 (m, 2H, CH2@), 4.90–4.83 (m, 2H,
H-20,40), 4.63 (d, J 11.8 Hz, 1H, CH–Ph), 4.57 (d, J
11.8 Hz, 1H, CH–Ph), 4.35 (dd, J 12.0, 7.0 Hz, 1H, H-
60a), 4.15–4.08 (m, 1H, H-10), 4.02 (dd, J 12.0, 3.8 Hz,
1H, H-60b), 3.91–3.85 (m, 1H, H-50), 3.71 (t, J 6.0 Hz,
1H, H-30), 2.45–2.30 (m, 1H, H-3a), 2.22–2.12 (m, 1H,
H-3b), 2.00 (s, 3H, Ac), 1.99 (s, 3H, Ac), 1.94 (s, 3H,
Ac). 13C NMR (CDCl3, 62.9 MHz): d 170.9, 170.1,
galactopyranosyl)-1-propene (12). This was prepared
following the method described for 4:18 methanesulfonyl
chloride (60 lL, 0.772 mmol) was added to a 0 ꢁC soln
of 3-(20,30,40-tri-O-benzyl-a-D-galactopyranosyl)-1-pro-
pene24 (260 mg, 0.537 mmol) and TEA (137 lL,
0.998 mmol) in CH2Cl2 (2 mL). The ice bath was re-
moved, and stirring was continued for 18 h before
MeOH (50 lL) was added. The soln was concentrated,
dissolved in EtOAc (20 mL) and washed successively
with water, NaHCO3 5% and brine. The organic layer
was dried over MgSO4, filtered and concentrated to an
oil, which was dissolved in DMF (2 mL) and added to

486
J. Xie et al. / Carbohydrate Research 340 (2005) 481–487
NaN3 (175 mg, 2.685 mmol). The reaction mixture was
heated at 90 ꢁC for 20 h. After evaporation, the residue
was diluted in EtOAc (20 mL), washed successively with
water, brine, dried over MgSO4, filtered, concentrated
and purified by preparative thin-layer chromatography
(1:2 Et2O–cyclohexane) to afford 12 as an oil (41 mg,
15.3%). [a]D +48.0 (c 1, CH2Cl2), Rf 0.52 (1:4 EtOAc–
15H, Ph), 5.78–5.64 (m, 1H, CH@), 5.09–5.02 (m, 3H,
H-30, CH2@), 4.73–4.51 (m, 6H, 3 · CH2–Ph), 4.27–
4.20 (m, 1H, H-50), 4.06–3.98 (m, 2H, H-10,60a), 3.91
(dd, J 5.3, 3.0 Hz, 1H, H-40), 3.78–3.71 (m, 2H, H-
20,60b), 2.40–2.10 (m, 2H, H-3), 2.05 (s, 3H, Ac).
1.2.16. 3-(30,40-Di-O-acetyl-20,60-di-O-benzyl-a-D-galac-
topyranosyl)-1-propene (15b). [a]D +60.0 (c 0.5,
CH2Cl2), Rf 0.24 (2:3 Et2O–cyclohexane); 1H NMR
(CDCl3, 250 MHz): d 7.38–7.25 (m, 10H, Ph), 5.89–
5.73 (m, 1H, CH@), 5.48 (dd, J 3.3, 2.0 Hz, 1H, H-40),
5.21 (dd, J 9.8, 3.3 Hz, 1H, H-30), 5.20–5.08 (m, 2H,
CH2@), 4.66 (d, J 12.0 Hz, 1H, CH–Ph), 4.59 (d, J
12.0 Hz, 1H, CH–Ph), 4.56 (d, J 12.0 Hz, 1H, CH–
Ph), 4.42 (d, J 12.0 Hz, 1H, CH–Ph), 4.20–4.12 (m,
1H, H-10), 4.03 (td, J 6.3, 2.0 Hz, H-50), 3.95 (dd, J
9.8, 5.8 Hz, 1H, H-20), 3.52 (dd, J 9.5, 6.0 Hz, 1H, H-
60a), 3.42 (dd, J 9.8, 6.3 Hz, 1H, H-60b), 2.55–2.49 (m,
2H, H-3), 2.04 (s, 3H, Ac), 2.00 (s, 3H, Ac). 13C NMR
(CDCl3, 62.9 MHz): d 170.2 (CO), 138.1, 137.9 (Cipso),
134.5 (CH@), 128.5, 128.0, 127.8, 127.7 (Ph), 117.4
(CH2@), 74.0 (C-10,20), 73.5, 73.3 (CH2–Ph), 70.2 (C-
30), 68.9 (C-40), 68.7 (C-50), 67.9 (C-60), 29.8 (C-3),
21.0, 20.8 (Me). Anal. Calcd for C27H32O7: C, 69.21;
H, 6.88. Found: C, 69.44; H, 6.97.
1
cyclohexane); H NMR (CDCl3, 250 MHz) d 7.26–7.14
(m, 15H, Ph), 5.85–5.57 (m, 1H, CH@), 5.04–4.95 (m,
2H, CH2@), 4.64–4.43 (m, 6H, 3 · CH2–Ph), 3.97–3.85
(m, 4H), 3.69–3.66 (m, 1H), 3.55–3.52 (m, 1H), 3.15
(dd, J = 13.0, 2.3 Hz, 1H, H-60), 2.35–2.24 (m, 2H, H-
3). 13C NMR (CDCl3, 62.9 MHz) d 138.2, 138.1 (Cipso),
134.7 (CH@), 128.5, 128.1, 127.9, 127.7 (Ph), 117.3
(CH2@), 76.1, 74.9, 73.7, 73.5 (CH), 73.4, 73.1, 72.4
(CH2–Ph), 69.3 (CH), 48.7 (C-60), 33.3 (C-3). Anal.
Calcd for C30H33N3O4: C, 72.12; H, 6.66; N, 8.41.
Found: C, 72.41; H, 6.79; N, 8.21.
1.2.13.
deoxy-a-D-galactopyranosyl)-1-propene
3-(30,40-Di-O-acetyl-60-azido-20-O-benzyl-60-
(13a). [a]D
+72.0 (c 1, CH2Cl2), Rf 0.33 (2:3 Et2O–cyclohexane);
1H NMR (CDCl3, 250 MHz): d 7.36–7.26 (m, 5H, Ph),
5.88–5.73 (m, 1H, CH@), 5.38 (dd, J 3.3, 2.5 Hz, 1H,
H-40), 5.20 (dd, J 9.3, 3.5 Hz, 1H, H-30), 5.19–5.10 (m,
2H, CH2@), 4.67 (d, J 11.8 Hz, 1H, CH–Ph), 4.59 (d,
J 11.8 Hz, 1H, CH–Ph), 4.21–4.13 (m, 1H, H-10), 3.99
(ddd, J 8.3, 4.0, 2.5 Hz, 1H, H-50), 3.91 (dd, J 9.3,
5.5 Hz, 1H, H-20), 3.48 (dd, J 10.5, 8.3 Hz, 1H, H-60a),
3.08 (dd, J 10.5, 4.0 Hz, 1H, H-60b), 2.51–2.47 (m, 2H,
H-3), 2.13 (s, 3H, Ac), 2.03 (s, 3H, Ac). 13C NMR
(CDCl3, 62.9 MHz): d 170.2 (CO), 137.9 (Cipso), 134.0
(CH@), 128.6, 128.1, 127.8 (Ph), 117.6 (CH2@), 73.7
(C-20), 73.4 (C-10), 73.3 (CH2–Ph), 69.6 (C-30,50), 68.9
(C-40), 50.6 (C-60), 30.2 (C-3), 21.0, 20.8 (Me). Anal.
Calcd for C20H25N3O6: C, 59.54; H, 6.25; N, 10.42.
Found: C, 59.70; H, 6.33; N, 10.30.
1.2.17. 3-(30,40,60-Tri-O-acetyl-20-O-benzyl-a-D-galacto-
pyranosyl)-1-propene (15c). [a]D +86.0 (c 0.3, CH2Cl2),
Rf 0.18 (2:3 Et2O–cyclohexane); 1H NMR (CDCl3,
250 MHz): d 7.34–7.26 (m, 5H, Ph), 5.81–5.67 (m, 1H,
CH@), 5.42 (dd, J 3.3, 2.3 Hz, 1H, H-40), 5.21 (dd, J
9.0, 3.3 Hz, 1H, H-30), 5.15–5.06 (m, 2H, CH2@), 4.66
(d, J 11.8 Hz, 1H, CH–Ph), 4.57 (d, J 11.8 Hz, 1H,
CH–Ph), 4.23–4.02 (m, 4H, H-10,50,60), 3.89 (dd, J 9.0,
5.3 Hz, 1H, H-20), 2.47–2.42 (m, 2H, H-3), 2.10 (s, 3H,
Ac), 2.03 (s, 3H, Ac), 2.02 (s, 3H, Ac). 13C NMR
(CDCl3, 62.9 MHz): d 170.8, 170.3 (CO), 138.0 (Cipso),
134.4 (CH@), 128.6, 128.1, 127.9 (Ph), 117.5 (CH2@),
74.0 (C-20), 73.4 (CH2–Ph), 73.2 (C-50 or C-10), 67.9
(C-30), 68.2 (C-40, C-10 or C-50), 61.8 (C-60), 30.5 (C-
3), 20.9 (Me). Anal. Calcd for C22H28O8: C, 62.85; H,
6.71. Found: C, 62.70; H, 6.59.
1.2.14.
3-(20,30,40-Tri-O-acetyl-60-azido-60-deoxy-a-D-
galactopyranosyl)-1-propene (13b). [a]D +86.7 (c 0.3,
CH2Cl2), Rf 0.19 (2:3 Et2O–cyclohexane); 1H NMR
(CDCl3, 250 MHz) d 5.86–5.75 (m, 1H, CH@), 5.40–
5.13 (m, 5H, H-20,30,40, CH2@), 4.36–4.29 (m, 1H, H-
10), 4.02–3.98 (m, 1H, H-50), 3.51 (dd, J 12.8, 8.3 Hz,
1H, H-60a), 3.10 (dd, J 12.8, 4.3 Hz, 1H, H-60b), 2.56–
2.28 (m, 2H, H-3), 2.14 (s, 3H, Ac), 2.07 (s, 3H, Ac),
2.03 (s, 3H, Ac). 13C NMR (CDCl3, 62.9 MHz): d
170.1 (CO), 133.3 (CH@), 118.1 (CH2@), 72.0 (C-10),
69.9 (C-50), 68.5, 68.2, 68.1 (C-20,30,40), 50.5 (C-60),
30.9 (C-3), 20.9 (Me). Anal. Calcd for C15H21N3O7: C,
50.70; H, 5.96; N, 11.83. Found: C, 50.90; H, 6.10; N,
11.74.
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