Epoxidation of glycals with oxone-acetone-tetrabutylammonium hydrogen sulfate: A convenient access to simple β-D-glycosides and to α-D-mannosamine and D-talosamine donors

Article abstract of DOI:10.1016/j.tetasy.2011.06.027

The addition of a phase transfer catalyst during the epoxidation of perbenzylated glycals with oxone- acetone under biphasic conditions allows their complete epoxidation. The epoxides were readily transformed into methyl 1,2-trans-β-D-glycosides or 1,2-trans-β-D-glycopyranosyl azides (D-gluco and-D-galacto configurations) bearing a free hydroxyl group at the 2-position. These glycosyl azides were converted to alkyl 1,2-trans-2-acetamido- 2-deoxy-α-D-pyranosides or alkyl 2-allyloxycarbonylamino-2- deoxy-α-D-pyranosides (D-manno and D-talo configurations) by a Staudinger reaction and a double inversion of configuration at C-1 and C-2.

Full text of DOI:10.1016/j.tetasy.2011.06.027

Tetrahedron: Asymmetry 22 (2011) 1197–1204
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Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Epoxidation of glycals with oxone–acetone–tetrabutylammonium hydrogen
sulfate: a convenient access to simple b-D-glycosides and to
a-D-mannosamine and D-talosamine donors
⇑
⇑
Dominique Lafont , Joseph D’Attoma, Rejane Gomez, Peter G. Goekjian
ICBMS-UMR 5246, Laboratoire LCO2-GLYCO, Université de Lyon, Université Claude Bernard Lyon 1, 43 bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The addition of a phase transfer catalyst during the epoxidation of perbenzylated glycals with oxone–
acetone under biphasic conditions allows their complete epoxidation. The epoxides were readily
Received 25 May 2011
Accepted 27 June 2011
Available online 4 August 2011
transformed into methyl 1,2-trans-b-
and- -galacto configurations) bearing a free hydroxyl group at the 2-position. These glycosyl azides were
converted to alkyl 1,2-trans-2-acetamido-2-deoxy- -pyranosides or alkyl 2-allyloxycarbonylamino-2-
deoxy- -pyranosides ( -manno and
inversion of configuration at C-1 and C-2.
D-glycosides or 1,2-trans-b-D-glycopyranosyl azides (D-gluco
D
a
-D
a
-D
D
D-talo configurations) by a Staudinger reaction and a double
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
and D-galactal with dimethyldioxirane generated in situ from ox-
one/acetone under biphasic conditions by adapting the procedure
reported in 1980 by Curci et al. to alkenes.18 An improved, more ro-
bust procedure adding a phase transfer catalyst is reported herein.
We investigated the nucleophilic ring-opening with an azide
anion, to obtain the C-2 unprotected 1,2-trans-b-D-glycopyranosyl
azides, followed by transformation into a sulfonate and a Stauding-
er reaction in the presence of an alcohol as a practical route to the
There has been sustained interest in 1,2-anhydrosugars over the
last 20 years due to their application in oligosaccharide synthesis.1
Danishefsky et al. in particular have extensively developed the use
of 1,2-anhydrosugars in oligosaccharide synthesis since 1989, by
epoxidation of glycals and reaction with another glycal,2 although
examples of disaccharide synthesis from Brigl’s anhydride (3,4,6-
tri-O-acetyl-1,2-anhydro-
a
-
D
-glucopyranose) were reported ear-
protected alkyl 2-amino-2-deoxy-a-D-manno- and talo-pyrano-
lier.3 1,2-Anhydrosugars have since been extensively used in the
synthesis of O-glycosides and oligosaccharides,2,4,5 as well as for
glycosyl donors, such as glycosyl fluorides,6,7 thioglycosides,6,8
and glycosyl phosphate5,8f,h,9 Access to C-glycosides have also been
described in the literature,10 and a few examples of N-glycosyl
derivatives were reported by this route.6,8a,11
sides. Access to glycosaminyl donors based on the migration of a
nitrogen atom from C-1 to C-2, via aziridine intermediates with
concomitant double inversion of stereochemistry has already been
described by us19 and Danishefsky20 for the preparation of glyco-
sides in a
expanded upon the C-2 acetamidoglycosylation reaction with gly-
cal donors, initially described in the
-gluco series,21 (transfer of an
anomeric acetamidate to the C-2 position with the formation of an
oxazoline intermediate) to the -manno series with the preparation
of -glycosides of the N-acetyl-
-mannosamine.22 Glycosyl
D-glucosamine series. More recently, Gin and co-workers
While other methods have been reported,12–14 1,2-anhydrosu-
gars are synthesized for the most part by the direct oxidation of gly-
cals with a solution of dimethyldioxirane (DMDO) in acetone.15 This
method gives high yields and very clean reactions, but presents a
number of practical drawbacks, in particular for the synthesis of rel-
atively simple precursors on larger scales, such as the preparation
and manipulation of organic peroxides, the low concentration of
the dimethyldioxirane solutions, and the difficulty in storing such
solutions over long periods of time. The use of dioxiranes formed
in situ from alternative ketones, such as trifluoroacetone, has been
D
D
a
D
azides23 have been used for the synthesis of glycomimetics24 and
glyclusters25 and are typically prepared by the nucleophilic
displacement of glycosyl bromides under biphasic conditions.26
N-Acetyl-D-mannosamine and its analogs are constituents of oligo-
saccharides of Gram-positive and Gram-negative bacteria,27 as
well as precursors of sialic acid and analogs,28 while talosamine
and talosaminuronic acid have been identified as components of
cell walls of bacteria such as Methanobacterium thermoautotrophi-
cum,29 Pseudoalteromonas nigrifaciens,30 Pneumococcus type V31
and others.32 Classical methods for the incorporation of the
reported.16 In 2006, Dondoni and co-workers17 described
practical, multi-gram epoxidation of 3,4,6-tri-O-benzyl-D-glucal
a
⇑
Corresponding authors.
E-mail addresses: lafont@univ-lyon1.fr (D. Lafont), goekjian@univ-lyon1.fr (P.G.
D
-mannosamine motif into various oligosaccharide chains33
Goekjian).
0957-4166/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2011.06.027

1198
D. Lafont et al. / Tetrahedron: Asymmetry 22 (2011) 1197–1204
include epimerization reactions at the C-2 carbon atom of furanos-
idic N-acetyl-
-glucosamine derivatives,34 reductions of a C-2
oxime,35 nucleophilic intra- or intermolecular substitutions on
glycosides 4, 6, and 7 were obtained in good yields and stereoselec-
tivity from perbenzylated glycals 1–3. Methyl 3,4,6-tri-O-benzyl-b-
D
D
-glucopyranoside 4 was obtained in high overall yield from
3,4,6-tri-O-benzyl- -glucal 1 as an 8:1 mixture of the b- -gluco 4
and -manno 5 stereoisomers (75% isolated yield of the pure-
b- -glucopyranoside along with 15% of a 1:2 mixture). Similarly,
methyl 3,4,6-tri-O-benzyl-b- -galactopyranoside and methyl
3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-b- -galactopyrano-
syl)-b- -Glucopyranoside 7 were obtained in 83% and 80% yield
from glycals 2 and 3, respectively (Scheme 1).
the C-2 leaving group of a b-
D
-glucopyranoside,36 or cyclization
D
D
of glucal 3-N-arylcarbamates, orchestrated by o-iodobenzoic acid37
or via rhodium(II)-catalyzed oxidative cyclizations.38 Rojas and
co-workers thus prepared the pentenyl glycosides of N-benzyloxy-
a-D
D
D
6
carbonyl-
a
-
D
-mannosamine, which were used as donors in
few examples of
D
glycosylation reactions. There are only
a
D
N-acetyl-D-talosamine syntheses in the literature, which include
nucleophilic substitutions on a C-2 sulfonate,39 stereoselective
reductions of a C-2 oxime,40 or dihydroxylation reactions on a
2-amino-3,4-glycal.41
The epoxide ring opening by an azido group has been described
previously in the literature: various 1,2-anhydrosugars have been
converted into the corresponding
yields by treatment with lithium azidohydridodiisobutylaluminate
in tetrahydrofuran11 and 3,4,6-tri-O-benzyl-b-
-gluco- and galac-
D-glycopyranosyl azides in good
D
2. Results and discussion
to-pyranosyl azides 8 and 10 were thus obtained in 73% and 78%
yield, respectively. Compound 8 has been previously synthesized
from the intermediate epoxide using tetrabutylammonium azide
in tetrahydrofuran6 or sodium azide and lithium perchlorate in
acetonitrile.42
In order to find a simpler method that would be applicable on a
gram-scale, we attempted to open directly the crude epoxide in
dichloromethane solution under the biphasic conditions described
by Roy and co-workers26 for the transformation of peracetylated
glycopyranosyl bromides into peracetylated glycopyranosyl azides
[tetrabutylammonium hydrogen sulfate (1 equiv), sodium azide
(4 equiv), dichloromethane, saturated NaHCO3 solution]:
During the epoxidation of 3,4,6-tri-O-benzyl-D-glucal according
to Dondoni and co-workers,17 [oxone (2 equiv), acetone, dichloro-
methane, saturated NaHCO3 solution], we had some difficulty in
obtaining consistent results, and observed that the reaction
seemed to depend upon a number of factors, including the speed
of the magnetic stirring. Since this reaction occurs under biphasic
conditions, we thought that the addition of a phase transfer cata-
lyst might facilitate the reaction. Thus, the presence of tetrabutyl-
ammonium hydrogen sulfate accelerated the reaction, as observed
by Curci18 in the case of cyclohexene, and the epoxide formation
was complete in 2 h; after ring opening with methanol, methyl
a
a
R4
R4
OBn
OBn
O
e
e
O
R4
BnO
R4
OMe
BnO
OH
R4e = OBn, R4a = H
1
4 R4e = OBn, R4a = H
2 R4e = H, R4a = OBn
6 R4e = H, R4a = OBn
3 R4e = (BnO)4-β-D-Gal, R4a =H
7 R4e = (BnO)4-β-D-Gal, R4a = H
b
a
a
R4
OBn
a
R4
OBn
e
c
O
R4
e
O
R4
BnO
N3
BnO
OH
O
8 R4e = OBn, R4a = H
R4e = H, R4a = OBn
10
d
BnO
OH
O
a
BnO
BnO
R4
OBn
e
O
R4
X
N3
BnO
5
X = OMe
X = N3
9
OMs
11 R4e = OBn, R4a = H
12
R4e = H, R4a = OBn
Scheme 1. Synthetic route to b-
D-1,2-trans-2-hydroxy (mesyloxy) glycosides and glycosyl azides. Reagents and conditions: (a) oxone (2 equiv), acetone, Bu4NHSO4
(0.33 equiv), NaHCO3, CH2Cl2, H2O; (b) MeOH, rt; (c) NaN3 (4 equiv), Bu4NHSO4 (1 equiv), CH2Cl2, NaHCO3, H2O; (d) MsCl, pyridine.

D. Lafont et al. / Tetrahedron: Asymmetry 22 (2011) 1197–1204
OBn BnO
1199
NHCOR'
O
BnO
BnO
O
BnO
BnO
N3
14
15
R' = Me
OMs
OMe
R' = OAll
11
a
b,c (R' = Me)
or b,d (R' = OAll)
BnO
BnO
BnO
NHPPh3OMs
O
OR
13 R = Me
16 R = Pent
b,d
BnO
BnO
BnO
NHCOOAll
O
17
OPent
Scheme 2. Synthetic route to 2-acetamido or 2-allyloxycarbonylamino-2-deoxy-
a-D-mannopyranosides. Reagents and conditions: (a) MeOH (10 equiv) or Pent-4-en-1-ol
(1.5 equiv), PPh3 (1.15 equiv), CH2Cl2, 0 °C to rt; (b) 1.5 N NaOH, MeOH, rt; (c) Ac2O, pyridine; (d) AllOCOCl, NaHCO3, CH2Cl2, H2O.
compounds 8 and 10 were thus obtained in 77% and 83% yield from
the corresponding perbenzylated glycals 1 and 2.
group was introduced in 1988 by Fraser-Reid et al. as a leaving
group at the anomeric center of a glycosyl donor.46,47
Starting from 3,4,6-tri-O-benzyl-
D
-glucal 1, as expected
a
Furthermore, the pentenyl glycosides of N-benzyloxycarbonyl-
more polar compound was isolated [3,4,6-tri-O-benzyl-
a
-
D
-
and N-allyloxycarbonyl-D-glucosamine have been shown to be effi-
mannopyranosyl azide 9, 9%], resulting from the minor forma-
tion of the epoxide on the b-face; nevertheless, the separation
of isomers 8 and 9 by column chromatography was relatively
easy.
cient donors in glycosylation reactions.38,43
When methanol was replaced by 4-penten-1-ol, the expected
pentenyl 2-allyloxycarbonylamino-3,4,6-tri-O-benzyl-2-deoxy-a-
D
-mannopyranoside 17 was prepared from 11, via the intermediate
Since it was possible to obtain 1,2-trans-
D- (and
L
-) glucosamine
salt 16, which was also characterized by 1H and 13C NMR; further-
more, since 4-penten-1-ol was expensive and more difficult to
eliminate than methanol, only 2 equiv were used; product 17
was obtained in 77% yield.
derivatives from 2-deoxy-2-iodo- (and L
a
-
D
-
-)mannopyranosyl
azides,19,43 by Staudinger reaction and intramolecular attack of
the iminophosphorane intermediate on the C-2 carbon–iodine
bound, formation of an aziridine and ring opening by an alcohol,
we assumed that the same reaction would also be possible from
If 3,4,6-tri-O-benzyl-2-O-mesyl-b-D-galactopyranosyl azide 12
was treated with triphenylphosphine and methanol, in dichloro-
methane as described for 11, the only reaction product was the
iminophosphorane 18, which was recovered in quantitative yield:
the result was the same in the absence of methanol (Scheme 3).
Product 18 was also characterized by 1H and 13C NMR data. This
could be due to steric problems (the presence of the benzyl group
at C-4) which hinder the formation of the boatlike conformation
necessary for the formation of the transient glycosyl aziridine.
Even after refluxing the salt 18 in methanol for 12 h, followed by
treatment with sodium hydroxide and reacetylation, methyl 2-
3,4,6-tri-O-benzyl-2-O-mesyl-b-
D
-glucopyranosyl azide 11 and
-galactopyranosyl azide 12,
3,4,6-tri-O-benzyl-2-O-mesyl-b-
D
which were obtained in 92 and 95% yield from 8 and 10,
respectively.
If compound 11 was treated with triphenylphosphine
(1.1 equiv) and methanol (10 equiv) in dichloromethane, between
0 and 20 °C, salt 13 was obtained in high yield; the a-manno con-
figuration was characterized by 1H NMR (d H-1 = 4.74 ppm, J1,2
=
1.9 Hz, d H-2 = 3.2 ppm, J2,3 = 3.7 Hz, J2,P = 11.0 Hz), 13C NMR (d C-
1 = 101.3 ppm, J1,P = 5.3 Hz, d C-2 = 55.0 ppm, d C-3 = 78.41 ppm,
J3,P = 2.3 Hz), coupled 1H–13C NMR (JH1-C1 = 170.6 Hz)44 and 2D
experiments (COSY, HSQC). Treatment of the salt 13 with 1.5 M
sodium hydroxide and methanol, followed by acetylation afforded
acetamido-3,4,6-tri-O-benzyl-2-deoxy-
obtained in only 51% yield. A second product N-acetyl-3,4,6-tri-
O-benzyl-2-deoxy-2-O-mesyl-b- -galactopyranosyl amine 20,
a-D-talopyranoside 19 was
D
probably resulting from the hydrolysis of the iminophosphorane,
was isolated in 21% yield. These results indicated that a higher
reaction temperature would be necessary to realize the rearrange-
ment of salt 18: in the presence of 10 equiv of 4-penten-1-ol, after
4 h at 100 °C in toluene and treatment as described for compound
17, pentenyl 2-allyloxycarbonylamino-3,4,6-tri-O-benzyl-2-deoxy-
the known methyl 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-a-D-
mannopyranoside 14 in 91% yield45 (Scheme 2). Similarly,
treatment of salt 13 with 1.5 M sodium hydroxide, and allyloxy-
carbonylation of the free NH2 derivative under biphasic condi-
tions (allyl chloroformate, dichloromethane, saturated NaHCO3
solution) afforded the methyl 2-allyloxycarbonylamino-3,4,6-tri-
a-
D-talopyranoside 21 was isolated in 69% yield. With a smaller
O-benzyl-2-deoxy-a-D-mannopyranoside 15 in 88% yield. Knowing
excess of 4-penten-1-ol (2 equiv), the yield decreased to 59%. The
that the transformation of the aminophosphonium salt 13 into the
carbamate 15 could be achieved in high yield, we investigated the
synthesis of the corresponding pentenyl glycoside: the pentenyl
a-stereochemistry for compound 19 and 21 was ascertained from
the 1H and 13C NMR data, and also from the JC1-H1 value in the cou-
pled 13C NMR spectrum (J = 170.9 Hz for 21).

1200
D. Lafont et al. / Tetrahedron: Asymmetry 22 (2011) 1197–1204
OBn
BnO
BnO
OBn
O
NHCOOAll
O
BnO
21
BnO
N3
OMs
OPent
12
a
e,c,f
OBn
BnO
O
N = PPh3
BnO
OMs
18
b,c,d
+
OBn
NHAc
OBn
BnO
BnO
BnO
O
O
NHAc
BnO
OMs
20
19
OMe
Scheme 3. Synthetic route to 2-acetamido- or 2-allyloxycarbonylamino-2-deoxy-
a-D-talopyranosides. Reagents and conditions: (a) PPh3 (1.15 equiv), CH2Cl2, 0 °C to rt; (b)
MeOH, 12 h, reflux; (c) 1.5 N NaOH, MeOH, rt; (d) Ac2O, pyridine; (e) Pent-4-en-1-ol (2–10 equiv), toluene, 100 °C; (f) AllOCOCl, NaHCO3, CH2Cl2, H2O.
CAUTION: sodium azide may react with dichloromethane to
3. Conclusion
form explosive diazidomethane: experiments must be conducted
behind a safety shield.48
In conclusion, the addition of tetrabutylammonium hydrogen
sulfate during the epoxidation of perbenzylated glycals with oxone
and acetone under biphasic conditions led reproducibly to com-
plete conversions: epoxides were formed quantitatively and could
be transformed directly in the presence of methanol to methyl 1,2-
4.2. Synthesis of methyl 1,2-trans-glycosides by epoxidation of
glycals and ring opening with methanol: general procedure
trans-b-
D
-glycopyranosides or under biphasic conditions to 1,2-
-glycopyranosyl azides bearing a free hydroxyl group at
A solution of oxone (1.475 g, 2.40 mmol) in water (5.8 mL) was
added dropwise at 0 °C for 15 min to a vigorously stirred biphasic
mixture of benzylated glycal (1.20 mmol), tetrabutylammonium
hydrogen sulfate (0.136 g, 0.40 mmol), acetone (0.5 mL), CH2Cl2
(5 mL) and a saturated NaHCO3 solution (8.3 mL). Stirring was main-
tained for 30 min at 0 °C, and 2 h at room temperature. The aqueous
phase was extracted with CH2Cl2 (2 ꢀ 30 mL) and the combined
organic phases were washed with water (10 mL) and dried over so-
dium sulfite (Na2SO3). After filtration, the solution was concentrated
in the presence of methanol (10 mL) and the residue was stirred
overnight in methanol (30 mL). Methanol was evaporated in vacuo
and the crude product was purified by column chromatography.
trans-b-
D
the C-2 position. After mesylation, the b-D-gluco- and b-D-galac-
to-pyranosyl azides were subjected to a Staudinger reaction in
the presence of 4-penten-1-ol, giving in a few steps, and after dou-
ble inversion of configuration at C-1 and C-2, pentenyl 1,2-trans-2-
allyloxycarbonylamino-2-deoxy-a-D-manno- and talo-pyranosides,
which could in turn be used as donors in glycosylation reactions.
4. Experimental
4.1. General
4.2.1. Methyl 3,4,6-tri-O-benzyl-b-D-glucopyranoside 4
The dichloromethane used for the Staudinger reactions was
washed twice with water, dried with CaCl2 and distilled from
CaH2. Methanol was distilled from magnesium. CH2Cl2 was stored
over 4 Å molecular sieves; and MeOH over 3 Å molecular sieves.
Thin layer chromatography was performed on aluminum sheets
coated with Silica Gel 60 F254 (E. Merck). Compounds were
visualized by spraying the TLC plates with dilute 15% aqueous
H2SO4, followed by charring at 150 °C for a few min. Column chro-
matography was performed on Silica-gel Silicycle P60 (230–400
mesh). 1H and 13C NMR spectra were recorded with Bruker
DRX300 or ALS300 spectrometers working at 300 and 75 MHz,
respectively with Me4Si or residual solvent peaks as internal stan-
dard, ESI high resolution measurements were obtained with a MAT
95XL (ThermoFinnigan) electromagnetic mass spectrometer. Ele-
mental analyses were performed by the ‘Laboratoire Central
d’Analyses du CNRS’ (Vernaison, France).
Compound 4 was obtained in 75% yield from 3,4,6-tri-O-benzyl-
-glucal 1 after purification by column chromatography (1:2 ethyl
D
acetate–petroleum ether). 0.362 g, Rf 0.60 (2:3 ethyl acetate–petro-
leum ether); Mp = 71–72 °C (ethanol), ½aꢁD ¼ ꢂ4:7 (c 1.0, CHCl3)
{lit.49 Mp = 72–75 °C, ½a D
ꢁ
¼ ꢂ5:0 (c 1.0, CHCl3)}; 1H NMR (CDCl3):
d 7.44–7.20 (m, 15H, 3C6H5), 4.97 and 4.90 (dd, 2H, J 11.3 Hz,
CH2Ph), 4.88 and 4.59 (dd, 2H, J 10.8 Hz, CH2Ph), 4.68 and 4.60
(dd, 2H, J 12.2 Hz, CH2Ph), 4.23 (d, 1H, J1,2 7.3 Hz, H-1), 3.81 (dd,
1H, J5,6a 2.1, J6a,6b 10.8 Hz, H-6a), 3.75 (dd, 1H, J5,6a 4.3 Hz, H-6b),
3.70–3.57 (m, 3H, H-2, H-3, H-4), 3.61 (s, 3H, CH3O), 3.53 (ddd,
1H, J4,5 9.9 Hz, H-5), 2.50 (s, 1H, OH).
Further elution gave a 1:2 b-D-gluco 4/a-D-manno 5 mixture
(0.085 g, 15%): a-manno isomer: Rf = 0.56 (2:3 ethyl acetate–petro-
leum ether). Selected 1H NMR data for 5: d 4.05 (dd, 1H, J1,2 1.5, J2,3
3.0 Hz, H-2), 3.39 (s, 3H, CH3O).

D. Lafont et al. / Tetrahedron: Asymmetry 22 (2011) 1197–1204
1201
4.2.2. Methyl 3,4,6-tri-O-benzyl-b-
D
-galactopyranoside 6
3.90–3.83 (m, 2H, H-6a, H-6b), 3.80 (dd, 1H, J3,4 8.9, J4,5 9.3 Hz,
H-4), 3.69 (dd, 1H, J2,3 8.9 Hz, H-3), 3.68–3.63 (m, 1H, H-5), 3.60
Compound 6 was obtained in 83% yield from 3,4,6-tri-O-benzyl-
-galactal 2 after purification by column chromatography (2:3
D
(dd, 1H, H-2); 13C NMR (CDCl3):
d 138.39, 137.86, 137.86,
ethyl acetate–petroleum ether). 0.462 g, Rf = 0.51 (2:3 ethyl ace-
128.47–127.69 (C6H5), 90.23 (C-1), 84.57 (C-3), 77.09, 77.04 (C-4,
C-5), 75.22, 74.94, 73.46 (CH2Ph), 73.93 (C-2), 68.29 (C-6).
tate–petroleum ether), Mp 98–99 °C (ethanol), ½aꢁD ¼ ꢂ6:4 (c 1.0,
CHCl3) {lit.50 Mp = 99–99.5 °C, ½a D
ꢁ
¼ ꢂ6:4 (c 1.0, CHCl3)}. 1H NMR
Further elution afforded 3,4,6-tri-O-benzyl-
syl azide 942 as an oil: 0.103 g, 9% yield. Rf 0.22 (1:3 ethyl ace-
tate–petroleum ether);
D = +180.0 (c 1.0, CHCl3); 1H NMR
a-D-mannopyrano-
(CDCl3): d 7.42–7.28 (m, 15H, 3C6H5), 4.90 and 4.63 (dd, 2H, J
11.6 Hz, CH2Ph), 4.75 and 4.66 (dd, 2H, J 11.8 Hz, CH2Ph), 4.51
and 4.45 (dd, 2H, J 11.7 Hz, CH2Ph), 4.20 (d, 1H, J1,2 7.7 Hz, H-1),
3.96 (dd, 1H, J2,3 9.7 Hz, H-2), 3.96 (br d, 1H, J3,4 2.8 Hz, H-4),
3.67–3.58 (m, 3H, H-5, H-6a, H-6b), 3.55 (s, 3H, CH3O), 3.45 (dd,
1H, H-3); 13C NMR (CDCl3): d 138.60, 138.15, 137.95, 128.59–
127.64 (C6H5), 104.23 (C-1), 82.06 (C-3), 76.76 (C-4), 74.58,
73.64, 72.48 (CH2Ph), 72.92, 71.36 (C-2, C-5), 68.78 (C-6), 57.04
(CH3O).
[a]
(CDCl3): d 7.45–7.20 (m, 15H, 3C6H5), 5.53 (d, 1H, J1,2 1.8 Hz, H-
1), 4.90 and 4.60 (dd, 2H, J 10.9 Hz, CH2Ph), 4.73 and 4.60 (dd,
2H, J 12.1 Hz, CH2Ph), 4.72 (s, 2H, CH2Ph), 4.03–3.77 (m, 6H, H-2,
H-3, H-4, H-5, H-6a, H6b), 2.82 (s, 1H, OH); 13C NMR (CDCl3): d
138.24, 137.99, 137.72, 128.53–127.88 (C6H5), 89.56 (C-1), 79.27
(C-3), 75.27, 73.64, 72.34 (PhCH2), 73.75, 73.36 (C-4, C-5), 68.63
(C-6), 68.36 (C-2).
4.2.3. Methyl 3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-b-
galactopyranosyl)-b- -glucopyranoside 7
Compound 7 was obtained from 3,6-di-O-benzyl-4-O-(2,3,4,6-
tetra-O-benzyl-b- -galactopyranosyl)- -glucal (0.424 g, 0.50
mmol) according to the general procedure. The pure glycoside
was recovered in 80% yield after purification by column chroma-
tography (2:3 ethyl acetate–petroleum ether). 0.358 g, oily mate-
D
-
4.3.2. 3,4,6-Tri-O-benzyl-b-
D
-galactopyranosyl azide 1011
-galactal
D
Compound 10 was obtained from 3,4,6-tri-O-benzyl-
D
2 (1.00 g, 2.40 mmol) in 83% yield after purification by column
chromatography (2:5 ethyl acetate–petroleum ether). 0.948 g, Rf
0.66 (1:2 ethyl acetate–petroleum ether); Mp = 78–79 °C,
D
D
3
[a
]
D = ꢂ10.7 (c 1.0, CHCl3); 1H NMR (CDCl3): d 7.45–7.20 (m, 15H,
3C6H5), 4.93 and 4.66 (dd, 2H, J 13.6 Hz CH2Ph), 4.78 and 4.65
(dd, 2H, J 11.8 Hz CH2Ph), 4.57 and 4.50 (dd, 2H, J 11.8 Hz CH2Ph),
4.56 (d, 1H, J1,2 8.5 Hz, H-1), 4.06 (dd, 1H, J3,4 2.7, J4,5 0.6 Hz, H-4),
3.95 (dd, 1H, J2,3 9.6 Hz, H-2), 3.76–3.66 (m, 3H, H-5, H-6a, H-6b),
3.48 (dd, 1H, H-3); 13C NMR (CDCl3): d 138.39, 137.83, 137.77,
128.72–127.80 (C6H5), 90.67 (C-1), 82.21 (C-3), 75.84 (C-4),
74.71, 73.73, 72.48 (CH2Ph), 72.64 (C-5), 70.70 (C-2), 68.44 (C-6).
rial; Rf 0.53 (2:3 ethyl acetate–petroleum ether) [
a]D = +9.6 (c 1.0,
CHCl3) {lit.5a D = +12 (c 1.0, CHCl3)}; 1H NMR (CDCl3): d 7.42–
[a]
7.28 (m, 30H, 6C6H5), 5.28 and 4.90 (dd, 2H, J 11.1 Hz, CH2Ph),
5.15 and 4.73 (dd, 2H, J 11.5 Hz, CH2Ph), 5.01 and 4.96 (dd, 2H, J
11.2 Hz, CH2Ph), 4.87 (s, 2H, CH2Ph), 4.73 and 4.57 (dd, 2H, J
12.1 Hz, CH2Ph), 4.63 (d, 1H, J1 ,2 7.7 Hz, H-10), 4.55 and 4.49 (dd,
2H, J 11.9 Hz, CH2Ph), 4.38 (d, 1H, J1,2 7.6 Hz, H-1), 4.16 (dd, 1H,
0
0
J3,4 9.0, J4,5 9.0 Hz, H-4), 4.09 (br d, 1H, J3 ,4 3.1, J4 ,5 0.5 Hz, H-40),
4.4. Synthesis of 1,2-trans-2-O-mesyl glycopyranosyl azides:
0
0
0
0
0
0
4.02 (dd, 1H, J5,6a 4.2, J6a,6b 11.2 Hz, H-6a), 3.97 (dd, 1H, J2 ,3
general procedure
9.5 Hz, H-20), 3.91 (dd, 1H, J5,6b 1.5 Hz, H-6b), 3.77–3.53 (m, H, H-
2, H-3, H-30, H-5, H-50, H-60a, H-60b), 3.70 (s, 3H, CH3O); 13C NMR
(CDCl3): d 139.01, 138.79, 138.50, 138.32, 138.03, 128.38–127.27
(C6H5), 103.62 (C-1), 102.75 (C-10), 82.69, 82.42, (C-3, C-30), 79.93
(C-20), 76.23 (C-4), 75.40 (C-5), 75.28, 74.69, 74.64 (CH2Ph), 73.60
(C-40), 73.49 (C-2), 73.41, 73.10 (CH2Ph), 73.01 (C-50), 72.53
(CH2Ph), 68.15 (C-6, C-60), 56.91 (CH3O).
A solution of mesyl chloride (0.286 mL, 3.70 mmol) in dry
CH2Cl2 (2 mL) was added dropwise to a cooled solution of alcohol
8 or 10 (1.00 g, 2.10 mmol) in pyridine (7 mL). The mixture was al-
lowed to reach room temperature and stirring was maintained
overnight. The mixture was poured into ice-water and extracted
with CH2Cl2 (3 ꢀ 20 mL). The organic phase was washed with a sat-
urated NaHCO3 solution (20 mL), brine (10 mL) and dried (Na2SO4).
After concentration, the residue was purified by column
chromatography.
4.3. Synthesis of 1,2-trans glycopyranosyl azides by epoxidation
of glycals and ring opening with sodium azide: general
procedure
4.4.1. 3,4,6-Tri-O-benzyl-2-O-mesyl-b-
D
-glucopyranosyl azide 11
-gluco-
The crude epoxide was prepared as described in Section 4.2.
from perbenzylated glycal 1 or 2 (1.20–2.40 mmol) and oxone
(2.40–4.80 mmol). After treatment, the organic phase was partially
concentrated in vacuo to 6–12 mL (at room temperature or below).
A saturated NaHCO3 solution (6–12 mL), sodium azide (0.312–
0.624 g, 4.80–9.60 mmol, 4 equiv) and tetrabutylammonium
hydrogen sulfate (1.20–2.40 mmol, 1 equiv) were added succes-
sively to the organic solution and the mixture was vigorously stir-
red for 4 h. After the addition of ethyl acetate (60 mL), the organic
phase was washed with a saturated NaHCO3 solution (10 mL), then
with brine (10 mL), dried (Na2SO4) and concentrated in vacuo. The
residue was purified by column chromatography.
Compound 11 was obtained from 3,4,6-tri-O-benzyl-b-
D
pyranosyl azide 8 (1.00 g, 2.40 mmol) after purification by column
chromatography (2:5 ethyl acetate–petroleum ether). 1.070 g (92%
yield), oily material, Rf 0.72 (1:2 ethyl acetate–petroleum ether),
[a
]
D = ꢂ36.9 (c 1.0, CHCl3); 1H NMR (CDCl3): d 7.50–7.20 (m, 15H,
3C6H5), 4.99–4.82 (m, 3H, CH2Ph), 4.73–4.58 (m, 3H, CH2Ph), 4.62
(d, 1H, J1,2 8.3 Hz, H-1), 4.50 (dd, 1H, J2,3 9.6 Hz, H-2), 3.85–3.73
(m, 4H, H-3, H-4, H-6a, H-6b), 3.63 (ddd, 1H, J4,5 9.4, J5,6a 2.4, J5,6b
3.4 Hz, H-5), 3.09 (s, 3H, CH3SO2).; 13C NMR (CDCl3): d 138.17,
137.93, 137.81, 128.94–128.39 (C6H5), 87.75 (C-1), 82.52 (C-3),
80.57, 77.57, 77.43 (C-2, C-4, C-5), 75.88, 75.32, 73.49 (CH2Ph),
68.06 (C-6), 39.56 (CH3SO2). Anal. Calcd for C28H31N3O7S
(553.63): C, 60.74; H, 5.64; N, 7.59. Found: C, 60.68; H, 5.46; N,
7.42.
4.3.1. 3,4,6-Tri-O-benzyl-b-
D-glucopyranosyl azide 8
Compound 8 was obtained from 3,4,6-tri-O-benzyl-
D-glucal 1
(1.00 g, 2.40 mmol) in 77% yield as a solid after purification by col-
umn chromatography (2:5 ethyl acetate–petroleum ether). 0.880 g,
4.4.2. 3,4,6-Tri-O-benzyl-2-O-mesyl-b-
12
D-galactopyranosyl azide
Rf 0.42 (1:3 ethyl acetate–petroleum ether), Mp 67 °C, [
a
]
D = ꢂ5.0
Compound 12 was obtained from 3,4,6-tri-O-benzyl-b-D-galac-
(c 1.0, CHCl3) {lit.6 Mp 64–67 °C, [
a
]
D = ꢂ4.7 (c 1.15, CHCl3)}; 1H
topyranosyl azide (10) (1.00 g, 2.40 mmol) after purification by
column chromatography (1:2 ethyl acetate–petroleum ether).
1.070 g, Rf 0.77 (1:2 ethyl acetate–petroleum ether), 95% yield.
NMR (CDCl3): d 7.40–7.20 (m, 15H, 3C6H5), 5.05 and 5.01 (dd, 2H,
J 11.5 Hz, CH2Ph), 4.97 and 4.71 (dd, 2H, J 10.9 Hz, CH2Ph), 4.77
and 4.68 (dd, 2H, J 12.2 Hz, CH2Ph), 4.63 (d, 1H, J1,2 8.4 Hz, H-1),
Mp 87–88 °C,
[
a]
D = ꢂ33.1 (c 1.0, CHCl3); 1H NMR (CDCl3):

1202
D. Lafont et al. / Tetrahedron: Asymmetry 22 (2011) 1197–1204
d 7.50–7.26 (m, 15H, 3C6H5), 4.96 and 4.64 (dd, 2H, J 11.6 Hz,
CH2Ph), 4.86 (dd, 1H, J1,2 8.7, J2,3 9.7 Hz, H-2), 4.77 and 4.68 (dd,
2H, J 11.5 Hz, CH2Ph), 4.65 (d, 1H, H-1), 4.07 (br d, 1H, J3,4 3.4, J4,5
1.0 Hz, H-4), 3.76–3.62 (m, 4H, H-3, H-5, H-6a, H-6b), 3.04 (s, 3H,
CH3SO2); 13C NMR (CDCl3): d 138.07, 137.66, 137.05, 128.72–
127.90 (C6H5), 88.12 (C-1), 80.11, 79.16, 77.44, 72.90 (C-2, C-3, C-
4, C-5), 74.86, 73.69, 72.61 (CH2Ph), 68.07 (C-6), 39.24 (CH3SO2).
Anal. Calcd for C28H31N3O7S (553.63): C, 60.74; H, 5.64; N, 7.59.
Found: C, 61.24; H, 5.60; N, 7.47.
added and the mixture was vigorously stirred for 4 h. After dilution
with CH2Cl2 (40 mL), the organic phase was washed with a satu-
rated NaHCO3 solution (10 mL), dried (Na2SO4) and concentrated.
The residue was purified by column chromatography (1:2 ethyl
acetate–petroleum ether). Pure product 15 was recovered in 88%
yield: 0.226 g; Rf 0.47 (1:3 ethyl acetate–petroleum ether),
[a]
D = +20.0 (c 1.0, CHCl3); 1H NMR (CDCl3): d 7.46–7.30 (m, 15H,
C6H5), 5.95 (m, 1H, CH@), 5.35 (br d, 1H, J 17.2 Hz, 0.5CH2@),
5.24 (d, 1H, J 10.5 Hz, 0.5CH2@), 5.19 (d, 1H, J2,NH 9.0 Hz, NH),
4.88 and 4.45 (dd, 2H, J 10.8 Hz, CH2Ph), 4.83 (d, 1H, J1,2 1.0 Hz,
H-1), 4.79 and 4.52 (dd, 2H, J 11.1 Hz, CH2Ph), 4.66 and 4.51 (dd,
2H, J 12.1 Hz, CH2Ph), 4.63–4.59 (m, 2H, CH2-CH@CH2), 4.39 (br
dd, 1H, J2,3 4.6 Hz, H-2), 4.05 (dd, 1H, J3,4 8.9 Hz, H-3), 3.80–3.64
(m, 4H, H-4, H-5, H-6a, H-6b), 3.37 (s, 3H, CH3O); 13C NMR (CDCl3):
d 156.25 (NHCOO), 138.39, 138.08, 138.01, 128.35–127.67 (C6H5),
132.83 (CH@), 117.85 (CH2@), 100.41 (C-1), 77.86 (C-3), 74.04 (C-
4), 70.53 (C-5), 75.15, 73.52, 71.13 (CH2Ph), 68.64 (C-6), 65.82 (allyl
CH2), 54.97 (CH3), 50.97 (C-2). Anal. Calcd for C32H37NO7 (547.64):
C, 70.18; H, 6.81; N, 2.56. Found: C, 69.31; H, 6.82; N, 2.34.
4.5. Methyl 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-a-D-
mannopyranoside 14
Triphenylphosphine (0.087 g, 0.33 mmol) was added to a cooled
solution (0 °C) of azidomesylate 11 (0.166 g, 0.30 mmol) and
MeOH (121 lL, 3.0 mmol, 10 equiv) in CH2Cl2 (1.5 mL) under an ar-
gon atmosphere and the mixture was allowed to reach room tem-
perature. Stirring was maintained overnight. Concentration of the
mixture gave the crude aminophosphonium salt 13, which was
characterized by NMR: 1H NMR (CDCl3): d 7.80–6.95 (m, 30H,
6C6H5), 4.83 and 4.72 (dd, 2H, J 11.0 Hz, CH2Ph), 4.72 and 4.62
(dd, 2H, J 12.1 Hz, CH2Ph), 4.67 and 4.31 (dd, 2H, J 11.6 Hz, CH2Ph),
4.74 (d, 1H, J1,2 1.9 Hz, H-1), 4.40 (dd, 1H, J3,4 9.1, J4,5 9.5 Hz, H-4),
4.18 (dd, 1H, J5,6a 8.0, J6a,6b 10.6 Hz, H-6a), 3.92 (dd, 1H, J5,6b 2.0 Hz,
H-6b), 3.86 (ddd, 1H, H-5), 3.78 (dd, 1H, J2,3 3.5 Hz, H-3), 3.29 (s,
3H, OCH3), 3.20 (dddd, 1H, J2,NH 11.0, J2,P 11.0 Hz H-2), 2.41 (s,
3H, CH3SO2); 13C NMR (CDCl3): d 138.27, 138.01, 137.50 (C-quat.
C6H5), 134.45 (J 2.6 Hz, Cpara), 133.78 (J 11.1 Hz, Cortho), 133.50,
133.34, 129.39 (J 13.3 Hz, Cmeta), 128.27–127.08 (C6H5), 100.33
(J1,P 5.3 Hz, C-1), 78.41 (J3,P 2.3 Hz, C-3), 75.20 (C-4), 74.52, 73.19,
72.91 (CH2Ph), 72.15 (C-5), 69.43 (C-6), 55.05 (C-2), 54.40
(OCH3), 38.83 (CH3SO2); 31P NMR (CDCl3): d 41.14. Salt 13 was stir-
red for 8 h in a mixture of 1.5 M sodium hydroxide (1 mL, 5 equiv)
4.7. Pentenyl 2-allyloxycarbonylamino-3,4,6-tri-O-benzyl-2-
deoxy-a-D-mannopyranoside 17
Triphenylphosphine (0.175 g, 0.67 mmol) was added to a cooled
solution (0 °C) of azidomesylate 11 (0.330 g, 0.60 mmol) and pent-
4-en-1-ol (124 lL, 1.20 mmol) in CH2Cl2 (1.5 mL) under an argon
atmosphere and the mixture was allowed to reach room tempera-
ture and stirred for 16 h. Concentration gave the crude aminophos-
phonium salt 16 characterized by NMR. 1H NMR d 7.80–7.05 (m,
30H, 6C6H5), 5.74 (dddd, 1H, pentenyl CH), 4.99–4.90 (m, 2H, pen-
tenyl CH2), 4.86 and 4.76 (dd, 2H, J 11.0 Hz, C6H5CH2), 4.73 and 4.60
(dd, 2H, J 12.1 Hz, C6H5CH2), 4.70 and 4.36 (dd, 2H, J 11.6 Hz,
C6H5CH2), 4.71 (d, 1H, J1,2 2.0 Hz, H-1), 4.45 (dd, 1H, J3,4 9.7, J4,5
9.0 Hz, H-4), 4.21 (dd, 1H, J5,6a 7.5, J6a,6b 10.6 Hz, H-6a), 3.94 (dd,
1H, J5,6b 1.9 Hz, H-6b), 3.89 (ddd, 1H, H-5), 3.83 (ddd, 1H, J2,3 3.8,
J3,P 0.9 Hz, H-3), 3.68 (ddd, 1H, J 6.6, J 6.6, J 9.7 Hz, 0.5 pentenyl
OCH2), 3.28 (ddd, 1H, J 6.6, J 6.6, J 9.7 Hz, 0.5 pentenyl OCH2),
3.18 (dddd, 1H, J2,NH 9.7, J2,P 12.0 Hz, H-2), 2.33 (s, 3H, CH3SO2),
2.05–1.94 (m, 2H, pentenyl CH2), 1.58–1.48 (m, 2H, pentenyl
CH2); 13C NMR (CDCl3): d 137.88, 137.79, 137.32, (C-quat. C6H5),
137.52 (pentenyl CH), 134.47 (J 2.4 Hz, Cpara), 133.60 (J 11.1 Hz,
Cortho), 129.30 (J 13.3 Hz, Cmeta), 128.32–127.02 (C6H5), 120.90 (J
104.1 Hz, Cipso), 114.51 (pentenyl@CH2), 99.33 (J1,P 4.9 Hz, C-1),
78.221 (J3,P 2.6 Hz, C-3), 74.99 (C-4), 74.48, 73.05, 72.83 (CH2Ph),
71.82 (C-5), 69.28 (C-6), 66.59 (pent OCH2), 55.05 (C-2), 38.74
(CH3SO2), 29.71, 27.91 (OCH2CH2CH2); 31P NMR (CDCl3): d 40.92.
Salt 16 was dissolved in a mixture of 1.5 M NaOH (2.1 mL,
3.15 mmol) and methanol (6 mL) and the mixture was stirred over-
and methanol (3 mL). After neutralization with acetic acid (69 lL,
1.20 mmol) and concentration to dryness, the free-amino deriva-
tive was acetylated overnight in a 1:2 acetic anhydride–pyridine
mixture (10 mL). The mixture was concentrated again and the
product was purified by column chromatography (6:1 ethyl ace-
tate–acetone). The pure product was recovered as an oil in 91%
yield. 138 mg, Rf 0.71 (6:1 ethyl acetate–acetone), [
a]D = +33.6 (c
1.0, CHCl3) {lit.45 D = +30.4 (c 1.0, CHCl3)}; 1H NMR (CDCl3): d
[a]
7.45–7.20 (m, 15H, 3C6H5), 6.04 (d, 1H, J2,NH 8.9 Hz, H-2), 4.90
and 4.47 (dd, 2H, J 10.8 Hz, CH2Ph), 4.77 (d, 1H, J1,2 1.6 Hz, H-1),
4.75 and 4.49 (dd, 2H, J 10.6 Hz, CH2Ph), 4.71 (ddd, 1H, J2,3
4.3 Hz, H-2), 4.66 and 4.50 (dd, 2H, J 11.9 Hz, CH2Ph), 4.07 (ddd,
1H, J4,5 8.6, J5,6a 1.6, J5,6b 4.7 Hz, H-5), 3.85–3.65 (m, 4H, H-3, H-4,
H-6a, H-6b), 3.38 (s, 3H, OCH3), 2.05 (s, 3H, CH3CON); 13C NMR
(CDCl3): d 170.47 (CH3CON), 138.42, 137.96, 137.88, (C-quat.
C6H5), 128.40–127.73 (C6H5), 100.42 (C-1), 77.73 (C-3), 74.03 (C-
4), 75.16, 71.63, 71.22 (CH2Ph), 70.43 (C-5), 68.70 (C-6), 55.06
(OCH3), 49.12 (C-2), 23.50 (CH3CON).
night before neutralization with acetic acid (145 lL, 2.55 mmol).
The crude mixture was concentrated and the residue was dissolved
in dichloromethane (6 mL) and water (2.5 mL) containing sodium
bicarbonate (100 mg). Allyl chloroformate (96 lL, 0.90 mmol)
4.6. Methyl 2-allyloxycarbonylamino-3,4,6-tri-O-benzyl-2-
deoxy-a-D-mannopyranoside 15
was added and the mixture was stirred vigorously for 4 h. The
aqueous phase was extracted with CH2Cl2, then the combined or-
ganic phases were washed with water, dried (Na2SO4) and concen-
trated. The crude product was purified by column chromatography
(1:3 ethyl acetate–petroleum ether). Pure product 17 was recov-
ered in 77% yield: 0.276 g; Rf 0.65 (1:3 ethyl acetate–petroleum
Triphenylphosphine (0.135 g, 0.515 mmol) was added to a
cooled solution (0 °C) of azidomesylate 11 (0.260 g, 0.47 mmol)
and MeOH (190 lL, 4.7 mmol, 10 equiv) in CH2Cl2 (1.5 mL) under
an argon atmosphere and the mixture was allowed to reach room
temperature. Stirring was maintained overnight and the solution
was concentrated; the residue was stirred for 8 h in a mixture of
1.5 M sodium hydroxide (1.42 mL, 5 equiv) and methanol
(4.5 mL). After neutralization with acetic acid (98 lL, 1.71 mmol)
and concentration to dryness the residue was dissolved in CH2Cl2
ether), [a]
D = +21.7 (c 1.0, CHCl3); 1H NMR (CDCl3): d 7.46–7.30
(m, 15H, C6H5), 6.02 (m, 1H, allyl CH2), 5.88 (m, 1H, pentenyl
CH@), 5.45–5.27 (m, 3H, allyl CH2@, NH), 5.15–5.00 (m, 2H, pente-
nyl CH2), 4.99 (d, 1H, J1,2 1.0 Hz, H-1), 4.97 and 4.54 (dd, 2H, J
10.8 Hz, CH2Ph), 4.90–4.62 (dd, 2H, J 11.8 Hz, CH2Ph), 4.73–4.57
(dd, 2H, J 11.5 Hz, CH2Ph), 4.72–4.66 (m, 2H, allyl CH2), 4.50
(ddd, 1H, J2,3 4.4, J2,NH 8.9 Hz, H-2), 4.16 (dd, 1H, J3,4 9.0 Hz, H-3),
3.90–3.82 (m, 2H, H-4, H-6a), 3.80–3.72 (m, 3H, H-4, H-6b,
(5 mL), after which water (2 mL), NaHCO3 (0.079 g, 0.94 mmol)
and allyl chloroformate (75 lL, 0.705 mmol) were successively

D. Lafont et al. / Tetrahedron: Asymmetry 22 (2011) 1197–1204
1203
pentenyl OCH), 3.51 (ddd, 1H, J 6.5, 6.5, 9.6 Hz, pentenyl OCH), 2.20
(m, 2H, OCH2CH2), 1.76 (m, 2H, OCH2CH2CH2). 13C NMR (CDCl3): d
156.21 (NHCOO), 138.32, 138.06, 137.96, 137.86 (pentenyl CH@),
128.29–127.63 (C6H5), 132.80 (allyl CH@), 117.74 (allyl CH2@),
115.02 (pentenyl CH2@), 99.35 (C-1), 77.93 (C-3), 74.07 (C-4),
75.16, 73.45, 71.12 (CH2Ph), 70.63 (C-5), 68.61 (C-6), 67.16 (pente-
nyl OCH2), 65.74 (allyl CH2), 54.97 (CH3), 51.11 (C-2), 30.21, 28.51
(OCH2CH2CH2). Anal. Calcd for C36H43NO7 (601.73): C, 71.86; H,
7.20; N, 2.33. Found; C, 71.90; H, 7.04; N, 2.11.
(ddd, 1H, J5,6a 6.8, J5,6b 6.8 Hz, H-5), 3.75 (dd, 1H, H-3), 3.62 (d,
2H, H-6a, H-6b), 2.89 (s, 3H, CH3SO2), 2.02 (s, 3H, CH3CON); 13C
NMR (CDCl3): d 170.87 (CH3CON), 138.24, 137.70, 137.02, (C-quat.
C6H5), 128.86–128.01 (C6H5), 80.56 (C-3), 78.74 (C-2), 78.21 (C-1),
75.24, 73.72, 72.62 (CH2Ph), 74.75 (C-5), 73.33 (C-4), 67.55 (C-6),
38.58 (SO2CH3), 23.45 (CH3CON). HMRS [M+H+] C30H36NO8S: calcd
570.2156, found 570.2148.
4.10. Pentenyl 2-allyloxycarbonylamino-3,4,6-tri-O-benzyl-2-
deoxy-a-D-talopyranoside 21
4.8. N-(3,4,6-Tri-O-benzyl-2-O-mesyl-b-D-
galactopyranosyl)triphenylphosphine imide 18
A mixture of salt 18 [obtained by reaction of azidomesylate 12
(0.250 g, 0.45 mmol) and triphenylphosphine (0.137 g, 0.52 mmol)
in dichloromethane (2 mL)] and 4-penten-1-ol (0.50 mL, 10 equiv)
was stirred for 4 h in toluene (1 mL) at 100 °C. The solution was
concentrated in vacuo and the crude product was treated overnight
with 1.5 M sodium hydroxide (1.5 mL) and methanol (8 mL). After
neutralization (AcOH), the solution was concentrated again; the
free-amino derivative was dissolved in dichloromethane (5 mL),
after which water (2 mL), sodium bicarbonate (72 mg) and allyl
Triphenylphosphine (0.175 g, 0.67 mmol) was added to a cooled
solution (0 °C) of azidomesylate 12 (0.330 g, 0.60 mmol) in CH2Cl2
(2.0 mL) under an argon atmosphere and the mixture was allowed
to reach room temperature and stirred for 16 h. Concentration gave
the crude imide salt 18 characterized by NMR. 1H NMR (CDCl3): d
7.80–7.25 (m, 30H, C6H5), 5.14 (dd, 1H, J1,2 8.1, J2,3 9.7 Hz, H-2),
5.04 and 4.67 (dd, 2H, J 11.7 Hz, CH2Ph), 4.80 and 4.76 (dd, 2H, J
12.3 Hz, CH2Ph), 4.60 (dd, 1H, J1,P 18.9 Hz, H-1), 4.44 and 4.39
(dd, 2H, J 12.2 Hz, CH2Ph), 3.99 (br d, 1H, J3,4 2.7 Hz, H-4), 3.62
(dd, 1H, H-3), 3.61–3.52 (m, 3H, H-5, H-6a, H-6b), 3.04 (s, 3H,
CH3SO2). 13C NMR (CDCl3): d 138.76, 138.02, 137.94 C-quat.C6H5),
133.54 (J 9.6 Hz, Cortho), 132.04 (J 2.6 Hz, Cpara), 131.40 (J 97.6, Cipso),
128.29–127.57 (Cmeta, C6H5), 88.93 (J1,P 3.8 Hz, C-1), 85.25 (J2,P
23.1 Hz, C-1), 81.31 (J3,P 3.7 Hz, C-1), 74.23 (C-4), 74.27, 73.28,
72.50 (CH2Ph), 73.80 (C-5), 69.30 (C-6), 39.65 (CH3SO2). 31P NMR
(CDCl3): d 30.37. HRMS [M+H+] C46H47NO7PS: calcd 788.2805,
found 788.2810.
chloroformate (70 lL, 0.66 mmol) were successively added and
the biphasic mixture was stirred vigorously for 4 h. The aqueous
phase was extracted with dichloromethane (2 ꢀ 10 mL), the com-
bined organic phases were washed with a saturated sodium bicar-
bonate solution (5 mL), dried and concentrated. The crude residue
was purified by column chromatography (1:3 ethyl acetate–petro-
leum ether), affording the pure glycoside 21 in 69% yield: 0.170 g,
oily material; Rf 0.73 (1:3 ethyl acetate–petroleum ether),
[a]
D = +16.3 (c 1.0, CHCl3). 1H NMR (CDCl3): d 7.45–7.30 (m, 15H,
3C6H5), 6.51 (d, 1H, J2,NH 9.1 Hz, NH), 5.97–5.85 (m, 1H, allyl
CH@), 5.81 (m, 1H, pentenyl CH@), 5.30–5.16 (m, 2H, allyl CH2@),
4.97 and 4.52 (dd, 2H, J 10.8 Hz, CH2Ph), 4.86 (d, 1H, J1,2 1.2 Hz,
H-1), 4.77 and 4.51 (dd, 2H, J 11.7 Hz, CH2Ph), 4.60–4.52 (m, 2H, al-
lyl CH2), 4.55 and 4.46 (dd, 2H, J 11.5 Hz, CH2Ph), 4.31 (ddd, 1H, J2,3
4.3 Hz, H-2), 3.97 (br dd, 1H, J4,5 0.8, J5,6a 7.1, J5,6b 6.0 Hz, H-5), 3.94
(br d, 1H, J3,4 2.9 Hz, H-4), 3.90 (dd, 1H, H-3), 3.66 (dd, 1H, J5,6a 7.1,
J6a,6b 9.2 Hz, H-6a), 3.69–3.62 (m, 1H, pentenyl OCH), 3.58 (dd, 1H,
J5,6b 6.0 Hz, H-6b), 3.46–3.38 (ddd, 1H, J 9.6, 9.4, 6.4 Hz, pentenyl
OCH), 2.16–2.07 (m, 2H, pentenyl CH2), 1.71–1.60 (m, 2H, pentenyl
CH2); 13C NMR (CDCl3): d 156.45 (NCOO), 138.22, 138.17, 138.09
(C-quat. C6H5), 138.14 (pentenyl CH@), 133.12 (allyl CH@),
128.64–127.61 (C6H5), 117.06 (allyl CH2@), 115.02 (pentenyl
CH2@), 100.45 (C-1), 75.54 (C-4), 75.39, 73.63, 70.02 (CH2Ph),
72.58 (C-3), 69.46 (C-5), 69.03 (C-6), 67.30 (pentenyl OCH2),
65.42 (allyl OCH2), 50.50 (C-2), 30.41 (pentenyl CH2), 48.53 (C-2),
28.73 (pentenyl CH2), 48.53 (C-2). HRMS [M+H+] C36H44NO7: calcd
602.3112, found 602.3117.
4.9. Methyl 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-
talopyranoside 19 and N-acetyl-3,4,6-tri-O-benzyl-2-O-mesyl-b-
a-D-
D
-galactopyranosyl amine 20
Salt 18 [obtained by reaction of azidomesylate 12 (0.250 g,
0.45 mmol) and triphenylphosphine (0.137 g, 0.52 mmol) in
dichloromethane (2 mL)] was refluxed for 12 h in methanol
(5 mL). After dilution with methanol (5 mL), 1.5 M sodium hydrox-
ide (1.6 mL, 2.4 mmol) was added and the mixture was stirred for
6 h. After neutralization with acetic acid and concentration, the
residue was acetylated overnight with a 2:1 pyridine–acetic anhy-
dride mixture (10 mL). The mixture was concentrated to dryness
and the products were recovered after purification by column
chromatography (2:3 ethyl acetate–petroleum ether). Compound
19 was obtained as an oily material in 51% yield: 0.119 mg, Rf
0.46 (1:1 ethyl acetate–petroleum ether), [a]D = +13.5 (c 1.0,
CHCl3). 1H NMR (CDCl3): d 7.41–7.29 (m, 15H, 3C6H5), 7.24 (d,
1H, J2,NH 8.7 Hz, NH), 4.90 and 4.55 (dd, 2H, J 10.3 Hz, CH2Ph),
4.73 (d, 1H, J1,2 1.3 Hz, H-1), 4.73 and 4.50 (dd, 2H, J 11.6 Hz,
CH2Ph), 4.65 and 4.53 (dd, 2H, J 11.7 Hz, CH2Ph), 4.60 (ddd, 1H,
J2,3 4.3 Hz, H-2), 4.03–3.96 (m, 2H, H-4, H-5), 3.93 (dd, 1H, J3,4
4.3 Hz, H-3), 3.78 (dd, 1H, J5,6a 7.3, J6a,6b 9.2 Hz, H-6a), 3.66 (dd,
1H, J5,6b 5.8 Hz, H-6b), 3.37 (s, 3H, OCH3), 1.77 (s, 3H, CH3CON);
13C NMR (CDCl3): d 170.46 (CH3CON), 138.22, 138.14, 137.98, (C-
quat. C6H5), 128.59–127.69 (C6H5), 101.12 (C-1), 75.76 (C-4),
75.51, 69.99, 68.82 (CH2Ph), 72.19 (C-3), 69.20 (C-5), 68.82 (C-6),
55.05 (C-2), 54.24 (OCH3), 48.53 (C-2), 23.37 (CH3CON). HMRS
[M+H+] C30H36NO6: calcd 506.2537, found 506.2546.
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