Regioselective de-O-benzylation of phenylsulfonylethylidene (PSE) acetals-containing benzylated monosaccharides using triisobutylaluminum (TIBAL)

Article abstract of DOI:10.1016/S0040-4020(02)01249-8

A series of benzylated monosaccharidic PSE acetals undergoes regioselective TIBAL-mediated de-O-benzylation, to afford monobenzyl ethers, readily available as building blocks for oligosaccharides synthesis.

Full text of DOI:10.1016/S0040-4020(02)01249-8

Tetrahedron 58 (2002) 9579–9583
Regioselective de-O-benzylation of phenylsulfonylethylidene
(PSE) acetals-containing benzylated monosaccharides using
triisobutylaluminum (TIBAL)
a
Berengere Chevalier-du Roizel, Elena Cabianca, Patrick Rollin and Pierre Sinay¨
b
b
a
,
*
´
`
a
´
´
´
Ecole Normale Superieure, Departement de Chimie, associe au CNRS, 24 rue Lhomond, 75231 Paris Cedex 05, France
´
b
´ ´
ICOA-UMR 6005, Universite d’Orleans, B.P. 6759, F-45067 Orleans Cedex 02, France
Received 31 July 2002; accepted 1 October 2002
Abstract—A series of benzylated monosaccharidic PSE acetals undergoes regioselective TIBAL-mediated de-O-benzylation, to afford
monobenzyl ethers, readily available as building blocks for oligosaccharides synthesis. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
A major strategical task in the field of carbohydrate
chemistry is the chemical synthesis of selectively protected
mono- or oligosaccharides. One of the most classical
protecting groups of carbohydrate hydroxyl functions is
probably the benzyl ether. It is easily1 installed, stable to a
wide range of reagents and readily removed in the presence
Scheme 1. TIBAL-promoted regioselective de-O-benzylation.
monosaccharidic benzylated PSE acetals and the results are
¨
of many various functionalities using Lewis/Bronsted acids,
compiled in Table 1. The results obtained conform to the
mechanism6 proposed before and give access to selectively
modified building blocks suitable for oligosaccharides
synthesis.
dissolving metals or catalytic hydrogenolysis. An attractive
access to partially benzylated carbohydrates is provided by
selective de-O-benzylation of easily available polybenzyl-
ated precursors. This has been previously achieved by
catalytic hydrogenolysis,2 controlled acetolysis3 or by
reacting Lewis acids4 such as SnCl4 and TiCl4 or mixtures5
like CrCl2/LiI. We recently reported6 that triisobutyl-
aluminum (TIBAL) led to highly regioselective mono-de-
O-benzylation of perbenzylated mono- and disaccharide
derivatives. We have also discovered7 that diisobutyl-
aluminum (DIBAL) was a reagent of choice to perform
remarkable regioselective mono- and bis-de-O-benzylation
of either a or b peralkylated (methyl or benzyl ethers)
cyclodextrins. As part of our program to evaluate the wider
scope and limitations of regioselective de-O-benzylation
using TIBAL and DIBAL, we have applied this method-
ology to the recently described8 phenylsulfonylethylidene
(PSE) acetals (Scheme 1) which display various interesting
properties as compared to benzylidene acetals.
2. Results and discussion
Application of the standard deprotection conditions to
methyl 2,3-di-O-benzyl-4,6-O-(2-phenylsulfonyl)-ethyl-
idene-a-D-glucopyranoside8 1 afforded the expected
mono-de-O-benzylated product 2 in nearly quantitative
yield (97%) (entry 1). As in the case6 of methyl 2,3,4,6-
tetra-O-benzyl-a-D-glucopyranoside, we can suggest that
two contiguous cis-oriented alkoxy groups are necessary for
the mono-de-O-benzylation reaction. A mono-reduction of
the two cis-located benzyloxy groups was then observed for
methyl 2,3-di-O-benzyl-4,6-O-(2-phenylsulfonyl)-ethyl-
idene-a-D-mannopyranoside8 3, giving (90% yield) a
mixture of monobenzyl ethers 4 and 5 in a 8:1 ratio (entry 2).
The scope and regioselectivity of the de-O-benzylation
reaction were evaluated using a panel of representative
According to the known procedure,8 methyl 2,3-di-O-
benzyl-4,6-O-(2-phenylsulfonyl)-ethylidene-a-D-altro-
pyranoside 6 was then prepared from the related 4,6-diol9
and the above PSE acetal reacted quickly with TIBAL to
afford the monobenzyl ether 7 in almost quantitative yield
(97%) (entry 3). However, traces of a side-product resulting
Keywords: monosaccharides; phenylsulfonylethylidene (PSE) acetals;
triisobutylaluminum (TIBAL); de-O-benzylation; regioselectivity.
*
Corresponding author. Tel.: þ33-1-44-32-33-90; fax: þ33-1-44-32-33-
97; e-mail: pierre.sinay@ens.fr
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)01249-8

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B. Chevalier-du Roizel et al. / Tetrahedron 58 (2002) 9579–9583
Table 1. Regioselective de-O-benzylation using TIBAL in anhydrous toluene at 508C
Entry
1
Reactant
Product
Yield
97%
Time
2 h
2
90% (8:1), 4:5
2 h
3
97%a
1 h
4
99% (1:5:3), 9:10:11
1 h
5
Decompositionb
None
None
5 daysc
6
Decompositionb
5 daysc
a
Traces of by-product coming from reduction at the anomeric position were also detected by MS.
No major compound was formed. TLC revealed the formation of many by-products, which were not isolated.
We had to wait 5 days for the complete consumption of starting material.
b
c
from reduction at the anomeric position could also be
O-benzyl-4,6-O-(2-phenylsulfonyl)-ethylidene-a-D-allo-
pyranoside 8, which reacted also very quickly and
efficiently with TIBAL to give a quantitative mixture of
compounds 9, 10 and 11 in a 1:5:3 ratio (entry 4). In this
particular case, substituents on the first three positions are
now all cis-oriented, which can explain why de-O-benzyl-
ation takes place on both 2- and 3-positions. Moreover, a
rather unusual—in such conditions—reduction is observed
at the anomeric center to yield the D-allitol derivative 11.
detected by mass spectrometry. Indeed, no de-O-benzyl-
ation on the 2-position was expected as substituents on the
first three positions are all trans-oriented. However, mono-
de-O-benzylation on the 3-position can be accounted for the
presence of a cis-oriented alkoxy group on either the
anomeric position or the 4-position. One can also wonder
whether the oxygen atoms on the sulfone may intervene in
this reaction. More complex was the case of methyl 2,3-di-

B. Chevalier-du Roizel et al. / Tetrahedron 58 (2002) 9579–9583
9581
Entry 5 shows that although located in a cis relationship, the
benzyloxy group on the 3-position of methyl 2,3-di-O-
benzyl-4,6-O-(2-phenylsulfonyl)-ethylidene-b-D-galacto-
pyranoside8 12 is not reduced. A similar absence of
reactivity has already been observed6 in the case of methyl
2,3,4,6-tetra-O-benzyl-b-D-galactopyranoside. As a result,
no major reaction occurs in this case and the starting
material is slowly decomposed. A similar slow degradation
is observed in the case of phenyl 2,3-di-O-benzyl-4,6-O-(2-
phenylsulfonyl)-ethylidene-1-thio-b-D-glucopyranoside
13, which contains no cis-oriented alkoxy-groups
(entry 6).
MgSO4, concentration under reduced pressure and silica gel
column purification (EtOAc/cyclohexane¼1/3), the altro-
side 6 (732 mg, 72%) was obtained as a colourless foam:
[a]2D3¼þ28 (c 1.0, CHCl3); MS (CI) m/z 563.0 [MNa]þ,
579.0 [MK]þ; 1H NMR (CDCl3) d 7.90–7.86 (m, 2H, o-SO2
H-Ar), 7.62–7.21 (m, 13H, H-Ar), 5.05 (t, 1H, J7–8
4.8 Hz, H-7), 4.57 (br s, 1H, H-1), 4.50–4.30 (m, 4H,
¼
2£CH2Ph), 4.07 (m, 2H, H-5þH-6a), 3.74 (dd, 1H, J3–4
¼
3.0 Hz, J4–5¼9.4 Hz, H-4),3.65(brt, 1H, J2–3¼ 2.6 Hz, H-3),
3.58 (br d, 1H, H-2), 3.48 (m 1H, H-6b), 3.47 (d, 2H,
J7–8¼4.8 Hz, H-8), 3.30 (s, 3H, OMe); 13C NMR (CDCl3) d
139.9, 138.4, 137.3, (Cquat-Ar), 133.7 (p-SO2 CH-Ar), 129.1–
127.4(CH-Ar),100.0(C-1),97.1(C-7),77.0(C-4),76.1(C-2),
72.7, 72.5 (CH2PhþC-3), 68.9 (C-6), 60.1 (C-8), 57.8 (C-5),
55.5 (OMe); Anal. calcd for C29H32O8S (540.61): C, 64.43; H,
5.97, found: C, 64.51; H, 6.01%.
3. Conclusion
In summary, the TIBAL-induced regioselective de-O-
benzylation of benzylated monosaccharidic PSE acetals
affords an operationally simple protocol for the regio-
selective cleavage of benzyl ethers. Functionalising the free
hydroxyl, then selectively removing8 the PSE protecting
group lead to selectively modified monosaccharides which
can in turn be protected on the primary position only, to
afford useful orthogonally protected building blocks for
oligosaccharides synthesis. This process constitutes an
elegant alternative to already existing methods requiring
regioselective O-benzylation10 or de-O-benzylation.11
Besides, this method may be extended to disaccharides
and other polyols. Alternate deprotecting methods and ring-
opening abilities of PSE acetals are currently under
investigation.
4.1.2. Methyl 2,3-di-O-benzyl-a-D-allopyranoside (14). A
60% aqueous acetic acid solution (4 mL) of the parent 4,6-
O-benzylidene acetal (680 mg, 1.47 mmol) prepared
according to Collins et al.12 was stirred at 808C until
complete consumption of the starting material (ca 1 h).
Evaporation then co-evaporation with toluene left a residue
which was purified by flash chromatography
(EtOAc/cyclohexane¼1/1) to afford syrupy compound 14
(490 mg, 89%): [a]2D3¼þ81 (c 1.0, CHCl3); MS (CI) m/z
1
397.0 [MNa]þ, 413.0 [MK]þ; H NMR (CDCl3) d 7.41–
7.22 (m, 10H, H-Ar), 5.17 (d, 1H, Jgem¼11.6 Hz, CHHPh);
4.74 (d, 1H, J1–2¼3.8 Hz, H-1), 4.65 (s, 2H, CH2Ph), 4.61
(d, 1H, Jgem¼11.6 Hz, CHHPh); 4.04 (br t, 1H, J3–4
¼
2.8 Hz, H-3), 3.78 (m, 3H, H-5þ2£H-6), 3.57–3.40 (m, 2H,
H-2þH-4), 3.42 (s, 3H, OMe), 2.65 (d, 1H, J¼10.8 Hz, OH-
4), 2.34 (br s, 1H, OH-6); 13C NMR (CDCl3) d 138.7, 137.7
(Cquat-Ar), 128.6–127.8 (CH-Ar), 97.9 (C-1), 76.8 (C-2),
75.5 (C-3), 74.3, 71.6 (CH2Ph), 68.2 (C-5), 66.9 (C-4), 62.3
(C-6), 56.0 (OMe); Anal. calcd for C21H26O6 (374.42): C,
67.36; H, 7.00, found: C, 67.43; H, 7.04%.
4. Experimental
4.1. General
Optical rotations were measured on a Perkin–Elmer 241
digital polarimeter with a path length of 1 dm. Mass spectra
were recorded on a Nermag R10-10 spectrometer, using
chemical ionisation with ammonia. Elemental analyses
4.1.3. Methyl 2,3-di-O-benzyl-4,6-O-(2-phenylsulfonyl)-
ethylidene-a-D-allopyranoside (8). As for the preparation
of 6, an ice-cold THF (13 mL) solution of the above 4,6-diol
(491 mg, 1.3 mmol) was reacted with (E)-1,2-bis(phenyl-
sulfonyl)-ethylene (404 mg, 1.31 mmol, 1 equiv.) to afford
after silica gel column purification chromatography
(EtOAc/cyclohexane¼1/3) the alloside 8 (566 mg, 80%)
as a colourless foam: [a]2D3¼þ9 (c 1.0, CHCl3); MS (CI) m/z
´
were performed by the Service d’Analyse de l’Universite
Pierre et Marie Curie, 75252 Paris Cedex 05, France. NMR
spectra were recorded on a Bruker AM-400 (400 and
1
100.6 MHz for H and 13C, respectively), using TMS as
internal standard. TLC was performed on silica gel 60 F254
(Merck) and developed by charring with concentrated
H2SO4. Flash column chromatography was performed
using silica gel 60 (230–400 mesh, Merck).
1
563.0 [MNa]þ, 579.0 [MK]þ; H NMR (CDCl3) d 7.89–
7.85 (m, 2H, o-SO2 H-Ar), 7.64–7.19 (m, 13H, H-Ar), 4.99
(t, 1H, Jvic¼4.8 Hz, H-7), 4.62 (d, 1H, J1–2¼4.0 Hz, H-1),
4.60–4.43 (m, 4H, CH2Ph), 4.09 (m, 2H, H-5þH-6a), 3.91
(br t, 1H, J2–3¼3.0 Hz, H-3), 3.30–3.50 (m, 4H, H-8þH-
2þH-6b), 3.38 (s, 3H, OMe), 3.24 (dd, 1H, J3–4¼2.4 Hz,
J4–5¼9.1 Hz, H-4); 13C NMR (CDCl3) d 139.9, 139.0,
137.6 (Cquat-Ar), 133.8 (p-SO2 CH-Ar), 129.1–127.1 (CH-
Ar), 99.9 (C-1), 96.7 (C-7), 79.2 (C-4), 74.8 (C-2), 73.9,
71.1 (CH2Ph), 73.0 (C-3), 68.9 (C-6), 60.0 (C-8), 57.4 (C-5),
56.2 (OMe); Anal. calcd for C29H32O8S (540.61): C, 64.43;
H, 5.97, found: C, 64.47; H, 6.02%.
Recently described PSE acetals 1, 3, 12, 13, as well as new
compounds 6 and 8, were prepared according to the
previously reported8 procedure.
4.1.1. Methyl 2,3-di-O-benzyl-4,6-O-(2-phenylsulfonyl)-
ethylidene-a-D-altropyranoside (6). An ice-cold THF
(19 mL) solution of the 4,6-diol (704 mg, 1.88 mmol)
prepared according to Dechaux et al.9 was treated by NaH
(182 mg, 3.8 mmol, 2 equiv., 50% in mineral oil). After
15 min stirring at rt (E)-1,2-bis(phenylsulfonyl)-ethylene
(580 mg, 1.88 mmol, 1 equiv.) and a few crystals of Bu4NBr
were added. The mixture was stirred 12 h at rt then treated
with brine and extracted with EtOAc. After drying over
4.2. General procedure using TIBAL
TIBAL (1.5 M in toluene, 6 equiv.) was added to a stirred
solution of starting material in anhydrous toluene (same

9582
B. Chevalier-du Roizel et al. / Tetrahedron 58 (2002) 9579–9583
volume as TIBAL) at rt under argon. The reaction mixture
was heated at 508C until TLC (EtOAc/cyclohexane¼1/2)
indicated no starting material but a major product. The
mixture was cooled to 08C, aqueous 1N HCl was carefully
added dropwise, and the mixture was stirred vigorously at rt
for 15 min. The mixture was filtered (Celitew) into a
separating funnel and washed thoroughly with EtOAc. The
organic layer was washed with brine, dried (MgSO4),
filtered and the solvent was removed in vacuo. The residue
Hz, CHHPh), 4.71 (d, 1H, J1–2¼1.3 Hz, H-1), 4.67 (d, 1H,
Jgem¼11.7 Hz, CHHPh), 4.06 (dd, 1H, J5 –6a¼4.5 Hz,
Jgem¼10.0 Hz, H-6a), 3.85 (dd, 1H, J2–3¼3.8 Hz, J3–4
¼
9.8 Hz, H-3), 3.77 (dd, 1H, J2–3¼3.8 Hz, J1–2¼1.3 Hz,
H-2), 3.68 (t, 1H, H-4), 3.62 (t, 1H, H-6b), 3.57 (dd, 1H,
Jgem¼14.7 Hz, J7–8a¼4.7 Hz, H-8a), 3.54 (td, 1H, J4–5
,
J5 – 6b,2£J5 – 6a, H-5), 3.51 (dd, 1H, Jgem¼14.7 Hz,
J7– 8b¼5.3 Hz, H-8b), 3.32 (s, 3H, OMe); 13C NMR
(CDCl3, TMS) d 139.8, 137.3 (2£Cquat-Ar), 133.8, 129.0,
128.6, 128.4, 128.2, 127.9 (10£CH-Ar), 99.1 (C-1), 97.0
(C-7), 79.4 (C-4), 78.3 (C-2), 73.7 (CH2Ph), 68.4 (C-6), 68.2
(C-3), 62.6 (C-5), 59.9 (C-8), 55.0 (OMe); Anal. calcd for
C22H26O8S (450.50): C, 58.65; H, 5.82, found: C, 58.86; H,
6.12%.
was
purified
by
flash
chromatography
(EtOAc/cyclohexane¼1/1) to afford the de-O-benzylated
product as a colourless foam.
4.2.1. Methyl 3-O-benzyl-4,6-O-(2-phenylsulfonyl)-ethyl-
idene-a-D-glucopyranoside (2). Compound 1 (309 mg,
0.57 mmol) was submitted to TIBAL (3.4 mL, 3.4 mmol,
1 M, 6 equiv.) in anhydrous toluene (3.5 mL), to afford,
after stirring 2 h at 508C, the mono-benzyl ether 2 (250 mg,
97%) as a colourless foam: [a]2D3¼þ102 (c 1.0, CHCl3); MS
4.2.3. Methyl 2-O-benzyl-4,6-O-(2-phenylsulfonyl)-ethyl-
idene-a-D-altropyranoside (7). Starting material
6
(105 mg, 0.20 mmol) was submitted to TIBAL (1.2 mL,
1.20 mmol, 1 M, 6 equiv.) in anhydrous toluene (1.2 mL), to
afford, after stirring 1 h at 508C, mono-benzyl ether 7
(84 mg, 97%) as a colourless foam: [a]2D3¼þ45 (c 1.0,
1
(CI) m/z 468 [MNH4]þ; H NMR (CDCl3) d 5.04 (t, 1H,
J7–8¼4.9 Hz, H-7), 4.86 (d, 1H, Jgem¼11.6 Hz, CHHPh),
4.77 (d, 1H, J1–2¼3.0 Hz, H-1), 4.71 (d, 1H, Jgem¼11.6 Hz,
CHHPh), 4.08 (dd, 1H, J5–6a¼4.8 Hz, Jgem¼10.2 Hz,
1
CHCl3); MS (CI) m/z 468 [MNH4]þ; H NMR (CDCl3) d
7.94–7.35 (m, 10H, 10£H-Ar), 5.16 (t, 1H, J7–8¼4.9 Hz,
H-7), 4.69 (br s, 1H, H-1), 4.63 (br s, 2H, CH2Ph), 4.11 (dd,
1H, Jgem¼10.3 Hz, J5–6a¼5.1 Hz, H-6a), 3.98 (br s, 1H,
H-3), 3.94 (td, 1H, J4–5,J5–6b,2£J5–6a, H-5), 3.76 (dd,
1H, J3–4¼2.9 Hz, J4–5¼9.9 Hz, H-4), 3.67 (br d, 1H,
J2–3¼3.2 Hz, H-2), 3.63 (t, 1H, J5–6b¼Jgem¼10.0 Hz,
H-6b), 3.57 (dd, 1H, Jgem¼14.6 Hz, J7–8a¼4.7 Hz, H-8a),
3.53 (dd, 1H, Jgem¼14.6 Hz, J7–8b¼5.1 Hz, H-8b), 3.37 (s,
3H, OMe); 13C NMR (CDCl3, TMS) d 139.6, 137.0
(2£Cquat-Ar), 133.7, 129.1–127.7 (10£CH-Ar), 99.8
(C-1), 97.2 (C-7), 76.4 (C-4), 76.3 (C-2), 72.5 (CH2Ph),
68.6 (C-6), 66.7 (C-3), 59.9 (C-8), 57.6 (C-5), 55.5 (OMe);
Anal. calcd for C22H26O8S (450.50): C, 58.65; H, 5.82,
found: C, 58.65; H, 6.14%.
H-6a), 3.68 (m, 2H, H-2þH-4), 3.53 (t, 1H, J5–6b
,
J6a–6b,10.0 Hz, H-6b), 3.51 (d, 2H, J7–8¼4.9 Hz, H-8),
3.43 (m, 1H, H-3), 3.42 (s, 3H, OMe); 13C NMR (CDCl3,
TMS) d 139.7, 138.3 (2£Cquat-Ar), 133.9, 129.1, 128.3,
128.1, 127.9, 127.7 (10£CH-Ar), 99.7 (C-1), 96.5 (C-7),
81.6 (C-3), 78.3 (C-4), 74.5 (CH2Ph), 72.1 (C-2), 68.5 (C-6),
61.9 (C-5), 59.9 (C-8), 55.4 (OMe); Anal. calcd for
C22H26O8S (450.50): C, 58.65; H, 5.82, found: C, 58.51;
H, 5.97%.
4.2.2. Methyl 3-O-benzyl-4,6-O-(2-phenylsulfonyl)-ethyl-
idene-a-D-mannopyranoside (4), methyl 2-O-benzyl-4,6-
O-(2-phenylsulfonyl)-ethylidene-a-D-mannopyranoside
(5). The precursor 3 (150 mg, 0.28 mmol) was submitted
to TIBAL (1.7 mL, 1.70 mmol, 1 M, 6 equiv.) in
anhydrous toluene (1.7 mL), to afford, after stirring 2 h at
508C, first, side-product 5 (12 mg, 10%), followed by major
product 4 (100 mg, 80%) both in the form of colourless
foams:
4.2.4. Methyl 3-O-benzyl-4,6-O-(2-phenylsulfonyl)-ethyl-
idene-a-D-allopyranoside (9), methyl 2-O-benzyl-4,6-O-
(2-phenylsulfonyl)-ethylidene-a-D-allopyranoside (10)
and 2,3-di-O-benzyl-4,6-O-(2-phenylsulfonyl)-ethyl-
idene-D-allitol (11). The precursor 8 (105 mg, 0.2 mmol)
was submitted to TIBAL (1.2 mL, 1.20 mmol, 1 M,
6 equiv.) in anhydrous toluene (1.2 mL), to afford, after
stirring 1 h at 508C, first, a mixture of compounds 9 and 11
(38 mg, 44%, 1:3), followed by 10 (48 mg, 55%), all in the
form of colourless foams. NMR data for compounds 9 and
11 were extrapolated from the NMR spectra of a sample of
their mixture. As a consequence, neither elemental analysis
nor optical rotation are given.
Compound 4. [a]2D3¼þ74 (c 1.0, CHCl3); MS (CI) m/z 468
[MNH4]þ; 1H NMR (CDCl3) d 7.97–7.38 (m, 10H, 10£CH-
Ar), 5.06 (t, 1H, J7–8¼4.9 Hz, H-7), 4.78 (d, 1H, Jgem¼11.9
Hz, CHHPh), 4.70 (d, 1H, J1–2¼1.3 Hz, H-1), 4.62 (d, 1H,
Jgem¼11.9 Hz, CHHPh), 4.05 (m, 1H, H-6a), 3.98 (dd, 1H,
J1–2¼1.3 Hz, J2–3¼3.4 Hz, H-2), 3.88 (br t, 1H, H-4), 3.74
(dd, 1H, J2–3¼3.4 Hz, J3–4¼9.5 Hz, H-3), 3.65–3.57 (m,
2H, H-5þH-6b), 3.54 (dd, 1H, Jgem¼14.5 Hz, J7–8a
¼
4.4 Hz, H-8a), 3.50 (dd, 1H, Jgem¼14.5 Hz, J7–8b¼5.2 Hz,
H-8b), 3.34 (s, 3H, OMe); 13C NMR (CDCl3, TMS) d
139.6, 137.8 (2£Cquat-Ar), 133.8, 129.1, 128.4, 128.1,
127.8, 127.7 (10£CH-Ar), 100.9 (C-1), 96.8 (C-7), 78.6
(C-4), 75.1 (C-3), 72.7 (CH2Ph), 69.5 (C-2), 68.4 (C-6),
62.5 (C-5), 59.9 (C-8), 54.9 (OMe); Anal. calcd for
C22H26O8S (450.50): C, 58.65; H, 5.82, found: C, 58.51;
H, 5.87%.
Compound 9. MS (CI) m/z 468 [MNH4]þ; 1H NMR (CDCl3)
d 7.94–7.30 (m, 10H, 10£H-Ar), 5.08 (t, 1H, J7–8¼4.9 Hz,
H-7), 4.64 (d, 1H, J1– 2¼3.7 Hz, H-1), 4.44 (d, 1H,
Jgem¼12.1 Hz, CHHPh), 4.26 (d, 1H, Jgem¼12.1 Hz,
CHHPh), 4.16 (m, 1H, H-6a), 4.02 (m, 1H, H-5), 3.86 (br
t, 1H, J2–3,J3–4,3.1 Hz, H-3), 3.64 (br m, 1H, H-2), 3.50
(m, 3H, H-8þH-6b), 3.40 (s, 3H, OMe), 3.39 (dd, 1H,
J4–5¼9.8 Hz, J3–4¼3.1 Hz, H-4); 13C NMR (CDCl3, TMS)
d 139.8, 138.6, (2£Cquat-Ar), 133.8, 129.0–127.1 (10£CH-
Ar), 99.7 (C-1), 96.9 (C-7), 79.1 (C-4), 75.9 (C-3), 74.5
(CH2Ph), 68.9 (C-6), 67.7 (C-2), 59.9 (C-8), 56.9 (C-5), 56.2
(OMe).
Compound 5. [a]2D3¼þ10 (c 0.5, CHCl3); MS (CI) m/z 468
[MNH4]þ; 1H NMR (CDCl3) d 7.98–7.30 (m, 10H, 10£CH-
Ar), 5.11 (t, 1H, J7–8¼4.5 Hz, H-7), 4.74 (d, 1H, Jgem¼11.7

B. Chevalier-du Roizel et al. / Tetrahedron 58 (2002) 9579–9583
9583
Compound 11. MS (CI) m/z 546 [MNH4]þ; 1H NMR
References
(CDCl3) d 7.94–7.30 (m, 15H, 15£H-Ar), 4.97 (t, 1H,
J7–8¼4.9 Hz, H-7), 4.68 (d, 1H, Jgem¼11.5 Hz, CHHPh),
4.62 (d, 2H, 2£CHHPh), 4.57 (d, 1H, Jgem¼11.3 Hz,
CHHPh), 4.10 (dd, 1H, J5– 6a¼5.4 Hz, Jgem¼11.0 Hz,
H-6a), 3.78 (m, 5H, 2£H-1þH-2þH-3þH-5), 3.66 (dd,
1H, J3–4¼3.6 Hz, J4–5¼9.2 Hz, H-4), 3.50 (m, 2H, H-8),
3.36 (t, 1H, J5–6b,Jgem, H-6b); 13C NMR (CDCl3, TMS) d
139.6, 137.6, 137.3 (3£Cquat-Ar), 133.8, 129.1–128.1
(15£CH-Ar), 96.0 (C-7), 80.6, 78.8 (C-2þC-3), 79.9
(C-4), 73.8, 73.0 (2£CH2Ph), 70.2 (C-6), 62.3 (C-5), 61.0
(C-1), 59.9 (C-8).
1. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis. 3rd ed. Wiley: New York, 1999; Chapter 2.
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2. (a) Beaupere, D.; Boutbaia, I.; Wadouachi, A.; Frechou, C.;
Demailly, G.; Uzan, R. New J. Chem. 1992, 16, 405–411.
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Carbohydr. Res. 1981, 95, 125–131. (c) Angibeaud, P.; Utille,
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811–817.
Compound 10. [a]2D3¼þ24 (c 1.0, CHCl3); MS (CI) m/z 468
[MNH4]þ; 1H NMR (CDCl3) d 7.93–7.37 (m, 10H, 10£H-
Ar), 5.10 (t, 1H, J7–8,4.8 Hz, H-7), 4.77 (d, 1H, Jgem¼12.3
Hz, CHHPh), 4.71 (d, 1H, J1–2¼3.5 Hz, H-1), 4.61 (d, 1H,
Jgem¼12.3 Hz, CHHPh), 4.24 (br s, 1H, H-3), 4.12 (dd, 1H,
Jgem¼10.1 Hz, J5 – 6a¼4.9 Hz, H-6a), 3.93 (dt, 1H,
5. Falck, J. R.; Barma, D. K.; Venkataraman, S. K.; Baati, R.;
Mioskowski, C. Tetrahedron Lett. 2002, 43, 963–966.
6. Sollogoub, M.; Das, S. K.; Mallet, J. M.; Sinay¨, P. C. R. Acad.
Sci. Paris 1999, 2, 441–448.
7. (a) Pearce, A. J.; Sinay¨, P. Angew. Chem. Int. Ed. 2000, 39,
3610–3612. (b) Wang, W.; Pearce, A. J.; Zhang, Y. M.; Sinay¨, P.
Tetrahedron: Asymmetry 2001, 12, 517–523. (c) du Roizel, B.;
Baltaze, J. P.; Sinay¨, P. Tetrahedron Lett. 2002, 43, 2371–2373.
J4–5,J56b,2£J5–6a¼10.0 Hz, H-5), 3.58 (dd, 1H, Jgem
¼
14.7 Hz, H-8a), 3.54 (dd, 1H, Jgem¼14.7 Hz, H-8b), 3.50
(t, 1H, J5–6b,Jgem¼10.0 Hz, H-6b), 3.45 (t, 1H, H-2), 3.40
(s, 3H, OMe), 3.22 (dd, 1H, J3–4¼2.5 Hz, J4–5¼9.7 Hz,
H-4), 3.16 (br s, 1H, OH); 13C NMR (CDCl3, TMS) d
139.6, 137.0 (2£Cquat-Ar), 137.0, 133.8, 128.9, 128.6,
128.2, 128.1, 127.9 (10£CH-Ar), 99.3 (C-1), 97.0 (C-7),
78.5 (C-4), 73.5 (C-2), 70.5 (CH2Ph), 68.6 (C-6), 66.7 (C-3),
59.8 (C-8), 57.1 (C-5), 55.8 (OMe); Anal. calcd for
C22H26O8S (450.50): C, 58.65; H, 5.82, found: C, 58.38;
H, 6.30%.
´
8. Chery, F.; Rollin, P.; De Lucchi, O.; Cossu, S. Synthesis 2001,
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Acknowledgements
`
11. Beaupere, D.; Boutbaiba, I.; Demailly, G.; Uzan, R.
´
The authors would like to thank Dr Florence Chery and Dr
Arnaud Tatibouet for their helpful contribution to this
project.
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¨