Phenylsulfonylethylidene (PSE) acetals: A novel protective group in carbohydrate chemistry

Article abstract of DOI:10.1055/s-2001-10817

A range of sugar-derived phenylsulfonylethylidene acetals were easily obtained from the corresponding diols and 1,2-bis(phenylsulfonyl)ethylene under basic conditions. Deprotection methods for such acetals have also been investigated.

Full text of DOI:10.1055/s-2001-10817

286
PAPER
Phenylsulfonylethylidene (PSE) Acetals: A Novel Protective Group in
Carbohydrate Chemistry
Florence Chéry,a Patrick Rollin,*a Ottorino De Lucchi,b Sergio Cossub
a Institut de Chimie Organique et Analytique, associé au CNRS, Université d’Orléans, B.P. 6759, F-45067 Orléans, France
Fax +33(2)38494579; E-mail patrick.rollin@univ-orleans.fr
b Dipartimento di Chimica, Università Ca’ Foscari di Venezia, Dorsoduro 2137, I-30123 Venezia, Italy
Received 1 August 2000; revised 20 October 2000
Following a double Michael addition pathway, either
(Z)- or (E)-1,2-bis(phenylsulfonyl)ethylene reacted at
room temperature with diverse a- and b-diols in THF, us-
ing NaH as the base and Bu4NBr as the phase transfer cat-
alyst. Saccharidic polyols reacted similarly in DMF, using
t-BuOK as the base. In all cases, the initial Michael addi-
tion of an alkoxide ion is followed by eliminative expul-
sion of a sulfinate ion. The resulting transient alkoxy vinyl
sulfone is then attacked by a second alkoxide ion in a
Michael type addition (Scheme 2).
Abstract: A range of sugar-derived phenylsulfonylethylidene ace-
tals were easily obtained from the corresponding diols and
1,2-bis(phenylsulfonyl)ethylene under basic conditions. Deprotec-
tion methods for such acetals have also been investigated.
Key words: protective groups, carbohydrates, acetals, sulfones,
Michael additions
Introduction
In carbohydrate chemistry, multistep protection and
deprotection strategies often require effective methods for
selective introduction-expulsion of protective groups.1
1,3-Dioxolanes and 1,3-dioxanes have proven to be very
useful tools for that purpose, and in addition they can dis-
play a number of interesting reactions different from a
simple deprotection.2 For example, benzylidene acetals
can undergo regiospecific oxidative3 and reductive open-
ings,4-6 giving diversely functionalized saccharides. Con-
sequently, there is a persistent demand for new cyclic
acetals showing atypical properties and displaying un-
common synthetic features. As our favorite theme is the
exploration of thiofunctionalized sugars, we have started
to investigate the preparation and the reactivity of phenyl-
sulfonylethylidene (PSE) acetals as carbohydrate protec-
tive groups.7
Scheme 2
Such a reaction using either (Z)- or (E)-1,2-bis(phenylsul-
fonyl)ethylene has been reported with particular emphasis
on the configuration of the substitution product with re-
spect to the starting olefin. It has been shown that the re-
action occurs with predominant configuration retention.10
(Z)- or (E)-1,2-Bis(phenylsulfonyl)ethylene can be easily
and inexpensively synthesized,11 which gave us the possi-
bility to test the scope of the reaction on various carbohy-
drate compounds. a- and b-Diols and polyols derived
from pyrano and furano sugars were synthesized easily
and rapidly according to well known literature procedures
(see experimental part). These substrates were then sub-
mitted with success to the above reaction conditions. (Ta-
bles 1 and 2)
Synthesis of PSE Acetals
Arylsulfonylalkynes as well as (Z)- and (E)-1,2-bis(phe-
nylsulfonyl)ethylene8 are well known powerful dieno-
philes in Diels-Alder reactions and good electrophilic
acceptors in the Michael addition. As an extension to re-
cent literature results,9 we report here that PSE acetals can
be readily prepared from unprotected glycosides under
basic conditions (Scheme 1).
Diversely substituted a-diols have been tested at first.
They react easily with either (Z)- or (E)-1,2-bis(phenyl-
sulfonyl)ethylene, forming dioxolane-type acetals 1-4
with good yields albeit - as expected - with poor diastereo-
selectivity. In contrast, b-diols gave exclusively the
equatorially-configurated dioxanes 5-14 in conformity
with the well documented case of 4,6-O-benzylidene
derivatives.
Scheme 1
Synthesis 2001, No. 2, 286–292 ISSN 0039-7881 © Thieme Stuttgart · New York

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Phenylsulfonylethylidene (PSE) Acetals
287
Table 1 Sugar Derived PSE 1,3-Dioxolanes
degradation and they were almost entirely recovered.
For example, suspending acetal 5 in 80% AcOH (50 mg/
5 mL) and stirring the mixture at 80 °C for 48 hours pro-
voked no modification and returned more than 96% of the
starting material. Other standard acidic conditions - 80%
HCO2H, 0.7 N H2SO4, 7 N HCl/CrCl3 or BF3•OEt2/
CH2Cl2/MeOH - proved equally ineffective. However,
when compound 5 was submitted to 9:1 TFA/H2O under
careful TLC monitoring (60 °C, 2 h), both benzyl groups
were expelled, whereas the PSE acetal remained unaffect-
ed (Scheme 3).
Product
R
Yield Epimeric
(%) Ratioa
1
2
3
R = H
94
6:4
5:4
5:4
R = OH 84
R = OBn 91
4
-
88
1:1
a * Refers to the carbon atom marked with an asterisk.
Scheme 3
The reluctance of PSE acetals to acid-catalyzed hydroly-
sis may be connected with the fact that both acetal oxygen
atoms become harder (therefore less prone to undergo
protonation) because of the presence of a sulfonyl group;
this behavior was previously observed in the case of other
acetals bearing electron-withdrawing groups.12
Properties of the PSE acetals
A thorough examination of deprotection conditions for
the PSE acetals has shown interesting results. Conven-
tional acetals are widely known to be prone to deprotec-
tion under acidic hydrolysis conditions. In our hands,
however, PSE acetals resisted standard hydrolytic condi-
tions. When submitted to hydrolysis (or alcoholysis) in di-
verse acidic medium conditions, PSE acetals showed no
Nevertheless, PSE acetals can be easily deprotected under
classical reductive conditions. For example, treatment of
either 11 or 5 by LiAlH4 in Et2O (optionally in the pres-
ence of AlCl3) delivered the corresponding well-known
Table 2 Sugar Derived PSE 1,3-Dioxanes
Product
Yield (%)
99
Product
Yield (%)
83
5
10
6
7
87
97
11
12
86
81
8
9
83
70
13
14
96
95
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288
F. Chéry et al.
PAPER
diols 1513,14 and 1615 in 78% and 77% yield respectively.
In contrast, milder reducing systems such as NaBH4 or
NaBH3CN/TFA proved ineffective whereas deprotection
and overreduction can be reached by submitting 5 to
DIBAH in refluxing toluene to produce after acetylation
the itol derivative 17 (Scheme 4).
Bu4NBr were added. After stirring for 12 h at r.t., the mixture was
treated with brine and extracted with EtOAc. The combined organic
phases were dried (MgSO4), concentrated under reduced pressure
and the crude product was purified by silica gel column chromatog-
raphy.
PSE Acetals from Polyols; General Procedure
To a solution of the polyol (1 equiv) in DMF (200 mg/5 mL) was
added t-BuOK (2 equiv). After 15 min at r.t., 1,2-bis(phenylsulfon-
yl)ethylene (1 equiv) and a few crystals of Bu4NBr were added. Af-
ter stirring for 12 h at r.t., the mixture was concentrated under re-
duced pressure and the crude product was purified by silica gel col-
umn chromatography.
3-Deoxy-1,2-O-isopropylidene-5,6-O-(2-phenylsulfonyl)ethyl-
idene-a-D-glucofuranoses (1A and B)
Obtained from 3-deoxy-1,2-O-isopropylidene-a-D-glucofuranose16
and purified by column chromatography on silica gel (petroleum
ether/EtOAc, 7:3) to afford the acetal in 94% yield as a colorless
gum; epimeric ratio A/B = 3:2; [a]D -2.0 (c = 1, CHCl3).
IS-MS: m/z = 371.0 [M + H]+, 393.0 [M + Na]+.
1H NMR: d = 1.28 (s, iPrdmajor), 1.29 (s, iPrdminor), 1.46 (s, iPrdmajor),
1.49 (s, iPrdminor), 1.45-1.58 (m, H-3bmajor, H-3bminor), 1.96 (dd,
J2-3a = <0.5, J3a-4 = 4.3, J3a-3b = 13.8 Hz, H-3aminor), 2.12 (dd, J2-3a
=
<0.5, J3a-4 = 4.3, J3a-3b = 13.2 Hz, H-3amajor), 3.42 (d, J = 4.9 Hz,
CH2SO2minor), 3.47 (d, J = 4.7 Hz, CH2SO2major), 3.72 (dd,
J5-6b = 6.1, J6a-6b = 8.3 Hz, H-6bminor), 3.83-4.13 (m, H-4major, H-
Scheme 4
4
minor, H-5major, H-5 minor, H-6amajor, H-6a minor, H-6bmajor), 4.66 (dd,
J1-2 = 3.8, J2-3a = <0.5, J2-3b = 4.6 Hz, H-2major), 4.71 (dd, J1-2 = 3.6,
J2-3a = <0.5, J2-3b = 4.7 Hz, H-2minor), 5.30 (t, J = 4.7 Hz, H-7major),
5.42 (t, J = 4.9 Hz, H-7minor), 5.71 (d, J1-2 = 3.8 Hz, H-1major), 5.75
(d, J1-2 = 3.6 Hz, H-1minor), 7.51-7.68 (m, H-Ar), 7.90-7.94 (m,
ortho-H-Ar PhSO2).
13C NMR: d = 26.5, 27.1 [C(CH3)2], 36.0 (C-3minor), 36.2 (C-3major),
59.8 (CH2SO2minor), 60.3 (CH2SO2major), 68.2, 68.4 (C-6major and C-
6minor), 77.4, 78.0, 78.2, 78.4, (C-4major, C-4minor, C-5major, C-5minor),
80.6 (C-2major and C-2minor), 99.6, 99.7 (C-7major and C-7minor), 106.1
Conclusion
A new class of cyclic acetals bearing a phenylsulfonyl
group have been synthesized under basic conditions, with
high yields and high regio- and stereoselectivity. The PSE
acetals resist acid-catalyzed hydrolysis but they can be
deprotected under reductive conditions and moreover
they display various interesting properties as compared to
benzylidene acetals. Chemical behavior and more precise-
ly the ring-opening ability of PSE acetals is currently un-
der investigation in our laboratory.
(C-1
and C-1 minor), 111.8, 111.9 [C(CH3)2], 128.7-134.2
major
(CHarom), 140.0 (Carom).
Anal. calcd for C17H22O7S: C 55.12, H 5.99. Found: C 55.22, H
6.01.
1,2-O-Isopropylidene-5,6-O-(2-phenylsulfonyl)ethylidene-a-D-
glucofuranoses (2A and B)
Solvents were dried and distilled by standard methods. All reagents
were of commercial quality (Acros, Aldrich or Lancaster) and were
used without purification. Petroleum ether used had bp 35-60 °C.
Reactions were carried out under dry argon and were monitored by
TLC analysis with silica gel plates (Kieselgel 60F254, Merck). Com-
pounds were visualized with UV light and heat treatment with 10%
H2SO4 in EtOH. Column chromatography was performed on silica
Obtained from 1,2-O-isopropylidene-a-D-glucofuranose17 and puri-
fied by column chromatography on silica gel (petroleum ether/ethyl
acetate 1:1) to afford the acetal in 84% yield as a colorless gum;
epimeric ratio A/B 5:4; [a]D -3.0 (c = 1, CHCl3).
IS-MS for C17H22O8S : m/z = 387.0 [M+H]+, 409.0 [M+Na]+,
1H NMR : d = 1.29 (s, iPrdmajor), 1.46 (s, iPrdmajor), 3.42 (d, J = 4.9
Hz, CH2SO2major), 3.46 (d, J = 4.9 Hz, CH2SO2 minor), 3.81-4.26 (m,
H-3major, H-3minor, H-4major, H-4minor, H-5major, H-5minor, H-6amajor, H-
6bmajor, H-6aminor, H-6bminor), 5.28 (t, J = 4.9 Hz, H-7minor), 5.46 (t,
J = 4.9 Hz, H-7major), 5.86 (d, J1-2 = 3.5 Hz, H-1 minor), 5.88 (d,
J1-2 = 3.6 Hz, H-1major), 7.52-7.70 (m, H-Ar), 7.87-7.94 (m, ortho-
H-Ar PhSO2).
13C NMR: d = 26.5, 26.9, 27.0 [C(CH3)2], 59.8 (CH2SO2minor), 60.3
(CH2SO2major), 68.5, 68.9 (C-6major and C-6minor), 73.4, 74.1, 75.1,
75.2, 81.1, 81.5 (C-3major, C-3minor, C-4major, C-4minor, C-5major, C-
gel 60 M (0.036-0.063 mm, Merck). 1H NMR (250 MHz) and 13
C
NMR (62.6 MHz) spectra (CDCl3, TMS as internal standard) were
recorded with a Bruker AVANCE DPX 250 spectrometer. Chemi-
cal shifts (d) are reported in ppm units by reference to TMS, cou-
pling constants (J) are reported in Hz and refer to apparent peak
multiplicity. Assignments are based on H,H- and C,H-COSY exper-
iments. Mass spectra were obtained in Ion Spray® (IS) method with
a API 300 Perkin Elmer SCIEX spectrometer. Specific rotations
were measured in CHCl3 at r.t. with a Perkin Elmer 410 polarimeter.
Melting points were determined with a Büchi SMP-20 melting point
apparatus and are uncorrected.
5
minor), 85.4 (C-2major and C-2minor), 99.2 (C-7major and C-7minor),
105.6 (C-1major), 105.7 (C-1minor), 112.8, 112.9 [C(CH3)2], 126.3-
134.4 129.4-134.2 (CHarom), 140.4, 140.5 (Carom).
PSE Acetals from Diols; General Procedure
Anal. calcd for C17H22O8S: C 52.84, H 5.74. Found: C 52.80, H
5.81.
To a solution of the diol (1 equiv) in THF (200 mg/5 mL) was added
NaH (2 equiv, 60% suspension in oil) at 0 °C. After 15 min at r.t.,
1,2-bis(phenylsulfonyl)ethylene (1 equiv) and a few crystals of
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Phenylsulfonylethylidene (PSE) Acetals
289
3-O-Benzyl-1,2-O-isopropylidene-5,6-O-(2-phenylsulfonyl)eth-
ylidene-a-D-glucofuranoses (3A and B)
CH2SO2), 3.59 (dt, 1 H, J4-5 = 9.6, J5-6a = 4.7, J5-6b = 10.1 Hz, H-5),
3.85 (t, 1 H, J2-3 = J3-4 = 9.1 Hz, H-3), 4.00 (dd, 1 H, J5-6a = 4.7,
J6a-6b = 10.1 Hz, H-6a), 4.51 (d, 1 H, J1-2 = 3.8 Hz, H-1), 4.64 and
4.81 (2 d, AB system, 2 H, Jgem = 12.1 Hz, PhCH2O), 4.74 and 4.78
(2 d, AB system, 2 H, Jgem = 11.2 Hz, PhCH2O), 4.98 (t, 1 H, J = 4.9
Hz, H-7), 7.29-7.61 (m, 13 H, H-Ar), 7.89-7.93 (m, 2 H, ortho-H-
Ar PhSO2).
Obtained
from
3-O-benzyl-1,2-O-isopropylidene-a-D-
glucofuranose18 and purified by column chromatography on silica
gel (petroleum ether/EtOAc, 7:3) to afford the acetal in 91% yield
as a colorless gum; epimeric ratio A/B 5:4, [a]D -16.0 (c = 1,
CHCl3).
IS-MS: m/z = 477.0 [M + H]+, 494.5 [M + NH4]+, 499.5 [M + Na]+.
13C NMR: d = 55.8 (OCH3), 60.3 (CH2SO2), 62.0 (C-5), 69.0 (C-6),
74.2 (PhCH2O), 75.2 (PhCH2O), 78.5 (C-3), 79.4 (C-2), 82.3 (C-4),
97.0 (C-7), 99.5 (C-1), 126.3-134.2 (CHarom), 138.4, 139.1, 140.2
(Carom).
1H NMR: d = 1.29 (s, iPrdmajor), 1.31 (s, iPrdminor), 1.46 (s, iPrdmajor),
1.48 (s, iPrdminor), 3.44 (d, J = 5.1 Hz, CH2SO2minor), 3.50 (d, J = 4.9
Hz, CH2SO2major), 4.17-4.30 (m, H-5major, H-5 minor), 3.97-4.06 (m,
H-4major, H-4 minor, H-6bmajor, H-6aminor, H-6bminor), 3.91 (dd,
J5-6a = 6.6 Hz, J6a-6b = 8.8 Hz, H-6amajor), 3.81 (d, J2-3 = <0.5, J3-
4 = 3.4 HZ, H-3major), 3.92 (d, J2-3 = <0.5, J3-4 = 3.4 Hz, H-3minor),
Anal. calcd for C29H32O8S: C 64.43, H 5.97. Found: C 64.37, H
6.05.
Methyl 2,3-Di-O-benzyl-4,6-O-(2-phenylsulfonyl)ethylidene-a-
D-mannopyranoside (6)
4.54 (d, J1-2 = 3.6, J2-3 = <0.5 Hz, H-2major), 4.56 (d, J1-2 = 3.6, J2-3
=
<0.5 Hz, H-2minor), 4.44 and 4.59 (2 d, AB system, Jgem = 11.7 Hz,
PhCH2Ominor), 4.44 and 4.58 (2 d, AB system, Jgem = 11.7 Hz,
PhCH2Omajor), 5.34 (t, J = 4.9 Hz, H-7major), 5.42 (t, J = 5.1 Hz, H-
7minor), 5.85 (d, J1-2 = 3.6 Hz, H-1minor), 5.87 (d, J1-2 = 3.6 Hz, H-
Obtained from methyl 2,3-di-O-benzyl-a-D-mannopyranoside20
and purified by column chromatography on silica gel (petroleum
ether/EtOAc, 8:2) to afford the acetal in 87% yield as a colorless
gum; [a]D +42.0 (c = 1, CHCl3).
1major), 7.23-7.65 (m, H-Ar), 7.91-7.95 (m, ortho-H-Ar PhSO2).
IS-MS: m/z = 558.0 [M + NH4]+, 563.0 [M + Na]+.
13C NMR: d = 26.6, 27.3, 30.1 [C(CH3)2], 60.2 (CH2SO2minor), 60.4
(CH2SO2major), 67.8 (C-6minor), 68.2 (C-6major), 72.7 (2 î PhCH2O),
73.3, 73.9 (C-5major and C-5minor), 80.7, 80.9 (C-4major and C-4minor),
81.8 (C-3minor), 82.1 (C-3major), 82.7 (C-2major and C-2minor), 99.1 (C-
7major), 99.3 (C-7minor), 105.6 (C-1major), 105.7 (C-1minor), 112.3,
1H NMR : d = 3.26 (s, 3 H, OCH3), 3.49 (d, 2 H, J = 5.1, CH2SO2),
3.54-3.65 (m, 2 H, H-5, H-6b), 3.77 (dd, 1 H, J2-3 = 3.2, J3-4 = 10.8
Hz, H-3), 3.76 (dd, 1 H, J1-2 = 1.5, J2-3 = 3.2 Hz, H-2), 3.94-4.04 (m,
1 H, H-6a), 3.98 (t, 1 H, J3-4 = J4-5 = 10.8 Hz, H-4), 4.62 (d, 1 H,
J1-2 = 1.5 Hz, H-1), 4.53 and 4.67 (2 d, AB system, 2 H, Jgem = 12.1
Hz, PhCH2O), 4.68 and 4.77 (2 d, AB system, 2 H, Jgem = 12.1 Hz,
PhCH2O), 5.03 (t, 1 H, J = 5.1 Hz, H-7), 7.30-7.69 (m, 13 H, H-
Ar), 7.91-7.95 (m, 2 H, ortho-H-Ar PhSO2).
13C NMR: d = 55.2 (OCH3), 60.5 (CH2SO2), 63.8 (C-5), 68.8 (C-6),
73.0 (PhCH2O), 73.9 (PhCH2O), 76.4 (C-2 and C-3), 79.4 (C-4),
97.3 (C-7), 100.7 (C-1), 127.8-134.0 (CHarom), 138.4, 139.1, 140.1
(Carom).
112.4 [C(CH3)2], 127.9-134.2 (CHarom), 137.6, 140.1 (Carom
)
.
Anal. calcd for C24H28O8S: C 60.49, H 5.92. Found: C 60.59, H
5.90.
3-O-Benzyl-1,2-O-isopropylidene-4,5-O-(2-phenylsulfonyl)eth-
ylidene-b-D-fructofuranoses (4 A and B)
Obtained from 3-O-benzyl-1,2-O-isopropylidene-b-D-fructo-
furanose19 and purified by column chromatography on silica gel
(petroleum ether/EtOAc, 7:3) to afford the acetal in 88% yield as a
colorless gum; epimeric ratio A/B 1:1; [a]D -47.0 (c = 3.4, CHCl3).
Anal. calcd for C29H32O8S: C 64.43, H 5.97. Found: C 64.33, H
5.87.
IS-MS: m/z = 494.5 [M + NH4]+, 499.5 [M + Na]+.
Methyl 2,3-Di-O-benzyl-4,6-O-(2-phenylsulfonyl)ethylidene-b-
D-galactopyranoside (7)
1H NMR : d = 1.37 (s, iPrd), 1.39 (s, iPrd), 1.45 (s, iPrd), 1.46 (s,
iPrd), 3.24 (d, J3-4 = 7.2 Hz, H-3), 3.36 (d, J3-4 = 7.4 Hz, H-3), 3.44
(dd, J7-8b = 4.2, J8a-8b = 14.5 Hz, H-8b), 3.45 (d, J = 4.9, CH2SO2),
3.54 (dd, J7-8a = 4.2 Hz, H-8a), 3.80 (d, J1a-1b = 8.5 Hz, H-1b), 3.83
(d, J1a-1b = 8.5 Hz, H-1b), 4.13-3.88 (m, H-1a, H-1a, H-5, H-5, H-
6a, H-6a, H-6b, H-6b), 4.34 (dd, J4-5 = 5.2 Hz, H-4), 4.41 (dd,
J4-5 = 5.2 Hz, H-4), 4.59 and 4.60 (2 d, AB system, Jgem = 11.7,
PhCH2O), 4.83 and 4.33 (2 d, AB system, Jgem = 11.9 Hz, PhCH2O),
5.40 (dd, J7-8a = 4.2, J7-8b = 4.2 Hz, H-7), 5.65 (t, J = 4.9 Hz, H-7),
7.29-7.32 (m, H-Ar), 7.50-7.65 (m, H-Ar PhSO2), 7.93-7.98 (m,
ortho-H-Ar PhSO2).
13C NMR: d = 26.3, 26.4, 27.1, 27.2 [C(CH3)2], 59.9, 60.1, 60.7,
61.1 (CH2SO2 and C-1), 72.0, 72.8, 73.5, 77.1 (PhCH2O and C-6),
72.1, 74.3, 76.3, 76.6 (C-3 and C-5), 77.8, 79.0 (C-4), 98.8, 99.8 (C-
7), 103.9 (C-2), 112.3, 112.4 [C(CH3)2], 127.8-129.1 (CHarom),
133.3-133.9 (CHarom), 134.1, 137.5, 139.2, 140.1 (Carom).
Obtained from methyl 2,3-di-O-benzyl-b-D-galactopyranoside21
and purified by column chromatography on silica gel (petroleum
ether/EtOAc, 1:1) to afford the acetal in 97% yield as a colorless
gum; [a]D +26.0 (c = 1, CHCl3).
IS-MS: m/z = 509.0 [M - OMe]+, 541.0 [M + H]+, 558.0 [M +
NH4]+, 563.0 [M + Na]+
1H NMR : d = 3.44-3.55 (m, 1 H, H-5), 3.47 (t, 1 H, J2-3 = 9.8,
J3-4 = 3.4 Hz, H-3), 3.53 (s, 3 H, OCH3), 3.55 (dd, 1 H, J1-2 = 7.2,
J2-3 = 9.8 Hz, H-2), 3.62 (d, 2 H, J = 5.1 Hz, CH2SO2), 3.83 (t, 1 H,
J5-6b = 1.9, J6a-6b = 12.5 Hz, H-6b), 4.02 (dd, 1 H, J3-4 = 3.4, J4-5 = 0.5
Hz, H-4), 4.07 (dd, 1 H, J5-6a = 1.7, J6a-6b = 12.5 Hz, H-6a), 4.22 (d,
1 H, J1-2 = 7.2 Hz, H-1), 4.68 and 4.82 (2 d, AB system, 2 H,
Jgem = 11.9 Hz, PhCH2O), 4.69 and 4.75 (2 d, AB system, 2 H,
Jgem = 10.8, PhCH2O), 5.17 (t, 1 H, J = 5.1, H-7), 7.29-7.58 (m, 13
H, H-Ar), 7.92-7.95 (m, 2 H, ortho-H-Ar PhSO2).
13C NMR: d = 56.2 (OCH3), 59.1 (CH2SO2), 64.8 (C-5), 67.6 (C-6),
71.2 (PhCH2O), 72.7 (C-4), 74.1 (PhCH2O), 77.1 (C-2), 77.6 (C-3),
95.7 (C-7), 103.6 (C-1), 126.5-132.4 (CHarom), 138.3, 139.0, 140.5
(Carom).
Anal. calcd for C24H28O8S: C 60.49, H 5.92. Found: C 60.40, H
5.80.
Methyl 2,3-Di-O-benzyl-4,6-O-(2-phenylsulfonyl)ethylidene-a-
D-glucopyranoside (5)
Obtained from methyl 2,3-di-O-benzyl-a-D-glucopyranoside15 and
purified by column chromatography on silica gel (petroleum ether/
EtOAc, 7:3) to afford the acetal in 99% yield as a colorless gum;
[a]D +23.0 (c = 1, CHCl3).
Anal. calcd for C29H32O8S: C 64.43, H 5.97. Found: C 64.55, H
6.12.
Phenyl 2,3-Di-O-benzyl-4,6-O-(2-phenylsulfonyl)ethylidene-1-
thio-b-D-glucopyranoside (8)
IS-MS: m/z = 563.0 [M + Na]+.
Obtained
from
phenyl
2,3-di-O-benzyl-1-thio-b-D-
1H NMR : d = 3.34 (s, 3 H, OCH3), 3.35 (t, 1 H, J3-4 = 9.1, J4-5 = 9.6
Hz, H-4), 3.43 (t, 1 H, J5-6b = 10.1, J6a-6b = 10.1 Hz, H-6b), 3.47 (dd,
1 H, J1-2 = 3.8, J2-3 = 9.1 Hz, H-2), 3.48 (d, 2 H, J = 4.9 Hz,
glucopyranoside22 and purified by column chromatography on sili-
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290
F. Chéry et al.
PAPER
ca gel (petroleum ether/EtOAc, 7:3) to afford the acetal in 83%
yield as a beige gum; [a]D +5.0 (c = 1, CHCl3).
IS-MS: m/z = 641.0 [M + Na]+.
1,2-O-Isopropylidene-3,5-O-(2-phenylsulfonyl)ethylidene-a-D-
xylofuranose (11)
Obtained from 1,2-O-isopropylidene-a-D-xylofuranose13,14 and pu-
rified by column chromatography on silica gel (petroleum ether/
EtOAc, 7:3) to afford the acetal in 88% yield as a colorless solid;26
mp 152-154 °C (CH2Cl2/Et2O); [a]D +3.0 (c = 1, CHCl3).
1H NMR: d = 3.25 (dt, 1 H, J4-5 = 10.4, J5-6a = 10.4, J5-6a = 4.9 Hz, H-
5), 3.44 (dd, 1 H, J1-2 = 9.8, J2-3 = 8.3 Hz, H-2), 3.46 (dd, 1 H,
J3-4 = 9.1, J4-5 = 10.4 Hz, H-4), 3.47 (d, 2 H, J = 4.9 Hz, CH2SO2),
3.54 (dd, 1 H, J5-6a = J6a-6b = 10.4 Hz, H-6b), 3.67 (dd, 1 H, J2-3 = 8.3,
J3-4 = 9.1 Hz, H-3), 4.13 (dd, 1 H, J5-6a = 4.9, J6a-6b = 10.4 Hz, H-6a),
4.66 (d, 1 H, J1-2 = 9.8 Hz, H-1), 4.68 and 4.83 (2 d, AB system, 2
H, Jgem = 11.3 Hz, PhCH2O), 4.78 and 4.84 (2 d, AB system, 2 H,
Jgem = 10.2 Hz, PhCH2O), 5.02 (t, 1 H, J = 4.9, H-7), 7.27-7.62 (m,
18 H, H-Ar), 7.90-7.94 (m, 2 H, ortho-H-Ar PhSO2).
IS-MS: m/z = 357.0 [M + H]+, 374.0 [M + NH4]+, 379.0 [M + Na]+.
1H NMR: d = 1.29 (s, 3 H, iPrd), 1.46 (s, 3 H, iPrd), 3.41 (dd, 1 H,
Jgem = 14.5, J = 5.1 Hz, CH2SO2), 3.42 (dd, 1 H, Jgem = 14.5, J = 5.1
Hz, CH2SO2), 3.92 (dd, 1 H, J4-5b = 1.9, J5a-5b = 13.2 Hz, H-5b), 4.00
(m, 1 H, H-4), 4.19 (d, 1 H, J2-3 = <0.5, J3-4 = 1.7 Hz, H-3), 4.18 (d,
1 H, J4-5a = <0.5, J5a-5b = 13.2 Hz, H-5a), 4.30 (d, 1 H, J1-2 = 3.6,
J2-3 = <0.5 Hz, H-2), 5.01 (t, 1 H, J = 5.1 Hz, H-7), 5.88 (d, 1 H,
J1-2 = 3.6 Hz, H-1), 7.52-7.69 (m, 3 H, H-Ar PhSO2), 7.87-7.91 (m,
2 H, ortho-H-Ar PhSO2).
13C NMR: d = 26.5, 27.0 [C(CH3)2], 60.6 (CH2SO2), 66.7 (C-5),
72.1 (C-4), 78.9 (C-3), 83.8 (C-2), 95.3 (C-1), 105.8 (C-7), 112.3
[C(CH3)2], 129.4-134.2 (CHarom), 140.2 (Carom).
13C : d = 60.3 (CH2SO2), 68.6 (C-5), 69.9 (C-6), 75.4 (PhCH2O),
76.3 (PhCH2O), 80.7 (C-2), 81.6 (C-4), 82.9 (C-3), (88.6 C-1), 96.8
(C-7), 128.1-128.8 (CH-Ar), 129.6, 133.3, 134.3, 138.3 (CIV-Ar).
Anal. calcd for C34H34O7S2: C 66.00, H 5.54. Found: C 66.33, H
5.34.
Benzyl 2-Acetamido-3-O-benzyl-2-deoxy-4,6-O-(2-phenylsulfo-
nylethylidene-b-D-glucopyranoside (9)
Obtained from benzyl 2-acetamido-3-O-benzyl-2-deoxy-b-D-
glucopyranoside23 and purified by column chromatography on sili-
ca gel (CH2Cl2/MeOH, 2%) to afford the acetal in 70% yield as a
beige gum; [a]D -28.0 (c = 3.2, CHCl3).
Anal. calcd for C16H20O7S: C 53.92, H 5.66. Found: C 54.17, H
5.87.
Methyl 4,6-O-(2-Phenylsulfonyl)ethylidene-b-D-galactopyrano-
side (12)
Obtained from commercially available methyl b-D-galactopyrano-
side and purified by column chromatography on silica gel (CH2Cl2/
MeOH, 5%) to afford the acetal in 81% yield as a colorless gum;
[a]D –17.0 (c = 1, CHCl3).
IS-MS: m/z = 585.5 [M + NH4]+.
1H NMR: d = 1.79 (s, 3 H, NHCOCH3), 3.26-3.36 (m, 1 H, H-2),
3.48 (d, 2 H, J = 4.9 Hz, CH2SO2), 3.40-3.56 (m, 3 H, H-4, H-5, H-
6b), 4.06 (t, 1 H, J2-3 = J3-4 = 9.4 Hz, H-3), 4.12 (dd, 1 H, J5-6a = 4.7,
J6a-6b = 10.4 Hz, H-6a), 4.48 and 4.75 (2 d, AB system, 2 H,
Jgem = 11.9 Hz, PhCH2O), 4.50 and 4.81 (2 d, AB system, 2 H,
Jgem = 11.9 Hz, PhCH2O), 4.91 (d, 1 H, J1-2 = 8.3 Hz, H-1), 4.99 (t,
1 H, J = 4.9 Hz, H-7), 5.59 (d, 1 H, Jvic = 5.7 Hz, NH), 7.28-7.31
(m, 11 H, H-Ar), 7.50-7.66 (m, 2 H, H-Ar PhSO2), 7.90-7.93 (m,
2 H, ortho-H-Ar PhSO2).
13C NMR: d = 23.8 (NHCOCH3), 57.5 (C-5), 60.3 (CH2SO2), 65.7
(C-2), 68.7 (C-6), 71.6 (PhCH2O), 74.6 (PhCH2O), 76.5 (C-4), 82.3
(C-3), 96.8 (C-7), 100.0 (C-1), 126.3-134.3 (CHarom), 137.5, 138.8,
140.1 (Carom), 170.7 (NHCOCH3).
IS-MS: m/z = 378.0 [M + NH4]+, 383.0 [M + Na]+, 399.0 [M + K]+.
1H NMR: d = 3.30 (m, 1 H, H-5), 3.49 (s, 3 H, OCH3), 3.48 (dd, 1
H, J1-2 = 7.4, J2-3 = 9.4 Hz, H-2), 3.53-3.65 (m, 3 H, H-3, CH2SO2),
3.85 (t, 1 H, J5-6b = 1.7, J6a-6b = 12.3 Hz, H-6b), 4.00 (d, 1 H,
J3-4 = 3.6, J4-5 = <0.5 Hz, H-4), 4.06 (dd, 1 H, J5-6a = 1.5, J6a-6b = 12.3
Hz, H-6a), 4.14 (d, 1 H, J1-2 = 7.4 Hz, H-1), 5.08 (t, 1 H, J = 4.9 Hz,
H-7), 7.51-7.68 (m, 3 H, H-Ar PhSO2), 7.88-7.91 (m, 2 H, ortho-
H-Ar PhSO2).
13C NMR: d = 57.6 (OCH3), 60.4 (CH2SO2), (66.5 C-5), 69.1 (C-6),
71.5 (C-2), 72.5 (C-3), 75.8 (C-4), 96.9 (C-7), 104.2 (C-1), 128.6
(CHarom), 129.6 (CHarom), 134.4 (CHarom), 140.1 (Carom).
Anal. calcd for C30H33NO8S: C 63.47, H 5.86. Found: C 63.57, H
5.99.
Anal. calcd for C15H20O8S: C 49.99, H 5.59. Found: C 50.19, H
5.44.
Methyl 2,3-Anhydro-4,6-O-(2-phenylsulfonyl)ethylidene-a-D-
allopyranoside (10)
Methyl 4,6-O-(Phenylsulfonyl)ethylidene-a-D-glucopyranoside
(13)
Obtained from commercially available methyl a-D-glucopyrano-
side and purified by column chromatography on silica gel (petro-
leum ether/EtOAc, 2:8) to afford the acetal in 96% yield as a
slightly colored gum; [a]D +76.0 (c = 1, CHCl3).
Obtained from methyl 2,3-anhydro-a-D-allopyranoside25 and puri-
fied by column chromatography on silica gel (petroleum ether/
EtOAc, 1:1) to afford the acetal in 83% yield as a colorless gum;
[a]D +83.0 (c = 1, CHCl3).
IS-MS: m/z = 311.0 [M - OMe]+, 343.0 [M + H]+, 360.0 [M +
IS-MS: m/z = 378.0 [M + NH4]+, 383.0 [M + Na]+.
NH4]+, 365.0 [M + Na]+.
1H NMR: d = 3.22 (t, 1 H, J3-4 = J4-5 = 9.2 Hz, H-4), 3.36 (s, 3 H,
OCH3), 3.42-3.59 (m, 5 H, H-2, H-5, H-6b, CH2SO2), 4.02 (dd, 1
H, J5-6a = 3.6, J6a-6b = 8.9 Hz, H-6a), 4.71 (d, 1 H, J1-2 = 3.8 Hz, H-1),
4.99 (t, 1 H, J = 4.9 Hz, H-7), 7.52-7.68 (m, 3 H, H-Ar PhSO2),
7.89-7.93 (m, 2 H, ortho-H-Ar PhSO2).
13C NMR: d = 55.6 (OCH3), 60.1 (CH2SO2), 62.1 (C-5), 68.9 (C-6),
71.6 (C-3), 73.2 (C-2), 81.0 (C-4), 97.2 (C-7), 100.1 (C-1), 128.7
(CHarom), 129.5 (CHarom), 134.3 (CHarom), 140.1(Carom).
1H NMR: d = 3.26 (dd, 1 H, J2-3 = 4.2, J3-4 = 1.3 Hz, H-3), 3.29 (s, 3
H, OCH3), 3.41 (dd, 1 H, J1-2 = 3.0, J2-3 = 4.2 Hz, H-2), 3.44 (t, 1 H,
J5-6b = 10.2, J6a-6b = 10.2 Hz, H-6b), 3.48 (d, 2 H, J = 4.9 Hz,
CH2SO2), 3.69 (dd, 1 H, J3-4 = 1.3, J4-5 = 9.2 Hz, H-4), 3.80 (dt, 1 H,
J4-5 = 9.2, J5-6a = 4.8, J5-6b = 10.2 Hz, H-5), 3.98 (dd, 1 H, J5-6a = 4.8,
J6a-6b = 10.2 Hz, H-6a), 4.80 (d, 1 H, J1-2 = 3.0 Hz, H-1), 5.11 (t, 1 H,
J = 4.9 Hz, H-7), 7.51-7.68 (m, 3 H, H-Ar PhSO2), 7.88-7.92 (m,
2 H, ortho-H-Ar PhSO2).
Anal. calcd for C15H20O8S: C 49.99, H 5.59. Found: C 49.88, H
5.66.
13C NMR: d = 50.6 (C-3), 53.5 (OCH3), 56.3 (C-2), 59.8 (C-5), 60.4
(CH2SO2), 68.8 (C-6), 77.9 (C-4), 95.5 (C-1), 97.9 (C-7), 126.8
(CHarom), 129.4 (CHarom), 134.3 (CHarom), 140.1 (Carom).
4,6-O-(2-Phenylsulfonyl)ethylidene-1,5-anhydro-arabino-hex-
1-enitol (14)
Obtained from commercially available D-glucal and purified by col-
umn chromatography on silica gel (CH2Cl2/MeOH, 2%) to afford
the acetal in 70% yield as a beige gum; [a]D +18.0 (c = 1.4, CHCl3).
Anal. calcd for C15H18O7S: C 52.62, H 5.30. Found: C 52.82, H
5.18.
Synthesis 2001, No. 2, 286–292 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Phenylsulfonylethylidene (PSE) Acetals
291
IS-MS: m/z = 330.5 [M + NH4]+, 335.5 [M + Na]+, 625.5 [2 M +
were dried (MgSO4) and concentrated under reduced pressure. The
crude residue was dissolved in pyridine (5 mL) and submitted to
peracetylation (0.5 mL Ac2O, 12 h at r.t.). After evaporation and co-
evaporation with toluene, the crude product was purified by column
chromatography on silica gel (petroleum ether/EtOAc, 1:1) to af-
ford 1,4,5,6-tetra-O-acetyl-2,3-di-O-benzyl-D-glucitol (17) as a col-
orless gum (55 mg, 50%); [a]D +7.0 (c = 1.1, CHCl3).
H]+, 642.5 [2 M + NH4]+, 647.5 [2 M + Na]+.
1H NMR: d = 3.45-3.61 (m, 2 H, H-4, H-5), 3.52 (d, 2 H, J = 4.9
Hz, CH2SO2), 3.64 (dd, 1 H, J5-6b = 4.1, J6a-6b = 9.4 Hz, H-6b), 4.13
(dd, 1 H, J5-6a = 3.5, J6a-6b = 9.4 Hz, H-6a), 4.21 (dt, 1 H, J1-3
=
J2-3 = 2.1, J3-4 = 7.1 Hz, H-3), 4.69 (dd, 1 H, J1-2 = 6.2, J2-3 = 2.1 Hz,
H-2), 5.08 (t, 1 H, J = 4.9 Hz, H-7), 6.25 (dd, 1 H, J1-2 = 6.2,
J1-3 = 2.1 Hz, H-1), 7.55-7.71 (m, 3 H, H-Ar PhSO2), 7.92-7.95 (m,
2 H, ortho-H-Ar PhSO2).
IS-MS: m/z = 423.5 [M - OBn]+, 548.5 [M + NH4]+, 553.5 [M +
Na]+.
13C NMR: d = 58.2 (CH2SO2), 64.5 (C-3), 66.1 (C-5), 66.2 (C-6),
78.7 (C-4), 97.2 (C-7), 103.8 (C-2), 128.8-134.5 (CHarom), 140.1
(Carom), 144.4 (C-1).
1H NMR: d = 2.00, 2.02, 2.04, 2.06 (4 s, 12 H, OCOCH3), 3.72 (dd,
1 H, J2-3 = 6.2, J3-4 = 4.2 Hz, H-3), 3.81 (dt, 1 H, J1a-2 = 3.2,
J1b-2 = 6.2, J2-3 = 6.2 Hz, H-2), 4.14 (dd, 1 H, J5-6b = 6.4, J6a-6b = 12.3
Hz, H-6b), 4.17 (dd, 1 H, J1b-2 = 6.2, J1a-1b = 12.4 Hz, H-1b), 4.33
(dd, 1 H, J5-6a = 2.7, J6a-6b = 12.3 Hz, H-6a), 4.45 (dd, 1 H, J1a-2 = 3.2,
J1a-1b = 12.4 Hz, H-1a), 4.51 and 4.67 (2 d, AB system, 2 H,
Jgem = 11.3 Hz, PhCH2O), 4.58 and 4.68 (2 d, AB system, 2 H,
Jgem = 11.3 Hz, PhCH2O), 5.33 (dt, 1 H, J4-5 = 5.5, J5-6a = 2.7,
J5-6b = 6.4 Hz, H-5), 5.40 (dd, 1 H, J3-4 = 4.2, J4-5 = 5.5 Hz, H-4),
7.24-7.37 (m, 10 H, H-Ar).
13C NMR: d = 19.5-19.6 (OCOCH3), 62.5 (C-6), 63.8 (C-1), 70.8
(C-5), 70.9 (C-4), 73.4 (PhCH2O), 74.8 (PhCH2O), 76.9 (C-2 and C-
3), 126.8-127.2 (CHarom), 136.1, 136.4 (Carom), 168.6, 168.7, 169.5
(OCOCH3).
Anal. calcd for C14H16O6S: C 53.83, H 5.16. Found: C 53.99, H
5.08.
Transformation of 5 in Acidic Medium
The acetal 5 was dissolved in a solution of 9:1 TFA/H2O (55 mg,
3 mL) and the mixture was stirred at 60 °C until complete consump-
tion of the starting material (ca 2 h). After evaporation and coevap-
oration with toluene, the crude product was purified by column
chromatography on silica gel (petroleum ether/EtOAc, 2:8) to af-
ford the de-O-benzylated PSE acetal 13 in 82% yield.
Deprotection of PSE Acetals: General Procedures
Anal. calcd for C28H34O10: C 63.38, H 6.46. Found: C 63.11, H 6.66.
Method A: The acetal 5 was dissolved in Et2O (10mL/mmol), then
LiAlH4 (6 equiv) was carefully added, and the mixture was stirred
2 h at r.t. After dilution with 10% HCl (5 mL) and EtOAc (5 mL),
the organic phase was decanted and the aqueous phase extracted
twice with EtOAc. The combined organic phases were dried
(MgSO4), concentrated under reduced pressure and the crude prod-
uct was purified by column chromatography on silica gel (petro-
leum ether/EtOAc, 1:1) to afford methyl 2,3-di-O-benzyl-a-D-
glucopyranoside15 (16) in 77% yield.
Acknowledgement
The MENRT is acknowledged for a grant (F. C.). The authors
would also like to thank Dr. D. Craig (Imperial College, London),
Dr. A. Tatibouët (ICOA) for helpful comments and discussions and
Dr. A. Imberty, C. Gautier and G. Chevalier for X-ray analysis.
References
16
1H NMR : d = 3.39 (s, 3 H, OCH3), 3.49-3.54 (m, 2 H, H-2, H-6b),
3.63 (m, 1 H, H-5), 3.73-3.83 (m, 3 H, H-3, H-4, H-6a), 4.62 (d, 1
H, J1-2 = 3.5 Hz, H-1), 4.67 and 4.77 (2 d, AB system, 2 H,
Jgem = 12.1 HZ, PhCH2O), 4.71 and 5.03 (2 d, AB system, 2 H,
Jgem = 11.7 Hz, PhCH2O), 7.29-7.39 (m, 10 H, H-Ar). All other an-
alytical data agree with the literature values.15
(1) Haines, A. H. Adv. Carbohydr. Chem. Biochem. 1981, 39, 13.
(2) Gelas, J. Adv. Carbohydr. Chem. Biochem. 1981, 39, 71.
(3) Hanessian, S. Methods Carbohydr. Chem. 1972, 6, 183.
(4) Garegg, P. J.; Hultberg, H. Carbohydr. Res. 1981, 93, C10.
(5) Umemura, K.; Matsuyama, H.; Kobayashi, M.; Kamigata, N.
Bull. Chem. Soc. Jpn 1989, 62, 3026.
(6) Pohl, N. L.; Kiessling, L. L. Tetrahedron Lett. 1997, 38, 6985.
(7) Chéry, F.; Rollin, P.; De Lucchi, O.; Cossu, S. Tetrahedron
Lett. 2000, 41, 2357.
Identical conditions applied to the acetal 11 resulted in the forma-
tion of 1,2-O-isopropylidene-a-D-xylofuranose (15)13,14 in 78%
yield as a colourless gum.
(8) De Lucchi, O.; Pasquato, L. In Encyclopedia of Reagents for
Organic Synthesis; Paquette, L., Ed.; Wiley & Sons: New
York, 1995; p 547, and references cited therein.
(9) Cossu, S.; De Lucchi, O.; Fabris, F.; Ballini, R.; Bosica, G.
Synthesis 1996, 12, 1481.
(10) Meek, J. S.; Fowler, J. S. J. Org. Chem. 1968, 985.
(11) Cossu, S.; De Lucchi, O. Org. Prep. Proc. Int. 1991, 23, 573.
(12) Frank, M.; Miethchen, R. Carbohydr. Res. 1998, 313, 49.
(13) Moravcová, J.; ²apková, J.; StanÀk, J. Carbohydr. Res. 1994,
263, 61.
(14) Xie, M.; Berges, D. A.; Robins, M. J. J. Org. Chem. 1996, 61,
5178.
(15) Davis, N. J.; Flitsch, S. L. J. Chem.Soc., Perkin Trans 1 1994,
4, 359.
(16) Bolon, P.; Jahnke, T. S.; Nair, V. Tetrahedron 1995, 51,
10443.
(17) Schmidt, O. T. Methods Carbohydr. Chem. 1963, 2, 322.
(18) Bonini, C. Tetrahedron 1989, 45, 2895.
(19) Kang, J.; Lim, G. J.; Yoon, S. K.; Kim, M. Y. J. Org. Chem.
1995, 60, 564.
15
1H NMR: d = 1.31 (s, 3 H, iPrd), 1.47 (s, 3 H, iPrd), 3.26 (br, 1 H,
OH), 3.99-4.19 (m, 2 H, H-5a, H-5b), 4.15 (m, 1 H, H-4), 4.25 (br,
1 H, OH), 4.31 (m, 1 H, H-3), 4.51 (d, 1 H, J1-2 = 3.7, J2-3 = <0.5 Hz,
H-2), 5.97 (d, 1 H, J1-2 = 3.7 Hz, H-1). All other analytical data
agree with the literature values.13,14
Method B: The acetal 5 was dissolved in Et2O/CH2Cl2 (1:1, 10mL/
mmol), then LiAlH4 (5 equiv) and AlCl3 (4 equiv) were carefully
added and the mixture was stirred 1 h at r.t. After dilution with 10%
HCl and EtOAc, the organic phase was decanted and the aqueous
phase was washed twice with EtOAc. The combined organic phases
were dried (MgSO4) concentrated under reduced pressure and the
crude product was purified by column chromatography on silica gel
to afford 1615 in 89% yield.
Reaction of 5 with DIBAH
To a solution of 5 (112 mg, 0.21 mmol) in anhyd toluene (5 mL) was
added DIBAH (1.5 M in toluene, 9 equiv) and the mixture was re-
fluxed for 3 h. After cooling and diluting with Et2O (10 mL) and
10% HCl (10 mL), the organic phase was decanted and the aqueous
phase extracted twice with EtOAc. The combined organic phases
(20) Winnik, F. M.; Brisson, J-R.; Carver, J. P.; Krepinsky, J. J.
Carbohydr. Res. 1982, 103, 15.
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F. Chéry et al.
PAPER
(21) Medgyes, G.; Jerkovitch, G.; Kuszmann, J.; Fügedi, P.
Carbohydr. Res. 1989, 186, 225.
(22) Trumtel, M.; Tavecchia, P.; Veyrières, A.; Sinaÿ, P.
Carbohydr. Res. 1990, 202, 257.
(25) Rehnberg, N.; Magnusson. G. J. Org. Chem. 1990, 55, 5467.
(26) The exclusive equatorial configuration of the
phenylsulfonylmethyl substituent in 11 was ascertained
through X-ray structure determination.
(23) Prepared through a standard 4-step sequence starting from the
3,4,6-tri-O-acetylated precursor;24 Chery, F. & Rollin, P.,
unpublished results.
Article Identifier:
(24) Thiem, J.; Wiesner, M. Carbohydr. Res. 1993, 249, 197.
1437-210X,E;2001,0,02,0286,0292,ftx,en;T01000SS.pdf
Synthesis 2001, No. 2, 286–292 ISSN 0039-7881 © Thieme Stuttgart · New York