Synthesis of vinyl sulfoxide-modified pent-2-enofuranosides and hex-2-enopyranosides and preliminary studies of their reactivity

Article abstract of DOI:10.1002/ejoc.201200637

Vinyl sulfoxide-modified pent-2-enofuranosides and hex-2-enopyranosides have been synthesized by using a controlled oxidation of C-3-deoxy-C-3-thioaryl furanosides and pyranosides, respectively, followed by mesylation of the C-2-hydroxyl group and elimination. In the furanose system, both diastereomers were formed in almost equal ratio, whereas the pyranose ring imposed diastereoselectivity of oxidation of the sulfur atom to produce only S _s isomers in good overall yields. Vinyl sulfoxide-modified 2-enofuranosides were treated with NaCH₂NO₂ to obtain C-2 branched chain sugars. Furanosyl sulfoxides yielded products that were similar to the adducts obtained by treatment of the corresponding sulfones with nitromethane. The sulfinyl group in thepyranosides influenced the diastereoselectivity of addition to produce adducts that differed from the products obtained from the corresponding vinyl sulfones under similar reaction conditions. Oxidation of furanosyl sulfides to sulfoxides afforded both diastereomers. The chirality of the sulfoxide group did not greatly influence the addition patterns of vinyl sulfoxide-modified pent-2-enofuranosides. Oxidation of pyranosyl sulfide gave only one diastereomer and the modified hex-2-enopyranosides significantly influenced the outcome of carbon nucleophile addition to these Michael acceptors. Copyright

Full text of DOI:10.1002/ejoc.201200637

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FULL PAPER
DOI: 10.1002/ejoc.201200637
Synthesis of Vinyl Sulfoxide-Modified Pent-2-enofuranosides and Hex-2-
enopyranosides and Preliminary Studies of Their Reactivity
Ananta Kumar Atta,[a] Debanjana Dey,[b] Atanu Bhaumik,[b] Chinmoy Manna,[b]
Tarun K. Pal,[b] and Tanmaya Pathak*[b]
Keywords: Carbohydrates / Sulfur / Sulfoxides / Chiral auxiliaries / Diastereoselectivity / Oxidation
Vinyl sulfoxide-modified pent-2-enofuranosides and hex-2-
enopyranosides have been synthesized by using a controlled
oxidation of C-3-deoxy-C-3-thioaryl furanosides and pyr-
anosides, respectively, followed by mesylation of the C-2-
hydroxyl group and elimination. In the furanose system, both
diastereomers were formed in almost equal ratio, whereas
the pyranose ring imposed diastereoselectivity of oxidation
of the sulfur atom to produce only Ss isomers in good overall
yields. Vinyl sulfoxide-modified 2-enofuranosides were
treated with NaCH2NO2 to obtain C-2 branched chain
sugars. Furanosyl sulfoxides yielded products that were sim-
ilar to the adducts obtained by treatment of the correspond-
ing sulfones with nitromethane. The sulfinyl group in the
pyranosides influenced the diastereoselectivity of addition to
produce adducts that differed from the products obtained
from the corresponding vinyl sulfones under similar reaction
conditions.
usefulness of vinyl sulfone-modified carbohydrates 1 and 2
(Figure 1) and related compounds as intermediates in the
synthesis of amino sugars,[6a–6e,6g,6h,6k,6p,6r] branched chain
sugars,[6f,6i,6p] carbocycles,[6j,6n,6o,6q,6s] and N-, O-, an S-het-
erocycles.[6l,6m,6q,6s,7] However, the diastereoselectivity of
addition reactions of vinyl sulfoxide-modified pent-2-eno-
furanosides and hex-2-enopyranosides have never been
studied.[4] We reported the addition of carbon nucleophiles
to the C-2 position of furanosides 1α/1β and pyranosides
2α/2β from a direction opposite to the disposition of the
anomeric methoxy groups and concluded that the anomeric
configurations of these Michael acceptors played a crucial
role in determining the diastereoselectivity of addition of
carbon nucleophiles.[6f] We therefore wanted to examine
whether the sulfinyl group of a vinyl sulfoxide-modified
carbohydrate could exert additional effects on the stereo-
chemical outcome of the addition reaction to these Michael
acceptors, particularly in view of the fact that sulfoxides are
well-known as chiral auxiliaries.[3]
Introduction
α,β-Unsaturated sulfoxides and vinyl sulfoxides in gene-
ral are versatile intermediates and useful building blocks in
synthetic chemistry because they are efficient partners in
Diels–Alder reactions[1] and powerful Michael acceptors
under radical or anionic conditions.[2] These compounds
are also useful in asymmetric synthesis due to the presence
of the sulfinyl group, which has been shown to be one of
the most efficient chiral auxiliaries.[1a,2e,3] Attempts have
been made in the past to combine the rich chemistry of
vinyl sulfoxide with those of carbohydrates by replacing an
endo- or exocyclic oxygen in a sugar system by a sulfoxide
group; it was expected that a combination of the chiralities
of sulfoxide sulfur and the inbuilt stereogenicity of carbo-
hydrates would create a complex and versatile chiral con-
troller that can be used in stereoselective synthesis.[4] Al-
though there are a reasonably large number of publications
on 5-thiopyranose monosaccharide S-oxides, anomeric gly-
copyranose sulfoxide, and, to a limited extent, on 6-deoxy-
6-sulfinyl-d-monosaccharides, only a few examples have re-
ported on sugars functionalized with sulfinyl substituents
at C-2 or C-3 of carbohydrates.[4,5] We have established the
[a] Department of Chemistry, Inha University,
Nam-gu, Incheon 402-751, Korea
[b] Department of Chemistry, Indian Institute of Technology
Kharagpur
Kharagpur 721302, India
Fax: +91-3222-282252
E-mail: tpathak@chem.iitkgp.ernet.in
Homepage: http://www.chem.iitkgp.ernet.in/faculty/PT/index.php
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/ejoc.201200637.
Figure 1. Vinyl sulfone-modified pent-2-enofuranosides and hex-2-
enopyranosides.
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(H2) of the α-isomer were found at δ = 6.53 ppm for 8RS
and δ = 6.36 ppm for 9SS. The olefinic proton (H2) of 8RS
and H4 (δ = 4.47–4.57 ppm) were deshielded and shielded,
respectively. The opposite phenomena occurred in the case
of 9SS, in which the olefinic proton (H2) and H4 (δ = 4.94–
4.97 ppm) were shielded and deshielded, respectively. Ac-
cording to the reported data,[10] the higher chemical shift
value of the vinylic proton is possible if the sulfur oxygen
was oriented towards the vinylic proton. Configurations of
15RS and 16SS were also established by comparing the
chemical shift values of the olefinic protons (δ = 6.53 ppm
for 15RS and δ = 6.25 ppm for 16SS) and the H4 protons
(δ = 4.53 ppm for 15RS and δ = 4.88–4.90 ppm for 16SS).
Results and Discussion
Synthesis of α and β-Anomeric Vinyl Sulfoxide-Modified
Pent-2-enofuranosides
Our synthesis of α and β-anomeric vinyl sulfoxide-modi-
fied pent-2-enofuranosides 8RS and 9SS (Scheme 1),[8]
started from the reported[9] α-anomeric sugar sulfide 3,
which was oxidized to sulfoxides 4RS and 6SS with NaIO4/
MeOH/H2O. The diastereomers were separated at this stage
to obtain the sulfoxides in almost equal ratio. The hydroxyl
groups of 4RS and 6SS were mesylated and the mesyl com-
pounds 5RS and 7SS were directly treated with 1,8-diazabi-
cyclo[5.4.0]undec-7-ene (DBU) in dichloromethane to af-
ford vinyl sulfoxides 8RS and 9SS, respectively, in excellent
yields (Scheme 1). The β-anomeric sulfide 10[9] was con-
verted into the expected vinyl sulfoxide-modified carbo-
hydrates 15RS and 16SS in a similar way via intermediates
11RS/12RS and 13SS/14SS, respectively (Scheme 2). It was
quite clear that, for both α- and β-methyl furanosides 3 and
10, there was virtually no selectivity of oxidation for the
formation of 8/9 and 15/16, respectively. However, the iso-
mers were separated and the configurations at the sulfur of
stereoisomers 8RS and 9SS were established on the basis of
their 1H NMR spectroscopic data. To establish the absolute
configuration at the sulfoxide sulfur of vinyl sulfoxides 8/9
1
and 15/16, we compared the H NMR spectroscopic data
of 8RS and 9SS with those reported for 2-aryl-3-sulfinyl-
2,5-dihydrofurans.[10] In the reported data, the vinylic pro-
ton was used as an excellent tool for assigning the stereo-
chemistry of the sulfur atom because of the highly deshield-
ing effect induced by the sulfinyl oxygen on the vinylic hy-
drogen.[10] The chemical shift values of olefinic protons
Scheme 2. Synthesis of β-anomeric vinyl sulfoxide-modified pent-
2-enofuranosides.
Reactions of α and β-Anomeric Vinyl Sulfoxide-Modified
Pent-2-enofuranosides with Nitromethane
Compounds 8RS and 9SS were separately treated with
nitromethane in the presence of sodium hydride to afford
branched-chain sugars 17RS and 18SS, respectively. Oxi-
dation of 17RS and 18SS afforded 19, which was also ob-
tained by reaction of vinyl sulfone 1α with nitromethane[6f]
under similar conditions (Scheme 3). The sodium salt of ni-
tromethane was also treated with the β-anomeric vinyl sulf-
oxide-modified carbohydrates 15RS and 16SS to generate
compounds 20RS and 21SS, respectively. Oxidation of 20RS
and 21SS afforded 22, which was also obtained by reaction
of vinyl sulfone 1β with nitromethane[6f] under similar con-
ditions (Scheme 4).
Scheme 1. Synthesis of α-anomeric vinyl sulfoxide-modified pent-
2-enofuranosides.
2
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Vinyl Sulfoxide-Modified Carbohydrates
Scheme 3. Reactions of α-anomeric vinyl sulfoxide-modified pent-
2-enofuranosides with nitromethane.
Scheme 5. Synthesis of α,β-anomeric vinyl sulfoxide-modified hex-
2-enopyranosides.
Scheme 4. Reactions of β-anomeric vinyl sulfoxide-modified pent-
2-enofuranosides with nitromethane.
Figure 2. Crystal structure of compound 24SS.
Synthesis of α and β-Anomeric Vinyl Sulfoxide-Modified
Reactions of α and β-Anomeric Vinyl Sulfoxide-Modified
Hex-2-enopyranoside
Hex-2-enopyranosides with Nitromethane
Benzylidene protected α-anomeric sulfide 23[9]
Compound 25SS was treated with nitromethane in the
(Scheme 5) was oxidized by using NaIO4/MeOH/H2O to af- presence of sodium hydride to afford 29SS as the major
ford, after purification, a single sulfoxide derivative 24SS. compound. To unambiguously identify the configurations
The hydroxyl group of 24SS was mesylated and the mesyl- at C2 and C3 of 29SS it was oxidized to afford 31; the latter
ated compound was treated with DBU in dichloromethane compound differed from 32, the addition product obtained
to afford a single compound 25SS (Scheme 5).
from the reactions of 2α with nitromethane.[6f] The stereo-
The structures of 24SS (Figure 2) and 25SS (see the Sup- chemistry of compound 31 was established on the basis of
porting Information) were unambiguously confirmed by X- its single crystal X-ray crystal structure. Another isomer,
ray analysis of their single crystals.
obtained in less than 5% yield from the same reaction, was
In the same way, β-anomeric sulfide 26 was converted identified as 30Ss (Scheme 6) after oxidation to the known
1
into a single compound 28SS through intermediate 27SS. analogue 32[6f] (mixed H NMR spectroscopic analysis).
The chemical shift of the olefinic proton (δ = 6.52 ppm) of
On the other hand, 28SS reacted similarly with nitro-
25SS is comparable with that of 28SS (δ = 6.51 ppm). How- methane in the presence of sodium hydride to generate
ever, the structure of 28SS was established in an indirect compounds 33SS and 34SS (Scheme 7). The oxidation
way from X-ray analysis of a single crystal of one of its product 35 of the minor compound 34Ss was identical
1
products (see below). It was clear from the analysis of the (mixed H NMR spectroscopic analysis) to the nitrometh-
analytical data that both of the anomers afforded only one ane adduct of 2β.[6f] Structure of compound 33SS was con-
sulfur epimer.
firmed by X-ray diffraction analysis of the single crystal.
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are in a linear arrangement in the very early transition
–
state.[12] We presume that in such a scenario IO4 would
also approach the sulfur atom of the PhS group from a
direction perpendicular to the planes comprised of –S–C3–
C1–O– (methoxy oxygen) for the α-anomer 23 and –S–C3–
C1–H– for the β-anomer 26, affording only SS stereoiso-
mers in both cases (Scheme 8). Such a positioning of the
phenyl group of SPh is not possible in the case of furanos-
ides 3 or 10 because of the pseudoaxial and pseudoequato-
rial nature of bonds in five-membered rings and, therefore,
–
there is no selectivity in the approach of IO4 towards the
sulfur. It is also evident from the reaction patterns of vinyl
sulfoxide-modified furanosides 3 or 10 that the directing ef-
fect of the anomeric methoxy group dominated over the
same of sulfoxides, which resulted in the formation of
arabino- and xylo-analogues 17RS/18SS and 20RS/21SS,
respectively, as expected (Schemes 3 and 4). The dominance
of the α-anomeric methoxy group over the directing effect
of sulfoxide is also evident in the addition of the carbon
nucleophile from the β-face of pyranosides 25SS
(Scheme 6). However, in contrast to the formation of 32
from 2α,[6f] it is plausible that the stereoelectronic repulsion
between sulfoxide and methoxy groups forced the sulfoxide
group to occupy the equatorial position, affording 29SS as
the major product (Scheme 6). With the exception of the
minor product 30SS, all other pyranosyl sulfoxide adducts
29SS, 33SS, and 34SS have their sulfoxide groups in equato-
rial positions, presumably to avoid stereoelectronic interac-
tions. It was reported earlier that vinyl sulfone 2β reacted
with either carbon or nitrogen nucleophiles to exclusively
produce gluco-analogues in which all functional groups at
C1–C5 occupy equatorial positions.[6a,6f] Although the for-
mation of 34SS followed the same trend, the delivery of
the carbanion from the β-face of 28SS affording 33SS is
probably the sole example of the directing effect of sulfoxide
among the vinyl sulfones-modified carbohydrates reported
in this study.
Scheme 6. Reactions of α-anomeric vinyl sulfoxide-modified hex-2-
enopyranosides with nitromethane.
As mentioned above, the configuration of the sulfur center
of 28SS was also indirectly confirmed from the crystal
structure of 33SS.
Scheme 7. Reactions of β-anomeric vinyl sulfoxide-modified hex-2-
enopyranosides with nitromethane.
We presume that the conformationally preferred orienta-
tion of the phenyl moiety of the of Ph–S group in com-
pounds 23 and 26 are comparable to the orientation of the
methyl group of cyclohexyl methyl ether; in the latter case,
the methyl group in the chair conformer of the molecule is
known to move away from the six-membered ring to accom-
modate the 1,3-diaxial interactions.[11] This is also evident
from the orientation of the thiophenyl group in the crystal
structure of the sulfoxide 24SS (Figure 2) and other pyran-
osyl compounds. DFT computations established that sulf-
–
Scheme 8. Plausible mode of attack of IO4 for the diastereoselec-
tive oxidation of the sulfur atoms of 23 and 26.
–
ides are oxidized mainly with IO4 under normal experi-
mental conditions. During the process, oxygen atoms of the
periodates attack the sulfides in a direction perpendicular
Conclusions
In the case of furanosyl systems, the sugar component
to the plane of the C–S–C atoms, and the S···O···I atoms did not have any influence on the oxidation of sulfides to
4
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Vinyl Sulfoxide-Modified Carbohydrates
duced pressure and the resulting residue was purified over silica gel
to afford pentosyl and hexosyl vinyl sulfoxide.
sulfoxides. The chirality of the sulfoxide group did not have
much influence on the reaction patterns of vinyl sulfoxide-
modified pent-2-enofuranosides. On the other hand, the
General Procedure for the Synthesis of Sulfones from Sulfoxides: To
pyranosyl moiety contributed to the selective formation of a well-stirred solution of sulfoxide (1 equiv.) in anhydrous MeOH
(10 mL/mmol) was added magnesium monoperoxyphthalate hexa-
hydrate (1.2 equiv./mmol), and the mixture was stirred at room
temperature under N2. After 2–3 h, the mixture was evaporated to
dryness under reduced pressure and the residue was dissolved in
aqueous saturated NaHCO3. The aqueous layer was washed with
EtOAc (3ϫ 10 mL) and the combined organic layer was dried with
anhydrous Na2SO4 and concentrated under reduced pressure to
give a residue that was purified over silica gel to afford sulfones in
40–62% yields.
only one of the diastereomers during oxidation, and vinyl
sulfoxide-modified hex-2-enopyranosides significantly in-
fluenced the outcome of carbon nucleophile addition to
these Michael acceptors. The formation of compound 29SS
indicated the influence the sulfoxide has on the protonation
pattern of the C-3 carbanion generated after the addition
of nitromethane nucleophile at C-2 of 25SS (Scheme 6). The
formation of 33SS was unexpected because no such com-
pound was obtained when vinyl sulfone 2β was treated with
nitromethane under similar conditions (Scheme 7). We have
therefore been successful in identifying the directing effect
of sulfoxide in the case of vinyl sulfoxide-modified carbo-
hydrates. Research is in progress on the usefulness of some
of these vinyl sulfoxide-modified carbohydrates as Michael
acceptors, partners in Diels–Alder reactions, and as chiral
auxiliaries.
Compound 4RS and 6SS: Compound 3 (2 g, 5.56 mmol) was con-
verted into sulfoxides 4RS and 6Ss by following the general pro-
cedure described above and the products were separated by column
chromatography.
Compound 4RS: Yield 1.05 g (50%); [α]2D6 = –1.01 (c = 0.30, CHCl3);
1H NMR (CDCl3): δ = 2.42 (s, 3 H), 3.14 (d, J = 2.8 Hz, 1 H),
3.39 (s, 3 H), 3.55 (dd, J = 1.6, 10.4 Hz, 1 H), 3.66 (d, J = 11.6 Hz,
1 H), 3.86–3.91 (m, 2 H), 4.59 (dd, J = 11.6, 28.8 Hz, 2 H), 4.86
(s, 2 H), 7.26–7.36 (m, 7 H), 7.59 (d, J = 8.4 Hz, 2 H) ppm; 13C
NMR (CDCl3): δ = 21.4, 54.4, 71.1 (CH2), 73.4, 73.7 (CH2), 75.6,
78.3, 108.7, 125.1, 127.9, 128.1, 128.6, 130.1, 136.6, 139.7,
142.4 ppm; HRMS (ESI+): calcd for C20H24O5SNa [M + Na]+
399.1242; found 399.1234.
Compound 6SS: Yield 0.83 g (40%); [α]2D6 = +186.28 (c = 0.20,
CHCl3). 1H NMR (CDCl3): δ = 2.38 (s, 3 H), 2.61 (d, J = 10.4 Hz,
1 H), 3.26–3.27 (m, 1 H), 3.37–3.40 (m, 4 H), 3.54 (d, J = 10.0 Hz,
1 H), 3.89 (s, 1 H), 4.34 (d, J = 12 Hz, 1 H), 4.63 (d, J = 10.0 Hz,
1 H), 4.98 (s, 1 H), 7.19–7.34 (m, 7 H), 7.51 (d, J = 7.6 Hz, 2
H) ppm; 13C NMR (CDCl3): δ = 21.5, 54.8, 69.2 (CH2), 73.0, 73.4
(CH2), 75.3, 76.2, 109.6, 125.1, 127.9 (2ϫ C), 128.5, 130.1, 136.8,
139.9, 142.6 ppm; HRMS (ESI+): calcd for C20H24O5SNa [M +
Na]+ 399.1242; found 399.1248.
Experimental Section
General Methods: Reactions were conducted either under a nitro-
gen atmosphere or in open air. Carbohydrates and other fine chem-
icals were obtained from commercial suppliers and were used with-
out purification. Solvents were dried and distilled following the
standard procedures. TLC was carried out on precoated silica gel
plates and the spots were visualized either with UV light or by
charring the plate dipped in 5% H2SO4/MeOH solution. Column
chromatography was performed on silica gel (230–400 mesh). 1H
and 13C NMR spectra were recorded at 400 and 100 MHz, respec-
tively, using CDCl3 as the solvent. DEPT experiments were carried
out to identify the methylene carbons. Optical rotations were re-
corded at 589 nm.
Compound 8RS: Compound 4RS (0.75 g, 1.99 mmol) was converted
into 5RS by following the general procedure described above. Com-
pound 5Rs (0.385 g, 0.85 mmol) was directly converted into 8RS
(0.255 g, 84%) by following the general procedure described above.
[α]2D6 = –97.14 (c = 0.06, CHCl3); 1H NMR (CDCl3): δ = 2.38 (s, 3
H), 3.35 (s, 3 H), 3.46–3.50 (m, 1 H), 3.56–3.59 (m, 1 H), 4.47–4.57
(m, 3 H), 5.88 (d, J = 3.6 Hz, 1 H), 6.53 (s, 1 H), 7.22–7.39 (m, 7
H), 7.46 (d, J = 8 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 21.4,
54.2, 71.1 (CH2), 73.6 (CH2), 82.2, 107.9, 125.9, 127.9, 128.0, 128.4,
128.7, 130.2, 137.3, 138.5, 142.6, 153.8 ppm; HRMS (ESI+): calcd
for C20H22O4SNa [M + Na]+ 381.1137; found 381.1131.
General Procedure for the Synthesis of Sulfoxides: To a well-stirred
solution of sulfide (1 equiv.) in MeOH (10 mL/mmol) was added
NaIO4 (1.2 eq/mmol) in H2O (5 mL/mmol), and the mixture was
stirred for 4–6 h at room temperature. The mixture was then evapo-
rated to dryness under reduced pressure and the residue was parti-
tioned between aqueous saturated NaHCO3 and EtOAc (3ϫ
10 mL). The combined organic layer was dried with anhydrous
Na2SO4, filtered, and the filtrate was concentrated under reduced
pressure to give a residue, which was purified over silica gel to
afford the required sulfoxide.
Compound 9SS: Compound 6SS (0.63 g, 1.68 mmol) was converted
into 7SS by following the general procedure described above. Com-
pound 7SS (0.645 g, 1.42 mmol) was directly converted into 9SS
(0.391 g, 77%) by following the general procedure described above.
General Procedure for the Synthesis of Mesylated Compounds: To a
well-stirred solution of sulfoxide (1 equiv.) in pyridine (5 mL/mmol)
was added methanesulfonyl chloride (4 equiv.) in pyridine (1 mL/
mmol of MsCl) dropwise at 0 °C under N2. After completion of the
addition, the reaction mixture was kept at +4 °C for 24 h (reaction
monitored by TLC analysis). The reaction mixture was poured into
aqueous saturated NaHCO3 and the product was extracted with
EtOAc (3ϫ 10 mL). The combined organic layer was dried with
anhydrous Na2SO4, filtered, and the filtrate was concentrated un-
der reduced pressure to give a residue, which was purified over
silica gel to afford the title compound.
1
[α]2D6 = +57.86 (c = 0.34, CHCl3); H NMR (CDCl3): δ = 2.41 (s,
3 H), 3.35 (s, 3 H), 3.51–3.55 (m, 1 H), 3.76 (dd, J = 2.4, 10.4 Hz,
1 H), 4.49 (dd, J = 12.0, 28.8 Hz, 2 H), 4.94–4.97 (m, 1 H), 5.87
(d, J = 4.0 Hz, 1 H), 6.36 (s, 1 H), 7.26–7.35 (m, 7 H), 7.49 (d, J
= 8 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 21.4, 54.5, 70.9 (CH2),
73.2 (CH2), 83.5, 107.6, 124.8, 127.5, 127.6, 128.2, 130.1, 133.0,
137.9, 139.0, 142.1, 149.4 ppm; HRMS (ESI+): calcd for
C20H22O4SNa [M + Na]+ 381.1137; found 381.1145.
General Procedure for the Synthesis of Pentosyl and Hexosyl Vinyl
Sulfoxides: The mesylated compound (1 equiv.) was treated with
DBU (2 equiv./mmol) in anhydrous CH2Cl2 (10 mL/mmol) at am-
bient temperature for 5–6 h. The solvent was evaporated under re-
Compounds 11RS and 13SS: Compound 10 (1.0 g, 2.78 mmol) was
converted into sulfoxides by following the general procedure de-
scribed above.
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2 H) ppm; 13C NMR (CDCl3): δ = 21.5, 46.0, 54.8, 66.3, 70.4
FULL PAPER
Compound 11RS: Yield 0.57 g (55%); [α]2D6 = –100.84 (c = 0.10,
1
CHCl3); H NMR (CDCl3): δ = 2.39 (s, 3 H), 2.93 (s, 1 H), 3.42 (CH2), 73.6 (CH2), 74.5 (CH2), 78.4, 105.6, 124.9, 127.8 (2ϫ C),
(s, 3 H), 3.45–3.47 (m, 1 H), 3.61–3.65 (m, 1 H), 3.79 (t, J = 8.4 Hz,
128.4, 130.2, 137.5, 139.2, 142.8 ppm; HRMS (ESI+): calcd for
1 H), 4.28 (q, J = 5.6, 12.4 Hz, 1 H), 4.54 (d, J = 11.2 Hz, 1 H), C21H25O6NSNa [M + Na]+ 442.1300; found 442.1307.
4.62 (d, J = 11.2 Hz, 1 H), 4.84 (d, J = 8.0 Hz, 1 H), 4.88 (s, 1 H),
Compound 18SS: Compound 9SS (0.40 g, 1.11 mmol) was con-
7.24–7.37 (m, 7 H), 7.53 (d, J = 8 Hz, 2 H) ppm; 13C NMR
verted into 18SS (0.26 g, 55%) by following the general procedure
(CDCl3): δ = 21.4, 56.0, 70.3 (CH2), 71.7, 73.6 (CH2), 76.7, 77.4,
described above. [α]2D6 = +210.51 (c = 0.08, CHCl3); 1H NMR
109.9, 124.8, 127.9, 128.1, 128.4, 130.0, 137.4, 140.2, 142.0 ppm;
(CDCl3): δ = 2.39 (s, 3 H), 2.76 (dd, J = 3.2, 10.8 Hz, 1 H), 3.03–
HRMS (ESI+): calcd for C20H24O5SNa [M + Na]+ 399.1242;
3.06 (m, 1 H), 3.39 (s, 3 H), 3.41–3.45 (m, 1 H), 3.49–3.54 (m, 1
found 399.1234.
H), 4.06–4.07 (m, 1 H), 4.13 (dd, J = 4.8, 13.6 Hz, 1 H), 4.26–4.33
Compound 13SS: Compound 10 (1.0 g, 2.78 mmol) was converted
into 13SS (0.42 g, 40%) by following the general procedure de-
scribed above. [α]2D6 = +58.86 (c = 0.15, CHCl3); 1H NMR (CDCl3):
δ = 1.39 (s, 1 H), 2.42 (s, 3 H), 3.35–3.38 (m, 1 H), 3.41 (s, 3 H),
3.86 (s, 1 H), 3.97–4.02 (m, 1 H), 4.12 (dd, J = 2.8, 10.4 Hz, 1 H),
4.68 (d, J = 1.6 Hz, 2 H), 4.79–4.80 (m, 2 H), 7.26–7.43 (m, 7 H),
7.61 (d, J = 8 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 21.5, 55.3,
70.2 (CH2), 73.4 (CH2), 74.0, 76.5, 79.4, 108.9, 125.6, 127.6, 127.8,
128.3, 130.0, 130.2, 138.0, 138.9, 142.6 ppm; HRMS (ESI+): calcd
for C20H24O5SNa [M + Na]+ 399.1242; found 399.1241.
(m, 2 H), 4.52 (d, J = 12.0 Hz, 1 H), 5.01 (s, 1 H), 7.21–7.26 (m, 4
H), 7.31–7.38 (m, 3 H), 7.48 (d, J = 8 Hz, 2 H) ppm; 13C NMR
(CDCl3): δ = 21.4, 44.5, 55.1, 66.7, 68.3 (CH2), 73.4 (CH2), 75.2
(CH2), 76.1, 106.3, 124.6, 127.8, 127.9, 128.5, 130.2, 137.2, 139.1,
142.7 ppm; HRMS (ESI+): calcd for C21H25NO6SNa [M + Na]+
442.1300; found 442.1302.
Compound 20RS: Compound 15RS (0.50 g, 1.39 mmol) was con-
verted into 20RS (0.30 g, 53%) by following the general procedure
described above. [α]2D6 = –132.81 (c = 0.15, CHCl3); 1H NMR
(CDCl3): δ = 2.38 (s, 3 H), 2.75–2.79 (m, 1 H), 3.04 (dd, J = 2.8,
10.4 Hz, 1 H), 3.38 (s, 4 H), 3.44–3.47 (m, 1 H), 4.19 (d, J = 12 Hz,
1 H), 4.36 (d, J = 12 Hz, 1 H), 4.51–4.52 (m, 1 H), 4.68–4.74 (m,
1 H), 4.88 (d, J = 4.0 Hz, 1 H), 5.10–5.16 (m, 1 H), 7.05–7.35 (m,
9 H) ppm; 13C NMR (CDCl3): δ = 21.3, 46.1, 56.1, 63.3, 71.8
(CH2), 72.4 (CH2), 72.9 (CH2), 73.0, 105.0, 123.8, 127.5, 127.6,
128.3, 130.0, 136.7, 137.7, 141.7 ppm; HRMS (ESI+): calcd for
C21H25NO6SNa [M + Na]+ 442.1300; found 442.1309.
Compound 15RS: Compound 11RS (1.19 g, 3.16 mmol) was con-
verted into 12RS by following the general procedure described
above. Compound 12RS (1.30 g, 2.86 mmol) was directly converted
into 15RS (0.865 g, 84%) by following the general procedure de-
scribed above. [α]2D6 = –188.43 (c = 0.11, CHCl3); 1H NMR
(CDCl3): δ = 2.38 (s, 3 H), 3.41 (s, 3 H), 3.52–3.56 (m, 1 H), 3.61–
3.64 (m, 1 H), 4.39 (t, J = 6.0 Hz, 1 H), 4.53 (dd, J = 11.6, 19.6 Hz,
2 H), 5.73 (s, 1 H), 6.53 (s, 1 H), 7.22–7.39 (m, 7 H), 7.43 (d, J =
8 Hz, 2 H) ppm. 13C NMR (CDCl3): δ = 21.4, 54.9, 72.6 (CH2),
73.6 (CH2), 82.3, 108.4, 125.6, 127.9, 128.0, 128.4, 128.8, 130.1,
137.4, 138.8, 142.4, 154.2 ppm. HRMS (ESI+): calcd for
C20H22O4SNa [M + Na]+ 381.1137; found 381.1138.
Compound 21SS: Compound 16SS (0.45 g, 1.25 mmol) was con-
verted into 21SS (0.24 g, 46%) by following the general procedure
described above. [α]2D6 = +1.23 (c = 0.13, CHCl3); 1H NMR
(CDCl3): δ = 2.44 (s, 3 H), 2.50–2.53 (m, 1 H), 3.17–3.20 (m, 1 H),
3.40 (s, 3 H), 3.60 (dd, J = 5.6, 13.2 Hz, 1 H), 3.91–4.00 (m, 1 H),
4.04–4.08 (m, 1 H), 4.26 (dd, J = 2.8, 10.4 Hz, 1 H), 4.69–4.73 (m,
3 H), 4.84 (d, J = 2.0 Hz, 1 H), 7.26–7.42 (m, 7 H), 7.62 (d, J =
8 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 21.5, 46.3, 55.5, 69.3, 70.0
(CH2), 73.6 (CH2), 74.1 (CH2), 79.6, 106.0, 125.6, 127.7, 127.9,
128.4, 130.4, 137.9, 138.8, 143.3 ppm; HRMS (ESI+): calcd for
C21H25NO6SNa [M + Na]+ 442.1300; found 442.1317.
Compound 16SS: Compound 13SS (0.56 g, 1.49 mmol) was con-
verted into 14SS by following the general procedure described
above. Compound 14SS (0.50 g, 1.10 mmol) was directly converted
into 16SS (0.331 g, 84%) by following the general procedure de-
scribed above. [α]2D6 = +93.69 (c = 0.03, CHCl3); 1H NMR (CDCl3):
δ = 2.41 (s, 3 H), 3.41 (s, 3 H), 3.49–3.53 (m, 1 H), 3.69 (dd, J =
3.2, 10.4 Hz, 1 H), 4.48 (dd, J = 12.0, 18.4 Hz, 2 H), 4.88–4.90 (m,
1 H), 5.69 (s, 1 H), 6.25 (s, 1 H), 7.26–7.35 (m, 7 H), 7.50 (s, J =
8 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 21.4, 55.1, 72.5 (CH2),
73.2 (CH2), 83.3, 107.7, 125.1, 127.5, 127.6, 128.2, 130.1, 132.0,
137.9, 138.5, 142.4, 150.5 ppm; HRMS (ESI+): calcd for
C20H22O4SNa [M + Na]+ 381.1137; found 381.1120.
Compound 24SS: Compound 23 (2.0 g, 5.15 mmol) was converted
into 24SS (1.73 g, 83%) by following the general procedure de-
scribed above. [α]2D6 = +192.56 (c = 0.10, CHCl3); 1H NMR
(CDCl3): δ = 3.54 (s, 3 H), 3.74–3.80 (m, 1 H), 3.89 (s, 1 H), 4.33–
4.38 (m, 3 H), 4.49 (d, J = 5.6 Hz, 1 H), 4.74–4.75 (m, 1 H), 4.80
(s, 1 H), 5.32 (s, 1 H), 7.00 (d, J = 7.2 Hz, 2 H), 7.19–7.37 (m, 6
H), 7.69 (d, J = 7.6 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 55.1,
61.0, 66.0, 66.4, 69.2 (CH2), 75.0, 101.0, 101.7, 125.9, 126.9, 127.8,
131.3, 136.5, 145.2 ppm; HRMS (ESI+): calcd for C20H23O6S [M
+ H]+ 391.1365; found 391.1323.
General Procedure for Nitromethane Addition: To a well-stirred
solution of NaH (8 equiv.) in DMF (5 mL/mmol) or 1,4-dioxane
(5 mL/mmol) was added nitromethane (11 equiv.) and the mixture
was stirred for 0.5 h at ambient temperature under an inert atmo-
sphere. The appropriate vinyl sulfone-modified carbohydrate
(1 equiv.) was added and the mixture was stirred for 2–3 h at 50–
60 °C. The reaction mixture was then partitioned between aqueous
saturated NaHCO3 and EtOAc (3ϫ 10 mL). The combined organic
layer was dried with anhydrous Na2SO4, filtered, and the filtrate
was concentrated under reduced pressure to give a residue that was
purified over silica gel to afford the title compound.
Compound 25SS: Compound 24SS (0.64 g, 1.64 mmol) was mesyl-
ated by following the general procedure. The crude mesylate was
converted into vinyl sulfoxide 25SS (0.50 g, 82%) by following the
general procedure described above. [α]2D6 = +77.08 (c = 0.06,
1
CHCl3); H NMR (CDCl3): δ = 3.49 (s, 3 H), 3.67–3.74 (m, 2 H),
4.00–4.06 (m, 1 H), 4.29–4.32 (m, 1 H), 5.07 (s, 1 H), 5.29 (s, 1 H),
6.52–6.53 (m, 1 H), 7.41–7.52 (m, 8 H), 7.52–7.67 (m, 2 H) ppm;
13C NMR (CDCl3): δ = 56.3, 63.8, 69.1 (CH2), 74.3, 96.8, 101.8,
124.7, 125.3, 126.6, 128.4, 129.3 (2ϫ C), 131.7, 136.7, 142.2,
147.2 ppm; HRMS (ESI+): calcd for C20H21O5S [M + H]+
373.1110; found 373.1073.
Compound 17RS: Compound 8RS (0.50 g, 1.39 mmol) was con-
verted into 17RS (0.41 g, 69%) by following the general procedure
described above. [α]2D6 = –32.99 (c = 0.09, CHCl3); 1H NMR
(CDCl3): δ = 2.43 (s, 3 H), 2.71–2.75 (m, 1 H), 3.04–3.06 (m, 1 H),
3.39 (s, 3 H), 3.42–3.45 (m, 1 H), 3.82–3.89 (m, 2 H), 4.29–4.35 (m,
1 H), 4.49 (d, J = 12 Hz, 1 H), 4.57 (d, J = 11.6 Hz, 1 H), 4.74–
4.75 (m, 1 H), 4.88 (s, 1 H), 7.26–7.38 (m, 7 H), 7.56 (d, J = 8 Hz,
Compound 27SS: Compound 26 (2.0 g, 5.15 mmol) was converted
into 27SS (1.67 g, 80%) by following the general procedure de-
6
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Vinyl Sulfoxide-Modified Carbohydrates
scribed above. [α]2D6 = +45.29 (c = 0.19, CHCl3); 1H NMR (CDCl3):
δ = 3.67 (s, 3 H), 3.78–3.85 (m, 2 H), 3.91–3.97 (m, 1 H), 4.01–4.03
CCDC-884993 (for 24Ss), -885022 (for 25Ss), -885023 (for 31),
and -885024 (for 33Ss) contain the supplementary crystallo-
(m, 1 H), 4.35–4.41 (m, 1 H), 4.48–4.52 (m, 1 H), 5.20 (d, J = graphic data for this paper. These data can be obtained free of
8.4 Hz, 1 H), 5.51 (s, 1 H), 5.82 (d, J = 10.8 Hz, 1 H), 7.40–7.47
(m, 8 H), 7.66 (d, J = 6.4 Hz, 2 H) ppm; 13C NMR (CDCl3): δ =
57.4, 65.3, 65.8, 69.0 (CH2), 74.8, 76.7, 101.8, 103.3, 124.9, 126.1,
128.3, 129.3, 129.4, 131.3, 136.5, 144.4 ppm; HRMS (ESI+): calcd
for C20H23O6S [M + H]+ 391.1215; found 391.1237.
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): 1H and 13C NMR spectra of all new compounds and ORTEP
drawings of compounds 25Ss, 31 and 33Ss.
Compound 28SS: Compound 27SS (1.7 g, 5.15 mmol) was mesyl-
ated by following the general procedure. The crude mesylate was
converted into vinyl sulfoxide 28SS (1.36 g, 84%) by following the
general procedure described above. [α]2D6 = –4.18 (c = 0.11, CHCl3);
1H NMR (CDCl3): δ = 3.48 (s, 3 H), 3.74–3.79 (m, 1 H), 3.84–3.90
(m, 2 H), 4.30–4.33 (m, 1 H), 5.32 (s, 1 H), 5.49 (s, 1 H), 6.51 (s, 1
H), 7.41–7.52 (m, 8 H), 7.67–7.69 (m, 2 H) ppm; 13C NMR
(CDCl3): δ = 55.5, 68.7 (CH2), 69.9, 74.1, 99.9, 101.7, 125.6, 125.8,
125.9, 128.4, 129.1 (2ϫ C), 131.8, 136.6, 141.9, 147.9 ppm; HRMS
(ESI+): calcd for C20H21O5S [M + H]+ 373.1110; found 373.1120.
Acknowledgments
T. P. thanks the Department of Science and Technology (DST),
New Delhi for financial support. A. K. A., D. D., A. B., C. M., and
T. K. P. thank the Council of Scientific and Industrial Research
(CSIR), New Delhi for fellowships. A. K. A. also thanks Inha Uni-
versity for facilitating the required assets. DST is also thanked for
the creation of the 400 MHz facility under the IRPHA program
and DST-FIST for the single-crystal X-ray facility.
Compound 29SS: Compound 25SS (0.20 g, 0.54 mmol) was con-
verted into 29SS (0.17 g, 73%) by following the general procedure
described above. [α]2D6 = +84.93 (c = 0.15, CHCl3); 1H NMR
(CDCl3): δ = 3.42 (s, 3 H), 3.51–3.54 (m, 1 H), 3.60–3.64 (m, 1 H),
3.78–3.83 (m, 1 H), 3.88–3.91 (m, 1 H), 4.12 (t, J = 10.4 Hz, 1 H),
4.19–4.22 (m, 1 H), 4.68 (s, 1 H), 4.73–4.80 (m, 1 H), 5.39 (dd, J
= 2.4, 14.8 Hz, 1 H), 5.48 (s, 1 H), 6.94 (d, J = 7.6 Hz, 2 H), 7.20–
7.33 (m, 6 H), 7.48 (d, J = 7.2 Hz, 2 H) ppm; 13C NMR (CDCl3):
δ = 41.8, 55.2, 59.3, 64.0, 69.2 (CH2), 71.3, 72.3 (CH2), 98.8, 101.6,
124.2, 126.1, 127.8, 128.7, 128.9, 130.2, 136.3, 141.84 ppm; HRMS
(ESI+): calcd for C21H24NO7S [M + H]+ 434.1273; found 434.1249.
[1] For reviews on Diels–Alder reactions, see: a) M. C. Carreno,
Chem. Rev. 1995, 95, 1717–1760; b) M. C. Carreno, S. Garcia-
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1988, pp. 823–849; k) G. H. Posner in Asymmetric Synth (Ed.:
J. D. Morrison), Academic Press, New York, 1983, vol. 2, p.
225–241.
Compound 31: Compound 29SS (0.10 g, 0.24 mmol) was converted
into 31 (0.06 g, 62%) by oxidation by following the general pro-
1
cedure. H NMR (CDCl3): δ = 3.36 (s, 3 H), 3.51–3.62 (m, 1 H),
3.75–3.78 (m, 2 H), 3.92–3.94 (m, 2 H), 4.15–4.18 (m, 1 H), 4.68–
4.74 (m, 2 H), 5.12–5.23 (m, 1 H), 5.51 (s, 1 H), 7.05–7.44 (m, 8
H), 7.71 (d, J = 8 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 38.8,
55.6, 60.5, 64.3, 69.2 (CH2), 72.3 (CH2), 75.4, 99.3, 102.6, 126.5,
128.3, 128.9, 129.1, 129.6, 133.9, 136.3, 140.9 ppm; C21H23NO8S
(449.47): calcd. C 56.12, H 5.16, N 3.12; found C 56.33, H 4.98, N
3.20.
Compound 33SS: Compound 28SS (0.20 g, 0.54 mmol) was con-
verted into 33SS (0.126 g, 54%) by following the general procedure
described above. 1H NMR (CDCl3): δ = 3.28 (dd, J = 5.2, 10.8 Hz,
1 H), 3.46 (s, 3 H), 3.48–3.54 (m, 1 H), 3.79–3.87 (m, 2 H), 4.07 (t,
J = 10 Hz, 1 H), 4.28 (dd, J = 4.8, 10.8 Hz, 1 H), 4.65–4.66 (m, 1
H), 4.91 (dd, J = 8, 15.2 Hz, 1 H), 5.10–5.14 (m, 1 H), 5.50 (s, 1
H), 6.98 (d, J = 7.2 Hz, 2 H), 7.21–7.36 (m, 6 H), 7.48 (d, J =
7.2 Hz, 2 H) ppm; 13C NMR (CDCl3): δ = 41.4, 56.8, 62.4, 68.9
(CH2), 69.0, 69.9 (CH2), 71.6, 101.5, 102.1, 124.2, 126.1, 127.8,
128.7, 129.0, 130.4, 136.2, 141.9 ppm; C21H23NO7S (433.48): calcd.
C 58.19, H 5.35, N 3.23; found C 58.23, H 5.48, N 3.46.
Compound 34SS: Compound 28SS (0.20 g, 0.54 mmol) was con-
verted into 34SS (0.054 g, 23%) by following the general procedure
described above. [α]2D6 = +59.05 (c = 0.04, CHCl3); 1H NMR
(CDCl3): δ = 2.59–2.60 (m, 1 H), 3.44–3.55 (m, 2 H), 3.56 (s, 3 H),
3.78 (t, J = 10.4 Hz, 1 H), 4.06 (t, J = 9.6 Hz, 1 H), 4.28 (dd, J =
4.8, 10.8 Hz, 1 H), 4.63 (d, J = 8.4 Hz, 1 H), 5.13–5.16 (m, 2 H),
5.42 (s, 1 H), 6.95 (d, J = 7.2 Hz, 2 H), 7.20–7.34 (m, 6 H), 7.52–
7.55 (m, 2 H) ppm; 13C NMR (CDCl3): δ = 40.7, 57.5, 60.8, 67.6,
68.8 (CH2), 72.4, 72.9 (CH2), 101.2, 101.9, 124.3, 125.9, 127.8,
128.9, 130.5, 136.2, 140.4 ppm; HRMS (ESI+): calcd for
C21H24NO7S [M + H]+ 434.1273; found 434.1257.
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Eur. J. Org. Chem. 0000, 0–0
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T. Pathak et al.
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[8] 8RS and 9SS denote R and S configurations of sulfur atom in
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Received: May 13, 2012
Published Online: ᭿
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Job/Unit: O20637
/KAP1
Date: 30-07-12 11:46:06
Pages: 9
Vinyl Sulfoxide-Modified Carbohydrates
Sulfoxide-Modified Carbohydrates
A. K. Atta, D. Dey, A. Bhaumik,
C. Manna, T. K. Pal, T. Pathak* ...... 1–9
Synthesis of Vinyl Sulfoxide-Modified
Pent-2-enofuranosides and Hex-2-enopyr-
anosides and Preliminary Studies of Their
Reactivity
Keywords: Carbohydrates / Sulfur / Sulf-
oxides / Chiral auxiliaries / Diastereoselec-
tivity / Oxidation
Oxidation of furanosyl sulfides to sulf-
oxides afforded both diastereomers. The
chirality of the sulfoxide group did not
greatly influence the addition patterns of
vinyl sulfoxide-modified pent-2-enofuran-
osides. Oxidation of pyranosyl sulfide gave
only one diastereomer and the modified
hex-2-enopyranosides significantly influ-
enced the outcome of carbon nucleophile
addition to these Michael acceptors.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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