Vinyl sulfone- and vinyl sulfoxide-modified tetrahydrofurans: A preliminary account of the enantiomeric synthesis of and diastereoselectivity of addition to new classes of Michael acceptors

Article abstract of DOI:10.1016/j.tet.2013.07.093

Enantiomerically pure 2-hydroxymethylene substituted-2,5-dihydro-3- (arylsulfonyl)- and 2-hydroxymethylene substituted-2,5-dihydro-3-(arylsulfinyl)- furans have been prepared from easily accessible carbohydrate derivatives for the first time. The strategy for accessing both these sulfones and sulfoxides is more efficient than the methods reported so far for the synthesis of this type of compounds. Hydroxymethylene group is sufficient to impose diastereoselectivity on the addition of a wide range of nucleophiles to vinyl sulfone-modified tetrahydrofurans. The benzyl protected hydroxymethylene group also suppresses the influence of chirally pure sulfoxides as two diastereomeric vinyl sulfoxide-modified tetrahydrofurans afforded the Michael adducts with same configurations at C-3 and C-4; this has been established by oxidizing the adducts, which were found to be identical to the products obtained by adding the same nucleophiles to the corresponding vinyl sulfones. These highly reactive Michael acceptors may be considered as a new addition to the arsenals of synthetic chemists interested in the functionalization of tetrahydrofurans.

Full text of DOI:10.1016/j.tet.2013.07.093

Accepted Manuscript
Vinyl Sulfone- and Vinyl Sulfoxide-Modified Tetrahydrofurans: A Preliminary Account
of the Enantiomeric Synthesis of and Diastereoselectivity of Addition to New Classes
of Michael Acceptors
Debanjana Dey, Atanu Bhaumik, Tanmaya Pathak
PII:
S0040-4020(13)01227-1
10.1016/j.tet.2013.07.093
TET 24675
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 2 June 2013
Revised Date: 18 July 2013
Accepted Date: 30 July 2013
Please cite this article as: Dey D, Bhaumik A, Pathak T, Vinyl Sulfone- and Vinyl Sulfoxide-Modified
Tetrahydrofurans: A Preliminary Account of the Enantiomeric Synthesis of and Diastereoselectivity of
Addition to New Classes of Michael Acceptors, Tetrahedron (2013), doi: 10.1016/j.tet.2013.07.093.
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ACCEPTED MANUSCRIPT
Vinyl Sulfone- and Vinyl Sulfoxide-Modified Tetrahydrofurans: A Preliminary Account of
the Enantiomeric Synthesis of and Diastereoselectivity of Addition to New Classes of
Michael Acceptors
Debanjana Dey, Atanu Bhaumik, Tanmaya Pathak*
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302
India
E. Mail: tpathak@chem.iitkgp.ernet.in
1

ACCEPTED MANUSCRIPT
X, Y =
H, OMe
X = OMe BnO
Y = H
X
Y
BnO
O
O
O
ribo-
epoxide
ArS
OMe
BnO
ArS
Michael
addition
OH
R
BnO
BnO
O
O
2
5
of O-, N-
and C-
nucleophiles
X = Y = H
OH
HO
S*
S*
R =
S
S
OMe, BnNH, iPrNH
morpholinyl, CH NO
CH(CO Me)
S* = ArO S Ar
Ar
2
O
2
2
..
..
O
2
2
configuration at C-2 controls diastereoselectivity of addition
Abstract
Enantiomerically pure 2-hydroxymethylene substituted -2,5-dihydro-3-(arylsulfonyl)- and 2-
hydroxymethylene substituted-2,5-dihydro-3-(arylsulfinyl)-furans have been prepared from
easily accessible carbohydrate derivatives for the first time. The strategy for accessing both
these sulfones and sufoxides is more efficient than the methods reported so far for the
synthesis of this type of compounds. Hydroxymethylene group is sufficient to impose
diastereoselectivity on the addition of a wide range of nucleophiles to vinyl sulfone-modified
tetrahydrofurans. The benzyl protected hydroxymethylene group also suppresses the
influence of chirally pure sulfoxides as two diastereomeric vinyl sulfoxide-modified
tetrahydrofurans afforded the Michael adducts with same configurations at C-2 and C-3; this
has been established by oxidizing the adducts which were found to be identical to the
products obtained by adding the same nucleophiles to the corresponding vinyl sulfones.
These highly reactive Michael acceptors may be considered as a new addition to the arsenals
of synthetic chemists interested in the functionalization of tetrahydrofurans.
Key-words: Vinyl sulfone, Vinyl sulfoxide, Tetrahydrofuran, Michael addition; Modified
tetrahydrofuran, Chiral auxiliary
2

ACCEPTED MANUSCRIPT
Introduction
1
2
α,β-unsaturated -sulfones and -sulfoxides are versatile reagents and useful building blocks
in synthetic chemistry because they have the potential to undergo Michael addition of carbon
3
,4
and various heteroatom nucleophiles as well as cycloaddition reactions. 2,5-Dihydro-3-
(alkyl/arylsulfonyl) furans 1a-e (Figure 1) represent the basic skeleton of a special class of
R3
R2
O
O
2
5
R1
RO S
PhO
2
S
2
1
2
3
2
2
2
2
2
2
a R = R = H, R = iPr
1
a R = Me; 1b R = Et
1
2
3
b R = R = H, R = Ph
1
1
1
c R = CH Cl; 1d R = Ph
e R = p-NO C H ;
f R = p-Tol
2
1
2
3
c R = H; R = Me; R = Ph
2
6
4
1
2
3
d R = Me; R = H; R = Ph
1
3
2
e R = R = H; R = Ph
1
3
f R = R = H;
OMe
HO
R
O
2
R =
OMe
S(O)nTol-p
OMe
O
3
3
a n = 2, R = i-Pr, Ph, p-F-Ph
b n = 1, R = vinyl, Et, i-Pr
Ph, Pyr
BnO
O
O
Ph
p-Tol(O)nS
ROS
R = p-Tol
6 n = 2
n = 1
ArOS
7
4
5
Figure 1. Selected examples of vinyl sulfone- and
vinyl sufoxide-modified tetrahydrofurans.
5
cyclic Michael acceptors with high potential as synthetic intermediates. . 2,5-Dihydro-3-
(phenylsulfonyl)-furan was used further as a dienophile for the regioselective Diels-Alder
reactions; the desired cyclic vinyl sulfone 1d was obtained by irradiating the 2,5-
6
dihydrofuran and phenylselenenyl benzenesulfonate followed by oxidation. Pyrroles derived
7
from 1f was utilized in the synthesis of porphyrins. A group of substituted 2,5-
dihydrofurans 2a-d was synthesized by the acid treatment of the corresponding enediols,
8
obtained through multi-step synthetic routes. 2-Substituted 4-benzenesulfonyl-2,5-
dihydrofuran 2e was synthesized from propargyl ethers through a complex reaction sequence
3

ACCEPTED MANUSCRIPT
of alkynyl(phenyl)iodonium salts which also afforded 2,5-dihydrofuran 2f, an intermediate
9
required for lignan synthesis. The sulfonyl diene monoepoxides were converted to the
1
0
corresponding sulfonyl dihydrofurans 3a under acid catalyzed conditions.
Realizing the importance of this class of compounds, attempts have also been made to
synthesize the 2,5-dihydro-3-(alkyl-/arylsulfinyl)furans because in addition to the
participation of these Michael acceptors in the reactions mentioned above, α,β-unsaturated
sulfoxides have the potential to act as efficient chiral auxiliaries in asymmetric synthesis.
3,4
Although the applications of acyclic varieties are well known, the ability of the cyclic vinyl
sulfoxides to differentiate between the diastereotopic faces of a proximal or even remote
reaction center is rarely documented. Nucleophilic epoxidation of hydroxyl sulfinyl dienes
1
1
produced the sulfinyl tetrahydrofurans 3b in poor yields. α-(Diethoxyphosphoryl)vinyl p-
tolyl sulfoxides on reactions with the sodium salt of α-hydroxyacetaldehyde, generated 3-p-
12
toluenesulfinyl-2,5-dihydrofuran 4. A complex multi-step route was devised to synthesize
2
,5-dihydron arylsulfinyl furan from (S)-o-(N,N-dimethylamino)phenyl methyl sulfoxide;
13
the reaction afforded a mixture of (2R,SR)-and (2S,SR)- of 5 in the ratio of 6:94.
Results and Discussion
The utilization of Michael acceptors like 1-5 (Figure 1) in synthetic chemistry would
inevitably depend on the availability of suitable preparative methods for easy access to these
compounds. It appears from the published reports mentioned above, that the strategies for
accessing substituted 3-(alkyl/aryl)-sulfonyl or -sulfinyl-2,5-dihydrofurans reported so far are
5
-13
cumbersome and low yielding. We and others have reported earlier that one of the easiest
14
2e
ways of incorporating vinyl sulfone or vinyl sulfoxide group in a furan (or pyran) ring is
to take advantage of easy S 2-type displacement of appropriately selected leaving group or
N
4

ACCEPTED MANUSCRIPT
epoxide ring opening on carbohydrates by sulfur nucleophiles. Oxidation of sulfur followed
by displacement of a leaving group at the β-position would produce the vinyl sulfone or vinyl
sulfoxide moiety. We report herein the synthesis and reaction patterns of enantiopure vinyl
sulfone- and vinyl sulfoxide-modified tetrahydrofurans 6 and 7 (Figure 1).
In order to have a pre-decided asymmetric centre at C-2 and also for accessing compound 6
(Figure 1) in relatively large amount, we selected the known ribo-epoxide as the starting
material. Thus the ribo-epoxide 8 was treated with p-thiocresol in the presence of 1,1,3,3-
15
tetramethylguanidine (TMG) to generate the corresponding sulfide 9. Compound 9 was
consecutively treated with trifluoroacetic acid (TFA) and sodium borohydride (NaBH ) to
4
afford acyclic compound 10. Selective tosylation of 10 gave the desired cyclic compound 11
having a furan moiety. Compound 11 was oxidized with magnesium monoperoxyphthalate
hexahydrate (MMPP) to the corresponding sulfone 12. The hydroxyl group of 12 was
mesylated and subsequent elimination of the mesyl group produced the desired vinyl sulfone
1
6
(Scheme 1). The appearance of the characteristic vinylic proton at δ 6.92 in H NMR and
STol-p
OMe
(i) 70% TFA,
rt, 10h
BnO
BnO
OMe
O
O
O
(
ii) NaBH4
ref 15
EtOH, rt, 4h
58% (in two
steps)
OH
9
8
TsCl,
Py:Toluene
STol-p
O
OH
BnO
o
(
1:1), 0 C
OH
7
2h, 78%
BnO
Tol-pS
OH
OH
1
1
1
0
MMPP,
MeOH, rt, BnO
h, 88%
MsCl, Py,
+4 C,
24h, 85%
SO Tol-p
2
o
BnO
O
O
6
OH
2
p-TolO S
2
6
1
Scheme 1. Synthesis of vinyl sulfone-modified tetrahydrofurans.
5

ACCEPTED MANUSCRIPT
1
3
the corresponding carbon at δ 140.5 in C NMR spectra of compound 6 indicated the
formation of the vinyl sulfone moiety. The carbon peaks at δ 70.9, 73.1 and 74.5 ppm
2
indicated the presence of three CH groups and there were four tertiary carbons at δ 136.4,
13
1
38.0, 141.5 and 144.9 ppm in the C NMR of compound 6. All these in combination with
HRMS data supported the proposed structure 6.
To synthesize the corresponding vinyl sulfoxides, compound 11 was oxidized under
1
6a
controlled conditions by sodium metaperiodate (NaIO
4
) and water-methanol mixture at
room temperature for 5h to give a mixture of diastereomeric sulfoxides which were easily
1
6a
separated to afford 13S
S
and 13R
S
roughly in 1:1 ratio. We reported earlier that the partial
oxidation of pyranoside ring by NaIO
4
produced only one sulfoxide, enantiomeric at sulfur
-
atom; in this case oxygen atoms of IO
4
attack the sulfides perpendicularly to the plane of C-
.
... ....
S-C atoms and the S O I atoms are in a linear arrangement in the very early transition
16b
state. However, in case of furanosides such a positioning of the aryl sulfide group was not
possible due to the pseudo-axial and pseudo- equatorial nature of bonds in a five membered
ring and therefore enantiomers with respect to the sulfur atom were produced in almost equal
16a
ratio. It appears that even in the absence of the anomeric methoxy group, similar pattern of
enantioselectivity with respect to sulfur is manifested in the oxidation of 11. The isomeric
sulfoxides 13S and 13R thus obtained, were reacted with mesyl chloride in pyridine at +4
S
S
o
C for 24h to produce the corresponding mesylated compounds 14S
Compounds 14S and 14R were then treated with DBU in DCM at room temperature for 3h
to generate the corresponding vinyl sulfoxides 7R and 7S respectively (Scheme 2). The
structure of compound 7R was confirmed by X-ray crystallography which indirectly helped
us to establish the structure of 7S . The absolute configuration at the sulfur of vinyl
sulfoxides 7R and 7S could also be confirmed by comparing the NMR data with those
S S
and 14R respectively.
S
S
S
S
S
S
S
S
6

ACCEPTED MANUSCRIPT
11
NaIO , H O
separation
4
2
Tol-p
O
Tol-p
.
.
O
..
S
S
BnO
BnO
O
O
OZ
OZ
1
3SS Z = H (50%)
4SS Z = Ms (89%)
13R
14R
S
S
Z = H (49%)
Z = Ms (92%)
MsCl, Py,
+4 C, 24h
1
o
DBU, DCM, 3 h
BnO
BnO
O
O
S
S
Tol-p
Tol-p
.
.
O
..
O
7RS (91%)
7SS (92%)
Scheme 2. Synthesis of vinyl sulfoxide-modified tetrahydrofurans
1
3
reported for 2-aryl-3-sulfinyl-2,5-dihydrofurans. In the reported data, the vinylic proton was
used as a tool for assigning the stereochemistry of sulfur atom because of the highly
1
3
deshielding effect induced by the sulfinyl oxygen on the vinylic hydrogen. The vinylic
1
proton of compound 7R appeared at δ 6.68 in its H NMR spectrum whereas that for the
S
compound 7S
was much more deshielded than that in 7S
chemical shift value of vinylic proton is possible if sulfur oxygen was oriented towards the
S
was at δ 6.56. Thus the chemical shift values showed that the vinylic proton of
13
7
R
S
S
. According to the reported data, the higher
S
vinylic proton. So from the above discussion it was clear that in compound 7S the sulfur
oxygen was oriented opposite to the vinylic proton.
To study the diastereoselectivity of addition reaction, vinyl sulfone modified tetrahydrofuran
was reacted with sodium methoxide in methanol and the reaction afforded a single
6
7

ACCEPTED MANUSCRIPT
diastereomer 15 (Scheme 3). Theoretically the reaction was supposed to produce four
diastereomers isomeric at C-2 and C-3 but the thermodynamically most stable isomer 15 was
obtained. The structure of 15 was unambiguously established via alternative synthesis. Thus,
BnO
BnO
OMe
O
O
NaOMe
2
5
MeOH, rt
36 h, 86%
Tol-pO S
SO Tol-p
2
2
6
15
Scheme 3 Formation of a single diastereomer
from the reactions of NaOMe/MeOMe vinyl sulfone 6.
compound 16 was methylated with methyl iodide in the presence of sodium hydride to
produce 17. Compound 17 was consecutively treated with TFA and NaBH to generate the
4
acyclic compound 18. Selective tosylation of 18 produced the desired cyclic compound 19
which on oxidation with MMPP afforded the desired diastereomer 15 (Scheme 4), which was
(
i) 70% TFA,
BnO
OR
rt, 24h
O
(
ii) NaBH , EtOH,
4
OMe
rt, 5h, 61% (in
two steps)
STol-p
MeI, NaH,
DMF, rt, 2.5h,
6%
16 R=H
17 R=Me
8
TsCl, Py:Toluene
o
(
1:1), 0 C, 72h,
OH
BnO
7
6%
OMe
O
OH
BnO
Tol-pS
OMe
X
18
MMPP, MeOH, 19 X= STol-p
rt, 6h, 84%
15 X=SO Tol-p
2
Scheme 4. Synthesis of diastereomer 15 from a thiosugar.
1
identical with the product obtained from 6 in scheme 3 (mixed H NMR). Thus the methoxide
ion attacked the electron deficient double bond from the β-face and the resulting carbanion at
8

ACCEPTED MANUSCRIPT
C-3 was also protonated from the β-face of 6 (cis-addition) to afford the thermodynamically
stable product.
At this point, we intended to study the influence of enantiomerically pure sulfoxide groups, if
any on the diastereoselectivity of addition of methoxide to vinyl sulfoxides 7R and 7S .
S
S
S
Thus, 7R was reacted with sodium methoxide in methanol at room temperature for 24h to
afford a single diastereomer 20S in excellent yield (Scheme 5). Vinyl sulfoxide 7S was
S
S
slow to react under similar reaction conditions and required 48h to afford the single
diasteromer 20R
S
as the Michael adduct. The stereochemistry of the C-2 and C-3 centers of
7
RS
7SS
NaOMe, MeOH, rt
BnO
BnO
OMe
OMe
O
O
S
S
Tol-p
Tol-p
O
.
.
O
..
20SS (24 h, 92%)
20RS (48 h, 91%)
MMPP, MeOH, 2h
15
Scheme 5. Matching of configurations at C-2 and C-3 of
adducts obtained from Michael acceptors 7Rs and 7S
S
.
the Michael addition products was confirmed by oxidizing 20S and 20R with MMPP in
S
S
methanol at room temperature affording 15 in each case (Scheme 5). Thus, irrespective of the
configurations of the sulfoxide groups, methoxide added from the β-face of the
tetrahydrofuran moiety.
9

ACCEPTED MANUSCRIPT
t
To generalize the study, vinyl sulfone 6 was reacted with nitromethane/KO Bu or
t
dimethylmalonate/ KO Bu to afford single diastereomers 21 and 22 in excellent yields
(Scheme 6). Compound 6 was also reacted with benzylamine, isopropylamine and
morpholine in methanol at an ambient temperature to afford adducts 23-25 respectively in
excellent yields (Scheme 6). The structure of compound 21 was confirmed by X-ray
crystallography and that of compound 22 was confirmed by comparing its spectral data with
those of 21. Similarly, the structure of the morpholino derivative 25 was confirmed by X-ray
crystallography. The structures of 23 and 24 were confirmed by comparing their spectral data
S S
with those of 25. Vinyl sulfoxide 7R and 7S were separately reacted with
t
CH NO /KO Bu, THF,
3
2
BnO
X
O
or
6
t
CH (CO Me) /KO Bu, THF,
2
2
2
or
benzylamine, MeOH,
SO Tol-p
2
or
2
2
2
2
1 X=CH NO (4h, 90%)
2 2
iso-propylamine, MeOH,
or
morpholine, MeOH
2 X=CH(CO Me) (4h, 91%)
2
2
3 X=NHBn (4h, 90%)
4 X=NHiPr (3h, 91%)
*
all reactions were performed
2
5 X= N
O (4h, 91%)
at room temperature
Scheme 6. Michael type addition of C- and N-nucleophiles
to vinyl sulfone-modified tetrahydrofuran 6.
o
dimethylmalonate/NaH in DMF at 60 C to generate single diastereomers 26S
S
and 26R
S
in
excellent yields (Scheme 7); benzylamine afforded the addition products 27S and 27R
S
S
S S S S
respectively (Scheme 7). Once again 26S /26R and 27S /27R pairs were oxidized with
MMPP to afford the corresponding addition products 22 and 23 respectively (Scheme 7)
obtained from vinyl sulfone 6. It should be noted that the oxidation reactions of amino
compounds were terminated within 0.5h to avoid over- oxidation. These experiments
established once again that like the addition pattern of methoxide, the diastereoselectivity of
10

ACCEPTED MANUSCRIPT
S S
addition of C- and N-nucleophiles to 6, 7R and 7S afforded thermodynamically more stable
products.
7
RS
7SS
CH (CO Me) , NaH
2
2
2
o
DMF, 60 C, 6h
or,
benzylamine, rt, 48h
BnO
BnO
X
X
O
O
S
S
Tol-p
Tol-p
O
.
.
O
..
2
2
6SS X=CH(CO Me) (93%)
26R
27R
S
S
X=CH(CO
2
Me)
2
(93%)
2
2
7SS X=NHBn (94%)
X=NHBn (94%)
MMPP
MeOH
27SS
or
MMPP
MeOH
2
6SS
or
6RS
2
2
23
2
27R
S
Scheme 7. Michael type addition of C- and N-nucleophiles
to vinyl sulfoxide-modified tetrahydrofuran 6.
Conclusion
We have devised a simple strategy for the synthesis of enantiomerically pure 2-
hydroxymethylene substituted -2,5-dihydro-3-(arylsulfonyl)- and 2-hydroxymethylene
substituted -2,5-dihydro-3-(arylsulfinyl)- furans from easily accessible carbohydrate
derivatives. Using carefully designed experiments with vinyl sulfone- and vinyl sulfoxide-
modified tetrahydrofurans, we have also established that the hydroxymethylene group is
sufficient to afford diastereoselective all trans products. The addition pattern is general in
nature because C- and N-nucleophiles also reacted in the similar fashion. Although α,β-
unsaturated sulfoxides are known as efficient chiral auxiliaries, our experiments with vinyl
sulfoxide-derived tetrahydrofurans have established that at least in our system, chirally pure
sulfoxides do not play any role to control the diastereoselectivity of addition products
because vinyl sulfoxide-modified tetrahydrofurans also afforded all trans products. From a
11

ACCEPTED MANUSCRIPT
synthetic point of view the well studied vinyl sulfone-modified tetrahydrofuran 6 is now a
1
,2,17
new addition to a class of highly reactive Michael acceptors
capable of efficiently
reacting with a wide range of nucleophiles to afford enantiomerically pure products.
Experimental Section
2
General methods: All reactions were conducted under N atmosphere. Melting points were
determined in open-end capillary tubes and are uncorrected. Carbohydrates and other fine
chemicals were obtained from commercial suppliers and are used without purification.
Solvents were dried and distilled following the standard procedures. TLC was carried out on
pre-coated plates (Merck silica gel 60, f254) in ethylacetate(EA)/pet ether (PE) mixture and
the spots were visualized with UV light or by charring the plate dipped in 5% H
2
SO
4
-MeOH
1
13
solution. Column chromatography was performed on silica gel (230-400 mesh). H and C
NMR for new compounds were recorded at 200/400 and 50/100 MHz respectively using
CDCl as the solvent. DEPT experiments had been carried out to identify the methylene
3
carbons. Optical rotations were recorded at 589 nm. Mass spectroscopy data were obtained
+
−
from mass analyzer consisting of TOF and quadrupole in either ESI or ESI mode.
(2S,3S,4R)-5-(Benzyloxy)-3-(p-tolylthio)pentane-1,2,4-triol (10): A solution of thiocresol
(13.1 g, 105.9 mmol) and TMG (10.6 ml, 84.72 mmol) in DMF (30 mL) was stirred at room
temperature for 0.5h. Compound 8 (5 g, 21.16 mmol) was added and the solution was heated
o
for 5h at 100 C. The mixture was partitioned between satd. aq. NaHCO
3
solution and
, filtered and the
filtrate was evaporated to dryness. The residue, thus obtained was purified over silica gel
2 4
EtOAc. Organic layers were pooled together, dried over anhyd. Na SO
1
5
column to afford 9 (6.1 g, 80%). A mixture of compound 9 (3.5 g, 9.71 mmol) and 70%
TFA in water (10 mL) was stirred at room temperature for 10h After completion of the
.
12

ACCEPTED MANUSCRIPT
3
reaction (TLC), the reaction mixture was poured into the ice cold satd. aq. NaHCO solution
and the product was extracted with EtOAc (3 X 10 mL). The combined organic layers were
dried over anhydr. Na SO , filtered, and the filtrate was concentrated under reduced pressure
(1.5 g, 38.9 mmol) was added to an ethanolic solution (40 mL) of this
2
4
to get a residue. NaBH
4
o
residue at 0 C and the mixture was stirred at room temperature. After 4h the reaction mixture
was concentrated under reduced pressure to get a residue. The residue was poured into satd.
aq. NaHCO solution and the product was extracted with EtOAc (3 X 10 mL). The combined
3
organic layers were dried over anhydr. Na
2 4
SO , filtered, and the filtrate was concentrated
under reduced pressure. The residue was purified by flash chromatography (40% EA/PE) to
25.1
D
get the sulfide 10 (1.96 g, 58%) as a colorless gum; Rf (40% EA/PE) 0.30; [α]
(+) 12.07
(
c 1.5, CHCl ); δΗ (400 MHz, CDCl ) 2.31 (3 H, s), 3.38 (1 H, s), 3.63-3.69 (2 H, m), 3.77-
3
3
3
.81 (1 H, m), 3.94-4.01 (2 H, m), 4.27 (1 H, t, J 4.0 Hz), 4.46 (2 H, q, J 11.6 Hz), 7.07 (2 H,
) 21.0, 56.2, 63.2 (CH ), 70.5, 71.6
), 127.9, 128.4, 129.9, 130.0, 131.6, 131.8, 137.2, 137.5; HRMS [ES ,
d, J 7.6 Hz), 7.25-7.35 (7 H, m); δC (100 MHz, CDCl
3
2
+
(CH
2
), 72.6, 73.4 (CH
2
+
(
M+Na) ]: for C H O NaS found 371.1275, requires 371.1293.
1
9
24
4
(3S,4S,5R)-5-(Benzyloxymethyl)-4-(p-tolylthio)-tetrahydrofuran-3-ol (11): A solution of
compound 10 (3.15 g, 9.04 mmol) in a mixture of anhydr. pyridine and toluene (1:1; 10 mL)
o
was treated drop-wise at 0 C with a solution of tosyl chloride (2.6 g, 13.6 mmol) in dry
o
tolune (10 ml) and the mixture was stirred for 0.5h. The reaction mixture was stored at +4 C
for 72h. The mixture was filtered through celite and the filtrate was evaporated to dryness.
Residual pyridine was co-evaporated with toluene. The residue was purified by flash
chromatography (25% EA/PE) to afford the cyclic compound 11 (2.33 g, 78%) as a yellowish
2
D
5.1
gummy compound; Rf (25% EA/PE) 0.32; [α]
3
(+) 20.07 (c 1.5, CHCl ); δH (400 MHz,
CDCl ) 2.33 (3 H, s), 3.59-3.61 (1 H, m), 3.70 (1 H, dd, J 9.6, 12.0 Hz), 3.75-3.77 (2 H, m),
3
13

ACCEPTED MANUSCRIPT
4
.27-4.31 (1 H, m), 4.38-4.39 (1 H, m), 4.52-4.55 (2 H, m), 4.62 (1 H, d, J 11.6 Hz), 7.11 (2
H, d, J 8 Hz), 7.26-7.35 (7 H, m); δC (100 MHz, CDCl
3
) 21.0, 57.1, 70.3 (CH
2 2
), 73.5 (CH ),
+
7
3.7 (CH ), 77.3, 78.7, 127.6, 127.8, 128.3, 130.0, 131.1, 131.3, 137.2, 138.0; HRMS [ES ,
2
+
(
M+Na) ]: for C19
H
22
O
3
NaS found 353.1188, requires 353.1187.
(3S,4S, 5R)-5-(Benzyloxymethyl)-4-tosyl-tetrahydrofuran-3-ol (12): To a solution of
compound 11 (4.39 g, 13.28 mmol) in MeOH (20 mL), MMPP (19.8 g, 40.03 mmol) was
added and the mixture was stirred for 6h at room temperature. After completion of the
reaction, the mixture was evaporated under reduced pressure. The solid residue was then
taken in a mixture of EtOAc and satd. aq. NaHCO
3
solution and the mixture was stirred for
SO , filtered and the filtrate was
1
h. Then organic part was separated, dried over anhydr. Na
2
4
evaporated to dryness. The residue thus obtained was purified by flash chromatography (33%
EA/PE) to afford compound 12 (4.23 g, 88%) as a white solid; Rf (33% EA/PE) 0.31; Mp
o
27.3
1
19 C; [α]
H, m), 3.71-3.74 (1 H, m), 3.91-3.94 (2 H, m), 4.26-4.30 (1 H, m), 4.44-4.51 (2 H, m), 4.62
1 H, d, J 11.6 Hz), 4.84-4.88 (1 H, m), 7.26-7.35 (7 H, m), 7.76 (2 H, d, J 8 Hz); δC (100
MHz, CDCl ) 21.6, 68.6 (CH ), 72.8, 73.4 (2 X CH ), 78.6, 127.6, 127.8, 128.1, 128.3, 130.1,
36.1, 137.8, 145.2; HRMS [ES , (M+H) ]: for C19 S found 363.1279, requires
63.1266.
D
3
(+) 21.31 (c 1.1, MeOH); δH (400 MHz, CDCl ) 2.44 (3 H, s), 3.59-3.63 (1
(
3
2
2
+
+
1
3
23 5
H O
(R)-2-(Benzyloxymethyl)-3-tosyl-2,5-dihydrofuran (6): A stirred solution of compound 12
o
(
2.0 g, 5.52 mmol) in dry pyridine (10 mL) was treated drop-wise at 0 C with a solution of
mesyl chloride (1.4 ml, 16.9 mmol) in dry pyridine (6 mL). After 0.5h the solution was stored
o
at +4 C for 24h. After completion (TLC), the reaction mixture was poured into ice-cold
water and the compound was extracted with EtOAc. The organic layer was separated, dried
14

ACCEPTED MANUSCRIPT
over anhydr. Na
2
SO
4
, filtered and the filtrate was evaporated to dryness. Residual pyridine
was co-evaporated with toluene. The residue thus obtained was purified by flash
chromatography (33% EA/PE) to afford 6 (1.62 g, 85%) as a yellowish gum; Rf (33%
2
D
5.1
EA/PE) 0.30; [α]
3 3
(+) 41.25 (c 1.28, CHCl ); δH (400 MHz, CDCl ) 2.42 (3 H, s), 3.53-
3
4
2
1
.57 (1 H, m), 3.74 (1 H, d, J 10.8 Hz), 4.40 (2 H, s), 4.70-4.74 (1 H, m), 4.81-4.86 (1 H, m),
.99 (1 H, s), 6.92 (1 H, s), 7.22-7.34 (8 H, m), 7.75 (2 H, d, J 8 Hz); δC (100 MHz, CDCl3)
1.6, 70.9 (CH
2
), 73.1 (CH
2
), 74.5 (CH
2
), 83.9, 127.3, 127.4, 128.0, 128.2, 129.9, 136.4,
+
+
38.0, 140.5, 141.5, 144.9; HRMS [ES , (M+Na) ]: for C19
H
20
O
4
NaS found 367.0974,
requires 367.0980.
(
3S,4S,5R)-5-(Benzyloxymethyl)-4-((S)-p-tolylsulfinyl)-tetrahydrofuran-3-ol (13S
S
) and
(
3S,4S,5R)-5-(Benzyloxymethyl)-4-((R)-p-tolylsulfinyl)-tetrahydrofuran-3-ol (13R
S
): To
a well-stirred solution of compound 11 (3.86 g, 11.69 mmol) in MeOH (30 mL) was added
NaIO (3.75 g, 17.54 mmol) in H O (8 mL) and the mixture was stirred at room temperature.
After 5h volatile matters were removed under reduced pressure and the residual aq. mixture
was partitioned between aq. satd. NaHCO solution and EtOAc (3 X 10 mL). The combined
organic layer was separated, dried over anhyd. Na SO , filtered and the filtrate was
4
2
3
2
4
concentrated under reduced pressure to get a residue. The residue was purified over silica gel
to afford the required sulfoxides. Compound 13S : Yellowish gum; Yield (2.26 g, 50%); Rf
(−) 27.21 (c 0.99, CHCl ); δH (400 MHz, CDCl ) 2.39 (3 H, s),
.31-3.34 (1 H, m), 3.59-3.63 (1 H, m), 3.65-3.69 (1 H, m), 3.76-3.80 (1 H, m), 4.24 (1 H, q,
S
2
5.3
(60% EA/PE) 0.3; [α]
D
3
3
3
J 6.8 Hz), 4.33 (1 H, q, J 12.4 Hz), 4.58 (2 H, s), 4.93 (1 H, q, J 5.2 Hz), 7.27 (2 H, d, J 8.0
Hz), 7.31-7.36 (5 H, m), 7.48 (2 H, d, J 8.0 Hz); δC (100 MHz, CDCl ) 21.4 69.5 (CH ),
), 77.6, 124.6, 127.9, 128.0, 128.4, 130.1, 137.4, 139.8,
3
2
7
1
1.2, 72.2, 73.6 (CH
2
), 73.8 (CH
2
+
+
42.0; HRMS [ES , (M+H) ]: for C H O S found 347.1304, requires 347.1317.
19
23
4
15

ACCEPTED MANUSCRIPT
o
Compound 13R
S
: White solid; Yield (1.98 g, 49%); Rf (80% EA/PE) 0.31; Mp 109 C;
(+) 54.46 (c 1.01, CHCl ); δH (400 MHz, CDCl ) 2.42 (3 H, s), 3.38-4.40 (1 H, m),
.50-3.54 (1 H, m), 4.00-4.06 (3 H, m), 4.15-4.18 (1 H, m), 4.53-4.57 (1 H, m), 4.64, (2 H, q,
) 21.5, 69.6
2
5.3
[
α]
D
3
3
3
J 12.0 Hz), 7.28-7.41 (7 H, m), 7.60 (2 H, d, J 8.0 Hz); δC (100 MHz, CDCl
3
(
CH ), 71.3, 73.6 (CH ), 74.3 (CH ), 74.7, 79.2, 125.6, 127.7, 127.9, 128.4, 130.2, 137.8,
2
2
2
+
+
1
38.6, 142.8; HRMS [ES , (M+H) ]: for C19
H
23
O
4
S found 347.1334, requires 347.1317.
(3S,4S,5R)-5-(Benzyloxymethyl)-4-((S)-p-tolylsulfinyl)-tetrahydrofuran-3-yl
methanesulfonate (14S ): Following the procedure described for the preparation of 6,
S
sulfoxide 13S (2.0 g, 5.78 mmol) was converted to 14S (2.18 g, 89%). White solid; Rf
S
S
o
25.3
D
(
50% EA/PE) 0.31; Mp 88 C; [α]
(−) 35.95 (c 1.05, CHCl ); δH(400 MHz, CDCl ) 2.36
3
3
(3 H, s), 2.45 (3 H, s), 3.42 (1 H, d, J 6.4 Hz), 3.83-3.90 (2 H, m), 3.94-3.99 (1 H, m), 4.28-
4
7
7
.32 (1 H, m), 4.46 (1 H, q, J 6.4 Hz), 4.56 (2 H, s), 5.40-5.42 (1 H, m), 7.25-7.30 (7 H, m),
.41 (2 H, d, J 8.0 Hz); δC (100 MHz, CDCl ) 21.4, 37.6, 68.8 (CH ), 70.0, 73.9 (2 X CH ),
3
2
2
+
+
8.1, 78.1, 124.4, 128.1, 128.1, 128.6, 130.3, 137.4, 139.1, 142.0; HRMS [ES , (M+H) ]: for
20 25 6 2
C H O S
found 425.1085, requires 425.1093.
(3S,4S,5R)-5-(Benzyloxymethyl)-4-((R)-p-tolylsulfinyl)-tetrahydrofuran-3-yl
methanesulfonate (14R ): Following the procedure described for the preparation of 6,
S
sulfoxide 13R (1.5 g, 4.33 mmol) was converted to 14R (1.69 g, 92%). Yellowish gum; Rf
S
S
2
D
5.3
(60%EA/PE) 0.32; [α]
(+) 49.57 (c 0.95, CHCl
3
3
); δH (400 MHz, CDCl ) 2.41 (3 H, s),
2
4
.52 (3 H, s), 3.67-3.70 (1 H, m), 3.86-3.89 (1 H, m), 3.99-4.08 (2 H, m), 4.22-4.27 (1 H, m),
.56-4.71 (3 H, m), 4.92-4.95 (1 H, m), 7.30-7.38 (7 H, m), 7.65 (2 H, d, J 8.0 Hz); δC (100
3 2 2 2
MHz, CDCl ) 21.4, 37.7, 69.5 (CH ), 71.3, 73.4 (CH ), 73.7 (CH ), 78.3, 79.1, 126.0, 127.8,
16

ACCEPTED MANUSCRIPT
+
+
1
28.5, 130.2, 137.5, 138.6, 146.1; HRMS [ES , (M+H) ]: for C20
25 6 2
H O S found 425.1085,
requires 425.1093.
(
R)-2-(Benzyloxymethyl)-3-((R)-p-tolylsulfinyl)-2,5-dihydrofuran (7R
compound 14S (2.15 g, 5.07 mmol) was treated with DBU (1.5 mL, 10.14 mmol) in DCM
15 mL) at ambient temperature for 3h. Solvent was evaporated under reduced pressure and
the resulting residue was purified by flash chromatography (40% EA/PE) to afford
corresponding vinyl sulfoxides 7R (1.51 g, 91%) as a brown solid; Rf (40% EA/PE) 0.34;
(−) 60.21 (c 0.98, CHCl ); δH (400 MHz, CDCl ) 2.36 (3 H, s), 3.44-3.52
2 H, m), 4.45 (2 H, q, J 12.0 Hz), 4.55 (1 H, bs), 4.69-4.74 (1 H, m), 4.81-4.86 (1 H, m),
S
): The mesylated
S
(
S
o
25.3
Mp 131 C; [α]
D
3
3
(
6
.68 (1 H, s), 7.22 (2 H, d, J 8.0 Hz), 7.29-7.36 (5 H, m), 7.45 (2 H, d, J 8.0 Hz); δC (100
MHz, CDCl
3
) 21.4, 71.5 (CH
2
), 73.5 (CH
2
), 75.5 (CH
2
), 88.3, 125.6, 127.7, 127.8, 128.3,
+
+
1
30.0, 131.4, 137.6, 138.6, 142.3, 146.3; HRMS [ES , (M+Na) ]: for C19
H
20
O
3
NaS found
3
51.1004, requires 351.1031.
(
R)-2-(Benzyloxymethyl)-3-((S)-p-tolylsulfinyl)-2,5-dihydrofuran (7S
S
): Following the
procedure described for the preparation of 7R , compound 14R (1.2 g, 2.83 mmol) was
S
S
2
5.3
converted to 7S
.93, CHCl ); δH (400 MHz, CDCl
Hz), 4.41 (2 H, q, J 12.4 Hz), 4.59-4.63 (1 H, m), 4.74-4.77 (2 H, m), 6.56 (1 H, s), 7.20-7.27
S
(0.85 g, 92%). Colorless gum; Rf (40% EA/PE) 0.30; [α]
D
(+) 28.94 (c
0
3
3
) 2.33 (3 H, s), 3.44-3.48 (1 H, m), 3.63 (1 H, d, J 10.8
(
(
[
7 H, m), 7.39 (2 H, d, J 8.0 Hz); δC (100 MHz, CDCl
3 2 2
) 21.4, 71.8 (CH ), 73.2 (CH ), 74.7
CH ), 84.0, 124.7, 127.4, 127.5, 128.2, 130.0, 136.3, 138.1, 138.3, 141.8, 143.3; HRMS
2
+
+
ES , (M+H) ]: for C H O S found 329.1190, requires 329.1211.
19
21
3
17

ACCEPTED MANUSCRIPT
(2R,3R,4R)-2-(Benzyloxymethyl)-4-methoxy-3-tosyl-tetrahydrofuran (15): Sodium
methoxide (0.02 g, 0.36 mmol) was added to an anhyd. methanolic solution (5 mL) of vinyl
sulfone 6 (0.043 g, 0.09 mmol) and the mixture was stirred at room temperature for 36h.
Volatile matters were removed under reduced pressure. The solid residue was then taken in a
mixture of EtOAc and satd. aq. NaHCO
layers were separated, dried over anhydr. Na
The residue thus obtained, was purified by flash chromatography (20% EA/PE) to afford
3
solution and the mixture was stirred for 1h. Organic
2
SO , filtered and the filtrate was evaporated.
4
o
25.1
compound 15 (0.04 g, 86%) as a white solid; Rf (20% EA/PE) 0.32; Mp 82 C; [α]
(+)
) 2.43 (3 H, s), 3.18 (3 H, s), 3.28-3.32 (1 H, m),
.50 (1 H, dd, J 3.2, 10.8 Hz), 3.67 (1 H, d, J 6.0 Hz), 3.80-3.84 (1 H, m), 4.03 (1 H, d, J 10.0
D
2
3
3 3
9.81 (c 1.02, CHCl ); δH (400 MHz, CDCl
Hz), 4.35-4.41 (3 H, m), 4.52 (1 H, d, J 12.0 Hz), 7.23-7.33 (7 H, m), 7.74 (2 H, d, J 8.0 Hz);
δC (100 MHz, CDCl
3
) 21.6, 56.9, 69.8, 69.9 (CH
2
), 73.0 (CH
2
), 73.3 (CH
2
), 78.6, 82.2,
+
+
1
27.6, 127.7, 128.3, 128.5, 130.0, 135.0, 137.8, 145.2; HRMS [ES , (M+Na) ]: for
20 24 5
C H O NaS found 399.1248, requires 399.1242.
(2R,3R,4R,5S)-2-(Benzyloxymethyl)-4,5-dimethoxy-3-(p-tolylthio)-tetrahydrofuran (17):
15
Sodium hydride (0.88 g, 18.5 mmol) was added to an ice-cold solution of compound 16
(2.66 g, 7.4 mmol) in anhyd. DMF (15 mL) and the mixture was stirred for 0.5h. Methyl
iodide (1.6 mL, 22.2 mmol) was added slowly to the mixture and it was stirred at room
temperature for 2.5h. After completion of the reaction, the whole mixture was poured into
ice-cold water and the compound was extracted with EtOAc. Organic layers were separated,
dried over anhydr. Na SO , filtered and the filtrate was evaporated to dryness. The residue
2
4
was purified by flash chromatography (20% EA/PE) to afford compound 17 (2.38 g, 86%) as
2
D
5.1
colorless gum; Rf (20% EA/PE) 0.32; [α]
3
(+) 91.74 (c 1.2, CHCl ); δH (400 MHz,
CDCl ) 2.33 (3 H, s), 3.30 (3 H, s), 3.12-3.40 (1 H, m), 3.42 (3 H, s), 3.54 (1 H, dd, J 5.2,
3
18

ACCEPTED MANUSCRIPT
1
0.8 Hz), 3.67 (1 H, dd, J 2.4, 10.8 Hz), 3.79 (1 H, d, J 4.0 Hz), 4.13-4.17 (1 H, m), 4.53 (2
H, q, J 12.0 Hz), 4.96 (1 H, s), 7.09 (2 H, d, J 8.0 Hz), 7.27-7.37 (7 H, m); δC (100 MHz,
CDCl
3
) 21.3, 51.7, 55.2, 58.0, 69.8 (CH
2
), 73.6 (CH
2
), 82.5, 91.9, 107.4, 127.8, 127.9, 128.5,
+
+
1
30.0, 130.7, 132.7, 137.8, 138.3; HRMS [ES , (M+Na) ]: for C21
H
26
O
4
NaS found 397.1433,
requires 397.1450.
(2R,3R,4R)-5-(Benzyloxy)-2-methoxy-3-(p-tolylthio)-pentane-1,4-diol (18): Following the
procedure described for the synthesis of 10, compound 17 (1.97 g, 5.3 mmol) was converted
2
7.4
to compound 18 (1.16 g, 61%).Colorless gum; Rf (33% EA/PE) 0.30; [α]
.0, CHCl ); δH (400 MHz, CDCl ) 2.31 (3 H, s), 3.43-3.47 (1 H, m), 3.49 (3 H, s), 3.70-3.77
2 H, m), 3.87-4.02 (4 H, m), 4.37 (2 H, q, J 11.6 Hz), 7.07 (2 H, d, J 8.0 Hz), 7.21 (2 H, d, J
.4 Hz), 7.26-7.34 (5 H, m); δC (100 MHz, CDCl ) 21.0, 53.3, 58.8, 62.1 (CH ), 71.5, 71.7
CH ), 73.2 (CH ), 80.8, 127.7, 127.8, 128.3, 129.8, 131.4, 132.1, 137.0, 137.7; HRMS [ES ,
D
(+) 12.99 (c
1
3
3
(
6
3
2
+
(
(
2
2
+
27 4
M+H) ]: for C20H O S found 363.1626, requires 363.1630.
(2R,3S,4R)-2-(Benzyloxy)-4-methoxy-3-(p-tolylthio)-tetrahydrofuran (19): Following the
procedure described for the preparation of 11, compound 18 (1.23 g, 3.39 mmol) was
2
7.4
converted to 19 (0.89 g, 76%); Colorless gum; Rf (20% EA/PE) 0.33; [α]
D
(+) 91.89 (c
1
3
.01, CHCl ); δH (400 MHz, CDCl ) 2.34 (3 H, s), 3.20 (3 H, s), 3.43-3.47 (1 H, m), 3.56-
3
3
.65 (2 H, m), 3.85-4.02 (4 H, m), 4.56 (2 H, s), 7.12 (2 H, d, J 7.6 Hz), 7.27-7.37 (7 H, m);
δC (100 MHz, CDCl
3
) 21.4, 52.5, 57.1, 71.1 (CH
2
), 71.9 (CH
2
), 73.6 (CH
2
), 83.7, 87.3,
+
+
1
27.8, 128.0, 128.6, 130.1, 130.6, 132.6, 137.9, 138.4; HRMS [ES , (M+H) ]: for C20
H
25
O
3
S
found 345.1515, requires 345.1524.
19

ACCEPTED MANUSCRIPT
Alternative synthesis of compound 15 from 19: Following the procedure described for the
preparation of 12, compound 19 (0.21 g, 0.50 mmol) was converted to 15 (0.19 g, 84%).
(
2R,3R,4R)-2-(Benzyloxymethyl)-4-methoxy-3-((S)-p-tolylsulfinyl)-tetrahydrofuran
20S ): Following the procedure described for the preparation of 15, vinyl sulfoxide 7R
0.07 g, 0.21 mmol) was converted to 20S (0.07 g, 92%). White solid; Rf (33% EA/PE)
(−) 77.31 (c 1.1, CHCl ); δH (400 MHz, CDCl ) 2.37 (3 H, s), 2.78-
(
S
S
(
S
o
25.3
0
2
4
.30; Mp 97 C; [α]
D
3
3
.82 (1 H, m), 3.17-3.22 (2 H, m), 3.33 (3 H, s), 3.69-3.73 (1 H, m), 3.98-4.01 (1 H, m), 4.26-
.32 (3 H, m), 4.42 (1 H, d, J 12.4 Hz), 7.19-7.33 (8 H, m), 7.42 (2 H, d, J 8.0 Hz); δC (100
MHz, CDCl ) 21.4, 57.1, 67.5, 70.8 (CH ), 71.9 (CH ), 73.1 (CH ), 74.8, 82.8, 124.0, 127.5,
3
2
2
2
+
+
1
27.6, 128.2, 129.9, 137.7, 137.9, 141.7; HRMS [ES , (M+H) ]: for C20
25 4
H O S found
3
61.1445, requires 361.1474.
(
2R,3R,4R)-2-(Benzyloxymethyl)-4-methoxy-3-((R)-p-tolylsulfinyl)-tetrahydrofuran
20R ): Following the procedure described for the preparation of 15, vinyl sulfoxide 7S
0.054 g, 0.16 mmol) was converted to 20R (0.053 g, 91%). White solid; Rf (33% EA/PE)
(+) 134.56 (c 1.1, CHCl ); δH (400 MHz, CDCl ) 2.43 (3 H, s),
(
S
S
(
S
o
25.3
0
3
1
.30; Mp 103 C; [α]
D
3
3
.00 (3 H, s). 3.19 (1 H, d, J 6.4 Hz), 3.45-3.56 (2 H, m), 3.81-3.84 (1 H, m), 4.05 (1 H, d, J
0.4 Hz), 4.21-4.25 (1 H, m), 4.28-4.29 (1 H, m), 4.54 (2 H, q, J 12.4 Hz), 7.28-7.38 (7 H,
m), 7.53 (2 H, d, J 8.4 Hz); δC (100 MHz, CDCl
3
) 21.7, 56.7, 70.4 (CH
), 78.4, 80.4, 124.8, 127.9, 127.9, 128.6, 130.2, 138.1, 138.8, 142.3; HRMS [ES ,
S found 361.1486, requires 361.1474.
2 2
), 70.7, 73.6 (CH ),
+
7
3.7 (CH
2
+
(
M+H) ]: for C20
H
25
O
4
Compound 15 from 20R
S S S S
or 20S : To a solution of 20S or 20S (0.2 g, 0.56 mmol) in
MeOH (7 mL), MMPP (0.56 g, 1.11 mmol) was added and the mixture was stirred for 2h at
20

ACCEPTED MANUSCRIPT
room temperature. After completion of the reaction, the mixture was evaporated under
reduced pressure. The solid residue was then taken in a mixture of EtOAc and satd. aq.
NaHCO
over anhydr. Na
obtained was purified over silica gel column to afford compound 15 (0.19 g, 91%).
3
solution and the mixture was stirred for 1h. Then organic part was separated, dried
2
SO , filtered and the filtrate was evaporated to dryness. The residue thus
4
(2R,3R,4R)-2-(Benzyloxymethyl)-4-(nitromethyl)-3-tosyl-tetrahydrofuran (21): A
t
mixture of nitromethane (0.09 mL, 1.74 mmol) and KO Bu (0.16 g, 1.45 mmol) in DMF (5
mL) was stirred at room temperature under N
.58 mmol) in THF (4mL) was added to the mixture and stirred at room temperature for 4h.
After completion of reaction, the mixture was evaporated under reduced pressure. The
residue was then taken in a mixture of EtOAc and satd. aq. NH Cl solution and the mixture
was stirred for 0.5h. The organic part was separated, dried over anhydr. Na SO , filtered and
2
atmosphere. After 0.5h compound 6 (0.2 g,
0
4
2
4
the filtrate was evaporated to dryness. The residue thus obtained was purified by flash
chromatography(20% EA/PE) to afford the compound 21 (0.21g, 90%) as white solid; Rf
o
25.1
D
(
20% EA/PE) 0.34; Mp 94 C; [α]
(+) 41.21 (c 0.99, CHCl
3
); δH (400 MHz, CDCl
3
) 2.45
(3 H, s), 3.21-3.24 (1 H, m), 3.34 (1 H, bs), 3.56-3.59 (1 H, m), 3.65 (1 H, d, J 12.0 Hz),
3
.81-3.83 (1 H, m), 4.00-4.04 (1 H, m), 4.36-4.55 (5 H, m), 7.24 (2 H, d, J 6.4 Hz), 7.33-7.35
(
5 H, m), 7.70 (2 H, d, J 7.6 Hz); δC (100 MHz, CDCl
3
) 21.7, 40.4, 66.1, 69.7 (CH
), 78.7, 127.8, 127.9, 128.5, 128.5, 130.2, 134.1, 137.3, 145.7;
S found 406.1313, requires 406.1324.
2
), 71.0
(CH
2
), 73.5 (CH
2
), 75.6 (CH
2
+
+
HRMS [ES , (M+H) ]: for C20
H24NO
6
Dimethyl-2-((3R,4R,5R)-5-(benzyloxymethyl)-4-tosyl-tetrahydrofuran-3-yl)malonate
t
(
22): A mixture of dimethylmalonate (0.2 mL, 1.74 mmol) and KO Bu (0.16 g, 1.45 mmol) in
DMF (5 mL) was reacted with compound 6 (0.2 g, 0.58 mmol) in THF (4 mL) following the
21

ACCEPTED MANUSCRIPT
procedure described for 21 to afford compound 22 (0.25 g, 91%) as white solid; Rf (20%
o
25.1
EA/PE) 0.31; Mp 113 C; [α]
H, s), 3.22 (1 H, dd, J 4.0, 10.4 Hz), 3.28-3.32 (1 H, m), 3.51 (1 H, dd, J 2.0, 10.8 Hz), 3.58
3 H, s), 3.63-3.70 (4 H, m), 3.77-3.79 (1 H, m), 3.84 (1 H, dd, J 2.8, 9.6 Hz), 3.98-4.01 (1 H,
m), 3.47-3.52 (3 H, m), 7.26-7.35 (7 H, m), 7.71 (2 H, d, J 8.0 Hz); δC (100 MHz, CDCl
D
3 3
(+) 41.21 (c 0.99, CHCl ); δH (400 MHz, CDCl ) 2.42 (3
(
3
)
2
1
1.6, 41.3, 52.6, 52.7, 52.8, 66.3, 70.0 (CH
2
), 71.5 (CH
2
2
), 73.4 (CH ), 79.0, 127.7, 127.8,
+
+
28.3, 128.8, 130.0, 134.6, 137.5, 145.2, 167.9, 168.1; HRMS [ES , (M+Na) ]: for
24 28 8
C H O NaS found 499.1397, requires 499.1403.
(3R,4R,5R)-N-benzyl-5-(benzyloxymethyl)-4-tosyl-tetrahydrofuran-3-amine (23): Benzyl
amine (0.6 mL, 5.8 mmol) was added to an anhyd. methanolic solution (5 mL) of vinyl
sulfone 6 (0.2 g, 0.58 mmol) and the mixture was stirred at room temperature for 4h. Volatile
matters were removed under reduced pressure. The residue was then taken in a mixture of
EtOAc and satd. aq. NH
was separated, dried over anhydr. Na
The residue thus obtained was purified by falsh chromatography to afford the compound 23
4
Cl solution and the mixture was stirred for 1h. Then organic part
2
SO , filtered and the filtrate was evaporated to dryness.
4
o
25.1
(
0.23 g, 90%) as brown solid; Rf (20% EA/PE) 0.32; Mp 103 C; [α]
CHCl ); δH (400 MHz, CDCl ) 2.45 (3 H, s), 3.32 (1 H, dd, J 2.8, 10.4 Hz), 3.51 (2 H, q, J
3.6 Hz), 3.65-3.71 (3 H, m), 3.85-3.92 (2 H, m), 4.41-4.56 (3 H, m), 7.09 (2 H, d, J 4.8 Hz),
.22-7.34 (10 H, m), 7.68 (2 H, d, J 8.0 Hz); δC (100 MHz, CDCl ) 21.6, 50.8 (CH ), 60.4,
9.3, 70.3 (CH ), 73.5 (CH ), 77.9, 127.0, 127.7, 127.8, 128.0, 128.3, 128.4, 128.5, 130.0,
D
(+) 53.30 (c 1.03,
3
3
1
7
6
1
4
3
2
2
2
+
+
34.9, 137.4, 138.9, 145.1; HRMS [ES , (M+H) ]: for C26
4
H30NO S found 452.1915, requires
52.1895.
22

ACCEPTED MANUSCRIPT
(3R,4R,5R)-5-(Benzyloxymethyl)-N-isopropyl-4-tosyl-tetrahydrofuran-3-amine (24):
Isopropylamine (0.9 mL, 11.6 mmol) was reacted with 6 (0.2 g, 0.58 mmol) following the
procedure described for 23 to afford the compound 24 (0.21 g, 91%) as colorless gum; Rf
2
5.1
(20% EA/PE) 0.30; [α]
D
3 3
(+) 39.15 (c 0.97, CHCl ); δH (400 MHz, CDCl ) 0.76 (6 H, t, J
6
.0 Hz), 2.43 (3 H, s), 2.47-2.53 (1 H, m), 3.22 (1 H, dd, J 3.2, 10.4 Hz), 3.61-3.70 (3 H, m),
.82 (1 H, d, J 9.2 Hz), 3.87-3.91 (2 H, m), 4.38-4.54 (3 H, m), 7.24-7.33 (7 H, m), 7.73 (2 H,
3
d, J 8.4 Hz); δC (100 MHz, CDCl
3
) 21.6, 21.7, 22.8, 45.4, 58.2, 69.0, 70.2 (CH
2
2
), 73.6 (CH ),
+
7
4.3 (CH
2
), 77.8, 127.9, 127.9, 128.4, 128.4, 130.0, 135.1, 137.4, 145.0; HRMS [ES ,
+
(
M+H) ]: for C22
H30NO
4
S found 404.1909, requires 404.1896.
4
-((3R,4R,5R)-5-(Benzyloxymethyl)-4-tosyl-tetrahydrofuran-3-yl)morpholine (25):
Morpholine (0.5 mL, 5.8 mmol) was reacted with 6 (0.2 g, 0.58 mmol) following the
procedure described for 23 to afford the compound 25 (0.22 g, 91%) as a brownish solid; Rf
o
25.1
D
(
20% EA/PE) 0.32; Mp 121 C; [α]
3 3
(+) 47.91 (c 1.00, CHCl ); δH (400 MHz, CDCl )
2
.35-2.42 (7 H, m), 2.18 (1 H, dd, J 4.4, 10.8 Hz), 3.47 (1 H, dd, J 2.0, 10.8 Hz), 3.52-3.55 (4
H, m), 3.74-3.85 (3 H, m), 4.08 (1 H, d, J 10.0 Hz), 4.22-4.24 (1 H, m), 4.39 (2 H, q, J 12.0
Hz), 7.21 (2 H, d, J 6.8 Hz), 7.26-7.33 (5 H, m), 7.72 (2 H, d, J 8.0 Hz); δC (100 MHz,
CDCl
3
) 21.6, 49.5 (CH
2
), 63.8, 66.8 (CH
2
), 67.5, 69.6 (CH
2
), 70.4 (CH
2
2
), 73.4 (CH ), 79.1,
+
+
1
27.6, 127.7, 128.3, 128.5, 129.9, 135.2, 137.6, 145.1; HRMS [ES , (M+Na) ]: for
C H NO NaS found 454.1680, requires 454.1664.
23
29
5
Dimethyl-2-((3R,4R,5R)-5-(benzyloxymethyl)-4-((S)-p-tosylsufinyl)-tetrahydrofuran-3-
yl)malonate (26S ): A mixture of dimethylmalonate (0.3 mL, 2.73 mmol) and NaH (0.1 g,
.26 mmol) in DMF (5 mL) in DMF (3 mL) was stirred at room temperature under N
atmosphere. After 0.5 h compound 7R (0.3 g, 0.91 mmol) was added to the mixture and
S
2
2
S
23

ACCEPTED MANUSCRIPT
o
heated at 60 C for 6h. After completion of reaction, the mixture was partitioned between
EtOAc and satd. aq. NaHCO solution. Then organic part was separated, dried over anhydr.
3
Na
2
SO
4
, filtered and the filtrate was evaporated to dryness. The residue thus obtained was
(0.39 g, 93%)
); δH (400 MHz,
) 2.37 (3 H, s), 2.47-2.50 (1 H, m), 3.16-3.22 (2 H, m), 3.32-3.37 (1 H, m), 3.67 (1 H,
d, J 8.8 Hz), 3.71-3.77 (7 H, m), 3.95-3.99 (1 H, m), 4.17 (1 H, d, J 12.0 Hz), 4.31-4.33 (1 H,
m), 4.40 (1 H, d, J 12.0 Hz), 7.15-7.41 (10 H, m); δC (100 MHz, CDCl ) 21.3, 42.7, 52.7,
purified by flash chromatography (25% EA/PE) to afford the compound 26S
S
2
D
5.3
as a yellowish gum; Rf (25% EA/PE) 0.30; [α]
CDCl
(−) 85.96 (c 0.89, CHCl
3
3
3
5
2.7, 53.3, 65.1, 70.9 (CH
2
), 71.3 (CH
2
), 73.1 (CH
2
), 74.8, 123.7, 127.6, 127.6, 128.2, 129.8,
+
+
1
37.7, 138.3, 141.3, 168.3, 168.6; HRMS [ES , (M+H) ]: for C H O S found 461.1620,
2
4
29
7
requires 461.1634.
(
3R,4R,5R)-N-benzyl-5-(benzyloxymethyl)-4-((S)-p-tolylsulfinyl)-tetrahydrofuran-3-
amine (27S ): A mixture of vinyl sulfoxide 7R (0.3 g, 0.91 mmol) and benzylamine (3.0
mL, 27.3 mmol) was stirred at room temperature for 48h. After completion of reaction, the
mixture was partitioned between EtOAc and satd. aq. NH Cl solution. Then organic part was
separated, dried over anhydr. Na SO , filtered and the filtrate was evaporated to dryness. The
S
S
4
2
4
residue thus obtained was purified by flash chromatography (40% EA/PE) to afford the
2
D
5.3
compound 27S
S
(0.37 g, 94%) as a yellowish gum; Rf (40% EA/PE) 0.32; [α]
(−) 71.87
(
c 0.98, CHCl
3
); δH (400 MHz, CDCl
3
) 2.40 (3 H, s), 2.70 (1 H, dd, J 3.2, 10.8 Hz), 3.16-
3
.17 (1 H, m), 3.45 (1 H, d, J 10.4 Hz), 3.63-3.65 (3 H, m), 3.79 (1 H, dd, J 5.2, 8.0 Hz), 3.93
(
1 H, d, J 9.2 Hz), 4.26-4.31 (2 H, m), 4.47 (1 H, d, J 12.0 Hz), 7.17-7.28 (13 H, m), 7.37 (2
H, d, J 8.0 Hz); δC (100 MHz, CDCl ) 21.5, 51.4 (CH ), 61.4, 68.1, 71.1 (CH ), 73.0 (CH ),
), 75.3, 124.2, 127.1, 127.8, 127.9, 128.1, 128.4, 128.5, 130.0, 137.7, 138.4, 139.4,
3
2
2
2
7
3.4 (CH
41.6; HRMS [ES , (M+H) ]: for C H NO S found 436.1935, requires 436.1946.
2
+
+
1
26
30
3
24

ACCEPTED MANUSCRIPT
Dimethyl-2-((3R,4R,5R)-5-(benzyloxymethyl)-4-((R)-p-tolylsulfinyl)-tetrahydrofuran-3-
yl)malonate (26R ): Dimethylmalonate (0.3 mL, 2.73 mmol) was reacted with compound
S
7
S S
S (0.3 g, 0.91 mmol) following the procedure described for 26S to afford the compound
2
5.3
2
6R
S
(0.40 g, 93%) as a colorless gum; Rf (25% EA/PE) 0.34; [α]
); δH (400 MHz, CDCl ) 2.38 (3 H, s), 3.24-3.36 (4 H, m), 3.42 (1 H, dd, J 3.6, 10.4
Hz), 3.61 (6 H, d, J 10.0 Hz), 3.85 (2 H, d, J 5.2 Hz), 4.17-4.21 (1 H, m), 4.48 (2 H, q, J 12.4
Hz), 7.26-7.35 (7 H, m), 7.48 (2 H, d, J 8.4 Hz); δC (100 MHz, CDCl ) 21.4, 39.2, 52.5, 52.6,
3.2, 66.6, 70.6 (CH ), 71.6 (CH ), 73.4 (CH ), 78.1, 124.8, 127.7, 127.7, 128.3, 130.0,
D
(+) 143.57 (c 0.98,
CHCl
3
3
3
5
1
4
2
2
2
+
+
37.6, 138.0, 142.2, 168.2; HRMS [ES , (M+H) ]: for C24
29 7
H O S found 461.1617, requires
61.1634.
(
3R,4R,5R)-N-benzyl-5-(benzyloxymethyl)-4-((R)-p-tolylsulfinyl)-tetrahydrofuran-3-
amine (27R ): Benzylamine (3.0 mL, 27.3 mmol) was reacted with 7S (0.3 g, 0.91 mmol)
following a procedure described for 27S to afford 27R (0.35 g, 94%) as a yellowish gum;
(−) 131.89 (c 0.98, CHCl ); δH (400 MHz, CDCl ) 2.40 (3 H,
S
S
S
S
2
D
5.3
Rf (40% EA/PE) 0.30; [α]
3
3
s), 3.20-3.27 (2 H, m), 3.42-3.52 (3 H, m), 3.74-3.92 (3 H, m), 4.15-4.18 (1 H, m), 4.47 (2 H,
q, J 12.0 Hz), 7.10 (2 H, d, J 6.4 Hz), 7.21-7.33 (10 H, m), 7.47 (2 H, d, J 8.0 Hz); δC (100
MHz, CDCl ) 21.4, 51.3 (CH ), 59.0, 69.9, 70.2 (CH ), 73.4 (CH ), 73.9 (CH ), 77.8, 124.6,
3
2
2
2
2
+
1
26.9, 127.5, 127.8, 128.0, 128.4, 128.7, 130.1, 137.5, 138.6, 139.3, 142.1; HRMS [ES ,
+
(
M+H) ]: for C26
H30NO
3
S found 436.1967, requires 436.1946.
S S S
Compound 22 from 26S or 26R : To a solution of compound 26S (0.2 g, 0.43 mmol) in
MeOH (5 mL), MMPP (0.43 g, 0.86 mmol) was added and the mixture was stirred for 2h at
room temperature. After completion of the reaction, the mixture was evaporated under
reduced pressure. The solid residue was then taken in a mixture of EtOAc and satd. aq.
25

ACCEPTED MANUSCRIPT
NaHCO
3
solution and the mixture was stirred for 1h. Then organic part was separated, dried
over anhydr. Na SO , filtered and the filtrate was evaporated to dryness. The residue thus
2
4
obtained was purified over silica gel column to afford compound 22 (0.19 g, 88%). All the
S
data were same as stated earlier in compound 22. Compound 26R was converted to 22 in a
similar fashion.
Compound 23 from 27S or 27R : To a solution of compound 27S (0.5 g, 1.15 mmol) in
S
S
S
MeOH (5 mL), MMPP (0.68 g, 1.37 mmol) was added and the mixture was stirred for 0.5h at
room temperature. After completion of the reaction, the mixture was evaporated under
reduced pressure. The solid residue was then taken in a mixture of EtOAc and satd. aq.
NaHCO
3
solution and the mixture was stirred for 1h. Then organic part was separated, dried
SO , filtered and the filtrate was evaporated to dryness. The residue thus
over anhydr. Na
2
4
obtained was purified over silica gel column to afford compound 23 (0.16 g, 31%). All the
data were same as stated earlier in compound 23. Compound 27R was converted to 23 in a
S
similar fashion.
Crystallographic data (excluding structure factors) for the structures 7R
S
(CCDC 931612), 21
(CCDC 949569) and 25 (CCDC 949570) in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC. Copies of
the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK, (fax: +44-(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.Uk).
Acknowledgements:
T. P. thanks the Department of Science and Technology (DST), New Delhi, India for
financial support. D. D. and A. B. thank the Council of Scientific and Industrial Research,
26

ACCEPTED MANUSCRIPT
New Delhi, India for fellowships. DST is also thanked for the creation of 400 MHz facility
under the IRPHA program and DST-FIST for the single crystal X-ray facility.
Supporting Information: NMR spectra of all new compounds and ORTEP diagram of
S
compounds 7R , 21 and 25.
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29