Synthesis of mixed glycosyl disulfides/selenenylsulfides using benzyltriethylammonium tetrathiomolybdate as a sulfur transfer reagent

Article abstract of DOI:10.1016/j.carres.2014.09.005

An easy and mild method has been developed for the synthesis of mixed glycosyl disulfides/selenenylsulfides from glycosyl halides and diaryl/dialkyl dichalcogenides in the presence of benzyltriethylammonium tetrathiomolybdate [(BnEt₃N)₂MoS₄]. The salient feature of this method is the sulfur transfer from [BnEt₃N]₂MoS₄ to form glycosyl disulfides which with excess tetrathiomolybdate further undergo exchange reaction with other dichalcogenides in a one-pot operation.

Full text of DOI:10.1016/j.carres.2014.09.005

Carbohydrate Research 402 (2015) 200–207
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Note
Synthesis of mixed glycosyl disulfides/selenenylsulfides using
benzyltriethylammonium tetrathiomolybdate as a sulfur transfer
reagent
⇑
Cheerladinne Venkateswarlu, Vibha Gautam, Srinivasan Chandrasekaran
Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 July 2014
Received in revised form 7 September 2014
Accepted 17 September 2014
Available online 28 September 2014
An easy and mild method has been developed for the synthesis of mixed glycosyl disulfides/selenenylsul-
fides from glycosyl halides and diaryl/dialkyl dichalcogenides in the presence of benzyltriethylammonium
tetrathiomolybdate [(BnEt3N)2MoS4]. The salient feature of this method is the sulfur transfer from
[BnEt3N]2MoS4 to form glycosyl disulfides which with excess tetrathiomolybdate further undergo
exchange reaction with other dichalcogenides in a one-pot operation.
Ó 2014 Elsevier Ltd. All rights reserved.
Keywords:
Tetrathiomolybdate
Sulfur transfer
Disulfide exchange
Glycosyl halide
Mixed glycosyl disulfide
Selenenylsulfide
The disulfide linkage plays an important role in carbohydrate
chemistry for the study glycopeptides,1 lectin binding,2,3 and car-
bohydrate structure.4,5 Moreover, in metabolic and other enzy-
matic studies, sugar disulfides are significantly important
entities.6,7 Many natural products and biologically active com-
pounds have disulfide linkage as a vital functional motif.8–10 Mixed
glycosyl disulfides have received attention as a new class of glyco-
syl donors in solution and in solid phase synthesis.11 Davis et al.
reported the advantages of mixed disulfides over thioglycosides.11
Due to the flexible nature of mixed disulfide linkage, the cleavage
of disulfide bond could be adjusted according to the reacting part-
ner.12 When the mixed disulfide is used as a linker in solid-sup-
ported glycosylation, the anomeric mixed disulfide linkage would
allow bidirectional (reductive or hydrolytic) cleavage, that would
be of great advantage in both the analysis and use of solid sup-
ported glycosylation systems. Due to the presence of two sulfur
atoms in mixed disulfides, the coordination potential of thiophile
may offer enhanced reactivity over single sulfur thioglycoside sys-
tems. On the other hand, glycosyl selenenylsulfides have been used
in protein glycoconjugation, which allows glycoconjugation with
mono- and oligosaccharides of up to seven saccharide units in size
at single and multiple sites in a variety of proteins.13
Usually, the synthesis of mixed disulfides involves the nucleo-
philic substitution of thiol onto sulfenyl derivatives. Sulfenyl
derivatives such as sulfenyl halides,14–18 sulfenic acids,19 S-alkyl
thiosulfates and S-aryl thiosulfates (Bunte salts),20 S-(alkylsulfa-
nyl)isothioureas,21,22 benzothiazol-2-yl disulfides,23 benzotriazolyl
sulfides,24 dithioperoxyesters,25 (alkylsulfanyl)dialkylsulfonium
salts,26 alkyl aryldithiopyridine N-oxides,27 N-alkyltetrazolyl
disulfides, sulfenamides,28 sulfenyl thiocyanates,29 4-nitro-
arenesulfenanilides,30 thiolsulfinates and thiolsulfonates,31,32
sulfanylsulfinamidines,33 thionitrites,34 sulfenyl thiocarbonates,35
thioimides, thiophosphonium salts,36,37 and thio-phthalimides38
are used for this purpose.39–45 Although sulfenyl derivatives are
widely used, they have problems such as stability, multistep synthe-
sis, and use of expensive reagents which limits the use of these
reagents.
Disulfide exchange reaction is one of the useful methods for the
synthesis of unsymmetrical disulfides which circumvents the use of
malodorous thiols. Yamaguchi and Arisawa reported RhH(PPh3)4
catalyzed disulfide exchange reaction between two structurally dif-
ferent disulfides to give unsymmetrical disulfides (Scheme 1).46
However, the limitation of this method is the use of expensive
phosphine rhodium complex and it is applicability to only a few
substrates. Hence, the search for alternative methods which are
more convenient is clearly warranted.
Our continuing efforts to explore the utility of benzyltriethyl-
ammonium tetrathiomolybdate, (BnNEt3)2MoS4 1 as a reagent in
⇑
Corresponding author. Tel.: +91 80 22932404; fax: +91 80 23600529.
E-mail address: scn@orgchem.iisc.ernet.in (S. Chandrasekaran).
http://dx.doi.org/10.1016/j.carres.2014.09.005
0008-6215/Ó 2014 Elsevier Ltd. All rights reserved.

C. Venkateswarlu et al. / Carbohydrate Research 402 (2015) 200–207
201
RhH(PPh3)4 ( 3 mol%)
CF3SO3H (6%)
S
S
S
p-tol3P (12%)
S
O
O
BocHN
BocHN
Acetone, reflux, 15 min
O
O
Scheme 1. Functionalization of cysteine via unsymmetrical disulfide exchange reaction.
organic synthesis led to the discovery of a number of useful meth-
odologies.47–58 Earlier, we have demonstrated the synthesis of
sugar disulfides using 1 as a sulfur transfer reagent.48 Also, we have
shown the application of 1 in tandem sulfur transfer reaction fol-
lowed by Michael addition in a one-pot fashion.49 Later the utility
of 1 has been demonstrated in the synthesis of unsymmetrical
b-sulfonamido disulfides from aziridines and disulfides.47 To fur-
ther explore the usefulness of the reagent 1, we planned the syn-
thesis of mixed glycosyl disulfides/selenenylsulfides via sulfur
transfer-dichalcogenide exchange reaction in one-pot (Scheme 2).
Reaction of glucosyl bromide 2a with disulfides 3 in the pres-
ence of 1: We commenced our study by reacting glucose derived
halides 2b–2f were studied for the disulfide exchange reaction
with diphenyl disulfide 3a in the presence of 1.
It was observed that the glycosyl halides 2b, 2c, 2e, and 2f in the
presence of diphenyl disulfide 3a and tetrathiomolybdate 1 under-
went disulfide exchange reaction in 3 h to form the corresponding
unsymmetrical mixed disulfides 4ba, 4ca, 4ea, and 4fa, respec-
tively, in moderate to good yields (Table 2, entries 2, 3, 5, and 6)
whereas glycosyl bromide 2d having bromine atom at C-6 position
took 8 h to furnish the mixed disulfide 4da in 51% yield (Table 2,
entry 4).
Further, we decided to extend this methodology to the synthe-
sis of glycosyl (phenylselenenyl)sulfides. Accordingly, glycosyl
halides 2a–2f were treated with tetrathiomolybdate 1 (2.2 equiv)
and diphenyl diselenide 3i (2.0 equiv) in CH3CN to give the corre-
sponding selenenylsulfides 4ai–4fi in moderate yields (Table 2).
The mechanism of the reaction is similar to that of the disulfide
exchange process. As in the synthesis of mixed disulfides, glycosyl
bromide 2d having bromine at C-6 position took a longer time
(10 h) for sulfur-selenium exchange process and resulted in the
corresponding selenenylsulfide 4di in only 38% yield (Table 2,
entry 4) compared to other glycosyl anomeric halides in which
the reactions were completed in 4 h with moderate to good yields
(Table 2, entries 1–3, 5, and 6).
The scope of the method was further extended to the synthesis
of trisaccharide 4fj and glycosyl amino acid 4ak having mixed
disulfide linkage. Initially lactose derived anomeric bromide 2f
was treated with 1 (2.2 equiv, CH3CN, 25 °C, 2 h) followed by the
addition of symmetrical glycosyl disulfide 3j (2 equiv) to furnish
the trisaccharide 4fj in 51% yield (Scheme 6).
For the synthesis glycosyl amino acid mixed disulfide 4ak,
similar synthetic sequence was followed except that the starting
materials were glucose derived anomeric bromide 2a and cysteine
derived Boc-Cys-OMe 3k (Scheme 7).
anomeric bromide 2a (1 equiv) with tetrathiomolybdate
1
(2.2 equiv, CH3CN, 25 °C, 2 h) followed by the addition of diphenyl
disulfide 3a (2 equiv),59 and it gave the desired mixed disulfide 4aa
(3 h) in 70% yield (Scheme 3).
The mechanism of the reaction is similar to the one proposed in
our earlier work on the synthesis of functionalized unsymmetrical
b-sulfonamido disulfides from aziridines and disulfides in the pres-
ence of tetrathiomolybdate.47 In light of this, it is visualized that
the intermediate A formed during the reaction of 2a with tetrathio-
molybdate 1 undergoes an exchange reaction with disulfide 3a (via
intermediates B and C) to furnish the corresponding mixed
disulfide 4aa (Scheme 4).
Encouraged by this result, we further studied the scope of this
reaction with other disulfides (3b–3h). The outcome of this detailed
study is summarized in Table 1. It was observed that disulfides 3d,
3e bearing electron withdrawing groups (–Cl, –NO2) gave the corre-
sponding mixed disulfides 4ad and 4ae in lower yields (Table 1,
entries 3 and 4)60,61 compared to disulfides 3b, 3c containing
electron donating groups (–Me, –OMe) (Table 1, entries 1 and 2).
Heteroaromatic disulfide such as dipyridyl disulfide 3f gave only
35% of the desired mixed disulfide 4af (Table 1, entry 5). Aliphatic
disulfides, dibenzyl disulfide 3g, and dimethyl disulfide 3h reacted
smoothly with 2a in the presence of 1 to give the corresponding
mixed disulfides 4ag and 4ah respectively (Table 1, entries 6 and 7).
In general, most of the methods reported on the synthesis of
mixed glycosyl dichalcogenides provide only moderate
yields.11,18,22,62 However, the methodologies that give very good
yield of mixed dichalcogenides19,24,38,63,64 use free chalcogenols
as the reaction partner. Hence, the present protocol that avoids
the use of free chalcogenols compares favorably with the existing
methods.
In summary, we have presented a one-pot method for the
synthesis of mixed glycosyl chalcogenides with sulfur transfer-
dichalcogenide exchange reaction using tetrathiomolybdate 1.
The significance of this method is mild reaction conditions and
avoiding the use of free chalcogenols. The application of the
method has been demonstrated in the synthesis of a trisaccharide
and glycosyl amino acid containing mixed disulfide linkage.
Studies aimed at exploring the utility of these compounds are
under progress in our laboratory.
Reaction of various glycosyl halides 2 and diphenyl dichalcoge-
nides (3a, 3i) in the presence of 1: This methodology was further
extended to various glycosyl halides (Scheme 5). The glycosyl
1. Experimental section
1.1. General methods
All the reactions were performed in oven dried apparatus and
were stirred magnetically. Melting point values reported are
uncorrected. Infrared spectra were recorded using an FTIR instru-
1)
(
[BnEt3N]2MoS4
(2.2 equiv)
ment and the frequencies are reported in wave number (cmꢀ1
)
O
O
R
Y
and intensities of the peak are denoted as s (strong), m (medium),
w (weak), and broad (br). 1H and 13C NMR spectra were recorded
on a Jeol 400 MHz (100 MHz, 13C) NMR spectrometer and cali-
brated using tetramethylsilane (TMS) for (1H) or residual undeu-
terated solvent (CDCl3) as an internal reference. Multiplicity is
indicated using the following abbreviations: s (singlet), d (doublet),
X
SYR
RO
RO
Y
R
CH3CN, rt
(2 equiv)
X = Cl or Br
Y = S, Se
Scheme 2. General scheme for the synthesis of mixed glycosyl disulfides and
selenenylsulfides.

202
C. Venkateswarlu et al. / Carbohydrate Research 402 (2015) 200–207
OAc
OAc
OAc
MoS42- (1),
MoS42- (1),
O
O
O
AcO
AcO
AcO
AcO
AcO
AcO
S
S
Ph
CH3CN,
rt, 2 h
3a
PhSSPh ( , 2
S
AcO
OAc
equiv), rt, 3h
OAc
2
Br
2a
2a¢
4aa (70%)
Scheme 3. Synthesis of glucosyl phenyl disulfide 4aa.
R'
2-
1)
MoS4
(
,
OAc
O
S
S
S
S
S
R'
R' Br
Mo
R'
R'
S
CH3CN,
rt, 2 h
R' =
AcO
AcO
R'
AcO
2a
A
2a'
OAc
O
R'
R
R'
R
S
S
S
S
S
S
S
3 h
S
R
S
AcO
AcO
A
Mo
Mo
S
Ph
R
S
S
S
S
OAc
4aa
R
3a
(R = Ph)
S
R
R'
S
B
C
Polymeric
thiomolybdates
Scheme 4. Mechanism for the formation of unsymmetrical disulfide 4aa.
dd (double doublet), t (triplet), m (multiplet), and bs (broad sin-
glet). High-resolution mass spectra (HRMS) were recorded on
micromass Q-TOF electrospray. Benzyltriethylammonium tetra-
thiomolybdate 1 was prepared as described earlier.56,57
(d, J = 8.0 Hz, 2H), 7.09 (d, J = 8.0 Hz, 2H), 5.29–5.22 (m, 2H),
5.14–5.09 (m, 1H), 4.63–4.58 (m, 1H), 4.19 (dd, J = 12.4, 8.0 Hz,
1H), 4.10 (dd, J = 12.5, 1.5 Hz, 1H), 3.77–3.72 (m, 1H), 2.32 (s,
3H), 2.02–2.01 (2s, 12H); 13C NMR (100 MHz, CDCl3): d 170.5,
170.1, 169.3, 169.1, 137.9, 133.3, 129.9, 129.5, 87.8, 76.0, 73.8,
69.3, 67.9, 61.9, 21.0, 20.60, 20.57, 20.5; HRMS (ESI-TOF) m/z: calcd
for C21H26O9S2Na (M+Na)+: 509.0916; found: 509.0916.
1.2. General procedure for the synthesis of mixed glycosyl
disulfides/selenenylsulfides
To a well-stirred solution of sugar halide (1 equiv) in CH3CN
(5 mL) benzyltriethylammonium tetrathiomolybdate 1 (1.1 equiv)
was added at once and stirred for 2 h. The reaction was monitored
by TLC. To this solution benzyltriethylammonium tetrathiomolyb-
date 1 (1.1 equiv) and diaryl(dialkyl) disulfide/diphenyl diselenide
(2 equiv) were added and the stirring was continued as mentioned.
The solvent was removed in vacuo and the residue was extracted
repeatedly (3 ꢁ 10 mL) with a DCM/ether mixture (1:4). The
extract was filtered through a thin pad of Celite and the filtrate
was concentrated in vacuo. The reaction mixture was further puri-
fied by column chromatography using ethyl acetate/petroleum
ether as eluent to yield the mixed disulfide/selenenylsulfide.
1.2.3. 4-Methoxyphenyl-(2,3,4,6-tetra-O-acetyl-b-
disulfide (4ac)24
Yield 72%; Rf = 0.5 (hexanes/ethyl acetate: 60:40); white crys-
D-glucopyranosyl)
24
talline solid; mp: 138–140 °C; [
(KBr): 1749 (s), 1592 (w), 1495 (w), 1373 (m), 1248 (s), 1228 (s),
1060 (m), 1042 (m) cmꢀ1 1H NMR (400 MHz, CDCl3): d 7.56 (d,
a]
ꢀ343.0 (c 0.6, CHCl3); FTIR
D
;
J = 8.0 Hz, 2H), 6.81 (d, J = 8.1 Hz, 2H), 5.30–5.23 (m, 2H), 5.13 (t,
J = 9.2 Hz, 1H), 4.61 (d, J = 8.8 Hz, 1H), 4.23 (dd, J = 12.3, 4.3 Hz,
1H), 4.13–4.09 (m, 1H), 3.80 (s, 3H), 3.77–3.75 (m, 1H), 2.06–2.00
(4s, 12H); 13C NMR (100 MHz, CDCl3): d 170.5, 170.2, 169.3,
169.1, 160.0, 133.3, 127.5, 114.4, 87.8, 76.1, 73.8, 69.3, 68.0, 61.9,
55.4, 20.7, 20.6, 20.5; HRMS (ESI-TOF) m/z: calcd for C21H26O10S2Na
(M+Na)+: 525.0865; found: 525.0866.
1.2.1. Phenyl-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)disulfide
(4aa)18,38
1.2.4. 4-Chlorophenyl-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)
Yield 70%; Rf = 0.5 (hexanes/ethyl acetate: 60:40); white crys-
disulfide (4ad)
24
talline solid; mp: 120–122 °C; [
(KBr): 1746 (s), 1377 (w), 1368 (w), 1253 (m), 1229 (s), 1094
(w), 1059 (m) cmꢀ1 1H NMR (400 MHz, CDCl3): d 7.60 (d,
a]
ꢀ140.1 (c 0.6, CHCl3); FTIR
Yield 62%; Rf = 0.5 (hexanes/ethyl acetate: 60:40); white solid;
D
25
mp: 132–134 °C; [
(bs), 1746 (s), 1382 (w), 1263 (m), 1231 (s), 1092 (w), 1056 (m),
1039 (m), 913 (w) cmꢀ1 1H NMR (400 MHz, CDCl3): d 7.54 (d,
J = 8.3 Hz, 2H), 7.25 (d, J = 8.4 Hz, 2H), 5.30–5.23 (m, 2H), 5.09 (t,
J = 9.3 Hz, 1H), 4.61 (d, J = 9.0 Hz, 1H), 4.18–4.08 (m, 2H), 3.76–
3.72 (m, 1H), 2.04–2.00 (4s, 12H); 13C NMR (100 MHz, CDCl3): d
170.4, 170.1, 169.3, 169.1, 135.4, 133.5, 130.3, 128.8, 87.4, 76.1,
73.7, 69.2, 67.8, 61.8, 20.6, 20.55, 20.53, 20.52; HRMS (ESI-TOF)
a]
ꢀ306.1 (c 1.5, CHCl3); FTIR (KBr): 3462
D
;
J = 7.9 Hz, 2H),7.30–7.23 (m, 3H), 5.29–5.22 (m, 2H), 5.13–5.08
(m, 1H), 4.62–4.60 (m, 1H), 4.17–4.07 (m, 2H), 3.76–3.72
(m, 1H), 2.02–1.99 (4s, 12H); 13C NMR (100 MHz, CDCl3): d 170.5,
170.2, 169.3, 169.1, 136.8, 128.9, 128.7, 127.4, 87.8, 76.0, 73.8,
69.3, 67.9, 61.9, 20.59, 20.57, 20.5; HRMS (ESI-TOF) m/z: calcd for
;
C
20H24O9S2Na (M+Na)+: 495.0759; found: 495.0758.
m/z: calcd for
C
20H23ClO9S2Na (M+Na)+: 529.0370; found:
1.2.2. 4-Tolylphenyl-(2,3,4,6-tetra-O-acetyl-b-
D-glucopyranosyl)
529.0370.
disulfide (4ab)
Yield 74%; Rf = 0.6 (hexanes/ethyl acetate: 60:40); white solid;
1.2.5. 4-Nitrophenyl-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)
disulfide (4ae)
22
mp: 110–112 °C; [
1431 (w), 1368 (m), 1255 (s), 1231 (s), 1097 (m), 1059 (m), 1043
(m), 913 (m) cmꢀ1 1H NMR (400 MHz, CDCl3):
7.49
a]
ꢀ218.3 (c 4.9, CHCl3); FTIR (KBr): 1747 (s),
D
Yield 53%; Rf = 0.6 (hexanes/ethyl acetate: 50:50); Pale yellow
25
;
d
solid; mp: 122–124 °C; [
a]
ꢀ269.9 (c 1.40, CHCl3); FTIR (KBr):
D

C. Venkateswarlu et al. / Carbohydrate Research 402 (2015) 200–207
203
Table 1
Synthesis of various mixed disulfides from glucosyl bromide 2a
Entry
R–S–S–R (R–)
Timea (h)
Mixed disulfide
Yield (%)
OAc
O
AcO
AcO
1
3
S
S
S
74
72
62
3b
S
S
S
OAc
4ab
OAc
OAc
OAc
MeO
OMe
Cl
O
AcO
AcO
2
3
4
3c
3
3
3
OAc
4ac
Cl
O
AcO
AcO
3d
OAc
4ad
O2N
NO2
O
AcO
AcO
S
3e
53
S
OAc
4ae
OAc
OAc
OAc
O
N
3f
AcO
AcO
5
6
7
8
3
3
35
65
68
S
S
S
S
S
S
N
OAc
4af
O
AcO
AcO
3g
OAc
4ag
H3C–
3h
O
AcO
AcO
CH3
OAc
4ah
a
Time required for disulfide exchange reaction.
1)
(
[BnEt3N]2MoS4
(s), 1373 (w), 1226 (s), 1060 (s), 1038 (w), 911 (w) cmꢀ1
;
1H
O
O
(2.2 equiv)
Ph
Y
NMR (400 MHz, CDCl3): 8.42 (d, J = 4.4 Hz, 1H), 7.84 (d,
d
X
SYPh
RO
RO
Y
Ph
(2 equiv)
3a
J = 8.1 Hz, 1H), 7.61 (t, J = 7.8 Hz, 1H), 7.11–7.08 (m, 1H), 5.28–
5.19 (m, 2H), 5.06 (t, J = 9.1, 1H), 4.70–4.65 (m, 1H), 4.04 (s, 2H),
3.72–3.67 (m, 1H), 2.08 (s, 3H), 2.01 (s, 6H), 1.91 (s, 3H); 13C
NMR (100 MHz, CDCl3): d 170.5, 170.3, 169.4, 169.3, 160.1, 149.0,
136.9, 121.0, 120.6, 88.3, 76.1, 73.8, 69.5, 68.0, 61.9, 20.8, 20.7,
20.6; HRMS (ESI-TOF) m/z: calcd for C19H23NO9S2Na (M+Na)+:
496.0712; found: 496.0719.
CH3CN, rt
X = Cl or Br
Y = S
(
)
4
2
3i
)
Se (
Scheme 5. Reaction of glycosyl halides 2 with diphenyl disulfide (3a)/diselenide
(3i) in the presence of benzyltriethylammonium tetrathiomolybdate 1.
1752 (s), 1516 (m), 1346 (m), 1242 (s), 1223 (s), 1060 (m), 1045 (m)
cmꢀ1; 1H NMR (400 MHz, CDCl3): d 8.14 (d, J = 8.8 Hz, 2H), 7.74 (d,
J = 8.8 Hz, 2H), 5.32–5.23 (m, 2H), 5.04 (t, J = 9.5 Hz, 1H), 4.64 (d,
J = 9.2 Hz, 1H), 4.07 (d, J = 3.5 Hz, 2H), 3.76–3.71 (m, 1H), 2.09 (s,
3H), 2.02 (s, 6H), 1.94 (s, 3H); 13C NMR (100 MHz, CDCl3): d 170.2,
170.1, 169.3, 169.1, 146.5, 146.1, 127.1, 123.6, 87.0, 76.2, 73.5,
69.1, 67.7, 61.6, 20.6, 20.54, 20.50, 20.46; HRMS (ESI-TOF) m/z: calcd
for C20H23NO11S2Na (M+Na)+: 540.0610; found: 540.0611.
1.2.7. Benzyl-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)disulfide
(4ag)18
Yield 65%; Rf = 0.5 (hexanes/ethyl acetate: 60:40); white solid;
25
mp: 118–120 °C; [
a]
ꢀ207.9 (c 1.0, CHCl3); FTIR (KBr): 1747 (s),
D
1367 (w), 1255 (s), 1228 (s), 1061 (m), 1041 (m), 912 (w) cmꢀ1
;
1H NMR (400 MHz, CDCl3): d 7.32 (bs, 5H), 5.32 (t, J = 9.4 Hz, 1H),
5.24 (t, J = 9.3 Hz, 1H), 5.13 (t, J = 9.6 Hz, 1H), 4.49 (d, J = 9.6 Hz,
1H), 4.27 (dd, J = 12.4, 4.8 Hz, 1H), 4.18 (dd, J = 12.4, 1.6 Hz, 1H),
4.03 (s, 2H), 3.75–3.70 (m, 1H), 2.09–2.02 (4s, 12H); 13C NMR
(100 MHz, CDCl3): d 170.5, 170.2, 169.4, 169.1, 136.7, 129.4,
128.5, 127.6, 87.8, 76.1, 73.8, 69.1, 68.0, 62.0, 44.4, 20.7, 20.64,
1.2.6. 2-Pyridyl-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)
disulfide (4af)
Yield 35%; Rf = 0.4 (hexanes/ethyl acetate: 50:50); Pale yellow
25
solid; mp: 96–98 °C; [
a]
ꢀ194.9 (c 0.5, CHCl3); FTIR (KBr): 1748
D

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C. Venkateswarlu et al. / Carbohydrate Research 402 (2015) 200–207
Table 2
Synthesis of glycosyl mixed disulfides and selenenylsulfides from 3a and 3i
Entry
Glycosyl halide
Glycosyl mixed disulfide/selenenylsulfide
Timea (h)
Yield (%)
OAc
OAc
O
O
AcO
AcO
AcO
AcO
Ph
1
2a
2b
Y = S (4aa)
=Se (4ai)
3
4
70
52
S
Y
OAc
OAc
Br
OAc
OAc
OAc
OAc
OBn
O
O
2
3
Y = S (4ba)
=Se (4bi)
3
4
72
55
S
Ph
AcO
AcO
Y
OAc
OAc
Br
OBn
O
O
BnO
BnO
BnO
2c
2d
2e
2f
Y = S (4ca)
=Se (4ci)
3
4
66
49
S
Ph
BnO
Y
OBn
OBn
Br
Br
Y
S
Ph
O
O
AcO
AcO
4
5
6
Y = S (4da)
=Se (4di)
8
51
38
AcO
AcO
OAc
OMe
OAc
OMe
S
10
OAc
OAc
O
O
AcO
AcO
AcO
AcO
Y = S (4ea)
=Se (4ei)
3
4
63
50
Ph
Y
AcHN
OAc
AcHN
OAc
Cl
OAc
AcO
OAc
AcO
OAc
OAc
O
O
O
O
O
AcO
O
AcO
Y = S (4fa)
=Se (4fi)
3
4
68
51
S
Ph
OAc
OAc
Y
OAc
OAc
Br
a
Time required for disulfide exchange reaction.
OAc
OAc
OAc
[BnEt3N]2MoS4 (1)
OAc
O
(2.2 equiv)
O
O
AcO
O
AcO
AcO
S
CH3CN, 12 h,
rt
OAc
AcO
OAc
3j (2 equiv)
OAc
2
Br
2f
OAc
OAc
OAc
O
O
AcO
O
AcO
AcO
S
OAc
OAc
OAc
S
OAc
O
OAc
4fj
(51%)
Scheme 6. Synthesis of trisaccharide containing mixed disulfide 4fj derived from 2f and 3j.
20.59, 20.56; HRMS (ESI-TOF) m/z: calcd for C21H26O9S2Na
4.17 (dd, J = 12.3, 1.7 Hz, 1H), 3.78–3.74 (m, 1H), 2.49 (s, 3H),
2.09 (s, 3H), 2.04 (s, 6H), 2.02 (s, 3H); 13C NMR (100 MHz, CDCl3):
d 170.5, 170.2, 169.4, 169.1, 87.9, 76.0, 73.8, 68.9, 68.0, 62.0, 24.6,
20.7, 20.63, 20.58, 20.5; HRMS (ESI-TOF) m/z: calcd for C15H22O9S2-
Na (M+Na)+: 433.0603; found: 433.0605.
(M+Na)+: 509.0916; found: 509.0913.
1.2.8. Methyl-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)disulfide
(4ah)65
Yield 68%; Rf = 0.5 (hexanes/ethyl acetate: 60:40); white solid;
22
mp: 89–90 °C; [
1380 (m), 1250 (s), 1228 (s), 1087 (m), 1054 (m), 1039 (m)
cmꢀ1 1H NMR (400 MHz, CDCl3): d 5.34–5.24 (m, 2H), 5.15–5.05
(m, 1H), 4.58 (d, J = 9.2 Hz, 1H), 4.23 (dd, J = 12.4, 4.6 Hz, 1H),
a
]
ꢀ92.2 (c 4.3, CHCl3); FTIR (KBr): 1748 (s),
1.2.9. Phenyl-(2,3,4,6-tetra-O-acetyl-b-D-galactopyranosyl)
D
disulfide (4ba)63
;
Yield 72%; Rf = 0.4 (hexanes/ethyl acetate: 70:30); white solid;
25
mp: 120–122 °C; [
a
]
ꢀ239.3 (c 3.2, CHCl3); FTIR (KBr): 1759
D

C. Venkateswarlu et al. / Carbohydrate Research 402 (2015) 200–207
205
COOMe
OAc
OAc
[BnEt3N]2MoS4 (1)
(2.2 equiv)
O
O
S
S
NHBoc
AcO
AcO
AcO
AcO
S
COOMe
NHBoc
S
CH3CN, 6 h,
rt
COOMe
(2 equiv)
OAc
OAc
Br
BocHN
3k
2a
4ak
(56%)
Scheme 7. Synthesis of glycosyl amino acid mixed disulfide 4ak derived from 2a and 3k.
(m), 1746 (m), 1728 (m), 1373 (w), 1254 (m), 1238 (s), 1219 (s),
1077 (w), 1050 (m) cmꢀ1 1H NMR (400 MHz, CDCl3): d 7.63–
(m), 1572 (w), 1376 (w), 1227 (s), 1054 (m), 1038 (m) cmꢀ1
;
1H
;
NMR (400 MHz, CDCl3): d 7.70–7.68 (m, 2H), 7.27 (bs, 3H), 5.29–
5.21 (m, 2H), 5.12 (t, J = 9.4 Hz, 1H), 4.62 (d, J = 9.0 Hz, 1H), 4.16
(dd, J = 12.5, 4.7 Hz, 1H), 4.08 (dd, J = 12.4, 1.9 Hz, 1H), 3.78–3.74
(m, 1H), 2.02–2.00 (3s, 12H); 13C NMR (100 MHz, CDCl3): d 170.6,
170.2, 169.4, 169.2, 132.1, 131.3, 128.9, 128.0, 85.7, 76.0, 73.7,
70.7, 68.0, 61.9, 20.62, 20.58, 20.5; HRMS (ESI-TOF) m/z: calcd for
7.60 (m, 2H), 7.32–7.23 (m, 3H), 5.47–5.41 (m, 2H), 5.08 (dd,
J = 10.0, 3.4 Hz, 1H), 4.61 (d, J = 9.9 Hz, 1H), 4.04–3.93 (m, 3H),
2.16 (s, 3H), 2.04 (s, 3H), 1.99 (s, 6H); 13C NMR (100 MHz, CDCl3):
d 170.3, 170.1, 170.0, 169.3, 137.1, 129.3, 128.8, 127.6, 89.6, 74.7,
71.8, 67.1, 66.8, 61.3, 20.7, 20.62, 20.59, 20.5; HRMS (ESI-TOF) m/
z: calcd for C20H24O9S2Na (M+Na)+: 495.0759; found: 495.0756.
C
20H24O9SSeNa (M+Na)+: 543.0204; found: 543.0202.
1.2.10. Phenyl-(2,3,4,6-tetra-O-benzyl-b-
D-glucopyranosyl)
1.2.14. Phenyl-2,3,4,6-tetra-O-acetyl-1-selenenylsulfide-b-D-
disulfide (4ca)64
galactopyranoside (4bi)13
Yield 66%; Rf = 0.4 (hexanes/ethyl acetate: 70:30); Gummy;
Yield 55%; Rf = 0.4 (hexanes/ethyl acetate: 60:40); white solid;
26
23
[
a]
ꢀ149.3 (c 4.6, CHCl3); FTIR (neat): 3063 (w), 3031 (w), 2917
mp: 120–122 °C; [
a]
ꢀ226.2 (c 3.7, CHCl3); FTIR (KBr): 1750 (s),
D
D
(w), 2865 (w), 1454 (w), 1361 (w), 1086 (s), 1027 (m), 738 (m),
1369 (w), 1221 (s), 1083 (w), 1055 (w) cmꢀ1 1H NMR (400 MHz,
;
697 (m) cmꢀ1
;
1H NMR (400 MHz, CDCl3): d 7.68 (dd, J = 8.1,
CDCl3): d 7.72–7.69 (m, 2H), 7.29–7.27 (m, 3H), 5.45–5.40 (m,
2H), 5.08 (dd, J = 10.0, 3.3 Hz, 1H), 4.64 (d, J = 9.8 Hz, 1H), 4.03–
3.94 (m, 3H), 2.17–1.99 (4s, 12H); 13C NMR (100 MHz, CDCl3): d
170.3, 170.1, 170.0, 169.4, 132.3, 131.7, 128.9, 128.1, 87.5, 74.7,
71.8, 68.1, 67.1, 61.3, 20.7, 20.64, 20.61, 20.5; HRMS (ESI-TOF) m/
z: calcd for C20H24O9SSeNa (M+Na)+: 543.0204 Found: 543.0208.
1.3 Hz, 2H), 7.40–7.16 (m, 23H), 4.90–4.80 (m, 5H), 4.72 (d,
J = 10.2 Hz, 1H), 4.62–4.51 (m, 3H), 3.80–3.63 (m, 4H), 3.54–3.46
(m, 2H); 13C NMR (100 MHz, CDCl3): d 138.4, 138.2, 138.0, 137.9,
137.4, 128.8–127.1 (Ar-C), 89.4, 86.7, 80.1, 79.5, 77.6, 75.8, 75.5,
75.2, 73.6, 69.0; HRMS (ESI-TOF) m/z: calcd for C40H40O5S2Na
(M+Na)+: 687.2215; found: 687.2217.
1.2.15. Phenyl-2,3,4,6-tetra-O-benzyl-1-selenenylsulfide-b-D-
1.2.11. Phenyl-(3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-b-
D-gluco-
glucopyranoside (4ci)
pyranosyl)disulfide (4ea)
Yield 49%; Rf = 0.4 (hexanes/ethyl acetate: 80:20); Gummy;
26
Yield 63%; Rf = 0.4 (ethyl acetate); white solid; mp: 188–190 °C;
[a
]
ꢀ169.2 (c 2.0, CHCl3); FTIR (neat): 2863 (w), 1751 (w), 1454
D
25
[
a]
D
ꢀ142.8 (c 7.3, CHCl3); FTIR (KBr): 1750 (m), 1538 (w), 1378
(w), 1361 (w), 1089 (s), 1072 (s), 1028 (w), 736 (m), 697 (m)
(m), 1372 (m), 1237 (s), 1085 (m), 1052 (s), 910 (w), 742 (m)
cmꢀ1 1H NMR (400 MHz, CDCl3): d 7.74–7.15 (m, 25H), 4.92–
;
cmꢀ1
;
1H NMR (400 MHz, CDCl3): d 7.61 (d, J = 7.6 Hz, 2H), 7.29–
4.75 (m, 5H), 4.59–4.41 (m, 4H), 3.74–3.49 (m, 6H); 13C NMR
(100 MHz, CDCl3): d 138.4, 138.2, 138.0, 137.8, 132.5, 131.5,
131.0, 129.2, 128.9, 128.44, 128.39, 128.3, 128.2, 127.92, 127.86,
127.8, 127.7, 127.6, 127.5, 127.5, 88.0, 86.6, 81.4, 79.5, 77.6, 77.2,
75.7, 75.4, 75.0, 73.5, 68.9; HRMS (ESI-TOF) m/z: calcd for C40H40
O5SSeNa (M+Na)+: 735.1659 found: 735.1658.
7.20 (m, 3H), 6.35 (d, J = 8.9 Hz, 1H), 5.33 (t, J = 9.8 Hz, 1H), 5.08
(t, J = 9.7 Hz, 1H), 4.85 (d, J = 10.3 Hz, 1H), 4.25 (q, J = 9.8 Hz, 1H),
4.14 (dd, J = 12.3, 4.6 Hz, 1H), 4.07 (dd, J = 12.3, 1.8 Hz, 1H), 3.80–
3.76 (m, 1H), 2.03–1.94 (4s, 12H); 13C NMR (100 MHz, CDCl3): d
170.8, 170.6, 170.4, 169.3, 137.1, 128.7, 128.6, 127.3, 88.9, 75.8,
73.3, 68.3, 62.1, 52.8, 23.2, 20.7, 20.6, 20.5; HRMS (ESI-TOF) m/z:
calcd for C20H25NO8S2Na (M+Na)+: 494.0919; found: 494.0919.
1.2.16. Phenyl-3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-1-
selenenylsulfide-b-D
-glucopyranoside (4ei)64
1.2.12. Phenyl-(2,3,4,6-tetra-O-acetyl-b-
(1?4)-20,30,60-tri-O-acetyl-b-
-glucopyranosyl)disulfide (4fa)
Yield 68%; Rf = 0.5 (hexanes/ethyl acetate: 20:80); white solid;
D
-galactopyranosyl-
Yield 50%; Rf = 0.4 (ethyl acetate); white solid; mp: 178–180 °C;
26
D
[
a
]
ꢀ237.3 (c 4.0, CHCl3); FTIR (KBr): 3373 (br), 1748 (s), 1656
D
(m), 1542 (m), 1377 (m), 1239 (s), 1084 (m), 1053 (s) cmꢀ1
;
1H
25
mp: 96–97 °C; [
1440 (w), 1371 (m), 1230 (s), 1056 (m), 911 (w), 745 (w), 603
(w) cmꢀ1 1H NMR (400 MHz, CDCl3): d 7.56 (d, J = 7.4 Hz, 2H),
a]
D
ꢀ161.4 (c 4.8, CHCl3); FTIR (KBr): 1751 (s),
NMR (400 MHz, CDCl3): d 7.71–7.69 (m, 2H), 7.29–7.25 (m, 3H),
5.98 (d, J = 9.0 Hz, 1H), 5.30 (t, J = 9.8 Hz, 1H), 5.10 (t, J = 9.7 Hz,
1H), 4.80 (d, J = 10.1 Hz, 1H), 4.27–4.19 (m, 1H), 4.16 (dd, J = 12.3,
4.6 Hz, 1H), 4.07 (dd, J = 12.2, 2.0 Hz,1H), 3.80–3.76 (m, 1H),
2.03–1.91 (4s, 12H); 13C NMR (100 MHz, CDCl3): d 171.0, 170.7,
170.3, 169.3, 132.4, 131.2, 129.0, 127.9, 86.8, 75.9, 73.4, 68.3,
62.2, 54.2, 23.2, 20.72, 20.68, 20.6; HRMS (ESI-TOF) m/z: calcd for
;
7.30–7.21 (m, 3H), 5.34 (d, J = 2.6 Hz, 1H), 5.24 (t, J = 9.1 Hz, 1H),
5.17 (t, J = 9.4 Hz, 1H), 5.09 (dd, J = 10.4, 7.8 Hz, 1H), 4.94 (dd,
J = 10.3, 3.3 Hz, 1H), 4.59 (d, J = 9.6 Hz, 1H), 4.48–4.45 (m, 2H),
4.15–4.01 (m, 3H), 3.87–3.79 (m, 2H), 3.68–3.64 (m, 1H), 2.15–
2.05 (3s, 9H), 2.03 (s, 6H), 1.97 (s, 3H), 1.96 (s, 3H); 13C NMR
(100 MHz, CDCl3): d 170.3, 170.2, 170.1, 170.0, 169.7, 169.4,
169.0, 136.9, 128.7, 128.2, 127.2, 101.0, 87.5, 76.9, 75.8, 73.6,
70.9, 70.7, 69.6, 69.0, 66.5, 61.9, 60.7, 20.75, 20.66, 20.60, 20.57,
20.5; HRMS (ESI-TOF) m/z: calcd for C32H40O17S2Na (M+Na)+:
783.1605; found: 783.1606.
C
20H25NO8SSeNa (M+Na)+: 542.0364; found: 542.0366.
1.2.17. Phenyl-2,3,6-tri-O-acetyl-4-O-(20,30,40,60-tetra-O-acetyl-b-
-galactopyranosyl)-1-selenenylsulfide-b- -glucopyranoside
(4fi)
Yield 51%; Rf = 0.4 (hexanes/ethyl acetate: 70:30); white solid;
D
D
25
mp: 74–76 °C; [
1371 (m), 1231 (s), 1055 (m), 912 (w) cmꢀ1
CDCl3): 7.66–7.63 (m, 2H), 7.27–7.25 (m, 3H), 5.34 (d,
a
]
ꢀ58.4 (c 2.2, CHCl3); FTIR (KBr): 1750 (s),
D
1.2.13. Phenyl-2,3,4,6-tetra-O-acetyl-1-selenenylsulfide-b-
D-
;
1H NMR (400 MHz,
glucopyranoside (4ai)13
d
Yield 52%; Rf = 0.4 (hexanes/ethyl acetate: 60:40); white solid;
J = 3.1 Hz, 1H), 5.25 (t, J = 9.2 Hz, 1H), 5.14–5.07 (m, 2H), 4.94
(dd, J = 10.4, 3.4 Hz, 1H), 4.60 (d, J = 9.7 Hz, 1H), 4.47–4.44 (m,
25
mp: 110–111 °C; [
a]
ꢀ194.24 (c 0.75, CHCl3); FTIR (KBr): 1752
D

206
C. Venkateswarlu et al. / Carbohydrate Research 402 (2015) 200–207
2H), 4.15–4.02 (m, 3H), 3.87–3.80 (m, 2H), 3.69–3.66 (m, 1H),
2.15–1.96 (7s, 21H); 13C NMR (100 MHz, CDCl3):
170.32,
1.3.2. Phenyl-methyl-2,3,4-tri-O-acetyl-6-deoxy-6-selenenyl-
sulfide- -glucopyranoside (4di)
Yield 38%; Rf = 0.5 (hexanes/ethyl acetate: 60:40); gummy; [
+199.9 (c 3.3, CHCl3); FTIR (neat): 1749 (s), 1373 (m), 1245 (s),
1224 (s), 1044 (s), 739 (m) cmꢀ1 1H NMR (400 MHz, CDCl3): d
d
a-D
22
170.26, 170.1, 170.0, 169.7, 169.5, 169.0, 132.1, 130.7, 129.0,
127.8, 101.0, 85.5, 76.8, 75.9, 73.5, 71.0, 70.9, 70.6, 69.0, 66.5,
62.0, 60.7, 20.8, 20.70, 20.66, 20.62, 20.59, 20.5; HRMS (ESI-TOF)
a]
D
;
m/z: calcd for
C
32H40O17SSeNa (M+Na)+: 831.1049; found:
7.62 (d, J = 7.4 Hz, 2H), 7.34–7.25 (m, 3H), 5.44 (t, J = 9.6 Hz, 1H),
4.92–4.83 (m, 3H), 4.03–3.98 (m, 1H), 3.36 (s, 3H), 3.03–2.94 (m,
2H), 2.07–1.96 (3s, 9H); 13C NMR (100 MHz, CDCl3): d 170.1,
170.0, 169.8, 131.4, 130.9, 129.3, 127.9, 96.4, 71.7, 70.9, 70.0,
68.4, 55.3, 40.1, 20.7, 20.65, 20.61; HRMS (ESI-TOF) m/z: calcd for
831.1049.
1.2.18. S-(2,3,4,6-tetra-O-acetyl-b-
(2,3,6-tri-O-acetyl-1-thio-b- -glucopyranosyl)-(1?4)-1,2,3,6-
tetra-O-acetyl-b- -galactopyranose (4fj)
Yield 51%; Rf = 0.4 (ethyl acetate); Gummy; [
CHCl3); FTIR (neat): 3411 (bs), 1752 (m), 1601 (m), 1437 (w),
1370 (w), 1225 (s), 1020 (s) cmꢀ1 1H NMR (400 MHz, CDCl3): d
D-glucopyranosyl)-(1?1)-O-
D
D
C
19H24O8SSeNa (M+Na)+: 515.0255; found: 515.0253.
22
a]
ꢀ54.5 (c 2.7,
D
Acknowledgments
;
5.35 (d, J = 2.2 Hz, 1H), 5.30–5.06 (m, 6H), 4.97 (dd, J = 10.4,
3.3 Hz, 1H), 4.61 (dd, J = 9.9, 4.2 Hz, 2H), 4.54 (d, J = 7.9 Hz, 1H),
4.33–4.05 (m, 6H), 3.91–3.67 (m, 4H), 2.18–1.97 (10s, 33H); 13C
NMR (100 MHz, CDCl3): d 170.7, 170.4, 170.3, 170.2, 170.1, 170.
0, 169.6, 169.5, 169.3, 169.0, 100.9, 87.1, 86.9, 77.2, 76.0, 75.7,
73.83, 73.78, 71.0, 70.6, 70.1, 69.7, 69.0, 67.8, 66.5, 61.6, 61.5,
60.6, 20.9, 20.8, 20.75, 20.67, 20.6, 20.54, 20.48; HRMS (ESI-TOF)
C.V.R. thanks CSIR for a Shyama Prasad Mukherjee (S.P.M.)
Senior Research Fellowship, V.G. thanks Department of Science
and Technology (DST), New Delhi for a fellowship under the
Women Scientists Programme, and SCN thanks the Department
of Science and Technology (DST) for the award of SERB Distin-
guished Fellow and the JNCASR, Jakkur for the Hindustan Lever
Professorship.
m/z: calcd for
C
40H54O26S2Na (M+Na)+: 1037.2242; found:
1037.2242.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.carres.2014.09.
005.
1.2.19. N-(tert-butoxycarbonyl)-
1-dithio-b-
-glucopyaranosyl disulfide) methyl ester (4ak)64
Yield 56%; Rf = 0.5 (hexanes/ethyl acetate: 50:50); white solid;
L-cysteine-(2,3,4,6-tetra-O-acetyl-
D
22
mp: 135–137 °C; [
1749 (s), 1690 (m), 1517 (m), 1369 (m), 1230 (s), 1166 (m), 1054
(s), 911 (w) cmꢀ1 1H NMR (400 MHz, CDCl3): d 5.35–5.24 (m,
a
]
D
+91.7 (c 1.7, CHCl3); FTIR (KBr): 3386 (br),
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3H), 5.16–5.11 (m, 1H), 4.71–4.57 (m, 2H), 4.28 (dd, J = 12.5,
4.6 Hz, 1H), 4.16 (dd, J = 12.4, 1.8 Hz, 1H), 3.81 (bs, 1H), 3.77 (s,
3H), 3.31 (dd, J = 13.8, 4.5 Hz, 1H), 3.09–3.03 (m, 1H), 2.09–2.01
(4s, 12H), 1.46 (s, 9H); 13C NMR (100 MHz, CDCl3): d 171.3,
170.6, 170.1, 169.3, 169.1, 155.0, 87.8, 80.2, 76.1, 73.8, 68.9, 67.8,
61.9, 52.9, 52.6, 42.6, 28.2, 20.60, 20.56, 20.5; HRMS (ESI-TOF) m/
z: calcd for C23H35NO13S2Na (M+Na)+: 620.1448; found: 620.1447.
1.3. Procedure for the synthesis of compounds 4da and 4di
To a well-stirred solution of methyl-2,3,4-tri-O-acetyl-6-deoxy-
6-bromo-a-D-glucopyranoside 2d (1 equiv) in CH3CN (5 mL), ben-
zyltriethylammonium tetrathiomolybdate 1 (1.1 equiv) was added
at once and stirred for 15 h. To this solution benzyltriethylammo-
nium tetrathiomolybdate 1 (1.1 equiv) and diphenyl disulfide/
diphenyl diselenide (2 equiv) were added and the stirring was con-
tinued. The solvent was removed in vacuo and the residue was
extracted repeatedly (3 ꢁ 10 mL) with
a DCM/ether mixture
(1:4). The extract was filtered through a thin pad of Celite and
the filtrate was concentrated in vacuo. The reaction mixture was
further purified by column chromatography to give the mixed
disulfide/selenenylsulfide.
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22
mp: 82–84 °C; [
a
]
D
+276.4 (c 4.8, CHCl3); FTIR (neat): 1749 (s),
1369 (w), 1245 (m), 1223 (s), 1068 (w), 1044 (m) cmꢀ1
;
1H NMR
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5.48–5.43 (m, 1H), 4.91–4.84 (m, 3H), 4.10–4.05 (m, 1H), 3.39 (s,
3H), 2.85–2.84 (m, 2H), 2.07–1.95 (3s, 9H) cmꢀ1
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(100 MHz, CDCl3): d 170.1, 170.0 169.8, 136.4, 129.4, 129.1,
128.5, 127.4, 96.4, 71.7, 70.9, 70.0, 67.3, 55.3, 40.5, 20.7, 20.63,
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467.0810; found: 467.0802.

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