Radical Mediated Diastereoselective Synthesis of Benzothiazole Sulfonyl Ethyl C-Glycosides

Article abstract of DOI:10.1081/CAR-120025328

Diastereoselective synthesis of a variety of benzothiazole sulfonyl ethyl C-glycosides has been developed by a radical mediated approach on the reaction of glycosyl bromides and benzothiazolyl vinyl sulfone in the presence of n-Bu₃SnH and AIBN

Full text of DOI:10.1081/CAR-120025328

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Radical Mediated Diastereoselective Synthesis of
Benzothiazole Sulfonyl Ethyl C‐Glycosides
Palakodety Radha Krishna a , B. Lavanya a , Y. Jyothi a & G. V.M. Sharma a
a 206/B, Discovery Laboratory , Organic Chemistry Division III , Indian Institute of Chemical
Technology , Hyderabad, 500 007, India
Published online: 23 Aug 2006.
To cite this article: Palakodety Radha Krishna , B. Lavanya , Y. Jyothi & G. V.M. Sharma (2003) Radical Mediated
Diastereoselective Synthesis of Benzothiazole Sulfonyl Ethyl C‐Glycosides, Journal of Carbohydrate Chemistry, 22:6, 423-431,
DOI: 10.1081/CAR-120025328
To link to this article: http://dx.doi.org/10.1081/CAR-120025328
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JOURNAL OF CARBOHYDRATE CHEMISTRY
Vol. 22, No. 6, pp. 423–431, 2003
Radical Mediated Diastereoselective Synthesis of
Benzothiazole Sulfonyl Ethyl C-Glycosides#
*
Palakodety Radha Krishna, B. Lavanya,
Y. Jyothi, and G. V. M. Sharma
Discovery Laboratory, Organic Chemistry Division III,
Indian Institute of Chemical Technology,
Hyderabad, India
ABSTRACT
Diastereoselective synthesis of a variety of benzothiazole sulfonyl ethyl C-glycosides
has been developed by a radical mediated approach on the reaction of glycosyl
bromides and benzothiazolyl vinyl sulfone in the presence of n-Bu3SnH and AIBN in
good yields.
Key Words: C-glycosides; Radical reaction; Benzothiazolyl vinyl sulfone;
Glycosyl halides.
#IICT Communication No. 4169
*
Correspondence: Palakodety Radha Krishna, 206/B, Discovery Laboratory, Organic Chemistry
Division III, Indian Institute of Chemical Technology, Hyderabad 500 007, India; E-mail:
prkgenius@iict.ap.nic.in.
423
DOI: 10.1081/CAR-120025328
0732-8303 (Print); 1532-2327 (Online)
www.dekker.com
Copyright D 2003 by Marcel Dekker, Inc.

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Krishna et al.
INTRODUCTION
The plethora of methods developed for the synthesis of C-glycosides and C-
saccharides bears testimony to the growing importance of glycosyl mimics. This class of
compounds has varied biological activity such as anti-tumor, anti-bacterial or anti-viral
activity[1,2] and plays effective roles as modulators and inhibitors,[3] which is attributed
to their higher hydrolytic tolerance as compared to natural counterparts. The importance
of C-glycoside sulfones (sulfones are non-ionic and increase membrane permeability),
like anomeric sugar phosphates,[4] as glycosyl transferase inhibitors, has given impetus
to the synthesis of sulfonyl methyl C-glycosides.[5] Our continued interest in glycosyl
mimics has resulted in newer methodologies for synthesis of C-alkyl glycosides,[6]
C-vinyl glycosides,[7] C-C disaccharides,[8] C-linked spiro saccharides[9] and pseudo
saccharide precursors.[10] Herein, we report a radical mediated protocol for the synthesis
of benzothiazole sulfonyl ethyl-C-glycosides from glycosyl bromides.
In earlier reports, C-glycoside sulfones were prepared by a Wittig approach[11] or
by a radical addition of thioacetic acid[5] to perbenzylated exocyclic glycal and the
oxidation of the thus formed C-glycoside sulfide to sulfone. Even though glycosyl
radicals have been generated and reacted with a variety of Michael acceptors[12–14] use
of vinyl sulfones for such a reaction resulting in C-glycoside sulfones is yet to be
realised. Hence, in the present study, benzothiazolyl vinyl sulfone[15] (1) was prepared
and used as a radical acceptor for the synthesis of C-glycoside sulfones.
RESULTS AND DISCUSSION
The requisite Michael acceptor, benzothiazolyl vinyl sulfone (1), was prepared
from mercaptobenzothiazole 2 in 3 steps (Scheme 1). Accordingly, reaction of ethylene
dichloride with mercaptobenzothiazole in acetone at reflux gave the corresponding
sulfide 3 (80%), which on reaction with either ammonium molybdate in the presence of
hydrogen peroxide [(NH4)2MoO4/H2O2] at room temperature or oxone in MeOH: H2O
(1: 1.25) resulted in the formation of 1 (67%).
The vinyl sulfone (1) was utilized as a Michael acceptor for the first time in the
reductive radical reaction of glycosyl bromides to give the C-glycoside sulfones.
Scheme 1.

Benzothiazole Sulfonyl Ethyl C-Glycosides
425
Scheme 2.
Accordingly, a mixture of acetobromo glucose (4) and vinyl sulfone (1) in ether was
treated with n-Bu3SnH in the presence of AIBN at reflux to afford the C-glycoside (11)
in 66% yield (Scheme 2), which was thoroughly characterised from spectral data. In the
1H NMR of 11, H-2 resonated at d 5.1 as a double doublet with coupling constants of
5.6 Hz (J1,2) and 9.0 Hz (J2,3) corroborative of the assigned structure.
The validity of the present methodology was demonstrated by the conversion of a
variety of sugar substrates such as aldohexoses 4–7, uronate 8, aldopentose 9 and
disaccharide 10 containing different protecting groups such as acetate, benzoate and
ester, into the corresponding C-glycoside sulfones, 11–14, 15, 16 and 17, respectively,
in 60–73% yields (Table 1). Similarly, the C-glycosides 12–17 were characterized as
1
a-C-glycoside sulphones by H NMR, 13C NMR and positive values of rotation. The
assigned structures 13 and 14 were further supported by NOESY spectra (Figure 1). For
instance, 13 showed NOESY cross peaks between H1-H2, H1-H1’a, H2-H2’a, and
between H3-H4, H3-H5 and H4-H6b, indicating that they are on the same side of the
sugar ring, respectively. It was also observed that there was no NOE between H1-H5
and H1-H3 confirming the compound to be an a anomer. Likewise 14 exhibited
NOESY cross peaks between H1-H1’a, H1-H6a, H2-H2’b and H3-H5. No NOE was
observed between H1 and H5 or H1 and H2, which unequivocally confirms the as-
signed structures. The stereoselective C-glycosidation, with a preference for the forma-
tion of a-anomers is in concurrence with the literature.[16]
In conclusion, a protocol for the conversion of glycosyl radicals into C-a-glycoside
sulfones using benzothiazolyl vinyl sulfone as Michael acceptor is achieved and
the resulting C-glycosyl sulfones would find use in glycochemistry. The advantage
of using 1, for C-glycoside sulfone synthesis is evident since thiazoles, benzothiazoles
and thiazolesulfones are important chromophores in several bioactive compounds
and therapeutics, biological evaluation of these C-glycosides[17] would be an attract-
ive proposition.
EXPERIMENTAL
General methods. Solvents were dried over standard drying agents and freshly
1
dried prior to use. H NMR (200 MHz, 400 MHz, 500 MHz) and 13C NMR (50 MHz,
100 MHz, 125 MHz) spectra were recorded in deuteriochloroform solution with
tetramethylsilane as an internal reference on Varian Gemini-200 MHz, Unity-400 MHz
and INOVA-500 MHz spectrometers and J values are given in Hz. 2D experiments like
NOESY were carried out with 2X192 transitions. The NOESY experiments were

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Krishna et al.
Table 1. Synthesis of C-glycosyl sulphones.
Starting material
Product
Time(h)
Yield(%)
12
15
66
71
11
73
21
22
70
63
22
60
23
68
performed with mixing time of 0.4 seconds. Optical rotations were measured with a
JASCO DIP-370 instrument and [a]D values are in units of 10À 1 deg cm2 gÀ 1 at 25°C.
Organic solutions were dried over anhydrous Na2SO4 and concentrated below 40°C
under vacuum. HRMS were recorded on V G Autospec Mass Spectrometer at 5 or 7 K
resolution using perfluoro kerosene as an internal reference.

Benzothiazole Sulfonyl Ethyl C-Glycosides
427
Figure 1. NOEs of compounds 13 and 14.
2-(2-Chloroethylsulfonyl)benzo[d][1,3]thiazole 3: To a solution of mercapto-
benzothiazole (2, 10 g, 59.8 mmol) in acetone (100 mL), K2CO3 (16.5 g, 119.7 mmol)
and ethylene dichloride (37 mL, 37.3 mmol) were added and the contents stirred at
reflux for 12 h. The solvent was evaporated and the residue extracted with ethyl
acetate, washed with brine (50 mL), dried (Na2SO4), concentrated and purified by
column chromatography (silica gel, EtOAc: hexane, 0.05:1) to afford monoalkylated
1
product 3 in 66% (9.0 g) yield as syrup. H NMR (200 MHz, CDCl3): d 7.86 (d, 1H, J
9.5 Hz, Ar-H), 7.7 (d, 1H, J 9.5 Hz, Ar-H), 7.40–7.20 (m, 2H, Ar-H), 3.90 (dd, 2H, J
9.5, 16.6 Hz, H-1), 3.65 (dd, 2H, J 9.5, 16.6 Hz, H-2).
Anal. Calcd for C9H8 ClNS2 : C 47.05, H 3.51, N 6.10, S 27.91; Found: C 47.03,
H 3.53, N 6.08, S 27.89.
2-Vinylsufonylbenzo[d][1,3]thiazole 1: Method A: The alkylated product 3
(9.0 g, 34.4 mmol) in ethanol (90 mL) was treated with (NH4)2MoO4 (12 g,
9.8 mmol) and H2O2 (40 mL, 30% solution) at 0°C and the stirred solution allowed
to attain room temperature. The reaction mixture was concentrated under reduced
pressure and the residue extracted with CH2Cl2 (2 Â 100 mL) to afford crude
product which was purified by chromatography (silica gel, EtOAc: hexane, 1:9) to
1
afford 1 in 66% yield (7.6 g) as a thick syrup. H NMR (200 MHz, CDCl3): d 8.20
(d, 1H, J 8.0 Hz, Ar-H), 8.00 (d, 1H, J 8.00 Hz, Ar-H), 7.82–7.54 (m, 2H, Ar-H),
7.00 (dd, 1H, J 12.0, 8.2 Hz, H-1a), 6.70 (d, 1H, J 16 Hz, H-1b), 6.38 (d, 1H, J
8 Hz, H-2).
Anal. Calcd for C9H7 NO2S2 : C 47.98, H 3.13, N 6.22, S 28.47; Found: C 47.95,
H 3.11, N 6.21, S 28.46.
Method B: Oxone (39.3 g, 34.54 mmol) was added to a solution of 3 (4.9 g,
18.72 mmol) in methanol:water (176 mL, 1:1.25), and the reaction mixture stirred
at room temperature overnight. The solvent was removed under reduced pressure,
the residue was dissolved in water (50 mL), extracted with CHCl3 (2 Â 50 mL),
washed with brine (1 Â 25 mL), dried (Na2SO4) and the organic solution concentrated

428
Krishna et al.
to give crude product which was purified by column chromatography (silica gel,
EtOAc: hexane, 1:9) to afford 1 in 67.5% yield (4.9 g) as a thick syrup.
2’-(Benzothiazolyl sulfonyl)-1’-(2,3,4,6-tetra-O-acetyl- -D-glucopyranosyl)-
ethane 11. A mixture of 2,3,4,6-tetra-O-acetyl-D-glucopyranosyl bromide[18] (4, 0.2
g, 0.48 mmol), 1 (1.6 g, 6.2 mmol), Bu3SnH (0.268 mL, 0.9 mmol) and AIBN (cat.) in
dry Et2O (10 mL) was stirred at reflux for 15 h. The solvent was evaporated under
reduced pressure and the residue purified by column chromatography (silica gel,
EtOAc: hexane, 2:3) to afford 11 in 66% yield (0.14 g) as colourless syrup. [a]D + 10.8
1
(c 1.0, CHCl3); H NMR (400 MHz, CDCl3): d 8.22 (d, 1H, J 7.6 Hz, Ar-H), 8.05 (d,
1H, J 7.6 Hz, Ar-H), 7.65 (m, 2H, Ar-H), 5.26 (t, 1H, J 9.0 Hz, H-3), 5.10 (dd, 1H, J
9.0, 5.6 Hz, H-2), 4.94 (t, 1H, J 8.8 Hz, H-4), 4.30–4.20 (m, 3H, H-1, H-6), 4.12 (m,
1H, H-5), 3.80 (m, 1H, H-2’a), 3.70 (m, 1H, H-2’b), 2.43–2.20 (m, 2H, H-1’), 2.08,
2.03, 2.02, 2.01 (4s, 12H, OAc); 13C NMR (50 MHz, CDCl3): d 171.6, 170.3, 170.0,
169.9, 128.1(2C), 127.7(2C), 125.3, 122.3, 117.5, 101.3, 75.8, 71.50, 69.80, 68.0, 66.7,
50.5, 29.0, 20.0(4C); FAB-MS (m/z): 558 (M++ 1); FAB-HRMS (M++ 1): calculated
for C23H28NO11S2. 558.110380; Found: 558.114059.
2’-(Benzothiazolyl sulfonyl)-1’-(2,3,4,6-tetra-O-benzoyl- -D-glucopyranosyl)-
ethane 12. 2,3,4,6-Tetra-O-benzoyl-D-glucopyranosyl bromide[18] (5, 0.1 g, 0.15
mmol), 1 (0.33 g, 1.27 mmol), Bu3SnH (0.05 mL, 0.17 mmol) and AIBN (cat.) in dry
Et2O (10 mL) was stirred at reflux for 15 h. Workup and purification by column
chromatography (silica gel, EtOAc: hexane, 3:7) as reported for compound 11 afforded
1
12 in 71% yield (0.09 g) as a thick syrup. [a]D + 29.2 (c 0.5, CHCl3); H NMR (400
MHz, CDCl3): d 8.0 (m, 10H, Ar-H), 7.4 (m, 14H, Ar-H), 5.75 (t, 1H, J 9.3 Hz, H-3),
5.5 (dd, 1H, J 6.9, 2.3 Hz, H-2), 5.3 (dd, 1H, J 4.6, 2.3 Hz, H-4), 4.65 (m, 3H, H-1, H-
5, H-6a), 4.40 (m, 1H, H-6b), 4.3 (m, 1H, H-2a), 3.85 (m, 1H, H-2’b), 2.45–2.03 (m,
2H, H-1’); FAB-MS (m/z): 558 (M++ 1).
Anal. Calcd for C47H43 NO11S2 : C 65.49, H 5.03, N 1.62, S 7.44; Found: C 65.3,
H 5.06, N 1.60, S 7.41.
2’-(Benzothiazolyl sulfonyl)-1’-(2,3,4,6-tetra-O-acetyl- -D-galactopyranosyl)-
ethane 13. 2,3,4,6-Tetra-O-acetyl-D-galactopyranosyl bromide[19] (6, 0.1 g, 0.15
mmol), 1 (0.81 g, 3.14 mmol), Bu3SnH (0.13 mL, 0.46 mmol) and AIBN (cat.) in dry
Et2O (10 mL) was stirred at reflux for 11 h. Workup and purification by column
chromatography (silica gel, EtOAc: hexane, 2:3) as reported for 11 afforded 13 in 73%
yield (0.16 g) as a thick syrup. [a] D+ 12.25 (c 0.8, CHCl3); 1H NMR (500 MHz,
CDCl3): d 8.20 (d, 1H, J 8.15 Hz, Ar-H), 8.05 (d, 1H, J 8.15 Hz, Ar-H), 7.65 (m, 2H,
Ar-H), 5.40 (br.t, 1H, J 5.73 Hz, H-4), 5.25 (dd, 1H, J 4.83, 8.76 Hz, H-3), 5.17 (dd,
1H, J 3.32, 8.76 Hz, H-2), 4.30 (m, 2H, H-5, 6a), 4.09 (dd, 1H, J 4.50, 11.14 Hz, H-
6b), 4.04 (dt, 1H, J 3.02, 7.55 Hz, H-1), 3.72–3.68 (m, 1H, H-2’b), 3.57–3.50 (m, 1H,
H-2’a), 2.36–2.28 (m, 2H, H-1’), 2.11, 2.06, 2.03, 2.01 (4s, 12H, OAc); 13C NMR (50
MHz, CDCl3): d 170.35(2C), 170.0(2C), 128.1, 127.7, 125.3, 122.3, 101.3, 75.8, 70.9,
70.8, 69.5, 69.3, 69.1(2C), 66.7, 60.8, 50.6, 20.5(4C); FAB-MS (m/z): 558 (M++ 1).
Anal. Calcd for C23H27 NO11S2 : C 49.54, H 4.88, N 2.51, S 11.50; Found: C
49.49, H 4.78, N 2.52, S 11.40.

Benzothiazole Sulfonyl Ethyl C-Glycosides
429
2’-(Benzothiazolyl sulfonyl)-1’-(2,3,4,6-tetra-O-acetyl- -D-mannopyranosyl)-
ethane 14. 2,3,4,6-Tetra-O-acetyl-D-mannopyranosyl bromide[18] (7, 0.10 g, 0.39
mmol), 1 (0.81 g, 3.13 mmol), Bu3SnH (0.13 mL, 0.39 mmol) and AIBN (cat.) in dry
Et2O (10 mL) was stirred at reflux for 15 h. Workup and purification of the residue by
column chromatography (silica gel, EtOAc: hexane, 2:3) as reported for 11 afforded 14
1
in 70% yield (0.15 g) as a syrup. [a] D+ 18.25 (c 1.0, CHCl3); H NMR (500 MHz,
CDCl3): d 8.20 (d, 1H, J 8.28 Hz, Ar-H), 8.04 (d, 1H, J 8.28 Hz, Ar-H), 7.65 (m, 2H,
Ar-H), 5.24 (dd, 1H, J 2.7, 5.7 Hz, H-4), 5.06 (dd, 1H, J 4.0, 7.2 Hz, H-3), 5.0 (dd, 1H,
J 2.3, 4.7 Hz, H-2), 4.51 (dd, 1H, J 7.8, 11.8 Hz, H-1), 4.11 (dt, 1H, H-6b), 4.0 (m, 1H,
H-7), 3.80 (m, 1H, H-6a), 3.75 (m, 1H, H-2’b), 3.45 (m, 1H, H-2’a), 2.40–2.20 (m, 2H,
H-1’), 2.20, 2.12, 2.09, 2.05 (4s, 12H, OAc); 13C NMR (50 MHz, CDCl3): d 172.0,
170.8(2C), 169.0, 128.5, 128.1, 127.9, 127.7, 125.6, 125.4, 122.3, 105, 71.64, 68.6,
68.1, 64.0, 62.7, 54.4, 20.9, 20.6(4C), FAB-MS (m/z): 558 (M++ 1).
Anal. Calcd for C23H27 NO11S2 : C 49.54, H 4.88, N 2.51, S 11.50; Found: C
49.51, H 4.82, N 2.52, S 11.48.
2’-(Benzothiazolyl sulfonyl)-1’-[methyl (2,3,4-tri-O-acetyl- -D-glucopyranosyl)
uronate)]ethane 15. Methyl (2,3,4-tri-O-acetyl-D-glucopyranosyl bromide)uronate[20]
(8, 0.10 g, 0.25 mmol), 1 (0.52 g, 2.0 mmol), Bu3SnH (0.08 mL, 0.29 mmol) and AIBN
(cat.) in dry Et2O (10 mL) was stirred at reflux for 22 h. Workup and purification of
the residue by column chromatography (silica gel, EtOAc: hexane, 2:3) as reported for
1
11 afforded 15 in 63% yield (0.08 g) as a syrup. [a]D + 16.40 (c 0.5, CHCl3); H NMR
(200 MHz, CDCl3): d 8.25 (d, 1H, J 8.16 Hz, Ar-H), 8.05 (d, 1H, J 8.16 Hz, Ar-H),
7.65 (m, 2H, Ar-H), 5.25 (br.s, 1H, H-5), 5.10 (t, 1H, J 7.3 Hz, H-3), 4.70 (br.t, 1H, J
6.6 Hz, H-2), 4.52 (br.s, 1H, H-4), 4.50 (br.d, 1H, J 9.5Hz, H-1), 3.80 (s, 3H, OCH3),
3.70 (m, 2H, H-2’), 2.35–2.20 (m, 2H, H-1’), 2.15 (br.s, 6H, OAc), 2.0 (s, 3H, OAc);
FAB-MS (m/z): 544 (M+ + 1).
Anal. Calcd for C22H26 NO11S2 : C 48.61, H 4.64, N 2.58, S 11.80; Found: C
48.53, H 4.86, N 2.60, S 11.76.
2’-(Benzothiazolyl sulfonyl)-1’-(2,3,4-tri-O-acetyl- -D-arabinopyranosyl)ethane
16. 2,3,4-Tri-O-acetyl-D-arabinopyranosyl bromide[18] (9, 0.1 g, 0.34 mmol), 1 (0.70
g, 2.7 mmol), Bu3SnH (0.12 mL, 0.41 mmol) and AIBN (cat.) in dry Et2O (10 mL) was
stirred at reflux for 11 h. Workup and purification of the residue by column
chromatography (silica gel, EtOAc: hexane, 3:7) as reported for 11 afforded 16 in 60%
yield (0.11g) as a thick syrup. [a]D + 20.40 (c 1.0, CHCl3); 1H NMR (200 MHz,
CDCl3): d 8.25 (dd, 1H, J 8.05, 2.3 Hz, Ar-H), 8.05 (dd, 1H, J 8.05, 2.3 Hz, Ar-H),
7.65 (m, 2H, Ar-H), 5.30 (t, 1H, J 4.3 Hz, H-4), 5.25 (dd, 1H, J 4.3, 7.8 Hz, H-3), 4.90
(dd, 1H, J 3.56, 7.8 Hz, H-2), 4.20 (d, 1H, J 4.65 Hz, H-5a), 3.90 (dt, 1H, J 3.0, 7.6 Hz,
H-1), 3.80 (dd, 1H, J 4.65, 2.3 Hz, H-5b), 3.70–3.40 (m, 2H, H-2’), 2.35–2.21 (m, 2H,
H-1’), 2.20, 2.15, 2.05 (3s, 9H, OAc); FAB-MS (m/z): 486 (M++ 1).
Anal. Calcd for C20H23 NO9S2 : C 49.48, H 4.77, N 2.88, S 13.21; Found: C 49.42,
H 4.76, N 2.86, S 13.24.
2’-(Benzothiazolyl sulfonyl)-1’-[2,3,4-tri-O-acetyl-6-O-(2’’,3’’,4’’,6’’-tetra-O-
acetyl- -D-glucopyranosyl)- -D-galactopyranosyl]ethane 17. 2, 3, 4-Tri-O-acetyl-6-
O-(2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl)-a-D-galactopyranosyl bromide[21] (10,

430
Krishna et al.
0.10 g, 0.29 mmol), 1 (0.60 g, 2.33 mmol), Bu3SnH (0.10 mL, 0.34 mmol) and AIBN
(cat.) in dry Et2O (10 mL) was stirred at reflux for 22 h. Workup and purification of
the residue by column chromatography (silica gel, EtOAc: hexane, 2:3) as reported for
1
11 afforded 17 in 68% yield (0.108 g) as a syrup. [a]D + 15.6 (c 1.0, CHCl3); H NMR
(400 MHz, CDCl3): d 8.20 (d, 1H, J 7.6 Hz, Ar-H), 8.05 (d, 1H, J 7.6 Hz, Ar-H), 7.65
(m, 2H, Ar-H), 5.36 (d, 1H, J 3.2 Hz, H-3@), 5.32 (t, 1H, J 7.2 Hz, H-3), 5.12 (t, 1H, J
9.0 Hz, H-4), 4.90 (dd, 1H, J 7.2, 3.5 Hz, H-2), 4.80 (m, 1H, H-2@), 4.52 (d, 1H, J 7.8
Hz, H-1@), 4.34 (dd, 1H, J 2.95, 11.8 Hz, H-6a), 4.20 (m, 2H, H-6b, H-1), 4.10 (dd, 2H,
J 2.68 Hz, H-6@), 3.90 (t, 1H, J 6.45 Hz, H-2’a), 3.80 (m, 1H, H-4@), 3.70 (m, 2H, H-5,
H-5@), 3.64 (t, 1H, J 7.2 Hz, H-2’b), 2.52–2.43 (m, 2H, H-1’), 2.15, 2.13, 2.10, 2.05 (7s,
21H, OAc); 13C NMR (100 MHz, CDCl3): d 170.2, 169.9, 169.7, 169.2, 128.1(2C),
127.8, 125.4, 122.3, 101.4, 96.1(2C), 75.9, 71.7(2C), 70.9(2C), 70.8(2C), 69.5, 69.3,
69.1(2C), 66.7, 61.9, 60.8, 50.6, 29.6, 20.5(7C); FAB-MS (m/z): 868 (M+ + 23).
Anal. Calcd for C47H43 NO11S2 : C 49.70, H 5.12 N 1.66 S 7.58; Found: C 49.69,
H5.16, N 1.64, S 7.54.
ACKNOWLEDGMENTS
Two of the authors, B. Lavanya and Y. Jyothi, are thankful to CSIR, New Delhi,
India for the financial support.
REFERENCES
1. Postema, M.H.D. C-glycoside Synthesis; CRC Press: London, 1995.
2. Levy, D.E.; Tang, C. The Chemistry of C-glycosides; Pergamon Press: Oxford,
1995.
3. Czernicki, S. New aspects of glycosylation reactions. In Carbohydrates –Synthetic
Methods and Applications in Medicinal Chemistry; Ogura, H., Hasegawa, A.,
Suami, T., Eds.; VCH Publications: New York, 1991; 28 and references cited
therein.
4. Unker, H.-D.; Fessner, W.-D. Diastereoselective syntheses of C-glycosylphosphates
via free radical glycosylation. Tetrahedron Lett. 1998, 39, 269–272.
5. Gervay, J.; Flaherty, T.M.; Holmes, D. Studies on the synthesis of C-glycoside
sulfones as potential glycosyl transferase inhibitors. Tetrahedron 1997, 53, 16355–
16364.
6. Sharma, G.V.M.; Chander, A.S.; Krishnudu, K.; Radha Krishna, P. A simple and
efficient PdCl2 mediated conversion of a, g-olefinic alcohols into C-glycosides.
Tetrahedron Lett. 1997, 38, 9051–9054.
7. Sharma, G.V.M.; Chander, A.S.; Krishnudu, K.; Radha Krishna, P. Pd(OAc)2
mediated oxidative cyclisation of g, d-olefinic alcohols: a new route to C-vinyl
furanosides. Tetrahedron Lett. 1998, 39, 6957–6960.
8. Sharma, G.V.M.; Hymavathi, L.; Radha Krishna, P. Carbon-carbon linked
disaccharides by de novo construction from furanyl sugar templates. Tetrahedron
Lett. 1997, 38, 6929–6932.
9. Sharma, G.V.M.; Reddy, V.G.; Radha Krishna, P. Synthesis of spiro carbon linked

Benzothiazole Sulfonyl Ethyl C-Glycosides
431
disaccharides: de novo synthesis from furan by chirality transfer from sugar derived
templates. Tetrahedron Lett. 1999, 40, 1783–1786.
10. Sharma, G.V.M.; Chander, A.S.; Radha Krishna, P.; Krishnudu, K.; Ramana Rao,
M.H.V.; Kunwar, A.C. ‘Off template site’ [3 + 3] annulation reaction on sugar
derived enal: stereoselective synthesis of C-C-linked pseudo-saccharide precursors.
Tetrahedron: Asymmetry 2000, 11, 2643–2646.
11. Davidson, A.H.; Hughes, L.R.; Qureshi, S.S.; Wright, B. Wittig reactions on
unprotected aldoses: formation of optically active tetrahydrofurans and tetrahydro-
pyrans. Tetrahedron Lett. 1988, 29, 693–696.
12. Spencer, R.P.; Schwartz, J. Titanium (III)-promoted stereoselective synthesis of
simple C-glycosides. J. Org. Chem. 1997, 62, 4204–4205.
13. Giese, B.; Dupuris, J.; Liesing, M.; Nix, M.; Lindner, H.J. Synthesis of C-pento,
-hexo and -hepto pyranosyl compounds via radical C C bond formation reactions.
Carbohydr. Res. 1987, 171, 329–335.
14. Giese, B.; Kopping, B.; Gobel, T.; Dickhaut, J.; Thoma, G.; Kulicke, K.J.; Trach, F.
Radical cyclization reactions. In Organic Reactions; Paquette, L.A., et al, Eds.;
John Wiley & Sons Inc.: New York, 1996; 48, 301–856.
15. Prilezhaeva, N.; Shmonia, L.I. Synthesis based on 2-benzothiazololyl vinyl sufide.
Zh. Org. Khim. 1966, 2 (10), 1883–1891.
16. Togo, H.; He, W.; Waki, Y.; Yokoyama, M. C-glycosidation technology with free
radical reactions. Synlett 1998, 700–717.
17. Jerome, K. 6-Ethoxybenzothiazole-2-sulfonamide, US patent, 1959, 2,868,800. In
The Merck Index; Merck & Co Inc.: NJ, 1996; 12, 641.
18. Vogel, A.I. Textbook of Practical Organic Chemistry; Longman Group Ltd.: UK,
1989; 647–648.
19. Bochkov, A.F.; Zaikov, G.E. Chemistry of the O-glycosidic Bond: Formation and
Cleavage; Pergamon Press: Oxford, UK, 1979; 61.
20. Chernyak, A.Y.; Sharma, G.V.M.; Kononov, L.O.; Radha Krishna, P.; Rama Rao,
A.V.; Kochetkov, N.K. Synthesis of glycuronamides of amino acids, constituents
of microbial polysaccharides and their conversion into neoglycoconjugates of
copolymer type. Glycoconj. J. 1991, 8, 82–89.
21. Sharma, G.V.M.; Radha Krishna, P. A practical synthesis of 2-azidoethyl a-
glycosides useful spacer-arm glycosides for the synthesis of neoglycoconjugates.
Carbohydr. Res. 1993, 243, 393–397.
Received October 16, 2002
Accepted May 30, 2003