Synthesis and X-ray analysis of butyl and glycosyl (2-arylamino-4,4- dimethyl-6-oxocyclohex-1-ene)carbodithioates and their possible cyclization to 2-thioxo-6,7-dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one derivatives

Article abstract of DOI:10.1016/j.carres.2010.11.005

Variety of butyl [2-arylamino-4,4-dimethyl-6-oxo-cyclohex-1-ene] carbodithioates (3a-c), 2-thioxo-6,7-dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one derivatives (5a-c), and the glucosyl carbodithioates 6a-c as well as galactosyl carbodithioates 7a-c have been

Full text of DOI:10.1016/j.carres.2010.11.005

Carbohydrate Research 346 (2011) 169–176
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis and X-ray analysis of butyl and glycosyl (2-arylamino-4,4-dimethyl-
6-oxocyclohex-1-ene)carbodithioates and their possible cyclization to
2-thioxo-6,7-dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one derivatives
El Sayed H. El Ashry a,b, , Aly A. Aly c, Mohammed R. Amer a, Muhammad R. Shah a, Seik W. Ng d
⇑
a H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan
b Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt
c Chemistry Department, Faculty of Science, Benha University, Benha, Egypt
d Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
a r t i c l e i n f o
a b s t r a c t
Article history:
Variety of butyl [2-arylamino-4,4-dimethyl-6-oxo-cyclohex-1-ene]carbodithioates (3a–c), 2-thioxo-6,7-
dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one derivatives (5a–c), and the glucosyl carbodithioates 6a–c
as well as galactosyl carbodithioates 7a–c have been synthesized from the reaction of enaminone deriv-
Received 24 September 2010
Received in revised form 2 November 2010
Accepted 4 November 2010
Available online 12 November 2010
atives 1a–c with carbon disulfide followed by the alkylation with n-butyl bromide and a-D-glycosyl bro-
mides, respectively. The amount of carbon disulfide plays a great role in the mode of reaction. The
structures of the synthesized compounds were elucidated by spectral data and X-ray crystallography.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Dimedone
Enaminones
Carbodithioates
Benzothiazines
Thioglycosides
X-ray
1. Introduction
by these compounds in biological processes.21 Therefore, tremen-
dous effort has been made to develop new procedures for the syn-
Much attention has been focused on compounds functionalized
with the – CSS-group because of their diversity as represented by
industrial chemicals, such as rodent repellents, vulcanization addi-
tives in rubber manufacturing, lubricants, and polymers in addition
to their metal chelating properties, which are used in analytical
chemistry and waste management. These compounds exhibit a
wide spectrum of biological activities1–4 and are used as fungicides
in pesticides and fumigants.4,5 They modulate the function of a
number of key proteins involved in apoptosis, oxidative stress,
transcription, and proteosome function.6 Thus, they are of poten-
tial therapeutic value for cancer,7–10 viral infection,11 antitumor
activity,12 inflammation,13 immunosuppressive agents,14 and anti-
oxidants, as well as inhibition of the replication of rhinovirus, influ-
enza virus, and polio virus.11–15 Their biological effects are
dependent on their structural characteristics that influence the sta-
bility decomposition and their metabolic products in vivo.16–20
A great demand for significant amounts of oligosaccharides and
glycoconjugates for biological, medicinal, and pharmacological
studies has been generated because of the important roles played
thesis of glycosides and developing strategies for the formation of
glycosidic bonds.21–24 However, efforts are still directed toward the
synthesis of glycosidic bonds, particularly in a stereoselective man-
ner. Glycosyl sulfanyl heterocycles have been regarded as good gly-
cosyl donors in addition to their biological activities such as the
inhibition of enzyme activity.25 Having the above aspects in mind
and in addition to the paucity of work that has been reported on
the glycosyl carbodithioates and their biological value26–28 as well
as their value as glycosyl donors for glycosyl bond formation, we
became interested in the synthesis of new members in this class
of compounds. We are also investigating their spectra and X-ray
crystallographic data as a continuation of our work,23,24 and our
interest29–32 in elucidating structures by X-ray crystallography.
2. Results and discussion
The reactivity of enaminones toward some electrophilic re-
agents was investigated in order to synthesize carbodithioates
and benzothiazine derivatives. Thus, the reaction of 1a–c33 with
carbon disulfide in dimethyl sulfoxide (DMSO) containing sodium
hydroxide followed by addition of n-butyl bromide afforded butyl
[2-arylamino-4,4-dimethyl-6-oxo-cyclohex-1-ene]carbodithioates
⇑
Corresponding author. Tel.: +20 3 4246601; fax: +20 3 427 1360.
E-mail address: eelashry60@hotmail.com (El Sayed H. El Ashry).
0008-6215/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2010.11.005

170
El Sayed H. El Ashry et al. / Carbohydrate Research 346 (2011) 169–176
(3a–c) via the loss of a molecule of HBr from the nonisolable inter-
mediates 2a–c.
have been considered as model study to be used in assigning the
glycosyl derivatives as alkylating agents.
On the other hand, the reaction of enaminones 1a–c with an ex-
cess of carbon disulfide in DMSO containing a catalytic amount of
NaOH followed by addition of n-butyl bromide furnished benzothi-
azine derivatives 5a–c, (Scheme 1). These thiazinones have been
presumably formed via the heterocyclization of the nonisolable
intermediates 4a–c. The conditions for the reactions are critical,
probably due to the ready loss of carbon disulfide from the reaction
mixture whose amount has a great role in the formation of an
intermediate such as 4a–c. The introduction of a carbodithioate
on the nitrogen of 2 before alkylation may be unlikely. The re-
ported34 methylation of similar analogs did not give good results
in our hands. The structural assignments of the butyl derivatives
The structures of 3 or 5 can be readily differentiated by their 1H
NMR spectra where 3 shows a signal at the low-field region at d
14.73–15.44 that is exchangeable with D2O and is due to the NH
proton. Such a signal at low field does not appear in the spectra
of compounds 5. On the other hand, the 13C NMR spectra of 3
showed a C@S resonance at dc 191.3, whereas the C@S of 5
appeared at dc 182.5–183.6. Moreover the H-8 appeared at dc
4.49–4.55, which is in agreement with an olefinic proton rather
than a methylene group.
Applying the above synthetic scheme, we further explored the
synthesis of thioglycoside analogs from the enaminones. Thus,
the reaction of enaminones 1a–c with carbon disulfide in the
2
2
2
-
+
H
Scheme 1.

El Sayed H. El Ashry et al. / Carbohydrate Research 346 (2011) 169–176
171
presence of sodium hydroxide and then glycosylation with
cosyl bromides, namely 20,30,40,60-tetra-O-acetyl-
-glucopyrano-
syl bromide and 20,30,40,60-tetra-O-acetyl-
-galactopyranosyl
bromide, gave (20,30,40,60-tetra-O-acetyl-b-
-glucopyranosyl) [2-
(arylamino)-4,4-dimethyl-6-oxocyclohex-1-ene]carbodithioates
6a–c and (20,30,40,60-tetra-O-acetyl-b-
-galactopyranosyl) [2-(aryla-
mino)-4,4-dimethyl-6-oxocyclohex-1-ene]carbodithioates (7a–c),
respectively. No products could be isolated having structure 8
(Scheme 2). The 1H NMR spectra of the glycosyl derivatives showed
signals in the range of d 15.23–16.02 indicating that the products
have structures 6 and 7 rather than 8. The anomeric protons ap-
peared in the range of d 5.72–5.76 with large coupling constants
a
-
D
-gly-
they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s.
planes refinement of F2 against all reflections. The weighted R-fac-
tor wR and goodness of fit S are based on F2, conventional R-factors
R are based on F, with F set to zero for negative F2. The threshold
expression of F2 2sigma (F2) is used only for calculating R-factors
(gt) etc. and is not relevant to the choice of reflections for refine-
ment. R-Factors based on F2 are statistically about twice as large
as those based on F and R-factors based on all data will be even lar-
ger.35–38
The single-crystal diffraction analysis of 5a showed the com-
pound has a bicyclic structure (Fig. 1, Table 1 and Supplementary
data Tables S1–S5) rather than the expected monocyclic structure
3a. The crystal data revealed that the C11–S3 bond length
(1.817(3) Å) is typical of a single bond, while the other C9–S1 bond
length (1.753(3) Å), suggesting a degree of conjugation in the 4-
(butylsulfanyl)-1-(4-chlorophenyl)-7,7-dimethyl-2-thioxo-6,7-
dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one.
a-D
a
-D
D
D
0
0
(J1 ,2 = 10.5–10.8 Hz) confirming the diaxial orientation of H-1 and
H-2 and indicating that the reaction of the donor with the acceptor
gave the b-glycoside.
The structures of 5a and 7a were confirmed by X-ray crystallog-
raphy as it will be shown in the following section.
On the other hand, C10–S2 displayed a bond length of 1.658 Å,
reflecting double bond character. The bond lengths C4–C5 and C6–
C9 are 1.361(7) Å and 1.358(5) Å, respectively, which revealed the
presence of unsaturation. A deviation of the methyl group C7 from
the mean path of benzothiazin-5-one was observed having torsion
angle of 83.0(4)° (C5–C4–C3–C7). The cyclohexene ring has an
envelope conformation, with atom C3 deviating from the plane of
the remaining five ring atoms (Fig. 1). The deviation of C3 from the
plane of the rest of the molecule caused reduction in the angle
formed between C2, C3, and C4 (C4–C3–C2, 108.4 (3)°). Intermo-
lecular S–S interactions link the molecules into a two-dimensional
network as shown in Figure 2.
3. X-ray analysis
Generally, calculated positions (C–H 0.93–0.99 Å) were adopted
for carbon-bound H-atoms and were included in the refinement in
the riding model approximation, with U(H) set to 1.2–1.5 U(C). The
amino H-atom was refined by keeping a distance restraint of N–H
at 0.88 0.01 Å; its temperature factor was freely refined and was
located in a difference Fourier map. All esds (except the esd in the
dihedral angle between two l.s. planes) are estimated using the full
covariance matrix. The cell esds are taken into account individually
in the estimation of esds in distances, angles, and torsion angles;
correlations between esds in cell parameters are only used when
NaOH/CS2
NaOH/CS2
Scheme 2.

172
El Sayed H. El Ashry et al. / Carbohydrate Research 346 (2011) 169–176
Figure 1. Displacement ellipsoids of 5a at the 50% probability level are shown along with labeling.
Table 1
Crystal data, collection and refinement for 5a
C20H22ClNOS3
Mr = 424.02
F000 = 444
Dx = 1.360 Mg mꢀ3
Monoclinic, P21
Mo Ka radiation, k = 0.71073 Å
Hall symbol: P 2yb
a = 12.0457 (3) Å
b = 6.4534 (2) Å
Cell parameters from 2674 reflections
h = 2.6–26.2°
l
= 0.50 mmꢀ1
c = 13.7375 (3) Å
T = 100 K
b = 104.198 (2)°
Prism, yellowish orange
0.30 ꢁ 0.03 ꢁ 0.03 mm
V = 1035.27 (5) Å3
Z = 2
Bruker SMART APEX diffractometer
Radiation source: fine-focus sealed tube
Monochromator: graphite
T = 100 K
4730 Independent reflections
4065 Reflections with I > 2
Rint = 0.035
r(I)
hmax = 27.5°
x
Scans
hmin = 1.5°
Absorption correction: Multi-scan SADABS (Sheldrick, 1996)
Tmin = 0.776, Tmax = 0.985
h = ꢀ15?15
k = ꢀ8?8
9856 Measured reflections
l = ꢀ17?17
Refinement on F2
Hydrogen site location: inferred from neighboring sites
H-atom parameters constrained
Least-squares matrix: full
R[F2 > 2 (F2)] = 0.041
r
w = 1/[
r
2(F2o) + (0.0578P)2] where P = (Fo2 þ 2F2c )/3
wR(F2) = 0.106
S = 1.05
4730 Reflections
239 Parameters
(D/r)max = 0.001
D
D
q
q
max = 0.44 e Åꢀ3
min = ꢀ0.29 e Åꢀ3
Extinction correction: none
1 Restraint
Absolute structure: Flack (Flack, 1983) parameter from 2133 Friedel pairs
Flack parameter: 0.26 (8)
Primary atom site location: structure-invariant direct methods
Secondary atom site location: difference Fourier map
The crystallographic analysis revealed that the sugar molecule
envelope conformation, with the C-9 atom bearing the two methyl
groups representing the flap. The acetoxymethyl group is equatori-
ally bonded to the C17 ring atom by making a torsion angle of O3–
C17–C21–O4, of 60.6(4)°. The acetoxymethyl group was found to
be running parallel with respect to cyclohexene ring as shown in
Figure 3. The acetyl group bonded to C18 was found to be axially
oriented with a torsion angle of 131.5(4)°, C17–C18–O6–C24 with
respect to sugar moiety. The acetyl groups attached to C19 and C20
are equatorially oriented bearing torsion angles C18–C19–O8–C26
136.9(4)° and C19–C20–O10–C28, ꢀ139.3(4)°, respectively. The 2-
(4-chloroanilino)-4,4-dimethyl-6-oxocyclohex-1-enecarbodithio-
ate group is axially bonded to C16 atom of the galactose sugar with
a torsion angle O3–C16–S1–C15, of ꢀ78.6(3)°. The 4-chloroaniline
ring is experiencing a torsion angle of 3.7(7)°, for C8–C7–N1–C1,
thus indicating a slight deviation in planarity with respect to the
cyclohexene ring (Tables S6–S9).
in (20,30,40,60-tetra-O-acetyl-b-
D-galactopyranosyl) [2-(4-chloroani-
lino)-4,4-dimethyl-6-oxocyclohex-1-ene]carbodithioate exists in
galactopyranose form Table 2. Examinations of bond lengths, an-
gles, and torsion angles demonstrate that the values conform to
those observed in other galactopyranose and carbodithioate ana-
logs.29–32 Intramolecular bond angles, lengths, and torsion angles
indicated that the galactopyranose ring is in the usual 4C1 confor-
mation, and the anomeric center of the sugar has b configuration.
No significant hydrogen bonds exist in the crystal except intermo-
lecular hydrogen bonding between NH–S. The acetyl group at-
tached to the primary hydroxyl group in the title compound is in
the gt position, which is known to be the favored orientation for
pyranose with the galacto configuration. The cyclohexene ring of
(20,30,40,60-tetra-O-acetyl-b-
no)-4,4-dimethyl-6-oxocyclohex-1-ene]carbodithioate adopts an
D-galactopyranosyl) [2-(4-chloroanili-

El Sayed H. El Ashry et al. / Carbohydrate Research 346 (2011) 169–176
173
Figure 2. Packing diagram of 5a showing S–S connectivities.
Table 2
Crystal data, collection, and refinement for 7a
C29H33ClNO10S2
Mr = 655.13
a = 13.4331 (8) Å
b = 8.6843 (5) Å
c = 13.9745 (8) Å
V = 1616.05 (16) Å3
Z = 2
Dx = 1.346 Mg mꢀ3
Mo K
a radiation, k = 0.71073 Å
l
= 0.30 mmꢀ1
a
= 90°
b = 97.560 (3)°
= 90°
T = 123 K
0.36 ꢁ 0.04 ꢁ 0.04 mm
c
Radiation source: fine-focus sealed tube
Monochromator: graphite
T = 123 K
Rint = 0.075
hmax = 27.5°
hmin = 1.5°
h = ꢀ17?17
k = ꢀ11?11
l = ꢀ18?17
11,306 Measured reflections
6693 Independent reflections
4129 Reflections with I > 2
r(I)
Refinement on F2
Hydrogen site location: inferred from neighboring sites
Least-squares matrix: full
H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2 F2)] = 0.062
r(
w = 1/[
r
2(F2o) + (0.038P)2] where P = (Fo2 þ 2F2c )/3
wR (F2) = 0.131
S = 0.96
6693 Reflections
394 Parameters
1 restraint
(D/r)max = 0.001
D
D
q
q
max = 0.39 e Åꢀ3
min = ꢀ0.37 e Åꢀ3
Extinction correction: none
Absolute structure: Flack, H. D., Acta Crystallogr., Sect. A 1983, 39, 876–881
Flack parameter: 0.03 (9)
Primary atom site location: structure-invariant direct methods
Secondary atom site location: difference Fourier map
20 min at room temperature and then n-butyl bromide (0.012
mol) was added. The reaction mixture was stirred for 24 h at room
temperature, then poured onto cold water (100 mL), and acidified
with 10% HCl. The product that separated out was filtered off,
dried, and purified by silica gel column chromatography (3:7
EtOAc–n-hexane) and recrystallized from MeOH to give 3a–c.
4. Experimental
4.1. General methods and materials
Melting points were determined with a Mel-Temp apparatus
(SMP10) in open capillaries and are uncorrected. TLC was per-
formed on E. Merck Silica Gel 60 F254 with detection by UV light
absorption. 1H NMR spectra were recorded on Bruker Avance AV
NMR spectrometer at 300 or 400 MHz, whereas the 13C NMR were
recorded on the same instrument at 75 or 100 MHz, respectively,
with TMS as the internal standard. Mass spectra were recorded
on a Finnigan (MAT312) or Jeol (JMS.600H) instrument, HRMS
were recorded with a Thermo Finnegan (MAT 95XP) instrument.
Solvents used were purified by simple distillation.
4.2.1. n-Butyl [2-(4-chlorophenylamino)-4,4-dimethyl-6-
oxocyclohex-1-ene]carbodithioate (3a)
Yield (52.5%, yellow crystals), mp 162–164 °C, TLC (8:2 n-hex-
ane–EtOAc): Rf 0.42, 1H NMR (CDCl3, 300 MHz) : d 0.93 (t, 3H,
J = 7.2 Hz, CH3-40), 1.01 (s, 6H, 2CH3), 1.44–1.51 (m, 2H, CH2-30),
1.66–1.74 (m, 2H, CH2-20), 2.14 (s, 2H, CH2-5), 2.45 (s, 2H, CH2-
3), 3.13 (t, 2H, J = 7.5 Hz, SCH2), 7.08 (d, 2H, ArH), 7.39 (d, 2H,
ArH), 15.44 (s, 1H, NH). FABMS: m/z = 382 [M++1], ESIMS: Calcd
for C19H25ClNOS2 (M++H), m/z 382.1066, Found 382.1067.
4.2. General procedure for preparation the carbodithioates 3a–c
4.2.2. n-Butyl [2-(4-bromophenylamino)-4,4-dimethyl-6-
oxocyclohex-1-ene]carbodithioate (3b)
To a cooled solution of enaminones 1a–c (0.01 mol) and NaOH
(0.4 g, 0.01 mol) in a mixture of DMSO (20 mL) and water (1 mL)
was added CS2 (0.03 mol). The reaction mixture was stirred for
Yield (49%, yellow crystals), mp 130–132 °C, TLC (6:4 n-hexane–
EtOAc): Rf 0.77, 1H NMR (CDCl3, 300 MHz): d 0.95 (t, 3H, J = 7.5 Hz,

174
El Sayed H. El Ashry et al. / Carbohydrate Research 346 (2011) 169–176
Figure 3. Displacement ellipsoid of 7a at 50% probability level are shown along with labeling.
CH3-40), 1.00 (s, 6H, 2CH3), 1.44–1.54 (m, 2H, CH2-30), 1.66–1.74
(m, 2H, CH2-20), 2.41 (s, 2H, CH2-5), 2.45 (s, 2H, CH2-3), 3.12 (t,
2H, SCH2), 7.02 (d, 2H, ArH), 7.54 (d, 2H, ArH), 15.40 (s, 1H, NH).
EIMS: m/z (%) = 425 (2), 370 (47), 338 (24), 306 (4), 55 (100).
ESIMS: Calcd for C19H24BrNOS2 (M++H), m/z 426.0561, Found
426.0558.
(s, 2H, CH2-6), 3.01 (t, 2H, SCH2), 4.55 (s, 1H, CH-8), 7.36 (d, 2H,
ArH), 7.61 (d, 2H, ArH).13C NMR (DMSO-d6, 75 MHz) :d13.4 (CH3-
40), 21.4 (C-30), 28.2 (2CH3), 29.9 (C-20), 30.8 (SCH2), 32.1 (C-7),
50.7 (C-6), 116.4 (C-8), 122.1, 130.4, 130.5, 133.6 (ArH), 133.5 (C-
10), 139.4 (C-9), 145.1 (C-S), 182.6 (C@S), 193.8 (C@O). EIMS: m/z
(%) = 423 (10), 408 (100), 366 (3), 276 (13), 170 (20), 123 (18), 57
(46). HREIMS (M+): Calcd for C20H22ClNOS3: m/z 423.0552, Found
423.0559.
4.2.3. n-Butyl [2-(2,4-dichlorophenylamino)-4,4-dimethyl-6-
oxocyclohex-1-ene]carbodithioate (3c)
Yield (34.5%, yellow crystals), mp 128–130 °C, TLC (8:2 n-hex-
ane–EtOAc): Rf 0.41, 1H NMR (CDCl3, 400 MHz): d 0.93 (t, 3H,
J = 7.2 Hz, CH3-40), 1.01 (s, 6H, 2CH3), 1.45–1.56 (m, 2H, CH2-30),
1.67–1.75 (m, 2H, CH2-20), 2.31 (s, 2H, CH2-5), 2.40 (s, 2H, CH2-
3), 3.14 (t, 2H, J = 7.6 Hz, SCH2), 7.51(d, 1H, J = 8.4 Hz, ArH), 7.31
(m, 1H, ArH), 7.51 (d, 1H, ArH), 14.73 (s, 1H, NH).13C NMR
(DMSO-d6, 125 MHz): d 13.5 (CH3-40), 21.9 (CH2-30), 27.3 (2CH3),
28.5 (CH2-20), 30.9 (C-4), 35.7 (SCH2), 41.2 (C-5), 50.8 (C-3), 118.4
(C-1), 128.1, 129.4, 130.5, 131.5, 132.5, 133.9 (ArH), 162.7 (C-2),
191.3 (C@S), 223.0 (C@O). EIMS: m/z (%) = 415 (12), 358 (100),
326 (12), 291 (20), 186 (6), 145 (6). HREIMS (M+): Calcd for
C19H23Cl2NOS2: m/z 415.0598, Found 415.0556.
4.3.2. 4-(Butylthio)-1-(4-bromophenyl)-7,7-dimethyl-2-thioxo-
6,7-dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one (5b)
Yield (35%, yellowish crystals), mp 173–175 °C, TLC (6:4 n-hex-
ane–EtOAc): Rf 0.75, 1H NMR (CDCl3, 300 MHz): d 0.92 (t, 9H,
3CH3), 1.40–1.50 (m, 2H, CH2-30), 1.63–1.73 (m, 2H, CH2-20), 2.34
(s, 2H, CH2-6), 2.99 (t, 2H, J = 7.5 Hz, SCH2), 4.55 (s, 1H, CH-8),
7.03–7.08 (m, 2H, ArH), 7.63–7.68 (m, 2H, ArH). 13C NMR
(DMSO-d6, 100 MHz): d 13.4 (CH3-40), 21.3 (CH2-30), 28.1 (2CH3),
29.9 (CH2-20), 30.8 (SCH2), 32.0 (C-7), 50.6 (C-6), 116.4 (C-8),
122.1, 130.8, 133.3, 139.8 (ArH), 136.7 (C-10), 141.8 (C-9), 145.1
(C-S), 182.5 (C@S), 193.8 (C@O). EIMS: m/z (%) = 467 (22), 452
(66), 412 (4), 320 (11), 214 (13), 123 (21), 57 (100). HREIMS
(M+): Calcd for C20H22BrNOS3: m/z 467.0047, Found 467.0027.
Anal. Calcd for C20H22BrNOS3: C, 51.27; H, 4.73; N, 2.99. Found:
C, 51.77; H, 4.64; N, 3.0.
4.3. General procedure for the preparation of benzothiazine
derivatives 5a–c
To a cooled solution of enaminones 1a–c (0.01 mol) and NaOH
(0.8 g, 0.02 mol) in a mixture of DMSO (20 mL) and water (2 mL)
was added CS2 (0.06 mol). The reaction mixture was stirred for
20 min at room temperature, and then n-butyl bromide (0.012
mol) was added. The reaction mixture was stirred for 24 h at room
temperature, then poured into cold water (100 mL), and acidified
with 10% HCl. The product that separated out was filtered off,
dried, and purified on silica gel column chromatography (3:7
EtOAc–n-hexane) and recrystallized from EtOH to give 5a–c.
4.3.3. 4-(Butylthio)-1-(2,4-dichlorophenyl)-7,7-dimethyl-2-
thioxo-6,7-dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one (5c)
Yield (25%, yellow crystals), mp 183–185 °C, TLC (8:2 n-hex-
ane–EtOAc): Rf 0.35, 1H NMR (CDCl3, 300 MHz): d 0.93 (t, 3H,
J = 7.5 Hz, CH3-40), 0.97 (s, 6H, 2CH3), 1.43–1.54 (m, 2H, CH2-
30), 1.63–1.73 (m, 2H, CH2-20), 2.35 (d, 2H, J = 1.5 Hz, CH2-6),
2.99 (t, 2H, J = 7.5 Hz, SCH2), 4.49 (s, 1H, CH-8), 7.19–7.24 (m,
1H, ArH), 7.38–7.42 (m, 1H, ArH), 7.57 (d, 1H, J = 2.1 Hz, ArH).
13C NMR (CDCl3, 75 MHz): d 13.6 (C-40), 22.0 (C-30), 28.6, 28.9
(2CH3), 30.9 (C-20), 31.0 (SCH2), 32.4 (C-7), 51.4 (C-6), 115.9
(C-8), 120.3, 128.9, 131.2, 131.5, 132.9, 135.6 (ArH), 135.8 (C-
10), 136.5 (C-9), 147.6 (C-S) 183.6 (C@S), 194.2 (C@O). EIMS:
m/z (%) 457 (44), 442 (50), 400(2), 366 (8), 334 (4), 185 (5).
4.3.1. 4-(Butylthio)-1-(4-chlorophenyl)-7,7-dimethyl-2-thioxo-
6,7-dihydro-1H-benzo[d][1,3]thiazin-5(2H)-one (5a)
Yield (29%, yellow crystals), mp 178–180 °C, TLC (n-hexane–
EtOAc 8:2): Rf 0.38, 1H NMR (DMSO-d6, 300 MHz): d 0.91 (m, 9H,
3CH3), 1.38–1.45 (m, 2H, CH2-30), 1.56–1.63 (m, 2H, CH2-20), 2.33

El Sayed H. El Ashry et al. / Carbohydrate Research 346 (2011) 169–176
175
HREIMS (M+): Calcd for C20H21Cl2NOS3: m/z 457.0162, Found
457.0174.
170.3, 170.7 (4C@O), 193.2 (C@S), 213.2 (C@O). FABMS: m/z 690
[M++1]. Anal. Calcd for C29H33Cl2NO10S2: C, 50.44; H, 4.82; N,
2.03. Found: C, 50.43; H, 4.77; N, 2.09.
4.4. General procedure for the preparation of thioglycosides 6a–
c and 7a–c
4.4.4. (20,30,40,60-Tetra-O-acetyl-b-
D-galactopyranosyl) [2-(4-
chlorophenylamino)-4,4-dimethyl-6-oxocyclohex-1-ene]-
carbodithioate (7a)
To a cooled solution of enaminones 1a–c (0.01 mol) and NaOH
(0.4 g, 0.01 mol) in mixture of DMSO (20 mL) and water (1 mL)
was added CS2 (0.03 mol). The reaction mixture was stirred for
Yield (30%, yellow crystals), mp 211–213 °C, TLC (6:4 n-hexane–
EtOAc): Rf 0.20, 1H NMR (CDCl3, 300 MHz): d 0.98, 0.99 (2s, 6H,
2CH3), 1.97, 1.99, 2.01, 2.12 (4s, 12H, 4OAc), 2.39 (s, 2H, CH2-5),
2.47 (s, 2H, CH2-3), 4.03–4.10 (m, 3H, H-600, H-50, H-60), 5.16 (dd,
1H, H-30), 5.46 (d, 1H, H-40), 5.56 (t, 1H, H-20), 5.72 (d, 1H,
20 min at room temperature and then
a-D-glycosyl bromides
(0.012 mol) were added. The reaction mixture was stirred for
24 h at room temperature, then poured onto cold water
(100 mL), and acidified with 10% HCl. The product that separated
out was filtered off, dried, and purified by silica gel column chro-
matography (3:7 EtOAc–n-hexane) and recrystallized from EtOH
to give 6a–c and 7a–c.
J1 ,2 = 10.5 Hz, H-10), 7.11 (dd, 2H, ArH), 7.42 (d, 2H, ArH), 16.02
(s, 1H, NH). FABMS: m/z 654 [M+ꢀ1], ESIMS: Calcd for
0
0
C
29H35ClNO10S2 (M++H): m/z 656.1391, Found 656.1380.
4.4.5. (20,30,40,60-Tetra-O-acetyl-b-
D-galactopyranosyl) [2-(4-
bromophenylamino)-4,4-dimethyl-6-oxocyclohex-1-ene]-
carbodithioate (7b)
4.4.1. (20,30,40,60-Tetra-O-acetyl-b-
D-glucopyranosyl) [2-(4-
chlorophenylamino)-4,4-dimethyl-6-oxocyclohex-1-ene]-
carbodithioate (6a)
Yield (38%, yellow crystals), mp 209–211 °C, TLC (6:4 n-hexane–
EtOAc): Rf 0.22, 1H NMR (CDCl3, 400 MHz): d 0.99, 1.0 (2s, 6H,
2CH3), 1.97, 1.99, 2.00, 2.13 (4s, 12H, 4OAc), 2.39 (s, 2H, CH2-5),
2.47 (s, 2H, CH2-3), 4.03–4.09 (m, 3H, H-600, H-50, H-60), 5.16 (dd,
1H, H-30), 5.45 (d, 1H, H-40), 5.54 (t, 1H, H-20), 5.73 (d, 1H,
Yield (30%, yellow crystals), mp 119–121 °C, TLC (6:4 n-hexane–
EtOAc): Rf 0.28, 1H NMR (DMSO-d6, 300 MHz): d 0.91, 0.92 (2s, 6H,
2CH3), 1.94, 1.95, 1.98 (3s, 12H, 4OAc), 2.35 (s, 2H, CH2-5), 2.67 (s,
2H, CH2-3), 3.92 (dd, 1H, H-600), 3.96–4.0 (m, 1H, H-50), 4.11 (dd, 1H,
H-60), 4.94 (t, 1H, J4 ,3 = J4 ,5 = 9.6 Hz, H-40), 5.11 (t, 1H, J2 ,3
=
J1 ,2 = 10.8 Hz, H-10), 7.10 (dd, 2H, ArH), 7.42 (d, 2H, ArH), 16.00
(s, 1H, NH). FABMS: m/z 700 [M++1], ESIMS: Calcd for
0
0
0
0
0
0
0
0
9.2 Hz, J2 ,1 = 10.5 Hz, H-20), 5.41 (t, 1H, H-30), 5.76 (d, 1H,
0
0
J1 ,2 = 10.5 Hz, H-10), 7.40 (d, 2H, ArH), 7.57 (s, 2H, ArH), 15.60 (s,
1H, NH). 13C NMR (DMSO-d6, 125 MHz): d 20.2, 20.3, 20.5 (4Ac),
27.3 (2CH3), 30.5 (C-4), 41.9 (C-5), 50.8 (C-3), 61.5 (C-60), 68.0 (C-
20), 68.4 (C-40), 73.7 (C-30),74.5 (C-50), 81.6 (C-10), 118.0 (C-1),
127.7, 129.6, 132.5, 134.6 (ArH), 168.9 (C-2), 169.0, 169.2, 169.5,
169.8 (4C@O), 192.9 (C@S), 210.5 (C@O). FABMS: m/z = 656
[M++1], ESIMS: Calcd for C29H35ClNO10S2 (M++H) m/z 656.1391,
Found 656.1357.
C
29H35BrNO10S2 (M++H) m/z 700.0886, Found 700.0960.
0
0
4.4.6. (20,30,40,60-Tetra-O-acetyl-b-
D-galactopyranosyl) [2-(2,4-
dichlorophenylamino)-4,4-dimethyl-6-oxocyclohex-1-ene]-
carbodithioate (7c)
Yield (28%, yellowish crystals), mp 207–209 °C, TLC (6:4 n-hex-
ane–EtOAc): Rf 0.61, 1H NMR (CDCl3, 300 MHz): d 1.52 (s, 6H,
2CH3), 1.97, 1.99, 2.01, 2.12 (4s, 12H, 4OAc), 2.33 (s, 2H, CH2-5),
2.40 (s, 2H, CH2-3), 4.05–4.11 (m, 3H, H-600, H-50, H-60), 5.16 (dd,
4.4.2. (20,30,40,60-Tetra-O-acetyl-b-
D-glucopyranosyl) [2-(4-
1H, H-30), 5.45 (d, 1H, H-40), 5.41 (t, 1H, J2 ,1 = 10.5 Hz,
J
0
0
0
0
20,30
bromophenylamino)-4,4-dimethyl-6-oxocyclohex-1-ene]-
carbodithioate (6b)
= 9.9 Hz, H-20), 5.74 (d, 1H, J1 ,2 = 10.5 Hz, H-10),7.14 (d, 1H,
ArH), 7.36 (dd, 1H, ArH), 7.56 (m, 1H, ArH), 15.77 (s, 1H, NH). FAB-
MS: m/z 688 [M+ꢀ1]. ESIMS: Calcd for C29H34Cl2NO10S2 (M++H) m/z
690.1001, Found 690.0940.
Yield (29%, yellow crystals), mp 125–127 °C, TLC (7:3 n-hexane–
EtOAc): Rf 0.45, 1H NMR (DMSO-d6, 300 MHz): d 0.92 (s, 6H, 2CH3),
1.94, 1.95, 1.98 (3s, 12H, 4OAc), 2.35 (s, 2H, CH2-5), 2.67 (s, 2H,
CH2-3), 3.93 (dd, 1H, H-600), 4.0–4.03 (m, 1H, H-50), 4.12 (dd, 1H,
Acknowledgments
H-60), 4.94 (t, 1H, J4 ,3 = J4 ,5 = 9.6 Hz, H-40), 5.11 (t, 1H, H-20),
0
0
0
0
5.41 (t, 1H, H-30), 5.76 (d, 1H, J 1 ,2 = 10.5 Hz, H-10), 7.32 (d, 2H,
ArH), 7.70 (d, 2H, ArH), 15.50 (s, 1H, NH). 13C NMR (DMSO-d6,
125 MHz): d 20.2, 20.3, 20.4 (4Ac), 27.3 (2CH3), 30.5 (C-4), 41.9
(C-5), 50.8 (C-3), 61.6 (C-60), 68.1 (C-20), 68.4 (C-40), 73.7 (C-
30),74.6 (C-50), 81.7 (C-10), 118.0 (C-1), 120.9, 127.9, 132.6, 135.1
(ArH), 168.9 (C-2), 169.2, 169.5, 169.9 (4C@O), 192.9 (C@S),
210.6 (C@O). FABMS: m/z = 700 [M++1], ESIMS: Calcd for C29H35
BrNO10S2 (M++H), m/z 700.0886, Found 700.0870.
We thank the Higher Education Commission of Pakistan (Pro-
ject No. 20-697/R&D/06/38) and the University of Malaya for sup-
porting this study.
0
0
Supplementary data
Crystallographic data, excluding structure factors, have been
deposited with the Cambridge Crystallographic Data Centre as sup-
plementary publication with CCDC No. 795086 for 5a and 795087
for 7a. Copies of the data can be obtained free of charge on appli-
cation with the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: +44 1223 336 033; e-mail: deposit@ccdc.cam.ac.uk). Sup-
plementary data associated with this article can be found, in the
online version, at doi:10.1016/j.carres.2010.11.005.
4.4.3. (20,30,40,60-Tetra-O-acetyl-b-
D-glucopyranosyl) [2-(2,4-
dichlorophenylamino)-4,4-dimethyl-6-oxocyclohex-1-ene]-
carbodithioate (6c)
Yield (32%, yellow crystals), mp 202–204 °C, TLC (6:4 n-hexane–
EtOAc): Rf 0.61, 1H NMR (DMSO-d6, 300 MHz): d 0.91 (s, 6H, 2CH3),
1.95, 1.96, 1.97, 1.98 (4s, 12H, 4OAc), 1.98 (s, 2H, CH2-5), 2.35 (s,
2H, CH2-3), 4.93 (d, 1H, H-600), 4.0–4.05 (m, 1H, H-50), 4.13 (dd,
References
1H, H-60), 4.94 (t, 1H, J4 ,3 = J4 ,5 = 9.6 Hz, H-40), 5.12 (t, 1H, H-20),
0
0
0
0
5.41 (t, 1H, H-30), 5.74 (d, 1H, J1 ,2 = 10.5 Hz, H-10), 7.53–7.60 (m,
2H, ArH), 7.89 (s, 1H, ArH), 15.23 (s, 1H, NH). 13C NMR (CDCl3,
75 MHz): d 20.6, 20.63, 20.7, 20.8 (4Ac), 27.9, 28.0 (2CH3), 30.8
(C-4), 42.9 (C-5), 51.6 (C-3), 62.0 (C-60), 68.4, 68.7 (C-20, C-40),
74.9 (C-30), 75.7 (C-50), 82.4 (C-10), 118.5 (C-1), 128.4, 129.1,
130.6, 132.2, 132.8, 135.1 (ArH), 169.2 (C-2), 169.4, 169.44,
1. (a) Ur-Rehman, Z.; Muhammada, N.; Shuja, S.; Ali, S.; Butler, I. S.; Meetsma, A.;
Khan, M. Polyhedron 2009, 28, 3439–3448; (b) Nieuwenhuizen, P. J.; Reedijk, J.;
van Duin, M.; McGill, W. J. Rubber Chem. Technol. 1997, 70, 368–429; (c) Fan, D.;
Afzaal, M.; Malik, M. A.; Nguyen, C. Q.; O’Brien, P.; Thomas, P. J. Coord. Chem.
Rev. 2007, 251, 1878–1888; (d) Knight, E. R.; Cowley, A. R.; Hogarth, G.; Wilton-
Ely, J. D. Dalton Trans. 2009, 607–609.
0
0
2. Waseem, A.; Yaqoob, M.; Nabi, A. Anal. Sci. 2009, 395–400.

176
El Sayed H. El Ashry et al. / Carbohydrate Research 346 (2011) 169–176
3. Cvek, B.; Dvorak, Z. Curr. Pharm. Des. 2007, 13, 3155–3167.
22. (a) Pornsuriyasak, P.; Gangadharmath, U. B.; Rath, N. P.; Demchenko, A. Org.
Lett. 2004, 6, 4515–4518. doi/abs/10.1021/ol048043y; (b) Demchenko, A. V.;
Kamat, M. N.; De Meo, C. Synlett 2003, 1287–1290; (c) Demchenko, A. V.;
Pornsuriyasak, P.; De Meo, C.; Malysheva, N. N. Angew. Chem., Int. Ed. 2004, 43,
3069–3072; (d) Gangadharmath, U. B.; Demchenko, A. V. Synlett 2004, 2191–
2193; (e) Demchenko, A. V.; Malysheva, N. N.; De Meo, C. Org. Lett. 2003, 5,
455–458.
23. (a) El Ashry, E. S. H.; Rashed, N.; Ibrahim, E. I. Tetrahedron 2008, 64, 10631–
10648; (b) El Ashry, E. S. H.; Rashed, N.; Ibrahim, E. I. Curr. Org. Synth. 2005, 2,
175–213; (c) El Ashry, E. S. H.; Aly, M. R. E. Pure Appl. Chem. 2007, 79, 2229–
2242.
24. (a) El Ashry, E. S. H.; Awad, L. F.; Atta, I. A. Tetrahedron 2006, 62, 2943–2998; (b)
Rezki, N.; Rashed, N.; Awad, L. F.; Ramadan, E.; Abdel-Maggeed, S. M.; El Ashry,
E. S. H. Phosphorus, Sulfur Silicon Relat. Elem. 2009, 184, 1759–1767; (c) Awad, O.
M. E.; Attia, W. E.; El Ashry, E. S. H. Carbohydr. Res. 2004, 339, 469–476; (d) El
Ashry, E. S. H.; Awad, L. F.; Abdel-Hamid, H.; Atta, I. A. J. Carbohydr. Chem. 2005,
24, 745–753.
25. (a) El Ashry, E. S. H.; Rashed, N.; Shobier, A. H. Pharmazie 2000, 55, 251–262; (b)
El Ashry, E. S. H.; Rashed, N.; Shobier, A. H. Pharmazie 2000, 55, 331–348; (c) El
Ashry, E. S. H.; Rashed, N.; Shobier, A. H. Pharmazie 2000, 55, 403–415; (d) El
Ashry, E. S. H.; El Nemr, A. Synthesis of Naturally Occurring Nitrogen Heterocycles
from Carbohydrates; Blackwell: Oxford, 2005; (e) Aly, A. A. Phosphorus, Sulfur,
Silicon Relat. Elem. 2003, 178, 2415–2429.
26. (a) Fuegedi, P.; Garegg, P. J.; Oscarson, S.; Rosen, G.; Silwanis, B. A. Carbohydr.
Res. 1991, 211, 157–162; (b) Elgemeie, G. H.; Zaghary, W. A.; Nasr, T. M.; Amin,
K. M. J. Carbohydr. Chem. 2008, 27, 345–356; (c) Bogusiak, J.; Szeja, W.
Tetrahedron Lett. 2001, 42, 2221–2223; (d) Behalo, M. S.; Aly, A. A. J. Chem. Res.,
Synop. 2009, 12, 753–755; (e) Bogusiak, J.; Szeja, W. Carbohydr. Res. 2001, 330,
141–144; (f) Wandzik, I.; Szeja, W. Pol. J. Chem. 1999, 73, 1163–1170; (g)
Bogusiak, J.; Szeja, W. Carbohydr. Res. 1996, 295, 235–243; (h) Tejima, S.;
Ishiguro, S. Chem. Pharm. Bull. 1967, 15, 255–263; (i) Byung-Hoon, L.; Barbara,
B.; Peter, S.; Norbert, F.; Manfred, W. J. Med. Chem. 1994, 37, 3154–3162.
27. Pieper, G. M.; Siebeneich, W.; Olds, C. L.; Lai, C.-S. Eur. J. Pharmacol. 2003, 472,
127–134.
4. (a) Shahzadi, S.; Ali, S.; Bhatti, M. H.; Fettouhi, M.; Athar, M. J. Organomet. Chem.
2006, 691, 1797–1802; (b) Yang, P.; Guo, M. Coord. Chem. Rev. 1999, 189, 185–
186; (c) Chadha, R. K.; Kumar, R.; Tuck, D. G. Can. J. Chem. 1987, 65, 1336–1342;
(d) Al-Allaf, T. A.; Mustafa, I. A.; Al-Mukhtar, S. E. Trans. Met. Chem. 1993, 18, 1–
5; (e) David, P. C.; Chrislyn, M. C. Pestic. Sci. 2006, 23, 93–102; (f) Rogachev, I.;
Kampel, V.; Gusis, V.; Cohen, N.; Gressel, J.; Warshawasky, A. Pestic. Biochem.
Physiol. 1998, 60, 133–145; (g) Ur-Rehman, A.; Hussain, M.; Ur-Rehman, Z.;
Rauf, A.; Nasim, F. H.; Tahir, A. A.; Ali, S. J. Organomet. Chem. 2010, 695, 1526–
1532.
5. (a) Boers, D.; van Amelsvoort, L.; Colosio, C.; Corsini, E.; Fustinoni, S.; Campo, L.;
Bosetti, C.; La Vecchia, C.; Vergieva, T.; Tarkowski, M.; Liesivuori, J.;
Steerenberg, P.; van Loveren, H. Hum. Exp. Toxicol. 2008, 27, 721–727; (b) Zel,
O. G.; Salman, A. Bioorg. Med. Chem. 2006, 14, 7804–7815; (c) Soledade, M.;
Pedras, C.; Jha, M. Bioorg. Med. Chem. 2006, 14, 4958–4979.
6. (a) Yin, H. D.; Xue, S. C. Appl. Organomet. Chem. 2006, 20, 283–289; (b)
Tabassum, S.; Pettinari, C. J. Organomet. Chem. 2006, 691, 1761–1766; (c)
Pellerito, C.; D’Agati, P.; Fiore, T.; Mansueto, C.; Mansueto, V.; Stocco, G.; Nagy,
L.; Pellerito, L. J. Inorg. Biochem. 2005, 99, 1294–1305; (d) Milacic, V.; Dou, Q. P.
Coord. Chem. Rev. 2009, 253, 1649–1660. pubmed/20047011; (e) Zhang, X.;
Frezza, M.; Milacic, V.; Ronconi, L.; Fan, Y.; Bi, C.; Fregona, D.; Dou, Q. P. J. Cell.
Biochem. 2010, 109, 162–172.
7. Bach, S. P.; Chinery, R.; O’Dwyer, S. T.; Potten, C. S.; Coffey, R. J.; Watson, A. J.
Gastroenterology 2000, 118, 81–89.
8. Daniel, K. G.; Chen, D.; Orlu, S.; Cui, Q. C.; Miller, F. R.; Dou, Q. P. Breast Cancer
Res. 2005, 7, 897–908.
9. Trevisan, A.; Marzano, C.; Cristofori, P.; Borella Venturini, M.; Giovagnini, L.;
Fregona, D. Arch. Toxicol. 2002, 76, 262–268.
10. Huang, W.; Ding, Y.; Miao, Y.; Liu, M.-Z.; Li, Y.; Yang, G.-F. Eur. J. Med. Chem.
2009, 44, 3687–3696.
11. Si, X.; McManus, B. M.; Zhang, J.; Yuan, J.; Cheung, C.; Esfandiarei, M.; Suarez,
A.; Morgan, A.; Luo, H. J. Virol. 2005, 79, 8014–8023.
12. Sofuoglu, M.; Kosten, T. R. CNS Drugs 2005, 19, 13–25.
13. Fang, I. M.; Yang, C. H.; Lin, C. P.; Yang, C. M.; Chen, M. S. Ocul. Pharmacol. Ther.
2005, 21, 95–106.
14. Pyatt, D. W.; Gruntmeir, J.; Stillman, W. S.; Irons, R. D. Toxicology 1998, 128, 83–
90.
28. El Ashry, E. S. H.; Amer, M. R.; Shah, M. R.; Ng, S. W. Acta Crystallogr., Sect. E
2009, 65, o1106.
29. El Ashry, E. S. H.; Amer, M. R.; Shah, M. R.; Ng, S. W. Acta Crystallogr., Sect. E
2009, 65, o597.
30. El Ashry, E. S. H.; Amer, M. R.; Shah, M. R.; Ng, S. W. Acta Crystallogr., Sect. E
2009, 65, o599.
15. (a) Noboru, U.; Kunio, O. J. Antimicrob. Chemother. 2003, 52, 8–10; (b) Uchide,
N.; Ohyama, K.; Bessho, T.; Yuan, B.; Yamakawa, T. Antiviral Res. 2002, 56, 207–
217.
16. Amarnath, V.; Amarnath, K.; Valentine, W. M. Curr. Top. Toxicol. 2007, 4, 39–44.
17. Gogoi, P. K.; Phukan, D. P.; Das, D. K. Asian J. Chem. 1999, 11, 1291–1295.
18. Chauhan, H. P. S.; Shaik, N. M. J. Inorg. Biochem. 2005, 99, 538–545.
19. Eng, G.; Song, X.; Duong, Q.; Strickman, D.; Glass, J.; May, L. Appl. Organomet.
Chem. 2003, 17, 218–225.
31. El Ashry, E. S. H.; Amer, M. R.; Shah, M. R.; Ng, S. W. Acta Crystallogr., Sect. E
2009, 65, o600.
32. Yamasaki, T.; Nishida, K.; Okawara, T.; Furukawa, M. Heterocycles 1998, 47,
315–327.
33. Tominaga, Y.; Okuda, H.; Kohra, S.; Mazume, H. J. Heterocycl. Chem. 1991, 28,
1245–1255.
34. Barbour, L. J. J. Supramol. Chem. 2001, 1, 189–191.
20. Viquez, O. M.; Lai, B.; Ahn, J. H.; Does, M. D.; Valentine, H. L.; Valentine, W. M.
Toxicol. Appl. Pharmacol. 2009, 239, 71–79.
21. (a) Zhu, X.; Schmidt, R. R. Angew. Chem., Int. Ed. 2009, 48, 1900–1934; (b)
Pachamuthu, K.; Schmidt, R. R. Chem. Rev. 2006, 106, 160–187; (c) Schmidt, R.
R.; Castro-Palomino, J. C.; Retz, O. Pure Appl. Chem. 1999, 71, 729–744; (d)
Schmidt, R. R. In Modern Methods in Carbohydrate Synthesis; Khan, S. H., O’Neill,
R. A., Eds.; Harwood: Amsterdam, 1996; pp 20–54; (e) Abdel-Rahman, A. A.-H.;
El Ashry, E. S. H.; Schmidt, R. R. Carbohydr. Res. 2002, 337, 195–206.
35. Bruker, APEX2 software (v2008.6-1) and SAINT (Version 7.60A); Bruker AXS Inc.:
Madison, WI, USA, 2008.
36. Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876–881.
37. Sheldrick, G. M. SADABS. Program for Empirical Absorption Correction of Area
Detector Data; University of Göttingen: Germany, 1996.
38. Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.