Synthesis, characterization, and biological evaluation of 10h-phenothiazines, their sulfones and ribofuranosides

Article abstract of DOI:10.1002/jhet.771

10H-phenothiazines are synthesized via Smiles rearrangement. These prepared phenothiazines act as a base to prepare ribofuranosides by treating them with b-D-ribofuranosyl-1-acetate-2,3,5-tribenzoate. 10H-phenothiazines on refluxing with hydrogen peroxide in glacial acetic acid gave 10H-phenothiazine-5,5- dioxides. The synthesized compounds were evaluated for their antioxidative properties through in vitro studies, and they are also screened for their antimicrobial activity. The structure of the synthesized compounds has been established by elemental analysis and spectroscopic data.

Full text of DOI:10.1002/jhet.771

710
Synthesis, Characterization, and Biological Evaluation of
10H-Phenothiazines, Their Sulfones and Ribofuranosides
Vol 49
,*
,*
Naveen Gautam Shikha Gupta Neha Ajmera, and D. C. Gautam
Department of Chemistry, University of Rajasthan, Jaipur 302004, India
*
E-mail: ngautam70@yahoo.co.in or shikha_urj@yahoo.com
Received September 8, 2010
DOI 10.1002/jhet.771
View this article online at wileyonlinelibrary.com.
10H-phenothiazines are synthesized via Smiles rearrangement. These prepared phenothiazines act as
a base to prepare ribofuranosides by treating them with b-D-ribofuranosyl-1-acetate-2,3,5-tribenzoate.
10H-phenothiazines on refluxing with hydrogen peroxide in glacial acetic acid gave 10H-phenothiazine-
5,5-dioxides. The synthesized compounds were evaluated for their antioxidative properties through in vitro
studies, and they are also screened for their antimicrobial activity. The structure of the synthesized
compounds has been established by elemental analysis and spectroscopic data.
J. Heterocyclic Chem., 49, 710 (2012).
INTRODUCTION
dinitrobenzotrifluride 2c) in ethanolic sodium acetate
solution. 1-Nitro-10H-phenothiazine 5d has been synthe-
sized by the reaction of 2-amino-3,4,5-trifluorobenzenethiol
1b with 4-chloro-3,5-dinitrobenzoic acid 2d (having two
nitro groups ortho to the reactive halogen atom) in alcohol
in presence of sodium hydroxide where the Smiles rear-
rangement occurs in situ. Compounds 5a–d on reflux-
ing with 30% hydrogen peroxide in glacial acetic acid
were converted into their corresponding sulfones 6a–d.
Treatment of the pasty mixture of 5a–d in toluene with
b-D-ribofuranosyl-1-acetate-2,3,5-tribenzoate in vacuum gave
the corresponding ribofuranosides 7a–d (Scheme 1).
Phenothiazines, their sulfones and ribofuranosides
constitute an important class of heterocycles. These
compounds are of immense importance and possess a
wide spectrum of pharmacological activities such as
analgesic, antihypertensive, antipsychotic, antibacterial,
and anti AIDS. Research is being persuaded to develop
potent anticancer agents. A slight change in substitution
pattern cause marked difference in their biological activity
[1–11]. Thus, we wish to report here synthesis of some new
10H-phenothiazines, their sulfones and ribofuranosides. The
structure of the synthesized compounds is determined on the
basis of their spectral data and elemental analysis. These
compounds are also screened for antioxidant [12–16] and
antimicrobial activity [17].
All the synthesized compounds were screened for
their antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl
(DPPH) radical scavenging assay and 2,2-azinobis(3-
•
ethylbenzothiazoline-6-sulfonic acid) ABTS + radical
cation decolorization assay and also screened for their
antimicrobial activity.
RESULTS AND DISCUSSION
The structure of these compounds were determined on
the basis of elemental analysis and spectral data.
The synthesis of various substituted 10H-phenothia-
zines 5a–c has been carried out by Smiles rearrange-
ment of substituted 2-formamido-20-nitrodiphenylsulfides
4a–c. The formyl derivatives have been prepared by
diphenyl sulfides 3a–c which in turn was prepared by
the condensation of 2-amino-4,6-dimethyl benzenethiol
1a with o-halonitrobenzenes (1,3,5-trichloro-2-nitroben-
zene 2a/1,5-dichloro-2,4-dinitrobenzene 2b/2-chloro-3,5-
IR spectra.
Compounds 5a–d and 6a–d showed a
band in the region 3410–3320 cmꢀ1 corresponding to
>NH stretching vibration. Two sharp and intense bands
in the region 1590–1560 cmꢀ1 and 1400–1370 cmꢀ1 are
ascribed to asymmetric and symmetric stretching vibra-
tion of —NO2 group in 5d.
© 2012 HeteroCorporation

May 2012
Synthesis, Characterization, and Biological Evaluation of 10H-Phenothiazines,
Their Sulfones and Ribofuranosides
711
Scheme 1
The characteristic absorption bands at 2900–2950 cmꢀ1
appeared due to C—H stretching vibration of CH3 group
for compounds 5a–c, 6a–c, and 7a–c. Compounds 6a–d
This study elucidated that the synthesized compounds
showed mixed radical scavenging activity in both DPPH
•
and ABTS + assay. (a) Compounds (5a, 7a, and 7d)
exhibit two intense peaks in the region 1365–1340 cmꢀ1
,
showed strong radical scavenging activity in DPPH assay
that have DPPH% inhibition ꢁ 50. (b) Compounds (5d,
6a, 6b, 6c, 6d, and 7c) showed moderate radical scaveng-
ing activity in DPPH assay that have DPPH% inhibition
ꢁ 30. (c) Compounds (5b, 5c, and 7b) showed mild radical
scavenging activity in DPPH assay that have DPPH% inhi-
bition < 30. (d) Compounds (5a, 5c, 7a, and 7d) were
and 1190–1110 cmꢀ1 is assigned for asymmetric and sym-
metric stretching vibration of sulfonyl group.
In compounds 7a–d, the NH band disappeared showing
its ribosylation. The bands due to C=O and C—O—C
appeared at 1760–1740 cmꢀ1 and 1190–1135 cmꢀ1
,
respectively.
•
found to be more active in ABTS + assay which showed
1H-NMR spectra. The 1H-NMR spectra of compounds
5a–d and 6a–d showed a singlet in the region d 8.65–
9.22 ppm due to N—H proton and a multiplet observed
in the region d 6.50–8.24 ppm corresponding to the
aromatic protons. A singlet observed in the region d
2.05–2.35 ppm corresponding to proton of methyl group
in compounds 5a–d, 6a–d, and 7a–d. In ribofuranosides
7a–d, a multiplet appeared at d 6.50–8.42 ppm due to
much decline in graph.
Regarding antibacterial activity, compounds 5d and 6d
against Coagulase positive staphylococci and compounds
5d, 6d, 7a, 7b, 7c, and 7d against Coagulase negative
staphylococci showed good activity. Other compounds
showed moderate to less activity against all bacterial strains.
Regarding antifungal activity, all compounds were found
moderate to less active against fungus Candida albicans.
0
aromatic protons. C4 –H and CH2 protons of the sugar
moiety gave a multiplet in the region d 4.20–4.92 ppm,
0
0
whereas C2 –H and C3 –H signals seen in the region d
5.65–5.98 ppm as multiplets. The doublet in the region d
EXPERIMENTAL
0
Melting points were determined in open capillary tubes and
are uncorrected. IR spectra were recorded in KBr on SHIMADZU
8400 S FTIR spectrophotometer. 1H-NMR and 13C-NMR
spectra were obtained from JEOL AL 300 FT NMR using TMS
(tetramethyl silane) as internal standard in CDCl3/DMSO-d6.
Mass spectra were recorded on JEOL SX 102/DA 600 using
6.42–6.33 ppm is attributed to C1 –H.
CONCLUSIONS
The structures proposed for the synthesized compounds are
well supported by spectroscopic data and elemental analysis.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

712
N. Gautam, S. Gupta, N. Ajmera, and D. C. Gautam
Vol 49
Table 1
Antioxidant activity of synthesized compounds.
Compound
DPPH% inhibition of
Compd.No.
R1
R2
R3
R4
R5
R6
R7
R8
1 mg/mL of the compound
5a
5b
5c
5d
6a
6b
6c
6d
7a
7b
7c
7d
H
H
H
F
H
H
H
F
H
H
H
F
CH3
CH3
CH3
F
CH3
CH3
CH3
F
CH3
CH3
CH3
F
H
H
H
F
H
H
H
F
H
H
H
F
CH3
CH3
CH3
H
CH3
CH3
CH3
H
CH3
CH3
CH3
H
H
H
CF3
NO2
H
Cl
Cl
H
H
NO2
NO2
COOH
H
NO2
NO2
COOH
H
Cl
H
H
H
Cl
H
H
H
Cl
H
H
H
79.21 ꢃ 0.02
24.53 ꢃ 0.01
28.55 ꢃ 1.05
33.33 ꢃ 0.07
31.25 ꢃ 0.08
35.35 ꢃ 1.1
45.00 ꢃ 1.5
41.00 ꢃ 1.2
75.37 ꢃ 0.09
17.98 ꢃ 0.60
36.31 ꢃ 0.08
66.44 ꢃ 0.05
H
Cl
Cl
H
H
CF3
NO2
H
H
CF3
NO2
H
Cl
Cl
H
NO2
NO2
COOH
H
Inhibition (%) of DPPH radical scavenging activity of various compounds at particular concentration. Stock solution of crude compound was prepared
as 1 mg/mL in methanol. Fifty microlitres of samples of particular concentration were added to 5 mL of 0.004% methanol solution of DPPH. After 30
min incubation in dark at room temperature, the absorbance was read against a blank at 517 nm.
Argon/Xenon as FAB (fast atom bombardment) gas. The purity
of synthesized compounds was checked by thin-layer chromatog-
raphy using silica gel “G” as adsorbent, and visualization was ac-
complished by UV light or iodine.
An ethanolic solution of potassium hydroxide (0.0036 mol in
5 mL ethanol) was added to refluxing solution of formyl
derivatives (0.01 mol). The content was heated for half an hour.
To this, a second lot of potassium hydroxide (0.0036 mol in
5 mL ethanol) was added and refluxed for 4 h. The content was
poured into a beaker containing crushed ice. The solid separated
out was filtered, washed with cold water and finally with 30%
ethanol, and recrystallized from methanol.
General procedure for the synthesis of 10H-phenothiazines
(5a–c).
To a stirred suspension of 0.01 mol of 2-amino-
4,6-dimethyl benzenethiol 1a in ethanol (20 mL) containing
sodium acetate (0.01 mol) in a round-bottomed flask fitted
with reflux condensor was added an alcoholic solution (10 mL)
of 0.01 mol of 1,3,5-trichloro-2-nitrobenzene 2a/1,5-dichloro-
2,4-dinitrobenzene 2b/2-chloro-3,5-dinitrobenzotrifluoride 2c.
The reaction mixture was refluxed for 4–5 h, concentrated and
cooled in an ice chamber overnight. The solid separated out was
filtered and washed with 30% ethanol. The diphenyl derivatives
(0.01 mol) were refluxed with 90% formic acid (20 mL) for 4 h.
The contents were then poured into a beaker containing crushed
ice; a solid that separated out was filtered, washed with water
until the filtrate was neutralized and crystallized from benzene.
2,4-Dichloro-6,8-dimethyl-10H-phenothiazine (5a).
This
compound was obtained as brownish crystals, m.p. 95ꢂC; yield
1
62%; IR: NH 3350, CCl 790, CH 2900 cmꢀ1; H-NMR: d 8.85
(s,1H, NH), 7.51–6.80 (m, 4H, ArH), 2.35 (s, 3H, CH3 at C6),
2.25 (s, 3H, CH3 at C8); 13C-NMR: d 121.4 (C-1), 135.5
(C-2), 130.5 (C-3), 137.2 (C-4), 138.4 (C-6), 132.2 (C-7), 138.8
(C-8), 122.2 (C-9), 16.8 (CH3 at C-6), 13.5 (CH3 at C-8);
ms: m/z 296 (M+), 298 (M + 2), 295 (30), 224 (52), 175 (100)
etc. Anal. Calcd. For C14H11NCl2S: C, 56.75; H, 3.71; N, 4.72.
Found: C, 56.91; H, 3.70; N, 4.75.
Table 2
Antioxidant activity of synthesized compounds (ABTS•+ assay).
ABTS•+ Activity at different
time intervals (min)
Compound
Compd. No.
R1
R2
R3
R4
R5
R6
R7
R8
0
1
2
4
6
5a
5b
5c
5d
6a
6b
6c
6d
7a
7b
7c
7d
H
H
H
F
H
H
H
F
H
H
H
F
CH3
CH3
CH3
F
CH3
CH3
CH3
F
CH3
CH3
CH3
F
H
H
H
F
H
H
H
F
H
H
H
F
CH3
CH3
CH3
H
CH3
CH3
CH3
H
CH3
CH3
CH3
H
H
H
CF3
NO2
H
Cl
Cl
H
H
NO2
NO2
COOH
H
NO2
NO2
COOH
H
Cl
H
H
H
Cl
H
H
H
Cl
H
H
H
0.687
0.711
0.713
0.695
0.723
0.722
0.721
0.727
0.692
0.708
0.719
0.692
0.106
0.525
0.284
0.686
0.310
0.620
0.251
0.321
0.337
0.526
0.502
0.266
0.06
0.025
0.465
0.031
0.174
0.282
0.618
0.249
0.319
0.039
0.438
0.358
0.099
0.017
0.439
0.02
0.506
0.131
0.377
0.282
0.618
0.250
0.319
0.049
0.481
0.445
0.145
H
0.119
0.282
0.618
0.249
0319
0.037
0.416
0.305
0.07
Cl
Cl
H
H
CF3
NO2
H
H
CF3
NO2
H
Cl
Cl
H
NO2
NO2
COOH
H
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

May 2012
Synthesis, Characterization, and Biological Evaluation of 10H-Phenothiazines,
Their Sulfones and Ribofuranosides
713
307 (M+), 309 (M + 2), 306 (32), 272 (55), 175 (100) etc. Anal.
Calcd. For C14H11N2O2ClS: C, 54.81; H, 3.58; N, 9.13. Found:
C, 54.99; H, 3.54; N, 9.08.
1-Trifluoromethyl-6,8-dimethyl-3-nitro-10H-phenothiazine
(5c). This compound was obtained as dark brownish crystals,
m.p. 148ꢂC; yield 72%; IR: NH 3390, CF3 1350,1105, CH
2910 cmꢀ1 1H-NMR: d 8.96 (s, 1H, NH), 8.24–7.06 (m, 4H,
;
ArH), 2.15 (s, 3H, CH3 at C6), 2.05 (s, 3H, CH3 at C8);
13C-NMR: d 162.2 (C-1), 128.8 (C-2), 148.6 (C-3), 126.6 (C-4),
138.5 (C-6), 131.4 (C-7), 139.0 (C-8), 123.2 (C-9), 15.8 (CH3
at C-6), 14.5 (CH3 at C-8); ms: m/z 340 (M+), 339 (28), 271
(65), 175 (100) etc. Anal. Calcd. For C15H11N2O2F3S: C, 52.94;
H, 3.23; N, 8.23. Found: C, 52.64; H, 3.19; N, 8.17.
3-Carboxy-7,8,9-trifluoro-1-nitro-10H-phenothiazine (5d).
Mixture of (0.01 mol) of 2-amino-3,4,5-trifluorobenzenethiol 1b,
sodium hydroxide (0.01 mol), and absolute alcohol (20 mL)
was taken in a round-bottomed flask (50 mL), fitted with the
reflux condenser, and was heated for 5 min. A total of 0.01
mol of substituted reactive o-halonitrobenzene 4-chloro-3,5-
dinitrobenzoic acid 2d (which contain two nitro group at both
ortho position to reactive halogen atom) was added with
stirring to this solution. The contents were refluxed for 2 h,
concentrated, cooled and filtered. The precipitate was washed
well with hot water and ethanol and crystallized from acetone.
This compound was obtained as blackish crystals, m.p. 145ꢂC;
yield 55%; IR: NH 3380, NO2 1590,1400, CF 1230 cmꢀ1
;
1H-NMR: d 9.10 (s, 1H, NH), 8.15–7.20 (m, 3H, ArH), 11.2
(s, 1H, COOH); 13C-NMR: d 148.1 (C-1), 122.1 (C-2), 145.2
(C-3), 121.2 (C-4), 111.2 (C-6),153.8 (C-7), 135.6 (C-8), 155.2
(C-9); ms: m/z 342 (M+), 325 (100), 312 (65), 296 (55), 295
(50) etc. Anal. Calcd. For C13H5N2O4F3S: C, 45.61; H, 1.46; N,
8.18. Found: C, 45.81; H, 1.45; N, 8.15.
General procedure for the synthesis of 10H-phenothiazine
sulfones (6a–d). A mixture of substituted 10H-phenothiazines
5a–d (0.01 mol), glacial acetic acid (20 mL), and 30% hydrogen
peroxide (5 mL) was refluxed for 15 min. Heating was stopped
and another lot of hydrogen peroxide (5 mL) was added. The
reaction mixture was again refluxed for 4 h. The contents were
poured into a beaker containing crushed ice. The yellow residue
obtained was filtered and washed with water and recrystallized
from ethanol.
2,4-Dichloro-6,8-dimethyl-10H-phenothiazine-5,5-dioxide
(sulfone) (6a). This compound was obtained as light yellowish
crystals, m.p. 240ꢂC; yield 58%; IR: NH 3360, CS 1060
cmꢀ1;1H-NMR: d 8.95 (s, 1H, NH), 7.62–6.80 (m, 4H, ArH),
2.36 (s, 3H, CH3 at C6), 2.28 (s, 3H, CH3 at C8); 13C-NMR: d
120.1 (C-1), 138.2 (C-2), 127.2 (C-3), 141.4 (C-4), 140.2 (C-6),
129.2 (C-7), 144.2 (C-8), 125.2 (C-9), 17.0 (CH3 at C-6), 14.1
(CH3 at C-8); ms: m/z 328 (M+), 330 (M+2), 327 (38), 257 (48),
207 (100) etc. Anal. Calcd. For C14H11NO2Cl2S: C, 51.21; H,
3.35; N, 4.26. Found: C, 51.56; H, 3.30; N, 4.15.
Figure 1. The effect of time on the suppression of absorbance of ABTS
by synthesized compounds. After addition of 1 mL of diluted ABTS solu-
tion (A 734 nm = 0.700 ꢃ 0.020) to 10 mL of the compound the absor-
bance reading was taken at 30ꢂC exactly 1 min., after initial mixing and
up to 6 min. All determinations were carried out in triplicates.
2-Chloro-6,8-dimethyl-3-nitro-10H-phenothiazine-5,5-dioxide
(sulfone) (6b).
This compound was obtained as light broꢀw1n
crystals, m.p. 270ꢂC; yield 52%; IR: NH 3395, CS 1070 cm
;
2-Chloro-6,8-dimethyl-3-nitro-10H-phenothiazine (5b). This
1H-NMR: d 9.01 (s, 1H, NH), 7.9–6.55 (m, 4H, ArH), 2.28
(s, 3H, CH3 at C6), 2.25 (s, 3H, CH3 at C8); 13C-NMR: d 118.2
(C-1), 139.1 (C-2), 144.1 (C-3), 132.2 (C-4), 144.2 (C-6),126.4
(C-7), 143.2 (C-8), 116.5 (C-9), 16.5 (CH3 at C-6), 13.5 (CH3 at
C-8); ms: m/z 339 (M+), 341 (M + 2), 338 (35), 304 (50), 207
(100) etc. Anal. Calcd. For C14H11N2O4ClS: C, 49.63; H, 3.24;
N, 8.27. Found: C, 49.83; H, 3.23; N, 8.21.
compound was obtained as reddish crystals, m.p. 200ꢂC; yield
1
85%; IR: NH 3370, CCl 785, CH 2940 cmꢀ1; H-NMR: d 8.82
(s, 1H, NH), 7.58–6.85 (m, 4H, ArH), 2.25 (s, 3H, CH3 at C6),
2.20 (s, 3H, CH3 at C8); 13C-NMR: d 121.2 (C-1), 135.8 (C-2),
148.8 (C-3), 125.0 (C-4), 139.2 (C-6), 131.8 (C-7), 138.0
(C-8), 121.9 (C-9), 15.5 (CH3 at C-6), 14.2 (CH3 at C-8); ms: m/z
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

714
N. Gautam, S. Gupta, N. Ajmera, and D. C. Gautam
Vol 49
Table 3
Antimicrobial activity of synthesized compounds.
Antibacterial activity
Anti fungal activity
Compound
(zone of inhibition in mm)
(zone of inhibition in mm)
Coagulis
positive
Coagulis
negative
Compd.
R1
R2
R3 R4
R5
R6
R7
R8 Enterobacter Staphylococci
Staphylococci
Candida albicans
5a
5b
5c
5d
6a
6b
6c
6d
H
H
H
F
H
H
H
F
H
H
H
F
CH3
CH3
CH3
F
CH3
CH3
CH3
F
CH3
CH3
CH3
F
H
H
H
F
H
H
H
F
H
H
H
F
CH3
CH3
CH3 CF3
H
CH3
CH3
CH3 CF3
H
CH3
CH3
H
H
Cl
Cl
H
H
NO2
NO2
COOH
H
NO2
NO2
COOH
H
Cl
H
H
H
Cl
H
H
H
Cl
H
H
H
–
–
12
16
10
–
–
15
–
–
12
–
–
17
–
12
–
12
17
11
–
11
16
–
11
10
12
18
10
14
–
16
20
17
20
15
15
–
10
10
12
22
11
13
16
–
14
10
21
18
–
–
25
NO2
H
H
H
Cl
Cl
H
NO2
H
H
H
7a
7b
7c
Cl
Cl
H
NO2
NO2
COOH
–
CH3 CF3
NO2
15
12
15
–
7d
H
H
Vancomycin
Gatifloxacin
Flucanazole
–
–
Note < 7 mm inactive;
7–9 mm weakly active;
10–12 mm, moderately
active; > 12 mm, active
< 7 mm, inactive;
7–11 mm, weakly active;
12–17 mm, moderately
active; > 17 mm active
1-Trifluoromethyl-6,8-dimethyl-3-nitro-10H-phenothiazine-
5,5-dioxide (sulfone) (6c). This compound was obtained as
creamish crystals, m.p. 230ꢂC; yield 48%; IR: NH 3410, CS
1040 cmꢀ1;1H-NMR: d 9.22 (s, 1H, NH), 8.02–6.85 (m, 4H,
ArH), 2.18 (s, 3H, CH3 at C6), 2.10 (s, 3H, CH3 at C8);
13C-NMR: d 158.1 (C-1), 131.2 (C-2), 145.1 (C-3), 134.3 (C-4),
143.1 (C-6), 128.2 (C-7), 145.1 (C-8), 114.2 (C-9), 14.3 (CH3
at C-6), 12.1 (CH3 at C-8); ms: m/z 372 (M+), 371 (35), 303
(50), 207 (100) etc. Anal. Calcd. For C15H11N2O4F3S: C, 48.38;
H, 2.95; N, 7.52. Found: C, 48.26; H, 2.91; N, 7.49.
filtered, concentrated and kept in refrigerator overnight to get
crystalline ribofuranosides.
N-(20,30,50-tri-O-benzoyl)-b-D-ribofuranosyl-2,4-dichloro-
6,8-dimethyl-10H-phenothiazine (7a). This compound was
obtained as shiny brownish crystals, m.p. 96ꢂC; yield 65%; IR
CCl 795, COC 1150 cmꢀ1 1H-NMR: d 7.8–6.55 (m, 19H,
;
ArH), 2.32 (s, 3H, CH3 at C6), 2.30 (s, 3H, CH3 at0 C8), 6.35
0
0
(d,1H, C1 -H), 5.66 (m,1H, C2 -H), 5.68 (m,1H, C3 -H), 4.21
(m,1H, C4 -H), 4.80 (CH2 proton); 13C NMR: d 122.5 ( C-1),
0
136.0 (C-2), 130.8 (C-3), 138.5 (C-4), 139.6 (C-6), 130.2 (C-7),
137.2 (C-8), 122.5 (C-9), 95.5 (C-1’), 89.0 (C-2’), 90.5 (C-3’),
97.0 (C-4’), 77 (CH2); ms: m/z 740 (M+), 742 (M + 2), 739
(31), 669 (58), 619 (100) etc. Anal. Calcd. For C40H31NO7Cl2S:
C, 64.86; H, 4.19; N, 1.89. Found: C, 64.98; H, 4.15; N, 1.88.
N-(20,30,50-tri-O-benzoyl)-b-D-ribofuranosyl-2-chloro-6,8-
dimethyl-3-nitro-10H- phenothiazine (7b). This compound
was obtained as dark brown crystals, m.p. 120ꢂC; yield 68%;
3-Carboxy-7,8,9-trifluoro-1-nitro-10H-phenothiazine-5,5-
dioxide (sulfone) (6d).
This compound was obtained as
blackish crystals, m.p. 250ꢂC; yield 50%; IR: NH 3390, NO2
1595,1410, CF 1240, CS 1080 cmꢀ1;1H-NMR: d 8.90 (s, 1H,
NH), 7.70–6.52 (m, 4H, ArH), 11.15 (s, 1H, COOH); 13C-NMR:
d 146.0 (C-1), 131.0 (C-2), 149.0 (C-3), 132.1 (C-4), 122.1
(C-6), 152.8 (C-7), 192.3 (C-8), 149.0 (C-9); ms: m/z 374 (M+),
357 (100), 354 (72), 328 (60), 327 (55) etc. Anal. Calcd. For
C13H5N2O6F3S: C, 41.71; H, 1.33; N, 7.48. Found: C, 41.89; H,
1.30; N, 7.45.
1
IR: CCl 790, COC 1150 cmꢀ1; H-NMR: d 7.50–6.52 (m,19H,
ArH), 2.20 (s,0 3H, CH3 at C6), 20.21 (s, 3H, CH3 at C8),
0
6.37 (d,1H, C1 -H), 5.65 (m,1H, C2 -H), 5.70 (m,1H, C3 -H),
General procedure for the synthesis of N-(20,30,50-tri-O-
benzoyl)-b-D-ribofuranosyl-10H-phenothiazines (7a–d). To
a solution of 5a–d (0.002 mol) in toluene, b-D-ribofuranose-
1-acetate-2,3,5-tribenzoate (0.002 mol) was added, and the
contents were refluxed in vaccum with stirring in an oil bath
at 155–160ꢂC for 15 min. The vaccum was removed and the
reaction mixture was protected from moisture by fitting a
guard tube. Stirring was further continued for 10 h, and
vaccum was applied for 10 min at every hour. The viscous
mass thus obtained was dissolved in methanol and boiled for
10 min and cooled to room temperature. The reaction
mixture was filtered and filtrate was evaporated to dryness.
The viscous residue, thus obtained was dissolved in ether,
4.25 (m,1H, C4 -H), 4.85 (CH2 proton); 13C-NMR: d 124.1
0
(C-1), 137.2 (C-2), 148.1 (C-3), 124.2 (C-4), 138.6 (C-6),130.2
(C-7), 137.2 (C-8), 120.1 (C-9), 92.1 (C-1’), 88.2 (C-2’), 91.0
(C-3’), 98.3 (C-4’), 79 (CH2); ms: m/z 751 (M+), 753 (M + 2),
750 (35), 716 (60), 619 (100) etc. Anal. Calcd. For
C40H31N2O9ClS: C, 63.95; H, 4.13; N, 3.73. Found: C, 63.62;
H, 4.02; N, 3.65.
N-(20,30,50-tri-O-benzoyl)-b-D-ribofuranosyl-1-trifluoromethyl-
6,8-dimethyl-3-nitro-10H-phenothiazine (7c). This compound
was obtained as shiny black crystals, m.p. 115ꢂC; yield 58%;
IR: CF3 1355,1100, COC 1190 cmꢀ1 1H-NMR: d 8.05–7.01
;
(m, 19H, ArH), 2.16 (s, 3H, CH3 at C6), 2.08 (s, 3H, CH3
0
0
at C8), 6.40 (d,1H, C1 -H), 5.68 (m,1H, C2 -H), 5.85 (m,1H,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

May 2012
Synthesis, Characterization, and Biological Evaluation of 10H-Phenothiazines,
Their Sulfones and Ribofuranosides
715
C3 -H), 4.35 (m,1H, C4 -H), 4.90 (CH2 proton); 13C-NMR: d
164.1 (C-1), 130.2 (C-2), 155.2 (C-3), 120.8 (C-4), 139.0 (C-6),
128.8 (C-7), 139.5 (C-8), 120.0 (C-9), 95.6 (C-1’), 90.0 (C-2’),
91.2 (C-3’), 96.2 (C-4’), 80 (CH2); ms: m/z 784 (M+), 783 (31),
715 (55), 619 (100) etc. Anal. Calcd. For C41H31N2O9F3S: C,
62.75; H, 3.95; N, 3.57. Found: C, 62.67; H, 3.92; N, 3.61.
N-(20,30,50-tri-O-benzoyl)-b-D-ribofuranosyl-3-carboxy-7,8,9-
trifluoro-1-nitro-10H-phenothiazine (7d). This compound was
obtained as blackish crystals, mp 105ꢂC; yield 45%; IR: NO2
taken at 30ꢂC at intervals of exactly 1–6 min later. All
determinations were carried out in triplicate (Table 2 and Fig. 1).
Antimicrobial activity. The synthesized compounds were
tested for their antibacterial activity by using Paper Disc method
[17] by measuring the zone of inhibition on agar plates with
Enterobacter, Coagulase positive Staphylococci, and Coagulase
negative staphylococci as test organisms at concentration of
100 mg per disc using vancomycin and gatifloxacin as standard
compounds and antifungal activity against Candida albicans at
concentration of 100 mg/disc using flucanazole as standard
compound (Table 3).
0
0
1580, 1400, CF 1235, COC 1185 cmꢀ1; H-NMR: d 8.25–6.90
(m,18H, ArH), 11.6 (s, 1H, COOH), 6.42 (d,1H, C1 -H), 5.98
1
0
0
0
0
(m,1H, C2 -H), 5.80 (m,1H, C3 -H), 4.40 (m,1H, C4 -H), 4.92
(CH2 proton); 13C-NMR: d 150.1( C-1), 124.2(C-2), 148.1 (C-3),
125.2 (C-4), 112.0 (C-6),150.2 (C-7), 136.1 (C-8), 151.5 (C-9),
95.0 (C-1’), 85.2 (C-2’), 94.1 (C-3’), 98.1 (C-4’), 75 (CH2); ms:
m/z 786 (M+), 769 (100), 756 (60), 740 (50), 739 (48) etc. Anal.
Calcd. For C39H25N2O11F3S: C, 59.54; H, 3.18; N, 3.56. Found:
C, 59.74; H, 3.20; N, 3.48.
Antioxidant activity. All the synthesized compounds were
screened for their antioxidant activity by 1,1-diphenyl-2-
picrylhydrazyl (DPPH) radical scavenging assay and 2,2-
azinobis(3-ethyl benzothiazoline-6-sulfonic acid) ABTS•+ radical
cation decolorization assay.
Acknowledgment. The authors thank Department of Chemistry,
University of Rajasthan, Jaipur for providing necessary facilities,
CDRI, Lucknow for mass spectral analysis, S.M.S. Medical
College, Jaipur, for antimicrobial activity, and Department of
Zoology, University of Rajasthan, Jaipur, for antioxidant
activity of synthesized compounds. UGC Research Award
Scheme is duly acknowledged for financial assistance.
REFERENCES AND NOTES
DPPH radical scavenging assay. Radical scavenging activity of
synthesized compounds against stable 1,1-diphenyl-2-picrylhydrazyl
(DPPH) radical was determined spectrophotometrically as described
by Cuendet et al. [15]. A stock solution containing 1 mg/mL of the
compound was prepared in methanol. Fifty microlitres of the solution
were added to 5 mL of a 0.004% methanol solution of DPPH. After
30 min of incubation in the dark at room temperature, the absorbance
was read against a blank at 517 nm.
[1] Bodea, C.; Faroasan, V.; Panea, T. Rev Roum de Chim 1966,
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[5] Bauer, A. W.; Kibby, W. M. M.; Sherries, J. C.; Truck, M. Am
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The assay was carried out in triplicate and the percentage of in-
hibition (Table 1) was calculated using the following formula.
[7] Singh, G.; Kumar, N.; Yadav, A. K. Heteroatom Chem 2003,
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[8] Kachee, T. L.; Gupta, V.; Gautam, D. C.; Gupta, R. R. Phos-
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ðAB ꢀ AAÞ
% Inhibition ¼
ꢄ 100
AB
[9] Rathore, B. S.; Kumar, M. Bioorg Med Chem 2006, 14, 5678.
[10] Gautam, V.; Sharma, M.; Samarth, R. M.; Gautam, N.; Kumar,
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[11] Dixit, R.; Dixit, Y.; Gautam, D. C.; Gautam, N. Phosphorus
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[12] Dixit, R.; Gautam, N.; Gautam, D. C. Jordan J Chem 2008, 3,
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[13] Sharma, P. R.; Gautam, D. C.; Gupta, V.; Gupta, R. R. Hetero-
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[14] Samarth, R. M.; Panwar, M.; Kumar, M.; Kumar, A. Mutagen-
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[15] Cuendet, M.; Hostettmann, K.; Potterat, O. Hel Chem Acta
1997, 80, 1144.
[16] Re, R.; Pellegrini, N.; Proteggente, A.; Pannala, A.; Yang, M.;
Rice-Evans, C. Free Radical Biol Med 1999, 26, 1231.
[17] Gould, J. C.; Browie, J. H. Edinb Med J 1950, 59, 178.
where AB = Absorption of blank, AA = Absorption of test.
ABTS radical cation decolorization assay.
The 2,2-
azinobis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation
(ABTS) decolorization test was also used to assess the
antioxidant activity of synthesized compounds. The ABTS•+
assay was carried out using the improved assay of Re et al.
[16]. In short, ABTS•+ was generated by oxidation of ABTS
with potassium persulphate. For this purpose, ABTS was
dissolved in deionized water at a concentration of 7 mM, and
potassium persulphate added to a concentration of 2.45 mM.
The reaction mixture was left at room temperature overnight
(12–16 h) in the dark before use; the ABTS solution then was
diluted with ethanol to an absorbance of 0.700 ꢃ 0.020 at
734 nm. After addition of 1 mL of the diluted ABTS solution to
10 mL of compound and mixing, absorbance readings were
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet