Synthesis and biological activities of some N-hydroxymethylene and N-methoxymethylene thiazines

Article abstract of DOI:10.1007/s00044-007-9059-y

A series of new 3,5-diaryl-N-hydroxymethylene-1,4-thiazine-1,1-dioxides and 3,5-diaryl-N-methoxymethylene-tetrahydro-1,4-thiazines-1,1-dioxides were synthesized and their antimicrobial activities were tested against Gram-positive (Bacillus subtilis, Streptococci) and Gram-negative bacteria (Escherichia coli and Klebsiella penumoniae) and against the fungi Penicillium inclobium and Aspergillus flavus. The synthesized compounds have been characterized on the basis of elemental analyses, infrared spectroscopy (IR), and nuclear magnetic resonance (NMR).

Full text of DOI:10.1007/s00044-007-9059-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2007) 16:402–407
DOI 10.1007/s00044-007-9059-y
ORIGINAL RESEARCH
Synthesis and biological activities of some
N-hydroxymethylene and N-methoxymethylene
thiazines
V. Sundari Æ G. Nagarajan Æ R. Valliappan
Received: 21 February 2007 / Accepted: 12 November 2007 / Published online: 19 December 2007
¨
Ó Birkhauser Boston 2007
Abstract A series of new 3,5-diaryl-N-hydroxymethylene-1,4-thiazine-1,1-diox-
ides and 3,5-diaryl-N-methoxymethylene-tetrahydro-1,4-thiazines-1,1-dioxides
were synthesized and their antimicrobial activities were tested against Gram-posi-
tive (Bacillus subtilis, Streptococci) and Gram-negative bacteria (Escherichia coli
and Klebsiella penumoniae) and against the fungi Penicillium inclobium and
Aspergillus flavus. The synthesized compounds have been characterized on the basis
of elemental analyses, infrared spectroscopy (IR), and nuclear magnetic resonance
(NMR).
Keywords Thiazine Á Antibacterial activity Á N-methoxymethylene derivatives
Introduction
The importance of heterocyclic compounds has long been recognized in the field of
synthetic organic chemistry. In recent years, the literature has been enriched with
progressive findings about the synthesis and pharmacological action of heterocycles.
The thiazine nucleus of benzothiazines, phenothiazines, and tetrahydro-1,4-
thiazines constitute an important class of sulfur and nitrogen heterocycles. They
are associated with diverse pharmacological properties, such as antibacterial,
antifungal, and antihistaminic activities (Kartrizky, 1985;Ramana Reddy et al.,
1990; Bhaskar Reddy, 2000; Sundari, 2004). In this work, we have focused our
interest on incorporating N-methoxymethylene into the thiazine (nucleus) moiety in
V. Sundari (&) Á G. Nagarajan
Division of Chemistry, FEAT, Annamalai University, Annamalai Nagar, chidambaram,
Tamil Nadu 608 002, India
e-mail: rmvs1962@yahoo.com
R. Valliappan
Chemistry Wing, DDE, Annamalai University, Annamalai Nagar, chidambaram, Tamil Nadu, India

Med Chem Res (2007) 16:402–407
403
one framework, hoping to obtain few compounds that possess better antimicrobial
activity. Ten new compounds have been synthesized and characterized.
Baliah and Rangarajan (1954) synthesized 3,5-diaryltetrahydro-1,4-thiazine-1,1-
dioxides (1) by the condensation of sulfonyl diacetic acid with aryl aldehydes and
ammonia. The N-methyl derivatives of substituted tetrahydro-1,4-thiazine-1,1-
dioxides were synthesized by Pandiarajan and Newton Benny (1994).
In the present study we synthesized some 3,5-diaryl-N-hydroxymethylene-
tetrahydro-1,4-thiazine-1,1-dioxides 4–6. This transformation is carried out by
treating thiazine with hot ethanol, formalin, and 10% sodium hydroxide solution.
The N-methoxymethylene derivatives 7–9 were prepared from their respective
N-hydroxymethylene thiazine with dry acetone, dimethyl sulfate and anhydrous
potassium carbonate by refluxing for four hours (Scheme 1). The structure of these
compounds was confirmed by elemental, IR, and 1H and 13C NMR spectral analysis.
The chemical data for compounds are given in Table 1.
O
O
S
H2O2/CH3COOH
20oC, 2h
S
COOHCH2
CH2COOH
COOHCH2
CH2COOH
2PhCHO +NH4OAc
Acetic acid
O
O
O
O
S
N
S
HCHO/10 % NaOH
H2O
N
H
CH2OH
X
X
X
X
4-6
1-3
DMSO
Me2CO/K2CO3
X
O
O
7= H
S
1
6
5
2
3
8 = -OCH3,
9 = -Cl
4
N
X
CH2OCH3
X
7-9
Scheme. 1

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Med Chem Res (2007) 16:402–407
Table 1 Chemical data of the synthesized compounds 4–9
Compounds
Melting point
Yield (%)
Molecular formula
Elemental analysis
C (%)
H (%)
N (%)
4
5
6
7
8
9
199
217
219
199
201
210
42
40
52
48
52
56
C17H17NO3S
C19H23NO5S
C17H17Cl2NO3S
C18H21NO3S
C19H22NO4S
C18H19NO3SCl
64.12
60.40
56.86
65.20
63.21
53.81
6.01
6.10
4.40
6.32
6.05
4.68
4.36
3.68
3.60
4.12
3.69
3.30
Biological activity
The screening of newly synthesized antimicrobial chemotherapeutic compounds
provides potentially effective treatments for many dreadful diseases. Biochemical
studies help to test the efficacy and existing toxicity of the compounds that possess
antimicrobial properties. Compounds 7–9 were evaluated for their antibacterial
activity in vitro against the Gram-positive cocci, such as Bacillus subtitles and
Streptococci, and Gram-negative bacilli, including Klebseilla pneumoniae, Escher-
chiae coli, using the disc method with concentrations of 25, 50, and 100 lg/ml.
Acetone was used as a control and norfloxacin was used as the standard.
To test for antibacterial activity, plates containing nutrient agar were seeded with
different organisms at a concentration of 2–3 9 10-7 colony forming units (CFU)
using a sterile swab. The filter paper discs containing the synthesized compounds
were placed at different positions with the help of fine-pointed forceps. The plates
were incubated at 37°C for 24 hours and the zone of inhibition was measured.
The antifungal activity of the synthesized compounds 7–9 was also tested. The
subculture and the viable count were carried out by the same procedure as for the
antibacterial studies. The temperature maintained at 28 1°C and the results were noted
after 72–96 hours. The concentration of the test compound was as described previously,
and solvent and griesoflavin (standard drug) were used for the antifungal studies.
The compounds with chloro- (25 lg/ml) or methoxy- (50 lg/ml) groups on the
phenyl moiety were found to have appreciable activity when compared to
unsubstituted compounds (at concentrations greater than 100 lg/ml) (Table 2).
Table 2 Antibacterial activity of compounds 7–9
Compound
K. pneumoniae
E. coli
B. subtilis
S. aureus
P. inclobium
A. flavus
7
7
9
6
7
7
6
8
11
16
22
–
11
16
22
–
12
15
22
–
12
15
22
–
11
14
–
10
12
–
9
Norfloxacin
Griesoflavin
22
22
Zone of inhibition: inactive \8 mm; moderate 9–12 mm; active [12 mm

Med Chem Res (2007) 16:402–407
405
Acute toxicity studies (LD50 determination)
Acute toxicity studies were undertaken to identify lethal dose 50 (LD50) of the
compounds 3 and 6, respectively. According to the method of Miller and Tainter (1944),
with little modification except that different doses were used, colony-bred male albino
mice weighing 20–30 g were taken and divided into five groups of ten animals each.
The observed percentage mortality results were converted into probit values,
which were then plotted against dose. The LD50 values of the active compounds
were found to be nontoxic in mice at oral doses of up to 1000 mg/kg.
Experimental section
General
Melting points were recorded in open capillary tube and are uncorrected. Melting
points and other data are recorded in Table 1. IR spectra were recorded in KBr on a
Perkin–Elmer spectrophotometer and 1H NMR spectra on a Bruker AMXC-500 FT
NMR spectrometer in CDCl3 using TMS as an internal standard. The chemical
shifts have been expressed in d ppm. The purity of the compounds was checked on
silica gel-coated aluminum plates (Merck).
General method for the preparation of 3,5-diaryl-tetrahydro-1,4-thiazine-1,1,-
dioxide (1–3)
All of the parent 3,5-diaryl-tetrahydro-1,4-thiazine-1,1-dioxides were prepared
according to the procedure of Baliah and Rangarajan (1954) by the condensation of
sulfonyl diacetic acid with araldehydes and ammonium acetate.
General method for the preparation of 3,5-diaryl-N-hydroxymethylene-
tetrahydro-1,4-thiazine-1,1-dioxides (4–6)
To the hot solution of the respective thiazines (1–3) (0.01 M) dissolved in 20 ml of
ethanol, 30 ml of formalin solution was added. A white precipitate was obtained.
Ten milliliters of 10% sodium hydroxide solution was added and shaken vigorously
to obtain a clear solution. This was kept overnight, and then sufficient water was
added to obtain a white precipitate. This was filtered, washed with enough cold
water to make it free from alkali, and then dried. The crude product was
recrystallized from aqueous ethanol. Homogeneity of the product was checked by
thin-layer chromatography (TLC).
3,5-Diphenyl-N-hydroxymethylene-tetrahydro-1,4-thiazine-1,1-dioxide (4)
IR: cm-1 (KBr) 1127.24, 1301.27, 1361.18 (SO2), 3346.48 (-OH). Mass: m/z 313
(M+) (M.F.: C17H17NO3S). 1H NMR: 3.16–3.38 H2 and H6 (m), 4.40 H3 and H5 (t),

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Med Chem Res (2007) 16:402–407
7.25–7.45 aryl (m), 2.10 N-CH2 (s), 4.60 CH2OH (s). 13C NMR: 59.81 (C2 and C6),
59.47 (C3 and C5), 70.10 (CH2OH), 127.17–140.73 (aromatic).
3,5-Bis(p-methoxyphenyl)-N-hydroxymethylene-tetrahydro-1,4-thiazine-1,1-
dioxide (5)
IR: cm-1 (KBr) 1115.09, 1301.30, 1353.68 (SO2), 3438.34 (-OH). Mass: m/z (M+)
371.45 (M.F.: C19H23NO5S) 1H NMR: 3.30 H2 and H6 (d), 4.40 H3 and H5 (t), 6.8, 7.11
aryl (d), 3.8 -OCH3 (s), 2.10 N-CH2 (s), 4.60 CH2OH (s). 13C NMR: 55.84(C2 and C6),
55.74(C3 and C5), 58.82 (O-CH3), 70.73 (CH2OH), 114.84–162.40 (Aromatic).
3,5-Bis(p-chlorophenyl)-N-hydroxymethylene-tetrahydro-1,4-thiazine-1,1-
dioxide (6)
IR: cm-1 (KBr) 1121.19, 1302.62, 1355.99 (SO2), 3440.28 (-OH). Mass: m/z 386.29
1
(M.F.: C17H17Cl2NO3S) H NMR: 3.16–3.35 H2 and H6 (m), 4.41 H3 and H5 (t),
7.25–7.45, Aryl (m), 2.10 N-CH2(s), 4.61 CH2OH (s). 13C NMR: 58.58 (C2 and C6),
58.74 (C3 and C5), 58.82 (O-CH3), 70.73 (CH2OH), 114.84–162.40 (aromatic).
General method of preparation of 3,5-diaryl-N-methoxymethylene-tetrahydro-
1,4-thiazine-1,1-dioxides (7–9)
About 0.005 M of N-hydroxymethylene thiazine (4–6) was dissolved in 25 ml of dry
acetone and 10 ml of dimethyl sulfate was added, followed by 3 g of anhydrous
potassium carbonate. This mixture was refluxed for four hours. After cooling to
room temperature the inorganic salt was filtered off and the filtrate was concentrated
and poured onto crushed ice. The solid obtained was filtered, washed with water and
recrystallized from methanol to yield 62% colorless crystalline compound. The
homogeneity of the product was determined by TLC.
3,5-Diphenyl-N-methoxymethylene-tetrahydro-1,4-thiazine-1,1-dioxide (7)
IR: cm-1 (KBr) 1120.44, 1306.25, 1331.19 (SO2), 1150–1085 (aliphatic ether
1
linkage) Mass: m/z 331.42 (M.F.: C18H21NO3S). H NMR: 3.12–3.30 H2 and H6
(m), 4.41 H3 and H5 (t), 7.25–7.45, aryl (m), 2.10 N-CH2(s), 3.92 CH3 (s). 13C
NMR: 58.12(C2 and C6), 59.57(C3 and C5), 67.12 (CH2O), 57.98 (OCH3), 127.17–
140.73 (aromatic).
3,5-Bis(p-methoxyphenyl)-N-methoxymethylene-tetrahydro-1,4-thiazine-1,1-
dioxide (8)
IR: cm-1 (KBr) 1111.23, 1301.32, 1345.23 (SO2), 1150–1085 (aliphatic ether
linkage) Mass: m/z: 391.47 (M.F.: C20H25NO5S) 1H NMR: 3.30 H2 and H6 (d), 4.40

Med Chem Res (2007) 16:402–407
407
H3 and H5 (t), 6.8, 7.11 aryl (d), 3.8 -OCH3 (s), 2.10 N-CH2 (s), 3.90 CH3 (s). 13C
NMR: 55.40 (C2 and C6), 55.14 (C3 and C5), 58.42 (O-CH3), 67.73 (CH2O), 57.45
(OCH3), 115.24–161.20 (aromatic) 132.49 (ipso).
3,5-Bis(p-chlorophenyl)-N-methoxymethylene-tetrahydro-1,4-thiazine-1,1-
dioxide (9)
IR: cm-1 (KBr) 1113.13, 1302.33, 1342.38 (SO2), 1150–1085 (aliphatic ether
linkage) Mass: m/z: 400.31 (M.F.: C18H19NO3SCl2). 1H NMR: 3.16–3.35 H2 and H6
(m), 4.41 H3 and H5 (t), 7.25–7.45 Aryl (m), 2.10 N-CH2 (s), 3.90 CH3 (s). 13C
NMR: 55.78 (C2 and C6), 59.24 (C3 and C5), 67.03 (CH2O), 114.84–162.40 57.12
(OCH3), 128.20–129.41 (aromatic) 141. 80 (ipso).
Acknowledgements The authors are grateful to the university authorities for providing the necessary
facilities to carry out this research work, and the sophisticated instrumentation facilities available at
Madurai Kamaraj University, IISc., Bangalore for recording the spectra, as well as the Department of
Microbiology and Central Animal House, Rajah Muthiah Medical College, for providing the facilities for
biological evaluation.
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