3H-[1,2]Dithiolo[3,4-b]pyridine-3-thione and its derivatives. Synthesis and antimicrobial activity

Article abstract of DOI:10.1016/S0014-827X(00)00084-7

A series of 2-substituted isothiazolo[5,4-b]pyridine-3(2H)-thiones, isothiazolo[5,4-b]pyridin-3(2H)-ones, N-substituted 2-sulfanylnicotinamides and the corresponding carbothioamide derivatives were synthesized and evaluated for their antimicrobial activity against several strains of Gram+ and Gram-bacteria and fungi. Chemical syntheses were resumed into a comprehensive cyclic route that enables the reversible conversion for each derivative of the series considered. Among the tested compounds the N-(aralkyl)-2-sulfanylnicotinamides show the highest fungitoxicity (MIC=1.25-5 μg/ml). The best activity towards Gram-positive bacteria was in the range of 2.5-5 μg/ml. Activity against Gram-negative bacteria was generally very poor for all compounds. Copyright

Full text of DOI:10.1016/S0014-827X(00)00084-7

www.elsevier.nl/locate/farmac
Il Farmaco 55 (2000) 669–679
3H-[1,2]Dithiolo[3,4-b]pyridine-3-thione and its derivatives
Synthesis and antimicrobial activity
Massimo Pregnolato a,*, Marco Terreni a, Daniela Ubiali a, Giuseppe Pagani a,
Pietro Borgna a, Fiorenzo Pastoni b, Fabrizio Zampollo b
a Dipartimento di Chimica Farmaceutica, Uni6ersita` degli Studi, 6ia Taramelli 12, 27100 Pa6ia, Italy
b Joint Research Centre, En6ironment Institute, Food and Drug, Laboratory of Microbiology, 6ia E. Fermi, 21020 Ispra (Va), Italy
Received 22 February 2000; accepted 31 July 2000
Abstract
A series of 2-substituted isothiazolo[5,4-b]pyridine-3(2H)-thiones, isothiazolo[5,4-b]pyridin-3(2H)-ones, N-substituted 2-sul-
fanylnicotinamides and the corresponding carbothioamide derivatives were synthesized and evaluated for their antimicrobial
activity against several strains of Gram+ and Gram−bacteria and fungi. Chemical syntheses were resumed into a comprehensive
cyclic route that enables the reversible conversion for each derivative of the series considered. Among the tested compounds the
N-(aralkyl)-2-sulfanylnicotinamides show the highest fungitoxicity (MIC=1.25–5 mg/ml). The best activity towards Gram-posi-
tive bacteria was in the range of 2.5–5 mg/ml. Activity against Gram-negative bacteria was generally very poor for all compounds.
© 2000 Elsevier Science S.A. All rights reserved.
Keywords: 3H-[1,2]Dithiolo[3,4-b]pyridine-3-thiones; Isothiazolo[5,4-b]pyridin-3(2H)-ones; Isothiazolo[5,4-b]pyridine-3(2H)-thiones; 2-Sulfanylni-
cotinamides; 2-Sulfanylpyridine-3-carbothioamides; Antimicrobial activity
potential use as products of industrial interest (agro-
chemicals, veterinary medicines and preservative addic-
1. Introduction
tives for inks, paints and photographics) [7–9]. An
extensive study on benzene substituents has been done
concluding that the position and the nature of the
substituent influence the S–N bond reactivity and, as a
consequence, the antimicrobial activity [10]. It has also
been determined that the N-substitutions can influence
the lipophilicity of the structure with a minor influence
During the last two decades, a large number of
2-substituted 1,2-benzisothiazolo-3(2H)-ones (A) [1–3]
and 1,2-benzisothiazolo-3(2H)-thiones (B) [4–6] (Fig.
1) have been claimed to have several biological activi-
ties. The antifungal and antibacterial properties of these
compounds have opened up the possibility of their
upon the antimicrobial activity [11]. The substitution of
sulfur (B) for oxygen (A) in the ketobenzisothiazole
system generally increases the strength of the S–N
bond; although a strict structure–activity relationship
could not be determined since a dynamic equilibrium
occurs in the biological test medium with the corre-
sponding 3-imino-3H-1,2-benzodithiole [12,13]. Consid-
Fig. 1. 1,2-benzisothiazol-3(2H)-ones (A); 1,2-benzisothiazol-3(2H)-
thiones (B); isothiazolo[5,4-b]pyridin-3(2H)-ones (C); isothiazolo[5,4-
erable attention has been successfully devoted to the
investigation of 1,2-benzisothiazolo-3(2H)-one isosters,
b]pyridine-3(2H)-thiones
(D);
2-sulfanylnicotinamides
(E);
namely isothiazolo[5,4-b]pyridin-3(2H)-ones (C), where
benzene is replaced by a pyridine ring [14,15]; some
patents claimed their fungicidal and antibacterial prop-
erties [16], their activity as inhibitors of blood platelet
aggregation [17] and as antiacne agents [18]. In our
2-sulfanylpyridine-3-carbothioamides (F).
* Corresponding author. Tel.: +39-0382-507 583; fax: +39-0382-
507 583.
E-mail address: maxp@pbl.unipv.it (M. Pregnolato).
0014-827X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0014-827X(00)00084-7

670
M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
Scheme 1. I: Lawesson’s reagent, toluene, 5 h, 75% yield. II: R–NH2, abs. EtOH, 75–83% yields. III: I2/NaHCO3, abs. EtOH, 60–70% yields.
IV: Hg(CH3COO)2, CHCl3/CH3COOH, 35–40% yields. V: H2S, EtOH, 80–85% yields. VI: Lawesson’s reagent, toluene, 30 min, 90% (ponderal
yield). VII: Lawesson’s reagent, toluene, 3 h, 70–77% yields. VIII: Hg(CH3COO)2, CHCl3/CH3COOH, 45–59% yields. IX: R–NH2 abs EtOH,
63–90% yields. X: I2/NaHCO3, abs. EtOH, 74–81% yields. XI: Lawesson’s reagent, toluene, 1.5 h, 26–31% yields. XII: H2S, EtOH, 78–82%
yields. XIII: P4S10, xylene, 2 h, 60–66% yields. XIV: Hg(CH3COO)2, CHCl3/CH3COOH, 32–37% yields.
previous paper [19] we studied the chemistry of isothia-
zolo[5,4-b]pyridine-3(2H)-thione (D) synthesizing some
N-substituted derivatives. Structure (D), the thio-ana-
logue of isothiazolo[5,4-b]pyridin-3(2H)-ones (C), is ex-
pected to have a similar biological activity and in this
paper some N-alkyl and N-aralkyl isothiazolo[5,4-
b]pyridine-3(2H)-thiones have been synthesized as po-
tential novel antimicrobial agents.
A lipophilicity study has also been done in order to
establish a potential structure–activity relationship for
these classes of compounds.
2. Results and discussion
Following new synthetic protocols, a cyclic route of
synthesis has been developed starting from 2-mercap-
tonicotinic acid (1) to give 3H-[1,2]dithiolo[3,4-
b]pyridine-3-thione (2). From compound 2 both the
thiocarbonyl- (D and F) and the carbonyl- derivatives
(C and E) can be easily prepared through different
pathways according to Scheme 1. All the obtained
products 3–7 (a–g) were tested for their antimicrobial
activity against several strains of Gram+, Gram−
bacteria and fungi, in order to evaluate both the effect
of the thiocarbonyl-oxocarbonyl substitution on the
SꢀN isothiazolo[5,4-b]pyridine ring opening (to give
structures 3 and 7), and the influence of the lipophilicity
apported by different N-alkyl or N-aralkyl chains.
2.1. Chemistry
Chemical syntheses are included into a comprehen-
sive cyclic route that enables the reversible conversion
for each derivative of the series considered (Scheme 1).
In order to obtain the desired compounds 3–7 (a–g)
and 8, novel synthetic procedures were exploited in-
volving the interconversion between oxo-carbonyl and
thio-carbonyl derivatives by using Lawesson’s reagent
(CꢁO“CꢁS) (Reactions I, VII, XI) [20] or mercuric
acetate (CꢁS“CꢁO) (Reactions IV, VIII, XIV) [14].
3H-[1,2]dithiolo[3,4-b]pyridine-3-thione (2) is usually
prepared by cyclization of 2-mercaptonicotinic acid (1)
with phosphorous pentasulfide in anhydrous pyridine in

M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
671
a good yield (95%) [14]; in this study, a novel approach
was attempted using Lawesson’s reagent and sulfur but
a lower yield was obtained (Reaction I, 75% yield). By
reaction between 2 and the appropriate primary amine,
the N-substituted 2-sulfanylpyridine-3-carbothioamides
3a–g were obtained in rapid equilibrium with the 2-thi-
oxo-1,2-dihydropyridine-3-carbothioamides forms [19]
(Reaction II, 75–83% yields). The preparation of isoth-
iazolo[5,4-b]pyridine-3(2H)-thiones 4a–g was per-
formed with iodine by oxidative cyclization of the
Isothiazolo[5,4-b]pyridin-3(2H)-ones 6a–g were ob-
tained by desulfurization of the corresponding thio-
derivatives 4a–g by mercuric acetate in glacial acetic
acid in 35–40% yield (Reaction IV) [14]. The complete
conversion of bicyclic 6a–g into the 2-sulfanylnicoti-
namides 7a–g occurred after treatment with hydrogen
sulfide (Reaction V, 80–85% yield). All synthesized
compounds were fully characterized and analytical data
are reported in Tables 1–5. In order to facilitate the
formation of derivatives to be tested, 3–7 (a–g), alter-
native synthetic routes have been accomplished. Thus,
the starting material (2) can easily be desulfurized by
treatment with mercuric acetate (Reaction VIII, 45–
59% yields) to give 3H-[1,2]-dithiolo[3,4-b]pyridin-3-
one (8), the starting material of the derivatives 6–7
(a–g). In fact, compounds 7a–g were obtained from 8
by reacting the appropriate amine in absolute ethanol
corresponding
2-sulfanylpyridine-3-carbothioamides
3a–g in ethanol (Reaction III, 60–70% yields). As
previously described [19], the reaction afforded a mix-
ture of N-substituted isothiazolo[5,4-b]pyridine-3(2H)-
thiones 4a–g and N-substituted-N-[3H-[1,2]-dithiolo-
[3,4-b]pyridin-3-ylidene]amines
5a–g,
respectively,
which can be separated by flash chromatography.
Table 1
2-Sulfanylpyridine-3-carbothioamides 3a–g
Comp.
R
m.p. (°C)
Rf (eluent a)
RM
Analyses (C, H, N)
3a
3b
3c
3d
3e
3f
n-C3H7
n-C4H9
167–169
141–143
123–126
122–124
162–164
144–148
133–135
0.41 (A/B (6:4))
0.20 (A/B (6:4))
0.38 (A/B (5:5))
0.37 (A/B (6:4))
0.24 (A/B (6:4))
0.27 (A/B (6:4))
0.28 (A/B (6:4))
−0.217
−0.128
−0.045
+0.084
−0.089
−0.085
+0.002
C9H12N2S2
C10H14N2S2
C11H16N2S2
C12H18N2S2
C13H12N2S2
C14H14N2S2
C15H16N2S2
n-C5H11
n-C6H13
Ph–CH2
Ph–(CH2)2
Ph–(CH2)3
3g
a A hexane; B ethyl acetate; C chloroform; D acetone. 1H NMR (CDCl3) are in accordance with those reported in Ref. [19].
Table 2
Isothiazolo[5,4-b]pyridine-3(2H)-thiones 4a–g
Comp.
R
m.p. (°C)
Rf (eluent a)
RM
Analyses (C, H, N)
4a
4b
4c
4d
4e
4f
n-C3H7
n-C4H9
125–127
105–107
73–75
0.58 (A/B (7:3))
0.61 (A/B (6:4))
0.47 (A/B (8:2))
0.23 (A/B (92:8))
0.26 (A/B (85:15))
0.70 (A/B (65:35))
0.38 (A/B (8:2))
−0.087
+0.002
+0.118
+0.220
+0.339
+0.357
+0.410
C9H10N2S2
C10H12N2S2
C11H14N2S2
C12H16N2S2
C13H10N2S2
C14H12N2S2
C15H14N2S2
n-C5H11
n-C6H13
Ph-CH2
Ph-(CH2)2
Ph-(CH2)3
55–60
162–164
111–115
88–90
4g
a A hexane; B ethyl acetate; C chloroform; D acetone. 1H NMR (CDCl3) are in accordance with those reported in Ref. [19].
Table 3
N-[3H-[1,2]-Dithiolo[3,4-b]pyridin-3-ylidene]amines 5a–g
Comp.
R
m.p. (°C)
Rf (eluent a)
RM
Analyses (C, H, N)
5a
5b
5c
5d
5e
5f
n-C3H7
n-C4H9
oil
0.75 (A/B (7:3))
0.73 (A/B (6:4))
0.60 (A/B (8:2))
0.36 (A/B (9:1))
0.35 (A/B (85:15))
0.82 (A/B (65:35))
0.48 (A/B (8:2))
−0.005
+0.077
+0.173
+0.311
+0.382
+0.426
+0.496
C9H10N2S2
C10H12N2S2
C11H14N2S2
C12H16N2S2
C13H10N2S2
C14H12N2S2
C15H14N2S2
42–46
50–52
60–61
61–62
111–113
oil
n-C5H11
n-C6H13
Ph–CH2
Ph–(CH2)2
Ph–(CH2)3
5g
a A hexane; B ethyl acetate; C chloroform; D acetone. 1H NMR (CDCl3) are in accordance with those reported in Ref. [19].

Table 4
Isothiazolo[5,4-b]pyridin-3(2H)-ones 6a–g
Comp.
6a
R
m.p. (°C)
71–72
68–69
oil
Rf (eluent a)
RM
Analyses
(C, H, N)
1H NMR (CDCl3)
n-C3H7
n-C4H9
n-C5H11
n-C6H13
Ph–CH2
0.26 (A/B (7:3))
0.28 (A/B (6:4))
0.17 (A/B (8:2))
0.33 (A/B (7:3))
0.30 (A/B (7:3))
−0.162
C9H10N2OS
C10H12N2OS
1.10 (t, 3H, CH3, J=7.4 Hz), 1.82 (sextet, 2H, CH2), 3.91 (t, 2H, N–CH2, J=7.4 Hz), 7.38 (dd, 1H,
5H, J6,5=4.5 Hz, J5,4=8.0 Hz), 8.29 (dd, 1H, 4H, J6,4=1.5 Hz, J5,4=8.0 Hz), 8.78 (dd, 1H, 6H,
J
6,5=1.5 Hz, J6,4=4.5 Hz)
6b
0.99 (t, 3H, CH3, J=7.4 Hz), 1.44 (sextet, 2H, CH2), 1.79 (quintet, 2H, CH2), 3.95 (t, 2H, N–CH2,
J=7.4 Hz), 7.33 (dd, 1H, 5H, J6,5=4.5 Hz, J5,4=8.0 Hz), 8.27 (dd, 1H, 4H, J6,4=1.5 Hz, J5,4=8.0
Hz), 8.77 (dd, 1H, 6H, J6,5=1.5 Hz, J6,4=4.5 Hz)
0.90 (t, 3H, CH3, J=7.4 Hz), 1.30–1.49 (m, 4H, CH2), 1.79 (quintet, 2H, CH2), 3.92 (t, 2H, N–CH2,
J=7.4 Hz), 7.42 (dd, 1H, 5H, J6,5=4.5 Hz, J5,4=8.0 Hz), 8.52 (dd, 1H, 4H, J6,4=1.5 Hz, J5,4=8.0
Hz), 8.78 (dd, 1H, 6H, J6,5=1.5 Hz, J6,4=4.5 Hz)
0.89 (t, 3H, CH3, J=7.4 Hz), 1.28–1.47 (m, 6H, CH2), 1.80 (quintet, 2H, CH2), 3.92 (t, 2H, N–CH2,
J=7.4 Hz), 7.42 (dd, 1H, 5H, J6,5=4.5 Hz, J5,4=8.0 Hz), 8.53 (dd, 1H, 4H, J6,4=1.5 Hz, J5,4=8.0
Hz), 8.78 (dd, 1H, 6H, J6,5=1.5 Hz, J6,4=4.5 Hz)
5.60 (s, 2H, N–CH2), 7.42 (m, 6H, 5H and phenyl), 8.55 (dd, 1H, 4H, J6,4=1.5 Hz, J5,4=8.0 Hz),
8.78 (dd, 1H, 6H, J6,5=1.5 Hz, J6,4=4.5 Hz)
3.05 (t, 2H, CH2–Ph, J=7.4 Hz), 4.18 (t, 2H, N–CH2, J=7.4 Hz), 7.32 (m, 5H, phenyl), 7.49 (dd,
1H, 5H, J6,5=4.5 Hz, J5,4=8.0 Hz), 8.55 (dd, 1H, 4H, J6,4=1.5 Hz, J5,4=8.0 Hz), 8.80 (dd, 1H,
6H, J6,5=1.5 Hz, J6,4=4.5 Hz)
2.18 (quintet, 2H, CH2–CH2–CH2), 2.75 (t, 2H, CH2–Ph, J=7.4 Hz), 3.99 (t, 2H, N–CH2, J=7.4
Hz), 7.65 (dd, 1H, 5H, J6,5=4.5 Hz, J5,4=8.0 Hz), 8.45 (dd, 1H, 4H, J6,4=1.5 Hz, J5,4=8.0 Hz),
8.85 (dd, 1H, 6H, J6,5=1.5 Hz, J6,4=4.5 Hz)
6c
+0.078
+0.194
C
11H14N2OS
/
6d
oil
C12H16N2OS
(
6e
6f
oil
C13H10N2OS
C14H12N2OS
Ph–(CH2)2 oil
Ph–(CH2)3 oil
0.27 (A/B (65:35)) −0.022
6
679
6g
0.32 (A/B (6:4))
+0.0653 C15H14N2OS
a A hexane; B ethyl acetate; C chloroform; D acetone.

Table 5
2-Sulfanylnicotinamides 7a–g
Comp.
7a
R
m.p. (°C)
145–150
128–130
127–130
108–112
174–175
Rf (eluent a)
RM
Analyses
(C, H, N)
1H NMR (CDCl3)
n-C3H7
n-C4H9
n-C5H11
n-C6H13
Ph–CH2
0.23 (A/B (2:8))
0.25 (A/B (2:8))
0.35 (A/B (2:8))
−0.231
−0.122
0.000
C9H12N2OS
C10H14N2OS
1.05 (t, 3H, CH3, J=7.4 Hz), 1.71 (sextet, 2H, CH2), 3.48 (q, 2H, N–CH2), 6.99 (dd, 1H, 5H,
J
J
6,5=7.5 Hz, J4,5=6.0 Hz), 7.78 (dd, 1H, 4H, J4,5=6.0 Hz, J6,4=1.7 Hz), 8.90 (dd, 1H, 6H,
6,5=7.5 Hz, J6,4=1.7 Hz), 10.80 (bs, 1H, NH or SH).
7b
0.97 (t, 3H, CH3, J=7.4 Hz), 1.48 (sextet, 2H, CH2), 1.68 (quintet, 2H, CH2), 3.52 (q, 2H, N–CH2),
7.00 (dd, 1H, 5H, J6,5=7.5 Hz, J4,5=6.0 Hz), 7.75 (dd, 1H, 4H, J4,5=6.0 Hz, J6,4=1.7 Hz), 8.90
(dd, 1H, 6H, J6,5=7.5 Hz, J6,4=1.7 Hz), 10.70 (bs, 1H, NH or SH)
/
7c
C
11H16N2OS
0.98 (t, 3H, CH3, J=7.4 Hz), 1.45–1.60 (m, 4H, CH2), 1.70 (quintet, 2H, CH2), 3.50 (q, 2H,
N–CH2), 6.95 (dd, 1H, 5H, J6,5=7.5 Hz, J4,5=6.0 Hz), 7.75 (dd, 1H, 4H, J4,5=6.0 Hz, J6,4=1.7
Hz), 8.90 (dd, 1H, 6H, J6,5=7.5 Hz, J6,4=1.7 Hz), 10.70 (bs, 1H, NH or SH)
0.90 (t, 3H, CH3, J=7.4 Hz), 1.20–1.50 (m, 6H, CH2), 1.55 (quintet, 2H, CH2), 3.48 (q, 2H,
N–CH2), 6.91 (dd, 1H, 5H, J6,5=7.5 Hz, J4,5=6.0 Hz), 7.69 (dd, 1H, 4H, J4,5=6.0 Hz, J6,4=1.7
Hz), 8.82 (dd, 1H, 6H, J6,5=7.5 Hz, J6,4=1.7 Hz), 10.78 (bs, 1H, NH or SH)
4.74 (d, 2H, N–CH2, J=7.0 Hz), 6.96 (dd, 1H, 5H, J6,5=7.5 Hz, J4,5=6.0 Hz), 7.37 (m, 5H, Ph),
7.66 (dd, 1H, 4H, J4,5=6.0 Hz, J6,4=1.7 Hz), 8.88 (dd, 1H, 6H, J6,5=7.5 Hz, J6,4=1.7 Hz), 11.14
(bs, 1H, SH or NH)
2.98 (t, 2H, CH2–Ph, J=7.4 Hz), 3.76 (q, 2H, N–CH2), 6.90 (dd, 1H, 5H, J6,5=7.5 Hz, J4,5=6.0
Hz),), 7.25 (m, 5H, Ph), 7.66 (dd, 1H, 4H, J4,5=6.0 Hz, J6,4=1.7 Hz), 8.82 (dd, 1H, 6H, J6,5=7.5
Hz, J6,4=1.7 Hz), 10.78 (bs, 1H, SH or NH)
2.14 (quintet, 2H, CH2–CH2–CH2), 2.72 (t, 2H, CH2–Ph, J=7.4 Hz), 3.86 (q, 2H, N–CH2), 7.25 (m,
5H, Ph), 7.37 (dd, 1H, 5H, J6,5=7.5 Hz, J4,5=6.0 Hz), 8.29 (dd, 1H, 4H, J4,5=6.0 Hz, J6,4=1.7
Hz), 8.77 (dd, 1H, 6H, J6,5=7.5 Hz, J6,4=1.7 Hz), 10.93 (bs, 1H, SH or NH)
7d
0.40 (C/D (8:2)) +0.0959 C12H18N2OS
(
7e
0.37 (C/D (8:2))
C13H12N2OS
C14H14N2OS
C15H16N2OS
6
7f
Ph–(CH2)2 155–160
Ph–(CH2)3 117–120
0.36 (C/D (8:2)) −0.104
679
7g
0.38 (A/B (8:2))
−0.022
a A hexane; B ethyl acetate; C chloroform; D acetone.

674
M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
Table 6
In vitro antimicrobial activity of N-substituted 2-sulfanylpyridine-3-carbothioamides (3a–g), MIC in mg/ml
Comp.
Fungi
Gram-positive bacteria
Gram-negative bacteria
Anaerobic
T. menta-
C. albicans
S. aureus
S. albus
B. subtilis
K. pneu-
E. coli
S. typhi
C. perfringens
grophytes
moniae
3a
3b
3c
3d
3e
3f
3g
5
15
15
10
10
15
10
2.5
5
20
25
30
20
20
30
10
2.5
7.5
10
30
20
10
10
20
30
10
5
10
20
15
10
10
15
20
10
0.5
1.5
0.5
10
15
15
10
10
15
20
2
40
50
50
50
50
\50
50
40
\50
2.5
1.5
40
\50
40
50
50
50
\50
30
\50
2.5
40
50
50
40
50
50
50
40
10
20
15
15
10
15
15
BIT-5-F a
BIT-6-CF3
Gentamicin
Cefotaxime
Clotrimazole
a
5
0.5
0.5
\50
2.5
1.5
2.5
1.5
0.25
NT
1.5
0.5
1.25
a BIT-5-F N-butyl-5-fluoro-1,2-benzisothiazol-3(2H)-one [10]; BIT-6-CF3 N-butyl-6-trifluoromethyl-1,2-benzisothiazol-3(2H)-one [10].
(Reaction IX, 63–90% yield). The cyclization of 7a–g
was performed by treatment with iodine and afforded
6a–g in high yields (Reaction X, 74–81% yields). A
mixture of compounds 4 and 5 (a–g) was obtained after
refluxing 6a–g with Lawesson’s reagent in toluene but
in this case the yields were low (Reaction XI, 26–31%
yields). The cyclic N-substituted isothiazolo[5,4-
b]pyridine-3(2H)-thiones 4a–g were easily opened by
hydrogen sulfide treatment (Reaction XII, 78–82%
yields). Finally, the conversion of 2-sulfanylpyridine-3-
carbothioamides 3a–g into their analogues 7a–g was
performed using mercuric acetate (Reaction XIV, 32–
37% yields).
2.2.2. Acti6ity against Gram-positi6e bacteria
(Staphylococcus aureus [Sau], Staphylococcus albus
[Sal], Bacillus subtilis [Bsu], Clostridium perfringens
[Cp])
Activities against Gram-positive bacteria were inter-
esting with MIC between 2.5 and 5 mg/ml. Compound
7g had the lowest MIC (MICSau;Sal;Bsu=2.5 mg/ml).
Interesting activities were also shown by compound 7f
(MICBsu=2.5 mg/ml; MICSal;Sau=5 mg/ml). The most
active compounds against C. perfringens were 7f–g
(MIC=2.5 mg/ml) and 7e (MIC=5 mg/ml) (Table 8).
2.2.3. Acti6ity against Gram-negati6e bacteria
(Escherichia coli, Salmonella typhi, Klebsiella
pneumoniae, Pseudomonas aeruginosa)
Activity against Gram-negative bacteria was gener-
ally very poor for all compounds (Tables 6–8). Particu-
larly, the MIC values against Pseudomonas aeruginosa
were \50 mg/ml (data not reported).
2.2. Antimicrobial acti6ity
The in vitro antifungal and antibacterial activities of
2-sulfanylpyridine-3-carbothioamides 3a–g, isothia-
zolo[5,4-b]pyridine-3(2H)-thiones 4a–g, N-[3H-[1,2]-
dithiolo[3,4-b]pyridin-3-ylidene]amines 5a–g, isothia-
zolo[5,4-b]pyridin-3(2H)-ones 6a–g and 2-sulfanylni-
cotinamides 7a–g derivatives are reported in Tables
6–8. Among the investigated compounds 7f and 7g,
bearing an arylalkyl group as N-substituent, displayed
the most interesting activities.
2.3. Structure–acti6ity relationships
The benzisothiazolone mechanism for antibacterial
action has been reported by Fuller et al. [21] and could
be explained by the reaction of the sulfur with the thiol
group of the glutathione, cysteine and other biomacro-
molecules. The lability of the benzisothiazolone S–N
bond is supposed to be important for S–S bond forma-
tion with biological targets [10] but a direct relationship
between this property and the activity has never been
demonstrated [12,13].
The presence of the pyridinic nitrogen in isothia-
zolo[5,4-b]pyridine moiety should increase the reactivity
of the S–N bond with respect to the analogues 1,2-ben-
zisotiazolones. In order to compare our compounds
2.2.1. Acti6ity against fungi (Tricophyton
mentagrophytes [Tm] and Candida albicans [Ca])
The fungitoxicity of the compounds tested was gener-
ally higher against T. mentagrophytes (MIC: 1.25–15
mg/ml) than C. albicans (MIC: 5–40 mg/ml). The most
active compounds were 7f and 7g (MICTm=1.25 mg/
ml; MICCa=5 mg/ml) and 7e (MICTm=2.5 mg/ml)
(Table 8).

M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
675
with some 1,2-benzisotiazolone derivatives, we included
in Tables 6–8 the N-butyl-5-fluoro-1,2-benzisothiazol-
3(2H)-one (BIT-5-F) and the N-butyl-6-trifluoro-
methyl-1,2-benzisothiazol-3(2H)-one (BIT-6-CF3) [10]
chosen as reference compounds because they have been
tested upon the same strains according to the same
Table 7
In vitro antimicrobial activity of 2-substituted isothiazolo[5,4-b]pyridine-3(2H)-thiones (4a–g) and N-[3H-[1,2]-dithiolo[3,4-b]pyridin-3-yli-
dene]amines (5a–g), MIC in mg/ml
Comp.
Fungi
Gram-positive bacteria
Gram-negative bacteria
Anaerobic
T. menta-
C. albicans
S. aureus
S. albus
B. subtilis
K. pneu-
E. coli
S. typhi
C. perfringens
grophytes
moniae
4a
4b
4c
4d
4e
4f
4g
5a
5b
5c
5d
5e
5f
5g
10
10
5
25
30
20
30
20
30
30
20
25
30
25
20
30
30
2.5
7.5
15
30
10
20
25
30
15
10
30
20
10
25
30
15
10
5
10
20
10
15
15
20
10
10
20
15
10
15
20
10
10
0.5
1.5
0.5
10
15
10
20
20
15
15
10
20
15
15
15
20
15
2
50
40
40
50
40
50
50
40
50
50
50
40
50
50
40
\50
2.5
1.5
40
\50
50
50
\50
50
50
40
\50
40
50
50
50
50
50
50
50
50
40
50
50
50
50
50
50
40
\50
2.5
1.5
10
15
10
15
15
20
15
10
20
20
15
20
20
15
15
15
15
10
10
15
15
10
10
15
10
2.5
5
\50
50
50
BIT-5-F a
BIT-6-CF3
Gentamicin
Cefotaxime
Clotrimazole
30
a
5
0.5
0.5
\50
2.5
1.5
2.5
1.5
0.25
NT
0.5
1.25
a BIT-5-F N-butyl-5-fluoro-1,2-benzisothiazol-3(2H)-one [10]; BIT-6-CF3 N-butyl-6-trifluoromethyl-1,2-benzisothiazol-3(2H)-one [10].
Table 8
In vitro antimicrobial activity of 2-substituted isothiazolo[5,4-b]pyridin-3(2H)-ones (6a–g) and 2-sulfanylnicotinamides (7a–g), MIC in mg/ml
Comp.
Fungi
Gram-positive bacteria
Gram-negative bacteria
Anaerobic
T. menta-
C. albicans
S. aureus
S. albus
B. subtilis
K. pneu-
E. coli
S. typhi
C. perfringens
grophytes
moniae
6a
6b
6c
6d
6e
6f
6g
7a
7b
7c
7d
7e
7f
7g
15
5
30
20
20
30
30
30
20
15
20
40
10
10
5
30
10
15
20
30
30
10
50
50
25
20
10
5
20
5
15
5
50
40
40
50
40
50
40
\50
50
\50
\50
\50
\50
\50
40
\50
\50
40
50
\50
50
\50
\50
50
\50
\50
\50
\50
\50
30
50
40
40
50
50
50
50
\50
50
\50
\50
\50
\50
\50
40
20
10
15
10
20
20
10
20
20
20
20
5
10
15
15
15
5
10
15
20
20
10
20
20
20
20
10
5
2.5
10
0.5
1.5
0.5
15
15
20
20
10
25
50
25
10
2.5
2.5
2.5
2
5
10
20
10
2.5
1.25
1.25
2.5
5
2.5
2.5
5
2.5
7.5
2.5
10
5
2.5
1.5
BIT-5-F a
BIT-6-CF3
Gentamicin
Cefotaxime
Clotrimazole
a
5
0.5
0.5
\50
2.5
\50
2.5
\50
2.5
0.25
NT
1.5
1.5
1.5
0.5
1.2
a BIT-5-F N-butyl-5-fluoro-1,2-benzisothiazol-3(2H)-one [10]; BIT-6-CF3 N-butyl-6-trifluoromethyl-1,2-benzisothiazol-3(2H)-one [10].

676
M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
experimental protocol. If we compare the N-butyl-
isothiazolo[5,4-b]pyridin-3(2H)-one 6b with BIT-5-F or
BIT-6-CF3 it is possible to state that the influence of the
pyridinic ring is not determinant for the activity; in
fact, the activities on Gram-positive bacteria and fungi
strains are almost comparable (Table 8). A low activity
on Gram-negative bacteria is observed for both classes
of compounds.
chromatography was performed using silica gel 60 (60–
200 mm, Merck). All other reagents are commercial
grade and were used without further purification.
3.2. Synthesis of
3H-[1,2]dithiolo[3,4-b]pyridine-3-thione (2)
Reaction I. A mixture of 2-mercaptonicotinic acid (1)
(10 g, 0.064 mol), sulfur (4 g, 0.0155 mol) and Lawes-
son’s reagent (62.5 g, 0.155 mol) was refluxed in anhy-
drous toluene (300 ml) for 5 h and then allowed to
stand at room temperature overnight. A solid material
was collected by filtration and purified by dry-column
flash chromatography (SiO2; eluent: gradient from n-
hexane 100 to n-hexane/ethyl acetate 90–10). Recrys-
tallization from ligroin afforded 8.77 g (75% yield) of
pure 2 as orange crystals.
Lipophilicity parameters are attractive physicochemi-
cal properties in QSAR studies and often chromato-
graphic parameters are used as substitutes for partition
coefficients. Retardation matches (RM) are true mea-
sures of lipophilicity and closely correlated with log P
[22–25]: higher RM values indicate higher lipophilicity.
The RM values have been determined for compounds
3–7 (see Section 3) and are reported in Tables 1–5. The
results indicate that, in the series considered, similar to
several other antibacterial structures [23], no linear
relationship between activity and lipophilicity is ob-
served. The present findings show that factors influenc-
ing the lipophilicity of the molecules such as different
N-side chains or oxo-thiono substitution do not play a
pivotal role in determine the antimicrobial activity.
In conclusion some considerations can be stated. The
presence of the pyridinic nitrogen in the isothiazolo[5,4-
b]pyridine moiety does not increase the activity. The
arylakyl moiety confers a better activity if compared
with the alkyl N-side chains. Among the synthesized
compounds, 2-sulfanylnicotinamides 7 are the most ac-
tive substances. This finding suggests that the bicyclic
structure is not determinant for the activity. In all cases
the antimicrobial activity of the studied compounds is
lower than that of the reference substances.
Rf 0.34 (n-hexane/ethyl acetate 9:1); m.p. 175–177°C;
1H NMR (CDCl3): l 7.41 (dd, 1H, J5,4=7.5 Hz, J5,6
=
5.0 Hz), 8.42 (dd, 1H, J4,5=7.5 Hz, J4,6=1.5 Hz), 8.85
(dd, 1H, J6,5=5.0 Hz, J6,4=1.5 Hz). Anal. C6H3NS3
(C, H, N).
Reaction VII. A solution of 3H-[1,2]-dithiolo[3,4-
b]pyridin-3-one (8) (0.5 g, 2.95 mmol) and Lawesson’s
reagent (0.6 g, 1.48 mmol) in anhydrous toluene was
refluxed for 3 h. After cooling to room temperature, the
resultant precipitate was isolated by filtration under
reduced pressure (70–77% yields). Analytical data were
consistent with those reported above.
Reaction XIII. A solution of 2-sulfanylpyridine-3-
carbothioamide 3a–g (0.023 mmol) and phosphorous
pentasulfide (0.029 mmol) in anhydrous xylene (5 ml)
was refluxed for 2 h. After cooling to room tempera-
ture, the solvent was removed in vacuo and the residual
raw material was purified by flash chromatography
(n-hexane/ethyl acetate 60–40), giving 2 in 60–66%
yields. Analytical data were consistent with those re-
ported above.
In order to better clarify the structure–activity rela-
tionships of these compounds, a chemometric approach
should be considered. In this concern a chemometric
study using WHIM descriptors [26] is in progress.
3. Experimental
3.3. Synthesis of 2-sulfanylpyridine-3-carbothioamides
3a–g
3.1. Chemistry
Reaction II.
A mixture of 3H-[1,2]dithiolo[3,4-
Melting points were measured using a Kofler hot-
stage apparatus and are uncorrected. H NMR spectra
b]pyridine-3-thione (2) (16 mmol) and the appropriate
amine (19 mmol) was refluxed in 150 ml of absolute
ethanol for 30–60 min, the optimum reaction time
being determined by TLC (eluent: see Table 1). After
cooling to room temperature, the solvent was removed
under reduced pressure and the residue was recrystal-
lized from the suitable solvent (75–83% yields). Analyt-
ical data are reported in Table 1.
Reaction XII. Hydrogen sulfide was bubbled into a
solution of isothiazolo[5,4-b]pyridine-3(2H)-thione 4a–
g (0.17 mmol) in ethanol at pH 7.4 (phosphate buffer)
till disappearance of the starting material (TLC, eluent:
see Table 2). The reaction mixture was extracted with
1
were recorded at 300 MHz using a Bruker ACE-300
spectrometer in CDCl3. 1H chemical shifts (l) were
reported with Me4Si (l=0.00 ppm) as internal stan-
dard. The following abbreviations are used: br broad, s
singlet, d doublet, dd double doublet, t triplet, and m
multiplet. Elemental analyses, indicated by the symbols,
were performed on a Carlo Erba 1106 elemental analy-
ser and were within 90.4% of the theoretical values.
All reactions were monitored by thin layer chromatog-
raphy carried out on 0.25 mm Merck silica gel (60 F254
)
and visualized by UV light (u=254 or 365 nm); flash

M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
677
ethyl acetate and the collected organic layers were
washed with phosphate buffer (pH 7.4) till neutrality.
After drying over anhydrous sodium sulfate, the solvent
was removed in vacuo affording the title compound
(78–82% yields).
disappearance of the starting material (TLC, eluent: see
Table 5). The reaction mixture was extracted with ethyl
acetate and the collected organic layers were washed
with phosphate buffer (pH 7.4) till neutrality. After
drying over anhydrous sodium sulfate, the solvent was
removed in vacuo affording the title compound (80–
85% yields). Analytical data are reported in Table 5.
Reaction IX. This reaction was performed by the
same method used for Reaction II except that 3H-[1,2]-
dithiolo[3,4-b]pyridin-3-one (8) was employed as start-
ing material. Compounds 7a–g were obtained with
yields between 63 and 90%.
Reaction XIV. This reaction was performed by the
same method used for Reaction IV except that the
appropriate 2-sulfanylpyridine-3-carbothioamide 3a–g
was employed as starting material. Compounds 7a–g
were obtained with yields around 32–37%.
3.4. Synthesis of isothiazolo[5,4-b]pyridine-3(2H)-
thiones 4a–g and N-[3H-[1,2]-dithiolo[3,4-b]pyridin-3-
ylidene]amines 5a–g
Reaction III. A solution of iodine in ethanol (6% v/v)
was added dropwise to a stirred mixture of the appro-
priate 2-sulfanylpyridine-3-carbothioamide 3a–g (6
mmol) and sodium bicarbonate (10 mmol) in absolute
ethanol (100 ml), till the persistance of the brown
colour. A precipitate was removed by filtration and
washed with dichloromethane. The collected organic
phases were evaporated under reduced pressure and the
resultant residue was purified by flash chromatography
(eluent: see Tables 2 and 3) affording 30–35% yields of
pure 4a–g and 30–35% yields of pure 5a–g. Analytical
data are reported in Tables 2 and 3.
Reaction XI. A solution of isothiazolo[5,4-b]pyridin-
3(2H)-one 6a–g (0.28 mmol) and Lawesson’s reagent
(0.14 mmol) in anhydrous toluene (5 ml) was refluxed
for 30 min. After cooling to room temperature, the
solvent was removed under reduced pressure and the
residue was purified by flash chromatography (eluent:
see Table 4) giving the desired compounds with yields
around 26–30%.
3.7. Synthesis of 3H-[1,2]-dithiolo[3,4-b]pyridin-3-one
(8)
Reaction VI. A solution of 2-sulfanylnicotinamide
7a–g (0.24 mmol) and Lawesson’s reagent (0.57 mmol)
in anhydrous toluene (5 ml) was refluxed for 30 min.
After cooling to room temperature, the solvent was
removed under reduced pressure and the residue was
purified by flash chromatography (n-hexane/ethyl ace-
tate 80–20). Yield 90%; Rf 0.63 (n-hexane/ethyl acetate
1
60–40); m.p. 94–96°C; H NMR (CDCl3): l 7.39 (dd,
1H, J5,4=7.5 Hz, J5,6=5.0 Hz), 8.23 (dd, 1H, J4,5=7.5
Hz, J4,6=1.5 Hz), 8.80 (dd, 1H, J6,5=5.0 Hz, J6,4=1.5
Hz). Anal. C6H3NOS2 (C, H, N).
Reaction VIII. This reaction was performed by the
same method used for Reaction IV except that 3H-
[1,2]dithiolo[3,4-b]pyridine-3-thione (2) was employed
as starting material. Product 8 was obtained in 59%
yield.
3.5. Synthesis of isothiazolo[5,4-b]pyridin-3(2H)-ones
6a–g
Reaction IV.
A
solution of isothiazolo[5,4-
b]pyridine-3(2H)-thione 4a–g (0.6 mmol) in chloroform
(2 ml) was added to a stirred suspension of mercuric
acetate (1.3 mmol) in glacial acetic acid (5 ml) at room
temperature. After 30 min (TLC, eluent: see Table 4)
the mixture was filtered through Celite and the solvent
was evaporated under reduced pressure. The residue
was purified by flash chromatography (eluent: see Table
4) (35–40% yields). Analytical data are reported in
Table 4.
Reaction X. This reaction was performed by the
same method used for Reaction III except that the
appropriate 2-sulfanylnicotinamide 7a–g was employed
as starting material. Compounds 6a–g were obtained in
74–81% yields.
3.8. Lipophilicity tests
The relative lipophilicity of the compounds was mea-
sured by reverse-phase thin-layer chromatography
[22,23]. Silanized silica gel plates Merck 60 F254 were
used as the non-polar stationary phase. The plates were
dried at 105°C for 1 h before use. The polar mobile
phase was a 2:1 v/v mixture of acetone and water. Each
compound was dissolved in chloroform (3 mg/ml) and
5 ml of the solution was applied to the plate. Experi-
ments were repeated five times with different arrange-
ments of the compounds on the plate. Rf are expressed
as means of the five determinations. RM were calculated
from the experimental Rf according to the equation:
3.6. Synthesis of 2-sulfanylnicotinamides 7a–g
RM=log[(1/Rf)−1]
Reaction V. Hydrogen sulfide was bubbled into a
solution of isothiazolo[5,4-b]pyridin-3(2H)-one 6a–g
(0.17 mmol) in ethanol at pH 7.4 (phosphate buffer) till
The calculated RM values are presented in Tables
1–5.

678
M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
inks, Jpn. Kokai Tokkyo Koho JP, 05,171,081. Chem. Ab-
3.9. Microbiology
stracts 120 (1994) 56889k.
[8] P.W. Austin, N-(Beta-branched alkyl)-1,2-benzisothiazolin-3-
ones, their preparation and use as industrial biocides (Zeneca
Ltd), PCT Int. Appl. WO 9416564. Chem. Abstracts 121
(1994) 295086y.
[9] S. Hirawa, T. Nakano, K. Suzuki, H. Nakao, Antifungal and
waterproof fabric and its production (Toray Industries; Osaka
Kasei Kk), Jpn. Kokai Tokkyo Koho JP, 06, 313 269. Chem.
Abstracts 122 (1995) 242251n.
[10] M.L. Carmellino, G. Pagani, M. Pregnolato, M. Terreni, F.
Pastoni, Antimicrobial activity of fluorinated 1,2-benzisothia-
zol-3(2H)-ones and 2,2%-dithiobis(benzamides), Eur. J. Med.
Chem. 29 (1994) 743–751.
[11] M.L. Carmellino, G. Pagani, M. Terreni, M. Pregnolato, P.
Borgna, Antimicrobial and genotoxic activities of N-hydrox-
yalkyl-1,2-benzisothiazol-3(2H)-one carbamic esters, Farmaco
52 (1997) 359–366.
[12] P. Borgna, M.L. Carmellino, N. Natangelo, G. Pagani, F.
Pastoni, M. Pregnolato, M. Terreni, Antimicrobial activity of
N-hydroxyalkyl-1,2-benzisothiazol-3(2H)-ones and their thiono-
analogues, Eur. J. Med. Chem. 31 (1996) 919–925.
[13] M. Pregnolato, P. Borgna, M. Terreni, Synthesis of 3H-
thieno[3,2-c]-1,2-dithiole-3-thione and its reaction with buty-
lamine, J. Heterocyclic Chem. 32 (1995) 847–850.
[14] K.H. Baggaley, L.J.A. Jennings, A.W.R. Tyrrell, Synthesis of
2-substituted isothiazolopyridin-3-ones, J. Heterocyclic Chem.
19 (1982) 1393.
The in vitro antimicrobial activity of the compounds
was determined against S. aureus (ATCC 6538), S.
albus (ATCC 12228), B. subtilis (ISM 6513) as Gram
positive; E. coli (ISM 6585), S. typhi (ATCC 19430), K.
pneumoniae (ATCC 4352), Pseudomonas aeruginosa
(ATCC 15442) as Gram negative; C. albicans (ATCC
2091) and T. mentagrophytes (ATCC 9129) as fungi.
The minimum inhibitory concentrations (MICs) were
defined as the lowest concentrations of the substances
that prevent visible growth. The evaluation of MIC was
carried out as previously reported [15] by the Bioscreen
Analyzer for bacterial strains and by the medium dilu-
tion technique for the fungal strains. Gentamicin and
cefotaxime were used as reference drugs for antibacte-
rial activity, while clotrimazole was used for antifungal
activity. Test and reference compounds were dissolved
in acetone–water solution (3:1) at concentrations of
1–100 mg/ml. It was determined that the solvent exhib-
ited no antimicrobial activity against any of the test
organisms and was used as negative control. The results
of all measurements are shown as kinetic growth curves
and their elaboration provided the reported antibacte-
rial activities, expressed as MICs (mg/ml).
[15] A. Monge, V. Martinez-Merino, E. Fernandez-Alvarez, Syn-
thesis of 2-substituted 3-oxoisothiazolo[5,4-b]pyridines, J. Hete-
rocyclic Chem. 22 (1985) 1353.
[16] J.L. Raney, M.C. Seidel (Rohm and Haas Co), Isothiazolopy-
ridinones, U.S. Patent 3,965,107 (Cl. 260–294.8C; C07D513/
04), 22 June 1976, Appl. 486,550, 08 Jul 1974. Chem Abstracts
85 (1976) 160072h.
Acknowledgements
[17] K.H. Baggaley (Beecham Group Ltd.), Isothiazolopyridines,
Ger. Offen. 2,718,707 (Cl. C07D513/04), 10 November 1977,
Brit. Appl. 76/17,165, 28 April 1976. Chem Abstracts 88
(1978) 50843q.
[18] B. Shroot, J. Maignam (Oreal S.A., Centre International de
Recherches Dermatologiques (CIRD)), Acne treatment with
isothiazolopyridinones, Ger. Offen. DE 3,342,538 (Cl.
A61K31/425), 30 May 1984. Chem. Abstracts 101
(1984)116736c.
Financial support for this research by the FAR 1999,
Universita` di Pavia, is gratefully acknowledged. We
thank Dr Luca Daniele for his help in chemical
syntheses.
References
[19] P. Borgna, M. Pregnolato, I.A. Gamba, G. Mellerio, On the
reaction between 3H-1,2-dithiolo[3,4-b]pyridine-3-thione and
primary alkyl and arylalkylamines, J. Heterocyclic Chem. 30
(1993) 1079–1084.
[20] S. Scheibye, B.S. Pedersen, S.O. Lawesson, Studies on
organophosphorus compounds XXI. The dimer of p-
methoxyphenylthionophosphine sulfide as thiation reagent. A
new route to thiocarboxamides, Bull. Soc. Chim. Belg. 87
(1978) 229–238.
[21] S.J. Fuller, S.P. Denyer, W.B. Hugo, D. Pemberton, P.M.
Woodcock, A.J. Buckley, The mode of action of 1,2-benzisoth-
iazolin-3-one on Staphylococcus aureus, Lett. Appl. Microbiol.
1 (1985) 13–15.
[22] C.B.C. Boyce, B.V. Milborrow, A simple assesment of parti-
tion data for correlating structure and biological activity using
thin-layer chromatography, Nature 208 (1965) 537–539.
[23] E. Tomlison, Chromatographihic hydrophobic parameters in
correlation analysis of structure–activity relationships, J. Chro-
matogr. 113 (1975) 1–45.
[1] L.L. Bambas, 1,2-Benzisothiazol-3(2)-ones. In: A. Weissburger
(Ed.), The Chemistry of Heterocyclic Compounds, Wiley-Inter-
science, New York, 1952, pp. 253–270.
[2] M. Davis, Benzisothiazoles. In: A.R. Katritzky, A.J. Boulton
(Eds.), Advances in Heterocyclic Chemistry, Academic Press,
New York, 1972, pp. 43–98.
[3] M. Davis, Recent advances in the chemistry of benzisothia-
zoles and other polycyclic isothiazoles. In: A.R. Katritzky,
A.J. Boulton (Eds.), Advances in Heterocyclic Chemistry, Aca-
demic Press, New York, 1985, pp. 105–133.
[4] L.L. Bambas, 1,2-Benzisothiazol-3(2)-thiones. In: A. Weiss-
burger (Ed.), The Chemistry of Heterocyclic Compounds, Wi-
ley-Interscience, New York, 1952, pp. 271–273.
[5] A. Baruffini, P. Borgna, F. Gialdi, R. Ponci, Benzoisotiazolin-
3-tioni ad attivita` antifungina, Farmaco Ed. Sci. 23 (1968)
3–15.
[6] P. Borgna, L. Vicarini, M.L. Carmellino, G. Pagani, Nuovi
derivati dell’1,2-benzoisotiazolin-3-tione ad attivita` antimicot-
ica, Farmaco Ed. Sci. 38 (1983) 801–810.
[24] G.L. Biagi, M. Recanatini, A.M. Barbaro, M.C. Guerra, A.
Sapone, P.A. Borea, M.C. Pietrogrande, Chromatographic
[7] J. Shimizu, Antimicrobial agent-containing aqueous jet-printing

M. Pregnolato et al. / Il Farmaco 55 (2000) 669–679
679
parameters as lipophilicity indices for QSAR studies. In: H.
Kalasz, L.S. Ettre (Eds.), New Approaches in Chromatography
’93, Fekete Sas Ko¨nyvkiado´, Budapest, 1993, pp. 215–234.
[25] K.P. Dross, R. Mannhold, R.F. Rekker, Drug lipophilicity in
QSAR practice II. Aspects of RM-determinations and their
interrelations with partition coefficients, Quant. Struct.-Act. Re-
lat. 11 (1992) 36–44.
[26] R. Todeschini, M. Lasagni, E. Marengo, New molecular descrip-
tors for 2D and 3D structures. Theory, J. Chemometrics 8 (1994)
263–272.
.