Benzothiadiazine dioxide dibenzyl derivatives as potent human cytomegalovirus inhibitors: Synthesis and comparative molecular field analysis

Article abstract of DOI:10.1021/jm000033p

The benzothiadiazine dioxide (BTD) derivatives are potent nonnucleoside human cytomegalovirus (HCMV) inhibitors. As part of our comprehensive structure-activity relationship study of these compounds, we have now synthesized N,N- and N, O-dibenzyl derivatives with different para-substituents (alkyl, phenyl, electron-donating, electron-withdrawing) in the phenyl ring of the benzyl moieties. The antiviral activity against HCMV (AD-169 strain) was also experimentally measured showing IC₅₀ values between 2.5 and 50 μM. Comparative molecular field analysis (CoMFA) was employed to generate a model, based upon 32 diverse BTD derivatives, to delineate structural and electrostatic features important for enhanced activity against HCMV. The steric (van der Waals) interactions with the receptor majoritary describes the variation in antiviral activity among the inhibitors. Finally, the CoMFA model was used to design two sets of novel BTD derivatives. Synthesis and subsequent anti-HCMV evaluation of these compounds enabled us to maintain the activity of this new kind of HCMV inhibitors.

Full text of DOI:10.1021/jm000033p

3218
J . Med. Chem. 2000, 43, 3218-3225
Ben zoth ia d ia zin e Dioxid e Diben zyl Der iva tives a s P oten t Hu m a n
Cytom ega lovir u s In h ibitor s: Syn th esis a n d Com p a r a tive Molecu la r F ield
An a lysis
Ana Martinez,*,† Carmen Gil,† Maria I. Abasolo,†,§ Ana Castro,† Ana M. Bruno,†,§ Concepcio´n Perez,†
Columbiana Prieto,‡ and J oaqu´ın Otero‡
Instituto de Quı´mica Me´dica (CSIC), J uan de la Cierva 3, 28006 Madrid, Spain, and Unidad de Virologia, Servicio de
Microbiologia, Hospital “Doce de Octubre”, 28041 Madrid, Spain
Received J anuary 26, 2000
The benzothiadiazine dioxide (BTD) derivatives are potent nonnucleoside human cytomega-
lovirus (HCMV) inhibitors. As part of our comprehensive structure-activity relationship study
of these compounds, we have now synthesized N,N- and N,O-dibenzyl derivatives with different
para-substituents (alkyl, phenyl, electron-donating, electron-withdrawing) in the phenyl ring
of the benzyl moieties. The antiviral activity against HCMV (AD-169 strain) was also
experimentally measured showing IC50 values between 2.5 and 50 µM. Comparative molecular
field analysis (CoMFA) was employed to generate a model, based upon 32 diverse BTD
derivatives, to delineate structural and electrostatic features important for enhanced activity
against HCMV. The steric (van der Waals) interactions with the receptor majoritary describes
the variation in antiviral activity among the inhibitors. Finally, the CoMFA model was used
to design two sets of novel BTD derivatives. Synthesis and subsequent anti-HCMV evaluation
of these compounds enabled us to maintain the activity of this new kind of HCMV inhibitors.
In tr od u ction
both viruses.13 The structure of these compounds is
quite unique, not only for the nature of the heterocyclic
base but also for the lack of the 5′-OH mimetic group
present in ganciclovir and other current anti-HCMV
drug, which points to a different mechanism of action.
Preliminary structure-activity analysis (SAR) showed
the necessity of a double substitution in the heterocycle
together with the lipophilicity in the acyclic side chain.
These factors were considered in the first optimization
step performed on this family of compounds leading to
the chlorophenylmethyl BTD derivatives as potent
nonnucleoside HCMV inhibitors active against some
actual drugs resistant strains.14
Human cytomegalovirus (HCMV) has been recognized
as one of the most important pathogens in immunocom-
promised hosts, particularly transplant recipients and
patients with acquired immune-deficiency syndrome
(AIDS).1,2 HCMV infection gives little, if any, complica-
tions in immunocompetent individuals but can cause
serious disease in infants infected before birth.3
The chemotherapy of HCMV has entered a new area.
In recent years, various compounds have been described
which achieve a selective inhibition of HCMV replication
by inhibition of the viral DNA polymerase. Ganciclovir,4
foscarnet,5 cidofovir,6 and recently fomivirsen7 have
been approved for the treatment of this viral infection.
Unfortunately, toxicity associated with these drugs, poor
oral bioavailability, and high relapse rates have made
their use less than optimal.8 In addition, concomitant
with the increased use of antiviral drugs, an increased
emergence of drug-resistant HCMV strains has been
reported.9 Considering the severity of HCMV infections
in immunocompromised patients, more effective and/
or less toxic drugs which act by new mechanisms to
circumvent resistance are still required.
As part of our comprehensive SAR study of those BTD
derivatives, we have now synthesized N,N- and N,O-
dibenzyl derivatives with different para-substituents
(alkyl, phenyl, electron-donating, electron-withdrawing)
in the phenyl ring of the benzyl moieties. The antiviral
activity against HCMV (AD-169 strain) was also ex-
perimentally measured.
To obtain further insights into the structural require-
ments for the biological activity of BTD as new anti-
HCMV drugs, we have employed the comparative
molecular field analysis (CoMFA) method. The CoMFA
methodology is based in the assumption that the
interaction between an inhibitor and the enzyme (recep-
tor) is primarily noncovalent in nature and shape-
dependent and identifies the quantitative influence on
potency of specific chemical features at particular
regions in space.15 One advantage of this approach when
the 3D structure of the receptor is unknown is the
graphical representation of the results of the analysis
as 3D grids where the steric and electrostatic contribu-
tions of the activities are displayed.16 The CoMFA model
here derived was then used to design two different novel
In our search for antiviral agents,10,11 we have re-
cently discovered new leads for the development of
drugs against HCMV and Varicella-Zoster virus (VVZ)
infection.12 The benzothiadiazine dioxide (BTD) modified
acyclonucleosides showed a marked activity against
* To whom correspondence should be addressed. Tel: 34 91-562-
2900. Fax: 34 91-564-4853. E-mail: iqmam06@pinar2.csis.es.
† CSIC.
‡ Hospital “Doce de Octubre”.
§ Permanent address: Centro de S´ıntesis y Estudio de Nuevos
Compuestos Antineopla´sicos, Departamento de Qu´ımica Orga´nica,
Facultad de Farmacia y Bioqu´ımica, Universidad de Buenos Aires,
J un´ın 956, 1113 Buenos Aires, Argentina.
10.1021/jm000033p CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/09/2000

BTD Dibenzyl Derivatives
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17 3219
Sch em e 1a
a
Reagents: (i) H2O/NaHCO3/R-C6H4-CH2X (X ) Cl or Br); (ii) DMF/NaH/C6H5-CH2Br.
sets of compounds. One of this new series has been
proved to be more potent HCMV inhibitors than those
previously prepared.
HMBC for long distance proton/carbon correlation.
Thus, N1-CH2 correlated exclusively with the quater-
nary carbon C-8a, while N3-CH2 or O-CH2 correlated
with the heterocyclic carbon C-4. In this last case, a
deshielding in both proton and carbon signals is ob-
served (Table 1), which additionally confirmed the
O-substitution.
Ch em istr y
On the basis of our preliminary results,13,14 N,N- or
N,O-dibenzyl BTD derivatives 2, 3, 5, 6, and 8 were
synthesized. The new disubstituted derivatives was
obtained by reaction of 4-hydroxy-2,1,3-benzothiadiazine
dioxide17 with 2 equiv of the corresponding para-
substituted benzyl halides in aqueous bicarbonate
(Scheme 1). In these conditions, a mixture of mono- and
disubstituted compounds were obtained. N,N-Dialkyla-
tion predominated in all cases here assayed over the
N,O-disubstitution, as we have previously observed for
di(biphenylmethyl) derivatives.18,19 These compounds
could be separated and isolated by circular thin-layer
chromatography.
Biologica l Resu lts
The new N,N- and N,O-dibenzyl BTD derivatives 2,
3, 5, 6, 8, and 11-18 here described were evaluated for
their activity against the laboratory strain of HCMV
AD-169. Antiviral activity was determined by plaque
reduction assay in confluent human embryonic lung
MRC-5 fibroblasts. Cytotoxicity measurements were
based on the inhibition of cell growth and was in all
cases >50 µM. Most of the compounds exhibit antiviral
activity against HMCV, some of them being equiactive
with the standard reference ganciclovir (Table 2). The
activity against HCMV is shown at concentrations that
were 3-10-fold lower than the concentration that was
toxic for the host cells, which confirmed that N,N-
dibenzyl BTD derivatives show a specific antiviral effect
against HCMV.20 However, the N,O-dibenzyl derivatives
show IC50 values similar to CC50 results. It is worth
mentioning that monobenzyl BTD derivatives were also
evaluated as anti-HCMV agents, but no inhibition was
found confirming that double heterocyclic substitution
is indispensable for antiviral action.
The antiviral data of biphenylmethyl BTD derivatives
19-23 previously synthesized18,19 are gathered in Table
2. We can note that despite the smaller size of the viral
plaque observed in these assays, the IC50 values deter-
mined for these compounds are greater than those of
ganciclovir. Steric factors and/or liphophilic factors can
be responsible for this decrease in the antiviral activity.
3D-QSAR Stu d ies. For this work, we have selected
32 N,N- and N,O-dibenzyl BTD derivatives whose anti-
HCMV activity was measured in our laboratory (Table
2). All the compounds were initially modeling with the
Tripos force field,21 using the default bond distances and
angles and Gastaiger-Marsili charges.22 Since the
As the chlorophenylmethyl BTD family14 showed an
increase in the biological activity with substitution in
the para-position of the benzyl group attached to N1,
while no chlorine atom in the benzyl group linked to
N3 enhanced the antiviral inhibition, the benzyl moiety
was introduced in the N3 position of the benzothiadi-
azine ring starting from the N1-monobenzyl BTD de-
rivatives 1, 4, 7, 9, and 10. In this case, benzylation took
place in a polar, nonprotic solvent such as DMF in the
presence of a strong, nonnucleophilic base such as NaH
(Scheme 1). N,N-Dibenzyl derivatives 11, 13, 15, 17, and
18 were obtained in good yields although traces of N,O-
dialkylation was also observed. In some cases, the
isolation and characterization of these minor compounds
12, 14, and 16 were possible.
The structures of all new compounds were elucidated
from their analytical and spectroscopic data (1H and 13C
NMR) which are collected in Table 1 and in the
Experimental section. Unequivocal assignment of all
chemical shifts (1H and 13C NMR) was done using
bidimensional experiments such as COSY or HMQC for
one-bond correlation. The site of alkylation was deter-
mined from the chemical shifts of benzylic CH2 signals
and by means of NOE experiments and sequences of

3220 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17
Martinez et al.
Ta ble 1. Some Representative 1H and 13C NMR Data (chemical shifts in CDCl3) of New BTD Derivatives
compd
R
R′
R′′
R′′′
X
C4
C4a
C8a
N1CH2 N3CH2 OCH2 N1CH2 N3CH2 OCH2
1
2
3
4
5
6
7
8
CF3
CF3
CF3
NO2
NO2 NO2
NO2
OMe
OMe OMe
CN
Me
Me
OMe
OMe
CN
165.64 119.64 141.96
162.33 122.31 138.06
165.61 112.37 138.121
165.63 119.68 141.88
161.81 122.01 139.56
165.00 112.40 141.09
165.81 119.49 142.17
162.09 123.19 139.71
165.67 119.60 141.87
162.15 122.88 139.83
164.73 112.77 140.93
162.14 123.17 139.79
165.70 112.47 142.96
161.83 122.34 139.40
165.76 111.27 142.57
161.98 122.47 138.34
162.11 123.59 139.89
162.34 121.87 140.67
162.31 122.45 139.98
162.31 121.90 140.48
162.22 124.10 138.98
161.81 122.87 139.38
162.18 122.68 139.86
162.23 122.71 140.03
46.11
55.37
49.13
46.10
55.39
49.01
45.89
56.17
46.28
56.09
49.16
55.17
48.82
55.19
49.04
56.12
56.19
57.38
54.79
58.68
43.05
53.72
54.07
54.24
52.01
56.62
56.20
56.50
5.06
4.96
5.25
5.09
4.96
5.29
4.89
4.84
5.03
4.79
5.14
4.76
5.14
4.88
5.24
4.89
4.79
3.51
5.19
3.52
4.43
4.86
3.99
3.89
3.77
5.30
5.17
5.20
CF3
45.90
45.66
5.04
5.04
CF3
69.72
69.15
5.56
5.63
NO2
46.04
46.54
46.52
46.42
4.96
4.93
4.92
4.97
10
11
12
13
14
15
16
17
18
39
40
41
42
43
44
45
46
47
48
49
H
H
H
H
H
H
70.74
70.75
71.05
5.48
5.48
5.50
CN
CF3
NO2
H
H
46.52
46.57
46.44
46.57
46.50
46.91
46.46
46.36
46.40
46.38
47.00
46.98
46.97
4.98
4.90
5.05
5.13
5.10
5.03
4.98
5.00
4.96
5.10
5.16
5.06
5.06
C6H11
1-naphthyl
isopropyl
propargyl
3-pyridyl
H
OMe
H
H
OMe
Me
CH2
CH2
CH2CH2 162.28 122.54 139.98
CO
CO
CO
162.32 122.69 139.84
162.35 122.56 139.91
162.34 122.54 139.79
benzyl group orientation to the BTD heterocycle could
be important for antiviral activity, we designated the
torsional angles θ1, θ2 and æ1, æ2 or φ1, φ2, which rotate
the benzyl groups, for conformational searching. To
discern the conformational surface of dibenzyl BTD
derivatives, we utilized GRIDSEARCH to rotate the four
angles previously described over 360° in 30° increments.
The low-energy conformation obtained was fully geo-
metrically optimized with the Tripos force field. Geom-
etry thus obtained for dibenzyl derivatives 24 and 25
was identical to that resulted from an ab initio calcula-
tion at the 6-31G* level with full optimization of the
geometric parameters, so molecular mechanic calcula-
tions were chosen for the structure modeling of all the
molecules of the training set. The atomic charges for
all analogues were calculated by three different way:
Gastaiger-Marsili algorithm, and Mulliken distribution
and fitting point charges to electrostatic potential at the
HF/6-31G* level via ab initio molecular orbital calcula-
tions using Gaussian 94.23 This calculation level has
been proved the best strategy for studying compounds
containing the aminosulfonylamino moiety.24 All of the
compounds in the training set (Table 2) have identical
BTD ring atoms, and these were used as the basis for
an alignment rule (atoms N1, S2, N3, C4, O4, C5, C6,
C7, and C8 were fit onto each other). Superimposition
of all molecules is shown in Figure 1.
computer. The CoMFA grid space was 2.0 Å in the x, y,
and z directions, and the grid region was automatically
generated by the CoMFA routine to encompass all
molecules with an extension of 4.0 Å in each direction.
An sp3 carbon and a charge of +1.0 were used as probes
to generate the interaction energies at each lattice point.
The default value of 30 kcal‚mol-1 was used as the
maximum electrostatic and steric energy cutoff. Several
CoMFA studies were generated considering the above-
mentioned fields in the alignment described using the
different calculated charges in the molecular training
set.
The PLS algorithm was initally used with the leave-
one-out cross-validation option to obtain the optimal
number of components needed for the subsequent
analysis of the data. Final non-cross-validated models
were only calculated for the two-field combinations
chosen on the basis of the q2 results. CoMFA results
are summarized in Table 3. Models had fairly high
predictive power (q2 > 0.5); no significant improvements
were achieved by changing the standard CoMFA set-
tings for grid size and minimun σ.
The relative contributions to the derived CoMFA
model (EPS charges, q2 ) 0.544) are 61.2% steric and
38.4% electrostatic, indicating that the variation in
antiviral activity among the inhibitors is dominated by
differences in the steric (van der Waals) interactions
with the receptor. Correlation between calculated and
experimental antiviral inhibition (log IC50) is shown in
CoMFA, using default parameters, was calculated in
the QSAR option of Sybyl 6.4 on a Silicon Graphics

BTD Dibenzyl Derivatives
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17 3221
Ta ble 2. Anti-HCMV (strain AD-169) Activity of N,N- and N,O-Dibenzyl BTD Derivatives
compd
R
R′
R′′
IC50 (µM)a
CC50 (µM)b
compd
R
R′
R′′
IC50 (µM)a
CC50 (µM)b
2
3
5
6
8
11
12
13
14
15
16
17
18
19c
20c
21c
22d
4-CF3
4-CF3
4-NO2
4-NO2
4-OMe
4-Me
4-CF3
15
23
53
53
57
2.5
10
7
61
8
29
3.3
8
>48
>48
>53
>53
>57
>63
>63
>61
>61
>62
>62
>56
>59
>47
>47
>55
>47
23d
4-Ph
H
H
4-Cl
2-Cl
3,4-Cl
3,4-Cl
4-Cl
3-Cl
H
2-Cl
H
3-Cl
3,4-Cl
3,4-Cl
4-Ph
47
5.3
7.9
3.3
33
15
48
3.6
36
6
4.8
12
3.6
4
26
5.9
>47
>66
>66
>56
>56
>48
>48
>60
>60
>60
>60
>60
>60
>56
>56
>98
4-CF3
4-NO2
24e
H
4-NO2
25e
H
26e
4-Cl
2-Cl
3,4-Cl
4-OMe
H
27e
28e
4-Me
H
H
H
29e
3,4-Cl
H
4-OMe
4-OMe
4-CN
4-CN
4-CF3
4-NO2
2-Ph
2-Ph
2-Ph
4-Ph
H
H
30e
H
31e
32e
4-Cl
H
2-Cl
H
33e
H
H
2-Ph
34e
35e
47
47
44
47
36e
H
2-Ph
37e
H
H
4-Ph
ganciclovir
a
50% inhibitory concentration, or concentration required to reduce virus plaque formation by 50%. Assays were performed in duplicate.
50% cytotoxic concentration, or concentration required to reduce cell growth by 50%. Assays were performed in duplicate. c Synthesis
b
described in ref 19. Synthesis described in ref 18. e Ref 14.
d
F igu r e 2. Plot of experimental versus calculated log IC50
values for training set compounds.
Ta ble 3. CoMFA Analysis Results
calcd charges in the training set
F igu r e 1. 3D-view of CoMFA training set. Compounds were
aligned based on non-hydrogen atoms in the BTD ring.
Gastaiger-Marsili
Mulliken
ESP
r2 cross-validated
r2 conventional
std error
no. of components
F value
contributions:
steric
electrostatic
0.525
0.935
0.125
4
0.470
0.905
0.151
4
0.544
0.943
0.121
5
Figure 2, while graphical representation, using com-
pound 30 as reference structure, is depicted in Figure
3. These color maps show the regions of space in which
variation of the field considered has the most effect on
the dependent variable, the inhibition of cytomegalovi-
rus growth in our case.
101.05
66.85
82.78
43.1
56.9
53.6
46.4
61.6
38.4
An examination of the CoMFA steric field revealed
that the para-positions of both benzyl substituents are
the most sensitive ones to the steric properties. There-
fore, bulky substituents on the benzyl group attached
to N1 of BTD are predicted to enhance the activity
against HCMV, while the opposite effect was observed
in the benzyl group attached to N3.
On the other hand, the CoMFA electrostatic contour
maps revealed that a high electron density (blue poly-
hedra) around the aminosulfonylamino moiety region
enhances the antiviral activity, which could explain the
lack of HCMV inhibition found in monobenzyl BTD
derivatives. Moreover a low electron density was local-

3222 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17
Martinez et al.
F igu r e 3. Views of CoMFA steric and electrostatic contour plots. Regions where increased steric bulk is associated with enhanced
activity are indicated in yellow, while regions where increased bulk is associated with diminished activity are indicated in green.
Regions where increased positive charge is favorable for activity are indicated in red, while regions where increased negative
charge is favorable for activity are indicated in blue.
Sch em e 2a
a
Reagents: (i) CH3C6H5; (ii) 6 N NaOH; (iii) DMF/NaH/R-CH2Br; (iv) DMF/NaH/R-C6H4-X-CH2Br.
ized around the N1 position. This fact could suggest that
electron-withdrawing groups should improve the anti-
viral activity.
38 in basic medium (DMF/NaH) afforded in good yields
exclusively the N,N-disubstituted BTD derivatives 39-
49 (Scheme 2). Some spectroscopic data (1H and 13C
NMR) of these new compounds are collected in Table 1.
Antiviral activity against HCMV (AD-169 strain) was
determined by plaque reduction assay. Data are col-
lected in Table 4. Compounds 45, 48, and 49, which have
been previously designed from the steric requirements
predicted in the CoMFA study, exhibit potent antiviral
activity against HCMV, with IC50 values lower than
those of previously described BTD derivatives and the
standard reference ganciclovir. It is worthmentioning
that substitution in the para-position of the phenyl ring
enhances the anti-HCMV activity as was predicted.
On the basis of these results, we propose the synthesis
of compounds bearing a benzyl group as optimal sub-
stitution at the N3 position. By contrast, we suggest two
modifications at the N1 position which allow to explore
the 3D requirements. The first one, based on steric
results, is elongation of the link between the BTD
heterocycle and the phenyl group. The second will be
compounds bearing different electrostatic environments
such as naphthalene, pyridyl, cyclohexyl, propargyl, or
isopropyl ones in that position. Thus, new designed
compounds were synthesized, and their activity against
HCMV was measured.
Op tim iza tion Step . For the preparation of the newly
designed BTD derivatives 39-49, an unambiguous
synthetic pathway was planned to avoid a mixture of
N,N- and N,O-disubstitution. Thus, we chose as starting
material 3-benzyl BTD 38 unequivocally prepared in an
efficient two-step synthesis following the Cohen and
Klarberg procedure17 from methyl anthranilate and
N-benzylsulfamoyl chloride.25 Alkylation of compound
Con clu sion s
Several N,N- and N,O-dibenzyl BTD derivatives were
synthesized, and their antiviral activity was evaluated
against HCMV. Most of them had good IC50 values
confirming the specific antiviral action previously ob-
served for this kind of nonnucleosidic compounds. 3D-
QSAR (CoMFA) analyses identified the most significant
steric and electrostatic interactions involved in anti-

BTD Dibenzyl Derivatives
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17 3223
Ta ble 4. Anti-HCMV (strain AD-169) Activity of Newly
Designed Dibenzyl BTD Derivatives
sodium bicarbonate (20 mL) were added 4-hydroxy-2,1,3-
benzothiadiazine dioxide17 (0.20 g, 1.0 mmol) and 4-(trifluo-
romethyl)phenylmethyl chloride (0.48 g, 2.5 mmol). The reac-
tion mixture was refluxed for 2 h. After cooling to room
temperature, the mixture was extracted with CH2Cl2 (2 × 10
mL). The aqueous phase was cooled and compound 1 was
isolated by filtration. Purification: recrystallization (toluene/
MeOH), yield 0.27 g (76%) as a white solid; mp 265-267 °C.
Anal. (C15F3H11N2O3S) C, H, N, S.
The organic phase was dried over sodium sulfate and the
solvent evaporated under reduced pressure; the residue was
chromatographed on circular thin-layer chromatography, using
CH2Cl2:hexane (1:1) as eluent. From the first fraction deriva-
tive 2 was isolated: yield 0.007 g (1%) as a syrup. Anal.
(C23F6H16N2O3S) C, H, N, S.
compd
39
40
41
42
43
44
45
46
47
48
49
R
X
R′ IC50 (µM)a CC50 (µM)b
cyclohexyl
1-naphthyl
isopropyl
propargyl
3-pyridyl
15.6
11.6
14.5
76.6
13.1
7.6
>65
>58
>72
>77
>66
>64
>59
>57
>61
>57
>59
>98
From the second fraction derivative 3 was isolated: yield
0.004 g (0.7%) as a syrup. Anal. (C23F6H16N2O3S) C, H, N, S.
1-[(4-Nitr oph en yl)m eth yl]-2,1,3-ben zoth iadiazin -4(3H)-
on e 2,2-Dioxid e (4), 1,3-Di[(4-n itr op h en yl)m eth yl]-2,1,3-
ben zoth ia d ia zin -4-on e 2,2-Dioxid e (5), a n d 1-[(4-Nitr o-
p h e n y l)m e t h y l]-4-[(4-n it r o p h e n y l)m e t h y lo x y ]-2,1,3-
ben zoth ia d ia zin e 2,2-Dioxid e (6). To an aqueous solution
of sodium bicarbonate (20 mL) were added 4-hydroxy-2,1,3-
benzothiadiazine dioxide17 (0.50 g, 2.5 mmol) and 4-nitrophe-
nylmethyl bromide (1.35 g, 6.2 mmol). The reaction mixture
was refluxed for 2 h. After cooling to room temperature, the
mixture was extracted with CH2Cl2 (2 × 10 mL). The aqueous
phase was cooled and compound 4 was isolated by filtration.
Purification: recrystallization (toluene/MeOH), yield 0.76 g
(92%) as a white solid; mp 270-272 °C. Anal. (C14H11N3O5S)
C, H, N, S.
CH2
H
CH2
CH2CH2
CO
OMe
H
H
OMe
Me
4.0
18.4
24.6
3.2
CO
CO
2.8
ganciclovir
5.9
a
50% inhibitory concentration, or concentration required to
reduce virus plaque formation by 50%. Assays were performed in
duplicate. b 50% cytotoxic concentration, or concentration required
to reduce cell growth by 50%. Assays were performed in duplicate.
The organic phase was dried over sodium sulfate and the
solvent evaporated under reduced pressure; the residue was
chromatographed on circular thin-layer chromatography, using
CH2Cl2:hexane (1:1) as eluent. From the first fraction deriva-
tive 5 was isolated: yield 0.01 g (1%) as a syrup. Anal.
(C21H16N4O7S) C, H, N, S.
HCMV activity suggesting that the steric component is
a predominant factor in the antiviral activity of these
analogues with electrostatic factors playing a smaller
yet significant role. Furthermore, the CoMFA model was
shown to have potential utility for designing new agents.
Thus, chemical modification of the N,N-dibenzyl BTDs
enables us to maintain the activity in the new series of
compounds belonging to this novel class of antiviral
agents. From the reported series, compounds 48 and 49
emerged as the most potent and selective inhibitors of
HCMV. Further studies are in progress to understand
the mechanism and target of interaction of these
compounds.
From the second fraction derivative 6 was isolated: yield
0.004 g (0.3%) as a syrup. Anal. (C21H16N4O7S) C, H, N, S.
1-[(4-Met h oxyp h en yl)m et h yl]-2,1,3-b en zot h ia d ia zin -
4(3H)-on e 2,2-Dioxid e (7) a n d 1,3-Di[(4-m eth oxyp h en yl)-
m eth yl]-2,1,3-ben zoth ia d ia zin on e 2,2-Dioxid e (8). To an
aqueous solution of sodium bicarbonate (20 mL) were added
4-hydroxy-2,1,3-benzothiadiazine dioxide17 (0.19 g, 1.0 mmol)
and 4-methoxyphenylmethyl chloride (0.39 g, 2.5 mmol). The
reaction mixture was refluxed for 2 h. After cooling to room
temperature, the mixture was extracted with CH2Cl2 (2 × 10
mL). The organic phase was dried over sodium sulfate and
the solvent evaporated under reduced pressure; the residue
was chromatographed on circular thin-layer chromatography,
using CH2Cl2:hexane (1:1) as eluent. Compound 8 was obtained
(0.03 g, 8%) as a syrup. Anal. (C23H22N2O5S) C, H, N, S.
The aqueous phase was extracted with AcOEt (10 × 10 mL),
the organic phase was dried over sodium sulfate and the
solvent evaporated under reduced pressure; the residue was
chromatographed on silica gel column using CH2Cl2/MeOH (50:
1) as eluent. Compound 7 was obtained (0.13 g, 43%) as a white
solid: mp 260-262 °C. Anal. (C15H14N2O4S) C, H, N, S.
1-[(4-Cyan oph en yl)m eth yl]-2,1,3-ben zoth iadiazin -4(3H)-
on e 2,2-Dioxid e (10). To an aqueous solution of sodium
bicarbonate (20 mL) were added 4-hydroxy-2,1,3-benzothia-
diazine dioxide17 (0.50 g, 2.5 mmol) and 4-cyanophenylmethyl
bromide (1.22 g, 6.2 mmol). The reaction mixture was refluxed
for 2 h. After cooling to room temperature, the mixture was
extracted with AcOEt (10 × 10 mL), the organic phase was
dried over sodium sulfate and the solvent evaporated under
reduced pressure. The residue was recrystallized from toluene/
MeOH yielding compound 10 (0.56 g, 72%) as a white solid:
mp 298-300 °C. Anal. (C15H11N3O3S) C, H, N, S.
Exp er im en ta l Section
Ch em ica l P r oced u r es. Melting points were determined
with a Reichert-J ung Thermovar apparatus and are uncor-
rected. Flash column chomatography was carried out at
medium pressure using silica gel (E. Merck, grade 60, particle
size 0.040-0.063 mm, 230-240 mesh ASTM) with the indi-
cated solvent as eluent. 1H NMR spectra were obtained on
Varian XL-300 and Gemini-200 spectrometers working at 300
and 200 MHz, respectively. Typical spectral parameters were
spectral width 10 ppm, pulse width 9 µs (57°), data size 32 K.
NOE difference spectra were measured under the same
conditions, using a presaturation time of 3 s. 13C NMR
experiments were carried out on the Varian Gemini-200
spectrometer operating at 50 MHz. Tha acquisiton parameters
were spectral width 16 kHz, acquisition time 0.99 s, pulse
width 9 µs (57°), data size 32 K. Chemical shifts are reported
in δ values (ppm) relative to internal Me4Si and J values are
reported in hertz (Hz). Elemental analyses were performed by
the analytical departement at CSIC and the results obtained
were within (0.4% of the theoretical values.
1-{[4-(Tr iflu or om eth yl)ph en yl]m eth yl}-2,1,3-ben zoth ia-
d ia zin -4(3H )-on e 2,2-Dioxid e (1), 1,3-Di{[4-t r iflu or o-
m eth yl)p h en yl]m eth yl}-2,1,3-ben zoth ia d ia zin -4-on e 2,2-
Dioxid e (2), a n d 1-{[4-(Tr iflu or om eth yl)p h en yl]m eth yl}-
4-{[4-(t r iflu or om et h yl)p h en yl]m et h yloxy}-2,1,3-b en zo-
th ia d ia zin e 2,2-Dioxid e (3). To an aqueous solution of
Gen er a l P r oced u r e for th e N3-Ben zyla tion of Ben -
zoth ia d ia zin e Der iva tives. To an equimolecular suspension
of sodium hydride in DMF (25 mL) were added the corre-
sponding monosubstitued benzothiadiazines and benzyl bro-
mide (1.5 mmol). The reaction mixture was refluxed for 2 h.

3224 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17
Martinez et al.
After cooling, the solvent was evaporated under reduced
pressure. The residue was dissolved in water and the aqueous
phase was extracted with CH2Cl2 (2 × 10 mL). The organic
phase was dried over sodium sulfate and the solvent evapo-
rated under reduced pressure. The residue was chromato-
graphed on circular thin-layer chromatography, using CH2Cl2:
hexane (1:1) as eluent.
1-[(4-Meth ylp h en yl)m eth yl]-3-ben zyl-2,1,3-ben zoth ia -
d ia zin -4-on e 2,2-Dioxid e (11) a n d 1-[(4-Meth ylp h en yl)-
m eth yl]-4-ben zyloxy-2,1,3-ben zoth ia d ia zin e 2,2-Dioxid e
(12). Reagents: benzothiadiazine 919 (0.07 g, 0.2 mmol), benzyl
bromide (0.05 g, 0.3 mmol). From the first fraction derivative
1-(Cycloh exylm eth yl)-3-ben zyl-2,1,3-ben zoth ia d ia zin -
4-on e 2,2-Dioxid e (39). Reagents: benzothiadiazine 38 (0.10
g, 0.3 mmol), cyclohexylmethyl bromide (0.07 g, 0.4 mmol);
yield 0.02 g (24%) as a white solid; mp 100-101 °C. Anal.
(C21H24N2O3S) C, H, N, S.
1-(1-Na p h th ylm eth yl)-3-ben zyl-2,1,3-ben zoth ia d ia zin -
4-on e 2,2-Dioxid e (40). Reagents: benzothiadiazine 38 (0.10
g, 0.3 mmol), 1-naphthylmethyl chloride (0.07 g, 0.4 mmol);
yield 0.04 g (29%) as a syrup. Anal. (C25H20N2O3S) C, H, N, S.
1-Isob u t yl-3-b en zyl-2,1,3-b en zot h ia d ia zin -4-on e 2,2-
Dioxid e (41). Reagents: benzothiadiazine 38 (0.10 g, 0.3
mmol), isobutyl bromide (0.05 g, 0.4 mmol); yield 0.02 g (21%)
as a syrup. Anal. (C18H20N2O3S) C, H, N, S.
11 was isolated as
a syrup: yield 0.03 g (43%). Anal.
(C22H20N2O3S) C, H, N, S.
1-P r op a r gyl-3-ben zyl-2,1,3-ben zoth ia d ia zin -4-on e 2,2-
Dioxid e (42). Reagents: benzothiadiazine 38 (0.10 g, 0.3
mmol), propargyl bromide (0.05 g, 0.4 mmol); yield 0.06 g (50%)
as a white solid; mp 119-120 °C. Anal. (C17H14N2O3S) C, H,
N, S.
1-(3-P yr id ylm eth yl)-3-ben zyl-2,1,3-ben zoth ia d ia zin -4-
on e 2,2-Dioxid e (43). Reagents: benzothiadiazine 38 (0.10
g, 0.3 mmol), 3-(bromomethyl)pyridine hydrobromide (0.11 g,
0.4 mmol); yield 0.05 g (43%) as a syrup. Anal. (C20H17N3O3S)
C, H, N, S.
From the second fraction derivative 12 was isolated as a
syrup: yield 0.003 g (4%). Anal. (C22H20N2O3S) C, H, N, S.
1-[(4-Meth oxyph en yl)m eth yl]-3-ben zyl-2,1,3-ben zoth ia-
d ia zin -4-on e 2,2-Dioxid e (13) a n d 1-[(4-Meth oxyp h en yl)-
m eth yl]-4-ben zyloxy-2,1,3-ben zoth ia d ia zin e 2,2-Dioxid e
(14). Reagents: benzothiadiazine 7 (0.13 g, 0.4 mmol), benzyl
bromide (0.10 g, 0.6 mmol). From the first fraction derivative
13 was isolated as a white solid: yield 0.02 g (14%); mp 143-
145 °C. Anal. (C22H20N2O4S) C, H, N, S.
From the second fraction derivative 14 was isolated as a
syrup: yield 0.004 g (2%). Anal. (C22H20N2O4S) C, H, N, S.
1-[(4-Cya n op h en yl)m eth yl]-3-ben zyl-2,1,3-ben zoth ia d i-
a zin -4-on e 2,2-Dioxid e (15) a n d 1-[(4-Cya n op h en yl)-
m eth yl]-4-ben zyloxy-2,1,3-ben zoth ia d ia zin e 2,2-Dioxid e
(16). Reagents: benzothiadiazine 10 (0.20 g, 0.6 mmol), benzyl
bromide (0.15 g, 0.9 mmol). From the first fraction derivative
15 was isolated as a white solid: yield 0.03 g (12%); mp 45-
47 °C. Anal. (C22H17N3O3S) C, H, N, S.
1-P h en yleth yl-3-ben zyl-2,1,3-ben zoth iadiazin -4-on e 2,2-
Dioxid e (44). Reagents: benzothiadiazine 38 (0.10 g, 0.3
mmol), phenylethyl bromide (0.07 g, 0.4 mmol); yield 0.02 g
(20%) as a syrup. Anal. (C22H20N2O3S) C, H, N, S.
1-[(4-Meth oxyp h en yl)eth yl]-3-ben zyl-2,1,3-ben zoth ia -
d ia zin -4-on e 2,2-Dioxid e (45). Reagents: benzothiadiazine
38 (0.10 g, 0.3 mmol), 4-(methoxy)phenylethyl chloride (0.07
g, 0.4 mmol); yield 0.02 g (14%) as a syrup. Anal. (C23H22N2O4S)
C, H, N, S.
From the second fraction derivative 16 was isolated as a
syrup: yield 0.004 g (2%). Anal. (C22H17N3O3S) C, H, N, S.
1-{[4-(Tr iflu or om eth yl)p h en yl]m eth yl}-3-ben zyl-2,1,3-
ben zoth ia d ia zin -4-on e 2,2-Dioxid e (17). Reagents: ben-
zothiadiazine 1 (0.15 g, 0.4 mmol), benzyl bromide (0.10 g, 0.6
mmol); yield 0.03 g (18%) as a syrup. Anal. (C22H17N2O3SF3)
C, H, N, S.
1-[(4-Nitr op h en yl)m eth yl]-3-ben zyl-2,1,3-ben zoth ia d i-
a zin -4-on e 2,2-Dioxid e (18). Reagents: benzothiadiazine 4
(0.20 g, 0.6 mmol), benzyl bromide (0.15 g, 0.9 mmol); yield
0.01 g (8%) as a syrup. Anal. (C21H17N3O5S) C, H, N, S.
3-Ben zyl-2,1,3-ben zoth ia d ia zin -4(1H)-on e 2,2-Dioxid e
(38). To a 0 °C cooled and stirred solution of benzylamine (10.7
g, 0.1 mol) in CH2Cl2 (100 mL) was added chlorosulfonic acid
(3.49 g, 0.03 mol) cautiously. The resulting suspension was
stirred for 0.5 h at room temperature and then filtered. The
collected solids were dissolved in toluene (50 mL) and treated
with phosphorus pentachloride (6.24 g, 0.03 mol). A midly
exothermic reaction took place. The solution was refluxed for
1 h and the solid was filtered off. The filtrate was concentrate
in vacuo and the syrupy residue (N-benzylsulfamoyl chloride)
thus obtained was used in the next synthetic step without
further purification.
1-P h en ylp r op yl-3-ben zyl-2,1,3-ben zoth ia d ia zin -4-on e
2,2-Dioxid e (46). Reagents: benzothiadiazine 38 (0.10 g, 0.3
mmol), phenylpropyl chloride (0.07 g, 0.4 mmol); yield 0.01 g
(8%) as a syrup. Anal. (C24H22N2O3S) C, H, N, S.
1-(P h en ylca r bon ylm eth yl)-3-ben zyl-2,1,3-ben zoth ia d i-
a zin -4-on e 2,2-Dioxid e (47). Reagents: benzothiadiazine 38
(0.10 g, 0.3 mmol), 2-bromoacetophenone (0.08 g, 0.4 mmol);
yield 0.02 g (15%) as a white solid; mp 118-120 °C. Anal.
(C22H18N2O4S) C, H, N, S.
1-[(4-Meth oxyp h en yl)ca r bon ylm eth yl]-3-ben zyl-2,1,3-
ben zoth ia d ia zin -4-on e 2,2-Dioxid e (48). Reagents: ben-
zothiadiazine 38 (0.10 g, 0.3 mmol), 2-bromo-4′-methoxyace-
tophenone (0.09 g, 0.4 mmol); yield 0.07 g (45%) as a white
solid; mp 135-136 °C. Anal. (C23H20N2O5S) C, H, N, S.
1-[(4-Met h ylp h en yl)ca r b on ylm et h yl]-3-b en zyl-2,1,3-
ben zoth ia d ia zin -4-on e 2,2-Dioxid e (49). Reagents: ben-
zothiadiazine 38 (0.10 g, 0.3 mmol), 2-bromo-4′-methylace-
tophenone (0.08 g, 0.4 mmol); yield 0.05 g (32%) as a white
solid; mp 130-132 °C. Anal. (C23H20N2O4S) C, H, N, S.
An tivir a l Eva lu a tion . Cells: Human embryonic lung
MRC-5 fibroblast were propagated in Hepes modified medium
199 supplemented with 10% inactivated fetal calf serum and
1% l-glutamine.
Methyl anthranilate (2.11 g, 0.01 mol) was dissolved in
toluene (10 mL). This mixture was added to an stirred solution
of N-benzylsulfamoyl chloride (3 g) previously prepared in
toluene (10 mL). After 3 h, 6 N sodium hydroxide solution (20
mL) was added. The aqueous layer was separated and made
acidic with concentrated hydrochloridic acid. Upon cooling the
mixture, a white crystalline solid precipitated: yield 2.71 g
(67%); mp 250-251 °C (lit.13 mp 250-251 °C).
Gen er a l P r oced u r e for N1-Alk yla tion of 3-Ben zylben -
zoth ia d ia zin e Dioxid e. To an equimolecular suspension of
sodium hydride in DMF (25 mL) were added N3-benzyl
benzothiadiazine 38 and the corresponding aqueous agent (1.5
mmol). The reaction mixture was refluxed for 12 h. The solvent
was evaporated under reduced pressure. The residue was
dissolved in water and the aqueous phase was extracted with
CH2Cl2 (2 × 10 mL). The organic phase was dried over sodium
sulfate and the solvent evaporated under reduced pressure.
The residue was chromatographed on circular thin-layer
chromatography, using CH2Cl2:hexane (1:1) as eluent.
Vir u ses: Virus stocks were prepared in MRC-5 cells as
infected cells. When 70% cytopathic effect was obtained, the
cells were trypsinized, resuspended in medium containing 10%
DMSO and stored in aliquots at -80 °C. The AD-169 strain
of human cytomegalovirus was used. Virus stocks consisted
of cell-free virus obtained from the supernatant of infected cell
cultures that had been sonicated and clarified by low-speed
centrifugation. The virus stocks were stored at -80 °C.
An tivir a l a ssa ys: Confluent MRC-5 cells grown in 24-well
plates were infected with the AD-169 strain at 100 (CMV)
plaque-forming units (PFU/well). After a 1.5-h incubation
period, residual virus was removed and the infected cells were
further incubated with Hepes modified medium 199 supple-
mented with 2% inactivated FCS and 1% L-glutamine contain-
ing serial dilutions of the test compounds (in duplicate). After
8 days of incubation at 37 °C in 5% CO2 atmosphere, the cells
were stained with 0.2% crystal violet in ethanol:water (20:80).
PFU (virus input: 100 PFU/well) was monitored microscopi-
cally. The antiviral activity is expressed as IC50 which repre-

BTD Dibenzyl Derivatives
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17 3225
(11) Esteban, A. I.; De Clercq, E.; Martinez, A. Synthesis and
Antiviral Activity of Modified 1,2,6-Thiadiazine Dioxide Acyclo-
nucleosides. Nucleosides Nucleotides 1997, 16, 265-276.
(12) Martinez, A.; Esteban, A. I.; De Clercq, E. Benzothiadiazine
Dioxide Acyclonucleosides as Lead Compounds for the Develop-
ment of New Agents Against Human Cytomegalovirus and
Varicella-Zoster Virus Infections. Bioorg. Med. Chem. Lett. 1997,
7, 1031-1032.
(13) Martinez, A.; Esteban, A. I.; Castro, A.; Gil, C.; Conde, S.; Andrei,
G.; Snoeck, R.; Balzarini, J .; De Clercq, E. Novel Potential Agents
For Human Cytomegalovirus Infection: Synthesis and Antiviral
Activity Evaluation of Benzothiadiazine Acyclonucleosides. J .
Med. Chem. 1999, 42, 1145-1150
(14) Martinez, A.; Gil, C.; Perez, C.; Castro, A.; Prieto, C.; Otero, J .
Chlorophenyl-methyl Benzothiadiazine Dioxides Derivatives:
Potent Human Cytomegalovirus Inhibitors. Bioorg. Med. Chem.
Lett. 1999, 9, 3133-3136.
(15) Cramer, R. D.; Patterson, D. E.; Bunce, J . D. Comparative
Molecular Field Analysis (CoMFA). 1. Effects of shape on binding
of steroids to carrier protein. J . Am. Chem. Soc. 1988, 110, 5959-
5967.
sents the compound concentration required to reduce virus
plaque formation by 50%. IC50 values were stimated from
graphic plots of the number of plaques (percentage of control)
as a function of the concentration of the test compounds.
Cytotoxicity a ssa ys: Cytotoxicity measurements were
based on the inhibition of MRC-5 cell growth. MRC-5 fibro-
blasts were seeded at a rate of 5 × 103 cells/well in microtiter
plates and allowed to prolifarate for 24 h. Different concentra-
tions of the test compounds were then added (in duplicate),
and after 3 days of incubation at 37 °C in 5% CO2 atmosphere,
the cell number was determined with a Coulter counter.
Cytotoxicity is expressed as CC50, which represents the
compound concentration required to reduce cell growth by 50%.
Ack n ow led gm en t. These investigations were sup-
ported by Fondo de Investigaciones Sanitarias (Project
No. FIS 98/253) and Comunidad de Madrid (Project No.
8.2/36.1/1999). One of us (C. Gil) acknowledges a grant
from Comunidad de Madrid.
(16) Pajeva, I. K.; Wiese, M. Interpretation of CoMFA Results. A
Probe Study. Quant. Struct.-Act. Relat. 1999, 18, 369-379.
(17) Cohen, E.; Klarberg, B. Sulfamoyl Chloride, Sulfamides and
Sulfimide. J . Am. Chem. Soc. 1962, 84, 1994-2002.
(18) Castro, A.; Gil, C.; Martinez, A. On the tautomerism of 2,1,3-
Benzothiadiazinone S,S-Dioxide and Related Compounds. Tet-
rahedron 1999, 55, 12405-12410.
(19) Mart´ınez, A.; Castro, A.; Gil, C.; Miralpeix, M.; Segarra, V.;
Dome´nech, T.; Beleta, J .; Palacios, J . M.; Ryder, H.; Miro´, X.;
Bonet, C.; Casacuberta, J . M.; Azor´ın, F.; Pin˜a, B.; Puigdome´nech
P. Benzyl Derivatives of 2,1,3-Benzo-and Benzothieno[3,2-a]-
thiadiazine 2,2-Dioxides: First Phosphodiesterase 7 Inhibitors.
J . Med. Chem. 2000, 43, 683-689.
Su p p or tin g In for m a tion Ava ila ble: 1H and 13C NMR
data and elemental analyses. This material is available free
of charge via the Internet at http://pubs.acs.org.
Refer en ces
(1) Alford, C. A.; Britt, W. J . Cytomegalovirus. In The human
Herpesviruses; Roizman, B., Whitley, R. J ., Lopez, C., Eds.;
Raven Press: New York, 1993; pp 227-255.
(2) Goldman, R. C.; Klein, L. L. Problems and Progress in Op-
portunistic Infections. Annu. Rep. Med. Chem. 1994, 29, 155-
164.
(3) Fowler, K. B.; Stagno, S.; Pass, R. F.; Britt, W. J .; Boll, T. J .;
Alford, C. A. The outcome of congenital cytomegalovirus infection
in relation to maternal antibody status. N. Engl. J . Med. 1992,
326, 663-667.
(4) Faulds, D.; Heel, R. C. Ganciclovir. A Review of its Antiviral
Activity, Pharmacokinetic Properties and Therapeutic Efficacy
in Cytomegalovirus Infections. Drugs 1990, 39, 597-638.
(5) Chrisp, P.; Clissold, S. P. Foscarnet. A Review of its Antiviral
Activity, Pharmacokinetic Properties and Therapeutic use in
Immunocompromised Patients with Cytomegalovirus Retinitis.
Drugs 1991, 41, 104-129.
(6) De Clercq, E. Therapeutic potential of HPMPC as an antiviral
drug. Rev. Med. Virol. 1993, 3, 85-96.
(7) Perry, C. M.; Barman-Balfour, J . A. Fomivirsen. Drugs 1999,
57, 375-380.
(8) Boivin, G.; Chou, S.; Quirk, M. R.; Erice, A.; J ordan, M. C.
Detection of Ganciclovir Resistance Mutations and Quantitation
of Cytomegalovirus (CMV) DNA in Leucocytes of Patients with
Fatal Disseminated CMV Disease. J . Infect. Dis. 1996, 173, 523-
528.
(9) Castro, A.; Martinez, A. Novel agents for the treatment of human
cytomegalovirus infection. Exp. Opin. Ther. Patents 2000, 10,
165-177.
(10) Martinez, A.; Esteban, A. I.; J uanes, O.; Conde, S.; Goya, P.; De
Clercq, E. New 1,2,6-Thiadiazine Dioxide Acyclonucleosides:
Synthesis and Antiviral Evaluation. Bioorg. Med. Chem. 1995,
3, 1527-1535.
(20) Martinez, A.; Gil, C.; Perez, C.; Castro, A. Patent E-9900954,
May 1999.
(21) SYBYL Molecular Modeling System, version 6.4; Tripos, Inc.:
St. Louis, MO, 1998.
(22) Gastaiger, J .; Marsili, M. Tetrahedron 1980, 36, 3219-3228.
(23) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
J ohnson, B. G.; Robb, M. A.; Cheeseman, J . R.; Keith, T.;
Petersson, G. A.; Montgomery, J . A.; Raghavachari, K.; Al-
Laham, M. A.; Zakrzewski, V. G.; Ortiz, J . V.; Foresman, J . B.;
Peng, C. Y.; Ayala, P. Y.; Chen, W.; Wong, M. W.; Andres, J . L.;
Replogle, E. S.; Gomperts, R.; Martin, R. L.; Fox, D. J .; Binkley,
J . S.; Defrees, D. J .; Baker, J .; Stewart, J . P.; Head-Gordon, M.;
Gonzalez, C.; Pople, J . A. Gaussian 94, revision B.3; Gaussian,
Inc.: Pittsburgh, PA, 1995.
(24) Alkorta, I.; Garcia-Gomez, C.; Paez, J . A.; Goya, P. Theoretical
and Experimental Analysis of Properties in Heterocycles Con-
taining the Aminosulphonylamino Moiety. J . Phys. Org. Chem.
1996, 9, 203-211.
(25) Kloek, J . A.; Leschinsky, K. L. An improve synthesis of sulfamoyl
chlorides. J . Org. Chem. 1976, 41, 25-27.
J M000033P