5'-alkyl-benzothiadiazides: a new subgroup of AMPA receptor modulators with improved affinity.

Article abstract of DOI:10.1016/S0968-0896(01)00405-9

AMPA receptors form a major subdivision of the glutamate receptor family that mediates excitatory synaptic transmission in the brain. Currents through AMPA receptors can be up- or down-regulated by compounds that allosterically modulate receptor kinetics through binding sites distinct from that for glutamate. One of those modulators is the benzothiadiazide IDRA-21 which has been reported to enhance synaptic transmission and be effective in behavioral tests, but typically requires threshold concentrations of at least 100 microM to be active in vitro. In this study, new benzothiadiazides were developed with IDRA-21 as lead compound and examined for their potency in modulating AMPA receptor kinetics. A significant increase in drug affinity was obtained by alkyl substitution at the 5'-position of IDRA-21; substitutions at other positions of the benzothiadiazide core generally did not yield a further gain in affinity and in some cases abolished drug binding. The 5'-ethyl derivative exhibited an EC(50) value in the order of 22 microM which represents about a 30-fold gain in affinity over that of IDRA-21. The EC(50) value is comparable to that of cyclothiazide, the most potent benzothiadiazide drug, but the effects on AMPA receptors differed substantially between these two compounds in that the 5'-ethyl derivative of IDRA-21 greatly increased the binding affinity for receptor agonists whereas cyclothiazide is known to reduce agonist binding. The structure--activity relationships reported here thus offer to provide new insights how receptor kinetics is linked to particular aspects of receptor--drug interactions.

Full text of DOI:10.1016/S0968-0896(01)00405-9

Bioorganic & Medicinal Chemistry 10 (2002) 1229–1248
50-Alkyl-benzothiadiazides: A New Subgroup of AMPA
Receptor Modulators with Improved Affinity
Dean Phillips,a Jennifer Sonnenberg,a Amy C. Arai,c Rishi Vaswani,b
Peter O. Krutzik,b Thomas Kleisli,b Markus Kessler,c Richard Granger,b
Gary Lynchb and A. Richard Chamberlina,*
aDepartment of Chemistry, University of California, Irvine, CA 92697, USA
bDepartment of Psychiatry, University of California, Irvine, CA 92697, USA
cDepartment of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA
Received 15 June 2001; accepted 15 October 2001
Abstract—AMPA receptors form a major subdivision of the glutamate receptor family that mediates excitatory synaptic transmis-
sion in the brain. Currents through AMPA receptors can be up- or down-regulated by compounds that allosterically modulate
receptor kinetics through binding sites distinct from that for glutamate. One of those modulators is the benzothiadiazide IDRA-21
which has been reported to enhance synaptic transmission and be effective in behavioral tests, but typically requires threshold
concentrations of at least 100 mM to be active in vitro. In this study, new benzothiadiazides were developed with IDRA-21 as lead
compound and examined for their potency in modulating AMPA receptor kinetics. A significant increase in drug affinity was
obtained by alkyl substitution at the 50-position of IDRA-21; substitutions at other positions of the benzothiadiazide core generally
did not yield a further gain in affinity and in some cases abolished drug binding. The 50-ethyl derivative exhibited an EC50 value
in the order of 22 mM which represents about a 30-fold gain in affinity over that of IDRA-21. The EC50 value is comparable to that
of cyclothiazide, the most potent benzothiadiazide drug, but the effects on AMPA receptors differed substantially between these
two compounds in that the 50-ethyl derivative of IDRA-21 greatly increased the binding affinity for receptor agonists whereas
cyclothiazide is known to reduce agonist binding. The structure–activity relationships reported here thus offer to provide
new insights how receptor kinetics is linked to particular aspects of receptor–drug interactions. # 2002 Published by Elsevier
Science Ltd.
Introduction
quently leads to neuronal degeneration.3 Major efforts
l-Glutamate is a ubiquitous excitatory neurotransmitter
in the mammalian central nervous system, playing a key
role in synaptic transmission and in plasticity processes
vital to early neuronal development and encoding of
memory. Receptor-selective agonists and antagonists
have been instrumental to characterize the main sub-
classes of glutamate receptors [i.e., N-methyl-d-aspar-
tate (NMDA), kainic acid, amino-3-hydroxy-5-methyl-
4-isoxazolepropionic acid (AMPA), and metabotropic
receptors].1 Selective inactivation or activation of these
receptors have also been targeted for intervention in
various neurological disorders.2 A convincing case has
been made that excessive glutamate receptor activation
occurs during stroke and similar insults, mainly due to
uncontrolled release of glutamate, and that this subse-
are accordingly being made to develop receptor
antagonists which afford protection during those critical
periods.3,4
Insufficient activation of glutamate receptors may be of
similar clinical importance, but is more likely associated
with chronic disorders. One example may be the pro-
gressive loss of synapses or neurons in age and age-
related disorders.5,6 Likewise, schizophrenia according
to recent insights may involve subnormal excitatory
activity in critical frontal regions of the brain.7 Lower
than normal excitatory drive would probably not cause
cellular dysfunction but would compromise the inte-
grative functions of the brain which depend on a
balanced activity of its component parts. An obvious
approach to correct the deficit would be to strengthen
the remaining functional connections. Compounds that
enhance glutamate receptor currents through allosteric
*Corresponding author. Tel.: +1-949-824-7089; fax: +1-949-824-
8571; e-mail: archambe@uci.edu
0968-0896/02/$ - see front matter # 2002 Published by Elsevier Science Ltd.
PII: S0968-0896(01)00405-9

1230
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
modulation seem particularly suitable for this purpose
because they would be expected to increase the gain of
synaptic transmission without disrupting the spatio-
temporal patterning of the information flow. The feasi-
bility of this approach has been documented in
behavioral studies which showed that up-modulators of
AMPA receptors may alleviate memory deficits in aged
rodents and humans8,9 and that they potentiate the
effects of antipsychotics in an experimental schizo-
phrenia model.10
on receptor desensitization. The utility of cyclothiazide
as a probe to study the behavioral consequences of
AMPA receptor modulation may also be limited
because of its clinically important action on renal func-
tion, a limited diffusion across the blood–brain barrier,
and the fact that cyclothiazide consists of eight stereo-
isomers, only some of which are active.26
Various investigators have therefore sought new ben-
zothiadiazides that are potent yet capable of enhancing
glutamatergic synaptic transmission. Yamada and
Tang13 tested clinically active analogues of cyclothiazide
and concluded that the 30-norbornenyl substituent is
essential for AMPA receptor affinity. Bertolino et al.27
examined instead a series of analogues of diazoxide and
discovered that the compound IDRA-21 is about 3
times more potent, with the added benefit of reduced
peripheral activity. Minor variants of IDRA-21 were
included in their tests but proved less effective. IDRA-
21 was found to be superior to cyclothiazide in enhan-
cing synaptic responses in hippocampal slices28 and it
produced desirable effects in behavioral tasks.22 How-
ever, its EC50 remains far below that of cyclothiazide
and concentrations of 200–500 mM are typically needed
in physiological experiments.28
The first such modulator was discovered by Ito et al.11
who showed that aniracetam selectively enhances cur-
rents through AMPA receptors by binding to a site dis-
tinct from that for glutamate. This was followed by the
discovery of other compounds that allosterically alter
AMPA receptor function12À19 and by efforts to charac-
terize the physiological and behavioral consequences of
such modulation.20À22 Among the first of these com-
pounds were diazoxide and cyclothiazide, both of which
are benzothiadiazides and hence structurally distinct
from aniracetam (Fig. 1). Both have been in clinical use
for peripheral actions unrelated to AMPA receptors.
Diazoxide was found to stimulate AMPA receptors at
concentrations (100–500 mM) similar to those needed
for its known action on certain potassium channels.12
Cyclothiazide is still one of the most potent modulators
in that it effectively blocks AMPA receptor desensitiza-
tion in excised-patch experiments at 10–30 mM;13 how-
ever, it produces small effects on synaptic responses,
presumably because desensitization is too slow to affect
receptor deactivation during the very brief synaptic
glutamate transients.23À25 Cyclothiazide is markedly
less effective in this regard than other types of mod-
ulators, including aniracetam and benzoylpiperidine
compounds,16À18,24 which probably act more promi-
nently on channel closing and agonist dissociation than
The present study used IDRA-21 as a lead compound
because of its proven efficacy in enhancing synaptic
responses. In this two-stage study, previously unex-
plored substitutions were made to the benzothiadiazide
core structure, in particular on the aromatic ring, in
hopes of improving the affinity of these compounds. In
the first stage, the most promising among 64 com-
pounds was identified using an indexed combinatorial
library approach. Analogues of this compound were
then synthesized in the second stage to establish more
comprehensive structure–activity relationships. Drugs
Figure 1. Structures of known AMPA receptor modulators. Depicted are eight known AMPA receptor modulators.

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1231
were characterized by measuring their effect on AMPA
receptor currents in excised-patches and on the binding
of radiolabeled agonists. The compounds discovered in
this study showed greatly improved affinity and distinct
effects on AMPA receptor kinetics that set them apart
from earlier benzothiazides. While this study was in
progress, Pirotte et al.29 showed that certain pyr-
idothiazine analogues of IDRA-21 exhibit similar gains
in AMPA receptor affinity.
Scheme 1.
pool from the x-axis and from the y-axis. Thus, if the
library does contain hits, their structures would be
identified at the intersection of an active pool from the
x-axis and an active pool from the y-axis. A hypothe-
tical example shows the intersection of an active pool
produced from the sulfonamide C and an active pool
produced from the aldehyde 5; the structure of the hit
would be postulated to be the individual compound
produced by these two building blocks (Fig. 2).
Resynthesis and testing of this particular would confirm
the assumption. As a general rule, for this approach to
be successful, the reactions need to be general, high
yielding, and very clean. If these criteria are not met,
then impurities in the reaction pools could make the
assay results inconclusive (Scheme 1, Table 1).
Results
Background on the indexed library approach
An indexed combinatorial library approach was
employed in order to expedite the discovery of new,
more potent IDRA-21 analogues.30,31 Pirrung et al. first
described this unique combinatorial approach for the
identification of acetylcholinesterase inhibitors, wherein
the compounds of the library are represented as a two-
dimensional matrix where each matrix element is the
resultant compound derived from the building blocks
envisioned on the x- and y-axes, respectively. For this
study, eight aldehydes (1–8) and eight sulfonamides (A–
H) were used to conceptualize an 8 Â 8 grid, where each
matrix element represents the benzothiadiazide pro-
duced from the reaction between a sulfonamide (A–H,
the x-axis) and an aldehyde (1–8, the y-axis). Rather
than preparing all members of the library individually
(64 in all in this study) and assaying them individually,
the indexed approach allows one to identify new ‘active
hits’ through preparing and assaying compound pools.
Here 16 pools (i.e., mixtures), containing eight new
benzothiazide compounds in each pool, were to be pre-
pared from combinations of the eight aldehydes orga-
nized along the y-axis (1–8) and the eight sulfonamides
organized along the x-axis (A–H). Following the pre-
paration of the compound pools, neurobiological assays
would be employed to determine whether a certain pool
contained any active hits. Each member of the library is
therefore tested twice, once each as a component of a
Library synthesis
The individual sulfonamides A–H were chosen based on
their availability from commercial starting materials
and their relation to the corresponding substructures of
cyclothiazide and IDRA-21. The resultant benzothia-
diazides would resemble cyclothiazide or IDRA-21, and
make it possible to examine the effects of various other
functional groups, namely bromide, chloride, nitro, sul-
fonamide, and alkyl at various positions on the aro-
matic ring. The commercially available aldehydes, 1–8,
were selected in order to explore the tolerance for vari-
ous functional groups at the 30-position. Aldehydes 1–3
yield IDRA-like compounds with different size alkyl
substituents; aldehydes 4–8 yield larger substituents that
are similar in size to the 30-norbornenyl moiety of
cyclothiazide.
Figure 2. Hypothetical indexed combinatorial library depicted as a two-dimensional matrix. The figure depicts the hypothetical result (5C) from a
completed indexed library search. As stated in the text, the most active compound(s) in a library are identified at the vertex of two pools of com-
pounds that share activity. Chemical synthesis of the individual compound should confirm the results from the library search.

1232
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
Scheme 2.
The sulfonamides were synthesized according to known
literature procedures (Scheme 2).32 Compounds A and F
were synthesized from p-chloroaniline (11) and o-ethyl-
aniline, respectively, via treatment with chlorosulfonyl-
isocyanate (CSI) followed by acid hydrolysis. Commer-
cially available 2-aminobenzenesulfonamide (C) was
treated with bromine in acetic acid to give the bromi-
nated product B. Sulfonamide F was treated with
N-chlorosuccinimide in refluxing acetonitrile to give D.
Compound 12 (the initial adduct of aniline and CSI)
was treated with nitric acid in refluxing sulfuric acid and
then hydrolyzed in 50% sulfuric acid to give E.
tory post-synaptic potentials (EPSP’s) in CA1 of
hippocampal slices; (iv) binding of [3H]AMPA to mem-
branes obtained from rat brain.
Excitatory neurotransmitter ([3H]AMPA) binding was
enhanced by less than 10% by all pools (125 mM max-
imal concentration of each element) except D, H, 1 and
4 (Fig. 3 A). The matrix component H4 is similar to
cyclothiazide with a cyclohexyl ring substituting for the
norbornenyl group present in the latter; it is shown
elsewhere that this analogue is equipotent to cyclothi-
azide.33 The latter reduces [3H]AMPA binding by about
half at the concentration used here34 and thus the effects
of pools H and 4 can be explained by the presence of the
cyclothiazide analogue H4. The large increase in
[3H]AMPA binding by pools D and 1 was of greater
interest because no other compound pools had caused a
binding increase under the assay conditions employed.
The fact that both pools produced an equal size increase
suggested that the effect might be produced by a single
component, the matrix element leading to D1.
The compound pools were prepared in order to expedite
the identification of new potential lead structures by the
indexed approach discussed earlier. Pools A–H were
prepared by treating individual sulfonamides with a
solution containing all eight aldehydes in equimolar
concentration to produce the pools of compounds that
make up the vertical columns. Pools 1–8 were prepared
by treating individual aldehydes with solutions equi-
molar in all sulfonamides to produce the pools of com-
pounds that make up the horizontal rows.
Pools D and 1 also showed superior efficacy in most
other tests (Fig. 3B). Pool D prolonged deactivation of
fast responses to glutamate more than 4-fold (500 mM),
the only other pool among A–H that produced some
effect being F which has a 5-ethyl group in common
with D. Pool 1 increased deactivation 2.6-fold; this
effect decreased as the size of the substituent on the
heterocyclic ring increased and disappeared with aro-
matic substitutions. Pools D, F, and 1 also effectively
reduced receptor desensitization (not shown), along
with pools H and 4, which contain the cyclothiazide
analogue. Effects on synaptic receptors were assessed
for pools A–H (250 mM) from the change in the half-
width of the field EPSP, which is a more reliable indi-
cator of AMPA receptor modulation than response
amplitude. The response width was increased by about
Biological testing of the indexed library
The various pools were prepared as discussed previously
and tested as mixtures of eight compounds. In order to
1
ensure that the reactions were complete, TLC and H
NMR analyses were performed on each pool. Since
AMPA receptor modulators differ considerably in the
way they alter receptor kinetics,17,18 multiple test cri-
teria were used to characterize the pools. We specifically
tested the effects on: (i) peak and steady-state currents
and rate of desensitization after step application of glu-
tamate to excised patches from rat hippocampal pyr-
amidal cells; (ii) response deactivation after a 1-ms
glutamate pulse to the excised patches; (iii) field excita-
Table 1. Library components for indexed combinatorial library
Sulfonamide
R1
R2
R3
R4
Aldehyde
R5
A
B
C
D
E
F
H
H
H
H
H
H
H
H
Cl
Cl
Cl
Br
H
Cl
H
H
H
H
H
H
H
H
1
2
3
4
5
6
7
8
CH3
CH(CH3)2
CHCHCH3
CH(CH2)5
C6H5
H
CH2CH3
H
CH2CH3
H
NO2
H
H
SO2NH2
3-Pyrido
4-CH3OC6H4
2,5-(CH3O)2C6H3
P
H
H

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1233
compound (Scheme 3) and biological testing confirmed
this result. Compound D1 enhances [3H]AMPA binding
with an EC50 of 22 mM (Fig. 4), which is similar in
magnitude to that of cyclothiazide (31 mM),34 but it
increases binding instead of decreasing it; a more
detailed analysis of the effects of D1 on physiology and
binding will be given elsewhere. Since the effect of an
ethyl substituent at the 50-position gave such pro-
nounced effects, examination of additional analogues
with similar substitution patterns was performed in the
second phase of this project.
Scheme 3.
50% by group D and by less than 15% by the other
pools (not shown); the relative lack of effect of H and A
was expected given that cyclothiazide produces only
small changes in synaptic responses and IDRA-21
(matrix element A1) needs concentrations of at least 500
mM to be effective.35
Synthesis of D1 analogues and SAR
In the previous stage of this investigation, it was dis-
covered that a simple alkyl substituent (ethyl) at the 50-
position of IDRA-21 led to enhanced binding and
activity. Since this previously untested substitution had
such a pronounced effect, a structure–activity study was
conducted by synthesizing and testing analogues of D1.
Three families of second-generation analogues were
examined: (1) halide and alkyl substitutions at various
positions on the aromatic ring, (2) alkyl substitutions at
the 30-position, and (3) alkyl substitutions on the 20- and
40-nitrogens. Screening new compounds primarily relied
on binding assays to determine affinity; if a compound
were reasonably potent, the more time-consuming patch
current measurements (electrophysiology) were per-
formed to verify physiological efficacy. By performing
these substitutions on the core structure of the ben-
zothiadiazide, a clearer understanding of the structure–
activity relationships (SARs) for these compounds was
developed.
The indexed library approach led to the identification of
a new compound inferred to be D1 that appeared to
have greatly improved affinity for AMPA receptors
compared to IDRA-21 and yet differed from cyclothi-
azide in important aspects. Individual synthesis of this
Figure 3. Effects of library pools on the binding of [3H]AMPA (A)
and on deactivation rate constants of patch responses (B). Aqueous
solutions of pools A–H and 1–8 were prepared by dissolving the reac-
tion product in DMSO (dimethylsulfoxide) to a concentration of 100
or 400 mM and then diluting these solutions 100-fold into the assay
buffer to give nominal concentrations of approximately 1 or 4 mM for
the total of all eight compounds, or 125 or 500 jiM for each individual
component of the pool. Precipitates in the final dilutions were removed
through 0.25 mm filters; no efforts were made to estimate actual con-
centrations and thus the values given represent upper limits. (A) Spe-
cific binding of [3HJAMPA to brain membranes was measured at
25 ꢀC in the presence of 50 mM KSCN and either 1% DMSO (con-
trol) or one of the pool mixtures containing up to 125 mM of each
component. Binding in the presence of the compounds was expressed
as a percentage of control binding (means and SEM of triplicate
determinations). (B) Pulses of 10 mM l-glutamate were applied for
one millisecond to excised patches in the absence and in the presence
of a pool mixture at a nominal concentration of 500 mM per com-
pound. For each condition, a single exponential was fitted to the decay
phase of the response. The time constants of these exponentials
(‘deactivation time constants’) were then used to calculate the ratio
‘with’ versus ‘without’ compound plotted on the y-axis.
Figure 4. Effect of Dl on [3H]AMPA binding. Binding of 50 nM
[3H]AMPA to rat brain membranes (25 ꢀC, with 50 mM KSCN)
was measured in the presence of the Dl concentrations indicated on
the x-axis and expressed as a percentage of the binding in the absence
of compound. A four-point logistic equation was fitted through to the
data points through nonlinear regression. Average values (mean and
SEM) from 11 separate experiments are: EC30 26.6Æ1.8 mM: maximal
binding: 269Æ6% of control; Hill coefficient: 2.2Æ0.1.

1234
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
other substituents at the 70-position; and (4) Group IV
analogues are tricyclic analogues derived from indolines
and contain either a hydrogen or a halide at the 70-
position. All members of Groups I–III (16a–u) were
prepared from commercially available anilines by treat-
ing the aniline with chlorosulfonyl isocyanate (CSI),
followed by acid hydrolysis32 and condensation with
acetaldehyde (Scheme 4). Compounds 18a–e (Group
IV) were synthesized similarly from their requisite
indolines.
Biological testing of Groups I–IV
Scheme 4.
The agonist [3H]-fluorowillardine was used in binding
tests because it allows binding to be measured without
non-physiological additives; EC50 values obtained with
this ligand are slightly lower than those from tests using
[3H]AMPA (Table 2). Table 2 shows the EC50 and the
amount of binding at saturating compound concentra-
tion, expressed as a percentage of that without com-
pound. If it was not possible to establish a reliable
concentration–effect relation by fitting a four-point
logistic equation, the percent of control binding at a
single concentration, usually near the solubility limit, is
given.
Groups I–IV
The first goal of this second stage was to gain a better
understanding of the role the halide and alkyl sub-
stituents play in the binding and activity of IDRA-21
and D1. Since results from prior studies,13 and from the
indexed library approach, suggested that longer alkyl
chain and aromatic substitutions at the 30-position lead
to a loss in activity, only compounds with a methyl
substituent at this position were synthesized. The ana-
logues were organized into groups based on their similar
aromatic substitution patterns: (1) Group I analogues
have an alkyl substituent at the 50-position and either a
hydrogen or a halide at the 70-position; (2) Group II
analogues have a methyl at the 50-position and contain
either a methyl or a chloride or both at various posi-
tions; (3) Group III analogues have either a halide,
methoxide, or hydrogen at the 50-position and various
Group I
Group I compounds bear alkyl substituents at R1 of
varying lengths, in combination with chloride, fluoride
and hydrogen substituents at R3. It is evident that
binding is affected by the substituent at the R1 position.
Table 2. Structures and effects of Groups I–IV
Group
I
Compd
R1
R2
R3
R4
EC50c (mM)
Max (%)
Concn (mM)
% effect
D1c
16a
16b
16c
16d
16e
16f
16g
16h
16i
16j
16k
16l
16m
16n
16o
16p
16q
16r
16s
16t
16u
18a
18b
18c
18d
18e
CH3CH2
CH3CH2
CH3CH2
CH(CH3)2
CH(CH3)2
CH3CH2CH2
CH3CH2CH2
CH3
CH3
CH3
CH3
CH3
CH3
CH3
F
H
H
H
H
H
H
H
H
H
Cl
F
H
H
H
H
H
H
H
H
H
H
H
H
H
Cl
H
H
H
H
H
H
H
H
H
H
H
H
H
17
29
101
34
>200
170
315
290
265
405
H
Cl
H
Cl
H
Cl
F
420
200
N.E.
96
90
115
190
150
179
II
H
CH3
Cl
CH3
CH3
Cl
H
H
H
H
H
H
H
H
H
H
H
H
H
H
50a
200
75a
94
H
H
H
H
Cl
N.E.
N.E.
N.E.
N.E.
N.E.
80a
III
500
400
F
Cl
Cl
CH3
CH3CH2
H
OCH3
CH3CH2
141
137
120
400
400
200
1000b
N.E.
114
120
N.E.
68
OCH3
OCH3
H
H
H
H
H
CH3
CH3
F
H
F
Cl
H
Cl
IV
247
76
85
67
203
254
184
223
320
18
aSolubility limit.
bAssay with [3H]AMPA as radioligand.
cBinding parameters are from typical experiments and were replicated within a factor of 1.3 in at least one additional experiment. The EC50 for D1 is
the mean value from nine experiments.
N.E., no effect.

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1235
Methyl substituted compounds (16g and 16h) allowed
binding of the agonist to increase to 150–200%, ethyl
substituted compounds (D1 and 16a,b) to 265–315%,
and propyl/isopropyl substituted compounds (16c–16f)
to about 400% of control. The highest binding affinity
was obtained with D1 [17.4Æ1.2 mM (SEM), n=9] and
its fluorinated analogue 16a (29 mM), with the isopropyl
bearing analogue 16c being slightly lower (34 mM).
Interestingly, when the ethyl substituent of D1 was
replaced with a propyl substituent, the affinity declined
precipitously (16e, 170 mM). When the 50-ethyl of D1
was replaced with a methyl group (16g), binding affinity
was reduced about 5-fold (97Æ7 mM, n=3). This com-
pound group also shows that a halide substituent at R3
confers a 5- to 10-fold gain in binding affinity and that F
and Cl are similarly effective.
different effects on amplitude and duration of EPSPs
and the 50-methyl compounds (16g and 16h) may pro-
vide certain advantages over longer chain analogues
despite the lower affinity. For this reason, most of the
compounds hereafter bear the 50-methyl group and
hence the affinities should be compared with those of
compounds 16g or 16h.
Group II
Group II analogues indicate that replacement of the
7-halide with a methyl leads to a loss in affinity. Halides
or methyl groups at R2 and R4 have even lower activity
than their R3-substituted counterparts. Compound 16j
(which bears an additional methyl group at R2) appears
to have reduced affinity but the extent of that change
could not be assessed due to poor solubility.
Excised patch experiments and EPSP measurements in
hippocampal slices confirmed that the length of the
50-alkyl group plays a substantial role in the activity of
these compounds (Table 5). These latter tests also indi-
cated, however, that methyl and ethyl substituents had
Group III
Compounds with a fluoro- (16n, 16o) or methoxy- (16r,
16s) substituent at R1 instead of an alkyl group have
Table 3. Group V compounds
Compd
R1
R2
H
Reagents
R3
R4
EC50 (mM)
Max (%)
Concn (mM)
% effect
N.E.
20a
CH3CH2
CH3
CH3
CH3
H
CH3
200
20b
20c
20d
20e
20f
20g
20h
20I
CH3CH2
CH3
Cl
F
F
F
F
F
F
F
CH3
CH3
H
>400
300
N.E.
CH3
127
178
145
119
CH3
H
CH3
H
100a
20a
N.E.
N.E.
N.E.
N.E.
CH3
H
CH3
H
40a
CH3
H
200
aSolubility limit.
N.E., no effect.

1236
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
little activity at 400–500 mM. It should be noted that
IDRA-21 itself, which has an EC50 value of about 1000
mM in physiological tests (not shown), produced only
small binding changes (ꢁ25% at 1 mM), and thus
binding testes are not suitable to rank the potencies of
these low affinity compounds. Interestingly, when R1 is
substituted with a chloride substituent in combination
with a methyl group at R3, the compound was nearly as
effective as 16g; however, the R3-ethyl substituted ana-
logue 16q had reduced affinity. Finally, compounds 16t
and 16u are IDRA-21 analogues in which the 70-Cl was
replaced with either a fluoride or an ethyl group; neither
of those substitutions seemed to produce a significant
improvement over IDRA-21 according to the binding
tests.
drop in affinity (178 mM, 20e) was observed in the 30-
ethyl substituted analogue. Analogues with larger sub-
stituents at the 30-position, such as the isopropyl (20f),
t-butyl (20g), n-butenyl (20 h), and phenyl (20i) groups,
showed no activity at concentrations below their solu-
bility limit of 100, 20, 40, and 200 mM, respectively. A
30-carboxyl analogue had no effect up to 1 mM (not
shown).
The achiral gem-dimethyl analogues (20a–c) of D1 and
16h exhibited a drastic loss in affinity. Compound 20b
had barely detectable effects at 200–400 mM and crude
estimates indicate an EC50 on the order of 400–600 mM.
Its affinity is thus at least 30 times lower than that of D1;
the implications of these results will be discussed later.
Group IV
Group VI
The indolyl-analogues in Group IV can be considered
conformationally constrained D1 analogues. Com-
pound 18e is thus similar to D1 in regards to the length
of the alkyl chain, and 18c is equally comparable in this
regard to 16g. Interestingly, the effects on binding of
18b and 18c are almost identical to those of 16g and 16h
with only a slight gain in affinity. The effects of com-
pound 18e were identical to those of D1 but not those of
16c. This indicates that the binding conformation of D1
may resemble that of the conformationally constrained
18e.
Groups I–IV showed the effects of substituting the aro-
matic ring at various positions, from which it was con-
cluded that a methyl group at the 50-position and a
halide at the 70-position are optimal. The 30-methyl
substituent was confirmed as the optimal group in the
Group V study. At this point in the research project, we
pursued analogues where the heterocyclic nitrogens
were substituted with the expectation of improving
binding affinity, physiological efficacy, and water solu-
bility (Group VI). Analogues that contain an alcohol,
ether, ester, carboxylic acid, or a nitrile were chosen as
synthetic targets because they could potentially enhance
the water solubility of the parent benzothiadiazide, and
would also diversify our SAR.
Group V compounds
Several 30-substituted benzothiadiazides were prepared
with the same aromatic substitution pattern as D1 in the
indexed combinatorial library study discussed earlier,
but only the 30-methyl substituted compound produced
any activity. A closer look at the effects that other
30-substituents would have on binding and biological
activity was taken; by doing so, SAR would be devel-
oped to help define the substitution limits of this posi-
tion. Several new analogues were prepared that
contained various 30-alkyl substituents (Group V). Fur-
thermore, there was a particular interest in examining
achiral D1 analogues. It is known that both cyclothi-
azide and IDRA-21 have enantiospecific activity,26,28
but if an achiral analogue has similar activity, then
enantiospecific syntheses and/or resolution of racemic
mixtures could be avoided. Thus, the gem-dimethyl
achiral analogues (20a–c) were prepared from the
requisite sulfonamide precursors by treatment with 2,2-
dimethoxypropane (Table 3). Also, the achiral dihydro
analogue 20d was obtained similarly by treatment with
formaldehyde. The other Group V analogues examined
the effects that larger alkyl chains have on activity.
Synthesis of Group VI compounds
Two synthetic routes were employed in order to obtain
the new analogues. In the first route, benzothiadiazides
16h and D1 were treated with sec-butyllithium at À78 ꢀC,
followed by the electrophile 21. The intermediate sulfates
were then hydrolyzed with aqueous acid to give 22a and
22b, respectively; however, this reaction sequence was
problematic. For example, if the temperature of the
reaction and the rate of addition were not carefully
controlled, direct addition of sec-butyllithium to the
heterocycle would result. In cases where the deprotona-
tion and addition of 21 were successful to produce the
required alkylated intermediate, the hydrolysis of the
sulfate with dilute acid led to concomitant hydrolysis of
the heterocycle, giving the aminobenzenesulfonamide as
the major side-product. Several other bases were also
examined such as sodium hydride, potassium carbonate,
and triethylamine, but only sec-butyllithium gave the
desired alkylated product. Nevertheless, this sequence
was successful enough to allow for the preparation of
suitable quantities of material for testing and for the
preparation of the methyl ether (23) and the acetate (24)
analogues (Scheme 5). A more general set of conditions
would need to be discovered in order to improve this
route for multiple analogue syntheses.
Biological testing of Group V compounds
It was found that 30-substitutions other than a methyl
group lead to a reduction in binding. For instance,
when the methyl group was replaced with a hydrogen
substituent (as in the case for 20d), a modest loss in
affinity was observed compared to its methyl counter-
part (EC50 127 mM vs 90 mM of 16 h). A nearly 2-fold
Despite the initial problems with sec-butyllithium as the
base, we were able to successfully alkylate the hetero-
cycle with several activated electrophiles. For example,

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1237
Scheme 5.
Scheme 6.
treatment of 16h with s-butyllithium followed by addi-
tion of methyl bromoacetate, bromoacetonitrile, and
benzyl bromide led to 26a–c, respectively. The N-4 ben-
zyl analogue (25) was also treated with s-butyllithium
followed by 21 to give 26f. While our work was in pro-
gress, Pirotte et al. reported that pyridothiadiazides
could be alkylated in good yield with potassium car-
bonate as the base in refluxing acetonitrile.29 When their
procedure was applied to our system with methyl bromo-
acetate, bromoacetonitrile, and benzyl bromide as the
electrophiles, clean conversion into the alkylated pro-
ducts resulted (Scheme 6). This second method proved
to be an effective alternative to the sec-butyllithium
procedure and was therefore adopted for further synth-
eses of 26a–c,f. Additionally, analogue 26d was
obtained via saponification of 26c and 26c was also
reduced with sodium borohydride in methanol to yield
alcohol 22a.
ent compounds (Table 4). Compound 22a, the hydroxy-
ethyl derivative of 16h, has an EC50 of 115 mM (versus
90 mM) and it had a slightly lower effect on increasing
agonist binding compared to the parent 16h (23% vs
50%). Similar results were obtained with the acetate
(24) derivative of 22a. Introducing a methyl carboxy
group at the N-2 position, either as the free acid (26d) or
as the methyl ester (26c), completely abolished any
activity, but the corresponding nitrile (26b) was as
potent as the parent compound 16h.
While this study was in progress, Desos et al. reported
that S 18986 (Scheme 7) was active at inhibiting AMPA
receptor desensitization in Xenopus oocytes.36 An ana-
logue of S 18986 was synthesized based on the structure
of 16h. This tricyclic compound (28) was obtained by
treating 19c with the tosyl aldehyde 27 followed by
heating to reflux. This compound had no effect on
binding below 100 mM and caused only a small (13%)
increase at 400 mM. It thus appears to be considerably
less potent than 16h and the 3-ethyl derivative 20e.
We also discovered that a completely regioselective
reduction of compound 20i to the corresponding N-4
benzyl product with sodium cyanoborohydride in acetic
acid at 0 ꢀC could be performed. The reduced product
was then condensed with acetaldehyde under standard
conditions to yield the N-4 benzylated analogue 27.
Alkylation with methyl bromoacetate gave ester 26e and
subsequent reduction with lithium aluminum hydride
yielded the alcohol 26f. The N-2 benzyl compound 26a
was obtained from 20i by regioselective benzylation
with sodium borohydride in methanol, followed by
condensation with acetaldehyde. Although these two
reductions were convenient, they were only effective
with the phenyl-substituted compounds.
Table 4. Binding data for Group VI compounds
Compd
EC50 (mM)
Max (%)
Concn (mM)
% effect
22a
22b
23
24
25
115
69
360b
143
123
477
40
120
200
15a
N.E.
N.E.
26a
26b
26c
26d
26e
26f
28
89
211
500
1 mM
50a
N.E.
N.E.
N.E.
N.E.
200
>200
Results for Group VI analogues
aSolubility limit.
bAssay with [3H]AMPA as radioligand.
N.E., no effect.
The binding data show that many of the Group VI
compounds have lower binding affinities than their par-

1238
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
Scheme 7.
receptor modulator. The patch experiments were used
Table 5. Patch data for selected compounds
to monitor the reliability of binding tests; a more com-
plete analysis of the effects of D1 on AMPA receptor
currents will be presented elsewhere. Most tests were
done at a compound concentration of 200 mM which in
the case of D1 completely blocked desensitization. At a
concentration of 30 mM, D1 raised to steady-state level
to 70% which is in qualitative agreement with an EC50
values of 17–25 mM determined in binding tests. It is
evident that the other compounds with reasonably high
potency in binding, such as 16a–c, 16h–j, and 16p, pro-
duced a commensurate blockade of desensitization at
200 mM whereas compounds inactive in binding pro-
duced only small effects.
Compd
Test concn (mM)
Steady state/peak (%)
D1
30
200
50
200
30
200
200
200
200
200
200
200
50
100
100
200
80
200
200
200
200
200
200
30
70
100
95
100
70
83
48
29
52
100
100
100
20
40
23
N.E.
20
88
30
38
16a
16b
16c
16d
16e
16f
16g
16h
16i
16j
16l
16m
16n
16o
16p
16q
16r
16s
16t
16u
18a
18b
18c
Discussion
The present study shows that alkyl substitution at the
50-position of the aromatic ring on the benzothiadiazide
core leads to substantial increases in binding affinity and
biological activity. D1 has an EC50 on the order of 15–
30 mM, which is similar to that of cyclothiazide in patch
clamp experiments (10–30 mM)13 and binding tests (31
mM),34 and about 30 times more potent than IDRA-21.
D1 itself completely blocked desensitization of gluta-
mate-induced responses at 100–200 mM and the binding
affinity of D1 analogues was highly dependent on the
size of the 5-alkyl group, as expected. EC50 values were
on the order of 100 mM for compounds with a methyl
substituent (16g) and as low as 170 mM for compounds
with a propyl substituent (16e). Binding affinities were
similar for Group I and Group IV analogues. Modi-
fications at other positions confirmed findings of earlier
studies: (i) a halide at the 70-position, (ii) the absence of
a substituent at the 60-position, and (iii) the presence of
a methyl group at the 30-position were all important for
optimal compound affinity (Fig. 5).
23
40
49
14
21
14
30
30
N.E., no effect.
Electrophysiology
Patch clamp experiments using patches excised from
hippocampal pyramidal cells were performed on several
of the compounds in Groups I–IV (Table 5). Applica-
tion of 1 mM glutamate to such a patch typically results
in an inward current that reaches a peak within a few
milliseconds and then decays due to a progressive
desensitization to a steady-state level which is 5–10% of
the peak current. The magnitude of the steady-state
current depends on the rates of desensitization and
resensitization, but it is also influenced by other kinetic
parameters such as the channel opening/closing rates
and thus is a sensitive indicator for the efficacy of any
Our data suggest that there is a substantial preference
for the 30-methyl group, an idea that is supported by the
abrupt loss in affinity for compounds 20a–i. The results
Figure 5. SAR summary.

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1239
from the achiral analogues 20a–c provide further evi-
dence that these compounds may bind stereospecifically.
When the 30-methyl group was embedded in a five-
membered ring (29), an abrupt loss in affinity was also
observed. Collectively, these observations suggest that
there may be very little space in the receptor-binding site
for substituents larger than a methyl group.
Interestingly, while our work was in progress, Pirotte et
al.29 reported that pyridothiadiazides had affinities and
physiological effects similar to those of IDRA-21 and
that, among over 50 derivatives tested, conferred the
most significant improvement in potency (Fig. 1). It
seems likely that the interaction of their compound with
the receptor may be equivalent to 18b, in which the N-4
ethyl group of the Pirotte compound is similar to the
N-4 substituent of 18b. In fact, the potency of the Pir-
otte compound in blocking desensitization appears to be
of similar magnitude to our compounds in that it
increased the steady-state current through AMPA
receptors by a factor of five at a concentration of 19 mM.
The addition of the 50-methyl or 50-ethyl groups may
enhance the van der Waals interaction between the
ligand and its receptor. An energy gain of ꢁ36 cal/A2
has been estimated for contact of an alkyl substituent
with its receptor.37 With estimated van der Waals sur-
face areas for methyl and ethyl substituents of 40 and 60
A2, respectively,37 the predicted increases in binding
energies due to these additional interactions would be
approximately 1.4 and 2.2 kcal/mol.38 Taking these
energies into account, an increase in binding affinity
over that of IDRA-21 by a factor of about 10 (for 16g)
and 40 (for D1) would be expected. Indeed, the values
are similar to those actually measured, suggesting that if
the observed gain in binding affinity is due to this effect,
it has approached its theoretical maximum. Since the
50-ethyl group in D1 occupies a major fraction of the 30–
60 pocket of the binding site, then analogues would be
confined to substitutions at the 70, 80, and N-20 posi-
tions. Since 20-substituted analogues were already pre-
pared (Group VI), substitutions at the 70- and 80-
positions remain to be examined.
Sekiguchi et al.19 and Ornstein et al.39 recently described
new potent AMPA receptor modulators (Fig. 1). Unlike
the mostly compact and rigid benzothiadiazides and
ampakines,17 these compounds are elongated and rather
flexible compounds. Whether their compounds and
benzothiadiazides interact with the same binding site on
the AMPA receptor remains to be determined; however,
if they do bind to the same site as the benzothiadiazides
and ampakines, then incorporating D1 into a larger
elongated structure might confer additional gains in
potency. This may be possible via attachment to the N-2
nitrogen of the heterocycle.
Experimental
General
Given that cyclothiazide and the simple benzothiadi-
azides such as IDRA-21 and the compounds described
here contain the same core structure, it would be logical
to assume that they dock in a similar manner to the
AMPA receptor; however, structure–activity compari-
sons indicate that this may not be the case. We prepared
a 30-norbornenyl substituted analogue of 16b (not
shown), and found it be inactive at 100 mM, whereas
16b itself increased binding by 80% at 100 mM. Con-
versely, in cyclothiazide the 30-norbornenyl group is
essential for binding and activity, illustrated by the fact
that closely related analogues that lacked this group
required millimolar concentrations to produce receptor
activation.13 Bertolino et al.27 tested a compound
(IDRA 22) that was identical to IDRA-21 except that
the aromatic ring was substituted with the same
60-chloride and 70-sulfonamide groups present in cyclo-
thiazide, and found that this compound had no effect in
their patch experiments. It thus seems likely that cyclo-
thiazide and the compounds shown here bind differently
to the modulator site or that they bind to two distinct
sites on the receptor. This may also account for the
observations that cyclothiazide and D1 produced very
different changes in many receptor properties. For one,
D1 increased binding of [3H]AMPA nearly 3-fold
whereas cyclothiazide reduces binding under the same
assay conditions by up to 90%.34 D1 also prolonged the
rate at which responses to 1-ms glutamate pulses deac-
tivate receptors by more than 4-fold, whereas cyclo-
thiazide had relatively small effects.24 It will be of
considerable interest to examine whether or not these
two types of benzothiadiazides interact with each other
in a competitive manner.
1H and 13C NMR spectra were obtained on a Bruker
DRX 500 (500 MHz), a DRX 400 (400 MHz), a GN 500
(500 MHz), or a QE 300 (300 MHz). For 1H NMR
spectra acquired in CDCl3, data are reported in ppm
and are calibrated according to internal CHCl3 (7.26
ppm); spectra measured in D2O are calibrated according
to internal HOD (4.80 ppm); spectra measured in
DMSO-d6 were referenced to internal TMS (0.0 ppm).
For 13C NMR spectra measured in CDCl3, data are
reported in ppm and are calibrated according to internal
CDCl3 (77.0 ppm) unless otherwise noted. Data are
reported as follows: chemical shift, multiplicity
(app=apparent, par obsc=partially obscured, ovrl-
p=overlapping, s=singlet, d=doublet, t=triplet,
q=quartet, m=multiplet, br=broad, abq=ab quar-
tet), coupling constant, and integration. Infrared (IR)
spectra were obtained on a Perkin-Elmer Model 1600
series FTIR spectrophotometer and are reported in
inverse-wavenumbers (cmÀ1). Melting points (mp) were
obtained from a Laboratory Devices Mel-Temp melt-
ing-point apparatus and are uncorrected. High resolu-
tion mass spectrometry were obtained from the
Departmental Mass Spectrometry facility. Thin-layer
chromatography (TLC) was performed on 0.25 mm
Merck pre-coated silica gel plates (60 F-254), and silica
gel chromatography was performed using ICN 200–400
mesh silica gel. Inert atmosphere operations were con-
ducted under nitrogen passed through a two Drierite
drying tubes in oven or flame-dried glassware. Anhy-
drous tetrahydrofuran (THF), dichloromethane
(DCM), and diethyl ether were filtered through two

1240
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
columns of activated basic alumina and transferred
under Ar (g) in a solvent purification system designed
and manufactured in house by J. C. Meyer. Dry toluene
was obtained similarly on the system by filtering
through two columns of Q5. Unless otherwise noted, all
crude reactions were processed as follows: organics were
dried over solid magnesium sulfate (MgSO4), filtered
and concentrated ein vacuo on a rotary evaporator. Dry
dimethylformamide (DMF) was obtained by passing
through two columns of activated molecular sieves. Tri-
ethylamine (TEA), hexamethylphosphoramide (HMPA),
hexamethyldisilazane (HMDS), and MeOH (MeOH)
were purified by distillation from calcium hydride.
Abbreviations: EtOAc (EtOAc), camphorsulfonic acid
(CSA), N-methylmorpholine-N-oxide (NMO), tetra-
propylammonium perruthenate (TPAP), magnesium sul-
fate (MgSO4). All other reagents were used as purchased
from Aldrich, Sigma-Aldrich, or Acros unless otherwise
stated.
129.1, 125.8, 124.5, 115.0, 23.5, 13.0. FT-IR (KBr) 3401,
3342, 1619-, 1437, 1325, 1185, 1143, 1096 cmÀ1. HRMS
calcd for C8H12N2O2S [M+] 200.0619, found 200.0623.
5-Chloro-3-ethyl-2-aminobenzensulfonamide (D). To a
solution of F (504 mg, 2.52 mmol) in 10 mL acetonitrile
was added N-chlorosuccinimide (316 mg, 2.37 mmol).
The mixture was heated to reflux for 12.5 h, cooled, fil-
tered and concentrated in vacuo. Reaction was incom-
plete by 1H NMR; the purple solides were redissolved in
acetonitrile and more NCS (102 mg, 0.76 mmol) added.
The mixture was refluxed for 15 min and worked up as
before. Column chromatography (40% ethyl acetate/
hexanes) gave pure D (522 mg, 94%); mp 134–135 ꢀC. 1H
NMR (300 MHz, DMSO-d6) d 7.45 (3H, m), 7.19 (1H, d,
J=2.1 Hz), 5.76 (2H, s), 2.53 (2H, q, J=7.3 Hz), 1.14
(3H, t, J=7.3 Hz); 13C NMR (75 MHz, DMSO-d6) d
141.9, 131.8, 131.2, 125.4, 124.8, 118.1, 23.4, 12.7. FT-IR
(KBr) 3458, 3428, 3358, 3269, 3080, 2970, 1631, 1556,
1541, 1452, 1312, 1188 cmÀ1. HRMS calcd for
C8H11ClN2O2S [M+] 234.0230, found 234.0227.
General procedure for the preparation of 2-amino-
benzenesulfonamides (general procedure A)
5-Nitro-2-aminobenzenesulfonamide (E). To a 0 ꢀC solu-
tion of 60% HNO3 (14 mL) and H2SO4 was added 12
(1.98 g, 10.0 mmol), prepared by the general method A
from aniline, portion-wise during a 1 h period. The
mixture was stirred for 20 h at room temperature and
quenched by pouring onto 100 g ice. The white-grey
solid was collected by filtration and stirred in 50 mL
50% H2SO4 and heated to 130 ꢀC until homogenous.
The reaction was cooled to room temperature and
poured onto 200 mL cold water. Neturalization was
achieved with 40% NaOH and extracted with ethyl
acetate (2 Â 100 mL). The combined organic extracts
were dried, filtered and concentrated to give pure E
(1.257 g, 58% for two steps); mp 218–219 ꢀC (lit. 214–
To a stirring solution of chlorosulfonyl isocyanate (0.45
mL, 4.6 mmol) in nitroethane (8 mL) at À42 ꢀC is added
the aniline (4 mmol) dropwise. The solution is stirred
until the intermediate chlorosulfonyl urea precipitates.
Aluminum chloride (612 mg, 4.6 mmol) is then added in
one portion and followed by warming to room tem-
perature over 1 h. The reaction is then heated to 110 ꢀC
for 1 h, then cooled to room temperature and decanted
into ice water. The resulting precipitate is filtered off, or
the oil is extracted with ethyl acetate and dried over
anhydrous MgSO4, to yield the crude product. The
crude product is then heated to 130–140 ꢀC in a solution
of 50% H2SO4 (aq) (10–15 mL) for 2 h. The homo-
genous reaction mixture is cooled to room temperature
and neutralized with 10 N NaOH. Extraction with ethyl
acetate (2 Â 20 mL) is followed the usual processing and
flash chromatography yields the pure compound.
215 ꢀC); H NMR (300 MHz, DMSO-d6) d 8.45 (1H, s),
1
8.11 (1H, dd, J=9.4, 1.4 Hz), 7.62 (2H, s), 7.14 (2H, br
s), 6.90 (1H, d, J=8.8 Hz). HRMS calcd for
C6H7N3O4S [M+] 217.0157, found 217.0516.
5-Chloro-2-aminobenzenesulfonamide (A). Compound A
was prepared by the general method, mp 151–152 ꢀC.
1H NMR (300 MHz, DMSO-d6) d 7.50 (1H, d, J=2.5
Hz), 7.40 (2H, s), 7.27 (1H, dd, J=8.8, 2.5 Hz), 6.82
(1H, d, J=8.8 Hz), 6.00 (2H, s). HRMS calcd for
C6H7ClN2O2S [M+] 205.9917, found 205.9916.
Indexed combinatorial synthesis
Stock solution of aldehydes. A stock solution containing
1.3 mmol of the following aldehydes was prepared in
0.87 mL acetonitrile to give a solution 0.75 M in each
aldehyde (acetaldehyde, isobutyraldehyde, crotonalde-
hyde, cyclohexylcarboxaldehyde, benzaldehyde, 3-pyri-
dine carboxaldehyde, p-anisaldehyde, and 2,5-dimethoxy
benzaldehyde). The solution was used in 0.1 mL por-
tions which are 0.075 mmol in each aldehyde.
5-Bromo-2-aminobenzenesulfonamide (B). Compound B
was prepared according to the literature.40 Isolated by
column chromatography (30% ethyl acetate/hexanes) as
a white solid (0.694 g, 48%), mp 178–180 ꢀC (lit.
179 ꢀC). H NMR (500 MHz, DMSO-d6) d 7.61 (1H, d,
Stock solution of 2-aminobenzensulfonamides. A stock
solution of 2-aminobenzenesulfonamdies was prepared
as follows: 0.9 mmol of compounds A–G in 30 mL aceto-
nitrile to give a solution 0.03 M in each compound. The
solution was used in 2.5 mL portions which contain
0.075 mmol of each compound.
1
J=1.2 Hz), 7.39 (3H, m), 6.77 (1H, d, J=8.8 Hz), 6.02
(2H, s). HRMS calcd for C6H7BrN2O2S [M+] 249.9412,
found 249.9404.
3-Ethyl-2-aminobenzenesulfonamide (F). Yꢀield 53% for
1
two steps by general method; mp 118–120 C. H NMR
(300 MHz, DMSO-d6) d 7.47 (1H, d, J=7.9 Hz), 7.25
(2H, s), 7.16 (1H, d, J=7.1 Hz), 6.60 (1H, t, J=7.7 Hz),
5.62 (2H, s), 2.51 (2H, q, J=7.3 Hz), 1.15 (3H, t, J=7.4
Hz); 13C NMR (75 MHz, DMSO-d6) d 142.8, 131.8,
Standard procedure for combinatorial reactions. Pools
A–G: To a solution of 2-aminobenzenesulfonamide (0.9
mmol, 1.5 equiv per aldehyde) in 2.5 mL acetonitrile was
added 3 A molecular sieves; the solution was stirred in

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1241
an ice bath for 5 min when the stock solution of alde-
hydes (0.1 mL, 0.075 mmol per aldehyde) was added. A
catalytic amount of (Æ) 10-camphorsulfonic acid was
added and the reaction mixture stirred to 2 h at 0 ꢀC and
2–16 h at room temperature. If reaction looked incom-
plete by TLC and NMR, the reactions were heated for
2–24 h at 80 ꢀC in an oil bath. The reaction was worked
up by filtration through Celite. Concentration of
organics gave a crude mixture that was used for biolo-
gical testing. Pools 1–8 A similar procedure to A–G was
used to prepare pools 1–8: except that the stock solution
of 2-aminobenzensulfonamides (2.5 mL, 0.075 mmol in
each compound) was stirred in the ice bath with mole-
cular sieves, followed by addition of a particular alde-
hyde (0.62 mmol, 1.05 equiv per sulfonamide).
5-Ethyl-3-methyl-3,4-dihydro-2H-benzo[1,2,4]thiadiazine
1,1-dioxide (16b). Compound 16b was prepared from 2-
ethylaniline by the general procedures A and C to give
an off-white powder (55%, three steps); mp 166–168 ꢀC.
1H NMR (500 MHz, DMSO-d6) d 7.53 (d, J=11.9 Hz,
1H), 7.36 (d, J=7.7 Hz, 1H), 7.20 (d, J=7.2 Hz, 1H),
6.73 (dd, J=7.6 Hz, 1H), 6.04 (s, 1H), 4.82 (m, 1H),
2.53 (app q, J=7.4 Hz, 2H), 1.50 (d, J=6.2 Hz, 3H),
1.14 (t, J=7.4 Hz, 3H); 13C NMR (125 MHz, DMSO-
d6) d 141.1, 131.2, 129.3, 121.4, 121.3, 116.3, 62.0, 23.1,
20.1, 12.9. FTIR (KBr) 3223, 2976, 2940, 2875, 1598,
1497, 1382, 1314, 1289 cmÀ1. HRMS (CI) calcd for
C10H14N2O2S [M+] 226.0768, found 226.0768.
7-Chloro - 5 - isopropyl - 3 - methyl - 3,4 - dihydro - 2H - ben-
zo[1,2,4]thiadiazine 1,1-dioxide (16c). Compound 16c
was prepared from 16d by the general procedure B to
give an off-white powder in 100% yield; mp 176–178 ꢀC.
1H NMR (300 MHz, DMSO-d6) d 7.70 (d, J=11.8 Hz,
1H), 7.37 (d, J=2.4 Hz, 1H), 7.27 (d, J=2.5 Hz, 1H),
4.8 (m, 1H), 3.15 (septet, J=6.8 Hz, 1H), 1.50 (d, J=6.3
Hz, 3H), 1.17 (d, J=6.9 Hz, 3H), 1.13 (d, J=6.9 Hz,
3H); 13C NMR (75 MHz, DMSO-d6) d 138.3, 136.3,
129.5, 123.7, 123.4, 121.7, 62.4, 27.5, 22.1, 21.9, 21.0.
FTIR (KBr) 3389, 3213, 2969, 2872, 1596, 1491, 1449,
General procedure for chlorination with N - Chloro -
succinimide (general procedure B)
The aminobenzenesulfonamide (prepared by the general
procedure A), or the benzothiadiazide (prepared by the
general procedures A and C) is dissolved in acetonitrile,
treated with N-chlorosuccinimide (1.3 equiv), and
heated to reflux for 5–12 h. The reaction is then cooled,
concentrated, and purified by flash chromatography to
afford the chlorinated product.
1420, 1316, 1290 cmÀ1
. HRMS (CI) calcd for
C11H15ClN2O2S [M+] 274.0543, found 274.0534.
7-Chloro-5-ethyl-3-methyl-3,4-dihydro - 2H - benzo[1,2,4]-
thiadiazine 1,1 - dioxide (D1) (general procedure C). A
solution of 5-chloro-3-ethyl-2-aminobenzenesulfona-
mide (407 mg, 1.74 mmol) containing 3 A molecular
sieves in acetonitrile (8.5 mL) was to 0 ꢀC. Acetaldehyde
(0.15 mL, 2.68 mmol) and (Æ) 10-camporsulfonic acid
(catalytic) were then added and the reaction stirred for
1 h. After the starting material was completely con-
sumed, the reaction was filtered through Celite and the
solvent was evaporated to give the crude D1. Purifica-
tion by filtering through a narrow pad of silica gel gave
pure D1 (443 mg, 98%) as a white solid; mp 181–183 ꢀC.
1H NMR (300 MHz, DMSO-d6) d 7.70 (d, J=11.8 Hz,
1H), 7.35 (d, J=2.2 Hz, 1H), 7.21 (d, J=2.2 Hz, 1H),
6.24 (s, 1H), 4.80 (m, 1H), 2.52 (m, 2H), 1.48 (d, J=7.1
Hz, 3H), 1.13 (t, J=7.4 Hz, 3H); 13C NMR (125 MHz,
DMSO-d6) d 140.2, 132.4, 131.1, 122.2, 120.5, 120.0,
62.2, 23.2, 20.1, 12.7. FTIR (KBr) 3406, 3233, 3002,
2943, 2884, 1491, 1439, 1310, 1282 cmÀ1. HRMS calcd
for C10H14N2O2S [M+] 260.0386, found 260.0386.
5-Isopropyl-3-methyl-3,4-dihydro-2H-benzo[1,2,4]thiadia-
zine 1,1-dioxide (16d). This was prepared from 2-iso-
propylaniline by the general procedures A and C to give
a white powder (54%, three steps); mp 202–204 ꢀC. H
1
NMR (500 MHz, DMSO-d6) d 7.50 (d, J=11.7 Hz, 1H),
7.36 (d, J=7.8 Hz, 1H), 7.28 (d, J=7.5 Hz, 1H), 6.76
(dd, J=7.7 Hz, 1H), 6.08 (s, 1H), 4.81 (m, 1H), 3.13
(septet, J=6.5 Hz, 1H), 1.50 (d, J=6.0 Hz, 3H), 1.16 (d,
J=6.6 Hz, 3H), 1.13 (d, J=6.6 Hz, 3H); 13C NMR
(75 MHz, DMSO-d6) d 140.6, 134.1, 128.7, 121.8, 121.4,
116.6, 62.1, 25.9, 22.6, 22.4, 20.3. FTIR (KBr) 3404,
3192, 2964, 2868, 1598, 1578, 1501, 1447, 1419, 1320,
1292 cmÀ1. HRMS (CI) calcd for C11H16N2O2S [M+]
240.0932, found 240.0930.
7-Chloro-3-methyl-5-propyl-3,4-dihydro-2H-benzo[1,2,4]-
thiadiazine 1,1-dioxide (16e). This was prepared from
16f by the general procedure B to give an off-white
powder in 67% yield; mp 150–151 ꢀC. 1H NMR
(500 MHz, DMSO-d6) d 7.71 (d, J=11.8 Hz, 1H), 7.36
(d, J=2.0 Hz, 1H), 7.22 (d, J=3.4 Hz, 1H), 6.24 (s, 1H),
4.81 (m, 1H), 2.53 (obscured by NMR solvent, 2H), 1.54
(sextet, J=7.6 Hz, 2H), 1.50 (d, J=6.0 Hz, 3H), 0.93 (t,
J=7.2 Hz, 3H); 13C NMR (125 MHz, DMSO-d6) d
132.3, 131.2, 122.6, 120.8, 120.1, 62.5, 32.1, 21.3, 20.4,
14.0. FTIR (KBr) 3395, 3225, 2963, 2932, 2873, 1597,
1496, 1383, 1312, 1243 cmÀ1. HRMS (CI) calcd for
C11H15ClN2O2S [M+] 274.0543, found 274.0554.
5-Ethyl-7-fluoro-3-methyl-3,4-dihydro-2H-benzo[1,2,4]-
thiadiazine-1,1-dioxide (16a). Compound 16a was syn-
thesized from 2-ethyl-4-fluoroaniline by the general
procedures A and C to give an off-white solid (69%,
three steps); mp 156–157 ꢀC. 1H NMR (500 MHz,
DMSO-d6) d 7.65 (d, J=11.8 Hz, 1H), 7.20 (dd, J=7.6,
2.8 Hz, 1H), 7.13 (dd, J=9.6, 2.8 Hz, 1H), 6.00 (s, 1H),
4.80 (m, 1H), 2.55 (quintet, J=7.4 Hz, 2H), 1.50 (d,
J=6.1 Hz, 3H), 1.15 (t, J=7.4 Hz, 3H); 13C NMR
(125 MHz, DMSO-d6) d 153.6 (d, J=236.3 Hz), 138.5,
133.1 (d, J=7.9 Hz), 121.7 (d, J=8.7 Hz), 119.3 (d,
J=24.4 Hz), 107.1 (d, J=23.6 Hz), 62.5, 23.5, 20.4,
12.9. FTIR (KBr) 3409, 3212, 2989, 2931, 1654, 1508,
1449, 1308, 1284 cm À1. HRMS (CI) calcd for
C10H13FN2O2S [M+] 244.0682, found 244.0691.
3-Methyl-5-propyl-3,4-dihydro-2H-benzo[1,2,4]thiadia-
zine 1,1-dioxide (16f). This was prepared from 2-propyl-
aniline by the general procedures A and C to give a tan
powder (33%, three steps); mp 179–180 ꢀC. H NMR
1
(500 MHz, DMSO-d6) d 7.52 (d, J=11.9 Hz, 1H), 7.35
(d, J=7.9 Hz, 1H), 7.17 (d, J=7.4 Hz, 1H), 6.71 (dd,

1242
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
J=7.5 Hz, 1H), 6.02 (s, 1H), 4.81 (m, 1H), 2.50
(obscured by NMR solvent, 2H), 1.55 (m, 2H), 1.50 (d,
J=6.3 Hz, 3H), 0.93 (d, J=7.3 Hz, 3H); 13C NMR
(125 MHz, DMSO-d6) d 141.6, 132.7, 128.2, 122.0,
121.8, 116.5, 62.4, 37.4, 21.4, 20.66, 14.1. FTIR (KBr)
3386, 3212, 2957, 2939, 2873, 1654, 1599, 1499, 1449,
(300 MHz, DMSO-d6) d 7.45 (d, J=11.8 Hz, 1H), 7.26
(d, J=8.1 Hz, 1H), 6.63 (d, J=8.1 Hz, 1H), 5.91 (s,
1H), 4.79 (m, 1H), 2.22 (s, 3H), 2.04 (s, 3H), 1.49 (d,
J=6.2 Hz, 3H); 13C NMR (125 MHz, DMSO-d6) d
142.2, 140.9, 122.4, 121.1, 120.4, 119.2, 62.6, 21.1, 20.1,
13.6. FTIR (KBr) 3407, 3198, 2990, 1596, 1507, 1474,
1447, 1384, 1301, 1284 cm À1. HRMS (CI) calcd for
C10H14N2O2S [M+] 226.0776, found 226.0780.
1384, 1314, 1290 cmÀ1
. HRMS (CI) calcd for
C11H16N2O2S [M+] 240.0932, found 240.0931.
7-Chloro-3,5-dimethyl-3,4-dihydro-2H-benzo[1,2,4]thia-
diazine 1,1-dioxide (16g). This was prepared from 4-
chloro-2-methylaniline by the general procedures A and
C to give a white powder (33%, three steps); mp 256–
258 ꢀC. 1H NMR (500 MHz, DMSO-d6) d 7.71 (d,
J=11.8 Hz, 1H), 7.36 (s, 1H), 7.30 (d, J=1.5 Hz, 1H),
6.21 (s, 1H), 4.83 (m, 1H), 2.16 (s, 3H), 1.50 (d, J=6.0
Hz, 3H); 13C NMR (75 MHz, DMSO-d6) d 141.3, 133.3,
127.4, 122.4, 120.8, 120.1, 62.6, 20.5, 18.0. FTIR (KBr)
3418, 3222, 2988, 2940, 1601, 1497, 1466, 1449, 1420,
1383, 1313 cm À1. HRMS for C9H11ClN2O2S [M+]
calcd 246.0230, found 246.0230.
6-Chloro-3,5-dimethyl-3,4-dihydro-2H-benzo[1,2,4]thia-
diazine 1,1-dioxide (16l). This was prepared from 3-
chloro-2-methylaniline by the general procedures A and
C to give a tan powder (72%, three steps); mp 184–
187 ꢀC. 1H NMR (300 MHz, DMSO-d6) d 7.67 (d,
J=11.8 Hz, 1H), 7.39 (d, J=8.6 Hz, 1H), 6.85 (d,
J=8.5 Hz, 1H), 6.34 (s, 1H), 4.85 (m, 1H), 2.22 (s, 3H),
1.51 (d, J=6.2 Hz, 3H); 13C (75 MHz, DMSO-d6) d
138.0, 123.6, 122.5, 121.4, 118.2, 63.4, 21.2, 15.4. FTIR
(KBr) 3400, 3220, 2992, 1578, 1499, 1445, 1384, 1319,
1288 cmÀ1. HRMS (CI) calcd for C9H11ClN2O2S [M+]
246.0230, found 246.0230.
7-Fluoro-3,5-dimethyl-3,4-dihydro-2H-benzo[1,2,4]thia-
diazine 1,1-dioxide (16 h). This was prepared from 4-
fluoro-2-methyl aniline by the general procedures A and
C to give a white solid (60%, three steps); mp 211–
214 ꢀC. 1H (500 MHz, DMSO-d6) d 7.67 (d, J=11.9 Hz,
1H), 7.21 (s, 1H), 7.18 (s, 1H), 5.97 (s, 1H), 4.80 (m,
1H), 2.17 (s, 3H), 1.49 (d, J=6.1 Hz, 3H); 13C NMR
(125 MHz, DMSO-d6) d 154.0 (d, J=236.3 Hz), 139.8,
128.3 (d, J=8.0 Hz), 122.1, 122.0 (d, J=23.9 Hz), 107.9
(d, J=23.6 Hz), 63.3, 21.2, 18.7. FTIR (KBr) 3394, 3223,
2924, 1499, 1384, 1316, 1238 cm À1. HRMS (CI) calcd
for C9H11FN2O2S [M+] 230.0525, found 230.0524.
8-Chloro-3,5-dimethyl-3,4-dihydro-2H-benzo[1,2,4]thia-
diazine 1,1-dioxide (16m). This was prepared from 5-
chloro-2-methyl aniline by the general procedures A and
C to give a tan powder (42%, three steps); mp 219–
220 ꢀC. 1H NMR (500 MHz, DMSO-d6) d 7.85 (d,
J=8.8 Hz, 1H), 7.15 (d, J=7.9 Hz, 1H), 6.74 (d, J=7.9
Hz, 1H), 6.20 (s, 1H), 4.77 (m, 1H), 2.12 (s, 3H), 1.49 (d,
J=6.2 Hz, 3H); 13C NMR (125 MHz, DMSO-d6) d
144.2, 133.0, 127.5, 123.3, 120.0, 117.9, 61.1, 19.8, 17.7.
FTIR (KBr) 3397, 3210, 2923, 1594, 1560, 1499, 1459,
1380, 1320, 1300, 1239 cmÀ1. HRMS (CI) calcd for
C9H11ClN2O2S [M+] 246.0230, found: 246.0233.
3,5,7-Trimethyl-3,4-dihydro-2H-benzo[1,2,4]thiadiazine
1,1-dioxide (16i). This was prepared from 2,4-dimethy-
laniline by the general procedures A and C to give a tan
5-Fluoro-3-methyl-3,4-dihydro-2H-benzo[1,2,4]thiadia-
zine 1,1-dioxide (16n). This was prepared from 2-fluor-
oaniline by the general procedꢀures A and C to give a
ꢀ
1
1
powder (16%, three steps); mp 225–230 C. H NMR
(500MHz, DMSO-d6) d 7.48 (d, J=11.9 Hz, 1H), 7.16 (s,
1H), 7.04 (s, 1H), 5.83 (s, 1H), 4.79 (m, 1H), 2.18 (s, 3H),
2.12 (s, 3H), 1.48 (d, J=6.1 Hz, 3H); 13C NMR
(125MHz, DMSO-d6) d 140.1, 134.9, 125.6, 124.6, 122.0,
121.3, 62.6, 20.7, 20.2, 18.1. FTIR (KBr) 3399, 3191,
1618, 1501, 1448, 1384, 1314, 1291 cm À1. HRMS (CI)
calcd for C10H14N2O2S [M+] 226.0776, found 226.0773.
yellowish powder; mp 208–210 C. H NMR (500 MHz,
DMSO-d6) d 7.73 (d, J=11.7 Hz, 1H), 7.34 (d, J=7.9
Hz, 1H), 7.29 (dd, J=11.4, 8.2 Hz, 1H), 6.99 (s, 1H),
6.73 (dd, J=7.8, 4.7 Hz, 1H), 4.86 (m, 1H), 1.48 (d,
J=6.1 Hz, 3H). FTIR (KBr) 3367, 3215, 1618, 1500,
1315, 1248 cmÀ1. HRMS (CI) calcd for C8H9FN2O2S
[M+] 216.0368, found 216.0368.
7-chloro-5-fluoro-3-methyl-3,4-dihydro-2H-1,2,4-benzo-
thiadiazine-1,1-dioxide (16o). This was prepared from
16n by the general procedure B to give a brown solid;
7-Chloro-3,5,6-trimethyl-3,4-dihydro-2H-benzo[1,2,4]-
thiadiazine 1,1-dioxide (16j). This was prepared from
16k by the general procedure B to give an off-white
powder in 100% yield; mp 251–253 ꢀC. 1H NMR
(300 MHz, DMSO-d6) d 7.67 (d, J=11.7 Hz, 1H), 7.38
(s, 1H), 6.10 (s, 1H), 4.81 (m, 1H), 2.30 (s, 3H), 2.13 (s,
3H), 1.50 (d, J=6.1 Hz, 3H); 13C NMR (75 MHz,
DMSO-d6) d 141.7, 139.0, 125.9, 122.6, 121.6, 121.5, 63.2,
21.2, 18.2, 15.4. FTIR (KBr) 3415, 3194, 2923, 1591,
1499, 1458, 1388, 1302, 1285 cmÀ1. HRMS (CI) calcd
for C10H13ClN2O2S [M+] 260.0386, found 260.0375.
mp 194–196 ꢀC. H NMR (500 MHz, DMSO-d6) d 7.90
1
(d, J=11.6 Hz, 1H), 7.53 (dd, J=11.3, 1.8 Hz, 1H), 7.41
(s, 1H), 7.22 (s, 1H), 4.87 (m, 1H), 1.48 (d, J=6.1 Hz,
3H). FTIR (KBr) 3365, 3240, 2924, 1499, 1337, 1252
cmÀ1. HRMS (CI) calcd for C8H8ClFN2O2S [M+]
249.9978, found 249.9972.
5-chloro-3,7-dimethyl-3,4-dihyrdo-2H-1,2,4-benzothiadia-
zine-1,1-dioxide (16p). This was prepared from 2-chloro-
4-methylaniline by the general procedures A and C to
give an off-white powder (54%, three steps); mp 239–
242 ꢀC. 1H NMR (500 MHz, DMSO-d6) d 7.76 (d,
J=11.7 Hz, 1H), 7.37 (s, 1H), 7.34 (s, 1H), 6.31 (s, 1H),
4.86 (m, 1H), 2.22 (s, 3H), 1.50 (d, J=6.1 Hz, 3H); 13C
3,5,6-Trimethyl-3,4-dihydro-2H-benzo[1,2,4]thiadiazine
1,1-dioxide (16k). This was prepared from 2,3-dimethyl-
aniline by the general procedures A and C to give a tan
powder (46%, three steps); mp 251–253 ꢀC. H NMR
1

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1243
NMR (125MHz, DMSO-d6) d 138.8, 134.3, 127.3, 123.8,
123.4, 119.5, 63.2, 21.0, 20.2. FTIR (KBr) 3370, 3204,
2980, 1501, 1325, 1309, 1223 cmÀ1. HRMS (CI) calcd for
C9H11ClN2O2S [M+] 246.0230, found 246.0235.
(125 MHz, DMSO-d6) d 153.1 (d, J=240.2 Hz), 140.6,
120.8 (d, J=23.6 Hz), 120.4 (d, J=7.9 Hz), 117.6 (d,
J=7.9 Hz), 109.3 (d, J=23.6 Hz), 61.9, 19.8. FTIR
(KBr) 3378, 3278, 3063, 2993, 1499, 1449, 1427, 1380,
1319, 1286, 1262, 1216, 1151 cmÀ1. HRMS (CI) calcd
for C8H9FN2O2S [M+] 216.0369, found 216.0367.
5-Chloro-7-ethyl-3-methyl-3,4-dihydro-2H-1,2,4-benzo-
thiadiazine-1,1-dioxide (16q). Compound 16q was pre-
pared from 16t by the general procedure B to give an
3-Methyl-1,2,3,4-tetrahydro-5-thia-2a,4-diaza-acenaph-
thylene 5,5-dioxide (18a). Compound 18a was prepared
from indoline by the general procedures A and C to give
a beige solid (27% yield, three steps); mp 193–196 ꢀC.
1H NMR (500 MHz, DMSO-d6) d 7.92 (d, J=12.4 Hz,
1H), 7.23 (d, J=7.4 Hz, 2H), 6.73 (dd, J=7.6 Hz, 1H),
4.60 (dq, J=11.7, 5.9 Hz, 1H), 3.61 (t app, J=8.7 Hz,
1H), 3.24 (q app, J=8.9 Hz, 1H), 3.02 (m, 2H), 1.41 (d,
J=6.2 Hz, 3H). FTIR (KBr) 3112, 2874, 2851, 1735,
1604, 1480, 1461, 1438 cmÀ1. HRMS (CI) calcd for
C10H12N2O2S [M+] 224.0619, found 224.0613.
off-white solid in 60% yield; mp 189–191 ꢀC. H NMR
1
(500 MHz, DMSO-d6) d 7.76 (d, J=11.5 Hz, 1H), 7.41
(d, J=1.6 Hz, 1H), 7.35 (s, 1H), 6.35 (s, 1H), 4.86 (m,
1H), 2.54 (q, J=7.5 Hz, 2H), 1.50 (d, J=6.1 Hz, 3H),
1.12 (t, J=7.5 Hz, 3H). FTIR (KBr) 3367, 3214, 2967,
1612, 1507, 1458, 1318, 1261, cmÀ1. HRMS (CI) calcd
for C10H13ClN2O2S [M+] 260.0386, found 260.0386.
5-Methoxy-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadia-
zine - 1,1 - dioxide (16r). Compound 16r was prepared
from o-anisidine by the general procedures A and C to
give an off-white powder (49%, three steps); mp 172–
173 ꢀC. 1H NMR (300 MHz, DMSO-d6) d 7.54 (d,
J=11.8 Hz, 1H), 7.08 (d, J=8.0 Hz, 1H), 7.00 (d,
J=7.9 Hz, 1H), 6.71 (t, J=8.0 Hz, 1H), 6.25 (s, 1H),
4.81 (m, 1H), 3.83 (s, 3H), 1.47 (d, J=6.1 Hz, 3H); 13C
NMR (125 MHz, DMSO-d6) d 146.6, 134.6, 116.2,
115.5, 112.9, 62.6, 56.3, 20.5. FTIR (KBr) 3397, 3320,
3219, 2990, 1605, 1582, 1506, 1458, 1412, 1386, 1321,
1289, 1251 cmÀ1. HRMS (CI) calcd for C9H12N2O3S
[M+] 228.0569, found 228.0560.
7-Fluoro-3-methyl-1,2,3,4-tetrahydro-5-thia-2a,4-diaza-
acenaphthylene 5,5 - dioxide (18b). Compound 18b was
prepared from 5-fluoroindoline by the general proce-
dures A and C to give a beige solid (23% yield, four
steps); mp 193–197 ꢀC. H NMR (300 MHz, DMSO-d6)
1
d 8.05 (d, J=11.0 Hz, 1H), 7.20 (dd, J=8.8, 0.6 Hz,
1H), 7.13 (d, J=8.5 Hz, 1H), 4.59 (dq, J=11.4, 5.8 Hz,
1H), 3.60 (app t, J=7.5 Hz, 1H), 3.23 (q app, J=9.7
Hz, 1H), 3.05 (m, 2H), 1.40 (d, J=6.1 Hz, 3H); 13C
NMR (75 MHz, DMSO-d6) d 155.2 (J=239.7), 145.8,
134.3 (J=8.9 Hz), 119.7 (J=6.5 Hz), 116.7 (J=23.5 Hz)
106.0 (J=25.3 Hz), 67.2, 49.7, 28.2, 18.6. FTIR (KBr)
5,7-Dimethoxy-3-methyl-3,4-dihydro-2H-1,2,4-benzothia-
diazine-1,1-dioxide (16s). Compound 16s was prepared
from 2,4-dimethoxyaniline by the general procedures A
3112, 2985, 2849, 1730, 1599, 1480, 1460, 1438 cmÀ1
.
HRMS (CI) calcd for C10H11FN2O2S [M+] 242.0525,
found 242.0526.
1
and C to give an off white solid; H NMR (300 MHz,
DMSO-d6) d 7.53 (d, J=11.9 Hz, 1H), 6.66 (d, J=2.3
Hz, 1H), 6.56 (d, J=2.3 Hz, 1H), 5.85 (s, 1H), 4.76 (m,
1H), 3.82 (s, 3H), 3.71 (s, 3H), 1.44 (d, J=6.3 Hz, 3H).
FTIR (KBr) 3379, 3228, 1500, 1319, 1286 cmÀ1. HRMS
(CI) calcd for C10H14N2O4S [M+] 258.0674, found
258.0670.
7-Chloro-3-methyl-1,2,3,4-tetrahydro-5-thia-2a,4-diaza-
acenaphthylene 5,5-dioxide (18c). Compound 18c was
prepared from 18a by the general procedure B to give an
beige solid (76% yield); mp 205–207 ꢀC. 1H NMR
(300 MHz, DMSO-d6) d 8.07 (d, J=11.3 Hz, 1H), 7.29
(s, 2H), 4.64 (dq, J=11.4, 6.1 Hz, 1H), 3.61 (td, J=8.5,
3.0 Hz, 1H), 3.30 (q app, J=8.9 Hz, 1H), 3.06 (m, 2H),
1.41 (d, J=6.2 Hz, 3H); 13C NMR (75 MHz, DMSO-d6)
d 148.3, 134.7, 128.46, 122.1, 121.1, 119.9, 67.2, 49.9,
28.5, 19.0. FTIR (KBr) 3278, 2865, 1604, 1588, 1491,
1466, 1437 cmÀ1. HRMS (CI) calcd for C10H11ClN2O2S
[M+] 258.0230, found 258.0227.
7-Ethyl-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine-
1,1 - dioxide (16t). Compound 16t was prepared from
4-ethylaniline by the general procedures A and C to give
an off-white powder (38%, three steps); mp 191–195 ꢀC.
1H NMR (300 MHz, DMSO-d6) d 7.40 (d, J =11.8 Hz,
1H), 7.26 (s, 1H), 7.16 (dd, J=8.6, 1.6 Hz, 1H), 6.93 (s,
1H), 6.71 (d, J=8.5 Hz, 1H), 4.77 (m, 1H), 2.50
(obscured by NMR solvent, 2H), 1.40 (d, J=6.1 Hz,
3H), 1.12 (t, J=7.5 Hz, 3H); 13C NMR (125 MHz,
DMSO-d6) d 142.3, 133.1, 132.2, 122.4, 121.2, 116.4,
62.3, 27.4, 20.5, 16.2. FTIR (KBr) 3352, 3206, 2964,
1617, 1508, 1320, 1288 cmÀ1. HRMS (CI) calcd for
C10H14N2O2S [M+] 226.0776, found 226.0774.
1,3-Dimethyl-1,2,3,4-tetrahydro-5-thia-2a,4-diaza-ace-
naphthylene 5 - oxide (18d). Compound 18d was pre-
pared as per 18b and isolated as a 2:1 mixture of
unassigned diastereomers; mp 168–173 ꢀC. 1H NMR
(500 MHz, DMSO-d6) d 7.93 (d, J=11.5 Hz, 0.33H),
7.86 (d, J=11.3 Hz, 0.67 Hz), 7.26–7.23 (m, 2H), 6.78
(t, J=7.6 Hz, 0.33H), 6.73 (t, J=7.6 Hz, 0.67H), 4.66
(app sextet, J=6.1 Hz, 0.67H), 4.55 (app sextet, J=6.1
Hz, 0.33H), 3.73 (t, J=8.4 Hz, 0.33H), 3.48 (t, J=8.7
Hz, 0.67H), 3.40–3.37 (m, 1H), 3.22 (dd, J=8.7, 2.4 Hz,
0.67H), 2.83 (dd, J=11.1, 8.5, 0.33H), 1.42–1.40 (m,
3H), 1.30 (d, J=6.7 Hz, 1H), 1.20 (d, J=7.0 Hz, 2H).
FTIR (KBr) 3434, 3323, 2959, 2853, 1597, 1488, 1449
cmÀ1. HRMS (CI) calcd for C11H14N2O2S [M+]
238.0776, found 238.0776.
7-Fluoro-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine-
1,1-dioxide (16u). Compound 16u was prepared from 4-
fluoroaniline by the general procedures A and C to give
a light gray powder (46%, three steps); mp 200–202 ꢀC.
1H NMR (500 MHz, DMSO-d6) d 7.57 (d, J=11.7 Hz,
1H), 7.31 (dd, J=8.0, 2.9 Hz, 1H), 7.22 (ddd, J=8.8,
2.9 Hz, 1H), 7.10 (s, 1H), 6.82 (dd, J=9.2, 4.5 Hz, 1H),
4.79 (m, 1H), 1.41 (d, J=6.1 Hz, 3H); 13C NMR

1244
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
7-Chloro-1,3-dimethyl-1,2,3,4-tetrahydro-5-thia-2a,4-
diaza-acenaphthylene 5-oxide (18e). Compound 18e was
prepared from 18d by the general procedure B; mp 184–
J=8.0 Hz, 1H), 7.20–7.17 (m, 2H), 6.38 (s, 1H), 4.61
(dd, J=8.0, 3.6 Hz, 2H), 2.11 (s, 3H); 13C NMR
(125 MHz, DMSO-d6) d 152.8 (d, J=236.3 Hz), 138.7,
127.2 (d, J=6.8 Hz), 121.4 (d, J=6.8 Hz), 120.9 (d,
J=23.0 Hz), 106.9 (d, J=23.9 Hz), 54.5, 17.6. FTIR
(KBr) 3421, 3204, 3063, 2943, 1502, 1384, 1380, 1302
cmÀ1. HRMS (CI) calcd for C8H9N2SO2F [M+]
216.0369, found 216.0369.
187 ꢀC. H NMR (400 MHz, CDCl3) d 7.37 (m, 1H),
1
7.09 (app t, J=1.6 Hz, 1H), 4.68 (dq, J=12.5, 6.1 Hz,
1H), 4.56 (d, J=12.6 Hz, 1H), 3.74 (app t, J=8.3 Hz,
1H), 3.47–3.40 (m, 1H), 2.80 (dd, J=11.3, 8.3 Hz, 1H),
1.52 (d, J=6.0 Hz, 3H), 1.36 (d, J=6.8 Hz, 3H). HRMS
(CI) calcd for C11H13ClN2O2S [M+] 272.0386, found
272.0380. FTIR (KBr) 3214, 2967, 2874, 1491, 1466,
3-Ethyl-7-fluoro-5-methyl-3,4-dihydro-2H-benzo[1,2,4]-
thiadiazine 1,1-dioxide (20e). Same as general procedure
C, except propionaldehyde was used, mp 185–186 ꢀC.
1H NMR (500 MHz, DMSO-d6) d 7.53 (d, J=11.8 Hz,
1H), 7.19 (m, 2H), 5.84 (s, br, 1H), 4.57–4.54 (m, 1H),
2.18 (s, 3H), 1.97 (m, 1H), 1.76 (m, 1H), 0.99 (t, J=7.4
Hz, 3H); 13C NMR (125 MHz, DMSO-d6) d 153.1 (d,
J=236.4 Hz), 138.7, 127.6 (d, J=7.0 Hz), 121.7 (d,
J=6.1 Hz), 120.9 (d, J=23.0 Hz), 106.8 (d, J=23.4
Hz), 67.5, 26.6, 17.7, 9.3. FTIR (KBr) 3386, 3298, 3215,
3073, 2980, 1490, 1473 cmÀ1. HRMS (CI) calcd for
C10H13FN2O2S [M+] 244.0682, found 244.0677.
1322 cmÀ1
.
5-Ethyl-3,3-dimethyl-3,4-dihydro-2H-benzo[1,2,4]thiadia-
zine 1,1 - dioxide (20a). Compound 19a (308.0, 1.54
mmol) was dissolved in acetonitrile (3 mL) and treated
with 2,2-dimethoxypropane (171.0 mg, 1.60 mmol) and
camphorsulfonic acid (48.6 mg, 0.21 mmol) and stirred
for 1 h. The reaction was then treated with saturated
NaHCO3 (3 mL) and extracted with ethyl acetate (2 Â 5
mL). The organic layer was processed in the usual way
to give the title compound (360.7 mg, 98%) as an off-
white solid; mp 143–145 ꢀC. 1H NMR (500 MHz,
DMSO-d6) d 7.63 (s, 1H), 7.35 (d, J=7.8 Hz, 1H), 7.17
(d, J=7.3 Hz, 1H), 6.69 (dd, J =7.8, 7.5 Hz, 1H), 5.98
(s, 1H), 2.50 (obscured by NMR solvent, 2H), 1.54
(s, 6H), 1.13 (t, J=7.4 Hz, 3H); 13C NMR
(125 MHz, DMSO-d6) d 141.2, 132.4, 130.3, 122.5,
121.8, 121.8, 117.0, 69.8, 29.4, 24.5, 14.1. FTIR
(KBr) 3354, 3191, 2977, 1598, 1570, 1560, 1491, 1447
cmÀ1. HRMS (CI) calcd for C11H16N2O2S [M+]
240.0932, found 240.0923.
7 - Fluoro - 3 - isopropyl - 5 - methyl - 3,4 - dihydro - 2H -
benzo[1,2,4]thiadiazine 1,1 - dioxide (20f). Same as gen-
eral procedure C, except isovaleradehyde was used, mp
ꢀ
1
178–183 C. H NMR (500 MHz, DMSO-d6) d 7.35 (d,
J=12.1 Hz, 1H), 7.22–7.18 (m, 2H), 5.60 (d, J=2.64
Hz, 1H), 4.43 (ddd, J=12.1, 6.0, 3.0 Hz, 1H), 2.18–2.15
(m, 4H), 1.05 (d, J=6.7 Hz, 3H), 1.01 (d, J=6.8 Hz,
3H); ); 13C NMR (125 MHz, DMSO-d6) d 153.2 (d,
J=237.7 Hz), 138.8, 128.1 (d, J=7.6 Hz), 122.3 (d,
J=7.2 Hz), 121.0 (d, J=22.9 Hz), 107.0 (d, J=24.3
Hz),70.8, 30.7, 18.7, 17.6, 17.0. FTIR (KBr) 3417, 3238,
7 - Chloro - 5 - ethyl - 3,3 - dimethyl - 3,4 - dihydro - 2H -
benzo[1,2,4]thiadiazine 1,1-dioxide (20b). Compound
19b was subjected to the same conditions as 19a to give
the title compound in quantitative yield; mp 145–
3204, 2969, 2880, 1495, 1422, 1344, 1311, 1232 cmÀ1
.
HRMS (CI) calcd for C11H15FN2O2S [M+] 258.0855,
found 258.0849.
148 ꢀC. H NMR (500 MHz, DMSO-d6) d 7.82 (s, 1H),
1
7.35 (s, 1H), 7.21 (s, 1H), 2.50 (obscured by NMR sol-
vent, 2H) 1.54 (s, 6H), 1.13 (t, J =7.4 Hz, 3H); 13C
NMR (125 MHz, DMSO-d6) d 140.1, 135.2, 131.9,
122.3, 121.3, 120.4, 69.9, 29.1, 24.2, 13.6. FTIR (KBr)
3385, 3225, 2973, 1596, 1498, 1458 cmÀ1. HRMS (CI)
calcd for C11H15ClN2O2S [M+] 274.0543, found
274.0544.
3 - tert - Butyl - 7 - fluoro - 5 - methyl - 3,4 - dihydro - 2H -
benzo[1,2,4]thiadiazine 1,1-dioxide (20g). Same as gen-
eral procedure C, except pivaldehyde was used, mp 252–
253 ꢀC. 1H NMR (500 MHz, DMSO-d6) d 7.30 (d,
J=12.4 Hz, 1H), 7.26–7.23 (m, 2H), 4.89 (d, J=3.3 Hz,
1H), 4.38 (dd, J=12.4, 3.4 Hz, 1H), 2.24 (s, 3H), 1.0 (s,
9H); 13C NMR (125 MHz, DMSO-d6) d 153.6 (d,
J=236.3 Hz), 138.6, 128.8 (d, J=7.5 Hz), 123.2 (d,
J=7.5 Hz), 121.0 (d, J=22.5 Hz), 107.0 (d, J=22.5
Hz),73.5, 35.1, 25.4, 17.4. FTIR (KBr) 3427, 3247, 3078,
7-Fluoro-3,3,5-trimethylÀ3,4-dihydro-2H-benzo[1,2,4]-
thiadiazine 1,1-dioxide (20c). Same procedure as 20b
with 19c (100%); mp 171–173 ꢀC. H NMR (400 MHz,
2974, 1496, 1478 cmÀ1
. HRMS (CI) calcd for
1
DMSO-d6) d 7.73 (s, 1H), 7.18–7.16 (m, 2H), 5.90 (s,
1H), 2.15 (s, 3H), 1.53 (s, 6H); 13C NMR (125 MHz,
DMSO-d6) d 153.6 (d, J=236.0 Hz), 138.7, 128.0 (d,
J=6.1 Hz), 122.0 (d, J=23.0 Hz), 121.1, 107.6 (d,
J=23.3 Hz), 69.8, 29.1, 18.8. FTIR (KBr) 3378, 3280,
3215, 2987, 2932, 1505, 1478, 1412 cmÀ1. HRMS (CI)
calcd for C10H13FN2O2S [M+] 244.0682, found
244.0683.
C12H17FN2O2S [M+] 272.0995, found 272.0991.
3 - (But - 3 - enyl) - 7 - fluoro - 5 - methyl - 3,4 - dihydro - 2H -
benzo[1,2,4]thiadiazine 1,1-dioxide (20 h). Same as gen-
eral procedure C, except 4-butenal was used, mp 151–
152 ꢀC. 1H NMR (400 MHz, DMSO-d6) d 7.61 (d,
J=11.8 Hz, 1H), 7.21–7.18 (m, 2H), 5.92–5.82 (m, 2H),
5.09 (d, J=17.2 Hz, 1H), 5.02 (d, J=9.3 Hz, 1H), 4.65
(m, 1H), 2.27–2.20 (m, 5H), 2.12–2.01 (m, 1H), 1.91–1.82
(m, 1H); 13C NMR (100 MHz, DMSO-d6) d 153.2 (d,
J=230.0 Hz), 138.7, 137,6, 127.7 (d, J=10.0 Hz), 121.8
(d, J=10.0 Hz), 121.1 (d, J=20.0 Hz), 115.5, 106.9 (d,
J=20.0 Hz), 65.6, 32.5, 28.4, 17.8. FTIR (KBr) 3317,
3118, 3062, 2929, 1477 cmÀ1. HRMS (CI) calcd for
C12H15FN2O2S [M+] 270.0838, found 270.0846.
7-Fluoro-5-methyl-3,4-dihydro-2H-benzo[1,2,4]thiadia-
zine 1,1 - dioxide (20d). Same as general procedure C,
except paraformaldehyde was used and the crude pro-
duct required additional refluxing in ethanol with cata-
lytic sulfuric acid to give the title compound; mp 212–
214 ꢀC. 1H NMR (400 MHz, DMSO-d6) d 7.70 (t,

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1245
7-Fluoro-5-methyl-3-phenyl-3,4-dihydro-2H-benzo[1,2,4]-
thiadiazine 1,1-dioxide (20i). Compound 19c (222 mg,
1.1 mmol) was dissolved in acetonitrile (9.0 mL) and
treated with benzaldehyde (0.35 mL, 3.4 mmol) and
camphorsulfonic acid (307 mg, 1.2 mmol) and stirred
for 24 h. The crude product was filtered through a pad
of Celite and concentrated in vacuo. Column chroma-
tography (25% ethyl acetate/hexanes) gave the pure
product (308 mg, 97%); mp 183–184 ꢀC. 1H NMR
(400 MHz, DMSO-d6) d 8.08 (d, J=12.0 Hz, 1H), 7.66
(m, 2H), 7.45 (m, 3H), 7.26 (m, 2H), 6.20 (app. d, J=1.5
Hz, 1H), 5.77 (d, J=13.8 Hz, 1H), 2.20 (s, 3H); 13C
NMR (100 MHz, DMSO-d6) d 153.5 (d, J=241.4 Hz),
139.0, 137.6, 129.0, 128.6 (d, J=6.8 Hz), 128.4, 127.6,
122.4 (J=6.8 Hz), 121.3 (d, J=22.9 Hz), 107.0 (d,
J=24.0 Hz), 68.7, 17.8. FTIR KBr) 3401, 3260, 3224,
mmol) was added, followed by NaH (30 mg (60% dis-
persion in oil), 0.75 mmol). The reaction was monitored
by TLC and quenched when starting material was no
longer detected. The reaction was subsequently warmed
to 0 ꢀC and quenched with pH 7 buffer, followed by
extraction with EtOAc (2 Â 10 mL), brine washes (1 Â
10 mL) and processing in the usual way. Column chro-
matography (50% ethyl acetate/hexanes) gave the title
compound (74 mg, 58%) as a white solid; mp 105–
107 ꢀC. 1H NMR (400 MHz, DMSO-d6) d 7.25 (m, 2H),
6.06 (d, J=4.0 Hz, 1H), 5.22 (m, 1H), 3.44 (app t,
J=7.3, 6.7 Hz, 2H), 3.25 (s, 3H), 3.10 (m, 1H), 2.84 (m,
1H), 2.20 (s, 3H), 1.52 (d, J=6.4 Hz, 3H); 13C NMR
(100 MHz, DMSO-d6) d 154.8 (d, J=220 Hz), 138.0,
128.3 (d, J=7.3 Hz), 121.5 (d, J=23.0 Hz), 119.5 (d,
J=7.3 Hz), 108.2 (d, J=24.0 Hz), 71.7, 65.7, 58.1, 40.7,
18.3, 17.1. FTIR (KBr) 3319, 3072, 2931, 2813, 1490,
1472, 1331 cmÀ1. HRMS (CI) calcd for C12H17FN2O3S
[M+] 288.0944, found 288.0947.
3072, 1490, 1313 cmÀ1
. HRMS (CI) calcd for
C14H13FN2O2S [M+] 293.0760, found 293.0760.
2-(7-Fluoro-3,5-dimethyl-1,1-dioxo-3,4-dihydro-1H-
benzo[1,2,4]thiadiazin-2-yl)-ethanol (22a). Compound 16
h (2.3 g, 9.9 mmol) was dissolved in THF (30 mL) and
cooled to À78 ꢀC. Then, s-butyllithium (12.0 mL, 1.1 M
in hexanes, 10.9 mmol) was added slowly over 20 min.
Ethylene glycol cyclic sulfate (1.84 g, 14.9 mmol) was
dissolved in THF (10 mL) and added via cannula. The
reaction stirred at À78 ꢀC for 1 h, then room tempera-
ture for 1 h. Concentrated HCl (2.5 mL) was added, and
the reaction stirred for an additional 18 h. Saturated
NaHCO3 (20 mL) was added and the reaction extracted
with EtOAc (3 Â 20 mL) and processed in the usual
way. Flash chromatography (70% EtOAc/hexanes)
gave the title compound (991 mg, 37% yield) as a white
Acetic acid 2-(7-fluoro-3,5-dimethyl-1,1-dioxo-3,4-dihy-
dro -1H -benzo[1,2,4] -thiadiazin -2-yl)- ethyl ester (24).
Alcohol 22a (147 mg, 0.56 mmol) was dissolved in pyr-
idine (1 mL) and cooled to 0 ꢀC, when acetic anhydride
(0.20 mL, 0.21 mmol) was added dropwise. The reaction
was warmed to room temperature and quenched with
1 N HCl (1 mL) and extracted with ethyl acetate,
washed with brine and processed in the usual way. Col-
umn chromatography (65% ethyl acetate/hexanes) gave
the title compound as a white solid (145 mg, 86%); mp
100–102 ꢀC. H NMR (400 MHz, DMSO-d6) d 7.26 (m,
1
2H), 6.10 (d, J=3.8 Hz, 1H), 5.23 (m, 1H), 4.12 (m,
2H), 3.21 (m, 1H), 2.93 (m, 1H), 2.20 (s, 3H), 2.00 (s,
3H), 1.53 (d, J=6.4 Hz, 3H); 13C NMR (100 MHz,
DMSO-d6) d 170.6, 154.0 (d, J=238 Hz), 138.3, 128.6
(d, J=7.0 Hz), 122.0 (d, J=23.0 Hz), 119.7 (d, J=7.0),
108.5 (d, J=24.3 Hz), 66.1, 63.5, 40.39, 21.0, 18.4, 18.0.
FTIR (KBr) 3354, 3072, 2987, 2961, 1728, 1472, 1326
cmÀ1. HRMS (CI) calcd for C13H17FN2O4S [M+]
316.0893, found 316.0891.
solid; mp 159–161 ꢀC. H NMR (400 MHz, DMSO-d6)
1
d 7.27–7.22 (m, 2H), 6.06 (d, J=4.0 Hz, 1H), 5.21 (dq,
J=6.4, 4.0 Hz, 1H), 3.54–3.44 (m, 2H), 2.98 (ddd,
J=14.5, 7.3, 7.3 Hz, 1H), 2.73 (ddd, J=11.0, 11.0, 5.2
Hz, 1H), 2.21 (s, 3H), 1.52 (d, J=6.4 Hz, 3H); 13C
NMR (125 MHz, DMSO-d6) d 153.6 (d, J=238.0 Hz),
138.1, 128.2 (d, J=7.5 Hz), 121.5 (d, J=23.0 Hz), 119.5
(d, J=6.0 Hz), 108.1, (d, J=24.4 Hz), 65.7, 60.9, 43.3,
18.4, 17.1. FTIR (KBr) 3509, 3342, 3072, 2978, 1625,
4-Benzyl-7-fluoro-2-(2-methoxy-ethyl)-3,5-dimethyl-3,4-
dihydro-2H-benzo[1,2,4] thiadiazine 1,1-dioxide (25).
Sodium cyanoborohydride (2.0 g, 32.0 mmol) was dis-
solved in glacial acetic acid (40.0 mL) and cooled to
0 ꢀC. Then, 20i (2.3 g, 7.7 mmol) was dissolved in THF
(10 mL) and added slowly via cannula to the sodium
cyanoborohydride solution. The reaction was stirred for
24 h and quenched with sat. NaHCO3 (200 mL) at 0 ꢀC
and stirred for an additional 2 h. The reaction contents
were extracted with ethyl acetate (3 Â 20 mL), washed
with brine (1 Â 20), and processed in the usual way.
Column chromatography (50% ethyl ether/hexanes)
gave the title compound (2.049 g, 90%), which was
immediately subjected to the next reaction.
1496, 1472, 1314 cmÀ1
. HRMS (CI) calcd for
C11H15FN2O3S [M+] 274.0787, found 274.0783.
2-(7-Chloro-5-ethyl-3-methyl-1,1-dioxo-3,4-dihydro-1H-
benzo[1,2,4]thiadiazin-2-yl)-ethanol (22b). Same as for
22a; mp 159–161 ꢀC. H NMR (400 MHz, DMSO-d6) d
1
7.42 (d, J=2.0 Hz, 1H), 7.28 (d, J=2.0 Hz, 1H), 6.35
(d, J=3.0 Hz, 1H), 5.2 (m, 1H), 4.81 (t, J=6.0 Hz, 1H),
3.51 (m, 2H), 2.96 (q, J=7.0 Hz, 1H), 2.75 (q, J=7.0
Hz, 1H), 2.55 (m, 2H), 1.53 (d, J=7.0 Hz, 3H), 1.15 (t,
J=7.0 Hz, 3H); 13C NMR (100 MHz, DMSO-d6) d
139.9, 133.4, 121.7, 122.0, 121.5, 121.1, 66.0, 61.3, 44.2,
23.4, 18.8, 12.9. FTIR (KBr) 3530, 3401, 2954, 2884,
1495, 1438, 1305, 1235, 1137, 1033, 859, 790, 686, 570
cmÀ1. HRMS calcd for C12H17SO3N2Cl [M+] 305.0726,
found 305.0724.
To the above material (157 mg, 53 mmol) was added
acetonitrile (4.0 mL) and 3 A mol sieves. Excess acetal-
dehyde (1.0 mL) was added dropwise, followed by a
catalytic amount of camphorsulfonic acid. After the
reaction was stirred for 5–6 h, it was filtered through a
pad of Celite and concentrated in vacuo to give the title
7-Fluoro-2-(2-methoxy-ethyl)-3,5-dimethyl-3,4-dihydro-
2H-benzo[1,2,4]thiadiazine1,1-dioxide (23). Alcohol 22a
(122 mg, 0.45 mmol) was dissolved in THF (2.6 mL)
and cooled to À78 ꢀC. Then iodomethane (0.10 mL, 1.6
compound (162 mg, 95%); mp 178–180 ꢀC. H NMR
1

1246
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
(400 MHz, DMSO-d6) d 8.55 (d, J=6.2 Hz, 1H), 7.52
(m, 2H), 7.46 (m, 3H), 7.40 (m, 3H), 7.30 (m, 1H), 4.48
(m, 1H), 4.26 (d, J=16.2 Hz, 1H), 4.20 (d, J=16.2 Hz,
1H), 2.36 (s, 3H), 1.30 (d, J=6.9 Hz, 3H); 13C NMR
(100 MHz, DMSO-d6) d 157.2 (d, J=244.8 Hz), 140.7
(d, J=2.5 Hz), 138.3, 137.9 (d, J=7.8 Hz), 132.3 (d,
J=7.3 Hz), 128.5, 127.4, 127.2, 122.2 (d, J=22.1 Hz),
108.0 (d, J=24.5 Hz), 66.3, 54.9, 19.9, 18.5. FTIR
(KBr) 3237, 3060, 3001, 2943, 2849, 1601, 1472, 1331
cmÀ1. HRMS (CI) calcd for C16H17FN2O2S [M+]
321.1073, found 321.1065.
ched with a saturated solution of NH4Cl (20 mL),
extracted with EtOAc, washed with brine (2 Â 10 mL),
and processed in the usual way to give the crude pro-
duct. Flash chromatography (50% ethyl acetate/hex-
anes) gave the title compound (1.05 g, 74%).
Method B (K2CO3). Compound 16 h (542 mg, 2.4
mmol) was dissolved in acetonitrile (10 mL) and treated
with K2CO3 (503 mg, 3.6 mmol) and methyl-
bromoacetate (0.35 mL, 3.7 mmol). The reaction was
then heated to reflux until starting material was com-
pletely consumed. Then, the reaction was cooled to
room temperature, diluted with water, extracted with
ethyl acetate, washed with brine, and processed in the
usual way to give the crude product. Flash chromato-
graphy (40% ethyl acetate/hexanes) gave the title com-
pound (681 mg, 96%); mp 150–151 ꢀC. 1H NMR
(400 MHz, DMSO-d6) d 7.27 (m, 2H), 6.10 (d, J=3.9
Hz, 1H), 5.28 (m, 1H), 3.83 (d, J=17.8 Hz, 1H), 3.67 (s,
3H), 3.60 (d, J=17.7 Hz, 2H), 2.21 (s, 3H), 1.48 (d,
J=6.4 Hz, 3H); 13C NMR (100 MHz, DMSO-d6) d
169.5, 153.8 (d, J=238.3 Hz), 137.9, 128.6 (d, J=7.0
Hz), 121.8 (d, J=23.1 Hz), 119.9 d, J=7.0 Hz), 108.0
(d, J=24.3 Hz), 65.7, 52.1, 42.7, 17.8, 17.7. FTIR (KBr)
3386, 3079, 2958, 1744, 1493, 1328 cmÀ1. HRMS (CI)
calcd for C12H15FN2O4S [M+] 302.0736, found
302.0736.
2 - Benzyl - 7 - fluoro - 3,5 - dimethyl - 3,4 - dihydro - 2H -
benzo[1,2,4]thiadiazine 1,1-dioxide (26a). Compound 16
h (190 mg, 0.833 mmol) was dissolved in acetonitrile (10
mL) and treated with benzylbromide (0.2 mL, 1.7
mmol), K2CO3 (200 mg, 1.4 mmol), and refluxed over-
night. Upon cooling, ethyl acetate (25 mL) was added
and the solution was washed with water. The combined
organic layers were processed in the usual way and the
crude product was purified by flash chromatography
(40% ethyl acetate: hexanes) tꢀo give the title compound
1
(180 mg, 68%); mp 138–139 C. H NMR (400 MHz,
DMSO-d6) d 7.33 (m, 7H), 6.25 (d, J=4.0 Hz, 1H), 5.37
(m, 1H), 4.15 (d, J=16.0 Hz, 1H), 4.07 (d, J=16.0 Hz,
1H), 2.23 (s, 3H), 1.42 (d, J=7.0 Hz, 3H); 13C NMR
(125 MHz, DMSO-d6) d 154.7 (d, J=238 Hz), 139.8,
139.1, 129.3, 129.0 (d, J=9 Hz), 128.4, 128.1, 127.9,
122.6 (d, J=23 Hz), 109.1 (d, J=24 Hz), 67.1, 45.4,
19.6, 18.8. FTIR (KBr) 3365, 3072, 2983, 1617, 1476,
1330, 1238, cmÀ1. HRMS calcd for C16H17SO2N2F
[M+] 320.0995, found 320.0985.
(7 - Fluoro - 3,5 - dimethyl - 1,1 - dioxo - 3,4 - dihydro - 1H -
benzo[1,2,4]thiadiazin-2-yl)-acetic acid (26d). Com-
pound 26c (453 mg, 1.5 mmol) was dissolved in THF (3
mL) and treated with a solution of sodium hydroxide (1
mL, 10 M, 10 mmol). The reaction was stirred for 1 h,
then acidified with 1 M HCl, and extracted with ethyl
acetate. The combined organics were processed in the
usual way to give the title compound (429 mg, 99%);
(7 - Fluoro - 3,5 - dimethyl - 1,1 - dioxo - 3,4 - dihydro - 1H -
benzo[1,2,4]thiadiazin-2-yl)-acetonitrile (26b). Com-
pound 16 h (325 mg, 1.4 mmol) was dissolved in acetoni-
trile (7 mL) and treated with K2CO3 (319 mg, 2.3 mmol),
bromoacetonitrile (0.20 mL, 2.9 mmol) and refluxed.
After 24 h, the reaction was cooled to room tempera-
ture, diluted with water, extracted with ethyl acetate,
washed with brine, and processed in the usual way.
Flash chromatography (40% ethyl acetate:hexanes) gave
mp 164–165 ꢀC. H NMR (300 MHz, DMSO-d6) d 7.27
1
(m, 2H), 6.08 (d, J=3.9 Hz, 1H), 5.28 (m, 1H), 3.69 (d,
J=17.9 Hz, 1H), 3.50 (d, J=17.9 Hz, 1H), 2.21 (s, 3H),
1.48 (d, J=6.4 Hz, 3H); 13C NMR (100 MHz, DMSO-
d6) d 170.4, 153.8 (d, J=238.3 Hz), 137.9, 128.6 (d,
J=7.0), 121.7 (d, J=23.0 Hz), 120.1 (d, J=7.0 Hz),
108.0 (d, J=24.0 Hz), 65.6, 42.5, 17.9, 17.7. FTIR
(KBr) 3384, 2942, 2755, 2662, 2557, 1732, 1488, 1324,
cmÀ1. HRMS (CI) calcd for C11H13FN2O4S [M+]
288.0580, found 288.0575.
the title compound (315 mg, 62%); mp 162–163 ꢀC. H
1
NMR (400 MHz, DMSO-d6) d 7.31 (m, 2H), 6.27 (d,
J=3.3 Hz, 1H), 5.29 (m, 1H), 4.22 (d, J=18.5 Hz, 1H),
4.14 (d, J=18.5 Hz, 1H), 2.20 (s, 3H), 1.62 (d, J=6.4 Hz,
3H); 13C NMR (100 MHz, DMSO-d6) d 153.8 (d,
J=238.5 Hz), 138.0, 128.4 (d, J=7.0 Hz), 122.1 (d,
J=23.1 Hz), 119.2 (d, J=7.4 Hz), 116.7, 108.0 (d, J=24.5
Hz), 65.8, 30.0, 17.9, 17.7. FTIR (KBr) 3386, 3063, 2991,
2556, 1491, 1335, 1335 cmÀ1. HRMS (CI) calcd for
C11H12FN3O2S [M+] 269.0634, found 269.0638.
(4-Benzyl-7-fluoro-3,5-dimethyl-1,1-dioxo-3,4-dihydro-
1H - benzo[1,2,4]thiadiazin-2-yl)-acetic acid methyl ester
(26e). Method A afforded 581 mg (59%) of 26e.
Method B afforded the title compound (649 mg, 99%);
ꢀ
1
mp 135–137 C. H NMR (400 MHz, DMSO-d6) d 7.43
(m, 7H), 4.55 (dd, J=16.0 Hz, 1H), 4.51 (q, J=7.0 Hz,
1H), 4.13 (dd, J=16.0 Hz, 1H), 4.01 (s, 2H), 3.65 (s,
3H), 2.37 (s, 3H), 1.39 (d, J=6.8 Hz, 3H). FTIR (KBr)
(7 - Fluoro - 3,5 - dimethyl - 1,1 - dioxo - 3,4 - dihydro - 1H -
benzo[1,2,4]thiadiazin-2-yl)-acetic acid methyl ester (26c)
method A (sec-BuLi). Compound 16 h (1.08 g, 4.7
mmol) was dissolved in THF (20 mL) and cooled to
À78 ꢀC. A solution of sec-butyllithium (7.0 mL, 0.73 M
in hexanes, 5.1 mmol) was added dropwise. Then, the
reaction was warmed to 0 ꢀC for 15 min and subse-
quently cooled to À78 ꢀC, when methylbromoacetate
(0.50 mL, 5.3 mmol) was added dropwise. The reaction
was stirred to room temperature overnight, then quen-
3069, 2979, 2868, 1762, 1604, 1476, 1437, 1364 cmÀ1
.
HRMS (CI) calcd for C19H21FN2O4S [M+] 392.1206,
found 392.1206.
2-(4-Benzyl-7-fluoro-3,5-dimethyl-1,1-dioxo-3,4-dihydro-
1H-benzo[1,2,4]thiadiazin-2-yl)-ethanol (26f). Com-
pound 26e (300 mg, 0.77 mmol) was dissolved in THF
(5.0 mL) and cooled to 0 ꢀC. Lithium aluminumhydride

D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
1247
(0.0404 g, 1.1 mmol) was dissolved in THF (6.0 mL)
and cooled to 0 ꢀC in a separate flask. The solution of
26e was then added dropwise to the stirring suspension
of LAH via cannula. Then, water (4.0 mL) was added
very slowly dropwise and stirred for 20 min. Next, a
solution of 15% NaOH (4.0 mL) was added dropwise
and stirred for an additional 20 min. Finally, water
(12.0 mL) was added and stirred for an additional 20
min. The suspension was filtered to remove the inor-
ganic salts and the filtrate was concentrated in vacuo to
give the title compound (278 mg, 98%); mp 104–106 ꢀC.
1H NMR (400 MHz, DMSO-d6) d 7.42 (m, 7H), 4.83
(app. t, J=5.0 Hz, 1H), 4.43 (q, J=6.8 Hz, 1H), 4.27
(dd, J=15.7 Hz, 1H), 4.09 (dd, J=15.7 Hz, 1H), 3.50
(m, 2H), 3.26 (dd, J=6.8 Hz, 2H), 2.39 (s, 3H), 1.37 (d,
J=6.8 Hz, 3H). HRMS (CI) calcd for C18H21FN2O3S
[M+] 364.1257, found 364.1254. FTIR (KBr) 3495,
3049, 2990, 2931, 2861, 1601, 1467, 1449, 1290, 1208,
25,000g). The supernatant was aspirated and the pellet
quickly rinsed with ice-cold buffered saline containing
50 mM KSCN (wash buffer). Compounds were added
from 100-fold concentrated solutions in dimethyl sulf-
oxide (DMSO); control samples received the equivalent
concentration of DMSO. Prior tests determined the
maximal solubility of each compound and verified that
the dilution procedure used in the binding test does not
result in compound precipitation. Background values
(‘non-specific binding’) were measured by inclusion of
5 mM l-glutamate and subtracted from total binding;
separate background values were determined for incu-
bations with and without compound. Protein content
was determined according to Bradford with the reagent
available from Bio-Rad. Binding curves were fitted to the
data points with non-linear regression (Prism, Graph-
Pad; San Diego, CA, USA). [3H]AMPA was purchased
from NEN/Dupont (Boston, MA, USA) and [3H]fluor-
owillardiine from Tocris Cookson, (St. Louis, MO,
USA). All other reagents were commercially available.
1149, 1102 cmÀ1
.
7-Fluoro-9-methyl-2,3,3a,4-tetrahydro-1H-5-thia-4,9b-
diaza - cyclopenta[a]naphthalene-5,5-dioxide (28). The
aldehyde (27) (190 mg, 0.79 mmol) was dissolved in
acetonitrile (8 mL) and cooled to 0 ꢀC. Then 19c (158
mg, 0.77 mmol) and CSA (37 mg, 0.16 mmol) were
added and the reaction stirred to room temperature
overnight. The reaction was then refluxed for 4 h, then
cooled to room temperature, concentrated in vacuo, and
purified by flash chromatography (25% EtOAc/hexanes
! 50% EtOAc/hexanes) to give the title compound
(64%); mp 149–150 ꢀC. 1H NMR (500 MHz, DMSO-d6)
d 7.73 (d, J=11.2 Hz, 1H), 7.36 (dd, J=7.5, 2.9 Hz,
1H), 7.30 (dd, J=9.5, 2.9 Hz, 1H), 4.98 (dd, J=11.1,
6.4 Hz, 1H), 3.68 (dd, J=16.1, 7.5 Hz, 1H), 2.98 (ddd,
J=9.0, 9.0, 4.7 Hz, 1H), 2.35–2.17 (m, 2H), 2.29 (s, 3H),
1.92–1.89 (m, 2H); 13C NMR (125 MHz, DMSO-d6) d
155.6 (d, J=242.0 Hz), 140.0, 134.0 (d, J=7.2 Hz), 128.0
(d, J=6.1 Hz), 122.1 (d, J=22.8 Hz), 107.3 (d, J=24.7
Hz), 71.8, 51.4, 31.2, 22.7, 19.9. FTIR (KBr) 3472, 3413,
1637, 1614, 1467, 1443 cmÀ1. HRMS (CI) calcd for
C11H13FN2O3S [M+] 256.0682, found 256.0680.
EC50 values obtained in the agonist binding assays have
generally been found to correspond to those from
physiological tests, and thus binding provides an effec-
tive method to determine the affinity of AMPA receptor
modulators. However, magnitude and direction of the
binding change differs between compounds and,
although some correlations have been found, there are
no simple relationships with changes in physiological
parameters. The size of the binding change also depends
on the assay conditions, and thus an active compound
might, in some circumstances, produce a zero-magni-
tude effect and appear inactive. To avoid such false
negatives, basic compound tests were routinely carried
out under two different assay conditions (e.g.,
[3H]AMPA plus KSCN versus [3H]fluorowillardiine
without KSCN).
Patch-clamp recordings from pyramidal neurons in the
field CA1
Patch clamp studies were carried out by Dr. Amy Arai
with outside-out patches excised from CA1 pyramidal
neurons of organotypic hippocampal slices. Slice cul-
tures were prepared from 13–14-day-old Sprague–Daw-
ley rats and grown for 2 weeks on cellulose membrane
inserts (Millipore CM) in the incubator. For recording,
a slice was transferred to a chamber and immersed in a
medium containing: NaCl 125 mM, KCl 2.5 mM,
KH2PO4 1.25 mM, CaCl2 2 mM, MgCl2 1 mM,
NaHCO3 5 mM, d-glucose 25 mM, and HEPES 20 mM
(pH 7.3). A patch was excised and relocated to an adja-
cent recording chamber perfused with recording med-
ium (NaCl 130 mM, KCl 3.5 mM, HEPES 20 mM,
MK-801 0.01 mM, and D-AP5 0.05 mM). Patch pip-
ettes had a resistance of 3–8 MOhm and were filled with
a solution containing: CsF 65 mM, CsCl 65 mM,
EGTA 10 mM, MgCl2 2 mM, ATP disodium salt 2
mM, and HEPES 10 mM (pH 7.3).
Biological Experimentals
Binding experiments
Binding experiments were carried out by Dr. Markus
Kessler with membranes from rat brain and were pre-
pared according to previously published procedures.17
Binding assays were conducted at 25 ꢀC with the cen-
trifugation method. Aliquots of the membrane suspen-
sion containing 100 mg protein in 200 mL were incubated
for 45 min with 50 nM [3H]AMPA or 20 nM [3H]fluoro-
willardiine, the compound to be tested, and appropriate
additions. Initial tests with [3H]AMPA as the radi-
oligand were carried out in the presence of 50 mM
KSCN), a chaotropic ion that greatly increases the affi-
nity for AMPA and without which binding could not be
reliable assayed; later assays utilized the more recent
radioligand [3H]fluorowillardiine which binds with high
affinity and does require the inclusion of KSCN. Incu-
bations were terminated by centrifugation (20 min at
A piezo system was employed to rapidly switch solu-
tions applied to the patch. In brief, background medium
and glutamate containing medium were flowing

1248
D. Phillips et al. / Bioorg. Med. Chem. 10 (2002) 1229–1248
continuously through two lines of a bifurcated pipette.
The excised patch was initially positioned in the back-
ground stream. Actuation of the piezo translater moved
the patch into the glutamate containing flow line and
returned it to the original position after 400–800 ms.
Data were acquired with a patch amplifier (AxoPatch-
1D) at filter frequency of 5 kHzand digitized at 10 kHz
with PClamp/ Digidata 1200 (Axon Instrument). To test
the effect of a compound, both flow lines were con-
nected to different reservoirs delivering ‘background
medium+compound’ and ‘glutamate containing med-
ium+compound’; after about 30 s equilibration, testing
was resumed. Typically, five responses were collected
and averaged for each condition and measurements
with a given patch were alternated repeatedly between
‘control condition’ and ‘test condition with compound’.
Steady-state/peak ratios from two to six patches were
averaged. Because of receptor desensitization, control
responses typically decay with a time constant of about
12 ms until the current reaches a steady-state level of 5–
10% of the peak current; compounds that effectively
block desensitization raise the steady-state level to 100%.
Holding potentials were 50 mV. Compound solutions
were typically prepared from 500-fold stock solution in
DMSO; the same final concentration of DMSO was
included in all compound and control solutions.
10. Johnson, S. A.; Luu, N. T.; Herbst, T. A.; Lutz, D.;
Rogers, G. A.; Lynch, G. J. Pharmacol. Exper. Ther. 1999,
289, 392.
11. Ito, I.; Tanabe, S.; Khoda, A.; Sugiyama, H. J. Physiol.
1990, 424, 533.
12. Yamada, K. A.; Rothman, S. M. J. Physiol. (Lond.) 1992,
458, 409.
13. Yamada, K. A.; Tang, C.-M. J. Neurosci. 1993, 13, 3904.
14. Yamada, K. A. Neuro. Biol. Dis. 1998, 5, 67.
15. Yamada, K. A. Exp. Opin. Invest. Drugs 2000, 9, 765.
16. Arai, A.; Kessler, M.; Xiao, P.; Ambros-Ingerson, J.;
Rogers, G.; Lynch, G. A. Brain Res. 1994, 638, 343.
17. Arai, A.; Kessler, M.; Ambros-Ingerson, J.; Quan, A.;
Yigiter, E.; Rogers, G.; Lynch, G. Neuroscience 1996, 75, 573.
18. Arai, A.; Kessler, M.; Rogers, G.; Lynch, G. J. Pharma-
col. Exp. Ther. 1996, 278, 627.
19. Sekiguchi, M.; Fleck, M. W.; Mayer, M. L.; Takeo, J.;
Chiba, Y.; Yamashita, S.; Wada, K. J. Neurosci. 1997, 17,
5760.
20. Arai, A.; Lynch, G. Brain Res. 1992, 598, 173.
21. Granger, R.; Staubli, U.; Davis, M.; Perez, Y.; Nilsson,
L.; Rogers, G. A.; Lynch, G. Synapse 1993, 15, 326.
22. Zivkovic, I., Thompson, D. M., Bertolino, M., Uzunov,
D., Dibella, M., Costa, E., Guidotti, A. J. Pharm. Exp. Ther.
1995, 272, 300.
23. Larson, J.; Le, T.; Hall, R.; Lynch, G. NeuroReport 1994,
5, 389.
24. Arai, A.; Lynch, G. Brain Res. 1998, 799, 230.
25. Hjelmstad, G. O.; Isaac, J. T.; Nicoll, R. A.; Malenka,
R. C. J. Neurophysiol. 1999, 81, 3096.
26. Hu, Y.; Yamada, K. A.; Chalmers, D. K.; Annavajjula,
D. P.; Covey, D. F. J. Am. Chem. Soc. 1996, 118, 4550.
27. Bertolino, M.; Baraldi, M.; Parenti, C.; Braghiroli, D.;
DiBella, M.; Vicini, S.; Costa, E. Recept. Channels 1993, 1,
267.
28. Uzunov, D. P.; Zivkovic, I.; Pirkle, W. H.; Costa, E.;
Guidotti, A. J. Pharmaceut. Sci. 1995, 84, 937.
29. Pirotte, B.; Podona, T.; Diouf, O.; de Tullio, P.; Lebrun,
P.; Dupont, L.; Somers, F.; Delarge, J.; Morain, P.; Lestage,
P.; Lepagnol, J. M. S. J. Med. Chem. 1998, 41, 2946.
30. Pirrung, M. C.; Chau, J. H.-L.; Chen, J. Chem. Biol. 1995,
2, 621.
Acknowledgements
This work was supported by grants from the AFOSR
(98-1-03317, to G.L.), the Central Research Committee
of the Southern Illinois University (201-08, to A.C.A),
and the National Institutes of Health (NS27600, to
A.R.C.)
References and Notes
31. Pirrung, M. C.; Chen, J. J. Am. Chem. Soc. 1995, 117,
1240.
32. Girard, Y., Atkinson, J. G., Rokach, J. J. Chem. Soc.,
Perkins Trans. 1 1979, 1043.
33. Kessler, M.; Rogers, G.; Arai, A. Neurosci. Lett. 2000,
207, 161.
1. Monaghan, D. T.; Bridges, R. J.; Cotman, C. W. Annu.
Rev. Pharmacol. Toxicol. 1989, 29, 365.
2. Bridges, R. J., Chamberlin, A. R. In Drug Design for
Neuroscience; Kozikowski, A. P., Ed.; Raven: New York,
1993; p 231.
3. Doble, A. Pharmacol. Ther. 1999, 81, 163.
34. Hall, R. A.; Kessler, M.; Quan, A.; Ambros-Ingerson, J.;
Lynch, G. Brain Res. 1993, 628, 345.
35. Arai, A.; Guidotti, A.; Costa, E.; Lynch, G. NeuroReport
1996, 7, 2211.
4. Kawasaki-Yatugi, S.; Ichiki, C.; Yatusugi, S.; Takahasahi,
M.; Shimizu-Sasamata, M.; Yamaguchi, T.; Minematsu, K.
Neuropharmacology 2000, 39, 211.
5. Masliah, E.; Mallory, M.; Hansen, L.; DeTeresa, R.; Terry,
R. D. Neurology 1993, 43, 192.
36. Desos, P.; Serkiz, B.; Morain, P.; Lepagnol, J.; Cordi, A.
Bioorg. Med. Chem. Lett. 1996, 6, 3003.
6. Kordower, J. H.; Chu, Y.; Stebbins, G. T.; DeKosky, S. T.;
Cochran, E. J.; Bennett, D.; Mufson, E. J. Ann. Neurol. 2001,
49, 202.
37. Gavezzotti, A. J. Am. Chem. Soc. 1985, 107, 962.
38. Jackson, M. B. Proc. Natl. Acad. Sci. U.S.A. 1989, 86,
2199.
7. Tamminga, C. A. Crit. Rev. Neurobiol. 1998, 12, 21.
8. Granger, R.; Deadwyler, S.; Davis, M.; Moskovitz, B.;
Kessler, M.; Rogers, G.; Lynch, G. Synapse 1996, 22, 332.
9. Lynch, G.; Granger, R.; Ambros-Ingerson, J.; Davis, C. M.;
Kessler, M.; Schehr, R. Exp. Neurol. 1997, 145, 89.
39. Ornstein, P. L.; Zimmerman, D. M.; Arnold, M. B.;
Bleisch, T. J.; Cantrell, B.; Simon, R.; Zarrinmayeh, H.;
Baker, S. R.; Gates, M.; Tizzano, J. P.; Bleakman, D. J. Med.
Chem. 2000, 43, 4354.
40. Parke, D. V.; Williams, R. T. J. Chem. Soc. 1950, 1757.