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

Bioorganic & Medicinal Chemistry 10 (2002) 1229–1248

5⁰-Alkyl-benzothiadiazides: A New Subgroup of AMPA

Receptor Modulators with Improved Aﬃnity

Dean Phillips,^aJennifer Sonnenberg,^aAmy C. Arai,^cRishi Vaswani,^b

Peter O. Krutzik,^bThomas Kleisli,^bMarkus Kessler,^cRichard Granger,^b

Gary Lynch^band A. Richard Chamberlin^a,*

^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 EC₅₀value

in the order of 22 mM which represents about a 30-fold gain in aﬃnity over that of IDRA-21. The EC₅₀value 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.³Major 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].¹Selective inactivation or activation of these

receptors have also been targeted for intervention in

various neurological disorders.²A 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.^5,6Likewise, schizophrenia according

to recent insights may involve subnormal excitatory

activity in critical frontal regions of the brain.⁷Lower

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 humans^8,9and 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

Tang¹³tested 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 slices²⁸and it

produced desirable eﬀects in behavioral tasks.²²How-

ever, its EC₅₀remains 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 function^12À19and by eﬀorts to charac-

terize the physiological and behavioral consequences of

such modulation.^20À22Among 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;¹³how-

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.^23À25Cyclothiazide is markedly

less eﬀective in this regard than other types of mod-

ulators, including aniracetam and benzoylpiperidine

compounds,^16À18,24which 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.²⁹showed 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.^30,31Pirrung 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).³²Compounds 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.³³The latter reduces [³H]AMPA binding by about

half at the concentration used here³⁴and 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,^17,18multiple 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

Cl

Br

H

Cl

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

SO₂NH₂

3-Pyrido

4-CH₃OC₆H₄

2,5-(CH₃O)₂C₆H₃

P

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 EC₅₀of 22 mM (Fig. 4), which is similar in

magnitude to that of cyclothiazide (31 mM),³⁴but 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: EC₃₀26.6Æ1.8 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 hydrolysis³²and 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; EC₅₀values obtained with

this ligand are slightly lower than those from tests using

[³H]AMPA (Table 2). Table 2 shows the EC₅₀and 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,¹³and 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 R¹of

varying lengths, in combination with chloride, ﬂuoride

and hydrogen substituents at R³. It is evident that

binding is aﬀected by the substituent at the R¹position.

Table 2. Structures and eﬀects of Groups I–IV

Group

I

Compd

R¹

R²

R³

R⁴

EC₅₀^c(mM)

Max (%)

Concn (mM)

% eﬀect

D1^c

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

CH(CH₃)₂

CH₃CH₂CH₂

CH₃

F

H

Cl

F

H

Cl

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

Cl

H

50^a

200

75^a

94

H

Cl

N.E.

80^a

III

500

400

F

Cl

CH₃

CH₃CH₂

H

OCH₃

CH₃CH₂

141

137

120

400

200

1000^b

N.E.

114

120

N.E.

68

OCH₃

H

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 EC₅₀for 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 R²and R⁴have 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 R¹instead 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

H

CH₃

200

20b

20c

20d

20e

20f

20g

20h

20I

CH₃CH₂

CH₃

Cl

F

CH₃

H

>400

300

N.E.

CH₃

127

178

145

119

CH₃

H

CH₃

H

100^a

20^a

N.E.

CH₃

H

CH₃

H

40^a

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 EC₅₀value 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 R¹is

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 EC₅₀on 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 (EC₅₀127 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.²⁹When 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 EC₅₀of 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.³⁶An 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

360^b

143

123

477

40

120

200

15^a

N.E.

26a

26b

26c

26d

26e

26f

28

89

211

500

1 mM

50^a

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

50

100

200

80

200

30

70

100

95

100

70

83

48

29

52

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 EC₅₀on the order of 15–

30 mM, which is similar to that of cyclothiazide in patch

clamp experiments (10–30 mM)¹³and binding tests (31

mM),³⁴and 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. EC₅₀values 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

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.²⁹reported 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.³⁷With estimated van der Waals sur-

face areas for methyl and ethyl substituents of 40 and 60

A², respectively,³⁷the predicted increases in binding

energies due to these additional interactions would be

approximately 1.4 and 2.2 kcal/mol.³⁸Taking 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–

6⁰pocket of the binding site, then analogues would be

conﬁned to substitutions at the 7⁰, 8⁰, and N-2⁰posi-

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.¹⁹and Ornstein et al.³⁹recently described

new potent AMPA receptor modulators (Fig. 1). Unlike

the mostly compact and rigid benzothiadiazides and

ampakines,¹⁷these 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.¹³Bertolino et al.²⁷tested 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%.³⁴D1 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.²⁴It 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-d₆were 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 (cm^À1). 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 cm^À1. 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 cm^À1. 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 H₂SO₄was 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% H₂SO₄and 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.⁴⁰Isolated 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). Y_ꢀield 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 cm^À1. 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 cm^À1

. 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 cm^À1. 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 cm^À1. 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 cm^À1. 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 cm^À1

. 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 cm^À1. 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 cm^À1. 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 proced_ꢀures A and C to give a

ꢀ

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 cm^À1. 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 cm^À1. 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

cm^À1. 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 cm^À1. 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 cm^À1. 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 cm^À1. 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, cm^À1. 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 cm^À1. 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 cm^À1

.

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 cm^À1. 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 cm^À1. 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 cm^À1. 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

cm^À1. 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

cm^À1. 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 cm^À1. HRMS (CI) calcd for

C₁₀H₁₃FN₂O₂S [M⁺] 244.0682, found 244.0677.

1322 cm^À1

.

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

cm^À1. 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 cm^À1

.

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 cm^À1. 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-trimethyl^À3^,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 cm^À1

. 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 cm^À1. 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 cm^À1. 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 cm^À1. HRMS (CI) calcd for C₁₂H₁₇FN₂O₃S

[M⁺] 288.0944, found 288.0947.

3072, 1490, 1313 cm^À1

. 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

cm^À1. 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 cm^À1

. 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

cm^À1. 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

cm^À1. 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 cm^À1. 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) t_ꢀo 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, cm^À1. 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,

cm^À1. 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 cm^À1. 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 cm^À1

.

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 cm^À1

.

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 cm^À1. HRMS (CI) calcd for

C₁₁H₁₃FN₂O₃S [M⁺] 256.0682, found 256.0680.

EC₅₀values 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,

KH₂PO₄1.25 mM, CaCl₂2 mM, MgCl₂1 mM,

NaHCO₃5 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, MgCl₂2 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.

Article Doi

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

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

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