Cardioselective antiischemic ATP-sensitive potassium channel (K(ATP)) openers. 6. Effect of modifications at C6 of benzopyranyl cyanoguanidines

Article abstract of DOI:10.1021/jm990196h

The effect on potency and selectivity of modification at the C6 position of the cardioprotective K(ATP) opener BMS-180448 (2) is described. Structure- activity studies show that a variety of electron-withdrawing groups (ketone, sulfone, sulfonamide, etc.)

Full text of DOI:10.1021/jm990196h

J . Med. Chem. 1999, 42, 3711-3717
3711
Ca r d ioselective An tiisch em ic ATP -Sen sitive P ota ssiu m Ch a n n el (KATP ) Op en er s.
6. Effect of Mod ifica tion s a t C6 of Ben zop yr a n yl Cya n ogu a n id in es
Charles Z. Ding, George C. Rovnyak, Raj N. Misra, Gary J . Grover, Arthur V. Miller, Syed Z. Ahmed,
Yolanda Kelly, Diane E. Normandin, Paul G. Sleph, and Karnail S. Atwal*
The Bristol-Myers Squibb Pharmaceutical Research Institute, P.O. Box 4000, Princeton, New J ersey 08543-4000
Received April 21, 1999
The effect on potency and selectivity of modifications at the C6 position of the cardioprotective
KATP opener BMS-180448 (2) is described. Structure-activity studies show that a variety of
electron-withdrawing groups (ketone, sulfone, sulfonamide, etc.) are tolerated for cardiopro-
tective activity as measured by EC25 values for an increase in time to the onset of contracture
in globally ischemic rat hearts. Changes made to the sulfonamido substituent indicate that
compounds derived from secondary lipophilic amines are preferred for good cardioprotective
potency and selectivity. The diisobutyl analogue 27 (EC25 ) 0.04 µM) is the most potent
compound of this series. The cardiac selectivity of 27 results from a combination of reduced
vasorelaxant potency and enhanced cardioprotective potency relative to the potent vasodilating
KATP openers (e.g., cromakalim). The diisobutylsulfonamide analogue 27 is over 4 orders of
magnitude more cardiac selective than cromakalim (1). These results support the hypothesis
that the cardioprotective and vasorelaxant properties of KATP openers follow distinct structure-
activity relationships. The mechanism of action of 27 appears to involve opening of the cardiac
KATP as its cardioprotective effects are abolished by the KATP blocker glyburide.
In tr od u ction
and explored the effect of modifications at C6. Those
studies provided the C6-sulfonamido class of compounds
with improved cardioprotective potency and selectivity
relative to 2a ,b. The structure-activity relationships
leading to this class of compounds are detailed in this
publication.
In experimental studies, KATP openers have direct
cardioprotective properties which are independent of
vasodilation.1 The first generation KATP openers (e.g.,
cromakalim, 1) possess a narrow window of efficacy for
their use as cardioprotective agents. Their potent pe-
ripheral and coronary vasodilating properties can com-
promise the tissue already at risk. Thus, the identifi-
cation of KATP openers that are more selective for the
ischemic myocardium is desired for this class of agents
to be safe and effective as cardioprotective agents. In
recent publications, we have reported that the cardio-
protective and vasorelaxant potencies of KATP openers
follow distinct structure-activity relationships.2 On the
basis of those studies, we identified cardioprotective
KATP openers (BMS-180448, 2a; BMS-191095, 2b) which,
despite being equipotent to the reference agents (e.g.,
cromakalim) as cardioprotectants, are significantly less
potent as vasorelaxants.3 Thus, compounds such as 2a
and 2b are valuable tools to explore the utility of this
class of compounds for the treatment of myocardial
ischemia.
Ch em istr y
Compounds (3-28) prepared for SAR studies are
summarized in Table 1. The benzopyranyl cyano-
guanidines described in this paper were prepared ac-
cording to Scheme 1. For most of the analogues, the
amine (32) can be prepared from the commercially
available 4-substituted phenol (29) via the epoxide (31)
by standard methods.4-6 While the racemic epoxide 31
can be obtained from the olefin 30 by epoxidation with
3-chloroperoxybenzoic acid, the chiral epoxide (31) is
prepared from 30 by the J acobsen epoxidation.7 The
amine (32) is coupled to the thiourea 33 in the presence
of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hy-
drochloride to give the desired product in 50-60% yield.
Details of this method have been described.8
The olefin amine 34 used in the synthesis of com-
pound 6 was prepared from the corresponding ketone
33 by methyllithium addition followed by dehydration
under acidic conditions (Scheme 2). The sulfonamido
analogues 9 and 12-28 were prepared from the known
sulfonyl chloride 359 by a sequence of steps which
involved treatment with an appropriate amine to give
the sulfonamide (36) followed by conversion to the final
product under standard conditions outlined in Scheme
1 (Scheme 3). The phosphinate precursor 38 for the
synthesis of compound 10 was prepared from the
corresponding iodide 37 under palladium catalyzed
conditions (Scheme 4).10 The amide precursor 42 for the
Structure-activity studies on the cyanoguanidine
portion of 2a failed to improve cardioprotective potency
beyond the micromolar level.4-6 Thus, we turned our
attention to the benzopyran portion of this compound
10.1021/jm990196h CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/17/1999

3712 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ding et al.
Ta ble 1. Cardioprotective and Vasorelaxant Potencies of C6 Substituted Benzopyran Analogues
a
EC25 for antiischemic (cardioprotective) potency is determined by measurement of increase in time to contracture in globally ischemic
isolated perfused rat hearts. Time to contracture is defined as the time necessary during total global ischemia to increase end diastolic
pressure by 5 mmHg. Each point on the concentration-response curve is an average of three to four rat hearts, and the EC25 value is
within (20%. The formula weight of the compound was used to prepare the testing solution of the compound to account for the solvent
b
present. IC50 for vasorelaxant potency is determined by relaxation of rat aorta precontracted with methoxamine. IC50 value is presented
as a mean with n ) 4 or higher. c Selectivity is defined as the ratio of the EC25 value for cardioprotection to the IC50 value for vasorelaxant
d
potency. Not determined.

Cardioselective Antiischemic KATP Openers
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3713
Ta ble 2. Physical Properties of Various Analogues
compound
mol. formula
see refs 3a,b
26H23ClN4O3
melting point (°C)a
microanalysisb
optical rotation RD (deg)
2a ,b
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
174-175 (A)
155-160
120-122
softens at 105
230-232
158-160
158
softens at 150
204-205
174
164
160
127-130
157-161
165
C, H, N, Cl
C, H, N, Cl
C, H, N, Cl
C, H, N, Cl
C, H, N, Cl
C, H, N, Cl, S
C, H, N, Cl, S
C, H, N, Cl, P
C, H, N, Cl
C, H, N
C, H, N, Cl, S
C, H, N, Cl, S
C, H, N, Cl, S
C, H, N, S
C, H, N, Cl, S
C, H, N, Cl, S
C, H, N
C, H, N, Cl, S
C, H, N, Cl, S
C, H, N, Cl, S
C, H, N, Cl, S
C, H, Cl, N, S
C, H, N, Cl, S
C, H, N, Cl, S
C, H, N
+13.6 (c ) 0.5, MeOH)
-3.9 (c ) 0.1, MeOH)
27H25ClN4O3‚0.2H2O
26H25ClN4O2‚0.6H2O
27H25ClN4O2‚0.21H2O
24H27ClN4O3‚0.69H2O
25H23ClN4SO4‚0.58H2O
25H24ClN5SO4‚1.5H2O
26H26ClN4O4P‚0.37H2O
26H24ClN5O3‚0.3H2O‚0.1EtOAc
24H28ClN5SO4‚0.20H2O
23H28ClN5SO4‚0.26H2O‚0.15toluene
23H26ClN5SO5‚0.36H2O
23H26ClN5SO4‚1.8H2O‚0.11CHCl3
25H30ClN5SO4‚1.3H2O
25H30ClN5SO4‚0.64H2O
19H20ClN5SO4‚0.34H2O
26H32ClN5SO4‚0.3H2O‚0.25CHCl3
26H32ClN5SO4‚1.7H2O‚0.1CHCl3
25H30ClN5SO4‚0.35H2O
31H34ClN5SO4
+31.3 (c ) 0.1, MeOH)
+18.0 (c ) 0.25, MeOH)
+7.8 (c ) 0.6, MeOH)
+27.2 (c ) 0.6, MeOH)
+7.4 (c ) 0.7, MeOH)
+1.1 (c ) 0.4, MeOH)
+3.5 (c ) 1.3, MeOH)
184
176-178
138-140
157-160
150
140
188-190
150
130-140
145-148
142-144
-15.0 (c ) 0.4, MeOH)
-4.0 (c ) 0.3, MeOH)
+12.7 (c ) 0.3, MeOH)
31H34ClN5SO4
26H34ClN5SO4‚0.20H2O
25H32ClN5SO4
23H25F3ClN5O4S‚0.03H2O
27H36ClN5SO4‚0.90H2O
24H30ClN5SO4‚0.20H2O
+0.5 (c ) 0.37, MeOH)
-1.7 (c ) 0.5, MeOH)
C, H, N, Cl, S
a
b
Melting point is reported for all unrecrystallized compounds. Microanalysis is within (0.4% except for compounds 9 and 16 for
which deviation higher than 0.4% was noted; 1H and 13C NMR and mass spectra are consistent with the structures assigned.
Sch em e 1a
Sch em e 4
Sch em e 5
a
Reaction conditions: (a) see references 4-6, 15; (b) dichlo-
romethane, bleach, the J acobsen’s catalyst; (c) THF, 2-propanol,
ammonium hydroxide; (d) 1-(3-(dimethylamino)propyl)-2-ethyl-
carbodiimide hydrochloride.
Sch em e 2
Resu lts a n d Discu ssion
Since the details of the molecular mechanism of action
of KATP openers are still elusive, we employed functional
tests to determine cardioprotective and vasorelaxant
potencies. Cardioprotective potencies were determined
by measurement of EC25 values for an increase in time
to the onset of contracture in globally ischemic isolated
perfused rat hearts.11 Time to contracture is defined as
the time necessary during total global ischemia to
increase end diastolic pressure by 5 mmHg compared
to the baseline value. Contracture develops due to rigor
bond formation which is presumably caused by depletion
of high energy phosphates. Vasorelaxant potencies were
determined by measurement of IC50 values for the
relaxation of the methoxamine contracted rat aorta, as
Sch em e 3
synthesis of compound 11 was generated from the
corresponding nitrile 39 by base hydrolysis (10 N NaOH,
EtOH), conversion of the acid 40 to the acid chloride
41, followed by treatment of 41 with aniline (THF, Et3N,
86% overall) (Scheme 5). Physical properties of the
various analogues prepared are summarized in
Table 2.

3714 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ding et al.
described previously.4-6 The ratio of the EC25 value for
the time to contracture and the IC50 value for the
vasorelaxant potency indicates selectivity in vitro for
the ischemic myocardium. Due to the nature of the
tests employed, potency values for cardioprotection and
vasorelaxation are empirical in nature.
impact on cardioprotective potency. The disubstituted
sulfonamides (e.g., 12) appear to be more potent than
the monosubstituted (9, 17) and protio (18) analogues.
Taken together, these data indicate that a disubstituted
sulfonamide carrying a lipophilic substituent is pre-
ferred for cardioprotective potency.
With the exception of compound 18 which was pre-
pared as a racemate, all compounds had 3S,4R-stereo-
chemistry at the benzopyran centers. Previous studies
have shown that for the benzopyranyl-cyanoguanidine
KATP openers (e.g., 2a ) most of the cardioprotective
potency resides in the 3S,4R-enantiomer.2 The starting
point for these studies was the benzophenone analogue
3 which showed a slightly improved cardioprotective
potency (EC25 ) 0.9 µM) compared to 2a (EC25 ) 2.5
µM) (Table 1). This improvement in cardioprotective
potency was not accompanied by a similar improvement
in vasorelaxant potency, which supports the hypothesis
that the structure-activity relationships for cardiopro-
tective and vasorelaxant activities of KATP openers are
distinct. The higher cardioprotective potency of 3 rela-
tive to 2a suggested that further improvement in
cardioprotective potency might be achieved by modifica-
tion of the C6 substituent. Thus we studied the effect
of substitution at C6 by keeping the rest of the molecule
constant.
Since the piperidine (12) and the diethylsulfonamide
(13) analogues were among the most potent compounds,
additional work was devoted to making modifications
to these substituents. Substitution of the piperidine ring
with methyl groups (19-21) is tolerated for cardiopro-
tective potency. However, a large substituent such as a
benzyl group (22, 23) offers no further improvement in
cardioprotective potency. Thus, there appears to be
certain restrictions as to the size of the substituent on
the piperidine ring. No further enhancement in cardio-
protective potency is seen with the fused analogues (e.g.,
24). The diethyl (13) to diisopropyl (25) change was
without an effect on cardioprotective potency as was the
diethyl (13) to trifluoroethyl-ethyl change (26). Further
increase in the size of the alkyl groups attached to the
sulfonamido nitrogen provided the diisobutylsulfon-
amide analogue 27 (EC25 ) 0.04 µM) which turned out
to be the most potent compound of this series. Com-
pound 27 is over 20-fold more potent than our starting
compound 3 (EC25 ) 0.9 µM). Both isobutyl groups of
27 appear to be necessary for optimum potency as the
isobutyl-methyl analogue 28 (IC50 ) 0.25 µM) is less
potent.
A comparison of cardioprotective and vasorelaxant
potencies of various analogues differing in the C6
substituent is summarized in Table 1. The homologue
4 of 3 has an EC25 value of 400 nM in the isolated
perfused rat hearts, making it 6-fold more potent than
2a . The benzyl (5) and the olefin (6) analogues show
reduced cardioprotective potencies relative to the ben-
zophenone lead 3, indicating that an electron-withdraw-
ing group at C6 is required for optimum cardioprotective
potency. The cardioprotective potency of the tert-butyl
analogue 7 of 3 suggests that the aromatic ring can be
replaced with a bulky alkyl group. We explored alter-
nate electron-withdrawing groups at C6. Replacement
of the ketone of 3 with a sulfone (8) maintains cardio-
protective potency but results in reduced cardiac selec-
tivity by virtue of enhanced vasorelaxant potency. While
the sulfonamide and the phosphinic ester analogues 9
and 10, respectively, have cardioprotective potencies
similar to that of 3, the amide analogue 11 is less potent.
These results suggest that the ketone of 3 can be
replaced with other electron-withdrawing groups. The
C6 substituent most likely plays the role of a hydrogen-
bonding acceptor.
For previous compounds (e.g., 2a ,b) in this series, the
cardiac selectivity was achieved by reduction of vasore-
laxant potency relative to the reference KATP openers
such as cromakalim (1).4-6 The improvement in cardiac
selectivity for 27 results from enhancement in cardio-
protective potency relative to 1 and 2a ,b. Taking into
account the ratio of cardioprotective to vasorelaxant
potency as a measure of cardiac selectivity, the sulfona-
mide analogue 27 is over 100-fold more cardiac selective
than the structurally related compound 2a . These
results further support that the structure-activity
relationships for cardioprotective and vasorelaxant
activities of KATP openers are distinct. We hypothesize
that these differences in structure-activity relation-
ships are due to the existence of different receptor
subtypes in smooth muscle and the cardiac tissue.12
Alternatively, the receptor environment (e.g., plasmale-
mal vs mitochondrial) could also account for these
differences in structure-activity relationships.
Further studies were undertaken to confirm the KATP
opening mechanism for the cardioprotective activity of
27, the most potent analogue of this series. Since the
biochemical tools to investigate the mechanism of KATP
openers are limited at the present time, we relied on
pharmacological studies using the KATP blocker gly-
buride. We studied the effect of the KATP blocker
glyburide on the cardioprotective activity of 27 in
globally ischemic isolated rat hearts (Figure 1). Time
to the onset of ischemic contracture was used as a
measure of cardioprotective activity. Three groups of rat
hearts (n ) 4) were given vehicle, compound 27 (0.3 µM),
and compound 27 (0.3 µM) plus glyburide (0.3 µM).
Previous studies have shown that this concentration of
glyburide has no effect on the time to the onset of
contracture.13 When given alone, compound 27 signifi-
Further work was concentrated on the sulfonamide
series of compounds due to the flexibility that they offer
for rapid exploration of structure-activity relationships.
Most of these compounds were evaluated for cardiopro-
tective potency. Only selected compounds were evalu-
ated for vasorelaxant potency to determine selectivity.
The piperidine derivative 12 is 7-fold more potent than
the benzenesulfonamide 9. Compound 12 is an order of
magnitude more potent than the previous lead com-
pound 2a . While the diethyl analogue 13 retains the
cardioprotective potency of 12, the morpholine analogue
14 is less potent. Comparison between 12 and 14
suggests that the polar groups are less tolerated in this
region of the molecule. As shown by the comparison
among 12, 15, and 16, the size of the ring has minimal

Cardioselective Antiischemic KATP Openers
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3715
cardiac selectivity of 27 results from a combination of
reduction in vasorelaxant potency and enhancement of
cardioprotective potency relative to the potent vasodi-
lating KATP openers (e.g., cromakalim). The mechanism
of action of the cardioprotective activity of 27 still
involves opening of the cardiac KATP as its cardiopro-
tective effects are abolished by co-treatment with the
KATP blocker glyburide.
Exp er im en ta l Section
Ch em istr y. All melting points were taken on a capillary
melting point apparatus and are uncorrected. The infrared
spectra were recorded with a Perkin-Elmer 983 spectropho-
1
tometer in KBr pellets. H NMR and 13C NMR spectra were
measured on J EOL GX-400 and FX-270 spectrometers with
tetramethylsilane as an internal standard. Mass spectra were
F igu r e 1. Effect of the KATP blocker glyburide (300 nM) on
the increase in time to the onset of contracture by compound
27 (300 nM). While having no effect when given alone,
glyburide completely abolished the increase in time to the
onset of contracture induced by 27.
obtained with
a Finnigan TSQ-4600 spectrometer. Flash
chromatography was run with Whatman LPS-1 silica gel and
Merck kieselgel 60 (230-400 mesh ASTM). All compounds
were characterized by 1H and 13C NMR and mass spectra.
Microanalysis of all crystalline compounds is consistent with
the structures assigned. The amount of solvent present in the
molecular formula was determined by 1H NMR spectra and
microanalysis. Karl Fischer analysis was performed in selected
cases to confirm the amount of water present.
cantly increased (21 min) time to the onset of contrac-
ture compared to the vehicle treated hearts (15.6 min).
The increase in time to contracture by 27 was abolished
by co-treatment with glyburide. In fact, the combination
of glyburide and compound 27 was slightly proischemic,
as shown by a small decrease in time to contracture
compared to the vehicle treated hearts. The proischemic
activity seen for a combination of 27 and glyburide is
similar to the results reported for other KATP openers
such as cromakalim.13 Thus the profile of cardioprotec-
tive activity of 27 in isolated perfused rat hearts is
The benzopyranylamines (32) can be prepared from the
corresponding phenols (29) by methods described in the
literature.4-6,17
A typ ica l p r oced u r e is illu str a ted for th e p r ep a r a tion
of (3S-tr a n s)-N-(4-ch lor oph en yl)-N′-cyan o-N′′-[6-[(dieth yl-
a m in o)su lfon yl]-3,4-d ih yd r o-3-h yd r oxy-2,2-d im e t h yl-
2H-1-ben zop yr a n -4-yl]gu a n id in e (13). A. N,N-Dieth yl-2,2-
d im eth yl-2H-1-ben zop yr a n -6-su lfon a m id e (36, R ) NEt2).
To a stirred solution of diethylamine (1.5 g, 20.5 mmol) in a
(1:1) mixture of water and CH2Cl2 (20 mL) at 0 °C was added
2,2-dimethyl-2H-1-benzopyran-6-sulfonyl chloride9 (1.0 g, 3.9
mmol) in portions. The resultant mixture was stirred at 0 °C
for 20 min and room temperature for 2 h. The organic layer
was separated, and the aqueous layer was reextracted with
dichloromethane. The combined organic extracts were dried
over MgSO4 concentrated in vacuo to give the title compound
as an oil (1.12 g, 100%). 1H NMR (CDCl3) δ 1.22 (t, J ) 7.0
Hz, 6 H), 1.54 (s, 6 H), 3.30 (q, J ) 7.0 Hz, 4 H), 5.78 (d, J )
10 Hz, 1 H), 6.40 (d, J ) 10 Hz, 1 H), 6.90 (d, J ) 8.8 Hz, 1 H),
7.50 (d, J ) 2.3 Hz, 1 H), 7.60 (dd, J ) 2.3; 8.8 Hz, 1 H). 13C
NMR (67.8 MHz, CDCl3): δ 14.17, 28.25, 41.96, 77.46, 116.57,
121.14, 125.38, 128.23, 131.86, 156.25.
similar to that seen for other agents of this class. Since
14
glyburide is known to be a specific blocker of KATP
,
these results suggest that the cardioprotective effects
of 27 are most likely mediated via opening of KATP in
the myocardium.
The details of the mechanism of action of KATP openers
are beginning to evolve. We have previously shown that
cardioprotective potencies of KATP openers correlate with
3
their binding affinities to the H-P1075 binding site in
cardiac and skeletal muscle membranes.15 The key to
the identification of the binding site was the presence
of nucleotides in the binding medium. The cardiac KATP
is hypothesized to be composed of two subunits: SUR2A
and Kir6.2.16 The binding site for KATP openers appears
to reside on the SUR2A. As for the binding site in
membranes,15 the binding to SUR2A requires the pres-
ence of ATP. Taken together, these data suggest that
KATP openers most likely express their cardioprotective
effects by binding to the SUR2A. A correlation between
binding affinities of KATP openers to SUR2A and their
cardioprotective potencies needs to be established to link
cardioprotective activity to the molecular site of action.
In conclusion, we have shown that modifications at
C6 of 2a lead to compounds (e.g., 27) with improved
cardioprotective potency and selectivity. The structure-
activity studies indicate that the sulfonamido analogues
derived from secondary lipophilic amines are more
potent than those derived from primary amines. The
sulfonamides in general appear to be more potent than
the corresponding amides. The diisobutylsulfonamide
analogue 27 (EC25 ) 0.04 µM) is the most potent
compound of this series. Unlike previous compounds
(e.g., 2a ) in this series for which the cardiac selectivity
was obtained by reduction of vasorelaxant potency, the
B. (1a S-cis)-N,N-Dieth yl-1a ,7b-d ih yd r o-2,2-d im eth yl-
2H -oxir en o[c][1]b en zop yr a n -6-su lfon a m id e (31,
R )
SO2NEt2). To a mixture of commercial sodium hypochlorite
solution (15.0 mL, 0.705 M, 10.5 mmol) and Na2HPO4 buffer
(6 mL, 50 µM) was added 1 N sodium hydroxide at 0 °C until
pH ∼ 11.3. To the resulting reaction mixture were added title
A compound (1.1 g, 3.7 mmol), (S,S)(+)-N,N′-bis(3,5-di-ter-
butylsalicylidene)-1,2-cyclohexanediamino-manganese(III) chlo-
ride (the J acobsen’s catalyst) (30 mg, 1 mol %) and 4-phe-
nylpyridine-N-oxide (20 mg). The resultant biphasic mixture
was stirred at 0 °C for 18 h and poured into methylene chloride
(50 mL), and the organic layer was separated. The aqueous
layer was extracted with methylene chloride (2 × 50 mL), and
the combined organic extracts were washed with saturated
NH4Cl solution and brine. After drying over MgSO4, the
solvent was removed in vacuo to give the title compound as
1
an oil (1.05 g, 91%). H NMR (CDCl3): δ 1.23 (t, J ) 7.0 Hz,
6 H), 1.38 (s, 3 H), 1.70 (s, 3 H), 3.30 (q, J ) 7.0 Hz, 4 H), 3.64
(d, J ) 4.1 Hz, 1 H), 4.04 (d, J ) 4.1 Hz, 1 H), 6.98 (d, J ) 8.8
Hz, 1 H), 7.78 (dd, J ) 1.8 Hz, 8.8 Hz, 1 H), 7.90 (d, J ) 1.8
Hz, 1 H).
C. (3S-tr a n s)-4-Am in o-N,N-d iet h yl-3,4-d ih yd r o-3-h y-
d r oxy-2,2-d im eth yl-2H-1-ben zop yr a n -6-su lfon a m id e (32,
R ) SO2NEt2). To a stirred solution of title B compound (910
mg, 2.5 mmol) in a mixture of THF and 2-propanol (15 mL,
2:1) was added ammonium hydroxide (3 mL), and the reaction

3716 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ding et al.
mixture was heated in a sealed tube at 75 °C (oil bath
temperature) for 24 h. The reaction mixture was cooled to room
temperature and concentrated in vacuo. The residue was
diluted with ethyl acetate (100 mL) and extracted with
saturated NaHCO3. The organic layer was dried and concen-
trated in vacuo, and the residue was crystallized from ethyl
acetate-cyclohexane to give a white solid (850 mg, 70%). [R]D
) +50.9° (c ) 0.90, MeOH). 1H NMR (CDCl3): δ 1.24 (s, 3 H),
1.43 (m, 2 H), 1.53 (s, 3 H), 1.65 (m, 4 H), 2.97 (m, 4 H), 3.35
(d, J ) 9.0 Hz, 1 H), 3.68 (d, J ) 9.0 Hz, 1 H), 6.90 (d, J ) 8.8
Hz, 1 H), 7.53 (dd, J ) 1.8, 8.8 Hz, 1 H), 7.80 (d, J ) 1.8 Hz,
1 H).
The olefin can be converted to the final product 10 by the same
procedure as described for the synthesis of 13 (Scheme 1).
2,2-Dim e t h yl-N -p h e n yl-2H -1-b e n zop yr a n -6-ca r b ox-
a m id e (41). A. 2,2-Dim eth yl-2H-1-ben zop yr a n -6-ca r box-
ylic a cid (40). A light yellow solution of 394-6,17 (25.0 g, 135
mmol) in ethanol (125 mL) was treated with 10 N sodium
hydroxide (125 mL). The reaction mixture was heated at reflux
temperature for 7 h, then cooled to 0 °C, and slowly treated
with concentrated hydrochloric acid (100 mL). The solid was
collected by filtration and washed several times with water.
The light yellow solid was dried in vacuo at 90 °C for 20 h to
afford the desired product (27.6 g, 100%) as a light yellow solid,
mp 155-157 °C.
B. 2,2-Dim eth yl-N-p h en yl-2H-1-ben zop yr a n -6-ca r box-
a m id e (41). To a light yellow solution of title A compound
(1.0 g. 4.9 mmol) in dichloromethane (8 mL) and DMF (3 drops)
at 0 °C under argon was added oxalyl chloride (521 mL, 5.97
mmol). The resulting yellow solution was stirred at 0 °C for
30 min and room temperature for 30 min. The crude reaction
mixture was concentrated in vacuo to give 2,2-dimethyl-2H-
1-benzopyran-6-carbonyl chloride (40) which in anhydrous
THF (8 mL) was added to a solution of aniline (670 mL, 7.35
mmol) and triethylamine (3 mL) in THF (8 mL) at 0 °C under
argon. The reaction mixture was allowed to warm to room
temperature and stirred for 2 h. The crude reaction mixture
was concentrated, diluted with ethyl acetate (100 mL), and
filtered. The filtrate was washed with brine, dried (MgSO4),
and concentrated. The resulting solid was triturated with ethyl
acetate/hexane to afford the desired compound (1.17 g, 86%)
as a white solid, mp 152-153 °C.
D. (3S-tr a n s)-N-(4-Ch lor op h en yl)-N′-cya n o-N′′-[6-[(d i-
eth ylam in o)su lfon yl]-3,4-dih ydr o-3-h ydr oxy-2,2-dim eth yl-
2H-1-ben zop yr a n -4-yl]gu a n id in e (13). To a stirred solution
of the title C compound (400 mg, 1.2 mmol) and N-chlorophe-
nyl-N′-cyanothiourea, monosodium salt8 (283 mg, 1.34 mmol)
in DMF (7 mL) was added 1-[3-(dimethylamino)propyl]-3-
ethylcarbodiimide hydrochloride (257 mg, 1.34 mmol) at room
temperature under argon. The reaction mixture was stirred
at room temperature for 18 h. The resultant mixture was
poured into a mixture of ethyl acetate (100 mL) and saturated
NH4Cl solution (50 mL). The ethyl acetate layer was separated,
and the aqueous layer was reextracted with ethyl acetate (2
× 50 mL). The combined organic layer was washed with brine
(50 mL). After the organic layer was dried over MgSO4, the
solvent was removed and the residue was purified by flash
chromatography on silica gel (ethyl acetate:hexane/1:1) to give
a colorless solid after trituration with ether (400 mg, 65%).
[R]D ) +7.8° (c ) 0.60, CH3OH). 1H NMR (CDCl3/CD3OD):
25
δ 1.22 (t, J ) 7.0 Hz, 6 H), 1.37 (s, 3 H), 1.60 (s, 3 H), 3.30 (q,
J ) 7.0 Hz, 4 H), 3.82 (d, J ) 10 Hz, 1 H), 5.15 (d, J ) 10 Hz,
1 H), 7.00 (d, J ) 8.8 Hz, 1 H), 7.45 (m, 4 H), 7.65 (m, 1 H),
7.80 (br s, 1 H). 13C NMR (CDCl3/CD3OD): δ 157.59, 133.14,
130.59, 129.23, 128.62, 127.15, 118.77, 81.31, 53.92, 43.53,
27.09, 18.68, 14.76.
The olefin can be converted to the final product by the same
procedure as described for the synthesis of compound 13.
Biologica l Assa ys. EC25 values for increasing time to
contracture were determined in isolated perfused globally
ischemic rat hearts. Compounds were initially evaluated at
10 µM concentration. Those demonstrating greater than 25%
increase in time to the onset of contracture were subjected to
concentration-response studies to determine EC25 values. To
compare the antiischemic and peripheral vasodilator potencies,
we determined IC50 values for the relaxation of the methox-
amine contracted rat aorta. Experimental details of both
methods are described.4-6
(3S-tr a n s)-4-Am in o-3,4-d ih yd r o-2,2-d im eth yl-6-(1-p h e-
n yleth en yl)-2H-1-ben zop yr a n -3-ol (34). To a solution of
ketone 33 (667 mg, 2.25 mmol), prepared in a standard
fashion,4-6,17 in dry THF (15 mL) cooled to -78° was added
dropwise methyllithium solution (7.0 mL, 1.4 M in ether, 9.8
mmol). After 5 min the resulting reaction mixture was
quenched by addition of methanol (1 mL) and warmed to 0
°C. To the resulting reaction mixture was added brine (50 mL),
and it was extracted with ether. The combined ether extract
was dried (Na2SO4) and concentrated to give the crude alcohol
as a pink oil which was taken up in dichloromethane (15 mL),
cooled in an ice bath, and treated with trifluoroacetic acid (1
mL). The reaction mixture turned yellow. After storage at 5
°C for 18 h, the reaction mixture was added to 25 mL of 1 N
sodium hydroxide and extracted with methylene chloride. The
combined organic extract was dried (Na2SO4) and concentrated
to give the title compound (475 mg, 72%) as a white solid, mp
108-109 °C.
Su p p or tin g In for m a tion Ava ila ble: Additional experi-
mental data. This material is available free of charge via the
Internet at http://pubs.acs.org.
Refer en ces
(1) (a) Coetzee, W. A. ATP-Sensitive Potassium Channels and
Myocardial Ischemia: Why Do They Open? Cardiovasc. Drugs
Ther. 1992, 6, 201-208. (b) Hearse, D. J . Activation of ATP-
sensitive Potassium Channels: a Novel Pharmacological Ap-
proach to Myocardial Protection. Cardiovasc. Res. 1995, 30,
1-17. (c) Atwal, K. S. Pharmacology and Structure-Activity
Relationships for KATP Modulators: Tissue-Selective KATP Open-
ers. J . Cardiovasc. Pharmacol. 1994, 24 (Suppl. 4), S12-S17.
(d) Atwal, K. S. Advances in the Structure-Activity Relation-
ships, Mechanism of Action, and Therapeutic Utilities of ATP-
Sensitive Potassium Channel Openers. Drug Dev. Res. 1994, 33,
250-262.3.
(2) (a) For BMS-180448 (2a ): Atwal, K. S.; Grover, G. J .; Ahmed,
S. Z.; Ferrara, F. N.; Harper, T. W.; Kim, K. S.; Sleph, P. G.;
Dzwonczyk, S.; Russell, A. D.; Moreland, S.; McCullough, J . R.;
Normandin, D. E. Cardioselective anti-ischemic ATP-sensitive
potassium channel openers. J . Med. Chem. 1993, 36, 3971-3974.
(b) For BMS-191095 (2b): Rovnyak, G. C.; Ahmed, S. Z.; Ding,
C. Z.; Dzwonczyk, S.; Ferrara, F. N.; Humpheries, W. G.; Grover,
G. J .; Santafianos, D.; Atwal, K. S.; Baird, A. J .; McLaughlin,
L. G.; Normandin, D. E.; Sleph, P. G.; Traeger, S. C. Cardiose-
The amine 34 can be converted to the final product 10
by the procedure described for the synthesis of compound 13
(step D).
6-(Meth oxyp h en ylp h osp h in yl)-2,2-d im eth yl-2H-1-ben -
zop yr a n (38). To a reaction mixture containing 37 (929 mg,
9.2 mmol), prepared in a standard fashion,4-6,17 phenylphos-
phinic acid, methyl ester18 (2.39 g, 8.36 mmol), and 4-meth-
ylmorpholine (929 mg, 9.2 mmol) in acetonitrile (25 mL) at
room temperature under argon was added tetrakis-triph-
enylphosphine palladium (0) (485 mg, 0.42 mmol).10 The
resulting heterogeneous reaction mixture was heated at 80 °C
for 45 min to give a yellow solution. It was cooled to room
temperature and concentrated in vacuo. The residue was
partitioned between ethyl acetate and 1 N hydrochloric acid.
The aqueous layer was separated and extracted with ethyl
acetate. The organic extracts were combined, washed with 5%
sodium thiosulfate solution, dried (MgSO4) and concentrated
in vacuo to give a dark oil. The crude oil was purified by flash
chromatography on silica gel (ethyl acetate:hexane/4:1) to
afford the title compound (2.18 g, 83%) as a pale yellow oil.
lective Antiischemic ATP-Sensitive Potassium Channel (KATP
)
Openers. 5. Identification of 4-(N-Aryl)-Substituted Benzopyran
Derivatives with High Selectivity. J . Med. Chem. 1997, 40, 24-
34.
(3) Atwal, K. S.; Grover, G. J . BMS-180448, A Glyburide-Reversible
Cardioprotective Agent with Minimal Vasodilator Activity. Car-
diovasc. Drug Rev. 1995, 13, 123-136.

Cardioselective Antiischemic KATP Openers
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3717
(4) Atwal, K. S.; Grover, G. J .; Ferrara, F. N.; Ahmed, S. Z.; Sleph,
P. G.; Dzwonczyk, S.; Normandin, D. E. Cardioselective anti-
ischemic ATP-sensitive potassium channel openers. 2. Structure-
Activity Studies on Benzopyranyl Cyanoguanidines; Modification
of the Benzopyran. J . Med. Chem. 1995, 38, 1966-1973.
(5) Atwal, K. S.; Grover, G. J .; Ahmed, S. Z.; Sleph, P. G.; Dzwonc-
zyk, S.; Baird, A. J .; Normandin, D. E. Cardioselective anti-
ischemic ATP-sensitive potassium channel openers 3. Structure-
Activity Studies on Benzopyranyl Cyanoguanidines; Modification
of the Cyanoguanidine Portion. J . Med. Chem. 1995, 38, 3238-
3245.
(6) Rovnyak, G. C.; Ahmed, S. Z.; Ding, C. Z.; Dzwonczyk, S.;
Ferrara, F. N.; Humpheries, W. G.; Grover, G. J .; Santafianos,
D.; Atwal, K. S.; Baird, A. J .; McLaughlin, L. G.; Normandin,
D. E.; Sleph, P. G.; Traeger, S. C. Cardioselective anti-ischemic
ATP-sensitive potassium channel (KATP) openers. 5. Identifica-
tion of 4-(N-Aryl)-Substituted Benzopyran Derivatives with High
Selectivity. J . Med. Chem. 1997, 40, 24-34.
(7) Lee, N. H.; Muci, A. R.; J acobsen, E. R. Enantiomerically Pure
Epoxychromans via Asymmetric Catalysis. Tetrahedron Lett.
1991, 32, 5055.
(8) Atwal, K. S.; Ahmed S. Z.; O’Reilly, B. C. A Facile Synthesis of
Cyanoguanidines from Thioureas. Tetrahedron Lett. 1989, 30,
7313-7316.
(9) Ding, C. Z. A Convenient Synthesis of 6-Substituted-2,2-Dim-
ethyl-2H-1-Benzopyrans. Synth. Comm. 1996, 26, 4267-4273.
(10) Lei, H.; Stoakes, M. S.; Schwabacher, A. W. Palladium Catalyzed
Preparation of Monoaryl and Diarylphosphinates from Methyl
Phosphinate. Synthesis 1992, 1255-60.
(11) Grover, G. J .; Newburger, J .; Sleph, P. G.; Dzwonczyk, S.; Taylor,
S. C.; Ahmed, S. Z.; Atwal, K. S. Cardioprotective Effects of the
Potassium Channel Opener Cromakalim: Stereoselectivity and
Effects on Myocardial Adenine Nucleotides. J . Pharmacol. Exp.
Ther. 1991, 257, 156-162.
(12) Atwal, K. S.; Grover, G. J . Treatment of Myocardial Ischemia
with ATP-Sensitive Potassium Channel (KATP) Openers. Curr.
Pharm. Des. 1996, 2, 585-595.
the Sulfonylurea receptor. Science 1995, 270, 1166. (b) Inagaki,
N.; Gonoi, T.; Clement, J . P., IV; Wang, C.; Aguilar-Bryan, L.;
Bryan J .; Seino, S. A Family of Sulfonylurea Receptors Deter-
mines the Pharmacological Properties of ATP-Sensitive K+
Channels. Neuron 1996, 16, 1011-1017.
(15) (a) Dickinson, K. E. J .; Bryson, C. C.; Cohen, R. B.; Rogers, L.;
Green, D. W.; Atwal, K. S. Nucleotide Regulation and Charac-
terization of Potassium Channel Opener Binding to Skeletal
Muscle Membranes. Mol. Pharmacol. 1997, 52, 1473-1481. (b)
Atwal, K. S.; Grover, G. J .; Lodge, N. J .; Normandin, D. E.;
Traeger, S. C.; Sleph, P. G.; Cohen, R. B.; Bryson, C. C.;
Dickinson, K. E. J . Binding of ATP-Sensitive Potassium Channel
(KATP) Openers to Cardiac Membranes: Correlation of Binding
Affinities with Cardioprotective and Smooth Muscle Relaxing
Potencies. J . Med. Chem. 1998, 41, 271-275.
(16) Schwanstecher, M.; Sieverding, C.; Dorschner, H.; Gross, I.;
Aguilar-Bryan. L.; Schwanstecher, C.; Bryan, J . Potassium
Channel Openers Require ATP to bind to and act Through
Sulfonylurea Receptors. EMBO J . 1998, 17, 5529-5535.
(17) (a) Ashwood, V. A.; Buckingham, R. E.; Cassidy, F.; Evans, J .
M.; Faruk, E. A.; Hamilton, T. C.; Nash, D. J .; Stemp, G.;
Willcock, K. Synthesis and Antihypertensive Activity of 4-(Cyclic
amido)-2H-1-benzopyrans. J . Med. Chem. 1986, 29, 2194-2201.
(b) Burrell, G.; Cassidy, F.; Evans, J . M.; Lightowler, D.; Stemp,
G. Variation in the Aromatic Ring of Cromakalim: Antihyper-
tensive Activity of Pyranopyridines and 6-Alkyl-2H-1-benzopy-
rans. J . Med. Chem. 1990, 33, 3023-3027. (c) Arch, J . R. S.;
Buckle, D. R.; Carey, C.; P.-Dobrzanski, H.; Faller, A.; Foster,
K. A.; H.-Frydrych, C. S. V.; Pinto, I. L.; Smith, D. G.; Taylor,
S. G. Relaxant Activity of 6-Cyano-2,2-dimethyl-2H-1-benzopy-
ran-4-carboxamides and -thiocarboxamides and Their Analogues
in Guinea Pig Trachealis. J . Med. Chem. 1991, 34, 2588-2594.
(d) Godfrey, J . D., J r.; Mueller, R. H.; Sedergran, T. C.;
Soundarajan, N.; Colandrea, V. J . Improved Synthesis of Aryl
1,1-Dimethylproparyl Ethers. Tetrahedron Lett. 1994, 35, 6405-
6408.
(13) (a) Grover, G. J .; Dzwonczyk, S.; Sleph, P. G. Reduction of
Ischemic Damage in Isolated Rat Hearts by the Potassium
Channel Opener RP 52891. Eur. J . Pharmacol. 1990, 69, 571-
581. (b) Sargent, C. A.; Smith, M. A.; Dzwonczyk, S.; Sleph, P.
G.; Grover, G. J . Effect of Potassium Channel Blockade on the
Anti-Ischemic Actions of Mechanistically Diverse Agents. J .
Pharmacol. Exp. Ther. 1991, 259, 97-103.
(18) Debruin, K. E.; Tang, C-L. W.; J ohnson, D. M.; Wilde, R. L.
Kinetic facial Selectivity in Nucleophilic Displacements at
Tetracoordinate Phosphorus: Kinetic and Stereochemistry in the
Reaction of Sodium Ethoxide with O,S-Dimethyl Phenylphospho-
nothioate. J . Am. Chem. Soc. 1989, 111, 5871-5879.
(14) (a) Inagaki, N.; Gonoi, T.; Clement, J . P., IV; Namba, N.;
Inazawa, J .; Gonzalez, G.; Aguilar-Bryan, L.; Seino, S.; Bryan,
J . Reconstitution of IKATP
:
An Inward Rectifier Subunit Plus
J M990196H