4,6-Disubstituted 2,2-dimethylchromans structurally related to the K ATP channel opener cromakalim: Design, synthesis, and effect on insulin release and vascular tone

Article abstract of DOI:10.1021/jm040789e

Five series (ureas, thioureas, carbamates, sulfonylureas, and amides) of 4,6-disubstituted-2,2-dimethylchromans structurally related to cromakalim were prepared and evaluated, as putative ATP-sensitive potassium channel activators, on rat pancreatic islets and rat aorta rings. The biological data indicate that most compounds were, like the reference molecule cromakalim, more active on the vascular smooth muscle tissue (myorelaxant effect on 30 mM KCl induced contractions of rat aorta rings) than on the pancreatic tissue (inhibition of 16.7 mM glucose induced insulin release from rat pancreatic islets). However, some drugs (8h, 8i, 9f, 9g, 9h, and 9i) markedly inhibited insulin release and exhibited an activity equivalent or greater than that of diazoxide. Compounds 9h and 9i were also found to be more active on pancreatic β-cells than on vascular smooth muscle cells. Last, the amide 6b was selected in order to examine its mechanism of action on vascular smooth muscle cells. Pharmacological results suggest that the compound acted as a K_ATP channel opener. In conclusion, the present data indicate that appropriate structural modifications can generate dimethylchromans with pharmacological profiles different from that of cromakalim.

Full text of DOI:10.1021/jm040789e

6
14
J. Med. Chem. 2005, 48, 614-621
4
,6-Disubstituted 2,2-Dimethylchromans Structurally Related to the KATP
Channel Opener Cromakalim: Design, Synthesis, and Effect on Insulin Release
and Vascular Tone
,
†
†
‡
‡
†
Sophie Sebille,* Pascal de Tullio, B e´ n e´ dicte Becker, Marie-H e´ l e` ne Antoine, St e´ phane Boverie,
†
‡
Bernard Pirotte, and Philippe Lebrun
Natural and Synthetic Drugs Research Center, Department of Medicinal Chemistry, Universit e´ de Li e` ge, 1 av. de l’H oˆ pital,
tour 4 (+5) Sart-Tilman, B-4000 Li e` ge, Belgium, and Laboratoire de Pharmacodynamie et de Th e´ rapeutique, Universit e´ Libre
de Bruxelles, 808 route de Lennik, B-1070 Bruxelles, Belgium
Received February 23, 2004
Five series (ureas, thioureas, carbamates, sulfonylureas, and amides) of 4,6-disubstituted-2,2-
dimethylchromans structurally related to cromakalim were prepared and evaluated, as putative
ATP-sensitive potassium channel activators, on rat pancreatic islets and rat aorta rings. The
biological data indicate that most compounds were, like the reference molecule cromakalim,
more active on the vascular smooth muscle tissue (myorelaxant effect on 30 mM KCl induced
contractions of rat aorta rings) than on the pancreatic tissue (inhibition of 16.7 mM glucose
induced insulin release from rat pancreatic islets). However, some drugs (8h, 8i, 9f, 9g, 9h,
and 9i) markedly inhibited insulin release and exhibited an activity equivalent or greater than
that of diazoxide. Compounds 9h and 9i were also found to be more active on pancreatic â-cells
than on vascular smooth muscle cells. Last, the amide 6b was selected in order to examine its
mechanism of action on vascular smooth muscle cells. Pharmacological results suggest that
the compound acted as a KATP channel opener. In conclusion, the present data indicate that
appropriate structural modifications can generate dimethylchromans with pharmacological
profiles different from that of cromakalim.
Introduction
Among the wide variety of potassium channels so far
described, the ATP-sensitive potassium channels (KATP
channels) are of particular interest because they couple
cell metabolism to cell excitability. Such ionic channels
are present in multiple cell types including endocrine
cells, skeletal and smooth muscle cells, cardiac cells,4
1
2-3
5
and central neurons. KATP channels are involved in
main physiological processes such as hormone secretion,
smooth muscle cell contractile activity, myocardial
6
protection, and neurotransmitters release. According
to their tissue localization, KATP channels do not exhibit
the same sensitivity toward modulators (openers and
blockers), which suggests the existence of several sub-
types of channels. Recent progresses in molecular biol-
ogy revealed that the KATP channel consists of an
octameric complex of two unrelated subunits: a pore-
forming subunit (KIR6.x) and the sulfonylurea receptor
Figure 1. Chemical stucture of cromakalim, diazoxide and
(
SURx). The latter regulatory subunit is expected to be
pinacidil.
the receptor protein, via multiple and distinct binding
sites, for most channel activators and blockers. The
7
challenge in the development of KATP modulators as
therapeutic agents is to search out compounds with the
best selectivity for a single KATP channel subtype.
Several compounds are known to activate KATP chan-
nels and have been named “potassium channel openers”
diversity of KATP channels results from assembly o7f
SURx and KIR6.x subunits in multiple combinations.
For example, the assembly of SUR1 and KIR6.2 subunits
forms the pancreatic (insulin-secreting) â-cell KATP
channel whereas the SUR2B with either KIR6.1 or
KIR6.2 subunits generates the smooth muscle KATP
channel. Such a feature is a key element for the design
of new KATP channel modulators. Indeed, one main
8
(PCOs). Cromakalim is an example of such compounds
(Figure 1). The drug exhibits a marked myorelaxant
activity resulting from the activation of smooth muscle
9
KATP channels. Cromakalim, however, is poorly active
as an inhibitor of insulin secretion.1
0,11
*
Author to whom correspondence should be addressed. Phone: 32-
To discover new potent and pancreatic â-cell selective
PCOs, a series of 4,6-disubstituted-2,2-dimethylchro-
mans structurally related to cromakalim were prepared
4
-3664368. Fax: 32-4-3664362. E-mail: Sophie.Sebille@ulg.ac.be
†
Universit e´ de Li e` ge.
Universit e´ Libre de Bruxelles.
‡
1
0.1021/jm040789e CCC: $30.25 © 2005 American Chemical Society
Published on Web 12/18/2004

4,6-Disubstituted 2,2-Dimethylchromans
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 615
Scheme 1. Synthesis of Cromakalim Analoguesa
a
Reagents: (i) (CH3CO)2O, H2SO4; (ii) AlCl3; (iii) acetone, pyrrolidine; (iv) NaBH4, CH3OH; (v) CH3CN, H2SO4; (vi) HCl 37%; (vii)
RNCO (8a-i), RNCS (9a-i), ClCOOEt (10a-c), or RSO2NCO (11a-c).
and evaluated on two different tissues: rat pancreatic
islets and rat aorta rings.
The present work can be considered as the first one
that aimed at developing original cromakalim analogues
activating the pancreatic â-cell KATP channels.
The R/S-4-amino-3,4-dihydro-2,2-dimethyl-6-halogeno-
2H-1-benzopyrans (7 a-c) are the key intermediates of
this synthetic process, giving, in the last step, access to
the target compounds. The fluoro and the bromo deriva-
tives (7a and 7c) are prepared according to the litera-
ture,12 starting from the appropriate parahalogenophen-
ols (1a and 1c).
Chemistry
Seven steps are needed to obtain the four series of
cromakalim analogues (ureas (8a-i), thioureas (9a-i),
carbamates (10a-c), and sulfonylureas (11a-c)) (Scheme
The R/S-4-(alkylaminocarbonylamino)-3,4-dihydro-
2,2-dimethyl-6-halogeno-2H-1-benzopyrans (ureas 8a-
f), the R/S-4-(aralkylaminocarbonylamino)-3,4-dihydro-
2,2-dimethyl-6-halogeno-2H-1-benzopyrans (ureas 8g-
1
).

6
16 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Sebille et al.
i), the R/S-4-(alkylaminothiocarbonylamino)-3,4-dihydro-
Table 1. Effects of Original Dimethylchromans on Insulin
Secretion from Rat Pancreatic Islets and on the Contractile
2,2-dimethyl-6-halogeno-2H-1-benzopyrans (thioureas
9a-f), and the R/S-4-(aralkylaminothiocarbonylamino)-
3,4-dihydro-2,2-dimethyl-6-halogeno-2H-1-benzopyr-
d
Activity of Rat Aorta Rings
ans (thioureas 9g-i) are obtained by reaction of the
appropriate isocyanate or isothiocyanate with the amine
function of compounds 7 a-c.
Treatment of intermediates 7a-c with ethyl chloro-
formate in the presence of pyridine leads to the car-
bamates 10a-c.
Compound 7b also gives access to the R/S-4-(arylsul-
fonylaminocarbonylamino)-3,4-dihydro-2,2-dimethyl-6-
chloro-2H-1-benzopyrans (sulfonylureas 11a-c) after
reaction with the appropriate arylsulfonyl isocyanate.
Results and Discussion
We have synthesized simplified analogues of cro-
makalim in order to obtain compounds with reduced
relaxant activity on smooth muscle cells. The electron-
withdrawing cyano group of cromakalim, favorable to
1
3,14
the myorelaxant activity,
was replaced with a
halogen atom, and the hydroxy group, which appears
also important for activity on smooth muscle cells,1
was removed. The synthesis of the compounds lacking
the C-3 hydroxy group was straightforward. Moreover,
to preserve the hydrogen bonding site at C-4 leading to
the KATP channel opening properties of benzopyrans,13,17
the 2-oxopyrrolidin-1-yl substituent in the 4 position of
cromakalim was replaced by an urea, a thiourea, a
sulfonylurea, a carbamate, or an amide group.
5,16
The newly synthesized analogues of cromakalim
ureas 8a-i, thioureas 9a-i, carbamates 10a-c, sul-
(
fonylureas 11a-c, and amides 6a-c) have been evalu-
ated as putative potassium channel openers on two in
vitro pharmacological models: rat pancreatic islets and
rat aorta rings.
In such models, PCOs such as diazoxide, pinacidil,
and cromakalim have been reported to reduce the
glucose-induced insulin output or to exhibit myorelaxant
1
8
a
nd: not determined. b Reference 19. c Reference 20. d Results
activity.
are expressed as means ( sem; n refers to the number of samples.
Table 1 depicts the biological data obtained with the
newly synthesized dimethylchromans. Cromakalim,
diazoxide, and pinacidil were used as reference com-
pounds.
Results obtained on rat pancreatic islets indicated
that, except for 8h, 8i, 9f, 9g, 9h, and 9i, none of the
chroman derivatives markedly inhibited (>30%) insulin
secretion.
They are substituted in the 4 position by a bulkier
group, i.e., an isopropyl or a benzyl group.
Vascular results obtained with thioureas derivatives
indicated that, except for the fluoro-substituted com-
pound 9g, drugs that are substituted by a chlorine or a
bromine atom in the 6 position exhibited a higher
vasorelaxant activity than the fluoro-substituted drugs
According to the chemical structure of the drugs, the
nature of the substituent in the 4 position appeared to
be important for the inhibitory effect on insulin release.
Indeed, compounds with a benzyl group in this position
(
compare compounds 9b and 9c with 9a, 9 e and 9 f
with 9d). Such a feature was also exhibited by the
ethylureas, the carbamates, and the amides (see below).
The carbamates (10a-c) and the sulfonylureas (11a-
c) were less active on precontracted rat aorta rings, but
as discussed above, the rank order of potency for the
carbamates was again F < Cl < Br. The chlorinated and
brominated amides (6b and 6c) induced a more marked
myorelaxation and these halogenoderivatives were again
more potent than the fluoro-substituted compound.
It was also found that many compounds were more
potent than diazoxide (IC50 ) 23.8 µM) although all
drugs were less active than pinacidil (IC50 ) 0.35 µM)
or cromakalim (IC50 ) 0.13 µM) on the vascular smooth
muscle tissue.
(benzylaminocarbonylamino (8h and 8i) and benzylami-
nothiocarbonylamino groups (9g, 9h, and 9i)) were
found to be more active than the other molecules on
pancreatic â-cells.
However, most derivatives exhibited myorelaxant
properties. Among the tested ureas, compounds 8b and
8c were found to be the most potent on the vascular
smooth muscle. They are substituted by a chlorine or a
bromine atom as the X substituent and by an ethylami-
nocarbonylamino group in the 4 position. Compounds
8d, 8e, 8f, 8h, and 8i are less potent as myorelaxants.

4,6-Disubstituted 2,2-Dimethylchromans
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 617
Table 2. Myorelaxant Effects of 6b and Cromakalim on 30 and 80 mM Induced Contraction of Rat Aorta Rings Incubated in the
a
Absence or the Presence of 1 and 10 µM Glibenclamide
rat aorta rings, 30 mM KCl ED50 (µM)
rat aorta rings,
80 mM KCl ED50 (µM)
compounds
0 µM glibenclamide
1 µM glibenclamide
10 µM glibenclamide
6
b
6.3 ( 0.7 (5)
0.14 ( 0.01 (4)
33.8 ( 6.0 (5)
1.8 ( 0.1 (4)
44.6 ( 3.0 (5)
15.2 ( 1.0 (4)
84.2 ( 11.5 (5)
> 300 (4)
(
()-cromakalim
a
Results are expressed as mean ( sem; number in parentheses refers to the number of samples.
All together, these results indicate that the capacity
of dimethylchromans to provoke a myorelaxant activity
was related to the nature of the halogen atom in the 6
position; the preferred substituents appeared to be a
chlorine or a bromine atom rather than a fluorine atom.
Moreover, for those compounds bearing a chlorine or a
bromine atom at the 6 position, the presence in the 4
position of small groups such as the ethylaminocarbo-
nylamino, the ethylaminothiocarbonylamino, or the
acetamido group further enhanced their myorelaxant
effect.
Our new drugs present a stereogenic center. The
tissue selectivity (pancreatic versus cardiovascular) of
the individual optical isomers remains to be determined.
Inhibition of insulin secretion from rat pancreatic
â-cells and relaxation of rat aorta rings may be depend-
ent on the activation of KATP channels but may also be
2
+
21
related to the direct inhibition of Ca channels.
Among the different compounds tested, 6b was proved
to be an effective myorelaxant (ED50 ) 6.6 µM) devoid
of inhibitory effect on insulin secretion (% of residual
insulin secretion at 10 µM ) 100%). This drug was
selected for further pharmacological evaluation in order
to identify its mechanism of action.
Figure 2. Effect of 6b (100 µM) on 86Rb outflow from aortic
rings perifused in the absence (b) and presence (O) of glib-
enclamide (10 µM) throughout. The perifusate contained 30
+
mM K . Mean values (( sem) refer to four individual experi-
ments.
+
First, the compound was tested on 30 mM K depo-
sustained, and reversible increase in 86Rb outflow from
prelabeled and perifused rat aorta rings (Figure 2).
When the same experiment was repeated in the pres-
ence of 10 µM glibenclamide in the perifusate, the
cationic response to 6b was markedly reduced. The
increment in 86Rb outflow represented 27.1 ( 3.0% of
that recorded in the control conditions. Incidentally,
cromakalim has previously been reported to provoke a
sustained, glibenclamide-sensitive, and rapidly revers-
larized rat aorta rings incubated in the absence and the
presence of 1 or 10 µM glibenclamide, a blocker of KATP
9,20
channels. If the drug 6b acted as a potassium channel
opener, then a reduction in myorelaxant activity should
22
be observed in the presence of glibenclamide. As shown
in Table 2, a dose-dependent decrease of the vasorelax-
ant effect of 6b was observed when increasing the
glibenclamide concentration in the bathing medium.
Under the same experimental conditions, the relaxant
potency of the reference compound cromakalim was also
markedly reduced (Table 2).
86
ible increase in Rb outflow from prelabeled and
perifused rat aortic rings.22
Second, the myorelaxant activity of 6b versus cro-
makalim was examined on rat aorta rings precontracted
by a 80 mM KCl solution (Table 2). Under the latter
Taken as a whole, the present findings suggest that
R/S-4-(N-acetylamino)-6-chloro-3,4-dihydro-2,2-dimeth-
yl-2H-1-benzopyran (6b) behaves as a KATP channel
opener expressing a pharmacological profile similar to
that of cromakalim.
+
condition, the vasodilator potency of K channel openers
should be reduced, compared to their activity on 30 mM
2
3,24
KCl induced contractions.
Conversely, drugs inter-
2
+
Conclusion
fering directly at the level of Ca channels, such as
Ca entry blockers, are expected to express the same
myorelaxant efficacy on 30 and 80 mM KCl precon-
2
+
The present work explored original compounds struc-
turally related to the potassium channel opener cro-
makalim.
2
3-25
tracted aorta rings.
Table 2 indicates that the
myorelaxant activity of the selected compound (ex-
pressed as the ED50 value) was strongly reduced in aorta
rings bathed in 80 mM KCl solution, as expected for a
Our pharmacological data indicate that most com-
pounds, although more active than the reference drug
cromakalim, did not express a pronounced inhibitory
effect on insulin secretion from rat pancreatic islets.
Some drugs substituted in the 4 position with a benzyl-
aminocarbonylamino (8h and 8i), an isopropylami-
nothiocarbonylamino (9f), or a benzylaminothiocarbo-
nylamino group (9g, 9h, and 9i) exhibited, however, a
biological activity equivalent or greater than that of
diazoxide. To our knowledge, this is the first report
+
23,24
K channel opener.
Cromakalim also exhibited a less
pronounced myorelaxant activity on 80 mM KCl depo-
larized rat aorta rings (Table 2).
Third, the effect of 6b was further characterized on
8
6
42
the rate of Rb ( K substitute) outflow from rat aortic
rings perifused in the absence and the presence of
glibenclamide (10 µM). Compound 6b provoked a rapid,

6
18 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Sebille et al.
describing cromakalim analogues with such an inhibi-
tory potency on the insulin releasing process.
ture raised to 120 °C. After being cooled, the mixture was
poured into a solution of sodium hydrogenocarbonate (8 g in 1
L of water) and extracted with diethyl ether. The organic layer
was washed with a saturated sodium hydrogenocarbonate
solution, dried over magnesium sulfate, and evaporated under
reduced pressure. The resulting oil (115 g, 87%) was used
directly in the next step (Scheme 1, synthesis of 3b).
Drugs 9h and 9i were the most potent dimethylchro-
mans at reducing the glucose-induced insulin release.
These compounds, however, also presented a vasore-
laxant activity. According to the fact that they were
found to be more active on pancreatic â-cells than on
vascular smooth muscle cells (estimated ED50 on â-cells
5-Chloro-2-hydroxyacetophenone (3b). The crude ester
2
b (100 g, 0.59 mol) was heated together with aluminum
chloride (132 g, 1 mol) at 160 °C for 2 h. The mixture was then
poured on water and extracted with diethyl ether. The extract
was dried over magnesium sulfate and evaporated under
reduced pressure. The product was dissolved in methanol. The
solution was treated with charcoal and filtered, and water was
added to the filtrate. The resulting precipitate was collected
by filtration, washed with water, and dried (72 g, 72%).
<
10 µM (9h) and ≈10 µM (9i), and ED50 on vascular
smooth muscle cells )20.2 µM (9h) and 24.8 µM (9i)),
some pancreatic tissue selectivity can be detected. This
feature should be noted because cromakalim, the parent
molecule, is known to be only slightly effective as
inhibitor of insulin release while being highly potent at
reducing the vascular tone. Thus, it is tempting to
speculate that these original dimethylchromans might
serve as new leads for further developments to identify
pharmacological entities with selective pancreatic â-cells
activity.
6
-Chloro-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-
one (4b). A solution of 3b (50 g, 0.29 mol), acetone (33 mL,
.45 mol), and pyrrolidine (37.5 mL, 0.45 mol) in methanol
1100 mL) was stirred at 25 °C overnight. On the next day,
0
(
the mixture was concentrated to a red oil. Water was added,
and the solution was adjusted to pH 1 with concentrated
hydrochloric acid. The product was extracted with diethyl
ether, and the organic layer was evaporated under reduced
pressure. The residue was then dissolved in a small volume
of methanol. The solution was treated with charcoal and
filtered, and water was added to the filtrate. The resulting oil
was extracted with diethyl ether. The organic layer was dried
over magnesium sulfate, filtered, and evaporated under vacuum.
The obtained oil (48 g, 79%; IR (KBr)) was used directly in
the next step (Scheme 1, synthesis of 5b).
R/S-6-Chloro-3,4-dihydro-2,2-dimethyl-2H-1-benzopy-
ran-4-ol (5b). Sodium borohydride (9.8 g, 0.26 mol) was added
to a stirred suspension of 4b (50 g, 0.24 mol) in methanol (700
mL) at 0 °C, and the mixture was maintained at this temper-
ature for a further 30 min. After the mixture was stirred for
an additional 30 min at ambient temperature, concentrated
hydrochloric acid was added until acid and the solvent were
evaporated under vacuum. Water was added to the residue,
and the product was extracted with ethyl acetate. The organic
layer was dried over magnesium sulfate, filtered, and evapo-
rated under reduced pressure. The product was recrystallized
in ether/petroleum ether (1:3). The resulting precipitate was
collected by filtration, washed with petroleum ether, and dried
Results obtained on vascular tissue indicated that
molecules with a chlorine or a bromine atom in the 6
position and a small chain in the 4 position (ethylami-
nocarbonylamino (8b and 8c), ethylaminothiocarbonyl-
amino (9b and 9c), isopropylaminothiocarbonylamino
(9e and 9f), or acetamido (6b and 6c) exhibited a
marked myorelaxant activity. These original compounds
were, however, less potent than cromakalim as vasore-
laxant.
Moreover, compounds 8b, 8c, 9b, 9c, 9e, 6b, and 6c
may be considered as rather selective for the vascular
tissue because their inhibitory effect, if any, on the
insulin releasing process was weak.
Last, measurements of 86Rb outflow and contractile
activity under different experimental conditions sug-
gested that the myorelaxant properties of compound 6b,
an original dimethylchroman apparently selective for
the vascular tissue, were related to the activation of
KATP channels.
(
H.
31 g, 61%). Mp: 98-101 °C. IR (KBr). Anal. (C11
2
H13ClO ) C,
In conclusion, we succeeded in developing novel
dimethylchromans that are much more selective for
insulin-secreting cells over vascular tissue than the
reference molecule, cromakalim. Some compounds were
even more potent than diazoxide at inhibiting the
insulin-secretory process.
The design of these new KATP channel openers calls
for further structural modulation to identify original
dimethylchromans with a powerful and selective activity
on insulin-secreting cells.
R/S-4-(N-Acetylamino)-6-chloro-3,4-dihydro-2,2-dimeth-
yl-2H-1-benzopyran (6b). A suspension of 5b (50 g, 0.23 mol)
in acetonitrile (600 mL) was added dropwise to a stirred
solution of acetonitrile (120 mL) in 98% sulfuric acid (30 mL)
kept between -10 and 0 °C. Stirring was continued for 1 h at
room temperature. The solution was poured into cold water,
and the precipitate was collected by filtration, washed with
water, and dried (50 g, 86%). Mp: 176-179 °C. IR (KBr). Anal.
(C H ClNO ) C, H, N.
1
3
16
2
R/S-4-Amino-6-chloro-3,4-dihydro-2,2-dimethyl-2H-1-
benzopyran (7b). A suspension of 6b (20 g, 79 mmol) in
concentrated hydrochloric acid (780 mL) was refluxed over-
night. Hydrochloric acid was removed under vacuum, and the
residue was dissolved in hot water (230 mL). The solution was
filtered, and 10% aqueous sodium hydroxide was added to the
filtrate until alkaline. The amine, which precipitated, was
collected by filtration, washed with water, and dried under
vacuum. This product (6.5 g, 39%; mp 70-73.5 °C; IR (KBr))
was used in the next steps (Scheme 1, synthesis of 8b, 8e, 8h,
Experimental Section
Chemistry. Melting points were determined on a B u¨ chi 530
capillary apparatus and are uncorrected. IR spectra were
recorded as KBr pellets on a Perkin-Elmer 1000 FTIR spec-
1
trophotometer. The H NMR spectra were recorded on a
6
Bruker AW-80 (80 MHz) instrument using d -DMSO as solvent
with HMDS as an internal standard; chemical shifts are
reported in δ values (ppm) relative to internal HMDS. The
abbreviations s ) singulet, d ) doublet, t ) triplet, q )
quadruplet, m ) multiplet, and b ) broad are used throughout.
Elemental analyses (C, H, N, S) were realized on a Carlo-Erba
EA 1108-elemental analyzer and were within (0.4% of the
theoretical values. All of the reactions were routinely checked
9
b, 9e, 9h, 10b, 11a, 11b, and 11c).
R/S-3,4-Dihydro-2,2-dimethyl-4-(ethylaminocarbon-
ylamino)-6-fluoro-2H-1-benzopyran (8a). Ethyl isocyanate
12
(
0.19 mL, 2.4 mmol) was added to a solution of 7a (0.4 g, 2
mmol) in methylene chloride (5 mL). After 20 min, the
resulting precipitate was collected by filtration, washed with
petroleum ether 40/60, and dried. The product was recrystal-
lized in methanol/water (1:3) (0.34 g, 62%). Mp: 199-201 °C.
by TLC on silica gel Merck 60 F524
.
4-Chlorophenyl Acetate (2b). 4-Chlorophenol (100 g, 0.78
1
mol) was dissolved in acetic anhydride (75 mL, 0.8 mol). Upon
addition of 1 drop of concentrated sulfuric acid, the tempera-
IR (KBr). H NMR (DMSO-d , 80 MHz). Anal. (C H FN O )
6
14 19
2
2
C, H, N.

4,6-Disubstituted 2,2-Dimethylchromans
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 619
R/S-6-Chloro-3,4-dihydro-2,2-dimethyl-4-(ethylamin-
(0.4 g, 2 mmol) and isopropyl isothiocyanate (0.26 mL, 2.4
1
ocarbonylamino)-2H-1-benzopyran (8b). The title com-
pound was obtained as described for 8a starting from 7b (0.4
mmol) (0.22 g, 36%). Mp: 143-145 °C. IR (KBr). H NMR
6 2
(DMSO-d , 80 MHz). Anal. (C15H21FN OS) C, H, N, S.
g, 1.9 mmol) and ethyl isocyanate (0.18 mL, 2.3 mmol) (0.44
R/S-6-Chloro-3,4-dihydro-2,2-dimethyl-4-(isopropylami-
nothiocarbonylamino)-2H-1-benzopyran (9e). The title
compound was obtained as described for 9a starting from 7b
(0.4 g, 1.9 mmol) and isopropyl isothiocyanate (0.24 mL, 2.3
mmol). The product was recrystallized in methanol/water (1:
1
g, 82%). Mp: 218-220 °C. IR (KBr). H NMR (DMSO-d
6
, 400
2 2
MHz). Anal. (C14H19ClN O ) C, H, N.
R/S-6-Bromo-3,4-dihydro-2,2-dimethyl-4-(ethylamin-
ocarbonylamino)-2H-1-benzopyran (8c). The title com-
12
1
pound was obtained as described for 8a starting from 7c (0.4
3) (0.33 g, 56%). Mp: 166-169 °C. IR (KBr). H NMR (DMSO-
g, 1.6 mmol) and ethyl isocyanate (0.15 mL, 1.9 mmol) (0.45
6 2
d , 80 MHz). Anal. (C15H21ClN OS) C, H, N, S.
1
g, 88%). Mp: 212-215 °C. IR (KBr). H NMR (DMSO-d
6
, 80
R/S-6-Bromo-3,4-dihydro-2,2-dimethyl-4-(isopropylami-
MHz). Anal. (C14
H
19BrN
2
O
2
) C, H, N.
nothiocarbonylamino)-2H-1-benzopyran (9f). The title
compound was obtained as described for 9a starting from 7c
(0.4 g, 1.6 mmol) and isopropyl isothiocyanate (0.2 mL, 1.9
R/S-3,4-Dihydro-2,2-dimethyl-6-fluoro-4-(isopropylami-
nocarbonylamino)-2H-1-benzopyran (8d). The title com-
pound was obtained as described for 8a starting from 7a (0.4
1
mmol) (0.40 g, 71%). Mp: 174-176 °C. IR (KBr). H NMR
g, 2 mmol) and isopropyl isocyanate (0.24 mL, 2.4 mmol) (0.39
6 2
(DMSO-d , 80 MHz). Anal. (C15H21BrN OS) C, H, N, S.
1
g, 68%). Mp: 211-214 °C. IR (KBr). H NMR (DMSO-d
6
, 80
R/S-4-(Benzylaminothiocarbonylamino)-3,4-dihydro-
2,2-dimethyl-6-fluoro-2H-1-benzopyran (9g). The title com-
pound was obtained as described for 8a starting from 7a (0.4
2 2
MHz). Anal. (C15H21FN O ) C, H, N.
R/S-6-Chloro-3,4-dihydro-2,2-dimethyl-4-(isopropylami-
nocarbonylamino)-2H-1-benzopyran (8e). The title com-
pound was obtained as described for 8a starting from 7b (0.4
g, 2 mmol) and benzyl isothiocyanate (0.33 mL, 2.4 mmol) (0.59
1
g, 84%). Mp: 169-171 °C. IR (KBr). H NMR (DMSO-d
6
, 80
g, 1.9 mmol) and isopropyl isocyanate (0.23 mL, 2.3 mmol)
2
MHz). Anal. (C19H21FN OS) C, H, N, S.
1
(
0.49 g, 96%). Mp: 225-227 °C. IR (KBr). H NMR (DMSO-
R/S-4-(Benzylaminothiocarbonylamino)-6-chloro-3,4-
dihydro-2,2-dimethyl-2H-1-benzopyran (9h). The title com-
pound was obtained as described for 8a starting from 7b (0.4
g, 1.9 mmol) and benzyl isothiocyanate (0.3 mL, 2.3 mmol)
6 2 2
d , 80 MHz). Anal. (C15H21ClN O ) C, H, N.
R/S-6-Bromo-3,4-dihydro-2,2-dimethyl-4-(isopropylami-
nocarbonylamino)-2H-1-benzopyran (8f). The title com-
pound was obtained as described for 8a starting from 7c (0.4
1
(0.58 g, 85%). Mp: 174-178 °C. IR (KBr). H NMR (DMSO-
g, 1.6 mmol) and isopropyl isocyanate (0.18 mL, 1.9 mmol)
6 2
d , 80 MHz). Anal. (C19H21ClN OS) C, H, N, S.
1
(
0.41 g, 77%). Mp: 225-227 °C. IR (KBr). H NMR (DMSO-
R/S-4-(Benzylaminothiocarbonylamino)-6-bromo-3,4-
d
6
, 80 MHz). Anal. (C15
H
21BrN
2
2
O ) C, H, N.
dihydro-2,2-dimethyl-2H-1-benzopyran (9i). The title com-
pound was obtained as described for 8a starting from 7c (0.4
g, 1.6 mmol) and benzyl isothiocyanate (0.25 mL, 1.9 mmol)
R/S-4-(Benzylaminocarbonylamino)-3,4-dihydro-2,2-
dimethyl-6-fluoro-2H-1-benzopyran (8g). The title com-
pound was obtained as described for 8a starting from 7a (0.4
1
(0.56 g, 88%). Mp: 186-191 °C. IR (KBr). H NMR (DMSO-
g, 2 mmol) and benzyl isocyanate (0.3 mL, 2.4 mmol) (0.55 g,
6 2
d , 80 MHz). Anal. (C19H21BrN OS) C, H, N, S.
1
8
2%). Mp: 195-197 °C. IR (KBr). H NMR (DMSO-d
6
, 80
R/S-3,4-Dihydro-2,2-dimethyl-4-(N-ethoxycarbonylami-
1
MHz). Anal. (C19
H
21FN
2
O
2
‚ /
2
H
2
O) C, H, N.
no)-6-fluoro-2H-1-benzopyran (10a). A solution of 7a (0.2
g, 1 mmol) in pyridine (2 mL) was stirred at 0 °C. Ethyl
chloroformate (0.2 mL, 2.09 mmol) was added to the mixture.
After 30 min, the solvent was removed under vacuum, and
water was added to the crude product. The crystalline solid
R/S-4-(Benzylaminocarbonylamino)-6-chloro-3,4-dihy-
dro-2,2-dimethyl-2H-1-benzopyran (8h). The title com-
pound was obtained as described for 8a starting from 7b (0.4
g, 1.9 mmol) and benzyl isocyanate (0.28 mL, 2.3 mmol) (0.50
1
g, 77%). Mp: 180-184 °C. IR (KBr). H NMR (DMSO-d
6
, 80
was collected by filtration, washed with water, and dried (0.18
1
MHz). Anal. (C19
H
21ClN
2
O
2
) C, H, N.
g, 64%). Mp: 106-111 °C. IR (KBr). H NMR (DMSO-d
6
, 80
R/S-4-(Benzylaminocarbonylamino)-6-bromo-3,4-dihy-
dro-2,2-dimethyl-2H-1-benzopyran (8i). The title compound
was obtained as described for 8a starting from 7c (0.4 g, 1.6
3
MHz). Anal. (C14H18FNO ) C, H, N.
R/S-6-Chloro-3,4-dihydro-2,2-dimethyl-4-(N-ethoxycar-
bonylamino)-2H-1-benzopyran (10b). The title compound
was obtained as described for 10a starting from 7b (0.2 g, 0.95
mmol) and benzyl isocyanate (0.23 mL, 1.9 mmol) (0.56 g,
1
1
9
2%). Mp: 194-199 °C. IR (KBr). H NMR (DMSO-d
6
, 80
mmol) (0.17 g, 63%). Mp: 141-144 °C. IR (KBr). H NMR
MHz). Anal. (C19
H
21BrN
2
O
2
) C, H, N.
6 3
(DMSO-d , 400 MHz). Anal. (C14H18ClNO ) C, H, N.
R/S-3,4-Dihydro-2,2-dimethyl-4-(ethylaminothiocarbo-
nylamino)-6-fluoro-2H-1-benzopyran (9a). Ethyl isothio-
cyanate (0.21 mL, 2.4 mmol) was added to a solution of 7a
R/S-6-Bromo-3,4-dihydro-2,2-dimethyl-4-(N-ethoxycar-
bonylamino)-2H-1-benzopyran (10c). The title compound
was obtained as described for 10a starting from 7c (0.2 g, 0.8
mmol). The product was recrystallized in methanol/water (1:
(
0.4 g, 2 mmol) in methylene chloride (5 mL). After 30 min,
1
the solvent was removed under vacuum, and the crude product
was triturated with ethyl acetate. The insoluble material was
collected by filtration, and petroleum ether was added to the
filtrate. The resulting precipitate was collected by filtration,
3) (0.19 g, 75%). Mp: 140-142 °C. IR (KBr). H NMR (DMSO-
6 3
d , 80 MHz). Anal. (C14H18BrNO ) C, H, N.
R/S-4-(Benzenesulfonylaminocarbonylamino)-6-chloro-
3,4-dihydro-2,2-dimethyl-2H-1-benzopyran (11a). The title
compound was obtained as described for 8a starting from 7b
(0.4 g, 1.9 mmol) and benzenesulfonyl isocyanate (0.3 mL, 2.3
washed with petroleum ether, and dried (0.31 g, 61%). Mp:
1
1
36-137 °C. IR (KBr). H NMR (DMSO-d
6
, 80 MHz). Anal.
1
(
C
14
H
19FN
2
OS) C, H, N, S.
mmol) (0.51 g, 68%). Mp: 205-206 °C. IR (KBr). H NMR
R/S-6-Chloro-3,4-dihydro-2,2-dimethyl-4-(ethylamin-
6 2 4
(DMSO-d , 80 MHz). Anal. (C18H19ClN O S) C, H, N, S.
othiocarbonylamino)-2H-1-benzopyran (9b). The title com-
pound was obtained as described for 8a starting from 7b (0.4
R/S-6-Chloro-3,4-dihydro-2,2-dimethyl-4-(4-methylben-
zenesulfonylaminocarbonylami-no)-2H-1-benzopyran
(11b). The title compound was obtained as described for 8a
starting from 7b (0.4 g, 1.9 mmol) and 4-methylbenzenesulfo-
g, 1.9 mmol) and ethyl isothiocyanate (0.2 mL, 2.3 mmol) (0.33
1
g, 58%). Mp: 171-176 °C. IR (KBr). H NMR (DMSO-d
6
, 400
MHz). Anal. (C14
H
19ClN
2
OS) C, H, N, S.
nyl isocyanate (0.35 mL, 2.3 mmol) (0.35 g, 45%). Mp: 219-
1
R/S-6-Bromo-3,4-dihydro-2,2-dimethyl-4-(ethylamin-
othiocarbonylamino)-2H-1-benzopyran (9c). The title com-
pound was obtained as described for 8a starting from 7c (0.4
222 °C. IR (KBr). H NMR (DMSO-d
6
, 400 MHz). Anal.
2 4
(C19H21ClN O S) C, H, N, S.
R/S-6-Chloro-4-(4-chlorobenzenesulfonylaminocarbon-
ylamino)-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran (11c).
The title compound was obtained as described for 8a starting
from 7b (0.4 g, 1.9 mmol) and 4-chlorobenzenesulfonyl isocy-
g, 1.6 mmol) and ethyl isothiocyanate (0.16 mL, 1.9 mmol)
1
(
0.23 g, 43%). Mp: 194-197 °C. IR (KBr). H NMR (DMSO-
6 2
d , 80 MHz). Anal. (C14H19BrN OS) C, H, N, S.
R/S-3,4-Dihydro-2,2-dimethyl-6-fluoro-4-(isopropylami-
nothiocarbonylamino)-2H-1-benzopyran (9d). The title
compound was obtained as described for 9a starting from 7a
anate (0.34 mL, 2.3 mmol) (0.63 g, 77%). Mp: 210-216 °C. IR
1
(KBr). H NMR (DMSO-d
6
, 80 MHz). Anal. (C18
H
18Cl
2
N
O
2 4
S)
C, H, N, S.

6
20 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Biological Assays. Cromakalim (Beecham Pharmaceutical,
Sebille et al.
(F.N.R.S., Belgium) from which B. Pirotte is Senior
Research Associate and P. Lebrun Research Director.
The technical assistance of Y. Abrassart, S. Counerotte,
D. Dewalque, M.-L. Pirard, B. Piscart, A.-M. Vanbel-
linghen, and A. Van Praet is also gratefully acknowl-
edged.
U.K.), diazoxide (Sigma Chemical, U.S.A.), and pinacidil
Therabel Pharma, Belgium) were tested as reference com-
pounds.
Measurement of Insulin Release from Incubated Rat
(
Pancreatic Islets. Experiments were performed with pan-
creatic islets isolated from adult fed Wistar rats (Iffa-Credo,
Belgium).
1
Groups of 10 islets, each derived from the same batch of
Supporting Information Available: IR spectra, H NMR
islets, were preincubated for 30 min at 37 °C in 1 mL of a
physiological salt medium (NaCl 115 mM, KCl 5 mM, CaCl
spectra, and elemental analyses. This material is available free
of charge via the Internet at http:/pubs.acs.org.
2
2
.56 mM, MgCl
.8 mM glucose, 0.5% (w/v) dialyzed albumin (Sigma), and
(95%) and CO (5%). The
2 3
1 mM, NaHCO 24 mM) supplemented with
2
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2.56
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(5%). After preincubation, the
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2
1 mM, NaHCO
(95%) and CO
3
(
(
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8
6
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86
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86
42
The validity of Rb ( K substitute) as a tracer for the study
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22,23
of K handling in aorta rings has been previously assessed.
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3-Alkylamino-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1,1-dioxides struc-
JM040789E