Novel potassium channel openers. Part 4: Transformation of the 1,4- benzoxazine skeleton into 1,4-benzothiazine, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroquinoxaline, indoline, and 1,5-benzoxazepine

Article abstract of DOI:10.1016/S0968-0896(99)00292-8

As part of a search for a new potassium channel opener, the 1,4- benzoxazine skeleton derived from the benzopyran skeleton of cromakalim, was transformed into other fused rings such as 1,4-benzothiazine, 1,2,3,4- tetrahydroquinoline, 1,2,3,4-tetrahydroqui

Full text of DOI:10.1016/S0968-0896(99)00292-8

Bioorganic & Medicinal Chemistry 8 (2000) 393±404
Novel Potassium Channel Openers. Part 4:y Transformation of the
1,4-Benzoxazine Skeleton into 1,4-Benzothiazine,
1,2,3,4-Tetrahydroquinoline, 1,2,3,4-Tetrahydroquinoxaline,
Indoline, and 1,5-Benzoxazepine
Yuzo Matsumoto, a,b,* Ryuji Tsuzuki, a,{ Akira Matsuhisa, a Toru Yoden, a,{
Yoko Yamagiwa, a Isao Yanagisawa, a Tadao Shibanuma a
and Hiroyuki Nohira b
aInstitute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., 21, Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
bGraduate School of Science and Engineering, Saitama University, Shimo-Ohkubo, Urawa, Saitama 338-8570, Japan
Received 10 September 1999; accepted 29 October 1999
AbstractÐAs part of a search for a new potassium channel opener, the 1,4-benzoxazine skeleton derived from the benzopyran
skeleton of cromakalim, was transformed into other fused rings such as 1,4-benzothiazine, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tet-
rahydroquinoxaline, indoline, and 1,5-benzoxazepine. The 1,4-benzothiazine derivative displayed approximately 20 times more
potent vasorelaxant activity than cromakalim. # 2000 Elsevier Science Ltd. All rights reserved.
Introduction
inhibiting intracellular calcium release, resulting in
smooth muscle relaxation and antispasmodic action.2
The use of potassium channel openers3±13 may, there-
fore, be valuable in treating disorders caused by smooth
muscle contraction, such as hypertension, angina pec-
toris, asthma14, urinary incontinence,15 and baldness.16
Additionally, these agents may a€ord cells a measure of
protection against ischemia, independent of their vaso-
dilating actions,17 and have antilipemic e€ects, lowering
low density lipoprotein (LDL) cholesterol and trigly-
cerides while increasing high density lipoprotein (HDL)
cholesterol.18
The KATP channels are an important class of ionic
channels whose function is regulated by changes in the
intracellular level of adenosine triphosphate. These
channels are closed when intracellular ATP levels are
elevated and open when intracellular ATP levels decline,
thus linking membrane potential to the metabolic state
of the cell.1 Opening them allows the passage of potas-
sium ions out of the cell, causing transmembrane
hyperpolarization and repolarization. These e€ects
reduce intracellular calcium concentration by a blocking
function of voltage-dependent calcium channels and
There are several prototypes of this class of compounds:
cromakalim,19 pinacidil,20 nicorandil,21 and aprikalim.22
Among these compounds, many structural modi®cation
studies have focused on cromakalim, a benzopyran
derivative, because it possessed the most potent activity.
As part of a program to develop new compounds by
modifying cromakalim, the synthesis and the biological
activity of a new series of 3,4-dihydro-2H-1,4-benzox-
azine derivatives, represented by I (Scheme 1) which
exhibited a strong KATP channel opening activity, was
previously reported.y Further searches for a new potas-
sium channel opener revealed several candidates. A ®rst
series of modi®cations transformed the 1,4-benzoxazine
Keywords: antihypertension; cardiovascular activity; potassium chan-
nel openers; vasodilators.
*Corresponding author. Tel.: +81-298-54-1547; fax: +81-298-52-
5387; e-mail: matsumoy@yamanouchi.co.jp
yFor previous paper in this series see: Part I, Matsumoto, Y.; Tsuzuki,
R.; Matsuhisa, A.; Takayama, K.; Yoden, T.; Uchida, W.; Asano, M.;
Fujita, S.; Yanagisawa, I.; Fujikura, T. Chem. Pharm. Bull. 1996, 44,
103; Part II, Matsumoto, Y.; Tsuzuki, R.; Matsuhisa, A.; Masuda, N.;
Yamagiwa, Y.; Yanagisawa, I.; Shibanuma, T.; Nohira, H. Chem.
Pharm. Bull. 1999, 47, 971.
{Present address: Chemical Technology Laboratories, Yamanouchi
Pharmaceutical Co. Ltd., 160-2, Matsukubo, Akahama, Takahagi-shi,
Ibaraki, 318-0001, Japan.
0968-0896/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(99)00292-8

394
Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
Scheme 1.
skeleton I into other [6, 6]-fused rings such as 1,4-ben-
zothiazine II, 1,2,3,4-tetrahydroquinoline III, and
1,2,3,4-tetrahydroquinoxaline IV (Scheme 1). Further
transformation of the [6, 6]-fused ring system yielded a
[6, 5]-fused ring system such as indoline V and a [6, 7]-
fused ring system such as 1,5-benzoxazepine VI. In this
paper our work on the synthesis and the structure±
activity relationship of these fused rings is described.
amidation with 3-aminoacetanilide and triethylamine
(Et3N), yielded the amide 13. Ring closure of 13 with
polyphosphoric acid (PPA) produced the 7-acetyl-
amino-1,2,3,4-tetrahydroquinolin-2,4-dione derivative,
14a, along with the minor 5-acetylamino derivative 14b
by-product in a 14a: 14b ratio of 6:1. After isolation of
14a by column-chromatography, reduction of 14a with
hydrogen over palladium-activated carbon (Pd-C) gave
15, which was deacetylated in acidic conditions to produce
the 7-amino derivative, 16. Compound 16 was converted
by the Sandmeyer reaction to the 7-nitro derivative 17,
which was N-alkylated with chloroacetone and K2CO3
to give 18. Reduction of 18 with a BH3±THF complex
gave the alcohol derivative, 19, which was oxidized by
Swern oxidation to give the ketone derivative 20.
Chemistry
In Scheme 1, an acetonyl group or a pyridine N-oxide
group was adopted mainly as the substituent R of the
fused rings II±VI, because with them the 1,4-benzox-
azine I exhibited potent activity.34 The synthesis strategy
for the preparation of the 1,4-benzothiazine derivatives
is outlined in Scheme 2. 2,4-Dinitrothiophenol, 2, pre-
pared from 2,4-dinitrochlorobenzene using Price's
method,23 was employed as the starting material. It was
alkylated with ethyl 2-bromoisobutyrate and potassium
carbonate (K2CO3) to give the thioether, 3. Reduction
of 3 with powdered iron and hydrochloric acid, fol-
lowed by ring closure with sodium hydroxide, gave 6-
amino-3-oxo-2H-1,4-benzothiazine (4). Transformation
of the amino group at position 6 into the nitro group
was achieved by using the Sandmeyer reaction24 to give
5, which was N-alkylated with chloroacetone and
K2CO3 to yield 6. Reduction of 6 with a borane-tetra-
hydrofuran (BH3±THF) complex, followed by Swern
oxidation of the resulting alcohol, gave the ketone deri-
vative 7. The 1,4-benzothiazine 1-oxide derivative 8, was
prepared by oxidation of 7 with an equivalent m-chloro-
perbenzoic acid (m-CPBA). In a second series of
reactions, oxidation of 1,4-benzothiazine 5 with excess
m-CPBA yielded 1,4-benzothiazine 1,1-dioxide deriva-
tive, 9, which was N-alkylated with chloroacetone and
K2CO3 to give 10. Reduction of 10 with a BH3±THF
complex followed by Swern oxidation, yielded 11.
The 1,2,3,4-tetrahydroquinoxaline derivatives 25a,b
were prepared as shown in Scheme 4. The starting
materials, 3,3-dialkyl-3,4-dihydro-1H-quinoxalin-2-one
derivatives, 21a,b, were prepared using Lai's proce-
dure.26 Reductive alkylation of 21a,b with formalde-
hyde and sodium cyanoborohydride yielded 22a,b,
which was followed by nitration27 with fuming nitric
acid in acetic anhydride at 0 ꢀC to give the 7-nitro-
1,2,3,4-tetrahydro-2-quinoxalinone derivatives 23a,b,
respectively. The position of the nitro group was deter-
mined by 1H NMR data of 23a or 23b revealing a
nuclear Overhauser e€ect (NOE) between the hydrogen
atoms at positions 4 and 5. Selective reduction of the
amide moiety of 23a,b with a BH3±THF complex gave
24a,b, respectively. By nucleophilic substitution of 24a,b
with 2-bromopyridine N-oxide in the presence of
sodium hydride (NaH) in DMF, 25a,b were obtained.
Indoline derivatives were prepared as shown in Scheme
5. The starting material, 6-nitro-2-indolinone derivative
26, was prepared using Holck's method.28 N-alkylation
of 26 with chloroacetone and K2CO3 produced 27,
which was reduced with a BH3±THF complex to give the
alcohol derivative 28. Compound 28 was converted by
Swern oxidation to the ketone derivative 29. N-Alkylation
of 26 with ethyl bromoacetate and NaH in DMF
gave the ester, 30, which was reduced with a BH3±THF
The 1,2,3,4-tetrahydroquinoline derivatives were pre-
pared by modifying Evans' work25 as shown in Scheme
3. Reaction of dimethylmalonic acid with thionyl chlo-
ride under re¯ux in THF, followed immediately by

Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
395
Scheme 2. (a) BrC(CH3)2COOC2H5, K2CO3, DMF; (b) Fe, HCl, EtOH; (c) NaOHaq, re¯ux; (d) (i) NaNO2, H2SO4, (ii) NaHCO3, NaNO2, CuSO4,
Cu2O; (e) ClCH2COCH3, K2CO3, DMF; (f) BH3-THF; (g) Swern oxidation; (h) m-CPBA; (i) m-CPBA excess.
Scheme 3. (j) (i) SOCl2, THF; (ii) 3-aminoacetanilide, Et3N; (k) polyphosphoric acid; (l) H2, Pd/C, Ac2O, H2SO4, AcOH; (m) HClaq., EtOH.
complex to give the alcohol derivative, 31. Selective
reduction of the amide moiety of 26 with a BH3±THF
complex gave 6-nitroindoline derivative, 32, which was
N-alkylated with ethyl bromoacetate and K2CO3 at
100 ꢀC in a solventless system to produce the ester 33.
The acetamide derivative, 34, was prepared by reaction
of the ester, 33, with methylamine. The pyridine N-oxide
derivative, 35, was prepared by nucleophilic substitution
of 32 with 2-bromopyridine N-oxide in the presence of
NaH in DMF.
The 2,3,4,5-tetrahydro-1,5-benzoxazepine derivative,
40, was prepared as shown in Scheme 6. Treatment of
3-(3-chloropropyl)-2-benzoxazolinone derivative 36,29

396
Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
Scheme 4. (n) HCHO, NaBH3CN, CH3COOH; (o) f. HNO3, Ac2O; (p) NaH, DMF, 2-bromopyridine 1-oxide hydrochloride.
Scheme 5. (q) BrCH2COOC2H5, NaH, DMF; (r) BrCH2COOC2H5, K2CO3, 100 ꢀC; (s) CH3NH2, MeOH.
with potassium hydroxide (KOH) in ethanol, followed
by heating in DMF, gave 5-ethoxycarbonyl-2,3,4,5-tet-
rahydro-1,5-benzoxazepine derivative 37. The ethoxy
carbonyl group was removed by aqueous KOH in an
EtOH re¯ux system to give 38. N-alkylation of 38 with
ethyl bromoacetate and K2CO3, followed by amidation
of the resulting ester 39, with methylamine, gave the
acetamide derivative 40.
(IC50) on 3,4-diaminopyridine-induced rhythmic con-
traction in coronary arteries isolated from dogs.30
Additionally, the in vivo hypotensive activity (maximum
decrease in mean blood pressure) of each compound was
evaluated in anesthetized dogs (Tables 1 and 2).
Initially, a series of compounds was investigated where
[6, 6]-fused ring system was retained but the atom at
position 1 was varied (Table 1). The transformation of
the oxygen atom of the 1,4-benzoxazine derivative 1,
which showed an almost 6-fold greater in vitro e-
cacy34 than cromakalim, to a sulfur atom conferred
even greater potency on the 1,4-benzothiazine derivative
7. But, the in vivo hypotensive activity of 7 was almost
Results and Discussion
The potassium channel-opening e€ects in vitro of the
compounds were assessed using their inhibitory e€ects

Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
397
Scheme 6. (t) (i) KOH, EtOH, (ii) DMF, 80 ꢀC; (u) KOHaq., EtOH, re¯ux.
Table 1. 1,4-Benzothiazines,quinolines, and quinoxalines
In vitro
In vivo
Compound
X
R2
R3
R4
IC50a mM
Dose mg/kg iv
Max decrease in MBPb
%
1
7
O
S
CH3
CH3
H
H
CH2COCH3
CH2COCH3
0.069‹0.017
0.022‹0.003
10
10
30
300
10
30
23‹9
19‹2
44‹1
27‹1
15‹5
30‹1
22‹7
NT
8
11
SO
SO2
CH3
CH3
H
H
CH2COCH3
CH2COCH3
1.3‹0.1
0.19‹0.5
20
19
18
25a
CH2
CH2
CH2
NCH2
CH3
CH3
CH3
CH3
H
H
O
H
CH2COCH3
CH2CH(OH)CH3
CH2COCH3
0.17‹0.04
>1 0
>1 0
30
N T c
N T
30
N T
20‹8
1.2‹0.5
25b
NCH3
-(CH2)4-
H
0.27‹0.07
0.39‹0.10
30
10
22‹10
28‹3
Cromakalim
aDrug concentration required to inhibit 3,4-diaminopyridine-induced rhythmic contraction in dog coronary artery by 50% (n=3±6).
bBlood pressure was measured in groups of 3±5 anesthetized dogs.
cNot tested.
Concerning several [6, 6]-fused ring system such as 1,4-benzoxazine, the order of structures conferring the best activities would be:
equal to that of 1 at 10 mg/kg iv. Surprisingly, oxidation
of sulfur to sulfur oxide, as shown in 8, caused an
approximate 50-times decrease in in vitro potency, but
further oxidation to sulfur dioxide, as shown in 11,
recovered some of the potency. The change of the oxygen
atom of 1 to a carbon atom to yield the 1,2,3,4-tetra-
hydroquinoline derivative, 20, conferred potency com-
parable to cromakalim. Reduction of the carbonyl
group of the acetonyl group of 20 to a hydroxyl group,
as shown in 19, caused a complete loss of in vitro
activity. Introduction of a carbonyl group to 20 at
position 3, as shown in 18, also resulted in a complete
loss of activity. The 1,2,3,4-tetrahydroquinoxaline deri-
vative 25a was found to be less active than cromakalim,
but transformation of the paired methyl groups at the 2
position of 25a to tetramethylene yielded the spiro deri-
vative 25b with an activity comparable to cromakalim.
Strictly speaking, from these data, a comparison
between the 1,4-benzothiazine 1,1-dioxide derivative 11,
and the 1,2,3,4-tetrahydroquinoxaline derivative, 25a,
should not be made, because that the substituent R4
between them is di€erent. But, since both the acetonyl
group and the pyridine N-oxide group conferred
almost the same potent activity, it could be deduced

398
Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
Table 2. 1-substituted indolines and bezoxazepine
In vitro
In vivo
Max decrease in MBPb
%
Compound
R1
R2
H
IC50 mM
Dose mg/kg iv
a
29
CH2COCH3
1.9‹0.8
30
100
1000
NTc
NT
12‹3
35‹4
15‹4
NT
28
31
33
34
27
35
CH2CH(OH)CH3
CH2CH2OH
CH2COOC2H5
CH2CONHCH3
CH2COCH3
H
H
H
H
O
H
>10
>10
>10
NT
2.2‹0.5
>10
0.69‹0.34
300
1000
30
32‹1
16‹2
21‹4
40
>10
300
31‹6
a±cSee footnotes in Table 1.
that 1,4-benzothiazine 1,1-dioxide was superior to
1,2,3,4-tetrahydroquinoxaline as a skeleton of potas-
sium channel openers. So, it could be speculated that for
the [6, 6]-fused ring system such as 1,4-benzoxazine, the
order of structures conferring the best activities was:
1,4-benzothiazine, 1,4-benzoxazine>1,2,3,4-tetrahydro-
quinoline, 1,4-benzothiazine 1,1-dioxide>1,2,3,4-tetra-
hydroquinoxaline, 1,4-benzothiazine 1-oxide as shown
below Table 1.
the order conferring the best activity was: [6, 6]>[6,
5]>[6, 7].
As an extension to these investigations, some molecular
modeling studies on the 1,4-benzoxazine derivative, 1,
the 1,4-benzothiazine derivative, 7, and the indoline
derivative, 29, were conducted. Initial modeling of these
compounds was performed using the SYBYL6.432 soft-
ware and optimization of their structures was done
using the MOPAC 6.0 AM1 Hamiltonian.33 The 2
rotatable-bonds of the common acetonyl group of these
compounds were rotated by 5ꢀ, from 0 to 355ꢀ, and
energy in each conformation was calculated. Molecular
overlaps between the energy minimized form of 1 and 7
or 1 and 29 are shown in Figures 1 and 2, respectively.
Each ®t structure of 7 or 29 falls within 4 kcal of its
energy minimized conformation. As shown in Figure 1,
the 1,4-benzoxazine derivative, 1, and 1,4-bezothiazine
derivative, 7, ®t very well, corresponding to the ®nding
of nearly equivalent potency. In Figure 2, although the
key functional groups of 1 and the indoline derivative
29 such as nitro, acetonyl, and the paired methyl groups
occupied almost similar spatial positions, the degree of
®t was worse than that of 1 and 7, corresponding to the
result that 29 had less potency than these compounds.
In the second series of compounds, the [6, 6]-fused ring
system was transformed to a [6, 5]-fused ring system
such as indoline or a [6, 7]-fused ring system such as 1,5-
benzoxazepine (Table 2). The indoline derivative, 29,
with acetonyl group at position 1 showed comparatively
potent activity. Reduction of the carbonyl group of the
acetonyl group yielded the alcohol, 28, which had no
drug activity. The other alcohol derivative, 31, also had
no activity. Transformation of the acetonyl group to the
ethyl acetate group, as shown in 33, also resulted in loss
of activity, but the N-methyl acetamide derivative, 34,
showed activity equal to the acetonyl derivative, 29.
Introduction of a carbonyl group at position 2 of 29, as
shown in 27, caused a loss of activity, which was the
same result as the case of the [6, 6]-fused ring such as the
1,2,3,4-tetrahydroquinolin-2-one derivative, 18. Intro-
duction of pyridine N-oxide into position 1 of indoline
of 29 a€orded 35 with a potency comparable to croma-
kalim. For the [6, 7]-fused ring, Buckle et al.31 reported
an interesting observation that whereas the paired
methyl groups in the benzopyran series are essential for
high potency, their presence in the benzoxepine series
was detrimental. So, we prepared the 1,5-benzoxazepine
derivative without the paired methyl groups, such as 40.
But disappointedly, 40 was found to have no activity
even at 10 mM. From these data, it could be speculated that
for the suitable fused ring system with an aniline moiety
such as 1,4-benzoxazine, indoline or 1,5-benzoxazepine,
Conclusion
As part of a search for a new potassium channel opener,
1,4-benzothiazine, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-
tetrahydroquinoxaline, indoline, and 1,5-benzoxazepine
derivatives were synthesized. For the [6, 6]-fused ring
system such as 1,4-benzoxazine, it could be speculated
that the order of structures conferring the best activities
was: 1,4-benzothiazine, 1,4-benzoxazine>1,2,3,4-tetra-
hydroquinoline, 1,4-benzothiazine 1,1-dioxide>1,2,3,4-
tetrahydroquinoxaline, 1,4-benzothiazine 1-oxide.

Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
399
chromatography was done on a 100±200 mesh silica gel
from Wako. Anhydrous MgSO4 or Na2SO4 was used as
drying agents for organic extraction. All solvent eva-
poration was performed under vacuum. Yields were not
optimized.
Ethyl 2-(2,4-dinitrophenylsulfanyl)-2-methylpropionate
(3). (a) A suspension of 2,4-dinitrothiophenol (0.5 g,
2.5 mmol), K2CO3 (0.35 g, 2.5 mmol), and ethyl 2-bro-
moisobutyrate (0.44 mL, 3.0 mmol) in 5 mL DMF was
stirred at 50 ꢀC for 7 h. The mixture was poured into
water and extracted with AcOEt. The extract was dried
and concentrated. The residue was column chromato-
graphed using a hexane:AcOEt mobile phase (9:1, v/v)
to yield 3 (0.59 g, yield 75%): mp 69±71 ꢀC. H NMR
1
(CDCl3) d: 1.25 (3H, t, J=7 Hz), 1.70 (6H, s), 4.23 (2H,
q, J=7 Hz), 7.67 (1H, d, J=9 Hz), 8.33 (1H, dd, J=2,
9 Hz), 8.90 (1H, d, J=2 Hz). Anal. calcd for
C12H14N2O6S: C, 45.86; H, 4.49; N, 8.91; S, 10.20.
Found: C, 45.72; H, 4.37; N, 8.94; S, 10.39.
Figure 1. Molecular overlap of compound 1 and 7.
6-Amino-3,4-dihydro-2,2-dimethyl-2H-1,4-benzothiazin-
3-one (4). (b) To a suspension of 3 (14.0 g, 44.5 mmol)
and iron powder (14.9 g, 267 mmol) in a 70 mL EtOH
and 70 mL H2O mixture was added dropwise a solution
of 11 mL 1N HCl and 11 mL EtOH. The reaction mix-
ture was re¯uxed for 2 h and ®ltered. The ®ltrate was
concentrated and extracted with AcOEt. The extract
was dried and concentrated. The residue was column
chromatographed using a CHCl3:AcOEt mobile phase
(9:1, v/v) to yield ethyl 2-(2,4-diaminophenylsulfanyl)-2-
methyl propionate (9.5g, 84%), which was immediately
1
used in the following reaction (c): H NMR (CDCl3) d:
1.21 (3H, t, J=7 Hz), 1.47 (6H, s), 3.86 (4H, brs), 4.10
(2H, q, J=7 Hz), 5.98±6.05 (2H, m), 7.02±7.12 (1H, m).
Figure 2. Molecular overlap of compound 1 and 29.
Concerning the suitable fused ring system, it could be
speculated that the order conferring the best activity
was: [6, 6]>[6, 5] >[6, 7]. Among these derivatives, the
1,4-benzothiazine derivative, 7, was found to be
approximately 20 times more potent in vitro than cro-
makalim, suggesting that 1,4-benzothiazine is a promis-
ing new skeleton for potassium channel openers.
(c) A solution of the aniline from the preceding reaction
(9.5 g, 37.3 mmol) in 112 mL 1N NaOH was re¯uxed for
0.5 h, followed by addition of a concentrated HCl solu-
tion to adjust the pH to 3. The aqueous solution was
washed with AcOEt, followed by the addition of an
NaHCO3 solution to adjust the pH to 6.5, and was
extracted with methyl ethyl ketone. The organic layer
was washed with brine, dried, and concentrated to yield
4 (6.6 g, 85%), a part of which was recrystallized from
MeOH: mp 192±193 C. H NMR (DMSO-d6) d: 1.30
(6H, s), 5.18 (2H, brs), 6.19±6.29 (2H, m), 6.84±6.94
(1H, m), 10.21 (1H, brs). Anal. calcd for C10H12N2OS:
C, 57.67; H, 5.81; N, 13.45; S, 15.40. Found: C, 57.50;
H, 5.81; N, 13.44; S, 15.58.
ꢀ
1
Experimental
Chemistry
All melting points were determined on a Yanaco MP-
500D micro melting point apparatus without correction.
Nuclear magnetic resonance (NMR) spectra were
recorded on a JEOL FX90Q, FX100, FX270 or FX400
spectrometer using tetramethylsilane as an internal
standard. The following abbreviations are used:
s=singlet, d=doublet, t=triplet, q=quartet, m=mul-
tiplet, dd=double doublet, brs=broad singlet. Mass
spectra (MS) were recorded with a Hitachi M-80 or
JEOL JMS-DX300 spectrometer. Elemental analysis
was done with a Yanaco MT-5. HPLC was carried out
using a Hitachi L-6000 pump, L-4000 UV-detector and
D-2500 recorder. Silica gel F254 (Merck) plates were
used for thin-layer chromatography (TLC). Column
3,4-Dihydro-2,2-dimethyl-6-nitro-2H-1,4-benzothiazin-3-
one (5). (d) A solution of 4 (0.63g, 3.0 mmol) in 0.9 mL
concd H2SO4 and 7.2 mL H2O was stirred at rt for
10 min, followed by the addition 3.6 g ice and NaNO2
(0.3 g, 4.4 mmol) in 0.6 mL H2O, cooled on ice and stir-
red for 5 min. The solution was added to a solution of
NaNO2 (12 g, 174 mmol), NaHCO3 (4.5 g, 53.6 mmol),
CuSO4 (2.4 g, 9.6 mmol), and Cu2O (0.9 g, 6.3 mmol) in
60 mL H2O cooled by ice. After stirring for 1 h, the
solution was extracted with AcOEt, washed with 1N
HCl and brine, dried, and concentrated. The residue
was column chromatographed using a hexane:AcOEt

400
Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
mobile phase (9:1, v/v) to yield 5, which was recrys-
tallized from AcOEt (0.2 g, 28%): mp 228±230 ꢀC. H
concentrated to yield 8, which was recrystallized from
AcOEt-hexane (0.27 g, 91%): mp 137±140 ꢀC. H NMR
1
1
NMR (CDCl3) d: 1.54 (6H, s), 7.44 (1H, d, J=8.5 Hz),
7.76 (1H, d, J=2 Hz), 7.89 (1H, dd, J=2, 8.5 Hz), 8.67
(1H, brs). Anal. calcd for C10H10N2O3S: C, 50.41; H,
4.23; N, 11.76; S, 13.46. Found: C, 50.19; H, 4.22; N,
11.68; S, 13.41.
(CDCl3) d: 1.22 (3H, s), 1.39 (3H, s), 2.29 (3H, s), 3.46
(2H, ABq, J=14 Hz), 4.29 (2H, ABq, J=16 Hz), 7.21
(1H, d, J=2 Hz), 7.57 (1H, dd, J=2, 8 Hz), 7.77 (1H, d,
J=8 Hz). Anal. calcd for C13H16N2O4S: C, 52.69; H,
5.44; N, 9.45; S, 10.82. Found: C, 52.53; H, 5.45; N,
9.39; S, 10.93.
4-Acetonyl-3,4-dihydro-2,2-dimethyl-6-nitro-2H-1,4-ben-
zothiazin-3-one (6). (e) A suspension of 5 (0.5 g,
2.1 mmol), chloroacetone (0.39 g, 4.2 mmol), and
K2CO3 (0.29 g, 2.1 mmol) in 5 mL DMF was stirred at
40ꢀC for 1 h, poured into ice water, extracted with
AcOEt, washed with brine, and concentrated. The residue
was column chromatographed using a CHCl3 mobile
phase to yield 6, which was crystallized from hexane
3,4-Dihydro-2,2-dimethyl-6-nitro-2H-1,4-benzothiazin-3-
one 1,1-dioxide (9). (i) m-CPBA (1.0 g, 4.2 mmol) was
added to a suspension of 5 (0.5 g, 2.1 mmol) in 10 mL
CH2Cl2 and the mixture was stirred at rt for 2 h. After
adding an aqueous solution of NaHCO3, the organic
layer was washed with brine, dried, and concentrated
to yield 9, which was recrystallized from AcOEt:hexane
(0.51 g, 90%): mp 244±246 ꢀC. 1H NMR (CDCl3) d:
1.66 (6H, s), 7.85±8.15 (3H, m), 8.90 (1H, brs). Anal.
calcd for C10H10N2O5S.0.3H2O: C, 43.57; H, 3.88; N,
10.16; S, 11.63. Found: C, 43.37; H, 3.62; N, 9.92; S,
11.54.
(0.4 g, 65%): mp 129±132 ꢀC. H NMR (CDCl3) d: 1.50
1
(6H, s), 2.35 (3H, s), 4.79 (2H, s), 7.50 (1H, d, J=8 Hz),
7.54 (1H, d, J=2 Hz), 7.91 (1H, dd, J=2, 8 Hz). Anal.
calcd for C13H14N2O4S: C, 53.05; H, 4.79; N, 9.52; S,
10.89. Found: C, 52.98; H, 4.67; N, 9.46; S, 10.84.
4-Acetonyl-3,4-dihydro-2,2-dimethyl-6-nitro-2H-1,4-ben-
zothiazine (7). (f) 1.0 M solution of BH3±THF complex
in THF (10 mL, 10 mmol) was added to a solution of 6
(0.39 g, 1.3 mmol) in 2 mL THF. The mixture was
re¯uxed for 6 h, followed by addition of 12 mL MeOH,
and stirred for 0.5 h. After addition of 1 mL of con-
centrated HCl solution, it was concentrated, extracted
with AcOEt, washed with 1N NaOH and brine, dried,
and concentrated. The residue was column chromato-
graphed using a hexane:AcOEt mobile phase (5:1, v/v)
to yield 4-(2-hydroxypropyl)-3,4-dihydro-2,2-dimethyl-
6-nitro-2H-1,4-benzothiazine (0.25 g, 68%): 1H NMR
(CDCl3) d: 1.31 (3H, d, J=6 Hz), 1.41 (3H, s), 1.43 (3H,
s), 3.24±3.60 (4H, m), 4.16±4.24 (1H, m), 7.06 (1H, d,
J=8 Hz), 7.42±7.54 (2H, m).
4-Acetonyl-3,4-dihydro-2,2-dimethyl-6-nitro-2H-1,4-ben-
zothiazin-3-one 1,1-dioxide (10). This compound was
prepared from 9 using procedures similar to (e): mp
129±132 ꢀC. 1H NMR (CDCl3) d: 1.62 (6H, s), 2.39 (3H,
s), 4.84 (2H, s), 7.63 (1H, m), 8.18 (2H, m). Anal. calcd
for C13H14N2O6S.0.5H2O: C, 46.56; H, 4.51; N, 8.35; S,
9.56. Found: C, 46.28; H, 4.12; N, 8.28; S, 9.60.
4-Acetonyl-3,4-dihydro-2,2-dimethyl-6-nitro-2H-1,4-ben-
zothiazine 1,1-dioxide (11). This compound was pre-
pared from 10 using procedures similar to (f) and (g):
mp 166±169 ꢀC. H NMR (CDCl3) d: 1.48 (6H, s), 2.30
1
(3H, s), 3.69 (2H, s), 4.26 (2H, s), 7.15 (1H, d, J=2 Hz),
7.63 (1H, dd, J=2, 8 Hz), 8.01 (1H, d, J=8 Hz). Anal.
calcd for C13H16N2O5S: C, 49.99; H, 5.16; N, 8.97; S,
10.27. Found: C, 49.71; H, 5.14; N, 8.93; S, 10.18.
(g) Dimethyl sulfoxide (0.3 mL, 3.6 mmol) in 1 mL
CH2Cl2 was slowly added to a solution of oxalyl chlo-
ride (0.18 mL, 1.8 mmol) in 2 mL CH2Cl2 at 50 to
60 ꢀC and the resulting mixture was stirred for 5 min.
The alcohol from the previous reaction (0.25 g,
0.89 mmol) was added to this solution over a period of
5 min and the mixture was stirred for 15 min. After
adding Et3N (0.7 mL, 5.0 mmol), the whole was diluted
with 10 mL H2O, and extracted with CH2Cl2. The
extract was washed with brine, dried, and concentrated.
The residue was column chromatographed using a hex-
ane:AcOEt mobile phase (5:1, v/v) to yield 7, which was
recrystallized from AcOEt:hexane (0.2 g, 80%): mp 109±
N-(3-Acetylaminophenyl)-2,2-dimethylmalonamic
acid
(13). (j) A solution of 2,2-dimethylmalonic acid (50 g,
380 mmol) and thionyl chloride (33 mL, 450 mmol) in
150 mL THF was re¯uxed for 2 h and then concentrated.
The residue was dissolved in 50 mL THF and the solu-
tion was slowly added into a solution of 3-aminoaceta-
nilide (57 g, 380 mmol) and Et3N (53 mL, 380 mmol) in
200 mL THF cooled by ice. After concentration, the
residue was dissolved in a 5N NaOH solution, keeping
its pH between 9 and 11, washed with AcOEt, and
acidi®ed by concd HCl solution. The resulting precipitate
was collected and washed with water to yield 13 (74 g,
74%): mp 189±191 ꢀC. 1H NMR (DMSO-d6) d: 1.41
(6H, s), 2.03 (3H, s), 7.19±7.37 (3H, m), 7.94 (1H, brs),
9.48 (1H, s), 9.89 (1H, s), 12.61 (1H, brs). Anal. calcd
ꢀ
1
112 C. H NMR (CDCl3) d: 1.44 (6H, s), 2.27 (3H, s),
3.38 (2H, s), 4.23 (2H, s), 7.09 (1H, d, J=8 Hz), 7.14
(1H, d, J=2 Hz), 7.52 (1H, dd, J=2, 8 Hz). Anal. calcd
for C13H16N2O3S: C, 55.70; H, 5.75; N, 9.99; S, 11.44.
Found: C, 55.56; H, 5.65; N, 10.00; S, 11.43.
.
for C13H16N2O4 0.1H2O: C, 58.68; H, 6.14; N, 10.53.
Found: C, 58.57; H, 6.08; N, 10.41.
4-Acetonyl-3,4-dihydro-2,2-dimethyl-6-nitro-2H-1,4-ben-
zothiazien 1-oxide (8). (h) m-CPBA (0.18 g, 1.0 mmol)
was added to a solution of 7 (0.28 g, 1.0 mmol) in 5 mL
CH2Cl2 cooled on ice and the mixture was stirred for
0.5 h. After adding an aqueous solution of NaHCO3,
the organic layer was washed with brine, dried, and
7-Acetylamino-3,4-dihydro-3,3-dimethyl-1H-quinolin-2,4-
dione (14a). (k) P2O5, 600 g, was added to 200 mL 85%
phosphoric acid and the mixture was stirred at 130 ꢀC
for 3 h. To this solution, 13 (70 g, 260 mmol) was added
and the mixture was stirred at 70 ꢀC for 14 h, then
poured into ice water. The precipitate was collected,

Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
401
dissolved in 250 mL DMF, and adsorbed to silica gel.
After removing the DMF by evaporation, it was column
chromatographed using a CHCl3±MeOH mobile phase
(95:5!1:1, v/v). The less polar fractions were combined
and concentrated to yield 5-acetylamino-3,4-dihydro-
3,3-dimethyl-1H-quinolin-2,4-dione (14b) which was
recrystallized from MeOH (4, 4 g, 7%): mp 255±257 ꢀC
1H NMR (DMSO-d6) d: 1.35 (6H, s), 2.17 (3H, s), 6.77
(1H, dd, J=1,9 Hz), 7.44±7.62 (1H, m), 8.16 (1H, dd,
J=1,10 Hz), 10.84 (1H, brs), 11.65 (1H, brs). Anal.
calcd for C13H14N2O3: C, 63.40; H, 5.73; N, 11.38.
Found: C, 63.32; H, 5.90; N, 11.35
1-(2-Hydroxypropyl)-3,3-dimethyl-7-nitro-1,2,3,4-tetra-
hydroquinoline (19). This compound was prepared from
18 using procedures similar to (f): mp 86±88 ꢀC 1H
NMR (CDCl3) d: 1.01 (3H, s), 1.02 (3H, s), 1.29 (3H, d),
1.83 (1H, d), 2.57 (2H, s), 3.09 (2H, s), 3.27±3.55 (2H,
m), 4.02±4.34 (1H, m), 6.96±7.06 (1H, m), 7.36±7.45
(2H, m). Anal. calcd for C14H20N2O3: C, 63.62; H, 7.63;
N, 10.60. Found: C, 63.59; H, 7.66; N, 10.57
1-Acetonyl-3,3-dimethyl-7-nitro-1,2,3,4-tetrahydroquino-
line (20). This compound was prepared from 19 using
procedures similar to (g): mp 90±92 ꢀC. 1H NMR
(CDCl3) d: 1.03 (6H, s), 2.22 (3H, s), 2.62 (2H, s), 3.04
(2H, s), 4.13 (2H, s), 6.99±7.08 (2H, m), 7.46 (1H, dd).
Anal. calcd for C14H18N2O3: C, 64.11; H, 6.92; N,
10.68. Found: C, 64.16; H, 7.01; N, 10.68
The polar fractions were combined and concentrated to
yield the 7-acetylamino derivative 14a which was
recrystallized from MeOH (26 g, 40%): mp 258±260 ꢀC
1H NMR (DMSO-d6) d: 1.30 (6H, s), 2.09 (3H, s), 7.20
(1H, dd), 7.56 (1H, d), 7.66 (1H, d), 10.34 (1H, brs),
10.44 (1H, brs). Anal. calcd for C13H14N2O3: C, 63.40;
H, 5.73; N, 11.38. Found: C, 63.29; H, 5.83; N, 11.36
3,4-Dihydro-3,3,4-trimethyl-1H-quinoxalin-2-one (22a).
(n) A mixture of 3,4-dihydro-3,3-dimethyl-1H-quinox-
alin-2-one, 21a (5.0 g, 28 mmol), 82 mL MeOH, 35%
11.5 mL formaldehyde, 2.9 g NaBH3CN, and 3.7 mL
CH3COOH was stirred for 1 h and concentrated. The
residue was extracted with CH2Cl2. The extract was
washed with an aqueous NaOH solution and brine,
dried, and concentrated to yield 22a, which was crystal-
lized from ether:hexane (3.9 g, 72%): mp 109±110 ꢀC 1H
NMR (CDCl3) d: 1.46 (6H, s), 2.83 (3H, s), 6.63±7.07
(4H, m), 9.04 (1H, brs). Anal. calcd for C11H14N2O
7-Acethylamino-3,4-dihydro-3,3-dimethyl-1H-quinolin-2-
one (15). (I) 14a (1.0 g, 4.1 mmol) was dissolved in
100 mL acetic acid. After addition of acetic anhydride
(0.46 mL, 4.9 mmol), concentrated H2SO4 (0.1 g,
0.97 mmol), and 10% Pd-C (0.1 g), hydrogenattion was
done at atmospheric pressure for 14 h, then, the solu-
tion was ®ltered. After the addition of NaHCO3 (0.11 g,
1.0 mmol), the ®ltrate was concentrated and extracted
with methylethylketone. The extract was washed with
water, dried, and concentrated to yield 15, which was
crystallized from Et2O (0.87 g, 92%): mp 266±268 ꢀC.
1H NMR (DMSO-d6) d: 1.03 (6H, s), 2.01 (3H, s), 2.66
(2H, s), 7.04 (2H, brs), 7.20 (1H, brs), 9.83 (1H, s), 10.00
.
0.1H2O: C, 68.80; H, 7.45; N, 14.59. Found: C, 69.00;
H, 7.40; N, 14.68. Compound 22b was prepared in the
same way: mp 155±156 ꢀC. H NMR (CDCl3) d: 1.71±
1
2.38 (8H, m), 2.82 (3H, s), 6.65±7.05 (4H, m), 8.96 (1H,
brs). Anal. calcd for C13H16N2O: C, 72.19; H, 7.46; N,
12.95. Found: C, 72.15; H, 7.64; N, 13.00.
.
(1H, s). Anal. calcd for C13H16N2O2 0.1H2O: C, 66.70;
H, 6.98; N, 11.97. Found: C, 66.48; H, 6.95; N, 11.89
3,4-Dihydro-3,3,4-trimethyl-7-nitro-1H-quinoxalin-2-one
(23a). (o) To a solution of 22a (2.0 g, 11 mmol) in 32 mL
acetic anhydride, fuming nitric acid (0.48 mL, 11 mmol)
was slowly added while cooled on ice. The mixture was
poured into an aqueous NaOH solution, and extracted
with CHCl3. The extract was concentrated and column
chromatographed using a hexane:AcOEt mobile phase
(5:1, v/v) to yield 23a which was recrystallized from
AcOEt (0.59g, 24%): mp 242±245 ꢀC. 1H NMR
(DMSO-d6) d: 1.39 (6H, s), 2.94 (3H, s), 6.83 (1H, d,
J=9 Hz), 7.64 (1H, d, J=3 Hz), 7.85 (1H, dd, J=3,
9 Hz). Anal. calcd for C11H13N3O3: C, 56.16; H, 5.57;
N, 17.86. Found: C, 55.93; H, 5.42; N, 17.95.
7-Amino-3,4-dihydro-3,3-dimethyl-1H-quinolin-2-one (16).
(m) A mixture of 15 (8.5 g, 37 mmol), 8.5 mL ethanol
and 8.5 mL concentrated HCl solution was re¯uxed
for 7 h. After adding 170 mL water and 8.5 mL 29%
ammonia in water, the precipitate was collected to yield
16 (6.1 g, 88%): mp 231±233 ꢀC. H NMR (DMSO-d6)
1
d: 1.02 (6H, s), 2.53 (2H, s), 4.92 (2H, s), 6.09±6.18
(2H, m), 6.76 (1H, d), 9.73 (1H, s). Anal. calcd for
.
C11H14N2O 0.1H2O: C, 68.80; H, 7.45; N, 14.59.
Found: C, 68.94; H, 7.66; N, 14.45
3,4-Dihydro-3,3-dimethyl-7-nitro-1H-quinolin-2-one (17).
This compound was prepared from 16 using proce-
dures similar to (d): mp 207±209 ꢀC. 1H NMR (DMSO-
d6) d: 1.08 (6H, s), 2.91 (2H, s), 7.44 (1H, d), 7.70 (1H,
d), 7.81 (1H, dd), 9.73 (1H, s). Anal. calcd for
C11H12N2O3: C, 59.99; H, 5.49; N, 12.72. Found: C,
59.69; H, 5.64; N, 12.59
Compound 23b was prepared in the same way: mp 237±
240 ꢀC. 1H NMR (DMSO-d6) d: 1.78±2.30 (8H, m), 2.93
(3H, s), 6.79 (1H, d, J=9 Hz), 7.63 (1H, d, J=3 Hz),
7.83 (1H, dd, J=3, 9 Hz), 10.82 (1H, brs). Anal. calcd
for C13H15N3O3 0.2H2O: C, 58.95; H, 5.86; N, 15.86.
Found: C, 58.69; H, 5.70; N, 16.24.
.
1-Acetonyl-3,4-dihydro-3,3-dimethyl-7-nitro-1H-quinolin-
2-one (18). This compound was prepared from 17 using
procedures similar to (e): mp 86±88 ꢀC. 1H NMR
(CDCl3) d: 1.22 (6H, s), 2.31 (3H, s), 2.92 (2H, s), 4.76
(2H, s), 7.32 (1H, d), 7.43 (1H, d), 7.90 (1H, dd). Anal.
calcd for C14H16N2O4: C, 60.86; H, 5.84; N, 10.14.
Found: C, 60.75; H, 5.82; N, 10.13
6-Nitro-1,2,3,4-tetrahydro-1,2,2-trimethylquinoxaline (24a).
This compound was prepared fꢀrom 23a using proce-
1
dures similar to (f): mp 125±126 C. H NMR (CDCl3)
d: 1.30 (6H, s), 2.91 (3H, s), 6.43 (1H, d, J=9 Hz), 7.35
(1H, d, J=3 Hz), 7.68 (1H, dd, J=3, 9 Hz). Anal. calcd
for C11H15N3O2: C, 59.71; H, 6.83; N, 18.99. Found: C,
59.51; H, 6.67; N, 18.81.

402
Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
Compound 24b was prepared in the same way: mp 115±
AcOEt. The extract was dried and concentrated. The
residue was column chromatographed using a CHCl3
mobile phase yield 30, which was recrystallized from
EtOH (0.34 g, 48%): mp 104±105 ꢀC. 1H NMR (CDCl3)
d: 1.30 (3H, t), 1.61 (6H, s), 4.25 (2H, q), 4.52 (2H, s),
7.30 (1H, d), 7.57 (1H, d), 8.00 (1H. dd). Anal. calcd for
C14H16N2O5: C, 57.53; H, 5.52; N, 9.58. Found: C,
57.40; H, 5.45; N, 9.58.
116 ꢀC. H NMR (CDCl3) d: 1.50±1.97 (8H, m), 2.93±
1
3.40 (5H, m), 6.43 (1H, d, J=9 Hz), 7.36 (1H, d,
J=3 Hz), 7.68 (1H, dd, J=3, 9 Hz). Anal. calcd for
C13H17N3O2: C, 63.14; H, 6.93; N, 16.99. Found: C,
62.95; H,6.90; N, 16.99.
2-(7-Nitro-1,2,3,4-tetrahydro-3,3,4-trimethyl-1-quinoxali-
nyl)pyridine 1-oxide (25a). (p) 24a (0.38 g, 1.7 mmol) was
dissolved in 2 mL DMF followed by the addition of
sodium hydride (60% in oil, 0.14 g, 3.4 mmol), then the
mixture was stirred for 20 min. 2-Bromopyridine N-
oxide hydrochloride (0.36 g, 1.7 mmol) was added. The
resulting mixture was stirred at 60 ꢀC for 3 h, then
poured into ice water and extracted with AcOEt. The
organic layer was concentrated and the residue was col-
umn chromatographed using AcOEt:MeOH mobile
phase (9:1, v/v) to yield 25a, which wasꢀ recrystallized
2-(3,3-Dimethyl-6-nitro-1-indolinyl)ethanol (31). This
compound was prepared from 30 using procedures
similar to (f): mp 61±64 ꢀC. H NMR (CDCl3) d: 1.32
1
(6H, s), 1.80 (1H, brs), 3.32 (2H, s), 3.33 (2H, t), 3.72±
3.96 (1H, m), 7.02 (1H, d), 7.23 (1H, d), 7.45 (1H. dd).
Anal. calcd for C12H16N2O3: C, 61.00; H, 6.83; N,
11.86. Found: C, 60.90; H, 6.85; N, 11.82.
3,3-Dimethyl-6-nitro-2,3-dihydro-1H-indole (32). This
compound was prepared from 26 using procedures
1
from EtOH (0.13 g, 25%): mp 180±182 C. H NMR
similar to (f): mp 58±59 ꢀC. H NMR (CDCl3) d: 1.34
(6H, s), 3.42 (2H, s), 3.97 (1H, brs), 7.07 (1H, d), 7.36
(1H, d), 7.60 (1H, dd), 10.48 (1H, s). Anal. calcd for
1
(DMSO-d6) d: 1.28 (6H, s), 2.98 (3H, s), 3.58 (2H, s),
6.58 (1H, d, J=2 Hz), 6.72 (1H, d, J=7 Hz), 7.27±7.31
(1H, m), 7.39±7.44 (1H, m), 7.52±7.54 (1H, m), 7.74
(1H, dd, J=2, 7 Hz), 8.32±8.34 (1H, m). Anal. calcd for
C16H18N4O3: C, 61.14; H, 5.77; N, 17.82. Found: C,
60.78; H, 5.73; N, 17.74.
.
C10H12N2O2 0.1H2O: C, 61.91; H, 6.34; N, 14.44.
Found: C, 61.73; H, 6.17; N, 14.32.
Ethyl (3,3-dimethyl-6-nitro-1-indolinyl)acetate (33). (r) A
mixture of 32 (1.0g, 5.2 mmol), K2CO3 (0.8 g, 5.8 mmol),
and 15 mL ethyl bromoacetate was stirred at 100 ꢀC for
16 h, then poured into water and extracted with AcOEt.
The organic layer was washed with brine, dried, and
concentrated. The residue was column chromatographed
using a hexane:AcOEt mobile phase (9:1, v/v) to give
33, which was recrystallized from hexane (1.2 g, 83%):
Compound 25b was prepared in the same way: mp 226±
228 ꢀC. H NMR (CDCl3) d: 1.74 (8H, brs), 3.00 (3H,
1
s), 3.72 (2H, s), 6.59 (1H, d, J=9 Hz), 7.04±7.37 (4H,
m), 7.84 (1H, dd, J=2, 9 Hz), 8.27 (1H, m). Anal. calcd
for C18H20N4O3: C, 63.52; H, 5.92; N, 16.46. Found: C,
63.31; H, 5.85; N, 16.31.
mp 50±53 ꢀC. H NMR (CDCl3) d: 1.25 (3H, t), 1.32
1
1-Acetonyl-3,3-dimethyl-6-nitroindolin-2-one (27). This
compound was prepared from 3,3-dimethyl-6-nitro-
indolin-2-one (26) using procedures similar to (e): mp
(6H, s), 3.42 (2H, s), 3.97 (2H, s), 4.18 (2H, q), 6.98±7.08
(2H, m), 7.56 (1H, dd). Anal. calcd for C14H18N2O4: C,
60.42; H, 6.52; N, 10.07. Found: C, 60.25; H, 6.48; N, 9.95.
150±152 ꢀC. H NMR (CDCl3) d: 1.46 (6H, brs), 2.30
1
(3H, s), 4.58 (2H, s), 7.36 (1H, d), 7.44 (1H, d), 8.00
(1H, dd). Anal. calcd for C13H14N2O4: C, 59.54; H,
5.38; N, 10.68. Found: C, 59.47; H, 5.39; N, 10.57.
2-(3,3-Dimethyl-6-nitro-1-indolinyl)-N-methylacetamide
(34). (s) 33 (0.25 g, 0.90 mmol) was added to a solution
of methylamine in MeOH (40%, 4 ml). The mixture was
stirred at 50 ꢀC for 30 min and concentrated to yield 34,
which was recrystallized from AcOEt:hexane (0.19 g,
1-(2-Hydroxypropyl)-3,3-dimethyl-6-nitroindoline (28).
This compound was prepared from 27 using proce-
dures similar to (f): mp 49±51 ꢀC. H NMR (CDCl3) d:
82%): mp 173±176 ꢀC. H NMR (CDCl3) d: 1.38 (6H,
1
1
1.29 (3H, d), 1.36 (6H, s), 2.07 (1H, d), 3.07±3.48 (4H,
m), 3.91±4.30 (1H, m), 7.06 (1H, d), 7.25 (1H, d), 7.60
(1H, dd). Anal. calcd for C13H18N2O3: C, 62.38; H,
7.25; N, 11.19. Found: C, 62.29; H, 7.17; N, 11.20.
s), 2.89 (3H, d), 3.35 (2H, s), 3.77 (2H, s), 6.43 (1H, brs),
7.13 (1H, d), 7.21 (1H, d), 7.70 (1H, dd). Anal. calcd for
.
C13H17N3O3 0.1H2O: C, 58.90; H, 6.54; N, 15.85.
Found: C, 58.99; H, 6.50; N, 15.86.
1-Acetonyl-3,3-dimethyl-6-nitroindoline (29). This com-
pound was prepared from 28 using procedures similar
to (g): oil 1H NMR (CDCl3) d: 1.35 (6H, s), 2.22 (3H, s),
3.38 (2H, s), 3.98 (2H, s), 7.01±7.11 (2H, m), 7.60 (1H,
dd). Anal. calcd for C13H16N2O3: C, 62.89; H, 6.50; N,
11.28. Found: C, 62.54; H, 6.44; N, 11.20.
2-(3,3-Dimethyl-6-nitro-1-indolinyl)pyridine 1-oxide (35).
This compound was prepared from 32 using procedures
similar to (p): mp 169±171 ꢀC. 1H NMR (CDCl3) d: 1.42
(6H, s), 4.03 (2H, s), 6.98±8.36 (7H, m). Anal. calcd for
C15H15N3O3: C, 63.15; H, 5.30; N, 14.73. Found: C,
62.75; H, 5.34; N, 14.64.
Ethyl (3,3-dimethyl-6-nitro-2-oxoindolin-1-yl)acetate (30).
(q) To a suspension of 26 (0.5 g, 2.4 mmol) in 10 mL
THF, NaH (60% in oil, 0.11 g, 2.7 mmol) was added
and the mixture was stirred for 0.5 h. Ethyl bromoace-
tate (0.4 mL, 3.6 mmol) was added and the resulting
solution was stirred for 5 min. After adding 5 mL EtOH,
the solution was concentrated and extracted with
Ethyl (7-nitro-2,3,4,5-tetrahydro-1,5-benzoxazepin-1-yl)-
carboxylate (37). (t) To a solution of KOH (2.83 g,
49 mmol) in 250 mL EtOH 3-(3-chloropropyl)-5-nitro-
3H-benzoxazol-2-one 36 (12.5 g, 49 mmol) was added.
The mixture was stirred for 1.5 h and concentrated. The
product was dissolved in 200 mL DMF and stirred at
80 ꢀC for 1 h, then poured into ice water and extracted

Y. Matsumoto et al. / Bioorg. Med. Chem. 8 (2000) 393±404
403
with AcOEt. The extract was washed with brine, dried,
and concentrated to yield 37, which was crystallized
from Et2O:hexane (9.2 g, 71%): mp 99±100 ꢀC. 1H
NMR (CDCl3) d: 1.28 (3H, t, J=7 Hz), 2.04±2.31 (2H,
m), 3.79±3.93 (2H, m), 4.13±4.35 (4H, m), 7.03 (1H, d,
J=9 Hz), 7.98 (1H, dd, J=3, 9 Hz), 8.21 (1H, m). Anal.
calcd for C12H14N2O5: C, 54.13; H, 5.30; N, 10.52.
Found: C, 54.04; H, 5.27; N, 10.51.
(ii) Hypotensive e€ects in dogs (i.v.). Mongrel dogs of
either sex were anesthetized with pentobarbital (30 mg/
kg, i.v.). The experiment was performed under arti®cial
respiration after tracheal intubation. Systemic blood
pressure was measured in the femoral artery with a
pressure transducer. The test compound was adminis-
tered through a cannula inserted into the femoral vein.
The mean blood pressure(MBP)-lowering in percentage
reduction is shown in Tables 1 and 2.
7-Nitro-2,3,4,5-tetrahydro-1,5-benzoxazepine (38). (u)
To a solution of KOH (5.5 g, 83 mmol) in 60 mL H2O
and 60 mL EtOH, 37 (11 g, 41 mmol) was added. The
mixture was re¯uxed for 7 h, concentrated, and extrac-
ted with AcOEt. The extract was washed with brine,
dried, and concentrated. The residue was column chro-
matographed using a benzene:hexane mobile phase (1:1,
v/v) to yield 38, which was crystallized from hexane
Acknowledgements
We wish to thank Associate Professor T. Hirose of Sai-
tama University and Drs. T. Takenaka, T. Tamura, T.
Fujikura, T. Mase, S. Tsukamoto, S. Sakamoto, S.
Fujita, and W. Uchida of Yamanouchi Pharmaceutical
Co. Ltd., for their encouragement and helpful discus-
sion. We are also thank to the sta€ of the Structure
Analysis Research for elemental analyses and spectral
measurements, and Mr. Steven E. Johnson for editing
the manuscript.
(5.1 g, 63%): mp 74±76 ꢀC. H NMR (CDCl3) d: 1.93±
1
2.19 (2H, m), 3.30±3.43 (2H, m), 4.19±4.32 (2H, m),
6.89±7.01 (1H, m), 7.56±7.68 (2H, m). Anal. calcd for
C9H10N2O3: C, 55.67; H, 5.19; N, 14.43. Found: C,
55.51; H, 5.10; N, 14.43.
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ꢀ
1
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