Note: Descriptions are shown in the official language in which they were submitted.
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NON-SEDATING BARBITURIC ACID DERIVATIVES
BACKGROUND OF THE INVENTION
[0001] The present invention relates to novel non-sedating barbituric acid
derivatives, pharmaceutical compositions containing them and methods of
neuroprotection in cases of cerebral ischemia, head trauma and other acute
neurologic injuries, and prevention of resulting neuronal damage. The
invention
also relates to the use of non-sedating barbituric acid derivatives given in a
manner and dosage effective to produce blood levels and brain levels of these
drugs and/or their active metabolites sufficient to provide a therapeutic
effect.
[0002) Barbituric acid and its derivatives have been known since the turn
of the century to possess pharmacological properties and some of them serve as
active ingredients in widely used drugs. Barbituric acid derivatives are known
to
act mainly as sedatives, hypnotics and anaesthetics. Certain derivatives also
have
an anticonvulsive effect and are therefore employed in the treatment of
epilepsy.
Thus, pharmaceutical compositions containing 5-ethyl-5-phenyl barbituric acid
(phenobarbital) are at present most widely used as drugs employed in the
treatment of epilepsy. However, like other barbituric acid derivatives,
phenobarbital has sedative and hypnotic effects, which are a disadvantage in
the
treatment of epilepsy. Therefore, a great effort has been devoted to the
search for
compounds which have anticonvulsant properties and at the same time are devoid
of sedative and hypnotic effects.
[0003] For example, a known derivative of barbituric acid is 5,5-diphenyl
barbituric acid, which was disclosed by S.M. McElvain in J. Am. Chem. Soc. 57,
1303 (1935), The
compound was found to be effective only in very large doses and therefore no
pharmacological application was suggested. Raines et at. reported in Bpilepsia
20,
105 (1979), that 5,5-
diphenyl barbituric acid has an anticonvulsant effect on rodents but with the
disadvantage of relatively short term activity. Additionally non-sedating
barbituric acid derivatives have been disclosed in Levitt, U.S. Patent No.
4,628,056, and Gutman et at., WO 02/007729 Al, published January 31, 2002,
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[0004] Ischemia (stroke) is the third leading cause of death in the United
States. When blood supply to the brain is reduced below a critical threshold,
a
cascade of biochemical events leads to irreversible damage to neurons and
brain
infarction. Research on treatment and prevention of ischemia is extensive but
unfortunately it remains at a basic stage and no adequate therapies are yet in
practice (Stroke Therapy: Basic clinical and pre-clinical directions, Leonard
P.
Miller, ed. (Wiley 1999)).
[0005] Barbiturates in high concentrations have been shown to be
neuroprotective in cerebral ischemia in rodents and primates, to reduce the
extent
of ischemia brain infarction, and to prevent or lessen brain damage (Hoff JT,
Smith AL, Hankinson HL, Nielsen SL, Stroke 1975, 6:28-33; Levy DE, Brierley
JB. Delayed pentobarbital administration limits ischemia brain damage in
gerbils;
Lightfoote WE II, Molinari GF, Chase TN, Stroke 1977, 8:627-628; Corkill G,
Chikovani OK, McLeish I, McDonald LW, Youmans JR, Surg. Neurol. 1976,
147-149). One theory as to how barbiturates prevent neuronal injury in
ischemia
is that they inhibit the ischemia-induced uncontrolled release of
neurotransmitters,
which can attain high, neurotoxic concentrations that cause neuronal death
(Bhardwaj A, Brannan T, Weinberger J, J Neural Transom 1990, 82:111-117).
[0006] The literature regarding the neuroprotective effects of anesthetic
barbiturates is over two decades old, but the clinical use of barbiturates has
been
severely limited because of toxicity. The dosages and blood and brain levels
necessary to confer neuroprotection are toxic and cause lethargy, stupor, and
coma. Even higher doses that might be more effective are lethal (Hoff JT,
Smith
AL, Hankinson HL, Nielsen SL, Stroke 1975, 6:28-33; Levy DE, Brierley JB.
Delayed pentobarbital administration limits ischemia brain damage in gerbils;
Lightfoote WE II, Molinari GF, Chase TN, Stroke 1977, 8:627-628; Corkill G,
Chikovani OK, McLeish I, McDonald LW, Youmans JR, Surg. Neurol. 1976,
147-149; Masuda Y, Utsui Y, Shiraishi Y, Karasawa T, Yoshida K, Shimizu M.,
Epilepsia 1979, 20:623-633.), making barbiturates unsuitable for treatment of
ischemia (Hoff JT, Smith AL, Hankinson HL, Nielsen SL, Stroke 1975, 6:28-33).
These toxic side effects establish a "functional ceiling" on dosage for
barbiturates,
and have discouraged further research into the use of anesthetic/sedative
barbiturates to protect from ischemia.
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[0007] Levitt et al., U.S. 4,628,056 describes non-sedating oxopyrimidine
derivatives and their use as anticonvulsants, anti-anxiety and muscle relaxant
agents. The literature does not suggest the use of such compounds as
neuroprotectant agents. Indeed, even in published studies about using sedative
barbiturates for neuroprotection there is no reference to non-sedating
barbiturate
compounds. It is generally believed that the anticonvulsant and
neuroprotective
effects of barbiturates are linked to their sedativethypnotic effects. For
example,
Lightfoote et al. suggested that the protective effects of pentobarbital are
due to
the duration of the barbiturate-induced anesthesia (Lightfoote WE II, Molinari
GF,
Chase TN, Stroke 1977, 8:627-628). This viewpoint has been reinforced by
biochemical studies at the cell receptor level that relate all these effects
to action
at the GABA receptor. Thus, the prior art teaches away from using sedative
barbiturates for neuroprotection because of their toxicity, and also teaches
away
from using non-sedative barbiturates as neuroprotectants because they lack
sedating or anesthetic properties.
[0008] Some barbituric acid derivatives of Formula I and their methods of
preparation are known.
O
R 2 N N RI
O O
R4 R3
(I)
For example, U.S. Patent No. 6,093,820,
describes the synthesis of N,N-bismethoxymethyl-5,5-
dipheyl barbitutric acid (Formula I, R'=R2=CR2OMe and R3=R =Ph). U.S. Patent
No. 4,628,056, which is incorporated by reference herein in its entirety,
describes
an alternative synthesis of this compound.
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SUMMARY OF THE INVENTION
[0009] It is therefore the object of the present invention to provide novel
non-sedating barbituric acid derivatives having a long acting neurological
activity
and being devoid of any significant hypnotic and sedative effects.
Neurological
activity may include neuroprotective, anti-stress and anti-strain,
anticonvulsant,
anti-seizure, muscle relaxant, anti-nervous strain, and anti-anxiety.
[0010] Non-sedating barbituric acid derivatives, also termed non-sedative
barbiturates, of the present invention have the general Formula I
O
R 2 N N R1
O O
R4 R3
(I)
wherein R' and R2 may be the same or different and are independently
hydrogen;
lower alkyl, optionally substituted by lower cycloalkyl, acyl, acyloxy, aryl,
aryloxy, lower alkoxy, thioalkyl or thioaryl, amino, alkylamino, dialkylamino,
or
one or more halogen atoms;
phenyl;
CH2XR5, wherein X is S or 0 and R5 is lower alkyl, aryl, or alkylaryl (e.g.,
benzyl);
C(O)XR6, wherein X is as defined above and R6 is lower alkyl or aryl;
CXR7, wherein X is as defined above and R7 is hydrogen, lower alkyl or aryl;
and
CH(XR8)2, wherein X is as defined above and R8 is a lower alkyl group, with
the
proviso that at least one of R' and R2 is not hydrogen.
R3 and R4 may be the same or different and are independently hydrogen;
aryl optionally containing one or more heteroatoms selected from the group
consisting of N, S and 0; lower acyloxy; phenyl; phenyl substituted with a
halogen, lower alkyl group, lower acyl group or derivative thereof or
acetamido;
benzyl; benzyl substituted on the ring by one or more halogens, lower alkyl
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groups or both; cycloalkyl, which optionally contains one or more heteroatoms
selected from the group consisting of N, 0 and S; lower alkyl; or lower alkyl
substituted with an aromatic moiety. At least one of R3 and R4 is an aromatic
ring
or an aromatic ring containing moiety. As used herein, lower alkyl refers to a
branched or straight chain alkyl group having eight or fewer carbons. Alkyl
also
includes hydrocarbon groups having one or two double or triple bonds in the
chain. The present invention also includes salts of the aforementioned
compounds. In the compounds and salts of the present invention,
1. when R' and/or R2 is methoxymethyl, R3 and R4 are not both phenyl,
are not both phenyl substituted by lower alkyl, and are not both phenyl
substituted
by halogen; and
2. when one of R3 and R4 is phenyl or benzyl, the other of R3 and R4 is not
ethyl; and
3. when at least one of R' and R2 is benzyl, then when one of R3 and R4 is
phenyl, the other of R3 and R4 is not allyl; and
4. when one of R' and R2 is methyl and the other is hydrogen, then when
one of R3 and R4 is phenyl, the other of R3 and R4 is not unsubstituted lower
alkyl;
and
5. when R' = R2 = Ra, where Ra is alkoxymethyl or (acyloxy)methyl, then
when one of R3 and R4 is 1-phenylethyl, the other of R3 and R4 is not
propionyloxy.
Furthermore, the following compounds are not included within the scope
of the present invention with respect to compositions, but can be used in
practicing the method of the invention.
a) 1-methyl-5-(1-phenylethyl)-5-propionyloxy-barbituric acid,
b) 1,3-diphenyl-5,5-(dibenzyl) barbituric acid,
c) 1,3,5-triphenyl barbituric acid, and
d) 5-benzyl-1,3-dimethyl barbituric acid.
[00111 In some exemplary embodiments, at least one of R' and R2 is lower
alkyl substituted by lower cycloalkyl, acyl, acyloxy, aryl, aryloxy, thioalkyl
or
thioaryl, amino, alkylamino, dialkylamino, or one or more halogen atoms;
phenyl;
CH2SR5, wherein R5 is lower alkyl, aryl, alkylaryl or benzyl; C(S)XR6, wherein
X
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is S or 0 and R6 is lower alkyl or aryl; CSR7, wherein R7 is hydrogen, lower
alkyl
or aryl; and CH(SR8)2, wherein R8 is a lower alkyl group.
[0012] In other exemplary embodiments, at least one of R3 and R4 is lower
acyloxy; phenyl substituted with a lower acyl group or derivative thereof or
acetamide; and cycloalkyl of which the ring optionally contains one or more
heteroatoms selected from the group consisting of N, 0 and S.
[0013] In certain exemplary embodiments of the invention, the
substituents R' and R2 are different and are individually selected from butyl,
benzyl, thiophenylmethyl, cyclopropylmethyl, 3,3,3-trifluoropropyl,
benzyloxymethyl, and alkoxymethyl. In other exemplary embodiments, R' and R2
are the same and are selected from butyl, benzyl, thiophenylmethyl,
cyclopropylmethyl, 3,3,3-trifluoropropyl, benzyloxymethyl, and alkoxymethyl.
In
other exemplary embodiments, one of R' and R2 is hydrogen and the other of R'
and R2 is selected from alkoxymethyl, butyl, benzyl, thiophenylmethyl,
cyclopropylmethyl, 3,3,3-trifluoropropyl, and benzyloxymethyl.
[0014] In other exemplary embodiments, at least one of R' and R2 are
methoxymethyl. In other exemplary embodiments, R3 and R4 are both aromatic
rings or aromatic ring containing moieties.
[0015] In certain exemplary embodiments, R3 and R4 are the same or
different and are independently phenyl; phenyl substituted with a halogen or
lower
alkyl group; cycloalkyl, which optionally contains one or more heteroatoms
selected from the group consisting of N, 0 and S; benzyl; benzyl substituted
on
the ring by one or more halogens, lower alkyl groups or both; lower alkyl; or
lower alkyl substituted with an aromatic moiety, provided that at least one of
R3
and R4 is phenyl or substituted phenyl.
[0016] In other exemplary embodiments, at least one of R3 and R4 are
selected from the group consisting of phenyl, benzyl, fluorophenyl and tolyl.
[0017] In other exemplary embodiments, at least one of R3 and R4 is
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[0018] selected from:
NHZ
O O
and
s
R3 and R4 may be the same or different.
[0019] Non-sedating barbituric acid derivatives according to the invention
may be administered to treat mammals for strain and stress conditions and
nervous
dysfunctions such as convulsions, seizure, muscle stiffness, nervous strain
and
anxiety. Non-sedating barbituric acid derivatives according to the invention
may
also be administered to achieve a neuroprotective effect.
[0020] The present invention also encompasses pharmaceutical
compositions having a compound of Formula I as the active ingredient together
with a pharmaceutically acceptable carrier.
[0021] The invention further provides an article of manufacture
comprising a container comprising a pharmaceutical composition and a label
with
indications for use as a treatment for strain and stress conditions; nervous
dysfunctions such as convulsions, seizure, muscle stiffness, nervous strain
and
anxiety, and/or as a neuroprotectant, the pharmaceutical composition
comprising a
non-sedating barbiturate compound in a pharmacologically effective amount
together with a pharmaceutically acceptable carrier or excipient.
DETAILED DESCRIPTION
[0022] In describing embodiments of the present invention, specific
terminology is employed for the sake of clarity. However, the invention is not
intended to be limited to the specific terminology so selected. It is to be
understood that each specific element includes all technical equivalents,
which
operate in a similar manner to accomplish a similar purpose. The above-
described
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embodiments of the invention may be modified or varied, and elements added or
omitted, without departing from the invention, as appreciated by those skilled
in
the art in light of the above teachings. Each reference cited here is
incorporated
by reference as if each were individually incorporated by reference.
[0023] Levitt et al., U.S. Patent No. 4,628,056, describes non-sedating
oxopyrimidine derivatives and their use as anticonvulsants, anti-anxiety and
muscle relaxant agents. Levitt further describes the preparation of some 1,3-
disubstituted-5,5-diphenyl barbituric acid derivatives. The diphenyl
substituents
of Levitt may be further substituted by lower alkyl or halogen. Gutman et al.,
U.S. Patent No. 6,093,820, describes methods of N-alkylating ureides that are
useful for preparing mono- and di-N substituted barbituric acid derivatives.
The
methods disclosed can be useful in preparing compounds useful in the present
invention. Gutman et al., WO 02/007729 Al,
describes the use of non-sedating barbiturate compounds as
neuroprotective agents.
[0024] The term "non-sedative barbituric acid derivatives" as used herein
encompasses the family of barbituric acid anticonvulsant compounds and
derivatives and structural analogs having the general Formula I, and salts
thereof
O
R2 N )", N RI
0 O
R4 R3
wherein R' and R2 may be the same or different and are independently
hydrogen;
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lower alkyl, optionally substituted by lower cycloalkyl, acyl, acyloxy, aryl,
aryloxy, lower alkoxy, thioalkyl or thioaryl, amino, alkylamino, dialkylamino,
or
one or more halogen atoms;
phenyl;
CH2XR5, wherein X is S or 0 and R5 is lower alkyl, aryl, or alkylaryl (e.g.,
benzyl);
C(0)XR6, wherein X is as defined above and R6 is lower alkyl or aryl;
CXR7, wherein X is as defined above and R7 is hydrogen, lower alkyl or aryl;
and
CH(XR8)2, wherein X is as defined above and R8 is a lower alkyl group, with
the
proviso that at least one of R1 and R2 is not hydrogen.
R3 and R4 may be the same or different and are independently hydrogen;
aryl optionally containing one or more heteroatoms selected from the group
consisting of N, S and 0; lower acyloxy; phenyl; phenyl substituted with a
halogen, lower alkyl group, lower acyl group or derivative thereof or
acetamido;
benzyl; benzyl substituted on the ring by one or more halogens, lower alkyl
groups or both; cycloalkyl, which optionally contains one or more heteroatoms
selected from the group consisting of N, 0 and S; lower alkyl; or lower alkyl
substituted with an aromatic moiety. At least one of R3 and R4 is an aromatic
ring
or an aromatic ring containing moiety. As used herein, lower alkyl refers to a
branched or straight chain alkyl group having eight or fewer carbons. Alkyl
also
includes hydrocarbon groups having one or two double or triple bonds in the
chain. The present invention also includes salts of the aforementioned
compounds. For new compounds and salts of the present invention,
1. when R' and/or R2 is methoxymethyl, R3 and R4 are not both phenyl,
are not both phenyl substituted by lower alkyl, and are not both phenyl
substituted
by halogen; and
2. when one of R3 and R4 is phenyl or benzyl, the other of R3 and R4 is not
ethyl; and
3. when at least one of R' and R2 is benzyl, then when one of R3 and R4 is
phenyl, the other is not allyl; and
4. when one of R' and R2 is methyl and the other is hydrogen, then when
one of R3 and R4 is phenyl, the other of R3 and R4 is not unsubstituted lower
alkyl;
and
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5. when R' = R2 = Ra, where Ra is alkoxymethyl or (acyloxy)methyl, then
when one of R3 and R4 is 1-phenylethyl, the other of R3 and R4 is not
propionyloxy.
Furthermore, the following compounds are not included within the scope
of the present invention with respect to compositions, but can be used in
practicing the method of the invention.
a) 1-methyl-5-(1-phenylethyl)-5-propionyloxy-barbituric acid,
O
\
N O
O=
HN
O
b) 1,3-diphenyl-5,5-(dibenzyl) barbituric acid,
o
N'K N
0 0
c) 1,3,5-triphenyl barbituric acid, and
\ 0 \
/ N'K N /
0 0
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d) 5-benzyl-1,3-dimethyl barbituric acid.
O
N 'K N
O O
[0025] In some exemplary embodiments, at least one of R' and R2 is lower
alkyl substituted by lower cycloalkyl, acyl, acyloxy, aryl, aryloxy, thioalkyl
or
thioaryl, amino, alkylamino, dialkylamino, or one or more halogen atoms;
phenyl;
CH2SR5, wherein R5 is lower alkyl, aryl, alkylaryl or benzyl; C(S)XR6, wherein
X
is S or 0 and R6 is lower alkyl or aryl; CSR7, wherein R7 is hydrogen, lower
alkyl
or aryl; and CH(SR8)2, wherein R8 is a lower alkyl group.
[0026] In other exemplary embodiments, at least one of R3 and R4 is lower
acyloxy; phenyl substituted with a lower acyl group or derivative thereof or
acetamide; and cycloalkyl of which the ring optionally contains one or more
heteroatoms selected from the group consisting of N, 0 and S.
[0027] In certain exemplary embodiments of the invention, the
substituents R' and R2 are different and are individually selected from butyl,
benzyl, thiophenylmethyl, cyclopropylmethyl, 3,3,3-trifluoropropyl,
benzyloxymethyl, and alkoxymethyl. In other exemplary embodiments, R1 and R2
are the same and are selected from butyl, benzyl, thiophenylmethyl,
cyclopropylmethyl, 3,3,3-trifluoropropyl, benzyloxymethyl, and alkoxymethyl.
In
other exemplary embodiments, one of R1 and R2 is hydrogen and the other of R'
and R2 is selected from alkoxymethyl, butyl, benzyl, thiophenylmethyl,
cyclopropylmethyl, 3,3,3-trifluoropropyl, and benzyloxymethyl. In other words,
one of R1 and R2 is hydrogen, and the other of R' and R2 is selected from:
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-CH2-O-(CH2)õ-CH3 with n >_ 0;
-(CH2)4-H; -CH2 / \ ; -CH2-S / \ ; -CH2
-CH2-CH2-CF3; and -CH2\
[0028] In other exemplary embodiments, at least one of R' and R2 are
methoxymethyl. In other exemplary embodiments, R3 and R4 are both aromatic
rings or aromatic ring containing moieties.
[0029] In certain exemplary embodiments, R3 and R4 are the same or
different and are independently phenyl; phenyl substituted with a halogen or
lower
alkyl group; cycloalkyl, which optionally comprises one or more heteroatoms
selected from the group consisting of N, 0 and S; benzyl; benzyl substituted
on
the ring by one or more halogens, lower alkyl groups or both; lower alkyl; or
lower alkyl substituted with an aromatic moiety, provided that at least one of
R3
and R4 is phenyl or substituted phenyl.
[0030] In other exemplary embodiments, at least one of R3 and R4 are
selected from the group consisting of phenyl, benzyl, fluorophenyl and tolyl.
[0031] In other exemplary embodiments, at least one of R3 and R4 is
selected from:
NHZ
and
s
R3 and R4 may be the same or different.
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[0032] R' and R2 may function as non-toxic leaving groups capable of
being removed in a biological system to give rise to a pharmacologically
active
species. The relatively slow loss of R' and/or R2 results in an extension of
the
metabolic half-life of the pharmacologically active species in mammals. R3 and
R4 may be chosen so that the resultant pharmacologically active compound
avoids
the sedative properties normally associated with barbituric acid derivatives.
A
modified version of the test described in Example 3 could serve as a test
method
for identifying compounds which do not have the sedative properties normally
associated with barbituric acid derivatives. For example, if a test animal to
which
the compound has been administered fails to respond to a large fraction of
imposed stimuli, the compound may be understood as having sedative properties.
By testing a compound with particular R3 and R4 substituents, compounds not
having the sedative properties normally associated with barbituric acid
derivatives
can be identified.
[0033] It has been reported (Rains A, Moros D et al., J. Exp. Biol.
(Abstracts) 1996, 895; Epilepsia 1996, 37:Suppl. 5) that N,N'-dimethoxymethyl-
5,5-diphenyl barbituric acid degrades metabolically to form diphenyl
barbituric
acid (DPB). It has also been learned that the degradation mechanism involves
formation of the monomethoxymethyl intermediate. According to the invention,
the N-substituted R'/R2 groups may be cleaved metabolically to produce the
R3/R4
substituted compounds with mono or no N substitution or the R'/R2 groups may
remain bound in an active compound.
[0034] Preferred compounds are those without adverse side effects.
Examples of adverse side effects are toxicity, which can be assessed by the
method of Example 2, and sedation, which can be assessed by the method of
Example 3, as described above.
[0035] Placement of the 1 and 3 substituents to prepare 1,3-
bis(substituted)-5,5-disubstituted barbituric acids according to the invention
may
be accomplished by reacting an appropriate 5,5-di(substituted) barbituric acid
with
an alkali hydride to form the corresponding barbiturate salt which is then
reacted
with a moiety having a leaving group in a process similar to that described by
Samour et al. in J. Med. Chem. 14, 187 (1971). In a more general method, mono-
and di-substituted compounds may be prepared according to the process
described
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in U.S. Patent No. 6,093,820 and modifications thereof. In general, a 5,5-
disubstituted barbituric acid derivative is reacted with excess base. The
dianion
formed is then reacted with one equivalent of an alkylating agent if the
monosubstituted derivative is desired, or two equivalents of alkylating agent,
if
the disubstituted derivative is desired.
[0036] Substituents at the 5-position may be prepared by reacting alloxan
with an appropriate starting material in a manner similar to the preparation
of
diphenyl barbituric acid described by McElvain, referenced above. These
substituents may also be placed on a 1,3-bis(substituted)-barbituric acid by
oxidation of the acid to the corresponding 1,3-dialkyl alloxan, which is then
reacted with an appropriate compound in a similar way to yield the desired
product.
[0037] Compounds in their free acid form may be converted by techniques
well known to persons of ordinary skill in the art into salts such as sodium,
potassium or other pharmacologically acceptable salts.
[0038] The proper choice of synthetic method would be readily recognized
by persons skilled in the art or readily derived through routine
experimentation
well known to persons of ordinary skill in the art of organic chemical
synthesis.
The novel compounds of the invention are not limited by their method of
manufacture, but may be prepared by the methods described herein, other
methods
known to persons skilled in the art, or methods yet to be developed.
[0039] The term "treatment", as used herein, is intended to encompass
administration of compounds according to the invention prophylactically to
prevent or suppress an undesired condition, and therapeutically to eliminate
or
reduce the extent or symptoms of the condition. Treatment according to the
invention is given to a human or other mammal having a disease or condition
creating a need of such treatment. Treatment also includes application of the
compound to cells or organs in vitro. Treatment may be by systemic or local
administration.
[0040] The non-sedative barbituric acid derivatives of the present
invention may be formulated into "pharmaceutical compositions" with
appropriate
pharmaceutically acceptable carriers, excipients or diluents. If appropriate,
pharmaceutical compositions may be formulated into preparations including, but
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not limited to, solid, semi-solid, liquid, or gaseous forms, such as tablets,
capsules,
powders, granules, ointments, solutions, suppositories, injections, inhalants,
and
aerosols, in the usual ways for their respective route of administration.
[0041] An effective amount is the amount of active ingredient
administered in a single dose or multiple doses necessary to achieve the
desired
pharmacological effect. A skilled practitioner can determine and optimize an
effective dose for an individual patient or to treat an individual condition
by
routine experimentation and titration well known to the skilled clinician. The
actual dose and schedule may vary depending on whether the compositions are
administered in combination with other drugs, or depending on inter-individual
differences in pharmacokinetics, drug disposition, and metabolism. Similarly,
amounts may vary for in vitro applications. It is within the skill in the art
to adjust
the dose in accordance with the necessities of a particular situation without
undue
experimentation. Where disclosed herein, dose ranges do not preclude use of a
higher or lower dose of a component, as might be warranted in a particular
application.
[0042] Neurological disorders include strain and stress conditions and
nervous dysfunctions such as convulsions, seizure, muscle stiffness, nervous
strain
and anxiety. The compounds of the present invention may be used as
anticonvulsive agents and can therefore be employed in the treatment of
epilepsy.
The compounds of the present invention may also be used as neuroprotective
agents for the treatment of cerebral ischemia, head trauma and other acute
neurologic injuries, and in the prevention of resulting neuronal damage. The
compounds may be used in individuals undergoing cardiac surgery or carotid
endarterectomy, and individuals at risk for atrial fibrillation, transient
ischemic
attacks (TIAs), cerebral ischemia, bacterial endocarditis, strokes, or
subarachnoid
hemorrhage due to a cerebral aneurysm. The compounds can also be used after an
acute event.
[0043] The useful doses of the non-sedative barbiturate useful for
neuroprotective purposes may exceed the minimum anticonvulsant dosage of the
barbiturate. In some embodiments of the present invention the useful dose of
the
non-sedative barbiturate is in the range of from about 2 times to about 5
times the
anticonvulsant dosage. In yet other contexts where the need of the mammal
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requires, the effective dose of the non-sedative barbiturate for
neuroprotective
purposes is in the range of from about 5 times to about 10 times the
anticonvulsant
dosage of the non-sedative, or even higher so long as the dose is clinically
acceptable. In particular, the useful doses may exceed the dose of a sedative
barbiturate, such as Phenobarbital, at which sedation occurs and may exceed
the
doses at which coma or death would occur for Phenobarbital.
[0044] The neuroprotective effect of the present methods can be used to
mitigate the effect of cerebral ischemia. The non-sedating barbiturate can be
administered orally, intravenously, transdermally, in combination with an
adjuvant, or transpulmonarily by means of a particulate or aerosol inhalant.
Moreover, within the scope of the invention, the non-sedating barbiturate can
be
administered preventively, prophylactically or therapeutically, at a
clinically
acceptable dose. The compound may be administered prophylactically before
evident neuronal damage, or therapeutically after onset of neuronal damage.
The
neuroprotective effect diminishes, or protects the subject from neuronal
damage
caused by head trauma or cerebral ischemia. The compound may be administered
in conjunction with cardiac surgery or carotid endarterectomy. The mammalian
subject may have or be at risk for atrial fibrillation, a transient ischemic
attack
(TIA), bacterial endocarditis, a stroke, head trauma, or subarachnoid
hemorrhage.
[0045] Typically, to achieve neuroprotection the non-sedating barbiturate
is administered in a dose sufficient to obtain blood concentrations of at
least about
g/ml of barbiturate or of an active metabolite thereof, preferably at least
about
100 g/ml, more preferably at least about 250 g/ml, and possibly as high as
200-
300 g/ml, or even higher. In contrast, the reported therapeutic range for
25 phenobarbital is lower, 10-30 .ig/ml blood levels. Thus, preferred ranges
are at or
above about 25, 30, 50, 75, 100, 200, 250, or 300 .tg/ml. Similar doses are
suitable for the other pharmaceutical effects described herein.
[0046] The invention includes a pharmaceutical composition comprising a
non-sedating barbiturate administered in an amount effective to have a
30 neurological effect. Preferably, the non-sedating barbiturate is
administered in
oral doses in the range of from about 25 to about 1,500 mg/kg/day body weight.
Preferably the dose is greater than about 50 mg/kg/day, or greater than about
100
mg/kg/day, or greater than 250 mg/kg/day. A preferred dose is one that is
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pharmacologically equivalent to a dose of about 1000 mg/kg/day in the rat.
Thus,
dosage forms may be sufficient individually or in multiple doses to provide a
dose
equal to or above about 1, 5, 10, 15, 20, 25, 50, 70, 100, 250, 500, 1000, or
1500
mg/kg body weight per day. For other therapeutic uses, lower doses are
suitable
in the range of over or about 0.1, 0.5, 1, 5, or 10 mg/kg body weight per day
and
other doses as are well known in respect to barbiturates.
[0047] The inventive barbituric acid derivatives have prolonged half-life
in humans making it possible to achieve substantial blood levels with lower
oral
dosages. Blood levels of non-sedating barbiturates greater than 100 g/ml may
be
achieved with, for example, dosages between about 40 and about 100 mg/kg/day,
and are within the scope of the invention. With parenteral administration of
non-
sedating barbiturates, similar blood concentrations are obtained with daily
dosages
of less than 25 mg/kg/day. However, first day loading dosages may still need
initial dosages of greater than 25 mg/kg.
[0048] It is generally believed that the neurological, e.g. anticonvulsant
and neuroprotective, effects of barbiturates are linked to their
sedative/hypnotic
effects. For example, Lightfoote et al. in Stroke 8, 627-628 (1977) suggested
that
the protective effects of pentobarbital are due to the duration of the
barbiturate-
induced anesthesia. This viewpoint has been reinforced by biochemical studies
at
the cell receptor level that relate all these effects to action at the GABA
receptor.
Thus, the prior art teaches away from using sedative barbiturates for
neuroprotection because of their toxicity, and also teaches away from using
non-
sedative barbiturates as neuroprotectants because they lack sedating or
anesthetic
properties.
[0049] The invention also provides for pharmaceutical compositions
comprising as active material a compound of the above general Formula I or a
pharmaceutically acceptable salt thereof together with one or more
pharmaceutically acceptable carriers, excipients or diluents. Any conventional
technique may be used for the preparation of pharmaceutical formulations
according to the invention. The active ingredient may be contained in a
formulation that provides quick release, sustained release or delayed release
after
administration to the patient.
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[0050] Pharmaceutical compositions that are useful in the methods of the
invention may be prepared, packaged, or sold in formulations suitable for
oral,
parenteral and topical administration. Other contemplated formulations include
nanoparticles, liposomal preparations, resealed erythrocytes containing the
active
ingredient, and immunologically-based formulations.
[0051] The formulations of the pharmaceutical compositions described
herein may be prepared by any method known or hereafter developed. In general,
preparation includes bringing the active ingredient into association with a
carrier
or one or more other additional components, and then, if necessary or
desirable,
shaping or packaging the product into a desired single- or multi-dose unit.
[0052] Prolonged activity is a valuable attribute of drugs in general and of
anticonvulsant drugs in particular. Aside from allowing infrequent
administration,
it also improves patients' compliance with the drug. Furthermore, serum and
tissue
levels, which are crucial for maintaining therapeutic effectiveness, are more
stable
with a long acting compound. Moreover, stable serum levels reduce the
incidence
of break-through seizures and possible other adverse effects.
[0053] As used herein, "additional components" include, but are not
limited to, one or more of the following: excipients; surface active agents;
dispersing agents; inert diluents; granulating and disintegrating agents;
binding
agents; lubricating agents; sweetening agents; flavoring agents; coloring
agents;
preservatives; physiologically degradable compositions such as gelatin;
aqueous
vehicles and solvents; oily vehicles and solvents; suspending agents;
dispersing or
wetting agents; emulsifying agents, demulcents; buffers; salts; thickening
agents;
fillers; emulsifying agents; antioxidants; antibiotics; antifungal agents;
stabilizing
agents; pharmaceutically acceptable polymeric or hydrophobic materials as well
as other components.
[0054] Although the descriptions of pharmaceutical compositions
provided herein are principally directed to pharmaceutical compositions which
are
suitable for administration to humans, it will be understood by the skilled
artisan,
based on this disclosure, that such compositions are generally suitable for
administration to any mammal. Preparation of compositions suitable for
administration to various animals is well understood, and the ordinarily
skilled
veterinary pharmacologist can design and perform such modifications with
routine
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experimentation based on pharmaceutical compositions for administration to
humans.
[0055] A pharmaceutical composition of the invention may be prepared,
packaged, or sold in bulk, as a single unit dose, or as a plurality of single
unit
doses. As used herein, a "unit dose" is a discrete amount of the
pharmaceutical
composition comprising a predetermined amount of the active ingredient. The
amount of the active ingredient in each unit dose is generally equal to the
total
amount of the active ingredient which would be administered or a convenient
fraction of a total dosage amount such as, for example, one-half or one-third
of
such a dosage.
[0056] A formulation of a pharmaceutical composition of the invention
suitable for oral administration may be in the form of a discrete solid dosage
unit.
Solid dosage units include, for example, a tablet, a caplet, a hard or soft
capsule, a
cachet, a troche, or a lozenge. Each solid dosage unit contains a
predetermined
amount of the active ingredient, for example a unit dose or fraction thereof.
Other
formulations suitable for administration include, but are not limited to, a
powdered or granular formulation, an aqueous or oily suspension, an aqueous or
oily solution, or an emulsion. As used herein, an "oily" liquid is one which
comprises a carbon or silicon based liquid thatis less polar than water.
[0057] A tablet comprising the active ingredient may be made, for
example, by compressing or molding the active ingredient, optionally
containing
one or more additional components. Compressed tablets may be prepared by
compressing, in a suitable device, the active ingredient in a free-flowing
form
such as a powder or granular preparation, optionally mixed with one or more of
a
binder, a lubricant, a glidant, an excipient, a surface active agent, and a
dispersing
agent. Molded tablets may be made by molding, in a suitable device, a mixture
of
the active ingredient, a pharmaceutically acceptable carrier, and at least
sufficient
liquid to moisten the mixture.
[0058] Tablets may be non-coated or they may be coated using methods
known in the art or methods to be developed. Coated tablets may be formulated
for delayed disintegration in the gastrointestinal tract of a subject, for
example, by
use of an enteric coating, thereby providing sustained release and absorption
of
the active ingredient. Tablets may further comprise a sweetening agent, a
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flavoring agent, a coloring agent, a preservative, or some combination of
these in
order to provide pharmaceutically elegant and palatable preparation.
[0059] Hard capsules comprising the active ingredient may be made using
a physiologically degradable composition, such as gelatin. Such hard capsules
comprise the active ingredient, and may further comprise additional components
including, for example, an inert solid diluent. Soft gelatin capsules
comprising the
active ingredient may be made using a physiologically degradable composition,
such as gelatin. Such soft capsules comprise the active ingredient, which may
be
mixed with water or an oil medium.
[0060] Liquid formulations of a pharmaceutical composition of the
invention which are suitable for administration may be prepared, packaged, and
sold either in liquid form or in the form of a dry product intended for
reconstitution with water or another suitable vehicle prior to use.
[0061] Liquid suspensions, in which the active ingredient is dispersed in
an aqueous or oily vehicle, and liquid solutions, in which the active
ingredient is
dissolved in an aqueous or oily vehicle, may be prepared using conventional
methods or methods to be developed. Liquid suspension of the active ingredient
may be in an aqueous or oily vehicle and may further include one or more
additional components such as, for example, suspending agents, dispersing or
wetting agents, emulsifying agents, demulcents, preservatives, buffers, salts,
flavorings, coloring agents, and sweetening agents. Oily suspensions may
further
comprise a thickening agent. Liquid solutions of the active ingredient may be
in
an aqueous or oily vehicle and may further include one or more additional
components such as, for example, preservatives, buffers, salts, flavorings,
coloring
agents, and sweetening agents.
[0062] Powdered and granular formulations according to the invention
may be prepared using known methods or methods to be developed. Such
formulations may be administered directly to a subject, or used, for example,
to
form tablets, to fill capsules, or to prepare an aqueous or oily suspension or
solution by addition of an aqueous or oily vehicle thereto. Powdered or
granular
formulations may further comprise one or more of a dispersing or wetting
agent, a
suspending agent, and a preservative. Additional excipients, such as fillers
and
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sweetening, flavoring, or coloring agents, may also be included in these
formulations.
[0063] A pharmaceutical composition of the invention may also be
prepared, packaged, or sold in the form of oil-in-water emulsion or a water-in-
oil
emulsion. Such compositions may further comprise one or more emulsifying
agents. These emulsions may also contain additional components including, for
example, sweetening or flavoring agents.
[00(A] The efficacy of the compounds of the invention with respect to
strain and stress conditions and nervous dysfunctions such as convulsions,
seizure,
muscle stiffness, nervous strain and anxiety may be tested as set forth in non-
limiting examples 1-3 below. Similarly, the neuroprotective ability of the
compounds may be tested as set forth by, for example, the general method
described in non-limiting example 4 with specific reference to non-limiting
examples 5-7. Other methods known or to be developed may similarly be used to
test the compounds of the invention.
[0065] Compounds according to the invention can be made by two general
synthetic routes, using methods generally known in the art, or modifications
thereof that are known or readily derived by persons of ordinary skill in the
art
without undue experimentation. Exemplary methods for various steps can be
found in, for example, Loudon, G.M., Organic Chemistry, Addison-Wesley, 1984;
U.S. Patent No. 4,628,056 to Levitt et al. (1986); U.S. Patent No. 6,093,820
to
Gutman et al. (2000); published European Patent Application No. 1083 172 Al to
Ashkinazi (2001); and U.S. Patent No. 5,750,766 to Krummel et at. (1998),
Scheme 1 is a
retrosynthetic analysis outlining routes to the inventive compounds.
(0066] Compounds of Formula I can be prepared by N-alkylation of an
appropriately substituted barbituric acid derivative (Formula II). Suitable
exemplary methods for N-alkylation of barbituric acids are given below in
Examples 8a, 8b, 9a, 9b, 10, 11, and 12. Other known methods will be known to
persons skilled in the art and may also be used. The required barbituric acid
derivatives of Formula lI can be prepared by condensation of urea with a
suitable
substituted malonic ester (Formula Ill). In an alternative synthetic route
(See
Example 8c), the barbituric acid derivatives of Formula I can be prepared by
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reacting a substituted urea (Formula IV) with a suitably substituted malonic
ester
(III). Preparation of substituted ureas is well known. Methods of preparing
compounds of Formula III are also known in the art. Suitable exemplary methods
of their preparation, in which R3 and/or R4 may substituted, are given in
Examples
13-16. Other methods will be known to persons skilled in the art and may also
be
used.
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Scheme I
t 2 Et
R R lc RtR2 Et
O O H H R3 Ra
R3 R4 I IV III
I: R,R2=alkyl
2: Rt, R2 = CHZ-O-alkyl
3: Rt, R2 = C(O)XR, X =O,S
4: R,R2=C(O)R
5: Rt,R2=CH2(ORk
6: R3=H;124=Ar
8a, 8b,9a, 9b, 10, 11, 12 7: R3 = H, Ar; le = Ar
8: R3 =H, CIS-Ar; R4 = CH2-Ar
9: R3,R4H,R
V
H,,, N---'H H2 NH2 14a, 15b, 16 Et Et
-`O O Et Et O O
R3 R4 H R4
O O
II R3 Ra
III 13, 14b, 15a, 16
Et Et
o0
H H
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EXAMPLE 1
[0067] The anticonvulsant activity of the barbituric acid derivatives of the
invention may be demonstrated or tested by evaluating the protection against a
maximal electro shock seizure (MES) in treated rats. MES tests are widely used
for the assessment of anticonvulsant properties of chemical compounds, mainly
due to the good correlation between the test results and the clinical finding
of
efficacy in patients suffering from epilepsy. In a typical MES test carried
out to
evaluate the anticonvulsant properties of barbituric acid derivatives of the
invention, corneal electrodes are employed, a current of about 150
milliamperes is
used and a 60 hertz stimulus applied for about 200 milliseconds. Rats are
tested on
the day prior to drug administration so as to eliminate from the study any
animals
failing to respond with a complete tonic convulsion including tonic hind-limb
extension (THE), which serves as the basis for the assessment of the efficacy
of
the active material employed. Animals protected from THE are regarded as
protected in the MES tests.
[0068] The test composition is dissolved in warm polyethylene glycol 400
or other suitable solvent and the solution administered in an initial dose of
about
500 mg/kg by stomach tube to, for example, Sprague-Dawley rats. These animals
are tested for maximum electro shock seizure (MES) at a predetermined time
after
administration, for example, about 6 and 23 hours after administration. All
animals are demonstrated to exhibit a full maximal seizure to electrical
stimulation prior to being accepted for the study.
EXAMPLE 2
[0069] The non-toxicity of barbituric acid derivatives of the invention can
be tested by repeated administration of a high dosage, as follows:
[0070] The test compound suspended in warm polyethylene glycol 400 or
other suitable solvent is administered in an initial dose of about 1500 mg/kg
by
gastric tube to, for example, Sprague Dawley rats. A similar dose is
administered
to same rats after 24 hours and again 48 hours after the first administration.
Animals are examined for several hours after administration, again prior to
the
next dosing, and through an additional 3 days after the last administration.
The
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toxic effects of administration are monitored as well as behavioral effects
such as,
for example, locomotion, escape behavior, feeding or any other observable
effect.
EXAMPLE 3
[0071] The tranquilizing and muscle relaxant properties of the barbituric
acid derivatives of the invention can be demonstrated by monitoring the
behavioral and motor effects observed with treated mice.
[0072] For example, the test composition in alkalinized saline may be
administered intraperitoneally to, for example, Swiss Webster mice. The time
required for animals receiving various doses to exhibit particular motor and
behavioral effects is noted. Effects monitored may include, for example,
muscle
hypotonia, motor activity, quietness and escape behavior. Toxic effects are
also
noted.
[0073] The efficacy of the composition can be evaluated relative to known
centrally acting skeletal muscle relaxants and/or tranquilizing drugs. The
combination of the tranquilizing effect without impairing the capacity of the
animal to react to its environment is highly desirable in agents used for the
treatment of anxiety. Hypnotic activity or depression of the central nervous
system is preferably not exhibited by the compositions of the invention.
EXAMPLE 4 - General Design for Determining Efficacy for Treatment of
Ischemia
[0074] The non-sedative barbituric acid derivatives of the invention (NSB)
may be tested in rats exposed to either reversible or irreversible ischemia.
Varying doses of drug are administered. The neuroprotective effect is compared
to
a negative control (placebo) and a positive control, pentobarbital, a known
neuroprotective but sedative barbiturate, given at doses known to reduce
infarct
volume in cerebral ischemia.
[0075] Animals are sacrificed several days after the onset of the ischemic
insult and the brains examined to determine the volume of brain infarction as
an
outcome measure of the drug's reduction of ischemic brain damage. The animals
are examined clinically and graded prior to sacrifice to determine if the drug
has
conferred any beneficial effect on relevant functions following ischemic
"stroke."
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[0076] Four experimental models are preferred for testing the
neuroprotective effects of the NSB drug. See Ginsberg MD, "Animal Models of
Global and Focal Cerebral ischemia," Chapter 34 in Welsh KMA et al., Primer on
Cerebrovascular Diseases, Academic Press, New York, 1997; and Pulsinelli WA,
Brierley JB, A new model of bilateral hemispheric ischemia in the
unanesthetized
rat, Stroke 1979, May - June 10(3):267-72.
1. Irreversible ischemia produced by middle cerebral artery
(MCA)
occlusion;
2. Reversible ischemia produced by MCA occlusion;
3. Transient global ischemia produced by cross-clamping the
aorta for a defined interval; and
4. Transient global ischemia produced by cauterizing both
vertebral arteries and reversibly clamping the common carotid
arteries.
[0077] In each experimental model, groups of rats are treated with either:
1. Negative control (placebo) via nasogastric (NG) tube;
2. Positive control: intraperitoneal (IP) dose of 70 mg/kg
pentobarbital; or
3. The NSB compound DMMDPB (or a compound being
tested for its utility in the present invention) via NG tube at
doses between 500 mg/kg and 1500 mg/kg for 7 days prior to
experimental infarctions.
The results are compared.
EXAMPLE 5 - Irreversible Cerebral Ischemia
[0078) Irreversible MCA occlusion is produced by ligating the carotid
artery and then inserting a filament into the origin of the MCA with the
animal
maintained under halothane anesthesia. Blood flow in the MCA is measured by
laser doppler and those animals in which a significant drop in blood flow
occurred
are considered to have experienced cerebral ischemia, and to be at risk for
subsequent damage (i.e., a stroke). No clinical strokes are expected in
animals
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that do not experience a precipitous drop in MCA blood flow. All animals
showing a drop in MCA blood flow are expected to experience strokes.
[0079] Animals at risk are then followed behaviorally and scored by
clinical findings using the Bederson grading scale as either:
0 no evidence of stroke
1 mild stroke
2 moderate stroke
3 severe stroke
[0080] Those animals that survive for three days are sacrificed and their
brains examined. Animals to be sacrificed are given, for example, chloral
hydrate
(35 mg/kg IP, and their brains fixed by intracardiac perfusion with
heparinized
0.9% saline followed by 10% buffered formalin. The brains are removed from the
cranial vault with care to leave the arachnoid intact with the intracranial
vessels
underneath. The fixed brains are frozen at. for example, 80 C. Coronal
sections
20 m thick are cut at 400 m intervals in a cryostat at -20 C, dried on a hot
plate
at 60 C, fixed in 90% ethanol for 10 minutes and stained with hematoxylin and
eosin (7). Infarcted brain is pale compared to the rest of the brain. The
amount of
infarcted brain is determined by microscopic inspection of the brain sections
and
calculation of infarct volumes in mm3.
EXAMPLE 6 - Reversible Cerebral Ischemia Model
[0081] Rats are pretreated as in Example 4 (above) and a similar
procedure is performed except that the filament occluding the MCA is removed
after 30 to 60 minutes, restoring blood flow through the MCA. Rats are then
followed clinically for three days, graded for their degree of stroke and then
sacrificed as in Example 5. The brains are removed and examined as described
above.
EXAMPLE 7
[0082] Rats are pretreated as in Example 4 (above) and then, during ether
anesthesia, the rats' vertebral arteries are electrocauterized through the
alar
foramina of the first cervical vertebra. Reversible clamps are then placed
loosely
around the common carotid arteries. After 24 hours, working with awake rats,
the
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carotid clamps are tightened to produce 4-vessel occlusion. Following 10-30
minutes of 4-vessel occlusion, the clamps are removed and 72 hours later the
animals sacrificed by perfusion fixation. Untreated rats routinely demonstrate
ischemic neuronal damage after 20 or 30 minutes of 4-vessel occlusion.
Multiple
areas of the forebrain, including the Hl and paramedian hippocampus, striatum,
and posterior neocortex are evaluated. The NSBs are shown to be
neuroprotective
under these circumstances.
EXAMPLE 8a - Preparation of Mono and Bis N-alkylated barbituric acids
[0083] A compound of Formula II is dissolved with potassium hydroxide
in ethanol. An alkyl halide, R'X, is dissolved in the solution; the solutes
react.
The product of Formula I with R'=R2=R'. (Loudon GM, Organic Chemistry,
Addison-Wesley (1984), p. 1194)
EXAMPLE 8b - Preparation of Mono and Bis N-alkylated barbituric acids
[0084] A compound of Formula II is dissolved with potassium hydroxide
in ethanol. An alkyl tosylate, R'O Ts, is dissolved in the solution; the
solutes
react. The product has Formula I with R'=R2=R'. (Loudon GM, Organic
Chemistry, Addison-Wesley (1984), p. 1194)
EXAMPLE 8c - Preparation of Mono and Bis N-alkylated barbituric acids by
condensation of a urea and a malonic ester
[0085] A urea substituted with an alkyl group at one or both amides is
used as a starting material (Formula IV). If disubstituted, the alkyl grouping
may
be the same or different, i.e., the first alkyl group may be R', and the
second alkyl
group may be R' or R", where R' and R" are different. The substituted urea is
then reacted with a malonic ester (Formula III), e.g., diethyl malonate, and
sodium
ethoxide in ethanol. The reaction product has Formula I with R'=R' and R2=H,
R' or R". (Loudon GM, Organic Chemistry, Addison-Wesley (1984), p. 1087;
Euro. Pat. Applic. No. 1 083 172 Al)
[0086] A range of alkyl groups having cycloalkyl, acyl, acyloxy, aryl,
aryloxy, alkoxy, alkylthio, arylthio, amino, alkylamino, dialkylamino, or
halogen
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groups can be substituted for R' and R2 of Formula I using methods similar to
those described in Examples 8a, 8b, and 8c.
EXAMPLE 9a - Preparation of N-alkoxyalkylated compounds
[0087] Dialkoxymethane (R'OCH2OR') is added at 0 C to
acetylmethanesulfonate. The temperature of the solution is raised to 25 C and
the
components allowed to react for 2 hours. The resultant solution is then added
gradually over 45 minutes to a mixture of a suitably substituted barbituric
acid
(Formula II) and sodium hydride (as a 60% dispersion in mineral oil) in dry
dimethylformamide. The resultant reaction mixture is stirred for about 15
minutes
and then diluted with hydrochloric acid, followed by dilution with ethyl
acetate.
The phases are separated and the ethyl acetate phase washed with a saturated
aqueous sodium chloride and then washed with aqueous sodium hydroxide. The
ethyl acetate phase is then dried over anhydrous sodium sulfate, filtered, and
concentrated to dryness. The dried product is then crystallized from toluene
and
has the structure of Formula I with R'=R2=CHZOR. (U.S. Pat. No. 6,093,820)
[0088] By using different barbituric acid derivatives as starting materials,
the R3 and R4 groups may be varied.
[0089] By using an excess of sodium hydride and one equivalent of
alkylating agent, monosubstitution is favored, such that most of the product
consists of material of Formula I with one of R' and R2 being substituted as
CH2OR' and the other being substituted with hydrogen.
EXAMPLE 9b - Alternative Preparation of N-alkoxyalkylated compounds
[0090] A suitable barbituric acid (Formula II) is dissolved in
dimethylformamide. Once the solution has cooled, sodium hydride is added and
the mixture stirred for 30 minutes. An appropriate chloromethyl alkyl ether is
added to the mixture over a period of about 30 minutes. The reaction mixture
is
then stirred for 1 hour, then poured into ice water. The solid precipitate is
filtered,
washed with water, and crystallized from ethanol. (U.S. Pat No. 4,628,056)
[0091] By using different barbituric acid derivatives as starting materials,
the R3 and R4 groups maybe varied.
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[0092] Different alkoxides can be substituted as R' and R2 by using
different chlorinated ethers. For example, groups of R'=R2=CH2OR' can be
formed wherein R' is alkyl, aryl, alkylaryl, or benzyl. Alkylthio groups can
be
substituted as R1 and R2 by using chlorinated thioethers. For example, groups
of
R'=R2=CH2SR' can be formed wherein R' is alkyl, aryl, alkylaryl, or benzyl.
EXAMPLE 10 - Preparation of N-acyloxy substituted barbituric acids
[0093] A compound of Formula II is dissolved with an alkyl
chloroformate in a solution containing sodium hydroxide. The product of the
reaction has Formula I with R'=R2=C(O)OR', wherein R' is alkyl.
[0094] By reacting a compound of Formula II with an aryl chloroformate
in a solution containing sodium hydroxide, a product is formed which has
Formula I with R'=R2=C(O)OR', wherein R' is aryl. (Loudon, pp. 1061-1064)
[0095] By reacting a compound of Formula I with a compound of the
formula, C1C(O)SR', wherein R' is alkyl or aryl, a product is formed which has
Formula I with R'=R2=C(O)OR' , wherein R' is alkyl or aryl.
EXAMPLE 11 - Preparation of N-acyl substituted barbituric acids
[0096] A compound of Formula II is dissolved with an acid chloride of the
formula C1C(O)R', where R' is hydrogen, alkyl, or aryl and allowed to react
over
an aqueous solution of sodium hydroxide. The product has Formula I, wherein
R'=R2=C(O)R'. (Loudon GM, Organic Chemistry, Addison-Wesley (1984), pp.
1062-1064)
EXAMPLE 12a - Preparation of N-acetal substituted barbituric acids
[0097] A compound having Formula II is dissolved in
dimethylformamide. Sodium hydride is added to the solution. A chlorinated
diether having the general formula, C1CH(OR')2, wherein R' is alkyl, is added
to
the solution. The reactant product is then purified. The product has Formula I
with R'=R2=CH(OR')2. (Loudon GM, Organic Chemistry, Addison-Wesley
(1984), pp. 1062-1064)
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EXAMPLE 12b - Preparation of N-arylmethyl substituted barbituric acid
[0098] A compound of Formula II is dissolved with potassium hydroxide
in ethanol. A halomethyl substituted aromatic compound, ArCH2X, wherein X is
halogen, is dissolved in the solution. The reaction product has Formula I with
R'=R2=CH2Ar. (Loudon GM, Organic Chemistry, Addison-Wesley (1984), p.
1194)
[0099] This synthesis method can also be conducted with benzyl chloride
substituted on the benzene ring with sulfur hydride, SH.
EXAMPLE 12c- Preparation of N-thioaryl substituted barbituric acid
[00100] A compound of Formula II is dissolved with potassium hydroxide
in ethanol. A thiohaloarylalkyl compound, R'ArSX, wherein X is halogen and R'
is H or alkyl, is dissolved in the solution. The reaction product has Formula
I with
R'=R2=SArR'.
EXAMPLE 13 - Preparation of 5-aryl substituted barbituric acid derivatives
[00101] A solution of magnesium in an inert solvent is made. The inert
solvent can be selected from the group consisting of diethylether,
dimethoxymethane, tert-butylmethylether, tetrahydropyran, diisopropylether,
toluene, and mesitylene and can be a mixture of these solvents. Including
either
1,2-dibromomethane or diethylether can be beneficial. In a first step, an
arylmethylhalide is added to the solution. The aryl group may be a
heteroaromatic
group containing nitrogen in the ring and optionally containing carbon,
oxygen, or
sulfur in the ring. The solution can also contain tri-n-butylamine.
[00102] Diethylcarbonate is then added to the solution followed by
neutralization with hydrochloric acid. The organic layer is then separated.
[00103] Sodium ethylate is added to the concentrated organic layer.
Ethanol is then distilled from the solution. The solution is neutralized with
hydrochloric acid. The organic layer is then separated, dried, and
concentrated in
vacuum to yield a diethyl arylmalonate.
[00104] The diethyl arylmalonate is then dissolved with urea and sodium
ethoxide in ethanol. The reaction product has Formula I with one of R3 and R4
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being aryl, and the other of R3 and R4 being hydrogen. (U.S. Pat. No.
5,750,766;
Loudon GM, Organic Chemistry, Addison-Wesley (1984), p. 1087)
EXAMPLE 14a- Preparation of 5-aryl substituted barbituric acid derivatives
[00105] Alloxan monohydrate (Formula I, with R3=R4=OH) is dissolved in
sulfuric acid. An aromatic compound (Ar-H) is added and the solution is heated
and time allowed for the reaction to occur. The reaction mixture is then
cooled,
and the sulfuric acid layer is separated. The sulfuric acid layer is poured
into cold
water to precipitate the product. The precipitated product is filtered,
washed, and
refiltered, dried, an, if necessary, chromatographed to obtain the pure
product of
Formula I with R3=R4=Ar. (U.S. Pat No. 4,628,056)
[00106] Using this method, a halogen-substituted benzene, e.g.,
fluorobenzene, can be used to obtain product of Formula I with R3=R4=PhX,
wherein X is halogen. (U.S. Pat No. 4,628,056)
[00107] Alternatively, an alkyl-substituted benzene, e.g., ethylbenzene, can
be used to obtain product of Formula I with R3=R4=PhR', wherein R' is alkyl.
(U.S. Pat No. 4,628,056)
[00108] In another variation, an acyl-substituted benzene can be used to
obtain product of Formula I with R3=R4=PhC(O)R', wherein R' is alkyl; or,
benzylformamide can be used to obtain a product of Formula I with
R3=R4=PhCH2C(O)NH2 or a dithiane-substituted benzene, having the structure
/ \ s
s
can be used to obtain a product of Formula I with R3=R4=Ph-dithiane.
EXAMPLE 14b- Preparation of 5-aryl substituted barbituric acid derivatives
[00109] A solution of magnesium, dimethoxymethane, and
dibromomethane is made. A halomethyl substituted aromatic compound in
dimethoxymethane is added and allowed to react. Cold diethoxycarbonate is
added to the solution. The solution is then neutralized with hydrochloric
acid.
The organic layer is separated and concentrated by distillation.
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[00110] Sodium ethylate is added to the concentrated organic layer.
Dimethoxymethane and ethanol are distilled from the solution. The solution is
neutralized with hydrochloric acid and the organic layer separated, dried with
magnesium sulfate, and concentrated in vacuum. The resultant product is an
aromatic substituted diethyl malonate.
[00111] The diethyl malonate is then dissolved with urea and sodium
ethoxide in ethanol and reacts. The reaction product has Formula I with one of
R3
and R4 being aromatic and the other of R3 and R4 being hydrogen. (U.S. Pat.
No.
5,750,766; Loudon GM, Organic Chemistry, Addison-Wesley (1984), p. 1087)
[00112] Persons of ordinary skill in the art can use this method or variants
thereof to synthesize barbituric acid derivatives from halomethyl substituted
aromatic compounds which have additional substituents on the ring, e.g.,
halogen,
alkyl, acyl, acyl derivative, or acetamido substituents on the ring, in order
to
obtain a product having Formula I with one of R3 and R4 being substituted
aromatic and the other of R3 and R4 being hydrogen.
[00113] This synthesis method can also be conducted with
chloromethylphenyl dithiane as the halomethyl substituted aromatic compound.
EXAMPLE 15a- Preparation of 5-arylmethyl substituted barbituric acid
derivatives
[00114] Diethyl malonate is dissolved with a bromomethyl substituted
aromatic compound, having formula ArCH2X, where Ar is aryl and X is halogen,
and sodium ethoxide in ethanol. The product is a mono-arylmethylmalonate ester
of formula ArCH2CH(CO2Et)2. The monoarylmethylmalonate ester is then
dissolved with urea and sodium ethoxide in ethanol and reacts. The reaction
product has Formula I with R'=R2=H, with one of R3 and R4 being CH2Ar, and
the other of R3 and R4 being hydrogen. (Loudon GM, Organic Chemistry,
Addison-Wesley (1984), pp. 617, 1086-1088)
[00115] The aromatic compound can be further substituted in the ring with,
e.g., a halogen or an alkyl group.
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EXAMPLE 15b - Preparation of 5,5-bis(arylmethyl) substituted barbituric acid
derivatives
[00116] Diethyl malonate is dissolved with a bromomethyl substituted
aromatic compound, having formula ArCH2X, where Ar is aryl and X is halogen,
and sodium ethoxide in ethanol. The product is a mono-arylmethylmalonate ester
of formula ArCH2CH(CO2Et)2. The mono-arylmethylmalonate ester is separated
from the solution. The separated mono-arlymethylmalonate ester is then
dissolved with an iodomethyl substituted aromatic compound, having formula
Ar'CH2I, where Ar' is aryl and Ar and Ar' may be the same or different, and
sodium ethoxide in ethanol. The product is a diarylmethyl-malonate ester of
formula (ArCH2)(Ar'CH2)C(CO2Et)2.
[00117] The di-arylmethylmalonate ester is then dissolved with urea and
sodium ethoxide in ethanol. The reaction product has Formula I with R3=CH2Ar;
R4=CH2Ar'. (Loudon GM, Organic Chemistry, Addison-Wesley (1984), pp. 617,
1086-1088)
[00118] The aromatic ring of either compound can be substituted with, e.g.,
a halogen or an alkyl group.
EXAMPLE 16a - Preparation of 5,5-dialkyl substituted barbituric acid
derivatives
[00119] A compound having Formula I with R3=R4=OH is dissolved with
tosyl chloride in pyridine to replace the hydroxy groups with tosyl groups.
The
resultant tosylate is isolated and redissolved with a lithium dialkylcuprate
having
the formula R'2Cu Li+, wherein R'=alkyl, in ether. The product has Formula I
with R3=R4=R'. (Loudon GM, Organic Chemistry, Addison-Wesley (1984), pp.
721-722)
EXAMPLE 16b- Preparation of 5-alkyl substituted barbituric acid derivatives
[00120] Diethyl malonate is dissolved with an alkyl bromide, having
formula R'Br, wherein R' is alkyl, and sodium ethoxide in ethanol. The product
is a mono-alkylmalonate ester of formula R'CH(CO2Et)2. The mono-
alkylmalonate ester is then dissolved with urea and sodium ethoxide in ethanol
and reacts. The reaction product has Formula I with one of R3 and R4 being R',
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and the other of R3 and R4 being hydrogen. (Loudon GM, Organic Chemistry,
Addison-Wesley (1984), pp. 1086-1088)
[00121] The alkyl, R', may be substituted; e.g., the alkyl, R', may be
substituted with an aromatic group.
EXAMPLE 16c - Preparation of 5,5-dialkyl substituted barbituric acid
derivatives
[00122] Diethyl malonate is dissolved with an alkyl bromide, having
formula R'Br, wherein R' is alkyl, and sodium ethoxide in ethanol. The product
is a mono-alkylmalonate ester of general formula R'CH(CO2Et)2. The mono-
alkylmalonate ester is separated from the solution. The separated mono-
alkylmalonate ester is then dissolved with an alkyl iodide, having formula
R"I,
wherein R" is alkyl and may be the same as or different from R', and sodium
ethoxide in ethanol. The product is a di-alkylmalonate ester of formula
R"R'C(CO2Et)2.
[00123] The di-alkylmalonate ester is then dissolved with urea and sodium
ethoxide in ethanol. The reaction product has Formula II with one of R3 and R4
being R', and the other of R3 and R4 being R". R' and R" may be the same or
different alkyls. (Loudon GM, Organic Chemistry, Addison-Wesley (1984), pp.
1086-1088)
[00124] The alkyls, R' and R", may be substituted; e.g., the R' and R"
alkyls may each be substituted with an aromatic group.
[00125] The embodiments illustrated and discussed in this specification are
intended only to teach those skilled in the art the best way known to the
inventors
to make and use the invention. Nothing in this specification should be
considered
as limiting the scope of the present invention. All examples presented are
representative and non-limiting. The above-described embodiments of the
invention may be modified or varied, without departing from the invention, as
appreciated by those skilled in the art in light of the above teachings. It is
therefore to be understood that, within the scope of the claims and their
equivalents, the invention may be practiced otherwise than as specifically
described.
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