CA1125288A - Heterocyclic compounds which are gaba-agonists and production of same - Google Patents
Heterocyclic compounds which are gaba-agonists and production of sameInfo
- Publication number
- CA1125288A CA1125288A CA377,128A CA377128A CA1125288A CA 1125288 A CA1125288 A CA 1125288A CA 377128 A CA377128 A CA 377128A CA 1125288 A CA1125288 A CA 1125288A
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- alkyl
- phenyl
- compound
- alkoxy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/55—Design of synthesis routes, e.g. reducing the use of auxiliary or protecting groups
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Abstract
Abstract.
The compound Ia Ia (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol) has been shown to possess GABA-related activity. The invention relates to Ia and derivatives thereof, covered by the formula I
I
in which R" is hydrogen, acetyl or a group of the general formula VII
VII
in which R5 is C1-8 alkyl; phenyl; phenyl substituted in the 4-position with halogen, lower alkoxy, or lower alkyl; or phenyl-alkyl in which the phenyl group may be substituted in the 4-posi-tion with halogen, lower alkoxy, or lower alkyl; and salts there-of. Novel intermediates for preparing I are IV
in which Alk is a lower alkyl group and Z is hydrogen or an amino-protecting group;
VIII' wherein Z is hydrogen or an amino-protecting group, T is a group convertible, by hydrolysis, into an oxy group, and Q is a leaving group which, on reaction with hydroxylamine, forms a hydroxamic acid group;
IX' wherein Z and T are as defined above;
V
wherein Z is as defined above, and W is hydrogen or a group removable to yield the free hydroxy group, with the proviso that at least one of Z and W is different from hydrogen.
The compound Ia Ia (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol) has been shown to possess GABA-related activity. The invention relates to Ia and derivatives thereof, covered by the formula I
I
in which R" is hydrogen, acetyl or a group of the general formula VII
VII
in which R5 is C1-8 alkyl; phenyl; phenyl substituted in the 4-position with halogen, lower alkoxy, or lower alkyl; or phenyl-alkyl in which the phenyl group may be substituted in the 4-posi-tion with halogen, lower alkoxy, or lower alkyl; and salts there-of. Novel intermediates for preparing I are IV
in which Alk is a lower alkyl group and Z is hydrogen or an amino-protecting group;
VIII' wherein Z is hydrogen or an amino-protecting group, T is a group convertible, by hydrolysis, into an oxy group, and Q is a leaving group which, on reaction with hydroxylamine, forms a hydroxamic acid group;
IX' wherein Z and T are as defined above;
V
wherein Z is as defined above, and W is hydrogen or a group removable to yield the free hydroxy group, with the proviso that at least one of Z and W is different from hydrogen.
Description
5~
This application is a division of copending Canadian application Serial ~o. 305,798 filed June 20, 1978.
The present invention relates to novel compounds having GABA--related activity.
GABA (~amma-aminobutyric acid) is known to be a neurotransmitter in the central nervous system (CNS) in mammals. GABA is found pre-dominantly in the brain where it is a dominant inhibitory trans-mitt~r (Curtis, D.R. and Johnston, G.A.R., Ergebn. Physiol., 1974, 69r 97 - 188).
It has been reported (Arzneimi~telforschung, 1968, 18, 311 - 315) that muscimol of the formula H
This application is a division of copending Canadian application Serial ~o. 305,798 filed June 20, 1978.
The present invention relates to novel compounds having GABA--related activity.
GABA (~amma-aminobutyric acid) is known to be a neurotransmitter in the central nervous system (CNS) in mammals. GABA is found pre-dominantly in the brain where it is a dominant inhibitory trans-mitt~r (Curtis, D.R. and Johnston, G.A.R., Ergebn. Physiol., 1974, 69r 97 - 188).
It has been reported (Arzneimi~telforschung, 1968, 18, 311 - 315) that muscimol of the formula H
2 2 ~o~N
~a substance found in fly amanita (Amanita muscaria~) has various interesting pharmacological properties and especially show~ an inh~bition o~ motoric functions. Later, it was reported that mus-c~mol is a very potent GABA agonist wi~h respect to bicuculline-sensitive postsynaptic receptors (Johnston et al., Biochem. Pharm-acol. , 1968, 17, 2488, a~d Curtis et al.,Braln Res., lg71, 32, 69 - 96), but it also hows actl~ity a~ ~n inhlbltor of the high '`, ~ ' ' ' , ~. 1 . . ' ~`j ` ' ~
`~ ` ' ~ ' ' ` ~ ' , , ` ,, ~' ` `
` ' 5Z8~
~a substance found in fly amanita (Amanita muscaria~) has various interesting pharmacological properties and especially show~ an inh~bition o~ motoric functions. Later, it was reported that mus-c~mol is a very potent GABA agonist wi~h respect to bicuculline-sensitive postsynaptic receptors (Johnston et al., Biochem. Pharm-acol. , 1968, 17, 2488, a~d Curtis et al.,Braln Res., lg71, 32, 69 - 96), but it also hows actl~ity a~ ~n inhlbltor of the high '`, ~ ' ' ' , ~. 1 . . ' ~`j ` ' ~
`~ ` ' ~ ' ' ` ~ ' , , ` ,, ~' ` `
` ' 5Z8~
- 3 affinity uptake of GA~,A in rat brain slices (Johnston, Psycho-pharmacologia, 1971, 22, 230 - 233). Reduced function in the GAB~
system is believed to be related to the etiology of parkinsonism, epilepsy, Huntington's chorea (Thomas No Chase and Judith R. Walters, GABA in Nervous System Function, edited hy Eo Roberts, T.N. Chase, and D.B~ Tower, Raven Press, New York, 1976, 497-513) and schizophreni and administration of agents influencing 'the GABA system is there-fore under consider~tion and research for the therapeutical treat-ment of such GABA system malfunction-related diseases. It is also under consideration to administer agents influencins the GABA
system against diseases in which malfunctions of the pituitary hormones are involved, e.g. diseases where a decreased secretion of prolactin is involved, and it is, furthermore, contemplated that such agents may be useful against artereoschlerotic diseases in the brain where a vasodilatation is desired. However, unfortunately, muscimol has toxic effects, such as narcotic effects (derealisation and depersonalisation), and the difference between the effective dose and the toxic dose of muscimol is very small (Arzneimittelforschung, 1968, 18, 311 - 315), which may limit or prevent the therapeutic use of muscimol. Furthermore, it would be h ghly desirable to provide a substance having a more specific GABA activity than muscimol which, as men~ioned above, shows con~
siderable GABA-uptake inhibitor activity in addition to its GABA -agonist activity. In an attempt to establish a structure/activity relation, various muscimol-analogues or muscimol-like substances have been synthesized and tested (P. Krogsgaard-Larsen et al., Journal of Neurochemistry, 1975, 25, 797 - 802 and 803 -809). However, none of the compounds tested showed a GABA agonist activity of the same potency as that of muscimol.
The present invention relates to novel compounds showin~ ~ABA--related activity, to saltsthereof with acids or bases, and to pharmaceutical compositions containin~ the novel co~poun~s or a salt thereof as an active in~redient. Moreover, the present invention relates to methods for the ~renaration of the novel compounds and salts thereof and to a method for the treat-ment o~ neuroloqical and ~sychiatrical disorders, such as enilepsy, par~insonism, schi.zo~hrenla and Huntin~ton's chorea, or diseases .. .
:. ~
. . .
5Z~ i
system is believed to be related to the etiology of parkinsonism, epilepsy, Huntington's chorea (Thomas No Chase and Judith R. Walters, GABA in Nervous System Function, edited hy Eo Roberts, T.N. Chase, and D.B~ Tower, Raven Press, New York, 1976, 497-513) and schizophreni and administration of agents influencing 'the GABA system is there-fore under consider~tion and research for the therapeutical treat-ment of such GABA system malfunction-related diseases. It is also under consideration to administer agents influencins the GABA
system against diseases in which malfunctions of the pituitary hormones are involved, e.g. diseases where a decreased secretion of prolactin is involved, and it is, furthermore, contemplated that such agents may be useful against artereoschlerotic diseases in the brain where a vasodilatation is desired. However, unfortunately, muscimol has toxic effects, such as narcotic effects (derealisation and depersonalisation), and the difference between the effective dose and the toxic dose of muscimol is very small (Arzneimittelforschung, 1968, 18, 311 - 315), which may limit or prevent the therapeutic use of muscimol. Furthermore, it would be h ghly desirable to provide a substance having a more specific GABA activity than muscimol which, as men~ioned above, shows con~
siderable GABA-uptake inhibitor activity in addition to its GABA -agonist activity. In an attempt to establish a structure/activity relation, various muscimol-analogues or muscimol-like substances have been synthesized and tested (P. Krogsgaard-Larsen et al., Journal of Neurochemistry, 1975, 25, 797 - 802 and 803 -809). However, none of the compounds tested showed a GABA agonist activity of the same potency as that of muscimol.
The present invention relates to novel compounds showin~ ~ABA--related activity, to saltsthereof with acids or bases, and to pharmaceutical compositions containin~ the novel co~poun~s or a salt thereof as an active in~redient. Moreover, the present invention relates to methods for the ~renaration of the novel compounds and salts thereof and to a method for the treat-ment o~ neuroloqical and ~sychiatrical disorders, such as enilepsy, par~insonism, schi.zo~hrenla and Huntin~ton's chorea, or diseases .. .
:. ~
. . .
5Z~ i
- 4 ~
in which malfunctions of the nituitary hormones are involved, or artereoschlerotic diseases in the brain where a vasodilata-tion is d~sired, by administering a therapeutically active amount of the novel compound or a non-toxic salt thereo~ to a living animal body including human beingsO
According to the present invention, it has now been found that the novel compound of the formula Ia OH ~
O ~O ~ H2N ~ ~ Ia (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol) . .
is well tolerated and is a very potent GABA agonist having a very specific activity! being inactive as a GABA-uptake inhibitor.
Particulars concerning the activity o~ this compound are given in the section "Test Results" below.
The potent, specific GABA agonist activity of the compound Ia is especially remarkable on the background of the fact that the known very closely related compounds, that is, .
~}l 5,6,7,8-tetrahydro-4H-isoxazolo-HN - [4,5-c]-azepine-3-ol (P. Krogs-gaard-Larsen, Acta Chem. Scand. B
N 31, 1977, 584 - 588, and P. Krogs-~_~' ~ ~ gaard-Larsen and G.A.R. Johnston, J. Neurochem., 1978, 30, 1377 - 1382).
in which malfunctions of the nituitary hormones are involved, or artereoschlerotic diseases in the brain where a vasodilata-tion is d~sired, by administering a therapeutically active amount of the novel compound or a non-toxic salt thereo~ to a living animal body including human beingsO
According to the present invention, it has now been found that the novel compound of the formula Ia OH ~
O ~O ~ H2N ~ ~ Ia (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol) . .
is well tolerated and is a very potent GABA agonist having a very specific activity! being inactive as a GABA-uptake inhibitor.
Particulars concerning the activity o~ this compound are given in the section "Test Results" below.
The potent, specific GABA agonist activity of the compound Ia is especially remarkable on the background of the fact that the known very closely related compounds, that is, .
~}l 5,6,7,8-tetrahydro-4H-isoxazolo-HN - [4,5-c]-azepine-3-ol (P. Krogs-gaard-Larsen, Acta Chem. Scand. B
N 31, 1977, 584 - 588, and P. Krogs-~_~' ~ ~ gaard-Larsen and G.A.R. Johnston, J. Neurochem., 1978, 30, 1377 - 1382).
- 5,6,7,8-tetrahydro-4H-isoxazolo-r~ tS,4-c~-azepine~3-ol (P. Krogs-gaard-Larsen, Acta Chem. Scand. B
¦ ll N 31, 1977, 584 - S88, and P. Xroqs-HN ~ O/ gaard-Larsen and G.A.R. Johnston, "4' J. Neurochem., 1978, 30, 1377 - 1382)o t ' ` '' . ~ ( .
' :
' ` :
~ ' 'h~8 o~ , ¦ 5,6,7,8-tetrahydro-4H-isoxazolo-~ ~ [4,5-d]-azepine-3-ol (P. Krogs-/ I N gaard-l,arsen et al., J. Neurochem., ll~ ~ / 1975, 25, 803, and P. Krogsgaard-Larsen and G.A.R. Johnstcn, J. Neuro-chem., 1978 , 30, 1377 - 1382).
,.
¦ 4,5,6,7-tetrahydroisoxazolo[~,5-c]-pyridine-3-ol (P. Krogsgaard-Larsen N et al., J. Neurochem., 1975, 25, l ~ / 803~ and P Krogsgaard-Larsen and "~' G.A.R. Johnston, J. Neurochem., 1978 30, 1377 - 1382).
._ ~
do not show such Dotent and specific GABA agonist activi~y.
Although the present invention is not to be limited by any t~eoxy, it is ~elieved that the remarkable selective activity of the compound Ia 15 ascribable to the particular position of the nitro-gen atom in the 6-membered ring in relation to the acidic hydroxy group in the 5-membered ring.
~he present invention tharefore relates to the novel comnound Ia and to derivatives thereof which upon administration will be decom-posed in situ to yield the parent com~oùnd Ia, in particular com-pounds of the general formula I
.
OH
R~- J I ~N I `:
wherein R" is hydrogen, acetyl o~ a group of the general formula ,~
VII ~;
o ~ ~
11 $:
- R5-O-C~
, .
wherein R5 i~ Cl_B alkyl; phenyl; phenyl substituted in the 4 ` position w~th halogen, lower alkoxy, or lower alkyl; or .~ . ,.: , , , ' , . ' ~ 6 -phenylalkyl such as benzyl or phenylethyl in which the phenyl group may be substituted in the 4-position with halo~en, lower alkoxy, or lower alkyl; and salts thereofO
It is believed that among the compounds I, the only species show-ing pronounced GABA a~onist activity in the brain is the compound Ia. However, the groups R'i which are di~ferent from hydro~en may enhance the penetration of the compounds into the brain in that they may enhance the ability of the compounds to pass the blood-brain barrier, and will thereafter be snlit of in situ to yield the parent compound. Also, a prolonged effect of Ia may be obtained via decomposition in situ of compounds wherein R" is different from hydrogen, to yield the parent compound.
In the present specification, "lower alkyl" and "lower alkoxy"
designate such groups containing 1 - 4 carbon atoms.
The compounds of the general formula I may exist in a tautomeric formJ as shown by the for~ula I' ., 11 ' .
~ Nll I
n~N o and in the present speciication and claims, the formula I is to be understood as covering also this tautomeric form and mixtures of the two tautomeric forms.
Examples of compounds of the general formula I in which R" is di~erent from hydrogen, are:
¦ ll N 31, 1977, 584 - S88, and P. Xroqs-HN ~ O/ gaard-Larsen and G.A.R. Johnston, "4' J. Neurochem., 1978, 30, 1377 - 1382)o t ' ` '' . ~ ( .
' :
' ` :
~ ' 'h~8 o~ , ¦ 5,6,7,8-tetrahydro-4H-isoxazolo-~ ~ [4,5-d]-azepine-3-ol (P. Krogs-/ I N gaard-l,arsen et al., J. Neurochem., ll~ ~ / 1975, 25, 803, and P. Krogsgaard-Larsen and G.A.R. Johnstcn, J. Neuro-chem., 1978 , 30, 1377 - 1382).
,.
¦ 4,5,6,7-tetrahydroisoxazolo[~,5-c]-pyridine-3-ol (P. Krogsgaard-Larsen N et al., J. Neurochem., 1975, 25, l ~ / 803~ and P Krogsgaard-Larsen and "~' G.A.R. Johnston, J. Neurochem., 1978 30, 1377 - 1382).
._ ~
do not show such Dotent and specific GABA agonist activi~y.
Although the present invention is not to be limited by any t~eoxy, it is ~elieved that the remarkable selective activity of the compound Ia 15 ascribable to the particular position of the nitro-gen atom in the 6-membered ring in relation to the acidic hydroxy group in the 5-membered ring.
~he present invention tharefore relates to the novel comnound Ia and to derivatives thereof which upon administration will be decom-posed in situ to yield the parent com~oùnd Ia, in particular com-pounds of the general formula I
.
OH
R~- J I ~N I `:
wherein R" is hydrogen, acetyl o~ a group of the general formula ,~
VII ~;
o ~ ~
11 $:
- R5-O-C~
, .
wherein R5 i~ Cl_B alkyl; phenyl; phenyl substituted in the 4 ` position w~th halogen, lower alkoxy, or lower alkyl; or .~ . ,.: , , , ' , . ' ~ 6 -phenylalkyl such as benzyl or phenylethyl in which the phenyl group may be substituted in the 4-position with halo~en, lower alkoxy, or lower alkyl; and salts thereofO
It is believed that among the compounds I, the only species show-ing pronounced GABA a~onist activity in the brain is the compound Ia. However, the groups R'i which are di~ferent from hydro~en may enhance the penetration of the compounds into the brain in that they may enhance the ability of the compounds to pass the blood-brain barrier, and will thereafter be snlit of in situ to yield the parent compound. Also, a prolonged effect of Ia may be obtained via decomposition in situ of compounds wherein R" is different from hydrogen, to yield the parent compound.
In the present specification, "lower alkyl" and "lower alkoxy"
designate such groups containing 1 - 4 carbon atoms.
The compounds of the general formula I may exist in a tautomeric formJ as shown by the for~ula I' ., 11 ' .
~ Nll I
n~N o and in the present speciication and claims, the formula I is to be understood as covering also this tautomeric form and mixtures of the two tautomeric forms.
Examples of compounds of the general formula I in which R" is di~erent from hydrogen, are:
6-acetyl-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol, methyl 3-hydroxy-4,5,6,7-tetrahydrolsoxazolo[5,4-c]pyridine~6--carboxylate, ethyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c~pyridine-6--carboxylate, .. , i - . ' ~ ' ` '' -` ; ' ' ' '3L~ ~;~,~
-- 7 ~
.
tert.butyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine~
-6-carboxylate, phenyl 3~hydroxy~4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-6--carboxylate, 4-chlorophenyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyri-dine-6-carboxylate, 4-methoxyphenyl 3-hydroxy-4,5,6,7-tetra~ydroiso~azolo[5,4~c]pyri-dine-6-carboxylate, benzyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-6--carboxylate, .
and salts thereof with bases.
Examples of salts of the compound of the formula Ia are acid addition salts thereof, such as ~harmaceutic-ally acceptable salts with inorganic acids, e.g. hydrochloric, hydrobromic, nitric, sulfuric, phosphoric acids and the like, or with organic acids, such as organic carboxylic acids, e.g. acetic, propionic, glycolic, malonic, succinic, maleic, fumaric, malic, tartaric, citric, glucuronic, benzoic, pamoic acid and the like, or organic sulfonic acids, e.g. methane sulfonic, ethane sulfonic, ben ene sulfonic, toluene sulfonic acid and the like, which salts may be prepared by procedures known ~ se, e.g. by adding the acid in question to the base, preferably in a solvent.
Compounds of formula I may form pharmaceutically acceptable salts with bases, such as metal salts, e.g. sodium, potassium, calcium or aluminium salts, and ammonium and substituted ammonium salts, e.g. salts of amines such as triethylaminet triethanolamine, ethylpiperidine, procaine, dibenzylamine and the like.
TEST RESULTS.
AffinitY Binding Experiments.
In order to study the interactions o~ the compound Ia with the ~entral GABA receptors in vitro, the compound Ia was tested in affinity binding experiments. The af~inity binding (sodium-inde-.. i .
~ ` , i ~"
., . . I`
. . ~ . -, .
.
...
-. ' .~ .
r ~ 8 --pendent bindin~) of GABA to membranes isolated from rat brains was studied as described by Enna, S.J. and Snyder, S.H., Brain Res., 1975, 100, 81 - 97~ IC50 values, inhibitor concentrations causing 50% inhibition of ~,AB~ binding were determined.
.
Inhibitor IC50 value Ia 0.13 - 0.005/uM
Muscimol 0.024 - O.003/uM
X) In earlier studies 2.6 - 0.6/uM was found~ The value stated (0.13 - 0.005/uM)is based on studies of 5 different concentrations of Ia, each dete~mined in triplicate, and the stated IC50 value is calculated by log probit analysis. The difference between the two TC50 values determined for Ia is the result of the development of an improved technique for the preparation of rat brain membranes.
~` ~
Microelectrophoretic Experiments.
.
In order to study the interactions o the compound Ia with the central GABA receptors in vivo, the compound Ia was tested in microelectrophoretic experiments. Experiments were performed on lumbar dorsal horn interneurones and Renshaw cells of cats an- ;
aesthetized with pentobar~itone sodium. The approximate potency of the depressant actions`of the compound was assessed relative to that of GABA on the basis of electrophoretic currents re-quired to produce equal and submaximal inhibitions of the firing o the central neurones. The inhibitory action of Ia on central neurones was antagonized by the specific GABA antagonist bicu-culline methochloride (BMC).
.
Potency relative Reversible anta-Compound to that af GABA gonism b BMC _ .
~A~A ~ ~ ~ yes `
Ia + ~ ~ + yes . ' . .
The compound Ia did not interact with the GABA u~take system at ~ . . .
, '' . ~
`
~- 9 - ' concentrations of 5 x 104 M, and it did not interact wikh the GABA metabolizing enzymes GABA:2-oxo-~lutarate aminotranserase and L-~lutamate l-carboxylase at concentrations of 10 3 M.
Based on the above-mentioned experiments~ the compound Ia is a specific and very potent GABA agonist.
Compound Ia has been compared with muscimol, the most potent GABA
agonist so far known, in a series of pharmacological experiments:
Toxicity.
Compound Ia has been shown to be a well-tolerated substance:
Acute Toxicity (Mice) Substance i.v. i.p. p.o.
_ Muscimol 7 12 22 Compound Ia,HBr80 145 ~320 --Thus, compound Ia is considerably less toxic than muscimol.
- ' ' ;~ :
Injections into Substantia Ni~ra in Rats.
a) Bilateral injections. 0.1, 0.5, and l.0/ug of Ia,HBr have been injected. The r~ts showed a pronounced stereo-typic behaviour.
; Ia was shown to be weaker than muscimol~ ~
i b) Unilateral injections. 0.1 and 0.5/ug of Ia,Hbr have been , 1.
r `i , ~ ' ' ':
.~ . .
injected. The rats showed a strong and prolonged contralateral turning.
Ia was found to be weaker than muscimolO
Pharmacoloqical Results in Mice.
a) Potentiation of methylphenidate-induced gnawing (Scheel-Kruger et al.: Muscimol differentially facilitates stereotypy but ant~-gonizes motilit~ induced by dopaminergic drugs. A complex GABA--DOPAMINE interaction. Life Sciences, 1978, Vol. 22, 75 - 84).
ED50 mg/kg (the dose which causes potentiation in 50~ of the animals) Muscimol,HBr 0.7 Compound Ia~HBr 3.0 bi Antagonism of morphine-induced motility (Christensen et al.:
Muscimol antagonizes morphine hypermo~ility without potentiation of analgesia. European J. PharmacolO, 1978, 48, 459 - 462).
MED mg/kg (minimum effective dose) Muscimol,HBr 0.6 Compound Ia,HBr 1Ø
c) Antagonism of isonia~ide induced convulsions (Modification (mice, two tlmes lower concentration of isoniazide) of Mao et al.:
Evidence for an involvement of GA~A in the mediation of cerebellar c-GMP decrease and the anticonvulsant action of diazepam.
~ Naunyn-Smiedeberg's ArchO Pharmacol. 1975, 289, 369 - 378).
; ~ MED mg/kg (minimum effective dose) Muscimol~HBr 0.6 ; Compound Ia,HBr 1.3.
,; , , ~
..
`
, . . . .
`:
.
~ 25;~
~ 11 -Conditions and procedure for isoniazide antayonism test:
Mice, male, 20 - 25 g.
Isoniazide 300 mg/kg s.c~
Macrolon cages type II.
The test compound is injected i.p. in the doses 0, 1/2, 1/8 and 1/32 of the determined "i.v. LD50". In case of insoluble sub-stances, the doses 0, 1/4, 1/16 and 1/64 of the determined "i.p.
LD50" are used. Five mice are used for each dose level. Immediate-ly after administration of test substance, isoniazide 300 mg/kg is injected s.c. This dose of isoniazide induces intermittent tonic clonic seizures within 60 minutes.
The calculations are performed as an "on line procedure" on the EDP-terminal. The results are recorded as % increase in time i until convulsions occur and in addition the least dose (MED) which shows significant effect (minimal effective dose, calculated by means of van der Waerden-test).
Conclusion:
Based on these experiments, compound Ia has been shown to be a potent GABA agonist. Compound Ia is weaker than muscimol but considerably less toxic.
The compounds of formula I may be prepared by ~ . .
a) subiecting a compound of the general formula V
O~
~ ~N V
N
Z ~ ' :
in which Z is hydrogen or an amino-protectin~ group readily re-~ `~ . ' ' ' ' ' . '.
.
j, .
'`' '' ~,'' ' " ' , ' ~ .
':
- '~' ' " ' ', ' ' ' .
' . ' ' ' . ' ' 2~
~ 12 -movable, e.g. by hydrolysis, suitably a group R" as defined above or a trityl or formyl group, and W is hydrogen or a group readily removable, e.g. by hydrolysis, to yleld the free hydroxy group, such as a lower alkyl group, aralkyl, tetrahydropyranyl, acetyl, arylsulfonyl, or lower alkoxycarbonyl, with the proviso that at least one of Z and W in formula V is different from hydrogen;
to removal of any group W different from hydrogen and any group Z
different from Ri' and, if desired, removal of any group Z which falls under the definition of R"; if desired, converting the compound of formula Ia if obtained as a salt thereof, into the zwittexion form thereof by treatment with a base or into another salt, and, if des-ired, converting the compound Ia, when obtained, into a compound I
in which R" is differe~t from hydrogen, by treatment with a reactive derivative of acetic acid or with an ester of the general formula whereln X' is a leaving group, and R5 is as defined above, or b) for the preparation of a compound of the general formula I
in which R" is different from hydrogen, subjecting a compound of the general formula IX"
NHOH
~ O IX"
R" -IV~T
in which R" is as defined above, except hydrogen, to hydrolysis and cyclization, and if desired, converting a resulting compound in which R" is different from hydrogen, into a salt thereof.
An example of a full synthesis of the compound Ia rom a known starting material appears ~rom the examples and rom the below Reaction Scheme I:
!
, ~
- 13 - ~Z5 REACTION SCHEME I:
, ~ ~ Pd-C ~2C03 "N O, HC 1 2 C 1- C
Cl H2 ~OCH3 ~3 0' 2H5 ~1~ c CH2-H ~ ~
. ~J;~:o 1's-OH, benzene C~ ~~~
(IVa) ICH (VIIIa) NHoH
(~H
NH20H ~/ ~ HC1 conc, N , ~ N J
KOH / ~' ~ or HC10 ~ ~~ ~ -O--C ~_~ 4Q=C
(IXa) ¦ (Va~
, .
OH o HBr-HOAc ~ W (C2H5) 3 N~ ~
, HlE3r H2 . ~-, ~, (Ial (Ia) salt t .
Ts-OH = p-to1uenesulonic acid ;; ``. . 1 . ' , - . ~ ;:
J
... : ' Compound IVa in reaction shceme I is a key ir,termediate in the above syn~hesis and in other synth~ses of the compounds of the pxesent invention. Similar key intermediates may cont~in other hydrolysable N-protecting groups and other lower alkyl groups, and hence, in its broad concept, this novel key intermediate of the present invention has the general formula IV
~Alk O IV
. ~\ ' ' '.
in which Alk is a lower alkyl group and Z is hydrogen or an amino-protecting group readily removable, e.g, by hydrolysis, suitably a group R" las defined above) or a trityl or formyl group. Hence, specific examples of Z are the following: hydrogen, methoxycar~onyl, etho~ycarbonyl, propyloxycarbonyl, tert.butyloxycarbonyl, ben~yloxycarbonyl, p chlorobenzyloxycarbonyl, trityl, formyl, acetyl. Other novel intermediates according to the present invention are the compounds of the formolae VIIIa and IXa in ;
reaction scheme I, and also the generic classes which they represent, which is, compounds of the general formula VIII' ~ VIIï ~ -Z-~b~. .
. . ~
in which Z is as defined above, T is a group convertible, by hydrolysis, into an oxo group, e.g., an acetal group such as ethylene dioxy, and Q is a leaving group which, on reaction with hydroxylamine, forms a hydroxamic acid group, examples of Q being halogen, especially chlorine and bromlne, hydroxy, the residue of an acid, the residue o~ an activated amide, the residue o~ an actl~ated ester, lower al~oxy, and the like, and compounds o~
- -- the general formula IX' 4 - ` ~
:, ., ~
' , I,UND-3~ C~N~D~
~IOM
O IX' ~ Z- ~ T
in which Z and T are as defined above, and also/ at the stage of compound Va (which is both a compound of the general formula I
and an intermediate for the preparation of compounds of the general formula I), an intermediate may be used which in generalized form has the formula V above.
~n interesting aspect of the present invention is the compound Ia as intermeaiate in the preparation of compounds of formula I
in which R" is different from hydrogen.
The present invention also relates to the total sequence of syn-thesis stages IV ~ VIII' ~ IX' -~ V -~ I and to the final stages thereof, i.e,, VIII' -~ IX' ~ V -~ I and IXI ~ V -~ I.
The conversion o ethyl 1-benzyl-3-oxQ-piperidine-~-carboxylate into the intermediate IV as exemplified by IVar is usually per-formed in lower alkanols, e.g. ethanol or ethanol/water. The removal of the N-benzyl group may be effected with gaseous hydrogen in tha presence of a hydrogenation catalyst, e.g.
platin~m, palladium or Raney nickel. The alkyl 3~oxo-4-carboxylate formed is dissolved, e.g. in water, and treated with an acid acceptor, e.g. alkalL carbonate, and an ester of chloro-formic acid, e.g. methyl chlorofoxmate~ The temperature is kept near 0C during the reaction. The compound IV is isolated by extraction into an organic solvent followed bv evaporation of the solvent.
The formation of the compound of formula VIII' as exemplified b~
' ' :
~! - 15 -. ~ - .
~,5~
the ethylene acetal VIIIa is usually performed in a solvent, e.g.
benzene, which forms an azeotropic rnixture with water~ The reac-tion is preferably carried out at reflux temperature and with a strong acid, e.g. a sulfonic acid as catalystO
The hydroxamic acid IX' as exemplified by IXa is synthesized by reacting VIIIa with hydroxylamine, preferably in wa-ter or a lower alcohol, e.g. methanol and usually at a temperature between -20C
- and room temperature, preferably at 0 - 10C. The ~ompound may be isolated and purified by a manner known ~ se, e.g. column chro-matography. When Q in formula VIII' is a halogen or the residue of an acid, the reaction is effected in the presence of a base. Alternatively, the piperidine carboxylic acid itself (VIII', Q=OH) may be reacted with hydroxylamine in the presence of a con-densing agent, e.g. dicyclohexyl carbodiimide or carbonyldiimida-zole. As solvent, an inert solvent, e.g. methylene chloride or chloroform can be used.
Tha hydrolysis of the acetal group of IXa or, quite generally, the conversion of T in compounds o formula IX' into an oxo group, followed by cyclization to a compound of formula V as exemplified by Va may be effected by an aqueous solution of a strong acid optionally also containing acetic acid, e.g. concentrated hydro-chloric acid or 70% perchloric acid at a temperature between 0C
and 100C, preferably at 50 - 80C. The compound V may be isolated by extraction with an organic solvent ox by evaporation of the water. The compound can be purified by column chromatography or by ~ crystallization.
Removal of the protecting group Z and/or W in compound V may he effected with a strong inorganic acid, eqg. hydrochloric or hydro-. bromic acid, in a solvent, e.g. glacial acetic acid or water, or a mixture of water and glacial acetic acid. The temperature may be kept between room temperature and the boilin~ point of the solvent.
The reaction time is usually short, e.g. less than 1 hour. The Xa salt may be isolated by evaporation of the solvent. The Ia salt ; may be transformed into Ia by treatmen* with a base, e.g. a tertiary - amine, in a solvent, usually a mixture o~ water and a lower alkanol.
' . ' ' ' . :- . . i ' : ' .. ' ~ :. - . `' ' ' ' .
.. ' :' ` "
, Compound Ia may be transormed into another salt as described above.
An interesting synthesis is illustrated in the below reaction scheme II in which a compound of the general formula I, as exem-plified by the compound Ia, is prepared:
.
REACTION SCHEME II:
1~
C ~ 1) NH20H, NaOH ~ N~O
~C / ~ / H3 (VIa) 1CH3 (IVa) /
`
OH ~9 N(C2H5~ ~f OCH3 (Va) (Ia) salt (Ia) `:"`1 ' ' ~.
.,..."
'' 1 .' '' ' ' . ' . ,~' "1 ' '' ~ . "
, .
' .. , ' . . . ' . ., , " .
., "' ~ ' .. ' ' '' ~ ' ~ ' . .
11'~52B8 The reaction of a compound of the general formula IV as exempli-fied by IVa with hydroxylamine may give a mixture of a compound of the general formula V and the corresponding isomeric compound V as exemplified by Va and VIa. The reaction may be effected at a temperature between -30~C and 50C, preferably between -30 and -10C. The solvent is usually water or a lower alkanol or mixtures thereof.
.
The process illustratéd in reaction scheme II, althouyh yielding a mixture of two isomers, is nevertheless advantageous. It is very time-saving in that it avoids the protection of the oxo group in compounds of the general formula IV and the subsequent hydroxamic acid formation. The compounds formed in the reaction of IV with hydroxylamine, as exemplified by Va and VIa, are easily separated by manners known ~ se, e.g. by column chromatography.
When it is desired to prepare compounds of the general formula I
in which R" is different from hydrogen, one may either omit the removal of the group Z if the group Z has the same identity as the desired group R", or one may introduce such group R" into the compound of the general formula Ia.
The introduction of the group R" may be performed by manners known E~ se. Thus, for example, when R" is a group of the above formula VII, the introduction may be performed by treatment of compound Ia with the appropriateO formic acid ester of the general formula X'-~-OR5 wherein X' is a leaving group, especially halogen, azido, etc., in the presence of an acid acceptor, for example an alkali carbonate. For example, the BOC-derivative can be made by means of tert.butyl azidoformate.
When R" is acetyl, a reactive derivative of acetic acid, e.g. acet-yl chloride or acetanhydride may be used for the introduction of the group R".
. ~
' .;
.
r ; ~ " ' , : ' , .
- ~ .
- : ' ' ~' ~' ' ' ' ' :' ' ~ ' ' 52~3 ~ 19 -- .
The compounds of the formula I, and salts thereof may be formulated for administration in any convenient way by analogy with other pharmaceuticals.
Thus, the composition comprising the compounds of the invention may be in th~ form of pharmaceutical preparations, e.g. in solid, semisolid or liquid form, which contain the active compound of the invention in admixture with a pharmaceutical organic or in-organic carrier or excipient suitable for enteral or parenteral application. The active ingredient may, e.g., be formulated with the usual carriers for tablets, pellets, capsules, suppositories, solutions, emulsions, aqueous suspensions and other suitable administration formsO Examples of carriers are glucose, lactose, gum acacia, gelatin, mannitol, starch paste, magnesium trisilicate, talc, corn starch, keratin, colloidal silica, potato starch, urea, and other carriers suitable for use in manufacturing compositions in solid, semisolid, or liquid form, and in addition auxiliary, stabilizing, thickening, colouring, flavouring, and preservative agents can be contained in the composition of this invention.
The active compound is included in the compositions of the inven-tion in an amount sufficient to produce the desired therapeutical effect upon administration. The dosage or therapeutically effective quantity of the compound varies and also depends upon the age and condition of each individual patient beiny treated.
A preferred tablet or capsule formulation for oral administration contains 0.1 - 200 mg, preferably 1 - 100, especially 5 - 50, mg of a compound of the formula I or a salt thereof per unit dosage which may be administeret 1 - 4 times per day or as a sustained release composition.
Injection preparations preferably contain 0.1 ~ 200 mg, preferably 1 - 100, especially S - 50, mg of a compound of the formula I
or a salt thereof per unit dosage. A preerred in~ected dose is about 0.5 to Z ml.
D ,~
' ,, ,' ' ' . ' ' . ` ~ ' ' . . ' . ' ' .
' '.
. . . ' ' ~ , .
s~
The invention also relates to the use of the compounds o~ the general formula I and salts thereo~ in medicaments for treating GABA system malfunction-related diseases, and a process of treating GABA system malfunction-related diseases in human beings by administering, to the human being, an effective dose o a compound of the general formula I, o~ a salt thereof.
In the above-mentioned compositions and the above-mentioned uses, it may be suitable or preferred to combine the compounds of the general formula I or a salt thereof with minor tranquillizers such as benzodiazepines or neuroleptics, for example butyrophenones such as haloperidol, phenothiazines such as chloropromazine, thioxanthene, and the like. In such combinations, compositions and combined usages, the neuroleptics are suitably administered in their effective amounts or, in a preferred embodiment in lower amounts than the amounts in which they would be effective when used alone.
The invention is further illustrated by the below working examples.
All compounds prepared according to the working examples have been subjected to elemental analysis for C, H, N and halogen, when present, and all agreed within + 0~3% with the calculated values.
Example 1. (Reaction scheme I).
a) Ethyl l-methoxycarbonyl-3-oxopiperidine-4-carboxylate (IVa).
A solution of ethyl l-benzyl-3-oxopiperidine-4-carboxylate (Iselin, B.M. and Hoffmann, K., Helv.Chim. Acta~ 1954, 37, 178) ~14.0 g; 47 mmol) in aqueous ethanol (300 ml; 50%) was , , ~ 21 ~
.
hydrogenated (ca. 300 kPa) in a PARR hydro~enation apparatus by using a 10% Pd C catalyst (1.4 g). The reaction mixture was filtered and evapora~ed to dryness in vacuo. To an ice cooled solution of the residue in water (50 ml) was added with stirring an iced solution of potassium carbonate (19.4 g; 140 mmol) in water (20 ml) followed by addition of methyl chloroformate (11.3 g; 120 mmol). Stirring was continued at 0C for 30 minutes and at 25C for 30 minutes. The mixture was extracted with three 100 ml portions of ether. The combined and dried (Na2SO4) ether phases were evaporated Ln vacuo to give 10.0 g of crude product. Ball--tube distillation at 40-- 130 Pa (oven temperature 170C) gave IVa (9.0 g; 84~) as a colourless oil, which slowly crystallized, m.p. 36--38 C. IR (film): 2980--2850 (several bands, m-s), 1700 (s), 1655 (s), 1620 (m) cm 1. lEI ~IMR (CC14): ~ 12.3 (1 H, s), 4.13 (q, J 7 Hz) and 4.0--3.9 (m) (a total of 4 H), 3,62 (3 H, s), 3,43 (2 H, t, J 6 Hz), 2.4--2.1 (2 H, m), 1.30 (3 H, t, J 7 Hz).
b) Ethyl 1-methoxycarbonyl-3-oxopiperidine-4-carbox~late i ethylene acetal (VIIIa).
A mixture of ethyl 1-methoxycarbonyl-3-oxopiperidine-4-carboxy-late (9.0 g; 39 mmol), ethylene glycol (100 ml), 4-toluenesulfo-nic acid (0.7 g), and benzene (500 ml) was refluxed for 6 days using a Dean-Stark water separator. The mixture was washed with aaueous sodium carbonate (300 ml; 1 M), wa~er (300 ml), and saturated aqueous sodium chloride (300 ml). The organic phase was dried (K2CO3) and evaporated in vacuo to give 8.6 g of an oil . CC [silica gel (Woelm 0.063--0.1 mm): 350 g; eluents:
methylene chloride to which ethyl acetate (20--35~) was added]
followed by ball-tube distillation at 40 Pa (oven temperature 170C) gave VIIIa (7.0 g; 65~) as a colourless oil. IR (film):
~970 (s), 2900 ~s), 1730 (s) cm 1. lH NMR (CC14~: ~ 4.05 (q, J 7 Hz) and 3.92 (s) (a total of 6 H), 3.60 (s) and 3.7--3.0 ~ (m) (a total of 7 H), 2.8--2.5 (1 H, t), 2.2--1.6 (2 H, m), 1.23 - ~3 H, t, J 7 ~Iz~. ~
- 1.
- .
5'~
c) l-Methoxycarbonyl-3-oxopiperidine-4-carbohydroxamic acid ethylene acetal (IXa).
To a stirred and iced solution of potassium hydroxide (7.3 g;
130 mmol) in methanol (30 ml) was added hydroxylammonium chloride (6.9 g; 100 mmol). After stirring at 0C for further 30 minutes a solution of ethyl 1-methoxycarbonyl-3-oxopiperidine-4-carboxy-late eth~lene acetal (6.8 g; 25 mmol) in methanol (20 ml) was added, and the mixture was left at 8C for 8 days. Upon addition of glacial acetic acid (15 ml) and filtration the filtrate was evaporated in vacuo to give a treacly mass. CC [silica gel (Woelm 0.063--0.1 mm): 250 g; eluents: ethyl acetate to which methanol (15--26%) and formic acid (1%) was added] af~orded IXa tl.9 g; 29%) as a crystalline and TLC-pure substance [~ : 0.23;
eluent: ethyl acetate-methanol-formic acid (90 9:1)]. An analyti-cal sample was recrystallized (ethanol-benzene) to give IXa as -colourless crystals, m.p. 150.0--152.0C. IR (KBr): 3700--3350 (m), 3280 (m), 3210 (s), 3055 (w), 3000--2870 (several bands, w-m), 1690 (s), 1640 (s), 1550 (w) cm 1. lH NMR [CDC13-DMSO-d6 (1~
~ 10.5--10.1 (1 ~, m), 4.9- 4.3 (1 H, m), 3O93 (s)/ 3.60 (s), and 4.1--3.1 (m) (a:total of 11 H), 2.~--2.6 (1 H, m), 2,2--1.8 (2 H, m).
d) Methyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c~pyridine-6--carboxylate (Va).
A solution of l-methoxycarbonyl-3-oxopiperidine-4-carbohydroxamic acid ethylene acetal (750 mg; 2.9 mmol) in concentrated hydrochloric acid (13 ml) was heated to 70C for 10 minutes. The mixture was evaporated in vacuo to give a black oil. CC [silica gel (Woelm 0.063--0.1 mm): 60 g; eluents: benzene to which ethyl acetate (40--70%) and formic acid (1~) was added] gave crystalline and TLC-pure Va (244 mg; 43%) [RF 0.27; eluent: benzene ethyl acetate-formic acid (50:50:1)]. An analytical sample was recrys~allized (benzene--cyclohexane) to give pure Va as colourless crystals, m.p. 136.0--138.0C. IR (XBr)~ 3700--3300 (m), 3300--2S00 (several bands, w-m), 1655 (s), 1525 (m), 1490 (s) cm 1~
UV [methannl (log ~)]: 212 (3~64) nmc H NMR (CDC13): ~ 10.6 (1 ~, I .
, ' ~' .' ' ' ` ~
- 23 ~
s), 4.43 ~2 H, s), 3.70 (s) and 3.8-~3.5 (t) (a total of 5 H), 2.6--2.3 (2 H, t)~
e) 3-~!ydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridinium bromide (Ia (salt)).
A solution of methyl 3~hydroxy-4,5,6,7-tetrahydroisoxazolo~5,4-c]-pyridine-6-carboxylate (309 mg; 1.6 mmol) in a solution of hydro-gen bromide in glacial acetic acid (3 ml; 43~) was refluxed for 15 minutes. Upon evaporation to dryness ln vacuo the residue was treated with the same reagent (3 ml) for further 15 minutes.
Evaporation of the reaction mixture to dryness in vacuo and re-crystalli3ation (methanol-ether) of the residue gave Ia (salt) (193 mg; 56%) as faintly reddish crystals, m~p. 162--163C (de-comp.). IR (KBr): 3700--3300 (m), 3070 (s), 3000-2300 (several bands, m-s), 1670 (m), 1580 (m), 1525 (s), 1505 (w) cm 1 UV (methanol): <210 nm. H NMR [D2O (sodium 3-(trimethylsilyl)-propanesulfonate was used as an internal standard)]: ~4.77 (ca.
5 H, s), 4.43 (2 H, t, J 1 Hz), 3.7--3.4 (2 H, q, J 6 and 7 Hz), 3.0--2.7 (2 H, t).
~ .
f) 4,5,6,7-Tetrahvdroisoxazolo[5,4-c]pyridin-3-ol zwitterion (Ia). !
i To a solution of 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyri dinium bromide (77 mg; 0.35 mmol) in water (0.6 ml) was added a solution of triethylamine (39 mg; 0.39 mmol) in ethanol (0.6 ml).
The mixture was left at 25C for 2 hours. Ia (42 mg; 86%) was isolated as colourless crystals, m~p. 242--244C (decomp.). IR
(XBr). 3700--2900 (s), 2900--1900 (several bands, m-s), 1670 (s), 1625 (m) cm 1. UV [methanol (log ~)]: 212 ~3.64) nm. pKA values ~H O, 25C~: 4.44 - 0.03, 8.48 - 0.04 ,.
Example 2. (Reaction scheme II~. ~
.
isoxazolo[5,4-c]pyridine-6--carboxylate (Va) and methyl 1,4,5,6 ,?, 7a~hexahydro-1-oxoisoza-zolol3,4-cl~yridine-5-carboxylnte (VIa).
;
,. - , ~
llZ5288 ~TJND-34 CANADA
To an iced solution of sodium hydroxide (9.6 g; 0.24 mol) and hydroxylammonium chloride (8.39 g; 0.12 mol) in water ~100 ml) was added wi~h stirring ethyl l-methoxycarbonyl-3-oxopiperidine-4-carboxylate (22.9 g; 0.1 mol). Upon standing at 5~C for 5 hours the solution was evaporated to dryness ln vacuo. The residue was dlssolved in concentrated hydrochloric acid (75 ml) and heated to 70C for 10 minutes. The mixture was evaporated in vacuo to the formation of a black residue, which was extracted with three 100 ml portions of chloroform. The co~bined chloroform phases were dried (Na~SO43 and evaporated in vacuo to the formation of a black semisolid residue. TLC ('silica gel F254), eluent:
benzene-ethyl acetate-formic acid (25:25:1)) showed the presence of two compounds with RF values 0.31 and 0.16 corresponding to Va and VIa, respectively. Column chromatography (silica gel: 300 g;
eluent: benzene-ethyl acetate-formic acid (30:20:1)) lead to Va and VIa.
Example 3.
Methyl 3-hydroxy-4,5,6,7-tetrahydrot5,4-c]pyridine-6-carboyxlate (Va) (Reaction Scheme I).
A solution o~ the hydroxamic acid (IXa) (10 g) i~ perchloric acid (70~; 35 ml) was heated to 60C for 30 minutes. Upon cooling, NaOH (40 ml; 28%) was added with stirring and cooling. The mixture was extracted with three 50 ml portions of chloroform.
The combined and dried ~MgSO4) chloroform phases were ~iltered `and evaporated to dryness in vacuo to form a residue which was di5solved in ethyl acetate t50 ml). Upon standing and cooling, Va was isolated as crystals (6.3 g; 82~). Isolation and washing twice with 30 ml portions o~ ethyl aceta~e yielded crystalline ~` Va, m.p. 139-141C.
Instead of heating to 60C ~ar 30 minutes, the same result may be aahieved on standing at amblent température ~or 16 hours.
.
. . .
' ' .
.
, sz~
~ - 25 -~ f 4,5~6,7-Tetrah~droisoxazolo[5,4-c]pyridlne-3-ol zwitterion (Ia).
A solution of methyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]-pyridine-6-carboxylate (Va) (37 g) in hydrogen bromide in glacial acetic acid (33% HBr, 250 ml) was left for 16 hours at ambient temperature. Evaporation to dryness ln vacuo gave the HBr salt of Ia as a yellowish crystalline material, which was dissolved in a mixture of water (100 ml) and ethanol (200 ml). Triethyl-amine was added until pH 6.5, which caused ~a zwitterion to crystallize. Upon standing for 3 hours at 5C and filtration, the precipitate was washed on the filter with a mixture of water (25 ml) and ethanol (50 ml) to give the zwitterion (26 g;
95%) as a white crystalline material, m.p. 242 - 244C (decomp.)~
. `
.. .. .
`' - ~ .
.
-- 7 ~
.
tert.butyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine~
-6-carboxylate, phenyl 3~hydroxy~4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-6--carboxylate, 4-chlorophenyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyri-dine-6-carboxylate, 4-methoxyphenyl 3-hydroxy-4,5,6,7-tetra~ydroiso~azolo[5,4~c]pyri-dine-6-carboxylate, benzyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-6--carboxylate, .
and salts thereof with bases.
Examples of salts of the compound of the formula Ia are acid addition salts thereof, such as ~harmaceutic-ally acceptable salts with inorganic acids, e.g. hydrochloric, hydrobromic, nitric, sulfuric, phosphoric acids and the like, or with organic acids, such as organic carboxylic acids, e.g. acetic, propionic, glycolic, malonic, succinic, maleic, fumaric, malic, tartaric, citric, glucuronic, benzoic, pamoic acid and the like, or organic sulfonic acids, e.g. methane sulfonic, ethane sulfonic, ben ene sulfonic, toluene sulfonic acid and the like, which salts may be prepared by procedures known ~ se, e.g. by adding the acid in question to the base, preferably in a solvent.
Compounds of formula I may form pharmaceutically acceptable salts with bases, such as metal salts, e.g. sodium, potassium, calcium or aluminium salts, and ammonium and substituted ammonium salts, e.g. salts of amines such as triethylaminet triethanolamine, ethylpiperidine, procaine, dibenzylamine and the like.
TEST RESULTS.
AffinitY Binding Experiments.
In order to study the interactions o~ the compound Ia with the ~entral GABA receptors in vitro, the compound Ia was tested in affinity binding experiments. The af~inity binding (sodium-inde-.. i .
~ ` , i ~"
., . . I`
. . ~ . -, .
.
...
-. ' .~ .
r ~ 8 --pendent bindin~) of GABA to membranes isolated from rat brains was studied as described by Enna, S.J. and Snyder, S.H., Brain Res., 1975, 100, 81 - 97~ IC50 values, inhibitor concentrations causing 50% inhibition of ~,AB~ binding were determined.
.
Inhibitor IC50 value Ia 0.13 - 0.005/uM
Muscimol 0.024 - O.003/uM
X) In earlier studies 2.6 - 0.6/uM was found~ The value stated (0.13 - 0.005/uM)is based on studies of 5 different concentrations of Ia, each dete~mined in triplicate, and the stated IC50 value is calculated by log probit analysis. The difference between the two TC50 values determined for Ia is the result of the development of an improved technique for the preparation of rat brain membranes.
~` ~
Microelectrophoretic Experiments.
.
In order to study the interactions o the compound Ia with the central GABA receptors in vivo, the compound Ia was tested in microelectrophoretic experiments. Experiments were performed on lumbar dorsal horn interneurones and Renshaw cells of cats an- ;
aesthetized with pentobar~itone sodium. The approximate potency of the depressant actions`of the compound was assessed relative to that of GABA on the basis of electrophoretic currents re-quired to produce equal and submaximal inhibitions of the firing o the central neurones. The inhibitory action of Ia on central neurones was antagonized by the specific GABA antagonist bicu-culline methochloride (BMC).
.
Potency relative Reversible anta-Compound to that af GABA gonism b BMC _ .
~A~A ~ ~ ~ yes `
Ia + ~ ~ + yes . ' . .
The compound Ia did not interact with the GABA u~take system at ~ . . .
, '' . ~
`
~- 9 - ' concentrations of 5 x 104 M, and it did not interact wikh the GABA metabolizing enzymes GABA:2-oxo-~lutarate aminotranserase and L-~lutamate l-carboxylase at concentrations of 10 3 M.
Based on the above-mentioned experiments~ the compound Ia is a specific and very potent GABA agonist.
Compound Ia has been compared with muscimol, the most potent GABA
agonist so far known, in a series of pharmacological experiments:
Toxicity.
Compound Ia has been shown to be a well-tolerated substance:
Acute Toxicity (Mice) Substance i.v. i.p. p.o.
_ Muscimol 7 12 22 Compound Ia,HBr80 145 ~320 --Thus, compound Ia is considerably less toxic than muscimol.
- ' ' ;~ :
Injections into Substantia Ni~ra in Rats.
a) Bilateral injections. 0.1, 0.5, and l.0/ug of Ia,HBr have been injected. The r~ts showed a pronounced stereo-typic behaviour.
; Ia was shown to be weaker than muscimol~ ~
i b) Unilateral injections. 0.1 and 0.5/ug of Ia,Hbr have been , 1.
r `i , ~ ' ' ':
.~ . .
injected. The rats showed a strong and prolonged contralateral turning.
Ia was found to be weaker than muscimolO
Pharmacoloqical Results in Mice.
a) Potentiation of methylphenidate-induced gnawing (Scheel-Kruger et al.: Muscimol differentially facilitates stereotypy but ant~-gonizes motilit~ induced by dopaminergic drugs. A complex GABA--DOPAMINE interaction. Life Sciences, 1978, Vol. 22, 75 - 84).
ED50 mg/kg (the dose which causes potentiation in 50~ of the animals) Muscimol,HBr 0.7 Compound Ia~HBr 3.0 bi Antagonism of morphine-induced motility (Christensen et al.:
Muscimol antagonizes morphine hypermo~ility without potentiation of analgesia. European J. PharmacolO, 1978, 48, 459 - 462).
MED mg/kg (minimum effective dose) Muscimol,HBr 0.6 Compound Ia,HBr 1Ø
c) Antagonism of isonia~ide induced convulsions (Modification (mice, two tlmes lower concentration of isoniazide) of Mao et al.:
Evidence for an involvement of GA~A in the mediation of cerebellar c-GMP decrease and the anticonvulsant action of diazepam.
~ Naunyn-Smiedeberg's ArchO Pharmacol. 1975, 289, 369 - 378).
; ~ MED mg/kg (minimum effective dose) Muscimol~HBr 0.6 ; Compound Ia,HBr 1.3.
,; , , ~
..
`
, . . . .
`:
.
~ 25;~
~ 11 -Conditions and procedure for isoniazide antayonism test:
Mice, male, 20 - 25 g.
Isoniazide 300 mg/kg s.c~
Macrolon cages type II.
The test compound is injected i.p. in the doses 0, 1/2, 1/8 and 1/32 of the determined "i.v. LD50". In case of insoluble sub-stances, the doses 0, 1/4, 1/16 and 1/64 of the determined "i.p.
LD50" are used. Five mice are used for each dose level. Immediate-ly after administration of test substance, isoniazide 300 mg/kg is injected s.c. This dose of isoniazide induces intermittent tonic clonic seizures within 60 minutes.
The calculations are performed as an "on line procedure" on the EDP-terminal. The results are recorded as % increase in time i until convulsions occur and in addition the least dose (MED) which shows significant effect (minimal effective dose, calculated by means of van der Waerden-test).
Conclusion:
Based on these experiments, compound Ia has been shown to be a potent GABA agonist. Compound Ia is weaker than muscimol but considerably less toxic.
The compounds of formula I may be prepared by ~ . .
a) subiecting a compound of the general formula V
O~
~ ~N V
N
Z ~ ' :
in which Z is hydrogen or an amino-protectin~ group readily re-~ `~ . ' ' ' ' ' . '.
.
j, .
'`' '' ~,'' ' " ' , ' ~ .
':
- '~' ' " ' ', ' ' ' .
' . ' ' ' . ' ' 2~
~ 12 -movable, e.g. by hydrolysis, suitably a group R" as defined above or a trityl or formyl group, and W is hydrogen or a group readily removable, e.g. by hydrolysis, to yleld the free hydroxy group, such as a lower alkyl group, aralkyl, tetrahydropyranyl, acetyl, arylsulfonyl, or lower alkoxycarbonyl, with the proviso that at least one of Z and W in formula V is different from hydrogen;
to removal of any group W different from hydrogen and any group Z
different from Ri' and, if desired, removal of any group Z which falls under the definition of R"; if desired, converting the compound of formula Ia if obtained as a salt thereof, into the zwittexion form thereof by treatment with a base or into another salt, and, if des-ired, converting the compound Ia, when obtained, into a compound I
in which R" is differe~t from hydrogen, by treatment with a reactive derivative of acetic acid or with an ester of the general formula whereln X' is a leaving group, and R5 is as defined above, or b) for the preparation of a compound of the general formula I
in which R" is different from hydrogen, subjecting a compound of the general formula IX"
NHOH
~ O IX"
R" -IV~T
in which R" is as defined above, except hydrogen, to hydrolysis and cyclization, and if desired, converting a resulting compound in which R" is different from hydrogen, into a salt thereof.
An example of a full synthesis of the compound Ia rom a known starting material appears ~rom the examples and rom the below Reaction Scheme I:
!
, ~
- 13 - ~Z5 REACTION SCHEME I:
, ~ ~ Pd-C ~2C03 "N O, HC 1 2 C 1- C
Cl H2 ~OCH3 ~3 0' 2H5 ~1~ c CH2-H ~ ~
. ~J;~:o 1's-OH, benzene C~ ~~~
(IVa) ICH (VIIIa) NHoH
(~H
NH20H ~/ ~ HC1 conc, N , ~ N J
KOH / ~' ~ or HC10 ~ ~~ ~ -O--C ~_~ 4Q=C
(IXa) ¦ (Va~
, .
OH o HBr-HOAc ~ W (C2H5) 3 N~ ~
, HlE3r H2 . ~-, ~, (Ial (Ia) salt t .
Ts-OH = p-to1uenesulonic acid ;; ``. . 1 . ' , - . ~ ;:
J
... : ' Compound IVa in reaction shceme I is a key ir,termediate in the above syn~hesis and in other synth~ses of the compounds of the pxesent invention. Similar key intermediates may cont~in other hydrolysable N-protecting groups and other lower alkyl groups, and hence, in its broad concept, this novel key intermediate of the present invention has the general formula IV
~Alk O IV
. ~\ ' ' '.
in which Alk is a lower alkyl group and Z is hydrogen or an amino-protecting group readily removable, e.g, by hydrolysis, suitably a group R" las defined above) or a trityl or formyl group. Hence, specific examples of Z are the following: hydrogen, methoxycar~onyl, etho~ycarbonyl, propyloxycarbonyl, tert.butyloxycarbonyl, ben~yloxycarbonyl, p chlorobenzyloxycarbonyl, trityl, formyl, acetyl. Other novel intermediates according to the present invention are the compounds of the formolae VIIIa and IXa in ;
reaction scheme I, and also the generic classes which they represent, which is, compounds of the general formula VIII' ~ VIIï ~ -Z-~b~. .
. . ~
in which Z is as defined above, T is a group convertible, by hydrolysis, into an oxo group, e.g., an acetal group such as ethylene dioxy, and Q is a leaving group which, on reaction with hydroxylamine, forms a hydroxamic acid group, examples of Q being halogen, especially chlorine and bromlne, hydroxy, the residue of an acid, the residue o~ an activated amide, the residue o~ an actl~ated ester, lower al~oxy, and the like, and compounds o~
- -- the general formula IX' 4 - ` ~
:, ., ~
' , I,UND-3~ C~N~D~
~IOM
O IX' ~ Z- ~ T
in which Z and T are as defined above, and also/ at the stage of compound Va (which is both a compound of the general formula I
and an intermediate for the preparation of compounds of the general formula I), an intermediate may be used which in generalized form has the formula V above.
~n interesting aspect of the present invention is the compound Ia as intermeaiate in the preparation of compounds of formula I
in which R" is different from hydrogen.
The present invention also relates to the total sequence of syn-thesis stages IV ~ VIII' ~ IX' -~ V -~ I and to the final stages thereof, i.e,, VIII' -~ IX' ~ V -~ I and IXI ~ V -~ I.
The conversion o ethyl 1-benzyl-3-oxQ-piperidine-~-carboxylate into the intermediate IV as exemplified by IVar is usually per-formed in lower alkanols, e.g. ethanol or ethanol/water. The removal of the N-benzyl group may be effected with gaseous hydrogen in tha presence of a hydrogenation catalyst, e.g.
platin~m, palladium or Raney nickel. The alkyl 3~oxo-4-carboxylate formed is dissolved, e.g. in water, and treated with an acid acceptor, e.g. alkalL carbonate, and an ester of chloro-formic acid, e.g. methyl chlorofoxmate~ The temperature is kept near 0C during the reaction. The compound IV is isolated by extraction into an organic solvent followed bv evaporation of the solvent.
The formation of the compound of formula VIII' as exemplified b~
' ' :
~! - 15 -. ~ - .
~,5~
the ethylene acetal VIIIa is usually performed in a solvent, e.g.
benzene, which forms an azeotropic rnixture with water~ The reac-tion is preferably carried out at reflux temperature and with a strong acid, e.g. a sulfonic acid as catalystO
The hydroxamic acid IX' as exemplified by IXa is synthesized by reacting VIIIa with hydroxylamine, preferably in wa-ter or a lower alcohol, e.g. methanol and usually at a temperature between -20C
- and room temperature, preferably at 0 - 10C. The ~ompound may be isolated and purified by a manner known ~ se, e.g. column chro-matography. When Q in formula VIII' is a halogen or the residue of an acid, the reaction is effected in the presence of a base. Alternatively, the piperidine carboxylic acid itself (VIII', Q=OH) may be reacted with hydroxylamine in the presence of a con-densing agent, e.g. dicyclohexyl carbodiimide or carbonyldiimida-zole. As solvent, an inert solvent, e.g. methylene chloride or chloroform can be used.
Tha hydrolysis of the acetal group of IXa or, quite generally, the conversion of T in compounds o formula IX' into an oxo group, followed by cyclization to a compound of formula V as exemplified by Va may be effected by an aqueous solution of a strong acid optionally also containing acetic acid, e.g. concentrated hydro-chloric acid or 70% perchloric acid at a temperature between 0C
and 100C, preferably at 50 - 80C. The compound V may be isolated by extraction with an organic solvent ox by evaporation of the water. The compound can be purified by column chromatography or by ~ crystallization.
Removal of the protecting group Z and/or W in compound V may he effected with a strong inorganic acid, eqg. hydrochloric or hydro-. bromic acid, in a solvent, e.g. glacial acetic acid or water, or a mixture of water and glacial acetic acid. The temperature may be kept between room temperature and the boilin~ point of the solvent.
The reaction time is usually short, e.g. less than 1 hour. The Xa salt may be isolated by evaporation of the solvent. The Ia salt ; may be transformed into Ia by treatmen* with a base, e.g. a tertiary - amine, in a solvent, usually a mixture o~ water and a lower alkanol.
' . ' ' ' . :- . . i ' : ' .. ' ~ :. - . `' ' ' ' .
.. ' :' ` "
, Compound Ia may be transormed into another salt as described above.
An interesting synthesis is illustrated in the below reaction scheme II in which a compound of the general formula I, as exem-plified by the compound Ia, is prepared:
.
REACTION SCHEME II:
1~
C ~ 1) NH20H, NaOH ~ N~O
~C / ~ / H3 (VIa) 1CH3 (IVa) /
`
OH ~9 N(C2H5~ ~f OCH3 (Va) (Ia) salt (Ia) `:"`1 ' ' ~.
.,..."
'' 1 .' '' ' ' . ' . ,~' "1 ' '' ~ . "
, .
' .. , ' . . . ' . ., , " .
., "' ~ ' .. ' ' '' ~ ' ~ ' . .
11'~52B8 The reaction of a compound of the general formula IV as exempli-fied by IVa with hydroxylamine may give a mixture of a compound of the general formula V and the corresponding isomeric compound V as exemplified by Va and VIa. The reaction may be effected at a temperature between -30~C and 50C, preferably between -30 and -10C. The solvent is usually water or a lower alkanol or mixtures thereof.
.
The process illustratéd in reaction scheme II, althouyh yielding a mixture of two isomers, is nevertheless advantageous. It is very time-saving in that it avoids the protection of the oxo group in compounds of the general formula IV and the subsequent hydroxamic acid formation. The compounds formed in the reaction of IV with hydroxylamine, as exemplified by Va and VIa, are easily separated by manners known ~ se, e.g. by column chromatography.
When it is desired to prepare compounds of the general formula I
in which R" is different from hydrogen, one may either omit the removal of the group Z if the group Z has the same identity as the desired group R", or one may introduce such group R" into the compound of the general formula Ia.
The introduction of the group R" may be performed by manners known E~ se. Thus, for example, when R" is a group of the above formula VII, the introduction may be performed by treatment of compound Ia with the appropriateO formic acid ester of the general formula X'-~-OR5 wherein X' is a leaving group, especially halogen, azido, etc., in the presence of an acid acceptor, for example an alkali carbonate. For example, the BOC-derivative can be made by means of tert.butyl azidoformate.
When R" is acetyl, a reactive derivative of acetic acid, e.g. acet-yl chloride or acetanhydride may be used for the introduction of the group R".
. ~
' .;
.
r ; ~ " ' , : ' , .
- ~ .
- : ' ' ~' ~' ' ' ' ' :' ' ~ ' ' 52~3 ~ 19 -- .
The compounds of the formula I, and salts thereof may be formulated for administration in any convenient way by analogy with other pharmaceuticals.
Thus, the composition comprising the compounds of the invention may be in th~ form of pharmaceutical preparations, e.g. in solid, semisolid or liquid form, which contain the active compound of the invention in admixture with a pharmaceutical organic or in-organic carrier or excipient suitable for enteral or parenteral application. The active ingredient may, e.g., be formulated with the usual carriers for tablets, pellets, capsules, suppositories, solutions, emulsions, aqueous suspensions and other suitable administration formsO Examples of carriers are glucose, lactose, gum acacia, gelatin, mannitol, starch paste, magnesium trisilicate, talc, corn starch, keratin, colloidal silica, potato starch, urea, and other carriers suitable for use in manufacturing compositions in solid, semisolid, or liquid form, and in addition auxiliary, stabilizing, thickening, colouring, flavouring, and preservative agents can be contained in the composition of this invention.
The active compound is included in the compositions of the inven-tion in an amount sufficient to produce the desired therapeutical effect upon administration. The dosage or therapeutically effective quantity of the compound varies and also depends upon the age and condition of each individual patient beiny treated.
A preferred tablet or capsule formulation for oral administration contains 0.1 - 200 mg, preferably 1 - 100, especially 5 - 50, mg of a compound of the formula I or a salt thereof per unit dosage which may be administeret 1 - 4 times per day or as a sustained release composition.
Injection preparations preferably contain 0.1 ~ 200 mg, preferably 1 - 100, especially S - 50, mg of a compound of the formula I
or a salt thereof per unit dosage. A preerred in~ected dose is about 0.5 to Z ml.
D ,~
' ,, ,' ' ' . ' ' . ` ~ ' ' . . ' . ' ' .
' '.
. . . ' ' ~ , .
s~
The invention also relates to the use of the compounds o~ the general formula I and salts thereo~ in medicaments for treating GABA system malfunction-related diseases, and a process of treating GABA system malfunction-related diseases in human beings by administering, to the human being, an effective dose o a compound of the general formula I, o~ a salt thereof.
In the above-mentioned compositions and the above-mentioned uses, it may be suitable or preferred to combine the compounds of the general formula I or a salt thereof with minor tranquillizers such as benzodiazepines or neuroleptics, for example butyrophenones such as haloperidol, phenothiazines such as chloropromazine, thioxanthene, and the like. In such combinations, compositions and combined usages, the neuroleptics are suitably administered in their effective amounts or, in a preferred embodiment in lower amounts than the amounts in which they would be effective when used alone.
The invention is further illustrated by the below working examples.
All compounds prepared according to the working examples have been subjected to elemental analysis for C, H, N and halogen, when present, and all agreed within + 0~3% with the calculated values.
Example 1. (Reaction scheme I).
a) Ethyl l-methoxycarbonyl-3-oxopiperidine-4-carboxylate (IVa).
A solution of ethyl l-benzyl-3-oxopiperidine-4-carboxylate (Iselin, B.M. and Hoffmann, K., Helv.Chim. Acta~ 1954, 37, 178) ~14.0 g; 47 mmol) in aqueous ethanol (300 ml; 50%) was , , ~ 21 ~
.
hydrogenated (ca. 300 kPa) in a PARR hydro~enation apparatus by using a 10% Pd C catalyst (1.4 g). The reaction mixture was filtered and evapora~ed to dryness in vacuo. To an ice cooled solution of the residue in water (50 ml) was added with stirring an iced solution of potassium carbonate (19.4 g; 140 mmol) in water (20 ml) followed by addition of methyl chloroformate (11.3 g; 120 mmol). Stirring was continued at 0C for 30 minutes and at 25C for 30 minutes. The mixture was extracted with three 100 ml portions of ether. The combined and dried (Na2SO4) ether phases were evaporated Ln vacuo to give 10.0 g of crude product. Ball--tube distillation at 40-- 130 Pa (oven temperature 170C) gave IVa (9.0 g; 84~) as a colourless oil, which slowly crystallized, m.p. 36--38 C. IR (film): 2980--2850 (several bands, m-s), 1700 (s), 1655 (s), 1620 (m) cm 1. lEI ~IMR (CC14): ~ 12.3 (1 H, s), 4.13 (q, J 7 Hz) and 4.0--3.9 (m) (a total of 4 H), 3,62 (3 H, s), 3,43 (2 H, t, J 6 Hz), 2.4--2.1 (2 H, m), 1.30 (3 H, t, J 7 Hz).
b) Ethyl 1-methoxycarbonyl-3-oxopiperidine-4-carbox~late i ethylene acetal (VIIIa).
A mixture of ethyl 1-methoxycarbonyl-3-oxopiperidine-4-carboxy-late (9.0 g; 39 mmol), ethylene glycol (100 ml), 4-toluenesulfo-nic acid (0.7 g), and benzene (500 ml) was refluxed for 6 days using a Dean-Stark water separator. The mixture was washed with aaueous sodium carbonate (300 ml; 1 M), wa~er (300 ml), and saturated aqueous sodium chloride (300 ml). The organic phase was dried (K2CO3) and evaporated in vacuo to give 8.6 g of an oil . CC [silica gel (Woelm 0.063--0.1 mm): 350 g; eluents:
methylene chloride to which ethyl acetate (20--35~) was added]
followed by ball-tube distillation at 40 Pa (oven temperature 170C) gave VIIIa (7.0 g; 65~) as a colourless oil. IR (film):
~970 (s), 2900 ~s), 1730 (s) cm 1. lH NMR (CC14~: ~ 4.05 (q, J 7 Hz) and 3.92 (s) (a total of 6 H), 3.60 (s) and 3.7--3.0 ~ (m) (a total of 7 H), 2.8--2.5 (1 H, t), 2.2--1.6 (2 H, m), 1.23 - ~3 H, t, J 7 ~Iz~. ~
- 1.
- .
5'~
c) l-Methoxycarbonyl-3-oxopiperidine-4-carbohydroxamic acid ethylene acetal (IXa).
To a stirred and iced solution of potassium hydroxide (7.3 g;
130 mmol) in methanol (30 ml) was added hydroxylammonium chloride (6.9 g; 100 mmol). After stirring at 0C for further 30 minutes a solution of ethyl 1-methoxycarbonyl-3-oxopiperidine-4-carboxy-late eth~lene acetal (6.8 g; 25 mmol) in methanol (20 ml) was added, and the mixture was left at 8C for 8 days. Upon addition of glacial acetic acid (15 ml) and filtration the filtrate was evaporated in vacuo to give a treacly mass. CC [silica gel (Woelm 0.063--0.1 mm): 250 g; eluents: ethyl acetate to which methanol (15--26%) and formic acid (1%) was added] af~orded IXa tl.9 g; 29%) as a crystalline and TLC-pure substance [~ : 0.23;
eluent: ethyl acetate-methanol-formic acid (90 9:1)]. An analyti-cal sample was recrystallized (ethanol-benzene) to give IXa as -colourless crystals, m.p. 150.0--152.0C. IR (KBr): 3700--3350 (m), 3280 (m), 3210 (s), 3055 (w), 3000--2870 (several bands, w-m), 1690 (s), 1640 (s), 1550 (w) cm 1. lH NMR [CDC13-DMSO-d6 (1~
~ 10.5--10.1 (1 ~, m), 4.9- 4.3 (1 H, m), 3O93 (s)/ 3.60 (s), and 4.1--3.1 (m) (a:total of 11 H), 2.~--2.6 (1 H, m), 2,2--1.8 (2 H, m).
d) Methyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c~pyridine-6--carboxylate (Va).
A solution of l-methoxycarbonyl-3-oxopiperidine-4-carbohydroxamic acid ethylene acetal (750 mg; 2.9 mmol) in concentrated hydrochloric acid (13 ml) was heated to 70C for 10 minutes. The mixture was evaporated in vacuo to give a black oil. CC [silica gel (Woelm 0.063--0.1 mm): 60 g; eluents: benzene to which ethyl acetate (40--70%) and formic acid (1~) was added] gave crystalline and TLC-pure Va (244 mg; 43%) [RF 0.27; eluent: benzene ethyl acetate-formic acid (50:50:1)]. An analytical sample was recrys~allized (benzene--cyclohexane) to give pure Va as colourless crystals, m.p. 136.0--138.0C. IR (XBr)~ 3700--3300 (m), 3300--2S00 (several bands, w-m), 1655 (s), 1525 (m), 1490 (s) cm 1~
UV [methannl (log ~)]: 212 (3~64) nmc H NMR (CDC13): ~ 10.6 (1 ~, I .
, ' ~' .' ' ' ` ~
- 23 ~
s), 4.43 ~2 H, s), 3.70 (s) and 3.8-~3.5 (t) (a total of 5 H), 2.6--2.3 (2 H, t)~
e) 3-~!ydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridinium bromide (Ia (salt)).
A solution of methyl 3~hydroxy-4,5,6,7-tetrahydroisoxazolo~5,4-c]-pyridine-6-carboxylate (309 mg; 1.6 mmol) in a solution of hydro-gen bromide in glacial acetic acid (3 ml; 43~) was refluxed for 15 minutes. Upon evaporation to dryness ln vacuo the residue was treated with the same reagent (3 ml) for further 15 minutes.
Evaporation of the reaction mixture to dryness in vacuo and re-crystalli3ation (methanol-ether) of the residue gave Ia (salt) (193 mg; 56%) as faintly reddish crystals, m~p. 162--163C (de-comp.). IR (KBr): 3700--3300 (m), 3070 (s), 3000-2300 (several bands, m-s), 1670 (m), 1580 (m), 1525 (s), 1505 (w) cm 1 UV (methanol): <210 nm. H NMR [D2O (sodium 3-(trimethylsilyl)-propanesulfonate was used as an internal standard)]: ~4.77 (ca.
5 H, s), 4.43 (2 H, t, J 1 Hz), 3.7--3.4 (2 H, q, J 6 and 7 Hz), 3.0--2.7 (2 H, t).
~ .
f) 4,5,6,7-Tetrahvdroisoxazolo[5,4-c]pyridin-3-ol zwitterion (Ia). !
i To a solution of 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyri dinium bromide (77 mg; 0.35 mmol) in water (0.6 ml) was added a solution of triethylamine (39 mg; 0.39 mmol) in ethanol (0.6 ml).
The mixture was left at 25C for 2 hours. Ia (42 mg; 86%) was isolated as colourless crystals, m~p. 242--244C (decomp.). IR
(XBr). 3700--2900 (s), 2900--1900 (several bands, m-s), 1670 (s), 1625 (m) cm 1. UV [methanol (log ~)]: 212 ~3.64) nm. pKA values ~H O, 25C~: 4.44 - 0.03, 8.48 - 0.04 ,.
Example 2. (Reaction scheme II~. ~
.
isoxazolo[5,4-c]pyridine-6--carboxylate (Va) and methyl 1,4,5,6 ,?, 7a~hexahydro-1-oxoisoza-zolol3,4-cl~yridine-5-carboxylnte (VIa).
;
,. - , ~
llZ5288 ~TJND-34 CANADA
To an iced solution of sodium hydroxide (9.6 g; 0.24 mol) and hydroxylammonium chloride (8.39 g; 0.12 mol) in water ~100 ml) was added wi~h stirring ethyl l-methoxycarbonyl-3-oxopiperidine-4-carboxylate (22.9 g; 0.1 mol). Upon standing at 5~C for 5 hours the solution was evaporated to dryness ln vacuo. The residue was dlssolved in concentrated hydrochloric acid (75 ml) and heated to 70C for 10 minutes. The mixture was evaporated in vacuo to the formation of a black residue, which was extracted with three 100 ml portions of chloroform. The co~bined chloroform phases were dried (Na~SO43 and evaporated in vacuo to the formation of a black semisolid residue. TLC ('silica gel F254), eluent:
benzene-ethyl acetate-formic acid (25:25:1)) showed the presence of two compounds with RF values 0.31 and 0.16 corresponding to Va and VIa, respectively. Column chromatography (silica gel: 300 g;
eluent: benzene-ethyl acetate-formic acid (30:20:1)) lead to Va and VIa.
Example 3.
Methyl 3-hydroxy-4,5,6,7-tetrahydrot5,4-c]pyridine-6-carboyxlate (Va) (Reaction Scheme I).
A solution o~ the hydroxamic acid (IXa) (10 g) i~ perchloric acid (70~; 35 ml) was heated to 60C for 30 minutes. Upon cooling, NaOH (40 ml; 28%) was added with stirring and cooling. The mixture was extracted with three 50 ml portions of chloroform.
The combined and dried ~MgSO4) chloroform phases were ~iltered `and evaporated to dryness in vacuo to form a residue which was di5solved in ethyl acetate t50 ml). Upon standing and cooling, Va was isolated as crystals (6.3 g; 82~). Isolation and washing twice with 30 ml portions o~ ethyl aceta~e yielded crystalline ~` Va, m.p. 139-141C.
Instead of heating to 60C ~ar 30 minutes, the same result may be aahieved on standing at amblent température ~or 16 hours.
.
. . .
' ' .
.
, sz~
~ - 25 -~ f 4,5~6,7-Tetrah~droisoxazolo[5,4-c]pyridlne-3-ol zwitterion (Ia).
A solution of methyl 3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]-pyridine-6-carboxylate (Va) (37 g) in hydrogen bromide in glacial acetic acid (33% HBr, 250 ml) was left for 16 hours at ambient temperature. Evaporation to dryness ln vacuo gave the HBr salt of Ia as a yellowish crystalline material, which was dissolved in a mixture of water (100 ml) and ethanol (200 ml). Triethyl-amine was added until pH 6.5, which caused ~a zwitterion to crystallize. Upon standing for 3 hours at 5C and filtration, the precipitate was washed on the filter with a mixture of water (25 ml) and ethanol (50 ml) to give the zwitterion (26 g;
95%) as a white crystalline material, m.p. 242 - 244C (decomp.)~
. `
.. .. .
`' - ~ .
.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for the production of a 4-carbohydroxamic acid derivative of the formula wherein Z is an amino-protecting group and T is a group convertible, by hydrolysis, into an oxo group, which comprises reacting a compound of the formula wherein Z is an amino-protecting group and T is a group convertible, by hydrolysis, into an oxo group, and wherein Q is a leaving group which, on reaction with hydroxylamine, forms a hydroxamic acid group, with hydroxylamine to produce the desired 4-carbohydroxamic acid product.
2. The method of Claim 1, wherein Z is selected from the class consisting of acetyl; a group of the formula R5-0-?-, in which R5 is C1-8 alkyl, phenyl, phenyl substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl, or phenyl-lower-alkyl in which the phenyl group may be substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl;
trityl; and formyl; and wherein T is an acctal group con-vertible, by hydrolysis, into an oxo group; lower-alkyl or lower-alkoxy in any of the foregoing containing one through four carbon atoms.
trityl; and formyl; and wherein T is an acctal group con-vertible, by hydrolysis, into an oxo group; lower-alkyl or lower-alkoxy in any of the foregoing containing one through four carbon atoms.
3. The method of Claim 1, wherein z is selected from the class consisting of acetyl; a group of the formula R5-O-?-, in which R5 is C1-8 alkyl, phenyl, phenyl substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl, or phenyl-lower-alkyl in which the phenyl group may be substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl;
trityl; and formyl; and wherein T is an acetal group con-vertible, by hydrolysis, into an oxo group; lower-alkyl or lower-alkoxy in any of the foregoing containing one through four carbon atoms; and wherein Q is selected from halogen, the radical of an organic acid, the radical of an activated organic amide, the radical of an activated organic ester, and alkoxy.
trityl; and formyl; and wherein T is an acetal group con-vertible, by hydrolysis, into an oxo group; lower-alkyl or lower-alkoxy in any of the foregoing containing one through four carbon atoms; and wherein Q is selected from halogen, the radical of an organic acid, the radical of an activated organic amide, the radical of an activated organic ester, and alkoxy.
4. The method of Claim 1, wherein Z is methoxycarbonyl and T is alkylenedioxy.
5. The method of Claim 1, wherein Z is methoxycarbonyl, T is alkylenedioxy, and Q is alkoxy.
6. The method of Claim 1, wherein Z is methoxycarbonyl, T is ethylenedioxy, and Q is ethoxy.
7. A compound of the formula wherein Z is an amino-protecting group and T is a group convertible, by hydrolysis, into an oxo group, whenever produced according to the method of Claim 1 or an obvious equivalent.
8. A compound of the formula where Z is selected from the class consisting of acetyl;
a group of the formula R5-0-?-, in which R5 is C1-8 alkyl, phenyl, phenyl substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl, or phenyl-lower-alkyl in which the phenyl group may be substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl; trityl; and formyl;
and wherein T is an acetal group convertible, by hydrolysis, into an oxo group; lower-alkyl or lower alkoxy in any of the foregoing containing one through four carbon atoms, whenever produced according to the method of Claim 2 or an obvious equivalent.
a group of the formula R5-0-?-, in which R5 is C1-8 alkyl, phenyl, phenyl substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl, or phenyl-lower-alkyl in which the phenyl group may be substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl; trityl; and formyl;
and wherein T is an acetal group convertible, by hydrolysis, into an oxo group; lower-alkyl or lower alkoxy in any of the foregoing containing one through four carbon atoms, whenever produced according to the method of Claim 2 or an obvious equivalent.
9. A compound of the formula wherein Z is selected from the class consisting of acetyl;
a group of the formula R5-0-?-, in which R5 is C1-8 alkyl, phenyl, phenyl substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl, or phenyl-lower-alkyl in which the phenyl group may be substituted in the 4 position with halogen, lower-alkoxy:, or lower-alkyl; trityl; and formyl;
and wherein: T is an acetal group convertible, by hydrolysis, into an oxo group; lower-alkyl or lower-alkoxy in any of the foregoing containing one through four carbon atoms, whenever produced according to the method of Claim 3 or an obvious equivalent.
a group of the formula R5-0-?-, in which R5 is C1-8 alkyl, phenyl, phenyl substituted in the 4-position with halogen, lower-alkoxy, or lower-alkyl, or phenyl-lower-alkyl in which the phenyl group may be substituted in the 4 position with halogen, lower-alkoxy:, or lower-alkyl; trityl; and formyl;
and wherein: T is an acetal group convertible, by hydrolysis, into an oxo group; lower-alkyl or lower-alkoxy in any of the foregoing containing one through four carbon atoms, whenever produced according to the method of Claim 3 or an obvious equivalent.
10. A compound of the formula wherein Z is methoxycarbonyl and T is alkylenedioxy whenever produced according to the method of Claim 4 or an obvious equivalent.
11. The compound 1-methoxycarbonyl-3-oxopiperidine-4-carbohydroxamic acid alkylene acetal whenever prepared according to the method of Claim 5 or an obvious equivalent.
12. The compound l-methoxycarbonyl-3-oxopiperidine-4-carbohydroxamic acid ethylene acetal whenever prepared according to the method of Claim 6 or an obvious equivalent.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA377,128A CA1125288A (en) | 1977-06-20 | 1981-05-07 | Heterocyclic compounds which are gaba-agonists and production of same |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2574077 | 1977-06-20 | ||
| GB25740/77 | 1977-06-20 | ||
| CA305,798A CA1107736A (en) | 1977-06-20 | 1978-06-20 | Heterocyclic compounds which are gaba-agonists and production of same |
| CA377,128A CA1125288A (en) | 1977-06-20 | 1981-05-07 | Heterocyclic compounds which are gaba-agonists and production of same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1125288A true CA1125288A (en) | 1982-06-08 |
Family
ID=27165716
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA377,128A Expired CA1125288A (en) | 1977-06-20 | 1981-05-07 | Heterocyclic compounds which are gaba-agonists and production of same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1125288A (en) |
-
1981
- 1981-05-07 CA CA377,128A patent/CA1125288A/en not_active Expired
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