Note: Descriptions are shown in the official language in which they were submitted.
X-59~9M -1-
IMPROVEMENTS IN OR RELATING TO
NOVEL HYPOTENSIVE AGENTS
This invention relates to novel hypotensive
agents and is also concerned with novel methods of
preparing those compounds.
There are presently a number of commercial
products avallable which are to a greater or lesser
extent e~fective in reducing elevated blood pressure in
humans, see, for instance, U.S. Patent No. 2,484,029
10 which describes the commercial product "Hydralazine",
1(2H)-phthalazinone hydrazone. However, these products
all have various undesirable side-efects, for instance,
postural hypotensive effects and tachycardia. Accordingly,
there continues to be a need for new hypotensive agents
l~ possessing fewer undesirable side-effects.
Surprisingly, in accordance with the present
invention, lt has been discovered that a stereoisomer
of the racemic form of the compound described in U.S.
Patent No. 4,198,415, see Example 2, possesses ex-
2~ tremely interesting hypotensive properties. It is tobe noted that this U.S. Patent teaches that such
compounds are prolactin inhibitors, useful in the
treatment of Parkinson's disease, a utility far .emcved
from that now found for the novel isomer provided
herein.
Thus, in accordance with the invention, the
stereoisomer illustrated below in the form o its
tautomers:
X-5949M -2-
/8\ /i~\--/8\
~N_~a ~9a 7T --~~N--Toa t9a '-i~
~/Hi~ CH=~ o
n~3H7 n~3H7
Ia Ib
is an effective hypotensive agent.
The above stereoisomer can be alternatively
10 designated as: 5-n-propyl-4,4a~,5,6,7,8,8aa,9-
octahydro-lH(and 2H)pyrazolo[3,4-g]-quinoline; as
trans~ 5-n-propyl-4,4a~5,6,7,8,8a,9-octahydro-lH-
(and 2H)pyrazolo[3,4-g]quinoline; as 4aR,8aR-5-n-
propyl-4,4a,5,6,7,8,8a,9-octahydro-lH(and 2H)pyrazolo-
[3,4-g]quinoline; or as trans-4aR-5-n-pxopyl-4,4a,5,6,-
7,8,8a,9-octahydro-lH(and 2H)pyrazolo[3,4-g]quinoline.
This invention also provides a novel method
of blocking norepinephrine release from peripheral sym-
pathetic nerve terminals that innervate arterial muscle
fibers in mammals which comprises administering to a
mammal having an elevated blood pressure an effective
dose of a tautomeric mixture of trans-4aR-5-n-propyl-
4,4a,5,6,7,8,~a,9-octahydro-lH(and 2H)-pyrazolo[3,4-
g]quinoline, represented by formula Ia or Ih above, or
25 a pharmaceutically-acceptable salt thereof, thereby
lowering the blood pressure of said mammal.
The above tau-tomeric pair (Ia and Ib) can be
prepared in optically pure form by:
(a) reacting trans-dl-5-n-propyl-4,4a,5,6,-
7,8,8a,9 octahydro-lH(and 2H)pyrazolo[3,4-g]qulnoline,
?d77
X-594~M _3_
with an excess of an optically active -tartaric acid of
the formula
HOOC- (CHOR ) 2-COOH II
O
wherein R2 is hydrogen or -C-R3 where R3 is Cl-C3
alkyl, phenyl, or substituted phenyl;
(b) separating the tartrate salt of the
trans-stereoisomer, thus formed;
(c) fractionally recrystallizing the tartrate
salt mixture to provide the desired trans-4aR tartrate
salt;
(d) reacting an aqueous solution of the
tartrate salt with excess base; and then
(e) isolating the trans-4aR-5-n-propyl-
4,~a,5,6,7,8,8a,9-octahydro-lH(and 2H)pyrazolo[3,4-g]-
quinoline free base thus formed; and
(f) optionally salifying the free base so
obtaine~ so as to obtain a pharmaceutically-acceptable
salt the-eof.
An optically active tartaric acid o, the
formula
HOOC-(CHOR )2-COOH II
O
whereln R2 is hydrogen or -C-R3 where R3 is Cl-C3
alkyl, or phenyl optionally substituted by groups
such as methyl, chloro or methoxy, is used in the above
process. The acid will of course be in the (D)-(-)
form. A preferred class of reagents of formula II are
7~
~-5949~ -4-
those where R2 is hydrogen, R3 is methyl, phenyl or p-
tolyl. An especially preferred reagent of formula II
is D-(-)-S-tartaric acid. The reaction can be effected
using a solvent, such as a Cl-C4 alkanol, preferably
methanol, and a-t a temperature from about 50C. to
reflux.
Conversion of the salt, e.g. pyrazolo[3,~-g]-
quinoline 3-(-)-S-tartrate, to the free base is readily
effected by dissolving the salt in waker and then
lO adding an excess of a base (NaOH, Na2C03, NH40~1). The
pyrazolo[3,4-g]quinoline, being insoluble in the basic
solution, separates and is extracted with a water-
immiscible organic solvent. The organic layer is
separated and dried. If it is desired to prepare a
15 different salt, a solution containing one equivalent of
a second non-toxic acid can then be added, and the salt
isolated by filtration or evaporation. Alternatively,
the solvent can be removed from the dried organic
extract and the free base obtained as a residue. The
20 free base can then be dissolved in a suitable solvent
and the different non-toxic acid added as a solution.
Compounds according to the above stxucture
~ contain two basic groups, the alkylated quinoline ring
- nitrogen and the pyrazole nitrogen not carrying the
hydroyen (N-l or N-2). The quinoline ring nitrogen is
the more basic of the two and forms acid addition salts
readily. Strong inorganic acids such as the mineral
acids or strong organic acids such as _-toluenesulfonic
acid, can form di-salts when employed in excess.
X-5949M -5-
Pharmaceutically-acceptable salts of the
compounds of formula Ia or Ib thus include mono
or di-salts derived from inorganic acids such as:
hydrochloric acid, nitric acid, phosphoric acid, sul-
furic acid, hydrobromic acid, hydriodic acid, phos-
phorous acid and the like, as well as salts derived
from organic acids such as aliphatic mono- and di-
carboxylic acids, phenyl-substituted alkanoic acids,
hydroxy alkanoic and alkandioic acids, aromatic acids,
10 aliphatic and aromatic sulfonic acids. Such pharma-
ceutically-acceptable salts thus include sulfate,
pyrosulfate, bisulfate, sulfite, bisulfite, nitrate,
phosphate, monohydrogenphosphate, dihydrogenphosphate,
metaphosphate, pyrophosphate, chloride, bromide, io-
15 dide, fluoride, acetate, propionate, decanoa~e, capry-
late, acrylate, formate, isobutyrate, caprate, heptano-
ate, propiolate, oxalate, malonate, succinate, suber-
ate, seba-ate, fumarate, maleate, mandelate, butyne-
1,4-dioate, hexyne-1,6-dioate, benzoate, chlorobenzo-
ate, methylbenzoate, dinitrobenzoate, hydroxybenzoate,methoxybenzGate, phthalate, terephthalate, benzene-
sulfonate, toluenesulfonate, chlorobenzenesul.onate,
xylenesulfonate, phenylacetate, phenylpropionate,
phenylbutyrate, citrate, lactate, ~-hydroxybutyrate,
glycollate, malate, tartrate, methanesulfonate, pro-
panesulfonate, naphthalene-l-sulfonate, naphthalene-2-
sulfonate and the li~e salts.
The preferred salt of this invention is
the mono HCl salt and can be prepared for example by
addin~ an equivalent of hydrogen chloride to an
g ~ 7~
X-5949M -6-
ethanol solution of the free base, followed by evapo-
ration of the ethanol and recrystallization of the
salt. If it is desired to make a disalt such as a
dihydrochloride salt, HCl gas can be passed into a
solution of the free base to the point of saturation
and the salt isolated by filtration.
The following examples further illustrate
the preparation of the compounds of the invantion.
Example 1
One equivalent of trans-dl-5-n-propyl-4,4a,-
5,6,7,8,8a,9-octahydro~lH~and 2H)pyrazolo[3,4-g]quino-
line was dissolved in methanol. One and one-tenths
equivalents of D-(-)-S-tartaric acid were added thereto
15 and the solution heated to boiling for about 10 min-
utes. Upon cooling to room temperature, a crystalline
precipitate formed which was separated by filtration.
Five-fold recrystallization of that precipitate from
methanol (0.1 g of tartrate salt per 1 ml of methanol)
20 yielded crystalline trans-4aR-5-n-propyl-4,4a,5,6,7,-
8,8a,9-octahydro-lH(and 2H)pyrazolo[3,4-g]quinoline,
D-(-)-S-tartrate melting at 201-202C; [a]~ (H2O)
= -95.5. The salt was of satisfactory optical purity
since the last recrystallization did not substantially
25 changa the rotation of plane polarized light.
The above salt was dissolved in water and the
aqueous solution made strongly basic with 14M aqueous
ammonium hydroxide. The alkaline aqueous layer was
extracted three times with an equal volume of a 3:1
30 chloroform:isopropanol solvent mixture. The or~anic
~%~f~
X-5949M -7-
extracts were combined, the combined extracts washed
with saturated aqueous sodium chloride and then dried.
Evaporation of the solvent yielded a colorless solid
comprising trans-4aR-5-n-propyl-4,4a,5,6,7,8,8a,9-
octahydro-lH(and 2H)pyra~olo[3,4-g]quinoline. This
solid was dissolved in methanol and precisely one
equivalent of 0.2N aqueous hydrochloric acid added.
The volatile constituents were removed by evaporation
ln vacuo and the resulting hydrochloride salt crystal-
lized from a methanol/ether solvent mixture. Trans-
4aR-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-lH(and 2H)-
pyrazolo[3,4-g]quinoline, hydrochloride thus prepared
melted at about 280C with decomposition; [a]D5(H20)
= -120.6-
15 Analysis Calculated: C, 61.04; H, 5.67; Cl, 13.86;
N, 16.43,
Found: C, 61.30; H, 5.51; Cl, 14.14;N, 16.62.
The inactive trans-(+)- or trans-4aS-isomer
is prepared by contacting the trans-dl-racemate with a
slight excess of L-(+)~R-tartaric acid.
The absolute configuration of the inactive
trans-(+) stereoisomer was shown by x-ray analysis of
its D-(-)-R-_-butyloxycarbonylphenylglycine salt to be
4aS-configuration. Thus, the active isomer is, by
process of elimination, the trans 4aR, or 4a~,8aa, or
4aR,8aR or trans-(-)-isomer.
~2~
X-59~9M -8-
This invention also concerns a pharmaceutical
composition comprising as active ingredient a tautomer
oE formula Ia or Ib as defined above, or a pharma-
ceutically-acceptable salt thereof, associated with a
pharmaceutically-acceptable carrier therefor.
In using the therapeutic process, a pharma-
ceutically-acceptable salt of a drug according to
formula Ia or Ib above formed with a non-toxic acid
is administered orally or parenterally to a mammal with
an elevated hlood pressure in which it is desirable to
lower blood pressure, by blocking norepinephrine re-
lease from peripheral sympathetic nerve terminals that
innervate arterial muscle fibers. For parenteral ad-
ministration, a water soluble salt of the drug, trans-
1 4aR-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-2H(and lH)-
pyrazolo[3,4-g]isoquinoline, is dissolved in an iso-
tonic salt solution and administered by the I.V. route.
Dose levels of from 0.5-500 mcg./kg. of mammalian
weight are found to be effective to block norepineph-
rine release and thereby reduce elevated blood pressurein spontaneously hypertensive rats (SHR). For oral
admlnistration, a pharmaceutically-acceptable salt of
the drug is mixed with standard pharmaceutical excipi-
ents such as starch and loaded into capsules, each
containing 0.1-15 mg. of active drug. Dosage levels of
from 0.1-3 mg./kg. have been Eound to be effective in
blocking norepinephrine release from sympathetic nerve
terminals, thereby lowering blood pressure in SHR, for
periods ranging up to six hours. Thus, the oral dosage
X-5949M -9_
would be administered 3-4 times per day, giving a daily
dosage range of about 0Ol to about 15 mg./kg. per day.
Other oral dosage forms, such as suspensions,
elixirs and tablets, can also be utilized and are
preparable by standard procedures.
The effect of the method o~ this invention in
blocking norepinephrine release from peripheral sym-
pathetic nerve terminals that innervate arterial muscle
fibers, thexeby reducing the blood pressure in spontane-
10 ously hypertensive rats, is shown by the followingexperiment:
Adult male spontaneously hypertensive rats
(SHR) (Taconic Farms, Germantown, New York), weighing
approximately 300 g. were anesthetized with pento-
15 barbital sodium (60 mg./kg., i.p.). The trachea wascannulated and SHR respired room air. Pulsatile arteri-
al blood pressure was measured from a cannulated carot-
id artery using a Statham transducer (P23 ID). Mean
arterial blood pressure was calculated as diastolic
20 blood pressure plus 1/3 pulse pressure. Cardiac rate
~ was monitored by a cardiotachometer which was triggered
i by the systolic pressure pulse. Drug solutions were
administered I.V. through a catheter placed in a fem-
oral vein. Arterial blood pressure and cardiac rate
25 were recorded on a multichannel oscillograph (Beckman,
Model R511A). Fi~teen minutes were allowed to elapse
following surgery for equilibration of the preparation.
'; ~-'
X-5949M -10-
Table 1 which follows gives the results of
this experiment using trans-4aR-5-n-propyl-4,4a,5,6,7,-
8,8a,9-octahydro-2H(and lH)pyrazolo[3,4-g3quinoline,
D-(-)-S-tartrate, plus the corresponding trans-4aS-
enantiomer and the parent trans-dl-racemate as the
hydrochloride salt for comparison purposes. Each drug
was administered I.V. to groups of four SHR at a series
of dose levels.
TABLE 1
Relative potencies of trans-5-n-propyl-4,-
4a,5,6,7,8,8a,9-octahydro-2H(and lH)pyrazolo[3,4-g]-
quinolines isomers and racemate.
Mean Arterial
Dose Blood Pressure
Compoundmcg./kg. % Change (~)
Trans-4aR 0.1 - 7.7 + 1.6
1 -14.3 + 1.6
-25.2 ~ 2.1
100 -38.6 + ~.3
Trans-4aS 0.1 - 8.5 + 0.8
1 - 5.1 ~ 0.8
- 5.0 + 0.3
100 - 4.6 + 0.3
1000 - 6.4 + 1.1
Trans-dl 1 -12.7 + 2.2
-22.4 + 0.7
100 -32.0 -~ 2.1
1000 -52.2 t 6.9
It is apparent that all the hypotensive
action of trans-dl-5-n-propyl-4,4a,5,6,7,8,8a,9-octa-
hvdro-lH(and 2H)-pyrazolo[3,4-g]quinoline resides in
30 the levo or trans-4aR stereoisomer.
x-5949~ -11-
l~ore direct evidence that trans-dl-5-n-
propyl-4,4a,5,6,7,~,8a,9-octahydro-lH(and 2H)-pyra-
zolo[3,4-g]quinoline blocks norepinephrine release from
peripheral sympathetic nerve terminals is illustrated
by the following experiment. In this experiment, SHR
were pithed by passing a steel rod through the right
orbit and down the entire length of the spinal column.
The rod was left in position for the duration of the
experiment. Immediately after pithing, SHR were venti-
10 lated with room air delivered from a rodent respirator(Harvard, Model ~80; tidal volume of 1 ml./100 g. body
weight, 60 cycles/min). The pithing rod was used to
stimulate the entire sympathetic outflow from the
spinal cord. Portions of the rod which lay in the
15 cervical and sacral cord were insulated. The sympathet-
ic outflow was stimulated by square wave pulses (50
volts, 1 msec duration for 30 sec) of frequencies of
0.25, 1, 4 and 8 Hz delivered from a stimulator (Grass,
Model S44). The pithing rod served as the stimulating
20 electrode while a needle inserted into the right hind-
limb musculature was the indifferent electrode. Skele-
tal muscle twitches were prevented by administration of
d-tubocurarine (1 mg./kg., I.V.). Increments in dia-
stolic blood pressure produced by electrical stimula-
25 tion of the sympathetic outflow were monitored from acannulated carotid arter~. The test drug was adminis-
tered I.V. at two dose levels to groups of four SI~R.
Table 2 which follows indicates that elec-
trical stimulation of the sympathetic outflow or I.V.
~-5949M -12-
administration of exogenous norepinephrine each pro-
duced the expected vasoconstrictor responses in control
pithed SHR, as indicated by the increments in diastolic
blood pressure. Pretreatment of other S~ with the
trans-dl-racemate attenuated neurogenic vasoconstrictor
responses in a dose-related manner. rrhis attenuation
was selective in that the test drug produced no con-
comitant antagonism of comparable vasoconstrictor re-
sponses resulting from administration of exogenous nore-
10 pinephrine. Thus, the composite data of Tables 1-2
indicate that doses of the trans-dl-racemate (and by
implication, of the trans-4aR isomer, the active com-
ponent of the racemate) which are hypotensive in intact
SHR, result in selective inhibition of norepinephrine
15 release from peripheral sympathetic nerve terminals.
TABLE 2
Selective antagonism of neurogenic vasocon-
strictor responses produced by trans-dl-5-n-propyl-
20 4,4a,5,6,7,8,8a,9-octahydro-lH-(and 2H)-pyrazolo-
[3,4-g]~uinoline.
Increase ln Dlastolic Blood
Pressure (mm. Hg.) Produced
by Electrical Stimulation of
the Sympathetic Outflow
Trans-dl-racemate
25 (mcg /ka , I V.) 0.25 Hz1 Hz 4 Hz 8 Hz
J ~ _
none 34+3 72+3 118+8 129+7
100 14+2 47~2 105~8 115+9
1000 10+1 26+4 65~8 89+12
-
X-59~9M -13-
Increase in Diastolic Blood Pres-
sure (mm. Hg~) Produced by
Exogenous Norepinephrine
Trans-dl-racemate 0.01 0~1 l lO
(mcg./kg., I.V.) mcy./kg. mcg./kg. mcg./kg. mc~./kg.
none 8+1 27~1 78+3 140~5
100 7+1 29+2 74~1 128~5
1000 10~l 30+2 80+1 1~0~4
The lack of alpha adrenergic receptor activi-
10 ty for trans-4aR-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-
lH(and 2H)pyrazolo[3,4-g]quinoline is illustrated by
the following experiment in which vasoconstrictor
activity (or lac~ thereof) can be demonstrated in
pithed SHR as a rise in baseline blood pressure,
15 vasoconstrictor activity resulting in a blood pressure
rise.
The effects on blood pressure as a measure of
the vasoconstrictor effects of trans-dl-5-n-propyl-
4,4a,5,6,7,8,8a,9-octahydro-lH(and 2H)-pyrazolo[3,4-g]-
20 quinoline and the trans-4aR stereoisomer were deter-
mined using norepinephrine as a control substance. Two
oth~r dopamine agonists, pergolide and lergotrile, were
also included plus the 7-methylmercaptomethyl deriva-
tive of trans-dl-5~n-propyl-4,4a,5,6,7,8,8a,9--octahydro-
25 lH(and 2H)pyrazolo[3,4-g]quinoline. Table 3 which
follows gives the results of this comparison. In the
table, column l, gives the name of the test compound,
column 2, the dose and column 3, the change in diastolic
blood pressure. Four pithed SHR rats were used at each
30 dose level for each drug.
~ t~ 7
X-5949M -14-
TABLE 3
Pelative blood pressure effects of trans-dl-
5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-lH(and 2H)pyra-
zolo[3,4-g]quinoline, the trans-4aR stereoisomer and
related compounds.
IV Change .in Diastolic
Dose in Blood Pressure
Compound mcg./kg. (mm. Hg )
Trans-dl 1 -t S + 1
+ 2 + 3
100 ~ 2 + 4
1000 + 7 + 1
Trans-4aR 1 - 4 + 1
- 5 + 1
100 - 4 + 1
1000 - 3 + 1
15 Norepinephrine ~01 + 8 + 1
.1 +27 + ~
1 +78 + 3
+140 + 5
Pergolide 1 -t 4
+19
100 +62
Lergotrile 10 -t 6
100 + 6
1000 +18
Trans-dl-5-n-propyl- 1 + 2 + 2
7-methylmercapto- 10 + 5 + 1
methyl-4,4a,5,6,7,- 100 -~17 + 1
25 3,8a,9-oCtahydro-lH- 1000 +49 + 1
(and 2H)-pyrazolo-
: [3,4-g]quinoline
From the above da-ta, it would also be expected that
the trans-4aR stereoisomer would not increase cardiac
32~
X-5949M -lS-
rate as does norepinephrine and this hypothesis has
been affirmed by experiment.
It is apparent from the data presented in
Tables 2-3 that trans-4aR-5 n-propyl-4,4a,5,6,7,8,8a,9-
octahydro-lH(and 2H)pyrazolo[3,4-g]quinoline and the
trans-dl racemate are neither a-receptor agonists
nor antagonists, and that their hypotensive action is not
caused by any a-receptor ef ect, but is probably at~rib-
utable solely to their abllity to block norepinephrine
10 release from peripheral sympathetic nerve terminals
that innervate arterial muscle fiber.
Trans-4aR-5-n-propyl-4,4a,5,6,7,8,8a,9-
octahydro-lH-(and 2H)quinoline can be considered as
related to the ergoline part structure (IV) except that
15 the pyrrole function is replaced by a pyrazole functio-.
: (Va and Vb).
~ O
!
S
.. . ... .
X-5949M -16-
t~ 7T fV``t
~ N-alkyl H~/-\ /N-alkyl
t1 ~ 01 1 5T~ T t~H
~ T/~/ IV
ergoline
III
where y is H and alkyl is CH3
Y Y
~ 6T I ~ T
Hll ~ Va ~ ~ Vb
where Y is H and alkyl is n_propyl.
Pergolide (see Table 2) is an ergoline where
25 alkyl i5 n-propyl and Y is methylmercaptomethyl. Ler-
gotrile ~from Table 21 is an ergoline where alkyl is
methyl, Y is CH2CN and there is a chlorine at 2~ The
related compound, trans-dl-5-n-propyl-7-methylmercapto-
methyl ~,4a,5,6,7,8,8a,9-octahydro-lH(and 2H)pyrazolo-
[3,4-g]~uinollne (Va and Vb where alkyl is n-propyl and
~ 2~ 7~
X-5949.~ -17-
Y is mPthylmercaptomethyl), is disclosed in U.S.
Patent 4,198,415, and is a substituted derivative
of the compound used in the process of this invention,
the trans~4aR derivative, Va and Vb where alkyl is also
5 n-propyl but Y is H. From the data in Table 2, it can
be seen that pergolide and trans-dl-5-n-propyl-7-
methylmercaptomethyl-4,4a,5,6,7,8,8a,9-octahydro-lH(and
~ 2H)pyrazolo~3,4-g]quinoline behave like norepinephrine
F in the pithed SHR. Thus, while these later compounds
-
10 are dopamine agonists, they also act on a-receptors.
Lergotrile, while it resembles the trans-4aR isomer use-
~- ful in the process of this invention in that it does
..
not act as a vascoconstrictor in pithed SHR, has unde-
sirable central effects such as a potential for produc-
15 ing hallucinations in humans and is thus not a purepresynaptic dopamine agonist as is the trans-4aR
isomer. The trans-4aR isomer is apparently unique as a
presynaptic dopamine agonist. As a consequence, it is
unique in its ability to lower an elevated blood pres-
20 sure in mammals by blocking norepinephrine release fromperipheral sympathetic nerve terminals that innervate
arterial muscle fibers withou~ other major pharmaceu-
tical activity.
.: ~
