Pharmaceutical compositions and method of inhibiting phenylethanolamine N-methyltransferase

This invention relates to new pharmaceutical compositions and methods of 
inhibiting phenylethanolamine N-methyltransferase with 2-indanamine 
compounds having 4 and/or 5 substituents. 
Epinephrine is a hormone, synthesized in the adrenal medulla, which is 
released into the blood stream in response to stress and produces profound 
physiological changes which serve to prepare the animal to cope with the 
stressor situation. For example, epinephrine produces anxiety, an increase 
in blood pressure, acceleration of heart rate and increase in cardiac 
output. These changes are detrimental in individuals with certain disease 
conditions such as angina pectoris, myocardial infarction and anxiety 
neuroses. 
Phenylethanolamine N-methyltransferase catalyzes the final step in the 
biosynthesis of epinephrine, that is the transfer of a methyl group from 
S-adenosylmethionine to norepinephrine to produce epinephrine. 
The 2-indanamine compounds of the pharmaceutical compositions and methods 
of this invention inhibit phenylethanolamine N-methyltransferase and thus 
reduce the formation of epinephrine. They are therefore useful in 
situations where there is overproduction of epinephrine or where 
epinephrine production is detrimental. 
The compounds which are the active ingredients of the pharmaceutical 
compositions and methods of this invention are represented by the 
following formula: 
##STR1## 
R is chloro, bromo, fluoro, iodo, trifluoromethyl, nitro, sulfamyl or 
methylthio with R being in either the 4 or 5 position; and 
R.sub.1 and R.sub.2 are hydrogen, methyl or ethyl; and pharmaceutically 
acceptable acid addition salts thereof. 
The compounds of this invention are prepared by the following procedure: 
##STR2## 
The terms R, R.sub.1 and R.sub.2 are as defined above. 
According to the above procedure, the 2-indanamines are prepared by 
reacting a substituted aniline with nitrous acid, methyl acrylate and 
cuprous bromide to form the corresponding substituted phenylpropionic 
acid. The acid is cyclized to the 1-indanone which in turn is converted to 
the 2-indanone and reduced to the desired 2-indanamine. The cyclization is 
carried out by treating the phenylpropionic acid with thionyl chloride and 
aluminum chloride or other Friedel-Craft catalysts. 
An alternative method of preparing the phenylpropionic acid may be carried 
out by brominating a 2,3 substituted toluene and alkylating the resultant 
compound with diethyl malonate. The cyclization of the phenylpropionic 
acid may also be carried out with an acid catalyst such as polyphosphoric 
acid. 
Pharmaceutically acceptable, acid addition salts of the compounds of 
Formula 1 are formed with organic and inorganic acids by methods known to 
the art. The base is reacted with an organic or inorganic acid in aqueous 
miscible solvent, such as acetone or ethanol, with isolation of the salt 
by concentration and cooling or in aqueous immiscible solvent, such as 
ethyl ether or chloroform, with the desired salt separating directly. 
Exemplary of the salts which are included in this invention are maleate, 
fumarate, benzoate, ascorbate, pamoate, succinate, bismethylenesalicylate, 
methanesulfonate, ethanedisulfonate, benzenesulfonate, acetate, 
propionate, tartrate, salicylate, citrate, gluconate, lactate, malate, 
mandelate, cinnamate, citraconate, aspartate, stearate, palmitate, 
itaconate, glycolate, p-aminobenzoate, glutamate, theophylline acetates, 
hydrochloride, hydrobromide, sulfate, cyclohexylsulfamate, phosphate and 
nitrate salts. 
2-Indanamines and 2-aminohalo substituted indanes are generally known in 
the art. The latter compounds are disclosed in German Patent No. 1,518,652 
as analgetics and vasodilators. 
The basic activity of the compounds of this invention is demonstrated by 
inhibition of phenylethanolamine N-methyltransferase in vitro by the assay 
procedure described by Pendleton and Snow, Molecular Pharmacology, 
9-718-725, 1973, at various compound concentrations. For example, 
following are in vitro results obtained from testing several compounds 
present in the pharmaceutical compositions and methods of this invention. 
______________________________________ 
##STR3## 
In Vitro Inhibition % 
SK&F No. R 10.sup.-4 
10.sup.-6M 
______________________________________ 
85391 5-NO.sub.2 96 23 
85506 5-Cl 96 37 
85347 5-Br 96 33 
______________________________________ 
In addition, the activity of the compounds of this invention is 
demonstrated in vivo by oral administration to rats at 50 mg./kg. three 
times over a 24 hour period. One hour after the last dose the rats are 
given a tracer dose of .sup.3 H-norepinephrine into a tail vein. 
Forty-five minutes later they are sacrificed by decapitation and the 
adrenals assayed for .sup.3 H-epinephrine and .sup.3 H-norepinephrine. A 
compound is considered active as a PNMT inhibitor if it significantly (at 
least p&lt;0.05) decreases the conversion of radioactive norepinephrine into 
epinephrine (R. G. Pendleton et al., J. Pharmacol. Exp. Ther., 
190:551-562, 1974, and R. G. Pendleton et al., J. Pharmacol. Exp. Ther., 
197:623-632, 1976). A preferred compound of this invention, 
5-sulfamoyl-2-aminoindane, significantly inhibited this conversion 
(p&lt;0.01) at a unit dose of 50 mg./kg. 
The pharmaceutical compositions of this invention to inhibit 
phenylethanolamine N-methyltransferase comprise a pharmaceutical carrier 
and, as the active ingredient, a 2-indanamine compound of Formula 1. The 
active ingredient will be present in the compositions of this invention in 
an effective amount to inhibit phenylethanolamine N-methyltransferase. 
Preferably, the compositions of this invention contain the active 
ingredient of Formula 1 in an amount of from about 50 mg. to about 1000 
mg., advantageously from about 100 mg. to about 500 mg., per dosage unit. 
The pharmaceutical carrier may be for example a solid or a liquid. 
Exemplary of solid carriers are lactose, magnesium stearate, terra alba, 
sucrose, talc, stearic acid, gelatin, agar, pectin or acacia. The amount 
of solid carrier will vary widely but preferably will be from about 25 mg. 
to about 1 gm. Exemplary of liquid carriers are syrup, peanut oil, olive 
oil, sesame oil, propylene glycol, polyethylene glycol (mol. wt. 200-400) 
and water. The carrier or diluent may include a time delay material well 
known to the art such as, for example, glyceryl monostearate or glyceryl 
distearate along or with a wax. 
A wide variety of pharmaceutical forms can be employed, for example, the 
preparation may take the form of tablets, capsules, powders, troches, 
lozenges, syrups, emulsions, sterile injectable liquids or liquid 
suspensions or solutions. 
The pharmaceutical compositions are prepared by conventional techniques 
involving procedures such as mixing, granulating and compressing or 
dissolving the ingredients as appropriate to the desired preparation. 
The method of inhibiting phenylethanolamine N-methyltransferase, according 
to this invention, comprises administering to an animal in an amount 
sufficient to inhibit phenylethanolamine N-methyltransferase a 
2-indanamine compound of Formula 1. 
Preferably the compounds of Formula 1 are administered in conventional 
dosage unit forms prepared by combining an appropriate dose of the 
compound with standard pharmaceutical carriers. 
Preferably the active ingredient of Formula 1 will be administered in a 
daily dosage regimen of from about 100 mg. to about 2000 mg., most 
preferably from about 200 mg. to about 1000 mg. Advantageously, equal 
doses will be administered preferably two to three times per day. When the 
administration is carried out as described above, inhibition of 
phenylethanolamine N-methyltransferase is produced. 
The route of administration of the pharmaceutical compositions of this 
invention and in accordance with the methods of this invention is 
internal, either parenteral or preferably oral, in an amount to produce 
the desired biological activity.

The following examples are not limiting but are illustrative of this 
invention. 
EXAMPLE 1 
6.35 g. of 2-chloroaniline (0.05 mole) in acetone (100 ml.) and 
concentrated hydrobromic acid (16 ml.) was stirred at -5.degree. C. and 
treated with a solution of 4.2 g. of sodium nitrite (0.06 mole) in water 
(10 ml.). Methyl acrylate (0.5 mole) (43 g.) and cuprous bromide (100 mg.) 
were then added at 0.degree. C. The reaction temperature was kept below 
15.degree. C. until nitrogen evolution ceased and then stirred at 
25.degree. C. for thirty minutes. The reaction mixture was poured into 
water and extracted with benzene which was dried over sodium sulfate and 
evaporated to give methyl 2-bromo-3-(2-chlorophenyl)propionate. 
The propionate, 138 g. (0.5 mole) was dissolved in glacial acetic acid (1 
l.) and stirred. Zinc dust 65 g. (1 mole) was added in portions and the 
mixture was stirred for one hour, filtered and evaporated to give methyl 
3-(2-chlorophenyl)propionate. 
Methyl 3-(2-chlorophenyl)propionate was refluxed in 10% aqueous sodium 
hydroxide (1 l.) for two hours and the reaction mixture was cooled, 
acidified and filtered. The filter cake was dissolved in hot aqueous 
sodium bicarbonate and filtered. The filtrate was acidified and filtered 
to yield 3-(2-chlorophenyl)propionic acid. 
The propionic acid 2.0 g. (0.011 mole) was suspended in benzene (27 ml.) 
and treated with 1.7 g. of thionyl chloride (0.014 mole) and dimethyl 
formamide (two drops). The reaction was refluxed for thirty minutes, 
filtered and evaporated to give 3-(2-chlorophenyl)propionyl chloride which 
was dissolved in chlorobenzene (12 ml.) and treated with anhydrous 
aluminum chloride 2.4 g. (18 mmoles). The reaction was stirred for one 
hour and poured onto ice. The chlorobenzene was evaporated in vacuo and 
the residue was extracted with chloroform which was washed, dried over 
sodium sulfate and evaporated to give 4-chloro-1-indanone. 
The above prepared indanone 1.66 g. (0.01 mole) was dissolved in ethanol 
(30 ml.) and treated with 0.5 g. of sodium borohydride (0.013 mole). The 
reaction was stirred at 25.degree. C. for one hour and evaporated. Ether 
was added to the residue followed by 10% hydrochloric acid. The ether was 
dried and evaporated to yield 4-chloro-1-indanol. 
1.68 g. of the indanol (0.01 mole) and a trace of p-toluene-sulfonic acid 
in benzene (30 ml.) was refluxed for four hours. The benzene solution was 
evaporated to give 4-chloro-1-indene and 4-chloro-2-indene. 
7.5 g. of the above mixture of indenes (0.05 mole) in chloroform (125 ml.) 
was treated with 10.0 g. of m-chloroperbenzoic acid (0.05 mole) at 
5.degree. C. The solution was allowed to warm to 25.degree. C. and was 
stirred for sixteen hours. The chloroform was evaporated and the residue 
was dissolved in carbon tetrachloride which was extracted with aqueous 
sodium bicarbonate, dried and evaporated to give a mixture of 
4-chloro-1,2-epoxyindane and 4-chloro-2,3-epoxyindane. 
The mixture of above epoxyindanes was dissolved in ether (100 ml.) and 
cooled. Boron trifluoride etherate (100 ml.) was added below 15.degree. C. 
and the reaction was stirred for thirty minutes. Water was added slowly 
and the ether layer was separated, washed with aqueous sodium bicarbonate, 
dried over sodium sulfate and evaporated. The residue was chromatographed 
on silica gel eluted with benzene to give 4-chloro-2-indanone. 
4-Chloro-2-indanone 3.3 g. (0.02 mole) and 4.2 g. of methoxyamine 
hydrochloride (0.05 mole) were dissolved in a mixture of ethanol (42 ml.) 
and pyridine (42 ml.) and heated on a steam bath for thirty minutes. The 
reaction was diluted with water and the O-methyl oxime of 
4-chloro-2-indanone was isolated by filtration. 
0.78 g. of the O-methyl oxime of 4-chloro-2-indanone (4 mmoles) dissolved 
in tetrahydrofuran (5 ml.) was treated with 1 M diborane in 
tetrahydrofuran (20 ml.) and refluxed for two hours in an argon 
atmosphere. Methanol was added and the solvent was evaporated. The residue 
was treated with 10% hydrochloric acid and heated on a steam bath for 
thirty minutes. The mixture was made alkaline and extracted with ether 
which was dried over potassium carbonate and evaporated to yield 
4-chloro-2-indanamine. 
EXAMPLE 2 
Following the procedure of Example 1, the following substituted aniline 
compounds: 
2-bromoaniline 
2-fluoroaniline 
2-iodoaniline 
2-nitroaniline 
2-trifluoromethylaniline 
are used as starting materials to give the following products respectively: 
4-bromo-2-indanamine 
4-fluoro-2-indanamine 
4-iodo-2-indanamine 
4-nitro-2-indanamine 
4-trifluoromethyl-2-indanamine 
EXAMPLE 3 
1.75 g. of N-acetyl-2-indanamine (0.01 mole) was added to 20 g. of 
chlorosulfonic acid (0.18 mole), stirred at -60.degree. C. and allowed to 
warm to 25.degree. C. The mixture was stirred until the reaction was 
complete, poured into cold water and extracted with ethyl acetate. 
Evaporation gave the crude N-acetyl-5-chlorosulfonyl-2-indanamine which 
was converted to N-acetyl-5-sulfamyl-2-indanamine with ammonia in THF. The 
N-acetyl sulfonamide was purified by recrystallization from water, m.p. 
237.degree.-239.degree. C. and hydrolyzed in refluxing 10% hydrochloric 
acid to give 5-sulfamyl-2-indanamine which was recrystallized from 
methanol-ether, m.p. 261.degree.-264.degree. C. 
EXAMPLE 4 
5.6 g. of N-acetyl-5-chlorosulfonyl-2-indanamine (0.02 mole) (as prepared 
in Example 3) is dissolved in acetic acid (50 ml.), warmed to 75.degree. 
C., and 19 g. of stannous chloride (0.1 mole) in concentrated hydrochloric 
acid (20 ml.) is added. An exotherm occurs. When the reduction is complete 
the mixture is cooled to 25.degree. C. and poured into water. The 
N-acetyl-5-mercapto-2-indanamine is filtered and suspended in methanol (50 
ml.) under a nitrogen atmosphere. 5.7 g. of methyl iodide (0.04 mole) and 
1.1 g. of sodium methoxide (0.02 mole) are added and the mixture is 
stirred for one hour. The mixture is filtered, evaporated and the residue 
purified by chromatography to give N-acetyl-5-methylthio-2-indanamine 
which is hydrolyzed following the procedure of Example 3 to give 
5-methylthio-2-indanamine. 
EXAMPLE 5 
A mixture of 0.4 g. of 5-chloro-2-indanone (0.0025 mole) was partially 
dissolved in methanol (10 ml.) and 0.4 g. of sodium cyanoborohydride 
(0.0065 mole) and 0.6 g. of dimethylamine hydrochloride (0.0075 mole) were 
added. The pH of the mixture was adjusted to 4.5 with 10% hydrochloric 
acid and 3 A molecular sieves were added. The mixture was stirred for 16 
hours at 25.degree. C., acidified, evaporated to dryness, dissolved in 10% 
hydrochloric acid, extracted with ether, basified and extracted with ether 
to yield N,N-dimethyl-5-chloro-2-aminoindane. 
EXAMPLE 6 
Following the procedure of Example 5, 5-chloro-2-indanone and methylamine 
hydrochloride gave N-methyl-5-chloro-2-indanamine. 
EXAMPLE 7 
______________________________________ 
Ingredients Mg./Capsule 
______________________________________ 
5-Chloro-2-indanamine 150 mg. 
Lactose 150 mg. 
______________________________________ 
The above ingredients are mixed and filled into a hard gelatin capsule. 
EXAMPLE 8 
______________________________________ 
Ingredients Mg./Tablet 
______________________________________ 
5-Sulfamyl-2-indanamine 
50 
Calcium sulfate dihydrate 
150 
Sucrose 25 
Starch 15 
Talc 5 
Stearic Acid 3 
______________________________________ 
The sucrose, calcium sulfate and indanamine are thoroughly mixed and 
granulated with hot 10% gelatin solution. The wetted mass is passed 
through a No. 6 mesh screen directly onto drying trays. The granules are 
dried at 120.degree. C. and passed through a No. 20 mesh screen, mixed 
with starch, talc and stearic acid and compressed into tablets. 
Two tablets are administered three times a day. 
EXAMPLE 9 
25 g. of 2-indanamine hydrochloride (0.15 mole), 20 g. of sodium acetate 
trihydrate (0.14 mole), and 40 g. of acetic anhydride (0.4 mole) were 
stirred at 25.degree. C. for sixteen hours. The mixture was evaporated and 
the residue was partitioned between chloroform and water. The chloroform 
extracts were pooled, washed with 10% hydrochloric acid and then with 5% 
aqueous sodium carbonate, dried and evaporated to yield 
N-acetyl-2-indanamine. 
18.5 g. of the acetamide (0.105 mole) was added in portions to nitric acid 
(185 ml.; d=1.51), stirred and maintained below 0.degree. C. The reaction 
was allowed to warm to 0.degree. C., poured onto crushed ice and extracted 
with chloroform which was washed with 5% aqueous sodium bicarbonate and 
evaporated to give crude N-acetyl-5-nitro-2-indanamine which was purified 
by crystallization from isopropanol, m.p. 143.degree.-144.degree. C. 
12.6 g. of N-acetyl-5-nitro-2-indanamine (0.057 mole) in ethanol (200 ml.) 
containing 0.5 g. of 10% palladium-on-carbon catalyst was treated with 
hydrogen until the theoretical amount of hydrogen was absorbed. The 
catalyst was filtered and the filtrate was treated with concentrated 
hydrochloric acid (5 ml.) and evaporated. The residue was recrystallized 
from ethanol to give N-acetyl-5-amino-2-indanamine hydrochloride, m.p. 
259.degree.-260.degree. C. (dec.) 
4.0 g. of N-acetyl-5-amino-2-indanamine hydrochloride (0.018 mole) stirred 
below 10.degree. C. in concentrated hydrochloric acid (6 ml.) and water 
(15 ml.) was treated with a solution of 1.5 g. of sodium nitrite (0.022 
mole) dissolved in water (5 ml.). The resulting solution of diazonium salt 
was added to a stirred mixture of 2 g. of cuprous chloride (0.021 mole) in 
concentrated hydrochloric acid (6 ml.) and water (10 ml.) which was then 
stirred for 90 minutes and allowed to warm to 25.degree. C. 
The resulting mixture was extracted with chloroform which was washed, dried 
and evaporated. The residue was dissolved in ethyl acetate-cyclohexane 
(3:2) and chromatographed on neutral alumina to give 
N-acetyl-5-chloro-2-indanamine which was recrystallized from carbon 
tetrachloride and then from carbon tetrachloride-petroleum ether, m.p. 
117.degree.-119.degree. C. 
The acetamide, 1 g. (0.005 mole) was stirred and refluxed in 3 N HCl (10 
ml.) for 3.5 hours and the mixture was evaporated. The residue was 
recrystallized from ethanol-ether and then from ethanol to give 
5-chloro-2-indanamine hydrochloride, m.p. 273.degree. C. (dec.) 
EXAMPLE 10 
N-Acetyl-5-nitro-2-indanamine, 1.5 g. (0.007 mole) as prepared in Example 9 
was refluxed in 10% hydrochloric acid for 3 hours. The mixture was 
evaporated and the crystalline residue recrystallized from methanol-ether 
to yield 5-nitro-2-indanamine hydrochloride, dec.&gt;280.degree. C. 
EXAMPLE 11 
Following the procedure of Example 9, 2.85 g. of N-acetyl-5-indanamine 
(0.015 mole) in 48% hydrobromic acid (4 ml.) and water (10 ml.) was 
diazotized with 1.1 g. of sodium nitrite (0.016 mole) in water and added 
to 2.2 g. of cuprous bromide in 48% hydrobromic acid (4 ml.) and water (5 
ml.) to give N-acetyl-5-bromo-2-indanamine which was recrystallized from 
chloroform-petroleum ether, m.p. 103.degree.-105.degree. C. 
The N-acetyl compound was hydrolyzed with 3 N hydrochloric acid and 
purified by recrystallization from ethanol to give 5-bromo-2-indanamine, 
m.p. 280.degree.-281.degree. C. (dec.)