Note: Descriptions are shown in the official language in which they were submitted.
~988~L
The present invention is concerned with certain mercaptans
possessing mucolytic activ;ty and is particularly concerned with certain
novel benzamidoalkyl mercaptans, compositions thereof and methods for
employing the mercaptans as mucolytic agents in con~rolling and combatlny
mucus bu;ld-up in an animal exhibiting or suffering from lung congestion.
A.L. Sheffner, Ann. N.Y. Acad. Sci. 106, 298-310 (1963) discloses
sulfhydryl-containing compounds having mucolytic activity and established
- the use of mucin mucoprotein as a tes~ media. None of the compounds
disclose~ by Sheffner were of the benzamidoalkyl mercaptan type. T.A.
10 Martin et al., in U.S. Patent 4,005,222 disclose mucolytic anilido alkyl
mercaptans distinguishable in part from compounds of the instant invention
in having the nitrogen interposed between carbonyl and phenyl rather
than between carbonyl and alkyl.
Benzamicloethyl mercaptan is a known compound, A.A. Goldberg
et al., J. Chem. Soc. 1948, 1919-26, but there has been no disclosure
of mucolytic activity.
The compounds of the present invention are novel benzamido-
alkyl mercaptans illustrated generally by the followin~ formula:
o
,~ C-NH-alk-SH
( )~ Formula I
wherein;
R is selected from hydrogen, halogen, lower-alkyl, lower-alkoxy,
amino, carboxy or trifluoromethyl,
-alk- is a straight or branched divalent alkylene radical of
2 to 4 carbon atoms, and
n is 1 to 3, and when n is more than 1, R may be the same or
different in various positions relative to one another on the ring,
..~; .
the compound wherein R is hydrogen, n is three and -alk- is -CH2-CH2-
being excluded since this is a known compound.
The compounds have mucolytic activity and are useful in d;ssolviny
and diluting mucus in warm-blooded animals exhibiting or su~ferlng -From
lung congestions.
In another aspect, the present invention provides a method of
preparing the benzamidoalkyl mercaptans defined above, said method comprising
either:
~ a) reacting a salt of the formula:
S -alk -NH2 o HX
(R)n
with alkali, wherein R, n and alk are as defined above and X is halogen or
(b) reacting an isothiouronium salt of the formula:
~ ~ C - NH - alk - S - C - NH2 ? HX
(R)n
with alkali wherein R, n, alk and X are defined above; or
(c) reacting an acid of the formula
COOH
(R)n
with a compound of the formula
HS - alk - NH2 . HX
where R, n, alk and X are as defined above with pyridine and phosphorus
trichloride.
813~
The compounds described hereinafter and represented by the
foregoing Formula I have been shown by a modification of the method of
S.J. Corne et al., J. Phys. 242, 116 (1974) as described hereinbelow to
have mucolytic activity in animals.
Compounds For which mucolytic activity was found to be of
the same order of magnitude as N-acetyl-L-cysteine on rat stomach mucus
are the preferred compounds which are as follows:
(1) 4-chlorobenzamido-ethylmercaptan
(2) 4-methylbenzamido-ethylmercaptan
(3) 4-methoxybenzamido-ethylmercaptan
The method used to establish mucolytic activity in compounds of
the present invention is as follows: Female
- 2a -
~2~
Sprague-Dawley (charles River Labs) 1~0-180 g. rats are
fasted 16 hours on wireJ housed two animals per cage. To
minimize coprophagia, the lights are left on during the
fast. Two cc. of water are given orally to each rat to
minimize internal debris. Thirty minutes later the rats
are sacrificed by cervical dislocation. The stoma~hs are
removed, trimmed of excess tissue and the epithelial
portion discarded. The glandular portion is cut suffi-
ciently along the greater and lesser curvature to cause
eversion of the stomacn before placing it in the drug
solution. Stomachs with a fecal odor or containing
visible-fecal matter are discarded. Stomachs ;are placed
in 10 cc. of solution (50% PEG-300-H20) containing 2.5 mg.
test compound/ml. for 40 minutes. After drug treatment
the stomachs are placed in 10 cc. Alcian Blue (Solution 1)
for 90 minutes where the dye complexes with the stomach
mucus. After two successive 10-minute washes in 10 cc.
o~ 0.25 M. sucrose (Solution 2), the stomachs are placed
in 10 cc. of 0.5 MgCl2 (Solution 3) for one hour to remove
the complexed dye. The MgCl2 supernatant is shaken with
10 cc. diethyl ether in a 60 cc. separatory funnel to
remove lip*ids. The aqueous phase is drained into a
Spectronic 20 Tube and th*e percent transmission is read
at 605 m~ in a Spectronic 20 Spectrophotometer. The per-
cent transmission is converted to ~g/ml of Alcian Blue
from a standard curve (P. Whiteman, Biochem~ J. 131, 351-57
~1973). Each drug or drug vehicle (control) is tested on
three stomachs. Mean differences between treated and
control values are expressed as percentages.
Solution 1 Alcian Blue, 0.05% w/v (1 liter)
54.8 g. sucrose (0.15 M)
6.8 g. sodium acetate
900. cc. deionized water
Dissolve with a magnetic stirrer and adjust to pH 5.8.
Add 500 mg. Alcian Blue 8GN (MathesonJ Coleman & Bell
~8E13). Fill to one liter in a volumetric flask. Refrig-
erate. Use only for one week.
* Trade Mark
~lZ98E3~
Solution 2 - Sucrose, 0.25 M (1 liter)
Add 85.6 g. of sucrose to 1 liter volumetric flask. Fill to
volume with cleionized water. Use only for one week.
Solution 3 - Magnesium Chloride. 0.5 M (1 liter)
Qdd 101.7 g. MgC12r6H20 (A.C.S.) to a one liter volumetric
flask. Fill to volume with deionized water.
Therefore, the present invention is directed to providing
certain novel benzamidoalkyl mercaptans having mucolytic activity in a
warm-blooded animal and to using them in combating mucus in an animal
suffering from or exhibiting lung congestion.
The compounds may be used in the form of nov~-l pharmaceutical
compositions for combating mucus in warm-blooded animals.
Advantages of the present invention will be apparent to one
skilled in the art and still others will become apparent from the following
description of the best mode of carrying out the present invention and
from the appended claims.
In the definition of the symbols and in Formula I given above
and where they appear elsewhere throughout the claims and specification
hereof, the terms have the following significance.
The "lower-alkyl" and "lower-alkoxy" substituents each have
from one to four carbon atoms which can be arranged as straight or
branched chains. Examples are methyl, ethyl, propyl, butyl, methoxy,
ethoxy, propoxy, and butoxy.
~(R)n refers to 1 to 3 substituents of R in various available
positions on the phenyl nucleus and when more than one substituent is
present, may be the same or different and may be in various position
combinations relative to each other.
- ~Lz~
The term "alk" represents a selection from among
ethylene (-CH2CH2-) J propylene (-CH2CH2CH2-),
lJ2-propylene (-ICHCH2-), 2J3-butylene (-~H -CH-).
CH3 CH3 C~3
Methods of Preparation
The mercaptans of the present invention are prepared
by one of three known methods as represented by the
following equations.
METHOD (1) Via carbothioic acid ester acid salts
(R)n C-Cl + HS-alk-NH2~HCl
O O
(R)n C S-alk-NH2 HCl ~ ~ C-NH-alk-SH
METHOD (2) Via isothiouronium salts
(.R)n ~ C-Cl + ~E~-alk-cl ---~ ~ (R)n
O S
(R)n C-NH-alk-Cl + NH2-C-NH2
O NH
(R)n ~ C-NH-alk-S-C-NH2~HCl
3 KOH ~ C-NH-alk-SH
H20 ( R~n,
38~
MæTHOD (3)
PCl3
~ COOH + HS-alk-~H2~HCl Pyridine
(R ~
O
C-~H-alk-SH
( R)n
Description of preparation of intermediates in Method (1)
follows.
2~
Preparation
Benzenecarbothioic Acid, 2-Aminoeth~,rl Ester, Mono-
hydrochloride.
A mixture of benzoylchloride, 15 ml~ (ca 0.13 mole)
and 2-aminoethanethiol hydrochloride, 4.54 g. (0.04 mole)
5 was heated (protected from moisture) over a stream jet for
2 hours. Slight cooling produced a mass of crystals.
After trituration with 60-110C. ligroine filtration and
drying, the crystals melted at 177-180C. Several
recrystallizations from anhydrous ethanol produced a
10 colorless solid which melted at 178.5-lfg.5C. Nuclear
Magnetic Resonance (NMR), Mass Spectrophotometer (MS), and
Infra Red (IR) analyses all supported structure of the
title compound. Yield was 5.1 g (59.1%).
Analysis:Calculated for CgHl2ClNOS: C,49.65; H,5.55,
N,6.43
Found : C,49,58; H,5.59;
N,6.49
Preparation 2
4-Methylbenzenecarbothioic Acid, 2-Aminoethyl Ester
Monohydrochloride.
A mixture of freshly distilled p-toluoyl chloride,
b.p. 122C./32 mm. Hg., 30 ml. (ca 0.18 moles) and 2-amino-
ethanethiol hydrochloride, 9.68 g. (0.085 moles) was heated
(protected from moisture) over a steam jet for 2.25 hours.
A solid crystalline mass formed on completion of the
25 reaction. The mass was cru~hed and carefully triturated
wi~h warm 60-110C. ligroine, and crystal~ were separated
by filtration and washed with warm ligroine. After two
recrystallizations from anhydrous ethanol, the product,
19.07 g. (97%), melted at 206.5-208C. ~ MS and IR
30 analyses all supported the structure of the title compound.
Analysis: calculated for CloHl4NOClS C,51.83; H,6 09;
Found : C~51.57; H,~;.o6;
~,6.11
~Z~81~
Preparation ~
4-Methoxybenzenecarbothioic Ac_d, 2-Aminoethyl Ester,
Monohydrochloride.
A mixture of p-anisoyl chloride, 23 ml (ca 0.135 mole)
and 2-aminoethanethiol hydrochloride, 7.4 g (o.065 mole)
was heated (protected from moisture) over a steam jet for
about 2 hours. The resultant crystalline mass was cru~hed
and carefully triturated with warm 60-110C. ligroine and
crystals were separated by filtration and washed with warm
ligroine. After two recrystallizations from anhydrous
~thanol~ the product, 14.6 g (90.6~ melt~d at 191.5-193 C.
NMR, ~ and IR analyses all supported the structure of the
title compound.
Analysis: calculated for CloHl4ClN04S: C,48.48; H,5.69;
N,5-65
Found : C,48.42, H,5.73;
~,5.66
Preparation 4
When in the procedure of Preparation 1, benzoyl
chloride is replaced by equal molar amounts of
3,4 J 5-trimethoxybenzoyl chloride,
3-trifluoromethylbenzoyl chloride,
3,4-dimethylbenzoyl chloride,
4-carboxybenzoyl chloride,
there are obtained
3J4,5-trimethoxybenzenecarbothioic acid, 2-amino-
ethyl ester, hydrochloride,
3-trifluoromethylbenzenecarbothioic acid, 2-amino-
ethyl ester, hydrochloride,
3,4-dimethylbenzenecarbothioic acid, 2-aminoethyl
ester, hydrochloride,
4-carboxybenzenecarbothioic acid, 2-aminoethyl
ester hydrochloride.
Preparation 5
When in the procedure of Preparation 1, 2-amino-
ethanethiol hydrochloride is replaced by equal molar
amounts of 3~aminopropanethiol hydrochloride, there is
obtained
9~
Benzenecarbothioic acid-~-aminopropylester hydro-
chloride.
Preparation 6
When in the procedure of Preparation l, ~-amino-
ethanethiol hydrochloride is replaced by equal molar
amounts of 3-aminopropanethiol hydrochloride and benzoyl
chloride is replaced by
p-toluoyl chloride J or
p-anisoyl chloride
there are obtained
4-methylbenzenecarbothioic acid, 3-aminopropyl
ester, hydrochloride,
4-methoxybenzenecarbothioic acid, 3-aminopropyl
ester, hydrochloride.
The following examples of preparation of compounds
are only intended to illustrate the present invention
and are not to be construed as limiting the invention in
any respect.
88~L
Example l
4-Chlorobenzamido-ethylmercaptan.
To a ~olution of 2-aminoethanethiOl hydrochloriae
22.7 g. (0.02 mole) in ~00 ml. of dry pyridine was ~dded
with stirring, phosphorus trichloride, 1~.7 g. (0.1 m~le3
in 50 ml. dry pyridine. Slight exothermic reaction was
noted. After ~tirring an additional ~0 min., p-chlorobenzoic
acid, 31.2 g. (0.2 mole) in lO0 ml. of dry pyridine was added.
The reaction mixture was heated to reflux for 4 hrs, cool~d
and poured onto 400 g. of ice. The reaction mix~ure was
extracted 4 times with 100 ml. portions of methylene ~hloride.
The combined 2xtract was wa~hed twice with 200 ml. ice
water, 4 times with lO0 ml. of 5~ sodium carbonate and twice
more with 200 ml. of ice water~ After drying over magnesium
~ulfate, the washed extract was concentrated by evaporation
to a cream colored oil which solidified on ~tanding. The
601id was 6tirred in warm water, filtered and the residue
washed twice with 200 ml. water and air dried to give 29 g.
of crude material~ ~he crude was dissolved in 400 ml. Df
methanol and 200 ml. of 10% 60dium carbonate ~olution added.
The solution was filtered and cooled overnight in a refrig-
erator. Tan a rphous material was filtered off and
discarded. Volume of ~he ~iltered solution was adjusted to
1 liter. The solution wa~ allowed to ~tand at 0 C. for
96 hrs. and the precipitate was collected by filtration and
dried. Yield o~ off-white product which melted at 73-78 C.
was 5 g. (15%).
Analysis: calculated for C~HloClNOS: C~50.12; ~,4.67; ~,6.49
Found : C,50.00, H,4.63; ~J6>5
Example 2
~0 When in the procedure ~ Example 1, 4-chlorobenzoic
acid is replaced by equal molar amounts of the following:
4-~luorobenzoic acid,
4-bromobenzoic acid,
2-chlorobenzoic acid, and
~5 3,4,5-trichlorobenzoic acid,
there are obtained
~z~
4-fluorobenzamido-ethylmercaptan
4-bromobenzamido-ethylmercaptan
- 2-chlorobenzamido-ethylmercaPtan, ~nd
3,4,5-trichlorobenzamido-ethylmercaptan.
4-Chlorobenzamido-proPylmercaptan.
~hen in the procedure vf Example 1, 2~mîn~propan~-
thiol hydrochloride is ~ubstituted $or 2-amin~e~hanethl~l
in ~qual ~olar amounts, the title compound is ~btained.
~
When in the pr~cedure oi Example 2, 2-aminopropane-
thiol hydrochloride is eubstituted for 2-amin~ethane~hi~l
hydrochloride in equal m~lar amount, there are obtain~d:
4-fluorobenzamido-propylmercaptan
4-bromobenzamido-propylmercaptan
2-chlorobenzamido-propylmercapt~n, and
~,4,5-trichlorobenzamido-propy}mercaptan~
Example 5
(a) Isothiouronium_Salt of N-(2-mercaptoethyl)benzamide.
A mixture of ~-(2-chloroethyl)benzamide, 18.~ g.
(0.10 mole) and thioureaJ 9.1 g. (0.12 mole) in 120 ml.
anhydrous ethanol were refluxed under nitrogen, excluding
moisture, overnight. Solvent was removed by distillation
and the resulting isothiouronium hydrochloride salt of
N-(2-mercaptoethyl)benzamideJ 25.2 g. (94.7%)J melted at
169-173C.
(b) Benzamido-ethylmercaptan.
The product of (a) was added to 300 ml. solution
of potassium hydroxide (2 moles) and warmed at about 90 C0
for 2-3 hours. The solution was cooledJ washed with ether
and acidified to p~ 3. The resultant turbid solution was
extracted with several portions of chloroform and the
combined extracts dried over magnesium sulfate. T~e
solution was evaporated under reduced pressure to give a
light syrup which was then diluted while warmed with 6~
110C. ligroine. The solid obtained was recrystallized
13LZ~
12
from benzene-ligroine to yield a colorless, crystalline
solid melting 62.5~65.5C. which weighed 13.1 g. (42.30 .
Analysis: Calculated for CgHllNOS: C,59.62; H,6.11; ~J7.7~
Found : C,59.50; H,5-98; N,7-59
Example 6
4-Methylbenzamido-ethylmercaptan.
To a solution of potassium hydroxide, 6.2 g. (0.11
mole) in 200 ml. of oxygen-free water was added in one
portion 4-methylbenzenecarbothioic acid, 2-aminoethyl
ester monohydrochloride, 12.0 g. (0.052 mole). Nitrogen
was bubbled through the suspension which was maintained
at reflux temperature for 1.5 hours. A small amount of
insoluble material was filtered off and discarded. The
alkaline filtrate was extracted with chloroform. The
aqueous alkaline solution was then acidified with conc.
hydrochloric acid and again extracted with chloroform.
The chloroform extracts were combined and dried and con-
centrated to a thin syrup. Addition of 60-110 C. ligroi~e
caused precipitation of crystalline solid, 9.31 g.,
melting at 110-113C. Yield of product after a single
recrystallization from benzene-ligroine (1:5) was 7.41 g.
(76.3%), melting at 112.5-114C.
Analysis: Calculated for CloHl3S~0: C,61.50; H,6.71;
~,7-17
Found : C,61.~4; H,6.65;
N,7.16
Example 7
4-Methoxybenzamido-ethyl Mercaptan.
To a solution of potassium hydroxide, 5.6 g. (0.10
mole) in 170 ml. of oxygen-free water under a nitrogen
atmosphere was added 4-methoxybenzenecarbothioic acid,
2-aminoethyl ester, monohydrochloride, 7.01 g. (0.0283
mole). The temperature was raised to and held at reflux
for 1.5 hr. Tetrahydrofuran, 30 ml. was added during the
~ast 30 minutes to effect full solution. After cooling,
the solution was extracted while alkaline with chloroform,
then acidified and extracted again. The extracts were
~L~2988~
combined, dried, concentrated and then diluted with
ligroine. The solid obtained was recrystallized from
benzene 60-110C. ligroine. The yield was 3.97 g~ (57.7%
based 2-aminoethanethiol hydrochloride), melting at
107-1~8~5oc~
Analysis Calculated for CloHl3N02S: C,56.85; Hl6.20;
N,6.63
Found ~ C,56.90; H,6.16;
N,6.64
Example 8
When in the procedure of Example 7, 4-methoxybenze~e-
carbothioic acid, 2-aminoethyl ester, monohydrochloride
is replaced by equal molar quantities by the following:
3,4,5-trimethoxybenzenecarbothioic acid, 2-amino-
ethyl ester, hydrochloride,
~-trifluoromethylbenzenecarbothioic acid, 2-amino-
ethyl ester, hydrochloride,
3,4-dimethylbenzenecarbothioic acid, 2-aminoethyl
ester, hydrochloride,
4-carboxybenzoylcarbothioic acid, 2-aminoethyl ester
hydrochloride,
there are obtained
3,4,5-trimethoxybanzamido-ethylmercaptan,
3-trifluoromethylbenzamido-ethylmercaptan,
3,4-dimethylbenzamido-ethylmercaptan,
4-carboxybenzamido-ethylmercaptan.
Example ~
When in the procedure of Example 7, 4-methoxybenzene-
carbothioic acid, 2-aminoethyl ester monohydrochloride is
replaced by equal molar amounts of
benzenecarbothioic acid-3-aminopropyl ester
hydrochloride,
4-methylbenzenecarbothioic acid, 3-aminopropyl
ester, hydrochloride, or
4-methoxybenzenecarbothioic acid, 3-aminopropyl
~5 ester, hydrochloride,
9~
14
there are obtained
benzamido-propyl mercaptan,
4-methylbenzamido-propyl mercaptan,
4-methoxybenzamido-propyl mercaptan.
` Example 10
(a) Isothiouronium Salt of N-~2-mercaptoethYl)-4-
aminobenzamide.
When in the procedure of Example 5(a).N-(2-chloro-
ethyl)4-aminobenzamide is substituted in equal molar amount
for N-(2-chloroethyl)benzamide, the title compound is
obtained.
(b) 4-Aminobenzamide-ethylmercapt n.
When in the procedure of Example 5(b)the
isothiouronium salt of N-(2-mercaptoethyl)-4-aminobenzamide
is substituted for isothiouronium salt of ~-(2-mercapto-
ethyl)benzamide in equal molar amount, 4-aminobenzamide-
ethyl-mercaptan is obtained.
8~
The pharmaceutical compositions of this invention
comprise halobenzamidoethyl (and propyl) mercaptans in
an amount sufficient to provide effective action against
lung congestion in mammalian subjects when applied
topically as an inhalant together with an acceptable
carrier therefor.
The compounds of Formula I are administer~d in an
amount sufficient to induce liquefaction of mucus in the
respiratory tract of warm-blooded animals in need thereof.
Intratracheal administration of the compounds of Formula I
are effected by various inhalation or instillation means
such as nose drops~ sprays, aerosols and the like.
Examples of pharmaceutically acceptable liquid carriers
are water and polyethyleneglycol-300. Another suitable
means of administration is by insufflation of micronized
particles or ultra-fine powder utilizing only the energy
of the inspiratory action or by use of aerosol propellants.
Generally, the amount of the compound in the inhalant
composition will vary from about 0.5 to 50 weight ~.
Solutions or suspensions having about 0.5 to 20~ by weight,
preferably 5-10 wt. ~, of the mucolytic agent of Formula I
are suitable for application by spraying with an atomizer,
nebulizer, aerosol and the like. Dusts containing about
25-75~ or more active agent in micronized form are also
suitable, about 50~ being preferable.
It will be readily apparent to those skilled in the
medical arts that the correct dosage of a compound to be
employed with any particular mammalian subject is determine
by the severity of the condition requiring mucolytic therapyJ
as well as the age, sex, weight and general physical
condition of the subject. Individual doses ranging from
5-100 mg for inhalation by man are suitable and may be
required for the mucolytic effect.
The pharmaceutical compositions may take the form of
dilution of the micronized compounds in dust~ or solutions
and suspensions in liquids suitably dispensed for inhalation.
16
A. owder for Administration via Inhaler Device.
4-chlorobenzamido ethyl mercaptan of Example 1,
micronized 2.5 g.
Lactose powder 2.5 g.
The powders are blended aseptically and filled into hard
gelatin capsules each containing 50 mg o the mixture.
This is suitable for dispersion into the inspired breath
by means of a breath-operated inhalex device containing
means for rupture of the capsule wall prior to dosing.
Various modifications and equivalents will be apparent
to one skilled in the art and may be made in the compounds,
compositions and methods of the present :Lnvention without
departing from the spirit and scope thereof, and it is
therefore understood that the invention is to be limited
only by the scope of the appended claims.
