The present invention relates to novel pharmacologically active mercapto-acetamide derivatives, more particularly to derivatives of N-(2-mercaptoacetyl) homocysteine, both in its cyclized v-thiolactonic form or in the open chain form, to the processes for their preparation and to the pharmaceutical compositions containing them. The new compounds have free-radical scavenging activity preventing cellular damage from toxic metabolites of oxygen such as superoxide radical, hydrogen peroxide and singlet oxygen.

The new compounds also have an in vivo local antiinflammatory activity as well as a mucolytic and mucokinetic activity. They can therefore be useful in the treatment of chronic and acute bronchitis, in the treatment of poisoning and in other pathologies due to the action of toxic free radicals.

More particularly, it is an object of the present invention to. provide mercaptoacetamide derivatives of formula (I):

wherein:

- R represents a hydrogen atom, a C _j _ ₃ alkyl, a C ₇ _ ₉ aralkyl or a group COR _j in which R _j is a C _j _ ₃ alkyl or a C ₇ _^ aralkyl, the aralkyl groups being unsubstituted or substituted on the phenyl ring by one or more halogens, C. _ ₃ alkyl or ^_- alkoxy;

- L is hydrogen

- Q is hydroxy

- or L and Q, together, form a bond, and physiological acceptable solvates, inclusion complexes and, when L is hydrogen and Q is hydroxy, physiological acceptable salts of said mercapto-acetamide derivates.

The compounds of formula (I) may exist as physiologically acceptable solvates, such as hydrates or inclusion complexes, for example with cyclodextrins which constitute a further feature of the present invention. The compounds of formula (I) according to the present invention contain a chiral centre. The present invention includes in its scope both the individual isomers and the mixtures thereof.

The compounds of formula (I) in which L is hydrogen and Q is hydroxyl are carboxylic acids and can exist also as salts with inorganic ions such as sodium, potassium, magnesium or aluminum, with organic ions such as quaternary ammonium compounds, or with organic bases such as, for instance, triethanolamine or tromethamine.

The compounds of general formula (I) of the present invention are prepared by a process which comprises reacting homocysteine- γ -thiolactone of formula (II):

with a functional derivative of mercaptoacetic acid of formula (III):

R-S-CH ₂ -COOH (III)

wherein R is as defined in claim 1, then when a compound of formula 1 in which

L is hydrogen and Q is hydroxyl is to be prepared, subjecting the compound thus obtained to a mild alkaline hydrolysis and optionally converting the compound thus obtained in one of its physiologically acceptable salts.

As functional derivatives of the acids of formula (III) and (IV) any compound capable of reacting with a free amino or mercapto group can be used, such as the acid chloride, the anhydride, a mixed anhydride, an active ester, such as the p-nitrophenylester, or the acid itself, duly activated with, for example, dicyclohexylcarbodiimide.

The reactions are carried out in an aprotic solvent such as toluene, acetonitrile, tetrahydrofurane, methylene chloride, 1,1-dichloroethane, chloroform or dimethylformamide at a temperature ranging from O ⁰ to 100°C, preferably at room temperature, between 20° and 30°C when the action of the amine (II) with the functional derivative of the acid (III) is to be performed, or between 40° and 70°C when the compound of formula (I), wherein R is hydrogen, is reacted with a functional derivative of the acid of formula (IV).

When the acid chloride is used as a functional derivative of the acids of formula

(III) or (IV), it is advantageous to carry out the condensation in the presence of an

acid acceptor such as sodium hydrogencarbonate or thiethylamine. The transformation of the cyclic compound thus obtained (formula I, where L and Q, together, form a bond) is carried out by mild hydrolysis in basic conditions using, for example, sodium hydrogen carbonate, sodium or potassium carbonate or sodium or potassium hydroxide. The reaction is carried out in alcohols like methanol, ethanol or isopropanol, or in water or in mixture of water with water miscible solvents like alcohols, acetone, acetonitrile, at temperatures ranging from 0°C to 100°C, preferably from 0°C to 25°C.

Compounds of formula II obtained by this method are in the form of salts: the free acid form can be isolated by conventional methods, such as, for instance, acid-base extraction or ion-exchange resins.

The new compounds of the present invention possess interesting pharmacological properties and are useful as active ingredients for pharmaceutical compositions. More particularly, the mercaptoacetamides of the present invention have shown a good free radical scavenging activity in the test of intoxication by paraquat in mice. Swiss female mice weighing 18-20 g, treated orally with the compounds under examination, are intoxicated, one hour after this administration, with 50 mg/kg of paraquat by intraperitoneal route. The animals are then observed for a week and deaths reported daily. In this test, the compounds of the present invention have shown a good scavenging activity, even superior to that of glutathione.

Moreover, the compounds of the present invention have good antiinflammatory activity. In the test of the carrageenin induced edema in rat paw they are as active as acetylsalicylic acid at the oral doese of 300 mg/kg. The compounds of the present invention also possess a good mucolytic activity as shown in the test of the bronchitis induced in rabbit by exposure to a sulfuric acid aerosol according to Cantorelli et al. - il Farmaco - Ed. Prat. 1979, 34, page 393. More particularly, compounds 1 and 4 to 7, administered, at an oral dose of 300 mg/kg, produced a percent lowering of mucus viscosity significantly greater than that of N-acetylcysteine administered at 400 mg/kg.

The compounds of the present invention have a very low toxicity, largely compatible with their use as medicaments presented in form of pharmaceutical compositions. According to a further feature of the present invention there are provided pharmaceutical compositions comprising as active ingredient at least one compound of formula (I) as hereinbefore defined or a physiologically compatible solvate or salt thereof in association with pharmaceutical carriers or excipients. For pharmaceutical administration the compounds of the present invention may be incorporated into the

conventional pharmaceutical preparations in either solid or liquid form. The composition may, for example, be presented in a form suitable for oral, rectal or aerosol administration. Preferred forms include tablets, coated tablets, capsules, sachets containing powder for oral administration, syrups, dry syrups, vials for aerosol. The active ingredient may be incorporated in excipients or carrier conventionally used in pharmaceutical compositions. Each dosage unit may conveniently contain from 50 mg to 1000 mg and preferably to 100 mg to 500 mg of the above ingredient. The following examples illustrate some of the new compounds according to the present invention: these examples are not to be in any way considered limitative of the scope of the invention itself. EXAMPLE I

N-r2-mβrcaaptoacetvn-2-oxo-3-aminotetrahvdro tiophenβ fComoound 1) To a solution of 15 g homocysteine-tiolactone in tetrahydrofurane (THF) (130 ml) dicyclohexylcarbodiimide (DCC) (26,4 g)and thioglycolic acid (11.8 g) were added. The mixture was stirred for 26 hours at room temperatur. The white precipitate was filtered off, the solvent was evaporated and the residue was purified by column cromatography (silicagel, methylene chloride/Methanol 99:1), obtained 14 g of the desired product. M.p. 70-72°C Analysis

CgH NO- _j S _j Calc.% C 37.67 H 4.74 N 7.32

Found.% C 37.70 H 4.71 N 7.29 According to the procedure above described, starting from homocysteine-^-thiolactone and, respectively, ethylthioacetic acid and benzylthioacetic acid, the following compounds were prepared.

N-(2-ethylthio) acetyl-2-oxo-3-aminotetrahvdrothiophene (Compound 2)

N-(2-benzylthio) acetyl-2-oxo-3-aminotetrahvdrothiophene (Compound 31 EXAMPLE 2

N-(2-acetyl) thioacetyl-2-oxo-3-aminotetrahvdrothiophene (Compound 4)

To a solution of compound I (3 g) in THF (20 ml) and triethylamine (2 ml) acetyl chloride (1.4 ml) was added.

The mixture was stirred for 5 min at 0°C. The solvent was evaporated and the residue purified by column chromatography (silicagel, methylene chloride/methanol

98:2) yielding 1.97 g of the title compound.

M.p. 105-108°C

Analysis

C ₈ H _I 1 0 ₃ S ₂ Calc.% C 41.18 H 4.75 N 6.00

Found.% C 41.13 H 4.78 N 5.95 According to the procedure above described, the following compounds were prepared: N-(2-ethoxycarbonvπ thioacetyl-l-oxo-3-aminotetrahvdrothiophene (Compound 5) as an oil. Analysis C _g H _j 3N0 ₄ S ₂ Calc.% C 41.05 H 4.97 N 5.32

Found.% C 40.95 H 5.03 N 5.30 N-(2-phenylacetvD thioacetyl-2-oxo-3-aminotetrahvdrothiophene (Compound 6). M.p. 98-I00°C Analysis C^H _j SNO^ Calc.% C 54.34 H 4.88 N 4.52

Found.% C 54.30 H 4.91 N 4.48

EXAMPLE 3

N-(2-mercaptoacetvn homocvsteine. sodium salt (Compound 7)

A suspension of compound 1 (3 g) in 16 ml of IN NaOH was stirred at room temperature until complete solution was obtained. Evaporation of the solvent afforded the title compound.

Method of preparation: the active ingredient, lactose and corn starch were mixed and homogeneously moistened with water. After screening of the moist mass and drying in a tray dryer, the mixture was again passed through a screen and magnesium stearate was added. The mixture was then pressed into tablets weighing 600 mg each. Each tablet contains 300 mg of active ingredient.

EXAMPLE 5

Qφsyle?

- Compound 4 300 mg

- Lactose 98 mg

- Magnesium stearate 2 mg

Method of preparation: the active ingredient was mixed with auxiliary products and the mixture was passed through a screen and mixed homogeneously in a suitable device. The resulting mixture was filled into hard gelatin capsules (400 mg per capsule). Each capsule contains 300 mg of the active ingredient. EXAMPLE 6 Suppositories

- Compound 6 300 mg

- Semisynthetic glycerides of fatty acids 900 mg

Methods of preparation: the semisynthetic glycerides of fatty acids were melted and the active ingredient was added while stirring. After cooling at the suitable temperature the mass was poured into preformed moulds for suppositories. Each suppository weighs 1200 mg and contains 300 mg of active ingredient.