(+)-(lS,2R)-2-[[N-(2-hydroxyIamino-2-oxoethyI)-N-methyl-a ιnino]carbonyI]cyclohexaπ e-1 -carboxylic acid, process for their preparation and pharmaceutical compositions containing therw

This invention refers to novel salts of

(+)-(lS,2R)-2-t[N-(2-hydroxylamino-2-oxoethyl)-N-methyl-a mino]carbonyl]cyclohexane- 1 -carboxylic acid with metal and organic bases having hypertensive activity, the process for their preparation and their use in pharmaceuticals, said salts being represented by the general formula (I)

wherein R and R\ if taken together, represent a bivalent cation selected from calcium, ethylene diamine, and other pharmaceutically acceptable cations or organic bases, or, if W = H ⁺ , R represents sodium, potassium, an imidazole group, lysine, choline, diethylamine, arginine, histidine.The

(+)-(lS,2R)-2-[[N-(2-hydroxylamino-2-oxoethyl)-N-methyl-a mino]carbonyl]cyclohexane- 1 -carboxylic acid 1, (D.C.I. Idrapril) is a compound disclosed in the European Patent Application No. 89106304.2 as a novel ACE- inhibitory agent and therefore having antihypertensive activity.

This acid, when kept exposed to the air in the normal environmental conditions of humidity and temperature, is subject to autodecomposition processes which give rise to impurities obviously incompatible with regard to a therapeutical use. Such degradation processes are also accelerated by a temperature increase of the acid kept in the above conditions. It has now been found and it is the main object of the present invention that the

novel salts according to this invention, as defined above, do not undergo to the autodecomposition and degradation processes previously mentioned. As it will be noted from the experimental data hereinafter reported, the salts of the invention, particularly if perfectly purified, are stable compounds in the normal environmental conditions. Further the salts remain unchanged with time either kept as such or included (in a solid state) in a pharmaceutical preparation (tablets, pills, capsules, lyophilized compositions and the like) provided for their therapeutical use. The utilisation of these salts in drugs allows to avoid the costly protective methods otherwise necessary to store and transform into pharmaceutical preparations the aforementioned acid.

The preparation of the compounds of the invention is based on a process characterized in that a compound, selected between

(+)-(lS,2R)-2-[[N-(2-(2-benzyl-hydroxyamino-2-oxoethyl)N- methyI-amino]carbonyl]cyclo hexane- 1 -carboxylic acid 2 and

(+)-(IS,2R)-2-[[N-(2-hydroxyIamino-2-oxoethyl)-N-methylam ϊno]carbonyllcyclohexane-l -carboxylic acid 1, is reacted with a compound selected among hydrates and carbonates or other suitable salts of alkaline and alkaline-earth metals, as defined in the present invention, as well as with organic bases, in an organic solvent or mixtures thereof with water, the reaction taking place, in the case of the starting product 2, contemporaneous hydrogenalysis of the protecting benzyl group with hydrogen at atmospheric pressure, in the presence of a suitable hydrogenation catalyst, the process being completed by isolating the desired salt of the acid. The following synthesis schemes illustrate the process of the present invention

r <*ι»

where Q is said hydroxide, or alkaline salt or calcium salt or an organic base.

In the as above defined process, the preferred hydrogenation catalyst is charcoal-supported Pd, but PtO _j ^h/A O, and Ni-Raney can also be used.

As to the organic solvent, propanol, tetrahydrofuran and dioxane are also suitable besides methanol and ethanol.

The following examples, that only illustrate and do not limit the scope of the invention, explain the specific aspects and the chemical-physical properties of the compounds of the invention.

EXAMPLE 1

(+)-(lS,2R)-2-[[N-(2-hydroxylamino-2-oxoethyl)-N-methyl-a mino]carbonyl]cyclohexane-

1 -carboxylic acid calcium salt.

To a vigorously stirred suspension of 15.2 g calcium hydroxide in water (152 ml), was added under nitrogen, a solution of 75 g of

(+)-(lS,2R)-2-I[N-2-benzylhydroxyamino-2-oxoethyl)N-methy Iamino]carbonyl]cylcohexan e-I -carboxylic acid 2, dissolved in methanol (1150 ml) and stirring continued for 20 minutes under nitrogen at 20°C.

After an addition of 15 g 10% Pd/Charcoal suspended in 152 ml water, hydrogenation of the product at 20°C with an initial H ₂ pressure of 1 Atm, is carried out for 3 hours.

Once the hydrogen absorption ceased (about 5000 ml absorbed), the catalyst was filtered and washed with awater/methanol (1/1) mixture (300 ml) and the filtrate, combined with the washings, concentrated under vacuum at 40°C until all the methanol has been removed.

The suspension thus obtained was treated twice with 200 ml methanol, removing thereafter, still under vacuum at 40°C, all the solvent.

The final suspension was cooled for 20 hours at 0-4°C and the precipitate was filtered and washed on the filter with 70 ml precooled water at 0-4°C.

55 g of (3) (yield 85%) as an ivory solid, having the following chemical-physical characteristics, were obtained:

Melting point > 250°C

H>° = + 35.3° (c=I, H ₂ 0)

Heavy metals < 30 ppm

Sulphuric ashes = 40.6% (on the product as obtained)

Ca (EDTA) = 11.7%

K.F. = 7.8%

Ethanol = 400 ppm

TLC: Stationary phase Merck F254 silicagel plates Mobile phase nBuOH/AcOH/H _j O = 6/2/2 Unitary spot at Rf = 0.7 HPLC : Nucleosil Column C- ₃ 5 j (250x4.6)

Eluent CH ₃ CN/H ₃ P0 ₄ 0.1% = 20/80

Flow rate 0.8 ml/min.

Wave lenght = 214 nm.

Injection of 20 ml 0.01% CH ₃ CN/H ₂ 0 solution ■= 20/80

The chiral purity of the product is assayed by HPLC on chiral column:

Kiral column AGP

Eluent CH ₃ CN/buffer at pH = 4.1 = 1/99

Flow 0.7 ml/min

Wave lenght «= 214 nm

Injection 20 y. of 0.01% CH ₃ CN/H ₂ 0 solution = 1/99

Chemical purity:total impurities = 0.5%

Optical purity > 98% EXAMPLE 2

(+)-(lS,2R)-2-[[N-(2-hydroxylamino-2-oxoethyl)-N-methylam ino]carbonyl]cyclohexane-l -carboxylic acid - calcium salt.

To a suspension of 15.2 g calcium hydroxide in 1500 ml water, under vigorous stirring and nitrogen flow, 50 g of

(+)-(lS,2R)-2-[[N-(2-hydroxylamino-2-oxoethyI)-N-methylam ino}carbonyl]cyclohexane-l -carboxylic acid 1 were added and the mixture was further vigorously stirred for 60 minutes at 20°C.

The light suspension thus obtained was filtered (on paper) and the filtrate was concentrated under vacuum at 40°C to 200 mL.

After cooling at 0-4°C for 24 hours, the precipitated product was filtered and washed on filter with 50 mL of precooled water at 0-4°C.

48.2 g of 3 (yield 84%) were obtained as ivory solid with the following characteristic: Melting point > 250°C

M>° - +34.8° (c=l, H ₂ 0)

Ca (EDTA) ^•* -= 10.1% (on the product as obtained)

K.F. = 9.04%

TLC Stationary phase Merck F254 silicagel plates Mobile phase nBuOH/AcOH/H ₂ 0= 6/2/2 Unitary spot HPLC: Analytical and chiral chromatography was carried out in conditions set forth in Example 1.

Chemical purity: total impurities - 1.0% Optical purity > 98% EXAMPLE 3

(+)-(lS,2R)-2-{[N-(2-hydroxylamino-2-oxoethyl)-N-methylam inolcarbonyIlcyclohexane-l -carboxylic acid sodium salt.

70 g of 2 were added, at 20°C under stirring, to 7.6 g sodium hydroxide dissolved in 95% ethanol (1050 mL).

This solution was added with 7g of 10% Pd charcoal suspended in 35 mL water under nitrogen and hydrogenated at 20°C with an initial H ₂ pressure of 1 Atm, for 3 hours.

Once the hydrogen absorption ceased (4850 mL absorbed), the catalyst was filtered and washed twice with 95% ethanol (150 mL).

The filtrate combined with the washings was evaporated under vacuum at 30°C to small volume. The residue was added twice with 200 mL acetone and again concentrated to small volume, then diluted with acetone (200 mL9 and the precipitated product was filtered and washed on filter with acetone (100 mL). 56 g of 4, were obtained as hygroscopic, white solid, with the following chemical-physical characteristics: Heavy metals < 20 ppm

Sulphuric ashes = 19% (on the product as obtained) J. = 2.5% Ethanol « 1.1% Acetone = ^* 5.8% TLC: Stationary phase Merck F254 silicagel plates

Mobile phase nBuOH/AcOH/H ₂ 0 = 6/2/2

Unitary spot R.f. = 0.7 HPLC: Analytical and chiral chromatography was carried out in the conditions set forth in Example 1. Chemical purity: total impurities = 2.0 %

Optical purity > 95%

EXAMPLE 4

(+)-(lS,2R)-2-[[N-(2-hydroxylamino-2-oxoethyl)-N-methylam ino]carbonyl]cyclohexane-l

-carboxylic acid L-lysine salt.

21 g lysine dissolved in water (38 mL) were added, under stirring, to a solution of

2 in 95% ethanol (725 mL).

Under nitrogen, this solution was added with 5g 10% Pd/Charcoal and hydrogenated at 20°C witt an initial H ₂ pressure of 1 Atm, for 3 hours.

Once the hydrogen absorption ceased (3600 mL H ₂ absorbed) the catalyst was filtered on paper and washed twice with absolute ethanol (150 mL).

The filtrate combined with the washings was concentrated to dryness under vacuum at 30°C and the residue was added twice with acetone (200 mL), thereafter removing the volatile portion under vacuum.

The resulting residue was added with acetone (200 mL) was filtered and washed on filter with acetone (100 mL).

49 g of 5 were obtained as hygroscopic, white solid.

HPLC analysis was effected in the conditions of Example 1: Impurities = 4% total

EXAMPLE 5

(+)-(lS,2R)-2-[[N-(2-hydroxylamino-2-oxoethyl)-N-methylam ino}carbonyl]cyclohexane-l

-carboxylic acid - potassium salt.

Following the same method as in example 4 with appropriate changings of reactants, a highly hygroscopic, white solid, with the following chemical-physical characteristics, was obtained:

TLC: Stationary phase Merck F254 silicagel plates

Mobile phase nBuOH/AcOH/H ₂ 0 = 6/2/2

Unitary spot R.f. = 0.7

HPLC Analytical and chiral chromatography, was carried out in the conditions of

Example 1.

Chemical purity : total impurities = 4.0 %

Optical purity > 90%

EXAMPLE 6

(+)-(lS,2R)-2-[[N-(2-hydroxylamino-2-oxoethyl)-N-methylam ino]carbonyl]cyclohexane-l

-carboxylic acid imidazole salt.

Following the same method as in Example 4, with appropriate changings, a hygroscopic, resinous product was obtained.

HPLC analysis was effected in the conditions of Example 1: Impurities = 10%

The compound 1 and the compounds of Example 1 and 3 having been obtained in solid form, and thus weighable and characterizable from the physical viewpoint, have been tested as regards relative stability at 60°C in air, in accordance with the following method.

2 g of substance are placed in a thermostatic stove at 60°C and, at prefixed times, a HPLC analysis is carried out to determine both purity and possible impurities of the compound.

Apparatus: Waters 600E Multisolvent delivery systemn

Tunable absorbance detector Waters 484 Injection loop 20 ji Integrato Waters 745 Data Module Nucleosil Column C- _g 5 ji (250 x 4.6) Mobile Phase Ch ₃ CN/H ₃ P0 ₄ 0.01%=20/80 Flow rate 0.9 ml/min. Detectoπ Wave length = 214 nm Sample preparation: Dissolve 20 mg of sample substance in 100 ml H ₂ 0/CH ₃ CN 80/20

20 jx injection

Retention time, under these conditions, is r.t. « 7.9 min.

Table 1 shows the results, and in the first column, the data for the acid 1, tested in the same way, are reported.

* Melted sample

10

The salts of the invention are also, within the suitable dosage ratios, practically comparable either for potency and for the activity lasting time to the acid 1. Such pharmacological equivalence has been experimentally demonstrated by comparing acid (1) with the calcium salt of Example 1 as shown by the experimental results listed in Table 2.

TABLE 2

The salts of this invention constitute the active ingredients for preparing pharmaceutical compositions both for oral and parenteral use.

Such compositions and preparations are made with the well-known pharmaceutical techniques and employing conventional excipients, carriers and solvents.

As regards the oral administration, dosages of from 25 to 150 mgs/day, and from

2.5-25 mgs/day for parenteral administration, are envisaged respectively.