NO116063B - - Google Patents

Description

Process for the production of serine derivatives.

The present invention relates to a method for the production of amino acid derivatives, namely addition salts of O-glycyl-serines with acids.

According to the invention, compounds with the general formula are produced

in which HY denotes an equivalent of a mineral acid, by allowing an N-carbobenzoxy derivative of serine to react with a haloacetyl halide or with the anhydride of a haloacetic acid so that the corresponding O-haloacetyl-N- carbobenzoxy-serine compound, allowing this halogen compound to react with a metal azide to give the corresponding O-azidoacetyl-N-carbobenzoxy-serine compound and subjecting the latter compound to reduction in the presence of at least one equivalent of a mineral acid, whereby the carbobenzoxy group is removed and the azide group is transferred to an amino group. These reactions can be shown schematically as indicated below. The formulas in this schematic presentation, as well as other formulas for compounds that can exist in optically isomeric forms, are in this description and in the claims to be understood as meaning that, unless otherwise specified, they only represent the optical Z-isomer or cZZ -form, i.e. the optically inactive form of the chemical compound in question. Unless otherwise stated, the same rule applies to the chemical names of compounds that may exist in optically isomeric forms. Thus, when the chemical name does not specify which optical isomeric form is intended, the name must be interpreted in its limited general sense, i.e. as denoting the optical Z-isomer or the dZ-racemic form.

In these formulas, R' denotes a benzyl group such as the benzyl radical itself, benzyl radicals with core substituents such as alkyl, alkoxy, carboxy, amino, nitro or similar radicals or halogen, benzyl radicals which are substituted in the side chain with alkyl and phenyl radicals and benzyl radicals which are substituted both in the side chain and in the nucleus with radicals as indicated above. HY denotes an equivalent of a mineral acid such as hydrochloric acid, hydrobromic acid, phosphoric acid, nitric acid, sulfamic acid and sulfuric acid and X denotes a halogen atom.

The reaction between the halogen acetyl halide or the halogen acetic anhydride and the N-carbobenzoxy derivative of serine is carried out in an organic solvent without hydroxyl groups at a temperature below approx. 125 C. Some of the solvents that can be used are hydrocarbons such as benzene and toluene, aliphatic esters such as ethyl acetate and butyl acetate, ethers such as dioxane and ethyl ether, aliphatic ketones such as acetone and methyl ethyl ketone and tertiary organic amines, e.g. those that will be mentioned in the following. The reaction can be carried out in the presence or absence of a basic catalyst. The preferred catalysts are tertiary organic amines such as pyridine, triethylamine, quinoline, N-ethylmorpholine, triisoamylamine and the like. When a tertiary organic amine is used as catalyst, a relatively low reaction temperature can be used, i.e. from 0-25° C. The halogen-acetyl derivatives used as starting material can be iodoacetyl, bromoacetyl or chloroacetyl compounds, in general it is preferred to use bromoacetyl and chloroacetyl derivatives.

The reaction between the O-haloacetyl-N-carbobenzoxy-serine compound and the metal azide to produce the corresponding O-azideacetyl-N-carbobenzoxy-serine compound can be carried out at temperatures between 15 and 100° C, but the preferred reaction temperatures are between 20 and 50° C. The preferred solvent for carrying out the reactions is water, organic solvents which are miscible with water, such as lower aliphatic alcohols and dioxane and mixtures of water and organic solvents which are miscible with water. Among the metal azides that can be used for the reaction are sodium azide, potassium azide, calcium azide, lithium azide and silver azide. When the O-haloacetyl-N-carbobenzoxy-serine compound used as starting material is a bromine or chlorine compound, it is advantageous to catalyze the reaction by adding to the reaction mixture small amounts of an inorganic iodide such as sodium iodide or potassium iodide.

The reduction of O-azidoacetyl-N-carbobenzoxy-serine compound to the corresponding O-glycyl-serine is carried out catalytically using gaseous hydrogen under pressure in the presence of a hydrogenation catalyst. The preferred catalysts are

noble metal catalysts such as palladium or platinum and are available either in the form of

finely divided metals or their oxides, or

such as these substances distributed on inert carriers. Some examples of the catalysts are platinum, palladium, palladium on charcoal, platinum oxide, palladium on barium sulphate, platinum black and the like. Raney nickel catalyst can also be used, but in cases where the reaction mixture contains halogen, a large excess of catalyst must be used. The reduction is carried out in the presence of at least one equivalent of a mineral acid and in a solvent at a pH value below 5.5. As a solvent, it is preferred to use water, lower aliphatic alcohols or mixtures of lower aliphatic alcohols with water. The temperature and water pressure can be varied considerably. In general, temperatures below 100° C and preferably temperatures in the vicinity of 20-35° C are used. Hydrogen pressures from 1 atmosphere to several hundred atmospheres can be used. However, high pressures are generally not necessary and satisfactory results can be obtained at pressures between one and four atmospheres.

The O-glycyl-serines in the form of free bases are unstable at PH values above about 6, consequently the product is isolated in the form of addition salts with mineral acids such as hydrochloric acid, hydrobromic acid, phosphoric acid, nitric acid, sulfamic acid and sulfuric acid.

The O-glycyl-serines can exist as both mono- and diaddition salts with acids. The terms "mono" and "di" as used here refer to the number of amino groups present in the form of a salt. Thus, the compounds (Cr,HsN204)2.H9S04 and C5HSN204.HC1 are designated monosulphate and monochlorine hydrogen salts, respectively, while the compounds C5HsN204.H2S04 and C-HSN204.2HC1 are designated disulfate and dichlorine hydrogen salts respectively. The products man. normally obtained in the method according to the invention are the monosalts, but if desired these compounds can be transferred to the di-salts during the isolation process by using an excess of strong acid and extracting the products from the solutions obtained thereby.

The addition salts of O-glycyl-serines with acids are important intermediates in the production of O-diazoacetyl-serines. The latter compounds which can be prepared from the addition salts of O-glycylserines with acids by reaction with a diazotizing agent have very valuable and unique therapeutic properties.

In the following, some embodiments of the invention are described as examples:

Example 1:

55.6 g of bromoacetyl bromide was slowly added to a suspension of 59.8 g of N-carbobenzoxy-dZ-serine in 200 cm-benzene. 75 ems ethyl acetate was added and. the mixture was heated on a steam bath until everything had dissolved. The reaction mixture was then heated to 32° C. for two hours or heated under reflux at a pressure of 30-50 mm Hg for 2 1/2 hours. The liquid was decanted from the rubbery substance that formed on the walls of the vessel and evaporated under reduced pressure until a considerable amount of white crystalline material separated. This substance was collected and the evaporation continued, whereby additional quantities of substances were obtained. This is crude N-carbobenzoxy-O-bromoacetyl-dZ-serine. It was purified by recrystallization in aqueous alcohol. The substance's melting point is 109-112° C and its constitutional formula is:

If desired, the reaction described above can be carried out in the presence of 23 g of triethylamine at a temperature of approx. 5° C.

2.26 g of sodium azide and water in an amount just sufficient to dissolve this compound were added to a solution of 5 g of N-carbobenzoxy-O-bromoacetyl-cZZ-serine in 100 cm 2 dioxane, and allowed the reaction mixture to stand for 3 days. The solvents were removed by distillation under reduced pressure and 100 cm<;> in water added to the oil obtained as a residue. The resulting solution was acidified to a pH of 2 with hydrochloric acid, whereby an oil separated. After cooling, this oil crystallized. The solid was collected and purified by recrystallization from benzene. The melting point of the product was 91—

. 92° C. The product is N-carbobenzoxy-O-azidoacetyl-dZ-serine with the formula: 4.66 cm- > 1 n hydrochloric acid (standardized) and 160 g of palladium black were added to a solution of 1.5 g of N-carbobenzoxy- O-azidoacetyl-cZZ-serine in 150 cc of 50% acetone and the resulting mixture was shaken for 3 hours with hydrogen at room temperature and under a pressure of 3 atmospheres. The catalyst was removed by filtration and the filtrate evaporated in vacuo to a volume of 10-20 cm;<->\ The residue was treated with ethanol, whereby the desired O-glycyl-dZ-serine monochlorohydrogen salt separated from the solution. This product that has the formula

was collected and dried. Its sm.p. is 173— 175° C (decomposition). If an equivalent amount of hydrobromic acid is used in this step of the method, the monobromic salt of O-glycyl-cZZ-serine is obtained as a product. Similarly, by using an equivalent amount of sulfuric acid, you will get the monosulphate.

Example 2:

7.9 g of chloroacetic anhydride in 50 cm^ of ethyl acetate was added to a suspension of 10 g of N-carbobenzoxy-cZZ-serine in 50 cm;! ethyl acetate. Two drops of concentrated sulfuric acid were added and the reaction mixture was gently heated for half an hour. It was then heated under reflux for 10 minutes, after which it was left to stand for about an hour. The ethyl acetate was removed by evaporation and the residue dried in vacuo. The residue was washed with petroleum ether and purified by recrystallization from benzene and aqueous ethanol. The product's m.p. was 120° C. This product is N-carbobenzoxy-O-chloroacetyl-cZZ-serine which has the formula:

0.762 g of sodium azide was added to a solution of 1.85 g of N-carbobenzoxy-O-chloroacetyl-dZ-serine in 25 ems of dioxane. Sufficient water was added to dissolve the sodium azide (approx. 5 cm") and the reaction mixture was allowed to stand for 8 hours at 40° C. and then 16 hours at room temperature. The solvents were removed by distillation in vacuum and the oil obtained as a residue was dissolved in 100 cc of water. The solution's pH value was adjusted to 2 with 5 N hydrochloric acid. The solution was cooled and the crystalline N-carbobenzoxy-O-azidoacetyl-dZ-serine was collected. Recrystallization in benzene gave the pure compound with m.p. 91-92° C.

250 mg of platinum oxide was suspended in 200 ems of 95 percent ethanol and reduced by shaking with gaseous hydrogen 2 g of N-carbobenzoxy-O-azidoacetyl-dZ-serine was dissolved in the mixture whereupon 6.25 cnVi of 1 N hydrochloric acid was added. The mixture was shaken at room temperature for 3 hours with hydrogen under a pressure of 2.4 atmospheres, the catalyst removed by filtration and the filtrate concentrated in vacuo to a volume of approx. 25 cm:>. Absolute ethanol was added to the residue whereby the desired O-glycyl-dZ-serine monochlorohydrogen salt separated out in crystalline form. The product was collected and dried, its m.p. is 173-175° C (decomposition).

Example 3:

24 g of bromoacetyl bromide was added to a suspension of 24 g of N-carbobenzoxy-Z-serine in 100 cm>> ethyl acetate and the mixture was cooled to 0-5° C. 12 g of triethanolamine was added dropwise, keeping the temperature at 5° C. or lower. The mixture was then allowed to slowly warm to room temperature. It was then left to stand for half an hour, filtered and the solvent evaporated from the filtrate. The oily residue which crystallized on cooling consisted of N-carbobenzoxy-O-bromoacetyl-Z-serine with m.p. 95-97° C.

The formula of this compound is:

3.4 g of sodium azide was added to a solution of 7.5 g of N-carbobenzoxy-O-bromoacetyl-Z-serine in 150 ems of purified dioxane. Sufficient water was added to dissolve the azide and the reaction mixture was kept at 40° C. for 6 hours. The solvents were removed by distillation in vacuo and the oil obtained as a residue was dissolved in 150 cm:! water. An excess of dilute hydrochloric acid was added to the aqueous solution whereby a light colored oil separated out. The mixture was allowed to cool, whereby the oil crystallized into the desired N-carbobenzoxy-O-azidoacetyl-Z-serine. This compound was collected and purified by recrystallization in • benzene. Of the connection

Of?

sm.p. is 82—84° C, [a]D = -f 33.6° C (1.92

wt. in chloroform). The formula of this compound is:

8.3 cm* of standardized 1 N hydrochloric acid and 200 mg of palladium species were added to a solution of 3 g of N-carbobenzoxy-O-azidoacetyl-Z-serine in 150 cm?> of aqueous ethanol and the mixture was shaken at room temperature with water under a pressure of 2.8—4.2 kg/cm-. After approx. After 3 hours of reaction, the vessels were vented and the catalyst removed by filtration. The solvents were distilled off from the filtrate under reduced pressure until the volume of the residue was about 35 cm>>. Absolute ethanol was added to the residue whereby the desired product separated in crystalline form. This product is the monochlorohydrogen salt of O-glycyl-Z-serine with m.p. 161.5°C

28°

(decomposition), [«1D = 10.36 (45 per cent in water.)

This compound has the formula:

Example 4:

7 g of chloroacetyl chloride were added to a solution of 12 g of N-carbobenzoxy-Z-serine in 50 cm 3 of ethyl acetate. The reaction mixture was kept at 0-15°C and 5 g of anhydrous pyridine was added dropwise to the solution. The reaction mixture was allowed to stand for one hour, after which the solvents were removed by distillation in vacuo. The residue was washed with water and petroleum ether, whereupon it was taken up in and crystallized from benzene. The obtained connection sm.p. was 77-78° C. This compound is N-carbobenzoxy-O-chloroacetyl-Z-serine having the formula: 0.9 g of sodium azide was added to 3 g of N-carbobenzoxy-O-chloroacetyl-Z-serine dissolved in 50 cm » purified dioxane. Sufficient water was added to dissolve the sodium azide and the reaction mixture was kept at 35-40° C. for 4 hours. It was then allowed to stand at room temperature for a further 16 hours, after which the solvents were removed under reduced pressure. The oil obtained as a residue was dissolved in 50 cm" of water and the resulting aqueous solution was acidified with 5 N hydrochloric acid to a pH value of 2. An oil separated from the solution and this oil crystallized after cooling and standing. The crystalline compound is N-carbobenzoxy-O-azidoacetyl-Z-serine. It was collected and purified by recrystallization from benzene. Sm.p. 82—84° C, 3.42 cm:; concentrated hydrochloric acid and 1 g of palladium black were added to a solution of 13 g of N-carbobenzoxy-O-azidoacetyl-Z-serine in 200 cm" of aqueous ethanol. The reaction mixture was shaken at room temperature for about 6 hours with hydrogen under a pressure of 2.8-4.2 kg/cm 2 . The catalyst was removed by filtering the solvent lene removed by vacuum distillation. The oil obtained as a residue was taken up in water and the solution extracted with ether. The ether extract was discarded and the aqueous solution evaporated in vacuo, whereby an oil was recovered. This oil was washed with ethanol, causing it to crystallize. The crystals were collected and dried. The product thus obtained is the monochlorohydrogen salt of O-glycyl-Z-serine with m.p. 161.5° C (decomposition).

The N-carbobenzoxy derivatives used as starting material in the process according to the invention can be prepared using the methods described in Ber. 65.1196 (1932) and in J. Biol. Chem. 146, 463 (1942) for the preparation of N-carbobenzoxy-Z-serine and N-carbobenzoxy-cZZ-serine.

Claims (5)

1. Process for the preparation of a salt of O-glycyl-Z-serine or O-glycyl-cZZ-serine with mineral acid, characterized by allowing an N-carbobenzoxy derivative of Z-serine or cZZ-serine with the general formula: where R' is a benzyl group or a benzyl group, which is substituted in the nucleus and/or the side chain reacts with haloacetyl halide or a haloacetic anhydride so that one obtains the corresponding O-haloacetyl-N-carbobenzoxy-serine phor bond, this compound allows react with a metal azide, so that one obtains the corresponding O-azidoacetyl-N-carbobenzoxyserine compound and subject this O-azidoacetyl-N-carbobenzoxyserine compound to reduction in the presence of at least one equivalent of a mineral acid, e.g. hydrochloric acid. 2. Method according to claim 1, characterized in that the reaction between the N-carbobenzoxy derivative of Z-serine or dl-serine and the haloacetyl halide or haloacetic anhydride is carried out in an organic solvent that does not contain hydroxyl groups and at a temperature below 125° C, preferably 0— 25° C. 3. Method according to claim 1, characterized in that the reaction between the N-carbobenzoxy derivative of Z-serine or cZZ-serine and the haloacetyl halide is carried out in the presence of a tertiary organic amine. 4. Process according to any of the preceding claims, characterized in that an alkali metal azide is used as the metal azide and in that the reaction between the azide and the O-haloacetyl-carbo-benzoxyserine compound is carried out at a temperature between 20 and 50°C. 5. Method according to any one of the preceding claims, characterized in that the reduction of the O-azidoacetyl-N-carbobenzoxy-serine compound is carried out with gaseous hydrogen under I pressure in the presence of a hydrogenation catalyst. tor, preferably a noble metal catalyst, and in a solvent containing at least 1 equivalent of a mineral acid, whereby the pH value is kept below 5.5.