GB1602525A - Fluorinated amino acids - Google Patents

Abstract

Novel alpha -fluoromethyl- alpha -amino acids and esters have the following formula <IMAGE> in which R is a substituted C1-C4-alkyl group and R1 has the meaning of H or C1-C18-alkyl. The compounds can be present as acid addition salts. The compounds of the formula I, as well as their pharmaceutically acceptable acid addition salts, are used as active compounds in medicaments which have a decarboxylase-inhibiting effect. Processes for preparing the novel compounds are described.

Description

(54) FLUORINATED AMINO ACIDS (71) We, MERCK & CO. INC., a Corporation duly organized and existing under the laws of the State of New Jersey, United States of America, of Rahway, New Jersey, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention is concerned with substituted a - fluoromethyl - a amino alkanoic acids.

An unsubstituted a - fluoromethyl - a - amino alkanoic acid, namely 2fluoromethylalanine, which has the formula:

is known [Kellonitsch et al. J. Org. Chem. 40, 3808-9 (1975)]. No specific biological activity for this compound is suggested. This compound (A) is prepared by fluorodehydroxylation of the corresponding 2-hydroxymethylalanine.

a-Methyl amino acids, such as L - a - methyl - 3,4 - dihydroxyphenylalanine (a-methyldopa, an antihypertensive agent), are known to have decarboxylaseinhibiting activity (Goodman, et al., The Pharmacological Basis of Therapeutics, MacMillan Company, New York, New York 1970, p. 577; Canadian Patent 737,907).

The present invention is based on the discovery of certain novel substituted a - fluoromethyl - a - amino alkanoic acids, at least some of which have decarboxylase-inhibiting activity significantly greater than that of a-methyl amino acids.

The present invention provides compounds having the formula:

where R is a substituted C1-C4 alkyl group and R, is H or C1-C18 alkyl.

Compounds that are pharmaceutically acceptable acid-addition salts of the formula I compounds are also included. In general, the salts are those of the formula I base with a suitable organic or inorganic acid. Preferred inorganic acid salts are the hydrohalides, e.g., hydrochlorides, hydroiodides and hydrobromides: the sulfates, and the phosphates. The hydrohalides, and especially the hydrochlorides, are especially preferred.

The formula I compounds have a chiral center and may occur in optically active forms, i.e., as optical isomers. These isomers are designated conventionally by the symbols L and D, + and-, and d, S and R or combinations thereof. Where the compound name or formula has no isomer designation, the name or formula includes the individual isomer mixtures and the racemates.

The compounds having the S-isomer configuration are, in general, preferred.

R is a substituted alkyl group exemplified by

where R2 is H or C2-C6 alkanoyl, e.g., CH,--CO, C113(CH2)4-CO or (CH3)3C- CO,

preferably

HOOC-CIlI2-; HOOC-CH2-CH2-;

H2N-CH2-CH2-CH2-; H2N-CH2CH2CH2CH2-; HO-CIlI2-;

and H3CS-CH2-CH2-.

R, is H, which is preferred, or C1-C18 alkyl. Examples of suitable alkyl groups are methyl, octadecyl, 2-ethylhexyl, t-butyl, hexyl, isopropyl, ethyl and undecyl: C1-C6 alkyl is preferred and ethyl is especially preferred.

Preferred compounds of formula I are those where R is

M2N-(CH2)2-, HOOC-C112-CH2-,

H2N-CH2-CH2-CH2-,

and H3CS-CH2-CH2-, especially where R1 is hydrogen.

Compounds that are particularly preferred have the formula

especially where R2 is hydrogen and R, is hydrogen or ethyl. Especially preferred formula II compounds are those where R, and R2 are hydrogen, with the S-isomer configuration being particularly preferred.

Another particularly preferred compound has the formula

especially where R, is hydrogen.

The S-isomer of formula III is particularly preferred.

Especially preferred compounds are those of the formulae

The compounds of the present invention have physiological or chemotherapeutic uses. In most cases, the biological activities of these compounds are in large measure a consequence of their potent decarboxylase inhibiting activities. Decarboxylases are enzymes which act on a-amino acid substrates, effecting decarboxylation to produce the corresponding amine. This action is illustrated as follows:

Decarboxylase L-CH-CO2H .L-CH2 NH2 NH2 L=Alkyl or aralkyl group amino acid substrate amine By inhibiting this decarboxylation, the biosynthetic pathway to a number of biologically significant amines can be modulated or inhibited with physiologically useful consequences. For example, a-fluoromethyl dopa inhibits dopadecarboxylase and can be used in combination with dopa to potentiate the latter's usefulness in the treatment of Parkinson's disease. a-Fluoromethyl-histidine inhibits biosynthesis of histamine via decarboxylation of histidine (EDso in mice -0.4 mglkg). Consequently, it and combinations with histamine antagonists have utilities in the prevention of gastric lesions and in treating allergic conditions. a Fluoromethyl ornithine by virtue of its ornithine decarboxylase inhibition interrupts polyamine biosynthesis and is of utility in the treatment of some neoplasms. a-Fluoromethyl-arginine is an effective antibacterial. a-Fluoromethyl- glutamic acid is a CNS stimulant.

The present compounds are also substantially specific in their decarboxylase inhibition activity, that is an a-fluoromethyl-a-amino acid generally inhibits the decarboxylation of the corresponding non a-fluoromethyl acid. For example, a- fluoromethyl dopa inhibits the decarboxylation of dopa: cu-fluoromethyl histidine will inhibit the decarboxylation of histidine, etc.

Because of this specificity and potency as decarboxylase inhibitors, the present compounds are also useful as diagnostic tools to determine the presence and importance of the corresponding decarboxylase in relation to diseases or to the functioning of biological systems. For example, the importance of y-amino-butyric acid in the central nervous system (CNS) may be studied by inhibiting its biosynthesis using an -fluoro-methyl-glutamic acid. This diagnostic utility is aided by the potent and in many instances irreversible decarboxylase inhibiting activity of the present a-fluoromethyl amino acids.

Representative compounds have been determined to have decarboxylaseinhibiting activity using conventional in-vitro assays.

a - Fluoromethyl - 3,4 - dihydroxyphenylalanine, a-fluoromethyl tyrosine, and a-fluoromethyl-meta-tyrosine have also been found to have antihypertensive activity. This activity is determined by observing the antihypertensive effect (blood pressure reduction) on (peroral or parenteral) administration of the compounds to a spontaneously hypertensive (SH) rat. This observed effect indicates that the compounds are effective as antihypertensive agents, when conventionally administered in suitable amounts in an appropriate pharmaceutical dosage form to a hypertensive human. The pharmaceutical dosage form is conventionally prepared and generally includes pharmaceutically acceptable diluents.

The compounds of the present invention may be prepared using any convenient method.

One such useful process involves the reaction of an a - hydroxymethyl - a amino acid with SF4 in liquid HF, as illustrated by the following equation:

The reaction is generally carried out at temperatures in the range -800C to 20"C. This general reaction is also referred to as fluorodehydroxylation and is described in the Journal of Organic Chemistry 40, 3809-10 (1975). BF3 may be used to promote the reaction.

It has now been discovered that the fluorodehydroxylation of certain arylsubstituted a - hydroxymethyl - a - amino acids is substantially improved by utilizing BF3 or AICI3 as a co-reactant with SF4. Specifically, this is an improved process for preparing a compound having the formula

where R' is an aryl group, that comprises reacting a compound having the formula

with a) SF4 and b) BF3 or Air13, in liquid HF at temperatures in the range -80"C to 20"C.

R' is an aryl group exemplified by preferably

Preferred R' groups are and

The compounds of formulae IV and V preferably have the S-isomer configuration.

This present process is preferably carried out at atmospheric pressure although pressures above atmospheric may be used. The reaction temperature ranges from -800C to 20", -80"C to OOC being preferred.

The present process may conveniently be carried out by introducing the SF4 and B F3 or AICI3 into the Formula V/HF reaction system initially. The process may also be carried out by first adding the SF4 to the reaction system, allowing the reaction to proceed for a period of time and then adding the BF3 or AICI3 and allowing the reaction to go to completion.

The use of BF3 or AICI3 in the SF4/HF reaction system substantially improves the yield of Formula IV product.

Another method for preparation of the substituted a - fluoromethyl - a amino alkanoic acids involves the application of photofluorination. For a description of this method, see Journal of the American Chemical Society, 92, 7494 (1970) and ibid., 98, 5591 (1976). For example, a-fluoromethyl-glutamic acid is prepared:

CH3 CH2F photo HOOC-C-CH2CH2COOH HOOC-C-CH3CH2COOH fluorination l H2 Both optical isomers of a-methylglutamic acid are known; thus this method is useful for preparation of both optical isomers of a-fluoromethylglutamic acid.

Similarly, a-fluoromethyl-ornithine is prepared by photofluorination of a- methyl-ornithine:

CTT photo- CH2F photo- I HOOC-C-Cll2CH2CH2NH2 HOOC-C-CH2CH2CH2NH2 fluorination NH2 NH2 Since both optical isomers of a-methylornithine are available, this method of synthesis can deliver both of the two optical isomers of a-fluoromethyl-ornithine.

a-Fluoromethyl-ornithine is a suitable starting material for synthesis of a- fluoromethyl-arginine by reaction with S-methylisothiourea:

An acid-addition salt of the present invention may be prepared by conventional treatment of the free amino acid with a useful acid generally in a suitable solvent.

A single enantiomer of the present compounds may also be obtained by (1) resolving the fluorinated amino acid racemate using conventional resolution techniques or (2) resolving the precursor a-hydroxymethyl-a-amino acid using conventional resolution techniques and then fluorodehydroxylating the precursor enantiomer. A conventional resolution technique involves forming a salt of the (r- amino acid with an optically active base and subsequently recovering the specific enantiomer from the salt.

Compounds of the formula

where R2 is C2-C6 alkanoyl are prepared by acylating the corresponding compound where R2 is hydrogen. Conventional acylating agents and conditions are used.

Compounds of the formula

where R, is C1-C18 alkyl are prepared by esterifying the corresponding compound where R, is hydrogen. Again, conventional esterification reagents and conditions are employed.

The following examples illustrate preparation of representative compounds of the present invention. All temperatures are in "C. The fluorodehydroxylation reactions described in the examples were performed in reactors made of KEL-F.

Melting points are determined in open capillary and are uncorrected. The words 'KEL-F', 'Dowex', 'Celite' and 'Darco' are Trade Marks.

EXAMPLE 1 Preparation of R,S-Alpha-(Fluoromethyl)-3-Hydroxy-Tyrosine

1.5 g of R,S,-(hydroxymethyl)-3-hydroxytyrosine hydrochloride (ahydroxymethyl-DOPA HCI) was dissolved in 50 ml of anhydrous hydrogen fluoride, while being cooled in a dry-ice-acetone bath. The HF solvent was then evaporated after removal of the cooling bath with a stream of nitrogen gas. This operation transformed the HCI salt into the HF salt of the starting material.

(Alternatively 1.3 g of the free amino acid may be used as starting material, thus eliminating the need for the above operation). The HF salt thus obtained was redissolved by passing into the reactor a stream of HF gas after cooling it in a dryice-acetone bath, until 30 ml of liquid HF had been collected in the reactor. Sulfur tetrafluoride gas (1.2 ml, measured in liquid state at -780C) was then passed in and the dry-ice-acetone cooling bath was then removed and replaced by a cooling bath kept at -12"C. After 15 hours of aging, the solvent was evaporated with a stream of N2, the residue was dissolved in 50 ml of 2.5 M aqueous HCI, evaporated to dryness in vacuo and subjected to amino acid analysis on Spinco-Beckman amino acid analyser. This analysis indicated the formation of a - fluoromethyl - 3 - hydroxy tyrosine. The product R,S - alpha - fluoromethyl - 3 - hydroxy - tyrosine is isolated by ion-exchange chromatography in the same manner as it is described in Example 2 for S - alpha - fluoromethyl - 3 - hydroxy - tyrosine.

EXAMPLE 2 Preparation of S-alpha-fluoromethyl-3-Hydroxy-Tyrosine A.) Preparation of R-a-hydroxymethyl-3-hydroxy-tyrosine 50 g of 3 - [3',4' - diacetoxyphenyl] - 2 - acetamido - 2 - acetoxymethyl propionic acid is added to 204 ml of 4 M aqueous KOH with stirring. After I hour of stirring (under nitrogen), the solution contains the potassium salt of 3 - (3',4' dihydroxyphenyl) - 2 - acetamido - 2 - hydroxymethyl - propionic acid, formed in essentially quantitative yield. Without isolation, by methylation with dimethyl sulfate, this compound is transformed into 3 - (3',4' - dimethoxyphenyl) - 2 acetamido - 2 - hydroxymethyl - propionic acid. This operation is performed at room temperature under N2 gas by dropwise addition with vigorous stirring of dimethyl sulfate (about 64 ml) and 4 M aqueous KOH solution (about 148 ml) over a period of about 1 hour.

The reaction mixture was stirred for another hour, then left standing overnight. Acidification (at 5--100C with 55 ml of conc. aqueous HCI), extraction with ethyl acetate (12x300 ml), drying over Na2SO4 and evaporation in vacuo gave R,S - 3 - (3',4' - dimethoxyphenyl) - 2 - acetamido - 2 - hydroxymethyl - propionic acid. It was purified by recrystallization from 1325 ml of acetonitrile, m.p. 154--60C (dec).

29.1 g of strychnine was suspended in 1.12 1 of ethanol, heated to reflux, then 26.1 g of R,S - 3- (3',4' - dimethoxyphenyl)- 2- acetamido - 2hydroxymethyl - propionic acid was added. The solution thus obtained was allowed to cool down and left standing overnight at room temperature. Crystals of the strychnine salt of antimer, "A" separate; m.p. 193--194"C ("HM").

The mother liquor of the above named precipitation was evaporated in vacuo to dryness and recrystallized from 270 ml of ethanol; the hot solution is allowed to cool to room temperature and left standing at room temperature for about 3 hours, then kept in the refrigerator for about 4 hours. The crystals formed were collected on a filter and after drying, recrystallized from acetonitrile to give the strychnine salt of antimer "B" of 3 - (3',4' - dimethoxy - phenyl) - 2 - acetamido - 2 hydroxymethyl - propionic acid, m.p. 13e132"C (dec.), yield 17.5 g.

17 g of this strychnine salt was decomposed by dissolving it first in 160 ml of water; 31 ml of 1 M aq. NaOH solution was added. The strychnine separated was removed by filtration and the solution evaporated to a small volume in vacuo and applied onto a small ion exchange resin column (150 ml of AG-X2 cation exchange Dowex 50 resin, 200/400 mesh). Elution with water, followed by evaporation in vacuo of the fractions which showed absorption, as indicated by an LKB UV absorption monitor (Uvicord 11-8300). This compound, antimer "B" of 3 - (3',4' - dimethoxyphenyl) - 2 - acetamido - 2 - hydroxymethyl - propionic acid showed [a]0: 78.3+0.5 (C, 1.425 in 0.1 M aq. NaOH).

Transformation of the above compound into the corresponding stereo-isomer of a - hydroxymethyl - 3 - hydroxytyrosine: 4.43 g of antimer "B" of 3 - (3',4' dimethoxyphenyl) - 2 - acetamido - 2 - hydroxymethylpropionic acid is dissolved in 100 ml conc. HC1 and sealed and heated for 90 minutes in a Fisher-Porter tube immersed into an oil bath of 1300C. The solvent is evaporated in vacuo and the above HCI treatment repeated. The residue thus obtained represents R - a hydroxymethyl - 3 - hydroxy - tyrosine hydrochloride.

B.) Fluorodehydroxylation 8 g of R - a - hydroxymethyl - 3 - hydroxy - tyrosine. HCI is charged to a Il reactor. The reactor is immersed in a dry-ice acetone bath and 80 ml of liquid H F is condensed on top of the substrate. To remove the HCI present, the cooling bath is removed and the HF solvent removed by passing in a stream of N2 gas. The reactor is immersed in the cooling bath again and a stream of HF gas is passed in until a liquid volume of about 250 ml collects. 6.2 ml of SF4 (17.6 mmol/ml: about 109 mmol) is then bubbled in, the solution aged for about I hour, the cooling bath exchanged for an ethylene-glycol bath kept at --160C and the solution aged for about 22 hours. Boron trifluoride gas is passed in untul saturation and the solution aged again at -16"C for 46 hours. The cooling bath is removed and the solvent evaporated by passing through it a vigorous steam of N2 gas. The residue is quenched in about 100 ml of ice-cold aqueous HCI (2.5 M), evaporated in vacuo, the residue dissolved in water and added onto a column of 2.2 1 of Dowex AG-50 X-8 cation-exchange resin (200/400 mesh). Elution with 0.25 M aq. HCI, containing 50/o methanol; in 8.5 hours, 7.2 1 of this solvent is pumped through the column.

This is followed by 7.2 1 of 0.4 M aq. HCI with 7.50/:, methanol in 8.5 hours, then concluding with 0.6 M aq. HCI with 10% methanol. 22 ml fractions are collected, 10 tubes per rack. Tubes in racks No. 45-66 contained the desired compound.

Evaporation in vacuo gave the HCI salt of the S-isomer of a - fluoromethyl - 3 hydroxy - tyrosine.

For liberation of the free amino acid, 4.826 g of this compound was dissolved in 90 ml of isopropanol and filtered through Celite. 6.2 ml of propylene oxide was added to the filtrate and the suspension kept at room temperature for 3.5 hours, then at about 5"C for another 2.5 hours. The S - a - fluoromethyl - 3 - hydroxy tyrosine thus formed was collected by filtration, washed with isopropanol and dried overnight in vacuo at 769C. [cr],: +9.3 +0.5, c, 1.82 in 1:1 mixture of trifluoroacetic acid and water.

EXAMPLE 3 Preparation of R-a-Fluoromethyl-3-Hydroxy-Tyrosine For preparation of the above named compound, the strychnine salt of antimer A of 3 - (3',4' - dimethoxyphenyl)- 2- acetamido - 2- hydroxymethyl propionic acid (Example 2 "HM") was carried through steps analogous to those in Example 2. The final product of the sequential steps was R - a - fluoromethyl - 3 hydroxy - tyrosine, with [],: --90 (c, 2.5 in a 1:1 mixture of H,O-trifluoroacetic acid).

EXAMPLE 4 R,S-a-Fluoromethyl-Tyrosine 1.05 g (0.005 mol) of R,S - a - hydroxymethyl - tyrosine is charged into a reactor. The reactor is immersed in a dry-ice-acetone bath and about 50 ml of liquid HF is collected by passing in a stream of HF gas. Under continuing cooling, SF4 gas (4 ml, measured in liquid state at -780C) is passed in, then BF3 gas until saturation at -780C. (Stirring with magnetic stirrer). The deep-red solution thus obtained is aged overnight at 780 C; the cooling bath is removed then, and the solvent evaporated by blowing a dry stream of nitrogen gas through it.

The residue is dissolved in 20 ml of 2.5 M aq. HCI and evaporated to dryness in vacuo. The residue is dissolved in water and applied to a strong acid cationexchange resin column, prepared with 100 ml of Dowex AG50-X-8 resin (200/400 mesh). The column is first washed with water (1.8 1), followed by 0.5 M aq. HCI. 20 ml fractions of the effluent are collected and the course of the elution is followed by an UV monitor of LKB, Model Uvicord II. The fractions corresponding to the main peak in the UV curve are combined and evaporated to dryness in vacuo, to yield the hydrochloride salt of R,S-fluoromethyl-tyrosine. 400 ml of this salt is dissolved in 6 ml of water; after a few minutes, crystallization of R,S - a fluoromethyl - tyrosine begins. After standing overnight at 50C, the product is filtered, washed with water, ethanol and diethyl ether and dried in vacuo at 760C, to give R,S - a - fluoromethyl - tyrosine.

EXAMPLE 5 R.S-a-Fluoromethyl-Histidine (FM HIST)

H cHj2OH CH2-C-CO2H CH -C-CO2H N4 M 1) Racemization I 2 2 2) Cut03 < 0 NH2 C 2C6g5 v J CH2C6H5 (L) (D,L) I II C1H2OH CH F 1 2 002 I" M71H22 CH2-C-COON I HF/SF4BF3 1IH2 H H n H (D,L) FM-HIST III IV A) Racemic N(im)Benzyl-Histidine 30 g of N(im)Benzyl-L-histidine is dissolved in 600 ml H2O and the solution heated in a high-pressure autoclave at 2000C for 8 hours with shaking. The autoclave is cooled to room temperature, the clear supernatant solution evaporated in vacuo to dryness to give the racemic N(im)benzyl-histidine as a colorless crystal.

B) R,S-er-Hydroxymethyl-Histidine Dihydrochloride 20 g of racemic N(im)benzyl-histidine is dissolved in 11 of hot water, then 40 g of basic cupric carbonate is added in portions and the mixture refluxed with stirring for 1 hour. The mixture is filtered while hot and the filtrate is evaporated in vacuo to give the Cu chelate of racemic N(im)benzyl-histidine as a blue solid.

A mixture of 31 ml of formalin (38% H2CO), 3.1 ml of pyridine and 2.13 g of Na2CO3 is heated with stirring to 70"C, then 20 g of the above named Cu chelate is added and the system heated and stirred at 75"C for 90 minutes. Evaporation in vacuo gives a blue solid residue. This is dissolved in a mixture of 50 ml of H2O with 50 ml of conc. NH40H and charged onto a cation-exchange resin column (Dowex 50-X-8, 300 ml resin in the NH4-form) and eluted with 2 M aq. NH40H solution.

The effluent is monitored with a LKB Uvicord II UV absorption monitor and 1.11 of the effluent is found to have UV absorption. This portion is evaporated in vacuo to a solid. The residue is dissolved in a mixture of 60 ml of H2O with 5 ml of conc.

aq. NH40H and charged onto an anion-exchange resin column (300 ml of Dowex 1 X-2 resin in the OH- form). The column is washed with water (2 1), and eluted with 2 M aq. HCI and monitored with a Uvicord II for UV absorption. The effluent fractions with ultraviolet absorption are combined and evaporated to dryness, to give substantially pure HCI salt of N(im)benzyl - a - hydroxymethyl - histidine (II) (new compound). This compound is transformed into a - hydroxymethyl histidine (III) in the following way: 12.5 g of II is dissolved in 200 ml of liquid NH3 (3-neck flask, equipped with "cold-finger" condenser filled with dry-ice-acetone), then sodium is added (5.5 g, cut in small pieces) until the blue color persists for 10 minutes. HN4CI is added then to consume the excess of Na (indicated by decolorization) and the NH3 solvent is allowed to evaporate under a stream of N2.

The product III thus obtained is purified by chromatography on a cation-exchange resin column (2.2 1 of Dowex-50-X-8, 200/400 mesh). Crude III is dissolved in 100 ml of H2O and applied onto the resin column. The column is washed first with water (4 1) and developed with aq. HCl (1.5 M, then 2 M). 20-ml fractions are collected, flow rate 600 ml/hr.

Fraction No. Pauly Reaction 1 "00 1.5 M HCI 401-670 2MHCl 671 & later + Fractions 671-760 are combined and evaporated in vacuo to dryness. to give R,S - a - hydroxymethyl - histidine 2 HCI (new compound).

C) R.S-a-Fluoromethyl-Histidine (IV) 2.73 g of R,S - a - hydroxymethyl - histidine 2 2 HCI is dissolved in 70 ml of liquid HF and then evaporated to dryness by passing in a stream of N2. The residue thus obtained represents the hydrofluoride salt of a-hydroxymethyl-histidine. It is redissolved in 200 ml of liquid HF (dry-ice-acetone cooling bath), then 9 ml SF4 is passed in (measured as liquid at -780C). The solution is stored overnight, while being kept in a cooling bath of -12"C. The solution is saturated then with BF3 gas, left standing for 5 hours, saturated again at -120C and left aging at the same temperature for 66 hours. The cooling-bath is then removed and the solvent evaporated by passing in a stream of N2. The residue represents mainly the HBF4 salt of a-fluoromethyl-histidine. This is dissolved in 100 ml of 2.5 M aq. HCI, evaporated to dryness and transformed into the HCI salt as follows: It is redissolved in H2O and applied onto a cation-exchange resin column (100 ml of Dowex AG50 X-2, 200/400 mesh) and eluted with H2O until effluent is neutral and free of F-. The product is released from the column by 3 M aq. HCI, evaporated to dryness in vacuo, to result in a residue consisting mainly of the dihydrochloride of IV. For final purification, this is rechromatographed on another AG-50-X-2 column (900 ml Elution with: 0.5 M aq. HCI -- 1.

1.0 M aq. HCI -- 1.51.

1.5 M aq. HCl - 3.3 1 (collection begins here, 20-ml fractions) 2.0 M aq. HCI -- 8.00 1.

The desired product IV is located by Pauly test. Fractions 390470 are combined and evaporated to dryness in vacuo to give pure dihydrochloride of IV.

Recrystallization from water-isopropanol (1:9 v/v) gives the crystalline monohydrochloride salt of a-fluorome

B) R,S-a-Hydroxymethyl Tyrosine Methyl Ether 29 g of the copper (Cu++) chelate of tyrosine methyl ether (0.064 mole) was added at 700C under stirring to a solution of 3.9 g of sodium carbonate, 52 ml of 37% aqueous formaldehyde and 5.2 ml of pyridine (nitrogen blanket). After completion of addition, there was added another 18 ml of formaldehyde solution and 1.6 ml of pyridine. After heating at 700C for 3.5 hr and allowing the solution to cool to room temperature in an additional 1.5 hr, the solution remained at room temperature overnight. In the morning, there appeared copious blue crystals which were filtered off and the filtrate concentrated to dryness in vacuo. After the residue had been dissolved in water and reconcentrated to dryness, it was dissolved in 90 ml of 4 N HCI. After filtration the solution was used to dissolve the above blue crystals. This required an additional 300 ml of 4 N HCI. The solution was then treated with hydrogen sulfide, filtered through a diatomaceous earth filter aid and concentrated to about 40 g of crude product. This was applied to a strong acid cation-exchange resin (0.5% of Dowex 50-X-8), eluted with 4 1 of water and then 2 N aqueous ammonia. The effluent was monitored with Uvicord Il (recording ultraviolet spectrophotometer) and the UV absorbing fraction was concentrated in vacuo to 22.16 g of pure R,S - cz - hydroxymethyl - tyrosine methyl ether.

C) R,S-N-Acetyl-a-Hydroxymethyl-Tyrosine Methyl Ether 19.7 g of R,S - a - hydroxymethyl - tyrosine methyl ether (87.5 mmol) was suspended in 200 ml of dry pyridine, then 68 ml of acetic anhydride was added.

After aging overnight at room temperature, the solution was concentrated in vacuo to dryness and azeotroped with 2x50 ml toluene. The residue was dissolved in 118 ml of methanol and 130 ml of aqueous 2.5 N NaOH solution and stirred at room temperature for 3.5 h. Acidification with 30 ml of conc. HCI followed by extraction with 4x200 ml of ethyl acetate, and then drying and concentration afforded 21 g of crude product. This was recrystallized from 75 ml of acetonitrile yielding 9.35 g of R,S - N - acetyl - a - hydroxymethyl - tyrosine methyl ether, mp 151--152"C dec.

D.) Optical Resolution of R,SN-Acetyl-a-Hydroxymethyl-Tyrosine Methyl Ether 10 g of R,S - N - acetyl - a - hydroxymethyl - tyrosine methyl ether and 6.18 g of d-ephedrine were dissolved in 50 ml of methanol. The solution was concentrated to dryness in vacuo and then redissolved in 50 ml of warm acetonitrile. Crystallization afforded 7.34 g of the d-ephedrine salt of R - N acetyl - a - hydroxymethyl - tyrosine methyl ether, mp 125--131"C (Crop A).

Crop A was recrystallized from 40 ml of acetonitrile affording 4.78 g of Crop B, mp 130--1340C. The mother liquors from A and B were combined and concentrated, and the residues dissolved in 22.4 ml of 2.5 N NaOH and 50 ml of H2O. The aqueous solutions were extracted with 2x75 ml ethyl acetate. The aqueous solutions were cooled and acidified with 5 ml of conc. HCI and the resultant solution extracted with 3x70 ml ethyl acetate. The dried organic solution was concentrated to 7.73 g (Crop C). Crop C and 4.7 g of l-ephedrine were dissolved in 50 ml of methanol and concentrated to 12.39 g (Crop D). This was recrystallized from 50 ml acetonitrile to yield 5.06 g of the l-ephedrine salt of S - N - acetyl - a hydroxymethyl - tyrosine methyl ether (Crop E), mp 131.5--133.5"C dec. Crop E was recrystallized from 27 ml of acetonitrile to give Crop F, 4.72 g, mp 130.5- 134.5 C dec. The mother liquors from Crop F and Crop E were combined and concentrated to 7.31 g (Crop G). Crop G was converted back to the free acid using the method used to obtain Crop C and there was obtained 3.0 g (Crop H). This was treated as was the initial R,S-material with 1.9 g of d-ephedrine. Recrystallization of the salt from 17 ml of acetonitrile afforded 2.4 g of Crop J, mp 127--130"C. Crop J was recrystallized to 2.06 g of Crop K, mp 130134 C dec.

Combined Crops B and K (6.52 g) were recrystallized from 40 ml of acetonitrile affording 6.06 g of the d-ephedrine salt of R - N - acetyl - a - hydroxymethyl - tyrosine methyl ether (75.8% overall).

The free acid was regenerated in the same manner as that by which the combined mother liquors of Crops A and B were converted to Crop C and there was obtained 3.50 g of R - N - acetyl - a - hydroxymethyl - tyrosine methyl ether: [a],=t920 (C, 1.35, 0.27 N NaOH).

E.) R-a-Hydroxymethyl-Tyrosine 3.3 g of R - N - acetyl - a - hydroxymethyl - tyrosine methyl ether was dissolved in 100 ml of conc. HCI and heated in a pressure tube at 130"C for 2 hr.

The solution was concentrated to dryness, the residue dissolved in 35 ml of H2O, filtered and treated with 1 ml of pyridine. 2.11 g of pure R - a - hydroxymethyl tyrosine (81%) crystallized out: [a]=0.860 (C, 1.15, 50% aqueous trifluoroacetic acid). The circular dichroism (CD) spectrum has the same sense as the CD of S a - methyl - tyrosine.

F.) S-a-Fluoromethyl-Tyrosine Following the procedure of Example 4, S - a - fluoromethyl - tyrosine was prepared from R - a - hydroxymethyl - tyrosine.

EXAMPLE 8 (j)-a-Fluoromethylglutamic Acid 6.56 g of a-methylglutamic acid hemihydrate was photofluorinated in liquid HF solution by the general technique described in Journal of the American Chemical Society, 92, 7494 (1970) and 98, 5591 (1976). The substrate was dissolved in 120 ml of liquid Hf and irradiated with a 2500 W ultraviolet light source under stirring while fluoroxy-trifluoro-methane (CF3OF) gas (3.0 ml as measured in liquid form at -780C) was passed in the course of 80 min, under cooling in a dry-iceacetone bath. After another 80-minute period with irradiation under similar conditions, an additional similar dose of CF3OF was added in 3 hours, continuing with the stirring, cooling and irradiation. The mixture was kept overnight in the dry-ice-acetone bath, then it was further fluorinated (with 3 ml of CF3OF, added in 5 hours with irradiation). Nitrogen gas was blown through the solution for removal of the solvent and the residue was evaporated with 2.5 N aq. HCI (2x) in vacuo. The residue was dissolved in 40 ml of water. To 10 ml of this solution 10 ml of conc.

was added and the mixture was refluxed for about 68 hours. After treatment with Darco G-60, the filtrate was evaporated in vacuo and the residue refluxed with 30 ml of conc. HCI for another 68-hour period. After treatment with Darco, the solution was evaporated to dryness, dissolved in 10 ml of conc. HCI and heated in a sealed glass tube for 24 hours in an oil-bath kept at 130135 . Evaporation in vacuo to dryness gave a residue which was dissolved in H2O and subjected to elution chromatography on a cation-exchange resin column, made of 360 ml of Dowex AG50-X12 (mesh 200/400). Eluants: 2.6 1 of H2O, followed by 0.1 N aq. HCI (1.5 1), then by 0.15 N aq. HCI. UV absorption of the effluent was monitored by a recording UV at 206 nm. 15-ml fractions of effluent were collected and 20 fractions, corresponding to the first ultraviolet absorbing peak, were combined and evaporated in vacuo to dryness, to give a-fluoromethyl-glutamic acid hydrochloride. For liberation of the amino acid, this was dissolved in isopropanol and filtered, and then propylene oxide was added. a-Fluoromethyl-glutamic acid.

0..7 H2O crystallized out of the solution. This compound is a time-dependent inhibitor of glutamic acid decarboxylase.

WHAT WE CLAIM IS: 1. A compound having the formula

wherein R is a substituted C1-C4 alkyl group and Rl is H or C1-C18 alkyl.

2. Pharmaceutically acceptable acid addition salts of a compound as claimed

Claims (1)

1. in Claim 1.

   3. A compound as claimed in Claim 1 having the S-isomer configuration.

   4. A compound as claimed in Claim I in which the substituted alkyl group is

   wherein R2 is H or C2-C6 alkanoyl.

   H2NCH2)2-CH2-, HOOC-CH2-CH2-, HO-C H2-,

   H3CSCH2-CH2 or

   and R1 is H.

   5. A compound as claimed in Claim 4 in which the substituted alkyl group is

   6. A compound having the formula

   where R1 and R2 are as defined in Claims 1 and 4 respectively.

   7. A compound as claimed in Claim 6 in which R2 is hydrogen and R, is H or ethyl.

   8. A compound as claimed in Claim 7 in which R1 is hydrogen.

   9. A compound as claimed in Claim 8 having the S-isomer configuration.

   10. A compound as claimed in Claim 1 having the formula

   11. A compound as claimed in Claim 10 having the formula

   12. A compound as claimed in Claim 11 having the S-isomer configuration.

   13. A compound as claimed in Claim 1 having the formula

   14. A compound as claimed in Claim 13 having the S-isomer configuration.

   15. A compound as claimed in Claim I having the formula

   16. A compound as claimed in Claim 15 having the S-isomer configuration.

   17. A compound as claimed in Claim 1 having the formula

   18. A compound as claimed in Claim 17 having the S-isomer configuration.

   19. A compound as claimed in Claim 1 having the formula

   20. A compound as claimed in Claim 19 having the S-isomer configuration.

   21. A compound as claimed in Claim 1 having the formula

   22. A compound as claimed in Claim 21 having the S-isomer configuration.

   23. A compound as claimed in Claim 1 having the formula:

   24. A compound as claimed in Claim 23 having the S-isomer configuration.

   25. A compound as claimed in Claim 1 having the formula:

   26. A compound as claimed in Claim 25 having the S-isomer configuration.

   27. A pharmaceutical composition containing a compound of Claim 1 or a pharmaceutically acceptable acid-addition salt thereof, together with a pharmaceutically acceptable diluent.

   28. A composition as claimed in Claim 27 in which the said compound has the formula

   where Rl is H or C1-C6 alkyl and R2 is H or C2-C6 alkanoyl.

   29. A composition as claimed in Claim 27 in which the said compound has the formula

   where R1 is H or C1-C6 alkyl.

   30. A composition as claimed in Claim 27 in which the said compound has the formula

   31. A process for preparing a compound of Claim 1 in which R1 is H which comprises fluorodehydroxylation of a compound having the formula

   by treatment with sulfur tetrafluoride in hydrofluoric acid.

   32. A process as claimed in Claim 31 in which R is

   33. A process as claimed in Claim 32 in which R is

   34. A process for preparing compounds having the formula

   where R' is an aryl group, comprising reacting a compound having the formula

   with SF4 in liquid HF at temperatures ranging from -800C to 200 C, in which BF3 or AICI3 is present in the reaction system.

   35. A process as claimed in Claim 34 in which R' is

   and the added compound is BF3.

   36. A process as claimed in Claim 35 in which R' is

   37. A process as claimed in Claim 35 in which the Formula IV and V compounds have the S-isomer configuration.

   38. A compound as claimed in Claim 1, when prepared by a process substantially as hereinbefore described in any one of the foregoing Examples.