Halomethyl derivatives of gamma-aminobutyric acid and related compounds

Novel compounds of the following general formula are useful pharmacological agents: ##STR1## wherein Y is FCH.sub.2 - or F.sub.2 CH-; R.sub.1 is hydroxy, a straight or branched alkoxy group of from 1 to 8 carbon atoms, -NR.sub.10 R.sub.11 wherein each of R.sub.10 and R.sub.11 is hydrogen or a straight or branched alkyl group of from 1 to 4 carbon atoms or ##STR2## wherein R.sub.12 is hydrogen, a straight or branched lower alkyl group of from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl; R.sub.2 is hydrogen, alkylcarbonyl wherein the alkyl moiety has from 1 to 4 carbon atoms and is straight or branched, alkoxycarbonyl wherein the alkoxy moiety has from 1 to 4 carbon atoms and is straight or branched or ##STR3## wherein R.sub.8 is hydrogen, a straight or branched lower alkyl group of from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl; and n is the integer 2 or 3; pharmaceutically acceptable salts and individual optical isomers thereof.

FIELD OF INVENTION 
This invention relates to novel pharmaceutically useful .alpha.-halomethyl 
derivatives of .gamma.-aminobutyric acid and related compounds which are 
useful pharmacological agents. 
BACKGROUND OF INVENTION 
Several previous studies have shown that .gamma.-aminobutyric acid is a 
major inhibitory transmitter of the central nervous system as reported, 
for example, by Y. Godin et al., J. Neurochemistry, 16 869 (1969) and that 
disturbance of the excitation and inhibition interplay can lead to 
diseased states such as Huntington's chorea (The Lancet, Nov. 9, 1974, pp. 
1122-1123), Parkinsonism, schizophrenia, epilepsy, depression, 
hyperkinesis and manic depression disorders, Biochem. Pharmacol. 23, 
2637-2649 (1974). Certain compounds are known to elevate brain levels of 
.gamma.-aminobutyric acid, for example, n-dipropylacetate (Simler et al., 
Biochem. Pharm. 22, 1701 (1973)) by competitively inhibiting 
.gamma.-aminobutyric acid transaminase resulting in a reversible effect 
which lasts for only about two hours. Also, 4-aminotetrolic acid (P. M. 
Beart et al., J. Neurochem. 19, 1849 (1972)) is known to be a competitive 
reversible inhibitor of .gamma.-aminobutyric acid transaminase. Also, 
.alpha.-vinyl- and .alpha.-acetylene-.gamma.-aminobutyric acids are 
disclosed respectively in U.S. Pat. Nos. 3,960,927, issued June 1, 1976, 
and 3,959,356, issued May 25, 1976, as irreversible inhibitors of 
.gamma.-aminobutyric acid transaminase. 
SUMMARY OF INVENTION 
The compounds of the present invention are represented by the following 
general formula: 
##STR4## 
In the above general Formula I Y is FCH.sub.2 - or F.sub.2 CH-; R.sub.1 is 
hydroxy, a straight or branched alkoxy group of from 1 to 8 carbon atoms, 
-NR.sub.10 R.sub.11 wherein each of R.sub.10 and R.sub.11 is hydrogen or a 
straight or branched alkyl group of from 1 to 4 carbon atoms or 
##STR5## 
wherein R.sub.12 is hydrogen, a straight or branched lower alkyl group of 
from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl; R.sub.2 is hydrogen, 
alkylcarbonyl wherein the alkyl moiety has from 1 to 4 carbon atoms and is 
straight or branched, alkoxycarbonyl wherein the alkoxy moiety has from 1 
to 4 carbon atoms and is straight or branched or 
##STR6## 
wherein R.sub.8 is hydrogen, a straight or branched lower alkyl group of 
from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl; and n is the integer 
2 or 3. 
Pharmaceutically acceptable salts and individual optical isomers of the 
compounds of general Formula I are also included within the scope of this 
invention. 
The compounds of general Formula I are useful pharmacological agents in 
that said compounds are irreversible inhibitors of .gamma.-aminobutyric 
acid transaminase. Certain of the compounds of general Formula I are also 
useful as intermediates in the preparation of useful pharmacological 
agents. 
DETAILED DESCRIPTION OF INVENTION 
In the above general Formula I the term alkylcarbonyl is taken to mean the 
group 
##STR7## 
wherein the alkyl moiety has from 1 to 4 carbon atoms and is a straight 
chain or branched chain. 
In the above general Formula I the term alkoxycarbonyl is taken to mean the 
group 
##STR8## 
wherein the alkyl moiety has from 1 to 4 carbon atoms and is a straight 
chain or branched chain. 
Illustrative examples of straight or branched alkyl groups having from 1 to 
4 carbon atoms as used herein are methyl, ethyl, n-propyl, isopropyl, 
n-butyl, and tert-butyl. 
Illustrative examples of straight or branched alkoxy groups having from 1 
to 8 carbon atoms as used herein are methoxy, ethoxy, isopropoxy, 
n-butoxy, tert-butoxy, n-pentyloxy, tert-pentyloxy, n-hexyloxy and 
n-octyloxy. 
Illustrative examples of pharmaceutically acceptable salts of the compounds 
of this invention include non-toxic acid addition salts formed with 
inorganic acids, such as hydrochloric, hydrobromic, sulfuric and 
phosphoric acid, and organic acids, such as, methane sulfonic, salicyclic, 
maleic, malonic, tartaric, citric and ascorbic acids; and non-toxic salts 
formed with inorganic or organic bases, such as, those of alkali metals, 
for example, sodium, potassium and lithium, alkaline earth metals, for 
example, calcium and magnesium, light metals of Group III A, for example, 
aluminum, organic amines, such as, primary, secondary or tertiary amines, 
for example, cyclohexylamine, ethylamine, pyridine, methylaminoethanol, 
ethanolamine and piperidine. The salts are prepared by conventional means. 
Preferred compounds of this invention are those of general Formula I 
wherein R.sub.2 is hydrogen or alkylcarbonyl wherein the alkyl moiety has 
from 1 to 4 carbon atoms and is straight or branched with compounds 
wherein R.sub.2 is hydrogen being more preferred. Another preferred 
embodiment of this invention is the compounds of general Formula I wherein 
R.sub.1 is hydroxy or a straight or branched alkoxy group of from 1 to 8 
carbon atoms. Compounds wherein R.sub.1 is hydroxy are more preferred. 
Also, compounds of general Formula I wherein Y is F.sub.2 CH- or FCH.sub.2 
- are preferred. The most preferred compounds of this invention are those 
of general Formula I wherein R.sub.1 is hydroxy, R.sub.2 is hydrogen, n is 
the integer 2 and Y is F.sub.2 CH- or FCH.sub.2 -. 
Illustrative examples of compounds of general Formula I are the following: 
4-amino-4-fluoromethylbutyric acid, 
4-amino-4-difluoromethylbutyric acid, 
5-amino-5-fluoromethylpentanoic acid, 
5-amino-5-difluoromethylpentanoic acid, 
4-amino-4-fluoromethylbutyramide, 
N,N-dimethyl 4-amino-4-difluoromethylbutyramide, 
N-ethyl 5-amino-5-fluoromethylpentamide, 
ethyl 4-amino-4-fluoromethylbutyrate, 
isopropyl 4-amino-4-difluoromethylbutyrate, 
1-(4-amino-4-difluoromethyl-1-oxobutylamino)acetic acid, 
4-difluoromethyl-4-(1-oxoethylamino)butyric acid, 
4-fluoromethyl-4-n-propoxycarbonylaminobutyric acid, and 
methyl 4-aminomethylcarbonylaminobutyrate. 
The compounds of general Formula I are useful as inhibitors of 
.gamma.-aminobutyric acid transaminase resulting in an increase in brain 
levels of .gamma.-aminobutyric acid rendering the compounds useful in the 
treatment of disorders of the central nervous system function consisting 
of involuntary movement associated with Huntington's chorea, Parkinsonism, 
extrapyramidal effects of drugs, for example, neuroleptics, seizure 
disorders associated with epilepsy, alcohol withdrawal, barbiturate 
withdrawal, psychoses associated with schizophrenia, depression, manic 
depression and hyperkenesis. The compounds of general Formula I are also 
useful as hypothermic agents, myorelaxants, cholinergic agents, 
antibacterial agents, anticonvulsive agents, analgesics, anorexigenic 
agents, antiobesity agents, tranquilizers, sedatives and central nervous 
system stimulants. 
The ability of the compounds of general Formula I to inhibit 
.gamma.-aminobutyric acid transaminase may be shown by the protective 
effect administration of the compound has on audiogenic seizures in mice 
of the DBA strain measured by the general method described by Simler et 
al., Biochem. Pharmacol. 22, 1701 (1973) which is currently used to 
evidence antiepileptic acitivity. 
The compounds of this invention can be administered in various manners to 
achieve the desired effect. The compounds can be administered alone or in 
the form of pharmaceutical preparations to the patient being treated 
either orally or parenterally, for example, subcutaneously, intravenously 
or interperitoneally. The amount of novel compound administered will vary 
and can be any effective amount. Depending upon the patient, the condition 
being treated and the mode of administration, the quantity of novel 
compound administered may vary over a wide range to provide from about 0.1 
mg/kg (milligram per kilogram) to about 300 mg/kg of body weight of the 
patient per day. Unit doses of these compounds can contain, for example, 
from about 50 mg to 2000 mg of the compounds and may be administered, for 
example, from 1 to 4 times daily. 
As used herein the term patient is taken to mean warm blooded animals, such 
as, mammals, for example, cats, dogs, rats, mice, guinea pigs, sheep, 
horses, bovine cows and humans. 
The solid unit dosage forms can be of the conventional type. Thus, the 
solid form can be a capsule which can be of the ordinary gelatin type 
containing a novel compound of this invention and a carrier, for example, 
lubricant and inert fillers, such as, lactose, sucrose and corn starch. In 
another embodiment, the novel compounds are tableted with conventional 
tablet bases such as lactose, sucrose or corn starch in combination with 
binders, such as, acacia, corn starch or gelatin, disintegrating agents, 
such as, corn starch, potato starch or alginic acid and a lubricant such 
as stearic acid or magnesium stearate. For parenteral administration the 
compounds may be administered as injectable dosages of a solution or 
suspension of a compound in a physiologically acceptable diluent with a 
pharmaceutical carrier which can be a sterile liquid such as water and 
oils with or without the addition of a surfactant and other 
pharmaceutically acceptable adjuvants. Illustrative of oils which can be 
employed in these preparations are those of petroleum, animal, vegetable 
or synthetic origin, for example, peanut oil, soybean oil and mineral oil. 
In general, water, saline, aqueous dextrose and related solutions, 
ethanols and glycols, such as, propylene glycol or polyethylene glycol are 
preferred liquid carriers, particularly for injectable solutions. The 
compounds can be administered in the form of a depot injection or implant 
preparation which may be formulated in such a manner as to permit a 
sustained release of the active ingredient. The active ingredient can be 
compressed into pellets or small cylinders and implanted subcutaneously or 
intramuscularly as depot injections or implants. Implants may employ inert 
materials, such as, biodegradable polymers or synthetic silicones, for 
example, Silastic, silicone rubber manufactured by the Dow-Corning 
Corporation. 
In the specific examples included hereinbelow illustrative examples of 
suitable pharmaceutical formulations are described. 
The compounds of this invention wherein R.sub.1 is hydroxy and R.sub.2 is 
hydrogen are useful as intermediates for the preparation of cephalosporin 
derivatives of the following general Formula III which are useful as 
antibacterial agents: 
##STR9## 
In the above general Formula III n and Y have the meanings defined in 
general Formula I; M is hydrogen or a negative charge; and X.sub.1 is 
hydrogen or acetoxy. 
The compounds of general Formula III and pharmaceutically acceptable salts 
and individual optical isomers thereof are novel compounds useful as 
antibiotics and can be administered in a manner similar to that of many 
well known cephalosporin derivatives, for example, cephalexin, 
cephalothin, or cephalogylcine. The compounds of general Formula III and 
pharmaceutically acceptable salts and isomers thereof can be administered 
alone or in the form of pharmaceutical preparations either orally or 
parenterally and topically to warm blooded animals, that is, birds and 
mammals, for example, cats, dogs, bovine cows, sheep, horses and humans. 
For oral administration the compounds may be administered in the form of 
tablets, capsules or pills or in the form of elixirs or suspensions. For 
parenteral administration the compounds may best be used in the form of a 
sterile aqueous solution which may contain other solutes, for example, 
enough saline or glucose to make the solution isotonic. For topical 
administration the compounds of general Formula III, salts and isomers 
thereof may be incorporated into creams or ointments. 
Illustrative examples of bacteria against which the compounds of general 
Formula III and the pharmaceutically acceptable salts and individual 
optical isomers thereof are active are Staphylococcus aureus, Salmonella 
schotmuehleri, Klebsiella pneumoniae, Diplococcus pneumoniae and 
Streptococcus pyogenes. 
Illustrative pharmaceutically acceptable non-toxic inorganic acid addition 
salts of the compounds of general Formula III are mineral acid addition 
salts, for example, hydrogen chloride, hydrogen bromide, sulfates, 
sulfamates, phosphates and organic acid addition salts are, for example, 
maleate, acetate, citrate, oxalate, succinate, benzoate, tartrate, 
fumarate, malate and ascorbate. The salts can be formed by conventional 
means. 
An illustrative example of a compound of general Formula III is 
7-[[4-amino-4-difluoromethylbutyryl]amino]-3-acetyloxymethyl-8-oxo-5-thia- 
1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid. 
The compounds of general Formula III are prepared by coupling 
7-aminocephalosporanic acid or a derivative thereof having the formula 
##STR10## 
wherein X.sub.1 and M have the meanings defined in general Formula III 
with an acid of the formula 
##STR11## 
wherein Y and n have the meanings defined in general Formula I, or a 
functional derivative thereof, such as, the acid chloride or acid 
anhydride and in the presence of a dehydrating agent, such as, 
dicyclohexylcarbodiimide when the free acid is employed. Prior to the 
coupling reaction the amino group is protected with a suitable blocking 
group, for example, benzyloxycarbonyl which is subsequently removed by 
acid or base hydrolysis. 
The coupling reaction is generally carried out in a solvent, such as, ethyl 
acetate, p-dioxane, chloroform or tetrahydrofuran in the presence of a 
base, such as, alkaline bicarbonate. The temperature of the reaction may 
vary from about -10.degree. to 100.degree. C., and the reaction time may 
vary from about 1/2 hour to 10 hours. The cephalospor in products are 
isolated by conventional procedures. 
The compounds of general Formula I wherein R.sub.1 is hydroxy, R.sub.2 is 
hydrogen and Y is FCH.sub.2 - are prepared by treating 1 equivalent of 
5-hydroxymethyl-2-pyrrolidone or 6-hydroxy-2-piperidone, as n varies from 
2 to 3, with 1 equivalent of a fluoroamine reagent of the formula 
##STR12## 
wherein each R.sub.3 is an alkyl group having from 1 to 4 carbon atoms, 
for example, methyl, ethyl, isopropyl, n-propyl or n-butyl followed by 
acid hydrolysis of the thus obtained 5-fluoromethyl-2-pyrrolidone or 
6-fluoromethyl-2-piperidone. Suitable solvents for the reaction are, for 
example, diethyl ether, acetonitrile, tetrahydrofuran, dimethyl formamide 
dichloromethane or p-dioxane with reaction temperatures varying from about 
-20.degree. C. to the boiling point of the reaction mixture and the 
reaction time varies from about 1 to 24 hours. Hydrolysis is achieved by 
treating 5-fluoromethyl-2-pyrrolidone or 6-fluoromethyl-2-piperidone with 
aqueous mineral acids, for example, hydrochloric, hydrobromic or sulfuric 
for about 1 to 24 hours at about 25.degree. C. to reflux temperature. 
The fluoroamine reagents of Formula VI are prepared as generally described 
in Org. Reactions 21, pages 158 and 159 (1974) from 
chlorotrifluoroethylene and an amine of the formula (R.sub.3).sub.2 NH 
wherein R.sub.3 has the meaning defined above. 
5-Hydroxymethyl-2-pyrrolidone is known in the art. 
6-Hydroxymethyl-2-piperidone may be obtained from an ester, for example, a 
lower alkyl, such as, methyl, ethyl, n-propyl, isopropyl or n-butyl ester, 
of 6-oxopiperidine-2-carboxylic acid prepared, for example, by treating 
the acid which is known in the art with an appropriate lower alcohol 
saturated with HCl gas by well known procedures. The 
6-oxopiperidine-2-carboxylate is reduced to the corresponding alcohol, 
that is, 6-hydroxymethyl-2-piperidone by chemical reduction using a metal 
hydride reducing agent or by catalytic reduction. Chemical reduction is 
achieved using, for example, lithium aluminum hydride or lithium 
borohydride in a solvent, such as, diethyl ether, tetrahydrofuran, 
dimethyl formamide, dimethoxyethane or p-dioxane, at a temperature varying 
from 0.degree. C. to the reflux temperature of the solvent for about 1/2 
hour to 48 hours. Catalytic reduction may be achieved using copper 
chromite in a solvent such as p-dioxane, dimethoxyethane or lower 
alcohols, for example, ethanol, at a pressure of 2000 to 3000 psi with 
temperatures varying from about 25.degree. to 200.degree. C. for about 1 
to 8 hours. 
Compounds of general Formula I wherein R.sub.1 is hydroxy, R.sub.2 is 
hydrogen and Y is F.sub.2 CH- are prepared by treating 1 equivalent of 
5-formyl-2-pyrrolidone or 6-formyl-2-piperidone as n varies from 2 to 3 
with 1 to 10 equivalents of an N,N-disubstituted aminosulfur trifluoride 
of the formula 
##STR13## 
optionally in the presence of a solvent, such as, diethyl ether, 
tetrahydrofuran, benzene, acetonitrile, p-dioxane, dimethoxyethane, 
dichloromethane or mixtures thereof at a temperature of about -20.degree. 
C. to the boiling point of the solvent for about 10 minutes to 24 hours 
followed by acid hydrolysis. Hydrolysis is achieved by treating the thus 
obtained 5-difluoromethyl-2-pyrrolidone or 6-difluoromethyl-2-piperidone 
with aqueous mineral acid, for example, hydrochloric, hydrobromic or 
sulfuric at a temperature of about 25.degree. C. to reflux temperature for 
about 1 to 24 hours. 
The N,N-disubstituted aminosulfur trifluorides of Formula VII are known in 
the art, for example, see Synthesis 1973, p. 788 or may be obtained by 
reacting an appropriate secondary amine with sulfur (IV) fluoride by 
procedures generally known in the art. 
5-Formyl-2-pyrrolidone and 6-formyl-2-piperidone are obtained respectively 
by oxidation of 5-hydroxymethyl-2-pyrrolidone or 
6-hydroxymethyl-2-piperidone or by reduction of 
5-oxopyrrolidine-2-carboxylic acid or 6-oxopiperidine-2-carboxylic acid or 
lower alkyl esters of said acids by procedures generally known in the art. 
For example, oxidation of the hydroxymethyl derivatives to the 
corresponding aldehydes may be achieved using pyridinium chlorochromate 
(Tetrahedron Lett. 1975, 2647); Collins' reagent, that is, a pyridine 
chromate complex (Tetrahedron Lett. 1968, 3363); a dichloro 
dimethylsulfide complex (J. Am. Chem. Soc. 94, 7586 (1972)) or a complex 
of N-chlorosuccinimide or N-bromosuccinimide with dimethylsulfide; or 
silver carbonate on celite (C.R. Acad. Science, Paris 267, 900 (1968)). 
Reduction of the acids, or esters thereof, to the corresponding aldehydes 
may be achieved by electrolytic reduction (Bull. Soc. Chim. Japan 25, 404 
(1952)); using diisobutylaluminum hydride (J. Org. Chem. 31, 1447 (1966)); 
or tributyloxylithium aluminum hydride (J. Org. Chem. 35, 458 (1970)). 
The compounds of general Formula I wherein R.sub.1 is hydroxy, R.sub.2 is 
hydrogen and Y is F.sub.3 C- are prepared by reducing a ketone of the 
formula 
##STR14## 
wherein m is the integer 2 or 3 as n varies from 2 to 3 in the compounds 
of Formula I, to the corresponding alcohol treating 1 equivalent of said 
alcohol with 1 equivalent of an imide, such as, phthalimide, succinimide 
or maleimide, 1.1 equivalents of a phosphine, for example, 
triphenylphosphine or a trialkylphosphine, such as, tri-n-butylphosphine 
and 1.1 equivalents of diethyl azodicarboxylate in a solvent, such as, 
ethers, for example, diethyl ether, tetrahydrofuran or p-dioxane or 
benzene or dimethoxyethane at about 0.degree. to 100.degree. C., 
preferably about 25.degree. C., for about 1/2 hour to 24 hours under an 
inert atmosphere, such as nitrogen or argon, oxidizing the thus formed 
imide derivative, that is, 1-trifluoromethyl-1-imidopent-4-ene or 
1-trifluoromethyl-1-imidohex-5-ene to the corresponding acid, namely 
4-trifluoromethyl-4-imidopentanoic acid and hydrolyzing the imido-acid 
derivatives to the corresponding free amines. 
Reduction of the appropriate ketone of Formula VIII to the corresponding 
alcohol is achieved chemically using, for example, 1 to 10 equivalents of 
a metal hydride reducing ragent, such as lithium borohydride, sodium 
borohydride, sodium cyanoborohydride, or lithium aluminum hydride, borane 
or dimethylthioborane or catalytically using, for example, Raney nickel, 
rhodium, palladium on charcoal, or platinum oxide. Overall the reaction 
time varies from about 10 minutes to 24 hours and the temperature varies 
from about -40.degree. to 100.degree. C. depending on the reducing reagent 
employed. When chemical reduction is employed the reaction time generally 
varies from about 10 minutes to 24 hours with temperatures varying from 
about -40.degree. to 65.degree. C. Suitable solvents for chemical 
reduction of compounds of general Formula VIII include lower alcohols, 
such as, methanol or ethanol or ethers, such as, diethyl ether or 
tetrahydrofuran. When catalytic reduction is employed the reaction time 
varies from about 1 hour to 24 hours, the reaction temperature varies from 
about 25.degree. to 100.degree. C. and the pressure varies from 1 to 120 
atmospheres. Suitable solvents for catalytic reduction of compounds of 
general Formula VIII include lower alcohols, for example, methanol or 
ethanol, acetic acid, or ethyl acetate. Chemical reduction is preferred. 
Oxidation of the 1-imido-1-trifluoromethylalkene derivatives to the 
corresponding acids is achieved using any oxidizing agent known in the art 
to oxidatively cleave double bonds, for example, ozone, sodium 
metaperiodate and potassium permanganate, potassium permanganate alone, 
osmium tetroxide and potassium permanganate or ruthenium tetroxide and 
sodium metaperiodate. The oxidation is carried out in solvents, such as, 
dichloromethane, carbon tetrachloride, p-dioxane, tetrahydrofuran, diethyl 
ether, acetone, pyridine, water or mixtures thereof at a pH of about 7 to 
10 with temperatures varying from 0.degree. to 80.degree. C. for about 1 
to 24 hours. 
Hydrolysis of the imide to the amine is achieved using a strong mineral 
acid, for example, hydrochloric acid, hydrobromic acid or sulfuric acid or 
an organic acid, for example, toluene sulfonic acid or trifluoroacetic 
acid in water at reflux temperature for about 4 to 48 hours, or using, for 
example, 1 to 3 equivalents of hydrazine, methylhydrazine or methylamine 
at a temperature of from about 25.degree. C. to reflux for about 1 to 12 
hours followed by treatment wih a strong mineral acid or organic acid as 
described above. 
The compounds of general Formula VIII are prepared by treating an alkenyl 
halide of the formula 
EQU H.sub.2 C.dbd.CH(CH.sub.2).sub.p --X IX 
wherein p is the integer 2 or 3 as m varies from 2 to 3 in the compounds of 
Formula VIII and X is halogen, such as, chlorine, bromine or iodine with 
triphenylphosphine in a suitable solvent, such as, hydrocarbons, for 
example, benzene or toluene, or lower alcohols, such as, methanol or 
ethanol, or acetonitrile, tetrahydrofuran, diethyl ether or 
dimethoxyethane at about 25.degree. C. to the reflux temperature of the 
solvent for about 10 minutes to 48 hours. On cooling a precipitate forms 
which is washed with solvent and recrystallized using, for example, ethyl 
acetate, acetonitrile or a lower alcohol, such as methanol or ethanol to 
give the appropriate alkenyl triphenylphosphonium salt which is added to 
excess (up to 25%) sodium or lithium metal dissolved in liquid ammonia to 
which is added a catalytic amount of ferric nitrate with stirring for 
about 10 minutes to 3 hours after which the ammonia is evaporated under an 
inert atmosphere, such as, nitrogen or argon. An appropriate solvent, such 
as, benzene, toluene, diethyl ether, tetrahydrofuran or dimethoxyethane is 
added and the resulting alka-dienylene phosphorane is collected. The 
alka-dienylenephosphorane is treated with an ester of, such as, a lower 
alkyl, for example, methyl, ethyl, n-propyl, isopropyl or n-butyl ester of 
trifluoroacetic acid in a solvent such as benzene, toluene, diethyl ether, 
tetrahydrofuran or dimethoxyethane under an inert atmosphere such as 
nitrogen or argon at a temperature of about 0.degree. C. to the reflux 
temperature of the solvent for about 30 minutes to 24 hours after which 
the reaction mixture is concentrated and distilled to give the appropriate 
1-alkoxy-1-trifluoromethylpent-1,4-diene and 
1-alkoxy-1-trifluoromethylhex-1,5-diene. The appropriate diene is treated 
with aqueous mineral acid, such as, hydrochloric or hydrobromic acid or an 
organic acid, such as, trifluoroacetic acid or p-toluenesulfonic acid 
using a cosolvent, such as, tetrahydrofuran, diethyl ether or benzene for 
about 30 minutes to 24 hours at a temperature of from about 0.degree. C. 
to the reflux temperature of the solvent to give the appropriate ketone. 
The amount of acid employed may vary from a catalytic amount to 
concentrated acid. 
Alternatively the compound of general Formula I wherein R.sub.1 is hydroxy, 
R.sub.2 is hydrogen, Y is F.sub.3 C- and n is 2 may be obtained by 
reducing an ester, for example, a lower alkyl, such as, methyl, ethyl, 
n-propyl, isopropyl or n-butyl ester of levulinic acid, that is, 
5,5,5-trifluoro-4-oxopentanoic acid, to the corresponding alcohol, 
treating 1 equivalent of said alcohol with 1 equivalent of an imide, such 
as, phthalimide, succinimide or maleimide, 1.1 equivalents of a phosphine, 
for example, triphenylphosphine or a trialkylphosphine, such as, 
tri-n-butylphosphine and 1.1 equivalents of diethyl azodicarboxylate in a 
solvent, such as, ethers, for example, diethyl ether, tetrahydrofuran or 
p-dioxane or benzene or dimethoxyethane at about 0.degree. to 100.degree. 
C., preferably about 25.degree. C., for about 1/2 hour to 24 hours under 
an inert atmosphere, such as, nitrogen or argon and hydrolyzing the thus 
formed imide to the corresponding free amine. 
Reduction of the appropriate ester of levulinic acid to the corresponding 
alcohol is achieved chemically using, for example, 1 to 10 equivalents of 
a metal hydride reducing reagent, such as lithium borohydride, sodium 
borohydride, sodium cyanoborohydride, or lithium aluminum hydride, borane 
or dimethylthioborane or catalytically using, for example, Raney nickel, 
rhodium, palladium on charcoal, or platinum oxide. Overall the reaction 
time varies from about 10 minutes to 24 hours and the temperature varies 
from about -40.degree. to 100.degree. C. depending on the reducing reagent 
employed. When chemical reduction is employed the reaction time generally 
varies from about 10 minutes to 24 hours with temperatures varying from 
about -40.degree. to 65.degree. C. Suitable solvents for chemical 
reduction of the ester include lower alcohols, such as, methanol or 
ethanol or ethers, such as, diethyl ether or tetrahydrofuran. When 
catalytic reduction is employed the reaction time varies from about 1 hour 
to 24 hours, the reaction temperature varies from about 25.degree. to 
100.degree. C. and the pressure varies from 1 to 120 atmospheres. Suitable 
solvents for catalytic reduction of the appropriate ester of levulinic 
acid include lower alcohols, for example, methanol or ethanol, acetic 
acid, or ethyl acetate. Catalytic reduction is preferred. 
Hydrolysis of the imide to the amine is achieved using a strong mineral 
acid, for example, hydrochloric acid, hydrobromic acid or sulfuric acid or 
an organic acid, for example, toluene sulfonic acid or trifluoroacetic 
acid in water at reflux temperature for about 4 to 48 hours, or using, for 
example, 1 to 3 equivalents of hydrazine, methylhydrazine or methylamine 
at a temperature of from about 25.degree. C. to reflux for about 1 to 12 
hours followed by treatment with a strong mineral acid or organic acid as 
described above. 
As indicated hereinabove tri-alkylphosphines, such as, 
tri-n-butylphosphine, may be employed in preparing compounds of general 
Formula I wherein Y is F.sub.3 C-. As used in the name tri-alkylphosphine 
the alkyl moiety has from 1 to 10 carbon atoms. The tri-alkylphosphines 
are known in the art or may be prepared by procedures generally known in 
the art. 
The compounds of general Formula I wherein R.sub.2 is alkylcarbonyl wherein 
the alkyl moiety is straight or branched and has from 1 to 4 carbon atoms 
are prepared by treating the corresponding derivatives wherein R.sub.2 is 
hydrogen with the acid halide of the formula 
##STR15## 
wherein halo is a halogen atom, for example, chlorine or bromine and 
R.sub.6 is a straight or branched alkyl group having from 1 to 4 carbon 
atoms in water in the presence of a base such as sodium hydroxide or 
triethylamine at a temperature of from 0.degree. C. to 25.degree. C. for 
from 1/2 hour to 6 hours. 
The compounds of general Formula I wherein R.sub.2 is alkoxycarbonyl 
wherein the alkoxy moiety is straight or branched and has from 1 to 4 
carbon atoms are prepared by treating the corresponding derivative wherein 
R.sub.2 is hydrogen with an alkyl haloformate of the formula 
##STR16## 
wherein halo is a halogen atom such as chlorine or bromine and R.sub.7 is 
a straight or branched alkyl group having from 1 to 4 carbon atoms in 
water in the presence of a base such as sodium hydroxide or triethylamine 
at a temperature of from about 0.degree. to 25.degree. C. for from about 
1/2 hour to 6 hours. 
The compounds of general Formula I wherein R.sub.2 is 
##STR17## 
wherein R.sub.8 is hydrogen, a straight or branched lower alkyl group of 
from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl are prepared by 
treating the corresponding derivative wherein R.sub.2 is hydrogen and 
R.sub.1 is a lower alkoxy group with an acid of the formula 
##STR18## 
or an anhydride thereof wherein the amino group is protected with a 
suitable blocking group such as benzyloxycarbonyl or tert-butoxycarbonyl 
and R.sub.8 has the meaning defined hereinabove in an ether, such as, 
tetrahydrofuran or dioxane, methylene chloride or chloroform and in the 
presence of a dehydrating agent when the free acid is employed, at a 
temperature of from about 0.degree. C. to 35.degree. C. for about 1 to 12 
hours followed by acid hydrolysis to remove the protecting groups. 
The compounds of general Formula I wherein R.sub.1 is a straight or 
branched alkoxy group of from 1 to 8 carbon atoms are prepared by treating 
the corresponding derivatives wherein R.sub.1 is hydroxy with thionyl 
chloride to form the acid chloride which is reacted with an alcohol of the 
formula R.sub.9 -OH, wherein R.sub.9 is a straight or branched alkyl group 
of from 1 to 8 carbon atoms, such as, methyl, ethyl, n-propyl, isopropyl, 
n-butyl, hexyl, or octyl, at about 25.degree. C. for from about 4 to 12 
hours. 
The compounds of general Formula I wherein R.sub.1 is -NR.sub.10 R.sub.11 
wherein each of R.sub.10 and R.sub.11 is hydrogen or a straight or 
branched lower alkyl of 1 to 4 carbon atoms are prepared by an acylation 
reaction of an acid halide, for example, an acid chloride, or the 
corresponding compound wherein R.sub.1 is hydroxy and R.sub.2 has the 
meaning defined in Formula I with the proviso that any free amino group is 
protected with a suitable protecting group, for example, carbobenzyloxy or 
tert-butoxycarbonyl with an excess of an appropriate amine which may be 
represented as HNR.sub.10 R.sub.11. The reaction is carried out in 
methylene chloride, chloroform, dimethylformamide, ethers such as 
tetrahydrofuran or dioxane or benzene at about 25.degree. C. for about 1 
to 4 hours. Suitable amines are, for example, ammonia, or a compound which 
is a potential source of ammonia, for example, hexamethylenetetramine; 
primary amines, for example, methylamine, ethylamine, or n-propylamine; 
and secondary amines such as dimethylamine, diethylamine or 
di-n-butylamine. Following the acylation reaction the amino protecting 
group is removed by treatment with acid, for example, hydrogen bromide in 
dioxane or hydrogenolysis. 
The compounds of general Formula I wherein R.sub.1 is 
##STR19## 
are prepared by reacting the corresponding derivative wherein R.sub.1 is 
hydroxy or a functional derivative thereof such as an acid anhydride and 
R.sub.2 has the meaning defined in Formula I with the proviso that any 
free amino group is protected with a suitable blocking group, such as 
benzyloxycarbonyl or tert-butoxycarbonyl with a compound of the formula 
##STR20## 
wherein R.sub.12 has the meaning defined in general Formula I and R.sub.13 
is a lower alkyl group, for example, methyl or ethyl in an ether, such as, 
tetrahydrofuran or dioxane at 0.degree. to about 50.degree. C. for about 1 
to 24 hours followed by acid hydrolysis to remove the protecting group, 
with the proviso that when the amine protected free acid is employed the 
reaction is carried out using a dehydrating agent such as 
dicyclohexylcarbodiimide. 
The individual optical isomers of the compounds of general Formula I 
wherein R.sub.2 is H may be separated by using a (+) or (-) 
binaphthylphosphoric acid salt by the method of R. Viterbo et al., 
Tetrahedron Letters 48, 4617 (1971). Other resolving agents such as (+) 
camphor-10-sulfonic acid may also be employed. The individual optical 
isomers of compounds of Formula I wherein R.sub.2 is other than H may be 
obtained as described herein for the racemate only starting with the 
resolved amine. 
The lactams of this invention as represented by general Formula II are 
prepared by generally known procedures from the appropriate amino acid of 
the formula 
##STR21## 
wherein n and Y have the meanings defined in general Formula I. The 
lactams may be obtained, for example, by treating an acid of Formula X 
with a dehydrating agent, such as, dicyclohexylcarbodiimide or by heating 
an ester, such as, a lower alkyl, for example, ethyl ester of the acid of 
Formula X in a lower alcohol solvent for about 1 to 24 hours at about 
80.degree. to 120.degree. C.

EXAMPLE 1 
7-[[4-Amino-4-fluoromethylbutyryl]amino]-3-acetyloxymethyl-8-oxo-5-thia-1-a 
zabicyclo[4.2.0]oct-2-ene-2-carboxylic acid 
A mixture of 1 g of 
3-acetyloxy-7-amino-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic 
acid and 1 g of 4-amino-4-fluoromethylbutyric acid chloride wherein the 
free amino group is protected with tert-butoxycarbonyl in 50 ml of ethyl 
acetate is refluxed for two hours after which the solvent is removed 
leaving a residue which is treated with mild acid and chromatographed on 
silica gel using benzene-acetone as the eluant to give 
7-[[4-amino-4-fluoromethylbutyryl]amino]-3-acetyloxymethyl-8-oxo-5-thia-1- 
azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid. 
EXAMPLE 2 
An illustrative composition for hard gelatin capsules is as follows: 
______________________________________ 
(a) 4-amino-4-fluoromethylbutyric acid 
20 mg 
(b) talc 5 mg 
(c) lactose 90 mg 
______________________________________ 
The formulation is prepared by passing the dry powders of (a) and (b) 
through a fine mesh screen and mixing them well. The powder is then filled 
into hard gelatin capsules at a net fill of 115 mg per capsule. 
EXAMPLE 3 
An illustrative composition for tablets is as follows: 
______________________________________ 
(a) 4-amino-4-difluoromethylbutyric acid 
20 mg 
(b) starch 43 mg 
(c) lactose 45 mg 
(d) magnesium stearate 2 mg 
______________________________________ 
The granulation obtained upon mixing the lactose with the compound (a) and 
part of the starch and granulated with starch paste is dried, screened, 
and mixed with the magnesium stearate. The mixture is compressed into 
tablets weighing 110 mg each. 
EXAMPLE 4 
An illustrative composition for an injectable suspension is the following 1 
ml ampul for an intramuscular injection. 
______________________________________ 
Weight percent 
______________________________________ 
(a) 4-amino-4-difluoromethylbutyric acid 
1.0 
(b) polyvinylpyrrolidone 0.5 
(c) lecithin 0.25 
(d) water for injection to make 
100.0 
______________________________________ 
The materials (a)-(d) are mixed, homogenized, and filled into 1 ml ampuls 
which are sealed and autoclaved 20 minutes at 121.degree. C. Each ampul 
contains 10 mg per ml of novel compound (a). 
EXAMPLE 5 
4-Amino-4-fluoromethylbutyric acid 
To a solution of 0.8 g (6.2 mmole) of 5-hydroxymethyl-2-pyrrolidone in a 
mixture of 20 ml of tetrahydrofuran and acetonitrile is added a solution 
of 1.2 g (6.4 mmole) of 2-chloro-1,1,-trifluorotriethylamine in 10 ml of 
tetrahydrofuran during 1/2 hour. The reaction mixture is allowed to stand 
at about 25.degree. C. for 15 hours after which the solution is washed 
with water, potassium hydroxide until neutral, water and then dried over 
magnesium sulfate and filtered. The filtrate is evaporated under reduced 
pressure leaving a residue which is distilled under high vacuum to afford 
5-fluoromethyl-2-pyrrolidone. The pyrrolidone (500 mg) is heated in 20 ml 
of 6 N hydrochloric acid at reflux for 12 hours after which the solution 
is concentrated under vacuo and the residue passed through an Amberlite 
column IR 120 H.sup.+. Elution with 1 M ammonium hydroxide affords 
4-amino-4-fluoromethylbutyric acid which is recrystallized from 
water/acetone. 
EXAMPLE 6 
4-Amino-4-difluoromethylbutyric acid 
(A) To a suspension of 15 mmole of pyridinium chlorochromate in 20 ml of 
methylene chloride is rapidly added at 25.degree. C. a suspension of 10 
mmole of 5-hydroxymethyl-2-pyrrolidone in 10 ml of acetonitrile. The 
mixture is stirred for 10 hours at 25.degree. C. then diluted with diethyl 
ether. Filtration of the organic phase through florisil and concentration 
of the solvent at reduced pressure affords 5-formyl-2-pyrrolidone. 
(B) To a solution of 0.07 mole of dimethylaminosulfur trifluoride in 30 ml 
of dioxane is added dropwise with stirring a solution of 0.01 mole of 
5-formyl-2-pyrrolidone in 10 ml of dioxane. Stirring is continued for 15 
hours at 25.degree. C. after which the reaction mixture is poured into ice 
water then extracted with ethyl acetate. The organic phase is separated, 
washed with water, dried over magnesium sulfate, filtered and concentrated 
under reduced pressure to yield 5-difluoromethyl-2-pyrrolidone. 
(C) When in the procedure of Example 5 500 mg of 
5-difluoromethyl-2-pyrrolidone is substituted for 
5-fluoromethyl-2-pyrrolidone, 4-amino-4-difluoromethylbutyric acid is 
obtained. 
EXAMPLE 7 
4-Amino-4-trifluoromethylbutyric acid 
A mixture of 20 ml of 1-bromo-3-butyne and 25 mmole of tirphenylphosphine 
in 50 ml of benzene is heated at reflux for 3 days. The solid which 
separates upon cooling is filtered, washed with benzene and dried under 
reduced pressure is afford triphenyl-3-butenylphosphonium bromide. To a 
solution of 100 ml of liquid ammonia is added 0.26 g of finely divided 
sodium and a catalytic amount of ferric nitrate. When the blue solution 
turns gray finely powdered triphenyl-3-butenylphosphonium bromide 
(2.10.sup.-2 mole) is added. The reaction mixture is stirred for 15 
minutes after which the ammonia is evaporated under a stream of nitrogen. 
To the resulting residue is added 100 ml of benzene, and the heterogeneous 
mixture is heated at reflux temperature for 10 minutes. The solid residue 
is filtered off and the filtrate is evaporated to dryness to give 
3-butenylidenephosphorane. To a solution of salt free 
3-butenylidenephosphorane (2.10.sup.-2 mole) in 100 ml of benzene is added 
6.6 g (5.10.sup.-2 mole) of ethyl trifluoroacetate. The reaction mixture 
is heated at reflux temperature for 12 hours under nitrogen. Concentration 
of the solvent leaves an oily residue which is purified by distillation to 
give 1-trifluoromethyl-1-ethoxy-1,4-pentadiene. A suspension of 10 g of 
1-trifluoromethyl-1-ethoxy-1,4-pentadiene in 20 ml of 1 N aqueous sulfuric 
acid is stirred for 20 minutes. Continuous extraction of the mixture with 
ether affords 1-trifluoromethylpent-4-ene-1-one. 
A solution of 15.2 g of 1-trifluoromethylpent-4-ene-1-one in 150 ml of 
methanol is heated at 0.degree. C. with 1.7 g of sodium borohydride. The 
reaction mixture is stirred for 2 hours at 25.degree. C. then neutralized 
with HCl. The residue obtained after evaporation of the solvent is 
extracted several times with chloroform, washed with brine, dried over 
magnesium sulfate and concentrated under reduced pressure to give 
1-trifluoromethylbut-4-ene-1-ol. A solution of 10 mmole of 
1-trifluoromethylbut-4-ene-1-ol, 10 ml of triphenylphosphine and 10 ml of 
diethyl azodicarboxylate in 25 ml of tetrahydrofuran is stirred under 
nitrogen at 25.degree. C. for 16 hours after which the solvent is 
evaporated under reduced pressure. The resulting residue is treated with 
benzene. The insoluble material is discarded and the semi-solid obtained 
after concentration of the filtrate under reduced pressure is 
recrystallized from methylene chloride-pentane to afford 
N-(1-trifluoromethyl-3-butenyl)phthalimide. To a solution of 25 mmole of 
the phthalimide in 25 ml of dioxane is added a solution of 12 mmole of 
potassium permanganate and 50 mmole of sodium metaperiodate in water. 
Potassium carbonate is added to adjust the pH of the solution to 8 and the 
reaction mixture is stirred for 24 hours at 25.degree. C. then acidified 
with sulfuric acid to a pH of 1 and extracted with ethyl acetate. The 
organic phase is washed with brine, dried over magnesium sulfate and 
concentrated under reduced pressure. The resulting residue is 
recrystallized from methylene chloride-pentane to give 
4-trifluoromethyl-4-phthalimidopentanoic acid. A solution of 20 ml of 
4-trifluoromethyl-4-phthalimidopentanoic acid and 20 mmole of hydrazine 
hydrate in 20 ml of ethanol is heated at reflux temperature for 12 hours. 
The solid which separates on cooling is filtered and washed with water. 
The filtrate is concentrated under reduced pressure to give a solid which 
is recrystallized from water/acetone to give 
4-amino-4-trifluoromethylpentanoic acid. 
EXAMPLE 8 
4-Amino-4-trifluoromethylbutyric acid 
To a solution of 30 mmole of 4-trifluoromethyl-4-oxobutyric acid ethyl 
ester in 20 ml of ethanol cooled to 0.degree. C. is added 30 mmole of 
sodium borohydride. The reaction mixture is stirred at 0.degree. C. for 4 
hours then acidified with M HCl to a pH of 1. The solvent is evaporated 
under reduced pressure and the residue is partitioned between water and 
ether. The organic phase is washed with brine, dried over magnesium 
sulfate and concentrated to give 4-trifluoromethyl-4-hydroxybutyric acid 
ethyl ester. A mixture of 20 mmole of 4-trifluoromethyl-4-hydroxybutyric 
acid ethyl ester, 22 mmole of triphenylphosphine, 20 mmole of phthalimide 
and 22 mmole of diethyl azodicarboxylate in 60 ml of tetrahydrofuran is 
heated at reflux temperature under nitrogen for 24 hours. The solvent is 
evaporated under reduced pressure, and the residue chromatographed on 
silica gel to give 4-trifluoromethyl-4-phthalimidobutyric acid ethyl 
ester. A suspension of 30 mmole of 4-trifluoromethyl-4-phthalimidobutyric 
acid ethyl ester in 20 ml of concentrated HCl is heated at reflux 
temperature for 24 hours. The solid which separates on cooling is 
filtered, and the filtrate concentrated under reduced pressure. The 
residue is dissolved in the minimum quantity of water, and the pH of the 
solution adjusted to 5 by the addition of sodium hydroxide. Acetone is 
added, and the precipitated 4-amino-4-trifluoromethylbutyric acid 
collected by filtration. 
EXAMPLE 9 
5-Amino-5-fluoromethylpentanoic acid 
When in the procedure of Example 5 an appropriate amount of 
6-hydroxymethyl-2-piperidone is substituted for 
5-hydroxymethyl-2-pyrrolidone, 5-amino-5-fluoromethylpentanoic acid is 
obtained. 
EXAMPLE 10 
5-Amino-5-difluoromethylpentanoic acid 
When in the procedure of Example 6 (A) an appropriate amount of 
6-hydroxymethyl-2-piperidone is substituted for 
5-hydroxymethyl-2-pyrrolidone, 6-formyl-2-piperidone is obtained. When an 
appropriate amount of 6-formyl-2-piperidone is substituted for 
5-formyl-2-pyrrolidone in the procedure of Example 6 (B), 
6-difluoromethyl-2-piperidone is obtained which, when substituted for 
5-difluoromethyl-2-pyrrolidone in an appropriate amount in the procedure 
of Example 5, yields 5-amino-5-difluoromethylpentanoic acid. 
EXAMPLE 11 
4-Difluoromethyl-4-(1-oxoethylamino)butyric acid 
To a solution of 2 mmole of 4-amino-4-difluoromethylbutyric acid in 5 ml of 
1 N sodium hydroxide at 0.degree. C. are added simultaneously from two 
syringes 160 mg of acetyl chloride diluted in 1 ml of dioxane and 2 ml of 
1 N sodium hydroxide. After 30 minutes at 0.degree. C. the solution is 
acidified by the addition of 6 N hydrochloric acid, then extracted well 
with dichloromethane. The organic phase is dried and concentrated to 
afford 4-difluoromethyl-4-(1-oxoethylamino)butyric acid. 
EXAMPLE 12 
N-Propyl 4-amino-4-difluoromethylbutyramide hydrobromide 
To a solution of 2 mmole of 4-amino-4-difluoromethylbutyric acid in 5 ml of 
1 N sodium hydroxide at 0.degree. C. are added simultaneously from two 
syringes 2 mmole of benzyl chloroformate in 1 ml of dioxane and 2 ml of 1 
N sodium hydroxide. After 30 minutes at 0.degree. C. the solution is 
acidified by the addition of 6 N hydrochloric acid, then extracted well 
with dichloromethane. The organic phase is dried and concentrated to 
afford 4-benzyloxycarbonylamino-4-difluoromethylbutyric acid which is 
dissolved in 15 ml of dichloromethane and treated with 2 mmole of thionyl 
chloride at 25.degree. C. for 1 hour after which 4 mmole of propyl amine 
is added. The solution is stirred at 25.degree. C. for one hour, then 
washed with water, dried and concentrated. The residue is treated with 6 
ml of a solution of dioxane containing 40% w/w hydrogen bromide and 
allowed to stand for 30 minutes at 25.degree. C. after which 50 ml of 
ether is added. The resulting precipitate is collected to afford N-propyl 
4-amino-4-difluoromethylbutyramide hydrobromide. 
EXAMPLE 13 
4-Amino-4-difluoromethylbutyric acid ethyl ester 
A solution of 2 mmole of 4-amino-4-difluoromethylbutyric acid in 15 ml of 
dichloromethane is treated with 2 mmole of thionyl chloride at 25.degree. 
C. for one hour after which 20 ml of ethanol is added. The solution is 
stirred at 25.degree. C. for one hour, washed with water, dried and 
concentrated to afford 4-amino-4-difluoromethylbutyric acid ethyl ester. 
EXAMPLE 14 
4-(2-Aminopropionylamino)-4-difluoromethylbutyric acid 
A solution of 1 mmole of 4-amino-4-difluoromethylbutyric acid ethyl ester 
in 4 ml of methylene chloride is treated with 1 mmole of 
N-carbobenzoxyalanine and 1 mmole of N,N'-dicyclohexylcarbodiimide for 10 
hours at 25.degree. C. The mixture is cooled to 0.degree. C. and the 
precipitated dicyclohexylurea filtered off. The filtrate is diluted with 
methylene chloride, washed with water, bicarbonate, dilute HCl then dried 
and concentrated. The residue is treated with 5 ml of ethanol and 5 ml of 
a 40% (w/w) solution of hydrogen bromide in dioxane for 30 minutes at 
25.degree. C. Ether (50 ml) is added and the resulting precipitate 
collected which is treated with 15 ml of 1 N sodium hydroxide for 10 hours 
at 25.degree. C. The pH of the solution is adjusted to neutral, and the 
product isolated from an Amberlite 120 H.sup.+ resin by elution with 2 M 
ammonium hydroxide affording 4-( 
2-aminopropionylamino)-4-difluoromethylbutyric acid.