Patent GB-788226-A (GB)
Title: Stereoisomers of ª‡-phenyl-ª‡-piperidyl-(2)-acetic acid and process of making same
IPC: C07D211/34
Filed: 1954-12-14
Abstract: The invention comprises the pharmacologically active, or b, diastereoisomers, free from the pharmacologically less active, or a, diastereoisomers of the racemates and optical antipodes of a -phenyl-a -piperidyl-(2)-acetic acid and its functional derivatives, such as the esters or amide, and comprises also a method for the preparation of the b-racemates or b-antipodes wherein an a-racemate or a-antipode of an a -phenyl - a  - piperidyl - (2) - acetic acid or its functional derivative is treated with an alkaline agent and if desired the free or functionally converted carboxylic group is subjected to conversion.  Suitably the a -phenol-a -piperidyl-(2)-acetic acid or its ester or amide is treated with an alkaline reagent such as an alkali metal or alkaline earth metal hydroxide, at an elevated temperature, the resulting b compound is converted to the free acid if desired, for example by treatment with strong acid, and is isolated by crystallization from water at a pH of about 6.  In examples: (1) a -phenyl-a -piperidyl acetic acid methyl ester, containing 20 per cent of b-racemate is converted to the b-racemate of potassium a -phenyl-a -piperidyl-(2)-acetate by treatment with aqueous potassium hydroxide the free acid is isolated by treatment with sulphuric acid and the product is converted to its methyl and butyl esters; (2) the a-racemate of a -phenyl-a -piperidyl-(2)-acetic acid (obtained by hydrolysis of the methyl ester) is converted into the b-racemate as in (1); (3) and (4) a -phenyl-a -piperidyl-(2)-acetamide (obtained by hydrogenation of the corresponding pyridine derivative) is converted to the b-racemate of the free acid as in (1); (5) a -phenyl-a -piperidyl-(2)-acetamide is converted to the b-racemate by treatment with trimethylbenzyl ammonium hydroxide and (6) laevo-a-isomer of a -phenyl-a -piperidyl-(2)-acetamide is heated with aqueous potassium hydroxide to give the dextro-b-antipode which is then converted to the free acid and the methyl ester.  The laevo-a-antipode of a  - phenyl - a - piperidyl - (2) - acetamide used as a starting material in Example (6) is isolated by fractional crystallization of the l-tartrate of the racemic mixture.  Specification 589,625, [Group IV], is referred to.ALSO:Pharmaceutical compositions comprise the b or pharmacologically active diastereoisomers of the racemates and optical antipodes of a -phenyl - a  - piperidyl - 2 - acetic acid or its functional derivatives such as the esters or the amide, and a carrier.  The compositions suitably contain 1 mg. to 50 mg. of active material per unit dose and may be admixed with water, gelatin, lactose, starch, magnesium stearate, talc, vegetable oils, benzyl alcohols, gum, polyalkylene glycols, petroleum jelly or cholesterol and may for example be made up as tablets, dragees, salves, creams, solutions, suspensions or emulsions.  Specified active materials include b-racemic a -phenyl-a -piperidyl acetic acid, its amide and its methyl and butyl ester, and the dextro-rotatory antipode of this acid, its amide and its methyl ester.  Buffers, preservatives, stabilizers, emulsifiers and other therapeutic substances may be present.  Specification 589,625 is referred to.