Process for obtaining cyclic amino acids

Abstract

The invention relates to a method of obtaining substantially-salt-free cyclic amino acids having formula (I),where n is a whole number selected from 2, 3 and 4,and, in particular, gabapentin (compound having formula (I) with n=3), with a high degree of purity. The inventive method comprises a step involving the electrolysis of a solution containing an addition salt of the cyclic amino acid with a mineral acid, which serves to eliminate the anion from the mineral acid for concentrations of no more than 3 ppm.

Description

FIELD OF THE ART[0001]The present invention relates to a new industrial process for obtaining cyclic amino acids, and particularly gabapentin, with a high degree of purity.PRIOR STATE OF THE ART[0002]Cyclic amino acids with the structure of formula (I)where n is an integer selected from 2, 3 and 4, have good pharmacological properties making them suitable to be used in the treatment of cerebral disorders such as epilepsy and hypokinesia, among others. They also bring about an improvement in brain functions, being particularly useful in the treatment of geriatric patients. Where n=2 the compound has a cyclopentane ring, where n=3, the ring is a cyclohexane ring, and where n=4, the ring is a cycloheptane ring. In particular, gabapentin (compound of formula (I) with n=3) is one of the compounds having the best pharmacological properties.[0003]Compounds of formula (I), including gabapentin among them, and several processes for obtaining them are described in Spanish patent ES 443723-A. ...

AI Technical Summary

Problems solved by technology

The most significant difficulty facing the processes for preparing cyclic amino acids of formula (I) from an addition salt thereof with a mineral acid is to provide a cyclic amino acid of formula (I), and particularly gabapentin, with a quality suitable for being used as an active ingredient in pharmaceutical formulations.

As described in European patent document EP 414263-A2, the presence of a mineral acid anion (for example, chloride) may cause stability problems in cyclic amino acids of formula (I) and in their pharmaceutical formulations, due to the production of the lactam of formula (II) as an impurity.

Nevertheless, these processes for obtaining the compound have drawbacks making them rather disadvantageous at the industrial scale.

It is necessary to mention among the main drawbacks the large volumes of solvent (demineralized water or short-chain alcohols) required, the chromatographic columns filled with ion exchange resin intended exclusively for said operation, the need to regenerate the resins, the large amount of material necessary for the metering and collection of the eluates, the evaporation of large amounts of liquids at a low temperature to prevent the formation of lactam, the long times used to reduce the mineral acid anion content to sufficiently low values, and the difficulty of being able to easily obtain gabapentin with the desired mineral acid anion content.

This process requires handling considerable amounts of resin, which must be regenerated before a new use, and it is difficult to obtain the end product with the desired mineral acid anion content.

These processes have the drawback, among others, that the obtained product may be contaminated with considerable amounts of the amine used in the neutralization step and which must then be eliminated by means of using additional purification steps.

However, among the drawbacks of this process the need to work with expensive facilities using high-pressure pumps and requiring long process times so as to obtain the product within the established quality parameters can be mentioned, especially when they involve contents on the order of ppm.

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