- PubMed Health A division of the National Library of Medicine at the National Institutes of Health.
- Keppra (levetiracetam) Final Printed Label April 2009. Center for Drug Evaluation and Research, U.S. Food and Drug Administration. Accessed 29 July 2011.
- Keppra UCB (manufacturer’s website)
- NIH MedLine drug information
- Levetiracetam was first disclosed in EP 162036 indicating particular therapeutic properties distinguishing it from the racemic form.
- Several processes for obtaining levetiracetam have been disclosed. One promising approach is the reaction of (S)-2-aminobutyramide (5) with an alkyl 4-halobutyrate or with a 4-halobutyryl halide followed by cyclization as outlined in EP 162036 . Clearly, said (S)-2-aminobutyramide (5) is a key intermediate in the preparation of levetiracetam and given the importance of the correct stereochemistry of levetiracetam also the correct stereochemistry in the key intermediates is of importance.
- The separation of stereoisomers is considered to be one of the difficult tasks in chemistry since chiral compounds exhibit identical physical properties in non-chiral environments. Although several approaches for the preparation of optically pure (S)-2-aminobutyramide (5) have been reported, many of these are related to resolution of racemic (R,S)-2-aminobutyramide (e.g. WO 2006/103696 ), optionally using catalytic amounts of an aldehyde such as described in JP 2007/191470 . However, an approach directly starting from the Schiff base of racemic (R,S)-2-aminobutyramide (i.e. compound (1)) is unavailable whereas there is a need for this as said Schiff bases are highly suitable from a preparative point of view as these compounds may be conveniently isolated from the aqueous media that they are usually prepared in. This is in contrast with the parent 2-aminobutyramide which is highly soluble in water and consequently difficult to obtain in sufficient purity.
- Several processes for obtaining levetiracetam have been disclosed in the art. Patent application EP 162,036-A1 discloses obtaining levetiracetam by reacting (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid with an alkyl haloformate and subsequently with ammonia, as summarized in the following scheme:
- The same document discloses obtaining levetiracetam by reacting (S)-2-aminobutanamide with an alkyl 4-halobutyrate or with a 4-halobutyryl halide, and subsequent cyclization of alkyl (S)-4-[[1-(aminocarbonyl)propyl]amino]butyrate or of (S)-N-[1-(aminocarbonyl)propyl]-4-halobutanamide thus obtained, as summarized in the attached scheme:
- The two previous processes have the drawback of operating at temperatures between -10°C and -60°C and the drawback of using intermediates for cyclization that are not readily obtained.
- A drawback of this industrial-scale process is that it requires special equipment and special precautions for handling the products.
- Other processes are known (for example US patents No 6,107,492 and6,124,473 ) in which levetiracetam is obtained by means of optical resolution of racemic etiracetam of formula (I). InUS patent No 6,107,492 resolution is performed by means of preparative high performance liquid chromatography or by means of a continuous simulated fluid bed chromatographic system with a chiral stationary phase. US patent No 6,124,473 discloses a continuous simulated fluid bed chromatographic system consisting of at least three chiral stationary phase columns. These industrial-scale resolution processes are affected by drawbacks related to using chromatography.
- The industrial-scale difficulties and hazard of hydrogenation can be mentioned in relation to these processes.
- Finally, patent application ES 447,346 describes a process for the preparation of a pyrrolidone derivative, in particular the 2-oxo-1-pyrrolidinylacetamide, which comprises first reacting pyrrolidone with formaldehyde and a secondary amine, then reacting the compound obtained with an alkylating agent such as dimethyl sulfate, followed by treating the compound obtained with sodium or potassium cyanide, and finally reacting the compound obtained with hydrogen peroxide in basic medium.
Journal of Chemistry Volume 2013 (2013), Article ID 176512, 5 pages http://dx.doi.org/10.1155/2013/176512
Enantioselective Synthesis of Antiepileptic Agent, (−)-Levetiracetam, through Evans Asymmetric Strategy
2Centre for Pharmaceutical Sciences, Institute of Science and Technology, Jawaharlal Nehru Technological University, Kukatpally, Hyderabad 500 072, India
3R&D Centre, Orchid Chemicals and Pharmaceuticals Ltd., 476/14, Sholinganallur, Chennai 600 119,