The synthesis of new diastereomers of (4S,8aS)- and (4R,8aS)-4-phenyl-perhydropyrrole[1,2-a]pyrazine-1,3-dione

The Synthesis and Absolute Configuration of Enantiomeric Pure (R)- and (S)-3-(piperidin-3-yl)-1H-Indole Derivatives

This article describes the synthesis of new chiral 3-(piperidin-3-yl)-1H-indole derivatives (R)-10a-c and (S)-11a-c from the corresponding diastereomers: (3R, 2R) and (3S, 2R)-2-[3-(1H-indol-3-yl)-1-piperidyl]-2-phenyl-acetamides (3R, 2R)-4a, (3R, 2R)-6b, (3R, 2R)-8c and (3S, 2R)-5a, (3S, 2R)-7b, (3S, 2R)-9c. Diastereomers were obtained by N-alkylation of derivatives of racemic 3-(piperidin-3-yl)-1H-indoles 1a-c using (S)-2-(4-toluenesulfonyloxy)-phenylacetic amide (S)-II. The same method was applied to obtain (3R, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3R, 2S)-2a and (3S, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3S, 2S)-3a diastereomers by treating amine 1a with (R)-2-(4-toluenesulfonyloxy)-phenylacetic acid methylester (R)-I. Systematic studies via single crystal X-ray crystallography were used to determine the molecular structure of the racemates 1a-c and the absolute configuration of the enantiomers. The solid racemates 1b and 1c were "true racemates" crystallizing in a centrosymmetric space group, while 1a formed a racemic conglomerate of homoenantiomeric crystals. The absolute configuration was determined for the enantiomeric pairs (R)-10a/(S)-11a, (R)-10b/(S)-11b, and (R)-12c/(S)-13c, as well as for (3S,2S)-3a. Spectra of ¹H, ¹³CNMR, HPLC, and HRMS for diastereomers and enantiomers were consistent with the determined structures.

Chirality as an Important Factor for the Development of New Antiepileptic Drugs

In recent years, chiral molecules (especially enantiomers) have occupied a significant place in pharmaceutical industry and have played a prominent role in the development of new drugs. Individual stereoisomers exhibit marked differences in pharmacodynamic, pharmacokinetic, and toxicological properties. Therefore, there is currently considerable interest in fully characterizing and examining both enantiomers in the early stages of new drug development. Despite the fact that epilepsy is a complex disease and that a given drug's mechanism of action may be multidirectional and not always fully understood, significant differences have been observed in the anticonvulsant activity of individual stereoisomers. Therefore, between 1996 and 2018, among 14 new antiepileptic drugs (AEDs) approved for the treatment of epilepsy, as many as seven are chiral and introduced to the market in the single-enantiomer (or diastereomer) form. This review provides an overview of the impact of chirality on the development and discovery of new AEDs that have entered into clinical trials or preclinical studies. These new AEDs were developed by applying the single-enantiomer approval strategy. Herein we focus our attention on the main synthetic pathways of stereoisomers, as well as on the influence of chirality on pharmacodynamic, pharmacokinetic, and/or toxicological properties.

Synthesis of a new scaffold: the 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione nucleus

This paper describes a modified method of preparation of a number of alpha-aryl-alpha-(pyridazin-3-yl)-acetonitriles via the C-arylation reaction of the corresponding carbanionsof phenylacetonitriles using 3-chloropyridazine derivatives. KOH and DMSO were used inthe deprotonation process, which made the reaction very simple and safe to perform.Nitriles were obtained in the hydrolysis reaction to the corresponding alpha-aryl-alpha-(pyridazin-3-yl)-acetamide derivatives, which were next subjected to cyclization to afford the finalproducts. A number of new derivatives of 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione weresynthesized in the cyclocondensation reaction of respective alpha-aryl-alpha-(pyridazin-3-yl)-acetamides with diethyl carbonate in the presence of EtONa. The structure andcomposition of the new compounds were confirmed by IR, (1)H- and (13)C- NMR analysesand by elemental C, H and N analysis.