A Large Scale Preparation of the Cognitive Enhancer Linopirdine

Chemical modulation of Kv7 potassium channels

The rising interest in Kv7 modulators originates from their ability to evoke fundamental electrophysiological perturbations in a tissue-specific manner. A large number of therapeutic applications are, in part, based on the clinical experience with two broad-spectrum Kv7 agonists, flupirtine and retigabine. Since precise molecular structures of human Kv7 channel subtypes in closed and open states have only very recently started to emerge, computational studies have traditionally been used to analyze binding modes and direct the development of more potent and selective Kv7 modulators with improved safety profiles. Herein, the synthetic and medicinal chemistry of small molecule modulators and the representative biological properties are summarized. Furthermore, new therapeutic applications supported by in vitro and in vivo assay data are suggested.

5-Bromo-1-(4-bromophenyl)isatin

In the title compound [systematic name: 5-bromo-1-(4-bromophenyl)-2,3-dihydro-1H-indole-2,3-dione], C14H7Br2NO2, all of the atoms except the C—H groups in the bromobenzene ring lie on a (010) crystallographic mirror plane, with the benzene ring completed by reflection. The dihedral angle between the ring systems is constrained to be 90° by symmetry. In the crystal, molecules are linked by weak C—H...Br interactions in the [001] direction and paired very weak C—H...O interactions to the same acceptor in the [100] direction, generating (010) sheets. Possible extremely weak π–π stacking occurs between the layers.

2-Fluoro-4-pyridinylmethyl analogues of linopirdine as orally active acetylcholine release-enhancing agents with good efficacy and duration of action

In an effort to improve the pharmacokinetic and pharmacodynamic properties of the cognition-enhancer linopirdine (DuP 996), a number of core structure analogues were prepared in which the 4-pyridyl pendant group was systematically replaced with 2-fluoro-4-pyridyl. This strategy resulted in the discovery of several compounds with improved activity in acetylcholine (ACh) release-enhancing assays, in vitro and in vivo. The most effective compound resulting from these studies, 10, 10-bis[(2-fluoro-4-pyridinyl)methyl]-9(10H)-anthracenone (9), is between 10 and 20 times more potent than linopirdine in increasing extracellular hippocampal ACh levels in the rat with a minimum effective dose of 1 mg/kg. In addition to superior potency, 9 possesses an improved pharmacokinetic profile compared to that of linopirdine. The half-life of 9 (2 h) in rats is 4-fold greater than that of linopirdine (0.5 h), and it showed a 6-fold improvement in brain-plasma distribution over linopirdine. On the basis of its pharmacologic, pharmacokinetic, absorption, and distribution properties, 9 (DMP543) has been advanced for clinical evaluation as a potential palliative therapeutic for treatment of Alzheimer's disease.