The first example of an unusual addition of chromone‐substituted acrylic acid to enamines is described. The process shows high versatility concerning both enamines and chromones. The reaction is catalyzed by tertiary amines and is highly likely of Morita–Baylis–Hillman‐type. The described compounds show combined moderate inhibitory action on BChE and antagonism towards NMDA receptors which makes them a perspective group for the development of anti‐Alzheimer drugs.

Pentamidine, diminazene and 4′,6‐diamidino‐2‐phenylindole (DAPI) are antiprotozoal diarylamidine compounds. In the present work, we have studied their action on native N‐methyl‐D‐aspartate (NMDA) receptors in rat hippocampal pyramidal neurons. All three compounds inhibited NMDA receptors at −80 mV holding voltage with IC50 of 0.41 ± 0.08, 13 ± 3 and 3.1 ± 0.6 μM, respectively. The inhibition by pentamidine was strongly voltage‐dependent, while that of DAPI was practically voltage‐independent. Inhibition by diminazene had both voltage‐dependent and voltage‐independent components. Diminazene and DAPI demonstrated tail currents and overshoots suggesting “foot‐in‐the‐door” mechanism of action. In contrast, pentamidine was partially trapped in the closed NMDA receptor channels. Such difference in the mechanism of action can be explained by the difference in the 3D structure of compounds. In the pentamidine molecule, two benzamidine groups are connected with a flexible linker, which allows the molecule to fold up and fit in the cavity of a closed NMDA receptor channel. Diminazene and DAPI, in contrast, have an extended form and could not be trapped.

The interest in AMPA receptors as a target for epilepsy treatment increased substantially after the approval of perampanel, a negative AMPA receptor allosteric antagonist, for the treatment of partial-onset seizures and generalized tonic-clonic seizures. Here we performed a screening for activity against native calcium-permeable AMPA receptors (CP-AMPARs) and calcium-impermeable AMPA receptors (CI-AMPARs) among different anticonvulsants using the whole-cell patch-clamp method on isolated Wistar rat brain neurons. Lamotrigine, topiramate, levetiracetam, felbamate, carbamazepine, tiagabin, vigabatrin, zonisamide, and gabapentin in 100-µM concentration were practically inactive against both major subtypes of AMPARs, while phenytoin reversibly inhibited them with IC50 of 30 ± 4 μM and 250 ± 60 µM for CI-AMPARs and CP-AMPARs, respectively. The action of phenytoin on CI-AMPARs was attenuated in experiments with high agonist concentrations, in the presence of cyclothiazide and at pH 9.0. Features of phenytoin action matched those of the CI-AMPARs pore blocker pentobarbital, being different from classical competitive inhibitors, negative allosteric inhibitors, and CP-AMPARs selective channel blockers. Close 3D similarity between phenytoin and pentobarbital also suggests a common binding site in the pore and mechanism of inhibition. The main target for phenytoin in the brain, which is believed to underlie its anticonvulsant properties, are voltage-gated sodium channels. Here we have shown for the first time that phenytoin inhibits CI-AMPARs with similar potency. Thus, AMPAR inhibition by phenytoin may contribute to its anticonvulsant properties as well as its side effects.

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The activity of biphenyl-based NMDA receptor allosteric modulator identified in virtual screening (IC50 = 5 μM) was improved 100 times (IC50 = 50 nM); SAR is consistent with ifenprodil analogs.