Minoru Ikoma

A series of structurally novel heterotricyclic α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor-selective antagonists

Background and purpose:  A new class of heterotricyclic glutamate analogues recently was generated by incorporating structural elements of two excitotoxic marine compounds, kainic acid and neodysiherbaine A. Rather than acting as convulsants, several of these ‘IKM’ compounds markedly depressed CNS activity in mice. Here, we characterize the pharmacological profile of the series with a focus on the most potent of these molecules, IKM‐159.

Improved synthesis and in vitro/in vivo activities of natural product-inspired, artificial glutamate analogs

Here, we report our second-generation synthesis of 12 artificial glutamate analogs, starting from heterotricycle intermediates 3a-3d, readily prepared in three steps including tandem Ugi/Diels-Alder reactions. The new synthesis employs imidate intermediates for the deoxygenation of pyrrolidones (10a-10d to 6a-6d), and each advanced intermediate 6a-6d was diversified into three glutamate analogs (1a-1d, 5a-5d, 7a-7d) in 1-2 steps. In vitro electrophysiological assays revealed that the new piperidine-type analog 7c alters neuronal function with lower potency than 1a. Conversely, intracranial injection of 7c into mice produced a greater degree of hypoactivity than 1a. Our recent investigation has revealed that this series of compounds antagonizes AMPA-type glutamate receptor-mediated currents in a subtype selective manner. The more efficient syntheses of this novel set of neuroactive molecules will facilitate their pharmacological characterization.