15 グルタミン酸海洋天然物の類縁体合成とAMPA受容体阻害剤の創製(口頭発表の部)

抄録

Ionotropic glutamate receptors (iGluRs) are involved in higher brain functions such as memory and learning, nociception, and a number of brain disorders. Here, we report the synthesis of twelve artificial glutamate analogs whose core structure was inspired by two marine-derived excitatory amino acids, dysiherbaine and kainia acid. Four 7-oxznorbornenes, 2a-2d, were prepared in two steps, starting from and Ugi four component coupling reaction followed by spontaneous Diels-Alder reaction between 2-furfural, 3-iodoacrylic acid, 4-methoxybenzylamine, and benzyl isocyanide. An unprecedented domino metathesis reaction with less reactive vinyl acetate as a cross metathesis substrate was then performed with the Hoveyda-Grubbs second-generation catalyst, to successfully deliver four heterotricycles 3a-3d in good yiels. After functional group transformations followed by diversification at the C-ring, twelve artificial glutamate analogs 6a-6d, 7a-7d, 8a-8d were synthesized in total 7.2-25.8% yield for 13-15 steps. Mice in vivo assays indicated that all analogs are biologically active; namely, 6b, 7a, 7b, and 8b produce hyperactivity in injected i.c.v., whereas other analogs induce hypoactiity in the animals. In vitro electrophysiological assays showed that some hypoactive analogs inhibit spontaneous excitatory synaptic currents in hippocampal neurons and glutamate-evoked currents from recombinant AMPA receptors. With these pharmacological profiles, synthesis of other analogs werer further performed, and pyrrolidone dicarboxylic acid analog IKM-159 was discovered as a more potent, AMPA receptor-selective antagonist.