Synthesis of a novel water-soluble cleft-type cyclophane as an N-methyl-D-aspartate receptor antagonist

Novel water-soluble N-methyl-D-aspartate (NMDA) receptor antagonists, 4,4'-bis([2-[N-(1,4,8,11-tetraazacyclotetradecan-1-yl)acetyl]-N-phenethyl]aminoethoxy)diphenylmethane octahydrochloride (1, ACPCm) and 4,4'-bis([2-[N-(1,4,7,10-tetraazacyclododecan-1-yl)acetyl]-N-phenethyl]aminoethoxy)diphenylmethane octahydrochloride (2, ACPCn), were synthesized and the effect of these cleft-type cyclophanes on NMDA receptors was then studied using voltage-clamp recordings of recombinant NMDA receptors expressed in Xenopus oocytes. ACPCm (1) and ACPCn (2) inhibited macroscopic currents in the NR1/NR2A, NR1/NR2B, NR1/NR2C and NR1/NR2D receptor subtypes in oocytes voltage-clamped at -70 mV. The IC50 values of ACPCm (1) and ACPCn (2) for NR1/NR2A and NR1/NR2B receptors were 1.06 microM and, 0.92 microM and 1.47 microM and, 1.49 microM, respectively. The inhibition by these compounds was voltage-dependent, that is, the degree of inhibition was in the order of negative holding potentials, -100 mV>-70 mV>-20 mV. These findings indicate that the cleft-type cyclophanes, ACPCm (1) and ACPCn (2) directly act on the channel pore of the NMDA receptors.