Inhibition of NaV1.6 sodium channel currents by a novel series of 1,4-disubstituted-triazole derivatives obtained via copper-catalyzed click chemistry

Abstract

We have synthesized and evaluated a series of 1,4-disubstituted-triazole derivatives for inhibition of the rat Na(V)1.6 sodium channel isoform, an isoform thought to play an important role in controlling neuronal firing. Starting from a series of 2,4(1H)-diarylimidazoles previously published, we decided to extend the SAR study by replacing the imidazole with a different heterocyclic scaffold and by varying the aryl substituents on the central aromatic ring. The 1,4-disubstituted 1,2,3-triazoles were prepared employing the copper-catalyzed azide-alkyne cycloaddition (CuAAC). Many of the new molecules were able to block the rNa(v)1.6 currents at 10 μM by over 20%, displaying IC(50) values ranging in the low micromolar, thus indicating that triazole can efficiently replace the central heterocyclic core. Moreover, the introduction of a long chain at C4 of the central triazole seems beneficial for increased rNa(v)1.6 current block, whereas the length of N1 substituent seems less crucial for inhibition, as long as a phenyl ring is not direcly connected to the triazole. These results provide additional information on the structural features necessary for block of the voltage-gated sodium channels. These new data will be exploited in the preparation of new compounds and could result in potentially useful AEDs.

Figure 1

2,4(1H)-Diarylimidazoles

Scheme 1

Reagents and conditions: (a) alkyne (2.0 mmol), azido-derivative (2.0 mmol), Na ascorbate (0.5 mmol), CuSO₄ (0.025 mmol), tBuOH/H₂O (1:1) (6 mL), 65 °C, overnight, 70–88% yields.

Scheme 2

Reagents and conditions: (a) alkyne (2.1 mmol), bromo-derivative (2.0 mmol), NaN₃ (2.1 mmol), Na ascorbate (0.5 mmol), CuSO₄ (0.1 mmol), tBuOH/H₂O (1:1) (6 mL), 65 °C, overnight, 72–96% yields.