Permanently Charged Chiral 1,4-Dihydropyridines:  Molecular Probes of L-Type Calcium Channels. Synthesis and Pharmacological Characterization of Methyl (ω-Trimethylalkylammonium) 1,4-Dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5- pyridinedicarboxylate Iodide, Calcium Channel Antagonists

We report the synthesis of the single enantiomers of permanently charged dihydropyridine derivatives (DHPs with alkyl linker lengths of two and eight carbon atoms) and their activities on cardiac and neuronal L-type calcium channels. Permanently charged chiral 1,4-dihydropyridines and methyl (ω-trimethylalkylammonium) 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate iodides were synthesized in high optical purities from (R)-(−) and (S)-(+)-1,4-dihydro-2,6-dimethyl-5-methoxycarbonyl-4-(3-nitrophenyl)-3-pyridinecarboxylic acid, obtained by resolution of racemic 1,4-dihydro-2,6-dimethyl-5-methoxycarbonyl-4-(3-nitrophenyl)-3-pyridinecarboxylic acid. Competition binding experiments with radioligand [3H]-(+)-PN200-110 and the block of whole cell barium currents through L-type calcium channels in GH4C1 cells show that the compounds with the eight-carbon alkyl linker optimally block the L-type Ca2+ channels, and that the S-enantiomer is more potent than the R-enantiomer.