Improved delivery through biological membranes. 1. Synthesis and properties of 1-methyl-1,6-dihydropyridine-2-carbaldoxime, a pro-drug of N-methylpyridinium-2-carbaldoxime chloride.

A dihydropyridine-pyridine type redox pro-drug system was developed for delivering quaternary pyridinium salts through biological membranes. As a first application, the dihydropyridine derivative of N-methylpyridinium-2-carbaldoxime chloride (2-PAM) was synthesized using a reduction-addition-elimination sequence. The dihydro-2-PAM obtained has all the required properties for an effective transport through lipoidal barriers and it reverts easily back to 2-PAM as a result of a chemical or enzymatic oxidation process.