N‐Malonyl‐1,2‐dihydroisoquinoline as a Novel Carrier for Specific Delivery of Drugs to the Brain

N‐Malonyl‐1,2‐dihydroisoquinoline derivatives were synthesized and investigated as a novel carrier system for site‐specific and sustained delivery of drugs to the brain. Such carriers are expected to be stable against air oxidation due to the presence of the carbonyl group close to nitrogen of the dihydroisoquinoline. Reduction of the prepared isoquinolinium quaternary derivatives with sodium dithionite afforded a novel group of N‐malonyl‐1,2‐dihydroisoquinoline chemical delivery systems (CDS). The synthesized N‐malonyl‐1,2‐dihydroisoquinoline chemical delivery systems were subjected to various chemical and biological investigations to evaluate their ability to cross the blood‐brain barrier (BBB), and to be oxidized biologically into their corresponding quaternary derivatives. The in‐vitro oxidation studies showed that the designed N‐malonyl‐1,2‐dihydroisoquinoline chemical delivery system could be oxidized into its corresponding quaternary derivatives at an adequate rate. The in‐vivo distribution studies showed that these N‐malonyl‐1,2‐dihydroisoquinoline chemical delivery systems were able to cross the blood‐brain barrier at detectable concentrations.