Specifically for the compound we moved forward with, ABP, synthesis followed techniques described previously [11 (link)] for two closely related compounds, N(3-trimethylaminopropyl)phenantridinium and 6-methoxy-N(3-aminopropyl)quilolinium. N(4-aminobutyl)phenantridinium (ABP) is a phenanthridine-based aminoalkyl moiety that is suitable for conjugation to dextran. Briefly, ABP was synthesized in a manner similar to N(3-trimethylaminopropyl)phenantridinium [11 (link)] by reflux of equimolar amounts of phenantridine and N(4-bromobutyl)phthalimide in acetonitrile overnight. A pale yellow–green precipitate was separated by filtration through Whatman-40 paper. From this intermediate phthalimide-protected compound, the phthalate group was removed by reflux in 6N HCl overnight and subsequent filtration, similar to procedures described for 6-methoxy-N(3-aminopropyl)quilolinium [11 (link)]. N(4-aminobutyl)phenantridinium (ABP) was twice recrystallized from hot 95% ethanol/5% deionized water and was stored as its chloride salt in a sealed glass vial protected from light until conjugation to glucose polymer (i.e., dextran).
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