This paper by M. E. Konshin and P. A. Petyunin describes the synthesis and biological actions of 9-alkylamino-1,2,3,4-tetrahydroacridines, a series of compounds with valuable pharmacological properties. The synthesis involves the preparation of N-alkyl derivatives of 9-amino-1,2,3,4-tetrahydroacridine ("tacrine") using alkylamides of 5-substituted anthranilic acids as starting materials. The compounds were obtained through a series of reactions, including the formation of cyclohexylidene derivatives and subsequent cyclization with phosphorus oxychloride. The resulting acridine derivatives exhibit various biological activities, such as lowering the excitability threshold of the central nervous system (CNS) and inducing convulsions. Some compounds also show analgesic and anti-curare activities. The compounds are white or slightly yellowish crystalline substances with basic properties and form water-soluble salts with mineral acids. The UV spectra of these compounds are similar to those of 4-aminoquinoline.This paper by M. E. Konshin and P. A. Petyunin describes the synthesis and biological actions of 9-alkylamino-1,2,3,4-tetrahydroacridines, a series of compounds with valuable pharmacological properties. The synthesis involves the preparation of N-alkyl derivatives of 9-amino-1,2,3,4-tetrahydroacridine ("tacrine") using alkylamides of 5-substituted anthranilic acids as starting materials. The compounds were obtained through a series of reactions, including the formation of cyclohexylidene derivatives and subsequent cyclization with phosphorus oxychloride. The resulting acridine derivatives exhibit various biological activities, such as lowering the excitability threshold of the central nervous system (CNS) and inducing convulsions. Some compounds also show analgesic and anti-curare activities. The compounds are white or slightly yellowish crystalline substances with basic properties and form water-soluble salts with mineral acids. The UV spectra of these compounds are similar to those of 4-aminoquinoline.