M. E. Konshin and P. A. Petyunin UDC 615.2:547.835].012.1 9-Amino-1,2,3,4-tetrahydroacridine ("tacrine") has valuable pharmacological properties [1, 2, 3]. In this paper, we describe the synthesis of several N-alkyl derivatives of this compound using a previously used method for preparing a series of 9-arylamino-1,2,3,4-tetrahydroacridines [4]. The alkylamides of 5-substituted anthranilic acids [(I)-(VIII), Table 1] were used as starting materials for most preparations. Compounds (I) and (II) were obtained from 5-methylisatoic anhydride. For (III)-(VIII), the method described in [6] was used, where methyl esters of 5-substituted anthranilic acids were treated with magnesium derivatives of the appropriate amines. The eight anthranilic acid alkylamides (I)-(VIII) gave, upon warming with cyclohexanone in benzene solution, the corresponding cyclohexylidene derivatives [(XIII)-(XX), Table 2] in good yield. The four compounds [(IX)-(XII), Table 2] without 5-substituents were obtained similarly from the alkylamides of unsubstituted anthranilic acid. The twelve cyclohexylideneanthranilic acid alkylamides [(IX)-(XX), Table 2] were cyclized by warming with excess phosphorus oxychloride, yielding 9-alkylamino-1,2,3,4-tetrahydroacridines (XXI)-(XXXII) in yields up to 97% (Table 3). Compounds (XXX) and (XXXII) were only obtained as hydrochlorides, while others were also prepared as free bases. The twelve acridine derivatives (Table 3) are white or slightly yellow crystalline substances with basic properties, forming water-soluble salts with mineral acids. Their UV spectra match those of 4-aminoquinoline [7], showing three absorption bands at λmax 222-224, 244-252, and 336-344 nm in ethanol. Hydrochloride spectra show a bathochromic shift in the long-wave band. These compounds (XXI)-(XXXII) lower the CNS excitability threshold and induce convulsions. The LD50 (ip) ranges from 20-35 mg/kg. Compounds (XXI), (XXIII), and (XXVII)-(XXX) showM. E. Konshin and P. A. Petyunin UDC 615.2:547.835].012.1 9-Amino-1,2,3,4-tetrahydroacridine ("tacrine") has valuable pharmacological properties [1, 2, 3]. In this paper, we describe the synthesis of several N-alkyl derivatives of this compound using a previously used method for preparing a series of 9-arylamino-1,2,3,4-tetrahydroacridines [4]. The alkylamides of 5-substituted anthranilic acids [(I)-(VIII), Table 1] were used as starting materials for most preparations. Compounds (I) and (II) were obtained from 5-methylisatoic anhydride. For (III)-(VIII), the method described in [6] was used, where methyl esters of 5-substituted anthranilic acids were treated with magnesium derivatives of the appropriate amines. The eight anthranilic acid alkylamides (I)-(VIII) gave, upon warming with cyclohexanone in benzene solution, the corresponding cyclohexylidene derivatives [(XIII)-(XX), Table 2] in good yield. The four compounds [(IX)-(XII), Table 2] without 5-substituents were obtained similarly from the alkylamides of unsubstituted anthranilic acid. The twelve cyclohexylideneanthranilic acid alkylamides [(IX)-(XX), Table 2] were cyclized by warming with excess phosphorus oxychloride, yielding 9-alkylamino-1,2,3,4-tetrahydroacridines (XXI)-(XXXII) in yields up to 97% (Table 3). Compounds (XXX) and (XXXII) were only obtained as hydrochlorides, while others were also prepared as free bases. The twelve acridine derivatives (Table 3) are white or slightly yellow crystalline substances with basic properties, forming water-soluble salts with mineral acids. Their UV spectra match those of 4-aminoquinoline [7], showing three absorption bands at λmax 222-224, 244-252, and 336-344 nm in ethanol. Hydrochloride spectra show a bathochromic shift in the long-wave band. These compounds (XXI)-(XXXII) lower the CNS excitability threshold and induce convulsions. The LD50 (ip) ranges from 20-35 mg/kg. Compounds (XXI), (XXIII), and (XXVII)-(XXX) show