The acetyl- and butyrylcholinesterase inhibiting natural product dictyophlebine 1 was subjected to different N-alkylation and hydrochlorination reactions by which five new and bioactive chemical derivatives (2 - 6) with pentyl, pent-4-en-1-yl, hex-5-en-1-yl, 4-chloropentyl and 5-chlorohexyl substituents at the 3-N position were obtained with high yield. The alkylated and chlorinated products 3 - 6 were found to have significantly higher inhibitory potential towards cholinesterase than the parent compound 1.