Synthesis and Cytotoxic Activity of Conjugates of (–)-Cytisine and Thermopsin Amine Derivatives with 1,3-Dimethyl-5-Formyluracil

New conjugates of the quinolizidine alkaloids (–)-cytisine and thermopsin were synthesized by alkylating their 9-amino derivatives with 1,3-dimethyl-5-formyluracil. The cytotoxic properties of the synthesized conjugates against cell lines HEK293, HepG2, and Jurkat were studied. Screening identified the lead compound 5-{[(3-benzyl-8-oxo-1,3,4,5,6,8-hexahydro-2H-1,5-methanopyrido[1,2-a][1,5]diazocin-9-yl)amino]methyl}-1,3-dimethylpyrimidine-2,4-(1H,3H)-dione, which suppressed metabolic activity of lymphoblastic leukemia cells with inhibitory concentration (IC 50 ) 20.6 ± 2.1 μM (IC 50 of reference compound 5-fluorouracil was 18.5 ± 3.3 μM).