New 3-(Dibenzyloxyphosphoryl)isoxazolidine Conjugates of N1-Benzylated Quinazoline-2,4-diones as Potential Cytotoxic Agents against Cancer Cell Lines.

In this study, a new series of cis and trans 5-substituted-3-(dibenzyloxyphosphoryl)isoxazolidines 16a - g were synthesized by the 1,3-dipolar cycloaddition reaction of N -benzyl- C -(dibenzyloxyphosphoryl)nitrone and selected N 1 -allyl- N 3 -benzylquinazoline-2,4-diones. All the obtained trans -isoxazolidines 16a - g and the samples enriched in respective cis -isomers were evaluated for anticancer activity against three tumor cell lines. All the tested compounds exhibited high activity against the prostate cancer cell line (PC-3). Isoxazolidines trans - 16a and trans - 16b and diastereoisomeric mixtures of isoxazolidines enriched in cis -isomer using HPLC, namely cis - 16a / trans - 16a (97:3) and cis - 16b / trans - 16b (90:10), showed the highest antiproliferative properties towards the PC-3 cell line (IC 50 = 9.84 ± 3.69-12.67 ± 3.45 μM). For the most active compounds, induction apoptosis tests and an evaluation of toxicity were conducted. Isoxazolidine trans - 16b showed the highest induction of apoptosis. Moreover, the most active compounds turned out safe in vitro as none affected the cell viability in the HEK293, HepG2, and HSF cellular models at all the tested concentrations. The results indicated isoxazolidine trans - 16b as a promising new lead structure in the search for effective anticancer drugs.