[Synthesis and antitumor activities of 1-(4-chlorophenyl)-beta-carboline derivatives]

The starting material L-tryptophan reacted with 4-chlorobenzaldehyde via Pictet-Spengler condensation and followed by oxidation and decarboxylation to afford the 1-(4-chlorophenyl)-beta-carboline. The intermediate was further reacted with alkyl halogenide by N(9)-alkylation and N2-quaternarization to obtain 12 novel 1-(4-chlorophenyl)-beta-carboline derivatives. The chemical structures of all target compounds were characterized by elemental analyses, MS and 1H NMR spectra. The antitumor activities of the target compounds were evaluated by MTT method. The results demonstrated that N2-quaternarized compounds enhanced the antitumor activity significantly. In particular, compound 15 was found to be the most potent compound with IC50 values lower than 5 micromol x L(-1) against 6 human tumor cells. These results confirmed that the N2-alkyl or aralkyl substituent on the beta-carboline ring played an important role in the modulation of the antitumor activities.