Ugi multicomponent-reaction: Syntheses of cytotoxic dehydroabietylamine derivatives.

Isocyanide-based multicomponent reactions - especially the standard four component Ugi reaction - provide an easy and powerful access to compounds with an auspicious pharmacological potential. Therefore, a set of 16 novel derivatives of the diterpene dehydroabietylamine was synthesized by the Ugi-4CR. The subsequent screening of the synthesized α-acylamino carboxamides in colorimetric sulforhodamine B assays revealed an in vitro cytotoxicity towards several human tumor cell lines. Particularly, the rhodamine B conjugates 14-16 showed a remarkable cytotoxic activity, characterized by EC50 values in a low three-digit nanomolar range. The screening of rhodamine B amide 17 that was obtained for comparison by a Schotten-Baumann reaction showed that the linkage of the rhodamine B moiety and the diterpene influences significantly its cytotoxic potency. While 14 was highly cytotoxic and acted as a mitocan, compound 17 was not cytotoxic at all. This observation underlines the importance of the type of coupling between the diterpene and the rhodamine part. The presence of a rhodamine B moiety in the molecules doesn't necessarily guarantee that the compound is cytotoxic.

Ethylenediamine Derived Carboxamides of Betulinic and Ursolic Acid as Potential Cytotoxic Agents.

Two easily accessible, natural occurring triterpenoids, betulinic and ursolic acid, were used as starting materials for the synthesis of novel cytotoxic agents. A set of 28 ethylenediamine-spacered carboxamides was prepared holding an additional substituent connected to the ethylenediamine group. The compounds were screened in SRB assays to evaluate their cytotoxic activity employing several human tumor cell lines. Betulinic acid-derived carboxamides 17⁻30 showed significantly higher cytotoxicity than their ursolic acid analogs 3⁻16. In particular, compounds 25 and 26 were highly cytotoxic, as indicated by EC50 values lower than 1 µM.

Hederagenin amide derivatives as potential antiproliferative agents.

In this study, a series of C-28 amides derivatives of hederagenin with or without the presence of an acetyl group at positions 3 and 23 in ring A, were synthetized aiming to develop potent cytotoxic agents. Their structures were confirmed by MS, IR, 1H NMR and 13C NMR spectroscopic analyses and their cytotoxic activities were screened in SRB assays using a panel of six human cancer cell lines. The majority of the amide derivatives were cytotoxic for a variety of human tumor cell lines. In general, the hydroxylated derivatives (1a-1d; EC50 in the range 1.2-22.5 µM) were less active than the acetylated derivatives (2a-2n; EC50 in the range 0.4-9.0 µM). Hydroxylated derivative bearing pyrrolidinyl substituent 1c, was the most active for HT29 human line cells (EC50 = 1.2 µM), however their acetylated derivative 2c was the most potent and selective against A2780, FaDu, SW1736 cells, showing EC50 values between 0.4 and 1.7 µM and SI between 5.6 and 24. Staining experiments combined with fluorescence microscopy indicate that the cell membrane became permeable, and finally a process of secondary necrosis was observed. In addition, the docking results showed that acetylated compounds display more affinity to HER2 than to USP7, indicating that HER2 is a most probable receptor, both proteins found in tumor cell line A2780.