Synthesis and antiproliferative properties of new hydrophilic esters of triterpenic acids.

To improve the properties of cytotoxic triterpenoid acids 1-5, a large set of hydrophilic esters was synthesized. We choose betulinic acid (1), dihydrobetulinic acid (2), 21-oxoacid 3 along with highly active des-E lupane acids 4 and 5 as a model set of compounds for esterification of which the properties needed to be improved. As ester moieties were used - methoxyethanol and 2-(2-methoxyethoxy)ethanol and glycolic unit (type a-d), pyrrolidinoethanol, piperidinoethanol and morpholinoethanol (type f-h), and monosaccharide groups (type i-l). As a result, 56 triterpenic esters (49 new compounds) were obtained and their cytotoxicity on four cancer cell lines and normal human fibroblasts was tested. All new compounds were fully soluble at all tested concentrations, which used to be a problem of the parent compounds 1 and 2. 16 compounds had IC50 < 10 µM on at least one cancer cell line, 12 compounds had cytotoxicity of <10 µM against at least three of four tested cancer cell lines. The highest activity was found for compound 3c (1.8 µM on MCF7, 2.8 µM on HeLa, and 1.6 µM on G-361 cells) which also had no toxicity on non-cancerous BJ fibroblasts at the highest tested concentration (50 µM). High selective cytotoxicity was also found in compounds 1k, 2k, 3c, and 3i that are ideal candidates for drug development. Therefore, more studies to identify the mechanism of action were performed in case of 1k, 3c, and 3g such as effects on cell cycle and apoptosis. It was found that compounds 3c and 3g can induce apoptosis via caspase-3 activation and modulation of protein Bcl-2 in G-361 cells. In conclusion, compounds 1k, 3c, and 3g show high and selective cytotoxicity, therefore they are significantly better candidates for anti-cancer drug development than the parent acids 1-5.

Synthesis and biochemical characterization of a series of 17α-perfluoroalkylated estradiols as selective ligands for estrogen receptor α.

Despite intensive research efforts, the distinct biological roles of two closely related estrogen receptors, ERα and ERß, are only partially understood. Therefore, ligands selective for either of two isotypes are useful research tools because they allow for exerting a desired subset of biological effects mediated by only one of the receptors. Here we report on the synthesis of a new class of potent and selective ligands for ERα represented by a series of 17α-substituted estradiols bearing lipophilic perfluoroalkyl chains. These 17α-perfluoroalkylated estradiols were synthesized by Ru-catalyzed cross metathesis reactions of 17α-allyl- or 17α-vinylestradiols with perfluoroalkylpropenes. Compounds were tested in both agonistic and antagonistic modes using a panel of stable steroid receptor reporter cell lines established in U2OS cells and consisting of ERα-LBD, ERß-LBD, GR-LBD, and MR-LBD reporters. Some of the compounds are potent and selective agonists of ERα, exhibiting weak partial to no detectable agonistic activity on ERß. Notably, 11c is the most ERα selective ligand of the prepared compounds because it activates ERα but inhibits ERß. In addition, some compounds are pure agonists on ERα but show mixed agonistic/antagonistic profile on ERß which is a typical pattern observed for selective estrogen receptor modulators (SERMs).

Synthesis of fluorinated brassinosteroids based on alkene cross-metathesis and preliminary biological assessment.

Three types of brassinosteroid analogues with perfluoroalkylated side chains were synthesized by using alkene cross-metathesis of a brassinosteroid derivative bearing a terminal alkene moiety with different (perfluoroalkyl)propenes. The presence of the double bonds in the cross-metathesis products allowed a facile one-step double dihydroxylation to provide intermediates that after Baeyer-Villiger oxidation afforded the target compounds. Biological activity of the prepared analogues was tested in GABA(A) receptor, cytotoxic, and brassinolide activity, which reached in some cases the same range as their nonfluorinated analogues.