Selective synthesis of A-ring Е-arylidene derivatives from ß-sitosterol and their activity.

A series of 24-ethylcholest-4-ene-3,6-dione 2E-arylidene-derivatives has been synthesized by a Claisen-Schmidt reaction from a natural phytosterol ß-sitosterol with yields of 80-85%. The structure of the obtained compounds was confirmed by NMR spectroscopy, including two-dimensional correlation experiments. The synthesized compounds were evaluated for their in vitro cytotoxicity and α-glucosidase inhibitory activity. It was established that compound 3 with pyridin-3-ylmethylene moiety exhibited a selective cytotoxic effect against the U251 cancer cell line with 99.31% inhibition of cancer cell growth. Compounds with pyridin-4-ylmethylene 4 and furan-2-ylmethylene-5 fragments were the most active inhibitors of α-glucosidase with IC50 64.00 and 38.95 µM, being 3- and 5-times more active than acarbose. Binding mode to α-glucosidase and ADMET characteristics for the lead molecule 5 were proposed computationally. To sum up, an efficient approach to the derivatives with promising antidiabetic activity based on available natural product ß-sitosterol is suggested.

Synthesis of C17-[5-methyl-1,3]-oxazoles by N-propargylation of triterpenic acids and evaluation of their cytotoxic activity.

A series of unexpected triterpenic C17-[5-methyl-1,3]-oxazoles along with targeted N-propargylamides was synthesized by an interaction of acid chlorides with propargylamine hydrochloride. We proposed that the formation of methyl oxazole passes through an alternative pathway by the participation of the terminal alkyne carbon atom and acid chloride intermediate with following intramolecular rearrangements. The synthesized compounds were evaluated for their cytotoxicity at the U.S. National Cancer Institute. 28-Nor-17-(5-methyloxazol-2-yl)-2-cyano-2,4-seco-3-nor-lup-4(23),20(29)-diene has demonstrated the highest activity with GI50 ranged from 1.03 to 16.4 µM against different cancer cell lines. Molecular docking in Kelch domain of Keap1 protein was performed to study a possible molecular target. Thus, we have shown for the first time that triterpenic C17-[5-methyl-1,3]-oxazoles are alternative products of the interaction of triterpenic acid chlorides with propargylamine hydrochloride and they have an advantage over corresponding N-propargylamides as cytotoxic agents.

[Synthesis and cytotoxicity of allobetulin derivatives].

The synthesis and screening of antitumor activity in vitro (cytotoxicity) of various oxygen, nitrogen, sulfur and platinum-containing derivatives of allobetulin, including different arrangements of the double bonds in the A and B rings, penta- and hexacyclic ring A, 21-acetyl-20,28-epoxy-18α,19ßH-ursane-isomeric cycle E, was carry out. (3R,5R)-19ß,28-Epoxy-4,5-seco-18α-olean-3(5)-ozonide and 2,3-indolo-21ß-acetyl-20ß,28-epoxy-18α, H-19ß-ursane showed significant cytotoxic activity against melanoma MeWo and Leukemia SR cells, appropriately. (3S,5S)-Diastereomer of the first compound showed no cytotoxicity.

[Synthesis of new olean-18(19)-ene derivatives from allobetulin].

Effective synthesis of new olean-18(19)-ene triterpenoids based on interaction of allobetulin or its acetate with phosphorous oxychloride in pyridine under reflux is described. The structures of the synthesized 17-chloromethyl-oleane-18(19)-enes have been established with the help of NMR-spectroscopy and X-Ray analysis.