The short way to chiral compounds with hexahydrofluoreno[9,1-bc]furan framework: Synthesis and cytotoxic activity

Unusual Cascade Reactions of 8-Acetoxy-6-hydroxymethyllimonene with Salicylic Aldehydes: Diverse Oxygen Heterocycles from Common Precursors

Chiral oxygen-containing heterocyclic compounds are of great interest for the development of pharmaceuticals. Monoterpenes and their derivatives are naturally abundant precursors of novel synthetic chiral oxygen-containing heterocyclic compounds. In this study, acid catalyzed reactions of salicylic aldehydes with (-)-8-acetoxy-6-hydroxymethyllimonene, readily accessible from α-pinene, leads to the formation of chiral polycyclic products of various structural types. Three of the six isolated chiral heterocyclic products obtained from salicylic aldehyde contain previously unknown polycyclic ring types. Having carried out the reaction in the presence of Brønsted or Lewis acids (Amberlyst 15, trifluoromethanesulfonic acid, trifluoroacetic acid and boron trifluoride etherate) or aluminosilicates (montmorillonite K10, halloysite nanotubes), we found that the nature of products depends on the catalyst as well as the reaction conditions (reaction time, reactant ratio, presence or absence of solvent). Detailed mechanistic insight on the complex cascade reactions for product formation is provided with extensive experimental and quantum mechanical computational studies.

New inhibitors of tyrosyl-DNA phosphodiesterase I (Tdp 1) combining 7-hydroxycoumarin and monoterpenoid moieties

A number of derivatives of 7-hydroxycoumarins containing aromatic or monoterpene substituents at hydroxy-group were synthesized based on a hit compound from a virtual screen. The ability of these compounds to inhibit tyrosyl-DNA phosphodiesterase I (Tdp 1), important target for anti-cancer therapy, was studied for the first time. It was found that the 7-hydroxycoumarin derivatives with monoterpene pinene moiety are effective inhibitors of Tdp 1 with the most active derivative (+)-25c with IC₅₀ value of 0.675μM. This compound has low cytotoxicity (CC₅₀>100μM) when tested against human cancer cells which is crucial for presupposed application in combination with clinically established anticancer drugs. The ability of the new compounds to enhance the cytotoxicity of camptothecin, an established topoisomerase 1 poison, was demonstrated.