An Enantioselective Aminocatalytic Cascade Reaction Affording Bioactive Hexahydroazulene Scaffolds.

A novel cascade reaction initiated by an enantioselective aminocatalysed 1,3-dipolar [6+4] cycloaddition between catalytically generated trienamines and 3-oxidopyridinium betaines is presented. The [6+4] cycloadduct spontaneously undergoes an intramolecular enamine-mediated aldol, hydrolysis, and E1cb sequence, which ultimately affords a chiral hexahydroazulene framework. In this process, three new C-C bonds and three new stereocenters are formed, enabled by a formal unfolding of the pyridine moiety from the dipolar reagent. The hexahydroazulenes are formed with excellent diastereo-, regio- and periselectivity (>20 : 1), up to 96 % ee, and yields up to 52 %. Synthetic elaborations of this scaffold were performed, providing access to a variety of functionalised hydroazulene compounds, of which some were found to display biological activity in U-2OS osteosarcoma cells in cell painting assays.

Synthesis and antitumoral evaluation of natural product-like compounds based on tropolone and benzotropolone derivatives.

We present the preparation of a series of novel natural product-like homobarrelenones, norcaranes, and dihydrofluorenones through a diversity-oriented synthetic (DOS) strategy that combines Diels-Alder reactions and phototransformations, as well as their biological evaluation against MCF-7, HT-29, and NCI-H460 human tumor cells. Six of these demonstrated activities in the micromolar range against the three cell lines, and none were predicted as cytotoxic against human nontumor cells according to in silico studies. In addition, within the set of active derivatives, three exhibited low unspecific cytotoxicity in a sperm motility assay. The rich functionality of the new compounds makes them ideal candidates for exhaustive structure-activity relationship studies.