Structure-activity relationship studies of retinoid cancer inhibition

Selective C-F bond carboxylation of gem-difluoroalkenes with CO2 by photoredox/palladium dual catalysis

The catalytic C-F bond carboxylation of organofluorines with CO2 gas remains a challenging problem in synthetic chemistry. Here, we describe a selective defluorinative carboxylation of gem-difluoroalkenes through photoredox/palladium dual catalysis. The C-F bond activation is enabled by single electron reduction through photoredox catalysis to generate a fluorovinyl radical, which subsequently participates in an unprecedented palladium-catalyzed carboxylation. This novel C-F functionalization proved applicable to a wide range of substituted gem-difluoroalkenes, providing a rapid access to valuable α-fluoroacrylic acids.

Reactivity profiles of ligands of mammalian retinoic acid receptors: a preliminary COREPA analysis

Retinoic acid and associated derivatives comprise a class of endogenous hormones that bind to and activate different families of retinoic acid receptors (RARs, RXRs), and control many aspects of vertebrate development. Identification of potential RAR and RXR ligands is of interest both from a pharmaceutical and toxicological perspective. The recently developed COREPA (COmmon REactivity PAttern) algorithm was used to establish reactivity profiles for a limited data set of retinoid receptor ligands in terms of activation of three RARs (alpha, beta, gamma) and an RXR (alpha). Conformational analysis of a training set of retinoids and related analogues in terms of thermodynamic stability of conformers and rotational barriers showed that these chemicals tend to be quite flexible. This flexibility, and the observation that relatively small energy differences between conformers can result in significant variations in electronic structure, highlighted the necessity of considering all energetically reasonable conformers in defining common reactivity profiles. The derived reactivity patterns for three different subclasses of the RAR (alpha, beta, gamma) were similar in terms of their global electrophilicity (nucleophilicity) and steric parameters. However, the profile of active chemicals with respect to interaction with the RXR-alpha differed qualitatively from that of the RARs. Variations in reactivity profiles for the RAR versus RXR families would be consistent with established differences in their affinity for endogenous retinoids, likely reflecting functional differences in the receptors.

Correspondence factor analysis of steroid libraries

The receptor binding of a library of 187 steroids to five steroid hormone receptors (estrogen, progestin, androgen, mineralocorticoid, and glucocorticoid) has been analyzed by correspondence factor analysis (CFA) in order to illustrate how the method could be used to derive structure-activity-relationships from much larger libraries. CFA is a cartographic multivariate technique that provides objective distribution maps of the data after reduction and filtering of redundant information and noise. The key to the analysis of very complex data tables is the formation of barycenters (steroids with one or more common structural fragments) that can be introduced into CFA analyses used as mathematical models. This is possible in CFA because the method uses X2-metrics and is based on the distributional equivalence of the rows and columns of the transformed data matrix. We have thus demonstrated, in purely objective statistical terms, the general conclusions on the specificity of various functional and other groups derived from prior analyses by expert intuition and reasoning. A finer analysis was made of a series of A-ring phenols showing the high degree of glucocorticoid receptor and progesterone receptor binding that can be generated by certain C-11-substitutions despite the presence of the phenolic A-ring characteristic of estrogen receptor-specific binding.