Identification of a chromone-based retinoid containing a polyolefinic side chain via facile synthetic routes.

Attempts to prepare substituted chromones as novel retinoids revealed that some chromones were unstable under Wadsworth-Horner-Emmons reaction conditions. Hence, Wittig reactions were used to prepare chromone-based compounds as potential retinoids. Firstly, Wittig reagents prepared from 3-bromomethyl-chromen-4-one were reacted with olefinic-aldehydes to provide the target compounds with all-trans side chains in good yield. The approach supplies a useful general route to structurally diverse chromone-based compounds possessing a variety of side chains. Sequential Wittig reactions were used also to prepare a chromone-based retinoid. These novel compounds were evaluated in binding assays and a high affinity RAR ligand was identified. Crystal structures obtained for two key precursors aided the interpretation of binding data.