A synthesis of 2,4-dihydroxyisoflavans and 2-Hydroxyisoflav-3-enes: Versatile precursors to isoflavanoids

A new synthesis of isoflavanoids has been developed by treatment of a salicylaldehyde with an arylglycidate salt. Reaction conditions have been found so that this condensation yields either a 2,4-dihydroxyisoflavan or a 2-hydroxyisoflav-3-ene. A 2-hydroxyisoflav-3-ene such as (8a) can then be converted into the isoflavylium salt (9b), isoflavan (11b), 2-hydroxyisoflavan (11a), isoflav-2-ene (13) or isoflav-3-ene (10d). Similarly, the 2-aminoisoflav-3-ene derivative (10f) can be obtained from (8d). The reaction of isoflavylium salts or (8a) with 3-mercaptopropionic acid gives isoflav-3-ene derivatives (15) potentially useful as haptens for conjugation with suitable macromolecules for the generation of antibodies.