Synthesis of (±)-7,3′- and 7,4′-di- O-methyleriodictyol and of velutin and pilloin

Abstract

Synthetic 2′-hydroxy-3,4′,6′-trimethoxy-4-benzyloxychalcone (I) affords (±)-7,3′-di- O-methyleriodictyol (II) and 7,3′-di- O-methylluteolin (or velutin, VII) identical with natural samples. Similarly synthetic 2′-hydroxy-4,4′,6′-trimethoxy-3-benzyloxychalcone (X) gives natural (±)-7,4′-di- O-methyleriodictyol (XI) and 7,4′-di- O-methylluteolin (or pilloin, IX). However, attempts to partially etherify II with one mole of prenyl bromide to obtain the natural prenyl ether failed; only the corresponding diprenyloxychalcone (IV) was obtained.