The Synthesis of Neobavaisoflavone and Related Compounds

The condensation of 7-benzoyloxy-4′-hydroxyisoflavone with 2-methyl-3-buten-2-ol gave 7-benzoyloxy-4′-hydroxy-3′-(3-methyl-2-butenyl)isoflavone. The hydrolysis of the alkylated isoflavone with dilute alkali afforded neobavaisoflavone [7,4′-dihydroxy-3′-(3-methyl-2-butenyl)isoflavone], which was then converted into isoneobavaisoflavone on heating with formic acid. 7-Benzyloxy-4′-hydroxyisoflavone was condensed with 2-methyl-3-buten-2-ol to give a chroman derivative, which was then converted into isoneobavaisoflavone by hydrolysis. 3′-(3-Methyl-2-butenyl)-5,7,4′-trihydroxyisoflavone was also synthesized from 7-benzoyloxy-5,4′-dihydroxyisoflavone in a similar manner.