Synthesis of Isoprenyl Chalcone “Sophoradin” Isolated from Sophora subprostrata

Abstract

Sophoradin (I) [2', 4, 4'-trihydroxy-3, 3', 5-tris (3-methyl-2-butenyl) chalcone] was synthesized through Claisen-Schmidt condensation followed by demethoxymethylation.
Isoprenylation of p-hydroxybenzaldehyde with 3, 3-dimethylallyl bromide in 10 potassium hydroxide solution gave 4-hydroxy-3, 5-bis (3-methyl-2-butenyl) benzaldehyde (IX). Methoxymethylation of 2, 4-dihydroxy-3-(3-methyl-2-butenyl) acetophenone (IV) and IX afforded 4-methoxymethoxy-IV (XVIII) and 4-methoxymethoxy-IX (XX). Condensation of XVIII and XX in 50% potassium hydroxide solution gave 2'-hydroxy-4, 4'-bis (methoxy-methoxy)-3, 3', 5-tris (3-methyl-2-butenyl) chalcone (XXII). Hydrolysis of XXII with methanolic hydrochloric acid gave I which was identified with natural I by mixed mp, and IR and NMR spectra.