Induced isoflavonoids from fungus-infected stems of pigeon pea (Cajanus cajan).

Four antifungal isoflavones [7-hydroxy-4'-methoxy-(1); 5,7,4'-trihydroxy-(2); 5,7,2',4'-tetrahydroxy-(3); 5,2',4'-trihydroxy-7-methoxy-(4)] and one isoflavanone [(5,2'-dihydroxy-7,4'-dimethoxy-(7)] have been isolated from the fungus-infected stems of Cajanus cajan. A sixth compound has been provisionally identified as 5,2'-dihydroxy-7,4'-dimethoxyisoflavone (5). The structure of 5,2'-dihydroxy-7,4'-dimethoxyisoflavanone (cajanol) was confirmed by synthesis from ferreirin (5,7,2'-trihydroxy-4'-methoxyisoflavanone).