STRUCTURE-ACTIVITY-RELATIONSHIPS OF RAPHANUSANINS AND THEIR ANALOGS

The structure-activity relationship of raphanusanins A and B {(3R*,6R*)-and (3R*,6S*)-3-[methoxy(methylthio)methyl]-2-pyrrolidinethione, respectively} and their analogues has been studied for the inhibition of the growth of lettuce hypocotyls and Amaranthus roots. Pyrrolidinethione compounds showed higher activity than pyrrolidinones. The presence of a methoxy(methylthio)methyl group or of a methylthiomethylene moiety at C-3 of pyrrolidinethione was a dominant factor for higher activity. The bis(methylthio)methyl derivative also gave a similar inhibitory activity. It was established that the active sites in the chemical structure of the raphanusanins and their analogues were the thioamide moiety at C-2 of the skeleton and a methoxy(methylthio)methyl, bis(methylthio)methyl, or methylthiomethylene group in the C-3 position of the side chain.