| Betulin, 20(29)-lupene-3{dollar}beta{dollar},28-diol, is a lupene-type triterpene occurring in remarkably high concentration (up to 11.9%) of the bark of birch, Betula papyrifera., a common tree in the northern United State, Canada, northern Europe, northern Asia and Siberia. Twenty-four betulin derivatives have been prepared and evaluated as antifeedants against three insects, bollworm (Heliothis zea), fall armyworm (Spodoptera frugiperda), and Colorado potato beetle (Leptinotarsa decemlineata, Say). Among those chemicals, 19{dollar}beta{dollar}-hydroxy-18{dollar}alpha{dollar}-olean-2-hydroxymethylene-3-oxo-28-oic, {dollar}gamma{dollar}-lactone 83 and 19{dollar}beta{dollar}-hydroxy-18{dollar}alpha{dollar}-olean-2,3-seco-28-oic acid, {dollar}gamma{dollar}-lactone, 2,3-diacid 85 showed feeding reduction activities of more than 50% at a dosage of 100{dollar}mu{dollar}g/cm{dollar}sp2{dollar} leaf-disk against third instar fall armyworm. 19{dollar}beta{dollar},28-Epoxy-18{dollar}alpha{dollar}-olean-2-hydroxymethylene-3-one 80, 19{dollar}beta{dollar}-hydroxy-18{dollar}alpha{dollar}-olean-1-en-2-formyl-3-oxo-28-oic acid, {dollar}gamma{dollar}-lactone 84, 3{dollar}beta{dollar}-O-acetyl-28-norbetulin-17{dollar}alpha{dollar}-hydroxyperoxide 105f, 3,28-O-diacetyl-30-hydroxyl betulin 113, and 20-keto-29-hydroxy-30-norbetulin 114 showed activities of more than 50% at a dosage of 100{dollar}mu{dollar}g/cm{dollar}sp2{dollar} leaf-disk against fourth instar Colorato potato beetle. Compounds 80 and 105f also showed activities of more than 50% against fourth instar bollworm. The evidence showed that the hydroxy functionality at the C30-position of 113 is essential to the activity and the stereochemistry at C17-position of 105f is the key to the activity. |
