Pentacyclic triterpenes

A method for protecting plants against fungus attack by a process comprising:

• applying to exposed plant surfaces a carrier and an effective amount of a composition containing:
• a pentacyclic triterpene compound exhibiting a structure according to formula III:
• 4
• wherein:
• R1=Me, CH2OH, CH2OY1, CH2O—X—OH, CH2O—X—OY1, CH2O—X—Y2, CH2O— X—Y3, CH2NHY1, CH2NY12,CH2Y3, CH2NH—X—OH, CH2NH—X—Y2, CH2NH—X—Y3, CH2NH—X—OY1, CH2OC(O)—OY1, CH2O—X—OY1, CO2Y1, COY3, COY2, CHO, CH═N(CH2)m(O(CH2)m)nR4, or CH═N(CH2)m(O(CH2)m)nY2;
• R2, R3=H, OH, OY1, O—X—OH, O—X—OY1, O—X—Y2, Y3, NHY1, NY12, Y3, NH—X— OH, NH—X—Y2, NH—X—Y3, NH—X—OY1, NY1—X—OH, NY1—X—Y2, NY1—X—Y3, or NY1—X—OY1;
• provided that one of R2 and R3 is H or that R2 and R3 together denote carbonyl oxygen;
• R4=H, OH, OY1, or Y3;
• Y1=H, alkyl of 1-30 carbon atoms, straight chain or branched, cycloalkyl of 3-30 carbon atoms, alkanyl of 3-30 carbon atoms, oxyalkyl of 4-30 carbon atoms, phenylalkyl of 7-30 carbon atoms, or phenoxyalkyl of 7-30 carbon atoms;
• Y2=NH2, NHY1, or NY12;
• Y3=—(O(CH2)m)nR4 or —(O(CH2)m)nY2, where m=2-4 and n=1-230;
• X=—OC(CH2)pCO— where p=1-22.