A-Ring-Modified Triterpenoids and Their Spermidine-Aldimines with Strong Antibacterial Activity

Synthesis of A-ring-modified lupane, oleanane and ursane type triterpenoid conjugates with spermidine through an aldimine linkage or diethylentriamine via an amide bond is described. These derivatives were evaluated for their in vitro antimicrobial properties against human pathogens. Except for derivatives 1 and 7, all compounds have moderate to weak minimum inhibitory concentrations (MICs) against Gram-positive Staphylococcus aureus bacteria, with MICs varying from 3.125 to 200 mu M. Compound 11 is efficient against Escherichia coli and Pseudomonas aeruginosa, with MICs of 25 and 50 mu M, respectively, while all other derivatives do not possess important antimicrobial activities against these Gram-negative bacteria.