Synthetic Access to the Chlorocyclopentane Cores of the Proposed Original and Revised Structures of Palau'amine

摘要

The pyrrole-imidazole alkaloids constitute a family of more than 100 natural products,among which palau'amine(1,Scheme 1)exists as one of the more structurally complex members.This polycyclic guanidine alkaloid,which was isolated from Stylotella aurantium,was found to possess potent cytotoxic,antibiotic,and immunosuppressive activities.Despite the fact that its acute toxicity is relatively low(LD_(50)=13 mg kg~(-1)in mice),palau'amine exhibited significant cytotoxicity in a variety of cancer cell lines,including P-388(IC_(50)=0.1mu g mL~(-1))and A-549(IC_(50)=0.2 mu g mL~(-1)).Moreover,1 exhibits remarkable immunosuppressive responses in the mixed lymphocyte assay(IC_(50)<18 ng mL~(-1)).