Copyrine alkaloids: synthesis, spectroscopic characterization, and antimycotic/antimycobacterial activity of A- and B-ring-functionalized sampangines.

Several A- and B-ring-substituted sampangines were synthesized and evaluated for antifungal and antimycobacterial activity against AIDS-related opportunistic infection pathogens. Electrophilic halogenation provided a channel for structural elaboration of the sampangine B-ring at position 4, while the synthesis of A-ring 3-substituted sampangines and benzo[4,5]sampangine (24) were achieved from the corresponding functionalized cleistopholines. Two-dimensional NMR spectroscopy was used to rigorously characterize the A- and B-ring substituent patterns. Structure-activity relationship studies revealed the activity of the sampangines was enhanced by the presence of a substituent at position 3 or by a 4,5-benzo group.