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Pseudolaric acid B [1] was isolated and identified as the main antifungal constituent of Pseudolarix kaempferi using bioassay-directed fractionation. Pseudolaric acid B was active against Trichophyton mentagrophytes, Torulopsis petrophilum, Microsporum gypseum, and Candida spp., while its methylated or hydrolyzed derivatives were not active against these same organisms. The minimum inhibitory concentrations and minimum fungicidal concentrations of pseudolaric acid B [1] against Candida and Torulopsis species were comparable with those of amphotericin B. The in vivo activity of pseudolaric acid B was evaluated in a murine model of disseminated candidiasis. Pseudolaric acid B [1] reduced the number of recovered colony-forming units significantly at different dosages. Infected mice treated intravenously with pseudolaric acid B [1] also had a longer survival time than those treated with vehicle alone.

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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.

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