Marine actinomycetes are known for their production of remarkable organic molecules, particularly those featuring polyoxygenated long-chain backbones. Determining the absolute configurations of these compounds remains a challenging task even today. In this study, we successfully established the planar structures and absolute configurations of two highly flexible amide alkaloids from Streptomyces sp. WU20: kueishanamides A (1) and B (2). These compounds possess a C13 linear backbone and each contains five stereogenic carbon centers. Our approach involved a combination of spectroscopic and computational methods, including J-based configurational analysis and VCD calculations, ensuring the unambiguous determination of their configurations. Kueishanamide A (1) and kueishanamide B (2) showed moderate antifungal activity against pathogenic fungus Crytococcus neoformans, with MIC values of 25 μg/mL each.
Keywords: Streptomyces sp. WU20; VCD analysis; amide alkaloids; antifungal activity; hydrothermal vent.
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