Marundihomalkins A–J and Marundisphingalkin A: Triglyceride-Lowering Marine Fungal Alkaloids Featuring Non-amide C–N Linkages between Polyketide and Homoisoleucine or Phytosphingosine

Eleven novel fungal alkaloids, marundihomalkins A–J (1–10) and marundisphingalkin A (11), featuring unprecedented non-amide C–N linkages between polyketide and homoisoleucine (homo-Ile) or phytosphingosine units, were isolated from the marine-derived fungus Microsphaeropsis arundinis HL1. Their structures, including four skeletal classes, were established by spectroscopic data, X-ray diffraction, and electronic circular dichroism calculations. This work provides the first structural evidence of homo-Ile as a natural biosynthetic building block and reports the inaugural phytosphingosine–polyketide hybrid alkaloid. 11 significantly inhibited adipogenesis in 3T3-L1 cells by PPAR signaling suppression.