Key relationships between the intramolecular H-bond-derived backbone conformation and the bioactivity of the novel fat-accumulation inhibitor (â)-ternatin are examined by analyses of the NMR spectroscopic data and CD spectra of designed analogues. The results reveal that the β-turn structure of (â)-ternatin is responsible for its potent fat-accumulation inhibitory effect against 3T3-L1 murine adipocytes.