Rare onocerane-type triterpenoid and γ-butyrolactone derivative isolated from Kermadecia sinuata

Genus Kermadecia (Proteaceae) showed interesting biological activities related to their macrocyclic derivatives (kermadecin). Nevertheless, chemistry of Kermadecia sinuata was not studied until now. Phytochemical investigation of the bark of K. sinuata led to the isolation of two previously undescribed compounds: 4-(hydroxymethyl)-3,5-diphenyldihydrofuran-2(3H)-one, kermafuranone (1) and (+)-(5S,8R,9R,10S,5’S,8’S,9’R,10’S)-onocerane-8,8’-diol (2), along with four known compounds: methyl haematommate (3), atranorine (4), β-sitosterol (5) and docosyl ferulate (6). The structures of these compounds were elucidated by HRESIMS and NMR spectroscopic data analysis, and the absolute configuration of compound 2 was determined by single-crystal X-ray diffraction analysis. This compound is the first non-symmetrical onocerane-8,8’-diol. Hypothesised biosynthesis pathway was suggested for kermafuranone (1).