New (4 → 2)-abeo-clerodane diterpenoids from the Polyalthia laui and their chemotaxonomic significance

Abstract

The phytochemical investigation of the Polyalthia laui led to the isolation of two new (4 → 2)-abeo-clerodane diterpenoids [(4 → 2)-abeo-6,16-dihydroxycleroda-2,13Z-dien-15-oic acid (1), and (4 → 2)-abeo-13-hydroxycleroda-2-en-15,16-olide-3-al (2)], together with seven known analogues [salvicinolide (3), (4 → 2)-abeo-16 (R/S)-2,13Z-kolavadien-15,16-olide-3-al (4), solidagonal acid (5), 16-hydroxycleroda-4 (18),13-dien-15,16-olide (6), 16-hydroxy-3,13Z-kolavadien-16,15-olide (7), cleroda-4 (18),13-dien-15,16-olide (8), 16-hydroxycleroda-3,13E-dien-15-oic acid (9)]. The structures were elucidated by extensive NMR and HRESIMS analysis. The chemotaxonomic significance of the isolates was also discussed. Compound 3 was reported from the genus of Polyalthia for the first time, and the 13C NMR data has not been published so far. All the compounds were isolated from the P. laui for the first time except 7 and 8.