Terpenoids from the fruits of Aphanamixis grandifolia

From the fruits of the tropical tree Aphanamixis grandifolia, six new evodulone-type (ring A-seco) limonoids aphanalides I-N (1-6), three new protolimonoids polystanins E-G (7-9), and three chain-like diterpenoids nemoralisins A-C (10 – 12), along with nine known compounds were isolated, whose structures were elucidated on the basis of extensive spectroscopic analysis. The limonoids varied mainly in ring D: a cyclopentenone ring for aphanalides I (1) and K (3), an oxetane ring between C-7 and C-14 for aphanalides J (2) and L (4), and a 14, 15-oxirane ring for aphanalides M (5) and N (6). Polystanin E (7) was an apo-tirucallane triterpenoid bearing a six-membered hemiketal at the side-chain, and polystanins F (8) and G (9) were two new tirucallane triterpenoids. Nemoralisins A-C (10 – 12) were three bicyclo-diterpenoids rarely found in meliaceae. The absolute configurations were determined by combination of single crystal X-ray diffraction analyses, CD exciton chirality method, Mosher's method and calculated electronic circular dichroism (ECD). The initial insect antifeedant activity to compounds 1-6 were evaluated, and compound 6 exhibited the most potential to such activity.