Triconnarins A–D: Four Secophragmalin-Type Limonoids from the Twigs and Leaves of Trichilia connaroides

Four novel secophragmalin-type limonoids, triconnarins A-D (1-4), have been identified from the small branches and leaves of Trichilia connaroides. Triconnarin A (1) featured an unprecedented 5/6/4/6/6 ring skeleton, which belonged to the rare 1,10-secophragmalin classes. Triconnarin B (2) was the first B-ring opening secophragmalin limonoid, whereas triconnarin C (3) possessed a unique 5/5-6/6 ring system. Compounds 1-3 were proven to demonstrate potent QR-inducing activity.