Novel, Complex Flavonoids from Mallotus philippensis (Kamala Tree)

One new flavanone, 4′‐hydroxyisorottlerin (2), and two new chalcone derivatives, kamalachalcones C (3) and D (4), were isolated from Mallotus philippensis (kamala tree). The largest compound (4; Mr 1098 g/mol) was shown to possess a unique, fused‐ring system made of two hydroxy‐chalcone units, giving rise to eight fused benzene/pyran units. From the same plant, the following six known compounds were also isolated: kamalachalcone A (5) and B (6), isoallorottlerin (7), isorottlerin (8), 5,7‐dihydroxy‐8‐methyl‐6‐prenylflavanone (9); 6,6‐dimethylpyrano(2″,3″: 7,6)‐5‐hydroxy‐8‐methylflavanone (10), and rottlerin (1). The structures of the new compounds were confirmed by in‐depth spectral analyses, including 2D‐NMR techniques, and the full 13C‐NMR assignments of the known flavanones 1 and 7–10 are published for the first time.