Chuktabrins A and B, two novel limonoids from the twigs and leaves of Chukrasia tabularis.

Two novel limonoids, chuktabrin A (1), featuring the unique motifs of a 1,3-dioxolan-2-one and a 3,4-dihydro-2 H-pyran, and chuktabrin B (2), possessing an unprecedented polycyclic skeleton, were isolated from Chukrasia tabularis. The structures of 1 and 2 bearing a biosynthetically extended C3 and C2 unit at C-15, respectively, were elucidated on the basis of spectroscopic data, and that of 1 was confirmed by a single-crystal X-ray diffraction.