Ciliatonoids D–M, highly modified limonoids from the twigs of Toona ciliata

A new ring-intact limonoid, ciliatonoid D (1), five new 7,8-seco limonoids, ciliatonoids E–I (2–6), three new 7,8-seco-29-nor limonoids, ciliatonoids J–L (7–9), and a new 7,8:9,11-diseco limonoid, ciliatonoid M (10), together with eleven known limonoids were isolated from the twigs of Toona ciliata. Their structures were established by comprehensive analyses of spectroscopic, electronic circular dichroism, single-crystal X-ray diffraction data. Compound 6 bears an uncommon 1,30-oxygen bridge. Compound 10 represents a rare example of a structure with 9,11-seco limonoid from Meliaceae. The orientation of the 14,15-epoxy moiety in a known limonoid, toonayunnanae C (12), was revised as in a β-orientation by quantum NMR calculations with ML-J-DP4 probability analysis. Compound 9 and a known analogue, toonanoronoid C (11), were found to show modest in vitro cytotoxicity against HL-60 (human premyelocytic leukemia) and P-388 (murine leukemia) cell lines.