Seven new α,β-diphenyl-γ-butyrolactones (1-7), three new lignans (8-10), five new neolignans (11-15), two new 1,3-biphenylpropanoids (16 and 17), and a new flavonol galactoside-lignan ester (18), together with 43 known compounds (19-61), were isolated from the twigs of Cinnamomum cassia. Their structures were elucidated by spectroscopic data analysis as well as chemical methods. The α,β-diphenyl-γ-butyrolactones are a class of unique natural compounds that have only been isolated from C. cassia. Compounds 11 and 12 are rare examples of neolignans possessing a 1,2-dioxetane moiety. Compound 13 is a new oxyneolignan possessing a unique C-9-O-C-9' linkage between the benzopyran and cinnamyl alcohol moieties. Compound 15 is the first example of a natural neolignan possessing a 2-styryl-3-phenyltetrahydrofuran skeleton. The isolated compounds were evaluated for their neuroprotective activities against tunicamycin-induced cytotoxicity in SH-SY5Y cells. Compounds 3, 5, 10, 11, 12, 20, 36, and 56 showed statistically significant neuroprotective activity with EC values ranging between 21 and 75 μM.

Six oligomeric sesquiterpenoids, aggreganoids A−F (1−6), were isolated from Lindera aggregata. Aggreganoid A (1) and B (2) are two unprecedented methine-or methylene-bridged sesquiterpenoid trimers possessing a unique C 46 skeleton. Aggreganoids C−F (3−6) are the first examples of carbon-bridged disesquiterpenoids with a C 33 or C 31 skeleton in the plant kingdom. Their structures and absolute configurations were elucidated by using spectroscopic methods and electronic circular dichroism calculations. A plausible biosynthetic pathway of these compounds was also proposed.

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Four disesquiterpenoid−geranylbenzofuranone conjugates, linderalides A−D (1−4), were isolated from Lindera aggregata. Compounds 1−3 represent the first examples of disesquiterpenoid−geranylbenzofuranone hybrids directly linked by two C−C bonds. Linderalide D ( 4) bears an unprecedented carbon skeleton featuring an unusual linearly 6/ 6/5/6/6 pentacyclic ring system fused by a sesquiterpenoid unit and a geranylbenzofuranone moiety. Their structures and absolute configurations were elucidated by extensive spectroscopic data and electronic circular dichroism analysis. Their biosynthetic pathways were also proposed.