Two unusual dendrobine-type alkaloids, findlayines E and F (1, 2), along with five known dendrobine-type alkaloids (3-7), were isolated from the stems of Dendrobium findlayanum Par. et Rchb. f. Compound 1 is the first example of dendrobine-type alkaloids with a 2-ethoxy-2-oxoethyl group attaching to the C-2, and compound 2 is a nor-dendrobine-type alkaloid, featuring a 5-decarboxylated structure. The structures of compounds 1 and 2 were elucidated by means of extensive spectroscopic analyses, and their absolute configuration were confirmed by electronic circular dichroism (ECD) calculations. All isolates were evaluated for their cytotoxicity against HL-60, SMMC-7721, A-549 and MCF-7 human cancer cells.
Keywords: Dendrobine-type alkaloids; Dendrobium findlayanum.
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