Dcalycinumines A—E, Alkaloids with Cytotoxic Activities of Nasopharyngeal Carcinoma Cells from Daphniphyllum calycinum

Abstract

Comprehensive SummaryFive novel Daphniphyllum alkaloids, named dcalycinumines A—E (1—4, 6), and eight previously described Daphniphyllum alkaloids (5, 7—13) were isolated from Daphniphyllum calycinum. Compound 1 is the first Daphniphyllum alkaloid possessing a highly rearranged 6/6/6/7/5/6 hexacyclic architecture with a unique 3‐methyl‐1‐azabicyclo [4,4,0] decane ring system. Compound 2 represents a rare diamino Daphniphyllum alkaloid with an unprecedented 6/5/5/6/6/5 carbon skeleton featuring a unique 1‐aza‐6‐azaspiro [4,5] decane unit, whereas 3 also represents a rare diamino Daphniphyllum alkaloid as a possible precursor of 2. Compound 4 is the second example of C‐22‐nor yuzurimine‐type alkaloids. Their structures and absolute configurations were elucidated by HRESIMS, NMR spectroscopic analyses, ECD calculations, and single‐crystal X‐ray diffraction. Moreover, compound 1 showed remarkable antitumor activities, which could inhibit the proliferation, migration and invasion of nasopharyngeal carcinoma cells, and promoted nasopharyngeal carcinoma cells apoptosis.