Hupertimines A-E, Fawcettimine-Type Lycopodium Alkaloids from Huperzia serrata

Five new fawcettimine-type Lycopodium alkaloids, hupertimines A-E (1-5), were discovered from the whole plant of Huperzia serrata, along with two known alkaloids, 8α-hydroxyphlegmariurine B (6) and 8β-hydroxyphlegmariurine B (7). The structures of 1-7 were identified through HR-MS, IR, ¹ H, ¹³ C, and 2D NMR, and single-crystal X-ray diffraction analysis. Structurally, compound 1 was the fourth example of Lycopodium alkaloid with an ether linkage between C-5 and C-13 and 2 was the third example of Lycopodium alkaloid with a 5/5/5/5/6 pentacyclic ring system and featuring a 1-aza-7-oxabicyclo[2.2.1]heptane unit. Compounds 1-7 were tested for their BACE1 inhibitory activity. In addition, the correct ¹ H- and ¹³ C-NMR data for 7 were reported in current study.