Fortuneicyclidins A and B, Pyrrolizidine Alkaloids with a 7-Azatetracyclo[5.4.3.0.0^2,8]tridecane Core, from Cephalotaxus fortunei

Fortuneicyclidins A (1) and B (2), a pair of epimeric pyrrolizidine alkaloids containing an unprecedented 7-azatetracyclo[5.4.3.0.02,8]tridecane core, were isolated from the seeds of Cephalotaxus fortunei, along with two biogenetically relative known analogues, 3 and 4. The structures were determined by multiple spectral techniques and chemical derivatization methods. Compound 1 showed inhibitory activity against...