Five new fawcettimine-related alkaloids from Lycopodium japonicum Thunb

Five new trace alkaloids with fawcettimine-related structures (1-5), i.e., 6-hydroxyl-6,7-dehydrolycoflexine (1), 6-hydroxyl-6,7-dehydro-8-deoxy-13-dehydroserratinine (2), together with three known ones (6-8), were isolated from the club moss Lycopodium japonicum Thunb. Their structures were elucidated by extensive NMR spectroscopic analysis, HRESIMS, CD and comparison with known ones. Compounds 1 and 2 are characterized by the enol moiety that is rarely reported in Lycopodium alkaloids, and Compound 5 is the second example of Lycopodium alkaloids with a C-16-C-4 linkage. A plausible biogenetic pathway for the isolates was proposed.