The semisynthesis of the Stemona alkaloids (3'R)-stemofolenol (1), (3'S)-stemofolenol (2), methylstemofoline (3), and (3'S)-hydroxystemofoline (5) and the unnatural analogues (11E)-methylstemofoline (15) and 3'R-hydroxystemofoline (11) has been achieved starting from (11Z)-1',2'-didehydrostemofoline (4). This synthesis allowed, for the first time, access to diastereomerically enriched samples of 1 and 2 and the assignment of their absolute configurations at C-3'. These compounds were obtained in sufficient quantities to allow for their biological testing. In a quantitative assay as AChE inhibitors, (11Z)-1',2'-didehydrostemofoline (4) and (3'S)-hydroxystemofoline (5) were found to be the most active.

The total synthesis of calystegine B4 was achieved in 10 steps from (–)‐D‐lyxose by using a new synthetic strategy to obtain the requisite protected hydroxylated 4‐aminocyclohept‐2‐en‐1‐one without the problem of regioisomer formation that was a problem in the earlier synthesis of this natural product. The key steps included a Petasis–borono‐Mannich reaction and a ring‐closing metathesis reaction.

This report is an overview of our research on phytochemical, synthetic and biological studies of the Stemona and Stichoneuron species of plants.