Iron-Catalyzed Skeletal Conversion of Lathyrane to Premyrsinane Euphorbia Diterpenes and Their Cytotoxic Activities

Two new premyrsinane-type diterpenes (2 and 3) as diastereomers were synthesized from lathyrane-type diterpene euphorbia factor L-3 (1) for the first time via an efficient Fe(acac)(3-) catalyzed skeleton conversion process. This conversion features a biogenetically inspired strategy that relies on a concise reductive olefin coupling involving intramolecular Michael addition with free radicals. The structures of 2 and 3 were elucidated by a combination of the interpretation of their spectroscopic data and single-crystal X-ray diffraction analysis. The premyrsinane diterpenes 2 and 3 exhibited cytotoxic activity against the 4T1 breast cancer cell line, while the parent compound euphorbia factor L-3 (1) was inactive. The current results not only confirmed the biogenetic relationship between lathyranes and premyrsinanes for the first time but also suggested a novel method for the preparation of naturally rare premyrsinane diterpenes with high bioactivity from the more abundant natural lathyrane diterpenes.

Automated summary

In this study, two new premyrsinane-type diterpenes were synthesized for the first time from lathyrane-type diterpene. These premyrsinane diterpenes showed cytotoxic activity against breast cancer cells, indicating a potential biogenetic relationship and a novel method for preparation.