Ir-Catalyzed Biomimetic Photoisomerization of Cyclopropane in Lathyrane-Type Euphorbia Diterpenes.

An efficient Ir-catalyzed biomimetic method for photoisomerization of cyclopropane in lathyrane-type Euphorbia diterpenes is reported. Lathyrane diterpenes featuring the trans -fused cyclopropane ( 1a - 5a ) were successfully prepared from cis -cyclopropane lathyranes ( 1 - 5 ) in excellent yields by this stereochemical permutations strategy, which first verified the biogenesis relationship between the lathyrane isomers. Moreover, 5a could further convert into another trans -isomer 5b . The present work provides a convenient route for easy access of naturally rare 12( Z )- trans -cyclopropane lathyranes.