(E/Z)‐Isomerization of 3′‐Epilutein

Abstract 3′‐Epilutein (=(all‐E,3R,3′S,6′R)‐4′,5′‐didehydro‐5′,6′‐dihydro‐β,β‐carotene‐3,3′‐diol; 1), isolated from the flowers of Caltha palustris, was submitted to both thermal isomerization and I2‐catalyzed photoisomerization. The structures of the main products (9Z)‐1, (9′Z)‐1, (13Z)‐1, (13′Z)‐1, (15Z)‐1, and (9Z,9′Z)‐1 were determined based on UV/VIS, CD, 1H‐NMR, and MS data.