Synthesis of C _(40)-symmetrical fully conjugated carotenoids by olefin metathesis

摘要

In an effort to push olefin metathesis to the limits of conjugation in reactants and products, the C _(40)-symmetrical carotenoids β,β-carotene (1), lycopene (2), (3R,3′R)-zeaxanthin (3), and rac-isozeaxanthin (4), which are conjugated undecaenes, have been synthesized from C _(21)-terminal hexaenes by treatment with Grubbs' second-generation Ru catalyst in dichloromethane at 50 °C.