Carotenoids and Related Polyenes. Part 2. Photoisomerization of an Allenic Carotenoid, Peridinin, and Allenic Model Compounds.

Iodine-catalysed photoisomerization of peridinin 1a gave the novel (6S)-allenic isomer 1b whose structure was confirmed by chemical synthesis. In addition, the photochemical behaviour of several model compounds having a part structure of allenic carotenoids was investigated. From these results, photoisomerization of the allenic double bond in allenic carotenoids was discussed.