General description

The 5,6-epoxy structure can give rise to a wide variety of carotenoid end-groups with the plausible biosynthetic transformations of the 5,6-epoxy-ß-ring to give diverse structures such as the cyclopentane carotenoids capsanthin and capsorubin, the retro-carotenoids eschscholtz- xanthin and rhodoxanthin, allenic carotenoids like the neoxanthin and fucoxanthin, 5,6-diols like the karpoxanthin and latoxanthin, 3,6-poxides as found in eutreptiellanone and cucurbitaxanthin, the 6-hydroxy-γ-ring structure found in prasinoxanthin and nigroxanthin, as well as the 5,6-seco-5,6-dione-end-group of semi-ß-carotenone.