Mimulaxanthin, the Main Carotenoid in Lamium montanum, Determination of its Absolute Configuration. Absolute Configuration of Deepoxyneoxanthin by its Correlation with Neoxanthin

Article abstract of DOI:10.1002/hlca.19800630848

The carotenoid mixture isolated from the yellow flowers of Lamium montanum PERS. (Labiatae) consists of more than 75percent of carotenoids with allenic end groups.Besides 32percent of neoxanthin/neochrome we isolated 44percent of mimulaxanthin (1a), a very rare carotenoid so far only found in Mimulus sp. (Scrophulariaceae).Its absolute configuration was determined by oxidative degradation to the known ketone 3 ("grasshopper ketone") and by spectroscopic and chiroptical comparisons with neoxanthin (6).Mimulaxanthin (1a) therefore is (3S,5R,6R,3'S,5'R,6'R)-6,7,6',7'-tetradehydro-5,6,5',6'-tetrahydro-β,β-carotene-3,5,3',5'-tetraol.Deepoxyneoxanthin, which was reisolated from Mimulus sp. is (3S,5R,6R,3'R)-6,7-didehydro-6,7-dihydro-β,β-carotene-3,5,3'-triol (2), as shown by spectroscopic and chemical correlation with neoxanthin (6; de-epoxydation by BuLi/FeCl3).