Abstract
In this study, carotenoid retinoates are described for the first time. The preparation was achieved by the azolide method. Various sec carotenols reacted with N-retinoylimidazol in the presence of catalytic amounts of sodium hydride. Mono- and diretinoates of (3R,3′R)-zeaxanthin and its (3S,3′S)-enantiomer, (9Z,9′Z; 3R,3′R)-alloxanthin, (3R,3′R)-7,8,7′,8′-tetrahydro-3,3′-dihydroxy-β,β-carotene-8,8′-dione and (3R,6R,3′R,6′R)-ε,ε-carotene-3,3′-diol (lactucaxanthin), as well as monoretinoates of (3R,3′RS,6′R)-3′-methoxy-β,ε-caroten-3-ol, (3R,3′RS,6′R)-3-methoxy-β,ε-caroten-3′-ol, (2R,6′RS)-β,ε-caroten-2-ol, (3R,3′S; meso)-astaxanthin and (2′R)-aleuriaxanthin are reported in this study. Spectroscopic properties (1H-NMR mass spectrometry, visible and circular dichroism spectra) are discussed. Studies on other carotenoid derivatives with two chromophores are referred to here.
Acknowledgements
We thank Professor K. Nakanishi, Columbia University, for suggesting this study. Skilled technical assistance including CD spectra was provided by student Einar Egeland. Vitamin A acid and the synthetic carotenoids were mainly gifts from Dr H. Mayer, Hoffmann-La Roche, Basel, except synthetic alloxanthin and 3,3′-dihydroxy-7,8,7′,8′-tetrahydro-β,β-carotene-8,8′-dione, which were gifts from Dr G. Saucy, formerly of Hoffmann-La Roche, Nutley. Sissel Hertzberg and Einar Egeland were supported by a research grant from Hoffmann-La-Roche, Basel, to Synnøve Liaaen-Jensen.