Preparation and Solvolysis Reactions of Unstable Carotenoid Sulphates

Preparation and Solvolysis Reactions of Unstable Carotenoid Sulphates 

Tertiary carotenoid sulphates obtained from carotenoids with end group m, secondary allylic sulphates derived from carotenols with end groups n, o and p and primary allylic sulphates obtained from an apocarotenol with end group q, are unstable and undergo methanolysis during the work-up procedure [15]. 

Thus the tertiary sulphates of azafrin (504, end group m) and of its methyl ester, and the secondary allylic sulphates of lutein (133, end groups d, n), lactucaxanthin (150, end group n), and isozeaxanthin (129, end group o), undergo rapid solvolysis reactions [15]. Product analysis supports solvolysis via tertiary or resonance-stabilized cations. 

Whereas steric hindrance of the tertiary hydroxy group of the allenic end group of fucoxanthin (369) and peridinin (558) is too great to allow silylation [16] or sulphation [11], carotenoids such as azafrin (504) and its methyl ester containing the diol end group m form 5-tri methyl si lyl ethers [17] and also 5-monosulphates slowly. Solvolysis products of the sulphates have been studied [15]. Azafrin 5-sulphate behaves as a detergent in aqueous solution [15]. 

The initially formed disulphate of lutein (133, end groups d and n) undergoes rapid methanolysis, providing a stable non-allylic 3-monosulphate. The methanolysis of the allylic 

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E. Preparation and Solvolysis Reactions of Unstable Carotenoid Sulphates... 

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