Confirmation of the Structures of Lutein and Zeaxanthin

A series of new esters of lutein (1a) have been prepared with the aim of confirming the structure of lutein via an X‐ray crystal‐structure analysis. Although well crystallized, only one of the derivatives, the (−)‐(1R)‐menthyl carbonate (1i) proved to be useful for a complete structure analysis. The same derivative of zeaxanthin (2a) also allowed its crystal structure to be determined. Both analyses represent the first successful X‐ray crystal structure analyses of the most important xanthophylls. At the same time, they confirm both the constitution and absolute configuration of 1a and 2a that had been deduced earlier by classical methods.