- 3 - hydroxy - β - ionone and - 3 - hydroxy - β - ionone are two important intermediates in the synthesis of carotenoids with β - end group such as lutein , zeaxanthin , β - cryptoxanthin , and their stereoisomers . among the various stereoisomers of these carotenoids , only - lutein , - zeaxanthin , and - β - cryptoxanthin are present in commonly consumed fruits and vegetables . there are 3 possible stereoisomers for zeaxanthin , these are : dietary - zeaxanthin , non - dietary - zeaxanthin , and non - dietary - zeaxanthin which is a presumed metabolite of dietary lutein . dietary lutein as well as 1 and 3 are accumulated in the human macula and have been implicated in the prevention of age - related macular degeneration . - β - cryptoxanthin is also present in selected ocular tissues at a very low concentration whereas its enantiomer - β - cryptoxanthin is absent in foods and human plasma . the present invention relates to a process for the synthesis of - 3 - hydroxy - β - ionone and its - enantiomer in high optical purity from commercially available - α - ionone . the key intermediate for the synthesis of these hydroxyionones is 3 - keto - α - ionone ketal that was prepared from - α - ionone after protection of this ketone as a 1 , 3 - dioxolane . reduction of 3 - keto - α - ionone ketal followed by deprotection , lead to 3 - hydroxy - α - ionone that was transformed into - 3 - hydroxy - β - ionone by base - catalyzed double bond isomerization in 46 % overall yield from - α - ionone . the racemic mixture of these hydroxyionones was then resolved by enzyme - mediated acylation in 96 % ee . - 3 - hydroxy - β - ionone and its - enantiomer were respectively transformed to - 3 - hydroxy - triphenylphosphonium chloride — c 15 - wittig salt ] and its - enantiomer — c 15 - wittig salt ] according to known procedures . double wittig condensation of these wittig salts with commercially available 2 , 5 - dimethylocta - 2 , 4 , 6 - triene - 1 , 8 - dial provided all 3 stereoisomers of zeaxanthin . similarly , — c 15 - wittig and its - enantiomer were each coupled with β - apo - 12 ′- carotenal to yield 4 and 5 .