Zeaxanthin (6.24 gm, 11 mmole) was slurried in 110 ml of chloroform under nitrogen and cooled on ice. To this stirred mixture, was added a solution of 6.14 gm (51.6 mmole) sodium bromate in 35 ml of water and acidified with 1 ml of 50% sulfuric acid. The three phase mixture was cooled on ice and 4 ml of a solution containing 4.84 gm (32.1 mmole) of potassium bromide in 15 ml of water was added rapidly to begin the reaction. After 1 hour, 7 ml of 3 N sodium hydroxide was added and the mixture was stirred for 15 minutes. The mixture was filtered over celite and the phases were separated. The organic layer was washed with basic water and separated. The chloroform was removed under vacuum at around 40° C. until a thick slurry remained. Ethanol (90 ml) was added and the remaining chloroform was removed by vacuum distillation. The reaction mixture was cooled and the product collected by filtration to yield 1.78 grams (28.5% yield) astaxanthin.
