| 摘要 |
A synthesis of novel Vitamin A intermediates from beta-ionone is described as well as a conversion of the intermediates to Vitamin A. The length of the conjugated aliphatic side chain of beta-ionone is increased while still ultimately obtaining the desired trans form of Vitamin A. In general, beta-ionone is ethynylated to ethynyl-beta-ionol, the hydroxyl of which is etherified to form an ethynyl-terminated, alkoxy-substituted, beta-ionol intermediate. The intermediate is coupled through its copper derivative with a compound like chloro-isopentenyl acetate to produce a C20 skeleton. By semi-hydrogenation, the acetylenic bond on the C20 skeleton is converted to an ethylenic bond, and by hydrolysis the terminal ester moiety is converted to a hydroxyl group. Treatment with a strong base removes the alkoxy group to produce Vitamin A.
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