Process for the preparation of meso-zeaxanthin

A process for the preparation of meso-zeaxanthin,

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• which comprises
• a) resolving a racemic mixture of the acetylenediols R-I and S-I
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• into its antipodes,
• b) converting the separated antipodes R-I and S-I in each case into the C15-phosphonium salts R-II and S-II respectively
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• in which Ph is aryl and X is an anion equivalent of an inorganic or organic acid,
• c) reacting the phosphonium salts R-II or S-II with a C10-dial monoacetal of the general formula III,
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• in which the substituents R1 and R2 independently of one another are C1-C8-alkyl or, together with the oxygen atoms and the carbon atom to which they are bonded, can form a 1,3-dioxolane or 1,3-dioxane ring of the following structures
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• in which R3 and R4 and also R5 in each case independently of one another can be hydrogen or C1-C4-alkyl, in a Wittig reaction to give the C25-acetals R-IV or S-IV,
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• d) converting the C25-acetals R-IV or S-IV into the C25-aldehydes R-V or S-V
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• e) and reacting the C2-5-aldehyde R-V with the C15-phosphonium salt S-II or the C25-aldehyde S-V with the C15-phosphonium salt R-II in a Wittig reaction to give sterically uniform meso-zeaxanthin.