Umwandlung eines Betacyans in ein Betaxanthin Synthese von Indicaxanthin aus Betanin

When betanin (III) was treated with S‐proline (IV), a base exchange took place which produced indicaxanthin (I). In this way this yellow pigment of the cactus fruit was partially synthesized by a method which should be generally applicable for the mutual interconversion of betacyanins and betaxanthins. For it was also possible to transform indicaxanthin into betanidin (II) by a base exchange with 5,6‐dihydroxy‐2,3‐dihydroindole‐2S‐carboxylic acid (V).