Synthesen in der Carotinoid‐Reihe. 1. Mitteilung. Die technische Synthese von β‐Carotin

The industrial β‐carotene manufacturing procedure based on Inhoffen's synthesis C19 + C2 + C19 = C40 is described. β‐Ionone is first lengthened to β‐C14‐aldehyde as in our vitamin A‐synthesis. By acetalisation, condensation with vinyl ether and treatment with acid the new β‐C16‐aldehyde is obtained. Repetition of the same reactions with propenyl ether leads to the β‐C19‐aldehyde. For the final steps simple methods were developed giving high yields. All the chemical, physical and biological constants of synthetic β‐carotene are identical with those of the natural compound. Exact data on light absorption are given. Extensive experiments with the synthetic β‐carotene on rats and rabbits show that even very large doses have no toxic effects.