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.